class RuboCop::Cop::VariableForce::Reference

This class represents each reference of a variable.

def explicit?

but it can be considered used implicitly by the `super` or `binding`.
In these cases, the variable `foo` is not explicitly referenced,

end
do_something(binding)
def some_method(foo)

Another case is `binding`:

end
super
def some_method(foo)

There's an implicit variable reference by the zero-arity `super`: 
def explicit?
  ![ZERO_ARITY_SUPER_TYPE, SEND_TYPE].include?(@node.type)
end

def initialize(node, scope) 

def initialize(node, scope)
  unless VARIABLE_REFERENCE_TYPES.include?(node.type)
    raise ArgumentError,
          "Node type must be any of #{VARIABLE_REFERENCE_TYPES}, " \
          "passed #{node.type}"
  end
  @node = node
  @scope = scope
end