aoqi@0: /*
aoqi@0:  * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.  Oracle designates this
aoqi@0:  * particular file as subject to the "Classpath" exception as provided
aoqi@0:  * by Oracle in the LICENSE file that accompanied this code.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  */
aoqi@0: 
aoqi@0: package com.sun.tools.javac.comp;
aoqi@0: 
aoqi@0: import com.sun.tools.javac.tree.JCTree;
aoqi@0: import com.sun.tools.javac.tree.JCTree.JCTypeCast;
aoqi@0: import com.sun.tools.javac.tree.TreeInfo;
aoqi@0: import com.sun.tools.javac.util.*;
aoqi@0: import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
aoqi@0: import com.sun.tools.javac.util.List;
aoqi@0: import com.sun.tools.javac.code.*;
aoqi@0: import com.sun.tools.javac.code.Type.*;
aoqi@0: import com.sun.tools.javac.code.Type.UndetVar.InferenceBound;
aoqi@0: import com.sun.tools.javac.code.Symbol.*;
aoqi@0: import com.sun.tools.javac.comp.DeferredAttr.AttrMode;
aoqi@0: import com.sun.tools.javac.comp.Infer.GraphSolver.InferenceGraph;
aoqi@0: import com.sun.tools.javac.comp.Infer.GraphSolver.InferenceGraph.Node;
aoqi@0: import com.sun.tools.javac.comp.Resolve.InapplicableMethodException;
aoqi@0: import com.sun.tools.javac.comp.Resolve.VerboseResolutionMode;
aoqi@0: import com.sun.tools.javac.util.GraphUtils.TarjanNode;
aoqi@0: 
aoqi@0: import java.util.ArrayList;
aoqi@0: import java.util.Collections;
aoqi@0: import java.util.EnumMap;
aoqi@0: import java.util.EnumSet;
aoqi@0: import java.util.HashMap;
aoqi@0: import java.util.HashSet;
aoqi@0: import java.util.LinkedHashSet;
aoqi@0: import java.util.Map;
aoqi@0: import java.util.Set;
aoqi@0: 
aoqi@0: import static com.sun.tools.javac.code.TypeTag.*;
aoqi@0: 
aoqi@0: /** Helper class for type parameter inference, used by the attribution phase.
aoqi@0:  *
aoqi@0:  *  <p><b>This is NOT part of any supported API.
aoqi@0:  *  If you write code that depends on this, you do so at your own risk.
aoqi@0:  *  This code and its internal interfaces are subject to change or
aoqi@0:  *  deletion without notice.</b>
aoqi@0:  */
aoqi@0: public class Infer {
aoqi@0:     protected static final Context.Key<Infer> inferKey =
aoqi@0:         new Context.Key<Infer>();
aoqi@0: 
aoqi@0:     Resolve rs;
aoqi@0:     Check chk;
aoqi@0:     Symtab syms;
aoqi@0:     Types types;
aoqi@0:     JCDiagnostic.Factory diags;
aoqi@0:     Log log;
aoqi@0: 
aoqi@0:     /** should the graph solver be used? */
aoqi@0:     boolean allowGraphInference;
aoqi@0: 
aoqi@0:     public static Infer instance(Context context) {
aoqi@0:         Infer instance = context.get(inferKey);
aoqi@0:         if (instance == null)
aoqi@0:             instance = new Infer(context);
aoqi@0:         return instance;
aoqi@0:     }
aoqi@0: 
aoqi@0:     protected Infer(Context context) {
aoqi@0:         context.put(inferKey, this);
aoqi@0: 
aoqi@0:         rs = Resolve.instance(context);
aoqi@0:         chk = Check.instance(context);
aoqi@0:         syms = Symtab.instance(context);
aoqi@0:         types = Types.instance(context);
aoqi@0:         diags = JCDiagnostic.Factory.instance(context);
aoqi@0:         log = Log.instance(context);
aoqi@0:         inferenceException = new InferenceException(diags);
aoqi@0:         Options options = Options.instance(context);
aoqi@0:         allowGraphInference = Source.instance(context).allowGraphInference()
aoqi@0:                 && options.isUnset("useLegacyInference");
aoqi@0:     }
aoqi@0: 
aoqi@0:     /** A value for prototypes that admit any type, including polymorphic ones. */
aoqi@0:     public static final Type anyPoly = new JCNoType();
aoqi@0: 
aoqi@0:    /**
aoqi@0:     * This exception class is design to store a list of diagnostics corresponding
aoqi@0:     * to inference errors that can arise during a method applicability check.
aoqi@0:     */
aoqi@0:     public static class InferenceException extends InapplicableMethodException {
aoqi@0:         private static final long serialVersionUID = 0;
aoqi@0: 
aoqi@0:         List<JCDiagnostic> messages = List.nil();
aoqi@0: 
aoqi@0:         InferenceException(JCDiagnostic.Factory diags) {
aoqi@0:             super(diags);
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         InapplicableMethodException setMessage() {
aoqi@0:             //no message to set
aoqi@0:             return this;
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         InapplicableMethodException setMessage(JCDiagnostic diag) {
aoqi@0:             messages = messages.append(diag);
aoqi@0:             return this;
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         public JCDiagnostic getDiagnostic() {
aoqi@0:             return messages.head;
aoqi@0:         }
aoqi@0: 
aoqi@0:         void clear() {
aoqi@0:             messages = List.nil();
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     protected final InferenceException inferenceException;
aoqi@0: 
aoqi@0:     // <editor-fold defaultstate="collapsed" desc="Inference routines">
aoqi@0:     /**
aoqi@0:      * Main inference entry point - instantiate a generic method type
aoqi@0:      * using given argument types and (possibly) an expected target-type.
aoqi@0:      */
aoqi@0:     Type instantiateMethod( Env<AttrContext> env,
aoqi@0:                             List<Type> tvars,
aoqi@0:                             MethodType mt,
aoqi@0:                             Attr.ResultInfo resultInfo,
aoqi@0:                             MethodSymbol msym,
aoqi@0:                             List<Type> argtypes,
aoqi@0:                             boolean allowBoxing,
aoqi@0:                             boolean useVarargs,
aoqi@0:                             Resolve.MethodResolutionContext resolveContext,
aoqi@0:                             Warner warn) throws InferenceException {
aoqi@0:         //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
aoqi@0:         final InferenceContext inferenceContext = new InferenceContext(tvars);  //B0
aoqi@0:         inferenceException.clear();
aoqi@0:         try {
aoqi@0:             DeferredAttr.DeferredAttrContext deferredAttrContext =
aoqi@0:                         resolveContext.deferredAttrContext(msym, inferenceContext, resultInfo, warn);
aoqi@0: 
aoqi@0:             resolveContext.methodCheck.argumentsAcceptable(env, deferredAttrContext,   //B2
aoqi@0:                     argtypes, mt.getParameterTypes(), warn);
aoqi@0: 
aoqi@0:             if (allowGraphInference &&
aoqi@0:                     resultInfo != null &&
aoqi@0:                     !warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)) {
aoqi@0:                 //inject return constraints earlier
aoqi@0:                 checkWithinBounds(inferenceContext, warn); //propagation
aoqi@0:                 Type newRestype = generateReturnConstraints(env.tree, resultInfo,  //B3
aoqi@0:                         mt, inferenceContext);
aoqi@0:                 mt = (MethodType)types.createMethodTypeWithReturn(mt, newRestype);
aoqi@0:                 //propagate outwards if needed
aoqi@0:                 if (resultInfo.checkContext.inferenceContext().free(resultInfo.pt)) {
aoqi@0:                     //propagate inference context outwards and exit
aoqi@0:                     inferenceContext.dupTo(resultInfo.checkContext.inferenceContext());
aoqi@0:                     deferredAttrContext.complete();
aoqi@0:                     return mt;
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             deferredAttrContext.complete();
aoqi@0: 
aoqi@0:             // minimize as yet undetermined type variables
aoqi@0:             if (allowGraphInference) {
aoqi@0:                 inferenceContext.solve(warn);
aoqi@0:             } else {
aoqi@0:                 inferenceContext.solveLegacy(true, warn, LegacyInferenceSteps.EQ_LOWER.steps); //minimizeInst
aoqi@0:             }
aoqi@0: 
aoqi@0:             mt = (MethodType)inferenceContext.asInstType(mt);
aoqi@0: 
aoqi@0:             if (!allowGraphInference &&
aoqi@0:                     inferenceContext.restvars().nonEmpty() &&
aoqi@0:                     resultInfo != null &&
aoqi@0:                     !warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)) {
aoqi@0:                 generateReturnConstraints(env.tree, resultInfo, mt, inferenceContext);
aoqi@0:                 inferenceContext.solveLegacy(false, warn, LegacyInferenceSteps.EQ_UPPER.steps); //maximizeInst
aoqi@0:                 mt = (MethodType)inferenceContext.asInstType(mt);
aoqi@0:             }
aoqi@0: 
aoqi@0:             if (resultInfo != null && rs.verboseResolutionMode.contains(VerboseResolutionMode.DEFERRED_INST)) {
aoqi@0:                 log.note(env.tree.pos, "deferred.method.inst", msym, mt, resultInfo.pt);
aoqi@0:             }
aoqi@0: 
aoqi@0:             // return instantiated version of method type
aoqi@0:             return mt;
aoqi@0:         } finally {
aoqi@0:             if (resultInfo != null || !allowGraphInference) {
aoqi@0:                 inferenceContext.notifyChange();
aoqi@0:             } else {
aoqi@0:                 inferenceContext.notifyChange(inferenceContext.boundedVars());
aoqi@0:             }
aoqi@0:             if (resultInfo == null) {
aoqi@0:                 /* if the is no result info then we can clear the capture types
aoqi@0:                  * cache without affecting any result info check
aoqi@0:                  */
aoqi@0:                 inferenceContext.captureTypeCache.clear();
aoqi@0:             }
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Generate constraints from the generic method's return type. If the method
aoqi@0:      * call occurs in a context where a type T is expected, use the expected
aoqi@0:      * type to derive more constraints on the generic method inference variables.
aoqi@0:      */
aoqi@0:     Type generateReturnConstraints(JCTree tree, Attr.ResultInfo resultInfo,
aoqi@0:             MethodType mt, InferenceContext inferenceContext) {
aoqi@0:         InferenceContext rsInfoInfContext = resultInfo.checkContext.inferenceContext();
aoqi@0:         Type from = mt.getReturnType();
aoqi@0:         if (mt.getReturnType().containsAny(inferenceContext.inferencevars) &&
aoqi@0:                 rsInfoInfContext != emptyContext) {
aoqi@0:             from = types.capture(from);
aoqi@0:             //add synthetic captured ivars
aoqi@0:             for (Type t : from.getTypeArguments()) {
aoqi@0:                 if (t.hasTag(TYPEVAR) && ((TypeVar)t).isCaptured()) {
aoqi@0:                     inferenceContext.addVar((TypeVar)t);
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         }
aoqi@0:         Type qtype = inferenceContext.asUndetVar(from);
aoqi@0:         Type to = resultInfo.pt;
aoqi@0: 
aoqi@0:         if (qtype.hasTag(VOID)) {
aoqi@0:             to = syms.voidType;
aoqi@0:         } else if (to.hasTag(NONE)) {
aoqi@0:             to = from.isPrimitive() ? from : syms.objectType;
aoqi@0:         } else if (qtype.hasTag(UNDETVAR)) {
aoqi@0:             if (resultInfo.pt.isReference()) {
aoqi@0:                 to = generateReturnConstraintsUndetVarToReference(
aoqi@0:                         tree, (UndetVar)qtype, to, resultInfo, inferenceContext);
aoqi@0:             } else {
aoqi@0:                 if (to.isPrimitive()) {
aoqi@0:                     to = generateReturnConstraintsPrimitive(tree, (UndetVar)qtype, to,
aoqi@0:                         resultInfo, inferenceContext);
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         }
aoqi@0:         Assert.check(allowGraphInference || !rsInfoInfContext.free(to),
aoqi@0:                 "legacy inference engine cannot handle constraints on both sides of a subtyping assertion");
aoqi@0:         //we need to skip capture?
aoqi@0:         Warner retWarn = new Warner();
aoqi@0:         if (!resultInfo.checkContext.compatible(qtype, rsInfoInfContext.asUndetVar(to), retWarn) ||
aoqi@0:                 //unchecked conversion is not allowed in source 7 mode
aoqi@0:                 (!allowGraphInference && retWarn.hasLint(Lint.LintCategory.UNCHECKED))) {
aoqi@0:             throw inferenceException
aoqi@0:                     .setMessage("infer.no.conforming.instance.exists",
aoqi@0:                     inferenceContext.restvars(), mt.getReturnType(), to);
aoqi@0:         }
aoqi@0:         return from;
aoqi@0:     }
aoqi@0: 
aoqi@0:     private Type generateReturnConstraintsPrimitive(JCTree tree, UndetVar from,
aoqi@0:             Type to, Attr.ResultInfo resultInfo, InferenceContext inferenceContext) {
aoqi@0:         if (!allowGraphInference) {
aoqi@0:             //if legacy, just return boxed type
aoqi@0:             return types.boxedClass(to).type;
aoqi@0:         }
aoqi@0:         //if graph inference we need to skip conflicting boxed bounds...
aoqi@0:         for (Type t : from.getBounds(InferenceBound.EQ, InferenceBound.UPPER,
aoqi@0:                 InferenceBound.LOWER)) {
aoqi@0:             Type boundAsPrimitive = types.unboxedType(t);
aoqi@0:             if (boundAsPrimitive == null || boundAsPrimitive.hasTag(NONE)) {
aoqi@0:                 continue;
aoqi@0:             }
aoqi@0:             return generateReferenceToTargetConstraint(tree, from, to,
aoqi@0:                     resultInfo, inferenceContext);
aoqi@0:         }
aoqi@0:         return types.boxedClass(to).type;
aoqi@0:     }
aoqi@0: 
aoqi@0:     private Type generateReturnConstraintsUndetVarToReference(JCTree tree,
aoqi@0:             UndetVar from, Type to, Attr.ResultInfo resultInfo,
aoqi@0:             InferenceContext inferenceContext) {
aoqi@0:         Type captureOfTo = types.capture(to);
aoqi@0:         /* T is a reference type, but is not a wildcard-parameterized type, and either
aoqi@0:          */
aoqi@0:         if (captureOfTo == to) { //not a wildcard parameterized type
aoqi@0:             /* i) B2 contains a bound of one of the forms alpha = S or S <: alpha,
aoqi@0:              *      where S is a wildcard-parameterized type, or
aoqi@0:              */
aoqi@0:             for (Type t : from.getBounds(InferenceBound.EQ, InferenceBound.LOWER)) {
aoqi@0:                 Type captureOfBound = types.capture(t);
aoqi@0:                 if (captureOfBound != t) {
aoqi@0:                     return generateReferenceToTargetConstraint(tree, from, to,
aoqi@0:                             resultInfo, inferenceContext);
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             /* ii) B2 contains two bounds of the forms S1 <: alpha and S2 <: alpha,
aoqi@0:              * where S1 and S2 have supertypes that are two different
aoqi@0:              * parameterizations of the same generic class or interface.
aoqi@0:              */
aoqi@0:             for (Type aLowerBound : from.getBounds(InferenceBound.LOWER)) {
aoqi@0:                 for (Type anotherLowerBound : from.getBounds(InferenceBound.LOWER)) {
aoqi@0:                     if (aLowerBound != anotherLowerBound &&
aoqi@0:                         commonSuperWithDiffParameterization(aLowerBound, anotherLowerBound)) {
aoqi@0:                         /* self comment check if any lower bound may be and undetVar,
aoqi@0:                          * in that case the result of this call may be a false positive.
aoqi@0:                          * Should this be restricted to non free types?
aoqi@0:                          */
aoqi@0:                         return generateReferenceToTargetConstraint(tree, from, to,
aoqi@0:                             resultInfo, inferenceContext);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         /* T is a parameterization of a generic class or interface, G,
aoqi@0:          * and B2 contains a bound of one of the forms alpha = S or S <: alpha,
aoqi@0:          * where there exists no type of the form G<...> that is a
aoqi@0:          * supertype of S, but the raw type G is a supertype of S
aoqi@0:          */
aoqi@0:         if (to.isParameterized()) {
aoqi@0:             for (Type t : from.getBounds(InferenceBound.EQ, InferenceBound.LOWER)) {
aoqi@0:                 Type sup = types.asSuper(t, to.tsym);
aoqi@0:                 if (sup != null && sup.isRaw()) {
aoqi@0:                     return generateReferenceToTargetConstraint(tree, from, to,
aoqi@0:                             resultInfo, inferenceContext);
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         }
aoqi@0:         return to;
aoqi@0:     }
aoqi@0: 
aoqi@0:     private boolean commonSuperWithDiffParameterization(Type t, Type s) {
aoqi@0:         Pair<Type, Type> supers = getParameterizedSupers(t, s);
aoqi@0:         return (supers != null && !types.isSameType(supers.fst, supers.snd));
aoqi@0:     }
aoqi@0: 
aoqi@0:     private Type generateReferenceToTargetConstraint(JCTree tree, UndetVar from,
aoqi@0:             Type to, Attr.ResultInfo resultInfo,
aoqi@0:             InferenceContext inferenceContext) {
aoqi@0:         inferenceContext.solve(List.of(from.qtype), new Warner());
vromero@2543:         inferenceContext.notifyChange();
aoqi@0:         Type capturedType = resultInfo.checkContext.inferenceContext()
aoqi@0:                 .cachedCapture(tree, from.inst, false);
aoqi@0:         if (types.isConvertible(capturedType,
aoqi@0:                 resultInfo.checkContext.inferenceContext().asUndetVar(to))) {
aoqi@0:             //effectively skip additional return-type constraint generation (compatibility)
aoqi@0:             return syms.objectType;
aoqi@0:         }
aoqi@0:         return to;
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:       * Infer cyclic inference variables as described in 15.12.2.8.
aoqi@0:       */
aoqi@0:     private void instantiateAsUninferredVars(List<Type> vars, InferenceContext inferenceContext) {
aoqi@0:         ListBuffer<Type> todo = new ListBuffer<>();
aoqi@0:         //step 1 - create fresh tvars
aoqi@0:         for (Type t : vars) {
aoqi@0:             UndetVar uv = (UndetVar)inferenceContext.asUndetVar(t);
aoqi@0:             List<Type> upperBounds = uv.getBounds(InferenceBound.UPPER);
aoqi@0:             if (Type.containsAny(upperBounds, vars)) {
aoqi@0:                 TypeSymbol fresh_tvar = new TypeVariableSymbol(Flags.SYNTHETIC, uv.qtype.tsym.name, null, uv.qtype.tsym.owner);
aoqi@0:                 fresh_tvar.type = new TypeVar(fresh_tvar, types.makeCompoundType(uv.getBounds(InferenceBound.UPPER)), null);
aoqi@0:                 todo.append(uv);
aoqi@0:                 uv.inst = fresh_tvar.type;
aoqi@0:             } else if (upperBounds.nonEmpty()) {
aoqi@0:                 uv.inst = types.glb(upperBounds);
aoqi@0:             } else {
aoqi@0:                 uv.inst = syms.objectType;
aoqi@0:             }
aoqi@0:         }
aoqi@0:         //step 2 - replace fresh tvars in their bounds
aoqi@0:         List<Type> formals = vars;
aoqi@0:         for (Type t : todo) {
aoqi@0:             UndetVar uv = (UndetVar)t;
aoqi@0:             TypeVar ct = (TypeVar)uv.inst;
aoqi@0:             ct.bound = types.glb(inferenceContext.asInstTypes(types.getBounds(ct)));
aoqi@0:             if (ct.bound.isErroneous()) {
aoqi@0:                 //report inference error if glb fails
aoqi@0:                 reportBoundError(uv, BoundErrorKind.BAD_UPPER);
aoqi@0:             }
aoqi@0:             formals = formals.tail;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Compute a synthetic method type corresponding to the requested polymorphic
aoqi@0:      * method signature. The target return type is computed from the immediately
aoqi@0:      * enclosing scope surrounding the polymorphic-signature call.
aoqi@0:      */
aoqi@0:     Type instantiatePolymorphicSignatureInstance(Env<AttrContext> env,
aoqi@0:                                             MethodSymbol spMethod,  // sig. poly. method or null if none
aoqi@0:                                             Resolve.MethodResolutionContext resolveContext,
aoqi@0:                                             List<Type> argtypes) {
aoqi@0:         final Type restype;
aoqi@0: 
aoqi@0:         //The return type for a polymorphic signature call is computed from
aoqi@0:         //the enclosing tree E, as follows: if E is a cast, then use the
aoqi@0:         //target type of the cast expression as a return type; if E is an
aoqi@0:         //expression statement, the return type is 'void' - otherwise the
aoqi@0:         //return type is simply 'Object'. A correctness check ensures that
aoqi@0:         //env.next refers to the lexically enclosing environment in which
aoqi@0:         //the polymorphic signature call environment is nested.
aoqi@0: 
aoqi@0:         switch (env.next.tree.getTag()) {
aoqi@0:             case TYPECAST:
aoqi@0:                 JCTypeCast castTree = (JCTypeCast)env.next.tree;
aoqi@0:                 restype = (TreeInfo.skipParens(castTree.expr) == env.tree) ?
aoqi@0:                     castTree.clazz.type :
aoqi@0:                     syms.objectType;
aoqi@0:                 break;
aoqi@0:             case EXEC:
aoqi@0:                 JCTree.JCExpressionStatement execTree =
aoqi@0:                         (JCTree.JCExpressionStatement)env.next.tree;
aoqi@0:                 restype = (TreeInfo.skipParens(execTree.expr) == env.tree) ?
aoqi@0:                     syms.voidType :
aoqi@0:                     syms.objectType;
aoqi@0:                 break;
aoqi@0:             default:
aoqi@0:                 restype = syms.objectType;
aoqi@0:         }
aoqi@0: 
aoqi@0:         List<Type> paramtypes = Type.map(argtypes, new ImplicitArgType(spMethod, resolveContext.step));
aoqi@0:         List<Type> exType = spMethod != null ?
aoqi@0:             spMethod.getThrownTypes() :
aoqi@0:             List.of(syms.throwableType); // make it throw all exceptions
aoqi@0: 
aoqi@0:         MethodType mtype = new MethodType(paramtypes,
aoqi@0:                                           restype,
aoqi@0:                                           exType,
aoqi@0:                                           syms.methodClass);
aoqi@0:         return mtype;
aoqi@0:     }
aoqi@0:     //where
aoqi@0:         class ImplicitArgType extends DeferredAttr.DeferredTypeMap {
aoqi@0: 
aoqi@0:             public ImplicitArgType(Symbol msym, Resolve.MethodResolutionPhase phase) {
vromero@2543:                 (rs.deferredAttr).super(AttrMode.SPECULATIVE, msym, phase);
aoqi@0:             }
aoqi@0: 
aoqi@0:             public Type apply(Type t) {
aoqi@0:                 t = types.erasure(super.apply(t));
aoqi@0:                 if (t.hasTag(BOT))
aoqi@0:                     // nulls type as the marker type Null (which has no instances)
aoqi@0:                     // infer as java.lang.Void for now
aoqi@0:                     t = types.boxedClass(syms.voidType).type;
aoqi@0:                 return t;
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:     /**
aoqi@0:       * This method is used to infer a suitable target SAM in case the original
aoqi@0:       * SAM type contains one or more wildcards. An inference process is applied
aoqi@0:       * so that wildcard bounds, as well as explicit lambda/method ref parameters
aoqi@0:       * (where applicable) are used to constraint the solution.
aoqi@0:       */
aoqi@0:     public Type instantiateFunctionalInterface(DiagnosticPosition pos, Type funcInterface,
aoqi@0:             List<Type> paramTypes, Check.CheckContext checkContext) {
aoqi@0:         if (types.capture(funcInterface) == funcInterface) {
aoqi@0:             //if capture doesn't change the type then return the target unchanged
aoqi@0:             //(this means the target contains no wildcards!)
aoqi@0:             return funcInterface;
aoqi@0:         } else {
aoqi@0:             Type formalInterface = funcInterface.tsym.type;
aoqi@0:             InferenceContext funcInterfaceContext =
aoqi@0:                     new InferenceContext(funcInterface.tsym.type.getTypeArguments());
aoqi@0: 
aoqi@0:             Assert.check(paramTypes != null);
aoqi@0:             //get constraints from explicit params (this is done by
aoqi@0:             //checking that explicit param types are equal to the ones
aoqi@0:             //in the functional interface descriptors)
aoqi@0:             List<Type> descParameterTypes = types.findDescriptorType(formalInterface).getParameterTypes();
aoqi@0:             if (descParameterTypes.size() != paramTypes.size()) {
aoqi@0:                 checkContext.report(pos, diags.fragment("incompatible.arg.types.in.lambda"));
aoqi@0:                 return types.createErrorType(funcInterface);
aoqi@0:             }
aoqi@0:             for (Type p : descParameterTypes) {
aoqi@0:                 if (!types.isSameType(funcInterfaceContext.asUndetVar(p), paramTypes.head)) {
aoqi@0:                     checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
aoqi@0:                     return types.createErrorType(funcInterface);
aoqi@0:                 }
aoqi@0:                 paramTypes = paramTypes.tail;
aoqi@0:             }
aoqi@0: 
aoqi@0:             try {
aoqi@0:                 funcInterfaceContext.solve(funcInterfaceContext.boundedVars(), types.noWarnings);
aoqi@0:             } catch (InferenceException ex) {
aoqi@0:                 checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
aoqi@0:             }
aoqi@0: 
aoqi@0:             List<Type> actualTypeargs = funcInterface.getTypeArguments();
aoqi@0:             for (Type t : funcInterfaceContext.undetvars) {
aoqi@0:                 UndetVar uv = (UndetVar)t;
aoqi@0:                 if (uv.inst == null) {
aoqi@0:                     uv.inst = actualTypeargs.head;
aoqi@0:                 }
aoqi@0:                 actualTypeargs = actualTypeargs.tail;
aoqi@0:             }
aoqi@0: 
aoqi@0:             Type owntype = funcInterfaceContext.asInstType(formalInterface);
aoqi@0:             if (!chk.checkValidGenericType(owntype)) {
aoqi@0:                 //if the inferred functional interface type is not well-formed,
aoqi@0:                 //or if it's not a subtype of the original target, issue an error
aoqi@0:                 checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
aoqi@0:             }
vromero@2543:             //propagate constraints as per JLS 18.2.1
vromero@2543:             checkContext.compatible(owntype, funcInterface, types.noWarnings);
aoqi@0:             return owntype;
aoqi@0:         }
aoqi@0:     }
aoqi@0:     // </editor-fold>
aoqi@0: 
aoqi@0:     // <editor-fold defaultstate="collapsed" desc="Bound checking">
aoqi@0:     /**
aoqi@0:      * Check bounds and perform incorporation
aoqi@0:      */
aoqi@0:     void checkWithinBounds(InferenceContext inferenceContext,
aoqi@0:                              Warner warn) throws InferenceException {
aoqi@0:         MultiUndetVarListener mlistener = new MultiUndetVarListener(inferenceContext.undetvars);
aoqi@0:         List<Type> saved_undet = inferenceContext.save();
aoqi@0:         try {
aoqi@0:             while (true) {
aoqi@0:                 mlistener.reset();
aoqi@0:                 if (!allowGraphInference) {
aoqi@0:                     //in legacy mode we lack of transitivity, so bound check
aoqi@0:                     //cannot be run in parallel with other incoprporation rounds
aoqi@0:                     for (Type t : inferenceContext.undetvars) {
aoqi@0:                         UndetVar uv = (UndetVar)t;
aoqi@0:                         IncorporationStep.CHECK_BOUNDS.apply(uv, inferenceContext, warn);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 for (Type t : inferenceContext.undetvars) {
aoqi@0:                     UndetVar uv = (UndetVar)t;
aoqi@0:                     //bound incorporation
aoqi@0:                     EnumSet<IncorporationStep> incorporationSteps = allowGraphInference ?
aoqi@0:                             incorporationStepsGraph : incorporationStepsLegacy;
aoqi@0:                     for (IncorporationStep is : incorporationSteps) {
aoqi@0:                         if (is.accepts(uv, inferenceContext)) {
aoqi@0:                             is.apply(uv, inferenceContext, warn);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 if (!mlistener.changed || !allowGraphInference) break;
aoqi@0:             }
aoqi@0:         }
aoqi@0:         finally {
aoqi@0:             mlistener.detach();
aoqi@0:             if (incorporationCache.size() == MAX_INCORPORATION_STEPS) {
aoqi@0:                 inferenceContext.rollback(saved_undet);
aoqi@0:             }
aoqi@0:             incorporationCache.clear();
aoqi@0:         }
aoqi@0:     }
aoqi@0:     //where
aoqi@0:         /**
aoqi@0:          * This listener keeps track of changes on a group of inference variable
aoqi@0:          * bounds. Note: the listener must be detached (calling corresponding
aoqi@0:          * method) to make sure that the underlying inference variable is
aoqi@0:          * left in a clean state.
aoqi@0:          */
aoqi@0:         class MultiUndetVarListener implements UndetVar.UndetVarListener {
aoqi@0: 
aoqi@0:             boolean changed;
aoqi@0:             List<Type> undetvars;
aoqi@0: 
aoqi@0:             public MultiUndetVarListener(List<Type> undetvars) {
aoqi@0:                 this.undetvars = undetvars;
aoqi@0:                 for (Type t : undetvars) {
aoqi@0:                     UndetVar uv = (UndetVar)t;
aoqi@0:                     uv.listener = this;
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             public void varChanged(UndetVar uv, Set<InferenceBound> ibs) {
aoqi@0:                 //avoid non-termination
aoqi@0:                 if (incorporationCache.size() < MAX_INCORPORATION_STEPS) {
aoqi@0:                     changed = true;
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             void reset() {
aoqi@0:                 changed = false;
aoqi@0:             }
aoqi@0: 
aoqi@0:             void detach() {
aoqi@0:                 for (Type t : undetvars) {
aoqi@0:                     UndetVar uv = (UndetVar)t;
aoqi@0:                     uv.listener = null;
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         };
aoqi@0: 
aoqi@0:         /** max number of incorporation rounds */
aoqi@0:         static final int MAX_INCORPORATION_STEPS = 100;
aoqi@0: 
aoqi@0:     /* If for two types t and s there is a least upper bound that is a
aoqi@0:      * parameterized type G, then there exists a supertype of 't' of the form
aoqi@0:      * G<T1, ..., Tn> and a supertype of 's' of the form G<S1, ..., Sn>
aoqi@0:      * which will be returned by this method. If no such supertypes exists then
aoqi@0:      * null is returned.
aoqi@0:      *
aoqi@0:      * As an example for the following input:
aoqi@0:      *
aoqi@0:      * t = java.util.ArrayList<java.lang.String>
aoqi@0:      * s = java.util.List<T>
aoqi@0:      *
aoqi@0:      * we get this ouput:
aoqi@0:      *
aoqi@0:      * Pair[java.util.List<java.lang.String>,java.util.List<T>]
aoqi@0:      */
aoqi@0:     private Pair<Type, Type> getParameterizedSupers(Type t, Type s) {
aoqi@0:         Type lubResult = types.lub(t, s);
aoqi@0:         if (lubResult == syms.errType || lubResult == syms.botType ||
aoqi@0:                 !lubResult.isParameterized()) {
aoqi@0:             return null;
aoqi@0:         }
aoqi@0:         Type asSuperOfT = types.asSuper(t, lubResult.tsym);
aoqi@0:         Type asSuperOfS = types.asSuper(s, lubResult.tsym);
aoqi@0:         return new Pair<>(asSuperOfT, asSuperOfS);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This enumeration defines an entry point for doing inference variable
aoqi@0:      * bound incorporation - it can be used to inject custom incorporation
aoqi@0:      * logic into the basic bound checking routine
aoqi@0:      */
aoqi@0:     enum IncorporationStep {
aoqi@0:         /**
aoqi@0:          * Performs basic bound checking - i.e. is the instantiated type for a given
aoqi@0:          * inference variable compatible with its bounds?
aoqi@0:          */
aoqi@0:         CHECK_BOUNDS() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 uv.substBounds(inferenceContext.inferenceVars(), inferenceContext.instTypes(), infer.types);
aoqi@0:                 infer.checkCompatibleUpperBounds(uv, inferenceContext);
aoqi@0:                 if (uv.inst != null) {
aoqi@0:                     Type inst = uv.inst;
aoqi@0:                     for (Type u : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                         if (!isSubtype(inst, inferenceContext.asUndetVar(u), warn, infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.UPPER);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     for (Type l : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                         if (!isSubtype(inferenceContext.asUndetVar(l), inst, warn, infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.LOWER);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     for (Type e : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                         if (!isSameType(inst, inferenceContext.asUndetVar(e), infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.EQ);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             @Override
aoqi@0:             boolean accepts(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 //applies to all undetvars
aoqi@0:                 return true;
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Check consistency of equality constraints. This is a slightly more aggressive
aoqi@0:          * inference routine that is designed as to maximize compatibility with JDK 7.
aoqi@0:          * Note: this is not used in graph mode.
aoqi@0:          */
aoqi@0:         EQ_CHECK_LEGACY() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 Type eq = null;
aoqi@0:                 for (Type e : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                     Assert.check(!inferenceContext.free(e));
aoqi@0:                     if (eq != null && !isSameType(e, eq, infer)) {
aoqi@0:                         infer.reportBoundError(uv, BoundErrorKind.EQ);
aoqi@0:                     }
aoqi@0:                     eq = e;
aoqi@0:                     for (Type l : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                         Assert.check(!inferenceContext.free(l));
aoqi@0:                         if (!isSubtype(l, e, warn, infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_LOWER);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     for (Type u : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                         if (inferenceContext.free(u)) continue;
aoqi@0:                         if (!isSubtype(e, u, warn, infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_UPPER);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Check consistency of equality constraints.
aoqi@0:          */
aoqi@0:         EQ_CHECK() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type e : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                     if (e.containsAny(inferenceContext.inferenceVars())) continue;
aoqi@0:                     for (Type u : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                         if (!isSubtype(e, inferenceContext.asUndetVar(u), warn, infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_UPPER);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     for (Type l : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                         if (!isSubtype(inferenceContext.asUndetVar(l), e, warn, infer)) {
aoqi@0:                             infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_LOWER);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha <: T} and {@code alpha :> S}
aoqi@0:          * perform {@code S <: T} (which could lead to new bounds).
aoqi@0:          */
aoqi@0:         CROSS_UPPER_LOWER() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b1 : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                     for (Type b2 : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                         isSubtype(inferenceContext.asUndetVar(b2), inferenceContext.asUndetVar(b1), warn , infer);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha <: T} and {@code alpha == S}
aoqi@0:          * perform {@code S <: T} (which could lead to new bounds).
aoqi@0:          */
aoqi@0:         CROSS_UPPER_EQ() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b1 : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                     for (Type b2 : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                         isSubtype(inferenceContext.asUndetVar(b2), inferenceContext.asUndetVar(b1), warn, infer);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha :> S} and {@code alpha == T}
aoqi@0:          * perform {@code S <: T} (which could lead to new bounds).
aoqi@0:          */
aoqi@0:         CROSS_EQ_LOWER() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b1 : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                     for (Type b2 : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                         isSubtype(inferenceContext.asUndetVar(b2), inferenceContext.asUndetVar(b1), warn, infer);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha <: P<T>} and
aoqi@0:          * {@code alpha <: P<S>} where P is a parameterized type,
aoqi@0:          * perform {@code T = S} (which could lead to new bounds).
aoqi@0:          */
aoqi@0:         CROSS_UPPER_UPPER() {
aoqi@0:             @Override
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 List<Type> boundList = uv.getBounds(InferenceBound.UPPER);
aoqi@0:                 List<Type> boundListTail = boundList.tail;
aoqi@0:                 while (boundList.nonEmpty()) {
aoqi@0:                     List<Type> tmpTail = boundListTail;
aoqi@0:                     while (tmpTail.nonEmpty()) {
aoqi@0:                         Type b1 = boundList.head;
aoqi@0:                         Type b2 = tmpTail.head;
vromero@2601:                         /* This wildcard check is temporary workaround. This code may need to be
vromero@2601:                          * revisited once spec bug JDK-7034922 is fixed.
vromero@2601:                          */
vromero@2601:                         if (b1 != b2 && !b1.hasTag(WILDCARD) && !b2.hasTag(WILDCARD)) {
aoqi@0:                             Pair<Type, Type> commonSupers = infer.getParameterizedSupers(b1, b2);
aoqi@0:                             if (commonSupers != null) {
aoqi@0:                                 List<Type> allParamsSuperBound1 = commonSupers.fst.allparams();
aoqi@0:                                 List<Type> allParamsSuperBound2 = commonSupers.snd.allparams();
aoqi@0:                                 while (allParamsSuperBound1.nonEmpty() && allParamsSuperBound2.nonEmpty()) {
aoqi@0:                                     //traverse the list of all params comparing them
aoqi@0:                                     if (!allParamsSuperBound1.head.hasTag(WILDCARD) &&
aoqi@0:                                         !allParamsSuperBound2.head.hasTag(WILDCARD)) {
aoqi@0:                                         isSameType(inferenceContext.asUndetVar(allParamsSuperBound1.head),
aoqi@0:                                             inferenceContext.asUndetVar(allParamsSuperBound2.head), infer);
aoqi@0:                                     }
aoqi@0:                                     allParamsSuperBound1 = allParamsSuperBound1.tail;
aoqi@0:                                     allParamsSuperBound2 = allParamsSuperBound2.tail;
aoqi@0:                                 }
aoqi@0:                                 Assert.check(allParamsSuperBound1.isEmpty() && allParamsSuperBound2.isEmpty());
aoqi@0:                             }
aoqi@0:                         }
aoqi@0:                         tmpTail = tmpTail.tail;
aoqi@0:                     }
aoqi@0:                     boundList = boundList.tail;
aoqi@0:                     boundListTail = boundList.tail;
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             @Override
aoqi@0:             boolean accepts(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 return !uv.isCaptured() &&
aoqi@0:                         uv.getBounds(InferenceBound.UPPER).nonEmpty();
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha == S} and {@code alpha == T}
aoqi@0:          * perform {@code S == T} (which could lead to new bounds).
aoqi@0:          */
aoqi@0:         CROSS_EQ_EQ() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b1 : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                     for (Type b2 : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                         if (b1 != b2) {
aoqi@0:                             isSameType(inferenceContext.asUndetVar(b2), inferenceContext.asUndetVar(b1), infer);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha <: beta} propagate lower bounds
aoqi@0:          * from alpha to beta; also propagate upper bounds from beta to alpha.
aoqi@0:          */
aoqi@0:         PROP_UPPER() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                     if (inferenceContext.inferenceVars().contains(b)) {
aoqi@0:                         UndetVar uv2 = (UndetVar)inferenceContext.asUndetVar(b);
aoqi@0:                         if (uv2.isCaptured()) continue;
aoqi@0:                         //alpha <: beta
aoqi@0:                         //0. set beta :> alpha
aoqi@0:                         addBound(InferenceBound.LOWER, uv2, inferenceContext.asInstType(uv.qtype), infer);
aoqi@0:                         //1. copy alpha's lower to beta's
aoqi@0:                         for (Type l : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                             addBound(InferenceBound.LOWER, uv2, inferenceContext.asInstType(l), infer);
aoqi@0:                         }
aoqi@0:                         //2. copy beta's upper to alpha's
aoqi@0:                         for (Type u : uv2.getBounds(InferenceBound.UPPER)) {
aoqi@0:                             addBound(InferenceBound.UPPER, uv, inferenceContext.asInstType(u), infer);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha :> beta} propagate lower bounds
aoqi@0:          * from beta to alpha; also propagate upper bounds from alpha to beta.
aoqi@0:          */
aoqi@0:         PROP_LOWER() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b : uv.getBounds(InferenceBound.LOWER)) {
aoqi@0:                     if (inferenceContext.inferenceVars().contains(b)) {
aoqi@0:                         UndetVar uv2 = (UndetVar)inferenceContext.asUndetVar(b);
aoqi@0:                         if (uv2.isCaptured()) continue;
aoqi@0:                         //alpha :> beta
aoqi@0:                         //0. set beta <: alpha
aoqi@0:                         addBound(InferenceBound.UPPER, uv2, inferenceContext.asInstType(uv.qtype), infer);
aoqi@0:                         //1. copy alpha's upper to beta's
aoqi@0:                         for (Type u : uv.getBounds(InferenceBound.UPPER)) {
aoqi@0:                             addBound(InferenceBound.UPPER, uv2, inferenceContext.asInstType(u), infer);
aoqi@0:                         }
aoqi@0:                         //2. copy beta's lower to alpha's
aoqi@0:                         for (Type l : uv2.getBounds(InferenceBound.LOWER)) {
aoqi@0:                             addBound(InferenceBound.LOWER, uv, inferenceContext.asInstType(l), infer);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Given a bound set containing {@code alpha == beta} propagate lower/upper
aoqi@0:          * bounds from alpha to beta and back.
aoqi@0:          */
aoqi@0:         PROP_EQ() {
aoqi@0:             public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type b : uv.getBounds(InferenceBound.EQ)) {
aoqi@0:                     if (inferenceContext.inferenceVars().contains(b)) {
aoqi@0:                         UndetVar uv2 = (UndetVar)inferenceContext.asUndetVar(b);
aoqi@0:                         if (uv2.isCaptured()) continue;
aoqi@0:                         //alpha == beta
aoqi@0:                         //0. set beta == alpha
aoqi@0:                         addBound(InferenceBound.EQ, uv2, inferenceContext.asInstType(uv.qtype), infer);
aoqi@0:                         //1. copy all alpha's bounds to beta's
aoqi@0:                         for (InferenceBound ib : InferenceBound.values()) {
aoqi@0:                             for (Type b2 : uv.getBounds(ib)) {
aoqi@0:                                 if (b2 != uv2) {
aoqi@0:                                     addBound(ib, uv2, inferenceContext.asInstType(b2), infer);
aoqi@0:                                 }
aoqi@0:                             }
aoqi@0:                         }
aoqi@0:                         //2. copy all beta's bounds to alpha's
aoqi@0:                         for (InferenceBound ib : InferenceBound.values()) {
aoqi@0:                             for (Type b2 : uv2.getBounds(ib)) {
aoqi@0:                                 if (b2 != uv) {
aoqi@0:                                     addBound(ib, uv, inferenceContext.asInstType(b2), infer);
aoqi@0:                                 }
aoqi@0:                             }
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         };
aoqi@0: 
aoqi@0:         abstract void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn);
aoqi@0: 
aoqi@0:         boolean accepts(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:             return !uv.isCaptured();
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean isSubtype(Type s, Type t, Warner warn, Infer infer) {
aoqi@0:             return doIncorporationOp(IncorporationBinaryOpKind.IS_SUBTYPE, s, t, warn, infer);
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean isSameType(Type s, Type t, Infer infer) {
aoqi@0:             return doIncorporationOp(IncorporationBinaryOpKind.IS_SAME_TYPE, s, t, null, infer);
aoqi@0:         }
aoqi@0: 
aoqi@0:         void addBound(InferenceBound ib, UndetVar uv, Type b, Infer infer) {
aoqi@0:             doIncorporationOp(opFor(ib), uv, b, null, infer);
aoqi@0:         }
aoqi@0: 
aoqi@0:         IncorporationBinaryOpKind opFor(InferenceBound boundKind) {
aoqi@0:             switch (boundKind) {
aoqi@0:                 case EQ:
aoqi@0:                     return IncorporationBinaryOpKind.ADD_EQ_BOUND;
aoqi@0:                 case LOWER:
aoqi@0:                     return IncorporationBinaryOpKind.ADD_LOWER_BOUND;
aoqi@0:                 case UPPER:
aoqi@0:                     return IncorporationBinaryOpKind.ADD_UPPER_BOUND;
aoqi@0:                 default:
aoqi@0:                     Assert.error("Can't get here!");
aoqi@0:                     return null;
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean doIncorporationOp(IncorporationBinaryOpKind opKind, Type op1, Type op2, Warner warn, Infer infer) {
aoqi@0:             IncorporationBinaryOp newOp = infer.new IncorporationBinaryOp(opKind, op1, op2);
aoqi@0:             Boolean res = infer.incorporationCache.get(newOp);
aoqi@0:             if (res == null) {
aoqi@0:                 infer.incorporationCache.put(newOp, res = newOp.apply(warn));
aoqi@0:             }
aoqi@0:             return res;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /** incorporation steps to be executed when running in legacy mode */
aoqi@0:     EnumSet<IncorporationStep> incorporationStepsLegacy = EnumSet.of(IncorporationStep.EQ_CHECK_LEGACY);
aoqi@0: 
aoqi@0:     /** incorporation steps to be executed when running in graph mode */
aoqi@0:     EnumSet<IncorporationStep> incorporationStepsGraph =
aoqi@0:             EnumSet.complementOf(EnumSet.of(IncorporationStep.EQ_CHECK_LEGACY));
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Three kinds of basic operation are supported as part of an incorporation step:
aoqi@0:      * (i) subtype check, (ii) same type check and (iii) bound addition (either
aoqi@0:      * upper/lower/eq bound).
aoqi@0:      */
aoqi@0:     enum IncorporationBinaryOpKind {
aoqi@0:         IS_SUBTYPE() {
aoqi@0:             @Override
aoqi@0:             boolean apply(Type op1, Type op2, Warner warn, Types types) {
aoqi@0:                 return types.isSubtypeUnchecked(op1, op2, warn);
aoqi@0:             }
aoqi@0:         },
aoqi@0:         IS_SAME_TYPE() {
aoqi@0:             @Override
aoqi@0:             boolean apply(Type op1, Type op2, Warner warn, Types types) {
aoqi@0:                 return types.isSameType(op1, op2);
aoqi@0:             }
aoqi@0:         },
aoqi@0:         ADD_UPPER_BOUND() {
aoqi@0:             @Override
aoqi@0:             boolean apply(Type op1, Type op2, Warner warn, Types types) {
aoqi@0:                 UndetVar uv = (UndetVar)op1;
aoqi@0:                 uv.addBound(InferenceBound.UPPER, op2, types);
aoqi@0:                 return true;
aoqi@0:             }
aoqi@0:         },
aoqi@0:         ADD_LOWER_BOUND() {
aoqi@0:             @Override
aoqi@0:             boolean apply(Type op1, Type op2, Warner warn, Types types) {
aoqi@0:                 UndetVar uv = (UndetVar)op1;
aoqi@0:                 uv.addBound(InferenceBound.LOWER, op2, types);
aoqi@0:                 return true;
aoqi@0:             }
aoqi@0:         },
aoqi@0:         ADD_EQ_BOUND() {
aoqi@0:             @Override
aoqi@0:             boolean apply(Type op1, Type op2, Warner warn, Types types) {
aoqi@0:                 UndetVar uv = (UndetVar)op1;
aoqi@0:                 uv.addBound(InferenceBound.EQ, op2, types);
aoqi@0:                 return true;
aoqi@0:             }
aoqi@0:         };
aoqi@0: 
aoqi@0:         abstract boolean apply(Type op1, Type op2, Warner warn, Types types);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This class encapsulates a basic incorporation operation; incorporation
aoqi@0:      * operations takes two type operands and a kind. Each operation performed
aoqi@0:      * during an incorporation round is stored in a cache, so that operations
aoqi@0:      * are not executed unnecessarily (which would potentially lead to adding
aoqi@0:      * same bounds over and over).
aoqi@0:      */
aoqi@0:     class IncorporationBinaryOp {
aoqi@0: 
aoqi@0:         IncorporationBinaryOpKind opKind;
aoqi@0:         Type op1;
aoqi@0:         Type op2;
aoqi@0: 
aoqi@0:         IncorporationBinaryOp(IncorporationBinaryOpKind opKind, Type op1, Type op2) {
aoqi@0:             this.opKind = opKind;
aoqi@0:             this.op1 = op1;
aoqi@0:             this.op2 = op2;
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         public boolean equals(Object o) {
aoqi@0:             if (!(o instanceof IncorporationBinaryOp)) {
aoqi@0:                 return false;
aoqi@0:             } else {
aoqi@0:                 IncorporationBinaryOp that = (IncorporationBinaryOp)o;
aoqi@0:                 return opKind == that.opKind &&
aoqi@0:                         types.isSameType(op1, that.op1, true) &&
aoqi@0:                         types.isSameType(op2, that.op2, true);
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         public int hashCode() {
aoqi@0:             int result = opKind.hashCode();
aoqi@0:             result *= 127;
aoqi@0:             result += types.hashCode(op1);
aoqi@0:             result *= 127;
aoqi@0:             result += types.hashCode(op2);
aoqi@0:             return result;
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean apply(Warner warn) {
aoqi@0:             return opKind.apply(op1, op2, warn, types);
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /** an incorporation cache keeps track of all executed incorporation-related operations */
aoqi@0:     Map<IncorporationBinaryOp, Boolean> incorporationCache =
aoqi@0:             new HashMap<IncorporationBinaryOp, Boolean>();
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Make sure that the upper bounds we got so far lead to a solvable inference
aoqi@0:      * variable by making sure that a glb exists.
aoqi@0:      */
aoqi@0:     void checkCompatibleUpperBounds(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:         List<Type> hibounds =
aoqi@0:                 Type.filter(uv.getBounds(InferenceBound.UPPER), new BoundFilter(inferenceContext));
aoqi@0:         Type hb = null;
aoqi@0:         if (hibounds.isEmpty())
aoqi@0:             hb = syms.objectType;
aoqi@0:         else if (hibounds.tail.isEmpty())
aoqi@0:             hb = hibounds.head;
aoqi@0:         else
aoqi@0:             hb = types.glb(hibounds);
aoqi@0:         if (hb == null || hb.isErroneous())
aoqi@0:             reportBoundError(uv, BoundErrorKind.BAD_UPPER);
aoqi@0:     }
aoqi@0:     //where
aoqi@0:         protected static class BoundFilter implements Filter<Type> {
aoqi@0: 
aoqi@0:             InferenceContext inferenceContext;
aoqi@0: 
aoqi@0:             public BoundFilter(InferenceContext inferenceContext) {
aoqi@0:                 this.inferenceContext = inferenceContext;
aoqi@0:             }
aoqi@0: 
aoqi@0:             @Override
aoqi@0:             public boolean accepts(Type t) {
aoqi@0:                 return !t.isErroneous() && !inferenceContext.free(t) &&
aoqi@0:                         !t.hasTag(BOT);
aoqi@0:             }
aoqi@0:         };
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This enumeration defines all possible bound-checking related errors.
aoqi@0:      */
aoqi@0:     enum BoundErrorKind {
aoqi@0:         /**
aoqi@0:          * The (uninstantiated) inference variable has incompatible upper bounds.
aoqi@0:          */
aoqi@0:         BAD_UPPER() {
aoqi@0:             @Override
aoqi@0:             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
aoqi@0:                 return ex.setMessage("incompatible.upper.bounds", uv.qtype,
aoqi@0:                         uv.getBounds(InferenceBound.UPPER));
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * An equality constraint is not compatible with an upper bound.
aoqi@0:          */
aoqi@0:         BAD_EQ_UPPER() {
aoqi@0:             @Override
aoqi@0:             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
aoqi@0:                 return ex.setMessage("incompatible.eq.upper.bounds", uv.qtype,
aoqi@0:                         uv.getBounds(InferenceBound.EQ), uv.getBounds(InferenceBound.UPPER));
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * An equality constraint is not compatible with a lower bound.
