"Concepts" should not be part of function headers

[monkyyy]

https://youtu.be/1p6So6vE5WM?si=tEbeBOQ-xXjJawMY

"if its a subset it automagically picks the right one because of 
our clever overload rules"

No, No, just No; every overload set with >5 memebers is a big 
ball of bugs such as `to`

These are *type assertions*; `isComaparable!(T,U)`=>bool could be 
made with a reusable error code by as `template 
assertComaparable(T,U,string func=__FUNCTION__)` =>
"max of int and string requires opCmp, consider:
   1) .to!string of the first argument
   2) .to!int of th 2nd argument
   3) implementing int.opCmp(string)
   4) implementing string.opCmp(int)
"