bare-name-capture-pattern / E1901

Message emitted:

The name capture `case %s` makes the remaining patterns unreachable. Use a dotted name (for example an enum) to fix this.

Description:

Emitted when a name capture pattern is used in a match statement and there are case statements below it.

Problematic code:

red = 0
green = 1
blue = 2


def func(color):
    match color:
        case red:  # [bare-name-capture-pattern]
            print("I see red!")
        case green:  # [bare-name-capture-pattern]
            print("Grass is green")
        case blue:
            print("I'm feeling the blues :(")

Correct code:

from enum import Enum


class Color(Enum):
    RED = 0
    GREEN = 1
    BLUE = 2


def func(color: Color) -> None:
    match color:
        case Color.RED:
            print("I see red!")
        case Color.GREEN:
            print("Grass is green")
        case Color.BLUE:
            print("I'm feeling the blues :(")

Related links:

• PEP 636

Created by the match_statements checker.