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Upgrade array_into_iter lint to include Deref-to-array types.

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This commit is contained in:
Mara Bos 2021-08-30 23:41:48 +02:00
parent 13edc17f65
commit 422ad3bec2
1 changed files with 29 additions and 23 deletions
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52
compiler/rustc_lint/src/array_into_iter.rs
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@ -74,39 +74,45 @@ impl<'tcx> LateLintPass<'tcx> for ArrayIntoIter {
_ => return, _ => return,
}; };
// As this is a method call expression, we have at least one // As this is a method call expression, we have at least one argument.
// argument.
let receiver_arg = &args[0]; let receiver_arg = &args[0];
let receiver_ty = cx.typeck_results().expr_ty(receiver_arg);
let adjustments = cx.typeck_results().expr_adjustments(receiver_arg);
// Peel all `Box<_>` layers. We have to special case `Box` here as let target = match adjustments.last() {
// `Box` is the only thing that values can be moved out of via Some(Adjustment { kind: Adjust::Borrow(_), target }) => target,
// method call. `Box::new([1]).into_iter()` should trigger this _ => return,
// lint. };
let mut recv_ty = cx.typeck_results().expr_ty(receiver_arg);
let mut num_box_derefs = 0; let types =
while recv_ty.is_box() { std::iter::once(receiver_ty).chain(adjustments.iter().map(|adj| adj.target));
num_box_derefs += 1;
recv_ty = recv_ty.boxed_ty(); let mut found_array = false;
for ty in types {
match ty.kind() {
// If we run into a &[T; N] or &[T] first, there's nothing to warn about.
// It'll resolve to the reference version.
ty::Ref(_, inner_ty, _) if inner_ty.is_array() => return,
ty::Ref(_, inner_ty, _) if matches!(inner_ty.kind(), ty::Slice(..)) => return,
// Found an actual array type without matching a &[T; N] first.
// This is the problematic case.
ty::Array(..) => {
found_array = true;
break;
}
_ => {}
}
} }
// Make sure we found an array after peeling the boxes. if !found_array {
if !matches!(recv_ty.kind(), ty::Array(..)) {
return; return;
} }
// Make sure that there is an autoref coercion at the expected
// position. The first `num_box_derefs` adjustments are the derefs
// of the box.
match cx.typeck_results().expr_adjustments(receiver_arg).get(num_box_derefs) {
Some(Adjustment { kind: Adjust::Borrow(_), .. }) => {}
_ => return,
}
// Emit lint diagnostic. // Emit lint diagnostic.
let target = match *cx.typeck_results().expr_ty_adjusted(receiver_arg).kind() { let target = match *target.kind() {
ty::Ref(_, inner_ty, _) if inner_ty.is_array() => "[T; N]", ty::Ref(_, inner_ty, _) if inner_ty.is_array() => "[T; N]",
ty::Ref(_, inner_ty, _) if matches!(inner_ty.kind(), ty::Slice(..)) => "[T]", ty::Ref(_, inner_ty, _) if matches!(inner_ty.kind(), ty::Slice(..)) => "[T]",
// We know the original first argument type is an array type, // We know the original first argument type is an array type,
// we know that the first adjustment was an autoref coercion // we know that the first adjustment was an autoref coercion
// and we know that `IntoIterator` is the trait involved. The // and we know that `IntoIterator` is the trait involved. The