Fix tuple multiplication in MergedSequenceNode (GH-4864)

Fixes https://github.com/cython/cython/issues/4861

Cython/Compiler/ExprNodes.py

@@ -8482,7 +8482,7 @@ class MergedSequenceNode(ExprNode):
         if type in (list_type, tuple_type) and args and args[0].is_sequence_constructor:
             # construct a list directly from the first argument that we can then extend
             if args[0].type is not list_type:
-                args[0] = ListNode(args[0].pos, args=args[0].args, is_temp=True)
+                args[0] = ListNode(args[0].pos, args=args[0].args, is_temp=True, mult_factor=args[0].mult_factor)
         ExprNode.__init__(self, pos, args=args, type=type)
 
     def calculate_constant_result(self):

tests/run/pep448_extended_unpacking.pyx

@@ -185,6 +185,24 @@ def unpack_list_literal_mult():
     return [*([1, 2, *([4, 5] * 2)] * 3)]
 
 
+def unpack_list_tuple_mult():
+    """
+    >>> unpack_list_tuple_mult()
+    [1, 1]
+    """
+    return [*(1,) * 2]
+
+
+def unpack_list_tuple_bad_mult():
+    """
+    >>> unpack_list_tuple_bad_mult()
+    Traceback (most recent call last):
+    ...
+    TypeError: can't multiply sequence by non-int of type 'float'
+    """
+    return [*(1,) * 1.5]
+
+
 @cython.test_fail_if_path_exists(
     "//ListNode//ListNode",
     "//MergedSequenceNode",