#14164: GHC hangs on type family dependency -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: merge Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: | InjectiveFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: indexed- | types/should_compile/T14164 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Ah I see. So the underlying invariant is * Applying a substitution S to a type t should result in a ''well-kinded'' type S(t). What do we need for that to be true? Perhaps this? If a is in fv(t)\dom(S) then fv(kind(a)) is disjoint from dom(S)? That is, if there is free variable in t that we aren't substituting, then we aren't substituting in its kind either. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14164#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler