1 /*
   2  * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.tools.javac.comp;
  27 
  28 import java.util.*;
  29 import java.util.function.BiConsumer;
  30 import java.util.function.BiPredicate;
  31 import java.util.function.Consumer;
  32 import java.util.function.Predicate;
  33 import java.util.function.Supplier;
  34 import java.util.function.ToIntBiFunction;
  35 import java.util.stream.Collectors;
  36 import java.util.stream.StreamSupport;
  37 
  38 import javax.lang.model.element.ElementKind;
  39 import javax.lang.model.element.NestingKind;
  40 import javax.tools.JavaFileManager;
  41 
  42 import com.sun.source.tree.CaseTree;
  43 import com.sun.tools.javac.code.*;
  44 import com.sun.tools.javac.code.Attribute.Compound;
  45 import com.sun.tools.javac.code.Directive.ExportsDirective;
  46 import com.sun.tools.javac.code.Directive.RequiresDirective;
  47 import com.sun.tools.javac.code.Source.Feature;
  48 import com.sun.tools.javac.comp.Annotate.AnnotationTypeMetadata;
  49 import com.sun.tools.javac.jvm.*;
  50 import com.sun.tools.javac.resources.CompilerProperties.Errors;
  51 import com.sun.tools.javac.resources.CompilerProperties.Fragments;
  52 import com.sun.tools.javac.resources.CompilerProperties.Warnings;
  53 import com.sun.tools.javac.tree.*;
  54 import com.sun.tools.javac.util.*;
  55 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticFlag;
  56 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
  57 import com.sun.tools.javac.util.JCDiagnostic.Error;
  58 import com.sun.tools.javac.util.JCDiagnostic.Fragment;
  59 import com.sun.tools.javac.util.JCDiagnostic.Warning;
  60 import com.sun.tools.javac.util.List;
  61 
  62 import com.sun.tools.javac.code.Lint;
  63 import com.sun.tools.javac.code.Lint.LintCategory;
  64 import com.sun.tools.javac.code.Scope.WriteableScope;
  65 import com.sun.tools.javac.code.Type.*;
  66 import com.sun.tools.javac.code.Symbol.*;
  67 import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;
  68 import com.sun.tools.javac.tree.JCTree.*;
  69 
  70 import static com.sun.tools.javac.code.Flags.*;
  71 import static com.sun.tools.javac.code.Flags.ANNOTATION;
  72 import static com.sun.tools.javac.code.Flags.SYNCHRONIZED;
  73 import static com.sun.tools.javac.code.Kinds.*;
  74 import static com.sun.tools.javac.code.Kinds.Kind.*;
  75 import static com.sun.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;
  76 import static com.sun.tools.javac.code.Scope.LookupKind.RECURSIVE;
  77 import static com.sun.tools.javac.code.TypeTag.*;
  78 import static com.sun.tools.javac.code.TypeTag.WILDCARD;
  79 
  80 import static com.sun.tools.javac.tree.JCTree.Tag.*;
  81 import javax.lang.model.element.Element;
  82 import javax.lang.model.element.ExecutableElement;
  83 import javax.lang.model.element.TypeElement;
  84 import javax.lang.model.type.DeclaredType;
  85 import javax.lang.model.type.TypeMirror;
  86 import javax.lang.model.util.ElementFilter;
  87 import javax.lang.model.util.ElementKindVisitor14;
  88 
  89 /** Type checking helper class for the attribution phase.
  90  *
  91  *  <p><b>This is NOT part of any supported API.
  92  *  If you write code that depends on this, you do so at your own risk.
  93  *  This code and its internal interfaces are subject to change or
  94  *  deletion without notice.</b>
  95  */
  96 public class Check {
  97     protected static final Context.Key<Check> checkKey = new Context.Key<>();
  98 
  99     // Flag bits indicating which item(s) chosen from a pair of items
 100     private static final int FIRST = 0x01;
 101     private static final int SECOND = 0x02;
 102 
 103     private final Names names;
 104     private final Log log;
 105     private final Resolve rs;
 106     private final Symtab syms;
 107     private final Enter enter;
 108     private final DeferredAttr deferredAttr;
 109     private final Infer infer;
 110     private final Types types;
 111     private final TypeAnnotations typeAnnotations;
 112     private final JCDiagnostic.Factory diags;
 113     private final JavaFileManager fileManager;
 114     private final Source source;
 115     private final Target target;
 116     private final Profile profile;
 117     private final Preview preview;
 118     private final boolean warnOnAnyAccessToMembers;
 119 
 120     public boolean disablePreviewCheck;
 121 
 122     // The set of lint options currently in effect. It is initialized
 123     // from the context, and then is set/reset as needed by Attr as it
 124     // visits all the various parts of the trees during attribution.
 125     private Lint lint;
 126 
 127     // The method being analyzed in Attr - it is set/reset as needed by
 128     // Attr as it visits new method declarations.
 129     private MethodSymbol method;
 130 
 131     public static Check instance(Context context) {
 132         Check instance = context.get(checkKey);
 133         if (instance == null)
 134             instance = new Check(context);
 135         return instance;
 136     }
 137 
 138     @SuppressWarnings("this-escape")
 139     protected Check(Context context) {
 140         context.put(checkKey, this);
 141 
 142         names = Names.instance(context);
 143         log = Log.instance(context);
 144         rs = Resolve.instance(context);
 145         syms = Symtab.instance(context);
 146         enter = Enter.instance(context);
 147         deferredAttr = DeferredAttr.instance(context);
 148         infer = Infer.instance(context);
 149         types = Types.instance(context);
 150         typeAnnotations = TypeAnnotations.instance(context);
 151         diags = JCDiagnostic.Factory.instance(context);
 152         Options options = Options.instance(context);
 153         lint = Lint.instance(context);
 154         fileManager = context.get(JavaFileManager.class);
 155 
 156         source = Source.instance(context);
 157         target = Target.instance(context);
 158         warnOnAnyAccessToMembers = options.isSet("warnOnAccessToMembers");
 159 
 160         disablePreviewCheck = false;
 161 
 162         Target target = Target.instance(context);
 163         syntheticNameChar = target.syntheticNameChar();
 164 
 165         profile = Profile.instance(context);
 166         preview = Preview.instance(context);
 167 
 168         boolean verboseDeprecated = lint.isEnabled(LintCategory.DEPRECATION);
 169         boolean verboseRemoval = lint.isEnabled(LintCategory.REMOVAL);
 170         boolean verboseUnchecked = lint.isEnabled(LintCategory.UNCHECKED);
 171         boolean enforceMandatoryWarnings = true;
 172 
 173         deprecationHandler = new MandatoryWarningHandler(log, null, verboseDeprecated,
 174                 enforceMandatoryWarnings, "deprecated", LintCategory.DEPRECATION);
 175         removalHandler = new MandatoryWarningHandler(log, null, verboseRemoval,
 176                 enforceMandatoryWarnings, "removal", LintCategory.REMOVAL);
 177         uncheckedHandler = new MandatoryWarningHandler(log, null, verboseUnchecked,
 178                 enforceMandatoryWarnings, "unchecked", LintCategory.UNCHECKED);
 179         sunApiHandler = new MandatoryWarningHandler(log, null, false,
 180                 enforceMandatoryWarnings, "sunapi", null);
 181 
 182         deferredLintHandler = DeferredLintHandler.instance(context);
 183 
 184         allowModules = Feature.MODULES.allowedInSource(source);
 185         allowRecords = Feature.RECORDS.allowedInSource(source);
 186         allowSealed = Feature.SEALED_CLASSES.allowedInSource(source);
 187     }
 188 
 189     /** Character for synthetic names
 190      */
 191     char syntheticNameChar;
 192 
 193     /** A table mapping flat names of all compiled classes for each module in this run
 194      *  to their symbols; maintained from outside.
 195      */
 196     private Map<Pair<ModuleSymbol, Name>,ClassSymbol> compiled = new HashMap<>();
 197 
 198     /** A handler for messages about deprecated usage.
 199      */
 200     private MandatoryWarningHandler deprecationHandler;
 201 
 202     /** A handler for messages about deprecated-for-removal usage.
 203      */
 204     private MandatoryWarningHandler removalHandler;
 205 
 206     /** A handler for messages about unchecked or unsafe usage.
 207      */
 208     private MandatoryWarningHandler uncheckedHandler;
 209 
 210     /** A handler for messages about using proprietary API.
 211      */
 212     private MandatoryWarningHandler sunApiHandler;
 213 
 214     /** A handler for deferred lint warnings.
 215      */
 216     private DeferredLintHandler deferredLintHandler;
 217 
 218     /** Are modules allowed
 219      */
 220     private final boolean allowModules;
 221 
 222     /** Are records allowed
 223      */
 224     private final boolean allowRecords;
 225 
 226     /** Are sealed classes allowed
 227      */
 228     private final boolean allowSealed;
 229 
 230 /* *************************************************************************
 231  * Errors and Warnings
 232  **************************************************************************/
 233 
 234     Lint setLint(Lint newLint) {
 235         Lint prev = lint;
 236         lint = newLint;
 237         return prev;
 238     }
 239 
 240     MethodSymbol setMethod(MethodSymbol newMethod) {
 241         MethodSymbol prev = method;
 242         method = newMethod;
 243         return prev;
 244     }
 245 
 246     /** Warn about deprecated symbol.
 247      *  @param pos        Position to be used for error reporting.
 248      *  @param sym        The deprecated symbol.
 249      */
 250     void warnDeprecated(DiagnosticPosition pos, Symbol sym) {
 251         if (sym.isDeprecatedForRemoval()) {
 252             if (!lint.isSuppressed(LintCategory.REMOVAL)) {
 253                 if (sym.kind == MDL) {
 254                     removalHandler.report(pos, Warnings.HasBeenDeprecatedForRemovalModule(sym));
 255                 } else {
 256                     removalHandler.report(pos, Warnings.HasBeenDeprecatedForRemoval(sym, sym.location()));
 257                 }
 258             }
 259         } else if (!lint.isSuppressed(LintCategory.DEPRECATION)) {
 260             if (sym.kind == MDL) {
 261                 deprecationHandler.report(pos, Warnings.HasBeenDeprecatedModule(sym));
 262             } else {
 263                 deprecationHandler.report(pos, Warnings.HasBeenDeprecated(sym, sym.location()));
 264             }
 265         }
 266     }
 267 
 268     /** Log a preview warning.
 269      *  @param pos        Position to be used for error reporting.
 270      *  @param msg        A Warning describing the problem.
 271      */
 272     public void warnPreviewAPI(DiagnosticPosition pos, Warning warnKey) {
 273         if (!lint.isSuppressed(LintCategory.PREVIEW))
 274             preview.reportPreviewWarning(pos, warnKey);
 275     }
 276 
 277     /** Log a preview warning.
 278      *  @param pos        Position to be used for error reporting.
 279      *  @param msg        A Warning describing the problem.
 280      */
 281     public void warnDeclaredUsingPreview(DiagnosticPosition pos, Symbol sym) {
 282         if (!lint.isSuppressed(LintCategory.PREVIEW))
 283             preview.reportPreviewWarning(pos, Warnings.DeclaredUsingPreview(kindName(sym), sym));
 284     }
 285 
 286     /** Warn about unchecked operation.
 287      *  @param pos        Position to be used for error reporting.
 288      *  @param msg        A string describing the problem.
 289      */
 290     public void warnUnchecked(DiagnosticPosition pos, Warning warnKey) {
 291         if (!lint.isSuppressed(LintCategory.UNCHECKED))
 292             uncheckedHandler.report(pos, warnKey);
 293     }
 294 
 295     /** Warn about unsafe vararg method decl.
 296      *  @param pos        Position to be used for error reporting.
 297      */
 298     void warnUnsafeVararg(DiagnosticPosition pos, Warning warnKey) {
 299         if (lint.isEnabled(LintCategory.VARARGS))
 300             log.warning(LintCategory.VARARGS, pos, warnKey);
 301     }
 302 
 303     public void warnStatic(DiagnosticPosition pos, Warning warnKey) {
 304         if (lint.isEnabled(LintCategory.STATIC))
 305             log.warning(LintCategory.STATIC, pos, warnKey);
 306     }
 307 
 308     /** Warn about division by integer constant zero.
 309      *  @param pos        Position to be used for error reporting.
 310      */
 311     void warnDivZero(DiagnosticPosition pos) {
 312         if (lint.isEnabled(LintCategory.DIVZERO))
 313             log.warning(LintCategory.DIVZERO, pos, Warnings.DivZero);
 314     }
 315 
 316     /**
 317      * Report any deferred diagnostics.
 318      */
 319     public void reportDeferredDiagnostics() {
 320         deprecationHandler.reportDeferredDiagnostic();
 321         removalHandler.reportDeferredDiagnostic();
 322         uncheckedHandler.reportDeferredDiagnostic();
 323         sunApiHandler.reportDeferredDiagnostic();
 324     }
 325 
 326 
 327     /** Report a failure to complete a class.
 328      *  @param pos        Position to be used for error reporting.
 329      *  @param ex         The failure to report.
 330      */
 331     public Type completionError(DiagnosticPosition pos, CompletionFailure ex) {
 332         log.error(JCDiagnostic.DiagnosticFlag.NON_DEFERRABLE, pos, Errors.CantAccess(ex.sym, ex.getDetailValue()));
 333         return syms.errType;
 334     }
 335 
 336     /** Report an error that wrong type tag was found.
 337      *  @param pos        Position to be used for error reporting.
 338      *  @param required   An internationalized string describing the type tag
 339      *                    required.
 340      *  @param found      The type that was found.
 341      */
 342     Type typeTagError(DiagnosticPosition pos, JCDiagnostic required, Object found) {
 343         // this error used to be raised by the parser,
 344         // but has been delayed to this point:
 345         if (found instanceof Type type && type.hasTag(VOID)) {
 346             log.error(pos, Errors.IllegalStartOfType);
 347             return syms.errType;
 348         }
 349         log.error(pos, Errors.TypeFoundReq(found, required));
 350         return types.createErrorType(found instanceof Type type ? type : syms.errType);
 351     }
 352 
 353     /** Report an error that symbol cannot be referenced before super
 354      *  has been called.
 355      *  @param pos        Position to be used for error reporting.
 356      *  @param sym        The referenced symbol.
 357      */
 358     void earlyRefError(DiagnosticPosition pos, Symbol sym) {
 359         log.error(pos, Errors.CantRefBeforeCtorCalled(sym));
 360     }
 361 
 362     /** Report duplicate declaration error.
 363      */
 364     void duplicateError(DiagnosticPosition pos, Symbol sym) {
 365         if (!sym.type.isErroneous()) {
 366             Symbol location = sym.location();
 367             if (location.kind == MTH &&
 368                     ((MethodSymbol)location).isStaticOrInstanceInit()) {
 369                 log.error(pos,
 370                           Errors.AlreadyDefinedInClinit(kindName(sym),
 371                                                         sym,
 372                                                         kindName(sym.location()),
 373                                                         kindName(sym.location().enclClass()),
 374                                                         sym.location().enclClass()));
 375             } else {
 376                 /* dont error if this is a duplicated parameter of a generated canonical constructor
 377                  * as we should have issued an error for the duplicated fields
 378                  */
 379                 if (location.kind != MTH ||
 380                         ((sym.owner.flags_field & GENERATEDCONSTR) == 0) ||
 381                         ((sym.owner.flags_field & RECORD) == 0)) {
 382                     log.error(pos,
 383                             Errors.AlreadyDefined(kindName(sym),
 384                                     sym,
 385                                     kindName(sym.location()),
 386                                     sym.location()));
 387                 }
 388             }
 389         }
 390     }
 391 
 392     /** Report array/varargs duplicate declaration
 393      */
 394     void varargsDuplicateError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
 395         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
 396             log.error(pos, Errors.ArrayAndVarargs(sym1, sym2, sym2.location()));
 397         }
 398     }
 399 
 400 /* ************************************************************************
 401  * duplicate declaration checking
 402  *************************************************************************/
 403 
 404     /** Check that variable does not hide variable with same name in
 405      *  immediately enclosing local scope.
 406      *  @param pos           Position for error reporting.
 407      *  @param v             The symbol.
 408      *  @param s             The scope.
 409      */
 410     void checkTransparentVar(DiagnosticPosition pos, VarSymbol v, Scope s) {
 411         for (Symbol sym : s.getSymbolsByName(v.name)) {
 412             if (sym.owner != v.owner) break;
 413             if (sym.kind == VAR &&
 414                 sym.owner.kind.matches(KindSelector.VAL_MTH) &&
 415                 v.name != names.error) {
 416                 duplicateError(pos, sym);
 417                 return;
 418             }
 419         }
 420     }
 421 
 422     /** Check that a class or interface does not hide a class or
 423      *  interface with same name in immediately enclosing local scope.
 424      *  @param pos           Position for error reporting.
 425      *  @param c             The symbol.
 426      *  @param s             The scope.
 427      */
 428     void checkTransparentClass(DiagnosticPosition pos, ClassSymbol c, Scope s) {
 429         for (Symbol sym : s.getSymbolsByName(c.name)) {
 430             if (sym.owner != c.owner) break;
 431             if (sym.kind == TYP && !sym.type.hasTag(TYPEVAR) &&
 432                 sym.owner.kind.matches(KindSelector.VAL_MTH) &&
 433                 c.name != names.error) {
 434                 duplicateError(pos, sym);
 435                 return;
 436             }
 437         }
 438     }
 439 
 440     /** Check that class does not have the same name as one of
 441      *  its enclosing classes, or as a class defined in its enclosing scope.
 442      *  return true if class is unique in its enclosing scope.
 443      *  @param pos           Position for error reporting.
 444      *  @param name          The class name.
 445      *  @param s             The enclosing scope.
 446      */
 447     boolean checkUniqueClassName(DiagnosticPosition pos, Name name, Scope s) {
 448         for (Symbol sym : s.getSymbolsByName(name, NON_RECURSIVE)) {
 449             if (sym.kind == TYP && sym.name != names.error) {
 450                 duplicateError(pos, sym);
 451                 return false;
 452             }
 453         }
 454         for (Symbol sym = s.owner; sym != null; sym = sym.owner) {
 455             if (sym.kind == TYP && sym.name == name && sym.name != names.error) {
 456                 duplicateError(pos, sym);
 457                 return true;
 458             }
 459         }
 460         return true;
 461     }
 462 
 463 /* *************************************************************************
 464  * Class name generation
 465  **************************************************************************/
 466 
 467 
 468     private Map<Pair<Name, Name>, Integer> localClassNameIndexes = new HashMap<>();
 469 
 470     /** Return name of local class.
 471      *  This is of the form   {@code <enclClass> $ n <classname> }
 472      *  where
 473      *    enclClass is the flat name of the enclosing class,
 474      *    classname is the simple name of the local class
 475      */
 476     public Name localClassName(ClassSymbol c) {
 477         Name enclFlatname = c.owner.enclClass().flatname;
 478         String enclFlatnameStr = enclFlatname.toString();
 479         Pair<Name, Name> key = new Pair<>(enclFlatname, c.name);
 480         Integer index = localClassNameIndexes.get(key);
 481         for (int i = (index == null) ? 1 : index; ; i++) {
 482             Name flatname = names.fromString(enclFlatnameStr
 483                     + syntheticNameChar + i + c.name);
 484             if (getCompiled(c.packge().modle, flatname) == null) {
 485                 localClassNameIndexes.put(key, i + 1);
 486                 return flatname;
 487             }
 488         }
 489     }
 490 
 491     public void clearLocalClassNameIndexes(ClassSymbol c) {
 492         if (c.owner != null && c.owner.kind != NIL) {
 493             localClassNameIndexes.remove(new Pair<>(
 494                     c.owner.enclClass().flatname, c.name));
 495         }
 496     }
 497 
 498     public void newRound() {
 499         compiled.clear();
 500         localClassNameIndexes.clear();
 501     }
 502 
 503     public void clear() {
 504         deprecationHandler.clear();
 505         removalHandler.clear();
 506         uncheckedHandler.clear();
 507         sunApiHandler.clear();
 508     }
 509 
 510     public void putCompiled(ClassSymbol csym) {
 511         compiled.put(Pair.of(csym.packge().modle, csym.flatname), csym);
 512     }
 513 
 514     public ClassSymbol getCompiled(ClassSymbol csym) {
 515         return compiled.get(Pair.of(csym.packge().modle, csym.flatname));
 516     }
 517 
 518     public ClassSymbol getCompiled(ModuleSymbol msym, Name flatname) {
 519         return compiled.get(Pair.of(msym, flatname));
 520     }
 521 
 522     public void removeCompiled(ClassSymbol csym) {
 523         compiled.remove(Pair.of(csym.packge().modle, csym.flatname));
 524     }
 525 
 526 /* *************************************************************************
 527  * Type Checking
 528  **************************************************************************/
 529 
 530     /**
 531      * A check context is an object that can be used to perform compatibility
 532      * checks - depending on the check context, meaning of 'compatibility' might
 533      * vary significantly.
 534      */
 535     public interface CheckContext {
 536         /**
 537          * Is type 'found' compatible with type 'req' in given context
 538          */
 539         boolean compatible(Type found, Type req, Warner warn);
 540         /**
 541          * Report a check error
 542          */
 543         void report(DiagnosticPosition pos, JCDiagnostic details);
 544         /**
 545          * Obtain a warner for this check context
 546          */
 547         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req);
 548 
 549         public InferenceContext inferenceContext();
 550 
 551         public DeferredAttr.DeferredAttrContext deferredAttrContext();
 552     }
 553 
 554     /**
 555      * This class represent a check context that is nested within another check
 556      * context - useful to check sub-expressions. The default behavior simply
 557      * redirects all method calls to the enclosing check context leveraging
 558      * the forwarding pattern.
 559      */
 560     static class NestedCheckContext implements CheckContext {
 561         CheckContext enclosingContext;
 562 
 563         NestedCheckContext(CheckContext enclosingContext) {
 564             this.enclosingContext = enclosingContext;
 565         }
 566 
 567         public boolean compatible(Type found, Type req, Warner warn) {
 568             return enclosingContext.compatible(found, req, warn);
 569         }
 570 
 571         public void report(DiagnosticPosition pos, JCDiagnostic details) {
 572             enclosingContext.report(pos, details);
 573         }
 574 
 575         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
 576             return enclosingContext.checkWarner(pos, found, req);
 577         }
 578 
 579         public InferenceContext inferenceContext() {
 580             return enclosingContext.inferenceContext();
 581         }
 582 
 583         public DeferredAttrContext deferredAttrContext() {
 584             return enclosingContext.deferredAttrContext();
 585         }
 586     }
 587 
 588     /**
 589      * Check context to be used when evaluating assignment/return statements
 590      */
 591     CheckContext basicHandler = new CheckContext() {
 592         public void report(DiagnosticPosition pos, JCDiagnostic details) {
 593             log.error(pos, Errors.ProbFoundReq(details));
 594         }
 595         public boolean compatible(Type found, Type req, Warner warn) {
 596             return types.isAssignable(found, req, warn);
 597         }
 598 
 599         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
 600             return convertWarner(pos, found, req);
 601         }
 602 
 603         public InferenceContext inferenceContext() {
 604             return infer.emptyContext;
 605         }
 606 
 607         public DeferredAttrContext deferredAttrContext() {
 608             return deferredAttr.emptyDeferredAttrContext;
 609         }
 610 
 611         @Override
 612         public String toString() {
 613             return "CheckContext: basicHandler";
 614         }
 615     };
 616 
 617     /** Check that a given type is assignable to a given proto-type.
 618      *  If it is, return the type, otherwise return errType.
 619      *  @param pos        Position to be used for error reporting.
 620      *  @param found      The type that was found.
 621      *  @param req        The type that was required.
 622      */
 623     public Type checkType(DiagnosticPosition pos, Type found, Type req) {
 624         return checkType(pos, found, req, basicHandler);
 625     }
 626 
 627     Type checkType(final DiagnosticPosition pos, final Type found, final Type req, final CheckContext checkContext) {
 628         final InferenceContext inferenceContext = checkContext.inferenceContext();
 629         if (inferenceContext.free(req) || inferenceContext.free(found)) {
 630             inferenceContext.addFreeTypeListener(List.of(req, found),
 631                     solvedContext -> checkType(pos, solvedContext.asInstType(found), solvedContext.asInstType(req), checkContext));
 632         }
 633         if (req.hasTag(ERROR))
 634             return req;
 635         if (req.hasTag(NONE))
 636             return found;
 637         if (checkContext.compatible(found, req, checkContext.checkWarner(pos, found, req))) {
 638             return found;
 639         } else {
 640             if (found.isNumeric() && req.isNumeric()) {
 641                 checkContext.report(pos, diags.fragment(Fragments.PossibleLossOfPrecision(found, req)));
 642                 return types.createErrorType(found);
 643             }
 644             checkContext.report(pos, diags.fragment(Fragments.InconvertibleTypes(found, req)));
 645             return types.createErrorType(found);
 646         }
 647     }
 648 
 649     /** Check that a given type can be cast to a given target type.
 650      *  Return the result of the cast.
 651      *  @param pos        Position to be used for error reporting.
 652      *  @param found      The type that is being cast.
 653      *  @param req        The target type of the cast.
 654      */
 655     Type checkCastable(DiagnosticPosition pos, Type found, Type req) {
 656         return checkCastable(pos, found, req, basicHandler);
 657     }
 658     Type checkCastable(DiagnosticPosition pos, Type found, Type req, CheckContext checkContext) {
 659         if (types.isCastable(found, req, castWarner(pos, found, req))) {
 660             return req;
 661         } else {
 662             checkContext.report(pos, diags.fragment(Fragments.InconvertibleTypes(found, req)));
 663             return types.createErrorType(found);
 664         }
 665     }
 666 
 667     /** Check for redundant casts (i.e. where source type is a subtype of target type)
 668      * The problem should only be reported for non-292 cast
 669      */
 670     public void checkRedundantCast(Env<AttrContext> env, final JCTypeCast tree) {
 671         if (!tree.type.isErroneous()
 672                 && types.isSameType(tree.expr.type, tree.clazz.type)
 673                 && !(ignoreAnnotatedCasts && TreeInfo.containsTypeAnnotation(tree.clazz))
 674                 && !is292targetTypeCast(tree)) {
 675             deferredLintHandler.report(() -> {
 676                 if (lint.isEnabled(LintCategory.CAST))
 677                     log.warning(LintCategory.CAST,
 678                             tree.pos(), Warnings.RedundantCast(tree.clazz.type));
 679             });
 680         }
 681     }
 682     //where
 683         private boolean is292targetTypeCast(JCTypeCast tree) {
 684             boolean is292targetTypeCast = false;
 685             JCExpression expr = TreeInfo.skipParens(tree.expr);
 686             if (expr.hasTag(APPLY)) {
 687                 JCMethodInvocation apply = (JCMethodInvocation)expr;
 688                 Symbol sym = TreeInfo.symbol(apply.meth);
 689                 is292targetTypeCast = sym != null &&
 690                     sym.kind == MTH &&
 691                     (sym.flags() & HYPOTHETICAL) != 0;
 692             }
 693             return is292targetTypeCast;
 694         }
 695 
 696         private static final boolean ignoreAnnotatedCasts = true;
 697 
 698     /** Check that a type is within some bounds.
 699      *
 700      *  Used in TypeApply to verify that, e.g., X in {@code V<X>} is a valid
 701      *  type argument.
 702      *  @param a             The type that should be bounded by bs.
 703      *  @param bound         The bound.
 704      */
 705     private boolean checkExtends(Type a, Type bound) {
 706          if (a.isUnbound()) {
 707              return true;
 708          } else if (!a.hasTag(WILDCARD)) {
 709              a = types.cvarUpperBound(a);
 710              return types.isSubtype(a, bound);
 711          } else if (a.isExtendsBound()) {
 712              return types.isCastable(bound, types.wildUpperBound(a), types.noWarnings);
 713          } else if (a.isSuperBound()) {
 714              return !types.notSoftSubtype(types.wildLowerBound(a), bound);
 715          }
 716          return true;
 717      }
 718 
 719     /** Check that type is different from 'void'.
 720      *  @param pos           Position to be used for error reporting.
 721      *  @param t             The type to be checked.
 722      */
 723     Type checkNonVoid(DiagnosticPosition pos, Type t) {
 724         if (t.hasTag(VOID)) {
 725             log.error(pos, Errors.VoidNotAllowedHere);
 726             return types.createErrorType(t);
 727         } else {
 728             return t;
 729         }
 730     }
 731 
 732     Type checkClassOrArrayType(DiagnosticPosition pos, Type t) {
 733         if (!t.hasTag(CLASS) && !t.hasTag(ARRAY) && !t.hasTag(ERROR)) {
 734             return typeTagError(pos,
 735                                 diags.fragment(Fragments.TypeReqClassArray),
 736                                 asTypeParam(t));
 737         } else {
 738             return t;
 739         }
 740     }
 741 
 742     /** Check that type is a class or interface type.
 743      *  @param pos           Position to be used for error reporting.
 744      *  @param t             The type to be checked.
 745      */
 746     Type checkClassType(DiagnosticPosition pos, Type t) {
 747         if (!t.hasTag(CLASS) && !t.hasTag(ERROR)) {
 748             return typeTagError(pos,
 749                                 diags.fragment(Fragments.TypeReqClass),
 750                                 asTypeParam(t));
 751         } else {
 752             return t;
 753         }
 754     }
 755     //where
 756         private Object asTypeParam(Type t) {
 757             return (t.hasTag(TYPEVAR))
 758                                     ? diags.fragment(Fragments.TypeParameter(t))
 759                                     : t;
 760         }
 761 
 762     /** Check that type is a valid qualifier for a constructor reference expression
 763      */
 764     Type checkConstructorRefType(DiagnosticPosition pos, Type t) {
 765         t = checkClassOrArrayType(pos, t);
 766         if (t.hasTag(CLASS)) {
 767             if ((t.tsym.flags() & (ABSTRACT | INTERFACE)) != 0) {
 768                 log.error(pos, Errors.AbstractCantBeInstantiated(t.tsym));
 769                 t = types.createErrorType(t);
 770             } else if ((t.tsym.flags() & ENUM) != 0) {
 771                 log.error(pos, Errors.EnumCantBeInstantiated);
 772                 t = types.createErrorType(t);
 773             } else {
 774                 t = checkClassType(pos, t, true);
 775             }
 776         } else if (t.hasTag(ARRAY)) {
 777             if (!types.isReifiable(((ArrayType)t).elemtype)) {
 778                 log.error(pos, Errors.GenericArrayCreation);
 779                 t = types.createErrorType(t);
 780             }
 781         }
 782         return t;
 783     }
 784 
 785     /** Check that type is a class or interface type.
 786      *  @param pos           Position to be used for error reporting.
 787      *  @param t             The type to be checked.
 788      *  @param noBounds    True if type bounds are illegal here.
 789      */
 790     Type checkClassType(DiagnosticPosition pos, Type t, boolean noBounds) {
 791         t = checkClassType(pos, t);
 792         if (noBounds && t.isParameterized()) {
 793             List<Type> args = t.getTypeArguments();
 794             while (args.nonEmpty()) {
 795                 if (args.head.hasTag(WILDCARD))
 796                     return typeTagError(pos,
 797                                         diags.fragment(Fragments.TypeReqExact),
 798                                         args.head);
 799                 args = args.tail;
 800             }
 801         }
 802         return t;
 803     }
 804 
 805     /** Check that type is a reference type, i.e. a class, interface or array type
 806      *  or a type variable.
 807      *  @param pos           Position to be used for error reporting.
 808      *  @param t             The type to be checked.
 809      */
 810     Type checkRefType(DiagnosticPosition pos, Type t) {
 811         if (t.isReference())
 812             return t;
 813         else
 814             return typeTagError(pos,
 815                                 diags.fragment(Fragments.TypeReqRef),
 816                                 t);
 817     }
 818 
 819     /** Check that each type is a reference type, i.e. a class, interface or array type
 820      *  or a type variable.
 821      *  @param trees         Original trees, used for error reporting.
 822      *  @param types         The types to be checked.
 823      */
 824     List<Type> checkRefTypes(List<JCExpression> trees, List<Type> types) {
 825         List<JCExpression> tl = trees;
 826         for (List<Type> l = types; l.nonEmpty(); l = l.tail) {
 827             l.head = checkRefType(tl.head.pos(), l.head);
 828             tl = tl.tail;
 829         }
 830         return types;
 831     }
 832 
 833     /** Check that type is a null or reference type.
 834      *  @param pos           Position to be used for error reporting.
 835      *  @param t             The type to be checked.
 836      */
 837     Type checkNullOrRefType(DiagnosticPosition pos, Type t) {
 838         if (t.isReference() || t.hasTag(BOT))
 839             return t;
 840         else
 841             return typeTagError(pos,
 842                                 diags.fragment(Fragments.TypeReqRef),
 843                                 t);
 844     }
 845 
 846     /** Check that flag set does not contain elements of two conflicting sets. s
 847      *  Return true if it doesn't.
 848      *  @param pos           Position to be used for error reporting.
 849      *  @param flags         The set of flags to be checked.
 850      *  @param set1          Conflicting flags set #1.
 851      *  @param set2          Conflicting flags set #2.
 852      */
 853     boolean checkDisjoint(DiagnosticPosition pos, long flags, long set1, long set2) {
 854         if ((flags & set1) != 0 && (flags & set2) != 0) {
 855             log.error(pos,
 856                       Errors.IllegalCombinationOfModifiers(asFlagSet(TreeInfo.firstFlag(flags & set1)),
 857                                                            asFlagSet(TreeInfo.firstFlag(flags & set2))));
 858             return false;
 859         } else
 860             return true;
 861     }
 862 
 863     /** Check that usage of diamond operator is correct (i.e. diamond should not
 864      * be used with non-generic classes or in anonymous class creation expressions)
 865      */
 866     Type checkDiamond(JCNewClass tree, Type t) {
 867         if (!TreeInfo.isDiamond(tree) ||
 868                 t.isErroneous()) {
 869             return checkClassType(tree.clazz.pos(), t, true);
 870         } else {
 871             if (tree.def != null && !Feature.DIAMOND_WITH_ANONYMOUS_CLASS_CREATION.allowedInSource(source)) {
 872                 log.error(DiagnosticFlag.SOURCE_LEVEL, tree.clazz.pos(),
 873                         Errors.CantApplyDiamond1(t, Feature.DIAMOND_WITH_ANONYMOUS_CLASS_CREATION.fragment(source.name)));
 874             }
 875             if (t.tsym.type.getTypeArguments().isEmpty()) {
 876                 log.error(tree.clazz.pos(),
 877                           Errors.CantApplyDiamond1(t,
 878                                                    Fragments.DiamondNonGeneric(t)));
 879                 return types.createErrorType(t);
 880             } else if (tree.typeargs != null &&
 881                     tree.typeargs.nonEmpty()) {
 882                 log.error(tree.clazz.pos(),
 883                           Errors.CantApplyDiamond1(t,
 884                                                    Fragments.DiamondAndExplicitParams(t)));
 885                 return types.createErrorType(t);
 886             } else {
 887                 return t;
 888             }
 889         }
 890     }
 891 
 892     /** Check that the type inferred using the diamond operator does not contain
 893      *  non-denotable types such as captured types or intersection types.
 894      *  @param t the type inferred using the diamond operator
 895      *  @return  the (possibly empty) list of non-denotable types.
 896      */
 897     List<Type> checkDiamondDenotable(ClassType t) {
 898         ListBuffer<Type> buf = new ListBuffer<>();
 899         for (Type arg : t.allparams()) {
 900             if (!checkDenotable(arg)) {
 901                 buf.append(arg);
 902             }
 903         }
 904         return buf.toList();
 905     }
 906 
 907     public boolean checkDenotable(Type t) {
 908         return denotableChecker.visit(t, null);
 909     }
 910         // where
 911 
 912         /** diamondTypeChecker: A type visitor that descends down the given type looking for non-denotable
 913          *  types. The visit methods return false as soon as a non-denotable type is encountered and true
 914          *  otherwise.
 915          */
 916         private static final Types.SimpleVisitor<Boolean, Void> denotableChecker = new Types.SimpleVisitor<Boolean, Void>() {
 917             @Override
 918             public Boolean visitType(Type t, Void s) {
 919                 return true;
 920             }
 921             @Override
 922             public Boolean visitClassType(ClassType t, Void s) {
 923                 if (t.isUnion() || t.isIntersection()) {
 924                     return false;
 925                 }
 926                 for (Type targ : t.allparams()) {
 927                     if (!visit(targ, s)) {
 928                         return false;
 929                     }
 930                 }
 931                 return true;
 932             }
 933 
 934             @Override
 935             public Boolean visitTypeVar(TypeVar t, Void s) {
 936                 /* Any type variable mentioned in the inferred type must have been declared as a type parameter
 937                   (i.e cannot have been produced by inference (18.4))
 938                 */
 939                 return (t.tsym.flags() & SYNTHETIC) == 0;
 940             }
 941 
 942             @Override
 943             public Boolean visitCapturedType(CapturedType t, Void s) {
 944                 /* Any type variable mentioned in the inferred type must have been declared as a type parameter
 945                   (i.e cannot have been produced by capture conversion (5.1.10))
 946                 */
 947                 return false;
 948             }
 949 
 950             @Override
 951             public Boolean visitArrayType(ArrayType t, Void s) {
 952                 return visit(t.elemtype, s);
 953             }
 954 
 955             @Override
 956             public Boolean visitWildcardType(WildcardType t, Void s) {
 957                 return visit(t.type, s);
 958             }
 959         };
 960 
 961     void checkVarargsMethodDecl(Env<AttrContext> env, JCMethodDecl tree) {
 962         MethodSymbol m = tree.sym;
 963         boolean hasTrustMeAnno = m.attribute(syms.trustMeType.tsym) != null;
 964         Type varargElemType = null;
 965         if (m.isVarArgs()) {
 966             varargElemType = types.elemtype(tree.params.last().type);
 967         }
 968         if (hasTrustMeAnno && !isTrustMeAllowedOnMethod(m)) {
 969             if (varargElemType != null) {
 970                 JCDiagnostic msg = Feature.PRIVATE_SAFE_VARARGS.allowedInSource(source) ?
 971                         diags.fragment(Fragments.VarargsTrustmeOnVirtualVarargs(m)) :
 972                         diags.fragment(Fragments.VarargsTrustmeOnVirtualVarargsFinalOnly(m));
 973                 log.error(tree,
 974                           Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym,
 975                                                            msg));
 976             } else {
 977                 log.error(tree,
 978                           Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym,
 979                                                            Fragments.VarargsTrustmeOnNonVarargsMeth(m)));
 980             }
 981         } else if (hasTrustMeAnno && varargElemType != null &&
 982                             types.isReifiable(varargElemType)) {
 983             warnUnsafeVararg(tree, Warnings.VarargsRedundantTrustmeAnno(
 984                                 syms.trustMeType.tsym,
 985                                 diags.fragment(Fragments.VarargsTrustmeOnReifiableVarargs(varargElemType))));
 986         }
 987         else if (!hasTrustMeAnno && varargElemType != null &&
 988                 !types.isReifiable(varargElemType)) {
 989             warnUnchecked(tree.params.head.pos(), Warnings.UncheckedVarargsNonReifiableType(varargElemType));
 990         }
 991     }
 992     //where
 993         private boolean isTrustMeAllowedOnMethod(Symbol s) {
 994             return (s.flags() & VARARGS) != 0 &&
 995                 (s.isConstructor() ||
 996                     (s.flags() & (STATIC | FINAL |
 997                                   (Feature.PRIVATE_SAFE_VARARGS.allowedInSource(source) ? PRIVATE : 0) )) != 0);
 998         }
 999 
1000     Type checkLocalVarType(DiagnosticPosition pos, Type t, Name name) {
1001         //check that resulting type is not the null type
1002         if (t.hasTag(BOT)) {
1003             log.error(pos, Errors.CantInferLocalVarType(name, Fragments.LocalCantInferNull));
1004             return types.createErrorType(t);
1005         } else if (t.hasTag(VOID)) {
1006             log.error(pos, Errors.CantInferLocalVarType(name, Fragments.LocalCantInferVoid));
1007             return types.createErrorType(t);
1008         }
1009 
1010         //upward project the initializer type
1011         return types.upward(t, types.captures(t)).baseType();
1012     }
1013 
1014     Type checkMethod(final Type mtype,
1015             final Symbol sym,
1016             final Env<AttrContext> env,
1017             final List<JCExpression> argtrees,
1018             final List<Type> argtypes,
1019             final boolean useVarargs,
1020             InferenceContext inferenceContext) {
1021         // System.out.println("call   : " + env.tree);
1022         // System.out.println("method : " + owntype);
1023         // System.out.println("actuals: " + argtypes);
1024         if (inferenceContext.free(mtype)) {
1025             inferenceContext.addFreeTypeListener(List.of(mtype),
1026                     solvedContext -> checkMethod(solvedContext.asInstType(mtype), sym, env, argtrees, argtypes, useVarargs, solvedContext));
1027             return mtype;
1028         }
1029         Type owntype = mtype;
1030         List<Type> formals = owntype.getParameterTypes();
1031         List<Type> nonInferred = sym.type.getParameterTypes();
1032         if (nonInferred.length() != formals.length()) nonInferred = formals;
1033         Type last = useVarargs ? formals.last() : null;
1034         if (sym.name == names.init && sym.owner == syms.enumSym) {
1035             formals = formals.tail.tail;
1036             nonInferred = nonInferred.tail.tail;
1037         }
1038         if ((sym.flags() & ANONCONSTR_BASED) != 0) {
1039             formals = formals.tail;
1040             nonInferred = nonInferred.tail;
1041         }
1042         List<JCExpression> args = argtrees;
1043         if (args != null) {
1044             //this is null when type-checking a method reference
1045             while (formals.head != last) {
1046                 JCTree arg = args.head;
1047                 Warner warn = convertWarner(arg.pos(), arg.type, nonInferred.head);
1048                 assertConvertible(arg, arg.type, formals.head, warn);
1049                 args = args.tail;
1050                 formals = formals.tail;
1051                 nonInferred = nonInferred.tail;
1052             }
1053             if (useVarargs) {
1054                 Type varArg = types.elemtype(last);
1055                 while (args.tail != null) {
1056                     JCTree arg = args.head;
1057                     Warner warn = convertWarner(arg.pos(), arg.type, varArg);
1058                     assertConvertible(arg, arg.type, varArg, warn);
1059                     args = args.tail;
1060                 }
1061             } else if ((sym.flags() & (VARARGS | SIGNATURE_POLYMORPHIC)) == VARARGS) {
1062                 // non-varargs call to varargs method
1063                 Type varParam = owntype.getParameterTypes().last();
1064                 Type lastArg = argtypes.last();
1065                 if (types.isSubtypeUnchecked(lastArg, types.elemtype(varParam)) &&
1066                     !types.isSameType(types.erasure(varParam), types.erasure(lastArg)))
1067                     log.warning(argtrees.last().pos(),
1068                                 Warnings.InexactNonVarargsCall(types.elemtype(varParam),varParam));
1069             }
1070         }
1071         if (useVarargs) {
1072             Type argtype = owntype.getParameterTypes().last();
1073             if (!types.isReifiable(argtype) &&
1074                 (sym.baseSymbol().attribute(syms.trustMeType.tsym) == null ||
1075                  !isTrustMeAllowedOnMethod(sym))) {
1076                 warnUnchecked(env.tree.pos(), Warnings.UncheckedGenericArrayCreation(argtype));
1077             }
1078             TreeInfo.setVarargsElement(env.tree, types.elemtype(argtype));
1079          }
1080          return owntype;
1081     }
1082     //where
1083     private void assertConvertible(JCTree tree, Type actual, Type formal, Warner warn) {
1084         if (types.isConvertible(actual, formal, warn))
1085             return;
1086 
1087         if (formal.isCompound()
1088             && types.isSubtype(actual, types.supertype(formal))
1089             && types.isSubtypeUnchecked(actual, types.interfaces(formal), warn))
1090             return;
1091     }
1092 
1093     /**
1094      * Check that type 't' is a valid instantiation of a generic class
1095      * (see JLS 4.5)
1096      *
1097      * @param t class type to be checked
1098      * @return true if 't' is well-formed
1099      */
1100     public boolean checkValidGenericType(Type t) {
1101         return firstIncompatibleTypeArg(t) == null;
1102     }
1103     //WHERE
1104         private Type firstIncompatibleTypeArg(Type type) {
1105             List<Type> formals = type.tsym.type.allparams();
1106             List<Type> actuals = type.allparams();
1107             List<Type> args = type.getTypeArguments();
1108             List<Type> forms = type.tsym.type.getTypeArguments();
1109             ListBuffer<Type> bounds_buf = new ListBuffer<>();
1110 
1111             // For matching pairs of actual argument types `a' and
1112             // formal type parameters with declared bound `b' ...
1113             while (args.nonEmpty() && forms.nonEmpty()) {
1114                 // exact type arguments needs to know their
1115                 // bounds (for upper and lower bound
1116                 // calculations).  So we create new bounds where
1117                 // type-parameters are replaced with actuals argument types.
1118                 bounds_buf.append(types.subst(forms.head.getUpperBound(), formals, actuals));
1119                 args = args.tail;
1120                 forms = forms.tail;
1121             }
1122 
1123             args = type.getTypeArguments();
1124             List<Type> tvars_cap = types.substBounds(formals,
1125                                       formals,
1126                                       types.capture(type).allparams());
1127             while (args.nonEmpty() && tvars_cap.nonEmpty()) {
1128                 // Let the actual arguments know their bound
1129                 args.head.withTypeVar((TypeVar)tvars_cap.head);
1130                 args = args.tail;
1131                 tvars_cap = tvars_cap.tail;
1132             }
1133 
1134             args = type.getTypeArguments();
1135             List<Type> bounds = bounds_buf.toList();
1136 
1137             while (args.nonEmpty() && bounds.nonEmpty()) {
1138                 Type actual = args.head;
1139                 if (!isTypeArgErroneous(actual) &&
1140                         !bounds.head.isErroneous() &&
1141                         !checkExtends(actual, bounds.head)) {
1142                     return args.head;
1143                 }
1144                 args = args.tail;
1145                 bounds = bounds.tail;
1146             }
1147 
1148             args = type.getTypeArguments();
1149             bounds = bounds_buf.toList();
1150 
1151             for (Type arg : types.capture(type).getTypeArguments()) {
1152                 if (arg.hasTag(TYPEVAR) &&
1153                         arg.getUpperBound().isErroneous() &&
1154                         !bounds.head.isErroneous() &&
1155                         !isTypeArgErroneous(args.head)) {
1156                     return args.head;
1157                 }
1158                 bounds = bounds.tail;
1159                 args = args.tail;
1160             }
1161 
1162             return null;
1163         }
1164         //where
1165         boolean isTypeArgErroneous(Type t) {
1166             return isTypeArgErroneous.visit(t);
1167         }
1168 
1169         Types.UnaryVisitor<Boolean> isTypeArgErroneous = new Types.UnaryVisitor<Boolean>() {
1170             public Boolean visitType(Type t, Void s) {
1171                 return t.isErroneous();
1172             }
1173             @Override
1174             public Boolean visitTypeVar(TypeVar t, Void s) {
1175                 return visit(t.getUpperBound());
1176             }
1177             @Override
1178             public Boolean visitCapturedType(CapturedType t, Void s) {
1179                 return visit(t.getUpperBound()) ||
1180                         visit(t.getLowerBound());
1181             }
1182             @Override
1183             public Boolean visitWildcardType(WildcardType t, Void s) {
1184                 return visit(t.type);
1185             }
1186         };
1187 
1188     /** Check that given modifiers are legal for given symbol and
1189      *  return modifiers together with any implicit modifiers for that symbol.
1190      *  Warning: we can't use flags() here since this method
1191      *  is called during class enter, when flags() would cause a premature
1192      *  completion.
1193      *  @param pos           Position to be used for error reporting.
1194      *  @param flags         The set of modifiers given in a definition.
1195      *  @param sym           The defined symbol.
1196      */
1197     long checkFlags(DiagnosticPosition pos, long flags, Symbol sym, JCTree tree) {
1198         long mask;
1199         long implicit = 0;
1200 
1201         switch (sym.kind) {
1202         case VAR:
1203             if (TreeInfo.isReceiverParam(tree))
1204                 mask = ReceiverParamFlags;
1205             else if (sym.owner.kind != TYP)
1206                 mask = LocalVarFlags;
1207             else if ((sym.owner.flags_field & INTERFACE) != 0)
1208                 mask = implicit = InterfaceVarFlags;
1209             else
1210                 mask = VarFlags;
1211             break;
1212         case MTH:
1213             if (sym.name == names.init) {
1214                 if ((sym.owner.flags_field & ENUM) != 0) {
1215                     // enum constructors cannot be declared public or
1216                     // protected and must be implicitly or explicitly
1217                     // private
1218                     implicit = PRIVATE;
1219                     mask = PRIVATE;
1220                 } else
1221                     mask = ConstructorFlags;
1222             }  else if ((sym.owner.flags_field & INTERFACE) != 0) {
1223                 if ((sym.owner.flags_field & ANNOTATION) != 0) {
1224                     mask = AnnotationTypeElementMask;
1225                     implicit = PUBLIC | ABSTRACT;
1226                 } else if ((flags & (DEFAULT | STATIC | PRIVATE)) != 0) {
1227                     mask = InterfaceMethodMask;
1228                     implicit = (flags & PRIVATE) != 0 ? 0 : PUBLIC;
1229                     if ((flags & DEFAULT) != 0) {
1230                         implicit |= ABSTRACT;
1231                     }
1232                 } else {
1233                     mask = implicit = InterfaceMethodFlags;
1234                 }
1235             } else if ((sym.owner.flags_field & RECORD) != 0) {
1236                 mask = RecordMethodFlags;
1237             } else {
1238                 mask = MethodFlags;
1239             }
1240             if ((flags & STRICTFP) != 0) {
1241                 warnOnExplicitStrictfp(pos);
1242             }
1243             // Imply STRICTFP if owner has STRICTFP set.
1244             if (((flags|implicit) & Flags.ABSTRACT) == 0 ||
1245                 ((flags) & Flags.DEFAULT) != 0)
1246                 implicit |= sym.owner.flags_field & STRICTFP;
1247             break;
1248         case TYP:
1249             if (sym.owner.kind.matches(KindSelector.VAL_MTH) ||
1250                     (sym.isDirectlyOrIndirectlyLocal() && (flags & ANNOTATION) != 0)) {
1251                 boolean implicitlyStatic = !sym.isAnonymous() &&
1252                         ((flags & RECORD) != 0 || (flags & ENUM) != 0 || (flags & INTERFACE) != 0);
1253                 boolean staticOrImplicitlyStatic = (flags & STATIC) != 0 || implicitlyStatic;
1254                 // local statics are allowed only if records are allowed too
1255                 mask = staticOrImplicitlyStatic && allowRecords && (flags & ANNOTATION) == 0 ? StaticLocalFlags : LocalClassFlags;
1256                 implicit = implicitlyStatic ? STATIC : implicit;
1257             } else if (sym.owner.kind == TYP) {
1258                 // statics in inner classes are allowed only if records are allowed too
1259                 mask = ((flags & STATIC) != 0) && allowRecords && (flags & ANNOTATION) == 0 ? ExtendedMemberStaticClassFlags : ExtendedMemberClassFlags;
1260                 if (sym.owner.owner.kind == PCK ||
1261                     (sym.owner.flags_field & STATIC) != 0) {
1262                     mask |= STATIC;
1263                 } else if (!allowRecords && ((flags & ENUM) != 0 || (flags & RECORD) != 0)) {
1264                     log.error(pos, Errors.StaticDeclarationNotAllowedInInnerClasses);
1265                 }
1266                 // Nested interfaces and enums are always STATIC (Spec ???)
1267                 if ((flags & (INTERFACE | ENUM | RECORD)) != 0 ) implicit = STATIC;
1268             } else {
1269                 mask = ExtendedClassFlags;
1270             }
1271             // Interfaces are always ABSTRACT
1272             if ((flags & INTERFACE) != 0) implicit |= ABSTRACT;
1273 
1274             if ((flags & ENUM) != 0) {
1275                 // enums can't be declared abstract, final, sealed or non-sealed
1276                 mask &= ~(ABSTRACT | FINAL | SEALED | NON_SEALED);
1277                 implicit |= implicitEnumFinalFlag(tree);
1278             }
1279             if ((flags & RECORD) != 0) {
1280                 // records can't be declared abstract
1281                 mask &= ~ABSTRACT;
1282                 implicit |= FINAL;
1283             }
1284             if ((flags & STRICTFP) != 0) {
1285                 warnOnExplicitStrictfp(pos);
1286             }
1287             // Imply STRICTFP if owner has STRICTFP set.
1288             implicit |= sym.owner.flags_field & STRICTFP;
1289             break;
1290         default:
1291             throw new AssertionError();
1292         }
1293         long illegal = flags & ExtendedStandardFlags & ~mask;
1294         if (illegal != 0) {
1295             if ((illegal & INTERFACE) != 0) {
1296                 log.error(pos, ((flags & ANNOTATION) != 0) ? Errors.AnnotationDeclNotAllowedHere : Errors.IntfNotAllowedHere);
1297                 mask |= INTERFACE;
1298             }
1299             else {
1300                 log.error(pos,
1301                         Errors.ModNotAllowedHere(asFlagSet(illegal)));
1302             }
1303         }
1304         else if ((sym.kind == TYP ||
1305                   // ISSUE: Disallowing abstract&private is no longer appropriate
1306                   // in the presence of inner classes. Should it be deleted here?
1307                   checkDisjoint(pos, flags,
1308                                 ABSTRACT,
1309                                 PRIVATE | STATIC | DEFAULT))
1310                  &&
1311                  checkDisjoint(pos, flags,
1312                                 STATIC | PRIVATE,
1313                                 DEFAULT)
1314                  &&
1315                  checkDisjoint(pos, flags,
1316                                ABSTRACT | INTERFACE,
1317                                FINAL | NATIVE | SYNCHRONIZED)
1318                  &&
1319                  checkDisjoint(pos, flags,
1320                                PUBLIC,
1321                                PRIVATE | PROTECTED)
1322                  &&
1323                  checkDisjoint(pos, flags,
1324                                PRIVATE,
1325                                PUBLIC | PROTECTED)
1326                  &&
1327                  checkDisjoint(pos, flags,
1328                                FINAL,
1329                                VOLATILE)
1330                  &&
1331                  (sym.kind == TYP ||
1332                   checkDisjoint(pos, flags,
1333                                 ABSTRACT | NATIVE,
1334                                 STRICTFP))
1335                  && checkDisjoint(pos, flags,
1336                                 FINAL,
1337                            SEALED | NON_SEALED)
1338                  && checkDisjoint(pos, flags,
1339                                 SEALED,
1340                            FINAL | NON_SEALED)
1341                  && checkDisjoint(pos, flags,
1342                                 SEALED,
1343                                 ANNOTATION)) {
1344             // skip
1345         }
1346         return flags & (mask | ~ExtendedStandardFlags) | implicit;
1347     }
1348 
1349     private void warnOnExplicitStrictfp(DiagnosticPosition pos) {
1350         DiagnosticPosition prevLintPos = deferredLintHandler.setPos(pos);
1351         try {
1352             deferredLintHandler.report(() -> {
1353                                            if (lint.isEnabled(LintCategory.STRICTFP)) {
1354                                                log.warning(LintCategory.STRICTFP,
1355                                                            pos, Warnings.Strictfp); }
1356                                        });
1357         } finally {
1358             deferredLintHandler.setPos(prevLintPos);
1359         }
1360     }
1361 
1362 
1363     /** Determine if this enum should be implicitly final.
1364      *
1365      *  If the enum has no specialized enum constants, it is final.
1366      *
1367      *  If the enum does have specialized enum constants, it is
1368      *  <i>not</i> final.
1369      */
1370     private long implicitEnumFinalFlag(JCTree tree) {
1371         if (!tree.hasTag(CLASSDEF)) return 0;
1372         class SpecialTreeVisitor extends JCTree.Visitor {
1373             boolean specialized;
1374             SpecialTreeVisitor() {
1375                 this.specialized = false;
1376             }
1377 
1378             @Override
1379             public void visitTree(JCTree tree) { /* no-op */ }
1380 
1381             @Override
1382             public void visitVarDef(JCVariableDecl tree) {
1383                 if ((tree.mods.flags & ENUM) != 0) {
1384                     if (tree.init instanceof JCNewClass newClass && newClass.def != null) {
1385                         specialized = true;
1386                     }
1387                 }
1388             }
1389         }
1390 
1391         SpecialTreeVisitor sts = new SpecialTreeVisitor();
1392         JCClassDecl cdef = (JCClassDecl) tree;
1393         for (JCTree defs: cdef.defs) {
1394             defs.accept(sts);
1395             if (sts.specialized) return allowSealed ? SEALED : 0;
1396         }
1397         return FINAL;
1398     }
1399 
1400 /* *************************************************************************
1401  * Type Validation
1402  **************************************************************************/
1403 
1404     /** Validate a type expression. That is,
1405      *  check that all type arguments of a parametric type are within
1406      *  their bounds. This must be done in a second phase after type attribution
1407      *  since a class might have a subclass as type parameter bound. E.g:
1408      *
1409      *  <pre>{@code
1410      *  class B<A extends C> { ... }
1411      *  class C extends B<C> { ... }
1412      *  }</pre>
1413      *
1414      *  and we can't make sure that the bound is already attributed because
1415      *  of possible cycles.
1416      *
1417      * Visitor method: Validate a type expression, if it is not null, catching
1418      *  and reporting any completion failures.
1419      */
1420     void validate(JCTree tree, Env<AttrContext> env) {
1421         validate(tree, env, true);
1422     }
1423     void validate(JCTree tree, Env<AttrContext> env, boolean checkRaw) {
1424         new Validator(env).validateTree(tree, checkRaw, true);
1425     }
1426 
1427     /** Visitor method: Validate a list of type expressions.
1428      */
1429     void validate(List<? extends JCTree> trees, Env<AttrContext> env) {
1430         for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
1431             validate(l.head, env);
1432     }
1433 
1434     /** A visitor class for type validation.
1435      */
1436     class Validator extends JCTree.Visitor {
1437 
1438         boolean checkRaw;
1439         boolean isOuter;
1440         Env<AttrContext> env;
1441 
1442         Validator(Env<AttrContext> env) {
1443             this.env = env;
1444         }
1445 
1446         @Override
1447         public void visitTypeArray(JCArrayTypeTree tree) {
1448             validateTree(tree.elemtype, checkRaw, isOuter);
1449         }
1450 
1451         @Override
1452         public void visitTypeApply(JCTypeApply tree) {
1453             if (tree.type.hasTag(CLASS)) {
1454                 List<JCExpression> args = tree.arguments;
1455                 List<Type> forms = tree.type.tsym.type.getTypeArguments();
1456 
1457                 Type incompatibleArg = firstIncompatibleTypeArg(tree.type);
1458                 if (incompatibleArg != null) {
1459                     for (JCTree arg : tree.arguments) {
1460                         if (arg.type == incompatibleArg) {
1461                             log.error(arg, Errors.NotWithinBounds(incompatibleArg, forms.head));
1462                         }
1463                         forms = forms.tail;
1464                      }
1465                  }
1466 
1467                 forms = tree.type.tsym.type.getTypeArguments();
1468 
1469                 boolean is_java_lang_Class = tree.type.tsym.flatName() == names.java_lang_Class;
1470 
1471                 // For matching pairs of actual argument types `a' and
1472                 // formal type parameters with declared bound `b' ...
1473                 while (args.nonEmpty() && forms.nonEmpty()) {
1474                     validateTree(args.head,
1475                             !(isOuter && is_java_lang_Class),
1476                             false);
1477                     args = args.tail;
1478                     forms = forms.tail;
1479                 }
1480 
1481                 // Check that this type is either fully parameterized, or
1482                 // not parameterized at all.
1483                 if (tree.type.getEnclosingType().isRaw())
1484                     log.error(tree.pos(), Errors.ImproperlyFormedTypeInnerRawParam);
1485                 if (tree.clazz.hasTag(SELECT))
1486                     visitSelectInternal((JCFieldAccess)tree.clazz);
1487             }
1488         }
1489 
1490         @Override
1491         public void visitTypeParameter(JCTypeParameter tree) {
1492             validateTrees(tree.bounds, true, isOuter);
1493             checkClassBounds(tree.pos(), tree.type);
1494         }
1495 
1496         @Override
1497         public void visitWildcard(JCWildcard tree) {
1498             if (tree.inner != null)
1499                 validateTree(tree.inner, true, isOuter);
1500         }
1501 
1502         @Override
1503         public void visitSelect(JCFieldAccess tree) {
1504             if (tree.type.hasTag(CLASS)) {
1505                 visitSelectInternal(tree);
1506 
1507                 // Check that this type is either fully parameterized, or
1508                 // not parameterized at all.
1509                 if (tree.selected.type.isParameterized() && tree.type.tsym.type.getTypeArguments().nonEmpty())
1510                     log.error(tree.pos(), Errors.ImproperlyFormedTypeParamMissing);
1511             }
1512         }
1513 
1514         public void visitSelectInternal(JCFieldAccess tree) {
1515             if (tree.type.tsym.isStatic() &&
1516                 tree.selected.type.isParameterized()) {
1517                 // The enclosing type is not a class, so we are
1518                 // looking at a static member type.  However, the
1519                 // qualifying expression is parameterized.
1520                 log.error(tree.pos(), Errors.CantSelectStaticClassFromParamType);
1521             } else {
1522                 // otherwise validate the rest of the expression
1523                 tree.selected.accept(this);
1524             }
1525         }
1526 
1527         @Override
1528         public void visitAnnotatedType(JCAnnotatedType tree) {
1529             tree.underlyingType.accept(this);
1530         }
1531 
1532         @Override
1533         public void visitTypeIdent(JCPrimitiveTypeTree that) {
1534             if (that.type.hasTag(TypeTag.VOID)) {
1535                 log.error(that.pos(), Errors.VoidNotAllowedHere);
1536             }
1537             super.visitTypeIdent(that);
1538         }
1539 
1540         /** Default visitor method: do nothing.
1541          */
1542         @Override
1543         public void visitTree(JCTree tree) {
1544         }
1545 
1546         public void validateTree(JCTree tree, boolean checkRaw, boolean isOuter) {
1547             if (tree != null) {
1548                 boolean prevCheckRaw = this.checkRaw;
1549                 this.checkRaw = checkRaw;
1550                 this.isOuter = isOuter;
1551 
1552                 try {
1553                     tree.accept(this);
1554                     if (checkRaw)
1555                         checkRaw(tree, env);
1556                 } catch (CompletionFailure ex) {
1557                     completionError(tree.pos(), ex);
1558                 } finally {
1559                     this.checkRaw = prevCheckRaw;
1560                 }
1561             }
1562         }
1563 
1564         public void validateTrees(List<? extends JCTree> trees, boolean checkRaw, boolean isOuter) {
1565             for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
1566                 validateTree(l.head, checkRaw, isOuter);
1567         }
1568     }
1569 
1570     void checkRaw(JCTree tree, Env<AttrContext> env) {
1571         if (lint.isEnabled(LintCategory.RAW) &&
1572             tree.type.hasTag(CLASS) &&
1573             !TreeInfo.isDiamond(tree) &&
1574             !withinAnonConstr(env) &&
1575             tree.type.isRaw()) {
1576             log.warning(LintCategory.RAW,
1577                     tree.pos(), Warnings.RawClassUse(tree.type, tree.type.tsym.type));
1578         }
1579     }
1580     //where
1581         private boolean withinAnonConstr(Env<AttrContext> env) {
1582             return env.enclClass.name.isEmpty() &&
1583                     env.enclMethod != null && env.enclMethod.name == names.init;
1584         }
1585 
1586 /* *************************************************************************
1587  * Exception checking
1588  **************************************************************************/
1589 
1590     /* The following methods treat classes as sets that contain
1591      * the class itself and all their subclasses
1592      */
1593 
1594     /** Is given type a subtype of some of the types in given list?
1595      */
1596     boolean subset(Type t, List<Type> ts) {
1597         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1598             if (types.isSubtype(t, l.head)) return true;
1599         return false;
1600     }
1601 
1602     /** Is given type a subtype or supertype of
1603      *  some of the types in given list?
1604      */
1605     boolean intersects(Type t, List<Type> ts) {
1606         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1607             if (types.isSubtype(t, l.head) || types.isSubtype(l.head, t)) return true;
1608         return false;
1609     }
1610 
1611     /** Add type set to given type list, unless it is a subclass of some class
1612      *  in the list.
1613      */
1614     List<Type> incl(Type t, List<Type> ts) {
1615         return subset(t, ts) ? ts : excl(t, ts).prepend(t);
1616     }
1617 
1618     /** Remove type set from type set list.
1619      */
1620     List<Type> excl(Type t, List<Type> ts) {
1621         if (ts.isEmpty()) {
1622             return ts;
1623         } else {
1624             List<Type> ts1 = excl(t, ts.tail);
1625             if (types.isSubtype(ts.head, t)) return ts1;
1626             else if (ts1 == ts.tail) return ts;
1627             else return ts1.prepend(ts.head);
1628         }
1629     }
1630 
1631     /** Form the union of two type set lists.
1632      */
1633     List<Type> union(List<Type> ts1, List<Type> ts2) {
1634         List<Type> ts = ts1;
1635         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1636             ts = incl(l.head, ts);
1637         return ts;
1638     }
1639 
1640     /** Form the difference of two type lists.
1641      */
1642     List<Type> diff(List<Type> ts1, List<Type> ts2) {
1643         List<Type> ts = ts1;
1644         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1645             ts = excl(l.head, ts);
1646         return ts;
1647     }
1648 
1649     /** Form the intersection of two type lists.
1650      */
1651     public List<Type> intersect(List<Type> ts1, List<Type> ts2) {
1652         List<Type> ts = List.nil();
1653         for (List<Type> l = ts1; l.nonEmpty(); l = l.tail)
1654             if (subset(l.head, ts2)) ts = incl(l.head, ts);
1655         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1656             if (subset(l.head, ts1)) ts = incl(l.head, ts);
1657         return ts;
1658     }
1659 
1660     /** Is exc an exception symbol that need not be declared?
1661      */
1662     boolean isUnchecked(ClassSymbol exc) {
1663         return
1664             exc.kind == ERR ||
1665             exc.isSubClass(syms.errorType.tsym, types) ||
1666             exc.isSubClass(syms.runtimeExceptionType.tsym, types);
1667     }
1668 
1669     /** Is exc an exception type that need not be declared?
1670      */
1671     boolean isUnchecked(Type exc) {
1672         return
1673             (exc.hasTag(TYPEVAR)) ? isUnchecked(types.supertype(exc)) :
1674             (exc.hasTag(CLASS)) ? isUnchecked((ClassSymbol)exc.tsym) :
1675             exc.hasTag(BOT);
1676     }
1677 
1678     boolean isChecked(Type exc) {
1679         return !isUnchecked(exc);
1680     }
1681 
1682     /** Same, but handling completion failures.
1683      */
1684     boolean isUnchecked(DiagnosticPosition pos, Type exc) {
1685         try {
1686             return isUnchecked(exc);
1687         } catch (CompletionFailure ex) {
1688             completionError(pos, ex);
1689             return true;
1690         }
1691     }
1692 
1693     /** Is exc handled by given exception list?
1694      */
1695     boolean isHandled(Type exc, List<Type> handled) {
1696         return isUnchecked(exc) || subset(exc, handled);
1697     }
1698 
1699     /** Return all exceptions in thrown list that are not in handled list.
1700      *  @param thrown     The list of thrown exceptions.
1701      *  @param handled    The list of handled exceptions.
1702      */
1703     List<Type> unhandled(List<Type> thrown, List<Type> handled) {
1704         List<Type> unhandled = List.nil();
1705         for (List<Type> l = thrown; l.nonEmpty(); l = l.tail)
1706             if (!isHandled(l.head, handled)) unhandled = unhandled.prepend(l.head);
1707         return unhandled;
1708     }
1709 
1710 /* *************************************************************************
1711  * Overriding/Implementation checking
1712  **************************************************************************/
1713 
1714     /** The level of access protection given by a flag set,
1715      *  where PRIVATE is highest and PUBLIC is lowest.
1716      */
1717     static int protection(long flags) {
1718         switch ((short)(flags & AccessFlags)) {
1719         case PRIVATE: return 3;
1720         case PROTECTED: return 1;
1721         default:
1722         case PUBLIC: return 0;
1723         case 0: return 2;
1724         }
1725     }
1726 
1727     /** A customized "cannot override" error message.
1728      *  @param m      The overriding method.
1729      *  @param other  The overridden method.
1730      *  @return       An internationalized string.
1731      */
1732     Fragment cannotOverride(MethodSymbol m, MethodSymbol other) {
1733         Symbol mloc = m.location();
1734         Symbol oloc = other.location();
1735 
1736         if ((other.owner.flags() & INTERFACE) == 0)
1737             return Fragments.CantOverride(m, mloc, other, oloc);
1738         else if ((m.owner.flags() & INTERFACE) == 0)
1739             return Fragments.CantImplement(m, mloc, other, oloc);
1740         else
1741             return Fragments.ClashesWith(m, mloc, other, oloc);
1742     }
1743 
1744     /** A customized "override" warning message.
1745      *  @param m      The overriding method.
1746      *  @param other  The overridden method.
1747      *  @return       An internationalized string.
1748      */
1749     Fragment uncheckedOverrides(MethodSymbol m, MethodSymbol other) {
1750         Symbol mloc = m.location();
1751         Symbol oloc = other.location();
1752 
1753         if ((other.owner.flags() & INTERFACE) == 0)
1754             return Fragments.UncheckedOverride(m, mloc, other, oloc);
1755         else if ((m.owner.flags() & INTERFACE) == 0)
1756             return Fragments.UncheckedImplement(m, mloc, other, oloc);
1757         else
1758             return Fragments.UncheckedClashWith(m, mloc, other, oloc);
1759     }
1760 
1761     /** A customized "override" warning message.
1762      *  @param m      The overriding method.
1763      *  @param other  The overridden method.
1764      *  @return       An internationalized string.
1765      */
1766     Fragment varargsOverrides(MethodSymbol m, MethodSymbol other) {
1767         Symbol mloc = m.location();
1768         Symbol oloc = other.location();
1769 
1770         if ((other.owner.flags() & INTERFACE) == 0)
1771             return Fragments.VarargsOverride(m, mloc, other, oloc);
1772         else  if ((m.owner.flags() & INTERFACE) == 0)
1773             return Fragments.VarargsImplement(m, mloc, other, oloc);
1774         else
1775             return Fragments.VarargsClashWith(m, mloc, other, oloc);
1776     }
1777 
1778     /** Check that this method conforms with overridden method 'other'.
1779      *  where `origin' is the class where checking started.
1780      *  Complications:
1781      *  (1) Do not check overriding of synthetic methods
1782      *      (reason: they might be final).
1783      *      todo: check whether this is still necessary.
1784      *  (2) Admit the case where an interface proxy throws fewer exceptions
1785      *      than the method it implements. Augment the proxy methods with the
1786      *      undeclared exceptions in this case.
1787      *  (3) When generics are enabled, admit the case where an interface proxy
1788      *      has a result type
1789      *      extended by the result type of the method it implements.
1790      *      Change the proxies result type to the smaller type in this case.
1791      *
1792      *  @param tree         The tree from which positions
1793      *                      are extracted for errors.
1794      *  @param m            The overriding method.
1795      *  @param other        The overridden method.
1796      *  @param origin       The class of which the overriding method
1797      *                      is a member.
1798      */
1799     void checkOverride(JCTree tree,
1800                        MethodSymbol m,
1801                        MethodSymbol other,
1802                        ClassSymbol origin) {
1803         // Don't check overriding of synthetic methods or by bridge methods.
1804         if ((m.flags() & (SYNTHETIC|BRIDGE)) != 0 || (other.flags() & SYNTHETIC) != 0) {
1805             return;
1806         }
1807 
1808         // Error if static method overrides instance method (JLS 8.4.8.2).
1809         if ((m.flags() & STATIC) != 0 &&
1810                    (other.flags() & STATIC) == 0) {
1811             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1812                       Errors.OverrideStatic(cannotOverride(m, other)));
1813             m.flags_field |= BAD_OVERRIDE;
1814             return;
1815         }
1816 
1817         // Error if instance method overrides static or final
1818         // method (JLS 8.4.8.1).
1819         if ((other.flags() & FINAL) != 0 ||
1820                  (m.flags() & STATIC) == 0 &&
1821                  (other.flags() & STATIC) != 0) {
1822             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1823                       Errors.OverrideMeth(cannotOverride(m, other),
1824                                           asFlagSet(other.flags() & (FINAL | STATIC))));
1825             m.flags_field |= BAD_OVERRIDE;
1826             return;
1827         }
1828 
1829         if ((m.owner.flags() & ANNOTATION) != 0) {
1830             // handled in validateAnnotationMethod
1831             return;
1832         }
1833 
1834         // Error if overriding method has weaker access (JLS 8.4.8.3).
1835         if (protection(m.flags()) > protection(other.flags())) {
1836             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1837                       (other.flags() & AccessFlags) == 0 ?
1838                               Errors.OverrideWeakerAccess(cannotOverride(m, other),
1839                                                           "package") :
1840                               Errors.OverrideWeakerAccess(cannotOverride(m, other),
1841                                                           asFlagSet(other.flags() & AccessFlags)));
1842             m.flags_field |= BAD_OVERRIDE;
1843             return;
1844         }
1845 
1846         if (shouldCheckPreview(m, other, origin)) {
1847             checkPreview(tree.pos(), m, other);
1848         }
1849 
1850         Type mt = types.memberType(origin.type, m);
1851         Type ot = types.memberType(origin.type, other);
1852         // Error if overriding result type is different
1853         // (or, in the case of generics mode, not a subtype) of
1854         // overridden result type. We have to rename any type parameters
1855         // before comparing types.
1856         List<Type> mtvars = mt.getTypeArguments();
1857         List<Type> otvars = ot.getTypeArguments();
1858         Type mtres = mt.getReturnType();
1859         Type otres = types.subst(ot.getReturnType(), otvars, mtvars);
1860 
1861         overrideWarner.clear();
1862         boolean resultTypesOK =
1863             types.returnTypeSubstitutable(mt, ot, otres, overrideWarner);
1864         if (!resultTypesOK) {
1865             if ((m.flags() & STATIC) != 0 && (other.flags() & STATIC) != 0) {
1866                 log.error(TreeInfo.diagnosticPositionFor(m, tree),
1867                           Errors.OverrideIncompatibleRet(Fragments.CantHide(m, m.location(), other,
1868                                         other.location()), mtres, otres));
1869                 m.flags_field |= BAD_OVERRIDE;
1870             } else {
1871                 log.error(TreeInfo.diagnosticPositionFor(m, tree),
1872                           Errors.OverrideIncompatibleRet(cannotOverride(m, other), mtres, otres));
1873                 m.flags_field |= BAD_OVERRIDE;
1874             }
1875             return;
1876         } else if (overrideWarner.hasNonSilentLint(LintCategory.UNCHECKED)) {
1877             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
1878                     Warnings.OverrideUncheckedRet(uncheckedOverrides(m, other), mtres, otres));
1879         }
1880 
1881         // Error if overriding method throws an exception not reported
1882         // by overridden method.
1883         List<Type> otthrown = types.subst(ot.getThrownTypes(), otvars, mtvars);
1884         List<Type> unhandledErased = unhandled(mt.getThrownTypes(), types.erasure(otthrown));
1885         List<Type> unhandledUnerased = unhandled(mt.getThrownTypes(), otthrown);
1886         if (unhandledErased.nonEmpty()) {
1887             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1888                       Errors.OverrideMethDoesntThrow(cannotOverride(m, other), unhandledUnerased.head));
1889             m.flags_field |= BAD_OVERRIDE;
1890             return;
1891         }
1892         else if (unhandledUnerased.nonEmpty()) {
1893             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
1894                           Warnings.OverrideUncheckedThrown(cannotOverride(m, other), unhandledUnerased.head));
1895             return;
1896         }
1897 
1898         // Optional warning if varargs don't agree
1899         if ((((m.flags() ^ other.flags()) & Flags.VARARGS) != 0)
1900             && lint.isEnabled(LintCategory.OVERRIDES)) {
1901             log.warning(TreeInfo.diagnosticPositionFor(m, tree),
1902                         ((m.flags() & Flags.VARARGS) != 0)
1903                         ? Warnings.OverrideVarargsMissing(varargsOverrides(m, other))
1904                         : Warnings.OverrideVarargsExtra(varargsOverrides(m, other)));
1905         }
1906 
1907         // Warn if instance method overrides bridge method (compiler spec ??)
1908         if ((other.flags() & BRIDGE) != 0) {
1909             log.warning(TreeInfo.diagnosticPositionFor(m, tree),
1910                         Warnings.OverrideBridge(uncheckedOverrides(m, other)));
1911         }
1912 
1913         // Warn if a deprecated method overridden by a non-deprecated one.
1914         if (!isDeprecatedOverrideIgnorable(other, origin)) {
1915             Lint prevLint = setLint(lint.augment(m));
1916             try {
1917                 checkDeprecated(() -> TreeInfo.diagnosticPositionFor(m, tree), m, other);
1918             } finally {
1919                 setLint(prevLint);
1920             }
1921         }
1922     }
1923     // where
1924         private boolean shouldCheckPreview(MethodSymbol m, MethodSymbol other, ClassSymbol origin) {
1925             if (m.owner != origin ||
1926                 //performance - only do the expensive checks when the overridden method is a Preview API:
1927                 (other.flags() & PREVIEW_API) == 0) {
1928                 return false;
1929             }
1930 
1931             for (Symbol s : types.membersClosure(origin.type, false).getSymbolsByName(m.name)) {
1932                 if (m != s && m.overrides(s, origin, types, false)) {
1933                     //only produce preview warnings or errors if "m" immediatelly overrides "other"
1934                     //without intermediate overriding methods:
1935                     return s == other;
1936                 }
1937             }
1938 
1939             return false;
1940         }
1941         private boolean isDeprecatedOverrideIgnorable(MethodSymbol m, ClassSymbol origin) {
1942             // If the method, m, is defined in an interface, then ignore the issue if the method
1943             // is only inherited via a supertype and also implemented in the supertype,
1944             // because in that case, we will rediscover the issue when examining the method
1945             // in the supertype.
1946             // If the method, m, is not defined in an interface, then the only time we need to
1947             // address the issue is when the method is the supertype implementation: any other
1948             // case, we will have dealt with when examining the supertype classes
1949             ClassSymbol mc = m.enclClass();
1950             Type st = types.supertype(origin.type);
1951             if (!st.hasTag(CLASS))
1952                 return true;
1953             MethodSymbol stimpl = m.implementation((ClassSymbol)st.tsym, types, false);
1954 
1955             if (mc != null && ((mc.flags() & INTERFACE) != 0)) {
1956                 List<Type> intfs = types.interfaces(origin.type);
1957                 return (intfs.contains(mc.type) ? false : (stimpl != null));
1958             }
1959             else
1960                 return (stimpl != m);
1961         }
1962 
1963 
1964     // used to check if there were any unchecked conversions
1965     Warner overrideWarner = new Warner();
1966 
1967     /** Check that a class does not inherit two concrete methods
1968      *  with the same signature.
1969      *  @param pos          Position to be used for error reporting.
1970      *  @param site         The class type to be checked.
1971      */
1972     public void checkCompatibleConcretes(DiagnosticPosition pos, Type site) {
1973         Type sup = types.supertype(site);
1974         if (!sup.hasTag(CLASS)) return;
1975 
1976         for (Type t1 = sup;
1977              t1.hasTag(CLASS) && t1.tsym.type.isParameterized();
1978              t1 = types.supertype(t1)) {
1979             for (Symbol s1 : t1.tsym.members().getSymbols(NON_RECURSIVE)) {
1980                 if (s1.kind != MTH ||
1981                     (s1.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
1982                     !s1.isInheritedIn(site.tsym, types) ||
1983                     ((MethodSymbol)s1).implementation(site.tsym,
1984                                                       types,
1985                                                       true) != s1)
1986                     continue;
1987                 Type st1 = types.memberType(t1, s1);
1988                 int s1ArgsLength = st1.getParameterTypes().length();
1989                 if (st1 == s1.type) continue;
1990 
1991                 for (Type t2 = sup;
1992                      t2.hasTag(CLASS);
1993                      t2 = types.supertype(t2)) {
1994                     for (Symbol s2 : t2.tsym.members().getSymbolsByName(s1.name)) {
1995                         if (s2 == s1 ||
1996                             s2.kind != MTH ||
1997                             (s2.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
1998                             s2.type.getParameterTypes().length() != s1ArgsLength ||
1999                             !s2.isInheritedIn(site.tsym, types) ||
2000                             ((MethodSymbol)s2).implementation(site.tsym,
2001                                                               types,
2002                                                               true) != s2)
2003                             continue;
2004                         Type st2 = types.memberType(t2, s2);
2005                         if (types.overrideEquivalent(st1, st2))
2006                             log.error(pos,
2007                                       Errors.ConcreteInheritanceConflict(s1, t1, s2, t2, sup));
2008                     }
2009                 }
2010             }
2011         }
2012     }
2013 
2014     /** Check that classes (or interfaces) do not each define an abstract
2015      *  method with same name and arguments but incompatible return types.
2016      *  @param pos          Position to be used for error reporting.
2017      *  @param t1           The first argument type.
2018      *  @param t2           The second argument type.
2019      */
2020     public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
2021                                             Type t1,
2022                                             Type t2,
2023                                             Type site) {
2024         if ((site.tsym.flags() & COMPOUND) != 0) {
2025             // special case for intersections: need to eliminate wildcards in supertypes
2026             t1 = types.capture(t1);
2027             t2 = types.capture(t2);
2028         }
2029         return firstIncompatibility(pos, t1, t2, site) == null;
2030     }
2031 
2032     /** Return the first method which is defined with same args
2033      *  but different return types in two given interfaces, or null if none
2034      *  exists.
2035      *  @param t1     The first type.
2036      *  @param t2     The second type.
2037      *  @param site   The most derived type.
2038      *  @return symbol from t2 that conflicts with one in t1.
2039      */
2040     private Symbol firstIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
2041         Map<TypeSymbol,Type> interfaces1 = new HashMap<>();
2042         closure(t1, interfaces1);
2043         Map<TypeSymbol,Type> interfaces2;
2044         if (t1 == t2)
2045             interfaces2 = interfaces1;
2046         else
2047             closure(t2, interfaces1, interfaces2 = new HashMap<>());
2048 
2049         for (Type t3 : interfaces1.values()) {
2050             for (Type t4 : interfaces2.values()) {
2051                 Symbol s = firstDirectIncompatibility(pos, t3, t4, site);
2052                 if (s != null) return s;
2053             }
2054         }
2055         return null;
2056     }
2057 
2058     /** Compute all the supertypes of t, indexed by type symbol. */
2059     private void closure(Type t, Map<TypeSymbol,Type> typeMap) {
2060         if (!t.hasTag(CLASS)) return;
2061         if (typeMap.put(t.tsym, t) == null) {
2062             closure(types.supertype(t), typeMap);
2063             for (Type i : types.interfaces(t))
2064                 closure(i, typeMap);
2065         }
2066     }
2067 
2068     /** Compute all the supertypes of t, indexed by type symbol (except those in typesSkip). */
2069     private void closure(Type t, Map<TypeSymbol,Type> typesSkip, Map<TypeSymbol,Type> typeMap) {
2070         if (!t.hasTag(CLASS)) return;
2071         if (typesSkip.get(t.tsym) != null) return;
2072         if (typeMap.put(t.tsym, t) == null) {
2073             closure(types.supertype(t), typesSkip, typeMap);
2074             for (Type i : types.interfaces(t))
2075                 closure(i, typesSkip, typeMap);
2076         }
2077     }
2078 
2079     /** Return the first method in t2 that conflicts with a method from t1. */
2080     private Symbol firstDirectIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
2081         for (Symbol s1 : t1.tsym.members().getSymbols(NON_RECURSIVE)) {
2082             Type st1 = null;
2083             if (s1.kind != MTH || !s1.isInheritedIn(site.tsym, types) ||
2084                     (s1.flags() & SYNTHETIC) != 0) continue;
2085             Symbol impl = ((MethodSymbol)s1).implementation(site.tsym, types, false);
2086             if (impl != null && (impl.flags() & ABSTRACT) == 0) continue;
2087             for (Symbol s2 : t2.tsym.members().getSymbolsByName(s1.name)) {
2088                 if (s1 == s2) continue;
2089                 if (s2.kind != MTH || !s2.isInheritedIn(site.tsym, types) ||
2090                         (s2.flags() & SYNTHETIC) != 0) continue;
2091                 if (st1 == null) st1 = types.memberType(t1, s1);
2092                 Type st2 = types.memberType(t2, s2);
2093                 if (types.overrideEquivalent(st1, st2)) {
2094                     List<Type> tvars1 = st1.getTypeArguments();
2095                     List<Type> tvars2 = st2.getTypeArguments();
2096                     Type rt1 = st1.getReturnType();
2097                     Type rt2 = types.subst(st2.getReturnType(), tvars2, tvars1);
2098                     boolean compat =
2099                         types.isSameType(rt1, rt2) ||
2100                         !rt1.isPrimitiveOrVoid() &&
2101                         !rt2.isPrimitiveOrVoid() &&
2102                         (types.covariantReturnType(rt1, rt2, types.noWarnings) ||
2103                          types.covariantReturnType(rt2, rt1, types.noWarnings)) ||
2104                          checkCommonOverriderIn(s1,s2,site);
2105                     if (!compat) {
2106                         if (types.isSameType(t1, t2)) {
2107                             log.error(pos, Errors.IncompatibleDiffRetSameType(t1,
2108                                     s2.name, types.memberType(t2, s2).getParameterTypes()));
2109                         } else {
2110                             log.error(pos, Errors.TypesIncompatible(t1, t2,
2111                                     Fragments.IncompatibleDiffRet(s2.name, types.memberType(t2, s2).getParameterTypes())));
2112                         }
2113                         return s2;
2114                     }
2115                 } else if (checkNameClash((ClassSymbol)site.tsym, s1, s2) &&
2116                         !checkCommonOverriderIn(s1, s2, site)) {
2117                     log.error(pos, Errors.NameClashSameErasureNoOverride(
2118                             s1.name, types.memberType(site, s1).asMethodType().getParameterTypes(), s1.location(),
2119                             s2.name, types.memberType(site, s2).asMethodType().getParameterTypes(), s2.location()));
2120                     return s2;
2121                 }
2122             }
2123         }
2124         return null;
2125     }
2126     //WHERE
2127     boolean checkCommonOverriderIn(Symbol s1, Symbol s2, Type site) {
2128         Map<TypeSymbol,Type> supertypes = new HashMap<>();
2129         Type st1 = types.memberType(site, s1);
2130         Type st2 = types.memberType(site, s2);
2131         closure(site, supertypes);
2132         for (Type t : supertypes.values()) {
2133             for (Symbol s3 : t.tsym.members().getSymbolsByName(s1.name)) {
2134                 if (s3 == s1 || s3 == s2 || s3.kind != MTH || (s3.flags() & (BRIDGE|SYNTHETIC)) != 0) continue;
2135                 Type st3 = types.memberType(site,s3);
2136                 if (types.overrideEquivalent(st3, st1) &&
2137                         types.overrideEquivalent(st3, st2) &&
2138                         types.returnTypeSubstitutable(st3, st1) &&
2139                         types.returnTypeSubstitutable(st3, st2)) {
2140                     return true;
2141                 }
2142             }
2143         }
2144         return false;
2145     }
2146 
2147     /** Check that a given method conforms with any method it overrides.
2148      *  @param tree         The tree from which positions are extracted
2149      *                      for errors.
2150      *  @param m            The overriding method.
2151      */
2152     void checkOverride(Env<AttrContext> env, JCMethodDecl tree, MethodSymbol m) {
2153         ClassSymbol origin = (ClassSymbol)m.owner;
2154         if ((origin.flags() & ENUM) != 0 && names.finalize.equals(m.name)) {
2155             if (m.overrides(syms.enumFinalFinalize, origin, types, false)) {
2156                 log.error(tree.pos(), Errors.EnumNoFinalize);
2157                 return;
2158             }
2159         }
2160         if (allowRecords && origin.isRecord()) {
2161             // let's find out if this is a user defined accessor in which case the @Override annotation is acceptable
2162             Optional<? extends RecordComponent> recordComponent = origin.getRecordComponents().stream()
2163                     .filter(rc -> rc.accessor == tree.sym && (rc.accessor.flags_field & GENERATED_MEMBER) == 0).findFirst();
2164             if (recordComponent.isPresent()) {
2165                 return;
2166             }
2167         }
2168 
2169         for (Type t = origin.type; t.hasTag(CLASS);
2170              t = types.supertype(t)) {
2171             if (t != origin.type) {
2172                 checkOverride(tree, t, origin, m);
2173             }
2174             for (Type t2 : types.interfaces(t)) {
2175                 checkOverride(tree, t2, origin, m);
2176             }
2177         }
2178 
2179         final boolean explicitOverride = m.attribute(syms.overrideType.tsym) != null;
2180         // Check if this method must override a super method due to being annotated with @Override
2181         // or by virtue of being a member of a diamond inferred anonymous class. Latter case is to
2182         // be treated "as if as they were annotated" with @Override.
2183         boolean mustOverride = explicitOverride ||
2184                 (env.info.isAnonymousDiamond && !m.isConstructor() && !m.isPrivate());
2185         if (mustOverride && !isOverrider(m)) {
2186             DiagnosticPosition pos = tree.pos();
2187             for (JCAnnotation a : tree.getModifiers().annotations) {
2188                 if (a.annotationType.type.tsym == syms.overrideType.tsym) {
2189                     pos = a.pos();
2190                     break;
2191                 }
2192             }
2193             log.error(pos,
2194                       explicitOverride ? (m.isStatic() ? Errors.StaticMethodsCannotBeAnnotatedWithOverride : Errors.MethodDoesNotOverrideSuperclass) :
2195                                 Errors.AnonymousDiamondMethodDoesNotOverrideSuperclass(Fragments.DiamondAnonymousMethodsImplicitlyOverride));
2196         }
2197     }
2198 
2199     void checkOverride(JCTree tree, Type site, ClassSymbol origin, MethodSymbol m) {
2200         TypeSymbol c = site.tsym;
2201         for (Symbol sym : c.members().getSymbolsByName(m.name)) {
2202             if (m.overrides(sym, origin, types, false)) {
2203                 if ((sym.flags() & ABSTRACT) == 0) {
2204                     checkOverride(tree, m, (MethodSymbol)sym, origin);
2205                 }
2206             }
2207         }
2208     }
2209 
2210     private Predicate<Symbol> equalsHasCodeFilter = s -> MethodSymbol.implementation_filter.test(s) &&
2211             (s.flags() & BAD_OVERRIDE) == 0;
2212 
2213     public void checkClassOverrideEqualsAndHashIfNeeded(DiagnosticPosition pos,
2214             ClassSymbol someClass) {
2215         /* At present, annotations cannot possibly have a method that is override
2216          * equivalent with Object.equals(Object) but in any case the condition is
2217          * fine for completeness.
2218          */
2219         if (someClass == (ClassSymbol)syms.objectType.tsym ||
2220             someClass.isInterface() || someClass.isEnum() ||
2221             (someClass.flags() & ANNOTATION) != 0 ||
2222             (someClass.flags() & ABSTRACT) != 0) return;
2223         //anonymous inner classes implementing interfaces need especial treatment
2224         if (someClass.isAnonymous()) {
2225             List<Type> interfaces =  types.interfaces(someClass.type);
2226             if (interfaces != null && !interfaces.isEmpty() &&
2227                 interfaces.head.tsym == syms.comparatorType.tsym) return;
2228         }
2229         checkClassOverrideEqualsAndHash(pos, someClass);
2230     }
2231 
2232     private void checkClassOverrideEqualsAndHash(DiagnosticPosition pos,
2233             ClassSymbol someClass) {
2234         if (lint.isEnabled(LintCategory.OVERRIDES)) {
2235             MethodSymbol equalsAtObject = (MethodSymbol)syms.objectType
2236                     .tsym.members().findFirst(names.equals);
2237             MethodSymbol hashCodeAtObject = (MethodSymbol)syms.objectType
2238                     .tsym.members().findFirst(names.hashCode);
2239             MethodSymbol equalsImpl = types.implementation(equalsAtObject,
2240                     someClass, false, equalsHasCodeFilter);
2241             boolean overridesEquals = equalsImpl != null &&
2242                                       equalsImpl.owner == someClass;
2243             boolean overridesHashCode = types.implementation(hashCodeAtObject,
2244                 someClass, false, equalsHasCodeFilter) != hashCodeAtObject;
2245 
2246             if (overridesEquals && !overridesHashCode) {
2247                 log.warning(LintCategory.OVERRIDES, pos,
2248                             Warnings.OverrideEqualsButNotHashcode(someClass));
2249             }
2250         }
2251     }
2252 
2253     public void checkHasMain(DiagnosticPosition pos, ClassSymbol c) {
2254         boolean found = false;
2255 
2256         for (Symbol sym : c.members().getSymbolsByName(names.main)) {
2257             if (sym.kind == MTH && (sym.flags() & PRIVATE) == 0) {
2258                 MethodSymbol meth = (MethodSymbol)sym;
2259                 if (!types.isSameType(meth.getReturnType(), syms.voidType)) {
2260                     continue;
2261                 }
2262                 if (meth.params.isEmpty()) {
2263                     found = true;
2264                     break;
2265                 }
2266                 if (meth.params.size() != 1) {
2267                     continue;
2268                 }
2269                 if (!types.isSameType(meth.params.head.type, types.makeArrayType(syms.stringType))) {
2270                     continue;
2271                 }
2272 
2273                 found = true;
2274                 break;
2275             }
2276         }
2277 
2278         if (!found) {
2279             log.error(pos, Errors.UnnamedClassDoesNotHaveMainMethod);
2280         }
2281     }
2282 
2283     public void checkModuleName (JCModuleDecl tree) {
2284         Name moduleName = tree.sym.name;
2285         Assert.checkNonNull(moduleName);
2286         if (lint.isEnabled(LintCategory.MODULE)) {
2287             JCExpression qualId = tree.qualId;
2288             while (qualId != null) {
2289                 Name componentName;
2290                 DiagnosticPosition pos;
2291                 switch (qualId.getTag()) {
2292                     case SELECT:
2293                         JCFieldAccess selectNode = ((JCFieldAccess) qualId);
2294                         componentName = selectNode.name;
2295                         pos = selectNode.pos();
2296                         qualId = selectNode.selected;
2297                         break;
2298                     case IDENT:
2299                         componentName = ((JCIdent) qualId).name;
2300                         pos = qualId.pos();
2301                         qualId = null;
2302                         break;
2303                     default:
2304                         throw new AssertionError("Unexpected qualified identifier: " + qualId.toString());
2305                 }
2306                 if (componentName != null) {
2307                     String moduleNameComponentString = componentName.toString();
2308                     int nameLength = moduleNameComponentString.length();
2309                     if (nameLength > 0 && Character.isDigit(moduleNameComponentString.charAt(nameLength - 1))) {
2310                         log.warning(Lint.LintCategory.MODULE, pos, Warnings.PoorChoiceForModuleName(componentName));
2311                     }
2312                 }
2313             }
2314         }
2315     }
2316 
2317     private boolean checkNameClash(ClassSymbol origin, Symbol s1, Symbol s2) {
2318         ClashFilter cf = new ClashFilter(origin.type);
2319         return (cf.test(s1) &&
2320                 cf.test(s2) &&
2321                 types.hasSameArgs(s1.erasure(types), s2.erasure(types)));
2322     }
2323 
2324 
2325     /** Check that all abstract members of given class have definitions.
2326      *  @param pos          Position to be used for error reporting.
2327      *  @param c            The class.
2328      */
2329     void checkAllDefined(DiagnosticPosition pos, ClassSymbol c) {
2330         MethodSymbol undef = types.firstUnimplementedAbstract(c);
2331         if (undef != null) {
2332             MethodSymbol undef1 =
2333                 new MethodSymbol(undef.flags(), undef.name,
2334                                  types.memberType(c.type, undef), undef.owner);
2335             log.error(pos,
2336                       Errors.DoesNotOverrideAbstract(c, undef1, undef1.location()));
2337         }
2338     }
2339 
2340     void checkNonCyclicDecl(JCClassDecl tree) {
2341         CycleChecker cc = new CycleChecker();
2342         cc.scan(tree);
2343         if (!cc.errorFound && !cc.partialCheck) {
2344             tree.sym.flags_field |= ACYCLIC;
2345         }
2346     }
2347 
2348     class CycleChecker extends TreeScanner {
2349 
2350         Set<Symbol> seenClasses = new HashSet<>();
2351         boolean errorFound = false;
2352         boolean partialCheck = false;
2353 
2354         private void checkSymbol(DiagnosticPosition pos, Symbol sym) {
2355             if (sym != null && sym.kind == TYP) {
2356                 Env<AttrContext> classEnv = enter.getEnv((TypeSymbol)sym);
2357                 if (classEnv != null) {
2358                     DiagnosticSource prevSource = log.currentSource();
2359                     try {
2360                         log.useSource(classEnv.toplevel.sourcefile);
2361                         scan(classEnv.tree);
2362                     }
2363                     finally {
2364                         log.useSource(prevSource.getFile());
2365                     }
2366                 } else if (sym.kind == TYP) {
2367                     checkClass(pos, sym, List.nil());
2368                 }
2369             } else if (sym == null || sym.kind != PCK) {
2370                 //not completed yet
2371                 partialCheck = true;
2372             }
2373         }
2374 
2375         @Override
2376         public void visitSelect(JCFieldAccess tree) {
2377             super.visitSelect(tree);
2378             checkSymbol(tree.pos(), tree.sym);
2379         }
2380 
2381         @Override
2382         public void visitIdent(JCIdent tree) {
2383             checkSymbol(tree.pos(), tree.sym);
2384         }
2385 
2386         @Override
2387         public void visitTypeApply(JCTypeApply tree) {
2388             scan(tree.clazz);
2389         }
2390 
2391         @Override
2392         public void visitTypeArray(JCArrayTypeTree tree) {
2393             scan(tree.elemtype);
2394         }
2395 
2396         @Override
2397         public void visitClassDef(JCClassDecl tree) {
2398             List<JCTree> supertypes = List.nil();
2399             if (tree.getExtendsClause() != null) {
2400                 supertypes = supertypes.prepend(tree.getExtendsClause());
2401             }
2402             if (tree.getImplementsClause() != null) {
2403                 for (JCTree intf : tree.getImplementsClause()) {
2404                     supertypes = supertypes.prepend(intf);
2405                 }
2406             }
2407             checkClass(tree.pos(), tree.sym, supertypes);
2408         }
2409 
2410         void checkClass(DiagnosticPosition pos, Symbol c, List<JCTree> supertypes) {
2411             if ((c.flags_field & ACYCLIC) != 0)
2412                 return;
2413             if (seenClasses.contains(c)) {
2414                 errorFound = true;
2415                 noteCyclic(pos, (ClassSymbol)c);
2416             } else if (!c.type.isErroneous()) {
2417                 try {
2418                     seenClasses.add(c);
2419                     if (c.type.hasTag(CLASS)) {
2420                         if (supertypes.nonEmpty()) {
2421                             scan(supertypes);
2422                         }
2423                         else {
2424                             ClassType ct = (ClassType)c.type;
2425                             if (ct.supertype_field == null ||
2426                                     ct.interfaces_field == null) {
2427                                 //not completed yet
2428                                 partialCheck = true;
2429                                 return;
2430                             }
2431                             checkSymbol(pos, ct.supertype_field.tsym);
2432                             for (Type intf : ct.interfaces_field) {
2433                                 checkSymbol(pos, intf.tsym);
2434                             }
2435                         }
2436                         if (c.owner.kind == TYP) {
2437                             checkSymbol(pos, c.owner);
2438                         }
2439                     }
2440                 } finally {
2441                     seenClasses.remove(c);
2442                 }
2443             }
2444         }
2445     }
2446 
2447     /** Check for cyclic references. Issue an error if the
2448      *  symbol of the type referred to has a LOCKED flag set.
2449      *
2450      *  @param pos      Position to be used for error reporting.
2451      *  @param t        The type referred to.
2452      */
2453     void checkNonCyclic(DiagnosticPosition pos, Type t) {
2454         checkNonCyclicInternal(pos, t);
2455     }
2456 
2457 
2458     void checkNonCyclic(DiagnosticPosition pos, TypeVar t) {
2459         checkNonCyclic1(pos, t, List.nil());
2460     }
2461 
2462     private void checkNonCyclic1(DiagnosticPosition pos, Type t, List<TypeVar> seen) {
2463         final TypeVar tv;
2464         if  (t.hasTag(TYPEVAR) && (t.tsym.flags() & UNATTRIBUTED) != 0)
2465             return;
2466         if (seen.contains(t)) {
2467             tv = (TypeVar)t;
2468             tv.setUpperBound(types.createErrorType(t));
2469             log.error(pos, Errors.CyclicInheritance(t));
2470         } else if (t.hasTag(TYPEVAR)) {
2471             tv = (TypeVar)t;
2472             seen = seen.prepend(tv);
2473             for (Type b : types.getBounds(tv))
2474                 checkNonCyclic1(pos, b, seen);
2475         }
2476     }
2477 
2478     /** Check for cyclic references. Issue an error if the
2479      *  symbol of the type referred to has a LOCKED flag set.
2480      *
2481      *  @param pos      Position to be used for error reporting.
2482      *  @param t        The type referred to.
2483      *  @return        True if the check completed on all attributed classes
2484      */
2485     private boolean checkNonCyclicInternal(DiagnosticPosition pos, Type t) {
2486         boolean complete = true; // was the check complete?
2487         //- System.err.println("checkNonCyclicInternal("+t+");");//DEBUG
2488         Symbol c = t.tsym;
2489         if ((c.flags_field & ACYCLIC) != 0) return true;
2490 
2491         if ((c.flags_field & LOCKED) != 0) {
2492             noteCyclic(pos, (ClassSymbol)c);
2493         } else if (!c.type.isErroneous()) {
2494             try {
2495                 c.flags_field |= LOCKED;
2496                 if (c.type.hasTag(CLASS)) {
2497                     ClassType clazz = (ClassType)c.type;
2498                     if (clazz.interfaces_field != null)
2499                         for (List<Type> l=clazz.interfaces_field; l.nonEmpty(); l=l.tail)
2500                             complete &= checkNonCyclicInternal(pos, l.head);
2501                     if (clazz.supertype_field != null) {
2502                         Type st = clazz.supertype_field;
2503                         if (st != null && st.hasTag(CLASS))
2504                             complete &= checkNonCyclicInternal(pos, st);
2505                     }
2506                     if (c.owner.kind == TYP)
2507                         complete &= checkNonCyclicInternal(pos, c.owner.type);
2508                 }
2509             } finally {
2510                 c.flags_field &= ~LOCKED;
2511             }
2512         }
2513         if (complete)
2514             complete = ((c.flags_field & UNATTRIBUTED) == 0) && c.isCompleted();
2515         if (complete) c.flags_field |= ACYCLIC;
2516         return complete;
2517     }
2518 
2519     /** Note that we found an inheritance cycle. */
2520     private void noteCyclic(DiagnosticPosition pos, ClassSymbol c) {
2521         log.error(pos, Errors.CyclicInheritance(c));
2522         for (List<Type> l=types.interfaces(c.type); l.nonEmpty(); l=l.tail)
2523             l.head = types.createErrorType((ClassSymbol)l.head.tsym, Type.noType);
2524         Type st = types.supertype(c.type);
2525         if (st.hasTag(CLASS))
2526             ((ClassType)c.type).supertype_field = types.createErrorType((ClassSymbol)st.tsym, Type.noType);
2527         c.type = types.createErrorType(c, c.type);
2528         c.flags_field |= ACYCLIC;
2529     }
2530 
2531     /** Check that all methods which implement some
2532      *  method conform to the method they implement.
2533      *  @param tree         The class definition whose members are checked.
2534      */
2535     void checkImplementations(JCClassDecl tree) {
2536         checkImplementations(tree, tree.sym, tree.sym);
2537     }
2538     //where
2539         /** Check that all methods which implement some
2540          *  method in `ic' conform to the method they implement.
2541          */
2542         void checkImplementations(JCTree tree, ClassSymbol origin, ClassSymbol ic) {
2543             for (List<Type> l = types.closure(ic.type); l.nonEmpty(); l = l.tail) {
2544                 ClassSymbol lc = (ClassSymbol)l.head.tsym;
2545                 if ((lc.flags() & ABSTRACT) != 0) {
2546                     for (Symbol sym : lc.members().getSymbols(NON_RECURSIVE)) {
2547                         if (sym.kind == MTH &&
2548                             (sym.flags() & (STATIC|ABSTRACT)) == ABSTRACT) {
2549                             MethodSymbol absmeth = (MethodSymbol)sym;
2550                             MethodSymbol implmeth = absmeth.implementation(origin, types, false);
2551                             if (implmeth != null && implmeth != absmeth &&
2552                                 (implmeth.owner.flags() & INTERFACE) ==
2553                                 (origin.flags() & INTERFACE)) {
2554                                 // don't check if implmeth is in a class, yet
2555                                 // origin is an interface. This case arises only
2556                                 // if implmeth is declared in Object. The reason is
2557                                 // that interfaces really don't inherit from
2558                                 // Object it's just that the compiler represents
2559                                 // things that way.
2560                                 checkOverride(tree, implmeth, absmeth, origin);
2561                             }
2562                         }
2563                     }
2564                 }
2565             }
2566         }
2567 
2568     /** Check that all abstract methods implemented by a class are
2569      *  mutually compatible.
2570      *  @param pos          Position to be used for error reporting.
2571      *  @param c            The class whose interfaces are checked.
2572      */
2573     void checkCompatibleSupertypes(DiagnosticPosition pos, Type c) {
2574         List<Type> supertypes = types.interfaces(c);
2575         Type supertype = types.supertype(c);
2576         if (supertype.hasTag(CLASS) &&
2577             (supertype.tsym.flags() & ABSTRACT) != 0)
2578             supertypes = supertypes.prepend(supertype);
2579         for (List<Type> l = supertypes; l.nonEmpty(); l = l.tail) {
2580             if (!l.head.getTypeArguments().isEmpty() &&
2581                 !checkCompatibleAbstracts(pos, l.head, l.head, c))
2582                 return;
2583             for (List<Type> m = supertypes; m != l; m = m.tail)
2584                 if (!checkCompatibleAbstracts(pos, l.head, m.head, c))
2585                     return;
2586         }
2587         checkCompatibleConcretes(pos, c);
2588     }
2589 
2590     /** Check that all non-override equivalent methods accessible from 'site'
2591      *  are mutually compatible (JLS 8.4.8/9.4.1).
2592      *
2593      *  @param pos  Position to be used for error reporting.
2594      *  @param site The class whose methods are checked.
2595      *  @param sym  The method symbol to be checked.
2596      */
2597     void checkOverrideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
2598          ClashFilter cf = new ClashFilter(site);
2599         //for each method m1 that is overridden (directly or indirectly)
2600         //by method 'sym' in 'site'...
2601 
2602         ArrayList<Symbol> symbolsByName = new ArrayList<>();
2603         types.membersClosure(site, false).getSymbolsByName(sym.name, cf).forEach(symbolsByName::add);
2604         for (Symbol m1 : symbolsByName) {
2605             if (!sym.overrides(m1, site.tsym, types, false)) {
2606                 continue;
2607             }
2608 
2609             //...check each method m2 that is a member of 'site'
2610             for (Symbol m2 : symbolsByName) {
2611                 if (m2 == m1) continue;
2612                 //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
2613                 //a member of 'site') and (ii) m1 has the same erasure as m2, issue an error
2614                 if (!types.isSubSignature(sym.type, types.memberType(site, m2)) &&
2615                         types.hasSameArgs(m2.erasure(types), m1.erasure(types))) {
2616                     sym.flags_field |= CLASH;
2617                     if (m1 == sym) {
2618                         log.error(pos, Errors.NameClashSameErasureNoOverride(
2619                             m1.name, types.memberType(site, m1).asMethodType().getParameterTypes(), m1.location(),
2620                             m2.name, types.memberType(site, m2).asMethodType().getParameterTypes(), m2.location()));
2621                     } else {
2622                         ClassType ct = (ClassType)site;
2623                         String kind = ct.isInterface() ? "interface" : "class";
2624                         log.error(pos, Errors.NameClashSameErasureNoOverride1(
2625                             kind,
2626                             ct.tsym.name,
2627                             m1.name,
2628                             types.memberType(site, m1).asMethodType().getParameterTypes(),
2629                             m1.location(),
2630                             m2.name,
2631                             types.memberType(site, m2).asMethodType().getParameterTypes(),
2632                             m2.location()));
2633                     }
2634                     return;
2635                 }
2636             }
2637         }
2638     }
2639 
2640     /** Check that all static methods accessible from 'site' are
2641      *  mutually compatible (JLS 8.4.8).
2642      *
2643      *  @param pos  Position to be used for error reporting.
2644      *  @param site The class whose methods are checked.
2645      *  @param sym  The method symbol to be checked.
2646      */
2647     void checkHideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
2648         ClashFilter cf = new ClashFilter(site);
2649         //for each method m1 that is a member of 'site'...
2650         for (Symbol s : types.membersClosure(site, true).getSymbolsByName(sym.name, cf)) {
2651             //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
2652             //a member of 'site') and (ii) 'sym' has the same erasure as m1, issue an error
2653             if (!types.isSubSignature(sym.type, types.memberType(site, s))) {
2654                 if (types.hasSameArgs(s.erasure(types), sym.erasure(types))) {
2655                     log.error(pos,
2656                               Errors.NameClashSameErasureNoHide(sym, sym.location(), s, s.location()));
2657                     return;
2658                 }
2659             }
2660          }
2661      }
2662 
2663      //where
2664      private class ClashFilter implements Predicate<Symbol> {
2665 
2666          Type site;
2667 
2668          ClashFilter(Type site) {
2669              this.site = site;
2670          }
2671 
2672          boolean shouldSkip(Symbol s) {
2673              return (s.flags() & CLASH) != 0 &&
2674                 s.owner == site.tsym;
2675          }
2676 
2677          @Override
2678          public boolean test(Symbol s) {
2679              return s.kind == MTH &&
2680                      (s.flags() & SYNTHETIC) == 0 &&
2681                      !shouldSkip(s) &&
2682                      s.isInheritedIn(site.tsym, types) &&
2683                      !s.isConstructor();
2684          }
2685      }
2686 
2687     void checkDefaultMethodClashes(DiagnosticPosition pos, Type site) {
2688         DefaultMethodClashFilter dcf = new DefaultMethodClashFilter(site);
2689         for (Symbol m : types.membersClosure(site, false).getSymbols(dcf)) {
2690             Assert.check(m.kind == MTH);
2691             List<MethodSymbol> prov = types.interfaceCandidates(site, (MethodSymbol)m);
2692             if (prov.size() > 1) {
2693                 ListBuffer<Symbol> abstracts = new ListBuffer<>();
2694                 ListBuffer<Symbol> defaults = new ListBuffer<>();
2695                 for (MethodSymbol provSym : prov) {
2696                     if ((provSym.flags() & DEFAULT) != 0) {
2697                         defaults = defaults.append(provSym);
2698                     } else if ((provSym.flags() & ABSTRACT) != 0) {
2699                         abstracts = abstracts.append(provSym);
2700                     }
2701                     if (defaults.nonEmpty() && defaults.size() + abstracts.size() >= 2) {
2702                         //strong semantics - issue an error if two sibling interfaces
2703                         //have two override-equivalent defaults - or if one is abstract
2704                         //and the other is default
2705                         Fragment diagKey;
2706                         Symbol s1 = defaults.first();
2707                         Symbol s2;
2708                         if (defaults.size() > 1) {
2709                             s2 = defaults.toList().tail.head;
2710                             diagKey = Fragments.IncompatibleUnrelatedDefaults(Kinds.kindName(site.tsym), site,
2711                                     m.name, types.memberType(site, m).getParameterTypes(),
2712                                     s1.location(), s2.location());
2713 
2714                         } else {
2715                             s2 = abstracts.first();
2716                             diagKey = Fragments.IncompatibleAbstractDefault(Kinds.kindName(site.tsym), site,
2717                                     m.name, types.memberType(site, m).getParameterTypes(),
2718                                     s1.location(), s2.location());
2719                         }
2720                         log.error(pos, Errors.TypesIncompatible(s1.location().type, s2.location().type, diagKey));
2721                         break;
2722                     }
2723                 }
2724             }
2725         }
2726     }
2727 
2728     //where
2729      private class DefaultMethodClashFilter implements Predicate<Symbol> {
2730 
2731          Type site;
2732 
2733          DefaultMethodClashFilter(Type site) {
2734              this.site = site;
2735          }
2736 
2737          @Override
2738          public boolean test(Symbol s) {
2739              return s.kind == MTH &&
2740                      (s.flags() & DEFAULT) != 0 &&
2741                      s.isInheritedIn(site.tsym, types) &&
2742                      !s.isConstructor();
2743          }
2744      }
2745 
2746     /** Report warnings for potentially ambiguous method declarations in the given site. */
2747     void checkPotentiallyAmbiguousOverloads(JCClassDecl tree, Type site) {
2748 
2749         // Skip if warning not enabled
2750         if (!lint.isEnabled(LintCategory.OVERLOADS))
2751             return;
2752 
2753         // Gather all of site's methods, including overridden methods, grouped by name (except Object methods)
2754         List<java.util.List<MethodSymbol>> methodGroups = methodsGroupedByName(site,
2755             new PotentiallyAmbiguousFilter(site), ArrayList::new);
2756 
2757         // Build the predicate that determines if site is responsible for an ambiguity
2758         BiPredicate<MethodSymbol, MethodSymbol> responsible = buildResponsiblePredicate(site, methodGroups);
2759 
2760         // Now remove overridden methods from each group, leaving only site's actual members
2761         methodGroups.forEach(list -> removePreempted(list, (m1, m2) -> m1.overrides(m2, site.tsym, types, false)));
2762 
2763         // Allow site's own declared methods (only) to apply @SuppressWarnings("overloads")
2764         methodGroups.forEach(list -> list.removeIf(
2765             m -> m.owner == site.tsym && !lint.augment(m).isEnabled(LintCategory.OVERLOADS)));
2766 
2767         // Warn about ambiguous overload method pairs for which site is responsible
2768         methodGroups.forEach(list -> compareAndRemove(list, (m1, m2) -> {
2769 
2770             // See if this is an ambiguous overload for which "site" is responsible
2771             if (!potentiallyAmbiguousOverload(site, m1, m2) || !responsible.test(m1, m2))
2772                 return 0;
2773 
2774             // Locate the warning at one of the methods, if possible
2775             DiagnosticPosition pos =
2776                 m1.owner == site.tsym ? TreeInfo.diagnosticPositionFor(m1, tree) :
2777                 m2.owner == site.tsym ? TreeInfo.diagnosticPositionFor(m2, tree) :
2778                 tree.pos();
2779 
2780             // Log the warning
2781             log.warning(LintCategory.OVERLOADS, pos,
2782                 Warnings.PotentiallyAmbiguousOverload(
2783                     m1.asMemberOf(site, types), m1.location(),
2784                     m2.asMemberOf(site, types), m2.location()));
2785 
2786             // Don't warn again for either of these two methods
2787             return FIRST | SECOND;
2788         }));
2789     }
2790 
2791     /** Build a predicate that determines, given two methods that are members of the given class,
2792      *  whether the class should be held "responsible" if the methods are potentially ambiguous.
2793      *
2794      *  Sometimes ambiguous methods are unavoidable because they're inherited from a supertype.
2795      *  For example, any subtype of Spliterator.OfInt will have ambiguities for both
2796      *  forEachRemaining() and tryAdvance() (in both cases the overloads are IntConsumer and
2797      *  Consumer&lt;? super Integer&gt;). So we only want to "blame" a class when that class is
2798      *  itself responsible for creating the ambiguity. We declare that a class C is "responsible"
2799      *  for the ambiguity between two methods m1 and m2 if there is no direct supertype T of C
2800      *  such that m1 and m2, or some overrides thereof, both exist in T and are ambiguous in T.
2801      *  As an optimization, we first check if either method is declared in C and does not override
2802      *  any other methods; in this case the class is definitely responsible.
2803      */
2804     BiPredicate<MethodSymbol, MethodSymbol> buildResponsiblePredicate(Type site,
2805         List<? extends Collection<MethodSymbol>> methodGroups) {
2806 
2807         // Define the "overrides" predicate
2808         BiPredicate<MethodSymbol, MethodSymbol> overrides = (m1, m2) -> m1.overrides(m2, site.tsym, types, false);
2809 
2810         // Map each method declared in site to a list of the supertype method(s) it directly overrides
2811         HashMap<MethodSymbol, ArrayList<MethodSymbol>> overriddenMethodsMap = new HashMap<>();
2812         methodGroups.forEach(list -> {
2813             for (MethodSymbol m : list) {
2814 
2815                 // Skip methods not declared in site
2816                 if (m.owner != site.tsym)
2817                     continue;
2818 
2819                 // Gather all supertype methods overridden by m, directly or indirectly
2820                 ArrayList<MethodSymbol> overriddenMethods = list.stream()
2821                   .filter(m2 -> m2 != m && overrides.test(m, m2))
2822                   .collect(Collectors.toCollection(ArrayList::new));
2823 
2824                 // Eliminate non-direct overrides
2825                 removePreempted(overriddenMethods, overrides);
2826 
2827                 // Add to map
2828                 overriddenMethodsMap.put(m, overriddenMethods);
2829             }
2830         });
2831 
2832         // Build the predicate
2833         return (m1, m2) -> {
2834 
2835             // Get corresponding supertype methods (if declared in site)
2836             java.util.List<MethodSymbol> overriddenMethods1 = overriddenMethodsMap.get(m1);
2837             java.util.List<MethodSymbol> overriddenMethods2 = overriddenMethodsMap.get(m2);
2838 
2839             // Quick check for the case where a method was added by site itself
2840             if (overriddenMethods1 != null && overriddenMethods1.isEmpty())
2841                 return true;
2842             if (overriddenMethods2 != null && overriddenMethods2.isEmpty())
2843                 return true;
2844 
2845             // Get each method's corresponding method(s) from supertypes of site
2846             java.util.List<MethodSymbol> supertypeMethods1 = overriddenMethods1 != null ?
2847               overriddenMethods1 : Collections.singletonList(m1);
2848             java.util.List<MethodSymbol> supertypeMethods2 = overriddenMethods2 != null ?
2849               overriddenMethods2 : Collections.singletonList(m2);
2850 
2851             // See if we can blame some direct supertype instead
2852             return types.directSupertypes(site).stream()
2853               .filter(stype -> stype != syms.objectType)
2854               .map(stype -> stype.tsym.type)                // view supertype in its original form
2855               .noneMatch(stype -> {
2856                 for (MethodSymbol sm1 : supertypeMethods1) {
2857                     if (!types.isSubtype(types.erasure(stype), types.erasure(sm1.owner.type)))
2858                         continue;
2859                     for (MethodSymbol sm2 : supertypeMethods2) {
2860                         if (!types.isSubtype(types.erasure(stype), types.erasure(sm2.owner.type)))
2861                             continue;
2862                         if (potentiallyAmbiguousOverload(stype, sm1, sm2))
2863                             return true;
2864                     }
2865                 }
2866                 return false;
2867             });
2868         };
2869     }
2870 
2871     /** Gather all of site's methods, including overridden methods, grouped and sorted by name,
2872      *  after applying the given filter.
2873      */
2874     <C extends Collection<MethodSymbol>> List<C> methodsGroupedByName(Type site,
2875             Predicate<Symbol> filter, Supplier<? extends C> groupMaker) {
2876         Iterable<Symbol> symbols = types.membersClosure(site, false).getSymbols(filter, RECURSIVE);
2877         return StreamSupport.stream(symbols.spliterator(), false)
2878           .map(MethodSymbol.class::cast)
2879           .collect(Collectors.groupingBy(m -> m.name, Collectors.toCollection(groupMaker)))
2880           .entrySet()
2881           .stream()
2882           .sorted(Comparator.comparing(e -> e.getKey().toString()))
2883           .map(Map.Entry::getValue)
2884           .collect(List.collector());
2885     }
2886 
2887     /** Compare elements in a list pair-wise in order to remove some of them.
2888      *  @param list mutable list of items
2889      *  @param comparer returns flag bit(s) to remove FIRST and/or SECOND
2890      */
2891     <T> void compareAndRemove(java.util.List<T> list, ToIntBiFunction<? super T, ? super T> comparer) {
2892         for (int index1 = 0; index1 < list.size() - 1; index1++) {
2893             T item1 = list.get(index1);
2894             for (int index2 = index1 + 1; index2 < list.size(); index2++) {
2895                 T item2 = list.get(index2);
2896                 int flags = comparer.applyAsInt(item1, item2);
2897                 if ((flags & SECOND) != 0)
2898                     list.remove(index2--);          // remove item2
2899                 if ((flags & FIRST) != 0) {
2900                     list.remove(index1--);          // remove item1
2901                     break;
2902                 }
2903             }
2904         }
2905     }
2906 
2907     /** Remove elements in a list that are preempted by some other element in the list.
2908      *  @param list mutable list of items
2909      *  @param preempts decides if one item preempts another, causing the second one to be removed
2910      */
2911     <T> void removePreempted(java.util.List<T> list, BiPredicate<? super T, ? super T> preempts) {
2912         compareAndRemove(list, (item1, item2) -> {
2913             int flags = 0;
2914             if (preempts.test(item1, item2))
2915                 flags |= SECOND;
2916             if (preempts.test(item2, item1))
2917                 flags |= FIRST;
2918             return flags;
2919         });
2920     }
2921 
2922     /** Filters method candidates for the "potentially ambiguous method" check */
2923     class PotentiallyAmbiguousFilter extends ClashFilter {
2924 
2925         PotentiallyAmbiguousFilter(Type site) {
2926             super(site);
2927         }
2928 
2929         @Override
2930         boolean shouldSkip(Symbol s) {
2931             return s.owner.type.tsym == syms.objectType.tsym || super.shouldSkip(s);
2932         }
2933     }
2934 
2935     /**
2936       * Report warnings for potentially ambiguous method declarations. Two declarations
2937       * are potentially ambiguous if they feature two unrelated functional interface
2938       * in same argument position (in which case, a call site passing an implicit
2939       * lambda would be ambiguous). This assumes they already have the same name.
2940       */
2941     boolean potentiallyAmbiguousOverload(Type site, MethodSymbol msym1, MethodSymbol msym2) {
2942         Assert.check(msym1.name == msym2.name);
2943         if (msym1 == msym2)
2944             return false;
2945         Type mt1 = types.memberType(site, msym1);
2946         Type mt2 = types.memberType(site, msym2);
2947         //if both generic methods, adjust type variables
2948         if (mt1.hasTag(FORALL) && mt2.hasTag(FORALL) &&
2949                 types.hasSameBounds((ForAll)mt1, (ForAll)mt2)) {
2950             mt2 = types.subst(mt2, ((ForAll)mt2).tvars, ((ForAll)mt1).tvars);
2951         }
2952         //expand varargs methods if needed
2953         int maxLength = Math.max(mt1.getParameterTypes().length(), mt2.getParameterTypes().length());
2954         List<Type> args1 = rs.adjustArgs(mt1.getParameterTypes(), msym1, maxLength, true);
2955         List<Type> args2 = rs.adjustArgs(mt2.getParameterTypes(), msym2, maxLength, true);
2956         //if arities don't match, exit
2957         if (args1.length() != args2.length())
2958             return false;
2959         boolean potentiallyAmbiguous = false;
2960         while (args1.nonEmpty() && args2.nonEmpty()) {
2961             Type s = args1.head;
2962             Type t = args2.head;
2963             if (!types.isSubtype(t, s) && !types.isSubtype(s, t)) {
2964                 if (types.isFunctionalInterface(s) && types.isFunctionalInterface(t) &&
2965                         types.findDescriptorType(s).getParameterTypes().length() > 0 &&
2966                         types.findDescriptorType(s).getParameterTypes().length() ==
2967                         types.findDescriptorType(t).getParameterTypes().length()) {
2968                     potentiallyAmbiguous = true;
2969                 } else {
2970                     return false;
2971                 }
2972             }
2973             args1 = args1.tail;
2974             args2 = args2.tail;
2975         }
2976         return potentiallyAmbiguous;
2977     }
2978 
2979     void checkAccessFromSerializableElement(final JCTree tree, boolean isLambda) {
2980         if (warnOnAnyAccessToMembers ||
2981             (lint.isEnabled(LintCategory.SERIAL) &&
2982             !lint.isSuppressed(LintCategory.SERIAL) &&
2983             isLambda)) {
2984             Symbol sym = TreeInfo.symbol(tree);
2985             if (!sym.kind.matches(KindSelector.VAL_MTH)) {
2986                 return;
2987             }
2988 
2989             if (sym.kind == VAR) {
2990                 if ((sym.flags() & PARAMETER) != 0 ||
2991                     sym.isDirectlyOrIndirectlyLocal() ||
2992                     sym.name == names._this ||
2993                     sym.name == names._super) {
2994                     return;
2995                 }
2996             }
2997 
2998             if (!types.isSubtype(sym.owner.type, syms.serializableType) &&
2999                 isEffectivelyNonPublic(sym)) {
3000                 if (isLambda) {
3001                     if (belongsToRestrictedPackage(sym)) {
3002                         log.warning(LintCategory.SERIAL, tree.pos(),
3003                                     Warnings.AccessToMemberFromSerializableLambda(sym));
3004                     }
3005                 } else {
3006                     log.warning(tree.pos(),
3007                                 Warnings.AccessToMemberFromSerializableElement(sym));
3008                 }
3009             }
3010         }
3011     }
3012 
3013     private boolean isEffectivelyNonPublic(Symbol sym) {
3014         if (sym.packge() == syms.rootPackage) {
3015             return false;
3016         }
3017 
3018         while (sym.kind != PCK) {
3019             if ((sym.flags() & PUBLIC) == 0) {
3020                 return true;
3021             }
3022             sym = sym.owner;
3023         }
3024         return false;
3025     }
3026 
3027     private boolean belongsToRestrictedPackage(Symbol sym) {
3028         String fullName = sym.packge().fullname.toString();
3029         return fullName.startsWith("java.") ||
3030                 fullName.startsWith("javax.") ||
3031                 fullName.startsWith("sun.") ||
3032                 fullName.contains(".internal.");
3033     }
3034 
3035     /** Check that class c does not implement directly or indirectly
3036      *  the same parameterized interface with two different argument lists.
3037      *  @param pos          Position to be used for error reporting.
3038      *  @param type         The type whose interfaces are checked.
3039      */
3040     void checkClassBounds(DiagnosticPosition pos, Type type) {
3041         checkClassBounds(pos, new HashMap<TypeSymbol,Type>(), type);
3042     }
3043 //where
3044         /** Enter all interfaces of type `type' into the hash table `seensofar'
3045          *  with their class symbol as key and their type as value. Make
3046          *  sure no class is entered with two different types.
3047          */
3048         void checkClassBounds(DiagnosticPosition pos,
3049                               Map<TypeSymbol,Type> seensofar,
3050                               Type type) {
3051             if (type.isErroneous()) return;
3052             for (List<Type> l = types.interfaces(type); l.nonEmpty(); l = l.tail) {
3053                 Type it = l.head;
3054                 if (type.hasTag(CLASS) && !it.hasTag(CLASS)) continue; // JLS 8.1.5
3055 
3056                 Type oldit = seensofar.put(it.tsym, it);
3057                 if (oldit != null) {
3058                     List<Type> oldparams = oldit.allparams();
3059                     List<Type> newparams = it.allparams();
3060                     if (!types.containsTypeEquivalent(oldparams, newparams))
3061                         log.error(pos,
3062                                   Errors.CantInheritDiffArg(it.tsym,
3063                                                             Type.toString(oldparams),
3064                                                             Type.toString(newparams)));
3065                 }
3066                 checkClassBounds(pos, seensofar, it);
3067             }
3068             Type st = types.supertype(type);
3069             if (type.hasTag(CLASS) && !st.hasTag(CLASS)) return; // JLS 8.1.4
3070             if (st != Type.noType) checkClassBounds(pos, seensofar, st);
3071         }
3072 
3073     /** Enter interface into into set.
3074      *  If it existed already, issue a "repeated interface" error.
3075      */
3076     void checkNotRepeated(DiagnosticPosition pos, Type it, Set<Symbol> its) {
3077         if (its.contains(it.tsym))
3078             log.error(pos, Errors.RepeatedInterface);
3079         else {
3080             its.add(it.tsym);
3081         }
3082     }
3083 
3084 /* *************************************************************************
3085  * Check annotations
3086  **************************************************************************/
3087 
3088     /**
3089      * Recursively validate annotations values
3090      */
3091     void validateAnnotationTree(JCTree tree) {
3092         class AnnotationValidator extends TreeScanner {
3093             @Override
3094             public void visitAnnotation(JCAnnotation tree) {
3095                 if (!tree.type.isErroneous() && tree.type.tsym.isAnnotationType()) {
3096                     super.visitAnnotation(tree);
3097                     validateAnnotation(tree);
3098                 }
3099             }
3100         }
3101         tree.accept(new AnnotationValidator());
3102     }
3103 
3104     /**
3105      *  {@literal
3106      *  Annotation types are restricted to primitives, String, an
3107      *  enum, an annotation, Class, Class<?>, Class<? extends
3108      *  Anything>, arrays of the preceding.
3109      *  }
3110      */
3111     void validateAnnotationType(JCTree restype) {
3112         // restype may be null if an error occurred, so don't bother validating it
3113         if (restype != null) {
3114             validateAnnotationType(restype.pos(), restype.type);
3115         }
3116     }
3117 
3118     void validateAnnotationType(DiagnosticPosition pos, Type type) {
3119         if (type.isPrimitive()) return;
3120         if (types.isSameType(type, syms.stringType)) return;
3121         if ((type.tsym.flags() & Flags.ENUM) != 0) return;
3122         if ((type.tsym.flags() & Flags.ANNOTATION) != 0) return;
3123         if (types.cvarLowerBound(type).tsym == syms.classType.tsym) return;
3124         if (types.isArray(type) && !types.isArray(types.elemtype(type))) {
3125             validateAnnotationType(pos, types.elemtype(type));
3126             return;
3127         }
3128         log.error(pos, Errors.InvalidAnnotationMemberType);
3129     }
3130 
3131     /**
3132      * "It is also a compile-time error if any method declared in an
3133      * annotation type has a signature that is override-equivalent to
3134      * that of any public or protected method declared in class Object
3135      * or in the interface annotation.Annotation."
3136      *
3137      * @jls 9.6 Annotation Types
3138      */
3139     void validateAnnotationMethod(DiagnosticPosition pos, MethodSymbol m) {
3140         for (Type sup = syms.annotationType; sup.hasTag(CLASS); sup = types.supertype(sup)) {
3141             Scope s = sup.tsym.members();
3142             for (Symbol sym : s.getSymbolsByName(m.name)) {
3143                 if (sym.kind == MTH &&
3144                     (sym.flags() & (PUBLIC | PROTECTED)) != 0 &&
3145                     types.overrideEquivalent(m.type, sym.type))
3146                     log.error(pos, Errors.IntfAnnotationMemberClash(sym, sup));
3147             }
3148         }
3149     }
3150 
3151     /** Check the annotations of a symbol.
3152      */
3153     public void validateAnnotations(List<JCAnnotation> annotations, JCTree declarationTree, Symbol s) {
3154         for (JCAnnotation a : annotations)
3155             validateAnnotation(a, declarationTree, s);
3156     }
3157 
3158     /** Check the type annotations.
3159      */
3160     public void validateTypeAnnotations(List<JCAnnotation> annotations, Symbol s, boolean isTypeParameter) {
3161         for (JCAnnotation a : annotations)
3162             validateTypeAnnotation(a, s, isTypeParameter);
3163     }
3164 
3165     /** Check an annotation of a symbol.
3166      */
3167     private void validateAnnotation(JCAnnotation a, JCTree declarationTree, Symbol s) {
3168         /** NOTE: if annotation processors are present, annotation processing rounds can happen after this method,
3169          *  this can impact in particular records for which annotations are forcibly propagated.
3170          */
3171         validateAnnotationTree(a);
3172         boolean isRecordMember = ((s.flags_field & RECORD) != 0 || s.enclClass() != null && s.enclClass().isRecord());
3173 
3174         boolean isRecordField = (s.flags_field & RECORD) != 0 &&
3175                 declarationTree.hasTag(VARDEF) &&
3176                 s.owner.kind == TYP;
3177 
3178         if (isRecordField) {
3179             // first we need to check if the annotation is applicable to records
3180             Name[] targets = getTargetNames(a);
3181             boolean appliesToRecords = false;
3182             for (Name target : targets) {
3183                 appliesToRecords =
3184                                 target == names.FIELD ||
3185                                 target == names.PARAMETER ||
3186                                 target == names.METHOD ||
3187                                 target == names.TYPE_USE ||
3188                                 target == names.RECORD_COMPONENT;
3189                 if (appliesToRecords) {
3190                     break;
3191                 }
3192             }
3193             if (!appliesToRecords) {
3194                 log.error(a.pos(), Errors.AnnotationTypeNotApplicable);
3195             } else {
3196                 /* lets now find the annotations in the field that are targeted to record components and append them to
3197                  * the corresponding record component
3198                  */
3199                 ClassSymbol recordClass = (ClassSymbol) s.owner;
3200                 RecordComponent rc = recordClass.getRecordComponent((VarSymbol)s);
3201                 SymbolMetadata metadata = rc.getMetadata();
3202                 if (metadata == null || metadata.isEmpty()) {
3203                     /* if not is empty then we have already been here, which is the case if multiple annotations are applied
3204                      * to the record component declaration
3205                      */
3206                     rc.appendAttributes(s.getRawAttributes().stream().filter(anno ->
3207                             Arrays.stream(getTargetNames(anno.type.tsym)).anyMatch(name -> name == names.RECORD_COMPONENT)
3208                     ).collect(List.collector()));
3209 
3210                     JCVariableDecl fieldAST = (JCVariableDecl) declarationTree;
3211                     for (JCAnnotation fieldAnnot : fieldAST.mods.annotations) {
3212                         for (JCAnnotation rcAnnot : rc.declarationFor().mods.annotations) {
3213                             if (rcAnnot.pos == fieldAnnot.pos) {
3214                                 rcAnnot.setType(fieldAnnot.type);
3215                                 break;
3216                             }
3217                         }
3218                     }
3219 
3220                     /* At this point, we used to carry over any type annotations from the VARDEF to the record component, but
3221                      * that is problematic, since we get here only when *some* annotation is applied to the SE5 (declaration)
3222                      * annotation location, inadvertently failing to carry over the type annotations when the VarDef has no
3223                      * annotations in the SE5 annotation location.
3224                      *
3225                      * Now type annotations are assigned to record components in a method that would execute irrespective of
3226                      * whether there are SE5 annotations on a VarDef viz com.sun.tools.javac.code.TypeAnnotations.TypeAnnotationPositions.visitVarDef
3227                      */
3228                 }
3229             }
3230         }
3231 
3232         /* the section below is tricky. Annotations applied to record components are propagated to the corresponding
3233          * record member so if an annotation has target: FIELD, it is propagated to the corresponding FIELD, if it has
3234          * target METHOD, it is propagated to the accessor and so on. But at the moment when method members are generated
3235          * there is no enough information to propagate only the right annotations. So all the annotations are propagated
3236          * to all the possible locations.
3237          *
3238          * At this point we need to remove all the annotations that are not in place before going on with the annotation
3239          * party. On top of the above there is the issue that there is no AST representing record components, just symbols
3240          * so the corresponding field has been holding all the annotations and it's metadata has been modified as if it
3241          * was both a field and a record component.
3242          *
3243          * So there are two places where we need to trim annotations from: the metadata of the symbol and / or the modifiers
3244          * in the AST. Whatever is in the metadata will be written to the class file, whatever is in the modifiers could
3245          * be see by annotation processors.
3246          *
3247          * The metadata contains both type annotations and declaration annotations. At this point of the game we don't
3248          * need to care about type annotations, they are all in the right place. But we could need to remove declaration
3249          * annotations. So for declaration annotations if they are not applicable to the record member, excluding type
3250          * annotations which are already correct, then we will remove it. For the AST modifiers if the annotation is not
3251          * applicable either as type annotation and or declaration annotation, only in that case it will be removed.
3252          *
3253          * So it could be that annotation is removed as a declaration annotation but it is kept in the AST modifier for
3254          * further inspection by annotation processors.
3255          *
3256          * For example:
3257          *
3258          *     import java.lang.annotation.*;
3259          *
3260          *     @Target({ElementType.TYPE_USE, ElementType.RECORD_COMPONENT})
3261          *     @Retention(RetentionPolicy.RUNTIME)
3262          *     @interface Anno { }
3263          *
3264          *     record R(@Anno String s) {}
3265          *
3266          * at this point we will have for the case of the generated field:
3267          *   - @Anno in the modifier
3268          *   - @Anno as a type annotation
3269          *   - @Anno as a declaration annotation
3270          *
3271          * the last one should be removed because the annotation has not FIELD as target but it was applied as a
3272          * declaration annotation because the field was being treated both as a field and as a record component
3273          * as we have already copied the annotations to the record component, now the field doesn't need to hold
3274          * annotations that are not intended for it anymore. Still @Anno has to be kept in the AST's modifiers as it
3275          * is applicable as a type annotation to the type of the field.
3276          */
3277 
3278         if (a.type.tsym.isAnnotationType()) {
3279             Optional<Set<Name>> applicableTargetsOp = getApplicableTargets(a, s);
3280             if (!applicableTargetsOp.isEmpty()) {
3281                 Set<Name> applicableTargets = applicableTargetsOp.get();
3282                 boolean notApplicableOrIsTypeUseOnly = applicableTargets.isEmpty() ||
3283                         applicableTargets.size() == 1 && applicableTargets.contains(names.TYPE_USE);
3284                 boolean isCompGeneratedRecordElement = isRecordMember && (s.flags_field & Flags.GENERATED_MEMBER) != 0;
3285                 boolean isCompRecordElementWithNonApplicableDeclAnno = isCompGeneratedRecordElement && notApplicableOrIsTypeUseOnly;
3286 
3287                 if (applicableTargets.isEmpty() || isCompRecordElementWithNonApplicableDeclAnno) {
3288                     if (isCompRecordElementWithNonApplicableDeclAnno) {
3289                             /* so we have found an annotation that is not applicable to a record member that was generated by the
3290                              * compiler. This was intentionally done at TypeEnter, now is the moment strip away the annotations
3291                              * that are not applicable to the given record member
3292                              */
3293                         JCModifiers modifiers = TreeInfo.getModifiers(declarationTree);
3294                             /* lets first remove the annotation from the modifier if it is not applicable, we have to check again as
3295                              * it could be a type annotation
3296                              */
3297                         if (modifiers != null && applicableTargets.isEmpty()) {
3298                             ListBuffer<JCAnnotation> newAnnotations = new ListBuffer<>();
3299                             for (JCAnnotation anno : modifiers.annotations) {
3300                                 if (anno != a) {
3301                                     newAnnotations.add(anno);
3302                                 }
3303                             }
3304                             modifiers.annotations = newAnnotations.toList();
3305                         }
3306                         // now lets remove it from the symbol
3307                         s.getMetadata().removeDeclarationMetadata(a.attribute);
3308                     } else {
3309                         log.error(a.pos(), Errors.AnnotationTypeNotApplicable);
3310                     }
3311                 }
3312                 /* if we are seeing the @SafeVarargs annotation applied to a compiler generated accessor,
3313                  * then this is an error as we know that no compiler generated accessor will be a varargs
3314                  * method, better to fail asap
3315                  */
3316                 if (isCompGeneratedRecordElement && !isRecordField && a.type.tsym == syms.trustMeType.tsym && declarationTree.hasTag(METHODDEF)) {
3317                     log.error(a.pos(), Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym, Fragments.VarargsTrustmeOnNonVarargsAccessor(s)));
3318                 }
3319             }
3320         }
3321 
3322         if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
3323             if (s.kind != TYP) {
3324                 log.error(a.pos(), Errors.BadFunctionalIntfAnno);
3325             } else if (!s.isInterface() || (s.flags() & ANNOTATION) != 0) {
3326                 log.error(a.pos(), Errors.BadFunctionalIntfAnno1(Fragments.NotAFunctionalIntf(s)));
3327             }
3328         }
3329     }
3330 
3331     public void validateTypeAnnotation(JCAnnotation a, Symbol s, boolean isTypeParameter) {
3332         Assert.checkNonNull(a.type);
3333         // we just want to validate that the anotation doesn't have any wrong target
3334         if (s != null) getApplicableTargets(a, s);
3335         validateAnnotationTree(a);
3336 
3337         if (a.hasTag(TYPE_ANNOTATION) &&
3338                 !a.annotationType.type.isErroneous() &&
3339                 !isTypeAnnotation(a, isTypeParameter)) {
3340             log.error(a.pos(), Errors.AnnotationTypeNotApplicableToType(a.type));
3341         }
3342     }
3343 
3344     /**
3345      * Validate the proposed container 'repeatable' on the
3346      * annotation type symbol 's'. Report errors at position
3347      * 'pos'.
3348      *
3349      * @param s The (annotation)type declaration annotated with a @Repeatable
3350      * @param repeatable the @Repeatable on 's'
3351      * @param pos where to report errors
3352      */
3353     public void validateRepeatable(TypeSymbol s, Attribute.Compound repeatable, DiagnosticPosition pos) {
3354         Assert.check(types.isSameType(repeatable.type, syms.repeatableType));
3355 
3356         Type t = null;
3357         List<Pair<MethodSymbol,Attribute>> l = repeatable.values;
3358         if (!l.isEmpty()) {
3359             Assert.check(l.head.fst.name == names.value);
3360             if (l.head.snd instanceof Attribute.Class) {
3361                 t = ((Attribute.Class)l.head.snd).getValue();
3362             }
3363         }
3364 
3365         if (t == null) {
3366             // errors should already have been reported during Annotate
3367             return;
3368         }
3369 
3370         validateValue(t.tsym, s, pos);
3371         validateRetention(t.tsym, s, pos);
3372         validateDocumented(t.tsym, s, pos);
3373         validateInherited(t.tsym, s, pos);
3374         validateTarget(t.tsym, s, pos);
3375         validateDefault(t.tsym, pos);
3376     }
3377 
3378     private void validateValue(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
3379         Symbol sym = container.members().findFirst(names.value);
3380         if (sym != null && sym.kind == MTH) {
3381             MethodSymbol m = (MethodSymbol) sym;
3382             Type ret = m.getReturnType();
3383             if (!(ret.hasTag(ARRAY) && types.isSameType(((ArrayType)ret).elemtype, contained.type))) {
3384                 log.error(pos,
3385                           Errors.InvalidRepeatableAnnotationValueReturn(container,
3386                                                                         ret,
3387                                                                         types.makeArrayType(contained.type)));
3388             }
3389         } else {
3390             log.error(pos, Errors.InvalidRepeatableAnnotationNoValue(container));
3391         }
3392     }
3393 
3394     private void validateRetention(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
3395         Attribute.RetentionPolicy containerRetention = types.getRetention(container);
3396         Attribute.RetentionPolicy containedRetention = types.getRetention(contained);
3397 
3398         boolean error = false;
3399         switch (containedRetention) {
3400         case RUNTIME:
3401             if (containerRetention != Attribute.RetentionPolicy.RUNTIME) {
3402                 error = true;
3403             }
3404             break;
3405         case CLASS:
3406             if (containerRetention == Attribute.RetentionPolicy.SOURCE)  {
3407                 error = true;
3408             }
3409         }
3410         if (error ) {
3411             log.error(pos,
3412                       Errors.InvalidRepeatableAnnotationRetention(container,
3413                                                                   containerRetention.name(),
3414                                                                   contained,
3415                                                                   containedRetention.name()));
3416         }
3417     }
3418 
3419     private void validateDocumented(Symbol container, Symbol contained, DiagnosticPosition pos) {
3420         if (contained.attribute(syms.documentedType.tsym) != null) {
3421             if (container.attribute(syms.documentedType.tsym) == null) {
3422                 log.error(pos, Errors.InvalidRepeatableAnnotationNotDocumented(container, contained));
3423             }
3424         }
3425     }
3426 
3427     private void validateInherited(Symbol container, Symbol contained, DiagnosticPosition pos) {
3428         if (contained.attribute(syms.inheritedType.tsym) != null) {
3429             if (container.attribute(syms.inheritedType.tsym) == null) {
3430                 log.error(pos, Errors.InvalidRepeatableAnnotationNotInherited(container, contained));
3431             }
3432         }
3433     }
3434 
3435     private void validateTarget(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
3436         // The set of targets the container is applicable to must be a subset
3437         // (with respect to annotation target semantics) of the set of targets
3438         // the contained is applicable to. The target sets may be implicit or
3439         // explicit.
3440 
3441         Set<Name> containerTargets;
3442         Attribute.Array containerTarget = getAttributeTargetAttribute(container);
3443         if (containerTarget == null) {
3444             containerTargets = getDefaultTargetSet();
3445         } else {
3446             containerTargets = new HashSet<>();
3447             for (Attribute app : containerTarget.values) {
3448                 if (!(app instanceof Attribute.Enum attributeEnum)) {
3449                     continue; // recovery
3450                 }
3451                 containerTargets.add(attributeEnum.value.name);
3452             }
3453         }
3454 
3455         Set<Name> containedTargets;
3456         Attribute.Array containedTarget = getAttributeTargetAttribute(contained);
3457         if (containedTarget == null) {
3458             containedTargets = getDefaultTargetSet();
3459         } else {
3460             containedTargets = new HashSet<>();
3461             for (Attribute app : containedTarget.values) {
3462                 if (!(app instanceof Attribute.Enum attributeEnum)) {
3463                     continue; // recovery
3464                 }
3465                 containedTargets.add(attributeEnum.value.name);
3466             }
3467         }
3468 
3469         if (!isTargetSubsetOf(containerTargets, containedTargets)) {
3470             log.error(pos, Errors.InvalidRepeatableAnnotationIncompatibleTarget(container, contained));
3471         }
3472     }
3473 
3474     /* get a set of names for the default target */
3475     private Set<Name> getDefaultTargetSet() {
3476         if (defaultTargets == null) {
3477             defaultTargets = Set.of(defaultTargetMetaInfo());
3478         }
3479 
3480         return defaultTargets;
3481     }
3482     private Set<Name> defaultTargets;
3483 
3484 
3485     /** Checks that s is a subset of t, with respect to ElementType
3486      * semantics, specifically {ANNOTATION_TYPE} is a subset of {TYPE},
3487      * and {TYPE_USE} covers the set {ANNOTATION_TYPE, TYPE, TYPE_USE,
3488      * TYPE_PARAMETER}.
3489      */
3490     private boolean isTargetSubsetOf(Set<Name> s, Set<Name> t) {
3491         // Check that all elements in s are present in t
3492         for (Name n2 : s) {
3493             boolean currentElementOk = false;
3494             for (Name n1 : t) {
3495                 if (n1 == n2) {
3496                     currentElementOk = true;
3497                     break;
3498                 } else if (n1 == names.TYPE && n2 == names.ANNOTATION_TYPE) {
3499                     currentElementOk = true;
3500                     break;
3501                 } else if (n1 == names.TYPE_USE &&
3502                         (n2 == names.TYPE ||
3503                          n2 == names.ANNOTATION_TYPE ||
3504                          n2 == names.TYPE_PARAMETER)) {
3505                     currentElementOk = true;
3506                     break;
3507                 }
3508             }
3509             if (!currentElementOk)
3510                 return false;
3511         }
3512         return true;
3513     }
3514 
3515     private void validateDefault(Symbol container, DiagnosticPosition pos) {
3516         // validate that all other elements of containing type has defaults
3517         Scope scope = container.members();
3518         for(Symbol elm : scope.getSymbols()) {
3519             if (elm.name != names.value &&
3520                 elm.kind == MTH &&
3521                 ((MethodSymbol)elm).defaultValue == null) {
3522                 log.error(pos,
3523                           Errors.InvalidRepeatableAnnotationElemNondefault(container, elm));
3524             }
3525         }
3526     }
3527 
3528     /** Is s a method symbol that overrides a method in a superclass? */
3529     boolean isOverrider(Symbol s) {
3530         if (s.kind != MTH || s.isStatic())
3531             return false;
3532         MethodSymbol m = (MethodSymbol)s;
3533         TypeSymbol owner = (TypeSymbol)m.owner;
3534         for (Type sup : types.closure(owner.type)) {
3535             if (sup == owner.type)
3536                 continue; // skip "this"
3537             Scope scope = sup.tsym.members();
3538             for (Symbol sym : scope.getSymbolsByName(m.name)) {
3539                 if (!sym.isStatic() && m.overrides(sym, owner, types, true))
3540                     return true;
3541             }
3542         }
3543         return false;
3544     }
3545 
3546     /** Is the annotation applicable to types? */
3547     protected boolean isTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
3548         List<Attribute> targets = typeAnnotations.annotationTargets(a.annotationType.type.tsym);
3549         return (targets == null) ?
3550                 (Feature.NO_TARGET_ANNOTATION_APPLICABILITY.allowedInSource(source) && isTypeParameter) :
3551                 targets.stream()
3552                         .anyMatch(attr -> isTypeAnnotation(attr, isTypeParameter));
3553     }
3554     //where
3555         boolean isTypeAnnotation(Attribute a, boolean isTypeParameter) {
3556             Attribute.Enum e = (Attribute.Enum)a;
3557             return (e.value.name == names.TYPE_USE ||
3558                     (isTypeParameter && e.value.name == names.TYPE_PARAMETER));
3559         }
3560 
3561     /** Is the annotation applicable to the symbol? */
3562     Name[] getTargetNames(JCAnnotation a) {
3563         return getTargetNames(a.annotationType.type.tsym);
3564     }
3565 
3566     public Name[] getTargetNames(TypeSymbol annoSym) {
3567         Attribute.Array arr = getAttributeTargetAttribute(annoSym);
3568         Name[] targets;
3569         if (arr == null) {
3570             targets = defaultTargetMetaInfo();
3571         } else {
3572             // TODO: can we optimize this?
3573             targets = new Name[arr.values.length];
3574             for (int i=0; i<arr.values.length; ++i) {
3575                 Attribute app = arr.values[i];
3576                 if (!(app instanceof Attribute.Enum attributeEnum)) {
3577                     return new Name[0];
3578                 }
3579                 targets[i] = attributeEnum.value.name;
3580             }
3581         }
3582         return targets;
3583     }
3584 
3585     boolean annotationApplicable(JCAnnotation a, Symbol s) {
3586         Optional<Set<Name>> targets = getApplicableTargets(a, s);
3587         /* the optional could be empty if the annotation is unknown in that case
3588          * we return that it is applicable and if it is erroneous that should imply
3589          * an error at the declaration site
3590          */
3591         return targets.isEmpty() || targets.isPresent() && !targets.get().isEmpty();
3592     }
3593 
3594     Optional<Set<Name>> getApplicableTargets(JCAnnotation a, Symbol s) {
3595         Attribute.Array arr = getAttributeTargetAttribute(a.annotationType.type.tsym);
3596         Name[] targets;
3597         Set<Name> applicableTargets = new HashSet<>();
3598 
3599         if (arr == null) {
3600             targets = defaultTargetMetaInfo();
3601         } else {
3602             // TODO: can we optimize this?
3603             targets = new Name[arr.values.length];
3604             for (int i=0; i<arr.values.length; ++i) {
3605                 Attribute app = arr.values[i];
3606                 if (!(app instanceof Attribute.Enum attributeEnum)) {
3607                     // recovery
3608                     return Optional.empty();
3609                 }
3610                 targets[i] = attributeEnum.value.name;
3611             }
3612         }
3613         for (Name target : targets) {
3614             if (target == names.TYPE) {
3615                 if (s.kind == TYP)
3616                     applicableTargets.add(names.TYPE);
3617             } else if (target == names.FIELD) {
3618                 if (s.kind == VAR && s.owner.kind != MTH)
3619                     applicableTargets.add(names.FIELD);
3620             } else if (target == names.RECORD_COMPONENT) {
3621                 if (s.getKind() == ElementKind.RECORD_COMPONENT) {
3622                     applicableTargets.add(names.RECORD_COMPONENT);
3623                 }
3624             } else if (target == names.METHOD) {
3625                 if (s.kind == MTH && !s.isConstructor())
3626                     applicableTargets.add(names.METHOD);
3627             } else if (target == names.PARAMETER) {
3628                 if (s.kind == VAR &&
3629                     (s.owner.kind == MTH && (s.flags() & PARAMETER) != 0)) {
3630                     applicableTargets.add(names.PARAMETER);
3631                 }
3632             } else if (target == names.CONSTRUCTOR) {
3633                 if (s.kind == MTH && s.isConstructor())
3634                     applicableTargets.add(names.CONSTRUCTOR);
3635             } else if (target == names.LOCAL_VARIABLE) {
3636                 if (s.kind == VAR && s.owner.kind == MTH &&
3637                       (s.flags() & PARAMETER) == 0) {
3638                     applicableTargets.add(names.LOCAL_VARIABLE);
3639                 }
3640             } else if (target == names.ANNOTATION_TYPE) {
3641                 if (s.kind == TYP && (s.flags() & ANNOTATION) != 0) {
3642                     applicableTargets.add(names.ANNOTATION_TYPE);
3643                 }
3644             } else if (target == names.PACKAGE) {
3645                 if (s.kind == PCK)
3646                     applicableTargets.add(names.PACKAGE);
3647             } else if (target == names.TYPE_USE) {
3648                 if (s.kind == VAR && s.owner.kind == MTH && s.type.hasTag(NONE)) {
3649                     //cannot type annotate implicitly typed locals
3650                     continue;
3651                 } else if (s.kind == TYP || s.kind == VAR ||
3652                         (s.kind == MTH && !s.isConstructor() &&
3653                                 !s.type.getReturnType().hasTag(VOID)) ||
3654                         (s.kind == MTH && s.isConstructor())) {
3655                     applicableTargets.add(names.TYPE_USE);
3656                 }
3657             } else if (target == names.TYPE_PARAMETER) {
3658                 if (s.kind == TYP && s.type.hasTag(TYPEVAR))
3659                     applicableTargets.add(names.TYPE_PARAMETER);
3660             } else if (target == names.MODULE) {
3661                 if (s.kind == MDL)
3662                     applicableTargets.add(names.MODULE);
3663             } else {
3664                 log.error(a, Errors.AnnotationUnrecognizedAttributeName(a.type, target));
3665                 return Optional.empty(); // Unknown ElementType
3666             }
3667         }
3668         return Optional.of(applicableTargets);
3669     }
3670 
3671     Attribute.Array getAttributeTargetAttribute(TypeSymbol s) {
3672         Attribute.Compound atTarget = s.getAnnotationTypeMetadata().getTarget();
3673         if (atTarget == null) return null; // ok, is applicable
3674         Attribute atValue = atTarget.member(names.value);
3675         return (atValue instanceof Attribute.Array attributeArray) ? attributeArray : null;
3676     }
3677 
3678     private Name[] dfltTargetMeta;
3679     private Name[] defaultTargetMetaInfo() {
3680         if (dfltTargetMeta == null) {
3681             ArrayList<Name> defaultTargets = new ArrayList<>();
3682             defaultTargets.add(names.PACKAGE);
3683             defaultTargets.add(names.TYPE);
3684             defaultTargets.add(names.FIELD);
3685             defaultTargets.add(names.METHOD);
3686             defaultTargets.add(names.CONSTRUCTOR);
3687             defaultTargets.add(names.ANNOTATION_TYPE);
3688             defaultTargets.add(names.LOCAL_VARIABLE);
3689             defaultTargets.add(names.PARAMETER);
3690             if (allowRecords) {
3691               defaultTargets.add(names.RECORD_COMPONENT);
3692             }
3693             if (allowModules) {
3694               defaultTargets.add(names.MODULE);
3695             }
3696             dfltTargetMeta = defaultTargets.toArray(new Name[0]);
3697         }
3698         return dfltTargetMeta;
3699     }
3700 
3701     /** Check an annotation value.
3702      *
3703      * @param a The annotation tree to check
3704      * @return true if this annotation tree is valid, otherwise false
3705      */
3706     public boolean validateAnnotationDeferErrors(JCAnnotation a) {
3707         boolean res = false;
3708         final Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
3709         try {
3710             res = validateAnnotation(a);
3711         } finally {
3712             log.popDiagnosticHandler(diagHandler);
3713         }
3714         return res;
3715     }
3716 
3717     private boolean validateAnnotation(JCAnnotation a) {
3718         boolean isValid = true;
3719         AnnotationTypeMetadata metadata = a.annotationType.type.tsym.getAnnotationTypeMetadata();
3720 
3721         // collect an inventory of the annotation elements
3722         Set<MethodSymbol> elements = metadata.getAnnotationElements();
3723 
3724         // remove the ones that are assigned values
3725         for (JCTree arg : a.args) {
3726             if (!arg.hasTag(ASSIGN)) continue; // recovery
3727             JCAssign assign = (JCAssign)arg;
3728             Symbol m = TreeInfo.symbol(assign.lhs);
3729             if (m == null || m.type.isErroneous()) continue;
3730             if (!elements.remove(m)) {
3731                 isValid = false;
3732                 log.error(assign.lhs.pos(),
3733                           Errors.DuplicateAnnotationMemberValue(m.name, a.type));
3734             }
3735         }
3736 
3737         // all the remaining ones better have default values
3738         List<Name> missingDefaults = List.nil();
3739         Set<MethodSymbol> membersWithDefault = metadata.getAnnotationElementsWithDefault();
3740         for (MethodSymbol m : elements) {
3741             if (m.type.isErroneous())
3742                 continue;
3743 
3744             if (!membersWithDefault.contains(m))
3745                 missingDefaults = missingDefaults.append(m.name);
3746         }
3747         missingDefaults = missingDefaults.reverse();
3748         if (missingDefaults.nonEmpty()) {
3749             isValid = false;
3750             Error errorKey = (missingDefaults.size() > 1)
3751                     ? Errors.AnnotationMissingDefaultValue1(a.type, missingDefaults)
3752                     : Errors.AnnotationMissingDefaultValue(a.type, missingDefaults);
3753             log.error(a.pos(), errorKey);
3754         }
3755 
3756         return isValid && validateTargetAnnotationValue(a);
3757     }
3758 
3759     /* Validate the special java.lang.annotation.Target annotation */
3760     boolean validateTargetAnnotationValue(JCAnnotation a) {
3761         // special case: java.lang.annotation.Target must not have
3762         // repeated values in its value member
3763         if (a.annotationType.type.tsym != syms.annotationTargetType.tsym ||
3764                 a.args.tail == null)
3765             return true;
3766 
3767         boolean isValid = true;
3768         if (!a.args.head.hasTag(ASSIGN)) return false; // error recovery
3769         JCAssign assign = (JCAssign) a.args.head;
3770         Symbol m = TreeInfo.symbol(assign.lhs);
3771         if (m.name != names.value) return false;
3772         JCTree rhs = assign.rhs;
3773         if (!rhs.hasTag(NEWARRAY)) return false;
3774         JCNewArray na = (JCNewArray) rhs;
3775         Set<Symbol> targets = new HashSet<>();
3776         for (JCTree elem : na.elems) {
3777             if (!targets.add(TreeInfo.symbol(elem))) {
3778                 isValid = false;
3779                 log.error(elem.pos(), Errors.RepeatedAnnotationTarget);
3780             }
3781         }
3782         return isValid;
3783     }
3784 
3785     void checkDeprecatedAnnotation(DiagnosticPosition pos, Symbol s) {
3786         if (lint.isEnabled(LintCategory.DEP_ANN) && s.isDeprecatableViaAnnotation() &&
3787             (s.flags() & DEPRECATED) != 0 &&
3788             !syms.deprecatedType.isErroneous() &&
3789             s.attribute(syms.deprecatedType.tsym) == null) {
3790             log.warning(LintCategory.DEP_ANN,
3791                     pos, Warnings.MissingDeprecatedAnnotation);
3792         }
3793         // Note: @Deprecated has no effect on local variables, parameters and package decls.
3794         if (lint.isEnabled(LintCategory.DEPRECATION) && !s.isDeprecatableViaAnnotation()) {
3795             if (!syms.deprecatedType.isErroneous() && s.attribute(syms.deprecatedType.tsym) != null) {
3796                 log.warning(LintCategory.DEPRECATION, pos,
3797                             Warnings.DeprecatedAnnotationHasNoEffect(Kinds.kindName(s)));
3798             }
3799         }
3800     }
3801 
3802     void checkDeprecated(final DiagnosticPosition pos, final Symbol other, final Symbol s) {
3803         checkDeprecated(() -> pos, other, s);
3804     }
3805 
3806     void checkDeprecated(Supplier<DiagnosticPosition> pos, final Symbol other, final Symbol s) {
3807         if ( (s.isDeprecatedForRemoval()
3808                 || s.isDeprecated() && !other.isDeprecated())
3809                 && (s.outermostClass() != other.outermostClass() || s.outermostClass() == null)
3810                 && s.kind != Kind.PCK) {
3811             deferredLintHandler.report(() -> warnDeprecated(pos.get(), s));
3812         }
3813     }
3814 
3815     void checkSunAPI(final DiagnosticPosition pos, final Symbol s) {
3816         if ((s.flags() & PROPRIETARY) != 0) {
3817             deferredLintHandler.report(() -> {
3818                 log.mandatoryWarning(pos, Warnings.SunProprietary(s));
3819             });
3820         }
3821     }
3822 
3823     void checkProfile(final DiagnosticPosition pos, final Symbol s) {
3824         if (profile != Profile.DEFAULT && (s.flags() & NOT_IN_PROFILE) != 0) {
3825             log.error(pos, Errors.NotInProfile(s, profile));
3826         }
3827     }
3828 
3829     void checkPreview(DiagnosticPosition pos, Symbol other, Symbol s) {
3830         if ((s.flags() & PREVIEW_API) != 0 && !preview.participatesInPreview(syms, other, s) && !disablePreviewCheck) {
3831             if ((s.flags() & PREVIEW_REFLECTIVE) == 0) {
3832                 if (!preview.isEnabled()) {
3833                     log.error(pos, Errors.IsPreview(s));
3834                 } else {
3835                     preview.markUsesPreview(pos);
3836                     deferredLintHandler.report(() -> warnPreviewAPI(pos, Warnings.IsPreview(s)));
3837                 }
3838             } else {
3839                     deferredLintHandler.report(() -> warnPreviewAPI(pos, Warnings.IsPreviewReflective(s)));
3840             }
3841         }
3842         if (preview.declaredUsingPreviewFeature(s)) {
3843             if (preview.isEnabled()) {
3844                 //for preview disabled do presumably so not need to do anything?
3845                 //If "s" is compiled from source, then there was an error for it already;
3846                 //if "s" is from classfile, there already was an error for the classfile.
3847                 preview.markUsesPreview(pos);
3848                 deferredLintHandler.report(() -> warnDeclaredUsingPreview(pos, s));
3849             }
3850         }
3851     }
3852 
3853 /* *************************************************************************
3854  * Check for recursive annotation elements.
3855  **************************************************************************/
3856 
3857     /** Check for cycles in the graph of annotation elements.
3858      */
3859     void checkNonCyclicElements(JCClassDecl tree) {
3860         if ((tree.sym.flags_field & ANNOTATION) == 0) return;
3861         Assert.check((tree.sym.flags_field & LOCKED) == 0);
3862         try {
3863             tree.sym.flags_field |= LOCKED;
3864             for (JCTree def : tree.defs) {
3865                 if (!def.hasTag(METHODDEF)) continue;
3866                 JCMethodDecl meth = (JCMethodDecl)def;
3867                 checkAnnotationResType(meth.pos(), meth.restype.type);
3868             }
3869         } finally {
3870             tree.sym.flags_field &= ~LOCKED;
3871             tree.sym.flags_field |= ACYCLIC_ANN;
3872         }
3873     }
3874 
3875     void checkNonCyclicElementsInternal(DiagnosticPosition pos, TypeSymbol tsym) {
3876         if ((tsym.flags_field & ACYCLIC_ANN) != 0)
3877             return;
3878         if ((tsym.flags_field & LOCKED) != 0) {
3879             log.error(pos, Errors.CyclicAnnotationElement(tsym));
3880             return;
3881         }
3882         try {
3883             tsym.flags_field |= LOCKED;
3884             for (Symbol s : tsym.members().getSymbols(NON_RECURSIVE)) {
3885                 if (s.kind != MTH)
3886                     continue;
3887                 checkAnnotationResType(pos, ((MethodSymbol)s).type.getReturnType());
3888             }
3889         } finally {
3890             tsym.flags_field &= ~LOCKED;
3891             tsym.flags_field |= ACYCLIC_ANN;
3892         }
3893     }
3894 
3895     void checkAnnotationResType(DiagnosticPosition pos, Type type) {
3896         switch (type.getTag()) {
3897         case CLASS:
3898             if ((type.tsym.flags() & ANNOTATION) != 0)
3899                 checkNonCyclicElementsInternal(pos, type.tsym);
3900             break;
3901         case ARRAY:
3902             checkAnnotationResType(pos, types.elemtype(type));
3903             break;
3904         default:
3905             break; // int etc
3906         }
3907     }
3908 
3909 /* *************************************************************************
3910  * Check for cycles in the constructor call graph.
3911  **************************************************************************/
3912 
3913     /** Check for cycles in the graph of constructors calling other
3914      *  constructors.
3915      */
3916     void checkCyclicConstructors(JCClassDecl tree) {
3917         // use LinkedHashMap so we generate errors deterministically
3918         Map<Symbol,Symbol> callMap = new LinkedHashMap<>();
3919 
3920         // enter each constructor this-call into the map
3921         for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
3922             JCMethodInvocation app = TreeInfo.firstConstructorCall(l.head);
3923             if (app == null) continue;
3924             JCMethodDecl meth = (JCMethodDecl) l.head;
3925             if (TreeInfo.name(app.meth) == names._this) {
3926                 callMap.put(meth.sym, TreeInfo.symbol(app.meth));
3927             } else {
3928                 meth.sym.flags_field |= ACYCLIC;
3929             }
3930         }
3931 
3932         // Check for cycles in the map
3933         Symbol[] ctors = new Symbol[0];
3934         ctors = callMap.keySet().toArray(ctors);
3935         for (Symbol caller : ctors) {
3936             checkCyclicConstructor(tree, caller, callMap);
3937         }
3938     }
3939 
3940     /** Look in the map to see if the given constructor is part of a
3941      *  call cycle.
3942      */
3943     private void checkCyclicConstructor(JCClassDecl tree, Symbol ctor,
3944                                         Map<Symbol,Symbol> callMap) {
3945         if (ctor != null && (ctor.flags_field & ACYCLIC) == 0) {
3946             if ((ctor.flags_field & LOCKED) != 0) {
3947                 log.error(TreeInfo.diagnosticPositionFor(ctor, tree, false, t -> t.hasTag(IDENT)),
3948                           Errors.RecursiveCtorInvocation);
3949             } else {
3950                 ctor.flags_field |= LOCKED;
3951                 checkCyclicConstructor(tree, callMap.remove(ctor), callMap);
3952                 ctor.flags_field &= ~LOCKED;
3953             }
3954             ctor.flags_field |= ACYCLIC;
3955         }
3956     }
3957 
3958 /* *************************************************************************
3959  * Miscellaneous
3960  **************************************************************************/
3961 
3962     /**
3963      *  Check for division by integer constant zero
3964      *  @param pos           Position for error reporting.
3965      *  @param operator      The operator for the expression
3966      *  @param operand       The right hand operand for the expression
3967      */
3968     void checkDivZero(final DiagnosticPosition pos, Symbol operator, Type operand) {
3969         if (operand.constValue() != null
3970             && operand.getTag().isSubRangeOf(LONG)
3971             && ((Number) (operand.constValue())).longValue() == 0) {
3972             int opc = ((OperatorSymbol)operator).opcode;
3973             if (opc == ByteCodes.idiv || opc == ByteCodes.imod
3974                 || opc == ByteCodes.ldiv || opc == ByteCodes.lmod) {
3975                 deferredLintHandler.report(() -> warnDivZero(pos));
3976             }
3977         }
3978     }
3979 
3980     /**
3981      *  Check for possible loss of precission
3982      *  @param pos           Position for error reporting.
3983      *  @param found    The computed type of the tree
3984      *  @param req  The computed type of the tree
3985      */
3986     void checkLossOfPrecision(final DiagnosticPosition pos, Type found, Type req) {
3987         if (found.isNumeric() && req.isNumeric() && !types.isAssignable(found, req)) {
3988             deferredLintHandler.report(() -> {
3989                 if (lint.isEnabled(LintCategory.LOSSY_CONVERSIONS))
3990                     log.warning(LintCategory.LOSSY_CONVERSIONS,
3991                             pos, Warnings.PossibleLossOfPrecision(found, req));
3992             });
3993         }
3994     }
3995 
3996     /**
3997      * Check for empty statements after if
3998      */
3999     void checkEmptyIf(JCIf tree) {
4000         if (tree.thenpart.hasTag(SKIP) && tree.elsepart == null &&
4001                 lint.isEnabled(LintCategory.EMPTY))
4002             log.warning(LintCategory.EMPTY, tree.thenpart.pos(), Warnings.EmptyIf);
4003     }
4004 
4005     /** Check that symbol is unique in given scope.
4006      *  @param pos           Position for error reporting.
4007      *  @param sym           The symbol.
4008      *  @param s             The scope.
4009      */
4010     boolean checkUnique(DiagnosticPosition pos, Symbol sym, Scope s) {
4011         if (sym.type.isErroneous())
4012             return true;
4013         if (sym.owner.name == names.any) return false;
4014         for (Symbol byName : s.getSymbolsByName(sym.name, NON_RECURSIVE)) {
4015             if (sym != byName &&
4016                     (byName.flags() & CLASH) == 0 &&
4017                     sym.kind == byName.kind &&
4018                     sym.name != names.error &&
4019                     (sym.kind != MTH ||
4020                      types.hasSameArgs(sym.type, byName.type) ||
4021                      types.hasSameArgs(types.erasure(sym.type), types.erasure(byName.type)))) {
4022                 if ((sym.flags() & VARARGS) != (byName.flags() & VARARGS)) {
4023                     sym.flags_field |= CLASH;
4024                     varargsDuplicateError(pos, sym, byName);
4025                     return true;
4026                 } else if (sym.kind == MTH && !types.hasSameArgs(sym.type, byName.type, false)) {
4027                     duplicateErasureError(pos, sym, byName);
4028                     sym.flags_field |= CLASH;
4029                     return true;
4030                 } else if ((sym.flags() & MATCH_BINDING) != 0 &&
4031                            (byName.flags() & MATCH_BINDING) != 0 &&
4032                            (byName.flags() & MATCH_BINDING_TO_OUTER) == 0) {
4033                     if (!sym.type.isErroneous()) {
4034                         log.error(pos, Errors.MatchBindingExists);
4035                         sym.flags_field |= CLASH;
4036                     }
4037                     return false;
4038                 } else {
4039                     duplicateError(pos, byName);
4040                     return false;
4041                 }
4042             }
4043         }
4044         return true;
4045     }
4046 
4047     /** Report duplicate declaration error.
4048      */
4049     void duplicateErasureError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
4050         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
4051             log.error(pos, Errors.NameClashSameErasure(sym1, sym2));
4052         }
4053     }
4054 
4055     /**Check that types imported through the ordinary imports don't clash with types imported
4056      * by other (static or ordinary) imports. Note that two static imports may import two clashing
4057      * types without an error on the imports.
4058      * @param toplevel       The toplevel tree for which the test should be performed.
4059      */
4060     void checkImportsUnique(JCCompilationUnit toplevel) {
4061         WriteableScope ordinallyImportedSoFar = WriteableScope.create(toplevel.packge);
4062         WriteableScope staticallyImportedSoFar = WriteableScope.create(toplevel.packge);
4063         WriteableScope topLevelScope = toplevel.toplevelScope;
4064 
4065         for (JCTree def : toplevel.defs) {
4066             if (!def.hasTag(IMPORT))
4067                 continue;
4068 
4069             JCImport imp = (JCImport) def;
4070 
4071             if (imp.importScope == null)
4072                 continue;
4073 
4074             for (Symbol sym : imp.importScope.getSymbols(sym -> sym.kind == TYP)) {
4075                 if (imp.isStatic()) {
4076                     checkUniqueImport(imp.pos(), ordinallyImportedSoFar, staticallyImportedSoFar, topLevelScope, sym, true);
4077                     staticallyImportedSoFar.enter(sym);
4078                 } else {
4079                     checkUniqueImport(imp.pos(), ordinallyImportedSoFar, staticallyImportedSoFar, topLevelScope, sym, false);
4080                     ordinallyImportedSoFar.enter(sym);
4081                 }
4082             }
4083 
4084             imp.importScope = null;
4085         }
4086     }
4087 
4088     /** Check that single-type import is not already imported or top-level defined,
4089      *  but make an exception for two single-type imports which denote the same type.
4090      *  @param pos                     Position for error reporting.
4091      *  @param ordinallyImportedSoFar  A Scope containing types imported so far through
4092      *                                 ordinary imports.
4093      *  @param staticallyImportedSoFar A Scope containing types imported so far through
4094      *                                 static imports.
4095      *  @param topLevelScope           The current file's top-level Scope
4096      *  @param sym                     The symbol.
4097      *  @param staticImport            Whether or not this was a static import
4098      */
4099     private boolean checkUniqueImport(DiagnosticPosition pos, Scope ordinallyImportedSoFar,
4100                                       Scope staticallyImportedSoFar, Scope topLevelScope,
4101                                       Symbol sym, boolean staticImport) {
4102         Predicate<Symbol> duplicates = candidate -> candidate != sym && !candidate.type.isErroneous();
4103         Symbol ordinaryClashing = ordinallyImportedSoFar.findFirst(sym.name, duplicates);
4104         Symbol staticClashing = null;
4105         if (ordinaryClashing == null && !staticImport) {
4106             staticClashing = staticallyImportedSoFar.findFirst(sym.name, duplicates);
4107         }
4108         if (ordinaryClashing != null || staticClashing != null) {
4109             if (ordinaryClashing != null)
4110                 log.error(pos, Errors.AlreadyDefinedSingleImport(ordinaryClashing));
4111             else
4112                 log.error(pos, Errors.AlreadyDefinedStaticSingleImport(staticClashing));
4113             return false;
4114         }
4115         Symbol clashing = topLevelScope.findFirst(sym.name, duplicates);
4116         if (clashing != null) {
4117             log.error(pos, Errors.AlreadyDefinedThisUnit(clashing));
4118             return false;
4119         }
4120         return true;
4121     }
4122 
4123     /** Check that a qualified name is in canonical form (for import decls).
4124      */
4125     public void checkCanonical(JCTree tree) {
4126         if (!isCanonical(tree))
4127             log.error(tree.pos(),
4128                       Errors.ImportRequiresCanonical(TreeInfo.symbol(tree)));
4129     }
4130         // where
4131         private boolean isCanonical(JCTree tree) {
4132             while (tree.hasTag(SELECT)) {
4133                 JCFieldAccess s = (JCFieldAccess) tree;
4134                 if (s.sym.owner.getQualifiedName() != TreeInfo.symbol(s.selected).getQualifiedName())
4135                     return false;
4136                 tree = s.selected;
4137             }
4138             return true;
4139         }
4140 
4141     /** Check that an auxiliary class is not accessed from any other file than its own.
4142      */
4143     void checkForBadAuxiliaryClassAccess(DiagnosticPosition pos, Env<AttrContext> env, ClassSymbol c) {
4144         if (lint.isEnabled(Lint.LintCategory.AUXILIARYCLASS) &&
4145             (c.flags() & AUXILIARY) != 0 &&
4146             rs.isAccessible(env, c) &&
4147             !fileManager.isSameFile(c.sourcefile, env.toplevel.sourcefile))
4148         {
4149             log.warning(pos,
4150                         Warnings.AuxiliaryClassAccessedFromOutsideOfItsSourceFile(c, c.sourcefile));
4151         }
4152     }
4153 
4154     /**
4155      * Check for a default constructor in an exported package.
4156      */
4157     void checkDefaultConstructor(ClassSymbol c, DiagnosticPosition pos) {
4158         if (lint.isEnabled(LintCategory.MISSING_EXPLICIT_CTOR) &&
4159             ((c.flags() & (ENUM | RECORD)) == 0) &&
4160             !c.isAnonymous() &&
4161             ((c.flags() & (PUBLIC | PROTECTED)) != 0) &&
4162             Feature.MODULES.allowedInSource(source)) {
4163             NestingKind nestingKind = c.getNestingKind();
4164             switch (nestingKind) {
4165                 case ANONYMOUS,
4166                      LOCAL -> {return;}
4167                 case TOP_LEVEL -> {;} // No additional checks needed
4168                 case MEMBER -> {
4169                     // For nested member classes, all the enclosing
4170                     // classes must be public or protected.
4171                     Symbol owner = c.owner;
4172                     while (owner != null && owner.kind == TYP) {
4173                         if ((owner.flags() & (PUBLIC | PROTECTED)) == 0)
4174                             return;
4175                         owner = owner.owner;
4176                     }
4177                 }
4178             }
4179 
4180             // Only check classes in named packages exported by its module
4181             PackageSymbol pkg = c.packge();
4182             if (!pkg.isUnnamed()) {
4183                 ModuleSymbol modle = pkg.modle;
4184                 for (ExportsDirective exportDir : modle.exports) {
4185                     // Report warning only if the containing
4186                     // package is unconditionally exported
4187                     if (exportDir.packge.equals(pkg)) {
4188                         if (exportDir.modules == null || exportDir.modules.isEmpty()) {
4189                             // Warning may be suppressed by
4190                             // annotations; check again for being
4191                             // enabled in the deferred context.
4192                             deferredLintHandler.report(() -> {
4193                                 if (lint.isEnabled(LintCategory.MISSING_EXPLICIT_CTOR))
4194                                    log.warning(LintCategory.MISSING_EXPLICIT_CTOR,
4195                                                pos, Warnings.MissingExplicitCtor(c, pkg, modle));
4196                                                        });
4197                         } else {
4198                             return;
4199                         }
4200                     }
4201                 }
4202             }
4203         }
4204         return;
4205     }
4206 
4207     private class ConversionWarner extends Warner {
4208         final String uncheckedKey;
4209         final Type found;
4210         final Type expected;
4211         public ConversionWarner(DiagnosticPosition pos, String uncheckedKey, Type found, Type expected) {
4212             super(pos);
4213             this.uncheckedKey = uncheckedKey;
4214             this.found = found;
4215             this.expected = expected;
4216         }
4217 
4218         @Override
4219         public void warn(LintCategory lint) {
4220             boolean warned = this.warned;
4221             super.warn(lint);
4222             if (warned) return; // suppress redundant diagnostics
4223             switch (lint) {
4224                 case UNCHECKED:
4225                     Check.this.warnUnchecked(pos(), Warnings.ProbFoundReq(diags.fragment(uncheckedKey), found, expected));
4226                     break;
4227                 case VARARGS:
4228                     if (method != null &&
4229                             method.attribute(syms.trustMeType.tsym) != null &&
4230                             isTrustMeAllowedOnMethod(method) &&
4231                             !types.isReifiable(method.type.getParameterTypes().last())) {
4232                         Check.this.warnUnsafeVararg(pos(), Warnings.VarargsUnsafeUseVarargsParam(method.params.last()));
4233                     }
4234                     break;
4235                 default:
4236                     throw new AssertionError("Unexpected lint: " + lint);
4237             }
4238         }
4239     }
4240 
4241     public Warner castWarner(DiagnosticPosition pos, Type found, Type expected) {
4242         return new ConversionWarner(pos, "unchecked.cast.to.type", found, expected);
4243     }
4244 
4245     public Warner convertWarner(DiagnosticPosition pos, Type found, Type expected) {
4246         return new ConversionWarner(pos, "unchecked.assign", found, expected);
4247     }
4248 
4249     public void checkFunctionalInterface(JCClassDecl tree, ClassSymbol cs) {
4250         Compound functionalType = cs.attribute(syms.functionalInterfaceType.tsym);
4251 
4252         if (functionalType != null) {
4253             try {
4254                 types.findDescriptorSymbol((TypeSymbol)cs);
4255             } catch (Types.FunctionDescriptorLookupError ex) {
4256                 DiagnosticPosition pos = tree.pos();
4257                 for (JCAnnotation a : tree.getModifiers().annotations) {
4258                     if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
4259                         pos = a.pos();
4260                         break;
4261                     }
4262                 }
4263                 log.error(pos, Errors.BadFunctionalIntfAnno1(ex.getDiagnostic()));
4264             }
4265         }
4266     }
4267 
4268     public void checkImportsResolvable(final JCCompilationUnit toplevel) {
4269         for (final JCImport imp : toplevel.getImports()) {
4270             if (!imp.staticImport || !imp.qualid.hasTag(SELECT))
4271                 continue;
4272             final JCFieldAccess select = imp.qualid;
4273             final Symbol origin;
4274             if (select.name == names.asterisk || (origin = TreeInfo.symbol(select.selected)) == null || origin.kind != TYP)
4275                 continue;
4276 
4277             TypeSymbol site = (TypeSymbol) TreeInfo.symbol(select.selected);
4278             if (!checkTypeContainsImportableElement(site, site, toplevel.packge, select.name, new HashSet<Symbol>())) {
4279                 log.error(imp.pos(),
4280                           Errors.CantResolveLocation(KindName.STATIC,
4281                                                      select.name,
4282                                                      null,
4283                                                      null,
4284                                                      Fragments.Location(kindName(site),
4285                                                                         site,
4286                                                                         null)));
4287             }
4288         }
4289     }
4290 
4291     // Check that packages imported are in scope (JLS 7.4.3, 6.3, 6.5.3.1, 6.5.3.2)
4292     public void checkImportedPackagesObservable(final JCCompilationUnit toplevel) {
4293         OUTER: for (JCImport imp : toplevel.getImports()) {
4294             if (!imp.staticImport && TreeInfo.name(imp.qualid) == names.asterisk) {
4295                 TypeSymbol tsym = imp.qualid.selected.type.tsym;
4296                 if (tsym.kind == PCK && tsym.members().isEmpty() &&
4297                     !(Feature.IMPORT_ON_DEMAND_OBSERVABLE_PACKAGES.allowedInSource(source) && tsym.exists())) {
4298                     log.error(DiagnosticFlag.RESOLVE_ERROR, imp.pos, Errors.DoesntExist(tsym));
4299                 }
4300             }
4301         }
4302     }
4303 
4304     private boolean checkTypeContainsImportableElement(TypeSymbol tsym, TypeSymbol origin, PackageSymbol packge, Name name, Set<Symbol> processed) {
4305         if (tsym == null || !processed.add(tsym))
4306             return false;
4307 
4308             // also search through inherited names
4309         if (checkTypeContainsImportableElement(types.supertype(tsym.type).tsym, origin, packge, name, processed))
4310             return true;
4311 
4312         for (Type t : types.interfaces(tsym.type))
4313             if (checkTypeContainsImportableElement(t.tsym, origin, packge, name, processed))
4314                 return true;
4315 
4316         for (Symbol sym : tsym.members().getSymbolsByName(name)) {
4317             if (sym.isStatic() &&
4318                 importAccessible(sym, packge) &&
4319                 sym.isMemberOf(origin, types)) {
4320                 return true;
4321             }
4322         }
4323 
4324         return false;
4325     }
4326 
4327     // is the sym accessible everywhere in packge?
4328     public boolean importAccessible(Symbol sym, PackageSymbol packge) {
4329         try {
4330             int flags = (int)(sym.flags() & AccessFlags);
4331             switch (flags) {
4332             default:
4333             case PUBLIC:
4334                 return true;
4335             case PRIVATE:
4336                 return false;
4337             case 0:
4338             case PROTECTED:
4339                 return sym.packge() == packge;
4340             }
4341         } catch (ClassFinder.BadClassFile err) {
4342             throw err;
4343         } catch (CompletionFailure ex) {
4344             return false;
4345         }
4346     }
4347 
4348     public Type checkProcessorType(JCExpression processor, Type resultType, Env<AttrContext> env) {
4349         Type processorType = processor.type;
4350         Type interfaceType = types.asSuper(processorType, syms.processorType.tsym);
4351 
4352         if (interfaceType != null) {
4353             List<Type> typeArguments = interfaceType.getTypeArguments();
4354 
4355             if (typeArguments.size() == 2) {
4356                 resultType = typeArguments.head;
4357             } else {
4358                 log.error(DiagnosticFlag.RESOLVE_ERROR, processor.pos,
4359                         Errors.ProcessorTypeCannotBeARawType(processorType.tsym));
4360             }
4361         } else {
4362             log.error(DiagnosticFlag.RESOLVE_ERROR, processor.pos,
4363                     Errors.NotAProcessorType(processorType.tsym));
4364         }
4365 
4366         return resultType;
4367     }
4368 
4369     public void checkLeaksNotAccessible(Env<AttrContext> env, JCClassDecl check) {
4370         JCCompilationUnit toplevel = env.toplevel;
4371 
4372         if (   toplevel.modle == syms.unnamedModule
4373             || toplevel.modle == syms.noModule
4374             || (check.sym.flags() & COMPOUND) != 0) {
4375             return ;
4376         }
4377 
4378         ExportsDirective currentExport = findExport(toplevel.packge);
4379 
4380         if (   currentExport == null //not exported
4381             || currentExport.modules != null) //don't check classes in qualified export
4382             return ;
4383 
4384         new TreeScanner() {
4385             Lint lint = env.info.lint;
4386             boolean inSuperType;
4387 
4388             @Override
4389             public void visitBlock(JCBlock tree) {
4390             }
4391             @Override
4392             public void visitMethodDef(JCMethodDecl tree) {
4393                 if (!isAPISymbol(tree.sym))
4394                     return;
4395                 Lint prevLint = lint;
4396                 try {
4397                     lint = lint.augment(tree.sym);
4398                     if (lint.isEnabled(LintCategory.EXPORTS)) {
4399                         super.visitMethodDef(tree);
4400                     }
4401                 } finally {
4402                     lint = prevLint;
4403                 }
4404             }
4405             @Override
4406             public void visitVarDef(JCVariableDecl tree) {
4407                 if (!isAPISymbol(tree.sym) && tree.sym.owner.kind != MTH)
4408                     return;
4409                 Lint prevLint = lint;
4410                 try {
4411                     lint = lint.augment(tree.sym);
4412                     if (lint.isEnabled(LintCategory.EXPORTS)) {
4413                         scan(tree.mods);
4414                         scan(tree.vartype);
4415                     }
4416                 } finally {
4417                     lint = prevLint;
4418                 }
4419             }
4420             @Override
4421             public void visitClassDef(JCClassDecl tree) {
4422                 if (tree != check)
4423                     return ;
4424 
4425                 if (!isAPISymbol(tree.sym))
4426                     return ;
4427 
4428                 Lint prevLint = lint;
4429                 try {
4430                     lint = lint.augment(tree.sym);
4431                     if (lint.isEnabled(LintCategory.EXPORTS)) {
4432                         scan(tree.mods);
4433                         scan(tree.typarams);
4434                         try {
4435                             inSuperType = true;
4436                             scan(tree.extending);
4437                             scan(tree.implementing);
4438                         } finally {
4439                             inSuperType = false;
4440                         }
4441                         scan(tree.defs);
4442                     }
4443                 } finally {
4444                     lint = prevLint;
4445                 }
4446             }
4447             @Override
4448             public void visitTypeApply(JCTypeApply tree) {
4449                 scan(tree.clazz);
4450                 boolean oldInSuperType = inSuperType;
4451                 try {
4452                     inSuperType = false;
4453                     scan(tree.arguments);
4454                 } finally {
4455                     inSuperType = oldInSuperType;
4456                 }
4457             }
4458             @Override
4459             public void visitIdent(JCIdent tree) {
4460                 Symbol sym = TreeInfo.symbol(tree);
4461                 if (sym.kind == TYP && !sym.type.hasTag(TYPEVAR)) {
4462                     checkVisible(tree.pos(), sym, toplevel.packge, inSuperType);
4463                 }
4464             }
4465 
4466             @Override
4467             public void visitSelect(JCFieldAccess tree) {
4468                 Symbol sym = TreeInfo.symbol(tree);
4469                 Symbol sitesym = TreeInfo.symbol(tree.selected);
4470                 if (sym.kind == TYP && sitesym.kind == PCK) {
4471                     checkVisible(tree.pos(), sym, toplevel.packge, inSuperType);
4472                 } else {
4473                     super.visitSelect(tree);
4474                 }
4475             }
4476 
4477             @Override
4478             public void visitAnnotation(JCAnnotation tree) {
4479                 if (tree.attribute.type.tsym.getAnnotation(java.lang.annotation.Documented.class) != null)
4480                     super.visitAnnotation(tree);
4481             }
4482 
4483         }.scan(check);
4484     }
4485         //where:
4486         private ExportsDirective findExport(PackageSymbol pack) {
4487             for (ExportsDirective d : pack.modle.exports) {
4488                 if (d.packge == pack)
4489                     return d;
4490             }
4491 
4492             return null;
4493         }
4494         private boolean isAPISymbol(Symbol sym) {
4495             while (sym.kind != PCK) {
4496                 if ((sym.flags() & Flags.PUBLIC) == 0 && (sym.flags() & Flags.PROTECTED) == 0) {
4497                     return false;
4498                 }
4499                 sym = sym.owner;
4500             }
4501             return true;
4502         }
4503         private void checkVisible(DiagnosticPosition pos, Symbol what, PackageSymbol inPackage, boolean inSuperType) {
4504             if (!isAPISymbol(what) && !inSuperType) { //package private/private element
4505                 log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessible(kindName(what), what, what.packge().modle));
4506                 return ;
4507             }
4508 
4509             PackageSymbol whatPackage = what.packge();
4510             ExportsDirective whatExport = findExport(whatPackage);
4511             ExportsDirective inExport = findExport(inPackage);
4512 
4513             if (whatExport == null) { //package not exported:
4514                 log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleUnexported(kindName(what), what, what.packge().modle));
4515                 return ;
4516             }
4517 
4518             if (whatExport.modules != null) {
4519                 if (inExport.modules == null || !whatExport.modules.containsAll(inExport.modules)) {
4520                     log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleUnexportedQualified(kindName(what), what, what.packge().modle));
4521                 }
4522             }
4523 
4524             if (whatPackage.modle != inPackage.modle && whatPackage.modle != syms.java_base) {
4525                 //check that relativeTo.modle requires transitive what.modle, somehow:
4526                 List<ModuleSymbol> todo = List.of(inPackage.modle);
4527 
4528                 while (todo.nonEmpty()) {
4529                     ModuleSymbol current = todo.head;
4530                     todo = todo.tail;
4531                     if (current == whatPackage.modle)
4532                         return ; //OK
4533                     if ((current.flags() & Flags.AUTOMATIC_MODULE) != 0)
4534                         continue; //for automatic modules, don't look into their dependencies
4535                     for (RequiresDirective req : current.requires) {
4536                         if (req.isTransitive()) {
4537                             todo = todo.prepend(req.module);
4538                         }
4539                     }
4540                 }
4541 
4542                 log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleNotRequiredTransitive(kindName(what), what, what.packge().modle));
4543             }
4544         }
4545 
4546     void checkModuleExists(final DiagnosticPosition pos, ModuleSymbol msym) {
4547         if (msym.kind != MDL) {
4548             deferredLintHandler.report(() -> {
4549                 if (lint.isEnabled(LintCategory.MODULE))
4550                     log.warning(LintCategory.MODULE, pos, Warnings.ModuleNotFound(msym));
4551             });
4552         }
4553     }
4554 
4555     void checkPackageExistsForOpens(final DiagnosticPosition pos, PackageSymbol packge) {
4556         if (packge.members().isEmpty() &&
4557             ((packge.flags() & Flags.HAS_RESOURCE) == 0)) {
4558             deferredLintHandler.report(() -> {
4559                 if (lint.isEnabled(LintCategory.OPENS))
4560                     log.warning(pos, Warnings.PackageEmptyOrNotFound(packge));
4561             });
4562         }
4563     }
4564 
4565     void checkModuleRequires(final DiagnosticPosition pos, final RequiresDirective rd) {
4566         if ((rd.module.flags() & Flags.AUTOMATIC_MODULE) != 0) {
4567             deferredLintHandler.report(() -> {
4568                 if (rd.isTransitive() && lint.isEnabled(LintCategory.REQUIRES_TRANSITIVE_AUTOMATIC)) {
4569                     log.warning(pos, Warnings.RequiresTransitiveAutomatic);
4570                 } else if (lint.isEnabled(LintCategory.REQUIRES_AUTOMATIC)) {
4571                     log.warning(pos, Warnings.RequiresAutomatic);
4572                 }
4573             });
4574         }
4575     }
4576 
4577     /**
4578      * Verify the case labels conform to the constraints. Checks constraints related
4579      * combinations of patterns and other labels.
4580      *
4581      * @param cases the cases that should be checked.
4582      */
4583     void checkSwitchCaseStructure(List<JCCase> cases) {
4584         for (List<JCCase> l = cases; l.nonEmpty(); l = l.tail) {
4585             JCCase c = l.head;
4586             if (c.labels.head instanceof JCConstantCaseLabel constLabel) {
4587                 if (TreeInfo.isNull(constLabel.expr)) {
4588                     if (c.labels.tail.nonEmpty()) {
4589                         if (c.labels.tail.head instanceof JCDefaultCaseLabel defLabel) {
4590                             if (c.labels.tail.tail.nonEmpty()) {
4591                                 log.error(c.labels.tail.tail.head.pos(), Errors.InvalidCaseLabelCombination);
4592                             }
4593                         } else {
4594                             log.error(c.labels.tail.head.pos(), Errors.InvalidCaseLabelCombination);
4595                         }
4596                     }
4597                 } else {
4598                     for (JCCaseLabel label : c.labels.tail) {
4599                         if (!(label instanceof JCConstantCaseLabel) || TreeInfo.isNullCaseLabel(label)) {
4600                             log.error(label.pos(), Errors.InvalidCaseLabelCombination);
4601                             break;
4602                         }
4603                     }
4604                 }
4605             } else if (c.labels.tail.nonEmpty()) {
4606                 var patterCaseLabels = c.labels.stream().filter(ll -> ll instanceof JCPatternCaseLabel).map(cl -> (JCPatternCaseLabel)cl);
4607                 var allUnderscore = patterCaseLabels.allMatch(pcl -> !hasBindings(pcl.getPattern()));
4608 
4609                 if (!allUnderscore) {
4610                     log.error(c.labels.tail.head.pos(), Errors.FlowsThroughFromPattern);
4611                 }
4612 
4613                 boolean allPatternCaseLabels = c.labels.stream().allMatch(p -> p instanceof JCPatternCaseLabel);
4614 
4615                 if (allPatternCaseLabels) {
4616                     preview.checkSourceLevel(c.labels.tail.head.pos(), Feature.UNNAMED_VARIABLES);
4617                 }
4618 
4619                 for (JCCaseLabel label : c.labels.tail) {
4620                     if (label instanceof JCConstantCaseLabel) {
4621                         log.error(label.pos(), Errors.InvalidCaseLabelCombination);
4622                         break;
4623                     }
4624                 }
4625             }
4626         }
4627 
4628         boolean isCaseStatementGroup = cases.nonEmpty() &&
4629                                        cases.head.caseKind == CaseTree.CaseKind.STATEMENT;
4630 
4631         if (isCaseStatementGroup) {
4632             boolean previousCompletessNormally = false;
4633             for (List<JCCase> l = cases; l.nonEmpty(); l = l.tail) {
4634                 JCCase c = l.head;
4635                 if (previousCompletessNormally &&
4636                     c.stats.nonEmpty() &&
4637                     c.labels.head instanceof JCPatternCaseLabel patternLabel &&
4638                     hasBindings(patternLabel.pat)) {
4639                     log.error(c.labels.head.pos(), Errors.FlowsThroughToPattern);
4640                 } else if (c.stats.isEmpty() &&
4641                            c.labels.head instanceof JCPatternCaseLabel patternLabel &&
4642                            hasBindings(patternLabel.pat) &&
4643                            hasStatements(l.tail)) {
4644                     log.error(c.labels.head.pos(), Errors.FlowsThroughFromPattern);
4645                 }
4646                 previousCompletessNormally = c.completesNormally;
4647             }
4648         }
4649     }
4650 
4651     boolean hasBindings(JCPattern p) {
4652         boolean[] bindings = new boolean[1];
4653 
4654         new TreeScanner() {
4655             @Override
4656             public void visitBindingPattern(JCBindingPattern tree) {
4657                 bindings[0] = !tree.var.sym.isUnnamedVariable();
4658                 super.visitBindingPattern(tree);
4659             }
4660         }.scan(p);
4661 
4662         return bindings[0];
4663     }
4664 
4665     boolean hasStatements(List<JCCase> cases) {
4666         for (List<JCCase> l = cases; l.nonEmpty(); l = l.tail) {
4667             if (l.head.stats.nonEmpty()) {
4668                 return true;
4669             }
4670         }
4671 
4672         return false;
4673     }
4674     void checkSwitchCaseLabelDominated(List<JCCase> cases) {
4675         List<Pair<JCCase, JCCaseLabel>> caseLabels = List.nil();
4676         boolean seenDefault = false;
4677         boolean seenDefaultLabel = false;
4678         boolean warnDominatedByDefault = false;
4679         for (List<JCCase> l = cases; l.nonEmpty(); l = l.tail) {
4680             JCCase c = l.head;
4681             for (JCCaseLabel label : c.labels) {
4682                 if (label.hasTag(DEFAULTCASELABEL)) {
4683                     seenDefault = true;
4684                     seenDefaultLabel |=
4685                             TreeInfo.isNullCaseLabel(c.labels.head);
4686                     continue;
4687                 }
4688                 if (TreeInfo.isNullCaseLabel(label)) {
4689                     if (seenDefault) {
4690                         log.error(label.pos(), Errors.PatternDominated);
4691                     }
4692                     continue;
4693                 }
4694                 if (seenDefault && !warnDominatedByDefault) {
4695                     if (label.hasTag(PATTERNCASELABEL) ||
4696                         (label instanceof JCConstantCaseLabel && seenDefaultLabel)) {
4697                         log.error(label.pos(), Errors.PatternDominated);
4698                         warnDominatedByDefault = true;
4699                     }
4700                 }
4701                 Type currentType = labelType(label);
4702                 for (Pair<JCCase, JCCaseLabel> caseAndLabel : caseLabels) {
4703                     JCCase testCase = caseAndLabel.fst;
4704                     JCCaseLabel testCaseLabel = caseAndLabel.snd;
4705                     Type testType = labelType(testCaseLabel);
4706                     if (types.isSubtype(currentType, testType) &&
4707                         !currentType.hasTag(ERROR) && !testType.hasTag(ERROR)) {
4708                         //the current label is potentially dominated by the existing (test) label, check:
4709                         boolean dominated = false;
4710                         if (label instanceof JCConstantCaseLabel) {
4711                             dominated |= !(testCaseLabel instanceof JCConstantCaseLabel) &&
4712                                          TreeInfo.unguardedCase(testCase);
4713                         } else if (label instanceof JCPatternCaseLabel patternCL &&
4714                                    testCaseLabel instanceof JCPatternCaseLabel testPatternCaseLabel &&
4715                                    (testCase.equals(c) || TreeInfo.unguardedCase(testCase))) {
4716                             dominated = patternDominated(testPatternCaseLabel.pat,
4717                                                          patternCL.pat);
4718                         }
4719                         if (dominated) {
4720                             log.error(label.pos(), Errors.PatternDominated);
4721                         }
4722                     }
4723                 }
4724                 caseLabels = caseLabels.prepend(Pair.of(c, label));
4725             }
4726         }
4727     }
4728         //where:
4729         private Type labelType(JCCaseLabel label) {
4730             return types.erasure(switch (label.getTag()) {
4731                 case PATTERNCASELABEL -> ((JCPatternCaseLabel) label).pat.type;
4732                 case CONSTANTCASELABEL -> types.boxedTypeOrType(((JCConstantCaseLabel) label).expr.type);
4733                 default -> throw Assert.error("Unexpected tree kind: " + label.getTag());
4734             });
4735         }
4736         private boolean patternDominated(JCPattern existingPattern, JCPattern currentPattern) {
4737             Type existingPatternType = types.erasure(existingPattern.type);
4738             Type currentPatternType = types.erasure(currentPattern.type);
4739             if (existingPatternType.isPrimitive() ^ currentPatternType.isPrimitive()) {
4740                 return false;
4741             }
4742             if (existingPatternType.isPrimitive()) {
4743                 return types.isSameType(existingPatternType, currentPatternType);
4744             } else {
4745                 if (!types.isSubtype(currentPatternType, existingPatternType)) {
4746                     return false;
4747                 }
4748             }
4749             if (currentPattern instanceof JCBindingPattern ||
4750                 currentPattern instanceof JCAnyPattern) {
4751                 return existingPattern instanceof JCBindingPattern ||
4752                        existingPattern instanceof JCAnyPattern;
4753             } else if (currentPattern instanceof JCRecordPattern currentRecordPattern) {
4754                 if (existingPattern instanceof JCBindingPattern ||
4755                     existingPattern instanceof JCAnyPattern) {
4756                     return true;
4757                 } else if (existingPattern instanceof JCRecordPattern existingRecordPattern) {
4758                     List<JCPattern> existingNested = existingRecordPattern.nested;
4759                     List<JCPattern> currentNested = currentRecordPattern.nested;
4760                     if (existingNested.size() != currentNested.size()) {
4761                         return false;
4762                     }
4763                     while (existingNested.nonEmpty()) {
4764                         if (!patternDominated(existingNested.head, currentNested.head)) {
4765                             return false;
4766                         }
4767                         existingNested = existingNested.tail;
4768                         currentNested = currentNested.tail;
4769                     }
4770                     return true;
4771                 } else {
4772                     Assert.error("Unknown pattern: " + existingPattern.getTag());
4773                 }
4774             } else {
4775                 Assert.error("Unknown pattern: " + currentPattern.getTag());
4776             }
4777             return false;
4778         }
4779 
4780     /** check if a type is a subtype of Externalizable, if that is available. */
4781     boolean isExternalizable(Type t) {
4782         try {
4783             syms.externalizableType.complete();
4784         } catch (CompletionFailure e) {
4785             return false;
4786         }
4787         return types.isSubtype(t, syms.externalizableType);
4788     }
4789 
4790     /**
4791      * Check structure of serialization declarations.
4792      */
4793     public void checkSerialStructure(JCClassDecl tree, ClassSymbol c) {
4794         (new SerialTypeVisitor()).visit(c, tree);
4795     }
4796 
4797     /**
4798      * This visitor will warn if a serialization-related field or
4799      * method is declared in a suspicious or incorrect way. In
4800      * particular, it will warn for cases where the runtime
4801      * serialization mechanism will silently ignore a mis-declared
4802      * entity.
4803      *
4804      * Distinguished serialization-related fields and methods:
4805      *
4806      * Methods:
4807      *
4808      * private void writeObject(ObjectOutputStream stream) throws IOException
4809      * ANY-ACCESS-MODIFIER Object writeReplace() throws ObjectStreamException
4810      *
4811      * private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException
4812      * private void readObjectNoData() throws ObjectStreamException
4813      * ANY-ACCESS-MODIFIER Object readResolve() throws ObjectStreamException
4814      *
4815      * Fields:
4816      *
4817      * private static final long serialVersionUID
4818      * private static final ObjectStreamField[] serialPersistentFields
4819      *
4820      * Externalizable: methods defined on the interface
4821      * public void writeExternal(ObjectOutput) throws IOException
4822      * public void readExternal(ObjectInput) throws IOException
4823      */
4824     private class SerialTypeVisitor extends ElementKindVisitor14<Void, JCClassDecl> {
4825         SerialTypeVisitor() {
4826             this.lint = Check.this.lint;
4827         }
4828 
4829         private static final Set<String> serialMethodNames =
4830             Set.of("writeObject", "writeReplace",
4831                    "readObject",  "readObjectNoData",
4832                    "readResolve");
4833 
4834         private static final Set<String> serialFieldNames =
4835             Set.of("serialVersionUID", "serialPersistentFields");
4836 
4837         // Type of serialPersistentFields
4838         private final Type OSF_TYPE = new Type.ArrayType(syms.objectStreamFieldType, syms.arrayClass);
4839 
4840         Lint lint;
4841 
4842         @Override
4843         public Void defaultAction(Element e, JCClassDecl p) {
4844             throw new IllegalArgumentException(Objects.requireNonNullElse(e.toString(), ""));
4845         }
4846 
4847         @Override
4848         public Void visitType(TypeElement e, JCClassDecl p) {
4849             runUnderLint(e, p, (symbol, param) -> super.visitType(symbol, param));
4850             return null;
4851         }
4852 
4853         @Override
4854         public Void visitTypeAsClass(TypeElement e,
4855                                      JCClassDecl p) {
4856             // Anonymous classes filtered out by caller.
4857 
4858             ClassSymbol c = (ClassSymbol)e;
4859 
4860             checkCtorAccess(p, c);
4861 
4862             // Check for missing serialVersionUID; check *not* done
4863             // for enums or records.
4864             VarSymbol svuidSym = null;
4865             for (Symbol sym : c.members().getSymbolsByName(names.serialVersionUID)) {
4866                 if (sym.kind == VAR) {
4867                     svuidSym = (VarSymbol)sym;
4868                     break;
4869                 }
4870             }
4871 
4872             if (svuidSym == null) {
4873                 log.warning(LintCategory.SERIAL, p.pos(), Warnings.MissingSVUID(c));
4874             }
4875 
4876             // Check for serialPersistentFields to gate checks for
4877             // non-serializable non-transient instance fields
4878             boolean serialPersistentFieldsPresent =
4879                     c.members()
4880                      .getSymbolsByName(names.serialPersistentFields, sym -> sym.kind == VAR)
4881                      .iterator()
4882                      .hasNext();
4883 
4884             // Check declarations of serialization-related methods and
4885             // fields
4886             for(Symbol el : c.getEnclosedElements()) {
4887                 runUnderLint(el, p, (enclosed, tree) -> {
4888                     String name = null;
4889                     switch(enclosed.getKind()) {
4890                     case FIELD -> {
4891                         if (!serialPersistentFieldsPresent) {
4892                             var flags = enclosed.flags();
4893                             if ( ((flags & TRANSIENT) == 0) &&
4894                                  ((flags & STATIC) == 0)) {
4895                                 Type varType = enclosed.asType();
4896                                 if (!canBeSerialized(varType)) {
4897                                     // Note per JLS arrays are
4898                                     // serializable even if the
4899                                     // component type is not.
4900                                     log.warning(LintCategory.SERIAL,
4901                                                 TreeInfo.diagnosticPositionFor(enclosed, tree),
4902                                                 Warnings.NonSerializableInstanceField);
4903                                 } else if (varType.hasTag(ARRAY)) {
4904                                     ArrayType arrayType = (ArrayType)varType;
4905                                     Type elementType = arrayType.elemtype;
4906                                     while (elementType.hasTag(ARRAY)) {
4907                                         arrayType = (ArrayType)elementType;
4908                                         elementType = arrayType.elemtype;
4909                                     }
4910                                     if (!canBeSerialized(elementType)) {
4911                                         log.warning(LintCategory.SERIAL,
4912                                                     TreeInfo.diagnosticPositionFor(enclosed, tree),
4913                                                     Warnings.NonSerializableInstanceFieldArray(elementType));
4914                                     }
4915                                 }
4916                             }
4917                         }
4918 
4919                         name = enclosed.getSimpleName().toString();
4920                         if (serialFieldNames.contains(name)) {
4921                             VarSymbol field = (VarSymbol)enclosed;
4922                             switch (name) {
4923                             case "serialVersionUID"       ->  checkSerialVersionUID(tree, e, field);
4924                             case "serialPersistentFields" ->  checkSerialPersistentFields(tree, e, field);
4925                             default -> throw new AssertionError();
4926                             }
4927                         }
4928                     }
4929 
4930                     // Correctly checking the serialization-related
4931                     // methods is subtle. For the methods declared to be
4932                     // private or directly declared in the class, the
4933                     // enclosed elements of the class can be checked in
4934                     // turn. However, writeReplace and readResolve can be
4935                     // declared in a superclass and inherited. Note that
4936                     // the runtime lookup walks the superclass chain
4937                     // looking for writeReplace/readResolve via
4938                     // Class.getDeclaredMethod. This differs from calling
4939                     // Elements.getAllMembers(TypeElement) as the latter
4940                     // will also pull in default methods from
4941                     // superinterfaces. In other words, the runtime checks
4942                     // (which long predate default methods on interfaces)
4943                     // do not admit the possibility of inheriting methods
4944                     // this way, a difference from general inheritance.
4945 
4946                     // The current implementation just checks the enclosed
4947                     // elements and does not directly check the inherited
4948                     // methods. If all the types are being checked this is
4949                     // less of a concern; however, there are cases that
4950                     // could be missed. In particular, readResolve and
4951                     // writeReplace could, in principle, by inherited from
4952                     // a non-serializable superclass and thus not checked
4953                     // even if compiled with a serializable child class.
4954                     case METHOD -> {
4955                         var method = (MethodSymbol)enclosed;
4956                         name = method.getSimpleName().toString();
4957                         if (serialMethodNames.contains(name)) {
4958                             switch (name) {
4959                             case "writeObject"      -> checkWriteObject(tree, e, method);
4960                             case "writeReplace"     -> checkWriteReplace(tree,e, method);
4961                             case "readObject"       -> checkReadObject(tree,e, method);
4962                             case "readObjectNoData" -> checkReadObjectNoData(tree, e, method);
4963                             case "readResolve"      -> checkReadResolve(tree, e, method);
4964                             default ->  throw new AssertionError();
4965                             }
4966                         }
4967                     }
4968                     }
4969                 });
4970             }
4971 
4972             return null;
4973         }
4974 
4975         boolean canBeSerialized(Type type) {
4976             return type.isPrimitive() || rs.isSerializable(type);
4977         }
4978 
4979         /**
4980          * Check that Externalizable class needs a public no-arg
4981          * constructor.
4982          *
4983          * Check that a Serializable class has access to the no-arg
4984          * constructor of its first nonserializable superclass.
4985          */
4986         private void checkCtorAccess(JCClassDecl tree, ClassSymbol c) {
4987             if (isExternalizable(c.type)) {
4988                 for(var sym : c.getEnclosedElements()) {
4989                     if (sym.isConstructor() &&
4990                         ((sym.flags() & PUBLIC) == PUBLIC)) {
4991                         if (((MethodSymbol)sym).getParameters().isEmpty()) {
4992                             return;
4993                         }
4994                     }
4995                 }
4996                 log.warning(LintCategory.SERIAL, tree.pos(),
4997                             Warnings.ExternalizableMissingPublicNoArgCtor);
4998             } else {
4999                 // Approximate access to the no-arg constructor up in
5000                 // the superclass chain by checking that the
5001                 // constructor is not private. This may not handle
5002                 // some cross-package situations correctly.
5003                 Type superClass = c.getSuperclass();
5004                 // java.lang.Object is *not* Serializable so this loop
5005                 // should terminate.
5006                 while (rs.isSerializable(superClass) ) {
5007                     try {
5008                         superClass = (Type)((TypeElement)(((DeclaredType)superClass)).asElement()).getSuperclass();
5009                     } catch(ClassCastException cce) {
5010                         return ; // Don't try to recover
5011                     }
5012                 }
5013                 // Non-Serializable superclass
5014                 try {
5015                     ClassSymbol supertype = ((ClassSymbol)(((DeclaredType)superClass).asElement()));
5016                     for(var sym : supertype.getEnclosedElements()) {
5017                         if (sym.isConstructor()) {
5018                             MethodSymbol ctor = (MethodSymbol)sym;
5019                             if (ctor.getParameters().isEmpty()) {
5020                                 if (((ctor.flags() & PRIVATE) == PRIVATE) ||
5021                                     // Handle nested classes and implicit this$0
5022                                     (supertype.getNestingKind() == NestingKind.MEMBER &&
5023                                      ((supertype.flags() & STATIC) == 0)))
5024                                     log.warning(LintCategory.SERIAL, tree.pos(),
5025                                                 Warnings.SerializableMissingAccessNoArgCtor(supertype.getQualifiedName()));
5026                             }
5027                         }
5028                     }
5029                 } catch (ClassCastException cce) {
5030                     return ; // Don't try to recover
5031                 }
5032                 return;
5033             }
5034         }
5035 
5036         private void checkSerialVersionUID(JCClassDecl tree, Element e, VarSymbol svuid) {
5037             // To be effective, serialVersionUID must be marked static
5038             // and final, but private is recommended. But alas, in
5039             // practice there are many non-private serialVersionUID
5040             // fields.
5041              if ((svuid.flags() & (STATIC | FINAL)) !=
5042                  (STATIC | FINAL)) {
5043                  log.warning(LintCategory.SERIAL,
5044                              TreeInfo.diagnosticPositionFor(svuid, tree),
5045                              Warnings.ImproperSVUID((Symbol)e));
5046              }
5047 
5048              // check svuid has type long
5049              if (!svuid.type.hasTag(LONG)) {
5050                  log.warning(LintCategory.SERIAL,
5051                              TreeInfo.diagnosticPositionFor(svuid, tree),
5052                              Warnings.LongSVUID((Symbol)e));
5053              }
5054 
5055              if (svuid.getConstValue() == null)
5056                  log.warning(LintCategory.SERIAL,
5057                             TreeInfo.diagnosticPositionFor(svuid, tree),
5058                              Warnings.ConstantSVUID((Symbol)e));
5059         }
5060 
5061         private void checkSerialPersistentFields(JCClassDecl tree, Element e, VarSymbol spf) {
5062             // To be effective, serialPersisentFields must be private, static, and final.
5063              if ((spf.flags() & (PRIVATE | STATIC | FINAL)) !=
5064                  (PRIVATE | STATIC | FINAL)) {
5065                  log.warning(LintCategory.SERIAL,
5066                              TreeInfo.diagnosticPositionFor(spf, tree),
5067                              Warnings.ImproperSPF);
5068              }
5069 
5070              if (!types.isSameType(spf.type, OSF_TYPE)) {
5071                  log.warning(LintCategory.SERIAL,
5072                              TreeInfo.diagnosticPositionFor(spf, tree),
5073                              Warnings.OSFArraySPF);
5074              }
5075 
5076             if (isExternalizable((Type)(e.asType()))) {
5077                 log.warning(LintCategory.SERIAL,
5078                             TreeInfo.diagnosticPositionFor(spf, tree),
5079                             Warnings.IneffectualSerialFieldExternalizable);
5080             }
5081 
5082             // Warn if serialPersistentFields is initialized to a
5083             // literal null.
5084             JCTree spfDecl = TreeInfo.declarationFor(spf, tree);
5085             if (spfDecl != null && spfDecl.getTag() == VARDEF) {
5086                 JCVariableDecl variableDef = (JCVariableDecl) spfDecl;
5087                 JCExpression initExpr = variableDef.init;
5088                  if (initExpr != null && TreeInfo.isNull(initExpr)) {
5089                      log.warning(LintCategory.SERIAL, initExpr.pos(),
5090                                  Warnings.SPFNullInit);
5091                  }
5092             }
5093         }
5094 
5095         private void checkWriteObject(JCClassDecl tree, Element e, MethodSymbol method) {
5096             // The "synchronized" modifier is seen in the wild on
5097             // readObject and writeObject methods and is generally
5098             // innocuous.
5099 
5100             // private void writeObject(ObjectOutputStream stream) throws IOException
5101             checkPrivateNonStaticMethod(tree, method);
5102             checkReturnType(tree, e, method, syms.voidType);
5103             checkOneArg(tree, e, method, syms.objectOutputStreamType);
5104             checkExceptions(tree, e, method, syms.ioExceptionType);
5105             checkExternalizable(tree, e, method);
5106         }
5107 
5108         private void checkWriteReplace(JCClassDecl tree, Element e, MethodSymbol method) {
5109             // ANY-ACCESS-MODIFIER Object writeReplace() throws
5110             // ObjectStreamException
5111 
5112             // Excluding abstract, could have a more complicated
5113             // rule based on abstract-ness of the class
5114             checkConcreteInstanceMethod(tree, e, method);
5115             checkReturnType(tree, e, method, syms.objectType);
5116             checkNoArgs(tree, e, method);
5117             checkExceptions(tree, e, method, syms.objectStreamExceptionType);
5118         }
5119 
5120         private void checkReadObject(JCClassDecl tree, Element e, MethodSymbol method) {
5121             // The "synchronized" modifier is seen in the wild on
5122             // readObject and writeObject methods and is generally
5123             // innocuous.
5124 
5125             // private void readObject(ObjectInputStream stream)
5126             //   throws IOException, ClassNotFoundException
5127             checkPrivateNonStaticMethod(tree, method);
5128             checkReturnType(tree, e, method, syms.voidType);
5129             checkOneArg(tree, e, method, syms.objectInputStreamType);
5130             checkExceptions(tree, e, method, syms.ioExceptionType, syms.classNotFoundExceptionType);
5131             checkExternalizable(tree, e, method);
5132         }
5133 
5134         private void checkReadObjectNoData(JCClassDecl tree, Element e, MethodSymbol method) {
5135             // private void readObjectNoData() throws ObjectStreamException
5136             checkPrivateNonStaticMethod(tree, method);
5137             checkReturnType(tree, e, method, syms.voidType);
5138             checkNoArgs(tree, e, method);
5139             checkExceptions(tree, e, method, syms.objectStreamExceptionType);
5140             checkExternalizable(tree, e, method);
5141         }
5142 
5143         private void checkReadResolve(JCClassDecl tree, Element e, MethodSymbol method) {
5144             // ANY-ACCESS-MODIFIER Object readResolve()
5145             // throws ObjectStreamException
5146 
5147             // Excluding abstract, could have a more complicated
5148             // rule based on abstract-ness of the class
5149             checkConcreteInstanceMethod(tree, e, method);
5150             checkReturnType(tree,e, method, syms.objectType);
5151             checkNoArgs(tree, e, method);
5152             checkExceptions(tree, e, method, syms.objectStreamExceptionType);
5153         }
5154 
5155         private void checkWriteExternalRecord(JCClassDecl tree, Element e, MethodSymbol method, boolean isExtern) {
5156             //public void writeExternal(ObjectOutput) throws IOException
5157             checkExternMethodRecord(tree, e, method, syms.objectOutputType, isExtern);
5158         }
5159 
5160         private void checkReadExternalRecord(JCClassDecl tree, Element e, MethodSymbol method, boolean isExtern) {
5161             // public void readExternal(ObjectInput) throws IOException
5162             checkExternMethodRecord(tree, e, method, syms.objectInputType, isExtern);
5163          }
5164 
5165         private void checkExternMethodRecord(JCClassDecl tree, Element e, MethodSymbol method, Type argType,
5166                                              boolean isExtern) {
5167             if (isExtern && isExternMethod(tree, e, method, argType)) {
5168                 log.warning(LintCategory.SERIAL,
5169                             TreeInfo.diagnosticPositionFor(method, tree),
5170                             Warnings.IneffectualExternalizableMethodRecord(method.getSimpleName().toString()));
5171             }
5172         }
5173 
5174         void checkPrivateNonStaticMethod(JCClassDecl tree, MethodSymbol method) {
5175             var flags = method.flags();
5176             if ((flags & PRIVATE) == 0) {
5177                 log.warning(LintCategory.SERIAL,
5178                             TreeInfo.diagnosticPositionFor(method, tree),
5179                             Warnings.SerialMethodNotPrivate(method.getSimpleName()));
5180             }
5181 
5182             if ((flags & STATIC) != 0) {
5183                 log.warning(LintCategory.SERIAL,
5184                             TreeInfo.diagnosticPositionFor(method, tree),
5185                             Warnings.SerialMethodStatic(method.getSimpleName()));
5186             }
5187         }
5188 
5189         /**
5190          * Per section 1.12 "Serialization of Enum Constants" of
5191          * the serialization specification, due to the special
5192          * serialization handling of enums, any writeObject,
5193          * readObject, writeReplace, and readResolve methods are
5194          * ignored as are serialPersistentFields and
5195          * serialVersionUID fields.
5196          */
5197         @Override
5198         public Void visitTypeAsEnum(TypeElement e,
5199                                     JCClassDecl p) {
5200             boolean isExtern = isExternalizable((Type)e.asType());
5201             for(Element el : e.getEnclosedElements()) {
5202                 runUnderLint(el, p, (enclosed, tree) -> {
5203                     String name = enclosed.getSimpleName().toString();
5204                     switch(enclosed.getKind()) {
5205                     case FIELD -> {
5206                         var field = (VarSymbol)enclosed;
5207                         if (serialFieldNames.contains(name)) {
5208                             log.warning(LintCategory.SERIAL,
5209                                         TreeInfo.diagnosticPositionFor(field, tree),
5210                                         Warnings.IneffectualSerialFieldEnum(name));
5211                         }
5212                     }
5213 
5214                     case METHOD -> {
5215                         var method = (MethodSymbol)enclosed;
5216                         if (serialMethodNames.contains(name)) {
5217                             log.warning(LintCategory.SERIAL,
5218                                         TreeInfo.diagnosticPositionFor(method, tree),
5219                                         Warnings.IneffectualSerialMethodEnum(name));
5220                         }
5221 
5222                         if (isExtern) {
5223                             switch(name) {
5224                             case "writeExternal" -> checkWriteExternalEnum(tree, e, method);
5225                             case "readExternal"  -> checkReadExternalEnum(tree, e, method);
5226                             }
5227                         }
5228                     }
5229 
5230                     // Also perform checks on any class bodies of enum constants, see JLS 8.9.1.
5231                     case ENUM_CONSTANT -> {
5232                         var field = (VarSymbol)enclosed;
5233                         JCVariableDecl decl = (JCVariableDecl) TreeInfo.declarationFor(field, p);
5234                         if (decl.init instanceof JCNewClass nc && nc.def != null) {
5235                             ClassSymbol enumConstantType = nc.def.sym;
5236                             visitTypeAsEnum(enumConstantType, p);
5237                         }
5238                     }
5239 
5240                     }});
5241             }
5242             return null;
5243         }
5244 
5245         private void checkWriteExternalEnum(JCClassDecl tree, Element e, MethodSymbol method) {
5246             //public void writeExternal(ObjectOutput) throws IOException
5247             checkExternMethodEnum(tree, e, method, syms.objectOutputType);
5248         }
5249 
5250         private void checkReadExternalEnum(JCClassDecl tree, Element e, MethodSymbol method) {
5251              // public void readExternal(ObjectInput) throws IOException
5252             checkExternMethodEnum(tree, e, method, syms.objectInputType);
5253          }
5254 
5255         private void checkExternMethodEnum(JCClassDecl tree, Element e, MethodSymbol method, Type argType) {
5256             if (isExternMethod(tree, e, method, argType)) {
5257                 log.warning(LintCategory.SERIAL,
5258                             TreeInfo.diagnosticPositionFor(method, tree),
5259                             Warnings.IneffectualExternMethodEnum(method.getSimpleName().toString()));
5260             }
5261         }
5262 
5263         private boolean isExternMethod(JCClassDecl tree, Element e, MethodSymbol method, Type argType) {
5264             long flags = method.flags();
5265             Type rtype = method.getReturnType();
5266 
5267             // Not necessary to check throws clause in this context
5268             return (flags & PUBLIC) != 0 && (flags & STATIC) == 0 &&
5269                 types.isSameType(syms.voidType, rtype) &&
5270                 hasExactlyOneArgWithType(tree, e, method, argType);
5271         }
5272 
5273         /**
5274          * Most serialization-related fields and methods on interfaces
5275          * are ineffectual or problematic.
5276          */
5277         @Override
5278         public Void visitTypeAsInterface(TypeElement e,
5279                                          JCClassDecl p) {
5280             for(Element el : e.getEnclosedElements()) {
5281                 runUnderLint(el, p, (enclosed, tree) -> {
5282                     String name = null;
5283                     switch(enclosed.getKind()) {
5284                     case FIELD -> {
5285                         var field = (VarSymbol)enclosed;
5286                         name = field.getSimpleName().toString();
5287                         switch(name) {
5288                         case "serialPersistentFields" -> {
5289                             log.warning(LintCategory.SERIAL,
5290                                         TreeInfo.diagnosticPositionFor(field, tree),
5291                                         Warnings.IneffectualSerialFieldInterface);
5292                         }
5293 
5294                         case "serialVersionUID" -> {
5295                             checkSerialVersionUID(tree, e, field);
5296                         }
5297                         }
5298                     }
5299 
5300                     case METHOD -> {
5301                         var method = (MethodSymbol)enclosed;
5302                         name = enclosed.getSimpleName().toString();
5303                         if (serialMethodNames.contains(name)) {
5304                             switch (name) {
5305                             case
5306                                 "readObject",
5307                                 "readObjectNoData",
5308                                 "writeObject"      -> checkPrivateMethod(tree, e, method);
5309 
5310                             case
5311                                 "writeReplace",
5312                                 "readResolve"      -> checkDefaultIneffective(tree, e, method);
5313 
5314                             default ->  throw new AssertionError();
5315                             }
5316 
5317                         }
5318                     }}
5319                 });
5320             }
5321 
5322             return null;
5323         }
5324 
5325         private void checkPrivateMethod(JCClassDecl tree,
5326                                         Element e,
5327                                         MethodSymbol method) {
5328             if ((method.flags() & PRIVATE) == 0) {
5329                 log.warning(LintCategory.SERIAL,
5330                             TreeInfo.diagnosticPositionFor(method, tree),
5331                             Warnings.NonPrivateMethodWeakerAccess);
5332             }
5333         }
5334 
5335         private void checkDefaultIneffective(JCClassDecl tree,
5336                                              Element e,
5337                                              MethodSymbol method) {
5338             if ((method.flags() & DEFAULT) == DEFAULT) {
5339                 log.warning(LintCategory.SERIAL,
5340                             TreeInfo.diagnosticPositionFor(method, tree),
5341                             Warnings.DefaultIneffective);
5342 
5343             }
5344         }
5345 
5346         @Override
5347         public Void visitTypeAsAnnotationType(TypeElement e,
5348                                               JCClassDecl p) {
5349             // Per the JLS, annotation types are not serializeable
5350             return null;
5351         }
5352 
5353         /**
5354          * From the Java Object Serialization Specification, 1.13
5355          * Serialization of Records:
5356          *
5357          * "The process by which record objects are serialized or
5358          * externalized cannot be customized; any class-specific
5359          * writeObject, readObject, readObjectNoData, writeExternal,
5360          * and readExternal methods defined by record classes are
5361          * ignored during serialization and deserialization. However,
5362          * a substitute object to be serialized or a designate
5363          * replacement may be specified, by the writeReplace and
5364          * readResolve methods, respectively. Any
5365          * serialPersistentFields field declaration is
5366          * ignored. Documenting serializable fields and data for
5367          * record classes is unnecessary, since there is no variation
5368          * in the serial form, other than whether a substitute or
5369          * replacement object is used. The serialVersionUID of a
5370          * record class is 0L unless explicitly declared. The
5371          * requirement for matching serialVersionUID values is waived
5372          * for record classes."
5373          */
5374         @Override
5375         public Void visitTypeAsRecord(TypeElement e,
5376                                       JCClassDecl p) {
5377             boolean isExtern = isExternalizable((Type)e.asType());
5378             for(Element el : e.getEnclosedElements()) {
5379                 runUnderLint(el, p, (enclosed, tree) -> {
5380                     String name = enclosed.getSimpleName().toString();
5381                     switch(enclosed.getKind()) {
5382                     case FIELD -> {
5383                         var field = (VarSymbol)enclosed;
5384                         switch(name) {
5385                         case "serialPersistentFields" -> {
5386                             log.warning(LintCategory.SERIAL,
5387                                         TreeInfo.diagnosticPositionFor(field, tree),
5388                                         Warnings.IneffectualSerialFieldRecord);
5389                         }
5390 
5391                         case "serialVersionUID" -> {
5392                             // Could generate additional warning that
5393                             // svuid value is not checked to match for
5394                             // records.
5395                             checkSerialVersionUID(tree, e, field);
5396                         }}
5397                     }
5398 
5399                     case METHOD -> {
5400                         var method = (MethodSymbol)enclosed;
5401                         switch(name) {
5402                         case "writeReplace" -> checkWriteReplace(tree, e, method);
5403                         case "readResolve"  -> checkReadResolve(tree, e, method);
5404 
5405                         case "writeExternal" -> checkWriteExternalRecord(tree, e, method, isExtern);
5406                         case "readExternal"  -> checkReadExternalRecord(tree, e, method, isExtern);
5407 
5408                         default -> {
5409                             if (serialMethodNames.contains(name)) {
5410                                 log.warning(LintCategory.SERIAL,
5411                                             TreeInfo.diagnosticPositionFor(method, tree),
5412                                             Warnings.IneffectualSerialMethodRecord(name));
5413                             }
5414                         }}
5415                     }}});
5416             }
5417             return null;
5418         }
5419 
5420         void checkConcreteInstanceMethod(JCClassDecl tree,
5421                                          Element enclosing,
5422                                          MethodSymbol method) {
5423             if ((method.flags() & (STATIC | ABSTRACT)) != 0) {
5424                     log.warning(LintCategory.SERIAL,
5425                                 TreeInfo.diagnosticPositionFor(method, tree),
5426                                 Warnings.SerialConcreteInstanceMethod(method.getSimpleName()));
5427             }
5428         }
5429 
5430         private void checkReturnType(JCClassDecl tree,
5431                                      Element enclosing,
5432                                      MethodSymbol method,
5433                                      Type expectedReturnType) {
5434             // Note: there may be complications checking writeReplace
5435             // and readResolve since they return Object and could, in
5436             // principle, have covariant overrides and any synthetic
5437             // bridge method would not be represented here for
5438             // checking.
5439             Type rtype = method.getReturnType();
5440             if (!types.isSameType(expectedReturnType, rtype)) {
5441                 log.warning(LintCategory.SERIAL,
5442                             TreeInfo.diagnosticPositionFor(method, tree),
5443                             Warnings.SerialMethodUnexpectedReturnType(method.getSimpleName(),
5444                                                                       rtype, expectedReturnType));
5445             }
5446         }
5447 
5448         private void checkOneArg(JCClassDecl tree,
5449                                  Element enclosing,
5450                                  MethodSymbol method,
5451                                  Type expectedType) {
5452             String name = method.getSimpleName().toString();
5453 
5454             var parameters= method.getParameters();
5455 
5456             if (parameters.size() != 1) {
5457                 log.warning(LintCategory.SERIAL,
5458                             TreeInfo.diagnosticPositionFor(method, tree),
5459                             Warnings.SerialMethodOneArg(method.getSimpleName(), parameters.size()));
5460                 return;
5461             }
5462 
5463             Type parameterType = parameters.get(0).asType();
5464             if (!types.isSameType(parameterType, expectedType)) {
5465                 log.warning(LintCategory.SERIAL,
5466                             TreeInfo.diagnosticPositionFor(method, tree),
5467                             Warnings.SerialMethodParameterType(method.getSimpleName(),
5468                                                                expectedType,
5469                                                                parameterType));
5470             }
5471         }
5472 
5473         private boolean hasExactlyOneArgWithType(JCClassDecl tree,
5474                                                  Element enclosing,
5475                                                  MethodSymbol method,
5476                                                  Type expectedType) {
5477             var parameters = method.getParameters();
5478             return (parameters.size() == 1) &&
5479                 types.isSameType(parameters.get(0).asType(), expectedType);
5480         }
5481 
5482 
5483         private void checkNoArgs(JCClassDecl tree, Element enclosing, MethodSymbol method) {
5484             var parameters = method.getParameters();
5485             if (!parameters.isEmpty()) {
5486                 log.warning(LintCategory.SERIAL,
5487                             TreeInfo.diagnosticPositionFor(parameters.get(0), tree),
5488                             Warnings.SerialMethodNoArgs(method.getSimpleName()));
5489             }
5490         }
5491 
5492         private void checkExternalizable(JCClassDecl tree, Element enclosing, MethodSymbol method) {
5493             // If the enclosing class is externalizable, warn for the method
5494             if (isExternalizable((Type)enclosing.asType())) {
5495                 log.warning(LintCategory.SERIAL,
5496                             TreeInfo.diagnosticPositionFor(method, tree),
5497                             Warnings.IneffectualSerialMethodExternalizable(method.getSimpleName()));
5498             }
5499             return;
5500         }
5501 
5502         private void checkExceptions(JCClassDecl tree,
5503                                      Element enclosing,
5504                                      MethodSymbol method,
5505                                      Type... declaredExceptions) {
5506             for (Type thrownType: method.getThrownTypes()) {
5507                 // For each exception in the throws clause of the
5508                 // method, if not an Error and not a RuntimeException,
5509                 // check if the exception is a subtype of a declared
5510                 // exception from the throws clause of the
5511                 // serialization method in question.
5512                 if (types.isSubtype(thrownType, syms.runtimeExceptionType) ||
5513                     types.isSubtype(thrownType, syms.errorType) ) {
5514                     continue;
5515                 } else {
5516                     boolean declared = false;
5517                     for (Type declaredException : declaredExceptions) {
5518                         if (types.isSubtype(thrownType, declaredException)) {
5519                             declared = true;
5520                             continue;
5521                         }
5522                     }
5523                     if (!declared) {
5524                         log.warning(LintCategory.SERIAL,
5525                                     TreeInfo.diagnosticPositionFor(method, tree),
5526                                     Warnings.SerialMethodUnexpectedException(method.getSimpleName(),
5527                                                                              thrownType));
5528                     }
5529                 }
5530             }
5531             return;
5532         }
5533 
5534         private <E extends Element> Void runUnderLint(E symbol, JCClassDecl p, BiConsumer<E, JCClassDecl> task) {
5535             Lint prevLint = lint;
5536             try {
5537                 lint = lint.augment((Symbol) symbol);
5538 
5539                 if (lint.isEnabled(LintCategory.SERIAL)) {
5540                     task.accept(symbol, p);
5541                 }
5542 
5543                 return null;
5544             } finally {
5545                 lint = prevLint;
5546             }
5547         }
5548 
5549     }
5550 
5551 }