[m-rev.] for review: delete references to Erlang in the compiler

[Julien Fischer]

On Wed, 28 Oct 2020, Zoltan Somogyi wrote:

> 2020-10-28 13:27 GMT+11:00 "Julien Fischer" <jfischer at opturion.com>:
>> That's true for foreign_code etc; however non erlang grade users may
>> have --libgrades-exclude erlang in their Mercury.options file (i.e.
>> becaue the current compiler breaks with the erlang grade when doing make install.)
>
> I can add a "we deleted support for Erlang" addendum to the error message
> for the unrecognized language in --libgrades-{include,exclude}.
>
> But tell me: why would anyone add --libgrades-exclude erlang? Wouldn't
> it be simpler just to not list erlang among the list of grades to install?
> I guess I don't understand the rationale of the --libgrades-exclude option
> itself, for any grade component.

Because I want to install a library in every grade that a Mercury
installation has installed except for Erlang, typically because the
Erlang backend is generating invalid code or doing soemthing else which
would otherwise break the installation process.   My mercury-json
library is setup to do exactly that for exactly that reason.

Julien.