#12580: Eagerly simplify inherently-coherent instances -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: 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 goldfire): For the instance to be accepted, don't we also need (`constraintI` implies `constraintC`)? Perhaps that's what you mean by the constraints being identical. To rephrase your proposal, you wish solving for `C` to pretend that `IncoherentInstances` is in effect, reducing to `constraintC`/`constraintI` even when another given is in scope. This seems plausible at first glance. Do you have a full concrete example of where this would change behavior? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12580#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler