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Always capture slice when pattern requires checking the length

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This commit is contained in:
clubby789 2023-05-21 23:06:06 +00:00
parent 9d871b0617
commit ace794c6d7
3 changed files with 209 additions and 91 deletions
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19
compiler/rustc_hir_typeck/src/expr_use_visitor.rs
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@ -438,12 +438,19 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
// to borrow discr.
needs_to_be_read = true;
}
PatKind::Or(_)
| PatKind::Box(_)
| PatKind::Slice(..)
| PatKind::Ref(..)
| PatKind::Wild => {
// If the PatKind is Or, Box, Slice or Ref, the decision is made later
PatKind::Slice(lhs, wild, rhs) => {
// We don't need to test the length if the pattern is `[..]`
if matches!((lhs, wild, rhs), (&[], Some(_), &[]))
// Arrays have a statically known size, so
// there is no need to read their length
|| discr_place.place.base_ty.is_array()
{
} else {
needs_to_be_read = true;
}
}
PatKind::Or(_) | PatKind::Box(_) | PatKind::Ref(..) | PatKind::Wild => {
// If the PatKind is Or, Box, or Ref, the decision is made later
// as these patterns contains subpatterns
// If the PatKind is Wild, the decision is made based on the other patterns being
// examined