It's not worth the extra complication. Every algorithm ever
written then has
to worry about it (though clearly many outside of Phobos
wouldn't bother), and
it's yet another thing that anyone writing a range-based
function has to take
into account. Any function which doesn't take it into account
will then end up
with wrong and bizarre behavior when it's given a range with a
transient
front.
My proposal was that for example isInputRange!R wouldn't compile
if R was transient. So as long as people used the existing
is***Range templates, the code that called an algorithm that only
works with non-transient ranges with a transient range wouldn't
compile. The functions that do support transient ranges could
check for isInputRange!(R, true) instead of checking for
isInputRange!R.
To be correct, most range-based functions would have to add
template
constraints to block ranges which mark themselves as transient.
If they already use is***Range constraints, they wouldn't have to
add anything.
