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 | */ |
25 | |
26 | package com.sun.tools.javac.comp; |
27 | |
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 | |
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.*; |
36 | |
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>(); |
47 | |
48 | /** A value for prototypes that admit any type, including polymorphic ones. */ |
49 | public static final Type anyPoly = new Type(NONE, null); |
50 | |
51 | Symtab syms; |
52 | Types types; |
53 | |
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 | } |
60 | |
61 | protected Infer(Context context) { |
62 | context.put(inferKey, this); |
63 | syms = Symtab.instance(context); |
64 | types = Types.instance(context); |
65 | } |
66 | |
67 | public static class NoInstanceException extends RuntimeException { |
68 | private static final long serialVersionUID = 0; |
69 | |
70 | boolean isAmbiguous; // exist several incomparable best instances? |
71 | |
72 | JCDiagnostic diagnostic; |
73 | |
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); |
102 | |
103 | /*************************************************************************** |
104 | * Auxiliary type values and classes |
105 | ***************************************************************************/ |
106 | |
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 | }; |
115 | |
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 | }; |
138 | |
139 | /*************************************************************************** |
140 | * Mini/Maximization of UndetVars |
141 | ***************************************************************************/ |
142 | |
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 | } |
188 | |
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; |
198 | else { |
199 | that.inst = types.lub(that.lobounds); |
200 | if (that.inst == null) |
201 | throw ambiguousNoInstanceException |
202 | .setMessage("no.unique.minimal.instance.exists", |
203 | that.qtype, that.lobounds); |
204 | } |
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 | } |
224 | |
225 | /*************************************************************************** |
226 | * Exported Methods |
227 | ***************************************************************************/ |
228 | |
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 |
258 | |
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); |
263 | |
264 | return getInstFun.apply(qtype1); |
265 | } |
266 | |
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; |
279 | |
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 | } |
306 | |
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 | } |
325 | |
326 | // minimize as yet undetermined type variables |
327 | for (Type t : undetvars) |
328 | minimizeInst((UndetVar) t, warn); |
329 | |
330 | /** Type variables instantiated to bottom */ |
331 | ListBuffer<Type> restvars = new ListBuffer<Type>(); |
332 | |
333 | /** Instantiated types or TypeVars if under-constrained */ |
334 | ListBuffer<Type> insttypes = new ListBuffer<Type>(); |
335 | |
336 | /** Instantiated types or UndetVars if under-constrained */ |
337 | ListBuffer<Type> undettypes = new ListBuffer<Type>(); |
338 | |
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); |
352 | |
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 | } |
360 | |
361 | // return instantiated version of method type |
362 | return types.subst(mt, tvars, insttypes.toList()); |
363 | } |
364 | //where |
365 | |
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 | } |
385 | |
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 | } |