#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 rwbarton): The fact that the binding of `fromScalar'` is a local one is not actually important here: the program with {{{ instance (Functor t, Num r) => T t r fromScalar' a = fromScalar a -- or turn on NoMonomorphismRestriction convert :: (T t (F r)) => Foo t r -> Foo t r convert (Scalar c) = Foo $ fromScalar' $ toF c }}} also gives the error about "Could not deduce (Num (F r)) arising from a use of ‘fromScalar'’". -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10338#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler