Move anyio version conditional to function

This should keep type checkers happy that aren't running code.

Author: Stealthii

asyncer/_compat.py

@@ -10,26 +10,21 @@
 PosArgsT = TypeVarTuple("PosArgsT")
 
 
-# AnyIO 4.1.0 renamed cancellable to abandon_on_cancel
-if "abandon_on_cancel" in inspect.getfullargspec(anyio.to_thread.run_sync).kwonlyargs:
-
-    async def run_sync(
-        func: Callable[[Unpack[PosArgsT]], T_Retval],
-        *args: Unpack[PosArgsT],
-        abandon_on_cancel: bool = False,
-        limiter: Union[CapacityLimiter, None] = None,
-    ) -> T_Retval:
+async def run_sync(
+    func: Callable[[Unpack[PosArgsT]], T_Retval],
+    *args: Unpack[PosArgsT],
+    abandon_on_cancel: bool = False,
+    limiter: Union[CapacityLimiter, None] = None,
+) -> T_Retval:
+    # AnyIO 4.1.0 renamed cancellable to abandon_on_cancel
+    if (
+        "abandon_on_cancel"
+        in inspect.getfullargspec(anyio.to_thread.run_sync).kwonlyargs
+    ):
         return await anyio.to_thread.run_sync(
             func, *args, abandon_on_cancel=abandon_on_cancel, limiter=limiter
         )
-else:
-
-    async def run_sync(
-        func: Callable[[Unpack[PosArgsT]], T_Retval],
-        *args: Unpack[PosArgsT],
-        abandon_on_cancel: bool = False,
-        limiter: Union[CapacityLimiter, None] = None,
-    ) -> T_Retval:
+    else:
         return await anyio.to_thread.run_sync(
             func, *args, cancellable=abandon_on_cancel, limiter=limiter
         )