Do not narrow array to empty when array_find_key() returns null

- Remove `array_find_key` from the bidirectional null narrowing in
  `TypeSpecifier::resolveIdentical` that was shared with `array_key_first`
  and `array_key_last`. Unlike those functions, `array_find_key` returns
  null when no element matches the callback, not when the array is empty.
- Keep the one-directional narrowing: `array_find_key() !== null` still
  correctly implies the array is non-empty.
- Update existing test assertions in `array-find-key-existing.php` and
  `NonexistentOffsetInArrayDimFetchRuleTest` to reflect the corrected
  behavior.
- Probed analogous functions (`array_search`, `array_find`,
  `array_key_first`, `array_key_last`): none have the same issue.
  `array_search` was never in the empty-array narrowing list.
  `array_key_first`/`array_key_last` correctly imply empty array when
  returning null.

Author: phpstan-bot

src/Analyser/TypeSpecifier.php

@@ -3139,14 +3139,23 @@ private function resolveNormalizedIdentical(Expr\BinaryOp\Identical $expr, Scope
 			$unwrappedLeftExpr instanceof FuncCall
 			&& $unwrappedLeftExpr->name instanceof Name
 			&& !$unwrappedLeftExpr->isFirstClassCallable()
-			&& in_array($unwrappedLeftExpr->name->toLowerString(), ['array_key_first', 'array_key_last', 'array_find_key'], true)
 			&& isset($unwrappedLeftExpr->getArgs()[0])
 			&& $rightType->isNull()->yes()
 		) {
-			$args = $unwrappedLeftExpr->getArgs();
-			$argType = $scope->getType($args[0]->value);
-			if ($argType->isArray()->yes()) {
-				return $this->create($args[0]->value, new NonEmptyArrayType(), $context->negate(), $scope)->setRootExpr($expr);
+			$funcName = $unwrappedLeftExpr->name->toLowerString();
+			$bothDirections = in_array($funcName, ['array_key_first', 'array_key_last'], true);
+			$notNullOnly = $funcName === 'array_find_key';
+			if ($bothDirections || $notNullOnly) {
+				$args = $unwrappedLeftExpr->getArgs();
+				$argType = $scope->getType($args[0]->value);
+				if ($argType->isArray()->yes()) {
+					if ($bothDirections) {
+						return $this->create($args[0]->value, new NonEmptyArrayType(), $context->negate(), $scope)->setRootExpr($expr);
+					}
+					if ($context->falsey()) {
+						return $this->create($args[0]->value, new NonEmptyArrayType(), $context->negate(), $scope)->setRootExpr($expr);
+					}
+				}
 			}
 		}
 

tests/PHPStan/Analyser/nsrt/array-find-key-existing.php

@@ -17,7 +17,7 @@ function arrayFindKeyNotNull(array $list, string $s): void
 		assertType('int<0, max>', $key);
 		assertType('string', $list[$key]);
 	} else {
-		assertType('array{}', $list);
+		assertType('list<string>', $list);
 		assertType('null', $key);
 		assertType('*ERROR*', $list[$key]);
 	}

tests/PHPStan/Analyser/nsrt/bug-14630.php

@@ -0,0 +1,53 @@
+<?php // lint >= 8.4
+
+declare(strict_types = 1);
+
+namespace Bug14630;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param object[] $a
+ * @param object[] $b
+ */
+function d(array $a, array $b, ?int $i): void
+{
+	foreach ($a as $afterDynamicPeriodDetail) {
+		$beforeDynamicPeriodKey = array_find_key($b, static fn ($beforeDynamicPeriodDetail): bool => $beforeDynamicPeriodDetail->getRange()->equals($afterDynamicPeriodDetail->getRange()));
+		if ($beforeDynamicPeriodKey === null) {
+			$splitFromPeriodRange = $i;
+			if ($splitFromPeriodRange !== null) {
+				$beforeDynamicPeriodKey = array_find_key($b, static fn ($beforeDynamicPeriodDetail): bool => $beforeDynamicPeriodDetail->getRange()->equals($splitFromPeriodRange));
+			}
+
+			assertType('int|string|null', $beforeDynamicPeriodKey);
+			if ($beforeDynamicPeriodKey === null) {
+				continue;
+			}
+		}
+	}
+}
+
+/**
+ * @param object[] $b
+ */
+function arrayFindKeyNullDoesNotImplyEmptyArray(array $b): void
+{
+	$key = array_find_key($b, static fn ($v): bool => $v->foo());
+	if ($key === null) {
+		assertType('array<object>', $b);
+		$key2 = array_find_key($b, static fn ($v): bool => $v->bar());
+		assertType('int|string|null', $key2);
+	}
+}
+
+/**
+ * @param object[] $b
+ */
+function arrayFindKeyNotNullImpliesNonEmptyArray(array $b): void
+{
+	$key = array_find_key($b, static fn ($v): bool => $v->foo());
+	if ($key !== null) {
+		assertType('non-empty-array<object>', $b);
+	}
+}

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -1333,7 +1333,7 @@ public function testArrayFindKeyExisting(): void
 
 		$this->analyse([__DIR__ . '/../../Analyser/nsrt/array-find-key-existing.php'], [
 			[
-				'Offset null does not exist on array{}.',
+				'Offset null does not exist on list<string>.',
 				22,
 			],
 			[