Fix isset() bug

Author: ondrejmirtes

src/Type/TypeCombinator.php

@@ -618,12 +618,13 @@ public static function intersect(Type ...$types): Type
 		}
 
 		// transform A & (B & C) to A & B & C
-		foreach ($types as $i => &$type) {
+		for ($i = 0; $i < count($types); $i++) {
+			$type = $types[$i];
 			if (!($type instanceof IntersectionType)) {
 				continue;
 			}
 
-			array_splice($types, $i, 1, $type->getTypes());
+			array_splice($types, $i--, 1, $type->getTypes());
 		}
 
 		// transform IntegerType & ConstantIntegerType to ConstantIntegerType

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -101,4 +101,9 @@ public function testNativePropertyTypes(): void
 		]);
 	}
 
+	public function testBug4290(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-4290.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/bug-4290.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Bug4290;
+
+class HelloWorld
+{
+	public function test(): void
+	{
+		$array = self::getArray();
+
+		$data = array_filter([
+			'status' => isset($array['status']) ? $array['status'] : null,
+			'value' => isset($array['value']) ? $array['value'] : null,
+		]);
+
+		if (count($data) === 0) {
+			return;
+		}
+
+		isset($data['status']) ? 1 : 0;
+	}
+
+	/**
+	 * @return string[]
+	 */
+	public static function getArray(): array
+	{
+		return ['value' => '100'];
+	}
+}