Apply suggestions from code review

diesel/src/connection/mod.rs

@@ -506,13 +506,18 @@ impl<DB: Backend + 'static> dyn BoxableConnection<DB> {
     }
 }
 
-// These traits are not part of the public API
-// because we want to replace them by with an associated type
-// in the child trait later if GAT's are finally stable
+// These traits are considered private for different reasons:
+//
+// `ConnectionSealed` to control who can implement `Connection`, 
+// so that we can later change the `Connection` trait
 //
 // `MultiConnectionHelper` is a workaround needed for the
 // `MultiConnection` derive. We might stabilize this trait with
 // the corresponding derive
+// 
+// `ConnectionHelperType` as a workaround for the `LoadRowIter` 
+// type def. That trait should not be used by any user outside of diesel, 
+// it purely exists for backward compatibility reasons.
 pub(crate) mod private {
 
     /// This trait restricts who can implement `Connection`

diesel/src/query_dsl/load_dsl.rs

@@ -21,6 +21,7 @@ pub(crate) use self::private::CompatibleType;
 ///
 /// [`RunQueryDsl`]: crate::RunQueryDsl
 pub trait LoadQuery<'query, Conn, U, B = DefaultLoadingMode>: RunQueryDsl<Conn> {
+    /// Return type of `LoadQuery::internal_load`
     type RowIter<'conn>: Iterator<Item = QueryResult<U>>
     where
         Conn: 'conn;

diesel/src/row.rs

@@ -41,7 +41,7 @@ pub trait Row<'a, DB: Backend>:
 {
     /// Field type returned by a `Row` implementation
     ///
-    /// * Crates using existing backend should not concern themself with the
+    /// * Crates using existing backends should not concern themself with the
     ///   concrete type of this associated type.
     ///
     /// * Crates implementing custom backends should provide their own type
@@ -148,8 +148,10 @@ where
 }
 
 // These traits are not part of the public API
-// because we want to replace them by with an associated type
-// in the child trait later if GAT's are finally stable
+// because:
+// * we want to control who can implment `Row` (for `RowSealed`)
+// * `PartialRow` is an implementation detail
+// * `RowLifetimeHelper` is an internal backward compatibility helper
 pub(crate) mod private {
     use super::*;