# V3204. The expression is always false due to implicit type conversion. Overflow check is incorrect.

The analyzer has detected an overflow check that does not work due to an implicit type conversion.

Let's take a look at an example:

    bool IsValidAddition(ushort x, ushort y)
    {
      if (x + y < x)
        return false;
      return true;
    }

The method should check whether an overflow occurs when two positive numbers are added. If it does occur, the sum should be less than either of its operands.

However, the check fails because the '+' operator does not have an overload for adding numbers of the 'ushort' type. As a result, both numbers are first converted to the 'int' type and then added together. Since values of the 'int' type are added, no overflow occurs.

To fix the check, explicitly cast the sum result to the 'ushort' type:

    bool IsValidAddition(ushort x, ushort y)
    {
      if ((ushort)(x + y) < x)
        return false;
      return true;
    }

Except for the 'ushort' type, there is no addition operator overload for numbers of the 'byte' type. These numbers are also implicitly cast to 'int' before the addition.

This diagnostic is classified as:

CWE-192