#9242: Implement {-# OVERLAPPABLE #-} and {-# INCOHERENT #-} pragmas -------------------------------------+------------------------------------- Reporter: simonpj | Owner: diatchki Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by diatchki): I know the code, so I don't mind doing it. Out of curiosity, do you have an example of when you may want to write just `OVERLAPPING` and not `OVERLAPABLE` or vice versa? The way I understand it, they have the following meanings: * `OVERLAPPING` says "I am a most general instance" (i.e., can overlap, but can't be overlapped), * `OVERLAPABLE` says "I am a most specific instance" (i.e., can't overlap, can be overlapped). So, they make some sense for the "edge-case" instances, but not for the ones inbetween, and I couldn't really think of good cases where I may want to put them on an instance. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9242#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler