opIndex for type list

[James Lu]

On Monday, 24 August 2020 at 14:19:14 UTC, data pulverizer wrote:
> Hi all,
>
> I am trying to implement `opIndex` (e.g. T[i]) for types in a 
> struct. So for I have `length`:
>
> ```d
> struct TList(T...)
> {
>   enum long length = T.length;
> }
> ```
>
> and have tried including
>
> ```d
> alias opIndex(long i) = T[i];
> ```
>
> or
>
> ```d
> alias opIndex(alias i) = T[i];
> ```
>
> called with
>
> ```d
> alias tList = AliasSeq!(bool, string, ubyte, short, ushort);
> TList!(tList)[0];
> ```
>
> but that doesn't work and I get the error:
>
> ```d
> opIndex cannot deduce function from argument types !()(int), 
> candidates are:
> opIndex(long i)
>
> ```

This is an interesting syntax, and it reminds me of Python's 
generic syntax. Will be interested to see how you use type 
opIndex.