aoqi@0:          */
aoqi@0:         BAD_EQ_LOWER() {
aoqi@0:             @Override
aoqi@0:             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
aoqi@0:                 return ex.setMessage("incompatible.eq.lower.bounds", uv.qtype,
aoqi@0:                         uv.getBounds(InferenceBound.EQ), uv.getBounds(InferenceBound.LOWER));
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Instantiated inference variable is not compatible with an upper bound.
aoqi@0:          */
aoqi@0:         UPPER() {
aoqi@0:             @Override
aoqi@0:             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
aoqi@0:                 return ex.setMessage("inferred.do.not.conform.to.upper.bounds", uv.inst,
aoqi@0:                         uv.getBounds(InferenceBound.UPPER));
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Instantiated inference variable is not compatible with a lower bound.
aoqi@0:          */
aoqi@0:         LOWER() {
aoqi@0:             @Override
aoqi@0:             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
aoqi@0:                 return ex.setMessage("inferred.do.not.conform.to.lower.bounds", uv.inst,
aoqi@0:                         uv.getBounds(InferenceBound.LOWER));
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Instantiated inference variable is not compatible with an equality constraint.
aoqi@0:          */
aoqi@0:         EQ() {
aoqi@0:             @Override
aoqi@0:             InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
aoqi@0:                 return ex.setMessage("inferred.do.not.conform.to.eq.bounds", uv.inst,
aoqi@0:                         uv.getBounds(InferenceBound.EQ));
aoqi@0:             }
aoqi@0:         };
aoqi@0: 
aoqi@0:         abstract InapplicableMethodException setMessage(InferenceException ex, UndetVar uv);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Report a bound-checking error of given kind
aoqi@0:      */
aoqi@0:     void reportBoundError(UndetVar uv, BoundErrorKind bk) {
aoqi@0:         throw bk.setMessage(inferenceException, uv);
aoqi@0:     }
aoqi@0:     // </editor-fold>
aoqi@0: 
aoqi@0:     // <editor-fold defaultstate="collapsed" desc="Inference engine">
aoqi@0:     /**
aoqi@0:      * Graph inference strategy - act as an input to the inference solver; a strategy is
aoqi@0:      * composed of two ingredients: (i) find a node to solve in the inference graph,
aoqi@0:      * and (ii) tell th engine when we are done fixing inference variables
aoqi@0:      */
aoqi@0:     interface GraphStrategy {
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * A NodeNotFoundException is thrown whenever an inference strategy fails
aoqi@0:          * to pick the next node to solve in the inference graph.
aoqi@0:          */
aoqi@0:         public static class NodeNotFoundException extends RuntimeException {
aoqi@0:             private static final long serialVersionUID = 0;
aoqi@0: 
aoqi@0:             InferenceGraph graph;
aoqi@0: 
aoqi@0:             public NodeNotFoundException(InferenceGraph graph) {
aoqi@0:                 this.graph = graph;
aoqi@0:             }
aoqi@0:         }
aoqi@0:         /**
aoqi@0:          * Pick the next node (leaf) to solve in the graph
aoqi@0:          */
aoqi@0:         Node pickNode(InferenceGraph g) throws NodeNotFoundException;
aoqi@0:         /**
aoqi@0:          * Is this the last step?
aoqi@0:          */
aoqi@0:         boolean done();
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Simple solver strategy class that locates all leaves inside a graph
aoqi@0:      * and picks the first leaf as the next node to solve
aoqi@0:      */
aoqi@0:     abstract class LeafSolver implements GraphStrategy {
aoqi@0:         public Node pickNode(InferenceGraph g) {
aoqi@0:             if (g.nodes.isEmpty()) {
aoqi@0:                 //should not happen
aoqi@0:                 throw new NodeNotFoundException(g);
aoqi@0:             };
aoqi@0:             return g.nodes.get(0);
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean isSubtype(Type s, Type t, Warner warn, Infer infer) {
aoqi@0:             return doIncorporationOp(IncorporationBinaryOpKind.IS_SUBTYPE, s, t, warn, infer);
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean isSameType(Type s, Type t, Infer infer) {
aoqi@0:             return doIncorporationOp(IncorporationBinaryOpKind.IS_SAME_TYPE, s, t, null, infer);
aoqi@0:         }
aoqi@0: 
aoqi@0:         void addBound(InferenceBound ib, UndetVar uv, Type b, Infer infer) {
aoqi@0:             doIncorporationOp(opFor(ib), uv, b, null, infer);
aoqi@0:         }
aoqi@0: 
aoqi@0:         IncorporationBinaryOpKind opFor(InferenceBound boundKind) {
aoqi@0:             switch (boundKind) {
aoqi@0:                 case EQ:
aoqi@0:                     return IncorporationBinaryOpKind.ADD_EQ_BOUND;
aoqi@0:                 case LOWER:
aoqi@0:                     return IncorporationBinaryOpKind.ADD_LOWER_BOUND;
aoqi@0:                 case UPPER:
aoqi@0:                     return IncorporationBinaryOpKind.ADD_UPPER_BOUND;
aoqi@0:                 default:
aoqi@0:                     Assert.error("Can't get here!");
aoqi@0:                     return null;
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         boolean doIncorporationOp(IncorporationBinaryOpKind opKind, Type op1, Type op2, Warner warn, Infer infer) {
aoqi@0:             IncorporationBinaryOp newOp = infer.new IncorporationBinaryOp(opKind, op1, op2);
aoqi@0:             Boolean res = infer.incorporationCache.get(newOp);
aoqi@0:             if (res == null) {
aoqi@0:                 infer.incorporationCache.put(newOp, res = newOp.apply(warn));
aoqi@0:             }
aoqi@0:             return res;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This solver uses an heuristic to pick the best leaf - the heuristic
aoqi@0:      * tries to select the node that has maximal probability to contain one
aoqi@0:      * or more inference variables in a given list
aoqi@0:      */
aoqi@0:     abstract class BestLeafSolver extends LeafSolver {
aoqi@0: 
aoqi@0:         /** list of ivars of which at least one must be solved */
aoqi@0:         List<Type> varsToSolve;
aoqi@0: 
aoqi@0:         BestLeafSolver(List<Type> varsToSolve) {
aoqi@0:             this.varsToSolve = varsToSolve;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Computes a path that goes from a given node to the leafs in the graph.
aoqi@0:          * Typically this will start from a node containing a variable in
aoqi@0:          * {@code varsToSolve}. For any given path, the cost is computed as the total
aoqi@0:          * number of type-variables that should be eagerly instantiated across that path.
aoqi@0:          */
aoqi@0:         Pair<List<Node>, Integer> computeTreeToLeafs(Node n) {
aoqi@0:             Pair<List<Node>, Integer> cachedPath = treeCache.get(n);
aoqi@0:             if (cachedPath == null) {
aoqi@0:                 //cache miss
aoqi@0:                 if (n.isLeaf()) {
aoqi@0:                     //if leaf, stop
aoqi@0:                     cachedPath = new Pair<List<Node>, Integer>(List.of(n), n.data.length());
aoqi@0:                 } else {
aoqi@0:                     //if non-leaf, proceed recursively
aoqi@0:                     Pair<List<Node>, Integer> path = new Pair<List<Node>, Integer>(List.of(n), n.data.length());
aoqi@0:                     for (Node n2 : n.getAllDependencies()) {
aoqi@0:                         if (n2 == n) continue;
aoqi@0:                         Pair<List<Node>, Integer> subpath = computeTreeToLeafs(n2);
aoqi@0:                         path = new Pair<List<Node>, Integer>(
aoqi@0:                                 path.fst.prependList(subpath.fst),
aoqi@0:                                 path.snd + subpath.snd);
aoqi@0:                     }
aoqi@0:                     cachedPath = path;
aoqi@0:                 }
aoqi@0:                 //save results in cache
aoqi@0:                 treeCache.put(n, cachedPath);
aoqi@0:             }
aoqi@0:             return cachedPath;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /** cache used to avoid redundant computation of tree costs */
aoqi@0:         final Map<Node, Pair<List<Node>, Integer>> treeCache =
aoqi@0:                 new HashMap<Node, Pair<List<Node>, Integer>>();
aoqi@0: 
aoqi@0:         /** constant value used to mark non-existent paths */
aoqi@0:         final Pair<List<Node>, Integer> noPath =
aoqi@0:                 new Pair<List<Node>, Integer>(null, Integer.MAX_VALUE);
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Pick the leaf that minimize cost
aoqi@0:          */
aoqi@0:         @Override
aoqi@0:         public Node pickNode(final InferenceGraph g) {
aoqi@0:             treeCache.clear(); //graph changes at every step - cache must be cleared
aoqi@0:             Pair<List<Node>, Integer> bestPath = noPath;
aoqi@0:             for (Node n : g.nodes) {
aoqi@0:                 if (!Collections.disjoint(n.data, varsToSolve)) {
aoqi@0:                     Pair<List<Node>, Integer> path = computeTreeToLeafs(n);
aoqi@0:                     //discard all paths containing at least a node in the
aoqi@0:                     //closure computed above
aoqi@0:                     if (path.snd < bestPath.snd) {
aoqi@0:                         bestPath = path;
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             if (bestPath == noPath) {
aoqi@0:                 //no path leads there
aoqi@0:                 throw new NodeNotFoundException(g);
aoqi@0:             }
aoqi@0:             return bestPath.fst.head;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * The inference process can be thought of as a sequence of steps. Each step
aoqi@0:      * instantiates an inference variable using a subset of the inference variable
aoqi@0:      * bounds, if certain condition are met. Decisions such as the sequence in which
aoqi@0:      * steps are applied, or which steps are to be applied are left to the inference engine.
aoqi@0:      */
aoqi@0:     enum InferenceStep {
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Instantiate an inference variables using one of its (ground) equality
aoqi@0:          * constraints
aoqi@0:          */
aoqi@0:         EQ(InferenceBound.EQ) {
aoqi@0:             @Override
aoqi@0:             Type solve(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 return filterBounds(uv, inferenceContext).head;
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Instantiate an inference variables using its (ground) lower bounds. Such
aoqi@0:          * bounds are merged together using lub().
aoqi@0:          */
aoqi@0:         LOWER(InferenceBound.LOWER) {
aoqi@0:             @Override
aoqi@0:             Type solve(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 List<Type> lobounds = filterBounds(uv, inferenceContext);
aoqi@0:                 //note: lobounds should have at least one element
aoqi@0:                 Type owntype = lobounds.tail.tail == null  ? lobounds.head : infer.types.lub(lobounds);
aoqi@0:                 if (owntype.isPrimitive() || owntype.hasTag(ERROR)) {
aoqi@0:                     throw infer.inferenceException
aoqi@0:                         .setMessage("no.unique.minimal.instance.exists",
aoqi@0:                                     uv.qtype, lobounds);
aoqi@0:                 } else {
aoqi@0:                     return owntype;
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Infer uninstantiated/unbound inference variables occurring in 'throws'
aoqi@0:          * clause as RuntimeException
aoqi@0:          */
aoqi@0:         THROWS(InferenceBound.UPPER) {
aoqi@0:             @Override
aoqi@0:             public boolean accepts(UndetVar t, InferenceContext inferenceContext) {
aoqi@0:                 if ((t.qtype.tsym.flags() & Flags.THROWS) == 0) {
aoqi@0:                     //not a throws undet var
aoqi@0:                     return false;
aoqi@0:                 }
aoqi@0:                 if (t.getBounds(InferenceBound.EQ, InferenceBound.LOWER, InferenceBound.UPPER)
aoqi@0:                             .diff(t.getDeclaredBounds()).nonEmpty()) {
aoqi@0:                     //not an unbounded undet var
aoqi@0:                     return false;
aoqi@0:                 }
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 for (Type db : t.getDeclaredBounds()) {
aoqi@0:                     if (t.isInterface()) continue;
aoqi@0:                     if (infer.types.asSuper(infer.syms.runtimeExceptionType, db.tsym) != null) {
aoqi@0:                         //declared bound is a supertype of RuntimeException
aoqi@0:                         return true;
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 //declared bound is more specific then RuntimeException - give up
aoqi@0:                 return false;
aoqi@0:             }
aoqi@0: 
aoqi@0:             @Override
aoqi@0:             Type solve(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 return inferenceContext.infer().syms.runtimeExceptionType;
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Instantiate an inference variables using its (ground) upper bounds. Such
aoqi@0:          * bounds are merged together using glb().
aoqi@0:          */
aoqi@0:         UPPER(InferenceBound.UPPER) {
aoqi@0:             @Override
aoqi@0:             Type solve(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 List<Type> hibounds = filterBounds(uv, inferenceContext);
aoqi@0:                 //note: hibounds should have at least one element
aoqi@0:                 Type owntype = hibounds.tail.tail == null  ? hibounds.head : infer.types.glb(hibounds);
aoqi@0:                 if (owntype.isPrimitive() || owntype.hasTag(ERROR)) {
aoqi@0:                     throw infer.inferenceException
aoqi@0:                         .setMessage("no.unique.maximal.instance.exists",
aoqi@0:                                     uv.qtype, hibounds);
aoqi@0:                 } else {
aoqi@0:                     return owntype;
aoqi@0:                 }
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Like the former; the only difference is that this step can only be applied
aoqi@0:          * if all upper bounds are ground.
aoqi@0:          */
aoqi@0:         UPPER_LEGACY(InferenceBound.UPPER) {
aoqi@0:             @Override
aoqi@0:             public boolean accepts(UndetVar t, InferenceContext inferenceContext) {
aoqi@0:                 return !inferenceContext.free(t.getBounds(ib)) && !t.isCaptured();
aoqi@0:             }
aoqi@0: 
aoqi@0:             @Override
aoqi@0:             Type solve(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 return UPPER.solve(uv, inferenceContext);
aoqi@0:             }
aoqi@0:         },
aoqi@0:         /**
aoqi@0:          * Like the former; the only difference is that this step can only be applied
aoqi@0:          * if all upper/lower bounds are ground.
aoqi@0:          */
aoqi@0:         CAPTURED(InferenceBound.UPPER) {
aoqi@0:             @Override
aoqi@0:             public boolean accepts(UndetVar t, InferenceContext inferenceContext) {
aoqi@0:                 return t.isCaptured() &&
aoqi@0:                         !inferenceContext.free(t.getBounds(InferenceBound.UPPER, InferenceBound.LOWER));
aoqi@0:             }
aoqi@0: 
aoqi@0:             @Override
aoqi@0:             Type solve(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:                 Infer infer = inferenceContext.infer();
aoqi@0:                 Type upper = UPPER.filterBounds(uv, inferenceContext).nonEmpty() ?
aoqi@0:                         UPPER.solve(uv, inferenceContext) :
aoqi@0:                         infer.syms.objectType;
aoqi@0:                 Type lower = LOWER.filterBounds(uv, inferenceContext).nonEmpty() ?
aoqi@0:                         LOWER.solve(uv, inferenceContext) :
aoqi@0:                         infer.syms.botType;
aoqi@0:                 CapturedType prevCaptured = (CapturedType)uv.qtype;
aoqi@0:                 return new CapturedType(prevCaptured.tsym.name, prevCaptured.tsym.owner, upper, lower, prevCaptured.wildcard);
aoqi@0:             }
aoqi@0:         };
aoqi@0: 
aoqi@0:         final InferenceBound ib;
aoqi@0: 
aoqi@0:         InferenceStep(InferenceBound ib) {
aoqi@0:             this.ib = ib;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Find an instantiated type for a given inference variable within
aoqi@0:          * a given inference context
aoqi@0:          */
aoqi@0:         abstract Type solve(UndetVar uv, InferenceContext inferenceContext);
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Can the inference variable be instantiated using this step?
aoqi@0:          */
aoqi@0:         public boolean accepts(UndetVar t, InferenceContext inferenceContext) {
aoqi@0:             return filterBounds(t, inferenceContext).nonEmpty() && !t.isCaptured();
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Return the subset of ground bounds in a given bound set (i.e. eq/lower/upper)
aoqi@0:          */
aoqi@0:         List<Type> filterBounds(UndetVar uv, InferenceContext inferenceContext) {
aoqi@0:             return Type.filter(uv.getBounds(ib), new BoundFilter(inferenceContext));
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This enumeration defines the sequence of steps to be applied when the
aoqi@0:      * solver works in legacy mode. The steps in this enumeration reflect
aoqi@0:      * the behavior of old inference routine (see JLS SE 7 15.12.2.7/15.12.2.8).
aoqi@0:      */
aoqi@0:     enum LegacyInferenceSteps {
aoqi@0: 
aoqi@0:         EQ_LOWER(EnumSet.of(InferenceStep.EQ, InferenceStep.LOWER)),
aoqi@0:         EQ_UPPER(EnumSet.of(InferenceStep.EQ, InferenceStep.UPPER_LEGACY));
aoqi@0: 
aoqi@0:         final EnumSet<InferenceStep> steps;
aoqi@0: 
aoqi@0:         LegacyInferenceSteps(EnumSet<InferenceStep> steps) {
aoqi@0:             this.steps = steps;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This enumeration defines the sequence of steps to be applied when the
aoqi@0:      * graph solver is used. This order is defined so as to maximize compatibility
aoqi@0:      * w.r.t. old inference routine (see JLS SE 7 15.12.2.7/15.12.2.8).
aoqi@0:      */
aoqi@0:     enum GraphInferenceSteps {
aoqi@0: 
aoqi@0:         EQ(EnumSet.of(InferenceStep.EQ)),
aoqi@0:         EQ_LOWER(EnumSet.of(InferenceStep.EQ, InferenceStep.LOWER)),
aoqi@0:         EQ_LOWER_THROWS_UPPER_CAPTURED(EnumSet.of(InferenceStep.EQ, InferenceStep.LOWER, InferenceStep.UPPER, InferenceStep.THROWS, InferenceStep.CAPTURED));
aoqi@0: 
aoqi@0:         final EnumSet<InferenceStep> steps;
aoqi@0: 
aoqi@0:         GraphInferenceSteps(EnumSet<InferenceStep> steps) {
aoqi@0:             this.steps = steps;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * There are two kinds of dependencies between inference variables. The basic
aoqi@0:      * kind of dependency (or bound dependency) arises when a variable mention
aoqi@0:      * another variable in one of its bounds. There's also a more subtle kind
aoqi@0:      * of dependency that arises when a variable 'might' lead to better constraints
aoqi@0:      * on another variable (this is typically the case with variables holding up
aoqi@0:      * stuck expressions).
aoqi@0:      */
aoqi@0:     enum DependencyKind implements GraphUtils.DependencyKind {
aoqi@0: 
aoqi@0:         /** bound dependency */
aoqi@0:         BOUND("dotted"),
aoqi@0:         /** stuck dependency */
aoqi@0:         STUCK("dashed");
aoqi@0: 
aoqi@0:         final String dotSyle;
aoqi@0: 
aoqi@0:         private DependencyKind(String dotSyle) {
aoqi@0:             this.dotSyle = dotSyle;
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         public String getDotStyle() {
aoqi@0:             return dotSyle;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * This is the graph inference solver - the solver organizes all inference variables in
aoqi@0:      * a given inference context by bound dependencies - in the general case, such dependencies
aoqi@0:      * would lead to a cyclic directed graph (hence the name); the dependency info is used to build
aoqi@0:      * an acyclic graph, where all cyclic variables are bundled together. An inference
aoqi@0:      * step corresponds to solving a node in the acyclic graph - this is done by
aoqi@0:      * relying on a given strategy (see GraphStrategy).
aoqi@0:      */
aoqi@0:     class GraphSolver {
aoqi@0: 
aoqi@0:         InferenceContext inferenceContext;
aoqi@0:         Map<Type, Set<Type>> stuckDeps;
aoqi@0:         Warner warn;
aoqi@0: 
aoqi@0:         GraphSolver(InferenceContext inferenceContext, Map<Type, Set<Type>> stuckDeps, Warner warn) {
aoqi@0:             this.inferenceContext = inferenceContext;
aoqi@0:             this.stuckDeps = stuckDeps;
aoqi@0:             this.warn = warn;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Solve variables in a given inference context. The amount of variables
aoqi@0:          * to be solved, and the way in which the underlying acyclic graph is explored
aoqi@0:          * depends on the selected solver strategy.
aoqi@0:          */
aoqi@0:         void solve(GraphStrategy sstrategy) {
aoqi@0:             checkWithinBounds(inferenceContext, warn); //initial propagation of bounds
aoqi@0:             InferenceGraph inferenceGraph = new InferenceGraph(stuckDeps);
aoqi@0:             while (!sstrategy.done()) {
aoqi@0:                 InferenceGraph.Node nodeToSolve = sstrategy.pickNode(inferenceGraph);
aoqi@0:                 List<Type> varsToSolve = List.from(nodeToSolve.data);
aoqi@0:                 List<Type> saved_undet = inferenceContext.save();
aoqi@0:                 try {
aoqi@0:                     //repeat until all variables are solved
aoqi@0:                     outer: while (Type.containsAny(inferenceContext.restvars(), varsToSolve)) {
aoqi@0:                         //for each inference phase
aoqi@0:                         for (GraphInferenceSteps step : GraphInferenceSteps.values()) {
aoqi@0:                             if (inferenceContext.solveBasic(varsToSolve, step.steps)) {
aoqi@0:                                 checkWithinBounds(inferenceContext, warn);
aoqi@0:                                 continue outer;
aoqi@0:                             }
aoqi@0:                         }
aoqi@0:                         //no progress
aoqi@0:                         throw inferenceException.setMessage();
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 catch (InferenceException ex) {
aoqi@0:                     //did we fail because of interdependent ivars?
aoqi@0:                     inferenceContext.rollback(saved_undet);
aoqi@0:                     instantiateAsUninferredVars(varsToSolve, inferenceContext);
aoqi@0:                     checkWithinBounds(inferenceContext, warn);
aoqi@0:                 }
aoqi@0:                 inferenceGraph.deleteNode(nodeToSolve);
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * The dependencies between the inference variables that need to be solved
aoqi@0:          * form a (possibly cyclic) graph. This class reduces the original dependency graph
aoqi@0:          * to an acyclic version, where cyclic nodes are folded into a single 'super node'.
aoqi@0:          */
aoqi@0:         class InferenceGraph {
aoqi@0: 
aoqi@0:             /**
aoqi@0:              * This class represents a node in the graph. Each node corresponds
aoqi@0:              * to an inference variable and has edges (dependencies) on other
aoqi@0:              * nodes. The node defines an entry point that can be used to receive
aoqi@0:              * updates on the structure of the graph this node belongs to (used to
aoqi@0:              * keep dependencies in sync).
aoqi@0:              */
aoqi@0:             class Node extends GraphUtils.TarjanNode<ListBuffer<Type>> {
aoqi@0: 
aoqi@0:                 /** map listing all dependencies (grouped by kind) */
aoqi@0:                 EnumMap<DependencyKind, Set<Node>> deps;
aoqi@0: 
aoqi@0:                 Node(Type ivar) {
aoqi@0:                     super(ListBuffer.of(ivar));
aoqi@0:                     this.deps = new EnumMap<DependencyKind, Set<Node>>(DependencyKind.class);
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 @Override
aoqi@0:                 public GraphUtils.DependencyKind[] getSupportedDependencyKinds() {
aoqi@0:                     return DependencyKind.values();
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 @Override
aoqi@0:                 public String getDependencyName(GraphUtils.Node<ListBuffer<Type>> to, GraphUtils.DependencyKind dk) {
aoqi@0:                     if (dk == DependencyKind.STUCK) return "";
aoqi@0:                     else {
aoqi@0:                         StringBuilder buf = new StringBuilder();
aoqi@0:                         String sep = "";
aoqi@0:                         for (Type from : data) {
aoqi@0:                             UndetVar uv = (UndetVar)inferenceContext.asUndetVar(from);
aoqi@0:                             for (Type bound : uv.getBounds(InferenceBound.values())) {
aoqi@0:                                 if (bound.containsAny(List.from(to.data))) {
aoqi@0:                                     buf.append(sep);
aoqi@0:                                     buf.append(bound);
aoqi@0:                                     sep = ",";
aoqi@0:                                 }
aoqi@0:                             }
aoqi@0:                         }
aoqi@0:                         return buf.toString();
aoqi@0:                     }
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 @Override
aoqi@0:                 public Iterable<? extends Node> getAllDependencies() {
aoqi@0:                     return getDependencies(DependencyKind.values());
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 @Override
aoqi@0:                 public Iterable<? extends TarjanNode<ListBuffer<Type>>> getDependenciesByKind(GraphUtils.DependencyKind dk) {
aoqi@0:                     return getDependencies((DependencyKind)dk);
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Retrieves all dependencies with given kind(s).
aoqi@0:                  */
aoqi@0:                 protected Set<Node> getDependencies(DependencyKind... depKinds) {
aoqi@0:                     Set<Node> buf = new LinkedHashSet<Node>();
aoqi@0:                     for (DependencyKind dk : depKinds) {
aoqi@0:                         Set<Node> depsByKind = deps.get(dk);
aoqi@0:                         if (depsByKind != null) {
aoqi@0:                             buf.addAll(depsByKind);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     return buf;
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Adds dependency with given kind.
aoqi@0:                  */
aoqi@0:                 protected void addDependency(DependencyKind dk, Node depToAdd) {
aoqi@0:                     Set<Node> depsByKind = deps.get(dk);
aoqi@0:                     if (depsByKind == null) {
aoqi@0:                         depsByKind = new LinkedHashSet<Node>();
aoqi@0:                         deps.put(dk, depsByKind);
aoqi@0:                     }
aoqi@0:                     depsByKind.add(depToAdd);
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Add multiple dependencies of same given kind.
aoqi@0:                  */
aoqi@0:                 protected void addDependencies(DependencyKind dk, Set<Node> depsToAdd) {
aoqi@0:                     for (Node n : depsToAdd) {
aoqi@0:                         addDependency(dk, n);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Remove a dependency, regardless of its kind.
aoqi@0:                  */
aoqi@0:                 protected Set<DependencyKind> removeDependency(Node n) {
aoqi@0:                     Set<DependencyKind> removedKinds = new HashSet<>();
aoqi@0:                     for (DependencyKind dk : DependencyKind.values()) {
aoqi@0:                         Set<Node> depsByKind = deps.get(dk);
aoqi@0:                         if (depsByKind == null) continue;
aoqi@0:                         if (depsByKind.remove(n)) {
aoqi@0:                             removedKinds.add(dk);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     return removedKinds;
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Compute closure of a give node, by recursively walking
aoqi@0:                  * through all its dependencies (of given kinds)
aoqi@0:                  */
aoqi@0:                 protected Set<Node> closure(DependencyKind... depKinds) {
aoqi@0:                     boolean progress = true;
aoqi@0:                     Set<Node> closure = new HashSet<Node>();
aoqi@0:                     closure.add(this);
aoqi@0:                     while (progress) {
aoqi@0:                         progress = false;
aoqi@0:                         for (Node n1 : new HashSet<Node>(closure)) {
aoqi@0:                             progress = closure.addAll(n1.getDependencies(depKinds));
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     return closure;
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Is this node a leaf? This means either the node has no dependencies,
aoqi@0:                  * or it just has self-dependencies.
aoqi@0:                  */
aoqi@0:                 protected boolean isLeaf() {
aoqi@0:                     //no deps, or only one self dep
aoqi@0:                     Set<Node> allDeps = getDependencies(DependencyKind.BOUND, DependencyKind.STUCK);
aoqi@0:                     if (allDeps.isEmpty()) return true;
aoqi@0:                     for (Node n : allDeps) {
aoqi@0:                         if (n != this) {
aoqi@0:                             return false;
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     return true;
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Merge this node with another node, acquiring its dependencies.
aoqi@0:                  * This routine is used to merge all cyclic node together and
aoqi@0:                  * form an acyclic graph.
aoqi@0:                  */
aoqi@0:                 protected void mergeWith(List<? extends Node> nodes) {
aoqi@0:                     for (Node n : nodes) {
aoqi@0:                         Assert.check(n.data.length() == 1, "Attempt to merge a compound node!");
aoqi@0:                         data.appendList(n.data);
aoqi@0:                         for (DependencyKind dk : DependencyKind.values()) {
aoqi@0:                             addDependencies(dk, n.getDependencies(dk));
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     //update deps
aoqi@0:                     EnumMap<DependencyKind, Set<Node>> deps2 = new EnumMap<DependencyKind, Set<Node>>(DependencyKind.class);
aoqi@0:                     for (DependencyKind dk : DependencyKind.values()) {
aoqi@0:                         for (Node d : getDependencies(dk)) {
aoqi@0:                             Set<Node> depsByKind = deps2.get(dk);
aoqi@0:                             if (depsByKind == null) {
aoqi@0:                                 depsByKind = new LinkedHashSet<Node>();
aoqi@0:                                 deps2.put(dk, depsByKind);
aoqi@0:                             }
aoqi@0:                             if (data.contains(d.data.first())) {
aoqi@0:                                 depsByKind.add(this);
aoqi@0:                             } else {
aoqi@0:                                 depsByKind.add(d);
aoqi@0:                             }
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     deps = deps2;
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 /**
aoqi@0:                  * Notify all nodes that something has changed in the graph
aoqi@0:                  * topology.
aoqi@0:                  */
aoqi@0:                 private void graphChanged(Node from, Node to) {
aoqi@0:                     for (DependencyKind dk : removeDependency(from)) {
aoqi@0:                         if (to != null) {
aoqi@0:                             addDependency(dk, to);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             /** the nodes in the inference graph */
aoqi@0:             ArrayList<Node> nodes;
aoqi@0: 
aoqi@0:             InferenceGraph(Map<Type, Set<Type>> optDeps) {
aoqi@0:                 initNodes(optDeps);
aoqi@0:             }
aoqi@0: 
aoqi@0:             /**
aoqi@0:              * Basic lookup helper for retrieving a graph node given an inference
aoqi@0:              * variable type.
aoqi@0:              */
aoqi@0:             public Node findNode(Type t) {
aoqi@0:                 for (Node n : nodes) {
aoqi@0:                     if (n.data.contains(t)) {
aoqi@0:                         return n;
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 return null;
aoqi@0:             }
aoqi@0: 
aoqi@0:             /**
aoqi@0:              * Delete a node from the graph. This update the underlying structure
aoqi@0:              * of the graph (including dependencies) via listeners updates.
aoqi@0:              */
aoqi@0:             public void deleteNode(Node n) {
aoqi@0:                 Assert.check(nodes.contains(n));
aoqi@0:                 nodes.remove(n);
aoqi@0:                 notifyUpdate(n, null);
aoqi@0:             }
aoqi@0: 
aoqi@0:             /**
aoqi@0:              * Notify all nodes of a change in the graph. If the target node is
aoqi@0:              * {@code null} the source node is assumed to be removed.
aoqi@0:              */
aoqi@0:             void notifyUpdate(Node from, Node to) {
aoqi@0:                 for (Node n : nodes) {
aoqi@0:                     n.graphChanged(from, to);
aoqi@0:                 }
aoqi@0:             }
aoqi@0: 
aoqi@0:             /**
aoqi@0:              * Create the graph nodes. First a simple node is created for every inference
aoqi@0:              * variables to be solved. Then Tarjan is used to found all connected components
aoqi@0:              * in the graph. For each component containing more than one node, a super node is
aoqi@0:              * created, effectively replacing the original cyclic nodes.
aoqi@0:              */
aoqi@0:             void initNodes(Map<Type, Set<Type>> stuckDeps) {
aoqi@0:                 //add nodes
aoqi@0:                 nodes = new ArrayList<Node>();
aoqi@0:                 for (Type t : inferenceContext.restvars()) {
aoqi@0:                     nodes.add(new Node(t));
aoqi@0:                 }
aoqi@0:                 //add dependencies
aoqi@0:                 for (Node n_i : nodes) {
aoqi@0:                     Type i = n_i.data.first();
aoqi@0:                     Set<Type> optDepsByNode = stuckDeps.get(i);
aoqi@0:                     for (Node n_j : nodes) {
aoqi@0:                         Type j = n_j.data.first();
aoqi@0:                         UndetVar uv_i = (UndetVar)inferenceContext.asUndetVar(i);
aoqi@0:                         if (Type.containsAny(uv_i.getBounds(InferenceBound.values()), List.of(j))) {
aoqi@0:                             //update i's bound dependencies
aoqi@0:                             n_i.addDependency(DependencyKind.BOUND, n_j);
aoqi@0:                         }
aoqi@0:                         if (optDepsByNode != null && optDepsByNode.contains(j)) {
aoqi@0:                             //update i's stuck dependencies
aoqi@0:                             n_i.addDependency(DependencyKind.STUCK, n_j);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 //merge cyclic nodes
aoqi@0:                 ArrayList<Node> acyclicNodes = new ArrayList<Node>();
aoqi@0:                 for (List<? extends Node> conSubGraph : GraphUtils.tarjan(nodes)) {
aoqi@0:                     if (conSubGraph.length() > 1) {
aoqi@0:                         Node root = conSubGraph.head;
aoqi@0:                         root.mergeWith(conSubGraph.tail);
aoqi@0:                         for (Node n : conSubGraph) {
aoqi@0:                             notifyUpdate(n, root);
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                     acyclicNodes.add(conSubGraph.head);
aoqi@0:                 }
aoqi@0:                 nodes = acyclicNodes;
aoqi@0:             }
aoqi@0: 
aoqi@0:             /**
aoqi@0:              * Debugging: dot representation of this graph
aoqi@0:              */
aoqi@0:             String toDot() {
aoqi@0:                 StringBuilder buf = new StringBuilder();
aoqi@0:                 for (Type t : inferenceContext.undetvars) {
aoqi@0:                     UndetVar uv = (UndetVar)t;
aoqi@0:                     buf.append(String.format("var %s - upper bounds = %s, lower bounds = %s, eq bounds = %s\\n",
aoqi@0:                             uv.qtype, uv.getBounds(InferenceBound.UPPER), uv.getBounds(InferenceBound.LOWER),
aoqi@0:                             uv.getBounds(InferenceBound.EQ)));
aoqi@0:                 }
aoqi@0:                 return GraphUtils.toDot(nodes, "inferenceGraph" + hashCode(), buf.toString());
aoqi@0:             }
aoqi@0:         }
aoqi@0:     }
aoqi@0:     // </editor-fold>
aoqi@0: 
aoqi@0:     // <editor-fold defaultstate="collapsed" desc="Inference context">
aoqi@0:     /**
aoqi@0:      * Functional interface for defining inference callbacks. Certain actions
aoqi@0:      * (i.e. subtyping checks) might need to be redone after all inference variables
aoqi@0:      * have been fixed.
aoqi@0:      */
aoqi@0:     interface FreeTypeListener {
aoqi@0:         void typesInferred(InferenceContext inferenceContext);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * An inference context keeps track of the set of variables that are free
aoqi@0:      * in the current context. It provides utility methods for opening/closing
aoqi@0:      * types to their corresponding free/closed forms. It also provide hooks for
aoqi@0:      * attaching deferred post-inference action (see PendingCheck). Finally,
aoqi@0:      * it can be used as an entry point for performing upper/lower bound inference
aoqi@0:      * (see InferenceKind).
aoqi@0:      */
aoqi@0:      class InferenceContext {
aoqi@0: 
aoqi@0:         /** list of inference vars as undet vars */
aoqi@0:         List<Type> undetvars;
aoqi@0: 
aoqi@0:         /** list of inference vars in this context */
aoqi@0:         List<Type> inferencevars;
aoqi@0: 
aoqi@0:         java.util.Map<FreeTypeListener, List<Type>> freeTypeListeners =
aoqi@0:                 new java.util.HashMap<FreeTypeListener, List<Type>>();
aoqi@0: 
aoqi@0:         List<FreeTypeListener> freetypeListeners = List.nil();
aoqi@0: 
aoqi@0:         public InferenceContext(List<Type> inferencevars) {
aoqi@0:             this.undetvars = Type.map(inferencevars, fromTypeVarFun);
aoqi@0:             this.inferencevars = inferencevars;
aoqi@0:         }
aoqi@0:         //where
aoqi@0:             Mapping fromTypeVarFun = new Mapping("fromTypeVarFunWithBounds") {
aoqi@0:                 // mapping that turns inference variables into undet vars
aoqi@0:                 public Type apply(Type t) {
aoqi@0:                     if (t.hasTag(TYPEVAR)) {
aoqi@0:                         TypeVar tv = (TypeVar)t;
aoqi@0:                         if (tv.isCaptured()) {
aoqi@0:                             return new CapturedUndetVar((CapturedType)tv, types);
aoqi@0:                         } else {
aoqi@0:                             return new UndetVar(tv, types);
aoqi@0:                         }
aoqi@0:                     } else {
aoqi@0:                         return t.map(this);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             };
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * add a new inference var to this inference context
aoqi@0:          */
aoqi@0:         void addVar(TypeVar t) {
aoqi@0:             this.undetvars = this.undetvars.prepend(fromTypeVarFun.apply(t));
aoqi@0:             this.inferencevars = this.inferencevars.prepend(t);
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * returns the list of free variables (as type-variables) in this
aoqi@0:          * inference context
aoqi@0:          */
aoqi@0:         List<Type> inferenceVars() {
aoqi@0:             return inferencevars;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * returns the list of uninstantiated variables (as type-variables) in this
aoqi@0:          * inference context
aoqi@0:          */
aoqi@0:         List<Type> restvars() {
aoqi@0:             return filterVars(new Filter<UndetVar>() {
aoqi@0:                 public boolean accepts(UndetVar uv) {
aoqi@0:                     return uv.inst == null;
aoqi@0:                 }
aoqi@0:             });
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * returns the list of instantiated variables (as type-variables) in this
aoqi@0:          * inference context
aoqi@0:          */
aoqi@0:         List<Type> instvars() {
aoqi@0:             return filterVars(new Filter<UndetVar>() {
aoqi@0:                 public boolean accepts(UndetVar uv) {
aoqi@0:                     return uv.inst != null;
aoqi@0:                 }
aoqi@0:             });
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Get list of bounded inference variables (where bound is other than
aoqi@0:          * declared bounds).
aoqi@0:          */
aoqi@0:         final List<Type> boundedVars() {
aoqi@0:             return filterVars(new Filter<UndetVar>() {
aoqi@0:                 public boolean accepts(UndetVar uv) {
aoqi@0:                     return uv.getBounds(InferenceBound.UPPER)
aoqi@0:                              .diff(uv.getDeclaredBounds())
aoqi@0:                              .appendList(uv.getBounds(InferenceBound.EQ, InferenceBound.LOWER)).nonEmpty();
aoqi@0:                 }
aoqi@0:             });
aoqi@0:         }
aoqi@0: 
aoqi@0:         /* Returns the corresponding inference variables.
aoqi@0:          */
aoqi@0:         private List<Type> filterVars(Filter<UndetVar> fu) {
aoqi@0:             ListBuffer<Type> res = new ListBuffer<>();
aoqi@0:             for (Type t : undetvars) {
aoqi@0:                 UndetVar uv = (UndetVar)t;
aoqi@0:                 if (fu.accepts(uv)) {
aoqi@0:                     res.append(uv.qtype);
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             return res.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * is this type free?
aoqi@0:          */
aoqi@0:         final boolean free(Type t) {
aoqi@0:             return t.containsAny(inferencevars);
aoqi@0:         }
aoqi@0: 
aoqi@0:         final boolean free(List<Type> ts) {
aoqi@0:             for (Type t : ts) {
aoqi@0:                 if (free(t)) return true;
aoqi@0:             }
aoqi@0:             return false;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Returns a list of free variables in a given type
aoqi@0:          */
aoqi@0:         final List<Type> freeVarsIn(Type t) {
aoqi@0:             ListBuffer<Type> buf = new ListBuffer<>();
aoqi@0:             for (Type iv : inferenceVars()) {
aoqi@0:                 if (t.contains(iv)) {
aoqi@0:                     buf.add(iv);
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             return buf.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         final List<Type> freeVarsIn(List<Type> ts) {
aoqi@0:             ListBuffer<Type> buf = new ListBuffer<>();
aoqi@0:             for (Type t : ts) {
aoqi@0:                 buf.appendList(freeVarsIn(t));
aoqi@0:             }
aoqi@0:             ListBuffer<Type> buf2 = new ListBuffer<>();
aoqi@0:             for (Type t : buf) {
aoqi@0:                 if (!buf2.contains(t)) {
aoqi@0:                     buf2.add(t);
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             return buf2.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Replace all free variables in a given type with corresponding
aoqi@0:          * undet vars (used ahead of subtyping/compatibility checks to allow propagation
aoqi@0:          * of inference constraints).
aoqi@0:          */
aoqi@0:         final Type asUndetVar(Type t) {
aoqi@0:             return types.subst(t, inferencevars, undetvars);
aoqi@0:         }
aoqi@0: 
aoqi@0:         final List<Type> asUndetVars(List<Type> ts) {
aoqi@0:             ListBuffer<Type> buf = new ListBuffer<>();
aoqi@0:             for (Type t : ts) {
aoqi@0:                 buf.append(asUndetVar(t));
aoqi@0:             }
aoqi@0:             return buf.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         List<Type> instTypes() {
aoqi@0:             ListBuffer<Type> buf = new ListBuffer<>();
aoqi@0:             for (Type t : undetvars) {
aoqi@0:                 UndetVar uv = (UndetVar)t;
aoqi@0:                 buf.append(uv.inst != null ? uv.inst : uv.qtype);
aoqi@0:             }
aoqi@0:             return buf.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Replace all free variables in a given type with corresponding
aoqi@0:          * instantiated types - if one or more free variable has not been
aoqi@0:          * fully instantiated, it will still be available in the resulting type.
aoqi@0:          */
aoqi@0:         Type asInstType(Type t) {
aoqi@0:             return types.subst(t, inferencevars, instTypes());
aoqi@0:         }
aoqi@0: 
aoqi@0:         List<Type> asInstTypes(List<Type> ts) {
aoqi@0:             ListBuffer<Type> buf = new ListBuffer<>();
aoqi@0:             for (Type t : ts) {
aoqi@0:                 buf.append(asInstType(t));
aoqi@0:             }
aoqi@0:             return buf.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Add custom hook for performing post-inference action
aoqi@0:          */
aoqi@0:         void addFreeTypeListener(List<Type> types, FreeTypeListener ftl) {
aoqi@0:             freeTypeListeners.put(ftl, freeVarsIn(types));
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Mark the inference context as complete and trigger evaluation
aoqi@0:          * of all deferred checks.
aoqi@0:          */
aoqi@0:         void notifyChange() {
aoqi@0:             notifyChange(inferencevars.diff(restvars()));
aoqi@0:         }
aoqi@0: 
aoqi@0:         void notifyChange(List<Type> inferredVars) {
aoqi@0:             InferenceException thrownEx = null;
aoqi@0:             for (Map.Entry<FreeTypeListener, List<Type>> entry :
aoqi@0:                     new HashMap<FreeTypeListener, List<Type>>(freeTypeListeners).entrySet()) {
aoqi@0:                 if (!Type.containsAny(entry.getValue(), inferencevars.diff(inferredVars))) {
aoqi@0:                     try {
aoqi@0:                         entry.getKey().typesInferred(this);
aoqi@0:                         freeTypeListeners.remove(entry.getKey());
aoqi@0:                     } catch (InferenceException ex) {
aoqi@0:                         if (thrownEx == null) {
aoqi@0:                             thrownEx = ex;
aoqi@0:                         }
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             //inference exception multiplexing - present any inference exception
aoqi@0:             //thrown when processing listeners as a single one
aoqi@0:             if (thrownEx != null) {
aoqi@0:                 throw thrownEx;
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Save the state of this inference context
aoqi@0:          */
aoqi@0:         List<Type> save() {
aoqi@0:             ListBuffer<Type> buf = new ListBuffer<>();
aoqi@0:             for (Type t : undetvars) {
aoqi@0:                 UndetVar uv = (UndetVar)t;
aoqi@0:                 UndetVar uv2 = new UndetVar((TypeVar)uv.qtype, types);
aoqi@0:                 for (InferenceBound ib : InferenceBound.values()) {
aoqi@0:                     for (Type b : uv.getBounds(ib)) {
aoqi@0:                         uv2.addBound(ib, b, types);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:                 uv2.inst = uv.inst;
aoqi@0:                 buf.add(uv2);
aoqi@0:             }
aoqi@0:             return buf.toList();
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Restore the state of this inference context to the previous known checkpoint
aoqi@0:          */
aoqi@0:         void rollback(List<Type> saved_undet) {
aoqi@0:              Assert.check(saved_undet != null && saved_undet.length() == undetvars.length());
aoqi@0:             //restore bounds (note: we need to preserve the old instances)
aoqi@0:             for (Type t : undetvars) {
aoqi@0:                 UndetVar uv = (UndetVar)t;
aoqi@0:                 UndetVar uv_saved = (UndetVar)saved_undet.head;
aoqi@0:                 for (InferenceBound ib : InferenceBound.values()) {
aoqi@0:                     uv.setBounds(ib, uv_saved.getBounds(ib));
aoqi@0:                 }
aoqi@0:                 uv.inst = uv_saved.inst;
aoqi@0:                 saved_undet = saved_undet.tail;
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Copy variable in this inference context to the given context
aoqi@0:          */
aoqi@0:         void dupTo(final InferenceContext that) {
aoqi@0:             that.inferencevars = that.inferencevars.appendList(
aoqi@0:                     inferencevars.diff(that.inferencevars));
aoqi@0:             that.undetvars = that.undetvars.appendList(
aoqi@0:                     undetvars.diff(that.undetvars));
aoqi@0:             //set up listeners to notify original inference contexts as
aoqi@0:             //propagated vars are inferred in new context
aoqi@0:             for (Type t : inferencevars) {
aoqi@0:                 that.freeTypeListeners.put(new FreeTypeListener() {
aoqi@0:                     public void typesInferred(InferenceContext inferenceContext) {
aoqi@0:                         InferenceContext.this.notifyChange();
aoqi@0:                     }
aoqi@0:                 }, List.of(t));
aoqi@0:             }
aoqi@0:         }
aoqi@0: 
aoqi@0:         private void solve(GraphStrategy ss, Warner warn) {
aoqi@0:             solve(ss, new HashMap<Type, Set<Type>>(), warn);
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Solve with given graph strategy.
aoqi@0:          */
aoqi@0:         private void solve(GraphStrategy ss, Map<Type, Set<Type>> stuckDeps, Warner warn) {
aoqi@0:             GraphSolver s = new GraphSolver(this, stuckDeps, warn);
aoqi@0:             s.solve(ss);
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Solve all variables in this context.
aoqi@0:          */
aoqi@0:         public void solve(Warner warn) {
aoqi@0:             solve(new LeafSolver() {
aoqi@0:                 public boolean done() {
aoqi@0:                     return restvars().isEmpty();
aoqi@0:                 }
aoqi@0:             }, warn);
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Solve all variables in the given list.
aoqi@0:          */
aoqi@0:         public void solve(final List<Type> vars, Warner warn) {
aoqi@0:             solve(new BestLeafSolver(vars) {
aoqi@0:                 public boolean done() {
aoqi@0:                     return !free(asInstTypes(vars));
aoqi@0:                 }
aoqi@0:             }, warn);
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Solve at least one variable in given list.
aoqi@0:          */
aoqi@0:         public void solveAny(List<Type> varsToSolve, Map<Type, Set<Type>> optDeps, Warner warn) {
aoqi@0:             solve(new BestLeafSolver(varsToSolve.intersect(restvars())) {
aoqi@0:                 public boolean done() {
aoqi@0:                     return instvars().intersect(varsToSolve).nonEmpty();
aoqi@0:                 }
aoqi@0:             }, optDeps, warn);
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Apply a set of inference steps
aoqi@0:          */
aoqi@0:         private boolean solveBasic(EnumSet<InferenceStep> steps) {
aoqi@0:             return solveBasic(inferencevars, steps);
aoqi@0:         }
aoqi@0: 
aoqi@0:         private boolean solveBasic(List<Type> varsToSolve, EnumSet<InferenceStep> steps) {
aoqi@0:             boolean changed = false;
aoqi@0:             for (Type t : varsToSolve.intersect(restvars())) {
aoqi@0:                 UndetVar uv = (UndetVar)asUndetVar(t);
aoqi@0:                 for (InferenceStep step : steps) {
aoqi@0:                     if (step.accepts(uv, this)) {
aoqi@0:                         uv.inst = step.solve(uv, this);
aoqi@0:                         changed = true;
aoqi@0:                         break;
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             return changed;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /**
aoqi@0:          * Instantiate inference variables in legacy mode (JLS 15.12.2.7, 15.12.2.8).
aoqi@0:          * During overload resolution, instantiation is done by doing a partial
aoqi@0:          * inference process using eq/lower bound instantiation. During check,
aoqi@0:          * we also instantiate any remaining vars by repeatedly using eq/upper
aoqi@0:          * instantiation, until all variables are solved.
aoqi@0:          */
aoqi@0:         public void solveLegacy(boolean partial, Warner warn, EnumSet<InferenceStep> steps) {
aoqi@0:             while (true) {
aoqi@0:                 boolean stuck = !solveBasic(steps);
aoqi@0:                 if (restvars().isEmpty() || partial) {
aoqi@0:                     //all variables have been instantiated - exit
aoqi@0:                     break;
aoqi@0:                 } else if (stuck) {
aoqi@0:                     //some variables could not be instantiated because of cycles in
aoqi@0:                     //upper bounds - provide a (possibly recursive) default instantiation
aoqi@0:                     instantiateAsUninferredVars(restvars(), this);
aoqi@0:                     break;
aoqi@0:                 } else {
aoqi@0:                     //some variables have been instantiated - replace newly instantiated
aoqi@0:                     //variables in remaining upper bounds and continue
aoqi@0:                     for (Type t : undetvars) {
aoqi@0:                         UndetVar uv = (UndetVar)t;
aoqi@0:                         uv.substBounds(inferenceVars(), instTypes(), types);
aoqi@0:                     }
aoqi@0:                 }
aoqi@0:             }
aoqi@0:             checkWithinBounds(this, warn);
aoqi@0:         }
aoqi@0: 
aoqi@0:         private Infer infer() {
aoqi@0:             //back-door to infer
aoqi@0:             return Infer.this;
aoqi@0:         }
aoqi@0: 
aoqi@0:         @Override
aoqi@0:         public String toString() {
aoqi@0:             return "Inference vars: " + inferencevars + '\n' +
aoqi@0:                    "Undet vars: " + undetvars;
aoqi@0:         }
aoqi@0: 
aoqi@0:         /* Method Types.capture() generates a new type every time it's applied
aoqi@0:          * to a wildcard parameterized type. This is intended functionality but
aoqi@0:          * there are some cases when what you need is not to generate a new
aoqi@0:          * captured type but to check that a previously generated captured type
aoqi@0:          * is correct. There are cases when caching a captured type for later
aoqi@0:          * reuse is sound. In general two captures from the same AST are equal.
aoqi@0:          * This is why the tree is used as the key of the map below. This map
aoqi@0:          * stores a Type per AST.
aoqi@0:          */
aoqi@0:         Map<JCTree, Type> captureTypeCache = new HashMap<>();
aoqi@0: 
aoqi@0:         Type cachedCapture(JCTree tree, Type t, boolean readOnly) {
aoqi@0:             Type captured = captureTypeCache.get(tree);
aoqi@0:             if (captured != null) {
aoqi@0:                 return captured;
aoqi@0:             }
aoqi@0: 
aoqi@0:             Type result = types.capture(t);
aoqi@0:             if (result != t && !readOnly) { // then t is a wildcard parameterized type
aoqi@0:                 captureTypeCache.put(tree, result);
aoqi@0:             }
aoqi@0:             return result;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     final InferenceContext emptyContext = new InferenceContext(List.<Type>nil());
aoqi@0:     // </editor-fold>
aoqi@0: }