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niteria authored
We want to remove the `Ord Unique` instance because there's no way to implement it in deterministic way and it's too easy to use by accident. We sometimes compute SCC for datatypes whose Ord instance is implemented in terms of Unique. The Ord constraint on SCC is just an artifact of some internal data structures. We can have an alternative implementation with a data structure that uses Uniquable instead. This does exactly that and I'm pleased that I didn't have to introduce any duplication to do that. Test Plan: ./validate I looked at performance tests and it's a tiny bit better. Reviewers: bgamari, simonmar, ezyang, austin, goldfire Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2359 GHC Trac Issues: #4012
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