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-rw-r--r--compiler/rustc_passes/src/loops.rs287
1 files changed, 287 insertions, 0 deletions
diff --git a/compiler/rustc_passes/src/loops.rs b/compiler/rustc_passes/src/loops.rs
new file mode 100644
index 000000000..cdda0e388
--- /dev/null
+++ b/compiler/rustc_passes/src/loops.rs
@@ -0,0 +1,287 @@
+use Context::*;
+
+use rustc_errors::{struct_span_err, Applicability};
+use rustc_hir as hir;
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::intravisit::{self, Visitor};
+use rustc_hir::{Destination, Movability, Node};
+use rustc_middle::hir::map::Map;
+use rustc_middle::hir::nested_filter;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::Session;
+use rustc_span::hygiene::DesugaringKind;
+use rustc_span::Span;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+enum Context {
+ Normal,
+ Loop(hir::LoopSource),
+ Closure(Span),
+ AsyncClosure(Span),
+ LabeledBlock,
+ AnonConst,
+}
+
+#[derive(Copy, Clone)]
+struct CheckLoopVisitor<'a, 'hir> {
+ sess: &'a Session,
+ hir_map: Map<'hir>,
+ cx: Context,
+}
+
+fn check_mod_loops(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
+ tcx.hir().visit_item_likes_in_module(
+ module_def_id,
+ &mut CheckLoopVisitor { sess: &tcx.sess, hir_map: tcx.hir(), cx: Normal },
+ );
+}
+
+pub(crate) fn provide(providers: &mut Providers) {
+ *providers = Providers { check_mod_loops, ..*providers };
+}
+
+impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
+ type NestedFilter = nested_filter::OnlyBodies;
+
+ fn nested_visit_map(&mut self) -> Self::Map {
+ self.hir_map
+ }
+
+ fn visit_anon_const(&mut self, c: &'hir hir::AnonConst) {
+ self.with_context(AnonConst, |v| intravisit::walk_anon_const(v, c));
+ }
+
+ fn visit_expr(&mut self, e: &'hir hir::Expr<'hir>) {
+ match e.kind {
+ hir::ExprKind::Loop(ref b, _, source, _) => {
+ self.with_context(Loop(source), |v| v.visit_block(&b));
+ }
+ hir::ExprKind::Closure(&hir::Closure {
+ ref fn_decl,
+ body,
+ fn_decl_span,
+ movability,
+ ..
+ }) => {
+ let cx = if let Some(Movability::Static) = movability {
+ AsyncClosure(fn_decl_span)
+ } else {
+ Closure(fn_decl_span)
+ };
+ self.visit_fn_decl(&fn_decl);
+ self.with_context(cx, |v| v.visit_nested_body(body));
+ }
+ hir::ExprKind::Block(ref b, Some(_label)) => {
+ self.with_context(LabeledBlock, |v| v.visit_block(&b));
+ }
+ hir::ExprKind::Break(break_label, ref opt_expr) => {
+ if let Some(e) = opt_expr {
+ self.visit_expr(e);
+ }
+
+ if self.require_label_in_labeled_block(e.span, &break_label, "break") {
+ // If we emitted an error about an unlabeled break in a labeled
+ // block, we don't need any further checking for this break any more
+ return;
+ }
+
+ let loop_id = match break_label.target_id {
+ Ok(loop_id) => Some(loop_id),
+ Err(hir::LoopIdError::OutsideLoopScope) => None,
+ Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
+ self.emit_unlabled_cf_in_while_condition(e.span, "break");
+ None
+ }
+ Err(hir::LoopIdError::UnresolvedLabel) => None,
+ };
+
+ if let Some(Node::Block(_)) = loop_id.and_then(|id| self.hir_map.find(id)) {
+ return;
+ }
+
+ if let Some(break_expr) = opt_expr {
+ let (head, loop_label, loop_kind) = if let Some(loop_id) = loop_id {
+ match self.hir_map.expect_expr(loop_id).kind {
+ hir::ExprKind::Loop(_, label, source, sp) => {
+ (Some(sp), label, Some(source))
+ }
+ ref r => {
+ span_bug!(e.span, "break label resolved to a non-loop: {:?}", r)
+ }
+ }
+ } else {
+ (None, None, None)
+ };
+ match loop_kind {
+ None | Some(hir::LoopSource::Loop) => (),
+ Some(kind) => {
+ let mut err = struct_span_err!(
+ self.sess,
+ e.span,
+ E0571,
+ "`break` with value from a `{}` loop",
+ kind.name()
+ );
+ err.span_label(
+ e.span,
+ "can only break with a value inside `loop` or breakable block",
+ );
+ if let Some(head) = head {
+ err.span_label(
+ head,
+ &format!(
+ "you can't `break` with a value in a `{}` loop",
+ kind.name()
+ ),
+ );
+ }
+ err.span_suggestion(
+ e.span,
+ &format!(
+ "use `break` on its own without a value inside this `{}` loop",
+ kind.name(),
+ ),
+ format!(
+ "break{}",
+ break_label
+ .label
+ .map_or_else(String::new, |l| format!(" {}", l.ident))
+ ),
+ Applicability::MaybeIncorrect,
+ );
+ if let (Some(label), None) = (loop_label, break_label.label) {
+ match break_expr.kind {
+ hir::ExprKind::Path(hir::QPath::Resolved(
+ None,
+ hir::Path {
+ segments: [segment],
+ res: hir::def::Res::Err,
+ ..
+ },
+ )) if label.ident.to_string()
+ == format!("'{}", segment.ident) =>
+ {
+ // This error is redundant, we will have already emitted a
+ // suggestion to use the label when `segment` wasn't found
+ // (hence the `Res::Err` check).
+ err.delay_as_bug();
+ }
+ _ => {
+ err.span_suggestion(
+ break_expr.span,
+ "alternatively, you might have meant to use the \
+ available loop label",
+ label.ident,
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ }
+ err.emit();
+ }
+ }
+ }
+
+ self.require_break_cx("break", e.span);
+ }
+ hir::ExprKind::Continue(destination) => {
+ self.require_label_in_labeled_block(e.span, &destination, "continue");
+
+ match destination.target_id {
+ Ok(loop_id) => {
+ if let Node::Block(block) = self.hir_map.find(loop_id).unwrap() {
+ struct_span_err!(
+ self.sess,
+ e.span,
+ E0696,
+ "`continue` pointing to a labeled block"
+ )
+ .span_label(e.span, "labeled blocks cannot be `continue`'d")
+ .span_label(block.span, "labeled block the `continue` points to")
+ .emit();
+ }
+ }
+ Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
+ self.emit_unlabled_cf_in_while_condition(e.span, "continue");
+ }
+ Err(_) => {}
+ }
+ self.require_break_cx("continue", e.span)
+ }
+ _ => intravisit::walk_expr(self, e),
+ }
+ }
+}
+
+impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
+ fn with_context<F>(&mut self, cx: Context, f: F)
+ where
+ F: FnOnce(&mut CheckLoopVisitor<'a, 'hir>),
+ {
+ let old_cx = self.cx;
+ self.cx = cx;
+ f(self);
+ self.cx = old_cx;
+ }
+
+ fn require_break_cx(&self, name: &str, span: Span) {
+ let err_inside_of = |article, ty, closure_span| {
+ struct_span_err!(self.sess, span, E0267, "`{}` inside of {} {}", name, article, ty)
+ .span_label(span, format!("cannot `{}` inside of {} {}", name, article, ty))
+ .span_label(closure_span, &format!("enclosing {}", ty))
+ .emit();
+ };
+
+ match self.cx {
+ LabeledBlock | Loop(_) => {}
+ Closure(closure_span) => err_inside_of("a", "closure", closure_span),
+ AsyncClosure(closure_span) => err_inside_of("an", "`async` block", closure_span),
+ Normal | AnonConst => {
+ struct_span_err!(self.sess, span, E0268, "`{}` outside of a loop", name)
+ .span_label(span, format!("cannot `{}` outside of a loop", name))
+ .emit();
+ }
+ }
+ }
+
+ fn require_label_in_labeled_block(
+ &mut self,
+ span: Span,
+ label: &Destination,
+ cf_type: &str,
+ ) -> bool {
+ if !span.is_desugaring(DesugaringKind::QuestionMark) && self.cx == LabeledBlock {
+ if label.label.is_none() {
+ struct_span_err!(
+ self.sess,
+ span,
+ E0695,
+ "unlabeled `{}` inside of a labeled block",
+ cf_type
+ )
+ .span_label(
+ span,
+ format!(
+ "`{}` statements that would diverge to or through \
+ a labeled block need to bear a label",
+ cf_type
+ ),
+ )
+ .emit();
+ return true;
+ }
+ }
+ false
+ }
+ fn emit_unlabled_cf_in_while_condition(&mut self, span: Span, cf_type: &str) {
+ struct_span_err!(
+ self.sess,
+ span,
+ E0590,
+ "`break` or `continue` with no label in the condition of a `while` loop"
+ )
+ .span_label(span, format!("unlabeled `{}` in the condition of a `while` loop", cf_type))
+ .emit();
+ }
+}
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