1 /*
2 * Copyright 2003-2009 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.code;
27
28 import java.lang.ref.SoftReference;
29 import java.util.*;
30
31 import com.sun.tools.javac.util.*;
32 import com.sun.tools.javac.util.List;
33
34 import com.sun.tools.javac.jvm.ClassReader;
35 import com.sun.tools.javac.comp.Check;
36
37 import static com.sun.tools.javac.code.Type.*;
38 import static com.sun.tools.javac.code.TypeTags.*;
39 import static com.sun.tools.javac.code.Symbol.*;
40 import static com.sun.tools.javac.code.Flags.*;
41 import static com.sun.tools.javac.code.BoundKind.*;
42 import static com.sun.tools.javac.util.ListBuffer.lb;
43
44 /**
45 * Utility class containing various operations on types.
46 *
47 * <p>Unless other names are more illustrative, the following naming
48 * conventions should be observed in this file:
49 *
50 * <dl>
51 * <dt>t</dt>
52 * <dd>If the first argument to an operation is a type, it should be named t.</dd>
53 * <dt>s</dt>
54 * <dd>Similarly, if the second argument to an operation is a type, it should be named s.</dd>
55 * <dt>ts</dt>
56 * <dd>If an operations takes a list of types, the first should be named ts.</dd>
57 * <dt>ss</dt>
58 * <dd>A second list of types should be named ss.</dd>
59 * </dl>
60 *
61 * <p><b>This is NOT part of any API supported by Sun Microsystems.
62 * If you write code that depends on this, you do so at your own risk.
63 * This code and its internal interfaces are subject to change or
64 * deletion without notice.</b>
65 */
66 public class Types {
67 protected static final Context.Key<Types> typesKey =
68 new Context.Key<Types>();
69
70 final Symtab syms;
71 final JavacMessages messages;
72 final Names names;
73 final boolean allowBoxing;
74 final ClassReader reader;
75 final Source source;
76 final Check chk;
77 List<Warner> warnStack = List.nil();
78 final Name capturedName;
79
80 // <editor-fold defaultstate="collapsed" desc="Instantiating">
81 public static Types instance(Context context) {
82 Types instance = context.get(typesKey);
83 if (instance == null)
84 instance = new Types(context);
85 return instance;
86 }
87
88 protected Types(Context context) {
89 context.put(typesKey, this);
90 syms = Symtab.instance(context);
91 names = Names.instance(context);
92 allowBoxing = Source.instance(context).allowBoxing();
93 reader = ClassReader.instance(context);
94 source = Source.instance(context);
95 chk = Check.instance(context);
96 capturedName = names.fromString("<captured wildcard>");
97 messages = JavacMessages.instance(context);
98 }
99 // </editor-fold>
100
101 // <editor-fold defaultstate="collapsed" desc="upperBound">
102 /**
103 * The "rvalue conversion".<br>
104 * The upper bound of most types is the type
105 * itself. Wildcards, on the other hand have upper
106 * and lower bounds.
107 * @param t a type
108 * @return the upper bound of the given type
109 */
110 public Type upperBound(Type t) {
111 return upperBound.visit(t);
112 }
113 // where
114 private final MapVisitor<Void> upperBound = new MapVisitor<Void>() {
115
116 @Override
117 public Type visitWildcardType(WildcardType t, Void ignored) {
118 if (t.isSuperBound())
119 return t.bound == null ? syms.objectType : t.bound.bound;
120 else
121 return visit(t.type);
122 }
123
124 @Override
125 public Type visitCapturedType(CapturedType t, Void ignored) {
126 return visit(t.bound);
127 }
128 };
129 // </editor-fold>
130
131 // <editor-fold defaultstate="collapsed" desc="lowerBound">
132 /**
133 * The "lvalue conversion".<br>
134 * The lower bound of most types is the type
135 * itself. Wildcards, on the other hand have upper
136 * and lower bounds.
137 * @param t a type
138 * @return the lower bound of the given type
139 */
140 public Type lowerBound(Type t) {
141 return lowerBound.visit(t);
142 }
143 // where
144 private final MapVisitor<Void> lowerBound = new MapVisitor<Void>() {
145
146 @Override
147 public Type visitWildcardType(WildcardType t, Void ignored) {
148 return t.isExtendsBound() ? syms.botType : visit(t.type);
149 }
150
151 @Override
152 public Type visitCapturedType(CapturedType t, Void ignored) {
153 return visit(t.getLowerBound());
154 }
155 };
156 // </editor-fold>
157
158 // <editor-fold defaultstate="collapsed" desc="isUnbounded">
159 /**
160 * Checks that all the arguments to a class are unbounded
161 * wildcards or something else that doesn't make any restrictions
162 * on the arguments. If a class isUnbounded, a raw super- or
163 * subclass can be cast to it without a warning.
164 * @param t a type
165 * @return true iff the given type is unbounded or raw
166 */
167 public boolean isUnbounded(Type t) {
168 return isUnbounded.visit(t);
169 }
170 // where
171 private final UnaryVisitor<Boolean> isUnbounded = new UnaryVisitor<Boolean>() {
172
173 public Boolean visitType(Type t, Void ignored) {
174 return true;
175 }
176
177 @Override
178 public Boolean visitClassType(ClassType t, Void ignored) {
179 List<Type> parms = t.tsym.type.allparams();
180 List<Type> args = t.allparams();
181 while (parms.nonEmpty()) {
182 WildcardType unb = new WildcardType(syms.objectType,
183 BoundKind.UNBOUND,
184 syms.boundClass,
185 (TypeVar)parms.head);
186 if (!containsType(args.head, unb))
187 return false;
188 parms = parms.tail;
189 args = args.tail;
190 }
191 return true;
192 }
193 };
194 // </editor-fold>
195
196 // <editor-fold defaultstate="collapsed" desc="asSub">
197 /**
198 * Return the least specific subtype of t that starts with symbol
199 * sym. If none exists, return null. The least specific subtype
200 * is determined as follows:
201 *
202 * <p>If there is exactly one parameterized instance of sym that is a
203 * subtype of t, that parameterized instance is returned.<br>
204 * Otherwise, if the plain type or raw type `sym' is a subtype of
205 * type t, the type `sym' itself is returned. Otherwise, null is
206 * returned.
207 */
208 public Type asSub(Type t, Symbol sym) {
209 return asSub.visit(t, sym);
210 }
211 // where
212 private final SimpleVisitor<Type,Symbol> asSub = new SimpleVisitor<Type,Symbol>() {
213
214 public Type visitType(Type t, Symbol sym) {
215 return null;
216 }
217
218 @Override
219 public Type visitClassType(ClassType t, Symbol sym) {
220 if (t.tsym == sym)
221 return t;
222 Type base = asSuper(sym.type, t.tsym);
223 if (base == null)
224 return null;
225 ListBuffer<Type> from = new ListBuffer<Type>();
226 ListBuffer<Type> to = new ListBuffer<Type>();
227 try {
228 adapt(base, t, from, to);
229 } catch (AdaptFailure ex) {
230 return null;
231 }
232 Type res = subst(sym.type, from.toList(), to.toList());
233 if (!isSubtype(res, t))
234 return null;
235 ListBuffer<Type> openVars = new ListBuffer<Type>();
236 for (List<Type> l = sym.type.allparams();
237 l.nonEmpty(); l = l.tail)
238 if (res.contains(l.head) && !t.contains(l.head))
239 openVars.append(l.head);
240 if (openVars.nonEmpty()) {
241 if (t.isRaw()) {
242 // The subtype of a raw type is raw
243 res = erasure(res);
244 } else {
245 // Unbound type arguments default to ?
246 List<Type> opens = openVars.toList();
247 ListBuffer<Type> qs = new ListBuffer<Type>();
248 for (List<Type> iter = opens; iter.nonEmpty(); iter = iter.tail) {
249 qs.append(new WildcardType(syms.objectType, BoundKind.UNBOUND, syms.boundClass, (TypeVar) iter.head));
250 }
251 res = subst(res, opens, qs.toList());
252 }
253 }
254 return res;
255 }
256
257 @Override
258 public Type visitErrorType(ErrorType t, Symbol sym) {
259 return t;
260 }
261 };
262 // </editor-fold>
263
264 // <editor-fold defaultstate="collapsed" desc="isConvertible">
265 /**
266 * Is t a subtype of or convertiable via boxing/unboxing
267 * convertions to s?
268 */
269 public boolean isConvertible(Type t, Type s, Warner warn) {
270 boolean tPrimitive = t.isPrimitive();
271 boolean sPrimitive = s.isPrimitive();
272 if (tPrimitive == sPrimitive)
273 return isSubtypeUnchecked(t, s, warn);
274 if (!allowBoxing) return false;
275 return tPrimitive
276 ? isSubtype(boxedClass(t).type, s)
277 : isSubtype(unboxedType(t), s);
278 }
279
280 /**
281 * Is t a subtype of or convertiable via boxing/unboxing
282 * convertions to s?
283 */
284 public boolean isConvertible(Type t, Type s) {
285 return isConvertible(t, s, Warner.noWarnings);
286 }
287 // </editor-fold>
288
289 // <editor-fold defaultstate="collapsed" desc="isSubtype">
290 /**
291 * Is t an unchecked subtype of s?
292 */
293 public boolean isSubtypeUnchecked(Type t, Type s) {
294 return isSubtypeUnchecked(t, s, Warner.noWarnings);
295 }
296 /**
297 * Is t an unchecked subtype of s?
298 */
299 public boolean isSubtypeUnchecked(Type t, Type s, Warner warn) {
300 if (t.tag == ARRAY && s.tag == ARRAY) {
301 return (((ArrayType)t).elemtype.tag <= lastBaseTag)
302 ? isSameType(elemtype(t), elemtype(s))
303 : isSubtypeUnchecked(elemtype(t), elemtype(s), warn);
304 } else if (isSubtype(t, s)) {
305 return true;
306 }
307 else if (t.tag == TYPEVAR) {
308 return isSubtypeUnchecked(t.getUpperBound(), s, warn);
309 }
310 else if (s.tag == UNDETVAR) {
311 UndetVar uv = (UndetVar)s;
312 if (uv.inst != null)
313 return isSubtypeUnchecked(t, uv.inst, warn);
314 }
315 else if (!s.isRaw()) {
316 Type t2 = asSuper(t, s.tsym);
317 if (t2 != null && t2.isRaw()) {
318 if (isReifiable(s))
319 warn.silentUnchecked();
320 else
321 warn.warnUnchecked();
322 return true;
323 }
324 }
325 return false;
326 }
327
328 /**
329 * Is t a subtype of s?<br>
330 * (not defined for Method and ForAll types)
331 */
332 final public boolean isSubtype(Type t, Type s) {
333 return isSubtype(t, s, true);
334 }
335 final public boolean isSubtypeNoCapture(Type t, Type s) {
336 return isSubtype(t, s, false);
337 }
338 public boolean isSubtype(Type t, Type s, boolean capture) {
339 if (t == s)
340 return true;
341
342 if (s.tag >= firstPartialTag)
343 return isSuperType(s, t);
344
345 if (s.isCompound()) {
346 for (Type s2 : interfaces(s).prepend(supertype(s))) {
347 if (!isSubtype(t, s2, capture))
348 return false;
349 }
350 return true;
351 }
352
353 Type lower = lowerBound(s);
354 if (s != lower)
355 return isSubtype(capture ? capture(t) : t, lower, false);
356
357 return isSubtype.visit(capture ? capture(t) : t, s);
358 }
359 // where
360 private TypeRelation isSubtype = new TypeRelation()
361 {
362 public Boolean visitType(Type t, Type s) {
363 switch (t.tag) {
364 case BYTE: case CHAR:
365 return (t.tag == s.tag ||
366 t.tag + 2 <= s.tag && s.tag <= DOUBLE);
367 case SHORT: case INT: case LONG: case FLOAT: case DOUBLE:
368 return t.tag <= s.tag && s.tag <= DOUBLE;
369 case BOOLEAN: case VOID:
370 return t.tag == s.tag;
371 case TYPEVAR:
372 return isSubtypeNoCapture(t.getUpperBound(), s);
373 case BOT:
374 return
375 s.tag == BOT || s.tag == CLASS ||
376 s.tag == ARRAY || s.tag == TYPEVAR ||
377 s.tag == FUNCTION;
378 case NONE:
379 return false;
380 default:
381 throw new AssertionError("isSubtype " + t.tag);
382 }
383 }
384
385 private Set<TypePair> cache = new HashSet<TypePair>();
386
387 private boolean containsTypeRecursive(Type t, Type s) {
388 TypePair pair = new TypePair(t, s);
389 if (cache.add(pair)) {
390 try {
391 return containsType(t.getTypeArguments(),
392 s.getTypeArguments());
393 } finally {
394 cache.remove(pair);
395 }
396 } else {
397 return containsType(t.getTypeArguments(),
398 rewriteSupers(s).getTypeArguments());
399 }
400 }
401
402 private Type rewriteSupers(Type t) {
403 if (!t.isParameterized())
404 return t;
405 ListBuffer<Type> from = lb();
406 ListBuffer<Type> to = lb();
407 adaptSelf(t, from, to);
408 if (from.isEmpty())
409 return t;
410 ListBuffer<Type> rewrite = lb();
411 boolean changed = false;
412 for (Type orig : to.toList()) {
413 Type s = rewriteSupers(orig);
414 if (s.isSuperBound() && !s.isExtendsBound()) {
415 s = new WildcardType(syms.objectType,
416 BoundKind.UNBOUND,
417 syms.boundClass);
418 changed = true;
419 } else if (s != orig) {
420 s = new WildcardType(upperBound(s),
421 BoundKind.EXTENDS,
422 syms.boundClass);
423 changed = true;
424 }
425 rewrite.append(s);
426 }
427 if (changed)
428 return subst(t.tsym.type, from.toList(), rewrite.toList());
429 else
430 return t;
431 }
432
433 @Override
434 public Boolean visitClassType(ClassType t, Type s) {
435 Type sup = asSuper(t, s.tsym);
436 return sup != null
437 && sup.tsym == s.tsym
438 // You're not allowed to write
439 // Vector<Object> vec = new Vector<String>();
440 // But with wildcards you can write
441 // Vector<? extends Object> vec = new Vector<String>();
442 // which means that subtype checking must be done
443 // here instead of same-type checking (via containsType).
444 && (!s.isParameterized() || containsTypeRecursive(s, sup))
445 && isSubtypeNoCapture(sup.getEnclosingType(),
446 s.getEnclosingType());
447 }
448
449 @Override
450 public Boolean visitMethodType(MethodType t, Type s) {
451 if (s.tsym == syms.objectType.tsym || s.tsym == syms.methodHandleType.tsym)
452 return true;
453
454 if (s.tag != FUNCTION)
455 return false;
456
457 //check covariance/contravariance
458 MethodType mType = (MethodType) s;
459 if (!(isSubtypeNoCapture(t.restype, mType.restype)))
460 return false;
461
462 List<Type> lt = t.argtypes;
463 List<Type> lmType = mType.argtypes;
464 while (lt.nonEmpty() && lmType.nonEmpty()) {
465 if (!(isSubtypeNoCapture(lmType.head, lt.head)))
466 return false;
467 lt = lt.tail;
468 lmType = lmType.tail;
469 }
470 return lt.isEmpty() && lmType.isEmpty();
471 }
472
473 @Override
474 public Boolean visitArrayType(ArrayType t, Type s) {
475 if (s.tag == ARRAY) {
476 if (t.elemtype.tag <= lastBaseTag)
477 return isSameType(t.elemtype, elemtype(s));
478 else
479 return isSubtypeNoCapture(t.elemtype, elemtype(s));
480 }
481
482 if (s.tag == CLASS) {
483 Name sname = s.tsym.getQualifiedName();
484 return sname == names.java_lang_Object
485 || sname == names.java_lang_Cloneable
486 || sname == names.java_io_Serializable;
487 }
488
489 return false;
490 }
491
492 @Override
493 public Boolean visitUndetVar(UndetVar t, Type s) {
494 //todo: test against origin needed? or replace with substitution?
495 if (t == s || t.qtype == s || s.tag == ERROR || s.tag == UNKNOWN)
496 return true;
497
498 if (t.inst != null)
499 return isSubtypeNoCapture(t.inst, s); // TODO: ", warn"?
500
501 t.hibounds = t.hibounds.prepend(s);
502 return true;
503 }
504
505 @Override
506 public Boolean visitErrorType(ErrorType t, Type s) {
507 return true;
508 }
509 };
510
511 /**
512 * Is t a subtype of every type in given list `ts'?<br>
513 * (not defined for Method and ForAll types)<br>
514 * Allows unchecked conversions.
515 */
516 public boolean isSubtypeUnchecked(Type t, List<Type> ts, Warner warn) {
517 for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
518 if (!isSubtypeUnchecked(t, l.head, warn))
519 return false;
520 return true;
521 }
522
523 /**
524 * Are corresponding elements of ts subtypes of ss? If lists are
525 * of different length, return false.
526 */
527 public boolean isSubtypes(List<Type> ts, List<Type> ss) {
528 while (ts.tail != null && ss.tail != null
529 /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
530 isSubtype(ts.head, ss.head)) {
531 ts = ts.tail;
532 ss = ss.tail;
533 }
534 return ts.tail == null && ss.tail == null;
535 /*inlined: ts.isEmpty() && ss.isEmpty();*/
536 }
537
538 /**
539 * Are corresponding elements of ts subtypes of ss, allowing
540 * unchecked conversions? If lists are of different length,
541 * return false.
542 **/
543 public boolean isSubtypesUnchecked(List<Type> ts, List<Type> ss, Warner warn) {
544 while (ts.tail != null && ss.tail != null
545 /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
546 isSubtypeUnchecked(ts.head, ss.head, warn)) {
547 ts = ts.tail;
548 ss = ss.tail;
549 }
550 return ts.tail == null && ss.tail == null;
551 /*inlined: ts.isEmpty() && ss.isEmpty();*/
552 }
553 // </editor-fold>
554
555 // <editor-fold defaultstate="collapsed" desc="isSuperType">
556 /**
557 * Is t a supertype of s?
558 */
559 public boolean isSuperType(Type t, Type s) {
560 switch (t.tag) {
561 case ERROR:
562 return true;
563 case UNDETVAR: {
564 UndetVar undet = (UndetVar)t;
565 if (t == s ||
566 undet.qtype == s ||
567 s.tag == ERROR ||
568 s.tag == BOT) return true;
569 if (undet.inst != null)
570 return isSubtype(s, undet.inst);
571 undet.lobounds = undet.lobounds.prepend(s);
572 return true;
573 }
574 default:
575 return isSubtype(s, t);
576 }
577 }
578 // </editor-fold>
579
580 // <editor-fold defaultstate="collapsed" desc="isSameType">
581 /**
582 * Are corresponding elements of the lists the same type? If
583 * lists are of different length, return false.
584 */
585 public boolean isSameTypes(List<Type> ts, List<Type> ss) {
586 while (ts.tail != null && ss.tail != null
587 /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
588 isSameType(ts.head, ss.head)) {
589 ts = ts.tail;
590 ss = ss.tail;
591 }
592 return ts.tail == null && ss.tail == null;
593 /*inlined: ts.isEmpty() && ss.isEmpty();*/
594 }
595
596 /**
597 * Is t the same type as s?
598 */
599 public boolean isSameType(Type t, Type s) {
600 return isSameType.visit(t, s);
601 }
602 // where
603 private TypeRelation isSameType = new TypeRelation() {
604
605 public Boolean visitType(Type t, Type s) {
606 if (t == s)
607 return true;
608
609 if (s.tag >= firstPartialTag)
610 return visit(s, t);
611
612 switch (t.tag) {
613 case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
614 case DOUBLE: case BOOLEAN: case VOID: case BOT: case NONE:
615 return t.tag == s.tag;
616 case TYPEVAR:
617 return s.isSuperBound()
618 && !s.isExtendsBound()
619 && visit(t, upperBound(s));
620 default:
621 throw new AssertionError("isSameType " + t.tag);
622 }
623 }
624
625 @Override
626 public Boolean visitWildcardType(WildcardType t, Type s) {
627 if (s.tag >= firstPartialTag)
628 return visit(s, t);
629 else
630 return false;
631 }
632
633 @Override
634 public Boolean visitClassType(ClassType t, Type s) {
635 if (t == s)
636 return true;
637
638 if (s.tag >= firstPartialTag)
639 return visit(s, t);
640
641 if (s.isSuperBound() && !s.isExtendsBound())
642 return visit(t, upperBound(s)) && visit(t, lowerBound(s));
643
644 if (t.isCompound() && s.isCompound()) {
645 if (!visit(supertype(t), supertype(s)))
646 return false;
647
648 HashSet<SingletonType> set = new HashSet<SingletonType>();
649 for (Type x : interfaces(t))
650 set.add(new SingletonType(x));
651 for (Type x : interfaces(s)) {
652 if (!set.remove(new SingletonType(x)))
653 return false;
654 }
655 return (set.size() == 0);
656 }
657 return t.tsym == s.tsym
658 && visit(t.getEnclosingType(), s.getEnclosingType())
659 && containsTypeEquivalent(t.getTypeArguments(), s.getTypeArguments());
660 }
661
662 @Override
663 public Boolean visitArrayType(ArrayType t, Type s) {
664 if (t == s)
665 return true;
666
667 if (s.tag >= firstPartialTag)
668 return visit(s, t);
669
670 return s.tag == ARRAY
671 && containsTypeEquivalent(t.elemtype, elemtype(s));
672 }
673
674 @Override
675 public Boolean visitMethodType(MethodType t, Type s) {
676 // isSameType for methods does not take thrown
677 // exceptions into account!
678 return hasSameArgs(t, s) && visit(t.getReturnType(), s.getReturnType());
679 }
680
681 @Override
682 public Boolean visitPackageType(PackageType t, Type s) {
683 return t == s;
684 }
685
686 @Override
687 public Boolean visitForAll(ForAll t, Type s) {
688 if (s.tag != FORALL)
689 return false;
690
691 ForAll forAll = (ForAll)s;
692 return hasSameBounds(t, forAll)
693 && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
694 }
695
696 @Override
697 public Boolean visitUndetVar(UndetVar t, Type s) {
698 if (s.tag == WILDCARD)
699 // FIXME, this might be leftovers from before capture conversion
700 return false;
701
702 if (t == s || t.qtype == s || s.tag == ERROR || s.tag == UNKNOWN)
703 return true;
704
705 if (t.inst != null)
706 return visit(t.inst, s);
707
708 t.inst = fromUnknownFun.apply(s);
709 for (List<Type> l = t.lobounds; l.nonEmpty(); l = l.tail) {
710 if (!isSubtype(l.head, t.inst))
711 return false;
712 }
713 for (List<Type> l = t.hibounds; l.nonEmpty(); l = l.tail) {
714 if (!isSubtype(t.inst, l.head))
715 return false;
716 }
717 return true;
718 }
719
720 @Override
721 public Boolean visitErrorType(ErrorType t, Type s) {
722 return true;
723 }
724 };
725 // </editor-fold>
726
727 // <editor-fold defaultstate="collapsed" desc="fromUnknownFun">
728 /**
729 * A mapping that turns all unknown types in this type to fresh
730 * unknown variables.
731 */
732 public Mapping fromUnknownFun = new Mapping("fromUnknownFun") {
733 public Type apply(Type t) {
734 if (t.tag == UNKNOWN) return new UndetVar(t);
735 else return t.map(this);
736 }
737 };
738 // </editor-fold>
739
740 // <editor-fold defaultstate="collapsed" desc="Contains Type">
741 public boolean containedBy(Type t, Type s) {
742 switch (t.tag) {
743 case UNDETVAR:
744 if (s.tag == WILDCARD) {
745 UndetVar undetvar = (UndetVar)t;
746 WildcardType wt = (WildcardType)s;
747 switch(wt.kind) {
748 case UNBOUND: //similar to ? extends Object
749 case EXTENDS: {
750 Type bound = upperBound(s);
751 // We should check the new upper bound against any of the
752 // undetvar's lower bounds.
753 for (Type t2 : undetvar.lobounds) {
754 if (!isSubtype(t2, bound))
755 return false;
756 }
757 undetvar.hibounds = undetvar.hibounds.prepend(bound);
758 break;
759 }
760 case SUPER: {
761 Type bound = lowerBound(s);
762 // We should check the new lower bound against any of the
763 // undetvar's lower bounds.
764 for (Type t2 : undetvar.hibounds) {
765 if (!isSubtype(bound, t2))
766 return false;
767 }
768 undetvar.lobounds = undetvar.lobounds.prepend(bound);
769 break;
770 }
771 }
772 return true;
773 } else {
774 return isSameType(t, s);
775 }
776 case ERROR:
777 return true;
778 default:
779 return containsType(s, t);
780 }
781 }
782
783 boolean containsType(List<Type> ts, List<Type> ss) {
784 while (ts.nonEmpty() && ss.nonEmpty()
785 && containsType(ts.head, ss.head)) {
786 ts = ts.tail;
787 ss = ss.tail;
788 }
789 return ts.isEmpty() && ss.isEmpty();
790 }
791
792 /**
793 * Check if t contains s.
794 *
795 * <p>T contains S if:
796 *
797 * <p>{@code L(T) <: L(S) && U(S) <: U(T)}
798 *
799 * <p>This relation is only used by ClassType.isSubtype(), that
800 * is,
801 *
802 * <p>{@code C<S> <: C<T> if T contains S.}
803 *
804 * <p>Because of F-bounds, this relation can lead to infinite
805 * recursion. Thus we must somehow break that recursion. Notice
806 * that containsType() is only called from ClassType.isSubtype().
807 * Since the arguments have already been checked against their
808 * bounds, we know:
809 *
810 * <p>{@code U(S) <: U(T) if T is "super" bound (U(T) *is* the bound)}
811 *
812 * <p>{@code L(T) <: L(S) if T is "extends" bound (L(T) is bottom)}
813 *
814 * @param t a type
815 * @param s a type
816 */
817 public boolean containsType(Type t, Type s) {
818 return containsType.visit(t, s);
819 }
820 // where
821 private TypeRelation containsType = new TypeRelation() {
822
823 private Type U(Type t) {
824 while (t.tag == WILDCARD) {
825 WildcardType w = (WildcardType)t;
826 if (w.isSuperBound())
827 return w.bound == null ? syms.objectType : w.bound.bound;
828 else
829 t = w.type;
830 }
831 return t;
832 }
833
834 private Type L(Type t) {
835 while (t.tag == WILDCARD) {
836 WildcardType w = (WildcardType)t;
837 if (w.isExtendsBound())
838 return syms.botType;
839 else
840 t = w.type;
841 }
842 return t;
843 }
844
845 public Boolean visitType(Type t, Type s) {
846 if (s.tag >= firstPartialTag)
847 return containedBy(s, t);
848 else
849 return isSameType(t, s);
850 }
851
852 void debugContainsType(WildcardType t, Type s) {
853 System.err.println();
854 System.err.format(" does %s contain %s?%n", t, s);
855 System.err.format(" %s U(%s) <: U(%s) %s = %s%n",
856 upperBound(s), s, t, U(t),
857 t.isSuperBound()
858 || isSubtypeNoCapture(upperBound(s), U(t)));
859 System.err.format(" %s L(%s) <: L(%s) %s = %s%n",
860 L(t), t, s, lowerBound(s),
861 t.isExtendsBound()
862 || isSubtypeNoCapture(L(t), lowerBound(s)));
863 System.err.println();
864 }
865
866 @Override
867 public Boolean visitWildcardType(WildcardType t, Type s) {
868 if (s.tag >= firstPartialTag)
869 return containedBy(s, t);
870 else {
871 // debugContainsType(t, s);
872 return isSameWildcard(t, s)
873 || isCaptureOf(s, t)
874 || ((t.isExtendsBound() || isSubtypeNoCapture(L(t), lowerBound(s))) &&
875 (t.isSuperBound() || isSubtypeNoCapture(upperBound(s), U(t))));
876 }
877 }
878
879 @Override
880 public Boolean visitUndetVar(UndetVar t, Type s) {
881 if (s.tag != WILDCARD)
882 return isSameType(t, s);
883 else
884 return false;
885 }
886
887 @Override
888 public Boolean visitErrorType(ErrorType t, Type s) {
889 return true;
890 }
891 };
892
893 public boolean isCaptureOf(Type s, WildcardType t) {
894 if (s.tag != TYPEVAR || !((TypeVar)s).isCaptured())
895 return false;
896 return isSameWildcard(t, ((CapturedType)s).wildcard);
897 }
898
899 public boolean isSameWildcard(WildcardType t, Type s) {
900 if (s.tag != WILDCARD)
901 return false;
902 WildcardType w = (WildcardType)s;
903 return w.kind == t.kind && w.type == t.type;
904 }
905
906 public boolean containsTypeEquivalent(List<Type> ts, List<Type> ss) {
907 while (ts.nonEmpty() && ss.nonEmpty()
908 && containsTypeEquivalent(ts.head, ss.head)) {
909 ts = ts.tail;
910 ss = ss.tail;
911 }
912 return ts.isEmpty() && ss.isEmpty();
913 }
914 // </editor-fold>
915
916 // <editor-fold defaultstate="collapsed" desc="isCastable">
917 public boolean isCastable(Type t, Type s) {
918 return isCastable(t, s, Warner.noWarnings);
919 }
920
921 /**
922 * Is t is castable to s?<br>
923 * s is assumed to be an erased type.<br>
924 * (not defined for Method and ForAll types).
925 */
926 public boolean isCastable(Type t, Type s, Warner warn) {
927 if (t == s)
928 return true;
929
930 if (t.isPrimitive() != s.isPrimitive())
931 return allowBoxing && isConvertible(t, s, warn);
932
933 if (warn != warnStack.head) {
934 try {
935 warnStack = warnStack.prepend(warn);
936 return isCastable.visit(t,s);
937 } finally {
938 warnStack = warnStack.tail;
939 }
940 } else {
941 return isCastable.visit(t,s);
942 }
943 }
944 // where
945 private TypeRelation isCastable = new TypeRelation() {
946
947 public Boolean visitType(Type t, Type s) {
948 if (s.tag == ERROR)
949 return true;
950
951 switch (t.tag) {
952 case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
953 case DOUBLE:
954 return s.tag <= DOUBLE;
955 case BOOLEAN:
956 return s.tag == BOOLEAN;
957 case VOID:
958 return false;
959 case BOT:
960 return isSubtype(t, s);
961 default:
962 throw new AssertionError();
963 }
964 }
965
966 @Override
967 public Boolean visitWildcardType(WildcardType t, Type s) {
968 return isCastable(upperBound(t), s, warnStack.head);
969 }
970
971 @Override
972 public Boolean visitClassType(ClassType t, Type s) {
973 if (s.tag == ERROR || s.tag == BOT)
974 return true;
975
976 if (s.tag == TYPEVAR) {
977 if (isCastable(s.getUpperBound(), t, Warner.noWarnings)) {
978 warnStack.head.warnUnchecked();
979 return true;
980 } else {
981 return false;
982 }
983 }
984
985 if (t.isCompound()) {
986 Warner oldWarner = warnStack.head;
987 warnStack.head = Warner.noWarnings;
988 if (!visit(supertype(t), s))
989 return false;
990 for (Type intf : interfaces(t)) {
991 if (!visit(intf, s))
992 return false;
993 }
994 if (warnStack.head.unchecked == true)
995 oldWarner.warnUnchecked();
996 return true;
997 }
998
999 if (s.isCompound()) {
1000 // call recursively to reuse the above code
1001 return visitClassType((ClassType)s, t);
1002 }
1003
1004 if (s.tag == CLASS || s.tag == ARRAY) {
1005 boolean upcast;
1006 if ((upcast = isSubtype(erasure(t), erasure(s)))
1007 || isSubtype(erasure(s), erasure(t))) {
1008 if (!upcast && s.tag == ARRAY) {
1009 if (!isReifiable(s))
1010 warnStack.head.warnUnchecked();
1011 return true;
1012 } else if (s.isRaw()) {
1013 return true;
1014 } else if (t.isRaw()) {
1015 if (!isUnbounded(s))
1016 warnStack.head.warnUnchecked();
1017 return true;
1018 }
1019 // Assume |a| <: |b|
1020 final Type a = upcast ? t : s;
1021 final Type b = upcast ? s : t;
1022 final boolean HIGH = true;
1023 final boolean LOW = false;
1024 final boolean DONT_REWRITE_TYPEVARS = false;
1025 Type aHigh = rewriteQuantifiers(a, HIGH, DONT_REWRITE_TYPEVARS);
1026 Type aLow = rewriteQuantifiers(a, LOW, DONT_REWRITE_TYPEVARS);
1027 Type bHigh = rewriteQuantifiers(b, HIGH, DONT_REWRITE_TYPEVARS);
1028 Type bLow = rewriteQuantifiers(b, LOW, DONT_REWRITE_TYPEVARS);
1029 Type lowSub = asSub(bLow, aLow.tsym);
1030 Type highSub = (lowSub == null) ? null : asSub(bHigh, aHigh.tsym);
1031 if (highSub == null) {
1032 final boolean REWRITE_TYPEVARS = true;
1033 aHigh = rewriteQuantifiers(a, HIGH, REWRITE_TYPEVARS);
1034 aLow = rewriteQuantifiers(a, LOW, REWRITE_TYPEVARS);
1035 bHigh = rewriteQuantifiers(b, HIGH, REWRITE_TYPEVARS);
1036 bLow = rewriteQuantifiers(b, LOW, REWRITE_TYPEVARS);
1037 lowSub = asSub(bLow, aLow.tsym);
1038 highSub = (lowSub == null) ? null : asSub(bHigh, aHigh.tsym);
1039 }
1040 if (highSub != null) {
1041 assert a.tsym == highSub.tsym && a.tsym == lowSub.tsym
1042 : a.tsym + " != " + highSub.tsym + " != " + lowSub.tsym;
1043 if (!disjointTypes(aHigh.allparams(), highSub.allparams())
1044 && !disjointTypes(aHigh.allparams(), lowSub.allparams())
1045 && !disjointTypes(aLow.allparams(), highSub.allparams())
1046 && !disjointTypes(aLow.allparams(), lowSub.allparams())) {
1047 if (upcast ? giveWarning(a, b) :
1048 giveWarning(b, a))
1049 warnStack.head.warnUnchecked();
1050 return true;
1051 }
1052 }
1053 if (isReifiable(s))
1054 return isSubtypeUnchecked(a, b);
1055 else
1056 return isSubtypeUnchecked(a, b, warnStack.head);
1057 }
1058
1059 // Sidecast
1060 if (s.tag == CLASS) {
1061 if ((s.tsym.flags() & INTERFACE) != 0) {
1062 return ((t.tsym.flags() & FINAL) == 0)
1063 ? sideCast(t, s, warnStack.head)
1064 : sideCastFinal(t, s, warnStack.head);
1065 } else if ((t.tsym.flags() & INTERFACE) != 0) {
1066 return ((s.tsym.flags() & FINAL) == 0)
1067 ? sideCast(t, s, warnStack.head)
1068 : sideCastFinal(t, s, warnStack.head);
1069 } else {
1070 // unrelated class types
1071 return false;
1072 }
1073 }
1074 }
1075 return false;
1076 }
1077
1078 @Override
1079 public Boolean visitArrayType(ArrayType t, Type s) {
1080 switch (s.tag) {
1081 case ERROR:
1082 case BOT:
1083 return true;
1084 case TYPEVAR:
1085 if (isCastable(s, t, Warner.noWarnings)) {
1086 warnStack.head.warnUnchecked();
1087 return true;
1088 } else {
1089 return false;
1090 }
1091 case CLASS:
1092 return isSubtype(t, s);
1093 case ARRAY:
1094 if (elemtype(t).tag <= lastBaseTag) {
1095 return elemtype(t).tag == elemtype(s).tag;
1096 } else {
1097 return visit(elemtype(t), elemtype(s));
1098 }
1099 default:
1100 return false;
1101 }
1102 }
1103
1104 @Override
1105 public Boolean visitTypeVar(TypeVar t, Type s) {
1106 switch (s.tag) {
1107 case ERROR:
1108 case BOT:
1109 return true;
1110 case TYPEVAR:
1111 if (isSubtype(t, s)) {
1112 return true;
1113 } else if (isCastable(t.bound, s, Warner.noWarnings)) {
1114 warnStack.head.warnUnchecked();
1115 return true;
1116 } else {
1117 return false;
1118 }
1119 default:
1120 return isCastable(t.bound, s, warnStack.head);
1121 }
1122 }
1123
1124 @Override
1125 public Boolean visitMethodType(MethodType t, Type s) {
1126 if (isSubtype(t, s))
1127 return true;
1128 if (s.tsym == syms.methodHandleType.tsym) {
1129 warnStack.head.warnUnchecked();
1130 return true;
1131 }
1132 if (s.tag != METHOD)
1133 return false;
1134 return isCastable(s, t);
1135 }
1136
1137 @Override
1138 public Boolean visitErrorType(ErrorType t, Type s) {
1139 return true;
1140 }
1141 };
1142 // </editor-fold>
1143
1144 // <editor-fold defaultstate="collapsed" desc="disjointTypes">
1145 public boolean disjointTypes(List<Type> ts, List<Type> ss) {
1146 while (ts.tail != null && ss.tail != null) {
1147 if (disjointType(ts.head, ss.head)) return true;
1148 ts = ts.tail;
1149 ss = ss.tail;
1150 }
1151 return false;
1152 }
1153
1154 /**
1155 * Two types or wildcards are considered disjoint if it can be
1156 * proven that no type can be contained in both. It is
1157 * conservative in that it is allowed to say that two types are
1158 * not disjoint, even though they actually are.
1159 *
1160 * The type C<X> is castable to C<Y> exactly if X and Y are not
1161 * disjoint.
1162 */
1163 public boolean disjointType(Type t, Type s) {
1164 return disjointType.visit(t, s);
1165 }
1166 // where
1167 private TypeRelation disjointType = new TypeRelation() {
1168
1169 private Set<TypePair> cache = new HashSet<TypePair>();
1170
1171 public Boolean visitType(Type t, Type s) {
1172 if (s.tag == WILDCARD)
1173 return visit(s, t);
1174 else
1175 return notSoftSubtypeRecursive(t, s) || notSoftSubtypeRecursive(s, t);
1176 }
1177
1178 private boolean isCastableRecursive(Type t, Type s) {
1179 TypePair pair = new TypePair(t, s);
1180 if (cache.add(pair)) {
1181 try {
1182 return Types.this.isCastable(t, s);
1183 } finally {
1184 cache.remove(pair);
1185 }
1186 } else {
1187 return true;
1188 }
1189 }
1190
1191 private boolean notSoftSubtypeRecursive(Type t, Type s) {
1192 TypePair pair = new TypePair(t, s);
1193 if (cache.add(pair)) {
1194 try {
1195 return Types.this.notSoftSubtype(t, s);
1196 } finally {
1197 cache.remove(pair);
1198 }
1199 } else {
1200 return false;
1201 }
1202 }
1203
1204 @Override
1205 public Boolean visitWildcardType(WildcardType t, Type s) {
1206 if (t.isUnbound())
1207 return false;
1208
1209 if (s.tag != WILDCARD) {
1210 if (t.isExtendsBound())
1211 return notSoftSubtypeRecursive(s, t.type);
1212 else // isSuperBound()
1213 return notSoftSubtypeRecursive(t.type, s);
1214 }
1215
1216 if (s.isUnbound())
1217 return false;
1218
1219 if (t.isExtendsBound()) {
1220 if (s.isExtendsBound())
1221 return !isCastableRecursive(t.type, upperBound(s));
1222 else if (s.isSuperBound())
1223 return notSoftSubtypeRecursive(lowerBound(s), t.type);
1224 } else if (t.isSuperBound()) {
1225 if (s.isExtendsBound())
1226 return notSoftSubtypeRecursive(t.type, upperBound(s));
1227 }
1228 return false;
1229 }
1230 };
1231 // </editor-fold>
1232
1233 // <editor-fold defaultstate="collapsed" desc="lowerBoundArgtypes">
1234 /**
1235 * Returns the lower bounds of the formals of a method.
1236 */
1237 public List<Type> lowerBoundArgtypes(Type t) {
1238 return map(t.getParameterTypes(), lowerBoundMapping);
1239 }
1240 private final Mapping lowerBoundMapping = new Mapping("lowerBound") {
1241 public Type apply(Type t) {
1242 return lowerBound(t);
1243 }
1244 };
1245 // </editor-fold>
1246
1247 // <editor-fold defaultstate="collapsed" desc="notSoftSubtype">
1248 /**
1249 * This relation answers the question: is impossible that
1250 * something of type `t' can be a subtype of `s'? This is
1251 * different from the question "is `t' not a subtype of `s'?"
1252 * when type variables are involved: Integer is not a subtype of T
1253 * where <T extends Number> but it is not true that Integer cannot
1254 * possibly be a subtype of T.
1255 */
1256 public boolean notSoftSubtype(Type t, Type s) {
1257 if (t == s) return false;
1258 if (t.tag == TYPEVAR) {
1259 TypeVar tv = (TypeVar) t;
1260 if (s.tag == TYPEVAR)
1261 s = s.getUpperBound();
1262 return !isCastable(tv.bound,
1263 s,
1264 Warner.noWarnings);
1265 }
1266 if (s.tag != WILDCARD)
1267 s = upperBound(s);
1268 if (s.tag == TYPEVAR)
1269 s = s.getUpperBound();
1270
1271 return !isSubtype(t, s);
1272 }
1273 // </editor-fold>
1274
1275 // <editor-fold defaultstate="collapsed" desc="isReifiable">
1276 public boolean isReifiable(Type t) {
1277 return isReifiable.visit(t);
1278 }
1279 // where
1280 private UnaryVisitor<Boolean> isReifiable = new UnaryVisitor<Boolean>() {
1281
1282 public Boolean visitType(Type t, Void ignored) {
1283 return true;
1284 }
1285
1286 @Override
1287 public Boolean visitClassType(ClassType t, Void ignored) {
1288 if (t.isCompound())
1289 return false;
1290 else {
1291 if (!t.isParameterized())
1292 return true;
1293
1294 for (Type param : t.allparams()) {
1295 if (!param.isUnbound())
1296 return false;
1297 }
1298 return true;
1299 }
1300 }
1301
1302 @Override
1303 public Boolean visitArrayType(ArrayType t, Void ignored) {
1304 return visit(t.elemtype);
1305 }
1306
1307 @Override
1308 public Boolean visitTypeVar(TypeVar t, Void ignored) {
1309 return false;
1310 }
1311
1312 @Override
1313 public Boolean visitMethodType(MethodType t, Void ignored) {
1314 if (!isReifiable(t.restype))
1315 return false;
1316 for(List<Type> l = t.argtypes; l.isEmpty(); l = l.tail) {
1317 if (!isReifiable(l.head))
1318 return false;
1319 }
1320 return true;
1321 }
1322 };
1323 // </editor-fold>
1324
1325 // <editor-fold defaultstate="collapsed" desc="Array Utils">
1326 public boolean isArray(Type t) {
1327 while (t.tag == WILDCARD)
1328 t = upperBound(t);
1329 return t.tag == ARRAY;
1330 }
1331
1332 /**
1333 * The element type of an array.
1334 */
1335 public Type elemtype(Type t) {
1336 switch (t.tag) {
1337 case WILDCARD:
1338 return elemtype(upperBound(t));
1339 case ARRAY:
1340 return ((ArrayType)t).elemtype;
1341 case FORALL:
1342 return elemtype(((ForAll)t).qtype);
1343 case ERROR:
1344 return t;
1345 default:
1346 return null;
1347 }
1348 }
1349
1350 /**
1351 * Mapping to take element type of an arraytype
1352 */
1353 private Mapping elemTypeFun = new Mapping ("elemTypeFun") {
1354 public Type apply(Type t) { return elemtype(t); }
1355 };
1356
1357 /**
1358 * The number of dimensions of an array type.
1359 */
1360 public int dimensions(Type t) {
1361 int result = 0;
1362 while (t.tag == ARRAY) {
1363 result++;
1364 t = elemtype(t);
1365 }
1366 return result;
1367 }
1368 // </editor-fold>
1369
1370 // <editor-fold defaultstate="collapsed" desc="asSuper">
1371 /**
1372 * Return the (most specific) base type of t that starts with the
1373 * given symbol. If none exists, return null.
1374 *
1375 * @param t a type
1376 * @param sym a symbol
1377 */
1378 public Type asSuper(Type t, Symbol sym) {
1379 return asSuper.visit(t, sym);
1380 }
1381 // where
1382 private SimpleVisitor<Type,Symbol> asSuper = new SimpleVisitor<Type,Symbol>() {
1383
1384 public Type visitType(Type t, Symbol sym) {
1385 return null;
1386 }
1387
1388 @Override
1389 public Type visitClassType(ClassType t, Symbol sym) {
1390 if (t.tsym == sym)
1391 return t;
1392
1393 Type st = supertype(t);
1394 if (st.tag == CLASS || st.tag == TYPEVAR || st.tag == ERROR) {
1395 Type x = asSuper(st, sym);
1396 if (x != null)
1397 return x;
1398 }
1399 if ((sym.flags() & INTERFACE) != 0) {
1400 for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
1401 Type x = asSuper(l.head, sym);
1402 if (x != null)
1403 return x;
1404 }
1405 }
1406 return null;
1407 }
1408
1409 @Override
1410 public Type visitArrayType(ArrayType t, Symbol sym) {
1411 return isSubtype(t, sym.type) ? sym.type : null;
1412 }
1413
1414 @Override
1415 public Type visitTypeVar(TypeVar t, Symbol sym) {
1416 if (t.tsym == sym)
1417 return t;
1418 else
1419 return asSuper(t.bound, sym);
1420 }
1421
1422 @Override
1423 public Type visitErrorType(ErrorType t, Symbol sym) {
1424 return t;
1425 }
1426 };
1427
1428 /**
1429 * Return the base type of t or any of its outer types that starts
1430 * with the given symbol. If none exists, return null.
1431 *
1432 * @param t a type
1433 * @param sym a symbol
1434 */
1435 public Type asOuterSuper(Type t, Symbol sym) {
1436 switch (t.tag) {
1437 case CLASS:
1438 do {
1439 Type s = asSuper(t, sym);
1440 if (s != null) return s;
1441 t = t.getEnclosingType();
1442 } while (t.tag == CLASS);
1443 return null;
1444 case ARRAY:
1445 return isSubtype(t, sym.type) ? sym.type : null;
1446 case TYPEVAR:
1447 return asSuper(t, sym);
1448 case ERROR:
1449 return t;
1450 default:
1451 return null;
1452 }
1453 }
1454
1455 /**
1456 * Return the base type of t or any of its enclosing types that
1457 * starts with the given symbol. If none exists, return null.
1458 *
1459 * @param t a type
1460 * @param sym a symbol
1461 */
1462 public Type asEnclosingSuper(Type t, Symbol sym) {
1463 switch (t.tag) {
1464 case CLASS:
1465 do {
1466 Type s = asSuper(t, sym);
1467 if (s != null) return s;
1468 Type outer = t.getEnclosingType();
1469 t = (outer.tag == CLASS) ? outer :
1470 (t.tsym.owner.enclClass() != null) ? t.tsym.owner.enclClass().type :
1471 Type.noType;
1472 } while (t.tag == CLASS);
1473 return null;
1474 case ARRAY:
1475 return isSubtype(t, sym.type) ? sym.type : null;
1476 case TYPEVAR:
1477 return asSuper(t, sym);
1478 case ERROR:
1479 return t;
1480 default:
1481 return null;
1482 }
1483 }
1484 // </editor-fold>
1485
1486 // <editor-fold defaultstate="collapsed" desc="memberType">
1487 /**
1488 * The type of given symbol, seen as a member of t.
1489 *
1490 * @param t a type
1491 * @param sym a symbol
1492 */
1493 public Type memberType(Type t, Symbol sym) {
1494 return (sym.flags() & STATIC) != 0
1495 ? sym.type
1496 : memberType.visit(t, sym);
1497 }
1498 // where
1499 private SimpleVisitor<Type,Symbol> memberType = new SimpleVisitor<Type,Symbol>() {
1500
1501 public Type visitType(Type t, Symbol sym) {
1502 return sym.type;
1503 }
1504
1505 @Override
1506 public Type visitWildcardType(WildcardType t, Symbol sym) {
1507 return memberType(upperBound(t), sym);
1508 }
1509
1510 @Override
1511 public Type visitClassType(ClassType t, Symbol sym) {
1512 Symbol owner = sym.owner;
1513 long flags = sym.flags();
1514 if (((flags & STATIC) == 0) && owner.type.isParameterized()) {
1515 Type base = asOuterSuper(t, owner);
1516 //if t is an intersection type T = CT & I1 & I2 ... & In
1517 //its supertypes CT, I1, ... In might contain wildcards
1518 //so we need to go through capture conversion
1519 base = t.isCompound() ? capture(base) : base;
1520 if (base != null) {
1521 List<Type> ownerParams = owner.type.allparams();
1522 List<Type> baseParams = base.allparams();
1523 if (ownerParams.nonEmpty()) {
1524 if (baseParams.isEmpty()) {
1525 // then base is a raw type
1526 return erasure(sym.type);
1527 } else {
1528 return subst(sym.type, ownerParams, baseParams);
1529 }
1530 }
1531 }
1532 }
1533 return sym.type;
1534 }
1535
1536 @Override
1537 public Type visitTypeVar(TypeVar t, Symbol sym) {
1538 return memberType(t.bound, sym);
1539 }
1540
1541 @Override
1542 public Type visitErrorType(ErrorType t, Symbol sym) {
1543 return t;
1544 }
1545 };
1546 // </editor-fold>
1547
1548 // <editor-fold defaultstate="collapsed" desc="isAssignable">
1549 public boolean isAssignable(Type t, Type s) {
1550 return isAssignable(t, s, Warner.noWarnings);
1551 }
1552
1553 /**
1554 * Is t assignable to s?<br>
1555 * Equivalent to subtype except for constant values and raw
1556 * types.<br>
1557 * (not defined for Method and ForAll types)
1558 */
1559 public boolean isAssignable(Type t, Type s, Warner warn) {
1560 if (t.tag == ERROR)
1561 return true;
1562 if (t.tag <= INT && t.constValue() != null) {
1563 int value = ((Number)t.constValue()).intValue();
1564 switch (s.tag) {
1565 case BYTE:
1566 if (Byte.MIN_VALUE <= value && value <= Byte.MAX_VALUE)
1567 return true;
1568 break;
1569 case CHAR:
1570 if (Character.MIN_VALUE <= value && value <= Character.MAX_VALUE)
1571 return true;
1572 break;
1573 case SHORT:
1574 if (Short.MIN_VALUE <= value && value <= Short.MAX_VALUE)
1575 return true;
1576 break;
1577 case INT:
1578 return true;
1579 case CLASS:
1580 switch (unboxedType(s).tag) {
1581 case BYTE:
1582 case CHAR:
1583 case SHORT:
1584 return isAssignable(t, unboxedType(s), warn);
1585 }
1586 break;
1587 }
1588 }
1589 return isConvertible(t, s, warn);
1590 }
1591 // </editor-fold>
1592
1593 // <editor-fold defaultstate="collapsed" desc="erasure">
1594 /**
1595 * The erasure of t {@code |t|} -- the type that results when all
1596 * type parameters in t are deleted.
1597 */
1598 public Type erasure(Type t) {
1599 return erasure(t, false);
1600 }
1601 //where
1602 private Type erasure(Type t, boolean recurse) {
1603 if (t.tag <= lastBaseTag)
1604 return t; /* fast special case */
1605 else
1606 return erasure.visit(t, recurse);
1607 }
1608 // where
1609 private SimpleVisitor<Type, Boolean> erasure = new SimpleVisitor<Type, Boolean>() {
1610 public Type visitType(Type t, Boolean recurse) {
1611 if (t.tag <= lastBaseTag)
1612 return t; /*fast special case*/
1613 else
1614 return t.map(recurse ? erasureRecFun : erasureFun);
1615 }
1616
1617 @Override
1618 public Type visitWildcardType(WildcardType t, Boolean recurse) {
1619 return erasure(upperBound(t), recurse);
1620 }
1621
1622 @Override
1623 public Type visitClassType(ClassType t, Boolean recurse) {
1624 Type erased = t.tsym.erasure(Types.this);
1625 if (recurse) {
1626 erased = new ErasedClassType(erased.getEnclosingType(),erased.tsym);
1627 }
1628 return erased;
1629 }
1630
1631 @Override
1632 public Type visitTypeVar(TypeVar t, Boolean recurse) {
1633 return erasure(t.bound, recurse);
1634 }
1635
1636 @Override
1637 public Type visitMethodType(MethodType t, Boolean recurse) {
1638 if (t.tag == FUNCTION)
1639 return syms.methodHandleType;
1640 return super.visitMethodType(t, recurse);
1641 }
1642
1643 @Override
1644 public Type visitErrorType(ErrorType t, Boolean recurse) {
1645 return t;
1646 }
1647 };
1648
1649 private Mapping erasureFun = new Mapping ("erasure") {
1650 public Type apply(Type t) { return erasure(t); }
1651 };
1652
1653 private Mapping erasureRecFun = new Mapping ("erasureRecursive") {
1654 public Type apply(Type t) { return erasureRecursive(t); }
1655 };
1656
1657 public List<Type> erasure(List<Type> ts) {
1658 return Type.map(ts, erasureFun);
1659 }
1660
1661 public Type erasureRecursive(Type t) {
1662 return erasure(t, true);
1663 }
1664
1665 public List<Type> erasureRecursive(List<Type> ts) {
1666 return Type.map(ts, erasureRecFun);
1667 }
1668 // </editor-fold>
1669
1670 // <editor-fold defaultstate="collapsed" desc="makeCompoundType">
1671 /**
1672 * Make a compound type from non-empty list of types
1673 *
1674 * @param bounds the types from which the compound type is formed
1675 * @param supertype is objectType if all bounds are interfaces,
1676 * null otherwise.
1677 */
1678 public Type makeCompoundType(List<Type> bounds,
1679 Type supertype) {
1680 ClassSymbol bc =
1681 new ClassSymbol(ABSTRACT|PUBLIC|SYNTHETIC|COMPOUND|ACYCLIC,
1682 Type.moreInfo
1683 ? names.fromString(bounds.toString())
1684 : names.empty,
1685 syms.noSymbol);
1686 if (bounds.head.tag == TYPEVAR)
1687 // error condition, recover
1688 bc.erasure_field = syms.objectType;
1689 else
1690 bc.erasure_field = erasure(bounds.head);
1691 bc.members_field = new Scope(bc);
1692 ClassType bt = (ClassType)bc.type;
1693 bt.allparams_field = List.nil();
1694 if (supertype != null) {
1695 bt.supertype_field = supertype;
1696 bt.interfaces_field = bounds;
1697 } else {
1698 bt.supertype_field = bounds.head;
1699 bt.interfaces_field = bounds.tail;
1700 }
1701 assert bt.supertype_field.tsym.completer != null
1702 || !bt.supertype_field.isInterface()
1703 : bt.supertype_field;
1704 return bt;
1705 }
1706
1707 /**
1708 * Same as {@link #makeCompoundType(List,Type)}, except that the
1709 * second parameter is computed directly. Note that this might
1710 * cause a symbol completion. Hence, this version of
1711 * makeCompoundType may not be called during a classfile read.
1712 */
1713 public Type makeCompoundType(List<Type> bounds) {
1714 Type supertype = (bounds.head.tsym.flags() & INTERFACE) != 0 ?
1715 supertype(bounds.head) : null;
1716 return makeCompoundType(bounds, supertype);
1717 }
1718
1719 /**
1720 * A convenience wrapper for {@link #makeCompoundType(List)}; the
1721 * arguments are converted to a list and passed to the other
1722 * method. Note that this might cause a symbol completion.
1723 * Hence, this version of makeCompoundType may not be called
1724 * during a classfile read.
1725 */
1726 public Type makeCompoundType(Type bound1, Type bound2) {
1727 return makeCompoundType(List.of(bound1, bound2));
1728 }
1729 // </editor-fold>
1730
1731 // <editor-fold defaultstate="collapsed" desc="supertype">
1732 public Type supertype(Type t) {
1733 return supertype.visit(t);
1734 }
1735 // where
1736 private UnaryVisitor<Type> supertype = new UnaryVisitor<Type>() {
1737
1738 public Type visitType(Type t, Void ignored) {
1739 // A note on wildcards: there is no good way to
1740 // determine a supertype for a super bounded wildcard.
1741 return null;
1742 }
1743
1744 @Override
1745 public Type visitClassType(ClassType t, Void ignored) {
1746 if (t.supertype_field == null) {
1747 Type supertype = ((ClassSymbol)t.tsym).getSuperclass();
1748 // An interface has no superclass; its supertype is Object.
1749 if (t.isInterface())
1750 supertype = ((ClassType)t.tsym.type).supertype_field;
1751 if (t.supertype_field == null) {
1752 List<Type> actuals = classBound(t).allparams();
1753 List<Type> formals = t.tsym.type.allparams();
1754 if (t.hasErasedSupertypes()) {
1755 t.supertype_field = erasureRecursive(supertype);
1756 } else if (formals.nonEmpty()) {
1757 t.supertype_field = subst(supertype, formals, actuals);
1758 }
1759 else {
1760 t.supertype_field = supertype;
1761 }
1762 }
1763 }
1764 return t.supertype_field;
1765 }
1766
1767 /**
1768 * The supertype is always a class type. If the type
1769 * variable's bounds start with a class type, this is also
1770 * the supertype. Otherwise, the supertype is
1771 * java.lang.Object.
1772 */
1773 @Override
1774 public Type visitTypeVar(TypeVar t, Void ignored) {
1775 if (t.bound.tag == TYPEVAR ||
1776 (!t.bound.isCompound() && !t.bound.isInterface())) {
1777 return t.bound;
1778 } else {
1779 return supertype(t.bound);
1780 }
1781 }
1782
1783 @Override
1784 public Type visitArrayType(ArrayType t, Void ignored) {
1785 if (t.elemtype.isPrimitive() || isSameType(t.elemtype, syms.objectType))
1786 return arraySuperType();
1787 else
1788 return new ArrayType(supertype(t.elemtype), t.tsym);
1789 }
1790
1791 @Override
1792 public Type visitErrorType(ErrorType t, Void ignored) {
1793 return t;
1794 }
1795 };
1796 // </editor-fold>
1797
1798 // <editor-fold defaultstate="collapsed" desc="interfaces">
1799 /**
1800 * Return the interfaces implemented by this class.
1801 */
1802 public List<Type> interfaces(Type t) {
1803 return interfaces.visit(t);
1804 }
1805 // where
1806 private UnaryVisitor<List<Type>> interfaces = new UnaryVisitor<List<Type>>() {
1807
1808 public List<Type> visitType(Type t, Void ignored) {
1809 return List.nil();
1810 }
1811
1812 @Override
1813 public List<Type> visitClassType(ClassType t, Void ignored) {
1814 if (t.interfaces_field == null) {
1815 List<Type> interfaces = ((ClassSymbol)t.tsym).getInterfaces();
1816 if (t.interfaces_field == null) {
1817 // If t.interfaces_field is null, then t must
1818 // be a parameterized type (not to be confused
1819 // with a generic type declaration).
1820 // Terminology:
1821 // Parameterized type: List<String>
1822 // Generic type declaration: class List<E> { ... }
1823 // So t corresponds to List<String> and
1824 // t.tsym.type corresponds to List<E>.
1825 // The reason t must be parameterized type is
1826 // that completion will happen as a side
1827 // effect of calling
1828 // ClassSymbol.getInterfaces. Since
1829 // t.interfaces_field is null after
1830 // completion, we can assume that t is not the
1831 // type of a class/interface declaration.
1832 assert t != t.tsym.type : t.toString();
1833 List<Type> actuals = t.allparams();
1834 List<Type> formals = t.tsym.type.allparams();
1835 if (t.hasErasedSupertypes()) {
1836 t.interfaces_field = erasureRecursive(interfaces);
1837 } else if (formals.nonEmpty()) {
1838 t.interfaces_field =
1839 upperBounds(subst(interfaces, formals, actuals));
1840 }
1841 else {
1842 t.interfaces_field = interfaces;
1843 }
1844 }
1845 }
1846 return t.interfaces_field;
1847 }
1848
1849 @Override
1850 public List<Type> visitTypeVar(TypeVar t, Void ignored) {
1851 if (t.bound.isCompound())
1852 return interfaces(t.bound);
1853
1854 if (t.bound.isInterface())
1855 return List.of(t.bound);
1856
1857 return List.nil();
1858 }
1859 };
1860 // </editor-fold>
1861
1862 // <editor-fold defaultstate="collapsed" desc="isDerivedRaw">
1863 Map<Type,Boolean> isDerivedRawCache = new HashMap<Type,Boolean>();
1864
1865 public boolean isDerivedRaw(Type t) {
1866 Boolean result = isDerivedRawCache.get(t);
1867 if (result == null) {
1868 result = isDerivedRawInternal(t);
1869 isDerivedRawCache.put(t, result);
1870 }
1871 return result;
1872 }
1873
1874 public boolean isDerivedRawInternal(Type t) {
1875 if (t.isErroneous())
1876 return false;
1877 return
1878 t.isRaw() ||
1879 supertype(t) != null && isDerivedRaw(supertype(t)) ||
1880 isDerivedRaw(interfaces(t));
1881 }
1882
1883 public boolean isDerivedRaw(List<Type> ts) {
1884 List<Type> l = ts;
1885 while (l.nonEmpty() && !isDerivedRaw(l.head)) l = l.tail;
1886 return l.nonEmpty();
1887 }
1888 // </editor-fold>
1889
1890 // <editor-fold defaultstate="collapsed" desc="setBounds">
1891 /**
1892 * Set the bounds field of the given type variable to reflect a
1893 * (possibly multiple) list of bounds.
1894 * @param t a type variable
1895 * @param bounds the bounds, must be nonempty
1896 * @param supertype is objectType if all bounds are interfaces,
1897 * null otherwise.
1898 */
1899 public void setBounds(TypeVar t, List<Type> bounds, Type supertype) {
1900 if (bounds.tail.isEmpty())
1901 t.bound = bounds.head;
1902 else
1903 t.bound = makeCompoundType(bounds, supertype);
1904 t.rank_field = -1;
1905 }
1906
1907 /**
1908 * Same as {@link #setBounds(Type.TypeVar,List,Type)}, except that
1909 * third parameter is computed directly. Note that this test
1910 * might cause a symbol completion. Hence, this version of
1911 * setBounds may not be called during a classfile read.
1912 */
1913 public void setBounds(TypeVar t, List<Type> bounds) {
1914 Type supertype = (bounds.head.tsym.flags() & INTERFACE) != 0 ?
1915 supertype(bounds.head) : null;
1916 setBounds(t, bounds, supertype);
1917 t.rank_field = -1;
1918 }
1919 // </editor-fold>
1920
1921 // <editor-fold defaultstate="collapsed" desc="getBounds">
1922 /**
1923 * Return list of bounds of the given type variable.
1924 */
1925 public List<Type> getBounds(TypeVar t) {
1926 if (t.bound.isErroneous() || !t.bound.isCompound())
1927 return List.of(t.bound);
1928 else if ((erasure(t).tsym.flags() & INTERFACE) == 0)
1929 return interfaces(t).prepend(supertype(t));
1930 else
1931 // No superclass was given in bounds.
1932 // In this case, supertype is Object, erasure is first interface.
1933 return interfaces(t);
1934 }
1935 // </editor-fold>
1936
1937 // <editor-fold defaultstate="collapsed" desc="classBound">
1938 /**
1939 * If the given type is a (possibly selected) type variable,
1940 * return the bounding class of this type, otherwise return the
1941 * type itself.
1942 */
1943 public Type classBound(Type t) {
1944 return classBound.visit(t);
1945 }
1946 // where
1947 private UnaryVisitor<Type> classBound = new UnaryVisitor<Type>() {
1948
1949 public Type visitType(Type t, Void ignored) {
1950 return t;
1951 }
1952
1953 @Override
1954 public Type visitClassType(ClassType t, Void ignored) {
1955 Type outer1 = classBound(t.getEnclosingType());
1956 if (outer1 != t.getEnclosingType())
1957 return new ClassType(outer1, t.getTypeArguments(), t.tsym);
1958 else
1959 return t;
1960 }
1961
1962 @Override
1963 public Type visitTypeVar(TypeVar t, Void ignored) {
1964 return classBound(supertype(t));
1965 }
1966
1967 @Override
1968 public Type visitErrorType(ErrorType t, Void ignored) {
1969 return t;
1970 }
1971 };
1972 // </editor-fold>
1973
1974 // <editor-fold defaultstate="collapsed" desc="sub signature / override equivalence">
1975 /**
1976 * Returns true iff the first signature is a <em>sub
1977 * signature</em> of the other. This is <b>not</b> an equivalence
1978 * relation.
1979 *
1980 * @see "The Java Language Specification, Third Ed. (8.4.2)."
1981 * @see #overrideEquivalent(Type t, Type s)
1982 * @param t first signature (possibly raw).
1983 * @param s second signature (could be subjected to erasure).
1984 * @return true if t is a sub signature of s.
1985 */
1986 public boolean isSubSignature(Type t, Type s) {
1987 return hasSameArgs(t, s) || hasSameArgs(t, erasure(s));
1988 }
1989
1990 /**
1991 * Returns true iff these signatures are related by <em>override
1992 * equivalence</em>. This is the natural extension of
1993 * isSubSignature to an equivalence relation.
1994 *
1995 * @see "The Java Language Specification, Third Ed. (8.4.2)."
1996 * @see #isSubSignature(Type t, Type s)
1997 * @param t a signature (possible raw, could be subjected to
1998 * erasure).
1999 * @param s a signature (possible raw, could be subjected to
2000 * erasure).
2001 * @return true if either argument is a sub signature of the other.
2002 */
2003 public boolean overrideEquivalent(Type t, Type s) {
2004 return hasSameArgs(t, s) ||
2005 hasSameArgs(t, erasure(s)) || hasSameArgs(erasure(t), s);
2006 }
2007
2008 private WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, MethodSymbol>>> implCache_check =
2009 new WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, MethodSymbol>>>();
2010
2011 private WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, MethodSymbol>>> implCache_nocheck =
2012 new WeakHashMap<MethodSymbol, SoftReference<Map<TypeSymbol, MethodSymbol>>>();
2013
2014 public MethodSymbol implementation(MethodSymbol ms, TypeSymbol origin, Types types, boolean checkResult) {
2015 Map<MethodSymbol, SoftReference<Map<TypeSymbol, MethodSymbol>>> implCache = checkResult ?
2016 implCache_check : implCache_nocheck;
2017 SoftReference<Map<TypeSymbol, MethodSymbol>> ref_cache = implCache.get(ms);
2018 Map<TypeSymbol, MethodSymbol> cache = ref_cache != null ? ref_cache.get() : null;
2019 if (cache == null) {
2020 cache = new HashMap<TypeSymbol, MethodSymbol>();
2021 implCache.put(ms, new SoftReference<Map<TypeSymbol, MethodSymbol>>(cache));
2022 }
2023 MethodSymbol impl = cache.get(origin);
2024 if (impl == null) {
2025 for (Type t = origin.type; t.tag == CLASS || t.tag == TYPEVAR; t = types.supertype(t)) {
2026 while (t.tag == TYPEVAR)
2027 t = t.getUpperBound();
2028 TypeSymbol c = t.tsym;
2029 for (Scope.Entry e = c.members().lookup(ms.name);
2030 e.scope != null;
2031 e = e.next()) {
2032 if (e.sym.kind == Kinds.MTH) {
2033 MethodSymbol m = (MethodSymbol) e.sym;
2034 if (m.overrides(ms, origin, types, checkResult) &&
2035 (m.flags() & SYNTHETIC) == 0) {
2036 impl = m;
2037 cache.put(origin, m);
2038 return impl;
2039 }
2040 }
2041 }
2042 }
2043 }
2044 return impl;
2045 }
2046
2047 /**
2048 * Does t have the same arguments as s? It is assumed that both
2049 * types are (possibly polymorphic) method types. Monomorphic
2050 * method types "have the same arguments", if their argument lists
2051 * are equal. Polymorphic method types "have the same arguments",
2052 * if they have the same arguments after renaming all type
2053 * variables of one to corresponding type variables in the other,
2054 * where correspondence is by position in the type parameter list.
2055 */
2056 public boolean hasSameArgs(Type t, Type s) {
2057 return hasSameArgs.visit(t, s);
2058 }
2059 // where
2060 private TypeRelation hasSameArgs = new TypeRelation() {
2061
2062 public Boolean visitType(Type t, Type s) {
2063 throw new AssertionError();
2064 }
2065
2066 @Override
2067 public Boolean visitMethodType(MethodType t, Type s) {
2068 return (s.tag == METHOD || s.tag == FUNCTION)
2069 && containsTypeEquivalent(t.argtypes, s.getParameterTypes());
2070 }
2071
2072 @Override
2073 public Boolean visitForAll(ForAll t, Type s) {
2074 if (s.tag != FORALL)
2075 return false;
2076
2077 ForAll forAll = (ForAll)s;
2078 return hasSameBounds(t, forAll)
2079 && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
2080 }
2081
2082 @Override
2083 public Boolean visitErrorType(ErrorType t, Type s) {
2084 return false;
2085 }
2086 };
2087 // </editor-fold>
2088
2089 // <editor-fold defaultstate="collapsed" desc="subst">
2090 public List<Type> subst(List<Type> ts,
2091 List<Type> from,
2092 List<Type> to) {
2093 return new Subst(from, to).subst(ts);
2094 }
2095
2096 /**
2097 * Substitute all occurrences of a type in `from' with the
2098 * corresponding type in `to' in 't'. Match lists `from' and `to'
2099 * from the right: If lists have different length, discard leading
2100 * elements of the longer list.
2101 */
2102 public Type subst(Type t, List<Type> from, List<Type> to) {
2103 return new Subst(from, to).subst(t);
2104 }
2105
2106 private class Subst extends UnaryVisitor<Type> {
2107 List<Type> from;
2108 List<Type> to;
2109
2110 public Subst(List<Type> from, List<Type> to) {
2111 int fromLength = from.length();
2112 int toLength = to.length();
2113 while (fromLength > toLength) {
2114 fromLength--;
2115 from = from.tail;
2116 }
2117 while (fromLength < toLength) {
2118 toLength--;
2119 to = to.tail;
2120 }
2121 this.from = from;
2122 this.to = to;
2123 }
2124
2125 Type subst(Type t) {
2126 if (from.tail == null)
2127 return t;
2128 else
2129 return visit(t);
2130 }
2131
2132 List<Type> subst(List<Type> ts) {
2133 if (from.tail == null)
2134 return ts;
2135 boolean wild = false;
2136 if (ts.nonEmpty() && from.nonEmpty()) {
2137 Type head1 = subst(ts.head);
2138 List<Type> tail1 = subst(ts.tail);
2139 if (head1 != ts.head || tail1 != ts.tail)
2140 return tail1.prepend(head1);
2141 }
2142 return ts;
2143 }
2144
2145 public Type visitType(Type t, Void ignored) {
2146 return t;
2147 }
2148
2149 @Override
2150 public Type visitMethodType(MethodType t, Void ignored) {
2151 List<Type> argtypes = subst(t.argtypes);
2152 Type restype = subst(t.restype);
2153 List<Type> thrown = subst(t.thrown);
2154 if (argtypes == t.argtypes &&
2155 restype == t.restype &&
2156 thrown == t.thrown)
2157 return t;
2158 else
2159 return new MethodType(t.tag, argtypes, restype, thrown, t.tsym);
2160 }
2161
2162 @Override
2163 public Type visitTypeVar(TypeVar t, Void ignored) {
2164 for (List<Type> from = this.from, to = this.to;
2165 from.nonEmpty();
2166 from = from.tail, to = to.tail) {
2167 if (t == from.head) {
2168 return to.head.withTypeVar(t);
2169 }
2170 }
2171 return t;
2172 }
2173
2174 @Override
2175 public Type visitClassType(ClassType t, Void ignored) {
2176 if (!t.isCompound()) {
2177 List<Type> typarams = t.getTypeArguments();
2178 List<Type> typarams1 = subst(typarams);
2179 Type outer = t.getEnclosingType();
2180 Type outer1 = subst(outer);
2181 if (typarams1 == typarams && outer1 == outer)
2182 return t;
2183 else
2184 return new ClassType(outer1, typarams1, t.tsym);
2185 } else {
2186 Type st = subst(supertype(t));
2187 List<Type> is = upperBounds(subst(interfaces(t)));
2188 if (st == supertype(t) && is == interfaces(t))
2189 return t;
2190 else
2191 return makeCompoundType(is.prepend(st));
2192 }
2193 }
2194
2195 @Override
2196 public Type visitWildcardType(WildcardType t, Void ignored) {
2197 Type bound = t.type;
2198 if (t.kind != BoundKind.UNBOUND)
2199 bound = subst(bound);
2200 if (bound == t.type) {
2201 return t;
2202 } else {
2203 if (t.isExtendsBound() && bound.isExtendsBound())
2204 bound = upperBound(bound);
2205 return new WildcardType(bound, t.kind, syms.boundClass, t.bound);
2206 }
2207 }
2208
2209 @Override
2210 public Type visitArrayType(ArrayType t, Void ignored) {
2211 Type elemtype = subst(t.elemtype);
2212 if (elemtype == t.elemtype)
2213 return t;
2214 else
2215 return new ArrayType(upperBound(elemtype), t.tsym);
2216 }
2217
2218 @Override
2219 public Type visitForAll(ForAll t, Void ignored) {
2220 List<Type> tvars1 = substBounds(t.tvars, from, to);
2221 Type qtype1 = subst(t.qtype);
2222 if (tvars1 == t.tvars && qtype1 == t.qtype) {
2223 return t;
2224 } else if (tvars1 == t.tvars) {
2225 return new ForAll(tvars1, qtype1);
2226 } else {
2227 return new ForAll(tvars1, Types.this.subst(qtype1, t.tvars, tvars1));
2228 }
2229 }
2230
2231 @Override
2232 public Type visitErrorType(ErrorType t, Void ignored) {
2233 return t;
2234 }
2235 }
2236
2237 public List<Type> substBounds(List<Type> tvars,
2238 List<Type> from,
2239 List<Type> to) {
2240 if (tvars.isEmpty())
2241 return tvars;
2242 ListBuffer<Type> newBoundsBuf = lb();
2243 boolean changed = false;
2244 // calculate new bounds
2245 for (Type t : tvars) {
2246 TypeVar tv = (TypeVar) t;
2247 Type bound = subst(tv.bound, from, to);
2248 if (bound != tv.bound)
2249 changed = true;
2250 newBoundsBuf.append(bound);
2251 }
2252 if (!changed)
2253 return tvars;
2254 ListBuffer<Type> newTvars = lb();
2255 // create new type variables without bounds
2256 for (Type t : tvars) {
2257 newTvars.append(new TypeVar(t.tsym, null, syms.botType));
2258 }
2259 // the new bounds should use the new type variables in place
2260 // of the old
2261 List<Type> newBounds = newBoundsBuf.toList();
2262 from = tvars;
2263 to = newTvars.toList();
2264 for (; !newBounds.isEmpty(); newBounds = newBounds.tail) {
2265 newBounds.head = subst(newBounds.head, from, to);
2266 }
2267 newBounds = newBoundsBuf.toList();
2268 // set the bounds of new type variables to the new bounds
2269 for (Type t : newTvars.toList()) {
2270 TypeVar tv = (TypeVar) t;
2271 tv.bound = newBounds.head;
2272 newBounds = newBounds.tail;
2273 }
2274 return newTvars.toList();
2275 }
2276
2277 public TypeVar substBound(TypeVar t, List<Type> from, List<Type> to) {
2278 Type bound1 = subst(t.bound, from, to);
2279 if (bound1 == t.bound)
2280 return t;
2281 else {
2282 // create new type variable without bounds
2283 TypeVar tv = new TypeVar(t.tsym, null, syms.botType);
2284 // the new bound should use the new type variable in place
2285 // of the old
2286 tv.bound = subst(bound1, List.<Type>of(t), List.<Type>of(tv));
2287 return tv;
2288 }
2289 }
2290 // </editor-fold>
2291
2292 // <editor-fold defaultstate="collapsed" desc="hasSameBounds">
2293 /**
2294 * Does t have the same bounds for quantified variables as s?
2295 */
2296 boolean hasSameBounds(ForAll t, ForAll s) {
2297 List<Type> l1 = t.tvars;
2298 List<Type> l2 = s.tvars;
2299 while (l1.nonEmpty() && l2.nonEmpty() &&
2300 isSameType(l1.head.getUpperBound(),
2301 subst(l2.head.getUpperBound(),
2302 s.tvars,
2303 t.tvars))) {
2304 l1 = l1.tail;
2305 l2 = l2.tail;
2306 }
2307 return l1.isEmpty() && l2.isEmpty();
2308 }
2309 // </editor-fold>
2310
2311 // <editor-fold defaultstate="collapsed" desc="newInstances">
2312 /** Create new vector of type variables from list of variables
2313 * changing all recursive bounds from old to new list.
2314 */
2315 public List<Type> newInstances(List<Type> tvars) {
2316 List<Type> tvars1 = Type.map(tvars, newInstanceFun);
2317 for (List<Type> l = tvars1; l.nonEmpty(); l = l.tail) {
2318 TypeVar tv = (TypeVar) l.head;
2319 tv.bound = subst(tv.bound, tvars, tvars1);
2320 }
2321 return tvars1;
2322 }
2323 static private Mapping newInstanceFun = new Mapping("newInstanceFun") {
2324 public Type apply(Type t) { return new TypeVar(t.tsym, t.getUpperBound(), t.getLowerBound()); }
2325 };
2326 // </editor-fold>
2327
2328 // <editor-fold defaultstate="collapsed" desc="createErrorType">
2329 public Type createErrorType(Type originalType) {
2330 return new ErrorType(originalType, syms.errSymbol);
2331 }
2332
2333 public Type createErrorType(ClassSymbol c, Type originalType) {
2334 return new ErrorType(c, originalType);
2335 }
2336
2337 public Type createErrorType(Name name, TypeSymbol container, Type originalType) {
2338 return new ErrorType(name, container, originalType);
2339 }
2340 // </editor-fold>
2341
2342 // <editor-fold defaultstate="collapsed" desc="rank">
2343 /**
2344 * The rank of a class is the length of the longest path between
2345 * the class and java.lang.Object in the class inheritance
2346 * graph. Undefined for all but reference types.
2347 */
2348 public int rank(Type t) {
2349 switch(t.tag) {
2350 case CLASS: {
2351 ClassType cls = (ClassType)t;
2352 if (cls.rank_field < 0) {
2353 Name fullname = cls.tsym.getQualifiedName();
2354 if (fullname == names.java_lang_Object)
2355 cls.rank_field = 0;
2356 else {
2357 int r = rank(supertype(cls));
2358 for (List<Type> l = interfaces(cls);
2359 l.nonEmpty();
2360 l = l.tail) {
2361 if (rank(l.head) > r)
2362 r = rank(l.head);
2363 }
2364 cls.rank_field = r + 1;
2365 }
2366 }
2367 return cls.rank_field;
2368 }
2369 case TYPEVAR: {
2370 TypeVar tvar = (TypeVar)t;
2371 if (tvar.rank_field < 0) {
2372 int r = rank(supertype(tvar));
2373 for (List<Type> l = interfaces(tvar);
2374 l.nonEmpty();
2375 l = l.tail) {
2376 if (rank(l.head) > r) r = rank(l.head);
2377 }
2378 tvar.rank_field = r + 1;
2379 }
2380 return tvar.rank_field;
2381 }
2382 case ERROR:
2383 return 0;
2384 default:
2385 throw new AssertionError();
2386 }
2387 }
2388 // </editor-fold>
2389
2390 /**
2391 * Helper method for generating a string representation of a given type
2392 * accordingly to a given locale
2393 */
2394 public String toString(Type t, Locale locale) {
2395 return Printer.createStandardPrinter(messages).visit(t, locale);
2396 }
2397
2398 /**
2399 * Helper method for generating a string representation of a given type
2400 * accordingly to a given locale
2401 */
2402 public String toString(Symbol t, Locale locale) {
2403 return Printer.createStandardPrinter(messages).visit(t, locale);
2404 }
2405
2406 // <editor-fold defaultstate="collapsed" desc="toString">
2407 /**
2408 * This toString is slightly more descriptive than the one on Type.
2409 *
2410 * @deprecated Types.toString(Type t, Locale l) provides better support
2411 * for localization
2412 */
2413 @Deprecated
2414 public String toString(Type t) {
2415 if (t.tag == FORALL) {
2416 ForAll forAll = (ForAll)t;
2417 return typaramsString(forAll.tvars) + forAll.qtype;
2418 }
2419 return "" + t;
2420 }
2421 // where
2422 private String typaramsString(List<Type> tvars) {
2423 StringBuffer s = new StringBuffer();
2424 s.append('<');
2425 boolean first = true;
2426 for (Type t : tvars) {
2427 if (!first) s.append(", ");
2428 first = false;
2429 appendTyparamString(((TypeVar)t), s);
2430 }
2431 s.append('>');
2432 return s.toString();
2433 }
2434 private void appendTyparamString(TypeVar t, StringBuffer buf) {
2435 buf.append(t);
2436 if (t.bound == null ||
2437 t.bound.tsym.getQualifiedName() == names.java_lang_Object)
2438 return;
2439 buf.append(" extends "); // Java syntax; no need for i18n
2440 Type bound = t.bound;
2441 if (!bound.isCompound()) {
2442 buf.append(bound);
2443 } else if ((erasure(t).tsym.flags() & INTERFACE) == 0) {
2444 buf.append(supertype(t));
2445 for (Type intf : interfaces(t)) {
2446 buf.append('&');
2447 buf.append(intf);
2448 }
2449 } else {
2450 // No superclass was given in bounds.
2451 // In this case, supertype is Object, erasure is first interface.
2452 boolean first = true;
2453 for (Type intf : interfaces(t)) {
2454 if (!first) buf.append('&');
2455 first = false;
2456 buf.append(intf);
2457 }
2458 }
2459 }
2460 // </editor-fold>
2461
2462 // <editor-fold defaultstate="collapsed" desc="Determining least upper bounds of types">
2463 /**
2464 * A cache for closures.
2465 *
2466 * <p>A closure is a list of all the supertypes and interfaces of
2467 * a class or interface type, ordered by ClassSymbol.precedes
2468 * (that is, subclasses come first, arbitrary but fixed
2469 * otherwise).
2470 */
2471 private Map<Type,List<Type>> closureCache = new HashMap<Type,List<Type>>();
2472
2473 /**
2474 * Returns the closure of a class or interface type.
2475 */
2476 public List<Type> closure(Type t) {
2477 List<Type> cl = closureCache.get(t);
2478 if (cl == null) {
2479 Type st = supertype(t);
2480 if (!t.isCompound()) {
2481 if (st.tag == CLASS) {
2482 cl = insert(closure(st), t);
2483 } else if (st.tag == TYPEVAR) {
2484 cl = closure(st).prepend(t);
2485 } else {
2486 cl = List.of(t);
2487 }
2488 } else {
2489 cl = closure(supertype(t));
2490 }
2491 for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail)
2492 cl = union(cl, closure(l.head));
2493 closureCache.put(t, cl);
2494 }
2495 return cl;
2496 }
2497
2498 /**
2499 * Insert a type in a closure
2500 */
2501 public List<Type> insert(List<Type> cl, Type t) {
2502 if (cl.isEmpty() || t.tsym.precedes(cl.head.tsym, this)) {
2503 return cl.prepend(t);
2504 } else if (cl.head.tsym.precedes(t.tsym, this)) {
2505 return insert(cl.tail, t).prepend(cl.head);
2506 } else {
2507 return cl;
2508 }
2509 }
2510
2511 /**
2512 * Form the union of two closures
2513 */
2514 public List<Type> union(List<Type> cl1, List<Type> cl2) {
2515 if (cl1.isEmpty()) {
2516 return cl2;
2517 } else if (cl2.isEmpty()) {
2518 return cl1;
2519 } else if (cl1.head.tsym.precedes(cl2.head.tsym, this)) {
2520 return union(cl1.tail, cl2).prepend(cl1.head);
2521 } else if (cl2.head.tsym.precedes(cl1.head.tsym, this)) {
2522 return union(cl1, cl2.tail).prepend(cl2.head);
2523 } else {
2524 return union(cl1.tail, cl2.tail).prepend(cl1.head);
2525 }
2526 }
2527
2528 /**
2529 * Intersect two closures
2530 */
2531 public List<Type> intersect(List<Type> cl1, List<Type> cl2) {
2532 if (cl1 == cl2)
2533 return cl1;
2534 if (cl1.isEmpty() || cl2.isEmpty())
2535 return List.nil();
2536 if (cl1.head.tsym.precedes(cl2.head.tsym, this))
2537 return intersect(cl1.tail, cl2);
2538 if (cl2.head.tsym.precedes(cl1.head.tsym, this))
2539 return intersect(cl1, cl2.tail);
2540 if (isSameType(cl1.head, cl2.head))
2541 return intersect(cl1.tail, cl2.tail).prepend(cl1.head);
2542 if (cl1.head.tsym == cl2.head.tsym &&
2543 cl1.head.tag == CLASS && cl2.head.tag == CLASS) {
2544 if (cl1.head.isParameterized() && cl2.head.isParameterized()) {
2545 Type merge = merge(cl1.head,cl2.head);
2546 return intersect(cl1.tail, cl2.tail).prepend(merge);
2547 }
2548 if (cl1.head.isRaw() || cl2.head.isRaw())
2549 return intersect(cl1.tail, cl2.tail).prepend(erasure(cl1.head));
2550 }
2551 return intersect(cl1.tail, cl2.tail);
2552 }
2553 // where
2554 class TypePair {
2555 final Type t1;
2556 final Type t2;
2557 TypePair(Type t1, Type t2) {
2558 this.t1 = t1;
2559 this.t2 = t2;
2560 }
2561 @Override
2562 public int hashCode() {
2563 return 127 * Types.this.hashCode(t1) + Types.this.hashCode(t2);
2564 }
2565 @Override
2566 public boolean equals(Object obj) {
2567 if (!(obj instanceof TypePair))
2568 return false;
2569 TypePair typePair = (TypePair)obj;
2570 return isSameType(t1, typePair.t1)
2571 && isSameType(t2, typePair.t2);
2572 }
2573 }
2574 Set<TypePair> mergeCache = new HashSet<TypePair>();
2575 private Type merge(Type c1, Type c2) {
2576 ClassType class1 = (ClassType) c1;
2577 List<Type> act1 = class1.getTypeArguments();
2578 ClassType class2 = (ClassType) c2;
2579 List<Type> act2 = class2.getTypeArguments();
2580 ListBuffer<Type> merged = new ListBuffer<Type>();
2581 List<Type> typarams = class1.tsym.type.getTypeArguments();
2582
2583 while (act1.nonEmpty() && act2.nonEmpty() && typarams.nonEmpty()) {
2584 if (containsType(act1.head, act2.head)) {
2585 merged.append(act1.head);
2586 } else if (containsType(act2.head, act1.head)) {
2587 merged.append(act2.head);
2588 } else {
2589 TypePair pair = new TypePair(c1, c2);
2590 Type m;
2591 if (mergeCache.add(pair)) {
2592 m = new WildcardType(lub(upperBound(act1.head),
2593 upperBound(act2.head)),
2594 BoundKind.EXTENDS,
2595 syms.boundClass);
2596 mergeCache.remove(pair);
2597 } else {
2598 m = new WildcardType(syms.objectType,
2599 BoundKind.UNBOUND,
2600 syms.boundClass);
2601 }
2602 merged.append(m.withTypeVar(typarams.head));
2603 }
2604 act1 = act1.tail;
2605 act2 = act2.tail;
2606 typarams = typarams.tail;
2607 }
2608 assert(act1.isEmpty() && act2.isEmpty() && typarams.isEmpty());
2609 return new ClassType(class1.getEnclosingType(), merged.toList(), class1.tsym);
2610 }
2611
2612 /**
2613 * Return the minimum type of a closure, a compound type if no
2614 * unique minimum exists.
2615 */
2616 private Type compoundMin(List<Type> cl) {
2617 if (cl.isEmpty()) return syms.objectType;
2618 List<Type> compound = closureMin(cl);
2619 if (compound.isEmpty())
2620 return null;
2621 else if (compound.tail.isEmpty())
2622 return compound.head;
2623 else
2624 return makeCompoundType(compound);
2625 }
2626
2627 /**
2628 * Return the minimum types of a closure, suitable for computing
2629 * compoundMin or glb.
2630 */
2631 private List<Type> closureMin(List<Type> cl) {
2632 ListBuffer<Type> classes = lb();
2633 ListBuffer<Type> interfaces = lb();
2634 while (!cl.isEmpty()) {
2635 Type current = cl.head;
2636 if (current.isInterface())
2637 interfaces.append(current);
2638 else
2639 classes.append(current);
2640 ListBuffer<Type> candidates = lb();
2641 for (Type t : cl.tail) {
2642 if (!isSubtypeNoCapture(current, t))
2643 candidates.append(t);
2644 }
2645 cl = candidates.toList();
2646 }
2647 return classes.appendList(interfaces).toList();
2648 }
2649
2650 /**
2651 * Return the least upper bound of pair of types. if the lub does
2652 * not exist return null.
2653 */
2654 public Type lub(Type t1, Type t2) {
2655 return lub(List.of(t1, t2));
2656 }
2657
2658 /**
2659 * Return the least upper bound (lub) of set of types. If the lub
2660 * does not exist return the type of null (bottom).
2661 */
2662 public Type lub(List<Type> ts) {
2663 final int ARRAY_BOUND = 1;
2664 final int CLASS_BOUND = 2;
2665 int boundkind = 0;
2666 for (Type t : ts) {
2667 switch (t.tag) {
2668 case CLASS:
2669 boundkind |= CLASS_BOUND;
2670 break;
2671 case ARRAY:
2672 boundkind |= ARRAY_BOUND;
2673 break;
2674 case TYPEVAR:
2675 do {
2676 t = t.getUpperBound();
2677 } while (t.tag == TYPEVAR);
2678 if (t.tag == ARRAY) {
2679 boundkind |= ARRAY_BOUND;
2680 } else {
2681 boundkind |= CLASS_BOUND;
2682 }
2683 break;
2684 default:
2685 if (t.isPrimitive())
2686 return syms.errType;
2687 }
2688 }
2689 switch (boundkind) {
2690 case 0:
2691 return syms.botType;
2692
2693 case ARRAY_BOUND:
2694 // calculate lub(A[], B[])
2695 List<Type> elements = Type.map(ts, elemTypeFun);
2696 for (Type t : elements) {
2697 if (t.isPrimitive()) {
2698 // if a primitive type is found, then return
2699 // arraySuperType unless all the types are the
2700 // same
2701 Type first = ts.head;
2702 for (Type s : ts.tail) {
2703 if (!isSameType(first, s)) {
2704 // lub(int[], B[]) is Cloneable & Serializable
2705 return arraySuperType();
2706 }
2707 }
2708 // all the array types are the same, return one
2709 // lub(int[], int[]) is int[]
2710 return first;
2711 }
2712 }
2713 // lub(A[], B[]) is lub(A, B)[]
2714 return new ArrayType(lub(elements), syms.arrayClass);
2715
2716 case CLASS_BOUND:
2717 // calculate lub(A, B)
2718 while (ts.head.tag != CLASS && ts.head.tag != TYPEVAR)
2719 ts = ts.tail;
2720 assert !ts.isEmpty();
2721 List<Type> cl = closure(ts.head);
2722 for (Type t : ts.tail) {
2723 if (t.tag == CLASS || t.tag == TYPEVAR)
2724 cl = intersect(cl, closure(t));
2725 }
2726 return compoundMin(cl);
2727
2728 default:
2729 // calculate lub(A, B[])
2730 List<Type> classes = List.of(arraySuperType());
2731 for (Type t : ts) {
2732 if (t.tag != ARRAY) // Filter out any arrays
2733 classes = classes.prepend(t);
2734 }
2735 // lub(A, B[]) is lub(A, arraySuperType)
2736 return lub(classes);
2737 }
2738 }
2739 // where
2740 private Type arraySuperType = null;
2741 private Type arraySuperType() {
2742 // initialized lazily to avoid problems during compiler startup
2743 if (arraySuperType == null) {
2744 synchronized (this) {
2745 if (arraySuperType == null) {
2746 // JLS 10.8: all arrays implement Cloneable and Serializable.
2747 arraySuperType = makeCompoundType(List.of(syms.serializableType,
2748 syms.cloneableType),
2749 syms.objectType);
2750 }
2751 }
2752 }
2753 return arraySuperType;
2754 }
2755 // </editor-fold>
2756
2757 // <editor-fold defaultstate="collapsed" desc="Greatest lower bound">
2758 public Type glb(List<Type> ts) {
2759 Type t1 = ts.head;
2760 for (Type t2 : ts.tail) {
2761 if (t1.isErroneous())
2762 return t1;
2763 t1 = glb(t1, t2);
2764 }
2765 return t1;
2766 }
2767 //where
2768 public Type glb(Type t, Type s) {
2769 if (s == null)
2770 return t;
2771 else if (isSubtypeNoCapture(t, s))
2772 return t;
2773 else if (isSubtypeNoCapture(s, t))
2774 return s;
2775
2776 List<Type> closure = union(closure(t), closure(s));
2777 List<Type> bounds = closureMin(closure);
2778
2779 if (bounds.isEmpty()) { // length == 0
2780 return syms.objectType;
2781 } else if (bounds.tail.isEmpty()) { // length == 1
2782 return bounds.head;
2783 } else { // length > 1
2784 int classCount = 0;
2785 for (Type bound : bounds)
2786 if (!bound.isInterface())
2787 classCount++;
2788 if (classCount > 1)
2789 return createErrorType(t);
2790 }
2791 return makeCompoundType(bounds);
2792 }
2793 // </editor-fold>
2794
2795 // <editor-fold defaultstate="collapsed" desc="hashCode">
2796 /**
2797 * Compute a hash code on a type.
2798 */
2799 public static int hashCode(Type t) {
2800 return hashCode.visit(t);
2801 }
2802 // where
2803 private static final UnaryVisitor<Integer> hashCode = new UnaryVisitor<Integer>() {
2804
2805 public Integer visitType(Type t, Void ignored) {
2806 return t.tag;
2807 }
2808
2809 @Override
2810 public Integer visitClassType(ClassType t, Void ignored) {
2811 int result = visit(t.getEnclosingType());
2812 result *= 127;
2813 result += t.tsym.flatName().hashCode();
2814 for (Type s : t.getTypeArguments()) {
2815 result *= 127;
2816 result += visit(s);
2817 }
2818 return result;
2819 }
2820
2821 @Override
2822 public Integer visitWildcardType(WildcardType t, Void ignored) {
2823 int result = t.kind.hashCode();
2824 if (t.type != null) {
2825 result *= 127;
2826 result += visit(t.type);
2827 }
2828 return result;
2829 }
2830
2831 @Override
2832 public Integer visitArrayType(ArrayType t, Void ignored) {
2833 return visit(t.elemtype) + 12;
2834 }
2835
2836 @Override
2837 public Integer visitTypeVar(TypeVar t, Void ignored) {
2838 return System.identityHashCode(t.tsym);
2839 }
2840
2841 @Override
2842 public Integer visitUndetVar(UndetVar t, Void ignored) {
2843 return System.identityHashCode(t);
2844 }
2845
2846 @Override
2847 public Integer visitErrorType(ErrorType t, Void ignored) {
2848 return 0;
2849 }
2850 };
2851 // </editor-fold>
2852
2853 // <editor-fold defaultstate="collapsed" desc="Return-Type-Substitutable">
2854 /**
2855 * Does t have a result that is a subtype of the result type of s,
2856 * suitable for covariant returns? It is assumed that both types
2857 * are (possibly polymorphic) method types. Monomorphic method
2858 * types are handled in the obvious way. Polymorphic method types
2859 * require renaming all type variables of one to corresponding
2860 * type variables in the other, where correspondence is by
2861 * position in the type parameter list. */
2862 public boolean resultSubtype(Type t, Type s, Warner warner) {
2863 List<Type> tvars = t.getTypeArguments();
2864 List<Type> svars = s.getTypeArguments();
2865 Type tres = t.getReturnType();
2866 Type sres = subst(s.getReturnType(), svars, tvars);
2867 return covariantReturnType(tres, sres, warner);
2868 }
2869
2870 /**
2871 * Return-Type-Substitutable.
2872 * @see <a href="http://java.sun.com/docs/books/jls/">The Java
2873 * Language Specification, Third Ed. (8.4.5)</a>
2874 */
2875 public boolean returnTypeSubstitutable(Type r1, Type r2) {
2876 if (hasSameArgs(r1, r2))
2877 return resultSubtype(r1, r2, Warner.noWarnings);
2878 else
2879 return covariantReturnType(r1.getReturnType(),
2880 erasure(r2.getReturnType()),
2881 Warner.noWarnings);
2882 }
2883
2884 public boolean returnTypeSubstitutable(Type r1,
2885 Type r2, Type r2res,
2886 Warner warner) {
2887 if (isSameType(r1.getReturnType(), r2res))
2888 return true;
2889 if (r1.getReturnType().isPrimitive() || r2res.isPrimitive())
2890 return false;
2891
2892 if (hasSameArgs(r1, r2))
2893 return covariantReturnType(r1.getReturnType(), r2res, warner);
2894 if (!source.allowCovariantReturns())
2895 return false;
2896 if (isSubtypeUnchecked(r1.getReturnType(), r2res, warner))
2897 return true;
2898 if (!isSubtype(r1.getReturnType(), erasure(r2res)))
2899 return false;
2900 warner.warnUnchecked();
2901 return true;
2902 }
2903
2904 /**
2905 * Is t an appropriate return type in an overrider for a
2906 * method that returns s?
2907 */
2908 public boolean covariantReturnType(Type t, Type s, Warner warner) {
2909 return
2910 isSameType(t, s) ||
2911 source.allowCovariantReturns() &&
2912 !t.isPrimitive() &&
2913 !s.isPrimitive() &&
2914 isAssignable(t, s, warner);
2915 }
2916 // </editor-fold>
2917
2918 // <editor-fold defaultstate="collapsed" desc="Box/unbox support">
2919 /**
2920 * Return the class that boxes the given primitive.
2921 */
2922 public ClassSymbol boxedClass(Type t) {
2923 return reader.enterClass(syms.boxedName[t.tag]);
2924 }
2925
2926 /**
2927 * Return the primitive type corresponding to a boxed type.
2928 */
2929 public Type unboxedType(Type t) {
2930 if (allowBoxing) {
2931 for (int i=0; i<syms.boxedName.length; i++) {
2932 Name box = syms.boxedName[i];
2933 if (box != null &&
2934 asSuper(t, reader.enterClass(box)) != null)
2935 return syms.typeOfTag[i];
2936 }
2937 }
2938 return Type.noType;
2939 }
2940 // </editor-fold>
2941
2942 // <editor-fold defaultstate="collapsed" desc="Capture conversion">
2943 /*
2944 * JLS 3rd Ed. 5.1.10 Capture Conversion:
2945 *
2946 * Let G name a generic type declaration with n formal type
2947 * parameters A1 ... An with corresponding bounds U1 ... Un. There
2948 * exists a capture conversion from G<T1 ... Tn> to G<S1 ... Sn>,
2949 * where, for 1 <= i <= n:
2950 *
2951 * + If Ti is a wildcard type argument (4.5.1) of the form ? then
2952 * Si is a fresh type variable whose upper bound is
2953 * Ui[A1 := S1, ..., An := Sn] and whose lower bound is the null
2954 * type.
2955 *
2956 * + If Ti is a wildcard type argument of the form ? extends Bi,
2957 * then Si is a fresh type variable whose upper bound is
2958 * glb(Bi, Ui[A1 := S1, ..., An := Sn]) and whose lower bound is
2959 * the null type, where glb(V1,... ,Vm) is V1 & ... & Vm. It is
2960 * a compile-time error if for any two classes (not interfaces)
2961 * Vi and Vj,Vi is not a subclass of Vj or vice versa.
2962 *
2963 * + If Ti is a wildcard type argument of the form ? super Bi,
2964 * then Si is a fresh type variable whose upper bound is
2965 * Ui[A1 := S1, ..., An := Sn] and whose lower bound is Bi.
2966 *
2967 * + Otherwise, Si = Ti.
2968 *
2969 * Capture conversion on any type other than a parameterized type
2970 * (4.5) acts as an identity conversion (5.1.1). Capture
2971 * conversions never require a special action at run time and
2972 * therefore never throw an exception at run time.
2973 *
2974 * Capture conversion is not applied recursively.
2975 */
2976 /**
2977 * Capture conversion as specified by JLS 3rd Ed.
2978 */
2979
2980 public List<Type> capture(List<Type> ts) {
2981 List<Type> buf = List.nil();
2982 for (Type t : ts) {
2983 buf = buf.prepend(capture(t));
2984 }
2985 return buf.reverse();
2986 }
2987 public Type capture(Type t) {
2988 if (t.tag != CLASS)
2989 return t;
2990 ClassType cls = (ClassType)t;
2991 if (cls.isRaw() || !cls.isParameterized())
2992 return cls;
2993
2994 ClassType G = (ClassType)cls.asElement().asType();
2995 List<Type> A = G.getTypeArguments();
2996 List<Type> T = cls.getTypeArguments();
2997 List<Type> S = freshTypeVariables(T);
2998
2999 List<Type> currentA = A;
3000 List<Type> currentT = T;
3001 List<Type> currentS = S;
3002 boolean captured = false;
3003 while (!currentA.isEmpty() &&
3004 !currentT.isEmpty() &&
3005 !currentS.isEmpty()) {
3006 if (currentS.head != currentT.head) {
3007 captured = true;
3008 WildcardType Ti = (WildcardType)currentT.head;
3009 Type Ui = currentA.head.getUpperBound();
3010 CapturedType Si = (CapturedType)currentS.head;
3011 if (Ui == null)
3012 Ui = syms.objectType;
3013 switch (Ti.kind) {
3014 case UNBOUND:
3015 Si.bound = subst(Ui, A, S);
3016 Si.lower = syms.botType;
3017 break;
3018 case EXTENDS:
3019 Si.bound = glb(Ti.getExtendsBound(), subst(Ui, A, S));
3020 Si.lower = syms.botType;
3021 break;
3022 case SUPER:
3023 Si.bound = subst(Ui, A, S);
3024 Si.lower = Ti.getSuperBound();
3025 break;
3026 }
3027 if (Si.bound == Si.lower)
3028 currentS.head = Si.bound;
3029 }
3030 currentA = currentA.tail;
3031 currentT = currentT.tail;
3032 currentS = currentS.tail;
3033 }
3034 if (!currentA.isEmpty() || !currentT.isEmpty() || !currentS.isEmpty())
3035 return erasure(t); // some "rare" type involved
3036
3037 if (captured)
3038 return new ClassType(cls.getEnclosingType(), S, cls.tsym);
3039 else
3040 return t;
3041 }
3042 // where
3043 public List<Type> freshTypeVariables(List<Type> types) {
3044 ListBuffer<Type> result = lb();
3045 for (Type t : types) {
3046 if (t.tag == WILDCARD) {
3047 Type bound = ((WildcardType)t).getExtendsBound();
3048 if (bound == null)
3049 bound = syms.objectType;
3050 result.append(new CapturedType(capturedName,
3051 syms.noSymbol,
3052 bound,
3053 syms.botType,
3054 (WildcardType)t));
3055 } else {
3056 result.append(t);
3057 }
3058 }
3059 return result.toList();
3060 }
3061 // </editor-fold>
3062
3063 // <editor-fold defaultstate="collapsed" desc="Internal utility methods">
3064 private List<Type> upperBounds(List<Type> ss) {
3065 if (ss.isEmpty()) return ss;
3066 Type head = upperBound(ss.head);
3067 List<Type> tail = upperBounds(ss.tail);
3068 if (head != ss.head || tail != ss.tail)
3069 return tail.prepend(head);
3070 else
3071 return ss;
3072 }
3073
3074 private boolean sideCast(Type from, Type to, Warner warn) {
3075 // We are casting from type $from$ to type $to$, which are
3076 // non-final unrelated types. This method
3077 // tries to reject a cast by transferring type parameters
3078 // from $to$ to $from$ by common superinterfaces.
3079 boolean reverse = false;
3080 Type target = to;
3081 if ((to.tsym.flags() & INTERFACE) == 0) {
3082 assert (from.tsym.flags() & INTERFACE) != 0;
3083 reverse = true;
3084 to = from;
3085 from = target;
3086 }
3087 List<Type> commonSupers = superClosure(to, erasure(from));
3088 boolean giveWarning = commonSupers.isEmpty();
3089 // The arguments to the supers could be unified here to
3090 // get a more accurate analysis
3091 while (commonSupers.nonEmpty()) {
3092 Type t1 = asSuper(from, commonSupers.head.tsym);
3093 Type t2 = commonSupers.head; // same as asSuper(to, commonSupers.head.tsym);
3094 if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
3095 return false;
3096 giveWarning = giveWarning || (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2));
3097 commonSupers = commonSupers.tail;
3098 }
3099 if (giveWarning && !isReifiable(reverse ? from : to))
3100 warn.warnUnchecked();
3101 if (!source.allowCovariantReturns())
3102 // reject if there is a common method signature with
3103 // incompatible return types.
3104 chk.checkCompatibleAbstracts(warn.pos(), from, to);
3105 return true;
3106 }
3107
3108 private boolean sideCastFinal(Type from, Type to, Warner warn) {
3109 // We are casting from type $from$ to type $to$, which are
3110 // unrelated types one of which is final and the other of
3111 // which is an interface. This method
3112 // tries to reject a cast by transferring type parameters
3113 // from the final class to the interface.
3114 boolean reverse = false;
3115 Type target = to;
3116 if ((to.tsym.flags() & INTERFACE) == 0) {
3117 assert (from.tsym.flags() & INTERFACE) != 0;
3118 reverse = true;
3119 to = from;
3120 from = target;
3121 }
3122 assert (from.tsym.flags() & FINAL) != 0;
3123 Type t1 = asSuper(from, to.tsym);
3124 if (t1 == null) return false;
3125 Type t2 = to;
3126 if (disjointTypes(t1.getTypeArguments(), t2.getTypeArguments()))
3127 return false;
3128 if (!source.allowCovariantReturns())
3129 // reject if there is a common method signature with
3130 // incompatible return types.
3131 chk.checkCompatibleAbstracts(warn.pos(), from, to);
3132 if (!isReifiable(target) &&
3133 (reverse ? giveWarning(t2, t1) : giveWarning(t1, t2)))
3134 warn.warnUnchecked();
3135 return true;
3136 }
3137
3138 private boolean giveWarning(Type from, Type to) {
3139 Type subFrom = asSub(from, to.tsym);
3140 return to.isParameterized() &&
3141 (!(isUnbounded(to) ||
3142 isSubtype(from, to) ||
3143 ((subFrom != null) && isSameType(subFrom, to))));
3144 }
3145
3146 private List<Type> superClosure(Type t, Type s) {
3147 List<Type> cl = List.nil();
3148 for (List<Type> l = interfaces(t); l.nonEmpty(); l = l.tail) {
3149 if (isSubtype(s, erasure(l.head))) {
3150 cl = insert(cl, l.head);
3151 } else {
3152 cl = union(cl, superClosure(l.head, s));
3153 }
3154 }
3155 return cl;
3156 }
3157
3158 private boolean containsTypeEquivalent(Type t, Type s) {
3159 return
3160 isSameType(t, s) || // shortcut
3161 containsType(t, s) && containsType(s, t);
3162 }
3163
3164 // <editor-fold defaultstate="collapsed" desc="adapt">
3165 /**
3166 * Adapt a type by computing a substitution which maps a source
3167 * type to a target type.
3168 *
3169 * @param source the source type
3170 * @param target the target type
3171 * @param from the type variables of the computed substitution
3172 * @param to the types of the computed substitution.
3173 */
3174 public void adapt(Type source,
3175 Type target,
3176 ListBuffer<Type> from,
3177 ListBuffer<Type> to) throws AdaptFailure {
3178 new Adapter(from, to).adapt(source, target);
3179 }
3180
3181 class Adapter extends SimpleVisitor<Void, Type> {
3182
3183 ListBuffer<Type> from;
3184 ListBuffer<Type> to;
3185 Map<Symbol,Type> mapping;
3186
3187 Adapter(ListBuffer<Type> from, ListBuffer<Type> to) {
3188 this.from = from;
3189 this.to = to;
3190 mapping = new HashMap<Symbol,Type>();
3191 }
3192
3193 public void adapt(Type source, Type target) throws AdaptFailure {
3194 visit(source, target);
3195 List<Type> fromList = from.toList();
3196 List<Type> toList = to.toList();
3197 while (!fromList.isEmpty()) {
3198 Type val = mapping.get(fromList.head.tsym);
3199 if (toList.head != val)
3200 toList.head = val;
3201 fromList = fromList.tail;
3202 toList = toList.tail;
3203 }
3204 }
3205
3206 @Override
3207 public Void visitClassType(ClassType source, Type target) throws AdaptFailure {
3208 if (target.tag == CLASS)
3209 adaptRecursive(source.allparams(), target.allparams());
3210 return null;
3211 }
3212
3213 @Override
3214 public Void visitArrayType(ArrayType source, Type target) throws AdaptFailure {
3215 if (target.tag == ARRAY)
3216 adaptRecursive(elemtype(source), elemtype(target));
3217 return null;
3218 }
3219
3220 @Override
3221 public Void visitWildcardType(WildcardType source, Type target) throws AdaptFailure {
3222 if (source.isExtendsBound())
3223 adaptRecursive(upperBound(source), upperBound(target));
3224 else if (source.isSuperBound())
3225 adaptRecursive(lowerBound(source), lowerBound(target));
3226 return null;
3227 }
3228
3229 @Override
3230 public Void visitTypeVar(TypeVar source, Type target) throws AdaptFailure {
3231 // Check to see if there is
3232 // already a mapping for $source$, in which case
3233 // the old mapping will be merged with the new
3234 Type val = mapping.get(source.tsym);
3235 if (val != null) {
3236 if (val.isSuperBound() && target.isSuperBound()) {
3237 val = isSubtype(lowerBound(val), lowerBound(target))
3238 ? target : val;
3239 } else if (val.isExtendsBound() && target.isExtendsBound()) {
3240 val = isSubtype(upperBound(val), upperBound(target))
3241 ? val : target;
3242 } else if (!isSameType(val, target)) {
3243 throw new AdaptFailure();
3244 }
3245 } else {
3246 val = target;
3247 from.append(source);
3248 to.append(target);
3249 }
3250 mapping.put(source.tsym, val);
3251 return null;
3252 }
3253
3254 @Override
3255 public Void visitType(Type source, Type target) {
3256 return null;
3257 }
3258
3259 private Set<TypePair> cache = new HashSet<TypePair>();
3260
3261 private void adaptRecursive(Type source, Type target) {
3262 TypePair pair = new TypePair(source, target);
3263 if (cache.add(pair)) {
3264 try {
3265 visit(source, target);
3266 } finally {
3267 cache.remove(pair);
3268 }
3269 }
3270 }
3271
3272 private void adaptRecursive(List<Type> source, List<Type> target) {
3273 if (source.length() == target.length()) {
3274 while (source.nonEmpty()) {
3275 adaptRecursive(source.head, target.head);
3276 source = source.tail;
3277 target = target.tail;
3278 }
3279 }
3280 }
3281 }
3282
3283 public static class AdaptFailure extends RuntimeException {
3284 static final long serialVersionUID = -7490231548272701566L;
3285 }
3286
3287 private void adaptSelf(Type t,
3288 ListBuffer<Type> from,
3289 ListBuffer<Type> to) {
3290 try {
3291 //if (t.tsym.type != t)
3292 adapt(t.tsym.type, t, from, to);
3293 } catch (AdaptFailure ex) {
3294 // Adapt should never fail calculating a mapping from
3295 // t.tsym.type to t as there can be no merge problem.
3296 throw new AssertionError(ex);
3297 }
3298 }
3299 // </editor-fold>
3300
3301 /**
3302 * Rewrite all type variables (universal quantifiers) in the given
3303 * type to wildcards (existential quantifiers). This is used to
3304 * determine if a cast is allowed. For example, if high is true
3305 * and {@code T <: Number}, then {@code List<T>} is rewritten to
3306 * {@code List<? extends Number>}. Since {@code List<Integer> <:
3307 * List<? extends Number>} a {@code List<T>} can be cast to {@code
3308 * List<Integer>} with a warning.
3309 * @param t a type
3310 * @param high if true return an upper bound; otherwise a lower
3311 * bound
3312 * @param rewriteTypeVars only rewrite captured wildcards if false;
3313 * otherwise rewrite all type variables
3314 * @return the type rewritten with wildcards (existential
3315 * quantifiers) only
3316 */
3317 private Type rewriteQuantifiers(Type t, boolean high, boolean rewriteTypeVars) {
3318 return new Rewriter(high, rewriteTypeVars).rewrite(t);
3319 }
3320
3321 class Rewriter extends UnaryVisitor<Type> {
3322
3323 boolean high;
3324 boolean rewriteTypeVars;
3325
3326 Rewriter(boolean high, boolean rewriteTypeVars) {
3327 this.high = high;
3328 this.rewriteTypeVars = rewriteTypeVars;
3329 }
3330
3331 Type rewrite(Type t) {
3332 ListBuffer<Type> from = new ListBuffer<Type>();
3333 ListBuffer<Type> to = new ListBuffer<Type>();
3334 adaptSelf(t, from, to);
3335 ListBuffer<Type> rewritten = new ListBuffer<Type>();
3336 List<Type> formals = from.toList();
3337 boolean changed = false;
3338 for (Type arg : to.toList()) {
3339 Type bound = visit(arg);
3340 if (arg != bound) {
3341 changed = true;
3342 bound = high ? makeExtendsWildcard(bound, (TypeVar)formals.head)
3343 : makeSuperWildcard(bound, (TypeVar)formals.head);
3344 }
3345 rewritten.append(bound);
3346 formals = formals.tail;
3347 }
3348 if (changed)
3349 return subst(t.tsym.type, from.toList(), rewritten.toList());
3350 else
3351 return t;
3352 }
3353
3354 public Type visitType(Type t, Void s) {
3355 return high ? upperBound(t) : lowerBound(t);
3356 }
3357
3358 @Override
3359 public Type visitCapturedType(CapturedType t, Void s) {
3360 return visitWildcardType(t.wildcard, null);
3361 }
3362
3363 @Override
3364 public Type visitTypeVar(TypeVar t, Void s) {
3365 if (rewriteTypeVars)
3366 return high ? t.bound : syms.botType;
3367 else
3368 return t;
3369 }
3370
3371 @Override
3372 public Type visitWildcardType(WildcardType t, Void s) {
3373 Type bound = high ? t.getExtendsBound() :
3374 t.getSuperBound();
3375 if (bound == null)
3376 bound = high ? syms.objectType : syms.botType;
3377 return bound;
3378 }
3379 }
3380
3381 /**
3382 * Create a wildcard with the given upper (extends) bound; create
3383 * an unbounded wildcard if bound is Object.
3384 *
3385 * @param bound the upper bound
3386 * @param formal the formal type parameter that will be
3387 * substituted by the wildcard
3388 */
3389 private WildcardType makeExtendsWildcard(Type bound, TypeVar formal) {
3390 if (bound == syms.objectType) {
3391 return new WildcardType(syms.objectType,
3392 BoundKind.UNBOUND,
3393 syms.boundClass,
3394 formal);
3395 } else {
3396 return new WildcardType(bound,
3397 BoundKind.EXTENDS,
3398 syms.boundClass,
3399 formal);
3400 }
3401 }
3402
3403 /**
3404 * Create a wildcard with the given lower (super) bound; create an
3405 * unbounded wildcard if bound is bottom (type of {@code null}).
3406 *
3407 * @param bound the lower bound
3408 * @param formal the formal type parameter that will be
3409 * substituted by the wildcard
3410 */
3411 private WildcardType makeSuperWildcard(Type bound, TypeVar formal) {
3412 if (bound.tag == BOT) {
3413 return new WildcardType(syms.objectType,
3414 BoundKind.UNBOUND,
3415 syms.boundClass,
3416 formal);
3417 } else {
3418 return new WildcardType(bound,
3419 BoundKind.SUPER,
3420 syms.boundClass,
3421 formal);
3422 }
3423 }
3424
3425 /**
3426 * A wrapper for a type that allows use in sets.
3427 */
3428 class SingletonType {
3429 final Type t;
3430 SingletonType(Type t) {
3431 this.t = t;
3432 }
3433 public int hashCode() {
3434 return Types.this.hashCode(t);
3435 }
3436 public boolean equals(Object obj) {
3437 return (obj instanceof SingletonType) &&
3438 isSameType(t, ((SingletonType)obj).t);
3439 }
3440 public String toString() {
3441 return t.toString();
3442 }
3443 }
3444 // </editor-fold>
3445
3446 // <editor-fold defaultstate="collapsed" desc="Visitors">
3447 /**
3448 * A default visitor for types. All visitor methods except
3449 * visitType are implemented by delegating to visitType. Concrete
3450 * subclasses must provide an implementation of visitType and can
3451 * override other methods as needed.
3452 *
3453 * @param <R> the return type of the operation implemented by this
3454 * visitor; use Void if no return type is needed.
3455 * @param <S> the type of the second argument (the first being the
3456 * type itself) of the operation implemented by this visitor; use
3457 * Void if a second argument is not needed.
3458 */
3459 public static abstract class DefaultTypeVisitor<R,S> implements Type.Visitor<R,S> {
3460 final public R visit(Type t, S s) { return t.accept(this, s); }
3461 public R visitClassType(ClassType t, S s) { return visitType(t, s); }
3462 public R visitWildcardType(WildcardType t, S s) { return visitType(t, s); }
3463 public R visitArrayType(ArrayType t, S s) { return visitType(t, s); }
3464 public R visitMethodType(MethodType t, S s) { return visitType(t, s); }
3465 public R visitPackageType(PackageType t, S s) { return visitType(t, s); }
3466 public R visitTypeVar(TypeVar t, S s) { return visitType(t, s); }
3467 public R visitCapturedType(CapturedType t, S s) { return visitType(t, s); }
3468 public R visitForAll(ForAll t, S s) { return visitType(t, s); }
3469 public R visitUndetVar(UndetVar t, S s) { return visitType(t, s); }
3470 public R visitErrorType(ErrorType t, S s) { return visitType(t, s); }
3471 }
3472
3473 /**
3474 * A default visitor for symbols. All visitor methods except
3475 * visitSymbol are implemented by delegating to visitSymbol. Concrete
3476 * subclasses must provide an implementation of visitSymbol and can
3477 * override other methods as needed.
3478 *
3479 * @param <R> the return type of the operation implemented by this
3480 * visitor; use Void if no return type is needed.
3481 * @param <S> the type of the second argument (the first being the
3482 * symbol itself) of the operation implemented by this visitor; use
3483 * Void if a second argument is not needed.
3484 */
3485 public static abstract class DefaultSymbolVisitor<R,S> implements Symbol.Visitor<R,S> {
3486 final public R visit(Symbol s, S arg) { return s.accept(this, arg); }
3487 public R visitClassSymbol(ClassSymbol s, S arg) { return visitSymbol(s, arg); }
3488 public R visitMethodSymbol(MethodSymbol s, S arg) { return visitSymbol(s, arg); }
3489 public R visitOperatorSymbol(OperatorSymbol s, S arg) { return visitSymbol(s, arg); }
3490 public R visitPackageSymbol(PackageSymbol s, S arg) { return visitSymbol(s, arg); }
3491 public R visitTypeSymbol(TypeSymbol s, S arg) { return visitSymbol(s, arg); }
3492 public R visitVarSymbol(VarSymbol s, S arg) { return visitSymbol(s, arg); }
3493 }
3494
3495 /**
3496 * A <em>simple</em> visitor for types. This visitor is simple as
3497 * captured wildcards, for-all types (generic methods), and
3498 * undetermined type variables (part of inference) are hidden.
3499 * Captured wildcards are hidden by treating them as type
3500 * variables and the rest are hidden by visiting their qtypes.
3501 *
3502 * @param <R> the return type of the operation implemented by this
3503 * visitor; use Void if no return type is needed.
3504 * @param <S> the type of the second argument (the first being the
3505 * type itself) of the operation implemented by this visitor; use
3506 * Void if a second argument is not needed.
3507 */
3508 public static abstract class SimpleVisitor<R,S> extends DefaultTypeVisitor<R,S> {
3509 @Override
3510 public R visitCapturedType(CapturedType t, S s) {
3511 return visitTypeVar(t, s);
3512 }
3513 @Override
3514 public R visitForAll(ForAll t, S s) {
3515 return visit(t.qtype, s);
3516 }
3517 @Override
3518 public R visitUndetVar(UndetVar t, S s) {
3519 return visit(t.qtype, s);
3520 }
3521 }
3522
3523 /**
3524 * A plain relation on types. That is a 2-ary function on the
3525 * form Type × Type → Boolean.
3526 * <!-- In plain text: Type x Type -> Boolean -->
3527 */
3528 public static abstract class TypeRelation extends SimpleVisitor<Boolean,Type> {}
3529
3530 /**
3531 * A convenience visitor for implementing operations that only
3532 * require one argument (the type itself), that is, unary
3533 * operations.
3534 *
3535 * @param <R> the return type of the operation implemented by this
3536 * visitor; use Void if no return type is needed.
3537 */
3538 public static abstract class UnaryVisitor<R> extends SimpleVisitor<R,Void> {
3539 final public R visit(Type t) { return t.accept(this, null); }
3540 }
3541
3542 /**
3543 * A visitor for implementing a mapping from types to types. The
3544 * default behavior of this class is to implement the identity
3545 * mapping (mapping a type to itself). This can be overridden in
3546 * subclasses.
3547 *
3548 * @param <S> the type of the second argument (the first being the
3549 * type itself) of this mapping; use Void if a second argument is
3550 * not needed.
3551 */
3552 public static class MapVisitor<S> extends DefaultTypeVisitor<Type,S> {
3553 final public Type visit(Type t) { return t.accept(this, null); }
3554 public Type visitType(Type t, S s) { return t; }
3555 }
3556 // </editor-fold>
3557 }