src/vs/editor/common/core/selection.ts/Selection/isISelection
class Selection:	public static isISelection(obj: any): obj is ISelection {
		return (
			obj
			&& (typeof obj.selectionStartLineNumber === 'number')
			&& (typeof obj.selectionStartColumn === 'number')
			&& (typeof obj.positionLineNumber === 'number')
			&& (typeof obj.positionColumn === 'number')
		);
	}