1 /*

     2  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package com.sun.tools.javac.comp;

    27 

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

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

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

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

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

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

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

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

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

    37 

    38 import javax.tools.JavaFileObject;

    39 

    40 import java.util.ArrayList;

    41 import java.util.HashSet;

    42 import java.util.Map;

    43 import java.util.Queue;

    44 import java.util.Set;

    45 import java.util.WeakHashMap;

    46 

    47 import static com.sun.tools.javac.code.TypeTags.*;

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

    49 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;

    50 

    51 /**

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

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

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

    55  * against an expected formal type.

    56  *

    57  *  <p><b>This is NOT part of any supported API.

    58  *  If you write code that depends on this, you do so at your own risk.

    59  *  This code and its internal interfaces are subject to change or

    60  *  deletion without notice.</b>

    61  */

    62 public class DeferredAttr extends JCTree.Visitor {

    63     protected static final Context.Key<DeferredAttr> deferredAttrKey =

    64         new Context.Key<DeferredAttr>();

    65 

    66     final Attr attr;

    67     final Check chk;

    68     final Enter enter;

    69     final Infer infer;

    70     final Log log;

    71     final Symtab syms;

    72     final TreeMaker make;

    73     final Types types;

    74 

    75     public static DeferredAttr instance(Context context) {

    76         DeferredAttr instance = context.get(deferredAttrKey);

    77         if (instance == null)

    78             instance = new DeferredAttr(context);

    79         return instance;

    80     }

    81 

    82     protected DeferredAttr(Context context) {

    83         context.put(deferredAttrKey, this);

    84         attr = Attr.instance(context);

    85         chk = Check.instance(context);

    86         enter = Enter.instance(context);

    87         infer = Infer.instance(context);

    88         log = Log.instance(context);

    89         syms = Symtab.instance(context);

    90         make = TreeMaker.instance(context);

    91         types = Types.instance(context);

    92     }

    93 

    94     /**

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

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

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

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

    99      */

   100     public class DeferredType extends Type {

   101 

   102         public JCExpression tree;

   103         Env<AttrContext> env;

   104         AttrMode mode;

   105         SpeculativeCache speculativeCache;

   106 

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

   108             super(DEFERRED, null);

   109             this.tree = tree;

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

   111             this.speculativeCache = new SpeculativeCache();

   112         }

   113 

   114         /**

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

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

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

   118          * has been added.

   119          */

   120         class SpeculativeCache {

   121 

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

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

   124 

   125             class Entry {

   126                 JCTree speculativeTree;

   127                 Resolve.MethodResolutionPhase phase;

   128 

   129                 public Entry(JCTree speculativeTree, MethodResolutionPhase phase) {

   130                     this.speculativeTree = speculativeTree;

   131                     this.phase = phase;

   132                 }

   133 

   134                 boolean matches(Resolve.MethodResolutionPhase phase) {

   135                     return this.phase == phase;

   136                 }

   137             }

   138 

   139             /**

   140              * Clone a speculative cache entry as a fresh entry associated

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

   142              * misses after Resolve.access())

   143              */

   144             void dupAllTo(Symbol from, Symbol to) {

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

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

   147                 if (entries != null) {

   148                     cache.put(to, entries);

   149                 }

   150             }

   151 

   152             /**

   153              * Retrieve a speculative cache entry corresponding to given symbol

   154              * and resolution phase

   155              */

   156             Entry get(Symbol msym, MethodResolutionPhase phase) {

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

   158                 if (entries == null) return null;

   159                 for (Entry e : entries) {

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

   161                 }

   162                 return null;

   163             }

   164 

   165             /**

   166              * Stores a speculative cache entry corresponding to given symbol

   167              * and resolution phase

   168              */

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

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

   171                 if (entries == null) {

   172                     entries = List.nil();

   173                 }

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

   175             }

   176         }

   177 

   178         /**

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

   180          */

   181         Type speculativeType(Symbol msym, MethodResolutionPhase phase) {

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

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

   184         }

   185 

   186         /**

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

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

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

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

   191          * attribution round must follow one or more speculative rounds.

   192          */

   193         Type check(ResultInfo resultInfo) {

   194             DeferredAttrContext deferredAttrContext =

   195                     resultInfo.checkContext.deferredAttrContext();

   196             Assert.check(deferredAttrContext != emptyDeferredAttrContext);

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

   198             if (stuckVars.nonEmpty()) {

   199                 deferredAttrContext.addDeferredAttrNode(this, resultInfo, stuckVars);

   200                 return Type.noType;

   201             } else {

   202                 try {

   203                     switch (deferredAttrContext.mode) {

   204                         case SPECULATIVE:

   205                             Assert.check(mode == null ||

   206                                     (mode == AttrMode.SPECULATIVE &&

   207                                     speculativeType(deferredAttrContext.msym, deferredAttrContext.phase).tag == NONE));

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

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

   210                             return speculativeTree.type;

   211                         case CHECK:

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

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

   214                     }

   215                     Assert.error();

   216                     return null;

   217                 } finally {

   218                     mode = deferredAttrContext.mode;

   219                 }

   220             }

   221         }

   222     }

   223 

   224     /**

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

   226      */

   227     public enum AttrMode {

   228         /**

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

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

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

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

   233          * expression tree will be left in a blank state.

   234          */

   235         SPECULATIVE,

   236         /**

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

   238          */

   239         CHECK;

   240     }

   241 

   242     /**

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

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

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

   246      * disabled during speculative type-checking.

   247      */

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

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

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

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

   252         Filter<JCDiagnostic> prevDeferDiagsFilter = log.deferredDiagFilter;

   253         Queue<JCDiagnostic> prevDeferredDiags = log.deferredDiagnostics;

   254         final JavaFileObject currentSource = log.currentSourceFile();

   255         try {

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

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

   258                 public boolean accepts(JCDiagnostic t) {

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

   260                 }

   261             };

   262             attr.attribTree(newTree, speculativeEnv, resultInfo);

   263             unenterScanner.scan(newTree);

   264             return newTree;

   265         } catch (Abort ex) {

   266             //if some very bad condition occurred during deferred attribution

   267             //we should dump all errors before killing javac

   268             log.reportDeferredDiagnostics();

   269             throw ex;

   270         } finally {

   271             unenterScanner.scan(newTree);

   272             log.deferredDiagFilter = prevDeferDiagsFilter;

   273             log.deferredDiagnostics = prevDeferredDiags;

   274         }

   275     }

   276     //where

   277         protected TreeScanner unenterScanner = new TreeScanner() {

   278             @Override

   279             public void visitClassDef(JCClassDecl tree) {

   280                 ClassSymbol csym = tree.sym;

   281                 enter.typeEnvs.remove(csym);

   282                 chk.compiled.remove(csym.flatname);

   283                 syms.classes.remove(csym.flatname);

   284                 super.visitClassDef(tree);

   285             }

   286         };

   287 

   288     /**

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

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

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

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

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

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

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

   296      * progressively instantiating all inference variables on which one or more

   297      * deferred attribution node is stuck.

   298      */

   299     class DeferredAttrContext {

   300 

   301         /** attribution mode */

   302         final AttrMode mode;

   303 

   304         /** symbol of the method being checked */

   305         final Symbol msym;

   306 

   307         /** method resolution step */

   308         final Resolve.MethodResolutionPhase phase;

   309 

   310         /** inference context */

   311         final InferenceContext inferenceContext;

   312 

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

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

   315 

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

   317             this.mode = mode;

   318             this.msym = msym;

   319             this.phase = phase;

   320             this.inferenceContext = inferenceContext;

   321         }

   322 

   323         /**

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

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

   326          */

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

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

   329         }

   330 

   331         /**

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

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

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

   335          * can be type-checked.

   336          */

   337         void complete() {

   338             while (!deferredAttrNodes.isEmpty()) {

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

   340                 boolean progress = false;

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

   342                 //attribution round can add new nodes to the list

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

   344                     if (!deferredAttrNode.isStuck()) {

   345                         deferredAttrNode.process();

   346                         deferredAttrNodes.remove(deferredAttrNode);

   347                         progress = true;

   348                     } else {

   349                         stuckVars.addAll(deferredAttrNode.stuckVars);

   350                     }

   351                 }

   352                 if (!progress) {

   353                     //remove all variables that have already been instantiated

   354                     //from the list of stuck variables

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

   356                     inferenceContext.notifyChange(types);

   357                 }

   358             }

   359         }

   360 

   361         /**

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

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

   364          */

   365         class DeferredAttrNode implements Infer.InferenceContext.FreeTypeListener {

   366 

   367             /** underlying deferred type */

   368             DeferredType dt;

   369 

   370             /** underlying target type information */

   371             ResultInfo resultInfo;

   372 

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

   374             List<Type> stuckVars;

   375 

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

   377                 this.dt = dt;

   378                 this.resultInfo = resultInfo;

   379                 this.stuckVars = stuckVars;

   380                 if (!stuckVars.isEmpty()) {

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

   382                 }

   383             }

   384 

   385             @Override

   386             public void typesInferred(InferenceContext inferenceContext) {

   387                 stuckVars = List.nil();

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

   389             }

   390 

   391             /**

   392              * is this node stuck?

   393              */

   394             boolean isStuck() {

   395                 return stuckVars.nonEmpty();

   396             }

   397 

   398             /**

   399              * Process a deferred attribution node.

   400              * Invariant: a stuck node cannot be processed.

   401              */

   402             void process() {

   403                 if (isStuck()) {

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

   405                 }

   406                 dt.check(resultInfo);

   407             }

   408         }

   409     }

   410 

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

   412     final DeferredAttrContext emptyDeferredAttrContext =

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

   414                 @Override

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

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

   417                 }

   418                 @Override

   419                 void complete() {

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

   421                 }

   422             };

   423 

   424     /**

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

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

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

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

   429      */

   430     class DeferredTypeMap extends Type.Mapping {

   431 

   432         DeferredAttrContext deferredAttrContext;

   433 

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

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

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

   437         }

   438 

   439         protected boolean validState(DeferredType dt) {

   440             return dt.mode != null &&

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

   442         }

   443 

   444         @Override

   445         public Type apply(Type t) {

   446             if (t.tag != DEFERRED) {

   447                 return t.map(this);

   448             } else {

   449                 DeferredType dt = (DeferredType)t;

   450                 Assert.check(validState(dt));

   451                 return typeOf(dt);

   452             }

   453         }

   454 

   455         protected Type typeOf(DeferredType dt) {

   456             switch (deferredAttrContext.mode) {

   457                 case CHECK:

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

   459                 case SPECULATIVE:

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

   461             }

   462             Assert.error();

   463             return null;

   464         }

   465     }

   466 

   467     /**

   468      * Specialized recovery deferred mapping.

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

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

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

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

   473      */

   474     public class RecoveryDeferredTypeMap extends DeferredTypeMap {

   475 

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

   477             super(mode, msym, phase);

   478         }

   479 

   480         @Override

   481         protected Type typeOf(DeferredType dt) {

   482             Type owntype = super.typeOf(dt);

   483             return owntype.tag == NONE ?

   484                         recover(dt) : owntype;

   485         }

   486 

   487         @Override

   488         protected boolean validState(DeferredType dt) {

   489             return true;

   490         }

   491 

   492         /**

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

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

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

   496          * representation. Remaining deferred types are attributed using

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

   498          */

   499         private Type recover(DeferredType dt) {

   500             dt.check(new RecoveryInfo());

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

   502                 case LAMBDA:

   503                 case REFERENCE:

   504                 case CONDEXPR:

   505                     //propagate those deferred types to the

   506                     //diagnostic formatter

   507                     return dt;

   508                 default:

   509                     return super.apply(dt);

   510             }

   511         }

   512 

   513         class RecoveryInfo extends ResultInfo {

   514 

   515             public RecoveryInfo() {

   516                 attr.super(Kinds.VAL, Type.recoveryType, new Check.NestedCheckContext(chk.basicHandler) {

   517                     @Override

   518                     public DeferredAttrContext deferredAttrContext() {

   519                         return deferredAttrContext;

   520                     }

   521                     @Override

   522                     public boolean compatible(Type found, Type req, Warner warn) {

   523                         return true;

   524                     }

   525                     @Override

   526                     public void report(DiagnosticPosition pos, JCDiagnostic details) {

   527                         //do nothing

   528                     }

   529                 });

   530             }

   531 

   532             @Override

   533             protected Type check(DiagnosticPosition pos, Type found) {

   534                 return chk.checkNonVoid(pos, super.check(pos, found));

   535             }

   536         }

   537     }

   538 

   539     /**

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

   541      * an AST node can be type-checked

   542      */

   543     @SuppressWarnings("fallthrough")

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

   545         switch (tree.getTag()) {

   546             case LAMBDA:

   547             case REFERENCE:

   548                 Assert.error("not supported yet");

   549             default:

   550                 return List.nil();

   551         }

   552     }

   553 }