module GraphQL::StaticValidation::UniqueDirectivesPerLocation

def validate_directive_location(node)
  used_directives = {}
  node.directives.each do |ast_directive|
    directive_name = ast_directive.name
    if (first_node = used_directives[directive_name])
      @directives_are_unique_errors_by_first_node ||= {}
      err = @directives_are_unique_errors_by_first_node[first_node] ||= begin
        error = GraphQL::StaticValidation::UniqueDirectivesPerLocationError.new(
          "The directive \"#{directive_name}\" can only be used once at this location.",
          nodes: [used_directives[directive_name]],
          directive: directive_name,
        )
        add_error(error)
        error
      end
      err.nodes << ast_directive
    elsif !((dir_defn = context.schema_directives[directive_name]) && dir_defn.repeatable?)
      used_directives[directive_name] = ast_directive
    end
  end
end