Re: [GHC] #11397: Type mismatch in local definitions in Haskell 98 code

11 Jan 2016

      #11397: Type mismatch in local definitions in Haskell 98 code
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        Reporter:  Lemming           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by monoidal):

 Smaller example:

 {{{
 module PairMismatch (f) where

 f :: a -> [Maybe a]
 f x =
    let switch l = [l Nothing, l (Just x)]
    in  switch id
 }}}

 While investigating this, I found two more programs that compile with GHC
 7.10 but fail with HEAD, I'm not sure if the cause is the same or
 different.

 {{{
 module PairMismatch2 (f) where

 u :: a
 u = u

 f :: a
 f = let switch l = l u in switch u
 }}}

 {{{
 module PairMismatch3 (f) where

 f :: a
 f = let switch l = l undefined in switch undefined
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11397#comment:2
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