nullCoalesce.unnecessary

Code example

<?php declare(strict_types = 1);

function alwaysDefinedNullableParam(?string $name): ?string
{
	return $name ?? null;
}

Why is it reported?

The ?? (null coalesce) operator returns its right side only when the left side is either undefined or null. When the right side is itself null, the operator can only ever produce null in that case -- exactly the value the left side already holds. Combined with a left side that is always defined, the whole ?? null never changes the result and is dead code.

In the example, $name is a parameter, so it is always set, and its value is already ?string. Writing $name ?? null returns $name when it is a string and null when it is null -- which is the same as just returning $name.

The same applies to ??= null, which assigns null only when the target is undefined or already null, and so never changes anything when the target is always set.

This check is part of Bleeding Edge.

How to fix it

Remove the redundant ?? null:

 function alwaysDefinedNullableParam(?string $name): ?string
 {
-	return $name ?? null;
+	return $name;
 }

Remove the redundant ??= null assignment:

 function assignCoalesceAlwaysSet(?string $name): void
 {
 	$x = $name;
-	$x ??= null;
 }

If the intent was to fall back to a non-null default, use that value on the right side instead:

 function alwaysDefinedNullableParam(?string $name): string
 {
-	return $name ?? null;
+	return $name ?? 'default';
 }