module GraphQL::StaticValidation::TypeStack::ArgumentStrategy

def pop(stack, node) 

def pop(stack, node)
  stack.argument_definitions.pop
  stack.path.pop
end

def push(stack, node)

Push it anyways so `pop` has something to pop.
It's possible that `argument_defn` will be nil.
Push `argument_defn` onto the stack. 
def push(stack, node)
  if stack.argument_definitions.last
    arg_type = stack.argument_definitions.last.type.unwrap
    if arg_type.kind.input_object?
      argument_defn = arg_type.input_fields[node.name]
    else
      argument_defn = nil
    end
  elsif stack.directive_definitions.last
    argument_defn = stack.directive_definitions.last.arguments[node.name]
  elsif stack.field_definitions.last
    argument_defn = stack.field_definitions.last.arguments[node.name]
  else
    argument_defn = nil
  end
  stack.argument_definitions.push(argument_defn)
  stack.path.push(node.name)
end