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