Use callable typehint where possible + Removed dead code (#996)

* Removed dead code

* Use callable typehint where possible

* Removed PHP5.3 workaround

src/Monolog/Handler/ProcessableHandlerTrait.php

@@ -28,9 +28,6 @@ trait ProcessableHandlerTrait
      */
     public function pushProcessor(callable $callback): HandlerInterface
     {
-        if (!is_callable($callback)) {
-            throw new \InvalidArgumentException('Processors must be valid callables (callback or object with an __invoke method), '.var_export($callback, true).' given');
-        }
         array_unshift($this->processors, $callback);
 
         return $this;

src/Monolog/Handler/TestHandler.php

@@ -109,12 +109,8 @@ class TestHandler extends AbstractProcessingHandler
         }, $level);
     }
 
-    public function hasRecordThatPasses($predicate, $level)
+    public function hasRecordThatPasses(callable $predicate, $level)
     {
-        if (!is_callable($predicate)) {
-            throw new \InvalidArgumentException("Expected a callable for hasRecordThatPasses");
-        }
-
         if (!isset($this->recordsByLevel[$level])) {
             return false;
         }

tests/Monolog/Handler/RotatingFileHandlerTest.php

@@ -19,13 +19,7 @@ use Monolog\Test\TestCase;
  */
 class RotatingFileHandlerTest extends TestCase
 {
-    /**
-     * This var should be private but then the anonymous function
-     * in the `setUp` method won't be able to set it. `$this` cant't
-     * be used in the anonymous function in `setUp` because PHP 5.3
-     * does not support it.
-     */
-    public $lastError;
+    private $lastError;
 
     public function setUp()
     {
@@ -35,10 +29,8 @@ class RotatingFileHandlerTest extends TestCase
             $this->markTestSkipped($dir.' must be writable to test the RotatingFileHandler.');
         }
         $this->lastError = null;
-        $self = $this;
-        // workaround with &$self used for PHP 5.3
-        set_error_handler(function ($code, $message) use (&$self) {
-            $self->lastError = [
+        set_error_handler(function ($code, $message) {
+            $this->lastError = [
                 'code' => $code,
                 'message' => $message,
             ];