1use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
4use rustc_hir as hir;
5use rustc_hir::def::Res;
6use rustc_hir::intravisit::{self, Visitor};
7use rustc_hir::{self, HirId};
8use rustc_middle::query::Providers;
9use rustc_middle::ty::TyCtxt;
10use rustc_span::Span;
11
12pub(crate) fn provide(providers: &mut Providers) {
13 providers.upvars_mentioned = |tcx, def_id| {
14 if !tcx.is_closure_like(def_id) {
15 return None;
16 }
17
18 let local_def_id = def_id.expect_local();
19 let body = tcx.hir().maybe_body_owned_by(local_def_id)?;
20
21 let mut local_collector = LocalCollector::default();
22 local_collector.visit_body(&body);
23
24 let mut capture_collector = CaptureCollector {
25 tcx,
26 locals: &local_collector.locals,
27 upvars: FxIndexMap::default(),
28 };
29 capture_collector.visit_body(&body);
30
31 if !capture_collector.upvars.is_empty() {
32 Some(tcx.arena.alloc(capture_collector.upvars))
33 } else {
34 None
35 }
36 };
37}
38
39#[derive(Default)]
40struct LocalCollector {
41 locals: FxHashSet<HirId>,
43}
44
45impl<'tcx> Visitor<'tcx> for LocalCollector {
46 fn visit_pat(&mut self, pat: &'tcx hir::Pat<'tcx>) {
47 if let hir::PatKind::Binding(_, hir_id, ..) = pat.kind {
48 self.locals.insert(hir_id);
49 }
50 intravisit::walk_pat(self, pat);
51 }
52}
53
54struct CaptureCollector<'a, 'tcx> {
55 tcx: TyCtxt<'tcx>,
56 locals: &'a FxHashSet<HirId>,
57 upvars: FxIndexMap<HirId, hir::Upvar>,
58}
59
60impl CaptureCollector<'_, '_> {
61 fn visit_local_use(&mut self, var_id: HirId, span: Span) {
62 if !self.locals.contains(&var_id) {
63 self.upvars.entry(var_id).or_insert(hir::Upvar { span });
64 }
65 }
66}
67
68impl<'tcx> Visitor<'tcx> for CaptureCollector<'_, 'tcx> {
69 fn visit_path(&mut self, path: &hir::Path<'tcx>, _: HirId) {
70 if let Res::Local(var_id) = path.res {
71 self.visit_local_use(var_id, path.span);
72 }
73
74 intravisit::walk_path(self, path);
75 }
76
77 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
78 if let hir::ExprKind::Closure(closure) = expr.kind {
79 if let Some(upvars) = self.tcx.upvars_mentioned(closure.def_id) {
80 for (&var_id, upvar) in upvars {
89 self.visit_local_use(var_id, upvar.span);
90 }
91 }
92 }
93
94 intravisit::walk_expr(self, expr);
95 }
96}