f2abf827c1
Refactor `where` predicates, and reserve for attributes support Refactor `WherePredicate` to `WherePredicateKind`, and reserve for attributes support in `where` predicates. This is a part of #115590 and is split from #132388. r? petrochenkov
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.