#5916: runST isn't free -------------------------------------+------------------------------------ Reporter: tibbe | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.6.2 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by nomeata): Turns out I spoke too soon (and that the test suite really does not cover this): This code {{{ #!haskell main = let f () = runST $ do ref <- newSTRef 0 modifySTRef ref (+1) readSTRef ref in print (f () + f ()) }}} will be broken by my approach (output `3` instead of `2`), as there are no free variables that differing – obvious, now that I see it. Too bad, was hoping to produce something usable today... at least I’ll add a possibly useful testcase. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5916#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler