8007463: Cleanup inference related classes
Summary: Make Infer.InferenceContext an inner class; adjust bound replacement logic in Type.UndetVar
Reviewed-by: jjg
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* 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
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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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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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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.EnumSet;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.WeakHashMap;
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<DeferredAttr>();
final Attr attr;
final Check chk;
final JCDiagnostic.Factory diags;
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);
diags = JCDiagnostic.Factory.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);
Names names = Names.instance(context);
stuckTree = make.Ident(names.empty).setType(Type.noType);
}
/** 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;
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;
}
}
/**
* 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) {
return check(resultInfo, stuckVars(tree, env, resultInfo), basicCompleter);
}
Type check(ResultInfo resultInfo, List<Type> stuckVars, DeferredTypeCompleter deferredTypeCompleter) {
DeferredAttrContext deferredAttrContext =
resultInfo.checkContext.deferredAttrContext();
Assert.check(deferredAttrContext != emptyDeferredAttrContext);
if (stuckVars.nonEmpty()) {
deferredAttrContext.addDeferredAttrNode(this, resultInfo, stuckVars);
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:
Assert.check(dt.mode == null ||
(dt.mode == AttrMode.SPECULATIVE &&
dt.speculativeType(deferredAttrContext.msym, deferredAttrContext.phase).hasTag(NONE)));
JCTree speculativeTree = attribSpeculative(dt.tree, dt.env, resultInfo);
dt.speculativeCache.put(deferredAttrContext.msym, speculativeTree, deferredAttrContext.phase);
return speculativeTree.type;
case CHECK:
Assert.check(dt.mode == AttrMode.SPECULATIVE);
return attr.attribTree(dt.tree, dt.env, resultInfo);
}
Assert.error();
return null;
}
};
/**
* 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;
final JavaFileObject currentSource = log.currentSourceFile();
Log.DeferredDiagnosticHandler deferredDiagnosticHandler =
new Log.DeferredDiagnosticHandler(log, new Filter<JCDiagnostic>() {
public boolean accepts(JCDiagnostic t) {
return t.getDiagnosticSource().getFile().equals(currentSource);
}
});
try {
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
deferredDiagnosticHandler.reportDeferredDiagnostics();
throw ex;
} finally {
unenterScanner.scan(newTree);
log.popDiagnosticHandler(deferredDiagnosticHandler);
}
}
//where
protected TreeScanner unenterScanner = new TreeScanner() {
@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;
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 LinkedHashSet<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.process()) {
stuckVars.addAll(deferredAttrNode.stuckVars);
} else {
deferredAttrNodes.remove(deferredAttrNode);
progress = true;
}
}
if (!progress) {
//remove all variables that have already been instantiated
//from the list of stuck variables
inferenceContext.solveAny(inferenceContext.freeVarsIn(List.from(stuckVars)));
inferenceContext.notifyChange();
}
}
}
/**
* Class representing a deferred attribution node. It keeps track of
* a deferred type, along with the expected target type information.
*/
class DeferredAttrNode implements Infer.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));
}
/**
* Process a deferred attribution node.
* Invariant: a stuck node cannot be processed.
*/
@SuppressWarnings("fallthrough")
boolean process() {
switch (mode) {
case SPECULATIVE:
dt.check(resultInfo, List.<Type>nil(), new StructuralStuckChecker());
return true;
case CHECK:
if (stuckVars.nonEmpty()) {
return false;
} else {
dt.check(resultInfo, stuckVars, basicCompleter);
return true;
}
default:
throw new AssertionError("Bad mode");
}
}
/**
* Structural checker for stuck expressions
*/
class StructuralStuckChecker extends TreeScanner implements DeferredTypeCompleter {
ResultInfo resultInfo;
public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {
this.resultInfo = resultInfo;
dt.tree.accept(this);
dt.speculativeCache.put(msym, stuckTree, phase);
return Type.noType;
}
@Override
public void visitLambda(JCLambda tree) {
Check.CheckContext checkContext = resultInfo.checkContext;
Type pt = resultInfo.pt;
if (inferenceContext.inferencevars.contains(pt)) {
//ok
return;
} else {
//must be a functional descriptor
try {
Type desc = types.findDescriptorType(pt);
if (desc.getParameterTypes().length() != tree.params.length()) {
checkContext.report(tree, diags.fragment("incompatible.arg.types.in.lambda"));
}
} catch (Types.FunctionDescriptorLookupError ex) {
checkContext.report(null, ex.getDiagnostic());
}
}
}
@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)) {
//ok
return;
} else {
try {
//TODO: we should speculative determine if there's a match
//based on arity - if yes, method is applicable.
types.findDescriptorType(pt);
} catch (Types.FunctionDescriptorLookupError ex) {
checkContext.report(null, ex.getDiagnostic());
}
}
}
}
}
}
/** an empty deferred attribution context - all methods throw exceptions */
final DeferredAttrContext emptyDeferredAttrContext =
new DeferredAttrContext(AttrMode.CHECK, null, MethodResolutionPhase.BOX, 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.hasTag(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 != null ? phase : MethodResolutionPhase.BOX);
}
@Override
protected Type typeOf(DeferredType dt) {
Type owntype = super.typeOf(dt);
return owntype == Type.noType ?
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(attr.new RecoveryInfo(deferredAttrContext));
return super.apply(dt);
}
}
/**
* Retrieves the list of inference variables that need to be inferred before
* an AST node can be type-checked
*/
@SuppressWarnings("fallthrough")
List<Type> stuckVars(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {
if (resultInfo.pt.hasTag(NONE) || resultInfo.pt.isErroneous()) {
return List.nil();
} else {
return stuckVarsInternal(tree, resultInfo.pt, resultInfo.checkContext.inferenceContext());
}
}
//where
private List<Type> stuckVarsInternal(JCTree tree, Type pt, Infer.InferenceContext inferenceContext) {
StuckChecker sc = new StuckChecker(pt, inferenceContext);
sc.scan(tree);
return List.from(sc.stuckVars);
}
/**
* 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 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
*/
abstract 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));
}
@Override
void skip(JCTree tree) {
//do nothing
}
}
/**
* 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, RETURN, SYNCHRONIZED, SWITCH, TRY, WHILELOOP));
}
@Override
void skip(JCTree tree) {
//do nothing
}
}
/**
* 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 StuckChecker extends PolyScanner {
Type pt;
Infer.InferenceContext inferenceContext;
Set<Type> stuckVars = new LinkedHashSet<Type>();
StuckChecker(Type pt, Infer.InferenceContext inferenceContext) {
this.pt = pt;
this.inferenceContext = inferenceContext;
}
@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);
}
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());
stuckVars.addAll(freeArgVars);
}
void scanLambdaBody(JCLambda lambda, final Type pt) {
if (lambda.getBodyKind() == JCTree.JCLambda.BodyKind.EXPRESSION) {
stuckVars.addAll(stuckVarsInternal(lambda.body, pt, inferenceContext));
} else {
LambdaReturnScanner lambdaScanner = new LambdaReturnScanner() {
@Override
public void visitReturn(JCReturn tree) {
if (tree.expr != null) {
stuckVars.addAll(stuckVarsInternal(tree.expr, pt, inferenceContext));
}
}
};
lambdaScanner.scan(lambda.body);
}
}
}
}