C#: Minor adjustment to limiting the number of extractor messages

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CSharp/Entities/Compilations/CompilerDiagnostic.cs

@@ -21,7 +21,6 @@ public CompilerDiagnostic(Context cx, Microsoft.CodeAnalysis.Diagnostic diag, Co
 
         protected override void Populate(TextWriter trapFile)
         {
-            // The below doesn't limit the extractor messages to the exact limit, but it's good enough.
             var key = diagnostic.Id;
             var messageCount = compilation.messageCounts.AddOrUpdate(key, 1, (_, c) => c + 1);
             if (messageCount > limit)

csharp/extractor/Semmle.Extraction/Entities/ExtractionMessage.cs

@@ -19,11 +19,10 @@ public ExtractionMessage(Context cx, Message msg) : base(cx)
 
         protected override void Populate(TextWriter trapFile)
         {
-            // The below doesn't limit the extractor messages to the exact limit, but it's good enough.
-            Interlocked.Increment(ref messageCount);
-            if (messageCount > limit)
+            var val = Interlocked.Increment(ref messageCount);
+            if (val > limit)
             {
-                if (messageCount == limit + 1)
+                if (val == limit + 1)
                 {
                     Context.ExtractionContext.Logger.LogWarning($"Stopped logging extractor messages after reaching {limit}");
                 }