Move System.Runtime.CompilerServices.CallConv* types to System.Privat…

…e.CoreLib and expose via System.Runtime. (#38473)

* Move the calling convention types used in the new calling convention modopt-based encoding down to System.Private.CoreLib/System.Runtime.

* Make S.R.CS.VisualC a partial facade so the tooling will generate the type forwards in the src assembly.

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -621,6 +621,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CallerFilePathAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CallerLineNumberAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CallerMemberNameAttribute.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CallingConventions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CompilationRelaxations.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CompilationRelaxationsAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\CompilerServices\CompilerGeneratedAttribute.cs" />

src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/CallingConventions.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    public class CallConvCdecl
+    {
+        public CallConvCdecl() { }
+    }
+    public class CallConvFastcall
+    {
+        public CallConvFastcall() { }
+    }
+    public class CallConvStdcall
+    {
+        public CallConvStdcall() { }
+    }
+    public class CallConvThiscall
+    {
+        public CallConvThiscall() { }
+    }
+}

src/libraries/System.Runtime.CompilerServices.VisualC/ref/System.Runtime.CompilerServices.VisualC.TypeForwards.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+// ------------------------------------------------------------------------------
+// Changes to this file must follow the https://aka.ms/api-review process.
+// ------------------------------------------------------------------------------
+
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallConvCdecl))]
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallConvStdcall))]
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallConvThiscall))]
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallConvFastcall))]

src/libraries/System.Runtime.CompilerServices.VisualC/ref/System.Runtime.CompilerServices.VisualC.cs

@@ -7,22 +7,6 @@
 
 namespace System.Runtime.CompilerServices
 {
-    public partial class CallConvCdecl
-    {
-        public CallConvCdecl() { }
-    }
-    public partial class CallConvFastcall
-    {
-        public CallConvFastcall() { }
-    }
-    public partial class CallConvStdcall
-    {
-        public CallConvStdcall() { }
-    }
-    public partial class CallConvThiscall
-    {
-        public CallConvThiscall() { }
-    }
     public static partial class CompilerMarshalOverride
     {
     }

src/libraries/System.Runtime.CompilerServices.VisualC/ref/System.Runtime.CompilerServices.VisualC.csproj

@@ -6,8 +6,9 @@
   <ItemGroup>
     <Compile Include="System.Runtime.CompilerServices.VisualC.cs" />
     <Compile Include="System.Runtime.CompilerServices.VisualC.manual.cs" />
+    <Compile Include="System.Runtime.CompilerServices.VisualC.TypeForwards.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\System.Runtime\ref\System.Runtime.csproj" />
   </ItemGroup>
-</Project>
+</Project>

src/libraries/System.Runtime.CompilerServices.VisualC/src/System.Runtime.CompilerServices.VisualC.csproj

@@ -2,6 +2,7 @@
   <PropertyGroup>
     <AssemblyName>System.Runtime.CompilerServices.VisualC</AssemblyName>
     <Nullable>enable</Nullable>
+    <IsPartialFacadeAssembly>true</IsPartialFacadeAssembly>
     <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- Shared CoreCLR -->
@@ -11,4 +12,4 @@
   <ItemGroup>
     <Reference Include="System.Runtime" />
   </ItemGroup>
-</Project>
+</Project>

src/libraries/System.Runtime.CompilerServices.VisualC/src/System/Runtime/CompilerServices/Attributes.cs

@@ -39,23 +39,6 @@ internal AssemblyAttributesGoHereSM()
         }
     }
 
-    // Types used in Custom Modifier to specify calling conventions.
-    public class CallConvCdecl
-    {
-    }
-
-    public class CallConvStdcall
-    {
-    }
-
-    public class CallConvThiscall
-    {
-    }
-
-    public class CallConvFastcall
-    {
-    }
-
     [AttributeUsage(AttributeTargets.All)]
     internal sealed class DecoratedNameAttribute : Attribute
     {

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -8993,6 +8993,22 @@ public void SetResult() { }
         public void SetStateMachine(System.Runtime.CompilerServices.IAsyncStateMachine stateMachine) { }
         public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : System.Runtime.CompilerServices.IAsyncStateMachine { }
     }
+    public partial class CallConvCdecl
+    {
+        public CallConvCdecl() { }
+    }
+    public partial class CallConvFastcall
+    {
+        public CallConvFastcall() { }
+    }
+    public partial class CallConvStdcall
+    {
+        public CallConvStdcall() { }
+    }
+    public partial class CallConvThiscall
+    {
+        public CallConvThiscall() { }
+    }
     [System.AttributeUsageAttribute(System.AttributeTargets.Parameter, AllowMultiple=false, Inherited=false)]
     public sealed partial class CallerArgumentExpressionAttribute : System.Attribute
     {