cvs commit: fptools/ghc/compiler/typecheck TcSimplify.lhs

[Simon Peyton Jones]

simonpj     2005/05/20 04:32:03 PDT

  Modified files:
    ghc/compiler/typecheck TcSimplify.lhs 
  Log:
  	Liberalise the defaulting rules for GHCi
  
  		Merge to STABLE?
  
  The H98 defaulting rules are these.  Group constraints of the form (C v),
  for some particular type variable v. Then default v if
  
  a) v appears only in this group (no implicit params or D [v])
  b) at least one of the C's is numeric
  c) all the C's are standard
  
  GHCi changed rules (b) to
  
  (b') at least one of the C's is numeric, or Eq,Ord,Show
  
  This commit further liberalises GHCi to change (c):
  
  (c') any of the C's are standard
  
  Otherwise the existence of a non-standard class (e.g. Random) is enough
  to kill defaulting altogether.
  
  Revision  Changes    Path
  1.157     +27 -28    fptools/ghc/compiler/typecheck/TcSimplify.lhs