demangle.go
func isCDtorConversion(a AST) bool {
	switch a := a.(type) {
	case *Qualified:
		return isCDtorConversion(a.Name)
	case *Constructor, *Destructor, *Cast:
		return true
	default:
		return false
	}
}
func isCDtorConversion(a AST) bool {
	switch a := a.(type) {
	case *Qualified:
		return isCDtorConversion(a.Name)
	case *Constructor, *Destructor, *Cast:
		return true
	default:
		return false
	}
}
// isCDtorConversion returns when an AST is a constructor, a
// destructor, or a conversion operator.