Fix a regression with Kotlin generic controllers

This commit reintroduces a more defensive parameter type check that
skips KClass casting for generic parameters.

Closes gh-32510

Author: sdeleuze

spring-core/src/main/java/org/springframework/core/CoroutinesUtils.java

@@ -128,11 +128,9 @@ public static Publisher<?> invokeSuspendingFunction(
 								Object arg = args[index];
 								if (!(parameter.isOptional() && arg == null)) {
 									KType type = parameter.getType();
-									if (!(type.isMarkedNullable() && arg == null)) {
-										KClass<?> kClass = (KClass<?>) type.getClassifier();
-										if (KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
-											arg = KClasses.getPrimaryConstructor(kClass).call(arg);
-										}
+									if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> kClass
+											&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
+										arg = KClasses.getPrimaryConstructor(kClass).call(arg);
 									}
 									argMap.put(parameter, arg);
 								}

spring-core/src/test/kotlin/org/springframework/core/CoroutinesUtilsTests.kt

@@ -226,6 +226,16 @@ class CoroutinesUtilsTests {
 		}
 	}
 
+	@Test
+	fun invokeSuspendingFunctionWithGenericParameter() {
+		val method = GenericController::class.java.declaredMethods.first { it.name.startsWith("handle") }
+		val horse = Animal("horse")
+		val mono = CoroutinesUtils.invokeSuspendingFunction(method, AnimalController(), horse, null) as Mono
+		runBlocking {
+			Assertions.assertThat(mono.awaitSingle()).isEqualTo(horse.name)
+		}
+	}
+
 	suspend fun suspendingFunction(value: String): String {
 		delay(1)
 		return value
@@ -293,6 +303,22 @@ class CoroutinesUtilsTests {
 		return "${this.message}-$limit"
 	}
 
+	interface Named {
+		val name: String
+	}
+
+	data class Animal(override val name: String) : Named
+
+	abstract class GenericController<T : Named> {
+
+		suspend fun handle(named: T): String {
+			delay(1)
+			return named.name;
+		}
+	}
+
+	private class AnimalController : GenericController<Animal>()
+
 	@JvmInline
 	value class ValueClass(val value: String)
 

spring-web/src/main/java/org/springframework/web/method/support/InvocableHandlerMethod.java

@@ -317,11 +317,9 @@ public static Object invokeFunction(Method method, Object target, Object[] args)
 						Object arg = args[index];
 						if (!(parameter.isOptional() && arg == null)) {
 							KType type = parameter.getType();
-							if (!(type.isMarkedNullable() && arg == null)) {
-								KClass<?> kClass = (KClass<?>) type.getClassifier();
-								if (KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
-									arg = KClasses.getPrimaryConstructor(kClass).call(arg);
-								}
+							if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> kClass
+									&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
+								arg = KClasses.getPrimaryConstructor(kClass).call(arg);
 							}
 							argMap.put(parameter, arg);
 						}

spring-web/src/test/kotlin/org/springframework/web/method/support/InvocableHandlerMethodKotlinTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -25,7 +25,7 @@ import org.springframework.web.testfixture.servlet.MockHttpServletRequest
 import org.springframework.web.testfixture.servlet.MockHttpServletResponse
 
 /**
- * Kotlin unit tests for {@link InvocableHandlerMethod}.
+ * Kotlin unit tests for [InvocableHandlerMethod].
  *
  * @author Sebastien Deleuze
  */
@@ -134,6 +134,14 @@ class InvocableHandlerMethodKotlinTests {
 		Assertions.assertThat(value).isEqualTo("foo-20")
 	}
 
+	@Test
+	fun genericParameter() {
+		val horse = Animal("horse")
+		composite.addResolver(StubArgumentResolver(Animal::class.java, horse))
+		val value = getInvocable(AnimalHandler::class.java, Named::class.java).invokeForRequest(request, null)
+		Assertions.assertThat(value).isEqualTo(horse.name)
+	}
+
 	private fun getInvocable(clazz: Class<*>, vararg argTypes: Class<*>): InvocableHandlerMethod {
 		val method = ResolvableMethod.on(clazz).argTypes(*argTypes).resolveMethod()
 		val handlerMethod = InvocableHandlerMethod(clazz.constructors.first().newInstance(), method)
@@ -202,6 +210,19 @@ class InvocableHandlerMethodKotlinTests {
 		}
 	}
 
+	private abstract class GenericHandler<T : Named> {
+
+		fun handle(named: T) = named.name
+	}
+
+	private class AnimalHandler : GenericHandler<Animal>()
+
+	interface Named {
+		val name: String
+	}
+
+	data class Animal(override val name: String) : Named
+
 	@JvmInline
 	value class LongValueClass(val value: Long)
 

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/InvocableHandlerMethod.java

@@ -328,11 +328,9 @@ public static Object invokeFunction(Method method, Object target, Object[] args,
 							Object arg = args[index];
 							if (!(parameter.isOptional() && arg == null)) {
 								KType type = parameter.getType();
-								if (!(type.isMarkedNullable() && arg == null)) {
-									KClass<?> kClass = (KClass<?>) type.getClassifier();
-									if (KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
-										arg = KClasses.getPrimaryConstructor(kClass).call(arg);
-									}
+								if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> kClass
+										&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
+									arg = KClasses.getPrimaryConstructor(kClass).call(arg);
 								}
 								argMap.put(parameter, arg);
 							}

spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/InvocableHandlerMethodKotlinTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -249,6 +249,15 @@ class InvocableHandlerMethodKotlinTests {
 		assertHandlerResultValue(result, "foo-20")
 	}
 
+	@Test
+	fun genericParameter() {
+		val horse = Animal("horse")
+		this.resolvers.add(stubResolver(horse))
+		val method = AnimalController::handle.javaMethod!!
+		val result = invoke(AnimalController(), method, null)
+		assertHandlerResultValue(result, horse.name)
+	}
+
 
 	private fun invokeForResult(handler: Any, method: Method, vararg providedArgs: Any): HandlerResult? {
 		return invoke(handler, method, *providedArgs).block(Duration.ofSeconds(5))
@@ -379,6 +388,19 @@ class InvocableHandlerMethodKotlinTests {
 		}
 	}
 
+	private abstract class GenericController<T : Named> {
+
+		fun handle(named: T) = named.name
+	}
+
+	private class AnimalController : GenericController<Animal>()
+
+	interface Named {
+		val name: String
+	}
+
+	data class Animal(override val name: String) : Named
+
 	@JvmInline
 	value class LongValueClass(val value: Long)