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
transmute: use diagnostic item
closes#66075, we now have no remaining uses of `match_def_path` in the compiler while some uses still remain in `clippy`.
cc @RalfJung
Validate constants during `const_eval_raw`
This PR implements the groundwork for https://github.com/rust-lang/rust/issues/72396
* constants are now validated during `const_eval_raw`
* to prevent cycle errors, we do not validate references to statics anymore beyond the fact that they are not dangling
* the `const_eval` query ICEs if used on `static` items
* as a side effect promoteds are now evaluated to `ConstValue::Scalar` again (since they are just a reference to the actual promoted allocation in most cases).
lint/ty: move fns to avoid abstraction violation
This PR moves `transparent_newtype_field` and `is_zst` to `LateContext` where they are used, rather than being on the `VariantDef` and `TyS` types, hopefully addressing @eddyb's concern [from this comment](https://github.com/rust-lang/rust/pull/74340#discussion_r456534910).
As a side effect, we now represent most promoteds as `ConstValue::Scalar` again. This is useful because all implict promoteds are just references anyway and most explicit promoteds are numeric arguments to `asm!` or SIMD instructions.
Auto-generate lint documentation.
This adds a tool which will generate the lint documentation in the rustc book automatically. This is motivated by keeping the documentation up-to-date, and consistently formatted. It also ensures the examples are correct and that they actually generate the expected lint. The lint groups table is also auto-generated. See https://github.com/rust-lang/compiler-team/issues/349 for the original proposal.
An outline of how this works:
- The `declare_lint!` macro now accepts a doc comment where the documentation is written. This is inspired by how clippy works.
- A new tool `src/tools/lint-docs` scrapes the documentation and adds it to the rustc book during the build.
- It runs each example and verifies its output and embeds the output in the book.
- It does a few formatting checks.
- It verifies that every lint is documented.
- Groups are collected from `rustc -W help`.
I updated the documentation for all the missing lints. I have also added an "Explanation" section to each lint providing a reason for the lint and suggestions on how to resolve it.
This can lead towards a future enhancement of possibly showing these docs via the `--explain` flag to make them easily accessible and discoverable.
This commit moves `transparent_newtype_field` and `is_zst` to
`LateContext` where they are used, rather than being on the `VariantDef`
and `TyS` types.
Signed-off-by: David Wood <david@davidtw.co>
