diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs index 5ac99ba147000..8956cbb2baefc 100644 --- a/src/librustc/mir/mod.rs +++ b/src/librustc/mir/mod.rs @@ -1808,6 +1808,23 @@ pub enum ProjectionElem { Downcast(Option, VariantIdx), } +impl ProjectionElem { + /// Returns `true` if the target of this projection may refer to a different region of memory + /// than the base. + fn is_indirect(&self) -> bool { + match self { + Self::Deref => true, + + | Self::Field(_, _) + | Self::Index(_) + | Self::ConstantIndex { .. } + | Self::Subslice { .. } + | Self::Downcast(_, _) + => false + } + } +} + /// Alias for projections as they appear in places, where the base is a place /// and the index is a local. pub type PlaceElem<'tcx> = ProjectionElem>; @@ -1869,6 +1886,14 @@ impl<'tcx> Place<'tcx> { } } + /// Returns `true` if this `Place` contains a `Deref` projection. + /// + /// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the + /// same region of memory as its base. + pub fn is_indirect(&self) -> bool { + self.iterate(|_, mut projections| projections.any(|proj| proj.elem.is_indirect())) + } + /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or /// a single deref of a local. // diff --git a/src/librustc_mir/borrow_check/path_utils.rs b/src/librustc_mir/borrow_check/path_utils.rs index 43a012e1494f8..bac08090817d9 100644 --- a/src/librustc_mir/borrow_check/path_utils.rs +++ b/src/librustc_mir/borrow_check/path_utils.rs @@ -3,7 +3,7 @@ use crate::borrow_check::places_conflict; use crate::borrow_check::AccessDepth; use crate::dataflow::indexes::BorrowIndex; use rustc::mir::{BasicBlock, Location, Body, Place, PlaceBase}; -use rustc::mir::{ProjectionElem, BorrowKind}; +use rustc::mir::BorrowKind; use rustc::ty::{self, TyCtxt}; use rustc_data_structures::graph::dominators::Dominators; @@ -133,20 +133,11 @@ pub(super) fn is_active<'tcx>( /// Determines if a given borrow is borrowing local data /// This is called for all Yield statements on movable generators pub(super) fn borrow_of_local_data(place: &Place<'_>) -> bool { - place.iterate(|place_base, place_projection| { - match place_base { - PlaceBase::Static(..) => return false, - PlaceBase::Local(..) => {}, - } - - for proj in place_projection { - // Reborrow of already borrowed data is ignored - // Any errors will be caught on the initial borrow - if proj.elem == ProjectionElem::Deref { - return false; - } - } + match place.base { + PlaceBase::Static(_) => false, - true - }) + // Reborrow of already borrowed data is ignored + // Any errors will be caught on the initial borrow + PlaceBase::Local(_) => !place.is_indirect(), + } } diff --git a/src/librustc_mir/dataflow/impls/borrowed_locals.rs b/src/librustc_mir/dataflow/impls/borrowed_locals.rs index d94ebdbae24ae..1c43a553cc3c9 100644 --- a/src/librustc_mir/dataflow/impls/borrowed_locals.rs +++ b/src/librustc_mir/dataflow/impls/borrowed_locals.rs @@ -93,19 +93,10 @@ struct BorrowedLocalsVisitor<'gk> { } fn find_local(place: &Place<'_>) -> Option { - place.iterate(|place_base, place_projection| { - for proj in place_projection { - if proj.elem == ProjectionElem::Deref { - return None; - } - } - - if let PlaceBase::Local(local) = place_base { - Some(*local) - } else { - None - } - }) + match place.base { + PlaceBase::Local(local) if !place.is_indirect() => Some(local), + _ => None, + } } impl<'tcx> Visitor<'tcx> for BorrowedLocalsVisitor<'_> {