bjoernager/rust
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Reject borrows of projections in ConstProp.

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This commit is contained in:
Camille GILLOT 2023-04-28 16:57:40 +00:00
parent e2caebc4a6
commit 1ffe9059c3
4 changed files with 22 additions and 19 deletions
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20
compiler/rustc_mir_transform/src/const_prop.rs
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@ -714,13 +714,22 @@ impl CanConstProp {
}
}
impl Visitor<'_> for CanConstProp {
impl<'tcx> Visitor<'tcx> for CanConstProp {
fn visit_place(&mut self, place: &Place<'tcx>, mut context: PlaceContext, loc: Location) {
use rustc_middle::mir::visit::PlaceContext::*;
// Dereferencing just read the addess of `place.local`.
if place.projection.first() == Some(&PlaceElem::Deref) {
context = NonMutatingUse(NonMutatingUseContext::Copy);
}
self.visit_local(place.local, context, loc);
self.visit_projection(place.as_ref(), context, loc);
}
fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
use rustc_middle::mir::visit::PlaceContext::*;
match context {
// Projections are fine, because `&mut foo.x` will be caught by
// `MutatingUseContext::Borrow` elsewhere.
MutatingUse(MutatingUseContext::Projection)
// These are just stores, where the storing is not propagatable, but there may be later
// mutations of the same local via `Store`
| MutatingUse(MutatingUseContext::Call)
@ -751,7 +760,6 @@ impl Visitor<'_> for CanConstProp {
NonMutatingUse(NonMutatingUseContext::Copy)
| NonMutatingUse(NonMutatingUseContext::Move)
| NonMutatingUse(NonMutatingUseContext::Inspect)
| NonMutatingUse(NonMutatingUseContext::Projection)
| NonMutatingUse(NonMutatingUseContext::PlaceMention)
| NonUse(_) => {}
@ -771,6 +779,8 @@ impl Visitor<'_> for CanConstProp {
trace!("local {:?} can't be propagated because it's used: {:?}", local, context);
self.can_const_prop[local] = ConstPropMode::NoPropagation;
}
MutatingUse(MutatingUseContext::Projection)
| NonMutatingUse(NonMutatingUseContext::Projection) => bug!("visit_place should not pass {context:?} for {local:?}"),
}
}
}