New in Rust 1.65, break from labeled blocks

[zw963]

Check the following code basically meet same issue with you.

Error: can't use variable name 'some_name' inside assignment to variable 'some_name'

It works! def keys keys = [] of String _keys = uninitialized (Array(String), Node?) -> _keys = ->(arr : Array(String), node : Node?) do return if node.nil? _keys.call(arr, node.left) arr << node.key unless node.key == "" _keys.call(arr, node.right) end _keys.call(keys, @root) keys end Although, i have to use return if node.nil? instead next if node.nil?(in ruby), return return to the _keys.call(...), not the method keys, this is expected,…