#14111: strange error when using data families with levity polymorphism and unboxed sums and data families -------------------------------------+------------------------------------- Reporter: carter | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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 goldfire): Ah. Now I understand better. Instantiating the shape is just incidental, done so that unification succeeds at all. The real action is in solving for any metavars in the data constructor type, and this unification does ''not'' affect anything about the head shape. Yes, that sounds reasonable. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14111#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler