Fix GenericTypeResolver type-variable collisions

Ahmed El amraouiyine · Ahmed El amraouiyine · commit 2a04d9e32eea · 2026-06-16T12:11:23.000+01:00
Signed-off-by: Ahmed El amraouiyine &lt;ahmed.elamraouiyine@vilavi.fr&gt;
diff --git a/spring-core/src/main/java/org/springframework/core/GenericTypeResolver.java b/spring-core/src/main/java/org/springframework/core/GenericTypeResolver.java
@@ -209,7 +209,7 @@ else if (typeArgument instanceof ParameterizedType) {
 
 	private static ResolvableType resolveVariable(TypeVariable<?> typeVariable, ResolvableType contextType) {
 		ResolvableType resolvedType;
-		if (contextType.hasGenerics()) {
+		if (contextType.hasGenerics() && declaresTypeVariable(typeVariable, contextType)) {
 			ResolvableType.VariableResolver variableResolver = contextType.asVariableResolver();
 			if (variableResolver == null) {
 				return ResolvableType.NONE;
@@ -239,6 +239,11 @@ private static ResolvableType resolveVariable(TypeVariable<?> typeVariable, Reso
 		return ResolvableType.NONE;
 	}
 
+	private static boolean declaresTypeVariable(TypeVariable<?> typeVariable, ResolvableType contextType) {
+		TypeVariable<?> variableToCompare = SerializableTypeWrapper.unwrap(typeVariable);
+		return (variableToCompare.getGenericDeclaration() == contextType.resolve());
+	}
+
 	/**
 	 * Resolve the specified generic type against the given TypeVariable map.
 	 * <p>Used by Spring Data.
diff --git a/spring-core/src/test/java/org/springframework/core/GenericTypeResolverTests.java b/spring-core/src/test/java/org/springframework/core/GenericTypeResolverTests.java
@@ -251,6 +251,14 @@ void resolveTypeFromGenericDefaultMethod() {
 		assertThat(resolvedType).isEqualTo(InheritsDefaultMethod.ConcreteType.class);
 	}
 
+	@Test  // gh-36890
+	void resolveTypeVariableCollisionAcrossInterfaces() {
+		Type type = method(Create.class, "create", Object.class).getGenericParameterTypes()[0];
+		Type resolvedType = resolveType(type, Controller.class);
+
+		assertThat(resolvedType).isEqualTo(Long.class);
+	}
+
 	@Test
 	void resolveTypeFromNestedParameterizedType() {
 		Type resolvedType = resolveType(method(MyInterfaceType.class, "get").getGenericReturnType(), MyCollectionInterfaceType.class);
@@ -504,4 +512,17 @@ static class ConcreteType implements InterfaceWithDefaultMethod.AbstractType {
 		}
 	}
 
+	interface Search<I, O> {
+	}
+
+	interface Create<I, O> {
+
+		default O create(I body) {
+			return null;
+		}
+	}
+
+	static class Controller implements Search<String, Long>, Create<Long, Long> {
+	}
+
 }
