Mercurial > jdk8-mips64-public > langtools / file revision

 /*

  * Copyright (c) 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

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  * questions.

  */

 package com.sun.tools.javac.comp;

 import com.sun.tools.javac.code.*;

 import com.sun.tools.javac.tree.*;

 import com.sun.tools.javac.util.*;

 import com.sun.tools.javac.code.Symbol.*;

 import com.sun.tools.javac.code.Type.*;

 import com.sun.tools.javac.comp.Attr.ResultInfo;

 import com.sun.tools.javac.comp.Infer.InferenceContext;

 import com.sun.tools.javac.comp.Resolve.MethodResolutionPhase;

 import com.sun.tools.javac.tree.JCTree.*;

 import javax.tools.JavaFileObject;

 import java.util.ArrayList;

 import java.util.HashSet;

 import java.util.Map;

 import java.util.Queue;

 import java.util.Set;

 import java.util.WeakHashMap;

 import static com.sun.tools.javac.code.TypeTag.DEFERRED;

 import static com.sun.tools.javac.code.TypeTag.NONE;

 import static com.sun.tools.javac.tree.JCTree.Tag.*;

 /**

  * This is an helper class that is used to perform deferred type-analysis.

  * Each time a poly expression occurs in argument position, javac attributes it

  * with a temporary 'deferred type' that is checked (possibly multiple times)

  * against an expected formal type.

  *

  *  <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 DeferredAttr extends JCTree.Visitor {

     protected static final Context.Key<DeferredAttr> deferredAttrKey =

         new Context.Key<DeferredAttr>();

     final Attr attr;

     final Check chk;

     final Enter enter;

     final Infer infer;

     final Log log;

     final Symtab syms;

     final TreeMaker make;

     final Types types;

     public static DeferredAttr instance(Context context) {

         DeferredAttr instance = context.get(deferredAttrKey);

         if (instance == null)

             instance = new DeferredAttr(context);

         return instance;

     }

     protected DeferredAttr(Context context) {

         context.put(deferredAttrKey, this);

         attr = Attr.instance(context);

         chk = Check.instance(context);

         enter = Enter.instance(context);

         infer = Infer.instance(context);

         log = Log.instance(context);

         syms = Symtab.instance(context);

         make = TreeMaker.instance(context);

         types = Types.instance(context);

     }

     /**

      * This type represents a deferred type. A deferred type starts off with

      * no information on the underlying expression type. Such info needs to be

      * discovered through type-checking the deferred type against a target-type.

      * Every deferred type keeps a pointer to the AST node from which it originated.

      */

     public class DeferredType extends Type {

         public JCExpression tree;

         Env<AttrContext> env;

         AttrMode mode;

         SpeculativeCache speculativeCache;

         DeferredType(JCExpression tree, Env<AttrContext> env) {

             super(DEFERRED, null);

             this.tree = tree;

             this.env = env.dup(tree, env.info.dup());

             this.speculativeCache = new SpeculativeCache();

         }

         /**

          * A speculative cache is used to keep track of all overload resolution rounds

          * that triggered speculative attribution on a given deferred type. Each entry

          * stores a pointer to the speculative tree and the resolution phase in which the entry

          * has been added.

          */

         class SpeculativeCache {

             private Map<Symbol, List<Entry>> cache =

                     new WeakHashMap<Symbol, List<Entry>>();

             class Entry {

                 JCTree speculativeTree;

                 Resolve.MethodResolutionPhase phase;

                 public Entry(JCTree speculativeTree, MethodResolutionPhase phase) {

                     this.speculativeTree = speculativeTree;

                     this.phase = phase;

                 }

                 boolean matches(Resolve.MethodResolutionPhase phase) {

                     return this.phase == phase;

                 }

             }

             /**

              * Clone a speculative cache entry as a fresh entry associated

              * with a new method (this maybe required to fixup speculative cache

              * misses after Resolve.access())

              */

             void dupAllTo(Symbol from, Symbol to) {

                 Assert.check(cache.get(to) == null);

                 List<Entry> entries = cache.get(from);

                 if (entries != null) {

                     cache.put(to, entries);

                 }

             }

             /**

              * Retrieve a speculative cache entry corresponding to given symbol

              * and resolution phase

              */

             Entry get(Symbol msym, MethodResolutionPhase phase) {

                 List<Entry> entries = cache.get(msym);

                 if (entries == null) return null;

                 for (Entry e : entries) {

                     if (e.matches(phase)) return e;

                 }

                 return null;

             }

             /**

              * Stores a speculative cache entry corresponding to given symbol

              * and resolution phase

              */

             void put(Symbol msym, JCTree speculativeTree, MethodResolutionPhase phase) {

                 List<Entry> entries = cache.get(msym);

                 if (entries == null) {

                     entries = List.nil();

                 }

                 cache.put(msym, entries.prepend(new Entry(speculativeTree, phase)));

             }

         }

         /**

          * Get the type that has been computed during a speculative attribution round

          */

         Type speculativeType(Symbol msym, MethodResolutionPhase phase) {

             SpeculativeCache.Entry e = speculativeCache.get(msym, phase);

             return e != null ? e.speculativeTree.type : Type.noType;

         }

         /**

          * Check a deferred type against a potential target-type. Depending on

          * the current attribution mode, a normal vs. speculative attribution

          * round is performed on the underlying AST node. There can be only one

          * speculative round for a given target method symbol; moreover, a normal

          * attribution round must follow one or more speculative rounds.

          */

         Type check(ResultInfo resultInfo) {

             DeferredAttrContext deferredAttrContext =

                     resultInfo.checkContext.deferredAttrContext();

             Assert.check(deferredAttrContext != emptyDeferredAttrContext);

             List<Type> stuckVars = stuckVars(tree, resultInfo);

             if (stuckVars.nonEmpty()) {

                 deferredAttrContext.addDeferredAttrNode(this, resultInfo, stuckVars);

                 return Type.noType;

             } else {

                 try {

                     switch (deferredAttrContext.mode) {

                         case SPECULATIVE:

                             Assert.check(mode == null ||

                                     (mode == AttrMode.SPECULATIVE &&

                                     speculativeType(deferredAttrContext.msym, deferredAttrContext.phase).hasTag(NONE)));

                             JCTree speculativeTree = attribSpeculative(tree, env, resultInfo);

                             speculativeCache.put(deferredAttrContext.msym, speculativeTree, deferredAttrContext.phase);

                             return speculativeTree.type;

                         case CHECK:

                             Assert.check(mode == AttrMode.SPECULATIVE);

                             return attr.attribTree(tree, env, resultInfo);

                     }

                     Assert.error();

                     return null;

                 } finally {

                     mode = deferredAttrContext.mode;

                 }

             }

         }

     }

     /**

      * The 'mode' in which the deferred type is to be type-checked

      */

     public enum AttrMode {

         /**

          * A speculative type-checking round is used during overload resolution

          * mainly to generate constraints on inference variables. Side-effects

          * arising from type-checking the expression associated with the deferred

          * type are reversed after the speculative round finishes. This means the

          * expression tree will be left in a blank state.

          */

         SPECULATIVE,

         /**

          * This is the plain type-checking mode. Produces side-effects on the underlying AST node

          */

         CHECK;

     }

     /**

      * Routine that performs speculative type-checking; the input AST node is

      * cloned (to avoid side-effects cause by Attr) and compiler state is

      * restored after type-checking. All diagnostics (but critical ones) are

      * disabled during speculative type-checking.

      */

     JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {

         JCTree newTree = new TreeCopier<Object>(make).copy(tree);

         Env<AttrContext> speculativeEnv = env.dup(newTree, env.info.dup(env.info.scope.dupUnshared()));

         speculativeEnv.info.scope.owner = env.info.scope.owner;

         Filter<JCDiagnostic> prevDeferDiagsFilter = log.deferredDiagFilter;

         Queue<JCDiagnostic> prevDeferredDiags = log.deferredDiagnostics;

         final JavaFileObject currentSource = log.currentSourceFile();

         try {

             log.deferredDiagnostics = new ListBuffer<JCDiagnostic>();

             log.deferredDiagFilter = new Filter<JCDiagnostic>() {

                 public boolean accepts(JCDiagnostic t) {

                     return t.getDiagnosticSource().getFile().equals(currentSource);

                 }

             };

             attr.attribTree(newTree, speculativeEnv, resultInfo);

             unenterScanner.scan(newTree);

             return newTree;

         } catch (Abort ex) {

             //if some very bad condition occurred during deferred attribution

             //we should dump all errors before killing javac

             log.reportDeferredDiagnostics();

             throw ex;

         } finally {

             unenterScanner.scan(newTree);

             log.deferredDiagFilter = prevDeferDiagsFilter;

             log.deferredDiagnostics = prevDeferredDiags;

         }

     }

     //where

         protected TreeScanner unenterScanner = new TreeScanner() {

             @Override

             public void visitClassDef(JCClassDecl tree) {

                 ClassSymbol csym = tree.sym;

                 enter.typeEnvs.remove(csym);

                 chk.compiled.remove(csym.flatname);

                 syms.classes.remove(csym.flatname);

                 super.visitClassDef(tree);

             }

         };

     /**

      * A deferred context is created on each method check. A deferred context is

      * used to keep track of information associated with the method check, such as

      * the symbol of the method being checked, the overload resolution phase,

      * the kind of attribution mode to be applied to deferred types and so forth.

      * As deferred types are processed (by the method check routine) stuck AST nodes

      * are added (as new deferred attribution nodes) to this context. The complete()

      * routine makes sure that all pending nodes are properly processed, by

      * progressively instantiating all inference variables on which one or more

      * deferred attribution node is stuck.

      */

     class DeferredAttrContext {

         /** attribution mode */

         final AttrMode mode;

         /** symbol of the method being checked */

         final Symbol msym;

         /** method resolution step */

         final Resolve.MethodResolutionPhase phase;

         /** inference context */

         final InferenceContext inferenceContext;

         /** list of deferred attribution nodes to be processed */

         ArrayList<DeferredAttrNode> deferredAttrNodes = new ArrayList<DeferredAttrNode>();

         DeferredAttrContext(AttrMode mode, Symbol msym, MethodResolutionPhase phase, InferenceContext inferenceContext) {

             this.mode = mode;

             this.msym = msym;

             this.phase = phase;

             this.inferenceContext = inferenceContext;

         }

         /**

          * Adds a node to the list of deferred attribution nodes - used by Resolve.rawCheckArgumentsApplicable

          * Nodes added this way act as 'roots' for the out-of-order method checking process.

          */

         void addDeferredAttrNode(final DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {

             deferredAttrNodes.add(new DeferredAttrNode(dt, resultInfo, stuckVars));

         }

         /**

          * Incrementally process all nodes, by skipping 'stuck' nodes and attributing

          * 'unstuck' ones. If at any point no progress can be made (no 'unstuck' nodes)

          * some inference variable might get eagerly instantiated so that all nodes

          * can be type-checked.

          */

         void complete() {

             while (!deferredAttrNodes.isEmpty()) {

                 Set<Type> stuckVars = new HashSet<Type>();

                 boolean progress = false;

                 //scan a defensive copy of the node list - this is because a deferred

                 //attribution round can add new nodes to the list

                 for (DeferredAttrNode deferredAttrNode : List.from(deferredAttrNodes)) {

                     if (!deferredAttrNode.isStuck()) {

                         deferredAttrNode.process();

                         deferredAttrNodes.remove(deferredAttrNode);

                         progress = true;

                     } else {

                         stuckVars.addAll(deferredAttrNode.stuckVars);

                     }

                 }

                 if (!progress) {

                     //remove all variables that have already been instantiated

                     //from the list of stuck variables

                     inferenceContext.solveAny(inferenceContext.freeVarsIn(List.from(stuckVars)), types, infer);

                     inferenceContext.notifyChange(types);

                 }

             }

         }

         /**

          * Class representing a deferred attribution node. It keeps track of

          * a deferred type, along with the expected target type information.

          */

         class DeferredAttrNode implements Infer.InferenceContext.FreeTypeListener {

             /** underlying deferred type */

             DeferredType dt;

             /** underlying target type information */

             ResultInfo resultInfo;

             /** list of uninferred inference variables causing this node to be stuck */

             List<Type> stuckVars;

             DeferredAttrNode(DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {

                 this.dt = dt;

                 this.resultInfo = resultInfo;

                 this.stuckVars = stuckVars;

                 if (!stuckVars.isEmpty()) {

                     resultInfo.checkContext.inferenceContext().addFreeTypeListener(stuckVars, this);

                 }

             }

             @Override

             public void typesInferred(InferenceContext inferenceContext) {

                 stuckVars = List.nil();

                 resultInfo = resultInfo.dup(inferenceContext.asInstType(resultInfo.pt, types));

             }

             /**

              * is this node stuck?

              */

             boolean isStuck() {

                 return stuckVars.nonEmpty();

             }

             /**

              * Process a deferred attribution node.

              * Invariant: a stuck node cannot be processed.

              */

             void process() {

                 if (isStuck()) {

                     throw new IllegalStateException("Cannot process a stuck deferred node");

                 }

                 dt.check(resultInfo);

             }

         }

     }

     /** an empty deferred attribution context - all methods throw exceptions */

     final DeferredAttrContext emptyDeferredAttrContext =

             new DeferredAttrContext(null, null, null, null) {

                 @Override

                 void addDeferredAttrNode(DeferredType dt, ResultInfo ri, List<Type> stuckVars) {

                     Assert.error("Empty deferred context!");

                 }

                 @Override

                 void complete() {

                     Assert.error("Empty deferred context!");

                 }

             };

     /**

      * Map a list of types possibly containing one or more deferred types

      * into a list of ordinary types. Each deferred type D is mapped into a type T,

      * where T is computed by retrieving the type that has already been

      * computed for D during a previous deferred attribution round of the given kind.

      */

     class DeferredTypeMap extends Type.Mapping {

         DeferredAttrContext deferredAttrContext;

         protected DeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {

             super(String.format("deferredTypeMap[%s]", mode));

             this.deferredAttrContext = new DeferredAttrContext(mode, msym, phase, infer.emptyContext);

         }

         protected boolean validState(DeferredType dt) {

             return dt.mode != null &&

                     deferredAttrContext.mode.ordinal() <= dt.mode.ordinal();

         }

         @Override

         public Type apply(Type t) {

             if (!t.hasTag(DEFERRED)) {

                 return t.map(this);

             } else {

                 DeferredType dt = (DeferredType)t;

                 Assert.check(validState(dt));

                 return typeOf(dt);

             }

         }

         protected Type typeOf(DeferredType dt) {

             switch (deferredAttrContext.mode) {

                 case CHECK:

                     return dt.tree.type == null ? Type.noType : dt.tree.type;

                 case SPECULATIVE:

                     return dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase);

             }

             Assert.error();

             return null;

         }

     }

     /**

      * Specialized recovery deferred mapping.

      * Each deferred type D is mapped into a type T, where T is computed either by

      * (i) retrieving the type that has already been computed for D during a previous

      * attribution round (as before), or (ii) by synthesizing a new type R for D

      * (the latter step is useful in a recovery scenario).

      */

     public class RecoveryDeferredTypeMap extends DeferredTypeMap {

         public RecoveryDeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {

             super(mode, msym, phase);

         }

         @Override

         protected Type typeOf(DeferredType dt) {

             Type owntype = super.typeOf(dt);

             return owntype.hasTag(NONE) ?

                         recover(dt) : owntype;

         }

         @Override

         protected boolean validState(DeferredType dt) {

             return true;

         }

         /**

          * Synthesize a type for a deferred type that hasn't been previously

          * reduced to an ordinary type. Functional deferred types and conditionals

          * are mapped to themselves, in order to have a richer diagnostic

          * representation. Remaining deferred types are attributed using

          * a default expected type (j.l.Object).

          */

         private Type recover(DeferredType dt) {

             dt.check(attr.new RecoveryInfo(deferredAttrContext));

             switch (TreeInfo.skipParens(dt.tree).getTag()) {

                 case LAMBDA:

                 case REFERENCE:

                 case CONDEXPR:

                     //propagate those deferred types to the

                     //diagnostic formatter

                     return dt;

                 default:

                     return super.apply(dt);

             }

         }

     }

     /**

      * Retrieves the list of inference variables that need to be inferred before

      * an AST node can be type-checked

      */

     @SuppressWarnings("fallthrough")

     List<Type> stuckVars(JCTree tree, ResultInfo resultInfo) {

         if (resultInfo.pt.hasTag(NONE) || resultInfo.pt.isErroneous()) {

             return List.nil();

         } else {

             StuckChecker sc = new StuckChecker(resultInfo);

             sc.scan(tree);

             return List.from(sc.stuckVars);

         }

     }

     /**

      * This visitor is used to check that structural expressions conform

      * to their target - this step is required as inference could end up

      * inferring types that make some of the nested expressions incompatible

      * with their corresponding instantiated target

      */

     class StuckChecker extends TreeScanner {

         Type pt;

         Filter<JCTree> treeFilter;

         Infer.InferenceContext inferenceContext;

         Set<Type> stuckVars = new HashSet<Type>();

         final Filter<JCTree> argsFilter = new Filter<JCTree>() {

             public boolean accepts(JCTree t) {

                 switch (t.getTag()) {

                     case CONDEXPR:

                     case LAMBDA:

                     case PARENS:

                     case REFERENCE:

                         return true;

                     default:

                         return false;

                 }

             }

         };

         final Filter<JCTree> lambdaBodyFilter = new Filter<JCTree>() {

             public boolean accepts(JCTree t) {

                 switch (t.getTag()) {

                     case BLOCK: case CASE: case CATCH: case DOLOOP:

                     case FOREACHLOOP: case FORLOOP: case RETURN:

                     case SYNCHRONIZED: case SWITCH: case TRY: case WHILELOOP:

                         return true;

                     default:

                         return false;

                 }

             }

         };

         StuckChecker(ResultInfo resultInfo) {

             this.pt = resultInfo.pt;

             this.inferenceContext = resultInfo.checkContext.inferenceContext();

             this.treeFilter = argsFilter;

         }

         @Override

         public void scan(JCTree tree) {

             if (tree != null && treeFilter.accepts(tree)) {

                 super.scan(tree);

             }

         }

         @Override

         public void visitLambda(JCLambda tree) {

             Type prevPt = pt;

             Filter<JCTree> prevFilter = treeFilter;

             try {

                 if (inferenceContext.inferenceVars().contains(pt)) {

                     stuckVars.add(pt);

                 }

                 if (!types.isFunctionalInterface(pt.tsym)) {

                     return;

                 }

                 Type descType = types.findDescriptorType(pt);

                 List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());

                 if (!TreeInfo.isExplicitLambda(tree) &&

                         freeArgVars.nonEmpty()) {

                     stuckVars.addAll(freeArgVars);

                 }

                 pt = descType.getReturnType();

                 if (tree.getBodyKind() == JCTree.JCLambda.BodyKind.EXPRESSION) {

                     scan(tree.getBody());

                 } else {

                     treeFilter = lambdaBodyFilter;

                     super.visitLambda(tree);

                 }

             } finally {

                 pt = prevPt;

                 treeFilter = prevFilter;

             }

         }

         @Override

         public void visitReference(JCMemberReference tree) {

             scan(tree.expr);

             if (inferenceContext.inferenceVars().contains(pt)) {

                 stuckVars.add(pt);

                 return;

             }

             if (!types.isFunctionalInterface(pt.tsym)) {

                 return;

             }

             Type descType = types.findDescriptorType(pt);

             List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());

             stuckVars.addAll(freeArgVars);

         }

         @Override

         public void visitReturn(JCReturn tree) {

             Filter<JCTree> prevFilter = treeFilter;

             try {

                 treeFilter = argsFilter;

                 if (tree.expr != null) {

                     scan(tree.expr);

                 }

             } finally {

                 treeFilter = prevFilter;

             }

         }

     }

 }