Fix eager token mapping panics

[Veykril]

No description provided.

[bors]

☔ The latest upstream changes (presumably #15251) made this pull request unmergeable. Please resolve the merge conflicts.

[Veykril]

Alright, I managed to make token mapping work again. There is still a problem here though, any macro calls in eager macro calls won't resolve properly, as they do not actually exist in any graspable expansion. That is in format_args!("{}", vec![]) the vec! call won't resolve in the IDE layer as it does not exist in the format_args output (as it was already expanded). We'll need to rewrite the eager expansion a bit by storing the expanded input in the db somewhere and then handle that as any other macro expansion. I don't have the time to do that right now though.

I also didn't check the perf impact of this PR but I hope its not too bad. (it will most likely increase mem usage a bit)
@bors r+

[bors]

📌 Commit 6a7b905 has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6a7b905 with merge 132ba2c...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 132ba2c to master...