demangle.go
func (st *state) clearTemplateArgs(args []AST) {
	for _, a := range args {
		st.setTemplate(a, nil)
	}
}
func (st *state) clearTemplateArgs(args []AST) {
	for _, a := range args {
		st.setTemplate(a, nil)
	}
}
// clearTemplateArgs gives an error for any unset Template field in
// args.  This handles erroneous cases where a cast operator with a
// forward referenced template is in the scope of another cast
// operator.