/* ****************************************************************************
 *
 * Copyright (c) Microsoft Corporation. 
 *
 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 
 * copy of the license can be found in the License.html file at the root of this distribution. If 
 * you cannot locate the  Apache License, Version 2.0, please send an email to 
 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
 * by the terms of the Apache License, Version 2.0.
 *
 * You must not remove this notice, or any other, from this software.
 *
 *
 * ***************************************************************************/

using System;
using System.Diagnostics;
using System.Dynamic.Utils;
using System.Reflection;
using System.Runtime.CompilerServices;

#if SILVERLIGHT
using System.Core;
#endif

#if CLR2
namespace Microsoft.Scripting.Ast {
#else
namespace System.Linq.Expressions {
#endif

    /// <summary>
    /// Represents an expression that has a unary operator.
    /// </summary>
#if !SILVERLIGHT
    [DebuggerTypeProxy(typeof(Expression.UnaryExpressionProxy))]
#endif
    public sealed class UnaryExpression : Expression {
        private readonly Expression _operand;
        private readonly MethodInfo _method;
        private readonly ExpressionType _nodeType;
        private readonly Type _type;

        internal UnaryExpression(ExpressionType nodeType, Expression expression, Type type, MethodInfo method) {
            _operand = expression;
            _method = method;
            _nodeType = nodeType;
            _type = type;
        }

        /// <summary>
        /// Gets the static type of the expression that this <see cref="Expression" /> represents. (Inherited from <see cref="Expression"/>.)
        /// </summary>
        /// <returns>The <see cref="Type"/> that represents the static type of the expression.</returns>
        public sealed override Type Type {
            get { return _type; }
        }

        /// <summary>
        /// Returns the node type of this <see cref="Expression" />. (Inherited from <see cref="Expression" />.)
        /// </summary>
        /// <returns>The <see cref="ExpressionType"/> that represents this expression.</returns>
        public sealed override ExpressionType NodeType {
            get { return _nodeType; }
        }

        /// <summary>
        /// Gets the operand of the unary operation.
        /// </summary>
        /// <returns> An <see cref="ExpressionType"/> that represents the operand of the unary operation.</returns>
        public Expression Operand {
            get { return _operand; }
        }

        /// <summary>
        /// Gets the implementing method for the unary operation.
        /// </summary>
        /// <returns>The <see cref="MethodInfo"/> that represents the implementing method.</returns>
        public MethodInfo Method {
            get { return _method; }
        }

        /// <summary>
        /// Gets a value that indicates whether the expression tree node represents a lifted call to an operator.
        /// </summary>
        /// <returns>true if the node represents a lifted call; otherwise, false.</returns>
        public bool IsLifted {
            get {
                if (NodeType == ExpressionType.TypeAs || NodeType == ExpressionType.Quote || NodeType == ExpressionType.Throw) {
                    return false;
                }
                bool operandIsNullable = TypeUtils.IsNullableType(_operand.Type);
                bool resultIsNullable = TypeUtils.IsNullableType(this.Type);
                if (_method != null) {
                    return (operandIsNullable && !TypeUtils.AreEquivalent(_method.GetParametersCached()[0].ParameterType, _operand.Type)) ||
                           (resultIsNullable && !TypeUtils.AreEquivalent(_method.ReturnType, this.Type));
                }
                return operandIsNullable || resultIsNullable;
            }
        }

        /// <summary>
        /// Gets a value that indicates whether the expression tree node represents a lifted call to an operator whose return type is lifted to a nullable type.
        /// </summary>
        /// <returns>true if the operator's return type is lifted to a nullable type; otherwise, false.</returns>
        public bool IsLiftedToNull {
            get {
                return IsLifted && TypeUtils.IsNullableType(this.Type);
            }
        }

        /// <summary>
        /// Dispatches to the specific visit method for this node type.
        /// </summary>
        protected internal override Expression Accept(ExpressionVisitor visitor) {
            return visitor.VisitUnary(this);
        }

        /// <summary>
        /// Gets a value that indicates whether the expression tree node can be reduced. 
        /// </summary>        
        public override bool CanReduce {
            get {
                switch (_nodeType) {
                    case ExpressionType.PreIncrementAssign:
                    case ExpressionType.PreDecrementAssign:
                    case ExpressionType.PostIncrementAssign:
                    case ExpressionType.PostDecrementAssign:
                        return true;
                }
                return false;
            }
        }

        /// <summary>
        /// Reduces the expression node to a simpler expression. 
        /// If CanReduce returns true, this should return a valid expression.
        /// This method is allowed to return another node which itself 
        /// must be reduced.
        /// </summary>
        /// <returns>The reduced expression.</returns>
        public override Expression Reduce() {
            if (CanReduce) {
                switch (_operand.NodeType) {
                    case ExpressionType.Index:
                        return ReduceIndex();
                    case ExpressionType.MemberAccess:
                        return ReduceMember();
                    default:
                        return ReduceVariable();
                }
            }
            return this;
        }

        private bool IsPrefix {
            get { return _nodeType == ExpressionType.PreIncrementAssign || _nodeType == ExpressionType.PreDecrementAssign; }
        }

        private UnaryExpression FunctionalOp(Expression operand) {
            ExpressionType functional;
            if (_nodeType == ExpressionType.PreIncrementAssign || _nodeType == ExpressionType.PostIncrementAssign) {
                functional = ExpressionType.Increment;
            } else {
                functional = ExpressionType.Decrement;
            }
            return new UnaryExpression(functional, operand, operand.Type, _method);
        }

        private Expression ReduceVariable() {
            if (IsPrefix) {
                // (op) var
                // ... is reduced into ...
                // var = op(var)
                return Assign(_operand, FunctionalOp(_operand));
            }
            // var (op)
            // ... is reduced into ...
            // temp = var
            // var = op(var)
            // temp
            var temp = Parameter(_operand.Type, null);
            return Block(
                new[] { temp },
                Assign(temp, _operand),
                Assign(_operand, FunctionalOp(temp)),
                temp
            );
        }

        private Expression ReduceMember() {
            var member = (MemberExpression)_operand;
            if (member.Expression == null) {
                //static member, reduce the same as variable
                return ReduceVariable();
            } else {
                var temp1 = Parameter(member.Expression.Type, null);
                var initTemp1 = Assign(temp1, member.Expression);
                member = MakeMemberAccess(temp1, member.Member);

                if (IsPrefix) {
                    // (op) value.member
                    // ... is reduced into ...
                    // temp1 = value
                    // temp1.member = op(temp1.member)
                    return Block(
                        new[] { temp1 },
                        initTemp1,
                        Assign(member, FunctionalOp(member))
                    );
                }

                // value.member (op)
                // ... is reduced into ...
                // temp1 = value
                // temp2 = temp1.member
                // temp1.member = op(temp2)
                // temp2
                var temp2 = Parameter(member.Type, null);
                return Block(
                    new[] { temp1, temp2 },
                    initTemp1,
                    Assign(temp2, member),
                    Assign(member, FunctionalOp(temp2)),
                    temp2
                );
            }
        }

        private Expression ReduceIndex() {
            // left[a0, a1, ... aN] (op)
            //
            // ... is reduced into ...
            //
            // tempObj = left
            // tempArg0 = a0
            // ...
            // tempArgN = aN
            // tempValue = tempObj[tempArg0, ... tempArgN]
            // tempObj[tempArg0, ... tempArgN] = op(tempValue)
            // tempValue

            bool prefix = IsPrefix;
            var index = (IndexExpression)_operand;
            int count = index.Arguments.Count;
            var block = new Expression[count + (prefix ? 2 : 4)];
            var temps = new ParameterExpression[count + (prefix ? 1 : 2)];
            var args = new ParameterExpression[count];

            int i = 0;
            temps[i] = Parameter(index.Object.Type, null);
            block[i] = Assign(temps[i], index.Object);
            i++;
            while (i <= count) {
                var arg = index.Arguments[i - 1];
                args[i - 1] = temps[i] = Parameter(arg.Type, null);
                block[i] = Assign(temps[i], arg);
                i++;
            }
            index = MakeIndex(temps[0], index.Indexer, new TrueReadOnlyCollection<Expression>(args));
            if (!prefix) {
                var lastTemp = temps[i] = Parameter(index.Type, null);
                block[i] = Assign(temps[i], index);
                i++;
                Debug.Assert(i == temps.Length);
                block[i++] = Assign(index, FunctionalOp(lastTemp));
                block[i++] = lastTemp;
            } else {
                Debug.Assert(i == temps.Length);
                block[i++] = Assign(index, FunctionalOp(index));
            }
            Debug.Assert(i == block.Length);
            return Block(new TrueReadOnlyCollection<ParameterExpression>(temps), new TrueReadOnlyCollection<Expression>(block));
        }

        /// <summary>
        /// Creates a new expression that is like this one, but using the
        /// supplied children. If all of the children are the same, it will
        /// return this expression.
        /// </summary>
        /// <param name="operand">The <see cref="Operand" /> property of the result.</param>
        /// <returns>This expression if no children changed, or an expression with the updated children.</returns>
        public UnaryExpression Update(Expression operand) {
            if (operand == Operand) {
                return this;
            }
            return Expression.MakeUnary(NodeType, operand, Type, Method);
        }
    }

    public partial class Expression {

        /// <summary>
        /// Creates a <see cref="UnaryExpression"></see>, given an operand, by calling the appropriate factory method.
        /// </summary>
        /// <param name="unaryType">The <see cref="ExpressionType"></see> that specifies the type of unary operation.</param>
        /// <param name="operand">An <see cref="Expression"></see> that represents the operand.</param>
        /// <param name="type">The <see cref="Type"></see> that specifies the type to be converted to (pass null if not applicable).</param>
        /// <returns>The <see cref="UnaryExpression"></see> that results from calling the appropriate factory method.</returns>
        /// <exception cref="ArgumentException">Thrown when <paramref name="unaryType"/> does not correspond to a unary expression.</exception>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="operand"/> is null.</exception>
        public static UnaryExpression MakeUnary(ExpressionType unaryType, Expression operand, Type type) {
            return MakeUnary(unaryType, operand, type, null);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"></see>, given an operand and implementing method, by calling the appropriate factory method.
        /// </summary>
        /// <param name="unaryType">The <see cref="ExpressionType"></see> that specifies the type of unary operation.</param>
        /// <param name="operand">An <see cref="Expression"></see> that represents the operand.</param>
        /// <param name="type">The <see cref="Type"></see> that specifies the type to be converted to (pass null if not applicable).</param>
        /// <param name="method">The <see cref="MethodInfo"></see> that represents the implementing method.</param>
        /// <returns>The <see cref="UnaryExpression"></see> that results from calling the appropriate factory method.</returns>
        /// <exception cref="ArgumentException">Thrown when <paramref name="unaryType"/> does not correspond to a unary expression.</exception> 
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="operand"/> is null.</exception>
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity")]
        public static UnaryExpression MakeUnary(ExpressionType unaryType, Expression operand, Type type, MethodInfo method) {
            switch (unaryType) {
                case ExpressionType.Negate:
                    return Negate(operand, method);
                case ExpressionType.NegateChecked:
                    return NegateChecked(operand, method);
                case ExpressionType.Not:
                    return Not(operand, method);
                case ExpressionType.IsFalse:
                    return IsFalse(operand, method);
                case ExpressionType.IsTrue:
                    return IsTrue(operand, method);
                case ExpressionType.OnesComplement:
                    return OnesComplement(operand, method);
                case ExpressionType.ArrayLength:
                    return ArrayLength(operand);
                case ExpressionType.Convert:
                    return Convert(operand, type, method);
                case ExpressionType.ConvertChecked:
                    return ConvertChecked(operand, type, method);
                case ExpressionType.Throw:
                    return Throw(operand, type);
                case ExpressionType.TypeAs:
                    return TypeAs(operand, type);
                case ExpressionType.Quote:
                    return Quote(operand);
                case ExpressionType.UnaryPlus:
                    return UnaryPlus(operand, method);
                case ExpressionType.Unbox:
                    return Unbox(operand, type);
                case ExpressionType.Increment:
                    return Increment(operand, method);
                case ExpressionType.Decrement:
                    return Decrement(operand, method);
                case ExpressionType.PreIncrementAssign:
                    return PreIncrementAssign(operand, method);
                case ExpressionType.PostIncrementAssign:
                    return PostIncrementAssign(operand, method);
                case ExpressionType.PreDecrementAssign:
                    return PreDecrementAssign(operand, method);
                case ExpressionType.PostDecrementAssign:
                    return PostDecrementAssign(operand, method);
                default:
                    throw Error.UnhandledUnary(unaryType);
            }
        }

        private static UnaryExpression GetUserDefinedUnaryOperatorOrThrow(ExpressionType unaryType, string name, Expression operand) {
            UnaryExpression u = GetUserDefinedUnaryOperator(unaryType, name, operand);
            if (u != null) {
                ValidateParamswithOperandsOrThrow(u.Method.GetParametersCached()[0].ParameterType, operand.Type, unaryType, name);
                return u;
            }
            throw Error.UnaryOperatorNotDefined(unaryType, operand.Type);
        }

        private static UnaryExpression GetUserDefinedUnaryOperator(ExpressionType unaryType, string name, Expression operand) {
            Type operandType = operand.Type;
            Type[] types = new Type[] { operandType };
            Type nnOperandType = TypeUtils.GetNonNullableType(operandType);
            BindingFlags flags = BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic;
            MethodInfo method = nnOperandType.GetMethodValidated(name, flags, null, types, null);
            if (method != null) {
                return new UnaryExpression(unaryType, operand, method.ReturnType, method);
            }
            // try lifted call
            if (TypeUtils.IsNullableType(operandType)) {
                types[0] = nnOperandType;
                method = nnOperandType.GetMethodValidated(name, flags, null, types, null);
                if (method != null && method.ReturnType.IsValueType && !TypeUtils.IsNullableType(method.ReturnType)) {
                    return new UnaryExpression(unaryType, operand, TypeUtils.GetNullableType(method.ReturnType), method);
                }
            }
            return null;
        }

        private static UnaryExpression GetMethodBasedUnaryOperator(ExpressionType unaryType, Expression operand, MethodInfo method) {
            System.Diagnostics.Debug.Assert(method != null);
            ValidateOperator(method);
            ParameterInfo[] pms = method.GetParametersCached();
            if (pms.Length != 1)
                throw Error.IncorrectNumberOfMethodCallArguments(method);
            if (ParameterIsAssignable(pms[0], operand.Type)) {
                ValidateParamswithOperandsOrThrow(pms[0].ParameterType, operand.Type, unaryType, method.Name);
                return new UnaryExpression(unaryType, operand, method.ReturnType, method);
            }
            // check for lifted call
            if (TypeUtils.IsNullableType(operand.Type) &&
                ParameterIsAssignable(pms[0], TypeUtils.GetNonNullableType(operand.Type)) &&
                method.ReturnType.IsValueType && !TypeUtils.IsNullableType(method.ReturnType)) {
                return new UnaryExpression(unaryType, operand, TypeUtils.GetNullableType(method.ReturnType), method);
            }

            throw Error.OperandTypesDoNotMatchParameters(unaryType, method.Name);
        }

        private static UnaryExpression GetUserDefinedCoercionOrThrow(ExpressionType coercionType, Expression expression, Type convertToType) {
            UnaryExpression u = GetUserDefinedCoercion(coercionType, expression, convertToType);
            if (u != null) {
                return u;
            }
            throw Error.CoercionOperatorNotDefined(expression.Type, convertToType);
        }

        private static UnaryExpression GetUserDefinedCoercion(ExpressionType coercionType, Expression expression, Type convertToType) {
            MethodInfo method = TypeUtils.GetUserDefinedCoercionMethod(expression.Type, convertToType, false);
            if (method != null) {
                return new UnaryExpression(coercionType, expression, convertToType, method);
            } else {
                return null;
            }
        }

        private static UnaryExpression GetMethodBasedCoercionOperator(ExpressionType unaryType, Expression operand, Type convertToType, MethodInfo method) {
            System.Diagnostics.Debug.Assert(method != null);
            ValidateOperator(method);
            ParameterInfo[] pms = method.GetParametersCached();
            if (pms.Length != 1) {
                throw Error.IncorrectNumberOfMethodCallArguments(method);
            }
            if (ParameterIsAssignable(pms[0], operand.Type) && TypeUtils.AreEquivalent(method.ReturnType, convertToType)) {
                return new UnaryExpression(unaryType, operand, method.ReturnType, method);
            }
            // check for lifted call
            if ((TypeUtils.IsNullableType(operand.Type) || TypeUtils.IsNullableType(convertToType)) &&
                ParameterIsAssignable(pms[0], TypeUtils.GetNonNullableType(operand.Type)) &&
                TypeUtils.AreEquivalent(method.ReturnType, TypeUtils.GetNonNullableType(convertToType))) {
                return new UnaryExpression(unaryType, operand, convertToType, method);
            }
            throw Error.OperandTypesDoNotMatchParameters(unaryType, method.Name);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"></see> that represents an arithmetic negation operation.
        /// </summary>
        /// <param name="expression">An <see cref="Expression"></see> to set the <see cref="P:UnaryExpression.Operand"></see> property equal to.</param>
        /// <returns>A <see cref="UnaryExpression"></see> that has the <see cref="P:Expression.NodeType"></see> property equal to <see cref="P:ExpressionType.Negate"></see> and the <see cref="P:UnaryExpression.Operand"></see> properties set to the specified value.</returns>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="expression"/> is null.</exception>
        /// <exception cref="InvalidOperationException">Thrown when the unary minus operator is not defined for <see cref="P:Expression.Type"></see></exception>
        public static UnaryExpression Negate(Expression expression) {
            return Negate(expression, null);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"></see> that represents an arithmetic negation operation.
        /// </summary>
        /// <param name="expression">An <see cref="Expression"></see> to set the <see cref="P:UnaryExpression.Operand"></see> property equal to.</param>
        /// <param name="method">A <see cref="MethodInfo"></see> to set the <see cref="P:UnaryExpression.Method"></see> property equal to.</param>
        /// <returns>A <see cref="UnaryExpression"></see> that has the <see cref="P:Expression.NodeType"></see> property equal to <see cref="P:ExpressionType.Negate"></see> and the <see cref="P:UnaryExpression.Operand"></see> and <see cref="P:UnaryExpression.Method"></see> properties set to the specified value.</returns>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="expression"/> is null.</exception>
        /// <exception cref="ArgumentException">Thrown when <paramref name="method"/> is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.</exception>
        /// <exception cref="InvalidOperationException">Thown when <paramref name="method"/> is null and the unary minus operator is not defined for expression.Type or expression.Type (or its corresponding non-nullable type if it is a nullable value type) is not assignable to the argument type of the method represented by method.</exception>
        public static UnaryExpression Negate(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsArithmetic(expression.Type) && !TypeUtils.IsUnsignedInt(expression.Type)) {
                    return new UnaryExpression(ExpressionType.Negate, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.Negate, "op_UnaryNegation", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.Negate, expression, method);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"></see> that represents a unary plus operation.
        /// </summary>
        /// <param name="expression">An <see cref="Expression"></see> to set the <see cref="UnaryExpression.Operand"></see> property equal to.</param>
        /// <returns>A <see cref="UnaryExpression"></see> that has the <see cref="Expression.NodeType"></see> property equal to <see cref="ExpressionType.UnaryPlus"></see> and the <see cref="UnaryExpression.Operand"></see> property set to the specified value.</returns>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="expression"/> is null.</exception>
        /// <exception cref="InvalidOperationException">Thown when the unary minus operator is not defined for expression.Type.</exception>
        public static UnaryExpression UnaryPlus(Expression expression) {
            return UnaryPlus(expression, null);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"></see> that represents a unary plus operation.
        /// </summary>
        /// <param name="expression">An <see cref="Expression"></see> to set the <see cref="UnaryExpression.Operand"></see> property equal to.</param>
        /// <param name="method">A <see cref="MethodInfo"></see> to set the <see cref="UnaryExpression.Method"></see> property equal to.</param>
        /// <returns>A <see cref="UnaryExpression"></see> that has the <see cref="Expression.NodeType"></see> property equal to <see cref="ExpressionType.UnaryPlus"></see> and the <see cref="UnaryExpression.Operand"></see> and <see cref="UnaryExpression.Method"></see>property set to the specified value.</returns>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="expression"/> is null.</exception>
        /// <exception cref="ArgumentException">Thrown when <paramref name="method"/> is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.</exception>
        /// <exception cref="InvalidOperationException">Thown when <paramref name="method"/> is null and the unary minus operator is not defined for expression.Type or expression.Type (or its corresponding non-nullable type if it is a nullable value type) is not assignable to the argument type of the method represented by method.</exception>
        public static UnaryExpression UnaryPlus(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsArithmetic(expression.Type)) {
                    return new UnaryExpression(ExpressionType.UnaryPlus, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.UnaryPlus, "op_UnaryPlus", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.UnaryPlus, expression, method);
        }

        /// <summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents an arithmetic negation operation that has overflow checking.</summary>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.NegateChecked" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property set to the specified value.</returns>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        /// <exception cref="T:System.ArgumentNullException">
        ///   Thrown when <paramref name="expression" /> is null.</exception>
        /// <exception cref="T:System.InvalidOperationException">Thrown when the unary minus operator is not defined for <paramref name="expression" />.Type.</exception> 
        public static UnaryExpression NegateChecked(Expression expression) {
            return NegateChecked(expression, null);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents an arithmetic negation operation that has overflow checking. The implementing method can be specified.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.NegateChecked" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> and <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> is null.</exception>
        ///<exception cref="T:System.ArgumentException">
        ///<paramref name="method" /> is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.</exception>
        ///<exception cref="T:System.InvalidOperationException">
        ///<paramref name="method" /> is null and the unary minus operator is not defined for <paramref name="expression" />.Type.-or-<paramref name="expression" />.Type (or its corresponding non-nullable type if it is a nullable value type) is not assignable to the argument type of the method represented by <paramref name="method" />.</exception>
        public static UnaryExpression NegateChecked(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsArithmetic(expression.Type) && !TypeUtils.IsUnsignedInt(expression.Type)) {
                    return new UnaryExpression(ExpressionType.NegateChecked, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.NegateChecked, "op_UnaryNegation", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.NegateChecked, expression, method);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a bitwise complement operation.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.Not" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property set to the specified value.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> is null.</exception>
        ///<exception cref="T:System.InvalidOperationException">The unary not operator is not defined for <paramref name="expression" />.Type.</exception>
        public static UnaryExpression Not(Expression expression) {
            return Not(expression, null);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a bitwise complement operation. The implementing method can be specified.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.Not" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> and <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> is null.</exception>
        ///<exception cref="T:System.ArgumentException">
        ///<paramref name="method" /> is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.</exception>
        ///<exception cref="T:System.InvalidOperationException">
        ///<paramref name="method" /> is null and the unary not operator is not defined for <paramref name="expression" />.Type.-or-<paramref name="expression" />.Type (or its corresponding non-nullable type if it is a nullable value type) is not assignable to the argument type of the method represented by <paramref name="method" />.</exception>
        public static UnaryExpression Not(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsIntegerOrBool(expression.Type)) {
                    return new UnaryExpression(ExpressionType.Not, expression, expression.Type, null);
                }
                UnaryExpression u = GetUserDefinedUnaryOperator(ExpressionType.Not, "op_LogicalNot", expression);
                if (u != null) {
                    return u;
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.Not, "op_OnesComplement", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.Not, expression, method);
        }

        /// <summary>
        /// Returns whether the expression evaluates to false.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to evaluate.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression IsFalse(Expression expression) {
            return IsFalse(expression, null);
        }

        /// <summary>
        /// Returns whether the expression evaluates to false.
        /// </summary>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to evaluate.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression IsFalse(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsBool(expression.Type)) {
                    return new UnaryExpression(ExpressionType.IsFalse, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.IsFalse, "op_False", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.IsFalse, expression, method);
        }

        /// <summary>
        /// Returns whether the expression evaluates to true.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to evaluate.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression IsTrue(Expression expression) {
            return IsTrue(expression, null);
        }

        /// <summary>
        /// Returns whether the expression evaluates to true.
        /// </summary>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to evaluate.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression IsTrue(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsBool(expression.Type)) {
                    return new UnaryExpression(ExpressionType.IsTrue, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.IsTrue, "op_True", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.IsTrue, expression, method);
        }

        /// <summary>
        /// Returns the expression representing the ones complement.
        /// </summary>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" />.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression OnesComplement(Expression expression) {
            return OnesComplement(expression, null);
        }

        /// <summary>
        /// Returns the expression representing the ones complement.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression" />.</param>
        /// <param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression OnesComplement(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsInteger(expression.Type)) {
                    return new UnaryExpression(ExpressionType.OnesComplement, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.OnesComplement, "op_OnesComplement", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.OnesComplement, expression, method);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents an explicit reference or boxing conversion where null is supplied if the conversion fails.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.TypeAs" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> and <see cref="P:System.Linq.Expressions.Expression.Type" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="type">A <see cref="T:System.Type" /> to set the <see cref="P:System.Linq.Expressions.Expression.Type" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> or <paramref name="type" /> is null.</exception>
        public static UnaryExpression TypeAs(Expression expression, Type type) {
            RequiresCanRead(expression, "expression");
            ContractUtils.RequiresNotNull(type, "type");
            TypeUtils.ValidateType(type);

            if (type.IsValueType && !TypeUtils.IsNullableType(type)) {
                throw Error.IncorrectTypeForTypeAs(type);
            }
            return new UnaryExpression(ExpressionType.TypeAs, expression, type, null);
        }

        /// <summary>
        /// <summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents an explicit unboxing.</summary>
        /// </summary>     
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to unbox.</param>
        /// <param name="type">The new <see cref="T:System.Type" /> of the expression.</param>
        /// <returns>An instance of <see cref="UnaryExpression"/>.</returns>
        public static UnaryExpression Unbox(Expression expression, Type type) {
            RequiresCanRead(expression, "expression");
            ContractUtils.RequiresNotNull(type, "type");
            if (!expression.Type.IsInterface && expression.Type != typeof(object)) {
                throw Error.InvalidUnboxType();
            }
            if (!type.IsValueType) throw Error.InvalidUnboxType();
            TypeUtils.ValidateType(type);
            return new UnaryExpression(ExpressionType.Unbox, expression, type, null);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a conversion operation.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.Convert" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> and <see cref="P:System.Linq.Expressions.Expression.Type" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="type">A <see cref="T:System.Type" /> to set the <see cref="P:System.Linq.Expressions.Expression.Type" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> or <paramref name="type" /> is null.</exception>
        ///<exception cref="T:System.InvalidOperationException">No conversion operator is defined between <paramref name="expression" />.Type and <paramref name="type" />.</exception>
        public static UnaryExpression Convert(Expression expression, Type type) {
            return Convert(expression, type, null);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a conversion operation for which the implementing method is specified.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.Convert" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" />, <see cref="P:System.Linq.Expressions.Expression.Type" />, and <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="type">A <see cref="T:System.Type" /> to set the <see cref="P:System.Linq.Expressions.Expression.Type" /> property equal to.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> or <paramref name="type" /> is null.</exception>
        ///<exception cref="T:System.ArgumentException">
        ///<paramref name="method" /> is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.</exception>
        ///<exception cref="T:System.Reflection.AmbiguousMatchException">More than one method that matches the <paramref name="method" /> description was found.</exception>
        ///<exception cref="T:System.InvalidOperationException">No conversion operator is defined between <paramref name="expression" />.Type and <paramref name="type" />.-or-<paramref name="expression" />.Type is not assignable to the argument type of the method represented by <paramref name="method" />.-or-The return type of the method represented by <paramref name="method" /> is not assignable to <paramref name="type" />.-or-<paramref name="expression" />.Type or <paramref name="type" /> is a nullable value type and the corresponding non-nullable value type does not equal the argument type or the return type, respectively, of the method represented by <paramref name="method" />.</exception>
        public static UnaryExpression Convert(Expression expression, Type type, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            ContractUtils.RequiresNotNull(type, "type");
            TypeUtils.ValidateType(type);

            if (method == null) {
                if (TypeUtils.HasIdentityPrimitiveOrNullableConversion(expression.Type, type) ||
                    TypeUtils.HasReferenceConversion(expression.Type, type)) {
                    return new UnaryExpression(ExpressionType.Convert, expression, type, null);
                }
                return GetUserDefinedCoercionOrThrow(ExpressionType.Convert, expression, type);
            }
            return GetMethodBasedCoercionOperator(ExpressionType.Convert, expression, type, method);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a conversion operation that throws an exception if the target type is overflowed.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.ConvertChecked" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> and <see cref="P:System.Linq.Expressions.Expression.Type" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="type">A <see cref="T:System.Type" /> to set the <see cref="P:System.Linq.Expressions.Expression.Type" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> or <paramref name="type" /> is null.</exception>
        ///<exception cref="T:System.InvalidOperationException">No conversion operator is defined between <paramref name="expression" />.Type and <paramref name="type" />.</exception>
        public static UnaryExpression ConvertChecked(Expression expression, Type type) {
            return ConvertChecked(expression, type, null);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a conversion operation that throws an exception if the target type is overflowed and for which the implementing method is specified.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.ConvertChecked" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" />, <see cref="P:System.Linq.Expressions.Expression.Type" />, and <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> properties set to the specified values.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<param name="type">A <see cref="T:System.Type" /> to set the <see cref="P:System.Linq.Expressions.Expression.Type" /> property equal to.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Method" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> or <paramref name="type" /> is null.</exception>
        ///<exception cref="T:System.ArgumentException">
        ///<paramref name="method" /> is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.</exception>
        ///<exception cref="T:System.Reflection.AmbiguousMatchException">More than one method that matches the <paramref name="method" /> description was found.</exception>
        ///<exception cref="T:System.InvalidOperationException">No conversion operator is defined between <paramref name="expression" />.Type and <paramref name="type" />.-or-<paramref name="expression" />.Type is not assignable to the argument type of the method represented by <paramref name="method" />.-or-The return type of the method represented by <paramref name="method" /> is not assignable to <paramref name="type" />.-or-<paramref name="expression" />.Type or <paramref name="type" /> is a nullable value type and the corresponding non-nullable value type does not equal the argument type or the return type, respectively, of the method represented by <paramref name="method" />.</exception>
        public static UnaryExpression ConvertChecked(Expression expression, Type type, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            ContractUtils.RequiresNotNull(type, "type");
            TypeUtils.ValidateType(type);

            if (method == null) {
                if (TypeUtils.HasIdentityPrimitiveOrNullableConversion(expression.Type, type)) {
                    return new UnaryExpression(ExpressionType.ConvertChecked, expression, type, null);
                }
                if (TypeUtils.HasReferenceConversion(expression.Type, type)) {
                    return new UnaryExpression(ExpressionType.Convert, expression, type, null);
                }
                return GetUserDefinedCoercionOrThrow(ExpressionType.ConvertChecked, expression, type);
            }
            return GetMethodBasedCoercionOperator(ExpressionType.ConvertChecked, expression, type, method);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents getting the length of a one-dimensional array.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.ArrayLength" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to <paramref name="array" />.</returns>
        ///<param name="array">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="array" /> is null.</exception>
        ///<exception cref="T:System.ArgumentException">
        ///<paramref name="array" />.Type does not represent an array type.</exception>
        public static UnaryExpression ArrayLength(Expression array) {
            ContractUtils.RequiresNotNull(array, "array");
            if (!array.Type.IsArray || !typeof(Array).IsAssignableFrom(array.Type)) {
                throw Error.ArgumentMustBeArray();
            }
            if (array.Type.GetArrayRank() != 1) {
                throw Error.ArgumentMustBeSingleDimensionalArrayType();
            }
            return new UnaryExpression(ExpressionType.ArrayLength, array, typeof(int), null);
        }

        ///<summary>Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents an expression that has a constant value of type <see cref="T:System.Linq.Expressions.Expression" />.</summary>
        ///<returns>A <see cref="T:System.Linq.Expressions.UnaryExpression" /> that has the <see cref="P:System.Linq.Expressions.Expression.NodeType" /> property equal to <see cref="F:System.Linq.Expressions.ExpressionType.Quote" /> and the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property set to the specified value.</returns>
        ///<param name="expression">An <see cref="T:System.Linq.Expressions.Expression" /> to set the <see cref="P:System.Linq.Expressions.UnaryExpression.Operand" /> property equal to.</param>
        ///<exception cref="T:System.ArgumentNullException">
        ///<paramref name="expression" /> is null.</exception>
        public static UnaryExpression Quote(Expression expression) {
            RequiresCanRead(expression, "expression");
            bool validQuote = expression is LambdaExpression;
#if SILVERLIGHT
            validQuote |= SilverlightQuirks;
#endif
            if (!validQuote) throw Error.QuotedExpressionMustBeLambda();
            return new UnaryExpression(ExpressionType.Quote, expression, expression.GetType(), null);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a rethrowing of an exception.
        /// </summary>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents a rethrowing of an exception.</returns>
        public static UnaryExpression Rethrow() {
            return Throw(null);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a rethrowing of an exception with a given type.
        /// </summary>
        ///<param name="type">The new <see cref="T:System.Type" /> of the expression.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents a rethrowing of an exception.</returns>
        public static UnaryExpression Rethrow(Type type) {
            return Throw(null, type);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a throwing of an exception.
        /// </summary>
        /// <param name="value">An <see cref="T:System.Linq.Expressions.Expression" />.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the exception.</returns>
        public static UnaryExpression Throw(Expression value) {
            return Throw(value, typeof(void));
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents a throwing of a value with a given type.
        /// </summary>
        /// <param name="value">An <see cref="T:System.Linq.Expressions.Expression" />.</param>
        /// <param name="type">The new <see cref="T:System.Type" /> of the expression.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the exception.</returns>
        public static UnaryExpression Throw(Expression value, Type type) {
            ContractUtils.RequiresNotNull(type, "type");
            TypeUtils.ValidateType(type);

            if (value != null) {
                RequiresCanRead(value, "value");
                if (value.Type.IsValueType) throw Error.ArgumentMustNotHaveValueType();
            }
            return new UnaryExpression(ExpressionType.Throw, value, type, null);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents the incrementing of the expression by 1.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to increment.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the incremented expression.</returns>
        public static UnaryExpression Increment(Expression expression) {
            return Increment(expression, null);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents the incrementing of the expression by 1.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to increment.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the incremented expression.</returns>
        public static UnaryExpression Increment(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsArithmetic(expression.Type)) {
                    return new UnaryExpression(ExpressionType.Increment, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.Increment, "op_Increment", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.Increment, expression, method);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents the decrementing of the expression by 1.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to decrement.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the decremented expression.</returns>
        public static UnaryExpression Decrement(Expression expression) {
            return Decrement(expression, null);
        }

        /// <summary>
        /// Creates a <see cref="T:System.Linq.Expressions.UnaryExpression" /> that represents the decrementing of the expression by 1.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to decrement.</param>
        ///<param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the decremented expression.</returns>
        public static UnaryExpression Decrement(Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            if (method == null) {
                if (TypeUtils.IsArithmetic(expression.Type)) {
                    return new UnaryExpression(ExpressionType.Decrement, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.Decrement, "op_Decrement", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.Decrement, expression, method);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that increments the expression by 1
        /// and assigns the result back to the expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PreIncrementAssign(Expression expression) {
            return MakeOpAssignUnary(ExpressionType.PreIncrementAssign, expression, null);

        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that increments the expression by 1
        /// and assigns the result back to the expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PreIncrementAssign(Expression expression, MethodInfo method) {
            return MakeOpAssignUnary(ExpressionType.PreIncrementAssign, expression, method);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that decrements the expression by 1
        /// and assigns the result back to the expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PreDecrementAssign(Expression expression) {
            return MakeOpAssignUnary(ExpressionType.PreDecrementAssign, expression, null);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that decrements the expression by 1
        /// and assigns the result back to the expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PreDecrementAssign(Expression expression, MethodInfo method) {
            return MakeOpAssignUnary(ExpressionType.PreDecrementAssign, expression, method);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that represents the assignment of the expression 
        /// followed by a subsequent increment by 1 of the original expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PostIncrementAssign(Expression expression) {
            return MakeOpAssignUnary(ExpressionType.PostIncrementAssign, expression, null);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that represents the assignment of the expression 
        /// followed by a subsequent increment by 1 of the original expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PostIncrementAssign(Expression expression, MethodInfo method) {
            return MakeOpAssignUnary(ExpressionType.PostIncrementAssign, expression, method);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that represents the assignment of the expression 
        /// followed by a subsequent decrement by 1 of the original expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PostDecrementAssign(Expression expression) {
            return MakeOpAssignUnary(ExpressionType.PostDecrementAssign, expression, null);
        }

        /// <summary>
        /// Creates a <see cref="UnaryExpression"/> that represents the assignment of the expression 
        /// followed by a subsequent decrement by 1 of the original expression.
        /// </summary>
        /// <param name="expression">An <see cref="T:System.Linq.Expressions.Expression"></see> to apply the operations on.</param>
        /// <param name="method">A <see cref="T:System.Reflection.MethodInfo" /> that represents the implementing method.</param>
        /// <returns>A <see cref="T:System.Linq.Expressions.UnaryExpression"/> that represents the resultant expression.</returns>
        public static UnaryExpression PostDecrementAssign(Expression expression, MethodInfo method) {
            return MakeOpAssignUnary(ExpressionType.PostDecrementAssign, expression, method);
        }

        private static UnaryExpression MakeOpAssignUnary(ExpressionType kind, Expression expression, MethodInfo method) {
            RequiresCanRead(expression, "expression");
            RequiresCanWrite(expression, "expression");

            UnaryExpression result;
            if (method == null) {
                if (TypeUtils.IsArithmetic(expression.Type)) {
                    return new UnaryExpression(kind, expression, expression.Type, null);
                }
                string name;
                if (kind == ExpressionType.PreIncrementAssign || kind == ExpressionType.PostIncrementAssign) {
                    name = "op_Increment";
                } else {
                    name = "op_Decrement";
                }
                result = GetUserDefinedUnaryOperatorOrThrow(kind, name, expression);
            } else {
                result = GetMethodBasedUnaryOperator(kind, expression, method);
            }
            // return type must be assignable back to the operand type
            if (!TypeUtils.AreReferenceAssignable(expression.Type, result.Type)) {
                throw Error.UserDefinedOpMustHaveValidReturnType(kind, method.Name);
            }
            return result;
        }
    }
}