Fix native union type with incomplete PHPDoc

Author: ondrejmirtes

src/Type/TypehintHelper.php

@@ -130,7 +130,22 @@ public static function decideType(
 
 			$resultType = $type->isSuperTypeOf(TemplateTypeHelper::resolveToBounds($phpDocType))->yes() ? $phpDocType : $type;
 
-			if (TypeCombinator::containsNull($type)) {
+			if ($type instanceof UnionType) {
+				$addToUnionTypes = [];
+				foreach ($type->getTypes() as $innerType) {
+					if (!$innerType->isSuperTypeOf($resultType)->no()) {
+						continue;
+					}
+
+					$addToUnionTypes[] = $innerType;
+				}
+
+				if (count($addToUnionTypes) > 0) {
+					$type = TypeCombinator::union($resultType, ...$addToUnionTypes);
+				} else {
+					$type = $resultType;
+				}
+			} elseif (TypeCombinator::containsNull($type)) {
 				$type = TypeCombinator::addNull($resultType);
 			} else {
 				$type = $resultType;

tests/PHPStan/Reflection/data/unionTypes.php

@@ -59,4 +59,23 @@ public function doBar(): array|false
 
 	}
 
+	/**
+	 * @param array<int, string> $foo
+	 */
+	public function doBaz(array|false $foo): void
+	{
+		assertType('array<int, string>|false', $foo);
+		assertNativeType('array|false', $foo);
+
+		assertType('array<int, string>|false', $this->doLorem());
+	}
+
+	/**
+	 * @return array<int, string>
+	 */
+	public function doLorem(): array|false
+	{
+
+	}
+
 }