#11715: Constraint vs * -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler (Type | Version: 8.0.1-rc1 checker) | Resolution: | Keywords: Typeable 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 int-index): Replying to [comment:27 goldfire]: A warning sounds like a plausible solution, provided that it's suppressed for class constraints. ---- Replying to [comment:28 Iceland_jack]: That's interesting, although I am not quite sure what "reference" means in this context. ---- Replying to [comment:29 simonpj]:
Of course, we can have two different `Ord` dictionaries by declaring two instances in different places.
You can't have both of them in scope. And unless they are orphan instances, which are frowned upon, you can't use both of them in one program.
provided we limit the ways you can construct a value of kind `Constraint`.
If I understand correctly, the plan is to abolish kind 'Constraint' in favor of 'Type'. So 'with' does make things more incoherent, as now you can have `Int => t` and `Int` is clearly not a singleton type, and you can have two distinct `Int`s in one scope. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11715#comment:30 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler