#11348: Local open type families instances ignored during type checking -------------------------------------+------------------------------------- Reporter: alexvieth | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc1 Resolution: fixed | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | typecheck/should_compile/T11348 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1762 Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Hooray Hooray Hooray! Thanks, Alex! This was a major engineering task that I shuddered at the thought of. It has lightened my day knowing that I won't have to do this. :) If that was fun for you, the next step is to support [https://en.wikipedia.org/wiki/Induction-recursion_%28type_theory%29 induction recursion]. I'm pretty sure I know how to do this, but it will take a similar engineering effort. It's not for the faint of heart, but this patch shows that your heart is not faint. As an added bonus, supporting induction recursion in GHC may be enough to publish a paper about, if that kind of thing is an incentive for you. Some notes (meant for myself, YMMV) I have on the subject are [https://ghc.haskell.org/trac/ghc/wiki/DependentHaskell/Internal#Separatingty... here]. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11348#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler