Revert "Address new warnings"

This reverts commit a03d8b8e.

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LoweredDynamicOperationFactory.cs

@@ -30,7 +30,7 @@ internal LoweredDynamicOperationFactory(SyntheticBoundNodeFactory factory, int m
         // that redefines these constants and is not supposed to run existing programs.
 
         /// <summary>
-        /// Corresponds to Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags.
+        /// Corresponds to <see cref="Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags"/>.
         /// </summary>
         [Flags]
         private enum CSharpBinderFlags
@@ -48,7 +48,7 @@ private enum CSharpBinderFlags
         }
 
         /// <summary>
-        /// Corresponds to Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags.
+        /// Corresponds to <see cref="Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags"/>.
         /// </summary>
         [Flags]
         private enum CSharpArgumentInfoFlags

src/Compilers/CSharp/Portable/Symbols/Attributes/AttributeData.cs

@@ -478,8 +478,8 @@ internal void DecodeClassInterfaceAttribute(AttributeSyntax nodeOpt, DiagnosticB
             switch (interfaceType)
             {
                 case ClassInterfaceType.None:
-                case Cci.Constants.ClassInterfaceType_AutoDispatch:
-                case Cci.Constants.ClassInterfaceType_AutoDual:
+                case ClassInterfaceType.AutoDispatch:
+                case ClassInterfaceType.AutoDual:
                     break;
 
                 default:
@@ -503,8 +503,8 @@ internal void DecodeInterfaceTypeAttribute(AttributeSyntax node, DiagnosticBag d
 
             switch (interfaceType)
             {
-                case Cci.Constants.ComInterfaceType_InterfaceIsDual:
-                case Cci.Constants.ComInterfaceType_InterfaceIsIDispatch:
+                case ComInterfaceType.InterfaceIsDual:
+                case ComInterfaceType.InterfaceIsIDispatch:
                 case ComInterfaceType.InterfaceIsIInspectable:
                 case ComInterfaceType.InterfaceIsIUnknown:
                     break;

src/Compilers/CSharp/Portable/Symbols/Metadata/PE/DynamicTypeDecoder.cs

@@ -9,7 +9,7 @@
 namespace Microsoft.CodeAnalysis.CSharp.Symbols.Metadata.PE
 {
     /// <summary>
-    /// Decodes System.Runtime.CompilerServices.DynamicAttribute applied to a specified metadata symbol and
+    /// Decodes <see cref="System.Runtime.CompilerServices.DynamicAttribute"/> applied to a specified metadata symbol and
     /// transforms the specified metadata type, using the decoded dynamic transforms attribute argument,
     /// by replacing each occurrence of <see cref="System.Object"/> type with dynamic type.
     /// </summary>
@@ -48,10 +48,10 @@ private DynamicTypeDecoder(ImmutableArray<bool> dynamicTransformFlags, bool have
         }
 
         /// <summary>
-        /// Decodes the attributes applied to the given <see paramref="targetSymbol"/> from metadata and checks if System.Runtime.CompilerServices.DynamicAttribute is applied.
+        /// Decodes the attributes applied to the given <see paramref="targetSymbol"/> from metadata and checks if <see cref="System.Runtime.CompilerServices.DynamicAttribute"/> is applied.
         /// If so, it transforms the given <see paramref="metadataType"/>, using the decoded dynamic transforms attribute argument,
         /// by replacing each occurrence of <see cref="System.Object"/> type with dynamic type.
-        /// If no System.Runtime.CompilerServices.DynamicAttribute is applied or the decoded dynamic transforms attribute argument is erroneous,
+        /// If no <see cref="System.Runtime.CompilerServices.DynamicAttribute"/> is applied or the decoded dynamic transforms attribute argument is erroneous,
         /// returns the unchanged <see paramref="metadataType"/>.
         /// </summary>
         /// <remarks>This method is a port of TypeManager::ImportDynamicTransformType from the native compiler.</remarks>

src/Compilers/CSharp/Portable/Symbols/ParameterSymbol.cs

@@ -91,7 +91,7 @@ internal bool IsMarshalAsObject
                 {
                     case UnmanagedType.Interface:
                     case UnmanagedType.IUnknown:
-                    case Cci.Constants.UnmanagedType_IDispatch:
+                    case UnmanagedType.IDispatch:
                         return true;
                 }
 

src/Compilers/Core/Portable/CodeAnalysis.csproj

@@ -14,8 +14,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <SolutionDir Condition="'$(SolutionDir)' == '' OR '$(SolutionDir)' == '*Undefined*'">..\..\..\..\</SolutionDir>
     <TargetFrameworkVersion>v5.0</TargetFrameworkVersion>
-    <TargetFrameworkProfile>
-    </TargetFrameworkProfile>
+    <TargetFrameworkProfile></TargetFrameworkProfile>
     <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <RestorePackages>true</RestorePackages>
     <DefineConstants>$(DefineConstants);COMPILERCORE</DefineConstants>
@@ -367,6 +366,7 @@
     <Compile Include="InternalUtilities\ReadOnlyUnmanagedMemoryStream.cs" />
     <Compile Include="InternalUtilities\ReferenceEqualityComparer.cs" />
     <Compile Include="InternalUtilities\SpecializedCollections.cs" />
+    <Compile Include="InternalUtilities\SpecializedCollections.Empty.Array.cs" />
     <Compile Include="InternalUtilities\SpecializedCollections.Empty.Collection.cs" />
     <Compile Include="InternalUtilities\SpecializedCollections.Empty.cs" />
     <Compile Include="InternalUtilities\SpecializedCollections.Empty.Dictionary.cs" />
@@ -797,4 +797,4 @@
   <ImportGroup Label="Targets">
     <Import Project="..\..\..\..\build\Targets\VSL.Imports.targets" />
   </ImportGroup>
-</Project>
\ No newline at end of file
+</Project>

src/Compilers/Core/Portable/InternalUtilities/HashAlgorithms.cs

@@ -70,7 +70,7 @@ public void TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCo
             s_transformFinalBlock.Invoke(_hashInstance, new object[] { inputBuffer, inputOffset, inputCount });
         }
 
-        public byte[] Hash => (byte[])s_hash.GetMethod.Invoke(_hashInstance, Array.Empty<object>());
+        public byte[] Hash => (byte[])s_hash.GetMethod.Invoke(_hashInstance, new object[] { });
 
         public void Dispose()
         {

src/Compilers/Core/Portable/InternalUtilities/SpecializedCollections.Empty.Array.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 Roslyn.Utilities
+{
+    internal partial class SpecializedCollections
+    {
+        private partial class Empty
+        {
+            internal class Array<T>
+            {
+                public static readonly T[] Instance = new T[0];
+            }
+        }
+    }
+}

src/Compilers/Core/Portable/InternalUtilities/SpecializedCollections.cs

@@ -11,7 +11,7 @@ internal static partial class SpecializedCollections
 
         public static T[] EmptyArray<T>()
         {
-            return System.Array.Empty<T>();
+            return Empty.Array<T>.Instance;
         }
 
         public static IEnumerator<T> EmptyEnumerator<T>()

src/Compilers/Core/Portable/Interop/IVsSQM.cs

@@ -142,24 +142,17 @@ internal interface IVsSqm2
     [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
     internal interface IVsSqmMulti
     {
-#pragma warning disable CS0618 // API is obsolete (https://github.com/dotnet/roslyn/issues/10637)
         [return: MarshalAs(UnmanagedType.VariantBool)]
-#pragma warning restore CS0618
         bool GetOptInStatus();
-
         void UnloadSessions(
             );
         void EndAllSessionsAndAbortUploads(
             );
-
-#pragma warning disable CS0618 // API is obsolete (https://github.com/dotnet/roslyn/issues/10637)
         void BeginSession(
             [In, MarshalAs(UnmanagedType.U4)] System.UInt32 sessionType,
             [In, MarshalAs(UnmanagedType.VariantBool)] System.Boolean alwaysSend,
             [Out, MarshalAs(UnmanagedType.U4)] out System.UInt32 sessionHandle
             );
-#pragma warning restore CS0618
-
         void EndSession(
             [In, MarshalAs(UnmanagedType.U4)] System.UInt32 sessionHandle
             );

src/Compilers/Core/Portable/MetadataReader/PEModule.cs

@@ -1192,8 +1192,8 @@ private static bool IsValidComInterfaceType(int comInterfaceType)
         {
             switch (comInterfaceType)
             {
-                case (int)Cci.Constants.ComInterfaceType_InterfaceIsDual:
-                case (int)Cci.Constants.ComInterfaceType_InterfaceIsIDispatch:
+                case (int)ComInterfaceType.InterfaceIsDual:
+                case (int)ComInterfaceType.InterfaceIsIDispatch:
                 case (int)ComInterfaceType.InterfaceIsIInspectable:
                 case (int)ComInterfaceType.InterfaceIsIUnknown:
                     return true;

src/Compilers/Core/Portable/NativePdbWriter/PdbWriter.cs

@@ -1262,9 +1262,7 @@ private void DefineLocalConstant(string name, object value, PrimitiveTypeCode ty
         private unsafe void DefineLocalConstantImpl(string name, object value, uint sigToken)
         {
             VariantStructure variant = new VariantStructure();
-#pragma warning disable CS0618 // API is obsolete (https://github.com/dotnet/roslyn/issues/10637)
             Marshal.GetNativeVariantForObject(value, new IntPtr(&variant));
-#pragma warning restore CS0618
             _symWriter.DefineConstant2(name, variant, sigToken);
         }
 

src/Compilers/Core/Portable/PEWriter/Constants.cs

@@ -16,17 +16,6 @@ internal static class Constants
 
         // Non-portable UnmanagedType values:
         public const UnmanagedType UnmanagedType_CustomMarshaler = (UnmanagedType)44;
-        public const UnmanagedType UnmanagedType_IDispatch = (UnmanagedType)26;
-        public const UnmanagedType UnmanagedType_SafeArray = (UnmanagedType)29;
-        public const UnmanagedType UnmanagedType_VBByRefStr = (UnmanagedType)34;
-        public const UnmanagedType UnmanagedType_AnsiBStr = (UnmanagedType)35;
-        public const UnmanagedType UnmanagedType_TBStr = (UnmanagedType)36;
-
-        public const ComInterfaceType ComInterfaceType_InterfaceIsDual = 0;
-        public const ComInterfaceType ComInterfaceType_InterfaceIsIDispatch = (ComInterfaceType)2;
-
-        public const ClassInterfaceType ClassInterfaceType_AutoDispatch = (ClassInterfaceType)1;
-        public const ClassInterfaceType ClassInterfaceType_AutoDual = (ClassInterfaceType)2;
 
         // Non-portable CompilationRelaxations value:
         public const int CompilationRelaxations_NoStringInterning = 0x0008;
@@ -118,55 +107,4 @@ internal enum TypeFlags : uint
         RTSpecialNameReserved = 0x00000800,
         HasSecurityReserved = 0x00040000,
     }
-
-    /// <summary>
-    /// System.Runtime.InteropServices.VarEnum is obsolete.
-    /// </summary>
-    internal enum VarEnum
-    {
-        VT_EMPTY = 0,
-        VT_NULL = 1,
-        VT_I2 = 2,
-        VT_I4 = 3,
-        VT_R4 = 4,
-        VT_R8 = 5,
-        VT_CY = 6,
-        VT_DATE = 7,
-        VT_BSTR = 8,
-        VT_DISPATCH = 9,
-        VT_ERROR = 10,
-        VT_BOOL = 11,
-        VT_VARIANT = 12,
-        VT_UNKNOWN = 13,
-        VT_DECIMAL = 14,
-        VT_I1 = 16,
-        VT_UI1 = 17,
-        VT_UI2 = 18,
-        VT_UI4 = 19,
-        VT_I8 = 20,
-        VT_UI8 = 21,
-        VT_INT = 22,
-        VT_UINT = 23,
-        VT_VOID = 24,
-        VT_HRESULT = 25,
-        VT_PTR = 26,
-        VT_SAFEARRAY = 27,
-        VT_CARRAY = 28,
-        VT_USERDEFINED = 29,
-        VT_LPSTR = 30,
-        VT_LPWSTR = 31,
-        VT_RECORD = 36,
-        VT_FILETIME = 64,
-        VT_BLOB = 65,
-        VT_STREAM = 66,
-        VT_STORAGE = 67,
-        VT_STREAMED_OBJECT = 68,
-        VT_STORED_OBJECT = 69,
-        VT_BLOB_OBJECT = 70,
-        VT_CF = 71,
-        VT_CLSID = 72,
-        VT_VECTOR = 0x1000,
-        VT_ARRAY = 0x2000,
-        VT_BYREF = 0x4000
-    }
 }

src/Compilers/Core/Portable/PEWriter/MetadataWriter.cs

@@ -4924,7 +4924,7 @@ private void SerializeMarshallingDescriptor(IMarshallingInformation marshallingI
 
                     break;
 
-                case Constants.UnmanagedType_SafeArray:
+                case UnmanagedType.SafeArray:
                     if (marshallingInformation.SafeArrayElementSubtype >= 0)
                     {
                         writer.WriteCompressedInteger((uint)marshallingInformation.SafeArrayElementSubtype);
@@ -4942,7 +4942,7 @@ private void SerializeMarshallingDescriptor(IMarshallingInformation marshallingI
                     break;
 
                 case UnmanagedType.Interface:
-                case Constants.UnmanagedType_IDispatch:
+                case UnmanagedType.IDispatch:
                 case UnmanagedType.IUnknown:
                     if (marshallingInformation.IidParameterIndex >= 0)
                     {

src/Compilers/Core/Portable/PEWriter/Miscellaneous.cs

@@ -3,8 +3,11 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Reflection;
+using System.Runtime.InteropServices;
+using Roslyn.Utilities;
 using EmitContext = Microsoft.CodeAnalysis.Emit.EmitContext;
 
 namespace Microsoft.Cci
@@ -163,7 +166,7 @@ short ParamIndex
         /// (The element type of a safe array is VARIANT. The "sub type" specifies the value of all of the tag fields (vt) of the element values. )
         /// -1 if it should be omitted from the marshal blob.
         /// </summary>
-        VarEnum SafeArrayElementSubtype
+        System.Runtime.InteropServices.VarEnum SafeArrayElementSubtype
         {
             get;
         }

src/Compilers/Core/Portable/PortableShim.cs

@@ -142,7 +142,7 @@ internal static class Path
 
             internal static readonly Func<string> GetTempFileName = (Func<string>)Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(GetTempFileName), paramTypes: Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(GetTempFileName), paramTypes: new Type[] { })
                 .CreateDelegate(typeof(Func<string>));
         }
 
@@ -441,7 +441,7 @@ internal static class Process
 
             internal static readonly Func<object> GetCurrentProcess = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(GetCurrentProcess), paramTypes: Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(GetCurrentProcess), paramTypes: new Type[] { })
                 .CreateDelegate<Func<object>>();
         }
 
@@ -455,7 +455,7 @@ internal static class RuntimeHelpers
 
             internal static readonly Action EnsureSufficientExecutionStack = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(EnsureSufficientExecutionStack), paramTypes: Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(EnsureSufficientExecutionStack), paramTypes: new Type[] { })
                 .CreateDelegate<Action>();
         }
 
@@ -469,11 +469,11 @@ internal static class StackTrace
 
             private static readonly ConstructorInfo s_Ctor = Type
                 .GetTypeInfo()
-                .GetDeclaredConstructor(Array.Empty<Type>());
+                .GetDeclaredConstructor(new Type[] { });
 
             private static readonly MethodInfo s_ToString = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod("ToString", Array.Empty<Type>());
+                .GetDeclaredMethod("ToString", new Type[] { });
 
             internal static string GetString()
             {
@@ -603,7 +603,7 @@ internal static class SHA1
 
             internal static readonly Func<IDisposable> Create = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(Create), Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(Create), new Type[] { })
                 .CreateDelegate<Func<IDisposable>>();
         }
 
@@ -617,7 +617,7 @@ internal static class SHA256
 
             internal static readonly Func<IDisposable> Create = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(Create), Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(Create), new Type[] { })
                 .CreateDelegate<Func<IDisposable>>();
         }
 
@@ -631,7 +631,7 @@ internal static class SHA384
 
             internal static readonly Func<IDisposable> Create = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(Create), Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(Create), new Type[] { })
                 .CreateDelegate<Func<IDisposable>>();
         }
 
@@ -645,7 +645,7 @@ internal static class SHA512
 
             internal static readonly Func<IDisposable> Create = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(Create), Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(Create), new Type[] { })
                 .CreateDelegate<Func<IDisposable>>();
         }
 
@@ -659,7 +659,7 @@ internal static class MD5
 
             internal static readonly Func<IDisposable> Create = Type
                 .GetTypeInfo()
-                .GetDeclaredMethod(nameof(Create), Array.Empty<Type>())
+                .GetDeclaredMethod(nameof(Create), new Type[] { })
                 .CreateDelegate<Func<IDisposable>>();
         }
     }

src/Compilers/Core/Portable/SqmServiceProvider.cs

@@ -67,9 +67,7 @@ private static QueryServiceDelegate TryGetSqmServiceDelegateCore(string baseDire
                 if (vssqmdll != IntPtr.Zero)
                 {
                     IntPtr queryServicePtr = SqmServiceProvider.GetProcAddress(vssqmdll, "QueryService");
-#pragma warning disable CS0618 // API is obsolete (https://github.com/dotnet/roslyn/issues/10637)
                     return (QueryServiceDelegate)Marshal.GetDelegateForFunctionPointer(queryServicePtr, typeof(QueryServiceDelegate));
-#pragma warning restore CS0618
                 }
             }
             catch (Exception e)

src/Compilers/Core/Portable/StrongName/CryptoBlobParser.cs

@@ -213,10 +213,8 @@ private static ImmutableArray<byte> CreateSnPublicKeyBlob(BlobHeader header, Rsa
 
         private unsafe static bool TryGetPublicKeyFromPublicKeyBlob(byte* blob, int blobLen, out ImmutableArray<byte> publicKey)
         {
-#pragma warning disable CS0618 // API is obsolete (https://github.com/dotnet/roslyn/issues/10637)
             var header = (BlobHeader)Marshal.PtrToStructure((IntPtr)blob, typeof(BlobHeader));
             var rsaPubKey = (RsaPubKey)Marshal.PtrToStructure((IntPtr)(blob + sizeof(BlobHeader)), typeof(RsaPubKey));
-#pragma warning restore CS0618
             var modulus = new byte[rsaPubKey.BitLen >> 3];
 
             // The key blob data just contains the modulus

src/Compilers/Core/Portable/Symbols/Attributes/MarshalAsAttributeDecoder.cs

@@ -25,7 +25,7 @@ internal static void Decode(ref DecodeWellKnownAttributeArguments<TAttributeSynt
                     break;
 
                 case UnmanagedType.Interface:
-                case Cci.Constants.UnmanagedType_IDispatch:
+                case UnmanagedType.IDispatch:
                 case UnmanagedType.IUnknown:
                     DecodeMarshalAsComInterface(ref arguments, unmanagedType, messageProvider);
                     break;
@@ -46,7 +46,7 @@ internal static void Decode(ref DecodeWellKnownAttributeArguments<TAttributeSynt
 
                     break;
 
-                case Cci.Constants.UnmanagedType_SafeArray:
+                case UnmanagedType.SafeArray:
                     DecodeMarshalAsSafeArray(ref arguments, messageProvider);
                     break;
 
@@ -62,7 +62,7 @@ internal static void Decode(ref DecodeWellKnownAttributeArguments<TAttributeSynt
 
                     break;
 
-                case Cci.Constants.UnmanagedType_VBByRefStr:
+                case UnmanagedType.VBByRefStr:
                     if (target == AttributeTargets.Field)
                     {
                         messageProvider.ReportMarshalUnmanagedTypeNotValidForFields(arguments.Diagnostics, arguments.AttributeSyntaxOpt, 0, "VBByRefStr", arguments.Attribute);
@@ -281,7 +281,7 @@ private static void DecodeMarshalAsSafeArray(ref DecodeWellKnownAttributeArgumen
         {
             Debug.Assert((object)arguments.AttributeSyntaxOpt != null);
 
-            Cci.VarEnum? elementTypeVariant = null;
+            VarEnum? elementTypeVariant = null;
             ITypeSymbol elementTypeSymbol = null;
             int symbolIndex = -1;
             bool hasErrors = false;
@@ -292,7 +292,7 @@ private static void DecodeMarshalAsSafeArray(ref DecodeWellKnownAttributeArgumen
                 switch (namedArg.Key)
                 {
                     case "SafeArraySubType":
-                        elementTypeVariant = namedArg.Value.DecodeValue<Cci.VarEnum>(SpecialType.System_Enum);
+                        elementTypeVariant = namedArg.Value.DecodeValue<VarEnum>(SpecialType.System_Enum);
                         if (elementTypeVariant < 0 || (int)elementTypeVariant > MarshalPseudoCustomAttributeData.MaxMarshalInteger)
                         {
                             messageProvider.ReportInvalidNamedArgument(arguments.Diagnostics, arguments.AttributeSyntaxOpt, position, arguments.Attribute.AttributeClass, namedArg.Key);
@@ -320,9 +320,9 @@ private static void DecodeMarshalAsSafeArray(ref DecodeWellKnownAttributeArgumen
 
             switch (elementTypeVariant)
             {
-                case Cci.VarEnum.VT_DISPATCH:
-                case Cci.VarEnum.VT_UNKNOWN:
-                case Cci.VarEnum.VT_RECORD:
+                case VarEnum.VT_DISPATCH:
+                case VarEnum.VT_UNKNOWN:
+                case VarEnum.VT_RECORD:
                     // only these variants accept specification of user defined subtype
                     break;
 

src/Compilers/Core/Portable/Symbols/Attributes/MarshalPseudoCustomAttributeData.cs

@@ -21,7 +21,7 @@ internal sealed class MarshalPseudoCustomAttributeData : Cci.IMarshallingInforma
 
         internal const int Invalid = -1;
         private const UnmanagedType InvalidUnmanagedType = (UnmanagedType)Invalid;
-        private const Cci.VarEnum InvalidVariantType = (Cci.VarEnum)Invalid;
+        private const VarEnum InvalidVariantType = (VarEnum)Invalid;
         internal const int MaxMarshalInteger = 0x1fffffff;
 
         #region Initialization
@@ -66,11 +66,11 @@ internal void SetMarshalAsFixedArray(UnmanagedType? elementType, int? elementCou
             _marshalArrayElementCount = elementCount ?? Invalid;
         }
 
-        internal void SetMarshalAsSafeArray(Cci.VarEnum? elementType, ITypeSymbol elementTypeSymbol)
+        internal void SetMarshalAsSafeArray(VarEnum? elementType, ITypeSymbol elementTypeSymbol)
         {
             Debug.Assert(elementType == null || elementType >= 0 && (int)elementType <= MaxMarshalInteger);
 
-            _marshalType = Cci.Constants.UnmanagedType_SafeArray;
+            _marshalType = UnmanagedType.SafeArray;
             _marshalArrayElementType = (int)(elementType ?? InvalidVariantType);
             _marshalTypeNameOrSymbol = elementTypeSymbol;
         }
@@ -103,7 +103,7 @@ int Cci.IMarshallingInformation.IidParameterIndex
                 Debug.Assert(
                     _marshalType == UnmanagedType.Interface ||
                     _marshalType == UnmanagedType.IUnknown ||
-                    _marshalType == Cci.Constants.UnmanagedType_IDispatch);
+                    _marshalType == UnmanagedType.IDispatch);
 
                 return _marshalParameterIndex;
             }
@@ -137,7 +137,7 @@ int Cci.IMarshallingInformation.NumberOfElements
         {
             get
             {
-                Debug.Assert(_marshalType == UnmanagedType.ByValTStr || _marshalType == UnmanagedType.LPArray || _marshalType == Cci.Constants.UnmanagedType_SafeArray || _marshalType == UnmanagedType.ByValArray);
+                Debug.Assert(_marshalType == UnmanagedType.ByValTStr || _marshalType == UnmanagedType.LPArray || _marshalType == UnmanagedType.SafeArray || _marshalType == UnmanagedType.ByValArray);
                 return _marshalArrayElementCount;
             }
         }
@@ -160,18 +160,18 @@ UnmanagedType Cci.IMarshallingInformation.ElementType
             }
         }
 
-        Cci.VarEnum Cci.IMarshallingInformation.SafeArrayElementSubtype
+        VarEnum Cci.IMarshallingInformation.SafeArrayElementSubtype
         {
             get
             {
-                Debug.Assert(_marshalType == Cci.Constants.UnmanagedType_SafeArray);
-                return (Cci.VarEnum)_marshalArrayElementType;
+                Debug.Assert(_marshalType == UnmanagedType.SafeArray);
+                return (VarEnum)_marshalArrayElementType;
             }
         }
 
         Cci.ITypeReference Cci.IMarshallingInformation.GetSafeArrayElementUserDefinedSubtype(EmitContext context)
         {
-            Debug.Assert(_marshalType == Cci.Constants.UnmanagedType_SafeArray);
+            Debug.Assert(_marshalType == UnmanagedType.SafeArray);
 
             if (_marshalTypeNameOrSymbol == null)
             {
@@ -189,7 +189,7 @@ Cci.ITypeReference Cci.IMarshallingInformation.GetSafeArrayElementUserDefinedSub
             Func<TTypeSymbol, TArg, TTypeSymbol> translator, TArg arg)
             where TTypeSymbol : ITypeSymbol
         {
-            if (_marshalType != Cci.Constants.UnmanagedType_SafeArray || _marshalTypeNameOrSymbol == null)
+            if (_marshalType != UnmanagedType.SafeArray || _marshalTypeNameOrSymbol == null)
             {
                 return this;
             }
@@ -201,7 +201,7 @@ Cci.ITypeReference Cci.IMarshallingInformation.GetSafeArrayElementUserDefinedSub
             }
 
             var result = new MarshalPseudoCustomAttributeData();
-            result.SetMarshalAsSafeArray((Cci.VarEnum)_marshalArrayElementType, translatedType);
+            result.SetMarshalAsSafeArray((VarEnum)_marshalArrayElementType, translatedType);
             return result;
         }
 

src/Compilers/VisualBasic/Portable/OptionsValidator.vb

@@ -60,7 +60,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 
                 Return parsedImportList.ToArray()
             Else
-                Return Array.Empty(Of GlobalImport)
+                Return New GlobalImport() {}
             End If
         End Function
 

src/Compilers/VisualBasic/Portable/Symbols/Attributes/AttributeData.vb

@@ -423,7 +423,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                                                          CType(ctorArgument.DecodeValue(Of Short)(SpecialType.System_Int16), ClassInterfaceType))
 
             Select Case interfaceType
-                Case ClassInterfaceType.None, Cci.Constants.ClassInterfaceType_AutoDispatch, Cci.Constants.ClassInterfaceType_AutoDual
+                Case ClassInterfaceType.None, ClassInterfaceType.AutoDispatch, ClassInterfaceType.AutoDual
                     Exit Select
                 Case Else
                     diagnostics.Add(ERRID.ERR_BadAttribute1, If(nodeOpt IsNot Nothing, nodeOpt.ArgumentList.Arguments(0).GetLocation(), NoLocation.Singleton), Me.AttributeClass)
@@ -448,7 +448,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                                CType(ctorArgument.DecodeValue(Of Short)(SpecialType.System_Int16), ComInterfaceType))
 
             Select Case interfaceType
-                Case Cci.Constants.ComInterfaceType_InterfaceIsDual, Cci.Constants.ComInterfaceType_InterfaceIsIDispatch, ComInterfaceType.InterfaceIsIInspectable, ComInterfaceType.InterfaceIsIUnknown
+                Case ComInterfaceType.InterfaceIsDual, ComInterfaceType.InterfaceIsIDispatch, ComInterfaceType.InterfaceIsIInspectable, ComInterfaceType.InterfaceIsIUnknown
                     Return True
                 Case Else
                     Return False

src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.vb

@@ -1421,7 +1421,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
             ' Is interface marked with 'InterfaceTypeAttribute( flags with ComInterfaceType.InterfaceIsIDispatch )' attribute
             Dim interfaceType As ComInterfaceType = Nothing
             If metadataModule.HasInterfaceTypeAttribute(Me._handle, interfaceType) AndAlso
-                (interfaceType And Cci.Constants.ComInterfaceType_InterfaceIsIDispatch) <> 0 Then
+                (interfaceType And ComInterfaceType.InterfaceIsIDispatch) <> 0 Then
                 Return True
             End If
 

src/Compilers/VisualBasic/Portable/Symbols/ParameterSymbol.vb

@@ -90,7 +90,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
         Friend ReadOnly Property IsMarshalAsObject As Boolean
             Get
                 Select Case Me.MarshallingType
-                    Case UnmanagedType.Interface, UnmanagedType.IUnknown, Cci.Constants.UnmanagedType_IDispatch
+                    Case UnmanagedType.Interface, UnmanagedType.IUnknown, UnmanagedType.IDispatch
                         Return True
                 End Select
 

src/Compilers/VisualBasic/Portable/Symbols/Source/SourceNamedTypeSymbol.vb

@@ -2029,7 +2029,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                     If Not attrdata.HasErrors Then
                         Dim interfaceType As ComInterfaceType = Nothing
                         If attrdata.DecodeInterfaceTypeAttribute(interfaceType) AndAlso
-                            (interfaceType And Cci.Constants.ComInterfaceType_InterfaceIsIDispatch) <> 0 Then
+                            (interfaceType And ComInterfaceType.InterfaceIsIDispatch) <> 0 Then
 
                             arguments.GetOrCreateData(Of TypeEarlyWellKnownAttributeData).HasAttributeForExtensibleInterface = True
                         End If

src/Compilers/VisualBasic/Portable/Symbols/Source/SourceNamedTypeSymbol_ComClass.vb

@@ -988,7 +988,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                             ImmutableArray.Create(
                                 New TypedConstant(_comClass.GetSpecialType(SpecialType.System_Int16),
                                                         TypedConstantKind.Primitive,
-                                                        CShort(Cci.Constants.ComInterfaceType_InterfaceIsIDispatch)))))
+                                                        CShort(ComInterfaceType.InterfaceIsIDispatch)))))
                     End If
 
                     AddSynthesizedAttribute(attributes, compilation.TrySynthesizeAttribute(

src/Compilers/VisualBasic/Portable/Symbols/Source/SourceParameterSymbol.vb

@@ -400,10 +400,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
 
                                 Select Case pinvoke.CharacterSet
                                     Case Cci.Constants.CharSet_None, CharSet.Ansi
-                                        info.SetMarshalAsSimpleType(Cci.Constants.UnmanagedType_AnsiBStr)
+                                        info.SetMarshalAsSimpleType(UnmanagedType.AnsiBStr)
 
                                     Case Cci.Constants.CharSet_Auto
-                                        info.SetMarshalAsSimpleType(Cci.Constants.UnmanagedType_TBStr)
+                                        info.SetMarshalAsSimpleType(UnmanagedType.TBStr)
 
                                     Case CharSet.Unicode
                                         info.SetMarshalAsSimpleType(UnmanagedType.BStr)
@@ -412,7 +412,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                                         Throw ExceptionUtilities.UnexpectedValue(pinvoke.CharacterSet)
                                 End Select
                             Else
-                                info.SetMarshalAsSimpleType(Cci.Constants.UnmanagedType_VBByRefStr)
+                                info.SetMarshalAsSimpleType(UnmanagedType.VBByRefStr)
                             End If
 
                             Return info

src/Compilers/VisualBasic/Portable/Symbols/TypeSymbol.vb

@@ -27,6 +27,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
         ' TODO (tomat): Consider changing this to an empty name. This name shouldn't ever leak to the user in error messages.
         Friend Shared ReadOnly ImplicitTypeName As String = "<invalid-global-code>"
 
+        Private Shared ReadOnly s_EmptyTypeSymbols() As TypeSymbol = {}
+
         Private _lazyAllInterfaces As ImmutableArray(Of NamedTypeSymbol)
         Private _lazyInterfacesAndTheirBaseInterfaces As ImmutableHashSet(Of NamedTypeSymbol)
 
@@ -43,7 +45,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
 
         Public Shared ReadOnly Property EmptyTypeSymbolsList As IList(Of TypeSymbol)
             Get
-                Return Array.Empty(Of TypeSymbol)
+                Return s_EmptyTypeSymbols
             End Get
         End Property
 

src/Compilers/VisualBasic/Portable/Syntax/VisualBasicSyntaxNode.vb

@@ -292,7 +292,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         End Property
 
         ' an empty collection of syntax errors.
-        Friend Shared EmptyErrorCollection As New ReadOnlyCollection(Of Diagnostic)(Array.Empty(Of VBDiagnostic))
+        Friend Shared EmptyErrorCollection As New ReadOnlyCollection(Of Diagnostic)(New VBDiagnostic() {})
 
         ''' <summary>
         ''' Get all syntax errors associated with this node, or any child nodes, grand-child nodes, etc. The errors

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

@@ -364,7 +364,7 @@ private static MethodSymbol GetSynthesizedMethod(CommonPEModuleBuilder moduleBui
             }
         }
 
-        private static readonly ReadOnlyCollection<byte> s_emptyBytes = new ReadOnlyCollection<byte>(Array.Empty<byte>());
+        private static readonly ReadOnlyCollection<byte> s_emptyBytes = new ReadOnlyCollection<byte>(new byte[0]);
 
         internal override ReadOnlyCollection<byte> CompileGetLocals(
             ArrayBuilder<LocalAndMethod> locals,

src/ExpressionEvaluator/Core/Source/ExpressionCompiler/DynamicFlagsCustomTypeInfo.cs

@@ -68,7 +68,7 @@ private DynamicFlagsCustomTypeInfo(ArrayBuilder<bool> dynamicFlags, int startInd
 
         /// <remarks>
         /// Not guaranteed to add the same number of flags as would
-        /// appear in a System.Runtime.CompilerServices.DynamicAttribute.
+        /// appear in a <see cref="System.Runtime.CompilerServices.DynamicAttribute"/>.
         /// It may have more (for padding) or fewer (for compactness) falses.
         /// It is, however, guaranteed to include the last true.
         /// </remarks>

src/ExpressionEvaluator/Core/Source/ResultProvider/Formatter.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.
-#pragma warning disable RS0007 // Avoid zero-length array allocations.
 
 using System;
 using System.Collections.ObjectModel;

src/ExpressionEvaluator/Core/Source/ResultProvider/Helpers/ArrayBuilder.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.
-#pragma warning disable RS0007 // Avoid zero-length array allocations.
 
 using System.Collections.Generic;
 using System.Collections.ObjectModel;

src/ExpressionEvaluator/Core/Source/ResultProvider/ResultProvider.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.
-#pragma warning disable RS0007 // Avoid zero-length array allocations.
 
 using System;
 using System.Collections.ObjectModel;

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

@@ -463,7 +463,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             End Using
         End Function
 
-        Private Shared ReadOnly s_emptyBytes As New ReadOnlyCollection(Of Byte)(Array.Empty(Of Byte))
+        Private Shared ReadOnly s_emptyBytes As New ReadOnlyCollection(Of Byte)(New Byte() {})
 
         Friend Overrides Function CompileGetLocals(
             locals As ArrayBuilder(Of LocalAndMethod),

src/Features/VisualBasic/Portable/EditAndContinue/VisualBasicEditAndContinueAnalyzer.vb

@@ -268,7 +268,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
                     ' Property: Attributes Modifiers [|Identifier$ Initializer|] ImplementsClause
                     Dim propertyStatement = DirectCast(node, PropertyStatementSyntax)
                     If propertyStatement.Initializer IsNot Nothing Then
-                        Return {propertyStatement.Identifier}.Concat(If(propertyStatement.AsClause?.DescendantTokens(), Array.Empty(Of SyntaxToken)())).Concat(propertyStatement.Initializer.DescendantTokens())
+                        Return {propertyStatement.Identifier}.Concat(If(propertyStatement.AsClause?.DescendantTokens(), {})).Concat(propertyStatement.Initializer.DescendantTokens())
                     End If
 
                     If HasAsNewClause(propertyStatement) Then

src/Samples/CSharp/Analyzers/CSharpAnalyzers/CSharpAnalyzers.Test/Helpers/DiagnosticResult.cs

@@ -45,7 +45,7 @@ public DiagnosticResultLocation[] Locations
             {
                 if (this.locations == null)
                 {
-                    return Array.Empty<DiagnosticResultLocation>();
+                    this.locations = new DiagnosticResultLocation[] { };
                 }
                 return this.locations;
             }

src/Test/PdbUtilities/Shared/CustomDebugInfoReader.cs

@@ -217,7 +217,7 @@ public static string DecodeForwardIteratorRecord(ImmutableArray<byte> bytes)
         }
 
         /// <summary>
-        /// Does for locals what System.Runtime.CompilerServices.DynamicAttribute does for parameters, return types, and fields.
+        /// Does for locals what <see cref="System.Runtime.CompilerServices.DynamicAttribute"/> does for parameters, return types, and fields.
         /// In particular, indicates which occurrences of <see cref="object"/> in the signature are really dynamic.
         /// </summary>
         /// <remarks>

src/Workspaces/Core/Portable/Workspaces.csproj

@@ -14,8 +14,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <SolutionDir Condition="'$(SolutionDir)' == '' OR '$(SolutionDir)' == '*Undefined*'">..\..\..\</SolutionDir>
     <TargetFrameworkVersion>v5.0</TargetFrameworkVersion>
-    <TargetFrameworkProfile>
-    </TargetFrameworkProfile>
+    <TargetFrameworkProfile></TargetFrameworkProfile>
     <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
   </PropertyGroup>
   <ItemGroup Label="Project References">
@@ -124,6 +123,9 @@
     <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\SpecializedCollections.cs">
       <Link>InternalUtilities\SpecializedCollections.cs</Link>
     </Compile>
+    <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\SpecializedCollections.Empty.Array.cs">
+      <Link>InternalUtilities\SpecializedCollections.Empty.Array.cs</Link>
+    </Compile>
     <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\SpecializedCollections.Empty.Collection.cs">
       <Link>InternalUtilities\SpecializedCollections.Empty.Collection.cs</Link>
     </Compile>
@@ -968,4 +970,4 @@
   <ImportGroup Label="Targets">
     <Import Project="..\..\..\..\build\Targets\VSL.Imports.targets" />
   </ImportGroup>
-</Project>
\ No newline at end of file
+</Project>