#8828: allow fully applied type families in instance heads -------------------------------------+------------------------------------ Reporter: aavogt | Owner: goldfire Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by simonpj): * owner: => goldfire Comment: Seems very reasonable. The rule would be this: you normalise the instance type, and check that there are no remaining type family calls. After all, with `-XFlexibleInstances` you can use type synonyms in instance heads, and this is just an extension of the same idea. c.f. http://www.haskell.org/ghc/docs/latest/html/users_guide/type-class- extensions.html#flexible-instance-head Richard will work on this in due course. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8828#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler