Make BlockSpan a struct type.

src/Compilers/Core/Portable/Collections/ArrayBuilderExtensions.cs

@@ -142,5 +142,14 @@ public static ImmutableArray<T> ToImmutableOrEmptyAndFree<T>(this ArrayBuilder<T
         {
             return builderOpt?.ToImmutableAndFree() ?? ImmutableArray<T>.Empty;
         }
+
+        public static void AddIfNotNull<T> (this ArrayBuilder<T> builder, T? value)
+            where T : struct
+        {
+            if (value != null)
+            {
+                builder.Add(value.Value);
+            }
+        }
     }
 }

src/Features/CSharp/Portable/Structure/CSharpStructureHelpers.cs

@@ -251,7 +251,7 @@ private static string GetCommentBannerText(SyntaxTrivia comment)
                 isCollapsible);
         }
 
-        public static BlockSpan CreateBlockSpan(
+        public static BlockSpan? CreateBlockSpan(
             SyntaxNode node, SyntaxToken syntaxToken, 
             string bannerText, bool autoCollapse,
             string type, bool isCollapsible)
@@ -266,7 +266,7 @@ private static string GetCommentBannerText(SyntaxTrivia comment)
                 isCollapsible);
         }
 
-        public static BlockSpan CreateBlockSpan(
+        public static BlockSpan? CreateBlockSpan(
             SyntaxNode node, SyntaxToken startToken, 
             int endPos, string bannerText, bool autoCollapse,
             string type, bool isCollapsible)
@@ -293,7 +293,7 @@ private static string GetCommentBannerText(SyntaxTrivia comment)
                 isCollapsible);
         }
 
-        public static BlockSpan CreateBlockSpan(
+        public static BlockSpan? CreateBlockSpan(
             SyntaxNode node, SyntaxToken startToken, 
             SyntaxToken endToken, string bannerText, bool autoCollapse,
             string type, bool isCollapsible)
@@ -321,7 +321,7 @@ private static string GetCommentBannerText(SyntaxTrivia comment)
 
         // Adds everything after 'syntaxToken' up to and including the end 
         // of node as a region.  The snippet to display is just "..."
-        public static BlockSpan CreateBlockSpan(
+        public static BlockSpan? CreateBlockSpan(
             SyntaxNode node, SyntaxToken syntaxToken, 
             bool autoCollapse, string type, bool isCollapsible)
         {
@@ -335,7 +335,7 @@ private static string GetCommentBannerText(SyntaxTrivia comment)
 
         // Adds everything after 'syntaxToken' up to and including the end 
         // of node as a region.  The snippet to display is just "..."
-        public static BlockSpan CreateBlockSpan(
+        public static BlockSpan? CreateBlockSpan(
             SyntaxNode node, SyntaxToken startToken, SyntaxToken endToken, 
             bool autoCollapse, string type, bool isCollapsible)
         {
@@ -350,7 +350,7 @@ private static string GetCommentBannerText(SyntaxTrivia comment)
         // Adds the span surrounding the syntax list as a region.  The
         // snippet shown is the text from the first line of the first 
         // node in the list.
-        public static BlockSpan CreateBlockSpan(
+        public static BlockSpan? CreateBlockSpan(
             IEnumerable<SyntaxNode> syntaxList, bool autoCollapse, 
             string type, bool isCollapsible)
         {

src/Features/CSharp/Portable/Structure/Providers/AccessorDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class AccessorDeclarationStructureProvider : AbstractSyntaxNodeStructur
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 accessorDeclaration,
                 accessorDeclaration.Keyword,
                 autoCollapse: true,
@@ -32,4 +31,4 @@ internal class AccessorDeclarationStructureProvider : AbstractSyntaxNodeStructur
                 isCollapsible: true));
         }
     }
-}
+}
\ No newline at end of file

src/Features/CSharp/Portable/Structure/Providers/AnonymousMethodExpressionStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -32,7 +31,7 @@ internal class AnonymousMethodExpressionStructureProvider : AbstractSyntaxNodeSt
                 ? anonymousMethod.ParameterList.GetLastToken(includeZeroWidth: true)
                 : anonymousMethod.DelegateKeyword;
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 anonymousMethod,
                 startToken,
                 lastToken,
@@ -41,4 +40,4 @@ internal class AnonymousMethodExpressionStructureProvider : AbstractSyntaxNodeSt
                 isCollapsible: true));
         }
     }
-}
+}
\ No newline at end of file

src/Features/CSharp/Portable/Structure/Providers/CompilationUnitStructureProvider.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.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -23,7 +22,7 @@ internal class CompilationUnitStructureProvider : AbstractSyntaxNodeStructurePro
             externsAndUsings.AddRange(compilationUnit.Usings);
             externsAndUsings.Sort((node1, node2) => node1.SpanStart.CompareTo(node2.SpanStart));
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 externsAndUsings, autoCollapse: true, 
                 type: BlockTypes.Imports, isCollapsible: true));
 
@@ -41,4 +40,4 @@ protected override bool SupportedInWorkspaceKind(string kind)
             return true;
         }
     }
-}
+}
\ No newline at end of file

src/Features/CSharp/Portable/Structure/Providers/ConstructorDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class ConstructorDeclarationStructureProvider : AbstractSyntaxNodeStruc
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 constructorDeclaration,
                 constructorDeclaration.ParameterList.GetLastToken(includeZeroWidth: true),
                 autoCollapse: true,
@@ -32,4 +31,4 @@ internal class ConstructorDeclarationStructureProvider : AbstractSyntaxNodeStruc
                 isCollapsible: true));
         }
     }
-}
+}
\ No newline at end of file

src/Features/CSharp/Portable/Structure/Providers/ConversionOperatorDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class ConversionOperatorDeclarationStructureProvider : AbstractSyntaxNo
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 operatorDeclaration,
                 operatorDeclaration.ParameterList.GetLastToken(includeZeroWidth: true),
                 autoCollapse: true,
@@ -32,4 +31,4 @@ internal class ConversionOperatorDeclarationStructureProvider : AbstractSyntaxNo
                 isCollapsible: true));
         }
     }
-}
+}
\ No newline at end of file

src/Features/CSharp/Portable/Structure/Providers/DestructorDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class DestructorDeclarationStructureProvider : AbstractSyntaxNodeStruct
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 destructorDeclaration,
                 destructorDeclaration.ParameterList.GetLastToken(includeZeroWidth: true),
                 autoCollapse: true,

src/Features/CSharp/Portable/Structure/Providers/EnumDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -19,7 +18,7 @@ internal class EnumDeclarationStructureProvider : AbstractSyntaxNodeStructurePro
             if (!enumDeclaration.OpenBraceToken.IsMissing &&
                 !enumDeclaration.CloseBraceToken.IsMissing)
             {
-                spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+                spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                     enumDeclaration,
                     enumDeclaration.Identifier,
                     autoCollapse: false,

src/Features/CSharp/Portable/Structure/Providers/EventDeclarationStructureProvider.cs

@@ -23,7 +23,7 @@ internal class EventDeclarationStructureProvider : AbstractSyntaxNodeStructurePr
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 eventDeclaration,
                 eventDeclaration.Identifier,
                 autoCollapse: true,

src/Features/CSharp/Portable/Structure/Providers/IndexerDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -25,7 +24,7 @@ internal class IndexerDeclarationStructureProvider : AbstractSyntaxNodeStructure
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 indexerDeclaration,
                 indexerDeclaration.ParameterList.GetLastToken(includeZeroWidth: true),
                 autoCollapse: true,

src/Features/CSharp/Portable/Structure/Providers/MethodDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class MethodDeclarationStructureProvider : AbstractSyntaxNodeStructureP
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 methodDeclaration,
                 methodDeclaration.ParameterList.GetLastToken(includeZeroWidth: true),
                 autoCollapse: true,

src/Features/CSharp/Portable/Structure/Providers/NamespaceDeclarationStructureProvider.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.Immutable;
 using System.Linq;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
@@ -21,7 +20,7 @@ internal class NamespaceDeclarationStructureProvider : AbstractSyntaxNodeStructu
             if (!namespaceDeclaration.OpenBraceToken.IsMissing &&
                 !namespaceDeclaration.CloseBraceToken.IsMissing)
             {
-                spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+                spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                     namespaceDeclaration,
                     namespaceDeclaration.Name.GetLastToken(includeZeroWidth: true),
                     autoCollapse: false,
@@ -40,7 +39,7 @@ internal class NamespaceDeclarationStructureProvider : AbstractSyntaxNodeStructu
                 CSharpStructureHelpers.CollectCommentBlockSpans(externsAndUsings.First(), spans);
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 externsAndUsings, autoCollapse: true, 
                 type: BlockTypes.Imports, isCollapsible: true));
 

src/Features/CSharp/Portable/Structure/Providers/OperatorDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class OperatorDeclarationStructureProvider : AbstractSyntaxNodeStructur
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 operatorDeclaration,
                 operatorDeclaration.ParameterList.GetLastToken(includeZeroWidth: true),
                 autoCollapse: true,

src/Features/CSharp/Portable/Structure/Providers/ParenthesizedLambdaExpressionStructureProvider.cs

@@ -34,7 +34,7 @@ internal class ParenthesizedLambdaExpressionStructureProvider : AbstractSyntaxNo
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 lambdaExpression,
                 lambdaExpression.ArrowToken,
                 lastToken,

src/Features/CSharp/Portable/Structure/Providers/PropertyDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -24,7 +23,7 @@ internal class PropertyDeclarationStructureProvider : AbstractSyntaxNodeStructur
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 propertyDeclaration,
                 propertyDeclaration.Identifier,
                 autoCollapse: true,
@@ -32,4 +31,4 @@ internal class PropertyDeclarationStructureProvider : AbstractSyntaxNodeStructur
                 isCollapsible: true));
         }
     }
-}
+}
\ No newline at end of file

src/Features/CSharp/Portable/Structure/Providers/SimpleLambdaExpressionStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -34,7 +33,7 @@ internal class SimpleLambdaExpressionStructureProvider : AbstractSyntaxNodeStruc
                 return;
             }
 
-            spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+            spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                 lambdaExpression,
                 lambdaExpression.ArrowToken,
                 lastToken,

src/Features/CSharp/Portable/Structure/Providers/TypeDeclarationStructureProvider.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.Immutable;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Structure;
@@ -28,7 +27,7 @@ internal class TypeDeclarationStructureProvider : AbstractSyntaxNodeStructurePro
                     : typeDeclaration.Kind() == SyntaxKind.StructDeclaration
                         ? BlockTypes.Structure
                         : BlockTypes.Class;
-                spans.Add(CSharpStructureHelpers.CreateBlockSpan(
+                spans.AddIfNotNull(CSharpStructureHelpers.CreateBlockSpan(
                     typeDeclaration,
                     lastToken,
                     autoCollapse: false,

src/Features/Core/Portable/Structure/BlockSpan.cs

@@ -4,7 +4,7 @@
 
 namespace Microsoft.CodeAnalysis.Structure
 {
-    internal class BlockSpan
+    internal struct BlockSpan
     {
         private const string Ellipses = "...";
 

src/Features/Core/Portable/Structure/Syntax/AbstractBlockStructureProvider.cs

@@ -80,17 +80,14 @@ public override async Task ProvideBlockStructureAsync(BlockStructureContext cont
 
             foreach (var span in spans)
             {
-                if (span != null)
-                {
-                    var updatedSpan = UpdateBlockSpan(span,
-                            showIndentGuidesForCodeLevelConstructs,
-                            showIndentGuidesForDeclarationLevelConstructs,
-                            showIndentGuidesForCommentsAndPreprocessorRegions,
-                            showOutliningForCodeLevelConstructs,
-                            showOutliningForDeclarationLevelConstructs,
-                            showOutliningForCommentsAndPreprocessorRegions);
-                    context.AddBlockSpan(updatedSpan);
-                }
+                var updatedSpan = UpdateBlockSpan(span,
+                        showIndentGuidesForCodeLevelConstructs,
+                        showIndentGuidesForDeclarationLevelConstructs,
+                        showIndentGuidesForCommentsAndPreprocessorRegions,
+                        showOutliningForCodeLevelConstructs,
+                        showOutliningForDeclarationLevelConstructs,
+                        showOutliningForCommentsAndPreprocessorRegions);
+                context.AddBlockSpan(updatedSpan);
             }
 
             spans.Free();

src/Features/VisualBasic/Portable/Structure/Providers/AccessorDeclarationStructureProvider.vb

@@ -16,7 +16,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(accessorDeclaration.Parent, AccessorBlockSyntax)
             If Not block?.EndBlockStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=accessorDeclaration,
                     autoCollapse:=True, type:=BlockTypes.Accessor, isCollapsible:=True))
             End If

src/Features/VisualBasic/Portable/Structure/Providers/CompilationUnitStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -12,10 +11,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
         Protected Overrides Sub CollectBlockSpans(compilationUnit As CompilationUnitSyntax,
                                                   spans As ArrayBuilder(Of BlockSpan),
                                                   cancellationToken As CancellationToken)
-            Dim regions As New List(Of BlockSpan)
-
             CollectCommentsRegions(compilationUnit, spans)
-            spans.Add(CreateRegion(
+            spans.AddIfNotNull(CreateRegion(
                 compilationUnit.Imports, bannerText:="Imports" & SpaceEllipsis,
                 autoCollapse:=True, type:=BlockTypes.Nonstructural, isCollapsible:=True))
             CollectCommentsRegions(compilationUnit.EndOfFileToken.LeadingTrivia, spans)

src/Features/VisualBasic/Portable/Structure/Providers/ConstructorDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -18,7 +17,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(constructorDeclaration.Parent, ConstructorBlockSyntax)
             If Not block?.EndBlockStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=constructorDeclaration, autoCollapse:=True,
                     type:=BlockTypes.Constructor, isCollapsible:=True))
             End If

src/Features/VisualBasic/Portable/Structure/Providers/DisabledTextTriviaStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.Text
@@ -18,7 +17,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                 Dim startPos = nodeSpan.Start
                 Dim endPos = startPos + trivia.ToString().TrimEnd().Length
 
-                spans.Add(CreateRegion(
+                spans.AddIfNotNull(CreateRegion(
                     span:=TextSpan.FromBounds(startPos, endPos),
                     bannerText:=Ellipsis, autoCollapse:=True,
                     type:=BlockTypes.Nonstructural, isCollapsible:=True))

src/Features/VisualBasic/Portable/Structure/Providers/DocumentationCommentStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Text
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
@@ -87,7 +86,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim fullSpan = TextSpan.FromBounds(startPos, endPos)
 
-            spans.Add(CreateRegion(
+            spans.AddIfNotNull(CreateRegion(
                 fullSpan, GetBannerText(documentationComment, cancellationToken),
                 autoCollapse:=True, type:=BlockTypes.Nonstructural, isCollapsible:=True))
         End Sub

src/Features/VisualBasic/Portable/Structure/Providers/EnumDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -16,7 +15,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(enumDeclaration.Parent, EnumBlockSyntax)
             If Not block?.EndEnumStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=enumDeclaration, autoCollapse:=True,
                     type:=BlockTypes.Enum, isCollapsible:=True))
 

src/Features/VisualBasic/Portable/Structure/Providers/EventDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -16,7 +15,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(eventDeclaration.Parent, EventBlockSyntax)
             If Not block?.EndEventStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=eventDeclaration, autoCollapse:=True,
                     type:=BlockTypes.Event, isCollapsible:=True))
 

src/Features/VisualBasic/Portable/Structure/Providers/MetadataAsSource/MetadataRegionDirectiveStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.Text
@@ -25,7 +24,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure.MetadataAsSource
                                                   cancellationToken As CancellationToken)
             Dim match = regionDirective.GetMatchingStartOrEndDirective(cancellationToken)
             If match IsNot Nothing Then
-                spans.Add(CreateRegion(
+                spans.AddIfNotNull(CreateRegion(
                     TextSpan.FromBounds(regionDirective.SpanStart, match.Span.End),
                     GetBannerText(regionDirective),
                     autoCollapse:=True,

src/Features/VisualBasic/Portable/Structure/Providers/MethodDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -16,7 +15,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(methodDeclaration.Parent, MethodBlockSyntax)
             If Not block?.EndBlockStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=methodDeclaration, autoCollapse:=True,
                     type:=BlockTypes.Method, isCollapsible:=True))
             End If

src/Features/VisualBasic/Portable/Structure/Providers/MultilineLambdaStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -13,7 +12,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                                                   spans As ArrayBuilder(Of BlockSpan),
                                                   cancellationToken As CancellationToken)
             If Not lambdaExpression.EndSubOrFunctionStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     lambdaExpression, bannerNode:=lambdaExpression.SubOrFunctionHeader, autoCollapse:=False,
                     type:=BlockTypes.AnonymousMethod, isCollapsible:=True))
             End If

src/Features/VisualBasic/Portable/Structure/Providers/NamespaceDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -16,7 +15,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(namespaceDeclaration.Parent, NamespaceBlockSyntax)
             If Not block?.EndNamespaceStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=namespaceDeclaration, autoCollapse:=False,
                     type:=BlockTypes.Namespace, isCollapsible:=True))
 

src/Features/VisualBasic/Portable/Structure/Providers/OperatorDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -16,7 +15,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(operatorDeclaration.Parent, OperatorBlockSyntax)
             If Not block?.EndBlockStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=operatorDeclaration, autoCollapse:=True,
                     type:=BlockTypes.Operator, isCollapsible:=True))
             End If

src/Features/VisualBasic/Portable/Structure/Providers/PropertyDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -16,7 +15,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
             Dim block = TryCast(propertyDeclaration.Parent, PropertyBlockSyntax)
             If Not block?.EndPropertyStatement.IsMissing Then
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=propertyDeclaration, autoCollapse:=True,
                     type:=BlockTypes.Property, isCollapsible:=True))
 

src/Features/VisualBasic/Portable/Structure/Providers/RegionDirectiveStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.Text
@@ -25,7 +24,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                                                   cancellationToken As CancellationToken)
             Dim matchingDirective = regionDirective.GetMatchingStartOrEndDirective(cancellationToken)
             If matchingDirective IsNot Nothing Then
-                spans.Add(CreateRegion(
+                spans.AddIfNotNull(CreateRegion(
                     TextSpan.FromBounds(regionDirective.SpanStart, matchingDirective.Span.End),
                     GetBannerText(regionDirective),
                     autoCollapse:=False,

src/Features/VisualBasic/Portable/Structure/Providers/TypeDeclarationStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -21,7 +20,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                     If(typeDeclaration.Kind() = SyntaxKind.StructureStatement, BlockTypes.Structure,
                     If(typeDeclaration.Kind() = SyntaxKind.ModuleStatement, BlockTypes.Module,
                         BlockTypes.Class)))
-                spans.Add(CreateRegionFromBlock(
+                spans.AddIfNotNull(CreateRegionFromBlock(
                     block, bannerNode:=typeDeclaration, autoCollapse:=False,
                     type:=type, isCollapsible:=True))
 

src/Features/VisualBasic/Portable/Structure/Providers/XmlExpressionStructureProvider.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Structure
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -23,7 +22,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
             Dim lineText = line.ToString().Substring(span.Start - line.Start)
             Dim bannerText = lineText & SpaceEllipsis
 
-            spans.Add(CreateRegion(
+            spans.AddIfNotNull(CreateRegion(
                 span, bannerText, autoCollapse:=False,
                 type:=BlockTypes.Xml, isCollapsible:=True))
         End Sub

src/Features/VisualBasic/Portable/Structure/VisualBasicStructureHelpers.vb

@@ -18,7 +18,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
             Return "' " & comment.ToString().Substring(1).Trim() & SpaceEllipsis
         End Function
 
-        Private Function CreateCommentsRegion(startComment As SyntaxTrivia, endComment As SyntaxTrivia) As BlockSpan
+        Private Function CreateCommentsRegion(startComment As SyntaxTrivia,
+                                              endComment As SyntaxTrivia) As BlockSpan?
             Return CreateRegion(
                 TextSpan.FromBounds(startComment.SpanStart, endComment.Span.End),
                 GetCommentBannerText(startComment),
@@ -50,7 +51,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                         trivia.Kind <> SyntaxKind.EndOfFileToken Then
 
                         If startComment IsNot Nothing Then
-                            spans.Add(CreateCommentsRegion(startComment.Value, endComment.Value))
+                            spans.AddIfNotNull(CreateCommentsRegion(startComment.Value, endComment.Value))
                             startComment = Nothing
                             endComment = Nothing
                         End If
@@ -59,7 +60,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
 
                 ' Add any final span
                 If startComment IsNot Nothing Then
-                    spans.Add(CreateCommentsRegion(startComment.Value, endComment.Value))
+                    spans.AddIfNotNull(CreateCommentsRegion(startComment.Value, endComment.Value))
                 End If
             End If
         End Sub
@@ -81,7 +82,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                 autoCollapse As Boolean,
                 type As String,
                 isCollapsible As Boolean,
-                Optional isDefaultCollapsed As Boolean = False) As BlockSpan
+                Optional isDefaultCollapsed As Boolean = False) As BlockSpan?
             Return New BlockSpan(
                 textSpan:=span,
                 bannerText:=bannerText,
@@ -96,7 +97,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                 bannerText As String,
                 autoCollapse As Boolean,
                 type As String,
-                isCollapsible As Boolean) As BlockSpan
+                isCollapsible As Boolean) As BlockSpan?
             Return CreateRegion(blockNode.Span, bannerText, autoCollapse, type, isCollapsible)
         End Function
 
@@ -105,7 +106,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                 bannerNode As SyntaxNode,
                 autoCollapse As Boolean,
                 type As String,
-                isCollapsible As Boolean) As BlockSpan
+                isCollapsible As Boolean) As BlockSpan?
             Return CreateRegion(
                 blockNode.Span, GetNodeBannerText(bannerNode),
                 autoCollapse, type, isCollapsible)
@@ -115,7 +116,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Structure
                                      bannerText As String,
                                      autoCollapse As Boolean,
                                      type As String,
-                                     isCollapsible As Boolean) As BlockSpan
+                                     isCollapsible As Boolean) As BlockSpan?
             If syntaxList.IsEmpty() Then
                 Return Nothing
             End If