Fix phpstan/phpstan#11488: Wrongly assumed undefined variable since 1.11.10

src/Analyser/TypeSpecifier.php

@@ -2520,6 +2520,38 @@
 				);
 			}
 
+			// For falsey context with unions of multiple constant arrays, directly
+			// filter union members by size to avoid TypeCombinator::remove issues
+			// where array types have supertype relationships (e.g. array{mixed} is
+			// a supertype of array{mixed, string|null, mixed}, causing remove to
+			// incorrectly eliminate all union members)
+			$arrays = $argType->getArrays();
+			if (
+				$context->falsey()
+				&& count($arrays) > 1
+				&& $argType->isConstantArray()->yes()
+				&& $rightType->isInteger()->yes()
+				&& $this->isNormalCountCall($unwrappedLeftExpr, $argType, $scope)->yes()
+			) {
+				$result = [];
+				foreach ($arrays as $innerType) {
+					$arraySize = $innerType->getArraySize();
+					$isSize = $rightType->isSuperTypeOf($arraySize);
+					if ($isSize->yes()) {
+						continue;
+					}
+
+					$result[] = $innerType;
+				}
+
+				if (count($result) > 0) {
+					$funcTypes = $this->create($unwrappedLeftExpr, $rightType, $context, $scope)->setRootExpr($expr);
+					return $funcTypes->unionWith(
+						$this->create($unwrappedLeftExpr->getArgs()[0]->value, TypeCombinator::union(...$result), TypeSpecifierContext::createTrue(), $scope)->setAlwaysOverwriteTypes()->setRootExpr($expr),
+					);
+				}
+			}
+
 			$specifiedTypes = $this->specifyTypesForCountFuncCall($unwrappedLeftExpr, $argType, $rightType, $context, $scope, $expr);
 			if ($specifiedTypes !== null) {
 				return $specifiedTypes;

tests/PHPStan/Analyser/nsrt/bug-11488.php

@@ -0,0 +1,24 @@
+<?php declare(strict_types = 1);
+
+namespace Bug11488;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+	/**
+	 * @param array{mixed}|array{mixed, string|null, mixed} $row
+	 */
+	protected function test(array $row): string
+	{
+		if (count($row) !== 1) {
+			assertType('array{mixed, string|null, mixed}', $row);
+
+			[$field, $operator, $value] = $row;
+			assertType('string|null', $operator);
+			return $operator ?? '=';
+		}
+
+		return '';
+	}
+}