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/*
* Copyright 2012 The Error Prone Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.errorprone.bugpatterns;
import static com.google.errorprone.util.ASTHelpers.isStatic;
import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableSet;
import com.google.errorprone.VisitorState;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.MemberReferenceTree.ReferenceMode;
import com.sun.source.tree.Tree;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Types;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCAnnotation;
import com.sun.tools.javac.tree.JCTree.JCMemberReference;
import com.sun.tools.javac.tree.TreeScanner;
import com.sun.tools.javac.util.Names;
import java.util.HashSet;
import java.util.Set;
/** Analyzes trees for references to their enclosing instance. */
public class CanBeStaticAnalyzer extends TreeScanner {
/** Returns true if the tree references its enclosing class. */
public static boolean referencesOuter(Tree tree, Symbol owner, VisitorState state) {
CanBeStaticAnalyzer scanner = new CanBeStaticAnalyzer(owner, state);
((JCTree) tree).accept(scanner);
return !scanner.canPossiblyBeStatic || !scanner.outerReferences.isEmpty();
}
public static CanBeStaticResult canBeStaticResult(Tree tree, Symbol owner, VisitorState state) {
CanBeStaticAnalyzer scanner = new CanBeStaticAnalyzer(owner, state);
((JCTree) tree).accept(scanner);
return CanBeStaticResult.of(scanner.canPossiblyBeStatic, scanner.outerReferences);
}
private final Names names;
private final Symbol owner;
private final VisitorState state;
private boolean canPossiblyBeStatic = true;
private final Set outerReferences = new HashSet<>();
private CanBeStaticAnalyzer(Symbol owner, VisitorState state) {
this.owner = owner;
this.state = state;
this.names = state.getNames();
}
@Override
public void visitIdent(JCTree.JCIdent tree) {
// check for unqualified references to instance members (fields and methods) declared
// in an enclosing scope
Symbol sym = tree.sym;
if (sym == null) {
return;
}
if (isStatic(sym)) {
return;
}
switch (sym.getKind()) {
case TYPE_PARAMETER:
// declaring a class as non-static just to access a type parameter is silly -
// why not just re-declare the type parameter instead of capturing it?
// TODO(cushon): consider making the suggestion anyways, maybe with a fix?
// fall through
case FIELD:
if (!isOwnedBy(sym, owner, state.getTypes())) {
canPossiblyBeStatic = false;
}
break;
case METHOD:
if (!isOwnedBy(sym, owner, state.getTypes())) {
outerReferences.add((MethodSymbol) sym);
}
break;
case CLASS:
Type enclosing = tree.type.getEnclosingType();
if (enclosing != null) {
enclosing.accept(new TypeVariableScanner(), null);
}
break;
default:
break;
}
}
private static boolean isOwnedBy(Symbol sym, Symbol owner, Types types) {
if (sym.owner == owner) {
return true;
}
if (owner instanceof TypeSymbol) {
return sym.isMemberOf((TypeSymbol) owner, types);
}
return false;
}
// check for implicit references to type parameters of the enclosing
// class in unqualified references to sibling types, e.g.:
//
// class Test {
// class One {}
// class Two {
// One one; // implicit Test.One
// }
// }
private class TypeVariableScanner extends Types.SimpleVisitor {
@Override
public Void visitTypeVar(Type.TypeVar t, Void unused) {
canPossiblyBeStatic = false;
return null;
}
@Override
public Void visitClassType(Type.ClassType t, Void unused) {
for (Type a : t.getTypeArguments()) {
a.accept(this, null);
}
if (t.getEnclosingType() != null) {
t.getEnclosingType().accept(this, null);
}
return null;
}
@Override
public Void visitType(Type type, Void unused) {
return null;
}
}
@Override
public void visitSelect(JCTree.JCFieldAccess tree) {
super.visitSelect(tree);
// check for qualified this/super references
if (tree.name == names._this || tree.name == names._super) {
canPossiblyBeStatic = false;
}
}
@Override
public void visitNewClass(JCTree.JCNewClass tree) {
super.visitNewClass(tree);
// check for constructor invocations where the type is a member of an enclosing class,
// the enclosing instance is passed as an explicit argument
Type type = ASTHelpers.getType(tree.clazz);
if (type == null) {
return;
}
if (memberOfEnclosing(owner, state, type.tsym)) {
canPossiblyBeStatic = false;
}
}
@Override
public void visitReference(JCMemberReference tree) {
super.visitReference(tree);
if (tree.getMode() != ReferenceMode.NEW) {
return;
}
if (memberOfEnclosing(owner, state, tree.expr.type.tsym)) {
canPossiblyBeStatic = false;
}
}
/** Is sym a non-static member of an enclosing class of currentClass? */
private static boolean memberOfEnclosing(Symbol owner, VisitorState state, Symbol sym) {
if (sym == null || !sym.hasOuterInstance()) {
return false;
}
for (ClassSymbol encl = owner.owner.enclClass();
encl != null;
encl = encl.owner != null ? encl.owner.enclClass() : null) {
if (sym.isMemberOf(encl, state.getTypes())) {
return true;
}
}
return false;
}
@Override
public void visitAnnotation(JCAnnotation tree) {
// skip annotations; the keys of key/value pairs look like unqualified method invocations
}
/** Stores the result of a can-be-static query. */
@AutoValue
public abstract static class CanBeStaticResult {
/**
* Whether the method could *possibly* be static: i.e., this is false if it references an
* instance field.
*/
public abstract boolean canPossiblyBeStatic();
/** Set of instance methods referenced by the method under inspection. */
public abstract ImmutableSet methodsReferenced();
public static CanBeStaticResult of(
boolean canPossiblyBeStatic, Set methodsReferenced) {
return new AutoValue_CanBeStaticAnalyzer_CanBeStaticResult(
canPossiblyBeStatic, ImmutableSet.copyOf(methodsReferenced));
}
}
}
