#10009: type inference regression when faking injective type families -------------------------------------+------------------------------------- Reporter: aavogt | Owner: Type: bug | Status: new Priority: high | Milestone: 7.12.1 Component: Compiler (Type | Version: 7.10.1-rc1 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #10226 | -------------------------------------+------------------------------------- Comment (by edsko): Reported this independently, didn't see this ticket, sorry. But we were just bitten by this in ide-backend as well (we can work around it with proxies). See https://ghc.haskell.org/trac/ghc/ticket/10226 for an independent example, might perhaps be useful as a second test case (and some detailed comments there as well). Note that I do *not* think, as per @simonpj 's comment above, that "It can always be fixed by adding a type signature". -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10009#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler