More bounds for better errors from #1623

Editor assessment

The phrase more bounds for better errors compresses two improvements into five vague words: which bounds, on what types, and which errors improve is unstated, with only the originating PR referenced. Type refactor and scope core are accurate. No body unpacks the claim, and no footers appear. The intent (tighter generics yielding clearer diagnostics) is guessable for Rust readers, but the headline makes them work for it.