[GHC] #1050: Using an inferred type as a type signature fails

[GHC]

#1050: Using an inferred type as a type signature fails
----------------------------------------+-----------------------------------
    Reporter:  simonpj                  |       Owner:                  
        Type:  bug                      |      Status:  new             
    Priority:  low                      |   Milestone:  _|_             
   Component:  Compiler (Type checker)  |     Version:  6.6             
    Keywords:                           |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple         |     Failure:  None/Unknown    
  Difficulty:  Unknown                  |    Testcase:                  
   Blockedby:                           |    Blocking:                  
     Related:                           |  
----------------------------------------+-----------------------------------
Changes (by morabbin):

  * failure:  => None/Unknown


Comment:

 Defect still present in GHC 7.6.1, but I'm seeing some oddness in the
 number of errors presented with multiples:
 {{{
 {-# LANGUAGE MultiParamTypeClasses #-}

 class C a b where
    op :: a -> a

 f1 :: C a b => a -> a
 f1 x = op x

 f2 :: C a b => a -> a
 f2 x = op x
 }}}
 If we give both type signatures, both fail. If we give neither, both fail
 (albeit with a different error). Leave out only ''one'' type signature,
 and only that function fails to type. Or, more likely, the other failure
 is not reported.

 I have files to attach if deemed worthwhile (no patch, just files that
 show the four behaviors).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1050#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler