protected abstract int CompareTo(VariableSymbol right);
protected override int CompareTo(VariableSymbol right) => CompareTo((ParameterVariableSymbol)right);
protected override int CompareTo(VariableSymbol right) => CompareTo((LocalVariableSymbol <T>)right);
private static int Compare(VariableInfo left, VariableInfo right, INamedTypeSymbol cancellationTokenType) => VariableSymbol.Compare(left._variableSymbol, right._variableSymbol, cancellationTokenType);