Fix method GetRootNamespace (RCS0015) (#1000)

Author: josefpihrt

ChangeLog.md

@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix refactoring ([RR0180](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RR0180.md)) ([#988](https://github.com/josefpihrt/roslynator/pull/988)).
 - Recognize `ArgumentNullException.ThrowIfNull` ([RCS1227](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1227.md)) ([#992](https://github.com/josefpihrt/roslynator/pull/992)).
 - Detect pattern matching in [RCS1146](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1146.md) ([#999](https://github.com/josefpihrt/roslynator/pull/999)).
+- Handle `using` directive that starts with `global::` [RCS0015](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS0015.md) ([#1000](https://github.com/josefpihrt/roslynator/pull/1000)).
 
 ## [4.1.2] - 2022-10-31
 

src/CSharp/CSharp/Extensions/SyntaxExtensions.cs

@@ -4211,10 +4211,15 @@ public static bool IsVoid(this TypeSyntax type)
     #region UsingDirectiveSyntax
     internal static IdentifierNameSyntax GetRootNamespace(this UsingDirectiveSyntax usingDirective)
     {
-        if (usingDirective.Name is IdentifierNameSyntax identifierName)
+        NameSyntax name = usingDirective.Name;
+
+        if (name is AliasQualifiedNameSyntax aliasQualifiedName)
+            name = aliasQualifiedName.Name;
+
+        if (name is IdentifierNameSyntax identifierName)
             return identifierName;
 
-        if (usingDirective.Name is QualifiedNameSyntax qualifiedName)
+        if (name is QualifiedNameSyntax qualifiedName)
         {
             NameSyntax left;
 
@@ -4233,7 +4238,7 @@ internal static IdentifierNameSyntax GetRootNamespace(this UsingDirectiveSyntax
         }
         else
         {
-            SyntaxDebug.Fail(usingDirective.Name);
+            SyntaxDebug.Fail(name);
         }
 
         return null;

src/Tests/Formatting.Analyzers.Tests/RCS0015BlankLineBetweenUsingDirectivesTests.cs

@@ -30,6 +30,30 @@ class C
 
 using System.Threading;
 
+class C
+{
+}
+", options: Options.AddConfigOption(ConfigOptionKeys.BlankLineBetweenUsingDirectives, ConfigOptionValues.BlankLineBetweenUsingDirectives_SeparateGroups));
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.BlankLineBetweenUsingDirectives)]
+    public async Task Test_AddEmptyLine_GlobalAlias()
+    {
+        await VerifyDiagnosticAndFixAsync(@"
+using global::System;[||]
+using Microsoft.CodeAnalysis;[||]
+using System.Threading;
+
+class C
+{
+}
+", @"
+using global::System;
+
+using Microsoft.CodeAnalysis;
+
+using System.Threading;
+
 class C
 {
 }