On Monday, 21 May 2018 at 20:29:26 UTC, Nick Sabalausky (Abscissa) wrote:
> Ouch, and the error message isn't very helpful either. I wonder what causes this to fail though, and whether it might simply be a compiler bug?

I'm pretty sure it's intended behavior. Templates are instantiated in the same module they're declared in [1], so since `_data` isn't visible in `std.algorithm`, `each` can't see it.

It's arguable that there ought to be an exception for `alias this`, but I expect that kind of change would require a DIP.

[1]: https://dlang.org/spec/template.html#instantiation_scope