This PR was merged into the 1.x branch.
Discussion
----------
Use class_exists instead of require
I think this is required for https://github.com/symfony/symfony/pull/23073 to pass. It's probably very similar to https://github.com/symfony/symfony/pull/22657.
A simple reproducer:
```php
<?php
use Twig\Node\Node;
require_once __DIR__ . '/vendor/autoload.php';
new Node();
new \Twig_Node();
```
[Without this patch](https://travis-ci.org/symfony/symfony/jobs/239712676#L2100):
```php
PHP Fatal error: Cannot declare class Twig_Node, because the name is already in use in vendor/twig/twig/lib/Twig/Node.php on line 20
```
With, everything works fine, whatever the two calls order.
Commits
-------
2c174e40 Use class_exists instead of require
This PR was merged into the 1.x branch.
Discussion
----------
Use class_exists instead of require to play nice with inlining
Should fix#2495
Commits
-------
dfe0dc2b Use class_exists instead of require to play nice with inlining
This PR was merged into the 1.x branch.
Discussion
----------
[Doc] Fixed documentation about 'Definition vs Runtime'
Commits
-------
c0b5eb9f [Doc] Fixed documentation about 'Definition vs Runtime'
This PR was merged into the 2.x branch.
Discussion
----------
[2.x] Allow using namespaced aliases as extension names
Commits
-------
08a88400 [2.x] Allow using namespaced aliases as extension names
This PR was merged into the 1.x branch.
Discussion
----------
[1.x] Allow using namespaced aliases as extension names
Commits
-------
c9a2f3db [1.x] Allow using namespaced aliases as extension names
This PR was merged into the 2.x branch.
Discussion
----------
[2.x] Add namespaced aliases
The 2.x-only part of #2484
Commits
-------
71265c40 [2.x] Add namespaced aliases
This PR was squashed before being merged into the 1.x branch (closes#2484).
Discussion
----------
Add namespaced aliases
Commits
-------
5420a5e3 Add the aliases
71af32b3 Add namespaced aliases
This PR was merged into the 2.x branch.
Discussion
----------
Fix `@final`-related deprecations
The run-time notices make Symfony fail because the check should exclude e.g. `Twig_SimpleFilter`.
But IMHO, we may not really need these run-time checks, if we say that relying on the DebugClassLoader + CHANGELOG in enough (which we did in the past).
Commits
-------
635b9e59 Fix `@final`-related deprecations
This PR was squashed before being merged into the 2.x branch (closes#2481).
Discussion
----------
Mark Twig_Node_Module as final via an annotation (will be final in 3.0)
Commits
-------
e5fb21f1 added deprecation notices for @final classes
93929e1d added @final classes in the deprecated document
3810368b marked Twig_Node_Module as final via an annotation (will be final in 3.0)
Fabien Potencier
Maxime Steinhausser
Nicolas Grekas
Grégoire Pineau