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