#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 v0d1ch): I have determined that in the failure case in this specific example we want the `Role` to be `Nominal` and we get a `[Type]` that looks like this: `[* -> *, Maybe]` while the `TyCon` is `F` How would I precede further with these informations ? I am also wondering if I should introduce new type that will give us the option to customize failure message instead of just `Nothing` ? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10789#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler