Support for @Order on nested configuration classes

Issue: SPR-15384

spring-context/src/test/java/org/springframework/context/annotation/ConfigurationClassPostProcessorTests.java

@@ -348,6 +348,18 @@ public class ConfigurationClassPostProcessorTests {
 		}
 	}
 
+	@Test
+	public void nestedConfigurationClassesProcessedInCorrectOrder() {
+		beanFactory.registerBeanDefinition("config", new RootBeanDefinition(ConfigWithOrderedNestedClasses.class));
+		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
+		pp.postProcessBeanFactory(beanFactory);
+
+		Foo foo = beanFactory.getBean(Foo.class);
+		assertTrue(foo instanceof ExtendedFoo);
+		Bar bar = beanFactory.getBean(Bar.class);
+		assertSame(foo, bar.foo);
+	}
+
 	@Test
 	public void scopedProxyTargetMarkedAsNonAutowireCandidate() {
 		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
@@ -833,6 +845,36 @@ public class ConfigurationClassPostProcessorTests {
 		}
 	}
 
+	@Configuration
+	static class ConfigWithOrderedNestedClasses {
+
+		@Configuration
+		@Order(1)
+		static class SingletonBeanConfig {
+
+			public @Bean Foo foo() {
+				return new Foo();
+			}
+
+			public @Bean Bar bar() {
+				return new Bar(foo());
+			}
+		}
+
+		@Configuration
+		@Order(2)
+		static class OverridingSingletonBeanConfig {
+
+			public @Bean ExtendedFoo foo() {
+				return new ExtendedFoo();
+			}
+
+			public @Bean Bar bar() {
+				return new Bar(foo());
+			}
+		}
+	}
+
 	static class Foo {
 	}