Fix documentation that build-failed

Author: amandasystems

Diff for: compiler/rustc_borrowck/src/constraints/mod.rs

@@ -100,7 +100,7 @@ impl<'tcx> OutlivesConstraintSet<'tcx> {
     /// eventually go away.
     ///
     /// For a more precise definition, see the documentation for
-    /// [`RegionTracker::has_incompatible_universes()`].
+    /// [`RegionTracker`] and its methods!.
     ///
     /// This edge case used to be handled during constraint propagation
     /// by iterating over the strongly connected components in the constraint

Diff for: compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -2213,7 +2213,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// Returns the representative `RegionVid` for a given SCC.
-    /// See `RegionTracker` for how a region variable ID is chosen.
+    /// See [`RegionTracker`] for how a region variable ID is chosen.
     ///
     /// It is a hacky way to manage checking regions for equality,
     /// since we can 'canonicalize' each region to the representative
@@ -2229,6 +2229,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         r == self.universal_regions.fr_static
     }
 
+    /// If the representative of an SCC is a placeholder, return
+    /// its originating `PlaceholderRegion`.
     pub(crate) fn placeholder_representative(
         &self,
         scc: ConstraintSccIndex,