jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/comp/Check.java@7aa2025bbb7b (annotated)

src/share/classes/com/sun/tools/javac/comp/Check.java@7aa2025bbb7b (annotated)

src/share/classes/com/sun/tools/javac/comp/Check.java

Wed, 16 Jan 2013 16:30:11 +0000

author: mcimadamore
date: Wed, 16 Jan 2013 16:30:11 +0000
changeset 1497: 7aa2025bbb7b
parent 1496: f785dcac17b7
child 1510: 7873d37f5b37
permissions: -rw-r--r--

8005299: Add FunctionalInterface checking to javac
Summary: Javac should check that types annotated with @FunctionalInterface are indeed functional interfaces
Reviewed-by: jjg

 /*
  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 package com.sun.tools.javac.comp;
 import java.util.*;
 import java.util.Set;
 import javax.tools.JavaFileManager;
 import com.sun.tools.javac.code.*;
 import com.sun.tools.javac.jvm.*;
 import com.sun.tools.javac.tree.*;
 import com.sun.tools.javac.util.*;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
 import com.sun.tools.javac.util.List;
 import com.sun.tools.javac.tree.JCTree.*;
 import com.sun.tools.javac.code.Lint;
 import com.sun.tools.javac.code.Lint.LintCategory;
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;
 import com.sun.tools.javac.comp.Infer.InferenceContext;
 import com.sun.tools.javac.comp.Infer.InferenceContext.FreeTypeListener;
 import static com.sun.tools.javac.code.Flags.*;
 import static com.sun.tools.javac.code.Flags.ANNOTATION;
 import static com.sun.tools.javac.code.Flags.SYNCHRONIZED;
 import static com.sun.tools.javac.code.Kinds.*;
 import static com.sun.tools.javac.code.TypeTag.*;
 import static com.sun.tools.javac.code.TypeTag.WILDCARD;
 import static com.sun.tools.javac.tree.JCTree.Tag.*;
 /** Type checking helper class for the attribution phase.
  *
  *  <p><b>This is NOT part of any supported API.
  *  If you write code that depends on this, you do so at your own risk.
  *  This code and its internal interfaces are subject to change or
  *  deletion without notice.</b>
  */
 public class Check {
     protected static final Context.Key<Check> checkKey =
         new Context.Key<Check>();
     private final Names names;
     private final Log log;
     private final Resolve rs;
     private final Symtab syms;
     private final Enter enter;
     private final DeferredAttr deferredAttr;
     private final Infer infer;
     private final Types types;
     private final JCDiagnostic.Factory diags;
     private boolean warnOnSyntheticConflicts;
     private boolean suppressAbortOnBadClassFile;
     private boolean enableSunApiLintControl;
     private final TreeInfo treeinfo;
     private final JavaFileManager fileManager;
     // The set of lint options currently in effect. It is initialized
     // from the context, and then is set/reset as needed by Attr as it
     // visits all the various parts of the trees during attribution.
     private Lint lint;
     // The method being analyzed in Attr - it is set/reset as needed by
     // Attr as it visits new method declarations.
     private MethodSymbol method;
     public static Check instance(Context context) {
         Check instance = context.get(checkKey);
         if (instance == null)
             instance = new Check(context);
         return instance;
     }
     protected Check(Context context) {
         context.put(checkKey, this);
         names = Names.instance(context);
         log = Log.instance(context);
         rs = Resolve.instance(context);
         syms = Symtab.instance(context);
         enter = Enter.instance(context);
         deferredAttr = DeferredAttr.instance(context);
         infer = Infer.instance(context);
         this.types = Types.instance(context);
         diags = JCDiagnostic.Factory.instance(context);
         Options options = Options.instance(context);
         lint = Lint.instance(context);
         treeinfo = TreeInfo.instance(context);
         fileManager = context.get(JavaFileManager.class);
         Source source = Source.instance(context);
         allowGenerics = source.allowGenerics();
         allowVarargs = source.allowVarargs();
         allowAnnotations = source.allowAnnotations();
         allowCovariantReturns = source.allowCovariantReturns();
         allowSimplifiedVarargs = source.allowSimplifiedVarargs();
         allowDefaultMethods = source.allowDefaultMethods();
         allowStrictMethodClashCheck = source.allowStrictMethodClashCheck();
         complexInference = options.isSet("complexinference");
         warnOnSyntheticConflicts = options.isSet("warnOnSyntheticConflicts");
         suppressAbortOnBadClassFile = options.isSet("suppressAbortOnBadClassFile");
         enableSunApiLintControl = options.isSet("enableSunApiLintControl");
         Target target = Target.instance(context);
         syntheticNameChar = target.syntheticNameChar();
         boolean verboseDeprecated = lint.isEnabled(LintCategory.DEPRECATION);
         boolean verboseUnchecked = lint.isEnabled(LintCategory.UNCHECKED);
         boolean verboseSunApi = lint.isEnabled(LintCategory.SUNAPI);
         boolean enforceMandatoryWarnings = source.enforceMandatoryWarnings();
         deprecationHandler = new MandatoryWarningHandler(log, verboseDeprecated,
                 enforceMandatoryWarnings, "deprecated", LintCategory.DEPRECATION);
         uncheckedHandler = new MandatoryWarningHandler(log, verboseUnchecked,
                 enforceMandatoryWarnings, "unchecked", LintCategory.UNCHECKED);
         sunApiHandler = new MandatoryWarningHandler(log, verboseSunApi,
                 enforceMandatoryWarnings, "sunapi", null);
         deferredLintHandler = DeferredLintHandler.immediateHandler;
     }
     /** Switch: generics enabled?
      */
     boolean allowGenerics;
     /** Switch: varargs enabled?
      */
     boolean allowVarargs;
     /** Switch: annotations enabled?
      */
     boolean allowAnnotations;
     /** Switch: covariant returns enabled?
      */
     boolean allowCovariantReturns;
     /** Switch: simplified varargs enabled?
      */
     boolean allowSimplifiedVarargs;
     /** Switch: default methods enabled?
      */
     boolean allowDefaultMethods;
     /** Switch: should unrelated return types trigger a method clash?
      */
     boolean allowStrictMethodClashCheck;
     /** Switch: -complexinference option set?
      */
     boolean complexInference;
     /** Character for synthetic names
      */
     char syntheticNameChar;
     /** A table mapping flat names of all compiled classes in this run to their
      *  symbols; maintained from outside.
      */
     public Map<Name,ClassSymbol> compiled = new HashMap<Name, ClassSymbol>();
     /** A handler for messages about deprecated usage.
      */
     private MandatoryWarningHandler deprecationHandler;
     /** A handler for messages about unchecked or unsafe usage.
      */
     private MandatoryWarningHandler uncheckedHandler;
     /** A handler for messages about using proprietary API.
      */
     private MandatoryWarningHandler sunApiHandler;
     /** A handler for deferred lint warnings.
      */
     private DeferredLintHandler deferredLintHandler;
 /* *************************************************************************
  * Errors and Warnings
  **************************************************************************/
     Lint setLint(Lint newLint) {
         Lint prev = lint;
         lint = newLint;
         return prev;
     }
     DeferredLintHandler setDeferredLintHandler(DeferredLintHandler newDeferredLintHandler) {
         DeferredLintHandler prev = deferredLintHandler;
         deferredLintHandler = newDeferredLintHandler;
         return prev;
     }
     MethodSymbol setMethod(MethodSymbol newMethod) {
         MethodSymbol prev = method;
         method = newMethod;
         return prev;
     }
     /** Warn about deprecated symbol.
      *  @param pos        Position to be used for error reporting.
      *  @param sym        The deprecated symbol.
      */
     void warnDeprecated(DiagnosticPosition pos, Symbol sym) {
         if (!lint.isSuppressed(LintCategory.DEPRECATION))
             deprecationHandler.report(pos, "has.been.deprecated", sym, sym.location());
     }
     /** Warn about unchecked operation.
      *  @param pos        Position to be used for error reporting.
      *  @param msg        A string describing the problem.
      */
     public void warnUnchecked(DiagnosticPosition pos, String msg, Object... args) {
         if (!lint.isSuppressed(LintCategory.UNCHECKED))
             uncheckedHandler.report(pos, msg, args);
     }
     /** Warn about unsafe vararg method decl.
      *  @param pos        Position to be used for error reporting.
      */
     void warnUnsafeVararg(DiagnosticPosition pos, String key, Object... args) {
         if (lint.isEnabled(LintCategory.VARARGS) && allowSimplifiedVarargs)
             log.warning(LintCategory.VARARGS, pos, key, args);
     }
     /** Warn about using proprietary API.
      *  @param pos        Position to be used for error reporting.
      *  @param msg        A string describing the problem.
      */
     public void warnSunApi(DiagnosticPosition pos, String msg, Object... args) {
         if (!lint.isSuppressed(LintCategory.SUNAPI))
             sunApiHandler.report(pos, msg, args);
     }
     public void warnStatic(DiagnosticPosition pos, String msg, Object... args) {
         if (lint.isEnabled(LintCategory.STATIC))
             log.warning(LintCategory.STATIC, pos, msg, args);
     }
     /**
      * Report any deferred diagnostics.
      */
     public void reportDeferredDiagnostics() {
         deprecationHandler.reportDeferredDiagnostic();
         uncheckedHandler.reportDeferredDiagnostic();
         sunApiHandler.reportDeferredDiagnostic();
     }
     /** Report a failure to complete a class.
      *  @param pos        Position to be used for error reporting.
      *  @param ex         The failure to report.
      */
     public Type completionError(DiagnosticPosition pos, CompletionFailure ex) {
         log.error(pos, "cant.access", ex.sym, ex.getDetailValue());
         if (ex instanceof ClassReader.BadClassFile
                 && !suppressAbortOnBadClassFile) throw new Abort();
         else return syms.errType;
     }
     /** Report an error that wrong type tag was found.
      *  @param pos        Position to be used for error reporting.
      *  @param required   An internationalized string describing the type tag
      *                    required.
      *  @param found      The type that was found.
      */
     Type typeTagError(DiagnosticPosition pos, Object required, Object found) {
         // this error used to be raised by the parser,
         // but has been delayed to this point:
         if (found instanceof Type && ((Type)found).hasTag(VOID)) {
             log.error(pos, "illegal.start.of.type");
             return syms.errType;
         }
         log.error(pos, "type.found.req", found, required);
         return types.createErrorType(found instanceof Type ? (Type)found : syms.errType);
     }
     /** Report an error that symbol cannot be referenced before super
      *  has been called.
      *  @param pos        Position to be used for error reporting.
      *  @param sym        The referenced symbol.
      */
     void earlyRefError(DiagnosticPosition pos, Symbol sym) {
         log.error(pos, "cant.ref.before.ctor.called", sym);
     }
     /** Report duplicate declaration error.
      */
     void duplicateError(DiagnosticPosition pos, Symbol sym) {
         if (!sym.type.isErroneous()) {
             Symbol location = sym.location();
             if (location.kind == MTH &&
                     ((MethodSymbol)location).isStaticOrInstanceInit()) {
                 log.error(pos, "already.defined.in.clinit", kindName(sym), sym,
                         kindName(sym.location()), kindName(sym.location().enclClass()),
                         sym.location().enclClass());
             } else {
                 log.error(pos, "already.defined", kindName(sym), sym,
                         kindName(sym.location()), sym.location());
             }
         }
     }
     /** Report array/varargs duplicate declaration
      */
     void varargsDuplicateError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
             log.error(pos, "array.and.varargs", sym1, sym2, sym2.location());
         }
     }
 /* ************************************************************************
  * duplicate declaration checking
  *************************************************************************/
     /** Check that variable does not hide variable with same name in
      *  immediately enclosing local scope.
      *  @param pos           Position for error reporting.
      *  @param v             The symbol.
      *  @param s             The scope.
      */
     void checkTransparentVar(DiagnosticPosition pos, VarSymbol v, Scope s) {
         if (s.next != null) {
             for (Scope.Entry e = s.next.lookup(v.name);
                  e.scope != null && e.sym.owner == v.owner;
                  e = e.next()) {
                 if (e.sym.kind == VAR &&
                     (e.sym.owner.kind & (VAR | MTH)) != 0 &&
                     v.name != names.error) {
                     duplicateError(pos, e.sym);
                     return;
                 }
             }
         }
     }
     /** Check that a class or interface does not hide a class or
      *  interface with same name in immediately enclosing local scope.
      *  @param pos           Position for error reporting.
      *  @param c             The symbol.
      *  @param s             The scope.
      */
     void checkTransparentClass(DiagnosticPosition pos, ClassSymbol c, Scope s) {
         if (s.next != null) {
             for (Scope.Entry e = s.next.lookup(c.name);
                  e.scope != null && e.sym.owner == c.owner;
                  e = e.next()) {
                 if (e.sym.kind == TYP && !e.sym.type.hasTag(TYPEVAR) &&
                     (e.sym.owner.kind & (VAR | MTH)) != 0 &&
                     c.name != names.error) {
                     duplicateError(pos, e.sym);
                     return;
                 }
             }
         }
     }
     /** Check that class does not have the same name as one of
      *  its enclosing classes, or as a class defined in its enclosing scope.
      *  return true if class is unique in its enclosing scope.
      *  @param pos           Position for error reporting.
      *  @param name          The class name.
      *  @param s             The enclosing scope.
      */
     boolean checkUniqueClassName(DiagnosticPosition pos, Name name, Scope s) {
         for (Scope.Entry e = s.lookup(name); e.scope == s; e = e.next()) {
             if (e.sym.kind == TYP && e.sym.name != names.error) {
                 duplicateError(pos, e.sym);
                 return false;
             }
         }
         for (Symbol sym = s.owner; sym != null; sym = sym.owner) {
             if (sym.kind == TYP && sym.name == name && sym.name != names.error) {
                 duplicateError(pos, sym);
                 return true;
             }
         }
         return true;
     }
 /* *************************************************************************
  * Class name generation
  **************************************************************************/
     /** Return name of local class.
      *  This is of the form   {@code <enclClass> $ n <classname> }
      *  where
      *    enclClass is the flat name of the enclosing class,
      *    classname is the simple name of the local class
      */
     Name localClassName(ClassSymbol c) {
         for (int i=1; ; i++) {
             Name flatname = names.
                 fromString("" + c.owner.enclClass().flatname +
                            syntheticNameChar + i +
                            c.name);
             if (compiled.get(flatname) == null) return flatname;
         }
     }
 /* *************************************************************************
  * Type Checking
  **************************************************************************/
     /**
      * A check context is an object that can be used to perform compatibility
      * checks - depending on the check context, meaning of 'compatibility' might
      * vary significantly.
      */
     public interface CheckContext {
         /**
          * Is type 'found' compatible with type 'req' in given context
          */
         boolean compatible(Type found, Type req, Warner warn);
         /**
          * Report a check error
          */
         void report(DiagnosticPosition pos, JCDiagnostic details);
         /**
          * Obtain a warner for this check context
          */
         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req);
         public Infer.InferenceContext inferenceContext();
         public DeferredAttr.DeferredAttrContext deferredAttrContext();
     }
     /**
      * This class represent a check context that is nested within another check
      * context - useful to check sub-expressions. The default behavior simply
      * redirects all method calls to the enclosing check context leveraging
      * the forwarding pattern.
      */
     static class NestedCheckContext implements CheckContext {
         CheckContext enclosingContext;
         NestedCheckContext(CheckContext enclosingContext) {
             this.enclosingContext = enclosingContext;
         }
         public boolean compatible(Type found, Type req, Warner warn) {
             return enclosingContext.compatible(found, req, warn);
         }
         public void report(DiagnosticPosition pos, JCDiagnostic details) {
             enclosingContext.report(pos, details);
         }
         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
             return enclosingContext.checkWarner(pos, found, req);
         }
         public Infer.InferenceContext inferenceContext() {
             return enclosingContext.inferenceContext();
         }
         public DeferredAttrContext deferredAttrContext() {
             return enclosingContext.deferredAttrContext();
         }
     }
     /**
      * Check context to be used when evaluating assignment/return statements
      */
     CheckContext basicHandler = new CheckContext() {
         public void report(DiagnosticPosition pos, JCDiagnostic details) {
             log.error(pos, "prob.found.req", details);
         }
         public boolean compatible(Type found, Type req, Warner warn) {
             return types.isAssignable(found, req, warn);
         }
         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
             return convertWarner(pos, found, req);
         }
         public InferenceContext inferenceContext() {
             return infer.emptyContext;
         }
         public DeferredAttrContext deferredAttrContext() {
             return deferredAttr.emptyDeferredAttrContext;
         }
     };
     /** Check that a given type is assignable to a given proto-type.
      *  If it is, return the type, otherwise return errType.
      *  @param pos        Position to be used for error reporting.
      *  @param found      The type that was found.
      *  @param req        The type that was required.
      */
     Type checkType(DiagnosticPosition pos, Type found, Type req) {
         return checkType(pos, found, req, basicHandler);
     }
     Type checkType(final DiagnosticPosition pos, final Type found, final Type req, final CheckContext checkContext) {
         final Infer.InferenceContext inferenceContext = checkContext.inferenceContext();
         if (inferenceContext.free(req)) {
             inferenceContext.addFreeTypeListener(List.of(req), new FreeTypeListener() {
                 @Override
                 public void typesInferred(InferenceContext inferenceContext) {
                     checkType(pos, found, inferenceContext.asInstType(req, types), checkContext);
                 }
             });
         }
         if (req.hasTag(ERROR))
             return req;
         if (req.hasTag(NONE))
             return found;
         if (checkContext.compatible(found, req, checkContext.checkWarner(pos, found, req))) {
             return found;
         } else {
             if (found.getTag().isSubRangeOf(DOUBLE) && req.getTag().isSubRangeOf(DOUBLE)) {
                 checkContext.report(pos, diags.fragment("possible.loss.of.precision", found, req));
                 return types.createErrorType(found);
             }
             checkContext.report(pos, diags.fragment("inconvertible.types", found, req));
             return types.createErrorType(found);
         }
     }
     /** Check that a given type can be cast to a given target type.
      *  Return the result of the cast.
      *  @param pos        Position to be used for error reporting.
      *  @param found      The type that is being cast.
      *  @param req        The target type of the cast.
      */
     Type checkCastable(DiagnosticPosition pos, Type found, Type req) {
         return checkCastable(pos, found, req, basicHandler);
     }
     Type checkCastable(DiagnosticPosition pos, Type found, Type req, CheckContext checkContext) {
         if (types.isCastable(found, req, castWarner(pos, found, req))) {
             return req;
         } else {
             checkContext.report(pos, diags.fragment("inconvertible.types", found, req));
             return types.createErrorType(found);
         }
     }
     /** Check for redundant casts (i.e. where source type is a subtype of target type)
      * The problem should only be reported for non-292 cast
      */
     public void checkRedundantCast(Env<AttrContext> env, JCTypeCast tree) {
         if (!tree.type.isErroneous() &&
                 (env.info.lint == null || env.info.lint.isEnabled(Lint.LintCategory.CAST))
                 && types.isSameType(tree.expr.type, tree.clazz.type)
                 && !is292targetTypeCast(tree)) {
             log.warning(Lint.LintCategory.CAST,
                     tree.pos(), "redundant.cast", tree.expr.type);
         }
     }
     //where
             private boolean is292targetTypeCast(JCTypeCast tree) {
                 boolean is292targetTypeCast = false;
                 JCExpression expr = TreeInfo.skipParens(tree.expr);
                 if (expr.hasTag(APPLY)) {
                     JCMethodInvocation apply = (JCMethodInvocation)expr;
                     Symbol sym = TreeInfo.symbol(apply.meth);
                     is292targetTypeCast = sym != null &&
                         sym.kind == MTH &&
                         (sym.flags() & HYPOTHETICAL) != 0;
                 }
                 return is292targetTypeCast;
             }
 //where
         /** Is type a type variable, or a (possibly multi-dimensional) array of
          *  type variables?
          */
         boolean isTypeVar(Type t) {
             return t.hasTag(TYPEVAR) || t.hasTag(ARRAY) && isTypeVar(types.elemtype(t));
         }
     /** Check that a type is within some bounds.
      *
      *  Used in TypeApply to verify that, e.g., X in {@code V<X>} is a valid
      *  type argument.
      *  @param a             The type that should be bounded by bs.
      *  @param bound         The bound.
      */
     private boolean checkExtends(Type a, Type bound) {
          if (a.isUnbound()) {
              return true;
          } else if (!a.hasTag(WILDCARD)) {
              a = types.upperBound(a);
              return types.isSubtype(a, bound);
          } else if (a.isExtendsBound()) {
              return types.isCastable(bound, types.upperBound(a), types.noWarnings);
          } else if (a.isSuperBound()) {
              return !types.notSoftSubtype(types.lowerBound(a), bound);
          }
          return true;
      }
     /** Check that type is different from 'void'.
      *  @param pos           Position to be used for error reporting.
      *  @param t             The type to be checked.
      */
     Type checkNonVoid(DiagnosticPosition pos, Type t) {
         if (t.hasTag(VOID)) {
             log.error(pos, "void.not.allowed.here");
             return types.createErrorType(t);
         } else {
             return t;
         }
     }
     Type checkClassOrArrayType(DiagnosticPosition pos, Type t) {
         if (!t.hasTag(CLASS) && !t.hasTag(ARRAY) && !t.hasTag(ERROR)) {
             return typeTagError(pos,
                                 diags.fragment("type.req.class.array"),
                                 asTypeParam(t));
         } else {
             return t;
         }
     }
     /** Check that type is a class or interface type.
      *  @param pos           Position to be used for error reporting.
      *  @param t             The type to be checked.
      */
     Type checkClassType(DiagnosticPosition pos, Type t) {
         if (!t.hasTag(CLASS) && !t.hasTag(ERROR)) {
             return typeTagError(pos,
                                 diags.fragment("type.req.class"),
                                 asTypeParam(t));
         } else {
             return t;
         }
     }
     //where
         private Object asTypeParam(Type t) {
             return (t.hasTag(TYPEVAR))
                                     ? diags.fragment("type.parameter", t)
                                     : t;
         }
     /** Check that type is a valid qualifier for a constructor reference expression
      */
     Type checkConstructorRefType(DiagnosticPosition pos, Type t) {
         t = checkClassOrArrayType(pos, t);
         if (t.hasTag(CLASS)) {
             if ((t.tsym.flags() & (ABSTRACT | INTERFACE)) != 0) {
                 log.error(pos, "abstract.cant.be.instantiated");
                 t = types.createErrorType(t);
             } else if ((t.tsym.flags() & ENUM) != 0) {
                 log.error(pos, "enum.cant.be.instantiated");
                 t = types.createErrorType(t);
             }
         }
         return t;
     }
     /** Check that type is a class or interface type.
      *  @param pos           Position to be used for error reporting.
      *  @param t             The type to be checked.
      *  @param noBounds    True if type bounds are illegal here.
      */
     Type checkClassType(DiagnosticPosition pos, Type t, boolean noBounds) {
         t = checkClassType(pos, t);
         if (noBounds && t.isParameterized()) {
             List<Type> args = t.getTypeArguments();
             while (args.nonEmpty()) {
                 if (args.head.hasTag(WILDCARD))
                     return typeTagError(pos,
                                         diags.fragment("type.req.exact"),
                                         args.head);
                 args = args.tail;
             }
         }
         return t;
     }
     /** Check that type is a reifiable class, interface or array type.
      *  @param pos           Position to be used for error reporting.
      *  @param t             The type to be checked.
      */
     Type checkReifiableReferenceType(DiagnosticPosition pos, Type t) {
         t = checkClassOrArrayType(pos, t);
         if (!t.isErroneous() && !types.isReifiable(t)) {
             log.error(pos, "illegal.generic.type.for.instof");
             return types.createErrorType(t);
         } else {
             return t;
         }
     }
     /** Check that type is a reference type, i.e. a class, interface or array type
      *  or a type variable.
      *  @param pos           Position to be used for error reporting.
      *  @param t             The type to be checked.
      */
     Type checkRefType(DiagnosticPosition pos, Type t) {
         if (t.isReference())
             return t;
         else
             return typeTagError(pos,
                                 diags.fragment("type.req.ref"),
                                 t);
     }
     /** Check that each type is a reference type, i.e. a class, interface or array type
      *  or a type variable.
      *  @param trees         Original trees, used for error reporting.
      *  @param types         The types to be checked.
      */
     List<Type> checkRefTypes(List<JCExpression> trees, List<Type> types) {
         List<JCExpression> tl = trees;
         for (List<Type> l = types; l.nonEmpty(); l = l.tail) {
             l.head = checkRefType(tl.head.pos(), l.head);
             tl = tl.tail;
         }
         return types;
     }
     /** Check that type is a null or reference type.
      *  @param pos           Position to be used for error reporting.
      *  @param t             The type to be checked.
      */
     Type checkNullOrRefType(DiagnosticPosition pos, Type t) {
         if (t.isNullOrReference())
             return t;
         else
             return typeTagError(pos,
                                 diags.fragment("type.req.ref"),
                                 t);
     }
     /** Check that flag set does not contain elements of two conflicting sets. s
      *  Return true if it doesn't.
      *  @param pos           Position to be used for error reporting.
      *  @param flags         The set of flags to be checked.
      *  @param set1          Conflicting flags set #1.
      *  @param set2          Conflicting flags set #2.
      */
     boolean checkDisjoint(DiagnosticPosition pos, long flags, long set1, long set2) {
         if ((flags & set1) != 0 && (flags & set2) != 0) {
             log.error(pos,
                       "illegal.combination.of.modifiers",
                       asFlagSet(TreeInfo.firstFlag(flags & set1)),
                       asFlagSet(TreeInfo.firstFlag(flags & set2)));
             return false;
         } else
             return true;
     }
     /** Check that usage of diamond operator is correct (i.e. diamond should not
      * be used with non-generic classes or in anonymous class creation expressions)
      */
     Type checkDiamond(JCNewClass tree, Type t) {
         if (!TreeInfo.isDiamond(tree) ||
                 t.isErroneous()) {
             return checkClassType(tree.clazz.pos(), t, true);
         } else if (tree.def != null) {
             log.error(tree.clazz.pos(),
                     "cant.apply.diamond.1",
                     t, diags.fragment("diamond.and.anon.class", t));
             return types.createErrorType(t);
         } else if (t.tsym.type.getTypeArguments().isEmpty()) {
             log.error(tree.clazz.pos(),
                 "cant.apply.diamond.1",
                 t, diags.fragment("diamond.non.generic", t));
             return types.createErrorType(t);
         } else if (tree.typeargs != null &&
                 tree.typeargs.nonEmpty()) {
             log.error(tree.clazz.pos(),
                 "cant.apply.diamond.1",
                 t, diags.fragment("diamond.and.explicit.params", t));
             return types.createErrorType(t);
         } else {
             return t;
         }
     }
     void checkVarargsMethodDecl(Env<AttrContext> env, JCMethodDecl tree) {
         MethodSymbol m = tree.sym;
         if (!allowSimplifiedVarargs) return;
         boolean hasTrustMeAnno = m.attribute(syms.trustMeType.tsym) != null;
         Type varargElemType = null;
         if (m.isVarArgs()) {
             varargElemType = types.elemtype(tree.params.last().type);
         }
         if (hasTrustMeAnno && !isTrustMeAllowedOnMethod(m)) {
             if (varargElemType != null) {
                 log.error(tree,
                         "varargs.invalid.trustme.anno",
                         syms.trustMeType.tsym,
                         diags.fragment("varargs.trustme.on.virtual.varargs", m));
             } else {
                 log.error(tree,
                             "varargs.invalid.trustme.anno",
                             syms.trustMeType.tsym,
                             diags.fragment("varargs.trustme.on.non.varargs.meth", m));
             }
         } else if (hasTrustMeAnno && varargElemType != null &&
                             types.isReifiable(varargElemType)) {
             warnUnsafeVararg(tree,
                             "varargs.redundant.trustme.anno",
                             syms.trustMeType.tsym,
                             diags.fragment("varargs.trustme.on.reifiable.varargs", varargElemType));
         }
         else if (!hasTrustMeAnno && varargElemType != null &&
                 !types.isReifiable(varargElemType)) {
             warnUnchecked(tree.params.head.pos(), "unchecked.varargs.non.reifiable.type", varargElemType);
         }
     }
     //where
         private boolean isTrustMeAllowedOnMethod(Symbol s) {
             return (s.flags() & VARARGS) != 0 &&
                 (s.isConstructor() ||
                     (s.flags() & (STATIC | FINAL)) != 0);
         }
     Type checkMethod(Type owntype,
                             Symbol sym,
                             Env<AttrContext> env,
                             final List<JCExpression> argtrees,
                             List<Type> argtypes,
                             boolean useVarargs,
                             boolean unchecked) {
         // System.out.println("call   : " + env.tree);
         // System.out.println("method : " + owntype);
         // System.out.println("actuals: " + argtypes);
         List<Type> formals = owntype.getParameterTypes();
         Type last = useVarargs ? formals.last() : null;
         if (sym.name==names.init &&
                 sym.owner == syms.enumSym)
                 formals = formals.tail.tail;
         List<JCExpression> args = argtrees;
         DeferredAttr.DeferredTypeMap checkDeferredMap =
                 deferredAttr.new DeferredTypeMap(DeferredAttr.AttrMode.CHECK, sym, env.info.pendingResolutionPhase);
         if (args != null) {
             //this is null when type-checking a method reference
             while (formals.head != last) {
                 JCTree arg = args.head;
                 Warner warn = convertWarner(arg.pos(), arg.type, formals.head);
                 assertConvertible(arg, arg.type, formals.head, warn);
                 args = args.tail;
                 formals = formals.tail;
             }
             if (useVarargs) {
                 Type varArg = types.elemtype(last);
                 while (args.tail != null) {
                     JCTree arg = args.head;
                     Warner warn = convertWarner(arg.pos(), arg.type, varArg);
                     assertConvertible(arg, arg.type, varArg, warn);
                     args = args.tail;
                 }
             } else if ((sym.flags() & VARARGS) != 0 && allowVarargs) {
                 // non-varargs call to varargs method
                 Type varParam = owntype.getParameterTypes().last();
                 Type lastArg = checkDeferredMap.apply(argtypes.last());
                 if (types.isSubtypeUnchecked(lastArg, types.elemtype(varParam)) &&
                         !types.isSameType(types.erasure(varParam), types.erasure(lastArg)))
                     log.warning(argtrees.last().pos(), "inexact.non-varargs.call",
                             types.elemtype(varParam), varParam);
             }
         }
         if (unchecked) {
             warnUnchecked(env.tree.pos(),
                     "unchecked.meth.invocation.applied",
                     kindName(sym),
                     sym.name,
                     rs.methodArguments(sym.type.getParameterTypes()),
                     rs.methodArguments(Type.map(argtypes, checkDeferredMap)),
                     kindName(sym.location()),
                     sym.location());
            owntype = new MethodType(owntype.getParameterTypes(),
                    types.erasure(owntype.getReturnType()),
                    types.erasure(owntype.getThrownTypes()),
                    syms.methodClass);
         }
         if (useVarargs) {
             JCTree tree = env.tree;
             Type argtype = owntype.getParameterTypes().last();
             if (!types.isReifiable(argtype) &&
                     (!allowSimplifiedVarargs ||
                     sym.attribute(syms.trustMeType.tsym) == null ||
                     !isTrustMeAllowedOnMethod(sym))) {
                 warnUnchecked(env.tree.pos(),
                                   "unchecked.generic.array.creation",
                                   argtype);
             }
             if (!((MethodSymbol)sym.baseSymbol()).isSignaturePolymorphic(types)) {
                 Type elemtype = types.elemtype(argtype);
                 switch (tree.getTag()) {
                     case APPLY:
                         ((JCMethodInvocation) tree).varargsElement = elemtype;
                         break;
                     case NEWCLASS:
                         ((JCNewClass) tree).varargsElement = elemtype;
                         break;
                     case REFERENCE:
                         ((JCMemberReference) tree).varargsElement = elemtype;
                         break;
                     default:
                         throw new AssertionError(""+tree);
                 }
             }
          }
          return owntype;
     }
     //where
         private void assertConvertible(JCTree tree, Type actual, Type formal, Warner warn) {
             if (types.isConvertible(actual, formal, warn))
                 return;
             if (formal.isCompound()
                 && types.isSubtype(actual, types.supertype(formal))
                 && types.isSubtypeUnchecked(actual, types.interfaces(formal), warn))
                 return;
         }
     /**
      * Check that type 't' is a valid instantiation of a generic class
      * (see JLS 4.5)
      *
      * @param t class type to be checked
      * @return true if 't' is well-formed
      */
     public boolean checkValidGenericType(Type t) {
         return firstIncompatibleTypeArg(t) == null;
     }
     //WHERE
         private Type firstIncompatibleTypeArg(Type type) {
             List<Type> formals = type.tsym.type.allparams();
             List<Type> actuals = type.allparams();
             List<Type> args = type.getTypeArguments();
             List<Type> forms = type.tsym.type.getTypeArguments();
             ListBuffer<Type> bounds_buf = new ListBuffer<Type>();
             // For matching pairs of actual argument types `a' and
             // formal type parameters with declared bound `b' ...
             while (args.nonEmpty() && forms.nonEmpty()) {
                 // exact type arguments needs to know their
                 // bounds (for upper and lower bound
                 // calculations).  So we create new bounds where
                 // type-parameters are replaced with actuals argument types.
                 bounds_buf.append(types.subst(forms.head.getUpperBound(), formals, actuals));
                 args = args.tail;
                 forms = forms.tail;
             }
             args = type.getTypeArguments();
             List<Type> tvars_cap = types.substBounds(formals,
                                       formals,
                                       types.capture(type).allparams());
             while (args.nonEmpty() && tvars_cap.nonEmpty()) {
                 // Let the actual arguments know their bound
                 args.head.withTypeVar((TypeVar)tvars_cap.head);
                 args = args.tail;
                 tvars_cap = tvars_cap.tail;
             }
             args = type.getTypeArguments();
             List<Type> bounds = bounds_buf.toList();
             while (args.nonEmpty() && bounds.nonEmpty()) {
                 Type actual = args.head;
                 if (!isTypeArgErroneous(actual) &&
                         !bounds.head.isErroneous() &&
                         !checkExtends(actual, bounds.head)) {
                     return args.head;
                 }
                 args = args.tail;
                 bounds = bounds.tail;
             }
             args = type.getTypeArguments();
             bounds = bounds_buf.toList();
             for (Type arg : types.capture(type).getTypeArguments()) {
                 if (arg.hasTag(TYPEVAR) &&
                         arg.getUpperBound().isErroneous() &&
                         !bounds.head.isErroneous() &&
                         !isTypeArgErroneous(args.head)) {
                     return args.head;
                 }
                 bounds = bounds.tail;
                 args = args.tail;
             }
             return null;
         }
         //where
         boolean isTypeArgErroneous(Type t) {
             return isTypeArgErroneous.visit(t);
         }
         Types.UnaryVisitor<Boolean> isTypeArgErroneous = new Types.UnaryVisitor<Boolean>() {
             public Boolean visitType(Type t, Void s) {
                 return t.isErroneous();
             }
             @Override
             public Boolean visitTypeVar(TypeVar t, Void s) {
                 return visit(t.getUpperBound());
             }
             @Override
             public Boolean visitCapturedType(CapturedType t, Void s) {
                 return visit(t.getUpperBound()) ||
                         visit(t.getLowerBound());
             }
             @Override
             public Boolean visitWildcardType(WildcardType t, Void s) {
                 return visit(t.type);
             }
         };
     /** Check that given modifiers are legal for given symbol and
      *  return modifiers together with any implicit modififiers for that symbol.
      *  Warning: we can't use flags() here since this method
      *  is called during class enter, when flags() would cause a premature
      *  completion.
      *  @param pos           Position to be used for error reporting.
      *  @param flags         The set of modifiers given in a definition.
      *  @param sym           The defined symbol.
      */
     long checkFlags(DiagnosticPosition pos, long flags, Symbol sym, JCTree tree) {
         long mask;
         long implicit = 0;
         switch (sym.kind) {
         case VAR:
             if (sym.owner.kind != TYP)
                 mask = LocalVarFlags;
             else if ((sym.owner.flags_field & INTERFACE) != 0)
                 mask = implicit = InterfaceVarFlags;
             else
                 mask = VarFlags;
             break;
         case MTH:
             if (sym.name == names.init) {
                 if ((sym.owner.flags_field & ENUM) != 0) {
                     // enum constructors cannot be declared public or
                     // protected and must be implicitly or explicitly
                     // private
                     implicit = PRIVATE;
                     mask = PRIVATE;
                 } else
                     mask = ConstructorFlags;
             }  else if ((sym.owner.flags_field & INTERFACE) != 0) {
                 if ((flags & DEFAULT) != 0) {
                     mask = InterfaceDefaultMethodMask;
                     implicit = PUBLIC | ABSTRACT;
                 } else {
                     mask = implicit = InterfaceMethodFlags;
                 }
             }
             else {
                 mask = MethodFlags;
             }
             // Imply STRICTFP if owner has STRICTFP set.
             if (((flags|implicit) & Flags.ABSTRACT) == 0)
               implicit |= sym.owner.flags_field & STRICTFP;
             break;
         case TYP:
             if (sym.isLocal()) {
                 mask = LocalClassFlags;
                 if (sym.name.isEmpty()) { // Anonymous class
                     // Anonymous classes in static methods are themselves static;
                     // that's why we admit STATIC here.
                     mask |= STATIC;
                     // JLS: Anonymous classes are final.
                     implicit |= FINAL;
                 }
                 if ((sym.owner.flags_field & STATIC) == 0 &&
                     (flags & ENUM) != 0)
                     log.error(pos, "enums.must.be.static");
             } else if (sym.owner.kind == TYP) {
                 mask = MemberClassFlags;
                 if (sym.owner.owner.kind == PCK ||
                     (sym.owner.flags_field & STATIC) != 0)
                     mask |= STATIC;
                 else if ((flags & ENUM) != 0)
                     log.error(pos, "enums.must.be.static");
                 // Nested interfaces and enums are always STATIC (Spec ???)
                 if ((flags & (INTERFACE | ENUM)) != 0 ) implicit = STATIC;
             } else {
                 mask = ClassFlags;
             }
             // Interfaces are always ABSTRACT
             if ((flags & INTERFACE) != 0) implicit |= ABSTRACT;
             if ((flags & ENUM) != 0) {
                 // enums can't be declared abstract or final
                 mask &= ~(ABSTRACT | FINAL);
                 implicit |= implicitEnumFinalFlag(tree);
             }
             // Imply STRICTFP if owner has STRICTFP set.
             implicit |= sym.owner.flags_field & STRICTFP;
             break;
         default:
             throw new AssertionError();
         }
         long illegal = flags & ExtendedStandardFlags & ~mask;
         if (illegal != 0) {
             if ((illegal & INTERFACE) != 0) {
                 log.error(pos, "intf.not.allowed.here");
                 mask |= INTERFACE;
             }
             else {
                 log.error(pos,
                           "mod.not.allowed.here", asFlagSet(illegal));
             }
         }
         else if ((sym.kind == TYP ||
                   // ISSUE: Disallowing abstract&private is no longer appropriate
                   // in the presence of inner classes. Should it be deleted here?
                   checkDisjoint(pos, flags,
                                 ABSTRACT,
                                 PRIVATE | STATIC | DEFAULT))
                  &&
                  checkDisjoint(pos, flags,
                                ABSTRACT | INTERFACE,
                                FINAL | NATIVE | SYNCHRONIZED)
                  &&
                  checkDisjoint(pos, flags,
                                PUBLIC,
                                PRIVATE | PROTECTED)
                  &&
                  checkDisjoint(pos, flags,
                                PRIVATE,
                                PUBLIC | PROTECTED)
                  &&
                  checkDisjoint(pos, flags,
                                FINAL,
                                VOLATILE)
                  &&
                  (sym.kind == TYP ||
                   checkDisjoint(pos, flags,
                                 ABSTRACT | NATIVE,
                                 STRICTFP))) {
             // skip
         }
         return flags & (mask | ~ExtendedStandardFlags) | implicit;
     }
     /** Determine if this enum should be implicitly final.
      *
      *  If the enum has no specialized enum contants, it is final.
      *
      *  If the enum does have specialized enum contants, it is
      *  <i>not</i> final.
      */
     private long implicitEnumFinalFlag(JCTree tree) {
         if (!tree.hasTag(CLASSDEF)) return 0;
         class SpecialTreeVisitor extends JCTree.Visitor {
             boolean specialized;
             SpecialTreeVisitor() {
                 this.specialized = false;
             };
             @Override
             public void visitTree(JCTree tree) { /* no-op */ }
             @Override
             public void visitVarDef(JCVariableDecl tree) {
                 if ((tree.mods.flags & ENUM) != 0) {
                     if (tree.init instanceof JCNewClass &&
                         ((JCNewClass) tree.init).def != null) {
                         specialized = true;
                     }
                 }
             }
         }
         SpecialTreeVisitor sts = new SpecialTreeVisitor();
         JCClassDecl cdef = (JCClassDecl) tree;
         for (JCTree defs: cdef.defs) {
             defs.accept(sts);
             if (sts.specialized) return 0;
         }
         return FINAL;
     }
 /* *************************************************************************
  * Type Validation
  **************************************************************************/
     /** Validate a type expression. That is,
      *  check that all type arguments of a parametric type are within
      *  their bounds. This must be done in a second phase after type attributon
      *  since a class might have a subclass as type parameter bound. E.g:
      *
      *  <pre>{@code
      *  class B<A extends C> { ... }
      *  class C extends B<C> { ... }
      *  }</pre>
      *
      *  and we can't make sure that the bound is already attributed because
      *  of possible cycles.
      *
      * Visitor method: Validate a type expression, if it is not null, catching
      *  and reporting any completion failures.
      */
     void validate(JCTree tree, Env<AttrContext> env) {
         validate(tree, env, true);
     }
     void validate(JCTree tree, Env<AttrContext> env, boolean checkRaw) {
         new Validator(env).validateTree(tree, checkRaw, true);
     }
     /** Visitor method: Validate a list of type expressions.
      */
     void validate(List<? extends JCTree> trees, Env<AttrContext> env) {
         for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
             validate(l.head, env);
     }
     /** A visitor class for type validation.
      */
     class Validator extends JCTree.Visitor {
         boolean isOuter;
         Env<AttrContext> env;
         Validator(Env<AttrContext> env) {
             this.env = env;
         }
         @Override
         public void visitTypeArray(JCArrayTypeTree tree) {
             tree.elemtype.accept(this);
         }
         @Override
         public void visitTypeApply(JCTypeApply tree) {
             if (tree.type.hasTag(CLASS)) {
                 List<JCExpression> args = tree.arguments;
                 List<Type> forms = tree.type.tsym.type.getTypeArguments();
                 Type incompatibleArg = firstIncompatibleTypeArg(tree.type);
                 if (incompatibleArg != null) {
                     for (JCTree arg : tree.arguments) {
                         if (arg.type == incompatibleArg) {
                             log.error(arg, "not.within.bounds", incompatibleArg, forms.head);
                         }
                         forms = forms.tail;
                      }
                  }
                 forms = tree.type.tsym.type.getTypeArguments();
                 boolean is_java_lang_Class = tree.type.tsym.flatName() == names.java_lang_Class;
                 // For matching pairs of actual argument types `a' and
                 // formal type parameters with declared bound `b' ...
                 while (args.nonEmpty() && forms.nonEmpty()) {
                     validateTree(args.head,
                             !(isOuter && is_java_lang_Class),
                             false);
                     args = args.tail;
                     forms = forms.tail;
                 }
                 // Check that this type is either fully parameterized, or
                 // not parameterized at all.
                 if (tree.type.getEnclosingType().isRaw())
                     log.error(tree.pos(), "improperly.formed.type.inner.raw.param");
                 if (tree.clazz.hasTag(SELECT))
                     visitSelectInternal((JCFieldAccess)tree.clazz);
             }
         }
         @Override
         public void visitTypeParameter(JCTypeParameter tree) {
             validateTrees(tree.bounds, true, isOuter);
             checkClassBounds(tree.pos(), tree.type);
         }
         @Override
         public void visitWildcard(JCWildcard tree) {
             if (tree.inner != null)
                 validateTree(tree.inner, true, isOuter);
         }
         @Override
         public void visitSelect(JCFieldAccess tree) {
             if (tree.type.hasTag(CLASS)) {
                 visitSelectInternal(tree);
                 // Check that this type is either fully parameterized, or
                 // not parameterized at all.
                 if (tree.selected.type.isParameterized() && tree.type.tsym.type.getTypeArguments().nonEmpty())
                     log.error(tree.pos(), "improperly.formed.type.param.missing");
             }
         }
         public void visitSelectInternal(JCFieldAccess tree) {
             if (tree.type.tsym.isStatic() &&
                 tree.selected.type.isParameterized()) {
                 // The enclosing type is not a class, so we are
                 // looking at a static member type.  However, the
                 // qualifying expression is parameterized.
                 log.error(tree.pos(), "cant.select.static.class.from.param.type");
             } else {
                 // otherwise validate the rest of the expression
                 tree.selected.accept(this);
             }
         }
         /** Default visitor method: do nothing.
          */
         @Override
         public void visitTree(JCTree tree) {
         }
         public void validateTree(JCTree tree, boolean checkRaw, boolean isOuter) {
             try {
                 if (tree != null) {
                     this.isOuter = isOuter;
                     tree.accept(this);
                     if (checkRaw)
                         checkRaw(tree, env);
                 }
             } catch (CompletionFailure ex) {
                 completionError(tree.pos(), ex);
             }
         }
         public void validateTrees(List<? extends JCTree> trees, boolean checkRaw, boolean isOuter) {
             for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
                 validateTree(l.head, checkRaw, isOuter);
         }
         void checkRaw(JCTree tree, Env<AttrContext> env) {
             if (lint.isEnabled(LintCategory.RAW) &&
                 tree.type.hasTag(CLASS) &&
                 !TreeInfo.isDiamond(tree) &&
                 !withinAnonConstr(env) &&
                 tree.type.isRaw()) {
                 log.warning(LintCategory.RAW,
                         tree.pos(), "raw.class.use", tree.type, tree.type.tsym.type);
             }
         }
         boolean withinAnonConstr(Env<AttrContext> env) {
             return env.enclClass.name.isEmpty() &&
                     env.enclMethod != null && env.enclMethod.name == names.init;
         }
     }
 /* *************************************************************************
  * Exception checking
  **************************************************************************/
     /* The following methods treat classes as sets that contain
      * the class itself and all their subclasses
      */
     /** Is given type a subtype of some of the types in given list?
      */
     boolean subset(Type t, List<Type> ts) {
         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
             if (types.isSubtype(t, l.head)) return true;
         return false;
     }
     /** Is given type a subtype or supertype of
      *  some of the types in given list?
      */
     boolean intersects(Type t, List<Type> ts) {
         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
             if (types.isSubtype(t, l.head) || types.isSubtype(l.head, t)) return true;
         return false;
     }
     /** Add type set to given type list, unless it is a subclass of some class
      *  in the list.
      */
     List<Type> incl(Type t, List<Type> ts) {
         return subset(t, ts) ? ts : excl(t, ts).prepend(t);
     }
     /** Remove type set from type set list.
      */
     List<Type> excl(Type t, List<Type> ts) {
         if (ts.isEmpty()) {
             return ts;
         } else {
             List<Type> ts1 = excl(t, ts.tail);
             if (types.isSubtype(ts.head, t)) return ts1;
             else if (ts1 == ts.tail) return ts;
             else return ts1.prepend(ts.head);
         }
     }
     /** Form the union of two type set lists.
      */
     List<Type> union(List<Type> ts1, List<Type> ts2) {
         List<Type> ts = ts1;
         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
             ts = incl(l.head, ts);
         return ts;
     }
     /** Form the difference of two type lists.
      */
     List<Type> diff(List<Type> ts1, List<Type> ts2) {
         List<Type> ts = ts1;
         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
             ts = excl(l.head, ts);
         return ts;
     }
     /** Form the intersection of two type lists.
      */
     public List<Type> intersect(List<Type> ts1, List<Type> ts2) {
         List<Type> ts = List.nil();
         for (List<Type> l = ts1; l.nonEmpty(); l = l.tail)
             if (subset(l.head, ts2)) ts = incl(l.head, ts);
         for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
             if (subset(l.head, ts1)) ts = incl(l.head, ts);
         return ts;
     }
     /** Is exc an exception symbol that need not be declared?
      */
     boolean isUnchecked(ClassSymbol exc) {
         return
             exc.kind == ERR ||
             exc.isSubClass(syms.errorType.tsym, types) ||
             exc.isSubClass(syms.runtimeExceptionType.tsym, types);
     }
     /** Is exc an exception type that need not be declared?
      */
     boolean isUnchecked(Type exc) {
         return
             (exc.hasTag(TYPEVAR)) ? isUnchecked(types.supertype(exc)) :
             (exc.hasTag(CLASS)) ? isUnchecked((ClassSymbol)exc.tsym) :
             exc.hasTag(BOT);
     }
     /** Same, but handling completion failures.
      */
     boolean isUnchecked(DiagnosticPosition pos, Type exc) {
         try {
             return isUnchecked(exc);
         } catch (CompletionFailure ex) {
             completionError(pos, ex);
             return true;
         }
     }
     /** Is exc handled by given exception list?
      */
     boolean isHandled(Type exc, List<Type> handled) {
         return isUnchecked(exc) || subset(exc, handled);
     }
     /** Return all exceptions in thrown list that are not in handled list.
      *  @param thrown     The list of thrown exceptions.
      *  @param handled    The list of handled exceptions.
      */
     List<Type> unhandled(List<Type> thrown, List<Type> handled) {
         List<Type> unhandled = List.nil();
         for (List<Type> l = thrown; l.nonEmpty(); l = l.tail)
             if (!isHandled(l.head, handled)) unhandled = unhandled.prepend(l.head);
         return unhandled;
     }
 /* *************************************************************************
  * Overriding/Implementation checking
  **************************************************************************/
     /** The level of access protection given by a flag set,
      *  where PRIVATE is highest and PUBLIC is lowest.
      */
     static int protection(long flags) {
         switch ((short)(flags & AccessFlags)) {
         case PRIVATE: return 3;
         case PROTECTED: return 1;
         default:
         case PUBLIC: return 0;
         case 0: return 2;
         }
     }
     /** A customized "cannot override" error message.
      *  @param m      The overriding method.
      *  @param other  The overridden method.
      *  @return       An internationalized string.
      */
     Object cannotOverride(MethodSymbol m, MethodSymbol other) {
         String key;
         if ((other.owner.flags() & INTERFACE) == 0)
             key = "cant.override";
         else if ((m.owner.flags() & INTERFACE) == 0)
             key = "cant.implement";
         else
             key = "clashes.with";
         return diags.fragment(key, m, m.location(), other, other.location());
     }
     /** A customized "override" warning message.
      *  @param m      The overriding method.
      *  @param other  The overridden method.
      *  @return       An internationalized string.
      */
     Object uncheckedOverrides(MethodSymbol m, MethodSymbol other) {
         String key;
         if ((other.owner.flags() & INTERFACE) == 0)
             key = "unchecked.override";
         else if ((m.owner.flags() & INTERFACE) == 0)
             key = "unchecked.implement";
         else
             key = "unchecked.clash.with";
         return diags.fragment(key, m, m.location(), other, other.location());
     }
     /** A customized "override" warning message.
      *  @param m      The overriding method.
      *  @param other  The overridden method.
      *  @return       An internationalized string.
      */
     Object varargsOverrides(MethodSymbol m, MethodSymbol other) {
         String key;
         if ((other.owner.flags() & INTERFACE) == 0)
             key = "varargs.override";
         else  if ((m.owner.flags() & INTERFACE) == 0)
             key = "varargs.implement";
         else
             key = "varargs.clash.with";
         return diags.fragment(key, m, m.location(), other, other.location());
     }
     /** Check that this method conforms with overridden method 'other'.
      *  where `origin' is the class where checking started.
      *  Complications:
      *  (1) Do not check overriding of synthetic methods
      *      (reason: they might be final).
      *      todo: check whether this is still necessary.
      *  (2) Admit the case where an interface proxy throws fewer exceptions
      *      than the method it implements. Augment the proxy methods with the
      *      undeclared exceptions in this case.
      *  (3) When generics are enabled, admit the case where an interface proxy
      *      has a result type
      *      extended by the result type of the method it implements.
      *      Change the proxies result type to the smaller type in this case.
      *
      *  @param tree         The tree from which positions
      *                      are extracted for errors.
      *  @param m            The overriding method.
      *  @param other        The overridden method.
      *  @param origin       The class of which the overriding method
      *                      is a member.
      */
     void checkOverride(JCTree tree,
                        MethodSymbol m,
                        MethodSymbol other,
                        ClassSymbol origin) {
         // Don't check overriding of synthetic methods or by bridge methods.
         if ((m.flags() & (SYNTHETIC|BRIDGE)) != 0 || (other.flags() & SYNTHETIC) != 0) {
             return;
         }
         // Error if static method overrides instance method (JLS 8.4.6.2).
         if ((m.flags() & STATIC) != 0 &&
                    (other.flags() & STATIC) == 0) {
             log.error(TreeInfo.diagnosticPositionFor(m, tree), "override.static",
                       cannotOverride(m, other));
             return;
         }
         // Error if instance method overrides static or final
         // method (JLS 8.4.6.1).
         if ((other.flags() & FINAL) != 0 ||
                  (m.flags() & STATIC) == 0 &&
                  (other.flags() & STATIC) != 0) {
             log.error(TreeInfo.diagnosticPositionFor(m, tree), "override.meth",
                       cannotOverride(m, other),
                       asFlagSet(other.flags() & (FINAL | STATIC)));
             return;
         }
         if ((m.owner.flags() & ANNOTATION) != 0) {
             // handled in validateAnnotationMethod
             return;
         }
         // Error if overriding method has weaker access (JLS 8.4.6.3).
         if ((origin.flags() & INTERFACE) == 0 &&
                  protection(m.flags()) > protection(other.flags())) {
             log.error(TreeInfo.diagnosticPositionFor(m, tree), "override.weaker.access",
                       cannotOverride(m, other),
                       other.flags() == 0 ?
                           Flag.PACKAGE :
                           asFlagSet(other.flags() & AccessFlags));
             return;
         }
         Type mt = types.memberType(origin.type, m);
         Type ot = types.memberType(origin.type, other);
         // Error if overriding result type is different
         // (or, in the case of generics mode, not a subtype) of
         // overridden result type. We have to rename any type parameters
         // before comparing types.
         List<Type> mtvars = mt.getTypeArguments();
         List<Type> otvars = ot.getTypeArguments();
         Type mtres = mt.getReturnType();
         Type otres = types.subst(ot.getReturnType(), otvars, mtvars);
         overrideWarner.clear();
         boolean resultTypesOK =
             types.returnTypeSubstitutable(mt, ot, otres, overrideWarner);
         if (!resultTypesOK) {
             if (!allowCovariantReturns &&
                 m.owner != origin &&
                 m.owner.isSubClass(other.owner, types)) {
                 // allow limited interoperability with covariant returns
             } else {
                 log.error(TreeInfo.diagnosticPositionFor(m, tree),
                           "override.incompatible.ret",
                           cannotOverride(m, other),
                           mtres, otres);
                 return;
             }
         } else if (overrideWarner.hasNonSilentLint(LintCategory.UNCHECKED)) {
             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
                     "override.unchecked.ret",
                     uncheckedOverrides(m, other),
                     mtres, otres);
         }
         // Error if overriding method throws an exception not reported
         // by overridden method.
         List<Type> otthrown = types.subst(ot.getThrownTypes(), otvars, mtvars);
         List<Type> unhandledErased = unhandled(mt.getThrownTypes(), types.erasure(otthrown));
         List<Type> unhandledUnerased = unhandled(mt.getThrownTypes(), otthrown);
         if (unhandledErased.nonEmpty()) {
             log.error(TreeInfo.diagnosticPositionFor(m, tree),
                       "override.meth.doesnt.throw",
                       cannotOverride(m, other),
                       unhandledUnerased.head);
             return;
         }
         else if (unhandledUnerased.nonEmpty()) {
             warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
                           "override.unchecked.thrown",
                          cannotOverride(m, other),
                          unhandledUnerased.head);
             return;
         }
         // Optional warning if varargs don't agree
         if ((((m.flags() ^ other.flags()) & Flags.VARARGS) != 0)
             && lint.isEnabled(LintCategory.OVERRIDES)) {
             log.warning(TreeInfo.diagnosticPositionFor(m, tree),
                         ((m.flags() & Flags.VARARGS) != 0)
                         ? "override.varargs.missing"
                         : "override.varargs.extra",
                         varargsOverrides(m, other));
         }
         // Warn if instance method overrides bridge method (compiler spec ??)
         if ((other.flags() & BRIDGE) != 0) {
             log.warning(TreeInfo.diagnosticPositionFor(m, tree), "override.bridge",
                         uncheckedOverrides(m, other));
         }
         // Warn if a deprecated method overridden by a non-deprecated one.
         if (!isDeprecatedOverrideIgnorable(other, origin)) {
             checkDeprecated(TreeInfo.diagnosticPositionFor(m, tree), m, other);
         }
     }
     // where
         private boolean isDeprecatedOverrideIgnorable(MethodSymbol m, ClassSymbol origin) {
             // If the method, m, is defined in an interface, then ignore the issue if the method
             // is only inherited via a supertype and also implemented in the supertype,
             // because in that case, we will rediscover the issue when examining the method
             // in the supertype.
             // If the method, m, is not defined in an interface, then the only time we need to
             // address the issue is when the method is the supertype implemementation: any other
             // case, we will have dealt with when examining the supertype classes
             ClassSymbol mc = m.enclClass();
             Type st = types.supertype(origin.type);
             if (!st.hasTag(CLASS))
                 return true;
             MethodSymbol stimpl = m.implementation((ClassSymbol)st.tsym, types, false);
             if (mc != null && ((mc.flags() & INTERFACE) != 0)) {
                 List<Type> intfs = types.interfaces(origin.type);
                 return (intfs.contains(mc.type) ? false : (stimpl != null));
             }
             else
                 return (stimpl != m);
         }
     // used to check if there were any unchecked conversions
     Warner overrideWarner = new Warner();
     /** Check that a class does not inherit two concrete methods
      *  with the same signature.
      *  @param pos          Position to be used for error reporting.
      *  @param site         The class type to be checked.
      */
     public void checkCompatibleConcretes(DiagnosticPosition pos, Type site) {
         Type sup = types.supertype(site);
         if (!sup.hasTag(CLASS)) return;
         for (Type t1 = sup;
              t1.tsym.type.isParameterized();
              t1 = types.supertype(t1)) {
             for (Scope.Entry e1 = t1.tsym.members().elems;
                  e1 != null;
                  e1 = e1.sibling) {
                 Symbol s1 = e1.sym;
                 if (s1.kind != MTH ||
                     (s1.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
                     !s1.isInheritedIn(site.tsym, types) ||
                     ((MethodSymbol)s1).implementation(site.tsym,
                                                       types,
                                                       true) != s1)
                     continue;
                 Type st1 = types.memberType(t1, s1);
                 int s1ArgsLength = st1.getParameterTypes().length();
                 if (st1 == s1.type) continue;
                 for (Type t2 = sup;
                      t2.hasTag(CLASS);
                      t2 = types.supertype(t2)) {
                     for (Scope.Entry e2 = t2.tsym.members().lookup(s1.name);
                          e2.scope != null;
                          e2 = e2.next()) {
                         Symbol s2 = e2.sym;
                         if (s2 == s1 ||
                             s2.kind != MTH ||
                             (s2.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
                             s2.type.getParameterTypes().length() != s1ArgsLength ||
                             !s2.isInheritedIn(site.tsym, types) ||
                             ((MethodSymbol)s2).implementation(site.tsym,
                                                               types,
                                                               true) != s2)
                             continue;
                         Type st2 = types.memberType(t2, s2);
                         if (types.overrideEquivalent(st1, st2))
                             log.error(pos, "concrete.inheritance.conflict",
                                       s1, t1, s2, t2, sup);
                     }
                 }
             }
         }
     }
     /** Check that classes (or interfaces) do not each define an abstract
      *  method with same name and arguments but incompatible return types.
      *  @param pos          Position to be used for error reporting.
      *  @param t1           The first argument type.
      *  @param t2           The second argument type.
      */
     public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
                                             Type t1,
                                             Type t2) {
         return checkCompatibleAbstracts(pos, t1, t2,
                                         types.makeCompoundType(t1, t2));
     }
     public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
                                             Type t1,
                                             Type t2,
                                             Type site) {
         return firstIncompatibility(pos, t1, t2, site) == null;
     }
     /** Return the first method which is defined with same args
      *  but different return types in two given interfaces, or null if none
      *  exists.
      *  @param t1     The first type.
      *  @param t2     The second type.
      *  @param site   The most derived type.
      *  @returns symbol from t2 that conflicts with one in t1.
      */
     private Symbol firstIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
         Map<TypeSymbol,Type> interfaces1 = new HashMap<TypeSymbol,Type>();
         closure(t1, interfaces1);
         Map<TypeSymbol,Type> interfaces2;
         if (t1 == t2)
             interfaces2 = interfaces1;
         else
             closure(t2, interfaces1, interfaces2 = new HashMap<TypeSymbol,Type>());
         for (Type t3 : interfaces1.values()) {
             for (Type t4 : interfaces2.values()) {
                 Symbol s = firstDirectIncompatibility(pos, t3, t4, site);
                 if (s != null) return s;
             }
         }
         return null;
     }
     /** Compute all the supertypes of t, indexed by type symbol. */
     private void closure(Type t, Map<TypeSymbol,Type> typeMap) {
         if (!t.hasTag(CLASS)) return;
         if (typeMap.put(t.tsym, t) == null) {
             closure(types.supertype(t), typeMap);
             for (Type i : types.interfaces(t))
                 closure(i, typeMap);
         }
     }
     /** Compute all the supertypes of t, indexed by type symbol (except thise in typesSkip). */
     private void closure(Type t, Map<TypeSymbol,Type> typesSkip, Map<TypeSymbol,Type> typeMap) {
         if (!t.hasTag(CLASS)) return;
         if (typesSkip.get(t.tsym) != null) return;
         if (typeMap.put(t.tsym, t) == null) {
             closure(types.supertype(t), typesSkip, typeMap);
             for (Type i : types.interfaces(t))
                 closure(i, typesSkip, typeMap);
         }
     }
     /** Return the first method in t2 that conflicts with a method from t1. */
     private Symbol firstDirectIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
         for (Scope.Entry e1 = t1.tsym.members().elems; e1 != null; e1 = e1.sibling) {
             Symbol s1 = e1.sym;
             Type st1 = null;
             if (s1.kind != MTH || !s1.isInheritedIn(site.tsym, types) ||
                     (s1.flags() & SYNTHETIC) != 0) continue;
             Symbol impl = ((MethodSymbol)s1).implementation(site.tsym, types, false);
             if (impl != null && (impl.flags() & ABSTRACT) == 0) continue;
             for (Scope.Entry e2 = t2.tsym.members().lookup(s1.name); e2.scope != null; e2 = e2.next()) {
                 Symbol s2 = e2.sym;
                 if (s1 == s2) continue;
                 if (s2.kind != MTH || !s2.isInheritedIn(site.tsym, types) ||
                         (s2.flags() & SYNTHETIC) != 0) continue;
                 if (st1 == null) st1 = types.memberType(t1, s1);
                 Type st2 = types.memberType(t2, s2);
                 if (types.overrideEquivalent(st1, st2)) {
                     List<Type> tvars1 = st1.getTypeArguments();
                     List<Type> tvars2 = st2.getTypeArguments();
                     Type rt1 = st1.getReturnType();
                     Type rt2 = types.subst(st2.getReturnType(), tvars2, tvars1);
                     boolean compat =
                         types.isSameType(rt1, rt2) ||
                         !rt1.isPrimitiveOrVoid() &&
                         !rt2.isPrimitiveOrVoid() &&
                         (types.covariantReturnType(rt1, rt2, types.noWarnings) ||
                          types.covariantReturnType(rt2, rt1, types.noWarnings)) ||
                          checkCommonOverriderIn(s1,s2,site);
                     if (!compat) {
                         log.error(pos, "types.incompatible.diff.ret",
                             t1, t2, s2.name +
                             "(" + types.memberType(t2, s2).getParameterTypes() + ")");
                         return s2;
                     }
                 } else if (checkNameClash((ClassSymbol)site.tsym, s1, s2) &&
                         !checkCommonOverriderIn(s1, s2, site)) {
                     log.error(pos,
                             "name.clash.same.erasure.no.override",
                             s1, s1.location(),
                             s2, s2.location());
                     return s2;
                 }
             }
         }
         return null;
     }
     //WHERE
     boolean checkCommonOverriderIn(Symbol s1, Symbol s2, Type site) {
         Map<TypeSymbol,Type> supertypes = new HashMap<TypeSymbol,Type>();
         Type st1 = types.memberType(site, s1);
         Type st2 = types.memberType(site, s2);
         closure(site, supertypes);
         for (Type t : supertypes.values()) {
             for (Scope.Entry e = t.tsym.members().lookup(s1.name); e.scope != null; e = e.next()) {
                 Symbol s3 = e.sym;
                 if (s3 == s1 || s3 == s2 || s3.kind != MTH || (s3.flags() & (BRIDGE|SYNTHETIC)) != 0) continue;
                 Type st3 = types.memberType(site,s3);
                 if (types.overrideEquivalent(st3, st1) && types.overrideEquivalent(st3, st2)) {
                     if (s3.owner == site.tsym) {
                         return true;
                     }
                     List<Type> tvars1 = st1.getTypeArguments();
                     List<Type> tvars2 = st2.getTypeArguments();
                     List<Type> tvars3 = st3.getTypeArguments();
                     Type rt1 = st1.getReturnType();
                     Type rt2 = st2.getReturnType();
                     Type rt13 = types.subst(st3.getReturnType(), tvars3, tvars1);
                     Type rt23 = types.subst(st3.getReturnType(), tvars3, tvars2);
                     boolean compat =
                         !rt13.isPrimitiveOrVoid() &&
                         !rt23.isPrimitiveOrVoid() &&
                         (types.covariantReturnType(rt13, rt1, types.noWarnings) &&
                          types.covariantReturnType(rt23, rt2, types.noWarnings));
                     if (compat)
                         return true;
                 }
             }
         }
         return false;
     }
     /** Check that a given method conforms with any method it overrides.
      *  @param tree         The tree from which positions are extracted
      *                      for errors.
      *  @param m            The overriding method.
      */
     void checkOverride(JCTree tree, MethodSymbol m) {
         ClassSymbol origin = (ClassSymbol)m.owner;
         if ((origin.flags() & ENUM) != 0 && names.finalize.equals(m.name))
             if (m.overrides(syms.enumFinalFinalize, origin, types, false)) {
                 log.error(tree.pos(), "enum.no.finalize");
                 return;
             }
         for (Type t = origin.type; t.hasTag(CLASS);
              t = types.supertype(t)) {
             if (t != origin.type) {
                 checkOverride(tree, t, origin, m);
             }
             for (Type t2 : types.interfaces(t)) {
                 checkOverride(tree, t2, origin, m);
             }
         }
     }
     void checkOverride(JCTree tree, Type site, ClassSymbol origin, MethodSymbol m) {
         TypeSymbol c = site.tsym;
         Scope.Entry e = c.members().lookup(m.name);
         while (e.scope != null) {
             if (m.overrides(e.sym, origin, types, false)) {
                 if ((e.sym.flags() & ABSTRACT) == 0) {
                     checkOverride(tree, m, (MethodSymbol)e.sym, origin);
                 }
             }
             e = e.next();
         }
     }
     private boolean checkNameClash(ClassSymbol origin, Symbol s1, Symbol s2) {
         ClashFilter cf = new ClashFilter(origin.type);
         return (cf.accepts(s1) &&
                 cf.accepts(s2) &&
                 types.hasSameArgs(s1.erasure(types), s2.erasure(types)));
     }
     /** Check that all abstract members of given class have definitions.
      *  @param pos          Position to be used for error reporting.
      *  @param c            The class.
      */
     void checkAllDefined(DiagnosticPosition pos, ClassSymbol c) {
         try {
             MethodSymbol undef = firstUndef(c, c);
             if (undef != null) {
                 if ((c.flags() & ENUM) != 0 &&
                     types.supertype(c.type).tsym == syms.enumSym &&
                     (c.flags() & FINAL) == 0) {
                     // add the ABSTRACT flag to an enum
                     c.flags_field |= ABSTRACT;
                 } else {
                     MethodSymbol undef1 =
                         new MethodSymbol(undef.flags(), undef.name,
                                          types.memberType(c.type, undef), undef.owner);
                     log.error(pos, "does.not.override.abstract",
                               c, undef1, undef1.location());
                 }
             }
         } catch (CompletionFailure ex) {
             completionError(pos, ex);
         }
     }
 //where
         /** Return first abstract member of class `c' that is not defined
          *  in `impl', null if there is none.
          */
         private MethodSymbol firstUndef(ClassSymbol impl, ClassSymbol c) {
             MethodSymbol undef = null;
             // Do not bother to search in classes that are not abstract,
             // since they cannot have abstract members.
             if (c == impl || (c.flags() & (ABSTRACT | INTERFACE)) != 0) {
                 Scope s = c.members();
                 for (Scope.Entry e = s.elems;
                      undef == null && e != null;
                      e = e.sibling) {
                     if (e.sym.kind == MTH &&
                         (e.sym.flags() & (ABSTRACT|IPROXY|DEFAULT)) == ABSTRACT) {
                         MethodSymbol absmeth = (MethodSymbol)e.sym;
                         MethodSymbol implmeth = absmeth.implementation(impl, types, true);
                         if (implmeth == null || implmeth == absmeth) {
                             //look for default implementations
                             if (allowDefaultMethods) {
                                 MethodSymbol prov = types.interfaceCandidates(impl.type, absmeth).head;
                                 if (prov != null && prov.overrides(absmeth, impl, types, true)) {
                                     implmeth = prov;
                                 }
                             }
                         }
                         if (implmeth == null || implmeth == absmeth) {
                             undef = absmeth;
                         }
                     }
                 }
                 if (undef == null) {
                     Type st = types.supertype(c.type);
                     if (st.hasTag(CLASS))
                         undef = firstUndef(impl, (ClassSymbol)st.tsym);
                 }
                 for (List<Type> l = types.interfaces(c.type);
                      undef == null && l.nonEmpty();
                      l = l.tail) {
                     undef = firstUndef(impl, (ClassSymbol)l.head.tsym);
                 }
             }
             return undef;
         }
     void checkNonCyclicDecl(JCClassDecl tree) {
         CycleChecker cc = new CycleChecker();
         cc.scan(tree);
         if (!cc.errorFound && !cc.partialCheck) {
             tree.sym.flags_field |= ACYCLIC;
         }
     }
     class CycleChecker extends TreeScanner {
         List<Symbol> seenClasses = List.nil();
         boolean errorFound = false;
         boolean partialCheck = false;
         private void checkSymbol(DiagnosticPosition pos, Symbol sym) {
             if (sym != null && sym.kind == TYP) {
                 Env<AttrContext> classEnv = enter.getEnv((TypeSymbol)sym);
                 if (classEnv != null) {
                     DiagnosticSource prevSource = log.currentSource();
                     try {
                         log.useSource(classEnv.toplevel.sourcefile);
                         scan(classEnv.tree);
                     }
                     finally {
                         log.useSource(prevSource.getFile());
                     }
                 } else if (sym.kind == TYP) {
                     checkClass(pos, sym, List.<JCTree>nil());
                 }
             } else {
                 //not completed yet
                 partialCheck = true;
             }
         }
         @Override
         public void visitSelect(JCFieldAccess tree) {
             super.visitSelect(tree);
             checkSymbol(tree.pos(), tree.sym);
         }
         @Override
         public void visitIdent(JCIdent tree) {
             checkSymbol(tree.pos(), tree.sym);
         }
         @Override
         public void visitTypeApply(JCTypeApply tree) {
             scan(tree.clazz);
         }
         @Override
         public void visitTypeArray(JCArrayTypeTree tree) {
             scan(tree.elemtype);
         }
         @Override
         public void visitClassDef(JCClassDecl tree) {
             List<JCTree> supertypes = List.nil();
             if (tree.getExtendsClause() != null) {
                 supertypes = supertypes.prepend(tree.getExtendsClause());
             }
             if (tree.getImplementsClause() != null) {
                 for (JCTree intf : tree.getImplementsClause()) {
                     supertypes = supertypes.prepend(intf);
                 }
             }
             checkClass(tree.pos(), tree.sym, supertypes);
         }
         void checkClass(DiagnosticPosition pos, Symbol c, List<JCTree> supertypes) {
             if ((c.flags_field & ACYCLIC) != 0)
                 return;
             if (seenClasses.contains(c)) {
                 errorFound = true;
                 noteCyclic(pos, (ClassSymbol)c);
             } else if (!c.type.isErroneous()) {
                 try {
                     seenClasses = seenClasses.prepend(c);
                     if (c.type.hasTag(CLASS)) {
                         if (supertypes.nonEmpty()) {
                             scan(supertypes);
                         }
                         else {
                             ClassType ct = (ClassType)c.type;
                             if (ct.supertype_field == null ||
                                     ct.interfaces_field == null) {
                                 //not completed yet
                                 partialCheck = true;
                                 return;
                             }
                             checkSymbol(pos, ct.supertype_field.tsym);
                             for (Type intf : ct.interfaces_field) {
                                 checkSymbol(pos, intf.tsym);
                             }
                         }
                         if (c.owner.kind == TYP) {
                             checkSymbol(pos, c.owner);
                         }
                     }
                 } finally {
                     seenClasses = seenClasses.tail;
                 }
             }
         }
     }
     /** Check for cyclic references. Issue an error if the
      *  symbol of the type referred to has a LOCKED flag set.
      *
      *  @param pos      Position to be used for error reporting.
      *  @param t        The type referred to.
      */
     void checkNonCyclic(DiagnosticPosition pos, Type t) {
         checkNonCyclicInternal(pos, t);
     }
     void checkNonCyclic(DiagnosticPosition pos, TypeVar t) {
         checkNonCyclic1(pos, t, List.<TypeVar>nil());
     }
     private void checkNonCyclic1(DiagnosticPosition pos, Type t, List<TypeVar> seen) {
         final TypeVar tv;
         if  (t.hasTag(TYPEVAR) && (t.tsym.flags() & UNATTRIBUTED) != 0)
             return;
         if (seen.contains(t)) {
             tv = (TypeVar)t;
             tv.bound = types.createErrorType(t);
             log.error(pos, "cyclic.inheritance", t);
         } else if (t.hasTag(TYPEVAR)) {
             tv = (TypeVar)t;
             seen = seen.prepend(tv);
             for (Type b : types.getBounds(tv))
                 checkNonCyclic1(pos, b, seen);
         }
     }
     /** Check for cyclic references. Issue an error if the
      *  symbol of the type referred to has a LOCKED flag set.
      *
      *  @param pos      Position to be used for error reporting.
      *  @param t        The type referred to.
      *  @returns        True if the check completed on all attributed classes
      */
     private boolean checkNonCyclicInternal(DiagnosticPosition pos, Type t) {
         boolean complete = true; // was the check complete?
         //- System.err.println("checkNonCyclicInternal("+t+");");//DEBUG
         Symbol c = t.tsym;
         if ((c.flags_field & ACYCLIC) != 0) return true;
         if ((c.flags_field & LOCKED) != 0) {
             noteCyclic(pos, (ClassSymbol)c);
         } else if (!c.type.isErroneous()) {
             try {
                 c.flags_field |= LOCKED;
                 if (c.type.hasTag(CLASS)) {
                     ClassType clazz = (ClassType)c.type;
                     if (clazz.interfaces_field != null)
                         for (List<Type> l=clazz.interfaces_field; l.nonEmpty(); l=l.tail)
                             complete &= checkNonCyclicInternal(pos, l.head);
                     if (clazz.supertype_field != null) {
                         Type st = clazz.supertype_field;
                         if (st != null && st.hasTag(CLASS))
                             complete &= checkNonCyclicInternal(pos, st);
                     }
                     if (c.owner.kind == TYP)
                         complete &= checkNonCyclicInternal(pos, c.owner.type);
                 }
             } finally {
                 c.flags_field &= ~LOCKED;
             }
         }
         if (complete)
             complete = ((c.flags_field & UNATTRIBUTED) == 0) && c.completer == null;
         if (complete) c.flags_field |= ACYCLIC;
         return complete;
     }
     /** Note that we found an inheritance cycle. */
     private void noteCyclic(DiagnosticPosition pos, ClassSymbol c) {
         log.error(pos, "cyclic.inheritance", c);
         for (List<Type> l=types.interfaces(c.type); l.nonEmpty(); l=l.tail)
             l.head = types.createErrorType((ClassSymbol)l.head.tsym, Type.noType);
         Type st = types.supertype(c.type);
         if (st.hasTag(CLASS))
             ((ClassType)c.type).supertype_field = types.createErrorType((ClassSymbol)st.tsym, Type.noType);
         c.type = types.createErrorType(c, c.type);
         c.flags_field |= ACYCLIC;
     }
     /**
      * Check that functional interface methods would make sense when seen
      * from the perspective of the implementing class
      */
     void checkFunctionalInterface(JCTree tree, Type funcInterface) {
         ClassType c = new ClassType(Type.noType, List.<Type>nil(), null);
         ClassSymbol csym = new ClassSymbol(0, names.empty, c, syms.noSymbol);
         c.interfaces_field = List.of(funcInterface);
         c.supertype_field = syms.objectType;
         c.tsym = csym;
         csym.members_field = new Scope(csym);
         csym.completer = null;
         checkImplementations(tree, csym, csym);
     }
     /** Check that all methods which implement some
      *  method conform to the method they implement.
      *  @param tree         The class definition whose members are checked.
      */
     void checkImplementations(JCClassDecl tree) {
         checkImplementations(tree, tree.sym, tree.sym);
     }
 //where
         /** Check that all methods which implement some
          *  method in `ic' conform to the method they implement.
          */
         void checkImplementations(JCTree tree, ClassSymbol origin, ClassSymbol ic) {
             for (List<Type> l = types.closure(ic.type); l.nonEmpty(); l = l.tail) {
                 ClassSymbol lc = (ClassSymbol)l.head.tsym;
                 if ((allowGenerics || origin != lc) && (lc.flags() & ABSTRACT) != 0) {
                     for (Scope.Entry e=lc.members().elems; e != null; e=e.sibling) {
                         if (e.sym.kind == MTH &&
                             (e.sym.flags() & (STATIC|ABSTRACT)) == ABSTRACT) {
                             MethodSymbol absmeth = (MethodSymbol)e.sym;
                             MethodSymbol implmeth = absmeth.implementation(origin, types, false);
                             if (implmeth != null && implmeth != absmeth &&
                                 (implmeth.owner.flags() & INTERFACE) ==
                                 (origin.flags() & INTERFACE)) {
                                 // don't check if implmeth is in a class, yet
                                 // origin is an interface. This case arises only
                                 // if implmeth is declared in Object. The reason is
                                 // that interfaces really don't inherit from
                                 // Object it's just that the compiler represents
                                 // things that way.
                                 checkOverride(tree, implmeth, absmeth, origin);
                             }
                         }
                     }
                 }
             }
         }
     /** Check that all abstract methods implemented by a class are
      *  mutually compatible.
      *  @param pos          Position to be used for error reporting.
      *  @param c            The class whose interfaces are checked.
      */
     void checkCompatibleSupertypes(DiagnosticPosition pos, Type c) {
         List<Type> supertypes = types.interfaces(c);
         Type supertype = types.supertype(c);
         if (supertype.hasTag(CLASS) &&
             (supertype.tsym.flags() & ABSTRACT) != 0)
             supertypes = supertypes.prepend(supertype);
         for (List<Type> l = supertypes; l.nonEmpty(); l = l.tail) {
             if (allowGenerics && !l.head.getTypeArguments().isEmpty() &&
                 !checkCompatibleAbstracts(pos, l.head, l.head, c))
                 return;
             for (List<Type> m = supertypes; m != l; m = m.tail)
                 if (!checkCompatibleAbstracts(pos, l.head, m.head, c))
                     return;
         }
         checkCompatibleConcretes(pos, c);
     }
     void checkConflicts(DiagnosticPosition pos, Symbol sym, TypeSymbol c) {
         for (Type ct = c.type; ct != Type.noType ; ct = types.supertype(ct)) {
             for (Scope.Entry e = ct.tsym.members().lookup(sym.name); e.scope == ct.tsym.members(); e = e.next()) {
                 // VM allows methods and variables with differing types
                 if (sym.kind == e.sym.kind &&
                     types.isSameType(types.erasure(sym.type), types.erasure(e.sym.type)) &&
                     sym != e.sym &&
                     (sym.flags() & Flags.SYNTHETIC) != (e.sym.flags() & Flags.SYNTHETIC) &&
                     (sym.flags() & IPROXY) == 0 && (e.sym.flags() & IPROXY) == 0 &&
                     (sym.flags() & BRIDGE) == 0 && (e.sym.flags() & BRIDGE) == 0) {
                     syntheticError(pos, (e.sym.flags() & SYNTHETIC) == 0 ? e.sym : sym);
                     return;
                 }
             }
         }
     }
     /** Check that all non-override equivalent methods accessible from 'site'
      *  are mutually compatible (JLS 8.4.8/9.4.1).
      *
      *  @param pos  Position to be used for error reporting.
      *  @param site The class whose methods are checked.
      *  @param sym  The method symbol to be checked.
      */
     void checkOverrideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
          ClashFilter cf = new ClashFilter(site);
         //for each method m1 that is overridden (directly or indirectly)
         //by method 'sym' in 'site'...
         for (Symbol m1 : types.membersClosure(site, false).getElementsByName(sym.name, cf)) {
             if (!sym.overrides(m1, site.tsym, types, false)) continue;
              //...check each method m2 that is a member of 'site'
              for (Symbol m2 : types.membersClosure(site, false).getElementsByName(sym.name, cf)) {
                 if (m2 == m1) continue;
                 //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
                 //a member of 'site') and (ii) m1 has the same erasure as m2, issue an error
                 if (!types.isSubSignature(sym.type, types.memberType(site, m2), allowStrictMethodClashCheck) &&
                         types.hasSameArgs(m2.erasure(types), m1.erasure(types))) {
                     sym.flags_field |= CLASH;
                     String key = m1 == sym ?
                             "name.clash.same.erasure.no.override" :
                             "name.clash.same.erasure.no.override.1";
                     log.error(pos,
                             key,
                             sym, sym.location(),
                             m2, m2.location(),
                             m1, m1.location());
                     return;
                 }
             }
         }
     }
     /** Check that all static methods accessible from 'site' are
      *  mutually compatible (JLS 8.4.8).
      *
      *  @param pos  Position to be used for error reporting.
      *  @param site The class whose methods are checked.
      *  @param sym  The method symbol to be checked.
      */
     void checkHideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
         ClashFilter cf = new ClashFilter(site);
         //for each method m1 that is a member of 'site'...
         for (Symbol s : types.membersClosure(site, true).getElementsByName(sym.name, cf)) {
             //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
             //a member of 'site') and (ii) 'sym' has the same erasure as m1, issue an error
             if (!types.isSubSignature(sym.type, types.memberType(site, s), allowStrictMethodClashCheck) &&
                     types.hasSameArgs(s.erasure(types), sym.erasure(types))) {
                 log.error(pos,
                         "name.clash.same.erasure.no.hide",
                         sym, sym.location(),
                         s, s.location());
                 return;
              }
          }
      }
      //where
      private class ClashFilter implements Filter<Symbol> {
          Type site;
          ClashFilter(Type site) {
              this.site = site;
          }
          boolean shouldSkip(Symbol s) {
              return (s.flags() & CLASH) != 0 &&
                 s.owner == site.tsym;
          }
          public boolean accepts(Symbol s) {
              return s.kind == MTH &&
                      (s.flags() & SYNTHETIC) == 0 &&
                      !shouldSkip(s) &&
                      s.isInheritedIn(site.tsym, types) &&
                      !s.isConstructor();
          }
      }
     void checkDefaultMethodClashes(DiagnosticPosition pos, Type site) {
         DefaultMethodClashFilter dcf = new DefaultMethodClashFilter(site);
         for (Symbol m : types.membersClosure(site, false).getElements(dcf)) {
             Assert.check(m.kind == MTH);
             List<MethodSymbol> prov = types.interfaceCandidates(site, (MethodSymbol)m);
             if (prov.size() > 1) {
                 ListBuffer<Symbol> abstracts = ListBuffer.lb();
                 ListBuffer<Symbol> defaults = ListBuffer.lb();
                 for (MethodSymbol provSym : prov) {
                     if ((provSym.flags() & DEFAULT) != 0) {
                         defaults = defaults.append(provSym);
                     } else if ((provSym.flags() & ABSTRACT) != 0) {
                         abstracts = abstracts.append(provSym);
                     }
                     if (defaults.nonEmpty() && defaults.size() + abstracts.size() >= 2) {
                         //strong semantics - issue an error if two sibling interfaces
                         //have two override-equivalent defaults - or if one is abstract
                         //and the other is default
                         String errKey;
                         Symbol s1 = defaults.first();
                         Symbol s2;
                         if (defaults.size() > 1) {
                             errKey = "types.incompatible.unrelated.defaults";
                             s2 = defaults.toList().tail.head;
                         } else {
                             errKey = "types.incompatible.abstract.default";
                             s2 = abstracts.first();
                         }
                         log.error(pos, errKey,
                                 Kinds.kindName(site.tsym), site,
                                 m.name, types.memberType(site, m).getParameterTypes(),
                                 s1.location(), s2.location());
                         break;
                     }
                 }
             }
         }
     }
     //where
      private class DefaultMethodClashFilter implements Filter<Symbol> {
          Type site;
          DefaultMethodClashFilter(Type site) {
              this.site = site;
          }
          public boolean accepts(Symbol s) {
              return s.kind == MTH &&
                      (s.flags() & DEFAULT) != 0 &&
                      s.isInheritedIn(site.tsym, types) &&
                      !s.isConstructor();
          }
      }
     /** Report a conflict between a user symbol and a synthetic symbol.
      */
     private void syntheticError(DiagnosticPosition pos, Symbol sym) {
         if (!sym.type.isErroneous()) {
             if (warnOnSyntheticConflicts) {
                 log.warning(pos, "synthetic.name.conflict", sym, sym.location());
             }
             else {
                 log.error(pos, "synthetic.name.conflict", sym, sym.location());
             }
         }
     }
     /** Check that class c does not implement directly or indirectly
      *  the same parameterized interface with two different argument lists.
