Destructure args in methods

[camsteffen]

changelog: none

This changes the main pattern in methods to match and destructure the method call args at the same time as the method name, and pass individual arg Exprs to the lint impls.

// before
["expect", ..] => expect::check(cx, expr, arg_lists[0]);
// after
("expect", [arg]) => expect::check(cx, expr, recv, arg);

This makes the code safer since there is no risk of out of bounds args[n] everywhere. There will be no more collecting method_names, arg_lists, method_spans as a separate step - everything comes out of the matches. Chained methods are parsed in a nested match. This makes the code more verbose in some ways, but IMO it is much easier to follow.

Definitely should wait for #6896. Just putting out the idea.

[rust-highfive]

r? @flip1995

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[bors]

☔ The latest upstream changes (presumably #6896) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #6952) made this pull request unmergeable. Please resolve the merge conflicts.

[flip1995]

I kinda disliked the first version of this PR, because I thought it made the logic harder. But I really like this version now. Great work!

[bors]

☔ The latest upstream changes (presumably #6342) made this pull request unmergeable. Please resolve the merge conflicts.

[camsteffen]

@bors r=flip1995

[bors]

📌 Commit 2108387 has been approved by flip1995

[bors]

⌛ Testing commit 2108387 with merge 487c2e8...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 487c2e8 to master...