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should_impl_trait - ignore methods with lifetime params #5725

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merged 6 commits into from
Aug 16, 2020

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@tnielens tnielens commented Jun 16, 2020

Fixes: #5617

changelog: don't lint should_implement_trait when an Iterator::next case has explicit parameters

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r? @yaahc

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties label Jun 16, 2020
yaahc
yaahc previously requested changes Jun 16, 2020
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Looks good, just needs a changelog: added to the body of the PR

cc @flip1995

clippy_lints/src/methods/mod.rs Outdated Show resolved Hide resolved
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ghost commented Jun 17, 2020

Does this check handle elided lifetimes?

    pub fn next<'b>(&'b mut self) -> Option<&'b mut T> {
        unimplemented!();
    }

is equivalent to

    pub fn next(&mut self) -> Option<&mut T> {
        unimplemented!();
    }

but will the second form be linted?

Also, I think this check should only apply to the next method specifally.
A method like

    fn eq<'a, 'b>(&'a self, other: &'b Self) -> bool { unimplemented!() }

can be moved to a PartialEq implementation regardless of lifetimes.

@yaahc yaahc added S-waiting-on-author Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status) and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties labels Jun 17, 2020
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The short-circuiting upon lifetime params is a little naive indeed.

I'll start by adding a test case for each trait method in the lint method list and see from there.

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I've added a test case for each checked method. All cases can be written with lifetime elision. If the user persists in writing explicitly lifetime params, he'll first hit the needles_lifetime lint.

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tnielens commented Jun 19, 2020

Does this check handle elided lifetimes?

It's a check done at hir level. Elided liftetimes are absent from the function declaration struct it seems.

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Three approaches to wrap this pr up:

  • This is a rare case, the user can explicitly allow the lint. Revert the lifetime filtering and keep test cases.
  • All trait methods implementations can be written with lifetime elision. The user is unlikely to write lifetimes explicitly down. If it does so he might have a good reason (like for the Iterator::next example, rust hasn't shipped GATs, the Iterator trait cannot model streaming iterators). Clippy should not lint these more complex cases as there is a risk of false positive. The pr is good so.
  • Iterator::next is a special case. Filter on explicit lifetimes only for that one. Other cases remain unchanged.

Any you'd agree with?

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  • Iterator::next is a special case. Filter on explicit lifetimes only for that one. Other cases remain unchanged.

Until now, I only remember issues complaining about the next method. To future prove this fix, you could add another field to the TRAIT_METHODS list, that specifies if the lint should be skipped, if there are lifetimes defined.

Extra points if you write a doc-comment for this list of tuples, what each field stands for (please :) ).


Sorry for ignoring this PR for so long, I didn't realize, that I was CCed.

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@tnielens tnielens force-pushed the should-impl-trait branch 3 times, most recently from 88e5dda to f300fcd Compare July 29, 2020 23:46
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I changed the TRAIT_METHODS items from a large tuple to a new struct. That clarifies a bit the role of each field.

@tnielens tnielens force-pushed the should-impl-trait branch 3 times, most recently from 3129220 to d8f898b Compare July 30, 2020 00:08
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tnielens commented Jul 30, 2020

Do you mind if I introduce an exclusion rule for the stderr line count limit?

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Please don't use double underscores for test names. If you want to structure the tests better rather put them in their own directory.

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Can you put the tests for this lint in its own directory? There's still an issue with undefined structs in the test cases.

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Please remove the tests/ui/should_impl_trait/corner_cases.stderr file and this should be good to go.

@flip1995 flip1995 added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties and removed S-waiting-on-author Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status) labels Jul 31, 2020
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flip1995 commented Aug 4, 2020

@bors r=flip1995,yaahc rollup=always

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bors commented Aug 4, 2020

📌 Commit 108032e has been approved by flip1995,yaahc

flip1995 added a commit to flip1995/rust-clippy that referenced this pull request Aug 4, 2020
…95,yaahc

should_impl_trait - ignore methods with lifetime params

Fixes: rust-lang#5617

changelog: don't lint should_implement_trait when an `Iterator::next` case has explicit parameters
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bors commented Aug 4, 2020

⌛ Testing commit 108032e with merge 9df7e19...

bors added a commit that referenced this pull request Aug 4, 2020
should_impl_trait - ignore methods with lifetime params

Fixes: #5617

changelog: don't lint should_implement_trait when an `Iterator::next` case has explicit parameters
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bors commented Aug 4, 2020

💔 Test failed - checks-action_test

bors added a commit that referenced this pull request Aug 4, 2020
Rollup of 6 pull requests

Successful merges:

 - #5725 (should_impl_trait - ignore methods with lifetime params)
 - #5837 (needless_collect: catch x: Vec<_> = iter.collect(); x.into_iter() ...)
 - #5846 (Handle mapping to Option in `map_flatten` lint)
 - #5848 (Add derive_ord_xor_partial_ord lint)
 - #5852 (Add lint for duplicate methods of trait bounds)
 - #5856 (Remove old Symbol reexport)

Failed merges:

r? @ghost

changelog: rollup
bors added a commit that referenced this pull request Aug 4, 2020
Rollup of 6 pull requests

Successful merges:

 - #5725 (should_impl_trait - ignore methods with lifetime params)
 - #5837 (needless_collect: catch x: Vec<_> = iter.collect(); x.into_iter() ...)
 - #5846 (Handle mapping to Option in `map_flatten` lint)
 - #5848 (Add derive_ord_xor_partial_ord lint)
 - #5852 (Add lint for duplicate methods of trait bounds)
 - #5856 (Remove old Symbol reexport)

Failed merges:

r? @ghost

changelog: rollup
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flip1995 commented Aug 4, 2020

Please fix the dogfood errors.

@flip1995 flip1995 added S-waiting-on-author Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status) and removed S-waiting-on-bors Status: The marked PR was approved and is only waiting bors labels Aug 4, 2020
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Thanks! Waiting for rustup

@flip1995 flip1995 added S-waiting-on-bors Status: The marked PR was approved and is only waiting bors and removed S-waiting-on-author Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status) labels Aug 12, 2020
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@bors r+

Thanks!

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bors commented Aug 16, 2020

📌 Commit f9ba829 has been approved by flip1995

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bors commented Aug 16, 2020

⌛ Testing commit f9ba829 with merge 3bd9889...

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bors commented Aug 16, 2020

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 3bd9889 to master...

@bors bors merged commit 3bd9889 into rust-lang:master Aug 16, 2020
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False positive in should_implement_trait
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