#15632: Undependable Dependencies -------------------------------------+------------------------------------- Reporter: AntC | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1-beta1 Resolution: | Keywords: | FunctionalDependencies, | OverlappingInstances Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: 10675, 9210, | Differential Rev(s): 8634 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by AntC): Replying to [comment:2 AntC]: I've implemented the suggestion, in a version of Hugs. So throw at me your awkward cases/counter-examples. (Hugs latest release/Sep 2006 only allows `FunDeps + Overlap` if all the overlapping instances are per the strictly unify-to-equal rule. Hugs instance heads must overlap in a strict substitution order; none of GHC's allowing the potential for overlap.) Seems to be working; I have a type-level type equality test; it handles the tricky cases I'm aware of, including this ticket. #10675 is rejected. Even handles overlap of instances for TRex records. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15632#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler