Why? I feel like there would be no benefits to use an enum here personally. At least I don't see any yet.

The purpose might be to remove this "SomeUselessStringThatNobodyNeeds".

If route name can be enum values, the UrlGenerator will have to support them. And that add a new challenge to generate a URL in Twig.

Benefits:

1. Gut feeling :-) From my understanding, enums were invented for cases like this; while having a class that contains just consts feels like misusing the class idea.
2. Indeed, getting rid of the overhead of having to define some string value (which the user doesn't need).
3. Built-in check for uniqueness: Duplicate values might happen with consts:

   const HOME    = 'foo';
   const CONTACT = 'foo';

   ... but are forbidden in enums.

The URL generator uses route names as array keys in the dumped cache code, allowing to get the route info in O(1) when generating URLs. So supporting enums there will be hard.

To me, enums are useful to restrict possibilities to a range of limited values. Route names don't fall in this category.
Using enums here would look like a hack to me and given the technical complication (eg what should debug:router, etc), I'm not convinced we should do it.

As much as I'd like to explore the possible uses of enums further: I agree with @nicolas-grekas that enums are not useful here. I wouldn't store route names in constants either, btw. The proposed changed would introduce complexity for now real benefit.

Let's close because we aready have downvotes from several core team members. Thanks for the proposal though.

Yeah, closing is OK. Just one more question: How do you guys manage your route names then? I was thinking the consts are a good idea, they're also mentioned at https://tomasvotruba.com/blog/2020/12/21/5-new-combos-opened-by-symfony-52-and-php-80/#2-Route-Names-Can-be-Constants

php/php-src#8825 could be a solution here, allowing seamless compatibility between enumerated routes and the routing component.

An even better idea would be to allow getting rid of the name completely: #49981