#5481: Associated type defaults + MultiParamTypeClasses error
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Reporter: illissius | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Compiler | Version: 7.3
Resolution: fixed | Keywords:
Testcase: | Blockedby:
Difficulty: | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: GHC rejects valid program |
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Comment(by simonpj):
No, it should work ''neither way''! In any type instance, whether
associated or not, the variables mentioned on the RHS must be a subset of
those on the LHS. So the above code should fail with
{{{
T5481.hs:6:5:
The RHS of an associated type declaration mentions type variable `b'
All such variables must be bound on the LHS
T5481.hs:8:5:
The RHS of an associated type declaration mentions type variable `a'
All such variables must be bound on the LHS
}}}
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5481#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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