module SyntaxTree::WithScope

def visit_var_ref(node)

Visits for keeping track of variable and argument usages 
def visit_var_ref(node)
  value = node.value
  if value.is_a?(Ident)
    definition = current_scope.find_local(value.value)
    current_scope.add_local_usage(value, definition.type) if definition
  end
  super
end