3 use rustc_errors::{struct_span_err, Applicability};
5 use rustc_hir::def_id::LocalDefId;
6 use rustc_hir::intravisit::{self, Visitor};
7 use rustc_hir::{Destination, Movability, Node};
8 use rustc_middle::hir::map::Map;
9 use rustc_middle::hir::nested_filter;
10 use rustc_middle::ty::query::Providers;
11 use rustc_middle::ty::TyCtxt;
12 use rustc_session::Session;
13 use rustc_span::hygiene::DesugaringKind;
16 #[derive(Clone, Copy, Debug, PartialEq)]
19 Loop(hir::LoopSource),
26 #[derive(Copy, Clone)]
27 struct CheckLoopVisitor<'a, 'hir> {
33 fn check_mod_loops(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
34 tcx.hir().visit_item_likes_in_module(
36 &mut CheckLoopVisitor { sess: &tcx.sess, hir_map: tcx.hir(), cx: Normal },
40 pub(crate) fn provide(providers: &mut Providers) {
41 *providers = Providers { check_mod_loops, ..*providers };
44 impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
45 type NestedFilter = nested_filter::OnlyBodies;
47 fn nested_visit_map(&mut self) -> Self::Map {
51 fn visit_anon_const(&mut self, c: &'hir hir::AnonConst) {
52 self.with_context(AnonConst, |v| intravisit::walk_anon_const(v, c));
55 fn visit_expr(&mut self, e: &'hir hir::Expr<'hir>) {
57 hir::ExprKind::Loop(ref b, _, source, _) => {
58 self.with_context(Loop(source), |v| v.visit_block(&b));
60 hir::ExprKind::Closure { ref fn_decl, body, fn_decl_span, movability, .. } => {
61 let cx = if let Some(Movability::Static) = movability {
62 AsyncClosure(fn_decl_span)
66 self.visit_fn_decl(&fn_decl);
67 self.with_context(cx, |v| v.visit_nested_body(body));
69 hir::ExprKind::Block(ref b, Some(_label)) => {
70 self.with_context(LabeledBlock, |v| v.visit_block(&b));
72 hir::ExprKind::Break(break_label, ref opt_expr) => {
73 if let Some(e) = opt_expr {
77 if self.require_label_in_labeled_block(e.span, &break_label, "break") {
78 // If we emitted an error about an unlabeled break in a labeled
79 // block, we don't need any further checking for this break any more
83 let loop_id = match break_label.target_id {
84 Ok(loop_id) => Some(loop_id),
85 Err(hir::LoopIdError::OutsideLoopScope) => None,
86 Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
87 self.emit_unlabled_cf_in_while_condition(e.span, "break");
90 Err(hir::LoopIdError::UnresolvedLabel) => None,
93 if let Some(Node::Block(_)) = loop_id.and_then(|id| self.hir_map.find(id)) {
97 if let Some(break_expr) = opt_expr {
98 let (head, loop_label, loop_kind) = if let Some(loop_id) = loop_id {
99 match self.hir_map.expect_expr(loop_id).kind {
100 hir::ExprKind::Loop(_, label, source, sp) => {
101 (Some(sp), label, Some(source))
104 span_bug!(e.span, "break label resolved to a non-loop: {:?}", r)
111 None | Some(hir::LoopSource::Loop) => (),
113 let mut err = struct_span_err!(
117 "`break` with value from a `{}` loop",
122 "can only break with a value inside `loop` or breakable block",
124 if let Some(head) = head {
128 "you can't `break` with a value in a `{}` loop",
136 "use `break` on its own without a value inside this `{}` loop",
143 .map_or_else(String::new, |l| format!(" {}", l.ident))
145 Applicability::MaybeIncorrect,
147 if let (Some(label), None) = (loop_label, break_label.label) {
148 match break_expr.kind {
149 hir::ExprKind::Path(hir::QPath::Resolved(
153 res: hir::def::Res::Err,
156 )) if label.ident.to_string()
157 == format!("'{}", segment.ident) =>
159 // This error is redundant, we will have already emitted a
160 // suggestion to use the label when `segment` wasn't found
161 // (hence the `Res::Err` check).
167 "alternatively, you might have meant to use the \
168 available loop label",
170 Applicability::MaybeIncorrect,
180 self.require_break_cx("break", e.span);
182 hir::ExprKind::Continue(destination) => {
183 self.require_label_in_labeled_block(e.span, &destination, "continue");
185 match destination.target_id {
187 if let Node::Block(block) = self.hir_map.find(loop_id).unwrap() {
192 "`continue` pointing to a labeled block"
194 .span_label(e.span, "labeled blocks cannot be `continue`'d")
195 .span_label(block.span, "labeled block the `continue` points to")
199 Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
200 self.emit_unlabled_cf_in_while_condition(e.span, "continue");
204 self.require_break_cx("continue", e.span)
206 _ => intravisit::walk_expr(self, e),
211 impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
212 fn with_context<F>(&mut self, cx: Context, f: F)
214 F: FnOnce(&mut CheckLoopVisitor<'a, 'hir>),
216 let old_cx = self.cx;
222 fn require_break_cx(&self, name: &str, span: Span) {
223 let err_inside_of = |article, ty, closure_span| {
224 struct_span_err!(self.sess, span, E0267, "`{}` inside of {} {}", name, article, ty)
225 .span_label(span, format!("cannot `{}` inside of {} {}", name, article, ty))
226 .span_label(closure_span, &format!("enclosing {}", ty))
231 LabeledBlock | Loop(_) => {}
232 Closure(closure_span) => err_inside_of("a", "closure", closure_span),
233 AsyncClosure(closure_span) => err_inside_of("an", "`async` block", closure_span),
234 Normal | AnonConst => {
235 struct_span_err!(self.sess, span, E0268, "`{}` outside of a loop", name)
236 .span_label(span, format!("cannot `{}` outside of a loop", name))
242 fn require_label_in_labeled_block(
248 if !span.is_desugaring(DesugaringKind::QuestionMark) && self.cx == LabeledBlock {
249 if label.label.is_none() {
254 "unlabeled `{}` inside of a labeled block",
260 "`{}` statements that would diverge to or through \
261 a labeled block need to bear a label",
271 fn emit_unlabled_cf_in_while_condition(&mut self, span: Span, cf_type: &str) {
276 "`break` or `continue` with no label in the condition of a `while` loop"
278 .span_label(span, format!("unlabeled `{}` in the condition of a `while` loop", cf_type))