7177387: Add target-typing support in method context
Summary: Add support for deferred types and speculative attribution
Reviewed-by: jjg, dlsmith
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* accompanied this code).
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package com.sun.tools.javac.comp;
import com.sun.tools.javac.code.*;
import com.sun.tools.javac.tree.*;
import com.sun.tools.javac.util.*;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.code.Type.*;
import com.sun.tools.javac.comp.Attr.ResultInfo;
import com.sun.tools.javac.comp.Infer.InferenceContext;
import com.sun.tools.javac.comp.Resolve.MethodResolutionPhase;
import com.sun.tools.javac.tree.JCTree.*;
import javax.tools.JavaFileObject;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.WeakHashMap;
import static com.sun.tools.javac.code.TypeTags.*;
import static com.sun.tools.javac.tree.JCTree.Tag.*;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
/**
* 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<DeferredAttr>();
final Attr attr;
final Check chk;
final Enter enter;
final Infer infer;
final Log log;
final Symtab syms;
final TreeMaker make;
final Types types;
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);
chk = Check.instance(context);
enter = Enter.instance(context);
infer = Infer.instance(context);
log = Log.instance(context);
syms = Symtab.instance(context);
make = TreeMaker.instance(context);
types = Types.instance(context);
}
/**
* 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;
SpeculativeCache speculativeCache;
DeferredType(JCExpression tree, Env<AttrContext> env) {
super(DEFERRED, null);
this.tree = tree;
this.env = env.dup(tree, env.info.dup());
this.speculativeCache = new SpeculativeCache();
}
/**
* 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<Symbol, List<Entry>>();
class Entry {
JCTree speculativeTree;
Resolve.MethodResolutionPhase phase;
public Entry(JCTree speculativeTree, MethodResolutionPhase phase) {
this.speculativeTree = speculativeTree;
this.phase = phase;
}
boolean matches(Resolve.MethodResolutionPhase phase) {
return this.phase == phase;
}
}
/**
* Clone a speculative cache entry as a fresh entry associated
* with a new method (this maybe required to fixup speculative cache
* misses after Resolve.access())
*/
void dupAllTo(Symbol from, Symbol to) {
Assert.check(cache.get(to) == null);
List<Entry> entries = cache.get(from);
if (entries != null) {
cache.put(to, entries);
}
}
/**
* 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(Symbol msym, JCTree speculativeTree, MethodResolutionPhase phase) {
List<Entry> entries = cache.get(msym);
if (entries == null) {
entries = List.nil();
}
cache.put(msym, entries.prepend(new Entry(speculativeTree, phase)));
}
}
/**
* 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;
}
/**
* 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) {
DeferredAttrContext deferredAttrContext =
resultInfo.checkContext.deferredAttrContext();
Assert.check(deferredAttrContext != emptyDeferredAttrContext);
List<Type> stuckVars = stuckVars(tree, resultInfo);
if (stuckVars.nonEmpty()) {
deferredAttrContext.addDeferredAttrNode(this, resultInfo, stuckVars);
return Type.noType;
} else {
try {
switch (deferredAttrContext.mode) {
case SPECULATIVE:
Assert.check(mode == null ||
(mode == AttrMode.SPECULATIVE &&
speculativeType(deferredAttrContext.msym, deferredAttrContext.phase).tag == NONE));
JCTree speculativeTree = attribSpeculative(tree, env, resultInfo);
speculativeCache.put(deferredAttrContext.msym, speculativeTree, deferredAttrContext.phase);
return speculativeTree.type;
case CHECK:
Assert.check(mode == AttrMode.SPECULATIVE);
return attr.attribTree(tree, env, resultInfo);
}
Assert.error();
return null;
} finally {
mode = deferredAttrContext.mode;
}
}
}
}
/**
* 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;
}
/**
* 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) {
JCTree newTree = new TreeCopier<Object>(make).copy(tree);
Env<AttrContext> speculativeEnv = env.dup(newTree, env.info.dup(env.info.scope.dupUnshared()));
speculativeEnv.info.scope.owner = env.info.scope.owner;
Filter<JCDiagnostic> prevDeferDiagsFilter = log.deferredDiagFilter;
Queue<JCDiagnostic> prevDeferredDiags = log.deferredDiagnostics;
final JavaFileObject currentSource = log.currentSourceFile();
try {
log.deferredDiagnostics = new ListBuffer<JCDiagnostic>();
log.deferredDiagFilter = new Filter<JCDiagnostic>() {
public boolean accepts(JCDiagnostic t) {
return t.getDiagnosticSource().getFile().equals(currentSource);
}
};
attr.attribTree(newTree, speculativeEnv, resultInfo);
unenterScanner.scan(newTree);
return newTree;
} catch (Abort ex) {
//if some very bad condition occurred during deferred attribution
//we should dump all errors before killing javac
log.reportDeferredDiagnostics();
throw ex;
} finally {
unenterScanner.scan(newTree);
log.deferredDiagFilter = prevDeferDiagsFilter;
log.deferredDiagnostics = prevDeferredDiags;
}
}
//where
protected TreeScanner unenterScanner = new TreeScanner() {
@Override
public void visitClassDef(JCClassDecl tree) {
ClassSymbol csym = tree.sym;
enter.typeEnvs.remove(csym);
chk.compiled.remove(csym.flatname);
syms.classes.remove(csym.flatname);
super.visitClassDef(tree);
}
};
/**
* 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;
/** list of deferred attribution nodes to be processed */
ArrayList<DeferredAttrNode> deferredAttrNodes = new ArrayList<DeferredAttrNode>();
DeferredAttrContext(AttrMode mode, Symbol msym, MethodResolutionPhase phase, InferenceContext inferenceContext) {
this.mode = mode;
this.msym = msym;
this.phase = phase;
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, List<Type> stuckVars) {
deferredAttrNodes.add(new DeferredAttrNode(dt, resultInfo, stuckVars));
}
/**
* 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()) {
Set<Type> stuckVars = new HashSet<Type>();
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.isStuck()) {
deferredAttrNode.process();
deferredAttrNodes.remove(deferredAttrNode);
progress = true;
} else {
stuckVars.addAll(deferredAttrNode.stuckVars);
}
}
if (!progress) {
//remove all variables that have already been instantiated
//from the list of stuck variables
inferenceContext.solveAny(inferenceContext.freeVarsIn(List.from(stuckVars)), types, infer);
inferenceContext.notifyChange(types);
}
}
}
/**
* Class representing a deferred attribution node. It keeps track of
* a deferred type, along with the expected target type information.
