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Add useless_anonymous_reexport lint #109003

Merged
merged 3 commits into from
Mar 19, 2023
Merged

Add useless_anonymous_reexport lint #109003

merged 3 commits into from
Mar 19, 2023

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GuillaumeGomez
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@GuillaumeGomez GuillaumeGomez commented Mar 10, 2023 •
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This is a follow-up of #108936. We once again show all anonymous re-exports in rustdoc, however we also wanted to add a lint to let users know that it very likely doesn't have the effect they think it has.

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rustbot commented Mar 10, 2023

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 10, 2023
@GuillaumeGomez GuillaumeGomez force-pushed the useless-anonymous-reexport-lint branch from fd77cfe to 0884258 Compare March 10, 2023 22:17
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This lint would probably be easier to implement in rustc_resolve::check_unused, which is the place where we lint unused imports already.

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@cjgillot It doesn't seem that they are considered as potentially unused since they don't appear in Resolver::potentially_unused_imports. Are you suggesting that I should add them directly into this Resolver and modify check_unused.rs heavily?

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UnusedImportCheckVisitor is responsible for populating the list of unused imports, beyond potentially_unused_imports. The check for the visibility of the use item is in visit_item.

potentially_unused_imports is a actually a small list with only extern crate and #[macro_use].

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So unless I missed something, UnusedImportCheckVisitor is using the EarlyLintPass. However, I need to have access to TyCtxt to compute the actual visibility of the re-export, so I don't think it's a good match. Also, in here we want to warn for useless re-exports, not about unused imports.

@GuillaumeGomez GuillaumeGomez force-pushed the useless-anonymous-reexport-lint branch from 0884258 to 6d2b775 Compare March 11, 2023 10:33
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Greatly improved the detection of re-export following suggestion.

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bors commented Mar 12, 2023

☔ The latest upstream changes (presumably #108682) made this pull request unmergeable. Please resolve the merge conflicts.

@GuillaumeGomez GuillaumeGomez force-pushed the useless-anonymous-reexport-lint branch from 6d2b775 to fcadc03 Compare March 12, 2023 14:12
cjgillot
cjgillot reviewed Mar 12, 2023
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tests/ui/lint/anonymous-reexport.rs
pub use self::my_mod::Foo as _;
pub use self::my_mod::TyFoo as _;
pub use self::my_mod::Bar as _; //~ ERROR
pub use self::my_mod::TyBar as _; //~ ERROR
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Should we suggest to remove it?
Could you add tests with nested uses:

pub use self::my_mod::{Bar as _};
pub use self::my_mod::{Bar as _, Foo as _};
pub use self::my_mod::{Bar as _, TyBar as _};

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Adding tests with nested uses.

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Should we suggest to remove it?

I'm not sure. If you prefer I add this suggestion, I can.

compiler/rustc_lint/messages.ftl Outdated Show resolved Hide resolved
@GuillaumeGomez GuillaumeGomez force-pushed the useless-anonymous-reexport-lint branch from e89c425 to 9272b69 Compare March 12, 2023 15:33
@GuillaumeGomez GuillaumeGomez force-pushed the useless-anonymous-reexport-lint branch from 9272b69 to 7b0fa08 Compare March 12, 2023 15:39
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Added what was missing.

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@bors r+

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bors commented Mar 18, 2023

📌 Commit 7b0fa08 has been approved by cjgillot

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 18, 2023
@Dylan-DPC Dylan-DPC mentioned this pull request Mar 19, 2023
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 19, 2023
@bors
Auto merge of rust-lang#109346 - Dylan-DPC:rollup-vszi5bn, r=Dylan-DPC
8826b68 
Rollup of 10 pull requests

Successful merges:

 - rust-lang#104100 (Allow using `Range` as an `Iterator` in const contexts. )
 - rust-lang#105793 (Add note for mismatched types because of circular dependencies)
 - rust-lang#108798 (move default backtrace setting to sys)
 - rust-lang#108829 (Use Edition 2021 :pat in matches macro)
 - rust-lang#108973 (Beautify pin! docs)
 - rust-lang#109003 (Add `useless_anonymous_reexport` lint)
 - rust-lang#109022 (read_buf_exact: on error, all read bytes are appended to the buffer)
 - rust-lang#109212 (fix: don't suggest similar method when unstable)
 - rust-lang#109243 (The name of NativeLib will be presented)
 - rust-lang#109324 (Implement FixedSizeEncoding for UnusedGenericParams.)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 462e7e7 into rust-lang:master Mar 19, 2023
@rustbot rustbot added this to the 1.70.0 milestone Mar 19, 2023
@GuillaumeGomez GuillaumeGomez deleted the useless-anonymous-reexport-lint branch March 19, 2023 19:10
petrochenkov
petrochenkov reviewed Mar 21, 2023
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compiler/rustc_lint/src/reexports.rs
if let ItemKind::Use(path, kind) = item.kind &&
!matches!(kind, UseKind::Glob) &&
item.ident.name == kw::Underscore &&
// We only want re-exports. If it's just a `use X;`, then we ignore it.
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Why is this important?
A private use some::Struct as _ is equally useless.

The original suggestion from @cjgillot to use UnusedImportCheckVisitor and report this early looks like the right direction.

This case doesn't need a separate lint, existing unused_imports should be perfectly fine.

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This lint multiplies entities without necessity, I think it is better to remove it before it hit stable.

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(I noticed this while auditing uses of imports in HIR for #109176 (comment).)

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This lint multiplies entities without necessity

How so?

I think it is better to remove it before it hit stable.

Replaced, sure. Otherwise please don't remove it altogether.

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How so?

Is there any scenario when you'd want to enable/deny reporting this case specifically, separately from other unused imports? I don't think so.

Replaced, sure. Otherwise please don't remove it altogether.

Yeah, I mean merge into unused_imports, not remove outright.

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(Also, the lint name doesn't match conventions.)

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Ok I see. Well, since both you and cjgillot think so, I'll move it into unused imports.

@GuillaumeGomez GuillaumeGomez mentioned this pull request Mar 22, 2023
Merged
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 23, 2023
@matthiaskrgr
Rollup merge of rust-lang#109487 - GuillaumeGomez:move-useless-reexpo…
3961ef5 
…rt-check, r=petrochenkov

Move useless_anynous_reexport lint into unused_imports

As mentioned in rust-lang#109003, this check should have been merged with `unused_imports` in the start.

r? `@petrochenkov`
RalfJung pushed a commit to RalfJung/miri that referenced this pull request Mar 24, 2023
@matthiaskrgr
Rollup merge of #109487 - GuillaumeGomez:move-useless-reexport-check,…
b5a04bf 
… r=petrochenkov

Move useless_anynous_reexport lint into unused_imports

As mentioned in rust-lang/rust#109003, this check should have been merged with `unused_imports` in the start.

r? `@petrochenkov`
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@GuillaumeGomez @rustbot @cjgillot @bors @petrochenkov @fmease @TaKO8Ki