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Resolve infinite_loop FP for nested loops #16724

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Resolve infinite_loop FP for nested loops #16724

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61 changes: 61 additions & 0 deletions clippy_lints/src/loops/infinite_loop.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,8 @@ pub(super) fn check<'tcx>(
inner_labels: label.into_iter().collect(),
loop_depth: 0,
is_finite: false,
ex: expr,
potential_breaks: Vec::new(),
};
loop_visitor.visit_block(loop_block);

Expand Down Expand Up @@ -152,6 +154,8 @@ struct LoopVisitor<'hir, 'tcx> {
inner_labels: Vec<Label>,
loop_depth: usize,
is_finite: bool,
ex: &'hir Expr<'hir>,
potential_breaks: Vec<&'hir Expr<'hir>>,
}

impl<'hir> Visitor<'hir> for LoopVisitor<'hir, '_> {
Expand All @@ -163,6 +167,63 @@ impl<'hir> Visitor<'hir> for LoopVisitor<'hir, '_> {
// Or, the depth is not zero but the label is matched.
if self.loop_depth == 0 || (label.is_some() && *label == self.label) {
self.is_finite = true;
// Or the label is not matched.
} else {
let mut ex_id = ex.hir_id;
loop {
match self.cx.tcx.parent_hir_node(ex_id) {
Node::Expr(parent_ex) => {
if self.ex.hir_id == parent_ex.hir_id {
break;
}
if let ExprKind::Loop(..) = parent_ex.kind
&& self.potential_breaks.iter().any(
|Expr {
hir_id: _,
kind,
span: _,
}| {
if let ExprKind::Break(hir::Destination { label: _, target_id }, ..) = kind
&& let Ok(t_id) = target_id
&& t_id.local_id < self.ex.hir_id.local_id
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@mikhailofff mikhailofff Mar 25, 2026

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Thanks for the review. I actually had this in mind. The use of potential_breaks in LoopVisitor is necessary to store the break statements that may terminate the original loop if it points to a loop that precedes the original loop. If the target_id only points to the loop that will actually be terminated by the break, then everything is fine. I hope.

{
return true;
}
false
},
)
{
self.is_finite = true;
break;
}
},
Node::Block(bl) => {
if let Some(e) = bl.expr
&& let ExprKind::Break(hir::Destination { .. }, ..) = e.kind
&& self
.potential_breaks
.iter()
.all(|br| br.hir_id.local_id > e.hir_id.local_id)
{
self.potential_breaks.push(e);
} else {
for stmt in bl.stmts {
if let hir::StmtKind::Semi(e) | hir::StmtKind::Expr(e) = stmt.kind
&& let ExprKind::Break(hir::Destination { .. }, ..) = e.kind
&& self
.potential_breaks
.iter()
.all(|br| br.hir_id.local_id > e.hir_id.local_id)
{
self.potential_breaks.push(e);
}
}
}
},
_ => (),
}
ex_id = self.cx.tcx.parent_hir_id(ex_id);
}
}
},
ExprKind::Continue(hir::Destination { label, .. }) => {
Expand Down
23 changes: 23 additions & 0 deletions tests/ui/infinite_loops.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -589,4 +589,27 @@ mod issue16155 {
}
}

#[rustfmt::skip]
mod issue16134 {
fn issue() {
'outer: loop {
let _: i32 = loop { loop { break 'outer } };
}
}

fn expr() {
'outer: loop { loop { loop { break 'outer } } }
}

fn stmt() {
'outer: loop { loop { loop { break 'outer; } } }
}

fn more_loops() {
'outer: loop {
let _: i32 = loop { loop { loop { loop { loop { break 'outer } } } } };
}
}
}

fn main() {}
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