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Avoid erase_regions_ty queries if there are no regions to erase #57674

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Merged
merged 1 commit into from
Jan 29, 2019
Merged

Avoid erase_regions_ty queries if there are no regions to erase #57674

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7 changes: 6 additions & 1 deletion src/librustc/ty/erase_regions.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use ty::{self, Ty, TyCtxt};
use ty::{self, Ty, TyCtxt, TypeFlags};
use ty::fold::{TypeFolder, TypeFoldable};

pub(super) fn provide(providers: &mut ty::query::Providers<'_>) {
Expand All @@ -21,6 +21,11 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
pub fn erase_regions<T>(self, value: &T) -> T
where T : TypeFoldable<'tcx>
{
// If there's nothing to erase avoid performing the query at all
if !value.has_type_flags(TypeFlags::HAS_RE_LATE_BOUND | TypeFlags::HAS_FREE_REGIONS) {
return value.clone();
}

let value1 = value.fold_with(&mut RegionEraserVisitor { tcx: self });
debug!("erase_regions({:?}) = {:?}", value, value1);
value1
Expand Down