Fix PHPStan warnings

.github/workflows/main.yaml

@@ -1,18 +1,16 @@
 name: CI
 
 on:
-  pull_request: null
-  push:
-    branches:
-      - master
+  - pull_request
+  - push
 
 jobs:
   tests:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         php: ['7.1', '7.2', '7.3', '7.4', '8.0', '8.1']
-    name: PHP ${{ matrix.php }} tests
+    name: PHP ${{ matrix.php }}
     steps:
       -   uses: actions/checkout@v2
       # required for "git tag" presence for MonorepoBuilder split and ChangelogLinker git tags resolver; default is 1
@@ -27,6 +25,7 @@ jobs:
       -   run: composer phpunit
 
   tests_lowest_dependencies:
+    name: Lowest dependencies
     runs-on: ubuntu-latest
     steps:
       -   uses: actions/checkout@v2
@@ -41,6 +40,7 @@ jobs:
       -   run: composer phpunit
 
   test_coverage:
+    name: Coverage
     runs-on: ubuntu-latest
     steps:
       -   uses: actions/checkout@v2
@@ -56,10 +56,9 @@ jobs:
             composer coverage
             # codecov.io
             bash <(curl -s https://codecov.io/bash)
-          env:
-            CODECOV_TOKEN: 'de38eee4-bbc9-43bc-811c-c96a7d6ec3b6'
 
   php-cs-fixer:
+    name: PHP CS Fixer
     runs-on: ubuntu-latest
     steps:
       -   uses: actions/checkout@v2
@@ -73,12 +72,13 @@ jobs:
       -   run: composer php-cs-fixer-dry-run
 
   phpstan:
+    name: PHPStan
     runs-on: ubuntu-latest
     steps:
       -   uses: actions/checkout@v2
       -   uses: shivammathur/setup-php@v2
           with:
-            php-version: 7.1
+            php-version: 8.1
             coverage: none
       -   run: composer install --no-progress
       -   run: composer phpstan

src/AbstractElement.php

@@ -219,7 +219,6 @@ protected static function addChildWithTypeToElement(SimpleXMLElement $parent, st
     protected static function addCData(string $cdataText, SimpleXMLElement $element): void
     {
         $node = dom_import_simplexml($element);
-        assert(false !== $node);
         $no = $node->ownerDocument;
         assert(null !== $no);
         $node->appendChild($no->createCDATASection($cdataText));

src/Feed.php

@@ -39,6 +39,7 @@ class Feed extends AbstractElement
 
     /**
      * @var array[]
+     *
      * @phpstan-var array<array{ns: string, uri: string, name: string, value: string, attributes: string[]}>
      */
     protected $customElements = [];
@@ -201,17 +202,16 @@ public function getSimpleXML(): SimpleXMLElement
     public function getDocument(): DOMDocument
     {
         $node = dom_import_simplexml($this->getSimpleXML());
-        assert(false !== $node);
         $no = $node->ownerDocument;
         assert(null !== $no);
 
         return $no;
     }
 
     /**
-     * @throws Exception
-     *
      * @return false|string
+     *
+     * @throws Exception
      */
     public function saveXML()
     {