#14180: Strange/bad error message binding unboxed type variable -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.3 Component: Compiler (Type | Version: 8.3 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): For what it's worth, the situation here appears to have changed slightly between GHC 8.4.3 and 8.6.1. In 8.4.3, one could work around this issue by replacing the `x` (in `MatchInt ('I# x) = '()`) with `_`. However, this is no longer be the case in 8.6.1, where even replacing `x` with `_` will yield this error: {{{ Bug.hs:6:17: error: • Couldn't match a lifted type with an unlifted type When matching kinds k0 :: * Int# :: TYPE 'IntRep Expected kind ‘Int#’, but ‘_’ has kind ‘k0’ • In the first argument of ‘ 'I#’, namely ‘_’ In the first argument of ‘MatchInt’, namely ‘( 'I# _)’ In the type family declaration for ‘MatchInt’ | 6 | MatchInt ('I# _) = '() | ^ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14180#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler