Regression in 1.1.405 involving loops

[Molkree]

Describe the bug
A clear and concise description of the behavior you are seeing and the expected behavior along with steps to reproduce it.
Pyright seems to be confused about variable type when modifying said variable inside the loop.
In this example, lines should infer as list[str].

Code or Screenshots

lines = ["ab", "bc", "ac", "ca"]  # lines: list[str]
while lines:  # lines: list[str] | list[str | Unknown]
    print(lines)  # lines: list[str] | list[Unknown]
    lines = [x for x in lines[1:]]  # x: str | Unknown

Working fine in 1.1.404
Broken in 1.1.405
Still broken in 1.1.408 (latest version as of today)