[GHC] #8221: Type checker hangs

3 Sep 2013

      #8221: Type checker hangs
----------------------------+----------------------------------------------
       Reporter:  maxs      |             Owner:
           Type:  bug       |            Status:  new
       Priority:  normal    |         Milestone:
      Component:  Compiler  |           Version:  7.7
       Keywords:  hangs     |  Operating System:  MacOS X
   Architecture:  arm       |   Type of failure:  GHC rejects valid program
     Difficulty:  Unknown   |         Test Case:
     Blocked By:            |          Blocking:
Related Tickets:            |
----------------------------+----------------------------------------------
 The following program gets GHC stuck in Renamer/typechecker. This compiles
 correctly in 7.6.3.

 {{{
 {-# LANGUAGE DeriveDataTypeable #-}

 module Type.Type where

 import Data.Data
 import qualified Data.UnionFind.IO as UF

 data SrcSpan = Span String | NoSpan String
     deriving (Eq, Ord, Data, Typeable)

 data Located e = L SrcSpan e
     deriving (Eq, Ord, Data, Typeable)
 }}}

 Removing either the:

 {{{
 import qualified Data.UnionFind.IO as UF
 }}}

 or

 {{{
 data Located e = L SrcSpan e
     deriving (Eq, Ord, Data, Typeable)
 }}}

 or

 Removing the Eq Ord from Located:
 {{{
 data Located e = L SrcSpan e
     deriving (Data, Typeable)
 }}}

 will allow it to terminate.

 ddump-tc-trace shows it is related to the derived typeable instance.

 The log is attached.

 I am compiling with:

 {{{
 arm-apple-darwin10-ghc -staticlib -ddump-tc-trace Type/Type.hs -v
 -threaded
 }}}

 I don't have a x86 build of HEAD handy, I think if someone could try this
 program in HEAD then we will know if it is ARM / GHC iOS / stage1 specific
 or not.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8221
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler