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redundant_semicolon and clippy::no_effect tripped without emitting line numbers #63967

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brson opened this issue Aug 28, 2019 · 7 comments · Fixed by #64387
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redundant_semicolon and clippy::no_effect tripped without emitting line numbers #63967

brson opened this issue Aug 28, 2019 · 7 comments · Fixed by #64387
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A-diagnostics Area: Messages for errors, warnings, and lints A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. C-bug Category: This is a bug. E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example P-high High priority regression-from-stable-to-nightly Performance or correctness regression from stable to nightly. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@brson
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brson commented Aug 28, 2019 •
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Using nightly-2019-08-26.

In this TiKV PR we upgraded the compiler. Our tidb_query component tripped the redundant_semicolon lint (and seemingly in turn clippy::no_effect) but rustc/clippy did not tell us the line number.

I couldn't find the code that triggered the lint and had to just allow both for the whole crate.

This issue has been assigned to @nathanwhit via this comment.
@brson
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brson commented Aug 28, 2019 •
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It can be reproduced by cloning that PR, removing the commit that adds the allows, and running make clippy.

This was referenced Aug 28, 2019
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@estebank
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Introduced in #62984. It has caused similar effects in other cases like #63947. CC #63679.

@estebank estebank added A-diagnostics Area: Messages for errors, warnings, and lints A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. C-bug Category: This is a bug. regression-from-stable-to-nightly Performance or correctness regression from stable to nightly. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 28, 2019
@Centril
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Centril commented Sep 5, 2019

cc @nathanwhit @varkor

@nikomatsakis nikomatsakis added the P-high High priority label Sep 5, 2019
@nikomatsakis
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Check-in from compiler team:

Marking as P-high " as this is a regression, though admittedly one without particularly serious consequences (the lint can always be allowed).

@nathanwhit or @varkor, perhaps one of you can take a stab at this? Please claim the issue if you do start working on it (even if it's just to write mentoring instructions).

@nikomatsakis nikomatsakis added the E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example label Sep 5, 2019
@nikomatsakis
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Also, it'd be great to get a minimized version of the problem. Therefore, marking as E-needs-mvce.

@nathanwhit
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I'll work on this. Looking into it a bit, I think it has to do with the lint's interaction with custom proc macro attributes. Specifically, when the item TokenStream passed to the attribute contains a redundant semicolon, every span in the TokenStream is the dummy span. This occurs in both this issue and #63947. It's definitely due to the changes to the parser, but I'm not sure why the changes would have that effect on the spans.
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@rustbot rustbot self-assigned this Sep 5, 2019
@nathanwhit nathanwhit mentioned this issue Sep 11, 2019
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Centril added a commit to Centril/rust that referenced this issue Sep 20, 2019
@Centril
Rollup merge of rust-lang#64387 - nathanwhit:redundant-semi-fix, r=va…
fa5d8ab 
…rkor

Fix redundant semicolon lint interaction with proc macro attributes

Fixes rust-lang#63967 and fixes rust-lang#63947, both of which were caused by the lint's changes to the parser interacting poorly with proc macro attributes and causing span information to be lost

r? @varkor
tmandry added a commit to tmandry/rust that referenced this issue Sep 20, 2019
@tmandry
Rollup merge of rust-lang#64387 - nathanwhit:redundant-semi-fix, r=va…
3754e61 
…rkor

Fix redundant semicolon lint interaction with proc macro attributes

Fixes rust-lang#63967 and fixes rust-lang#63947, both of which were caused by the lint's changes to the parser interacting poorly with proc macro attributes and causing span information to be lost

r? @varkor
tmandry added a commit to tmandry/rust that referenced this issue Sep 20, 2019
@tmandry
Rollup merge of rust-lang#64387 - nathanwhit:redundant-semi-fix, r=va…
736b4ae 
…rkor

Fix redundant semicolon lint interaction with proc macro attributes

Fixes rust-lang#63967 and fixes rust-lang#63947, both of which were caused by the lint's changes to the parser interacting poorly with proc macro attributes and causing span information to be lost

r? @varkor
tmandry added a commit to tmandry/rust that referenced this issue Sep 20, 2019
@tmandry
Rollup merge of rust-lang#64387 - nathanwhit:redundant-semi-fix, r=va…
50df43d 
…rkor

Fix redundant semicolon lint interaction with proc macro attributes

Fixes rust-lang#63967 and fixes rust-lang#63947, both of which were caused by the lint's changes to the parser interacting poorly with proc macro attributes and causing span information to be lost

r? @varkor
tmandry added a commit to tmandry/rust that referenced this issue Sep 20, 2019
@tmandry
Rollup merge of rust-lang#64387 - nathanwhit:redundant-semi-fix, r=va…
1d4f769 
…rkor

Fix redundant semicolon lint interaction with proc macro attributes

Fixes rust-lang#63967 and fixes rust-lang#63947, both of which were caused by the lint's changes to the parser interacting poorly with proc macro attributes and causing span information to be lost

r? @varkor
@pnkfelix
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@nathanwhit just in case you didn't see, the attempt to fix this with your PR #64387 failed the rollup, see #64387 (comment)

@bors bors closed this as completed in 55a3ead Sep 29, 2019
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A-diagnostics Area: Messages for errors, warnings, and lints A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. C-bug Category: This is a bug. E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example P-high High priority regression-from-stable-to-nightly Performance or correctness regression from stable to nightly. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Fix redundant semicolon lint interaction with proc macro attributes nathanwhit/rust
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@brson @nikomatsakis @pnkfelix @Centril @estebank @nathanwhit @rustbot