Address PR feedback from Aleksey

src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs

@@ -1709,7 +1709,7 @@ private void CompleteTree(SyntaxTree tree)
                     if (_lazyCompilationUnitCompletedTrees.Count == this.SyntaxTrees.Length)
                     {
                         // if that was the last tree, signal the end of compilation
-                        EnsureCompilationCompleted();
+                        CompleteCompilationEventQueue_NoLock();
                     }
                 }
             }
@@ -1949,9 +1949,9 @@ internal ImmutableArray<Diagnostic> GetDiagnostics(CompilationStage stage, bool
 
                 builder.AddRange(GetSourceDeclarationDiagnostics(cancellationToken: cancellationToken));
 
-                if (this.EventQueue != null && this.SyntaxTrees.Length == 0)
+                if (EventQueue != null && SyntaxTrees.Length == 0)
                 {
-                    EnsureCompilationCompleted();
+                    EnsureCompilationEventQueueCompleted();
                 }
             }
 

src/Compilers/Core/Portable/Compilation/Compilation.cs

@@ -851,22 +851,29 @@ public INamedTypeSymbol GetTypeByMetadataName(string fullyQualifiedMetadataName)
         /// </summary>
         public abstract ImmutableArray<Diagnostic> GetDiagnostics(CancellationToken cancellationToken = default(CancellationToken));
 
-        internal void EnsureCompilationCompleted()
+        internal void EnsureCompilationEventQueueCompleted()
         {
-            Debug.Assert(this.EventQueue != null);
+            Debug.Assert(EventQueue != null);
 
-            lock (this.EventQueue)
+            lock (EventQueue)
             {
-                if (!this.EventQueue.IsCompleted)
+                if (!EventQueue.IsCompleted)
                 {
-                    // Signal the end of compilation.
-                    EventQueue.TryEnqueue(new CompilationCompletedEvent(this));
-                    EventQueue.PromiseNotToEnqueue();
-                    EventQueue.TryComplete();
+                    CompleteCompilationEventQueue_NoLock();
                 }
             }
         }
 
+        internal void CompleteCompilationEventQueue_NoLock()
+        {
+            Debug.Assert(EventQueue != null);
+            
+            // Signal the end of compilation.
+            EventQueue.TryEnqueue(new CompilationCompletedEvent(this));
+            EventQueue.PromiseNotToEnqueue();
+            EventQueue.TryComplete();
+        }
+
         internal abstract CommonMessageProvider MessageProvider { get; }
 
         /// <param name="accumulator">Bag to which filtered diagnostics will be added.</param>

src/Compilers/VisualBasic/Portable/Compilation/VisualBasicCompilation.vb

@@ -1644,7 +1644,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 
                     If _lazyCompilationUnitCompletedTrees.Count = SyntaxTrees.Length Then
                         ' if that was the last tree, signal the end of compilation
-                        EnsureCompilationCompleted()
+                        CompleteCompilationEventQueue_NoLock()
                     End If
                 End If
             End SyncLock
@@ -1924,8 +1924,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                 builder.AddRange(SourceAssembly.GetAllDeclarationErrors(cancellationToken))
                 builder.AddRange(GetClsComplianceDiagnostics(cancellationToken))
 
-                If Me.EventQueue IsNot Nothing AndAlso Me.SyntaxTrees.Length = 0 Then
-                    EnsureCompilationCompleted()
+                If EventQueue IsNot Nothing AndAlso SyntaxTrees.Length = 0 Then
+                    EnsureCompilationEventQueueCompleted()
                 End If
             End If