Replying to [comment:5 rwbarton]:
In this case it seems that what we want to do is rewrite the left hand side of the new rule itself. Not sure if this is a good idea in general
#10595: BuiltinRules override other rules in some cases. -------------------------------------+------------------------------------- Reporter: gjsimms | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.11 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): Replying to [comment:6 simonpj]: though.
That sounds delicate and I have no idea what will really happen. The
solution I proposed is simple and robust. Agreed, but when the method in question belongs to a type class defined in another package (as in the original report), this solution is non-modular. A second library that defines `d'` cannot define a rule for `d' exp` that coexists with a rule for `d exp` unless the two libraries agree on a "`exp'`". It would be nicer if the rules could somehow refer directly to the- instance-of-exp-for-Double. Of course, this is in feature request territory. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10595#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler