code: func (st *state) templateArgs() []AST {
  	if len(st.str) == 0 || (st.str[0] != 'I' && st.str[0] != 'J') {
  		panic("internal error")
  	}
  	st.advance(1)
  
  	var ret []AST
  	for len(st.str) == 0 || st.str[0] != 'E' {
  		arg := st.templateArg()
  		ret = append(ret, arg)
  	}
  	st.advance(1)
  	return ret
  }
docs: // <template-args> ::= I <template-arg>+ E