GenericTypeResolver returns null for entirely unresolvable type arguments only

Issue: SPR-11763

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

@@ -243,10 +243,10 @@ public abstract class GenericTypeResolver {
 	 */
 	public static Class<?>[] resolveTypeArguments(Class<?> clazz, Class<?> genericIfc) {
 		ResolvableType type = ResolvableType.forClass(clazz).as(genericIfc);
-		if (!type.hasGenerics() || type.hasUnresolvableGenerics()) {
+		if (!type.hasGenerics() || type.isEntirelyUnresolvable()) {
 			return null;
 		}
-		return type.resolveGenerics();
+		return type.resolveGenerics(Object.class);
 	}
 
 	/**

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

@@ -416,7 +416,24 @@ public final class ResolvableType implements Serializable {
 	}
 
 	/**
-	 * Determine whether the underlying type has unresolvable generics:
+	 * Return {@code true} if this type contains unresolvable generics only,
+	 * that is, no substitute for any of its declared type variables.
+	 */
+	boolean isEntirelyUnresolvable() {
+		if (this == NONE) {
+			return false;
+		}
+		ResolvableType[] generics = getGenerics();
+		for (ResolvableType generic : generics) {
+			if (!generic.isUnresolvableTypeVariable() && !generic.isWildcardWithoutBounds()) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	/**
+	 * Determine whether the underlying type has any unresolvable generics:
 	 * either through an unresolvable type variable on the type itself
 	 * or through implementing a generic interface in a raw fashion,
 	 * i.e. without substituting that interface's type variables.
@@ -634,8 +651,8 @@ public final class ResolvableType implements Serializable {
 	/**
 	 * Convenience method that will {@link #getGeneric(int...) get} and
 	 * {@link #resolve() resolve} a specific generic parameters.
-	 * @param indexes the indexes that refer to the generic parameter (may be omitted to
-	 * return the first generic)
+	 * @param indexes the indexes that refer to the generic parameter
+	 * (may be omitted to return the first generic)
 	 * @return a resolved {@link Class} or {@code null}
 	 * @see #getGeneric(int...)
 	 * @see #resolve()
@@ -645,11 +662,11 @@ public final class ResolvableType implements Serializable {
 	}
 
 	/**
-	 * Resolve this type to a {@link java.lang.Class}, returning {@code null} if the type
-	 * cannot be resolved. This method will consider bounds of {@link TypeVariable}s and
-	 * {@link WildcardType}s if direct resolution fails; however, bounds of
-	 * {@code Object.class} will be ignored.
-	 * @return the resolved {@link Class} or {@code null}
+	 * Resolve this type to a {@link java.lang.Class}, returning {@code null}
+	 * if the type cannot be resolved. This method will consider bounds of
+	 * {@link TypeVariable}s and {@link WildcardType}s if direct resolution fails;
+	 * however, bounds of {@code Object.class} will be ignored.
+	 * @return the resolved {@link Class}, or {@code null} if not resolvable
 	 * @see #resolve(Class)
 	 * @see #resolveGeneric(int...)
 	 * @see #resolveGenerics()

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

@@ -16,6 +16,7 @@
 
 package org.springframework.core;
 
+import java.io.Serializable;
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
 import java.lang.reflect.TypeVariable;
@@ -166,11 +167,21 @@ public class GenericTypeResolverTests {
 	public void getGenericsOnArrayFromReturnCannotBeResolved() throws Exception {
 		// SPR-11044
 		Class<?> resolved = GenericTypeResolver.resolveReturnType(
-				WithArrayBase.class.getDeclaredMethod("array", Object[].class),
-				WithArray.class);
+				WithArrayBase.class.getDeclaredMethod("array", Object[].class), WithArray.class);
 		assertThat(resolved, equalTo((Class) Object[].class));
 	}
 
+	@Test
+	public void resolveIncompleteTypeVariables() {
+		// SPR-11763
+		Class<?>[] resolved = GenericTypeResolver.resolveTypeArguments(IdFixingRepository.class, Repository.class);
+		assertNotNull(resolved);
+		assertEquals(2, resolved.length);
+		assertEquals(Object.class, resolved[0]);
+		assertEquals(Long.class, resolved[1]);
+	}
+
+
 	public interface MyInterfaceType<T> {
 	}
 
@@ -314,4 +325,10 @@ public class GenericTypeResolverTests {
 	static abstract class WithArray<T> extends WithArrayBase<T> {
 	}
 
+	interface Repository<T, ID extends Serializable> {
+	}
+
+	interface IdFixingRepository<T> extends Repository<T, Long> {
+	}
+
 }