#14968: QuantifiedConstraints: Can't be RHS of type family instances -------------------------------------+------------------------------------- Reporter: josef | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.5 checker) | Keywords: Resolution: | QuantifiedConstraints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #9269 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I'm not sure what the return kind has anything to do with this. Ultimately, the issue is impredicativity, which is going to be a problem regardless of whether you're working over `*`, `Constraint` (as in your example), `Bool` (as in the example in https://ghc.haskell.org/trac/ghc/ticket/9269#comment:1), or something else. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14968#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler