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Fixing Issue #16003: #16231

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Fixing Issue #16003: #16231

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716214d
fix: preserve panic behavior in needless_range_loop lint; update .std…
Aadi11z Dec 13, 2025
a3f3f9c
Format code to pass cargo dev fmt
Aadi11z Dec 13, 2025
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11 changes: 11 additions & 0 deletions clippy_lints/src/loops/needless_range_loop.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -166,6 +166,13 @@ pub(super) fn check<'tcx>(
} else {
let repl = if starts_at_zero && take_is_empty {
format!("&{ref_mut}{indexed}")
} else if !take_is_empty {
// Adding condition for when 'take' is not empty Fixing `.take(n)` with slicing to preserve panic
// semantics
format!(
"{indexed}[..{}].{method}(){method_2}",
snippet(cx, end.unwrap().span, "..")
)
} else {
format!("{indexed}.{method}(){method_1}{method_2}")
};
Expand All @@ -181,6 +188,10 @@ pub(super) fn check<'tcx>(
vec![(pat.span, "<item>".to_string()), (span, repl)],
Applicability::HasPlaceholders,
);
diag.note(
"this suggestion preserves panic behavior, but the panic will occur \
before iteration if the upper bound exceeds the collection length",
);
},
);
}
Expand Down
23 changes: 17 additions & 6 deletions tests/ui/needless_range_loop.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 0..vec.len() {
| ^^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
= note: `-D clippy::needless-range-loop` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::needless_range_loop)]`
help: consider using an iterator
Expand All @@ -18,6 +19,7 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 0..vec.len() {
| ^^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..vec.len() {
Expand All @@ -30,6 +32,7 @@ error: the loop variable `j` is only used to index `STATIC`
LL | for j in 0..4 {
| ^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for j in 0..4 {
Expand All @@ -42,6 +45,7 @@ error: the loop variable `j` is only used to index `CONST`
LL | for j in 0..4 {
| ^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for j in 0..4 {
Expand All @@ -66,10 +70,11 @@ error: the loop variable `i` is only used to index `vec2`
LL | for i in 0..vec.len() {
| ^^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..vec.len() {
LL + for <item> in vec2.iter().take(vec.len()) {
LL + for <item> in vec2[..vec.len()].iter() {
|

error: the loop variable `i` is only used to index `vec`
Expand All @@ -78,6 +83,7 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 5..vec.len() {
| ^^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 5..vec.len() {
Expand All @@ -90,10 +96,11 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 0..MAX_LEN {
| ^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..MAX_LEN {
LL + for <item> in vec.iter().take(MAX_LEN) {
LL + for <item> in vec[..MAX_LEN].iter() {
|

error: the loop variable `i` is only used to index `vec`
Expand All @@ -102,10 +109,11 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 0..=MAX_LEN {
| ^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..=MAX_LEN {
LL + for <item> in vec.iter().take(MAX_LEN + 1) {
LL + for <item> in vec[..MAX_LEN].iter() {
|

error: the loop variable `i` is only used to index `vec`
Expand All @@ -114,10 +122,11 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 5..10 {
| ^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 5..10 {
LL + for <item> in vec.iter().take(10).skip(5) {
LL + for <item> in vec[..10].iter().skip(5) {
|

error: the loop variable `i` is only used to index `vec`
Expand All @@ -126,10 +135,11 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in 5..=10 {
| ^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 5..=10 {
LL + for <item> in vec.iter().take(10 + 1).skip(5) {
LL + for <item> in vec[..10].iter().skip(5) {
|

error: the loop variable `i` is used to index `vec`
Expand Down Expand Up @@ -186,10 +196,11 @@ error: the loop variable `i` is only used to index `a`
LL | for i in 0..MAX_LEN {
| ^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..MAX_LEN {
LL + for <item> in a.iter().take(MAX_LEN) {
LL + for <item> in a[..MAX_LEN].iter() {
|

error: aborting due to 16 previous errors
Expand Down
16 changes: 12 additions & 4 deletions tests/ui/needless_range_loop2.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,13 @@ error: the loop variable `i` is only used to index `ns`
LL | for i in 3..10 {
| ^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
= note: `-D clippy::needless-range-loop` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::needless_range_loop)]`
help: consider using an iterator
|
LL - for i in 3..10 {
LL + for <item> in ns.iter().take(10).skip(3) {
LL + for <item> in ns[..10].iter().skip(3) {
|

error: the loop variable `i` is only used to index `ms`
Expand All @@ -18,6 +19,7 @@ error: the loop variable `i` is only used to index `ms`
LL | for i in 0..ms.len() {
| ^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..ms.len() {
Expand All @@ -30,6 +32,7 @@ error: the loop variable `i` is only used to index `ms`
LL | for i in 0..ms.len() {
| ^^^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..ms.len() {
Expand All @@ -42,10 +45,11 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in x..x + 4 {
| ^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in x..x + 4 {
LL + for <item> in vec.iter_mut().skip(x).take(4) {
LL + for <item> in vec[..x + 4].iter_mut().take(4) {
|

error: the loop variable `i` is only used to index `vec`
Expand All @@ -54,10 +58,11 @@ error: the loop variable `i` is only used to index `vec`
LL | for i in x..=x + 4 {
| ^^^^^^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in x..=x + 4 {
LL + for <item> in vec.iter_mut().skip(x).take(4 + 1) {
LL + for <item> in vec[..x + 4].iter_mut().take(4 + 1) {
|

error: the loop variable `i` is only used to index `arr`
Expand All @@ -66,6 +71,7 @@ error: the loop variable `i` is only used to index `arr`
LL | for i in 0..3 {
| ^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..3 {
Expand All @@ -78,10 +84,11 @@ error: the loop variable `i` is only used to index `arr`
LL | for i in 0..2 {
| ^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 0..2 {
LL + for <item> in arr.iter().take(2) {
LL + for <item> in arr[..2].iter() {
|

error: the loop variable `i` is only used to index `arr`
Expand All @@ -90,6 +97,7 @@ error: the loop variable `i` is only used to index `arr`
LL | for i in 1..3 {
| ^^^^
|
= note: this suggestion preserves panic behavior, but the panic will occur before iteration if the upper bound exceeds the collection length
help: consider using an iterator
|
LL - for i in 1..3 {
Expand Down