[fixes projectlombok#3225] Handle ambiguous extension methods

src/eclipseAgent/lombok/eclipse/agent/PatchExtensionMethod.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012-2023 The Project Lombok Authors.
+ * Copyright (C) 2012-2024 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -321,9 +321,11 @@ public static TypeBinding resolveType(TypeBinding resolvedType, MessageSend meth
 				MethodBinding fixedBinding = scope.getMethod(extensionMethod.declaringClass, methodCall.selector, argumentTypes.toArray(new TypeBinding[0]), methodCall);
 				if (fixedBinding instanceof ProblemMethodBinding) {
 					methodCall.arguments = originalArgs;
-					if (fixedBinding.declaringClass != null) {
-						PostponedInvalidMethodError.invoke(scope.problemReporter(), methodCall, fixedBinding, scope);
+					// Sometimes the declaring class is null, in that case we have to create a new ProblemMethodBinding using the extension method's declaring class
+					if (fixedBinding.declaringClass == null) {
+						fixedBinding = new ProblemMethodBinding(fixedBinding.selector, fixedBinding.parameters, extensionMethod.declaringClass, fixedBinding.problemId());
 					}
+					PostponedInvalidMethodError.invoke(scope.problemReporter(), methodCall, fixedBinding, scope);
 				} else {
 					// If the extension method uses varargs, the last fixed binding parameter is an array but 
 					// the method arguments are not. Even thought we already know that the method is fine we still

test/transform/resource/after-delombok/ExtensionMethodAmbiguousFunctional.java

@@ -0,0 +1,17 @@
+//skip-idempotent
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+class ExtensionMethodAmbiguousFunctional {
+	public void test() {
+		ExtensionMethodAmbiguousFunctional.Extensions.ambiguous("", System.out::println);
+	}
+
+	static class Extensions {
+		public static <T, R> void ambiguous(T t, Function<T, R> function) {
+		}
+
+		public static <T> void ambiguous(T t, Consumer<T> function) {
+		}
+	}
+}

test/transform/resource/after-ecj/ExtensionMethodAmbiguousFunctional.java

@@ -0,0 +1,20 @@
+import java.util.function.Consumer;
+import java.util.function.Function;
+import lombok.experimental.ExtensionMethod;
+@ExtensionMethod({ExtensionMethodAmbiguousFunctional.Extensions.class}) class ExtensionMethodAmbiguousFunctional {
+  static class Extensions {
+    Extensions() {
+      super();
+    }
+    public static <T, R>void ambiguous(T t, Function<T, R> function) {
+    }
+    public static <T>void ambiguous(T t, Consumer<T> function) {
+    }
+  }
+  ExtensionMethodAmbiguousFunctional() {
+    super();
+  }
+  public void test() {
+    "".ambiguous(System.out::println);
+  }
+}

test/transform/resource/before/ExtensionMethodAmbiguousFunctional.java

@@ -0,0 +1,20 @@
+//version 8:
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import lombok.experimental.ExtensionMethod;
+
+@ExtensionMethod({ExtensionMethodAmbiguousFunctional.Extensions.class})
+class ExtensionMethodAmbiguousFunctional {
+	public void test() {
+		"".ambiguous(System.out::println);
+	}
+
+	static class Extensions {
+		public static <T, R> void ambiguous(T t, Function<T, R> function) {
+		}
+
+		public static <T> void ambiguous(T t, Consumer<T> function) {
+		}
+	}
+}

test/transform/resource/messages-delombok/ExtensionMethodAmbiguousFunctional.java.messages

@@ -0,0 +1 @@
+9 reference to ambiguous is ambiguous both method <T,R>ambiguous(T,java.util.function.Function<T,R>) in ExtensionMethodAmbiguousFunctional.Extensions and method <T>ambiguous(T,java.util.function.Consumer<T>) in ExtensionMethodAmbiguousFunctional.Extensions match

test/transform/resource/messages-ecj/ExtensionMethodAmbiguousFunctional.java.messages

@@ -0,0 +1 @@
+10 The method ambiguous(String, Function<String,Object>) is ambiguous for the type ExtensionMethodAmbiguousFunctional.Extensions