Java example source code file (Infer.java)
The Infer.java Java example source code
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package com.sun.tools.javac.comp;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCTypeCast;
import com.sun.tools.javac.tree.TreeInfo;
import com.sun.tools.javac.util.*;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
import com.sun.tools.javac.util.List;
import com.sun.tools.javac.code.*;
import com.sun.tools.javac.code.Type.*;
import com.sun.tools.javac.code.Type.UndetVar.InferenceBound;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.comp.DeferredAttr.AttrMode;
import com.sun.tools.javac.comp.Infer.GraphSolver.InferenceGraph;
import com.sun.tools.javac.comp.Infer.GraphSolver.InferenceGraph.Node;
import com.sun.tools.javac.comp.Resolve.InapplicableMethodException;
import com.sun.tools.javac.comp.Resolve.VerboseResolutionMode;
import com.sun.tools.javac.util.GraphUtils.TarjanNode;
import java.util.ArrayList;
import java.util.Collections;
import java.util.EnumMap;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import static com.sun.tools.javac.code.TypeTag.*;
/** Helper class for type parameter inference, used by the attribution phase.
*
* <p>This is NOT part of any supported API.
* If you write code that depends on this, you do so at your own risk.
* This code and its internal interfaces are subject to change or
* deletion without notice.</b>
*/
public class Infer {
protected static final Context.Key<Infer> inferKey =
new Context.Key<Infer>();
Resolve rs;
Check chk;
Symtab syms;
Types types;
JCDiagnostic.Factory diags;
Log log;
/** should the graph solver be used? */
boolean allowGraphInference;
public static Infer instance(Context context) {
Infer instance = context.get(inferKey);
if (instance == null)
instance = new Infer(context);
return instance;
}
protected Infer(Context context) {
context.put(inferKey, this);
rs = Resolve.instance(context);
chk = Check.instance(context);
syms = Symtab.instance(context);
types = Types.instance(context);
diags = JCDiagnostic.Factory.instance(context);
log = Log.instance(context);
inferenceException = new InferenceException(diags);
Options options = Options.instance(context);
allowGraphInference = Source.instance(context).allowGraphInference()
&& options.isUnset("useLegacyInference");
}
/** A value for prototypes that admit any type, including polymorphic ones. */
public static final Type anyPoly = new JCNoType();
/**
* This exception class is design to store a list of diagnostics corresponding
* to inference errors that can arise during a method applicability check.
*/
public static class InferenceException extends InapplicableMethodException {
private static final long serialVersionUID = 0;
List<JCDiagnostic> messages = List.nil();
InferenceException(JCDiagnostic.Factory diags) {
super(diags);
}
@Override
InapplicableMethodException setMessage() {
//no message to set
return this;
}
@Override
InapplicableMethodException setMessage(JCDiagnostic diag) {
messages = messages.append(diag);
return this;
}
@Override
public JCDiagnostic getDiagnostic() {
return messages.head;
}
void clear() {
messages = List.nil();
}
}
protected final InferenceException inferenceException;
// <editor-fold defaultstate="collapsed" desc="Inference routines">
/**
* Main inference entry point - instantiate a generic method type
* using given argument types and (possibly) an expected target-type.
*/
public Type instantiateMethod(Env<AttrContext> env,
List<Type> tvars,
MethodType mt,
Attr.ResultInfo resultInfo,
Symbol msym,
List<Type> argtypes,
boolean allowBoxing,
boolean useVarargs,
Resolve.MethodResolutionContext resolveContext,
Warner warn) throws InferenceException {
//-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
final InferenceContext inferenceContext = new InferenceContext(tvars);
inferenceException.clear();
try {
DeferredAttr.DeferredAttrContext deferredAttrContext =
resolveContext.deferredAttrContext(msym, inferenceContext, resultInfo, warn);
resolveContext.methodCheck.argumentsAcceptable(env, deferredAttrContext,
argtypes, mt.getParameterTypes(), warn);
if (allowGraphInference &&
resultInfo != null &&
!warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)) {
//inject return constraints earlier
checkWithinBounds(inferenceContext, warn); //propagation
Type newRestype = generateReturnConstraints(resultInfo, mt, inferenceContext);
mt = (MethodType)types.createMethodTypeWithReturn(mt, newRestype);
//propagate outwards if needed
if (resultInfo.checkContext.inferenceContext().free(resultInfo.pt)) {
//propagate inference context outwards and exit
inferenceContext.dupTo(resultInfo.checkContext.inferenceContext());
deferredAttrContext.complete();
return mt;
}
}
deferredAttrContext.complete();
// minimize as yet undetermined type variables
if (allowGraphInference) {
inferenceContext.solve(warn);
} else {
inferenceContext.solveLegacy(true, warn, LegacyInferenceSteps.EQ_LOWER.steps); //minimizeInst
}
mt = (MethodType)inferenceContext.asInstType(mt);
if (!allowGraphInference &&
inferenceContext.restvars().nonEmpty() &&
resultInfo != null &&
!warn.hasNonSilentLint(Lint.LintCategory.UNCHECKED)) {
generateReturnConstraints(resultInfo, mt, inferenceContext);
inferenceContext.solveLegacy(false, warn, LegacyInferenceSteps.EQ_UPPER.steps); //maximizeInst
mt = (MethodType)inferenceContext.asInstType(mt);
}
if (resultInfo != null && rs.verboseResolutionMode.contains(VerboseResolutionMode.DEFERRED_INST)) {
log.note(env.tree.pos, "deferred.method.inst", msym, mt, resultInfo.pt);
}
// return instantiated version of method type
return mt;
} finally {
if (resultInfo != null || !allowGraphInference) {
inferenceContext.notifyChange();
} else {
inferenceContext.notifyChange(inferenceContext.boundedVars());
}
}
}
/**
* Generate constraints from the generic method's return type. If the method
* call occurs in a context where a type T is expected, use the expected
* type to derive more constraints on the generic method inference variables.
*/
Type generateReturnConstraints(Attr.ResultInfo resultInfo,
MethodType mt, InferenceContext inferenceContext) {
Type from = mt.getReturnType();
if (mt.getReturnType().containsAny(inferenceContext.inferencevars) &&
resultInfo.checkContext.inferenceContext() != emptyContext) {
from = types.capture(from);
//add synthetic captured ivars
for (Type t : from.getTypeArguments()) {
if (t.hasTag(TYPEVAR) && ((TypeVar)t).isCaptured()) {
inferenceContext.addVar((TypeVar)t);
}
}
}
Type qtype1 = inferenceContext.asFree(from);
Type to = returnConstraintTarget(qtype1, resultInfo.pt);
Assert.check(allowGraphInference || !resultInfo.checkContext.inferenceContext().free(to),
"legacy inference engine cannot handle constraints on both sides of a subtyping assertion");
//we need to skip capture?
Warner retWarn = new Warner();
if (!resultInfo.checkContext.compatible(qtype1, resultInfo.checkContext.inferenceContext().asFree(to), retWarn) ||
//unchecked conversion is not allowed in source 7 mode
(!allowGraphInference && retWarn.hasLint(Lint.LintCategory.UNCHECKED))) {
throw inferenceException
.setMessage("infer.no.conforming.instance.exists",
inferenceContext.restvars(), mt.getReturnType(), to);
}
return from;
}
Type returnConstraintTarget(Type from, Type to) {
if (from.hasTag(VOID)) {
return syms.voidType;
} else if (to.hasTag(NONE)) {
return from.isPrimitive() ? from : syms.objectType;
} else if (from.hasTag(UNDETVAR) && to.isPrimitive()) {
if (!allowGraphInference) {
//if legacy, just return boxed type
return types.boxedClass(to).type;
}
//if graph inference we need to skip conflicting boxed bounds...
UndetVar uv = (UndetVar)from;
for (Type t : uv.getBounds(InferenceBound.EQ, InferenceBound.LOWER)) {
Type boundAsPrimitive = types.unboxedType(t);
if (boundAsPrimitive == null) continue;
if (types.isConvertible(boundAsPrimitive, to)) {
//effectively skip return-type constraint generation (compatibility)
return syms.objectType;
}
}
return types.boxedClass(to).type;
} else {
return to;
}
}
/**
* Infer cyclic inference variables as described in 15.12.2.8.
