#7543: Constraint synonym instances -------------------------------------+------------------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by goldfire): The other thing we could do is support this feature at synonym-definition time. When defining a type synonym such that the head of the RHS is a class, record this fact in the `TyCon` and corresponding iface info. If such a synonym appears as the head of an instance declaration, we use this tidbit to do the name lookup. This would be easier to explain, at least, and wouldn't require much upheaval either. Actually, this is probably simpler than my idea in comment:7. About looking up instances: we really need to move beyond `grep` for this sort of thing! Of course, I exclusively use `grep` for this sort of thing... because I don't have a better option to hand. But that's a story for another day. In the meantime, worrying about obfuscation via synonyms is valid, but also not something that (I believe) should hold this up. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7543#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler