Use pooled arrays.

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/AbstractReferenceFinder.cs

@@ -94,7 +94,7 @@ protected async Task<ImmutableArray<Document>> FindDocumentsAsync(Project projec
                 return ImmutableArray<Document>.Empty;
             }
 
-            ImmutableArray<Document>.Builder documents = null;
+            var documents = ArrayBuilder<Document>.GetInstance();
             foreach (var document in project.Documents)
             {
                 if (scope != null && !scope.Contains(document))
@@ -104,19 +104,11 @@ protected async Task<ImmutableArray<Document>> FindDocumentsAsync(Project projec
 
                 if (await predicateAsync(document, cancellationToken).ConfigureAwait(false))
                 {
-                    documents = documents ?? ImmutableArray.CreateBuilder<Document>();
                     documents.Add(document);
                 }
             }
 
-            if (documents == null)
-            {
-                return ImmutableArray<Document>.Empty;
-            }
-            else
-            {
-                return documents.ToImmutable();
-            }
+            return documents.ToImmutableAndFree();
         }
 
         /// <summary>
@@ -285,7 +277,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
             var syntaxTree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
-            var locations = ImmutableArray.CreateBuilder<ReferenceLocation>();
+            var locations = ArrayBuilder<ReferenceLocation>.GetInstance();
             foreach (var token in tokens)
             {
                 cancellationToken.ThrowIfCancellationRequested();
@@ -304,7 +296,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
                 }
             }
 
-            return locations.ToImmutable();
+            return locations.ToImmutableAndFree();
         }
 
         protected static Task<ImmutableArray<ReferenceLocation>> FindReferencesInDocumentAsync(
@@ -402,24 +394,17 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
             ImmutableArray<ReferenceLocation> nonAliasReferences,
             CancellationToken cancellationToken)
         {
-            ImmutableArray<IAliasSymbol>.Builder aliasSymbols = null;
+            var aliasSymbols = ArrayBuilder<IAliasSymbol>.GetInstance();
             foreach (var r in nonAliasReferences)
             {
                 var symbol = await GetAliasSymbolAsync(document, r, cancellationToken).ConfigureAwait(false);
                 if (symbol != null)
                 {
-                    if (aliasSymbols == null)
-                    {
-                        aliasSymbols = ImmutableArray.CreateBuilder<IAliasSymbol>();
-                    }
-
                     aliasSymbols.Add(symbol);
                 }
             }
 
-            return aliasSymbols != null
-                ? aliasSymbols.Distinct().ToImmutableArray()
-                : ImmutableArray<IAliasSymbol>.Empty;
+            return aliasSymbols.ToImmutableAndFree();
         }
 
         private static async Task<ImmutableArray<ReferenceLocation>> FindReferencesThroughAliasSymbolsAsync(
@@ -430,7 +415,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
             CancellationToken cancellationToken)
         {
             var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
-            var allAliasReferences = ImmutableArray.CreateBuilder<ReferenceLocation>();
+            var allAliasReferences = ArrayBuilder<ReferenceLocation>.GetInstance();
             foreach (var aliasSymbol in aliasSymbols)
             {
                 var aliasReferences = await FindReferencesInDocumentUsingIdentifierAsync(symbol, aliasSymbol.Name, document, cancellationToken, findParentNode).ConfigureAwait(false);
@@ -446,7 +431,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
                 }
             }
 
-            return allAliasReferences.ToImmutable();
+            return allAliasReferences.ToImmutableAndFree();
         }
 
         private static async Task<ImmutableArray<ReferenceLocation>> FindReferencesThroughAliasSymbolsAsync(
@@ -457,7 +442,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
             CancellationToken cancellationToken)
         {
             var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
-            var allAliasReferences = ImmutableArray.CreateBuilder<ReferenceLocation>();
+            var allAliasReferences = ArrayBuilder<ReferenceLocation>.GetInstance();
             foreach (var aliasSymbol in aliasSymbols)
             {
                 var aliasReferences = await FindReferencesInDocumentUsingIdentifierAsync(aliasSymbol.Name, document, symbolsMatch, cancellationToken).ConfigureAwait(false);
@@ -473,7 +458,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
                 }
             }
 
-            return allAliasReferences.ToImmutable();
+            return allAliasReferences.ToImmutableAndFree();
         }
 
         protected Task<ImmutableArray<Document>> FindDocumentsWithForEachStatementsAsync(Project project, IImmutableSet<Document> documents, CancellationToken cancellationToken)
@@ -497,7 +482,7 @@ protected Task<ImmutableArray<Document>> FindDocumentsWithForEachStatementsAsync
                 var syntaxRoot = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
                 var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
-                var locations = ImmutableArray.CreateBuilder<ReferenceLocation>();
+                var locations = ArrayBuilder<ReferenceLocation>.GetInstance();
 
                 var originalUnreducedSymbolDefinition = symbol.GetOriginalUnreducedDefinition();
 
@@ -517,7 +502,7 @@ protected Task<ImmutableArray<Document>> FindDocumentsWithForEachStatementsAsync
                     }
                 }
 
-                return locations.ToImmutable();
+                return locations.ToImmutableAndFree();
             }
             else
             {

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/NamedTypeSymbolReferenceFinder.cs

@@ -25,41 +25,32 @@ protected override bool CanFind(INamedTypeSymbol symbol)
             IImmutableSet<Project> projects,
             CancellationToken cancellationToken)
         {
-            ImmutableArray<SymbolAndProjectId>.Builder result = null;
+            var result = ArrayBuilder<SymbolAndProjectId>.GetInstance();
 
             var symbol = symbolAndProjectId.Symbol;
             if (symbol.AssociatedSymbol != null)
             {
-                result = Add(result, symbolAndProjectId, ImmutableArray.Create(symbol.AssociatedSymbol));
+                Add(result, symbolAndProjectId, ImmutableArray.Create(symbol.AssociatedSymbol));
             }
 
             // cascade to constructors
-            result = Add(result, symbolAndProjectId, symbol.Constructors);
+            Add(result, symbolAndProjectId, symbol.Constructors);
 
             // cascade to destructor
-            result = Add(result, symbolAndProjectId, symbol.GetMembers(WellKnownMemberNames.DestructorName));
+            Add(result, symbolAndProjectId, symbol.GetMembers(WellKnownMemberNames.DestructorName));
 
-            return Task.FromResult<ImmutableArray<SymbolAndProjectId>>(
-                result == null 
-                    ? ImmutableArray<SymbolAndProjectId>.Empty
-                    : result.ToImmutable());
+            return Task.FromResult(result.ToImmutableAndFree());
         }
 
-        private ImmutableArray<SymbolAndProjectId>.Builder Add<TSymbol>(
-            ImmutableArray<SymbolAndProjectId>.Builder result,
+        private void Add<TSymbol>(
+            ArrayBuilder<SymbolAndProjectId> result,
             SymbolAndProjectId symbolAndProjectId,
             ImmutableArray<TSymbol> enumerable) where TSymbol : ISymbol
         {
-            if (enumerable != null)
-            {
-                result = result ?? ImmutableArray.CreateBuilder<SymbolAndProjectId>();
             result.AddRange(enumerable.Select(
                 s => symbolAndProjectId.WithSymbol((ISymbol)s)));
         }
 
-            return result;
-        }
-
         protected override async Task<ImmutableArray<Document>> DetermineDocumentsToSearchAsync(
             INamedTypeSymbol symbol,
             Project project,

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/ParameterSymbolReferenceFinder.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
@@ -8,7 +7,6 @@
 using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Utilities;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.FindSymbols.Finders
 {
@@ -69,7 +67,7 @@ protected override bool CanFind(IParameterSymbol symbol)
             SymbolAndProjectId<IParameterSymbol> parameterAndProjectId,
             CancellationToken cancellationToken)
         {
-            ImmutableArray<SymbolAndProjectId>.Builder results = null;
+            var results = ArrayBuilder<SymbolAndProjectId>.GetInstance();
 
             var parameter = parameterAndProjectId.Symbol;
             if (parameter.ContainingSymbol.IsAnonymousFunction())
@@ -94,7 +92,6 @@ protected override bool CanFind(IParameterSymbol symbol)
                                 var container = GetContainer(semanticModel, parameterNode, syntaxFactsService);
                                 if (container != null)
                                 {
-                                    results = ImmutableArray.CreateBuilder<SymbolAndProjectId>();
                                     results.AddRange(CascadeBetweenAnonymousFunctionParameters(
                                         document, semanticModel, container, parameterAndProjectId, convertedType, cancellationToken));
                                 }
@@ -110,20 +107,13 @@ protected override bool CanFind(IParameterSymbol symbol)
                     int ordinal = parameter.Ordinal;
                     if (invokeMethod != null && ordinal < invokeMethod.Parameters.Length)
                     {
-                        if (results == null)
-                        {
-                            results = ImmutableArray.CreateBuilder<SymbolAndProjectId>();
-                        }
-
                         results.Add(parameterAndProjectId.WithSymbol(
                             invokeMethod.Parameters[ordinal]));
                     }
                 }
             }
 
-            return results == null
-                ? ImmutableArray<SymbolAndProjectId>.Empty
-                : results.ToImmutable();
+            return results.ToImmutableAndFree();
         }
 
         private ImmutableArray<SymbolAndProjectId> CascadeBetweenAnonymousFunctionParameters(
@@ -134,7 +124,7 @@ protected override bool CanFind(IParameterSymbol symbol)
             ITypeSymbol convertedType1,
             CancellationToken cancellationToken)
         {
-            var result = ImmutableArray.CreateBuilder<SymbolAndProjectId>();
+            var result = ArrayBuilder<SymbolAndProjectId>.GetInstance();
 
             var parameter = parameterAndProjectId.Symbol;
             var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
@@ -159,7 +149,7 @@ protected override bool CanFind(IParameterSymbol symbol)
                 }
             }
 
-            return result.ToImmutable();
+            return result.ToImmutableAndFree();
         }
 
         private bool ParameterNamesMatch(ISyntaxFactsService syntaxFacts, IMethodSymbol methodSymbol1, IMethodSymbol methodSymbol2)
@@ -195,7 +185,7 @@ private SyntaxNode GetContainer(SemanticModel semanticModel, SyntaxNode paramete
             SymbolAndProjectId<IParameterSymbol> parameterAndProjectId,
             CancellationToken cancellationToken)
         {
-            var results = ImmutableArray.CreateBuilder<SymbolAndProjectId>();
+            var results = ArrayBuilder<SymbolAndProjectId>.GetInstance();
 
             var parameter = parameterAndProjectId.Symbol;
             var ordinal = parameter.Ordinal;
@@ -278,13 +268,13 @@ private SyntaxNode GetContainer(SemanticModel semanticModel, SyntaxNode paramete
                 }
             }
 
-            return results.ToImmutable();
+            return results.ToImmutableAndFree();
         }
 
         private ImmutableArray<SymbolAndProjectId> CascadeBetweenPartialMethodParameters(
             SymbolAndProjectId<IParameterSymbol> parameterAndProjectId)
         {
-            var result = ImmutableArray.CreateBuilder<SymbolAndProjectId>();
+            var result = ArrayBuilder<SymbolAndProjectId>.GetInstance();
 
             var parameter = parameterAndProjectId.Symbol;
             if (parameter.ContainingSymbol is IMethodSymbol)
@@ -304,7 +294,7 @@ private SyntaxNode GetContainer(SemanticModel semanticModel, SyntaxNode paramete
                 }
             }
 
-            return result.ToImmutable();
+            return result.ToImmutableAndFree();
         }
     }
 }
\ No newline at end of file

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/PropertySymbolReferenceFinder.cs

@@ -135,7 +135,7 @@ private static bool IsForEachProperty(IPropertySymbol symbol)
 
             var elementAccessExpressionsAndIndexerMemberCref = elementAccessExpressions.Concat(indexerMemberCref);
 
-            var locations = ImmutableArray.CreateBuilder<ReferenceLocation>();
+            var locations = ArrayBuilder<ReferenceLocation>.GetInstance();
 
             foreach (var node in elementAccessExpressionsAndIndexerMemberCref)
             {
@@ -172,7 +172,7 @@ private static bool IsForEachProperty(IPropertySymbol symbol)
                 }
             }
 
-            return locations.ToImmutable();
+            return locations.ToImmutableAndFree();
         }
     }
 }