Removing lint for constant usize array indexing
This commit removes the logic in this PR that linted out-of-bounds constant `usize` indexing on arrays. That case is already handled by rustc's `const_err` lint. Beyond removing the linting logic, the test file and its associated stderr were updated to verify that const `usize` indexing operations on arrays are no longer handled by this `indexing_slicing` lint.
This commit is contained in:
Shea Newton
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commit
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@ -34,9 +34,9 @@ declare_clippy_lint! {
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"out of bounds constant indexing"
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}
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/// **What it does:** Checks for usage of indexing or slicing. Does not report
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/// on arrays if we can tell that the indexing or slicing operations are in
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/// bounds.
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/// **What it does:** Checks for usage of indexing or slicing. Arrays are special cased, this lint
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/// does report on arrays if we can tell that slicing operations are in bounds and does not
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/// lint on constant `usize` indexing on arrays because that is handled by rustc's `const_err` lint.
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///
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/// **Why is this bad?** Indexing and slicing can panic at runtime and there are
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/// safe alternatives.
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@ -64,13 +64,11 @@ declare_clippy_lint! {
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/// let y = [0, 1, 2, 3];
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///
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/// // Bad
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/// y[10];
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/// &y[10..100];
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/// &y[10..];
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/// &y[..100];
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///
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/// // Good
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/// y[2];
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/// &y[2..];
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/// &y[..2];
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/// &y[0..3];
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@ -132,20 +130,10 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IndexingSlicing {
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);
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} else {
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// Catchall non-range index, i.e. [n] or [n << m]
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if let ty::TyArray(_, s) = ty.sty {
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let size: u128 = s.assert_usize(cx.tcx).unwrap().into();
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if let ty::TyArray(..) = ty.sty {
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// Index is a constant uint.
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if let Some((Constant::Int(const_index), _)) = constant(cx, cx.tables, index) {
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if size <= const_index {
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utils::span_lint(
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cx,
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OUT_OF_BOUNDS_INDEXING,
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expr.span,
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"const index is out of bounds",
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);
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}
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// Else index is in bounds, ok.
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if let Some(..) = constant(cx, cx.tables, index) {
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// Let rustc's `const_err` lint handle constant `usize` indexing on arrays.
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return;
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}
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}
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@ -13,8 +13,8 @@ fn main() {
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&x[..index];
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&x[index_from..index_to];
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&x[index_from..][..index_to]; // Two lint reports, one for [index_from..] and another for [..index_to].
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x[4];
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x[1 << 3];
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x[4]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays.
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x[1 << 3]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays.
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&x[..=4];
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&x[1..5];
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&x[5..][..10]; // Two lint reports, one for [5..] and another for [..10].
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@ -44,7 +44,7 @@ fn main() {
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&y[..]; // Ok, should not produce stderr.
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let empty: [i8; 0] = [];
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empty[0];
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empty[0]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays.
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&empty[1..5];
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&empty[0..=4];
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&empty[..=4];
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@ -75,7 +75,7 @@ fn main() {
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const N: usize = 15; // Out of bounds
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const M: usize = 3; // In bounds
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x[N];
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x[N]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays.
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x[M]; // Ok, should not produce stderr.
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v[N];
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v[M];
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@ -47,25 +47,13 @@ error: slicing may panic.
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= help: Consider using `.get(n..)` or .get_mut(n..)` instead
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error: const index is out of bounds
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--> $DIR/indexing_slicing.rs:16:5
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16 | x[4];
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| ^^^^
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= note: `-D out-of-bounds-indexing` implied by `-D warnings`
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error: const index is out of bounds
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--> $DIR/indexing_slicing.rs:17:5
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17 | x[1 << 3];
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| ^^^^^^^^^
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error: range is out of bounds
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--> $DIR/indexing_slicing.rs:18:6
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18 | &x[..=4];
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| ^^^^^^^
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= note: `-D out-of-bounds-indexing` implied by `-D warnings`
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error: range is out of bounds
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--> $DIR/indexing_slicing.rs:19:6
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@ -159,12 +147,6 @@ error: slicing may panic.
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= help: Consider using `.get(..n)`or `.get_mut(..n)` instead
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error: const index is out of bounds
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--> $DIR/indexing_slicing.rs:47:5
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47 | empty[0];
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| ^^^^^^^^
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error: range is out of bounds
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--> $DIR/indexing_slicing.rs:48:6
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@ -269,12 +251,6 @@ error: slicing may panic.
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= help: Consider using `.get(..n)`or `.get_mut(..n)` instead
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error: const index is out of bounds
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--> $DIR/indexing_slicing.rs:78:5
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78 | x[N];
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| ^^^^
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error: indexing may panic.
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--> $DIR/indexing_slicing.rs:80:5
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@ -291,5 +267,5 @@ error: indexing may panic.
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= help: Consider using `.get(n)` or `.get_mut(n)` instead
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error: aborting due to 41 previous errors
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error: aborting due to 37 previous errors
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