Make GetDescendents bail out when the first match is found

Previously, it first got all matches by walking the entire subtree, then ordered the results by start index and finally took the first one.

Now, it uses a depth-first search approach to find the first result and bails out as soon as a match is found.

Author: MDoerner

Rubberduck.Parsing/ParserRuleContextExtensions.cs

@@ -197,8 +197,31 @@ public static bool ContainsTokenIndex(this ParserRuleContext context, int tokenI
         /// </summary>
         public static TContext GetDescendent<TContext>(this ParserRuleContext context) where TContext : ParserRuleContext
         {
-            var descendents = GetDescendents<TContext>(context);
-            return descendents.OrderBy(descendent => descendent.Start.TokenIndex).FirstOrDefault();
+            if (context?.children == null)
+            {
+                return null;
+            }
+
+            foreach (var child in context.children)
+            {
+                if (child == null)
+                {
+                    continue;
+                }
+
+                if (child is TContext match)
+                {
+                    return match;
+                }
+                
+                var childResult = (child as ParserRuleContext)?.GetDescendent<TContext>();
+                if (childResult != null)
+                {
+                    return childResult;
+                }
+            }
+
+            return null;
         }
 
         /// <summary>
@@ -228,6 +251,12 @@ public static VBAParser.EndOfLineContext GetFirstEndOfLine(this VBAParser.EndOfS
         {
             //This dedicated method exists for performance reasons on hot-paths.
             var individualEndOfStatements = endOfStatement.individualNonEOFEndOfStatement();
+
+            if (individualEndOfStatements == null)
+            {
+                return null;
+            }
+
             foreach (var individualEndOfStatement in individualEndOfStatements)
             {
                 var endOfLine = individualEndOfStatement.endOfLine();