Add tests for count narrowing with optional keys and IntegerRange sizeType

Address review concerns from PR #5239:
- Test that IntegerRange sizeType doesn't incorrectly lose arrays with optional keys
  (fully covering range correctly removes, partially covering range correctly keeps)
- Test sequential count checks preserve narrowing across multiple branches
- Test that other variable type specifications are not lost from the early return

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

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-14314.php

@@ -18,3 +18,101 @@ function () {
 		assertType('array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}', $matches);
 	}
 };
+
+class Bug14314Test
+{
+	/**
+	 * Test: union with array{} and arrays with optional keys
+	 * @param array{}|array{0: string, 1: string, 2?: string} $arr
+	 */
+	public function testOptionalKeysWithEmpty(array $arr): void
+	{
+		assertType('array{}|array{0: string, 1: string, 2?: string}', $arr);
+		if (count($arr) === 3) {
+			assertType('array{string, string, string}', $arr);
+			return;
+		}
+		// Fallback keeps full array{0: string, 1: string, 2?: string} since its size
+		// range (2..3) is not fully contained in sizeType (3)
+		assertType('array{}|array{0: string, 1: string, 2?: string}', $arr);
+	}
+
+	/**
+	 * Test: IntegerRange sizeType fully covers optional key size range - array is correctly removed
+	 * @param array{}|array{0: string, 1: string, 2?: string} $arr
+	 * @param int<2, 3> $twoOrThree
+	 */
+	public function testIntRangeFullyCoveringOptionalKeys(array $arr, int $twoOrThree): void
+	{
+		if (count($arr) === $twoOrThree) {
+			assertType('array{0: string, 1: string, 2?: string}', $arr);
+			return;
+		}
+		// int<2,3> fully covers the optional-key array's size range (2..3),
+		// so the array is correctly removed in the falsey branch
+		assertType('array{}', $arr);
+	}
+
+	/**
+	 * Test: IntegerRange partially covers optional key size range - array is kept
+	 * @param array{}|array{0: string, 1: string, 2?: string, 3?: string} $arr
+	 * @param int<2, 3> $twoOrThree
+	 */
+	public function testIntRangePartiallyCoveringOptionalKeys(array $arr, int $twoOrThree): void
+	{
+		if (count($arr) === $twoOrThree) {
+			assertType('array{0: string, 1: string, 2?: string, 3?: string}', $arr);
+			return;
+		}
+		// int<2,3> does NOT fully cover size range (2..4), so the array is kept
+		assertType('array{}|array{0: string, 1: string, 2?: string, 3?: string}', $arr);
+	}
+
+	/**
+	 * Test: IntegerRange sizeType with union of constant arrays including array{}
+	 * @param array{}|array{string}|array{string, string, string, string} $arr
+	 * @param int<2, 4> $twoToFour
+	 */
+	public function testIntRangeWithUnionAndEmpty(array $arr, int $twoToFour): void
+	{
+		if (count($arr) === $twoToFour) {
+			assertType('array{string, string, string, string}', $arr);
+			return;
+		}
+		assertType('array{}|array{string, string, string, string}|array{string}', $arr);
+	}
+}
+
+// Test: sequential count checks preserve narrowing correctly
+function () {
+	preg_match('/^(.)$/', '', $m) || preg_match('/^(.)(.)(.)$/', '', $m) || preg_match('/^(.)(.)(.)(.)(.)(.)$/', '', $m);
+	assertType('array{}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}|array{non-falsy-string, non-empty-string}', $m);
+	if (count($m) === 2) {
+		assertType('array{non-falsy-string, non-empty-string}', $m);
+		return;
+	}
+	assertType('array{}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}', $m);
+	if (count($m) === 4) {
+		assertType('array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}', $m);
+		return;
+	}
+	assertType('array{}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string}', $m);
+	if (count($m) === 7) {
+		assertType('array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string, non-empty-string}', $m);
+	}
+};
+
+// Test: count narrowing does not lose other variable types
+function (int $x) {
+	preg_match('/^(.)$/', '', $matches) || preg_match('/^(.)(.)(.)$/', '', $matches);
+	if ($x > 0) {
+		assertType('int<1, max>', $x);
+		if (count($matches) === 2) {
+			assertType('array{non-falsy-string, non-empty-string}', $matches);
+			assertType('int<1, max>', $x);
+			return;
+		}
+		assertType('array{}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}', $matches);
+		assertType('int<1, max>', $x);
+	}
+};