Spurious type error using result of re.match in lambda inside map

Consider the following testcase:

import re
r = re.compile("([a-z]+)")
if m := re.match(r, "abc"):
  matches = map(lambda i: m.group(i), [1])
  print(next(matches))

I expect this to pass type checking successfully, but mypy instead complains about the map line as follows:

mypy ./t.py
t.py:4: error: Item "None" of "Match[str] | None" has no attribute "group"  [union-attr]
Found 1 error in 1 file (checked 1 source file)

The bug only seems to happen if the lambda appears directly inside the call to map. E.g. if I pre-declare it as follows:

import re
r = re.compile("([a-z]+)")
if m := re.match(r, "abc"):
  fn = lambda i: m.group(i)
  matches = map(fn, [1])
  print(next(matches))

then this type-checks OK. My environment is as follows:

$ mypy --version
mypy 1.15.0 (compiled: yes)
$ python3 --version
Python 3.13.2

Start with the supplied testcase and run mypy 1.15.0 on Python 3.13.2, comparing the inline lambda passed to map with the separately assigned lambda. Done means the inline form type-checks without the reported union-attr error while preserving the existing behavior.