assert: reverse return values of internal getLen()

Reverse order of return values of internal function getLen() to be more
consistent with stdlib (ex: os.LookupEnv).

Old: func (any) (ok bool, length int)
New: func (any) (length int, ok bool)

assert/assertions.go

@@ -731,14 +731,14 @@ func NotEmpty(t TestingT, object interface{}, msgAndArgs ...interface{}) bool {
 
 }
 
-// getLen try to get length of object.
-// return (false, 0) if impossible.
-func getLen(x interface{}) (ok bool, length int) {
+// getLen tries to get the length of an object.
+// It returns (0, false) if impossible.
+func getLen(x interface{}) (length int, ok bool) {
 	v := reflect.ValueOf(x)
 	defer func() {
 		ok = recover() == nil
 	}()
-	return true, v.Len()
+	return v.Len(), true
 }
 
 // Len asserts that the specified object has specific length.
@@ -749,7 +749,7 @@ func Len(t TestingT, object interface{}, length int, msgAndArgs ...interface{})
 	if h, ok := t.(tHelper); ok {
 		h.Helper()
 	}
-	ok, l := getLen(object)
+	l, ok := getLen(object)
 	if !ok {
 		return Fail(t, fmt.Sprintf("\"%s\" could not be applied builtin len()", object), msgAndArgs...)
 	}

assert/assertions_test.go

@@ -1582,7 +1582,7 @@ func Test_getLen(t *testing.T) {
 		struct{}{},
 	}
 	for _, v := range falseCases {
-		ok, l := getLen(v)
+		l, ok := getLen(v)
 		False(t, ok, "Expected getLen fail to get length of %#v", v)
 		Equal(t, 0, l, "getLen should return 0 for %#v", v)
 	}
@@ -1611,7 +1611,7 @@ func Test_getLen(t *testing.T) {
 	}
 
 	for _, c := range trueCases {
-		ok, l := getLen(c.v)
+		l, ok := getLen(c.v)
 		True(t, ok, "Expected getLen success to get length of %#v", c.v)
 		Equal(t, c.l, l)
 	}