range search would be nice
add scaffolding for symmetric_difference/union
make TreeSet tests a bit more paranoid
implement set union
implement symmetric_difference
fix bug in union implementation (missing return)
docstring/comment fixes
add TreeSetIterator
cleanup
make is_disjoint O(n+m) instead of O(n*log(m))
make intersection O(n+m) instead of O(n*log(m))
make is_superset/is_subset O(n+m) instead of O(n*log(m))
indentation fix
re-borrow in heir_swap (fixes compile)
When decoding types, indicate to the def-id conversion function what kind of
def-id we have, so that the inliner can distinguish between external and
internal def-ids.  Also add some comments explaining the distinction!

Fixes #4516.

r=graydon
Propagate expected types through block expressions.

r=graydon
Correct tests

rs=breakage
rustc: One Less Bad Copy
core: Add private global data interface. #3915
Add `finally` method for deferred execution