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Refactor DebruijnIndex to be 0-based #50475

Merged
merged 13 commits into from
May 29, 2018
Merged

Refactor DebruijnIndex to be 0-based #50475

merged 13 commits into from
May 29, 2018

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csmoe
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@csmoe csmoe commented May 6, 2018

Fixes #49813

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r? @estebank

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warning Warning warning

  • These commits modify submodules.

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 6, 2018
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csmoe commented May 6, 2018

r? @nikomatsakis

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@@ -1866,22 +1866,22 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
trait_ref: &hir::PolyTraitRef,
modifier: hir::TraitBoundModifier,
) {
self.binder_depth += 1;
self.outer_index.shifted_in(1);
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Probably this should be shift_in

}

fn visit_lifetime(&mut self, lifetime_ref: &hir::Lifetime) {
if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.id) {
match lifetime {
Region::LateBound(debruijn, _, _) | Region::LateBoundAnon(debruijn, _)
if debruijn.index < self.binder_depth =>
if debruijn.index < self.outer_index.index =>
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Can we make this debruijn < self.outer_index?

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Another request: Add the #[must_use] attribute to shifted_in and shifted_out

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bors commented May 10, 2018

☔ The latest upstream changes (presumably #50200) made this pull request unmergeable. Please resolve the merge conflicts.

@csmoe csmoe force-pushed the debr branch 2 times, most recently from 5e560d5 to ee5db9f Compare May 12, 2018 01:26
|
= help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
= help: consider giving it an explicit bounded or 'static lifetime

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@nikomatsakis what's going wrong here? error checking is skipped for this function.

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{
self.have_bound_regions = true;
}
_ => {
self.lifetimes
.insert(lifetime.from_depth(self.binder_depth));
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OK, I suspect this is where the bug is coming from. The binder_depth in the "before code" is equal to index, but (if you look at the definition of from_depth) you will see that used to be computing adjusting by depth - 1, basically.

I think the way I would want to compute the "depth" by giving two debruijn indices. In particular, we might do something like self.outer_index.depth_from(INNERMOST), where we have:

impl DebruijnIndex {
    /// Assuming that these two debruijn indices are both in scope,
    /// returns the number of binding levels *between* them.
    /// This is often used if `outer` represents some starting binding
    /// and `self` represents the current innermost binding; it would then
    /// compute the number of bindings passed over so far.
    ///
    /// As the name suggests, `outer` is assumed  to be the
    /// outermost depth of the two.
    fn depth_from(self, outer: DebruijnIndex) -> usize {
        assert!(self.index >= other.index); // or return the absolute value
        self.index - other.index
    }
}

@nikomatsakis nikomatsakis added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 14, 2018
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bors commented May 16, 2018

☔ The latest upstream changes (presumably #48523) made this pull request unmergeable. Please resolve the merge conflicts.

@@ -990,7 +990,7 @@ impl<'a, 'gcx, 'tcx> ParamTy {
pub struct DebruijnIndex {
/// We maintain the invariant that this is never 0. So 1 indicates
/// the innermost binder. To ensure this, create with `DebruijnIndex::new`.
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This comment is wrong now, right? Also, why make the field private, especially now that there's no invariant?

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Comments repairing is listed in my TODO, it'll be fixed once the key change works.
the field is private: new impl DebruijnIndex provide enough pub-methods to manipulate it.

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Hmm. Maybe the external interface should use usize? Not sure if super relevant.

@csmoe csmoe force-pushed the debr branch 2 times, most recently from 47e4120 to 8dbe74b Compare May 18, 2018 04:31
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nikomatsakis and others added 10 commits May 28, 2018 19:47
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
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@bors r+

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bors commented May 28, 2018

📌 Commit 783fe4f has been approved by nikomatsakis

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 28, 2018
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@bors r-

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels May 28, 2018
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@bors r+

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bors commented May 29, 2018

📌 Commit 783fe4f has been approved by nikomatsakis

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 29, 2018
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bors commented May 29, 2018

⌛ Testing commit 783fe4f with merge 5ae5361...

bors added a commit that referenced this pull request May 29, 2018
Refactor DebruijnIndex to be 0-based

Fixes #49813
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bors commented May 29, 2018

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 5ae5361 to master...

@bors bors merged commit 783fe4f into rust-lang:master May 29, 2018
@csmoe csmoe deleted the debr branch July 13, 2018 08:43
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7 participants