Mon, 21 Jan 2013 20:13:56 +0000
8005244: Implement overload resolution as per latest spec EDR
Summary: Add support for stuck expressions and provisional applicability
Reviewed-by: jjg
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 Log log;
72 final Symtab syms;
73 final TreeMaker make;
74 final Types types;
76 public static DeferredAttr instance(Context context) {
77 DeferredAttr instance = context.get(deferredAttrKey);
78 if (instance == null)
79 instance = new DeferredAttr(context);
80 return instance;
81 }
83 protected DeferredAttr(Context context) {
84 context.put(deferredAttrKey, this);
85 attr = Attr.instance(context);
86 chk = Check.instance(context);
87 diags = JCDiagnostic.Factory.instance(context);
88 enter = Enter.instance(context);
89 infer = Infer.instance(context);
90 log = Log.instance(context);
91 syms = Symtab.instance(context);
92 make = TreeMaker.instance(context);
93 types = Types.instance(context);
94 Names names = Names.instance(context);
95 stuckTree = make.Ident(names.empty).setType(Type.noType);
96 }
98 /** shared tree for stuck expressions */
99 final JCTree stuckTree;
101 /**
102 * This type represents a deferred type. A deferred type starts off with
103 * no information on the underlying expression type. Such info needs to be
104 * discovered through type-checking the deferred type against a target-type.
105 * Every deferred type keeps a pointer to the AST node from which it originated.
106 */
107 public class DeferredType extends Type {
109 public JCExpression tree;
110 Env<AttrContext> env;
111 AttrMode mode;
112 SpeculativeCache speculativeCache;
114 DeferredType(JCExpression tree, Env<AttrContext> env) {
115 super(DEFERRED, null);
116 this.tree = tree;
117 this.env = env.dup(tree, env.info.dup());
118 this.speculativeCache = new SpeculativeCache();
119 }
121 /**
122 * A speculative cache is used to keep track of all overload resolution rounds
123 * that triggered speculative attribution on a given deferred type. Each entry
124 * stores a pointer to the speculative tree and the resolution phase in which the entry
125 * has been added.
126 */
127 class SpeculativeCache {
129 private Map<Symbol, List<Entry>> cache =
130 new WeakHashMap<Symbol, List<Entry>>();
132 class Entry {
133 JCTree speculativeTree;
134 Resolve.MethodResolutionPhase phase;
136 public Entry(JCTree speculativeTree, MethodResolutionPhase phase) {
137 this.speculativeTree = speculativeTree;
138 this.phase = phase;
139 }
141 boolean matches(Resolve.MethodResolutionPhase phase) {
142 return this.phase == phase;
143 }
144 }
146 /**
147 * Retrieve a speculative cache entry corresponding to given symbol
148 * and resolution phase
149 */
150 Entry get(Symbol msym, MethodResolutionPhase phase) {
151 List<Entry> entries = cache.get(msym);
152 if (entries == null) return null;
153 for (Entry e : entries) {
154 if (e.matches(phase)) return e;
155 }
156 return null;
157 }
159 /**
160 * Stores a speculative cache entry corresponding to given symbol
161 * and resolution phase
162 */
163 void put(Symbol msym, JCTree speculativeTree, MethodResolutionPhase phase) {
164 List<Entry> entries = cache.get(msym);
165 if (entries == null) {
166 entries = List.nil();
167 }
168 cache.put(msym, entries.prepend(new Entry(speculativeTree, phase)));
169 }
170 }
172 /**
173 * Get the type that has been computed during a speculative attribution round
174 */
175 Type speculativeType(Symbol msym, MethodResolutionPhase phase) {
176 SpeculativeCache.Entry e = speculativeCache.get(msym, phase);
177 return e != null ? e.speculativeTree.type : Type.noType;
178 }
180 /**
181 * Check a deferred type against a potential target-type. Depending on
182 * the current attribution mode, a normal vs. speculative attribution
183 * round is performed on the underlying AST node. There can be only one
184 * speculative round for a given target method symbol; moreover, a normal
185 * attribution round must follow one or more speculative rounds.
186 */
187 Type check(ResultInfo resultInfo) {
188 return check(resultInfo, stuckVars(tree, env, resultInfo), basicCompleter);
189 }
191 Type check(ResultInfo resultInfo, List<Type> stuckVars, DeferredTypeCompleter deferredTypeCompleter) {
192 DeferredAttrContext deferredAttrContext =
193 resultInfo.checkContext.deferredAttrContext();
194 Assert.check(deferredAttrContext != emptyDeferredAttrContext);
195 if (stuckVars.nonEmpty()) {
196 deferredAttrContext.addDeferredAttrNode(this, resultInfo, stuckVars);
197 return Type.noType;
198 } else {
199 try {
200 return deferredTypeCompleter.complete(this, resultInfo, deferredAttrContext);
201 } finally {
202 mode = deferredAttrContext.mode;
203 }
204 }
205 }
206 }
208 /**
209 * A completer for deferred types. Defines an entry point for type-checking
210 * a deferred type.
211 */
212 interface DeferredTypeCompleter {
213 /**
214 * Entry point for type-checking a deferred type. Depending on the
215 * circumstances, type-checking could amount to full attribution
216 * or partial structural check (aka potential applicability).
217 */
218 Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext);
219 }
221 /**
222 * A basic completer for deferred types. This completer type-checks a deferred type
223 * using attribution; depending on the attribution mode, this could be either standard
224 * or speculative attribution.
225 */
226 DeferredTypeCompleter basicCompleter = new DeferredTypeCompleter() {
227 public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
228 switch (deferredAttrContext.mode) {
229 case SPECULATIVE:
230 Assert.check(dt.mode == null ||
231 (dt.mode == AttrMode.SPECULATIVE &&
232 dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase).hasTag(NONE)));
233 JCTree speculativeTree = attribSpeculative(dt.tree, dt.env, resultInfo);
234 dt.speculativeCache.put(deferredAttrContext.msym, speculativeTree, deferredAttrContext.phase);
235 return speculativeTree.type;
236 case CHECK:
237 Assert.check(dt.mode == AttrMode.SPECULATIVE);
238 return attr.attribTree(dt.tree, dt.env, resultInfo);
239 }
240 Assert.error();
241 return null;
242 }
243 };
245 /**
246 * The 'mode' in which the deferred type is to be type-checked
247 */
248 public enum AttrMode {
249 /**
250 * A speculative type-checking round is used during overload resolution
251 * mainly to generate constraints on inference variables. Side-effects
252 * arising from type-checking the expression associated with the deferred
253 * type are reversed after the speculative round finishes. This means the
254 * expression tree will be left in a blank state.
255 */
256 SPECULATIVE,
257 /**
258 * This is the plain type-checking mode. Produces side-effects on the underlying AST node
259 */
260 CHECK;
261 }
263 /**
264 * Routine that performs speculative type-checking; the input AST node is
265 * cloned (to avoid side-effects cause by Attr) and compiler state is
266 * restored after type-checking. All diagnostics (but critical ones) are
267 * disabled during speculative type-checking.
268 */
269 JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {
270 JCTree newTree = new TreeCopier<Object>(make).copy(tree);
271 Env<AttrContext> speculativeEnv = env.dup(newTree, env.info.dup(env.info.scope.dupUnshared()));
272 speculativeEnv.info.scope.owner = env.info.scope.owner;
273 final JavaFileObject currentSource = log.currentSourceFile();
274 Log.DeferredDiagnosticHandler deferredDiagnosticHandler =
275 new Log.DeferredDiagnosticHandler(log, new Filter<JCDiagnostic>() {
276 public boolean accepts(JCDiagnostic t) {
277 return t.getDiagnosticSource().getFile().equals(currentSource);
278 }
279 });
280 try {
281 attr.attribTree(newTree, speculativeEnv, resultInfo);
282 unenterScanner.scan(newTree);
283 return newTree;
284 } catch (Abort ex) {
285 //if some very bad condition occurred during deferred attribution
286 //we should dump all errors before killing javac
287 deferredDiagnosticHandler.reportDeferredDiagnostics();
288 throw ex;
289 } finally {
290 unenterScanner.scan(newTree);
291 log.popDiagnosticHandler(deferredDiagnosticHandler);
292 }
293 }
294 //where
295 protected TreeScanner unenterScanner = new TreeScanner() {
296 @Override
297 public void visitClassDef(JCClassDecl tree) {
298 ClassSymbol csym = tree.sym;
299 //if something went wrong during method applicability check
300 //it is possible that nested expressions inside argument expression
301 //are left unchecked - in such cases there's nothing to clean up.
302 if (csym == null) return;
303 enter.typeEnvs.remove(csym);
304 chk.compiled.remove(csym.flatname);
305 syms.classes.remove(csym.flatname);
306 super.visitClassDef(tree);
307 }
308 };
310 /**
311 * A deferred context is created on each method check. A deferred context is
312 * used to keep track of information associated with the method check, such as
313 * the symbol of the method being checked, the overload resolution phase,
314 * the kind of attribution mode to be applied to deferred types and so forth.
315 * As deferred types are processed (by the method check routine) stuck AST nodes
316 * are added (as new deferred attribution nodes) to this context. The complete()
317 * routine makes sure that all pending nodes are properly processed, by
318 * progressively instantiating all inference variables on which one or more
319 * deferred attribution node is stuck.
320 */
321 class DeferredAttrContext {
323 /** attribution mode */
324 final AttrMode mode;
326 /** symbol of the method being checked */
327 final Symbol msym;
329 /** method resolution step */
330 final Resolve.MethodResolutionPhase phase;
332 /** inference context */
333 final InferenceContext inferenceContext;
335 /** list of deferred attribution nodes to be processed */
336 ArrayList<DeferredAttrNode> deferredAttrNodes = new ArrayList<DeferredAttrNode>();
338 DeferredAttrContext(AttrMode mode, Symbol msym, MethodResolutionPhase phase, InferenceContext inferenceContext) {
339 this.mode = mode;
340 this.msym = msym;
341 this.phase = phase;
342 this.inferenceContext = inferenceContext;
343 }
345 /**
346 * Adds a node to the list of deferred attribution nodes - used by Resolve.rawCheckArgumentsApplicable
347 * Nodes added this way act as 'roots' for the out-of-order method checking process.
348 */
349 void addDeferredAttrNode(final DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {
350 deferredAttrNodes.add(new DeferredAttrNode(dt, resultInfo, stuckVars));
351 }
353 /**
354 * Incrementally process all nodes, by skipping 'stuck' nodes and attributing
355 * 'unstuck' ones. If at any point no progress can be made (no 'unstuck' nodes)
356 * some inference variable might get eagerly instantiated so that all nodes
357 * can be type-checked.
358 */
359 void complete() {
360 while (!deferredAttrNodes.isEmpty()) {
361 Set<Type> stuckVars = new LinkedHashSet<Type>();
362 boolean progress = false;
363 //scan a defensive copy of the node list - this is because a deferred
364 //attribution round can add new nodes to the list
365 for (DeferredAttrNode deferredAttrNode : List.from(deferredAttrNodes)) {
366 if (!deferredAttrNode.process()) {
367 stuckVars.addAll(deferredAttrNode.stuckVars);
368 } else {
369 deferredAttrNodes.remove(deferredAttrNode);
370 progress = true;
371 }
372 }
373 if (!progress) {
374 //remove all variables that have already been instantiated
375 //from the list of stuck variables
376 inferenceContext.solveAny(inferenceContext.freeVarsIn(List.from(stuckVars)), types, infer);
377 inferenceContext.notifyChange(types);
378 }
379 }
380 }
382 /**
383 * Class representing a deferred attribution node. It keeps track of
384 * a deferred type, along with the expected target type information.
385 */
386 class DeferredAttrNode implements Infer.InferenceContext.FreeTypeListener {
388 /** underlying deferred type */
389 DeferredType dt;
391 /** underlying target type information */
392 ResultInfo resultInfo;
394 /** list of uninferred inference variables causing this node to be stuck */
395 List<Type> stuckVars;
397 DeferredAttrNode(DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {
398 this.dt = dt;
399 this.resultInfo = resultInfo;
400 this.stuckVars = stuckVars;
401 if (!stuckVars.isEmpty()) {
402 resultInfo.checkContext.inferenceContext().addFreeTypeListener(stuckVars, this);
403 }
404 }
406 @Override
407 public void typesInferred(InferenceContext inferenceContext) {
408 stuckVars = List.nil();
409 resultInfo = resultInfo.dup(inferenceContext.asInstType(resultInfo.pt, types));
410 }
412 /**
413 * Process a deferred attribution node.
414 * Invariant: a stuck node cannot be processed.
415 */
416 @SuppressWarnings("fallthrough")
417 boolean process() {
418 switch (mode) {
419 case SPECULATIVE:
420 dt.check(resultInfo, List.<Type>nil(), new StructuralStuckChecker());
421 return true;
422 case CHECK:
423 if (stuckVars.nonEmpty()) {
424 return false;
425 } else {
426 dt.check(resultInfo, stuckVars, basicCompleter);
427 return true;
428 }
429 default:
430 throw new AssertionError("Bad mode");
431 }
432 }
434 /**
435 * Structural checker for stuck expressions
436 */
437 class StructuralStuckChecker extends TreeScanner implements DeferredTypeCompleter {
439 ResultInfo resultInfo;
441 public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
442 this.resultInfo = resultInfo;
443 dt.tree.accept(this);
444 dt.speculativeCache.put(msym, stuckTree, phase);
445 return Type.noType;
446 }
448 @Override
449 public void visitLambda(JCLambda tree) {
450 Check.CheckContext checkContext = resultInfo.checkContext;
451 Type pt = resultInfo.pt;
452 if (inferenceContext.inferencevars.contains(pt)) {
453 //ok
454 return;
455 } else {
456 //must be a functional descriptor
457 try {
458 Type desc = types.findDescriptorType(pt);
459 if (desc.getParameterTypes().length() != tree.params.length()) {
460 checkContext.report(tree, diags.fragment("incompatible.arg.types.in.lambda"));
461 }
462 } catch (Types.FunctionDescriptorLookupError ex) {
463 checkContext.report(null, ex.getDiagnostic());
464 }
465 }
466 }
468 @Override
469 public void visitNewClass(JCNewClass tree) {
470 //do nothing
471 }
473 @Override
474 public void visitApply(JCMethodInvocation tree) {
475 //do nothing
476 }
478 @Override
479 public void visitReference(JCMemberReference tree) {
480 Check.CheckContext checkContext = resultInfo.checkContext;
481 Type pt = resultInfo.pt;
482 if (inferenceContext.inferencevars.contains(pt)) {
483 //ok
484 return;
485 } else {
486 try {
487 //TODO: we should speculative determine if there's a match
488 //based on arity - if yes, method is applicable.
489 types.findDescriptorType(pt);
490 } catch (Types.FunctionDescriptorLookupError ex) {
491 checkContext.report(null, ex.getDiagnostic());
492 }
493 }
494 }
495 }
496 }
497 }
499 /** an empty deferred attribution context - all methods throw exceptions */
500 final DeferredAttrContext emptyDeferredAttrContext =
501 new DeferredAttrContext(AttrMode.CHECK, null, MethodResolutionPhase.BOX, null) {
502 @Override
503 void addDeferredAttrNode(DeferredType dt, ResultInfo ri, List<Type> stuckVars) {
504 Assert.error("Empty deferred context!");
505 }
506 @Override
507 void complete() {
508 Assert.error("Empty deferred context!");
509 }
510 };
512 /**
513 * Map a list of types possibly containing one or more deferred types
514 * into a list of ordinary types. Each deferred type D is mapped into a type T,
515 * where T is computed by retrieving the type that has already been
516 * computed for D during a previous deferred attribution round of the given kind.
517 */
518 class DeferredTypeMap extends Type.Mapping {
520 DeferredAttrContext deferredAttrContext;
522 protected DeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
523 super(String.format("deferredTypeMap[%s]", mode));
524 this.deferredAttrContext = new DeferredAttrContext(mode, msym, phase, infer.emptyContext);
525 }
527 protected boolean validState(DeferredType dt) {
528 return dt.mode != null &&
529 deferredAttrContext.mode.ordinal() <= dt.mode.ordinal();
530 }
532 @Override
533 public Type apply(Type t) {
534 if (!t.hasTag(DEFERRED)) {
535 return t.map(this);
536 } else {
537 DeferredType dt = (DeferredType)t;
538 Assert.check(validState(dt));
539 return typeOf(dt);
540 }
541 }
543 protected Type typeOf(DeferredType dt) {
544 switch (deferredAttrContext.mode) {
545 case CHECK:
546 return dt.tree.type == null ? Type.noType : dt.tree.type;
547 case SPECULATIVE:
548 return dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase);
549 }
550 Assert.error();
551 return null;
552 }
553 }
555 /**
556 * Specialized recovery deferred mapping.
557 * Each deferred type D is mapped into a type T, where T is computed either by
558 * (i) retrieving the type that has already been computed for D during a previous
559 * attribution round (as before), or (ii) by synthesizing a new type R for D
560 * (the latter step is useful in a recovery scenario).
561 */
562 public class RecoveryDeferredTypeMap extends DeferredTypeMap {
564 public RecoveryDeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
565 super(mode, msym, phase != null ? phase : MethodResolutionPhase.BOX);
566 }
568 @Override
569 protected Type typeOf(DeferredType dt) {
570 Type owntype = super.typeOf(dt);
571 return owntype == Type.noType ?
572 recover(dt) : owntype;
573 }
575 @Override
576 protected boolean validState(DeferredType dt) {
577 return true;
578 }
580 /**
581 * Synthesize a type for a deferred type that hasn't been previously
582 * reduced to an ordinary type. Functional deferred types and conditionals
583 * are mapped to themselves, in order to have a richer diagnostic
584 * representation. Remaining deferred types are attributed using
585 * a default expected type (j.l.Object).
586 */
587 private Type recover(DeferredType dt) {
588 dt.check(attr.new RecoveryInfo(deferredAttrContext));
589 return super.apply(dt);
590 }
591 }
593 /**
594 * Retrieves the list of inference variables that need to be inferred before
595 * an AST node can be type-checked
596 */
597 @SuppressWarnings("fallthrough")
598 List<Type> stuckVars(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {
599 if (resultInfo.pt.hasTag(NONE) || resultInfo.pt.isErroneous()) {
600 return List.nil();
601 } else {
602 return stuckVarsInternal(tree, resultInfo.pt, resultInfo.checkContext.inferenceContext());
603 }
604 }
605 //where
606 private List<Type> stuckVarsInternal(JCTree tree, Type pt, Infer.InferenceContext inferenceContext) {
607 StuckChecker sc = new StuckChecker(pt, inferenceContext);
608 sc.scan(tree);
609 return List.from(sc.stuckVars);
610 }
612 /**
613 * A special tree scanner that would only visit portions of a given tree.
614 * The set of nodes visited by the scanner can be customized at construction-time.
615 */
616 abstract static class FilterScanner extends TreeScanner {
618 final Filter<JCTree> treeFilter;
620 FilterScanner(final Set<JCTree.Tag> validTags) {
621 this.treeFilter = new Filter<JCTree>() {
622 public boolean accepts(JCTree t) {
623 return validTags.contains(t.getTag());
624 }
625 };
626 }
628 @Override
629 public void scan(JCTree tree) {
630 if (tree != null) {
631 if (treeFilter.accepts(tree)) {
632 super.scan(tree);
633 } else {
634 skip(tree);
635 }
636 }
637 }
639 /**
640 * handler that is executed when a node has been discarded
641 */
642 abstract void skip(JCTree tree);
643 }
645 /**
646 * A tree scanner suitable for visiting the target-type dependent nodes of
647 * a given argument expression.
648 */
649 static class PolyScanner extends FilterScanner {
651 PolyScanner() {
652 super(EnumSet.of(CONDEXPR, PARENS, LAMBDA, REFERENCE));
653 }
655 @Override
656 void skip(JCTree tree) {
657 //do nothing
658 }
659 }
661 /**
662 * A tree scanner suitable for visiting the target-type dependent nodes nested
663 * within a lambda expression body.
664 */
665 static class LambdaReturnScanner extends FilterScanner {
667 LambdaReturnScanner() {
668 super(EnumSet.of(BLOCK, CASE, CATCH, DOLOOP, FOREACHLOOP,
669 FORLOOP, RETURN, SYNCHRONIZED, SWITCH, TRY, WHILELOOP));
670 }
672 @Override
673 void skip(JCTree tree) {
674 //do nothing
675 }
676 }
678 /**
679 * This visitor is used to check that structural expressions conform
680 * to their target - this step is required as inference could end up
681 * inferring types that make some of the nested expressions incompatible
682 * with their corresponding instantiated target
683 */
684 class StuckChecker extends PolyScanner {
686 Type pt;
687 Infer.InferenceContext inferenceContext;
688 Set<Type> stuckVars = new LinkedHashSet<Type>();
690 StuckChecker(Type pt, Infer.InferenceContext inferenceContext) {
691 this.pt = pt;
692 this.inferenceContext = inferenceContext;
693 }
695 @Override
696 public void visitLambda(JCLambda tree) {
697 if (inferenceContext.inferenceVars().contains(pt)) {
698 stuckVars.add(pt);
699 }
700 if (!types.isFunctionalInterface(pt)) {
701 return;
702 }
703 Type descType = types.findDescriptorType(pt);
704 List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());
705 if (tree.paramKind == JCLambda.ParameterKind.IMPLICIT &&
706 freeArgVars.nonEmpty()) {
707 stuckVars.addAll(freeArgVars);
708 }
709 scanLambdaBody(tree, descType.getReturnType());
710 }
712 @Override
713 public void visitReference(JCMemberReference tree) {
714 scan(tree.expr);
715 if (inferenceContext.inferenceVars().contains(pt)) {
716 stuckVars.add(pt);
717 return;
718 }
719 if (!types.isFunctionalInterface(pt)) {
720 return;
721 }
723 Type descType = types.findDescriptorType(pt);
724 List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());
725 stuckVars.addAll(freeArgVars);
726 }
728 void scanLambdaBody(JCLambda lambda, final Type pt) {
729 if (lambda.getBodyKind() == JCTree.JCLambda.BodyKind.EXPRESSION) {
730 stuckVars.addAll(stuckVarsInternal(lambda.body, pt, inferenceContext));
731 } else {
732 LambdaReturnScanner lambdaScanner = new LambdaReturnScanner() {
733 @Override
734 public void visitReturn(JCReturn tree) {
735 if (tree.expr != null) {
736 stuckVars.addAll(stuckVarsInternal(tree.expr, pt, inferenceContext));
737 }
738 }
739 };
740 lambdaScanner.scan(lambda.body);
741 }
742 }
743 }
744 }