Properties with native types can be used in isset() in case they are uninitialized

Author: ondrejmirtes

src/Rules/IssetCheck.php

@@ -7,6 +7,7 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Rules\Properties\PropertyDescriptor;
 use PHPStan\Rules\Properties\PropertyReflectionFinder;
+use PHPStan\Type\MixedType;
 use PHPStan\Type\NullType;
 use PHPStan\Type\Type;
 use PHPStan\Type\VerbosityLevel;
@@ -93,6 +94,13 @@ public function check(Expr $expr, Scope $scope, string $operatorDescription, ?Ru
 				return null;
 			}
 
+			$nativeType = $propertyReflection->getNativeType();
+			if (!$nativeType instanceof MixedType) {
+				if (!$scope->isSpecified($expr)) {
+					return null;
+				}
+			}
+
 			$propertyDescription = $this->propertyDescriptor->describeProperty($propertyReflection, $expr);
 			$propertyType = $propertyReflection->getWritableType();
 

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -81,4 +81,24 @@ public function testRule(): void
 		]);
 	}
 
+	public function testNativePropertyTypes(): void
+	{
+		if (PHP_VERSION_ID < 70400) {
+			$this->markTestSkipped('Test requires PHP 7.4.');
+		}
+		$this->analyse([__DIR__ . '/data/isset-native-property-types.php'], [
+			/*[
+				// no way to achieve this with current PHP Reflection API
+				// There's ReflectionClass::getDefaultProperties()
+				// but it cannot differentiate between `public int $foo` and `public int $foo = null`;
+				'Property IssetNativePropertyTypes\Foo::$hasDefaultValue (int) in isset() is not nullable.',
+				17,
+			],*/
+			[
+				'Property IssetNativePropertyTypes\Foo::$isAssignedBefore (int) in isset() is not nullable.',
+				20,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/isset-native-property-types.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace IssetNativePropertyTypes;
+
+class Foo
+{
+
+	public int $hasDefaultValue = 0;
+
+	public int $isAssignedBefore;
+
+	public int $canBeUninitialized;
+
+}
+
+function (Foo $foo): void {
+	echo isset($foo->hasDefaultValue) ? $foo->hasDefaultValue : null;
+
+	$foo->isAssignedBefore = 5;
+	echo isset($foo->isAssignedBefore) ? $foo->isAssignedBefore : null;
+
+	echo isset($foo->canBeUninitialized) ? $foo->canBeUninitialized : null;
+};