encoding/xml: use reflect.Value.IsZero

IsZero does the same thing, using this rather than writing it again.

Change-Id: I62810ac2d1a6e189feac03b022c8931fb6993e19
GitHub-Last-Rev: 1d5fd10
GitHub-Pull-Request: #63519
Reviewed-on: https://go-review.googlesource.com/c/go/+/534935
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: apocelipes

src/encoding/xml/marshal.go

@@ -1120,16 +1120,12 @@ func isEmptyValue(v reflect.Value) bool {
 	switch v.Kind() {
 	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
 		return v.Len() == 0
-	case reflect.Bool:
-		return !v.Bool()
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		return v.Int() == 0
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		return v.Uint() == 0
-	case reflect.Float32, reflect.Float64:
-		return v.Float() == 0
-	case reflect.Interface, reflect.Pointer:
-		return v.IsNil()
+	case reflect.Bool,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
+		reflect.Float32, reflect.Float64,
+		reflect.Interface, reflect.Pointer:
+		return v.IsZero()
 	}
 	return false
 }