Update SA1302 conflict resolution to handle nested types

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/NamingRules/SA1302CodeFixProvider.cs

@@ -57,11 +57,21 @@ private static async Task<Solution> CreateChangedSolutionAsync(Document document
             INamedTypeSymbol interfaceType = declaredSymbol as INamedTypeSymbol;
             if (interfaceType != null)
             {
-                var containingNamespace = semanticModel.Compilation.GetCompilationNamespace(interfaceType.ContainingNamespace);
-                while (containingNamespace.GetMembers(newName).Any())
+                var containingSymbol = interfaceType.ContainingSymbol as INamespaceOrTypeSymbol;
+                var containingNamespace = containingSymbol as INamespaceSymbol;
+                if (containingNamespace != null)
                 {
-                    index++;
-                    newName = baseName + index;
+                    // Make sure to use the compilation namespace so interfaces in referenced assemblies are considered
+                    containingSymbol = semanticModel.Compilation.GetCompilationNamespace(containingNamespace);
+                }
+
+                if (containingSymbol != null)
+                {
+                    while (containingSymbol.GetMembers(newName).Any())
+                    {
+                        index++;
+                        newName = baseName + index;
+                    }
                 }
             }
 

StyleCop.Analyzers/StyleCop.Analyzers.Test/NamingRules/SA1302UnitTests.cs

@@ -208,6 +208,64 @@ public interface IFoo { }";
             await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
+        [Fact]
+        public async Task TestNestedInterfaceDeclarationDoesNotStartWithIWithConflictAsync()
+        {
+            string testCode = @"
+public class Outer
+{
+    public interface Foo
+    {
+    }
+
+    public interface IFoo { }
+}";
+            string fixedCode = @"
+public class Outer
+{
+    public interface IFoo1
+    {
+    }
+
+    public interface IFoo { }
+}";
+
+            DiagnosticResult expected = this.CSharpDiagnostic().WithLocation(4, 22);
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
+        }
+
+        [Fact]
+        public async Task TestNestedInterfaceDeclarationDoesNotStartWithIWithNonInterfaceConflictAsync()
+        {
+            string testCode = @"
+public class Outer
+{
+    public interface Foo
+    {
+    }
+
+    private int IFoo => 0;
+}";
+            string fixedCode = @"
+public class Outer
+{
+    public interface IFoo1
+    {
+    }
+
+    private int IFoo => 0;
+}";
+
+            DiagnosticResult expected = this.CSharpDiagnostic().WithLocation(4, 22);
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
+        }
+
         [Fact]
         public async Task TestInterfaceDeclarationDoesNotStartWithIWithConflictInAnotherAssemblyAsync()
         {