Updated after CR

Author: vweijsters

StyleCop.Analyzers/StyleCop.Analyzers.Test/ReadabilityRules/SX1101UnitTests.cs

@@ -199,6 +199,28 @@ public int this[int index]
             await this.VerifyCSharpDiagnosticAsync(testCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
         }
 
+        /// <summary>
+        /// Verifies that a necessary this prefix will not produce any diagnostics.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
+        [Fact]
+        public async Task VerifyThatNecessaryPrefixWillNotProduceDiagnosticsAsync()
+        {
+            var testCode = @"
+public class TestClass
+{
+    private int test;
+
+    public void TestMethod(int test)
+    {
+        this.test = test;
+    }
+}
+";
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
+
         /// <inheritdoc/>
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/SX1101DoNotPrefixLocalMembersWithThis.cs

@@ -3,9 +3,13 @@
 
 namespace StyleCop.Analyzers.ReadabilityRules
 {
+    using System;
+    using System.Collections.Generic;
     using System.Collections.Immutable;
+    using System.Linq;
     using Microsoft.CodeAnalysis;
     using Microsoft.CodeAnalysis.CSharp;
+    using Microsoft.CodeAnalysis.CSharp.Syntax;
     using Microsoft.CodeAnalysis.Diagnostics;
 
     [DiagnosticAnalyzer(LanguageNames.CSharp)]
@@ -42,8 +46,31 @@ private static void HandleThisExpression(SyntaxNodeAnalysisContext context)
         {
             if (context.Node.Parent.IsKind(SyntaxKind.SimpleMemberAccessExpression))
             {
-                context.ReportDiagnostic(Diagnostic.Create(Descriptor, context.Node.GetLocation()));
+                var memberAccessExpression = (MemberAccessExpressionSyntax)context.Node.Parent;
+                var memberName = memberAccessExpression.Name.ToString();
+
+                var parameters = GetMethodParameters(context.Node);
+                if (!parameters.Contains(memberName))
+                {
+                    context.ReportDiagnostic(Diagnostic.Create(Descriptor, context.Node.GetLocation()));
+                }
+            }
+        }
+
+        private static IList<string> GetMethodParameters(SyntaxNode node)
+        {
+            while ((node != null) && !node.IsKind(SyntaxKind.MethodDeclaration))
+            {
+                node = node.Parent;
             }
+
+            if (node == null)
+            {
+                return new List<string>();
+            }
+
+            var methodDeclaration = (MethodDeclarationSyntax)node;
+            return methodDeclaration.ParameterList.Parameters.Select(p => p.Identifier.ValueText).ToList();
         }
     }
 }

StyleCopAnalyzers.sln

@@ -217,7 +217,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "documentation", "documentat
 		documentation\SA1650.md = documentation\SA1650.md
 		documentation\SA1651.md = documentation\SA1651.md
 		documentation\SA1652.md = documentation\SA1652.md
-		SX1101.md = SX1101.md
+		documentation\SX1101.md = documentation\SX1101.md
 		documentation\SX1309.md = documentation\SX1309.md
 		documentation\SX1309S.md = documentation\SX1309S.md
 	EndProjectSection

SX1101.md documentation/SX1101.mdSX1101.md renamed to documentation/SX1101.md

@@ -21,7 +21,7 @@ A call to an instance member of the local class or a base class is prefixed with
 
 ## Rule description
 
-A violation of this rule occurs whenever the code contains a call to an instance member of the local class or a base class which is prefixed with `this.`.
+A violation of this rule occurs whenever the code contains a call to an instance member of the local class or a base class which is prefixed with `this.`. An exception is made when the name of a method parameter conflicts with identifier after the `this.` prefix, in that case no violation is reported.
 This rule is disabled by default. When enabling this rule, the [SA1101](SA1101.md) rule must be disabled.
 
 ## How to fix violations