Refactor DebruijnIndex to be 0-based#50475

Merged

bors merged 13 commits intorust-lang:masterfrom

May 29, 2018

Commits on May 28, 2018

introduce `shifted_in`, `shifted_out` and friends

nikomatsakis
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csmoe
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port `fold_regions` and friends to use debruijn indices directly

nikomatsakis
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csmoe
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make `shifted_in` and `shifted_out` const fns

nikomatsakis
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csmoe
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stop invoking `DebruijnIndex::new` directly

nikomatsakis
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csmoe
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port `nice_region_error` code to not track depth but rather index

nikomatsakis
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csmoe
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rewrite the hasher to not access `depth` field

nikomatsakis
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csmoe
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refactor `resolve_lifetime` to track outer-index, not depth

nikomatsakis
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csmoe
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replace use of DebruijnIndex in `for_each_free_region`

nikomatsakis
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csmoe
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convert `LateBoundRegionsCollector` to track a debruijn index

nikomatsakis
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csmoe
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replace `binder_depth` in `LateBoundRegionsDetector`

nikomatsakis
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csmoe
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remove use of depth from `TyS` and replace with a debruijn index

nikomatsakis
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csmoe
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make depth private

nikomatsakis
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csmoe
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change to 0-based indices

nikomatsakis
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csmoe
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