[Move] #[allow(unused_mut_ref)] does not work properly with lambda functions

[admin-aftermath]

If you mark an argument of a macro lambda function as mutable, but never use it mutably, you will receive the following warning:

Mutable reference is never used mutably, consider switching to an immutable reference '&' instead. This warning can be suppressed with '#[allow(unused_mut_ref)]' applied to the 'module' or module member ('const', 'fun', or 'struct').

When the latter option is done, it doesn't not suppress the warning. For example,

[github-actions]

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[cgswords]

Hi, thank you for the bug report. Can you please provide a sample call / value for $f? My minimal example does not reproduce this error.