[m-rev.] for review: decide each type's representation just once

[Julien Fischer]

On Tue, 20 Feb 2018, Zoltan Somogyi wrote:

> On Thu, 15 Feb 2018 16:17:22 +1100, Peter Wang <novalazy at gmail.com> wrote:
>> You could commit it for a few days (however long it takes to produce a
>> source distribution) so that we can check for any differences on other
>> programs.
>
> At least two ROTDs have this diff now. Has anyone found any problems?

No, but I'll do a more extensive set of bootchecks with it this
afternoon.

> If yes, please tell me before tomorrow evening, as a plan to start working
> on non-backwards-compatible changes to type representations by then.
>
> I expect that most improvements to type representation will have the effect
> of requiring a program to be compiled either (a) entirely with a compiler
> that does not have the improvement, or (b) entirely with a compiler
> that *does* have the improvement. If some modules are compiled
> with one kind of compiler and some module are compiled with the other,
> then modules on differing sides of the divide will make inconsistent
> assumptions about how the affected types are represented, which means
> that the executable won't work properly.
>
> Introducing an invisible grade component for each improvement
> seems like overkill to me. Are people ok with recompiling whole programs
> when their (manually or automatically) installed compiler changes?

It's fine by me.

Julien.