DSL EXPRESSION:
begin { @u[2] = @v[1] }


AST:
* statement block
    * begin block
        * statement block
            * assignment "="
                * array or map index access "[]"
                    * direct oosvar value "u"
                    * int literal "2"
                * array or map index access "[]"
                    * direct oosvar value "v"
                    * int literal "1"

