src/vs/platform/contextkey/common/contextkey.ts/ContextKeyNotExpr/substituteConstants
class ContextKeyNotExpr:	public substituteConstants(): ContextKeyExpression | undefined {
		const constantValue = CONSTANT_VALUES.get(this.key);
		if (typeof constantValue === 'boolean') {
			return (constantValue ? ContextKeyFalseExpr.INSTANCE : ContextKeyTrueExpr.INSTANCE);
		}
		return this;
	}