template specialization and template mixin

[Jack Applegame]

This code compiles , as expected
    struct A {
      void func(string s : "foo")() {
        pragma(msg, "func for foo");
      }
      void func(string s)() {
        pragma(msg, "func for others: " ~ s);
      }
    }

    void main() {
      A a;
      a.func!"foo"();
      a.func!"bar"();
    }
Why this doesn't compile?
    mixin template M() {
      void func(string s)() {
        pragma(msg, "func for others: " ~ s);
      }
    }

    struct A {
      mixin M;
      void func(string s : "foo")() {
        pragma(msg, "func for foo");
      }
    }

    void main() {
      A a;
      a.func!"foo"();
      a.func!"bar"(); // Error
    }