bug #16467 Fixing bad type-hint auto-wiring bug (weaverryan)

This PR was squashed before being merged into the 2.8 branch (closes #16467).

Discussion
----------

Fixing bad type-hint auto-wiring bug

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Previously, if you type-hinted a bad class name, we did not set the argument value. In fact, with `continue`, we skipped setting the argument, which meant that if argument 2 was skipped, then argument 3 would be put into argument 2's location.

But really, if I type-hint a non-existent class, this should throw a clear exception. afaik, in the original PR, it was said that we cannot throw an exception for a non-existent class because a later compiler-pass may manipulate those class names and "fix" them to be real classes. But, that's an edge case, and I think if you're using advanced functionality like that, you should not use auto-wiring. Throwing an exception is much more user-friendly. I personally hit this issue and was trying to figure out what was going wrong :).

About the exception message: I would like to tell the user which class is type-hinted correctly, but getting the type-hinted class for a non-existent class is not possible with reflection.

Thanks!

cc @dunglas

Commits
-------

b7b182e Fixing bad type-hint auto-wiring bug

src/Symfony/Component/DependencyInjection/Compiler/AutowirePass.php

@@ -104,7 +104,7 @@ class AutowirePass implements CompilerPassInterface
                 // Typehint against a non-existing class
 
                 if (!$parameter->isDefaultValueAvailable()) {
-                    continue;
+                    throw new RuntimeException(sprintf('Cannot autowire argument %s for %s because the type-hinted class does not exist (%s).', $index + 1, $definition->getClass(), $reflectionException->getMessage()), 0, $reflectionException);
                 }
 
                 $value = $parameter->getDefaultValue();

src/Symfony/Component/DependencyInjection/Tests/Compiler/AutowirePassTest.php

@@ -201,6 +201,21 @@ class AutowirePassTest extends \PHPUnit_Framework_TestCase
 
         $this->assertCount(0, $container->getDefinition('bar')->getArguments());
     }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage Cannot autowire argument 2 for Symfony\Component\DependencyInjection\Tests\Compiler\BadTypeHintedArgument because the type-hinted class does not exist (Class Symfony\Component\DependencyInjection\Tests\Compiler\NotARealClass does not exist).
+     */
+    public function testClassNotFoundThrowsException()
+    {
+        $container = new ContainerBuilder();
+
+        $aDefinition = $container->register('a', __NAMESPACE__.'\BadTypeHintedArgument');
+        $aDefinition->setAutowired(true);
+
+        $pass = new AutowirePass();
+        $pass->process($container);
+    }
 }
 
 class Foo
@@ -298,3 +313,10 @@ class OptionalParameter
     {
     }
 }
+
+class BadTypeHintedArgument
+{
+    public function __construct(Dunglas $k, NotARealClass $r)
+    {
+    }
+}