jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/comp/Resolve.java@db91d860156a (annotated)

src/share/classes/com/sun/tools/javac/comp/Resolve.java@db91d860156a (annotated)

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

Tue, 08 Jan 2013 10:16:26 +0100

author: mcimadamore
date: Tue, 08 Jan 2013 10:16:26 +0100
changeset 1480: db91d860156a
parent 1479: 38d3d1027f5a
child 1496: f785dcac17b7
permissions: -rw-r--r--

8005179: Cleanup Resolve.AmbiguityError
Summary: Linearize nested ambiguity errors
Reviewed-by: jjg

 /*
  * Copyright (c) 1999, 2012, 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 com.sun.tools.javac.api.Formattable.LocalizedString;
 import com.sun.tools.javac.code.*;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.comp.Attr.ResultInfo;
 import com.sun.tools.javac.comp.Check.CheckContext;
 import com.sun.tools.javac.comp.DeferredAttr.AttrMode;
 import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;
 import com.sun.tools.javac.comp.DeferredAttr.DeferredType;
 import com.sun.tools.javac.comp.Infer.InferenceContext;
 import com.sun.tools.javac.comp.Infer.InferenceContext.FreeTypeListener;
 import com.sun.tools.javac.comp.Resolve.MethodResolutionContext.Candidate;
 import com.sun.tools.javac.jvm.*;
 import com.sun.tools.javac.tree.*;
 import com.sun.tools.javac.tree.JCTree.*;
 import com.sun.tools.javac.tree.JCTree.JCMemberReference.ReferenceKind;
 import com.sun.tools.javac.util.*;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticFlag;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticType;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.EnumMap;
 import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 import javax.lang.model.element.ElementVisitor;
 import static com.sun.tools.javac.code.Flags.*;
 import static com.sun.tools.javac.code.Flags.BLOCK;
 import static com.sun.tools.javac.code.Kinds.*;
 import static com.sun.tools.javac.code.Kinds.ERRONEOUS;
 import static com.sun.tools.javac.code.TypeTag.*;
 import static com.sun.tools.javac.comp.Resolve.MethodResolutionPhase.*;
 import static com.sun.tools.javac.tree.JCTree.Tag.*;
 /** Helper class for name resolution, used mostly by 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 Resolve {
     protected static final Context.Key<Resolve> resolveKey =
         new Context.Key<Resolve>();
     Names names;
     Log log;
     Symtab syms;
     Attr attr;
     DeferredAttr deferredAttr;
     Check chk;
     Infer infer;
     ClassReader reader;
     TreeInfo treeinfo;
     Types types;
     JCDiagnostic.Factory diags;
     public final boolean boxingEnabled; // = source.allowBoxing();
     public final boolean varargsEnabled; // = source.allowVarargs();
     public final boolean allowMethodHandles;
     public final boolean allowDefaultMethods;
     private final boolean debugResolve;
     final EnumSet<VerboseResolutionMode> verboseResolutionMode;
     Scope polymorphicSignatureScope;
     protected Resolve(Context context) {
         context.put(resolveKey, this);
         syms = Symtab.instance(context);
         varNotFound = new
             SymbolNotFoundError(ABSENT_VAR);
         methodNotFound = new
             SymbolNotFoundError(ABSENT_MTH);
         typeNotFound = new
             SymbolNotFoundError(ABSENT_TYP);
         names = Names.instance(context);
         log = Log.instance(context);
         attr = Attr.instance(context);
         deferredAttr = DeferredAttr.instance(context);
         chk = Check.instance(context);
         infer = Infer.instance(context);
         reader = ClassReader.instance(context);
         treeinfo = TreeInfo.instance(context);
         types = Types.instance(context);
         diags = JCDiagnostic.Factory.instance(context);
         Source source = Source.instance(context);
         boxingEnabled = source.allowBoxing();
         varargsEnabled = source.allowVarargs();
         Options options = Options.instance(context);
         debugResolve = options.isSet("debugresolve");
         verboseResolutionMode = VerboseResolutionMode.getVerboseResolutionMode(options);
         Target target = Target.instance(context);
         allowMethodHandles = target.hasMethodHandles();
         allowDefaultMethods = source.allowDefaultMethods();
         polymorphicSignatureScope = new Scope(syms.noSymbol);
         inapplicableMethodException = new InapplicableMethodException(diags);
     }
     /** error symbols, which are returned when resolution fails
      */
     private final SymbolNotFoundError varNotFound;
     private final SymbolNotFoundError methodNotFound;
     private final SymbolNotFoundError typeNotFound;
     public static Resolve instance(Context context) {
         Resolve instance = context.get(resolveKey);
         if (instance == null)
             instance = new Resolve(context);
         return instance;
     }
     // <editor-fold defaultstate="collapsed" desc="Verbose resolution diagnostics support">
     enum VerboseResolutionMode {
         SUCCESS("success"),
         FAILURE("failure"),
         APPLICABLE("applicable"),
         INAPPLICABLE("inapplicable"),
         DEFERRED_INST("deferred-inference"),
         PREDEF("predef"),
         OBJECT_INIT("object-init"),
         INTERNAL("internal");
         final String opt;
         private VerboseResolutionMode(String opt) {
             this.opt = opt;
         }
         static EnumSet<VerboseResolutionMode> getVerboseResolutionMode(Options opts) {
             String s = opts.get("verboseResolution");
             EnumSet<VerboseResolutionMode> res = EnumSet.noneOf(VerboseResolutionMode.class);
             if (s == null) return res;
             if (s.contains("all")) {
                 res = EnumSet.allOf(VerboseResolutionMode.class);
             }
             Collection<String> args = Arrays.asList(s.split(","));
             for (VerboseResolutionMode mode : values()) {
                 if (args.contains(mode.opt)) {
                     res.add(mode);
                 } else if (args.contains("-" + mode.opt)) {
                     res.remove(mode);
                 }
             }
             return res;
         }
     }
     void reportVerboseResolutionDiagnostic(DiagnosticPosition dpos, Name name, Type site,
             List<Type> argtypes, List<Type> typeargtypes, Symbol bestSoFar) {
         boolean success = bestSoFar.kind < ERRONEOUS;
         if (success && !verboseResolutionMode.contains(VerboseResolutionMode.SUCCESS)) {
             return;
         } else if (!success && !verboseResolutionMode.contains(VerboseResolutionMode.FAILURE)) {
             return;
         }
         if (bestSoFar.name == names.init &&
                 bestSoFar.owner == syms.objectType.tsym &&
                 !verboseResolutionMode.contains(VerboseResolutionMode.OBJECT_INIT)) {
             return; //skip diags for Object constructor resolution
         } else if (site == syms.predefClass.type &&
                 !verboseResolutionMode.contains(VerboseResolutionMode.PREDEF)) {
             return; //skip spurious diags for predef symbols (i.e. operators)
         } else if (currentResolutionContext.internalResolution &&
                 !verboseResolutionMode.contains(VerboseResolutionMode.INTERNAL)) {
             return;
         }
         int pos = 0;
         int mostSpecificPos = -1;
         ListBuffer<JCDiagnostic> subDiags = ListBuffer.lb();
         for (Candidate c : currentResolutionContext.candidates) {
             if (currentResolutionContext.step != c.step ||
                     (c.isApplicable() && !verboseResolutionMode.contains(VerboseResolutionMode.APPLICABLE)) ||
                     (!c.isApplicable() && !verboseResolutionMode.contains(VerboseResolutionMode.INAPPLICABLE))) {
                 continue;
             } else {
                 subDiags.append(c.isApplicable() ?
                         getVerboseApplicableCandidateDiag(pos, c.sym, c.mtype) :
                         getVerboseInapplicableCandidateDiag(pos, c.sym, c.details));
                 if (c.sym == bestSoFar)
                     mostSpecificPos = pos;
                 pos++;
             }
         }
         String key = success ? "verbose.resolve.multi" : "verbose.resolve.multi.1";
         List<Type> argtypes2 = Type.map(argtypes,
                     deferredAttr.new RecoveryDeferredTypeMap(AttrMode.SPECULATIVE, bestSoFar, currentResolutionContext.step));
         JCDiagnostic main = diags.note(log.currentSource(), dpos, key, name,
                 site.tsym, mostSpecificPos, currentResolutionContext.step,
                 methodArguments(argtypes2),
                 methodArguments(typeargtypes));
         JCDiagnostic d = new JCDiagnostic.MultilineDiagnostic(main, subDiags.toList());
         log.report(d);
     }
     JCDiagnostic getVerboseApplicableCandidateDiag(int pos, Symbol sym, Type inst) {
         JCDiagnostic subDiag = null;
         if (sym.type.hasTag(FORALL)) {
             subDiag = diags.fragment("partial.inst.sig", inst);
         }
         String key = subDiag == null ?
                 "applicable.method.found" :
                 "applicable.method.found.1";
         return diags.fragment(key, pos, sym, subDiag);
     }
     JCDiagnostic getVerboseInapplicableCandidateDiag(int pos, Symbol sym, JCDiagnostic subDiag) {
         return diags.fragment("not.applicable.method.found", pos, sym, subDiag);
     }
     // </editor-fold>
 /* ************************************************************************
  * Identifier resolution
  *************************************************************************/
     /** An environment is "static" if its static level is greater than
      *  the one of its outer environment
      */
     protected static boolean isStatic(Env<AttrContext> env) {
         return env.info.staticLevel > env.outer.info.staticLevel;
     }
     /** An environment is an "initializer" if it is a constructor or
      *  an instance initializer.
      */
     static boolean isInitializer(Env<AttrContext> env) {
         Symbol owner = env.info.scope.owner;
         return owner.isConstructor() ||
             owner.owner.kind == TYP &&
             (owner.kind == VAR ||
              owner.kind == MTH && (owner.flags() & BLOCK) != 0) &&
             (owner.flags() & STATIC) == 0;
     }
     /** Is class accessible in given evironment?
      *  @param env    The current environment.
      *  @param c      The class whose accessibility is checked.
      */
     public boolean isAccessible(Env<AttrContext> env, TypeSymbol c) {
         return isAccessible(env, c, false);
     }
     public boolean isAccessible(Env<AttrContext> env, TypeSymbol c, boolean checkInner) {
         boolean isAccessible = false;
         switch ((short)(c.flags() & AccessFlags)) {
             case PRIVATE:
                 isAccessible =
                     env.enclClass.sym.outermostClass() ==
                     c.owner.outermostClass();
                 break;
             case 0:
                 isAccessible =
                     env.toplevel.packge == c.owner // fast special case
                     ||
                     env.toplevel.packge == c.packge()
                     ||
                     // Hack: this case is added since synthesized default constructors
                     // of anonymous classes should be allowed to access
                     // classes which would be inaccessible otherwise.
                     env.enclMethod != null &&
                     (env.enclMethod.mods.flags & ANONCONSTR) != 0;
                 break;
             default: // error recovery
             case PUBLIC:
                 isAccessible = true;
                 break;
             case PROTECTED:
                 isAccessible =
                     env.toplevel.packge == c.owner // fast special case
                     ||
                     env.toplevel.packge == c.packge()
                     ||
                     isInnerSubClass(env.enclClass.sym, c.owner);
                 break;
         }
         return (checkInner == false || c.type.getEnclosingType() == Type.noType) ?
             isAccessible :
             isAccessible && isAccessible(env, c.type.getEnclosingType(), checkInner);
     }
     //where
         /** Is given class a subclass of given base class, or an inner class
          *  of a subclass?
          *  Return null if no such class exists.
          *  @param c     The class which is the subclass or is contained in it.
          *  @param base  The base class
          */
         private boolean isInnerSubClass(ClassSymbol c, Symbol base) {
             while (c != null && !c.isSubClass(base, types)) {
                 c = c.owner.enclClass();
             }
             return c != null;
         }
     boolean isAccessible(Env<AttrContext> env, Type t) {
         return isAccessible(env, t, false);
     }
     boolean isAccessible(Env<AttrContext> env, Type t, boolean checkInner) {
         return (t.hasTag(ARRAY))
             ? isAccessible(env, types.elemtype(t))
             : isAccessible(env, t.tsym, checkInner);
     }
     /** Is symbol accessible as a member of given type in given evironment?
      *  @param env    The current environment.
      *  @param site   The type of which the tested symbol is regarded
      *                as a member.
      *  @param sym    The symbol.
      */
     public boolean isAccessible(Env<AttrContext> env, Type site, Symbol sym) {
         return isAccessible(env, site, sym, false);
     }
     public boolean isAccessible(Env<AttrContext> env, Type site, Symbol sym, boolean checkInner) {
         if (sym.name == names.init && sym.owner != site.tsym) return false;
         switch ((short)(sym.flags() & AccessFlags)) {
         case PRIVATE:
             return
                 (env.enclClass.sym == sym.owner // fast special case
                  ||
                  env.enclClass.sym.outermostClass() ==
                  sym.owner.outermostClass())
                 &&
                 sym.isInheritedIn(site.tsym, types);
         case 0:
             return
                 (env.toplevel.packge == sym.owner.owner // fast special case
                  ||
                  env.toplevel.packge == sym.packge())
                 &&
                 isAccessible(env, site, checkInner)
                 &&
                 sym.isInheritedIn(site.tsym, types)
                 &&
                 notOverriddenIn(site, sym);
         case PROTECTED:
             return
                 (env.toplevel.packge == sym.owner.owner // fast special case
                  ||
                  env.toplevel.packge == sym.packge()
                  ||
                  isProtectedAccessible(sym, env.enclClass.sym, site)
                  ||
                  // OK to select instance method or field from 'super' or type name
                  // (but type names should be disallowed elsewhere!)
                  env.info.selectSuper && (sym.flags() & STATIC) == 0 && sym.kind != TYP)
                 &&
                 isAccessible(env, site, checkInner)
                 &&
                 notOverriddenIn(site, sym);
         default: // this case includes erroneous combinations as well
             return isAccessible(env, site, checkInner) && notOverriddenIn(site, sym);
         }
     }
     //where
     /* `sym' is accessible only if not overridden by
      * another symbol which is a member of `site'
      * (because, if it is overridden, `sym' is not strictly
      * speaking a member of `site'). A polymorphic signature method
      * cannot be overridden (e.g. MH.invokeExact(Object[])).
      */
     private boolean notOverriddenIn(Type site, Symbol sym) {
         if (sym.kind != MTH || sym.isConstructor() || sym.isStatic())
             return true;
         else {
             Symbol s2 = ((MethodSymbol)sym).implementation(site.tsym, types, true);
             return (s2 == null || s2 == sym || sym.owner == s2.owner ||
                     !types.isSubSignature(types.memberType(site, s2), types.memberType(site, sym)));
         }
     }
     //where
         /** Is given protected symbol accessible if it is selected from given site
          *  and the selection takes place in given class?
          *  @param sym     The symbol with protected access
          *  @param c       The class where the access takes place
          *  @site          The type of the qualifier
          */
         private
         boolean isProtectedAccessible(Symbol sym, ClassSymbol c, Type site) {
             while (c != null &&
                    !(c.isSubClass(sym.owner, types) &&
                      (c.flags() & INTERFACE) == 0 &&
                      // In JLS 2e 6.6.2.1, the subclass restriction applies
                      // only to instance fields and methods -- types are excluded
                      // regardless of whether they are declared 'static' or not.
                      ((sym.flags() & STATIC) != 0 || sym.kind == TYP || site.tsym.isSubClass(c, types))))
                 c = c.owner.enclClass();
             return c != null;
         }
     /**
      * Performs a recursive scan of a type looking for accessibility problems
      * from current attribution environment
      */
     void checkAccessibleType(Env<AttrContext> env, Type t) {
         accessibilityChecker.visit(t, env);
     }
     /**
      * Accessibility type-visitor
      */
     Types.SimpleVisitor<Void, Env<AttrContext>> accessibilityChecker =
             new Types.SimpleVisitor<Void, Env<AttrContext>>() {
         void visit(List<Type> ts, Env<AttrContext> env) {
             for (Type t : ts) {
                 visit(t, env);
             }
         }
         public Void visitType(Type t, Env<AttrContext> env) {
             return null;
         }
         @Override
         public Void visitArrayType(ArrayType t, Env<AttrContext> env) {
             visit(t.elemtype, env);
             return null;
         }
         @Override
         public Void visitClassType(ClassType t, Env<AttrContext> env) {
             visit(t.getTypeArguments(), env);
             if (!isAccessible(env, t, true)) {
                 accessBase(new AccessError(t.tsym), env.tree.pos(), env.enclClass.sym, t, t.tsym.name, true);
             }
             return null;
         }
         @Override
         public Void visitWildcardType(WildcardType t, Env<AttrContext> env) {
             visit(t.type, env);
             return null;
         }
         @Override
         public Void visitMethodType(MethodType t, Env<AttrContext> env) {
             visit(t.getParameterTypes(), env);
             visit(t.getReturnType(), env);
             visit(t.getThrownTypes(), env);
             return null;
         }
     };
     /** Try to instantiate the type of a method so that it fits
      *  given type arguments and argument types. If succesful, return
      *  the method's instantiated type, else return null.
      *  The instantiation will take into account an additional leading
      *  formal parameter if the method is an instance method seen as a member
      *  of un underdetermined site In this case, we treat site as an additional
      *  parameter and the parameters of the class containing the method as
      *  additional type variables that get instantiated.
      *
      *  @param env         The current environment
      *  @param site        The type of which the method is a member.
      *  @param m           The method symbol.
      *  @param argtypes    The invocation's given value arguments.
      *  @param typeargtypes    The invocation's given type arguments.
      *  @param allowBoxing Allow boxing conversions of arguments.
      *  @param useVarargs Box trailing arguments into an array for varargs.
      */
     Type rawInstantiate(Env<AttrContext> env,
                         Type site,
                         Symbol m,
                         ResultInfo resultInfo,
                         List<Type> argtypes,
                         List<Type> typeargtypes,
                         boolean allowBoxing,
                         boolean useVarargs,
                         MethodCheck methodCheck,
                         Warner warn) throws Infer.InferenceException {
         Type mt = types.memberType(site, m);
         // tvars is the list of formal type variables for which type arguments
         // need to inferred.
         List<Type> tvars = List.nil();
         if (typeargtypes == null) typeargtypes = List.nil();
         if (!mt.hasTag(FORALL) && typeargtypes.nonEmpty()) {
             // This is not a polymorphic method, but typeargs are supplied
             // which is fine, see JLS 15.12.2.1
         } else if (mt.hasTag(FORALL) && typeargtypes.nonEmpty()) {
             ForAll pmt = (ForAll) mt;
             if (typeargtypes.length() != pmt.tvars.length())
                 throw inapplicableMethodException.setMessage("arg.length.mismatch"); // not enough args
             // Check type arguments are within bounds
             List<Type> formals = pmt.tvars;
             List<Type> actuals = typeargtypes;
             while (formals.nonEmpty() && actuals.nonEmpty()) {
                 List<Type> bounds = types.subst(types.getBounds((TypeVar)formals.head),
                                                 pmt.tvars, typeargtypes);
                 for (; bounds.nonEmpty(); bounds = bounds.tail)
                     if (!types.isSubtypeUnchecked(actuals.head, bounds.head, warn))
                         throw inapplicableMethodException.setMessage("explicit.param.do.not.conform.to.bounds",actuals.head, bounds);
                 formals = formals.tail;
                 actuals = actuals.tail;
             }
             mt = types.subst(pmt.qtype, pmt.tvars, typeargtypes);
         } else if (mt.hasTag(FORALL)) {
             ForAll pmt = (ForAll) mt;
             List<Type> tvars1 = types.newInstances(pmt.tvars);
             tvars = tvars.appendList(tvars1);
             mt = types.subst(pmt.qtype, pmt.tvars, tvars1);
         }
         // find out whether we need to go the slow route via infer
         boolean instNeeded = tvars.tail != null; /*inlined: tvars.nonEmpty()*/
         for (List<Type> l = argtypes;
              l.tail != null/*inlined: l.nonEmpty()*/ && !instNeeded;
              l = l.tail) {
             if (l.head.hasTag(FORALL)) instNeeded = true;
         }
         if (instNeeded)
             return infer.instantiateMethod(env,
                                     tvars,
                                     (MethodType)mt,
                                     resultInfo,
                                     m,
                                     argtypes,
                                     allowBoxing,
                                     useVarargs,
                                     currentResolutionContext,
                                     methodCheck,
                                     warn);
         methodCheck.argumentsAcceptable(env, currentResolutionContext.deferredAttrContext(m, infer.emptyContext),
                                 argtypes, mt.getParameterTypes(), warn);
         return mt;
     }
     Type checkMethod(Env<AttrContext> env,
                      Type site,
                      Symbol m,
                      ResultInfo resultInfo,
                      List<Type> argtypes,
                      List<Type> typeargtypes,
                      Warner warn) {
         MethodResolutionContext prevContext = currentResolutionContext;
         try {
             currentResolutionContext = new MethodResolutionContext();
             currentResolutionContext.attrMode = DeferredAttr.AttrMode.CHECK;
             MethodResolutionPhase step = currentResolutionContext.step = env.info.pendingResolutionPhase;
             return rawInstantiate(env, site, m, resultInfo, argtypes, typeargtypes,
                     step.isBoxingRequired(), step.isVarargsRequired(), resolveMethodCheck, warn);
         }
         finally {
             currentResolutionContext = prevContext;
         }
     }
     /** Same but returns null instead throwing a NoInstanceException
      */
     Type instantiate(Env<AttrContext> env,
                      Type site,
                      Symbol m,
                      ResultInfo resultInfo,
                      List<Type> argtypes,
                      List<Type> typeargtypes,
                      boolean allowBoxing,
                      boolean useVarargs,
                      MethodCheck methodCheck,
                      Warner warn) {
         try {
             return rawInstantiate(env, site, m, resultInfo, argtypes, typeargtypes,
                                   allowBoxing, useVarargs, methodCheck, warn);
         } catch (InapplicableMethodException ex) {
             return null;
         }
     }
     /**
      * This interface defines an entry point that should be used to perform a
      * method check. A method check usually consist in determining as to whether
      * a set of types (actuals) is compatible with another set of types (formals).
      * Since the notion of compatibility can vary depending on the circumstances,
      * this interfaces allows to easily add new pluggable method check routines.
      */
     interface MethodCheck {
         /**
          * Main method check routine. A method check usually consist in determining
          * as to whether a set of types (actuals) is compatible with another set of
          * types (formals). If an incompatibility is found, an unchecked exception
          * is assumed to be thrown.
          */
         void argumentsAcceptable(Env<AttrContext> env,
                                 DeferredAttrContext deferredAttrContext,
                                 List<Type> argtypes,
                                 List<Type> formals,
                                 Warner warn);
     }
     /**
      * Helper enum defining all method check diagnostics (used by resolveMethodCheck).
      */
     enum MethodCheckDiag {
         /**
          * Actuals and formals differs in length.
          */
         ARITY_MISMATCH("arg.length.mismatch", "infer.arg.length.mismatch"),
         /**
          * An actual is incompatible with a formal.
          */
         ARG_MISMATCH("no.conforming.assignment.exists", "infer.no.conforming.assignment.exists"),
         /**
          * An actual is incompatible with the varargs element type.
          */
         VARARG_MISMATCH("varargs.argument.mismatch", "infer.varargs.argument.mismatch"),
         /**
          * The varargs element type is inaccessible.
          */
         INACCESSIBLE_VARARGS("inaccessible.varargs.type", "inaccessible.varargs.type");
         final String basicKey;
         final String inferKey;
         MethodCheckDiag(String basicKey, String inferKey) {
             this.basicKey = basicKey;
             this.inferKey = inferKey;
         }
     }
     /**
      * Main method applicability routine. Given a list of actual types A,
      * a list of formal types F, determines whether the types in A are
      * compatible (by method invocation conversion) with the types in F.
      *
      * Since this routine is shared between overload resolution and method
      * type-inference, a (possibly empty) inference context is used to convert
      * formal types to the corresponding 'undet' form ahead of a compatibility
      * check so that constraints can be propagated and collected.
      *
      * Moreover, if one or more types in A is a deferred type, this routine uses
      * DeferredAttr in order to perform deferred attribution. If one or more actual
      * deferred types are stuck, they are placed in a queue and revisited later
      * after the remainder of the arguments have been seen. If this is not sufficient
      * to 'unstuck' the argument, a cyclic inference error is called out.
      *
      * A method check handler (see above) is used in order to report errors.
      */
     MethodCheck resolveMethodCheck = new MethodCheck() {
         @Override
         public void argumentsAcceptable(final Env<AttrContext> env,
                                     DeferredAttrContext deferredAttrContext,
                                     List<Type> argtypes,
                                     List<Type> formals,
                                     Warner warn) {
             //should we expand formals?
             boolean useVarargs = deferredAttrContext.phase.isVarargsRequired();
             //inference context used during this method check
             InferenceContext inferenceContext = deferredAttrContext.inferenceContext;
             Type varargsFormal = useVarargs ? formals.last() : null;
             if (varargsFormal == null &&
                     argtypes.size() != formals.size()) {
                 report(MethodCheckDiag.ARITY_MISMATCH, inferenceContext); // not enough args
             }
             while (argtypes.nonEmpty() && formals.head != varargsFormal) {
                 ResultInfo mresult = methodCheckResult(false, formals.head, deferredAttrContext, warn);
                 mresult.check(null, argtypes.head);
                 argtypes = argtypes.tail;
                 formals = formals.tail;
             }
             if (formals.head != varargsFormal) {
                 report(MethodCheckDiag.ARITY_MISMATCH, inferenceContext); // not enough args
             }
             if (useVarargs) {
                 //note: if applicability check is triggered by most specific test,
                 //the last argument of a varargs is _not_ an array type (see JLS 15.12.2.5)
                 final Type elt = types.elemtype(varargsFormal);
                 ResultInfo mresult = methodCheckResult(true, elt, deferredAttrContext, warn);
                 while (argtypes.nonEmpty()) {
                     mresult.check(null, argtypes.head);
                     argtypes = argtypes.tail;
                 }
                 //check varargs element type accessibility
                 varargsAccessible(env, elt, inferenceContext);
             }
         }
         private void report(MethodCheckDiag diag, InferenceContext inferenceContext, Object... args) {
             boolean inferDiag = inferenceContext != infer.emptyContext;
             InapplicableMethodException ex = inferDiag ?
                     infer.inferenceException : inapplicableMethodException;
             if (inferDiag && (!diag.inferKey.equals(diag.basicKey))) {
                 Object[] args2 = new Object[args.length + 1];
                 System.arraycopy(args, 0, args2, 1, args.length);
                 args2[0] = inferenceContext.inferenceVars();
                 args = args2;
             }
             throw ex.setMessage(inferDiag ? diag.inferKey : diag.basicKey, args);
         }
         private void varargsAccessible(final Env<AttrContext> env, final Type t, final InferenceContext inferenceContext) {
             if (inferenceContext.free(t)) {
                 inferenceContext.addFreeTypeListener(List.of(t), new FreeTypeListener() {
                     @Override
                     public void typesInferred(InferenceContext inferenceContext) {
                         varargsAccessible(env, inferenceContext.asInstType(t, types), inferenceContext);
                     }
                 });
             } else {
                 if (!isAccessible(env, t)) {
                     Symbol location = env.enclClass.sym;
                     report(MethodCheckDiag.INACCESSIBLE_VARARGS, inferenceContext, t, Kinds.kindName(location), location);
                 }
             }
         }
         private ResultInfo methodCheckResult(final boolean varargsCheck, Type to,
                 final DeferredAttr.DeferredAttrContext deferredAttrContext, Warner rsWarner) {
             CheckContext checkContext = new MethodCheckContext(!deferredAttrContext.phase.isBoxingRequired(), deferredAttrContext, rsWarner) {
                 MethodCheckDiag methodDiag = varargsCheck ?
                                  MethodCheckDiag.VARARG_MISMATCH : MethodCheckDiag.ARG_MISMATCH;
                 @Override
                 public void report(DiagnosticPosition pos, JCDiagnostic details) {
                     report(methodDiag, deferredAttrContext.inferenceContext, details);
                 }
             };
             return new MethodResultInfo(to, checkContext);
         }
     };
     /**
      * Check context to be used during method applicability checks. A method check
      * context might contain inference variables.
      */
     abstract class MethodCheckContext implements CheckContext {
         boolean strict;
         DeferredAttrContext deferredAttrContext;
         Warner rsWarner;
         public MethodCheckContext(boolean strict, DeferredAttrContext deferredAttrContext, Warner rsWarner) {
            this.strict = strict;
            this.deferredAttrContext = deferredAttrContext;
            this.rsWarner = rsWarner;
         }
         public boolean compatible(Type found, Type req, Warner warn) {
             return strict ?
                     types.isSubtypeUnchecked(found, deferredAttrContext.inferenceContext.asFree(req, types), warn) :
                     types.isConvertible(found, deferredAttrContext.inferenceContext.asFree(req, types), warn);
         }
         public void report(DiagnosticPosition pos, JCDiagnostic details) {
             throw inapplicableMethodException.setMessage(details);
         }
         public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
             return rsWarner;
         }
         public InferenceContext inferenceContext() {
             return deferredAttrContext.inferenceContext;
         }
         public DeferredAttrContext deferredAttrContext() {
             return deferredAttrContext;
         }
     }
     /**
      * ResultInfo class to be used during method applicability checks. Check
      * for deferred types goes through special path.
      */
     class MethodResultInfo extends ResultInfo {
         public MethodResultInfo(Type pt, CheckContext checkContext) {
             attr.super(VAL, pt, checkContext);
         }
         @Override
         protected Type check(DiagnosticPosition pos, Type found) {
             if (found.hasTag(DEFERRED)) {
                 DeferredType dt = (DeferredType)found;
                 return dt.check(this);
             } else {
                 return super.check(pos, chk.checkNonVoid(pos, types.capture(types.upperBound(found.baseType()))));
             }
         }
         @Override
         protected MethodResultInfo dup(Type newPt) {
             return new MethodResultInfo(newPt, checkContext);
         }
         @Override
         protected ResultInfo dup(CheckContext newContext) {
             return new MethodResultInfo(pt, newContext);
         }
     }
     public static class InapplicableMethodException extends RuntimeException {
         private static final long serialVersionUID = 0;
         JCDiagnostic diagnostic;
         JCDiagnostic.Factory diags;
         InapplicableMethodException(JCDiagnostic.Factory diags) {
             this.diagnostic = null;
             this.diags = diags;
         }
         InapplicableMethodException setMessage() {
             return setMessage((JCDiagnostic)null);
         }
         InapplicableMethodException setMessage(String key) {
             return setMessage(key != null ? diags.fragment(key) : null);
         }
         InapplicableMethodException setMessage(String key, Object... args) {
             return setMessage(key != null ? diags.fragment(key, args) : null);
         }
         InapplicableMethodException setMessage(JCDiagnostic diag) {
             this.diagnostic = diag;
             return this;
         }
         public JCDiagnostic getDiagnostic() {
             return diagnostic;
         }
     }
     private final InapplicableMethodException inapplicableMethodException;
 /* ***************************************************************************
  *  Symbol lookup
  *  the following naming conventions for arguments are used
  *
  *       env      is the environment where the symbol was mentioned
  *       site     is the type of which the symbol is a member
  *       name     is the symbol's name
  *                if no arguments are given
  *       argtypes are the value arguments, if we search for a method
  *
  *  If no symbol was found, a ResolveError detailing the problem is returned.
  ****************************************************************************/
     /** Find field. Synthetic fields are always skipped.
      *  @param env     The current environment.
      *  @param site    The original type from where the selection takes place.
      *  @param name    The name of the field.
      *  @param c       The class to search for the field. This is always
      *                 a superclass or implemented interface of site's class.
      */
     Symbol findField(Env<AttrContext> env,
                      Type site,
                      Name name,
                      TypeSymbol c) {
         while (c.type.hasTag(TYPEVAR))
             c = c.type.getUpperBound().tsym;
         Symbol bestSoFar = varNotFound;
         Symbol sym;
         Scope.Entry e = c.members().lookup(name);
         while (e.scope != null) {
             if (e.sym.kind == VAR && (e.sym.flags_field & SYNTHETIC) == 0) {
                 return isAccessible(env, site, e.sym)
                     ? e.sym : new AccessError(env, site, e.sym);
             }
             e = e.next();
         }
         Type st = types.supertype(c.type);
         if (st != null && (st.hasTag(CLASS) || st.hasTag(TYPEVAR))) {
             sym = findField(env, site, name, st.tsym);
             if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         for (List<Type> l = types.interfaces(c.type);
              bestSoFar.kind != AMBIGUOUS && l.nonEmpty();
              l = l.tail) {
             sym = findField(env, site, name, l.head.tsym);
             if (bestSoFar.kind < AMBIGUOUS && sym.kind < AMBIGUOUS &&
                 sym.owner != bestSoFar.owner)
                 bestSoFar = new AmbiguityError(bestSoFar, sym);
             else if (sym.kind < bestSoFar.kind)
                 bestSoFar = sym;
         }
         return bestSoFar;
     }
     /** Resolve a field identifier, throw a fatal error if not found.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the method invocation.
      *  @param site      The type of the qualifying expression, in which
      *                   identifier is searched.
      *  @param name      The identifier's name.
      */
     public VarSymbol resolveInternalField(DiagnosticPosition pos, Env<AttrContext> env,
                                           Type site, Name name) {
         Symbol sym = findField(env, site, name, site.tsym);
         if (sym.kind == VAR) return (VarSymbol)sym;
         else throw new FatalError(
                  diags.fragment("fatal.err.cant.locate.field",
                                 name));
     }
     /** Find unqualified variable or field with given name.
      *  Synthetic fields always skipped.
      *  @param env     The current environment.
      *  @param name    The name of the variable or field.
      */
     Symbol findVar(Env<AttrContext> env, Name name) {
         Symbol bestSoFar = varNotFound;
         Symbol sym;
         Env<AttrContext> env1 = env;
         boolean staticOnly = false;
         while (env1.outer != null) {
             if (isStatic(env1)) staticOnly = true;
             Scope.Entry e = env1.info.scope.lookup(name);
             while (e.scope != null &&
                    (e.sym.kind != VAR ||
                     (e.sym.flags_field & SYNTHETIC) != 0))
                 e = e.next();
             sym = (e.scope != null)
                 ? e.sym
                 : findField(
                     env1, env1.enclClass.sym.type, name, env1.enclClass.sym);
             if (sym.exists()) {
                 if (staticOnly &&
                     sym.kind == VAR &&
                     sym.owner.kind == TYP &&
                     (sym.flags() & STATIC) == 0)
                     return new StaticError(sym);
                 else
                     return sym;
             } else if (sym.kind < bestSoFar.kind) {
                 bestSoFar = sym;
             }
             if ((env1.enclClass.sym.flags() & STATIC) != 0) staticOnly = true;
             env1 = env1.outer;
         }
         sym = findField(env, syms.predefClass.type, name, syms.predefClass);
         if (sym.exists())
             return sym;
         if (bestSoFar.exists())
             return bestSoFar;
         Scope.Entry e = env.toplevel.namedImportScope.lookup(name);
         for (; e.scope != null; e = e.next()) {
             sym = e.sym;
             Type origin = e.getOrigin().owner.type;
             if (sym.kind == VAR) {
                 if (e.sym.owner.type != origin)
                     sym = sym.clone(e.getOrigin().owner);
                 return isAccessible(env, origin, sym)
                     ? sym : new AccessError(env, origin, sym);
             }
         }
         Symbol origin = null;
         e = env.toplevel.starImportScope.lookup(name);
         for (; e.scope != null; e = e.next()) {
             sym = e.sym;
             if (sym.kind != VAR)
                 continue;
             // invariant: sym.kind == VAR
             if (bestSoFar.kind < AMBIGUOUS && sym.owner != bestSoFar.owner)
                 return new AmbiguityError(bestSoFar, sym);
             else if (bestSoFar.kind >= VAR) {
                 origin = e.getOrigin().owner;
                 bestSoFar = isAccessible(env, origin.type, sym)
                     ? sym : new AccessError(env, origin.type, sym);
             }
         }
         if (bestSoFar.kind == VAR && bestSoFar.owner.type != origin.type)
             return bestSoFar.clone(origin);
         else
             return bestSoFar;
     }
     Warner noteWarner = new Warner();
     /** Select the best method for a call site among two choices.
      *  @param env              The current environment.
      *  @param site             The original type from where the
      *                          selection takes place.
      *  @param argtypes         The invocation's value arguments,
      *  @param typeargtypes     The invocation's type arguments,
      *  @param sym              Proposed new best match.
      *  @param bestSoFar        Previously found best match.
      *  @param allowBoxing Allow boxing conversions of arguments.
      *  @param useVarargs Box trailing arguments into an array for varargs.
      */
     @SuppressWarnings("fallthrough")
     Symbol selectBest(Env<AttrContext> env,
                       Type site,
                       List<Type> argtypes,
                       List<Type> typeargtypes,
                       Symbol sym,
                       Symbol bestSoFar,
                       boolean allowBoxing,
                       boolean useVarargs,
                       boolean operator) {
         if (sym.kind == ERR ||
                 !sym.isInheritedIn(site.tsym, types) ||
                 (useVarargs && (sym.flags() & VARARGS) == 0)) {
             return bestSoFar;
         }
         Assert.check(sym.kind < AMBIGUOUS);
         try {
             Type mt = rawInstantiate(env, site, sym, null, argtypes, typeargtypes,
                                allowBoxing, useVarargs, resolveMethodCheck, types.noWarnings);
             if (!operator)
                 currentResolutionContext.addApplicableCandidate(sym, mt);
         } catch (InapplicableMethodException ex) {
             if (!operator)
                 currentResolutionContext.addInapplicableCandidate(sym, ex.getDiagnostic());
             switch (bestSoFar.kind) {
                 case ABSENT_MTH:
                     return new InapplicableSymbolError(currentResolutionContext);
                 case WRONG_MTH:
                     if (operator) return bestSoFar;
                     bestSoFar = new InapplicableSymbolsError(currentResolutionContext);
                 default:
                     return bestSoFar;
             }
         }
         if (!isAccessible(env, site, sym)) {
             return (bestSoFar.kind == ABSENT_MTH)
                 ? new AccessError(env, site, sym)
                 : bestSoFar;
         }
         return (bestSoFar.kind > AMBIGUOUS)
             ? sym
             : mostSpecific(argtypes, sym, bestSoFar, env, site,
                            allowBoxing && operator, useVarargs);
     }
     /* Return the most specific of the two methods for a call,
      *  given that both are accessible and applicable.
      *  @param m1               A new candidate for most specific.
      *  @param m2               The previous most specific candidate.
      *  @param env              The current environment.
      *  @param site             The original type from where the selection
      *                          takes place.
      *  @param allowBoxing Allow boxing conversions of arguments.
      *  @param useVarargs Box trailing arguments into an array for varargs.
      */
     Symbol mostSpecific(List<Type> argtypes, Symbol m1,
                         Symbol m2,
                         Env<AttrContext> env,
                         final Type site,
                         boolean allowBoxing,
                         boolean useVarargs) {
         switch (m2.kind) {
         case MTH:
             if (m1 == m2) return m1;
             boolean m1SignatureMoreSpecific =
                     signatureMoreSpecific(argtypes, env, site, m1, m2, allowBoxing, useVarargs);
             boolean m2SignatureMoreSpecific =
                     signatureMoreSpecific(argtypes, env, site, m2, m1, allowBoxing, useVarargs);
             if (m1SignatureMoreSpecific && m2SignatureMoreSpecific) {
                 Type mt1 = types.memberType(site, m1);
                 Type mt2 = types.memberType(site, m2);
                 if (!types.overrideEquivalent(mt1, mt2))
                     return ambiguityError(m1, m2);
                 // same signature; select (a) the non-bridge method, or
                 // (b) the one that overrides the other, or (c) the concrete
                 // one, or (d) merge both abstract signatures
                 if ((m1.flags() & BRIDGE) != (m2.flags() & BRIDGE))
                     return ((m1.flags() & BRIDGE) != 0) ? m2 : m1;
                 // if one overrides or hides the other, use it
                 TypeSymbol m1Owner = (TypeSymbol)m1.owner;
                 TypeSymbol m2Owner = (TypeSymbol)m2.owner;
                 if (types.asSuper(m1Owner.type, m2Owner) != null &&
                     ((m1.owner.flags_field & INTERFACE) == 0 ||
                      (m2.owner.flags_field & INTERFACE) != 0) &&
                     m1.overrides(m2, m1Owner, types, false))
                     return m1;
                 if (types.asSuper(m2Owner.type, m1Owner) != null &&
                     ((m2.owner.flags_field & INTERFACE) == 0 ||
                      (m1.owner.flags_field & INTERFACE) != 0) &&
                     m2.overrides(m1, m2Owner, types, false))
                     return m2;
                 boolean m1Abstract = (m1.flags() & ABSTRACT) != 0;
                 boolean m2Abstract = (m2.flags() & ABSTRACT) != 0;
                 if (m1Abstract && !m2Abstract) return m2;
                 if (m2Abstract && !m1Abstract) return m1;
                 // both abstract or both concrete
                 return ambiguityError(m1, m2);
             }
             if (m1SignatureMoreSpecific) return m1;
             if (m2SignatureMoreSpecific) return m2;
             return ambiguityError(m1, m2);
         case AMBIGUOUS:
             //check if m1 is more specific than all ambiguous methods in m2
             AmbiguityError e = (AmbiguityError)m2;
             for (Symbol s : e.ambiguousSyms) {
                 if (mostSpecific(argtypes, m1, s, env, site, allowBoxing, useVarargs) != m1) {
                     return e.addAmbiguousSymbol(m1);
                 }
             }
             return m1;
         default:
             throw new AssertionError();
         }
     }
     //where
     private boolean signatureMoreSpecific(List<Type> actuals, Env<AttrContext> env, Type site, Symbol m1, Symbol m2, boolean allowBoxing, boolean useVarargs) {
         Symbol m12 = adjustVarargs(m1, m2, useVarargs);
         Symbol m22 = adjustVarargs(m2, m1, useVarargs);
         Type mtype1 = types.memberType(site, m12);
         Type mtype2 = types.memberType(site, m22);
         //check if invocation is more specific
         if (invocationMoreSpecific(env, site, m22, mtype1.getParameterTypes(), allowBoxing, useVarargs)) {
             return true;
         }
         //perform structural check
         List<Type> formals1 = mtype1.getParameterTypes();
         Type lastFormal1 = formals1.last();
         List<Type> formals2 = mtype2.getParameterTypes();
         Type lastFormal2 = formals2.last();
         ListBuffer<Type> newFormals = ListBuffer.lb();
         boolean hasStructuralPoly = false;
         for (Type actual : actuals) {
             //perform formal argument adaptation in case actuals > formals (varargs)
             Type f1 = formals1.isEmpty() ?
                     lastFormal1 : formals1.head;
             Type f2 = formals2.isEmpty() ?
                     lastFormal2 : formals2.head;
             //is this a structural actual argument?
             boolean isStructuralPoly = actual.hasTag(DEFERRED) &&
                     (((DeferredType)actual).tree.hasTag(LAMBDA) ||
                     ((DeferredType)actual).tree.hasTag(REFERENCE));
             Type newFormal = f1;
             if (isStructuralPoly) {
                 //for structural arguments only - check that corresponding formals
                 //are related - if so replace formal with <null>
                 hasStructuralPoly = true;
                 DeferredType dt = (DeferredType)actual;
                 Type t1 = deferredAttr.new DeferredTypeMap(AttrMode.SPECULATIVE, m1, currentResolutionContext.step).apply(dt);
                 Type t2 = deferredAttr.new DeferredTypeMap(AttrMode.SPECULATIVE, m2, currentResolutionContext.step).apply(dt);
                 if (t1.isErroneous() || t2.isErroneous() || !isStructuralSubtype(t1, t2)) {
                     //not structural subtypes - simply fail
                     return false;
                 } else {
                     newFormal = syms.botType;
                 }
             }
             newFormals.append(newFormal);
             if (newFormals.length() > mtype2.getParameterTypes().length()) {
                 //expand m2's type so as to fit the new formal arity (varargs)
                 m22.type = types.createMethodTypeWithParameters(m22.type, m22.type.getParameterTypes().append(f2));
             }
             formals1 = formals1.isEmpty() ? formals1 : formals1.tail;
             formals2 = formals2.isEmpty() ? formals2 : formals2.tail;
         }
         if (!hasStructuralPoly) {
             //if no structural actual was found, we're done
             return false;
         }
         //perform additional adaptation if actuals < formals (varargs)
         for (Type t : formals1) {
             newFormals.append(t);
         }
         //check if invocation (with tweaked args) is more specific
         return invocationMoreSpecific(env, site, m22, newFormals.toList(), allowBoxing, useVarargs);
     }
     //where
     private boolean invocationMoreSpecific(Env<AttrContext> env, Type site, Symbol m2, List<Type> argtypes1, boolean allowBoxing, boolean useVarargs) {
         MethodResolutionContext prevContext = currentResolutionContext;
         try {
             currentResolutionContext = new MethodResolutionContext();
             currentResolutionContext.step = allowBoxing ? BOX : BASIC;
             noteWarner.clear();
             Type mst = instantiate(env, site, m2, null,
                     types.lowerBounds(argtypes1), null,
                     allowBoxing, false, resolveMethodCheck, noteWarner);
             return mst != null &&
                     !noteWarner.hasLint(Lint.LintCategory.UNCHECKED);
         } finally {
             currentResolutionContext = prevContext;
         }
     }
     //where
     private Symbol adjustVarargs(Symbol to, Symbol from, boolean useVarargs) {
         List<Type> fromArgs = from.type.getParameterTypes();
         List<Type> toArgs = to.type.getParameterTypes();
         if (useVarargs &&
                 (from.flags() & VARARGS) != 0 &&
                 (to.flags() & VARARGS) != 0) {
             Type varargsTypeFrom = fromArgs.last();
             Type varargsTypeTo = toArgs.last();
             ListBuffer<Type> args = ListBuffer.lb();
             if (toArgs.length() < fromArgs.length()) {
                 //if we are checking a varargs method 'from' against another varargs
                 //method 'to' (where arity of 'to' < arity of 'from') then expand signature
                 //of 'to' to 'fit' arity of 'from' (this means adding fake formals to 'to'
                 //until 'to' signature has the same arity as 'from')
                 while (fromArgs.head != varargsTypeFrom) {
                     args.append(toArgs.head == varargsTypeTo ? types.elemtype(varargsTypeTo) : toArgs.head);
                     fromArgs = fromArgs.tail;
                     toArgs = toArgs.head == varargsTypeTo ?
                         toArgs :
                         toArgs.tail;
                 }
             } else {
                 //formal argument list is same as original list where last
                 //argument (array type) is removed
                 args.appendList(toArgs.reverse().tail.reverse());
             }
             //append varargs element type as last synthetic formal
             args.append(types.elemtype(varargsTypeTo));
             Type mtype = types.createMethodTypeWithParameters(to.type, args.toList());
             return new MethodSymbol(to.flags_field & ~VARARGS, to.name, mtype, to.owner);
         } else {
             return to;
         }
     }
     //where
     boolean isStructuralSubtype(Type s, Type t) {
         Type ret_s = types.findDescriptorType(s).getReturnType();
         Type ret_t = types.findDescriptorType(t).getReturnType();
         //covariant most specific check for function descriptor return type
         if (!types.isSubtype(ret_s, ret_t)) {
             return false;
         }
         List<Type> args_s = types.findDescriptorType(s).getParameterTypes();
         List<Type> args_t = types.findDescriptorType(t).getParameterTypes();
         //arity must be identical
         if (args_s.length() != args_t.length()) {
             return false;
         }
         //invariant most specific check for function descriptor parameter types
         if (!types.isSameTypes(args_t, args_s)) {
             return false;
         }
         return true;
     }
     //where
     Type mostSpecificReturnType(Type mt1, Type mt2) {
         Type rt1 = mt1.getReturnType();
         Type rt2 = mt2.getReturnType();
         if (mt1.hasTag(FORALL) && mt2.hasTag(FORALL)) {
             //if both are generic methods, adjust return type ahead of subtyping check
             rt1 = types.subst(rt1, mt1.getTypeArguments(), mt2.getTypeArguments());
         }
         //first use subtyping, then return type substitutability
         if (types.isSubtype(rt1, rt2)) {
             return mt1;
         } else if (types.isSubtype(rt2, rt1)) {
             return mt2;
         } else if (types.returnTypeSubstitutable(mt1, mt2)) {
             return mt1;
         } else if (types.returnTypeSubstitutable(mt2, mt1)) {
             return mt2;
         } else {
             return null;
         }
     }
     //where
     Symbol ambiguityError(Symbol m1, Symbol m2) {
         if (((m1.flags() | m2.flags()) & CLASH) != 0) {
             return (m1.flags() & CLASH) == 0 ? m1 : m2;
         } else {
             return new AmbiguityError(m1, m2);
         }
     }
     Symbol findMethodInScope(Env<AttrContext> env,
             Type site,
             Name name,
             List<Type> argtypes,
             List<Type> typeargtypes,
             Scope sc,
             Symbol bestSoFar,
             boolean allowBoxing,
             boolean useVarargs,
             boolean operator,
             boolean abstractok) {
         for (Symbol s : sc.getElementsByName(name, new LookupFilter(abstractok))) {
             bestSoFar = selectBest(env, site, argtypes, typeargtypes, s,
                     bestSoFar, allowBoxing, useVarargs, operator);
         }
         return bestSoFar;
     }
     //where
         class LookupFilter implements Filter<Symbol> {
             boolean abstractOk;
             LookupFilter(boolean abstractOk) {
                 this.abstractOk = abstractOk;
             }
             public boolean accepts(Symbol s) {
                 long flags = s.flags();
                 return s.kind == MTH &&
                         (flags & SYNTHETIC) == 0 &&
                         (abstractOk ||
                         (flags & DEFAULT) != 0 ||
                         (flags & ABSTRACT) == 0);
             }
         };
     /** Find best qualified method matching given name, type and value
      *  arguments.
      *  @param env       The current environment.
      *  @param site      The original type from where the selection
      *                   takes place.
      *  @param name      The method's name.
      *  @param argtypes  The method's value arguments.
      *  @param typeargtypes The method's type arguments
      *  @param allowBoxing Allow boxing conversions of arguments.
      *  @param useVarargs Box trailing arguments into an array for varargs.
      */
     Symbol findMethod(Env<AttrContext> env,
                       Type site,
                       Name name,
                       List<Type> argtypes,
                       List<Type> typeargtypes,
                       boolean allowBoxing,
                       boolean useVarargs,
                       boolean operator) {
         Symbol bestSoFar = methodNotFound;
         bestSoFar = findMethod(env,
                           site,
                           name,
                           argtypes,
                           typeargtypes,
                           site.tsym.type,
                           bestSoFar,
                           allowBoxing,
                           useVarargs,
                           operator);
         reportVerboseResolutionDiagnostic(env.tree.pos(), name, site, argtypes, typeargtypes, bestSoFar);
         return bestSoFar;
     }
     // where
     private Symbol findMethod(Env<AttrContext> env,
                               Type site,
                               Name name,
                               List<Type> argtypes,
                               List<Type> typeargtypes,
                               Type intype,
                               Symbol bestSoFar,
                               boolean allowBoxing,
                               boolean useVarargs,
                               boolean operator) {
         @SuppressWarnings({"unchecked","rawtypes"})
         List<Type>[] itypes = (List<Type>[])new List[] { List.<Type>nil(), List.<Type>nil() };
         InterfaceLookupPhase iphase = InterfaceLookupPhase.ABSTRACT_OK;
         for (TypeSymbol s : superclasses(intype)) {
             bestSoFar = findMethodInScope(env, site, name, argtypes, typeargtypes,
                     s.members(), bestSoFar, allowBoxing, useVarargs, operator, true);
             if (name == names.init) return bestSoFar;
             iphase = (iphase == null) ? null : iphase.update(s, this);
             if (iphase != null) {
                 for (Type itype : types.interfaces(s.type)) {
                     itypes[iphase.ordinal()] = types.union(types.closure(itype), itypes[iphase.ordinal()]);
                 }
             }
         }
         Symbol concrete = bestSoFar.kind < ERR &&
                 (bestSoFar.flags() & ABSTRACT) == 0 ?
                 bestSoFar : methodNotFound;
         for (InterfaceLookupPhase iphase2 : InterfaceLookupPhase.values()) {
             if (iphase2 == InterfaceLookupPhase.DEFAULT_OK && !allowDefaultMethods) break;
             //keep searching for abstract methods
             for (Type itype : itypes[iphase2.ordinal()]) {
                 if (!itype.isInterface()) continue; //skip j.l.Object (included by Types.closure())
                 if (iphase2 == InterfaceLookupPhase.DEFAULT_OK &&
                         (itype.tsym.flags() & DEFAULT) == 0) continue;
                 bestSoFar = findMethodInScope(env, site, name, argtypes, typeargtypes,
                         itype.tsym.members(), bestSoFar, allowBoxing, useVarargs, operator, true);
                 if (concrete != bestSoFar &&
                         concrete.kind < ERR  && bestSoFar.kind < ERR &&
                         types.isSubSignature(concrete.type, bestSoFar.type)) {
                     //this is an hack - as javac does not do full membership checks
                     //most specific ends up comparing abstract methods that might have
                     //been implemented by some concrete method in a subclass and,
                     //because of raw override, it is possible for an abstract method
                     //to be more specific than the concrete method - so we need
                     //to explicitly call that out (see CR 6178365)
                     bestSoFar = concrete;
                 }
             }
         }
         return bestSoFar;
     }
     enum InterfaceLookupPhase {
         ABSTRACT_OK() {
             @Override
             InterfaceLookupPhase update(Symbol s, Resolve rs) {
                 //We should not look for abstract methods if receiver is a concrete class
                 //(as concrete classes are expected to implement all abstracts coming
                 //from superinterfaces)
                 if ((s.flags() & (ABSTRACT | INTERFACE | ENUM)) != 0) {
                     return this;
                 } else if (rs.allowDefaultMethods) {
                     return DEFAULT_OK;
                 } else {
                     return null;
                 }
             }
         },
         DEFAULT_OK() {
             @Override
             InterfaceLookupPhase update(Symbol s, Resolve rs) {
                 return this;
             }
         };
         abstract InterfaceLookupPhase update(Symbol s, Resolve rs);
     }
     /**
      * Return an Iterable object to scan the superclasses of a given type.
      * It's crucial that the scan is done lazily, as we don't want to accidentally
      * access more supertypes than strictly needed (as this could trigger completion
      * errors if some of the not-needed supertypes are missing/ill-formed).
      */
     Iterable<TypeSymbol> superclasses(final Type intype) {
         return new Iterable<TypeSymbol>() {
             public Iterator<TypeSymbol> iterator() {
                 return new Iterator<TypeSymbol>() {
                     List<TypeSymbol> seen = List.nil();
                     TypeSymbol currentSym = symbolFor(intype);
                     TypeSymbol prevSym = null;
                     public boolean hasNext() {
                         if (currentSym == syms.noSymbol) {
                             currentSym = symbolFor(types.supertype(prevSym.type));
                         }
                         return currentSym != null;
                     }
                     public TypeSymbol next() {
                         prevSym = currentSym;
                         currentSym = syms.noSymbol;
                         Assert.check(prevSym != null || prevSym != syms.noSymbol);
                         return prevSym;
                     }
                     public void remove() {
                         throw new UnsupportedOperationException();
                     }
                     TypeSymbol symbolFor(Type t) {
                         if (!t.hasTag(CLASS) &&
                                 !t.hasTag(TYPEVAR)) {
                             return null;
                         }
                         while (t.hasTag(TYPEVAR))
                             t = t.getUpperBound();
                         if (seen.contains(t.tsym)) {
                             //degenerate case in which we have a circular
                             //class hierarchy - because of ill-formed classfiles
                             return null;
                         }
                         seen = seen.prepend(t.tsym);
                         return t.tsym;
                     }
                 };
             }
         };
     }
     /** Find unqualified method matching given name, type and value arguments.
      *  @param env       The current environment.
      *  @param name      The method's name.
      *  @param argtypes  The method's value arguments.
      *  @param typeargtypes  The method's type arguments.
      *  @param allowBoxing Allow boxing conversions of arguments.
      *  @param useVarargs Box trailing arguments into an array for varargs.
      */
     Symbol findFun(Env<AttrContext> env, Name name,
                    List<Type> argtypes, List<Type> typeargtypes,
                    boolean allowBoxing, boolean useVarargs) {
         Symbol bestSoFar = methodNotFound;
         Symbol sym;
         Env<AttrContext> env1 = env;
         boolean staticOnly = false;
         while (env1.outer != null) {
             if (isStatic(env1)) staticOnly = true;
             sym = findMethod(
                 env1, env1.enclClass.sym.type, name, argtypes, typeargtypes,
                 allowBoxing, useVarargs, false);
             if (sym.exists()) {
                 if (staticOnly &&
                     sym.kind == MTH &&
                     sym.owner.kind == TYP &&
                     (sym.flags() & STATIC) == 0) return new StaticError(sym);
                 else return sym;
             } else if (sym.kind < bestSoFar.kind) {
                 bestSoFar = sym;
             }
             if ((env1.enclClass.sym.flags() & STATIC) != 0) staticOnly = true;
             env1 = env1.outer;
         }
         sym = findMethod(env, syms.predefClass.type, name, argtypes,
                          typeargtypes, allowBoxing, useVarargs, false);
         if (sym.exists())
             return sym;
         Scope.Entry e = env.toplevel.namedImportScope.lookup(name);
         for (; e.scope != null; e = e.next()) {
             sym = e.sym;
             Type origin = e.getOrigin().owner.type;
             if (sym.kind == MTH) {
                 if (e.sym.owner.type != origin)
                     sym = sym.clone(e.getOrigin().owner);
                 if (!isAccessible(env, origin, sym))
                     sym = new AccessError(env, origin, sym);
                 bestSoFar = selectBest(env, origin,
                                        argtypes, typeargtypes,
                                        sym, bestSoFar,
                                        allowBoxing, useVarargs, false);
             }
         }
         if (bestSoFar.exists())
             return bestSoFar;
         e = env.toplevel.starImportScope.lookup(name);
         for (; e.scope != null; e = e.next()) {
             sym = e.sym;
             Type origin = e.getOrigin().owner.type;
             if (sym.kind == MTH) {
                 if (e.sym.owner.type != origin)
                     sym = sym.clone(e.getOrigin().owner);
                 if (!isAccessible(env, origin, sym))
                     sym = new AccessError(env, origin, sym);
                 bestSoFar = selectBest(env, origin,
                                        argtypes, typeargtypes,
                                        sym, bestSoFar,
                                        allowBoxing, useVarargs, false);
             }
         }
         return bestSoFar;
     }
     /** Load toplevel or member class with given fully qualified name and
      *  verify that it is accessible.
      *  @param env       The current environment.
      *  @param name      The fully qualified name of the class to be loaded.
      */
     Symbol loadClass(Env<AttrContext> env, Name name) {
         try {
             ClassSymbol c = reader.loadClass(name);
             return isAccessible(env, c) ? c : new AccessError(c);
         } catch (ClassReader.BadClassFile err) {
             throw err;
         } catch (CompletionFailure ex) {
             return typeNotFound;
         }
     }
     /** Find qualified member type.
      *  @param env       The current environment.
      *  @param site      The original type from where the selection takes
      *                   place.
      *  @param name      The type's name.
      *  @param c         The class to search for the member type. This is
      *                   always a superclass or implemented interface of
      *                   site's class.
      */
     Symbol findMemberType(Env<AttrContext> env,
                           Type site,
                           Name name,
                           TypeSymbol c) {
         Symbol bestSoFar = typeNotFound;
         Symbol sym;
         Scope.Entry e = c.members().lookup(name);
         while (e.scope != null) {
             if (e.sym.kind == TYP) {
                 return isAccessible(env, site, e.sym)
                     ? e.sym
                     : new AccessError(env, site, e.sym);
             }
             e = e.next();
         }
         Type st = types.supertype(c.type);
         if (st != null && st.hasTag(CLASS)) {
             sym = findMemberType(env, site, name, st.tsym);
             if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         for (List<Type> l = types.interfaces(c.type);
              bestSoFar.kind != AMBIGUOUS && l.nonEmpty();
              l = l.tail) {
             sym = findMemberType(env, site, name, l.head.tsym);
             if (bestSoFar.kind < AMBIGUOUS && sym.kind < AMBIGUOUS &&
                 sym.owner != bestSoFar.owner)
                 bestSoFar = new AmbiguityError(bestSoFar, sym);
             else if (sym.kind < bestSoFar.kind)
                 bestSoFar = sym;
         }
         return bestSoFar;
     }
     /** Find a global type in given scope and load corresponding class.
      *  @param env       The current environment.
      *  @param scope     The scope in which to look for the type.
      *  @param name      The type's name.
      */
     Symbol findGlobalType(Env<AttrContext> env, Scope scope, Name name) {
         Symbol bestSoFar = typeNotFound;
         for (Scope.Entry e = scope.lookup(name); e.scope != null; e = e.next()) {
             Symbol sym = loadClass(env, e.sym.flatName());
             if (bestSoFar.kind == TYP && sym.kind == TYP &&
                 bestSoFar != sym)
                 return new AmbiguityError(bestSoFar, sym);
             else if (sym.kind < bestSoFar.kind)
                 bestSoFar = sym;
         }
         return bestSoFar;
     }
     /** Find an unqualified type symbol.
      *  @param env       The current environment.
      *  @param name      The type's name.
      */
     Symbol findType(Env<AttrContext> env, Name name) {
         Symbol bestSoFar = typeNotFound;
         Symbol sym;
         boolean staticOnly = false;
         for (Env<AttrContext> env1 = env; env1.outer != null; env1 = env1.outer) {
             if (isStatic(env1)) staticOnly = true;
             for (Scope.Entry e = env1.info.scope.lookup(name);
                  e.scope != null;
                  e = e.next()) {
                 if (e.sym.kind == TYP) {
                     if (staticOnly &&
                         e.sym.type.hasTag(TYPEVAR) &&
                         e.sym.owner.kind == TYP) return new StaticError(e.sym);
                     return e.sym;
                 }
             }
             sym = findMemberType(env1, env1.enclClass.sym.type, name,
                                  env1.enclClass.sym);
             if (staticOnly && sym.kind == TYP &&
                 sym.type.hasTag(CLASS) &&
                 sym.type.getEnclosingType().hasTag(CLASS) &&
                 env1.enclClass.sym.type.isParameterized() &&
                 sym.type.getEnclosingType().isParameterized())
                 return new StaticError(sym);
             else if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
             JCClassDecl encl = env1.baseClause ? (JCClassDecl)env1.tree : env1.enclClass;
             if ((encl.sym.flags() & STATIC) != 0)
                 staticOnly = true;
         }
         if (!env.tree.hasTag(IMPORT)) {
             sym = findGlobalType(env, env.toplevel.namedImportScope, name);
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
             sym = findGlobalType(env, env.toplevel.packge.members(), name);
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
             sym = findGlobalType(env, env.toplevel.starImportScope, name);
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         return bestSoFar;
     }
     /** Find an unqualified identifier which matches a specified kind set.
      *  @param env       The current environment.
      *  @param name      The identifier's name.
      *  @param kind      Indicates the possible symbol kinds
      *                   (a subset of VAL, TYP, PCK).
      */
     Symbol findIdent(Env<AttrContext> env, Name name, int kind) {
         Symbol bestSoFar = typeNotFound;
         Symbol sym;
         if ((kind & VAR) != 0) {
             sym = findVar(env, name);
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         if ((kind & TYP) != 0) {
             sym = findType(env, name);
             if (sym.kind==TYP) {
                  reportDependence(env.enclClass.sym, sym);
             }
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         if ((kind & PCK) != 0) return reader.enterPackage(name);
         else return bestSoFar;
     }
     /** Report dependencies.
      * @param from The enclosing class sym
      * @param to   The found identifier that the class depends on.
      */
     public void reportDependence(Symbol from, Symbol to) {
         // Override if you want to collect the reported dependencies.
     }
     /** Find an identifier in a package which matches a specified kind set.
      *  @param env       The current environment.
      *  @param name      The identifier's name.
      *  @param kind      Indicates the possible symbol kinds
      *                   (a nonempty subset of TYP, PCK).
      */
     Symbol findIdentInPackage(Env<AttrContext> env, TypeSymbol pck,
                               Name name, int kind) {
         Name fullname = TypeSymbol.formFullName(name, pck);
         Symbol bestSoFar = typeNotFound;
         PackageSymbol pack = null;
         if ((kind & PCK) != 0) {
             pack = reader.enterPackage(fullname);
             if (pack.exists()) return pack;
         }
         if ((kind & TYP) != 0) {
             Symbol sym = loadClass(env, fullname);
             if (sym.exists()) {
                 // don't allow programs to use flatnames
                 if (name == sym.name) return sym;
             }
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         return (pack != null) ? pack : bestSoFar;
     }
     /** Find an identifier among the members of a given type `site'.
      *  @param env       The current environment.
      *  @param site      The type containing the symbol to be found.
      *  @param name      The identifier's name.
      *  @param kind      Indicates the possible symbol kinds
      *                   (a subset of VAL, TYP).
      */
     Symbol findIdentInType(Env<AttrContext> env, Type site,
                            Name name, int kind) {
         Symbol bestSoFar = typeNotFound;
         Symbol sym;
         if ((kind & VAR) != 0) {
             sym = findField(env, site, name, site.tsym);
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         if ((kind & TYP) != 0) {
             sym = findMemberType(env, site, name, site.tsym);
             if (sym.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         return bestSoFar;
     }
 /* ***************************************************************************
  *  Access checking
  *  The following methods convert ResolveErrors to ErrorSymbols, issuing
  *  an error message in the process
  ****************************************************************************/
     /** If `sym' is a bad symbol: report error and return errSymbol
      *  else pass through unchanged,
      *  additional arguments duplicate what has been used in trying to find the
      *  symbol {@literal (--> flyweight pattern)}. This improves performance since we
      *  expect misses to happen frequently.
      *
      *  @param sym       The symbol that was found, or a ResolveError.
      *  @param pos       The position to use for error reporting.
      *  @param location  The symbol the served as a context for this lookup
      *  @param site      The original type from where the selection took place.
      *  @param name      The symbol's name.
      *  @param qualified Did we get here through a qualified expression resolution?
      *  @param argtypes  The invocation's value arguments,
      *                   if we looked for a method.
      *  @param typeargtypes  The invocation's type arguments,
      *                   if we looked for a method.
      *  @param logResolveHelper helper class used to log resolve errors
      */
     Symbol accessInternal(Symbol sym,
                   DiagnosticPosition pos,
                   Symbol location,
                   Type site,
                   Name name,
                   boolean qualified,
                   List<Type> argtypes,
                   List<Type> typeargtypes,
                   LogResolveHelper logResolveHelper) {
         if (sym.kind >= AMBIGUOUS) {
             ResolveError errSym = (ResolveError)sym;
             sym = errSym.access(name, qualified ? site.tsym : syms.noSymbol);
             argtypes = logResolveHelper.getArgumentTypes(errSym, sym, name, argtypes);
             if (logResolveHelper.resolveDiagnosticNeeded(site, argtypes, typeargtypes)) {
                 logResolveError(errSym, pos, location, site, name, argtypes, typeargtypes);
             }
         }
         return sym;
     }
     /**
      * Variant of the generalized access routine, to be used for generating method
      * resolution diagnostics
      */
     Symbol accessMethod(Symbol sym,
                   DiagnosticPosition pos,
                   Symbol location,
                   Type site,
                   Name name,
                   boolean qualified,
                   List<Type> argtypes,
                   List<Type> typeargtypes) {
         return accessInternal(sym, pos, location, site, name, qualified, argtypes, typeargtypes, methodLogResolveHelper);
     }
     /** Same as original accessMethod(), but without location.
      */
     Symbol accessMethod(Symbol sym,
                   DiagnosticPosition pos,
                   Type site,
                   Name name,
                   boolean qualified,
                   List<Type> argtypes,
                   List<Type> typeargtypes) {
         return accessMethod(sym, pos, site.tsym, site, name, qualified, argtypes, typeargtypes);
     }
     /**
      * Variant of the generalized access routine, to be used for generating variable,
      * type resolution diagnostics
      */
     Symbol accessBase(Symbol sym,
                   DiagnosticPosition pos,
                   Symbol location,
                   Type site,
                   Name name,
                   boolean qualified) {
         return accessInternal(sym, pos, location, site, name, qualified, List.<Type>nil(), null, basicLogResolveHelper);
     }
     /** Same as original accessBase(), but without location.
      */
     Symbol accessBase(Symbol sym,
                   DiagnosticPosition pos,
                   Type site,
                   Name name,
                   boolean qualified) {
         return accessBase(sym, pos, site.tsym, site, name, qualified);
     }
     interface LogResolveHelper {
         boolean resolveDiagnosticNeeded(Type site, List<Type> argtypes, List<Type> typeargtypes);
         List<Type> getArgumentTypes(ResolveError errSym, Symbol accessedSym, Name name, List<Type> argtypes);
     }
     LogResolveHelper basicLogResolveHelper = new LogResolveHelper() {
         public boolean resolveDiagnosticNeeded(Type site, List<Type> argtypes, List<Type> typeargtypes) {
             return !site.isErroneous();
         }
         public List<Type> getArgumentTypes(ResolveError errSym, Symbol accessedSym, Name name, List<Type> argtypes) {
             return argtypes;
         }
     };
     LogResolveHelper methodLogResolveHelper = new LogResolveHelper() {
         public boolean resolveDiagnosticNeeded(Type site, List<Type> argtypes, List<Type> typeargtypes) {
             return !site.isErroneous() &&
                         !Type.isErroneous(argtypes) &&
                         (typeargtypes == null || !Type.isErroneous(typeargtypes));
         }
         public List<Type> getArgumentTypes(ResolveError errSym, Symbol accessedSym, Name name, List<Type> argtypes) {
             return (syms.operatorNames.contains(name)) ?
                     argtypes :
                     Type.map(argtypes, new ResolveDeferredRecoveryMap(accessedSym));
         }
         class ResolveDeferredRecoveryMap extends DeferredAttr.RecoveryDeferredTypeMap {
             public ResolveDeferredRecoveryMap(Symbol msym) {
                 deferredAttr.super(AttrMode.SPECULATIVE, msym, currentResolutionContext.step);
             }
             @Override
             protected Type typeOf(DeferredType dt) {
                 Type res = super.typeOf(dt);
                 if (!res.isErroneous()) {
                     switch (TreeInfo.skipParens(dt.tree).getTag()) {
                         case LAMBDA:
                         case REFERENCE:
                             return dt;
                         case CONDEXPR:
                             return res == Type.recoveryType ?
                                     dt : res;
                     }
                 }
                 return res;
             }
         }
     };
     /** Check that sym is not an abstract method.
      */
     void checkNonAbstract(DiagnosticPosition pos, Symbol sym) {
         if ((sym.flags() & ABSTRACT) != 0 && (sym.flags() & DEFAULT) == 0)
             log.error(pos, "abstract.cant.be.accessed.directly",
                       kindName(sym), sym, sym.location());
     }
 /* ***************************************************************************
  *  Debugging
  ****************************************************************************/
     /** print all scopes starting with scope s and proceeding outwards.
      *  used for debugging.
      */
     public void printscopes(Scope s) {
         while (s != null) {
             if (s.owner != null)
                 System.err.print(s.owner + ": ");
             for (Scope.Entry e = s.elems; e != null; e = e.sibling) {
                 if ((e.sym.flags() & ABSTRACT) != 0)
                     System.err.print("abstract ");
                 System.err.print(e.sym + " ");
             }
             System.err.println();
             s = s.next;
         }
     }
     void printscopes(Env<AttrContext> env) {
         while (env.outer != null) {
             System.err.println("------------------------------");
             printscopes(env.info.scope);
             env = env.outer;
         }
     }
     public void printscopes(Type t) {
         while (t.hasTag(CLASS)) {
             printscopes(t.tsym.members());
             t = types.supertype(t);
         }
     }
 /* ***************************************************************************
  *  Name resolution
  *  Naming conventions are as for symbol lookup
  *  Unlike the find... methods these methods will report access errors
  ****************************************************************************/
     /** Resolve an unqualified (non-method) identifier.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the identifier use.
      *  @param name      The identifier's name.
      *  @param kind      The set of admissible symbol kinds for the identifier.
      */
     Symbol resolveIdent(DiagnosticPosition pos, Env<AttrContext> env,
                         Name name, int kind) {
         return accessBase(
             findIdent(env, name, kind),
             pos, env.enclClass.sym.type, name, false);
     }
     /** Resolve an unqualified method identifier.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the method invocation.
      *  @param name      The identifier's name.
      *  @param argtypes  The types of the invocation's value arguments.
      *  @param typeargtypes  The types of the invocation's type arguments.
      */
     Symbol resolveMethod(DiagnosticPosition pos,
                          Env<AttrContext> env,
                          Name name,
                          List<Type> argtypes,
                          List<Type> typeargtypes) {
         return lookupMethod(env, pos, env.enclClass.sym, new BasicLookupHelper(name, env.enclClass.sym.type, argtypes, typeargtypes) {
             @Override
             Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
                 return findFun(env, name, argtypes, typeargtypes,
                         phase.isBoxingRequired(),
                         phase.isVarargsRequired());
             }
         });
     }
     /** Resolve a qualified method identifier
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the method invocation.
      *  @param site      The type of the qualifying expression, in which
      *                   identifier is searched.
      *  @param name      The identifier's name.
      *  @param argtypes  The types of the invocation's value arguments.
      *  @param typeargtypes  The types of the invocation's type arguments.
      */
     Symbol resolveQualifiedMethod(DiagnosticPosition pos, Env<AttrContext> env,
                                   Type site, Name name, List<Type> argtypes,
                                   List<Type> typeargtypes) {
         return resolveQualifiedMethod(pos, env, site.tsym, site, name, argtypes, typeargtypes);
     }
     Symbol resolveQualifiedMethod(DiagnosticPosition pos, Env<AttrContext> env,
                                   Symbol location, Type site, Name name, List<Type> argtypes,
                                   List<Type> typeargtypes) {
         return resolveQualifiedMethod(new MethodResolutionContext(), pos, env, location, site, name, argtypes, typeargtypes);
     }
     private Symbol resolveQualifiedMethod(MethodResolutionContext resolveContext,
                                   DiagnosticPosition pos, Env<AttrContext> env,
                                   Symbol location, Type site, Name name, List<Type> argtypes,
                                   List<Type> typeargtypes) {
         return lookupMethod(env, pos, location, resolveContext, new BasicLookupHelper(name, site, argtypes, typeargtypes) {
             @Override
             Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
                 return findMethod(env, site, name, argtypes, typeargtypes,
                         phase.isBoxingRequired(),
                         phase.isVarargsRequired(), false);
             }
             @Override
             Symbol access(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, Symbol sym) {
                 if (sym.kind >= AMBIGUOUS) {
                     sym = super.access(env, pos, location, sym);
                 } else if (allowMethodHandles) {
                     MethodSymbol msym = (MethodSymbol)sym;
                     if (msym.isSignaturePolymorphic(types)) {
                         return findPolymorphicSignatureInstance(env, sym, argtypes);
                     }
                 }
                 return sym;
             }
         });
     }
     /** Find or create an implicit method of exactly the given type (after erasure).
      *  Searches in a side table, not the main scope of the site.
      *  This emulates the lookup process required by JSR 292 in JVM.
      *  @param env       Attribution environment
      *  @param spMethod  signature polymorphic method - i.e. MH.invokeExact
      *  @param argtypes  The required argument types
      */
     Symbol findPolymorphicSignatureInstance(Env<AttrContext> env,
                                             final Symbol spMethod,
                                             List<Type> argtypes) {
         Type mtype = infer.instantiatePolymorphicSignatureInstance(env,
                 (MethodSymbol)spMethod, currentResolutionContext, argtypes);
         for (Symbol sym : polymorphicSignatureScope.getElementsByName(spMethod.name)) {
             if (types.isSameType(mtype, sym.type)) {
                return sym;
             }
         }
         // create the desired method
         long flags = ABSTRACT | HYPOTHETICAL | spMethod.flags() & Flags.AccessFlags;
         Symbol msym = new MethodSymbol(flags, spMethod.name, mtype, spMethod.owner) {
             @Override
             public Symbol baseSymbol() {
                 return spMethod;
             }
         };
         polymorphicSignatureScope.enter(msym);
         return msym;
     }
     /** Resolve a qualified method identifier, throw a fatal error if not
      *  found.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the method invocation.
      *  @param site      The type of the qualifying expression, in which
      *                   identifier is searched.
      *  @param name      The identifier's name.
      *  @param argtypes  The types of the invocation's value arguments.
      *  @param typeargtypes  The types of the invocation's type arguments.
      */
     public MethodSymbol resolveInternalMethod(DiagnosticPosition pos, Env<AttrContext> env,
                                         Type site, Name name,
                                         List<Type> argtypes,
                                         List<Type> typeargtypes) {
         MethodResolutionContext resolveContext = new MethodResolutionContext();
         resolveContext.internalResolution = true;
         Symbol sym = resolveQualifiedMethod(resolveContext, pos, env, site.tsym,
                 site, name, argtypes, typeargtypes);
         if (sym.kind == MTH) return (MethodSymbol)sym;
         else throw new FatalError(
                  diags.fragment("fatal.err.cant.locate.meth",
                                 name));
     }
     /** Resolve constructor.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the constructor invocation.
      *  @param site      The type of class for which a constructor is searched.
      *  @param argtypes  The types of the constructor invocation's value
      *                   arguments.
      *  @param typeargtypes  The types of the constructor invocation's type
      *                   arguments.
      */
     Symbol resolveConstructor(DiagnosticPosition pos,
                               Env<AttrContext> env,
                               Type site,
                               List<Type> argtypes,
                               List<Type> typeargtypes) {
         return resolveConstructor(new MethodResolutionContext(), pos, env, site, argtypes, typeargtypes);
     }
     private Symbol resolveConstructor(MethodResolutionContext resolveContext,
                               final DiagnosticPosition pos,
                               Env<AttrContext> env,
                               Type site,
                               List<Type> argtypes,
                               List<Type> typeargtypes) {
         return lookupMethod(env, pos, site.tsym, resolveContext, new BasicLookupHelper(names.init, site, argtypes, typeargtypes) {
             @Override
             Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
                 return findConstructor(pos, env, site, argtypes, typeargtypes,
                         phase.isBoxingRequired(),
                         phase.isVarargsRequired());
             }
         });
     }
     /** Resolve a constructor, throw a fatal error if not found.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the method invocation.
      *  @param site      The type to be constructed.
      *  @param argtypes  The types of the invocation's value arguments.
      *  @param typeargtypes  The types of the invocation's type arguments.
      */
     public MethodSymbol resolveInternalConstructor(DiagnosticPosition pos, Env<AttrContext> env,
                                         Type site,
                                         List<Type> argtypes,
                                         List<Type> typeargtypes) {
         MethodResolutionContext resolveContext = new MethodResolutionContext();
         resolveContext.internalResolution = true;
         Symbol sym = resolveConstructor(resolveContext, pos, env, site, argtypes, typeargtypes);
         if (sym.kind == MTH) return (MethodSymbol)sym;
         else throw new FatalError(
                  diags.fragment("fatal.err.cant.locate.ctor", site));
     }
     Symbol findConstructor(DiagnosticPosition pos, Env<AttrContext> env,
                               Type site, List<Type> argtypes,
                               List<Type> typeargtypes,
                               boolean allowBoxing,
                               boolean useVarargs) {
         Symbol sym = findMethod(env, site,
                                     names.init, argtypes,
                                     typeargtypes, allowBoxing,
                                     useVarargs, false);
         chk.checkDeprecated(pos, env.info.scope.owner, sym);
         return sym;
     }
     /** Resolve constructor using diamond inference.
      *  @param pos       The position to use for error reporting.
      *  @param env       The environment current at the constructor invocation.
      *  @param site      The type of class for which a constructor is searched.
      *                   The scope of this class has been touched in attribution.
      *  @param argtypes  The types of the constructor invocation's value
      *                   arguments.
      *  @param typeargtypes  The types of the constructor invocation's type
      *                   arguments.
      */
     Symbol resolveDiamond(DiagnosticPosition pos,
                               Env<AttrContext> env,
                               Type site,
                               List<Type> argtypes,
                               List<Type> typeargtypes) {
         return lookupMethod(env, pos, site.tsym, new BasicLookupHelper(names.init, site, argtypes, typeargtypes) {
             @Override
             Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
                 return findDiamond(env, site, argtypes, typeargtypes,
                         phase.isBoxingRequired(),
                         phase.isVarargsRequired());
             }
             @Override
             Symbol access(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, Symbol sym) {
                 if (sym.kind >= AMBIGUOUS) {
                     final JCDiagnostic details = sym.kind == WRONG_MTH ?
                                     ((InapplicableSymbolError)sym).errCandidate().details :
                                     null;
                     sym = new InapplicableSymbolError(sym.kind, "diamondError", currentResolutionContext) {
                         @Override
                         JCDiagnostic getDiagnostic(DiagnosticType dkind, DiagnosticPosition pos,
                                 Symbol location, Type site, Name name, List<Type> argtypes, List<Type> typeargtypes) {
                             String key = details == null ?
                                 "cant.apply.diamond" :
                                 "cant.apply.diamond.1";
                             return diags.create(dkind, log.currentSource(), pos, key,
                                     diags.fragment("diamond", site.tsym), details);
                         }
                     };
                     sym = accessMethod(sym, pos, site, names.init, true, argtypes, typeargtypes);
                     env.info.pendingResolutionPhase = currentResolutionContext.step;
                 }
                 return sym;
             }
         });
     }
     /** This method scans all the constructor symbol in a given class scope -
      *  assuming that the original scope contains a constructor of the kind:
      *  {@code Foo(X x, Y y)}, where X,Y are class type-variables declared in Foo,
      *  a method check is executed against the modified constructor type:
      *  {@code <X,Y>Foo<X,Y>(X x, Y y)}. This is crucial in order to enable diamond
      *  inference. The inferred return type of the synthetic constructor IS
      *  the inferred type for the diamond operator.
      */
     private Symbol findDiamond(Env<AttrContext> env,
                               Type site,
                               List<Type> argtypes,
                               List<Type> typeargtypes,
                               boolean allowBoxing,
                               boolean useVarargs) {
         Symbol bestSoFar = methodNotFound;
         for (Scope.Entry e = site.tsym.members().lookup(names.init);
              e.scope != null;
              e = e.next()) {
             final Symbol sym = e.sym;
             //- System.out.println(" e " + e.sym);
             if (sym.kind == MTH &&
                 (sym.flags_field & SYNTHETIC) == 0) {
                     List<Type> oldParams = e.sym.type.hasTag(FORALL) ?
                             ((ForAll)sym.type).tvars :
                             List.<Type>nil();
                     Type constrType = new ForAll(site.tsym.type.getTypeArguments().appendList(oldParams),
                             types.createMethodTypeWithReturn(sym.type.asMethodType(), site));
                     MethodSymbol newConstr = new MethodSymbol(sym.flags(), names.init, constrType, site.tsym) {
                         @Override
                         public Symbol baseSymbol() {
                             return sym;
                         }
                     };
                     bestSoFar = selectBest(env, site, argtypes, typeargtypes,
                             newConstr,
                             bestSoFar,
                             allowBoxing,
                             useVarargs,
                             false);
             }
         }
         return bestSoFar;
     }
     /** Resolve operator.
      *  @param pos       The position to use for error reporting.
      *  @param optag     The tag of the operation tree.
      *  @param env       The environment current at the operation.
      *  @param argtypes  The types of the operands.
      */
     Symbol resolveOperator(DiagnosticPosition pos, JCTree.Tag optag,
                            Env<AttrContext> env, List<Type> argtypes) {
         MethodResolutionContext prevResolutionContext = currentResolutionContext;
         try {
             currentResolutionContext = new MethodResolutionContext();
             Name name = treeinfo.operatorName(optag);
             env.info.pendingResolutionPhase = currentResolutionContext.step = BASIC;
             Symbol sym = findMethod(env, syms.predefClass.type, name, argtypes,
                                     null, false, false, true);
             if (boxingEnabled && sym.kind >= WRONG_MTHS)
                 env.info.pendingResolutionPhase = currentResolutionContext.step = BOX;
                 sym = findMethod(env, syms.predefClass.type, name, argtypes,
                                  null, true, false, true);
             return accessMethod(sym, pos, env.enclClass.sym.type, name,
                           false, argtypes, null);
         }
         finally {
             currentResolutionContext = prevResolutionContext;
         }
     }
     /** Resolve operator.
      *  @param pos       The position to use for error reporting.
      *  @param optag     The tag of the operation tree.
      *  @param env       The environment current at the operation.
      *  @param arg       The type of the operand.
      */
     Symbol resolveUnaryOperator(DiagnosticPosition pos, JCTree.Tag optag, Env<AttrContext> env, Type arg) {
         return resolveOperator(pos, optag, env, List.of(arg));
     }
     /** Resolve binary operator.
      *  @param pos       The position to use for error reporting.
      *  @param optag     The tag of the operation tree.
      *  @param env       The environment current at the operation.
      *  @param left      The types of the left operand.
      *  @param right     The types of the right operand.
      */
     Symbol resolveBinaryOperator(DiagnosticPosition pos,
                                  JCTree.Tag optag,
                                  Env<AttrContext> env,
                                  Type left,
                                  Type right) {
         return resolveOperator(pos, optag, env, List.of(left, right));
     }
     /**
      * Resolution of member references is typically done as a single
      * overload resolution step, where the argument types A are inferred from
      * the target functional descriptor.
      *
      * If the member reference is a method reference with a type qualifier,
      * a two-step lookup process is performed. The first step uses the
      * expected argument list A, while the second step discards the first
      * type from A (which is treated as a receiver type).
      *
      * There are two cases in which inference is performed: (i) if the member
      * reference is a constructor reference and the qualifier type is raw - in
      * which case diamond inference is used to infer a parameterization for the
      * type qualifier; (ii) if the member reference is an unbound reference
      * where the type qualifier is raw - in that case, during the unbound lookup
      * the receiver argument type is used to infer an instantiation for the raw
      * qualifier type.
      *
      * When a multi-step resolution process is exploited, it is an error
      * if two candidates are found (ambiguity).
      *
      * This routine returns a pair (T,S), where S is the member reference symbol,
      * and T is the type of the class in which S is defined. This is necessary as
      * the type T might be dynamically inferred (i.e. if constructor reference
      * has a raw qualifier).
      */
     Pair<Symbol, ReferenceLookupHelper> resolveMemberReference(DiagnosticPosition pos,
                                   Env<AttrContext> env,
                                   JCMemberReference referenceTree,
                                   Type site,
                                   Name name, List<Type> argtypes,
                                   List<Type> typeargtypes,
                                   boolean boxingAllowed) {
         MethodResolutionPhase maxPhase = boxingAllowed ? VARARITY : BASIC;
         //step 1 - bound lookup
         ReferenceLookupHelper boundLookupHelper = name.equals(names.init) ?
                 new ConstructorReferenceLookupHelper(referenceTree, site, argtypes, typeargtypes, maxPhase) :
                 new MethodReferenceLookupHelper(referenceTree, name, site, argtypes, typeargtypes, maxPhase);
         Env<AttrContext> boundEnv = env.dup(env.tree, env.info.dup());
         Symbol boundSym = lookupMethod(boundEnv, env.tree.pos(), site.tsym, boundLookupHelper);
         //step 2 - unbound lookup
         ReferenceLookupHelper unboundLookupHelper = boundLookupHelper.unboundLookup();
         Env<AttrContext> unboundEnv = env.dup(env.tree, env.info.dup());
         Symbol unboundSym = lookupMethod(unboundEnv, env.tree.pos(), site.tsym, unboundLookupHelper);
         //merge results
         Pair<Symbol, ReferenceLookupHelper> res;
         if (unboundSym.kind != MTH) {
             res = new Pair<Symbol, ReferenceLookupHelper>(boundSym, boundLookupHelper);
             env.info.pendingResolutionPhase = boundEnv.info.pendingResolutionPhase;
         } else if (boundSym.kind == MTH) {
             res = new Pair<Symbol, ReferenceLookupHelper>(ambiguityError(boundSym, unboundSym), boundLookupHelper);
             env.info.pendingResolutionPhase = boundEnv.info.pendingResolutionPhase;
         } else {
             res = new Pair<Symbol, ReferenceLookupHelper>(unboundSym, unboundLookupHelper);
             env.info.pendingResolutionPhase = unboundEnv.info.pendingResolutionPhase;
         }
         return res;
     }
     /**
      * Helper for defining custom method-like lookup logic; a lookup helper
      * provides hooks for (i) the actual lookup logic and (ii) accessing the
      * lookup result (this step might result in compiler diagnostics to be generated)
      */
     abstract class LookupHelper {
         /** name of the symbol to lookup */
         Name name;
         /** location in which the lookup takes place */
         Type site;
         /** actual types used during the lookup */
         List<Type> argtypes;
         /** type arguments used during the lookup */
         List<Type> typeargtypes;
         /** Max overload resolution phase handled by this helper */
         MethodResolutionPhase maxPhase;
         LookupHelper(Name name, Type site, List<Type> argtypes, List<Type> typeargtypes, MethodResolutionPhase maxPhase) {
             this.name = name;
             this.site = site;
             this.argtypes = argtypes;
             this.typeargtypes = typeargtypes;
             this.maxPhase = maxPhase;
         }
         /**
          * Should lookup stop at given phase with given result
          */
         protected boolean shouldStop(Symbol sym, MethodResolutionPhase phase) {
             return phase.ordinal() > maxPhase.ordinal() ||
                     sym.kind < ERRONEOUS || sym.kind == AMBIGUOUS;
         }
         /**
          * Search for a symbol under a given overload resolution phase - this method
          * is usually called several times, once per each overload resolution phase
          */
         abstract Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase);
         /**
          * Validate the result of the lookup
          */
         abstract Symbol access(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, Symbol sym);
     }
     abstract class BasicLookupHelper extends LookupHelper {
         BasicLookupHelper(Name name, Type site, List<Type> argtypes, List<Type> typeargtypes) {
             super(name, site, argtypes, typeargtypes, MethodResolutionPhase.VARARITY);
         }
         @Override
         Symbol access(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, Symbol sym) {
             if (sym.kind == AMBIGUOUS) {
                 AmbiguityError a_err = (AmbiguityError)sym;
                 sym = a_err.mergeAbstracts(site);
             }
             if (sym.kind >= AMBIGUOUS) {
                 //if nothing is found return the 'first' error
                 sym = accessMethod(sym, pos, location, site, name, true, argtypes, typeargtypes);
             }
             return sym;
         }
     }
     /**
      * Helper class for member reference lookup. A reference lookup helper
      * defines the basic logic for member reference lookup; a method gives
      * access to an 'unbound' helper used to perform an unbound member
      * reference lookup.
      */
     abstract class ReferenceLookupHelper extends LookupHelper {
         /** The member reference tree */
         JCMemberReference referenceTree;
         ReferenceLookupHelper(JCMemberReference referenceTree, Name name, Type site,
                 List<Type> argtypes, List<Type> typeargtypes, MethodResolutionPhase maxPhase) {
             super(name, site, argtypes, typeargtypes, maxPhase);
             this.referenceTree = referenceTree;
         }
         /**
          * Returns an unbound version of this lookup helper. By default, this
          * method returns an dummy lookup helper.
          */
         ReferenceLookupHelper unboundLookup() {
             //dummy loopkup helper that always return 'methodNotFound'
             return new ReferenceLookupHelper(referenceTree, name, site, argtypes, typeargtypes, maxPhase) {
                 @Override
                 ReferenceLookupHelper unboundLookup() {
                     return this;
                 }
                 @Override
                 Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
                     return methodNotFound;
                 }
                 @Override
                 ReferenceKind referenceKind(Symbol sym) {
                     Assert.error();
                     return null;
                 }
             };
         }
         /**
          * Get the kind of the member reference
          */
         abstract JCMemberReference.ReferenceKind referenceKind(Symbol sym);
         Symbol access(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, Symbol sym) {
             if (sym.kind == AMBIGUOUS) {
                 AmbiguityError a_err = (AmbiguityError)sym;
                 sym = a_err.mergeAbstracts(site);
             }
             //skip error reporting
             return sym;
         }
     }
     /**
      * Helper class for method reference lookup. The lookup logic is based
      * upon Resolve.findMethod; in certain cases, this helper class has a
      * corresponding unbound helper class (see UnboundMethodReferenceLookupHelper).
      * In such cases, non-static lookup results are thrown away.
      */
     class MethodReferenceLookupHelper extends ReferenceLookupHelper {
         MethodReferenceLookupHelper(JCMemberReference referenceTree, Name name, Type site,
                 List<Type> argtypes, List<Type> typeargtypes, MethodResolutionPhase maxPhase) {
             super(referenceTree, name, site, argtypes, typeargtypes, maxPhase);
         }
         protected Symbol lookupReferenceInternal(Env<AttrContext> env, MethodResolutionPhase phase) {
             return findMethod(env, site, name, argtypes, typeargtypes,
                     phase.isBoxingRequired(), phase.isVarargsRequired(), syms.operatorNames.contains(name));
         }
         protected Symbol adjustLookupResult(Env<AttrContext> env, Symbol sym) {
             return !TreeInfo.isStaticSelector(referenceTree.expr, names) ||
                         sym.kind != MTH ||
                         sym.isStatic() ? sym : new StaticError(sym);
         }
         @Override
         final Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
             return adjustLookupResult(env, lookupReferenceInternal(env, phase));
         }
         @Override
         ReferenceLookupHelper unboundLookup() {
             if (TreeInfo.isStaticSelector(referenceTree.expr, names) &&
                     argtypes.nonEmpty() &&
                     types.isSubtypeUnchecked(argtypes.head, site)) {
                 return new UnboundMethodReferenceLookupHelper(referenceTree, name,
                         site, argtypes, typeargtypes, maxPhase);
             } else {
                 return super.unboundLookup();
             }
         }
         @Override
         ReferenceKind referenceKind(Symbol sym) {
             if (sym.isStatic()) {
                 return ReferenceKind.STATIC;
             } else {
                 Name selName = TreeInfo.name(referenceTree.getQualifierExpression());
                 return selName != null && selName == names._super ?
                         ReferenceKind.SUPER :
                         ReferenceKind.BOUND;
             }
         }
     }
     /**
      * Helper class for unbound method reference lookup. Essentially the same
      * as the basic method reference lookup helper; main difference is that static
      * lookup results are thrown away. If qualifier type is raw, an attempt to
      * infer a parameterized type is made using the first actual argument (that
      * would otherwise be ignored during the lookup).
      */
     class UnboundMethodReferenceLookupHelper extends MethodReferenceLookupHelper {
         UnboundMethodReferenceLookupHelper(JCMemberReference referenceTree, Name name, Type site,
                 List<Type> argtypes, List<Type> typeargtypes, MethodResolutionPhase maxPhase) {
             super(referenceTree, name,
                     site.isRaw() ? types.asSuper(argtypes.head, site.tsym) : site,
                     argtypes.tail, typeargtypes, maxPhase);
         }
         @Override
         protected Symbol adjustLookupResult(Env<AttrContext> env, Symbol sym) {
             return sym.kind != MTH || !sym.isStatic() ? sym : new StaticError(sym);
         }
         @Override
         ReferenceLookupHelper unboundLookup() {
             return this;
         }
         @Override
         ReferenceKind referenceKind(Symbol sym) {
             return ReferenceKind.UNBOUND;
         }
     }
     /**
      * Helper class for constructor reference lookup. The lookup logic is based
      * upon either Resolve.findMethod or Resolve.findDiamond - depending on
      * whether the constructor reference needs diamond inference (this is the case
      * if the qualifier type is raw). A special erroneous symbol is returned
      * if the lookup returns the constructor of an inner class and there's no
      * enclosing instance in scope.
      */
     class ConstructorReferenceLookupHelper extends ReferenceLookupHelper {
         boolean needsInference;
         ConstructorReferenceLookupHelper(JCMemberReference referenceTree, Type site, List<Type> argtypes,
                 List<Type> typeargtypes, MethodResolutionPhase maxPhase) {
             super(referenceTree, names.init, site, argtypes, typeargtypes, maxPhase);
             if (site.isRaw()) {
                 this.site = new ClassType(site.getEnclosingType(), site.tsym.type.getTypeArguments(), site.tsym);
                 needsInference = true;
             }
         }
         @Override
         protected Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
             Symbol sym = needsInference ?
                 findDiamond(env, site, argtypes, typeargtypes, phase.isBoxingRequired(), phase.isVarargsRequired()) :
                 findMethod(env, site, name, argtypes, typeargtypes,
                         phase.isBoxingRequired(), phase.isVarargsRequired(), syms.operatorNames.contains(name));
             return sym.kind != MTH ||
                           site.getEnclosingType().hasTag(NONE) ||
                           hasEnclosingInstance(env, site) ?
                           sym : new InvalidSymbolError(Kinds.MISSING_ENCL, sym, null) {
                     @Override
                     JCDiagnostic getDiagnostic(DiagnosticType dkind, DiagnosticPosition pos, Symbol location, Type site, Name name, List<Type> argtypes, List<Type> typeargtypes) {
                        return diags.create(dkind, log.currentSource(), pos,
                             "cant.access.inner.cls.constr", site.tsym.name, argtypes, site.getEnclosingType());
                     }
                 };
         }
         @Override
         ReferenceKind referenceKind(Symbol sym) {
             return site.getEnclosingType().hasTag(NONE) ?
                     ReferenceKind.TOPLEVEL : ReferenceKind.IMPLICIT_INNER;
         }
     }
     /**
      * Main overload resolution routine. On each overload resolution step, a
      * lookup helper class is used to perform the method/constructor lookup;
      * at the end of the lookup, the helper is used to validate the results
      * (this last step might trigger overload resolution diagnostics).
      */
     Symbol lookupMethod(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, LookupHelper lookupHelper) {
         return lookupMethod(env, pos, location, new MethodResolutionContext(), lookupHelper);
     }
     Symbol lookupMethod(Env<AttrContext> env, DiagnosticPosition pos, Symbol location,
             MethodResolutionContext resolveContext, LookupHelper lookupHelper) {
         MethodResolutionContext prevResolutionContext = currentResolutionContext;
         try {
             Symbol bestSoFar = methodNotFound;
             currentResolutionContext = resolveContext;
             for (MethodResolutionPhase phase : methodResolutionSteps) {
                 if (!phase.isApplicable(boxingEnabled, varargsEnabled) ||
                         lookupHelper.shouldStop(bestSoFar, phase)) break;
                 MethodResolutionPhase prevPhase = currentResolutionContext.step;
                 Symbol prevBest = bestSoFar;
                 currentResolutionContext.step = phase;
                 bestSoFar = phase.mergeResults(bestSoFar, lookupHelper.lookup(env, phase));
                 env.info.pendingResolutionPhase = (prevBest == bestSoFar) ? prevPhase : phase;
             }
             return lookupHelper.access(env, pos, location, bestSoFar);
         } finally {
             currentResolutionContext = prevResolutionContext;
         }
     }
     /**
      * Resolve `c.name' where name == this or name == super.
      * @param pos           The position to use for error reporting.
      * @param env           The environment current at the expression.
      * @param c             The qualifier.
      * @param name          The identifier's name.
      */
     Symbol resolveSelf(DiagnosticPosition pos,
                        Env<AttrContext> env,
                        TypeSymbol c,
                        Name name) {
         Env<AttrContext> env1 = env;
         boolean staticOnly = false;
         while (env1.outer != null) {
             if (isStatic(env1)) staticOnly = true;
             if (env1.enclClass.sym == c) {
                 Symbol sym = env1.info.scope.lookup(name).sym;
                 if (sym != null) {
                     if (staticOnly) sym = new StaticError(sym);
                     return accessBase(sym, pos, env.enclClass.sym.type,
                                   name, true);
                 }
             }
             if ((env1.enclClass.sym.flags() & STATIC) != 0) staticOnly = true;
             env1 = env1.outer;
         }
         if (allowDefaultMethods && c.isInterface() &&
                 name == names._super && !isStatic(env) &&
                 types.isDirectSuperInterface(c, env.enclClass.sym)) {
             //this might be a default super call if one of the superinterfaces is 'c'
             for (Type t : pruneInterfaces(env.enclClass.type)) {
                 if (t.tsym == c) {
                     env.info.defaultSuperCallSite = t;
                     return new VarSymbol(0, names._super,
                             types.asSuper(env.enclClass.type, c), env.enclClass.sym);
                 }
             }
             //find a direct superinterface that is a subtype of 'c'
             for (Type i : types.interfaces(env.enclClass.type)) {
                 if (i.tsym.isSubClass(c, types) && i.tsym != c) {
                     log.error(pos, "illegal.default.super.call", c,
                             diags.fragment("redundant.supertype", c, i));
                     return syms.errSymbol;
                 }
             }
             Assert.error();
         }
         log.error(pos, "not.encl.class", c);
         return syms.errSymbol;
     }
     //where
     private List<Type> pruneInterfaces(Type t) {
         ListBuffer<Type> result = ListBuffer.lb();
         for (Type t1 : types.interfaces(t)) {
             boolean shouldAdd = true;
             for (Type t2 : types.interfaces(t)) {
                 if (t1 != t2 && types.isSubtypeNoCapture(t2, t1)) {
                     shouldAdd = false;
                 }
             }
             if (shouldAdd) {
                 result.append(t1);
             }
         }
         return result.toList();
     }
     /**
      * Resolve `c.this' for an enclosing class c that contains the
      * named member.
      * @param pos           The position to use for error reporting.
      * @param env           The environment current at the expression.
      * @param member        The member that must be contained in the result.
      */
     Symbol resolveSelfContaining(DiagnosticPosition pos,
                                  Env<AttrContext> env,
                                  Symbol member,
                                  boolean isSuperCall) {
         Symbol sym = resolveSelfContainingInternal(env, member, isSuperCall);
         if (sym == null) {
             log.error(pos, "encl.class.required", member);
             return syms.errSymbol;
         } else {
             return accessBase(sym, pos, env.enclClass.sym.type, sym.name, true);
         }
     }
     boolean hasEnclosingInstance(Env<AttrContext> env, Type type) {
         Symbol encl = resolveSelfContainingInternal(env, type.tsym, false);
         return encl != null && encl.kind < ERRONEOUS;
     }
     private Symbol resolveSelfContainingInternal(Env<AttrContext> env,
                                  Symbol member,
                                  boolean isSuperCall) {
         Name name = names._this;
         Env<AttrContext> env1 = isSuperCall ? env.outer : env;
         boolean staticOnly = false;
         if (env1 != null) {
             while (env1 != null && env1.outer != null) {
                 if (isStatic(env1)) staticOnly = true;
                 if (env1.enclClass.sym.isSubClass(member.owner, types)) {
                     Symbol sym = env1.info.scope.lookup(name).sym;
                     if (sym != null) {
                         if (staticOnly) sym = new StaticError(sym);
                         return sym;
                     }
                 }
                 if ((env1.enclClass.sym.flags() & STATIC) != 0)
                     staticOnly = true;
                 env1 = env1.outer;
             }
         }
         return null;
     }
     /**
      * Resolve an appropriate implicit this instance for t's container.
      * JLS 8.8.5.1 and 15.9.2
      */
     Type resolveImplicitThis(DiagnosticPosition pos, Env<AttrContext> env, Type t) {
         return resolveImplicitThis(pos, env, t, false);
     }
     Type resolveImplicitThis(DiagnosticPosition pos, Env<AttrContext> env, Type t, boolean isSuperCall) {
         Type thisType = (((t.tsym.owner.kind & (MTH|VAR)) != 0)
                          ? resolveSelf(pos, env, t.getEnclosingType().tsym, names._this)
                          : resolveSelfContaining(pos, env, t.tsym, isSuperCall)).type;
         if (env.info.isSelfCall && thisType.tsym == env.enclClass.sym)
             log.error(pos, "cant.ref.before.ctor.called", "this");
         return thisType;
     }
 /* ***************************************************************************
  *  ResolveError classes, indicating error situations when accessing symbols
  ****************************************************************************/
     //used by TransTypes when checking target type of synthetic cast
     public void logAccessErrorInternal(Env<AttrContext> env, JCTree tree, Type type) {
         AccessError error = new AccessError(env, env.enclClass.type, type.tsym);
         logResolveError(error, tree.pos(), env.enclClass.sym, env.enclClass.type, null, null, null);
     }
     //where
     private void logResolveError(ResolveError error,
             DiagnosticPosition pos,
             Symbol location,
             Type site,
             Name name,
             List<Type> argtypes,
             List<Type> typeargtypes) {
         JCDiagnostic d = error.getDiagnostic(JCDiagnostic.DiagnosticType.ERROR,
                 pos, location, site, name, argtypes, typeargtypes);
         if (d != null) {
             d.setFlag(DiagnosticFlag.RESOLVE_ERROR);
             log.report(d);
         }
     }
     private final LocalizedString noArgs = new LocalizedString("compiler.misc.no.args");
     public Object methodArguments(List<Type> argtypes) {
         if (argtypes == null || argtypes.isEmpty()) {
             return noArgs;
         } else {
             ListBuffer<Object> diagArgs = ListBuffer.lb();
             for (Type t : argtypes) {
                 if (t.hasTag(DEFERRED)) {
                     diagArgs.append(((DeferredAttr.DeferredType)t).tree);
                 } else {
                     diagArgs.append(t);
                 }
             }
             return diagArgs;
         }
     }
     /**
      * Root class for resolution errors. Subclass of ResolveError
      * represent a different kinds of resolution error - as such they must
      * specify how they map into concrete compiler diagnostics.
      */
     abstract class ResolveError extends Symbol {
         /** The name of the kind of error, for debugging only. */
         final String debugName;
         ResolveError(int kind, String debugName) {
             super(kind, 0, null, null, null);
             this.debugName = debugName;
         }
         @Override
         public <R, P> R accept(ElementVisitor<R, P> v, P p) {
             throw new AssertionError();
         }
         @Override
         public String toString() {
             return debugName;
         }
         @Override
         public boolean exists() {
             return false;
         }
         /**
          * Create an external representation for this erroneous symbol to be
          * used during attribution - by default this returns the symbol of a
          * brand new error type which stores the original type found
          * during resolution.
          *
          * @param name     the name used during resolution
          * @param location the location from which the symbol is accessed
          */
         protected Symbol access(Name name, TypeSymbol location) {
             return types.createErrorType(name, location, syms.errSymbol.type).tsym;
         }
         /**
          * Create a diagnostic representing this resolution error.
          *
          * @param dkind     The kind of the diagnostic to be created (e.g error).
          * @param pos       The position to be used for error reporting.
          * @param site      The original type from where the selection took place.
          * @param name      The name of the symbol to be resolved.
          * @param argtypes  The invocation's value arguments,
          *                  if we looked for a method.
          * @param typeargtypes  The invocation's type arguments,
          *                      if we looked for a method.
          */
         abstract JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes);
     }
     /**
      * This class is the root class of all resolution errors caused by
      * an invalid symbol being found during resolution.
      */
     abstract class InvalidSymbolError extends ResolveError {
         /** The invalid symbol found during resolution */
         Symbol sym;
         InvalidSymbolError(int kind, Symbol sym, String debugName) {
             super(kind, debugName);
             this.sym = sym;
         }
         @Override
         public boolean exists() {
             return true;
         }
         @Override
         public String toString() {
              return super.toString() + " wrongSym=" + sym;
         }
         @Override
         public Symbol access(Name name, TypeSymbol location) {
             if ((sym.kind & ERRONEOUS) == 0 && (sym.kind & TYP) != 0)
                 return types.createErrorType(name, location, sym.type).tsym;
             else
                 return sym;
         }
     }
     /**
      * InvalidSymbolError error class indicating that a symbol matching a
      * given name does not exists in a given site.
