demangle.go
func (st *state) functionType() AST {
	st.checkChar('F')
	if len(st.str) > 0 && st.str[0] == 'Y' {
		// Function has C linkage.  We don't print this.
		st.advance(1)
	}
	ret := st.bareFunctionType(true)
	r := st.refQualifier()
	if r != "" {
		ret = &MethodWithQualifiers{Method: ret, Qualifiers: nil, RefQualifier: r}
	}
	if len(st.str) == 0 || st.str[0] != 'E' {
		st.fail("expected E after function type")
	}
	st.advance(1)
	return ret
}
func (st *state) functionType() AST {
	st.checkChar('F')
	if len(st.str) > 0 && st.str[0] == 'Y' {
		// Function has C linkage.  We don't print this.
		st.advance(1)
	}
	ret := st.bareFunctionType(true)
	r := st.refQualifier()
	if r != "" {
		ret = &MethodWithQualifiers{Method: ret, Qualifiers: nil, RefQualifier: r}
	}
	if len(st.str) == 0 || st.str[0] != 'E' {
		st.fail("expected E after function type")
	}
	st.advance(1)
	return ret
}
// <function-type> ::= F [Y] <bare-function-type> [<ref-qualifier>] E