Rework interior mutability detection

[Alexendoo]

Replaces the existing interior mutability detection, the two main changes being

• It now follows references/pointers e.g. struct S(&Cell)
  • mutable_key_type ignores pointers as it did before
• The ignore_interior_mutability config now applies to types containing the ignored type, e.g. http::HeaderName

Fixes #7752
Fixes #9776
Fixes #9801

changelog: [mutable_key_type], [declare_interior_mutable_const]: now considers types that have references to interior mutable types as interior mutable

[rustbot]

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[llogiq]

mutable_key_type ignores pointers as it did before

Isn't that a regression? There's a test case with a Result<&mut _, ()> key which appears to no longer be linted.

[Alexendoo]

Forgot to mention that, the old version considered any &mut reference interior mutable but that was incorrect. The examples of &mut usize/Result<&mut usize, ()> have no interior mutability

[llogiq]

For the mutable_key_type the problem is any mutability, not just interior mutability, so having a &mut T as a key should be linted nonetheless, as the &mut could be used to mutate the referenced value, which would violate the contract of HashMap and/or BTreeMap.

[Alexendoo]

You can only get & access to a key in place, and you cannot mutate through a &&mut

[llogiq]

True. OK then.

@bors r+

[bors]

📌 Commit f7aef63 has been approved by llogiq

It is now in the queue for this repository.

[bors]

⌛ Testing commit f7aef63 with merge 8eafeeb...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 8eafeeb to master...