cannot use local __lambda1 as parameter to non-global template

[aliak]

On Friday, 26 July 2019 at 16:20:10 UTC, aliak wrote:
> Can someone help me understand the details around why this 
> fails?
>
> import std;
>
> struct W(T) {
>     T value;
>     auto hook(handlers...)() {
>         return handlers[0](value);
>     }
> }
>
> template f(handlers...) {
>     auto ref f(T)(auto ref T value) {
>         return value.hook!handlers;
>     }
> }
>
> @nogc void main() {
>     auto a = W!int(3);
>     auto b = a.f!((_) => "yes");
> }
>
> If I specifically type the lambda I pass in to f (i.e. (int _) 
> => "yes") then it works. Or if I make hook a global template 
> that takes a W!T as the first parameter it also works. Is there 
> a work around for this?

Err sorry, that was ldc pre the 5710 bug fix. In DMD I get this:

Error: @nogc function D main cannot call non- at nogc function 
onlineapp.main.f!(W!int).f

I guess it's allocating a delegate somewhere. Can I fix that?