#10185: Coercible solver incomplete with non-variable transitivity -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: low | Milestone: ⊥ Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- If I say {{{ import Data.Coerce import Data.Proxy foo :: (Coercible (a b) (c d), Coercible (c d) (e f)) => Proxy (c d) -> a b -> e f foo _ = coerce }}} I get an error, because GHC isn't smart enough to figure out transitivity in this case. It ''can'' do it with bare variables, but not variable applications. It's possible there's a way to do this, but we'll wait for someone to shout before investing effort. Do shout if this lack of functionality is ruining your day! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10185 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler