Type inference with "or" between two lists doesn't work properly

Bug Report

When two lists whose elements have different types appear in an or expression, type inferencing doesn't work properly if the second list is a literal. If the second list is assigned to a variable first, the type inference works.

For instance, if my_str_list is a List[str] and my_int_list is a List[int], the expression my_str_list or my_int_list has inferred type Union[List[str], List[int]], while my_str_list or [1, 2, 3] has inferred type List[str] (accompanied by an error saying the elements of the literal list are the wrong type).

To Reproduce

The following file:

list_of_ints: list[int] = [1,2,3]

reveal_type(["a", "b"] or [1,2,3])  # Produces error. Revealed type is 'builtins.list[builtins.str*]'
reveal_type(["a", "b"] or 123)  # Works. Revealed type is 'Union[builtins.list[builtins.str*], Literal[123]?]'
reveal_type(123 or [1,2,3])  # Works. Revealed type is 'Union[Literal[123]?, builtins.list[builtins.int*]]'
reveal_type(["a", "b"] or list_of_ints)  # Works. Revealed type is 'Union[builtins.list[builtins.str*], builtins.list[builtins.int]]'

gives output

file.py:3: note: Revealed type is 'builtins.list[builtins.str*]'
file.py:3: error: List item 0 has incompatible type "int"; expected "str"
file.py:3: error: List item 1 has incompatible type "int"; expected "str"
file.py:3: error: List item 2 has incompatible type "int"; expected "str"
file.py:4: note: Revealed type is 'Union[builtins.list[builtins.str*], Literal[123]?]'
file.py:5: note: Revealed type is 'Union[Literal[123]?, builtins.list[builtins.int*]]'
file.py:6: note: Revealed type is 'Union[builtins.list[builtins.str*], builtins.list[builtins.int]]'
Found 3 errors in 1 file (checked 1 source file)

Expected Behavior

Expected no error and reveal_type(["a", "b"] or [1,2,3]) to be Union[List[str], List[int]] or even List[int] if mypy is able to determine that ["a", "b"] is a truthy value.

Actual Behavior

reveal_type(["a", "b"] or [1,2,3]) is List[str] and there is error claiming the types of the literal list are wrong.

Your Environment

• Mypy version used: 0.812
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.9.5
• Operating system and version: Red Hat Enterprise Linux Server 7.9 (Maipo)

Use the supplied reproduction file with mypy and no command-line flags, checking the reveal_type results for the or expressions. Trace the type-inference handling for or expressions involving list literals. Done means the two-list expression produces no element-type errors and reveals a union of the list types, or the more precise truthiness-based result described in the issue.