Fix unexpected MatchError() behaviour (#375)

Resolves #374

Co-authored-by: Marcela Campo <mcampo@pivotal.io>
Co-authored-by: George Blue <gblue@pivotal.io>
Co-authored-by: David Ansari <dansari@pivotal.io>

matchers/match_error_matcher.go

@@ -24,10 +24,6 @@ func (matcher *MatchErrorMatcher) Match(actual interface{}) (success bool, err e
 	actualErr := actual.(error)
 	expected := matcher.Expected
 
-	if isPtrToErrorType(expected) {
-		return xerrors.As(actualErr, expected), nil
-	}
-
 	if isError(expected) {
 		return reflect.DeepEqual(actualErr, expected) || xerrors.Is(actualErr, expected.(error)), nil
 	}
@@ -46,7 +42,7 @@ func (matcher *MatchErrorMatcher) Match(actual interface{}) (success bool, err e
 	}
 
 	return false, fmt.Errorf(
-		"MatchError must be passed an error, a pointer to a type that implements error, a string, or a Matcher that can match on strings. Got:\n%s",
+		"MatchError must be passed an error, a string, or a Matcher that can match on strings. Got:\n%s",
 		format.Object(expected, 1))
 }
 
@@ -57,17 +53,3 @@ func (matcher *MatchErrorMatcher) FailureMessage(actual interface{}) (message st
 func (matcher *MatchErrorMatcher) NegatedFailureMessage(actual interface{}) (message string) {
 	return format.Message(actual, "not to match error", matcher.Expected)
 }
-
-func isPtrToErrorType(a interface{}) bool {
-	if isNil(a) {
-		return false
-	}
-
-	typeOfA := reflect.TypeOf(a)
-	if typeOfA.Kind() != reflect.Ptr {
-		return false
-	}
-
-	errorType := reflect.TypeOf((*error)(nil)).Elem()
-	return typeOfA.Elem().Implements(errorType)
-}

matchers/match_error_matcher_test.go

@@ -40,12 +40,10 @@ var _ = Describe("MatchErrorMatcher", func() {
 			})
 		})
 
-		Context("when passed non-nil pointer to a type that implements error", func() {
-			It("should succeed when any error in the chain matches the passed pointer", func() {
-				err := xerrors.Errorf("outer error wrapping: %w", CustomError{})
-
-				var expectedErrType CustomError
-				Expect(err).Should(MatchError(&expectedErrType))
+		Context("when actual an expected are both pointers to an error", func() {
+			It("should succeed when errors are deeply equal", func() {
+				err := CustomError{}
+				Expect(&err).To(MatchError(&err))
 			})
 		})