[GHC] #11449: Treat '_' consistently in type declarations
GHC
ghc-devs at haskell.org
Mon Jan 18 13:00:40 UTC 2016
#11449: Treat '_' consistently in type declarations
-------------------------------------+-------------------------------------
Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.10.3
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
-------------------------------------+-------------------------------------
Comment (by goldfire):
I would love to see (A) accepted (perhaps with some language extension).
I think (C) should be rejected. After all, the type variable ''is'' used
there. It's used in the type family declaration, where `a` is not
''bound'' -- it is ''used''.
Accordingly,
{{{
class C a where
type F a
type F a = Int
}}}
should not emit any warnings. The only bound variable, `a`, is indeed
used.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11449#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
More information about the ghc-tickets
mailing list