Lock is not immediately released after acquiring value in function argument

[pinkiebell]

Version
v1.21.1

Platform
Linux 5.18.19 #1 SMP
aarch64 GNU/Linux

Description

Link to reproduce

There is a deadlock in the above example that only happens if we acquire a lock as part of a function call/arguments.
The body of the function will in turn acquire a lock again and deadlocks in the above example.

As a user I expect that the lock will be released after the value was loaded, like in local let bindings. But this is not the case here.

[sfackler]

This is how the Rust language works - temporary values are destroyed upon the completion of the statement that created them, so in this case the guard returned by the lock call will remain alive until the call to func completes.

[pinkiebell]

Thanks for the fast answer. I wasn't sure about how rust determines how that should work.
Is that documented somewhere?

Btw, Feel free to close this issue 👍

[sfackler]

https://doc.rust-lang.org/reference/expressions.html#temporaries