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|
//! Upvar (closure capture) collection from cross-body HIR uses of `Res::Local`s.
use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
use rustc_hir as hir;
use rustc_hir::def::Res;
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::{self, HirId};
use rustc_middle::query::Providers;
use rustc_middle::ty::TyCtxt;
use rustc_span::Span;
pub fn provide(providers: &mut Providers) {
providers.upvars_mentioned = |tcx, def_id| {
if !tcx.is_closure(def_id) {
return None;
}
let local_def_id = def_id.expect_local();
let body = tcx.hir().body(tcx.hir().maybe_body_owned_by(local_def_id)?);
let mut local_collector = LocalCollector::default();
local_collector.visit_body(body);
let mut capture_collector = CaptureCollector {
tcx,
locals: &local_collector.locals,
upvars: FxIndexMap::default(),
};
capture_collector.visit_body(body);
if !capture_collector.upvars.is_empty() {
Some(tcx.arena.alloc(capture_collector.upvars))
} else {
None
}
};
}
#[derive(Default)]
struct LocalCollector {
// FIXME(eddyb) perhaps use `ItemLocalId` instead?
locals: FxHashSet<HirId>,
}
impl<'tcx> Visitor<'tcx> for LocalCollector {
fn visit_pat(&mut self, pat: &'tcx hir::Pat<'tcx>) {
if let hir::PatKind::Binding(_, hir_id, ..) = pat.kind {
self.locals.insert(hir_id);
}
intravisit::walk_pat(self, pat);
}
}
struct CaptureCollector<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
locals: &'a FxHashSet<HirId>,
upvars: FxIndexMap<HirId, hir::Upvar>,
}
impl CaptureCollector<'_, '_> {
fn visit_local_use(&mut self, var_id: HirId, span: Span) {
if !self.locals.contains(&var_id) {
self.upvars.entry(var_id).or_insert(hir::Upvar { span });
}
}
}
impl<'tcx> Visitor<'tcx> for CaptureCollector<'_, 'tcx> {
fn visit_path(&mut self, path: &hir::Path<'tcx>, _: hir::HirId) {
if let Res::Local(var_id) = path.res {
self.visit_local_use(var_id, path.span);
}
intravisit::walk_path(self, path);
}
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
if let hir::ExprKind::Closure(closure) = expr.kind {
if let Some(upvars) = self.tcx.upvars_mentioned(closure.def_id) {
// Every capture of a closure expression is a local in scope,
// that is moved/copied/borrowed into the closure value, and
// for this analysis they are like any other access to a local.
//
// E.g. in `|b| |c| (a, b, c)`, the upvars of the inner closure
// are `a` and `b`, and while `a` is not directly used in the
// outer closure, it needs to be an upvar there too, so that
// the inner closure can take it (from the outer closure's env).
for (&var_id, upvar) in upvars {
self.visit_local_use(var_id, upvar.span);
}
}
}
intravisit::walk_expr(self, expr);
}
}
|
