List is incompatible with Sequence in parameter

[isac322]

• Are you reporting a bug, or opening a feature request?

A Bug maybe?

• Please insert below the code you are checking with mypy

test.py:

from typing import Sequence, List

class A:
    def test(self, t: Sequence[int]) -> Sequence[str]:
        pass

class B(A):
    def test(self, t: List[int]) -> List[str]:
        pas

• What is the actual output?

mypy test.py

test.py:8: error: Argument 1 of "test" is incompatible with supertype "A"; supertype defines the argument type as "Iterable[int]"
Found 1 error in 1 file (checked 1 source file)

• What is the output you expect?

mypy test.py

Success: no issues found in 1 source file

• What are the versions of mypy and Python you are using?

  • mypy: 0.740
  • python: 2.7.13 and 3.7.6 (tested both)

• Do you see the same issue after installing mypy from Git master?

Yes (on 989626a)

[JukkaL]

This signature violates Liskov substitution principle (https://en.wikipedia.org/wiki/Liskov_substitution_principle). You can use # type: ignore[override] to silence the error (add it to the line that genreates the error) if you don't care about the unsafety.