WARNING pragmas in `Prelude.undefined` and `Prelude.error`

[Vilem Liepelt]

> On 23 Dec 2019, at 18:10, Daniel Díaz Casanueva <dhelta.diaz at gmail.com> wrote:
> 
> Some warnings are not included in -Wall (for instance -Wincomplete-uni-patterns). New warning flags can be added without breaking any code.

Agreed, Daniel, but if we added a warning/deprecation pragma to the library (which is what I had asked about), then this would get triggered by -Wdeprecations which is part of -Wall. I'm not sure adding a flag specifically for usages of `error`/`undefined` makes much sense. E.g. what if I bind those names to genuine values?