Add documentation.

src/EditorFeatures/Core/Implementation/FindReferences/DefinitionLocation.DocumentDefinitionLocation.cs

@@ -6,6 +6,10 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.FindReferences
 {
     internal partial class DefinitionLocation
     {
+        /// <summary>
+        /// Implementation of a <see cref="DefinitionLocation"/> that sits on top of a 
+        /// <see cref="DocumentLocation"/>.
+        /// </summary>
         private sealed class DocumentDefinitionLocation : DefinitionLocation
         {
             private readonly DocumentLocation _location;
@@ -18,15 +22,8 @@ public DocumentDefinitionLocation(DocumentLocation location)
             public override ImmutableArray<TaggedText> OriginationParts =>
                 ImmutableArray.Create(new TaggedText(TextTags.Text, _location.Document.Project.Name));
 
-            public override bool CanNavigateTo()
-            {
-                return _location.CanNavigateTo();
-            }
-
-            public override bool TryNavigateTo()
-            {
-                return _location.TryNavigateTo();
-            }
+            public override bool CanNavigateTo() => _location.CanNavigateTo();
+            public override bool TryNavigateTo() => _location.TryNavigateTo();
         }
     }
-}
+}
\ No newline at end of file

src/EditorFeatures/Core/Implementation/FindReferences/DefinitionLocation.NonNavigatingDefinitionLocation.cs

@@ -6,6 +6,11 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.FindReferences
 {
     internal partial class DefinitionLocation
     {
+        /// <summary>
+        /// Implementation of a <see cref="DefinitionLocation"/> used for definitions
+        /// that cannot be navigated to.  For example, C# and VB namespaces cannot be
+        /// navigated to.
+        /// </summary>
         private sealed class NonNavigatingDefinitionLocation : DefinitionLocation
         {
             private readonly ImmutableArray<TaggedText> _originationParts;

src/EditorFeatures/Core/Implementation/FindReferences/DefinitionLocation.SymbolDefinitionLocation.cs

@@ -10,6 +10,13 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.FindReferences
 {
     internal partial class DefinitionLocation
     {
+        /// <summary>
+        /// Implementation of a <see cref="DefinitionLocation"/> that sits on top of an
+        /// <see cref="ISymbol"/>.  In order to not keep anything alive too long, we only
+        /// hold onto IDs and Keys.  When the user tries to navigate to an item we will 
+        /// attempt to find the symbol again in the current solution snapshot and 
+        /// navigate to it there.
+        /// </summary>
         private sealed class SymbolDefinitionLocation : DefinitionLocation
         {
             private readonly Workspace _workspace;