rustc_borrowck/
consumers.rs

1//! This file provides API for compiler consumers.
2
3use rustc_data_structures::fx::FxHashMap;
4use rustc_hir::def_id::LocalDefId;
5use rustc_index::IndexVec;
6use rustc_middle::bug;
7use rustc_middle::mir::{Body, Promoted};
8use rustc_middle::ty::TyCtxt;
9
10pub use super::borrow_set::{BorrowData, BorrowSet, TwoPhaseActivation};
11pub use super::constraints::OutlivesConstraint;
12pub use super::dataflow::{BorrowIndex, Borrows, calculate_borrows_out_of_scope_at_location};
13pub use super::place_ext::PlaceExt;
14pub use super::places_conflict::{PlaceConflictBias, places_conflict};
15pub use super::polonius::legacy::{
16    PoloniusFacts as PoloniusInput, PoloniusLocationTable, PoloniusOutput, PoloniusRegionVid,
17    RichLocation, RustcFacts,
18};
19pub use super::region_infer::RegionInferenceContext;
20use crate::{BorrowCheckRootCtxt, do_mir_borrowck};
21
22/// Struct used during mir borrowck to collect bodies with facts for a typeck root and all
23/// its nested bodies.
24pub(crate) struct BorrowckConsumer<'tcx> {
25    options: ConsumerOptions,
26    bodies: FxHashMap<LocalDefId, BodyWithBorrowckFacts<'tcx>>,
27}
28
29impl<'tcx> BorrowckConsumer<'tcx> {
30    pub(crate) fn new(options: ConsumerOptions) -> Self {
31        Self { options, bodies: Default::default() }
32    }
33
34    pub(crate) fn insert_body(&mut self, def_id: LocalDefId, body: BodyWithBorrowckFacts<'tcx>) {
35        if self.bodies.insert(def_id, body).is_some() {
36            bug!("unexpected previous body for {def_id:?}");
37        }
38    }
39
40    /// Should the Polonius input facts be computed?
41    pub(crate) fn polonius_input(&self) -> bool {
42        matches!(
43            self.options,
44            ConsumerOptions::PoloniusInputFacts | ConsumerOptions::PoloniusOutputFacts
45        )
46    }
47
48    /// Should we run Polonius and collect the output facts?
49    pub(crate) fn polonius_output(&self) -> bool {
50        matches!(self.options, ConsumerOptions::PoloniusOutputFacts)
51    }
52}
53
54/// Options determining the output behavior of [`get_bodies_with_borrowck_facts`].
55///
56/// If executing under `-Z polonius` the choice here has no effect, and everything as if
57/// [`PoloniusOutputFacts`](ConsumerOptions::PoloniusOutputFacts) had been selected
58/// will be retrieved.
59#[derive(Debug, Copy, Clone)]
60pub enum ConsumerOptions {
61    /// Retrieve the [`Body`] along with the [`BorrowSet`]
62    /// and [`RegionInferenceContext`]. If you would like the body only, use
63    /// [`TyCtxt::mir_promoted`].
64    ///
65    /// These can be used in conjunction with [`calculate_borrows_out_of_scope_at_location`].
66    RegionInferenceContext,
67    /// The recommended option. Retrieves the maximal amount of information
68    /// without significant slowdowns.
69    ///
70    /// Implies [`RegionInferenceContext`](ConsumerOptions::RegionInferenceContext),
71    /// and additionally retrieve the [`PoloniusLocationTable`] and [`PoloniusInput`] that
72    /// would be given to Polonius. Critically, this does not run Polonius, which
73    /// one may want to avoid due to performance issues on large bodies.
74    PoloniusInputFacts,
75    /// Implies [`PoloniusInputFacts`](ConsumerOptions::PoloniusInputFacts),
76    /// and additionally runs Polonius to calculate the [`PoloniusOutput`].
77    PoloniusOutputFacts,
78}
79
80/// A `Body` with information computed by the borrow checker. This struct is
81/// intended to be consumed by compiler consumers.
82///
83/// We need to include the MIR body here because the region identifiers must
84/// match the ones in the Polonius facts.
85pub struct BodyWithBorrowckFacts<'tcx> {
86    /// A mir body that contains region identifiers.
87    pub body: Body<'tcx>,
88    /// The mir bodies of promoteds.
89    pub promoted: IndexVec<Promoted, Body<'tcx>>,
90    /// The set of borrows occurring in `body` with data about them.
91    pub borrow_set: BorrowSet<'tcx>,
92    /// Context generated during borrowck, intended to be passed to
93    /// [`calculate_borrows_out_of_scope_at_location`].
94    pub region_inference_context: RegionInferenceContext<'tcx>,
95    /// The table that maps Polonius points to locations in the table.
96    /// Populated when using [`ConsumerOptions::PoloniusInputFacts`]
97    /// or [`ConsumerOptions::PoloniusOutputFacts`].
98    pub location_table: Option<PoloniusLocationTable>,
99    /// Polonius input facts.
100    /// Populated when using [`ConsumerOptions::PoloniusInputFacts`]
101    /// or [`ConsumerOptions::PoloniusOutputFacts`].
102    pub input_facts: Option<Box<PoloniusInput>>,
103    /// Polonius output facts. Populated when using
104    /// [`ConsumerOptions::PoloniusOutputFacts`].
105    pub output_facts: Option<Box<PoloniusOutput>>,
106}
107
108/// This function computes borrowck facts for the given def id and all its nested bodies.
109/// It must be called with a typeck root which will then borrowck all nested bodies as well.
110/// The [`ConsumerOptions`] determine which facts are returned. This function makes a copy
111/// of the bodies because it needs to regenerate the region identifiers. It should never be
112/// invoked during a typical compilation session due to the unnecessary overhead of
113/// returning [`BodyWithBorrowckFacts`].
114///
115/// Note:
116/// *   This function will panic if the required bodies were already stolen. This
117///     can, for example, happen when requesting a body of a `const` function
118///     because they are evaluated during typechecking. The panic can be avoided
119///     by overriding the `mir_borrowck` query. You can find a complete example
120///     that shows how to do this at `tests/ui-fulldeps/obtain-borrowck.rs`.
121///
122/// *   Polonius is highly unstable, so expect regular changes in its signature or other details.
123pub fn get_bodies_with_borrowck_facts(
124    tcx: TyCtxt<'_>,
125    root_def_id: LocalDefId,
126    options: ConsumerOptions,
127) -> FxHashMap<LocalDefId, BodyWithBorrowckFacts<'_>> {
128    let mut root_cx =
129        BorrowCheckRootCtxt::new(tcx, root_def_id, Some(BorrowckConsumer::new(options)));
130
131    // See comment in `rustc_borrowck::mir_borrowck`
132    let nested_bodies = tcx.nested_bodies_within(root_def_id);
133    for def_id in nested_bodies {
134        root_cx.get_or_insert_nested(def_id);
135    }
136
137    do_mir_borrowck(&mut root_cx, root_def_id);
138    root_cx.consumer.unwrap().bodies
139}
rustc_borrowck/consumers.rs

rustc_borrowck/
consumers.rs
