minor #4522 Add @template on RuntimeLoaderinterface (Twig 4) (smnandre)

This PR was merged into the 4.x branch.

Discussion
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Add `@template` on RuntimeLoaderinterface (Twig 4)

Do php-stan annotation have an impact on BC promise?

The interface uses the term "class" already.. i'm guessing it's ok ?

Commits
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c24c71a3ca Add `@template` on RuntimeLoaderinterface (Twig 4)

src/RuntimeLoader/RuntimeLoaderInterface.php

@@ -21,7 +21,11 @@ interface RuntimeLoaderInterface
     /**
      * Creates the runtime implementation of a Twig element (filter/function/test).
      *
-     * @return object|null The runtime instance or null if the loader does not know how to create the runtime for this class
+     * @template TRuntime of object
+     *
+     * @param class-string<TRuntime> $class A runtime class name
+     *
+     * @return TRuntime|null The runtime instance or null if the loader does not know how to create the runtime for this class
      */
     public function load(string $class): ?object;
 }