Polish

Closes gh-11788

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/PropertyMapper.java

@@ -264,7 +264,7 @@ public final class PropertyMapper {
 		 * @param target the target type to match
 		 * @return a new filtered source instance
 		 */
-		public <R> Source<R> whenInstanceOf(Class<R> target) {
+		public <R extends T> Source<R> whenInstanceOf(Class<R> target) {
 			return when(target::isInstance).as(target::cast);
 		}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/PropertyMapperTests.java

@@ -151,7 +151,8 @@ public class PropertyMapperTests {
 
 	@Test
 	public void whenInstanceOfWhenValueIsNotTargetTypeShouldNotMatch() {
-		this.map.from(() -> 123).whenInstanceOf(Double.class).toCall(Assert::fail);
+		this.map.from(() -> (Number) 123L).whenInstanceOf(Double.class)
+				.toCall(Assert::fail);
 	}
 
 	@Test