message: Add TextEdit#is()
diff: @@ -388,6 +388,11 @@ export namespace TextEdit {
  export function del(range: Range): TextEdit {
  return { range, newText: '' };
  }
  +
  + export function is(value: any): value is TextEdit {
  + const candidate = value as TextEdit;
  + return Is.string(candidate.newText) && Range.is(candidate.range);
  + }
  }
  