src/vs/workbench/api/common/extHostTypes.ts/Position/isPosition
class Position:	static isPosition(other: any): other is Position {
		if (!other) {
			return false;
		}
		if (other instanceof Position) {
			return true;
		}
		let { line, character } = <Position>other;
		if (typeof line === 'number' && typeof character === 'number') {
			return true;
		}
		return false;
	}