jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/comp/Infer.java@19c900c703c6 (annotated)

src/share/classes/com/sun/tools/javac/comp/Infer.java@19c900c703c6 (annotated)

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

Mon, 24 Jan 2011 15:44:15 +0000

author: mcimadamore
date: Mon, 24 Jan 2011 15:44:15 +0000
changeset 828: 19c900c703c6
parent 820: 2d5aff89aaa3
child 832: 57e3b9bc7fb8
permissions: -rw-r--r--

6943278: spurious error message for inference and type-variable with erroneous bound
Summary: type-inference should ignore erroneous bounds
Reviewed-by: jjg

 /*
  * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 package com.sun.tools.javac.comp;
 import com.sun.tools.javac.tree.JCTree;
 import com.sun.tools.javac.tree.JCTree.JCTypeCast;
 import com.sun.tools.javac.tree.TreeInfo;
 import com.sun.tools.javac.util.*;
 import com.sun.tools.javac.util.List;
 import com.sun.tools.javac.code.*;
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.code.Type.ForAll.ConstraintKind;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.util.JCDiagnostic;
 import static com.sun.tools.javac.code.TypeTags.*;
 /** Helper class for type parameter inference, used by the attribution phase.
  *
  *  <p><b>This is NOT part of any supported API.
  *  If you write code that depends on this, you do so at your own risk.
  *  This code and its internal interfaces are subject to change or
  *  deletion without notice.</b>
  */
 public class Infer {
     protected static final Context.Key<Infer> inferKey =
         new Context.Key<Infer>();
     /** A value for prototypes that admit any type, including polymorphic ones. */
     public static final Type anyPoly = new Type(NONE, null);
     Symtab syms;
     Types types;
     Check chk;
     Resolve rs;
     JCDiagnostic.Factory diags;
     public static Infer instance(Context context) {
         Infer instance = context.get(inferKey);
         if (instance == null)
             instance = new Infer(context);
         return instance;
     }
     protected Infer(Context context) {
         context.put(inferKey, this);
         syms = Symtab.instance(context);
         types = Types.instance(context);
         rs = Resolve.instance(context);
         chk = Check.instance(context);
         diags = JCDiagnostic.Factory.instance(context);
         ambiguousNoInstanceException =
             new NoInstanceException(true, diags);
         unambiguousNoInstanceException =
             new NoInstanceException(false, diags);
         invalidInstanceException =
             new InvalidInstanceException(diags);
     }
     public static class InferenceException extends Resolve.InapplicableMethodException {
         private static final long serialVersionUID = 0;
         InferenceException(JCDiagnostic.Factory diags) {
             super(diags);
         }
     }
     public static class NoInstanceException extends InferenceException {
         private static final long serialVersionUID = 1;
         boolean isAmbiguous; // exist several incomparable best instances?
         NoInstanceException(boolean isAmbiguous, JCDiagnostic.Factory diags) {
             super(diags);
             this.isAmbiguous = isAmbiguous;
         }
     }
     public static class InvalidInstanceException extends InferenceException {
         private static final long serialVersionUID = 2;
         InvalidInstanceException(JCDiagnostic.Factory diags) {
             super(diags);
         }
     }
     private final NoInstanceException ambiguousNoInstanceException;
     private final NoInstanceException unambiguousNoInstanceException;
     private final InvalidInstanceException invalidInstanceException;
 /***************************************************************************
  * Auxiliary type values and classes
  ***************************************************************************/
     /** A mapping that turns type variables into undetermined type variables.
      */
     Mapping fromTypeVarFun = new Mapping("fromTypeVarFun") {
             public Type apply(Type t) {
                 if (t.tag == TYPEVAR) return new UndetVar(t);
                 else return t.map(this);
             }
         };
     /** A mapping that returns its type argument with every UndetVar replaced
      *  by its `inst' field. Throws a NoInstanceException
      *  if this not possible because an `inst' field is null.
      *  Note: mutually referring undertvars will be left uninstantiated
      *  (that is, they will be replaced by the underlying type-variable).
      */
     Mapping getInstFun = new Mapping("getInstFun") {
             public Type apply(Type t) {
                 switch (t.tag) {
                     case UNKNOWN:
                         throw ambiguousNoInstanceException
                             .setMessage("undetermined.type");
                     case UNDETVAR:
                         UndetVar that = (UndetVar) t;
                         if (that.inst == null)
                             throw ambiguousNoInstanceException
                                 .setMessage("type.variable.has.undetermined.type",
                                             that.qtype);
                         return isConstraintCyclic(that) ?
                             that.qtype :
                             apply(that.inst);
                         default:
                             return t.map(this);
                 }
             }
             private boolean isConstraintCyclic(UndetVar uv) {
                 Types.UnaryVisitor<Boolean> constraintScanner =
                         new Types.UnaryVisitor<Boolean>() {
                     List<Type> seen = List.nil();
                     Boolean visit(List<Type> ts) {
                         for (Type t : ts) {
                             if (visit(t)) return true;
                         }
                         return false;
                     }
                     public Boolean visitType(Type t, Void ignored) {
                         return false;
                     }
                     @Override
                     public Boolean visitClassType(ClassType t, Void ignored) {
                         if (t.isCompound()) {
                             return visit(types.supertype(t)) ||
                                     visit(types.interfaces(t));
                         } else {
                             return visit(t.getTypeArguments());
                         }
                     }
                     @Override
                     public Boolean visitWildcardType(WildcardType t, Void ignored) {
                         return visit(t.type);
                     }
                     @Override
                     public Boolean visitUndetVar(UndetVar t, Void ignored) {
                         if (seen.contains(t)) {
                             return true;
                         } else {
                             seen = seen.prepend(t);
                             return visit(t.inst);
                         }
                     }
                 };
                 return constraintScanner.visit(uv);
             }
         };
 /***************************************************************************
  * Mini/Maximization of UndetVars
  ***************************************************************************/
     /** Instantiate undetermined type variable to its minimal upper bound.
      *  Throw a NoInstanceException if this not possible.
      */
     void maximizeInst(UndetVar that, Warner warn) throws NoInstanceException {
         List<Type> hibounds = Type.filter(that.hibounds, errorFilter);
         if (that.inst == null) {
             if (hibounds.isEmpty())
                 that.inst = syms.objectType;
             else if (hibounds.tail.isEmpty())
                 that.inst = hibounds.head;
             else
                 that.inst = types.glb(hibounds);
         }
         if (that.inst == null ||
             that.inst.isErroneous())
             throw ambiguousNoInstanceException
                 .setMessage("no.unique.maximal.instance.exists",
                             that.qtype, hibounds);
     }
     //where
         private boolean isSubClass(Type t, final List<Type> ts) {
             t = t.baseType();
             if (t.tag == TYPEVAR) {
                 List<Type> bounds = types.getBounds((TypeVar)t);
                 for (Type s : ts) {
                     if (!types.isSameType(t, s.baseType())) {
                         for (Type bound : bounds) {
                             if (!isSubClass(bound, List.of(s.baseType())))
                                 return false;
                         }
                     }
                 }
             } else {
                 for (Type s : ts) {
                     if (!t.tsym.isSubClass(s.baseType().tsym, types))
                         return false;
                 }
             }
             return true;
         }
     private Filter<Type> errorFilter = new Filter<Type>() {
         @Override
         public boolean accepts(Type t) {
             return !t.isErroneous();
         }
     };
     /** Instantiate undetermined type variable to the lub of all its lower bounds.
      *  Throw a NoInstanceException if this not possible.
      */
     void minimizeInst(UndetVar that, Warner warn) throws NoInstanceException {
         List<Type> lobounds = Type.filter(that.lobounds, errorFilter);
         if (that.inst == null) {
             if (lobounds.isEmpty())
                 that.inst = syms.botType;
             else if (lobounds.tail.isEmpty())
                 that.inst = lobounds.head.isPrimitive() ? syms.errType : lobounds.head;
             else {
                 that.inst = types.lub(lobounds);
             }
             if (that.inst == null || that.inst.tag == ERROR)
                     throw ambiguousNoInstanceException
                         .setMessage("no.unique.minimal.instance.exists",
                                     that.qtype, lobounds);
             // VGJ: sort of inlined maximizeInst() below.  Adding
             // bounds can cause lobounds that are above hibounds.
             List<Type> hibounds = Type.filter(that.hibounds, errorFilter);
             if (hibounds.isEmpty())
                 return;
             Type hb = null;
             if (hibounds.tail.isEmpty())
                 hb = hibounds.head;
             else for (List<Type> bs = hibounds;
                       bs.nonEmpty() && hb == null;
                       bs = bs.tail) {
                 if (isSubClass(bs.head, hibounds))
                     hb = types.fromUnknownFun.apply(bs.head);
             }
             if (hb == null ||
                 !types.isSubtypeUnchecked(hb, hibounds, warn) ||
                 !types.isSubtypeUnchecked(that.inst, hb, warn))
                 throw ambiguousNoInstanceException;
         }
     }
 /***************************************************************************
  * Exported Methods
  ***************************************************************************/
     /** Try to instantiate expression type `that' to given type `to'.
      *  If a maximal instantiation exists which makes this type
      *  a subtype of type `to', return the instantiated type.
      *  If no instantiation exists, or if several incomparable
      *  best instantiations exist throw a NoInstanceException.
      */
     public Type instantiateExpr(ForAll that,
                                 Type to,
                                 Warner warn) throws InferenceException {
         List<Type> undetvars = Type.map(that.tvars, fromTypeVarFun);
         for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail) {
             UndetVar uv = (UndetVar) l.head;
             TypeVar tv = (TypeVar)uv.qtype;
             ListBuffer<Type> hibounds = new ListBuffer<Type>();
             for (Type t : that.getConstraints(tv, ConstraintKind.EXTENDS)) {
                 hibounds.append(types.subst(t, that.tvars, undetvars));
             }
             List<Type> inst = that.getConstraints(tv, ConstraintKind.EQUAL);
             if (inst.nonEmpty() && inst.head.tag != BOT) {
                 uv.inst = inst.head;
             }
             uv.hibounds = hibounds.toList();
         }
         Type qtype1 = types.subst(that.qtype, that.tvars, undetvars);
         if (!types.isSubtype(qtype1,
                 qtype1.tag == UNDETVAR ? types.boxedTypeOrType(to) : to)) {
             throw unambiguousNoInstanceException
                 .setMessage("infer.no.conforming.instance.exists",
                             that.tvars, that.qtype, to);
         }
         for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail)
             maximizeInst((UndetVar) l.head, warn);
         // System.out.println(" = " + qtype1.map(getInstFun));//DEBUG
         // check bounds
         List<Type> targs = Type.map(undetvars, getInstFun);
         if (Type.containsAny(targs, that.tvars)) {
             //replace uninferred type-vars
             targs = types.subst(targs,
                     that.tvars,
                     instaniateAsUninferredVars(undetvars, that.tvars));
         }
         return chk.checkType(warn.pos(), that.inst(targs, types), to);
     }
     //where
     private List<Type> instaniateAsUninferredVars(List<Type> undetvars, List<Type> tvars) {
         ListBuffer<Type> new_targs = ListBuffer.lb();
         //step 1 - create syntethic captured vars
         for (Type t : undetvars) {
             UndetVar uv = (UndetVar)t;
             Type newArg = new CapturedType(t.tsym.name, t.tsym, uv.inst, syms.botType, null);
             new_targs = new_targs.append(newArg);
         }
         //step 2 - replace synthetic vars in their bounds
         for (Type t : new_targs.toList()) {
             CapturedType ct = (CapturedType)t;
             ct.bound = types.subst(ct.bound, tvars, new_targs.toList());
             WildcardType wt = new WildcardType(ct.bound, BoundKind.EXTENDS, syms.boundClass);
             ct.wildcard = wt;
         }
         return new_targs.toList();
     }
     /** Instantiate method type `mt' by finding instantiations of
      *  `tvars' so that method can be applied to `argtypes'.
      */
     public Type instantiateMethod(final Env<AttrContext> env,
                                   List<Type> tvars,
                                   MethodType mt,
                                   final Symbol msym,
                                   final List<Type> argtypes,
                                   final boolean allowBoxing,
                                   final boolean useVarargs,
                                   final Warner warn) throws InferenceException {
         //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
         List<Type> undetvars = Type.map(tvars, fromTypeVarFun);
         List<Type> formals = mt.argtypes;
         //need to capture exactly once - otherwise subsequent
         //applicability checks might fail
         final List<Type> capturedArgs = types.capture(argtypes);
         List<Type> actuals = capturedArgs;
         List<Type> actualsNoCapture = argtypes;
         // instantiate all polymorphic argument types and
         // set up lower bounds constraints for undetvars
         Type varargsFormal = useVarargs ? formals.last() : null;
         if (varargsFormal == null &&
                 actuals.size() != formals.size()) {
             throw unambiguousNoInstanceException
                 .setMessage("infer.arg.length.mismatch");
         }
         while (actuals.nonEmpty() && formals.head != varargsFormal) {
             Type formal = formals.head;
             Type actual = actuals.head.baseType();
             Type actualNoCapture = actualsNoCapture.head.baseType();
             if (actual.tag == FORALL)
                 actual = instantiateArg((ForAll)actual, formal, tvars, warn);
             Type undetFormal = types.subst(formal, tvars, undetvars);
             boolean works = allowBoxing
                 ? types.isConvertible(actual, undetFormal, warn)
                 : types.isSubtypeUnchecked(actual, undetFormal, warn);
             if (!works) {
                 throw unambiguousNoInstanceException
                     .setMessage("infer.no.conforming.assignment.exists",
                                 tvars, actualNoCapture, formal);
             }
             formals = formals.tail;
             actuals = actuals.tail;
             actualsNoCapture = actualsNoCapture.tail;
         }
         if (formals.head != varargsFormal) // not enough args
             throw unambiguousNoInstanceException.setMessage("infer.arg.length.mismatch");
         // for varargs arguments as well
         if (useVarargs) {
             Type elemType = types.elemtype(varargsFormal);
             Type elemUndet = types.subst(elemType, tvars, undetvars);
             while (actuals.nonEmpty()) {
                 Type actual = actuals.head.baseType();
                 Type actualNoCapture = actualsNoCapture.head.baseType();
                 if (actual.tag == FORALL)
                     actual = instantiateArg((ForAll)actual, elemType, tvars, warn);
                 boolean works = types.isConvertible(actual, elemUndet, warn);
                 if (!works) {
                     throw unambiguousNoInstanceException
                         .setMessage("infer.no.conforming.assignment.exists",
                                     tvars, actualNoCapture, elemType);
                 }
                 actuals = actuals.tail;
                 actualsNoCapture = actualsNoCapture.tail;
             }
         }
         // minimize as yet undetermined type variables
         for (Type t : undetvars)
             minimizeInst((UndetVar) t, warn);
         /** Type variables instantiated to bottom */
         ListBuffer<Type> restvars = new ListBuffer<Type>();
         /** Undet vars instantiated to bottom */
         final ListBuffer<Type> restundet = new ListBuffer<Type>();
         /** Instantiated types or TypeVars if under-constrained */
         ListBuffer<Type> insttypes = new ListBuffer<Type>();
         /** Instantiated types or UndetVars if under-constrained */
         ListBuffer<Type> undettypes = new ListBuffer<Type>();
         for (Type t : undetvars) {
             UndetVar uv = (UndetVar)t;
             if (uv.inst.tag == BOT) {
                 restvars.append(uv.qtype);
                 restundet.append(uv);
                 insttypes.append(uv.qtype);
                 undettypes.append(uv);
                 uv.inst = null;
             } else {
                 insttypes.append(uv.inst);
                 undettypes.append(uv.inst);
             }
         }
         checkWithinBounds(tvars, undettypes.toList(), warn);
         mt = (MethodType)types.subst(mt, tvars, insttypes.toList());
         if (!restvars.isEmpty()) {
             // if there are uninstantiated variables,
             // quantify result type with them
             final List<Type> inferredTypes = insttypes.toList();
             final List<Type> all_tvars = tvars; //this is the wrong tvars
             final MethodType mt2 = new MethodType(mt.argtypes, null, mt.thrown, syms.methodClass);
             mt2.restype = new ForAll(restvars.toList(), mt.restype) {
                 @Override
                 public List<Type> getConstraints(TypeVar tv, ConstraintKind ck) {
                     for (Type t : restundet.toList()) {
                         UndetVar uv = (UndetVar)t;
                         if (uv.qtype == tv) {
                             switch (ck) {
                                 case EXTENDS: return uv.hibounds.appendList(types.subst(types.getBounds(tv), all_tvars, inferredTypes));
                                 case SUPER: return uv.lobounds;
                                 case EQUAL: return uv.inst != null ? List.of(uv.inst) : List.<Type>nil();
                             }
                         }
                     }
                     return List.nil();
                 }
                 @Override
                 public Type inst(List<Type> inferred, Types types) throws NoInstanceException {
                     List<Type> formals = types.subst(mt2.argtypes, tvars, inferred);
                     if (!rs.argumentsAcceptable(capturedArgs, formals,
                            allowBoxing, useVarargs, warn)) {
                       // inferred method is not applicable
                       throw invalidInstanceException.setMessage("inferred.do.not.conform.to.params", formals, argtypes);
                     }
                     // check that inferred bounds conform to their bounds
                     checkWithinBounds(all_tvars,
                            types.subst(inferredTypes, tvars, inferred), warn);
                     if (useVarargs) {
                         chk.checkVararg(env.tree.pos(), formals, msym);
                     }
                     return super.inst(inferred, types);
             }};
             return mt2;
         }
         else if (!rs.argumentsAcceptable(capturedArgs, mt.getParameterTypes(), allowBoxing, useVarargs, warn)) {
             // inferred method is not applicable
             throw invalidInstanceException.setMessage("inferred.do.not.conform.to.params", mt.getParameterTypes(), argtypes);
         }
         else {
             // return instantiated version of method type
             return mt;
         }
     }
     //where
         /** Try to instantiate argument type `that' to given type `to'.
          *  If this fails, try to insantiate `that' to `to' where
          *  every occurrence of a type variable in `tvars' is replaced
          *  by an unknown type.
          */
         private Type instantiateArg(ForAll that,
                                     Type to,
                                     List<Type> tvars,
                                     Warner warn) throws InferenceException {
             List<Type> targs;
             try {
                 return instantiateExpr(that, to, warn);
             } catch (NoInstanceException ex) {
                 Type to1 = to;
                 for (List<Type> l = tvars; l.nonEmpty(); l = l.tail)
                     to1 = types.subst(to1, List.of(l.head), List.of(syms.unknownType));
                 return instantiateExpr(that, to1, warn);
             }
         }
     /** check that type parameters are within their bounds.
      */
     void checkWithinBounds(List<Type> tvars,
                                    List<Type> arguments,
                                    Warner warn)
         throws InvalidInstanceException {
         for (List<Type> tvs = tvars, args = arguments;
              tvs.nonEmpty();
              tvs = tvs.tail, args = args.tail) {
             if (args.head instanceof UndetVar ||
                     tvars.head.getUpperBound().isErroneous()) continue;
             List<Type> bounds = types.subst(types.getBounds((TypeVar)tvs.head), tvars, arguments);
             if (!types.isSubtypeUnchecked(args.head, bounds, warn))
                 throw invalidInstanceException
                     .setMessage("inferred.do.not.conform.to.bounds",
                                 args.head, bounds);
         }
     }
     /**
      * Compute a synthetic method type corresponding to the requested polymorphic
      * method signature. The target return type is computed from the immediately
      * enclosing scope surrounding the polymorphic-signature call.
      */
     Type instantiatePolymorphicSignatureInstance(Env<AttrContext> env, Type site,
                                             Name name,
                                             MethodSymbol spMethod,  // sig. poly. method or null if none
                                             List<Type> argtypes) {
         final Type restype;
         //The return type for a polymorphic signature call is computed from
         //the enclosing tree E, as follows: if E is a cast, then use the
         //target type of the cast expression as a return type; if E is an
         //expression statement, the return type is 'void' - otherwise the
         //return type is simply 'Object'. A correctness check ensures that
         //env.next refers to the lexically enclosing environment in which
         //the polymorphic signature call environment is nested.
         switch (env.next.tree.getTag()) {
             case JCTree.TYPECAST:
                 JCTypeCast castTree = (JCTypeCast)env.next.tree;
                 restype = (TreeInfo.skipParens(castTree.expr) == env.tree) ?
                     castTree.clazz.type :
                     syms.objectType;
                 break;
             case JCTree.EXEC:
                 JCTree.JCExpressionStatement execTree =
                         (JCTree.JCExpressionStatement)env.next.tree;
                 restype = (TreeInfo.skipParens(execTree.expr) == env.tree) ?
                     syms.voidType :
                     syms.objectType;
                 break;
             default:
                 restype = syms.objectType;
         }
         List<Type> paramtypes = Type.map(argtypes, implicitArgType);
         List<Type> exType = spMethod != null ?
             spMethod.getThrownTypes() :
             List.of(syms.throwableType); // make it throw all exceptions
         MethodType mtype = new MethodType(paramtypes,
                                           restype,
                                           exType,
                                           syms.methodClass);
         return mtype;
     }
     //where
         Mapping implicitArgType = new Mapping ("implicitArgType") {
                 public Type apply(Type t) {
                     t = types.erasure(t);
                     if (t.tag == BOT)
                         // nulls type as the marker type Null (which has no instances)
                         // infer as java.lang.Void for now
                         t = types.boxedClass(syms.voidType).type;
                     return t;
                 }
         };
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/comp/Infer.java@19c900c703c6 (annotated)

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