#14319: Stuck kind families can lead to lousy error messages -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.3 checker) | Keywords: TypeInType, Resolution: | TypeFamilies Operating System: Unknown/Multiple | Architecture: Type of failure: Poor/confusing | Unknown/Multiple error message | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Actually, no. I can get just as bad an error message at the term level: {{{#!hs f :: forall (s :: Symbol). Proxy s -> F s f _ _ = undefined }}} produces {{{ ArityError.hs:14:1: error: • Couldn't match expected type ‘F s’ with actual type ‘p0 -> a0’ The type variables ‘p0’, ‘a0’ are ambiguous • The equation(s) for ‘f’ have two arguments, but its type ‘Proxy s -> F s’ has only one • Relevant bindings include f :: Proxy s -> F s (bound at ArityError.hs:14:1) | 14 | f _ _ = undefined | ^^^^^^^^^^^^^^^^^ }}} So we have the same problem there. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14319#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler