#11471: Kind polymorphism and unboxed types: bad things are happening -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.10.3 checker) | Keywords: TypeInType, Resolution: | LevityPolymorphism Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Re comment:2: Try with `-fprint-explicit-coercions`. Here's what I think is happening, though I don't have a fresh enough build locally to check: `foo :: Proxy a -> F a -> F a` becomes `foo :: forall k2 (a :: *). Proxy * a -> F k2 a -> F k2 a`. Note that `F` is not polymorphic in the kind of `a`, which defaults to `*`. We also know that `k2` must be either `*` or `#`, because `F k2 a :: k2` is an argument of an arrow. GHC wisely defaults it to `*`, leading to the second error. Once we clean up kind errors with coercions, I think the error messages will improve. There's also clearly the word `kind` appearing where `type` should in the first message. But these errors are legitimate. As for the larger issue, we'll need to discuss. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11471#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler