/*
* Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.tools.javac.comp;
import com.sun.source.tree.LambdaExpressionTree.BodyKind;
import com.sun.source.tree.NewClassTree;
import com.sun.tools.javac.code.*;
import com.sun.tools.javac.code.Type.TypeMapping;
import com.sun.tools.javac.comp.ArgumentAttr.LocalCacheContext;
import com.sun.tools.javac.comp.Resolve.ResolveError;
import com.sun.tools.javac.resources.CompilerProperties.Fragments;
import com.sun.tools.javac.tree.*;
import com.sun.tools.javac.util.*;
import com.sun.tools.javac.util.DefinedBy.Api;
import com.sun.tools.javac.util.GraphUtils.DependencyKind;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.comp.Attr.ResultInfo;
import com.sun.tools.javac.comp.Resolve.MethodResolutionPhase;
import com.sun.tools.javac.tree.JCTree.*;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticType;
import com.sun.tools.javac.util.Log.DeferredDiagnosticHandler;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;
import java.util.function.Function;
import static com.sun.tools.javac.code.TypeTag.*;
import static com.sun.tools.javac.tree.JCTree.Tag.*;
/**
* This is an helper class that is used to perform deferred type-analysis.
* Each time a poly expression occurs in argument position, javac attributes it
* with a temporary 'deferred type' that is checked (possibly multiple times)
* against an expected formal type.
*
* <p><b>This is NOT part of any supported API.
* If you write code that depends on this, you do so at your own risk.
* This code and its internal interfaces are subject to change or
* deletion without notice.</b>
*/
public class DeferredAttr extends JCTree.Visitor {
protected static final Context.Key<DeferredAttr> deferredAttrKey = new Context.Key<>();
final Attr attr;
final ArgumentAttr argumentAttr;
final Check chk;
final JCDiagnostic.Factory diags;
final Enter enter;
final Infer infer;
final Resolve rs;
final Log log;
final Symtab syms;
final TreeMaker make;
final TreeCopier<Void> treeCopier;
final TypeMapping<Void> deferredCopier;
final Types types;
final Flow flow;
final Names names;
final TypeEnvs typeEnvs;
public static DeferredAttr instance(Context context) {
DeferredAttr instance = context.get(deferredAttrKey);
if (instance == null)
instance = new DeferredAttr(context);
return instance;
}
protected DeferredAttr(Context context) {
context.put(deferredAttrKey, this);
attr = Attr.instance(context);
argumentAttr = ArgumentAttr.instance(context);
chk = Check.instance(context);
diags = JCDiagnostic.Factory.instance(context);
enter = Enter.instance(context);
infer = Infer.instance(context);
rs = Resolve.instance(context);
log = Log.instance(context);
syms = Symtab.instance(context);
make = TreeMaker.instance(context);
types = Types.instance(context);
flow = Flow.instance(context);
names = Names.instance(context);
stuckTree = make.Ident(names.empty).setType(Type.stuckType);
typeEnvs = TypeEnvs.instance(context);
emptyDeferredAttrContext =
new DeferredAttrContext(AttrMode.CHECK, null, MethodResolutionPhase.BOX, infer.emptyContext, null, null) {
@Override
void addDeferredAttrNode(DeferredType dt, ResultInfo ri, DeferredStuckPolicy deferredStuckPolicy) {
Assert.error("Empty deferred context!");
}
@Override
void complete() {
Assert.error("Empty deferred context!");
}
@Override
public String toString() {
return "Empty deferred context!";
}
};
// For speculative attribution, skip the class definition in <>.
treeCopier =
new TreeCopier<Void>(make) {
@Override @DefinedBy(Api.COMPILER_TREE)
public JCTree visitNewClass(NewClassTree node, Void p) {
JCNewClass t = (JCNewClass) node;
if (TreeInfo.isDiamond(t)) {
JCExpression encl = copy(t.encl, p);
List<JCExpression> typeargs = copy(t.typeargs, p);
JCExpression clazz = copy(t.clazz, p);
List<JCExpression> args = copy(t.args, p);
JCClassDecl def = null;
return make.at(t.pos).NewClass(encl, typeargs, clazz, args, def);
} else {
return super.visitNewClass(node, p);
}
}
};
deferredCopier = new TypeMapping<Void> () {
@Override
public Type visitType(Type t, Void v) {
if (t.hasTag(DEFERRED)) {
DeferredType dt = (DeferredType) t;
return new DeferredType(treeCopier.copy(dt.tree), dt.env);
}
return t;
}
};
}
/** shared tree for stuck expressions */
final JCTree stuckTree;
/**
* This type represents a deferred type. A deferred type starts off with
* no information on the underlying expression type. Such info needs to be
* discovered through type-checking the deferred type against a target-type.
* Every deferred type keeps a pointer to the AST node from which it originated.
*/
public class DeferredType extends Type {
public JCExpression tree;
Env<AttrContext> env;
AttrMode mode;
boolean pertinentToApplicability = true;
SpeculativeCache speculativeCache;
DeferredType(JCExpression tree, Env<AttrContext> env) {
super(null, TypeMetadata.EMPTY);
this.tree = tree;
this.env = attr.copyEnv(env);
this.speculativeCache = new SpeculativeCache();
}
@Override
public DeferredType cloneWithMetadata(TypeMetadata md) {
throw new AssertionError("Cannot add metadata to a deferred type");
}
@Override
public TypeTag getTag() {
return DEFERRED;
}
@Override @DefinedBy(Api.LANGUAGE_MODEL)
public String toString() {
return "DeferredType";
}
/**
* A speculative cache is used to keep track of all overload resolution rounds
* that triggered speculative attribution on a given deferred type. Each entry
* stores a pointer to the speculative tree and the resolution phase in which the entry
* has been added.
*/
class SpeculativeCache {
private Map<Symbol, List<Entry>> cache = new WeakHashMap<>();
class Entry {
JCTree speculativeTree;
ResultInfo resultInfo;
public Entry(JCTree speculativeTree, ResultInfo resultInfo) {
this.speculativeTree = speculativeTree;
this.resultInfo = resultInfo;
}
boolean matches(MethodResolutionPhase phase) {
return resultInfo.checkContext.deferredAttrContext().phase == phase;
}
}
/**
* Retrieve a speculative cache entry corresponding to given symbol
* and resolution phase
*/
Entry get(Symbol msym, MethodResolutionPhase phase) {
List<Entry> entries = cache.get(msym);
if (entries == null) return null;
for (Entry e : entries) {
if (e.matches(phase)) return e;
}
return null;
}
/**
* Stores a speculative cache entry corresponding to given symbol
* and resolution phase
*/
void put(JCTree speculativeTree, ResultInfo resultInfo) {
Symbol msym = resultInfo.checkContext.deferredAttrContext().msym;
List<Entry> entries = cache.get(msym);
if (entries == null) {
entries = List.nil();
}
cache.put(msym, entries.prepend(new Entry(speculativeTree, resultInfo)));
}
}
/**
* Get the type that has been computed during a speculative attribution round
*/
Type speculativeType(Symbol msym, MethodResolutionPhase phase) {
SpeculativeCache.Entry e = speculativeCache.get(msym, phase);
return e != null ? e.speculativeTree.type : Type.noType;
}
JCTree speculativeTree(DeferredAttrContext deferredAttrContext) {
DeferredType.SpeculativeCache.Entry e = speculativeCache.get(deferredAttrContext.msym, deferredAttrContext.phase);
return e != null ? e.speculativeTree : stuckTree;
}
DeferredTypeCompleter completer() {
return basicCompleter;
}
/**
* Check a deferred type against a potential target-type. Depending on
* the current attribution mode, a normal vs. speculative attribution
* round is performed on the underlying AST node. There can be only one
* speculative round for a given target method symbol; moreover, a normal
* attribution round must follow one or more speculative rounds.
*/
Type check(ResultInfo resultInfo) {
DeferredStuckPolicy deferredStuckPolicy;
if (resultInfo.pt.hasTag(NONE) || resultInfo.pt.isErroneous()) {
deferredStuckPolicy = dummyStuckPolicy;
} else if (resultInfo.checkContext.deferredAttrContext().mode == AttrMode.SPECULATIVE ||
resultInfo.checkContext.deferredAttrContext().insideOverloadPhase()) {
deferredStuckPolicy = new OverloadStuckPolicy(resultInfo, this);
} else {
deferredStuckPolicy = new CheckStuckPolicy(resultInfo, this);
}
return check(resultInfo, deferredStuckPolicy, completer());
}
private Type check(ResultInfo resultInfo, DeferredStuckPolicy deferredStuckPolicy,
DeferredTypeCompleter deferredTypeCompleter) {
DeferredAttrContext deferredAttrContext =
resultInfo.checkContext.deferredAttrContext();
Assert.check(deferredAttrContext != emptyDeferredAttrContext);
if (deferredStuckPolicy.isStuck()) {
pertinentToApplicability = false;
deferredAttrContext.addDeferredAttrNode(this, resultInfo, deferredStuckPolicy);
return Type.noType;
} else {
try {
return deferredTypeCompleter.complete(this, resultInfo, deferredAttrContext);
} finally {
mode = deferredAttrContext.mode;
}
}
}
}
/**
* A completer for deferred types. Defines an entry point for type-checking
* a deferred type.
*/
interface DeferredTypeCompleter {
/**
* Entry point for type-checking a deferred type. Depending on the
* circumstances, type-checking could amount to full attribution
* or partial structural check (aka potential applicability).
*/
Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext);
}
/**
* A basic completer for deferred types. This completer type-checks a deferred type
* using attribution; depending on the attribution mode, this could be either standard
* or speculative attribution.
*/
DeferredTypeCompleter basicCompleter = new DeferredTypeCompleter() {
public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
switch (deferredAttrContext.mode) {
case SPECULATIVE:
//Note: if a symbol is imported twice we might do two identical
//speculative rounds...
Assert.check(dt.mode == null || dt.mode == AttrMode.SPECULATIVE);
JCTree speculativeTree = attribSpeculative(dt.tree, dt.env, resultInfo);
dt.speculativeCache.put(speculativeTree, resultInfo);
return speculativeTree.type;
case CHECK:
Assert.check(dt.mode != null);
return attr.attribTree(dt.tree, dt.env, resultInfo);
}
Assert.error();
return null;
}
};
/**
* Policy for detecting stuck expressions. Different criteria might cause
* an expression to be judged as stuck, depending on whether the check
* is performed during overload resolution or after most specific.
*/
interface DeferredStuckPolicy {
/**
* Has the policy detected that a given expression should be considered stuck?
*/
boolean isStuck();
/**
* Get the set of inference variables a given expression depends upon.
*/
Set<Type> stuckVars();
/**
* Get the set of inference variables which might get new constraints
* if a given expression is being type-checked.
*/
Set<Type> depVars();
}
/**
* Basic stuck policy; an expression is never considered to be stuck.
*/
DeferredStuckPolicy dummyStuckPolicy = new DeferredStuckPolicy() {
@Override
public boolean isStuck() {
return false;
}
@Override
public Set<Type> stuckVars() {
return Collections.emptySet();
}
@Override
public Set<Type> depVars() {
return Collections.emptySet();
}
};
/**
* The 'mode' in which the deferred type is to be type-checked
*/
public enum AttrMode {
/**
* A speculative type-checking round is used during overload resolution
* mainly to generate constraints on inference variables. Side-effects
* arising from type-checking the expression associated with the deferred
* type are reversed after the speculative round finishes. This means the
* expression tree will be left in a blank state.
*/
SPECULATIVE,
/**
* This is the plain type-checking mode. Produces side-effects on the underlying AST node
*/
CHECK
}
/**
* Performs speculative attribution of a lambda body and returns the speculative lambda tree,
* in the absence of a target-type. Since {@link Attr#visitLambda(JCLambda)} cannot type-check
* lambda bodies w/o a suitable target-type, this routine 'unrolls' the lambda by turning it
* into a regular block, speculatively type-checks the block and then puts back the pieces.
*/
JCLambda attribSpeculativeLambda(JCLambda that, Env<AttrContext> env, ResultInfo resultInfo) {
ListBuffer<JCStatement> stats = new ListBuffer<>();
stats.addAll(that.params);
if (that.getBodyKind() == JCLambda.BodyKind.EXPRESSION) {
stats.add(make.Return((JCExpression)that.body));
} else {
stats.add((JCBlock)that.body);
}
JCBlock lambdaBlock = make.Block(0, stats.toList());
Env<AttrContext> localEnv = attr.lambdaEnv(that, env);
try {
localEnv.info.returnResult = resultInfo;
JCBlock speculativeTree = (JCBlock)attribSpeculative(lambdaBlock, localEnv, resultInfo);
List<JCVariableDecl> args = speculativeTree.getStatements().stream()
.filter(s -> s.hasTag(Tag.VARDEF))
.map(t -> (JCVariableDecl)t)
.collect(List.collector());
JCTree lambdaBody = speculativeTree.getStatements().last();
if (lambdaBody.hasTag(Tag.RETURN)) {
lambdaBody = ((JCReturn)lambdaBody).expr;
}
JCLambda speculativeLambda = make.Lambda(args, lambdaBody);
attr.preFlow(speculativeLambda);
flow.analyzeLambda(env, speculativeLambda, make, false);
return speculativeLambda;
} finally {
localEnv.info.scope.leave();
}
}
/**
* Routine that performs speculative type-checking; the input AST node is
* cloned (to avoid side-effects cause by Attr) and compiler state is
* restored after type-checking. All diagnostics (but critical ones) are
* disabled during speculative type-checking.
*/
JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {
return attribSpeculative(tree, env, resultInfo, treeCopier,
(newTree)->new DeferredAttrDiagHandler(log, newTree));
}
<Z> JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo, TreeCopier<Z> deferredCopier,
Function<JCTree, DeferredDiagnosticHandler> diagHandlerCreator) {
final JCTree newTree = deferredCopier.copy(tree);
Env<AttrContext> speculativeEnv = env.dup(newTree, env.info.dup(env.info.scope.dupUnshared(env.info.scope.owner)));
speculativeEnv.info.isSpeculative = true;
Log.DeferredDiagnosticHandler deferredDiagnosticHandler = diagHandlerCreator.apply(newTree);
try {
attr.attribTree(newTree, speculativeEnv, resultInfo);
return newTree;
} finally {
new UnenterScanner(env.toplevel.modle).scan(newTree);
log.popDiagnosticHandler(deferredDiagnosticHandler);
}
}
//where
class UnenterScanner extends TreeScanner {
private final ModuleSymbol msym;
public UnenterScanner(ModuleSymbol msym) {
this.msym = msym;
}
@Override
public void visitClassDef(JCClassDecl tree) {
ClassSymbol csym = tree.sym;
//if something went wrong during method applicability check
//it is possible that nested expressions inside argument expression
//are left unchecked - in such cases there's nothing to clean up.
if (csym == null) return;
typeEnvs.remove(csym);
chk.removeCompiled(csym);
chk.clearLocalClassNameIndexes(csym);
syms.removeClass(msym, csym.flatname);
super.visitClassDef(tree);
}
}
static class DeferredAttrDiagHandler extends Log.DeferredDiagnosticHandler {
static class PosScanner extends TreeScanner {
DiagnosticPosition pos;
boolean found = false;
PosScanner(DiagnosticPosition pos) {
this.pos = pos;
}
@Override
public void scan(JCTree tree) {
if (tree != null &&
tree.pos() == pos) {
found = true;
}
super.scan(tree);
}
}
DeferredAttrDiagHandler(Log log, JCTree newTree) {
super(log, new Filter<JCDiagnostic>() {
public boolean accepts(JCDiagnostic d) {
PosScanner posScanner = new PosScanner(d.getDiagnosticPosition());
posScanner.scan(newTree);
return posScanner.found;
}
});
}
}
/**
* A deferred context is created on each method check. A deferred context is
* used to keep track of information associated with the method check, such as
* the symbol of the method being checked, the overload resolution phase,
* the kind of attribution mode to be applied to deferred types and so forth.
* As deferred types are processed (by the method check routine) stuck AST nodes
* are added (as new deferred attribution nodes) to this context. The complete()
* routine makes sure that all pending nodes are properly processed, by
* progressively instantiating all inference variables on which one or more
* deferred attribution node is stuck.
*/
class DeferredAttrContext {
/** attribution mode */
final AttrMode mode;
/** symbol of the method being checked */
final Symbol msym;
/** method resolution step */
final Resolve.MethodResolutionPhase phase;
/** inference context */
final InferenceContext inferenceContext;
/** parent deferred context */
final DeferredAttrContext parent;
/** Warner object to report warnings */
final Warner warn;
/** list of deferred attribution nodes to be processed */
ArrayList<DeferredAttrNode> deferredAttrNodes = new ArrayList<>();
DeferredAttrContext(AttrMode mode, Symbol msym, MethodResolutionPhase phase,
InferenceContext inferenceContext, DeferredAttrContext parent, Warner warn) {
this.mode = mode;
this.msym = msym;
this.phase = phase;
this.parent = parent;
this.warn = warn;
this.inferenceContext = inferenceContext;
}
/**
* Adds a node to the list of deferred attribution nodes - used by Resolve.rawCheckArgumentsApplicable
* Nodes added this way act as 'roots' for the out-of-order method checking process.
*/
void addDeferredAttrNode(final DeferredType dt, ResultInfo resultInfo,
DeferredStuckPolicy deferredStuckPolicy) {
deferredAttrNodes.add(new DeferredAttrNode(dt, resultInfo, deferredStuckPolicy));
}
/**
* Incrementally process all nodes, by skipping 'stuck' nodes and attributing
* 'unstuck' ones. If at any point no progress can be made (no 'unstuck' nodes)
* some inference variable might get eagerly instantiated so that all nodes
* can be type-checked.
*/
void complete() {
while (!deferredAttrNodes.isEmpty()) {
boolean progress = false;
//scan a defensive copy of the node list - this is because a deferred
//attribution round can add new nodes to the list
for (DeferredAttrNode deferredAttrNode : List.from(deferredAttrNodes)) {
if (deferredAttrNode.process(this)) {
deferredAttrNodes.remove(deferredAttrNode);
progress = true;
}
}
if (!progress) {
if (insideOverloadPhase()) {
for (DeferredAttrNode deferredNode: deferredAttrNodes) {
deferredNode.dt.tree.type = Type.noType;
}
return;
}
//remove all variables that have already been instantiated
//from the list of stuck variables
try {
//find stuck expression to unstuck
DeferredAttrNode toUnstuck = pickDeferredNode();
inferenceContext.solveAny(List.from(toUnstuck.deferredStuckPolicy.stuckVars()), warn);
inferenceContext.notifyChange();
} catch (Infer.GraphStrategy.NodeNotFoundException ex) {
//this means that we are in speculative mode and the
//set of contraints are too tight for progess to be made.
//Just leave the remaining expressions as stuck.
break;
}
}
}
}
public boolean insideOverloadPhase() {
DeferredAttrContext dac = this;
if (dac == emptyDeferredAttrContext) {
return false;
}
if (dac.mode == AttrMode.SPECULATIVE) {
return true;
}
return dac.parent.insideOverloadPhase();
}
/**
* Pick the deferred node to be unstuck. The chosen node is the first strongly connected
* component containing exactly one node found in the dependency graph induced by deferred nodes.
* If no such component is found, the first deferred node is returned.
*/
DeferredAttrNode pickDeferredNode() {
List<StuckNode> nodes = deferredAttrNodes.stream()
.map(StuckNode::new)
.collect(List.collector());
//init stuck expression graph; a deferred node A depends on a deferred node B iff
//the intersection between A's input variable and B's output variable is non-empty.
for (StuckNode sn1 : nodes) {
for (Type t : sn1.data.deferredStuckPolicy.stuckVars()) {
for (StuckNode sn2 : nodes) {
if (sn1 != sn2 && sn2.data.deferredStuckPolicy.depVars().contains(t)) {
sn1.deps.add(sn2);
}
}
}
}
//compute tarjan on the stuck graph
List<? extends StuckNode> csn = GraphUtils.tarjan(nodes).get(0);
return csn.length() == 1 ? csn.get(0).data : deferredAttrNodes.get(0);
}
class StuckNode extends GraphUtils.TarjanNode<DeferredAttrNode, StuckNode> {
Set<StuckNode> deps = new HashSet<>();
StuckNode(DeferredAttrNode data) {
super(data);
}
@Override
public DependencyKind[] getSupportedDependencyKinds() {
return new DependencyKind[] { Infer.DependencyKind.STUCK };
}
@Override
public Collection<? extends StuckNode> getDependenciesByKind(DependencyKind dk) {
if (dk == Infer.DependencyKind.STUCK) {
return deps;
} else {
throw new IllegalStateException();
}
}
@Override
public Iterable<? extends StuckNode> getAllDependencies() {
return deps;
}
}
}
/**
* Class representing a deferred attribution node. It keeps track of
* a deferred type, along with the expected target type information.
*/
class DeferredAttrNode {
/** underlying deferred type */
DeferredType dt;
/** underlying target type information */
ResultInfo resultInfo;
/** stuck policy associated with this node */
DeferredStuckPolicy deferredStuckPolicy;
DeferredAttrNode(DeferredType dt, ResultInfo resultInfo, DeferredStuckPolicy deferredStuckPolicy) {
this.dt = dt;
this.resultInfo = resultInfo;
this.deferredStuckPolicy = deferredStuckPolicy;
}
/**
* Process a deferred attribution node.
* Invariant: a stuck node cannot be processed.
