[GHC] #1382: Monad GHC.Prim.Any1 gets derived in a context

[GHC]

#1382: Monad GHC.Prim.Any1  gets derived in a context
--------------------------------------------+-------------------------------
    Reporter:  iampure at gmail.comguest       |        Owner:  simonpj
        Type:  bug                          |       Status:  new    
    Priority:  high                         |    Milestone:         
   Component:  Compiler (Type checker)      |      Version:  6.7    
    Severity:  critical                     |   Resolution:         
    Keywords:  Any1 context type-inference  |   Difficulty:  Unknown
          Os:  Unknown                      |     Testcase:         
Architecture:  Unknown                      |  
--------------------------------------------+-------------------------------
Changes (by simonpj):

  * version:  6.6.1 => 6.7
  * owner:  => simonpj

Comment:

 Just to clarify,  you don't mean GHC 6.6.1, do you?  For that I get
 {{{
 BugBug.hs:66:24:
     Ambiguous type variable `m' in the constraint:
       `Monad m'
         arising from use of `default_visitor' at BugBug.hs:66:24-38
     Probable fix: add a type signature that fixes these type variable(s)
 }}}
 In the HEAD, I agree something odd happens:
 {{{
 bash-3.1$ $gpj -c BugBug.hs -ddump-types
 TYPE SIGNATURES
     ...
   test :: forall (m :: * -> *) state (g :: * -> * -> *) a b state1.
             (Gr g, Show b, Show a, Monad GHC.Prim.Any1, Monad m) =>
             Foo m (g a b) state (Maybe [A])
 }}}
 I'll look into it. Meanwhile, use GHC 6.6.1!

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1382>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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