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================
Using directives
================

using A;
using A.B;
using global::A.B;
using A, B;

---

(source_file
 (using_directive
  (symbol (identifier)))
 (using_directive
  (symbol (symbol (identifier)) (identifier)))
 (using_directive
  (symbol (symbol (identifier)) (identifier)))
 (using_directive
  (symbol (identifier))
  (symbol (identifier))))