Accept assignable match for covariant return type

See gh-35936

Author: jhoeller

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

@@ -202,15 +202,15 @@ private static boolean isResolvedTypeMatch(Method genericMethod, Method candidat
 	private static boolean checkResolvedTypeMatch(Method genericMethod, Method candidateMethod, Class<?> clazz) {
 		// First, compare return type.
 		ResolvableType genericReturnType = ResolvableType.forMethodReturnType(genericMethod, clazz);
-		if (!ClassUtils.resolvePrimitiveIfNecessary(candidateMethod.getReturnType()).equals(
-				ClassUtils.resolvePrimitiveIfNecessary(genericReturnType.toClass()))) {
+		if (!ClassUtils.resolvePrimitiveIfNecessary(genericReturnType.toClass()).isAssignableFrom(
+				ClassUtils.resolvePrimitiveIfNecessary(candidateMethod.getReturnType()))) {
 			return false;
 		}
 		Class<?>[] candidateParameters = candidateMethod.getParameterTypes();
 		for (int i = 0; i < candidateParameters.length; i++) {
 			ResolvableType genericParameter = ResolvableType.forMethodParameter(genericMethod, i, clazz);
-			if (!ClassUtils.resolvePrimitiveIfNecessary(candidateParameters[i]).equals(
-					ClassUtils.resolvePrimitiveIfNecessary(genericParameter.toClass()))) {
+			if (!ClassUtils.resolvePrimitiveIfNecessary(genericParameter.toClass()).equals(
+					ClassUtils.resolvePrimitiveIfNecessary(candidateParameters[i]))) {
 				return false;
 			}
 		}

spring-core/src/test/java/org/springframework/core/BridgeMethodResolverTests.java

@@ -113,6 +113,14 @@ else if (method.getName().equals("getValues")) {
 		}
 	}
 
+	@Test
+	void findBridgedMethodForCovariantReturnType() throws Exception {
+		Method originalMethod = OuterSubclass.class.getDeclaredMethod("getInner");
+		for (Method method: OuterSubclass.class.getDeclaredMethods()) {
+			assertThat(BridgeMethodResolver.findBridgedMethod(method)).isEqualTo(originalMethod);
+		}
+	}
+
 	@Test
 	void findBridgedMethodInHierarchyWithBoundedGenerics() throws Exception {
 		Method originalMethod = Bar.class.getDeclaredMethod("someMethod", Object.class, Object.class);
@@ -425,6 +433,7 @@ void someMethod(T theArg, Object otherArg) {
 	public abstract static class SubBar<T extends StringProducer> extends InterBar<T> {
 	}
 
+
 	public interface StringProducer extends CharSequence {
 	}
 
@@ -506,6 +515,31 @@ static class ConcreteMethods implements DefaultMethods {
 	}
 
 
+	static class Outer {
+
+		Inner getInner() {
+			return new Inner();
+		}
+	}
+
+
+	static class OuterSubclass extends Outer {
+
+		@Override
+		InnerSubclass getInner() {
+			return new InnerSubclass();
+		}
+	}
+
+
+	static class Inner {
+	}
+
+
+	static class InnerSubclass extends Inner {
+	}
+
+
 	public static class Enclosing<T> {
 
 		public class Enclosed<S> {
@@ -899,22 +933,18 @@ public interface Receiver<E extends Event> {
 
 
 	public interface MessageBroadcaster extends Receiver<MessageEvent> {
-
 	}
 
 
 	public static class RemovedMessageEvent extends MessageEvent {
-
 	}
 
 
 	public static class NewMessageEvent extends MessageEvent {
-
 	}
 
 
 	public static class ModifiedMessageEvent extends MessageEvent {
-
 	}