      */
     class SymbolNotFoundError extends ResolveError {
         SymbolNotFoundError(int kind) {
             super(kind, "symbol not found error");
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             argtypes = argtypes == null ? List.<Type>nil() : argtypes;
             typeargtypes = typeargtypes == null ? List.<Type>nil() : typeargtypes;
             if (name == names.error)
                 return null;
             if (syms.operatorNames.contains(name)) {
                 boolean isUnaryOp = argtypes.size() == 1;
                 String key = argtypes.size() == 1 ?
                     "operator.cant.be.applied" :
                     "operator.cant.be.applied.1";
                 Type first = argtypes.head;
                 Type second = !isUnaryOp ? argtypes.tail.head : null;
                 return diags.create(dkind, log.currentSource(), pos,
                         key, name, first, second);
             }
             boolean hasLocation = false;
             if (location == null) {
                 location = site.tsym;
             }
             if (!location.name.isEmpty()) {
                 if (location.kind == PCK && !site.tsym.exists()) {
                     return diags.create(dkind, log.currentSource(), pos,
                         "doesnt.exist", location);
                 }
                 hasLocation = !location.name.equals(names._this) &&
                         !location.name.equals(names._super);
             }
             boolean isConstructor = kind == ABSENT_MTH && name == names.init;
             KindName kindname = isConstructor ? KindName.CONSTRUCTOR : absentKind(kind);
             Name idname = isConstructor ? site.tsym.name : name;
             String errKey = getErrorKey(kindname, typeargtypes.nonEmpty(), hasLocation);
             if (hasLocation) {
                 return diags.create(dkind, log.currentSource(), pos,
                         errKey, kindname, idname, //symbol kindname, name
                         typeargtypes, args(argtypes), //type parameters and arguments (if any)
                         getLocationDiag(location, site)); //location kindname, type
             }
             else {
                 return diags.create(dkind, log.currentSource(), pos,
                         errKey, kindname, idname, //symbol kindname, name
                         typeargtypes, args(argtypes)); //type parameters and arguments (if any)
             }
         }
         //where
         private Object args(List<Type> args) {
             return args.isEmpty() ? args : methodArguments(args);
         }
         private String getErrorKey(KindName kindname, boolean hasTypeArgs, boolean hasLocation) {
             String key = "cant.resolve";
             String suffix = hasLocation ? ".location" : "";
             switch (kindname) {
                 case METHOD:
                 case CONSTRUCTOR: {
                     suffix += ".args";
                     suffix += hasTypeArgs ? ".params" : "";
                 }
             }
             return key + suffix;
         }
         private JCDiagnostic getLocationDiag(Symbol location, Type site) {
             if (location.kind == VAR) {
                 return diags.fragment("location.1",
                     kindName(location),
                     location,
                     location.type);
             } else {
                 return diags.fragment("location",
                     typeKindName(site),
                     site,
                     null);
             }
         }
     }
     /**
      * InvalidSymbolError error class indicating that a given symbol
      * (either a method, a constructor or an operand) is not applicable
      * given an actual arguments/type argument list.
      */
     class InapplicableSymbolError extends ResolveError {
         protected MethodResolutionContext resolveContext;
         InapplicableSymbolError(MethodResolutionContext context) {
             this(WRONG_MTH, "inapplicable symbol error", context);
         }
         protected InapplicableSymbolError(int kind, String debugName, MethodResolutionContext context) {
             super(kind, debugName);
             this.resolveContext = context;
         }
         @Override
         public String toString() {
             return super.toString();
         }
         @Override
         public boolean exists() {
             return true;
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             if (name == names.error)
                 return null;
             if (syms.operatorNames.contains(name)) {
                 boolean isUnaryOp = argtypes.size() == 1;
                 String key = argtypes.size() == 1 ?
                     "operator.cant.be.applied" :
                     "operator.cant.be.applied.1";
                 Type first = argtypes.head;
                 Type second = !isUnaryOp ? argtypes.tail.head : null;
                 return diags.create(dkind, log.currentSource(), pos,
                         key, name, first, second);
             }
             else {
                 Candidate c = errCandidate();
                 Symbol ws = c.sym.asMemberOf(site, types);
                 return diags.create(dkind, log.currentSource(), pos,
                           "cant.apply.symbol",
                           kindName(ws),
                           ws.name == names.init ? ws.owner.name : ws.name,
                           methodArguments(ws.type.getParameterTypes()),
                           methodArguments(argtypes),
                           kindName(ws.owner),
                           ws.owner.type,
                           c.details);
             }
         }
         @Override
         public Symbol access(Name name, TypeSymbol location) {
             return types.createErrorType(name, location, syms.errSymbol.type).tsym;
         }
         private Candidate errCandidate() {
             Candidate bestSoFar = null;
             for (Candidate c : resolveContext.candidates) {
                 if (c.isApplicable()) continue;
                 bestSoFar = c;
             }
             Assert.checkNonNull(bestSoFar);
             return bestSoFar;
         }
     }
     /**
      * ResolveError error class indicating that a set of symbols
      * (either methods, constructors or operands) is not applicable
      * given an actual arguments/type argument list.
      */
     class InapplicableSymbolsError extends InapplicableSymbolError {
         InapplicableSymbolsError(MethodResolutionContext context) {
             super(WRONG_MTHS, "inapplicable symbols", context);
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             if (!resolveContext.candidates.isEmpty()) {
                 JCDiagnostic err = diags.create(dkind,
                         log.currentSource(),
                         pos,
                         "cant.apply.symbols",
                         name == names.init ? KindName.CONSTRUCTOR : absentKind(kind),
                         name == names.init ? site.tsym.name : name,
                         methodArguments(argtypes));
                 return new JCDiagnostic.MultilineDiagnostic(err, candidateDetails(site));
             } else {
                 return new SymbolNotFoundError(ABSENT_MTH).getDiagnostic(dkind, pos,
                     location, site, name, argtypes, typeargtypes);
             }
         }
         //where
         List<JCDiagnostic> candidateDetails(Type site) {
             Map<Symbol, JCDiagnostic> details = new LinkedHashMap<Symbol, JCDiagnostic>();
             for (Candidate c : resolveContext.candidates) {
                 if (c.isApplicable()) continue;
                 JCDiagnostic detailDiag = diags.fragment("inapplicable.method",
                         Kinds.kindName(c.sym),
                         c.sym.location(site, types),
                         c.sym.asMemberOf(site, types),
                         c.details);
                 details.put(c.sym, detailDiag);
             }
             return List.from(details.values());
         }
     }
     /**
      * An InvalidSymbolError error class indicating that a symbol is not
      * accessible from a given site
      */
     class AccessError extends InvalidSymbolError {
         private Env<AttrContext> env;
         private Type site;
         AccessError(Symbol sym) {
             this(null, null, sym);
         }
         AccessError(Env<AttrContext> env, Type site, Symbol sym) {
             super(HIDDEN, sym, "access error");
             this.env = env;
             this.site = site;
             if (debugResolve)
                 log.error("proc.messager", sym + " @ " + site + " is inaccessible.");
         }
         @Override
         public boolean exists() {
             return false;
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             if (sym.owner.type.hasTag(ERROR))
                 return null;
             if (sym.name == names.init && sym.owner != site.tsym) {
                 return new SymbolNotFoundError(ABSENT_MTH).getDiagnostic(dkind,
                         pos, location, site, name, argtypes, typeargtypes);
             }
             else if ((sym.flags() & PUBLIC) != 0
                 || (env != null && this.site != null
                     && !isAccessible(env, this.site))) {
                 return diags.create(dkind, log.currentSource(),
                         pos, "not.def.access.class.intf.cant.access",
                     sym, sym.location());
             }
             else if ((sym.flags() & (PRIVATE | PROTECTED)) != 0) {
                 return diags.create(dkind, log.currentSource(),
                         pos, "report.access", sym,
                         asFlagSet(sym.flags() & (PRIVATE | PROTECTED)),
                         sym.location());
             }
             else {
                 return diags.create(dkind, log.currentSource(),
                         pos, "not.def.public.cant.access", sym, sym.location());
             }
         }
     }
     /**
      * InvalidSymbolError error class indicating that an instance member
      * has erroneously been accessed from a static context.
      */
     class StaticError extends InvalidSymbolError {
         StaticError(Symbol sym) {
             super(STATICERR, sym, "static error");
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             Symbol errSym = ((sym.kind == TYP && sym.type.hasTag(CLASS))
                 ? types.erasure(sym.type).tsym
                 : sym);
             return diags.create(dkind, log.currentSource(), pos,
                     "non-static.cant.be.ref", kindName(sym), errSym);
         }
     }
     /**
      * InvalidSymbolError error class indicating that a pair of symbols
      * (either methods, constructors or operands) are ambiguous
      * given an actual arguments/type argument list.
      */
     class AmbiguityError extends ResolveError {
         /** The other maximally specific symbol */
         List<Symbol> ambiguousSyms = List.nil();
         @Override
         public boolean exists() {
             return true;
         }
         AmbiguityError(Symbol sym1, Symbol sym2) {
             super(AMBIGUOUS, "ambiguity error");
             ambiguousSyms = flatten(sym2).appendList(flatten(sym1));
         }
         private List<Symbol> flatten(Symbol sym) {
             if (sym.kind == AMBIGUOUS) {
                 return ((AmbiguityError)sym).ambiguousSyms;
             } else {
                 return List.of(sym);
             }
         }
         AmbiguityError addAmbiguousSymbol(Symbol s) {
             ambiguousSyms = ambiguousSyms.prepend(s);
             return this;
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             List<Symbol> diagSyms = ambiguousSyms.reverse();
             Symbol s1 = diagSyms.head;
             Symbol s2 = diagSyms.tail.head;
             Name sname = s1.name;
             if (sname == names.init) sname = s1.owner.name;
             return diags.create(dkind, log.currentSource(),
                       pos, "ref.ambiguous", sname,
                       kindName(s1),
                       s1,
                       s1.location(site, types),
                       kindName(s2),
                       s2,
                       s2.location(site, types));
         }
         /**
          * If multiple applicable methods are found during overload and none of them
          * is more specific than the others, attempt to merge their signatures.
          */
         Symbol mergeAbstracts(Type site) {
             Symbol fst = ambiguousSyms.last();
             Symbol res = fst;
             for (Symbol s : ambiguousSyms.reverse()) {
                 Type mt1 = types.memberType(site, res);
                 Type mt2 = types.memberType(site, s);
                 if ((s.flags() & ABSTRACT) == 0 ||
                         !types.overrideEquivalent(mt1, mt2) ||
                         !types.isSameTypes(fst.erasure(types).getParameterTypes(),
                                        s.erasure(types).getParameterTypes())) {
                     //ambiguity cannot be resolved
                     return this;
                 } else {
                     Type mst = mostSpecificReturnType(mt1, mt2);
                     if (mst == null) {
                         // Theoretically, this can't happen, but it is possible
                         // due to error recovery or mixing incompatible class files
                         return this;
                     }
                     Symbol mostSpecific = mst == mt1 ? res : s;
                     List<Type> allThrown = chk.intersect(mt1.getThrownTypes(), mt2.getThrownTypes());
                     Type newSig = types.createMethodTypeWithThrown(mostSpecific.type, allThrown);
                     res = new MethodSymbol(
                             mostSpecific.flags(),
                             mostSpecific.name,
                             newSig,
                             mostSpecific.owner);
                 }
             }
             return res;
         }
         @Override
         protected Symbol access(Name name, TypeSymbol location) {
             return ambiguousSyms.last();
         }
     }
     enum MethodResolutionPhase {
         BASIC(false, false),
         BOX(true, false),
         VARARITY(true, true) {
             @Override
             public Symbol mergeResults(Symbol bestSoFar, Symbol sym) {
                 switch (sym.kind) {
                     case WRONG_MTH:
                         return (bestSoFar.kind == WRONG_MTH || bestSoFar.kind == WRONG_MTHS) ?
                             bestSoFar :
                             sym;
                     case ABSENT_MTH:
                         return bestSoFar;
                     default:
                         return sym;
                 }
             }
         };
         final boolean isBoxingRequired;
         final boolean isVarargsRequired;
         MethodResolutionPhase(boolean isBoxingRequired, boolean isVarargsRequired) {
            this.isBoxingRequired = isBoxingRequired;
            this.isVarargsRequired = isVarargsRequired;
         }
         public boolean isBoxingRequired() {
             return isBoxingRequired;
         }
         public boolean isVarargsRequired() {
             return isVarargsRequired;
         }
         public boolean isApplicable(boolean boxingEnabled, boolean varargsEnabled) {
             return (varargsEnabled || !isVarargsRequired) &&
                    (boxingEnabled || !isBoxingRequired);
         }
         public Symbol mergeResults(Symbol prev, Symbol sym) {
             return sym;
         }
     }
     final List<MethodResolutionPhase> methodResolutionSteps = List.of(BASIC, BOX, VARARITY);
     /**
      * A resolution context is used to keep track of intermediate results of
      * overload resolution, such as list of method that are not applicable
      * (used to generate more precise diagnostics) and so on. Resolution contexts
      * can be nested - this means that when each overload resolution routine should
      * work within the resolution context it created.
      */
     class MethodResolutionContext {
         private List<Candidate> candidates = List.nil();
         MethodResolutionPhase step = null;
         private boolean internalResolution = false;
         private DeferredAttr.AttrMode attrMode = DeferredAttr.AttrMode.SPECULATIVE;
         void addInapplicableCandidate(Symbol sym, JCDiagnostic details) {
             Candidate c = new Candidate(currentResolutionContext.step, sym, details, null);
             candidates = candidates.append(c);
         }
         void addApplicableCandidate(Symbol sym, Type mtype) {
             Candidate c = new Candidate(currentResolutionContext.step, sym, null, mtype);
             candidates = candidates.append(c);
         }
         DeferredAttrContext deferredAttrContext(Symbol sym, InferenceContext inferenceContext) {
             return deferredAttr.new DeferredAttrContext(attrMode, sym, step, inferenceContext);
         }
         /**
          * This class represents an overload resolution candidate. There are two
          * kinds of candidates: applicable methods and inapplicable methods;
          * applicable methods have a pointer to the instantiated method type,
          * while inapplicable candidates contain further details about the
          * reason why the method has been considered inapplicable.
          */
         class Candidate {
             final MethodResolutionPhase step;
             final Symbol sym;
             final JCDiagnostic details;
             final Type mtype;
             private Candidate(MethodResolutionPhase step, Symbol sym, JCDiagnostic details, Type mtype) {
                 this.step = step;
                 this.sym = sym;
                 this.details = details;
                 this.mtype = mtype;
             }
             @Override
             public boolean equals(Object o) {
                 if (o instanceof Candidate) {
                     Symbol s1 = this.sym;
                     Symbol s2 = ((Candidate)o).sym;
                     if  ((s1 != s2 &&
                             (s1.overrides(s2, s1.owner.type.tsym, types, false) ||
                             (s2.overrides(s1, s2.owner.type.tsym, types, false)))) ||
                             ((s1.isConstructor() || s2.isConstructor()) && s1.owner != s2.owner))
                         return true;
                 }
                 return false;
             }
             boolean isApplicable() {
                 return mtype != null;
             }
         }
         DeferredAttr.AttrMode attrMode() {
             return attrMode;
         }
         boolean internal() {
             return internalResolution;
         }
     }
     MethodResolutionContext currentResolutionContext = null;
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/comp/Resolve.java@db91d860156a (annotated)

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