*/
private void instantiateAsUninferredVars(List<Type> vars, InferenceContext inferenceContext) {
ListBuffer<Type> todo = new ListBuffer<>();
//step 1 - create fresh tvars
for (Type t : vars) {
UndetVar uv = (UndetVar)inferenceContext.asFree(t);
List<Type> upperBounds = uv.getBounds(InferenceBound.UPPER);
if (Type.containsAny(upperBounds, vars)) {
TypeSymbol fresh_tvar = new TypeVariableSymbol(Flags.SYNTHETIC, uv.qtype.tsym.name, null, uv.qtype.tsym.owner);
fresh_tvar.type = new TypeVar(fresh_tvar, types.makeCompoundType(uv.getBounds(InferenceBound.UPPER)), null);
todo.append(uv);
uv.inst = fresh_tvar.type;
} else if (upperBounds.nonEmpty()) {
uv.inst = types.glb(upperBounds);
} else {
uv.inst = syms.objectType;
}
}
//step 2 - replace fresh tvars in their bounds
List<Type> formals = vars;
for (Type t : todo) {
UndetVar uv = (UndetVar)t;
TypeVar ct = (TypeVar)uv.inst;
ct.bound = types.glb(inferenceContext.asInstTypes(types.getBounds(ct)));
if (ct.bound.isErroneous()) {
//report inference error if glb fails
reportBoundError(uv, BoundErrorKind.BAD_UPPER);
}
formals = formals.tail;
}
}
/**
* Compute a synthetic method type corresponding to the requested polymorphic
* method signature. The target return type is computed from the immediately
* enclosing scope surrounding the polymorphic-signature call.
*/
Type instantiatePolymorphicSignatureInstance(Env<AttrContext> env,
MethodSymbol spMethod, // sig. poly. method or null if none
Resolve.MethodResolutionContext resolveContext,
List<Type> argtypes) {
final Type restype;
//The return type for a polymorphic signature call is computed from
//the enclosing tree E, as follows: if E is a cast, then use the
//target type of the cast expression as a return type; if E is an
//expression statement, the return type is 'void' - otherwise the
//return type is simply 'Object'. A correctness check ensures that
//env.next refers to the lexically enclosing environment in which
//the polymorphic signature call environment is nested.
switch (env.next.tree.getTag()) {
case TYPECAST:
JCTypeCast castTree = (JCTypeCast)env.next.tree;
restype = (TreeInfo.skipParens(castTree.expr) == env.tree) ?
castTree.clazz.type :
syms.objectType;
break;
case EXEC:
JCTree.JCExpressionStatement execTree =
(JCTree.JCExpressionStatement)env.next.tree;
restype = (TreeInfo.skipParens(execTree.expr) == env.tree) ?
syms.voidType :
syms.objectType;
break;
default:
restype = syms.objectType;
}
List<Type> paramtypes = Type.map(argtypes, new ImplicitArgType(spMethod, resolveContext.step));
List<Type> exType = spMethod != null ?
spMethod.getThrownTypes() :
List.of(syms.throwableType); // make it throw all exceptions
MethodType mtype = new MethodType(paramtypes,
restype,
exType,
syms.methodClass);
return mtype;
}
//where
class ImplicitArgType extends DeferredAttr.DeferredTypeMap {
public ImplicitArgType(Symbol msym, Resolve.MethodResolutionPhase phase) {
rs.deferredAttr.super(AttrMode.SPECULATIVE, msym, phase);
}
public Type apply(Type t) {
t = types.erasure(super.apply(t));
if (t.hasTag(BOT))
// nulls type as the marker type Null (which has no instances)
// infer as java.lang.Void for now
t = types.boxedClass(syms.voidType).type;
return t;
}
}
/**
* This method is used to infer a suitable target SAM in case the original
* SAM type contains one or more wildcards. An inference process is applied
* so that wildcard bounds, as well as explicit lambda/method ref parameters
* (where applicable) are used to constraint the solution.
*/
public Type instantiateFunctionalInterface(DiagnosticPosition pos, Type funcInterface,
List<Type> paramTypes, Check.CheckContext checkContext) {
if (types.capture(funcInterface) == funcInterface) {
//if capture doesn't change the type then return the target unchanged
//(this means the target contains no wildcards!)
