1) If this feature existed in Python 3.11 exactly as described, would
you use it?
... except in the sense that as I trainer I have to teach the warts in Python, and would need to warn students they might see that.
2) Independently: Is the syntactic distinction between "=" and "=>" a
A few weeks later than the prior long discussion that I read in full, it took a triple take not to read it as >= (which would mean something syntactical in many cases, just not what is intended).
3) If "yes" to question 1, would you use it for any/all of (a) mutable
defaults, (b) referencing things that might have changed, (c)
referencing other arguments, (d) something else?
I would always recommend against its use if I had any influence on code review.
4) If "no" to question 1, is there some other spelling or other small
change that WOULD mean you would use it? (Some examples in the PEP.)
Yes, the delay/later/defer keyword approach is not confusing, and does not preempt a later feature that would actually be worth having.
5) Do you know how to compile CPython from source, and would you be
willing to try this out? Please? :)
I do know how, but it is unlikely I'll have time.