GH-1260 Additional fix to Kotlin type resolution for generics

This is specifically relevant to the way Kotlin represents types. For example List<Message> resolves to List <? extends Message> which becomes the WildCard unlike in Java

Resolves #1260

spring-cloud-function-kotlin/src/test/java/org/springframework/cloud/function/kotlin/KotlinTypeDiscoveryTests.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2019-2025 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 org.springframework.cloud.function.kotlin;
+
+
+
+import java.lang.reflect.Type;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.cloud.function.context.catalog.FunctionTypeUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class KotlinTypeDiscoveryTests {
+
+	@Test
+	public void testOutputInputTypes() {
+		Type functionType = FunctionTypeUtils.discoverFunctionTypeFromClass(KotlinComponentMessageFunction.class);
+		Type outputType = FunctionTypeUtils.getOutputType(functionType);
+		assertThat(FunctionTypeUtils.isMessage(outputType)).isTrue();
+
+		Type inputType = FunctionTypeUtils.getInputType(functionType);
+		assertThat(FunctionTypeUtils.isMessage(inputType)).isTrue();
+	}
+}

spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinComponentMessageFunction.kt

@@ -0,0 +1,15 @@
+package org.springframework.cloud.function.kotlin
+
+import org.springframework.messaging.Message
+import org.springframework.messaging.MessageHeaders
+import org.springframework.messaging.support.MessageBuilder
+import org.springframework.stereotype.Component
+
+import java.util.function.Function
+
+@Component
+class KotlinComponentMessageFunction : (List<Message<Char>>) -> List<Message<Char>> {
+	override fun invoke(input: List<Message<Char>>): List<Message<Char>> {
+		return input
+	}
+}