Mercurial > hg > icedtea9-forest > langtools
view src/share/classes/com/sun/tools/javac/comp/Infer.java @ 1283:6f0ed5a89c25
7154127: Inference cleanup: remove bound check analysis from visitors in Types.java
Summary: Remove bound checking rules from recursive subtype visitors in Types.java and replace with centralized bound-checking logic
Reviewed-by: jjg, dlsmith
author | mcimadamore |
---|---|
date | Wed, 11 Apr 2012 10:50:11 +0100 |
parents | 2827076dbf64 |
children | af6a4c24f4e3 |
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/* * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.tools.javac.comp; import com.sun.tools.javac.tree.JCTree; import com.sun.tools.javac.tree.JCTree.JCTypeCast; import com.sun.tools.javac.tree.TreeInfo; import com.sun.tools.javac.util.*; import com.sun.tools.javac.util.List; import com.sun.tools.javac.code.*; import com.sun.tools.javac.code.Type.*; import com.sun.tools.javac.code.Symbol.*; import com.sun.tools.javac.comp.Resolve.InapplicableMethodException; import com.sun.tools.javac.comp.Resolve.VerboseResolutionMode; import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition; import static com.sun.tools.javac.code.TypeTags.*; /** Helper class for type parameter inference, used by the attribution phase. * * <p><b>This is NOT part of any supported API. * If you write code that depends on this, you do so at your own risk. * This code and its internal interfaces are subject to change or * deletion without notice.</b> */ public class Infer { protected static final Context.Key<Infer> inferKey = new Context.Key<Infer>(); /** A value for prototypes that admit any type, including polymorphic ones. */ public static final Type anyPoly = new Type(NONE, null); Symtab syms; Types types; Check chk; Resolve rs; Log log; JCDiagnostic.Factory diags; public static Infer instance(Context context) { Infer instance = context.get(inferKey); if (instance == null) instance = new Infer(context); return instance; } protected Infer(Context context) { context.put(inferKey, this); syms = Symtab.instance(context); types = Types.instance(context); rs = Resolve.instance(context); log = Log.instance(context); chk = Check.instance(context); diags = JCDiagnostic.Factory.instance(context); ambiguousNoInstanceException = new NoInstanceException(true, diags); unambiguousNoInstanceException = new NoInstanceException(false, diags); invalidInstanceException = new InvalidInstanceException(diags); } public static class InferenceException extends InapplicableMethodException { private static final long serialVersionUID = 0; InferenceException(JCDiagnostic.Factory diags) { super(diags); } } public static class NoInstanceException extends InferenceException { private static final long serialVersionUID = 1; boolean isAmbiguous; // exist several incomparable best instances? NoInstanceException(boolean isAmbiguous, JCDiagnostic.Factory diags) { super(diags); this.isAmbiguous = isAmbiguous; } } public static class InvalidInstanceException extends InferenceException { private static final long serialVersionUID = 2; InvalidInstanceException(JCDiagnostic.Factory diags) { super(diags); } } private final NoInstanceException ambiguousNoInstanceException; private final NoInstanceException unambiguousNoInstanceException; private final InvalidInstanceException invalidInstanceException; /*************************************************************************** * Auxiliary type values and classes ***************************************************************************/ /** A mapping that turns type variables into undetermined type variables. */ List<Type> makeUndetvars(List<Type> tvars) { List<Type> undetvars = Type.map(tvars, fromTypeVarFun); for (Type t : undetvars) { UndetVar uv = (UndetVar)t; uv.hibounds = types.getBounds((TypeVar)uv.qtype); } return undetvars; } //where Mapping fromTypeVarFun = new Mapping("fromTypeVarFun") { public Type apply(Type t) { if (t.tag == TYPEVAR) return new UndetVar(t); else return t.map(this); } }; /*************************************************************************** * Mini/Maximization of UndetVars ***************************************************************************/ /** Instantiate undetermined type variable to its minimal upper bound. * Throw a NoInstanceException if this not possible. */ void maximizeInst(UndetVar that, Warner warn) throws NoInstanceException { List<Type> hibounds = Type.filter(that.hibounds, errorFilter); if (that.eq.isEmpty()) { if (hibounds.isEmpty()) that.inst = syms.objectType; else if (hibounds.tail.isEmpty()) that.inst = hibounds.head; else that.inst = types.glb(hibounds); } else { that.inst = that.eq.head; } if (that.inst == null || that.inst.isErroneous()) throw ambiguousNoInstanceException .setMessage("no.unique.maximal.instance.exists", that.qtype, hibounds); } private Filter<Type> errorFilter = new Filter<Type>() { @Override public boolean accepts(Type t) { return !t.isErroneous(); } }; /** Instantiate undetermined type variable to the lub of all its lower bounds. * Throw a NoInstanceException if this not possible. */ void minimizeInst(UndetVar that, Warner warn) throws NoInstanceException { List<Type> lobounds = Type.filter(that.lobounds, errorFilter); if (that.eq.isEmpty()) { if (lobounds.isEmpty()) that.inst = syms.botType; else if (lobounds.tail.isEmpty()) that.inst = lobounds.head.isPrimitive() ? syms.errType : lobounds.head; else { that.inst = types.lub(lobounds); } if (that.inst == null || that.inst.tag == ERROR) throw ambiguousNoInstanceException .setMessage("no.unique.minimal.instance.exists", that.qtype, lobounds); } else { that.inst = that.eq.head; } } Type asUndetType(Type t, List<Type> undetvars) { return types.subst(t, inferenceVars(undetvars), undetvars); } List<Type> inferenceVars(List<Type> undetvars) { ListBuffer<Type> tvars = ListBuffer.lb(); for (Type uv : undetvars) { tvars.append(((UndetVar)uv).qtype); } return tvars.toList(); } /*************************************************************************** * Exported Methods ***************************************************************************/ /** Try to instantiate expression type `that' to given type `to'. * If a maximal instantiation exists which makes this type * a subtype of type `to', return the instantiated type. * If no instantiation exists, or if several incomparable * best instantiations exist throw a NoInstanceException. */ public Type instantiateExpr(ForAll that, Type to, Warner warn) throws InferenceException { List<Type> undetvars = that.undetvars(); Type qtype1 = types.subst(that.qtype, that.tvars, undetvars); if (!types.isSubtype(qtype1, qtype1.tag == UNDETVAR ? types.boxedTypeOrType(to) : to)) { throw unambiguousNoInstanceException .setMessage("infer.no.conforming.instance.exists", that.tvars, that.qtype, to); } List<Type> insttypes; while (true) { boolean stuck = true; insttypes = List.nil(); for (Type t : undetvars) { UndetVar uv = (UndetVar)t; if (uv.inst == null && (uv.eq.nonEmpty() || !Type.containsAny(uv.hibounds, that.tvars))) { maximizeInst((UndetVar)t, warn); stuck = false; } insttypes = insttypes.append(uv.inst == null ? uv.qtype : uv.inst); } if (!Type.containsAny(insttypes, that.tvars)) { //all variables have been instantiated - exit break; } else if (stuck) { //some variables could not be instantiated because of cycles in //upper bounds - provide a (possibly recursive) default instantiation insttypes = types.subst(insttypes, that.tvars, instantiateAsUninferredVars(undetvars, that.tvars)); break; } else { //some variables have been instantiated - replace newly instantiated //variables in remaining upper bounds and continue for (Type t : undetvars) { UndetVar uv = (UndetVar)t; uv.hibounds = types.subst(uv.hibounds, that.tvars, insttypes); } } } return that.inst(insttypes, types); } /** * Infer cyclic inference variables as described in 15.12.2.8. */ private List<Type> instantiateAsUninferredVars(List<Type> undetvars, List<Type> tvars) { Assert.check(undetvars.length() == tvars.length()); ListBuffer<Type> insttypes = ListBuffer.lb(); ListBuffer<Type> todo = ListBuffer.lb(); //step 1 - create fresh tvars for (Type t : undetvars) { UndetVar uv = (UndetVar)t; if (uv.inst == null) { TypeSymbol fresh_tvar = new TypeSymbol(Flags.SYNTHETIC, uv.qtype.tsym.name, null, uv.qtype.tsym.owner); fresh_tvar.type = new TypeVar(fresh_tvar, types.makeCompoundType(uv.hibounds), null); todo.append(uv); uv.inst = fresh_tvar.type; } insttypes.append(uv.inst); } //step 2 - replace fresh tvars in their bounds List<Type> formals = tvars; for (Type t : todo) { UndetVar uv = (UndetVar)t; TypeVar ct = (TypeVar)uv.inst; ct.bound = types.glb(types.subst(types.getBounds(ct), tvars, insttypes.toList())); if (ct.bound.isErroneous()) { //report inference error if glb fails reportBoundError(uv, BoundErrorKind.BAD_UPPER); } formals = formals.tail; } return insttypes.toList(); } /** Instantiate method type `mt' by finding instantiations of * `tvars' so that method can be applied to `argtypes'. */ public Type instantiateMethod(final Env<AttrContext> env, List<Type> tvars, MethodType mt, final Symbol msym, final List<Type> argtypes, final boolean allowBoxing, final boolean useVarargs, final Warner warn) throws InferenceException { //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG final List<Type> undetvars = makeUndetvars(tvars); final List<Type> capturedArgs = rs.checkRawArgumentsAcceptable(env, undetvars, argtypes, mt.getParameterTypes(), allowBoxing, useVarargs, warn, new InferenceCheckHandler(undetvars)); // minimize as yet undetermined type variables for (Type t : undetvars) minimizeInst((UndetVar) t, warn); /** Type variables instantiated to bottom */ ListBuffer<Type> restvars = new ListBuffer<Type>(); /** Undet vars instantiated to bottom */ final ListBuffer<Type> restundet = new ListBuffer<Type>(); /** Instantiated types or TypeVars if under-constrained */ ListBuffer<Type> insttypes = new ListBuffer<Type>(); /** Instantiated types or UndetVars if under-constrained */ ListBuffer<Type> undettypes = new ListBuffer<Type>(); for (Type t : undetvars) { UndetVar uv = (UndetVar)t; if (uv.inst.tag == BOT) { restvars.append(uv.qtype); restundet.append(uv); insttypes.append(uv.qtype); undettypes.append(uv); uv.inst = null; } else { insttypes.append(uv.inst); undettypes.append(uv.inst); } } checkWithinBounds(tvars, undetvars, insttypes.toList(), warn); mt = (MethodType)types.subst(mt, tvars, insttypes.toList()); if (!restvars.isEmpty()) { // if there are uninstantiated variables, // quantify result type with them final List<Type> inferredTypes = insttypes.toList(); final List<Type> all_tvars = tvars; //this is the wrong tvars return new UninferredMethodType(env.tree.pos(), msym, mt, restvars.toList()) { @Override List<Type> undetvars() { return restundet.toList(); } @Override void instantiateReturnType(Type restype, List<Type> inferred, Types types) throws NoInstanceException { Type owntype = new MethodType(types.subst(getParameterTypes(), tvars, inferred), restype, types.subst(getThrownTypes(), tvars, inferred), qtype.tsym); // check that actuals conform to inferred formals warn.clear(); checkArgumentsAcceptable(env, capturedArgs, owntype.getParameterTypes(), allowBoxing, useVarargs, warn); // check that inferred bounds conform to their bounds checkWithinBounds(all_tvars, undetvars, types.subst(inferredTypes, tvars, inferred), warn); qtype = chk.checkMethod(owntype, msym, env, TreeInfo.args(env.tree), capturedArgs, useVarargs, warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)); } }; } else { // check that actuals conform to inferred formals checkArgumentsAcceptable(env, capturedArgs, mt.getParameterTypes(), allowBoxing, useVarargs, warn); // return instantiated version of method type return mt; } } //where /** inference check handler **/ class InferenceCheckHandler implements Resolve.MethodCheckHandler { List<Type> undetvars; public InferenceCheckHandler(List<Type> undetvars) { this.undetvars = undetvars; } public InapplicableMethodException arityMismatch() { return unambiguousNoInstanceException.setMessage("infer.arg.length.mismatch"); } public InapplicableMethodException argumentMismatch(boolean varargs, Type found, Type expected) { String key = varargs ? "infer.varargs.argument.mismatch" : "infer.no.conforming.assignment.exists"; return unambiguousNoInstanceException.setMessage(key, inferenceVars(undetvars), found, expected); } public InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected) { return unambiguousNoInstanceException.setMessage("inaccessible.varargs.type", expected, Kinds.kindName(location), location); } } /** * A delegated type representing a partially uninferred method type. * The return type of a partially uninferred method type is a ForAll * type - when the return type is instantiated (see Infer.instantiateExpr) * the underlying method type is also updated. */ abstract class UninferredMethodType extends DelegatedType { final List<Type> tvars; final Symbol msym; final DiagnosticPosition pos; public UninferredMethodType(DiagnosticPosition pos, Symbol msym, MethodType mtype, List<Type> tvars) { super(METHOD, new MethodType(mtype.argtypes, null, mtype.thrown, mtype.tsym)); this.tvars = tvars; this.msym = msym; this.pos = pos; asMethodType().restype = new UninferredReturnType(tvars, mtype.restype); } @Override public MethodType asMethodType() { return qtype.asMethodType(); } @Override public Type map(Mapping f) { return qtype.map(f); } abstract void instantiateReturnType(Type restype, List<Type> inferred, Types types); abstract List<Type> undetvars(); class UninferredReturnType extends ForAll { public UninferredReturnType(List<Type> tvars, Type restype) { super(tvars, restype); } @Override public Type inst(List<Type> actuals, Types types) { Type newRestype = super.inst(actuals, types); instantiateReturnType(newRestype, actuals, types); if (rs.verboseResolutionMode.contains(VerboseResolutionMode.DEFERRED_INST)) { log.note(pos, "deferred.method.inst", msym, UninferredMethodType.this.qtype, newRestype); } return UninferredMethodType.this.qtype.getReturnType(); } @Override public List<Type> undetvars() { return UninferredMethodType.this.undetvars(); } } } private void checkArgumentsAcceptable(Env<AttrContext> env, List<Type> actuals, List<Type> formals, boolean allowBoxing, boolean useVarargs, Warner warn) { try { rs.checkRawArgumentsAcceptable(env, actuals, formals, allowBoxing, useVarargs, warn); } catch (InapplicableMethodException ex) { // inferred method is not applicable throw invalidInstanceException.setMessage(ex.getDiagnostic()); } } /** check that type parameters are within their bounds. */ void checkWithinBounds(List<Type> tvars, List<Type> undetvars, List<Type> arguments, Warner warn) throws InvalidInstanceException { List<Type> args = arguments; for (Type t : undetvars) { UndetVar uv = (UndetVar)t; uv.hibounds = types.subst(uv.hibounds, tvars, arguments); uv.lobounds = types.subst(uv.lobounds, tvars, arguments); uv.eq = types.subst(uv.eq, tvars, arguments); checkCompatibleUpperBounds(uv, tvars); if (args.head.tag != TYPEVAR || !args.head.containsAny(tvars)) { Type inst = args.head; for (Type u : uv.hibounds) { if (!types.isSubtypeUnchecked(inst, types.subst(u, tvars, undetvars), warn)) { reportBoundError(uv, BoundErrorKind.UPPER); } } for (Type l : uv.lobounds) { if (!types.isSubtypeUnchecked(types.subst(l, tvars, undetvars), inst, warn)) { reportBoundError(uv, BoundErrorKind.LOWER); } } for (Type e : uv.eq) { if (!types.isSameType(inst, types.subst(e, tvars, undetvars))) { reportBoundError(uv, BoundErrorKind.EQ); } } } args = args.tail; } } void checkCompatibleUpperBounds(UndetVar uv, List<Type> tvars) { // VGJ: sort of inlined maximizeInst() below. Adding // bounds can cause lobounds that are above hibounds. ListBuffer<Type> hiboundsNoVars = ListBuffer.lb(); for (Type t : Type.filter(uv.hibounds, errorFilter)) { if (!t.containsAny(tvars)) { hiboundsNoVars.append(t); } } List<Type> hibounds = hiboundsNoVars.toList(); Type hb = null; if (hibounds.isEmpty()) hb = syms.objectType; else if (hibounds.tail.isEmpty()) hb = hibounds.head; else hb = types.glb(hibounds); if (hb == null || hb.isErroneous()) reportBoundError(uv, BoundErrorKind.BAD_UPPER); } enum BoundErrorKind { BAD_UPPER() { @Override InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) { return ex.setMessage("incompatible.upper.bounds", uv.qtype, uv.hibounds); } }, UPPER() { @Override InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) { return ex.setMessage("inferred.do.not.conform.to.upper.bounds", uv.inst, uv.hibounds); } }, LOWER() { @Override InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) { return ex.setMessage("inferred.do.not.conform.to.lower.bounds", uv.inst, uv.lobounds); } }, EQ() { @Override InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) { return ex.setMessage("inferred.do.not.conform.to.eq.bounds", uv.inst, uv.eq); } }; abstract InapplicableMethodException setMessage(InferenceException ex, UndetVar uv); } //where void reportBoundError(UndetVar uv, BoundErrorKind bk) { throw bk.setMessage(uv.inst == null ? ambiguousNoInstanceException : invalidInstanceException, uv); } /** * Compute a synthetic method type corresponding to the requested polymorphic * method signature. The target return type is computed from the immediately * enclosing scope surrounding the polymorphic-signature call. */ Type instantiatePolymorphicSignatureInstance(Env<AttrContext> env, MethodSymbol spMethod, // sig. poly. method or null if none List<Type> argtypes) { final Type restype; //The return type for a polymorphic signature call is computed from //the enclosing tree E, as follows: if E is a cast, then use the //target type of the cast expression as a return type; if E is an //expression statement, the return type is 'void' - otherwise the //return type is simply 'Object'. A correctness check ensures that //env.next refers to the lexically enclosing environment in which //the polymorphic signature call environment is nested. switch (env.next.tree.getTag()) { case TYPECAST: JCTypeCast castTree = (JCTypeCast)env.next.tree; restype = (TreeInfo.skipParens(castTree.expr) == env.tree) ? castTree.clazz.type : syms.objectType; break; case EXEC: JCTree.JCExpressionStatement execTree = (JCTree.JCExpressionStatement)env.next.tree; restype = (TreeInfo.skipParens(execTree.expr) == env.tree) ? syms.voidType : syms.objectType; break; default: restype = syms.objectType; } List<Type> paramtypes = Type.map(argtypes, implicitArgType); List<Type> exType = spMethod != null ? spMethod.getThrownTypes() : List.of(syms.throwableType); // make it throw all exceptions MethodType mtype = new MethodType(paramtypes, restype, exType, syms.methodClass); return mtype; } //where Mapping implicitArgType = new Mapping ("implicitArgType") { public Type apply(Type t) { t = types.erasure(t); if (t.tag == BOT) // nulls type as the marker type Null (which has no instances) // infer as java.lang.Void for now t = types.boxedClass(syms.voidType).type; return t; } }; }