0baf4406da
Make it clearer that we're just checking for an RPITIT Tiny nit to use `is_impl_trait_in_trait` more, to make it clearer that we're just checking whether a def-id is an RPITIT, rather than doing something meaningful with the `opt_rpitit_info`. r? `@spastorino`
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.