Fix handling of value class with private constructor

See gh-32536

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

@@ -330,7 +330,9 @@ public class InvocableHandlerMethod extends HandlerMethod {
 								KType type = parameter.getType();
 								if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> kClass
 										&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
-									arg = KClasses.getPrimaryConstructor(kClass).call(arg);
+									KFunction<?> valueClassConstructor = KClasses.getPrimaryConstructor(kClass);
+									KCallablesJvm.setAccessible(valueClassConstructor, true);
+									arg = valueClassConstructor.call(arg);
 								}
 								argMap.put(parameter, arg);
 							}

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

@@ -222,6 +222,14 @@ class InvocableHandlerMethodKotlinTests {
 		assertHandlerResultValue(result, "null")
 	}
 
+	@Test
+	fun valueClassWithPrivateConstructor() {
+		this.resolvers.add(stubResolver(1L, Long::class.java))
+		val method = ValueClassController::valueClassWithPrivateConstructor.javaMethod!!
+		val result = invoke(ValueClassController(), method, 1L)
+		assertHandlerResultValue(result, "1")
+	}
+
 	@Test
 	fun propertyAccessor() {
 		this.resolvers.add(stubResolver(null, String::class.java))
@@ -368,6 +376,8 @@ class InvocableHandlerMethodKotlinTests {
 		fun valueClassWithNullable(limit: LongValueClass?) =
 			"${limit?.value}"
 
+		fun valueClassWithPrivateConstructor(limit: ValueClassWithPrivateConstructor) =
+			"${limit.value}"
 	}
 
 	class PropertyAccessorController {
@@ -416,5 +426,12 @@ class InvocableHandlerMethodKotlinTests {
 		}
 	}
 
+	@JvmInline
+	value class ValueClassWithPrivateConstructor private constructor(val value: Long) {
+		companion object {
+			fun from(value: Long) = ValueClassWithPrivateConstructor(value)
+		}
+	}
+
 	class CustomException(message: String) : Throwable(message)
 }