i use:

void swap(T)(ref T a, ref T b) {
  T t = a;
  a...

Not really nessesary, but nice to have...
int a = 1;
int b = 2;
a <=> b...

...kill it because it is
trying to swap my machine to death).

I can make...

...for me. Not to mention having to swap gdb for ddbg or whatever it is...

...See C++, there are much of swap functions, and much of nothrowing problem in swap.

...size of structure where swap members becomes more efficient than swap via a temporary is...

...three lines in a template function called "swap".  If the compiler can recognize that's...

Uh? If 'swap(a,b)' is ok, then you put swap as a function call...

...It is whole lot easy to recognise "swap(a,b)" or even "a<->b" as...

...couldn't recognize that this is a swap operation:
   tmp = a;
   a = b;
   b = tmp...