internal: fix phpstan errors

src/Clover/Dto/ClassDto.php

@@ -14,6 +14,9 @@ class ClassDto
     ) {
     }
 
+    /**
+     * @return array<string, string>
+     */
     public function getProperties(): array
     {
         return $this->properties;

src/Clover/Dto/LineDto.php

@@ -22,6 +22,9 @@ class LineDto
         return $this->count;
     }
 
+    /**
+     * @return array<string, string>
+     */
     public function getProperties(): array
     {
         return $this->properties;

src/Clover/Parser.php

@@ -57,6 +57,10 @@ class Parser implements ElementsDictionary
         return new LineDto($properties, (int) $count);
     }
 
+    /**
+     * @param \SimpleXMLElement $xml
+     * @return array<array-key, \SimpleXMLElement>
+     */
     public function getAttributes(\SimpleXMLElement $xml): array
     {
         return ((array) $xml->attributes())['@attributes'] ?? [];

src/Clover/Renderer.php

@@ -14,7 +14,7 @@ class Renderer
 {
     /**
      * @param Accumulator $accumulator
-     * @return array
+     * @return array{0: string, 1: Metrics}
      * @throws \DOMException
      */
     public function renderAccumulator(Accumulator $accumulator): array
@@ -71,7 +71,7 @@ class Renderer
 
         $xmlProject->appendChild($this->renderMetricsProject($xmlDocument, $projectMetrics));
 
-        return [$xmlDocument->saveXML(), $projectMetrics];
+        return [(string) $xmlDocument->saveXML(), $projectMetrics];
     }
 
     /**

src/Command/CloverMergeCommand.php

@@ -56,6 +56,11 @@ final class CloverMergeCommand extends CliCommand
     }
 
     /**
+     * @param array<array-key, string> $files
+     * @param string $output
+     * @param string|null $workdir
+     * @param bool $stats
+     * @return int
      * @throws ExecuteException
      */
     public function execute(array $files, string $output, ?string $workdir, bool $stats): int