Preserve TemplateTypeArray when merging array types

src/Type/TypeCombinator.php

@@ -17,6 +17,7 @@
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\Generic\GenericClassStringType;
+use PHPStan\Type\Generic\TemplateArrayType;
 use PHPStan\Type\Generic\TemplateBenevolentUnionType;
 use PHPStan\Type\Generic\TemplateType;
 use PHPStan\Type\Generic\TemplateTypeFactory;
@@ -699,11 +700,35 @@ private static function processArrayTypes(array $arrayTypes): array
 		}
 
 		if ($generalArrayOccurred) {
+			$scopes = [];
+			$useTemplateArray = true;
+			foreach ($arrayTypes as $arrayType) {
+				if (!$arrayType instanceof TemplateArrayType) {
+					$useTemplateArray = false;
+					break;
+				}
+
+				$scopes[$arrayType->getScope()->describe()] = $arrayType;
+			}
+
+			$arrayType = new ArrayType(
+				self::union(...$keyTypesForGeneralArray),
+				self::union(...self::optimizeConstantArrays($valueTypesForGeneralArray)),
+			);
+
+			if ($useTemplateArray && count($scopes) === 1) {
+				$templateArray = array_values($scopes)[0];
+				$arrayType = new TemplateArrayType(
+					$templateArray->getScope(),
+					$templateArray->getStrategy(),
+					$templateArray->getVariance(),
+					$templateArray->getName(),
+					$arrayType,
+				);
+			}
+
 			return [
-				self::intersect(new ArrayType(
-					self::union(...$keyTypesForGeneralArray),
-					self::union(...self::optimizeConstantArrays($valueTypesForGeneralArray)),
-				), ...$accessoryTypes),
+				self::intersect($arrayType, ...$accessoryTypes),
 			];
 		}
 

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -42,6 +42,7 @@ public function dataFileAsserts(): iterable
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/generic-enum-class-string.php');
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7162.php');
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-10201.php');
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-10445.php');
 		}
 
 		require_once __DIR__ . '/data/generic-generalization.php';

tests/PHPStan/Analyser/data/bug-10445.php

@@ -0,0 +1,49 @@
+<?php // lint >= 8.1
+
+namespace Bug10445;
+
+use function PHPStan\Testing\assertType;
+
+enum Error {
+	case A;
+	case B;
+	case C;
+}
+
+/**
+ * @template T of array
+ */
+class Response
+{
+	/**
+	 * @param ?T $data
+	 * @param Error[] $errors
+	 */
+	public function __construct(
+		public ?array $data,
+		public array $errors = [],
+	) {
+	}
+
+	/**
+	 * @return array{
+	 *   result: ?T,
+	 *   errors?: string[],
+	 * }
+	 */
+	public function format(): array
+	{
+		$output = [
+			'result' => $this->data,
+		];
+		assertType('array{result: T of array (class Bug10445\Response, argument)|null}', $output);
+		if (count($this->errors) > 0) {
+			$output['errors'] = array_map(fn ($e) => $e->name, $this->errors);
+			assertType("array{result: T of array (class Bug10445\Response, argument)|null, errors: non-empty-array<'A'|'B'|'C'>}", $output);
+		} else {
+			assertType('array{result: T of array (class Bug10445\Response, argument)|null}', $output);
+		}
+		assertType("array{result: T of array (class Bug10445\Response, argument)|null, errors?: non-empty-array<'A'|'B'|'C'>}", $output);
+		return $output;
+	}
+}