src/vs/platform/contextkey/common/contextkey.ts/ContextKeyDefinedExpr/create
class ContextKeyDefinedExpr:	public static create(key: string, negated: ContextKeyExpression | null = null): ContextKeyExpression {
		const constantValue = CONSTANT_VALUES.get(key);
		if (typeof constantValue === 'boolean') {
			return constantValue ? ContextKeyTrueExpr.INSTANCE : ContextKeyFalseExpr.INSTANCE;
		}
		return new ContextKeyDefinedExpr(key, negated);
	}