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replace use of DebruijnIndex in `for_each_free_region` 

Co-authored-by: csmoe <35686186+csmoe@users.noreply.github.com>
This commit is contained in:
Niko Matsakis 2018-05-28 10:13:21 -04:00
parent 34c9ae77f7
commit 4aeb6efb6d
1 changed files with 25 additions and 5 deletions
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30
src/librustc/ty/fold.rs
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@ -243,10 +243,30 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
where F: FnMut(ty::Region<'tcx>),
T: TypeFoldable<'tcx>,
{
value.visit_with(&mut RegionVisitor { current_depth: 0, callback });
value.visit_with(&mut RegionVisitor {
outer_index: ty::DebruijnIndex::INNERMOST,
callback
});
struct RegionVisitor<F> {
current_depth: u32,
/// The index of a binder *just outside* the things we have
/// traversed. If we encounter a bound region bound by this
/// binder or one outer to it, it appears free. Example:
///
/// ```
/// for<'a> fn(for<'b> fn(), T)
/// ^ ^ ^ ^
/// | | | | here, would be shifted in 1
/// | | | here, would be shifted in 2
/// | | here, would be INNTERMOST shifted in by 1
/// | here, initially, binder would be INNERMOST
/// ```
///
/// You see that, initially, *any* bound value is free,
/// because we've not traversed any binders. As we pass
/// through a binder, we shift the `outer_index` by 1 to
/// account for the new binder that encloses us.
outer_index: ty::DebruijnIndex,
callback: F,
}
@ -254,16 +274,16 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
where F : FnMut(ty::Region<'tcx>)
{
fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, t: &Binder<T>) -> bool {
self.current_depth += 1;
self.outer_index.shift_in(1);
t.skip_binder().visit_with(self);
self.current_depth -= 1;
self.outer_index.shift_out(1);
false // keep visiting
}
fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
match *r {
ty::ReLateBound(debruijn, _) if debruijn.depth <= self.current_depth => {
ty::ReLateBound(debruijn, _) if debruijn < self.outer_index => {
/* ignore bound regions */
}
_ => (self.callback)(r),