#13962: GHCi allows unsaturated type family -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #12089 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): The muddiness all comes down to this: If GHC knows `m a ~ Maybe Int`, should it choose `m ~ Maybe` and `a ~ Int`? After all, if `m` could be an unsaturated type family, committing to the above decomposition would be wrong. This kind of inference seems unlikely in `:kind` or `:kind!`, though I can't rule it out if someone tried to. In the end, I think we should just keep the current behavior. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13962#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler