Renamed Arc::try_unique to get_mut

[kvark]

As requested by @kballard in #23844

[rust-highfive]

r? @pcwalton

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[kvark]

Hmm, the doc check gives me these errors, which I don't know how to fix:

---- arc::get_mut_0 stdout ----
        <anon>:6:22: 6:27 error: unresolved import `alloc::arc::Arc`. Did you mean `self::alloc::arc`?
<anon>:6     use alloc::arc::{Arc, get_mut};
                              ^~~~~
<anon>:6:27: 6:32 error: unresolved import `alloc::arc::get_mut`. Did you mean `self::alloc::arc`?
<anon>:6     use alloc::arc::{Arc, get_mut};
                                   ^~~~~

[alexcrichton]

I think you'll want to leave this fn main wrapper as otherwise the extern crate alloc is injected into the wrong scope.

[kvark]

Ok, that explains it ;)

[kvark]

@alexcrichton Please have another look.

[alexcrichton]

@bors: r+ bc1aef3

[bors]

⌛ Testing commit bc1aef3 with merge 6d78aa6...

[bors]

💔 Test failed - auto-mac-64-nopt-t

[Manishearth]

thread '<unnamed>' panicked at 'assertion failed: !p.wait().unwrap().success()', /Users/rustbuild/src/rust-buildbot/slave/auto-mac-64-nopt-t/build/src/libstd/old_io/process.rs:1139
test old_io::process::tests::test_kill ... FAILED

Might be an intermittent?

[kvark]

This error seems unrelated

[Manishearth]

@bors: retry

[Manishearth]

(If it passes this time around, we should file it as an intermittent)

[bors]

⌛ Testing commit bc1aef3 with merge de6742b...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-32-nopt-t, auto-win-32-opt, auto-win-64-nopt-t, auto-win-64-opt