#14440: Duplicate type family instances are permitted -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.1 checker) | Resolution: | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): See Section 3.6 of the [https://www.microsoft.com/en- us/research/publication/closed-type-families-with-overlapping-equations/ Closed type families] paper. Having identical RHSs is a degenerate case of Definition 10. But perhaps it's so degenerate that it should be reported with a warning; I'm not sure. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14440#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler