Skip to content

Fix never_loop forget to remove break in nested loop #15356

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Sep 5, 2025
Merged

Fix never_loop forget to remove break in nested loop #15356

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
59 changes: 48 additions & 11 deletions clippy_lints/src/loops/never_loop.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,10 @@ pub(super) fn check<'tcx>(
for_loop: Option<&ForLoop<'_>>,
) {
match never_loop_block(cx, block, &mut Vec::new(), loop_id) {
NeverLoopResult::Diverging { ref break_spans } => {
NeverLoopResult::Diverging {
ref break_spans,
ref never_spans,
} => {
span_lint_and_then(cx, NEVER_LOOP, span, "this loop never actually loops", |diag| {
if let Some(ForLoop {
arg: iterator,
Expand All @@ -34,12 +37,16 @@ pub(super) fn check<'tcx>(
{
// If the block contains a break or continue, or if the loop has a label, `MachineApplicable` is not
// appropriate.
let app = if !contains_any_break_or_continue(block) && label.is_none() {
let mut app = if !contains_any_break_or_continue(block) && label.is_none() {
Applicability::MachineApplicable
} else {
Applicability::Unspecified
};

if !never_spans.is_empty() {
app = Applicability::HasPlaceholders;
}

let mut suggestions = vec![(
for_span.with_hi(iterator.span.hi()),
for_to_if_let_sugg(cx, iterator, pat),
Expand All @@ -51,6 +58,13 @@ pub(super) fn check<'tcx>(
suggestions,
app,
);

for span in never_spans {
diag.span_help(
*span,
"this code is unreachable. Consider moving the reachable parts out",
);
}
}
});
},
Expand All @@ -77,13 +91,16 @@ fn contains_any_break_or_continue(block: &Block<'_>) -> bool {
/// The first two bits of information are in this enum, and the last part is in the
/// `local_labels` variable, which contains a list of `(block_id, reachable)` pairs ordered by
/// scope.
#[derive(Clone)]
#[derive(Clone, Debug)]
enum NeverLoopResult {
/// A continue may occur for the main loop.
MayContinueMainLoop,
/// We have not encountered any main loop continue,
/// but we are diverging (subsequent control flow is not reachable)
Diverging { break_spans: Vec<Span> },
Diverging {
break_spans: Vec<Span>,
never_spans: Vec<Span>,
},
/// We have not encountered any main loop continue,
/// and subsequent control flow is (possibly) reachable
Normal,
Expand Down Expand Up @@ -128,14 +145,18 @@ fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult
(
NeverLoopResult::Diverging {
break_spans: mut break_spans1,
never_spans: mut never_spans1,
},
NeverLoopResult::Diverging {
break_spans: mut break_spans2,
never_spans: mut never_spans2,
},
) => {
break_spans1.append(&mut break_spans2);
never_spans1.append(&mut never_spans2);
NeverLoopResult::Diverging {
break_spans: break_spans1,
never_spans: never_spans1,
}
},
}
Expand Down Expand Up @@ -207,6 +228,8 @@ fn all_spans_after_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> Vec<Span> {
}

return vec![stmt.span];
} else if let Node::Block(_) = cx.tcx.parent_hir_node(expr.hir_id) {
return vec![expr.span];
}

vec![]
Expand Down Expand Up @@ -270,10 +293,13 @@ fn never_loop_expr<'tcx>(
ExprKind::Match(e, arms, _) => {
let e = never_loop_expr(cx, e, local_labels, main_loop_id);
combine_seq(e, || {
arms.iter()
.fold(NeverLoopResult::Diverging { break_spans: vec![] }, |a, b| {
combine_branches(a, never_loop_expr(cx, b.body, local_labels, main_loop_id))
})
arms.iter().fold(
NeverLoopResult::Diverging {
break_spans: vec![],
never_spans: vec![],
},
|a, b| combine_branches(a, never_loop_expr(cx, b.body, local_labels, main_loop_id)),
)
})
},
ExprKind::Block(b, _) => {
Expand All @@ -296,6 +322,7 @@ fn never_loop_expr<'tcx>(
} else {
NeverLoopResult::Diverging {
break_spans: all_spans_after_expr(cx, expr),
never_spans: vec![],
}
}
},
Expand All @@ -306,7 +333,10 @@ fn never_loop_expr<'tcx>(
combine_seq(first, || {
// checks if break targets a block instead of a loop
mark_block_as_reachable(expr, local_labels);
NeverLoopResult::Diverging { break_spans: vec![] }
NeverLoopResult::Diverging {
break_spans: vec![],
never_spans: vec![],
}
})
},
ExprKind::Break(dest, e) => {
Expand All @@ -322,11 +352,15 @@ fn never_loop_expr<'tcx>(
} else {
all_spans_after_expr(cx, expr)
},
never_spans: vec![],
}
})
},
ExprKind::Become(e) => combine_seq(never_loop_expr(cx, e, local_labels, main_loop_id), || {
NeverLoopResult::Diverging { break_spans: vec![] }
NeverLoopResult::Diverging {
break_spans: vec![],
never_spans: vec![],
}
}),
ExprKind::InlineAsm(asm) => combine_seq_many(asm.operands.iter().map(|(o, _)| match o {
InlineAsmOperand::In { expr, .. } | InlineAsmOperand::InOut { expr, .. } => {
Expand Down Expand Up @@ -356,7 +390,10 @@ fn never_loop_expr<'tcx>(
};
let result = combine_seq(result, || {
if cx.typeck_results().expr_ty(expr).is_never() {
NeverLoopResult::Diverging { break_spans: vec![] }
NeverLoopResult::Diverging {
break_spans: vec![],
never_spans: all_spans_after_expr(cx, expr),
}
} else {
NeverLoopResult::Normal
}
Expand Down
24 changes: 24 additions & 0 deletions tests/ui/never_loop.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -498,3 +498,27 @@ fn issue15059() {
()
}
}

fn issue15350() {
'bar: for _ in 0..100 {
//~^ never_loop
loop {
//~^ never_loop
println!("This will still run");
break 'bar;
}
}

'foo: for _ in 0..100 {
//~^ never_loop
loop {
//~^ never_loop
println!("This will still run");
loop {
//~^ never_loop
println!("This will still run");
break 'foo;
}
}
}
}
97 changes: 96 additions & 1 deletion tests/ui/never_loop.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -193,6 +193,19 @@ LL | | return;
LL | | }
| |_____^
|
help: this code is unreachable. Consider moving the reachable parts out
--> tests/ui/never_loop.rs:436:9
|
LL | / loop {
LL | |
LL | | break 'outer;
LL | | }
| |_________^
help: this code is unreachable. Consider moving the reachable parts out
--> tests/ui/never_loop.rs:440:9
|
LL | return;
| ^^^^^^^
help: if you need the first element of the iterator, try writing
|
LL - 'outer: for v in 0..10 {
Expand Down Expand Up @@ -297,5 +310,87 @@ LL ~
LL ~
|

error: aborting due to 24 previous errors
error: this loop never actually loops
--> tests/ui/never_loop.rs:503:5
|
LL | / 'bar: for _ in 0..100 {
LL | |
LL | | loop {
... |
LL | | }
| |_____^
|
help: this code is unreachable. Consider moving the reachable parts out
--> tests/ui/never_loop.rs:505:9
|
LL | / loop {
LL | |
LL | | println!("This will still run");
LL | | break 'bar;
LL | | }
| |_________^
help: if you need the first element of the iterator, try writing
|
LL - 'bar: for _ in 0..100 {
LL + if let Some(_) = (0..100).next() {
|

error: this loop never actually loops
--> tests/ui/never_loop.rs:505:9
|
LL | / loop {
LL | |
LL | | println!("This will still run");
LL | | break 'bar;
LL | | }
| |_________^

error: this loop never actually loops
--> tests/ui/never_loop.rs:512:5
|
LL | / 'foo: for _ in 0..100 {
LL | |
LL | | loop {
... |
LL | | }
| |_____^
|
help: this code is unreachable. Consider moving the reachable parts out
--> tests/ui/never_loop.rs:514:9
|
LL | / loop {
LL | |
LL | | println!("This will still run");
LL | | loop {
... |
LL | | }
| |_________^
help: if you need the first element of the iterator, try writing
|
LL - 'foo: for _ in 0..100 {
LL + if let Some(_) = (0..100).next() {
|

error: this loop never actually loops
--> tests/ui/never_loop.rs:514:9
|
LL | / loop {
LL | |
LL | | println!("This will still run");
LL | | loop {
... |
LL | | }
| |_________^

error: this loop never actually loops
--> tests/ui/never_loop.rs:517:13
|
LL | / loop {
LL | |
LL | | println!("This will still run");
LL | | break 'foo;
LL | | }
| |_____________^

error: aborting due to 29 previous errors

2 changes: 1 addition & 1 deletion tests/ui/never_loop_fixable.fixed
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#![allow(clippy::iter_next_slice, clippy::needless_return)]
#![allow(clippy::iter_next_slice, clippy::needless_return, clippy::redundant_pattern_matching)]

fn no_break_or_continue_loop() {
if let Some(i) = [1, 2, 3].iter().next() {
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/never_loop_fixable.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#![allow(clippy::iter_next_slice, clippy::needless_return)]
#![allow(clippy::iter_next_slice, clippy::needless_return, clippy::redundant_pattern_matching)]

fn no_break_or_continue_loop() {
for i in [1, 2, 3].iter() {
Expand Down