Mon, 18 Mar 2013 14:40:32 -0700
8008425: Remove interim new javax.lang.model API for type-annotations
Reviewed-by: darcy
1 /*
2 * Copyright (c) 1999, 2013, 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.tree.JCTree;
29 import com.sun.tools.javac.tree.JCTree.JCTypeCast;
30 import com.sun.tools.javac.tree.TreeInfo;
31 import com.sun.tools.javac.util.*;
32 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
33 import com.sun.tools.javac.util.List;
34 import com.sun.tools.javac.code.*;
35 import com.sun.tools.javac.code.Type.*;
36 import com.sun.tools.javac.code.Type.UndetVar.InferenceBound;
37 import com.sun.tools.javac.code.Symbol.*;
38 import com.sun.tools.javac.comp.DeferredAttr.AttrMode;
39 import com.sun.tools.javac.comp.Infer.GraphSolver.InferenceGraph;
40 import com.sun.tools.javac.comp.Infer.GraphSolver.InferenceGraph.Node;
41 import com.sun.tools.javac.comp.Resolve.InapplicableMethodException;
42 import com.sun.tools.javac.comp.Resolve.VerboseResolutionMode;
44 import java.util.HashMap;
45 import java.util.Map;
46 import java.util.Set;
48 import java.util.ArrayList;
49 import java.util.Collections;
50 import java.util.EnumSet;
51 import java.util.HashSet;
53 import static com.sun.tools.javac.code.TypeTag.*;
55 /** Helper class for type parameter inference, used by the attribution phase.
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 Infer {
63 protected static final Context.Key<Infer> inferKey =
64 new Context.Key<Infer>();
66 Resolve rs;
67 Check chk;
68 Symtab syms;
69 Types types;
70 JCDiagnostic.Factory diags;
71 Log log;
73 /** should the graph solver be used? */
74 boolean allowGraphInference;
76 public static Infer instance(Context context) {
77 Infer instance = context.get(inferKey);
78 if (instance == null)
79 instance = new Infer(context);
80 return instance;
81 }
83 protected Infer(Context context) {
84 context.put(inferKey, this);
86 rs = Resolve.instance(context);
87 chk = Check.instance(context);
88 syms = Symtab.instance(context);
89 types = Types.instance(context);
90 diags = JCDiagnostic.Factory.instance(context);
91 log = Log.instance(context);
92 inferenceException = new InferenceException(diags);
93 Options options = Options.instance(context);
94 allowGraphInference = Source.instance(context).allowGraphInference()
95 && options.isUnset("useLegacyInference");
96 }
98 /** A value for prototypes that admit any type, including polymorphic ones. */
99 public static final Type anyPoly = new Type(NONE, null);
101 /**
102 * This exception class is design to store a list of diagnostics corresponding
103 * to inference errors that can arise during a method applicability check.
104 */
105 public static class InferenceException extends InapplicableMethodException {
106 private static final long serialVersionUID = 0;
108 List<JCDiagnostic> messages = List.nil();
110 InferenceException(JCDiagnostic.Factory diags) {
111 super(diags);
112 }
114 @Override
115 InapplicableMethodException setMessage(JCDiagnostic diag) {
116 messages = messages.append(diag);
117 return this;
118 }
120 @Override
121 public JCDiagnostic getDiagnostic() {
122 return messages.head;
123 }
125 void clear() {
126 messages = List.nil();
127 }
128 }
130 protected final InferenceException inferenceException;
132 // <editor-fold defaultstate="collapsed" desc="Inference routines">
133 /**
134 * Main inference entry point - instantiate a generic method type
135 * using given argument types and (possibly) an expected target-type.
136 */
137 public Type instantiateMethod(Env<AttrContext> env,
138 List<Type> tvars,
139 MethodType mt,
140 Attr.ResultInfo resultInfo,
141 Symbol msym,
142 List<Type> argtypes,
143 boolean allowBoxing,
144 boolean useVarargs,
145 Resolve.MethodResolutionContext resolveContext,
146 Resolve.MethodCheck methodCheck,
147 Warner warn) throws InferenceException {
148 //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
149 final InferenceContext inferenceContext = new InferenceContext(tvars);
150 inferenceException.clear();
151 try {
152 DeferredAttr.DeferredAttrContext deferredAttrContext =
153 resolveContext.deferredAttrContext(msym, inferenceContext, resultInfo, warn);
155 methodCheck.argumentsAcceptable(env, deferredAttrContext,
156 argtypes, mt.getParameterTypes(), warn);
158 if (allowGraphInference &&
159 resultInfo != null &&
160 !warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)) {
161 //inject return constraints earlier
162 checkWithinBounds(inferenceContext, warn); //propagation
163 generateReturnConstraints(resultInfo, mt, inferenceContext);
164 //propagate outwards if needed
165 if (resultInfo.checkContext.inferenceContext().free(resultInfo.pt)) {
166 //propagate inference context outwards and exit
167 inferenceContext.dupTo(resultInfo.checkContext.inferenceContext());
168 deferredAttrContext.complete();
169 return mt;
170 }
171 }
173 deferredAttrContext.complete();
175 // minimize as yet undetermined type variables
176 if (allowGraphInference) {
177 inferenceContext.solve(warn);
178 } else {
179 inferenceContext.solveLegacy(true, warn, LegacyInferenceSteps.EQ_LOWER.steps); //minimizeInst
180 }
182 mt = (MethodType)inferenceContext.asInstType(mt);
184 if (!allowGraphInference &&
185 inferenceContext.restvars().nonEmpty() &&
186 resultInfo != null &&
187 !warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)) {
188 generateReturnConstraints(resultInfo, mt, inferenceContext);
189 inferenceContext.solveLegacy(false, warn, LegacyInferenceSteps.EQ_UPPER.steps); //maximizeInst
190 mt = (MethodType)inferenceContext.asInstType(mt);
191 }
193 if (resultInfo != null && rs.verboseResolutionMode.contains(VerboseResolutionMode.DEFERRED_INST)) {
194 log.note(env.tree.pos, "deferred.method.inst", msym, mt, resultInfo.pt);
195 }
197 // return instantiated version of method type
198 return mt;
199 } finally {
200 if (resultInfo != null || !allowGraphInference) {
201 inferenceContext.notifyChange();
202 } else {
203 inferenceContext.notifyChange(inferenceContext.boundedVars());
204 }
205 }
206 }
208 /**
209 * Generate constraints from the generic method's return type. If the method
210 * call occurs in a context where a type T is expected, use the expected
211 * type to derive more constraints on the generic method inference variables.
212 */
213 void generateReturnConstraints(Attr.ResultInfo resultInfo,
214 MethodType mt, InferenceContext inferenceContext) {
215 Type qtype1 = inferenceContext.asFree(mt.getReturnType());
216 Type to = returnConstraintTarget(qtype1, resultInfo.pt);
217 Assert.check(allowGraphInference || !resultInfo.checkContext.inferenceContext().free(to),
218 "legacy inference engine cannot handle constraints on both sides of a subtyping assertion");
219 //we need to skip capture?
220 Warner retWarn = new Warner();
221 if (!resultInfo.checkContext.compatible(qtype1, resultInfo.checkContext.inferenceContext().asFree(to), retWarn) ||
222 //unchecked conversion is not allowed
223 retWarn.hasLint(Lint.LintCategory.UNCHECKED)) {
224 throw inferenceException
225 .setMessage("infer.no.conforming.instance.exists",
226 inferenceContext.restvars(), mt.getReturnType(), to);
227 }
228 }
229 //where
230 private Type returnConstraintTarget(Type from, Type to) {
231 if (from.hasTag(VOID)) {
232 return syms.voidType;
233 } else if (to.hasTag(NONE)) {
234 return from.isPrimitive() ? from : syms.objectType;
235 } else if (from.hasTag(UNDETVAR) && to.isPrimitive()) {
236 if (!allowGraphInference) {
237 //if legacy, just return boxed type
238 return types.boxedClass(to).type;
239 }
240 //if graph inference we need to skip conflicting boxed bounds...
241 UndetVar uv = (UndetVar)from;
242 for (Type t : uv.getBounds(InferenceBound.EQ, InferenceBound.LOWER)) {
243 Type boundAsPrimitive = types.unboxedType(t);
244 if (boundAsPrimitive == null) continue;
245 if (types.isConvertible(boundAsPrimitive, to)) {
246 //effectively skip return-type constraint generation (compatibility)
247 return syms.objectType;
248 }
249 }
250 return types.boxedClass(to).type;
251 } else {
252 return to;
253 }
254 }
256 /**
257 * Infer cyclic inference variables as described in 15.12.2.8.
258 */
259 private void instantiateAsUninferredVars(List<Type> vars, InferenceContext inferenceContext) {
260 ListBuffer<Type> todo = ListBuffer.lb();
261 //step 1 - create fresh tvars
262 for (Type t : vars) {
263 UndetVar uv = (UndetVar)inferenceContext.asFree(t);
264 List<Type> upperBounds = uv.getBounds(InferenceBound.UPPER);
265 if (Type.containsAny(upperBounds, vars)) {
266 TypeSymbol fresh_tvar = new TypeSymbol(Flags.SYNTHETIC, uv.qtype.tsym.name, null, uv.qtype.tsym.owner);
267 fresh_tvar.type = new TypeVar(fresh_tvar, types.makeCompoundType(uv.getBounds(InferenceBound.UPPER)), null);
268 todo.append(uv);
269 uv.inst = fresh_tvar.type;
270 } else if (upperBounds.nonEmpty()) {
271 uv.inst = types.glb(upperBounds);
272 } else {
273 uv.inst = syms.objectType;
274 }
275 }
276 //step 2 - replace fresh tvars in their bounds
277 List<Type> formals = vars;
278 for (Type t : todo) {
279 UndetVar uv = (UndetVar)t;
280 TypeVar ct = (TypeVar)uv.inst;
281 ct.bound = types.glb(inferenceContext.asInstTypes(types.getBounds(ct)));
282 if (ct.bound.isErroneous()) {
283 //report inference error if glb fails
284 reportBoundError(uv, BoundErrorKind.BAD_UPPER);
285 }
286 formals = formals.tail;
287 }
288 }
290 /**
291 * Compute a synthetic method type corresponding to the requested polymorphic
292 * method signature. The target return type is computed from the immediately
293 * enclosing scope surrounding the polymorphic-signature call.
294 */
295 Type instantiatePolymorphicSignatureInstance(Env<AttrContext> env,
296 MethodSymbol spMethod, // sig. poly. method or null if none
297 Resolve.MethodResolutionContext resolveContext,
298 List<Type> argtypes) {
299 final Type restype;
301 //The return type for a polymorphic signature call is computed from
302 //the enclosing tree E, as follows: if E is a cast, then use the
303 //target type of the cast expression as a return type; if E is an
304 //expression statement, the return type is 'void' - otherwise the
305 //return type is simply 'Object'. A correctness check ensures that
306 //env.next refers to the lexically enclosing environment in which
307 //the polymorphic signature call environment is nested.
309 switch (env.next.tree.getTag()) {
310 case TYPECAST:
311 JCTypeCast castTree = (JCTypeCast)env.next.tree;
312 restype = (TreeInfo.skipParens(castTree.expr) == env.tree) ?
313 castTree.clazz.type :
314 syms.objectType;
315 break;
316 case EXEC:
317 JCTree.JCExpressionStatement execTree =
318 (JCTree.JCExpressionStatement)env.next.tree;
319 restype = (TreeInfo.skipParens(execTree.expr) == env.tree) ?
320 syms.voidType :
321 syms.objectType;
322 break;
323 default:
324 restype = syms.objectType;
325 }
327 List<Type> paramtypes = Type.map(argtypes, new ImplicitArgType(spMethod, resolveContext.step));
328 List<Type> exType = spMethod != null ?
329 spMethod.getThrownTypes() :
330 List.of(syms.throwableType); // make it throw all exceptions
332 MethodType mtype = new MethodType(paramtypes,
333 restype,
334 exType,
335 syms.methodClass);
336 return mtype;
337 }
338 //where
339 class ImplicitArgType extends DeferredAttr.DeferredTypeMap {
341 public ImplicitArgType(Symbol msym, Resolve.MethodResolutionPhase phase) {
342 rs.deferredAttr.super(AttrMode.SPECULATIVE, msym, phase);
343 }
345 public Type apply(Type t) {
346 t = types.erasure(super.apply(t));
347 if (t.hasTag(BOT))
348 // nulls type as the marker type Null (which has no instances)
349 // infer as java.lang.Void for now
350 t = types.boxedClass(syms.voidType).type;
351 return t;
352 }
353 }
355 /**
356 * This method is used to infer a suitable target SAM in case the original
357 * SAM type contains one or more wildcards. An inference process is applied
358 * so that wildcard bounds, as well as explicit lambda/method ref parameters
359 * (where applicable) are used to constraint the solution.
360 */
361 public Type instantiateFunctionalInterface(DiagnosticPosition pos, Type funcInterface,
362 List<Type> paramTypes, Check.CheckContext checkContext) {
363 if (types.capture(funcInterface) == funcInterface) {
364 //if capture doesn't change the type then return the target unchanged
365 //(this means the target contains no wildcards!)
366 return funcInterface;
367 } else {
368 Type formalInterface = funcInterface.tsym.type;
369 InferenceContext funcInterfaceContext =
370 new InferenceContext(funcInterface.tsym.type.getTypeArguments());
372 Assert.check(paramTypes != null);
373 //get constraints from explicit params (this is done by
374 //checking that explicit param types are equal to the ones
375 //in the functional interface descriptors)
376 List<Type> descParameterTypes = types.findDescriptorType(formalInterface).getParameterTypes();
377 if (descParameterTypes.size() != paramTypes.size()) {
378 checkContext.report(pos, diags.fragment("incompatible.arg.types.in.lambda"));
379 return types.createErrorType(funcInterface);
380 }
381 for (Type p : descParameterTypes) {
382 if (!types.isSameType(funcInterfaceContext.asFree(p), paramTypes.head)) {
383 checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
384 return types.createErrorType(funcInterface);
385 }
386 paramTypes = paramTypes.tail;
387 }
389 try {
390 funcInterfaceContext.solve(funcInterfaceContext.boundedVars(), types.noWarnings);
391 } catch (InferenceException ex) {
392 checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
393 }
395 List<Type> actualTypeargs = funcInterface.getTypeArguments();
396 for (Type t : funcInterfaceContext.undetvars) {
397 UndetVar uv = (UndetVar)t;
398 if (uv.inst == null) {
399 uv.inst = actualTypeargs.head;
400 }
401 actualTypeargs = actualTypeargs.tail;
402 }
404 Type owntype = funcInterfaceContext.asInstType(formalInterface);
405 if (!chk.checkValidGenericType(owntype)) {
406 //if the inferred functional interface type is not well-formed,
407 //or if it's not a subtype of the original target, issue an error
408 checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
409 }
410 return owntype;
411 }
412 }
413 // </editor-fold>
415 // <editor-fold defaultstate="collapsed" desc="Bound checking">
416 /**
417 * Check bounds and perform incorporation
418 */
419 void checkWithinBounds(InferenceContext inferenceContext,
420 Warner warn) throws InferenceException {
421 MultiUndetVarListener mlistener = new MultiUndetVarListener(inferenceContext.undetvars);
422 try {
423 while (true) {
424 mlistener.reset();
425 if (!allowGraphInference) {
426 //in legacy mode we lack of transitivity, so bound check
427 //cannot be run in parallel with other incoprporation rounds
428 for (Type t : inferenceContext.undetvars) {
429 UndetVar uv = (UndetVar)t;
430 IncorporationStep.CHECK_BOUNDS.apply(uv, inferenceContext, warn);
431 }
432 }
433 for (Type t : inferenceContext.undetvars) {
434 UndetVar uv = (UndetVar)t;
435 //bound incorporation
436 EnumSet<IncorporationStep> incorporationSteps = allowGraphInference ?
437 incorporationStepsGraph : incorporationStepsLegacy;
438 for (IncorporationStep is : incorporationSteps) {
439 is.apply(uv, inferenceContext, warn);
440 }
441 }
442 if (!mlistener.changed || !allowGraphInference) break;
443 }
444 }
445 finally {
446 mlistener.detach();
447 }
448 }
449 //where
450 /**
451 * This listener keeps track of changes on a group of inference variable
452 * bounds. Note: the listener must be detached (calling corresponding
453 * method) to make sure that the underlying inference variable is
454 * left in a clean state.
455 */
456 class MultiUndetVarListener implements UndetVar.UndetVarListener {
458 int rounds;
459 boolean changed;
460 List<Type> undetvars;
462 public MultiUndetVarListener(List<Type> undetvars) {
463 this.undetvars = undetvars;
464 for (Type t : undetvars) {
465 UndetVar uv = (UndetVar)t;
466 uv.listener = this;
467 }
468 }
470 public void varChanged(UndetVar uv, Set<InferenceBound> ibs) {
471 //avoid non-termination
472 if (rounds < MAX_INCORPORATION_STEPS) {
473 changed = true;
474 }
475 }
477 void reset() {
478 rounds++;
479 changed = false;
480 }
482 void detach() {
483 for (Type t : undetvars) {
484 UndetVar uv = (UndetVar)t;
485 uv.listener = null;
486 }
487 }
488 };
490 /** max number of incorporation rounds */
491 static final int MAX_INCORPORATION_STEPS = 100;
493 /**
494 * This enumeration defines an entry point for doing inference variable
495 * bound incorporation - it can be used to inject custom incorporation
496 * logic into the basic bound checking routine
497 */
498 enum IncorporationStep {
499 /**
500 * Performs basic bound checking - i.e. is the instantiated type for a given
501 * inference variable compatible with its bounds?
502 */
503 CHECK_BOUNDS() {
504 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
505 Infer infer = inferenceContext.infer();
506 uv.substBounds(inferenceContext.inferenceVars(), inferenceContext.instTypes(), infer.types);
507 infer.checkCompatibleUpperBounds(uv, inferenceContext);
508 if (uv.inst != null) {
509 Type inst = uv.inst;
510 for (Type u : uv.getBounds(InferenceBound.UPPER)) {
511 if (!infer.types.isSubtypeUnchecked(inst, inferenceContext.asFree(u), warn)) {
512 infer.reportBoundError(uv, BoundErrorKind.UPPER);
513 }
514 }
515 for (Type l : uv.getBounds(InferenceBound.LOWER)) {
516 if (!infer.types.isSubtypeUnchecked(inferenceContext.asFree(l), inst, warn)) {
517 infer.reportBoundError(uv, BoundErrorKind.LOWER);
518 }
519 }
520 for (Type e : uv.getBounds(InferenceBound.EQ)) {
521 if (!infer.types.isSameType(inst, inferenceContext.asFree(e))) {
522 infer.reportBoundError(uv, BoundErrorKind.EQ);
523 }
524 }
525 }
526 }
527 },
528 /**
529 * Check consistency of equality constraints. This is a slightly more aggressive
530 * inference routine that is designed as to maximize compatibility with JDK 7.
531 * Note: this is not used in graph mode.
532 */
533 EQ_CHECK_LEGACY() {
534 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
535 Infer infer = inferenceContext.infer();
536 Type eq = null;
537 for (Type e : uv.getBounds(InferenceBound.EQ)) {
538 Assert.check(!inferenceContext.free(e));
539 if (eq != null && !infer.types.isSameType(e, eq)) {
540 infer.reportBoundError(uv, BoundErrorKind.EQ);
541 }
542 eq = e;
543 for (Type l : uv.getBounds(InferenceBound.LOWER)) {
544 Assert.check(!inferenceContext.free(l));
545 if (!infer.types.isSubtypeUnchecked(l, e, warn)) {
546 infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_LOWER);
547 }
548 }
549 for (Type u : uv.getBounds(InferenceBound.UPPER)) {
550 if (inferenceContext.free(u)) continue;
551 if (!infer.types.isSubtypeUnchecked(e, u, warn)) {
552 infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_UPPER);
553 }
554 }
555 }
556 }
557 },
558 /**
559 * Check consistency of equality constraints.
560 */
561 EQ_CHECK() {
562 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
563 Infer infer = inferenceContext.infer();
564 for (Type e : uv.getBounds(InferenceBound.EQ)) {
565 if (e.containsAny(inferenceContext.inferenceVars())) continue;
566 for (Type u : uv.getBounds(InferenceBound.UPPER)) {
567 if (!infer.types.isSubtypeUnchecked(e, inferenceContext.asFree(u), warn)) {
568 infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_UPPER);
569 }
570 }
571 for (Type l : uv.getBounds(InferenceBound.LOWER)) {
572 if (!infer.types.isSubtypeUnchecked(inferenceContext.asFree(l), e, warn)) {
573 infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_LOWER);
574 }
575 }
576 }
577 }
578 },
579 /**
580 * Given a bound set containing {@code alpha <: T} and {@code alpha :> S}
581 * perform {@code S <: T} (which could lead to new bounds).
582 */
583 CROSS_UPPER_LOWER() {
584 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
585 Infer infer = inferenceContext.infer();
586 for (Type b1 : uv.getBounds(InferenceBound.UPPER)) {
587 for (Type b2 : uv.getBounds(InferenceBound.LOWER)) {
588 if (!inferenceContext.inferenceVars().contains(b1) &&
589 !inferenceContext.inferenceVars().contains(b2) &&
590 infer.types.asSuper(b2, b1.tsym) != null) {
591 infer.types.isSubtypeUnchecked(inferenceContext.asFree(b2), inferenceContext.asFree(b1));
592 }
593 }
594 }
595 }
596 },
597 /**
598 * Given a bound set containing {@code alpha <: T} and {@code alpha == S}
599 * perform {@code S <: T} (which could lead to new bounds).
600 */
601 CROSS_UPPER_EQ() {
602 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
603 Infer infer = inferenceContext.infer();
604 for (Type b1 : uv.getBounds(InferenceBound.UPPER)) {
605 for (Type b2 : uv.getBounds(InferenceBound.EQ)) {
606 if (!inferenceContext.inferenceVars().contains(b1) &&
607 !inferenceContext.inferenceVars().contains(b2) &&
608 infer.types.asSuper(b2, b1.tsym) != null) {
609 infer.types.isSubtypeUnchecked(inferenceContext.asFree(b2), inferenceContext.asFree(b1));
610 }
611 }
612 }
613 }
614 },
615 /**
616 * Given a bound set containing {@code alpha :> S} and {@code alpha == T}
617 * perform {@code S <: T} (which could lead to new bounds).
618 */
619 CROSS_EQ_LOWER() {
620 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
621 Infer infer = inferenceContext.infer();
622 for (Type b1 : uv.getBounds(InferenceBound.EQ)) {
623 for (Type b2 : uv.getBounds(InferenceBound.LOWER)) {
624 if (!inferenceContext.inferenceVars().contains(b1) &&
625 !inferenceContext.inferenceVars().contains(b2) &&
626 infer.types.asSuper(b2, b1.tsym) != null) {
627 infer.types.isSubtypeUnchecked(inferenceContext.asFree(b2), inferenceContext.asFree(b1));
628 }
629 }
630 }
631 }
632 },
633 /**
634 * Given a bound set containing {@code alpha <: beta} propagate lower bounds
635 * from alpha to beta; also propagate upper bounds from beta to alpha.
636 */
637 PROP_UPPER() {
638 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
639 Infer infer = inferenceContext.infer();
640 for (Type b : uv.getBounds(InferenceBound.UPPER)) {
641 if (inferenceContext.inferenceVars().contains(b)) {
642 UndetVar uv2 = (UndetVar)inferenceContext.asFree(b);
643 //alpha <: beta
644 //0. set beta :> alpha
645 uv2.addBound(InferenceBound.LOWER, uv.qtype, infer.types);
646 //1. copy alpha's lower to beta's
647 for (Type l : uv.getBounds(InferenceBound.LOWER)) {
648 uv2.addBound(InferenceBound.LOWER, inferenceContext.asInstType(l), infer.types);
649 }
650 //2. copy beta's upper to alpha's
651 for (Type u : uv2.getBounds(InferenceBound.UPPER)) {
652 uv.addBound(InferenceBound.UPPER, inferenceContext.asInstType(u), infer.types);
653 }
654 }
655 }
656 }
657 },
658 /**
659 * Given a bound set containing {@code alpha :> beta} propagate lower bounds
660 * from beta to alpha; also propagate upper bounds from alpha to beta.
661 */
662 PROP_LOWER() {
663 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
664 Infer infer = inferenceContext.infer();
665 for (Type b : uv.getBounds(InferenceBound.LOWER)) {
666 if (inferenceContext.inferenceVars().contains(b)) {
667 UndetVar uv2 = (UndetVar)inferenceContext.asFree(b);
668 //alpha :> beta
669 //0. set beta <: alpha
670 uv2.addBound(InferenceBound.UPPER, uv.qtype, infer.types);
671 //1. copy alpha's upper to beta's
672 for (Type u : uv.getBounds(InferenceBound.UPPER)) {
673 uv2.addBound(InferenceBound.UPPER, inferenceContext.asInstType(u), infer.types);
674 }
675 //2. copy beta's lower to alpha's
676 for (Type l : uv2.getBounds(InferenceBound.LOWER)) {
677 uv.addBound(InferenceBound.LOWER, inferenceContext.asInstType(l), infer.types);
678 }
679 }
680 }
681 }
682 },
683 /**
684 * Given a bound set containing {@code alpha == beta} propagate lower/upper
685 * bounds from alpha to beta and back.
686 */
687 PROP_EQ() {
688 public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
689 Infer infer = inferenceContext.infer();
690 for (Type b : uv.getBounds(InferenceBound.EQ)) {
691 if (inferenceContext.inferenceVars().contains(b)) {
692 UndetVar uv2 = (UndetVar)inferenceContext.asFree(b);
693 //alpha == beta
694 //0. set beta == alpha
695 uv2.addBound(InferenceBound.EQ, uv.qtype, infer.types);
696 //1. copy all alpha's bounds to beta's
697 for (InferenceBound ib : InferenceBound.values()) {
698 for (Type b2 : uv.getBounds(ib)) {
699 if (b2 != uv2) {
700 uv2.addBound(ib, inferenceContext.asInstType(b2), infer.types);
701 }
702 }
703 }
704 //2. copy all beta's bounds to alpha's
705 for (InferenceBound ib : InferenceBound.values()) {
706 for (Type b2 : uv2.getBounds(ib)) {
707 if (b2 != uv) {
708 uv.addBound(ib, inferenceContext.asInstType(b2), infer.types);
709 }
710 }
711 }
712 }
713 }
714 }
715 };
717 abstract void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn);
718 }
720 /** incorporation steps to be executed when running in legacy mode */
721 EnumSet<IncorporationStep> incorporationStepsLegacy = EnumSet.of(IncorporationStep.EQ_CHECK_LEGACY);
723 /** incorporation steps to be executed when running in graph mode */
724 EnumSet<IncorporationStep> incorporationStepsGraph =
725 EnumSet.complementOf(EnumSet.of(IncorporationStep.EQ_CHECK_LEGACY));
727 /**
728 * Make sure that the upper bounds we got so far lead to a solvable inference
729 * variable by making sure that a glb exists.
730 */
731 void checkCompatibleUpperBounds(UndetVar uv, InferenceContext inferenceContext) {
732 List<Type> hibounds =
733 Type.filter(uv.getBounds(InferenceBound.UPPER), new BoundFilter(inferenceContext));
734 Type hb = null;
735 if (hibounds.isEmpty())
736 hb = syms.objectType;
737 else if (hibounds.tail.isEmpty())
738 hb = hibounds.head;
739 else
740 hb = types.glb(hibounds);
741 if (hb == null || hb.isErroneous())
742 reportBoundError(uv, BoundErrorKind.BAD_UPPER);
743 }
744 //where
745 protected static class BoundFilter implements Filter<Type> {
747 InferenceContext inferenceContext;
749 public BoundFilter(InferenceContext inferenceContext) {
750 this.inferenceContext = inferenceContext;
751 }
753 @Override
754 public boolean accepts(Type t) {
755 return !t.isErroneous() && !inferenceContext.free(t) &&
756 !t.hasTag(BOT);
757 }
758 };
760 /**
761 * This enumeration defines all possible bound-checking related errors.
762 */
763 enum BoundErrorKind {
764 /**
765 * The (uninstantiated) inference variable has incompatible upper bounds.
766 */
767 BAD_UPPER() {
768 @Override
769 InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
770 return ex.setMessage("incompatible.upper.bounds", uv.qtype,
771 uv.getBounds(InferenceBound.UPPER));
772 }
773 },
774 /**
775 * An equality constraint is not compatible with an upper bound.
776 */
777 BAD_EQ_UPPER() {
778 @Override
779 InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
780 return ex.setMessage("incompatible.eq.upper.bounds", uv.qtype,
781 uv.getBounds(InferenceBound.EQ), uv.getBounds(InferenceBound.UPPER));
782 }
783 },
784 /**
785 * An equality constraint is not compatible with a lower bound.
786 */
787 BAD_EQ_LOWER() {
788 @Override
789 InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
790 return ex.setMessage("incompatible.eq.lower.bounds", uv.qtype,
791 uv.getBounds(InferenceBound.EQ), uv.getBounds(InferenceBound.LOWER));
792 }
793 },
794 /**
795 * Instantiated inference variable is not compatible with an upper bound.
796 */
797 UPPER() {
798 @Override
799 InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
800 return ex.setMessage("inferred.do.not.conform.to.upper.bounds", uv.inst,
801 uv.getBounds(InferenceBound.UPPER));
802 }
803 },
804 /**
805 * Instantiated inference variable is not compatible with a lower bound.
806 */
807 LOWER() {
808 @Override
809 InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
810 return ex.setMessage("inferred.do.not.conform.to.lower.bounds", uv.inst,
811 uv.getBounds(InferenceBound.LOWER));
812 }
813 },
814 /**
815 * Instantiated inference variable is not compatible with an equality constraint.
816 */
817 EQ() {
818 @Override
819 InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
820 return ex.setMessage("inferred.do.not.conform.to.eq.bounds", uv.inst,
821 uv.getBounds(InferenceBound.EQ));
822 }
823 };
825 abstract InapplicableMethodException setMessage(InferenceException ex, UndetVar uv);
826 }
828 /**
829 * Report a bound-checking error of given kind
830 */
831 void reportBoundError(UndetVar uv, BoundErrorKind bk) {
832 throw bk.setMessage(inferenceException, uv);
833 }
834 // </editor-fold>
836 // <editor-fold defaultstate="collapsed" desc="Inference engine">
837 /**
838 * Graph inference strategy - act as an input to the inference solver; a strategy is
839 * composed of two ingredients: (i) find a node to solve in the inference graph,
840 * and (ii) tell th engine when we are done fixing inference variables
841 */
842 interface GraphStrategy {
843 /**
844 * Pick the next node (leaf) to solve in the graph
845 */
846 Node pickNode(InferenceGraph g);
847 /**
848 * Is this the last step?
849 */
850 boolean done();
851 }
853 /**
854 * Simple solver strategy class that locates all leaves inside a graph
855 * and picks the first leaf as the next node to solve
856 */
857 abstract class LeafSolver implements GraphStrategy {
858 public Node pickNode(InferenceGraph g) {
859 Assert.check(!g.nodes.isEmpty(), "No nodes to solve!");
860 return g.nodes.get(0);
861 }
862 }
864 /**
865 * This solver uses an heuristic to pick the best leaf - the heuristic
866 * tries to select the node that has maximal probability to contain one
867 * or more inference variables in a given list
868 */
869 abstract class BestLeafSolver extends LeafSolver {
871 List<Type> varsToSolve;
873 BestLeafSolver(List<Type> varsToSolve) {
874 this.varsToSolve = varsToSolve;
875 }
877 /**
878 * Computes the cost associated with a given node; the cost is computed
879 * as the total number of type-variables that should be eagerly instantiated
880 * in order to get to some of the variables in {@code varsToSolve} from
881 * a given node
882 */
883 void computeCostIfNeeded(Node n, Map<Node, Integer> costMap) {
884 if (costMap.containsKey(n)) {
885 return;
886 } else if (!Collections.disjoint(n.data, varsToSolve)) {
887 costMap.put(n, n.data.size());
888 } else {
889 int subcost = Integer.MAX_VALUE;
890 costMap.put(n, subcost); //avoid loops
891 for (Node n2 : n.getDependencies()) {
892 computeCostIfNeeded(n2, costMap);
893 subcost = Math.min(costMap.get(n2), subcost);
894 }
895 //update cost map to reflect real cost
896 costMap.put(n, subcost == Integer.MAX_VALUE ?
897 Integer.MAX_VALUE :
898 n.data.size() + subcost);
899 }
900 }
902 /**
903 * Pick the leaf that minimize cost
904 */
905 @Override
906 public Node pickNode(final InferenceGraph g) {
907 final Map<Node, Integer> costMap = new HashMap<Node, Integer>();
908 ArrayList<Node> leaves = new ArrayList<Node>();
909 for (Node n : g.nodes) {
910 computeCostIfNeeded(n, costMap);
911 if (n.isLeaf(n)) {
912 leaves.add(n);
913 }
914 }
915 Assert.check(!leaves.isEmpty(), "No nodes to solve!");
916 Collections.sort(leaves, new java.util.Comparator<Node>() {
917 public int compare(Node n1, Node n2) {
918 return costMap.get(n1) - costMap.get(n2);
919 }
920 });
921 return leaves.get(0);
922 }
923 }
925 /**
926 * The inference process can be thought of as a sequence of steps. Each step
927 * instantiates an inference variable using a subset of the inference variable
928 * bounds, if certain condition are met. Decisions such as the sequence in which
929 * steps are applied, or which steps are to be applied are left to the inference engine.
930 */
931 enum InferenceStep {
933 /**
934 * Instantiate an inference variables using one of its (ground) equality
935 * constraints
936 */
937 EQ(InferenceBound.EQ) {
938 @Override
939 Type solve(UndetVar uv, InferenceContext inferenceContext) {
940 return filterBounds(uv, inferenceContext).head;
941 }
942 },
943 /**
944 * Instantiate an inference variables using its (ground) lower bounds. Such
945 * bounds are merged together using lub().
946 */
947 LOWER(InferenceBound.LOWER) {
948 @Override
949 Type solve(UndetVar uv, InferenceContext inferenceContext) {
950 Infer infer = inferenceContext.infer();
951 List<Type> lobounds = filterBounds(uv, inferenceContext);
952 Type owntype = infer.types.lub(lobounds);
953 if (owntype.hasTag(ERROR)) {
954 throw infer.inferenceException
955 .setMessage("no.unique.minimal.instance.exists",
956 uv.qtype, lobounds);
957 } else {
958 return owntype;
959 }
960 }
961 },
962 /**
963 * Instantiate an inference variables using its (ground) upper bounds. Such
964 * bounds are merged together using glb().
965 */
966 UPPER(InferenceBound.UPPER) {
967 @Override
968 Type solve(UndetVar uv, InferenceContext inferenceContext) {
969 Infer infer = inferenceContext.infer();
970 List<Type> hibounds = filterBounds(uv, inferenceContext);
971 Type owntype = infer.types.glb(hibounds);
972 if (owntype.isErroneous()) {
973 throw infer.inferenceException
974 .setMessage("no.unique.maximal.instance.exists",
975 uv.qtype, hibounds);
976 } else {
977 return owntype;
978 }
979 }
980 },
981 /**
982 * Like the former; the only difference is that this step can only be applied
983 * if all upper bounds are ground.
984 */
985 UPPER_LEGACY(InferenceBound.UPPER) {
986 @Override
987 public boolean accepts(UndetVar t, InferenceContext inferenceContext) {
988 return !inferenceContext.free(t.getBounds(ib));
989 }
991 @Override
992 Type solve(UndetVar uv, InferenceContext inferenceContext) {
993 return UPPER.solve(uv, inferenceContext);
994 }
995 };
997 final InferenceBound ib;
999 InferenceStep(InferenceBound ib) {
1000 this.ib = ib;
1001 }
1003 /**
1004 * Find an instantiated type for a given inference variable within
1005 * a given inference context
1006 */
1007 abstract Type solve(UndetVar uv, InferenceContext inferenceContext);
1009 /**
1010 * Can the inference variable be instantiated using this step?
1011 */
1012 public boolean accepts(UndetVar t, InferenceContext inferenceContext) {
1013 return filterBounds(t, inferenceContext).nonEmpty();
1014 }
1016 /**
1017 * Return the subset of ground bounds in a given bound set (i.e. eq/lower/upper)
1018 */
1019 List<Type> filterBounds(UndetVar uv, InferenceContext inferenceContext) {
1020 return Type.filter(uv.getBounds(ib), new BoundFilter(inferenceContext));
1021 }
1022 }
1024 /**
1025 * This enumeration defines the sequence of steps to be applied when the
1026 * solver works in legacy mode. The steps in this enumeration reflect
1027 * the behavior of old inference routine (see JLS SE 7 15.12.2.7/15.12.2.8).
1028 */
1029 enum LegacyInferenceSteps {
1031 EQ_LOWER(EnumSet.of(InferenceStep.EQ, InferenceStep.LOWER)),
1032 EQ_UPPER(EnumSet.of(InferenceStep.EQ, InferenceStep.UPPER_LEGACY));
1034 final EnumSet<InferenceStep> steps;
1036 LegacyInferenceSteps(EnumSet<InferenceStep> steps) {
1037 this.steps = steps;
1038 }
1039 }
1041 /**
1042 * This enumeration defines the sequence of steps to be applied when the
1043 * graph solver is used. This order is defined so as to maximize compatibility
1044 * w.r.t. old inference routine (see JLS SE 7 15.12.2.7/15.12.2.8).
1045 */
1046 enum GraphInferenceSteps {
1048 EQ(EnumSet.of(InferenceStep.EQ)),
1049 EQ_LOWER(EnumSet.of(InferenceStep.EQ, InferenceStep.LOWER)),
1050 EQ_LOWER_UPPER(EnumSet.of(InferenceStep.EQ, InferenceStep.LOWER, InferenceStep.UPPER));
1052 final EnumSet<InferenceStep> steps;
1054 GraphInferenceSteps(EnumSet<InferenceStep> steps) {
1055 this.steps = steps;
1056 }
1057 }
1059 /**
1060 * This is the graph inference solver - the solver organizes all inference variables in
1061 * a given inference context by bound dependencies - in the general case, such dependencies
1062 * would lead to a cyclic directed graph (hence the name); the dependency info is used to build
1063 * an acyclic graph, where all cyclic variables are bundled together. An inference
1064 * step corresponds to solving a node in the acyclic graph - this is done by
1065 * relying on a given strategy (see GraphStrategy).
1066 */
1067 class GraphSolver {
1069 InferenceContext inferenceContext;
1070 Warner warn;
1072 GraphSolver(InferenceContext inferenceContext, Warner warn) {
1073 this.inferenceContext = inferenceContext;
1074 this.warn = warn;
1075 }
1077 /**
1078 * Solve variables in a given inference context. The amount of variables
1079 * to be solved, and the way in which the underlying acyclic graph is explored
1080 * depends on the selected solver strategy.
1081 */
1082 void solve(GraphStrategy sstrategy) {
1083 checkWithinBounds(inferenceContext, warn); //initial propagation of bounds
1084 InferenceGraph inferenceGraph = new InferenceGraph();
1085 while (!sstrategy.done()) {
1086 InferenceGraph.Node nodeToSolve = sstrategy.pickNode(inferenceGraph);
1087 List<Type> varsToSolve = List.from(nodeToSolve.data);
1088 inferenceContext.save();
1089 try {
1090 //repeat until all variables are solved
1091 outer: while (Type.containsAny(inferenceContext.restvars(), varsToSolve)) {
1092 //for each inference phase
1093 for (GraphInferenceSteps step : GraphInferenceSteps.values()) {
1094 if (inferenceContext.solveBasic(varsToSolve, step.steps)) {
1095 checkWithinBounds(inferenceContext, warn);
1096 continue outer;
1097 }
1098 }
1099 //no progress
1100 throw inferenceException;
1101 }
1102 }
1103 catch (InferenceException ex) {
1104 inferenceContext.rollback();
1105 instantiateAsUninferredVars(varsToSolve, inferenceContext);
1106 checkWithinBounds(inferenceContext, warn);
1107 }
1108 inferenceGraph.deleteNode(nodeToSolve);
1109 }
1110 }
1112 /**
1113 * The dependencies between the inference variables that need to be solved
1114 * form a (possibly cyclic) graph. This class reduces the original dependency graph
1115 * to an acyclic version, where cyclic nodes are folded into a single 'super node'.
1116 */
1117 class InferenceGraph {
1119 /**
1120 * This class represents a node in the graph. Each node corresponds
1121 * to an inference variable and has edges (dependencies) on other
1122 * nodes. The node defines an entry point that can be used to receive
1123 * updates on the structure of the graph this node belongs to (used to
1124 * keep dependencies in sync).
1125 */
1126 class Node extends GraphUtils.TarjanNode<ListBuffer<Type>> {
1128 Set<Node> deps;
1130 Node(Type ivar) {
1131 super(ListBuffer.of(ivar));
1132 this.deps = new HashSet<Node>();
1133 }
1135 @Override
1136 public Iterable<? extends Node> getDependencies() {
1137 return deps;
1138 }
1140 @Override
1141 public String printDependency(GraphUtils.Node<ListBuffer<Type>> to) {
1142 StringBuilder buf = new StringBuilder();
1143 String sep = "";
1144 for (Type from : data) {
1145 UndetVar uv = (UndetVar)inferenceContext.asFree(from);
1146 for (Type bound : uv.getBounds(InferenceBound.values())) {
1147 if (bound.containsAny(List.from(to.data))) {
1148 buf.append(sep);
1149 buf.append(bound);
1150 sep = ",";
1151 }
1152 }
1153 }
1154 return buf.toString();
1155 }
1157 boolean isLeaf(Node n) {
1158 //no deps, or only one self dep
1159 return (n.deps.isEmpty() ||
1160 n.deps.size() == 1 && n.deps.contains(n));
1161 }
1163 void mergeWith(List<? extends Node> nodes) {
1164 for (Node n : nodes) {
1165 Assert.check(n.data.length() == 1, "Attempt to merge a compound node!");
1166 data.appendList(n.data);
1167 deps.addAll(n.deps);
1168 }
1169 //update deps
1170 Set<Node> deps2 = new HashSet<Node>();
1171 for (Node d : deps) {
1172 if (data.contains(d.data.first())) {
1173 deps2.add(this);
1174 } else {
1175 deps2.add(d);
1176 }
1177 }
1178 deps = deps2;
1179 }
1181 void graphChanged(Node from, Node to) {
1182 if (deps.contains(from)) {
1183 deps.remove(from);
1184 if (to != null) {
1185 deps.add(to);
1186 }
1187 }
1188 }
1189 }
1191 /** the nodes in the inference graph */
1192 ArrayList<Node> nodes;
1194 InferenceGraph() {
1195 initNodes();
1196 }
1198 /**
1199 * Delete a node from the graph. This update the underlying structure
1200 * of the graph (including dependencies) via listeners updates.
1201 */
1202 public void deleteNode(Node n) {
1203 Assert.check(nodes.contains(n));
1204 nodes.remove(n);
1205 notifyUpdate(n, null);
1206 }
1208 /**
1209 * Notify all nodes of a change in the graph. If the target node is
1210 * {@code null} the source node is assumed to be removed.
1211 */
1212 void notifyUpdate(Node from, Node to) {
1213 for (Node n : nodes) {
1214 n.graphChanged(from, to);
1215 }
1216 }
1218 /**
1219 * Create the graph nodes. First a simple node is created for every inference
1220 * variables to be solved. Then Tarjan is used to found all connected components
1221 * in the graph. For each component containing more than one node, a super node is
1222 * created, effectively replacing the original cyclic nodes.
1223 */
1224 void initNodes() {
1225 nodes = new ArrayList<Node>();
1226 for (Type t : inferenceContext.restvars()) {
1227 nodes.add(new Node(t));
1228 }
1229 for (Node n_i : nodes) {
1230 Type i = n_i.data.first();
1231 for (Node n_j : nodes) {
1232 Type j = n_j.data.first();
1233 UndetVar uv_i = (UndetVar)inferenceContext.asFree(i);
1234 if (Type.containsAny(uv_i.getBounds(InferenceBound.values()), List.of(j))) {
1235 //update i's deps
1236 n_i.deps.add(n_j);
1237 }
1238 }
1239 }
1240 ArrayList<Node> acyclicNodes = new ArrayList<Node>();
1241 for (List<? extends Node> conSubGraph : GraphUtils.tarjan(nodes)) {
1242 if (conSubGraph.length() > 1) {
1243 Node root = conSubGraph.head;
1244 root.mergeWith(conSubGraph.tail);
1245 for (Node n : conSubGraph) {
1246 notifyUpdate(n, root);
1247 }
1248 }
1249 acyclicNodes.add(conSubGraph.head);
1250 }
1251 nodes = acyclicNodes;
1252 }
1254 /**
1255 * Debugging: dot representation of this graph
1256 */
1257 String toDot() {
1258 StringBuilder buf = new StringBuilder();
1259 for (Type t : inferenceContext.undetvars) {
1260 UndetVar uv = (UndetVar)t;
1261 buf.append(String.format("var %s - upper bounds = %s, lower bounds = %s, eq bounds = %s\\n",
1262 uv.qtype, uv.getBounds(InferenceBound.UPPER), uv.getBounds(InferenceBound.LOWER),
1263 uv.getBounds(InferenceBound.EQ)));
1264 }
1265 return GraphUtils.toDot(nodes, "inferenceGraph" + hashCode(), buf.toString());
1266 }
1267 }
1268 }
1269 // </editor-fold>
1271 // <editor-fold defaultstate="collapsed" desc="Inference context">
1272 /**
1273 * Functional interface for defining inference callbacks. Certain actions
1274 * (i.e. subtyping checks) might need to be redone after all inference variables
1275 * have been fixed.
1276 */
1277 interface FreeTypeListener {
1278 void typesInferred(InferenceContext inferenceContext);
1279 }
1281 /**
1282 * An inference context keeps track of the set of variables that are free
1283 * in the current context. It provides utility methods for opening/closing
1284 * types to their corresponding free/closed forms. It also provide hooks for
1285 * attaching deferred post-inference action (see PendingCheck). Finally,
1286 * it can be used as an entry point for performing upper/lower bound inference
1287 * (see InferenceKind).
1288 */
1289 class InferenceContext {
1291 /** list of inference vars as undet vars */
1292 List<Type> undetvars;
1294 /** list of inference vars in this context */
1295 List<Type> inferencevars;
1297 /** backed up inference variables */
1298 List<Type> saved_undet;
1300 java.util.Map<FreeTypeListener, List<Type>> freeTypeListeners =
1301 new java.util.HashMap<FreeTypeListener, List<Type>>();
1303 List<FreeTypeListener> freetypeListeners = List.nil();
1305 public InferenceContext(List<Type> inferencevars) {
1306 this.undetvars = Type.map(inferencevars, fromTypeVarFun);
1307 this.inferencevars = inferencevars;
1308 }
1309 //where
1310 Mapping fromTypeVarFun = new Mapping("fromTypeVarFunWithBounds") {
1311 // mapping that turns inference variables into undet vars
1312 public Type apply(Type t) {
1313 if (t.hasTag(TYPEVAR)) return new UndetVar((TypeVar)t, types);
1314 else return t.map(this);
1315 }
1316 };
1318 /**
1319 * returns the list of free variables (as type-variables) in this
1320 * inference context
1321 */
1322 List<Type> inferenceVars() {
1323 return inferencevars;
1324 }
1326 /**
1327 * returns the list of uninstantiated variables (as type-variables) in this
1328 * inference context
1329 */
1330 List<Type> restvars() {
1331 return filterVars(new Filter<UndetVar>() {
1332 public boolean accepts(UndetVar uv) {
1333 return uv.inst == null;
1334 }
1335 });
1336 }
1338 /**
1339 * returns the list of instantiated variables (as type-variables) in this
1340 * inference context
1341 */
1342 List<Type> instvars() {
1343 return filterVars(new Filter<UndetVar>() {
1344 public boolean accepts(UndetVar uv) {
1345 return uv.inst != null;
1346 }
1347 });
1348 }
1350 /**
1351 * Get list of bounded inference variables (where bound is other than
1352 * declared bounds).
1353 */
1354 final List<Type> boundedVars() {
1355 return filterVars(new Filter<UndetVar>() {
1356 public boolean accepts(UndetVar uv) {
1357 return uv.getBounds(InferenceBound.UPPER)
1358 .diff(uv.getDeclaredBounds())
1359 .appendList(uv.getBounds(InferenceBound.EQ, InferenceBound.LOWER)).nonEmpty();
1360 }
1361 });
1362 }
1364 private List<Type> filterVars(Filter<UndetVar> fu) {
1365 ListBuffer<Type> res = ListBuffer.lb();
1366 for (Type t : undetvars) {
1367 UndetVar uv = (UndetVar)t;
1368 if (fu.accepts(uv)) {
1369 res.append(uv.qtype);
1370 }
1371 }
1372 return res.toList();
1373 }
1375 /**
1376 * is this type free?
1377 */
1378 final boolean free(Type t) {
1379 return t.containsAny(inferencevars);
1380 }
1382 final boolean free(List<Type> ts) {
1383 for (Type t : ts) {
1384 if (free(t)) return true;
1385 }
1386 return false;
1387 }
1389 /**
1390 * Returns a list of free variables in a given type
1391 */
1392 final List<Type> freeVarsIn(Type t) {
1393 ListBuffer<Type> buf = ListBuffer.lb();
1394 for (Type iv : inferenceVars()) {
1395 if (t.contains(iv)) {
1396 buf.add(iv);
1397 }
1398 }
1399 return buf.toList();
1400 }
1402 final List<Type> freeVarsIn(List<Type> ts) {
1403 ListBuffer<Type> buf = ListBuffer.lb();
1404 for (Type t : ts) {
1405 buf.appendList(freeVarsIn(t));
1406 }
1407 ListBuffer<Type> buf2 = ListBuffer.lb();
1408 for (Type t : buf) {
1409 if (!buf2.contains(t)) {
1410 buf2.add(t);
1411 }
1412 }
1413 return buf2.toList();
1414 }
1416 /**
1417 * Replace all free variables in a given type with corresponding
1418 * undet vars (used ahead of subtyping/compatibility checks to allow propagation
1419 * of inference constraints).
1420 */
1421 final Type asFree(Type t) {
1422 return types.subst(t, inferencevars, undetvars);
1423 }
1425 final List<Type> asFree(List<Type> ts) {
1426 ListBuffer<Type> buf = ListBuffer.lb();
1427 for (Type t : ts) {
1428 buf.append(asFree(t));
1429 }
1430 return buf.toList();
1431 }
1433 List<Type> instTypes() {
1434 ListBuffer<Type> buf = ListBuffer.lb();
1435 for (Type t : undetvars) {
1436 UndetVar uv = (UndetVar)t;
1437 buf.append(uv.inst != null ? uv.inst : uv.qtype);
1438 }
1439 return buf.toList();
1440 }
1442 /**
1443 * Replace all free variables in a given type with corresponding
1444 * instantiated types - if one or more free variable has not been
1445 * fully instantiated, it will still be available in the resulting type.
1446 */
1447 Type asInstType(Type t) {
1448 return types.subst(t, inferencevars, instTypes());
1449 }
1451 List<Type> asInstTypes(List<Type> ts) {
1452 ListBuffer<Type> buf = ListBuffer.lb();
1453 for (Type t : ts) {
1454 buf.append(asInstType(t));
1455 }
1456 return buf.toList();
1457 }
1459 /**
1460 * Add custom hook for performing post-inference action
1461 */
1462 void addFreeTypeListener(List<Type> types, FreeTypeListener ftl) {
1463 freeTypeListeners.put(ftl, freeVarsIn(types));
1464 }
1466 /**
1467 * Mark the inference context as complete and trigger evaluation
1468 * of all deferred checks.
1469 */
1470 void notifyChange() {
1471 notifyChange(inferencevars.diff(restvars()));
1472 }
1474 void notifyChange(List<Type> inferredVars) {
1475 InferenceException thrownEx = null;
1476 for (Map.Entry<FreeTypeListener, List<Type>> entry :
1477 new HashMap<FreeTypeListener, List<Type>>(freeTypeListeners).entrySet()) {
1478 if (!Type.containsAny(entry.getValue(), inferencevars.diff(inferredVars))) {
1479 try {
1480 entry.getKey().typesInferred(this);
1481 freeTypeListeners.remove(entry.getKey());
1482 } catch (InferenceException ex) {
1483 if (thrownEx == null) {
1484 thrownEx = ex;
1485 }
1486 }
1487 }
1488 }
1489 //inference exception multiplexing - present any inference exception
1490 //thrown when processing listeners as a single one
1491 if (thrownEx != null) {
1492 throw thrownEx;
1493 }
1494 }
1496 /**
1497 * Save the state of this inference context
1498 */
1499 void save() {
1500 ListBuffer<Type> buf = ListBuffer.lb();
1501 for (Type t : undetvars) {
1502 UndetVar uv = (UndetVar)t;
1503 UndetVar uv2 = new UndetVar((TypeVar)uv.qtype, types);
1504 for (InferenceBound ib : InferenceBound.values()) {
1505 for (Type b : uv.getBounds(ib)) {
1506 uv2.addBound(ib, b, types);
1507 }
1508 }
1509 uv2.inst = uv.inst;
1510 buf.add(uv2);
1511 }
1512 saved_undet = buf.toList();
1513 }
1515 /**
1516 * Restore the state of this inference context to the previous known checkpoint
1517 */
1518 void rollback() {
1519 Assert.check(saved_undet != null && saved_undet.length() == undetvars.length());
1520 undetvars = saved_undet;
1521 saved_undet = null;
1522 }
1524 /**
1525 * Copy variable in this inference context to the given context
1526 */
1527 void dupTo(final InferenceContext that) {
1528 that.inferencevars = that.inferencevars.appendList(inferencevars);
1529 that.undetvars = that.undetvars.appendList(undetvars);
1530 //set up listeners to notify original inference contexts as
1531 //propagated vars are inferred in new context
1532 for (Type t : inferencevars) {
1533 that.freeTypeListeners.put(new FreeTypeListener() {
1534 public void typesInferred(InferenceContext inferenceContext) {
1535 InferenceContext.this.notifyChange();
1536 }
1537 }, List.of(t));
1538 }
1539 }
1541 /**
1542 * Solve with given graph strategy.
1543 */
1544 private void solve(GraphStrategy ss, Warner warn) {
1545 GraphSolver s = new GraphSolver(this, warn);
1546 s.solve(ss);
1547 }
1549 /**
1550 * Solve all variables in this context.
1551 */
1552 public void solve(Warner warn) {
1553 solve(new LeafSolver() {
1554 public boolean done() {
1555 return restvars().isEmpty();
1556 }
1557 }, warn);
1558 }
1560 /**
1561 * Solve all variables in the given list.
1562 */
1563 public void solve(final List<Type> vars, Warner warn) {
1564 solve(new BestLeafSolver(vars) {
1565 public boolean done() {
1566 return !free(asInstTypes(vars));
1567 }
1568 }, warn);
1569 }
1571 /**
1572 * Solve at least one variable in given list.
1573 */
1574 public void solveAny(List<Type> varsToSolve, Warner warn) {
1575 checkWithinBounds(this, warn); //propagate bounds
1576 List<Type> boundedVars = boundedVars().intersect(restvars()).intersect(varsToSolve);
1577 if (boundedVars.isEmpty()) {
1578 throw inferenceException.setMessage("cyclic.inference",
1579 freeVarsIn(varsToSolve));
1580 }
1581 solve(new BestLeafSolver(boundedVars) {
1582 public boolean done() {
1583 return instvars().intersect(varsToSolve).nonEmpty();
1584 }
1585 }, warn);
1586 }
1588 /**
1589 * Apply a set of inference steps
1590 */
1591 private boolean solveBasic(EnumSet<InferenceStep> steps) {
1592 return solveBasic(inferencevars, steps);
1593 }
1595 private boolean solveBasic(List<Type> varsToSolve, EnumSet<InferenceStep> steps) {
1596 boolean changed = false;
1597 for (Type t : varsToSolve.intersect(restvars())) {
1598 UndetVar uv = (UndetVar)asFree(t);
1599 for (InferenceStep step : steps) {
1600 if (step.accepts(uv, this)) {
1601 uv.inst = step.solve(uv, this);
1602 changed = true;
1603 break;
1604 }
1605 }
1606 }
1607 return changed;
1608 }
1610 /**
1611 * Instantiate inference variables in legacy mode (JLS 15.12.2.7, 15.12.2.8).
1612 * During overload resolution, instantiation is done by doing a partial
1613 * inference process using eq/lower bound instantiation. During check,
1614 * we also instantiate any remaining vars by repeatedly using eq/upper
1615 * instantiation, until all variables are solved.
1616 */
1617 public void solveLegacy(boolean partial, Warner warn, EnumSet<InferenceStep> steps) {
1618 while (true) {
1619 boolean stuck = !solveBasic(steps);
1620 if (restvars().isEmpty() || partial) {
1621 //all variables have been instantiated - exit
1622 break;
1623 } else if (stuck) {
1624 //some variables could not be instantiated because of cycles in
1625 //upper bounds - provide a (possibly recursive) default instantiation
1626 instantiateAsUninferredVars(restvars(), this);
1627 break;
1628 } else {
1629 //some variables have been instantiated - replace newly instantiated
1630 //variables in remaining upper bounds and continue
1631 for (Type t : undetvars) {
1632 UndetVar uv = (UndetVar)t;
1633 uv.substBounds(inferenceVars(), instTypes(), types);
1634 }
1635 }
1636 }
1637 checkWithinBounds(this, warn);
1638 }
1640 private Infer infer() {
1641 //back-door to infer
1642 return Infer.this;
1643 }
1644 }
1646 final InferenceContext emptyContext = new InferenceContext(List.<Type>nil());
1647 // </editor-fold>
1648 }