MethodParameter.equals checks nesting level and containing class

Closes gh-23352

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

 /*
- * 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.
@@ -29,6 +29,7 @@ import java.util.Map;
 
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Helper class that encapsulates the specification of a method parameter, i.e. a {@link Method}
@@ -71,7 +72,7 @@ public class MethodParameter {
 
 	private final int parameterIndex;
 
-	private int nestingLevel = 1;
+	private int nestingLevel;
 
 	/** Map from Integer level to Integer type index */
 	Map<Integer, Integer> typeIndexesPerLevel;
@@ -612,7 +613,11 @@ public class MethodParameter {
 			return false;
 		}
 		MethodParameter otherParam = (MethodParameter) other;
-		return (this.parameterIndex == otherParam.parameterIndex && getMember().equals(otherParam.getMember()));
+		return (this.containingClass == otherParam.containingClass &&
+				ObjectUtils.nullSafeEquals(this.typeIndexesPerLevel, otherParam.typeIndexesPerLevel) &&
+				this.nestingLevel == otherParam.nestingLevel &&
+				this.parameterIndex == otherParam.parameterIndex &&
+				getMember().equals(otherParam.getMember()));
 	}
 
 	@Override

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

 /*
- * 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.
@@ -22,6 +22,7 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
+import java.util.ArrayList;
 import java.util.concurrent.Callable;
 
 import org.junit.Before;
@@ -130,6 +131,44 @@ public class MethodParameterTests {
 				methodParameter.getGenericParameterType());
 	}
 
+	@Test
+	public void multipleResolveParameterTypeCalls() throws Exception {
+		Method method = ArrayList.class.getMethod("get", int.class);
+		MethodParameter methodParameter = MethodParameter.forMethodOrConstructor(method, -1);
+		assertEquals(Object.class, methodParameter.getParameterType());
+		GenericTypeResolver.resolveParameterType(methodParameter, StringList.class);
+		assertEquals(String.class, methodParameter.getParameterType());
+		GenericTypeResolver.resolveParameterType(methodParameter, IntegerList.class);
+		assertEquals(Integer.class, methodParameter.getParameterType());
+	}
+
+	@Test
+	public void equalsAndHashCodeConsidersContainingClass() throws Exception {
+		Method method = ArrayList.class.getMethod("get", int.class);
+		MethodParameter m1 = MethodParameter.forMethodOrConstructor(method, -1);
+		MethodParameter m2 = MethodParameter.forMethodOrConstructor(method, -1);
+		MethodParameter m3 = MethodParameter.forMethodOrConstructor(method, -1).nested();
+		assertEquals(m1, m2);
+		assertNotEquals(m1, m3);
+		assertEquals(m1.hashCode(), m2.hashCode());
+	}
+
+	@Test
+	public void equalsAndHashCodeConsidersNesting() throws Exception {
+		Method method = ArrayList.class.getMethod("get", int.class);
+		MethodParameter m1 = MethodParameter.forMethodOrConstructor(method, -1);
+		GenericTypeResolver.resolveParameterType(m1, StringList.class);
+		MethodParameter m2 = MethodParameter.forMethodOrConstructor(method, -1);
+		GenericTypeResolver.resolveParameterType(m2, StringList.class);
+		MethodParameter m3 = MethodParameter.forMethodOrConstructor(method, -1);
+		GenericTypeResolver.resolveParameterType(m3, IntegerList.class);
+		MethodParameter m4 = MethodParameter.forMethodOrConstructor(method, -1);
+		assertEquals(m1, m2);
+		assertNotEquals(m1, m3);
+		assertNotEquals(m1, m4);
+		assertEquals(m1.hashCode(), m2.hashCode());
+	}
+
 
 	public int method(String p1, long p2) {
 		return 42;
@@ -154,4 +193,12 @@ public class MethodParameterTests {
 	private @interface Param {
 	}
 
+	@SuppressWarnings("serial")
+	private static class StringList extends ArrayList<String> {
+	}
+
+	@SuppressWarnings("serial")
+	private static class IntegerList extends ArrayList<Integer> {
+	}
+
 }