#8221: Type checker hangs ----------------------------------------------+--------------------------- Reporter: maxs | Owner: dreixel Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Resolution: | Keywords: hangs Operating System: Unknown/Multiple | Architecture: arm Type of failure: GHC rejects valid program | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: ----------------------------------------------+--------------------------- Comment (by monoidal): Here is a smaller testcase. The bug is not related to Typeable. File A.hs: {{{ module A where import Data.IORef data Link a = Link !(IORef (Link a)) | X deriving Eq }}} File T.hs: {{{ module T where import A data Located e = L () e deriving Eq }}} Run `ghc-7.7 -O A.hs` and then `ghc-7.7 T.hs`, the second command should hang. While investigating this, I also found that compiling this contrived file with HEAD and -O hangs, while 7.6.3 succeeds. However, it is probably a different issue because deriving is not used: {{{ module M where data Link a = Link !(Link a) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8221#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler