Compile-time fold expression vs recursive template

[Stefan Koch]

On Friday, 19 June 2020 at 17:04:57 UTC, Nick Treleaven wrote:
> On Saturday, 13 June 2020 at 12:35:58 UTC, Paul Backus wrote:
>> [...]
>
> I realized my FoldExpression feature invented too much syntax. 
> Really all we need is a way to limit what a template can do, 
> i.e. (1) not cache instantiations and (2) not declare symbols 
> (aside from eponymous symbols) so it can share a single Scope 
> instance in dmd. That Scope instance would be reused upon each 
> recursion, and only one recursion is allowed in each inner 
> `static if` branch. That could be done just by recognizing a 
> special identifer __Fold:
>
> [...]

We should talk and band together.
Multiple competing proposals won't help here.

We at least have gained some clarity about the problem.
Now let's gain some clarity about the solution space.