#13262: Allow type synonym family application in instance head if it reduces away -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: feature request | Status: new Priority: lowest | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | 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 goldfire): This has been proposed before (though I can't find where), and I find the idea quite distasteful. Consider what this would mean at the term level: {{{ f :: Bool -> Int f (not True) = 5 f True = 6 }}} Parsing challenges aside, there's nothing at all wrong with the above declaration. But do we really want programmers to be able to do this? It's the same at the type level. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13262#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler