#9171: Clarify error messages when there is a kind mismatch ----------------------------------------------+---------------------------- Reporter: MikeIzbicki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects valid program | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Comment (by goldfire): kosmikus is right -- kind variables are properly seen as arguments to a type family, and the OP's code is correctly rejected. However, the error message is quite suboptimal. I wonder if there's a way to detect that kinds are at issue and to suggest `-fprint-explicit-kinds` (which would make the problem more apparent). As a strawman proposal, we could just look at the rendered output; if the "expected" and "actual" are identical, suggest `-fprint-explicit-kinds`. Leaving this ticket open as a request to fine-tune error message. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9171#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler