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

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

src/share/classes/com/sun/tools/javac/code/Types.java

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

author: mcimadamore
date: Wed, 16 Jan 2013 16:30:11 +0000
changeset 1497: 7aa2025bbb7b
parent 1452: de1ec6fc93fe
child 1510: 7873d37f5b37
permissions: -rw-r--r--

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

 /*
  * Copyright (c) 2003, 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.code;
 import java.lang.ref.SoftReference;
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.WeakHashMap;
 import com.sun.tools.javac.code.Attribute.RetentionPolicy;
 import com.sun.tools.javac.code.Lint.LintCategory;
 import com.sun.tools.javac.code.Type.UndetVar.InferenceBound;
 import com.sun.tools.javac.comp.Check;
 import com.sun.tools.javac.jvm.ClassReader;
 import com.sun.tools.javac.util.*;
 import com.sun.tools.javac.util.List;
 import static com.sun.tools.javac.code.BoundKind.*;
 import static com.sun.tools.javac.code.Flags.*;
 import static com.sun.tools.javac.code.Scope.*;
 import static com.sun.tools.javac.code.Symbol.*;
 import static com.sun.tools.javac.code.Type.*;
 import static com.sun.tools.javac.code.TypeTag.*;
 import static com.sun.tools.javac.util.ListBuffer.lb;
 /**
  * Utility class containing various operations on types.
  *
  * <p>Unless other names are more illustrative, the following naming
  * conventions should be observed in this file:
  *
  * <dl>
  * <dt>t</dt>
  * <dd>If the first argument to an operation is a type, it should be named t.</dd>
  * <dt>s</dt>
  * <dd>Similarly, if the second argument to an operation is a type, it should be named s.</dd>
  * <dt>ts</dt>
  * <dd>If an operations takes a list of types, the first should be named ts.</dd>
  * <dt>ss</dt>
  * <dd>A second list of types should be named ss.</dd>
  * </dl>
  *
  * <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 Types {
     protected static final Context.Key<Types> typesKey =
         new Context.Key<Types>();
     final Symtab syms;
     final JavacMessages messages;
     final Names names;
     final boolean allowBoxing;
     final boolean allowCovariantReturns;
     final boolean allowObjectToPrimitiveCast;
     final boolean allowDefaultMethods;
     final ClassReader reader;
     final Check chk;
     JCDiagnostic.Factory diags;
     List<Warner> warnStack = List.nil();
     final Name capturedName;
     private final FunctionDescriptorLookupError functionDescriptorLookupError;
     public final Warner noWarnings;
     // <editor-fold defaultstate="collapsed" desc="Instantiating">
     public static Types instance(Context context) {
         Types instance = context.get(typesKey);
         if (instance == null)
             instance = new Types(context);
         return instance;
     }
     protected Types(Context context) {
         context.put(typesKey, this);
         syms = Symtab.instance(context);
         names = Names.instance(context);
         Source source = Source.instance(context);
         allowBoxing = source.allowBoxing();
         allowCovariantReturns = source.allowCovariantReturns();
         allowObjectToPrimitiveCast = source.allowObjectToPrimitiveCast();
         allowDefaultMethods = source.allowDefaultMethods();
         reader = ClassReader.instance(context);
         chk = Check.instance(context);
         capturedName = names.fromString("<captured wildcard>");
         messages = JavacMessages.instance(context);
         diags = JCDiagnostic.Factory.instance(context);
         functionDescriptorLookupError = new FunctionDescriptorLookupError();
         noWarnings = new Warner(null);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="upperBound">
     /**
      * The "rvalue conversion".<br>
      * The upper bound of most types is the type
      * itself.  Wildcards, on the other hand have upper
      * and lower bounds.
      * @param t a type
      * @return the upper bound of the given type
      */
     public Type upperBound(Type t) {
         return upperBound.visit(t);
     }
     // where
         private final MapVisitor<Void> upperBound = new MapVisitor<Void>() {
             @Override
             public Type visitWildcardType(WildcardType t, Void ignored) {
                 if (t.isSuperBound())
                     return t.bound == null ? syms.objectType : t.bound.bound;
                 else
                     return visit(t.type);
             }
             @Override
             public Type visitCapturedType(CapturedType t, Void ignored) {
                 return visit(t.bound);
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="lowerBound">
     /**
      * The "lvalue conversion".<br>
      * The lower bound of most types is the type
      * itself.  Wildcards, on the other hand have upper
      * and lower bounds.
      * @param t a type
      * @return the lower bound of the given type
      */
     public Type lowerBound(Type t) {
         return lowerBound.visit(t);
     }
     // where
         private final MapVisitor<Void> lowerBound = new MapVisitor<Void>() {
             @Override
             public Type visitWildcardType(WildcardType t, Void ignored) {
                 return t.isExtendsBound() ? syms.botType : visit(t.type);
             }
             @Override
             public Type visitCapturedType(CapturedType t, Void ignored) {
                 return visit(t.getLowerBound());
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isUnbounded">
     /**
      * Checks that all the arguments to a class are unbounded
      * wildcards or something else that doesn't make any restrictions
      * on the arguments. If a class isUnbounded, a raw super- or
      * subclass can be cast to it without a warning.
      * @param t a type
      * @return true iff the given type is unbounded or raw
      */
     public boolean isUnbounded(Type t) {
         return isUnbounded.visit(t);
     }
     // where
         private final UnaryVisitor<Boolean> isUnbounded = new UnaryVisitor<Boolean>() {
             public Boolean visitType(Type t, Void ignored) {
                 return true;
             }
             @Override
             public Boolean visitClassType(ClassType t, Void ignored) {
                 List<Type> parms = t.tsym.type.allparams();
                 List<Type> args = t.allparams();
                 while (parms.nonEmpty()) {
                     WildcardType unb = new WildcardType(syms.objectType,
                                                         BoundKind.UNBOUND,
                                                         syms.boundClass,
                                                         (TypeVar)parms.head);
                     if (!containsType(args.head, unb))
                         return false;
                     parms = parms.tail;
                     args = args.tail;
                 }
                 return true;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="asSub">
     /**
      * Return the least specific subtype of t that starts with symbol
      * sym.  If none exists, return null.  The least specific subtype
      * is determined as follows:
      *
      * <p>If there is exactly one parameterized instance of sym that is a
      * subtype of t, that parameterized instance is returned.<br>
      * Otherwise, if the plain type or raw type `sym' is a subtype of
      * type t, the type `sym' itself is returned.  Otherwise, null is
      * returned.
      */
     public Type asSub(Type t, Symbol sym) {
         return asSub.visit(t, sym);
     }
     // where
         private final SimpleVisitor<Type,Symbol> asSub = new SimpleVisitor<Type,Symbol>() {
             public Type visitType(Type t, Symbol sym) {
                 return null;
             }
             @Override
             public Type visitClassType(ClassType t, Symbol sym) {
                 if (t.tsym == sym)
                     return t;
                 Type base = asSuper(sym.type, t.tsym);
                 if (base == null)
                     return null;
                 ListBuffer<Type> from = new ListBuffer<Type>();
                 ListBuffer<Type> to = new ListBuffer<Type>();
                 try {
                     adapt(base, t, from, to);
                 } catch (AdaptFailure ex) {
                     return null;
                 }
                 Type res = subst(sym.type, from.toList(), to.toList());
                 if (!isSubtype(res, t))
                     return null;
                 ListBuffer<Type> openVars = new ListBuffer<Type>();
                 for (List<Type> l = sym.type.allparams();
                      l.nonEmpty(); l = l.tail)
                     if (res.contains(l.head) && !t.contains(l.head))
                         openVars.append(l.head);
                 if (openVars.nonEmpty()) {
                     if (t.isRaw()) {
                         // The subtype of a raw type is raw
                         res = erasure(res);
                     } else {
                         // Unbound type arguments default to ?
                         List<Type> opens = openVars.toList();
                         ListBuffer<Type> qs = new ListBuffer<Type>();
                         for (List<Type> iter = opens; iter.nonEmpty(); iter = iter.tail) {
                             qs.append(new WildcardType(syms.objectType, BoundKind.UNBOUND, syms.boundClass, (TypeVar) iter.head));
                         }
                         res = subst(res, opens, qs.toList());
                     }
                 }
                 return res;
             }
             @Override
             public Type visitErrorType(ErrorType t, Symbol sym) {
                 return t;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isConvertible">
     /**
      * Is t a subtype of or convertible via boxing/unboxing
      * conversion to s?
      */
     public boolean isConvertible(Type t, Type s, Warner warn) {
         if (t.tag == ERROR)
             return true;
         boolean tPrimitive = t.isPrimitive();
         boolean sPrimitive = s.isPrimitive();
         if (tPrimitive == sPrimitive) {
             return isSubtypeUnchecked(t, s, warn);
         }
         if (!allowBoxing) return false;
         return tPrimitive
             ? isSubtype(boxedClass(t).type, s)
             : isSubtype(unboxedType(t), s);
     }
     /**
      * Is t a subtype of or convertiable via boxing/unboxing
      * convertions to s?
      */
     public boolean isConvertible(Type t, Type s) {
         return isConvertible(t, s, noWarnings);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="findSam">
     /**
      * Exception used to report a function descriptor lookup failure. The exception
      * wraps a diagnostic that can be used to generate more details error
      * messages.
      */
     public static class FunctionDescriptorLookupError extends RuntimeException {
         private static final long serialVersionUID = 0;
         JCDiagnostic diagnostic;
         FunctionDescriptorLookupError() {
             this.diagnostic = null;
         }
         FunctionDescriptorLookupError setMessage(JCDiagnostic diag) {
             this.diagnostic = diag;
             return this;
         }
         public JCDiagnostic getDiagnostic() {
             return diagnostic;
         }
     }
     /**
      * A cache that keeps track of function descriptors associated with given
      * functional interfaces.
      */
     class DescriptorCache {
         private WeakHashMap<TypeSymbol, Entry> _map = new WeakHashMap<TypeSymbol, Entry>();
         class FunctionDescriptor {
             Symbol descSym;
             FunctionDescriptor(Symbol descSym) {
                 this.descSym = descSym;
             }
             public Symbol getSymbol() {
                 return descSym;
             }
             public Type getType(Type origin) {
                 return memberType(origin, descSym);
             }
         }
         class Entry {
             final FunctionDescriptor cachedDescRes;
             final int prevMark;
             public Entry(FunctionDescriptor cachedDescRes,
                     int prevMark) {
                 this.cachedDescRes = cachedDescRes;
                 this.prevMark = prevMark;
             }
             boolean matches(int mark) {
                 return  this.prevMark == mark;
             }
         }
         FunctionDescriptor get(TypeSymbol origin) throws FunctionDescriptorLookupError {
             Entry e = _map.get(origin);
             CompoundScope members = membersClosure(origin.type, false);
             if (e == null ||
                     !e.matches(members.getMark())) {
                 FunctionDescriptor descRes = findDescriptorInternal(origin, members);
                 _map.put(origin, new Entry(descRes, members.getMark()));
                 return descRes;
             }
             else {
                 return e.cachedDescRes;
             }
         }
         /**
          * Compute the function descriptor associated with a given functional interface
          */
         public FunctionDescriptor findDescriptorInternal(TypeSymbol origin, CompoundScope membersCache) throws FunctionDescriptorLookupError {
             if (!origin.isInterface() || (origin.flags() & ANNOTATION) != 0) {
                 //t must be an interface
                 throw failure("not.a.functional.intf", origin);
             }
             final ListBuffer<Symbol> abstracts = ListBuffer.lb();
             for (Symbol sym : membersCache.getElements(new DescriptorFilter(origin))) {
                 Type mtype = memberType(origin.type, sym);
                 if (abstracts.isEmpty() ||
                         (sym.name == abstracts.first().name &&
                         overrideEquivalent(mtype, memberType(origin.type, abstracts.first())))) {
                     abstracts.append(sym);
                 } else {
                     //the target method(s) should be the only abstract members of t
                     throw failure("not.a.functional.intf.1",  origin,
                             diags.fragment("incompatible.abstracts", Kinds.kindName(origin), origin));
                 }
             }
             if (abstracts.isEmpty()) {
                 //t must define a suitable non-generic method
                 throw failure("not.a.functional.intf.1", origin,
                             diags.fragment("no.abstracts", Kinds.kindName(origin), origin));
             } else if (abstracts.size() == 1) {
                 return new FunctionDescriptor(abstracts.first());
             } else { // size > 1
                 FunctionDescriptor descRes = mergeDescriptors(origin, abstracts.toList());
                 if (descRes == null) {
                     //we can get here if the functional interface is ill-formed
                     ListBuffer<JCDiagnostic> descriptors = ListBuffer.lb();
                     for (Symbol desc : abstracts) {
                         String key = desc.type.getThrownTypes().nonEmpty() ?
                                 "descriptor.throws" : "descriptor";
                         descriptors.append(diags.fragment(key, desc.name,
                                 desc.type.getParameterTypes(),
                                 desc.type.getReturnType(),
                                 desc.type.getThrownTypes()));
                     }
                     JCDiagnostic.MultilineDiagnostic incompatibleDescriptors =
                             new JCDiagnostic.MultilineDiagnostic(diags.fragment("incompatible.descs.in.functional.intf",
                             Kinds.kindName(origin), origin), descriptors.toList());
                     throw failure(incompatibleDescriptors);
                 }
                 return descRes;
             }
         }
         /**
          * Compute a synthetic type for the target descriptor given a list
          * of override-equivalent methods in the functional interface type.
          * The resulting method type is a method type that is override-equivalent
          * and return-type substitutable with each method in the original list.
          */
         private FunctionDescriptor mergeDescriptors(TypeSymbol origin, List<Symbol> methodSyms) {
             //pick argument types - simply take the signature that is a
             //subsignature of all other signatures in the list (as per JLS 8.4.2)
             List<Symbol> mostSpecific = List.nil();
             outer: for (Symbol msym1 : methodSyms) {
                 Type mt1 = memberType(origin.type, msym1);
                 for (Symbol msym2 : methodSyms) {
                     Type mt2 = memberType(origin.type, msym2);
                     if (!isSubSignature(mt1, mt2)) {
                         continue outer;
                     }
                 }
                 mostSpecific = mostSpecific.prepend(msym1);
             }
             if (mostSpecific.isEmpty()) {
                 return null;
             }
             //pick return types - this is done in two phases: (i) first, the most
             //specific return type is chosen using strict subtyping; if this fails,
             //a second attempt is made using return type substitutability (see JLS 8.4.5)
             boolean phase2 = false;
             Symbol bestSoFar = null;
             while (bestSoFar == null) {
                 outer: for (Symbol msym1 : mostSpecific) {
                     Type mt1 = memberType(origin.type, msym1);
                     for (Symbol msym2 : methodSyms) {
                         Type mt2 = memberType(origin.type, msym2);
                         if (phase2 ?
                                 !returnTypeSubstitutable(mt1, mt2) :
                                 !isSubtypeInternal(mt1.getReturnType(), mt2.getReturnType())) {
                             continue outer;
                         }
                     }
                     bestSoFar = msym1;
                 }
                 if (phase2) {
                     break;
                 } else {
                     phase2 = true;
                 }
             }
             if (bestSoFar == null) return null;
             //merge thrown types - form the intersection of all the thrown types in
             //all the signatures in the list
             List<Type> thrown = null;
             for (Symbol msym1 : methodSyms) {
                 Type mt1 = memberType(origin.type, msym1);
                 thrown = (thrown == null) ?
                     mt1.getThrownTypes() :
                     chk.intersect(mt1.getThrownTypes(), thrown);
             }
             final List<Type> thrown1 = thrown;
             return new FunctionDescriptor(bestSoFar) {
                 @Override
                 public Type getType(Type origin) {
                     Type mt = memberType(origin, getSymbol());
                     return new MethodType(mt.getParameterTypes(), mt.getReturnType(), thrown1, syms.methodClass);
                 }
             };
         }
         boolean isSubtypeInternal(Type s, Type t) {
             return (s.isPrimitive() && t.isPrimitive()) ?
                     isSameType(t, s) :
                     isSubtype(s, t);
         }
         FunctionDescriptorLookupError failure(String msg, Object... args) {
             return failure(diags.fragment(msg, args));
         }
         FunctionDescriptorLookupError failure(JCDiagnostic diag) {
             return functionDescriptorLookupError.setMessage(diag);
         }
     }
     private DescriptorCache descCache = new DescriptorCache();
     /**
      * Find the method descriptor associated to this class symbol - if the
      * symbol 'origin' is not a functional interface, an exception is thrown.
      */
     public Symbol findDescriptorSymbol(TypeSymbol origin) throws FunctionDescriptorLookupError {
         return descCache.get(origin).getSymbol();
     }
     /**
      * Find the type of the method descriptor associated to this class symbol -
      * if the symbol 'origin' is not a functional interface, an exception is thrown.
      */
     public Type findDescriptorType(Type origin) throws FunctionDescriptorLookupError {
         return descCache.get(origin.tsym).getType(origin);
     }
     /**
      * Is given type a functional interface?
      */
     public boolean isFunctionalInterface(TypeSymbol tsym) {
         try {
             findDescriptorSymbol(tsym);
             return true;
         } catch (FunctionDescriptorLookupError ex) {
             return false;
         }
     }
     // </editor-fold>
    /**
     * Scope filter used to skip methods that should be ignored (such as methods
     * overridden by j.l.Object) during function interface conversion/marker interface checks
     */
     class DescriptorFilter implements Filter<Symbol> {
        TypeSymbol origin;
        DescriptorFilter(TypeSymbol origin) {
            this.origin = origin;
        }
        @Override
        public boolean accepts(Symbol sym) {
            return sym.kind == Kinds.MTH &&
                    (sym.flags() & (ABSTRACT | DEFAULT)) == ABSTRACT &&
                    !overridesObjectMethod(origin, sym) &&
                    (interfaceCandidates(origin.type, (MethodSymbol)sym).head.flags() & DEFAULT) == 0;
        }
     };
     // <editor-fold defaultstate="collapsed" desc="isMarker">
     /**
      * A cache that keeps track of marker interfaces
      */
     class MarkerCache {
         private WeakHashMap<TypeSymbol, Entry> _map = new WeakHashMap<TypeSymbol, Entry>();
         class Entry {
             final boolean isMarkerIntf;
             final int prevMark;
             public Entry(boolean isMarkerIntf,
                     int prevMark) {
                 this.isMarkerIntf = isMarkerIntf;
                 this.prevMark = prevMark;
             }
             boolean matches(int mark) {
                 return  this.prevMark == mark;
             }
         }
         boolean get(TypeSymbol origin) throws FunctionDescriptorLookupError {
             Entry e = _map.get(origin);
             CompoundScope members = membersClosure(origin.type, false);
             if (e == null ||
                     !e.matches(members.getMark())) {
                 boolean isMarkerIntf = isMarkerInterfaceInternal(origin, members);
                 _map.put(origin, new Entry(isMarkerIntf, members.getMark()));
                 return isMarkerIntf;
             }
             else {
                 return e.isMarkerIntf;
             }
         }
         /**
          * Is given symbol a marker interface
          */
         public boolean isMarkerInterfaceInternal(TypeSymbol origin, CompoundScope membersCache) throws FunctionDescriptorLookupError {
             return !origin.isInterface() ?
                     false :
                     !membersCache.getElements(new DescriptorFilter(origin)).iterator().hasNext();
         }
     }
     private MarkerCache markerCache = new MarkerCache();
     /**
      * Is given type a marker interface?
      */
     public boolean isMarkerInterface(Type site) {
         return markerCache.get(site.tsym);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isSubtype">
     /**
      * Is t an unchecked subtype of s?
      */
     public boolean isSubtypeUnchecked(Type t, Type s) {
         return isSubtypeUnchecked(t, s, noWarnings);
     }
     /**
      * Is t an unchecked subtype of s?
      */
     public boolean isSubtypeUnchecked(Type t, Type s, Warner warn) {
         boolean result = isSubtypeUncheckedInternal(t, s, warn);
         if (result) {
             checkUnsafeVarargsConversion(t, s, warn);
         }
         return result;
     }
     //where
         private boolean isSubtypeUncheckedInternal(Type t, Type s, Warner warn) {
             if (t.hasTag(ARRAY) && s.hasTag(ARRAY)) {
                 if (((ArrayType)t).elemtype.isPrimitive()) {
                     return isSameType(elemtype(t), elemtype(s));
                 } else {
                     return isSubtypeUnchecked(elemtype(t), elemtype(s), warn);
                 }
             } else if (isSubtype(t, s)) {
                 return true;
             }
             else if (t.tag == TYPEVAR) {
                 return isSubtypeUnchecked(t.getUpperBound(), s, warn);
             }
             else if (!s.isRaw()) {
                 Type t2 = asSuper(t, s.tsym);
                 if (t2 != null && t2.isRaw()) {
                     if (isReifiable(s))
                         warn.silentWarn(LintCategory.UNCHECKED);
                     else
                         warn.warn(LintCategory.UNCHECKED);
                     return true;
                 }
             }
             return false;
         }
         private void checkUnsafeVarargsConversion(Type t, Type s, Warner warn) {
             if (t.tag != ARRAY || isReifiable(t)) return;
             ArrayType from = (ArrayType)t;
             boolean shouldWarn = false;
             switch (s.tag) {
                 case ARRAY:
                     ArrayType to = (ArrayType)s;
                     shouldWarn = from.isVarargs() &&
                             !to.isVarargs() &&
                             !isReifiable(from);
                     break;
                 case CLASS:
                     shouldWarn = from.isVarargs();
                     break;
             }
             if (shouldWarn) {
                 warn.warn(LintCategory.VARARGS);
             }
         }
     /**
      * Is t a subtype of s?<br>
      * (not defined for Method and ForAll types)
      */
     final public boolean isSubtype(Type t, Type s) {
         return isSubtype(t, s, true);
     }
     final public boolean isSubtypeNoCapture(Type t, Type s) {
         return isSubtype(t, s, false);
     }
     public boolean isSubtype(Type t, Type s, boolean capture) {
         if (t == s)
             return true;
         if (s.isPartial())
             return isSuperType(s, t);
         if (s.isCompound()) {
             for (Type s2 : interfaces(s).prepend(supertype(s))) {
                 if (!isSubtype(t, s2, capture))
                     return false;
             }
             return true;
         }
         Type lower = lowerBound(s);
         if (s != lower)
             return isSubtype(capture ? capture(t) : t, lower, false);
         return isSubtype.visit(capture ? capture(t) : t, s);
     }
     // where
         private TypeRelation isSubtype = new TypeRelation()
         {
             public Boolean visitType(Type t, Type s) {
                 switch (t.tag) {
                  case BYTE:
                      return (!s.hasTag(CHAR) && t.getTag().isSubRangeOf(s.getTag()));
                  case CHAR:
                      return (!s.hasTag(SHORT) && t.getTag().isSubRangeOf(s.getTag()));
                  case SHORT: case INT: case LONG:
                  case FLOAT: case DOUBLE:
                      return t.getTag().isSubRangeOf(s.getTag());
                  case BOOLEAN: case VOID:
                      return t.hasTag(s.getTag());
                  case TYPEVAR:
                      return isSubtypeNoCapture(t.getUpperBound(), s);
                  case BOT:
                      return
                          s.hasTag(BOT) || s.hasTag(CLASS) ||
                          s.hasTag(ARRAY) || s.hasTag(TYPEVAR);
                  case WILDCARD: //we shouldn't be here - avoids crash (see 7034495)
                  case NONE:
                      return false;
                  default:
                      throw new AssertionError("isSubtype " + t.tag);
                  }
             }
             private Set<TypePair> cache = new HashSet<TypePair>();
             private boolean containsTypeRecursive(Type t, Type s) {
                 TypePair pair = new TypePair(t, s);
                 if (cache.add(pair)) {
                     try {
                         return containsType(t.getTypeArguments(),
                                             s.getTypeArguments());
                     } finally {
                         cache.remove(pair);
                     }
                 } else {
                     return containsType(t.getTypeArguments(),
                                         rewriteSupers(s).getTypeArguments());
                 }
             }
             private Type rewriteSupers(Type t) {
                 if (!t.isParameterized())
                     return t;
                 ListBuffer<Type> from = lb();
                 ListBuffer<Type> to = lb();
                 adaptSelf(t, from, to);
                 if (from.isEmpty())
                     return t;
                 ListBuffer<Type> rewrite = lb();
                 boolean changed = false;
                 for (Type orig : to.toList()) {
                     Type s = rewriteSupers(orig);
                     if (s.isSuperBound() && !s.isExtendsBound()) {
                         s = new WildcardType(syms.objectType,
                                              BoundKind.UNBOUND,
                                              syms.boundClass);
                         changed = true;
                     } else if (s != orig) {
                         s = new WildcardType(upperBound(s),
                                              BoundKind.EXTENDS,
                                              syms.boundClass);
                         changed = true;
                     }
                     rewrite.append(s);
                 }
                 if (changed)
                     return subst(t.tsym.type, from.toList(), rewrite.toList());
                 else
                     return t;
             }
             @Override
             public Boolean visitClassType(ClassType t, Type s) {
                 Type sup = asSuper(t, s.tsym);
                 return sup != null
                     && sup.tsym == s.tsym
                     // You're not allowed to write
                     //     Vector<Object> vec = new Vector<String>();
                     // But with wildcards you can write
                     //     Vector<? extends Object> vec = new Vector<String>();
                     // which means that subtype checking must be done
                     // here instead of same-type checking (via containsType).
                     && (!s.isParameterized() || containsTypeRecursive(s, sup))
                     && isSubtypeNoCapture(sup.getEnclosingType(),
                                           s.getEnclosingType());
             }
             @Override
             public Boolean visitArrayType(ArrayType t, Type s) {
                 if (s.tag == ARRAY) {
                     if (t.elemtype.isPrimitive())
                         return isSameType(t.elemtype, elemtype(s));
                     else
                         return isSubtypeNoCapture(t.elemtype, elemtype(s));
                 }
                 if (s.tag == CLASS) {
                     Name sname = s.tsym.getQualifiedName();
                     return sname == names.java_lang_Object
                         || sname == names.java_lang_Cloneable
                         || sname == names.java_io_Serializable;
                 }
                 return false;
             }
             @Override
             public Boolean visitUndetVar(UndetVar t, Type s) {
                 //todo: test against origin needed? or replace with substitution?
                 if (t == s || t.qtype == s || s.tag == ERROR || s.tag == UNKNOWN) {
                     return true;
                 } else if (s.tag == BOT) {
                     //if 's' is 'null' there's no instantiated type U for which
                     //U <: s (but 'null' itself, which is not a valid type)
                     return false;
                 }
                 t.addBound(InferenceBound.UPPER, s, Types.this);
                 return true;
             }
             @Override
             public Boolean visitErrorType(ErrorType t, Type s) {
                 return true;
             }
         };
     /**
      * Is t a subtype of every type in given list `ts'?<br>
      * (not defined for Method and ForAll types)<br>
      * Allows unchecked conversions.
      */
     public boolean isSubtypeUnchecked(Type t, List<Type> ts, Warner warn) {
         for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
             if (!isSubtypeUnchecked(t, l.head, warn))
                 return false;
         return true;
     }
     /**
      * Are corresponding elements of ts subtypes of ss?  If lists are
      * of different length, return false.
      */
     public boolean isSubtypes(List<Type> ts, List<Type> ss) {
         while (ts.tail != null && ss.tail != null
                /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
                isSubtype(ts.head, ss.head)) {
             ts = ts.tail;
             ss = ss.tail;
         }
         return ts.tail == null && ss.tail == null;
         /*inlined: ts.isEmpty() && ss.isEmpty();*/
     }
     /**
      * Are corresponding elements of ts subtypes of ss, allowing
      * unchecked conversions?  If lists are of different length,
      * return false.
      **/
     public boolean isSubtypesUnchecked(List<Type> ts, List<Type> ss, Warner warn) {
         while (ts.tail != null && ss.tail != null
                /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
                isSubtypeUnchecked(ts.head, ss.head, warn)) {
             ts = ts.tail;
             ss = ss.tail;
         }
         return ts.tail == null && ss.tail == null;
         /*inlined: ts.isEmpty() && ss.isEmpty();*/
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isSuperType">
     /**
      * Is t a supertype of s?
      */
     public boolean isSuperType(Type t, Type s) {
         switch (t.tag) {
         case ERROR:
             return true;
         case UNDETVAR: {
             UndetVar undet = (UndetVar)t;
             if (t == s ||
                 undet.qtype == s ||
                 s.tag == ERROR ||
                 s.tag == BOT) return true;
             undet.addBound(InferenceBound.LOWER, s, this);
             return true;
         }
         default:
             return isSubtype(s, t);
         }
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isSameType">
     /**
      * Are corresponding elements of the lists the same type?  If
      * lists are of different length, return false.
      */
     public boolean isSameTypes(List<Type> ts, List<Type> ss) {
         while (ts.tail != null && ss.tail != null
                /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
                isSameType(ts.head, ss.head)) {
             ts = ts.tail;
             ss = ss.tail;
         }
         return ts.tail == null && ss.tail == null;
         /*inlined: ts.isEmpty() && ss.isEmpty();*/
     }
     /**
      * Is t the same type as s?
      */
     public boolean isSameType(Type t, Type s) {
         return isSameType.visit(t, s);
     }
     // where
         private TypeRelation isSameType = new TypeRelation() {
             public Boolean visitType(Type t, Type s) {
                 if (t == s)
                     return true;
                 if (s.isPartial())
                     return visit(s, t);
                 switch (t.tag) {
                 case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
                 case DOUBLE: case BOOLEAN: case VOID: case BOT: case NONE:
                     return t.tag == s.tag;
                 case TYPEVAR: {
                     if (s.tag == TYPEVAR) {
                         //type-substitution does not preserve type-var types
                         //check that type var symbols and bounds are indeed the same
                         return t.tsym == s.tsym &&
                                 visit(t.getUpperBound(), s.getUpperBound());
                     }
                     else {
                         //special case for s == ? super X, where upper(s) = u
                         //check that u == t, where u has been set by Type.withTypeVar
                         return s.isSuperBound() &&
                                 !s.isExtendsBound() &&
                                 visit(t, upperBound(s));
                     }
                 }
                 default:
                     throw new AssertionError("isSameType " + t.tag);
                 }
             }
             @Override
             public Boolean visitWildcardType(WildcardType t, Type s) {
                 if (s.isPartial())
                     return visit(s, t);
                 else
                     return false;
             }
             @Override
             public Boolean visitClassType(ClassType t, Type s) {
                 if (t == s)
                     return true;
                 if (s.isPartial())
                     return visit(s, t);
                 if (s.isSuperBound() && !s.isExtendsBound())
                     return visit(t, upperBound(s)) && visit(t, lowerBound(s));
                 if (t.isCompound() && s.isCompound()) {
                     if (!visit(supertype(t), supertype(s)))
                         return false;
                     HashSet<UniqueType> set = new HashSet<UniqueType>();
                     for (Type x : interfaces(t))
                         set.add(new UniqueType(x, Types.this));
                     for (Type x : interfaces(s)) {
                         if (!set.remove(new UniqueType(x, Types.this)))
                             return false;
                     }
                     return (set.isEmpty());
                 }
                 return t.tsym == s.tsym
                     && visit(t.getEnclosingType(), s.getEnclosingType())
                     && containsTypeEquivalent(t.getTypeArguments(), s.getTypeArguments());
             }
             @Override
             public Boolean visitArrayType(ArrayType t, Type s) {
                 if (t == s)
                     return true;
                 if (s.isPartial())
                     return visit(s, t);
                 return s.hasTag(ARRAY)
                     && containsTypeEquivalent(t.elemtype, elemtype(s));
             }
             @Override
             public Boolean visitMethodType(MethodType t, Type s) {
                 // isSameType for methods does not take thrown
                 // exceptions into account!
                 return hasSameArgs(t, s) && visit(t.getReturnType(), s.getReturnType());
             }
             @Override
             public Boolean visitPackageType(PackageType t, Type s) {
                 return t == s;
             }
             @Override
             public Boolean visitForAll(ForAll t, Type s) {
                 if (s.tag != FORALL)
                     return false;
                 ForAll forAll = (ForAll)s;
                 return hasSameBounds(t, forAll)
                     && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
             }
             @Override
             public Boolean visitUndetVar(UndetVar t, Type s) {
                 if (s.tag == WILDCARD)
                     // FIXME, this might be leftovers from before capture conversion
                     return false;
                 if (t == s || t.qtype == s || s.tag == ERROR || s.tag == UNKNOWN)
                     return true;
                 t.addBound(InferenceBound.EQ, s, Types.this);
                 return true;
             }
             @Override
             public Boolean visitErrorType(ErrorType t, Type s) {
                 return true;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Contains Type">
     public boolean containedBy(Type t, Type s) {
         switch (t.tag) {
         case UNDETVAR:
             if (s.tag == WILDCARD) {
                 UndetVar undetvar = (UndetVar)t;
                 WildcardType wt = (WildcardType)s;
                 switch(wt.kind) {
                     case UNBOUND: //similar to ? extends Object
                     case EXTENDS: {
                         Type bound = upperBound(s);
                         undetvar.addBound(InferenceBound.UPPER, bound, this);
                         break;
                     }
                     case SUPER: {
                         Type bound = lowerBound(s);
                         undetvar.addBound(InferenceBound.LOWER, bound, this);
                         break;
                     }
                 }
                 return true;
             } else {
                 return isSameType(t, s);
             }
         case ERROR:
             return true;
         default:
             return containsType(s, t);
         }
     }
     boolean containsType(List<Type> ts, List<Type> ss) {
         while (ts.nonEmpty() && ss.nonEmpty()
                && containsType(ts.head, ss.head)) {
             ts = ts.tail;
             ss = ss.tail;
         }
         return ts.isEmpty() && ss.isEmpty();
     }
     /**
      * Check if t contains s.
      *
      * <p>T contains S if:
      *
      * <p>{@code L(T) <: L(S) && U(S) <: U(T)}
      *
      * <p>This relation is only used by ClassType.isSubtype(), that
      * is,
      *
      * <p>{@code C<S> <: C<T> if T contains S.}
      *
      * <p>Because of F-bounds, this relation can lead to infinite
      * recursion.  Thus we must somehow break that recursion.  Notice
      * that containsType() is only called from ClassType.isSubtype().
      * Since the arguments have already been checked against their
      * bounds, we know:
      *
      * <p>{@code U(S) <: U(T) if T is "super" bound (U(T) *is* the bound)}
      *
      * <p>{@code L(T) <: L(S) if T is "extends" bound (L(T) is bottom)}
      *
      * @param t a type
      * @param s a type
      */
     public boolean containsType(Type t, Type s) {
         return containsType.visit(t, s);
     }
     // where
         private TypeRelation containsType = new TypeRelation() {
             private Type U(Type t) {
                 while (t.tag == WILDCARD) {
                     WildcardType w = (WildcardType)t;
                     if (w.isSuperBound())
                         return w.bound == null ? syms.objectType : w.bound.bound;
                     else
                         t = w.type;
                 }
                 return t;
             }
             private Type L(Type t) {
                 while (t.tag == WILDCARD) {
                     WildcardType w = (WildcardType)t;
                     if (w.isExtendsBound())
                         return syms.botType;
                     else
                         t = w.type;
                 }
                 return t;
             }
             public Boolean visitType(Type t, Type s) {
                 if (s.isPartial())
                     return containedBy(s, t);
                 else
                     return isSameType(t, s);
             }
 //            void debugContainsType(WildcardType t, Type s) {
 //                System.err.println();
 //                System.err.format(" does %s contain %s?%n", t, s);
 //                System.err.format(" %s U(%s) <: U(%s) %s = %s%n",
 //                                  upperBound(s), s, t, U(t),
 //                                  t.isSuperBound()
 //                                  || isSubtypeNoCapture(upperBound(s), U(t)));
 //                System.err.format(" %s L(%s) <: L(%s) %s = %s%n",
 //                                  L(t), t, s, lowerBound(s),
 //                                  t.isExtendsBound()
 //                                  || isSubtypeNoCapture(L(t), lowerBound(s)));
 //                System.err.println();
 //            }
             @Override
             public Boolean visitWildcardType(WildcardType t, Type s) {
                 if (s.isPartial())
                     return containedBy(s, t);
                 else {
 //                    debugContainsType(t, s);
                     return isSameWildcard(t, s)
                         || isCaptureOf(s, t)
                         || ((t.isExtendsBound() || isSubtypeNoCapture(L(t), lowerBound(s))) &&
                             (t.isSuperBound() || isSubtypeNoCapture(upperBound(s), U(t))));
                 }
             }
             @Override
             public Boolean visitUndetVar(UndetVar t, Type s) {
                 if (s.tag != WILDCARD)
                     return isSameType(t, s);
                 else
                     return false;
             }
             @Override
             public Boolean visitErrorType(ErrorType t, Type s) {
                 return true;
             }
         };
     public boolean isCaptureOf(Type s, WildcardType t) {
         if (s.tag != TYPEVAR || !((TypeVar)s).isCaptured())
             return false;
         return isSameWildcard(t, ((CapturedType)s).wildcard);
     }
     public boolean isSameWildcard(WildcardType t, Type s) {
         if (s.tag != WILDCARD)
             return false;
         WildcardType w = (WildcardType)s;
         return w.kind == t.kind && w.type == t.type;
     }
     public boolean containsTypeEquivalent(List<Type> ts, List<Type> ss) {
         while (ts.nonEmpty() && ss.nonEmpty()
                && containsTypeEquivalent(ts.head, ss.head)) {
             ts = ts.tail;
             ss = ss.tail;
         }
         return ts.isEmpty() && ss.isEmpty();
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isCastable">
     public boolean isCastable(Type t, Type s) {
         return isCastable(t, s, noWarnings);
     }
     /**
      * Is t is castable to s?<br>
      * s is assumed to be an erased type.<br>
      * (not defined for Method and ForAll types).
      */
     public boolean isCastable(Type t, Type s, Warner warn) {
         if (t == s)
             return true;
         if (t.isPrimitive() != s.isPrimitive())
             return allowBoxing && (
                     isConvertible(t, s, warn)
                     || (allowObjectToPrimitiveCast &&
                         s.isPrimitive() &&
                         isSubtype(boxedClass(s).type, t)));
         if (warn != warnStack.head) {
             try {
                 warnStack = warnStack.prepend(warn);
                 checkUnsafeVarargsConversion(t, s, warn);
                 return isCastable.visit(t,s);
             } finally {
                 warnStack = warnStack.tail;
             }
         } else {
             return isCastable.visit(t,s);
         }
     }
     // where
         private TypeRelation isCastable = new TypeRelation() {
             public Boolean visitType(Type t, Type s) {
                 if (s.tag == ERROR)
                     return true;
                 switch (t.tag) {
                 case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
                 case DOUBLE:
                     return s.isNumeric();
                 case BOOLEAN:
                     return s.tag == BOOLEAN;
                 case VOID:
                     return false;
                 case BOT:
                     return isSubtype(t, s);
                 default:
                     throw new AssertionError();
                 }
             }
             @Override
             public Boolean visitWildcardType(WildcardType t, Type s) {
                 return isCastable(upperBound(t), s, warnStack.head);
             }
             @Override
             public Boolean visitClassType(ClassType t, Type s) {
                 if (s.tag == ERROR || s.tag == BOT)
                     return true;
                 if (s.tag == TYPEVAR) {
                     if (isCastable(t, s.getUpperBound(), noWarnings)) {
                         warnStack.head.warn(LintCategory.UNCHECKED);
                         return true;
                     } else {
                         return false;
                     }
                 }
                 if (t.isCompound()) {
                     Warner oldWarner = warnStack.head;
                     warnStack.head = noWarnings;
                     if (!visit(supertype(t), s))
                         return false;
                     for (Type intf : interfaces(t)) {
                         if (!visit(intf, s))
                             return false;
                     }
                     if (warnStack.head.hasLint(LintCategory.UNCHECKED))
                         oldWarner.warn(LintCategory.UNCHECKED);
                     return true;
                 }
                 if (s.isCompound()) {
                     // call recursively to reuse the above code
                     return visitClassType((ClassType)s, t);
                 }
                 if (s.tag == CLASS || s.tag == ARRAY) {
                     boolean upcast;
                     if ((upcast = isSubtype(erasure(t), erasure(s)))
                         || isSubtype(erasure(s), erasure(t))) {
                         if (!upcast && s.tag == ARRAY) {
                             if (!isReifiable(s))
                                 warnStack.head.warn(LintCategory.UNCHECKED);
                             return true;
                         } else if (s.isRaw()) {
                             return true;
                         } else if (t.isRaw()) {
                             if (!isUnbounded(s))
                                 warnStack.head.warn(LintCategory.UNCHECKED);
                             return true;
                         }
                         // Assume |a| <: |b|
                         final Type a = upcast ? t : s;
                         final Type b = upcast ? s : t;
                         final boolean HIGH = true;
                         final boolean LOW = false;
                         final boolean DONT_REWRITE_TYPEVARS = false;
                         Type aHigh = rewriteQuantifiers(a, HIGH, DONT_REWRITE_TYPEVARS);
                         Type aLow  = rewriteQuantifiers(a, LOW,  DONT_REWRITE_TYPEVARS);
                         Type bHigh = rewriteQuantifiers(b, HIGH, DONT_REWRITE_TYPEVARS);
                         Type bLow  = rewriteQuantifiers(b, LOW,  DONT_REWRITE_TYPEVARS);
                         Type lowSub = asSub(bLow, aLow.tsym);
                         Type highSub = (lowSub == null) ? null : asSub(bHigh, aHigh.tsym);
                         if (highSub == null) {
                             final boolean REWRITE_TYPEVARS = true;
                             aHigh = rewriteQuantifiers(a, HIGH, REWRITE_TYPEVARS);
                             aLow  = rewriteQuantifiers(a, LOW,  REWRITE_TYPEVARS);
                             bHigh = rewriteQuantifiers(b, HIGH, REWRITE_TYPEVARS);
                             bLow  = rewriteQuantifiers(b, LOW,  REWRITE_TYPEVARS);
                             lowSub = asSub(bLow, aLow.tsym);
                             highSub = (lowSub == null) ? null : asSub(bHigh, aHigh.tsym);
                         }
                         if (highSub != null) {
                             if (!(a.tsym == highSub.tsym && a.tsym == lowSub.tsym)) {
                                 Assert.error(a.tsym + " != " + highSub.tsym + " != " + lowSub.tsym);
                             }
                             if (!disjointTypes(aHigh.allparams(), highSub.allparams())
                                 && !disjointTypes(aHigh.allparams(), lowSub.allparams())
                                 && !disjointTypes(aLow.allparams(), highSub.allparams())
                                 && !disjointTypes(aLow.allparams(), lowSub.allparams())) {
                                 if (upcast ? giveWarning(a, b) :
                                     giveWarning(b, a))
                                     warnStack.head.warn(LintCategory.UNCHECKED);
                                 return true;
                             }
                         }
                         if (isReifiable(s))
                             return isSubtypeUnchecked(a, b);
                         else
                             return isSubtypeUnchecked(a, b, warnStack.head);
                     }
                     // Sidecast
                     if (s.tag == CLASS) {
                         if ((s.tsym.flags() & INTERFACE) != 0) {
                             return ((t.tsym.flags() & FINAL) == 0)
                                 ? sideCast(t, s, warnStack.head)
                                 : sideCastFinal(t, s, warnStack.head);
                         } else if ((t.tsym.flags() & INTERFACE) != 0) {
                             return ((s.tsym.flags() & FINAL) == 0)
                                 ? sideCast(t, s, warnStack.head)
                                 : sideCastFinal(t, s, warnStack.head);
                         } else {
                             // unrelated class types
                             return false;
                         }
                     }
                 }
                 return false;
             }
             @Override
             public Boolean visitArrayType(ArrayType t, Type s) {
                 switch (s.tag) {
                 case ERROR:
                 case BOT:
                     return true;
                 case TYPEVAR:
                     if (isCastable(s, t, noWarnings)) {
                         warnStack.head.warn(LintCategory.UNCHECKED);
                         return true;
                     } else {
                         return false;
                     }
                 case CLASS:
                     return isSubtype(t, s);
                 case ARRAY:
                     if (elemtype(t).isPrimitive() || elemtype(s).isPrimitive()) {
                         return elemtype(t).tag == elemtype(s).tag;
                     } else {
                         return visit(elemtype(t), elemtype(s));
                     }
                 default:
                     return false;
                 }
             }
             @Override
             public Boolean visitTypeVar(TypeVar t, Type s) {
                 switch (s.tag) {
                 case ERROR:
                 case BOT:
                     return true;
                 case TYPEVAR:
                     if (isSubtype(t, s)) {
                         return true;
                     } else if (isCastable(t.bound, s, noWarnings)) {
                         warnStack.head.warn(LintCategory.UNCHECKED);
                         return true;
                     } else {
                         return false;
                     }
                 default:
                     return isCastable(t.bound, s, warnStack.head);
                 }
             }
             @Override
             public Boolean visitErrorType(ErrorType t, Type s) {
                 return true;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="disjointTypes">
     public boolean disjointTypes(List<Type> ts, List<Type> ss) {
         while (ts.tail != null && ss.tail != null) {
             if (disjointType(ts.head, ss.head)) return true;
             ts = ts.tail;
             ss = ss.tail;
         }
         return false;
     }
     /**
      * Two types or wildcards are considered disjoint if it can be
      * proven that no type can be contained in both. It is
      * conservative in that it is allowed to say that two types are
      * not disjoint, even though they actually are.
      *
      * The type {@code C<X>} is castable to {@code C<Y>} exactly if
      * {@code X} and {@code Y} are not disjoint.
      */
     public boolean disjointType(Type t, Type s) {
         return disjointType.visit(t, s);
     }
     // where
         private TypeRelation disjointType = new TypeRelation() {
             private Set<TypePair> cache = new HashSet<TypePair>();
             public Boolean visitType(Type t, Type s) {
                 if (s.tag == WILDCARD)
                     return visit(s, t);
                 else
                     return notSoftSubtypeRecursive(t, s) || notSoftSubtypeRecursive(s, t);
             }
             private boolean isCastableRecursive(Type t, Type s) {
                 TypePair pair = new TypePair(t, s);
                 if (cache.add(pair)) {
                     try {
                         return Types.this.isCastable(t, s);
                     } finally {
                         cache.remove(pair);
                     }
                 } else {
                     return true;
                 }
             }
             private boolean notSoftSubtypeRecursive(Type t, Type s) {
                 TypePair pair = new TypePair(t, s);
                 if (cache.add(pair)) {
                     try {
                         return Types.this.notSoftSubtype(t, s);
                     } finally {
                         cache.remove(pair);
                     }
                 } else {
                     return false;
                 }
             }
             @Override
             public Boolean visitWildcardType(WildcardType t, Type s) {
                 if (t.isUnbound())
                     return false;
                 if (s.tag != WILDCARD) {
                     if (t.isExtendsBound())
                         return notSoftSubtypeRecursive(s, t.type);
                     else // isSuperBound()
                         return notSoftSubtypeRecursive(t.type, s);
                 }
                 if (s.isUnbound())
                     return false;
                 if (t.isExtendsBound()) {
                     if (s.isExtendsBound())
                         return !isCastableRecursive(t.type, upperBound(s));
                     else if (s.isSuperBound())
                         return notSoftSubtypeRecursive(lowerBound(s), t.type);
                 } else if (t.isSuperBound()) {
                     if (s.isExtendsBound())
                         return notSoftSubtypeRecursive(t.type, upperBound(s));
                 }
                 return false;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="lowerBoundArgtypes">
     /**
      * Returns the lower bounds of the formals of a method.
      */
     public List<Type> lowerBoundArgtypes(Type t) {
         return lowerBounds(t.getParameterTypes());
     }
     public List<Type> lowerBounds(List<Type> ts) {
         return map(ts, lowerBoundMapping);
     }
     private final Mapping lowerBoundMapping = new Mapping("lowerBound") {
             public Type apply(Type t) {
                 return lowerBound(t);
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="notSoftSubtype">
     /**
      * This relation answers the question: is impossible that
      * something of type `t' can be a subtype of `s'? This is
      * different from the question "is `t' not a subtype of `s'?"
      * when type variables are involved: Integer is not a subtype of T
      * where {@code <T extends Number>} but it is not true that Integer cannot
      * possibly be a subtype of T.
      */
     public boolean notSoftSubtype(Type t, Type s) {
         if (t == s) return false;
         if (t.tag == TYPEVAR) {
             TypeVar tv = (TypeVar) t;
             return !isCastable(tv.bound,
                                relaxBound(s),
                                noWarnings);
         }
         if (s.tag != WILDCARD)
             s = upperBound(s);
         return !isSubtype(t, relaxBound(s));
     }
     private Type relaxBound(Type t) {
         if (t.tag == TYPEVAR) {
             while (t.tag == TYPEVAR)
                 t = t.getUpperBound();
             t = rewriteQuantifiers(t, true, true);
         }
         return t;
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isReifiable">
     public boolean isReifiable(Type t) {
         return isReifiable.visit(t);
     }
     // where
         private UnaryVisitor<Boolean> isReifiable = new UnaryVisitor<Boolean>() {
             public Boolean visitType(Type t, Void ignored) {
                 return true;
             }
             @Override
             public Boolean visitClassType(ClassType t, Void ignored) {
                 if (t.isCompound())
                     return false;
                 else {
                     if (!t.isParameterized())
                         return true;
                     for (Type param : t.allparams()) {
                         if (!param.isUnbound())
                             return false;
                     }
                     return true;
                 }
             }
             @Override
             public Boolean visitArrayType(ArrayType t, Void ignored) {
                 return visit(t.elemtype);
             }
             @Override
             public Boolean visitTypeVar(TypeVar t, Void ignored) {
                 return false;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Array Utils">
     public boolean isArray(Type t) {
         while (t.tag == WILDCARD)
             t = upperBound(t);
         return t.tag == ARRAY;
     }
     /**
      * The element type of an array.
      */
     public Type elemtype(Type t) {
         switch (t.tag) {
         case WILDCARD:
             return elemtype(upperBound(t));
         case ARRAY:
             return ((ArrayType)t).elemtype;
         case FORALL:
             return elemtype(((ForAll)t).qtype);
         case ERROR:
             return t;
         default:
             return null;
         }
     }
     public Type elemtypeOrType(Type t) {
         Type elemtype = elemtype(t);
         return elemtype != null ?
             elemtype :
             t;
     }
     /**
      * Mapping to take element type of an arraytype
      */
     private Mapping elemTypeFun = new Mapping ("elemTypeFun") {
         public Type apply(Type t) { return elemtype(t); }
     };
     /**
      * The number of dimensions of an array type.
      */
     public int dimensions(Type t) {
         int result = 0;
         while (t.tag == ARRAY) {
             result++;
             t = elemtype(t);
         }
         return result;
     }
     /**
      * Returns an ArrayType with the component type t
      *
      * @param t The component type of the ArrayType
      * @return the ArrayType for the given component
      */
     public ArrayType makeArrayType(Type t) {
         if (t.tag == VOID ||
             t.tag == PACKAGE) {
             Assert.error("Type t must not be a VOID or PACKAGE type, " + t.toString());
         }
         return new ArrayType(t, syms.arrayClass);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="asSuper">
     /**
      * Return the (most specific) base type of t that starts with the
      * given symbol.  If none exists, return null.
      *
      * @param t a type
      * @param sym a symbol
      */
     public Type asSuper(Type t, Symbol sym) {
         return asSuper.visit(t, sym);
     }
     // where
         private SimpleVisitor<Type,Symbol> asSuper = new SimpleVisitor<Type,Symbol>() {
             public Type visitType(Type t, Symbol sym) {
                 return null;
             }
             @Override
             public Type visitClassType(ClassType t, Symbol sym) {
                 if (t.tsym == sym)
                     return t;
                 Type st = supertype(t);
                 if (st.tag == CLASS || st.tag == TYPEVAR || st.tag == ERROR) {
                     Type x = asSuper(st, sym);
                     if (x != null)
                         return x;
                 }
                 if ((sym.flags() & INTERFACE) != 0) {
                     for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
                         Type x = asSuper(l.head, sym);
                         if (x != null)
                             return x;
                     }
                 }
                 return null;
             }
             @Override
             public Type visitArrayType(ArrayType t, Symbol sym) {
                 return isSubtype(t, sym.type) ? sym.type : null;
             }
             @Override
             public Type visitTypeVar(TypeVar t, Symbol sym) {
                 if (t.tsym == sym)
                     return t;
                 else
                     return asSuper(t.bound, sym);
             }
             @Override
             public Type visitErrorType(ErrorType t, Symbol sym) {
                 return t;
             }
         };
     /**
      * Return the base type of t or any of its outer types that starts
      * with the given symbol.  If none exists, return null.
      *
      * @param t a type
      * @param sym a symbol
      */
     public Type asOuterSuper(Type t, Symbol sym) {
         switch (t.tag) {
         case CLASS:
             do {
                 Type s = asSuper(t, sym);
                 if (s != null) return s;
                 t = t.getEnclosingType();
             } while (t.tag == CLASS);
             return null;
         case ARRAY:
             return isSubtype(t, sym.type) ? sym.type : null;
         case TYPEVAR:
             return asSuper(t, sym);
         case ERROR:
             return t;
         default:
             return null;
         }
     }
     /**
      * Return the base type of t or any of its enclosing types that
      * starts with the given symbol.  If none exists, return null.
      *
      * @param t a type
      * @param sym a symbol
      */
     public Type asEnclosingSuper(Type t, Symbol sym) {
         switch (t.tag) {
         case CLASS:
             do {
                 Type s = asSuper(t, sym);
                 if (s != null) return s;
                 Type outer = t.getEnclosingType();
                 t = (outer.tag == CLASS) ? outer :
                     (t.tsym.owner.enclClass() != null) ? t.tsym.owner.enclClass().type :
                     Type.noType;
             } while (t.tag == CLASS);
             return null;
         case ARRAY:
             return isSubtype(t, sym.type) ? sym.type : null;
         case TYPEVAR:
             return asSuper(t, sym);
         case ERROR:
             return t;
         default:
             return null;
         }
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="memberType">
     /**
      * The type of given symbol, seen as a member of t.
      *
      * @param t a type
      * @param sym a symbol
      */
     public Type memberType(Type t, Symbol sym) {
         return (sym.flags() & STATIC) != 0
             ? sym.type
             : memberType.visit(t, sym);
         }
     // where
         private SimpleVisitor<Type,Symbol> memberType = new SimpleVisitor<Type,Symbol>() {
             public Type visitType(Type t, Symbol sym) {
                 return sym.type;
             }
             @Override
             public Type visitWildcardType(WildcardType t, Symbol sym) {
                 return memberType(upperBound(t), sym);
             }
             @Override
             public Type visitClassType(ClassType t, Symbol sym) {
                 Symbol owner = sym.owner;
                 long flags = sym.flags();
                 if (((flags & STATIC) == 0) && owner.type.isParameterized()) {
                     Type base = asOuterSuper(t, owner);
                     //if t is an intersection type T = CT & I1 & I2 ... & In
                     //its supertypes CT, I1, ... In might contain wildcards
                     //so we need to go through capture conversion
                     base = t.isCompound() ? capture(base) : base;
                     if (base != null) {
                         List<Type> ownerParams = owner.type.allparams();
                         List<Type> baseParams = base.allparams();
                         if (ownerParams.nonEmpty()) {
                             if (baseParams.isEmpty()) {
                                 // then base is a raw type
                                 return erasure(sym.type);
                             } else {
                                 return subst(sym.type, ownerParams, baseParams);
                             }
                         }
                     }
                 }
                 return sym.type;
             }
             @Override
             public Type visitTypeVar(TypeVar t, Symbol sym) {
                 return memberType(t.bound, sym);
             }
             @Override
             public Type visitErrorType(ErrorType t, Symbol sym) {
                 return t;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isAssignable">
     public boolean isAssignable(Type t, Type s) {
         return isAssignable(t, s, noWarnings);
     }
     /**
      * Is t assignable to s?<br>
      * Equivalent to subtype except for constant values and raw
      * types.<br>
      * (not defined for Method and ForAll types)
      */
     public boolean isAssignable(Type t, Type s, Warner warn) {
         if (t.tag == ERROR)
             return true;
         if (t.tag.isSubRangeOf(INT) && t.constValue() != null) {
             int value = ((Number)t.constValue()).intValue();
             switch (s.tag) {
             case BYTE:
                 if (Byte.MIN_VALUE <= value && value <= Byte.MAX_VALUE)
                     return true;
                 break;
             case CHAR:
                 if (Character.MIN_VALUE <= value && value <= Character.MAX_VALUE)
                     return true;
                 break;
             case SHORT:
                 if (Short.MIN_VALUE <= value && value <= Short.MAX_VALUE)
                     return true;
                 break;
             case INT:
                 return true;
             case CLASS:
                 switch (unboxedType(s).tag) {
                 case BYTE:
                 case CHAR:
                 case SHORT:
                     return isAssignable(t, unboxedType(s), warn);
                 }
                 break;
             }
         }
         return isConvertible(t, s, warn);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="erasure">
     /**
      * The erasure of t {@code |t|} -- the type that results when all
      * type parameters in t are deleted.
      */
     public Type erasure(Type t) {
         return eraseNotNeeded(t)? t : erasure(t, false);
     }
     //where
     private boolean eraseNotNeeded(Type t) {
         // We don't want to erase primitive types and String type as that
         // operation is idempotent. Also, erasing these could result in loss
         // of information such as constant values attached to such types.
         return (t.isPrimitive()) || (syms.stringType.tsym == t.tsym);
     }
     private Type erasure(Type t, boolean recurse) {
         if (t.isPrimitive())
             return t; /* fast special case */
         else
             return erasure.visit(t, recurse);
         }
     // where
         private SimpleVisitor<Type, Boolean> erasure = new SimpleVisitor<Type, Boolean>() {
             public Type visitType(Type t, Boolean recurse) {
                 if (t.isPrimitive())
                     return t; /*fast special case*/
                 else
                     return t.map(recurse ? erasureRecFun : erasureFun);
             }
             @Override
             public Type visitWildcardType(WildcardType t, Boolean recurse) {
                 return erasure(upperBound(t), recurse);
             }
             @Override
             public Type visitClassType(ClassType t, Boolean recurse) {
                 Type erased = t.tsym.erasure(Types.this);
                 if (recurse) {
                     erased = new ErasedClassType(erased.getEnclosingType(),erased.tsym);
                 }
                 return erased;
             }
             @Override
             public Type visitTypeVar(TypeVar t, Boolean recurse) {
                 return erasure(t.bound, recurse);
             }
             @Override
             public Type visitErrorType(ErrorType t, Boolean recurse) {
                 return t;
             }
         };
     private Mapping erasureFun = new Mapping ("erasure") {
             public Type apply(Type t) { return erasure(t); }
         };
     private Mapping erasureRecFun = new Mapping ("erasureRecursive") {
         public Type apply(Type t) { return erasureRecursive(t); }
     };
     public List<Type> erasure(List<Type> ts) {
         return Type.map(ts, erasureFun);
     }
     public Type erasureRecursive(Type t) {
         return erasure(t, true);
     }
     public List<Type> erasureRecursive(List<Type> ts) {
         return Type.map(ts, erasureRecFun);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="makeCompoundType">
     /**
      * Make a compound type from non-empty list of types
      *
      * @param bounds            the types from which the compound type is formed
      * @param supertype         is objectType if all bounds are interfaces,
      *                          null otherwise.
      */
     public Type makeCompoundType(List<Type> bounds) {
         return makeCompoundType(bounds, bounds.head.tsym.isInterface());
     }
     public Type makeCompoundType(List<Type> bounds, boolean allInterfaces) {
         Assert.check(bounds.nonEmpty());
         Type firstExplicitBound = bounds.head;
         if (allInterfaces) {
             bounds = bounds.prepend(syms.objectType);
         }
         ClassSymbol bc =
             new ClassSymbol(ABSTRACT|PUBLIC|SYNTHETIC|COMPOUND|ACYCLIC,
                             Type.moreInfo
                                 ? names.fromString(bounds.toString())
                                 : names.empty,
                             null,
                             syms.noSymbol);
         bc.type = new IntersectionClassType(bounds, bc, allInterfaces);
         bc.erasure_field = (bounds.head.tag == TYPEVAR) ?
                 syms.objectType : // error condition, recover
                 erasure(firstExplicitBound);
         bc.members_field = new Scope(bc);
         return bc.type;
     }
     /**
      * A convenience wrapper for {@link #makeCompoundType(List)}; the
      * arguments are converted to a list and passed to the other
      * method.  Note that this might cause a symbol completion.
      * Hence, this version of makeCompoundType may not be called
      * during a classfile read.
      */
     public Type makeCompoundType(Type bound1, Type bound2) {
         return makeCompoundType(List.of(bound1, bound2));
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="supertype">
     public Type supertype(Type t) {
         return supertype.visit(t);
     }
     // where
         private UnaryVisitor<Type> supertype = new UnaryVisitor<Type>() {
             public Type visitType(Type t, Void ignored) {
                 // A note on wildcards: there is no good way to
                 // determine a supertype for a super bounded wildcard.
                 return null;
             }
             @Override
             public Type visitClassType(ClassType t, Void ignored) {
                 if (t.supertype_field == null) {
                     Type supertype = ((ClassSymbol)t.tsym).getSuperclass();
                     // An interface has no superclass; its supertype is Object.
                     if (t.isInterface())
                         supertype = ((ClassType)t.tsym.type).supertype_field;
                     if (t.supertype_field == null) {
                         List<Type> actuals = classBound(t).allparams();
                         List<Type> formals = t.tsym.type.allparams();
                         if (t.hasErasedSupertypes()) {
                             t.supertype_field = erasureRecursive(supertype);
                         } else if (formals.nonEmpty()) {
                             t.supertype_field = subst(supertype, formals, actuals);
                         }
                         else {
                             t.supertype_field = supertype;
                         }
                     }
                 }
                 return t.supertype_field;
             }
             /**
              * The supertype is always a class type. If the type
              * variable's bounds start with a class type, this is also
              * the supertype.  Otherwise, the supertype is
              * java.lang.Object.
              */
             @Override
             public Type visitTypeVar(TypeVar t, Void ignored) {
                 if (t.bound.tag == TYPEVAR ||
                     (!t.bound.isCompound() && !t.bound.isInterface())) {
                     return t.bound;
                 } else {
                     return supertype(t.bound);
                 }
             }
             @Override
             public Type visitArrayType(ArrayType t, Void ignored) {
                 if (t.elemtype.isPrimitive() || isSameType(t.elemtype, syms.objectType))
                     return arraySuperType();
                 else
                     return new ArrayType(supertype(t.elemtype), t.tsym);
             }
             @Override
             public Type visitErrorType(ErrorType t, Void ignored) {
                 return t;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="interfaces">
     /**
      * Return the interfaces implemented by this class.
      */
     public List<Type> interfaces(Type t) {
         return interfaces.visit(t);
     }
     // where
         private UnaryVisitor<List<Type>> interfaces = new UnaryVisitor<List<Type>>() {
             public List<Type> visitType(Type t, Void ignored) {
                 return List.nil();
             }
             @Override
             public List<Type> visitClassType(ClassType t, Void ignored) {
                 if (t.interfaces_field == null) {
                     List<Type> interfaces = ((ClassSymbol)t.tsym).getInterfaces();
                     if (t.interfaces_field == null) {
                         // If t.interfaces_field is null, then t must
                         // be a parameterized type (not to be confused
                         // with a generic type declaration).
                         // Terminology:
                         //    Parameterized type: List<String>
                         //    Generic type declaration: class List<E> { ... }
                         // So t corresponds to List<String> and
                         // t.tsym.type corresponds to List<E>.
                         // The reason t must be parameterized type is
                         // that completion will happen as a side
                         // effect of calling
                         // ClassSymbol.getInterfaces.  Since
                         // t.interfaces_field is null after
                         // completion, we can assume that t is not the
                         // type of a class/interface declaration.
                         Assert.check(t != t.tsym.type, t);
                         List<Type> actuals = t.allparams();
                         List<Type> formals = t.tsym.type.allparams();
                         if (t.hasErasedSupertypes()) {
                             t.interfaces_field = erasureRecursive(interfaces);
                         } else if (formals.nonEmpty()) {
                             t.interfaces_field =
                                 upperBounds(subst(interfaces, formals, actuals));
                         }
                         else {
                             t.interfaces_field = interfaces;
                         }
                     }
                 }
                 return t.interfaces_field;
             }
             @Override
             public List<Type> visitTypeVar(TypeVar t, Void ignored) {
                 if (t.bound.isCompound())
                     return interfaces(t.bound);
                 if (t.bound.isInterface())
                     return List.of(t.bound);
                 return List.nil();
             }
         };
     public boolean isDirectSuperInterface(TypeSymbol isym, TypeSymbol origin) {
         for (Type i2 : interfaces(origin.type)) {
             if (isym == i2.tsym) return true;
         }
         return false;
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="isDerivedRaw">
     Map<Type,Boolean> isDerivedRawCache = new HashMap<Type,Boolean>();
     public boolean isDerivedRaw(Type t) {
         Boolean result = isDerivedRawCache.get(t);
         if (result == null) {
             result = isDerivedRawInternal(t);
             isDerivedRawCache.put(t, result);
         }
         return result;
     }
     public boolean isDerivedRawInternal(Type t) {
         if (t.isErroneous())
             return false;
         return
             t.isRaw() ||
             supertype(t) != null && isDerivedRaw(supertype(t)) ||
             isDerivedRaw(interfaces(t));
     }
     public boolean isDerivedRaw(List<Type> ts) {
         List<Type> l = ts;
         while (l.nonEmpty() && !isDerivedRaw(l.head)) l = l.tail;
         return l.nonEmpty();
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="setBounds">
     /**
      * Set the bounds field of the given type variable to reflect a
      * (possibly multiple) list of bounds.
      * @param t                 a type variable
      * @param bounds            the bounds, must be nonempty
      * @param supertype         is objectType if all bounds are interfaces,
      *                          null otherwise.
      */
     public void setBounds(TypeVar t, List<Type> bounds) {
         setBounds(t, bounds, bounds.head.tsym.isInterface());
     }
     /**
      * Same as {@link #setBounds(Type.TypeVar,List,Type)}, except that
      * third parameter is computed directly, as follows: if all
      * all bounds are interface types, the computed supertype is Object,
      * otherwise the supertype is simply left null (in this case, the supertype
      * is assumed to be the head of the bound list passed as second argument).
      * Note that this check might cause a symbol completion. Hence, this version of
      * setBounds may not be called during a classfile read.
      */
     public void setBounds(TypeVar t, List<Type> bounds, boolean allInterfaces) {
         t.bound = bounds.tail.isEmpty() ?
                 bounds.head :
                 makeCompoundType(bounds, allInterfaces);
         t.rank_field = -1;
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="getBounds">
     /**
      * Return list of bounds of the given type variable.
      */
     public List<Type> getBounds(TypeVar t) {
         if (t.bound.hasTag(NONE))
             return List.nil();
         else if (t.bound.isErroneous() || !t.bound.isCompound())
             return List.of(t.bound);
         else if ((erasure(t).tsym.flags() & INTERFACE) == 0)
             return interfaces(t).prepend(supertype(t));
         else
             // No superclass was given in bounds.
             // In this case, supertype is Object, erasure is first interface.
             return interfaces(t);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="classBound">
     /**
      * If the given type is a (possibly selected) type variable,
      * return the bounding class of this type, otherwise return the
      * type itself.
      */
     public Type classBound(Type t) {
         return classBound.visit(t);
     }
     // where
         private UnaryVisitor<Type> classBound = new UnaryVisitor<Type>() {
             public Type visitType(Type t, Void ignored) {
                 return t;
             }
             @Override
             public Type visitClassType(ClassType t, Void ignored) {
                 Type outer1 = classBound(t.getEnclosingType());
                 if (outer1 != t.getEnclosingType())
                     return new ClassType(outer1, t.getTypeArguments(), t.tsym);
                 else
                     return t;
             }
             @Override
             public Type visitTypeVar(TypeVar t, Void ignored) {
                 return classBound(supertype(t));
             }
             @Override
             public Type visitErrorType(ErrorType t, Void ignored) {
                 return t;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="sub signature / override equivalence">
     /**
      * Returns true iff the first signature is a <em>sub
      * signature</em> of the other.  This is <b>not</b> an equivalence
      * relation.
      *
      * @jls section 8.4.2.
      * @see #overrideEquivalent(Type t, Type s)
      * @param t first signature (possibly raw).
      * @param s second signature (could be subjected to erasure).
      * @return true if t is a sub signature of s.
      */
     public boolean isSubSignature(Type t, Type s) {
         return isSubSignature(t, s, true);
     }
     public boolean isSubSignature(Type t, Type s, boolean strict) {
         return hasSameArgs(t, s, strict) || hasSameArgs(t, erasure(s), strict);
     }
     /**
      * Returns true iff these signatures are related by <em>override
      * equivalence</em>.  This is the natural extension of
      * isSubSignature to an equivalence relation.
      *
      * @jls section 8.4.2.
      * @see #isSubSignature(Type t, Type s)
      * @param t a signature (possible raw, could be subjected to
      * erasure).
      * @param s a signature (possible raw, could be subjected to
      * erasure).
      * @return true if either argument is a sub signature of the other.
      */
     public boolean overrideEquivalent(Type t, Type s) {
         return hasSameArgs(t, s) ||
             hasSameArgs(t, erasure(s)) || hasSameArgs(erasure(t), s);
     }
     public boolean overridesObjectMethod(TypeSymbol origin, Symbol msym) {
         for (Scope.Entry e = syms.objectType.tsym.members().lookup(msym.name) ; e.scope != null ; e = e.next()) {
             if (msym.overrides(e.sym, origin, Types.this, true)) {
                 return true;
             }
         }
         return false;
     }
     // <editor-fold defaultstate="collapsed" desc="Determining method implementation in given site">
     class ImplementationCache {
         private WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, Entry>>> _map =
                 new WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, Entry>>>();
         class Entry {
             final MethodSymbol cachedImpl;
             final Filter<Symbol> implFilter;
             final boolean checkResult;
             final int prevMark;
             public Entry(MethodSymbol cachedImpl,
                     Filter<Symbol> scopeFilter,
                     boolean checkResult,
                     int prevMark) {
                 this.cachedImpl = cachedImpl;
                 this.implFilter = scopeFilter;
                 this.checkResult = checkResult;
                 this.prevMark = prevMark;
             }
             boolean matches(Filter<Symbol> scopeFilter, boolean checkResult, int mark) {
                 return this.implFilter == scopeFilter &&
                         this.checkResult == checkResult &&
                         this.prevMark == mark;
             }
         }
         MethodSymbol get(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Filter<Symbol> implFilter) {
             SoftReference<Map<TypeSymbol, Entry>> ref_cache = _map.get(ms);
             Map<TypeSymbol, Entry> cache = ref_cache != null ? ref_cache.get() : null;
             if (cache == null) {
                 cache = new HashMap<TypeSymbol, Entry>();
                 _map.put(ms, new SoftReference<Map<TypeSymbol, Entry>>(cache));
             }
             Entry e = cache.get(origin);
             CompoundScope members = membersClosure(origin.type, true);
             if (e == null ||
                     !e.matches(implFilter, checkResult, members.getMark())) {
                 MethodSymbol impl = implementationInternal(ms, origin, checkResult, implFilter);
                 cache.put(origin, new Entry(impl, implFilter, checkResult, members.getMark()));
                 return impl;
             }
             else {
                 return e.cachedImpl;
             }
         }
         private MethodSymbol implementationInternal(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Filter<Symbol> implFilter) {
             for (Type t = origin.type; t.tag == CLASS || t.tag == TYPEVAR; t = supertype(t)) {
                 while (t.tag == TYPEVAR)
                     t = t.getUpperBound();
                 TypeSymbol c = t.tsym;
                 for (Scope.Entry e = c.members().lookup(ms.name, implFilter);
                      e.scope != null;
                      e = e.next(implFilter)) {
                     if (e.sym != null &&
                              e.sym.overrides(ms, origin, Types.this, checkResult))
                         return (MethodSymbol)e.sym;
                 }
             }
             return null;
         }
     }
     private ImplementationCache implCache = new ImplementationCache();
     public MethodSymbol implementation(MethodSymbol ms, TypeSymbol origin, boolean checkResult, Filter<Symbol> implFilter) {
         return implCache.get(ms, origin, checkResult, implFilter);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="compute transitive closure of all members in given site">
     class MembersClosureCache extends SimpleVisitor<CompoundScope, Boolean> {
         private WeakHashMap<TypeSymbol, Entry> _map =
                 new WeakHashMap<TypeSymbol, Entry>();
         class Entry {
             final boolean skipInterfaces;
             final CompoundScope compoundScope;
             public Entry(boolean skipInterfaces, CompoundScope compoundScope) {
                 this.skipInterfaces = skipInterfaces;
                 this.compoundScope = compoundScope;
             }
             boolean matches(boolean skipInterfaces) {
                 return this.skipInterfaces == skipInterfaces;
             }
         }
         List<TypeSymbol> seenTypes = List.nil();
         /** members closure visitor methods **/
         public CompoundScope visitType(Type t, Boolean skipInterface) {
             return null;
         }
         @Override
         public CompoundScope visitClassType(ClassType t, Boolean skipInterface) {
             if (seenTypes.contains(t.tsym)) {
                 //this is possible when an interface is implemented in multiple
                 //superclasses, or when a classs hierarchy is circular - in such
                 //cases we don't need to recurse (empty scope is returned)
                 return new CompoundScope(t.tsym);
             }
             try {
                 seenTypes = seenTypes.prepend(t.tsym);
                 ClassSymbol csym = (ClassSymbol)t.tsym;
                 Entry e = _map.get(csym);
                 if (e == null || !e.matches(skipInterface)) {
                     CompoundScope membersClosure = new CompoundScope(csym);
                     if (!skipInterface) {
                         for (Type i : interfaces(t)) {
                             membersClosure.addSubScope(visit(i, skipInterface));
                         }
                     }
                     membersClosure.addSubScope(visit(supertype(t), skipInterface));
                     membersClosure.addSubScope(csym.members());
                     e = new Entry(skipInterface, membersClosure);
                     _map.put(csym, e);
                 }
                 return e.compoundScope;
             }
             finally {
                 seenTypes = seenTypes.tail;
             }
         }
         @Override
         public CompoundScope visitTypeVar(TypeVar t, Boolean skipInterface) {
             return visit(t.getUpperBound(), skipInterface);
         }
     }
     private MembersClosureCache membersCache = new MembersClosureCache();
     public CompoundScope membersClosure(Type site, boolean skipInterface) {
         return membersCache.visit(site, skipInterface);
     }
     // </editor-fold>
     //where
     public List<MethodSymbol> interfaceCandidates(Type site, MethodSymbol ms) {
         Filter<Symbol> filter = new MethodFilter(ms, site);
         List<MethodSymbol> candidates = List.nil();
         for (Symbol s : membersClosure(site, false).getElements(filter)) {
             if (!site.tsym.isInterface() && !s.owner.isInterface()) {
                 return List.of((MethodSymbol)s);
             } else if (!candidates.contains(s)) {
                 candidates = candidates.prepend((MethodSymbol)s);
             }
         }
         return prune(candidates, ownerComparator);
     }
     public List<MethodSymbol> prune(List<MethodSymbol> methods, Comparator<MethodSymbol> cmp) {
         ListBuffer<MethodSymbol> methodsMin = ListBuffer.lb();
         for (MethodSymbol m1 : methods) {
             boolean isMin_m1 = true;
             for (MethodSymbol m2 : methods) {
                 if (m1 == m2) continue;
                 if (cmp.compare(m2, m1) < 0) {
                     isMin_m1 = false;
                     break;
                 }
             }
             if (isMin_m1)
                 methodsMin.append(m1);
         }
         return methodsMin.toList();
     }
     Comparator<MethodSymbol> ownerComparator = new Comparator<MethodSymbol>() {
         public int compare(MethodSymbol s1, MethodSymbol s2) {
             return s1.owner.isSubClass(s2.owner, Types.this) ? -1 : 1;
         }
     };
     // where
             private class MethodFilter implements Filter<Symbol> {
                 Symbol msym;
                 Type site;
                 MethodFilter(Symbol msym, Type site) {
                     this.msym = msym;
                     this.site = site;
                 }
                 public boolean accepts(Symbol s) {
                     return s.kind == Kinds.MTH &&
                             s.name == msym.name &&
                             s.isInheritedIn(site.tsym, Types.this) &&
                             overrideEquivalent(memberType(site, s), memberType(site, msym));
                 }
             };
     // </editor-fold>
     /**
      * Does t have the same arguments as s?  It is assumed that both
      * types are (possibly polymorphic) method types.  Monomorphic
      * method types "have the same arguments", if their argument lists
      * are equal.  Polymorphic method types "have the same arguments",
      * if they have the same arguments after renaming all type
      * variables of one to corresponding type variables in the other,
      * where correspondence is by position in the type parameter list.
      */
     public boolean hasSameArgs(Type t, Type s) {
         return hasSameArgs(t, s, true);
     }
     public boolean hasSameArgs(Type t, Type s, boolean strict) {
         return hasSameArgs(t, s, strict ? hasSameArgs_strict : hasSameArgs_nonstrict);
     }
     private boolean hasSameArgs(Type t, Type s, TypeRelation hasSameArgs) {
         return hasSameArgs.visit(t, s);
     }
     // where
         private class HasSameArgs extends TypeRelation {
             boolean strict;
             public HasSameArgs(boolean strict) {
                 this.strict = strict;
             }
             public Boolean visitType(Type t, Type s) {
                 throw new AssertionError();
             }
             @Override
             public Boolean visitMethodType(MethodType t, Type s) {
                 return s.tag == METHOD
                     && containsTypeEquivalent(t.argtypes, s.getParameterTypes());
             }
             @Override
             public Boolean visitForAll(ForAll t, Type s) {
                 if (s.tag != FORALL)
                     return strict ? false : visitMethodType(t.asMethodType(), s);
                 ForAll forAll = (ForAll)s;
                 return hasSameBounds(t, forAll)
                     && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
             }
             @Override
             public Boolean visitErrorType(ErrorType t, Type s) {
                 return false;
             }
         };
         TypeRelation hasSameArgs_strict = new HasSameArgs(true);
         TypeRelation hasSameArgs_nonstrict = new HasSameArgs(false);
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="subst">
     public List<Type> subst(List<Type> ts,
                             List<Type> from,
                             List<Type> to) {
         return new Subst(from, to).subst(ts);
     }
     /**
      * Substitute all occurrences of a type in `from' with the
      * corresponding type in `to' in 't'. Match lists `from' and `to'
      * from the right: If lists have different length, discard leading
      * elements of the longer list.
      */
     public Type subst(Type t, List<Type> from, List<Type> to) {
         return new Subst(from, to).subst(t);
     }
     private class Subst extends UnaryVisitor<Type> {
         List<Type> from;
         List<Type> to;
         public Subst(List<Type> from, List<Type> to) {
             int fromLength = from.length();
             int toLength = to.length();
             while (fromLength > toLength) {
                 fromLength--;
                 from = from.tail;
             }
             while (fromLength < toLength) {
                 toLength--;
                 to = to.tail;
             }
             this.from = from;
             this.to = to;
         }
         Type subst(Type t) {
             if (from.tail == null)
                 return t;
             else
                 return visit(t);
             }
         List<Type> subst(List<Type> ts) {
             if (from.tail == null)
                 return ts;
             boolean wild = false;
             if (ts.nonEmpty() && from.nonEmpty()) {
                 Type head1 = subst(ts.head);
                 List<Type> tail1 = subst(ts.tail);
                 if (head1 != ts.head || tail1 != ts.tail)
                     return tail1.prepend(head1);
             }
             return ts;
         }
         public Type visitType(Type t, Void ignored) {
             return t;
         }
         @Override
         public Type visitMethodType(MethodType t, Void ignored) {
             List<Type> argtypes = subst(t.argtypes);
             Type restype = subst(t.restype);
             List<Type> thrown = subst(t.thrown);
             if (argtypes == t.argtypes &&
                 restype == t.restype &&
                 thrown == t.thrown)
                 return t;
             else
                 return new MethodType(argtypes, restype, thrown, t.tsym);
         }
         @Override
         public Type visitTypeVar(TypeVar t, Void ignored) {
             for (List<Type> from = this.from, to = this.to;
                  from.nonEmpty();
                  from = from.tail, to = to.tail) {
                 if (t == from.head) {
                     return to.head.withTypeVar(t);
                 }
             }
             return t;
         }
         @Override
         public Type visitClassType(ClassType t, Void ignored) {
             if (!t.isCompound()) {
                 List<Type> typarams = t.getTypeArguments();
                 List<Type> typarams1 = subst(typarams);
                 Type outer = t.getEnclosingType();
                 Type outer1 = subst(outer);
                 if (typarams1 == typarams && outer1 == outer)
                     return t;
                 else
                     return new ClassType(outer1, typarams1, t.tsym);
             } else {
                 Type st = subst(supertype(t));
                 List<Type> is = upperBounds(subst(interfaces(t)));
                 if (st == supertype(t) && is == interfaces(t))
                     return t;
                 else
                     return makeCompoundType(is.prepend(st));
             }
         }
         @Override
         public Type visitWildcardType(WildcardType t, Void ignored) {
             Type bound = t.type;
             if (t.kind != BoundKind.UNBOUND)
                 bound = subst(bound);
             if (bound == t.type) {
                 return t;
             } else {
                 if (t.isExtendsBound() && bound.isExtendsBound())
                     bound = upperBound(bound);
                 return new WildcardType(bound, t.kind, syms.boundClass, t.bound);
             }
         }
         @Override
         public Type visitArrayType(ArrayType t, Void ignored) {
             Type elemtype = subst(t.elemtype);
             if (elemtype == t.elemtype)
                 return t;
             else
                 return new ArrayType(upperBound(elemtype), t.tsym);
         }
         @Override
         public Type visitForAll(ForAll t, Void ignored) {
             if (Type.containsAny(to, t.tvars)) {
                 //perform alpha-renaming of free-variables in 't'
                 //if 'to' types contain variables that are free in 't'
                 List<Type> freevars = newInstances(t.tvars);
                 t = new ForAll(freevars,
                         Types.this.subst(t.qtype, t.tvars, freevars));
             }
             List<Type> tvars1 = substBounds(t.tvars, from, to);
             Type qtype1 = subst(t.qtype);
             if (tvars1 == t.tvars && qtype1 == t.qtype) {
                 return t;
             } else if (tvars1 == t.tvars) {
                 return new ForAll(tvars1, qtype1);
             } else {
                 return new ForAll(tvars1, Types.this.subst(qtype1, t.tvars, tvars1));
             }
         }
         @Override
         public Type visitErrorType(ErrorType t, Void ignored) {
             return t;
         }
     }
     public List<Type> substBounds(List<Type> tvars,
                                   List<Type> from,
                                   List<Type> to) {
         if (tvars.isEmpty())
             return tvars;
         ListBuffer<Type> newBoundsBuf = lb();
         boolean changed = false;
         // calculate new bounds
         for (Type t : tvars) {
             TypeVar tv = (TypeVar) t;
             Type bound = subst(tv.bound, from, to);
             if (bound != tv.bound)
                 changed = true;
             newBoundsBuf.append(bound);
         }
         if (!changed)
             return tvars;
         ListBuffer<Type> newTvars = lb();
         // create new type variables without bounds
         for (Type t : tvars) {
             newTvars.append(new TypeVar(t.tsym, null, syms.botType));
         }
         // the new bounds should use the new type variables in place
         // of the old
         List<Type> newBounds = newBoundsBuf.toList();
         from = tvars;
         to = newTvars.toList();
         for (; !newBounds.isEmpty(); newBounds = newBounds.tail) {
             newBounds.head = subst(newBounds.head, from, to);
         }
         newBounds = newBoundsBuf.toList();
         // set the bounds of new type variables to the new bounds
         for (Type t : newTvars.toList()) {
             TypeVar tv = (TypeVar) t;
             tv.bound = newBounds.head;
             newBounds = newBounds.tail;
         }
         return newTvars.toList();
     }
     public TypeVar substBound(TypeVar t, List<Type> from, List<Type> to) {
         Type bound1 = subst(t.bound, from, to);
         if (bound1 == t.bound)
             return t;
         else {
             // create new type variable without bounds
             TypeVar tv = new TypeVar(t.tsym, null, syms.botType);
             // the new bound should use the new type variable in place
             // of the old
             tv.bound = subst(bound1, List.<Type>of(t), List.<Type>of(tv));
             return tv;
         }
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="hasSameBounds">
     /**
      * Does t have the same bounds for quantified variables as s?
      */
     boolean hasSameBounds(ForAll t, ForAll s) {
         List<Type> l1 = t.tvars;
         List<Type> l2 = s.tvars;
         while (l1.nonEmpty() && l2.nonEmpty() &&
                isSameType(l1.head.getUpperBound(),
                           subst(l2.head.getUpperBound(),
                                 s.tvars,
                                 t.tvars))) {
             l1 = l1.tail;
             l2 = l2.tail;
         }
         return l1.isEmpty() && l2.isEmpty();
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="newInstances">
     /** Create new vector of type variables from list of variables
      *  changing all recursive bounds from old to new list.
      */
     public List<Type> newInstances(List<Type> tvars) {
         List<Type> tvars1 = Type.map(tvars, newInstanceFun);
         for (List<Type> l = tvars1; l.nonEmpty(); l = l.tail) {
             TypeVar tv = (TypeVar) l.head;
             tv.bound = subst(tv.bound, tvars, tvars1);
         }
         return tvars1;
     }
     private static final Mapping newInstanceFun = new Mapping("newInstanceFun") {
             public Type apply(Type t) { return new TypeVar(t.tsym, t.getUpperBound(), t.getLowerBound()); }
         };
     // </editor-fold>
     public Type createMethodTypeWithParameters(Type original, List<Type> newParams) {
         return original.accept(methodWithParameters, newParams);
     }
     // where
         private final MapVisitor<List<Type>> methodWithParameters = new MapVisitor<List<Type>>() {
             public Type visitType(Type t, List<Type> newParams) {
                 throw new IllegalArgumentException("Not a method type: " + t);
             }
             public Type visitMethodType(MethodType t, List<Type> newParams) {
                 return new MethodType(newParams, t.restype, t.thrown, t.tsym);
             }
             public Type visitForAll(ForAll t, List<Type> newParams) {
                 return new ForAll(t.tvars, t.qtype.accept(this, newParams));
             }
         };
     public Type createMethodTypeWithThrown(Type original, List<Type> newThrown) {
         return original.accept(methodWithThrown, newThrown);
     }
     // where
         private final MapVisitor<List<Type>> methodWithThrown = new MapVisitor<List<Type>>() {
             public Type visitType(Type t, List<Type> newThrown) {
                 throw new IllegalArgumentException("Not a method type: " + t);
             }
             public Type visitMethodType(MethodType t, List<Type> newThrown) {
                 return new MethodType(t.argtypes, t.restype, newThrown, t.tsym);
             }
             public Type visitForAll(ForAll t, List<Type> newThrown) {
                 return new ForAll(t.tvars, t.qtype.accept(this, newThrown));
             }
         };
     public Type createMethodTypeWithReturn(Type original, Type newReturn) {
         return original.accept(methodWithReturn, newReturn);
     }
     // where
         private final MapVisitor<Type> methodWithReturn = new MapVisitor<Type>() {
             public Type visitType(Type t, Type newReturn) {
                 throw new IllegalArgumentException("Not a method type: " + t);
             }
             public Type visitMethodType(MethodType t, Type newReturn) {
                 return new MethodType(t.argtypes, newReturn, t.thrown, t.tsym);
             }
             public Type visitForAll(ForAll t, Type newReturn) {
                 return new ForAll(t.tvars, t.qtype.accept(this, newReturn));
             }
         };
     // <editor-fold defaultstate="collapsed" desc="createErrorType">
     public Type createErrorType(Type originalType) {
         return new ErrorType(originalType, syms.errSymbol);
     }
     public Type createErrorType(ClassSymbol c, Type originalType) {
         return new ErrorType(c, originalType);
     }
     public Type createErrorType(Name name, TypeSymbol container, Type originalType) {
         return new ErrorType(name, container, originalType);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="rank">
     /**
      * The rank of a class is the length of the longest path between
      * the class and java.lang.Object in the class inheritance
      * graph. Undefined for all but reference types.
      */
     public int rank(Type t) {
         switch(t.tag) {
         case CLASS: {
             ClassType cls = (ClassType)t;
             if (cls.rank_field < 0) {
                 Name fullname = cls.tsym.getQualifiedName();
                 if (fullname == names.java_lang_Object)
                     cls.rank_field = 0;
                 else {
                     int r = rank(supertype(cls));
                     for (List<Type> l = interfaces(cls);
                          l.nonEmpty();
                          l = l.tail) {
                         if (rank(l.head) > r)
                             r = rank(l.head);
                     }
                     cls.rank_field = r + 1;
                 }
             }
             return cls.rank_field;
         }
         case TYPEVAR: {
             TypeVar tvar = (TypeVar)t;
             if (tvar.rank_field < 0) {
                 int r = rank(supertype(tvar));
                 for (List<Type> l = interfaces(tvar);
                      l.nonEmpty();
                      l = l.tail) {
                     if (rank(l.head) > r) r = rank(l.head);
                 }
                 tvar.rank_field = r + 1;
             }
             return tvar.rank_field;
         }
         case ERROR:
             return 0;
         default:
             throw new AssertionError();
         }
     }
     // </editor-fold>
     /**
      * Helper method for generating a string representation of a given type
      * accordingly to a given locale
      */
     public String toString(Type t, Locale locale) {
         return Printer.createStandardPrinter(messages).visit(t, locale);
     }
     /**
      * Helper method for generating a string representation of a given type
      * accordingly to a given locale
      */
     public String toString(Symbol t, Locale locale) {
         return Printer.createStandardPrinter(messages).visit(t, locale);
     }
     // <editor-fold defaultstate="collapsed" desc="toString">
     /**
      * This toString is slightly more descriptive than the one on Type.
      *
      * @deprecated Types.toString(Type t, Locale l) provides better support
      * for localization
      */
     @Deprecated
     public String toString(Type t) {
         if (t.tag == FORALL) {
             ForAll forAll = (ForAll)t;
             return typaramsString(forAll.tvars) + forAll.qtype;
         }
         return "" + t;
     }
     // where
         private String typaramsString(List<Type> tvars) {
             StringBuilder s = new StringBuilder();
             s.append('<');
             boolean first = true;
             for (Type t : tvars) {
                 if (!first) s.append(", ");
                 first = false;
                 appendTyparamString(((TypeVar)t), s);
             }
             s.append('>');
             return s.toString();
         }
         private void appendTyparamString(TypeVar t, StringBuilder buf) {
             buf.append(t);
             if (t.bound == null ||
                 t.bound.tsym.getQualifiedName() == names.java_lang_Object)
                 return;
             buf.append(" extends "); // Java syntax; no need for i18n
             Type bound = t.bound;
             if (!bound.isCompound()) {
                 buf.append(bound);
             } else if ((erasure(t).tsym.flags() & INTERFACE) == 0) {
                 buf.append(supertype(t));
                 for (Type intf : interfaces(t)) {
                     buf.append('&');
                     buf.append(intf);
                 }
             } else {
                 // No superclass was given in bounds.
                 // In this case, supertype is Object, erasure is first interface.
                 boolean first = true;
                 for (Type intf : interfaces(t)) {
                     if (!first) buf.append('&');
                     first = false;
                     buf.append(intf);
                 }
             }
         }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Determining least upper bounds of types">
     /**
      * A cache for closures.
      *
      * <p>A closure is a list of all the supertypes and interfaces of
      * a class or interface type, ordered by ClassSymbol.precedes
      * (that is, subclasses come first, arbitrary but fixed
      * otherwise).
      */
     private Map<Type,List<Type>> closureCache = new HashMap<Type,List<Type>>();
     /**
      * Returns the closure of a class or interface type.
      */
     public List<Type> closure(Type t) {
         List<Type> cl = closureCache.get(t);
         if (cl == null) {
             Type st = supertype(t);
             if (!t.isCompound()) {
                 if (st.tag == CLASS) {
                     cl = insert(closure(st), t);
                 } else if (st.tag == TYPEVAR) {
                     cl = closure(st).prepend(t);
                 } else {
                     cl = List.of(t);
                 }
             } else {
                 cl = closure(supertype(t));
             }
             for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail)
                 cl = union(cl, closure(l.head));
             closureCache.put(t, cl);
         }
         return cl;
     }
     /**
      * Insert a type in a closure
      */
     public List<Type> insert(List<Type> cl, Type t) {
         if (cl.isEmpty() || t.tsym.precedes(cl.head.tsym, this)) {
             return cl.prepend(t);
         } else if (cl.head.tsym.precedes(t.tsym, this)) {
             return insert(cl.tail, t).prepend(cl.head);
         } else {
             return cl;
         }
     }
     /**
      * Form the union of two closures
      */
     public List<Type> union(List<Type> cl1, List<Type> cl2) {
         if (cl1.isEmpty()) {
             return cl2;
         } else if (cl2.isEmpty()) {
             return cl1;
         } else if (cl1.head.tsym.precedes(cl2.head.tsym, this)) {
             return union(cl1.tail, cl2).prepend(cl1.head);
         } else if (cl2.head.tsym.precedes(cl1.head.tsym, this)) {
             return union(cl1, cl2.tail).prepend(cl2.head);
         } else {
             return union(cl1.tail, cl2.tail).prepend(cl1.head);
         }
     }
     /**
      * Intersect two closures
      */
     public List<Type> intersect(List<Type> cl1, List<Type> cl2) {
         if (cl1 == cl2)
             return cl1;
         if (cl1.isEmpty() || cl2.isEmpty())
             return List.nil();
         if (cl1.head.tsym.precedes(cl2.head.tsym, this))
             return intersect(cl1.tail, cl2);
         if (cl2.head.tsym.precedes(cl1.head.tsym, this))
             return intersect(cl1, cl2.tail);
         if (isSameType(cl1.head, cl2.head))
             return intersect(cl1.tail, cl2.tail).prepend(cl1.head);
         if (cl1.head.tsym == cl2.head.tsym &&
             cl1.head.tag == CLASS && cl2.head.tag == CLASS) {
             if (cl1.head.isParameterized() && cl2.head.isParameterized()) {
                 Type merge = merge(cl1.head,cl2.head);
                 return intersect(cl1.tail, cl2.tail).prepend(merge);
             }
             if (cl1.head.isRaw() || cl2.head.isRaw())
                 return intersect(cl1.tail, cl2.tail).prepend(erasure(cl1.head));
         }
         return intersect(cl1.tail, cl2.tail);
     }
     // where
         class TypePair {
             final Type t1;
             final Type t2;
             TypePair(Type t1, Type t2) {
                 this.t1 = t1;
                 this.t2 = t2;
             }
             @Override
             public int hashCode() {
                 return 127 * Types.this.hashCode(t1) + Types.this.hashCode(t2);
             }
             @Override
             public boolean equals(Object obj) {
                 if (!(obj instanceof TypePair))
                     return false;
                 TypePair typePair = (TypePair)obj;
                 return isSameType(t1, typePair.t1)
                     && isSameType(t2, typePair.t2);
             }
         }
         Set<TypePair> mergeCache = new HashSet<TypePair>();
         private Type merge(Type c1, Type c2) {
             ClassType class1 = (ClassType) c1;
             List<Type> act1 = class1.getTypeArguments();
             ClassType class2 = (ClassType) c2;
             List<Type> act2 = class2.getTypeArguments();
             ListBuffer<Type> merged = new ListBuffer<Type>();
             List<Type> typarams = class1.tsym.type.getTypeArguments();
             while (act1.nonEmpty() && act2.nonEmpty() && typarams.nonEmpty()) {
                 if (containsType(act1.head, act2.head)) {
                     merged.append(act1.head);
                 } else if (containsType(act2.head, act1.head)) {
                     merged.append(act2.head);
                 } else {
                     TypePair pair = new TypePair(c1, c2);
                     Type m;
                     if (mergeCache.add(pair)) {
                         m = new WildcardType(lub(upperBound(act1.head),
                                                  upperBound(act2.head)),
                                              BoundKind.EXTENDS,
                                              syms.boundClass);
                         mergeCache.remove(pair);
                     } else {
                         m = new WildcardType(syms.objectType,
                                              BoundKind.UNBOUND,
                                              syms.boundClass);
                     }
                     merged.append(m.withTypeVar(typarams.head));
                 }
                 act1 = act1.tail;
                 act2 = act2.tail;
                 typarams = typarams.tail;
             }
             Assert.check(act1.isEmpty() && act2.isEmpty() && typarams.isEmpty());
             return new ClassType(class1.getEnclosingType(), merged.toList(), class1.tsym);
         }
     /**
      * Return the minimum type of a closure, a compound type if no
      * unique minimum exists.
      */
     private Type compoundMin(List<Type> cl) {
         if (cl.isEmpty()) return syms.objectType;
         List<Type> compound = closureMin(cl);
         if (compound.isEmpty())
             return null;
         else if (compound.tail.isEmpty())
             return compound.head;
         else
             return makeCompoundType(compound);
     }
     /**
      * Return the minimum types of a closure, suitable for computing
      * compoundMin or glb.
      */
     private List<Type> closureMin(List<Type> cl) {
         ListBuffer<Type> classes = lb();
         ListBuffer<Type> interfaces = lb();
         while (!cl.isEmpty()) {
             Type current = cl.head;
             if (current.isInterface())
                 interfaces.append(current);
             else
                 classes.append(current);
             ListBuffer<Type> candidates = lb();
             for (Type t : cl.tail) {
                 if (!isSubtypeNoCapture(current, t))
                     candidates.append(t);
             }
             cl = candidates.toList();
         }
         return classes.appendList(interfaces).toList();
     }
     /**
      * Return the least upper bound of pair of types.  if the lub does
      * not exist return null.
      */
     public Type lub(Type t1, Type t2) {
         return lub(List.of(t1, t2));
     }
     /**
      * Return the least upper bound (lub) of set of types.  If the lub
      * does not exist return the type of null (bottom).
      */
     public Type lub(List<Type> ts) {
         final int ARRAY_BOUND = 1;
         final int CLASS_BOUND = 2;
         int boundkind = 0;
         for (Type t : ts) {
             switch (t.tag) {
             case CLASS:
                 boundkind |= CLASS_BOUND;
                 break;
             case ARRAY:
                 boundkind |= ARRAY_BOUND;
                 break;
             case  TYPEVAR:
                 do {
                     t = t.getUpperBound();
                 } while (t.tag == TYPEVAR);
                 if (t.tag == ARRAY) {
                     boundkind |= ARRAY_BOUND;
                 } else {
                     boundkind |= CLASS_BOUND;
                 }
                 break;
             default:
                 if (t.isPrimitive())
                     return syms.errType;
             }
         }
         switch (boundkind) {
         case 0:
             return syms.botType;
         case ARRAY_BOUND:
             // calculate lub(A[], B[])
             List<Type> elements = Type.map(ts, elemTypeFun);
             for (Type t : elements) {
                 if (t.isPrimitive()) {
                     // if a primitive type is found, then return
                     // arraySuperType unless all the types are the
                     // same
                     Type first = ts.head;
                     for (Type s : ts.tail) {
                         if (!isSameType(first, s)) {
                              // lub(int[], B[]) is Cloneable & Serializable
                             return arraySuperType();
                         }
                     }
                     // all the array types are the same, return one
                     // lub(int[], int[]) is int[]
                     return first;
                 }
             }
             // lub(A[], B[]) is lub(A, B)[]
             return new ArrayType(lub(elements), syms.arrayClass);
         case CLASS_BOUND:
             // calculate lub(A, B)
             while (ts.head.tag != CLASS && ts.head.tag != TYPEVAR)
                 ts = ts.tail;
             Assert.check(!ts.isEmpty());
             //step 1 - compute erased candidate set (EC)
             List<Type> cl = erasedSupertypes(ts.head);
             for (Type t : ts.tail) {
                 if (t.tag == CLASS || t.tag == TYPEVAR)
                     cl = intersect(cl, erasedSupertypes(t));
             }
             //step 2 - compute minimal erased candidate set (MEC)
             List<Type> mec = closureMin(cl);
             //step 3 - for each element G in MEC, compute lci(Inv(G))
             List<Type> candidates = List.nil();
             for (Type erasedSupertype : mec) {
                 List<Type> lci = List.of(asSuper(ts.head, erasedSupertype.tsym));
                 for (Type t : ts) {
                     lci = intersect(lci, List.of(asSuper(t, erasedSupertype.tsym)));
                 }
                 candidates = candidates.appendList(lci);
             }
             //step 4 - let MEC be { G1, G2 ... Gn }, then we have that
             //lub = lci(Inv(G1)) & lci(Inv(G2)) & ... & lci(Inv(Gn))
             return compoundMin(candidates);
         default:
             // calculate lub(A, B[])
             List<Type> classes = List.of(arraySuperType());
             for (Type t : ts) {
                 if (t.tag != ARRAY) // Filter out any arrays
                     classes = classes.prepend(t);
             }
             // lub(A, B[]) is lub(A, arraySuperType)
             return lub(classes);
         }
     }
     // where
         List<Type> erasedSupertypes(Type t) {
             ListBuffer<Type> buf = lb();
             for (Type sup : closure(t)) {
                 if (sup.tag == TYPEVAR) {
                     buf.append(sup);
                 } else {
                     buf.append(erasure(sup));
                 }
             }
             return buf.toList();
         }
         private Type arraySuperType = null;
         private Type arraySuperType() {
             // initialized lazily to avoid problems during compiler startup
             if (arraySuperType == null) {
                 synchronized (this) {
                     if (arraySuperType == null) {
                         // JLS 10.8: all arrays implement Cloneable and Serializable.
                         arraySuperType = makeCompoundType(List.of(syms.serializableType,
                                                                   syms.cloneableType), true);
                     }
                 }
             }
             return arraySuperType;
         }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Greatest lower bound">
     public Type glb(List<Type> ts) {
         Type t1 = ts.head;
         for (Type t2 : ts.tail) {
             if (t1.isErroneous())
                 return t1;
             t1 = glb(t1, t2);
         }
         return t1;
     }
     //where
     public Type glb(Type t, Type s) {
         if (s == null)
             return t;
         else if (t.isPrimitive() || s.isPrimitive())
             return syms.errType;
         else if (isSubtypeNoCapture(t, s))
             return t;
         else if (isSubtypeNoCapture(s, t))
             return s;
         List<Type> closure = union(closure(t), closure(s));
         List<Type> bounds = closureMin(closure);
         if (bounds.isEmpty()) {             // length == 0
             return syms.objectType;
         } else if (bounds.tail.isEmpty()) { // length == 1
             return bounds.head;
         } else {                            // length > 1
             int classCount = 0;
             for (Type bound : bounds)
                 if (!bound.isInterface())
                     classCount++;
             if (classCount > 1)
                 return createErrorType(t);
         }
         return makeCompoundType(bounds);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="hashCode">
     /**
      * Compute a hash code on a type.
      */
     public int hashCode(Type t) {
         return hashCode.visit(t);
     }
     // where
         private static final UnaryVisitor<Integer> hashCode = new UnaryVisitor<Integer>() {
             public Integer visitType(Type t, Void ignored) {
                 return t.tag.ordinal();
             }
             @Override
             public Integer visitClassType(ClassType t, Void ignored) {
                 int result = visit(t.getEnclosingType());
                 result *= 127;
                 result += t.tsym.flatName().hashCode();
                 for (Type s : t.getTypeArguments()) {
                     result *= 127;
                     result += visit(s);
                 }
                 return result;
             }
             @Override
             public Integer visitMethodType(MethodType t, Void ignored) {
                 int h = METHOD.ordinal();
                 for (List<Type> thisargs = t.argtypes;
                      thisargs.tail != null;
                      thisargs = thisargs.tail)
                     h = (h << 5) + visit(thisargs.head);
                 return (h << 5) + visit(t.restype);
             }
             @Override
             public Integer visitWildcardType(WildcardType t, Void ignored) {
                 int result = t.kind.hashCode();
                 if (t.type != null) {
                     result *= 127;
                     result += visit(t.type);
                 }
                 return result;
             }
             @Override
             public Integer visitArrayType(ArrayType t, Void ignored) {
                 return visit(t.elemtype) + 12;
             }
             @Override
             public Integer visitTypeVar(TypeVar t, Void ignored) {
                 return System.identityHashCode(t.tsym);
             }
             @Override
             public Integer visitUndetVar(UndetVar t, Void ignored) {
                 return System.identityHashCode(t);
             }
             @Override
             public Integer visitErrorType(ErrorType t, Void ignored) {
                 return 0;
             }
         };
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Return-Type-Substitutable">
     /**
      * Does t have a result that is a subtype of the result type of s,
      * suitable for covariant returns?  It is assumed that both types
      * are (possibly polymorphic) method types.  Monomorphic method
      * types are handled in the obvious way.  Polymorphic method types
      * require renaming all type variables of one to corresponding
      * type variables in the other, where correspondence is by
      * position in the type parameter list. */
     public boolean resultSubtype(Type t, Type s, Warner warner) {
         List<Type> tvars = t.getTypeArguments();
         List<Type> svars = s.getTypeArguments();
         Type tres = t.getReturnType();
         Type sres = subst(s.getReturnType(), svars, tvars);
         return covariantReturnType(tres, sres, warner);
     }
     /**
      * Return-Type-Substitutable.
      * @jls section 8.4.5
      */
     public boolean returnTypeSubstitutable(Type r1, Type r2) {
         if (hasSameArgs(r1, r2))
             return resultSubtype(r1, r2, noWarnings);
         else
             return covariantReturnType(r1.getReturnType(),
                                        erasure(r2.getReturnType()),
                                        noWarnings);
     }
     public boolean returnTypeSubstitutable(Type r1,
                                            Type r2, Type r2res,
                                            Warner warner) {
         if (isSameType(r1.getReturnType(), r2res))
             return true;
         if (r1.getReturnType().isPrimitive() || r2res.isPrimitive())
             return false;
         if (hasSameArgs(r1, r2))
             return covariantReturnType(r1.getReturnType(), r2res, warner);
         if (!allowCovariantReturns)
             return false;
         if (isSubtypeUnchecked(r1.getReturnType(), r2res, warner))
             return true;
         if (!isSubtype(r1.getReturnType(), erasure(r2res)))
             return false;
         warner.warn(LintCategory.UNCHECKED);
         return true;
     }
     /**
      * Is t an appropriate return type in an overrider for a
      * method that returns s?
      */
     public boolean covariantReturnType(Type t, Type s, Warner warner) {
         return
             isSameType(t, s) ||
             allowCovariantReturns &&
             !t.isPrimitive() &&
             !s.isPrimitive() &&
             isAssignable(t, s, warner);
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Box/unbox support">
     /**
      * Return the class that boxes the given primitive.
      */
     public ClassSymbol boxedClass(Type t) {
         return reader.enterClass(syms.boxedName[t.tag.ordinal()]);
     }
     /**
      * Return the boxed type if 't' is primitive, otherwise return 't' itself.
      */
     public Type boxedTypeOrType(Type t) {
         return t.isPrimitive() ?
             boxedClass(t).type :
             t;
     }
     /**
      * Return the primitive type corresponding to a boxed type.
      */
     public Type unboxedType(Type t) {
         if (allowBoxing) {
             for (int i=0; i<syms.boxedName.length; i++) {
                 Name box = syms.boxedName[i];
                 if (box != null &&
                     asSuper(t, reader.enterClass(box)) != null)
                     return syms.typeOfTag[i];
             }
         }
         return Type.noType;
     }
     /**
      * Return the unboxed type if 't' is a boxed class, otherwise return 't' itself.
      */
     public Type unboxedTypeOrType(Type t) {
         Type unboxedType = unboxedType(t);
         return unboxedType.tag == NONE ? t : unboxedType;
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Capture conversion">
     /*
      * JLS 5.1.10 Capture Conversion:
      *
      * Let G name a generic type declaration with n formal type
      * parameters A1 ... An with corresponding bounds U1 ... Un. There
      * exists a capture conversion from G<T1 ... Tn> to G<S1 ... Sn>,
      * where, for 1 <= i <= n:
      *
      * + If Ti is a wildcard type argument (4.5.1) of the form ? then
      *   Si is a fresh type variable whose upper bound is
      *   Ui[A1 := S1, ..., An := Sn] and whose lower bound is the null
      *   type.
      *
      * + If Ti is a wildcard type argument of the form ? extends Bi,
      *   then Si is a fresh type variable whose upper bound is
      *   glb(Bi, Ui[A1 := S1, ..., An := Sn]) and whose lower bound is
      *   the null type, where glb(V1,... ,Vm) is V1 & ... & Vm. It is
      *   a compile-time error if for any two classes (not interfaces)
      *   Vi and Vj,Vi is not a subclass of Vj or vice versa.
      *
      * + If Ti is a wildcard type argument of the form ? super Bi,
      *   then Si is a fresh type variable whose upper bound is
      *   Ui[A1 := S1, ..., An := Sn] and whose lower bound is Bi.
      *
      * + Otherwise, Si = Ti.
      *
      * Capture conversion on any type other than a parameterized type
      * (4.5) acts as an identity conversion (5.1.1). Capture
      * conversions never require a special action at run time and
      * therefore never throw an exception at run time.
      *
      * Capture conversion is not applied recursively.
      */
     /**
      * Capture conversion as specified by the JLS.
      */
     public List<Type> capture(List<Type> ts) {
         List<Type> buf = List.nil();
         for (Type t : ts) {
             buf = buf.prepend(capture(t));
         }
         return buf.reverse();
     }
     public Type capture(Type t) {
         if (t.tag != CLASS)
             return t;
         if (t.getEnclosingType() != Type.noType) {
             Type capturedEncl = capture(t.getEnclosingType());
             if (capturedEncl != t.getEnclosingType()) {
                 Type type1 = memberType(capturedEncl, t.tsym);
                 t = subst(type1, t.tsym.type.getTypeArguments(), t.getTypeArguments());
             }
         }
         ClassType cls = (ClassType)t;
         if (cls.isRaw() || !cls.isParameterized())
             return cls;
         ClassType G = (ClassType)cls.asElement().asType();
         List<Type> A = G.getTypeArguments();
         List<Type> T = cls.getTypeArguments();
         List<Type> S = freshTypeVariables(T);
         List<Type> currentA = A;
         List<Type> currentT = T;
         List<Type> currentS = S;
         boolean captured = false;
         while (!currentA.isEmpty() &&
                !currentT.isEmpty() &&
                !currentS.isEmpty()) {
             if (currentS.head != currentT.head) {
                 captured = true;
                 WildcardType Ti = (WildcardType)currentT.head;
                 Type Ui = currentA.head.getUpperBound();
                 CapturedType Si = (CapturedType)currentS.head;
                 if (Ui == null)
                     Ui = syms.objectType;
                 switch (Ti.kind) {
                 case UNBOUND:
                     Si.bound = subst(Ui, A, S);
                     Si.lower = syms.botType;
                     break;
                 case EXTENDS:
                     Si.bound = glb(Ti.getExtendsBound(), subst(Ui, A, S));
                     Si.lower = syms.botType;
                     break;
                 case SUPER:
                     Si.bound = subst(Ui, A, S);
                     Si.lower = Ti.getSuperBound();
                     break;
                 }
                 if (Si.bound == Si.lower)
                     currentS.head = Si.bound;
             }
             currentA = currentA.tail;
             currentT = currentT.tail;
             currentS = currentS.tail;
         }
         if (!currentA.isEmpty() || !currentT.isEmpty() || !currentS.isEmpty())
             return erasure(t); // some "rare" type involved
         if (captured)
             return new ClassType(cls.getEnclosingType(), S, cls.tsym);
         else
             return t;
     }
     // where
         public List<Type> freshTypeVariables(List<Type> types) {
             ListBuffer<Type> result = lb();
             for (Type t : types) {
                 if (t.tag == WILDCARD) {
                     Type bound = ((WildcardType)t).getExtendsBound();
                     if (bound == null)
                         bound = syms.objectType;
                     result.append(new CapturedType(capturedName,
                                                    syms.noSymbol,
                                                    bound,
                                                    syms.botType,
                                                    (WildcardType)t));
                 } else {
                     result.append(t);
                 }
             }
             return result.toList();
         }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Internal utility methods">
     private List<Type> upperBounds(List<Type> ss) {
         if (ss.isEmpty()) return ss;
         Type head = upperBound(ss.head);
         List<Type> tail = upperBounds(ss.tail);
         if (head != ss.head || tail != ss.tail)
             return tail.prepend(head);
         else
             return ss;
     }
     private boolean sideCast(Type from, Type to, Warner warn) {
         // We are casting from type $from$ to type $to$, which are
         // non-final unrelated types.  This method
         // tries to reject a cast by transferring type parameters
         // from $to$ to $from$ by common superinterfaces.
         boolean reverse = false;
         Type target = to;
         if ((to.tsym.flags() & INTERFACE) == 0) {
             Assert.check((from.tsym.flags() & INTERFACE) != 0);
             reverse = true;
             to = from;
             from = target;
         }
         List<Type> commonSupers = superClosure(to, erasure(from));
         boolean giveWarning = commonSupers.isEmpty();
         // The arguments to the supers could be unified here to
         // get a more accurate analysis
         while (commonSupers.nonEmpty()) {
             Type t1 = asSuper(from, commonSupers.head.tsym);
             Type t2 = commonSupers.head; // same as asSuper(to, commonSupers.head.tsym);
             if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
                 return false;
             giveWarning = giveWarning || (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2));
             commonSupers = commonSupers.tail;
         }
         if (giveWarning && !isReifiable(reverse ? from : to))
             warn.warn(LintCategory.UNCHECKED);
         if (!allowCovariantReturns)
             // reject if there is a common method signature with
             // incompatible return types.
             chk.checkCompatibleAbstracts(warn.pos(), from, to);
         return true;
     }
     private boolean sideCastFinal(Type from, Type to, Warner warn) {
         // We are casting from type $from$ to type $to$, which are
         // unrelated types one of which is final and the other of
         // which is an interface.  This method
         // tries to reject a cast by transferring type parameters
         // from the final class to the interface.
         boolean reverse = false;
         Type target = to;
         if ((to.tsym.flags() & INTERFACE) == 0) {
             Assert.check((from.tsym.flags() & INTERFACE) != 0);
             reverse = true;
             to = from;
             from = target;
         }
         Assert.check((from.tsym.flags() & FINAL) != 0);
         Type t1 = asSuper(from, to.tsym);
         if (t1 == null) return false;
         Type t2 = to;
         if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
             return false;
         if (!allowCovariantReturns)
             // reject if there is a common method signature with
             // incompatible return types.
             chk.checkCompatibleAbstracts(warn.pos(), from, to);
         if (!isReifiable(target) &&
             (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2)))
             warn.warn(LintCategory.UNCHECKED);
         return true;
     }
     private boolean giveWarning(Type from, Type to) {
         Type subFrom = asSub(from, to.tsym);
         return to.isParameterized() &&
                 (!(isUnbounded(to) ||
                 isSubtype(from, to) ||
                 ((subFrom != null) && containsType(to.allparams(), subFrom.allparams()))));
     }
     private List<Type> superClosure(Type t, Type s) {
         List<Type> cl = List.nil();
         for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
             if (isSubtype(s, erasure(l.head))) {
                 cl = insert(cl, l.head);
             } else {
                 cl = union(cl, superClosure(l.head, s));
             }
         }
         return cl;
     }
     private boolean containsTypeEquivalent(Type t, Type s) {
         return
             isSameType(t, s) || // shortcut
             containsType(t, s) && containsType(s, t);
     }
     // <editor-fold defaultstate="collapsed" desc="adapt">
     /**
      * Adapt a type by computing a substitution which maps a source
      * type to a target type.
