[GHC] #8165: Use GeneralizedNewtypeDeriving to automatically create associated type families
GHC
ghc-devs at haskell.org
Tue Oct 25 13:14:21 UTC 2016
#8165: Use GeneralizedNewtypeDeriving to automatically create associated type
families
-------------------------------------+-------------------------------------
Reporter: MikeIzbicki | Owner: RyanGlScott
Type: feature request | Status: new
Priority: normal | Milestone: 8.2.1
Component: Compiler (Type | Version: 7.6.3
checker) |
Resolution: | Keywords: TypeFamilies
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: #2721 | Differential Rev(s):
Wiki Page: |
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Changes (by RyanGlScott):
* owner: goldfire => RyanGlScott
Comment:
Right, I didn't say the last type parameter of `T` had to be the newtype.
Rather, the last type parameter of the class `C` (`z` in the example in
comment:18) just has to occur somewhere in the type parameters of `T`.
> I'm far from sure if this is really worth the effort of explaining and
implementing it.
I disagree! Really, this is a quite straightforward idea (with a couple of
small gotchas, like the one you observed), and I've implemented most of it
already—I just need to polish up the documentation, update the GHC wiki,
and post a Phabricator Diff.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8165#comment:19>
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