Thanks!
It looks like ExtendedDefaultRules already allows default variables that
co-occur with multiparameter constraints and non-standard classes. So
maybe that solves my issue with (Num a, Convertible a Double).
Does the defaulting for RuntimeRep interact with class defaulting?
-BenRI
On 7/26/23 12:11 PM, Simon Peyton Jones wrote:
No: I don't know of anyone planning to implement this proposal --
indeed I had forgotten about it -- so it's waiting for someone to take
it on.
There are some slightly tricky loose ends around defaulting that it'd
be good to nail down first:
https://gitlab.haskell.org/ghc/ghc/-/issues/20686
Simon
On Wed, 26 Jul 2023 at 11:00, Benjamin Redelings
<benjamin.redeli...@gmail.com> wrote:
Hi,
If I understand correctly, the traditional defaulting rules prevent
defaulting variables with constraints like (Num a, Convertible a
Double), but the NamedDefaults proposal would allow defaulting a ~
Double in this case due to the relaxed defaulting rules in section
2.5
of the proposal:
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0409-exportable-named-default.rst#id2
1. Is there any plan to start implementing NamedDefaults? I saw the
comment from Simon P-J that it would not be fun to implement
because it
might require orphan default declarations... so perhaps there's no
plan
to implement this?
2. Would it be worth adding a separate LANGUAGE option that just
implements the relaxed defaulting rules in section 2.5?
Specifically (a)
allowing variables with multiparameter constraints and (b) allowing
variables with constraints that are not in the Prelude.
3. Am I correct in assuming that the relaxed defaulting rules require
NamedDefaults to be enabled in the importing module, and not just
in the
imported model?
-BenRI
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