Auto merge of rust-lang#6537 - flip1995:beta, r=ebroto

[beta] Backport of rust-lang#6375 - field_reassign_with_default fix

With the pinned nightly we can test backports to our beta branch now 🎉

cc rust-lang#6515

changelog: beta 1.50: Backport of private fields fix in [`field_reassign_with_default`] lints

Auto merge of rust-lang#6296 - flip1995:rustup, r=flip1995

Rustup

r? `@ghost`

changelog: none

Fix rustup fallout

Auto merge of rust-lang#6044 - rschoon:rc-buffer, r=yaahc

Add `rc_buffer` lint for checking Rc<String> and friends

Fixes rust-lang#2623

This is a bit different from the original PR attempting to implement this type of lint.   Rather than linting against converting into the unwanted types, this PR lints against declaring the unwanted type in a struct or function definition.

I'm reasonably happy with what I have here, although I used the fully qualified type names for the Path and OsString suggestions, and I'm not sure if I should have just used the short versions instead, even if they might not have been declared via use.

Also, I don't know if "buffer type" is the best way to put it or not.  Alternatively I could call it a "growable type" or "growable buffer type", but I was thinking of PathBuf when I started making the lint.

changelog: Add `rc_buffer` lint

Auto merge of rust-lang#5740 - lzutao:unused-unused, r=flip1995

Remove unused allowed unused attributes

changelog: none

Avoid triggering similar names on code from expansion

Auto merge of rust-lang#5652 - rust-lang:flip1995-patch-1, r=yaahc

Fail bors on missing changelog

Bors stopped failed if the changelog was missing. Instead it waited 2h (?) and then timed out.

changelog: none

Auto merge of rust-lang#5652 - rust-lang:flip1995-patch-1, r=yaahc

Fail bors on missing changelog

Bors stopped failed if the changelog was missing. Instead it waited 2h (?) and then timed out.

changelog: none

Auto merge of rust-lang#5652 - rust-lang:flip1995-patch-1, r=yaahc

Fail bors on missing changelog

Bors stopped failed if the changelog was missing. Instead it waited 2h (?) and then timed out.

changelog: none

Merge pull request rust-lang#5584 from Mark-Simulacrum/beta-next

Add hint for collect type