*/
class DeferredAttrNode implements Infer.InferenceContext.FreeTypeListener {
/** underlying deferred type */
DeferredType dt;
/** underlying target type information */
ResultInfo resultInfo;
/** list of uninferred inference variables causing this node to be stuck */
List<Type> stuckVars;
DeferredAttrNode(DeferredType dt, ResultInfo resultInfo, List<Type> stuckVars) {
this.dt = dt;
this.resultInfo = resultInfo;
this.stuckVars = stuckVars;
if (!stuckVars.isEmpty()) {
resultInfo.checkContext.inferenceContext().addFreeTypeListener(stuckVars, this);
}
}
@Override
public void typesInferred(InferenceContext inferenceContext) {
stuckVars = List.nil();
resultInfo = resultInfo.dup(inferenceContext.asInstType(resultInfo.pt, types));
}
/**
* is this node stuck?
*/
boolean isStuck() {
return stuckVars.nonEmpty();
}
/**
* Process a deferred attribution node.
* Invariant: a stuck node cannot be processed.
*/
void process() {
if (isStuck()) {
throw new IllegalStateException("Cannot process a stuck deferred node");
}
dt.check(resultInfo);
}
}
}
/** an empty deferred attribution context - all methods throw exceptions */
final DeferredAttrContext emptyDeferredAttrContext =
new DeferredAttrContext(null, null, null, null) {
@Override
void addDeferredAttrNode(DeferredType dt, ResultInfo ri, List<Type> stuckVars) {
Assert.error("Empty deferred context!");
}
@Override
void complete() {
Assert.error("Empty deferred context!");
}
};
/**
* 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 Type.Mapping {
DeferredAttrContext deferredAttrContext;
protected DeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
super(String.format("deferredTypeMap[%s]", mode));
this.deferredAttrContext = new DeferredAttrContext(mode, msym, phase, infer.emptyContext);
}
protected boolean validState(DeferredType dt) {
return dt.mode != null &&
deferredAttrContext.mode.ordinal() <= dt.mode.ordinal();
}
@Override
public Type apply(Type t) {
if (t.tag != DEFERRED) {
return t.map(this);
} else {
DeferredType dt = (DeferredType)t;
Assert.check(validState(dt));
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);
}
@Override
protected Type typeOf(DeferredType dt) {
Type owntype = super.typeOf(dt);
return owntype.tag == NONE ?
recover(dt) : owntype;
}
@Override
protected boolean validState(DeferredType dt) {
return true;
}
/**
* 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(new RecoveryInfo());
switch (TreeInfo.skipParens(dt.tree).getTag()) {
case LAMBDA:
case REFERENCE:
case CONDEXPR:
//propagate those deferred types to the
//diagnostic formatter
return dt;
default:
return super.apply(dt);
}
}
class RecoveryInfo extends ResultInfo {
public RecoveryInfo() {
attr.super(Kinds.VAL, Type.recoveryType, new Check.NestedCheckContext(chk.basicHandler) {
@Override
public DeferredAttrContext deferredAttrContext() {
return deferredAttrContext;
}
@Override
public boolean compatible(Type found, Type req, Warner warn) {
return true;
}
@Override
public void report(DiagnosticPosition pos, JCDiagnostic details) {
//do nothing
}
});
}
@Override
protected Type check(DiagnosticPosition pos, Type found) {
return chk.checkNonVoid(pos, super.check(pos, found));
}
}
}
/**
* Retrieves the list of inference variables that need to be inferred before
* an AST node can be type-checked
*/
@SuppressWarnings("fallthrough")
List<Type> stuckVars(JCExpression tree, ResultInfo resultInfo) {
switch (tree.getTag()) {
case LAMBDA:
case REFERENCE:
Assert.error("not supported yet");
default:
return List.nil();
}
}
}