Running rustdoc on code using quote generates false lint warnings for unused_braces #70814
Comments
shepmaster
added
A-lints
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/cc @lcnr |
Hang on, could this be because of the transformation |
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Simplified repro source, both inner blocks are necessary for some reason: pub fn repro() {
{
{
use std;
}
}
} |
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@Nemo157 My guess it's because |
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I just hit a similar error message in rustc (not rustdoc). Unused braces lint with no span or other information. I don't have a reproducer currently, since it's from a big crate and I don't have much to go by. |
Workaround for rust-lang/rust#70814
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I'm getting Is this related or should I create a new issue? Using Nightly 1.44.0 2020-04-16 |
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@grantperry is this inside a macro? |
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@lcnr yes it is. Sounds like it's something you already know about? |
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If you are using a proc macro using |
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I tried to fix this by checking if the surrounding expression comes from an expansion, but this didn't actually fix this. 🤔 @matklad do you have an idea/can this be fixed in quote? My approach stilled warned for the following, which seems to be the same issue afaict. rust/src/librustc_macros/src/query.rs Lines 362 to 370 in 4ca5fd2 |
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I don't think I am familiar with the code in question @lcnr |
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Sorry, mb 😓 meant @dtolnay as he is the owner of |
dtolnay
added
the
regression-from-stable-to-nightly
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Labeling regression-from-stable-to-nightly. I would consider accepting a workaround in quote if somebody who is not me sends a PR and it is a very simple fix, but really this needs to be fixed in rustdoc / rustc. |
jonas-schievink
added
the
I-prioritize
LeSeulArtichaut
added
the
E-needs-bisection
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Let’s try to find the cause of the regression |
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Error: Only Rust team members can ping teams. Please let |
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@rustbot ping cleanup |
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Hey Cleanup Crew ICE-breakers! This bug has been identified as a good cc @AminArria @chrissimpkins @contrun @DutchGhost @elshize @ethanboxx @h-michael @HallerPatrick @hdhoang @hellow554 @imtsuki @jakevossen5 @kanru @KarlK90 @LeSeulArtichaut @MAdrianMattocks @matheus-consoli @mental32 @nmccarty @Noah-Kennedy @pard68 @PeytonT @pierreN @Redblueflame @RobbieClarken @RobertoSnap @robjtede @SarthakSingh31 @senden9 @shekohex @sinato @spastorino @turboladen @woshilapin @yerke |
rustbot
added
the
ICEBreaker-Cleanup-Crew
Quick and dirty fix of the unused_braces lint cc @lcnr Adresses rust-lang#70814 This at least prevents lint output, if no span is available. Even though this also prevents the `unused_parens` lint from emitting, when the `DUMMY_SP` is used there, but I think that should be ok, since error messages without a span are quite useless anyway. Clippy CI is currently blocked on this bug. If this quick and dirty fix should be rejected, I could try to work around this in Clippy. r? @shepmaster
* Remove serde-derive dependency * Fix clippy * Fix nightly clippy * Remove some extern crate * 0.5.0 is unreleased! * Tweak deny warnings - According to https://users.rust-lang.org/t/how-to-fail-a-build-with-warnings/2687/7 * Check in Cargo.lock for more reproducible tests * Tighten ring dependency version requirement * Fix url crate to 2.1.0 - Pending regression * Fix doctest * Workaround regression cf. rust-lang/rust#70814 * Fix format * Rearrange steps to check fmt first * Relax url and exclude 2.1.1 * Fix tests
Mark-Simulacrum
added
regression-from-stable-to-stable
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I think e42337b a fixed this issue. It didn't add a test though so perhaps mark as needs-test? |
Workaround for rust-lang/rust#70814
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@osa1 it didn't : |
The modified lint correctly provide a span in its suggestion.
```shell
error: unnecessary braces around block return value
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:9:5
|
LL | / {
LL | | {
| |________^
LL | use std;
LL | }
| __________^
LL | | }
| |_____^
|
note: the lint level is defined here
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:6:9
|
LL | #![deny(unused_braces)]
| ^^^^^^^^^^^^^
help: remove these braces
|
LL ~ {
LL | use std;
LL ~ }
|
```
It is unclear to which extend rust-lang#70814 is still an issue, as the inital MCVE does not trigger the lint on stable
either,[rust playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=b6ff31a449c0b73a08daac8ee43b1fa6)
Currently the lint faces a severe limitation: since it only catches single-line block, running rustfmt beforehand will remove all occurences of it, because it breaks them into multiline blocks.
We do not check match `Arm` for two reasons:
- In case it does not use commas to separate arms, removing the block would result in a compilation error
Example:
```
match expr {
pat => {()}
_ => println!("foo")
}
```
- Do not lint multiline match arms used for formatting reasons
```
match expr {
pat => {
somewhat_long_expression
}
// ...
}
Delete `unused-braces-lint` test
The modified lint correctly provide a span in its suggestion.
```shell
error: unnecessary braces around block return value
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:9:5
|
LL | / {
LL | | {
| |________^
LL | use std;
LL | }
| __________^
LL | | }
| |_____^
|
note: the lint level is defined here
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:6:9
|
LL | #![deny(unused_braces)]
| ^^^^^^^^^^^^^
help: remove these braces
|
LL ~ {
LL | use std;
LL ~ }
|
```
It is unclear to which extend rust-lang#70814 is still an issue, as the inital MCVE does not trigger the lint on stable
either,[rust playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=b6ff31a449c0b73a08daac8ee43b1fa6)
Fix code with expanded `unused_braces` lint
Also allow `unused_braces` on tests
Currently the lint faces a severe limitation: since it only catches single-line block, running rustfmt beforehand will remove all occurences of it, because it breaks them into multiline blocks.
We do not check match `Arm` for two reasons:
- In case it does not use commas to separate arms, removing the block would result in a compilation error
Example:
```
match expr {
pat => {()}
_ => println!("foo")
}
```
- Do not lint multiline match arms used for formatting reasons
```
match expr {
pat => {
somewhat_long_expression
}
// ...
}
```
Delete `unused-braces-lint` test
The modified lint correctly provide a span in its suggestion.
```shell
error: unnecessary braces around block return value
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:9:5
|
LL | / {
LL | | {
| |________^
LL | use std;
LL | }
| __________^
LL | | }
| |_____^
|
note: the lint level is defined here
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:6:9
|
LL | #![deny(unused_braces)]
| ^^^^^^^^^^^^^
help: remove these braces
|
LL ~ {
LL | use std;
LL ~ }
|
```
It is unclear to which extend rust-lang#70814 is still an issue, as the inital MCVE does not trigger the lint on stable either,[rust playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=b6ff31a449c0b73a08daac8ee43b1fa6)
Fix code with expanded `unused_braces` lint
Also allow `unused_braces` on tests
Mute `unused_braces` on `match_ast!`
Currently the lint faces a severe limitation: since it only catches single-line block, running rustfmt beforehand will remove all occurences of it, because it breaks them into multiline blocks.
We do not check match `Arm` for two reasons:
- In case it does not use commas to separate arms, removing the block would result in a compilation error
Example:
```
match expr {
pat => {()}
_ => println!("foo")
}
```
- Do not lint multiline match arms used for formatting reasons
```
match expr {
pat => {
somewhat_long_expression
}
// ...
}
```
Delete `unused-braces-lint` test
The modified lint correctly provide a span in its suggestion.
```shell
error: unnecessary braces around block return value
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:9:5
|
LL | / {
LL | | {
| |________^
LL | use std;
LL | }
| __________^
LL | | }
| |_____^
|
note: the lint level is defined here
--> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:6:9
|
LL | #![deny(unused_braces)]
| ^^^^^^^^^^^^^
help: remove these braces
|
LL ~ {
LL | use std;
LL ~ }
|
```
It is unclear to which extend rust-lang#70814 is still an issue, as the inital MCVE does not trigger the lint on stable either,[rust playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=b6ff31a449c0b73a08daac8ee43b1fa6)
Fix code with expanded `unused_braces` lint
Also allow `unused_braces` on tests
Mute `unused_braces` on `match_ast!`
I tried this code:
I think this is a basic and common usage of the quote crate.
I expected to see no warnings:
Instead, warnings are generated (and my CI build fails due to the
deny):Note that the warning only appears when running rustdoc.
Meta
rustc +nightly-2020-04-04 --version --verbose:The text was updated successfully, but these errors were encountered: