Literal list ternary behave unexpected

[randolf-scholz]

https://mypy-play.net/?mypy=1.17.0&python=3.12&gist=25e4031ca17d70626baee7a468ac4d9f

def ternary_list[T, S](x: list[T], y: list[S]) -> None:
    a = x if "" else y
    reveal_type(a)  # list[T] | list[S] ✅

def ternary_list2() -> None:
    a = list[int]() if "" else list[str]()
    reveal_type(a)  # list[int] | list[str] ✅

def ternary_list_literal() -> None:
    a = [1] if "" else ["a"]  # E: List item 0 has incompatible type "str"
    reveal_type(a) # list[int] ???

I would have expected list[int] | list[str] in the literal case as well.

[randolf-scholz]

More generally:

from typing import reveal_type

def test(b: bool) -> None:
    l = [1] if b else ["a"]
    reveal_type(l)  # list[int] ???

    t = (1,) if b else ("a",)
    reveal_type(t)  # tuple[int] | tuple[str] ✅

    s = {1} if b else {"a"}
    reveal_type(s)  # set[int] ???

    d = {1:1} if b else {"a": "a"}
    reveal_type(d)  # dict[int, int]  ???

pyright and pyrefly both consistently predict the union type:

• Code sample in pyright playground
• pyrefly sandbox

ty gives some Unknown for each case other than tuple: https://play.ty.dev/637631f2-8536-4b4a-9c7a-364d3df77355