[m-rev.] for review: document ':- pragma foreign_export_enum' for Erlang.

[Julien Fischer]

On Thu, 8 Sep 2016, Paul Bone wrote:

>> @@ -8695,6 +8696,15 @@ The effect of this declaration is that Mercury values of type
>>  @var{MercuryTypeName} will be passed to and from Erlang foreign_procs
>>  as having some representation unknown to Mercury.
>>
>> + at node Using pragma foreign_export_enum for Erlang
>> + at subsubsection Using pragma foreign_export_enum for Erlang
>> +
>> +Values of Mercury enumeration types may be referred to from Erlang code using
>> +the convention for discriminated union types described in
>> + at ref{Erlang data passing conventions}.
>> +As such, @samp{pragma foreign_export_enum} declarations are neither required or
>> +supported for Erlang.
>> +
>>  @node Using pragma foreign_proc for Erlang
>>  @subsubsection Using pragma foreign_proc for Erlang
>>
>
> Perhaps the title shouldn't imply the existence of foreign_export_enum for
> Erlang.  Maybe something like "Using Mercury enums in Erlang".

The title is consistent with what we do in other language specific
subsections when a pragma is not supported. Also, the name of the
pragma should be mentioned: that's what people looking for how
that pragma works in Erlang will be looking for.

Julien.