Multiple alias this, what's the hold up?

[Timon Gehr]

On 17.06.19 09:29, Walter Bright wrote:
> On 6/16/2019 4:46 PM, Timon Gehr wrote:
>> mixin(import("std/stdio.d"));
> 
> Template mixins are something else:
> 
> https://dlang.org/spec/template-mixin.html
In my answer I explicitly stated that for the purpose of my argument, 
mixing in commutes with parsing. There isn't an obvious way to turn a 
module into a mixin template, so it was easier to make my point with a 
string mixin.

To elaborate on my previous preemptive strike against your complaint, 
from that page of the spec:

"Unlike a template instantiation, a template mixin's body is evaluated 
within the scope where the mixin appears, not where the template 
declaration is defined."

This is not how `alias this` works. I know that importing a scope is 
part of how the `mixin` template is implemented. What I am saying is 
`alias this` should use the same kind of lookup rules, but without the 
mixing in -- only the importing.



PS: And anyhow, how ironic! :)

- I know what template mixins are. I implemented [1] them in a D 
compiler frontend. I know that importing [2] the _newly generated_ scope 
is one step in the implementation.

- In general, I know most of the language spec by heart. I also know 
about almost all aspects of D semantics that are missing or wrong in the 
language specification.

[1] https://github.com/tgehr/d-compiler/blob/master/semantic.d#L3308

[2] https://github.com/tgehr/d-compiler/blob/master/semantic.d#L3348