Fix an error when LHS is of MemberExpr type

Author: AFanaei

mypy/semanal.py

@@ -2123,7 +2123,7 @@ def analyze_namedtuple_assign(self, s: AssignmentStmt) -> bool:
         if len(s.lvalues) != 1 or type(s.lvalues[0]) not in [NameExpr, MemberExpr]:
             return False
         lvalue = s.lvalues[0]
-        name = lvalue.name
+        name = lvalue.name if isinstance(lvalue, NameExpr) else None
         is_named_tuple, info = self.named_tuple_analyzer.check_namedtuple(s.rvalue, name,
                                                                           self.is_func_scope())
         if not is_named_tuple: