#14824: automatically select instance -------------------------------------+------------------------------------- Reporter: zaoqi | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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 zaoqi): Replying to [comment:3 zaoqi]:
Replying to [comment:2 AntC]:
I'm afraid we'll need a bit of elaboration to know what this means.
What do you expect to see? Your instance declarations do not give implementations for method `m`.
There are no `FunctionalDependencies` so all of those instances are valid. If I write `b -> a` in that, `Type inference` can't work correctly.
I can't write `a -> b`.
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14824#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler