bjoernager/rust
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Consider static specially

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This commit is contained in:
Michael Goulet 2023-09-21 05:51:40 +00:00
parent e425d85518
commit 371d8a8215
3 changed files with 48 additions and 8 deletions
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28
compiler/rustc_borrowck/src/type_check/liveness/trace.rs
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@ -619,13 +619,21 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
inflowing_loans: &'b SparseBitMatrix<RegionVid, BorrowIndex>,
}
impl<'tcx> MakeAllRegionsLive<'_, '_, 'tcx> {
/// We can prove that an alias is live two ways:
/// 1. All the components are live.
/// 2. There is a known outlives bound or where-clause, and that
/// region is live.
/// We search through the item bounds and where clauses for
/// either `'static` or a unique outlives region, and if one is
/// found, we just need to prove that that region is still live.
/// If one is not found, then we continue to walk through the alias.
fn make_alias_live(&mut self, t: Ty<'tcx>) -> ControlFlow<!> {
let ty::Alias(_kind, alias_ty) = t.kind() else {
bug!();
bug!("`make_alias_live` only takes alias types");
};
let tcx = self.typeck.infcx.tcx;
let param_env = self.typeck.param_env;
let mut outlives_bounds = tcx
let outlives_bounds: Vec<_> = tcx
.item_bounds(alias_ty.def_id)
.iter_instantiated(tcx, alias_ty.args)
.filter_map(|clause| {
@ -653,12 +661,16 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
t,
)
}
}));
if let Some(r) = outlives_bounds.next()
&& !r.is_late_bound()
&& outlives_bounds.all(|other_r| {
other_r == r
})
}))
.collect();
// If we find `'static`, then we know the alias doesn't capture *any* regions.
// Otherwise, all of the outlives regions should be equal -- if they're not,
// we don't really know how to proceed, so we continue recursing through the
// alias.
if outlives_bounds.contains(&tcx.lifetimes.re_static) {
ControlFlow::Continue(())
} else if let Some(r) = outlives_bounds.first()
&& outlives_bounds[1..].iter().all(|other_r| other_r == r)
{
r.visit_with(self)
} else {