Fix SA1135 getting reported for top-level namespaces

Author: sharwell

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

@@ -307,5 +307,17 @@ namespace Test
 
             await VerifyCSharpFixAsync(testCode, expected, fixedCode, CancellationToken.None).ConfigureAwait(false);
         }
+
+        [Fact]
+        public async Task TestFullyQualifiedTopLevelNamespaceAsync()
+        {
+            var testCode = @"
+namespace MyNamespace {
+  using System;
+}
+";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }

StyleCop.Analyzers/StyleCop.Analyzers/Helpers/SymbolNameHelpers.cs

@@ -85,10 +85,14 @@ private static void AppendQualifiedSymbolName(StringBuilder builder, ISymbol sym
                 break;
 
             default:
-                builder
-                    .Append(symbol.ContainingNamespace.ToDisplayString())
-                    .Append(".")
-                    .Append(symbol.Name);
+                if (!symbol.ContainingNamespace.IsGlobalNamespace)
+                {
+                    builder
+                        .Append(symbol.ContainingNamespace.ToDisplayString())
+                        .Append(".");
+                }
+
+                builder.Append(symbol.Name);
                 break;
             }
         }