Make readonly. Add docs.

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/FinderLocation.cs

@@ -3,10 +3,27 @@
 
 namespace Microsoft.CodeAnalysis.FindSymbols.Finders
 {
-    internal struct FinderLocation
+    internal readonly struct FinderLocation
     {
-        public SyntaxNode Node;
-        public ReferenceLocation Location;
+        /// <summary>
+        /// The actual node that we found the reference on.  Normally the 'Name' portion
+        /// of any piece of syntax.  Might also be something like a 'foreach' statement node
+        /// when finding results for something like GetEnumerator.
+        /// </summary>
+        public readonly SyntaxNode Node;
+
+        /// <summary>
+        /// The location we want want to return through the FindRefs API.  The location contains
+        /// additional information (like if this was a Write, or if it was Implicit).  This value
+        /// also has a <see cref="ReferenceLocation.Location"/> property.  Importantly, this value
+        /// is not necessarily the same location you would get by calling <see cref="Node"/>.<see
+        /// cref="SyntaxNode.GetLocation"/>.  Instead, this location is where we want to navigate
+        /// the user to.  A case where this can be different is with an indexer reference.  The <see
+        /// cref="Node"/> will be the node for the full 'ElementAccessExpression', whereas the 
+        /// location we will take the user to will be the zero-length position immediately preceding
+        /// the `[` character.
+        /// </summary>
+        public readonly ReferenceLocation Location;
 
         public FinderLocation(SyntaxNode node, ReferenceLocation location)
         {

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/NamedTypeSymbolReferenceFinder.cs

@@ -110,17 +110,17 @@ protected override bool CanFind(INamedTypeSymbol symbol)
             }
 
             var result = ArrayBuilder<FinderLocation>.GetInstance();
-            foreach (var reference in namedTypeReferences)
+            foreach (var finderLocation in namedTypeReferences)
             {
-                if (Contains(constructorReferences, reference))
+                if (Contains(constructorReferences, finderLocation))
                 {
-                    var localReference = reference;
-                    localReference.Location.IsDuplicateReferenceLocation = true;
-                    result.Add(localReference);
+                    var location = finderLocation.Location;
+                    location.IsDuplicateReferenceLocation = true;
+                    result.Add(finderLocation);
                 }
                 else
                 {
-                    result.Add(reference);
+                    result.Add(finderLocation);
                 }
             }