Fix getargs argument passing (#18350)

Fixes mypyc/mypyc#1078

Introduced in #17930

See the first commit to see the bug (wrong condition)

---------

Co-authored-by: Marc Mueller <[email protected]>

Author: hauntsaninja

mypyc/lib-rt/getargs.c

@@ -250,13 +250,12 @@ vgetargskeywords(PyObject *args, PyObject *kwargs, const char *format,
                 current_arg = Py_NewRef(PyTuple_GET_ITEM(args, i));
             }
             else if (nkwargs && i >= pos) {
-                int res = PyDict_GetItemStringRef(kwargs, kwlist[i], &current_arg);
-                if (res == 1) {
-                    --nkwargs;
-                }
-                else if (res == -1) {
+                if (unlikely(PyDict_GetItemStringRef(kwargs, kwlist[i], &current_arg) < 0)) {
                     return 0;
                 }
+                if (current_arg) {
+                    --nkwargs;
+                }
             }
             else {
                 current_arg = NULL;
@@ -371,11 +370,12 @@ vgetargskeywords(PyObject *args, PyObject *kwargs, const char *format,
         Py_ssize_t j;
         /* make sure there are no arguments given by name and position */
         for (i = pos; i < bound_pos_args && i < len; i++) {
-            int res = PyDict_GetItemStringRef(kwargs, kwlist[i], &current_arg);
-            if (res == 1) {
-                Py_DECREF(current_arg);
+            PyObject *current_arg;
+            if (unlikely(PyDict_GetItemStringRef(kwargs, kwlist[i], &current_arg) < 0)) {
+                goto latefail;
             }
-            else if (unlikely(res == 0)) {
+            if (unlikely(current_arg != NULL)) {
+                Py_DECREF(current_arg);
                 /* arg present in tuple and in dict */
                 PyErr_Format(PyExc_TypeError,
                              "argument for %.200s%s given by name ('%s') "
@@ -385,9 +385,6 @@ vgetargskeywords(PyObject *args, PyObject *kwargs, const char *format,
                              kwlist[i], i+1);
                 goto latefail;
             }
-            else if (unlikely(res == -1)) {
-                goto latefail;
-            }
         }
         /* make sure there are no extraneous keyword arguments */
         j = 0;

mypyc/test-data/run-classes.test

@@ -467,6 +467,21 @@ a = A(10)
 assert a.foo() == 11
 assert foo() == 21
 
+[case testClassKwargs]
+class X:
+    def __init__(self, msg: str, **variables: int) -> None:
+         pass
+[file driver.py]
+import traceback
+from native import X
+X('hello', a=0)
+try:
+    X('hello', msg='hello')
+except TypeError as e:
+    print(f"{type(e).__name__}: {e}")
+[out]
+TypeError: argument for __init__() given by name ('msg') and position (1)
+
 [case testGenericClass]
 from typing import TypeVar, Generic, Sequence
 T = TypeVar('T')