Cannot Instantiate SumType

[Paul Backus]

On Monday, 20 September 2021 at 11:21:28 UTC, surlymoor wrote:
> The error in question...
> ```
> Error: variable 
> `std.typecons.ReplaceTypeUnless!(isSumTypeInstance, This, 
> SumType!(Foo!(bar)), Foo!(bar)).F!(bar).replaceTemplateArgs` 
> type `void` is inferred from initializer `bar()`, and variables 
> cannot be of type `void`
> ```

Looks like this is a bug in `ReplaceType`:

```d
import std.typecons;

struct Foo(alias f) {}
void bar() {}
alias _ = ReplaceType!(int, int, Foo!bar);
```

I've submitted a bug report here: 
https://issues.dlang.org/show_bug.cgi?id=22325

[1]: https://phobos.dpldocs.info/std.typecons.ReplaceType.html