Remove unnecessary loop in SerializableTypeWrapper

Since arbitrary levels of proxies do not occur, this commit replaces
the `while` loop in SerializableTypeWrapper.unwrap() with a simple
`if` statement.

Closes gh-23415

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -51,6 +51,7 @@ import org.springframework.util.ReflectionUtils;
  *
  * @author Phillip Webb
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 4.0
  */
 final class SerializableTypeWrapper {
@@ -89,8 +90,8 @@ final class SerializableTypeWrapper {
 	 */
 	@SuppressWarnings("unchecked")
 	public static <T extends Type> T unwrap(T type) {
-		Type unwrapped = type;
-		while (unwrapped instanceof SerializableTypeProxy) {
+		Type unwrapped = null;
+		if (type instanceof SerializableTypeProxy) {
 			unwrapped = ((SerializableTypeProxy) type).getTypeProvider().getType();
 		}
 		return (unwrapped != null ? (T) unwrapped : type);

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

@@ -33,8 +33,6 @@ import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-
-
 /**
  * Tests for {@link SerializableTypeWrapper}.
  *