#11735: Optimize coercionKind -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I still say that most uses of `mkNthCo` already know the right role -- though perhaps this role may not be as obvious to someone who isn't me. Just supplying the role would be much better than computing it, of course. I don't agree with Simon's suggestion about `mkNthCoDirect` -- this is a first step toward invariants that are not upheld. Instead, I would have `mkNthCo` require a role and make a new `mkNthCoNoRole` that computes it. The naming of the functions should discourage the use of the second. The Note explaining why I originally bundled `coercionKind` and `coercionRole` points to a test case. Does that give a concrete testing ground? You might also look in the git history around that note to see if that gives you any pointers. Agreed about not cluttering `IfaceCoercion`. And, yes, I will take a look at `simplCast` tomorrow. (Though it's deeply scary when Simon says "My brain melted" and then asks me to take a look!) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11735#comment:29 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler