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Auto merge of #88650 - sapessi:issue-77175-fix, r=estebank

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Skip single use lifetime lint for generated opaque types

Fix: #77175

The opaque type generated by the desugaring process of an async function uses the lifetimes defined by the originating function. The DefId for the lifetimes in the opaque type are different from the ones in the originating async function - as they should be, as far as I understand, and could therefore be considered a single use lifetimes, this causes the single_use_lifetimes lint to fail compilation if explicitly denied. This fix skips the lint for lifetimes used only once in generated opaque types for an async function that are declared in the parent async function definition.

More info in the comments on the original issue: 1 and 2
This commit is contained in:
bors 2021-09-18 11:56:23 +00:00
commit 23afad6e7f
2 changed files with 41 additions and 1 deletions
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23
compiler/rustc_resolve/src/late/lifetimes.rs
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@ -2024,7 +2024,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
// ensure that we issue lints in a repeatable order
def_ids.sort_by_cached_key(|&def_id| self.tcx.def_path_hash(def_id));
for def_id in def_ids {
'lifetimes: for def_id in def_ids {
debug!("check_uses_for_lifetimes_defined_by_scope: def_id = {:?}", def_id);
let lifetimeuseset = self.lifetime_uses.remove(&def_id);
@ -2067,6 +2067,27 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
{
continue;
}
// opaque types generated when desugaring an async function can have a single
// use lifetime even if it is explicitly denied (Issue #77175)
if let hir::Node::Item(hir::Item {
kind: hir::ItemKind::OpaqueTy(ref opaque),
..
}) = self.tcx.hir().get(parent_hir_id)
{
if opaque.origin != hir::OpaqueTyOrigin::AsyncFn {
continue 'lifetimes;
}
// We want to do this only if the liftime identifier is already defined
// in the async function that generated this. Otherwise it could be
// an opaque type defined by the developer and we still want this
// lint to fail compilation
for p in opaque.generics.params {
if defined_by.contains_key(&p.name) {
continue 'lifetimes;
}
}
}
}
}