1 /*
   2  * Copyright (c) 1999, 2019, 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.Supplier;
  30 
  31 import javax.tools.JavaFileManager;
  32 
  33 import com.sun.tools.javac.code.*;
  34 import com.sun.tools.javac.code.Attribute.Compound;
  35 import com.sun.tools.javac.code.Directive.ExportsDirective;
  36 import com.sun.tools.javac.code.Directive.RequiresDirective;
  37 import com.sun.tools.javac.code.Source.Feature;
  38 import com.sun.tools.javac.comp.Annotate.AnnotationTypeMetadata;
  39 import com.sun.tools.javac.jvm.*;
  40 import com.sun.tools.javac.resources.CompilerProperties.Errors;
  41 import com.sun.tools.javac.resources.CompilerProperties.Fragments;
  42 import com.sun.tools.javac.resources.CompilerProperties.Warnings;
  43 import com.sun.tools.javac.tree.*;
  44 import com.sun.tools.javac.util.*;
  45 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticFlag;
  46 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
  47 import com.sun.tools.javac.util.JCDiagnostic.Error;
  48 import com.sun.tools.javac.util.JCDiagnostic.Fragment;
  49 import com.sun.tools.javac.util.JCDiagnostic.Warning;
  50 import com.sun.tools.javac.util.List;
  51 
  52 import com.sun.tools.javac.code.Lint;
  53 import com.sun.tools.javac.code.Lint.LintCategory;
  54 import com.sun.tools.javac.code.Scope.WriteableScope;
  55 import com.sun.tools.javac.code.Type.*;
  56 import com.sun.tools.javac.code.Symbol.*;
  57 import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;
  58 import com.sun.tools.javac.comp.Infer.FreeTypeListener;
  59 import com.sun.tools.javac.tree.JCTree.*;
  60 
  61 import static com.sun.tools.javac.code.Flags.*;
  62 import static com.sun.tools.javac.code.Flags.ANNOTATION;
  63 import static com.sun.tools.javac.code.Flags.SYNCHRONIZED;
  64 import static com.sun.tools.javac.code.Kinds.*;
  65 import static com.sun.tools.javac.code.Kinds.Kind.*;
  66 import static com.sun.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;
  67 import static com.sun.tools.javac.code.TypeTag.*;
  68 import static com.sun.tools.javac.code.TypeTag.WILDCARD;
  69 
  70 import static com.sun.tools.javac.tree.JCTree.Tag.*;
  71 
  72 /** Type checking helper class for the attribution phase.
  73  *
  74  *  <p><b>This is NOT part of any supported API.
  75  *  If you write code that depends on this, you do so at your own risk.
  76  *  This code and its internal interfaces are subject to change or
  77  *  deletion without notice.</b>
  78  */
  79 public class Check {
  80     protected static final Context.Key<Check> checkKey = new Context.Key<>();
  81 
  82     private final Names names;
  83     private final Log log;
  84     private final Resolve rs;
  85     private final Symtab syms;
  86     private final Enter enter;
  87     private final DeferredAttr deferredAttr;
  88     private final Infer infer;
  89     private final Types types;
  90     private final TypeAnnotations typeAnnotations;
  91     private final JCDiagnostic.Factory diags;
  92     private final JavaFileManager fileManager;
  93     private final Source source;
  94     private final Target target;
  95     private final Profile profile;
  96     private final boolean warnOnAnyAccessToMembers;
  97 
  98     // The set of lint options currently in effect. It is initialized
  99     // from the context, and then is set/reset as needed by Attr as it
 100     // visits all the various parts of the trees during attribution.
 101     private Lint lint;
 102 
 103     // The method being analyzed in Attr - it is set/reset as needed by
 104     // Attr as it visits new method declarations.
 105     private MethodSymbol method;
 106 
 107     public static Check instance(Context context) {
 108         Check instance = context.get(checkKey);
 109         if (instance == null)
 110             instance = new Check(context);
 111         return instance;
 112     }
 113 
 114     protected Check(Context context) {
 115         context.put(checkKey, this);
 116 
 117         names = Names.instance(context);
 118         dfltTargetMeta = new Name[] { names.PACKAGE, names.TYPE,
 119             names.FIELD, names.METHOD, names.CONSTRUCTOR,
 120             names.ANNOTATION_TYPE, names.LOCAL_VARIABLE, names.PARAMETER};
 121         log = Log.instance(context);
 122         rs = Resolve.instance(context);
 123         syms = Symtab.instance(context);
 124         enter = Enter.instance(context);
 125         deferredAttr = DeferredAttr.instance(context);
 126         infer = Infer.instance(context);
 127         types = Types.instance(context);
 128         typeAnnotations = TypeAnnotations.instance(context);
 129         diags = JCDiagnostic.Factory.instance(context);
 130         Options options = Options.instance(context);
 131         lint = Lint.instance(context);
 132         fileManager = context.get(JavaFileManager.class);
 133 
 134         source = Source.instance(context);
 135         target = Target.instance(context);
 136         warnOnAnyAccessToMembers = options.isSet("warnOnAccessToMembers");
 137 
 138         Target target = Target.instance(context);
 139         syntheticNameChar = target.syntheticNameChar();
 140 
 141         profile = Profile.instance(context);
 142 
 143         boolean verboseDeprecated = lint.isEnabled(LintCategory.DEPRECATION);
 144         boolean verboseRemoval = lint.isEnabled(LintCategory.REMOVAL);
 145         boolean verboseUnchecked = lint.isEnabled(LintCategory.UNCHECKED);
 146         boolean enforceMandatoryWarnings = true;
 147 
 148         deprecationHandler = new MandatoryWarningHandler(log, verboseDeprecated,
 149                 enforceMandatoryWarnings, "deprecated", LintCategory.DEPRECATION);
 150         removalHandler = new MandatoryWarningHandler(log, verboseRemoval,
 151                 enforceMandatoryWarnings, "removal", LintCategory.REMOVAL);
 152         uncheckedHandler = new MandatoryWarningHandler(log, verboseUnchecked,
 153                 enforceMandatoryWarnings, "unchecked", LintCategory.UNCHECKED);
 154         sunApiHandler = new MandatoryWarningHandler(log, false,
 155                 enforceMandatoryWarnings, "sunapi", null);
 156 
 157         deferredLintHandler = DeferredLintHandler.instance(context);
 158     }
 159 
 160     /** Character for synthetic names
 161      */
 162     char syntheticNameChar;
 163 
 164     /** A table mapping flat names of all compiled classes for each module in this run
 165      *  to their symbols; maintained from outside.
 166      */
 167     private Map<Pair<ModuleSymbol, Name>,ClassSymbol> compiled = new HashMap<>();
 168 
 169     /** A handler for messages about deprecated usage.
 170      */
 171     private MandatoryWarningHandler deprecationHandler;
 172 
 173     /** A handler for messages about deprecated-for-removal usage.
 174      */
 175     private MandatoryWarningHandler removalHandler;
 176 
 177     /** A handler for messages about unchecked or unsafe usage.
 178      */
 179     private MandatoryWarningHandler uncheckedHandler;
 180 
 181     /** A handler for messages about using proprietary API.
 182      */
 183     private MandatoryWarningHandler sunApiHandler;
 184 
 185     /** A handler for deferred lint warnings.
 186      */
 187     private DeferredLintHandler deferredLintHandler;
 188 
 189 /* *************************************************************************
 190  * Errors and Warnings
 191  **************************************************************************/
 192 
 193     Lint setLint(Lint newLint) {
 194         Lint prev = lint;
 195         lint = newLint;
 196         return prev;
 197     }
 198 
 199     MethodSymbol setMethod(MethodSymbol newMethod) {
 200         MethodSymbol prev = method;
 201         method = newMethod;
 202         return prev;
 203     }
 204 
 205     /** Warn about deprecated symbol.
 206      *  @param pos        Position to be used for error reporting.
 207      *  @param sym        The deprecated symbol.
 208      */
 209     void warnDeprecated(DiagnosticPosition pos, Symbol sym) {
 210         if (sym.isDeprecatedForRemoval()) {
 211             if (!lint.isSuppressed(LintCategory.REMOVAL)) {
 212                 if (sym.kind == MDL) {
 213                     removalHandler.report(pos, Warnings.HasBeenDeprecatedForRemovalModule(sym));
 214                 } else {
 215                     removalHandler.report(pos, Warnings.HasBeenDeprecatedForRemoval(sym, sym.location()));
 216                 }
 217             }
 218         } else if (!lint.isSuppressed(LintCategory.DEPRECATION)) {
 219             if (sym.kind == MDL) {
 220                 deprecationHandler.report(pos, Warnings.HasBeenDeprecatedModule(sym));
 221             } else {
 222                 deprecationHandler.report(pos, Warnings.HasBeenDeprecated(sym, sym.location()));
 223             }
 224         }
 225     }
 226 
 227     /** Warn about unchecked operation.
 228      *  @param pos        Position to be used for error reporting.
 229      *  @param msg        A string describing the problem.
 230      */
 231     public void warnUnchecked(DiagnosticPosition pos, Warning warnKey) {
 232         if (!lint.isSuppressed(LintCategory.UNCHECKED))
 233             uncheckedHandler.report(pos, warnKey);
 234     }
 235 
 236     /** Warn about unsafe vararg method decl.
 237      *  @param pos        Position to be used for error reporting.
 238      */
 239     void warnUnsafeVararg(DiagnosticPosition pos, Warning warnKey) {
 240         if (lint.isEnabled(LintCategory.VARARGS))
 241             log.warning(LintCategory.VARARGS, pos, warnKey);
 242     }
 243 
 244     public void warnStatic(DiagnosticPosition pos, Warning warnKey) {
 245         if (lint.isEnabled(LintCategory.STATIC))
 246             log.warning(LintCategory.STATIC, pos, warnKey);
 247     }
 248 
 249     /** Warn about division by integer constant zero.
 250      *  @param pos        Position to be used for error reporting.
 251      */
 252     void warnDivZero(DiagnosticPosition pos) {
 253         if (lint.isEnabled(LintCategory.DIVZERO))
 254             log.warning(LintCategory.DIVZERO, pos, Warnings.DivZero);
 255     }
 256 
 257     /**
 258      * Report any deferred diagnostics.
 259      */
 260     public void reportDeferredDiagnostics() {
 261         deprecationHandler.reportDeferredDiagnostic();
 262         removalHandler.reportDeferredDiagnostic();
 263         uncheckedHandler.reportDeferredDiagnostic();
 264         sunApiHandler.reportDeferredDiagnostic();
 265     }
 266 
 267 
 268     /** Report a failure to complete a class.
 269      *  @param pos        Position to be used for error reporting.
 270      *  @param ex         The failure to report.
 271      */
 272     public Type completionError(DiagnosticPosition pos, CompletionFailure ex) {
 273         log.error(JCDiagnostic.DiagnosticFlag.NON_DEFERRABLE, pos, Errors.CantAccess(ex.sym, ex.getDetailValue()));
 274         return syms.errType;
 275     }
 276 
 277     /** Report an error that wrong type tag was found.
 278      *  @param pos        Position to be used for error reporting.
 279      *  @param required   An internationalized string describing the type tag
 280      *                    required.
 281      *  @param found      The type that was found.
 282      */
 283     Type typeTagError(DiagnosticPosition pos, JCDiagnostic required, Object found) {
 284         // this error used to be raised by the parser,
 285         // but has been delayed to this point:
 286         if (found instanceof Type && ((Type)found).hasTag(VOID)) {
 287             log.error(pos, Errors.IllegalStartOfType);
 288             return syms.errType;
 289         }
 290         log.error(pos, Errors.TypeFoundReq(found, required));
 291         return types.createErrorType(found instanceof Type ? (Type)found : syms.errType);
 292     }
 293 
 294     /** Report an error that symbol cannot be referenced before super
 295      *  has been called.
 296      *  @param pos        Position to be used for error reporting.
 297      *  @param sym        The referenced symbol.
 298      */
 299     void earlyRefError(DiagnosticPosition pos, Symbol sym) {
 300         log.error(pos, Errors.CantRefBeforeCtorCalled(sym));
 301     }
 302 
 303     /** Report duplicate declaration error.
 304      */
 305     void duplicateError(DiagnosticPosition pos, Symbol sym) {
 306         if (!sym.type.isErroneous()) {
 307             Symbol location = sym.location();
 308             if (location.kind == MTH &&
 309                     ((MethodSymbol)location).isStaticOrInstanceInit()) {
 310                 log.error(pos,
 311                           Errors.AlreadyDefinedInClinit(kindName(sym),
 312                                                         sym,
 313                                                         kindName(sym.location()),
 314                                                         kindName(sym.location().enclClass()),
 315                                                         sym.location().enclClass()));
 316             } else {
 317                 log.error(pos,
 318                           Errors.AlreadyDefined(kindName(sym),
 319                                                 sym,
 320                                                 kindName(sym.location()),
 321                                                 sym.location()));
 322             }
 323         }
 324     }
 325 
 326     /** Report array/varargs duplicate declaration
 327      */
 328     void varargsDuplicateError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
 329         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
 330             log.error(pos, Errors.ArrayAndVarargs(sym1, sym2, sym2.location()));
 331         }
 332     }
 333 
 334 /* ************************************************************************
 335  * duplicate declaration checking
 336  *************************************************************************/
 337 
 338     /** Check that variable does not hide variable with same name in
 339      *  immediately enclosing local scope.
 340      *  @param pos           Position for error reporting.
 341      *  @param v             The symbol.
 342      *  @param s             The scope.
 343      */
 344     void checkTransparentVar(DiagnosticPosition pos, VarSymbol v, Scope s) {
 345         for (Symbol sym : s.getSymbolsByName(v.name)) {
 346             if (sym.owner != v.owner) break;
 347             if (sym.kind == VAR &&
 348                 sym.owner.kind.matches(KindSelector.VAL_MTH) &&
 349                 v.name != names.error) {
 350                 duplicateError(pos, sym);
 351                 return;
 352             }
 353         }
 354     }
 355 
 356     /** Check that a class or interface does not hide a class or
 357      *  interface with same name in immediately enclosing local scope.
 358      *  @param pos           Position for error reporting.
 359      *  @param c             The symbol.
 360      *  @param s             The scope.
 361      */
 362     void checkTransparentClass(DiagnosticPosition pos, ClassSymbol c, Scope s) {
 363         for (Symbol sym : s.getSymbolsByName(c.name)) {
 364             if (sym.owner != c.owner) break;
 365             if (sym.kind == TYP && !sym.type.hasTag(TYPEVAR) &&
 366                 sym.owner.kind.matches(KindSelector.VAL_MTH) &&
 367                 c.name != names.error) {
 368                 duplicateError(pos, sym);
 369                 return;
 370             }
 371         }
 372     }
 373 
 374     /** Check that class does not have the same name as one of
 375      *  its enclosing classes, or as a class defined in its enclosing scope.
 376      *  return true if class is unique in its enclosing scope.
 377      *  @param pos           Position for error reporting.
 378      *  @param name          The class name.
 379      *  @param s             The enclosing scope.
 380      */
 381     boolean checkUniqueClassName(DiagnosticPosition pos, Name name, Scope s) {
 382         for (Symbol sym : s.getSymbolsByName(name, NON_RECURSIVE)) {
 383             if (sym.kind == TYP && sym.name != names.error) {
 384                 duplicateError(pos, sym);
 385                 return false;
 386             }
 387         }
 388         for (Symbol sym = s.owner; sym != null; sym = sym.owner) {
 389             if (sym.kind == TYP && sym.name == name && sym.name != names.error) {
 390                 duplicateError(pos, sym);
 391                 return true;
 392             }
 393         }
 394         return true;
 395     }
 396 
 397 /* *************************************************************************
 398  * Class name generation
 399  **************************************************************************/
 400 
 401 
 402     private Map<Pair<Name, Name>, Integer> localClassNameIndexes = new HashMap<>();
 403 
 404     /** Return name of local class.
 405      *  This is of the form   {@code <enclClass> $ n <classname> }
 406      *  where
 407      *    enclClass is the flat name of the enclosing class,
 408      *    classname is the simple name of the local class
 409      */
 410     Name localClassName(ClassSymbol c) {
 411         Name enclFlatname = c.owner.enclClass().flatname;
 412         String enclFlatnameStr = enclFlatname.toString();
 413         Pair<Name, Name> key = new Pair<>(enclFlatname, c.name);
 414         Integer index = localClassNameIndexes.get(key);
 415         for (int i = (index == null) ? 1 : index; ; i++) {
 416             Name flatname = names.fromString(enclFlatnameStr
 417                     + syntheticNameChar + i + c.name);
 418             if (getCompiled(c.packge().modle, flatname) == null) {
 419                 localClassNameIndexes.put(key, i + 1);
 420                 return flatname;
 421             }
 422         }
 423     }
 424 
 425     void clearLocalClassNameIndexes(ClassSymbol c) {
 426         if (c.owner != null && c.owner.kind != NIL) {
 427             localClassNameIndexes.remove(new Pair<>(
 428                     c.owner.enclClass().flatname, c.name));
 429         }
 430     }
 431 
 432     public void newRound() {
 433         compiled.clear();
 434         localClassNameIndexes.clear();
 435     }
 436 
 437     public void putCompiled(ClassSymbol csym) {
 438         compiled.put(Pair.of(csym.packge().modle, csym.flatname), csym);
 439     }
 440 
 441     public ClassSymbol getCompiled(ClassSymbol csym) {
 442         return compiled.get(Pair.of(csym.packge().modle, csym.flatname));
 443     }
 444 
 445     public ClassSymbol getCompiled(ModuleSymbol msym, Name flatname) {
 446         return compiled.get(Pair.of(msym, flatname));
 447     }
 448 
 449     public void removeCompiled(ClassSymbol csym) {
 450         compiled.remove(Pair.of(csym.packge().modle, csym.flatname));
 451     }
 452 
 453 /* *************************************************************************
 454  * Type Checking
 455  **************************************************************************/
 456 
 457     /**
 458      * A check context is an object that can be used to perform compatibility
 459      * checks - depending on the check context, meaning of 'compatibility' might
 460      * vary significantly.
 461      */
 462     public interface CheckContext {
 463         /**
 464          * Is type 'found' compatible with type 'req' in given context
 465          */
 466         boolean compatible(Type found, Type req, Warner warn);
 467         /**
 468          * Report a check error
 469          */
 470         void report(DiagnosticPosition pos, JCDiagnostic details);
 471         /**
 472          * Obtain a warner for this check context
 473          */
 474         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req);
 475 
 476         public InferenceContext inferenceContext();
 477 
 478         public DeferredAttr.DeferredAttrContext deferredAttrContext();
 479     }
 480 
 481     /**
 482      * This class represent a check context that is nested within another check
 483      * context - useful to check sub-expressions. The default behavior simply
 484      * redirects all method calls to the enclosing check context leveraging
 485      * the forwarding pattern.
 486      */
 487     static class NestedCheckContext implements CheckContext {
 488         CheckContext enclosingContext;
 489 
 490         NestedCheckContext(CheckContext enclosingContext) {
 491             this.enclosingContext = enclosingContext;
 492         }
 493 
 494         public boolean compatible(Type found, Type req, Warner warn) {
 495             return enclosingContext.compatible(found, req, warn);
 496         }
 497 
 498         public void report(DiagnosticPosition pos, JCDiagnostic details) {
 499             enclosingContext.report(pos, details);
 500         }
 501 
 502         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
 503             return enclosingContext.checkWarner(pos, found, req);
 504         }
 505 
 506         public InferenceContext inferenceContext() {
 507             return enclosingContext.inferenceContext();
 508         }
 509 
 510         public DeferredAttrContext deferredAttrContext() {
 511             return enclosingContext.deferredAttrContext();
 512         }
 513     }
 514 
 515     /**
 516      * Check context to be used when evaluating assignment/return statements
 517      */
 518     CheckContext basicHandler = new CheckContext() {
 519         public void report(DiagnosticPosition pos, JCDiagnostic details) {
 520             log.error(pos, Errors.ProbFoundReq(details));
 521         }
 522         public boolean compatible(Type found, Type req, Warner warn) {
 523             return types.isAssignable(found, req, warn);
 524         }
 525 
 526         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
 527             return convertWarner(pos, found, req);
 528         }
 529 
 530         public InferenceContext inferenceContext() {
 531             return infer.emptyContext;
 532         }
 533 
 534         public DeferredAttrContext deferredAttrContext() {
 535             return deferredAttr.emptyDeferredAttrContext;
 536         }
 537 
 538         @Override
 539         public String toString() {
 540             return "CheckContext: basicHandler";
 541         }
 542     };
 543 
 544     /** Check that a given type is assignable to a given proto-type.
 545      *  If it is, return the type, otherwise return errType.
 546      *  @param pos        Position to be used for error reporting.
 547      *  @param found      The type that was found.
 548      *  @param req        The type that was required.
 549      */
 550     public Type checkType(DiagnosticPosition pos, Type found, Type req) {
 551         return checkType(pos, found, req, basicHandler);
 552     }
 553 
 554     Type checkType(final DiagnosticPosition pos, final Type found, final Type req, final CheckContext checkContext) {
 555         final InferenceContext inferenceContext = checkContext.inferenceContext();
 556         if (inferenceContext.free(req) || inferenceContext.free(found)) {
 557             inferenceContext.addFreeTypeListener(List.of(req, found),
 558                     solvedContext -> checkType(pos, solvedContext.asInstType(found), solvedContext.asInstType(req), checkContext));
 559         }
 560         if (req.hasTag(ERROR))
 561             return req;
 562         if (req.hasTag(NONE))
 563             return found;
 564         if (checkContext.compatible(found, req, checkContext.checkWarner(pos, found, req))) {
 565             return found;
 566         } else {
 567             if (found.isNumeric() && req.isNumeric()) {
 568                 checkContext.report(pos, diags.fragment(Fragments.PossibleLossOfPrecision(found, req)));
 569                 return types.createErrorType(found);
 570             }
 571             checkContext.report(pos, diags.fragment(Fragments.InconvertibleTypes(found, req)));
 572             return types.createErrorType(found);
 573         }
 574     }
 575 
 576     /** Check that a given type can be cast to a given target type.
 577      *  Return the result of the cast.
 578      *  @param pos        Position to be used for error reporting.
 579      *  @param found      The type that is being cast.
 580      *  @param req        The target type of the cast.
 581      */
 582     Type checkCastable(DiagnosticPosition pos, Type found, Type req) {
 583         return checkCastable(pos, found, req, basicHandler);
 584     }
 585     Type checkCastable(DiagnosticPosition pos, Type found, Type req, CheckContext checkContext) {
 586         if (types.isCastable(found, req, castWarner(pos, found, req))) {
 587             return req;
 588         } else {
 589             checkContext.report(pos, diags.fragment(Fragments.InconvertibleTypes(found, req)));
 590             return types.createErrorType(found);
 591         }
 592     }
 593 
 594     /** Check for redundant casts (i.e. where source type is a subtype of target type)
 595      * The problem should only be reported for non-292 cast
 596      */
 597     public void checkRedundantCast(Env<AttrContext> env, final JCTypeCast tree) {
 598         if (!tree.type.isErroneous()
 599                 && types.isSameType(tree.expr.type, tree.clazz.type)
 600                 && !(ignoreAnnotatedCasts && TreeInfo.containsTypeAnnotation(tree.clazz))
 601                 && !is292targetTypeCast(tree)) {
 602             deferredLintHandler.report(() -> {
 603                 if (lint.isEnabled(LintCategory.CAST))
 604                     log.warning(LintCategory.CAST,
 605                             tree.pos(), Warnings.RedundantCast(tree.clazz.type));
 606             });
 607         }
 608     }
 609     //where
 610         private boolean is292targetTypeCast(JCTypeCast tree) {
 611             boolean is292targetTypeCast = false;
 612             JCExpression expr = TreeInfo.skipParens(tree.expr);
 613             if (expr.hasTag(APPLY)) {
 614                 JCMethodInvocation apply = (JCMethodInvocation)expr;
 615                 Symbol sym = TreeInfo.symbol(apply.meth);
 616                 is292targetTypeCast = sym != null &&
 617                     sym.kind == MTH &&
 618                     (sym.flags() & HYPOTHETICAL) != 0;
 619             }
 620             return is292targetTypeCast;
 621         }
 622 
 623         private static final boolean ignoreAnnotatedCasts = true;
 624 
 625     /** Check that a type is within some bounds.
 626      *
 627      *  Used in TypeApply to verify that, e.g., X in {@code V<X>} is a valid
 628      *  type argument.
 629      *  @param a             The type that should be bounded by bs.
 630      *  @param bound         The bound.
 631      */
 632     private boolean checkExtends(Type a, Type bound) {
 633          if (a.isUnbound()) {
 634              return true;
 635          } else if (!a.hasTag(WILDCARD)) {
 636              a = types.cvarUpperBound(a);
 637              return types.isSubtype(a, bound);
 638          } else if (a.isExtendsBound()) {
 639              return types.isCastable(bound, types.wildUpperBound(a), types.noWarnings);
 640          } else if (a.isSuperBound()) {
 641              return !types.notSoftSubtype(types.wildLowerBound(a), bound);
 642          }
 643          return true;
 644      }
 645 
 646     /** Check that type is different from 'void'.
 647      *  @param pos           Position to be used for error reporting.
 648      *  @param t             The type to be checked.
 649      */
 650     Type checkNonVoid(DiagnosticPosition pos, Type t) {
 651         if (t.hasTag(VOID)) {
 652             log.error(pos, Errors.VoidNotAllowedHere);
 653             return types.createErrorType(t);
 654         } else {
 655             return t;
 656         }
 657     }
 658 
 659     Type checkClassOrArrayType(DiagnosticPosition pos, Type t) {
 660         if (!t.hasTag(CLASS) && !t.hasTag(ARRAY) && !t.hasTag(ERROR)) {
 661             return typeTagError(pos,
 662                                 diags.fragment(Fragments.TypeReqClassArray),
 663                                 asTypeParam(t));
 664         } else {
 665             return t;
 666         }
 667     }
 668 
 669     /** Check that type is a class or interface type.
 670      *  @param pos           Position to be used for error reporting.
 671      *  @param t             The type to be checked.
 672      */
 673     Type checkClassType(DiagnosticPosition pos, Type t) {
 674         if (!t.hasTag(CLASS) && !t.hasTag(ERROR)) {
 675             return typeTagError(pos,
 676                                 diags.fragment(Fragments.TypeReqClass),
 677                                 asTypeParam(t));
 678         } else {
 679             return t;
 680         }
 681     }
 682     //where
 683         private Object asTypeParam(Type t) {
 684             return (t.hasTag(TYPEVAR))
 685                                     ? diags.fragment(Fragments.TypeParameter(t))
 686                                     : t;
 687         }
 688 
 689     /** Check that type is a valid qualifier for a constructor reference expression
 690      */
 691     Type checkConstructorRefType(DiagnosticPosition pos, Type t) {
 692         t = checkClassOrArrayType(pos, t);
 693         if (t.hasTag(CLASS)) {
 694             if ((t.tsym.flags() & (ABSTRACT | INTERFACE)) != 0) {
 695                 log.error(pos, Errors.AbstractCantBeInstantiated(t.tsym));
 696                 t = types.createErrorType(t);
 697             } else if ((t.tsym.flags() & ENUM) != 0) {
 698                 log.error(pos, Errors.EnumCantBeInstantiated);
 699                 t = types.createErrorType(t);
 700             } else {
 701                 t = checkClassType(pos, t, true);
 702             }
 703         } else if (t.hasTag(ARRAY)) {
 704             if (!types.isReifiable(((ArrayType)t).elemtype)) {
 705                 log.error(pos, Errors.GenericArrayCreation);
 706                 t = types.createErrorType(t);
 707             }
 708         }
 709         return t;
 710     }
 711 
 712     /** Check that type is a class or interface type.
 713      *  @param pos           Position to be used for error reporting.
 714      *  @param t             The type to be checked.
 715      *  @param noBounds    True if type bounds are illegal here.
 716      */
 717     Type checkClassType(DiagnosticPosition pos, Type t, boolean noBounds) {
 718         t = checkClassType(pos, t);
 719         if (noBounds && t.isParameterized()) {
 720             List<Type> args = t.getTypeArguments();
 721             while (args.nonEmpty()) {
 722                 if (args.head.hasTag(WILDCARD))
 723                     return typeTagError(pos,
 724                                         diags.fragment(Fragments.TypeReqExact),
 725                                         args.head);
 726                 args = args.tail;
 727             }
 728         }
 729         return t;
 730     }
 731 
 732     /** Check that type is a reference type, i.e. a class, interface or array type
 733      *  or a type variable.
 734      *  @param pos           Position to be used for error reporting.
 735      *  @param t             The type to be checked.
 736      */
 737     Type checkRefType(DiagnosticPosition pos, Type t) {
 738         if (t.isReference())
 739             return t;
 740         else
 741             return typeTagError(pos,
 742                                 diags.fragment(Fragments.TypeReqRef),
 743                                 t);
 744     }
 745 
 746     /** Check that each type is a reference type, i.e. a class, interface or array type
 747      *  or a type variable.
 748      *  @param trees         Original trees, used for error reporting.
 749      *  @param types         The types to be checked.
 750      */
 751     List<Type> checkRefTypes(List<JCExpression> trees, List<Type> types) {
 752         List<JCExpression> tl = trees;
 753         for (List<Type> l = types; l.nonEmpty(); l = l.tail) {
 754             l.head = checkRefType(tl.head.pos(), l.head);
 755             tl = tl.tail;
 756         }
 757         return types;
 758     }
 759 
 760     /** Check that type is a null or reference type.
 761      *  @param pos           Position to be used for error reporting.
 762      *  @param t             The type to be checked.
 763      */
 764     Type checkNullOrRefType(DiagnosticPosition pos, Type t) {
 765         if (t.isReference() || t.hasTag(BOT))
 766             return t;
 767         else
 768             return typeTagError(pos,
 769                                 diags.fragment(Fragments.TypeReqRef),
 770                                 t);
 771     }
 772 
 773     /** Check that flag set does not contain elements of two conflicting sets. s
 774      *  Return true if it doesn't.
 775      *  @param pos           Position to be used for error reporting.
 776      *  @param flags         The set of flags to be checked.
 777      *  @param set1          Conflicting flags set #1.
 778      *  @param set2          Conflicting flags set #2.
 779      */
 780     boolean checkDisjoint(DiagnosticPosition pos, long flags, long set1, long set2) {
 781         if ((flags & set1) != 0 && (flags & set2) != 0) {
 782             log.error(pos,
 783                       Errors.IllegalCombinationOfModifiers(asFlagSet(TreeInfo.firstFlag(flags & set1)),
 784                                                            asFlagSet(TreeInfo.firstFlag(flags & set2))));
 785             return false;
 786         } else
 787             return true;
 788     }
 789 
 790     /** Check that usage of diamond operator is correct (i.e. diamond should not
 791      * be used with non-generic classes or in anonymous class creation expressions)
 792      */
 793     Type checkDiamond(JCNewClass tree, Type t) {
 794         if (!TreeInfo.isDiamond(tree) ||
 795                 t.isErroneous()) {
 796             return checkClassType(tree.clazz.pos(), t, true);
 797         } else {
 798             if (tree.def != null && !Feature.DIAMOND_WITH_ANONYMOUS_CLASS_CREATION.allowedInSource(source)) {
 799                 log.error(DiagnosticFlag.SOURCE_LEVEL, tree.clazz.pos(),
 800                         Errors.CantApplyDiamond1(t, Feature.DIAMOND_WITH_ANONYMOUS_CLASS_CREATION.fragment(source.name)));
 801             }
 802             if (t.tsym.type.getTypeArguments().isEmpty()) {
 803                 log.error(tree.clazz.pos(),
 804                           Errors.CantApplyDiamond1(t,
 805                                                    Fragments.DiamondNonGeneric(t)));
 806                 return types.createErrorType(t);
 807             } else if (tree.typeargs != null &&
 808                     tree.typeargs.nonEmpty()) {
 809                 log.error(tree.clazz.pos(),
 810                           Errors.CantApplyDiamond1(t,
 811                                                    Fragments.DiamondAndExplicitParams(t)));
 812                 return types.createErrorType(t);
 813             } else {
 814                 return t;
 815             }
 816         }
 817     }
 818 
 819     /** Check that the type inferred using the diamond operator does not contain
 820      *  non-denotable types such as captured types or intersection types.
 821      *  @param t the type inferred using the diamond operator
 822      *  @return  the (possibly empty) list of non-denotable types.
 823      */
 824     List<Type> checkDiamondDenotable(ClassType t) {
 825         ListBuffer<Type> buf = new ListBuffer<>();
 826         for (Type arg : t.allparams()) {
 827             if (!checkDenotable(arg)) {
 828                 buf.append(arg);
 829             }
 830         }
 831         return buf.toList();
 832     }
 833 
 834     public boolean checkDenotable(Type t) {
 835         return denotableChecker.visit(t, null);
 836     }
 837         // where
 838 
 839         /** diamondTypeChecker: A type visitor that descends down the given type looking for non-denotable
 840          *  types. The visit methods return false as soon as a non-denotable type is encountered and true
 841          *  otherwise.
 842          */
 843         private static final Types.SimpleVisitor<Boolean, Void> denotableChecker = new Types.SimpleVisitor<Boolean, Void>() {
 844             @Override
 845             public Boolean visitType(Type t, Void s) {
 846                 return true;
 847             }
 848             @Override
 849             public Boolean visitClassType(ClassType t, Void s) {
 850                 if (t.isUnion() || t.isIntersection()) {
 851                     return false;
 852                 }
 853                 for (Type targ : t.allparams()) {
 854                     if (!visit(targ, s)) {
 855                         return false;
 856                     }
 857                 }
 858                 return true;
 859             }
 860 
 861             @Override
 862             public Boolean visitTypeVar(TypeVar t, Void s) {
 863                 /* Any type variable mentioned in the inferred type must have been declared as a type parameter
 864                   (i.e cannot have been produced by inference (18.4))
 865                 */
 866                 return (t.tsym.flags() & SYNTHETIC) == 0;
 867             }
 868 
 869             @Override
 870             public Boolean visitCapturedType(CapturedType t, Void s) {
 871                 /* Any type variable mentioned in the inferred type must have been declared as a type parameter
 872                   (i.e cannot have been produced by capture conversion (5.1.10))
 873                 */
 874                 return false;
 875             }
 876 
 877             @Override
 878             public Boolean visitArrayType(ArrayType t, Void s) {
 879                 return visit(t.elemtype, s);
 880             }
 881 
 882             @Override
 883             public Boolean visitWildcardType(WildcardType t, Void s) {
 884                 return visit(t.type, s);
 885             }
 886         };
 887 
 888     void checkVarargsMethodDecl(Env<AttrContext> env, JCMethodDecl tree) {
 889         MethodSymbol m = tree.sym;
 890         boolean hasTrustMeAnno = m.attribute(syms.trustMeType.tsym) != null;
 891         Type varargElemType = null;
 892         if (m.isVarArgs()) {
 893             varargElemType = types.elemtype(tree.params.last().type);
 894         }
 895         if (hasTrustMeAnno && !isTrustMeAllowedOnMethod(m)) {
 896             if (varargElemType != null) {
 897                 JCDiagnostic msg = Feature.PRIVATE_SAFE_VARARGS.allowedInSource(source) ?
 898                         diags.fragment(Fragments.VarargsTrustmeOnVirtualVarargs(m)) :
 899                         diags.fragment(Fragments.VarargsTrustmeOnVirtualVarargsFinalOnly(m));
 900                 log.error(tree,
 901                           Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym,
 902                                                            msg));
 903             } else {
 904                 log.error(tree,
 905                           Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym,
 906                                                            Fragments.VarargsTrustmeOnNonVarargsMeth(m)));
 907             }
 908         } else if (hasTrustMeAnno && varargElemType != null &&
 909                             types.isReifiable(varargElemType)) {
 910             warnUnsafeVararg(tree, Warnings.VarargsRedundantTrustmeAnno(
 911                                 syms.trustMeType.tsym,
 912                                 diags.fragment(Fragments.VarargsTrustmeOnReifiableVarargs(varargElemType))));
 913         }
 914         else if (!hasTrustMeAnno && varargElemType != null &&
 915                 !types.isReifiable(varargElemType)) {
 916             warnUnchecked(tree.params.head.pos(), Warnings.UncheckedVarargsNonReifiableType(varargElemType));
 917         }
 918     }
 919     //where
 920         private boolean isTrustMeAllowedOnMethod(Symbol s) {
 921             return (s.flags() & VARARGS) != 0 &&
 922                 (s.isConstructor() ||
 923                     (s.flags() & (STATIC | FINAL |
 924                                   (Feature.PRIVATE_SAFE_VARARGS.allowedInSource(source) ? PRIVATE : 0) )) != 0);
 925         }
 926 
 927     Type checkLocalVarType(DiagnosticPosition pos, Type t, Name name) {
 928         //check that resulting type is not the null type
 929         if (t.hasTag(BOT)) {
 930             log.error(pos, Errors.CantInferLocalVarType(name, Fragments.LocalCantInferNull));
 931             return types.createErrorType(t);
 932         } else if (t.hasTag(VOID)) {
 933             log.error(pos, Errors.CantInferLocalVarType(name, Fragments.LocalCantInferVoid));
 934             return types.createErrorType(t);
 935         }
 936 
 937         //upward project the initializer type
 938         return types.upward(t, types.captures(t));
 939     }
 940 
 941     Type checkMethod(final Type mtype,
 942             final Symbol sym,
 943             final Env<AttrContext> env,
 944             final List<JCExpression> argtrees,
 945             final List<Type> argtypes,
 946             final boolean useVarargs,
 947             InferenceContext inferenceContext) {
 948         // System.out.println("call   : " + env.tree);
 949         // System.out.println("method : " + owntype);
 950         // System.out.println("actuals: " + argtypes);
 951         if (inferenceContext.free(mtype)) {
 952             inferenceContext.addFreeTypeListener(List.of(mtype),
 953                     solvedContext -> checkMethod(solvedContext.asInstType(mtype), sym, env, argtrees, argtypes, useVarargs, solvedContext));
 954             return mtype;
 955         }
 956         Type owntype = mtype;
 957         List<Type> formals = owntype.getParameterTypes();
 958         List<Type> nonInferred = sym.type.getParameterTypes();
 959         if (nonInferred.length() != formals.length()) nonInferred = formals;
 960         Type last = useVarargs ? formals.last() : null;
 961         if (sym.name == names.init && sym.owner == syms.enumSym) {
 962             formals = formals.tail.tail;
 963             nonInferred = nonInferred.tail.tail;
 964         }
 965         if ((sym.flags() & ANONCONSTR_BASED) != 0) {
 966             formals = formals.tail;
 967             nonInferred = nonInferred.tail;
 968         }
 969         List<JCExpression> args = argtrees;
 970         if (args != null) {
 971             //this is null when type-checking a method reference
 972             while (formals.head != last) {
 973                 JCTree arg = args.head;
 974                 Warner warn = convertWarner(arg.pos(), arg.type, nonInferred.head);
 975                 assertConvertible(arg, arg.type, formals.head, warn);
 976                 args = args.tail;
 977                 formals = formals.tail;
 978                 nonInferred = nonInferred.tail;
 979             }
 980             if (useVarargs) {
 981                 Type varArg = types.elemtype(last);
 982                 while (args.tail != null) {
 983                     JCTree arg = args.head;
 984                     Warner warn = convertWarner(arg.pos(), arg.type, varArg);
 985                     assertConvertible(arg, arg.type, varArg, warn);
 986                     args = args.tail;
 987                 }
 988             } else if ((sym.flags() & (VARARGS | SIGNATURE_POLYMORPHIC)) == VARARGS) {
 989                 // non-varargs call to varargs method
 990                 Type varParam = owntype.getParameterTypes().last();
 991                 Type lastArg = argtypes.last();
 992                 if (types.isSubtypeUnchecked(lastArg, types.elemtype(varParam)) &&
 993                     !types.isSameType(types.erasure(varParam), types.erasure(lastArg)))
 994                     log.warning(argtrees.last().pos(),
 995                                 Warnings.InexactNonVarargsCall(types.elemtype(varParam),varParam));
 996             }
 997         }
 998         if (useVarargs) {
 999             Type argtype = owntype.getParameterTypes().last();
1000             if (!types.isReifiable(argtype) &&
1001                 (sym.baseSymbol().attribute(syms.trustMeType.tsym) == null ||
1002                  !isTrustMeAllowedOnMethod(sym))) {
1003                 warnUnchecked(env.tree.pos(), Warnings.UncheckedGenericArrayCreation(argtype));
1004             }
1005             TreeInfo.setVarargsElement(env.tree, types.elemtype(argtype));
1006          }
1007          return owntype;
1008     }
1009     //where
1010     private void assertConvertible(JCTree tree, Type actual, Type formal, Warner warn) {
1011         if (types.isConvertible(actual, formal, warn))
1012             return;
1013 
1014         if (formal.isCompound()
1015             && types.isSubtype(actual, types.supertype(formal))
1016             && types.isSubtypeUnchecked(actual, types.interfaces(formal), warn))
1017             return;
1018     }
1019 
1020     /**
1021      * Check that type 't' is a valid instantiation of a generic class
1022      * (see JLS 4.5)
1023      *
1024      * @param t class type to be checked
1025      * @return true if 't' is well-formed
1026      */
1027     public boolean checkValidGenericType(Type t) {
1028         return firstIncompatibleTypeArg(t) == null;
1029     }
1030     //WHERE
1031         private Type firstIncompatibleTypeArg(Type type) {
1032             List<Type> formals = type.tsym.type.allparams();
1033             List<Type> actuals = type.allparams();
1034             List<Type> args = type.getTypeArguments();
1035             List<Type> forms = type.tsym.type.getTypeArguments();
1036             ListBuffer<Type> bounds_buf = new ListBuffer<>();
1037 
1038             // For matching pairs of actual argument types `a' and
1039             // formal type parameters with declared bound `b' ...
1040             while (args.nonEmpty() && forms.nonEmpty()) {
1041                 // exact type arguments needs to know their
1042                 // bounds (for upper and lower bound
1043                 // calculations).  So we create new bounds where
1044                 // type-parameters are replaced with actuals argument types.
1045                 bounds_buf.append(types.subst(forms.head.getUpperBound(), formals, actuals));
1046                 args = args.tail;
1047                 forms = forms.tail;
1048             }
1049 
1050             args = type.getTypeArguments();
1051             List<Type> tvars_cap = types.substBounds(formals,
1052                                       formals,
1053                                       types.capture(type).allparams());
1054             while (args.nonEmpty() && tvars_cap.nonEmpty()) {
1055                 // Let the actual arguments know their bound
1056                 args.head.withTypeVar((TypeVar)tvars_cap.head);
1057                 args = args.tail;
1058                 tvars_cap = tvars_cap.tail;
1059             }
1060 
1061             args = type.getTypeArguments();
1062             List<Type> bounds = bounds_buf.toList();
1063 
1064             while (args.nonEmpty() && bounds.nonEmpty()) {
1065                 Type actual = args.head;
1066                 if (!isTypeArgErroneous(actual) &&
1067                         !bounds.head.isErroneous() &&
1068                         !checkExtends(actual, bounds.head)) {
1069                     return args.head;
1070                 }
1071                 args = args.tail;
1072                 bounds = bounds.tail;
1073             }
1074 
1075             args = type.getTypeArguments();
1076             bounds = bounds_buf.toList();
1077 
1078             for (Type arg : types.capture(type).getTypeArguments()) {
1079                 if (arg.hasTag(TYPEVAR) &&
1080                         arg.getUpperBound().isErroneous() &&
1081                         !bounds.head.isErroneous() &&
1082                         !isTypeArgErroneous(args.head)) {
1083                     return args.head;
1084                 }
1085                 bounds = bounds.tail;
1086                 args = args.tail;
1087             }
1088 
1089             return null;
1090         }
1091         //where
1092         boolean isTypeArgErroneous(Type t) {
1093             return isTypeArgErroneous.visit(t);
1094         }
1095 
1096         Types.UnaryVisitor<Boolean> isTypeArgErroneous = new Types.UnaryVisitor<Boolean>() {
1097             public Boolean visitType(Type t, Void s) {
1098                 return t.isErroneous();
1099             }
1100             @Override
1101             public Boolean visitTypeVar(TypeVar t, Void s) {
1102                 return visit(t.getUpperBound());
1103             }
1104             @Override
1105             public Boolean visitCapturedType(CapturedType t, Void s) {
1106                 return visit(t.getUpperBound()) ||
1107                         visit(t.getLowerBound());
1108             }
1109             @Override
1110             public Boolean visitWildcardType(WildcardType t, Void s) {
1111                 return visit(t.type);
1112             }
1113         };
1114 
1115     /** Check that given modifiers are legal for given symbol and
1116      *  return modifiers together with any implicit modifiers for that symbol.
1117      *  Warning: we can't use flags() here since this method
1118      *  is called during class enter, when flags() would cause a premature
1119      *  completion.
1120      *  @param pos           Position to be used for error reporting.
1121      *  @param flags         The set of modifiers given in a definition.
1122      *  @param sym           The defined symbol.
1123      */
1124     long checkFlags(DiagnosticPosition pos, long flags, Symbol sym, JCTree tree) {
1125         long mask;
1126         long implicit = 0;
1127 
1128         switch (sym.kind) {
1129         case VAR:
1130             if (TreeInfo.isReceiverParam(tree))
1131                 mask = ReceiverParamFlags;
1132             else if (sym.owner.kind != TYP)
1133                 mask = LocalVarFlags;
1134             else if ((sym.owner.flags_field & INTERFACE) != 0)
1135                 mask = implicit = InterfaceVarFlags;
1136             else
1137                 mask = VarFlags;
1138             break;
1139         case MTH:
1140             if (sym.name == names.init) {
1141                 if ((sym.owner.flags_field & ENUM) != 0) {
1142                     // enum constructors cannot be declared public or
1143                     // protected and must be implicitly or explicitly
1144                     // private
1145                     implicit = PRIVATE;
1146                     mask = PRIVATE;
1147                 } else
1148                     mask = ConstructorFlags;
1149             }  else if ((sym.owner.flags_field & INTERFACE) != 0) {
1150                 if ((sym.owner.flags_field & ANNOTATION) != 0) {
1151                     mask = AnnotationTypeElementMask;
1152                     implicit = PUBLIC | ABSTRACT;
1153                 } else if ((flags & (DEFAULT | STATIC | PRIVATE)) != 0) {
1154                     mask = InterfaceMethodMask;
1155                     implicit = (flags & PRIVATE) != 0 ? 0 : PUBLIC;
1156                     if ((flags & DEFAULT) != 0) {
1157                         implicit |= ABSTRACT;
1158                     }
1159                 } else {
1160                     mask = implicit = InterfaceMethodFlags;
1161                 }
1162             } else {
1163                 mask = MethodFlags;
1164             }
1165             // Imply STRICTFP if owner has STRICTFP set.
1166             if (((flags|implicit) & Flags.ABSTRACT) == 0 ||
1167                 ((flags) & Flags.DEFAULT) != 0)
1168                 implicit |= sym.owner.flags_field & STRICTFP;
1169             break;
1170         case TYP:
1171             if (sym.isLocal()) {
1172                 mask = LocalClassFlags;
1173                 if ((sym.owner.flags_field & STATIC) == 0 &&
1174                     (flags & ENUM) != 0)
1175                     log.error(pos, Errors.EnumsMustBeStatic);
1176             } else if (sym.owner.kind == TYP) {
1177                 mask = MemberClassFlags;
1178                 if (sym.owner.owner.kind == PCK ||
1179                     (sym.owner.flags_field & STATIC) != 0)
1180                     mask |= STATIC;
1181                 else if ((flags & ENUM) != 0)
1182                     log.error(pos, Errors.EnumsMustBeStatic);
1183                 // Nested interfaces and enums are always STATIC (Spec ???)
1184                 if ((flags & (INTERFACE | ENUM)) != 0 ) implicit = STATIC;
1185             } else {
1186                 mask = ClassFlags;
1187             }
1188             // Interfaces are always ABSTRACT
1189             if ((flags & INTERFACE) != 0) implicit |= ABSTRACT;
1190 
1191             if ((flags & ENUM) != 0) {
1192                 // enums can't be declared abstract or final
1193                 mask &= ~(ABSTRACT | FINAL);
1194                 implicit |= implicitEnumFinalFlag(tree);
1195             }
1196             // Imply STRICTFP if owner has STRICTFP set.
1197             implicit |= sym.owner.flags_field & STRICTFP;
1198             break;
1199         default:
1200             throw new AssertionError();
1201         }
1202         long illegal = flags & ExtendedStandardFlags & ~mask;
1203         if (illegal != 0) {
1204             if ((illegal & INTERFACE) != 0) {
1205                 log.error(pos, ((flags & ANNOTATION) != 0) ? Errors.AnnotationDeclNotAllowedHere : Errors.IntfNotAllowedHere);
1206                 mask |= INTERFACE;
1207             }
1208             else {
1209                 log.error(pos,
1210                           Errors.ModNotAllowedHere(asFlagSet(illegal)));
1211             }
1212         }
1213         else if ((sym.kind == TYP ||
1214                   // ISSUE: Disallowing abstract&private is no longer appropriate
1215                   // in the presence of inner classes. Should it be deleted here?
1216                   checkDisjoint(pos, flags,
1217                                 ABSTRACT,
1218                                 PRIVATE | STATIC | DEFAULT))
1219                  &&
1220                  checkDisjoint(pos, flags,
1221                                 STATIC | PRIVATE,
1222                                 DEFAULT)
1223                  &&
1224                  checkDisjoint(pos, flags,
1225                                ABSTRACT | INTERFACE,
1226                                FINAL | NATIVE | SYNCHRONIZED)
1227                  &&
1228                  checkDisjoint(pos, flags,
1229                                PUBLIC,
1230                                PRIVATE | PROTECTED)
1231                  &&
1232                  checkDisjoint(pos, flags,
1233                                PRIVATE,
1234                                PUBLIC | PROTECTED)
1235                  &&
1236                  checkDisjoint(pos, flags,
1237                                FINAL,
1238                                VOLATILE)
1239                  &&
1240                  (sym.kind == TYP ||
1241                   checkDisjoint(pos, flags,
1242                                 ABSTRACT | NATIVE,
1243                                 STRICTFP))) {
1244             // skip
1245         }
1246         return flags & (mask | ~ExtendedStandardFlags) | implicit;
1247     }
1248 
1249 
1250     /** Determine if this enum should be implicitly final.
1251      *
1252      *  If the enum has no specialized enum contants, it is final.
1253      *
1254      *  If the enum does have specialized enum contants, it is
1255      *  <i>not</i> final.
1256      */
1257     private long implicitEnumFinalFlag(JCTree tree) {
1258         if (!tree.hasTag(CLASSDEF)) return 0;
1259         class SpecialTreeVisitor extends JCTree.Visitor {
1260             boolean specialized;
1261             SpecialTreeVisitor() {
1262                 this.specialized = false;
1263             }
1264 
1265             @Override
1266             public void visitTree(JCTree tree) { /* no-op */ }
1267 
1268             @Override
1269             public void visitVarDef(JCVariableDecl tree) {
1270                 if ((tree.mods.flags & ENUM) != 0) {
1271                     if (tree.init instanceof JCNewClass &&
1272                         ((JCNewClass) tree.init).def != null) {
1273                         specialized = true;
1274                     }
1275                 }
1276             }
1277         }
1278 
1279         SpecialTreeVisitor sts = new SpecialTreeVisitor();
1280         JCClassDecl cdef = (JCClassDecl) tree;
1281         for (JCTree defs: cdef.defs) {
1282             defs.accept(sts);
1283             if (sts.specialized) return 0;
1284         }
1285         return FINAL;
1286     }
1287 
1288 /* *************************************************************************
1289  * Type Validation
1290  **************************************************************************/
1291 
1292     /** Validate a type expression. That is,
1293      *  check that all type arguments of a parametric type are within
1294      *  their bounds. This must be done in a second phase after type attribution
1295      *  since a class might have a subclass as type parameter bound. E.g:
1296      *
1297      *  <pre>{@code
1298      *  class B<A extends C> { ... }
1299      *  class C extends B<C> { ... }
1300      *  }</pre>
1301      *
1302      *  and we can't make sure that the bound is already attributed because
1303      *  of possible cycles.
1304      *
1305      * Visitor method: Validate a type expression, if it is not null, catching
1306      *  and reporting any completion failures.
1307      */
1308     void validate(JCTree tree, Env<AttrContext> env) {
1309         validate(tree, env, true);
1310     }
1311     void validate(JCTree tree, Env<AttrContext> env, boolean checkRaw) {
1312         new Validator(env).validateTree(tree, checkRaw, true);
1313     }
1314 
1315     /** Visitor method: Validate a list of type expressions.
1316      */
1317     void validate(List<? extends JCTree> trees, Env<AttrContext> env) {
1318         for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
1319             validate(l.head, env);
1320     }
1321 
1322     /** A visitor class for type validation.
1323      */
1324     class Validator extends JCTree.Visitor {
1325 
1326         boolean checkRaw;
1327         boolean isOuter;
1328         Env<AttrContext> env;
1329 
1330         Validator(Env<AttrContext> env) {
1331             this.env = env;
1332         }
1333 
1334         @Override
1335         public void visitTypeArray(JCArrayTypeTree tree) {
1336             validateTree(tree.elemtype, checkRaw, isOuter);
1337         }
1338 
1339         @Override
1340         public void visitTypeApply(JCTypeApply tree) {
1341             if (tree.type.hasTag(CLASS)) {
1342                 List<JCExpression> args = tree.arguments;
1343                 List<Type> forms = tree.type.tsym.type.getTypeArguments();
1344 
1345                 Type incompatibleArg = firstIncompatibleTypeArg(tree.type);
1346                 if (incompatibleArg != null) {
1347                     for (JCTree arg : tree.arguments) {
1348                         if (arg.type == incompatibleArg) {
1349                             log.error(arg, Errors.NotWithinBounds(incompatibleArg, forms.head));
1350                         }
1351                         forms = forms.tail;
1352                      }
1353                  }
1354 
1355                 forms = tree.type.tsym.type.getTypeArguments();
1356 
1357                 boolean is_java_lang_Class = tree.type.tsym.flatName() == names.java_lang_Class;
1358 
1359                 // For matching pairs of actual argument types `a' and
1360                 // formal type parameters with declared bound `b' ...
1361                 while (args.nonEmpty() && forms.nonEmpty()) {
1362                     validateTree(args.head,
1363                             !(isOuter && is_java_lang_Class),
1364                             false);
1365                     args = args.tail;
1366                     forms = forms.tail;
1367                 }
1368 
1369                 // Check that this type is either fully parameterized, or
1370                 // not parameterized at all.
1371                 if (tree.type.getEnclosingType().isRaw())
1372                     log.error(tree.pos(), Errors.ImproperlyFormedTypeInnerRawParam);
1373                 if (tree.clazz.hasTag(SELECT))
1374                     visitSelectInternal((JCFieldAccess)tree.clazz);
1375             }
1376         }
1377 
1378         @Override
1379         public void visitTypeParameter(JCTypeParameter tree) {
1380             validateTrees(tree.bounds, true, isOuter);
1381             checkClassBounds(tree.pos(), tree.type);
1382         }
1383 
1384         @Override
1385         public void visitWildcard(JCWildcard tree) {
1386             if (tree.inner != null)
1387                 validateTree(tree.inner, true, isOuter);
1388         }
1389 
1390         @Override
1391         public void visitSelect(JCFieldAccess tree) {
1392             if (tree.type.hasTag(CLASS)) {
1393                 visitSelectInternal(tree);
1394 
1395                 // Check that this type is either fully parameterized, or
1396                 // not parameterized at all.
1397                 if (tree.selected.type.isParameterized() && tree.type.tsym.type.getTypeArguments().nonEmpty())
1398                     log.error(tree.pos(), Errors.ImproperlyFormedTypeParamMissing);
1399             }
1400         }
1401 
1402         public void visitSelectInternal(JCFieldAccess tree) {
1403             if (tree.type.tsym.isStatic() &&
1404                 tree.selected.type.isParameterized()) {
1405                 // The enclosing type is not a class, so we are
1406                 // looking at a static member type.  However, the
1407                 // qualifying expression is parameterized.
1408                 log.error(tree.pos(), Errors.CantSelectStaticClassFromParamType);
1409             } else {
1410                 // otherwise validate the rest of the expression
1411                 tree.selected.accept(this);
1412             }
1413         }
1414 
1415         @Override
1416         public void visitAnnotatedType(JCAnnotatedType tree) {
1417             tree.underlyingType.accept(this);
1418         }
1419 
1420         @Override
1421         public void visitTypeIdent(JCPrimitiveTypeTree that) {
1422             if (that.type.hasTag(TypeTag.VOID)) {
1423                 log.error(that.pos(), Errors.VoidNotAllowedHere);
1424             }
1425             super.visitTypeIdent(that);
1426         }
1427 
1428         /** Default visitor method: do nothing.
1429          */
1430         @Override
1431         public void visitTree(JCTree tree) {
1432         }
1433 
1434         public void validateTree(JCTree tree, boolean checkRaw, boolean isOuter) {
1435             if (tree != null) {
1436                 boolean prevCheckRaw = this.checkRaw;
1437                 this.checkRaw = checkRaw;
1438                 this.isOuter = isOuter;
1439 
1440                 try {
1441                     tree.accept(this);
1442                     if (checkRaw)
1443                         checkRaw(tree, env);
1444                 } catch (CompletionFailure ex) {
1445                     completionError(tree.pos(), ex);
1446                 } finally {
1447                     this.checkRaw = prevCheckRaw;
1448                 }
1449             }
1450         }
1451 
1452         public void validateTrees(List<? extends JCTree> trees, boolean checkRaw, boolean isOuter) {
1453             for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
1454                 validateTree(l.head, checkRaw, isOuter);
1455         }
1456     }
1457 
1458     void checkRaw(JCTree tree, Env<AttrContext> env) {
1459         if (lint.isEnabled(LintCategory.RAW) &&
1460             tree.type.hasTag(CLASS) &&
1461             !TreeInfo.isDiamond(tree) &&
1462             !withinAnonConstr(env) &&
1463             tree.type.isRaw()) {
1464             log.warning(LintCategory.RAW,
1465                     tree.pos(), Warnings.RawClassUse(tree.type, tree.type.tsym.type));
1466         }
1467     }
1468     //where
1469         private boolean withinAnonConstr(Env<AttrContext> env) {
1470             return env.enclClass.name.isEmpty() &&
1471                     env.enclMethod != null && env.enclMethod.name == names.init;
1472         }
1473 
1474 /* *************************************************************************
1475  * Exception checking
1476  **************************************************************************/
1477 
1478     /* The following methods treat classes as sets that contain
1479      * the class itself and all their subclasses
1480      */
1481 
1482     /** Is given type a subtype of some of the types in given list?
1483      */
1484     boolean subset(Type t, List<Type> ts) {
1485         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1486             if (types.isSubtype(t, l.head)) return true;
1487         return false;
1488     }
1489 
1490     /** Is given type a subtype or supertype of
1491      *  some of the types in given list?
1492      */
1493     boolean intersects(Type t, List<Type> ts) {
1494         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1495             if (types.isSubtype(t, l.head) || types.isSubtype(l.head, t)) return true;
1496         return false;
1497     }
1498 
1499     /** Add type set to given type list, unless it is a subclass of some class
1500      *  in the list.
1501      */
1502     List<Type> incl(Type t, List<Type> ts) {
1503         return subset(t, ts) ? ts : excl(t, ts).prepend(t);
1504     }
1505 
1506     /** Remove type set from type set list.
1507      */
1508     List<Type> excl(Type t, List<Type> ts) {
1509         if (ts.isEmpty()) {
1510             return ts;
1511         } else {
1512             List<Type> ts1 = excl(t, ts.tail);
1513             if (types.isSubtype(ts.head, t)) return ts1;
1514             else if (ts1 == ts.tail) return ts;
1515             else return ts1.prepend(ts.head);
1516         }
1517     }
1518 
1519     /** Form the union of two type set lists.
1520      */
1521     List<Type> union(List<Type> ts1, List<Type> ts2) {
1522         List<Type> ts = ts1;
1523         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1524             ts = incl(l.head, ts);
1525         return ts;
1526     }
1527 
1528     /** Form the difference of two type lists.
1529      */
1530     List<Type> diff(List<Type> ts1, List<Type> ts2) {
1531         List<Type> ts = ts1;
1532         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1533             ts = excl(l.head, ts);
1534         return ts;
1535     }
1536 
1537     /** Form the intersection of two type lists.
1538      */
1539     public List<Type> intersect(List<Type> ts1, List<Type> ts2) {
1540         List<Type> ts = List.nil();
1541         for (List<Type> l = ts1; l.nonEmpty(); l = l.tail)
1542             if (subset(l.head, ts2)) ts = incl(l.head, ts);
1543         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1544             if (subset(l.head, ts1)) ts = incl(l.head, ts);
1545         return ts;
1546     }
1547 
1548     /** Is exc an exception symbol that need not be declared?
1549      */
1550     boolean isUnchecked(ClassSymbol exc) {
1551         return
1552             exc.kind == ERR ||
1553             exc.isSubClass(syms.errorType.tsym, types) ||
1554             exc.isSubClass(syms.runtimeExceptionType.tsym, types);
1555     }
1556 
1557     /** Is exc an exception type that need not be declared?
1558      */
1559     boolean isUnchecked(Type exc) {
1560         return
1561             (exc.hasTag(TYPEVAR)) ? isUnchecked(types.supertype(exc)) :
1562             (exc.hasTag(CLASS)) ? isUnchecked((ClassSymbol)exc.tsym) :
1563             exc.hasTag(BOT);
1564     }
1565 
1566     boolean isChecked(Type exc) {
1567         return !isUnchecked(exc);
1568     }
1569 
1570     /** Same, but handling completion failures.
1571      */
1572     boolean isUnchecked(DiagnosticPosition pos, Type exc) {
1573         try {
1574             return isUnchecked(exc);
1575         } catch (CompletionFailure ex) {
1576             completionError(pos, ex);
1577             return true;
1578         }
1579     }
1580 
1581     /** Is exc handled by given exception list?
1582      */
1583     boolean isHandled(Type exc, List<Type> handled) {
1584         return isUnchecked(exc) || subset(exc, handled);
1585     }
1586 
1587     /** Return all exceptions in thrown list that are not in handled list.
1588      *  @param thrown     The list of thrown exceptions.
1589      *  @param handled    The list of handled exceptions.
1590      */
1591     List<Type> unhandled(List<Type> thrown, List<Type> handled) {
1592         List<Type> unhandled = List.nil();
1593         for (List<Type> l = thrown; l.nonEmpty(); l = l.tail)
1594             if (!isHandled(l.head, handled)) unhandled = unhandled.prepend(l.head);
1595         return unhandled;
1596     }
1597 
1598 /* *************************************************************************
1599  * Overriding/Implementation checking
1600  **************************************************************************/
1601 
1602     /** The level of access protection given by a flag set,
1603      *  where PRIVATE is highest and PUBLIC is lowest.
1604      */
1605     static int protection(long flags) {
1606         switch ((short)(flags & AccessFlags)) {
1607         case PRIVATE: return 3;
1608         case PROTECTED: return 1;
1609         default:
1610         case PUBLIC: return 0;
1611         case 0: return 2;
1612         }
1613     }
1614 
1615     /** A customized "cannot override" error message.
1616      *  @param m      The overriding method.
1617      *  @param other  The overridden method.
1618      *  @return       An internationalized string.
1619      */
1620     Fragment cannotOverride(MethodSymbol m, MethodSymbol other) {
1621         Symbol mloc = m.location();
1622         Symbol oloc = other.location();
1623 
1624         if ((other.owner.flags() & INTERFACE) == 0)
1625             return Fragments.CantOverride(m, mloc, other, oloc);
1626         else if ((m.owner.flags() & INTERFACE) == 0)
1627             return Fragments.CantImplement(m, mloc, other, oloc);
1628         else
1629             return Fragments.ClashesWith(m, mloc, other, oloc);
1630     }
1631 
1632     /** A customized "override" warning message.
1633      *  @param m      The overriding method.
1634      *  @param other  The overridden method.
1635      *  @return       An internationalized string.
1636      */
1637     Fragment uncheckedOverrides(MethodSymbol m, MethodSymbol other) {
1638         Symbol mloc = m.location();
1639         Symbol oloc = other.location();
1640 
1641         if ((other.owner.flags() & INTERFACE) == 0)
1642             return Fragments.UncheckedOverride(m, mloc, other, oloc);
1643         else if ((m.owner.flags() & INTERFACE) == 0)
1644             return Fragments.UncheckedImplement(m, mloc, other, oloc);
1645         else
1646             return Fragments.UncheckedClashWith(m, mloc, other, oloc);
1647     }
1648 
1649     /** A customized "override" warning message.
1650      *  @param m      The overriding method.
1651      *  @param other  The overridden method.
1652      *  @return       An internationalized string.
1653      */
1654     Fragment varargsOverrides(MethodSymbol m, MethodSymbol other) {
1655         Symbol mloc = m.location();
1656         Symbol oloc = other.location();
1657 
1658         if ((other.owner.flags() & INTERFACE) == 0)
1659             return Fragments.VarargsOverride(m, mloc, other, oloc);
1660         else  if ((m.owner.flags() & INTERFACE) == 0)
1661             return Fragments.VarargsImplement(m, mloc, other, oloc);
1662         else
1663             return Fragments.VarargsClashWith(m, mloc, other, oloc);
1664     }
1665 
1666     /** Check that this method conforms with overridden method 'other'.
1667      *  where `origin' is the class where checking started.
1668      *  Complications:
1669      *  (1) Do not check overriding of synthetic methods
1670      *      (reason: they might be final).
1671      *      todo: check whether this is still necessary.
1672      *  (2) Admit the case where an interface proxy throws fewer exceptions
1673      *      than the method it implements. Augment the proxy methods with the
1674      *      undeclared exceptions in this case.
1675      *  (3) When generics are enabled, admit the case where an interface proxy
1676      *      has a result type
1677      *      extended by the result type of the method it implements.
1678      *      Change the proxies result type to the smaller type in this case.
1679      *
1680      *  @param tree         The tree from which positions
1681      *                      are extracted for errors.
1682      *  @param m            The overriding method.
1683      *  @param other        The overridden method.
1684      *  @param origin       The class of which the overriding method
1685      *                      is a member.
1686      */
1687     void checkOverride(JCTree tree,
1688                        MethodSymbol m,
1689                        MethodSymbol other,
1690                        ClassSymbol origin) {
1691         // Don't check overriding of synthetic methods or by bridge methods.
1692         if ((m.flags() & (SYNTHETIC|BRIDGE)) != 0 || (other.flags() & SYNTHETIC) != 0) {
1693             return;
1694         }
1695 
1696         // Error if static method overrides instance method (JLS 8.4.6.2).
1697         if ((m.flags() & STATIC) != 0 &&
1698                    (other.flags() & STATIC) == 0) {
1699             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1700                       Errors.OverrideStatic(cannotOverride(m, other)));
1701             m.flags_field |= BAD_OVERRIDE;
1702             return;
1703         }
1704 
1705         // Error if instance method overrides static or final
1706         // method (JLS 8.4.6.1).
1707         if ((other.flags() & FINAL) != 0 ||
1708                  (m.flags() & STATIC) == 0 &&
1709                  (other.flags() & STATIC) != 0) {
1710             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1711                       Errors.OverrideMeth(cannotOverride(m, other),
1712                                           asFlagSet(other.flags() & (FINAL | STATIC))));
1713             m.flags_field |= BAD_OVERRIDE;
1714             return;
1715         }
1716 
1717         if ((m.owner.flags() & ANNOTATION) != 0) {
1718             // handled in validateAnnotationMethod
1719             return;
1720         }
1721 
1722         // Error if overriding method has weaker access (JLS 8.4.6.3).
1723         if (protection(m.flags()) > protection(other.flags())) {
1724             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1725                       (other.flags() & AccessFlags) == 0 ?
1726                               Errors.OverrideWeakerAccess(cannotOverride(m, other),
1727                                                           "package") :
1728                               Errors.OverrideWeakerAccess(cannotOverride(m, other),
1729                                                           asFlagSet(other.flags() & AccessFlags)));
1730             m.flags_field |= BAD_OVERRIDE;
1731             return;
1732         }
1733 
1734         Type mt = types.memberType(origin.type, m);
1735         Type ot = types.memberType(origin.type, other);
1736         // Error if overriding result type is different
1737         // (or, in the case of generics mode, not a subtype) of
1738         // overridden result type. We have to rename any type parameters
1739         // before comparing types.
1740         List<Type> mtvars = mt.getTypeArguments();
1741         List<Type> otvars = ot.getTypeArguments();
1742         Type mtres = mt.getReturnType();
1743         Type otres = types.subst(ot.getReturnType(), otvars, mtvars);
1744 
1745         overrideWarner.clear();
1746         boolean resultTypesOK =
1747             types.returnTypeSubstitutable(mt, ot, otres, overrideWarner);
1748         if (!resultTypesOK) {
1749             if ((m.flags() & STATIC) != 0 && (other.flags() & STATIC) != 0) {
1750                 log.error(TreeInfo.diagnosticPositionFor(m, tree),
1751                           Errors.OverrideIncompatibleRet(Fragments.CantHide(m, m.location(), other,
1752                                         other.location()), mtres, otres));
1753                 m.flags_field |= BAD_OVERRIDE;
1754             } else {
1755                 log.error(TreeInfo.diagnosticPositionFor(m, tree),
1756                           Errors.OverrideIncompatibleRet(cannotOverride(m, other), mtres, otres));
1757                 m.flags_field |= BAD_OVERRIDE;
1758             }
1759             return;
1760         } else if (overrideWarner.hasNonSilentLint(LintCategory.UNCHECKED)) {
1761             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
1762                     Warnings.OverrideUncheckedRet(uncheckedOverrides(m, other), mtres, otres));
1763         }
1764 
1765         // Error if overriding method throws an exception not reported
1766         // by overridden method.
1767         List<Type> otthrown = types.subst(ot.getThrownTypes(), otvars, mtvars);
1768         List<Type> unhandledErased = unhandled(mt.getThrownTypes(), types.erasure(otthrown));
1769         List<Type> unhandledUnerased = unhandled(mt.getThrownTypes(), otthrown);
1770         if (unhandledErased.nonEmpty()) {
1771             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1772                       Errors.OverrideMethDoesntThrow(cannotOverride(m, other), unhandledUnerased.head));
1773             m.flags_field |= BAD_OVERRIDE;
1774             return;
1775         }
1776         else if (unhandledUnerased.nonEmpty()) {
1777             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
1778                           Warnings.OverrideUncheckedThrown(cannotOverride(m, other), unhandledUnerased.head));
1779             return;
1780         }
1781 
1782         // Optional warning if varargs don't agree
1783         if ((((m.flags() ^ other.flags()) & Flags.VARARGS) != 0)
1784             && lint.isEnabled(LintCategory.OVERRIDES)) {
1785             log.warning(TreeInfo.diagnosticPositionFor(m, tree),
1786                         ((m.flags() & Flags.VARARGS) != 0)
1787                         ? Warnings.OverrideVarargsMissing(varargsOverrides(m, other))
1788                         : Warnings.OverrideVarargsExtra(varargsOverrides(m, other)));
1789         }
1790 
1791         // Warn if instance method overrides bridge method (compiler spec ??)
1792         if ((other.flags() & BRIDGE) != 0) {
1793             log.warning(TreeInfo.diagnosticPositionFor(m, tree),
1794                         Warnings.OverrideBridge(uncheckedOverrides(m, other)));
1795         }
1796 
1797         // Warn if a deprecated method overridden by a non-deprecated one.
1798         if (!isDeprecatedOverrideIgnorable(other, origin)) {
1799             Lint prevLint = setLint(lint.augment(m));
1800             try {
1801                 checkDeprecated(() -> TreeInfo.diagnosticPositionFor(m, tree), m, other);
1802             } finally {
1803                 setLint(prevLint);
1804             }
1805         }
1806     }
1807     // where
1808         private boolean isDeprecatedOverrideIgnorable(MethodSymbol m, ClassSymbol origin) {
1809             // If the method, m, is defined in an interface, then ignore the issue if the method
1810             // is only inherited via a supertype and also implemented in the supertype,
1811             // because in that case, we will rediscover the issue when examining the method
1812             // in the supertype.
1813             // If the method, m, is not defined in an interface, then the only time we need to
1814             // address the issue is when the method is the supertype implemementation: any other
1815             // case, we will have dealt with when examining the supertype classes
1816             ClassSymbol mc = m.enclClass();
1817             Type st = types.supertype(origin.type);
1818             if (!st.hasTag(CLASS))
1819                 return true;
1820             MethodSymbol stimpl = m.implementation((ClassSymbol)st.tsym, types, false);
1821 
1822             if (mc != null && ((mc.flags() & INTERFACE) != 0)) {
1823                 List<Type> intfs = types.interfaces(origin.type);
1824                 return (intfs.contains(mc.type) ? false : (stimpl != null));
1825             }
1826             else
1827                 return (stimpl != m);
1828         }
1829 
1830 
1831     // used to check if there were any unchecked conversions
1832     Warner overrideWarner = new Warner();
1833 
1834     /** Check that a class does not inherit two concrete methods
1835      *  with the same signature.
1836      *  @param pos          Position to be used for error reporting.
1837      *  @param site         The class type to be checked.
1838      */
1839     public void checkCompatibleConcretes(DiagnosticPosition pos, Type site) {
1840         Type sup = types.supertype(site);
1841         if (!sup.hasTag(CLASS)) return;
1842 
1843         for (Type t1 = sup;
1844              t1.hasTag(CLASS) && t1.tsym.type.isParameterized();
1845              t1 = types.supertype(t1)) {
1846             for (Symbol s1 : t1.tsym.members().getSymbols(NON_RECURSIVE)) {
1847                 if (s1.kind != MTH ||
1848                     (s1.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
1849                     !s1.isInheritedIn(site.tsym, types) ||
1850                     ((MethodSymbol)s1).implementation(site.tsym,
1851                                                       types,
1852                                                       true) != s1)
1853                     continue;
1854                 Type st1 = types.memberType(t1, s1);
1855                 int s1ArgsLength = st1.getParameterTypes().length();
1856                 if (st1 == s1.type) continue;
1857 
1858                 for (Type t2 = sup;
1859                      t2.hasTag(CLASS);
1860                      t2 = types.supertype(t2)) {
1861                     for (Symbol s2 : t2.tsym.members().getSymbolsByName(s1.name)) {
1862                         if (s2 == s1 ||
1863                             s2.kind != MTH ||
1864                             (s2.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
1865                             s2.type.getParameterTypes().length() != s1ArgsLength ||
1866                             !s2.isInheritedIn(site.tsym, types) ||
1867                             ((MethodSymbol)s2).implementation(site.tsym,
1868                                                               types,
1869                                                               true) != s2)
1870                             continue;
1871                         Type st2 = types.memberType(t2, s2);
1872                         if (types.overrideEquivalent(st1, st2))
1873                             log.error(pos,
1874                                       Errors.ConcreteInheritanceConflict(s1, t1, s2, t2, sup));
1875                     }
1876                 }
1877             }
1878         }
1879     }
1880 
1881     /** Check that classes (or interfaces) do not each define an abstract
1882      *  method with same name and arguments but incompatible return types.
1883      *  @param pos          Position to be used for error reporting.
1884      *  @param t1           The first argument type.
1885      *  @param t2           The second argument type.
1886      */
1887     public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
1888                                             Type t1,
1889                                             Type t2,
1890                                             Type site) {
1891         if ((site.tsym.flags() & COMPOUND) != 0) {
1892             // special case for intersections: need to eliminate wildcards in supertypes
1893             t1 = types.capture(t1);
1894             t2 = types.capture(t2);
1895         }
1896         return firstIncompatibility(pos, t1, t2, site) == null;
1897     }
1898 
1899     /** Return the first method which is defined with same args
1900      *  but different return types in two given interfaces, or null if none
1901      *  exists.
1902      *  @param t1     The first type.
1903      *  @param t2     The second type.
1904      *  @param site   The most derived type.
1905      *  @returns symbol from t2 that conflicts with one in t1.
1906      */
1907     private Symbol firstIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
1908         Map<TypeSymbol,Type> interfaces1 = new HashMap<>();
1909         closure(t1, interfaces1);
1910         Map<TypeSymbol,Type> interfaces2;
1911         if (t1 == t2)
1912             interfaces2 = interfaces1;
1913         else
1914             closure(t2, interfaces1, interfaces2 = new HashMap<>());
1915 
1916         for (Type t3 : interfaces1.values()) {
1917             for (Type t4 : interfaces2.values()) {
1918                 Symbol s = firstDirectIncompatibility(pos, t3, t4, site);
1919                 if (s != null) return s;
1920             }
1921         }
1922         return null;
1923     }
1924 
1925     /** Compute all the supertypes of t, indexed by type symbol. */
1926     private void closure(Type t, Map<TypeSymbol,Type> typeMap) {
1927         if (!t.hasTag(CLASS)) return;
1928         if (typeMap.put(t.tsym, t) == null) {
1929             closure(types.supertype(t), typeMap);
1930             for (Type i : types.interfaces(t))
1931                 closure(i, typeMap);
1932         }
1933     }
1934 
1935     /** Compute all the supertypes of t, indexed by type symbol (except thise in typesSkip). */
1936     private void closure(Type t, Map<TypeSymbol,Type> typesSkip, Map<TypeSymbol,Type> typeMap) {
1937         if (!t.hasTag(CLASS)) return;
1938         if (typesSkip.get(t.tsym) != null) return;
1939         if (typeMap.put(t.tsym, t) == null) {
1940             closure(types.supertype(t), typesSkip, typeMap);
1941             for (Type i : types.interfaces(t))
1942                 closure(i, typesSkip, typeMap);
1943         }
1944     }
1945 
1946     /** Return the first method in t2 that conflicts with a method from t1. */
1947     private Symbol firstDirectIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
1948         for (Symbol s1 : t1.tsym.members().getSymbols(NON_RECURSIVE)) {
1949             Type st1 = null;
1950             if (s1.kind != MTH || !s1.isInheritedIn(site.tsym, types) ||
1951                     (s1.flags() & SYNTHETIC) != 0) continue;
1952             Symbol impl = ((MethodSymbol)s1).implementation(site.tsym, types, false);
1953             if (impl != null && (impl.flags() & ABSTRACT) == 0) continue;
1954             for (Symbol s2 : t2.tsym.members().getSymbolsByName(s1.name)) {
1955                 if (s1 == s2) continue;
1956                 if (s2.kind != MTH || !s2.isInheritedIn(site.tsym, types) ||
1957                         (s2.flags() & SYNTHETIC) != 0) continue;
1958                 if (st1 == null) st1 = types.memberType(t1, s1);
1959                 Type st2 = types.memberType(t2, s2);
1960                 if (types.overrideEquivalent(st1, st2)) {
1961                     List<Type> tvars1 = st1.getTypeArguments();
1962                     List<Type> tvars2 = st2.getTypeArguments();
1963                     Type rt1 = st1.getReturnType();
1964                     Type rt2 = types.subst(st2.getReturnType(), tvars2, tvars1);
1965                     boolean compat =
1966                         types.isSameType(rt1, rt2) ||
1967                         !rt1.isPrimitiveOrVoid() &&
1968                         !rt2.isPrimitiveOrVoid() &&
1969                         (types.covariantReturnType(rt1, rt2, types.noWarnings) ||
1970                          types.covariantReturnType(rt2, rt1, types.noWarnings)) ||
1971                          checkCommonOverriderIn(s1,s2,site);
1972                     if (!compat) {
1973                         log.error(pos, Errors.TypesIncompatible(t1, t2,
1974                                 Fragments.IncompatibleDiffRet(s2.name, types.memberType(t2, s2).getParameterTypes())));
1975                         return s2;
1976                     }
1977                 } else if (checkNameClash((ClassSymbol)site.tsym, s1, s2) &&
1978                         !checkCommonOverriderIn(s1, s2, site)) {
1979                     log.error(pos, Errors.NameClashSameErasureNoOverride(
1980                             s1.name, types.memberType(site, s1).asMethodType().getParameterTypes(), s1.location(),
1981                             s2.name, types.memberType(site, s2).asMethodType().getParameterTypes(), s2.location()));
1982                     return s2;
1983                 }
1984             }
1985         }
1986         return null;
1987     }
1988     //WHERE
1989     boolean checkCommonOverriderIn(Symbol s1, Symbol s2, Type site) {
1990         Map<TypeSymbol,Type> supertypes = new HashMap<>();
1991         Type st1 = types.memberType(site, s1);
1992         Type st2 = types.memberType(site, s2);
1993         closure(site, supertypes);
1994         for (Type t : supertypes.values()) {
1995             for (Symbol s3 : t.tsym.members().getSymbolsByName(s1.name)) {
1996                 if (s3 == s1 || s3 == s2 || s3.kind != MTH || (s3.flags() & (BRIDGE|SYNTHETIC)) != 0) continue;
1997                 Type st3 = types.memberType(site,s3);
1998                 if (types.overrideEquivalent(st3, st1) &&
1999                         types.overrideEquivalent(st3, st2) &&
2000                         types.returnTypeSubstitutable(st3, st1) &&
2001                         types.returnTypeSubstitutable(st3, st2)) {
2002                     return true;
2003                 }
2004             }
2005         }
2006         return false;
2007     }
2008 
2009     /** Check that a given method conforms with any method it overrides.
2010      *  @param tree         The tree from which positions are extracted
2011      *                      for errors.
2012      *  @param m            The overriding method.
2013      */
2014     void checkOverride(Env<AttrContext> env, JCMethodDecl tree, MethodSymbol m) {
2015         ClassSymbol origin = (ClassSymbol)m.owner;
2016         if ((origin.flags() & ENUM) != 0 && names.finalize.equals(m.name))
2017             if (m.overrides(syms.enumFinalFinalize, origin, types, false)) {
2018                 log.error(tree.pos(), Errors.EnumNoFinalize);
2019                 return;
2020             }
2021         for (Type t = origin.type; t.hasTag(CLASS);
2022              t = types.supertype(t)) {
2023             if (t != origin.type) {
2024                 checkOverride(tree, t, origin, m);
2025             }
2026             for (Type t2 : types.interfaces(t)) {
2027                 checkOverride(tree, t2, origin, m);
2028             }
2029         }
2030 
2031         final boolean explicitOverride = m.attribute(syms.overrideType.tsym) != null;
2032         // Check if this method must override a super method due to being annotated with @Override
2033         // or by virtue of being a member of a diamond inferred anonymous class. Latter case is to
2034         // be treated "as if as they were annotated" with @Override.
2035         boolean mustOverride = explicitOverride ||
2036                 (env.info.isAnonymousDiamond && !m.isConstructor() && !m.isPrivate());
2037         if (mustOverride && !isOverrider(m)) {
2038             DiagnosticPosition pos = tree.pos();
2039             for (JCAnnotation a : tree.getModifiers().annotations) {
2040                 if (a.annotationType.type.tsym == syms.overrideType.tsym) {
2041                     pos = a.pos();
2042                     break;
2043                 }
2044             }
2045             log.error(pos,
2046                       explicitOverride ? (m.isStatic() ? Errors.StaticMethodsCannotBeAnnotatedWithOverride : Errors.MethodDoesNotOverrideSuperclass) :
2047                                 Errors.AnonymousDiamondMethodDoesNotOverrideSuperclass(Fragments.DiamondAnonymousMethodsImplicitlyOverride));
2048         }
2049     }
2050 
2051     void checkOverride(JCTree tree, Type site, ClassSymbol origin, MethodSymbol m) {
2052         TypeSymbol c = site.tsym;
2053         for (Symbol sym : c.members().getSymbolsByName(m.name)) {
2054             if (m.overrides(sym, origin, types, false)) {
2055                 if ((sym.flags() & ABSTRACT) == 0) {
2056                     checkOverride(tree, m, (MethodSymbol)sym, origin);
2057                 }
2058             }
2059         }
2060     }
2061 
2062     private Filter<Symbol> equalsHasCodeFilter = s -> MethodSymbol.implementation_filter.accepts(s) &&
2063             (s.flags() & BAD_OVERRIDE) == 0;
2064 
2065     public void checkClassOverrideEqualsAndHashIfNeeded(DiagnosticPosition pos,
2066             ClassSymbol someClass) {
2067         /* At present, annotations cannot possibly have a method that is override
2068          * equivalent with Object.equals(Object) but in any case the condition is
2069          * fine for completeness.
2070          */
2071         if (someClass == (ClassSymbol)syms.objectType.tsym ||
2072             someClass.isInterface() || someClass.isEnum() ||
2073             (someClass.flags() & ANNOTATION) != 0 ||
2074             (someClass.flags() & ABSTRACT) != 0) return;
2075         //anonymous inner classes implementing interfaces need especial treatment
2076         if (someClass.isAnonymous()) {
2077             List<Type> interfaces =  types.interfaces(someClass.type);
2078             if (interfaces != null && !interfaces.isEmpty() &&
2079                 interfaces.head.tsym == syms.comparatorType.tsym) return;
2080         }
2081         checkClassOverrideEqualsAndHash(pos, someClass);
2082     }
2083 
2084     private void checkClassOverrideEqualsAndHash(DiagnosticPosition pos,
2085             ClassSymbol someClass) {
2086         if (lint.isEnabled(LintCategory.OVERRIDES)) {
2087             MethodSymbol equalsAtObject = (MethodSymbol)syms.objectType
2088                     .tsym.members().findFirst(names.equals);
2089             MethodSymbol hashCodeAtObject = (MethodSymbol)syms.objectType
2090                     .tsym.members().findFirst(names.hashCode);
2091             boolean overridesEquals = types.implementation(equalsAtObject,
2092                 someClass, false, equalsHasCodeFilter).owner == someClass;
2093             boolean overridesHashCode = types.implementation(hashCodeAtObject,
2094                 someClass, false, equalsHasCodeFilter) != hashCodeAtObject;
2095 
2096             if (overridesEquals && !overridesHashCode) {
2097                 log.warning(LintCategory.OVERRIDES, pos,
2098                             Warnings.OverrideEqualsButNotHashcode(someClass));
2099             }
2100         }
2101     }
2102 
2103     public void checkModuleName (JCModuleDecl tree) {
2104         Name moduleName = tree.sym.name;
2105         Assert.checkNonNull(moduleName);
2106         if (lint.isEnabled(LintCategory.MODULE)) {
2107             JCExpression qualId = tree.qualId;
2108             while (qualId != null) {
2109                 Name componentName;
2110                 DiagnosticPosition pos;
2111                 switch (qualId.getTag()) {
2112                     case SELECT:
2113                         JCFieldAccess selectNode = ((JCFieldAccess) qualId);
2114                         componentName = selectNode.name;
2115                         pos = selectNode.pos();
2116                         qualId = selectNode.selected;
2117                         break;
2118                     case IDENT:
2119                         componentName = ((JCIdent) qualId).name;
2120                         pos = qualId.pos();
2121                         qualId = null;
2122                         break;
2123                     default:
2124                         throw new AssertionError("Unexpected qualified identifier: " + qualId.toString());
2125                 }
2126                 if (componentName != null) {
2127                     String moduleNameComponentString = componentName.toString();
2128                     int nameLength = moduleNameComponentString.length();
2129                     if (nameLength > 0 && Character.isDigit(moduleNameComponentString.charAt(nameLength - 1))) {
2130                         log.warning(Lint.LintCategory.MODULE, pos, Warnings.PoorChoiceForModuleName(componentName));
2131                     }
2132                 }
2133             }
2134         }
2135     }
2136 
2137     private boolean checkNameClash(ClassSymbol origin, Symbol s1, Symbol s2) {
2138         ClashFilter cf = new ClashFilter(origin.type);
2139         return (cf.accepts(s1) &&
2140                 cf.accepts(s2) &&
2141                 types.hasSameArgs(s1.erasure(types), s2.erasure(types)));
2142     }
2143 
2144 
2145     /** Check that all abstract members of given class have definitions.
2146      *  @param pos          Position to be used for error reporting.
2147      *  @param c            The class.
2148      */
2149     void checkAllDefined(DiagnosticPosition pos, ClassSymbol c) {
2150         MethodSymbol undef = types.firstUnimplementedAbstract(c);
2151         if (undef != null) {
2152             MethodSymbol undef1 =
2153                 new MethodSymbol(undef.flags(), undef.name,
2154                                  types.memberType(c.type, undef), undef.owner);
2155             log.error(pos,
2156                       Errors.DoesNotOverrideAbstract(c, undef1, undef1.location()));
2157         }
2158     }
2159 
2160     void checkNonCyclicDecl(JCClassDecl tree) {
2161         CycleChecker cc = new CycleChecker();
2162         cc.scan(tree);
2163         if (!cc.errorFound && !cc.partialCheck) {
2164             tree.sym.flags_field |= ACYCLIC;
2165         }
2166     }
2167 
2168     class CycleChecker extends TreeScanner {
2169 
2170         List<Symbol> seenClasses = List.nil();
2171         boolean errorFound = false;
2172         boolean partialCheck = false;
2173 
2174         private void checkSymbol(DiagnosticPosition pos, Symbol sym) {
2175             if (sym != null && sym.kind == TYP) {
2176                 Env<AttrContext> classEnv = enter.getEnv((TypeSymbol)sym);
2177                 if (classEnv != null) {
2178                     DiagnosticSource prevSource = log.currentSource();
2179                     try {
2180                         log.useSource(classEnv.toplevel.sourcefile);
2181                         scan(classEnv.tree);
2182                     }
2183                     finally {
2184                         log.useSource(prevSource.getFile());
2185                     }
2186                 } else if (sym.kind == TYP) {
2187                     checkClass(pos, sym, List.nil());
2188                 }
2189             } else {
2190                 //not completed yet
2191                 partialCheck = true;
2192             }
2193         }
2194 
2195         @Override
2196         public void visitSelect(JCFieldAccess tree) {
2197             super.visitSelect(tree);
2198             checkSymbol(tree.pos(), tree.sym);
2199         }
2200 
2201         @Override
2202         public void visitIdent(JCIdent tree) {
2203             checkSymbol(tree.pos(), tree.sym);
2204         }
2205 
2206         @Override
2207         public void visitTypeApply(JCTypeApply tree) {
2208             scan(tree.clazz);
2209         }
2210 
2211         @Override
2212         public void visitTypeArray(JCArrayTypeTree tree) {
2213             scan(tree.elemtype);
2214         }
2215 
2216         @Override
2217         public void visitClassDef(JCClassDecl tree) {
2218             List<JCTree> supertypes = List.nil();
2219             if (tree.getExtendsClause() != null) {
2220                 supertypes = supertypes.prepend(tree.getExtendsClause());
2221             }
2222             if (tree.getImplementsClause() != null) {
2223                 for (JCTree intf : tree.getImplementsClause()) {
2224                     supertypes = supertypes.prepend(intf);
2225                 }
2226             }
2227             checkClass(tree.pos(), tree.sym, supertypes);
2228         }
2229 
2230         void checkClass(DiagnosticPosition pos, Symbol c, List<JCTree> supertypes) {
2231             if ((c.flags_field & ACYCLIC) != 0)
2232                 return;
2233             if (seenClasses.contains(c)) {
2234                 errorFound = true;
2235                 noteCyclic(pos, (ClassSymbol)c);
2236             } else if (!c.type.isErroneous()) {
2237                 try {
2238                     seenClasses = seenClasses.prepend(c);
2239                     if (c.type.hasTag(CLASS)) {
2240                         if (supertypes.nonEmpty()) {
2241                             scan(supertypes);
2242                         }
2243                         else {
2244                             ClassType ct = (ClassType)c.type;
2245                             if (ct.supertype_field == null ||
2246                                     ct.interfaces_field == null) {
2247                                 //not completed yet
2248                                 partialCheck = true;
2249                                 return;
2250                             }
2251                             checkSymbol(pos, ct.supertype_field.tsym);
2252                             for (Type intf : ct.interfaces_field) {
2253                                 checkSymbol(pos, intf.tsym);
2254                             }
2255                         }
2256                         if (c.owner.kind == TYP) {
2257                             checkSymbol(pos, c.owner);
2258                         }
2259                     }
2260                 } finally {
2261                     seenClasses = seenClasses.tail;
2262                 }
2263             }
2264         }
2265     }
2266 
2267     /** Check for cyclic references. Issue an error if the
2268      *  symbol of the type referred to has a LOCKED flag set.
2269      *
2270      *  @param pos      Position to be used for error reporting.
2271      *  @param t        The type referred to.
2272      */
2273     void checkNonCyclic(DiagnosticPosition pos, Type t) {
2274         checkNonCyclicInternal(pos, t);
2275     }
2276 
2277 
2278     void checkNonCyclic(DiagnosticPosition pos, TypeVar t) {
2279         checkNonCyclic1(pos, t, List.nil());
2280     }
2281 
2282     private void checkNonCyclic1(DiagnosticPosition pos, Type t, List<TypeVar> seen) {
2283         final TypeVar tv;
2284         if  (t.hasTag(TYPEVAR) && (t.tsym.flags() & UNATTRIBUTED) != 0)
2285             return;
2286         if (seen.contains(t)) {
2287             tv = (TypeVar)t;
2288             tv.setUpperBound(types.createErrorType(t));
2289             log.error(pos, Errors.CyclicInheritance(t));
2290         } else if (t.hasTag(TYPEVAR)) {
2291             tv = (TypeVar)t;
2292             seen = seen.prepend(tv);
2293             for (Type b : types.getBounds(tv))
2294                 checkNonCyclic1(pos, b, seen);
2295         }
2296     }
2297 
2298     /** Check for cyclic references. Issue an error if the
2299      *  symbol of the type referred to has a LOCKED flag set.
2300      *
2301      *  @param pos      Position to be used for error reporting.
2302      *  @param t        The type referred to.
2303      *  @returns        True if the check completed on all attributed classes
2304      */
2305     private boolean checkNonCyclicInternal(DiagnosticPosition pos, Type t) {
2306         boolean complete = true; // was the check complete?
2307         //- System.err.println("checkNonCyclicInternal("+t+");");//DEBUG
2308         Symbol c = t.tsym;
2309         if ((c.flags_field & ACYCLIC) != 0) return true;
2310 
2311         if ((c.flags_field & LOCKED) != 0) {
2312             noteCyclic(pos, (ClassSymbol)c);
2313         } else if (!c.type.isErroneous()) {
2314             try {
2315                 c.flags_field |= LOCKED;
2316                 if (c.type.hasTag(CLASS)) {
2317                     ClassType clazz = (ClassType)c.type;
2318                     if (clazz.interfaces_field != null)
2319                         for (List<Type> l=clazz.interfaces_field; l.nonEmpty(); l=l.tail)
2320                             complete &= checkNonCyclicInternal(pos, l.head);
2321                     if (clazz.supertype_field != null) {
2322                         Type st = clazz.supertype_field;
2323                         if (st != null && st.hasTag(CLASS))
2324                             complete &= checkNonCyclicInternal(pos, st);
2325                     }
2326                     if (c.owner.kind == TYP)
2327                         complete &= checkNonCyclicInternal(pos, c.owner.type);
2328                 }
2329             } finally {
2330                 c.flags_field &= ~LOCKED;
2331             }
2332         }
2333         if (complete)
2334             complete = ((c.flags_field & UNATTRIBUTED) == 0) && c.isCompleted();
2335         if (complete) c.flags_field |= ACYCLIC;
2336         return complete;
2337     }
2338 
2339     /** Note that we found an inheritance cycle. */
2340     private void noteCyclic(DiagnosticPosition pos, ClassSymbol c) {
2341         log.error(pos, Errors.CyclicInheritance(c));
2342         for (List<Type> l=types.interfaces(c.type); l.nonEmpty(); l=l.tail)
2343             l.head = types.createErrorType((ClassSymbol)l.head.tsym, Type.noType);
2344         Type st = types.supertype(c.type);
2345         if (st.hasTag(CLASS))
2346             ((ClassType)c.type).supertype_field = types.createErrorType((ClassSymbol)st.tsym, Type.noType);
2347         c.type = types.createErrorType(c, c.type);
2348         c.flags_field |= ACYCLIC;
2349     }
2350 
2351     /** Check that all methods which implement some
2352      *  method conform to the method they implement.
2353      *  @param tree         The class definition whose members are checked.
2354      */
2355     void checkImplementations(JCClassDecl tree) {
2356         checkImplementations(tree, tree.sym, tree.sym);
2357     }
2358     //where
2359         /** Check that all methods which implement some
2360          *  method in `ic' conform to the method they implement.
2361          */
2362         void checkImplementations(JCTree tree, ClassSymbol origin, ClassSymbol ic) {
2363             for (List<Type> l = types.closure(ic.type); l.nonEmpty(); l = l.tail) {
2364                 ClassSymbol lc = (ClassSymbol)l.head.tsym;
2365                 if ((lc.flags() & ABSTRACT) != 0) {
2366                     for (Symbol sym : lc.members().getSymbols(NON_RECURSIVE)) {
2367                         if (sym.kind == MTH &&
2368                             (sym.flags() & (STATIC|ABSTRACT)) == ABSTRACT) {
2369                             MethodSymbol absmeth = (MethodSymbol)sym;
2370                             MethodSymbol implmeth = absmeth.implementation(origin, types, false);
2371                             if (implmeth != null && implmeth != absmeth &&
2372                                 (implmeth.owner.flags() & INTERFACE) ==
2373                                 (origin.flags() & INTERFACE)) {
2374                                 // don't check if implmeth is in a class, yet
2375                                 // origin is an interface. This case arises only
2376                                 // if implmeth is declared in Object. The reason is
2377                                 // that interfaces really don't inherit from
2378                                 // Object it's just that the compiler represents
2379                                 // things that way.
2380                                 checkOverride(tree, implmeth, absmeth, origin);
2381                             }
2382                         }
2383                     }
2384                 }
2385             }
2386         }
2387 
2388     /** Check that all abstract methods implemented by a class are
2389      *  mutually compatible.
2390      *  @param pos          Position to be used for error reporting.
2391      *  @param c            The class whose interfaces are checked.
2392      */
2393     void checkCompatibleSupertypes(DiagnosticPosition pos, Type c) {
2394         List<Type> supertypes = types.interfaces(c);
2395         Type supertype = types.supertype(c);
2396         if (supertype.hasTag(CLASS) &&
2397             (supertype.tsym.flags() & ABSTRACT) != 0)
2398             supertypes = supertypes.prepend(supertype);
2399         for (List<Type> l = supertypes; l.nonEmpty(); l = l.tail) {
2400             if (!l.head.getTypeArguments().isEmpty() &&
2401                 !checkCompatibleAbstracts(pos, l.head, l.head, c))
2402                 return;
2403             for (List<Type> m = supertypes; m != l; m = m.tail)
2404                 if (!checkCompatibleAbstracts(pos, l.head, m.head, c))
2405                     return;
2406         }
2407         checkCompatibleConcretes(pos, c);
2408     }
2409 
2410     /** Check that all non-override equivalent methods accessible from 'site'
2411      *  are mutually compatible (JLS 8.4.8/9.4.1).
2412      *
2413      *  @param pos  Position to be used for error reporting.
2414      *  @param site The class whose methods are checked.
2415      *  @param sym  The method symbol to be checked.
2416      */
2417     void checkOverrideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
2418          ClashFilter cf = new ClashFilter(site);
2419         //for each method m1 that is overridden (directly or indirectly)
2420         //by method 'sym' in 'site'...
2421 
2422         List<MethodSymbol> potentiallyAmbiguousList = List.nil();
2423         boolean overridesAny = false;
2424         ArrayList<Symbol> symbolsByName = new ArrayList<>();
2425         types.membersClosure(site, false).getSymbolsByName(sym.name, cf).forEach(symbolsByName::add);
2426         for (Symbol m1 : symbolsByName) {
2427             if (!sym.overrides(m1, site.tsym, types, false)) {
2428                 if (m1 == sym) {
2429                     continue;
2430                 }
2431 
2432                 if (!overridesAny) {
2433                     potentiallyAmbiguousList = potentiallyAmbiguousList.prepend((MethodSymbol)m1);
2434                 }
2435                 continue;
2436             }
2437 
2438             if (m1 != sym) {
2439                 overridesAny = true;
2440                 potentiallyAmbiguousList = List.nil();
2441             }
2442 
2443             //...check each method m2 that is a member of 'site'
2444             for (Symbol m2 : symbolsByName) {
2445                 if (m2 == m1) continue;
2446                 //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
2447                 //a member of 'site') and (ii) m1 has the same erasure as m2, issue an error
2448                 if (!types.isSubSignature(sym.type, types.memberType(site, m2), Feature.STRICT_METHOD_CLASH_CHECK.allowedInSource(source)) &&
2449                         types.hasSameArgs(m2.erasure(types), m1.erasure(types))) {
2450                     sym.flags_field |= CLASH;
2451                     if (m1 == sym) {
2452                         log.error(pos, Errors.NameClashSameErasureNoOverride(
2453                             m1.name, types.memberType(site, m1).asMethodType().getParameterTypes(), m1.location(),
2454                             m2.name, types.memberType(site, m2).asMethodType().getParameterTypes(), m2.location()));
2455                     } else {
2456                         ClassType ct = (ClassType)site;
2457                         String kind = ct.isInterface() ? "interface" : "class";
2458                         log.error(pos, Errors.NameClashSameErasureNoOverride1(
2459                             kind,
2460                             ct.tsym.name,
2461                             m1.name,
2462                             types.memberType(site, m1).asMethodType().getParameterTypes(),
2463                             m1.location(),
2464                             m2.name,
2465                             types.memberType(site, m2).asMethodType().getParameterTypes(),
2466                             m2.location()));
2467                     }
2468                     return;
2469                 }
2470             }
2471         }
2472 
2473         if (!overridesAny) {
2474             for (MethodSymbol m: potentiallyAmbiguousList) {
2475                 checkPotentiallyAmbiguousOverloads(pos, site, sym, m);
2476             }
2477         }
2478     }
2479 
2480     /** Check that all static methods accessible from 'site' are
2481      *  mutually compatible (JLS 8.4.8).
2482      *
2483      *  @param pos  Position to be used for error reporting.
2484      *  @param site The class whose methods are checked.
2485      *  @param sym  The method symbol to be checked.
2486      */
2487     void checkHideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
2488         ClashFilter cf = new ClashFilter(site);
2489         //for each method m1 that is a member of 'site'...
2490         for (Symbol s : types.membersClosure(site, true).getSymbolsByName(sym.name, cf)) {
2491             //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
2492             //a member of 'site') and (ii) 'sym' has the same erasure as m1, issue an error
2493             if (!types.isSubSignature(sym.type, types.memberType(site, s), Feature.STRICT_METHOD_CLASH_CHECK.allowedInSource(source))) {
2494                 if (types.hasSameArgs(s.erasure(types), sym.erasure(types))) {
2495                     log.error(pos,
2496                               Errors.NameClashSameErasureNoHide(sym, sym.location(), s, s.location()));
2497                     return;
2498                 } else {
2499                     checkPotentiallyAmbiguousOverloads(pos, site, sym, (MethodSymbol)s);
2500                 }
2501             }
2502          }
2503      }
2504 
2505      //where
2506      private class ClashFilter implements Filter<Symbol> {
2507 
2508          Type site;
2509 
2510          ClashFilter(Type site) {
2511              this.site = site;
2512          }
2513 
2514          boolean shouldSkip(Symbol s) {
2515              return (s.flags() & CLASH) != 0 &&
2516                 s.owner == site.tsym;
2517          }
2518 
2519          public boolean accepts(Symbol s) {
2520              return s.kind == MTH &&
2521                      (s.flags() & SYNTHETIC) == 0 &&
2522                      !shouldSkip(s) &&
2523                      s.isInheritedIn(site.tsym, types) &&
2524                      !s.isConstructor();
2525          }
2526      }
2527 
2528     void checkDefaultMethodClashes(DiagnosticPosition pos, Type site) {
2529         DefaultMethodClashFilter dcf = new DefaultMethodClashFilter(site);
2530         for (Symbol m : types.membersClosure(site, false).getSymbols(dcf)) {
2531             Assert.check(m.kind == MTH);
2532             List<MethodSymbol> prov = types.interfaceCandidates(site, (MethodSymbol)m);
2533             if (prov.size() > 1) {
2534                 ListBuffer<Symbol> abstracts = new ListBuffer<>();
2535                 ListBuffer<Symbol> defaults = new ListBuffer<>();
2536                 for (MethodSymbol provSym : prov) {
2537                     if ((provSym.flags() & DEFAULT) != 0) {
2538                         defaults = defaults.append(provSym);
2539                     } else if ((provSym.flags() & ABSTRACT) != 0) {
2540                         abstracts = abstracts.append(provSym);
2541                     }
2542                     if (defaults.nonEmpty() && defaults.size() + abstracts.size() >= 2) {
2543                         //strong semantics - issue an error if two sibling interfaces
2544                         //have two override-equivalent defaults - or if one is abstract
2545                         //and the other is default
2546                         Fragment diagKey;
2547                         Symbol s1 = defaults.first();
2548                         Symbol s2;
2549                         if (defaults.size() > 1) {
2550                             s2 = defaults.toList().tail.head;
2551                             diagKey = Fragments.IncompatibleUnrelatedDefaults(Kinds.kindName(site.tsym), site,
2552                                     m.name, types.memberType(site, m).getParameterTypes(),
2553                                     s1.location(), s2.location());
2554 
2555                         } else {
2556                             s2 = abstracts.first();
2557                             diagKey = Fragments.IncompatibleAbstractDefault(Kinds.kindName(site.tsym), site,
2558                                     m.name, types.memberType(site, m).getParameterTypes(),
2559                                     s1.location(), s2.location());
2560                         }
2561                         log.error(pos, Errors.TypesIncompatible(s1.location().type, s2.location().type, diagKey));
2562                         break;
2563                     }
2564                 }
2565             }
2566         }
2567     }
2568 
2569     //where
2570      private class DefaultMethodClashFilter implements Filter<Symbol> {
2571 
2572          Type site;
2573 
2574          DefaultMethodClashFilter(Type site) {
2575              this.site = site;
2576          }
2577 
2578          public boolean accepts(Symbol s) {
2579              return s.kind == MTH &&
2580                      (s.flags() & DEFAULT) != 0 &&
2581                      s.isInheritedIn(site.tsym, types) &&
2582                      !s.isConstructor();
2583          }
2584      }
2585 
2586     /**
2587       * Report warnings for potentially ambiguous method declarations. Two declarations
2588       * are potentially ambiguous if they feature two unrelated functional interface
2589       * in same argument position (in which case, a call site passing an implicit
2590       * lambda would be ambiguous).
2591       */
2592     void checkPotentiallyAmbiguousOverloads(DiagnosticPosition pos, Type site,
2593             MethodSymbol msym1, MethodSymbol msym2) {
2594         if (msym1 != msym2 &&
2595                 Feature.DEFAULT_METHODS.allowedInSource(source) &&
2596                 lint.isEnabled(LintCategory.OVERLOADS) &&
2597                 (msym1.flags() & POTENTIALLY_AMBIGUOUS) == 0 &&
2598                 (msym2.flags() & POTENTIALLY_AMBIGUOUS) == 0) {
2599             Type mt1 = types.memberType(site, msym1);
2600             Type mt2 = types.memberType(site, msym2);
2601             //if both generic methods, adjust type variables
2602             if (mt1.hasTag(FORALL) && mt2.hasTag(FORALL) &&
2603                     types.hasSameBounds((ForAll)mt1, (ForAll)mt2)) {
2604                 mt2 = types.subst(mt2, ((ForAll)mt2).tvars, ((ForAll)mt1).tvars);
2605             }
2606             //expand varargs methods if needed
2607             int maxLength = Math.max(mt1.getParameterTypes().length(), mt2.getParameterTypes().length());
2608             List<Type> args1 = rs.adjustArgs(mt1.getParameterTypes(), msym1, maxLength, true);
2609             List<Type> args2 = rs.adjustArgs(mt2.getParameterTypes(), msym2, maxLength, true);
2610             //if arities don't match, exit
2611             if (args1.length() != args2.length()) return;
2612             boolean potentiallyAmbiguous = false;
2613             while (args1.nonEmpty() && args2.nonEmpty()) {
2614                 Type s = args1.head;
2615                 Type t = args2.head;
2616                 if (!types.isSubtype(t, s) && !types.isSubtype(s, t)) {
2617                     if (types.isFunctionalInterface(s) && types.isFunctionalInterface(t) &&
2618                             types.findDescriptorType(s).getParameterTypes().length() > 0 &&
2619                             types.findDescriptorType(s).getParameterTypes().length() ==
2620                             types.findDescriptorType(t).getParameterTypes().length()) {
2621                         potentiallyAmbiguous = true;
2622                     } else {
2623                         break;
2624                     }
2625                 }
2626                 args1 = args1.tail;
2627                 args2 = args2.tail;
2628             }
2629             if (potentiallyAmbiguous) {
2630                 //we found two incompatible functional interfaces with same arity
2631                 //this means a call site passing an implicit lambda would be ambigiuous
2632                 msym1.flags_field |= POTENTIALLY_AMBIGUOUS;
2633                 msym2.flags_field |= POTENTIALLY_AMBIGUOUS;
2634                 log.warning(LintCategory.OVERLOADS, pos,
2635                             Warnings.PotentiallyAmbiguousOverload(msym1, msym1.location(),
2636                                                                   msym2, msym2.location()));
2637                 return;
2638             }
2639         }
2640     }
2641 
2642     void checkAccessFromSerializableElement(final JCTree tree, boolean isLambda) {
2643         if (warnOnAnyAccessToMembers ||
2644             (lint.isEnabled(LintCategory.SERIAL) &&
2645             !lint.isSuppressed(LintCategory.SERIAL) &&
2646             isLambda)) {
2647             Symbol sym = TreeInfo.symbol(tree);
2648             if (!sym.kind.matches(KindSelector.VAL_MTH)) {
2649                 return;
2650             }
2651 
2652             if (sym.kind == VAR) {
2653                 if ((sym.flags() & PARAMETER) != 0 ||
2654                     sym.isLocal() ||
2655                     sym.name == names._this ||
2656                     sym.name == names._super) {
2657                     return;
2658                 }
2659             }
2660 
2661             if (!types.isSubtype(sym.owner.type, syms.serializableType) &&
2662                 isEffectivelyNonPublic(sym)) {
2663                 if (isLambda) {
2664                     if (belongsToRestrictedPackage(sym)) {
2665                         log.warning(LintCategory.SERIAL, tree.pos(),
2666                                     Warnings.AccessToMemberFromSerializableLambda(sym));
2667                     }
2668                 } else {
2669                     log.warning(tree.pos(),
2670                                 Warnings.AccessToMemberFromSerializableElement(sym));
2671                 }
2672             }
2673         }
2674     }
2675 
2676     private boolean isEffectivelyNonPublic(Symbol sym) {
2677         if (sym.packge() == syms.rootPackage) {
2678             return false;
2679         }
2680 
2681         while (sym.kind != PCK) {
2682             if ((sym.flags() & PUBLIC) == 0) {
2683                 return true;
2684             }
2685             sym = sym.owner;
2686         }
2687         return false;
2688     }
2689 
2690     private boolean belongsToRestrictedPackage(Symbol sym) {
2691         String fullName = sym.packge().fullname.toString();
2692         return fullName.startsWith("java.") ||
2693                 fullName.startsWith("javax.") ||
2694                 fullName.startsWith("sun.") ||
2695                 fullName.contains(".internal.");
2696     }
2697 
2698     /** Check that class c does not implement directly or indirectly
2699      *  the same parameterized interface with two different argument lists.
2700      *  @param pos          Position to be used for error reporting.
2701      *  @param type         The type whose interfaces are checked.
2702      */
2703     void checkClassBounds(DiagnosticPosition pos, Type type) {
2704         checkClassBounds(pos, new HashMap<TypeSymbol,Type>(), type);
2705     }
2706 //where
2707         /** Enter all interfaces of type `type' into the hash table `seensofar'
2708          *  with their class symbol as key and their type as value. Make
2709          *  sure no class is entered with two different types.
2710          */
2711         void checkClassBounds(DiagnosticPosition pos,
2712                               Map<TypeSymbol,Type> seensofar,
2713                               Type type) {
2714             if (type.isErroneous()) return;
2715             for (List<Type> l = types.interfaces(type); l.nonEmpty(); l = l.tail) {
2716                 Type it = l.head;
2717                 if (type.hasTag(CLASS) && !it.hasTag(CLASS)) continue; // JLS 8.1.5
2718 
2719                 Type oldit = seensofar.put(it.tsym, it);
2720                 if (oldit != null) {
2721                     List<Type> oldparams = oldit.allparams();
2722                     List<Type> newparams = it.allparams();
2723                     if (!types.containsTypeEquivalent(oldparams, newparams))
2724                         log.error(pos,
2725                                   Errors.CantInheritDiffArg(it.tsym,
2726                                                             Type.toString(oldparams),
2727                                                             Type.toString(newparams)));
2728                 }
2729                 checkClassBounds(pos, seensofar, it);
2730             }
2731             Type st = types.supertype(type);
2732             if (type.hasTag(CLASS) && !st.hasTag(CLASS)) return; // JLS 8.1.4
2733             if (st != Type.noType) checkClassBounds(pos, seensofar, st);
2734         }
2735 
2736     /** Enter interface into into set.
2737      *  If it existed already, issue a "repeated interface" error.
2738      */
2739     void checkNotRepeated(DiagnosticPosition pos, Type it, Set<Type> its) {
2740         if (its.contains(it))
2741             log.error(pos, Errors.RepeatedInterface);
2742         else {
2743             its.add(it);
2744         }
2745     }
2746 
2747 /* *************************************************************************
2748  * Check annotations
2749  **************************************************************************/
2750 
2751     /**
2752      * Recursively validate annotations values
2753      */
2754     void validateAnnotationTree(JCTree tree) {
2755         class AnnotationValidator extends TreeScanner {
2756             @Override
2757             public void visitAnnotation(JCAnnotation tree) {
2758                 if (!tree.type.isErroneous() && tree.type.tsym.isAnnotationType()) {
2759                     super.visitAnnotation(tree);
2760                     validateAnnotation(tree);
2761                 }
2762             }
2763         }
2764         tree.accept(new AnnotationValidator());
2765     }
2766 
2767     /**
2768      *  {@literal
2769      *  Annotation types are restricted to primitives, String, an
2770      *  enum, an annotation, Class, Class<?>, Class<? extends
2771      *  Anything>, arrays of the preceding.
2772      *  }
2773      */
2774     void validateAnnotationType(JCTree restype) {
2775         // restype may be null if an error occurred, so don't bother validating it
2776         if (restype != null) {
2777             validateAnnotationType(restype.pos(), restype.type);
2778         }
2779     }
2780 
2781     void validateAnnotationType(DiagnosticPosition pos, Type type) {
2782         if (type.isPrimitive()) return;
2783         if (types.isSameType(type, syms.stringType)) return;
2784         if ((type.tsym.flags() & Flags.ENUM) != 0) return;
2785         if ((type.tsym.flags() & Flags.ANNOTATION) != 0) return;
2786         if (types.cvarLowerBound(type).tsym == syms.classType.tsym) return;
2787         if (types.isArray(type) && !types.isArray(types.elemtype(type))) {
2788             validateAnnotationType(pos, types.elemtype(type));
2789             return;
2790         }
2791         log.error(pos, Errors.InvalidAnnotationMemberType);
2792     }
2793 
2794     /**
2795      * "It is also a compile-time error if any method declared in an
2796      * annotation type has a signature that is override-equivalent to
2797      * that of any public or protected method declared in class Object
2798      * or in the interface annotation.Annotation."
2799      *
2800      * @jls 9.6 Annotation Types
2801      */
2802     void validateAnnotationMethod(DiagnosticPosition pos, MethodSymbol m) {
2803         for (Type sup = syms.annotationType; sup.hasTag(CLASS); sup = types.supertype(sup)) {
2804             Scope s = sup.tsym.members();
2805             for (Symbol sym : s.getSymbolsByName(m.name)) {
2806                 if (sym.kind == MTH &&
2807                     (sym.flags() & (PUBLIC | PROTECTED)) != 0 &&
2808                     types.overrideEquivalent(m.type, sym.type))
2809                     log.error(pos, Errors.IntfAnnotationMemberClash(sym, sup));
2810             }
2811         }
2812     }
2813 
2814     /** Check the annotations of a symbol.
2815      */
2816     public void validateAnnotations(List<JCAnnotation> annotations, Symbol s) {
2817         for (JCAnnotation a : annotations)
2818             validateAnnotation(a, s);
2819     }
2820 
2821     /** Check the type annotations.
2822      */
2823     public void validateTypeAnnotations(List<JCAnnotation> annotations, boolean isTypeParameter) {
2824         for (JCAnnotation a : annotations)
2825             validateTypeAnnotation(a, isTypeParameter);
2826     }
2827 
2828     /** Check an annotation of a symbol.
2829      */
2830     private void validateAnnotation(JCAnnotation a, Symbol s) {
2831         validateAnnotationTree(a);
2832 
2833         if (a.type.tsym.isAnnotationType() && !annotationApplicable(a, s))
2834             log.error(a.pos(), Errors.AnnotationTypeNotApplicable);
2835 
2836         if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
2837             if (s.kind != TYP) {
2838                 log.error(a.pos(), Errors.BadFunctionalIntfAnno);
2839             } else if (!s.isInterface() || (s.flags() & ANNOTATION) != 0) {
2840                 log.error(a.pos(), Errors.BadFunctionalIntfAnno1(Fragments.NotAFunctionalIntf(s)));
2841             }
2842         }
2843     }
2844 
2845     public void validateTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
2846         Assert.checkNonNull(a.type);
2847         validateAnnotationTree(a);
2848 
2849         if (a.hasTag(TYPE_ANNOTATION) &&
2850                 !a.annotationType.type.isErroneous() &&
2851                 !isTypeAnnotation(a, isTypeParameter)) {
2852             log.error(a.pos(), Errors.AnnotationTypeNotApplicableToType(a.type));
2853         }
2854     }
2855 
2856     /**
2857      * Validate the proposed container 'repeatable' on the
2858      * annotation type symbol 's'. Report errors at position
2859      * 'pos'.
2860      *
2861      * @param s The (annotation)type declaration annotated with a @Repeatable
2862      * @param repeatable the @Repeatable on 's'
2863      * @param pos where to report errors
2864      */
2865     public void validateRepeatable(TypeSymbol s, Attribute.Compound repeatable, DiagnosticPosition pos) {
2866         Assert.check(types.isSameType(repeatable.type, syms.repeatableType));
2867 
2868         Type t = null;
2869         List<Pair<MethodSymbol,Attribute>> l = repeatable.values;
2870         if (!l.isEmpty()) {
2871             Assert.check(l.head.fst.name == names.value);
2872             t = ((Attribute.Class)l.head.snd).getValue();
2873         }
2874 
2875         if (t == null) {
2876             // errors should already have been reported during Annotate
2877             return;
2878         }
2879 
2880         validateValue(t.tsym, s, pos);
2881         validateRetention(t.tsym, s, pos);
2882         validateDocumented(t.tsym, s, pos);
2883         validateInherited(t.tsym, s, pos);
2884         validateTarget(t.tsym, s, pos);
2885         validateDefault(t.tsym, pos);
2886     }
2887 
2888     private void validateValue(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
2889         Symbol sym = container.members().findFirst(names.value);
2890         if (sym != null && sym.kind == MTH) {
2891             MethodSymbol m = (MethodSymbol) sym;
2892             Type ret = m.getReturnType();
2893             if (!(ret.hasTag(ARRAY) && types.isSameType(((ArrayType)ret).elemtype, contained.type))) {
2894                 log.error(pos,
2895                           Errors.InvalidRepeatableAnnotationValueReturn(container,
2896                                                                         ret,
2897                                                                         types.makeArrayType(contained.type)));
2898             }
2899         } else {
2900             log.error(pos, Errors.InvalidRepeatableAnnotationNoValue(container));
2901         }
2902     }
2903 
2904     private void validateRetention(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
2905         Attribute.RetentionPolicy containerRetention = types.getRetention(container);
2906         Attribute.RetentionPolicy containedRetention = types.getRetention(contained);
2907 
2908         boolean error = false;
2909         switch (containedRetention) {
2910         case RUNTIME:
2911             if (containerRetention != Attribute.RetentionPolicy.RUNTIME) {
2912                 error = true;
2913             }
2914             break;
2915         case CLASS:
2916             if (containerRetention == Attribute.RetentionPolicy.SOURCE)  {
2917                 error = true;
2918             }
2919         }
2920         if (error ) {
2921             log.error(pos,
2922                       Errors.InvalidRepeatableAnnotationRetention(container,
2923                                                                   containerRetention.name(),
2924                                                                   contained,
2925                                                                   containedRetention.name()));
2926         }
2927     }
2928 
2929     private void validateDocumented(Symbol container, Symbol contained, DiagnosticPosition pos) {
2930         if (contained.attribute(syms.documentedType.tsym) != null) {
2931             if (container.attribute(syms.documentedType.tsym) == null) {
2932                 log.error(pos, Errors.InvalidRepeatableAnnotationNotDocumented(container, contained));
2933             }
2934         }
2935     }
2936 
2937     private void validateInherited(Symbol container, Symbol contained, DiagnosticPosition pos) {
2938         if (contained.attribute(syms.inheritedType.tsym) != null) {
2939             if (container.attribute(syms.inheritedType.tsym) == null) {
2940                 log.error(pos, Errors.InvalidRepeatableAnnotationNotInherited(container, contained));
2941             }
2942         }
2943     }
2944 
2945     private void validateTarget(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
2946         // The set of targets the container is applicable to must be a subset
2947         // (with respect to annotation target semantics) of the set of targets
2948         // the contained is applicable to. The target sets may be implicit or
2949         // explicit.
2950 
2951         Set<Name> containerTargets;
2952         Attribute.Array containerTarget = getAttributeTargetAttribute(container);
2953         if (containerTarget == null) {
2954             containerTargets = getDefaultTargetSet();
2955         } else {
2956             containerTargets = new HashSet<>();
2957             for (Attribute app : containerTarget.values) {
2958                 if (!(app instanceof Attribute.Enum)) {
2959                     continue; // recovery
2960                 }
2961                 Attribute.Enum e = (Attribute.Enum)app;
2962                 containerTargets.add(e.value.name);
2963             }
2964         }
2965 
2966         Set<Name> containedTargets;
2967         Attribute.Array containedTarget = getAttributeTargetAttribute(contained);
2968         if (containedTarget == null) {
2969             containedTargets = getDefaultTargetSet();
2970         } else {
2971             containedTargets = new HashSet<>();
2972             for (Attribute app : containedTarget.values) {
2973                 if (!(app instanceof Attribute.Enum)) {
2974                     continue; // recovery
2975                 }
2976                 Attribute.Enum e = (Attribute.Enum)app;
2977                 containedTargets.add(e.value.name);
2978             }
2979         }
2980 
2981         if (!isTargetSubsetOf(containerTargets, containedTargets)) {
2982             log.error(pos, Errors.InvalidRepeatableAnnotationIncompatibleTarget(container, contained));
2983         }
2984     }
2985 
2986     /* get a set of names for the default target */
2987     private Set<Name> getDefaultTargetSet() {
2988         if (defaultTargets == null) {
2989             Set<Name> targets = new HashSet<>();
2990             targets.add(names.ANNOTATION_TYPE);
2991             targets.add(names.CONSTRUCTOR);
2992             targets.add(names.FIELD);
2993             targets.add(names.LOCAL_VARIABLE);
2994             targets.add(names.METHOD);
2995             targets.add(names.PACKAGE);
2996             targets.add(names.PARAMETER);
2997             targets.add(names.TYPE);
2998 
2999             defaultTargets = java.util.Collections.unmodifiableSet(targets);
3000         }
3001 
3002         return defaultTargets;
3003     }
3004     private Set<Name> defaultTargets;
3005 
3006 
3007     /** Checks that s is a subset of t, with respect to ElementType
3008      * semantics, specifically {ANNOTATION_TYPE} is a subset of {TYPE},
3009      * and {TYPE_USE} covers the set {ANNOTATION_TYPE, TYPE, TYPE_USE,
3010      * TYPE_PARAMETER}.
3011      */
3012     private boolean isTargetSubsetOf(Set<Name> s, Set<Name> t) {
3013         // Check that all elements in s are present in t
3014         for (Name n2 : s) {
3015             boolean currentElementOk = false;
3016             for (Name n1 : t) {
3017                 if (n1 == n2) {
3018                     currentElementOk = true;
3019                     break;
3020                 } else if (n1 == names.TYPE && n2 == names.ANNOTATION_TYPE) {
3021                     currentElementOk = true;
3022                     break;
3023                 } else if (n1 == names.TYPE_USE &&
3024                         (n2 == names.TYPE ||
3025                          n2 == names.ANNOTATION_TYPE ||
3026                          n2 == names.TYPE_PARAMETER)) {
3027                     currentElementOk = true;
3028                     break;
3029                 }
3030             }
3031             if (!currentElementOk)
3032                 return false;
3033         }
3034         return true;
3035     }
3036 
3037     private void validateDefault(Symbol container, DiagnosticPosition pos) {
3038         // validate that all other elements of containing type has defaults
3039         Scope scope = container.members();
3040         for(Symbol elm : scope.getSymbols()) {
3041             if (elm.name != names.value &&
3042                 elm.kind == MTH &&
3043                 ((MethodSymbol)elm).defaultValue == null) {
3044                 log.error(pos,
3045                           Errors.InvalidRepeatableAnnotationElemNondefault(container, elm));
3046             }
3047         }
3048     }
3049 
3050     /** Is s a method symbol that overrides a method in a superclass? */
3051     boolean isOverrider(Symbol s) {
3052         if (s.kind != MTH || s.isStatic())
3053             return false;
3054         MethodSymbol m = (MethodSymbol)s;
3055         TypeSymbol owner = (TypeSymbol)m.owner;
3056         for (Type sup : types.closure(owner.type)) {
3057             if (sup == owner.type)
3058                 continue; // skip "this"
3059             Scope scope = sup.tsym.members();
3060             for (Symbol sym : scope.getSymbolsByName(m.name)) {
3061                 if (!sym.isStatic() && m.overrides(sym, owner, types, true))
3062                     return true;
3063             }
3064         }
3065         return false;
3066     }
3067 
3068     /** Is the annotation applicable to types? */
3069     protected boolean isTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
3070         List<Attribute> targets = typeAnnotations.annotationTargets(a.annotationType.type.tsym);
3071         return (targets == null) ?
3072                 false :
3073                 targets.stream()
3074                         .anyMatch(attr -> isTypeAnnotation(attr, isTypeParameter));
3075     }
3076     //where
3077         boolean isTypeAnnotation(Attribute a, boolean isTypeParameter) {
3078             Attribute.Enum e = (Attribute.Enum)a;
3079             return (e.value.name == names.TYPE_USE ||
3080                     (isTypeParameter && e.value.name == names.TYPE_PARAMETER));
3081         }
3082 
3083     /** Is the annotation applicable to the symbol? */
3084     boolean annotationApplicable(JCAnnotation a, Symbol s) {
3085         Attribute.Array arr = getAttributeTargetAttribute(a.annotationType.type.tsym);
3086         Name[] targets;
3087 
3088         if (arr == null) {
3089             targets = defaultTargetMetaInfo(a, s);
3090         } else {
3091             // TODO: can we optimize this?
3092             targets = new Name[arr.values.length];
3093             for (int i=0; i<arr.values.length; ++i) {
3094                 Attribute app = arr.values[i];
3095                 if (!(app instanceof Attribute.Enum)) {
3096                     return true; // recovery
3097                 }
3098                 Attribute.Enum e = (Attribute.Enum) app;
3099                 targets[i] = e.value.name;
3100             }
3101         }
3102         for (Name target : targets) {
3103             if (target == names.TYPE) {
3104                 if (s.kind == TYP)
3105                     return true;
3106             } else if (target == names.FIELD) {
3107                 if (s.kind == VAR && s.owner.kind != MTH)
3108                     return true;
3109             } else if (target == names.METHOD) {
3110                 if (s.kind == MTH && !s.isConstructor())
3111                     return true;
3112             } else if (target == names.PARAMETER) {
3113                 if (s.kind == VAR && s.owner.kind == MTH &&
3114                       (s.flags() & PARAMETER) != 0) {
3115                     return true;
3116                 }
3117             } else if (target == names.CONSTRUCTOR) {
3118                 if (s.kind == MTH && s.isConstructor())
3119                     return true;
3120             } else if (target == names.LOCAL_VARIABLE) {
3121                 if (s.kind == VAR && s.owner.kind == MTH &&
3122                       (s.flags() & PARAMETER) == 0) {
3123                     return true;
3124                 }
3125             } else if (target == names.ANNOTATION_TYPE) {
3126                 if (s.kind == TYP && (s.flags() & ANNOTATION) != 0) {
3127                     return true;
3128                 }
3129             } else if (target == names.PACKAGE) {
3130                 if (s.kind == PCK)
3131                     return true;
3132             } else if (target == names.TYPE_USE) {
3133                 if (s.kind == VAR && s.owner.kind == MTH && s.type.hasTag(NONE)) {
3134                     //cannot type annotate implictly typed locals
3135                     return false;
3136                 } else if (s.kind == TYP || s.kind == VAR ||
3137                         (s.kind == MTH && !s.isConstructor() &&
3138                                 !s.type.getReturnType().hasTag(VOID)) ||
3139                         (s.kind == MTH && s.isConstructor())) {
3140                     return true;
3141                 }
3142             } else if (target == names.TYPE_PARAMETER) {
3143                 if (s.kind == TYP && s.type.hasTag(TYPEVAR))
3144                     return true;
3145             } else
3146                 return true; // Unknown ElementType. This should be an error at declaration site,
3147                              // assume applicable.
3148         }
3149         return false;
3150     }
3151 
3152 
3153     Attribute.Array getAttributeTargetAttribute(TypeSymbol s) {
3154         Attribute.Compound atTarget = s.getAnnotationTypeMetadata().getTarget();
3155         if (atTarget == null) return null; // ok, is applicable
3156         Attribute atValue = atTarget.member(names.value);
3157         if (!(atValue instanceof Attribute.Array)) return null; // error recovery
3158         return (Attribute.Array) atValue;
3159     }
3160 
3161     private final Name[] dfltTargetMeta;
3162     private Name[] defaultTargetMetaInfo(JCAnnotation a, Symbol s) {
3163         return dfltTargetMeta;
3164     }
3165 
3166     /** Check an annotation value.
3167      *
3168      * @param a The annotation tree to check
3169      * @return true if this annotation tree is valid, otherwise false
3170      */
3171     public boolean validateAnnotationDeferErrors(JCAnnotation a) {
3172         boolean res = false;
3173         final Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
3174         try {
3175             res = validateAnnotation(a);
3176         } finally {
3177             log.popDiagnosticHandler(diagHandler);
3178         }
3179         return res;
3180     }
3181 
3182     private boolean validateAnnotation(JCAnnotation a) {
3183         boolean isValid = true;
3184         AnnotationTypeMetadata metadata = a.annotationType.type.tsym.getAnnotationTypeMetadata();
3185 
3186         // collect an inventory of the annotation elements
3187         Set<MethodSymbol> elements = metadata.getAnnotationElements();
3188 
3189         // remove the ones that are assigned values
3190         for (JCTree arg : a.args) {
3191             if (!arg.hasTag(ASSIGN)) continue; // recovery
3192             JCAssign assign = (JCAssign)arg;
3193             Symbol m = TreeInfo.symbol(assign.lhs);
3194             if (m == null || m.type.isErroneous()) continue;
3195             if (!elements.remove(m)) {
3196                 isValid = false;
3197                 log.error(assign.lhs.pos(),
3198                           Errors.DuplicateAnnotationMemberValue(m.name, a.type));
3199             }
3200         }
3201 
3202         // all the remaining ones better have default values
3203         List<Name> missingDefaults = List.nil();
3204         Set<MethodSymbol> membersWithDefault = metadata.getAnnotationElementsWithDefault();
3205         for (MethodSymbol m : elements) {
3206             if (m.type.isErroneous())
3207                 continue;
3208 
3209             if (!membersWithDefault.contains(m))
3210                 missingDefaults = missingDefaults.append(m.name);
3211         }
3212         missingDefaults = missingDefaults.reverse();
3213         if (missingDefaults.nonEmpty()) {
3214             isValid = false;
3215             Error errorKey = (missingDefaults.size() > 1)
3216                     ? Errors.AnnotationMissingDefaultValue1(a.type, missingDefaults)
3217                     : Errors.AnnotationMissingDefaultValue(a.type, missingDefaults);
3218             log.error(a.pos(), errorKey);
3219         }
3220 
3221         return isValid && validateTargetAnnotationValue(a);
3222     }
3223 
3224     /* Validate the special java.lang.annotation.Target annotation */
3225     boolean validateTargetAnnotationValue(JCAnnotation a) {
3226         // special case: java.lang.annotation.Target must not have
3227         // repeated values in its value member
3228         if (a.annotationType.type.tsym != syms.annotationTargetType.tsym ||
3229                 a.args.tail == null)
3230             return true;
3231 
3232         boolean isValid = true;
3233         if (!a.args.head.hasTag(ASSIGN)) return false; // error recovery
3234         JCAssign assign = (JCAssign) a.args.head;
3235         Symbol m = TreeInfo.symbol(assign.lhs);
3236         if (m.name != names.value) return false;
3237         JCTree rhs = assign.rhs;
3238         if (!rhs.hasTag(NEWARRAY)) return false;
3239         JCNewArray na = (JCNewArray) rhs;
3240         Set<Symbol> targets = new HashSet<>();
3241         for (JCTree elem : na.elems) {
3242             if (!targets.add(TreeInfo.symbol(elem))) {
3243                 isValid = false;
3244                 log.error(elem.pos(), Errors.RepeatedAnnotationTarget);
3245             }
3246         }
3247         return isValid;
3248     }
3249 
3250     void checkDeprecatedAnnotation(DiagnosticPosition pos, Symbol s) {
3251         if (lint.isEnabled(LintCategory.DEP_ANN) && s.isDeprecatableViaAnnotation() &&
3252             (s.flags() & DEPRECATED) != 0 &&
3253             !syms.deprecatedType.isErroneous() &&
3254             s.attribute(syms.deprecatedType.tsym) == null) {
3255             log.warning(LintCategory.DEP_ANN,
3256                     pos, Warnings.MissingDeprecatedAnnotation);
3257         }
3258         // Note: @Deprecated has no effect on local variables, parameters and package decls.
3259         if (lint.isEnabled(LintCategory.DEPRECATION) && !s.isDeprecatableViaAnnotation()) {
3260             if (!syms.deprecatedType.isErroneous() && s.attribute(syms.deprecatedType.tsym) != null) {
3261                 log.warning(LintCategory.DEPRECATION, pos,
3262                             Warnings.DeprecatedAnnotationHasNoEffect(Kinds.kindName(s)));
3263             }
3264         }
3265     }
3266 
3267     void checkDeprecated(final DiagnosticPosition pos, final Symbol other, final Symbol s) {
3268         checkDeprecated(() -> pos, other, s);
3269     }
3270 
3271     void checkDeprecated(Supplier<DiagnosticPosition> pos, final Symbol other, final Symbol s) {
3272         if ( (s.isDeprecatedForRemoval()
3273                 || s.isDeprecated() && !other.isDeprecated())
3274                 && (s.outermostClass() != other.outermostClass() || s.outermostClass() == null)) {
3275             deferredLintHandler.report(() -> warnDeprecated(pos.get(), s));
3276         }
3277     }
3278 
3279     void checkSunAPI(final DiagnosticPosition pos, final Symbol s) {
3280         if ((s.flags() & PROPRIETARY) != 0) {
3281             deferredLintHandler.report(() -> {
3282                 log.mandatoryWarning(pos, Warnings.SunProprietary(s));
3283             });
3284         }
3285     }
3286 
3287     void checkProfile(final DiagnosticPosition pos, final Symbol s) {
3288         if (profile != Profile.DEFAULT && (s.flags() & NOT_IN_PROFILE) != 0) {
3289             log.error(pos, Errors.NotInProfile(s, profile));
3290         }
3291     }
3292 
3293 /* *************************************************************************
3294  * Check for recursive annotation elements.
3295  **************************************************************************/
3296 
3297     /** Check for cycles in the graph of annotation elements.
3298      */
3299     void checkNonCyclicElements(JCClassDecl tree) {
3300         if ((tree.sym.flags_field & ANNOTATION) == 0) return;
3301         Assert.check((tree.sym.flags_field & LOCKED) == 0);
3302         try {
3303             tree.sym.flags_field |= LOCKED;
3304             for (JCTree def : tree.defs) {
3305                 if (!def.hasTag(METHODDEF)) continue;
3306                 JCMethodDecl meth = (JCMethodDecl)def;
3307                 checkAnnotationResType(meth.pos(), meth.restype.type);
3308             }
3309         } finally {
3310             tree.sym.flags_field &= ~LOCKED;
3311             tree.sym.flags_field |= ACYCLIC_ANN;
3312         }
3313     }
3314 
3315     void checkNonCyclicElementsInternal(DiagnosticPosition pos, TypeSymbol tsym) {
3316         if ((tsym.flags_field & ACYCLIC_ANN) != 0)
3317             return;
3318         if ((tsym.flags_field & LOCKED) != 0) {
3319             log.error(pos, Errors.CyclicAnnotationElement(tsym));
3320             return;
3321         }
3322         try {
3323             tsym.flags_field |= LOCKED;
3324             for (Symbol s : tsym.members().getSymbols(NON_RECURSIVE)) {
3325                 if (s.kind != MTH)
3326                     continue;
3327                 checkAnnotationResType(pos, ((MethodSymbol)s).type.getReturnType());
3328             }
3329         } finally {
3330             tsym.flags_field &= ~LOCKED;
3331             tsym.flags_field |= ACYCLIC_ANN;
3332         }
3333     }
3334 
3335     void checkAnnotationResType(DiagnosticPosition pos, Type type) {
3336         switch (type.getTag()) {
3337         case CLASS:
3338             if ((type.tsym.flags() & ANNOTATION) != 0)
3339                 checkNonCyclicElementsInternal(pos, type.tsym);
3340             break;
3341         case ARRAY:
3342             checkAnnotationResType(pos, types.elemtype(type));
3343             break;
3344         default:
3345             break; // int etc
3346         }
3347     }
3348 
3349 /* *************************************************************************
3350  * Check for cycles in the constructor call graph.
3351  **************************************************************************/
3352 
3353     /** Check for cycles in the graph of constructors calling other
3354      *  constructors.
3355      */
3356     void checkCyclicConstructors(JCClassDecl tree) {
3357         Map<Symbol,Symbol> callMap = new HashMap<>();
3358 
3359         // enter each constructor this-call into the map
3360         for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
3361             JCMethodInvocation app = TreeInfo.firstConstructorCall(l.head);
3362             if (app == null) continue;
3363             JCMethodDecl meth = (JCMethodDecl) l.head;
3364             if (TreeInfo.name(app.meth) == names._this) {
3365                 callMap.put(meth.sym, TreeInfo.symbol(app.meth));
3366             } else {
3367                 meth.sym.flags_field |= ACYCLIC;
3368             }
3369         }
3370 
3371         // Check for cycles in the map
3372         Symbol[] ctors = new Symbol[0];
3373         ctors = callMap.keySet().toArray(ctors);
3374         for (Symbol caller : ctors) {
3375             checkCyclicConstructor(tree, caller, callMap);
3376         }
3377     }
3378 
3379     /** Look in the map to see if the given constructor is part of a
3380      *  call cycle.
3381      */
3382     private void checkCyclicConstructor(JCClassDecl tree, Symbol ctor,
3383                                         Map<Symbol,Symbol> callMap) {
3384         if (ctor != null && (ctor.flags_field & ACYCLIC) == 0) {
3385             if ((ctor.flags_field & LOCKED) != 0) {
3386                 log.error(TreeInfo.diagnosticPositionFor(ctor, tree),
3387                           Errors.RecursiveCtorInvocation);
3388             } else {
3389                 ctor.flags_field |= LOCKED;
3390                 checkCyclicConstructor(tree, callMap.remove(ctor), callMap);
3391                 ctor.flags_field &= ~LOCKED;
3392             }
3393             ctor.flags_field |= ACYCLIC;
3394         }
3395     }
3396 
3397 /* *************************************************************************
3398  * Miscellaneous
3399  **************************************************************************/
3400 
3401     /**
3402      *  Check for division by integer constant zero
3403      *  @param pos           Position for error reporting.
3404      *  @param operator      The operator for the expression
3405      *  @param operand       The right hand operand for the expression
3406      */
3407     void checkDivZero(final DiagnosticPosition pos, Symbol operator, Type operand) {
3408         if (operand.constValue() != null
3409             && operand.getTag().isSubRangeOf(LONG)
3410             && ((Number) (operand.constValue())).longValue() == 0) {
3411             int opc = ((OperatorSymbol)operator).opcode;
3412             if (opc == ByteCodes.idiv || opc == ByteCodes.imod
3413                 || opc == ByteCodes.ldiv || opc == ByteCodes.lmod) {
3414                 deferredLintHandler.report(() -> warnDivZero(pos));
3415             }
3416         }
3417     }
3418 
3419     /**
3420      * Check for empty statements after if
3421      */
3422     void checkEmptyIf(JCIf tree) {
3423         if (tree.thenpart.hasTag(SKIP) && tree.elsepart == null &&
3424                 lint.isEnabled(LintCategory.EMPTY))
3425             log.warning(LintCategory.EMPTY, tree.thenpart.pos(), Warnings.EmptyIf);
3426     }
3427 
3428     /** Check that symbol is unique in given scope.
3429      *  @param pos           Position for error reporting.
3430      *  @param sym           The symbol.
3431      *  @param s             The scope.
