/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Microsoft Public License. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Microsoft Public License, 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 Microsoft Public License.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System;
using System.Dynamic.Utils;
using System.Diagnostics;
#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 conditional operator.
/// </summary>
#if !SILVERLIGHT
[DebuggerTypeProxy(typeof(Expression.ConditionalExpressionProxy))]
#endif
public class ConditionalExpression : Expression {
private readonly Expression _test;
private readonly Expression _true;
internal ConditionalExpression(Expression test, Expression ifTrue) {
_test = test;
_true = ifTrue;
}
internal static ConditionalExpression Make(Expression test, Expression ifTrue, Expression ifFalse, Type type) {
if (ifTrue.Type != type || ifFalse.Type != type) {
return new FullConditionalExpressionWithType(test, ifTrue, ifFalse, type);
} if (ifFalse is DefaultExpression && ifFalse.Type == typeof(void)) {
return new ConditionalExpression(test, ifTrue);
} else {
return new FullConditionalExpression(test, ifTrue, ifFalse);
}
}
/// <summary>
/// Returns the node type of this Expression. Extension nodes should return
/// ExpressionType.Extension when overriding this method.
/// </summary>
/// <returns>The <see cref="ExpressionType"/> of the expression.</returns>
public sealed override ExpressionType NodeType {
get { return ExpressionType.Conditional; }
}
/// <summary>
/// Gets the static type of the expression that this <see cref="Expression" /> represents.
/// </summary>
/// <returns>The <see cref="Type"/> that represents the static type of the expression.</returns>
public override Type Type {
get { return IfTrue.Type; }
}
/// <summary>
/// Gets the test of the conditional operation.
/// </summary>
public Expression Test {
get { return _test; }
}
/// <summary>
/// Gets the expression to execute if the test evaluates to true.
/// </summary>
public Expression IfTrue {
get { return _true; }
}
/// <summary>
/// Gets the expression to execute if the test evaluates to false.
/// </summary>
public Expression IfFalse {
get { return GetFalse(); }
}
internal virtual Expression GetFalse() {
return Expression.Empty();
}
/// <summary>
/// Dispatches to the specific visit method for this node type.
/// </summary>
protected internal override Expression Accept(ExpressionVisitor visitor) {
return visitor.VisitConditional(this);
}
/// <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="test">The <see cref="Test" /> property of the result.</param>
/// <param name="ifTrue">The <see cref="IfTrue" /> property of the result.</param>
/// <param name="ifFalse">The <see cref="IfFalse" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public ConditionalExpression Update(Expression test, Expression ifTrue, Expression ifFalse) {
if (test == Test && ifTrue == IfTrue && ifFalse == IfFalse) {
return this;
}
return Expression.Condition(test, ifTrue, ifFalse, Type);
}
}
internal class FullConditionalExpression : ConditionalExpression {
private readonly Expression _false;
internal FullConditionalExpression(Expression test, Expression ifTrue, Expression ifFalse)
: base(test, ifTrue) {
_false = ifFalse;
}
internal override Expression GetFalse() {
return _false;
}
}
internal class FullConditionalExpressionWithType : FullConditionalExpression {
private readonly Type _type;
internal FullConditionalExpressionWithType(Expression test, Expression ifTrue, Expression ifFalse, Type type)
: base(test, ifTrue, ifFalse) {
_type = type;
}
public sealed override Type Type {
get { return _type; }
}
}
public partial class Expression {
/// <summary>
/// Creates a <see cref="ConditionalExpression"/>.
/// </summary>
/// <param name="test">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.Test"/> property equal to.</param>
/// <param name="ifTrue">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfTrue"/> property equal to.</param>
/// <param name="ifFalse">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfFalse"/> property equal to.</param>
/// <returns>A <see cref="ConditionalExpression"/> that has the <see cref="P:Expression.NodeType"/> property equal to
/// <see cref="F:ExpressionType.Conditional"/> and the <see cref="P:ConditionalExpression.Test"/>, <see cref="P:ConditionalExpression.IfTrue"/>,
/// and <see cref="P:ConditionalExpression.IfFalse"/> properties set to the specified values.</returns>
public static ConditionalExpression Condition(Expression test, Expression ifTrue, Expression ifFalse) {
RequiresCanRead(test, "test");
RequiresCanRead(ifTrue, "ifTrue");
RequiresCanRead(ifFalse, "ifFalse");
if (test.Type != typeof(bool)) {
throw Error.ArgumentMustBeBoolean();
}
if (!TypeUtils.AreEquivalent(ifTrue.Type, ifFalse.Type)) {
throw Error.ArgumentTypesMustMatch();
}
return ConditionalExpression.Make(test, ifTrue, ifFalse, ifTrue.Type);
}
/// <summary>
/// Creates a <see cref="ConditionalExpression"/>.
/// </summary>
/// <param name="test">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.Test"/> property equal to.</param>
/// <param name="ifTrue">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfTrue"/> property equal to.</param>
/// <param name="ifFalse">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfFalse"/> property equal to.</param>
/// <param name="type">A <see cref="Type"/> to set the <see cref="P:Expression.Type"/> property equal to.</param>
/// <returns>A <see cref="ConditionalExpression"/> that has the <see cref="P:Expression.NodeType"/> property equal to
/// <see cref="F:ExpressionType.Conditional"/> and the <see cref="P:ConditionalExpression.Test"/>, <see cref="P:ConditionalExpression.IfTrue"/>,
/// and <see cref="P:ConditionalExpression.IfFalse"/> properties set to the specified values.</returns>
/// <remarks>This method allows explicitly unifying the result type of the conditional expression in cases where the types of <paramref name="ifTrue"/>
/// and <paramref name="ifFalse"/> expressions are not equal. Types of both <paramref name="ifTrue"/> and <paramref name="ifFalse"/> must be implicitly
/// reference assignable to the result type. The <paramref name="type"/> is allowed to be <see cref="System.Void"/>.</remarks>
public static ConditionalExpression Condition(Expression test, Expression ifTrue, Expression ifFalse, Type type) {
RequiresCanRead(test, "test");
RequiresCanRead(ifTrue, "ifTrue");
RequiresCanRead(ifFalse, "ifFalse");
ContractUtils.RequiresNotNull(type, "type");
if (test.Type != typeof(bool)) {
throw Error.ArgumentMustBeBoolean();
}
if (type != typeof(void)) {
if (!TypeUtils.AreReferenceAssignable(type, ifTrue.Type) ||
!TypeUtils.AreReferenceAssignable(type, ifFalse.Type)) {
throw Error.ArgumentTypesMustMatch();
}
}
return ConditionalExpression.Make(test, ifTrue, ifFalse, type);
}
/// <summary>
/// Creates a <see cref="ConditionalExpression"/>.
/// </summary>
/// <param name="test">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.Test"/> property equal to.</param>
/// <param name="ifTrue">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfTrue"/> property equal to.</param>
/// <returns>A <see cref="ConditionalExpression"/> that has the <see cref="P:Expression.NodeType"/> property equal to
/// <see cref="F:ExpressionType.Conditional"/> and the <see cref="P:ConditionalExpression.Test"/>, <see cref="P:ConditionalExpression.IfTrue"/>,
/// properties set to the specified values. The <see cref="P:ConditionalExpression.IfFalse"/> property is set to default expression and
/// the type of the resulting <see cref="ConditionalExpression"/> returned by this method is <see cref="System.Void"/>.</returns>
public static ConditionalExpression IfThen(Expression test, Expression ifTrue) {
return Condition(test, ifTrue, Expression.Empty(), typeof(void));
}
/// <summary>
/// Creates a <see cref="ConditionalExpression"/>.
/// </summary>
/// <param name="test">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.Test"/> property equal to.</param>
/// <param name="ifTrue">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfTrue"/> property equal to.</param>
/// <param name="ifFalse">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfFalse"/> property equal to.</param>
/// <returns>A <see cref="ConditionalExpression"/> that has the <see cref="P:Expression.NodeType"/> property equal to
/// <see cref="F:ExpressionType.Conditional"/> and the <see cref="P:ConditionalExpression.Test"/>, <see cref="P:ConditionalExpression.IfTrue"/>,
/// and <see cref="P:ConditionalExpression.IfFalse"/> properties set to the specified values. The type of the resulting <see cref="ConditionalExpression"/>
/// returned by this method is <see cref="System.Void"/>.</returns>
public static ConditionalExpression IfThenElse(Expression test, Expression ifTrue, Expression ifFalse) {
return Condition(test, ifTrue, ifFalse, typeof(void));
}
}
}
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