#8506: misleading error message for duplicate type class instances ---------------------------------------------+----------------------------- Reporter: carter | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.6.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: parser/should_fail/T8506 | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: ---------------------------------------------+----------------------------- Comment (by carter): awesome, thanks! I merely wanted to highlight the distinction of {{{ src/Numerical/Types/Shape.hs:97:17: Unexpected type `Z' where type variable expected In the declaration of `Shape Z' }}} when theres a data family in the class vs {{{ src/Numerical/Types/Shape.hs:88:16: Unexpected type `Z' where type variable expected In the declaration of `Shapable Z' }}} because it wasn't clear to me, and that was part of why the original original snippet was especially confusing. Namely that it seemed to be saying I couldn't instantiate a data family (in addition to the whole typeclass dec needs to have variables as parameters) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8506#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler