utf.d: use safe construct for .ptr instead

[WalterBright]

Blocking dlang/dmd#5860

[andralex]

noice

[andralex]

Auto-merge toggled on

[schveiguy]

Hm... since we know that r has a 0 termination, we know that r[0] is valid.

Seems like a wasteful bounds check. But of course, this can be a further enhancement, needs a @trusted escape.

ugh, and then there's the r.length = s.length + 1 followed by r.length = 0. Which does nothing except throw away an allocation :)

[WalterBright]

ugh, and then there's the r.length = s.length + 1 followed by r.length = 0. Which does nothing except throw away an allocation :)

It's meant to reserve the space, not throw away the allocation.

[aG0aep6G]

It's meant to reserve the space, not throw away the allocation.

Would need assumeSafeAppend to make that work.