#14626: No need to enter a scrutinised value -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: heisenbug Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: performance Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13861 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by alexbiehl): Right, though `GHC.IO.Handle.Types`, which contains `Handle__`, has {{{ {-# OPTIONS_GHC -funbox-strict-fields #-} }}} in its header. Given this, our example `data H = H !(IORef Char)` turns into {{{ $WH $WH = \ dt_aV9 -> case dt_aV9 `cast` Co:2 of { STRef dt_aVb -> H dt_aVb } }}} So we are indeed storing a `MutVar#` here. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14626#comment:31 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler