1 /*
   2  * Copyright (c) 1999, 2013, 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 
  30 import javax.tools.JavaFileManager;
  31 
  32 import com.sun.tools.javac.code.*;
  33 import com.sun.tools.javac.jvm.*;
  34 import com.sun.tools.javac.tree.*;
  35 import com.sun.tools.javac.util.*;
  36 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
  37 import com.sun.tools.javac.util.List;
  38 
  39 import com.sun.tools.javac.code.Lint;
  40 import com.sun.tools.javac.code.Lint.LintCategory;
  41 import com.sun.tools.javac.code.Type.*;
  42 import com.sun.tools.javac.code.Symbol.*;
  43 import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;
  44 import com.sun.tools.javac.comp.Infer.InferenceContext;
  45 import com.sun.tools.javac.comp.Infer.FreeTypeListener;
  46 import com.sun.tools.javac.tree.JCTree.*;
  47 import com.sun.tools.javac.tree.JCTree.JCPolyExpression.*;
  48 
  49 import static com.sun.tools.javac.code.Flags.*;
  50 import static com.sun.tools.javac.code.Flags.ANNOTATION;
  51 import static com.sun.tools.javac.code.Flags.SYNCHRONIZED;
  52 import static com.sun.tools.javac.code.Kinds.*;
  53 import static com.sun.tools.javac.code.TypeTag.*;
  54 import static com.sun.tools.javac.code.TypeTag.WILDCARD;
  55 
  56 import static com.sun.tools.javac.tree.JCTree.Tag.*;
  57 
  58 /** Type checking helper class for the attribution phase.
  59  *
  60  *  <p><b>This is NOT part of any supported API.
  61  *  If you write code that depends on this, you do so at your own risk.
  62  *  This code and its internal interfaces are subject to change or
  63  *  deletion without notice.</b>
  64  */
  65 public class Check {
  66     protected static final Context.Key<Check> checkKey =
  67         new Context.Key<Check>();
  68 
  69     private final Names names;
  70     private final Log log;
  71     private final Resolve rs;
  72     private final Symtab syms;
  73     private final Enter enter;
  74     private final DeferredAttr deferredAttr;
  75     private final Infer infer;
  76     private final Types types;
  77     private final JCDiagnostic.Factory diags;
  78     private boolean warnOnSyntheticConflicts;
  79     private boolean suppressAbortOnBadClassFile;
  80     private boolean enableSunApiLintControl;
  81     private final TreeInfo treeinfo;
  82     private final JavaFileManager fileManager;
  83     private final Profile profile;
  84 
  85     // The set of lint options currently in effect. It is initialized
  86     // from the context, and then is set/reset as needed by Attr as it
  87     // visits all the various parts of the trees during attribution.
  88     private Lint lint;
  89 
  90     // The method being analyzed in Attr - it is set/reset as needed by
  91     // Attr as it visits new method declarations.
  92     private MethodSymbol method;
  93 
  94     public static Check instance(Context context) {
  95         Check instance = context.get(checkKey);
  96         if (instance == null)
  97             instance = new Check(context);
  98         return instance;
  99     }
 100 
 101     protected Check(Context context) {
 102         context.put(checkKey, this);
 103 
 104         names = Names.instance(context);
 105         dfltTargetMeta = new Name[] { names.PACKAGE, names.TYPE,
 106             names.FIELD, names.METHOD, names.CONSTRUCTOR,
 107             names.ANNOTATION_TYPE, names.LOCAL_VARIABLE, names.PARAMETER};
 108         log = Log.instance(context);
 109         rs = Resolve.instance(context);
 110         syms = Symtab.instance(context);
 111         enter = Enter.instance(context);
 112         deferredAttr = DeferredAttr.instance(context);
 113         infer = Infer.instance(context);
 114         types = Types.instance(context);
 115         diags = JCDiagnostic.Factory.instance(context);
 116         Options options = Options.instance(context);
 117         lint = Lint.instance(context);
 118         treeinfo = TreeInfo.instance(context);
 119         fileManager = context.get(JavaFileManager.class);
 120 
 121         Source source = Source.instance(context);
 122         allowGenerics = source.allowGenerics();
 123         allowVarargs = source.allowVarargs();
 124         allowAnnotations = source.allowAnnotations();
 125         allowCovariantReturns = source.allowCovariantReturns();
 126         allowSimplifiedVarargs = source.allowSimplifiedVarargs();
 127         allowDefaultMethods = source.allowDefaultMethods();
 128         allowStrictMethodClashCheck = source.allowStrictMethodClashCheck();
 129         complexInference = options.isSet("complexinference");
 130         warnOnSyntheticConflicts = options.isSet("warnOnSyntheticConflicts");
 131         suppressAbortOnBadClassFile = options.isSet("suppressAbortOnBadClassFile");
 132         enableSunApiLintControl = options.isSet("enableSunApiLintControl");
 133 
 134         Target target = Target.instance(context);
 135         syntheticNameChar = target.syntheticNameChar();
 136 
 137         profile = Profile.instance(context);
 138 
 139         boolean verboseDeprecated = lint.isEnabled(LintCategory.DEPRECATION);
 140         boolean verboseUnchecked = lint.isEnabled(LintCategory.UNCHECKED);
 141         boolean verboseSunApi = lint.isEnabled(LintCategory.SUNAPI);
 142         boolean enforceMandatoryWarnings = source.enforceMandatoryWarnings();
 143 
 144         deprecationHandler = new MandatoryWarningHandler(log, verboseDeprecated,
 145                 enforceMandatoryWarnings, "deprecated", LintCategory.DEPRECATION);
 146         uncheckedHandler = new MandatoryWarningHandler(log, verboseUnchecked,
 147                 enforceMandatoryWarnings, "unchecked", LintCategory.UNCHECKED);
 148         sunApiHandler = new MandatoryWarningHandler(log, verboseSunApi,
 149                 enforceMandatoryWarnings, "sunapi", null);
 150 
 151         deferredLintHandler = DeferredLintHandler.instance(context);
 152     }
 153 
 154     /** Switch: generics enabled?
 155      */
 156     boolean allowGenerics;
 157 
 158     /** Switch: varargs enabled?
 159      */
 160     boolean allowVarargs;
 161 
 162     /** Switch: annotations enabled?
 163      */
 164     boolean allowAnnotations;
 165 
 166     /** Switch: covariant returns enabled?
 167      */
 168     boolean allowCovariantReturns;
 169 
 170     /** Switch: simplified varargs enabled?
 171      */
 172     boolean allowSimplifiedVarargs;
 173 
 174     /** Switch: default methods enabled?
 175      */
 176     boolean allowDefaultMethods;
 177 
 178     /** Switch: should unrelated return types trigger a method clash?
 179      */
 180     boolean allowStrictMethodClashCheck;
 181 
 182     /** Switch: -complexinference option set?
 183      */
 184     boolean complexInference;
 185 
 186     /** Character for synthetic names
 187      */
 188     char syntheticNameChar;
 189 
 190     /** A table mapping flat names of all compiled classes in this run to their
 191      *  symbols; maintained from outside.
 192      */
 193     public Map<Name,ClassSymbol> compiled = new HashMap<Name, ClassSymbol>();
 194 
 195     /** A handler for messages about deprecated usage.
 196      */
 197     private MandatoryWarningHandler deprecationHandler;
 198 
 199     /** A handler for messages about unchecked or unsafe usage.
 200      */
 201     private MandatoryWarningHandler uncheckedHandler;
 202 
 203     /** A handler for messages about using proprietary API.
 204      */
 205     private MandatoryWarningHandler sunApiHandler;
 206 
 207     /** A handler for deferred lint warnings.
 208      */
 209     private DeferredLintHandler deferredLintHandler;
 210 
 211 /* *************************************************************************
 212  * Errors and Warnings
 213  **************************************************************************/
 214 
 215     Lint setLint(Lint newLint) {
 216         Lint prev = lint;
 217         lint = newLint;
 218         return prev;
 219     }
 220 
 221     MethodSymbol setMethod(MethodSymbol newMethod) {
 222         MethodSymbol prev = method;
 223         method = newMethod;
 224         return prev;
 225     }
 226 
 227     /** Warn about deprecated symbol.
 228      *  @param pos        Position to be used for error reporting.
 229      *  @param sym        The deprecated symbol.
 230      */
 231     void warnDeprecated(DiagnosticPosition pos, Symbol sym) {
 232         if (!lint.isSuppressed(LintCategory.DEPRECATION))
 233             deprecationHandler.report(pos, "has.been.deprecated", sym, sym.location());
 234     }
 235 
 236     /** Warn about unchecked operation.
 237      *  @param pos        Position to be used for error reporting.
 238      *  @param msg        A string describing the problem.
 239      */
 240     public void warnUnchecked(DiagnosticPosition pos, String msg, Object... args) {
 241         if (!lint.isSuppressed(LintCategory.UNCHECKED))
 242             uncheckedHandler.report(pos, msg, args);
 243     }
 244 
 245     /** Warn about unsafe vararg method decl.
 246      *  @param pos        Position to be used for error reporting.
 247      */
 248     void warnUnsafeVararg(DiagnosticPosition pos, String key, Object... args) {
 249         if (lint.isEnabled(LintCategory.VARARGS) && allowSimplifiedVarargs)
 250             log.warning(LintCategory.VARARGS, pos, key, args);
 251     }
 252 
 253     /** Warn about using proprietary API.
 254      *  @param pos        Position to be used for error reporting.
 255      *  @param msg        A string describing the problem.
 256      */
 257     public void warnSunApi(DiagnosticPosition pos, String msg, Object... args) {
 258         if (!lint.isSuppressed(LintCategory.SUNAPI))
 259             sunApiHandler.report(pos, msg, args);
 260     }
 261 
 262     public void warnStatic(DiagnosticPosition pos, String msg, Object... args) {
 263         if (lint.isEnabled(LintCategory.STATIC))
 264             log.warning(LintCategory.STATIC, pos, msg, args);
 265     }
 266 
 267     /**
 268      * Report any deferred diagnostics.
 269      */
 270     public void reportDeferredDiagnostics() {
 271         deprecationHandler.reportDeferredDiagnostic();
 272         uncheckedHandler.reportDeferredDiagnostic();
 273         sunApiHandler.reportDeferredDiagnostic();
 274     }
 275 
 276 
 277     /** Report a failure to complete a class.
 278      *  @param pos        Position to be used for error reporting.
 279      *  @param ex         The failure to report.
 280      */
 281     public Type completionError(DiagnosticPosition pos, CompletionFailure ex) {
 282         log.error(JCDiagnostic.DiagnosticFlag.NON_DEFERRABLE, pos, "cant.access", ex.sym, ex.getDetailValue());
 283         if (ex instanceof ClassReader.BadClassFile
 284                 && !suppressAbortOnBadClassFile) throw new Abort();
 285         else return syms.errType;
 286     }
 287 
 288     /** Report an error that wrong type tag was found.
 289      *  @param pos        Position to be used for error reporting.
 290      *  @param required   An internationalized string describing the type tag
 291      *                    required.
 292      *  @param found      The type that was found.
 293      */
 294     Type typeTagError(DiagnosticPosition pos, Object required, Object found) {
 295         // this error used to be raised by the parser,
 296         // but has been delayed to this point:
 297         if (found instanceof Type && ((Type)found).hasTag(VOID)) {
 298             log.error(pos, "illegal.start.of.type");
 299             return syms.errType;
 300         }
 301         log.error(pos, "type.found.req", found, required);
 302         return types.createErrorType(found instanceof Type ? (Type)found : syms.errType);
 303     }
 304 
 305     /** Report an error that symbol cannot be referenced before super
 306      *  has been called.
 307      *  @param pos        Position to be used for error reporting.
 308      *  @param sym        The referenced symbol.
 309      */
 310     void earlyRefError(DiagnosticPosition pos, Symbol sym) {
 311         log.error(pos, "cant.ref.before.ctor.called", sym);
 312     }
 313 
 314     /** Report duplicate declaration error.
 315      */
 316     void duplicateError(DiagnosticPosition pos, Symbol sym) {
 317         if (!sym.type.isErroneous()) {
 318             Symbol location = sym.location();
 319             if (location.kind == MTH &&
 320                     ((MethodSymbol)location).isStaticOrInstanceInit()) {
 321                 log.error(pos, "already.defined.in.clinit", kindName(sym), sym,
 322                         kindName(sym.location()), kindName(sym.location().enclClass()),
 323                         sym.location().enclClass());
 324             } else {
 325                 log.error(pos, "already.defined", kindName(sym), sym,
 326                         kindName(sym.location()), sym.location());
 327             }
 328         }
 329     }
 330 
 331     /** Report array/varargs duplicate declaration
 332      */
 333     void varargsDuplicateError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
 334         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
 335             log.error(pos, "array.and.varargs", sym1, sym2, sym2.location());
 336         }
 337     }
 338 
 339 /* ************************************************************************
 340  * duplicate declaration checking
 341  *************************************************************************/
 342 
 343     /** Check that variable does not hide variable with same name in
 344      *  immediately enclosing local scope.
 345      *  @param pos           Position for error reporting.
 346      *  @param v             The symbol.
 347      *  @param s             The scope.
 348      */
 349     void checkTransparentVar(DiagnosticPosition pos, VarSymbol v, Scope s) {
 350         if (s.next != null) {
 351             for (Scope.Entry e = s.next.lookup(v.name);
 352                  e.scope != null && e.sym.owner == v.owner;
 353                  e = e.next()) {
 354                 if (e.sym.kind == VAR &&
 355                     (e.sym.owner.kind & (VAR | MTH)) != 0 &&
 356                     v.name != names.error) {
 357                     duplicateError(pos, e.sym);
 358                     return;
 359                 }
 360             }
 361         }
 362     }
 363 
 364     /** Check that a class or interface does not hide a class or
 365      *  interface with same name in immediately enclosing local scope.
 366      *  @param pos           Position for error reporting.
 367      *  @param c             The symbol.
 368      *  @param s             The scope.
 369      */
 370     void checkTransparentClass(DiagnosticPosition pos, ClassSymbol c, Scope s) {
 371         if (s.next != null) {
 372             for (Scope.Entry e = s.next.lookup(c.name);
 373                  e.scope != null && e.sym.owner == c.owner;
 374                  e = e.next()) {
 375                 if (e.sym.kind == TYP && !e.sym.type.hasTag(TYPEVAR) &&
 376                     (e.sym.owner.kind & (VAR | MTH)) != 0 &&
 377                     c.name != names.error) {
 378                     duplicateError(pos, e.sym);
 379                     return;
 380                 }
 381             }
 382         }
 383     }
 384 
 385     /** Check that class does not have the same name as one of
 386      *  its enclosing classes, or as a class defined in its enclosing scope.
 387      *  return true if class is unique in its enclosing scope.
 388      *  @param pos           Position for error reporting.
 389      *  @param name          The class name.
 390      *  @param s             The enclosing scope.
 391      */
 392     boolean checkUniqueClassName(DiagnosticPosition pos, Name name, Scope s) {
 393         for (Scope.Entry e = s.lookup(name); e.scope == s; e = e.next()) {
 394             if (e.sym.kind == TYP && e.sym.name != names.error) {
 395                 duplicateError(pos, e.sym);
 396                 return false;
 397             }
 398         }
 399         for (Symbol sym = s.owner; sym != null; sym = sym.owner) {
 400             if (sym.kind == TYP && sym.name == name && sym.name != names.error) {
 401                 duplicateError(pos, sym);
 402                 return true;
 403             }
 404         }
 405         return true;
 406     }
 407 
 408 /* *************************************************************************
 409  * Class name generation
 410  **************************************************************************/
 411 
 412     /** Return name of local class.
 413      *  This is of the form   {@code <enclClass> $ n <classname> }
 414      *  where
 415      *    enclClass is the flat name of the enclosing class,
 416      *    classname is the simple name of the local class
 417      */
 418     Name localClassName(ClassSymbol c) {
 419         for (int i=1; ; i++) {
 420             Name flatname = names.
 421                 fromString("" + c.owner.enclClass().flatname +
 422                            syntheticNameChar + i +
 423                            c.name);
 424             if (compiled.get(flatname) == null) return flatname;
 425         }
 426     }
 427 
 428 /* *************************************************************************
 429  * Type Checking
 430  **************************************************************************/
 431 
 432     /**
 433      * A check context is an object that can be used to perform compatibility
 434      * checks - depending on the check context, meaning of 'compatibility' might
 435      * vary significantly.
 436      */
 437     public interface CheckContext {
 438         /**
 439          * Is type 'found' compatible with type 'req' in given context
 440          */
 441         boolean compatible(Type found, Type req, Warner warn);
 442         /**
 443          * Report a check error
 444          */
 445         void report(DiagnosticPosition pos, JCDiagnostic details);
 446         /**
 447          * Obtain a warner for this check context
 448          */
 449         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req);
 450 
 451         public Infer.InferenceContext inferenceContext();
 452 
 453         public DeferredAttr.DeferredAttrContext deferredAttrContext();
 454     }
 455 
 456     /**
 457      * This class represent a check context that is nested within another check
 458      * context - useful to check sub-expressions. The default behavior simply
 459      * redirects all method calls to the enclosing check context leveraging
 460      * the forwarding pattern.
 461      */
 462     static class NestedCheckContext implements CheckContext {
 463         CheckContext enclosingContext;
 464 
 465         NestedCheckContext(CheckContext enclosingContext) {
 466             this.enclosingContext = enclosingContext;
 467         }
 468 
 469         public boolean compatible(Type found, Type req, Warner warn) {
 470             return enclosingContext.compatible(found, req, warn);
 471         }
 472 
 473         public void report(DiagnosticPosition pos, JCDiagnostic details) {
 474             enclosingContext.report(pos, details);
 475         }
 476 
 477         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
 478             return enclosingContext.checkWarner(pos, found, req);
 479         }
 480 
 481         public Infer.InferenceContext inferenceContext() {
 482             return enclosingContext.inferenceContext();
 483         }
 484 
 485         public DeferredAttrContext deferredAttrContext() {
 486             return enclosingContext.deferredAttrContext();
 487         }
 488     }
 489 
 490     /**
 491      * Check context to be used when evaluating assignment/return statements
 492      */
 493     CheckContext basicHandler = new CheckContext() {
 494         public void report(DiagnosticPosition pos, JCDiagnostic details) {
 495             log.error(pos, "prob.found.req", details);
 496         }
 497         public boolean compatible(Type found, Type req, Warner warn) {
 498             return types.isAssignable(found, req, warn);
 499         }
 500 
 501         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
 502             return convertWarner(pos, found, req);
 503         }
 504 
 505         public InferenceContext inferenceContext() {
 506             return infer.emptyContext;
 507         }
 508 
 509         public DeferredAttrContext deferredAttrContext() {
 510             return deferredAttr.emptyDeferredAttrContext;
 511         }
 512     };
 513 
 514     /** Check that a given type is assignable to a given proto-type.
 515      *  If it is, return the type, otherwise return errType.
 516      *  @param pos        Position to be used for error reporting.
 517      *  @param found      The type that was found.
 518      *  @param req        The type that was required.
 519      */
 520     Type checkType(DiagnosticPosition pos, Type found, Type req) {
 521         return checkType(pos, found, req, basicHandler);
 522     }
 523 
 524     Type checkType(final DiagnosticPosition pos, final Type found, final Type req, final CheckContext checkContext) {
 525         final Infer.InferenceContext inferenceContext = checkContext.inferenceContext();
 526         if (inferenceContext.free(req)) {
 527             inferenceContext.addFreeTypeListener(List.of(req), new FreeTypeListener() {
 528                 @Override
 529                 public void typesInferred(InferenceContext inferenceContext) {
 530                     checkType(pos, found, inferenceContext.asInstType(req), checkContext);
 531                 }
 532             });
 533         }
 534         if (req.hasTag(ERROR))
 535             return req;
 536         if (req.hasTag(NONE))
 537             return found;
 538         if (checkContext.compatible(found, req, checkContext.checkWarner(pos, found, req))) {
 539             return found;
 540         } else {
 541             if (found.isNumeric() && req.isNumeric()) {
 542                 checkContext.report(pos, diags.fragment("possible.loss.of.precision", found, req));
 543                 return types.createErrorType(found);
 544             }
 545             checkContext.report(pos, diags.fragment("inconvertible.types", found, req));
 546             return types.createErrorType(found);
 547         }
 548     }
 549 
 550     /** Check that a given type can be cast to a given target type.
 551      *  Return the result of the cast.
 552      *  @param pos        Position to be used for error reporting.
 553      *  @param found      The type that is being cast.
 554      *  @param req        The target type of the cast.
 555      */
 556     Type checkCastable(DiagnosticPosition pos, Type found, Type req) {
 557         return checkCastable(pos, found, req, basicHandler);
 558     }
 559     Type checkCastable(DiagnosticPosition pos, Type found, Type req, CheckContext checkContext) {
 560         if (types.isCastable(found, req, castWarner(pos, found, req))) {
 561             return req;
 562         } else {
 563             checkContext.report(pos, diags.fragment("inconvertible.types", found, req));
 564             return types.createErrorType(found);
 565         }
 566     }
 567 
 568     /** Check for redundant casts (i.e. where source type is a subtype of target type)
 569      * The problem should only be reported for non-292 cast
 570      */
 571     public void checkRedundantCast(Env<AttrContext> env, final JCTypeCast tree) {
 572         if (!tree.type.isErroneous()
 573                 && types.isSameType(tree.expr.type, tree.clazz.type)
 574                 && !(ignoreAnnotatedCasts && TreeInfo.containsTypeAnnotation(tree.clazz))
 575                 && !is292targetTypeCast(tree)) {
 576             deferredLintHandler.report(new DeferredLintHandler.LintLogger() {
 577                 @Override
 578                 public void report() {
 579                     if (lint.isEnabled(Lint.LintCategory.CAST))
 580                         log.warning(Lint.LintCategory.CAST,
 581                                 tree.pos(), "redundant.cast", tree.expr.type);
 582                 }
 583             });
 584         }
 585     }
 586     //where
 587         private boolean is292targetTypeCast(JCTypeCast tree) {
 588             boolean is292targetTypeCast = false;
 589             JCExpression expr = TreeInfo.skipParens(tree.expr);
 590             if (expr.hasTag(APPLY)) {
 591                 JCMethodInvocation apply = (JCMethodInvocation)expr;
 592                 Symbol sym = TreeInfo.symbol(apply.meth);
 593                 is292targetTypeCast = sym != null &&
 594                     sym.kind == MTH &&
 595                     (sym.flags() & HYPOTHETICAL) != 0;
 596             }
 597             return is292targetTypeCast;
 598         }
 599 
 600         private static final boolean ignoreAnnotatedCasts = true;
 601 
 602     /** Check that a type is within some bounds.
 603      *
 604      *  Used in TypeApply to verify that, e.g., X in {@code V<X>} is a valid
 605      *  type argument.
 606      *  @param a             The type that should be bounded by bs.
 607      *  @param bound         The bound.
 608      */
 609     private boolean checkExtends(Type a, Type bound) {
 610          if (a.isUnbound()) {
 611              return true;
 612          } else if (!a.hasTag(WILDCARD)) {
 613              a = types.upperBound(a);
 614              return types.isSubtype(a, bound);
 615          } else if (a.isExtendsBound()) {
 616              return types.isCastable(bound, types.upperBound(a), types.noWarnings);
 617          } else if (a.isSuperBound()) {
 618              return !types.notSoftSubtype(types.lowerBound(a), bound);
 619          }
 620          return true;
 621      }
 622 
 623     /** Check that type is different from 'void'.
 624      *  @param pos           Position to be used for error reporting.
 625      *  @param t             The type to be checked.
 626      */
 627     Type checkNonVoid(DiagnosticPosition pos, Type t) {
 628         if (t.hasTag(VOID)) {
 629             log.error(pos, "void.not.allowed.here");
 630             return types.createErrorType(t);
 631         } else {
 632             return t;
 633         }
 634     }
 635 
 636     Type checkClassOrArrayType(DiagnosticPosition pos, Type t) {
 637         if (!t.hasTag(CLASS) && !t.hasTag(ARRAY) && !t.hasTag(ERROR)) {
 638             return typeTagError(pos,
 639                                 diags.fragment("type.req.class.array"),
 640                                 asTypeParam(t));
 641         } else {
 642             return t;
 643         }
 644     }
 645 
 646     /** Check that type is a class or interface type.
 647      *  @param pos           Position to be used for error reporting.
 648      *  @param t             The type to be checked.
 649      */
 650     Type checkClassType(DiagnosticPosition pos, Type t) {
 651         if (!t.hasTag(CLASS) && !t.hasTag(ERROR)) {
 652             return typeTagError(pos,
 653                                 diags.fragment("type.req.class"),
 654                                 asTypeParam(t));
 655         } else {
 656             return t;
 657         }
 658     }
 659     //where
 660         private Object asTypeParam(Type t) {
 661             return (t.hasTag(TYPEVAR))
 662                                     ? diags.fragment("type.parameter", t)
 663                                     : t;
 664         }
 665 
 666     /** Check that type is a valid qualifier for a constructor reference expression
 667      */
 668     Type checkConstructorRefType(DiagnosticPosition pos, Type t) {
 669         t = checkClassOrArrayType(pos, t);
 670         if (t.hasTag(CLASS)) {
 671             if ((t.tsym.flags() & (ABSTRACT | INTERFACE)) != 0) {
 672                 log.error(pos, "abstract.cant.be.instantiated", t.tsym);
 673                 t = types.createErrorType(t);
 674             } else if ((t.tsym.flags() & ENUM) != 0) {
 675                 log.error(pos, "enum.cant.be.instantiated");
 676                 t = types.createErrorType(t);
 677             } else {
 678                 t = checkClassType(pos, t, true);
 679             }
 680         } else if (t.hasTag(ARRAY)) {
 681             if (!types.isReifiable(((ArrayType)t).elemtype)) {
 682                 log.error(pos, "generic.array.creation");
 683                 t = types.createErrorType(t);
 684             }
 685         }
 686         return t;
 687     }
 688 
 689     /** Check that type is a class or interface type.
 690      *  @param pos           Position to be used for error reporting.
 691      *  @param t             The type to be checked.
 692      *  @param noBounds    True if type bounds are illegal here.
 693      */
 694     Type checkClassType(DiagnosticPosition pos, Type t, boolean noBounds) {
 695         t = checkClassType(pos, t);
 696         if (noBounds && t.isParameterized()) {
 697             List<Type> args = t.getTypeArguments();
 698             while (args.nonEmpty()) {
 699                 if (args.head.hasTag(WILDCARD))
 700                     return typeTagError(pos,
 701                                         diags.fragment("type.req.exact"),
 702                                         args.head);
 703                 args = args.tail;
 704             }
 705         }
 706         return t;
 707     }
 708 
 709     // Analog of checkClassType that calls checkClassOrArrayType instead
 710     Type checkClassOrArrayType(DiagnosticPosition pos,
 711                                Type t, boolean noBounds) {
 712         t = checkClassOrArrayType(pos, t);
 713         if (noBounds && t.isParameterized()) {
 714             List<Type> args = t.getTypeArguments();
 715             while (args.nonEmpty()) {
 716                 if (args.head.hasTag(WILDCARD))
 717                     return typeTagError(pos,
 718                                         diags.fragment("type.req.exact"),
 719                                         args.head);
 720                 args = args.tail;
 721             }
 722         }
 723         return t;
 724     }
 725 
 726     /** Check that type is a reifiable class, interface or array type.
 727      *  @param pos           Position to be used for error reporting.
 728      *  @param t             The type to be checked.
 729      */
 730     Type checkReifiableReferenceType(DiagnosticPosition pos, Type t) {
 731         t = checkClassOrArrayType(pos, t);
 732         if (!t.isErroneous() && !types.isReifiable(t)) {
 733             log.error(pos, "illegal.generic.type.for.instof");
 734             return types.createErrorType(t);
 735         } else {
 736             return t;
 737         }
 738     }
 739 
 740     /** Check that type is a reference type, i.e. a class, interface or array type
 741      *  or a type variable.
 742      *  @param pos           Position to be used for error reporting.
 743      *  @param t             The type to be checked.
 744      */
 745     Type checkRefType(DiagnosticPosition pos, Type t) {
 746         if (t.isReference())
 747             return t;
 748         else
 749             return typeTagError(pos,
 750                                 diags.fragment("type.req.ref"),
 751                                 t);
 752     }
 753 
 754     /** Check that each type is a reference type, i.e. a class, interface or array type
 755      *  or a type variable.
 756      *  @param trees         Original trees, used for error reporting.
 757      *  @param types         The types to be checked.
 758      */
 759     List<Type> checkRefTypes(List<JCExpression> trees, List<Type> types) {
 760         List<JCExpression> tl = trees;
 761         for (List<Type> l = types; l.nonEmpty(); l = l.tail) {
 762             l.head = checkRefType(tl.head.pos(), l.head);
 763             tl = tl.tail;
 764         }
 765         return types;
 766     }
 767 
 768     /** Check that type is a null or reference type.
 769      *  @param pos           Position to be used for error reporting.
 770      *  @param t             The type to be checked.
 771      */
 772     Type checkNullOrRefType(DiagnosticPosition pos, Type t) {
 773         if (t.isReference() || t.hasTag(BOT))
 774             return t;
 775         else
 776             return typeTagError(pos,
 777                                 diags.fragment("type.req.ref"),
 778                                 t);
 779     }
 780 
 781     /** Check that flag set does not contain elements of two conflicting sets. s
 782      *  Return true if it doesn't.
 783      *  @param pos           Position to be used for error reporting.
 784      *  @param flags         The set of flags to be checked.
 785      *  @param set1          Conflicting flags set #1.
 786      *  @param set2          Conflicting flags set #2.
 787      */
 788     boolean checkDisjoint(DiagnosticPosition pos, long flags, long set1, long set2) {
 789         if ((flags & set1) != 0 && (flags & set2) != 0) {
 790             log.error(pos,
 791                       "illegal.combination.of.modifiers",
 792                       asFlagSet(TreeInfo.firstFlag(flags & set1)),
 793                       asFlagSet(TreeInfo.firstFlag(flags & set2)));
 794             return false;
 795         } else
 796             return true;
 797     }
 798 
 799     /** Check that usage of diamond operator is correct (i.e. diamond should not
 800      * be used with non-generic classes or in anonymous class creation expressions)
 801      */
 802     Type checkDiamond(JCNewClass tree, Type t) {
 803         if (!TreeInfo.isDiamond(tree) ||
 804                 t.isErroneous()) {
 805             return checkClassType(tree.clazz.pos(), t, true);
 806         } else if (tree.def != null) {
 807             log.error(tree.clazz.pos(),
 808                     "cant.apply.diamond.1",
 809                     t, diags.fragment("diamond.and.anon.class", t));
 810             return types.createErrorType(t);
 811         } else if (t.tsym.type.getTypeArguments().isEmpty()) {
 812             log.error(tree.clazz.pos(),
 813                 "cant.apply.diamond.1",
 814                 t, diags.fragment("diamond.non.generic", t));
 815             return types.createErrorType(t);
 816         } else if (tree.typeargs != null &&
 817                 tree.typeargs.nonEmpty()) {
 818             log.error(tree.clazz.pos(),
 819                 "cant.apply.diamond.1",
 820                 t, diags.fragment("diamond.and.explicit.params", t));
 821             return types.createErrorType(t);
 822         } else {
 823             return t;
 824         }
 825     }
 826 
 827     void checkVarargsMethodDecl(Env<AttrContext> env, JCMethodDecl tree) {
 828         MethodSymbol m = tree.sym;
 829         if (!allowSimplifiedVarargs) return;
 830         boolean hasTrustMeAnno = m.attribute(syms.trustMeType.tsym) != null;
 831         Type varargElemType = null;
 832         if (m.isVarArgs()) {
 833             varargElemType = types.elemtype(tree.params.last().type);
 834         }
 835         if (hasTrustMeAnno && !isTrustMeAllowedOnMethod(m)) {
 836             if (varargElemType != null) {
 837                 log.error(tree,
 838                         "varargs.invalid.trustme.anno",
 839                         syms.trustMeType.tsym,
 840                         diags.fragment("varargs.trustme.on.virtual.varargs", m));
 841             } else {
 842                 log.error(tree,
 843                             "varargs.invalid.trustme.anno",
 844                             syms.trustMeType.tsym,
 845                             diags.fragment("varargs.trustme.on.non.varargs.meth", m));
 846             }
 847         } else if (hasTrustMeAnno && varargElemType != null &&
 848                             types.isReifiable(varargElemType)) {
 849             warnUnsafeVararg(tree,
 850                             "varargs.redundant.trustme.anno",
 851                             syms.trustMeType.tsym,
 852                             diags.fragment("varargs.trustme.on.reifiable.varargs", varargElemType));
 853         }
 854         else if (!hasTrustMeAnno && varargElemType != null &&
 855                 !types.isReifiable(varargElemType)) {
 856             warnUnchecked(tree.params.head.pos(), "unchecked.varargs.non.reifiable.type", varargElemType);
 857         }
 858     }
 859     //where
 860         private boolean isTrustMeAllowedOnMethod(Symbol s) {
 861             return (s.flags() & VARARGS) != 0 &&
 862                 (s.isConstructor() ||
 863                     (s.flags() & (STATIC | FINAL)) != 0);
 864         }
 865 
 866     Type checkMethod(final Type mtype,
 867             final Symbol sym,
 868             final Env<AttrContext> env,
 869             final List<JCExpression> argtrees,
 870             final List<Type> argtypes,
 871             final boolean useVarargs,
 872             InferenceContext inferenceContext) {
 873         // System.out.println("call   : " + env.tree);
 874         // System.out.println("method : " + owntype);
 875         // System.out.println("actuals: " + argtypes);
 876         if (inferenceContext.free(mtype)) {
 877             inferenceContext.addFreeTypeListener(List.of(mtype), new FreeTypeListener() {
 878                 public void typesInferred(InferenceContext inferenceContext) {
 879                     checkMethod(inferenceContext.asInstType(mtype), sym, env, argtrees, argtypes, useVarargs, inferenceContext);
 880                 }
 881             });
 882             return mtype;
 883         }
 884         Type owntype = mtype;
 885         List<Type> formals = owntype.getParameterTypes();
 886         List<Type> nonInferred = sym.type.getParameterTypes();
 887         if (nonInferred.length() != formals.length()) nonInferred = formals;
 888         Type last = useVarargs ? formals.last() : null;
 889         if (sym.name == names.init && sym.owner == syms.enumSym) {
 890             formals = formals.tail.tail;
 891             nonInferred = nonInferred.tail.tail;
 892         }
 893         List<JCExpression> args = argtrees;
 894         if (args != null) {
 895             //this is null when type-checking a method reference
 896             while (formals.head != last) {
 897                 JCTree arg = args.head;
 898                 Warner warn = convertWarner(arg.pos(), arg.type, nonInferred.head);
 899                 assertConvertible(arg, arg.type, formals.head, warn);
 900                 args = args.tail;
 901                 formals = formals.tail;
 902                 nonInferred = nonInferred.tail;
 903             }
 904             if (useVarargs) {
 905                 Type varArg = types.elemtype(last);
 906                 while (args.tail != null) {
 907                     JCTree arg = args.head;
 908                     Warner warn = convertWarner(arg.pos(), arg.type, varArg);
 909                     assertConvertible(arg, arg.type, varArg, warn);
 910                     args = args.tail;
 911                 }
 912             } else if ((sym.flags() & (VARARGS | SIGNATURE_POLYMORPHIC)) == VARARGS &&
 913                     allowVarargs) {
 914                 // non-varargs call to varargs method
 915                 Type varParam = owntype.getParameterTypes().last();
 916                 Type lastArg = argtypes.last();
 917                 if (types.isSubtypeUnchecked(lastArg, types.elemtype(varParam)) &&
 918                     !types.isSameType(types.erasure(varParam), types.erasure(lastArg)))
 919                     log.warning(argtrees.last().pos(), "inexact.non-varargs.call",
 920                                 types.elemtype(varParam), varParam);
 921             }
 922         }
 923         if (useVarargs) {
 924             Type argtype = owntype.getParameterTypes().last();
 925             if (!types.isReifiable(argtype) &&
 926                 (!allowSimplifiedVarargs ||
 927                  sym.attribute(syms.trustMeType.tsym) == null ||
 928                  !isTrustMeAllowedOnMethod(sym))) {
 929                 warnUnchecked(env.tree.pos(),
 930                                   "unchecked.generic.array.creation",
 931                                   argtype);
 932             }
 933             if ((sym.baseSymbol().flags() & SIGNATURE_POLYMORPHIC) == 0) {
 934                 TreeInfo.setVarargsElement(env.tree, types.elemtype(argtype));
 935             }
 936          }
 937          PolyKind pkind = (sym.type.hasTag(FORALL) &&
 938                  sym.type.getReturnType().containsAny(((ForAll)sym.type).tvars)) ?
 939                  PolyKind.POLY : PolyKind.STANDALONE;
 940          TreeInfo.setPolyKind(env.tree, pkind);
 941          return owntype;
 942     }
 943     //where
 944     private void assertConvertible(JCTree tree, Type actual, Type formal, Warner warn) {
 945         if (types.isConvertible(actual, formal, warn))
 946             return;
 947 
 948         if (formal.isCompound()
 949             && types.isSubtype(actual, types.supertype(formal))
 950             && types.isSubtypeUnchecked(actual, types.interfaces(formal), warn))
 951             return;
 952     }
 953 
 954     /**
 955      * Check that type 't' is a valid instantiation of a generic class
 956      * (see JLS 4.5)
 957      *
 958      * @param t class type to be checked
 959      * @return true if 't' is well-formed
 960      */
 961     public boolean checkValidGenericType(Type t) {
 962         return firstIncompatibleTypeArg(t) == null;
 963     }
 964     //WHERE
 965         private Type firstIncompatibleTypeArg(Type type) {
 966             List<Type> formals = type.tsym.type.allparams();
 967             List<Type> actuals = type.allparams();
 968             List<Type> args = type.getTypeArguments();
 969             List<Type> forms = type.tsym.type.getTypeArguments();
 970             ListBuffer<Type> bounds_buf = new ListBuffer<Type>();
 971 
 972             // For matching pairs of actual argument types `a' and
 973             // formal type parameters with declared bound `b' ...
 974             while (args.nonEmpty() && forms.nonEmpty()) {
 975                 // exact type arguments needs to know their
 976                 // bounds (for upper and lower bound
 977                 // calculations).  So we create new bounds where
 978                 // type-parameters are replaced with actuals argument types.
 979                 bounds_buf.append(types.subst(forms.head.getUpperBound(), formals, actuals));
 980                 args = args.tail;
 981                 forms = forms.tail;
 982             }
 983 
 984             args = type.getTypeArguments();
 985             List<Type> tvars_cap = types.substBounds(formals,
 986                                       formals,
 987                                       types.capture(type).allparams());
 988             while (args.nonEmpty() && tvars_cap.nonEmpty()) {
 989                 // Let the actual arguments know their bound
 990                 args.head.withTypeVar((TypeVar)tvars_cap.head);
 991                 args = args.tail;
 992                 tvars_cap = tvars_cap.tail;
 993             }
 994 
 995             args = type.getTypeArguments();
 996             List<Type> bounds = bounds_buf.toList();
 997 
 998             while (args.nonEmpty() && bounds.nonEmpty()) {
 999                 Type actual = args.head;
1000                 if (!isTypeArgErroneous(actual) &&
1001                         !bounds.head.isErroneous() &&
1002                         !checkExtends(actual, bounds.head)) {
1003                     return args.head;
1004                 }
1005                 args = args.tail;
1006                 bounds = bounds.tail;
1007             }
1008 
1009             args = type.getTypeArguments();
1010             bounds = bounds_buf.toList();
1011 
1012             for (Type arg : types.capture(type).getTypeArguments()) {
1013                 if (arg.hasTag(TYPEVAR) &&
1014                         arg.getUpperBound().isErroneous() &&
1015                         !bounds.head.isErroneous() &&
1016                         !isTypeArgErroneous(args.head)) {
1017                     return args.head;
1018                 }
1019                 bounds = bounds.tail;
1020                 args = args.tail;
1021             }
1022 
1023             return null;
1024         }
1025         //where
1026         boolean isTypeArgErroneous(Type t) {
1027             return isTypeArgErroneous.visit(t);
1028         }
1029 
1030         Types.UnaryVisitor<Boolean> isTypeArgErroneous = new Types.UnaryVisitor<Boolean>() {
1031             public Boolean visitType(Type t, Void s) {
1032                 return t.isErroneous();
1033             }
1034             @Override
1035             public Boolean visitTypeVar(TypeVar t, Void s) {
1036                 return visit(t.getUpperBound());
1037             }
1038             @Override
1039             public Boolean visitCapturedType(CapturedType t, Void s) {
1040                 return visit(t.getUpperBound()) ||
1041                         visit(t.getLowerBound());
1042             }
1043             @Override
1044             public Boolean visitWildcardType(WildcardType t, Void s) {
1045                 return visit(t.type);
1046             }
1047         };
1048 
1049     /** Check that given modifiers are legal for given symbol and
1050      *  return modifiers together with any implicit modifiers for that symbol.
1051      *  Warning: we can't use flags() here since this method
1052      *  is called during class enter, when flags() would cause a premature
1053      *  completion.
1054      *  @param pos           Position to be used for error reporting.
1055      *  @param flags         The set of modifiers given in a definition.
1056      *  @param sym           The defined symbol.
1057      */
1058     long checkFlags(DiagnosticPosition pos, long flags, Symbol sym, JCTree tree) {
1059         long mask;
1060         long implicit = 0;
1061 
1062         switch (sym.kind) {
1063         case VAR:
1064             if (sym.owner.kind != TYP)
1065                 mask = LocalVarFlags;
1066             else if ((sym.owner.flags_field & INTERFACE) != 0)
1067                 mask = implicit = InterfaceVarFlags;
1068             else
1069                 mask = VarFlags;
1070             break;
1071         case MTH:
1072             if (sym.name == names.init) {
1073                 if ((sym.owner.flags_field & ENUM) != 0) {
1074                     // enum constructors cannot be declared public or
1075                     // protected and must be implicitly or explicitly
1076                     // private
1077                     implicit = PRIVATE;
1078                     mask = PRIVATE;
1079                 } else
1080                     mask = ConstructorFlags;
1081             }  else if ((sym.owner.flags_field & INTERFACE) != 0) {
1082                 if ((sym.owner.flags_field & ANNOTATION) != 0) {
1083                     mask = AnnotationTypeElementMask;
1084                     implicit = PUBLIC | ABSTRACT;
1085                 } else if ((flags & (DEFAULT | STATIC)) != 0) {
1086                     mask = InterfaceMethodMask;
1087                     implicit = PUBLIC;
1088                     if ((flags & DEFAULT) != 0) {
1089                         implicit |= ABSTRACT;
1090                     }
1091                 } else {
1092                     mask = implicit = InterfaceMethodFlags;
1093                 }
1094             } else {
1095                 mask = MethodFlags;
1096             }
1097             // Imply STRICTFP if owner has STRICTFP set.
1098             if (((flags|implicit) & Flags.ABSTRACT) == 0 ||
1099                 ((flags) & Flags.DEFAULT) != 0)
1100                 implicit |= sym.owner.flags_field & STRICTFP;
1101             break;
1102         case TYP:
1103             if (sym.isLocal()) {
1104                 mask = LocalClassFlags;
1105                 if (sym.name.isEmpty()) { // Anonymous class
1106                     // Anonymous classes in static methods are themselves static;
1107                     // that's why we admit STATIC here.
1108                     mask |= STATIC;
1109                     // JLS: Anonymous classes are final.
1110                     implicit |= FINAL;
1111                 }
1112                 if ((sym.owner.flags_field & STATIC) == 0 &&
1113                     (flags & ENUM) != 0)
1114                     log.error(pos, "enums.must.be.static");
1115             } else if (sym.owner.kind == TYP) {
1116                 mask = MemberClassFlags;
1117                 if (sym.owner.owner.kind == PCK ||
1118                     (sym.owner.flags_field & STATIC) != 0)
1119                     mask |= STATIC;
1120                 else if ((flags & ENUM) != 0)
1121                     log.error(pos, "enums.must.be.static");
1122                 // Nested interfaces and enums are always STATIC (Spec ???)
1123                 if ((flags & (INTERFACE | ENUM)) != 0 ) implicit = STATIC;
1124             } else {
1125                 mask = ClassFlags;
1126             }
1127             // Interfaces are always ABSTRACT
1128             if ((flags & INTERFACE) != 0) implicit |= ABSTRACT;
1129 
1130             if ((flags & ENUM) != 0) {
1131                 // enums can't be declared abstract or final
1132                 mask &= ~(ABSTRACT | FINAL);
1133                 implicit |= implicitEnumFinalFlag(tree);
1134             }
1135             // Imply STRICTFP if owner has STRICTFP set.
1136             implicit |= sym.owner.flags_field & STRICTFP;
1137             break;
1138         default:
1139             throw new AssertionError();
1140         }
1141         long illegal = flags & ExtendedStandardFlags & ~mask;
1142         if (illegal != 0) {
1143             if ((illegal & INTERFACE) != 0) {
1144                 log.error(pos, "intf.not.allowed.here");
1145                 mask |= INTERFACE;
1146             }
1147             else {
1148                 log.error(pos,
1149                           "mod.not.allowed.here", asFlagSet(illegal));
1150             }
1151         }
1152         else if ((sym.kind == TYP ||
1153                   // ISSUE: Disallowing abstract&private is no longer appropriate
1154                   // in the presence of inner classes. Should it be deleted here?
1155                   checkDisjoint(pos, flags,
1156                                 ABSTRACT,
1157                                 PRIVATE | STATIC | DEFAULT))
1158                  &&
1159                  checkDisjoint(pos, flags,
1160                                 STATIC,
1161                                 DEFAULT)
1162                  &&
1163                  checkDisjoint(pos, flags,
1164                                ABSTRACT | INTERFACE,
1165                                FINAL | NATIVE | SYNCHRONIZED)
1166                  &&
1167                  checkDisjoint(pos, flags,
1168                                PUBLIC,
1169                                PRIVATE | PROTECTED)
1170                  &&
1171                  checkDisjoint(pos, flags,
1172                                PRIVATE,
1173                                PUBLIC | PROTECTED)
1174                  &&
1175                  checkDisjoint(pos, flags,
1176                                FINAL,
1177                                VOLATILE)
1178                  &&
1179                  (sym.kind == TYP ||
1180                   checkDisjoint(pos, flags,
1181                                 ABSTRACT | NATIVE,
1182                                 STRICTFP))) {
1183             // skip
1184         }
1185         return flags & (mask | ~ExtendedStandardFlags) | implicit;
1186     }
1187 
1188 
1189     /** Determine if this enum should be implicitly final.
1190      *
1191      *  If the enum has no specialized enum contants, it is final.
1192      *
1193      *  If the enum does have specialized enum contants, it is
1194      *  <i>not</i> final.
1195      */
1196     private long implicitEnumFinalFlag(JCTree tree) {
1197         if (!tree.hasTag(CLASSDEF)) return 0;
1198         class SpecialTreeVisitor extends JCTree.Visitor {
1199             boolean specialized;
1200             SpecialTreeVisitor() {
1201                 this.specialized = false;
1202             };
1203 
1204             @Override
1205             public void visitTree(JCTree tree) { /* no-op */ }
1206 
1207             @Override
1208             public void visitVarDef(JCVariableDecl tree) {
1209                 if ((tree.mods.flags & ENUM) != 0) {
1210                     if (tree.init instanceof JCNewClass &&
1211                         ((JCNewClass) tree.init).def != null) {
1212                         specialized = true;
1213                     }
1214                 }
1215             }
1216         }
1217 
1218         SpecialTreeVisitor sts = new SpecialTreeVisitor();
1219         JCClassDecl cdef = (JCClassDecl) tree;
1220         for (JCTree defs: cdef.defs) {
1221             defs.accept(sts);
1222             if (sts.specialized) return 0;
1223         }
1224         return FINAL;
1225     }
1226 
1227 /* *************************************************************************
1228  * Type Validation
1229  **************************************************************************/
1230 
1231     /** Validate a type expression. That is,
1232      *  check that all type arguments of a parametric type are within
1233      *  their bounds. This must be done in a second phase after type attribution
1234      *  since a class might have a subclass as type parameter bound. E.g:
1235      *
1236      *  <pre>{@code
1237      *  class B<A extends C> { ... }
1238      *  class C extends B<C> { ... }
1239      *  }</pre>
1240      *
1241      *  and we can't make sure that the bound is already attributed because
1242      *  of possible cycles.
1243      *
1244      * Visitor method: Validate a type expression, if it is not null, catching
1245      *  and reporting any completion failures.
1246      */
1247     void validate(JCTree tree, Env<AttrContext> env) {
1248         validate(tree, env, true);
1249     }
1250     void validate(JCTree tree, Env<AttrContext> env, boolean checkRaw) {
1251         new Validator(env).validateTree(tree, checkRaw, true);
1252     }
1253 
1254     /** Visitor method: Validate a list of type expressions.
1255      */
1256     void validate(List<? extends JCTree> trees, Env<AttrContext> env) {
1257         for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
1258             validate(l.head, env);
1259     }
1260 
1261     /** A visitor class for type validation.
1262      */
1263     class Validator extends JCTree.Visitor {
1264 
1265         boolean checkRaw;
1266         boolean isOuter;
1267         Env<AttrContext> env;
1268 
1269         Validator(Env<AttrContext> env) {
1270             this.env = env;
1271         }
1272 
1273         @Override
1274         public void visitTypeArray(JCArrayTypeTree tree) {
1275             validateTree(tree.elemtype, checkRaw, isOuter);
1276         }
1277 
1278         @Override
1279         public void visitTypeApply(JCTypeApply tree) {
1280             if (tree.type.hasTag(CLASS)) {
1281                 List<JCExpression> args = tree.arguments;
1282                 List<Type> forms = tree.type.tsym.type.getTypeArguments();
1283 
1284                 Type incompatibleArg = firstIncompatibleTypeArg(tree.type);
1285                 if (incompatibleArg != null) {
1286                     for (JCTree arg : tree.arguments) {
1287                         if (arg.type == incompatibleArg) {
1288                             log.error(arg, "not.within.bounds", incompatibleArg, forms.head);
1289                         }
1290                         forms = forms.tail;
1291                      }
1292                  }
1293 
1294                 forms = tree.type.tsym.type.getTypeArguments();
1295 
1296                 boolean is_java_lang_Class = tree.type.tsym.flatName() == names.java_lang_Class;
1297 
1298                 // For matching pairs of actual argument types `a' and
1299                 // formal type parameters with declared bound `b' ...
1300                 while (args.nonEmpty() && forms.nonEmpty()) {
1301                     validateTree(args.head,
1302                             !(isOuter && is_java_lang_Class),
1303                             false);
1304                     args = args.tail;
1305                     forms = forms.tail;
1306                 }
1307 
1308                 // Check that this type is either fully parameterized, or
1309                 // not parameterized at all.
1310                 if (tree.type.getEnclosingType().isRaw())
1311                     log.error(tree.pos(), "improperly.formed.type.inner.raw.param");
1312                 if (tree.clazz.hasTag(SELECT))
1313                     visitSelectInternal((JCFieldAccess)tree.clazz);
1314             }
1315         }
1316 
1317         @Override
1318         public void visitTypeParameter(JCTypeParameter tree) {
1319             validateTrees(tree.bounds, true, isOuter);
1320             checkClassBounds(tree.pos(), tree.type);
1321         }
1322 
1323         @Override
1324         public void visitWildcard(JCWildcard tree) {
1325             if (tree.inner != null)
1326                 validateTree(tree.inner, true, isOuter);
1327         }
1328 
1329         @Override
1330         public void visitSelect(JCFieldAccess tree) {
1331             if (tree.type.hasTag(CLASS)) {
1332                 visitSelectInternal(tree);
1333 
1334                 // Check that this type is either fully parameterized, or
1335                 // not parameterized at all.
1336                 if (tree.selected.type.isParameterized() && tree.type.tsym.type.getTypeArguments().nonEmpty())
1337                     log.error(tree.pos(), "improperly.formed.type.param.missing");
1338             }
1339         }
1340 
1341         public void visitSelectInternal(JCFieldAccess tree) {
1342             if (tree.type.tsym.isStatic() &&
1343                 tree.selected.type.isParameterized()) {
1344                 // The enclosing type is not a class, so we are
1345                 // looking at a static member type.  However, the
1346                 // qualifying expression is parameterized.
1347                 log.error(tree.pos(), "cant.select.static.class.from.param.type");
1348             } else {
1349                 // otherwise validate the rest of the expression
1350                 tree.selected.accept(this);
1351             }
1352         }
1353 
1354         @Override
1355         public void visitAnnotatedType(JCAnnotatedType tree) {
1356             tree.underlyingType.accept(this);
1357         }
1358 
1359         /** Default visitor method: do nothing.
1360          */
1361         @Override
1362         public void visitTree(JCTree tree) {
1363         }
1364 
1365         public void validateTree(JCTree tree, boolean checkRaw, boolean isOuter) {
1366             if (tree != null) {
1367                 boolean prevCheckRaw = this.checkRaw;
1368                 this.checkRaw = checkRaw;
1369                 this.isOuter = isOuter;
1370 
1371                 try {
1372                     tree.accept(this);
1373                     if (checkRaw)
1374                         checkRaw(tree, env);
1375                 } catch (CompletionFailure ex) {
1376                     completionError(tree.pos(), ex);
1377                 } finally {
1378                     this.checkRaw = prevCheckRaw;
1379                 }
1380             }
1381         }
1382 
1383         public void validateTrees(List<? extends JCTree> trees, boolean checkRaw, boolean isOuter) {
1384             for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
1385                 validateTree(l.head, checkRaw, isOuter);
1386         }
1387     }
1388 
1389     void checkRaw(JCTree tree, Env<AttrContext> env) {
1390         if (lint.isEnabled(LintCategory.RAW) &&
1391             tree.type.hasTag(CLASS) &&
1392             !TreeInfo.isDiamond(tree) &&
1393             !withinAnonConstr(env) &&
1394             tree.type.isRaw()) {
1395             log.warning(LintCategory.RAW,
1396                     tree.pos(), "raw.class.use", tree.type, tree.type.tsym.type);
1397         }
1398     }
1399     //where
1400         private boolean withinAnonConstr(Env<AttrContext> env) {
1401             return env.enclClass.name.isEmpty() &&
1402                     env.enclMethod != null && env.enclMethod.name == names.init;
1403         }
1404 
1405 /* *************************************************************************
1406  * Exception checking
1407  **************************************************************************/
1408 
1409     /* The following methods treat classes as sets that contain
1410      * the class itself and all their subclasses
1411      */
1412 
1413     /** Is given type a subtype of some of the types in given list?
1414      */
1415     boolean subset(Type t, List<Type> ts) {
1416         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1417             if (types.isSubtype(t, l.head)) return true;
1418         return false;
1419     }
1420 
1421     /** Is given type a subtype or supertype of
1422      *  some of the types in given list?
1423      */
1424     boolean intersects(Type t, List<Type> ts) {
1425         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
1426             if (types.isSubtype(t, l.head) || types.isSubtype(l.head, t)) return true;
1427         return false;
1428     }
1429 
1430     /** Add type set to given type list, unless it is a subclass of some class
1431      *  in the list.
1432      */
1433     List<Type> incl(Type t, List<Type> ts) {
1434         return subset(t, ts) ? ts : excl(t, ts).prepend(t);
1435     }
1436 
1437     /** Remove type set from type set list.
1438      */
1439     List<Type> excl(Type t, List<Type> ts) {
1440         if (ts.isEmpty()) {
1441             return ts;
1442         } else {
1443             List<Type> ts1 = excl(t, ts.tail);
1444             if (types.isSubtype(ts.head, t)) return ts1;
1445             else if (ts1 == ts.tail) return ts;
1446             else return ts1.prepend(ts.head);
1447         }
1448     }
1449 
1450     /** Form the union of two type set lists.
1451      */
1452     List<Type> union(List<Type> ts1, List<Type> ts2) {
1453         List<Type> ts = ts1;
1454         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1455             ts = incl(l.head, ts);
1456         return ts;
1457     }
1458 
1459     /** Form the difference of two type lists.
1460      */
1461     List<Type> diff(List<Type> ts1, List<Type> ts2) {
1462         List<Type> ts = ts1;
1463         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1464             ts = excl(l.head, ts);
1465         return ts;
1466     }
1467 
1468     /** Form the intersection of two type lists.
1469      */
1470     public List<Type> intersect(List<Type> ts1, List<Type> ts2) {
1471         List<Type> ts = List.nil();
1472         for (List<Type> l = ts1; l.nonEmpty(); l = l.tail)
1473             if (subset(l.head, ts2)) ts = incl(l.head, ts);
1474         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
1475             if (subset(l.head, ts1)) ts = incl(l.head, ts);
1476         return ts;
1477     }
1478 
1479     /** Is exc an exception symbol that need not be declared?
1480      */
1481     boolean isUnchecked(ClassSymbol exc) {
1482         return
1483             exc.kind == ERR ||
1484             exc.isSubClass(syms.errorType.tsym, types) ||
1485             exc.isSubClass(syms.runtimeExceptionType.tsym, types);
1486     }
1487 
1488     /** Is exc an exception type that need not be declared?
1489      */
1490     boolean isUnchecked(Type exc) {
1491         return
1492             (exc.hasTag(TYPEVAR)) ? isUnchecked(types.supertype(exc)) :
1493             (exc.hasTag(CLASS)) ? isUnchecked((ClassSymbol)exc.tsym) :
1494             exc.hasTag(BOT);
1495     }
1496 
1497     /** Same, but handling completion failures.
1498      */
1499     boolean isUnchecked(DiagnosticPosition pos, Type exc) {
1500         try {
1501             return isUnchecked(exc);
1502         } catch (CompletionFailure ex) {
1503             completionError(pos, ex);
1504             return true;
1505         }
1506     }
1507 
1508     /** Is exc handled by given exception list?
1509      */
1510     boolean isHandled(Type exc, List<Type> handled) {
1511         return isUnchecked(exc) || subset(exc, handled);
1512     }
1513 
1514     /** Return all exceptions in thrown list that are not in handled list.
1515      *  @param thrown     The list of thrown exceptions.
1516      *  @param handled    The list of handled exceptions.
1517      */
1518     List<Type> unhandled(List<Type> thrown, List<Type> handled) {
1519         List<Type> unhandled = List.nil();
1520         for (List<Type> l = thrown; l.nonEmpty(); l = l.tail)
1521             if (!isHandled(l.head, handled)) unhandled = unhandled.prepend(l.head);
1522         return unhandled;
1523     }
1524 
1525 /* *************************************************************************
1526  * Overriding/Implementation checking
1527  **************************************************************************/
1528 
1529     /** The level of access protection given by a flag set,
1530      *  where PRIVATE is highest and PUBLIC is lowest.
1531      */
1532     static int protection(long flags) {
1533         switch ((short)(flags & AccessFlags)) {
1534         case PRIVATE: return 3;
1535         case PROTECTED: return 1;
1536         default:
1537         case PUBLIC: return 0;
1538         case 0: return 2;
1539         }
1540     }
1541 
1542     /** A customized "cannot override" error message.
1543      *  @param m      The overriding method.
1544      *  @param other  The overridden method.
1545      *  @return       An internationalized string.
1546      */
1547     Object cannotOverride(MethodSymbol m, MethodSymbol other) {
1548         String key;
1549         if ((other.owner.flags() & INTERFACE) == 0)
1550             key = "cant.override";
1551         else if ((m.owner.flags() & INTERFACE) == 0)
1552             key = "cant.implement";
1553         else
1554             key = "clashes.with";
1555         return diags.fragment(key, m, m.location(), other, other.location());
1556     }
1557 
1558     /** A customized "override" warning message.
1559      *  @param m      The overriding method.
1560      *  @param other  The overridden method.
1561      *  @return       An internationalized string.
1562      */
1563     Object uncheckedOverrides(MethodSymbol m, MethodSymbol other) {
1564         String key;
1565         if ((other.owner.flags() & INTERFACE) == 0)
1566             key = "unchecked.override";
1567         else if ((m.owner.flags() & INTERFACE) == 0)
1568             key = "unchecked.implement";
1569         else
1570             key = "unchecked.clash.with";
1571         return diags.fragment(key, m, m.location(), other, other.location());
1572     }
1573 
1574     /** A customized "override" warning message.
1575      *  @param m      The overriding method.
1576      *  @param other  The overridden method.
1577      *  @return       An internationalized string.
1578      */
1579     Object varargsOverrides(MethodSymbol m, MethodSymbol other) {
1580         String key;
1581         if ((other.owner.flags() & INTERFACE) == 0)
1582             key = "varargs.override";
1583         else  if ((m.owner.flags() & INTERFACE) == 0)
1584             key = "varargs.implement";
1585         else
1586             key = "varargs.clash.with";
1587         return diags.fragment(key, m, m.location(), other, other.location());
1588     }
1589 
1590     /** Check that this method conforms with overridden method 'other'.
1591      *  where `origin' is the class where checking started.
1592      *  Complications:
1593      *  (1) Do not check overriding of synthetic methods
1594      *      (reason: they might be final).
1595      *      todo: check whether this is still necessary.
1596      *  (2) Admit the case where an interface proxy throws fewer exceptions
1597      *      than the method it implements. Augment the proxy methods with the
1598      *      undeclared exceptions in this case.
1599      *  (3) When generics are enabled, admit the case where an interface proxy
1600      *      has a result type
1601      *      extended by the result type of the method it implements.
1602      *      Change the proxies result type to the smaller type in this case.
1603      *
1604      *  @param tree         The tree from which positions
1605      *                      are extracted for errors.
1606      *  @param m            The overriding method.
1607      *  @param other        The overridden method.
1608      *  @param origin       The class of which the overriding method
1609      *                      is a member.
1610      */
1611     void checkOverride(JCTree tree,
1612                        MethodSymbol m,
1613                        MethodSymbol other,
1614                        ClassSymbol origin) {
1615         // Don't check overriding of synthetic methods or by bridge methods.
1616         if ((m.flags() & (SYNTHETIC|BRIDGE)) != 0 || (other.flags() & SYNTHETIC) != 0) {
1617             return;
1618         }
1619 
1620         // Error if static method overrides instance method (JLS 8.4.6.2).
1621         if ((m.flags() & STATIC) != 0 &&
1622                    (other.flags() & STATIC) == 0) {
1623             log.error(TreeInfo.diagnosticPositionFor(m, tree), "override.static",
1624                       cannotOverride(m, other));
1625             m.flags_field |= BAD_OVERRIDE;
1626             return;
1627         }
1628 
1629         // Error if instance method overrides static or final
1630         // method (JLS 8.4.6.1).
1631         if ((other.flags() & FINAL) != 0 ||
1632                  (m.flags() & STATIC) == 0 &&
1633                  (other.flags() & STATIC) != 0) {
1634             log.error(TreeInfo.diagnosticPositionFor(m, tree), "override.meth",
1635                       cannotOverride(m, other),
1636                       asFlagSet(other.flags() & (FINAL | STATIC)));
1637             m.flags_field |= BAD_OVERRIDE;
1638             return;
1639         }
1640 
1641         if ((m.owner.flags() & ANNOTATION) != 0) {
1642             // handled in validateAnnotationMethod
1643             return;
1644         }
1645 
1646         // Error if overriding method has weaker access (JLS 8.4.6.3).
1647         if ((origin.flags() & INTERFACE) == 0 &&
1648                  protection(m.flags()) > protection(other.flags())) {
1649             log.error(TreeInfo.diagnosticPositionFor(m, tree), "override.weaker.access",
1650                       cannotOverride(m, other),
1651                       other.flags() == 0 ?
1652                           "package" :
1653                           asFlagSet(other.flags() & AccessFlags));
1654             m.flags_field |= BAD_OVERRIDE;
1655             return;
1656         }
1657 
1658         Type mt = types.memberType(origin.type, m);
1659         Type ot = types.memberType(origin.type, other);
1660         // Error if overriding result type is different
1661         // (or, in the case of generics mode, not a subtype) of
1662         // overridden result type. We have to rename any type parameters
1663         // before comparing types.
1664         List<Type> mtvars = mt.getTypeArguments();
1665         List<Type> otvars = ot.getTypeArguments();
1666         Type mtres = mt.getReturnType();
1667         Type otres = types.subst(ot.getReturnType(), otvars, mtvars);
1668 
1669         overrideWarner.clear();
1670         boolean resultTypesOK =
1671             types.returnTypeSubstitutable(mt, ot, otres, overrideWarner);
1672         if (!resultTypesOK) {
1673             if (!allowCovariantReturns &&
1674                 m.owner != origin &&
1675                 m.owner.isSubClass(other.owner, types)) {
1676                 // allow limited interoperability with covariant returns
1677             } else {
1678                 log.error(TreeInfo.diagnosticPositionFor(m, tree),
1679                           "override.incompatible.ret",
1680                           cannotOverride(m, other),
1681                           mtres, otres);
1682                 m.flags_field |= BAD_OVERRIDE;
1683                 return;
1684             }
1685         } else if (overrideWarner.hasNonSilentLint(LintCategory.UNCHECKED)) {
1686             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
1687                     "override.unchecked.ret",
1688                     uncheckedOverrides(m, other),
1689                     mtres, otres);
1690         }
1691 
1692         // Error if overriding method throws an exception not reported
1693         // by overridden method.
1694         List<Type> otthrown = types.subst(ot.getThrownTypes(), otvars, mtvars);
1695         List<Type> unhandledErased = unhandled(mt.getThrownTypes(), types.erasure(otthrown));
1696         List<Type> unhandledUnerased = unhandled(mt.getThrownTypes(), otthrown);
1697         if (unhandledErased.nonEmpty()) {
1698             log.error(TreeInfo.diagnosticPositionFor(m, tree),
1699                       "override.meth.doesnt.throw",
1700                       cannotOverride(m, other),
1701                       unhandledUnerased.head);
1702             m.flags_field |= BAD_OVERRIDE;
1703             return;
1704         }
1705         else if (unhandledUnerased.nonEmpty()) {
1706             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
1707                           "override.unchecked.thrown",
1708                          cannotOverride(m, other),
1709                          unhandledUnerased.head);
1710             return;
1711         }
1712 
1713         // Optional warning if varargs don't agree
1714         if ((((m.flags() ^ other.flags()) & Flags.VARARGS) != 0)
1715             && lint.isEnabled(LintCategory.OVERRIDES)) {
1716             log.warning(TreeInfo.diagnosticPositionFor(m, tree),
1717                         ((m.flags() & Flags.VARARGS) != 0)
1718                         ? "override.varargs.missing"
1719                         : "override.varargs.extra",
1720                         varargsOverrides(m, other));
1721         }
1722 
1723         // Warn if instance method overrides bridge method (compiler spec ??)
1724         if ((other.flags() & BRIDGE) != 0) {
1725             log.warning(TreeInfo.diagnosticPositionFor(m, tree), "override.bridge",
1726                         uncheckedOverrides(m, other));
1727         }
1728 
1729         // Warn if a deprecated method overridden by a non-deprecated one.
1730         if (!isDeprecatedOverrideIgnorable(other, origin)) {
1731             checkDeprecated(TreeInfo.diagnosticPositionFor(m, tree), m, other);
1732         }
1733     }
1734     // where
1735         private boolean isDeprecatedOverrideIgnorable(MethodSymbol m, ClassSymbol origin) {
1736             // If the method, m, is defined in an interface, then ignore the issue if the method
1737             // is only inherited via a supertype and also implemented in the supertype,
1738             // because in that case, we will rediscover the issue when examining the method
1739             // in the supertype.
1740             // If the method, m, is not defined in an interface, then the only time we need to
1741             // address the issue is when the method is the supertype implemementation: any other
1742             // case, we will have dealt with when examining the supertype classes
1743             ClassSymbol mc = m.enclClass();
1744             Type st = types.supertype(origin.type);
1745             if (!st.hasTag(CLASS))
1746                 return true;
1747             MethodSymbol stimpl = m.implementation((ClassSymbol)st.tsym, types, false);
1748 
1749             if (mc != null && ((mc.flags() & INTERFACE) != 0)) {
1750                 List<Type> intfs = types.interfaces(origin.type);
1751                 return (intfs.contains(mc.type) ? false : (stimpl != null));
1752             }
1753             else
1754                 return (stimpl != m);
1755         }
1756 
1757 
1758     // used to check if there were any unchecked conversions
1759     Warner overrideWarner = new Warner();
1760 
1761     /** Check that a class does not inherit two concrete methods
1762      *  with the same signature.
1763      *  @param pos          Position to be used for error reporting.
1764      *  @param site         The class type to be checked.
1765      */
1766     public void checkCompatibleConcretes(DiagnosticPosition pos, Type site) {
1767         Type sup = types.supertype(site);
1768         if (!sup.hasTag(CLASS)) return;
1769 
1770         for (Type t1 = sup;
1771              t1.hasTag(CLASS) && t1.tsym.type.isParameterized();
1772              t1 = types.supertype(t1)) {
1773             for (Scope.Entry e1 = t1.tsym.members().elems;
1774                  e1 != null;
1775                  e1 = e1.sibling) {
1776                 Symbol s1 = e1.sym;
1777                 if (s1.kind != MTH ||
1778                     (s1.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
1779                     !s1.isInheritedIn(site.tsym, types) ||
1780                     ((MethodSymbol)s1).implementation(site.tsym,
1781                                                       types,
1782                                                       true) != s1)
1783                     continue;
1784                 Type st1 = types.memberType(t1, s1);
1785                 int s1ArgsLength = st1.getParameterTypes().length();
1786                 if (st1 == s1.type) continue;
1787 
1788                 for (Type t2 = sup;
1789                      t2.hasTag(CLASS);
1790                      t2 = types.supertype(t2)) {
1791                     for (Scope.Entry e2 = t2.tsym.members().lookup(s1.name);
1792                          e2.scope != null;
1793                          e2 = e2.next()) {
1794                         Symbol s2 = e2.sym;
1795                         if (s2 == s1 ||
1796                             s2.kind != MTH ||
1797                             (s2.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
1798                             s2.type.getParameterTypes().length() != s1ArgsLength ||
1799                             !s2.isInheritedIn(site.tsym, types) ||
1800                             ((MethodSymbol)s2).implementation(site.tsym,
1801                                                               types,
1802                                                               true) != s2)
1803                             continue;
1804                         Type st2 = types.memberType(t2, s2);
1805                         if (types.overrideEquivalent(st1, st2))
1806                             log.error(pos, "concrete.inheritance.conflict",
1807                                       s1, t1, s2, t2, sup);
1808                     }
1809                 }
1810             }
1811         }
1812     }
1813 
1814     /** Check that classes (or interfaces) do not each define an abstract
1815      *  method with same name and arguments but incompatible return types.
1816      *  @param pos          Position to be used for error reporting.
1817      *  @param t1           The first argument type.
1818      *  @param t2           The second argument type.
1819      */
1820     public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
1821                                             Type t1,
1822                                             Type t2) {
1823         return checkCompatibleAbstracts(pos, t1, t2,
1824                                         types.makeCompoundType(t1, t2));
1825     }
1826 
1827     public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
1828                                             Type t1,
1829                                             Type t2,
1830                                             Type site) {
1831         return firstIncompatibility(pos, t1, t2, site) == null;
1832     }
1833 
1834     /** Return the first method which is defined with same args
1835      *  but different return types in two given interfaces, or null if none
1836      *  exists.
1837      *  @param t1     The first type.
1838      *  @param t2     The second type.
1839      *  @param site   The most derived type.
1840      *  @returns symbol from t2 that conflicts with one in t1.
1841      */
1842     private Symbol firstIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
1843         Map<TypeSymbol,Type> interfaces1 = new HashMap<TypeSymbol,Type>();
1844         closure(t1, interfaces1);
1845         Map<TypeSymbol,Type> interfaces2;
1846         if (t1 == t2)
1847             interfaces2 = interfaces1;
1848         else
1849             closure(t2, interfaces1, interfaces2 = new HashMap<TypeSymbol,Type>());
1850 
1851         for (Type t3 : interfaces1.values()) {
1852             for (Type t4 : interfaces2.values()) {
1853                 Symbol s = firstDirectIncompatibility(pos, t3, t4, site);
1854                 if (s != null) return s;
1855             }
1856         }
1857         return null;
1858     }
1859 
1860     /** Compute all the supertypes of t, indexed by type symbol. */
1861     private void closure(Type t, Map<TypeSymbol,Type> typeMap) {
1862         if (!t.hasTag(CLASS)) return;
1863         if (typeMap.put(t.tsym, t) == null) {
1864             closure(types.supertype(t), typeMap);
1865             for (Type i : types.interfaces(t))
1866                 closure(i, typeMap);
1867         }
1868     }
1869 
1870     /** Compute all the supertypes of t, indexed by type symbol (except thise in typesSkip). */
1871     private void closure(Type t, Map<TypeSymbol,Type> typesSkip, Map<TypeSymbol,Type> typeMap) {
1872         if (!t.hasTag(CLASS)) return;
1873         if (typesSkip.get(t.tsym) != null) return;
1874         if (typeMap.put(t.tsym, t) == null) {
1875             closure(types.supertype(t), typesSkip, typeMap);
1876             for (Type i : types.interfaces(t))
1877                 closure(i, typesSkip, typeMap);
1878         }
1879     }
1880 
1881     /** Return the first method in t2 that conflicts with a method from t1. */
1882     private Symbol firstDirectIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
1883         for (Scope.Entry e1 = t1.tsym.members().elems; e1 != null; e1 = e1.sibling) {
1884             Symbol s1 = e1.sym;
1885             Type st1 = null;
1886             if (s1.kind != MTH || !s1.isInheritedIn(site.tsym, types) ||
1887                     (s1.flags() & SYNTHETIC) != 0) continue;
1888             Symbol impl = ((MethodSymbol)s1).implementation(site.tsym, types, false);
1889             if (impl != null && (impl.flags() & ABSTRACT) == 0) continue;
1890             for (Scope.Entry e2 = t2.tsym.members().lookup(s1.name); e2.scope != null; e2 = e2.next()) {
1891                 Symbol s2 = e2.sym;
1892                 if (s1 == s2) continue;
1893                 if (s2.kind != MTH || !s2.isInheritedIn(site.tsym, types) ||
1894                         (s2.flags() & SYNTHETIC) != 0) continue;
1895                 if (st1 == null) st1 = types.memberType(t1, s1);
1896                 Type st2 = types.memberType(t2, s2);
1897                 if (types.overrideEquivalent(st1, st2)) {
1898                     List<Type> tvars1 = st1.getTypeArguments();
1899                     List<Type> tvars2 = st2.getTypeArguments();
1900                     Type rt1 = st1.getReturnType();
1901                     Type rt2 = types.subst(st2.getReturnType(), tvars2, tvars1);
1902                     boolean compat =
1903                         types.isSameType(rt1, rt2) ||
1904                         !rt1.isPrimitiveOrVoid() &&
1905                         !rt2.isPrimitiveOrVoid() &&
1906                         (types.covariantReturnType(rt1, rt2, types.noWarnings) ||
1907                          types.covariantReturnType(rt2, rt1, types.noWarnings)) ||
1908                          checkCommonOverriderIn(s1,s2,site);
1909                     if (!compat) {
1910                         log.error(pos, "types.incompatible.diff.ret",
1911                             t1, t2, s2.name +
1912                             "(" + types.memberType(t2, s2).getParameterTypes() + ")");
1913                         return s2;
1914                     }
1915                 } else if (checkNameClash((ClassSymbol)site.tsym, s1, s2) &&
1916                         !checkCommonOverriderIn(s1, s2, site)) {
1917                     log.error(pos,
1918                             "name.clash.same.erasure.no.override",
1919                             s1, s1.location(),
1920                             s2, s2.location());
1921                     return s2;
1922                 }
1923             }
1924         }
1925         return null;
1926     }
1927     //WHERE
1928     boolean checkCommonOverriderIn(Symbol s1, Symbol s2, Type site) {
1929         Map<TypeSymbol,Type> supertypes = new HashMap<TypeSymbol,Type>();
1930         Type st1 = types.memberType(site, s1);
1931         Type st2 = types.memberType(site, s2);
1932         closure(site, supertypes);
1933         for (Type t : supertypes.values()) {
1934             for (Scope.Entry e = t.tsym.members().lookup(s1.name); e.scope != null; e = e.next()) {
1935                 Symbol s3 = e.sym;
1936                 if (s3 == s1 || s3 == s2 || s3.kind != MTH || (s3.flags() & (BRIDGE|SYNTHETIC)) != 0) continue;
1937                 Type st3 = types.memberType(site,s3);
1938                 if (types.overrideEquivalent(st3, st1) &&
1939                         types.overrideEquivalent(st3, st2) &&
1940                         types.returnTypeSubstitutable(st3, st1) &&
1941                         types.returnTypeSubstitutable(st3, st2)) {
1942                     return true;
1943                 }
1944             }
1945         }
1946         return false;
1947     }
1948 
1949     /** Check that a given method conforms with any method it overrides.
1950      *  @param tree         The tree from which positions are extracted
1951      *                      for errors.
1952      *  @param m            The overriding method.
1953      */
1954     void checkOverride(JCTree tree, MethodSymbol m) {
1955         ClassSymbol origin = (ClassSymbol)m.owner;
1956         if ((origin.flags() & ENUM) != 0 && names.finalize.equals(m.name))
1957             if (m.overrides(syms.enumFinalFinalize, origin, types, false)) {
1958                 log.error(tree.pos(), "enum.no.finalize");
1959                 return;
1960             }
1961         for (Type t = origin.type; t.hasTag(CLASS);
1962              t = types.supertype(t)) {
1963             if (t != origin.type) {
1964                 checkOverride(tree, t, origin, m);
1965             }
1966             for (Type t2 : types.interfaces(t)) {
1967                 checkOverride(tree, t2, origin, m);
1968             }
1969         }
1970     }
1971 
1972     void checkOverride(JCTree tree, Type site, ClassSymbol origin, MethodSymbol m) {
1973         TypeSymbol c = site.tsym;
1974         Scope.Entry e = c.members().lookup(m.name);
1975         while (e.scope != null) {
1976             if (m.overrides(e.sym, origin, types, false)) {
1977                 if ((e.sym.flags() & ABSTRACT) == 0) {
1978                     checkOverride(tree, m, (MethodSymbol)e.sym, origin);
1979                 }
1980             }
1981             e = e.next();
1982         }
1983     }
1984 
1985     private Filter<Symbol> equalsHasCodeFilter = new Filter<Symbol>() {
1986         public boolean accepts(Symbol s) {
1987             return MethodSymbol.implementation_filter.accepts(s) &&
1988                     (s.flags() & BAD_OVERRIDE) == 0;
1989 
1990         }
1991     };
1992 
1993     public void checkClassOverrideEqualsAndHashIfNeeded(DiagnosticPosition pos,
1994             ClassSymbol someClass) {
1995         /* At present, annotations cannot possibly have a method that is override
1996          * equivalent with Object.equals(Object) but in any case the condition is
1997          * fine for completeness.
1998          */
1999         if (someClass == (ClassSymbol)syms.objectType.tsym ||
2000             someClass.isInterface() || someClass.isEnum() ||
2001             (someClass.flags() & ANNOTATION) != 0 ||
2002             (someClass.flags() & ABSTRACT) != 0) return;
2003         //anonymous inner classes implementing interfaces need especial treatment
2004         if (someClass.isAnonymous()) {
2005             List<Type> interfaces =  types.interfaces(someClass.type);
2006             if (interfaces != null && !interfaces.isEmpty() &&
2007                 interfaces.head.tsym == syms.comparatorType.tsym) return;
2008         }
2009         checkClassOverrideEqualsAndHash(pos, someClass);
2010     }
2011 
2012     private void checkClassOverrideEqualsAndHash(DiagnosticPosition pos,
2013             ClassSymbol someClass) {
2014         if (lint.isEnabled(LintCategory.OVERRIDES)) {
2015             MethodSymbol equalsAtObject = (MethodSymbol)syms.objectType
2016                     .tsym.members().lookup(names.equals).sym;
2017             MethodSymbol hashCodeAtObject = (MethodSymbol)syms.objectType
2018                     .tsym.members().lookup(names.hashCode).sym;
2019             boolean overridesEquals = types.implementation(equalsAtObject,
2020                 someClass, false, equalsHasCodeFilter).owner == someClass;
2021             boolean overridesHashCode = types.implementation(hashCodeAtObject,
2022                 someClass, false, equalsHasCodeFilter) != hashCodeAtObject;
2023 
2024             if (overridesEquals && !overridesHashCode) {
2025                 log.warning(LintCategory.OVERRIDES, pos,
2026                         "override.equals.but.not.hashcode", someClass);
2027             }
2028         }
2029     }
2030 
2031     private boolean checkNameClash(ClassSymbol origin, Symbol s1, Symbol s2) {
2032         ClashFilter cf = new ClashFilter(origin.type);
2033         return (cf.accepts(s1) &&
2034                 cf.accepts(s2) &&
2035                 types.hasSameArgs(s1.erasure(types), s2.erasure(types)));
2036     }
2037 
2038 
2039     /** Check that all abstract members of given class have definitions.
2040      *  @param pos          Position to be used for error reporting.
2041      *  @param c            The class.
2042      */
2043     void checkAllDefined(DiagnosticPosition pos, ClassSymbol c) {
2044         try {
2045             MethodSymbol undef = firstUndef(c, c);
2046             if (undef != null) {
2047                 if ((c.flags() & ENUM) != 0 &&
2048                     types.supertype(c.type).tsym == syms.enumSym &&
2049                     (c.flags() & FINAL) == 0) {
2050                     // add the ABSTRACT flag to an enum
2051                     c.flags_field |= ABSTRACT;
2052                 } else {
2053                     MethodSymbol undef1 =
2054                         new MethodSymbol(undef.flags(), undef.name,
2055                                          types.memberType(c.type, undef), undef.owner);
2056                     log.error(pos, "does.not.override.abstract",
2057                               c, undef1, undef1.location());
2058                 }
2059             }
2060         } catch (CompletionFailure ex) {
2061             completionError(pos, ex);
2062         }
2063     }
2064 //where
2065         /** Return first abstract member of class `c' that is not defined
2066          *  in `impl', null if there is none.
2067          */
2068         private MethodSymbol firstUndef(ClassSymbol impl, ClassSymbol c) {
2069             MethodSymbol undef = null;
2070             // Do not bother to search in classes that are not abstract,
2071             // since they cannot have abstract members.
2072             if (c == impl || (c.flags() & (ABSTRACT | INTERFACE)) != 0) {
2073                 Scope s = c.members();
2074                 for (Scope.Entry e = s.elems;
2075                      undef == null && e != null;
2076                      e = e.sibling) {
2077                     if (e.sym.kind == MTH &&
2078                         (e.sym.flags() & (ABSTRACT|IPROXY|DEFAULT)) == ABSTRACT) {
2079                         MethodSymbol absmeth = (MethodSymbol)e.sym;
2080                         MethodSymbol implmeth = absmeth.implementation(impl, types, true);
2081                         if (implmeth == null || implmeth == absmeth) {
2082                             //look for default implementations
2083                             if (allowDefaultMethods) {
2084                                 MethodSymbol prov = types.interfaceCandidates(impl.type, absmeth).head;
2085                                 if (prov != null && prov.overrides(absmeth, impl, types, true)) {
2086                                     implmeth = prov;
2087                                 }
2088                             }
2089                         }
2090                         if (implmeth == null || implmeth == absmeth) {
2091                             undef = absmeth;
2092                         }
2093                     }
2094                 }
2095                 if (undef == null) {
2096                     Type st = types.supertype(c.type);
2097                     if (st.hasTag(CLASS))
2098                         undef = firstUndef(impl, (ClassSymbol)st.tsym);
2099                 }
2100                 for (List<Type> l = types.interfaces(c.type);
2101                      undef == null && l.nonEmpty();
2102                      l = l.tail) {
2103                     undef = firstUndef(impl, (ClassSymbol)l.head.tsym);
2104                 }
2105             }
2106             return undef;
2107         }
2108 
2109     void checkNonCyclicDecl(JCClassDecl tree) {
2110         CycleChecker cc = new CycleChecker();
2111         cc.scan(tree);
2112         if (!cc.errorFound && !cc.partialCheck) {
2113             tree.sym.flags_field |= ACYCLIC;
2114         }
2115     }
2116 
2117     class CycleChecker extends TreeScanner {
2118 
2119         List<Symbol> seenClasses = List.nil();
2120         boolean errorFound = false;
2121         boolean partialCheck = false;
2122 
2123         private void checkSymbol(DiagnosticPosition pos, Symbol sym) {
2124             if (sym != null && sym.kind == TYP) {
2125                 Env<AttrContext> classEnv = enter.getEnv((TypeSymbol)sym);
2126                 if (classEnv != null) {
2127                     DiagnosticSource prevSource = log.currentSource();
2128                     try {
2129                         log.useSource(classEnv.toplevel.sourcefile);
2130                         scan(classEnv.tree);
2131                     }
2132                     finally {
2133                         log.useSource(prevSource.getFile());
2134                     }
2135                 } else if (sym.kind == TYP) {
2136                     checkClass(pos, sym, List.<JCTree>nil());
2137                 }
2138             } else {
2139                 //not completed yet
2140                 partialCheck = true;
2141             }
2142         }
2143 
2144         @Override
2145         public void visitSelect(JCFieldAccess tree) {
2146             super.visitSelect(tree);
2147             checkSymbol(tree.pos(), tree.sym);
2148         }
2149 
2150         @Override
2151         public void visitIdent(JCIdent tree) {
2152             checkSymbol(tree.pos(), tree.sym);
2153         }
2154 
2155         @Override
2156         public void visitTypeApply(JCTypeApply tree) {
2157             scan(tree.clazz);
2158         }
2159 
2160         @Override
2161         public void visitTypeArray(JCArrayTypeTree tree) {
2162             scan(tree.elemtype);
2163         }
2164 
2165         @Override
2166         public void visitClassDef(JCClassDecl tree) {
2167             List<JCTree> supertypes = List.nil();
2168             if (tree.getExtendsClause() != null) {
2169                 supertypes = supertypes.prepend(tree.getExtendsClause());
2170             }
2171             if (tree.getImplementsClause() != null) {
2172                 for (JCTree intf : tree.getImplementsClause()) {
2173                     supertypes = supertypes.prepend(intf);
2174                 }
2175             }
2176             checkClass(tree.pos(), tree.sym, supertypes);
2177         }
2178 
2179         void checkClass(DiagnosticPosition pos, Symbol c, List<JCTree> supertypes) {
2180             if ((c.flags_field & ACYCLIC) != 0)
2181                 return;
2182             if (seenClasses.contains(c)) {
2183                 errorFound = true;
2184                 noteCyclic(pos, (ClassSymbol)c);
2185             } else if (!c.type.isErroneous()) {
2186                 try {
2187                     seenClasses = seenClasses.prepend(c);
2188                     if (c.type.hasTag(CLASS)) {
2189                         if (supertypes.nonEmpty()) {
2190                             scan(supertypes);
2191                         }
2192                         else {
2193                             ClassType ct = (ClassType)c.type;
2194                             if (ct.supertype_field == null ||
2195                                     ct.interfaces_field == null) {
2196                                 //not completed yet
2197                                 partialCheck = true;
2198                                 return;
2199                             }
2200                             checkSymbol(pos, ct.supertype_field.tsym);
2201                             for (Type intf : ct.interfaces_field) {
2202                                 checkSymbol(pos, intf.tsym);
2203                             }
2204                         }
2205                         if (c.owner.kind == TYP) {
2206                             checkSymbol(pos, c.owner);
2207                         }
2208                     }
2209                 } finally {
2210                     seenClasses = seenClasses.tail;
2211                 }
2212             }
2213         }
2214     }
2215 
2216     /** Check for cyclic references. Issue an error if the
2217      *  symbol of the type referred to has a LOCKED flag set.
2218      *
2219      *  @param pos      Position to be used for error reporting.
2220      *  @param t        The type referred to.
2221      */
2222     void checkNonCyclic(DiagnosticPosition pos, Type t) {
2223         checkNonCyclicInternal(pos, t);
2224     }
2225 
2226 
2227     void checkNonCyclic(DiagnosticPosition pos, TypeVar t) {
2228         checkNonCyclic1(pos, t, List.<TypeVar>nil());
2229     }
2230 
2231     private void checkNonCyclic1(DiagnosticPosition pos, Type t, List<TypeVar> seen) {
2232         final TypeVar tv;
2233         if  (t.hasTag(TYPEVAR) && (t.tsym.flags() & UNATTRIBUTED) != 0)
2234             return;
2235         if (seen.contains(t)) {
2236             tv = (TypeVar)t.unannotatedType();
2237             tv.bound = types.createErrorType(t);
2238             log.error(pos, "cyclic.inheritance", t);
2239         } else if (t.hasTag(TYPEVAR)) {
2240             tv = (TypeVar)t.unannotatedType();
2241             seen = seen.prepend(tv);
2242             for (Type b : types.getBounds(tv))
2243                 checkNonCyclic1(pos, b, seen);
2244         } else if (t.hasTag(ARRAY)) {
2245             final ArrayType at = (ArrayType)t.unannotatedType();
2246             checkNonCyclic1(pos, at.elemtype, seen);
2247         }
2248     }
2249 
2250     /** Check for cyclic references. Issue an error if the
2251      *  symbol of the type referred to has a LOCKED flag set.
2252      *
2253      *  @param pos      Position to be used for error reporting.
2254      *  @param t        The type referred to.
2255      *  @returns        True if the check completed on all attributed classes
2256      */
2257     private boolean checkNonCyclicInternal(DiagnosticPosition pos, Type t) {
2258         boolean complete = true; // was the check complete?
2259         //- System.err.println("checkNonCyclicInternal("+t+");");//DEBUG
2260         Symbol c = t.tsym;
2261         if ((c.flags_field & ACYCLIC) != 0) return true;
2262 
2263         if ((c.flags_field & LOCKED) != 0) {
2264             noteCyclic(pos, (ClassSymbol)c);
2265         } else if (!c.type.isErroneous()) {
2266             try {
2267                 c.flags_field |= LOCKED;
2268                 if (c.type.hasTag(CLASS)) {
2269                     ClassType clazz = (ClassType)c.type;
2270                     if (clazz.interfaces_field != null)
2271                         for (List<Type> l=clazz.interfaces_field; l.nonEmpty(); l=l.tail)
2272                             complete &= checkNonCyclicInternal(pos, l.head);
2273                     if (clazz.supertype_field != null) {
2274                         Type st = clazz.supertype_field;
2275                         if (st != null && st.hasTag(CLASS))
2276                             complete &= checkNonCyclicInternal(pos, st);
2277                     }
2278                     if (c.owner.kind == TYP)
2279                         complete &= checkNonCyclicInternal(pos, c.owner.type);
2280                 }
2281             } finally {
2282                 c.flags_field &= ~LOCKED;
2283             }
2284         }
2285         if (complete)
2286             complete = ((c.flags_field & UNATTRIBUTED) == 0) && c.completer == null;
2287         if (complete) c.flags_field |= ACYCLIC;
2288         return complete;
2289     }
2290 
2291     /** Note that we found an inheritance cycle. */
2292     private void noteCyclic(DiagnosticPosition pos, ClassSymbol c) {
2293         log.error(pos, "cyclic.inheritance", c);
2294         for (List<Type> l=types.interfaces(c.type); l.nonEmpty(); l=l.tail)
2295             l.head = types.createErrorType((ClassSymbol)l.head.tsym, Type.noType);
2296         Type st = types.supertype(c.type);
2297         if (st.hasTag(CLASS))
2298             ((ClassType)c.type).supertype_field = types.createErrorType((ClassSymbol)st.tsym, Type.noType);
2299         c.type = types.createErrorType(c, c.type);
2300         c.flags_field |= ACYCLIC;
2301     }
2302 
2303     /** Check that all methods which implement some
2304      *  method conform to the method they implement.
2305      *  @param tree         The class definition whose members are checked.
2306      */
2307     void checkImplementations(JCClassDecl tree) {
2308         checkImplementations(tree, tree.sym, tree.sym);
2309     }
2310     //where
2311         /** Check that all methods which implement some
2312          *  method in `ic' conform to the method they implement.
2313          */
2314         void checkImplementations(JCTree tree, ClassSymbol origin, ClassSymbol ic) {
2315             for (List<Type> l = types.closure(ic.type); l.nonEmpty(); l = l.tail) {
2316                 ClassSymbol lc = (ClassSymbol)l.head.tsym;
2317                 if ((allowGenerics || origin != lc) && (lc.flags() & ABSTRACT) != 0) {
2318                     for (Scope.Entry e=lc.members().elems; e != null; e=e.sibling) {
2319                         if (e.sym.kind == MTH &&
2320                             (e.sym.flags() & (STATIC|ABSTRACT)) == ABSTRACT) {
2321                             MethodSymbol absmeth = (MethodSymbol)e.sym;
2322                             MethodSymbol implmeth = absmeth.implementation(origin, types, false);
2323                             if (implmeth != null && implmeth != absmeth &&
2324                                 (implmeth.owner.flags() & INTERFACE) ==
2325                                 (origin.flags() & INTERFACE)) {
2326                                 // don't check if implmeth is in a class, yet
2327                                 // origin is an interface. This case arises only
2328                                 // if implmeth is declared in Object. The reason is
2329                                 // that interfaces really don't inherit from
2330                                 // Object it's just that the compiler represents
2331                                 // things that way.
2332                                 checkOverride(tree, implmeth, absmeth, origin);
2333                             }
2334                         }
2335                     }
2336                 }
2337             }
2338         }
2339 
2340     /** Check that all abstract methods implemented by a class are
2341      *  mutually compatible.
2342      *  @param pos          Position to be used for error reporting.
2343      *  @param c            The class whose interfaces are checked.
2344      */
2345     void checkCompatibleSupertypes(DiagnosticPosition pos, Type c) {
2346         List<Type> supertypes = types.interfaces(c);
2347         Type supertype = types.supertype(c);
2348         if (supertype.hasTag(CLASS) &&
2349             (supertype.tsym.flags() & ABSTRACT) != 0)
2350             supertypes = supertypes.prepend(supertype);
2351         for (List<Type> l = supertypes; l.nonEmpty(); l = l.tail) {
2352             if (allowGenerics && !l.head.getTypeArguments().isEmpty() &&
2353                 !checkCompatibleAbstracts(pos, l.head, l.head, c))
2354                 return;
2355             for (List<Type> m = supertypes; m != l; m = m.tail)
2356                 if (!checkCompatibleAbstracts(pos, l.head, m.head, c))
2357                     return;
2358         }
2359         checkCompatibleConcretes(pos, c);
2360     }
2361 
2362     void checkConflicts(DiagnosticPosition pos, Symbol sym, TypeSymbol c) {
2363         for (Type ct = c.type; ct != Type.noType ; ct = types.supertype(ct)) {
2364             for (Scope.Entry e = ct.tsym.members().lookup(sym.name); e.scope == ct.tsym.members(); e = e.next()) {
2365                 // VM allows methods and variables with differing types
2366                 if (sym.kind == e.sym.kind &&
2367                     types.isSameType(types.erasure(sym.type), types.erasure(e.sym.type)) &&
2368                     sym != e.sym &&
2369                     (sym.flags() & Flags.SYNTHETIC) != (e.sym.flags() & Flags.SYNTHETIC) &&
2370                     (sym.flags() & IPROXY) == 0 && (e.sym.flags() & IPROXY) == 0 &&
2371                     (sym.flags() & BRIDGE) == 0 && (e.sym.flags() & BRIDGE) == 0) {
2372                     syntheticError(pos, (e.sym.flags() & SYNTHETIC) == 0 ? e.sym : sym);
2373                     return;
2374                 }
2375             }
2376         }
2377     }
2378 
2379     /** Check that all non-override equivalent methods accessible from 'site'
2380      *  are mutually compatible (JLS 8.4.8/9.4.1).
2381      *
2382      *  @param pos  Position to be used for error reporting.
2383      *  @param site The class whose methods are checked.
2384      *  @param sym  The method symbol to be checked.
2385      */
2386     void checkOverrideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
2387          ClashFilter cf = new ClashFilter(site);
2388         //for each method m1 that is overridden (directly or indirectly)
2389         //by method 'sym' in 'site'...
2390         for (Symbol m1 : types.membersClosure(site, false).getElementsByName(sym.name, cf)) {
2391              if (!sym.overrides(m1, site.tsym, types, false)) {
2392                  checkPotentiallyAmbiguousOverloads(pos, site, sym, (MethodSymbol)m1);
2393                  continue;
2394              }
2395              //...check each method m2 that is a member of 'site'
2396              for (Symbol m2 : types.membersClosure(site, false).getElementsByName(sym.name, cf)) {
2397                 if (m2 == m1) continue;
2398                 //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
2399                 //a member of 'site') and (ii) m1 has the same erasure as m2, issue an error
2400                 if (!types.isSubSignature(sym.type, types.memberType(site, m2), allowStrictMethodClashCheck) &&
2401                         types.hasSameArgs(m2.erasure(types), m1.erasure(types))) {
2402                     sym.flags_field |= CLASH;
2403                     String key = m1 == sym ?
2404                             "name.clash.same.erasure.no.override" :
2405                             "name.clash.same.erasure.no.override.1";
2406                     log.error(pos,
2407                             key,
2408                             sym, sym.location(),
2409                             m2, m2.location(),
2410                             m1, m1.location());
2411                     return;
2412                 }
2413             }
2414         }
2415     }
2416 
2417 
2418 
2419     /** Check that all static methods accessible from 'site' are
2420      *  mutually compatible (JLS 8.4.8).
2421      *
2422      *  @param pos  Position to be used for error reporting.
2423      *  @param site The class whose methods are checked.
2424      *  @param sym  The method symbol to be checked.
2425      */
2426     void checkHideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
2427         ClashFilter cf = new ClashFilter(site);
2428         //for each method m1 that is a member of 'site'...
2429         for (Symbol s : types.membersClosure(site, true).getElementsByName(sym.name, cf)) {
2430             //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
2431             //a member of 'site') and (ii) 'sym' has the same erasure as m1, issue an error
2432             if (!types.isSubSignature(sym.type, types.memberType(site, s), allowStrictMethodClashCheck)) {
2433                 if (types.hasSameArgs(s.erasure(types), sym.erasure(types))) {
2434                     log.error(pos,
2435                             "name.clash.same.erasure.no.hide",
2436                             sym, sym.location(),
2437                             s, s.location());
2438                     return;
2439                 } else {
2440                     checkPotentiallyAmbiguousOverloads(pos, site, sym, (MethodSymbol)s);
2441                 }
2442             }
2443          }
2444      }
2445 
2446      //where
2447      private class ClashFilter implements Filter<Symbol> {
2448 
2449          Type site;
2450 
2451          ClashFilter(Type site) {
2452              this.site = site;
2453          }
2454 
2455          boolean shouldSkip(Symbol s) {
2456              return (s.flags() & CLASH) != 0 &&
2457                 s.owner == site.tsym;
2458          }
2459 
2460          public boolean accepts(Symbol s) {
2461              return s.kind == MTH &&
2462                      (s.flags() & SYNTHETIC) == 0 &&
2463                      !shouldSkip(s) &&
2464                      s.isInheritedIn(site.tsym, types) &&
2465                      !s.isConstructor();
2466          }
2467      }
2468 
2469     void checkDefaultMethodClashes(DiagnosticPosition pos, Type site) {
2470         DefaultMethodClashFilter dcf = new DefaultMethodClashFilter(site);
2471         for (Symbol m : types.membersClosure(site, false).getElements(dcf)) {
2472             Assert.check(m.kind == MTH);
2473             List<MethodSymbol> prov = types.interfaceCandidates(site, (MethodSymbol)m);
2474             if (prov.size() > 1) {
2475                 ListBuffer<Symbol> abstracts = new ListBuffer<>();
2476                 ListBuffer<Symbol> defaults = new ListBuffer<>();
2477                 for (MethodSymbol provSym : prov) {
2478                     if ((provSym.flags() & DEFAULT) != 0) {
2479                         defaults = defaults.append(provSym);
2480                     } else if ((provSym.flags() & ABSTRACT) != 0) {
2481                         abstracts = abstracts.append(provSym);
2482                     }
2483                     if (defaults.nonEmpty() && defaults.size() + abstracts.size() >= 2) {
2484                         //strong semantics - issue an error if two sibling interfaces
2485                         //have two override-equivalent defaults - or if one is abstract
2486                         //and the other is default
2487                         String errKey;
2488                         Symbol s1 = defaults.first();
2489                         Symbol s2;
2490                         if (defaults.size() > 1) {
2491                             errKey = "types.incompatible.unrelated.defaults";
2492                             s2 = defaults.toList().tail.head;
2493                         } else {
2494                             errKey = "types.incompatible.abstract.default";
2495                             s2 = abstracts.first();
2496                         }
2497                         log.error(pos, errKey,
2498                                 Kinds.kindName(site.tsym), site,
2499                                 m.name, types.memberType(site, m).getParameterTypes(),
2500                                 s1.location(), s2.location());
2501                         break;
2502                     }
2503                 }
2504             }
2505         }
2506     }
2507 
2508     //where
2509      private class DefaultMethodClashFilter implements Filter<Symbol> {
2510 
2511          Type site;
2512 
2513          DefaultMethodClashFilter(Type site) {
2514              this.site = site;
2515          }
2516 
2517          public boolean accepts(Symbol s) {
2518              return s.kind == MTH &&
2519                      (s.flags() & DEFAULT) != 0 &&
2520                      s.isInheritedIn(site.tsym, types) &&
2521                      !s.isConstructor();
2522          }
2523      }
2524 
2525     /**
2526       * Report warnings for potentially ambiguous method declarations. Two declarations
2527       * are potentially ambiguous if they feature two unrelated functional interface
2528       * in same argument position (in which case, a call site passing an implicit
2529       * lambda would be ambiguous).
2530       */
2531     void checkPotentiallyAmbiguousOverloads(DiagnosticPosition pos, Type site,
2532             MethodSymbol msym1, MethodSymbol msym2) {
2533         if (msym1 != msym2 &&
2534                 allowDefaultMethods &&
2535                 lint.isEnabled(LintCategory.OVERLOADS) &&
2536                 (msym1.flags() & POTENTIALLY_AMBIGUOUS) == 0 &&
2537                 (msym2.flags() & POTENTIALLY_AMBIGUOUS) == 0) {
2538             Type mt1 = types.memberType(site, msym1);
2539             Type mt2 = types.memberType(site, msym2);
2540             //if both generic methods, adjust type variables
2541             if (mt1.hasTag(FORALL) && mt2.hasTag(FORALL) &&
2542                     types.hasSameBounds((ForAll)mt1, (ForAll)mt2)) {
2543                 mt2 = types.subst(mt2, ((ForAll)mt2).tvars, ((ForAll)mt1).tvars);
2544             }
2545             //expand varargs methods if needed
2546             int maxLength = Math.max(mt1.getParameterTypes().length(), mt2.getParameterTypes().length());
2547             List<Type> args1 = rs.adjustArgs(mt1.getParameterTypes(), msym1, maxLength, true);
2548             List<Type> args2 = rs.adjustArgs(mt2.getParameterTypes(), msym2, maxLength, true);
2549             //if arities don't match, exit
2550             if (args1.length() != args2.length()) return;
2551             boolean potentiallyAmbiguous = false;
2552             while (args1.nonEmpty() && args2.nonEmpty()) {
2553                 Type s = args1.head;
2554                 Type t = args2.head;
2555                 if (!types.isSubtype(t, s) && !types.isSubtype(s, t)) {
2556                     if (types.isFunctionalInterface(s) && types.isFunctionalInterface(t) &&
2557                             types.findDescriptorType(s).getParameterTypes().length() > 0 &&
2558                             types.findDescriptorType(s).getParameterTypes().length() ==
2559                             types.findDescriptorType(t).getParameterTypes().length()) {
2560                         potentiallyAmbiguous = true;
2561                     } else {
2562                         break;
2563                     }
2564                 }
2565                 args1 = args1.tail;
2566                 args2 = args2.tail;
2567             }
2568             if (potentiallyAmbiguous) {
2569                 //we found two incompatible functional interfaces with same arity
2570                 //this means a call site passing an implicit lambda would be ambigiuous
2571                 msym1.flags_field |= POTENTIALLY_AMBIGUOUS;
2572                 msym2.flags_field |= POTENTIALLY_AMBIGUOUS;
2573                 log.warning(LintCategory.OVERLOADS, pos, "potentially.ambiguous.overload",
2574                             msym1, msym1.location(),
2575                             msym2, msym2.location());
2576                 return;
2577             }
2578         }
2579     }
2580 
2581     /** Report a conflict between a user symbol and a synthetic symbol.
2582      */
2583     private void syntheticError(DiagnosticPosition pos, Symbol sym) {
2584         if (!sym.type.isErroneous()) {
2585             if (warnOnSyntheticConflicts) {
2586                 log.warning(pos, "synthetic.name.conflict", sym, sym.location());
2587             }
2588             else {
2589                 log.error(pos, "synthetic.name.conflict", sym, sym.location());
2590             }
2591         }
2592     }
2593 
2594     /** Check that class c does not implement directly or indirectly
2595      *  the same parameterized interface with two different argument lists.
2596      *  @param pos          Position to be used for error reporting.
2597      *  @param type         The type whose interfaces are checked.
2598      */
2599     void checkClassBounds(DiagnosticPosition pos, Type type) {
2600         checkClassBounds(pos, new HashMap<TypeSymbol,Type>(), type);
2601     }
2602 //where
2603         /** Enter all interfaces of type `type' into the hash table `seensofar'
2604          *  with their class symbol as key and their type as value. Make
2605          *  sure no class is entered with two different types.
2606          */
2607         void checkClassBounds(DiagnosticPosition pos,
2608                               Map<TypeSymbol,Type> seensofar,
2609                               Type type) {
2610             if (type.isErroneous()) return;
2611             for (List<Type> l = types.interfaces(type); l.nonEmpty(); l = l.tail) {
2612                 Type it = l.head;
2613                 Type oldit = seensofar.put(it.tsym, it);
2614                 if (oldit != null) {
2615                     List<Type> oldparams = oldit.allparams();
2616                     List<Type> newparams = it.allparams();
2617                     if (!types.containsTypeEquivalent(oldparams, newparams))
2618                         log.error(pos, "cant.inherit.diff.arg",
2619                                   it.tsym, Type.toString(oldparams),
2620                                   Type.toString(newparams));
2621                 }
2622                 checkClassBounds(pos, seensofar, it);
2623             }
2624             Type st = types.supertype(type);
2625             if (st != null) checkClassBounds(pos, seensofar, st);
2626         }
2627 
2628     /** Enter interface into into set.
2629      *  If it existed already, issue a "repeated interface" error.
2630      */
2631     void checkNotRepeated(DiagnosticPosition pos, Type it, Set<Type> its) {
2632         if (its.contains(it))
2633             log.error(pos, "repeated.interface");
2634         else {
2635             its.add(it);
2636         }
2637     }
2638 
2639 /* *************************************************************************
2640  * Check annotations
2641  **************************************************************************/
2642 
2643     /**
2644      * Recursively validate annotations values
2645      */
2646     void validateAnnotationTree(JCTree tree) {
2647         class AnnotationValidator extends TreeScanner {
2648             @Override
2649             public void visitAnnotation(JCAnnotation tree) {
2650                 if (!tree.type.isErroneous()) {
2651                     super.visitAnnotation(tree);
2652                     validateAnnotation(tree);
2653                 }
2654             }
2655         }
2656         tree.accept(new AnnotationValidator());
2657     }
2658 
2659     /**
2660      *  {@literal
2661      *  Annotation types are restricted to primitives, String, an
2662      *  enum, an annotation, Class, Class<?>, Class<? extends
2663      *  Anything>, arrays of the preceding.
2664      *  }
2665      */
2666     void validateAnnotationType(JCTree restype) {
2667         // restype may be null if an error occurred, so don't bother validating it
2668         if (restype != null) {
2669             validateAnnotationType(restype.pos(), restype.type);
2670         }
2671     }
2672 
2673     void validateAnnotationType(DiagnosticPosition pos, Type type) {
2674         if (type.isPrimitive()) return;
2675         if (types.isSameType(type, syms.stringType)) return;
2676         if ((type.tsym.flags() & Flags.ENUM) != 0) return;
2677         if ((type.tsym.flags() & Flags.ANNOTATION) != 0) return;
2678         if (types.lowerBound(type).tsym == syms.classType.tsym) return;
2679         if (types.isArray(type) && !types.isArray(types.elemtype(type))) {
2680             validateAnnotationType(pos, types.elemtype(type));
2681             return;
2682         }
2683         log.error(pos, "annotation.invalid.element.type");
2684     }
2685 
2686     /**
2687      * "It is also a compile-time error if any method declared in an
2688      * annotation type has a signature that is override-equivalent to
2689      * that of any public or protected method declared in class Object
2690      * or in the interface annotation.Annotation."
2691      *
2692      * @jls 9.6 Annotation Types
2693      */
2694     void validateAnnotationMethod(DiagnosticPosition pos, MethodSymbol m) {
2695         for (Type sup = syms.annotationType; sup.hasTag(CLASS); sup = types.supertype(sup)) {
2696             Scope s = sup.tsym.members();
2697             for (Scope.Entry e = s.lookup(m.name); e.scope != null; e = e.next()) {
2698                 if (e.sym.kind == MTH &&
2699                     (e.sym.flags() & (PUBLIC | PROTECTED)) != 0 &&
2700                     types.overrideEquivalent(m.type, e.sym.type))
2701                     log.error(pos, "intf.annotation.member.clash", e.sym, sup);
2702             }
2703         }
2704     }
2705 
2706     /** Check the annotations of a symbol.
2707      */
2708     public void validateAnnotations(List<JCAnnotation> annotations, Symbol s) {
2709         for (JCAnnotation a : annotations)
2710             validateAnnotation(a, s);
2711     }
2712 
2713     /** Check the type annotations.
2714      */
2715     public void validateTypeAnnotations(List<JCAnnotation> annotations, boolean isTypeParameter) {
2716         for (JCAnnotation a : annotations)
2717             validateTypeAnnotation(a, isTypeParameter);
2718     }
2719 
2720     /** Check an annotation of a symbol.
2721      */
2722     private void validateAnnotation(JCAnnotation a, Symbol s) {
2723         validateAnnotationTree(a);
2724 
2725         if (!annotationApplicable(a, s))
2726             log.error(a.pos(), "annotation.type.not.applicable");
2727 
2728         if (a.annotationType.type.tsym == syms.overrideType.tsym) {
2729             if (!isOverrider(s))
2730                 log.error(a.pos(), "method.does.not.override.superclass");
2731         }
2732 
2733         if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
2734             if (s.kind != TYP) {
2735                 log.error(a.pos(), "bad.functional.intf.anno");
2736             } else {
2737                 try {
2738                     types.findDescriptorSymbol((TypeSymbol)s);
2739                 } catch (Types.FunctionDescriptorLookupError ex) {
2740                     log.error(a.pos(), "bad.functional.intf.anno.1", ex.getDiagnostic());
2741                 }
2742             }
2743         }
2744     }
2745 
2746     public void validateTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
2747         Assert.checkNonNull(a.type, "annotation tree hasn't been attributed yet: " + a);
2748         validateAnnotationTree(a);
2749 
2750         if (!isTypeAnnotation(a, isTypeParameter))
2751             log.error(a.pos(), "annotation.type.not.applicable");
2752     }
2753 
2754     /**
2755      * Validate the proposed container 'repeatable' on the
2756      * annotation type symbol 's'. Report errors at position
2757      * 'pos'.
2758      *
2759      * @param s The (annotation)type declaration annotated with a @Repeatable
2760      * @param repeatable the @Repeatable on 's'
2761      * @param pos where to report errors
2762      */
2763     public void validateRepeatable(TypeSymbol s, Attribute.Compound repeatable, DiagnosticPosition pos) {
2764         Assert.check(types.isSameType(repeatable.type, syms.repeatableType));
2765 
2766         Type t = null;
2767         List<Pair<MethodSymbol,Attribute>> l = repeatable.values;
2768         if (!l.isEmpty()) {
2769             Assert.check(l.head.fst.name == names.value);
2770             t = ((Attribute.Class)l.head.snd).getValue();
2771         }
2772 
2773         if (t == null) {
2774             // errors should already have been reported during Annotate
2775             return;
2776         }
2777 
2778         validateValue(t.tsym, s, pos);
2779         validateRetention(t.tsym, s, pos);
2780         validateDocumented(t.tsym, s, pos);
2781         validateInherited(t.tsym, s, pos);
2782         validateTarget(t.tsym, s, pos);
2783         validateDefault(t.tsym, s, pos);
2784     }
2785 
2786     private void validateValue(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
2787         Scope.Entry e = container.members().lookup(names.value);
2788         if (e.scope != null && e.sym.kind == MTH) {
2789             MethodSymbol m = (MethodSymbol) e.sym;
2790             Type ret = m.getReturnType();
2791             if (!(ret.hasTag(ARRAY) && types.isSameType(((ArrayType)ret).elemtype, contained.type))) {
2792                 log.error(pos, "invalid.repeatable.annotation.value.return",
2793                         container, ret, types.makeArrayType(contained.type));
2794             }
2795         } else {
2796             log.error(pos, "invalid.repeatable.annotation.no.value", container);
2797         }
2798     }
2799 
2800     private void validateRetention(Symbol container, Symbol contained, DiagnosticPosition pos) {
2801         Attribute.RetentionPolicy containerRetention = types.getRetention(container);
2802         Attribute.RetentionPolicy containedRetention = types.getRetention(contained);
2803 
2804         boolean error = false;
2805         switch (containedRetention) {
2806         case RUNTIME:
2807             if (containerRetention != Attribute.RetentionPolicy.RUNTIME) {
2808                 error = true;
2809             }
2810             break;
2811         case CLASS:
2812             if (containerRetention == Attribute.RetentionPolicy.SOURCE)  {
2813                 error = true;
2814             }
2815         }
2816         if (error ) {
2817             log.error(pos, "invalid.repeatable.annotation.retention",
2818                       container, containerRetention,
2819                       contained, containedRetention);
2820         }
2821     }
2822 
2823     private void validateDocumented(Symbol container, Symbol contained, DiagnosticPosition pos) {
2824         if (contained.attribute(syms.documentedType.tsym) != null) {
2825             if (container.attribute(syms.documentedType.tsym) == null) {
2826                 log.error(pos, "invalid.repeatable.annotation.not.documented", container, contained);
2827             }
2828         }
2829     }
2830 
2831     private void validateInherited(Symbol container, Symbol contained, DiagnosticPosition pos) {
2832         if (contained.attribute(syms.inheritedType.tsym) != null) {
2833             if (container.attribute(syms.inheritedType.tsym) == null) {
2834                 log.error(pos, "invalid.repeatable.annotation.not.inherited", container, contained);
2835             }
2836         }
2837     }
2838 
2839     private void validateTarget(Symbol container, Symbol contained, DiagnosticPosition pos) {
2840         // The set of targets the container is applicable to must be a subset
2841         // (with respect to annotation target semantics) of the set of targets
2842         // the contained is applicable to. The target sets may be implicit or
2843         // explicit.
2844 
2845         Set<Name> containerTargets;
2846         Attribute.Array containerTarget = getAttributeTargetAttribute(container);
2847         if (containerTarget == null) {
2848             containerTargets = getDefaultTargetSet();
2849         } else {
2850             containerTargets = new HashSet<Name>();
2851         for (Attribute app : containerTarget.values) {
2852             if (!(app instanceof Attribute.Enum)) {
2853                 continue; // recovery
2854             }
2855             Attribute.Enum e = (Attribute.Enum)app;
2856             containerTargets.add(e.value.name);
2857         }
2858         }
2859 
2860         Set<Name> containedTargets;
2861         Attribute.Array containedTarget = getAttributeTargetAttribute(contained);
2862         if (containedTarget == null) {
2863             containedTargets = getDefaultTargetSet();
2864         } else {
2865             containedTargets = new HashSet<Name>();
2866         for (Attribute app : containedTarget.values) {
2867             if (!(app instanceof Attribute.Enum)) {
2868                 continue; // recovery
2869             }
2870             Attribute.Enum e = (Attribute.Enum)app;
2871             containedTargets.add(e.value.name);
2872         }
2873         }
2874 
2875         if (!isTargetSubsetOf(containerTargets, containedTargets)) {
2876             log.error(pos, "invalid.repeatable.annotation.incompatible.target", container, contained);
2877         }
2878     }
2879 
2880     /* get a set of names for the default target */
2881     private Set<Name> getDefaultTargetSet() {
2882         if (defaultTargets == null) {
2883             Set<Name> targets = new HashSet<Name>();
2884             targets.add(names.ANNOTATION_TYPE);
2885             targets.add(names.CONSTRUCTOR);
2886             targets.add(names.FIELD);
2887             targets.add(names.LOCAL_VARIABLE);
2888             targets.add(names.METHOD);
2889             targets.add(names.PACKAGE);
2890             targets.add(names.PARAMETER);
2891             targets.add(names.TYPE);
2892 
2893             defaultTargets = java.util.Collections.unmodifiableSet(targets);
2894         }
2895 
2896         return defaultTargets;
2897     }
2898     private Set<Name> defaultTargets;
2899 
2900 
2901     /** Checks that s is a subset of t, with respect to ElementType
2902      * semantics, specifically {ANNOTATION_TYPE} is a subset of {TYPE}
2903      */
2904     private boolean isTargetSubsetOf(Set<Name> s, Set<Name> t) {
2905         // Check that all elements in s are present in t
2906         for (Name n2 : s) {
2907             boolean currentElementOk = false;
2908             for (Name n1 : t) {
2909                 if (n1 == n2) {
2910                     currentElementOk = true;
2911                     break;
2912                 } else if (n1 == names.TYPE && n2 == names.ANNOTATION_TYPE) {
2913                     currentElementOk = true;
2914                     break;
2915                 }
2916             }
2917             if (!currentElementOk)
2918                 return false;
2919         }
2920         return true;
2921     }
2922 
2923     private void validateDefault(Symbol container, Symbol contained, DiagnosticPosition pos) {
2924         // validate that all other elements of containing type has defaults
2925         Scope scope = container.members();
2926         for(Symbol elm : scope.getElements()) {
2927             if (elm.name != names.value &&
2928                 elm.kind == Kinds.MTH &&
2929                 ((MethodSymbol)elm).defaultValue == null) {
2930                 log.error(pos,
2931                           "invalid.repeatable.annotation.elem.nondefault",
2932                           container,
2933                           elm);
2934             }
2935         }
2936     }
2937 
2938     /** Is s a method symbol that overrides a method in a superclass? */
2939     boolean isOverrider(Symbol s) {
2940         if (s.kind != MTH || s.isStatic())
2941             return false;
2942         MethodSymbol m = (MethodSymbol)s;
2943         TypeSymbol owner = (TypeSymbol)m.owner;
2944         for (Type sup : types.closure(owner.type)) {
2945             if (sup == owner.type)
2946                 continue; // skip "this"
2947             Scope scope = sup.tsym.members();
2948             for (Scope.Entry e = scope.lookup(m.name); e.scope != null; e = e.next()) {
2949                 if (!e.sym.isStatic() && m.overrides(e.sym, owner, types, true))
2950                     return true;
2951             }
2952         }
2953         return false;
2954     }
2955 
2956     /** Is the annotation applicable to type annotations? */
2957     protected boolean isTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
2958         Attribute.Compound atTarget =
2959             a.annotationType.type.tsym.attribute(syms.annotationTargetType.tsym);
2960         if (atTarget == null) {
2961             // An annotation without @Target is not a type annotation.
2962             return false;
2963         }
2964 
2965         Attribute atValue = atTarget.member(names.value);
2966         if (!(atValue instanceof Attribute.Array)) {
2967             return false; // error recovery
2968         }
2969 
2970         Attribute.Array arr = (Attribute.Array) atValue;
2971         for (Attribute app : arr.values) {
2972             if (!(app instanceof Attribute.Enum)) {
2973                 return false; // recovery
2974             }
2975             Attribute.Enum e = (Attribute.Enum) app;
2976 
2977             if (e.value.name == names.TYPE_USE)
2978                 return true;
2979             else if (isTypeParameter && e.value.name == names.TYPE_PARAMETER)
2980                 return true;
2981         }
2982         return false;
2983     }
2984 
2985     /** Is the annotation applicable to the symbol? */
2986     boolean annotationApplicable(JCAnnotation a, Symbol s) {
2987         Attribute.Array arr = getAttributeTargetAttribute(a.annotationType.type.tsym);
2988         Name[] targets;
2989 
2990         if (arr == null) {
2991             targets = defaultTargetMetaInfo(a, s);
2992         } else {
2993             // TODO: can we optimize this?
2994             targets = new Name[arr.values.length];
2995             for (int i=0; i<arr.values.length; ++i) {
2996                 Attribute app = arr.values[i];
2997                 if (!(app instanceof Attribute.Enum)) {
2998                     return true; // recovery
2999                 }
3000                 Attribute.Enum e = (Attribute.Enum) app;
3001                 targets[i] = e.value.name;
3002             }
3003         }
3004         for (Name target : targets) {
3005             if (target == names.TYPE)
3006                 { if (s.kind == TYP) return true; }
3007             else if (target == names.FIELD)
3008                 { if (s.kind == VAR && s.owner.kind != MTH) return true; }
3009             else if (target == names.METHOD)
3010                 { if (s.kind == MTH && !s.isConstructor()) return true; }
3011             else if (target == names.PARAMETER)
3012                 { if (s.kind == VAR &&
3013                       s.owner.kind == MTH &&
3014                       (s.flags() & PARAMETER) != 0)
3015                     return true;
3016                 }
3017             else if (target == names.CONSTRUCTOR)
3018                 { if (s.kind == MTH && s.isConstructor()) return true; }
3019             else if (target == names.LOCAL_VARIABLE)
3020                 { if (s.kind == VAR && s.owner.kind == MTH &&
3021                       (s.flags() & PARAMETER) == 0)
3022                     return true;
3023                 }
3024             else if (target == names.ANNOTATION_TYPE)
3025                 { if (s.kind == TYP && (s.flags() & ANNOTATION) != 0)
3026                     return true;
3027                 }
3028             else if (target == names.PACKAGE)
3029                 { if (s.kind == PCK) return true; }
3030             else if (target == names.TYPE_USE)
3031                 { if (s.kind == TYP ||
3032                       s.kind == VAR ||
3033                       (s.kind == MTH && !s.isConstructor() &&
3034                       !s.type.getReturnType().hasTag(VOID)) ||
3035                       (s.kind == MTH && s.isConstructor()))
3036                     return true;
3037                 }
3038             else if (target == names.TYPE_PARAMETER)
3039                 { if (s.kind == TYP && s.type.hasTag(TYPEVAR))
3040                     return true;
3041                 }
3042             else
3043                 return true; // recovery
3044         }
3045         return false;
3046     }
3047 
3048 
3049     Attribute.Array getAttributeTargetAttribute(Symbol s) {
3050         Attribute.Compound atTarget =
3051             s.attribute(syms.annotationTargetType.tsym);
3052         if (atTarget == null) return null; // ok, is applicable
3053         Attribute atValue = atTarget.member(names.value);
3054         if (!(atValue instanceof Attribute.Array)) return null; // error recovery
3055         return (Attribute.Array) atValue;
3056     }
3057 
3058     private final Name[] dfltTargetMeta;
3059     private Name[] defaultTargetMetaInfo(JCAnnotation a, Symbol s) {
3060         return dfltTargetMeta;
3061     }
3062 
3063     /** Check an annotation value.
3064      *
3065      * @param a The annotation tree to check
3066      * @return true if this annotation tree is valid, otherwise false
3067      */
3068     public boolean validateAnnotationDeferErrors(JCAnnotation a) {
3069         boolean res = false;
3070         final Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
3071         try {
3072             res = validateAnnotation(a);
3073         } finally {
3074             log.popDiagnosticHandler(diagHandler);
3075         }
3076         return res;
3077     }
3078 
3079     private boolean validateAnnotation(JCAnnotation a) {
3080         boolean isValid = true;
3081         // collect an inventory of the annotation elements
3082         Set<MethodSymbol> members = new LinkedHashSet<MethodSymbol>();
3083         for (Scope.Entry e = a.annotationType.type.tsym.members().elems;
3084                 e != null;
3085                 e = e.sibling)
3086             if (e.sym.kind == MTH && e.sym.name != names.clinit &&
3087                     (e.sym.flags() & SYNTHETIC) == 0)
3088                 members.add((MethodSymbol) e.sym);
3089 
3090         // remove the ones that are assigned values
3091         for (JCTree arg : a.args) {
3092             if (!arg.hasTag(ASSIGN)) continue; // recovery
3093             JCAssign assign = (JCAssign) arg;
3094             Symbol m = TreeInfo.symbol(assign.lhs);
3095             if (m == null || m.type.isErroneous()) continue;
3096             if (!members.remove(m)) {
3097                 isValid = false;
3098                 log.error(assign.lhs.pos(), "annotation.duplicate.element",
3099                           m.name, a.type);
3100             }
3101         }
3102 
3103         // all the remaining ones better have default values
3104         List<Name> missingDefaults = List.nil();
3105         for (MethodSymbol m : members) {
3106             if (m.defaultValue == null && !m.type.isErroneous()) {
3107                 missingDefaults = missingDefaults.append(m.name);
3108             }
3109         }
3110         missingDefaults = missingDefaults.reverse();
3111         if (missingDefaults.nonEmpty()) {
3112             isValid = false;
3113             String key = (missingDefaults.size() > 1)
3114                     ? "annotation.missing.default.value.1"
3115                     : "annotation.missing.default.value";
3116             log.error(a.pos(), key, a.type, missingDefaults);
3117         }
3118 
3119         // special case: java.lang.annotation.Target must not have
3120         // repeated values in its value member
3121         if (a.annotationType.type.tsym != syms.annotationTargetType.tsym ||
3122             a.args.tail == null)
3123             return isValid;
3124 
3125         if (!a.args.head.hasTag(ASSIGN)) return false; // error recovery
3126         JCAssign assign = (JCAssign) a.args.head;
3127         Symbol m = TreeInfo.symbol(assign.lhs);
3128         if (m.name != names.value) return false;
3129         JCTree rhs = assign.rhs;
3130         if (!rhs.hasTag(NEWARRAY)) return false;
3131         JCNewArray na = (JCNewArray) rhs;
3132         Set<Symbol> targets = new HashSet<Symbol>();
3133         for (JCTree elem : na.elems) {
3134             if (!targets.add(TreeInfo.symbol(elem))) {
3135                 isValid = false;
3136                 log.error(elem.pos(), "repeated.annotation.target");
3137             }
3138         }
3139         return isValid;
3140     }
3141 
3142     void checkDeprecatedAnnotation(DiagnosticPosition pos, Symbol s) {
3143         if (allowAnnotations &&
3144             lint.isEnabled(LintCategory.DEP_ANN) &&
3145             (s.flags() & DEPRECATED) != 0 &&
3146             !syms.deprecatedType.isErroneous() &&
3147             s.attribute(syms.deprecatedType.tsym) == null) {
3148             log.warning(LintCategory.DEP_ANN,
3149                     pos, "missing.deprecated.annotation");
3150         }
3151     }
3152 
3153     void checkDeprecated(final DiagnosticPosition pos, final Symbol other, final Symbol s) {
3154         if ((s.flags() & DEPRECATED) != 0 &&
3155                 (other.flags() & DEPRECATED) == 0 &&
3156                 s.outermostClass() != other.outermostClass()) {
3157             deferredLintHandler.report(new DeferredLintHandler.LintLogger() {
3158                 @Override
3159                 public void report() {
3160                     warnDeprecated(pos, s);
3161                 }
3162             });
3163         }
3164     }
3165 
3166     void checkSunAPI(final DiagnosticPosition pos, final Symbol s) {
3167         if ((s.flags() & PROPRIETARY) != 0) {
3168             deferredLintHandler.report(new DeferredLintHandler.LintLogger() {
3169                 public void report() {
3170                     if (enableSunApiLintControl)
3171                       warnSunApi(pos, "sun.proprietary", s);
3172                     else
3173                       log.mandatoryWarning(pos, "sun.proprietary", s);
3174                 }
3175             });
3176         }
3177     }
3178 
3179     void checkProfile(final DiagnosticPosition pos, final Symbol s) {
3180         if (profile != Profile.DEFAULT && (s.flags() & NOT_IN_PROFILE) != 0) {
3181             log.error(pos, "not.in.profile", s, profile);
3182         }
3183     }
3184 
3185 /* *************************************************************************
3186  * Check for recursive annotation elements.
3187  **************************************************************************/
3188 
3189     /** Check for cycles in the graph of annotation elements.
3190      */
3191     void checkNonCyclicElements(JCClassDecl tree) {
3192         if ((tree.sym.flags_field & ANNOTATION) == 0) return;
3193         Assert.check((tree.sym.flags_field & LOCKED) == 0);
3194         try {
3195             tree.sym.flags_field |= LOCKED;
3196             for (JCTree def : tree.defs) {
3197                 if (!def.hasTag(METHODDEF)) continue;
3198                 JCMethodDecl meth = (JCMethodDecl)def;
3199                 checkAnnotationResType(meth.pos(), meth.restype.type);
3200             }
3201         } finally {
3202             tree.sym.flags_field &= ~LOCKED;
3203             tree.sym.flags_field |= ACYCLIC_ANN;
3204         }
3205     }
3206 
3207     void checkNonCyclicElementsInternal(DiagnosticPosition pos, TypeSymbol tsym) {
3208         if ((tsym.flags_field & ACYCLIC_ANN) != 0)
3209             return;
3210         if ((tsym.flags_field & LOCKED) != 0) {
3211             log.error(pos, "cyclic.annotation.element");
3212             return;
3213         }
3214         try {
3215             tsym.flags_field |= LOCKED;
3216             for (Scope.Entry e = tsym.members().elems; e != null; e = e.sibling) {
3217                 Symbol s = e.sym;
3218                 if (s.kind != Kinds.MTH)
3219                     continue;
3220                 checkAnnotationResType(pos, ((MethodSymbol)s).type.getReturnType());
3221             }
3222         } finally {
3223             tsym.flags_field &= ~LOCKED;
3224             tsym.flags_field |= ACYCLIC_ANN;
3225         }
3226     }
3227 
3228     void checkAnnotationResType(DiagnosticPosition pos, Type type) {
3229         switch (type.getTag()) {
3230         case CLASS:
3231             if ((type.tsym.flags() & ANNOTATION) != 0)
3232                 checkNonCyclicElementsInternal(pos, type.tsym);
3233             break;
3234         case ARRAY:
3235             checkAnnotationResType(pos, types.elemtype(type));
3236             break;
3237         default:
3238             break; // int etc
3239         }
3240     }
3241 
3242 /* *************************************************************************
3243  * Check for cycles in the constructor call graph.
3244  **************************************************************************/
3245 
3246     /** Check for cycles in the graph of constructors calling other
3247      *  constructors.
3248      */
3249     void checkCyclicConstructors(JCClassDecl tree) {
3250         Map<Symbol,Symbol> callMap = new HashMap<Symbol, Symbol>();
3251 
3252         // enter each constructor this-call into the map
3253         for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
3254             JCMethodInvocation app = TreeInfo.firstConstructorCall(l.head);
3255             if (app == null) continue;
3256             JCMethodDecl meth = (JCMethodDecl) l.head;
3257             if (TreeInfo.name(app.meth) == names._this) {
3258                 callMap.put(meth.sym, TreeInfo.symbol(app.meth));
3259             } else {
3260                 meth.sym.flags_field |= ACYCLIC;
3261             }
3262         }
3263 
3264         // Check for cycles in the map
3265         Symbol[] ctors = new Symbol[0];
3266         ctors = callMap.keySet().toArray(ctors);
3267         for (Symbol caller : ctors) {
3268             checkCyclicConstructor(tree, caller, callMap);
3269         }
3270     }
3271 
3272     /** Look in the map to see if the given constructor is part of a
3273      *  call cycle.
3274      */
3275     private void checkCyclicConstructor(JCClassDecl tree, Symbol ctor,
3276                                         Map<Symbol,Symbol> callMap) {
3277         if (ctor != null && (ctor.flags_field & ACYCLIC) == 0) {
3278             if ((ctor.flags_field & LOCKED) != 0) {
3279                 log.error(TreeInfo.diagnosticPositionFor(ctor, tree),
3280                           "recursive.ctor.invocation");
3281             } else {
3282                 ctor.flags_field |= LOCKED;
3283                 checkCyclicConstructor(tree, callMap.remove(ctor), callMap);
3284                 ctor.flags_field &= ~LOCKED;
3285             }
3286             ctor.flags_field |= ACYCLIC;
3287         }
3288     }
3289 
3290 /* *************************************************************************
3291  * Miscellaneous
3292  **************************************************************************/
3293 
3294     /**
3295      * Return the opcode of the operator but emit an error if it is an
3296      * error.
3297      * @param pos        position for error reporting.
3298      * @param operator   an operator
3299      * @param tag        a tree tag
3300      * @param left       type of left hand side
3301      * @param right      type of right hand side
3302      */
3303     int checkOperator(DiagnosticPosition pos,
3304                        OperatorSymbol operator,
3305                        JCTree.Tag tag,
3306                        Type left,
3307                        Type right) {
3308         if (operator.opcode == ByteCodes.error) {
3309             log.error(pos,
3310                       "operator.cant.be.applied.1",
3311                       treeinfo.operatorName(tag),
3312                       left, right);
3313         }
3314         return operator.opcode;
3315     }
3316 
3317 
3318     /**
3319      *  Check for division by integer constant zero
3320      *  @param pos           Position for error reporting.
3321      *  @param operator      The operator for the expression
3322      *  @param operand       The right hand operand for the expression
3323      */
3324     void checkDivZero(DiagnosticPosition pos, Symbol operator, Type operand) {
3325         if (operand.constValue() != null
3326             && lint.isEnabled(LintCategory.DIVZERO)
3327             && operand.getTag().isSubRangeOf(LONG)
3328             && ((Number) (operand.constValue())).longValue() == 0) {
3329             int opc = ((OperatorSymbol)operator).opcode;
3330             if (opc == ByteCodes.idiv || opc == ByteCodes.imod
3331                 || opc == ByteCodes.ldiv || opc == ByteCodes.lmod) {
3332                 log.warning(LintCategory.DIVZERO, pos, "div.zero");
3333             }
3334         }
3335     }
3336 
3337     /**
3338      * Check for empty statements after if
3339      */
3340     void checkEmptyIf(JCIf tree) {
3341         if (tree.thenpart.hasTag(SKIP) && tree.elsepart == null &&
3342                 lint.isEnabled(LintCategory.EMPTY))
3343             log.warning(LintCategory.EMPTY, tree.thenpart.pos(), "empty.if");
3344     }
3345 
3346     /** Check that symbol is unique in given scope.
3347      *  @param pos           Position for error reporting.
3348      *  @param sym           The symbol.
3349      *  @param s             The scope.
3350      */
3351     boolean checkUnique(DiagnosticPosition pos, Symbol sym, Scope s) {
3352         if (sym.type.isErroneous())
3353             return true;
3354         if (sym.owner.name == names.any) return false;
3355         for (Scope.Entry e = s.lookup(sym.name); e.scope == s; e = e.next()) {
3356             if (sym != e.sym &&
3357                     (e.sym.flags() & CLASH) == 0 &&
3358                     sym.kind == e.sym.kind &&
3359                     sym.name != names.error &&
3360                     (sym.kind != MTH ||
3361                      types.hasSameArgs(sym.type, e.sym.type) ||
3362                      types.hasSameArgs(types.erasure(sym.type), types.erasure(e.sym.type)))) {
3363                 if ((sym.flags() & VARARGS) != (e.sym.flags() & VARARGS)) {
3364                     varargsDuplicateError(pos, sym, e.sym);
3365                     return true;
3366                 } else if (sym.kind == MTH && !types.hasSameArgs(sym.type, e.sym.type, false)) {
3367                     duplicateErasureError(pos, sym, e.sym);
3368                     sym.flags_field |= CLASH;
3369                     return true;
3370                 } else {
3371                     duplicateError(pos, e.sym);
3372                     return false;
3373                 }
3374             }
3375         }
3376         return true;
3377     }
3378 
3379     /** Report duplicate declaration error.
3380      */
3381     void duplicateErasureError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
3382         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
3383             log.error(pos, "name.clash.same.erasure", sym1, sym2);
3384         }
3385     }
3386 
3387     /** Check that single-type import is not already imported or top-level defined,
3388      *  but make an exception for two single-type imports which denote the same type.
3389      *  @param pos           Position for error reporting.
3390      *  @param sym           The symbol.
3391      *  @param s             The scope
3392      */
3393     boolean checkUniqueImport(DiagnosticPosition pos, Symbol sym, Scope s) {
3394         return checkUniqueImport(pos, sym, s, false);
3395     }
3396 
3397     /** Check that static single-type import is not already imported or top-level defined,
3398      *  but make an exception for two single-type imports which denote the same type.
3399      *  @param pos           Position for error reporting.
3400      *  @param sym           The symbol.
3401      *  @param s             The scope
3402      */
3403     boolean checkUniqueStaticImport(DiagnosticPosition pos, Symbol sym, Scope s) {
3404         return checkUniqueImport(pos, sym, s, true);
3405     }
3406 
3407     /** Check that single-type import is not already imported or top-level defined,
3408      *  but make an exception for two single-type imports which denote the same type.
3409      *  @param pos           Position for error reporting.
3410      *  @param sym           The symbol.
3411      *  @param s             The scope.
3412      *  @param staticImport  Whether or not this was a static import
3413      */
3414     private boolean checkUniqueImport(DiagnosticPosition pos, Symbol sym, Scope s, boolean staticImport) {
3415         for (Scope.Entry e = s.lookup(sym.name); e.scope != null; e = e.next()) {
3416             // is encountered class entered via a class declaration?
3417             boolean isClassDecl = e.scope == s;
3418             if ((isClassDecl || sym != e.sym) &&
3419                 sym.kind == e.sym.kind &&
3420                 sym.name != names.error &&
3421                 (!staticImport || !e.isStaticallyImported())) {
3422                 if (!e.sym.type.isErroneous()) {
3423                     String what = e.sym.getSimpleName().toString();
3424                     if (!isClassDecl) {
3425                         if (staticImport)
3426                             log.error(pos, "already.defined.static.single.import", what);
3427                         else
3428                         log.error(pos, "already.defined.single.import", what);
3429                     }
3430                     else if (sym != e.sym)
3431                         log.error(pos, "already.defined.this.unit", what);
3432                 }
3433                 return false;
3434             }
3435         }
3436         return true;
3437     }
3438 
3439     /** Check that a qualified name is in canonical form (for import decls).
3440      */
3441     public void checkCanonical(JCTree tree) {
3442         if (!isCanonical(tree))
3443             log.error(tree.pos(), "import.requires.canonical",
3444                       TreeInfo.symbol(tree));
3445     }
3446         // where
3447         private boolean isCanonical(JCTree tree) {
3448             while (tree.hasTag(SELECT)) {
3449                 JCFieldAccess s = (JCFieldAccess) tree;
3450                 if (s.sym.owner != TreeInfo.symbol(s.selected))
3451                     return false;
3452                 tree = s.selected;
3453             }
3454             return true;
3455         }
3456 
3457     /** Check that an auxiliary class is not accessed from any other file than its own.
3458      */
3459     void checkForBadAuxiliaryClassAccess(DiagnosticPosition pos, Env<AttrContext> env, ClassSymbol c) {
3460         if (lint.isEnabled(Lint.LintCategory.AUXILIARYCLASS) &&
3461             (c.flags() & AUXILIARY) != 0 &&
3462             rs.isAccessible(env, c) &&
3463             !fileManager.isSameFile(c.sourcefile, env.toplevel.sourcefile))
3464         {
3465             log.warning(pos, "auxiliary.class.accessed.from.outside.of.its.source.file",
3466                         c, c.sourcefile);
3467         }
3468     }
3469 
3470     private class ConversionWarner extends Warner {
3471         final String uncheckedKey;
3472         final Type found;
3473         final Type expected;
3474         public ConversionWarner(DiagnosticPosition pos, String uncheckedKey, Type found, Type expected) {
3475             super(pos);
3476             this.uncheckedKey = uncheckedKey;
3477             this.found = found;
3478             this.expected = expected;
3479         }
3480 
3481         @Override
3482         public void warn(LintCategory lint) {
3483             boolean warned = this.warned;
3484             super.warn(lint);
3485             if (warned) return; // suppress redundant diagnostics
3486             switch (lint) {
3487                 case UNCHECKED:
3488                     Check.this.warnUnchecked(pos(), "prob.found.req", diags.fragment(uncheckedKey), found, expected);
3489                     break;
3490                 case VARARGS:
3491                     if (method != null &&
3492                             method.attribute(syms.trustMeType.tsym) != null &&
3493                             isTrustMeAllowedOnMethod(method) &&
3494                             !types.isReifiable(method.type.getParameterTypes().last())) {
3495                         Check.this.warnUnsafeVararg(pos(), "varargs.unsafe.use.varargs.param", method.params.last());
3496                     }
3497                     break;
3498                 default:
3499                     throw new AssertionError("Unexpected lint: " + lint);
3500             }
3501         }
3502     }
3503 
3504     public Warner castWarner(DiagnosticPosition pos, Type found, Type expected) {
3505         return new ConversionWarner(pos, "unchecked.cast.to.type", found, expected);
3506     }
3507 
3508     public Warner convertWarner(DiagnosticPosition pos, Type found, Type expected) {
3509         return new ConversionWarner(pos, "unchecked.assign", found, expected);
3510     }
3511 }