[GHC] #771: GHC typing too constrained

[GHC]

#771: GHC typing too constrained
-----------------------+----------------------------------------------------
  Reporter:  guest     |          Owner:               
      Type:  bug       |         Status:  new          
  Priority:  normal    |      Milestone:               
 Component:  Compiler  |        Version:  6.4.1        
  Severity:  normal    |       Keywords:  type checking
Difficulty:  Unknown   |   Architecture:  x86          
        Os:  Linux     |  
-----------------------+----------------------------------------------------
for the following program:
 ----------------------------
 module Bug where

 f :: Maybe Bool
 f = g ()

 g () = do f
           error "bug?"
 ----------------------------
 If I ask ghci (version: 6.4.1) what the type of g is, it says:
 ----------------------------
 *Bug> :t g
 g :: () -> Maybe Bool
 ----------------------------

 However, I think it should be:
 ----------------------------
 Bug> :t g
 g :: () -> Maybe a
 ----------------------------
 as reported by Hugs (version: March 2005).

 I first thought this was a monomorphism-restriction gotcha, but g is
 obviously a function, not a constant. And Hugs reports the more general
 expected type anyhow.

 I'm curious to see if this is a real bug or some weird interaction with
 ghci..

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/771>
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