Change `span_suggestion` (and variants) to take `impl ToString` rather
than `String` for the suggested code, as this simplifies the
requirements on the diagnostic derive.
Signed-off-by: David Wood <david.wood@huawei.com>
This lets us clone just the parts within a `TokenTree` that need
cloning, rather than the entire thing. This is a surprisingly large
performance win, up to 4% on `async-std-1.10.0`.
This makes `CloseDelim` handling more like `OpenDelim` handling, which
produces `OpenDelim` and pushes the stack at the same time. It requires
some adjustment to `parse_token_tree` now that we don't remain within
the frame after getting the `CloseDelim`.
A Google search of the error message fails to return any relevant
resuts, suggesting this has never occurred in practice. And removeing it
reduces instruction counts by up to 2% on some benchmarks.
The loop is there to handle a `NoDelim` open/close token. This commit
changes `TokenCursor::inlined_next` so it never returns such a token.
This is a performance win because the conditional test in `bump()` is
removed.
If the parser needs changing in the future to handle `NoDelim` tokens,
then `inlined_next()` can easily be changed to return them.
The `DelimToken` here is `NoDelim`, which means the returned delim
tokens will just be ignored by `Parser::bump()`. This commit changes
things so the delim tokens won't be returned.
This will facilitate the change in the next commit.
`boolean` arguments aren't great, but the function is only used in three
places within this one file.
In particular, avoid wrapping a token within `TokenTree::Token` and then
immediately matching it and returning the token within. Just return the
token immediately.
Parse inner attributes on inline const block
According to https://github.com/rust-lang/rust/pull/84414#issuecomment-826150936, inner attributes are intended to be supported *"in all containers for statements (or some subset of statements)"*.
This PR adds inner attribute parsing and pretty-printing for inline const blocks (https://github.com/rust-lang/rust/issues/76001), which contain statements just like an unsafe block or a loop body.
```rust
let _ = const {
#![allow(...)]
let x = ();
x
};
```
By heap allocating the argument within `NtPath`, `NtVis`, and `NtStmt`.
This slightly reduces cumulative and peak allocation amounts, most
notably on `deep-vector`.
`MultiSpan` contains labels, which are more complicated with the
introduction of diagnostic translation and will use types from
`rustc_errors` - however, `rustc_errors` depends on `rustc_span` so
`rustc_span` cannot use types like `DiagnosticMessage` without
dependency cycles. Introduce a new `rustc_error_messages` crate that can
contain `DiagnosticMessage` and `MultiSpan`.
Signed-off-by: David Wood <david.wood@huawei.com>
It's only needed for macro expansion, not as a general element in the
AST. This commit removes it, adds `NtOrTt` for the parser and macro
expansion cases, and renames the variants in `NamedMatch` to better
match the new type.
The call site within `Parser::bump` is hot.
Also add an inline annotation to `Parser::next_tok`. It was already
being inlined by the compiler; this just makes sure that continues.
* Recover from invalid `'label: ` before block.
* Make suggestion to enclose statements in a block multipart.
* Point at `match`, `while`, `loop` and `unsafe` keywords when failing
to parse their expression.
* Do not suggest `{ ; }`.
* Do not suggest `|` when very unlikely to be what was wanted (in `let`
statements).
This commit focuses on emitting clean errors for the following syntax
error:
```
Some(42).map(|a|
dbg!(a);
a
);
```
Previous implementation tried to recover after parsing the closure body
(the `dbg` expression) by replacing the next `;` with a `,`, which made
the next expression belong to the next function argument. As such, the
following errors were emitted (among others):
- the semicolon token was not expected,
- a is not in scope,
- Option::map is supposed to take one argument, not two.
This commit allows us to gracefully handle this situation by adding
giving the parser the ability to remember when it has just parsed a
closure body inside a function call. When this happens, we can treat the
unexpected `;` specifically and try to parse as much statements as
possible in order to eat the whole block. When we can't parse statements
anymore, we generate a clean error indicating that the braces are
missing, and return an ExprKind::Err.
Point at unclosed delimiters as part of the primary MultiSpan
Both the place where the parser encounters a needed closed delimiter and
the unclosed opening delimiter are important, so they should get the
same level of highlighting in the output.
_Context: https://twitter.com/mwk4/status/1430631546432675840_
Both the place where the parser encounters a needed closed delimiter and
the unclosed opening delimiter are important, so they should get the
same level of highlighting in the output.
# Stabilization report
## Summary
This stabilizes using macro expansion in key-value attributes, like so:
```rust
#[doc = include_str!("my_doc.md")]
struct S;
#[path = concat!(env!("OUT_DIR"), "/generated.rs")]
mod m;
```
See the changes to the reference for details on what macros are allowed;
see Petrochenkov's excellent blog post [on internals](https://internals.rust-lang.org/t/macro-expansion-points-in-attributes/11455)
for alternatives that were considered and rejected ("why accept no more
and no less?")
This has been available on nightly since 1.50 with no major issues.
## Notes
### Accepted syntax
The parser accepts arbitrary Rust expressions in this position, but any expression other than a macro invocation will ultimately lead to an error because it is not expected by the built-in expression forms (e.g., `#[doc]`). Note that decorators and the like may be able to observe other expression forms.
### Expansion ordering
Expansion of macro expressions in "inert" attributes occurs after decorators have executed, analogously to macro expressions appearing in the function body or other parts of decorator input.
There is currently no way for decorators to accept macros in key-value position if macro expansion must be performed before the decorator executes (if the macro can simply be copied into the output for later expansion, that can work).
## Test cases
- https://github.com/rust-lang/rust/blob/master/src/test/ui/attributes/key-value-expansion-on-mac.rs
- https://github.com/rust-lang/rust/blob/master/src/test/rustdoc/external-doc.rs
The feature has also been dogfooded extensively in the compiler and
standard library:
- https://github.com/rust-lang/rust/pull/83329
- https://github.com/rust-lang/rust/pull/83230
- https://github.com/rust-lang/rust/pull/82641
- https://github.com/rust-lang/rust/pull/80534
## Implementation history
- Initial proposal: https://github.com/rust-lang/rust/issues/55414#issuecomment-554005412
- Experiment to see how much code it would break: https://github.com/rust-lang/rust/pull/67121
- Preliminary work to restrict expansion that would conflict with this
feature: https://github.com/rust-lang/rust/pull/77271
- Initial implementation: https://github.com/rust-lang/rust/pull/78837
- Fix for an ICE: https://github.com/rust-lang/rust/pull/80563
## Unresolved Questions
~~https://github.com/rust-lang/rust/pull/83366#issuecomment-805180738 listed some concerns, but they have been resolved as of this final report.~~
## Additional Information
There are two workarounds that have a similar effect for `#[doc]`
attributes on nightly. One is to emulate this behavior by using a limited version of this feature that was stabilized for historical reasons:
```rust
macro_rules! forward_inner_docs {
($e:expr => $i:item) => {
#[doc = $e]
$i
};
}
forward_inner_docs!(include_str!("lib.rs") => struct S {});
```
This also works for other attributes (like `#[path = concat!(...)]`).
The other is to use `doc(include)`:
```rust
#![feature(external_doc)]
#[doc(include = "lib.rs")]
struct S {}
```
The first works, but is non-trivial for people to discover, and
difficult to read and maintain. The second is a strange special-case for
a particular use of the macro. This generalizes it to work for any use
case, not just including files.
I plan to remove `doc(include)` when this is stabilized. The
`forward_inner_docs` workaround will still compile without warnings, but
I expect it to be used less once it's no longer necessary.
