Do not union array shape with empty array, use optional offset instead

Author: ondrejmirtes

phpstan-baseline.neon

@@ -1698,7 +1698,7 @@ parameters:
 		-
 			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantArrayType is error\-prone and deprecated\. Use Type\:\:getConstantArrays\(\) instead\.$#'
 			identifier: phpstanApi.instanceofType
-			count: 14
+			count: 16
 			path: src/Type/TypeCombinator.php
 
 		-

src/PhpDoc/TypeNodeResolver.php

@@ -674,8 +674,8 @@ static function (string $variance): TemplateTypeVariance {
 					&& ($finiteTypes[0] instanceof ConstantStringType || $finiteTypes[0] instanceof ConstantIntegerType)
 				) {
 					$arrayBuilder = ConstantArrayTypeBuilder::createEmpty();
-					$arrayBuilder->setOffsetValueType($finiteTypes[0], $genericTypes[1]);
-					$arrayType = TypeCombinator::union($arrayBuilder->getArray(), ConstantArrayTypeBuilder::createEmpty()->getArray());
+					$arrayBuilder->setOffsetValueType($finiteTypes[0], $genericTypes[1], true);
+					$arrayType = $arrayBuilder->getArray();
 				} else {
 					$arrayType = new ArrayType($keyType, $genericTypes[1]);
 				}

src/Type/TypeCombinator.php

@@ -1216,6 +1216,28 @@ public static function intersect(Type ...$types): Type
 						continue 2;
 					}
 
+					if (
+						$types[$i] instanceof ConstantArrayType
+						&& count($types[$i]->getKeyTypes()) === 1
+						&& $types[$j] instanceof NonEmptyArrayType
+					) {
+						$types[$i] = $types[$i]->makeOffsetRequired($types[$i]->getKeyTypes()[0]);
+						array_splice($types, $j--, 1);
+						$typesCount--;
+						continue;
+					}
+
+					if (
+						$types[$j] instanceof ConstantArrayType
+						&& count($types[$j]->getKeyTypes()) === 1
+						&& $types[$i] instanceof NonEmptyArrayType
+					) {
+						$types[$j] = $types[$j]->makeOffsetRequired($types[$j]->getKeyTypes()[0]);
+						array_splice($types, $i--, 1);
+						$typesCount--;
+						continue 2;
+					}
+
 					if ($types[$i] instanceof ConstantArrayType && $types[$j] instanceof HasOffsetValueType) {
 						$offsetType = $types[$j]->getOffsetType();
 						$valueType = $types[$j]->getValueType();

tests/PHPStan/Analyser/nsrt/array-shape-from-general-array-with-single-finite-key.php

@@ -12,7 +12,7 @@ class Foo
 	 */
 	public function doFoo(array $a): void
 	{
-		assertType('array{}|array{1: string}', $a);
+		assertType('array{1?: string}', $a);
 	}
 
 	/**