Mercurial > jdk8-mips64-public > langtools / file revision
src/share/classes/com/sun/tools/javac/comp/Infer.java@38bd6375f37d
src/share/classes/com/sun/tools/javac/comp/Infer.java
Tue, 04 Mar 2008 15:45:20 +0000
- author
- mcimadamore
- date
- Tue, 04 Mar 2008 15:45:20 +0000
- changeset 8
- 38bd6375f37d
- parent 5
- b45f8d4794b7
- child 17
- 6e4cefcce80a
- permissions
- -rw-r--r--
6663588: Compiler goes into infinite loop for Cyclic Inheritance test case
Summary: interplay between cyclic inheritance and tvar bounds hangs javac
Reviewed-by: jjg
1 /*
2 * Copyright 1999-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any 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.*;
33 import static com.sun.tools.javac.code.Flags.*;
34 import static com.sun.tools.javac.code.Kinds.*;
35 import static com.sun.tools.javac.code.TypeTags.*;
37 /** Helper class for type parameter inference, used by the attribution phase.
38 *
39 * <p><b>This is NOT part of any API supported by Sun Microsystems. If
40 * you write code that depends on this, you do so at your own risk.
41 * This code and its internal interfaces are subject to change or
42 * deletion without notice.</b>
43 */
44 public class Infer {
45 protected static final Context.Key<Infer> inferKey =
46 new Context.Key<Infer>();
48 /** A value for prototypes that admit any type, including polymorphic ones. */
49 public static final Type anyPoly = new Type(NONE, null);
51 Symtab syms;
52 Types types;
54 public static Infer instance(Context context) {
55 Infer instance = context.get(inferKey);
56 if (instance == null)
57 instance = new Infer(context);
58 return instance;
59 }
61 protected Infer(Context context) {
62 context.put(inferKey, this);
63 syms = Symtab.instance(context);
64 types = Types.instance(context);
65 }
67 public static class NoInstanceException extends RuntimeException {
68 private static final long serialVersionUID = 0;
70 boolean isAmbiguous; // exist several incomparable best instances?
72 JCDiagnostic diagnostic;
74 NoInstanceException(boolean isAmbiguous) {
75 this.diagnostic = null;
76 this.isAmbiguous = isAmbiguous;
77 }
78 NoInstanceException setMessage(String key) {
79 this.diagnostic = JCDiagnostic.fragment(key);
80 return this;
81 }
82 NoInstanceException setMessage(String key, Object arg1) {
83 this.diagnostic = JCDiagnostic.fragment(key, arg1);
84 return this;
85 }
86 NoInstanceException setMessage(String key, Object arg1, Object arg2) {
87 this.diagnostic = JCDiagnostic.fragment(key, arg1, arg2);
88 return this;
89 }
90 NoInstanceException setMessage(String key, Object arg1, Object arg2, Object arg3) {
91 this.diagnostic = JCDiagnostic.fragment(key, arg1, arg2, arg3);
92 return this;
93 }
94 public JCDiagnostic getDiagnostic() {
95 return diagnostic;
96 }
97 }
98 private final NoInstanceException ambiguousNoInstanceException =
99 new NoInstanceException(true);
100 private final NoInstanceException unambiguousNoInstanceException =
101 new NoInstanceException(false);
103 /***************************************************************************
104 * Auxiliary type values and classes
105 ***************************************************************************/
107 /** A mapping that turns type variables into undetermined type variables.
108 */
109 Mapping fromTypeVarFun = new Mapping("fromTypeVarFun") {
110 public Type apply(Type t) {
111 if (t.tag == TYPEVAR) return new UndetVar(t);
112 else return t.map(this);
113 }
114 };
116 /** A mapping that returns its type argument with every UndetVar replaced
117 * by its `inst' field. Throws a NoInstanceException
118 * if this not possible because an `inst' field is null.
119 */
120 Mapping getInstFun = new Mapping("getInstFun") {
121 public Type apply(Type t) {
122 switch (t.tag) {
123 case UNKNOWN:
124 throw ambiguousNoInstanceException
125 .setMessage("undetermined.type");
126 case UNDETVAR:
127 UndetVar that = (UndetVar) t;
128 if (that.inst == null)
129 throw ambiguousNoInstanceException
130 .setMessage("type.variable.has.undetermined.type",
131 that.qtype);
132 return apply(that.inst);
133 default:
134 return t.map(this);
135 }
136 }
137 };
139 /***************************************************************************
140 * Mini/Maximization of UndetVars
141 ***************************************************************************/
143 /** Instantiate undetermined type variable to its minimal upper bound.
144 * Throw a NoInstanceException if this not possible.
145 */
146 void maximizeInst(UndetVar that, Warner warn) throws NoInstanceException {
147 if (that.inst == null) {
148 if (that.hibounds.isEmpty())
149 that.inst = syms.objectType;
150 else if (that.hibounds.tail.isEmpty())
151 that.inst = that.hibounds.head;
152 else {
153 for (List<Type> bs = that.hibounds;
154 bs.nonEmpty() && that.inst == null;
155 bs = bs.tail) {
156 // System.out.println("hibounds = " + that.hibounds);//DEBUG
157 if (isSubClass(bs.head, that.hibounds))
158 that.inst = types.fromUnknownFun.apply(bs.head);
159 }
160 if (that.inst == null || !types.isSubtypeUnchecked(that.inst, that.hibounds, warn))
161 throw ambiguousNoInstanceException
162 .setMessage("no.unique.maximal.instance.exists",
163 that.qtype, that.hibounds);
164 }
165 }
166 }
167 //where
168 private boolean isSubClass(Type t, final List<Type> ts) {
169 t = t.baseType();
170 if (t.tag == TYPEVAR) {
171 List<Type> bounds = types.getBounds((TypeVar)t);
172 for (Type s : ts) {
173 if (!types.isSameType(t, s.baseType())) {
174 for (Type bound : bounds) {
175 if (!isSubClass(bound, List.of(s.baseType())))
176 return false;
177 }
178 }
179 }
180 } else {
181 for (Type s : ts) {
182 if (!t.tsym.isSubClass(s.baseType().tsym, types))
183 return false;
184 }
185 }
186 return true;
187 }
189 /** Instaniate undetermined type variable to the lub of all its lower bounds.
190 * Throw a NoInstanceException if this not possible.
191 */
192 void minimizeInst(UndetVar that, Warner warn) throws NoInstanceException {
193 if (that.inst == null) {
194 if (that.lobounds.isEmpty())
195 that.inst = syms.botType;
196 else if (that.lobounds.tail.isEmpty())
197 that.inst = that.lobounds.head.isPrimitive() ? syms.errType : that.lobounds.head;
198 else {
199 that.inst = types.lub(that.lobounds);
200 }
201 if (that.inst == null || that.inst == syms.errType)
202 throw ambiguousNoInstanceException
203 .setMessage("no.unique.minimal.instance.exists",
204 that.qtype, that.lobounds);
205 // VGJ: sort of inlined maximizeInst() below. Adding
206 // bounds can cause lobounds that are above hibounds.
207 if (that.hibounds.isEmpty())
208 return;
209 Type hb = null;
210 if (that.hibounds.tail.isEmpty())
211 hb = that.hibounds.head;
212 else for (List<Type> bs = that.hibounds;
213 bs.nonEmpty() && hb == null;
214 bs = bs.tail) {
215 if (isSubClass(bs.head, that.hibounds))
216 hb = types.fromUnknownFun.apply(bs.head);
217 }
218 if (hb == null ||
219 !types.isSubtypeUnchecked(hb, that.hibounds, warn) ||
220 !types.isSubtypeUnchecked(that.inst, hb, warn))
221 throw ambiguousNoInstanceException;
222 }
223 }
225 /***************************************************************************
226 * Exported Methods
227 ***************************************************************************/
229 /** Try to instantiate expression type `that' to given type `to'.
230 * If a maximal instantiation exists which makes this type
231 * a subtype of type `to', return the instantiated type.
232 * If no instantiation exists, or if several incomparable
233 * best instantiations exist throw a NoInstanceException.
234 */
235 public Type instantiateExpr(ForAll that,
236 Type to,
237 Warner warn) throws NoInstanceException {
238 List<Type> undetvars = Type.map(that.tvars, fromTypeVarFun);
239 for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail) {
240 UndetVar v = (UndetVar) l.head;
241 ListBuffer<Type> hibounds = new ListBuffer<Type>();
242 for (List<Type> l1 = types.getBounds((TypeVar) v.qtype); l1.nonEmpty(); l1 = l1.tail) {
243 if (!l1.head.containsSome(that.tvars)) {
244 hibounds.append(l1.head);
245 }
246 }
247 v.hibounds = hibounds.toList();
248 }
249 Type qtype1 = types.subst(that.qtype, that.tvars, undetvars);
250 if (!types.isSubtype(qtype1, to)) {
251 throw unambiguousNoInstanceException
252 .setMessage("no.conforming.instance.exists",
253 that.tvars, that.qtype, to);
254 }
255 for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail)
256 maximizeInst((UndetVar) l.head, warn);
257 // System.out.println(" = " + qtype1.map(getInstFun));//DEBUG
259 // check bounds
260 List<Type> targs = Type.map(undetvars, getInstFun);
261 targs = types.subst(targs, that.tvars, targs);
262 checkWithinBounds(that.tvars, targs, warn);
264 return getInstFun.apply(qtype1);
265 }
267 /** Instantiate method type `mt' by finding instantiations of
268 * `tvars' so that method can be applied to `argtypes'.
269 */
270 public Type instantiateMethod(List<Type> tvars,
271 MethodType mt,
272 List<Type> argtypes,
273 boolean allowBoxing,
274 boolean useVarargs,
275 Warner warn) throws NoInstanceException {
276 //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
277 List<Type> undetvars = Type.map(tvars, fromTypeVarFun);
278 List<Type> formals = mt.argtypes;
280 // instantiate all polymorphic argument types and
281 // set up lower bounds constraints for undetvars
282 Type varargsFormal = useVarargs ? formals.last() : null;
283 while (argtypes.nonEmpty() && formals.head != varargsFormal) {
284 Type ft = formals.head;
285 Type at = argtypes.head.baseType();
286 if (at.tag == FORALL)
287 at = instantiateArg((ForAll) at, ft, tvars, warn);
288 Type sft = types.subst(ft, tvars, undetvars);
289 boolean works = allowBoxing
290 ? types.isConvertible(at, sft, warn)
291 : types.isSubtypeUnchecked(at, sft, warn);
292 if (!works) {
293 throw unambiguousNoInstanceException
294 .setMessage("no.conforming.assignment.exists",
295 tvars, at, ft);
296 }
297 formals = formals.tail;
298 argtypes = argtypes.tail;
299 }
300 if (formals.head != varargsFormal || // not enough args
301 !useVarargs && argtypes.nonEmpty()) { // too many args
302 // argument lists differ in length
303 throw unambiguousNoInstanceException
304 .setMessage("arg.length.mismatch");
305 }
307 // for varargs arguments as well
308 if (useVarargs) {
309 Type elt = types.elemtype(varargsFormal);
310 Type sft = types.subst(elt, tvars, undetvars);
311 while (argtypes.nonEmpty()) {
312 Type ft = sft;
313 Type at = argtypes.head.baseType();
314 if (at.tag == FORALL)
315 at = instantiateArg((ForAll) at, ft, tvars, warn);
316 boolean works = types.isConvertible(at, sft, warn);
317 if (!works) {
318 throw unambiguousNoInstanceException
319 .setMessage("no.conforming.assignment.exists",
320 tvars, at, ft);
321 }
322 argtypes = argtypes.tail;
323 }
324 }
326 // minimize as yet undetermined type variables
327 for (Type t : undetvars)
328 minimizeInst((UndetVar) t, warn);
330 /** Type variables instantiated to bottom */
331 ListBuffer<Type> restvars = new ListBuffer<Type>();
333 /** Instantiated types or TypeVars if under-constrained */
334 ListBuffer<Type> insttypes = new ListBuffer<Type>();
336 /** Instantiated types or UndetVars if under-constrained */
337 ListBuffer<Type> undettypes = new ListBuffer<Type>();
339 for (Type t : undetvars) {
340 UndetVar uv = (UndetVar)t;
341 if (uv.inst.tag == BOT) {
342 restvars.append(uv.qtype);
343 insttypes.append(uv.qtype);
344 undettypes.append(uv);
345 uv.inst = null;
346 } else {
347 insttypes.append(uv.inst);
348 undettypes.append(uv.inst);
349 }
350 }
351 checkWithinBounds(tvars, undettypes.toList(), warn);
353 if (!restvars.isEmpty()) {
354 // if there are uninstantiated variables,
355 // quantify result type with them
356 mt = new MethodType(mt.argtypes,
357 new ForAll(restvars.toList(), mt.restype),
358 mt.thrown, syms.methodClass);
359 }
361 // return instantiated version of method type
362 return types.subst(mt, tvars, insttypes.toList());
363 }
364 //where
366 /** Try to instantiate argument type `that' to given type `to'.
367 * If this fails, try to insantiate `that' to `to' where
368 * every occurrence of a type variable in `tvars' is replaced
369 * by an unknown type.
370 */
371 private Type instantiateArg(ForAll that,
372 Type to,
373 List<Type> tvars,
374 Warner warn) throws NoInstanceException {
375 List<Type> targs;
376 try {
377 return instantiateExpr(that, to, warn);
378 } catch (NoInstanceException ex) {
379 Type to1 = to;
380 for (List<Type> l = tvars; l.nonEmpty(); l = l.tail)
381 to1 = types.subst(to1, List.of(l.head), List.of(syms.unknownType));
382 return instantiateExpr(that, to1, warn);
383 }
384 }
386 /** check that type parameters are within their bounds.
387 */
388 private void checkWithinBounds(List<Type> tvars,
389 List<Type> arguments,
390 Warner warn)
391 throws NoInstanceException {
392 for (List<Type> tvs = tvars, args = arguments;
393 tvs.nonEmpty();
394 tvs = tvs.tail, args = args.tail) {
395 if (args.head instanceof UndetVar) continue;
396 List<Type> bounds = types.subst(types.getBounds((TypeVar)tvs.head), tvars, arguments);
397 if (!types.isSubtypeUnchecked(args.head, bounds, warn))
398 throw unambiguousNoInstanceException
399 .setMessage("inferred.do.not.conform.to.bounds",
400 arguments, tvars);
401 }
402 }
403 }
