Thanks a lot for the report and the reproducer, and sorry for the regression that my patch introduced.
It has been a while since I wrote any Python, so I did not notice it.
What seems to be happening is that python-font-lock-assignment-matcher is giving up too early.
Replacing its definition by
(defun python-font-lock-assignment-matcher (regexp)
"Font lock matcher for assignments based on REGEXP.
Return nil if REGEXP matched within a `paren' context (to avoid,
e.g., default values for arguments or passing arguments by name
being treated as assignments) or is followed by an '=' sign (to
avoid '==' being treated as an assignment."
(let ((res nil))
(while (and (setq res (re-search-forward regexp limit t))
(or (python-syntax-context 'paren)
(equal (char-after (point)) ?=))))
should fix the issue.
Would you be able to give it a try?
Unfortunately some issues still remain, all of which can be illustrated by a file containing the following code:
CustomInt = int
def f(x: CustomInt) -> CustomInt:
y = x + 1
ys: Sequence[CustomInt] = [y, y + 1]
res: CustomInt = sum(ys) + 1
When such a file is first opened:
- The y in y = x + 1 is not highlighted — this is fixed by subsequent edits
- The CustomInt in -> CustomInt is highlighted — this is fixed by subsequent edits
- The CustomInt in Sequence[CustomInt] is highlighted — this is not fixed by subsequent edits
These are caused by the type hints (in the case of 1. — by the type hints in the function's signature).
I am not sure how one would fix them.
Regarding reverting the patch: It can be done easily, but the previous code had even more bugs happening around type hints.