1 //! Upvar (closure capture) collection from cross-body HIR uses of `Res::Local`s.
3 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
5 use rustc_hir::def::Res;
6 use rustc_hir::intravisit::{self, Visitor};
7 use rustc_hir::{self, HirId};
8 use rustc_middle::ty::query::Providers;
9 use rustc_middle::ty::TyCtxt;
12 pub fn provide(providers: &mut Providers) {
13 providers.upvars_mentioned = |tcx, def_id| {
14 if !tcx.is_closure(def_id) {
18 let local_def_id = def_id.expect_local();
19 let body = tcx.hir().body(tcx.hir().maybe_body_owned_by(local_def_id)?);
21 let mut local_collector = LocalCollector::default();
22 local_collector.visit_body(body);
24 let mut capture_collector = CaptureCollector {
26 locals: &local_collector.locals,
27 upvars: FxIndexMap::default(),
29 capture_collector.visit_body(body);
31 if !capture_collector.upvars.is_empty() {
32 Some(tcx.arena.alloc(capture_collector.upvars))
40 struct LocalCollector {
41 // FIXME(eddyb) perhaps use `ItemLocalId` instead?
42 locals: FxHashSet<HirId>,
45 impl<'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);
50 intravisit::walk_pat(self, pat);
54 struct CaptureCollector<'a, 'tcx> {
56 locals: &'a FxHashSet<HirId>,
57 upvars: FxIndexMap<HirId, hir::Upvar>,
60 impl 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 });
68 impl<'tcx> Visitor<'tcx> for CaptureCollector<'_, 'tcx> {
69 fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) {
70 if let Res::Local(var_id) = path.res {
71 self.visit_local_use(var_id, path.span);
74 intravisit::walk_path(self, path);
77 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
78 if let hir::ExprKind::Closure { .. } = expr.kind {
79 let closure_def_id = self.tcx.hir().local_def_id(expr.hir_id);
80 if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) {
81 // Every capture of a closure expression is a local in scope,
82 // that is moved/copied/borrowed into the closure value, and
83 // for this analysis they are like any other access to a local.
85 // E.g. in `|b| |c| (a, b, c)`, the upvars of the inner closure
86 // are `a` and `b`, and while `a` is not directly used in the
87 // outer closure, it needs to be an upvar there too, so that
88 // the inner closure can take it (from the outer closure's env).
89 for (&var_id, upvar) in upvars {
90 self.visit_local_use(var_id, upvar.span);
95 intravisit::walk_expr(self, expr);