#9562: Type families + hs-boot files = unsafeCoerce -------------------------------------+------------------------------------- Reporter: goldfire | Owner: ezyang Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: #10270 | Differential Revisions: -------------------------------------+------------------------------------- Changes (by ezyang): * owner: => ezyang Comment: Sure, assuming we decide on a resolution. A relaxation on Richard's proposal is to allow ONLY the left-hand side of type families to be specified in the hs-boot file. This is because we don’t really need the type families to reduce, unless people want them to, and reduces burden on hs-boot file writers, because having to pull in identifiers from the RHS could be pretty annoying. We'd need to add a new syntactic form for RHS-less type families. As for normal instance declarations, the situation here is no worse than the classic diamond example, where two conflicting instances can be used without triggering an error, so I'm less inclined to demand that case. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9562#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler