Why does Resharper complain when I compare a double to zero?

Question

If I do

double d = 0;
if (d == 0) {
  ...
}

Resharper complains at the comparison d == 0 about "Comparison of floating point number with equality operator. Possible loss of precision while rounding values."

Why? It cannot be difficult to represent exact zero as a double or a float can it?

I understand such a warning would be relevant if I compared to some other value such as 0.2 for which there is no exact binary representation.

Answer 1

Resharper does not analyze how the double variable got its value.

After a few calculations a double value is rarely exact so resharper warns you that comparing a double with an exact value is not a good idea.

double x = Math.Sqrt(2);
double d = x * x;

Console.WriteLine(d == 2);