Result C# 2022

Result.cs

public abstract record Result<TOk, TError>
{
    public sealed record Ok(TOk Value) : Result<TOk, TError>
    {
        public override TOk Default(TOk defaultValueIfError) => Value;
        public override T Match<T>(Func<TOk, T> ok, Func<TError, T> error) => ok(Value);
        public override Result<TMap, TError> Select<TMap>(Func<TOk, TMap> map) => map(Value);
        public override Result<TMap, TError> Bind<TMap>(Func<TOk, Result<TMap, TError>> bind) => bind(Value);
        public override bool IsError => false;
    }

    public sealed record Error(TError Err) : Result<TOk, TError>
    {
        public override TOk Default(TOk defaultValueIfError) => defaultValueIfError;
        public override T Match<T>(Func<TOk, T> ok, Func<TError, T> error) => error(Err);
        public override Result<TMap, TError> Select<TMap>(Func<TOk, TMap> map) => Err;
        public override Result<TMap, TError> Bind<TMap>(Func<TOk, Result<TMap, TError>> bind) => Err;
        public override bool IsError => true;
    }

    public static implicit operator Result<TOk, TError>(TOk value) => new Ok(value);
    public static implicit operator Result<TOk, TError>(TError value) => new Error(value);

    public abstract TOk Default(TOk defaultValueIfError);
    public abstract T Match<T>(Func<TOk, T> ok, Func<TError, T> error);

    public abstract Result<TMap, TError> Select<TMap>(Func<TOk, TMap> map);
    public abstract Result<TMap, TError> Bind<TMap>(Func<TOk, Result<TMap, TError>> bind);

    public Result<TResult, TError> SelectMany<TMap, TResult>(
        Func<TOk, Result<TMap, TError>> bind,
        Func<TOk, TMap, TResult> project) =>
        Bind(a => bind(a).Select(b => project(a, b)));

    public abstract bool IsError { get; }
    public bool IsOk => !IsError;
}