#15170: GHC HEAD panic (dischargeFmv) -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.6.1 Component: Compiler (Type | Version: 8.5 checker) | Resolution: fixed | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Compile-time | Test Case: crash or panic | polykinds/T15170 Blocked By: | Blocking: Related Tickets: #14880, #15076 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => closed * resolution: => fixed * related: => #14880, #15076 Comment: Thanks, Simon! Ironically, I was writing this to work around #14880/#15076, and while I applied the workaround to `f`, I forgot to apply it to `g`. This is the function that I //meant// to write: {{{#!hs dcomp :: forall (a :: Type) (b :: a ~> Type) (c :: forall (x :: a). Proxy x ~> b @@ x ~> Type) (f :: forall (x :: a) (y :: b @@ x). Proxy x ~> Proxy y ~> c @@ ('Proxy :: Proxy x) @@ y) (g :: forall (x :: a). Proxy x ~> b @@ x) (x :: a). SingKind (c @@ ('Proxy :: Proxy x) @@ (g @@ ('Proxy :: Proxy x))) => (forall (xx :: a) (yy :: b @@ xx). Sing (f @@ ('Proxy :: Proxy xx) @@ ('Proxy :: Proxy yy))) -> (forall (xx :: a). Sing (g @@ ('Proxy :: Proxy xx))) -> Sing a -> Demote (c @@ ('Proxy :: Proxy x) @@ (g @@ ('Proxy :: Proxy x))) dcomp _sf _ _ = undefined }}} And after your most recent patch, this compiles without a hitch, even with `-dcore-lint`! I think we can close this in favor of #14880/#15076, as the Core Lint error in the original program is just a dressed-up version of the program in #15076. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15170#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler