[GHC] #10403: GHC crashes on a partial type signature

11 May 2015


      #10403: GHC crashes on a partial type signature
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              Reporter:              |             Owner:
  Artyom.Kazak                       |            Status:  new
                  Type:  bug         |         Milestone:
              Priority:  normal      |           Version:  7.10.1
             Component:  Compiler    |  Operating System:  Linux
              Keywords:              |   Type of failure:  Compile-time
          Architecture:  x86_64      |  crash
  (amd64)                            |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
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 The following code crashes GHC 7.10.1 as is, but doesn't result in a crash
 if the signature is specified completely or isn't specified at all
 (inferred):

 {{{#!hs
 {-# LANGUAGE PartialTypeSignatures #-}
 module Main where

 data I a = I a
 instance Functor I where
     fmap f (I a) = I (f a)

 newtype B t a = B a
 instance Functor (B t) where
     fmap f (B a) = B (f a)

 newtype H f = H (f ())

 app :: H (B t)
 app = h (H . I) (B ())

 h :: _
 --h :: Functor m => (a -> b) -> m a -> H m
 h f b = (H . fmap (const ())) (fmap f b)
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10403
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