Bug Report

Mypy reportsUnsupported operand types for + when concatenating two lists, when the second operand is a subtype of the first.

This was previously mentioned inthis comment in#5492

Below is a simple concise example

To Reproduce

classA:passclassB(A):passdeffoo(a:list[A])->None:passl1:list[A]= [A(),B()]l2:list[B]= [B()]l3=l1+l2foo(l2+l1)# OK, no errorfoo(l3)# also OKfoo(l1+l2)# ERROR: Unsupported operand types for + ("List[A]" and "List[B]")  [operator]mypy(error)

gist link

Expected Behavior
No error on the last line

Actual Behavior
Reports spurious error

Your Environment

• Mypy version used: mypy 1.2.0
• Mypy command-line flags: None
• Mypy configuration options frommypy.ini (and other config files): from pyproject.toml

ignore_missing_imports = trueshow_column_numbers = truewarn_redundant_casts = truewarn_unused_ignores = truewarn_unused_configs = truefollow_imports = "normal"plugins = ["pydantic.mypy"]

• Python version used: 3.10