Document SynthesizedAnnotationInvocationHandler constructor

Issue: SPR-11512

Author: sbrannen

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -1061,7 +1061,7 @@ public static <A extends Annotation> A synthesizeAnnotation(A annotation, Annota
 			return annotation;
 		}
 
-		InvocationHandler handler = new SynthesizedAnnotationInvocationHandler(annotatedElement, annotation,
+		InvocationHandler handler = new SynthesizedAnnotationInvocationHandler(annotation, annotatedElement,
 			getAttributeAliasMap(annotationType));
 		A synthesizedAnnotation = (A) Proxy.newProxyInstance(ClassUtils.getDefaultClassLoader(), new Class<?>[] {
 			(Class<A>) annotationType, SynthesizedAnnotation.class }, handler);

spring-core/src/main/java/org/springframework/core/annotation/SynthesizedAnnotationInvocationHandler.java

@@ -58,7 +58,16 @@ class SynthesizedAnnotationInvocationHandler implements InvocationHandler {
 	private final Map<String, String> aliasMap;
 
 
-	SynthesizedAnnotationInvocationHandler(AnnotatedElement annotatedElement, Annotation annotation,
+	/**
+	 * Construct a new {@code SynthesizedAnnotationInvocationHandler}.
+	 *
+	 * @param annotation the annotation to synthesize
+	 * @param annotatedElement the element that is annotated with the supplied
+	 * annotation; may be {@code null} if unknown
+	 * @param aliasMap the map of attribute alias pairs, declared via
+	 * {@code @AliasFor} in the supplied annotation
+	 */
+	SynthesizedAnnotationInvocationHandler(Annotation annotation, AnnotatedElement annotatedElement,
 			Map<String, String> aliasMap) {
 		this.annotatedElement = annotatedElement;
 		this.annotation = annotation;