Can you shrink it further?

[safety0ff via Digitalmars-d]

On Sunday, 9 October 2016 at 22:11:50 UTC, Andrei Alexandrescu 
wrote:
> I suspect there are cleverer things that can be done.

Less clever seemed to work for me:

void popFront1(ref char[] s) @trusted pure nothrow {
   immutable c = s[0];
   if (c < 0x80 || c >= 0xFE) {
     s = s.ptr[1 .. s.length];
   } else {
     import core.bitop;
     size_t i = 7u - bsr(~c); // N.B. changed uint to size_t
     import std.algorithm;
     s = s.ptr[min(i, s.length) .. s.length];
   }
}