'int' is enough for 'length' to migrate code from x86 to x64

[FrankLike via Digitalmars-d]

>> auto x = foo();
>> auto y = bar();
>> auto z = baz();
>>
>> if (x - y > z) { ... }
>>
>>
>> This might be a bug, if one of these functions returns an 
>> unsigned
>> type.  Good luck finding that. Note that if all functions 
>> return
>> unsigned, there isn't even any signed-unsigned mismatch.
>>
>> I believe the correct statement, is "With only a bit of care 
>> one can use
>> D's unsigned types for positive numbers and believe that one's 
>> code is
>> correct, even though it contains subtle bugs."
>
> Well I'm sorry but I quite disagree. -- Andrei

This might be a bug.

'Length' always needs to compare sizes. 'Width' and 'Height' like 
it.

************************ dfl/drawing.d line:185 -218 
**************************

	///
	Size opAdd(Size sz)
	{
		Size result;
		result.width = width + sz.width;
		result.height = height + sz.height;
		return result;
	}
	
	
	///
	Size opSub(Size sz)
	{
		Size result;
		result.width = width - sz.width;
		result.height = height - sz.height;
		return result;
	}
	
	
	///
	void opAddAssign(Size sz)
	{
		width += sz.width;
		height += sz.height;
	}
	
	
	///
	void opSubAssign(Size sz)
	{
		width -= sz.width;
		height -= sz.height;
	}
***********************end*************************
  if the type of width and height  are size_t,then their values 
will be error.


small test:
-----------------------
import std.stdio;

void main()
{
	size_t width = 10;
	size_t height = 20;
	writeln("before width is ",width," ,height is ",height);
     height -= 1;
     width -= height;
     writeln("after width is ",width," ,height is ",height);
}
----------
"after width is " ERROR.