/*
* Copyright 2017 Google Inc. All Rights Reserved.
*
* 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.common.collect.ImmutableSet.toImmutableSet;
import static com.google.errorprone.BugPattern.Category.JDK;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import com.google.common.base.Objects;
import com.google.common.collect.MoreCollectors;
import com.google.common.collect.Streams;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.TypeParameterTree;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.TypeVariableSymbol;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.TreeScanner;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import javax.lang.model.element.Name;
@BugPattern(
name = "TypeParameterShadowing",
summary = "Type parameter declaration overrides another type parameter already declared",
category = JDK,
severity = WARNING
)
public class TypeParameterShadowing extends BugChecker
implements MethodTreeMatcher, ClassTreeMatcher {
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
if (tree.getTypeParameters().isEmpty()) {
return Description.NO_MATCH;
}
return findDuplicatesOf(tree, tree.getTypeParameters(), state);
}
@Override
public Description matchClass(ClassTree tree, VisitorState state) {
if (tree.getTypeParameters().isEmpty()) {
return Description.NO_MATCH;
}
return findDuplicatesOf(tree, tree.getTypeParameters(), state);
}
private Description findDuplicatesOf(
Tree tree, List<? extends TypeParameterTree> typeParameters, VisitorState state) {
Symbol symbol = ASTHelpers.getSymbol(tree);
if (symbol == null) {
return Description.NO_MATCH;
}
List<TypeVariableSymbol> enclosingTypeSymbols = typeVariablesEnclosing(symbol);
if (enclosingTypeSymbols.isEmpty()) {
return Description.NO_MATCH;
}
List<TypeVariableSymbol> conflictingTypeSymbols = new ArrayList<>();
typeParameters.forEach(param ->
enclosingTypeSymbols
.stream()
.filter(tvs -> tvs.name.contentEquals(param.getName()))
.findFirst()
.ifPresent(conflictingTypeSymbols::add));
if (conflictingTypeSymbols.isEmpty()) {
return Description.NO_MATCH;
}
Description.Builder descriptionBuilder = buildDescription(tree);
String message =
"Found aliased type parameters: "
+ conflictingTypeSymbols
.stream()
.map(tvs -> tvs.name + " declared in " + tvs.owner.getSimpleName())
.collect(Collectors.joining("\n"));
descriptionBuilder.setMessage(message);
Set<String> typeVarsInScope =
Streams.concat(enclosingTypeSymbols.stream(), symbol.getTypeParameters().stream())
.map(v -> v.name.toString())
.collect(toImmutableSet());
SuggestedFix.Builder fixBuilder = SuggestedFix.builder();
conflictingTypeSymbols
.stream()
.map(
v ->
renameTypeVariable(
tree,
typeParameters,
v.name,
replacementTypeVarName(v.name, typeVarsInScope),
state))
.forEach(fixBuilder::merge);
descriptionBuilder.addFix(fixBuilder.build());
return descriptionBuilder.build();
}
private static final Pattern TRAILING_DIGIT_EXTRACTOR = Pattern.compile("^(.*?)(\\d+)$");
// T -> T2
// T2 -> T3
// T -> T4 (if T2 and T3 already exist)
private String replacementTypeVarName(Name name, Set<String> superTypeVars) {
String baseName = name.toString();
int typeVarNum = 2;
Matcher matcher = TRAILING_DIGIT_EXTRACTOR.matcher(name);
if (matcher.matches()) {
baseName = matcher.group(1);
typeVarNum = Integer.parseInt(matcher.group(2)) + 1;
}
String replacementName;
while (superTypeVars.contains(replacementName = baseName + typeVarNum)) {
typeVarNum++;
}
return replacementName;
}
private static SuggestedFix renameTypeVariable(
Tree sourceTree,
List<? extends TypeParameterTree> typeParameters,
Name typeVariable,
String typeVarReplacement,
VisitorState state) {
TypeParameterTree matchingTypeParam =
typeParameters.stream().filter(t -> t.getName().contentEquals(typeVariable)).collect(
MoreCollectors.onlyElement());
Symbol typeVariableSymbol = ASTHelpers.getSymbol(matchingTypeParam);
// replace only the type parameter name (and not any upper bounds)
String name = matchingTypeParam.getName().toString();
int pos = ((JCTree) matchingTypeParam).getStartPosition();
SuggestedFix.Builder fixBuilder =
SuggestedFix.builder().replace(pos, pos + name.length(), typeVarReplacement);
((JCTree) sourceTree)
.accept(
new TreeScanner() {
@Override
public void visitIdent(JCTree.JCIdent tree) {
Symbol identSym = ASTHelpers.getSymbol(tree);
if (Objects.equal(identSym, typeVariableSymbol)) {
// Lambda parameters can be desugared early, so we need to make sure the source
// is there. In the example below, we would try to suggest replacing the node 't'
// with T2, since the compiler desugars to g((T t) -> false). The extra condition
// prevents us from doing that.
// Foo<T> {
// <G> void g(Predicate<G> p) {},
// <T> void blah() {
// g(t -> false);
// }
// }
if (Objects.equal(state.getSourceForNode(tree), name)) {
fixBuilder.replace(tree, typeVarReplacement);
}
}
}
});
return fixBuilder.build();
}
private static List<TypeVariableSymbol> typeVariablesEnclosing(Symbol sym) {
List<TypeVariableSymbol> typeVarScopes = new ArrayList<>();
outer:
while (!sym.isStatic()) {
sym = sym.owner;
switch (sym.getKind()) {
case PACKAGE:
break outer;
case METHOD:
case CLASS:
typeVarScopes.addAll(sym.getTypeParameters());
break;
default: // fall out
}
}
return typeVarScopes;
}
}