gh-104050: Argument clinic: enable mypy's --warn-return-any setting (…

…#107405)

Tools/clinic/clinic.py

@@ -4288,10 +4288,11 @@ def eval_ast_expr(
         globals: dict[str, Any],
         *,
         filename: str = '-'
-) -> FunctionType:
+) -> Any:
     """
-    Takes an ast.Expr node.  Compiles and evaluates it.
-    Returns the result of the expression.
+    Takes an ast.Expr node.  Compiles it into a function object,
+    then calls the function object with 0 arguments.
+    Returns the result of that function call.
 
     globals represents the globals dict the expression
     should see.  (There's no equivalent for "locals" here.)

Tools/clinic/mypy.ini

@@ -5,11 +5,8 @@ pretty = True
 # make sure clinic can still be run on Python 3.10
 python_version = 3.10
 
-# be strict...
+# and be strict!
 strict = True
 strict_concatenate = True
 enable_error_code = ignore-without-code,redundant-expr
 warn_unreachable = True
-
-# ...except for one extra rule we can't enable just yet
-warn_return_any = False