class RuboCop::Cop::Lint::UselessSetterCall::MethodVariableTracker

the method.
and if a variable contains object passed as argument at the end of
This class tracks variable assignments in a method body

def constructor?(node) 

def constructor?(node)
  return true if node.literal?
  return false unless node.send_type?
  node.method?(:new)
end

def contain_local_object?(variable_name) 

def contain_local_object?(variable_name)
  return @local[variable_name] if @local
  @local = {}
  scan(@body_node) { |node| process_assignment_node(node) }
  @local[variable_name]
end

def initialize(body_node) 

def initialize(body_node)
  @body_node = body_node
  @local = nil
end

def process_assignment(asgn_node, rhs_node) 

def process_assignment(asgn_node, rhs_node)
  lhs_variable_name, = *asgn_node
  @local[lhs_variable_name] = if rhs_node.variable?
                                rhs_variable_name, = *rhs_node
                                @local[rhs_variable_name]
                              else
                                constructor?(rhs_node)
                              end
end

def process_assignment_node(node) 

def process_assignment_node(node)
  case node.type
  when :masgn
    process_multiple_assignment(node)
  when :or_asgn, :and_asgn
    process_logical_operator_assignment(node)
  when :op_asgn
    process_binary_operator_assignment(node)
  when *ASSIGNMENT_TYPES
    _, rhs_node = *node
    process_assignment(node, rhs_node) if rhs_node
  end
end

def process_binary_operator_assignment(op_asgn_node) 

def process_binary_operator_assignment(op_asgn_node)
  lhs_node, = *op_asgn_node
  return unless ASSIGNMENT_TYPES.include?(lhs_node.type)
  lhs_variable_name, = *lhs_node
  @local[lhs_variable_name] = true
  throw :skip_children
end

def process_logical_operator_assignment(asgn_node) 

def process_logical_operator_assignment(asgn_node)
  lhs_node, rhs_node = *asgn_node
  return unless ASSIGNMENT_TYPES.include?(lhs_node.type)
  process_assignment(lhs_node, rhs_node)
  throw :skip_children
end

def process_multiple_assignment(masgn_node) 

def process_multiple_assignment(masgn_node)
  mlhs_node, mrhs_node = *masgn_node
  mlhs_node.children.each_with_index do |lhs_node, index|
    next unless ASSIGNMENT_TYPES.include?(lhs_node.type)
    lhs_variable_name, = *lhs_node
    rhs_node = mrhs_node.children[index]
    if mrhs_node.array_type? && rhs_node
      process_assignment(lhs_variable_name, rhs_node)
    else
      @local[lhs_variable_name] = true
    end
  end
  throw :skip_children
end

def scan(node, &block) 

def scan(node, &block)
  catch(:skip_children) do
    yield node
    node.each_child_node { |child_node| scan(child_node, &block) }
  end
end