dispose on failure codepath.

src/Workspaces/Core/Portable/SymbolKey/SymbolKey.SymbolKeyReader.cs

@@ -453,7 +453,7 @@ private SymbolKeyResolution ReadWorker(SymbolKeyType type)
 
             /// <summary>
             /// Reads an array of symbols out from the key.  Note: the number of symbols returned 
-            /// will either be the same as the original amount writtern, or <c>default</c> will be 
+            /// will either be the same as the original amount written, or <c>default</c> will be 
             /// returned. It will never be less or more.  <c>default</c> will be returned if any 
             /// elements could not be resolved to the requested <typeparamref name="TSymbol"/> type 
             /// in the provided <see cref="Compilation"/>.
@@ -471,6 +471,7 @@ private SymbolKeyResolution ReadWorker(SymbolKeyType type)
                     }
                     else
                     {
+                        result.Dispose();
                         return default;
                     }
                 }