SharpDevelop/ICSharpCode.NRefactory.CSharp/Refactoring/CodeIssues/RedundantWhereWithPredicateIssue.cs

using System.Collections.Generic;
using System.Linq;
using ICSharpCode.NRefactory.Semantics;
using ICSharpCode.NRefactory.TypeSystem;
using ICSharpCode.NRefactory.PatternMatching;

namespace ICSharpCode.NRefactory.CSharp.Refactoring
{
	[IssueDescription("Any() should be used with predicate and Where() removed",
	                  Description= "Detects redundant Where() with predicate calls followed by Any().",
	                  Category = IssueCategories.CodeQualityIssues,
	                  Severity = Severity.Hint)]
	public class RedundantWhereWithPredicateIssue : ICodeIssueProvider
	{
		static readonly AstNode pattern =
			new InvocationExpression (
				new MemberReferenceExpression (
				new NamedNode ("whereInvoke",
			               new InvocationExpression (
				new MemberReferenceExpression (new AnyNode ("target"), "Where"),
				new AnyNode ())),
				"Any"));
		
		public IEnumerable<CodeIssue> GetIssues(BaseRefactoringContext context)
		{
			return new GatherVisitor(context).GetIssues();
		}
		
		class GatherVisitor : GatherVisitorBase
		{
			public GatherVisitor (BaseRefactoringContext ctx) : base (ctx)
			{
			}
			
			public override void VisitInvocationExpression (InvocationExpression anyInvoke)
			{
				base.VisitInvocationExpression (anyInvoke);
				
				var match = pattern.Match (anyInvoke);
				if (!match.Success)
					return;
				
				var anyResolve = ctx.Resolve (anyInvoke) as InvocationResolveResult;
				if (anyResolve == null || anyResolve.Member.FullName != "System.Linq.Enumerable.Any")
					return;
				var whereInvoke = match.Get<InvocationExpression> ("whereInvoke").Single ();
				var whereResolve = ctx.Resolve (whereInvoke) as InvocationResolveResult;
				if (whereResolve == null || whereResolve.Member.FullName != "System.Linq.Enumerable.Where")
					return;
				if (whereResolve.Member.Parameters.Count != 2)
					return;
				var predResolve = whereResolve.Member.Parameters [1];
				if (predResolve.Type.TypeParameterCount != 2)
					return;
				
				AddIssue (anyInvoke, "Redundant Where() call with predicate followed by Any()", script => {
					var arg = whereInvoke.Arguments.Single ().Clone ();
					var target = match.Get<Expression> ("target").Single ().Clone ();
					script.Replace (anyInvoke, new InvocationExpression (new MemberReferenceExpression (target, "Any"), arg));
				});
			}
		}
	}
}