Wrong result with enum

[Salih Dincer]

is this a issue, do you need to case?

```d
enum tLimit = 10_000;  // (1) true result
enum wLimit = 100_000; // (2) wrong result

void main()
{
   size_t subTest1 = tLimit;
   assert(subTest1 == tLimit);        /* no error */

   size_t subTest2 = wLimit;
   assert(subTest2 == wLimit);        /* no error */

   size_t gauss = (tLimit * (tLimit + 1)) / 2;
   assert(gauss == 50_005_000);       /* no error */

   gauss = (wLimit * (wLimit + 1)) / 2;
   assert(gauss == 5_000_050_000);    /* failure

   // Fleeting Solution:
     enum size_t limit = 100_000;
     gauss = (limit * (limit + 1)) / 2;
     assert(gauss == 5_000_050_000); //* no error */

} /* Small Version:

void main(){
   enum t = 10_000;
   size_t a = t * t;
   assert(a == 100_000_000);    // No Error

   enum w = 100_000;
   size_t b = w * w;
   assert(b == 10_000_000_000); // Assert Failure
}
*/
```