Weak mode varargs

Author: ecprice

mypy/checkexpr.py

@@ -482,7 +482,9 @@ def check_argument_count(self, callee: CallableType, actual_types: List[Type],
             elif kind in [nodes.ARG_POS, nodes.ARG_OPT,
                           nodes.ARG_NAMED] and is_duplicate_mapping(
                     formal_to_actual[i], actual_kinds):
-                self.msg.duplicate_argument_value(callee, i, context)
+                if (self.chk.typing_mode_full() or
+                        isinstance(actual_type, TupleType)):
+                    self.msg.duplicate_argument_value(callee, i, context)
             elif (kind == nodes.ARG_NAMED and formal_to_actual[i] and
                   actual_kinds[formal_to_actual[i][0]] != nodes.ARG_NAMED):
                 # Positional argument when expecting a keyword argument.

mypy/test/data/check-weak-typing.test

@@ -191,3 +191,18 @@ x = [1]
 # XXX: not clear what the right result here is
 x[0]() # E: "int" not callable
 [builtins fixtures/list.py]
+
+[case testWeakArgsKws]
+# mypy: weak=global
+
+def f(x, y):
+    return x+y
+
+args = [1]
+f(*args, y=2)
+args = (1, 2)
+f(*args, y=2) # E: "f" gets multiple values for keyword argument "y"
+args = (1,)
+f(*args, y=2)
+[builtins fixtures/dict.py]
+[out]