text: //
  // EventUnsubscriptionViaAnonymousDelegateIssue.cs
  //
  // Author:
  //       Mike Krüger <mkrueger@xamarin.com>
  //
  // Copyright (c) 2013 Xamarin Inc. (http://xamarin.com)
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using ICSharpCode.NRefactory.PatternMatching;
  using ICSharpCode.NRefactory.Refactoring;
  using ICSharpCode.NRefactory.Semantics;
  
  namespace ICSharpCode.NRefactory.CSharp.Refactoring
  {
  	[IssueDescription("Event unsubscription via anonymous delegate",
  	                  Description="Event unsubscription via anonymous delegate is useless",
  	                  Category = IssueCategories.CodeQualityIssues,
  	                  Severity = Severity.Warning,
  	                  AnalysisDisableKeyword = "EventUnsubscriptionViaAnonymousDelegate")]
  	public class EventUnsubscriptionViaAnonymousDelegateIssue : GatherVisitorCodeIssueProvider
  	{
  		protected override IGatherVisitor CreateVisitor(BaseRefactoringContext context)
  		{
  			return new GatherVisitor(context);
  		}
  
  		class GatherVisitor : GatherVisitorBase<EventUnsubscriptionViaAnonymousDelegateIssue>
  		{
  			public GatherVisitor (BaseRefactoringContext ctx) : base (ctx)
  			{
  			}
  
  			public override void VisitAssignmentExpression(AssignmentExpression assignmentExpression)
  			{
  				base.VisitAssignmentExpression(assignmentExpression);
  				if (assignmentExpression.Operator != AssignmentOperatorType.Subtract)
  					return;
  				if (!(assignmentExpression.Right is AnonymousMethodExpression || assignmentExpression.Right is LambdaExpression))
  					return;
  				var rr = ctx.Resolve(assignmentExpression.Left) as MemberResolveResult;
  				if (rr == null || rr.Member.SymbolKind != ICSharpCode.NRefactory.TypeSystem.SymbolKind.Event)
  					return;
  				AddIssue(new CodeIssue(
  					assignmentExpression.OperatorToken,
  					ctx.TranslateString("Event unsubscription via anonymous delegate is useless")
  				));
  			}
  		}
  	}
  }
  
  