urllib.request.urlopen() type is unknown

[user202729]

Describe the Bug

Consider the following code

import shutil
import urllib.request as request
with request.urlopen("https://duckduckgo.com") as remote, open("main.html", 'wb') as local:
    shutil.copyfileobj(remote, local)

It runs successfully at runtime, but pyrefly gives an error

ERROR `Buffer` is not assignable to upper bound `bytes | str` of type variable `AnyStr` [bad-specialization]
 --> a.py:4:23
  |
4 |     shutil.copyfileobj(remote, local)
  |                       ^^^^^^^^^^^^^^^
  |
 INFO 1 error

This is because remote has type Unknown (Any in mypy). For comparison, mypy is more tolerant, and if the argument is Any, it will not type-check this argument.

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeSIEAtsbgE4AuABHABYCuD0AOutbYybs6UKBGyE6MAI7t4zVHCZTZ83gHcIDVsply4DQsKi5iMdAApuIVgwbE4iAPRPM7AMYBrN14DmuQndcKmsASiZFXSpcBhgAGiZTcysQKlQIdEJbKihrBIBydWx88MiTd1QoRF4mWpYOLihA01JIWFxsACsLKWjYhPLK0N4QOJBOaDgSckQQAGImAFVGrVImMHZ0dy5cdDheXkwYMHX6NIYAfXR2KmwYOgt8RCYMhnCAWgA%2BFgY6avQ6roGMIAWBrAA5G53P5MYD4AC%2B1hGYzIUjAUFIhAYwSgFAWAAVSGiMSwMDgCEwguhIL5hKgdpleAsAMowGBMWz2RwuVHHDGEei%2BJzmVy4dxwJxUml0hlOU50CIAN3SUFQ2FglN20ro9Igu0SxAZU14ZG0u3eivucD1AIAvExrABmQgARgATEj0CB4WNUNsIJaAGLQGAUNBYPBEMjeoA

(Only applicable for extension issues) IDE Information

No response

[jackulau]

looking into this!