3432      */
3433     boolean checkUnique(DiagnosticPosition pos, Symbol sym, Scope s) {
3434         if (sym.type.isErroneous())
3435             return true;
3436         if (sym.owner.name == names.any) return false;
3437         for (Symbol byName : s.getSymbolsByName(sym.name, NON_RECURSIVE)) {
3438             if (sym != byName &&
3439                     (byName.flags() & CLASH) == 0 &&
3440                     sym.kind == byName.kind &&
3441                     sym.name != names.error &&
3442                     (sym.kind != MTH ||
3443                      types.hasSameArgs(sym.type, byName.type) ||
3444                      types.hasSameArgs(types.erasure(sym.type), types.erasure(byName.type)))) {
3445                 if ((sym.flags() & VARARGS) != (byName.flags() & VARARGS)) {
3446                     sym.flags_field |= CLASH;
3447                     varargsDuplicateError(pos, sym, byName);
3448                     return true;
3449                 } else if (sym.kind == MTH && !types.hasSameArgs(sym.type, byName.type, false)) {
3450                     duplicateErasureError(pos, sym, byName);
3451                     sym.flags_field |= CLASH;
3452                     return true;
3453                 } else if ((sym.flags() & MATCH_BINDING) != 0 &&
3454                            (byName.flags() & MATCH_BINDING) != 0 &&
3455                            (byName.flags() & MATCH_BINDING_TO_OUTER) == 0) {
3456                     //this error will be reported separatelly in MatchBindingsComputer
3457                     return false;
3458                 } else {
3459                     duplicateError(pos, byName);
3460                     return false;
3461                 }
3462             }
3463         }
3464         return true;
3465     }
3466 
3467     /** Report duplicate declaration error.
3468      */
3469     void duplicateErasureError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
3470         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
3471             log.error(pos, Errors.NameClashSameErasure(sym1, sym2));
3472         }
3473     }
3474 
3475     /**Check that types imported through the ordinary imports don't clash with types imported
3476      * by other (static or ordinary) imports. Note that two static imports may import two clashing
3477      * types without an error on the imports.
3478      * @param toplevel       The toplevel tree for which the test should be performed.
3479      */
3480     void checkImportsUnique(JCCompilationUnit toplevel) {
3481         WriteableScope ordinallyImportedSoFar = WriteableScope.create(toplevel.packge);
3482         WriteableScope staticallyImportedSoFar = WriteableScope.create(toplevel.packge);
3483         WriteableScope topLevelScope = toplevel.toplevelScope;
3484 
3485         for (JCTree def : toplevel.defs) {
3486             if (!def.hasTag(IMPORT))
3487                 continue;
3488 
3489             JCImport imp = (JCImport) def;
3490 
3491             if (imp.importScope == null)
3492                 continue;
3493 
3494             for (Symbol sym : imp.importScope.getSymbols(sym -> sym.kind == TYP)) {
3495                 if (imp.isStatic()) {
3496                     checkUniqueImport(imp.pos(), ordinallyImportedSoFar, staticallyImportedSoFar, topLevelScope, sym, true);
3497                     staticallyImportedSoFar.enter(sym);
3498                 } else {
3499                     checkUniqueImport(imp.pos(), ordinallyImportedSoFar, staticallyImportedSoFar, topLevelScope, sym, false);
3500                     ordinallyImportedSoFar.enter(sym);
3501                 }
3502             }
3503 
3504             imp.importScope = null;
3505         }
3506     }
3507 
3508     /** Check that single-type import is not already imported or top-level defined,
3509      *  but make an exception for two single-type imports which denote the same type.
3510      *  @param pos                     Position for error reporting.
3511      *  @param ordinallyImportedSoFar  A Scope containing types imported so far through
3512      *                                 ordinary imports.
3513      *  @param staticallyImportedSoFar A Scope containing types imported so far through
3514      *                                 static imports.
3515      *  @param topLevelScope           The current file's top-level Scope
3516      *  @param sym                     The symbol.
3517      *  @param staticImport            Whether or not this was a static import
3518      */
3519     private boolean checkUniqueImport(DiagnosticPosition pos, Scope ordinallyImportedSoFar,
3520                                       Scope staticallyImportedSoFar, Scope topLevelScope,
3521                                       Symbol sym, boolean staticImport) {
3522         Filter<Symbol> duplicates = candidate -> candidate != sym && !candidate.type.isErroneous();
3523         Symbol ordinaryClashing = ordinallyImportedSoFar.findFirst(sym.name, duplicates);
3524         Symbol staticClashing = null;
3525         if (ordinaryClashing == null && !staticImport) {
3526             staticClashing = staticallyImportedSoFar.findFirst(sym.name, duplicates);
3527         }
3528         if (ordinaryClashing != null || staticClashing != null) {
3529             if (ordinaryClashing != null)
3530                 log.error(pos, Errors.AlreadyDefinedSingleImport(ordinaryClashing));
3531             else
3532                 log.error(pos, Errors.AlreadyDefinedStaticSingleImport(staticClashing));
3533             return false;
3534         }
3535         Symbol clashing = topLevelScope.findFirst(sym.name, duplicates);
3536         if (clashing != null) {
3537             log.error(pos, Errors.AlreadyDefinedThisUnit(clashing));
3538             return false;
3539         }
3540         return true;
3541     }
3542 
3543     /** Check that a qualified name is in canonical form (for import decls).
3544      */
3545     public void checkCanonical(JCTree tree) {
3546         if (!isCanonical(tree))
3547             log.error(tree.pos(),
3548                       Errors.ImportRequiresCanonical(TreeInfo.symbol(tree)));
3549     }
3550         // where
3551         private boolean isCanonical(JCTree tree) {
3552             while (tree.hasTag(SELECT)) {
3553                 JCFieldAccess s = (JCFieldAccess) tree;
3554                 if (s.sym.owner.getQualifiedName() != TreeInfo.symbol(s.selected).getQualifiedName())
3555                     return false;
3556                 tree = s.selected;
3557             }
3558             return true;
3559         }
3560 
3561     /** Check that an auxiliary class is not accessed from any other file than its own.
3562      */
3563     void checkForBadAuxiliaryClassAccess(DiagnosticPosition pos, Env<AttrContext> env, ClassSymbol c) {
3564         if (lint.isEnabled(Lint.LintCategory.AUXILIARYCLASS) &&
3565             (c.flags() & AUXILIARY) != 0 &&
3566             rs.isAccessible(env, c) &&
3567             !fileManager.isSameFile(c.sourcefile, env.toplevel.sourcefile))
3568         {
3569             log.warning(pos,
3570                         Warnings.AuxiliaryClassAccessedFromOutsideOfItsSourceFile(c, c.sourcefile));
3571         }
3572     }
3573 
3574     private class ConversionWarner extends Warner {
3575         final String uncheckedKey;
3576         final Type found;
3577         final Type expected;
3578         public ConversionWarner(DiagnosticPosition pos, String uncheckedKey, Type found, Type expected) {
3579             super(pos);
3580             this.uncheckedKey = uncheckedKey;
3581             this.found = found;
3582             this.expected = expected;
3583         }
3584 
3585         @Override
3586         public void warn(LintCategory lint) {
3587             boolean warned = this.warned;
3588             super.warn(lint);
3589             if (warned) return; // suppress redundant diagnostics
3590             switch (lint) {
3591                 case UNCHECKED:
3592                     Check.this.warnUnchecked(pos(), Warnings.ProbFoundReq(diags.fragment(uncheckedKey), found, expected));
3593                     break;
3594                 case VARARGS:
3595                     if (method != null &&
3596                             method.attribute(syms.trustMeType.tsym) != null &&
3597                             isTrustMeAllowedOnMethod(method) &&
3598                             !types.isReifiable(method.type.getParameterTypes().last())) {
3599                         Check.this.warnUnsafeVararg(pos(), Warnings.VarargsUnsafeUseVarargsParam(method.params.last()));
3600                     }
3601                     break;
3602                 default:
3603                     throw new AssertionError("Unexpected lint: " + lint);
3604             }
3605         }
3606     }
3607 
3608     public Warner castWarner(DiagnosticPosition pos, Type found, Type expected) {
3609         return new ConversionWarner(pos, "unchecked.cast.to.type", found, expected);
3610     }
3611 
3612     public Warner convertWarner(DiagnosticPosition pos, Type found, Type expected) {
3613         return new ConversionWarner(pos, "unchecked.assign", found, expected);
3614     }
3615 
3616     public void checkFunctionalInterface(JCClassDecl tree, ClassSymbol cs) {
3617         Compound functionalType = cs.attribute(syms.functionalInterfaceType.tsym);
3618 
3619         if (functionalType != null) {
3620             try {
3621                 types.findDescriptorSymbol((TypeSymbol)cs);
3622             } catch (Types.FunctionDescriptorLookupError ex) {
3623                 DiagnosticPosition pos = tree.pos();
3624                 for (JCAnnotation a : tree.getModifiers().annotations) {
3625                     if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
3626                         pos = a.pos();
3627                         break;
3628                     }
3629                 }
3630                 log.error(pos, Errors.BadFunctionalIntfAnno1(ex.getDiagnostic()));
3631             }
3632         }
3633     }
3634 
3635     public void checkImportsResolvable(final JCCompilationUnit toplevel) {
3636         for (final JCImport imp : toplevel.getImports()) {
3637             if (!imp.staticImport || !imp.qualid.hasTag(SELECT))
3638                 continue;
3639             final JCFieldAccess select = (JCFieldAccess) imp.qualid;
3640             final Symbol origin;
3641             if (select.name == names.asterisk || (origin = TreeInfo.symbol(select.selected)) == null || origin.kind != TYP)
3642                 continue;
3643 
3644             TypeSymbol site = (TypeSymbol) TreeInfo.symbol(select.selected);
3645             if (!checkTypeContainsImportableElement(site, site, toplevel.packge, select.name, new HashSet<Symbol>())) {
3646                 log.error(imp.pos(),
3647                           Errors.CantResolveLocation(KindName.STATIC,
3648                                                      select.name,
3649                                                      null,
3650                                                      null,
3651                                                      Fragments.Location(kindName(site),
3652                                                                         site,
3653                                                                         null)));
3654             }
3655         }
3656     }
3657 
3658     // Check that packages imported are in scope (JLS 7.4.3, 6.3, 6.5.3.1, 6.5.3.2)
3659     public void checkImportedPackagesObservable(final JCCompilationUnit toplevel) {
3660         OUTER: for (JCImport imp : toplevel.getImports()) {
3661             if (!imp.staticImport && TreeInfo.name(imp.qualid) == names.asterisk) {
3662                 TypeSymbol tsym = ((JCFieldAccess)imp.qualid).selected.type.tsym;
3663                 if (tsym.kind == PCK && tsym.members().isEmpty() &&
3664                     !(Feature.IMPORT_ON_DEMAND_OBSERVABLE_PACKAGES.allowedInSource(source) && tsym.exists())) {
3665                     log.error(DiagnosticFlag.RESOLVE_ERROR, imp.pos, Errors.DoesntExist(tsym));
3666                 }
3667             }
3668         }
3669     }
3670 
3671     private boolean checkTypeContainsImportableElement(TypeSymbol tsym, TypeSymbol origin, PackageSymbol packge, Name name, Set<Symbol> processed) {
3672         if (tsym == null || !processed.add(tsym))
3673             return false;
3674 
3675             // also search through inherited names
3676         if (checkTypeContainsImportableElement(types.supertype(tsym.type).tsym, origin, packge, name, processed))
3677             return true;
3678 
3679         for (Type t : types.interfaces(tsym.type))
3680             if (checkTypeContainsImportableElement(t.tsym, origin, packge, name, processed))
3681                 return true;
3682 
3683         for (Symbol sym : tsym.members().getSymbolsByName(name)) {
3684             if (sym.isStatic() &&
3685                 importAccessible(sym, packge) &&
3686                 sym.isMemberOf(origin, types)) {
3687                 return true;
3688             }
3689         }
3690 
3691         return false;
3692     }
3693 
3694     // is the sym accessible everywhere in packge?
3695     public boolean importAccessible(Symbol sym, PackageSymbol packge) {
3696         try {
3697             int flags = (int)(sym.flags() & AccessFlags);
3698             switch (flags) {
3699             default:
3700             case PUBLIC:
3701                 return true;
3702             case PRIVATE:
3703                 return false;
3704             case 0:
3705             case PROTECTED:
3706                 return sym.packge() == packge;
3707             }
3708         } catch (ClassFinder.BadClassFile err) {
3709             throw err;
3710         } catch (CompletionFailure ex) {
3711             return false;
3712         }
3713     }
3714 
3715     public void checkLeaksNotAccessible(Env<AttrContext> env, JCClassDecl check) {
3716         JCCompilationUnit toplevel = env.toplevel;
3717 
3718         if (   toplevel.modle == syms.unnamedModule
3719             || toplevel.modle == syms.noModule
3720             || (check.sym.flags() & COMPOUND) != 0) {
3721             return ;
3722         }
3723 
3724         ExportsDirective currentExport = findExport(toplevel.packge);
3725 
3726         if (   currentExport == null //not exported
3727             || currentExport.modules != null) //don't check classes in qualified export
3728             return ;
3729 
3730         new TreeScanner() {
3731             Lint lint = env.info.lint;
3732             boolean inSuperType;
3733 
3734             @Override
3735             public void visitBlock(JCBlock tree) {
3736             }
3737             @Override
3738             public void visitMethodDef(JCMethodDecl tree) {
3739                 if (!isAPISymbol(tree.sym))
3740                     return;
3741                 Lint prevLint = lint;
3742                 try {
3743                     lint = lint.augment(tree.sym);
3744                     if (lint.isEnabled(LintCategory.EXPORTS)) {
3745                         super.visitMethodDef(tree);
3746                     }
3747                 } finally {
3748                     lint = prevLint;
3749                 }
3750             }
3751             @Override
3752             public void visitVarDef(JCVariableDecl tree) {
3753                 if (!isAPISymbol(tree.sym) && tree.sym.owner.kind != MTH)
3754                     return;
3755                 Lint prevLint = lint;
3756                 try {
3757                     lint = lint.augment(tree.sym);
3758                     if (lint.isEnabled(LintCategory.EXPORTS)) {
3759                         scan(tree.mods);
3760                         scan(tree.vartype);
3761                     }
3762                 } finally {
3763                     lint = prevLint;
3764                 }
3765             }
3766             @Override
3767             public void visitClassDef(JCClassDecl tree) {
3768                 if (tree != check)
3769                     return ;
3770 
3771                 if (!isAPISymbol(tree.sym))
3772                     return ;
3773 
3774                 Lint prevLint = lint;
3775                 try {
3776                     lint = lint.augment(tree.sym);
3777                     if (lint.isEnabled(LintCategory.EXPORTS)) {
3778                         scan(tree.mods);
3779                         scan(tree.typarams);
3780                         try {
3781                             inSuperType = true;
3782                             scan(tree.extending);
3783                             scan(tree.implementing);
3784                         } finally {
3785                             inSuperType = false;
3786                         }
3787                         scan(tree.defs);
3788                     }
3789                 } finally {
3790                     lint = prevLint;
3791                 }
3792             }
3793             @Override
3794             public void visitTypeApply(JCTypeApply tree) {
3795                 scan(tree.clazz);
3796                 boolean oldInSuperType = inSuperType;
3797                 try {
3798                     inSuperType = false;
3799                     scan(tree.arguments);
3800                 } finally {
3801                     inSuperType = oldInSuperType;
3802                 }
3803             }
3804             @Override
3805             public void visitIdent(JCIdent tree) {
3806                 Symbol sym = TreeInfo.symbol(tree);
3807                 if (sym.kind == TYP && !sym.type.hasTag(TYPEVAR)) {
3808                     checkVisible(tree.pos(), sym, toplevel.packge, inSuperType);
3809                 }
3810             }
3811 
3812             @Override
3813             public void visitSelect(JCFieldAccess tree) {
3814                 Symbol sym = TreeInfo.symbol(tree);
3815                 Symbol sitesym = TreeInfo.symbol(tree.selected);
3816                 if (sym.kind == TYP && sitesym.kind == PCK) {
3817                     checkVisible(tree.pos(), sym, toplevel.packge, inSuperType);
3818                 } else {
3819                     super.visitSelect(tree);
3820                 }
3821             }
3822 
3823             @Override
3824             public void visitAnnotation(JCAnnotation tree) {
3825                 if (tree.attribute.type.tsym.getAnnotation(java.lang.annotation.Documented.class) != null)
3826                     super.visitAnnotation(tree);
3827             }
3828 
3829         }.scan(check);
3830     }
3831         //where:
3832         private ExportsDirective findExport(PackageSymbol pack) {
3833             for (ExportsDirective d : pack.modle.exports) {
3834                 if (d.packge == pack)
3835                     return d;
3836             }
3837 
3838             return null;
3839         }
3840         private boolean isAPISymbol(Symbol sym) {
3841             while (sym.kind != PCK) {
3842                 if ((sym.flags() & Flags.PUBLIC) == 0 && (sym.flags() & Flags.PROTECTED) == 0) {
3843                     return false;
3844                 }
3845                 sym = sym.owner;
3846             }
3847             return true;
3848         }
3849         private void checkVisible(DiagnosticPosition pos, Symbol what, PackageSymbol inPackage, boolean inSuperType) {
3850             if (!isAPISymbol(what) && !inSuperType) { //package private/private element
3851                 log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessible(kindName(what), what, what.packge().modle));
3852                 return ;
3853             }
3854 
3855             PackageSymbol whatPackage = what.packge();
3856             ExportsDirective whatExport = findExport(whatPackage);
3857             ExportsDirective inExport = findExport(inPackage);
3858 
3859             if (whatExport == null) { //package not exported:
3860                 log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleUnexported(kindName(what), what, what.packge().modle));
3861                 return ;
3862             }
3863 
3864             if (whatExport.modules != null) {
3865                 if (inExport.modules == null || !whatExport.modules.containsAll(inExport.modules)) {
3866                     log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleUnexportedQualified(kindName(what), what, what.packge().modle));
3867                 }
3868             }
3869 
3870             if (whatPackage.modle != inPackage.modle && whatPackage.modle != syms.java_base) {
3871                 //check that relativeTo.modle requires transitive what.modle, somehow:
3872                 List<ModuleSymbol> todo = List.of(inPackage.modle);
3873 
3874                 while (todo.nonEmpty()) {
3875                     ModuleSymbol current = todo.head;
3876                     todo = todo.tail;
3877                     if (current == whatPackage.modle)
3878                         return ; //OK
3879                     if ((current.flags() & Flags.AUTOMATIC_MODULE) != 0)
3880                         continue; //for automatic modules, don't look into their dependencies
3881                     for (RequiresDirective req : current.requires) {
3882                         if (req.isTransitive()) {
3883                             todo = todo.prepend(req.module);
3884                         }
3885                     }
3886                 }
3887 
3888                 log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleNotRequiredTransitive(kindName(what), what, what.packge().modle));
3889             }
3890         }
3891 
3892     void checkModuleExists(final DiagnosticPosition pos, ModuleSymbol msym) {
3893         if (msym.kind != MDL) {
3894             deferredLintHandler.report(() -> {
3895                 if (lint.isEnabled(LintCategory.MODULE))
3896                     log.warning(LintCategory.MODULE, pos, Warnings.ModuleNotFound(msym));
3897             });
3898         }
3899     }
3900 
3901     void checkPackageExistsForOpens(final DiagnosticPosition pos, PackageSymbol packge) {
3902         if (packge.members().isEmpty() &&
3903             ((packge.flags() & Flags.HAS_RESOURCE) == 0)) {
3904             deferredLintHandler.report(() -> {
3905                 if (lint.isEnabled(LintCategory.OPENS))
3906                     log.warning(pos, Warnings.PackageEmptyOrNotFound(packge));
3907             });
3908         }
3909     }
3910 
3911     void checkModuleRequires(final DiagnosticPosition pos, final RequiresDirective rd) {
3912         if ((rd.module.flags() & Flags.AUTOMATIC_MODULE) != 0) {
3913             deferredLintHandler.report(() -> {
3914                 if (rd.isTransitive() && lint.isEnabled(LintCategory.REQUIRES_TRANSITIVE_AUTOMATIC)) {
3915                     log.warning(pos, Warnings.RequiresTransitiveAutomatic);
3916                 } else if (lint.isEnabled(LintCategory.REQUIRES_AUTOMATIC)) {
3917                     log.warning(pos, Warnings.RequiresAutomatic);
3918                 }
3919             });
3920         }
3921     }
3922 
3923 }