#10789: Notify user when a kind mismatch holds up a type family reduction -------------------------------------+------------------------------------- Reporter: goldfire | Owner: v0d1ch Type: feature request | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: newcomer, | TypeFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13192 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire):
How would I proceed further with these informations ?
Not quite sure how to answer this. You might need to continue tracing the code path into `tcMatchTys`.
I am also wondering if I should introduce new type that will give us the
option to customize failure message instead of just `Nothing` ? Yes, I think so. For example, instead of `Nothing`, maybe it would work well to return an `Int` that gives the index of the first argument that mismatches. Then, the error-message generator could see if that index corresponds to an invisible argument; if so, suggest `-fprint-explicit- kinds`. Perhaps there's a better design, as well.
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10789#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler