
#14420: Data families should not instantiate to non-Type kinds -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Resolution: | Keywords: TypeFamilies 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 monoidal): The definition `data Bool = False | True` defines a closed type: the only values of type `Bool` are `False` and `True`, pattern matching on both of them defines a total function. A function `Bool -> A` is equivalent to a tuple `(A,A)`. It's natural to expect the same behavior on the kind level: the promoted kind `Bool` should have only two inhabitants, type `False` and `True`. Currently, this doesn't hold. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14420#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler