Are there GHC extensions we'd like to incorporate wholesale?

[wren romano]

On Wed, May 4, 2016 at 2:51 AM, Dominique Devriese
<dominique.devriese at cs.kuleuven.be> wrote:
> As an outsider, I would like to suggest thinking about MonoLocalBinds.  GHC
> has a rather convincing story (at least to me) that "(local) let should not
> be generalised" (since it becomes problematic in combination with several
> other language extensions) and the journal version of the OutsideIn(X) paper
> has empirical data that indicates it is not a big problem to remove.  If
> there is a concern about backwards compatibility, perhaps the committee
> could deprecate local let generalisation in Haskell2020 and remove it in a
> subsequent iteration of the report?


FWIW, I'm against MonoLocalBinds. I understand the rational given in
the paper, but I disagree with it. In my experience the medicine is
worse than the disease.

It used to be that where-clauses where a nice clean way of organizing
code, especially for things like the worker/wrapper transform; but
with MonoLocalBinds all the benefits of where-clauses are eliminated.
For every local binding I'm forced to provide a type signature
—because part of the whole *point* of factoring things out is that
you're going to use them repeatedly, which for GADTs virtually
guarantees the uses will be at different index types and therefore
will require universal quantification— and these requisite type
signatures almost entirely duplicate information provided by the
signature for the primary/top-level binding. Indeed, in almost every
situation I end up needing to manually provide type signatures which
are identical to what let-generalization would have inferred. This
repetition is not merely annoying, it actively harms legibility and
maintainability of code.

-- 
Live well,
~wren