#15740: Type family with higher-rank result is too accepting -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.8.1 Component: Compiler | Version: 8.6.1 Resolution: | Keywords: TypeFamilies, | TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #15793 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Simon appears to have stumbled upon this separately, in his ongoing work captured in Phab:D5305. The fix appears to be a small change to `kcTyFamEqnRhs` to instantiate only invisible arguments that are within the arity of the tyfam; right now, it wrongly instantiates ''all'' invisible arguments. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15740#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler