Recover and suggest to use ; to construct array type by xizheyin · Pull Request #143905 · rust-lang/rust (original) (raw)

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@xizheyin

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Jul 13, 2025

xizheyin

Comment on lines 15 to 18

help: use `=` if you meant to assign
|
LL - let b: [i32, 5];
LL + let b = [i32, 5];

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This suggestion is wrong, but it have nothing with this PR. Because the old diagnostic has the same help message.

Old Diagnostic:

error: expected one of `!`, `(`, `+`, `::`, `;`, `<`, or `]`, found `,`
 --> src/main.rs:3:16
  |
3 |     let b: [i32, 5];
  |          -     ^ expected one of 7 possible tokens
  |          |
  |          while parsing the type for `b`
  |          help: use `=` if you meant to assign

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Jul 13, 2025

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Reminder, once the PR becomes ready for a review, use @rustbot ready.

@xizheyin

Also, why can't we emit the error and then return TyKind::Array, so we can recover successfully rather than propagating an error?

Yeah, I have tried to recover it to TyKind::Array, but It emit a regression. In this test, it will emit error: expected ; or ], found , immidiately, which is wrong. It just want call parse_ty_common for Some(x), while in this case, it parse it into Array and give a wrong suggestion.

https://github.com/rust-lang/rust/blob/master/tests/ui/issues/issue-50571.rs
https://github.com/rust-lang/rust/blob/master/tests/ui/issues/issue-50571.stderr

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Jul 14, 2025

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I personally think it's fine to regress #50571, since it's an issue that only has to do with edition 2015 and is a rare enough.

I'd still like to see a better recovery that actually ends up returning Ok(TyKind::Array(...)).

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Jul 14, 2025

@xizheyin

Signed-off-by: xizheyin xizheyin@smail.nju.edu.cn

xizheyin

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help: you might have meant to use `;` as the separator
|
LL | type v = [isize ;* 3];
| +

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This regression is somewhat werid, because parse_expr_anon_const take it as a deref of 3. That maybe reasonable for

const L = &3;
type V = [isize * L];

After applying the suggestion, it is correct.

But IMO, it does not matter in this * case, because after applying the suggestion, compiler will report something like you can not deref a integer, which is reasonable.

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We could perhaps special case both , and * as separators here?

Comment on lines +38 to +48

error: expected `;` or `]`, found `5`
--> $DIR/array-type-no-semi.rs:15:17
|
LL | let e: [i32 5];
| ^ expected `;` or `]`
|
= note: you might have meant to write a slice or array type
help: you might have meant to use `;` as the separator
|
LL | let e: [i32 ;5];
| +

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Here is the new case like [i32 5].

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Jul 14, 2025

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cc @jieyouxu

@xizheyin xizheyin changed the titleSuggest use ; to construct array type when other token exists Recover and suggest to use ; to construct array type

Jul 14, 2025

jieyouxu

compiler-errors

help: you might have meant to use `;` as the separator
|
LL | type v = [isize ;* 3];
| +

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We could perhaps special case both , and * as separators here?

Comment on lines 609 to 614

let length = match self.parse_expr_anon_const() {
Ok(length) => length,
Err(e) => {
e.cancel();
self.bump();
match self.parse_expr_anon_const() {

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Instead of parsing once then parsing again, could you do:

let suggestion_span = if self.eat(comma) || self.eat(asterisk) {
    // Consume common erroneous separators.
    self.prev_token.span
} else {
    self.token.span.shrink_to_lo()
};

/// then parse the length.

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Should other separators be considered, such as :?

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I think , and * are fine for now

@xizheyin

Signed-off-by: xizheyin xizheyin@smail.nju.edu.cn

@xizheyin

Yeah, I have instead specially judge , and *.

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📌 Commit ed88af2 has been approved by compiler-errors

It is now in the queue for this repository.

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Jul 15, 2025

bors added a commit that referenced this pull request

Jul 15, 2025

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Rollup of 13 pull requests

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r? @ghost @rustbot modify labels: rollup

rust-timer added a commit that referenced this pull request

Jul 15, 2025

@rust-timer

Rollup merge of #143905 - xizheyin:143828, r=compiler-errors

Recover and suggest to use ; to construct array type

Fixes #143828

r? compiler

github-actions bot pushed a commit to rust-lang/rustc-dev-guide that referenced this pull request

Jul 17, 2025

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Muscraft pushed a commit to Muscraft/rust that referenced this pull request

Jul 21, 2025

@samueltardieu @Muscraft

Recover and suggest to use ; to construct array type

Fixes rust-lang#143828

r? compiler

Muscraft pushed a commit to Muscraft/rust that referenced this pull request

Jul 21, 2025

@bors @Muscraft

Zalathar added a commit to Zalathar/rust that referenced this pull request

Nov 9, 2025

@Zalathar

Recover [T: N] as [T; N]

; is similar and (keyboard-wise) next to :, so a verbose suggestion may help to see the difference.

Parent PR: rust-lang#143905

@rustbot label +A-parser +A-array +A-diagnostics +A-suggestion-diagnostics +D-papercut

rust-timer added a commit that referenced this pull request

Nov 9, 2025

@rust-timer

Rollup merge of #148680 - ShE3py:array-colon, r=JonathanBrouwer

Recover [T: N] as [T; N]

; is similar and (keyboard-wise) next to :, so a verbose suggestion may help to see the difference.

Parent PR: #143905

@rustbot label +A-parser +A-array +A-diagnostics +A-suggestion-diagnostics +D-papercut

github-actions bot pushed a commit to rust-lang/miri that referenced this pull request

Nov 10, 2025

@Zalathar

Recover [T: N] as [T; N]

; is similar and (keyboard-wise) next to :, so a verbose suggestion may help to see the difference.

Parent PR: rust-lang/rust#143905

@rustbot label +A-parser +A-array +A-diagnostics +A-suggestion-diagnostics +D-papercut

makai410 pushed a commit to makai410/rustc_public that referenced this pull request

Nov 10, 2025

@Zalathar

Recover [T: N] as [T; N]

; is similar and (keyboard-wise) next to :, so a verbose suggestion may help to see the difference.

Parent PR: rust-lang/rust#143905

@rustbot label +A-parser +A-array +A-diagnostics +A-suggestion-diagnostics +D-papercut

makai410 pushed a commit to makai410/rust that referenced this pull request

Nov 10, 2025

@Zalathar

Recover [T: N] as [T; N]

; is similar and (keyboard-wise) next to :, so a verbose suggestion may help to see the difference.

Parent PR: rust-lang#143905

@rustbot label +A-parser +A-array +A-diagnostics +A-suggestion-diagnostics +D-papercut

makai410 pushed a commit to makai410/rustc_public that referenced this pull request

Nov 16, 2025

@Zalathar

Recover [T: N] as [T; N]

; is similar and (keyboard-wise) next to :, so a verbose suggestion may help to see the difference.

Parent PR: rust-lang/rust#143905

@rustbot label +A-parser +A-array +A-diagnostics +A-suggestion-diagnostics +D-papercut

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