Always create alias for invokables

The same behaviour we have in zend-servicemanager.
Proper configuration should be:

'invokables' => [
    Name\Service::class => Name\Service::class,
],

or when we want to use alias:

'invokables' => [
    'alias' => Name\Service::class,
],

then serivce will be available on:
- alias: $container->get('alias');
- class name: $container->get(Name\Service::class);
and it will be exactly the same instance.

src/Config.php

@@ -83,11 +83,13 @@ private function injectInvokables(Container $container, array $dependencies)
         }
 
         foreach ($dependencies['invokables'] as $name => $object) {
-            if (is_int($name)) {
-                $name = $object;
+            if ($name !== $object) {
+                $container[$name] = function (Container $c) use ($object) {
+                    return $c->offsetGet($object);
+                };
             }
 
-            $container[$name] = function (Container $c) use ($object) {
+            $container[$object] = function (Container $c) use ($object) {
                 return new $object();
             };
         }

test/ConfigTest.php

@@ -335,7 +335,7 @@ public function testInjectMultipleDelegators()
         );
     }
 
-    public function testInvokablesWithoutAlias()
+    public function testInvokableWithAlias()
     {
         $dependencies = [
             'invokables' => [
@@ -348,5 +348,25 @@ public function testInvokablesWithoutAlias()
         self::assertTrue($this->container->offsetExists(TestAsset\Service::class));
         $service = $this->container->offsetGet(TestAsset\Service::class);
         self::assertInstanceOf(TestAsset\Service::class, $service);
+        self::assertTrue($this->container->offsetExists('0'));
+    }
+
+    public function testInvokableWithoutAlias()
+    {
+        $dependencies = [
+            'invokables' => [
+                'alias' => TestAsset\Service::class,
+            ],
+        ];
+
+        (new Config(['dependencies' => $dependencies]))->configureContainer($this->container);
+
+        self::assertTrue($this->container->offsetExists('alias'));
+        $service = $this->container->offsetGet('alias');
+        self::assertInstanceOf(TestAsset\Service::class, $service);
+        self::assertTrue($this->container->offsetExists(TestAsset\Service::class));
+        $originService = $this->container->offsetGet(TestAsset\Service::class);
+        self::assertInstanceOf(TestAsset\Service::class, $originService);
+        self::assertSame($service, $originService);
     }
 }