Merge pull request #2346 from tmat/Fix2284

Enc: Fixes lambda id mapping

src/Compilers/CSharp/Portable/Lowering/LambdaRewriter/LambdaRewriter.cs

@@ -929,7 +929,7 @@ private DebugId GetClosureId(SyntaxNode syntax, ArrayBuilder<ClosureDebugInfo> c
             }
 
             int syntaxOffset = _topLevelMethod.CalculateLocalSyntaxOffset(syntax.SpanStart, syntax.SyntaxTree);
-            closureDebugInfo.Add(new ClosureDebugInfo(syntaxOffset, closureId.Generation));
+            closureDebugInfo.Add(new ClosureDebugInfo(syntaxOffset, closureId));
 
             return closureId;
         }
@@ -977,7 +977,7 @@ private DebugId GetLambdaId(SyntaxNode syntax, ClosureKind closureKind, int clos
             }
 
             int syntaxOffset = _topLevelMethod.CalculateLocalSyntaxOffset(lambdaOrLambdaBodySyntax.SpanStart, lambdaOrLambdaBodySyntax.SyntaxTree);
-            _lambdaDebugInfoBuilder.Add(new LambdaDebugInfo(syntaxOffset, closureOrdinal, lambdaId.Generation));
+            _lambdaDebugInfoBuilder.Add(new LambdaDebugInfo(syntaxOffset, lambdaId, closureOrdinal));
             return lambdaId;
         }
 

src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueClosureTests.cs

@@ -914,7 +914,7 @@ public void F()
         }
 
         [Fact]
-        public void LambdasMultipleGenerations()
+        public void LambdasMultipleGenerations1()
         {
             var source0 = MarkedSource(@"
 using System;
@@ -1134,6 +1134,148 @@ .locals init (int V_0)
 ");
         }
 
+        [Fact, WorkItem(2284, "https://github.com/dotnet/roslyn/issues/2284")]
+        public void LambdasMultipleGenerations2()
+        {
+            var source0 = MarkedSource(@"
+using System;
+using System.Linq;
+
+class C
+{
+    private int[] _titles = new int[] { 1, 2 };
+    Action A;
+
+    private void F()
+    {
+        // edit 1
+        // var z = from title in _titles
+        //         where title > 0 
+        //         select title;
+
+        A += <N:0>() =>
+        <N:1>{
+            Console.WriteLine(1);
+
+            // edit 2
+            // Console.WriteLine(2);
+        }</N:1></N:0>;
+    }
+}");
+            var source1 = MarkedSource(@"
+using System;
+using System.Linq;
+
+class C
+{
+    private int[] _titles = new int[] { 1, 2 };
+    Action A;
+
+    private void F()
+    {
+        // edit 1
+        var <N:3>z = from title in _titles 
+                     <N:2>where title > 0</N:2>
+                     select title</N:3>;
+
+        A += <N:0>() =>
+        <N:1>{
+            Console.WriteLine(1);
+
+            // edit 2
+            // Console.WriteLine(2);
+        }</N:1></N:0>;
+    }
+}");
+            var source2 = MarkedSource(@"
+using System;
+using System.Linq;
+
+class C
+{
+    private int[] _titles = new int[] { 1, 2 };
+    Action A;
+
+    private void F()
+    {
+        // edit 1
+        var <N:3>z = from title in _titles
+                     <N:2>where title > 0</N:2> 
+                     select title</N:3>;
+
+        A += <N:0>() =>
+        <N:1>{
+            Console.WriteLine(1);
+
+            // edit 2
+            Console.WriteLine(2);
+        }</N:1></N:0>;
+    }
+}");
+
+            var compilation0 = CreateCompilationWithMscorlib(source0.Tree, new[] { SystemCoreRef }, options: ComSafeDebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            var compilation1 = compilation0.WithSource(source1.Tree);
+            var compilation2 = compilation1.WithSource(source2.Tree);
+            var v0 = CompileAndVerify(compilation0);
+            var md0 = ModuleMetadata.CreateFromImage(v0.EmittedAssemblyData);
+
+            var f0 = compilation0.GetMember<MethodSymbol>("C.F");
+            var f1 = compilation1.GetMember<MethodSymbol>("C.F");
+            var f2 = compilation2.GetMember<MethodSymbol>("C.F");
+
+            var generation0 = EmitBaseline.CreateInitialBaseline(md0, v0.CreateSymReader().GetEncMethodDebugInfo);
+
+            var diff1 = compilation1.EmitDifference(
+                generation0,
+                ImmutableArray.Create(new SemanticEdit(SemanticEditKind.Update, f0, f1, GetSyntaxMapFromMarkers(source0, source1), preserveLocalVariables: true)));
+
+            var md1 = diff1.GetMetadata();
+            var reader1 = md1.Reader;
+
+            // new lambda "<F>b__2_0#1" has been added:
+            diff1.VerifySynthesizedMembers(
+                "C: {<>c}",
+                "C.<>c: {<>9__2_0#1, <>9__2_0, <F>b__2_0#1, <F>b__2_0}");
+
+            // lambda body unchanged:
+            diff1.VerifyIL("C.<>c.<F>b__2_0", @"
+{
+  // Code size       11 (0xb)
+  .maxstack  1
+  IL_0000:  nop
+  IL_0001:  ldc.i4.1
+  IL_0002:  call       ""void System.Console.WriteLine(int)""
+  IL_0007:  nop
+  IL_0008:  br.s       IL_000a
+  IL_000a:  ret
+}");
+
+            var diff2 = compilation2.EmitDifference(
+                diff1.NextGeneration,
+                ImmutableArray.Create(new SemanticEdit(SemanticEditKind.Update, f1, f2, GetSyntaxMapFromMarkers(source1, source2), preserveLocalVariables: true)));
+
+            // no new members:
+            diff2.VerifySynthesizedMembers(
+                "C: {<>c}",
+                "C.<>c: {<>9__2_0#1, <>9__2_0, <F>b__2_0#1, <F>b__2_0}");
+
+            // lambda body updated:
+            diff2.VerifyIL("C.<>c.<F>b__2_0", @"
+{
+  // Code size       18 (0x12)
+  .maxstack  1
+  IL_0000:  nop
+  IL_0001:  ldc.i4.1
+  IL_0002:  call       ""void System.Console.WriteLine(int)""
+  IL_0007:  nop
+  IL_0008:  ldc.i4.2
+  IL_0009:  call       ""void System.Console.WriteLine(int)""
+  IL_000e:  nop
+  IL_000f:  br.s       IL_0011
+  IL_0011:  ret
+}");
+        }
+
         [Fact]
         public void UniqueSynthesizedNames1()
         {

src/Compilers/Core/CodeAnalysisTest/Emit/CustomDebugInfoTests.cs

@@ -214,14 +214,14 @@ public void EditAndContinueLambdaAndClosureMap_NegativeSyntaxOffsets()
             var slots = ImmutableArray<LocalSlotDebugInfo>.Empty;
 
             var closures = ImmutableArray.Create(
-                new ClosureDebugInfo(-100, 0),
-                new ClosureDebugInfo(10, 0),
-                new ClosureDebugInfo(-200, 0));
+                new ClosureDebugInfo(-100, new DebugId(0, 0)),
+                new ClosureDebugInfo(10, new DebugId(1, 0)),
+                new ClosureDebugInfo(-200, new DebugId(2, 0)));
 
             var lambdas = ImmutableArray.Create(
-                new LambdaDebugInfo(20, 1, 0),
-                new LambdaDebugInfo(-50, 0, 0),
-                new LambdaDebugInfo(-180, LambdaDebugInfo.StaticClosureOrdinal, 0));
+                new LambdaDebugInfo(20, new DebugId(0, 0), 1),
+                new LambdaDebugInfo(-50, new DebugId(1, 0), 0),
+                new LambdaDebugInfo(-180, new DebugId(2, 0), LambdaDebugInfo.StaticClosureOrdinal));
 
             var customMetadata = new Cci.MemoryStream();
             var cmw = new Cci.BinaryWriter(customMetadata);
@@ -244,7 +244,7 @@ public void EditAndContinueLambdaAndClosureMap_NoClosures()
             var slots = ImmutableArray<LocalSlotDebugInfo>.Empty;
 
             var closures = ImmutableArray<ClosureDebugInfo>.Empty;
-            var lambdas = ImmutableArray.Create(new LambdaDebugInfo(20, LambdaDebugInfo.StaticClosureOrdinal, 0));
+            var lambdas = ImmutableArray.Create(new LambdaDebugInfo(20, new DebugId(0, 0), LambdaDebugInfo.StaticClosureOrdinal));
 
             var customMetadata = new Cci.MemoryStream();
             var cmw = new Cci.BinaryWriter(customMetadata);
@@ -293,14 +293,14 @@ public void EncCdiAlignment()
                new LocalSlotDebugInfo(SynthesizedLocalKind.TryAwaitPendingCaughtException, new LocalDebugId(-20000, 10)));
 
             var closures = ImmutableArray.Create(
-               new ClosureDebugInfo(-100, 0),
-               new ClosureDebugInfo(10, 0),
-               new ClosureDebugInfo(-200, 0));
+               new ClosureDebugInfo(-100, new DebugId(0, 0)),
+               new ClosureDebugInfo(10, new DebugId(1, 0)),
+               new ClosureDebugInfo(-200, new DebugId(2, 0)));
 
             var lambdas = ImmutableArray.Create(
-                new LambdaDebugInfo(20, 1, 0),
-                new LambdaDebugInfo(-50, 0, 0),
-                new LambdaDebugInfo(-180, LambdaDebugInfo.StaticClosureOrdinal, 0));
+                new LambdaDebugInfo(20, new DebugId(0, 0), 1),
+                new LambdaDebugInfo(-50, new DebugId(1, 0), 0),
+                new LambdaDebugInfo(-180, new DebugId(2, 0), LambdaDebugInfo.StaticClosureOrdinal));
 
             var debugInfo = new EditAndContinueMethodDebugInformation(1, slots, closures, lambdas);
             var records = new ArrayBuilder<Cci.MemoryStream>();

src/Compilers/Core/Portable/CodeGen/ClosureDebugInfo.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;
-using Roslyn.Utilities;
 using System.Diagnostics;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CodeGen
 {
+    [DebuggerDisplay("{GetDebuggerDisplay(), nq}")]
     internal struct ClosureDebugInfo : IEquatable<ClosureDebugInfo>
     {
         public readonly int SyntaxOffset;
-        public readonly int Generation;
+        public readonly DebugId ClosureId;
 
-        public ClosureDebugInfo(int syntaxOffset, int generation)
+        public ClosureDebugInfo(int syntaxOffset, DebugId closureId)
         {
-            Debug.Assert(generation >= 0);
-
             SyntaxOffset = syntaxOffset;
-            Generation = generation;
+            ClosureId = closureId;
         }
 
         public bool Equals(ClosureDebugInfo other)
         {
             return SyntaxOffset == other.SyntaxOffset &&
-                   Generation == other.Generation;
+                   ClosureId.Equals(other.ClosureId);
         }
 
         public override bool Equals(object obj)
@@ -32,12 +31,12 @@ public override bool Equals(object obj)
 
         public override int GetHashCode()
         {
-            return Hash.Combine(SyntaxOffset, Generation);
+            return Hash.Combine(SyntaxOffset, ClosureId.GetHashCode());
         }
 
-        public override string ToString()
+        internal string GetDebuggerDisplay()
         {
-            return $"(#{Generation} @{SyntaxOffset})";
+            return $"({ClosureId.GetDebuggerDisplay()} @{SyntaxOffset})";
         }
     }
 }

src/Compilers/Core/Portable/CodeGen/DebugId.cs

@@ -13,6 +13,7 @@ namespace Microsoft.CodeAnalysis.CodeGen
     /// When used for a synthesized method the ordinal and generation numbers are included its name.
     /// For user defined methods the ordinal is included in Custom Debug Information record attached to the method.
     /// </remarks>
+    [DebuggerDisplay("{GetDebuggerDisplay(), nq}")]
     internal struct DebugId : IEquatable<DebugId>
     {
         public const int UndefinedOrdinal = -1;
@@ -51,5 +52,10 @@ public override int GetHashCode()
         {
             return Hash.Combine(this.Ordinal, this.Generation);
         }
+
+        internal string GetDebuggerDisplay()
+        {
+            return (Generation > 0) ? $"{Ordinal}#{Generation}" : Ordinal.ToString();
+        }
     }
 }

src/Compilers/Core/Portable/CodeGen/LambdaDebugInfo.cs

@@ -12,6 +12,7 @@ namespace Microsoft.CodeAnalysis.CodeGen
     /// <remarks>
     /// The information is emitted to PDB in Custom Debug Information record for a method containing the lambda.
     /// </remarks>
+    [DebuggerDisplay("{GetDebuggerDisplay(), nq}")]
     internal struct LambdaDebugInfo : IEquatable<LambdaDebugInfo>
     {
         /// <summary>
@@ -26,27 +27,26 @@ internal struct LambdaDebugInfo : IEquatable<LambdaDebugInfo>
         /// </summary>
         public readonly int ClosureOrdinal;
 
-        public readonly int Generation;
+        public readonly DebugId LambdaId;
 
         public const int StaticClosureOrdinal = -1;
         public const int ThisOnlyClosureOrdinal = -2;
         public const int MinClosureOrdinal = ThisOnlyClosureOrdinal;
 
-        public LambdaDebugInfo(int syntaxOffset, int closureOrdinal, int generation)
+        public LambdaDebugInfo(int syntaxOffset, DebugId lambdaId, int closureOrdinal)
         {
             Debug.Assert(closureOrdinal >= MinClosureOrdinal);
-            Debug.Assert(generation >= 0);
 
             SyntaxOffset = syntaxOffset;
             ClosureOrdinal = closureOrdinal;
-            Generation = generation;
+            LambdaId = lambdaId;
         }
 
         public bool Equals(LambdaDebugInfo other)
         {
             return SyntaxOffset == other.SyntaxOffset
                 && ClosureOrdinal == other.ClosureOrdinal 
-                && Generation == other.Generation;
+                && LambdaId.Equals(other.LambdaId);
         }
 
         public override bool Equals(object obj)
@@ -57,15 +57,15 @@ public override bool Equals(object obj)
         public override int GetHashCode()
         {
             return Hash.Combine(ClosureOrdinal, 
-                   Hash.Combine(SyntaxOffset, Generation));
+                   Hash.Combine(SyntaxOffset, LambdaId.GetHashCode()));
         }
 
-        public override string ToString()
+        internal string GetDebuggerDisplay()
         {
             return 
-                ClosureOrdinal == StaticClosureOrdinal ? $"(#{Generation} @{SyntaxOffset}, static)" :
-                ClosureOrdinal == ThisOnlyClosureOrdinal ? $"(#{Generation} @{SyntaxOffset}, this)" :
-                $"(#{Generation} @{SyntaxOffset} in {ClosureOrdinal})";
+                ClosureOrdinal == StaticClosureOrdinal ? $"({LambdaId.GetDebuggerDisplay()} @{SyntaxOffset}, static)" :
+                ClosureOrdinal == ThisOnlyClosureOrdinal ? $"(#{LambdaId.GetDebuggerDisplay()} @{SyntaxOffset}, this)" :
+                $"({LambdaId.GetDebuggerDisplay()} @{SyntaxOffset} in {ClosureOrdinal})";
         }
     }
 }

src/Compilers/Core/Portable/Emit/EditAndContinue/DefinitionMap.cs

@@ -287,13 +287,13 @@ internal VariableSlotAllocator TryCreateVariableSlotAllocator(EmitBaseline basel
             for (int i = 0; i < lambdaDebugInfo.Length; i++)
             {
                 var lambdaInfo = lambdaDebugInfo[i];
-                lambdas[lambdaInfo.SyntaxOffset] = KeyValuePair.Create(new DebugId(i, lambdaInfo.Generation), lambdaInfo.ClosureOrdinal);
+                lambdas[lambdaInfo.SyntaxOffset] = KeyValuePair.Create(lambdaInfo.LambdaId, lambdaInfo.ClosureOrdinal);
             }
 
             for (int i = 0; i < closureDebugInfo.Length; i++)
             {
                 var closureInfo = closureDebugInfo[i];
-                closures[closureInfo.SyntaxOffset] = new DebugId(i, closureInfo.Generation);
+                closures[closureInfo.SyntaxOffset] = closureInfo.ClosureId;
             }
 
             lambdaMap = lambdas;

src/Compilers/Core/Portable/Emit/EditAndContinueMethodDebugInformation.cs

@@ -209,7 +209,8 @@ internal void SerializeLocalSlots(Cci.BinaryWriter writer)
                     {
                         int syntaxOffset = blobReader.ReadCompressedInteger();
 
-                        closuresBuilder.Add(new ClosureDebugInfo(syntaxOffset + syntaxOffsetBaseline, generation: 0));
+                        var closureId = new DebugId(closuresBuilder.Count, generation: 0);
+                        closuresBuilder.Add(new ClosureDebugInfo(syntaxOffset + syntaxOffsetBaseline, closureId));
                     }
 
                     while (blobReader.RemainingBytes > 0)
@@ -222,7 +223,8 @@ internal void SerializeLocalSlots(Cci.BinaryWriter writer)
                             throw CreateInvalidDataException(compressedLambdaMap, blobReader.Offset);
                         }
 
-                        lambdasBuilder.Add(new LambdaDebugInfo(syntaxOffset + syntaxOffsetBaseline, closureOrdinal, generation: 0));
+                        var lambdaId = new DebugId(lambdasBuilder.Count, generation: 0);
+                        lambdasBuilder.Add(new LambdaDebugInfo(syntaxOffset + syntaxOffsetBaseline, lambdaId, closureOrdinal));
                     }
                 }
                 catch (BadImageFormatException)
@@ -268,7 +270,7 @@ internal void SerializeLambdaMap(Cci.BinaryWriter writer)
             foreach (LambdaDebugInfo info in this.Lambdas)
             {
                 Debug.Assert(info.ClosureOrdinal >= LambdaDebugInfo.MinClosureOrdinal);
-                Debug.Assert(info.Generation == 0);
+                Debug.Assert(info.LambdaId.Generation == 0);
 
                 writer.WriteCompressedUInt((uint)(info.SyntaxOffset - syntaxOffsetBaseline));
                 writer.WriteCompressedUInt((uint)(info.ClosureOrdinal - LambdaDebugInfo.MinClosureOrdinal));

src/Compilers/VisualBasic/Portable/Lowering/LambdaRewriter/LambdaRewriter.vb

@@ -965,7 +965,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             End If
 
             Dim syntaxOffset As Integer = _topLevelMethod.CalculateLocalSyntaxOffset(syntax.SpanStart, syntax.SyntaxTree)
-            closureDebugInfo.Add(New ClosureDebugInfo(syntaxOffset, closureId.Generation))
+            closureDebugInfo.Add(New ClosureDebugInfo(syntaxOffset, closureId))
             Return closureId
         End Function
 
@@ -1006,7 +1006,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             End If
 
             Dim syntaxOffset As Integer = _topLevelMethod.CalculateLocalSyntaxOffset(lambdaOrLambdaBodySyntax.SpanStart, lambdaOrLambdaBodySyntax.SyntaxTree)
-            _lambdaDebugInfoBuilder.Add(New LambdaDebugInfo(syntaxOffset, closureOrdinal, lambdaId.Generation))
+            _lambdaDebugInfoBuilder.Add(New LambdaDebugInfo(syntaxOffset, lambdaId, closureOrdinal))
             Return lambdaId
         End Function
 

src/Compilers/VisualBasic/Test/Emit/Emit/EditAndContinue/EditAndContinueClosureTests.vb

@@ -895,7 +895,7 @@ End Class
         ' TODO: port C# tests, add more VB specific tests
 
         <Fact>
-        Public Sub LambdasMultipleGenerations()
+        Public Sub LambdasMultipleGenerations1()
             Dim source0 = MarkedSource("
 Imports System
 Class C
@@ -1116,5 +1116,138 @@ End Class
 }
 ")
         End Sub
+
+        <Fact, WorkItem(2284, "https://github.com/dotnet/roslyn/issues/2284")>
+        Public Sub LambdasMultipleGenerations2()
+            Dim source0 = MarkedSource("
+Imports System
+Imports System.Linq
+
+Class C
+    Private _titles As Integer() = New Integer() {1, 2}
+    Dim A As Action
+
+    Private Sub F()
+        ' edit 1
+        ' Dim z = From title In _titles
+        '         Where title > 0 
+        '         Select title
+
+        A = <N:0>Sub ()
+            Console.WriteLine(1)
+
+            ' edit 2
+            ' Console.WriteLine(2)
+        End Sub</N:0>
+    End Sub
+End Class
+")
+            Dim source1 = MarkedSource("
+Imports System
+Imports System.Linq
+
+Class C
+    Private _titles As Integer() = New Integer() {1, 2}
+    Dim A As Action
+
+    Private Sub F()
+        ' edit 1
+        Dim <N:3>z</N:3> = From title In _titles
+                           <N:2>Where title > 0</N:2>
+                           Select <N:1:ExpressionRangeVariable>title</N:1>
+
+        A = <N:0>Sub ()
+            Console.WriteLine(1)
+
+            ' edit 2
+            ' Console.WriteLine(2)
+        End Sub</N:0>
+    End Sub
+End Class")
+
+            Dim source2 = MarkedSource("
+Imports System
+Imports System.Linq
+
+Class C
+    Private _titles As Integer() = New Integer() {1, 2}
+    Dim A As Action
+
+    Private Sub F()
+        ' edit 1
+        Dim <N:3>z</N:3> = From title In _titles
+                           <N:2>Where title > 0</N:2>
+                           Select <N:1:ExpressionRangeVariable>title</N:1>
+
+        A = <N:0>Sub ()
+            Console.WriteLine(1)
+
+            ' edit 2
+            Console.WriteLine(2)
+        End Sub</N:0>
+    End Sub
+End Class")
+
+            Dim compilation0 = CreateCompilationWithReferences(source0.Tree, {MscorlibRef, SystemCoreRef}, options:=ComSafeDebugDll.WithMetadataImportOptions(MetadataImportOptions.All))
+            Dim compilation1 = compilation0.WithSource(source1.Tree)
+            Dim compilation2 = compilation1.WithSource(source2.Tree)
+
+            Dim v0 = CompileAndVerify(compilation0)
+            Dim md0 = ModuleMetadata.CreateFromImage(v0.EmittedAssemblyData)
+
+            Dim f0 = compilation0.GetMember(Of MethodSymbol)("C.F")
+            Dim f1 = compilation1.GetMember(Of MethodSymbol)("C.F")
+            Dim f2 = compilation2.GetMember(Of MethodSymbol)("C.F")
+
+            Dim generation0 = EmitBaseline.CreateInitialBaseline(md0, AddressOf v0.CreateSymReader().GetEncMethodDebugInfo)
+
+            Dim diff1 = compilation1.EmitDifference(
+                generation0,
+                ImmutableArray.Create(New SemanticEdit(SemanticEditKind.Update, f0, f1, GetSyntaxMapFromMarkers(source0, source1), preserveLocalVariables:=True)))
+
+            Dim md1 = diff1.GetMetadata()
+            Dim reader1 = md1.Reader
+
+            ' new lambda "_Lambda$__3-0#1" has been added
+            diff1.VerifySynthesizedMembers(
+                "C: {_Closure$__}",
+                "C._Closure$__: {$I3-0#1, $I3-1#1, $I3-0, _Lambda$__3-0#1, _Lambda$__3-1#1, _Lambda$__3-0}")
+
+            ' lambda body unchanged
+            diff1.VerifyIL("C._Closure$__._Lambda$__3-0", "
+{
+  // Code size        9 (0x9)
+  .maxstack  1
+  IL_0000:  nop
+  IL_0001:  ldc.i4.1
+  IL_0002:  call       ""Sub System.Console.WriteLine(Integer)""
+  IL_0007:  nop
+  IL_0008:  ret
+}")
+
+            Dim diff2 = compilation2.EmitDifference(
+                diff1.NextGeneration,
+                ImmutableArray.Create(New SemanticEdit(SemanticEditKind.Update, f1, f2, GetSyntaxMapFromMarkers(source1, source2), preserveLocalVariables:=True)))
+
+            ' no new members
+            diff2.VerifySynthesizedMembers(
+                "C: {_Closure$__}",
+                "C._Closure$__: {$I3-0#1, $I3-1#1, $I3-0, _Lambda$__3-0#1, _Lambda$__3-1#1, _Lambda$__3-0}")
+
+            ' lambda body updated
+            diff2.VerifyIL("C._Closure$__._Lambda$__3-0", "
+{
+  // Code size       16 (0x10)
+  .maxstack  1
+  IL_0000:  nop
+  IL_0001:  ldc.i4.1
+  IL_0002:  call       ""Sub System.Console.WriteLine(Integer)""
+  IL_0007:  nop
+  IL_0008:  ldc.i4.2
+  IL_0009:  call       ""Sub System.Console.WriteLine(Integer)""
+  IL_000e:  nop
+  IL_000f:  ret
+}")
+        End Sub
     End Class
 End Namespace

src/Test/Utilities/SourceWithMarkedNodes.cs

@@ -104,12 +104,22 @@ private SyntaxNode GetNode(SyntaxNode root, ValueTuple<TextSpan, int, int> spanA
         {
             var map0 = source0.MapMarksToSyntaxNodes();
             var map1 = source1.MapSyntaxNodesToMarks();
-
+#if DUMP
+            Console.WriteLine("========");
+#endif
             return new Func<SyntaxNode, SyntaxNode>(node1 =>
             {
                 int mark;
                 SyntaxNode result;
-                return map1.TryGetValue(node1, out mark) && map0.TryGetValue(mark, out result) ? result : null;
+                if (map1.TryGetValue(node1, out mark) && map0.TryGetValue(mark, out result))
+                {
+                    return result;
+                }
+
+#if DUMP
+                Console.WriteLine($"? {node1.RawKind} [[{node1}]]");
+#endif
+                return null;
             });
         }
     }