Oh nice. Just found 2 nightly features which look like they might bring us closer to one of the two major type level things Iam missing hard in : "extistenia types" (the other one are )

type_alias_impl_trait:
https://doc.rust-lang.org/unstable-book/language-features/type-alias-impl-trait.html

impl_trait_in_assoc_type:
https://doc.rust-lang.org/nightly/unstable-book/language-features/impl-trait-in-assoc-type.html