From 5be0d9ca72c19723f895603850e5a16c3a84fdc6 Mon Sep 17 00:00:00 2001
From: Carter Kozak <ckozak@ckozak.net>
Date: Wed, 1 Jul 2020 09:02:28 -0400
Subject: [PATCH] fix #1431: Avoid rewriting lambdas into ambiguous references
 (#1432)

Avoid rewriting lambdas into ambiguous references
---
 .../errorprone/LambdaMethodReference.java     |  9 +++----
 .../errorprone/LambdaMethodReferenceTest.java | 25 +++++++++++++++++++
 changelog/@unreleased/pr-1432.v2.yml          |  5 ++++
 3 files changed, 33 insertions(+), 6 deletions(-)
 create mode 100644 changelog/@unreleased/pr-1432.v2.yml

diff --git a/baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/LambdaMethodReference.java b/baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/LambdaMethodReference.java
index 188a51a00..3fad79386 100644
--- a/baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/LambdaMethodReference.java
+++ b/baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/LambdaMethodReference.java
@@ -59,8 +59,6 @@
 @SuppressWarnings("checkstyle:CyclomaticComplexity")
 public final class LambdaMethodReference extends BugChecker implements BugChecker.LambdaExpressionTreeMatcher {
 
-    private static final String MESSAGE = "Lambda should be a method reference";
-
     @Override
     public Description matchLambdaExpression(LambdaExpressionTree tree, VisitorState state) {
         LambdaExpressionTree.BodyKind bodyKind = tree.getBodyKind();
@@ -150,8 +148,7 @@ private Description convertVariableInstanceMethods(
             return Description.NO_MATCH;
         }
         return buildFix(methodSymbol, methodInvocation, root, state, isLocal(methodInvocation))
-                .map(fix ->
-                        buildDescription(root).setMessage(MESSAGE).addFix(fix).build())
+                .map(fix -> buildDescription(root).addFix(fix).build())
                 .orElse(Description.NO_MATCH);
     }
 
@@ -170,8 +167,8 @@ private Description convertMethodInvocations(
         }
 
         return buildFix(methodSymbol, methodInvocation, root, state, isLocal(methodInvocation))
-                .map(fix ->
-                        buildDescription(root).setMessage(MESSAGE).addFix(fix).build())
+                .filter(fix -> SuggestedFixes.compilesWithFix(fix, state))
+                .map(fix -> buildDescription(root).addFix(fix).build())
                 .orElse(Description.NO_MATCH);
     }
 
diff --git a/baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/LambdaMethodReferenceTest.java b/baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/LambdaMethodReferenceTest.java
index b2bd0c435..33b1d7169 100644
--- a/baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/LambdaMethodReferenceTest.java
+++ b/baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/LambdaMethodReferenceTest.java
@@ -727,4 +727,29 @@ public void testGuavaToJavaUtilOptional() {
                 .expectUnchanged()
                 .doTest();
     }
+
+    @Test
+    public void testSuperAmbiguous() {
+        refactor()
+                .addInputLines(
+                        "Test.java",
+                        "import java.util.function.BiConsumer;",
+                        "import java.util.function.Consumer;",
+                        "class Test {",
+                        "  interface One {",
+                        "    void call(Consumer<String> a);",
+                        "    void call(BiConsumer<String, String> a);",
+                        "  }",
+                        "  interface Two {",
+                        "    void apply(String a, String b);",
+                        "    void apply(String a);",
+                        "  }",
+                        "  void f(One one, Two two) {",
+                        // Lambda conversion requires a cast which wouldn't necessarily be cleaner.
+                        "    one.call(value -> two.apply(value));",
+                        "  }",
+                        "}")
+                .expectUnchanged()
+                .doTest();
+    }
 }
diff --git a/changelog/@unreleased/pr-1432.v2.yml b/changelog/@unreleased/pr-1432.v2.yml
new file mode 100644
index 000000000..9df9b3ac5
--- /dev/null
+++ b/changelog/@unreleased/pr-1432.v2.yml
@@ -0,0 +1,5 @@
+type: fix
+fix:
+  description: Avoid rewriting lambdas into ambiguous references
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/1432