Is this a bug?

[Timon Gehr via Digitalmars-d]

On 10.12.2016 09:09, Is it possible to store different generic types? wrote:
> I'm pretty sure the following code should work, but it doesn't.
>
> ```
> bool intersect(ptrdiff_t targetX, ptrdiff_t targetY, size_t targetWidth,
> size_t targetHeight, ptrdiff_t x, ptrdiff_t y, size_t width, size_t height)
> {
>  return targetX < x + width &&
>        x < targetX + targetWidth &&
>        targetY < y + height &&
>        y < targetY + targetHeight;
> }
>
> void main() {
>     import std.stdio;
>     writeln(intersect(0,0,800,600,     0,150,148,148));
>     writeln(intersect(0,0,800,600,     -10,150,148,148));
> }
> ```
>
> It outputs:
> ```
> true
> false
> ```
>
> On the contrary if you write the same piece of code in other languages
> ex. C#
> ...

Try to write it in C or C++.

> (Ran it through Linqpad)
> ```
> bool intersect(int targetX, int targetY, uint targetWidth, uint
> targetHeight, int x, int y, uint width, uint height)
> {
>  return targetX < x + width &&
>        x < targetX + targetWidth &&
>        targetY < y + height &&
>        y < targetY + targetHeight;
> }
>
> void Main() {
>     intersect(0,0,800,600,     0,150,148,148).Dump();
>     intersect(0,0,800,600,     -10,150,148,148).Dump();
> }
> ```
>
> Then it outputs:
> ```
> true
> true
> ```
>
> Is it a bug or is it intended behavior?
>
>

This is intended (but surprising, and IMHO bad) behaviour, as D follows 
C integral promotion rules. (C# does not.) Mixed signed/unsigned 
operations first convert both arguments to unsigned.