Fix10768

[garrigue]

This is an alternative fix to #10768.
Compared to #11339, it duplicates types of first class modules, the same way as in Typecore.type_cases, rather than disabling scope checking, which is potentially dangerous.

[garrigue]

Thanks.

[Octachron]

@garrigue : do you plan to cherry-pick the fix to the 5.0 branch later, or should I take care of it?

[garrigue]

I'll do it just now.

[garrigue]

To cherry-pick, I had to adapt the results to not having #10364.
Which lets me wonder whether it might be better to have #10364 in 5.0.
This is a kind of bug fix, but it types less programs rather than more...

[Octachron]

That sounds reasonable to me, #10364 is a rather old bug fix that was frozen during multicore integration. It makes sense to integrate it before the first alpha but let's ask for @trefis's opinion as the reviewer.

However, looking at the testsuite changes for #10364, I only see functions with improved error messages, one function that now type in non-principal mode, and two functions that type in principal mode but with a warning. Do you have an example of a program that no longer typecheck?

[garrigue]

You're right. The principal mode is stricter, but only for warnings, so this makes sense to cherry-pick it.