#16412: Type family signatures in indefinite modules -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.6.4 Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Backpack does not allow type family signatures in indefinite modules. As an example, although GHC does accept: {{{ -- indefinite module data Foo :: Bool -- implementing module type Foo = 'True }}} It does not accept: {{{ -- indefinite module type family Foo (b :: Bool) :: Bool -- implementing module type family Foo (b :: Bool) :: Bool where Foo 'True = 'False Foo 'False = 'True }}} I'm not sure if there is a fundamental reason for this (e.g. a requirement that everything is matchable). It would be helpful for the thing I'm experimenting with if this restriction could be lifted. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16412 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler