Lots and lots of places in the code had broken < operators because they
are returning something like:
foo < other.foo or bar < other.bar;
but this breaks both the strict weak ordering requirements that are
required for the "Compare" requirement for things like
std::map/set/priority_queue.
For example:
a = {.foo=1, .bar=3}
b = {.foo=3, .bar=1}
does not have an ordering over a and b (both `a < b` and `b < a` are
satisfied at the same time).
This needs to be instead something like:
foo < other.foo or (foo == other.foo and bar < other.bar)
but that's a bit clunkier, and it is easier to use std::tie for tuple's
built-in < comparison which does the right thing:
std::tie(foo, bar) < std::tie(other.foo, other.bar)
(Initially I noticed this in SockAddr/sockaddr_in6, but upon further
investigation this extends to the major of multi-field `operator<`'s.)
This fixes it by using std::tie (or something similar) everywhere we are
doing multi-field inequalities.
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