return funcInterface;
} else {
Type formalInterface = funcInterface.tsym.type;
InferenceContext funcInterfaceContext =
new InferenceContext(funcInterface.tsym.type.getTypeArguments());
Assert.check(paramTypes != null);
//get constraints from explicit params (this is done by
//checking that explicit param types are equal to the ones
//in the functional interface descriptors)
List<Type> descParameterTypes = types.findDescriptorType(formalInterface).getParameterTypes();
if (descParameterTypes.size() != paramTypes.size()) {
checkContext.report(pos, diags.fragment("incompatible.arg.types.in.lambda"));
return types.createErrorType(funcInterface);
}
for (Type p : descParameterTypes) {
if (!types.isSameType(funcInterfaceContext.asFree(p), paramTypes.head)) {
checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
return types.createErrorType(funcInterface);
}
paramTypes = paramTypes.tail;
}
try {
funcInterfaceContext.solve(funcInterfaceContext.boundedVars(), types.noWarnings);
} catch (InferenceException ex) {
checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
}
List<Type> actualTypeargs = funcInterface.getTypeArguments();
for (Type t : funcInterfaceContext.undetvars) {
UndetVar uv = (UndetVar)t;
if (uv.inst == null) {
uv.inst = actualTypeargs.head;
}
actualTypeargs = actualTypeargs.tail;
}
Type owntype = funcInterfaceContext.asInstType(formalInterface);
if (!chk.checkValidGenericType(owntype)) {
//if the inferred functional interface type is not well-formed,
//or if it's not a subtype of the original target, issue an error
checkContext.report(pos, diags.fragment("no.suitable.functional.intf.inst", funcInterface));
}
return owntype;
}
}
// </editor-fold>
// <editor-fold defaultstate="collapsed" desc="Bound checking">
/**
* Check bounds and perform incorporation
*/
void checkWithinBounds(InferenceContext inferenceContext,
Warner warn) throws InferenceException {
MultiUndetVarListener mlistener = new MultiUndetVarListener(inferenceContext.undetvars);
List<Type> saved_undet = inferenceContext.save();
try {
while (true) {
mlistener.reset();
if (!allowGraphInference) {
//in legacy mode we lack of transitivity, so bound check
//cannot be run in parallel with other incoprporation rounds
for (Type t : inferenceContext.undetvars) {
UndetVar uv = (UndetVar)t;
IncorporationStep.CHECK_BOUNDS.apply(uv, inferenceContext, warn);
}
}
for (Type t : inferenceContext.undetvars) {
UndetVar uv = (UndetVar)t;
//bound incorporation
EnumSet<IncorporationStep> incorporationSteps = allowGraphInference ?
incorporationStepsGraph : incorporationStepsLegacy;
for (IncorporationStep is : incorporationSteps) {
if (is.accepts(uv, inferenceContext)) {
is.apply(uv, inferenceContext, warn);
}
}
}
if (!mlistener.changed || !allowGraphInference) break;
}
}
finally {
mlistener.detach();
if (incorporationCache.size() == MAX_INCORPORATION_STEPS) {
inferenceContext.rollback(saved_undet);
}
incorporationCache.clear();
}
}
//where
/**
* This listener keeps track of changes on a group of inference variable
* bounds. Note: the listener must be detached (calling corresponding
* method) to make sure that the underlying inference variable is
* left in a clean state.
*/
class MultiUndetVarListener implements UndetVar.UndetVarListener {
boolean changed;
List<Type> undetvars;
public MultiUndetVarListener(List<Type> undetvars) {
this.undetvars = undetvars;
for (Type t : undetvars) {
UndetVar uv = (UndetVar)t;
uv.listener = this;
}
}
public void varChanged(UndetVar uv, Set<InferenceBound> ibs) {
//avoid non-termination
if (incorporationCache.size() < MAX_INCORPORATION_STEPS) {
changed = true;
}
}
void reset() {
changed = false;
}
void detach() {
for (Type t : undetvars) {
UndetVar uv = (UndetVar)t;
uv.listener = null;
}
}
};
/** max number of incorporation rounds */
static final int MAX_INCORPORATION_STEPS = 100;
/**
* This enumeration defines an entry point for doing inference variable
* bound incorporation - it can be used to inject custom incorporation
* logic into the basic bound checking routine
*/
enum IncorporationStep {
/**
* Performs basic bound checking - i.e. is the instantiated type for a given
* inference variable compatible with its bounds?
*/
CHECK_BOUNDS() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
uv.substBounds(inferenceContext.inferenceVars(), inferenceContext.instTypes(), infer.types);
infer.checkCompatibleUpperBounds(uv, inferenceContext);
if (uv.inst != null) {
Type inst = uv.inst;
for (Type u : uv.getBounds(InferenceBound.UPPER)) {
if (!isSubtype(inst, inferenceContext.asFree(u), warn, infer)) {
infer.reportBoundError(uv, BoundErrorKind.UPPER);
}
}
for (Type l : uv.getBounds(InferenceBound.LOWER)) {
if (!isSubtype(inferenceContext.asFree(l), inst, warn, infer)) {
infer.reportBoundError(uv, BoundErrorKind.LOWER);
}
}
for (Type e : uv.getBounds(InferenceBound.EQ)) {
if (!isSameType(inst, inferenceContext.asFree(e), infer)) {
infer.reportBoundError(uv, BoundErrorKind.EQ);
}
}
}
}
@Override
boolean accepts(UndetVar uv, InferenceContext inferenceContext) {
//applies to all undetvars
return true;
}
},
/**
* Check consistency of equality constraints. This is a slightly more aggressive
* inference routine that is designed as to maximize compatibility with JDK 7.
* Note: this is not used in graph mode.
*/
EQ_CHECK_LEGACY() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
Type eq = null;
for (Type e : uv.getBounds(InferenceBound.EQ)) {
Assert.check(!inferenceContext.free(e));
if (eq != null && !isSameType(e, eq, infer)) {
infer.reportBoundError(uv, BoundErrorKind.EQ);
}
eq = e;
for (Type l : uv.getBounds(InferenceBound.LOWER)) {
Assert.check(!inferenceContext.free(l));
if (!isSubtype(l, e, warn, infer)) {
infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_LOWER);
}
}
for (Type u : uv.getBounds(InferenceBound.UPPER)) {
if (inferenceContext.free(u)) continue;
if (!isSubtype(e, u, warn, infer)) {
infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_UPPER);
}
}
}
}
},
/**
* Check consistency of equality constraints.
*/
EQ_CHECK() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type e : uv.getBounds(InferenceBound.EQ)) {
if (e.containsAny(inferenceContext.inferenceVars())) continue;
for (Type u : uv.getBounds(InferenceBound.UPPER)) {
if (!isSubtype(e, inferenceContext.asFree(u), warn, infer)) {
infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_UPPER);
}
}
for (Type l : uv.getBounds(InferenceBound.LOWER)) {
if (!isSubtype(inferenceContext.asFree(l), e, warn, infer)) {
infer.reportBoundError(uv, BoundErrorKind.BAD_EQ_LOWER);
}
}
}
}
},
/**
* Given a bound set containing {@code alpha <: T} and {@code alpha :> S}
* perform {@code S <: T} (which could lead to new bounds).
*/
CROSS_UPPER_LOWER() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b1 : uv.getBounds(InferenceBound.UPPER)) {
for (Type b2 : uv.getBounds(InferenceBound.LOWER)) {
isSubtype(inferenceContext.asFree(b2), inferenceContext.asFree(b1), warn , infer);
}
}
}
},
/**
* Given a bound set containing {@code alpha <: T} and {@code alpha == S}
* perform {@code S <: T} (which could lead to new bounds).
*/
CROSS_UPPER_EQ() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b1 : uv.getBounds(InferenceBound.UPPER)) {
for (Type b2 : uv.getBounds(InferenceBound.EQ)) {
isSubtype(inferenceContext.asFree(b2), inferenceContext.asFree(b1), warn, infer);
}
}
}
},
/**
* Given a bound set containing {@code alpha :> S} and {@code alpha == T}
* perform {@code S <: T} (which could lead to new bounds).
*/
CROSS_EQ_LOWER() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b1 : uv.getBounds(InferenceBound.EQ)) {
for (Type b2 : uv.getBounds(InferenceBound.LOWER)) {
isSubtype(inferenceContext.asFree(b2), inferenceContext.asFree(b1), warn, infer);
}
}
}
},
/**
* Given a bound set containing {@code alpha == S} and {@code alpha == T}
* perform {@code S == T} (which could lead to new bounds).
*/
CROSS_EQ_EQ() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b1 : uv.getBounds(InferenceBound.EQ)) {
for (Type b2 : uv.getBounds(InferenceBound.EQ)) {
if (b1 != b2) {
isSameType(inferenceContext.asFree(b2), inferenceContext.asFree(b1), infer);
}
}
}
}
},
/**
* Given a bound set containing {@code alpha <: beta} propagate lower bounds
* from alpha to beta; also propagate upper bounds from beta to alpha.
*/
PROP_UPPER() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b : uv.getBounds(InferenceBound.UPPER)) {
if (inferenceContext.inferenceVars().contains(b)) {
UndetVar uv2 = (UndetVar)inferenceContext.asFree(b);
if (uv2.isCaptured()) continue;
//alpha <: beta
//0. set beta :> alpha
addBound(InferenceBound.LOWER, uv2, inferenceContext.asInstType(uv.qtype), infer);
//1. copy alpha's lower to beta's
for (Type l : uv.getBounds(InferenceBound.LOWER)) {
addBound(InferenceBound.LOWER, uv2, inferenceContext.asInstType(l), infer);
}
//2. copy beta's upper to alpha's
for (Type u : uv2.getBounds(InferenceBound.UPPER)) {
addBound(InferenceBound.UPPER, uv, inferenceContext.asInstType(u), infer);
}
}
}
}
},
/**
* Given a bound set containing {@code alpha :> beta} propagate lower bounds
* from beta to alpha; also propagate upper bounds from alpha to beta.
*/
PROP_LOWER() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b : uv.getBounds(InferenceBound.LOWER)) {
if (inferenceContext.inferenceVars().contains(b)) {
UndetVar uv2 = (UndetVar)inferenceContext.asFree(b);
if (uv2.isCaptured()) continue;
//alpha :> beta
//0. set beta <: alpha
addBound(InferenceBound.UPPER, uv2, inferenceContext.asInstType(uv.qtype), infer);
//1. copy alpha's upper to beta's
for (Type u : uv.getBounds(InferenceBound.UPPER)) {
addBound(InferenceBound.UPPER, uv2, inferenceContext.asInstType(u), infer);
}
//2. copy beta's lower to alpha's
for (Type l : uv2.getBounds(InferenceBound.LOWER)) {
addBound(InferenceBound.LOWER, uv, inferenceContext.asInstType(l), infer);
}
}
}
}
},
/**
* Given a bound set containing {@code alpha == beta} propagate lower/upper
* bounds from alpha to beta and back.
*/
PROP_EQ() {
public void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn) {
Infer infer = inferenceContext.infer();
for (Type b : uv.getBounds(InferenceBound.EQ)) {
if (inferenceContext.inferenceVars().contains(b)) {
UndetVar uv2 = (UndetVar)inferenceContext.asFree(b);
if (uv2.isCaptured()) continue;
//alpha == beta
//0. set beta == alpha
addBound(InferenceBound.EQ, uv2, inferenceContext.asInstType(uv.qtype), infer);
//1. copy all alpha's bounds to beta's
for (InferenceBound ib : InferenceBound.values()) {
for (Type b2 : uv.getBounds(ib)) {
if (b2 != uv2) {
addBound(ib, uv2, inferenceContext.asInstType(b2), infer);
}
}
}
//2. copy all beta's bounds to alpha's
for (InferenceBound ib : InferenceBound.values()) {
for (Type b2 : uv2.getBounds(ib)) {
if (b2 != uv) {
addBound(ib, uv, inferenceContext.asInstType(b2), infer);
}
}
}
}
}
}
};
abstract void apply(UndetVar uv, InferenceContext inferenceContext, Warner warn);
boolean accepts(UndetVar uv, InferenceContext inferenceContext) {
return !uv.isCaptured();
}
boolean isSubtype(Type s, Type t, Warner warn, Infer infer) {
return doIncorporationOp(IncorporationBinaryOpKind.IS_SUBTYPE, s, t, warn, infer);
}
boolean isSameType(Type s, Type t, Infer infer) {
return doIncorporationOp(IncorporationBinaryOpKind.IS_SAME_TYPE, s, t, null, infer);
}
void addBound(InferenceBound ib, UndetVar uv, Type b, Infer infer) {
doIncorporationOp(opFor(ib), uv, b, null, infer);
}
IncorporationBinaryOpKind opFor(InferenceBound boundKind) {
switch (boundKind) {
case EQ:
return IncorporationBinaryOpKind.ADD_EQ_BOUND;
case LOWER:
return IncorporationBinaryOpKind.ADD_LOWER_BOUND;
case UPPER:
return IncorporationBinaryOpKind.ADD_UPPER_BOUND;
default:
Assert.error("Can't get here!");
return null;
}
}
boolean doIncorporationOp(IncorporationBinaryOpKind opKind, Type op1, Type op2, Warner warn, Infer infer) {
IncorporationBinaryOp newOp = infer.new IncorporationBinaryOp(opKind, op1, op2);
Boolean res = infer.incorporationCache.get(newOp);
if (res == null) {
infer.incorporationCache.put(newOp, res = newOp.apply(warn));
}
return res;
}
}
/** incorporation steps to be executed when running in legacy mode */
EnumSet<IncorporationStep> incorporationStepsLegacy = EnumSet.of(IncorporationStep.EQ_CHECK_LEGACY);
/** incorporation steps to be executed when running in graph mode */
EnumSet<IncorporationStep> incorporationStepsGraph =
EnumSet.complementOf(EnumSet.of(IncorporationStep.EQ_CHECK_LEGACY));
/**
* Three kinds of basic operation are supported as part of an incorporation step:
* (i) subtype check, (ii) same type check and (iii) bound addition (either
* upper/lower/eq bound).
*/
enum IncorporationBinaryOpKind {
IS_SUBTYPE() {
@Override
boolean apply(Type op1, Type op2, Warner warn, Types types) {
return types.isSubtypeUnchecked(op1, op2, warn);
}
},
IS_SAME_TYPE() {
@Override
boolean apply(Type op1, Type op2, Warner warn, Types types) {
return types.isSameType(op1, op2);
}
},
ADD_UPPER_BOUND() {
@Override
boolean apply(Type op1, Type op2, Warner warn, Types types) {
UndetVar uv = (UndetVar)op1;
uv.addBound(InferenceBound.UPPER, op2, types);
return true;
}
},
ADD_LOWER_BOUND() {
@Override
boolean apply(Type op1, Type op2, Warner warn, Types types) {
UndetVar uv = (UndetVar)op1;
uv.addBound(InferenceBound.LOWER, op2, types);
return true;
}
},
ADD_EQ_BOUND() {
@Override
boolean apply(Type op1, Type op2, Warner warn, Types types) {
UndetVar uv = (UndetVar)op1;
uv.addBound(InferenceBound.EQ, op2, types);
return true;
}
};
abstract boolean apply(Type op1, Type op2, Warner warn, Types types);
}
/**
* This class encapsulates a basic incorporation operation; incorporation
* operations takes two type operands and a kind. Each operation performed
* during an incorporation round is stored in a cache, so that operations
* are not executed unnecessarily (which would potentially lead to adding
* same bounds over and over).
*/
class IncorporationBinaryOp {
IncorporationBinaryOpKind opKind;
Type op1;
Type op2;
IncorporationBinaryOp(IncorporationBinaryOpKind opKind, Type op1, Type op2) {
this.opKind = opKind;
this.op1 = op1;
this.op2 = op2;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof IncorporationBinaryOp)) {
return false;
} else {
IncorporationBinaryOp that = (IncorporationBinaryOp)o;
return opKind == that.opKind &&
types.isSameType(op1, that.op1, true) &&
types.isSameType(op2, that.op2, true);
}
}
@Override
public int hashCode() {
int result = opKind.hashCode();
result *= 127;
result += types.hashCode(op1);
result *= 127;
result += types.hashCode(op2);
return result;
}
boolean apply(Warner warn) {
return opKind.apply(op1, op2, warn, types);
}
}
/** an incorporation cache keeps track of all executed incorporation-related operations */
Map<IncorporationBinaryOp, Boolean> incorporationCache =
new HashMap<IncorporationBinaryOp, Boolean>();
/**
* Make sure that the upper bounds we got so far lead to a solvable inference
* variable by making sure that a glb exists.
*/
void checkCompatibleUpperBounds(UndetVar uv, InferenceContext inferenceContext) {
List<Type> hibounds =
Type.filter(uv.getBounds(InferenceBound.UPPER), new BoundFilter(inferenceContext));
Type hb = null;
if (hibounds.isEmpty())
hb = syms.objectType;
else if (hibounds.tail.isEmpty())
hb = hibounds.head;
else
hb = types.glb(hibounds);
if (hb == null || hb.isErroneous())
reportBoundError(uv, BoundErrorKind.BAD_UPPER);
}
//where
protected static class BoundFilter implements Filter<Type> {
InferenceContext inferenceContext;
public BoundFilter(InferenceContext inferenceContext) {
this.inferenceContext = inferenceContext;
}
@Override
public boolean accepts(Type t) {
return !t.isErroneous() && !inferenceContext.free(t) &&
!t.hasTag(BOT);
}
};
/**
* This enumeration defines all possible bound-checking related errors.
*/
enum BoundErrorKind {
/**
* The (uninstantiated) inference variable has incompatible upper bounds.
*/
BAD_UPPER() {
@Override
InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
return ex.setMessage("incompatible.upper.bounds", uv.qtype,
uv.getBounds(InferenceBound.UPPER));
}
},
/**
* An equality constraint is not compatible with an upper bound.
*/
BAD_EQ_UPPER() {
@Override
InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
return ex.setMessage("incompatible.eq.upper.bounds", uv.qtype,
uv.getBounds(InferenceBound.EQ), uv.getBounds(InferenceBound.UPPER));
}
},
/**
* An equality constraint is not compatible with a lower bound.
*/
BAD_EQ_LOWER() {
@Override
InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
return ex.setMessage("incompatible.eq.lower.bounds", uv.qtype,
uv.getBounds(InferenceBound.EQ), uv.getBounds(InferenceBound.LOWER));
}
},
/**
* Instantiated inference variable is not compatible with an upper bound.
*/
UPPER() {
@Override
InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
return ex.setMessage("inferred.do.not.conform.to.upper.bounds", uv.inst,
uv.getBounds(InferenceBound.UPPER));
}
},
/**
* Instantiated inference variable is not compatible with a lower bound.
*/
LOWER() {
@Override
InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
return ex.setMessage("inferred.do.not.conform.to.lower.bounds", uv.inst,
uv.getBounds(InferenceBound.LOWER));
}
},
/**
* Instantiated inference variable is not compatible with an equality constraint.
*/
EQ() {
@Override
InapplicableMethodException setMessage(InferenceException ex, UndetVar uv) {
return ex.setMessage("inferred.do.not.conform.to.eq.bounds", uv.inst,
uv.getBounds(InferenceBound.EQ));
}
};
abstract InapplicableMethodException setMessage(InferenceException ex, UndetVar uv);
}
/**
* Report a bound-checking error of given kind
*/
void reportBoundError(UndetVar uv, BoundErrorKind bk) {
throw bk.setMessage(inferenceException, uv);
}
// </editor-fold>
// <editor-fold defaultstate="collapsed" desc="Inference engine">
/**
* Graph inference strategy - act as an input to the inference solver; a strategy is
* composed of two ingredients: (i) find a node to solve in the inference graph,
* and (ii) tell th engine when we are done fixing inference variables
*/
interface GraphStrategy {
/**
* A NodeNotFoundException is thrown whenever an inference strategy fails
* to pick the next node to solve in the inference graph.
*/
public static class NodeNotFoundException extends RuntimeException {
private static final long serialVersionUID = 0;
InferenceGraph graph;
public NodeNotFoundException(InferenceGraph graph) {
this.graph = graph;
}
}
/**
* Pick the next node (leaf) to solve in the graph
*/
Node pickNode(InferenceGraph g) throws NodeNotFoundException;
/**
* Is this the last step?
*/
boolean done();
}
/**
* Simple solver strategy class that locates all leaves inside a graph
* and picks the first leaf as the next node to solve
*/
abstract class LeafSolver implements GraphStrategy {
public Node pickNode(InferenceGraph g) {
if (g.nodes.isEmpty()) {
//should not happen
throw new NodeNotFoundException(g);
};
return g.nodes.get(0);
}
boolean isSubtype(Type s, Type t, Warner warn, Infer infer) {
return doIncorporationOp(IncorporationBinaryOpKind.IS_SUBTYPE, s, t, warn, infer);
}
boolean isSameType(Type s, Type t, Infer infer) {
return doIncorporationOp(IncorporationBinaryOpKind.IS_SAME_TYPE, s, t, null, infer);
}
void addBound(InferenceBound ib, UndetVar uv, Type b, Infer infer) {
doIncorporationOp(opFor(ib), uv, b, null, infer);
}
IncorporationBinaryOpKind opFor(InferenceBound boundKind) {
switch (boundKind) {
case EQ:
return IncorporationBinaryOpKind.ADD_EQ_BOUND;
case LOWER:
return IncorporationBinaryOpKind.ADD_LOWER_BOUND;
case UPPER:
return IncorporationBinaryOpKind.ADD_UPPER_BOUND;
default:
Assert.error("Can't get here!");
return null;
}
}
boolean doIncorporationOp(IncorporationBinaryOpKind opKind, Type op1, Type op2, Warner warn, Infer infer) {
IncorporationBinaryOp newOp = infer.new IncorporationBinaryOp(opKind, op1, op2);
Boolean res = infer.incorporationCache.get(newOp);
if (res == null) {
infer.incorporationCache.put(newOp, res = newOp.apply(warn));
}
return res;
}
}
/**
* This solver uses an heuristic to pick the best leaf - the heuristic
* tries to select the node that has maximal probability to contain one
* or more inference variables in a given list
*/
abstract class BestLeafSolver extends LeafSolver {
/** list of ivars of which at least one must be solved */
List<Type> varsToSolve;
BestLeafSolver(List<Type> varsToSolve) {
this.varsToSolve = varsToSolve;
}
/**
* Computes a path that goes from a given node to the leafs in the graph.
* Typically this will start from a node containing a variable in
* {@code varsToSolve}. For any given path, the cost is computed as the total
* number of type-variables that should be eagerly instantiated across that path.
*/
Pair<List
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