Remove CSharp/VBOperation cloners.

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

@@ -474,11 +474,6 @@ internal virtual IOperation GetOperationWorker(CSharpSyntaxNode node, Cancellati
             return null;
         }
 
-        internal override IOperation CloneOperationCore(IOperation operation)
-        {
-            return CSharpOperationCloner.Instance.Visit(operation);
-        }
-
         #region GetSymbolInfo
 
         /// <summary>

src/Compilers/CSharp/Portable/Operations/CSharpOperationCloner.cs

-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
-
-using Microsoft.CodeAnalysis.Operations;
-
-namespace Microsoft.CodeAnalysis.CSharp
-{
-    internal class CSharpOperationCloner : OperationCloner
-    {
-        public static OperationCloner Instance { get; } = new CSharpOperationCloner();
-    }
-}

src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs

@@ -36,7 +36,7 @@ public IOperation Create(BoundNode boundNode)
             // always return cloned one
             if (boundNode.Kind == BoundKind.ImplicitReceiver)
             {
-                return _semanticModel.CloneOperation(CreateInternal(boundNode));
+                return OperationCloner.CloneOperation(CreateInternal(boundNode));
             }
 
             return _cache.GetOrAdd(boundNode, n => CreateInternal(n));

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

@@ -86,13 +86,6 @@ public IOperation GetOperation(SyntaxNode node, CancellationToken cancellationTo
 
         protected abstract IOperation GetOperationCore(SyntaxNode node, CancellationToken cancellationToken);
 
-        /// <summary>
-        /// Deep Clone given IOperation
-        /// </summary>
-        internal T CloneOperation<T>(T operation) where T : IOperation => (T)CloneOperationCore(operation);
-
-        internal abstract IOperation CloneOperationCore(IOperation operation);
-
         /// <summary>
         /// Returns true if this is a SemanticModel that ignores accessibility rules when answering semantic questions.
         /// </summary>

src/Compilers/Core/Portable/Operations/OperationCloner.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Immutable;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Operations
 {
-    internal abstract class OperationCloner : OperationVisitor<object, IOperation>
+    internal sealed class OperationCloner : OperationVisitor<object, IOperation>
     {
-        protected T Visit<T>(T node) where T : IOperation
+        private static readonly Lazy<OperationCloner> _lazyInstance = new Lazy<OperationCloner>(() => new OperationCloner());
+
+        /// <summary>
+        /// Deep clone given IOperation
+        /// </summary>
+        public static T CloneOperation<T>(T operation) where T : IOperation
+        {
+            return _lazyInstance.Value.Visit(operation);
+        }
+
+        private T Visit<T>(T node) where T : IOperation
         {
             return (T)Visit(node, argument: null);
         }

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

@@ -143,10 +143,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Return Nothing
         End Function
 
-        Friend Overrides Function CloneOperationCore(operation As IOperation) As IOperation
-            Return VisualBasicOperationCloner.Instance.Visit(operation)
-        End Function
-
         ''' <summary>
         ''' Returns what symbol(s), if any, the given expression syntax bound to in the program.
         '''

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationCloner.vb

-' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
-Imports Microsoft.CodeAnalysis.Operations
-
-Namespace Microsoft.CodeAnalysis.VisualBasic
-    Friend Class VisualBasicOperationCloner
-        Inherits OperationCloner
-
-        Public Shared ReadOnly Property Instance As OperationCloner = New VisualBasicOperationCloner()
-    End Class
-End Namespace

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb

@@ -32,7 +32,7 @@ Namespace Microsoft.CodeAnalysis.Operations
                 ' since same bound node appears in multiple places in the tree
                 ' we can't use bound node to operation map.
                 ' for now, we will just create new operation and return cloned
-                Return _semanticModel.CloneOperation(CreateInternal(boundNode))
+                Return OperationCloner.CloneOperation(CreateInternal(boundNode))
             End If
 
             ' A BoundUserDefined conversion is always the operand of a BoundConversion, and is handled

src/Test/Utilities/Portable/CommonTestBase.cs

@@ -618,7 +618,7 @@ internal static void VerifyClone(SemanticModel model)
                     continue;
                 }
 
-                var clonedOperation = model.CloneOperation(operation);
+                var clonedOperation = OperationCloner.CloneOperation(operation);
 
                 // check whether cloned IOperation is same as original one
                 var original = OperationTreeVerifier.GetOperationTree(model.Compilation, operation);