match.unhandled - Phpstan

Code example

php

<?php declare(strict_types = 1);

enum Suit
{
	case Hearts;
	case Diamonds;
	case Clubs;
	case Spades;
}

function suitToColor(Suit $suit): string
{
	return match ($suit) {
		Suit::Hearts, Suit::Diamonds => 'red',
		Suit::Clubs => 'black',
	};
}

Why is it reported?

The match expression does not cover all possible values of the subject type. PHP throws an \UnhandledMatchError at runtime when no match arm matches the subject value.

In the example above, the Suit::Spades case is not handled, so passing it to suitToColor() would cause a runtime error.

How to fix it

Add the missing match arms to handle all possible values:

diff-php

 return match ($suit) {
 	Suit::Hearts, Suit::Diamonds => 'red',
 	Suit::Clubs => 'black',
+	Suit::Spades => 'black',
 };

Alternatively, add a default arm to catch any remaining values:

diff-php

 return match ($suit) {
 	Suit::Hearts, Suit::Diamonds => 'red',
-	Suit::Clubs => 'black',
+	Suit::Clubs, Suit::Spades => 'black',
 };