Constrained TypeVar lost after binop

[rchen152]

Describe the Bug

Pyrefly reports a false positive on the following code:

from typing import TypeVar

T = TypeVar("T", str, int)

def foo(a: T) -> T:
    doubled = 2 * a
    return a + doubled  # E: `+` is not supported between `str` and `int`

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN0AVZjABqqSgB10UgXQC8g4WMoAKCSAHqANHTgNKO1gwCUUqZhhg6YXLhWpEg43QC0APkGIpdH3Uy4AV2xYTHk6ACY6ACo6VG9fShgGAMp0WLoAaj9A4JhMEC0QAIZoOBJyRBAAYjoAVRKoCCZrAPQAYxLcdDgzLEtrXhpUBgB9dACabBhVfEcjZ3ddfS80hKSUtLB1ADkJqcpHYHwAX3UpApAyRLAoUkIGWigKGoAFUmvb3QwcAjo2rsgbBSwwgXUIUhqAGUYDA6AALBgMYhwRAAelRV0st0IvDYqJg6FR-jacFR-3QgOBnUJA0osQAbqhoKhcn8ARAgZQQV06LhiNSylIyAw4V0XPTpnBQWkFOoAMyEACM4TO6BAx0KqA6EAlADFoDAKGgsHgiGR1UA

(Only applicable for extension issues) IDE Information

No response