#10832: Generalize injective type families -------------------------------------+------------------------------------- Reporter: jstolarek | Owner: jstolarek Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Keywords: TypeFamilies, Resolution: | InjectiveFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #6018 | Differential Rev(s): Phab:D1287 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Are we exploring avenues like [https://ghc.haskell.org/trac/ghc/ticket/6018#comment:48 head-injectivity] or partial injectivity? Richard's example tells us `x ~ Just y` if `F x ~ True` {{{#!hs type family F a where F (Just x) = True F Nothing = False }}} but similarly {{{#!hs type family G a where G (Just x) = (x, x) G Nothing = (Int, Int) }}} means `x ~ Int` if `G (Just x) ~ (Int, Int)` — is that useful? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10832#comment:18 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler