demangle.go
func doDemangle(name string, options ...Option) (ret AST, err error) {
	// When the demangling routines encounter an error, they panic
	// with a value of type demangleErr.
	defer func() {
		if r := recover(); r != nil {
			if de, ok := r.(demangleErr); ok {
				ret = nil
				err = de
				return
			}
			panic(r)
		}
	}()

	params := true
	clones := true
	verbose := false
	for _, o := range options {
		switch o {
		case NoParams:
			params = false
			clones = false
		case NoTemplateParams:
		// This is a valid option but only affect printing of the AST.
		case NoClones:
			clones = false
		case Verbose:
			verbose = true
		default:
			return nil, fmt.Errorf("unrecognized demangler option %v", o)
		}
	}

	st := &state{str: name, verbose: verbose}
	a := st.encoding(params, notForLocalName)

	// Accept a clone suffix.
	if clones {
		for len(st.str) > 1 && st.str[0] == '.' && (isLower(st.str[1]) || st.str[1] == '_' || isDigit(st.str[1])) {
			a = st.cloneSuffix(a)
		}
	}

	if clones && len(st.str) > 0 {
		st.fail("unparsed characters at end of mangled name")
	}

	return a, nil
}
func doDemangle(name string, options ...Option) (ret AST, err error) {
	// When the demangling routines encounter an error, they panic
	// with a value of type demangleErr.
	defer func() {
		if r := recover(); r != nil {
			if de, ok := r.(demangleErr); ok {
				ret = nil
				err = de
				return
			}
			panic(r)
		}
	}()

	params := true
	clones := true
	verbose := false
	for _, o := range options {
		switch o {
		case NoParams:
			params = false
			clones = false
		case NoTemplateParams:
		// This is a valid option but only affect printing of the AST.
		case NoClones:
			clones = false
		case Verbose:
			verbose = true
		default:
			return nil, fmt.Errorf("unrecognized demangler option %v", o)
		}
	}

	st := &state{str: name, verbose: verbose}
	a := st.encoding(params, notForLocalName)

	// Accept a clone suffix.
	if clones {
		for len(st.str) > 1 && st.str[0] == '.' && (isLower(st.str[1]) || st.str[1] == '_' || isDigit(st.str[1])) {
			a = st.cloneSuffix(a)
		}
	}

	if clones && len(st.str) > 0 {
		st.fail("unparsed characters at end of mangled name")
	}

	return a, nil
}
// The doDemangle function is the entry point into the demangler proper.