Unity-Technologies/UnityCsReference · error · ExpressionNotValidException

Invalid character '{rightSymbol}' in expression

Error message

Invalid character '{rightSymbol}' in expression

What it means

Thrown by ParseExpression (VersionRanges.cs:119) when the LAST character is neither an allowed version last-character (a digit or letter, per the version type traits) nor one of the legal right delimiters ']' or ')'. It is the lexical rejection of an unsupported closing token, mirroring error 721 for the trailing position.

Source

Thrown at Editor/Mono/Scripting/ScriptCompilation/VersionRanges.cs:119

            if (!versionTypeTraits.IsAllowedFirstCharacter(expression[0]))
            {
                leftSymbol = expression[0];
                if (!Contains(k_LeftValidSymbols, leftSymbol))
                {
                    throw new ExpressionNotValidException($"Invalid character '{leftSymbol}' in expression", expression);
                }

                begin++;
            }

            var lastChar = expression[end];
            if (!versionTypeTraits.IsAllowedLastCharacter(lastChar))
            {
                rightSymbol = lastChar;

                if (!Contains(k_RightValidSymbols, rightSymbol))
                {
                    throw new ExpressionNotValidException($"Invalid character '{rightSymbol}' in expression", expression);
                }

                end--;
            }

            if ((leftSymbol != default(char) && rightSymbol == default(char)) ||
                (leftSymbol == default(char) && rightSymbol != default(char)))
            {
                throw new ExpressionNotValidException("Incomplete expression, missing symbol in start or end", expression);
            }

            int nextVersion;
            string leftVersionString = PopVersionString(expression, begin, end, out nextVersion, versionTypeTraits);
            var hasLeftVersion = !string.IsNullOrEmpty(leftVersionString);
            if (hasLeftVersion)
            {
                expressionParsedData.leftVersion = (TVersion)m_versionTypeStaticFunctionalityProxy.Parse(leftVersionString);
            }

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Close the range with the proper delimiter: '[1.0,2.0,' -> '[1.0,2.0]'.
2. Remove operator suffixes: '2.0>=' -> '(,2.0]'; '2.0<=' -> '(,2.0]'.
3. Trim trailing whitespace and stray punctuation: '1.0 ' -> '1.0', '1.0.' -> '1.0'.
4. Complete the version token so it does not end in '.' or '*'.

Example fix

// before
"[1.0,2.0,"   // or "2.0<="  or "1.0 "
// after
"[1.0,2.0]"   // or "(,2.0]" or "1.0"

// Last char must be a digit, a letter, ']', or ')'.
static bool HasValidClosing(string e) =>
    !string.IsNullOrEmpty(e) &&
    (char.IsDigit(e[e.Length-1]) ||
     VersionTypeTraitsUtils.IsCharLetter(e[e.Length-1]) ||
     e[e.Length-1] == ']' || e[e.Length-1] == ')');

static bool ClosesWithLegalToken(string e) =>
    !string.IsNullOrEmpty(e) &&
    (char.IsDigit(e[e.Length-1]) ||
     (e[e.Length-1] >= 'a' && e[e.Length-1] <= 'z') ||
     (e[e.Length-1] >= 'A' && e[e.Length-1] <= 'Z') ||
     e[e.Length-1] == ']' || e[e.Length-1] == ')');

try { var def = ranges.GetExpression(expr); }
catch (ExpressionNotValidException ex) when (ex.Message.Contains("Invalid character")) {
    ReportToUser($"{expr}: bad closing character. End with a digit, letter, ']' or ')'.");
}

When it happens

Trigger: Expressions whose last character is '<', '>', '=', ',', whitespace, '.', '*', '+', '[', '(', etc. Concrete inputs: '[1.0,2.0,' (trailing comma, missing closer), '2.0<=' or '2.0>=', '1.0 ' (trailing space), '1.0.' (dangling dot), '1.0*' (trailing wildcard at end), '[1.0('.

Common situations: Typing a half-finished range and forgetting the closing delimiter ('[1.0,2.0,'); a trailing space from copy-paste; an operator suffix ('2.0>='); an incomplete version token ending in '.' ('1.0.').

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Invalid character '{leftSymbol}' in expression
• Incomplete expression, missing symbol in start or end
• '{value}' is not valid in the expression
• '{expression}' is not a valid expression
• Unknown expression: {expression}

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/59f9c6ce67b36878. Report an issue: GitHub.