[GHC] #13065: Prohibit user-defined Generic and Generic1 instances
GHC
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Wed Jan 4 17:31:17 UTC 2017
#13065: Prohibit user-defined Generic and Generic1 instances
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Reporter: dfeuer | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 8.4.1
Component: Compiler | Version: 8.0.1
Resolution: | Keywords: Generics
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: Other | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Changes (by simonpj):
* cc: RyanGlScott (added)
Comment:
I'd like to know what Ryan Scott thinks of this idea. We have some
classes (like `Typeable`) where you can't give user instances, but it
seems less clear-cut for `Generic`.
The efficiency issue is to do with the costs of doing the type-family
consistency checks for all the `Generic` instances.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13065#comment:1>
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