Auto merge of #77274 - tmiasko:liveness-cnd, r=lcnr
Liveness refactoring continued * Move body_owner field from IrMaps to Liveness (the only user of the field). * Use upvars instead of FnKind to check for closures (avoids FnKind, will be useful when checking all bodies, not just fns). * Use visit_param to add variables corresponding to params. * Store upvars_mentioned inside Liveness struct. * Inline visitor implementation for IrMaps, avoiding unnecessary indirection. * Test interaction with automatically_derived attribute (not covered by any of existing tests). No functional changes intended.
This commit is contained in:
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commit
381b445ff5
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@ -138,40 +138,8 @@ fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt<'_>) -> String {
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}
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}
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impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
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type Map = Map<'tcx>;
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::OnlyBodies(self.tcx.hir())
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}
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fn visit_fn(
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&mut self,
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fk: FnKind<'tcx>,
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fd: &'tcx hir::FnDecl<'tcx>,
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b: hir::BodyId,
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s: Span,
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id: HirId,
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) {
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visit_fn(self, fk, fd, b, s, id);
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}
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fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
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visit_local(self, l);
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}
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fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
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visit_expr(self, ex);
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}
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fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
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visit_arm(self, a);
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}
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}
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fn check_mod_liveness(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
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tcx.hir().visit_item_likes_in_module(
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module_def_id,
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&mut IrMaps::new(tcx, module_def_id).as_deep_visitor(),
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);
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tcx.hir().visit_item_likes_in_module(module_def_id, &mut IrMaps::new(tcx).as_deep_visitor());
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}
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pub fn provide(providers: &mut Providers) {
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@ -227,7 +195,6 @@ enum VarKind {
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struct IrMaps<'tcx> {
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tcx: TyCtxt<'tcx>,
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body_owner: LocalDefId,
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live_node_map: HirIdMap<LiveNode>,
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variable_map: HirIdMap<Variable>,
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capture_info_map: HirIdMap<Rc<Vec<CaptureInfo>>>,
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@ -236,10 +203,9 @@ struct IrMaps<'tcx> {
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}
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impl IrMaps<'tcx> {
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fn new(tcx: TyCtxt<'tcx>, body_owner: LocalDefId) -> IrMaps<'tcx> {
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fn new(tcx: TyCtxt<'tcx>) -> IrMaps<'tcx> {
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IrMaps {
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tcx,
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body_owner,
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live_node_map: HirIdMap::default(),
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variable_map: HirIdMap::default(),
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capture_info_map: Default::default(),
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@ -302,44 +268,117 @@ impl IrMaps<'tcx> {
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fn set_captures(&mut self, hir_id: HirId, cs: Vec<CaptureInfo>) {
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self.capture_info_map.insert(hir_id, Rc::new(cs));
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}
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}
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fn visit_fn<'tcx>(
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ir: &mut IrMaps<'tcx>,
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fk: FnKind<'tcx>,
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decl: &'tcx hir::FnDecl<'tcx>,
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body_id: hir::BodyId,
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sp: Span,
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id: hir::HirId,
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) {
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debug!("visit_fn {:?}", id);
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// swap in a new set of IR maps for this function body:
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let def_id = ir.tcx.hir().local_def_id(id);
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let mut fn_maps = IrMaps::new(ir.tcx, def_id);
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// Don't run unused pass for #[derive()]
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if let FnKind::Method(..) = fk {
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let parent = ir.tcx.hir().get_parent_item(id);
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if let Some(Node::Item(i)) = ir.tcx.hir().find(parent) {
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if i.attrs.iter().any(|a| ir.tcx.sess.check_name(a, sym::automatically_derived)) {
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return;
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fn add_from_pat(&mut self, pat: &hir::Pat<'tcx>) {
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// For struct patterns, take note of which fields used shorthand
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// (`x` rather than `x: x`).
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let mut shorthand_field_ids = HirIdSet::default();
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let mut pats = VecDeque::new();
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pats.push_back(pat);
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while let Some(pat) = pats.pop_front() {
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use rustc_hir::PatKind::*;
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match &pat.kind {
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Binding(.., inner_pat) => {
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pats.extend(inner_pat.iter());
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}
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Struct(_, fields, _) => {
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let ids = fields.iter().filter(|f| f.is_shorthand).map(|f| f.pat.hir_id);
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shorthand_field_ids.extend(ids);
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}
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Ref(inner_pat, _) | Box(inner_pat) => {
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pats.push_back(inner_pat);
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}
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TupleStruct(_, inner_pats, _) | Tuple(inner_pats, _) | Or(inner_pats) => {
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pats.extend(inner_pats.iter());
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}
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Slice(pre_pats, inner_pat, post_pats) => {
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pats.extend(pre_pats.iter());
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pats.extend(inner_pat.iter());
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pats.extend(post_pats.iter());
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}
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_ => {}
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}
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}
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pat.each_binding(|_, hir_id, _, ident| {
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self.add_live_node_for_node(hir_id, VarDefNode(ident.span));
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self.add_variable(Local(LocalInfo {
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id: hir_id,
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name: ident.name,
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is_shorthand: shorthand_field_ids.contains(&hir_id),
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}));
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});
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}
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}
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impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
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type Map = Map<'tcx>;
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::OnlyBodies(self.tcx.hir())
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}
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debug!("creating fn_maps: {:p}", &fn_maps);
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fn visit_fn(
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&mut self,
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fk: FnKind<'tcx>,
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decl: &'tcx hir::FnDecl<'tcx>,
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body_id: hir::BodyId,
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sp: Span,
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id: HirId,
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) {
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debug!("visit_fn {:?}", id);
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let body = ir.tcx.hir().body(body_id);
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// swap in a new set of IR maps for this function body:
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let def_id = self.tcx.hir().local_def_id(id);
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let mut fn_maps = IrMaps::new(self.tcx);
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if let Some(upvars) = ir.tcx.upvars_mentioned(def_id) {
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for (&var_hir_id, _upvar) in upvars {
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let var_name = ir.tcx.hir().name(var_hir_id);
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fn_maps.add_variable(Upvar(var_hir_id, var_name));
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// Don't run unused pass for #[derive()]
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if let FnKind::Method(..) = fk {
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let parent = self.tcx.hir().get_parent_item(id);
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if let Some(Node::Item(i)) = self.tcx.hir().find(parent) {
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if i.attrs.iter().any(|a| self.tcx.sess.check_name(a, sym::automatically_derived)) {
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return;
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}
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}
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}
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debug!("creating fn_maps: {:p}", &fn_maps);
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let body = self.tcx.hir().body(body_id);
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if let Some(upvars) = self.tcx.upvars_mentioned(def_id) {
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for (&var_hir_id, _upvar) in upvars {
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let var_name = self.tcx.hir().name(var_hir_id);
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fn_maps.add_variable(Upvar(var_hir_id, var_name));
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}
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}
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// gather up the various local variables, significant expressions,
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// and so forth:
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intravisit::walk_fn(&mut fn_maps, fk, decl, body_id, sp, id);
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// compute liveness
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let mut lsets = Liveness::new(&mut fn_maps, def_id);
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let entry_ln = lsets.compute(&body, sp, id);
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lsets.log_liveness(entry_ln, id);
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// check for various error conditions
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lsets.visit_body(body);
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lsets.warn_about_unused_upvars(entry_ln);
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lsets.warn_about_unused_args(body, entry_ln);
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}
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for param in body.params {
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fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
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self.add_from_pat(&local.pat);
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intravisit::walk_local(self, local);
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}
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fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
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self.add_from_pat(&arm.pat);
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intravisit::walk_arm(self, arm);
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}
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fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
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let is_shorthand = match param.pat.kind {
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rustc_hir::PatKind::Struct(..) => true,
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_ => false,
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@ -350,150 +389,83 @@ fn visit_fn<'tcx>(
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} else {
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Param(hir_id, ident.name)
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};
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fn_maps.add_variable(var);
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})
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self.add_variable(var);
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});
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intravisit::walk_param(self, param);
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}
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// gather up the various local variables, significant expressions,
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// and so forth:
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intravisit::walk_fn(&mut fn_maps, fk, decl, body_id, sp, id);
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// compute liveness
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let mut lsets = Liveness::new(&mut fn_maps, def_id);
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let entry_ln = lsets.compute(fk, &body, sp, id);
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lsets.log_liveness(entry_ln, id);
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// check for various error conditions
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lsets.visit_body(body);
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lsets.warn_about_unused_upvars(entry_ln);
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lsets.warn_about_unused_args(body, entry_ln);
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}
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fn add_from_pat(ir: &mut IrMaps<'_>, pat: &hir::Pat<'_>) {
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// For struct patterns, take note of which fields used shorthand
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// (`x` rather than `x: x`).
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let mut shorthand_field_ids = HirIdSet::default();
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let mut pats = VecDeque::new();
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pats.push_back(pat);
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while let Some(pat) = pats.pop_front() {
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use rustc_hir::PatKind::*;
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match &pat.kind {
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Binding(.., inner_pat) => {
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pats.extend(inner_pat.iter());
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fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
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match expr.kind {
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// live nodes required for uses or definitions of variables:
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hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => {
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debug!("expr {}: path that leads to {:?}", expr.hir_id, path.res);
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if let Res::Local(_var_hir_id) = path.res {
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self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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}
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intravisit::walk_expr(self, expr);
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}
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Struct(_, fields, _) => {
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let ids = fields.iter().filter(|f| f.is_shorthand).map(|f| f.pat.hir_id);
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shorthand_field_ids.extend(ids);
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hir::ExprKind::Closure(..) => {
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// Interesting control flow (for loops can contain labeled
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// breaks or continues)
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self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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// Make a live_node for each captured variable, with the span
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// being the location that the variable is used. This results
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// in better error messages than just pointing at the closure
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// construction site.
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let mut call_caps = Vec::new();
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let closure_def_id = self.tcx.hir().local_def_id(expr.hir_id);
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if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) {
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call_caps.extend(upvars.iter().map(|(&var_id, upvar)| {
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let upvar_ln = self.add_live_node(UpvarNode(upvar.span));
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CaptureInfo { ln: upvar_ln, var_hid: var_id }
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}));
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}
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self.set_captures(expr.hir_id, call_caps);
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intravisit::walk_expr(self, expr);
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}
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Ref(inner_pat, _) | Box(inner_pat) => {
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pats.push_back(inner_pat);
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// live nodes required for interesting control flow:
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hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) => {
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self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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intravisit::walk_expr(self, expr);
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}
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TupleStruct(_, inner_pats, _) | Tuple(inner_pats, _) | Or(inner_pats) => {
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pats.extend(inner_pats.iter());
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hir::ExprKind::Binary(op, ..) if op.node.is_lazy() => {
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self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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intravisit::walk_expr(self, expr);
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}
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Slice(pre_pats, inner_pat, post_pats) => {
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pats.extend(pre_pats.iter());
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pats.extend(inner_pat.iter());
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pats.extend(post_pats.iter());
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// otherwise, live nodes are not required:
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hir::ExprKind::Index(..)
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| hir::ExprKind::Field(..)
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| hir::ExprKind::Array(..)
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| hir::ExprKind::Call(..)
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| hir::ExprKind::MethodCall(..)
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| hir::ExprKind::Tup(..)
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| hir::ExprKind::Binary(..)
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| hir::ExprKind::AddrOf(..)
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| hir::ExprKind::Cast(..)
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| hir::ExprKind::DropTemps(..)
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| hir::ExprKind::Unary(..)
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| hir::ExprKind::Break(..)
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| hir::ExprKind::Continue(_)
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| hir::ExprKind::Lit(_)
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| hir::ExprKind::Ret(..)
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| hir::ExprKind::Block(..)
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| hir::ExprKind::Assign(..)
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| hir::ExprKind::AssignOp(..)
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| hir::ExprKind::Struct(..)
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| hir::ExprKind::Repeat(..)
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| hir::ExprKind::InlineAsm(..)
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| hir::ExprKind::LlvmInlineAsm(..)
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| hir::ExprKind::Box(..)
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| hir::ExprKind::Yield(..)
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| hir::ExprKind::Type(..)
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| hir::ExprKind::Err
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| hir::ExprKind::Path(hir::QPath::TypeRelative(..))
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| hir::ExprKind::Path(hir::QPath::LangItem(..)) => {
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intravisit::walk_expr(self, expr);
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}
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_ => {}
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}
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}
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pat.each_binding(|_, hir_id, _, ident| {
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ir.add_live_node_for_node(hir_id, VarDefNode(ident.span));
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ir.add_variable(Local(LocalInfo {
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id: hir_id,
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name: ident.name,
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is_shorthand: shorthand_field_ids.contains(&hir_id),
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}));
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});
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}
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fn visit_local<'tcx>(ir: &mut IrMaps<'tcx>, local: &'tcx hir::Local<'tcx>) {
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add_from_pat(ir, &local.pat);
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intravisit::walk_local(ir, local);
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}
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fn visit_arm<'tcx>(ir: &mut IrMaps<'tcx>, arm: &'tcx hir::Arm<'tcx>) {
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add_from_pat(ir, &arm.pat);
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intravisit::walk_arm(ir, arm);
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}
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fn visit_expr<'tcx>(ir: &mut IrMaps<'tcx>, expr: &'tcx Expr<'tcx>) {
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match expr.kind {
|
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// live nodes required for uses or definitions of variables:
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hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => {
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debug!("expr {}: path that leads to {:?}", expr.hir_id, path.res);
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if let Res::Local(_var_hir_id) = path.res {
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ir.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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}
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intravisit::walk_expr(ir, expr);
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}
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hir::ExprKind::Closure(..) => {
|
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// Interesting control flow (for loops can contain labeled
|
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// breaks or continues)
|
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ir.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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|
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// Make a live_node for each captured variable, with the span
|
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// being the location that the variable is used. This results
|
||||
// in better error messages than just pointing at the closure
|
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// construction site.
|
||||
let mut call_caps = Vec::new();
|
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let closure_def_id = ir.tcx.hir().local_def_id(expr.hir_id);
|
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if let Some(upvars) = ir.tcx.upvars_mentioned(closure_def_id) {
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call_caps.extend(upvars.iter().map(|(&var_id, upvar)| {
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let upvar_ln = ir.add_live_node(UpvarNode(upvar.span));
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CaptureInfo { ln: upvar_ln, var_hid: var_id }
|
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}));
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}
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ir.set_captures(expr.hir_id, call_caps);
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let old_body_owner = ir.body_owner;
|
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ir.body_owner = closure_def_id;
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intravisit::walk_expr(ir, expr);
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ir.body_owner = old_body_owner;
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}
|
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|
||||
// live nodes required for interesting control flow:
|
||||
hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) => {
|
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ir.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
|
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intravisit::walk_expr(ir, expr);
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}
|
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hir::ExprKind::Binary(op, ..) if op.node.is_lazy() => {
|
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ir.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
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intravisit::walk_expr(ir, expr);
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}
|
||||
|
||||
// otherwise, live nodes are not required:
|
||||
hir::ExprKind::Index(..)
|
||||
| hir::ExprKind::Field(..)
|
||||
| hir::ExprKind::Array(..)
|
||||
| hir::ExprKind::Call(..)
|
||||
| hir::ExprKind::MethodCall(..)
|
||||
| hir::ExprKind::Tup(..)
|
||||
| hir::ExprKind::Binary(..)
|
||||
| hir::ExprKind::AddrOf(..)
|
||||
| hir::ExprKind::Cast(..)
|
||||
| hir::ExprKind::DropTemps(..)
|
||||
| hir::ExprKind::Unary(..)
|
||||
| hir::ExprKind::Break(..)
|
||||
| hir::ExprKind::Continue(_)
|
||||
| hir::ExprKind::Lit(_)
|
||||
| hir::ExprKind::Ret(..)
|
||||
| hir::ExprKind::Block(..)
|
||||
| hir::ExprKind::Assign(..)
|
||||
| hir::ExprKind::AssignOp(..)
|
||||
| hir::ExprKind::Struct(..)
|
||||
| hir::ExprKind::Repeat(..)
|
||||
| hir::ExprKind::InlineAsm(..)
|
||||
| hir::ExprKind::LlvmInlineAsm(..)
|
||||
| hir::ExprKind::Box(..)
|
||||
| hir::ExprKind::Yield(..)
|
||||
| hir::ExprKind::Type(..)
|
||||
| hir::ExprKind::Err
|
||||
| hir::ExprKind::Path(hir::QPath::TypeRelative(..))
|
||||
| hir::ExprKind::Path(hir::QPath::LangItem(..)) => {
|
||||
intravisit::walk_expr(ir, expr);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -605,8 +577,10 @@ const ACC_USE: u32 = 4;
|
|||
|
||||
struct Liveness<'a, 'tcx> {
|
||||
ir: &'a mut IrMaps<'tcx>,
|
||||
body_owner: LocalDefId,
|
||||
typeck_results: &'a ty::TypeckResults<'tcx>,
|
||||
param_env: ty::ParamEnv<'tcx>,
|
||||
upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
|
||||
successors: IndexVec<LiveNode, LiveNode>,
|
||||
rwu_table: RWUTable,
|
||||
|
||||
|
|
@ -626,9 +600,10 @@ struct Liveness<'a, 'tcx> {
|
|||
}
|
||||
|
||||
impl<'a, 'tcx> Liveness<'a, 'tcx> {
|
||||
fn new(ir: &'a mut IrMaps<'tcx>, def_id: LocalDefId) -> Liveness<'a, 'tcx> {
|
||||
let typeck_results = ir.tcx.typeck(def_id);
|
||||
let param_env = ir.tcx.param_env(def_id);
|
||||
fn new(ir: &'a mut IrMaps<'tcx>, body_owner: LocalDefId) -> Liveness<'a, 'tcx> {
|
||||
let typeck_results = ir.tcx.typeck(body_owner);
|
||||
let param_env = ir.tcx.param_env(body_owner);
|
||||
let upvars = ir.tcx.upvars_mentioned(body_owner);
|
||||
|
||||
let closure_ln = ir.add_live_node(ClosureNode);
|
||||
let exit_ln = ir.add_live_node(ExitNode);
|
||||
|
|
@ -638,8 +613,10 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
|
|||
|
||||
Liveness {
|
||||
ir,
|
||||
body_owner,
|
||||
typeck_results,
|
||||
param_env,
|
||||
upvars,
|
||||
successors: IndexVec::from_elem_n(INVALID_NODE, num_live_nodes),
|
||||
rwu_table: RWUTable::new(num_live_nodes * num_vars),
|
||||
closure_ln,
|
||||
|
|
@ -868,13 +845,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
|
|||
self.rwu_table.assign_unpacked(idx, rwu);
|
||||
}
|
||||
|
||||
fn compute(
|
||||
&mut self,
|
||||
fk: FnKind<'_>,
|
||||
body: &hir::Body<'_>,
|
||||
span: Span,
|
||||
id: hir::HirId,
|
||||
) -> LiveNode {
|
||||
fn compute(&mut self, body: &hir::Body<'_>, span: Span, id: hir::HirId) -> LiveNode {
|
||||
debug!("compute: using id for body, {:?}", body.value);
|
||||
|
||||
// # Liveness of captured variables
|
||||
|
|
@ -893,12 +864,12 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
|
|||
// if they are live on the entry to the closure, since only the closure
|
||||
// itself can access them on subsequent calls.
|
||||
|
||||
if let Some(upvars) = self.ir.tcx.upvars_mentioned(self.ir.body_owner) {
|
||||
if let Some(upvars) = self.upvars {
|
||||
// Mark upvars captured by reference as used after closure exits.
|
||||
for (&var_hir_id, upvar) in upvars.iter().rev() {
|
||||
let upvar_id = ty::UpvarId {
|
||||
var_path: ty::UpvarPath { hir_id: var_hir_id },
|
||||
closure_expr_id: self.ir.body_owner,
|
||||
closure_expr_id: self.body_owner,
|
||||
};
|
||||
match self.typeck_results.upvar_capture(upvar_id) {
|
||||
ty::UpvarCapture::ByRef(_) => {
|
||||
|
|
@ -912,9 +883,11 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
|
|||
|
||||
let succ = self.propagate_through_expr(&body.value, self.exit_ln);
|
||||
|
||||
match fk {
|
||||
FnKind::Method(..) | FnKind::ItemFn(..) => return succ,
|
||||
FnKind::Closure(..) => {}
|
||||
if self.upvars.is_none() {
|
||||
// Either not a closure, or closure without any captured variables.
|
||||
// No need to determine liveness of captured variables, since there
|
||||
// are none.
|
||||
return succ;
|
||||
}
|
||||
|
||||
let ty = self.typeck_results.node_type(id);
|
||||
|
|
@ -926,7 +899,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
|
|||
},
|
||||
ty::Generator(..) => return succ,
|
||||
_ => {
|
||||
span_bug!(span, "type of closure expr {:?} is not a closure {:?}", id, ty,);
|
||||
span_bug!(span, "{} has upvars so it should have a closure type: {:?}", id, ty);
|
||||
}
|
||||
};
|
||||
|
||||
|
|
@ -1565,7 +1538,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
|
|||
}
|
||||
|
||||
fn warn_about_unused_upvars(&self, entry_ln: LiveNode) {
|
||||
let upvars = match self.ir.tcx.upvars_mentioned(self.ir.body_owner) {
|
||||
let upvars = match self.upvars {
|
||||
None => return,
|
||||
Some(upvars) => upvars,
|
||||
};
|
||||
|
|
@ -1573,7 +1546,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
|
|||
let var = self.variable(var_hir_id, upvar.span);
|
||||
let upvar_id = ty::UpvarId {
|
||||
var_path: ty::UpvarPath { hir_id: var_hir_id },
|
||||
closure_expr_id: self.ir.body_owner,
|
||||
closure_expr_id: self.body_owner,
|
||||
};
|
||||
match self.typeck_results.upvar_capture(upvar_id) {
|
||||
ty::UpvarCapture::ByValue(_) => {}
|
||||
|
|
|
|||
|
|
@ -0,0 +1,38 @@
|
|||
// Test for interaction between #[automatically_derived] attribute used by
|
||||
// built-in derives and lints generated by liveness pass.
|
||||
//
|
||||
// edition:2018
|
||||
// check-pass
|
||||
#![warn(unused)]
|
||||
|
||||
pub trait T: Sized {
|
||||
const N: usize;
|
||||
fn t(&self) -> Self;
|
||||
}
|
||||
|
||||
impl T for u32 {
|
||||
const N: usize = {
|
||||
let a = 0; // FIXME should warn about unused variable
|
||||
4
|
||||
};
|
||||
|
||||
fn t(&self) -> Self {
|
||||
let b = 16; //~ WARN unused variable: `b`
|
||||
0
|
||||
}
|
||||
}
|
||||
|
||||
#[automatically_derived]
|
||||
impl T for i32 {
|
||||
const N: usize = {
|
||||
let c = 0;
|
||||
4
|
||||
};
|
||||
|
||||
fn t(&self) -> Self {
|
||||
let d = 17;
|
||||
0
|
||||
}
|
||||
}
|
||||
|
||||
fn main() {}
|
||||
|
|
@ -0,0 +1,15 @@
|
|||
warning: unused variable: `b`
|
||||
--> $DIR/liveness-derive.rs:20:13
|
||||
|
|
||||
LL | let b = 16;
|
||||
| ^ help: if this is intentional, prefix it with an underscore: `_b`
|
||||
|
|
||||
note: the lint level is defined here
|
||||
--> $DIR/liveness-derive.rs:6:9
|
||||
|
|
||||
LL | #![warn(unused)]
|
||||
| ^^^^^^
|
||||
= note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
|
||||
|
||||
warning: 1 warning emitted
|
||||
|
||||
Loading…
Reference in New Issue