Make target-typed completion an experiment

src/Features/Core/Portable/Completion/Providers/AbstractSymbolCompletionProvider.cs

@@ -8,6 +8,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.ErrorReporting;
+using Microsoft.CodeAnalysis.Experiments;
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Options;
@@ -31,6 +32,8 @@ internal abstract class AbstractSymbolCompletionProvider : CommonCompletionProvi
         private static int s_cachedPosition;
         private static readonly object s_cacheGate = new object();
 
+        private bool? _shouldCreateTargetTypeCompletionFilter = null;
+
         protected AbstractSymbolCompletionProvider()
         {
         }
@@ -63,9 +66,12 @@ protected virtual CompletionItemRules GetCompletionItemRules(IReadOnlyList<ISymb
                         symbolGroup.Key.displayText, symbolGroup.Key.suffix, symbolGroup.Key.insertionText, symbolGroup.ToList(), context,
                         invalidProjectMap: null, totalProjects: null, preselect: preselect);
 
-                if (symbolGroup.Any(s => ShouldIncludeInTargetTypedCompletionList(s, inferredTypes, context.SemanticModel, context.Position)))
+                if (ShouldCreateTargetTypeCompletionFilter(context.Workspace))
                 {
-                    item = item.AddTag(WellKnownTags.MatchingType);
+                    if (symbolGroup.Any(s => ShouldIncludeInTargetTypedCompletionList(s, inferredTypes, context.SemanticModel, context.Position)))
+                    {
+                        item = item.AddTag(WellKnownTags.MatchingType);
+                    }
                 }
 
                 itemListBuilder.Add(item);
@@ -74,6 +80,17 @@ protected virtual CompletionItemRules GetCompletionItemRules(IReadOnlyList<ISymb
             return itemListBuilder.ToImmutable();
         }
 
+        private bool ShouldCreateTargetTypeCompletionFilter(Workspace workspace)
+        {
+            if (!_shouldCreateTargetTypeCompletionFilter.HasValue)
+            {
+                var experimentationService = workspace.Services.GetService<IExperimentationService>();
+                _shouldCreateTargetTypeCompletionFilter = experimentationService.IsExperimentEnabled(WellKnownExperimentNames.TargetTypedCompletionFilter);
+            }
+
+            return _shouldCreateTargetTypeCompletionFilter == true;
+        }
+
         private bool ShouldIncludeInTargetTypedCompletionList(ISymbol symbol, ImmutableArray<ITypeSymbol> inferredTypes, SemanticModel semanticModel, int position)
         {
             // When searching for identifiers of type C, exclude the symbol for the `C` type itself.

src/Workspaces/Core/Portable/Experiments/IExperimentationService.cs

@@ -23,5 +23,6 @@ internal static class WellKnownExperimentNames
         public const string CompletionAPI = nameof(CompletionAPI);
         public const string PartialLoadMode = "Roslyn.PartialLoadMode";
         public const string TypeImportCompletion = "Roslyn.TypeImportCompletion";
+        public const string TargetTypedCompletionFilter = "Roslyn.TargetTypedCompletionFilter";
     }
 }