Add PosArgT typing to trio.run (#3022)

* add PosArgT typing to run()

* add type tests

src/trio/_core/_run.py

@@ -2184,8 +2184,8 @@ def setup_runner(
 
 
 def run(
-    async_fn: Callable[..., Awaitable[RetT]],
-    *args: object,
+    async_fn: Callable[[Unpack[PosArgT]], Awaitable[RetT]],
+    *args: Unpack[PosArgT],
     clock: Clock | None = None,
     instruments: Sequence[Instrument] = (),
     restrict_keyboard_interrupt_to_checkpoints: bool = False,

src/trio/_core/_tests/test_run.py

@@ -76,7 +76,7 @@ async def trivial(x: T) -> T:
 
     with pytest.raises(TypeError):
         # Missing an argument
-        _core.run(trivial)
+        _core.run(trivial)  # type: ignore[arg-type]
 
     with pytest.raises(TypeError):
         # Not an async function

src/trio/_core/_tests/type_tests/run.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+from typing import Sequence, overload
+
+import trio
+from typing_extensions import assert_type
+
+
+async def sleep_sort(values: Sequence[float]) -> list[float]:
+    return [1]
+
+
+async def has_optional(arg: int | None = None) -> int:
+    return 5
+
+
+@overload
+async def foo_overloaded(arg: int) -> str: ...
+
+
+@overload
+async def foo_overloaded(arg: str) -> int: ...
+
+
+async def foo_overloaded(arg: int | str) -> int | str:
+    if isinstance(arg, str):
+        return 5
+    return "hello"
+
+
+v = trio.run(
+    sleep_sort, (1, 3, 5, 2, 4), clock=trio.testing.MockClock(autojump_threshold=0)
+)
+assert_type(v, "list[float]")
+trio.run(sleep_sort, ["hi", "there"])  # type: ignore[arg-type]
+trio.run(sleep_sort)  # type: ignore[arg-type]
+
+r = trio.run(has_optional)
+assert_type(r, int)
+r = trio.run(has_optional, 5)
+trio.run(has_optional, 7, 8)  # type: ignore[arg-type]
+trio.run(has_optional, "hello")  # type: ignore[arg-type]
+
+
+assert_type(trio.run(foo_overloaded, 5), str)
+assert_type(trio.run(foo_overloaded, ""), int)