In Ash Framework, we have declarative ways to construct runtime behavior
using behaviors. So an Ash resource might look like this:
```elixir
defmodule MyApp.User do
use Ash.Resource
alias MyApp.User.Changes.HashPassword
attributes do
uuid_primary_key :id
....
end
actions do
create :register do
change HashPassword
end
end
end
```
However, by default, this would incur a compile time dependency. This
compile time dependency is unnecessary, as we won't call any functions on
this module or use it in any way until runtime.
That optimization is well and good, but due to transitive compile time
dependencies, we see some interesting behavior. Something you'd often see
in a change module is things like pattern matching on other resources, or
the resource in question in function heads. Resources are meant to be
introspectable at compile time, and so this runtime dependency on a change,
with a compile time dependency on a resource, incurs a transitive compile
time dependency. This problem multiplies over time, and causes users to
have to do things solely to optimize compile times, like only use map
pattern matches instead of struct pattern matches.
So what we do is we actually disable the lexical tracker when accepting
certain parts of the DSL. This prevents *any* dependency. Naturally, at
compile time you are no longer safe to call a resource's change module as
changes in that module won't cause recompiles, but that was never a thing
you should have done in the first place so I'm not worried about that.
This leads us to the primary issue: disabling the lexical tracker when
expanding aliases also causes warnings about unused aliases, even though
they *are* used. I believe I've brought this issue up before and we were
hoping that the feature introduced in 1.14 for `defimpl` would help, but
that only helps prevent compile time issues, which is something I had
already solved for in the same way it was solved for 1.14. I've laid it all
out to help clarify exactly *why* I need it so perhaps someone can point me
in a better direction.
The simplest thing that could help:
A way to tell the lexical tracker that an alias has just been referenced
without inducing any kind of compile or runtime dependency. The idea is to
just prevent it from warning about the alias.
I'm open to other solutions as well.
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