Add new ArrayUnpackingRule

conf/bleedingEdge.neon

@@ -4,5 +4,6 @@ parameters:
 		skipCheckGenericClasses: []
 		explicitMixedInUnknownGenericNew: true
 		arrayFilter: true
+		arrayUnpacking: true
 	stubFiles:
 		- ../stubs/bleedingEdge/Countable.stub

conf/config.level3.neon

@@ -1,6 +1,10 @@
 includes:
 	- config.level2.neon
 
+conditionalTags:
+	PHPStan\Rules\Arrays\ArrayUnpackingRule:
+		phpstan.rules.rule: %featureToggles.arrayUnpacking%
+
 rules:
 	- PHPStan\Rules\Arrays\ArrayDestructuringRule
 	- PHPStan\Rules\Arrays\IterableInForeachRule
@@ -74,3 +78,6 @@ services:
 			reportMaybes: %reportMaybes%
 		tags:
 			- phpstan.rules.rule
+
+	-
+		class: PHPStan\Rules\Arrays\ArrayUnpackingRule

conf/config.neon

@@ -29,6 +29,7 @@ parameters:
 			- RecursiveCallbackFilterIterator
 		explicitMixedInUnknownGenericNew: false
 		arrayFilter: false
+		arrayUnpacking: false
 	fileExtensions:
 		- php
 	checkAdvancedIsset: false
@@ -207,6 +208,7 @@ parametersSchema:
 		skipCheckGenericClasses: listOf(string()),
 		explicitMixedInUnknownGenericNew: bool(),
 		arrayFilter: bool(),
+		arrayUnpacking: bool(),
 	])
 	fileExtensions: listOf(string())
 	checkAdvancedIsset: bool()

src/Rules/Arrays/ArrayUnpackingRule.php

@@ -0,0 +1,43 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Arrays;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\ArrayItem;
+use PHPStan\Analyser\Scope;
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\StringType;
+
+/**
+ * @implements Rule<ArrayItem>
+ */
+class ArrayUnpackingRule implements Rule
+{
+
+	public function __construct(private PhpVersion $phpVersion)
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return ArrayItem::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if ($node->unpack === false || $this->phpVersion->supportsArrayUnpackingWithStringKeys()) {
+			return [];
+		}
+
+		$valueType = $scope->getType($node->value);
+
+		if ((new StringType())->isSuperTypeOf($valueType->getIterableKeyType())->no()) {
+			return [];
+		}
+
+		return [RuleErrorBuilder::message('Array unpacking cannot be used on array that potentially has string keys.')->build()];
+	}
+
+}

tests/PHPStan/Rules/Arrays/ArrayUnpackingRuleTest.php

@@ -0,0 +1,68 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Arrays;
+
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use const PHP_VERSION_ID;
+
+/**
+ * @extends RuleTestCase<ArrayUnpackingRule>
+ */
+class ArrayUnpackingRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new ArrayUnpackingRule(self::getContainer()->getByType(PhpVersion::class));
+	}
+
+	public function testRule(): void
+	{
+		if (PHP_VERSION_ID >= 80100) {
+			$this->markTestSkipped('Test requires PHP version <= 8.0');
+		}
+
+		$this->analyse([__DIR__ . '/data/array-unpacking.php'], [
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				7,
+			],
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				18,
+			],
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				24,
+			],
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				29,
+			],
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				40,
+			],
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				52,
+			],
+			[
+				'Array unpacking cannot be used on array that potentially has string keys.',
+				63,
+			],
+		]);
+	}
+
+	public function testRuleOnPHP81(): void
+	{
+		if (PHP_VERSION_ID < 80100) {
+			$this->markTestSkipped('Test requires PHP 8.1+');
+		}
+
+		$this->analyse([__DIR__ . '/data/array-unpacking.php'], []);
+	}
+
+}

tests/PHPStan/Rules/Arrays/data/array-unpacking.php

@@ -0,0 +1,66 @@
+<?php // lint >= 7.4
+
+namespace ArrayUnpacking;
+
+$foo = ['foo' => 'bar', 1, 2, 3];
+
+$bar = [...$foo];
+
+/** @param array<int, string> $bar */
+function intKeyedArray(array $bar)
+{
+	$baz = [...$bar];
+}
+
+/** @param array<string, string> $bar */
+function stringKeyedArray(array $bar)
+{
+	$baz = [...$bar];
+}
+
+/** @param array<array-key, string> $bar */
+function unionKeyedArray(array $bar)
+{
+	$baz = [...$bar];
+}
+
+function mixedKeyedArray(array $bar)
+{
+	$baz = [...$bar];
+}
+
+/**
+ * @param array<mixed, string> $foo
+ * @param array<int, string> $bar
+ */
+function multipleUnpacking(array $foo, array $bar)
+{
+	$baz = [
+		...$bar,
+		...$foo,
+	];
+}
+
+/**
+ * @param array<mixed, string> $foo
+ * @param array<string, string> $bar
+ */
+function foo(array $foo, array $bar)
+{
+	$baz = [
+		$bar,
+		...$foo
+	];
+}
+
+/**
+ * @param array{foo: string, bar:int} $foo
+ * @param array{1, 2, 3, 4} $bar
+ */
+function unpackingArrayShapes(array $foo, array $bar)
+{
+	$baz = [
+		...$foo,
+		...$bar,
+	];
+}