Uniquable RdrName instance
jan.stolarek at p.lodz.pl
Mon Jun 16 19:33:06 UTC 2014
> 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.
> Why do you want this?
I'm working on #7282 - RebindableSyntax and Arrows. Here's a snippet from desugaring of arrow
leaves = concatMap leavesMatch matches
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.
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