jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/comp/Infer.java@2eca84194807 (annotated)

src/share/classes/com/sun/tools/javac/comp/Infer.java@2eca84194807 (annotated)

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

Tue, 25 Sep 2012 11:55:34 +0100

author: mcimadamore
date: Tue, 25 Sep 2012 11:55:34 +0100
changeset 1337: 2eca84194807
parent 1298: 2d75e7c952b8
child 1338: ad2ca2a4ab5e
permissions: -rw-r--r--

7175433: Inference cleanup: add helper class to handle inference variables
Summary: Add class to handle inference variables instantiation and associated info
Reviewed-by: jjg, dlsmith

 /*
  * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 package com.sun.tools.javac.comp;
 import com.sun.tools.javac.code.*;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.comp.Resolve.InapplicableMethodException;
 import com.sun.tools.javac.comp.Resolve.VerboseResolutionMode;
 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.util.JCDiagnostic.DiagnosticPosition;
 import java.util.HashMap;
 import java.util.Map;
 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;
     Log log;
     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);
         log = Log.instance(context);
         chk = Check.instance(context);
         diags = JCDiagnostic.Factory.instance(context);
         inferenceException = new InferenceException(diags);
     }
    /**
     * This exception class is design to store a list of diagnostics corresponding
     * to inference errors that can arise during a method applicability check.
     */
     public static class InferenceException extends InapplicableMethodException {
         private static final long serialVersionUID = 0;
         List<JCDiagnostic> messages = List.nil();
         InferenceException(JCDiagnostic.Factory diags) {
             super(diags);
         }
         @Override
         InapplicableMethodException setMessage(JCDiagnostic diag) {
             messages = messages.append(diag);
             return this;
         }
         @Override
         public JCDiagnostic getDiagnostic() {
             return messages.head;
         }
         void clear() {
             messages = List.nil();
         }
     }
     private final InferenceException inferenceException;
 /***************************************************************************
  * 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 InferenceException {
         List<Type> hibounds = Type.filter(that.hibounds, boundFilter);
         if (that.eq.isEmpty()) {
             if (hibounds.isEmpty())
                 that.inst = syms.objectType;
             else if (hibounds.tail.isEmpty())
                 that.inst = hibounds.head;
             else
                 that.inst = types.glb(hibounds);
         } else {
             that.inst = that.eq.head;
         }
         if (that.inst == null ||
             that.inst.isErroneous())
             throw inferenceException
                 .setMessage("no.unique.maximal.instance.exists",
                             that.qtype, hibounds);
     }
     private Filter<Type> boundFilter = new Filter<Type>() {
         @Override
         public boolean accepts(Type t) {
             return !t.isErroneous() && t.tag != BOT;
         }
     };
     /** 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 InferenceException {
         List<Type> lobounds = Type.filter(that.lobounds, boundFilter);
         if (that.eq.isEmpty()) {
             if (lobounds.isEmpty()) {
                 //do nothing - the inference variable is under-constrained
                 return;
             } 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 inferenceException
                         .setMessage("no.unique.minimal.instance.exists",
                                     that.qtype, lobounds);
         } else {
             that.inst = that.eq.head;
         }
     }
 /***************************************************************************
  * Exported Methods
  ***************************************************************************/
     /**
      * Instantiate uninferred inference variables (JLS 15.12.2.8). First
      * if the method return type is non-void, we derive constraints from the
      * expected type - then we use declared bound well-formedness to derive additional
      * constraints. If no instantiation exists, or if several incomparable
      * best instantiations exist throw a NoInstanceException.
      */
     public void instantiateUninferred(DiagnosticPosition pos,
             InferenceContext inferenceContext,
             MethodType mtype,
             Attr.ResultInfo resultInfo,
             Warner warn) throws InferenceException {
         Type to = resultInfo.pt;
         if (to.tag == NONE) {
             to = mtype.getReturnType().tag <= VOID ?
                     mtype.getReturnType() : syms.objectType;
         }
         Type qtype1 = inferenceContext.asFree(mtype.getReturnType(), types);
         if (!types.isSubtype(qtype1,
                 qtype1.tag == UNDETVAR ? types.boxedTypeOrType(to) : to)) {
             throw inferenceException
                     .setMessage("infer.no.conforming.instance.exists",
                     inferenceContext.restvars(), mtype.getReturnType(), to);
         }
         while (true) {
             boolean stuck = true;
             for (Type t : inferenceContext.undetvars) {
                 UndetVar uv = (UndetVar)t;
                 if (uv.inst == null && (uv.eq.nonEmpty() || !inferenceContext.free(uv.hibounds))) {
                     maximizeInst((UndetVar)t, warn);
                     stuck = false;
                 }
             }
             if (inferenceContext.restvars().isEmpty()) {
                 //all variables have been instantiated - exit
                 break;
             } else if (stuck) {
                 //some variables could not be instantiated because of cycles in
                 //upper bounds - provide a (possibly recursive) default instantiation
                 instantiateAsUninferredVars(inferenceContext);
                 break;
             } else {
                 //some variables have been instantiated - replace newly instantiated
                 //variables in remaining upper bounds and continue
                 for (Type t : inferenceContext.undetvars) {
                     UndetVar uv = (UndetVar)t;
                     uv.hibounds = inferenceContext.asInstTypes(uv.hibounds, types);
                 }
             }
         }
     }
     /**
      * Infer cyclic inference variables as described in 15.12.2.8.
      */
     private void instantiateAsUninferredVars(InferenceContext inferenceContext) {
         ListBuffer<Type> todo = ListBuffer.lb();
         //step 1 - create fresh tvars
         for (Type t : inferenceContext.undetvars) {
             UndetVar uv = (UndetVar)t;
             if (uv.inst == null) {
                 TypeSymbol fresh_tvar = new TypeSymbol(Flags.SYNTHETIC, uv.qtype.tsym.name, null, uv.qtype.tsym.owner);
                 fresh_tvar.type = new TypeVar(fresh_tvar, types.makeCompoundType(uv.hibounds), null);
                 todo.append(uv);
                 uv.inst = fresh_tvar.type;
             }
         }
         //step 2 - replace fresh tvars in their bounds
         List<Type> formals = inferenceContext.inferenceVars();
         for (Type t : todo) {
             UndetVar uv = (UndetVar)t;
             TypeVar ct = (TypeVar)uv.inst;
             ct.bound = types.glb(inferenceContext.asInstTypes(types.getBounds(ct), types));
             if (ct.bound.isErroneous()) {
                 //report inference error if glb fails
                 reportBoundError(uv, BoundErrorKind.BAD_UPPER);
             }
             formals = formals.tail;
         }
     }
     /** Instantiate a generic method type by finding instantiations for all its
      * inference variables so that it can be applied to a given argument type list.
      */
     public Type instantiateMethod(Env<AttrContext> env,
                                   List<Type> tvars,
                                   MethodType mt,
                                   Attr.ResultInfo resultInfo,
                                   Symbol msym,
                                   List<Type> argtypes,
                                   boolean allowBoxing,
                                   boolean useVarargs,
                                   Warner warn) throws InferenceException {
         //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
         final InferenceContext inferenceContext = new InferenceContext(tvars, types);
         inferenceException.clear();
         try {
             rs.checkRawArgumentsAcceptable(env, inferenceContext, argtypes, mt.getParameterTypes(),
                     allowBoxing, useVarargs, warn, new InferenceCheckHandler(inferenceContext));
             // minimize as yet undetermined type variables
             for (Type t : inferenceContext.undetvars) {
                 minimizeInst((UndetVar)t, warn);
             }
             checkWithinBounds(inferenceContext, warn);
             mt = (MethodType)inferenceContext.asInstType(mt, types);
             List<Type> restvars = inferenceContext.restvars();
             if (!restvars.isEmpty()) {
                 if (resultInfo != null) {
                     instantiateUninferred(env.tree.pos(), inferenceContext, mt, resultInfo, warn);
                     checkWithinBounds(inferenceContext, warn);
                     mt = (MethodType)inferenceContext.asInstType(mt, types);
                     if (rs.verboseResolutionMode.contains(VerboseResolutionMode.DEFERRED_INST)) {
                         log.note(env.tree.pos, "deferred.method.inst", msym, mt, resultInfo.pt);
                     }
                 }
             }
             // return instantiated version of method type
             return mt;
         } finally {
             inferenceContext.notifyChange(types);
         }
     }
     //where
         /** inference check handler **/
         class InferenceCheckHandler implements Resolve.MethodCheckHandler {
             InferenceContext inferenceContext;
             public InferenceCheckHandler(InferenceContext inferenceContext) {
                 this.inferenceContext = inferenceContext;
             }
             public InapplicableMethodException arityMismatch() {
                 return inferenceException.setMessage("infer.arg.length.mismatch", inferenceContext.inferenceVars());
             }
             public InapplicableMethodException argumentMismatch(boolean varargs, JCDiagnostic details) {
                 String key = varargs ?
                         "infer.varargs.argument.mismatch" :
                         "infer.no.conforming.assignment.exists";
                 return inferenceException.setMessage(key,
                         inferenceContext.inferenceVars(), details);
             }
             public InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected) {
                 return inferenceException.setMessage("inaccessible.varargs.type",
                         expected, Kinds.kindName(location), location);
             }
         }
     /** check that type parameters are within their bounds.
      */
     void checkWithinBounds(InferenceContext inferenceContext,
                            Warner warn)
         throws InferenceException {
         List<Type> tvars = inferenceContext.inferenceVars();
         for (Type t : inferenceContext.undetvars) {
             UndetVar uv = (UndetVar)t;
             uv.hibounds = inferenceContext.asInstTypes(uv.hibounds, types);
             uv.lobounds = inferenceContext.asInstTypes(uv.lobounds, types);
             uv.eq = inferenceContext.asInstTypes(uv.eq, types);
             checkCompatibleUpperBounds(uv, inferenceContext.inferenceVars());
             if (!inferenceContext.restvars().contains(tvars.head)) {
                 Type inst = inferenceContext.asInstType(t, types);
                 for (Type u : uv.hibounds) {
                     if (!types.isSubtypeUnchecked(inst, inferenceContext.asFree(u, types), warn)) {
                         reportBoundError(uv, BoundErrorKind.UPPER);
                     }
                 }
                 for (Type l : uv.lobounds) {
                     if (!types.isSubtypeUnchecked(inferenceContext.asFree(l, types), inst, warn)) {
                         reportBoundError(uv, BoundErrorKind.LOWER);
                     }
                 }
                 for (Type e : uv.eq) {
                     if (!types.isSameType(inst, inferenceContext.asFree(e, types))) {
                         reportBoundError(uv, BoundErrorKind.EQ);
                     }
                 }
             }
             tvars = tvars.tail;
         }
     }
     void checkCompatibleUpperBounds(UndetVar uv, List<Type> tvars) {
         // VGJ: sort of inlined maximizeInst() below.  Adding
         // bounds can cause lobounds that are above hibounds.
         ListBuffer<Type> hiboundsNoVars = ListBuffer.lb();
         for (Type t : Type.filter(uv.hibounds, boundFilter)) {
             if (!t.containsAny(tvars)) {
                 hiboundsNoVars.append(t);
             }
         }
         List<Type> hibounds = hiboundsNoVars.toList();
         Type hb = null;
         if (hibounds.isEmpty())
             hb = syms.objectType;
         else if (hibounds.tail.isEmpty())
             hb = hibounds.head;
         else
             hb = types.glb(hibounds);
         if (hb == null || hb.isErroneous())
             reportBoundError(uv, BoundErrorKind.BAD_UPPER);
     }
     enum BoundErrorKind {
         BAD_UPPER() {
             @Override
             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
                 return ex.setMessage("incompatible.upper.bounds", uv.qtype, uv.hibounds);
             }
         },
         UPPER() {
             @Override
             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
                 return ex.setMessage("inferred.do.not.conform.to.upper.bounds", uv.inst, uv.hibounds);
             }
         },
         LOWER() {
             @Override
             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
                 return ex.setMessage("inferred.do.not.conform.to.lower.bounds", uv.inst, uv.lobounds);
             }
         },
         EQ() {
             @Override
             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
                 return ex.setMessage("inferred.do.not.conform.to.eq.bounds", uv.inst, uv.eq);
             }
         };
         abstract InapplicableMethodException setMessage(InferenceException ex, UndetVar uv);
     }
     //where
     void reportBoundError(UndetVar uv, BoundErrorKind bk) {
         throw bk.setMessage(inferenceException, uv);
     }
     /**
      * 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,
                                             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 TYPECAST:
                 JCTypeCast castTree = (JCTypeCast)env.next.tree;
                 restype = (TreeInfo.skipParens(castTree.expr) == env.tree) ?
                     castTree.clazz.type :
                     syms.objectType;
                 break;
             case 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;
                 }
         };
     /**
      * Mapping that turns inference variables into undet vars
      * (used by inference context)
      */
     static Mapping fromTypeVarFun = new Mapping("fromTypeVarFun") {
         public Type apply(Type t) {
             if (t.tag == TYPEVAR) return new UndetVar(t);
             else return t.map(this);
         }
     };
     /**
      * An inference context keeps track of the set of variables that are free
      * in the current context. It provides utility methods for opening/closing
      * types to their corresponding free/closed forms. It also provide hooks for
      * attaching deferred post-inference action (see PendingCheck). Finally,
      * it can be used as an entry point for performing upper/lower bound inference
      * (see InferenceKind).
      */
     static class InferenceContext {
         /**
         * Single-method-interface for defining inference callbacks. Certain actions
         * (i.e. subtyping checks) might need to be redone after all inference variables
         * have been fixed.
         */
         interface FreeTypeListener {
             void typesInferred(InferenceContext inferenceContext);
         }
         /** list of inference vars as undet vars */
         List<Type> undetvars;
         /** list of inference vars in this context */
         List<Type> inferencevars;
         java.util.Map<FreeTypeListener, List<Type>> freeTypeListeners =
                 new java.util.HashMap<FreeTypeListener, List<Type>>();
         List<FreeTypeListener> freetypeListeners = List.nil();
         public InferenceContext(List<Type> inferencevars, Types types) {
             this.undetvars = Type.map(inferencevars, fromTypeVarFun);
             this.inferencevars = inferencevars;
             for (Type t : this.undetvars) {
                 UndetVar uv = (UndetVar)t;
                 uv.hibounds = types.getBounds((TypeVar)uv.qtype);
             }
         }
         /**
          * returns the list of free variables (as type-variables) in this
          * inference context
          */
         List<Type> inferenceVars() {
             return inferencevars;
         }
         /**
          * returns the list of uninstantiated variables (as type-variables) in this
          * inference context (usually called after instantiate())
          */
         List<Type> restvars() {
             List<Type> undetvars = this.undetvars;
             ListBuffer<Type> restvars = ListBuffer.lb();
             for (Type t : instTypes()) {
                 UndetVar uv = (UndetVar)undetvars.head;
                 if (uv.qtype == t) {
                     restvars.append(t);
                 }
                 undetvars = undetvars.tail;
             }
             return restvars.toList();
         }
         /**
          * is this type free?
          */
         final boolean free(Type t) {
             return t.containsAny(inferencevars);
         }
         final boolean free(List<Type> ts) {
             for (Type t : ts) {
                 if (free(t)) return true;
             }
             return false;
         }
         /**
          * Returns a list of free variables in a given type
          */
         final List<Type> freeVarsIn(Type t) {
             ListBuffer<Type> buf = ListBuffer.lb();
             for (Type iv : inferenceVars()) {
                 if (t.contains(iv)) {
                     buf.add(iv);
                 }
             }
             return buf.toList();
         }
         final List<Type> freeVarsIn(List<Type> ts) {
             ListBuffer<Type> buf = ListBuffer.lb();
             for (Type t : ts) {
                 buf.appendList(freeVarsIn(t));
             }
             ListBuffer<Type> buf2 = ListBuffer.lb();
             for (Type t : buf) {
                 if (!buf2.contains(t)) {
                     buf2.add(t);
                 }
             }
             return buf2.toList();
         }
         /**
          * Replace all free variables in a given type with corresponding
          * undet vars (used ahead of subtyping/compatibility checks to allow propagation
          * of inference constraints).
          */
         final Type asFree(Type t, Types types) {
             return types.subst(t, inferencevars, undetvars);
         }
         final List<Type> asFree(List<Type> ts, Types types) {
             ListBuffer<Type> buf = ListBuffer.lb();
             for (Type t : ts) {
                 buf.append(asFree(t, types));
             }
             return buf.toList();
         }
         List<Type> instTypes() {
             ListBuffer<Type> buf = ListBuffer.lb();
             for (Type t : undetvars) {
                 UndetVar uv = (UndetVar)t;
                 buf.append(uv.inst != null ? uv.inst : uv.qtype);
             }
             return buf.toList();
         }
         /**
          * Replace all free variables in a given type with corresponding
          * instantiated types - if one or more free variable has not been
          * fully instantiated, it will still be available in the resulting type.
          */
         Type asInstType(Type t, Types types) {
             return types.subst(t, inferencevars, instTypes());
         }
         List<Type> asInstTypes(List<Type> ts, Types types) {
             ListBuffer<Type> buf = ListBuffer.lb();
             for (Type t : ts) {
                 buf.append(asInstType(t, types));
             }
             return buf.toList();
         }
         /**
          * Add custom hook for performing post-inference action
          */
         void addFreeTypeListener(List<Type> types, FreeTypeListener ftl) {
             freeTypeListeners.put(ftl, freeVarsIn(types));
         }
         /**
          * Mark the inference context as complete and trigger evaluation
          * of all deferred checks.
          */
         void notifyChange(Types types) {
             InferenceException thrownEx = null;
             for (Map.Entry<FreeTypeListener, List<Type>> entry :
                     new HashMap<FreeTypeListener, List<Type>>(freeTypeListeners).entrySet()) {
                 if (!Type.containsAny(entry.getValue(), restvars())) {
                     try {
                         entry.getKey().typesInferred(this);
                         freeTypeListeners.remove(entry.getKey());
                     } catch (InferenceException ex) {
                         if (thrownEx == null) {
                             thrownEx = ex;
                         }
                     }
                 }
             }
             //inference exception multiplexing - present any inference exception
             //thrown when processing listeners as a single one
             if (thrownEx != null) {
                 throw thrownEx;
             }
         }
     }
     final InferenceContext emptyContext = new InferenceContext(List.<Type>nil(), types);
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/comp/Infer.java@2eca84194807 (annotated)

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