Integer overflow exception – WhereIsMyAnswer

Why I get a compiler error here:

int a = 2147483647 + 10;

and not here, if I’m performing the same operation:

int ten = 10;
int b = 2147483647 + ten;

I’m learning the usage of checked and the MSDN web site doesn’t clear why the OverflowException is raised in the first code snippet:

By default, an expression that contains only constant values causes a
compiler error if the expression produces a value that is outside the
range of the destination type. If the expression contains one or more
non-constant values, the compiler does not detect the overflow.

It only explains the behavior but not the reasons for that behavior. I’d like to know what happens under the hood.