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Don't consider overloads to have a functional interface clash if the …
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…parameters are subtypes of another overload.

JLS defines that more specific overloads win, so, for example, `ImmutableFunction` wins over `Function`.

PiperOrigin-RevId: 530843370
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graememorgan authored and Error Prone Team committed May 10, 2023
1 parent 94a93e9 commit 7335ba2
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Original file line number Diff line number Diff line change
Expand Up @@ -17,10 +17,12 @@
package com.google.errorprone.bugpatterns;

import static com.google.common.collect.ImmutableList.toImmutableList;
import static com.google.common.collect.Streams.zip;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.isSubtype;
import static java.util.stream.Collectors.joining;

import com.google.common.collect.HashMultimap;
Expand All @@ -39,6 +41,7 @@
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symbol.CompletionFailure;
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.comp.Check;
Expand All @@ -58,7 +61,7 @@ public Description matchClass(ClassTree tree, VisitorState state) {
ClassSymbol origin = getSymbol(tree);
Types types = state.getTypes();
// collect declared and inherited methods whose signature contains a functional interface
SetMultimap<String, MethodSymbol> methods = HashMultimap.create();
SetMultimap<String, MethodSymbol> methodsByName = HashMultimap.create();
for (Symbol sym :
types.membersClosure(getType(tree), /* skipInterface= */ false).getSymbols()) {
if (!(sym instanceof MethodSymbol)) {
Expand All @@ -72,7 +75,27 @@ public Description matchClass(ClassTree tree, VisitorState state) {
if (msym.isConstructor() && !msym.owner.equals(origin)) {
continue;
}
methods.put(functionalInterfaceSignature(state, msym), msym);
methodsByName.put(msym.getSimpleName().toString(), msym);
}

// Only consider methods which don't have strictly more specific overloads; these won't actually
// clash.
SetMultimap<String, MethodSymbol> methodsBySignature = HashMultimap.create();
for (MethodSymbol msym : methodsByName.values()) {
if (methodsByName.get(msym.getSimpleName().toString()).stream()
.anyMatch(
o ->
!msym.overrides(o, (TypeSymbol) msym.owner, types, /* checkResult= */ true)
&& !o.equals(msym)
&& o.getParameters().length() == msym.getParameters().length()
&& zip(
msym.getParameters().stream(),
o.getParameters().stream(),
(a, b) -> isSubtype(a.type, b.type, state))
.allMatch(x -> x))) {
continue;
}
methodsBySignature.put(functionalInterfaceSignature(state, msym), msym);
}
// check if any declared members clash with another declared or inherited member
// (don't report clashes between inherited members)
Expand All @@ -86,9 +109,10 @@ public Description matchClass(ClassTree tree, VisitorState state) {
continue;
}
List<MethodSymbol> clash =
new ArrayList<>(methods.removeAll(functionalInterfaceSignature(state, msym)));
new ArrayList<>(methodsBySignature.removeAll(functionalInterfaceSignature(state, msym)));

// Ignore inherited methods that are overridden in the original class. Note that we have to
// Ignore inherited methodsBySignature that are overridden in the original class. Note that we
// have to
// handle transitive inheritance explicitly to handle cases where the visibility of an
// overridden method is expanded somewhere in the type hierarchy.
Deque<MethodSymbol> worklist = new ArrayDeque<>();
Expand All @@ -105,7 +129,7 @@ public Description matchClass(ClassTree tree, VisitorState state) {
}

if (!clash.isEmpty()) {
// ignore if there are overridden clashing methods in class
// ignore if there are overridden clashing methodsBySignature in class
if (ASTHelpers.findSuperMethod(msym, types).isPresent()
&& clash.stream()
.anyMatch(
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Original file line number Diff line number Diff line change
Expand Up @@ -369,4 +369,18 @@ public void positive_overridesInClassAndNewClashingPairInSameClass() {
"}")
.doTest();
}

@Test
public void oneIsMoreSpecific_notAmbiguous() {
testHelper
.addSourceLines(
"Test.java",
"import java.util.function.Consumer;",
"public class Test {",
" void foo(Consumer<String> c) {}",
" void foo(SubConsumer<String> c) {}",
" interface SubConsumer<T> extends Consumer<T> {}",
"}")
.doTest();
}
}

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