#14967: Optimizer Casting Caf with nominal type -------------------------------------+------------------------------------- Reporter: etn | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: coerce, | nominal Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by etn): After looking for an example where this breaks without unsafe operations, I realized that this is almost certainly a safe transformation under the assumption of referential transparency. What this now amounts to is that there needs to be a way to prevent this from occurring in the case that a value cannot be shared between types. This issue came up when implementing Applicative, and I have realized that it is probably impossible to avoid this unless we can disable thunk-rewriting for particular thunks. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14967#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler