/* ****************************************************************************
*
* 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.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Dynamic.Utils;
using System.Reflection;
#if SILVERLIGHT
using System.Core;
#endif
#if CLR2
namespace Microsoft.Scripting.Ast{
#else
namespace System.Linq.Expressions {
#endif
/// <summary>
/// Represents a control expression that handles multiple selections by passing control to a <see cref="SwitchCase"/>.
/// </summary>
#if !SILVERLIGHT
[DebuggerTypeProxy(typeof(Expression.SwitchExpressionProxy))]
#endif
public sealed class SwitchExpression : Expression {
private readonly Type _type;
private readonly Expression _switchValue;
private readonly ReadOnlyCollection<SwitchCase> _cases;
private readonly Expression _defaultBody;
private readonly MethodInfo _comparison;
internal SwitchExpression(Type type, Expression switchValue, Expression defaultBody, MethodInfo comparison, ReadOnlyCollection<SwitchCase> cases) {
_type = type;
_switchValue = switchValue;
_defaultBody = defaultBody;
_comparison = comparison;
_cases = cases;
}
/// <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 sealed override Type Type {
get { return _type; }
}
/// <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.Switch; }
}
/// <summary>
/// Gets the test for the switch.
/// </summary>
public Expression SwitchValue {
get { return _switchValue; }
}
/// <summary>
/// Gets the collection of <see cref="SwitchCase"/> objects for the switch.
/// </summary>
public ReadOnlyCollection<SwitchCase> Cases {
get { return _cases; }
}
/// <summary>
/// Gets the test for the switch.
/// </summary>
public Expression DefaultBody {
get { return _defaultBody; }
}
/// <summary>
/// Gets the equality comparison method, if any.
/// </summary>
public MethodInfo Comparison {
get { return _comparison; }
}
/// <summary>
/// Dispatches to the specific visit method for this node type.
/// </summary>
protected internal override Expression Accept(ExpressionVisitor visitor) {
return visitor.VisitSwitch(this);
}
internal bool IsLifted {
get {
if (_switchValue.Type.IsNullableType()) {
return (_comparison == null) ||
!TypeUtils.AreEquivalent(_switchValue.Type, _comparison.GetParametersCached()[0].ParameterType.GetNonRefType());
}
return false;
}
}
/// <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="switchValue">The <see cref="SwitchValue" /> property of the result.</param>
/// <param name="cases">The <see cref="Cases" /> property of the result.</param>
/// <param name="defaultBody">The <see cref="DefaultBody" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public SwitchExpression Update(Expression switchValue, IEnumerable<SwitchCase> cases, Expression defaultBody) {
if (switchValue == SwitchValue && cases == Cases && defaultBody == DefaultBody) {
return this;
}
return Expression.Switch(Type, switchValue, defaultBody, Comparison, cases);
}
}
public partial class Expression {
/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Expression switchValue, params SwitchCase[] cases) {
return Switch(switchValue, null, null, (IEnumerable<SwitchCase>)cases);
}
/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="defaultBody">The result of the switch if no cases are matched.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Expression switchValue, Expression defaultBody, params SwitchCase[] cases) {
return Switch(switchValue, defaultBody, null, (IEnumerable<SwitchCase>)cases);
}
/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="defaultBody">The result of the switch if no cases are matched.</param>
/// <param name="comparison">The equality comparison method to use.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Expression switchValue, Expression defaultBody, MethodInfo comparison, params SwitchCase[] cases) {
return Switch(switchValue, defaultBody, comparison, (IEnumerable<SwitchCase>)cases);
}
/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="type">The result type of the switch.</param>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="defaultBody">The result of the switch if no cases are matched.</param>
/// <param name="comparison">The equality comparison method to use.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Type type, Expression switchValue, Expression defaultBody, MethodInfo comparison, params SwitchCase[] cases) {
return Switch(type, switchValue, defaultBody, comparison, (IEnumerable<SwitchCase>)cases);
}
/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="defaultBody">The result of the switch if no cases are matched.</param>
/// <param name="comparison">The equality comparison method to use.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Expression switchValue, Expression defaultBody, MethodInfo comparison, IEnumerable<SwitchCase> cases) {
return Switch(null, switchValue, defaultBody, comparison, cases);
}
/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="type">The result type of the switch.</param>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="defaultBody">The result of the switch if no cases are matched.</param>
/// <param name="comparison">The equality comparison method to use.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Type type, Expression switchValue, Expression defaultBody, MethodInfo comparison, IEnumerable<SwitchCase> cases) {
RequiresCanRead(switchValue, "switchValue");
if (switchValue.Type == typeof(void)) throw Error.ArgumentCannotBeOfTypeVoid();
var caseList = cases.ToReadOnly();
ContractUtils.RequiresNotEmpty(caseList, "cases");
ContractUtils.RequiresNotNullItems(caseList, "cases");
// Type of the result. Either provided, or it is type of the branches.
Type resultType = type ?? caseList[0].Body.Type;
bool customType = type != null;
if (comparison != null) {
var pms = comparison.GetParametersCached();
if (pms.Length != 2) {
throw Error.IncorrectNumberOfMethodCallArguments(comparison);
}
// Validate that the switch value's type matches the comparison method's
// left hand side parameter type.
var leftParam = pms[0];
bool liftedCall = false;
if (!ParameterIsAssignable(leftParam, switchValue.Type)) {
liftedCall = ParameterIsAssignable(leftParam, switchValue.Type.GetNonNullableType());
if (!liftedCall) {
throw Error.SwitchValueTypeDoesNotMatchComparisonMethodParameter(switchValue.Type, leftParam.ParameterType);
}
}
var rightParam = pms[1];
foreach (var c in caseList) {
ContractUtils.RequiresNotNull(c, "cases");
ValidateSwitchCaseType(c.Body, customType, resultType, "cases");
for (int i = 0; i < c.TestValues.Count; i++) {
// When a comparison method is provided, test values can have different type but have to
// be reference assignable to the right hand side parameter of the method.
Type rightOperandType = c.TestValues[i].Type;
if (liftedCall) {
if (!rightOperandType.IsNullableType()) {
throw Error.TestValueTypeDoesNotMatchComparisonMethodParameter(rightOperandType, rightParam.ParameterType);
}
rightOperandType = rightOperandType.GetNonNullableType();
}
if (!ParameterIsAssignable(rightParam, rightOperandType)) {
throw Error.TestValueTypeDoesNotMatchComparisonMethodParameter(rightOperandType, rightParam.ParameterType);
}
}
}
} else {
// When comparison method is not present, all the test values must have
// the same type. Use the first test value's type as the baseline.
var firstTestValue = caseList[0].TestValues[0];
foreach (var c in caseList) {
ContractUtils.RequiresNotNull(c, "cases");
ValidateSwitchCaseType(c.Body, customType, resultType, "cases");
// When no comparison method is provided, require all test values to have the same type.
for (int i = 0; i < c.TestValues.Count; i++) {
if (!TypeUtils.AreEquivalent(firstTestValue.Type, c.TestValues[i].Type)) {
throw new ArgumentException(Strings.AllTestValuesMustHaveSameType, "cases");
}
}
}
// Now we need to validate that switchValue.Type and testValueType
// make sense in an Equal node. Fortunately, Equal throws a
// reasonable error, so just call it.
var equal = Equal(switchValue, firstTestValue, false, comparison);
// Get the comparison function from equals node.
comparison = equal.Method;
}
if (defaultBody == null) {
if (resultType != typeof(void)) throw Error.DefaultBodyMustBeSupplied();
} else {
ValidateSwitchCaseType(defaultBody, customType, resultType, "defaultBody");
}
// if we have a non-boolean userdefined equals, we don't want it.
if (comparison != null && comparison.ReturnType != typeof(bool)) {
throw Error.EqualityMustReturnBoolean(comparison);
}
return new SwitchExpression(resultType, switchValue, defaultBody, comparison, caseList);
}
/// <summary>
/// If custom type is provided, all branches must be reference assignable to the result type.
/// If no custom type is provided, all branches must have the same type - resultType.
/// </summary>
private static void ValidateSwitchCaseType(Expression @case, bool customType, Type resultType, string parameterName) {
if (customType) {
if (resultType != typeof(void)) {
if (!TypeUtils.AreReferenceAssignable(resultType, @case.Type)) {
throw new ArgumentException(Strings.ArgumentTypesMustMatch, parameterName);
}
}
} else {
if (!TypeUtils.AreEquivalent(resultType, @case.Type)) {
throw new ArgumentException(Strings.AllCaseBodiesMustHaveSameType, parameterName);
}
}
}
}
}
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