Introduce a hoisted local scope abstraction

Since hoisted locals are fields, they are in scope throughout the entire
method body.  However, from the user's perspective, they are still locals,
so we attempt to retain their original scopes during debugging.
Unfortunately, C# and VB use different mechanisms for doing so.  In order
to make the code more consistent, and to simplify consumption of the new
PDB format (which is more similar to C#), we introduce an abstract type
InScopeHoistedLocals that represents the set of in-scope hoisted locals in
a consistent way in both languages (and both PDB formats).

src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CSharpExpressionCompiler.csproj

@@ -67,6 +67,7 @@
     <Compile Include="Binders\EEMethodBinder.cs" />
     <Compile Include="Binders\WithTypeArgumentsBinder.cs" />
     <Compile Include="Binders\PlaceholderLocalBinder.cs" />
+    <Compile Include="CSharpInScopeHoistedLocals.cs" />
     <Compile Include="SymUnmanagedReaderExtensions.cs" />
     <Compile Include="CompilationContext.cs" />
     <Compile Include="CompilationExtensions.cs" />
@@ -118,4 +119,4 @@
     <Import Project="..\..\..\..\..\build\VSL.Imports.Closed.targets" />
     <Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$(SolutionDir)\.nuget\NuGet.targets')" />
   </ImportGroup>
-</Project>
+</Project>
\ No newline at end of file

src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CSharpInScopeHoistedLocals.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.Diagnostics;
+using Microsoft.CodeAnalysis.CSharp.Symbols;
+
+namespace Microsoft.CodeAnalysis.ExpressionEvaluator
+{
+    internal sealed class CSharpInScopeHoistedLocals : InScopeHoistedLocals
+    {
+        private readonly ImmutableSortedSet<int> _indices;
+
+        public CSharpInScopeHoistedLocals(ImmutableSortedSet<int> indices)
+        {
+            _indices = indices;
+        }
+
+        public override bool IsInScope(string fieldName)
+        {
+            int index;
+            if (GeneratedNames.TryParseSlotIndex(fieldName, out index))
+            {
+                return _indices.Contains(index);
+            }
+            else
+            {
+                Debug.Assert(false, $"Expected hoisted local field name, found '{fieldName}'");
+                return true;
+            }
+        }
+    }
+}

src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs

@@ -49,7 +49,7 @@ internal sealed class CompilationContext
             MetadataDecoder metadataDecoder,
             MethodSymbol currentFrame,
             ImmutableArray<LocalSymbol> locals,
-            ImmutableSortedSet<int> inScopeHoistedLocalIndices,
+            InScopeHoistedLocals inScopeHoistedLocals,
             MethodDebugInfo methodDebugInfo,
             CSharpSyntaxNode syntax)
         {
@@ -88,7 +88,7 @@ internal sealed class CompilationContext
                 GetDisplayClassVariables(
                     currentFrame,
                     _locals,
-                    inScopeHoistedLocalIndices,
+                    inScopeHoistedLocals,
                     out displayClassVariableNamesInOrder,
                     out _displayClassVariables,
                     out _hoistedParameterNames);
@@ -1053,7 +1053,7 @@ private static DkmClrCompilationResultFlags GetLocalResultFlags(LocalSymbol loca
         private static void GetDisplayClassVariables(
             MethodSymbol method,
             ImmutableArray<LocalSymbol> locals,
-            ImmutableSortedSet<int> inScopeHoistedLocalIndices,
+            InScopeHoistedLocals inScopeHoistedLocals,
             out ImmutableArray<string> displayClassVariableNamesInOrder,
             out ImmutableDictionary<string, DisplayClassVariable> displayClassVariables,
             out ImmutableHashSet<string> hoistedParameterNames)
@@ -1133,7 +1133,7 @@ private static DkmClrCompilationResultFlags GetLocalResultFlags(LocalSymbol loca
                         displayClassVariableNamesInOrderBuilder,
                         displayClassVariablesBuilder,
                         parameterNames,
-                        inScopeHoistedLocalIndices,
+                        inScopeHoistedLocals,
                         instance,
                         pooledHoistedParameterNames);
                 }
@@ -1220,7 +1220,7 @@ private static DkmClrCompilationResultFlags GetLocalResultFlags(LocalSymbol loca
             ArrayBuilder<string> displayClassVariableNamesInOrderBuilder,
             Dictionary<string, DisplayClassVariable> displayClassVariablesBuilder,
             HashSet<string> parameterNames,
-            ImmutableSortedSet<int> inScopeHoistedLocalIndices,
+            InScopeHoistedLocals inScopeHoistedLocals,
             DisplayClassInstanceAndFields instance,
             HashSet<string> hoistedParameterNames)
         {
@@ -1252,8 +1252,7 @@ private static DkmClrCompilationResultFlags GetLocalResultFlags(LocalSymbol loca
                         // Filter out hoisted locals that are known to be out-of-scope at the current IL offset.
                         // Hoisted locals with invalid indices will be included since more information is better
                         // than less in error scenarios.
-                        int slotIndex;
-                        if (GeneratedNames.TryParseSlotIndex(fieldName, out slotIndex) && !inScopeHoistedLocalIndices.Contains(slotIndex))
+                        if (!inScopeHoistedLocals.IsInScope(fieldName))
                         {
                             continue;
                         }

src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/EvaluationContext.cs

@@ -32,7 +32,7 @@ internal sealed class EvaluationContext : EvaluationContextBase
         private readonly MetadataDecoder _metadataDecoder;
         private readonly MethodSymbol _currentFrame;
         private readonly ImmutableArray<LocalSymbol> _locals;
-        private readonly ImmutableSortedSet<int> _inScopeHoistedLocalIndices;
+        private readonly InScopeHoistedLocals _inScopeHoistedLocals;
         private readonly MethodDebugInfo _methodDebugInfo;
 
         private EvaluationContext(
@@ -42,10 +42,10 @@ internal sealed class EvaluationContext : EvaluationContextBase
             MetadataDecoder metadataDecoder,
             MethodSymbol currentFrame,
             ImmutableArray<LocalSymbol> locals,
-            ImmutableSortedSet<int> inScopeHoistedLocalIndices,
+            InScopeHoistedLocals inScopeHoistedLocals,
             MethodDebugInfo methodDebugInfo)
         {
-            Debug.Assert(inScopeHoistedLocalIndices != null);
+            Debug.Assert(inScopeHoistedLocals != null);
 
             this.MetadataBlocks = metadataBlocks;
             this.MethodContextReuseConstraints = methodContextReuseConstraints;
@@ -53,7 +53,7 @@ internal sealed class EvaluationContext : EvaluationContextBase
             _metadataDecoder = metadataDecoder;
             _currentFrame = currentFrame;
             _locals = locals;
-            _inScopeHoistedLocalIndices = inScopeHoistedLocalIndices;
+            _inScopeHoistedLocals = inScopeHoistedLocals;
             _methodDebugInfo = methodDebugInfo;
         }
 
@@ -93,7 +93,7 @@ internal sealed class EvaluationContext : EvaluationContextBase
                 metadataDecoder,
                 currentFrame,
                 default(ImmutableArray<LocalSymbol>),
-                ImmutableSortedSet<int>.Empty,
+                InScopeHoistedLocals.Empty,
                 default(MethodDebugInfo));
         }
 
@@ -149,7 +149,7 @@ internal sealed class EvaluationContext : EvaluationContextBase
 
             var localNames = containingScopes.GetLocalNames();
 
-            var inScopeHoistedLocalIndices = ImmutableSortedSet<int>.Empty;
+            var inScopeHoistedLocals = InScopeHoistedLocals.Empty;
             var methodDebugInfo = default(MethodDebugInfo);
 
             if (typedSymReader != null)
@@ -158,7 +158,8 @@ internal sealed class EvaluationContext : EvaluationContextBase
                 {
                     // TODO (https://github.com/dotnet/roslyn/issues/702): switch on the type of typedSymReader and call the appropriate helper.
                     methodDebugInfo = typedSymReader.GetMethodDebugInfo(methodToken, methodVersion, localNames.FirstOrDefault());
-                    inScopeHoistedLocalIndices = methodDebugInfo.GetInScopeHoistedLocalIndices(ilOffset, ref methodContextReuseConstraints);
+                    var inScopeHoistedLocalIndices = methodDebugInfo.GetInScopeHoistedLocalIndices(ilOffset, ref methodContextReuseConstraints);
+                    inScopeHoistedLocals = new CSharpInScopeHoistedLocals(inScopeHoistedLocalIndices);
                 }
                 catch (InvalidOperationException)
                 {
@@ -186,7 +187,7 @@ internal sealed class EvaluationContext : EvaluationContextBase
                 metadataDecoder,
                 currentFrame,
                 locals,
-                inScopeHoistedLocalIndices,
+                inScopeHoistedLocals,
                 methodDebugInfo);
         }
 
@@ -197,7 +198,7 @@ internal CompilationContext CreateCompilationContext(CSharpSyntaxNode syntax)
                 _metadataDecoder,
                 _currentFrame,
                 _locals,
-                _inScopeHoistedLocalIndices,
+                _inScopeHoistedLocals,
                 _methodDebugInfo,
                 syntax);
         }

src/ExpressionEvaluator/Core/Source/ExpressionCompiler/ExpressionCompiler.csproj

@@ -39,6 +39,7 @@
     <Compile Include="FrameDecoder.cs" />
     <Compile Include="InstructionDecoder.cs" />
     <Compile Include="LanguageInstructionDecoder.cs" />
+    <Compile Include="PDB\InScopeHoistedLocals.cs" />
     <Compile Include="PDB\HoisedLocalScopeRecord.cs" />
     <Compile Include="PDB\ExternAliasRecord.cs" />
     <Compile Include="PDB\MethodDebugInfo.cs" />

src/ExpressionEvaluator/Core/Source/ExpressionCompiler/PDB/InScopeHoistedLocals.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.
+
+namespace Microsoft.CodeAnalysis.ExpressionEvaluator
+{
+    internal abstract class InScopeHoistedLocals
+    {
+        public static readonly InScopeHoistedLocals Empty = new EmptyInScopeHoistedLocals();
+
+        public abstract bool IsInScope(string fieldName);
+
+        private sealed class EmptyInScopeHoistedLocals : InScopeHoistedLocals
+        {
+            public override bool IsInScope(string fieldName)
+            {
+                return false;
+            }
+        }
+    }
+}

src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/BasicExpressionCompiler.vbproj

@@ -78,6 +78,7 @@
     <Compile Include="Binders\SuppressObsoleteDiagnosticsBinder.vb" />
     <Compile Include="CompilationContext.vb" />
     <Compile Include="CompilationExtensions.vb" />
+    <Compile Include="VisualBasicInScopeHoistedLocalsByName.vb" />
     <Compile Include="EETypeNameDecoder.vb" />
     <Compile Include="SymUnmanagedReaderExtensions.vb" />
     <Compile Include="InternalsVisibleTo.vb" />
@@ -141,4 +142,4 @@
     <Import Project="..\..\..\..\..\build\VSL.Imports.Closed.targets" />
     <Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$(SolutionDir)\.nuget\NuGet.targets')" />
   </ImportGroup>
-</Project>
+</Project>
\ No newline at end of file

src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/CompilationContext.vb

@@ -46,7 +46,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             metadataDecoder As MetadataDecoder,
             currentFrame As MethodSymbol,
             locals As ImmutableArray(Of LocalSymbol),
-            hoistedLocalFieldNames As ImmutableHashSet(Of String),
+            inScopeHoistedLocals As InScopeHoistedLocals,
             methodDebugInfo As MethodDebugInfo,
             syntax As ExecutableStatementSyntax)
 
@@ -93,7 +93,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             If _methodNotType Then
                 _locals = locals
                 Dim displayClassVariableNamesInOrder As ImmutableArray(Of String) = Nothing
-                GetDisplayClassVariables(currentFrame, locals, hoistedLocalFieldNames, displayClassVariableNamesInOrder, _displayClassVariables, _hoistedParameterNames)
+                GetDisplayClassVariables(currentFrame, locals, inScopeHoistedLocals, displayClassVariableNamesInOrder, _displayClassVariables, _hoistedParameterNames)
                 Debug.Assert(displayClassVariableNamesInOrder.Length = _displayClassVariables.Count)
                 _localsForBinding = GetLocalsForBinding(locals, displayClassVariableNamesInOrder, _displayClassVariables)
             Else
@@ -947,7 +947,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
         Private Shared Sub GetDisplayClassVariables(
             method As MethodSymbol,
             locals As ImmutableArray(Of LocalSymbol),
-            hoistedLocalFieldNames As ImmutableHashSet(Of String),
+            inScopeHoistedLocals As InScopeHoistedLocals,
             <Out> ByRef displayClassVariableNamesInOrder As ImmutableArray(Of String),
             <Out> ByRef displayClassVariables As ImmutableDictionary(Of String, DisplayClassVariable),
             <Out> ByRef hoistedParameterNames As ImmutableHashSet(Of String))
@@ -1017,7 +1017,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
                         displayClassVariableNamesInOrderBuilder,
                         displayClassVariablesBuilder,
                         parameterNames,
-                        hoistedLocalFieldNames,
+                        inScopeHoistedLocals,
                         instance,
                         pooledHoistedParameterNames)
                 Next
@@ -1136,7 +1136,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             displayClassVariableNamesInOrder As ArrayBuilder(Of String),
             displayClassVariablesBuilder As Dictionary(Of String, DisplayClassVariable),
             parameterNames As HashSet(Of String),
-            hoistedLocalFieldNames As ImmutableHashSet(Of String),
+            inScopeHoistedLocals As InScopeHoistedLocals,
             instance As DisplayClassInstanceAndFields,
             hoistedParameterNames As HashSet(Of String))
 
@@ -1165,7 +1165,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
                     variableKind = DisplayClassVariableKind.Local
                     variableName = Nothing
                     Dim unusedIndex As Integer = Nothing
-                    If Not hoistedLocalFieldNames.Contains(fieldName) OrElse Not GeneratedNames.TryParseStateMachineHoistedUserVariableName(fieldName, variableName, unusedIndex) Then
+                    If Not inScopeHoistedLocals.IsInScope(fieldName) OrElse Not GeneratedNames.TryParseStateMachineHoistedUserVariableName(fieldName, variableName, unusedIndex) Then
                         Continue For
                     End If
                 ElseIf IsHoistedMeFieldName(fieldName) Then

src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/EvaluationContext.vb

@@ -35,7 +35,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
         Private ReadOnly _metadataDecoder As MetadataDecoder
         Private ReadOnly _currentFrame As MethodSymbol
         Private ReadOnly _locals As ImmutableArray(Of LocalSymbol)
-        Private ReadOnly _hoistedLocalFieldNames As ImmutableHashSet(Of String)
+        Private ReadOnly _inScopeHoistedLocals As InScopeHoistedLocals
         Private ReadOnly _methodDebugInfo As MethodDebugInfo
 
         Private Sub New(
@@ -45,7 +45,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             metadataDecoder As MetadataDecoder,
             currentFrame As MethodSymbol,
             locals As ImmutableArray(Of LocalSymbol),
-            hoistedLocalFieldNames As ImmutableHashSet(Of String),
+            inScopeHoistedLocals As InScopeHoistedLocals,
             methodDebugInfo As MethodDebugInfo)
 
             Me.MetadataBlocks = metadataBlocks
@@ -54,7 +54,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             _metadataDecoder = metadataDecoder
             _currentFrame = currentFrame
             _locals = locals
-            _hoistedLocalFieldNames = hoistedLocalFieldNames
+            _inScopeHoistedLocals = inScopeHoistedLocals
             _methodDebugInfo = methodDebugInfo
         End Sub
 
@@ -94,7 +94,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
                 metadataDecoder,
                 currentFrame,
                 locals:=Nothing,
-                hoistedLocalFieldNames:=Nothing,
+                inScopeHoistedLocals:=Nothing,
                 methodDebugInfo:=Nothing)
         End Function
 
@@ -149,8 +149,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             Dim currentFrame = compilation.GetMethod(moduleVersionId, methodHandle)
             Debug.Assert(currentFrame IsNot Nothing)
             Dim metadataDecoder = New MetadataDecoder(DirectCast(currentFrame.ContainingModule, PEModuleSymbol), currentFrame)
-            Dim hoistedLocalFieldNames As ImmutableHashSet(Of String) = Nothing
-            Dim localNames = GetLocalNames(containingScopes, hoistedLocalFieldNames)
+            Dim inScopeHoistedLocalNames As ImmutableHashSet(Of String) = Nothing
+            Dim localNames = GetLocalNames(containingScopes, inScopeHoistedLocalNames)
             Dim localInfo = metadataDecoder.GetLocalInfo(localSignatureToken)
             Dim localBuilder = ArrayBuilder(Of LocalSymbol).GetInstance()
             GetLocals(localBuilder, currentFrame, localNames, localInfo)
@@ -160,13 +160,18 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             Dim locals = localBuilder.ToImmutableAndFree()
 
             Dim methodDebugInfo As MethodDebugInfo
+            Dim inScopeHoistedLocals As InScopeHoistedLocals
             If IsDteeEntryPoint(currentFrame) Then
                 methodDebugInfo = SynthesizeMethodDebugInfoForDtee(lazyAssemblyReaders.Value)
+                Debug.Assert(inScopeHoistedLocalNames.Count = 0)
+                inScopeHoistedLocals = InScopeHoistedLocals.Empty
             ElseIf typedSymReader IsNot Nothing Then
                 ' TODO (https://github.com/dotnet/roslyn/issues/702): Switch on the type of typedSymReader and call the appropriate helper.
                 methodDebugInfo = typedSymReader.GetMethodDebugInfo(methodToken, methodVersion)
+                InScopeHoistedLocals = New VisualBasicInScopeHoistedLocalsByName(inScopeHoistedLocalNames)
             Else
                 methodDebugInfo = Nothing
+                InScopeHoistedLocals = InScopeHoistedLocals.Empty
             End If
 
             Return New EvaluationContext(
@@ -176,24 +181,24 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
                 metadataDecoder,
                 currentFrame,
                 locals,
-                hoistedLocalFieldNames,
+                InScopeHoistedLocals,
                 methodDebugInfo)
         End Function
 
-        Private Shared Function GetLocalNames(scopes As ArrayBuilder(Of ISymUnmanagedScope), <Out> ByRef hoistedLocalFieldNames As ImmutableHashSet(Of String)) As ImmutableArray(Of String)
+        Private Shared Function GetLocalNames(scopes As ArrayBuilder(Of ISymUnmanagedScope), <Out> ByRef inScopeHoistedLocalNames As ImmutableHashSet(Of String)) As ImmutableArray(Of String)
             Dim localNames = ArrayBuilder(Of String).GetInstance()
-            Dim hoistedLocalFieldNamesBuilder As ImmutableHashSet(Of String).Builder = Nothing
+            Dim inScopeHoistedLocalsBuilder As ImmutableHashSet(Of String).Builder = Nothing
             For Each localName In scopes.GetLocalNames()
                 If localName IsNot Nothing AndAlso localName.StartsWith(StringConstants.StateMachineHoistedUserVariablePrefix, StringComparison.Ordinal) Then
-                    If hoistedLocalFieldNamesBuilder Is Nothing Then
-                        hoistedLocalFieldNamesBuilder = ImmutableHashSet.CreateBuilder(Of String)()
+                    If inScopeHoistedLocalsBuilder Is Nothing Then
+                        inScopeHoistedLocalsBuilder = ImmutableHashSet.CreateBuilder(Of String)()
                     End If
-                    hoistedLocalFieldNamesBuilder.Add(localName)
+                    inScopeHoistedLocalsBuilder.Add(localName)
                 Else
                     localNames.Add(localName)
                 End If
             Next
-            hoistedLocalFieldNames = If(hoistedLocalFieldNamesBuilder Is Nothing, ImmutableHashSet(Of String).Empty, hoistedLocalFieldNamesBuilder.ToImmutable())
+            inScopeHoistedLocalNames = If(inScopeHoistedLocalsBuilder Is Nothing, ImmutableHashSet(Of String).Empty, inScopeHoistedLocalsBuilder.ToImmutable())
             Return localNames.ToImmutableAndFree()
         End Function
 
@@ -302,7 +307,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
                 _metadataDecoder,
                 _currentFrame,
                 _locals,
-                _hoistedLocalFieldNames,
+                _inScopeHoistedLocals,
                 _methodDebugInfo,
                 syntax)
         End Function

src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/VisualBasicInScopeHoistedLocalsByName.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 Microsoft.CodeAnalysis.ExpressionEvaluator
+
+Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
+
+    Friend NotInheritable Class VisualBasicInScopeHoistedLocalsByName
+        Inherits InScopeHoistedLocals
+
+        Private ReadOnly _fieldNames As ImmutableHashSet(Of String)
+
+        Public Sub New(fieldNames As ImmutableHashSet(Of String))
+            _fieldNames = fieldNames
+        End Sub
+
+        Public Overrides Function IsInScope(fieldName As String) As Boolean
+            Return _fieldNames.Contains(fieldName)
+        End Function
+    End Class
+End Namespace