Struct rustc_mir_dataflow::impls::borrowed_locals::MaybeBorrowedLocals

pub struct MaybeBorrowedLocals {
    ignore_borrow_on_drop: bool,
}

A dataflow analysis that tracks whether a pointer or reference could possibly exist that points to a given local.

At present, this is used as a very limited form of alias analysis. For example, MaybeBorrowedLocals is used to compute which locals are live during a yield expression for immovable generators.

Fields

ignore_borrow_on_drop: bool

Implementations

impl MaybeBorrowedLocals

pub fn all_borrows() -> Self

A dataflow analysis that records whether a pointer or reference exists that may alias the given local.

impl MaybeBorrowedLocals

pub fn unsound_ignore_borrow_on_drop(self) -> Self

During dataflow analysis, ignore the borrow that may occur when a place is dropped.

Drop terminators may call custom drop glue (Drop::drop), which takes &mut self as a parameter. In the general case, a drop impl could launder that reference into the surrounding environment through a raw pointer, thus creating a valid *mut pointing to the dropped local. We are not yet willing to declare this particular case UB, so we must treat all dropped locals as mutably borrowed for now. See discussion on #61069.

In some contexts, we know that this borrow will never occur. For example, during const-eval, custom drop glue cannot be run. Code that calls this should document the assumptions that justify ignoring Drop terminators in this way.

fn transfer_function<'a, T>(
    &'a self,
    trans: &'a mut T
) -> TransferFunction<'a, T>

Trait Implementations

impl<'tcx> AnalysisDomain<'tcx> for MaybeBorrowedLocals

type Domain = BitSet<Local>

The type that holds the dataflow state at any given point in the program.

const NAME: &'static str

A descriptive name for this analysis. Used only for debugging.

fn bottom_value(&self, body: &Body<'tcx>) -> Self::Domain

The initial value of the dataflow state upon entry to each basic block.

fn initialize_start_block(&self, _: &Body<'tcx>, _: &mut Self::Domain)

Mutates the initial value of the dataflow state upon entry to the START_BLOCK.

type Direction: Direction = Forward

The direction of this analysis. Either Forward or Backward.

impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals

type Idx = Local

fn statement_effect(
    &self,
    trans: &mut impl GenKill<Self::Idx>,
    statement: &Statement<'tcx>,
    location: Location
)

See Analysis::apply_statement_effect.

fn terminator_effect(
    &self,
    trans: &mut impl GenKill<Self::Idx>,
    terminator: &Terminator<'tcx>,
    location: Location
)

See Analysis::apply_terminator_effect.

fn call_return_effect(
    &self,
    _trans: &mut impl GenKill<Self::Idx>,
    _block: BasicBlock,
    _return_places: CallReturnPlaces<'_, 'tcx>
)

See Analysis::apply_call_return_effect.

fn before_statement_effect(
    &self,
    _trans: &mut impl GenKill<Self::Idx>,
    _statement: &Statement<'tcx>,
    _location: Location
)

See Analysis::apply_before_statement_effect.

fn before_terminator_effect(
    &self,
    _trans: &mut impl GenKill<Self::Idx>,
    _terminator: &Terminator<'tcx>,
    _location: Location
)

See Analysis::apply_before_terminator_effect.

fn yield_resume_effect(
    &self,
    _trans: &mut impl GenKill<Self::Idx>,
    _resume_block: BasicBlock,
    _resume_place: Place<'tcx>
)

See Analysis::apply_yield_resume_effect.

fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
    &self,
    _block: BasicBlock,
    _discr: &Operand<'tcx>,
    _edge_effects: &mut impl SwitchIntEdgeEffects<G>
)

See Analysis::apply_switch_int_edge_effects.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.

Size: 1 byte