Merged PR 694738: Migrate to the latest C# compiler that supports C# 11

Migrate to the latest C# compiler that supports C# 11

The PR adds 'RequiredMemberAttribute' to support 'required' members from C# 11.

The latest compiler changed the behavior for '<<' operator making it checked. This PR addresses this by using 'unchecked' in the cases where the overflow is possible.

Related work items: #2017950

Public/Sdk/Public/Managed/Tools/Csc/csc.dsc

@@ -5,13 +5,9 @@ import {Artifact, Cmd, Tool, Transformer} from "Sdk.Transformers";
 import * as Shared from "Sdk.Managed.Shared";
 import * as RoslynAnalyzers from "Sdk.Managed.Tools.RoslynAnalyzers";
 
-const pkgContents = Context.getCurrentHost().os === "win"
-    ? importFrom("Microsoft.Net.Compilers").Contents.all
-    : importFrom("Microsoft.NETCore.Compilers").Contents.all;
+const pkgContents = importFrom("Microsoft.Net.Compilers.Toolset").Contents.all;
 
-const cscTool = Context.getCurrentHost().os === "win"
-    ? r`tools/csc.exe`
-    : r`tools/bincore/csc.dll`;
+const cscTool = r`tasks/net6.0/bincore/csc.dll`;
 
 export const tool: Transformer.ToolDefinition = Shared.Factory.createTool({
     exe: pkgContents.getFile(cscTool),
@@ -190,15 +186,16 @@ export function compile(inputArgs: Arguments) : Result {
         // compensate for the unobserved ones.
         unsafe: args.shared ?
             {
-                childProcessesToBreakawayFromSandbox: isCurrentHostOsWindows
-                    ? [ a`VBCSCompiler.exe` ]
-                    : [ a`dotnet` ],
+                childProcessesToBreakawayFromSandbox: isCurrentHostOsWindows ? [a`dotnet.exe`] : [a`dotnet`],
+
                 trustStaticallyDeclaredAccesses: true,
             } : undefined,
     };
 
+    // Microsoft.Net.Compilers.Toolset contains csc.dll for all platforms.
+    cscExecuteArgs = importFrom("Sdk.Managed.Frameworks").Helpers.wrapInDotNetExeForCurrentOs(getDotNetCoreVersion(cscExecuteArgs), cscExecuteArgs);
+
     if (!isCurrentHostOsWindows) {
-        cscExecuteArgs = importFrom("Sdk.Managed.Frameworks").Helpers.wrapInDotNetExeForCurrentOs(getDotNetCoreVersion(cscExecuteArgs), cscExecuteArgs);
         cscExecuteArgs = cscExecuteArgs.merge<Transformer.ExecuteArguments>({
             tool: { 
                 // Conceptually, we want to set 'dependsOnCurrentHostOSDirectories' to true and not specify 'untrackedDirectoryScopes' here;

Public/Sdk/SelfHost/BuildXL/BuildXLSdk.dsc

@@ -463,7 +463,7 @@ export function test(args: TestArguments) : TestResult {
 export const notNullAttributesFile = f`NotNullAttributes.cs`;
 
 const callerArgumentExpressionAttributeFile = f`CallerArgumentExpressionAttribute.cs`;
-
+const requiredAttributeFile = f`RequiredAttribute.cs`;
 const isExternalInit = f`IsExternalInit.cs`;
 
 /**
@@ -848,6 +848,14 @@ function processArguments(args: Arguments, targetType: Csc.TargetType) : Argumen
         });
     }
 
+    // Required members is needed for non .net7 target frameworks.
+    // Uncomment once the .net7 PR is in.
+    // if (qualifier.targetFramework !== "net7.0") {
+        args = args.merge({
+            sources: [requiredAttributeFile]
+        });
+    // }
+
     // Adding 'CallerArgumentExpressionAttribute' unless spcified not to.
     if (!isDotNetCoreApp && args.addCallerArgumentExpressionAttribute !== false) {
         args = args.merge({

Public/Sdk/SelfHost/BuildXL/RequiredAttribute.cs

@@ -0,0 +1,35 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+// Copied from https://github/dotnet/runtime
+
+#if !NET7_0_OR_GREATER
+
+namespace System.Runtime.CompilerServices;
+
+/// <summary>Specifies that a type has required members or that a member is required.</summary>
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
+internal sealed class RequiredMemberAttribute : Attribute { }
+
+/// <summary>
+/// Indicates that compiler support for a particular feature is required for the location where this attribute is applied.
+/// </summary>
+[AttributeUsage(AttributeTargets.All, AllowMultiple = true, Inherited = false)]
+internal sealed class CompilerFeatureRequiredAttribute : Attribute
+{
+    public CompilerFeatureRequiredAttribute(string featureName)
+    {
+        FeatureName = featureName;
+    }
+
+    /// <summary>
+    /// The name of the compiler feature.
+    /// </summary>
+    public string FeatureName { get; }
+
+    /// <summary>
+    /// If true, the compiler can choose to allow access to the location where this attribute is applied if it does not understand <see cref="FeatureName"/>.
+    /// </summary>
+    public bool IsOptional { get; init; }
+}
+#endif

Public/Src/Cache/ContentStore/Distributed/NuCache/BinManager.cs

@@ -225,8 +225,11 @@ namespace BuildXL.Cache.ContentStore.Distributed.NuCache
         /// </param>
         public Result<MachineId[]> GetDesignatedLocations(ContentHash hash, bool includeExpired)
         {
-            uint binNumber = (uint)((hash[0] | hash[1] << 8) % NumberOfBins);
-            return GetDesignatedLocations(binNumber, includeExpired);
+            unchecked
+            {
+                uint binNumber = (uint)((hash[0] | hash[1] << 8) % NumberOfBins);
+                return GetDesignatedLocations(binNumber, includeExpired);
+            }
         }
 
         /// <nodoc />

Public/Src/Cache/ContentStore/Distributed/NuCache/MachineIdSets/BitMachineIdSet.cs

@@ -163,7 +163,13 @@ namespace BuildXL.Cache.ContentStore.Distributed.NuCache
                         yield return new MachineId(((i - Offset) * 8) + position);
                     }
 
-                    @char <<= 1;
+                    // C# 11 compiler makes the '<<' operator checked potentially causing OverflowException
+                    // if @char will get above byte.MaxValue.
+                    unchecked
+                    {
+                        @char <<= 1;
+                    }
+                    
                     position++;
                 }
             }
@@ -206,7 +212,13 @@ namespace BuildXL.Cache.ContentStore.Distributed.NuCache
                     machineIdIndex++;
                 }
 
-                redisChar <<= 1;
+                // C# 11 compiler makes the '<<' operator checked potentially causing OverflowException
+                // if @char will get above byte.MaxValue.
+                unchecked
+                {
+                    redisChar <<= 1;
+                }
+                
                 position++;
             }
 
@@ -225,7 +237,10 @@ namespace BuildXL.Cache.ContentStore.Distributed.NuCache
 
             // The bit mask uses the most significant bits to specify lower machine ids.
             // It means that 0b10000010 is translated into machines 0 and 6, but not 1 and 7.
-            return (data[dataIndex] & (1 << (7 - (index % 8)))) != 0;
+            unchecked
+            {
+                return (data[dataIndex] & (1 << (7 - (index % 8)))) != 0;
+            }
         }
         
         private static void SetValue(byte[] data, int offset, int index, bool value)

Public/Src/Cache/ContentStore/Distributed/NuCache/PartitionId.cs

@@ -103,9 +103,12 @@ namespace BuildXL.Cache.ContentStore.Distributed.NuCache
             partitionCount = Math.Min(Math.Max(minValue, partitionCount), maxValue);
 
             // Round to power of two
-            var powerOfTwo = Bits.HighestBitSet((uint)partitionCount);
-            partitionCount = (int)(powerOfTwo < partitionCount ? powerOfTwo << 1 : powerOfTwo);
-            return partitionCount;
+            unchecked
+            {
+                var powerOfTwo = Bits.HighestBitSet((uint)partitionCount);
+                partitionCount = (int)(powerOfTwo < partitionCount ? powerOfTwo << 1 : powerOfTwo);
+                return partitionCount;
+            }
         }
     }
 }

Public/Src/Cache/ContentStore/Hashing/DedupNode.cs

@@ -211,7 +211,11 @@ namespace BuildXL.Cache.ContentStore.Hashing
             {
                 int bitShift = 8 * i;
                 ulong b = br.ReadByte();
-                b <<= bitShift;
+                unchecked
+                {
+                    b <<= bitShift;
+                }
+                
                 value |= b;
             }
 

Public/Src/Cache/ContentStore/Interfaces/FileSystem/FileInfo.cs

@@ -9,16 +9,16 @@ namespace BuildXL.Cache.ContentStore.Interfaces.FileSystem
     ///     Information about a file.
     /// </summary>
     [SuppressMessage("Microsoft.Performance", "CA1815:OverrideEqualsAndOperatorEqualsOnValueTypes")]
-    public struct FileInfo
+    public readonly struct FileInfo
     {
         /// <summary>
         ///     Full path to the file.
         /// </summary>
-        public AbsolutePath FullPath;
+        public required AbsolutePath FullPath { get; init; }
 
         /// <summary>
         ///     Size of the file in bytes.
         /// </summary>
-        public long Length;
+        public required long Length { get; init; }
     }
 }

Public/Src/Cache/ContentStore/InterfacesTest/Hashing/ShortReadOnlyFixedBytesTests.cs

@@ -111,7 +111,7 @@ namespace BuildXL.Cache.ContentStore.InterfacesTest.Hashing
             Assert.Equal(v1, v2);
         }
 
-        private ReadOnlySpan<byte> ToSpan(ReadOnlyFixedBytes fixedBytes)
+        private ReadOnlySpan<byte> ToSpan(in ReadOnlyFixedBytes fixedBytes)
         {
 #if NETCOREAPP
             return MemoryHelpers.AsBytesUnsafe(fixedBytes);

Public/Src/Cache/ContentStore/Library/FileSystem/PassThroughFileSystem.cs

@@ -191,7 +191,10 @@ namespace BuildXL.Cache.ContentStore.FileSystem
                         throw ThrowLastWin32Error(path.Path, errorMessage);
                     }
 
-                    return (((ulong)handleInfo.FileIndexHigh) << 32) | handleInfo.FileIndexLow;
+                    unchecked
+                    {
+                        return (((ulong)handleInfo.FileIndexHigh) << 32) | handleInfo.FileIndexLow;
+                    }
                 }
             }
         }

Public/Src/Cache/ContentStore/Library/Service/BufferSerializeContext.cs

@@ -99,7 +99,10 @@ namespace BuildXL.Cache.ContentStore.Service
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public int DeserializeInt32()
         {
-            return _buffer[_offset++] | (_buffer[_offset++] << 8) | (_buffer[_offset++] << 16) | (_buffer[_offset++] << 24);
+            unchecked
+            {
+                return _buffer[_offset++] | (_buffer[_offset++] << 8) | (_buffer[_offset++] << 16) | (_buffer[_offset++] << 24);
+            }
         }
 
         /// <summary>
@@ -126,15 +129,18 @@ namespace BuildXL.Cache.ContentStore.Service
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public long DeserializeInt64()
         {
-            return
-                _buffer[_offset++] |
-                (long)_buffer[_offset++] << 8 |
-                (long)_buffer[_offset++] << 16 |
-                (long)_buffer[_offset++] << 24 |
-                (long)_buffer[_offset++] << 32 |
-                (long)_buffer[_offset++] << 40 |
-                (long)_buffer[_offset++] << 48 |
-                (long)_buffer[_offset++] << 56;
+            unchecked
+            {
+                return
+                    _buffer[_offset++] |
+                    (long)_buffer[_offset++] << 8 |
+                    (long)_buffer[_offset++] << 16 |
+                    (long)_buffer[_offset++] << 24 |
+                    (long)_buffer[_offset++] << 32 |
+                    (long)_buffer[_offset++] << 40 |
+                    (long)_buffer[_offset++] << 48 |
+                    (long)_buffer[_offset++] << 56;
+            }
         }
 
         /// <summary>

Public/Src/Cache/ContentStore/Library/Stores/RocksDbFileSystemContentStore.cs

@@ -276,7 +276,10 @@ namespace BuildXL.Cache.ContentStore.Stores
 
             for (var i = 0; i < Math.Min(value.Length, sizeof(long)); i++)
             {
-                output |= ((long)value[i]) << (8 * i);
+                unchecked
+                {
+                    output |= ((long)value[i]) << (8 * i);
+                }
             }
             return output;
         }

Public/Src/FrontEnd/Script/Ast/Expressions/AssignmentExpression.cs

@@ -145,7 +145,10 @@ namespace BuildXL.FrontEnd.Script.Expressions
                                 Converter.ExpectNumber(value, position: 1), LocationForLogging(context, env));
                             break;
                         case AssignmentOperator.LeftShiftAssignment:
-                            frame[Index] = NumberLiteral.Box(Converter.ExpectNumber(frame[Index], position: 0) << Converter.ExpectNumber(value, position: 1));
+                            unchecked
+                            {
+                                frame[Index] = NumberLiteral.Box(Converter.ExpectNumber(frame[Index], position: 0) << Converter.ExpectNumber(value, position: 1));
+                            }
                             break;
                         case AssignmentOperator.RightShiftAssignment:
                             frame[Index] = NumberLiteral.Box(NumberOperations.SignPropagatingRightShift(

Public/Src/FrontEnd/Script/Ast/Expressions/BinaryExpression.cs

@@ -201,7 +201,10 @@ namespace BuildXL.FrontEnd.Script.Expressions
 
                             break;
                         case BinaryOperator.LeftShift:
-                            return EvaluationResult.Create(Converter.ExpectNumber(left, position: 0) << Converter.ExpectNumber(right, position: 1));
+                            unchecked
+                            {
+                                return EvaluationResult.Create(Converter.ExpectNumber(left, position: 0) << Converter.ExpectNumber(right, position: 1));
+                            }
                         case BinaryOperator.SignPropagatingRightShift:
                             return EvaluationResult.Create(NumberOperations.SignPropagatingRightShift(
                                     Converter.ExpectNumber(left, position: 0),

Public/Src/FrontEnd/Script/RuntimeModel/AstBridge/ConstantEvaluator.cs

@@ -86,8 +86,10 @@ namespace BuildXL.FrontEnd.Script.RuntimeModel.AstBridge
                                     return Script.Core.NumberOperations.SignPropagatingRightShift(left.Value, right.Value);
 
                                 case TypeScript.Net.Types.SyntaxKind.LessThanLessThanToken:
-                                    return GetNumber(left) << GetNumber(right);
-
+                                    unchecked
+                                    {
+                                        return GetNumber(left) << GetNumber(right);
+                                    }
                                 case TypeScript.Net.Types.SyntaxKind.AsteriskToken:
                                     return GetNumber(left) * GetNumber(right);
                                 case TypeScript.Net.Types.SyntaxKind.SlashToken:

Public/Src/FrontEnd/TypeScript.Net/TypeScript.Net/Types/Number.cs

@@ -83,7 +83,10 @@ namespace TypeScript.Net.Types
         /// <nodoc />
         public static Number operator <<(Number left, int right)
         {
-            return new Number(left.AsInt64() << right);
+            unchecked
+            {
+                return new Number(left.AsInt64() << right);
+            }
         }
 
         /// <nodoc />

Public/Src/Utilities/Utilities/FileArtifactWithAttributes.cs

@@ -85,7 +85,10 @@ namespace BuildXL.Utilities
             Contract.Requires(((byte)fileExistence) <= MaxFileExistence);
 
             m_path = path;
-            m_rewriteCountAndFileExistenceAndFileRewrite = ((uint)rewriteCount | (uint)((byte)fileExistence << RewriteCountSize) | (isUndeclaredFileRewrite ? UndeclaredFileRewriteMask : 0));
+            unchecked
+            {
+                m_rewriteCountAndFileExistenceAndFileRewrite = ((uint)rewriteCount | (uint)((byte)fileExistence << RewriteCountSize) | (isUndeclaredFileRewrite ? UndeclaredFileRewriteMask : 0));
+            }
         }
 
         /// <summary>

Public/Src/Utilities/Utilities/FileEnvelopeId.cs

@@ -369,11 +369,14 @@ namespace BuildXL.Utilities
         {
             // HashCodeHelper performs a stable hash code computation.
             // We take into account the other header fields, and the file length.
-            return HashCodeHelper.Combine(
-                HashCodeHelper.GetOrdinalHashCode64(m_name),
-                HashCodeHelper.GetOrdinalHashCode64(id.Value),
-                Version | (long)(((ulong)(uint)m_version) << 32),
-                length);
+            unchecked
+            {
+                return HashCodeHelper.Combine(
+                    HashCodeHelper.GetOrdinalHashCode64(m_name),
+                    HashCodeHelper.GetOrdinalHashCode64(id.Value),
+                    Version | (long)(((ulong)(uint)m_version) << 32),
+                    length);
+            }
         }
 
         /// <summary>

Public/Src/Utilities/Utilities/HierarchicalNameTable.cs

@@ -1291,7 +1291,7 @@ namespace BuildXL.Utilities
             // The null node has a special owner-less ID (and we don't allow flags on it). Don't add an owner tag or equality would break.
             return index == 0
                     ? new HierarchicalNameId(0)
-                    : new HierarchicalNameId(index | (DebugTag << DebugTagShift));
+                    : new HierarchicalNameId(unchecked(index | (DebugTag << DebugTagShift)));
         }
 
         private static int GetIndexFromId(HierarchicalNameId id)
@@ -1387,7 +1387,7 @@ namespace BuildXL.Utilities
 
             Contract.Assert((int)flags > 0 && (int)flags <= DebugTagValueMask);
 
-            int shiftedFlags = (int)flags << DebugTagShift;
+            int shiftedFlags = unchecked((int)flags << DebugTagShift);
 
             int nodeIndex = GetIndexFromId(name);
             m_nodes.GetEntryBuffer(nodeIndex, out int index, out Node[] buffer);
@@ -1446,7 +1446,7 @@ namespace BuildXL.Utilities
 
             Contract.Assert((int)flags > 0 && (int)flags <= DebugTagValueMask);
 
-            int shiftedFlags = (int)flags << DebugTagShift;
+            int shiftedFlags = unchecked((int)flags << DebugTagShift);
 
             int nodeIndex = GetIndexFromId(name);
             m_nodes.GetEntryBuffer(nodeIndex, out int index, out Node[] buffer);

Public/Src/Utilities/Utilities/Serialization/SpanReader.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 #nullable enable
 
