false error with simple nested structure

[zoranbosnjak]

Bug Report

mypy reports error where it is not suppose to.

To Reproduce

from typing import *                                                                                       
                                                                                                           
# types                                                                                                    
MyDict = TypedDict('MyDict', {"a" : int, "b" : str}, total=False)                                          
MyUnion = Union[                                                                                           
    Tuple[Literal["arg_int"], int],                                                                        
    Tuple[Literal["arg_str"], str],                                                                        
    Tuple[Literal["arg_dict"], MyDict]                                                                     
]                                                                                                          
                                                                                                           
# variables                                                                                                
var1 : MyUnion = ('arg_int', 1)                                                                            
var2 : MyUnion = ('arg_str', 'test')                                                                       
var3 : MyUnion = ('arg_dict', {'a': 1})    

Expected Behavior

No error is expected in this case.

Actual Behavior

The following error is reported:

error: Incompatible types in assignment (expression has type "tuple[str, dict[str, int]]", variable has type "tuple[Literal['arg_int'], int] | tuple[Literal['arg_str'], str] | tuple[Literal['arg_dict'], MyDict]")  [assignment]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.9.0
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.11.8

Also tryed with mypy playground with all latest versions and got the same result.