Migrating to Laravel 5, route:cache throwing exception - laravel

Question

Moving from Laravel 4.2 to 5.0
We have about ~200 routes in our API, most of them were Closures. So I've spent the better part of the last couple days converting them all to controller routes. Everything is back to being stable, but when I try to run php artisan route:cache it throws an exception
[Exception]
Serialization of 'Closure' is not allowed
I did a ctrl+f for function, and the only ones left in the routes file are the two Route::group entries (which, yes, are closures...but surely only routes count...).
Any guidance? After the tediousness of the last two days, this error is...not what I wanted to see.
EDIT: Full stacktrace
Route cache cleared!
[Exception]
Serialization of 'Closure' is not allowed
Exception trace:
() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Foundation\Console\RouteCacheCommand.php:95
serialize() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Foundation\Console\RouteCacheCommand.php:95
Illuminate\Foundation\Console\RouteCacheCommand->buildRouteCacheFile() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Foundation\Console\RouteCacheCommand.php:65
Illuminate\Foundation\Console\RouteCacheCommand->fire() at n/a:n/a
call_user_func_array() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Container\Container.php:523
Illuminate\Container\Container->call() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Console\Command.php:115
Illuminate\Console\Command->execute() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\symfony\console\Symfony\Component\Console\Command\Command.php:257
Symfony\Component\Console\Command\Command->run() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Console\Command.php:101
Illuminate\Console\Command->run() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\symfony\console\Symfony\Component\Console\Application.php:874
Symfony\Component\Console\Application->doRunCommand() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\symfony\console\Symfony\Component\Console\Application.php:195
Symfony\Component\Console\Application->doRun() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\symfony\console\Symfony\Component\Console\Application.php:126
Symfony\Component\Console\Application->run() at C:\Users\cjtho_000\Desktop\ecapi_l5\vendor\laravel\framework\src\Illuminate\Foundation\Console\Kernel.php:94
Illuminate\Foundation\Console\Kernel->handle() at C:\Users\cjtho_000\Desktop\ecapi_l5\artisan:36
EDIT 2: removed the route groups to test, still throws the exception

Answer 1

Turns out, the entirely unhelpful error message was trying to tell me that I had a duplicate route (copy paste error, I had two get routes matching the same uri).
Removing the duplicate fixed the issue.

Answer 2

Per your stack trace,
vendor\laravel\framework\src\Illuminate\Foundation\Console\RouteCacheCommand.php:95
serialize() at vendor\laravel\framework\src\Illuminate\Foundation\Console\RouteCacheCommand.php:95
Laravel is trying to serialize the routes collection on line 95 of RouteCacheCommand.php.
The error you're getting
Serialization of 'Closure' is not allowed
looks like its PHP's standard "someone tried to serialize an anonymous function" exception message (vs. it might be a custom Laravel exception).
All this means something is adding an anonymous function (i.e. "closure") to your route collection. If you're 100% sure you've removed them all from routes.php, my guess would be the route's in third party code somewhere.
It's best not to guess. Try some debugging code that's something like the following
//un-tested pseudo debugging code
//get the application's routes, using the same
//technique as the route:cache command
$app = require /path/to/your/laravel/bootstrap/app.php';
$app->make('Illuminate\Contracts\Console\Kernel')->bootstrap();
$routes = $app['router']->getRoutes();
//go through each route
foreach($routes as $route)
{
//if the route is a closure
if(is_object($route) && ($route instanceof Closure))
{
//use reflection to find out which file the closure is defined in
$r = new ReflectionFunction($route);
var_dump($route->getFileName ());
}
}
This will let you figure out where the closure that's causing your problems is defined, which should be enough to point to the problem.