type-alias-without-annotation (PYI026)

Derived from the flake8-pyi linter.

Fix is always available.

What it does

Checks for type alias definitions that are not annotated with typing.TypeAlias.

Why is this bad?

In Python, a type alias is defined by assigning a type to a variable (e.g., Vector = list[float]).

It's best to annotate type aliases with the typing.TypeAlias type to make it clear that the statement is a type alias declaration, as opposed to a normal variable assignment.

Example

Vector = list[float]

Use instead:

from typing import TypeAlias

Vector: TypeAlias = list[float]