Fix phpstan/phpstan#14314: Incorrect count narrowing removes unrelated constant arrays from union

- Added fallback in TypeSpecifier::specifyTypesForCountFuncCall for falsey context
- When recursive truthy call fails (remaining size includes 0), directly filter
  constant arrays by their exact sizes instead of using TypeCombinator::remove
- This avoids the issue where remove() considers a shorter constant array as a
  supertype of a longer one, incorrectly eliminating both from the union
- New regression test in tests/PHPStan/Analyser/nsrt/bug-14314.php

Author: VincentLanglet

src/Analyser/TypeSpecifier.php

@@ -1294,6 +1294,27 @@ private function specifyTypesForCountFuncCall(
 					return $result;
 				}
 			}
+
+			// Fallback: directly filter constant arrays by their exact sizes.
+			// This avoids using TypeCombinator::remove() with falsey context,
+			// which can incorrectly remove arrays whose count doesn't match
+			// but whose shape is a subtype of the matched array.
+			$keptTypes = [];
+			foreach ($type->getConstantArrays() as $arrayType) {
+				if ($sizeType->isSuperTypeOf($arrayType->getArraySize())->yes()) {
+					continue;
+				}
+
+				$keptTypes[] = $arrayType;
+			}
+			if ($keptTypes !== []) {
+				return $this->create(
+					$countFuncCall->getArgs()[0]->value,
+					TypeCombinator::union(...$keptTypes),
+					$context->negate(),
+					$scope,
+				)->setRootExpr($rootExpr);
+			}
 		}
 
 		$resultTypes = [];

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

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug14314;
+
+use function PHPStan\Testing\assertType;
+
+function () {
+	preg_match('/^(.)$/', '', $matches) || preg_match('/^(.)(.)(.)$/', '', $matches);
+	assertType('array{}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}|array{non-falsy-string, non-empty-string}', $matches);
+	if (count($matches) === 2) {
+		assertType('array{non-falsy-string, non-empty-string}', $matches);
+		return;
+	}
+	assertType('array{}|array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}', $matches);
+	if (count($matches) === 4) {
+		assertType('array{non-falsy-string, non-empty-string, non-empty-string, non-empty-string}', $matches);
+	}
+};