So the (degenerate) optional chain in:
for e in optSeq? { … }
is not (as I thought): optSeq?
Then is it optSeq?{ ... }
?
or perhaps even the whole for e in optSeq? { … }
?
That required some mental gymnastics to understand. I would not want to be the one writing the docs for this, or explaining the concepts for learners that are inclined to "really getting it".