Auto merge of #113201 - oli-obk:recursive_type_alias, r=estebank,compiler-errors

Permit recursive weak type aliases

I saw #63097 and thought "we can do ~~better~~ funnier". So here it is. It's not useful, but it's certainly something. This may actually become feasible with lazy norm (so in 5 years (constant, not reducing over time)).

r? `@estebank`

cc `@GuillaumeGomez`

Author: bors