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No unnecessary parentheses warning in types #64169

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oli-cosmian opened this issue Sep 5, 2019 · 5 comments · Fixed by #65112
Closed

No unnecessary parentheses warning in types #64169

oli-cosmian opened this issue Sep 5, 2019 · 5 comments · Fixed by #65112
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A-lint Area: Lints (warnings about flaws in source code) such as unused_mut. C-enhancement Category: An issue proposing an enhancement or a PR with one. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. E-help-wanted Call for participation: Help is requested to fix this issue. E-mentor Call for participation: This issue has a mentor. Use #t-compiler/help on Zulip for discussion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@oli-cosmian
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oli-cosmian commented Sep 5, 2019 •
edited by rustbot
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Types can be parenthesized, which is useful for e.g. dyn (Foo + 'static) or similar, but often these parentheses are unnecessary. Whenever a trivial type is parenthesized the compiler should suggest to remove the parentheses

pub fn foo() -> (i32) { 42 }

(Playground)

Errors:

   Compiling playground v0.0.1 (/playground)
    Finished dev [unoptimized + debuginfo] target(s) in 0.64s

This issue has been assigned to @sjmann via this comment.
@csmoe csmoe added the A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix`. label Sep 5, 2019
@Centril Centril added A-lint Area: Lints (warnings about flaws in source code) such as unused_mut. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. C-enhancement Category: An issue proposing an enhancement or a PR with one. and removed A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix`. labels Sep 5, 2019
@Centril
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Centril commented Sep 5, 2019

I think this falls under the spirit of the unused_parens lint and the language team does not need to approve this as I think it is obviously right.

Mentoring instructions:

See #64128 for a PR that recently changed the semantics of the unused_parens lint. You'll want to introduce fn check_ty and then match on the ty.node: TyKind while keeping in mind to avoid suggesting the removal of parenthesis that would result in a compilation error.

@Centril Centril added E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. E-help-wanted Call for participation: Help is requested to fix this issue. E-mentor Call for participation: This issue has a mentor. Use #t-compiler/help on Zulip for discussion. labels Sep 5, 2019
@sjmann
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sjmann commented Sep 5, 2019

Would it be ok if I try to tackle this as a first time contributor? Seems like a nice starter issue.

@Centril
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Centril commented Sep 5, 2019

@sjmann sure, go right ahead!

@rustbot assign @sjmann

@rustbot rustbot self-assigned this Sep 5, 2019
@ijt
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ijt commented Sep 30, 2019

@sjmann, are you still working on this?

@jack-t
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jack-t commented Oct 4, 2019

Hi —

I've got what I believe is a working PR over here. There's a kind of chicken-and-egg problem with building core with the lint, though. I'm not totally sure how to solve it.

Thanks!

@jack-t jack-t mentioned this issue Oct 25, 2019
Merged
tmandry added a commit to tmandry/rust that referenced this issue Oct 30, 2019
@tmandry
Rollup merge of rust-lang#65112 - jack-t:type-parens-lint, r=varkor
da5d7a7 
Add lint and tests for unnecessary parens around types

This is my first contribution to the Rust project, so I apologize if I'm not doing things the right way.

The PR fixes rust-lang#64169. It adds a lint and tests for unnecessary parentheses around types. I've run `tidy` and `rustfmt` — I'm not totally sure it worked right, though — and I've tried to follow the instructions linked in the readme.

I tried to think through all the variants of `ast::TyKind` to find exceptions to this lint, and I could only find the one mentioned in the original issue, which concerns types with `dyn`. I'm not a Rust expert, thought, so I may well be missing something.

There's also a problem with getting this to build. The new lint catches several things in the, e.g., `core`. Because `x.py` seems to build with an equivalent of `-Werror`, what would have been warnings cause the build to break. I got it to build and the tests to pass with `--warnings warn` on my `x.py build` and `x.py test` commands.
Centril added a commit to Centril/rust that referenced this issue Oct 30, 2019
@Centril
Rollup merge of rust-lang#65112 - jack-t:type-parens-lint, r=varkor
5272df0 
Add lint and tests for unnecessary parens around types

This is my first contribution to the Rust project, so I apologize if I'm not doing things the right way.

The PR fixes rust-lang#64169. It adds a lint and tests for unnecessary parentheses around types. I've run `tidy` and `rustfmt` — I'm not totally sure it worked right, though — and I've tried to follow the instructions linked in the readme.

I tried to think through all the variants of `ast::TyKind` to find exceptions to this lint, and I could only find the one mentioned in the original issue, which concerns types with `dyn`. I'm not a Rust expert, thought, so I may well be missing something.

There's also a problem with getting this to build. The new lint catches several things in the, e.g., `core`. Because `x.py` seems to build with an equivalent of `-Werror`, what would have been warnings cause the build to break. I got it to build and the tests to pass with `--warnings warn` on my `x.py build` and `x.py test` commands.
tmandry added a commit to tmandry/rust that referenced this issue Oct 31, 2019
@tmandry
Rollup merge of rust-lang#65112 - jack-t:type-parens-lint, r=varkor
255a713 
Add lint and tests for unnecessary parens around types

This is my first contribution to the Rust project, so I apologize if I'm not doing things the right way.

The PR fixes rust-lang#64169. It adds a lint and tests for unnecessary parentheses around types. I've run `tidy` and `rustfmt` — I'm not totally sure it worked right, though — and I've tried to follow the instructions linked in the readme.

I tried to think through all the variants of `ast::TyKind` to find exceptions to this lint, and I could only find the one mentioned in the original issue, which concerns types with `dyn`. I'm not a Rust expert, thought, so I may well be missing something.

There's also a problem with getting this to build. The new lint catches several things in the, e.g., `core`. Because `x.py` seems to build with an equivalent of `-Werror`, what would have been warnings cause the build to break. I got it to build and the tests to pass with `--warnings warn` on my `x.py build` and `x.py test` commands.
@bors bors closed this as completed in 9175247 Nov 1, 2019
@viniciusd viniciusd mentioned this issue Nov 10, 2019
Merged
LukeMathWalker pushed a commit to rust-ndarray/ndarray that referenced this issue Nov 11, 2019
@viniciusd @LukeMathWalker
Remove unnecessary parens around types (#750)
3b9a8b6 
[LINT]: Address rust-lang/rust#64169
This was referenced Jan 4, 2020
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@davidMcneil davidMcneil mentioned this issue Jan 13, 2020
Merged
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A-lint Area: Lints (warnings about flaws in source code) such as unused_mut. C-enhancement Category: An issue proposing an enhancement or a PR with one. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. E-help-wanted Call for participation: Help is requested to fix this issue. E-mentor Call for participation: This issue has a mentor. Use #t-compiler/help on Zulip for discussion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Add lint and tests for unnecessary parens around types jack-t/rust
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@ijt @Centril @jack-t @sjmann @csmoe @rustbot @oli-cosmian