cvs commit: fptools/ghc/compiler/typecheck Inst.lhs TcRnDriver.lhs TcSimplify.lhs TcType.lhs

simonpj     2003/06/20 04:14:22 PDT

  Modified files:
    ghc/compiler/typecheck Inst.lhs TcRnDriver.lhs TcSimplify.lhs 
                           TcType.lhs 
  Log:
        ------------------------------
        Fix a small quantification bug
        ------------------------------
  
  We were quantifying over too few type variables, because fdPredsOfInsts was
  being too eager to discard predicates. This only affects rather obscure
  programs.  Here's the one Iavor found:
  
        class C a b where f :: a -> b
        g x = fst (f x)
  
  We want to get the type
        g :: forall a b c.  C a (b,c) => a -> b
  but GHC 6.0 bogusly gets
        g :: forall a b.  C a (b,()) => a -> b
  
  A test is in should_compile/tc168
  
  Revision  Changes    Path
  1.118     +9 -6      fptools/ghc/compiler/typecheck/Inst.lhs
  1.35      +5 -5      fptools/ghc/compiler/typecheck/TcRnDriver.lhs
  1.117     +1 -0      fptools/ghc/compiler/typecheck/TcSimplify.lhs
  1.91      +1 -7      fptools/ghc/compiler/typecheck/TcType.lhs