#11066: Inacessible branch should be warning - otherwise breaks type soundness? -------------------------------------+------------------------------------- Reporter: rrnewton | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: #8128, #8740 | Differential Rev(s): Phab:D1454 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): But `foo (unsafeCoerce Refl)` asks GHC to come up with a proof of `1 :~: Gcd 3 4` and pass it as an implicit argument. Which it cannot do. (Remember this isn't the usual `Gcd`; it's a hypothetical nullary function.) So in fact I can't call `foo`. Rather than speculate about Ed let's see if he wants to say anything himself. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11066#comment:29 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler