This might be nice to use in the specific case. However, its important to note that in the general case, you need a type variable because it is used in multiple positions. In the function below (taken from the proposal), one is stating that T is the same type in all usages.

    func Join(type T strseq)(a []T, sep T) (ret T)

This below version is different, each variable could be a different type (that satisfies strseq).

    func Join(a []strseq, sep strseq) (ret strseq)