New Rule: Use Sequence instead of list to annotate arguments

[jd-solanki]

Hi 👋🏻

Thanks for the amazing & blazing fast ecosystem 🫡

With the following code:

from pydantic import BaseModel

class Itembase(BaseModel):
    title: str

class ItemRead(Itembase): ...

def my_util(Itembase): ...

items = [ItemRead(title"my title")]

my_utils(items) # 🚨 Type Error: `Type parameter "_T@list" is invariant, Consider switching from "list" to "Sequence" which is covariant`

I checked the typing module and found this quote:

Note that to annotate arguments, it is preferred to use an abstract collection type such as Sequence or Iterable rather than to use list or typing.List.

Hence, I'm raising an issue that'll enforce using Sequence instead of list

[twoertwein]

If ruff can analyze the minimally needed types/methods for arguments and, based on that, suggests widening the type (for example, from list to Sequence), that would be amazing!

A blanket recommendation without some guard rails to replace list with Sequence would probably produce too many false positives.

[mikeshardmind]

Changing list to Sequence is often incorrect. MutableSequence is less likely to be a problem, but even that can cause issue if you are relying on the sequence being an actual list somewhere else. This would be extremely disruptive in many code bases due to interactions with other code outside of someone's control (you can't call a function expecting a list when you only know it's a sequence, for example)