handle missing pos args at the end

Author: KevinRK29

mypy/checkexpr.py

@@ -2361,8 +2361,9 @@ def _detect_missing_positional_arg(
         """Try to identify a single missing positional argument using type alignment.
 
         If the caller and callee are just positional arguments and exactly one arg is missing,
-        we scan left to right to find which argument skipped. If there is an error, report it 
-        and return True, or return False to fall back to normal checking.
+        we scan left to right to find which argument skipped. If only the last argument is missing, 
+        we return False since it's already handled in a desired manner. If there is an error, 
+        report it and return True, or return False to fall back to normal checking.
         """
         if not all(k == ARG_POS for k in callee.arg_kinds):
             return False
@@ -2387,6 +2388,9 @@ def _detect_missing_positional_arg(
         if skip_idx is None or j != len(arg_types):
             return False
 
+        if skip_idx == len(callee.arg_types) - 1:
+            return False
+
         param_name = callee.arg_names[skip_idx]
         callee_name = callable_name(callee)
         if param_name is None or callee_name is None:

test-data/unit/check-functions.test

@@ -3793,6 +3793,22 @@ main:3: error: Missing positional argument "z" in call to "f"
 main:3: error: Argument 1 to "f" has incompatible type "str"; expected "int"
 main:3: error: Argument 2 to "f" has incompatible type "int"; expected "str"
 
+[case testMissingPositionalArgNoShiftPatternLast]
+def f(x: int, y: str, z: bytes) -> None: ...
+
+f(123, "wrong")
+[builtins fixtures/primitives.pyi]
+[out]
+main:3: error: Missing positional argument "z" in call to "f"
+
+[case testMissingPositionalArgNoShiftPatternNone]
+def f(x: int) -> None: ...
+
+f()
+[builtins fixtures/primitives.pyi]
+[out]
+main:3: error: Missing positional argument "x" in call to "f"
+
 [case testMissingPositionalArgMultipleMissing]
 def f(a: int, b: str, c: float, d: list[int]) -> None: ...