      *
      * @param source    the source type
      * @param target    the target type
      * @param from      the type variables of the computed substitution
      * @param to        the types of the computed substitution.
      */
     public void adapt(Type source,
                        Type target,
                        ListBuffer<Type> from,
                        ListBuffer<Type> to) throws AdaptFailure {
         new Adapter(from, to).adapt(source, target);
     }
     class Adapter extends SimpleVisitor<Void, Type> {
         ListBuffer<Type> from;
         ListBuffer<Type> to;
         Map<Symbol,Type> mapping;
         Adapter(ListBuffer<Type> from, ListBuffer<Type> to) {
             this.from = from;
             this.to = to;
             mapping = new HashMap<Symbol,Type>();
         }
         public void adapt(Type source, Type target) throws AdaptFailure {
             visit(source, target);
             List<Type> fromList = from.toList();
             List<Type> toList = to.toList();
             while (!fromList.isEmpty()) {
                 Type val = mapping.get(fromList.head.tsym);
                 if (toList.head != val)
                     toList.head = val;
                 fromList = fromList.tail;
                 toList = toList.tail;
             }
         }
         @Override
         public Void visitClassType(ClassType source, Type target) throws AdaptFailure {
             if (target.tag == CLASS)
                 adaptRecursive(source.allparams(), target.allparams());
             return null;
         }
         @Override
         public Void visitArrayType(ArrayType source, Type target) throws AdaptFailure {
             if (target.tag == ARRAY)
                 adaptRecursive(elemtype(source), elemtype(target));
             return null;
         }
         @Override
         public Void visitWildcardType(WildcardType source, Type target) throws AdaptFailure {
             if (source.isExtendsBound())
                 adaptRecursive(upperBound(source), upperBound(target));
             else if (source.isSuperBound())
                 adaptRecursive(lowerBound(source), lowerBound(target));
             return null;
         }
         @Override
         public Void visitTypeVar(TypeVar source, Type target) throws AdaptFailure {
             // Check to see if there is
             // already a mapping for $source$, in which case
             // the old mapping will be merged with the new
             Type val = mapping.get(source.tsym);
             if (val != null) {
                 if (val.isSuperBound() && target.isSuperBound()) {
                     val = isSubtype(lowerBound(val), lowerBound(target))
                         ? target : val;
                 } else if (val.isExtendsBound() && target.isExtendsBound()) {
                     val = isSubtype(upperBound(val), upperBound(target))
                         ? val : target;
                 } else if (!isSameType(val, target)) {
                     throw new AdaptFailure();
                 }
             } else {
                 val = target;
                 from.append(source);
                 to.append(target);
             }
             mapping.put(source.tsym, val);
             return null;
         }
         @Override
         public Void visitType(Type source, Type target) {
             return null;
         }
         private Set<TypePair> cache = new HashSet<TypePair>();
         private void adaptRecursive(Type source, Type target) {
             TypePair pair = new TypePair(source, target);
             if (cache.add(pair)) {
                 try {
                     visit(source, target);
                 } finally {
                     cache.remove(pair);
                 }
             }
         }
         private void adaptRecursive(List<Type> source, List<Type> target) {
             if (source.length() == target.length()) {
                 while (source.nonEmpty()) {
                     adaptRecursive(source.head, target.head);
                     source = source.tail;
                     target = target.tail;
                 }
             }
         }
     }
     public static class AdaptFailure extends RuntimeException {
         static final long serialVersionUID = -7490231548272701566L;
     }
     private void adaptSelf(Type t,
                            ListBuffer<Type> from,
                            ListBuffer<Type> to) {
         try {
             //if (t.tsym.type != t)
                 adapt(t.tsym.type, t, from, to);
         } catch (AdaptFailure ex) {
             // Adapt should never fail calculating a mapping from
             // t.tsym.type to t as there can be no merge problem.
             throw new AssertionError(ex);
         }
     }
     // </editor-fold>
     /**
      * Rewrite all type variables (universal quantifiers) in the given
      * type to wildcards (existential quantifiers).  This is used to
      * determine if a cast is allowed.  For example, if high is true
      * and {@code T <: Number}, then {@code List<T>} is rewritten to
      * {@code List<?  extends Number>}.  Since {@code List<Integer> <:
      * List<? extends Number>} a {@code List<T>} can be cast to {@code
      * List<Integer>} with a warning.
      * @param t a type
      * @param high if true return an upper bound; otherwise a lower
      * bound
      * @param rewriteTypeVars only rewrite captured wildcards if false;
      * otherwise rewrite all type variables
      * @return the type rewritten with wildcards (existential
      * quantifiers) only
      */
     private Type rewriteQuantifiers(Type t, boolean high, boolean rewriteTypeVars) {
         return new Rewriter(high, rewriteTypeVars).visit(t);
     }
     class Rewriter extends UnaryVisitor<Type> {
         boolean high;
         boolean rewriteTypeVars;
         Rewriter(boolean high, boolean rewriteTypeVars) {
             this.high = high;
             this.rewriteTypeVars = rewriteTypeVars;
         }
         @Override
         public Type visitClassType(ClassType t, Void s) {
             ListBuffer<Type> rewritten = new ListBuffer<Type>();
             boolean changed = false;
             for (Type arg : t.allparams()) {
                 Type bound = visit(arg);
                 if (arg != bound) {
                     changed = true;
                 }
                 rewritten.append(bound);
             }
             if (changed)
                 return subst(t.tsym.type,
                         t.tsym.type.allparams(),
                         rewritten.toList());
             else
                 return t;
         }
         public Type visitType(Type t, Void s) {
             return high ? upperBound(t) : lowerBound(t);
         }
         @Override
         public Type visitCapturedType(CapturedType t, Void s) {
             Type w_bound = t.wildcard.type;
             Type bound = w_bound.contains(t) ?
                         erasure(w_bound) :
                         visit(w_bound);
             return rewriteAsWildcardType(visit(bound), t.wildcard.bound, t.wildcard.kind);
         }
         @Override
         public Type visitTypeVar(TypeVar t, Void s) {
             if (rewriteTypeVars) {
                 Type bound = t.bound.contains(t) ?
                         erasure(t.bound) :
                         visit(t.bound);
                 return rewriteAsWildcardType(bound, t, EXTENDS);
             } else {
                 return t;
             }
         }
         @Override
         public Type visitWildcardType(WildcardType t, Void s) {
             Type bound2 = visit(t.type);
             return t.type == bound2 ? t : rewriteAsWildcardType(bound2, t.bound, t.kind);
         }
         private Type rewriteAsWildcardType(Type bound, TypeVar formal, BoundKind bk) {
             switch (bk) {
                case EXTENDS: return high ?
                        makeExtendsWildcard(B(bound), formal) :
                        makeExtendsWildcard(syms.objectType, formal);
                case SUPER: return high ?
                        makeSuperWildcard(syms.botType, formal) :
                        makeSuperWildcard(B(bound), formal);
                case UNBOUND: return makeExtendsWildcard(syms.objectType, formal);
                default:
                    Assert.error("Invalid bound kind " + bk);
                    return null;
             }
         }
         Type B(Type t) {
             while (t.tag == WILDCARD) {
                 WildcardType w = (WildcardType)t;
                 t = high ?
                     w.getExtendsBound() :
                     w.getSuperBound();
                 if (t == null) {
                     t = high ? syms.objectType : syms.botType;
                 }
             }
             return t;
         }
     }
     /**
      * Create a wildcard with the given upper (extends) bound; create
      * an unbounded wildcard if bound is Object.
      *
      * @param bound the upper bound
      * @param formal the formal type parameter that will be
      * substituted by the wildcard
      */
     private WildcardType makeExtendsWildcard(Type bound, TypeVar formal) {
         if (bound == syms.objectType) {
             return new WildcardType(syms.objectType,
                                     BoundKind.UNBOUND,
                                     syms.boundClass,
                                     formal);
         } else {
             return new WildcardType(bound,
                                     BoundKind.EXTENDS,
                                     syms.boundClass,
                                     formal);
         }
     }
     /**
      * Create a wildcard with the given lower (super) bound; create an
      * unbounded wildcard if bound is bottom (type of {@code null}).
      *
      * @param bound the lower bound
      * @param formal the formal type parameter that will be
      * substituted by the wildcard
      */
     private WildcardType makeSuperWildcard(Type bound, TypeVar formal) {
         if (bound.tag == BOT) {
             return new WildcardType(syms.objectType,
                                     BoundKind.UNBOUND,
                                     syms.boundClass,
                                     formal);
         } else {
             return new WildcardType(bound,
                                     BoundKind.SUPER,
                                     syms.boundClass,
                                     formal);
         }
     }
     /**
      * A wrapper for a type that allows use in sets.
      */
     public static class UniqueType {
         public final Type type;
         final Types types;
         public UniqueType(Type type, Types types) {
             this.type = type;
             this.types = types;
         }
         public int hashCode() {
             return types.hashCode(type);
         }
         public boolean equals(Object obj) {
             return (obj instanceof UniqueType) &&
                 types.isSameType(type, ((UniqueType)obj).type);
         }
         public String toString() {
             return type.toString();
         }
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Visitors">
     /**
      * A default visitor for types.  All visitor methods except
      * visitType are implemented by delegating to visitType.  Concrete
      * subclasses must provide an implementation of visitType and can
      * override other methods as needed.
      *
      * @param <R> the return type of the operation implemented by this
      * visitor; use Void if no return type is needed.
      * @param <S> the type of the second argument (the first being the
      * type itself) of the operation implemented by this visitor; use
      * Void if a second argument is not needed.
      */
     public static abstract class DefaultTypeVisitor<R,S> implements Type.Visitor<R,S> {
         final public R visit(Type t, S s)               { return t.accept(this, s); }
         public R visitClassType(ClassType t, S s)       { return visitType(t, s); }
         public R visitWildcardType(WildcardType t, S s) { return visitType(t, s); }
         public R visitArrayType(ArrayType t, S s)       { return visitType(t, s); }
         public R visitMethodType(MethodType t, S s)     { return visitType(t, s); }
         public R visitPackageType(PackageType t, S s)   { return visitType(t, s); }
         public R visitTypeVar(TypeVar t, S s)           { return visitType(t, s); }
         public R visitCapturedType(CapturedType t, S s) { return visitType(t, s); }
         public R visitForAll(ForAll t, S s)             { return visitType(t, s); }
         public R visitUndetVar(UndetVar t, S s)         { return visitType(t, s); }
         public R visitErrorType(ErrorType t, S s)       { return visitType(t, s); }
     }
     /**
      * A default visitor for symbols.  All visitor methods except
      * visitSymbol are implemented by delegating to visitSymbol.  Concrete
      * subclasses must provide an implementation of visitSymbol and can
      * override other methods as needed.
      *
      * @param <R> the return type of the operation implemented by this
      * visitor; use Void if no return type is needed.
      * @param <S> the type of the second argument (the first being the
      * symbol itself) of the operation implemented by this visitor; use
      * Void if a second argument is not needed.
      */
     public static abstract class DefaultSymbolVisitor<R,S> implements Symbol.Visitor<R,S> {
         final public R visit(Symbol s, S arg)                   { return s.accept(this, arg); }
         public R visitClassSymbol(ClassSymbol s, S arg)         { return visitSymbol(s, arg); }
         public R visitMethodSymbol(MethodSymbol s, S arg)       { return visitSymbol(s, arg); }
         public R visitOperatorSymbol(OperatorSymbol s, S arg)   { return visitSymbol(s, arg); }
         public R visitPackageSymbol(PackageSymbol s, S arg)     { return visitSymbol(s, arg); }
         public R visitTypeSymbol(TypeSymbol s, S arg)           { return visitSymbol(s, arg); }
         public R visitVarSymbol(VarSymbol s, S arg)             { return visitSymbol(s, arg); }
     }
     /**
      * A <em>simple</em> visitor for types.  This visitor is simple as
      * captured wildcards, for-all types (generic methods), and
      * undetermined type variables (part of inference) are hidden.
      * Captured wildcards are hidden by treating them as type
      * variables and the rest are hidden by visiting their qtypes.
      *
      * @param <R> the return type of the operation implemented by this
      * visitor; use Void if no return type is needed.
      * @param <S> the type of the second argument (the first being the
      * type itself) of the operation implemented by this visitor; use
      * Void if a second argument is not needed.
      */
     public static abstract class SimpleVisitor<R,S> extends DefaultTypeVisitor<R,S> {
         @Override
         public R visitCapturedType(CapturedType t, S s) {
             return visitTypeVar(t, s);
         }
         @Override
         public R visitForAll(ForAll t, S s) {
             return visit(t.qtype, s);
         }
         @Override
         public R visitUndetVar(UndetVar t, S s) {
             return visit(t.qtype, s);
         }
     }
     /**
      * A plain relation on types.  That is a 2-ary function on the
      * form Type&nbsp;&times;&nbsp;Type&nbsp;&rarr;&nbsp;Boolean.
      * <!-- In plain text: Type x Type -> Boolean -->
      */
     public static abstract class TypeRelation extends SimpleVisitor<Boolean,Type> {}
     /**
      * A convenience visitor for implementing operations that only
      * require one argument (the type itself), that is, unary
      * operations.
      *
      * @param <R> the return type of the operation implemented by this
      * visitor; use Void if no return type is needed.
      */
     public static abstract class UnaryVisitor<R> extends SimpleVisitor<R,Void> {
         final public R visit(Type t) { return t.accept(this, null); }
     }
     /**
      * A visitor for implementing a mapping from types to types.  The
      * default behavior of this class is to implement the identity
      * mapping (mapping a type to itself).  This can be overridden in
      * subclasses.
      *
      * @param <S> the type of the second argument (the first being the
      * type itself) of this mapping; use Void if a second argument is
      * not needed.
      */
     public static class MapVisitor<S> extends DefaultTypeVisitor<Type,S> {
         final public Type visit(Type t) { return t.accept(this, null); }
         public Type visitType(Type t, S s) { return t; }
     }
     // </editor-fold>
     // <editor-fold defaultstate="collapsed" desc="Annotation support">
     public RetentionPolicy getRetention(Attribute.Compound a) {
         return getRetention(a.type.tsym);
     }
     public RetentionPolicy getRetention(Symbol sym) {
         RetentionPolicy vis = RetentionPolicy.CLASS; // the default
         Attribute.Compound c = sym.attribute(syms.retentionType.tsym);
         if (c != null) {
             Attribute value = c.member(names.value);
             if (value != null && value instanceof Attribute.Enum) {
                 Name levelName = ((Attribute.Enum)value).value.name;
                 if (levelName == names.SOURCE) vis = RetentionPolicy.SOURCE;
                 else if (levelName == names.CLASS) vis = RetentionPolicy.CLASS;
                 else if (levelName == names.RUNTIME) vis = RetentionPolicy.RUNTIME;
                 else ;// /* fail soft */ throw new AssertionError(levelName);
             }
         }
         return vis;
     }
     // </editor-fold>
 }

Mercurial > jdk8-mips64-public > langtools / annotate

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

src/share/classes/com/sun/tools/javac/code/Types.java