[FEATURE] Add experimental support for PHPStan 2.x

.github/workflows/tests.yaml

@@ -10,13 +10,14 @@ on:
 
 jobs:
   tests:
-    name: Tests (PHP ${{ matrix.php-version }} & ${{ matrix.dependencies }} dependencies)
+    name: Tests (PHP ${{ matrix.php-version }}, PHPStan v${{ matrix.phpstan-version }} & ${{ matrix.dependencies }} dependencies)
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         php-version: ["8.1", "8.2", "8.3"]
-        dependencies: ["locked", "highest", "lowest"]
+        phpstan-version: ["1", "2"]
+        dependencies: ["highest", "lowest"]
     steps:
       - uses: actions/checkout@v4
         with:
@@ -34,6 +35,7 @@ jobs:
       - name: Install Composer dependencies
         uses: ramsey/composer-install@v2
         with:
+          composer-options: --with=phpstan/phpstan:^${{ matrix.phpstan-version }}
           dependency-versions: ${{ matrix.dependencies }}
 
       # Run tests

composer.json

@@ -13,9 +13,9 @@
 	],
 	"require": {
 		"php": "~8.1.0 || ~8.2.0 || ~8.3.0",
-		"phpstan/phpstan": "^1.9",
-		"phpstan/phpstan-deprecation-rules": "^1.1",
-		"phpstan/phpstan-strict-rules": "^1.4"
+		"phpstan/phpstan": "^1.9 || ^2.0@dev",
+		"phpstan/phpstan-deprecation-rules": "^1.1 || ^2.0@dev",
+		"phpstan/phpstan-strict-rules": "^1.4 || ^2.0@dev"
 	},
 	"require-dev": {
 		"armin/editorconfig-cli": "^1.8 || ^2.0",
@@ -24,6 +24,7 @@
 		"ergebnis/composer-normalize": "^2.29",
 		"phpunit/phpunit": "^10.1 || ^11.0"
 	},
+	"prefer-stable": true,
 	"autoload": {
 		"psr-4": {
 			"EliasHaeussler\\PHPStanConfig\\": "src/"