src/vs/workbench/api/common/extHostTypes.ts/TextEdit/isTextEdit
class TextEdit:	static isTextEdit(thing: any): thing is TextEdit {
		if (thing instanceof TextEdit) {
			return true;
		}
		if (!thing) {
			return false;
		}
		return Range.isRange((<TextEdit>thing))
			&& typeof (<TextEdit>thing).newText === 'string';
	}