#12102: “Constraints in kinds” illegal family application in instance (+ documentation issues?) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | typecheck/should_fail/T12102 Blocked By: | Blocking: Related Tickets: #13780, #15872, | Differential Rev(s): Phab:D5397 #16263 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Hang on. The Note explains that * equality constraints `(~)` and `(~~)` should be fine; * other constraints like `Eq a` should be illegal; * `(~#)` isn't a constraint at all; see `Note [Types for coercions, predicates, and evidence]` in `TyCoRep` We should both make the user manual reflect this, and fix any bugs (which surely exist). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12102#comment:21 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler