Added PHPStan

Author: morozov

Makefile

@@ -2,6 +2,7 @@ install:
 	composer install
 test:
 	vendor/bin/phpunit --color
+	vendor/bin/phpstan analyze -l7 src tests
 coverage:
 	$(eval TMPDIR=$(shell mktemp -d))
 	vendor/bin/phpunit --coverage-html=$(TMPDIR)

composer.json

@@ -16,13 +16,20 @@
   },
   "require-dev": {
     "phpunit/phpunit": "^6.1",
-    "php-vfs/php-vfs": "^v1.3"
+    "php-vfs/php-vfs": "^v1.3",
+    "phpstan/phpstan": "^0.9"
   },
   "autoload": {
     "psr-4": {
       "DiffSniffer\\": "src/"
     }
   },
+  "autoload-dev": {
+    "psr-4": {
+      "DiffSniffer\\Tests\\": "tests/",
+      "PHP_CodeSniffer\\" : "vendor/squizlabs/php_codesniffer/src/"
+    }
+  },
   "extra": {
     "branch-alias": {
       "dev-master": "3.0.x-dev"

src/ConfigLoader.php

@@ -83,7 +83,7 @@ private function loadComposerConfig(string $path) : array
      */
     private function loadPhpCodeSnifferConfig(string $path) : array
     {
-        $phpCodeSnifferConfig = null;
+        $phpCodeSnifferConfig = [];
 
         require $path;
 
@@ -93,7 +93,7 @@ private function loadPhpCodeSnifferConfig(string $path) : array
     /**
      * Resolves relative installed paths against the configuration file path
      *
-     * @param array Configuration parameters
+     * @param array $config Configuration parameters
      * @param string $configPath Configuration file paths
      * @return array Configuration parameters
      */

src/Iterator.php

@@ -52,7 +52,7 @@ public function getIterator() : Traversable
             new RecursiveArrayIterator(
                 new EmptyIterator()
             ),
-            null,
+            '',
             $this->config,
             $this->ruleSet
         ));

src/Reporter.php

@@ -14,7 +14,7 @@ class Reporter extends BaseReporter
     /**
      * @var Diff
      */
-    private $diff = [];
+    private $diff;
 
     public function __construct(Diff $diff, Config $config)
     {

tests/RunnerTest.php

@@ -11,9 +11,11 @@ class RunnerTest extends TestCase
 {
     public function testEarlyReturn()
     {
+        /** @var Config|\PHPUnit_Framework_MockObject_MockObject $config */
         $config = $this->createMock(Config::class);
         $runner = new Runner($config);
 
+        /** @var Changeset|\PHPUnit_Framework_MockObject_MockObject $changeSet */
         $changeSet = $this->createMock(Changeset::class);
         $changeSet->expects($this->once())
             ->method('getDiff')