rustc_borrowck/diagnostics/
find_use.rs

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1use std::collections::VecDeque;
2
3use rustc_data_structures::fx::FxIndexSet;
4use rustc_middle::mir::visit::{MirVisitable, PlaceContext, Visitor};
5use rustc_middle::mir::{self, Body, Local, Location};
6use rustc_middle::ty::{RegionVid, TyCtxt};
7
8use crate::def_use::{self, DefUse};
9use crate::region_infer::{Cause, RegionInferenceContext};
10
11pub(crate) fn find<'tcx>(
12    body: &Body<'tcx>,
13    regioncx: &RegionInferenceContext<'tcx>,
14    tcx: TyCtxt<'tcx>,
15    region_vid: RegionVid,
16    start_point: Location,
17) -> Option<Cause> {
18    let mut uf = UseFinder { body, regioncx, tcx, region_vid, start_point };
19
20    uf.find()
21}
22
23struct UseFinder<'a, 'tcx> {
24    body: &'a Body<'tcx>,
25    regioncx: &'a RegionInferenceContext<'tcx>,
26    tcx: TyCtxt<'tcx>,
27    region_vid: RegionVid,
28    start_point: Location,
29}
30
31impl<'a, 'tcx> UseFinder<'a, 'tcx> {
32    fn find(&mut self) -> Option<Cause> {
33        let mut queue = VecDeque::new();
34        let mut visited = FxIndexSet::default();
35
36        queue.push_back(self.start_point);
37        while let Some(p) = queue.pop_front() {
38            if !self.regioncx.region_contains(self.region_vid, p) {
39                continue;
40            }
41
42            if !visited.insert(p) {
43                continue;
44            }
45
46            let block_data = &self.body[p.block];
47
48            match self.def_use(p, block_data.visitable(p.statement_index)) {
49                Some(DefUseResult::Def) => {}
50
51                Some(DefUseResult::UseLive { local }) => {
52                    return Some(Cause::LiveVar(local, p));
53                }
54
55                Some(DefUseResult::UseDrop { local }) => {
56                    return Some(Cause::DropVar(local, p));
57                }
58
59                None => {
60                    if p.statement_index < block_data.statements.len() {
61                        queue.push_back(p.successor_within_block());
62                    } else {
63                        queue.extend(
64                            block_data
65                                .terminator()
66                                .successors()
67                                .filter(|&bb| {
68                                    Some(&mir::UnwindAction::Cleanup(bb))
69                                        != block_data.terminator().unwind()
70                                })
71                                .map(|bb| Location { statement_index: 0, block: bb }),
72                        );
73                    }
74                }
75            }
76        }
77
78        None
79    }
80
81    fn def_use(&self, location: Location, thing: &dyn MirVisitable<'tcx>) -> Option<DefUseResult> {
82        let mut visitor = DefUseVisitor {
83            body: self.body,
84            tcx: self.tcx,
85            region_vid: self.region_vid,
86            def_use_result: None,
87        };
88
89        thing.apply(location, &mut visitor);
90
91        visitor.def_use_result
92    }
93}
94
95struct DefUseVisitor<'a, 'tcx> {
96    body: &'a Body<'tcx>,
97    tcx: TyCtxt<'tcx>,
98    region_vid: RegionVid,
99    def_use_result: Option<DefUseResult>,
100}
101
102enum DefUseResult {
103    Def,
104    UseLive { local: Local },
105    UseDrop { local: Local },
106}
107
108impl<'a, 'tcx> Visitor<'tcx> for DefUseVisitor<'a, 'tcx> {
109    fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
110        let local_ty = self.body.local_decls[local].ty;
111
112        let mut found_it = false;
113        self.tcx.for_each_free_region(&local_ty, |r| {
114            if r.as_var() == self.region_vid {
115                found_it = true;
116            }
117        });
118
119        if found_it {
120            self.def_use_result = match def_use::categorize(context) {
121                Some(DefUse::Def) => Some(DefUseResult::Def),
122                Some(DefUse::Use) => Some(DefUseResult::UseLive { local }),
123                Some(DefUse::Drop) => Some(DefUseResult::UseDrop { local }),
124                None => None,
125            };
126        }
127    }
128}
rustc_borrowck/diagnostics/find_use.rs

rustc_borrowck/diagnostics/
find_use.rs
