patch applied (ghc): Improve error reporting for non-rigid GADT matches

[Simon Peyton Jones]

Thu Oct 30 07:39:47 PDT 2008  simonpj at microsoft.com
  * Improve error reporting for non-rigid GADT matches
  
  Following suggestions from users, this patch improves the error message
  when a GADT match needs a rigid type:
  
   tcfail172.hs:19:10:
       GADT pattern match in non-rigid context for `Nil'
  -      Solution: add a type signature
  +      Probable solution: add a type signature for `is_normal'
       In the pattern: Nil
       In the definition of `is_normal': is_normal Nil = True
  
  Now GHC tries to tell you what to give a type signature *for*.
  Thanks to Daniel Gorin and others for the suggestions.
  

    M ./compiler/hsSyn/HsExpr.lhs -4 +4
    M ./compiler/typecheck/TcArrows.lhs -3 +3
    M ./compiler/typecheck/TcMatches.lhs -9 +9
    M ./compiler/typecheck/TcPat.lhs -28 +45

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20081030143947-1287e-0b0f16b670d0d780ca2eebbee5886814fec0b55e.gz