Parser: Uninterpolate when checking for const closures, try bikeshed blocks & in relevant diagnostic code - #162704
Open
fmease wants to merge 3 commits into
Open
Parser: Uninterpolate when checking for const closures, try bikeshed blocks & in relevant diagnostic code#162704fmease wants to merge 3 commits into
fmease wants to merge 3 commits into
Conversation
This makes code like this compile:
#![feature(try_blocks_heterogeneous)]
macro_rules! make { ($kw:ident) => { try $kw Option<()> {} } }
fn scope() { make!(bikeshed); }
rustbot
added
S-waiting-on-review
Collaborator
|
r? @adwinwhite rustbot has assigned @adwinwhite. Use Why was this reviewer chosen?The reviewer was selected based on:
|
fmease
commented
Sep 12, 2026
| // Let's check if the previous token could denote the start of an item | ||
| // whose kind can have generics. | ||
| if let Some((Ident { name, .. }, IdentIsRaw::No)) = self.prev_token.ident() | ||
| && let kw::Fn | kw::Type | kw::Struct | kw::Enum | kw::Union | kw::Trait = name |
Member
Author
There was a problem hiding this comment.
Makes us now also emit the suggestion for code like below:
macro_rules! make { ($kw:ident) => { $kw<T> f() {} } }
make!(fn);Compiler Output
error: expected identifier, found `<`
--> t.rs:12:41
|
12 | macro_rules! make { ($kw:ident) => { $kw<T> f() {} } }
| ^ expected identifier
13 | make!(fn);
| --------- in this macro invocation
|
= note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: place the generic parameter name after the fn name
|
12 - macro_rules! make { ($kw:ident) => { $kw<T> f() {} } }
12 + macro_rules! make { ($kw:ident) => { $kw f<T>() {} } }
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| if let Some((ident, IdentIsRaw::No)) = self.prev_token.ident() |
Member
Author
There was a problem hiding this comment.
Apart from the "interpolated identifier" business, this now makes this code aware of r#: It will no longer show the suggestion for code like r#function f() {} as the user has clearly requested function not to act as a keyword.
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| if let Some((ident, IdentIsRaw::No)) = self.prev_token.ident() |
Member
Author
There was a problem hiding this comment.
Makes us now also emit the suggestion for code like below:
macro_rules! make { ($kw:ident) => { $kw f() {} } }
make!(function);Compiler Output
error: expected one of `!` or `::`, found `f`
--> t.rs:4:42
|
4 | macro_rules! make { ($kw:ident) => { $kw f() {} } }
| --- ^ expected one of `!` or `::`
| |
| help: write `fn` instead of `function` to declare a function
5 | make!(function);
| --------------- in this macro invocation
|
= note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
| if let TokenKind::Ident(_, _) = prev_token.kind { | ||
| e.span_suggestion_verbose( | ||
| self.expect(exp!(CloseBracket)).map_err(|mut err| { | ||
| if prev_token.is_non_reserved_ident() { |
Member
Author
There was a problem hiding this comment.
Makes us now also emit the suggestion for code like below:
macro_rules! make { ($ident:ident) => { $ident[0;] } }
fn scope() { make!(ident); }Compiler Output
error: expected one of `.`, `?`, `]`, or an operator, found `;`
--> t.rs:20:49
|
20 | macro_rules! make { ($ident:ident) => { $ident[0;] } }
| ^ expected one of `.`, `?`, `]`, or an operator
21 | fn scope() { make!(ident); }
| ------------ in this macro invocation
|
= note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: you might have meant to call a macro
|
20 | macro_rules! make { ($ident:ident) => { $ident![0;] } }
| +
| *t == token::OpenBrace | ||
| || t.is_metavar_block() | ||
| || t.kind == TokenKind::Ident(sym::bikeshed, IdentIsRaw::No) | ||
| *t == token::OpenBrace || t.is_metavar_block() || t.is_keyword(sym::bikeshed) |
Member
Author
There was a problem hiding this comment.
As the commit message already states this makes us accept code like:
#![feature(try_blocks_heterogeneous)]
macro_rules! make { ($kw:ident) => { try $kw Option<()> {} } }
fn scope() { make!(bikeshed); }Previously, we would error out with expected expression, found reserved keyword `try`.
| }) | ||
| .map(|(ident, _)| ident); | ||
| .non_reserved_ident() | ||
| .filter(|_| self.look_ahead(1, |&tok| tok == token::Colon)); |
Member
Author
There was a problem hiding this comment.
Drive-by cleanup. Taken straight from PR #161775 which incidentally also introduces Token::non_reserved_ident (it's just so useful! :D)
| self.is_keyword_ahead(0, &[kw::Const]) | ||
| && self.look_ahead(1, |t| match &t.kind { | ||
| // async closures do not work with const closures, so we do not parse that here. | ||
| && self.look_ahead(1, |t| match t.uninterpolate().kind { |
Member
Author
There was a problem hiding this comment.
See the added UI test for what this makes us accept.
| t.is_metavar_block() | ||
| || t.kind == token::OpenBrace | ||
| || t.is_non_raw_ident_where(|ident| { | ||
| matches!(ident.name, kw::For | kw::Loop | kw::While) |
Member
Author
There was a problem hiding this comment.
Makes us now also emit this customized diagnostic plus its suggestion for code like:
macro_rules! make { ($kw:ident) => { label: $kw {} } }
fn scope() { make!(loop); }Compiler Output
error: malformed loop label
--> t.rs:8:38
|
8 | macro_rules! make { ($kw:ident) => { label: $kw {} } }
| ^^^^^
9 | fn scope() { make!(loop); }
| ----------- in this macro invocation
|
= note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: use the correct loop label format
|
8 | macro_rules! make { ($kw:ident) => { 'label: $kw {} } }
| +
warning: unused label
--> t.rs:8:38
|
8 | macro_rules! make { ($kw:ident) => { label: $kw {} } }
| ^^^^^
9 | fn scope() { make!(loop); }
| ----------- in this macro invocation
|
= note: `#[warn(unused_labels)]` (part of `#[warn(unused)]`) on by default
= note: this warning originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
| } | ||
| }) | ||
| // If we encounter a type like `impl 'a Sized`, suggest `impl 'a + Sized`. | ||
| if self.token.is_lifetime() |
Member
Author
There was a problem hiding this comment.
Apart from the "interpolated identifier" business this makes the diagnostic aware of keywords. Previously, it would also trigger on inputs like impl 'a if.
| } | ||
| }) | ||
| // If we encounter a type like `impl 'a Sized`, suggest `impl 'a + Sized`. | ||
| if self.token.is_lifetime() |
Member
Author
There was a problem hiding this comment.
Makes us now also emit this custom diagnostic for code like:
macro_rules! make { ($ident:ident) => { impl 'static $ident; } }
fn scope() -> make!(Trait) {}Compiler Output (Excerpt)
error: expected `+` between lifetime and Trait
--> t.rs:16:46
|
16 | macro_rules! make { ($ident:ident) => { impl 'static $ident; } }
| ^^^^^^^
17 | fn scope() -> make!(Trait) {}
| ------------ in this macro invocation
|
= note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: add `+`
|
16 | macro_rules! make { ($ident:ident) => { impl 'static + $ident; } }
| +
Member
Author
|
Note that I won't be adding any of these code snippets as UI tests because that would be disproportionate. I hope that's understandable :) |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
On main, various places in the parser manually check for
TokenKind::Ident(…)while in most cases that's not correct / complete as it doesn't account for interpolated identifiers (TokenKind::NtIdent(…), "non-terminal" identifiers, i.e., ones that originate from macro metavariables$ident).I've looked at all occurrences of
TokenKind::Ident&token::Identin the parser to see if each place was intentionally ignoringNtIdentor not. I found out that the code pertaining to const closures (unstable featureconst_closures), to try bikeshed blocks (unstable featuretry_blocks_heterogeneous) and to some diagnostics & parse error recoveries did not intend to ignore interpolated identifiers. This PR rectifies that.Note that in most cases, it's not necessary to manually match against
NtIdentas you can simply utilize helpers likeToken::uninterpolate,Token::ident,Token::is_keyword,Token::is_non_raw_identwhich handle them internally.I also took the chance to clean up in each vicinity.
(No LLM was or will be used by me during the entire creation process of this PR)