private Token ReadNumber()

in src/Parsing/Impl/Tokens/Tokenizer.cs [1053:1141]
74 lines of code
37 McCabe index (conditional complexity)

        private Token ReadNumber(int start) {
            var b = 10;
            if (start == '0') {
                if (NextChar('x') || NextChar('X')) {
                    return ReadHexNumber();
                } else if (LanguageVersion >= PythonLanguageVersion.V26) {
                    if ((NextChar('b') || NextChar('B'))) {
                        return ReadBinaryNumber();
                    } else if (NextChar('o') || NextChar('O')) {
                        return ReadOctalNumber();
                    }
                }

                b = 8;
            }

            while (true) {
                var ch = NextChar();

                switch (ch) {
                    case '.':
                        return ReadFraction();

                    case 'e':
                    case 'E':
                        return ReadExponent();

                    case 'j':
                    case 'J':
                        MarkTokenEnd();

                        // TODO: parse in place
                        if (Verbatim) {
                            var tokenStr = GetTokenString();
                            return new VerbatimConstantValueToken(LiteralParser.ParseImaginary(tokenStr), tokenStr);
                        }
                        return new ConstantValueToken(LiteralParser.ParseImaginary(GetTokenString()));

                    case 'l':
                    case 'L': {
                            MarkTokenEnd();

                            var tokenStr = GetTokenString();
                            try {
                                if (Verbatim) {
                                    return new VerbatimConstantValueToken(ParseBigInteger(tokenStr, b), tokenStr);
                                }
                                return new ConstantValueToken(ParseBigInteger(tokenStr, b));
                            } catch (ArgumentException e) {
                                return new ErrorToken(e.Message, tokenStr);
                            }
                        }

                    case '_':
                        if (LanguageVersion < PythonLanguageVersion.V36) {
                            goto default;
                        }
                        break;

                    case '0':
                    case '1':
                    case '2':
                    case '3':
                    case '4':
                    case '5':
                    case '6':
                    case '7':
                    case '8':
                    case '9':
                        break;

                    default:
                        BufferBack();
                        MarkTokenEnd();

                        var image = GetTokenString();
                        var val = ParseInteger(GetTokenString(), b);
                        if (b == 8 && LanguageVersion.Is3x() && (!(val is int) || !((int)val == 0))) {
                            ReportSyntaxError(BufferTokenSpan, "invalid token", ErrorCodes.SyntaxError);
                        }

                        if (Verbatim) {
                            return new VerbatimConstantValueToken(val, image);
                        }
                        // TODO: parse in place
                        return new ConstantValueToken(val);
                }
            }
        }