Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / Microsoft / Scripting / Compiler / ConstantCheck.cs / 1305376 / ConstantCheck.cs
/* **************************************************************************** * * 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.Diagnostics; using System.Dynamic.Utils; namespace System.Linq.Expressions { internal enum AnalyzeTypeIsResult { KnownFalse, KnownTrue, KnownAssignable, // need null check only Unknown, // need full runtime check } internal static class ConstantCheck { internal static bool IsNull(Expression e) { if (e.NodeType == ExpressionType.Constant) { return ((ConstantExpression)e).Value == null; } return false; } ////// If the result of a TypeBinaryExpression is known statically, this /// returns the result, otherwise it returns null, meaning we'll need /// to perform the IsInst instruction at runtime. /// /// The result of this function must be equivalent to IsInst, or /// null. /// internal static AnalyzeTypeIsResult AnalyzeTypeIs(TypeBinaryExpression typeIs) { return AnalyzeTypeIs(typeIs.Expression, typeIs.TypeOperand); } ////// If the result of a unary TypeAs expression is known statically, this /// returns the result, otherwise it returns null, meaning we'll need /// to perform the IsInst instruction at runtime. /// /// The result of this function must be equivalent to IsInst, or /// null. /// internal static AnalyzeTypeIsResult AnalyzeTypeIs(UnaryExpression typeAs) { Debug.Assert(typeAs.NodeType == ExpressionType.TypeAs); return AnalyzeTypeIs(typeAs.Operand, typeAs.Type); } ////// If the result of an isinst opcode is known statically, this /// returns the result, otherwise it returns null, meaning we'll need /// to perform the IsInst instruction at runtime. /// /// The result of this function must be equivalent to IsInst, or /// null. /// private static AnalyzeTypeIsResult AnalyzeTypeIs(Expression operand, Type testType) { Type operandType = operand.Type; // Oddly, we allow void operands // This is LinqV1 behavior of TypeIs if (operandType == typeof(void)) { return AnalyzeTypeIsResult.KnownFalse; } // // Type comparisons treat nullable types as if they were the // underlying type. The reason is when you box a nullable it // becomes a boxed value of the underlying type, or null. // Type nnOperandType = operandType.GetNonNullableType(); Type nnTestType = testType.GetNonNullableType(); // // See if we can determine the answer based on the static types // // Extensive testing showed that Type.IsAssignableFrom, // Type.IsInstanceOfType, and the isinst instruction were all // equivalent when used against a live object // if (nnTestType.IsAssignableFrom(nnOperandType)) { // If the operand is a value type (other than nullable), we // know the result is always true. if (operandType.IsValueType && !operandType.IsNullableType()) { return AnalyzeTypeIsResult.KnownTrue; } // For reference/nullable types, we need to compare to null at runtime return AnalyzeTypeIsResult.KnownAssignable; } // We used to have an if IsSealed, return KnownFalse check here. // but that doesn't handle generic types & co/contravariance correctly. // So just use IsInst, which we know always gives us the right answer. // Otherwise we need a full runtime check return AnalyzeTypeIsResult.Unknown; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
Link Menu
This book is available now!
Buy at Amazon US or
Buy at Amazon UK
- AspProxy.cs
- WorkflowInstanceRecord.cs
- ScriptingProfileServiceSection.cs
- EpmCustomContentDeSerializer.cs
- TaskHelper.cs
- PageThemeParser.cs
- PartialTrustHelpers.cs
- HandoffBehavior.cs
- ExpandoClass.cs
- AuthenticationSection.cs
- ConfigXmlElement.cs
- RIPEMD160.cs
- RoutedEventArgs.cs
- DefaultBinder.cs
- MethodImplAttribute.cs
- TextRange.cs
- DesignSurface.cs
- Token.cs
- ZipIOExtraFieldElement.cs
- OlePropertyStructs.cs
- SelectionEditingBehavior.cs
- GeometryGroup.cs
- DeferredRunTextReference.cs
- RegionIterator.cs
- InheritablePropertyChangeInfo.cs
- EntityDataSourceWrapper.cs
- ToolStripContentPanel.cs
- SettingsAttributes.cs
- ColorConverter.cs
- SocketException.cs
- ValidationPropertyAttribute.cs
- NativeObjectSecurity.cs
- NativeMethods.cs
- baseaxisquery.cs
- WebHttpDispatchOperationSelector.cs
- dataSvcMapFileLoader.cs
- RecordsAffectedEventArgs.cs
- VersionedStream.cs
- ResourcesChangeInfo.cs
- LinqDataSourceInsertEventArgs.cs
- AbstractDataSvcMapFileLoader.cs
- StorageEntityContainerMapping.cs
- ProfileProvider.cs
- CroppedBitmap.cs
- UrlMappingCollection.cs
- ItemAutomationPeer.cs
- JsonFormatWriterGenerator.cs
- OutputCacheProfile.cs
- MenuAutomationPeer.cs
- WorkflowCreationContext.cs
- ThemeDictionaryExtension.cs
- DependencyObjectProvider.cs
- GPPOINT.cs
- ScrollViewer.cs
- UnitySerializationHolder.cs
- ImageKeyConverter.cs
- PersonalizationProviderCollection.cs
- OutputWindow.cs
- FixedSOMPage.cs
- SelectionItemProviderWrapper.cs
- DesignerAdRotatorAdapter.cs
- SecurityDescriptor.cs
- FrameworkRichTextComposition.cs
- ElementsClipboardData.cs
- Transform.cs
- SessionEndedEventArgs.cs
- AuthenticationService.cs
- StatusBarItemAutomationPeer.cs
- AccessViolationException.cs
- TableLayout.cs
- ApplicationId.cs
- ValueType.cs
- TextBlock.cs
- OleDbErrorCollection.cs
- ReturnValue.cs
- TextEditor.cs
- ApplicationBuildProvider.cs
- XmlSignatureProperties.cs
- EntityViewGenerationConstants.cs
- unsafeIndexingFilterStream.cs
- ItemPager.cs
- ImageInfo.cs
- Compiler.cs
- InstanceLockQueryResult.cs
- ModelTreeManager.cs
- NavigationWindow.cs
- SweepDirectionValidation.cs
- BamlWriter.cs
- _HelperAsyncResults.cs
- WindowShowOrOpenTracker.cs
- FreeFormDesigner.cs
- UnauthorizedWebPart.cs
- ObjectQueryProvider.cs
- Timeline.cs
- ColumnMapCopier.cs
- NamedObject.cs
- DbMetaDataCollectionNames.cs
- XPathSingletonIterator.cs
- AdRotator.cs
- AnnouncementInnerClient11.cs