Accept empty list unpacking for function without parameter (#7392)

Also assume `Any` as `*args`  could be empty.

Fixes #4997.

Author: onlined

mypy/checkexpr.py

@@ -1235,7 +1235,9 @@ def check_for_extra_actual_arguments(self,
         for i, kind in enumerate(actual_kinds):
             if i not in all_actuals and (
                     kind != nodes.ARG_STAR or
-                    not is_empty_tuple(actual_types[i])):
+                    # We accept the other iterables than tuple (including Any)
+                    # as star arguments because they could be empty, resulting no arguments.
+                    is_non_empty_tuple(actual_types[i])):
                 # Extra actual: not matched by a formal argument.
                 ok = False
                 if kind != nodes.ARG_NAMED:
@@ -3836,9 +3838,9 @@ def is_async_def(t: Type) -> bool:
     return isinstance(t, Instance) and t.type.fullname() == 'typing.Coroutine'
 
 
-def is_empty_tuple(t: Type) -> bool:
+def is_non_empty_tuple(t: Type) -> bool:
     t = get_proper_type(t)
-    return isinstance(t, TupleType) and not t.items
+    return isinstance(t, TupleType) and bool(t.items)
 
 
 def is_duplicate_mapping(mapping: List[int], actual_kinds: List[int]) -> bool:

test-data/unit/check-varargs.test

@@ -353,7 +353,7 @@ class CC(C): pass
 from typing import Any
 d, a = None, None # type: (Any, A)
 f(a, a, *d) # Fail
-f(a, *d)    # Fail
+f(a, *d)    # Ok
 f(*d)       # Ok
 
 g(*d)
@@ -366,7 +366,6 @@ class A: pass
 [builtins fixtures/list.pyi]
 [out]
 main:3: error: Too many arguments for "f"
-main:4: error: Too many arguments for "f"
 
 [case testListVarArgsAndSubtyping]
 from typing import List
@@ -448,6 +447,21 @@ def f(x: int, *, y: str) -> None: pass
 f(y='x', *(1,))
 [builtins fixtures/list.pyi]
 
+[case testVarArgsEmptyList]
+from typing import List
+
+def foo() -> None:
+    pass
+
+lst: List[int] = []
+foo(*lst)
+[builtins fixtures/list.pyi]
+
+[case testVarArgsEmptyTuple]
+def foo() -> None:
+    pass
+
+foo(*())
 
 -- Overloads + varargs
 -- -------------------