Currently I can move function/class to namespace by renaming to [namespace_name]::[name], wrapping it in namespace [namespace_name] { ... }, removing [namespace_name]:: where it is not needed like in function constructor names, etc.
I think that it's partially hacky way after all and it can't be easily used to move class out of namespace, and also not adding [namespace_name]:: could be done automatically, so it would be useful if functionality "Move to (Other) Namespace..." would be added.
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