Report float and null offset based on PHP version

src/Php/PhpVersion.php

@@ -414,4 +414,14 @@ public function hasPDOSubclasses(): bool
 		return $this->versionId >= 80400;
 	}
 
+	public function deprecatesImplicitlyFloatConversionToInt(): bool
+	{
+		return $this->versionId >= 80100;
+	}
+
+	public function deprecatesNullArrayOffset(): bool
+	{
+		return $this->versionId >= 80500;
+	}
+
 }

src/Rules/Arrays/AllowedArrayKeysTypes.php

@@ -2,6 +2,7 @@
 
 namespace PHPStan\Rules\Arrays;
 
+use PHPStan\Php\PhpVersion;
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\BooleanType;
 use PHPStan\Type\Constant\ConstantBooleanType;
@@ -21,15 +22,22 @@
 final class AllowedArrayKeysTypes
 {
 
-	public static function getType(): Type
+	public static function getType(PhpVersion $phpVersion): Type
 	{
-		return new UnionType([
+		$allowedTypes = [
 			new IntegerType(),
 			new StringType(),
-			new FloatType(),
 			new BooleanType(),
-			new NullType(),
-		]);
+		];
+
+		if (!$phpVersion->deprecatesImplicitlyFloatConversionToInt()) {
+			$allowedTypes[] = new FloatType();
+		}
+		if (!$phpVersion->deprecatesNullArrayOffset()) {
+			$allowedTypes[] = new NullType();
+		}
+
+		return new UnionType($allowedTypes);
 	}
 
 	public static function narrowOffsetKeyType(Type $varType, Type $keyType): ?Type

src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php

@@ -6,6 +6,7 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\AutowiredParameter;
 use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Rules\RuleLevelHelper;
@@ -23,6 +24,7 @@ final class InvalidKeyInArrayDimFetchRule implements Rule
 
 	public function __construct(
 		private RuleLevelHelper $ruleLevelHelper,
+		private PhpVersion $phpVersion,
 		#[AutowiredParameter]
 		private bool $reportMaybes,
 	)
@@ -56,17 +58,18 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
+		$phpVersion = $this->phpVersion;
 		$dimensionType = $this->ruleLevelHelper->findTypeToCheck(
 			$scope,
 			$node->dim,
 			'',
-			static fn (Type $dimType): bool => AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimType)->yes(),
+			static fn (Type $dimType): bool => AllowedArrayKeysTypes::getType($phpVersion)->isSuperTypeOf($dimType)->yes(),
 		)->getType();
 		if ($dimensionType instanceof ErrorType) {
 			return [];
 		}
 
-		$isSuperType = AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimensionType);
+		$isSuperType = AllowedArrayKeysTypes::getType($phpVersion)->isSuperTypeOf($dimensionType);
 		if ($isSuperType->yes() || ($isSuperType->maybe() && !$this->reportMaybes)) {
 			return [];
 		}

tests/PHPStan/Rules/Arrays/InvalidKeyInArrayDimFetchRuleTest.php

@@ -2,6 +2,7 @@
 
 namespace PHPStan\Rules\Arrays;
 
+use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleLevelHelper;
 use PHPStan\Testing\RuleTestCase;
@@ -16,7 +17,11 @@ class InvalidKeyInArrayDimFetchRuleTest extends RuleTestCase
 	protected function getRule(): Rule
 	{
 		$ruleLevelHelper = new RuleLevelHelper(self::createReflectionProvider(), true, false, true, true, true, false, true);
-		return new InvalidKeyInArrayDimFetchRule($ruleLevelHelper, true);
+		return new InvalidKeyInArrayDimFetchRule(
+			$ruleLevelHelper,
+			self::getContainer()->getByType(PhpVersion::class),
+			true
+		);
 	}
 
 	public function testInvalidKey(): void