Improve diagnostics for let x += 1
#71976
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rust-highfive
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akraines
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May 7, 2020
akraines
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akraines
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akraines
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May 7, 2020
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Feel free to ignore the correction, I just noticed it when I was perusing the code and figured I may as well make my first mini contribution :-) |
estebank
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May 7, 2020
src/test/ui/parser/let-binop.stderr
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| LL | b += 1; | ||
| | -- | ||
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| error[E0067]: can't reassign to a uninitialized variable |
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I would prefer different wording here, but I'm not sure what :-/
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I agree the wording isn't ideal but I don't have any better ideas right now. The E0067 error description is: An invalid left-hand side expression was used on an assignment operation. however I think it's harder to understand. I might be biased though :)
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This cannot be an error at parse time. This should probably be combined with 870a7de and reported somewhere at resolution or HIR lowering time. |
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A trait object cannot be part of a pattern, can it? |
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@estebank |
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I would be ok if this PR only recovered |
@petrochenkov do you mean leaving |
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@mibac138 (Also if the recovery logic is larger than a few lines, then it's preferable to move it to |
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When parsing `let x: i8 += 1` the compiler interprets `i8` as a trait which makes it more complicated to do error recovery. More advanced error recovery is not implemented in this commit.
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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@estebank @petrochenkov this looks good for a merge? |
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@bors r+ |
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📌 Commit 98532a3 has been approved by |
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Manishearth
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Jun 16, 2020
Improve diagnostics for `let x += 1` Fixes(?) rust-lang#66736 The code responsible for the `E0404` errors is [here](https://github.com/rust-lang/rust/blob/master/src/librustc_parse/parser/ty.rs#L399-L424) which I don't think can be easily modified to prevent emitting an error in one specific case. Because of this I couldn't get rid of `E0404` and instead added `E0067` along with a help message which will fix the problem. r? @estebank
Dylan-DPC-zz
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Jun 17, 2020
Improve diagnostics for `let x += 1` Fixes(?) rust-lang#66736 The code responsible for the `E0404` errors is [here](https://github.com/rust-lang/rust/blob/master/src/librustc_parse/parser/ty.rs#L399-L424) which I don't think can be easily modified to prevent emitting an error in one specific case. Because of this I couldn't get rid of `E0404` and instead added `E0067` along with a help message which will fix the problem. r? @estebank
Dylan-DPC-zz
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Jun 17, 2020
Improve diagnostics for `let x += 1` Fixes(?) rust-lang#66736 The code responsible for the `E0404` errors is [here](https://github.com/rust-lang/rust/blob/master/src/librustc_parse/parser/ty.rs#L399-L424) which I don't think can be easily modified to prevent emitting an error in one specific case. Because of this I couldn't get rid of `E0404` and instead added `E0067` along with a help message which will fix the problem. r? @estebank
tesuji
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Jun 17, 2020
| _ => self.eat(&token::Eq), | ||
| }; | ||
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| Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None }) |
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Suggested change
| Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None }) | |
| if eq_consumed || eq_optional { self.parse_expr().map(Some) } else { Ok(None) } |
tmandry
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Jun 17, 2020
Improve diagnostics for `let x += 1` Fixes(?) rust-lang#66736 The code responsible for the `E0404` errors is [here](https://github.com/rust-lang/rust/blob/master/src/librustc_parse/parser/ty.rs#L399-L424) which I don't think can be easily modified to prevent emitting an error in one specific case. Because of this I couldn't get rid of `E0404` and instead added `E0067` along with a help message which will fix the problem. r? @estebank
Manishearth
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Jun 18, 2020
Improve diagnostics for `let x += 1` Fixes(?) rust-lang#66736 The code responsible for the `E0404` errors is [here](https://github.com/rust-lang/rust/blob/master/src/librustc_parse/parser/ty.rs#L399-L424) which I don't think can be easily modified to prevent emitting an error in one specific case. Because of this I couldn't get rid of `E0404` and instead added `E0067` along with a help message which will fix the problem. r? @estebank
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Jun 19, 2020
…arth Rollup of 17 pull requests Successful merges: - rust-lang#70551 (Make all uses of ty::Error delay a span bug) - rust-lang#71338 (Expand "recursive opaque type" diagnostic) - rust-lang#71976 (Improve diagnostics for `let x += 1`) - rust-lang#72279 (add raw_ref macros) - rust-lang#72628 (Add tests for 'impl Default for [T; N]') - rust-lang#72804 (Further tweak lifetime errors involving `dyn Trait` and `impl Trait` in return position) - rust-lang#72814 (remove visit_terminator_kind from MIR visitor) - rust-lang#72836 (Complete the std::time documentation to warn about the inconsistencies between OS) - rust-lang#72968 (Only highlight doc search results via mouseover if mouse has moved) - rust-lang#73034 (Export `#[inline]` fns with extern indicators) - rust-lang#73315 (Clean up some weird command strings) - rust-lang#73320 (Make new type param suggestion more targetted) - rust-lang#73361 (Tweak "non-primitive cast" error) - rust-lang#73425 (Mention functions pointers in the documentation) - rust-lang#73428 (Fix typo in librustc_ast docs) - rust-lang#73447 (Improve document for `Result::as_deref(_mut)` methods) - rust-lang#73476 (Added tooltip for should_panic code examples) Failed merges: r? @ghost
Lonami
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Jun 24, 2020
| let _ = a; | ||
| let b += 1; //~ ERROR can't reassign to an uninitialized variable | ||
| let _ = b; | ||
| let c *= 1; //~ ERROR can't reassign to an uninitialized variable |
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What happens if it's already initialized?
let d = 1;
let d += 2;There was a problem hiding this comment.
error: can't reassign to an uninitialized variable
--> src/main.rs:3:7
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3 | let d += 2;
| ^^ help: initialize the variable
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Yes, but one could argue I just initialized it above (same name).
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Maybe change the wording for initialized variables? Can't reassign to initialized variable, it should only be either let d = 2 or d += 2, can we even use let with +=?
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+= cannot be used with let to my knowledge. Perhaps we could radically change the wording approach:
note: only `=` can be used in `let` bindings
help: change this `+=` for `=`
help: remove `let` (if it was initialized before)
Dylan-DPC-zz
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Mar 14, 2021
…avidtwco Improve the wording for the `can't reassign` error Follow-up for rust-lang#71976 (comment). Fixes rust-lang#66736
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Mar 14, 2021
…idtwco Improve the wording for the `can't reassign` error Follow-up for rust-lang#71976 (comment). Fixes rust-lang#66736
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Fixes(?) #66736
The code responsible for the
E0404errors is here which I don't think can be easily modified to prevent emitting an error in one specific case. Because of this I couldn't get rid ofE0404and instead addedE0067along with a help message which will fix the problem.r? @estebank