Urgau

@jsha Couldn't you use it with the `filter` tag ? ```tera {% filter spaceless %} Foo {% endfilter %} ```

> I guess it would become `Foo`? No, spaceless only remove spaces between `>` and `

Isn't this going against [T-types solution](https://github.com/rust-lang/rust/issues/121621#issuecomment-1976826895) ? (which is being implemented in https://github.com/rust-lang/rust/pull/122747, @lcnr) It was even [approved by T-lang](https://github.com/rust-lang/rust/issues/121621#issuecomment-1982002471).

@matthiaskrgr I think that rollup failed because of https://github.com/rust-lang/rust/pull/120232. This PR doesn't modify anything that would cause the errors seen in the rollup.

@estebank ping.

r? compiler

r? @Nadrieril (as discussed privately)

I've addressed all the review comments and CI passes; this is ready. @rustbot ready

> To me, "aliased type" strictly refers to the right-hand side of the `type A = B` syntax, so I would find this feature much less confusing if it simply...

@rustbot ready