jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/comp/Resolve.java@51fb17abfc32 (annotated)

src/share/classes/com/sun/tools/javac/comp/Resolve.java@51fb17abfc32 (annotated)

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

Tue, 24 Jan 2012 17:52:02 +0000

author: mcimadamore
date: Tue, 24 Jan 2012 17:52:02 +0000
changeset 1186: 51fb17abfc32
parent 1127: ca49d50318dc
child 1215: 161230ec7c73
permissions: -rw-r--r--

7129801: Merge the two method applicability routines
Summary: Resolve.java and Infer.java should reuse the same method applicability check routine
Reviewed-by: dlsmith, 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.Type.*;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.jvm.*;
 import com.sun.tools.javac.tree.*;
 import com.sun.tools.javac.tree.JCTree.*;
 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.EnumSet;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 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.TypeTags.*;
 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;
     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;
     private final boolean debugResolve;
     final EnumSet<VerboseResolutionMode> verboseResolutionMode;
     Scope polymorphicSignatureScope;
     enum VerboseResolutionMode {
         SUCCESS("success"),
         FAILURE("failure"),
         APPLICABLE("applicable"),
         INAPPLICABLE("inapplicable"),
         DEFERRED_INST("deferred-inference"),
         PREDEF("predef"),
         OBJECT_INIT("object-init"),
         INTERNAL("internal");
         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;
         }
     }
     public static Resolve instance(Context context) {
         Resolve instance = context.get(resolveKey);
         if (instance == null)
             instance = new Resolve(context);
         return instance;
     }
     protected Resolve(Context context) {
         context.put(resolveKey, this);
         syms = Symtab.instance(context);
         varNotFound = new
             SymbolNotFoundError(ABSENT_VAR);
         wrongMethod = new
             InapplicableSymbolError(syms.errSymbol);
         wrongMethods = new
             InapplicableSymbolsError(syms.errSymbol);
         methodNotFound = new
             SymbolNotFoundError(ABSENT_MTH);
         typeNotFound = new
             SymbolNotFoundError(ABSENT_TYP);
         names = Names.instance(context);
         log = Log.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();
         polymorphicSignatureScope = new Scope(syms.noSymbol);
         inapplicableMethodException = new InapplicableMethodException(diags);
     }
     /** error symbols, which are returned when resolution fails
      */
     final SymbolNotFoundError varNotFound;
     final InapplicableSymbolError wrongMethod;
     final InapplicableSymbolsError wrongMethods;
     final SymbolNotFoundError methodNotFound;
     final SymbolNotFoundError typeNotFound;
 /* ************************************************************************
  * Identifier resolution
  *************************************************************************/
     /** An environment is "static" if its static level is greater than
      *  the one of its outer environment
      */
     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.tag == 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 ||
                     s2.isPolymorphicSignatureGeneric() ||
                     !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;
         }
     /** 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,
                         List<Type> argtypes,
                         List<Type> typeargtypes,
                         boolean allowBoxing,
                         boolean useVarargs,
                         Warner warn)
         throws Infer.InferenceException {
         boolean polymorphicSignature = m.isPolymorphicSignatureGeneric() && allowMethodHandles;
         if (useVarargs && (m.flags() & VARARGS) == 0)
             throw inapplicableMethodException.setMessage();
         Type mt = types.memberType(site, m);
         // tvars is the list of formal type variables for which type arguments
         // need to inferred.
         List<Type> tvars = null;
         if (env.info.tvars != null) {
             tvars = types.newInstances(env.info.tvars);
             mt = types.subst(mt, env.info.tvars, tvars);
         }
         if (typeargtypes == null) typeargtypes = List.nil();
         if (mt.tag != 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.tag == 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.tag == 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()*/
                 polymorphicSignature;
         for (List<Type> l = argtypes;
              l.tail != null/*inlined: l.nonEmpty()*/ && !instNeeded;
              l = l.tail) {
             if (l.head.tag == FORALL) instNeeded = true;
         }
         if (instNeeded)
             return polymorphicSignature ?
                 infer.instantiatePolymorphicSignatureInstance(env, site, m.name, (MethodSymbol)m, argtypes) :
                 infer.instantiateMethod(env,
                                     tvars,
                                     (MethodType)mt,
                                     m,
                                     argtypes,
                                     allowBoxing,
                                     useVarargs,
                                     warn);
         checkRawArgumentsAcceptable(env, argtypes, mt.getParameterTypes(),
                                 allowBoxing, useVarargs, warn);
         return mt;
     }
     /** Same but returns null instead throwing a NoInstanceException
      */
     Type instantiate(Env<AttrContext> env,
                      Type site,
                      Symbol m,
                      List<Type> argtypes,
                      List<Type> typeargtypes,
                      boolean allowBoxing,
                      boolean useVarargs,
                      Warner warn) {
         try {
             return rawInstantiate(env, site, m, argtypes, typeargtypes,
                                   allowBoxing, useVarargs, warn);
         } catch (InapplicableMethodException ex) {
             return null;
         }
     }
     /** Check if a parameter list accepts a list of args.
      */
     boolean argumentsAcceptable(Env<AttrContext> env,
                                 List<Type> argtypes,
                                 List<Type> formals,
                                 boolean allowBoxing,
                                 boolean useVarargs,
                                 Warner warn) {
         try {
             checkRawArgumentsAcceptable(env, argtypes, formals, allowBoxing, useVarargs, warn);
             return true;
         } catch (InapplicableMethodException ex) {
             return false;
         }
     }
     /**
      * A check handler is used by the main method applicability routine in order
      * to handle specific method applicability failures. It is assumed that a class
      * implementing this interface should throw exceptions that are a subtype of
      * InapplicableMethodException (see below). Such exception will terminate the
      * method applicability check and propagate important info outwards (for the
      * purpose of generating better diagnostics).
      */
     interface MethodCheckHandler {
         /* The number of actuals and formals differ */
         InapplicableMethodException arityMismatch();
         /* An actual argument type does not conform to the corresponding formal type */
         InapplicableMethodException argumentMismatch(boolean varargs, Type found, Type expected);
         /* The element type of a varargs is not accessible in the current context */
         InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected);
     }
     /**
      * Basic method check handler used within Resolve - all methods end up
      * throwing InapplicableMethodException; a diagnostic fragment that describes
      * the cause as to why the method is not applicable is set on the exception
      * before it is thrown.
      */
     MethodCheckHandler resolveHandler = new MethodCheckHandler() {
             public InapplicableMethodException arityMismatch() {
                 return inapplicableMethodException.setMessage("arg.length.mismatch");
             }
             public InapplicableMethodException argumentMismatch(boolean varargs, Type found, Type expected) {
                 String key = varargs ?
                         "varargs.argument.mismatch" :
                         "no.conforming.assignment.exists";
                 return inapplicableMethodException.setMessage(key,
                         found, expected);
             }
             public InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected) {
                 return inapplicableMethodException.setMessage("inaccessible.varargs.type",
                         expected, Kinds.kindName(location), location);
             }
     };
     void checkRawArgumentsAcceptable(Env<AttrContext> env,
                                 List<Type> argtypes,
                                 List<Type> formals,
                                 boolean allowBoxing,
                                 boolean useVarargs,
                                 Warner warn) {
         checkRawArgumentsAcceptable(env, List.<Type>nil(), argtypes, formals,
                 allowBoxing, useVarargs, warn, resolveHandler);
     }
     /**
      * 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, it is crucial that actual types are converted to the
      * corresponding 'undet' form (i.e. where inference variables are replaced
      * with undetvars) so that constraints can be propagated and collected.
      *
      * Moreover, if one or more types in A is a poly type, this routine calls
      * Infer.instantiateArg in order to complete the poly type (this might involve
      * deferred attribution).
      *
      * A method check handler (see above) is used in order to report errors.
      */
     List<Type> checkRawArgumentsAcceptable(Env<AttrContext> env,
                                 List<Type> undetvars,
                                 List<Type> argtypes,
                                 List<Type> formals,
                                 boolean allowBoxing,
                                 boolean useVarargs,
                                 Warner warn,
                                 MethodCheckHandler handler) {
         Type varargsFormal = useVarargs ? formals.last() : null;
         ListBuffer<Type> checkedArgs = ListBuffer.lb();
         if (varargsFormal == null &&
                 argtypes.size() != formals.size()) {
             throw handler.arityMismatch(); // not enough args
         }
         while (argtypes.nonEmpty() && formals.head != varargsFormal) {
             Type undetFormal = infer.asUndetType(formals.head, undetvars);
             Type capturedActual = types.capture(argtypes.head);
             boolean works = allowBoxing ?
                     types.isConvertible(capturedActual, undetFormal, warn) :
                     types.isSubtypeUnchecked(capturedActual, undetFormal, warn);
             if (!works) {
                 throw handler.argumentMismatch(false, argtypes.head, formals.head);
             }
             checkedArgs.append(capturedActual);
             argtypes = argtypes.tail;
             formals = formals.tail;
         }
         if (formals.head != varargsFormal) {
             throw handler.arityMismatch(); // 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)
             Type elt = types.elemtype(varargsFormal);
             Type eltUndet = infer.asUndetType(elt, undetvars);
             while (argtypes.nonEmpty()) {
                 Type capturedActual = types.capture(argtypes.head);
                 if (!types.isConvertible(capturedActual, eltUndet, warn)) {
                     throw handler.argumentMismatch(true, argtypes.head, elt);
                 }
                 checkedArgs.append(capturedActual);
                 argtypes = argtypes.tail;
             }
             //check varargs element type accessibility
             if (undetvars.isEmpty() && !isAccessible(env, elt)) {
                 Symbol location = env.enclClass.sym;
                 throw handler.inaccessibleVarargs(location, elt);
             }
         }
         return checkedArgs.toList();
     }
     // where
         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() {
                 this.diagnostic = null;
                 return this;
             }
             InapplicableMethodException setMessage(String key) {
                 this.diagnostic = key != null ? diags.fragment(key) : null;
                 return this;
             }
             InapplicableMethodException setMessage(String key, Object... args) {
                 this.diagnostic = key != null ? diags.fragment(key, args) : null;
                 return this;
             }
             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.tag == 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.tag == CLASS || st.tag == 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) return bestSoFar;
         if (!sym.isInheritedIn(site.tsym, types)) return bestSoFar;
         Assert.check(sym.kind < AMBIGUOUS);
         try {
             Type mt = rawInstantiate(env, site, sym, argtypes, typeargtypes,
                                allowBoxing, useVarargs, Warner.noWarnings);
             if (!operator) addVerboseApplicableCandidateDiag(sym ,mt);
         } catch (InapplicableMethodException ex) {
             if (!operator) addVerboseInapplicableCandidateDiag(sym, ex.getDiagnostic());
             switch (bestSoFar.kind) {
             case ABSENT_MTH:
                 return wrongMethod.setWrongSym(sym, ex.getDiagnostic());
             case WRONG_MTH:
                 if (operator) return bestSoFar;
                 wrongMethods.addCandidate(currentStep, wrongMethod.sym, wrongMethod.explanation);
             case WRONG_MTHS:
                 return wrongMethods.addCandidate(currentStep, sym, ex.getDiagnostic());
             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(sym, bestSoFar, env, site,
                            allowBoxing && operator, useVarargs);
     }
     //where
         void addVerboseApplicableCandidateDiag(Symbol sym, Type inst) {
             if (!verboseResolutionMode.contains(VerboseResolutionMode.APPLICABLE))
                 return;
             JCDiagnostic subDiag = null;
             if (inst.getReturnType().tag == FORALL) {
                 Type diagType = types.createMethodTypeWithReturn(inst.asMethodType(),
                                                                 ((ForAll)inst.getReturnType()).qtype);
                 subDiag = diags.fragment("partial.inst.sig", diagType);
             } else if (sym.type.tag == FORALL) {
                 subDiag = diags.fragment("full.inst.sig", inst.asMethodType());
             }
             String key = subDiag == null ?
                     "applicable.method.found" :
                     "applicable.method.found.1";
             verboseResolutionCandidateDiags.put(sym,
                     diags.fragment(key, verboseResolutionCandidateDiags.size(), sym, subDiag));
         }
         void addVerboseInapplicableCandidateDiag(Symbol sym, JCDiagnostic subDiag) {
             if (!verboseResolutionMode.contains(VerboseResolutionMode.INAPPLICABLE))
                 return;
             verboseResolutionCandidateDiags.put(sym,
                     diags.fragment("not.applicable.method.found", verboseResolutionCandidateDiags.size(), sym, subDiag));
         }
     /* 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(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(env, site, m1, m2, allowBoxing, useVarargs);
             boolean m2SignatureMoreSpecific = signatureMoreSpecific(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
                 if (!m1Abstract && !m2Abstract)
                     return ambiguityError(m1, m2);
                 // check that both signatures have the same erasure
                 if (!types.isSameTypes(m1.erasure(types).getParameterTypes(),
                                        m2.erasure(types).getParameterTypes()))
                     return ambiguityError(m1, m2);
                 // both abstract, neither overridden; merge throws clause and result type
                 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 ambiguityError(m1, m2);
                 }
                 Symbol mostSpecific = mst == mt1 ? m1 : m2;
                 List<Type> allThrown = chk.intersect(mt1.getThrownTypes(), mt2.getThrownTypes());
                 Type newSig = types.createMethodTypeWithThrown(mostSpecific.type, allThrown);
                 MethodSymbol result = new MethodSymbol(
                         mostSpecific.flags(),
                         mostSpecific.name,
                         newSig,
                         mostSpecific.owner) {
                     @Override
                     public MethodSymbol implementation(TypeSymbol origin, Types types, boolean checkResult) {
                         if (origin == site.tsym)
                             return this;
                         else
                             return super.implementation(origin, types, checkResult);
                     }
                 };
                 return result;
             }
             if (m1SignatureMoreSpecific) return m1;
             if (m2SignatureMoreSpecific) return m2;
             return ambiguityError(m1, m2);
         case AMBIGUOUS:
             AmbiguityError e = (AmbiguityError)m2;
             Symbol err1 = mostSpecific(m1, e.sym, env, site, allowBoxing, useVarargs);
             Symbol err2 = mostSpecific(m1, e.sym2, env, site, allowBoxing, useVarargs);
             if (err1 == err2) return err1;
             if (err1 == e.sym && err2 == e.sym2) return m2;
             if (err1 instanceof AmbiguityError &&
                 err2 instanceof AmbiguityError &&
                 ((AmbiguityError)err1).sym == ((AmbiguityError)err2).sym)
                 return ambiguityError(m1, m2);
             else
                 return ambiguityError(err1, err2);
         default:
             throw new AssertionError();
         }
     }
     //where
     private boolean signatureMoreSpecific(Env<AttrContext> env, Type site, Symbol m1, Symbol m2, boolean allowBoxing, boolean useVarargs) {
         noteWarner.clear();
         Type mtype1 = types.memberType(site, adjustVarargs(m1, m2, useVarargs));
         Type mtype2 = instantiate(env, site, adjustVarargs(m2, m1, useVarargs),
                 types.lowerBoundArgtypes(mtype1), null,
                 allowBoxing, false, noteWarner);
         return mtype2 != null &&
                 !noteWarner.hasLint(Lint.LintCategory.UNCHECKED);
     }
     //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
     Type mostSpecificReturnType(Type mt1, Type mt2) {
         Type rt1 = mt1.getReturnType();
         Type rt2 = mt2.getReturnType();
         if (mt1.tag == FORALL && mt2.tag == 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);
         }
     }
     /** 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) {
         verboseResolutionCandidateDiags.clear();
         Symbol bestSoFar = methodNotFound;
         bestSoFar = findMethod(env,
                           site,
                           name,
                           argtypes,
                           typeargtypes,
                           site.tsym.type,
                           true,
                           bestSoFar,
                           allowBoxing,
                           useVarargs,
                           operator,
                           new HashSet<TypeSymbol>());
         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,
                               boolean abstractok,
                               Symbol bestSoFar,
                               boolean allowBoxing,
                               boolean useVarargs,
                               boolean operator,
                               Set<TypeSymbol> seen) {
         for (Type ct = intype; ct.tag == CLASS || ct.tag == TYPEVAR; ct = types.supertype(ct)) {
             while (ct.tag == TYPEVAR)
                 ct = ct.getUpperBound();
             ClassSymbol c = (ClassSymbol)ct.tsym;
             if (!seen.add(c)) return bestSoFar;
             if ((c.flags() & (ABSTRACT | INTERFACE | ENUM)) == 0)
                 abstractok = false;
             for (Scope.Entry e = c.members().lookup(name);
                  e.scope != null;
                  e = e.next()) {
                 //- System.out.println(" e " + e.sym);
                 if (e.sym.kind == MTH &&
                     (e.sym.flags_field & SYNTHETIC) == 0) {
                     bestSoFar = selectBest(env, site, argtypes, typeargtypes,
                                            e.sym, bestSoFar,
                                            allowBoxing,
                                            useVarargs,
                                            operator);
                 }
             }
             if (name == names.init)
                 break;
             //- System.out.println(" - " + bestSoFar);
             if (abstractok) {
                 Symbol concrete = methodNotFound;
                 if ((bestSoFar.flags() & ABSTRACT) == 0)
                     concrete = bestSoFar;
                 for (List<Type> l = types.interfaces(c.type);
                      l.nonEmpty();
                      l = l.tail) {
                     bestSoFar = findMethod(env, site, name, argtypes,
                                            typeargtypes,
                                            l.head, abstractok, bestSoFar,
                                            allowBoxing, useVarargs, operator, seen);
                 }
                 if (concrete != bestSoFar &&
                     concrete.kind < ERR  && bestSoFar.kind < ERR &&
                     types.isSubSignature(concrete.type, bestSoFar.type))
                     bestSoFar = concrete;
             }
         }
         return bestSoFar;
     }
     //where
         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 (internalResolution && !verboseResolutionMode.contains(VerboseResolutionMode.INTERNAL)) {
                 return;
             }
             int pos = 0;
             for (Symbol s : verboseResolutionCandidateDiags.keySet()) {
                 if (s == bestSoFar) break;
                 pos++;
             }
             String key = success ? "verbose.resolve.multi" : "verbose.resolve.multi.1";
             JCDiagnostic main = diags.note(log.currentSource(), dpos, key, name, site.tsym, pos, currentStep,
                     methodArguments(argtypes), methodArguments(typeargtypes));
             JCDiagnostic d = new JCDiagnostic.MultilineDiagnostic(main, List.from(verboseResolutionCandidateDiags.values().toArray(new JCDiagnostic[verboseResolutionCandidateDiags.size()])));
             log.report(d);
         }
     /** 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.tag == 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.tag == 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.tag == CLASS &&
                 sym.type.getEnclosingType().tag == 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 indentifier'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.exists()) return sym;
             else if (sym.kind < bestSoFar.kind) bestSoFar = sym;
         }
         if ((kind & PCK) != 0) return reader.enterPackage(name);
         else return bestSoFar;
     }
     /** 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 (--> 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 site      The original type from where the selection took place.
      *  @param name      The symbol's name.
      *  @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.
      */
     Symbol access(Symbol sym,
                   DiagnosticPosition pos,
                   Symbol location,
                   Type site,
                   Name name,
                   boolean qualified,
                   List<Type> argtypes,
                   List<Type> typeargtypes) {
         if (sym.kind >= AMBIGUOUS) {
             ResolveError errSym = (ResolveError)sym;
             if (!site.isErroneous() &&
                 !Type.isErroneous(argtypes) &&
                 (typeargtypes==null || !Type.isErroneous(typeargtypes)))
                 logResolveError(errSym, pos, location, site, name, argtypes, typeargtypes);
             sym = errSym.access(name, qualified ? site.tsym : syms.noSymbol);
         }
         return sym;
     }
     /** Same as original access(), but without location.
      */
     Symbol access(Symbol sym,
                   DiagnosticPosition pos,
                   Type site,
                   Name name,
                   boolean qualified,
                   List<Type> argtypes,
                   List<Type> typeargtypes) {
         return access(sym, pos, site.tsym, site, name, qualified, argtypes, typeargtypes);
     }
     /** Same as original access(), but without type arguments and arguments.
      */
     Symbol access(Symbol sym,
                   DiagnosticPosition pos,
                   Symbol location,
                   Type site,
                   Name name,
                   boolean qualified) {
         if (sym.kind >= AMBIGUOUS)
             return access(sym, pos, location, site, name, qualified, List.<Type>nil(), null);
         else
             return sym;
     }
     /** Same as original access(), but without location, type arguments and arguments.
      */
     Symbol access(Symbol sym,
                   DiagnosticPosition pos,
                   Type site,
                   Name name,
                   boolean qualified) {
         return access(sym, pos, site.tsym, site, name, qualified);
     }
     /** Check that sym is not an abstract method.
      */
     void checkNonAbstract(DiagnosticPosition pos, Symbol sym) {
         if ((sym.flags() & ABSTRACT) != 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.tag == 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 access(
             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) {
         Symbol sym = startResolution();
         List<MethodResolutionPhase> steps = methodResolutionSteps;
         while (steps.nonEmpty() &&
                steps.head.isApplicable(boxingEnabled, varargsEnabled) &&
                sym.kind >= ERRONEOUS) {
             currentStep = steps.head;
             sym = findFun(env, name, argtypes, typeargtypes,
                     steps.head.isBoxingRequired,
                     env.info.varArgs = steps.head.isVarargsRequired);
             methodResolutionCache.put(steps.head, sym);
             steps = steps.tail;
         }
         if (sym.kind >= AMBIGUOUS) {//if nothing is found return the 'first' error
             MethodResolutionPhase errPhase =
                     firstErroneousResolutionPhase();
             sym = access(methodResolutionCache.get(errPhase),
                     pos, env.enclClass.sym.type, name, false, argtypes, typeargtypes);
             env.info.varArgs = errPhase.isVarargsRequired;
         }
         return sym;
     }
     private Symbol startResolution() {
         wrongMethod.clear();
         wrongMethods.clear();
         return methodNotFound;
     }
     /** 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) {
         Symbol sym = startResolution();
         List<MethodResolutionPhase> steps = methodResolutionSteps;
         while (steps.nonEmpty() &&
                steps.head.isApplicable(boxingEnabled, varargsEnabled) &&
                sym.kind >= ERRONEOUS) {
             currentStep = steps.head;
             sym = findMethod(env, site, name, argtypes, typeargtypes,
                     steps.head.isBoxingRequired(),
                     env.info.varArgs = steps.head.isVarargsRequired(), false);
             methodResolutionCache.put(steps.head, sym);
             steps = steps.tail;
         }
         if (sym.kind >= AMBIGUOUS) {
             if (site.tsym.isPolymorphicSignatureGeneric()) {
                 //polymorphic receiver - synthesize new method symbol
                 env.info.varArgs = false;
                 sym = findPolymorphicSignatureInstance(env,
                         site, name, null, argtypes);
             }
             else {
                 //if nothing is found return the 'first' error
                 MethodResolutionPhase errPhase =
                         firstErroneousResolutionPhase();
                 sym = access(methodResolutionCache.get(errPhase),
                         pos, location, site, name, true, argtypes, typeargtypes);
                 env.info.varArgs = errPhase.isVarargsRequired;
             }
         } else if (allowMethodHandles && sym.isPolymorphicSignatureGeneric()) {
             //non-instantiated polymorphic signature - synthesize new method symbol
             env.info.varArgs = false;
             sym = findPolymorphicSignatureInstance(env,
                     site, name, (MethodSymbol)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 site      The original type from where the selection takes place.
      *  @param name      The method's name.
      *  @param spMethod  A template for the implicit method, or null.
      *  @param argtypes  The required argument types.
      *  @param typeargtypes  The required type arguments.
      */
     Symbol findPolymorphicSignatureInstance(Env<AttrContext> env, Type site,
                                             Name name,
                                             MethodSymbol spMethod,  // sig. poly. method or null if none
                                             List<Type> argtypes) {
         Type mtype = infer.instantiatePolymorphicSignatureInstance(env,
                 site, name, spMethod, argtypes);
         long flags = ABSTRACT | HYPOTHETICAL | POLYMORPHIC_SIGNATURE |
                     (spMethod != null ?
                         spMethod.flags() & Flags.AccessFlags :
                         Flags.PUBLIC | Flags.STATIC);
         Symbol m = null;
         for (Scope.Entry e = polymorphicSignatureScope.lookup(name);
              e.scope != null;
              e = e.next()) {
             Symbol sym = e.sym;
             if (types.isSameType(mtype, sym.type) &&
                 (sym.flags() & Flags.STATIC) == (flags & Flags.STATIC) &&
                 types.isSameType(sym.owner.type, site)) {
                m = sym;
                break;
             }
         }
         if (m == null) {
             // create the desired method
             m = new MethodSymbol(flags, name, mtype, site.tsym);
             polymorphicSignatureScope.enter(m);
         }
         return m;
     }
     /** 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) {
         boolean prevInternal = internalResolution;
         try {
             internalResolution = true;
             Symbol sym = resolveQualifiedMethod(
                 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));
         }
         finally {
             internalResolution = prevInternal;
         }
     }
     /** 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) {
         Symbol sym = startResolution();
         List<MethodResolutionPhase> steps = methodResolutionSteps;
         while (steps.nonEmpty() &&
                steps.head.isApplicable(boxingEnabled, varargsEnabled) &&
                sym.kind >= ERRONEOUS) {
             currentStep = steps.head;
             sym = resolveConstructor(pos, env, site, argtypes, typeargtypes,
                     steps.head.isBoxingRequired(),
                     env.info.varArgs = steps.head.isVarargsRequired());
             methodResolutionCache.put(steps.head, sym);
             steps = steps.tail;
         }
         if (sym.kind >= AMBIGUOUS) {//if nothing is found return the 'first' error
             MethodResolutionPhase errPhase = firstErroneousResolutionPhase();
             sym = access(methodResolutionCache.get(errPhase),
                     pos, site, names.init, true, argtypes, typeargtypes);
             env.info.varArgs = errPhase.isVarargsRequired();
         }
         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) {
         Symbol sym = startResolution();
         List<MethodResolutionPhase> steps = methodResolutionSteps;
         while (steps.nonEmpty() &&
                steps.head.isApplicable(boxingEnabled, varargsEnabled) &&
                sym.kind >= ERRONEOUS) {
             currentStep = steps.head;
             sym = resolveConstructor(pos, env, site, argtypes, typeargtypes,
                     steps.head.isBoxingRequired(),
                     env.info.varArgs = steps.head.isVarargsRequired());
             methodResolutionCache.put(steps.head, sym);
             steps = steps.tail;
         }
         if (sym.kind >= AMBIGUOUS) {
             final JCDiagnostic details = sym.kind == WRONG_MTH ?
                 ((InapplicableSymbolError)sym).explanation :
                 null;
             Symbol errSym = new ResolveError(WRONG_MTH, "diamond error") {
                 @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);
                 }
             };
             MethodResolutionPhase errPhase = firstErroneousResolutionPhase();
             sym = access(errSym, pos, site, names.init, true, argtypes, typeargtypes);
             env.info.varArgs = errPhase.isVarargsRequired();
         }
         return sym;
     }
     /** 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.
      *  @param allowBoxing Allow boxing and varargs conversions.
      *  @param useVarargs Box trailing arguments into an array for varargs.
      */
     Symbol resolveConstructor(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 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) {
         Symbol sym = resolveConstructor(
             pos, env, site, argtypes, typeargtypes);
         if (sym.kind == MTH) return (MethodSymbol)sym;
         else throw new FatalError(
                  diags.fragment("fatal.err.cant.locate.ctor", site));
     }
     /** 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) {
         startResolution();
         Name name = treeinfo.operatorName(optag);
         Symbol sym = findMethod(env, syms.predefClass.type, name, argtypes,
                                 null, false, false, true);
         if (boxingEnabled && sym.kind >= WRONG_MTHS)
             sym = findMethod(env, syms.predefClass.type, name, argtypes,
                              null, true, false, true);
         return access(sym, pos, env.enclClass.sym.type, name,
                       false, argtypes, null);
     }
     /** 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));
     }
     /**
      * 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 access(sym, pos, env.enclClass.sym.type,
                                   name, true);
                 }
             }
             if ((env1.enclClass.sym.flags() & STATIC) != 0) staticOnly = true;
             env1 = env1.outer;
         }
         log.error(pos, "not.encl.class", c);
         return syms.errSymbol;
     }
     /**
      * 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) {
         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 access(sym, pos, env.enclClass.sym.type,
                                       name, true);
                     }
                 }
                 if ((env1.enclClass.sym.flags() & STATIC) != 0)
                     staticOnly = true;
                 env1 = env1.outer;
             }
         }
         log.error(pos, "encl.class.required", member);
         return syms.errSymbol;
     }
     /**
      * 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
  ****************************************************************************/
     public void logAccessError(Env<AttrContext> env, JCTree tree, Type type) {
         AccessError error = new AccessError(env, type.getEnclosingType(), type.tsym);
         logResolveError(error, tree.pos(), type.getEnclosingType().tsym, type.getEnclosingType(), 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) {
         return argtypes == null || argtypes.isEmpty() ? noArgs : argtypes;
     }
     /**
      * 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.
      */
     private 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);
         /**
          * A name designates an operator if it consists
          * of a non-empty sequence of operator symbols +-~!/*%&|^<>=
          */
         boolean isOperator(Name name) {
             int i = 0;
             while (i < name.getByteLength() &&
                    "+-~!*/%&|^<>=".indexOf(name.getByteAt(i)) >= 0) i++;
             return i > 0 && i == name.getByteLength();
         }
     }
     /**
      * 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 >= AMBIGUOUS)
                 return ((ResolveError)sym).access(name, location);
             else 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 (isOperator(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.table.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, 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, argtypes); //type parameters and arguments (if any)
             }
         }
         //where
         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 InvalidSymbolError {
         /** An auxiliary explanation set in case of instantiation errors. */
         JCDiagnostic explanation;
         InapplicableSymbolError(Symbol sym) {
             super(WRONG_MTH, sym, "inapplicable symbol error");
         }
         /** Update sym and explanation and return this.
          */
         InapplicableSymbolError setWrongSym(Symbol sym, JCDiagnostic explanation) {
             this.sym = sym;
             if (this.sym == sym && explanation != null)
                 this.explanation = explanation; //update the details
             return this;
         }
         /** Update sym and return this.
          */
         InapplicableSymbolError setWrongSym(Symbol sym) {
             this.sym = sym;
             return this;
         }
         @Override
         public String toString() {
             return super.toString() + " explanation=" + explanation;
         }
         @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 (isOperator(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 {
                 Symbol ws = sym.asMemberOf(site, types);
                 return diags.create(dkind, log.currentSource(), pos,
                           "cant.apply.symbol" + (explanation != null ? ".1" : ""),
                           kindName(ws),
                           ws.name == names.init ? ws.owner.name : ws.name,
                           methodArguments(ws.type.getParameterTypes()),
                           methodArguments(argtypes),
                           kindName(ws.owner),
                           ws.owner.type,
                           explanation);
             }
         }
         void clear() {
             explanation = null;
         }
         @Override
         public Symbol access(Name name, TypeSymbol location) {
             return types.createErrorType(name, location, syms.errSymbol.type).tsym;
         }
     }
     /**
      * 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 ResolveError {
         private List<Candidate> candidates = List.nil();
         InapplicableSymbolsError(Symbol sym) {
             super(WRONG_MTHS, "inapplicable symbols");
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             if (candidates.nonEmpty()) {
                 JCDiagnostic err = diags.create(dkind,
                         log.currentSource(),
                         pos,
                         "cant.apply.symbols",
                         name == names.init ? KindName.CONSTRUCTOR : absentKind(kind),
                         getName(),
                         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) {
             List<JCDiagnostic> details = List.nil();
             for (Candidate c : candidates)
                 details = details.prepend(c.getDiagnostic(site));
             return details.reverse();
         }
         Symbol addCandidate(MethodResolutionPhase currentStep, Symbol sym, JCDiagnostic details) {
             Candidate c = new Candidate(currentStep, sym, details);
             if (c.isValid() && !candidates.contains(c))
                 candidates = candidates.append(c);
             return this;
         }
         void clear() {
             candidates = List.nil();
         }
         private Name getName() {
             Symbol sym = candidates.head.sym;
             return sym.name == names.init ?
                 sym.owner.name :
                 sym.name;
         }
         private class Candidate {
             final MethodResolutionPhase step;
             final Symbol sym;
             final JCDiagnostic details;
             private Candidate(MethodResolutionPhase step, Symbol sym, JCDiagnostic details) {
                 this.step = step;
                 this.sym = sym;
                 this.details = details;
             }
             JCDiagnostic getDiagnostic(Type site) {
                 return diags.fragment("inapplicable.method",
                         Kinds.kindName(sym),
                         sym.location(site, types),
                         sym.asMemberOf(site, types),
                         details);
             }
             @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 isValid() {
                 return  (((sym.flags() & VARARGS) != 0 && step == VARARITY) ||
                           (sym.flags() & VARARGS) == 0 && step == (boxingEnabled ? BOX : BASIC));
             }
         }
     }
     /**
      * 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.tag == 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.tag == 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 InvalidSymbolError {
         /** The other maximally specific symbol */
         Symbol sym2;
         AmbiguityError(Symbol sym1, Symbol sym2) {
             super(AMBIGUOUS, sym1, "ambiguity error");
             this.sym2 = sym2;
         }
         @Override
         JCDiagnostic getDiagnostic(JCDiagnostic.DiagnosticType dkind,
                 DiagnosticPosition pos,
                 Symbol location,
                 Type site,
                 Name name,
                 List<Type> argtypes,
                 List<Type> typeargtypes) {
             AmbiguityError pair = this;
             while (true) {
                 if (pair.sym.kind == AMBIGUOUS)
                     pair = (AmbiguityError)pair.sym;
                 else if (pair.sym2.kind == AMBIGUOUS)
                     pair = (AmbiguityError)pair.sym2;
                 else break;
             }
             Name sname = pair.sym.name;
             if (sname == names.init) sname = pair.sym.owner.name;
             return diags.create(dkind, log.currentSource(),
                       pos, "ref.ambiguous", sname,
                       kindName(pair.sym),
                       pair.sym,
                       pair.sym.location(site, types),
                       kindName(pair.sym2),
                       pair.sym2,
                       pair.sym2.location(site, types));
         }
     }
     enum MethodResolutionPhase {
         BASIC(false, false),
         BOX(true, false),
         VARARITY(true, true);
         boolean isBoxingRequired;
         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);
         }
     }
     private Map<MethodResolutionPhase, Symbol> methodResolutionCache =
         new HashMap<MethodResolutionPhase, Symbol>(MethodResolutionPhase.values().length);
     private Map<Symbol, JCDiagnostic> verboseResolutionCandidateDiags =
         new LinkedHashMap<Symbol, JCDiagnostic>();
     final List<MethodResolutionPhase> methodResolutionSteps = List.of(BASIC, BOX, VARARITY);
     private MethodResolutionPhase currentStep = null;
     private boolean internalResolution = false;
     private MethodResolutionPhase firstErroneousResolutionPhase() {
         MethodResolutionPhase bestSoFar = BASIC;
         Symbol sym = methodNotFound;
         List<MethodResolutionPhase> steps = methodResolutionSteps;
         while (steps.nonEmpty() &&
                steps.head.isApplicable(boxingEnabled, varargsEnabled) &&
                sym.kind >= WRONG_MTHS) {
             sym = methodResolutionCache.get(steps.head);
             bestSoFar = steps.head;
             steps = steps.tail;
         }
         return bestSoFar;
     }
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/comp/Resolve.java@51fb17abfc32 (annotated)

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