*/
@SuppressWarnings("fallthrough")
boolean process(final DeferredAttrContext deferredAttrContext) {
switch (deferredAttrContext.mode) {
case SPECULATIVE:
if (deferredStuckPolicy.isStuck()) {
dt.check(resultInfo, dummyStuckPolicy, new StructuralStuckChecker());
return true;
} else {
Assert.error("Cannot get here");
}
case CHECK:
if (deferredStuckPolicy.isStuck()) {
//stuck expression - see if we can propagate
if (deferredAttrContext.parent != emptyDeferredAttrContext &&
Type.containsAny(deferredAttrContext.parent.inferenceContext.inferencevars,
List.from(deferredStuckPolicy.stuckVars()))) {
deferredAttrContext.parent.addDeferredAttrNode(dt,
resultInfo.dup(new Check.NestedCheckContext(resultInfo.checkContext) {
@Override
public InferenceContext inferenceContext() {
return deferredAttrContext.parent.inferenceContext;
}
@Override
public DeferredAttrContext deferredAttrContext() {
return deferredAttrContext.parent;
}
}), deferredStuckPolicy);
dt.tree.type = Type.stuckType;
return true;
} else {
return false;
}
} else {
Assert.check(!deferredAttrContext.insideOverloadPhase(),
"attribution shouldn't be happening here");
ResultInfo instResultInfo =
resultInfo.dup(deferredAttrContext.inferenceContext.asInstType(resultInfo.pt));
dt.check(instResultInfo, dummyStuckPolicy, basicCompleter);
return true;
}
default:
throw new AssertionError("Bad mode");
}
}
/**
* Structural checker for stuck expressions
*/
class StructuralStuckChecker extends TreeScanner implements DeferredTypeCompleter {
ResultInfo resultInfo;
InferenceContext inferenceContext;
Env<AttrContext> env;
public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
this.resultInfo = resultInfo;
this.inferenceContext = deferredAttrContext.inferenceContext;
this.env = dt.env;
dt.tree.accept(this);
dt.speculativeCache.put(stuckTree, resultInfo);
return Type.noType;
}
@Override
public void visitLambda(JCLambda tree) {
Check.CheckContext checkContext = resultInfo.checkContext;
Type pt = resultInfo.pt;
if (!inferenceContext.inferencevars.contains(pt)) {
//must be a functional descriptor
Type descriptorType = null;
try {
descriptorType = types.findDescriptorType(pt);
} catch (Types.FunctionDescriptorLookupError ex) {
checkContext.report(null, ex.getDiagnostic());
}
if (descriptorType.getParameterTypes().length() != tree.params.length()) {
checkContext.report(tree,
diags.fragment("incompatible.arg.types.in.lambda"));
}
Type currentReturnType = descriptorType.getReturnType();
boolean returnTypeIsVoid = currentReturnType.hasTag(VOID);
if (tree.getBodyKind() == BodyKind.EXPRESSION) {
boolean isExpressionCompatible = !returnTypeIsVoid ||
TreeInfo.isExpressionStatement((JCExpression)tree.getBody());
if (!isExpressionCompatible) {
resultInfo.checkContext.report(tree.pos(),
diags.fragment("incompatible.ret.type.in.lambda",
diags.fragment("missing.ret.val", currentReturnType)));
}
} else {
LambdaBodyStructChecker lambdaBodyChecker =
new LambdaBodyStructChecker();
tree.body.accept(lambdaBodyChecker);
boolean isVoidCompatible = lambdaBodyChecker.isVoidCompatible;
if (returnTypeIsVoid) {
if (!isVoidCompatible) {
resultInfo.checkContext.report(tree.pos(),
diags.fragment("unexpected.ret.val"));
}
} else {
boolean isValueCompatible = lambdaBodyChecker.isPotentiallyValueCompatible
&& !canLambdaBodyCompleteNormally(tree);
if (!isValueCompatible && !isVoidCompatible) {
log.error(tree.body.pos(),
"lambda.body.neither.value.nor.void.compatible");
}
if (!isValueCompatible) {
resultInfo.checkContext.report(tree.pos(),
diags.fragment("incompatible.ret.type.in.lambda",
diags.fragment("missing.ret.val", currentReturnType)));
}
}
}
}
}
boolean canLambdaBodyCompleteNormally(JCLambda tree) {
List<JCVariableDecl> oldParams = tree.params;
LocalCacheContext localCacheContext = argumentAttr.withLocalCacheContext();
try {
tree.params = tree.params.stream()
.map(vd -> make.VarDef(vd.mods, vd.name, make.Erroneous(), null))
.collect(List.collector());
return attribSpeculativeLambda(tree, env, attr.unknownExprInfo).canCompleteNormally;
} finally {
localCacheContext.leave();
tree.params = oldParams;
}
}
@Override
public void visitNewClass(JCNewClass tree) {
//do nothing
}
@Override
public void visitApply(JCMethodInvocation tree) {
//do nothing
}
@Override
public void visitReference(JCMemberReference tree) {
Check.CheckContext checkContext = resultInfo.checkContext;
Type pt = resultInfo.pt;
if (!inferenceContext.inferencevars.contains(pt)) {
try {
types.findDescriptorType(pt);
} catch (Types.FunctionDescriptorLookupError ex) {
checkContext.report(null, ex.getDiagnostic());
}
Env<AttrContext> localEnv = env.dup(tree);
JCExpression exprTree = (JCExpression)attribSpeculative(tree.getQualifierExpression(), localEnv,
attr.memberReferenceQualifierResult(tree));
ListBuffer<Type> argtypes = new ListBuffer<>();
for (Type t : types.findDescriptorType(pt).getParameterTypes()) {
argtypes.append(Type.noType);
}
JCMemberReference mref2 = new TreeCopier<Void>(make).copy(tree);
mref2.expr = exprTree;
Symbol lookupSym =
rs.resolveMemberReference(localEnv, mref2, exprTree.type,
tree.name, argtypes.toList(), List.nil(), rs.arityMethodCheck,
inferenceContext, rs.structuralReferenceChooser).fst;
switch (lookupSym.kind) {
case WRONG_MTH:
case WRONG_MTHS:
//note: as argtypes are erroneous types, type-errors must
//have been caused by arity mismatch
checkContext.report(tree, diags.fragment(Fragments.IncompatibleArgTypesInMref));
break;
case ABSENT_MTH:
case STATICERR:
//if no method found, or method found with wrong staticness, report better message
checkContext.report(tree, ((ResolveError)lookupSym).getDiagnostic(DiagnosticType.FRAGMENT,
tree, exprTree.type.tsym, exprTree.type, tree.name, argtypes.toList(), List.nil()));
break;
}
}
}
}
/* This visitor looks for return statements, its analysis will determine if
* a lambda body is void or value compatible. We must analyze return
* statements contained in the lambda body only, thus any return statement
* contained in an inner class or inner lambda body, should be ignored.
*/
class LambdaBodyStructChecker extends TreeScanner {
boolean isVoidCompatible = true;
boolean isPotentiallyValueCompatible = true;
@Override
public void visitClassDef(JCClassDecl tree) {
// do nothing
}
@Override
public void visitLambda(JCLambda tree) {
// do nothing
}
@Override
public void visitNewClass(JCNewClass tree) {
// do nothing
}
@Override
public void visitReturn(JCReturn tree) {
if (tree.expr != null) {
isVoidCompatible = false;
} else {
isPotentiallyValueCompatible = false;
}
}
}
}
/** an empty deferred attribution context - all methods throw exceptions */
final DeferredAttrContext emptyDeferredAttrContext;
/**
* Map a list of types possibly containing one or more deferred types
* into a list of ordinary types. Each deferred type D is mapped into a type T,
* where T is computed by retrieving the type that has already been
* computed for D during a previous deferred attribution round of the given kind.
*/
class DeferredTypeMap extends TypeMapping<Void> {
DeferredAttrContext deferredAttrContext;
protected DeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
this.deferredAttrContext = new DeferredAttrContext(mode, msym, phase,
infer.emptyContext, emptyDeferredAttrContext, types.noWarnings);
}
@Override
public Type visitType(Type t, Void _unused) {
if (!t.hasTag(DEFERRED)) {
return super.visitType(t, null);
} else {
DeferredType dt = (DeferredType)t;
return typeOf(dt);
}
}
protected Type typeOf(DeferredType dt) {
switch (deferredAttrContext.mode) {
case CHECK:
return dt.tree.type == null ? Type.noType : dt.tree.type;
case SPECULATIVE:
return dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase);
}
Assert.error();
return null;
}
}
/**
* Specialized recovery deferred mapping.
* Each deferred type D is mapped into a type T, where T is computed either by
* (i) retrieving the type that has already been computed for D during a previous
* attribution round (as before), or (ii) by synthesizing a new type R for D
* (the latter step is useful in a recovery scenario).
*/
public class RecoveryDeferredTypeMap extends DeferredTypeMap {
public RecoveryDeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
super(mode, msym, phase != null ? phase : MethodResolutionPhase.BOX);
}
@Override
protected Type typeOf(DeferredType dt) {
Type owntype = super.typeOf(dt);
return owntype == Type.noType ?
recover(dt) : owntype;
}
/**
* Synthesize a type for a deferred type that hasn't been previously
* reduced to an ordinary type. Functional deferred types and conditionals
* are mapped to themselves, in order to have a richer diagnostic
* representation. Remaining deferred types are attributed using
* a default expected type (j.l.Object).
*/
private Type recover(DeferredType dt) {
dt.check(attr.new RecoveryInfo(deferredAttrContext) {
@Override
protected Type check(DiagnosticPosition pos, Type found) {
return chk.checkNonVoid(pos, super.check(pos, found));
}
});
return super.visit(dt);
}
}
/**
* A special tree scanner that would only visit portions of a given tree.
* The set of nodes visited by the scanner can be customized at construction-time.
*/
abstract static class FilterScanner extends com.sun.tools.javac.tree.TreeScanner {
final Filter<JCTree> treeFilter;
FilterScanner(final Set<JCTree.Tag> validTags) {
this.treeFilter = new Filter<JCTree>() {
public boolean accepts(JCTree t) {
return validTags.contains(t.getTag());
}
};
}
@Override
public void scan(JCTree tree) {
if (tree != null) {
if (treeFilter.accepts(tree)) {
super.scan(tree);
} else {
skip(tree);
}
}
}
/**
* handler that is executed when a node has been discarded
*/
void skip(JCTree tree) {}
}
/**
* A tree scanner suitable for visiting the target-type dependent nodes of
* a given argument expression.
*/
static class PolyScanner extends FilterScanner {
PolyScanner() {
super(EnumSet.of(CONDEXPR, PARENS, LAMBDA, REFERENCE));
}
}
/**
* A tree scanner suitable for visiting the target-type dependent nodes nested
* within a lambda expression body.
*/
static class LambdaReturnScanner extends FilterScanner {
LambdaReturnScanner() {
super(EnumSet.of(BLOCK, CASE, CATCH, DOLOOP, FOREACHLOOP,
FORLOOP, IF, RETURN, SYNCHRONIZED, SWITCH, TRY, WHILELOOP));
}
}
/**
* This visitor is used to check that structural expressions conform
* to their target - this step is required as inference could end up
* inferring types that make some of the nested expressions incompatible
* with their corresponding instantiated target
*/
class CheckStuckPolicy extends PolyScanner implements DeferredStuckPolicy, Infer.FreeTypeListener {
Type pt;
InferenceContext inferenceContext;
Set<Type> stuckVars = new LinkedHashSet<>();
Set<Type> depVars = new LinkedHashSet<>();
@Override
public boolean isStuck() {
return !stuckVars.isEmpty();
}
@Override
public Set<Type> stuckVars() {
return stuckVars;
}
@Override
public Set<Type> depVars() {
return depVars;
}
public CheckStuckPolicy(ResultInfo resultInfo, DeferredType dt) {
this.pt = resultInfo.pt;
this.inferenceContext = resultInfo.checkContext.inferenceContext();
scan(dt.tree);
if (!stuckVars.isEmpty()) {
resultInfo.checkContext.inferenceContext()
.addFreeTypeListener(List.from(stuckVars), this);
}
}
@Override
public void typesInferred(InferenceContext inferenceContext) {
stuckVars.clear();
}
@Override
public void visitLambda(JCLambda tree) {
if (inferenceContext.inferenceVars().contains(pt)) {
stuckVars.add(pt);
}
if (!types.isFunctionalInterface(pt)) {
return;
}
Type descType = types.findDescriptorType(pt);
List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());
if (tree.paramKind == JCLambda.ParameterKind.IMPLICIT &&
freeArgVars.nonEmpty()) {
stuckVars.addAll(freeArgVars);
depVars.addAll(inferenceContext.freeVarsIn(descType.getReturnType()));
}
scanLambdaBody(tree, descType.getReturnType());
}
@Override
public void visitReference(JCMemberReference tree) {
scan(tree.expr);
if (inferenceContext.inferenceVars().contains(pt)) {
stuckVars.add(pt);
return;
}
if (!types.isFunctionalInterface(pt)) {
return;
}
Type descType = types.findDescriptorType(pt);
List<Type> freeArgVars = inferenceContext.freeVarsIn(descType.getParameterTypes());
if (freeArgVars.nonEmpty() &&
tree.overloadKind == JCMemberReference.OverloadKind.OVERLOADED) {
stuckVars.addAll(freeArgVars);
depVars.addAll(inferenceContext.freeVarsIn(descType.getReturnType()));
}
}
void scanLambdaBody(JCLambda lambda, final Type pt) {
if (lambda.getBodyKind() == JCTree.JCLambda.BodyKind.EXPRESSION) {
Type prevPt = this.pt;
try {
this.pt = pt;
scan(lambda.body);
} finally {
this.pt = prevPt;
}
} else {
LambdaReturnScanner lambdaScanner = new LambdaReturnScanner() {
@Override
public void visitReturn(JCReturn tree) {
if (tree.expr != null) {
Type prevPt = CheckStuckPolicy.this.pt;
try {
CheckStuckPolicy.this.pt = pt;
CheckStuckPolicy.this.scan(tree.expr);
} finally {
CheckStuckPolicy.this.pt = prevPt;
}
}
}
};
lambdaScanner.scan(lambda.body);
}
}
}
/**
* This visitor is used to check that structural expressions conform
* to their target - this step is required as inference could end up
* inferring types that make some of the nested expressions incompatible
* with their corresponding instantiated target
*/
class OverloadStuckPolicy extends CheckStuckPolicy implements DeferredStuckPolicy {
boolean stuck;
@Override
public boolean isStuck() {
return super.isStuck() || stuck;
}
public OverloadStuckPolicy(ResultInfo resultInfo, DeferredType dt) {
super(resultInfo, dt);
}
@Override
public void visitLambda(JCLambda tree) {
super.visitLambda(tree);
if (tree.paramKind == JCLambda.ParameterKind.IMPLICIT) {
stuck = true;
}
}
@Override
public void visitReference(JCMemberReference tree) {
super.visitReference(tree);
if (tree.overloadKind == JCMemberReference.OverloadKind.OVERLOADED) {
stuck = true;
}
}
}
}