Remove MutexGuard::map, as it is not safe in combination with Condvar.

[reem]

It could return in the future if it returned a different guard type, which
could not be used with Condvar, otherwise it is unsafe as another thread
can invalidate an "inner" reference during a Condvar::wait.

cc #27746

[rust-highfive]

r? @aturon

(rust_highfive has picked a reviewer for you, use r? to override)

[reem]

r? @alexcrichton

[huonw]

Whoops, nice catch! cc @rust-lang/libs

[sfackler]

Bummer. I wonder if we can leave a comment in somewhere noting that this is intentionally missing so it doesn't get added back later by someone.

[alexcrichton]

As this was only merge two days ago, I'm gonna go ahead an r+ this. We should probably continue discussion on the cell_extras stabilization issue, but nice catch @reem!

@bors: r+ a61983f

[bors]

⌛ Testing commit a61983f with merge 915fa2a...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt

[huonw]

Hm, shouldn't this have been #[deprecated] before removal?

[sfackler]

The feature only existed for like 2 days and had serious soundness issues.
A deprecation period seems like a bit much personally.
On Sat, Feb 6, 2016 at 2:55 PM Huon Wilson notifications@github.com wrote:

Hm, shouldn't this have been #[deprecated] before removal?

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#31428 (comment).

[huonw]

Oh, sorry, yeah. For some reason, I had in my mind that Mutex had these before, and it was RwLock that got these new APIs (despite me suggesting that the original PR be expanded to include this...).