#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 simonpj):
I'm afraid to say that coercionRole (NthCo ...) manifestly does require coercionKind
Aha. So it does. Very well, yes let's do this * Cache the role (of the result of `NthCo i co`) in the `NthCo` data constructor * Make `mkNth` compute that cached role by calling `coercionKind` and `coercionRole` (in the final equation where we build `NthCo`). * Possible gloss: in some calls to `mkNthCo` we know the role, and we even know that the various short-cuts in `mkNthCo` won't succeed. So we can just use `NthCo` directly -- or define `mkNthCoDirect = NthCo` and call `mkNthCoDirect`. Perhaps not worth it; but when we do know the role it seems a bit silly not to use it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11735#comment:23 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler