| 1 | /* |
| 2 | * Copyright 1999-2006 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package com.sun.tools.javac.comp; |
| 27 | |
| 28 | import com.sun.tools.javac.util.*; |
| 29 | import com.sun.tools.javac.util.List; |
| 30 | import com.sun.tools.javac.code.*; |
| 31 | import com.sun.tools.javac.code.Type.*; |
| 32 | |
| 33 | import static com.sun.tools.javac.code.Flags.*; |
| 34 | import static com.sun.tools.javac.code.Kinds.*; |
| 35 | import static com.sun.tools.javac.code.TypeTags.*; |
| 36 | |
| 37 | /** Helper class for type parameter inference, used by the attribution phase. |
| 38 | * |
| 39 | * <p><b>This is NOT part of any API supported by Sun Microsystems. If |
| 40 | * you write code that depends on this, you do so at your own risk. |
| 41 | * This code and its internal interfaces are subject to change or |
| 42 | * deletion without notice.</b> |
| 43 | */ |
| 44 | public class Infer { |
| 45 | protected static final Context.Key<Infer> inferKey = |
| 46 | new Context.Key<Infer>(); |
| 47 | |
| 48 | /** A value for prototypes that admit any type, including polymorphic ones. */ |
| 49 | public static final Type anyPoly = new Type(NONE, null); |
| 50 | |
| 51 | Symtab syms; |
| 52 | Types types; |
| 53 | |
| 54 | public static Infer instance(Context context) { |
| 55 | Infer instance = context.get(inferKey); |
| 56 | if (instance == null) |
| 57 | instance = new Infer(context); |
| 58 | return instance; |
| 59 | } |
| 60 | |
| 61 | protected Infer(Context context) { |
| 62 | context.put(inferKey, this); |
| 63 | syms = Symtab.instance(context); |
| 64 | types = Types.instance(context); |
| 65 | } |
| 66 | |
| 67 | public static class NoInstanceException extends RuntimeException { |
| 68 | private static final long serialVersionUID = 0; |
| 69 | |
| 70 | boolean isAmbiguous; // exist several incomparable best instances? |
| 71 | |
| 72 | JCDiagnostic diagnostic; |
| 73 | |
| 74 | NoInstanceException(boolean isAmbiguous) { |
| 75 | this.diagnostic = null; |
| 76 | this.isAmbiguous = isAmbiguous; |
| 77 | } |
| 78 | NoInstanceException setMessage(String key) { |
| 79 | this.diagnostic = JCDiagnostic.fragment(key); |
| 80 | return this; |
| 81 | } |
| 82 | NoInstanceException setMessage(String key, Object arg1) { |
| 83 | this.diagnostic = JCDiagnostic.fragment(key, arg1); |
| 84 | return this; |
| 85 | } |
| 86 | NoInstanceException setMessage(String key, Object arg1, Object arg2) { |
| 87 | this.diagnostic = JCDiagnostic.fragment(key, arg1, arg2); |
| 88 | return this; |
| 89 | } |
| 90 | NoInstanceException setMessage(String key, Object arg1, Object arg2, Object arg3) { |
| 91 | this.diagnostic = JCDiagnostic.fragment(key, arg1, arg2, arg3); |
| 92 | return this; |
| 93 | } |
| 94 | public JCDiagnostic getDiagnostic() { |
| 95 | return diagnostic; |
| 96 | } |
| 97 | } |
| 98 | private final NoInstanceException ambiguousNoInstanceException = |
| 99 | new NoInstanceException(true); |
| 100 | private final NoInstanceException unambiguousNoInstanceException = |
| 101 | new NoInstanceException(false); |
| 102 | |
| 103 | /*************************************************************************** |
| 104 | * Auxiliary type values and classes |
| 105 | ***************************************************************************/ |
| 106 | |
| 107 | /** A mapping that turns type variables into undetermined type variables. |
| 108 | */ |
| 109 | Mapping fromTypeVarFun = new Mapping("fromTypeVarFun") { |
| 110 | public Type apply(Type t) { |
| 111 | if (t.tag == TYPEVAR) return new UndetVar(t); |
| 112 | else return t.map(this); |
| 113 | } |
| 114 | }; |
| 115 | |
| 116 | /** A mapping that returns its type argument with every UndetVar replaced |
| 117 | * by its `inst' field. Throws a NoInstanceException |
| 118 | * if this not possible because an `inst' field is null. |
| 119 | */ |
| 120 | Mapping getInstFun = new Mapping("getInstFun") { |
| 121 | public Type apply(Type t) { |
| 122 | switch (t.tag) { |
| 123 | case UNKNOWN: |
| 124 | throw ambiguousNoInstanceException |
| 125 | .setMessage("undetermined.type"); |
| 126 | case UNDETVAR: |
| 127 | UndetVar that = (UndetVar) t; |
| 128 | if (that.inst == null) |
| 129 | throw ambiguousNoInstanceException |
| 130 | .setMessage("type.variable.has.undetermined.type", |
| 131 | that.qtype); |
| 132 | return apply(that.inst); |
| 133 | default: |
| 134 | return t.map(this); |
| 135 | } |
| 136 | } |
| 137 | }; |
| 138 | |
| 139 | /*************************************************************************** |
| 140 | * Mini/Maximization of UndetVars |
| 141 | ***************************************************************************/ |
| 142 | |
| 143 | /** Instantiate undetermined type variable to its minimal upper bound. |
| 144 | * Throw a NoInstanceException if this not possible. |
| 145 | */ |
| 146 | void maximizeInst(UndetVar that, Warner warn) throws NoInstanceException { |
| 147 | if (that.inst == null) { |
| 148 | if (that.hibounds.isEmpty()) |
| 149 | that.inst = syms.objectType; |
| 150 | else if (that.hibounds.tail.isEmpty()) |
| 151 | that.inst = that.hibounds.head; |
| 152 | else { |
| 153 | for (List<Type> bs = that.hibounds; |
| 154 | bs.nonEmpty() && that.inst == null; |
| 155 | bs = bs.tail) { |
| 156 | // System.out.println("hibounds = " + that.hibounds);//DEBUG |
| 157 | if (isSubClass(bs.head, that.hibounds)) |
| 158 | that.inst = types.fromUnknownFun.apply(bs.head); |
| 159 | } |
| 160 | if (that.inst == null || !types.isSubtypeUnchecked(that.inst, that.hibounds, warn)) |
| 161 | throw ambiguousNoInstanceException |
| 162 | .setMessage("no.unique.maximal.instance.exists", |
| 163 | that.qtype, that.hibounds); |
| 164 | } |
| 165 | } |
| 166 | } |
| 167 | //where |
| 168 | private boolean isSubClass(Type t, final List<Type> ts) { |
| 169 | t = t.baseType(); |
| 170 | if (t.tag == TYPEVAR) { |
| 171 | List<Type> bounds = types.getBounds((TypeVar)t); |
| 172 | for (Type s : ts) { |
| 173 | if (!types.isSameType(t, s.baseType())) { |
| 174 | for (Type bound : bounds) { |
| 175 | if (!isSubClass(bound, List.of(s.baseType()))) |
| 176 | return false; |
| 177 | } |
| 178 | } |
| 179 | } |
| 180 | } else { |
| 181 | for (Type s : ts) { |
| 182 | if (!t.tsym.isSubClass(s.baseType().tsym, types)) |
| 183 | return false; |
| 184 | } |
| 185 | } |
| 186 | return true; |
| 187 | } |
| 188 | |
| 189 | /** Instaniate undetermined type variable to the lub of all its lower bounds. |
| 190 | * Throw a NoInstanceException if this not possible. |
| 191 | */ |
| 192 | void minimizeInst(UndetVar that, Warner warn) throws NoInstanceException { |
| 193 | if (that.inst == null) { |
| 194 | if (that.lobounds.isEmpty()) |
| 195 | that.inst = syms.botType; |
| 196 | else if (that.lobounds.tail.isEmpty()) |
| 197 | that.inst = that.lobounds.head; |
| 198 | else { |
| 199 | that.inst = types.lub(that.lobounds); |
| 200 | if (that.inst == null) |
| 201 | throw ambiguousNoInstanceException |
| 202 | .setMessage("no.unique.minimal.instance.exists", |
| 203 | that.qtype, that.lobounds); |
| 204 | } |
| 205 | // VGJ: sort of inlined maximizeInst() below. Adding |
| 206 | // bounds can cause lobounds that are above hibounds. |
| 207 | if (that.hibounds.isEmpty()) |
| 208 | return; |
| 209 | Type hb = null; |
| 210 | if (that.hibounds.tail.isEmpty()) |
| 211 | hb = that.hibounds.head; |
| 212 | else for (List<Type> bs = that.hibounds; |
| 213 | bs.nonEmpty() && hb == null; |
| 214 | bs = bs.tail) { |
| 215 | if (isSubClass(bs.head, that.hibounds)) |
| 216 | hb = types.fromUnknownFun.apply(bs.head); |
| 217 | } |
| 218 | if (hb == null || |
| 219 | !types.isSubtypeUnchecked(hb, that.hibounds, warn) || |
| 220 | !types.isSubtypeUnchecked(that.inst, hb, warn)) |
| 221 | throw ambiguousNoInstanceException; |
| 222 | } |
| 223 | } |
| 224 | |
| 225 | /*************************************************************************** |
| 226 | * Exported Methods |
| 227 | ***************************************************************************/ |
| 228 | |
| 229 | /** Try to instantiate expression type `that' to given type `to'. |
| 230 | * If a maximal instantiation exists which makes this type |
| 231 | * a subtype of type `to', return the instantiated type. |
| 232 | * If no instantiation exists, or if several incomparable |
| 233 | * best instantiations exist throw a NoInstanceException. |
| 234 | */ |
| 235 | public Type instantiateExpr(ForAll that, |
| 236 | Type to, |
| 237 | Warner warn) throws NoInstanceException { |
| 238 | List<Type> undetvars = Type.map(that.tvars, fromTypeVarFun); |
| 239 | for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail) { |
| 240 | UndetVar v = (UndetVar) l.head; |
| 241 | ListBuffer<Type> hibounds = new ListBuffer<Type>(); |
| 242 | for (List<Type> l1 = types.getBounds((TypeVar) v.qtype); l1.nonEmpty(); l1 = l1.tail) { |
| 243 | if (!l1.head.containsSome(that.tvars)) { |
| 244 | hibounds.append(l1.head); |
| 245 | } |
| 246 | } |
| 247 | v.hibounds = hibounds.toList(); |
| 248 | } |
| 249 | Type qtype1 = types.subst(that.qtype, that.tvars, undetvars); |
| 250 | if (!types.isSubtype(qtype1, to)) { |
| 251 | throw unambiguousNoInstanceException |
| 252 | .setMessage("no.conforming.instance.exists", |
| 253 | that.tvars, that.qtype, to); |
| 254 | } |
| 255 | for (List<Type> l = undetvars; l.nonEmpty(); l = l.tail) |
| 256 | maximizeInst((UndetVar) l.head, warn); |
| 257 | // System.out.println(" = " + qtype1.map(getInstFun));//DEBUG |
| 258 | |
| 259 | // check bounds |
| 260 | List<Type> targs = Type.map(undetvars, getInstFun); |
| 261 | targs = types.subst(targs, that.tvars, targs); |
| 262 | checkWithinBounds(that.tvars, targs, warn); |
| 263 | |
| 264 | return getInstFun.apply(qtype1); |
| 265 | } |
| 266 | |
| 267 | /** Instantiate method type `mt' by finding instantiations of |
| 268 | * `tvars' so that method can be applied to `argtypes'. |
| 269 | */ |
| 270 | public Type instantiateMethod(List<Type> tvars, |
| 271 | MethodType mt, |
| 272 | List<Type> argtypes, |
| 273 | boolean allowBoxing, |
| 274 | boolean useVarargs, |
| 275 | Warner warn) throws NoInstanceException { |
| 276 | //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG |
| 277 | List<Type> undetvars = Type.map(tvars, fromTypeVarFun); |
| 278 | List<Type> formals = mt.argtypes; |
| 279 | |
| 280 | // instantiate all polymorphic argument types and |
| 281 | // set up lower bounds constraints for undetvars |
| 282 | Type varargsFormal = useVarargs ? formals.last() : null; |
| 283 | while (argtypes.nonEmpty() && formals.head != varargsFormal) { |
| 284 | Type ft = formals.head; |
| 285 | Type at = argtypes.head.baseType(); |
| 286 | if (at.tag == FORALL) |
| 287 | at = instantiateArg((ForAll) at, ft, tvars, warn); |
| 288 | Type sft = types.subst(ft, tvars, undetvars); |
| 289 | boolean works = allowBoxing |
| 290 | ? types.isConvertible(at, sft, warn) |
| 291 | : types.isSubtypeUnchecked(at, sft, warn); |
| 292 | if (!works) { |
| 293 | throw unambiguousNoInstanceException |
| 294 | .setMessage("no.conforming.assignment.exists", |
| 295 | tvars, at, ft); |
| 296 | } |
| 297 | formals = formals.tail; |
| 298 | argtypes = argtypes.tail; |
| 299 | } |
| 300 | if (formals.head != varargsFormal || // not enough args |
| 301 | !useVarargs && argtypes.nonEmpty()) { // too many args |
| 302 | // argument lists differ in length |
| 303 | throw unambiguousNoInstanceException |
| 304 | .setMessage("arg.length.mismatch"); |
| 305 | } |
| 306 | |
| 307 | // for varargs arguments as well |
| 308 | if (useVarargs) { |
| 309 | Type elt = types.elemtype(varargsFormal); |
| 310 | Type sft = types.subst(elt, tvars, undetvars); |
| 311 | while (argtypes.nonEmpty()) { |
| 312 | Type ft = sft; |
| 313 | Type at = argtypes.head.baseType(); |
| 314 | if (at.tag == FORALL) |
| 315 | at = instantiateArg((ForAll) at, ft, tvars, warn); |
| 316 | boolean works = types.isConvertible(at, sft, warn); |
| 317 | if (!works) { |
| 318 | throw unambiguousNoInstanceException |
| 319 | .setMessage("no.conforming.assignment.exists", |
| 320 | tvars, at, ft); |
| 321 | } |
| 322 | argtypes = argtypes.tail; |
| 323 | } |
| 324 | } |
| 325 | |
| 326 | // minimize as yet undetermined type variables |
| 327 | for (Type t : undetvars) |
| 328 | minimizeInst((UndetVar) t, warn); |
| 329 | |
| 330 | /** Type variables instantiated to bottom */ |
| 331 | ListBuffer<Type> restvars = new ListBuffer<Type>(); |
| 332 | |
| 333 | /** Instantiated types or TypeVars if under-constrained */ |
| 334 | ListBuffer<Type> insttypes = new ListBuffer<Type>(); |
| 335 | |
| 336 | /** Instantiated types or UndetVars if under-constrained */ |
| 337 | ListBuffer<Type> undettypes = new ListBuffer<Type>(); |
| 338 | |
| 339 | for (Type t : undetvars) { |
| 340 | UndetVar uv = (UndetVar)t; |
| 341 | if (uv.inst.tag == BOT) { |
| 342 | restvars.append(uv.qtype); |
| 343 | insttypes.append(uv.qtype); |
| 344 | undettypes.append(uv); |
| 345 | uv.inst = null; |
| 346 | } else { |
| 347 | insttypes.append(uv.inst); |
| 348 | undettypes.append(uv.inst); |
| 349 | } |
| 350 | } |
| 351 | checkWithinBounds(tvars, undettypes.toList(), warn); |
| 352 | |
| 353 | if (!restvars.isEmpty()) { |
| 354 | // if there are uninstantiated variables, |
| 355 | // quantify result type with them |
| 356 | mt = new MethodType(mt.argtypes, |
| 357 | new ForAll(restvars.toList(), mt.restype), |
| 358 | mt.thrown, syms.methodClass); |
| 359 | } |
| 360 | |
| 361 | // return instantiated version of method type |
| 362 | return types.subst(mt, tvars, insttypes.toList()); |
| 363 | } |
| 364 | //where |
| 365 | |
| 366 | /** Try to instantiate argument type `that' to given type `to'. |
| 367 | * If this fails, try to insantiate `that' to `to' where |
| 368 | * every occurrence of a type variable in `tvars' is replaced |
| 369 | * by an unknown type. |
| 370 | */ |
| 371 | private Type instantiateArg(ForAll that, |
| 372 | Type to, |
| 373 | List<Type> tvars, |
| 374 | Warner warn) throws NoInstanceException { |
| 375 | List<Type> targs; |
| 376 | try { |
| 377 | return instantiateExpr(that, to, warn); |
| 378 | } catch (NoInstanceException ex) { |
| 379 | Type to1 = to; |
| 380 | for (List<Type> l = tvars; l.nonEmpty(); l = l.tail) |
| 381 | to1 = types.subst(to1, List.of(l.head), List.of(syms.unknownType)); |
| 382 | return instantiateExpr(that, to1, warn); |
| 383 | } |
| 384 | } |
| 385 | |
| 386 | /** check that type parameters are within their bounds. |
| 387 | */ |
| 388 | private void checkWithinBounds(List<Type> tvars, |
| 389 | List<Type> arguments, |
| 390 | Warner warn) |
| 391 | throws NoInstanceException { |
| 392 | for (List<Type> tvs = tvars, args = arguments; |
| 393 | tvs.nonEmpty(); |
| 394 | tvs = tvs.tail, args = args.tail) { |
| 395 | if (args.head instanceof UndetVar) continue; |
| 396 | List<Type> bounds = types.subst(types.getBounds((TypeVar)tvs.head), tvars, arguments); |
| 397 | if (!types.isSubtypeUnchecked(args.head, bounds, warn)) |
| 398 | throw unambiguousNoInstanceException |
| 399 | .setMessage("inferred.do.not.conform.to.bounds", |
| 400 | arguments, tvars); |
| 401 | } |
| 402 | } |
| 403 | } |