#7939: RHS of associated type not kind-checked ------------------------------------------+--------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC accepts invalid program | Difficulty: Unknown Testcase: ghci/scripts/T7939 | Blockedby: Blocking: | Related: ------------------------------------------+--------------------------------- Comment(by goldfire): I've implemented the plan above, but there is still at least one dark corner. Consider this: {{{ class Foo a where type Bar a b }}} What should the kind of {{{Bar}}} be? Because classes are kind-polymorphic by default (which is good), the kind of {{{a}}} must be {{{k}}}. But, what about {{{b}}}? Right now, in both HEAD and my implementation with the fix for this ticket, {{{Bar}}} has the kind {{{k1 -> k2 -> *}}}. We don't generalize the result kind (as described above), but we still do generalize all arguments. It wouldn't be hard to separate out the arguments that are bound in the class head, generalize those and not generalize the others, but that seems even stranger somehow. Thoughts? Expect a patch soon. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7939#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler