Different behavior when switching arguments using same generic type?

[Holt59]

Disclaimer: Not sure if this is a bug or expected behavior but that was at least unexpected for me and I did not manage to find relevant information here or on the typing repository (or documentation).

Describe the bug
In the example below, f1 and f2 are similar except for the order of arguments, in f1, the callable is after the container, and the type of the callable is properly deduced, but in f2, the callable comes first and its type is not properly deduced.

from collections.abc import Iterable
from typing import Callable, Mapping, cast


def f1[K, V](vs: Iterable[Mapping[K, V]], fn: Callable[[Iterable[V]], V]): ...
def f2[K, V](fn: Callable[[Iterable[V]], V], vs: Iterable[Mapping[K, V]]): ...


# both ok
f1(({"a": 1, "b": 2},), sum)
f2(sum, ({"a": 1, "b": 2},))

# f1 ok, f2 ko
f1(({"a": {1}, "b": {2}},), lambda s: cast(set[int], set()).union(*s))
f2(lambda s: cast(set[int], set()).union(*s), ({"a": {1}, "b": {2}},))

Full error:

.\test2.py
  .\test2.py:15:4 - error: Argument type is partially unknown
    Argument corresponds to parameter "fn" in function "f2"
    Argument type is "(s: Iterable[set[int | Unknown]]) -> set[int | Unknown]" (reportUnknownArgumentType)
  .\test2.py:15:11 - error: Type of parameter "s" is partially unknown (reportUnknownLambdaType)
  .\test2.py:15:14 - error: Return type of lambda, "set[int | Unknown]", is partially unknown (reportUnknownLambdaType)
  .\test2.py:15:43 - error: Argument type is partially unknown
    Argument corresponds to parameter "s" in function "union"
    Argument type is "set[int | Unknown]" (reportUnknownArgumentType)
  .\test2.py:15:47 - error: Argument type is partially unknown
    Argument corresponds to parameter "vs" in function "f2"
    Argument type is "tuple[dict[str, set[int | Unknown]]]" (reportUnknownArgumentType)
5 errors, 0 warnings, 0 informations

VS Code extension or command-line

CLI, pyright 1.1.362

[erictraut]

This is addressed in pyright 1.1.364.