Tue, 05 Mar 2013 14:19:49 +0000
8009129: Illegal access error when calling method reference
Summary: Javac generates method handle referencing non public type
Reviewed-by: jjg, rfield
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 */
26 package com.sun.tools.javac.comp;
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.*;
38 import javax.tools.JavaFileObject;
40 import java.util.ArrayList;
41 import java.util.EnumSet;
42 import java.util.LinkedHashSet;
43 import java.util.Map;
44 import java.util.Queue;
45 import java.util.Set;
46 import java.util.WeakHashMap;
48 import static com.sun.tools.javac.code.TypeTag.*;
49 import static com.sun.tools.javac.tree.JCTree.Tag.*;
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>();
66 final Attr attr;
67 final Check chk;
68 final JCDiagnostic.Factory diags;
69 final Enter enter;
70 final Infer infer;
71 final Resolve rs;
72 final Log log;
73 final Symtab syms;
74 final TreeMaker make;
75 final Types types;
77 public static DeferredAttr instance(Context context) {
78 DeferredAttr instance = context.get(deferredAttrKey);
79 if (instance == null)
80 instance = new DeferredAttr(context);
81 return instance;
82 }
84 protected DeferredAttr(Context context) {
85 context.put(deferredAttrKey, this);
86 attr = Attr.instance(context);
87 chk = Check.instance(context);
88 diags = JCDiagnostic.Factory.instance(context);
89 enter = Enter.instance(context);
90 infer = Infer.instance(context);
91 rs = Resolve.instance(context);
92 log = Log.instance(context);
93 syms = Symtab.instance(context);
94 make = TreeMaker.instance(context);
95 types = Types.instance(context);
96 Names names = Names.instance(context);
97 stuckTree = make.Ident(names.empty).setType(Type.noType);
98 }
100 /** shared tree for stuck expressions */
101 final JCTree stuckTree;
103 /**
104 * This type represents a deferred type. A deferred type starts off with
105 * no information on the underlying expression type. Such info needs to be
106 * discovered through type-checking the deferred type against a target-type.
107 * Every deferred type keeps a pointer to the AST node from which it originated.
108 */
109 public class DeferredType extends Type {
111 public JCExpression tree;
112 Env<AttrContext> env;
113 AttrMode mode;
114 SpeculativeCache speculativeCache;
116 DeferredType(JCExpression tree, Env<AttrContext> env) {
117 super(DEFERRED, null);
118 this.tree = tree;
119 this.env = env.dup(tree, env.info.dup());
120 this.speculativeCache = new SpeculativeCache();
121 }
123 /**
124 * A speculative cache is used to keep track of all overload resolution rounds
125 * that triggered speculative attribution on a given deferred type. Each entry
126 * stores a pointer to the speculative tree and the resolution phase in which the entry
127 * has been added.
128 */
129 class SpeculativeCache {
131 private Map<Symbol, List<Entry>> cache =
132 new WeakHashMap<Symbol, List<Entry>>();
134 class Entry {
135 JCTree speculativeTree;
136 Resolve.MethodResolutionPhase phase;
138 public Entry(JCTree speculativeTree, MethodResolutionPhase phase) {
139 this.speculativeTree = speculativeTree;
140 this.phase = phase;
141 }
143 boolean matches(Resolve.MethodResolutionPhase phase) {
144 return this.phase == phase;
145 }
146 }
148 /**
149 * Retrieve a speculative cache entry corresponding to given symbol
150 * and resolution phase
151 */
152 Entry get(Symbol msym, MethodResolutionPhase phase) {
153 List<Entry> entries = cache.get(msym);
154 if (entries == null) return null;
155 for (Entry e : entries) {
156 if (e.matches(phase)) return e;
157 }
158 return null;
159 }
161 /**
162 * Stores a speculative cache entry corresponding to given symbol
163 * and resolution phase
164 */
165 void put(Symbol msym, JCTree speculativeTree, MethodResolutionPhase phase) {
166 List<Entry> entries = cache.get(msym);
167 if (entries == null) {
168 entries = List.nil();
169 }
170 cache.put(msym, entries.prepend(new Entry(speculativeTree, phase)));
171 }
172 }
174 /**
175 * Get the type that has been computed during a speculative attribution round
176 */
177 Type speculativeType(Symbol msym, MethodResolutionPhase phase) {
178 SpeculativeCache.Entry e = speculativeCache.get(msym, phase);
179 return e != null ? e.speculativeTree.type : Type.noType;
180 }
182 /**
183 * Check a deferred type against a potential target-type. Depending on
184 * the current attribution mode, a normal vs. speculative attribution
185 * round is performed on the underlying AST node. There can be only one
186 * speculative round for a given target method symbol; moreover, a normal
187 * attribution round must follow one or more speculative rounds.
188 */
189 Type check(ResultInfo resultInfo) {
190 return check(resultInfo, stuckVars(tree, env, resultInfo), basicCompleter);
191 }
193 Type check(ResultInfo resultInfo, List<Type> stuckVars, DeferredTypeCompleter deferredTypeCompleter) {
194 DeferredAttrContext deferredAttrContext =
195 resultInfo.checkContext.deferredAttrContext();
196 Assert.check(deferredAttrContext != emptyDeferredAttrContext);
197 if (stuckVars.nonEmpty()) {
198 deferredAttrContext.addDeferredAttrNode(this, resultInfo, stuckVars);
199 return Type.noType;
200 } else {
201 try {
202 return deferredTypeCompleter.complete(this, resultInfo, deferredAttrContext);
203 } finally {
204 mode = deferredAttrContext.mode;
205 }
206 }
207 }
208 }
210 /**
211 * A completer for deferred types. Defines an entry point for type-checking
212 * a deferred type.
213 */
214 interface DeferredTypeCompleter {
215 /**
216 * Entry point for type-checking a deferred type. Depending on the
217 * circumstances, type-checking could amount to full attribution
218 * or partial structural check (aka potential applicability).
219 */
220 Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext);
221 }
223 /**
224 * A basic completer for deferred types. This completer type-checks a deferred type
225 * using attribution; depending on the attribution mode, this could be either standard
226 * or speculative attribution.
227 */
228 DeferredTypeCompleter basicCompleter = new DeferredTypeCompleter() {
229 public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
230 switch (deferredAttrContext.mode) {
231 case SPECULATIVE:
232 Assert.check(dt.mode == null ||
233 (dt.mode == AttrMode.SPECULATIVE &&
234 dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase).hasTag(NONE)));
235 JCTree speculativeTree = attribSpeculative(dt.tree, dt.env, resultInfo);
236 dt.speculativeCache.put(deferredAttrContext.msym, speculativeTree, deferredAttrContext.phase);
237 return speculativeTree.type;
238 case CHECK:
239 Assert.check(dt.mode != null);
240 return attr.attribTree(dt.tree, dt.env, resultInfo);
241 }
242 Assert.error();
243 return null;
244 }
245 };
247 DeferredTypeCompleter dummyCompleter = new DeferredTypeCompleter() {
248 public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
249 Assert.check(deferredAttrContext.mode == AttrMode.CHECK);
250 return dt.tree.type = Type.noType;
251 }
252 };
254 /**
255 * The 'mode' in which the deferred type is to be type-checked
256 */
257 public enum AttrMode {
258 /**
259 * A speculative type-checking round is used during overload resolution
260 * mainly to generate constraints on inference variables. Side-effects
261 * arising from type-checking the expression associated with the deferred
262 * type are reversed after the speculative round finishes. This means the
263 * expression tree will be left in a blank state.
264 */
265 SPECULATIVE,
266 /**
267 * This is the plain type-checking mode. Produces side-effects on the underlying AST node
268 */
269 CHECK;
270 }
272 /**
273 * Routine that performs speculative type-checking; the input AST node is
274 * cloned (to avoid side-effects cause by Attr) and compiler state is
275 * restored after type-checking. All diagnostics (but critical ones) are
276 * disabled during speculative type-checking.
277 */
278 JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {
279 final JCTree newTree = new TreeCopier<Object>(make).copy(tree);
280 Env<AttrContext> speculativeEnv = env.dup(newTree, env.info.dup(env.info.scope.dupUnshared()));
281 speculativeEnv.info.scope.owner = env.info.scope.owner;
282 Log.DeferredDiagnosticHandler deferredDiagnosticHandler =
283 new Log.DeferredDiagnosticHandler(log, new Filter<JCDiagnostic>() {
284 public boolean accepts(final JCDiagnostic d) {
285 class PosScanner extends TreeScanner {
286 boolean found = false;
288 @Override
289 public void scan(JCTree tree) {
290 if (tree != null &&
291 tree.pos() == d.getDiagnosticPosition()) {
292 found = true;
293 }
294 super.scan(tree);
295 }
296 };
297 PosScanner posScanner = new PosScanner();
298 posScanner.scan(newTree);
299 return posScanner.found;
300 }
301 });
302 try {
303 attr.attribTree(newTree, speculativeEnv, resultInfo);
304 unenterScanner.scan(newTree);
305 return newTree;
306 } finally {
307 unenterScanner.scan(newTree);
308 log.popDiagnosticHandler(deferredDiagnosticHandler);
309 }
310 }
311 //where
312 protected TreeScanner unenterScanner = new TreeScanner() {
313 @Override
314 public void visitClassDef(JCClassDecl tree) {
315 ClassSymbol csym = tree.sym;
316 //if something went wrong during method applicability check
317 //it is possible that nested expressions inside argument expression
318 //are left unchecked - in such cases there's nothing to clean up.
319 if (csym == null) return;
320 enter.typeEnvs.remove(csym);
321 chk.compiled.remove(csym.flatname);
322 syms.classes.remove(csym.flatname);
323 super.visitClassDef(tree);
324 }
325 };
327 /**
328 * A deferred context is created on each method check. A deferred context is
329 * used to keep track of information associated with the method check, such as
330 * the symbol of the method being checked, the overload resolution phase,
331 * the kind of attribution mode to be applied to deferred types and so forth.
332 * As deferred types are processed (by the method check routine) stuck AST nodes
333 * are added (as new deferred attribution nodes) to this context. The complete()
334 * routine makes sure that all pending nodes are properly processed, by
335 * progressively instantiating all inference variables on which one or more
336 * deferred attribution node is stuck.
337 */
338 class DeferredAttrContext {
340 /** attribution mode */
341 final AttrMode mode;
343 /** symbol of the method being checked */
344 final Symbol msym;
346 /** method resolution step */
347 final Resolve.MethodResolutionPhase phase;
349 /** inference context */
350 final InferenceContext inferenceContext;
352 /** parent deferred context */
353 final DeferredAttrContext parent;
355 /** Warner object to report warnings */
356 final Warner warn;
358 /** list of deferred attribution nodes to be processed */
359 ArrayList<DeferredAttrNode> deferredAttrNodes = new ArrayList<DeferredAttrNode>();
361 DeferredAttrContext(AttrMode mode, Symbol msym, MethodResolutionPhase phase,
362 InferenceContext inferenceContext, DeferredAttrContext parent, Warner warn) {
363 this.mode = mode;
364 this.msym = msym;
365 this.phase = phase;
366 this.parent = parent;
367 this.warn = warn;
368 this.inferenceContext = inferenceContext;
369 }
371 /**
372 * Adds a node to the list of deferred attribution nodes - used by Resolve.rawCheckArgumentsApplicable
373 * Nodes added this way act as 'roots' for the out-of-order method checking process.
374 */
375 void addDeferredAttrNode(final DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {
376 deferredAttrNodes.add(new DeferredAttrNode(dt, resultInfo, stuckVars));
377 }
379 /**
380 * Incrementally process all nodes, by skipping 'stuck' nodes and attributing
381 * 'unstuck' ones. If at any point no progress can be made (no 'unstuck' nodes)
382 * some inference variable might get eagerly instantiated so that all nodes
383 * can be type-checked.
384 */
385 void complete() {
386 while (!deferredAttrNodes.isEmpty()) {
387 Set<Type> stuckVars = new LinkedHashSet<Type>();
388 boolean progress = false;
389 //scan a defensive copy of the node list - this is because a deferred
390 //attribution round can add new nodes to the list
391 for (DeferredAttrNode deferredAttrNode : List.from(deferredAttrNodes)) {
392 if (!deferredAttrNode.process(this)) {
393 stuckVars.addAll(deferredAttrNode.stuckVars);
394 } else {
395 deferredAttrNodes.remove(deferredAttrNode);
396 progress = true;
397 }
398 }
399 if (!progress) {
400 //remove all variables that have already been instantiated
401 //from the list of stuck variables
402 inferenceContext.solveAny(List.from(stuckVars), warn);
403 inferenceContext.notifyChange();
404 }
405 }
406 }
407 }
409 /**
410 * Class representing a deferred attribution node. It keeps track of
411 * a deferred type, along with the expected target type information.
412 */
413 class DeferredAttrNode implements Infer.FreeTypeListener {
415 /** underlying deferred type */
416 DeferredType dt;
418 /** underlying target type information */
419 ResultInfo resultInfo;
421 /** list of uninferred inference variables causing this node to be stuck */
422 List<Type> stuckVars;
424 DeferredAttrNode(DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {
425 this.dt = dt;
426 this.resultInfo = resultInfo;
427 this.stuckVars = stuckVars;
428 if (!stuckVars.isEmpty()) {
429 resultInfo.checkContext.inferenceContext().addFreeTypeListener(stuckVars, this);
430 }
431 }
433 @Override
434 public void typesInferred(InferenceContext inferenceContext) {
435 stuckVars = List.nil();
436 resultInfo = resultInfo.dup(inferenceContext.asInstType(resultInfo.pt));
437 }
439 /**
440 * Process a deferred attribution node.
441 * Invariant: a stuck node cannot be processed.
442 */
443 @SuppressWarnings("fallthrough")
444 boolean process(DeferredAttrContext deferredAttrContext) {
445 switch (deferredAttrContext.mode) {
446 case SPECULATIVE:
447 dt.check(resultInfo, List.<Type>nil(), new StructuralStuckChecker());
448 return true;
449 case CHECK:
450 if (stuckVars.nonEmpty()) {
451 //stuck expression - see if we can propagate
452 if (deferredAttrContext.parent != emptyDeferredAttrContext &&
453 Type.containsAny(deferredAttrContext.parent.inferenceContext.inferencevars, List.from(stuckVars))) {
454 deferredAttrContext.parent.deferredAttrNodes.add(this);
455 dt.check(resultInfo, List.<Type>nil(), dummyCompleter);
456 return true;
457 } else {
458 return false;
459 }
460 } else {
461 dt.check(resultInfo, stuckVars, basicCompleter);
462 return true;
463 }
464 default:
465 throw new AssertionError("Bad mode");
466 }
467 }
469 /**
470 * Structural checker for stuck expressions
471 */
472 class StructuralStuckChecker extends TreeScanner implements DeferredTypeCompleter {
474 ResultInfo resultInfo;
475 InferenceContext inferenceContext;
476 Env<AttrContext> env;
478 public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
479 this.resultInfo = resultInfo;
480 this.inferenceContext = deferredAttrContext.inferenceContext;
481 this.env = dt.env.dup(dt.tree, dt.env.info.dup());
482 dt.tree.accept(this);
483 dt.speculativeCache.put(deferredAttrContext.msym, stuckTree, deferredAttrContext.phase);
484 return Type.noType;
485 }
487 @Override
488 public void visitLambda(JCLambda tree) {
489 Check.CheckContext checkContext = resultInfo.checkContext;
490 Type pt = resultInfo.pt;
491 if (inferenceContext.inferencevars.contains(pt)) {
492 //ok
493 return;
494 } else {
495 //must be a functional descriptor
496 try {
497 Type desc = types.findDescriptorType(pt);
498 if (desc.getParameterTypes().length() != tree.params.length()) {
499 checkContext.report(tree, diags.fragment("incompatible.arg.types.in.lambda"));
500 }
501 } catch (Types.FunctionDescriptorLookupError ex) {
502 checkContext.report(null, ex.getDiagnostic());
503 }
504 }
505 }
507 @Override
508 public void visitNewClass(JCNewClass tree) {
509 //do nothing
510 }
512 @Override
513 public void visitApply(JCMethodInvocation tree) {
514 //do nothing
515 }
517 @Override
518 public void visitReference(JCMemberReference tree) {
519 Check.CheckContext checkContext = resultInfo.checkContext;
520 Type pt = resultInfo.pt;
521 if (inferenceContext.inferencevars.contains(pt)) {
522 //ok
523 return;
524 } else {
525 try {
526 types.findDescriptorType(pt);
527 } catch (Types.FunctionDescriptorLookupError ex) {
528 checkContext.report(null, ex.getDiagnostic());
529 }
530 JCExpression exprTree = (JCExpression)attribSpeculative(tree.getQualifierExpression(), env,
531 attr.memberReferenceQualifierResult(tree));
532 ListBuffer<Type> argtypes = ListBuffer.lb();
533 for (Type t : types.findDescriptorType(pt).getParameterTypes()) {
534 argtypes.append(syms.errType);
535 }
536 JCMemberReference mref2 = new TreeCopier<Void>(make).copy(tree);
537 mref2.expr = exprTree;
538 Pair<Symbol, ?> lookupRes =
539 rs.resolveMemberReference(tree, env, mref2, exprTree.type, tree.name, argtypes.toList(), null, true);
540 switch (lookupRes.fst.kind) {
541 //note: as argtypes are erroneous types, type-errors must
542 //have been caused by arity mismatch
543 case Kinds.ABSENT_MTH:
544 case Kinds.WRONG_MTH:
545 case Kinds.WRONG_MTHS:
546 case Kinds.STATICERR:
547 case Kinds.MISSING_ENCL:
548 checkContext.report(null, diags.fragment("incompatible.arg.types.in.mref"));
549 }
550 }
551 }
552 }
553 }
555 /** an empty deferred attribution context - all methods throw exceptions */
556 final DeferredAttrContext emptyDeferredAttrContext =
557 new DeferredAttrContext(AttrMode.CHECK, null, MethodResolutionPhase.BOX, null, null, null) {
558 @Override
559 void addDeferredAttrNode(DeferredType dt, ResultInfo ri, List<Type> stuckVars) {
560 Assert.error("Empty deferred context!");
561 }
562 @Override
563 void complete() {
564 Assert.error("Empty deferred context!");
565 }
566 };
568 /**
569 * Map a list of types possibly containing one or more deferred types
570 * into a list of ordinary types. Each deferred type D is mapped into a type T,
571 * where T is computed by retrieving the type that has already been
572 * computed for D during a previous deferred attribution round of the given kind.
573 */
574 class DeferredTypeMap extends Type.Mapping {
576 DeferredAttrContext deferredAttrContext;
578 protected DeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
579 super(String.format("deferredTypeMap[%s]", mode));
580 this.deferredAttrContext = new DeferredAttrContext(mode, msym, phase,
581 infer.emptyContext, emptyDeferredAttrContext, types.noWarnings);
582 }
584 protected boolean validState(DeferredType dt) {
585 return dt.mode != null &&
586 deferredAttrContext.mode.ordinal() <= dt.mode.ordinal();
587 }
589 @Override
590 public Type apply(Type t) {
591 if (!t.hasTag(DEFERRED)) {
592 return t.map(this);
593 } else {
594 DeferredType dt = (DeferredType)t;
595 Assert.check(validState(dt));
596 return typeOf(dt);
597 }
598 }
600 protected Type typeOf(DeferredType dt) {
601 switch (deferredAttrContext.mode) {
602 case CHECK:
603 return dt.tree.type == null ? Type.noType : dt.tree.type;
604 case SPECULATIVE:
605 return dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase);
606 }
607 Assert.error();
608 return null;
609 }
610 }
612 /**
613 * Specialized recovery deferred mapping.
614 * Each deferred type D is mapped into a type T, where T is computed either by
615 * (i) retrieving the type that has already been computed for D during a previous
616 * attribution round (as before), or (ii) by synthesizing a new type R for D
617 * (the latter step is useful in a recovery scenario).
618 */
619 public class RecoveryDeferredTypeMap extends DeferredTypeMap {
621 public RecoveryDeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
622 super(mode, msym, phase != null ? phase : MethodResolutionPhase.BOX);
623 }
625 @Override
626 protected Type typeOf(DeferredType dt) {
627 Type owntype = super.typeOf(dt);
628 return owntype == Type.noType ?
629 recover(dt) : owntype;
630 }
632 @Override
633 protected boolean validState(DeferredType dt) {
634 return true;
635 }
637 /**
638 * Synthesize a type for a deferred type that hasn't been previously
639 * reduced to an ordinary type. Functional deferred types and conditionals
640 * are mapped to themselves, in order to have a richer diagnostic
641 * representation. Remaining deferred types are attributed using
642 * a default expected type (j.l.Object).
643 */
644 private Type recover(DeferredType dt) {
645 dt.check(attr.new RecoveryInfo(deferredAttrContext));
646 return super.apply(dt);
647 }
648 }
650 /**
651 * Retrieves the list of inference variables that need to be inferred before
652 * an AST node can be type-checked
653 */
654 @SuppressWarnings("fallthrough")
655 List<Type> stuckVars(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {
656 if (resultInfo.pt.hasTag(NONE) || resultInfo.pt.isErroneous()) {
657 return List.nil();
658 } else {
659 return stuckVarsInternal(tree, resultInfo.pt, resultInfo.checkContext.inferenceContext());
660 }
661 }
662 //where
663 private List<Type> stuckVarsInternal(JCTree tree, Type pt, Infer.InferenceContext inferenceContext) {
664 StuckChecker sc = new StuckChecker(pt, inferenceContext);
665 sc.scan(tree);
666 return List.from(sc.stuckVars);
667 }
669 /**
670 * A special tree scanner that would only visit portions of a given tree.
671 * The set of nodes visited by the scanner can be customized at construction-time.
672 */
673 abstract static class FilterScanner extends TreeScanner {
675 final Filter<JCTree> treeFilter;
677 FilterScanner(final Set<JCTree.Tag> validTags) {
678 this.treeFilter = new Filter<JCTree>() {
679 public boolean accepts(JCTree t) {
680 return validTags.contains(t.getTag());
681 }
682 };
683 }
685 @Override
686 public void scan(JCTree tree) {
687 if (tree != null) {
688 if (treeFilter.accepts(tree)) {
689 super.scan(tree);
690 } else {
691 skip(tree);
692 }
693 }
694 }
696 /**
697 * handler that is executed when a node has been discarded
698 */
699 abstract void skip(JCTree tree);
700 }
702 /**
703 * A tree scanner suitable for visiting the target-type dependent nodes of
704 * a given argument expression.
705 */
706 static class PolyScanner extends FilterScanner {
708 PolyScanner() {
709 super(EnumSet.of(CONDEXPR, PARENS, LAMBDA, REFERENCE));
710 }
712 @Override
713 void skip(JCTree tree) {
714 //do nothing
715 }
716 }
718 /**
719 * A tree scanner suitable for visiting the target-type dependent nodes nested
720 * within a lambda expression body.
721 */
722 static class LambdaReturnScanner extends FilterScanner {
724 LambdaReturnScanner() {
725 super(EnumSet.of(BLOCK, CASE, CATCH, DOLOOP, FOREACHLOOP,
726 FORLOOP, RETURN, SYNCHRONIZED, SWITCH, TRY, WHILELOOP));
727 }
729 @Override
730 void skip(JCTree tree) {
731 //do nothing
732 }
733 }
735 /**
736 * This visitor is used to check that structural expressions conform
737 * to their target - this step is required as inference could end up
738 * inferring types that make some of the nested expressions incompatible
739 * with their corresponding instantiated target
740 */
741 class StuckChecker extends PolyScanner {
743 Type pt;
744 Infer.InferenceContext inferenceContext;
745 Set<Type> stuckVars = new LinkedHashSet<Type>();
747 StuckChecker(Type pt, Infer.InferenceContext inferenceContext) {
748 this.pt = pt;
749 this.inferenceContext = inferenceContext;
750 }
752 @Override
753 public void visitLambda(JCLambda tree) {
754 if (inferenceContext.inferenceVars().contains(pt)) {
755 stuckVars.add(pt);
756 }
757 if (!types.isFunctionalInterface(pt)) {
758 return;
759 }
760 Type descType = types.findDescriptorType(pt);
761 List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());
762 if (tree.paramKind == JCLambda.ParameterKind.IMPLICIT &&
763 freeArgVars.nonEmpty()) {
764 stuckVars.addAll(freeArgVars);
765 }
766 scanLambdaBody(tree, descType.getReturnType());
767 }
769 @Override
770 public void visitReference(JCMemberReference tree) {
771 scan(tree.expr);
772 if (inferenceContext.inferenceVars().contains(pt)) {
773 stuckVars.add(pt);
774 return;
775 }
776 if (!types.isFunctionalInterface(pt)) {
777 return;
778 }
780 Type descType = types.findDescriptorType(pt);
781 List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());
782 stuckVars.addAll(freeArgVars);
783 }
785 void scanLambdaBody(JCLambda lambda, final Type pt) {
786 if (lambda.getBodyKind() == JCTree.JCLambda.BodyKind.EXPRESSION) {
787 stuckVars.addAll(stuckVarsInternal(lambda.body, pt, inferenceContext));
788 } else {
789 LambdaReturnScanner lambdaScanner = new LambdaReturnScanner() {
790 @Override
791 public void visitReturn(JCReturn tree) {
792 if (tree.expr != null) {
793 stuckVars.addAll(stuckVarsInternal(tree.expr, pt, inferenceContext));
794 }
795 }
796 };
797 lambdaScanner.scan(lambda.body);
798 }
799 }
800 }
801 }