yow..c

rb_enc_symname_type(const char *name, long len, rb_encoding *enc, unsigned int allowed_attrset)
{
    const char *m = name;
    const char *e = m + len;
    int type = ID_JUNK;

    if (!rb_enc_asciicompat(enc)) return -1;
    if (!m || len <= 0) return -1;
    switch (*m) {
      case '\0':
	return -1;

      case '$':
	type = ID_GLOBAL;
	if (is_special_global_name(++m, e, enc)) return type;
	goto id;

      case '@':
	type = ID_INSTANCE;
	if (*++m == '@') {
	    ++m;
	    type = ID_CLASS;
	}
	goto id;

      case '<':
	switch (*++m) {
	  case '<': ++m; break;
	  case '=': if (*++m == '>') ++m; break;
	  default: break;
	}
	break;

      case '>':
	switch (*++m) {
	  case '>': case '=': ++m; break;
	}
	break;

      case '=':
	switch (*++m) {
	  case '~': ++m; break;
	  case '=': if (*++m == '=') ++m; break;
	  default: return -1;
	}
	break;

      case '*':
	if (*++m == '*') ++m;
	break;

      case '+': case '-':
	if (*++m == '@') ++m;
	break;

      case '|': case '^': case '&': case '/': case '%': case '~': case '`':
	++m;
	break;

      case '[':
	if (m[1] != ']') goto id;
	++m;
	if (*++m == '=') ++m;
	break;

      case '!':
	if (len == 1) return ID_JUNK;
	switch (*++m) {
	  case '=': case '~': ++m; break;
	  default:
	    if (allowed_attrset & (1U << ID_JUNK)) goto id;
	    return -1;
	}
	break;

      default:
	type = rb_sym_constant_char_p(m, e-m, enc) ? ID_CONST : ID_LOCAL;
      id:
	if (m >= e || (*m != '_' && !ISALPHA(*m) && ISASCII(*m))) {
	    if (len > 1 && *(e-1) == '=') {
		type = rb_enc_symname_type(name, len-1, enc, allowed_attrset);
		if (type != ID_ATTRSET) return ID_ATTRSET;
	    }
	    return -1;
	}
	while (m < e && is_identchar(m, e, enc)) m += rb_enc_mbclen(m, e, enc);
	if (m >= e) break;
	switch (*m) {
	  case '!': case '?':
	    if (type == ID_GLOBAL || type == ID_CLASS || type == ID_INSTANCE) return -1;
	    type = ID_JUNK;
	    ++m;
	    if (m + 1 < e || *m != '=') break;
	    /* fall through */
	  case '=':
	    if (!(allowed_attrset & (1U << type))) return -1;
	    type = ID_ATTRSET;
	    ++m;
	    break;
	}
	break;
    }
    return m == e ? type : -1;
}