Directive definition compatibility

[Quramy]

We can't the original @argumentDefinitions and @arguments directive definitions.

## (A)
directive @arguments(
  # There must be name(s) of arguments of this directive
) on FRAGMENT_SPREAD

However, what are the names of arguments of @arguments ? They might be named in client-side developer's source code, such as:

query MyQuery($todoCount: Int!) {
  ...TodosFragment @argument(count: $todoCount)
}

The problem is that the directive definition (A) can't know the directive's arguments input name is count. In other words, The argument name of the directive should be fixed name. For example:

scalar ArgumentDefinitionSet
directive @arguments(
  _defs: ArgumentDefinitionSet
) on FRAGMENT_SPREAD

The above example is absolutely valid( https://graphql.github.io/graphql-spec/June2018/#sec-Type-System.Directives ).