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_
Path remapping: Make behavior of diagnostics output dependent on presence of --remap-path-prefix.
This PR fixes a regression (#87745) with `--remap-path-prefix` where the flag stopped causing diagnostic messages to be remapped as well. The regression was introduced in https://github.com/rust-lang/rust/pull/83813 where we erroneously assumed that remapping of diagnostic messages was not desired anymore (because #70642 partially undid that functionality with nobody objecting).
The issue is fixed by making `--remap-path-prefix` remap diagnostic messages again, including for paths that have been remapped in upstream crates (e.g. the standard library). This means that "sysroot-localization" (implemented in #70642) is also disabled if `rustc` is invoked with `--remap-path-prefix`. The assumption is that once someone starts explicitly remapping paths they also don't want paths to their local Rust installation in their build output.
In the future we might want to give more fine-grained control over this behavior via compiler flags (see https://github.com/rust-lang/rfcs/pull/3127 for a related RFC). For now this PR is intended as a regression fix.
This PR is an alternative to https://github.com/rust-lang/rust/pull/88191, which makes diagnostic messages be remapped unconditionally. That approach, however, would effectively revert #70642.
Fixes https://github.com/rust-lang/rust/issues/87745.
cc `@cbeuw`
r? `@ghost`
Introduce `let...else`
Tracking issue: #87335
The trickiest part for me was enforcing the diverging else block with clear diagnostics. Perhaps the obvious solution is to expand to `let _: ! = ..`, but I decided against this because, when a "mismatched type" error is found in typeck, there is no way to trace where in the HIR the expected type originated, AFAICT. In order to pass down this information, I believe we should introduce `Expectation::LetElseNever(HirId)` or maybe add `HirId` to `Expectation::HasType`, but I left that as a future enhancement. For now, I simply assert that the block is `!` with a custom `ObligationCauseCode`, and I think this is clear enough, at least to start. The downside here is that the error points at the entire block rather than the specific expression with the wrong type. I left a todo to this effect.
Overall, I believe this PR is feature-complete with regard to the RFC.
Old error output:
3 | let _: usize = $f;
| ----- ^ expected `usize`, found struct `Baz`
| |
| expected due to this
New error output:
3 | let _: usize = $f;
| ----- ^^ expected `usize`, found struct `Baz`
| |
| expected due to this
Old error output:
= note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
help: wrap this expression in parentheses
|
4 | break '_l $f(;)
| ^ ^
New error output:
= note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
help: wrap this expression in parentheses
|
4 | break '_l ($f);
| ^ ^
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.
- [x] Removed `?const` and change uses of `?const`
- [x] Added `~const` to the AST. It is gated behind const_trait_impl.
- [x] Validate `~const` in ast_validation.
- [ ] Add enum `BoundConstness` to the HIR. (With variants `NotConst` and
`ConstIfConst` allowing future extensions)
- [ ] Adjust trait selection and pre-existing code to use `BoundConstness`.
- [ ] Optional steps (*for this PR, obviously*)
- [ ] Fix#88155
- [ ] Do something with constness bounds in chalk
Remove `Session.used_attrs` and move logic to `CheckAttrVisitor`
Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).
`Session.check_name` is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
`Attribute.has_name`
Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in `CheckAttrVisitor` for a particular attribute.
We no longer emit unused attribute warnings for the `#[rustc_dummy]`
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.
With this commit, a large source of global untracked state is removed.
Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).
`Session.check_name` is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
`Attribute.has_name`
Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in `CheckAttrVisitor` for a particular attribute.
We no longer emit unused attribute warnings for the `#[rustc_dummy]`
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.
With this commit, a large source of global untracked state is removed.
Allow labeled loops as value expressions for `break`
Fixes#86948. This is currently allowed:
```rust
return 'label: loop { break 'label 42; };
break ('label: loop { break 'label 42; });
break 1 + 'label: loop { break 'label 42; };
break 'outer 'inner: loop { break 'inner 42; };
```
But not this:
```rust
break 'label: loop { break 'label 42; };
```
I have fixed this, so that the above now parses as an unlabeled break with a labeled loop as its value expression.
Fix a parser ICE on invalid `fn` body
Fixes#87635
A better fix would add a check for `fn` body on `expected_one_of_not_found` but I haven't come up with a graceful way. Any idea?
r? ```@oli-obk``` ```@estebank```
After this commit, `unsafe async fn ...` now suggests the `async unsafe` fix
instead of misunderstanding the issue.
This is not perfect for repeated keywords (`const async const`) and for
keywords that are misplaced after `extern "some abi"` because of the way
`check_fn_font_matter` works, but changing it breaks so many tests and
diagnostics it has been judged too high a cost for this PR.
rfc3052 followup: Remove authors field from Cargo manifests
Since RFC 3052 soft deprecated the authors field, hiding it from
crates.io, docs.rs, and making Cargo not add it by default, and it is
not generally up to date/useful information for contributors, we may as well
remove it from crates in this repo.
Suggest `br` if the unknown string prefix `rb` is found
Currently, for the following code:
```rust
fn main() {
rb"abc";
}
```
we issue the following suggestion:
```
help: consider inserting whitespace here
|
2 | rb "abc";
| --
```
With my changes (only in edition 2021, where unknown prefixes became an error), I get:
```
help: use `br` for a raw byte string
|
2 | br"abc";
| ^^
```
Since RFC 3052 soft deprecated the authors field anyway, hiding it from
crates.io, docs.rs, and making Cargo not add it by default, and it is
not generally up to date/useful information, we should remove it from
crates in this repo.
Add diagnostics for mistyped inclusive range
Inclusive ranges are correctly typed as `..=`. However, it's quite easy to think of it as being like `==`, and type `..==` instead. This PR adds helpful diagnostics for this case.
Resolves#86395 (there are some other cases there, but I think those should probably have separate issues).
r? `@estebank`
Stabilize "RangeFrom" patterns in 1.55
Implements a partial stabilization of #67264 and #37854.
Reference PR: https://github.com/rust-lang/reference/pull/900
# Stabilization Report
This stabilizes the `X..` pattern, shown as such, offering an exhaustive match for unsigned integers:
```rust
match x as u32 {
0 => println!("zero!"),
1.. => println!("positive number!"),
}
```
Currently if a Rust author wants to write such a match on an integer, they must use `1..={integer}::MAX` . By allowing a "RangeFrom" style pattern, this simplifies the match to not require the MAX path and thus not require specifically repeating the type inside the match, allowing for easier refactoring. This is particularly useful for instances like the above case, where different behavior on "0" vs. "1 or any positive number" is desired, and the actual MAX is unimportant.
Notably, this excepts slice patterns which include half-open ranges from stabilization, as the wisdom of those is still subject to some debate.
## Practical Applications
Instances of this specific usage have appeared in the compiler:
16143d1067/compiler/rustc_middle/src/ty/inhabitedness/mod.rs (L219)673d0db5e3/compiler/rustc_ty_utils/src/ty.rs (L524)
And I have noticed there are also a handful of "in the wild" users who have deployed it to similar effect, especially in the case of rejecting any value of a certain number or greater. It simply makes it much more ergonomic to write an irrefutable match, as done in Katholieke Universiteit Leuven's [SCALE and MAMBA project](05e5db00d5/WebAssembly/scale_std/src/fixed_point.rs (L685-L695)).
## Tests
There were already many tests in [src/test/ui/half-open-range/patterns](90a2e5e3fe/src/test/ui/half-open-range-patterns), as well as [generic pattern tests that test the `exclusive_range_pattern` feature](673d0db5e3/src/test/ui/pattern/usefulness/integer-ranges/reachability.rs), many dating back to the feature's introduction and remaining standing to this day. However, this stabilization comes with some additional tests to explore the... sometimes interesting behavior of interactions with other patterns. e.g. There is, at least, a mild diagnostic improvement in some edge cases, because before now, the pattern `0..=(5+1)` encounters the `half_open_range_patterns` feature gate and can thus emit the request to enable the feature flag, while also emitting the "inclusive range with no end" diagnostic. There is no intent to allow an `X..=` pattern that I am aware of, so removing the flag request is a strict improvement. The arrival of the `J | K` "or" pattern also enables some odd formations.
Some of the behavior tested for here is derived from experiments in this [Playground](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=58777b3c715c85165ac4a70d93efeefc) example, linked at https://github.com/rust-lang/rust/issues/67264#issuecomment-812770692, which may be useful to reference to observe the current behavior more closely.
In addition tests constituting an explanation of the "slicing range patterns" syntax issue are included in this PR.
## Desiderata
The exclusive range patterns and half-open range patterns are fairly strongly requested by many authors, as they make some patterns much more natural to write, but there is disagreement regarding the "closed" exclusive range pattern or the "RangeTo" pattern, especially where it creates "off by one" gaps in the presence of a "catch-all" wildcard case. Also, there are obviously no range analyses in place that will force diagnostics for e.g. highly overlapping matches. I believe these should be warned on, ideally, and I think it would be reasonable to consider such a blocker to stabilizing this feature, but there is no technical issue with the feature as-is from the purely syntactic perspective as such overlapping or missed matches can already be generated today with such a catch-all case. And part of the "point" of the feature, at least from my view, is to make it easier to omit wildcard matches: a pattern with such an "open" match produces an irrefutable match and does not need the wild card case, making it easier to benefit from exhaustiveness checking.
## History
- Implemented:
- Partially via exclusive ranges: https://github.com/rust-lang/rust/pull/35712
- Fully with half-open ranges: https://github.com/rust-lang/rust/pull/67258
- Unresolved Questions:
- The precedence concerns of https://github.com/rust-lang/rust/pull/48501 were considered as likely requiring adjustment but probably wanting a uniform consistent change across all pattern styles, given https://github.com/rust-lang/rust/issues/67264#issuecomment-720711656, but it is still unknown what changes might be desired
- How we want to handle slice patterns in ranges seems to be an open question still, as witnessed in the discussion of this PR!
I checked but I couldn't actually find an RFC for this, and given "approved provisionally by lang team without an RFC", I believe this might require an RFC before it can land? Unsure of procedure here, on account of this being stabilizing a subset of a feature of syntax.
r? `@scottmcm`
Fix ICE when misplaced visibility cannot be properly parsed
Fixes#86895
The issue was that a failure to parse the visibility was causing the original error to be dropped before being emitted.
The resulting error isn't quite as nice as when the visibility is parsed properly, but I'm not sure which error to prioritize here. Displaying both errors might be too confusing.
r? ```@estebank```
Recover from `&dyn mut ...` parse errors
Consider this example:
```rust
fn main() {
let r: &dyn mut Trait;
}
```
This currently leads to:
```
error: expected one of `!`, `(`, `;`, `=`, `?`, `for`, lifetime, or path, found keyword `mut`
--> src/main.rs:2:17
|
2 | let r: &dyn mut Trait;
| ^^^ expected one of 8 possible tokens
error: aborting due to previous error
```
However, especially for beginners, I think it is easy to get `&dyn mut` and `&mut dyn` confused. With my changes, I get a help message, and the parser even recovers:
```
error: `mut` must precede `dyn`
--> test.rs:2:12
|
2 | let r: &dyn mut Trait;
| ^^^^^^^^ help: place `mut` before `dyn`: `&mut dyn`
error[E0405]: cannot find trait `Trait` in this scope
--> test.rs:2:21
|
2 | let r: &dyn mut Trait;
| ^^^^^ not found in this scope
error: aborting due to 2 previous errors
```
Remove unused dependencies from compiler crates
Various compiler crates have dependencies that they don't appear to use. I used some scripting to detect such dependencies, filtered them based on some manual review, and removed those that do indeed appear to be entirely unused.
Use HTTPS links where possible
While looking at #86583, I wondered how many other (insecure) HTTP links were in `rustc`. This changes most other `http` links to `https`. While most of the links are in comments or documentation, there are a few other HTTP links that are used by CI that are changed to HTTPS.
Notes:
- I didn't change any to or in licences
- Some links don't support HTTPS :(
- Some `http` links were dead, in those cases I upgraded them to their new places (all of which used HTTPS)
Re-add support for parsing (and pretty-printing) inner-attributes in match body
Re-add support for parsing (and pretty-printing) inner-attributes within body of a `match`.
In other words, we can do `match EXPR { #![inner_attr] ARM_1 ARM_2 ... }` again.
I believe this unbreaks the only four crates that crater flagged as broken by PR #83312.
(I am putting this up so that the lang-team can check it out and decide whether it changes their mind about what to do regarding PR #83312.)
Fix two ICEs in the parser
This pull request fixes#84104 and fixes#84148. The latter is caused by an invalid `assert_ne!()` in the parser, which I have simply removed because the error is then caught in another part of the parser.
#84104 is somewhat more subtle and has to do with a suggestion to remove extraneous `<` characters; for instance:
```rust
fn main() {
foo::<Ty<<<i32>();
}
```
currently leads to
```
error: unmatched angle brackets
--> unmatched-langle.rs:2:10
|
2 | foo::<Ty<<<i32>();
| ^^^ help: remove extra angle brackets
```
which is obviously wrong and stems from the fact that the code for issuing the above suggestion does not consider the possibility that there might be other tokens in between the opening angle brackets. In #84104, this has led to a span being generated that ends in the middle of a multi-byte character (because the code issuing the suggestion thought that it was only skipping over `<`, which are single-byte), causing an ICE.
Remove unused feature gates
The first commit removes a usage of a feature gate, but I don't expect it to be controversial as the feature gate was only used to workaround a limitation of rust in the past. (closures never being `Clone`)
The second commit uses `#[allow_internal_unstable]` to avoid leaking the `trusted_step` feature gate usage from inside the index newtype macro. It didn't work for the `min_specialization` feature gate though.
The third commit removes (almost) all feature gates from the compiler that weren't used anyway.
# 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.
Recover from invalid `struct` item syntax
Parse unsupported "default field const values":
```rust
struct S {
field: Type = const_val,
}
```
Recover from small `:` typo and provide suggestion:
```rust
struct S {
field; Type,
field2= Type,
}
```
Fix `--remap-path-prefix` not correctly remapping `rust-src` component paths and unify handling of path mapping with virtualized paths
This PR fixes#73167 ("Binaries end up containing path to the rust-src component despite `--remap-path-prefix`") by preventing real local filesystem paths from reaching compilation output if the path is supposed to be remapped.
`RealFileName::Named` introduced in #72767 is now renamed as `LocalPath`, because this variant wraps a (most likely) valid local filesystem path.
`RealFileName::Devirtualized` is renamed as `Remapped` to be used for remapped path from a real path via `--remap-path-prefix` argument, as well as real path inferred from a virtualized (during compiler bootstrapping) `/rustc/...` path. The `local_path` field is now an `Option<PathBuf>`, as it will be set to `None` before serialisation, so it never reaches any build output. Attempting to serialise a non-`None` `local_path` will cause an assertion faliure.
When a path is remapped, a `RealFileName::Remapped` variant is created. The original path is preserved in `local_path` field and the remapped path is saved in `virtual_name` field. Previously, the `local_path` is directly modified which goes against its purpose of "suitable for reading from the file system on the local host".
`rustc_span::SourceFile`'s fields `unmapped_path` (introduced by #44940) and `name_was_remapped` (introduced by #41508 when `--remap-path-prefix` feature originally added) are removed, as these two pieces of information can be inferred from the `name` field: if it's anything other than a `FileName::Real(_)`, or if it is a `FileName::Real(RealFileName::LocalPath(_))`, then clearly `name_was_remapped` would've been false and `unmapped_path` would've been `None`. If it is a `FileName::Real(RealFileName::Remapped{local_path, virtual_name})`, then `name_was_remapped` would've been true and `unmapped_path` would've been `Some(local_path)`.
cc `@eddyb` who implemented `/rustc/...` path devirtualisation
Parse unsupported "default field const values":
```rust
struct S {
field: Type = const_val,
}
```
Recover from small `:` typo and provide suggestion:
```rust
struct S {
field; Type,
field2= Type,
}
```
In other words, we can do `match EXPR { #![inner_attr] ARM_1 ARM_2 ... }` again.
I believe this unbreaks the only four crates that crater flagged as broken by PR 83312.
(I am putting this up so that the lang-team can check it out and decide whether
it changes their mind about what to do regarding PR 83312.)
Improve diagnostics for functions in `struct` definitions
Tries to implement #76421.
This is probably going to need unit tests, but I wanted to hear from review all the cases tests should cover.
I'd like to follow up with the "mechanically applicable suggestion here that adds an impl block" step, but I'd need guidance. My idea for now would be to try to parse a function, and if that succeeds, create a dummy `ast::Item` impl block to then format it using `pprust`. Would that be a viable approach? Is there a better alternative?
r? `@matklad` cc `@estebank`
This PR modifies the macro expansion infrastructure to handle attributes
in a fully token-based manner. As a result:
* Derives macros no longer lose spans when their input is modified
by eager cfg-expansion. This is accomplished by performing eager
cfg-expansion on the token stream that we pass to the derive
proc-macro
* Inner attributes now preserve spans in all cases, including when we
have multiple inner attributes in a row.
This is accomplished through the following changes:
* New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced.
These are very similar to a normal `TokenTree`, but they also track
the position of attributes and attribute targets within the stream.
They are built when we collect tokens during parsing.
An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when
we invoke a macro.
* Token capturing and `LazyTokenStream` are modified to work with
`AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which
is created during the parsing of a nested AST node to make the 'outer'
AST node aware of the attributes and attribute target stored deeper in the token stream.
* When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`),
we tokenize and reparse our target, capturing additional information about the locations of
`#[cfg]` and `#[cfg_attr]` attributes at any depth within the target.
This is a performance optimization, allowing us to perform less work
in the typical case where captured tokens never have eager cfg-expansion run.
Avoid `;` -> `,` recovery and unclosed `}` recovery from being too verbose
Those two recovery attempts have a very bad interaction that causes too
unnecessary output. Add a simple gate to avoid interpreting a `;` as a
`,` when there are unclosed braces.
Fix#83498.
Those two recovery attempts have a very bad interaction that causes too
unnecessary output. Add a simple gate to avoid interpreting a `;` as a
`,` when there are unclosed braces.
Previously, we would silently remove any `None`-delimiters when
capturing a `TokenStream`, 'flattenting' them to their inner tokens.
This was not normally visible, since we usually have
`TokenKind::Interpolated` (which gets converted to a `None`-delimited
group during macro invocation) instead of an actual `None`-delimited
group.
However, there are a couple of cases where this becomes visible to
proc-macros:
1. A cross-crate `macro_rules!` macro has a `None`-delimited group
stored in its body (as a result of being produced by another
`macro_rules!` macro). The cross-crate `macro_rules!` invocation
can then expand to an attribute macro invocation, which needs
to be able to see the `None`-delimited group.
2. A proc-macro can invoke an attribute proc-macro with its re-collected
input. If there are any nonterminals present in the input, they will
get re-collected to `None`-delimited groups, which will then get
captured as part of the attribute macro invocation.
Both of these cases are incredibly obscure, so there hopefully won't be
any breakage. This change will allow more agressive 'flattenting' of
nonterminals in #82608 without losing `None`-delimited groups.
ast/hir: Rename field-related structures
I always forget what `ast::Field` and `ast::StructField` mean despite working with AST for long time, so this PR changes the naming to less confusing and more consistent.
- `StructField` -> `FieldDef` ("field definition")
- `Field` -> `ExprField` ("expression field", not "field expression")
- `FieldPat` -> `PatField` ("pattern field", not "field pattern")
Various visiting and other methods working with the fields are renamed correspondingly too.
The second commit reduces the size of `ExprKind` by boxing fields of `ExprKind::Struct` in preparation for https://github.com/rust-lang/rust/pull/80080.
StructField -> FieldDef ("field definition")
Field -> ExprField ("expression field", not "field expression")
FieldPat -> PatField ("pattern field", not "field pattern")
Also rename visiting and other methods working on them.
Avoid sorting predicates by `DefId`
Fixes issue #82920
Even if an item does not change between compilation sessions, it may end
up with a different `DefId`, since inserting/deleting an item affects
the `DefId`s of all subsequent items. Therefore, we use a `DefPathHash`
in the incremental compilation system, which is stable in the face of
changes to unrelated items.
In particular, the query system will consider the inputs to a query to
be unchanged if any `DefId`s in the inputs have their `DefPathHash`es
unchanged. Queries are pure functions, so the query result should be
unchanged if the query inputs are unchanged.
Unfortunately, it's possible to inadvertantly make a query result
incorrectly change across compilations, by relying on the specific value
of a `DefId`. Specifically, if the query result is a slice that gets
sorted by `DefId`, the precise order will depend on how the `DefId`s got
assigned in a particular compilation session. If some definitions end up
with different `DefId`s (but the same `DefPathHash`es) in a subsequent
compilation session, we will end up re-computing a *different* value for
the query, even though the query system expects the result to unchanged
due to the unchanged inputs.
It turns out that we have been sorting the predicates computed during
`astconv` by their `DefId`. These predicates make their way into the
`super_predicates_that_define_assoc_type`, which ends up getting used to
compute the vtables of trait objects. This, re-ordering these predicates
between compilation sessions can lead to undefined behavior at runtime -
the query system will re-use code built with a *differently ordered*
vtable, resulting in the wrong method being invoked at runtime.
This PR avoids sorting by `DefId` in `astconv`, fixing the
miscompilation. However, it's possible that other instances of this
issue exist - they could also be easily introduced in the future.
To fully fix this issue, we should
1. Turn on `-Z incremental-verify-ich` by default. This will cause the
compiler to ICE whenver an 'unchanged' query result changes between
compilation sessions, instead of causing a miscompilation.
2. Remove the `Ord` impls for `CrateNum` and `DefId`. This will make it
difficult to introduce ICEs in the first place.
or-patterns: disallow in `let` bindings
~~Blocked on https://github.com/rust-lang/rust/pull/81869~~
Disallows top-level or-patterns before type ascription. We want to reserve this syntactic space for possible future generalized type ascription.
r? ``@petrochenkov``
Suggest character encoding is incorrect when encountering random null bytes
This adds a note whenever null bytes are seen at the start of a token unexpectedly, since those tend to come from UTF-16 encoded files without a [BOM](https://en.wikipedia.org/wiki/Byte_order_mark) (if a UTF-16 BOM appears it won't be valid UTF-8, but if there is no BOM it be both valid UTF-16 and valid but garbled UTF-8). This approach was suggested in https://github.com/rust-lang/rust/issues/73979#issuecomment-653976451.
Closes#73979.
This adds recovery when in array type syntax user writes
[X; Y<Z, ...>]
instead of
[X; Y::<Z, ...>]
Fixes#82566
Note that whenever we parse an expression and know that the next token
cannot be `,`, we should be calling
check_mistyped_turbofish_with_multiple_type_params for this recovery.
Previously we only did this for statement parsing (e.g. `let x = f<a,
b>;`). We now also do it when parsing the length field in array type
syntax.
check_mistyped_turbofish_with_multiple_type_params was previously
expecting type arguments between angle brackets, which is not right, as
we can also see const expressions. We now use generic argument parser
instead of type parser.
Test with one, two, and three generic arguments added to check
consistentcy between
1. check_no_chained_comparison: Called after parsing a nested binop
application like `x < A > ...` where angle brackets are interpreted as
binary operators and `A` is an expression.
2. check_mistyped_turbofish_with_multiple_type_params: called by
`parse_full_stmt` when we expect to see a semicolon after parsing an
expression but don't see it.
(In `T2<1, 2>::C;`, the expression is `T2 < 1`)
When token-based attribute handling is implemeneted in #80689,
we will need to access tokens from `HasAttrs` (to perform
cfg-stripping), and we will to access attributes from `HasTokens` (to
construct a `PreexpTokenStream`).
This PR merges the `HasAttrs` and `HasTokens` traits into a new
`AstLike` trait. The previous `HasAttrs` impls from `Vec<Attribute>` and `AttrVec`
are removed - they aren't attribute targets, so the impls never really
made sense.
Improve suggestion for tuple struct pattern matching errors.
Closes#80174
This change allows numbers to be parsed as field names when pattern matching on structs, which allows us to provide better error messages when tuple structs are matched using a struct pattern.
r? ``@estebank``
ast: Keep expansion status for out-of-line module items
I.e. whether a module `mod foo;` is already loaded from a file or not.
This is a pre-requisite to correctly treating inner attributes on such modules (https://github.com/rust-lang/rust/issues/81661).
With this change AST structures for `mod` items diverge even more for AST structure for the crate root, which previously used `ast::Mod`.
Therefore this PR removes `ast::Mod` from `ast::Crate` in the first commit, these two things are sufficiently different from each other, at least at syntactic level.
Customization points for visiting a "`mod` item or crate root" were also removed from AST visitors (`fn visit_mod`).
`ast::Mod` itself was refactored away in the second commit in favor of `ItemKind::Mod(Unsafe, ModKind)`.
Crate root is sufficiently different from `mod` items, at least at syntactic level.
Also remove customization point for "`mod` item or crate root" from AST visitors.
Along the way, we also implement a handful of diagnostics improvements
and fixes, particularly with respect to the special handling of `||` in
place of `|` and when there are leading verts in function params, which
don't allow top-level or-patterns anyway.
Rollup of 11 pull requests
Successful merges:
- #80523 (#[doc(inline)] sym_generated)
- #80920 (Visit more targets when validating attributes)
- #81720 (Updated smallvec version due to RUSTSEC-2021-0003)
- #81891 ([rustdoc-json] Make `header` a vec of modifiers, and FunctionPointer consistent)
- #81912 (Implement the precise analysis pass for lint `disjoint_capture_drop_reorder`)
- #81914 (Fixing bad suggestion for `_` in `const` type when a function #81885)
- #81919 (BTreeMap: fix internal comments)
- #81927 (Add a regression test for #32498)
- #81965 (Fix MIR pretty printer for non-local DefIds)
- #82029 (Use debug log level for developer oriented logs)
- #82056 (fix ice (#82032))
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
This is a pure refactoring split out from #80689.
It represents the most invasive part of that PR, requiring changes in
every caller of `parse_outer_attributes`
In order to eagerly expand `#[cfg]` attributes while preserving the
original `TokenStream`, we need to know the range of tokens that
corresponds to every attribute target. This is accomplished by making
`parse_outer_attributes` return an opaque `AttrWrapper` struct. An
`AttrWrapper` must be converted to a plain `AttrVec` by passing it to
`collect_tokens_trailing_token`. This makes it difficult to accidentally
construct an AST node with attributes without calling `collect_tokens_trailing_token`,
since AST nodes store an `AttrVec`, not an `AttrWrapper`.
As a result, we now call `collect_tokens_trailing_token` for attribute
targets which only support inert attributes, such as generic arguments
and struct fields. Currently, the constructed `LazyTokenStream` is
simply discarded. Future PRs will record the token range corresponding
to the attribute target, allowing those tokens to be removed from an
enclosing `collect_tokens_trailing_token` call if necessary.
The panic happens when in recovery parsing a full `impl`
(`parse_item_impl`) fails and we drop the `DiagnosticBuilder` for the
recovery suggestion and return the `parse_item_impl` error.
We now raise the original error "expected identifier found `impl`" when
parsing the `impl` fails.
Note that the regression test is slightly simplified version of the
original repro in #81806, to make the error output smaller and more
resilient to unrelated changes in parser error messages.
Fixes#81806
Box the biggest ast::ItemKind variants
This PR is a different approach on https://github.com/rust-lang/rust/pull/81400, aiming to save memory in humongous ASTs.
The three affected item kind enums are:
- `ast::ItemKind` (208 -> 112 bytes)
- `ast::AssocItemKind` (176 -> 72 bytes)
- `ast::ForeignItemKind` (176 -> 72 bytes)
Improve handling of spans around macro result parse errors
Fixes#81543
After we expand a macro, we try to parse the resulting tokens as a AST
node. This commit makes several improvements to how we handle spans when
an error occurs:
* Only ovewrite the original `Span` if it's a dummy span. This preserves
a more-specific span if one is available.
* Use `self.prev_token` instead of `self.token` when emitting an error
message after encountering EOF, since an EOF token always has a dummy
span
* Make `SourceMap::next_point` leave dummy spans unused. A dummy span
does not have a logical 'next point', since it's a zero-length span.
Re-using the span span preserves its 'dummy-ness' for other checks
Fixes#81543
After we expand a macro, we try to parse the resulting tokens as a AST
node. This commit makes several improvements to how we handle spans when
an error occurs:
* Only ovewrite the original `Span` if it's a dummy span. This preserves
a more-specific span if one is available.
* Use `self.prev_token` instead of `self.token` when emitting an error
message after encountering EOF, since an EOF token always has a dummy
span
* Make `SourceMap::next_point` leave dummy spans unused. A dummy span
does not have a logical 'next point', since it's a zero-length span.
Re-using the span span preserves its 'dummy-ness' for other checks
Clone entire `TokenCursor` when collecting tokens
Reverts PR #80830Fixestaiki-e/pin-project#312
We can have an arbitrary number of `None`-delimited group frames pushed
on the stack due to proc-macro invocations, which can legally be exited.
Attempting to account for this would add a lot of complexity for a tiny
performance gain, so let's just use the original strategy.
Reverts PR #80830Fixestaiki-e/pin-project#312
We can have an arbitrary number of `None`-delimited group frames pushed
on the stack due to proc-macro invocations, which can legally be exited.
Attempting to account for this would add a lot of complexity for a tiny
performance gain, so let's just use the original strategy.
Improve diagnostics when parsing angle args
https://github.com/rust-lang/rust/pull/79266 introduced parsing of generic arguments in associated type constraints, this however resulted in possibly very confusing error messages in cases in which closing angle brackets were missing such as in `Vec<(u32, _, _) = vec![]`, which outputs an incorrectly parsed equality constraint error, as noted by `@cynecx.`
This PR tries to provide better error messages in such cases.
r? `@petrochenkov`
Refactor token collection to capture trailing token immediately
Split out from https://github.com/rust-lang/rust/pull/80689 - when we start capturing more information about attribute targets, we'll need to know in advance if we're capturing a trailing token or not.
r? `@ghost`
Currently, when a user uses a struct pattern to pattern match on
a tuple struct, the errors we emit generally suggest adding fields
using their field names, which are numbers. However, numbers are
not valid identifiers, so the suggestions, which use the shorthand
notation, are not valid syntax. This commit changes those errors
to suggest using the actual tuple struct pattern syntax instead,
which is a more actionable suggestion.
Fixes#81007
Previously, we would fail to collect tokens in the proper place when
only builtin attributes were present. As a result, we would end up with
attribute tokens in the collected `TokenStream`, leading to duplication
when we attempted to prepend the attributes from the AST node.
We now explicitly track when token collection must be performed due to
nomterminal parsing.
Set tokens on AST node in `collect_tokens`
A new `HasTokens` trait is introduced, which is used to move logic from
the callers of `collect_tokens` into the body of `collect_tokens`.
In addition to reducing duplication, this paves the way for PR #80689,
which needs to perform additional logic during token collection.
A new `HasTokens` trait is introduced, which is used to move logic from
the callers of `collect_tokens` into the body of `collect_tokens`.
In addition to reducing duplication, this paves the way for PR #80689,
which needs to perform additional logic during token collection.
Rework diagnostics for wrong number of generic args (fixes#66228 and #71924)
This PR reworks the `wrong number of {} arguments` message, so that it provides more details and contextual hints.
Suggest async {} for async || {}
Fixes#76011
This adds support for adding help diagnostics to the feature gating checks and
then uses it for the async_closure gate to add the extra bit of help
information as described in the issue.
We will never need to pop past our starting frame during token
capturing. Using an empty stack allows us to avoid pointless heap
allocations/deallocations.
- Adds optional default values to const generic parameters in the AST
and HIR
- Parses these optional default values
- Adds a `const_generics_defaults` feature gate
Implemented a compiler diagnostic for move async mistake
Fixes#79694
First time contributing, so I hope I'm doing everything right.
(If not, please correct me!)
This code performs a check when a move capture clause is parsed. The check is to detect if the user has reversed the async move keywords and to provide a diagnostic with a suggestion to fix it.
Checked code:
```rust
fn main() {
move async { };
}
```
Previous output:
```txt
PS C:\Repos\move_async_test> cargo build
Compiling move_async_test v0.1.0 (C:\Repos\move_async_test)
error: expected one of `|` or `||`, found keyword `async`
--> src\main.rs:2:10
|
2 | move async { };
| ^^^^^ expected one of `|` or `||`
error: aborting due to previous error
error: could not compile `move_async_test`
```
New output:
```txt
PS C:\Repos\move_async_test> cargo +dev build
Compiling move_async_test v0.1.0 (C:\Repos\move_async_test)
error: the order of `move` and `async` is incorrect
--> src\main.rs:2:13
|
2 | let _ = move async { };
| ^^^^^^^^^^
|
help: try switching the order
|
2 | let _ = async move { };
| ^^^^^^^^^^
error: aborting due to previous error
error: could not compile `move_async_test`
```
Is there a file/module where these kind of things are tested?
Would love some feedback 😄
Ran the tidy check
Following the diagnostic guide better
Diagnostic generation is now relegated to its own function in the diagnostics module.
Added tests
Fixed the ui test
Properly capture trailing 'unglued' token
If we try to capture the `Vec<u8>` in `Option<Vec<u8>>`, we'll
need to capture a `>` token which was 'unglued' from a `>>` token.
The processing of unglueing a token for parsing purposes bypasses the
usual capturing infrastructure, so we currently lose the trailing `>`.
As a result, we fall back to the reparsed `TokenStream`, causing us to
lose spans.
This commit makes token capturing keep track of a trailing 'unglued'
token. Note that we don't need to care about unglueing except at the end
of the captured tokens - if we capture both the first and second unglued
tokens, then we'll end up capturing the full 'glued' token, which
already works correctly.
Recover on `const impl<> X for Y`
`@leonardo-m` mentioned that `const impl Foo for Bar` could be recovered from in #79287.
I'm not sure about the error strings as they are, I think it should probably be something like the error that `expected_one_of_not_found` makes + the suggestion to flip the keywords, but I'm not sure how exactly to do that. Also, I decided not to try to handle `const unsafe impl` or `unsafe const impl` cause I figured that `unsafe impl const` would be pretty rare anyway (if it's even valid?), and it wouldn't be worth making the code more messy.
If we try to capture the `Vec<u8>` in `Option<Vec<u8>>`, we'll
need to capture a `>` token which was 'unglued' from a `>>` token.
The processing of unglueing a token for parsing purposes bypasses the
usual capturing infrastructure, so we currently lose the trailing `>`.
As a result, we fall back to the reparsed `TokenStream`, causing us to
lose spans.
This commit makes token capturing keep track of a trailing 'unglued'
token. Note that we don't need to care about unglueing except at the end
of the captured tokens - if we capture both the first and second unglued
tokens, then we'll end up capturing the full 'glued' token, which
already works correctly.
Update error to reflect that integer literals can have float suffixes
For example, `1` is parsed as an integer literal, but it can be turned
into a float with the suffix `f32`. Now the error calls them "numeric
literals" and notes that you can add a float suffix since they can be
either integers or floats.
rustc_parse: fix ConstBlock expr span
The span for a ConstBlock expression should presumably run through the end of the block it contains and not stop at the keyword, just like is done with similar block-containing expression kinds, such as a TryBlock
Properly handle attributes on statements
We now collect tokens for the underlying node wrapped by `StmtKind`
nstead of storing tokens directly in `Stmt`.
`LazyTokenStream` now supports capturing a trailing semicolon after it
is initially constructed. This allows us to avoid refactoring statement
parsing to wrap the parsing of the semicolon in `parse_tokens`.
Attributes on item statements
(e.g. `fn foo() { #[bar] struct MyStruct; }`) are now treated as
item attributes, not statement attributes, which is consistent with how
we handle attributes on other kinds of statements. The feature-gating
code is adjusted so that proc-macro attributes are still allowed on item
statements on stable.
Two built-in macros (`#[global_allocator]` and `#[test]`) needed to be
adjusted to support being passed `Annotatable::Stmt`.
For example, `1` is parsed as an integer literal, but it can be turned
into a float with the suffix `f32`. Now the error calls them "numeric
literals" and notes that you can add a float suffix since they can be
either integers or floats.
When parsing a statement (e.g. inside a function body),
we now consider `struct Foo {};` and `$stmt;` to each consist
of two statements: `struct Foo {}` and `;`, and `$stmt` and `;`.
As a result, an attribute macro invoke as
`fn foo() { #[attr] struct Bar{}; }` will see `struct Bar{}` as its
input. Additionally, the 'unused semicolon' lint now fires in more
places.
We now collect tokens for the underlying node wrapped by `StmtKind`
instead of storing tokens directly in `Stmt`.
`LazyTokenStream` now supports capturing a trailing semicolon after it
is initially constructed. This allows us to avoid refactoring statement
parsing to wrap the parsing of the semicolon in `parse_tokens`.
Attributes on item statements
(e.g. `fn foo() { #[bar] struct MyStruct; }`) are now treated as
item attributes, not statement attributes, which is consistent with how
we handle attributes on other kinds of statements. The feature-gating
code is adjusted so that proc-macro attributes are still allowed on item
statements on stable.
Two built-in macros (`#[global_allocator]` and `#[test]`) needed to be
adjusted to support being passed `Annotatable::Stmt`.
Cache pretty-print/retokenize result to avoid compile time blowup
Fixes#79242
If a `macro_rules!` recursively builds up a nested nonterminal
(passing it to a proc-macro at each step), we will end up repeatedly
pretty-printing/retokenizing the same nonterminals. Unfortunately, the
'probable equality' check we do has a non-trivial cost, which leads to a
blowup in compilation time.
As a workaround, we cache the result of the 'probable equality' check,
which eliminates the compilation time blowup for the linked issue. This
commit only touches a single file (other than adding tests), so it
should be easy to backport.
The proper solution is to remove the pretty-print/retokenize hack
entirely. However, this will almost certainly break a large number of
crates that were relying on hygiene bugs created by using the reparsed
`TokenStream`. As a result, we will definitely not want to backport
such a change.
Fixes#79242
If a `macro_rules!` recursively builds up a nested nonterminal
(passing it to a proc-macro at each step), we will end up repeatedly
pretty-printing/retokenizing the same nonterminals. Unfortunately, the
'probable equality' check we do has a non-trivial cost, which leads to a
blowup in compilation time.
As a workaround, we cache the result of the 'probable equality' check,
which eliminates the compilation time blowup for the linked issue. This
commit only touches a single file (other than adding tests), so it
should be easy to backport.
The proper solution is to remove the pretty-print/retokenize hack
entirely. However, this will almost certainly break a large number of
crates that were relying on hygiene bugs created by using the reparsed
`TokenStream`. As a result, we will definitely not want to backport
such a change.
Make `_` an expression, to discard values in destructuring assignments
This is the third and final step towards implementing destructuring assignment (RFC: rust-lang/rfcs#2909, tracking issue: #71126). This PR is the third and final part of #71156, which was split up to allow for easier review.
With this PR, an underscore `_` is parsed as an expression but is allowed *only* on the left-hand side of a destructuring assignment. There it simply discards a value, similarly to the wildcard `_` in patterns. For instance,
```rust
(a, _) = (1, 2)
```
will simply assign 1 to `a` and discard the 2. Note that for consistency,
```
_ = foo
```
is also allowed and equivalent to just `foo`.
Thanks to ````@varkor```` who helped with the implementation, particularly around pre-expansion gating.
r? ````@petrochenkov````
rustc_parse: Remove optimization for 0-length streams in `collect_tokens`
The optimization conflates empty token streams with unknown token stream, which is at least suspicious, and doesn't affect performance because 0-length token streams are very rare.
r? `@Aaron1011`
The optimization conflates empty token streams with unknown token stream, which is at least suspicious, and doesn't affect performance because 0-length token streams are very rare.
Implement destructuring assignment for structs and slices
This is the second step towards implementing destructuring assignment (RFC: rust-lang/rfcs#2909, tracking issue: #71126). This PR is the second part of #71156, which was split up to allow for easier review.
Note that the first PR (#78748) is not merged yet, so it is included as the first commit in this one. I thought this would allow the review to start earlier because I have some time this weekend to respond to reviews. If ``@petrochenkov`` prefers to wait until the first PR is merged, I totally understand, of course.
This PR implements destructuring assignment for (tuple) structs and slices. In order to do this, the following *parser change* was necessary: struct expressions are not required to have a base expression, i.e. `Struct { a: 1, .. }` becomes legal (in order to act like a struct pattern).
Unfortunately, this PR slightly regresses the diagnostics implemented in #77283. However, it is only a missing help message in `src/test/ui/issues/issue-77218.rs`. Other instances of this diagnostic are not affected. Since I don't exactly understand how this help message works and how to fix it yet, I was hoping it's OK to regress this temporarily and fix it in a follow-up PR.
Thanks to ``@varkor`` who helped with the implementation, particularly around the struct rest changes.
r? ``@petrochenkov``
Do not collect tokens for doc comments
Doc comment is a single token and AST has all the information to re-create it precisely.
Doc comments are also responsible for majority of calls to `collect_tokens` (with `num_calls == 1` and `num_calls == 0`, cc https://github.com/rust-lang/rust/pull/78736).
(I also moved token collection into `fn parse_attribute` to deduplicate code a bit.)
r? `@Aaron1011`
rustc_ast: Do not panic by default when visiting macro calls
Panicking by default made sense when we didn't have HIR or MIR and everything worked on AST, but now all AST visitors run early and majority of them have to deal with macro calls, often by ignoring them.
The second commit renames `visit_mac` to `visit_mac_call`, the corresponding structures were renamed earlier in https://github.com/rust-lang/rust/pull/69589.
Fixes#78675
We now bail out of `prepend_attrs` if we ended up capturing any inner
attributes (which can happen in several places, due to token capturing
for `macro_rules!` arguments.
Adjust turbofish help message for const generics
Types are no longer special. (This message arguably only makes sense with `min_const_generics` or more, but we'll be there soon.)
r? @lcnr
Tweak invalid `fn` header and body parsing
* Rely on regular "expected"/"found" parser error for `fn`, fix#77115
* Recover empty `fn` bodies when encountering `}`
* Recover trailing `>` in return types
* Recover from non-type in array type `[<BAD TOKEN>; LEN]`
Suggest that expressions that look like const generic arguments should be enclosed in brackets
I pulled out the changes for const expressions from https://github.com/rust-lang/rust/pull/71592 (without the trait object diagnostic changes) and made some small changes; the implementation is `@estebank's.`
We're also going to want to make some changes separately to account for trait objects (they result in poor diagnostics, as is evident from one of the test cases here), such as an adaption of https://github.com/rust-lang/rust/pull/72273.
Fixes https://github.com/rust-lang/rust/issues/70753.
r? `@petrochenkov`
Tweak match arm semicolon removal suggestion to account for futures
* Tweak and extend "use `.await`" suggestions
* Suggest removal of semicolon on prior match arm
* Account for `impl Future` when suggesting semicolon removal
* Silence some errors when encountering `await foo()?` as can't be certain what the intent was
*Thanks to https://twitter.com/a_hoverbear/status/1318960787105353728 for pointing this out!*
Unconditionally capture tokens for attributes.
This allows us to avoid synthesizing tokens in `prepend_attr`, since we
have the original tokens available.
We still need to synthesize tokens when expanding `cfg_attr`,
but this is an unavoidable consequence of the syntax of `cfg_attr` -
the user does not supply the `#` and `[]` tokens that a `cfg_attr`
expands to.
This is based on PR https://github.com/rust-lang/rust/pull/77250 - this PR exposes a bug in the current `collect_tokens` implementation, which is fixed by the rewrite.
This allows us to avoid synthesizing tokens in `prepend_attr`, since we
have the original tokens available.
We still need to synthesize tokens when expanding `cfg_attr`,
but this is an unavoidable consequence of the syntax of `cfg_attr` -
the user does not supply the `#` and `[]` tokens that a `cfg_attr`
expands to.
Rewrite `collect_tokens` implementations to use a flattened buffer
Instead of trying to collect tokens at each depth, we 'flatten' the
stream as we go allong, pushing open/close delimiters to our buffer
just like regular tokens. One capturing is complete, we reconstruct a
nested `TokenTree::Delimited` structure, producing a normal
`TokenStream`.
The reconstructed `TokenStream` is not created immediately - instead, it is
produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This
closure stores a clone of the original `TokenCursor`, plus a record of the
number of calls to `next()/next_desugared()`. This is sufficient to reconstruct
the tokenstream seen by the callback without storing any additional state. If
the tokenstream is never used (e.g. when a captured `macro_rules!` argument is
never passed to a proc macro), we never actually create a `TokenStream`.
This implementation has a number of advantages over the previous one:
* It is significantly simpler, with no edge cases around capturing the
start/end of a delimited group.
* It can be easily extended to allow replacing tokens an an arbitrary
'depth' by just using `Vec::splice` at the proper position. This is
important for PR #76130, which requires us to track information about
attributes along with tokens.
* The lazy approach to `TokenStream` construction allows us to easily
parse an AST struct, and then decide after the fact whether we need a
`TokenStream`. This will be useful when we start collecting tokens for
`Attribute` - we can discard the `LazyTokenStream` if the parsed
attribute doesn't need tokens (e.g. is a builtin attribute).
The performance impact seems to be neglibile (see
https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a
small slowdown on a few benchmarks, but it only rises above 1% for incremental
builds, where it represents a larger fraction of the much smaller instruction
count. There a ~1% speedup on a few other incremental benchmarks - my guess is
that the speedups and slowdowns will usually cancel out in practice.
Instead of trying to collect tokens at each depth, we 'flatten' the
stream as we go allong, pushing open/close delimiters to our buffer
just like regular tokens. One capturing is complete, we reconstruct a
nested `TokenTree::Delimited` structure, producing a normal
`TokenStream`.
The reconstructed `TokenStream` is not created immediately - instead, it is
produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This
closure stores a clone of the original `TokenCursor`, plus a record of the
number of calls to `next()/next_desugared()`. This is sufficient to reconstruct
the tokenstream seen by the callback without storing any additional state. If
the tokenstream is never used (e.g. when a captured `macro_rules!` argument is
never passed to a proc macro), we never actually create a `TokenStream`.
This implementation has a number of advantages over the previous one:
* It is significantly simpler, with no edge cases around capturing the
start/end of a delimited group.
* It can be easily extended to allow replacing tokens an an arbitrary
'depth' by just using `Vec::splice` at the proper position. This is
important for PR #76130, which requires us to track information about
attributes along with tokens.
* The lazy approach to `TokenStream` construction allows us to easily
parse an AST struct, and then decide after the fact whether we need a
`TokenStream`. This will be useful when we start collecting tokens for
`Attribute` - we can discard the `LazyTokenStream` if the parsed
attribute doesn't need tokens (e.g. is a builtin attribute).
The performance impact seems to be neglibile (see
https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a
small slowdown on a few benchmarks, but it only rises above 1% for incremental
builds, where it represents a larger fraction of the much smaller instruction
count. There a ~1% speedup on a few other incremental benchmarks - my guess is
that the speedups and slowdowns will usually cancel out in practice.
rustc_parse: fix spans on cast and range exprs with attrs
Currently the span for cast and range expressions does not include the span of attributes associated to the lhs which is causing some issues for us in rustfmt.
```rust
fn foo() -> i64 {
#[attr]
1u64 as i64
}
fn bar() -> Range<i32> {
#[attr]
1..2
}
```
This corrects the span for cast and range expressions to fully include the span of child nodes
