1 files changed, 3 insertions, 2 deletions
diff --git a/compiler/rustc_borrowck/src/region_infer/values.rs b/compiler/rustc_borrowck/src/region_infer/values.rs
index c3dfeedc2..8132800f1 100644
--- a/compiler/rustc_borrowck/src/region_infer/values.rs
+++ b/compiler/rustc_borrowck/src/region_infer/values.rs
@@ -181,12 +181,13 @@ impl<N: Idx> LivenessValues<N> {
 /// Maps from `ty::PlaceholderRegion` values that are used in the rest of
 /// rustc to the internal `PlaceholderIndex` values that are used in
 /// NLL.
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub(crate) struct PlaceholderIndices {
     indices: FxIndexSet<ty::PlaceholderRegion>,
 }
 
 impl PlaceholderIndices {
+    /// Returns the `PlaceholderIndex` for the inserted `PlaceholderRegion`
     pub(crate) fn insert(&mut self, placeholder: ty::PlaceholderRegion) -> PlaceholderIndex {
         let (index, _) = self.indices.insert_full(placeholder);
         index.into()
@@ -234,7 +235,7 @@ pub(crate) struct RegionValues<N: Idx> {
     free_regions: SparseBitMatrix<N, RegionVid>,
 
     /// Placeholders represent bound regions -- so something like `'a`
-    /// in for<'a> fn(&'a u32)`.
+    /// in `for<'a> fn(&'a u32)`.
     placeholders: SparseBitMatrix<N, PlaceholderIndex>,
 }