#16013: :kind! accepts unsaturated type aliases -------------------------------------+------------------------------------- Reporter: dmwit | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: 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 dmwit): Okay, so further thinking, I'd like to retract part of the complaint. I believe I understand why it decides on kind `*`, and agree that's a sensible answer. (Namely: I thought in my head `Id :: k -> k`, but the compiler chose `Id :: k -> *`, following exactly the rules set out in the documentation, so the compiler was right and I was wrong. And I thought in my head `Id a = a` matches all types so `Id Foo` should reduce to `Foo` if it works at all, but the compiler thought `Id a = a` only matches when `a :: *`, so `Id Foo` is a stuck term not one that can reduce, and again the compiler was right and I was wrong.) But I still think it should probably complain about applying a type family or type alias to an unsaturated type alias. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16013#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler