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Auto merge of #81110 - LeSeulArtichaut:fix-unused-unsafe-label, r=RalfJung

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Fix `unused_unsafe` label with `unsafe_block_in_unsafe_fn

Previously, the following code:

```rust
#![feature(unsafe_block_in_unsafe_fn)]

unsafe fn foo() {
    unsafe { unsf() }
}

unsafe fn unsf() {}
```

Would give the following warning:

```
warning: unnecessary `unsafe` block
 --> src/lib.rs:4:5
  |
4 |     unsafe { unsf() }
  |     ^^^^^^ unnecessary `unsafe` block
  |
  = note: `#[warn(unused_unsafe)]` on by default
```
which doesn't point out that the block is in an `unsafe fn`.

Tracking issue: #71668
cc #79208
This commit is contained in:
bors 2021-01-19 08:59:37 +00:00
commit 47121d6d88
3 changed files with 73 additions and 49 deletions
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17
compiler/rustc_mir/src/transform/check_unsafety.rs
View file

@ -568,24 +568,23 @@ fn is_enclosed(
tcx: TyCtxt<'_>,
used_unsafe: &FxHashSet<hir::HirId>,
id: hir::HirId,
) -> Option<(String, hir::HirId)> {
unsafe_op_in_unsafe_fn_allowed: bool,
) -> Option<(&'static str, hir::HirId)> {
let parent_id = tcx.hir().get_parent_node(id);
if parent_id != id {
if used_unsafe.contains(&parent_id) {
Some(("block".to_string(), parent_id))
Some(("block", parent_id))
} else if let Some(Node::Item(&hir::Item {
kind: hir::ItemKind::Fn(ref sig, _, _), ..
})) = tcx.hir().find(parent_id)
{
if sig.header.unsafety == hir::Unsafety::Unsafe
&& !tcx.features().unsafe_block_in_unsafe_fn
{
Some(("fn".to_string(), parent_id))
if sig.header.unsafety == hir::Unsafety::Unsafe && unsafe_op_in_unsafe_fn_allowed {
Some(("fn", parent_id))
} else {
None
}
} else {
is_enclosed(tcx, used_unsafe, parent_id)
is_enclosed(tcx, used_unsafe, parent_id, unsafe_op_in_unsafe_fn_allowed)
}
} else {
None
@ -598,7 +597,9 @@ fn report_unused_unsafe(tcx: TyCtxt<'_>, used_unsafe: &FxHashSet<hir::HirId>, id
let msg = "unnecessary `unsafe` block";
let mut db = lint.build(msg);
db.span_label(span, msg);
if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
if let Some((kind, id)) =
is_enclosed(tcx, used_unsafe, id, unsafe_op_in_unsafe_fn_allowed(tcx, id))
{
db.span_label(
tcx.sess.source_map().guess_head_span(tcx.hir().span(id)),
format!("because it's nested under this `unsafe` {}", kind),