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
	{
		static readonly AstNode pattern =
			new InvocationExpression (
				new MemberReferenceExpression (
					new NamedNode ("whereInvoke",
						new InvocationExpression (
							new MemberReferenceExpression (new AnyNode (), "Where"),
							new Expression[] { new AnyNode () })),
					"Any"),
				new Expression[] {});

		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)
			{
				var match = pattern.Match (anyInvoke);
				if (!match.Success)
					return;

				var anyResolve = ctx.Resolve (anyInvoke) as InvocationResolveResult;
				if (anyResolve.Member.FullName != "System.Linq.Enumerable.Any")
					return;
				var whereInvoke = match.Get<InvocationExpression> ("whereInvoke").Single ();
				var whereResolve = ctx.Resolve (whereInvoke) as InvocationResolveResult;
				if (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 ();
					script.Replace (anyInvoke, new InvocationExpression (whereInvoke.Target.Clone (),
					                                                     new Expression[] { arg }));
				});
			}
		}
	}
}