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Fix inconsistencies in handling of inert attributes on statements

When the 'early' and 'late' visitors visit an attribute target, they
activate any lint attributes (e.g. `#[allow]`) that apply to it.
This can affect warnings emitted on sibiling attributes. For example,
the following code does not produce an `unused_attributes` for
`#[inline]`, since the sibiling `#[allow(unused_attributes)]` suppressed
the warning.

```rust
trait Foo {
    #[allow(unused_attributes)] #[inline] fn first();
    #[inline] #[allow(unused_attributes)] fn second();
}
```

However, we do not do this for statements - instead, the lint attributes
only become active when we visit the struct nested inside `StmtKind`
(e.g. `Item`).

Currently, this is difficult to observe due to another issue - the
`HasAttrs` impl for `StmtKind` ignores attributes for `StmtKind::Item`.
As a result, the `unused_doc_comments` lint will never see attributes on
item statements.

This commit makes two interrelated fixes to the handling of inert
(non-proc-macro) attributes on statements:

* The `HasAttr` impl for `StmtKind` now returns attributes for
  `StmtKind::Item`, treating it just like every other `StmtKind`
  variant. The only place relying on the old behavior was macro
  which has been updated to explicitly ignore attributes on item
  statements. This allows the `unused_doc_comments` lint to fire for
  item statements.
* The `early` and `late` lint visitors now activate lint attributes when
  invoking the callback for `Stmt`. This ensures that a lint
  attribute (e.g. `#[allow(unused_doc_comments)]`) can be applied to
  sibiling attributes on an item statement.

For now, the `unused_doc_comments` lint is explicitly disabled on item
statements, which preserves the current behavior. The exact locatiosn
where this lint should fire are being discussed in PR #78306
This commit is contained in:
Aaron Hill 2020-10-23 18:17:00 -04:00
parent 07a63e6d1f
commit ac384ac2db
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12 changed files with 94 additions and 22 deletions

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@ -816,7 +816,7 @@ impl<'hir> Map<'hir> {
Some(Node::Variant(ref v)) => Some(&v.attrs[..]),
Some(Node::Field(ref f)) => Some(&f.attrs[..]),
Some(Node::Expr(ref e)) => Some(&*e.attrs),
Some(Node::Stmt(ref s)) => Some(s.kind.attrs()),
Some(Node::Stmt(ref s)) => Some(s.kind.attrs(|id| self.item(id.id))),
Some(Node::Arm(ref a)) => Some(&*a.attrs),
Some(Node::GenericParam(param)) => Some(&param.attrs[..]),
// Unit/tuple structs/variants take the attributes straight from