Ensure a concrete type with parametrric subtype is detected

If user defines their own @Beans from conrete types that implement
Function<...> then their type signature is detectable from the
class.

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/ContextFunctionCatalogAutoConfigurationTests.java

@@ -211,6 +211,17 @@ public class ContextFunctionCatalogAutoConfigurationTests {
 				.isAssignableFrom(Integer.class);
 	}
 
+	@Test
+	public void nonParametericTypeFunction() {
+		create(NonParametricTypeSingletonConfiguration.class);
+		assertThat(context.getBean("function")).isInstanceOf(Function.class);
+		assertThat(catalog.lookupFunction("function")).isInstanceOf(Function.class);
+		assertThat(inspector.getInputType(catalog.lookupFunction("function")))
+				.isAssignableFrom(Integer.class);
+		assertThat(inspector.getInputWrapper(catalog.lookupFunction("function")))
+				.isAssignableFrom(Integer.class);
+	}
+
 	@Test
 	public void componentScanBeanFunction() {
 		create(ComponentScanBeanConfiguration.class);
@@ -487,6 +498,15 @@ public class ContextFunctionCatalogAutoConfigurationTests {
 		}
 	}
 
+	@EnableAutoConfiguration
+	@Configuration
+	protected static class NonParametricTypeSingletonConfiguration {
+		@Bean
+		public SingletonFunction function() {
+			return new SingletonFunction();
+		}
+	}
+
 	protected static class SingletonFunction implements Function<Integer, String> {
 
 		@Override