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src/share/classes/com/sun/tools/javac/comp/Infer.java@366a7b9b5627
src/share/classes/com/sun/tools/javac/comp/Infer.java
Thu, 10 Jun 2010 17:09:56 -0700
- author
- jjg
- date
- Thu, 10 Jun 2010 17:09:56 -0700
- changeset 582
- 366a7b9b5627
- parent 581
- f2fdd52e4e87
- child 615
- 36c4ec4525b4
- permissions
- -rw-r--r--
6960407: Potential rebranding issues in openjdk/langtools repository sources
Reviewed-by: darcy
1 /*
2 * Copyright (c) 1999, 2009, 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.util.*;
29 import com.sun.tools.javac.util.List;
30 import com.sun.tools.javac.code.*;
31 import com.sun.tools.javac.code.Type.*;
32 import com.sun.tools.javac.code.Type.ForAll.ConstraintKind;
33 import com.sun.tools.javac.code.Symbol.*;
34 import com.sun.tools.javac.util.JCDiagnostic;
36 import static com.sun.tools.javac.code.TypeTags.*;
38 /** Helper class for type parameter inference, used by the attribution phase.
39 *
40 * <p><b>This is NOT part of any supported API.
41 * If you write code that depends on this, you do so at your own risk.
42 * This code and its internal interfaces are subject to change or
43 * deletion without notice.</b>
44 */
45 public class Infer {
46 protected static final Context.Key<Infer> inferKey =
47 new Context.Key<Infer>();
49 /** A value for prototypes that admit any type, including polymorphic ones. */
50 public static final Type anyPoly = new Type(NONE, null);
52 Symtab syms;
53 Types types;
54 Check chk;
55 Resolve rs;
56 JCDiagnostic.Factory diags;
58 public static Infer instance(Context context) {
59 Infer instance = context.get(inferKey);
60 if (instance == null)
61 instance = new Infer(context);
62 return instance;
63 }
65 protected Infer(Context context) {
66 context.put(inferKey, this);
67 syms = Symtab.instance(context);
68 types = Types.instance(context);
69 rs = Resolve.instance(context);
70 chk = Check.instance(context);
71 diags = JCDiagnostic.Factory.instance(context);
72 ambiguousNoInstanceException =
73 new NoInstanceException(true, diags);
74 unambiguousNoInstanceException =
75 new NoInstanceException(false, diags);
76 invalidInstanceException =
77 new InvalidInstanceException(diags);
79 }
81 public static class InferenceException extends RuntimeException {
82 private static final long serialVersionUID = 0;
84 JCDiagnostic diagnostic;
85 JCDiagnostic.Factory diags;
87 InferenceException(JCDiagnostic.Factory diags) {
88 this.diagnostic = null;
89 this.diags = diags;
90 }
92 InferenceException setMessage(String key, Object... args) {
93 this.diagnostic = diags.fragment(key, args);
94 return this;
95 }
97 public JCDiagnostic getDiagnostic() {
98 return diagnostic;
99 }
100 }
102 public static class NoInstanceException extends InferenceException {
103 private static final long serialVersionUID = 1;
105 boolean isAmbiguous; // exist several incomparable best instances?
107 NoInstanceException(boolean isAmbiguous, JCDiagnostic.Factory diags) {
108 super(diags);
109 this.isAmbiguous = isAmbiguous;
110 }
111 }
113 public static class InvalidInstanceException extends InferenceException {
114 private static final long serialVersionUID = 2;
116 InvalidInstanceException(JCDiagnostic.Factory diags) {
117 super(diags);
118 }
119 }
121 private final NoInstanceException ambiguousNoInstanceException;
122 private final NoInstanceException unambiguousNoInstanceException;
123 private final InvalidInstanceException invalidInstanceException;
125 /***************************************************************************
126 * Auxiliary type values and classes
127 ***************************************************************************/
129 /** A mapping that turns type variables into undetermined type variables.
130 */
131 Mapping fromTypeVarFun = new Mapping("fromTypeVarFun") {
132 public Type apply(Type t) {
133 if (t.tag == TYPEVAR) return new UndetVar(t);
134 else return t.map(this);
135 }
136 };
138 /** A mapping that returns its type argument with every UndetVar replaced
139 * by its `inst' field. Throws a NoInstanceException
140 * if this not possible because an `inst' field is null.
141 */
142 Mapping getInstFun = new Mapping("getInstFun") {
143 public Type apply(Type t) {
144 switch (t.tag) {
145 case UNKNOWN:
146 throw ambiguousNoInstanceException
147 .setMessage("undetermined.type");
148 case UNDETVAR:
149 UndetVar that = (UndetVar) t;
150 if (that.inst == null)
151 throw ambiguousNoInstanceException
152 .setMessage("type.variable.has.undetermined.type",
153 that.qtype);
154 return apply(that.inst);
155 default:
156 return t.map(this);
157 }
158 }
159 };
161 /***************************************************************************
162 * Mini/Maximization of UndetVars
163 ***************************************************************************/
165 /** Instantiate undetermined type variable to its minimal upper bound.
166 * Throw a NoInstanceException if this not possible.
167 */
168 void maximizeInst(UndetVar that, Warner warn) throws NoInstanceException {
169 if (that.inst == null) {
170 if (that.hibounds.isEmpty())
171 that.inst = syms.objectType;
172 else if (that.hibounds.tail.isEmpty())
173 that.inst = that.hibounds.head;
174 else
175 that.inst = types.glb(that.hibounds);
176 }
177 if (that.inst == null ||
178 that.inst.isErroneous())
179 throw ambiguousNoInstanceException
180 .setMessage("no.unique.maximal.instance.exists",
181 that.qtype, that.hibounds);
182 }
183 //where
184 private boolean isSubClass(Type t, final List<Type> ts) {
185 t = t.baseType();
186 if (t.tag == TYPEVAR) {
187 List<Type> bounds = types.getBounds((TypeVar)t);
188 for (Type s : ts) {
189 if (!types.isSameType(t, s.baseType())) {
190 for (Type bound : bounds) {
191 if (!isSubClass(bound, List.of(s.baseType())))
192 return false;
193 }
194 }
195 }
196 } else {
197 for (Type s : ts) {
198 if (!t.tsym.isSubClass(s.baseType().tsym, types))
199 return false;
200 }
201 }
202 return true;
203 }
205 /** Instantiate undetermined type variable to the lub of all its lower bounds.
206 * Throw a NoInstanceException if this not possible.
207 */
208 void minimizeInst(UndetVar that, Warner warn) throws NoInstanceException {
209 if (that.inst == null) {
210 if (that.lobounds.isEmpty())
211 that.inst = syms.botType;
212 else if (that.lobounds.tail.isEmpty())
213 that.inst = that.lobounds.head.isPrimitive() ? syms.errType : that.lobounds.head;
214 else {
215 that.inst = types.lub(that.lobounds);
216 }
217 if (that.inst == null || that.inst.tag == ERROR)
218 throw ambiguousNoInstanceException
219 .setMessage("no.unique.minimal.instance.exists",
220 that.qtype, that.lobounds);
221 // VGJ: sort of inlined maximizeInst() below. Adding
222 // bounds can cause lobounds that are above hibounds.
223 if (that.hibounds.isEmpty())
224 return;
225 Type hb = null;
226 if (that.hibounds.tail.isEmpty())
227 hb = that.hibounds.head;
228 else for (List<Type> bs = that.hibounds;
229 bs.nonEmpty() && hb == null;
230 bs = bs.tail) {
231 if (isSubClass(bs.head, that.hibounds))
232 hb = types.fromUnknownFun.apply(bs.head);
233 }
234 if (hb == null ||
235 !types.isSubtypeUnchecked(hb, that.hibounds, warn) ||
236 !types.isSubtypeUnchecked(that.inst, hb, warn))
237 throw ambiguousNoInstanceException;
238 }
239 }
241 /***************************************************************************
242 * Exported Methods
243 ***************************************************************************/
245 /** Try to instantiate expression type `that' to given type `to'.
246 * If a maximal instantiation exists which makes this type
247 * a subtype of type `to', return the instantiated type.
248 * If no instantiation exists, or if several incomparable
249 * best instantiations exist throw a NoInstanceException.
250 */
251 public Type instantiateExpr(ForAll that,
252 Type to,
253 Warner warn) throws InferenceException {
254 List<Type> undetvars = Type.map(that.tvars, fromTypeVarFun);
255 for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail) {
256 UndetVar uv = (UndetVar) l.head;
257 TypeVar tv = (TypeVar)uv.qtype;
258 ListBuffer<Type> hibounds = new ListBuffer<Type>();
259 for (Type t : that.getConstraints(tv, ConstraintKind.EXTENDS).prependList(types.getBounds(tv))) {
260 if (!t.containsSome(that.tvars) && t.tag != BOT) {
261 hibounds.append(t);
262 }
263 }
264 List<Type> inst = that.getConstraints(tv, ConstraintKind.EQUAL);
265 if (inst.nonEmpty() && inst.head.tag != BOT) {
266 uv.inst = inst.head;
267 }
268 uv.hibounds = hibounds.toList();
269 }
270 Type qtype1 = types.subst(that.qtype, that.tvars, undetvars);
271 if (!types.isSubtype(qtype1, to)) {
272 throw unambiguousNoInstanceException
273 .setMessage("no.conforming.instance.exists",
274 that.tvars, that.qtype, to);
275 }
276 for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail)
277 maximizeInst((UndetVar) l.head, warn);
278 // System.out.println(" = " + qtype1.map(getInstFun));//DEBUG
280 // check bounds
281 List<Type> targs = Type.map(undetvars, getInstFun);
282 targs = types.subst(targs, that.tvars, targs);
283 checkWithinBounds(that.tvars, targs, warn);
284 return chk.checkType(warn.pos(), that.inst(targs, types), to);
285 }
287 /** Instantiate method type `mt' by finding instantiations of
288 * `tvars' so that method can be applied to `argtypes'.
289 */
290 public Type instantiateMethod(final Env<AttrContext> env,
291 List<Type> tvars,
292 MethodType mt,
293 final Symbol msym,
294 final List<Type> argtypes,
295 final boolean allowBoxing,
296 final boolean useVarargs,
297 final Warner warn) throws InferenceException {
298 //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
299 List<Type> undetvars = Type.map(tvars, fromTypeVarFun);
300 List<Type> formals = mt.argtypes;
301 //need to capture exactly once - otherwise subsequent
302 //applicability checks might fail
303 final List<Type> capturedArgs = types.capture(argtypes);
304 List<Type> actuals = capturedArgs;
305 List<Type> actualsNoCapture = argtypes;
306 // instantiate all polymorphic argument types and
307 // set up lower bounds constraints for undetvars
308 Type varargsFormal = useVarargs ? formals.last() : null;
309 while (actuals.nonEmpty() && formals.head != varargsFormal) {
310 Type formal = formals.head;
311 Type actual = actuals.head.baseType();
312 Type actualNoCapture = actualsNoCapture.head.baseType();
313 if (actual.tag == FORALL)
314 actual = instantiateArg((ForAll)actual, formal, tvars, warn);
315 Type undetFormal = types.subst(formal, tvars, undetvars);
316 boolean works = allowBoxing
317 ? types.isConvertible(actual, undetFormal, warn)
318 : types.isSubtypeUnchecked(actual, undetFormal, warn);
319 if (!works) {
320 throw unambiguousNoInstanceException
321 .setMessage("no.conforming.assignment.exists",
322 tvars, actualNoCapture, formal);
323 }
324 formals = formals.tail;
325 actuals = actuals.tail;
326 actualsNoCapture = actualsNoCapture.tail;
327 }
328 if (formals.head != varargsFormal || // not enough args
329 !useVarargs && actuals.nonEmpty()) { // too many args
330 // argument lists differ in length
331 throw unambiguousNoInstanceException
332 .setMessage("arg.length.mismatch");
333 }
335 // for varargs arguments as well
336 if (useVarargs) {
337 Type elemType = types.elemtype(varargsFormal);
338 Type elemUndet = types.subst(elemType, tvars, undetvars);
339 while (actuals.nonEmpty()) {
340 Type actual = actuals.head.baseType();
341 Type actualNoCapture = actualsNoCapture.head.baseType();
342 if (actual.tag == FORALL)
343 actual = instantiateArg((ForAll)actual, elemType, tvars, warn);
344 boolean works = types.isConvertible(actual, elemUndet, warn);
345 if (!works) {
346 throw unambiguousNoInstanceException
347 .setMessage("no.conforming.assignment.exists",
348 tvars, actualNoCapture, elemType);
349 }
350 actuals = actuals.tail;
351 actualsNoCapture = actualsNoCapture.tail;
352 }
353 }
355 // minimize as yet undetermined type variables
356 for (Type t : undetvars)
357 minimizeInst((UndetVar) t, warn);
359 /** Type variables instantiated to bottom */
360 ListBuffer<Type> restvars = new ListBuffer<Type>();
362 /** Undet vars instantiated to bottom */
363 final ListBuffer<Type> restundet = new ListBuffer<Type>();
365 /** Instantiated types or TypeVars if under-constrained */
366 ListBuffer<Type> insttypes = new ListBuffer<Type>();
368 /** Instantiated types or UndetVars if under-constrained */
369 ListBuffer<Type> undettypes = new ListBuffer<Type>();
371 for (Type t : undetvars) {
372 UndetVar uv = (UndetVar)t;
373 if (uv.inst.tag == BOT) {
374 restvars.append(uv.qtype);
375 restundet.append(uv);
376 insttypes.append(uv.qtype);
377 undettypes.append(uv);
378 uv.inst = null;
379 } else {
380 insttypes.append(uv.inst);
381 undettypes.append(uv.inst);
382 }
383 }
384 checkWithinBounds(tvars, undettypes.toList(), warn);
386 mt = (MethodType)types.subst(mt, tvars, insttypes.toList());
388 if (!restvars.isEmpty()) {
389 // if there are uninstantiated variables,
390 // quantify result type with them
391 final List<Type> inferredTypes = insttypes.toList();
392 final List<Type> all_tvars = tvars; //this is the wrong tvars
393 final MethodType mt2 = new MethodType(mt.argtypes, null, mt.thrown, syms.methodClass);
394 mt2.restype = new ForAll(restvars.toList(), mt.restype) {
395 @Override
396 public List<Type> getConstraints(TypeVar tv, ConstraintKind ck) {
397 for (Type t : restundet.toList()) {
398 UndetVar uv = (UndetVar)t;
399 if (uv.qtype == tv) {
400 switch (ck) {
401 case EXTENDS: return uv.hibounds;
402 case SUPER: return uv.lobounds;
403 case EQUAL: return uv.inst != null ? List.of(uv.inst) : List.<Type>nil();
404 }
405 }
406 }
407 return List.nil();
408 }
410 @Override
411 public Type inst(List<Type> inferred, Types types) throws NoInstanceException {
412 List<Type> formals = types.subst(mt2.argtypes, tvars, inferred);
413 if (!rs.argumentsAcceptable(capturedArgs, formals,
414 allowBoxing, useVarargs, warn)) {
415 // inferred method is not applicable
416 throw invalidInstanceException.setMessage("inferred.do.not.conform.to.params", formals, argtypes);
417 }
418 // check that inferred bounds conform to their bounds
419 checkWithinBounds(all_tvars,
420 types.subst(inferredTypes, tvars, inferred), warn);
421 if (useVarargs) {
422 chk.checkVararg(env.tree.pos(), formals, msym, env);
423 }
424 return super.inst(inferred, types);
425 }};
426 return mt2;
427 }
428 else if (!rs.argumentsAcceptable(capturedArgs, mt.getParameterTypes(), allowBoxing, useVarargs, warn)) {
429 // inferred method is not applicable
430 throw invalidInstanceException.setMessage("inferred.do.not.conform.to.params", mt.getParameterTypes(), argtypes);
431 }
432 else {
433 // return instantiated version of method type
434 return mt;
435 }
436 }
437 //where
439 /** Try to instantiate argument type `that' to given type `to'.
440 * If this fails, try to insantiate `that' to `to' where
441 * every occurrence of a type variable in `tvars' is replaced
442 * by an unknown type.
443 */
444 private Type instantiateArg(ForAll that,
445 Type to,
446 List<Type> tvars,
447 Warner warn) throws InferenceException {
448 List<Type> targs;
449 try {
450 return instantiateExpr(that, to, warn);
451 } catch (NoInstanceException ex) {
452 Type to1 = to;
453 for (List<Type> l = tvars; l.nonEmpty(); l = l.tail)
454 to1 = types.subst(to1, List.of(l.head), List.of(syms.unknownType));
455 return instantiateExpr(that, to1, warn);
456 }
457 }
459 /** check that type parameters are within their bounds.
460 */
461 private void checkWithinBounds(List<Type> tvars,
462 List<Type> arguments,
463 Warner warn)
464 throws InvalidInstanceException {
465 for (List<Type> tvs = tvars, args = arguments;
466 tvs.nonEmpty();
467 tvs = tvs.tail, args = args.tail) {
468 if (args.head instanceof UndetVar) continue;
469 List<Type> bounds = types.subst(types.getBounds((TypeVar)tvs.head), tvars, arguments);
470 if (!types.isSubtypeUnchecked(args.head, bounds, warn))
471 throw invalidInstanceException
472 .setMessage("inferred.do.not.conform.to.bounds",
473 args.head, bounds);
474 }
475 }
476 }
