Apply symmetric fix for integer range generalization in gotGreater && gotSmaller case

Instead of immediately widening to IntegerType (plain int) when integer ranges
grow in both directions, compute the actual observed min/max bounds from both
iterations using IntegerRangeType::fromInterval(). This mirrors the fix already
applied for constant integers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Analyser/MutatingScope.php

@@ -4204,7 +4204,37 @@ private function generalizeType(Type $a, Type $b, int $depth): Type
 					}
 
 					if ($gotGreater && $gotSmaller) {
-						$resultTypes[] = new IntegerType();
+						$newMin = $min;
+						$newMax = $max;
+						foreach ($integerRanges['b'] as $range) {
+							if ($range->getMin() === null) {
+								$rangeMin = PHP_INT_MIN;
+							} else {
+								$rangeMin = $range->getMin();
+							}
+							if ($range->getMax() === null) {
+								$rangeMax = PHP_INT_MAX;
+							} else {
+								$rangeMax = $range->getMax();
+							}
+
+							if ($rangeMin < $newMin) {
+								$newMin = $rangeMin;
+							}
+							if ($rangeMax <= $newMax) {
+								continue;
+							}
+
+							$newMax = $rangeMax;
+						}
+
+						if ($newMin === PHP_INT_MIN) {
+							$newMin = null;
+						}
+						if ($newMax === PHP_INT_MAX) {
+							$newMax = null;
+						}
+						$resultTypes[] = IntegerRangeType::fromInterval($newMin, $newMax);
 					} elseif ($gotGreater) {
 						$resultTypes[] = IntegerRangeType::fromInterval($min, null);
 					} elseif ($gotSmaller) {

tests/PHPStan/Analyser/nsrt/bug-12163.php

@@ -100,3 +100,22 @@ public function iterateRowColumnIndices(int $rows, int $columns): void
 		}
 	}
 }
+
+class Test4
+{
+	/**
+	 * @param int<5, 10> $index
+	 */
+	public function integerRangeGrowsBothDirections(int $size, int $index): void
+	{
+		for ($i = 0; $i < $size; $i++) {
+			assertType('int<3, 12>', $index);
+			if ($index > 7) {
+				$index = rand(3, 4);
+			} else {
+				$index = $index + 5;
+			}
+		}
+		assertType('int<3, 12>', $index);
+	}
+}