[GHC] #12938: Polykinded associated type family rejected on false pretenses
GHC
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Wed Dec 7 03:52:05 UTC 2016
#12938: Polykinded associated type family rejected on false pretenses
-------------------------------------+-------------------------------------
Reporter: goldfire | Owner: goldfire
Type: bug | Status: new
Priority: normal | Milestone: 8.2.1
Component: Compiler | Version: 8.0.1
Keywords: TypeInType | Operating System: Unknown/Multiple
Architecture: | Type of failure: None/Unknown
Unknown/Multiple |
Test Case: | Blocked By:
Blocking: | Related Tickets:
Differential Rev(s): | Wiki Page:
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If I say
{{{
class HasRep a where
type Rep a :: TYPE r
}}}
I get
{{{
• Kind variable ‘r’ is implicitly bound in datatype
‘Rep’, but does not appear as the kind of any
of its type variables. Perhaps you meant
to bind it (with TypeInType) explicitly somewhere?
Type variables with inferred kinds: a
• In the class declaration for ‘HasRep’
}}}
This definition should be accepted, though, as `r` is just an invisible
parameter to the associated type family. (I don't know how ''useful'' this
is, but it's not bogus.)
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12938>
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