Add missing constructors to SynthesizingMethodParameter

This commit primarily allows for a `SynthesizingMethodParameter` to be
created for a `Constructor` parameter but also introduces an additional
overloaded constructor from `MethodParameter`.

Issue: SPR-14054

Author: sbrannen

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

@@ -48,15 +48,18 @@
  */
 public class MethodParameter {
 
-	private static Class<?> javaUtilOptionalClass = null;
+	private static final Class<?> javaUtilOptionalClass;
 
 	static {
+		Class<?> clazz;
 		try {
-			javaUtilOptionalClass = ClassUtils.forName("java.util.Optional", MethodParameter.class.getClassLoader());
+			clazz = ClassUtils.forName("java.util.Optional", MethodParameter.class.getClassLoader());
 		}
 		catch (ClassNotFoundException ex) {
 			// Java 8 not available - Optional references simply not supported then.
+			clazz = null;
 		}
+		javaUtilOptionalClass = clazz;
 	}
 
 
@@ -312,7 +315,7 @@ public MethodParameter nested() {
 	}
 
 	/**
-	 * Return whether this method parameter is declared as optiona
+	 * Return whether this method parameter is declared as optional
 	 * in the form of Java 8's {@link java.util.Optional}.
 	 * @since 4.3
 	 */

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

@@ -17,6 +17,7 @@
 package org.springframework.core.annotation;
 
 import java.lang.annotation.Annotation;
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 
 import org.springframework.core.MethodParameter;
@@ -34,7 +35,8 @@
 public class SynthesizingMethodParameter extends MethodParameter {
 
 	/**
-	 * Create a new {@code SynthesizingMethodParameter} for the given method.
+	 * Create a new {@code SynthesizingMethodParameter} for the given method,
+	 * with nesting level 1.
 	 * @param method the Method to specify a parameter for
 	 * @param parameterIndex the index of the parameter: -1 for the method
 	 * return type; 0 for the first method parameter; 1 for the second method
@@ -44,6 +46,47 @@ public SynthesizingMethodParameter(Method method, int parameterIndex) {
 		super(method, parameterIndex);
 	}
 
+	/**
+	 * Create a new {@code SynthesizingMethodParameter} for the given method.
+	 * @param method the Method to specify a parameter for
+	 * @param parameterIndex the index of the parameter: -1 for the method
+	 * return type; 0 for the first method parameter; 1 for the second method
+	 * parameter, etc.
+	 * @param nestingLevel the nesting level of the target type
+	 * (typically 1; e.g. in case of a List of Lists, 1 would indicate the
+	 * nested List, whereas 2 would indicate the element of the nested List)
+	 */
+	public SynthesizingMethodParameter(Method method, int parameterIndex, int nestingLevel) {
+		super(method, parameterIndex, nestingLevel);
+	}
+
+	/**
+	 * Create a new {@code SynthesizingMethodParameter} for the given constructor,
+	 * with nesting level 1.
+	 * @param constructor the Constructor to specify a parameter for
+	 * @param parameterIndex the index of the parameter
+	 */
+	public SynthesizingMethodParameter(Constructor<?> constructor, int parameterIndex) {
+		super(constructor, parameterIndex);
+	}
+
+	/**
+	 * Create a new {@code SynthesizingMethodParameter} for the given constructor.
+	 * @param constructor the Constructor to specify a parameter for
+	 * @param parameterIndex the index of the parameter
+	 * @param nestingLevel the nesting level of the target type
+	 * (typically 1; e.g. in case of a List of Lists, 1 would indicate the
+	 * nested List, whereas 2 would indicate the element of the nested List)
+	 */
+	public SynthesizingMethodParameter(Constructor<?> constructor, int parameterIndex, int nestingLevel) {
+		super(constructor, parameterIndex, nestingLevel);
+	}
+
+	/**
+	 * Copy constructor, resulting in an independent {@code SynthesizingMethodParameter}
+	 * based on the same metadata and cache state that the original object was in.
+	 * @param original the original SynthesizingMethodParameter object to copy from
+	 */
 	protected SynthesizingMethodParameter(SynthesizingMethodParameter original) {
 		super(original);
 	}