#10338: GHC Forgets Constraints -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 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 simonpj): But that's very reasonable isn't it? What type do you expect to be inferred for `fromScalar'`? Well, you get a constraint `T t r` arising from the call to `fromScalar` in its RHS, and GHC solves that constraint using the instance declaration, so we get the inferred type {{{ fromScalar' :: (Functor t, Num r) => r -> t r }}} And now you can see why you get the complaint when it's called in `convert`. What did you think would happen? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10338#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler