bpo-36518: Store keyword arguments that matches passed positional arguments into varkw.

Lib/inspect.py

@@ -1362,6 +1362,7 @@ def getcallargs(*func_and_positional, **named):
     possible_kwargs = set(args + kwonlyargs)
     if varkw:
         arg2value[varkw] = {}
+        possible_kwargs -= set(args[:n])
     for kw, value in named.items():
         if kw not in possible_kwargs:
             if not varkw:

Lib/test/test_extcall.py

@@ -228,11 +228,13 @@
     >>> d
     {}
 
-
-    >>> g(1, 2, 3, **{'x': 4, 'y': 5})
+    >>> h(1, 2, **{'a': 4, 'h': 5})
     Traceback (most recent call last):
       ...
-    TypeError: g() got multiple values for argument 'x'
+    TypeError: h() got multiple values for argument 'a'
+
+    >>> g(1, 2, 3, **{'x': 4, 'y': 5})
+    1 (2, 3) {'x': 4, 'y': 5}
 
     >>> f(**{1:2})
     Traceback (most recent call last):

Lib/test/test_inspect.py

@@ -1436,6 +1436,7 @@ def test_varkw(self):
         self.assertEqualCallArgs(f, '**collections.UserDict(a=2, b=3, c=4)')
         self.assertEqualCallArgs(f, '2, c=4, **collections.UserDict(b=3)')
         self.assertEqualCallArgs(f, 'b=2, **collections.UserDict(a=3, c=4)')
+        self.assertEqualCallArgs(f, '1, a=2')
 
     def test_varkw_only(self):
         # issue11256:

Python/ceval.c

@@ -3858,15 +3858,15 @@ _PyEval_EvalCodeWithName(PyObject *_co, PyObject *globals, PyObject *locals,
         /* Speed hack: do raw pointer compares. As names are
            normally interned this should almost always hit. */
         co_varnames = ((PyTupleObject *)(co->co_varnames))->ob_item;
-        for (j = 0; j < total_args; j++) {
+        for (j = (kwdict ? n : 0); j < total_args; j++) {
             PyObject *name = co_varnames[j];
             if (name == keyword) {
                 goto kw_found;
             }
         }
 
         /* Slow fallback, just in case */
-        for (j = 0; j < total_args; j++) {
+        for (j = (kwdict ? n : 0); j < total_args; j++) {
             PyObject *name = co_varnames[j];
             int cmp = PyObject_RichCompareBool( keyword, name, Py_EQ);
             if (cmp > 0) {