280 lines
11 KiB
Rust
280 lines
11 KiB
Rust
use Context::*;
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use rustc_errors::{struct_span_err, Applicability};
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use rustc_hir as hir;
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use rustc_hir::def_id::LocalDefId;
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use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
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use rustc_hir::{Destination, Movability, Node};
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use rustc_middle::hir::map::Map;
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::TyCtxt;
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use rustc_session::Session;
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use rustc_span::hygiene::DesugaringKind;
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use rustc_span::Span;
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#[derive(Clone, Copy, Debug, PartialEq)]
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enum Context {
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Normal,
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Loop(hir::LoopSource),
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Closure(Span),
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AsyncClosure(Span),
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LabeledBlock,
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AnonConst,
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}
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#[derive(Copy, Clone)]
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struct CheckLoopVisitor<'a, 'hir> {
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sess: &'a Session,
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hir_map: Map<'hir>,
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cx: Context,
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}
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fn check_mod_loops(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 CheckLoopVisitor { sess: &tcx.sess, hir_map: tcx.hir(), cx: Normal }.as_deep_visitor(),
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);
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}
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pub(crate) fn provide(providers: &mut Providers) {
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*providers = Providers { check_mod_loops, ..*providers };
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}
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impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
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type Map = Map<'hir>;
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::OnlyBodies(self.hir_map)
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}
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fn visit_anon_const(&mut self, c: &'hir hir::AnonConst) {
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self.with_context(AnonConst, |v| intravisit::walk_anon_const(v, c));
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}
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fn visit_expr(&mut self, e: &'hir hir::Expr<'hir>) {
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match e.kind {
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hir::ExprKind::Loop(ref b, _, source, _) => {
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self.with_context(Loop(source), |v| v.visit_block(&b));
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}
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hir::ExprKind::Closure(_, ref function_decl, b, span, movability) => {
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let cx = if let Some(Movability::Static) = movability {
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AsyncClosure(span)
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} else {
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Closure(span)
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};
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self.visit_fn_decl(&function_decl);
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self.with_context(cx, |v| v.visit_nested_body(b));
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}
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hir::ExprKind::Block(ref b, Some(_label)) => {
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self.with_context(LabeledBlock, |v| v.visit_block(&b));
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}
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hir::ExprKind::Break(break_label, ref opt_expr) => {
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if let Some(e) = opt_expr {
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self.visit_expr(e);
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}
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if self.require_label_in_labeled_block(e.span, &break_label, "break") {
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// If we emitted an error about an unlabeled break in a labeled
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// block, we don't need any further checking for this break any more
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return;
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}
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let loop_id = match break_label.target_id {
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Ok(loop_id) => Some(loop_id),
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Err(hir::LoopIdError::OutsideLoopScope) => None,
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Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
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self.emit_unlabled_cf_in_while_condition(e.span, "break");
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None
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}
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Err(hir::LoopIdError::UnresolvedLabel) => None,
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};
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if let Some(Node::Block(_)) = loop_id.and_then(|id| self.hir_map.find(id)) {
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return;
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}
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if let Some(break_expr) = opt_expr {
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let (head, loop_label, loop_kind) = if let Some(loop_id) = loop_id {
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match self.hir_map.expect_expr(loop_id).kind {
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hir::ExprKind::Loop(_, label, source, sp) => {
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(Some(sp), label, Some(source))
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}
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ref r => {
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span_bug!(e.span, "break label resolved to a non-loop: {:?}", r)
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}
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}
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} else {
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(None, None, None)
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};
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match loop_kind {
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None | Some(hir::LoopSource::Loop) => (),
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Some(kind) => {
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let mut err = struct_span_err!(
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self.sess,
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e.span,
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E0571,
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"`break` with value from a `{}` loop",
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kind.name()
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);
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err.span_label(
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e.span,
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"can only break with a value inside `loop` or breakable block",
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);
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if let Some(head) = head {
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err.span_label(
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head,
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&format!(
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"you can't `break` with a value in a `{}` loop",
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kind.name()
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),
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);
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}
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err.span_suggestion(
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e.span,
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&format!(
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"use `break` on its own without a value inside this `{}` loop",
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kind.name(),
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),
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format!(
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"break{}",
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break_label
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.label
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.map_or_else(String::new, |l| format!(" {}", l.ident))
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),
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Applicability::MaybeIncorrect,
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);
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if let (Some(label), None) = (loop_label, break_label.label) {
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match break_expr.kind {
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hir::ExprKind::Path(hir::QPath::Resolved(
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None,
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hir::Path {
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segments: [segment],
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res: hir::def::Res::Err,
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..
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},
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)) if label.ident.to_string()
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== format!("'{}", segment.ident) =>
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{
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// This error is redundant, we will have already emitted a
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// suggestion to use the label when `segment` wasn't found
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// (hence the `Res::Err` check).
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err.delay_as_bug();
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}
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_ => {
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err.span_suggestion(
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break_expr.span,
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"alternatively, you might have meant to use the \
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available loop label",
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label.ident.to_string(),
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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err.emit();
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}
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}
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}
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self.require_break_cx("break", e.span);
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}
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hir::ExprKind::Continue(destination) => {
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self.require_label_in_labeled_block(e.span, &destination, "continue");
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match destination.target_id {
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Ok(loop_id) => {
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if let Node::Block(block) = self.hir_map.find(loop_id).unwrap() {
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struct_span_err!(
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self.sess,
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e.span,
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E0696,
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"`continue` pointing to a labeled block"
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)
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.span_label(e.span, "labeled blocks cannot be `continue`'d")
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.span_label(block.span, "labeled block the `continue` points to")
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.emit();
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}
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}
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Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
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self.emit_unlabled_cf_in_while_condition(e.span, "continue");
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}
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Err(_) => {}
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}
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self.require_break_cx("continue", e.span)
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}
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_ => intravisit::walk_expr(self, e),
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}
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}
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}
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impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
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fn with_context<F>(&mut self, cx: Context, f: F)
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where
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F: FnOnce(&mut CheckLoopVisitor<'a, 'hir>),
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{
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let old_cx = self.cx;
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self.cx = cx;
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f(self);
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self.cx = old_cx;
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}
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fn require_break_cx(&self, name: &str, span: Span) {
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let err_inside_of = |article, ty, closure_span| {
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struct_span_err!(self.sess, span, E0267, "`{}` inside of {} {}", name, article, ty)
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.span_label(span, format!("cannot `{}` inside of {} {}", name, article, ty))
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.span_label(closure_span, &format!("enclosing {}", ty))
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.emit();
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};
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match self.cx {
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LabeledBlock | Loop(_) => {}
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Closure(closure_span) => err_inside_of("a", "closure", closure_span),
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AsyncClosure(closure_span) => err_inside_of("an", "`async` block", closure_span),
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Normal | AnonConst => {
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struct_span_err!(self.sess, span, E0268, "`{}` outside of a loop", name)
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.span_label(span, format!("cannot `{}` outside of a loop", name))
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.emit();
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}
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}
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}
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fn require_label_in_labeled_block(
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&mut self,
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span: Span,
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label: &Destination,
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cf_type: &str,
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) -> bool {
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if !span.is_desugaring(DesugaringKind::QuestionMark) && self.cx == LabeledBlock {
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if label.label.is_none() {
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struct_span_err!(
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self.sess,
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span,
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E0695,
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"unlabeled `{}` inside of a labeled block",
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cf_type
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)
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.span_label(
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span,
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format!(
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"`{}` statements that would diverge to or through \
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a labeled block need to bear a label",
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cf_type
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),
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)
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.emit();
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return true;
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}
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}
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false
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}
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fn emit_unlabled_cf_in_while_condition(&mut self, span: Span, cf_type: &str) {
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struct_span_err!(
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self.sess,
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span,
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E0590,
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"`break` or `continue` with no label in the condition of a `while` loop"
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)
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.span_label(span, format!("unlabeled `{}` in the condition of a `while` loop", cf_type))
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.emit();
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}
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}
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