Reuse resolve_label to check lifetime shadowing.

compiler/rustc_resolve/src/late.rs

@@ -1548,13 +1548,9 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
 
  /// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved
  /// label and reports an error if the label is not found or is unreachable.
- fn resolve_label(&mut self, mut label: Ident) -> Option<NodeId> {
+ fn resolve_label(&mut self, mut label: Ident) -> Result<(NodeId, Span), ResolutionError<'a>> {
  let mut suggestion = None;
 
- // Preserve the original span so that errors contain "in this macro invocation"
- // information.
- let original_span = label.span;
-
  for i in (0..self.label_ribs.len()).rev() {
  let rib = &self.label_ribs[i];
 
@@ -1570,18 +1566,13 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
  if let Some((ident, id)) = rib.bindings.get_key_value(&ident) {
  let definition_span = ident.span;
  return if self.is_label_valid_from_rib(i) {
- Some(*id)
+ Ok((*id, definition_span))
  } else {
- self.report_error(
- original_span,
- ResolutionError::UnreachableLabel {
- name: label.name,
- definition_span,
- suggestion,
- },
- );
-
- None
+ Err(ResolutionError::UnreachableLabel {
+ name: label.name,
+ definition_span,
+ suggestion,
+ })
  };
  }
 
@@ -1590,11 +1581,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
  suggestion = suggestion.or_else(|| self.suggestion_for_label_in_rib(i, label));
  }
 
- self.report_error(
- original_span,
- ResolutionError::UndeclaredLabel { name: label.name, suggestion },
- );
- None
+ Err(ResolutionError::UndeclaredLabel { name: label.name, suggestion })
  }
 
  /// Determine whether or not a label from the `rib_index`th label rib is reachable.
@@ -3152,17 +3139,12 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
  self.diagnostic_metadata.unused_labels.insert(id, label.ident.span);
  }
 
- let ident = label.ident.normalize_to_macro_rules();
- for rib in self.label_ribs.iter_mut().rev() {
- if let Some((&orig_ident, _)) = rib.bindings.get_key_value(&ident) {
- diagnostics::signal_label_shadowing(self.r.session, orig_ident, label.ident)
- }
- if rib.kind.is_label_barrier() {
- break;
- }
+ if let Ok((_, orig_span)) = self.resolve_label(label.ident) {
+ diagnostics::signal_label_shadowing(self.r.session, orig_span, label.ident)
  }
 
  self.with_label_rib(NormalRibKind, |this| {
+ let ident = label.ident.normalize_to_macro_rules();
  this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
  f(this);
  });
@@ -3266,10 +3248,15 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
  }
 
  ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
- if let Some(node_id) = self.resolve_label(label.ident) {
- // Since this res is a label, it is never read.
- self.r.label_res_map.insert(expr.id, node_id);
- self.diagnostic_metadata.unused_labels.remove(&node_id);
+ match self.resolve_label(label.ident) {
+ Ok((node_id, _)) => {
+ // Since this res is a label, it is never read.
+ self.r.label_res_map.insert(expr.id, node_id);
+ self.diagnostic_metadata.unused_labels.remove(&node_id);
+ }
+ Err(error) => {
+ self.report_error(label.ident.span, error);
+ }
  }
 
  // visit `break` argument if any

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -2066,15 +2066,17 @@ pub fn signal_lifetime_shadowing(
  err.emit();
 }
 
-/// Shadowing involving a label is only a warning, due to issues with
-/// labels and lifetimes not being macro-hygienic.
-pub fn signal_label_shadowing(sess: &Session, orig: Ident, shadower: Ident) {
+/// Shadowing involving a label is only a warning for historical reasons.
+//FIXME: make this a proper lint.
+pub fn signal_label_shadowing(sess: &Session, orig: Span, shadower: Ident) {
+ let name = shadower.name;
+ let shadower = shadower.span;
  let mut err = sess.struct_span_warn(
- shadower.span,
- &format!("label name `{}` shadows a label name that is already in scope", orig.name),
+ shadower,
+ &format!("label name `{}` shadows a label name that is already in scope", name),
  );
- err.span_label(orig.span, "first declared here");
- err.span_label(shadower.span, format!("label `{}` already in scope", orig.name));
+ err.span_label(orig, "first declared here");
+ err.span_label(shadower, format!("label `{}` already in scope", name));
  err.emit();
 }