I understand that it's not desirable to move everything to corelib.c, especially things that can be implemented simply and concisely in Janet. However, for these three functions I think it may be warranted. Each of these functions compares multiple types, and are used in several places throughout boot.janet, and not only in compile-time expanded macros.

For example, in flatten:

(use spork/test)
(timeit-loop [:timeout 1] :flatten (flatten [[[1 2] 3] 4 [5 [6 7 8] 9]]))

master:

flatten 1.000s, 1.556µs/body

branch:

flatten 1.000s, 0.8098µs/body

Nearly half the time taken is spent checking the type.

For the interested, moving these functions increases the size of the executable by 128 bytes, at least on my system:
master:

$ du -b /usr/local/bin/janet
797104	/usr/local/bin/janet

branch:

$ du -b /usr/local/bin/janet
797232	/usr/local/bin/janet