Restoring the return type of the Expression<TDelegate>.Update

The method is a public API and is used to return Expression<TDelegate>

Author: VSadov

src/System.Linq.Expressions/src/System/Linq/Expressions/DebugViewWriter.cs

@@ -430,7 +430,7 @@ protected internal override Expression VisitParameter(ParameterExpression node)
             return node;
         }
 
-        protected internal override Expression VisitLambda(LambdaExpression node)
+        protected internal override Expression VisitLambda<T>(Expression<T> node)
         {
             Out(
                 String.Format(CultureInfo.CurrentCulture,

src/System.Linq.Expressions/src/System/Linq/Expressions/ExpressionStringBuilder.cs

@@ -326,7 +326,7 @@ protected internal override Expression VisitParameter(ParameterExpression node)
             return node;
         }
 
-        protected internal override Expression VisitLambda(LambdaExpression node)
+        protected internal override Expression VisitLambda<T>(Expression<T> node)
         {
             if (node.Parameters.Count == 1)
             {

src/System.Linq.Expressions/src/System/Linq/Expressions/ExpressionVisitor.cs

@@ -364,18 +364,6 @@ protected internal virtual Expression VisitLabel(LabelExpression node)
         /// <returns>The modified expression, if it or any subexpression was modified;
         /// otherwise, returns the original expression.</returns>
         protected internal virtual Expression VisitLambda<T>(Expression<T> node)
-        {
-            return VisitLambda((LambdaExpression)node);
-        }
-
-        /// <summary>
-        /// Visits the children of the <see cref="LambdaExpression" />.
-        /// </summary>
-        /// <typeparam name="T">The type of the delegate.</typeparam>
-        /// <param name="node">The expression to visit.</param>
-        /// <returns>The modified expression, if it or any subexpression was modified;
-        /// otherwise, returns the original expression.</returns>
-        protected internal virtual Expression VisitLambda(LambdaExpression node)
         {
             return node.Update(Visit(node.Body), VisitAndConvert(node.Parameters, "VisitLambda"));
         }

src/System.Linq.Expressions/src/System/Linq/Expressions/LambdaExpression.cs

@@ -120,23 +120,6 @@ public Delegate Compile()
 #endif 
         }
 
-        /// <summary>
-        /// Dispatches to the specific visit method for this node type.
-        /// </summary>
-        protected internal override Expression Accept(ExpressionVisitor visitor)
-        {
-            return visitor.VisitLambda(this);
-        }
-
-        public virtual LambdaExpression Update(Expression body, IEnumerable<ParameterExpression> parameters)
-        {
-            if (body == Body && parameters == Parameters)
-            {
-                return this;
-            }
-            return Expression.Lambda(Type, body, Name, TailCall, parameters);
-        }
-
 #if FEATURE_CORECLR
         internal abstract LambdaExpression Accept(Compiler.StackSpiller spiller);
 #endif 
@@ -178,7 +161,7 @@ public Expression(Expression body, string name, bool tailCall, ReadOnlyCollectio
         /// <param name="body">The <see cref="LambdaExpression.Body">Body</see> property of the result.</param>
         /// <param name="parameters">The <see cref="LambdaExpression.Parameters">Parameters</see> property of the result.</param>
         /// <returns>This expression if no children changed, or an expression with the updated children.</returns>
-        public override LambdaExpression Update(Expression body, IEnumerable<ParameterExpression> parameters)
+        public Expression<TDelegate> Update(Expression body, IEnumerable<ParameterExpression> parameters)
         {
             if (body == Body && parameters == Parameters)
             {