Implicit integer conversions Before Preconditions

[jmh530]

In the code below, `x` and `y` are implicitly converted to `uint` 
and `ushort` before the function preconditions are run.

Is there any way to change this behavior? It feels unintuitive 
and I can't find in the spec where it says when the conversions 
in this case occur, but it clearly happens before the 
preconditions are run.

```d
import std.stdio: writeln;

void foo(uint x)
     in (x >= 0)
{
     writeln(x);
}

void foo(ushort x)
     in (x >= 0)
{
     writeln(x);
}

void main() {
     int x = -1;
     foo(x); //prints 4294967295
     short y = -1;
     foo(y); //prints 65535
}
```