Remove unused type parameter declarations in MockMvc result matchers

Prior to this commit, several of the ResultMatcher methods used in
MockMvc declared unused type parameters (e.g., <T>). This was obviously
the result of copying an existing method that actually needs the type
parameter for proper casting.

For example, the following in RequestResultMatchers ...

public <T> ResultMatcher attribute(String name, Object expectedValue) {
    // ...
}

... should actually be declared without <T>, since T is not used in the
implementation or in the return type:

public ResultMatcher attribute(String name, Object expectedValue) {
    // ...
}

This commit removes all unused type parameter declarations in MockMvc
result matchers.

Side Effects:

Now that we have removed the unused type parameter declarations, users
will see the following side effects if they had previously declared a
type argument when invoking such methods.

- Java: an "Unused type arguments for the non generic method ..."
  warning will be generated by the compiler, but the code will continue
  to work unmodified.

- Kotlin: a "Type inference failed: Not enough information to infer
  parameter T in fun ..." compiler error will be raised, causing the
  code to no longer compile (see
  https://youtrack.jetbrains.com/issue/KT-5464). Removal of the type
  argument declaration will allow the code to work correctly again.

Closes gh-23858

spring-test/src/main/java/org/springframework/test/web/servlet/result/FlashAttributeResultMatchers.java

@@ -54,14 +54,14 @@ public class FlashAttributeResultMatchers {
 	/**
 	 * Assert a flash attribute's value.
 	 */
-	public <T> ResultMatcher attribute(String name, Object value) {
+	public ResultMatcher attribute(String name, Object value) {
 		return result -> assertEquals("Flash attribute '" + name + "'", value, result.getFlashMap().get(name));
 	}
 
 	/**
 	 * Assert the existence of the given flash attributes.
 	 */
-	public <T> ResultMatcher attributeExists(String... names) {
+	public ResultMatcher attributeExists(String... names) {
 		return result -> {
 			for (String name : names) {
 				assertNotNull("Flash attribute '" + name + "' does not exist", result.getFlashMap().get(name));
@@ -72,7 +72,7 @@ public class FlashAttributeResultMatchers {
 	/**
 	 * Assert the number of flash attributes.
 	 */
-	public <T> ResultMatcher attributeCount(int count) {
+	public ResultMatcher attributeCount(int count) {
 		return result -> assertEquals("FlashMap size", count, result.getFlashMap().size());
 	}
 

spring-test/src/main/java/org/springframework/test/web/servlet/result/HeaderResultMatchers.java

@@ -65,7 +65,7 @@ public class HeaderResultMatchers {
 	 * Iterable {@link Matcher}.
 	 * @since 4.3
 	 */
-	public <T> ResultMatcher stringValues(String name, Matcher<Iterable<String>> matcher) {
+	public ResultMatcher stringValues(String name, Matcher<Iterable<String>> matcher) {
 		return result -> {
 			List<String> values = result.getResponse().getHeaders(name);
 			assertThat("Response header '" + name + "'", values, matcher);

spring-test/src/main/java/org/springframework/test/web/servlet/result/ModelResultMatchers.java

@@ -172,7 +172,7 @@ public class ModelResultMatchers {
 	 * Assert a field error code for a model attribute using a {@link org.hamcrest.Matcher}.
 	 * @since 4.1
 	 */
-	public <T> ResultMatcher attributeHasFieldErrorCode(String name, String fieldName,
+	public ResultMatcher attributeHasFieldErrorCode(String name, String fieldName,
 			Matcher<? super String> matcher) {
 
 		return mvcResult -> {
@@ -189,7 +189,7 @@ public class ModelResultMatchers {
 	/**
 	 * Assert the total number of errors in the model.
 	 */
-	public <T> ResultMatcher errorCount(int expectedCount) {
+	public ResultMatcher errorCount(int expectedCount) {
 		return result -> {
 			int actualCount = getErrorCount(getModelAndView(result).getModelMap());
 			assertEquals("Binding/validation error count", expectedCount, actualCount);
@@ -199,7 +199,7 @@ public class ModelResultMatchers {
 	/**
 	 * Assert the model has errors.
 	 */
-	public <T> ResultMatcher hasErrors() {
+	public ResultMatcher hasErrors() {
 		return result -> {
 			int count = getErrorCount(getModelAndView(result).getModelMap());
 			assertTrue("Expected binding/validation errors", count != 0);
@@ -209,7 +209,7 @@ public class ModelResultMatchers {
 	/**
 	 * Assert the model has no errors.
 	 */
-	public <T> ResultMatcher hasNoErrors() {
+	public ResultMatcher hasNoErrors() {
 		return result -> {
 			ModelAndView mav = getModelAndView(result);
 			for (Object value : mav.getModel().values()) {
@@ -223,7 +223,7 @@ public class ModelResultMatchers {
 	/**
 	 * Assert the number of model attributes.
 	 */
-	public <T> ResultMatcher size(int size) {
+	public ResultMatcher size(int size) {
 		return result -> {
 			ModelAndView mav = getModelAndView(result);
 			int actual = 0;

spring-test/src/main/java/org/springframework/test/web/servlet/result/RequestResultMatchers.java

@@ -98,7 +98,7 @@ public class RequestResultMatchers {
 	 * or {@link WebAsyncTask}. The value matched is the value returned from the
 	 * {@code Callable} or the exception raised.
 	 */
-	public <T> ResultMatcher asyncResult(Object expectedResult) {
+	public ResultMatcher asyncResult(Object expectedResult) {
 		return result -> {
 			HttpServletRequest request = result.getRequest();
 			assertAsyncStarted(request);
@@ -120,7 +120,7 @@ public class RequestResultMatchers {
 	/**
 	 * Assert a request attribute value.
 	 */
-	public <T> ResultMatcher attribute(String name, Object expectedValue) {
+	public ResultMatcher attribute(String name, Object expectedValue) {
 		return result ->
 				assertEquals("Request attribute '" + name + "'", expectedValue, result.getRequest().getAttribute(name));
 	}
@@ -141,7 +141,7 @@ public class RequestResultMatchers {
 	/**
 	 * Assert a session attribute value.
 	 */
-	public <T> ResultMatcher sessionAttribute(String name, Object value) {
+	public ResultMatcher sessionAttribute(String name, Object value) {
 		return result -> {
 			HttpSession session = result.getRequest().getSession();
 			Assert.state(session != null, "No HttpSession");