@@ -85,7 +86,17 @@ namespace BuildXL.Utilities.Serialization
             Position += length;
             return result;
         }
-        
+
+        /// <nodoc />
+        public ReadOnlySpan<T> Read<T>(int count)
+            where T : unmanaged
+        {
+            // Reading a span instead of reading bytes to avoid unnecessary allocations.
+            var itemSpan = ReadSpan(Unsafe.SizeOf<T>() * count);
+            var result = MemoryMarshal.Cast<byte, T>(itemSpan);
+            return result;
+        }
+
         internal void EnsureLength(int minLength)
         {
             if (RemainingLength < minLength)

Public/Src/Utilities/Utilities/Serialization/SpanSerializationExtensions.cs

@@ -143,7 +143,10 @@ namespace BuildXL.Utilities.Serialization
             {
                 // ReadByte handles end of stream cases for us.
                 byteReadJustNow = reader.ReadByte();
-                result |= (byteReadJustNow & 0x7Fu) << shift;
+                unchecked
+                {
+                    result |= (byteReadJustNow & 0x7Fu) << shift;
+                }
 
                 if (byteReadJustNow <= 0x7Fu)
                 {
@@ -240,16 +243,6 @@ namespace BuildXL.Utilities.Serialization
             return result;
         }
 
-        /// <nodoc />
-        public static ReadOnlySpan<T> Read<T>(this ref SpanReader reader, int count)
-            where T : unmanaged
-        {
-            // Reading a span instead of reading bytes to avoid unnecessary allocations.
-            var itemSpan = reader.ReadSpan(Unsafe.SizeOf<T>() * count);
-            var result = MemoryMarshal.Cast<byte, T>(itemSpan);
-            return result;
-        }
-
         /// <nodoc />
         public static void Write(this ref SpanWriter writer, byte value) => writer.WriteByte(value); // Using a special overload instead of using a generic method for performance reasons
         

Public/Src/Utilities/Utilities/StringBuilderSegment.cs

@@ -124,7 +124,7 @@ namespace BuildXL.Utilities
             int end = m_index + Length;
             for (int i = m_index; i < end; i++)
             {
-                var storedCh = (char)((buffer[index++] << 8) | buffer[index++]);
+                var storedCh = unchecked((char)((buffer[index++] << 8) | buffer[index++]));
                 if (storedCh != m_value[i])
                 {
                     return false;

Public/Src/Utilities/Utilities/StringSegment.cs

@@ -147,7 +147,7 @@ namespace BuildXL.Utilities
             int end = m_index + Length;
             for (int i = m_index; i < end; i++)
             {
-                var storedCh = (char)((buffer[index++] << 8) | buffer[index++]);
+                var storedCh = unchecked((char)((buffer[index++] << 8) | buffer[index++]));
                 if (storedCh != m_value[i])
                 {
                     return false;

Public/Src/Utilities/Utilities/StringTable.cs

@@ -358,8 +358,8 @@ namespace BuildXL.Utilities
                 index2++; // skip the marker
                 for (int i = 0; i < length1; i++)
                 {
-                    var ch1 = (char)((buffer1[index1 + (2 * i)] << 8) | buffer1[index1 + (2 * i) + 1]);
-                    var ch2 = (char)((buffer2[index2 + (2 * i)] << 8) | buffer2[index2 + (2 * i) + 1]);
+                    var ch1 = unchecked((char)((buffer1[index1 + (2 * i)] << 8) | buffer1[index1 + (2 * i) + 1]));
+                    var ch2 = unchecked((char)((buffer2[index2 + (2 * i)] << 8) | buffer2[index2 + (2 * i) + 1]));
                     if (ch1.ToUpperInvariantFast() != ch2.ToUpperInvariantFast())
                     {
                         return false;
@@ -491,7 +491,7 @@ namespace BuildXL.Utilities
                 index++; // skip the marker
                 while (length-- > 0)
                 {
-                    var ch = (char)((buffer[index++] << 8) | buffer[index++]);
+                    var ch = unchecked((char)((buffer[index++] << 8) | buffer[index++]));
                     ch = ch.ToUpperInvariantFast();
                     unchecked
                     {
@@ -606,7 +606,7 @@ namespace BuildXL.Utilities
                     if (space < BytesPerBuffer - byteIndex)
                     {
                         // there's room in the buffer so try to claim it
-                        int next = (bufferNum << BytesPerBufferBits) | (byteIndex + space);
+                        int next = unchecked((bufferNum << BytesPerBufferBits) | (byteIndex + space));
                         if (Interlocked.CompareExchange(ref m_nextId, next, current) == current)
                         {
                             // got some room, now go fill it in
@@ -671,12 +671,12 @@ namespace BuildXL.Utilities
                     if (space >= BytesPerBuffer)
                     {
                         // force writing into a fresh buffer
-                        Volatile.Write(ref m_nextId, (bufferNum << BytesPerBufferBits) | BytesPerBufferMask);
+                        Volatile.Write(ref m_nextId, unchecked((bufferNum << BytesPerBufferBits) | BytesPerBufferMask));
                     }
                     else
                     {
                         // force writing into this new buffer
-                        Volatile.Write(ref m_nextId, (bufferNum << BytesPerBufferBits) | space);
+                        Volatile.Write(ref m_nextId, unchecked((bufferNum << BytesPerBufferBits) | space));
                     }
 
                     // go write the string at the base of the new buffer
@@ -808,7 +808,7 @@ namespace BuildXL.Utilities
                 index++; // skip the marker
                 while (length-- > 0)
                 {
-                    destination[destinationIndex++] = (char)((buffer[index++] << 8) | buffer[index++]);
+                    destination[destinationIndex++] = unchecked((char)((buffer[index++] << 8) | buffer[index++]));
                 }
             }
 
@@ -844,7 +844,7 @@ namespace BuildXL.Utilities
                 index++; // skip the marker
                 while (length-- > 0)
                 {
-                    destination.Append((char)((buffer[index++] << 8) | buffer[index++]));
+                    destination.Append(unchecked((char)((buffer[index++] << 8) | buffer[index++])));
                 }
             }
         }

Shared/Scripts/BuildDistributedTest.cmd

@@ -18,7 +18,7 @@ if NOT DEFINED DBD_TESTGEN_COUNT (
 )
 
 if NOT DEFINED TEST_COMMITID (
-    set TEST_COMMITID=9f28a24a2aee8196187349a9e9bc9d6d60c6c901
+    set TEST_COMMITID=e011e12fdabc0011eacd2e9dad95ce0e108c5b8c
 )
 
 set TEST_SOLUTION_ROOT=%ENLISTMENTROOT%\Out\Tests\SMDB

cg/nuget/cgmanifest.json

@@ -1963,6 +1963,15 @@
         }
       }
     },
+    {
+      "Component": {
+        "Type": "NuGet",
+        "NuGet": {
+          "Name": "Microsoft.Net.Compilers.Toolset",
+          "Version": "4.4.0"
+        }
+      }
+    },
     {
       "Component": {
         "Type": "NuGet",

config.dsc

@@ -90,8 +90,11 @@ config({
                 { id: "System.Diagnostics.DiagnosticSource", version: "4.0.0-beta-23516", alias: "System.Diagnostics.DiagnosticsSource.ForEventHub"},
 
                 // Roslyn
+                // The old compiler used by integration tests only.
                 { id: "Microsoft.Net.Compilers", version: "4.0.1" }, // Update Public/Src/Engine/UnitTests/Engine/Test.BuildXL.Engine.dsc if you change the version of Microsoft.Net.Compilers.
                 { id: "Microsoft.NETCore.Compilers", version: "4.0.1" },
+                // The package with an actual csc.dll
+                { id: "Microsoft.Net.Compilers.Toolset", version: "4.4.0" },
 
                 { id: "Microsoft.CodeAnalysis.Common", version: "3.5.0" },
                 { id: "Microsoft.CodeAnalysis.CSharp", version: "3.5.0" },