src/vs/platform/contextkey/common/contextkey.ts/ContextKeyAndExpr/negate
class ContextKeyAndExpr:	public negate(): ContextKeyExpression {
		let result: ContextKeyExpression[] = [];
		for (let expr of this.expr) {
			result.push(expr.negate());
		}
		return ContextKeyOrExpr.create(result)!;
	}