791a53f380
Reorder check_item_type diagnostics so they occur next to the corresponding `check_well_formed` diagnostics The first commit is just a cleanup. The second commit moves most checks from `check_mod_item_types` into `check_well_formed`, invoking the checks in lockstep per-item instead of iterating over all items twice.
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.