Add test for edge case where the preprocessor directive name is missing

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test/SpacingRules/SA1006UnitTests.cs

@@ -106,6 +106,20 @@ more invalid text
             await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
+        [Fact]
+        public async Task TestMissingDirectiveNameOnLastLineAsync()
+        {
+            string testCode = @"
+class ClassName
+{
+}
+# ";
+
+            DiagnosticResult expected = this.CSharpCompilerError("CS1024").WithMessage("Preprocessor directive expected").WithLocation(5, 1);
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+        }
+
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {
             yield return new SA1006PreprocessorKeywordsMustNotBePrecededBySpace();

StyleCop.Analyzers/StyleCop.Analyzers/SpacingRules/SA1006PreprocessorKeywordsMustNotBePrecededBySpace.cs

@@ -8,6 +8,7 @@ namespace StyleCop.Analyzers.SpacingRules
     using Microsoft.CodeAnalysis;
     using Microsoft.CodeAnalysis.CSharp;
     using Microsoft.CodeAnalysis.Diagnostics;
+    using StyleCop.Analyzers.Helpers;
 
     /// <summary>
     /// A C# preprocessor-type keyword is preceded by space.
@@ -82,7 +83,7 @@ private static void HandleHashToken(SyntaxTreeAnalysisContext context, SyntaxTok
             }
 
             SyntaxToken targetToken = token.GetNextToken(includeDirectives: true);
-            if (targetToken.IsMissing)
+            if (targetToken.IsMissingOrDefault())
             {
                 return;
             }