New lint to detect &std::path::MAIN_SEPARATOR.to_string()

[samueltardieu]

Fixes #10480

changelog: [manual_main_separator_str] new lint

[rustbot]

r? @flip1995

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[samueltardieu]

r? @llogiq

[llogiq]

I wonder if we could extend the unnecessary_to_owned lint instead of creating a new one. Also doesn't that work with all &str constants? Why single out MAIN_SEPARATOR?

[samueltardieu]

I wonder if we could extend the unnecessary_to_owned lint instead of creating a new one. Also doesn't that work with all &str constants? Why single out MAIN_SEPARATOR?

It depends on the existence of a &str constant (std::path::MAIN_SEPARATOR_STR) with the same content as the char constant (std::path::MAIN_SEPARATOR).

[llogiq]

Ah, I hadn't noticed the difference here.

I'd like to see some more tests, otherwise this looks good.

[llogiq]

What about lets without a given type? Or other expressions that are not direct local bindings?

[samueltardieu]

I have added new tests, such as initializing a struct field with this expression or passing it as a function argument.

I've also made it work when it is a method receiver (see the test with encode_utf16()), without an explicit &.

[samueltardieu]

@llogiq Is there anything more you'd like me to do on this one?

[bors]

☔ The latest upstream changes (presumably #10481) made this pull request unmergeable. Please resolve the merge conflicts.

[llogiq]

Thank you!

@bors r+

[bors]

📌 Commit ffabdab has been approved by llogiq

It is now in the queue for this repository.

[bors]

⌛ Testing commit ffabdab with merge d3c8442...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing d3c8442 to master...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing d3c8442 to master...