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

Instead of widening to plain int when both bounds expand, compute the
actual combined min/max from both iterations using IntegerRangeType::fromInterval().
This mirrors the fix already applied for constant integers at line 4114.

Added test cases (Test4, Test5) exercising the integer range path.

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

Author: phpstan-bot

src/Analyser/MutatingScope.php

@@ -4204,7 +4204,19 @@ 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) {
+							$rangeMin = $range->getMin();
+							$rangeMax = $range->getMax();
+							if ($newMin !== null && ($rangeMin === null || $rangeMin < $newMin)) {
+								$newMin = $rangeMin;
+							}
+							if ($newMax !== null && ($rangeMax === null || $rangeMax > $newMax)) {
+								$newMax = $rangeMax;
+							}
+						}
+						$resultTypes[] = IntegerRangeType::fromInterval($newMin, $newMax);
 					} elseif ($gotGreater) {
 						$resultTypes[] = IntegerRangeType::fromInterval($min, null);
 					} elseif ($gotSmaller) {

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

@@ -70,6 +70,46 @@ public function iterateRowColumnIndicesDecrementing(int $rows, int $columns, int
 	}
 }
 
+class Test4
+{
+	/**
+	 * @param int<0, 10> $index
+	 */
+	public function integerRangeGeneralization(int $rows, int $index): void
+	{
+		if ($rows < 1) return;
+
+		for ($i = 0; $i < $rows; $i++) {
+			assertType('int<-3, 13>', $index);
+			if ($index > 5) {
+				$index++;
+			} else {
+				$index--;
+			}
+		}
+	}
+}
+
+class Test5
+{
+	/**
+	 * @param int<5, 15> $index
+	 */
+	public function integerRangeGeneralizationBothDirections(int $rows, int $index): void
+	{
+		if ($rows < 1) return;
+
+		for ($i = 0; $i < $rows; $i++) {
+			assertType('int<-10, max>', $index);
+			if ($index > 10) {
+				$index++;
+			} else {
+				$index = -$index;
+			}
+		}
+	}
+}
+
 class Bug12163
 {
 	/**