Update SA1135UsingDirectivesMustBeQualified to not crash on a UsingDirectiveSyntax without a Name

#3882

Author: bjornhellander

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp10/ReadabilityRules/SA1135CSharp10UnitTests.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.Test.CSharp10.ReadabilityRules
 {
     using System.Threading;

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp12/ReadabilityRules/SA1135CSharp12UnitTests.cs

@@ -3,9 +3,55 @@
 
 namespace StyleCop.Analyzers.Test.CSharp12.ReadabilityRules
 {
+    using System.Collections.Generic;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.CodeAnalysis.Testing;
     using StyleCop.Analyzers.Test.CSharp11.ReadabilityRules;
+    using Xunit;
+
+    using static StyleCop.Analyzers.Test.Verifiers.StyleCopCodeFixVerifier<
+        StyleCop.Analyzers.ReadabilityRules.SA1135UsingDirectivesMustBeQualified,
+        StyleCop.Analyzers.ReadabilityRules.SA1135CodeFixProvider>;
 
     public partial class SA1135CSharp12UnitTests : SA1135CSharp11UnitTests
     {
+        public static IEnumerable<object[]> CorrectAliasableTypes => new[]
+        {
+            new[] { "string" },
+            new[] { "(string, int)" },
+            new[] { "(System.String, System.Int32)" },
+            new[] { "bool[]" },
+            new[] { "System.Boolean[]" },
+        };
+
+        [Theory]
+        [MemberData(nameof(CorrectAliasableTypes))]
+        [WorkItem(3882, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3882")]
+        public async Task TestUsingTypeAliasOutsideNamespaceAsync(string type)
+        {
+            var testCode = $@"
+using MyType = {type};
+
+namespace TestNamespace
+{{
+}}";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
+
+        [Theory]
+        [MemberData(nameof(CorrectAliasableTypes))]
+        [WorkItem(3882, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3882")]
+        public async Task TestUsingTypeAliasInsideNamespaceAsync(string type)
+        {
+            var testCode = $@"
+namespace TestNamespace
+{{
+    using MyType = {type};
+}}";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp7/ReadabilityRules/SA1135CSharp7UnitTests.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.Test.CSharp7.ReadabilityRules
 {
     using System.Threading;

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp8/ReadabilityRules/SA1135CSharp8UnitTests.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.Test.CSharp8.ReadabilityRules
 {
     using System.Threading;

StyleCop.Analyzers/StyleCop.Analyzers.Test/ReadabilityRules/SA1135UnitTests.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.Test.ReadabilityRules
 {
     using System.Threading;

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/SA1135UsingDirectivesMustBeQualified.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.ReadabilityRules
 {
     using System.Collections.Immutable;
@@ -82,6 +80,12 @@ private static void CheckUsingDeclaration(SyntaxNodeAnalysisContext context, Usi
                 return;
             }
 
+            if (usingDirective.Name == null)
+            {
+                // This happens for e.g. "using X = string;" or "using T = (X, Y);"
+                return;
+            }
+
             var symbol = context.SemanticModel.GetSymbolInfo(usingDirective.Name, context.CancellationToken).Symbol;
             if (symbol == null)
             {