Fix UsingCodeFixProvider handling of aliases

This change can result in the output of this code fix containing duplicate
using directives, but this situation does not break the semantics of code
and only produces a build warning.

Fixes #1770

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/OrderingRules/UsingCodeFixProvider.cs

@@ -690,7 +690,7 @@ private List<UsingDirectiveSyntax> GenerateUsings(List<UsingDirectiveSyntax> usi
                         .WithAdditionalAnnotations(UsingCodeFixAnnotation);
 
                     // filter duplicate using declarations, preferring to keep the one with an alias
-                    var existingUsing = result.Find(u => string.Equals(u.Name.ToUnaliasedString(), processedUsing.Name.ToUnaliasedString(), StringComparison.Ordinal));
+                    var existingUsing = result.Find(u => string.Equals(u.Name.ToNormalizedString(), processedUsing.Name.ToNormalizedString(), StringComparison.Ordinal));
                     if (existingUsing != null)
                     {
                         if (!existingUsing.HasNamespaceAliasQualifier() && processedUsing.HasNamespaceAliasQualifier())

StyleCop.Analyzers/StyleCop.Analyzers.Test/OrderingRules/SA1210CombinedSystemDirectivesUnitTests.cs

@@ -102,6 +102,7 @@ namespace Food
     using global::System;
     using global::System.IO;
     using global::System.Linq;
+    using System;
     using System.Threading;
     using XYZ = System.IO;
 }";
@@ -135,10 +136,12 @@ namespace Food
 
             var fixedTestCode = @"namespace Food
 {
+    using Food;
     using global::Food;
     using global::System;
     using global::System.IO;
     using global::System.Linq;
+    using System;
     using System.Threading;
 }";
 
@@ -225,6 +228,13 @@ protected override string GetSettings()
             return CombinedUsingDirectivesTestSettings;
         }
 
+        /// <inheritdoc/>
+        protected override IEnumerable<string> GetDisabledDiagnostics()
+        {
+            // Using directive appeared previously in this namespace
+            yield return "CS0105";
+        }
+
         /// <inheritdoc/>
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {

StyleCop.Analyzers/StyleCop.Analyzers.Test/OrderingRules/SA1210UnitTests.cs

@@ -155,6 +155,7 @@ namespace Foo
 
             var fixedTestCode = @"namespace Foo
 {
+    using System;
     using System.Threading;
     using global::Foo;
     using global::System;
@@ -173,7 +174,9 @@ namespace Foo
         [Fact]
         public async Task TestInvalidOrderedUsingDirectivesWithNamespaceAliasQualifierAsync()
         {
-            var testCode = @"using System.Threading;
+            var testCode = @"extern alias corlib;
+using System.Threading;
+using corlib::System;
 using global::System.IO;
 using global::System.Linq;
 using global::System;
@@ -186,9 +189,13 @@ namespace Foo
     using System;
 }";
 
-            var fixedTestCode = @"namespace Foo
+            var fixedTestCode = @"extern alias corlib;
+namespace Foo
 {
+    using System;
     using System.Threading;
+    using corlib::System;
+    using Foo;
     using global::Foo;
     using global::System;
     using global::System.IO;
@@ -197,9 +204,9 @@ namespace Foo
 
             DiagnosticResult[] expected =
             {
-                this.CSharpDiagnostic().WithLocation(3, 1),
-                this.CSharpDiagnostic().WithLocation(4, 1),
-                this.CSharpDiagnostic().WithLocation(5, 1)
+                this.CSharpDiagnostic().WithLocation(5, 1),
+                this.CSharpDiagnostic().WithLocation(6, 1),
+                this.CSharpDiagnostic().WithLocation(7, 1)
             };
 
             await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
@@ -308,6 +315,13 @@ public async Task TestPreprocessorDirectivesAsync()
             await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
         }
 
+        /// <inheritdoc/>
+        protected override IEnumerable<string> GetDisabledDiagnostics()
+        {
+            // Using directive appeared previously in this namespace
+            yield return "CS0105";
+        }
+
         /// <inheritdoc/>
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {