Only create one instance of each incremental analyzer...

The previous code was pulling on the Select IEnumerable twice, causing
CreateIncrementalAnalyzer to be called twice.

src/Features/Core/Portable/SolutionCrawler/WorkCoordinator.IncrementalAnalyzerProcessor.cs

@@ -75,10 +75,9 @@ private IDiagnosticAnalyzerService GetDiagnosticAnalyzerService(IEnumerable<Lazy
                 private static ImmutableArray<IIncrementalAnalyzer> GetActiveFileIncrementalAnalyzers(
                     Registration registration, IEnumerable<Lazy<IIncrementalAnalyzerProvider, IncrementalAnalyzerProviderMetadata>> providers)
                 {
-                    var analyzers = providers.Where(p => p.Metadata.HighPriorityForActiveFile && p.Metadata.WorkspaceKinds.Contains(registration.Workspace.Kind))
-                                             .Select(p => p.Value.CreateIncrementalAnalyzer(registration.Workspace));
+                    var matchingProviders = providers.Where(p => p.Metadata.HighPriorityForActiveFile && p.Metadata.WorkspaceKinds.Contains(registration.Workspace.Kind));
 
-                    var orderedAnalyzers = OrderAnalyzers(analyzers);
+                    var orderedAnalyzers = GetOrderedAnalyzers(registration, matchingProviders);
 
                     SolutionCrawlerLogger.LogActiveFileAnalyzers(registration.CorrelationId, registration.Workspace, orderedAnalyzers);
                     return orderedAnalyzers;
@@ -87,20 +86,21 @@ private IDiagnosticAnalyzerService GetDiagnosticAnalyzerService(IEnumerable<Lazy
                 private static ImmutableArray<IIncrementalAnalyzer> GetIncrementalAnalyzers(
                     Registration registration, IEnumerable<Lazy<IIncrementalAnalyzerProvider, IncrementalAnalyzerProviderMetadata>> providers)
                 {
-                    var analyzers = providers.Where(p => p.Metadata.WorkspaceKinds.Contains(registration.Workspace.Kind))
-                                             .Select(p => p.Value.CreateIncrementalAnalyzer(registration.Workspace));
+                    var matchingProviders = providers.Where(p => p.Metadata.WorkspaceKinds.Contains(registration.Workspace.Kind));
 
-                    var orderedAnalyzers = OrderAnalyzers(analyzers);
+                    var orderedAnalyzers = GetOrderedAnalyzers(registration, matchingProviders);
 
                     SolutionCrawlerLogger.LogAnalyzers(registration.CorrelationId, registration.Workspace, orderedAnalyzers);
                     return orderedAnalyzers;
                 }
 
-                private static ImmutableArray<IIncrementalAnalyzer> OrderAnalyzers(IEnumerable<IIncrementalAnalyzer> analyzers)
+                private static ImmutableArray<IIncrementalAnalyzer> GetOrderedAnalyzers(
+                    Registration registration, IEnumerable<Lazy<IIncrementalAnalyzerProvider, IncrementalAnalyzerProviderMetadata>> providers)
                 {
-                    return SpecializedCollections.SingletonEnumerable(analyzers.FirstOrDefault(a => a is BaseDiagnosticIncrementalAnalyzer))
-                                                                               .Concat(analyzers.Where(a => !(a is BaseDiagnosticIncrementalAnalyzer)))
-                                                                               .WhereNotNull().ToImmutableArray();
+                    // Sort list so BaseDiagnosticIncrementalAnalyzers (if any) come first.  OrderBy orders 'false' keys before 'true'.
+                    return providers.Select(p => p.Value.CreateIncrementalAnalyzer(registration.Workspace))
+                                    .OrderBy(a => !(a is BaseDiagnosticIncrementalAnalyzer))
+                                    .ToImmutableArray();
                 }
 
                 public void Enqueue(WorkItem item)