      *  @param pos          Position to be used for error reporting.
      *  @param type         The type whose interfaces are checked.
      */
     void checkClassBounds(DiagnosticPosition pos, Type type) {
         checkClassBounds(pos, new HashMap<TypeSymbol,Type>(), type);
     }
 //where
         /** Enter all interfaces of type `type' into the hash table `seensofar'
          *  with their class symbol as key and their type as value. Make
          *  sure no class is entered with two different types.
          */
         void checkClassBounds(DiagnosticPosition pos,
                               Map<TypeSymbol,Type> seensofar,
                               Type type) {
             if (type.isErroneous()) return;
             for (List<Type> l = types.interfaces(type); l.nonEmpty(); l = l.tail) {
                 Type it = l.head;
                 Type oldit = seensofar.put(it.tsym, it);
                 if (oldit != null) {
                     List<Type> oldparams = oldit.allparams();
                     List<Type> newparams = it.allparams();
                     if (!types.containsTypeEquivalent(oldparams, newparams))
                         log.error(pos, "cant.inherit.diff.arg",
                                   it.tsym, Type.toString(oldparams),
                                   Type.toString(newparams));
                 }
                 checkClassBounds(pos, seensofar, it);
             }
             Type st = types.supertype(type);
             if (st != null) checkClassBounds(pos, seensofar, st);
         }
     /** Enter interface into into set.
      *  If it existed already, issue a "repeated interface" error.
      */
     void checkNotRepeated(DiagnosticPosition pos, Type it, Set<Type> its) {
         if (its.contains(it))
             log.error(pos, "repeated.interface");
         else {
             its.add(it);
         }
     }
 /* *************************************************************************
  * Check annotations
  **************************************************************************/
     /**
      * Recursively validate annotations values
      */
     void validateAnnotationTree(JCTree tree) {
         class AnnotationValidator extends TreeScanner {
             @Override
             public void visitAnnotation(JCAnnotation tree) {
                 if (!tree.type.isErroneous()) {
                     super.visitAnnotation(tree);
                     validateAnnotation(tree);
                 }
             }
         }
         tree.accept(new AnnotationValidator());
     }
     /**
      *  {@literal
      *  Annotation types are restricted to primitives, String, an
      *  enum, an annotation, Class, Class<?>, Class<? extends
      *  Anything>, arrays of the preceding.
      *  }
      */
     void validateAnnotationType(JCTree restype) {
         // restype may be null if an error occurred, so don't bother validating it
         if (restype != null) {
             validateAnnotationType(restype.pos(), restype.type);
         }
     }
     void validateAnnotationType(DiagnosticPosition pos, Type type) {
         if (type.isPrimitive()) return;
         if (types.isSameType(type, syms.stringType)) return;
         if ((type.tsym.flags() & Flags.ENUM) != 0) return;
         if ((type.tsym.flags() & Flags.ANNOTATION) != 0) return;
         if (types.lowerBound(type).tsym == syms.classType.tsym) return;
         if (types.isArray(type) && !types.isArray(types.elemtype(type))) {
             validateAnnotationType(pos, types.elemtype(type));
             return;
         }
         log.error(pos, "invalid.annotation.member.type");
     }
     /**
      * "It is also a compile-time error if any method declared in an
      * annotation type has a signature that is override-equivalent to
      * that of any public or protected method declared in class Object
      * or in the interface annotation.Annotation."
      *
      * @jls 9.6 Annotation Types
      */
     void validateAnnotationMethod(DiagnosticPosition pos, MethodSymbol m) {
         for (Type sup = syms.annotationType; sup.hasTag(CLASS); sup = types.supertype(sup)) {
             Scope s = sup.tsym.members();
             for (Scope.Entry e = s.lookup(m.name); e.scope != null; e = e.next()) {
                 if (e.sym.kind == MTH &&
                     (e.sym.flags() & (PUBLIC | PROTECTED)) != 0 &&
                     types.overrideEquivalent(m.type, e.sym.type))
                     log.error(pos, "intf.annotation.member.clash", e.sym, sup);
             }
         }
     }
     /** Check the annotations of a symbol.
      */
     public void validateAnnotations(List<JCAnnotation> annotations, Symbol s) {
         for (JCAnnotation a : annotations)
             validateAnnotation(a, s);
     }
     /** Check an annotation of a symbol.
      */
     private void validateAnnotation(JCAnnotation a, Symbol s) {
         validateAnnotationTree(a);
         if (!annotationApplicable(a, s))
             log.error(a.pos(), "annotation.type.not.applicable");
         if (a.annotationType.type.tsym == syms.overrideType.tsym) {
             if (!isOverrider(s))
                 log.error(a.pos(), "method.does.not.override.superclass");
         }
         if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
             if (s.kind != TYP) {
                 log.error(a.pos(), "bad.functional.intf.anno");
             } else {
                 try {
                     types.findDescriptorSymbol((TypeSymbol)s);
                 } catch (Types.FunctionDescriptorLookupError ex) {
                     log.error(a.pos(), "bad.functional.intf.anno.1", ex.getDiagnostic());
                 }
             }
         }
     }
     /**
      * Validate the proposed container 'repeatable' on the
      * annotation type symbol 's'. Report errors at position
      * 'pos'.
      *
      * @param s The (annotation)type declaration annotated with a @Repeatable
      * @param repeatable the @Repeatable on 's'
      * @param pos where to report errors
      */
     public void validateRepeatable(TypeSymbol s, Attribute.Compound repeatable, DiagnosticPosition pos) {
         Assert.check(types.isSameType(repeatable.type, syms.repeatableType));
         Type t = null;
         List<Pair<MethodSymbol,Attribute>> l = repeatable.values;
         if (!l.isEmpty()) {
             Assert.check(l.head.fst.name == names.value);
             t = ((Attribute.Class)l.head.snd).getValue();
         }
         if (t == null) {
             // errors should already have been reported during Annotate
             return;
         }
         validateValue(t.tsym, s, pos);
         validateRetention(t.tsym, s, pos);
         validateDocumented(t.tsym, s, pos);
         validateInherited(t.tsym, s, pos);
         validateTarget(t.tsym, s, pos);
         validateDefault(t.tsym, s, pos);
     }
     private void validateValue(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
         Scope.Entry e = container.members().lookup(names.value);
         if (e.scope != null && e.sym.kind == MTH) {
             MethodSymbol m = (MethodSymbol) e.sym;
             Type ret = m.getReturnType();
             if (!(ret.hasTag(ARRAY) && types.isSameType(((ArrayType)ret).elemtype, contained.type))) {
                 log.error(pos, "invalid.repeatable.annotation.value.return",
                         container, ret, types.makeArrayType(contained.type));
             }
         } else {
             log.error(pos, "invalid.repeatable.annotation.no.value", container);
         }
     }
     private void validateRetention(Symbol container, Symbol contained, DiagnosticPosition pos) {
         Attribute.RetentionPolicy containerRetention = types.getRetention(container);
         Attribute.RetentionPolicy containedRetention = types.getRetention(contained);
         boolean error = false;
         switch (containedRetention) {
         case RUNTIME:
             if (containerRetention != Attribute.RetentionPolicy.RUNTIME) {
                 error = true;
             }
             break;
         case CLASS:
             if (containerRetention == Attribute.RetentionPolicy.SOURCE)  {
                 error = true;
             }
         }
         if (error ) {
             log.error(pos, "invalid.repeatable.annotation.retention",
                       container, containerRetention,
                       contained, containedRetention);
         }
     }
     private void validateDocumented(Symbol container, Symbol contained, DiagnosticPosition pos) {
         if (contained.attribute(syms.documentedType.tsym) != null) {
             if (container.attribute(syms.documentedType.tsym) == null) {
                 log.error(pos, "invalid.repeatable.annotation.not.documented", container, contained);
             }
         }
     }
     private void validateInherited(Symbol container, Symbol contained, DiagnosticPosition pos) {
         if (contained.attribute(syms.inheritedType.tsym) != null) {
             if (container.attribute(syms.inheritedType.tsym) == null) {
                 log.error(pos, "invalid.repeatable.annotation.not.inherited", container, contained);
             }
         }
     }
     private void validateTarget(Symbol container, Symbol contained, DiagnosticPosition pos) {
         Attribute.Array containedTarget = getAttributeTargetAttribute(contained);
         // If contained has no Target, we are done
         if (containedTarget == null) {
             return;
         }
         // If contained has Target m1, container must have a Target
         // annotation, m2, and m2 must be a subset of m1. (This is
         // trivially true if contained has no target as per above).
         // contained has target, but container has not, error
         Attribute.Array containerTarget = getAttributeTargetAttribute(container);
         if (containerTarget == null) {
             log.error(pos, "invalid.repeatable.annotation.incompatible.target", container, contained);
             return;
         }
         Set<Name> containerTargets = new HashSet<Name>();
         for (Attribute app : containerTarget.values) {
             if (!(app instanceof Attribute.Enum)) {
                 continue; // recovery
             }
             Attribute.Enum e = (Attribute.Enum)app;
             containerTargets.add(e.value.name);
         }
         Set<Name> containedTargets = new HashSet<Name>();
         for (Attribute app : containedTarget.values) {
             if (!(app instanceof Attribute.Enum)) {
                 continue; // recovery
             }
             Attribute.Enum e = (Attribute.Enum)app;
             containedTargets.add(e.value.name);
         }
         if (!isTargetSubset(containedTargets, containerTargets)) {
             log.error(pos, "invalid.repeatable.annotation.incompatible.target", container, contained);
         }
     }
     /** Checks that t is a subset of s, with respect to ElementType
      * semantics, specifically {ANNOTATION_TYPE} is a subset of {TYPE}
      */
     private boolean isTargetSubset(Set<Name> s, Set<Name> t) {
         // Check that all elements in t are present in s
         for (Name n2 : t) {
             boolean currentElementOk = false;
             for (Name n1 : s) {
                 if (n1 == n2) {
                     currentElementOk = true;
                     break;
                 } else if (n1 == names.TYPE && n2 == names.ANNOTATION_TYPE) {
                     currentElementOk = true;
                     break;
                 }
             }
             if (!currentElementOk)
                 return false;
         }
         return true;
     }
     private void validateDefault(Symbol container, Symbol contained, DiagnosticPosition pos) {
         // validate that all other elements of containing type has defaults
         Scope scope = container.members();
         for(Symbol elm : scope.getElements()) {
             if (elm.name != names.value &&
                 elm.kind == Kinds.MTH &&
                 ((MethodSymbol)elm).defaultValue == null) {
                 log.error(pos,
                           "invalid.repeatable.annotation.elem.nondefault",
                           container,
                           elm);
             }
         }
     }
     /** Is s a method symbol that overrides a method in a superclass? */
     boolean isOverrider(Symbol s) {
         if (s.kind != MTH || s.isStatic())
             return false;
         MethodSymbol m = (MethodSymbol)s;
         TypeSymbol owner = (TypeSymbol)m.owner;
         for (Type sup : types.closure(owner.type)) {
             if (sup == owner.type)
                 continue; // skip "this"
             Scope scope = sup.tsym.members();
             for (Scope.Entry e = scope.lookup(m.name); e.scope != null; e = e.next()) {
                 if (!e.sym.isStatic() && m.overrides(e.sym, owner, types, true))
                     return true;
             }
         }
         return false;
     }
     /** Is the annotation applicable to the symbol? */
     boolean annotationApplicable(JCAnnotation a, Symbol s) {
         Attribute.Array arr = getAttributeTargetAttribute(a.annotationType.type.tsym);
         if (arr == null) {
             return true;
         }
         for (Attribute app : arr.values) {
             if (!(app instanceof Attribute.Enum)) return true; // recovery
             Attribute.Enum e = (Attribute.Enum) app;
             if (e.value.name == names.TYPE)
                 { if (s.kind == TYP) return true; }
             else if (e.value.name == names.FIELD)
                 { if (s.kind == VAR && s.owner.kind != MTH) return true; }
             else if (e.value.name == names.METHOD)
                 { if (s.kind == MTH && !s.isConstructor()) return true; }
             else if (e.value.name == names.PARAMETER)
                 { if (s.kind == VAR &&
                       s.owner.kind == MTH &&
                       (s.flags() & PARAMETER) != 0)
                     return true;
                 }
             else if (e.value.name == names.CONSTRUCTOR)
                 { if (s.kind == MTH && s.isConstructor()) return true; }
             else if (e.value.name == names.LOCAL_VARIABLE)
                 { if (s.kind == VAR && s.owner.kind == MTH &&
                       (s.flags() & PARAMETER) == 0)
                     return true;
                 }
             else if (e.value.name == names.ANNOTATION_TYPE)
                 { if (s.kind == TYP && (s.flags() & ANNOTATION) != 0)
                     return true;
                 }
             else if (e.value.name == names.PACKAGE)
                 { if (s.kind == PCK) return true; }
             else if (e.value.name == names.TYPE_USE)
                 { if (s.kind == TYP ||
                       s.kind == VAR ||
                       (s.kind == MTH && !s.isConstructor() &&
                        !s.type.getReturnType().hasTag(VOID)))
                     return true;
                 }
             else
                 return true; // recovery
         }
         return false;
     }
     Attribute.Array getAttributeTargetAttribute(Symbol s) {
         Attribute.Compound atTarget =
             s.attribute(syms.annotationTargetType.tsym);
         if (atTarget == null) return null; // ok, is applicable
         Attribute atValue = atTarget.member(names.value);
         if (!(atValue instanceof Attribute.Array)) return null; // error recovery
         return (Attribute.Array) atValue;
     }
     /** Check an annotation value.
      *
      * @param a The annotation tree to check
      * @return true if this annotation tree is valid, otherwise false
      */
     public boolean validateAnnotationDeferErrors(JCAnnotation a) {
         boolean res = false;
         final Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
         try {
             res = validateAnnotation(a);
         } finally {
             log.popDiagnosticHandler(diagHandler);
         }
         return res;
     }
     private boolean validateAnnotation(JCAnnotation a) {
         boolean isValid = true;
         // collect an inventory of the annotation elements
         Set<MethodSymbol> members = new LinkedHashSet<MethodSymbol>();
         for (Scope.Entry e = a.annotationType.type.tsym.members().elems;
              e != null;
              e = e.sibling)
             if (e.sym.kind == MTH)
                 members.add((MethodSymbol) e.sym);
         // remove the ones that are assigned values
         for (JCTree arg : a.args) {
             if (!arg.hasTag(ASSIGN)) continue; // recovery
             JCAssign assign = (JCAssign) arg;
             Symbol m = TreeInfo.symbol(assign.lhs);
             if (m == null || m.type.isErroneous()) continue;
             if (!members.remove(m)) {
                 isValid = false;
                 log.error(assign.lhs.pos(), "duplicate.annotation.member.value",
                           m.name, a.type);
             }
         }
         // all the remaining ones better have default values
         List<Name> missingDefaults = List.nil();
         for (MethodSymbol m : members) {
             if (m.defaultValue == null && !m.type.isErroneous()) {
                 missingDefaults = missingDefaults.append(m.name);
             }
         }
         missingDefaults = missingDefaults.reverse();
         if (missingDefaults.nonEmpty()) {
             isValid = false;
             String key = (missingDefaults.size() > 1)
                     ? "annotation.missing.default.value.1"
                     : "annotation.missing.default.value";
             log.error(a.pos(), key, a.type, missingDefaults);
         }
         // special case: java.lang.annotation.Target must not have
         // repeated values in its value member
         if (a.annotationType.type.tsym != syms.annotationTargetType.tsym ||
             a.args.tail == null)
             return isValid;
         if (!a.args.head.hasTag(ASSIGN)) return false; // error recovery
         JCAssign assign = (JCAssign) a.args.head;
         Symbol m = TreeInfo.symbol(assign.lhs);
         if (m.name != names.value) return false;
         JCTree rhs = assign.rhs;
         if (!rhs.hasTag(NEWARRAY)) return false;
         JCNewArray na = (JCNewArray) rhs;
         Set<Symbol> targets = new HashSet<Symbol>();
         for (JCTree elem : na.elems) {
             if (!targets.add(TreeInfo.symbol(elem))) {
                 isValid = false;
                 log.error(elem.pos(), "repeated.annotation.target");
             }
         }
         return isValid;
     }
     void checkDeprecatedAnnotation(DiagnosticPosition pos, Symbol s) {
         if (allowAnnotations &&
             lint.isEnabled(LintCategory.DEP_ANN) &&
             (s.flags() & DEPRECATED) != 0 &&
             !syms.deprecatedType.isErroneous() &&
             s.attribute(syms.deprecatedType.tsym) == null) {
             log.warning(LintCategory.DEP_ANN,
                     pos, "missing.deprecated.annotation");
         }
     }
     void checkDeprecated(final DiagnosticPosition pos, final Symbol other, final Symbol s) {
         if ((s.flags() & DEPRECATED) != 0 &&
                 (other.flags() & DEPRECATED) == 0 &&
                 s.outermostClass() != other.outermostClass()) {
             deferredLintHandler.report(new DeferredLintHandler.LintLogger() {
                 @Override
                 public void report() {
                     warnDeprecated(pos, s);
                 }
             });
         }
     }
     void checkSunAPI(final DiagnosticPosition pos, final Symbol s) {
         if ((s.flags() & PROPRIETARY) != 0) {
             deferredLintHandler.report(new DeferredLintHandler.LintLogger() {
                 public void report() {
                     if (enableSunApiLintControl)
                       warnSunApi(pos, "sun.proprietary", s);
                     else
                       log.mandatoryWarning(pos, "sun.proprietary", s);
                 }
             });
         }
     }
 /* *************************************************************************
  * Check for recursive annotation elements.
  **************************************************************************/
     /** Check for cycles in the graph of annotation elements.
      */
     void checkNonCyclicElements(JCClassDecl tree) {
         if ((tree.sym.flags_field & ANNOTATION) == 0) return;
         Assert.check((tree.sym.flags_field & LOCKED) == 0);
         try {
             tree.sym.flags_field |= LOCKED;
             for (JCTree def : tree.defs) {
                 if (!def.hasTag(METHODDEF)) continue;
                 JCMethodDecl meth = (JCMethodDecl)def;
                 checkAnnotationResType(meth.pos(), meth.restype.type);
             }
         } finally {
             tree.sym.flags_field &= ~LOCKED;
             tree.sym.flags_field |= ACYCLIC_ANN;
         }
     }
     void checkNonCyclicElementsInternal(DiagnosticPosition pos, TypeSymbol tsym) {
         if ((tsym.flags_field & ACYCLIC_ANN) != 0)
             return;
         if ((tsym.flags_field & LOCKED) != 0) {
             log.error(pos, "cyclic.annotation.element");
             return;
         }
         try {
             tsym.flags_field |= LOCKED;
             for (Scope.Entry e = tsym.members().elems; e != null; e = e.sibling) {
                 Symbol s = e.sym;
                 if (s.kind != Kinds.MTH)
                     continue;
                 checkAnnotationResType(pos, ((MethodSymbol)s).type.getReturnType());
             }
         } finally {
             tsym.flags_field &= ~LOCKED;
             tsym.flags_field |= ACYCLIC_ANN;
         }
     }
     void checkAnnotationResType(DiagnosticPosition pos, Type type) {
         switch (type.getTag()) {
         case CLASS:
             if ((type.tsym.flags() & ANNOTATION) != 0)
                 checkNonCyclicElementsInternal(pos, type.tsym);
             break;
         case ARRAY:
             checkAnnotationResType(pos, types.elemtype(type));
             break;
         default:
             break; // int etc
         }
     }
 /* *************************************************************************
  * Check for cycles in the constructor call graph.
  **************************************************************************/
     /** Check for cycles in the graph of constructors calling other
      *  constructors.
      */
     void checkCyclicConstructors(JCClassDecl tree) {
         Map<Symbol,Symbol> callMap = new HashMap<Symbol, Symbol>();
         // enter each constructor this-call into the map
         for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
             JCMethodInvocation app = TreeInfo.firstConstructorCall(l.head);
             if (app == null) continue;
             JCMethodDecl meth = (JCMethodDecl) l.head;
             if (TreeInfo.name(app.meth) == names._this) {
                 callMap.put(meth.sym, TreeInfo.symbol(app.meth));
             } else {
                 meth.sym.flags_field |= ACYCLIC;
             }
         }
         // Check for cycles in the map
         Symbol[] ctors = new Symbol[0];
         ctors = callMap.keySet().toArray(ctors);
         for (Symbol caller : ctors) {
             checkCyclicConstructor(tree, caller, callMap);
         }
     }
     /** Look in the map to see if the given constructor is part of a
      *  call cycle.
      */
     private void checkCyclicConstructor(JCClassDecl tree, Symbol ctor,
                                         Map<Symbol,Symbol> callMap) {
         if (ctor != null && (ctor.flags_field & ACYCLIC) == 0) {
             if ((ctor.flags_field & LOCKED) != 0) {
                 log.error(TreeInfo.diagnosticPositionFor(ctor, tree),
                           "recursive.ctor.invocation");
             } else {
                 ctor.flags_field |= LOCKED;
                 checkCyclicConstructor(tree, callMap.remove(ctor), callMap);
                 ctor.flags_field &= ~LOCKED;
             }
             ctor.flags_field |= ACYCLIC;
         }
     }
 /* *************************************************************************
  * Miscellaneous
  **************************************************************************/
     /**
      * Return the opcode of the operator but emit an error if it is an
      * error.
      * @param pos        position for error reporting.
      * @param operator   an operator
      * @param tag        a tree tag
      * @param left       type of left hand side
      * @param right      type of right hand side
      */
     int checkOperator(DiagnosticPosition pos,
                        OperatorSymbol operator,
                        JCTree.Tag tag,
                        Type left,
                        Type right) {
         if (operator.opcode == ByteCodes.error) {
             log.error(pos,
                       "operator.cant.be.applied.1",
                       treeinfo.operatorName(tag),
                       left, right);
         }
         return operator.opcode;
     }
     /**
      *  Check for division by integer constant zero
      *  @param pos           Position for error reporting.
      *  @param operator      The operator for the expression
      *  @param operand       The right hand operand for the expression
      */
     void checkDivZero(DiagnosticPosition pos, Symbol operator, Type operand) {
         if (operand.constValue() != null
             && lint.isEnabled(LintCategory.DIVZERO)
             && (operand.getTag().isSubRangeOf(LONG))
             && ((Number) (operand.constValue())).longValue() == 0) {
             int opc = ((OperatorSymbol)operator).opcode;
             if (opc == ByteCodes.idiv || opc == ByteCodes.imod
                 || opc == ByteCodes.ldiv || opc == ByteCodes.lmod) {
                 log.warning(LintCategory.DIVZERO, pos, "div.zero");
             }
         }
     }
     /**
      * Check for empty statements after if
      */
     void checkEmptyIf(JCIf tree) {
         if (tree.thenpart.hasTag(SKIP) && tree.elsepart == null &&
                 lint.isEnabled(LintCategory.EMPTY))
             log.warning(LintCategory.EMPTY, tree.thenpart.pos(), "empty.if");
     }
     /** Check that symbol is unique in given scope.
      *  @param pos           Position for error reporting.
      *  @param sym           The symbol.
      *  @param s             The scope.
      */
     boolean checkUnique(DiagnosticPosition pos, Symbol sym, Scope s) {
         if (sym.type.isErroneous())
             return true;
         if (sym.owner.name == names.any) return false;
         for (Scope.Entry e = s.lookup(sym.name); e.scope == s; e = e.next()) {
             if (sym != e.sym &&
                     (e.sym.flags() & CLASH) == 0 &&
                     sym.kind == e.sym.kind &&
                     sym.name != names.error &&
                     (sym.kind != MTH || types.hasSameArgs(types.erasure(sym.type), types.erasure(e.sym.type)))) {
                 if ((sym.flags() & VARARGS) != (e.sym.flags() & VARARGS)) {
                     varargsDuplicateError(pos, sym, e.sym);
                     return true;
                 } else if (sym.kind == MTH && !types.hasSameArgs(sym.type, e.sym.type, false)) {
                     duplicateErasureError(pos, sym, e.sym);
                     sym.flags_field |= CLASH;
                     return true;
                 } else {
                     duplicateError(pos, e.sym);
                     return false;
                 }
             }
         }
         return true;
     }
     /** Report duplicate declaration error.
      */
     void duplicateErasureError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
         if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
             log.error(pos, "name.clash.same.erasure", sym1, sym2);
         }
     }
     /** Check that single-type import is not already imported or top-level defined,
      *  but make an exception for two single-type imports which denote the same type.
      *  @param pos           Position for error reporting.
      *  @param sym           The symbol.
      *  @param s             The scope
      */
     boolean checkUniqueImport(DiagnosticPosition pos, Symbol sym, Scope s) {
         return checkUniqueImport(pos, sym, s, false);
     }
     /** Check that static single-type import is not already imported or top-level defined,
      *  but make an exception for two single-type imports which denote the same type.
      *  @param pos           Position for error reporting.
      *  @param sym           The symbol.
      *  @param s             The scope
      */
     boolean checkUniqueStaticImport(DiagnosticPosition pos, Symbol sym, Scope s) {
         return checkUniqueImport(pos, sym, s, true);
     }
     /** Check that single-type import is not already imported or top-level defined,
      *  but make an exception for two single-type imports which denote the same type.
      *  @param pos           Position for error reporting.
      *  @param sym           The symbol.
      *  @param s             The scope.
      *  @param staticImport  Whether or not this was a static import
      */
     private boolean checkUniqueImport(DiagnosticPosition pos, Symbol sym, Scope s, boolean staticImport) {
         for (Scope.Entry e = s.lookup(sym.name); e.scope != null; e = e.next()) {
             // is encountered class entered via a class declaration?
             boolean isClassDecl = e.scope == s;
             if ((isClassDecl || sym != e.sym) &&
                 sym.kind == e.sym.kind &&
                 sym.name != names.error) {
                 if (!e.sym.type.isErroneous()) {
                     String what = e.sym.toString();
                     if (!isClassDecl) {
                         if (staticImport)
                             log.error(pos, "already.defined.static.single.import", what);
                         else
                             log.error(pos, "already.defined.single.import", what);
                     }
                     else if (sym != e.sym)
                         log.error(pos, "already.defined.this.unit", what);
                 }
                 return false;
             }
         }
         return true;
     }
     /** Check that a qualified name is in canonical form (for import decls).
      */
     public void checkCanonical(JCTree tree) {
         if (!isCanonical(tree))
             log.error(tree.pos(), "import.requires.canonical",
                       TreeInfo.symbol(tree));
     }
         // where
         private boolean isCanonical(JCTree tree) {
             while (tree.hasTag(SELECT)) {
                 JCFieldAccess s = (JCFieldAccess) tree;
                 if (s.sym.owner != TreeInfo.symbol(s.selected))
                     return false;
                 tree = s.selected;
             }
             return true;
         }
     /** Check that an auxiliary class is not accessed from any other file than its own.
      */
     void checkForBadAuxiliaryClassAccess(DiagnosticPosition pos, Env<AttrContext> env, ClassSymbol c) {
         if (lint.isEnabled(Lint.LintCategory.AUXILIARYCLASS) &&
             (c.flags() & AUXILIARY) != 0 &&
             rs.isAccessible(env, c) &&
             !fileManager.isSameFile(c.sourcefile, env.toplevel.sourcefile))
         {
             log.warning(pos, "auxiliary.class.accessed.from.outside.of.its.source.file",
                         c, c.sourcefile);
         }
     }
     private class ConversionWarner extends Warner {
         final String uncheckedKey;
         final Type found;
         final Type expected;
         public ConversionWarner(DiagnosticPosition pos, String uncheckedKey, Type found, Type expected) {
             super(pos);
             this.uncheckedKey = uncheckedKey;
             this.found = found;
             this.expected = expected;
         }
         @Override
         public void warn(LintCategory lint) {
             boolean warned = this.warned;
             super.warn(lint);
             if (warned) return; // suppress redundant diagnostics
             switch (lint) {
                 case UNCHECKED:
                     Check.this.warnUnchecked(pos(), "prob.found.req", diags.fragment(uncheckedKey), found, expected);
                     break;
                 case VARARGS:
                     if (method != null &&
                             method.attribute(syms.trustMeType.tsym) != null &&
                             isTrustMeAllowedOnMethod(method) &&
                             !types.isReifiable(method.type.getParameterTypes().last())) {
                         Check.this.warnUnsafeVararg(pos(), "varargs.unsafe.use.varargs.param", method.params.last());
                     }
                     break;
                 default:
                     throw new AssertionError("Unexpected lint: " + lint);
             }
         }
     }
     public Warner castWarner(DiagnosticPosition pos, Type found, Type expected) {
         return new ConversionWarner(pos, "unchecked.cast.to.type", found, expected);
     }
     public Warner convertWarner(DiagnosticPosition pos, Type found, Type expected) {
         return new ConversionWarner(pos, "unchecked.assign", found, expected);
     }
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/comp/Check.java@7aa2025bbb7b (annotated)

src/share/classes/com/sun/tools/javac/comp/Check.java