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[missing_asserts_for_indexing]: accept length equality checks #11837

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Dec 1, 2023
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21 changes: 16 additions & 5 deletions clippy_lints/src/missing_asserts_for_indexing.rs
Original file line number Diff line number Diff line change
@@ -52,7 +52,7 @@ declare_clippy_lint! {
/// Use instead:
/// ```no_run
/// fn sum(v: &[u8]) -> u8 {
/// assert!(v.len() > 4);
/// assert!(v.len() > 3);
/// // no bounds checks
/// v[0] + v[1] + v[2] + v[3]
/// }
@@ -87,6 +87,9 @@ enum LengthComparison {
LengthLessThanOrEqualInt,
/// `5 <= v.len()`
IntLessThanOrEqualLength,
/// `5 == v.len()`
/// `v.len() == 5`
LengthEqualInt,
}

/// Extracts parts out of a length comparison expression.
@@ -114,6 +117,8 @@ fn len_comparison<'hir>(
(Rel::Lt, _, int_lit_pat!(right)) => Some((LengthComparison::LengthLessThanInt, *right as usize, left)),
(Rel::Le, int_lit_pat!(left), _) => Some((LengthComparison::IntLessThanOrEqualLength, *left as usize, right)),
(Rel::Le, _, int_lit_pat!(right)) => Some((LengthComparison::LengthLessThanOrEqualInt, *right as usize, left)),
(Rel::Eq, int_lit_pat!(left), _) => Some((LengthComparison::LengthEqualInt, *left as usize, right)),
(Rel::Eq, _, int_lit_pat!(right)) => Some((LengthComparison::LengthEqualInt, *right as usize, left)),
_ => None,
}
}
@@ -316,11 +321,11 @@ fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>
continue;
};

match entry {
match *entry {
IndexEntry::AssertWithIndex {
highest_index,
asserted_len,
indexes,
ref indexes,
comparison,
assert_span,
slice,
@@ -343,6 +348,12 @@ fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>
"assert!({}.len() > {highest_index})",
snippet(cx, slice.span, "..")
)),
// `highest_index` here is rather a length, so we need to add 1 to it
LengthComparison::LengthEqualInt if asserted_len < highest_index + 1 => Some(format!(
"assert!({}.len() == {})",
snippet(cx, slice.span, ".."),
highest_index + 1
)),
_ => None,
};

@@ -354,7 +365,7 @@ fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>
indexes,
|diag| {
diag.span_suggestion(
*assert_span,
assert_span,
"provide the highest index that is indexed with",
sugg,
Applicability::MachineApplicable,
@@ -364,7 +375,7 @@ fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>
}
},
IndexEntry::IndexWithoutAssert {
indexes,
ref indexes,
highest_index,
slice,
} if indexes.len() > 1 => {
15 changes: 15 additions & 0 deletions tests/ui/missing_asserts_for_indexing.fixed
Original file line number Diff line number Diff line change
@@ -118,4 +118,19 @@ fn index_different_slice_in_same_expr(v1: &[u8], v2: &[u8]) {
let _ = v1[0] + v2[1];
}

fn issue11835(v1: &[u8], v2: &[u8], v3: &[u8], v4: &[u8]) {
assert!(v1.len() == 3);
assert!(v2.len() == 4);
assert!(v3.len() == 3);
assert!(4 == v4.len());

let _ = v1[0] + v1[1] + v1[2];
//~^ ERROR: indexing into a slice multiple times with an `assert` that does not cover the
let _ = v2[0] + v2[1] + v2[2];

let _ = v3[0] + v3[1] + v3[2];
//~^ ERROR: indexing into a slice multiple times with an `assert` that does not cover the
let _ = v4[0] + v4[1] + v4[2];
}

fn main() {}
15 changes: 15 additions & 0 deletions tests/ui/missing_asserts_for_indexing.rs
Original file line number Diff line number Diff line change
@@ -118,4 +118,19 @@ fn index_different_slice_in_same_expr(v1: &[u8], v2: &[u8]) {
let _ = v1[0] + v2[1];
}

fn issue11835(v1: &[u8], v2: &[u8], v3: &[u8], v4: &[u8]) {
assert!(v1.len() == 2);
assert!(v2.len() == 4);
assert!(2 == v3.len());
assert!(4 == v4.len());

let _ = v1[0] + v1[1] + v1[2];
//~^ ERROR: indexing into a slice multiple times with an `assert` that does not cover the
let _ = v2[0] + v2[1] + v2[2];

let _ = v3[0] + v3[1] + v3[2];
//~^ ERROR: indexing into a slice multiple times with an `assert` that does not cover the
let _ = v4[0] + v4[1] + v4[2];
}

fn main() {}
54 changes: 53 additions & 1 deletion tests/ui/missing_asserts_for_indexing.stderr
Original file line number Diff line number Diff line change
@@ -249,5 +249,57 @@ LL | let _ = v1[0] + v1[12];
| ^^^^^^
= note: asserting the length before indexing will elide bounds checks

error: aborting due to 9 previous errors
error: indexing into a slice multiple times with an `assert` that does not cover the highest index
--> $DIR/missing_asserts_for_indexing.rs:127:13
|
LL | assert!(v1.len() == 2);
| ---------------------- help: provide the highest index that is indexed with: `assert!(v1.len() == 3)`
...
LL | let _ = v1[0] + v1[1] + v1[2];
| ^^^^^^^^^^^^^^^^^^^^^
|
note: slice indexed here
--> $DIR/missing_asserts_for_indexing.rs:127:13
|
LL | let _ = v1[0] + v1[1] + v1[2];
| ^^^^^
note: slice indexed here
--> $DIR/missing_asserts_for_indexing.rs:127:21
|
LL | let _ = v1[0] + v1[1] + v1[2];
| ^^^^^
note: slice indexed here
--> $DIR/missing_asserts_for_indexing.rs:127:29
|
LL | let _ = v1[0] + v1[1] + v1[2];
| ^^^^^
= note: asserting the length before indexing will elide bounds checks

error: indexing into a slice multiple times with an `assert` that does not cover the highest index
--> $DIR/missing_asserts_for_indexing.rs:131:13
|
LL | assert!(2 == v3.len());
| ---------------------- help: provide the highest index that is indexed with: `assert!(v3.len() == 3)`
...
LL | let _ = v3[0] + v3[1] + v3[2];
| ^^^^^^^^^^^^^^^^^^^^^
|
note: slice indexed here
--> $DIR/missing_asserts_for_indexing.rs:131:13
|
LL | let _ = v3[0] + v3[1] + v3[2];
| ^^^^^
note: slice indexed here
--> $DIR/missing_asserts_for_indexing.rs:131:21
|
LL | let _ = v3[0] + v3[1] + v3[2];
| ^^^^^
note: slice indexed here
--> $DIR/missing_asserts_for_indexing.rs:131:29
|
LL | let _ = v3[0] + v3[1] + v3[2];
| ^^^^^
= note: asserting the length before indexing will elide bounds checks

error: aborting due to 11 previous errors