DO NOT BATCH MERGE WITH #77324, WILL RESULT IN BROKEN CI
Currently, calling super() inside _init() throws a
RETURN_VALUE_DISCARDED warning. The analyzer identifies super() as being a
constructor, which therefore returns an object of the relevant class.
However, super() isn't really a constructor by itself: in this case, it
is _part_ of the constructor, and so doesn't "return" a value.
A test case for this is already in #77324, which contains the warning. I
am duplicating it here, without the warning, and it should conflict with
the other PR.
25c90836fd