From fc7ed29838cc092056658e61238ecc49a4ea45ce Mon Sep 17 00:00:00 2001
From: Marc Bruggmann <mbruggmann@users.noreply.github.com>
Date: Thu, 4 Jul 2024 17:12:51 +0200
Subject: [PATCH] Don't use lambdas for methods with type parameters. (#310)

See the re-enabled testcase.
Fixes #309
---
 .../staticanalysis/UseLambdaForFunctionalInterface.java      | 5 +++++
 .../staticanalysis/UseLambdaForFunctionalInterfaceTest.java  | 1 -
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterface.java b/src/main/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterface.java
index bd6367896..ba3296dfd 100644
--- a/src/main/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterface.java
+++ b/src/main/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterface.java
@@ -96,6 +96,11 @@ public J visitNewClass(J.NewClass newClass, ExecutionContext ctx) {
                         StringBuilder templateBuilder = new StringBuilder();
                         J.MethodDeclaration methodDeclaration = (J.MethodDeclaration) n.getBody().getStatements().get(0);
 
+                        // If the functional interface method has type parameters, we can't replace it with a lambda.
+                        if (methodDeclaration.getTypeParameters() != null && !methodDeclaration.getTypeParameters().isEmpty()) {
+                            return n;
+                        }
+
                         if (methodDeclaration.getParameters().get(0) instanceof J.Empty) {
                             templateBuilder.append("() -> {");
                         } else {
diff --git a/src/test/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterfaceTest.java b/src/test/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterfaceTest.java
index dd30a98a2..06bc31140 100644
--- a/src/test/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterfaceTest.java
+++ b/src/test/java/org/openrewrite/staticanalysis/UseLambdaForFunctionalInterfaceTest.java
@@ -736,7 +736,6 @@ public MapDropdownChoice(Supplier<? extends Map<K, ? extends V>> choiceMap) {
         );
     }
 
-    @Disabled
     @Test
     @Issue("https://github.com/openrewrite/rewrite-static-analysis/issues/309")
     void dontUseLambdaForMethodWithTypeParameter() {