std::unique_lock::operator= (3) Linux Manual Page

std::unique_lock<Mutex>::operator= – std::unique_lock<Mutex>::operator=

Synopsis

unique_lock& operator=( unique_lock&& other );  (since C++11)

Move assignment operator. Replaces the contents with those of other using move semantics.
If prior to the call *this has an associated mutex and has acquired ownership of it, the mutex is unlocked.

Parameters

other – another unique_lock to replace the state with

Return value

*this

Exceptions

Throws nothing