Deprecate the Formatter::flags method, fix #46237

[SimonSapin]

This fixes #46237.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @sfackler (or someone else) soon.

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[sfackler]

@alexcrichton this isn't going to mess with any of the fmt impl's internals, right?

[SimonSapin]

git grep '\.flags()' (excluding submodules) shows zero matches. I’m counting on CI to tell us if something else needs to be adjusted.

[sfackler]

Ah great!

@bors r+

[bors]

📌 Commit 5e11c8f has been approved by sfackler

[sfackler]

cc @rust-lang/libs

[dtolnay]

LGTM

[bors]

⌛ Testing commit 5e11c8f with merge 8270faf...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: sfackler
Pushing 8270faf to master...