feat: treat void as null for null coalescing operator #2494

Original file line number	Diff line number	Diff line change
Expand Up		@@ -8,6 +8,7 @@
		use PHPStan\Rules\Rule;
		use PHPStan\Type\NullType;
		use PHPStan\Type\Type;
	use PHPStan\Type\VoidType;

		/**
		* @implements Rule<Node\Expr>
Expand All		@@ -27,12 +28,13 @@ public function getNodeType(): string
		public function processNode(Node $node, Scope $scope): array
		{
		$typeMessageCallback = static function (Type $type): ?string {
	$isVoid = (new VoidType())->isSuperTypeOf($type);
		$isNull = (new NullType())->isSuperTypeOf($type);
	if ($isNull->maybe()) {
	if ($isNull->maybe() \|\| $isVoid->maybe()) {
		return null;
		}

	if ($isNull->yes()) {
	if ($isNull->yes() \|\| $isVoid->yes()) {
		return 'is always null';
		}

Expand Down

13 changes: 13 additions & 0 deletions tests/PHPStan/Rules/Variables/NullCoalesceRuleTest.php

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -368,4 +368,17 @@ public function testBug8084(): void
		$this->analyse([__DIR__ . '/data/bug-8084.php'], []);
		}

	public function testVoid(): void
	{
	$this->treatPhpDocTypesAsCertain = true;
	$this->strictUnnecessaryNullsafePropertyFetch = true;

	$this->analyse([__DIR__ . '/data/null-coalesce-void.php'], [
	[
	'Expression on left side of ?? is always null.',
	22,
	],
	]);
	}

		}

22 changes: 22 additions & 0 deletions tests/PHPStan/Rules/Variables/data/null-coalesce-void.php

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,22 @@
	<?php // lint >= 8.0

	namespace CoalesceRuleVoid;

	/** @return array\|void */
	function get_post_custom_keys($maybe = false)
	{
	if ($maybe) {
	return;
	}

	return [];
	}

	function foo_bar(): void
	{
	return;
	}

	$test1 = get_post_custom_keys(true) ?? 'foo';

	$test2 = foo_bar() ?? 'bar';

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