Re: Uniquable RdrName instance

would making arrow remindable involve dropping the arr == haksell functions assumption or doing something that would allow generalized arrows? On Mon, Jun 16, 2014 at 5:14 PM, Nicolas Frisby wrote:

FYI it's #7828, not #7282.

Jan, I'm very glad you're working on this. Thanks!

On Mon, Jun 16, 2014 at 2:33 PM, Jan Stolarek wrote:

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Why do you want this? The danger I see lurking is that you might find two RdrNames that give the same answer to getUnique but represent different Yes, that's exactly my concern.

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Why do you want this? I'm working on #7282 - RebindableSyntax and Arrows. Here's a snippet from desugaring of arrow notation:

leaves = concatMap leavesMatch matches where leavesMatch :: LMatch Id (Located (body Id)) -> [(Located (body Id), IdSet)] leavesMatch (L _ (Match pats _ (GRHSs grhss binds))) = let defined_vars = mkVarSet (collectPatsBinders pats) `unionVarSet` mkVarSet (collectLocalBinders binds) in [(body, mkVarSet (collectLStmtsBinders stmts) `unionVarSet` defined_vars) | L _ (GRHS stmts body) <- grhss]

This is in the desugarer. But I need to also know `length leaves` at the renaming stage, which means I need to call `concatMap leavesMatch matches`. The problem is that in the renamer my datatypes are not parametrised by `Id`. I turned `Id` into a type parameter `id`, but then I can't use VarSets. I could use more general UniqueSets but only if `id` type parameter is an instance of Uniquable. And since in the renamer the datatypes are parametrized with RdrName this leads me to wanting Uniqable RdrName instance.

Janek _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs

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