Upgrade our .NET SDK to 5.0 RC 1

eng/targets/Imports.targets

@@ -404,4 +404,10 @@
     </ItemGroup>
   </Target>
 
+  <!-- Override this to work around https://github.com/dotnet/sdk/issues/13427. The property doesn't
+       appear to be used for anything other than controlling the warning. -->
+  <PropertyGroup>
+    <_MicrosoftWindowsDesktopSdkImported>false</_MicrosoftWindowsDesktopSdkImported>
+  </PropertyGroup>
+
 </Project>

global.json

@@ -1,11 +1,11 @@
 {
   "sdk": {
-    "version": "5.0.100-preview.8.20417.9",
+    "version": "5.0.100-rc.1.20452.10",
     "allowPrerelease": true,
     "rollForward": "major"
   },
   "tools": {
-    "dotnet": "5.0.100-preview.8.20417.9",
+    "dotnet": "5.0.100-rc.1.20452.10",
     "vs": {
       "version": "16.8"
     },

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

@@ -0,0 +1,94 @@
+// 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.
+
+#nullable enable
+
+#if !NET5_0
+
+namespace System.Runtime.Versioning
+{
+    /// <summary>
+    /// Base type for all platform-specific API attributes.
+    /// </summary>
+    internal abstract class OSPlatformAttribute : Attribute
+    {
+        private protected OSPlatformAttribute(string platformName)
+        {
+            PlatformName = platformName;
+        }
+
+        public string PlatformName { get; }
+    }
+
+    /// <summary>
+    /// Records the platform that the project targeted.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    internal sealed class TargetPlatformAttribute : OSPlatformAttribute
+    {
+        public TargetPlatformAttribute(string platformName)
+            : base(platformName)
+        {
+        }
+    }
+
+    /// <summary>
+    /// Records the operating system (and minimum version) that supports an API. Multiple attributes can be
+    /// applied to indicate support on multiple operating systems.
+    /// </summary>
+    /// <remarks>
+    /// <para>Callers can apply a <see cref="SupportedOSPlatformAttribute" />
+    /// or use guards to prevent calls to APIs on unsupported operating systems.</para>
+    ///
+    /// <para>A given platform should only be specified once.</para>
+    /// </remarks>
+    [AttributeUsage(
+        AttributeTargets.Assembly
+        | AttributeTargets.Class
+        | AttributeTargets.Constructor
+        | AttributeTargets.Enum
+        | AttributeTargets.Event
+        | AttributeTargets.Field
+        | AttributeTargets.Method
+        | AttributeTargets.Module
+        | AttributeTargets.Property
+        | AttributeTargets.Struct,
+        AllowMultiple = true, Inherited = false)]
+    internal sealed class SupportedOSPlatformAttribute : OSPlatformAttribute
+    {
+        public SupportedOSPlatformAttribute(string platformName)
+            : base(platformName)
+        {
+        }
+    }
+
+    /// <summary>
+    /// Marks APIs that were removed in a given operating system version.
+    /// </summary>
+    /// <remarks>
+    /// Primarily used by OS bindings to indicate APIs that are only available in
+    /// earlier versions.
+    /// </remarks>
+    [AttributeUsage(
+        AttributeTargets.Assembly
+        | AttributeTargets.Class
+        | AttributeTargets.Constructor
+        | AttributeTargets.Enum
+        | AttributeTargets.Event
+        | AttributeTargets.Field
+        | AttributeTargets.Method
+        | AttributeTargets.Module
+        | AttributeTargets.Property
+        | AttributeTargets.Struct,
+        AllowMultiple = true, Inherited = false)]
+    internal sealed class UnsupportedOSPlatformAttribute : OSPlatformAttribute
+    {
+        public UnsupportedOSPlatformAttribute(string platformName)
+            : base(platformName)
+        {
+        }
+    }
+}
+
+#endif

src/Compilers/VisualBasic/Portable/Semantics/OverloadResolution.vb

@@ -502,12 +502,12 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 #If DEBUG Then
         ' Compile time asserts.
         Private Const s_delegateRelaxationLevelMask_AssertZero = SmallFieldMask.DelegateRelaxationLevelMask - ConversionKind.DelegateRelaxationLevelMask
-        Private _delegateRelaxationLevelMask_Assert1(s_delegateRelaxationLevelMask_AssertZero) As Boolean
-        Private _delegateRelaxationLevelMask_Assert2(-s_delegateRelaxationLevelMask_AssertZero) As Boolean
+        Private ReadOnly _delegateRelaxationLevelMask_Assert1(s_delegateRelaxationLevelMask_AssertZero) As Boolean
+        Private ReadOnly _delegateRelaxationLevelMask_Assert2(-s_delegateRelaxationLevelMask_AssertZero) As Boolean
 
         Private Const s_inferenceLevelMask_AssertZero = CByte((SmallFieldMask.InferenceLevelMask >> SmallFieldMask.InferenceLevelShift) <> ((TypeArgumentInference.InferenceLevel.Invalid << 1) - 1))
-        Private _inferenceLevelMask_Assert1(s_inferenceLevelMask_AssertZero) As Boolean
-        Private _inferenceLevelMask_Assert2(-s_inferenceLevelMask_AssertZero) As Boolean
+        Private ReadOnly _inferenceLevelMask_Assert1(s_inferenceLevelMask_AssertZero) As Boolean
+        Private ReadOnly _inferenceLevelMask_Assert2(-s_inferenceLevelMask_AssertZero) As Boolean
 #End If
         Public Structure OptionalArgument
             Public ReadOnly DefaultValue As BoundExpression

src/Interactive/HostProcess/InteractiveHost32.csproj

@@ -16,6 +16,10 @@
     <ProjectReference Include="..\Host\Microsoft.CodeAnalysis.InteractiveHost.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Compile Include="..\..\Compilers\Core\Portable\InternalUtilities\PlatformAttributes.cs" Link="Utilities\PlatformAttributes.cs" />
+  </ItemGroup>
+
   <!--
     InteractiveHost32 is deployed to the same directory as InteractiveHost64 as it shares the same dependencies.
 

src/Interactive/HostProcess/InteractiveHost64.csproj

@@ -22,6 +22,10 @@
     <ProjectReference Include="..\Host\Microsoft.CodeAnalysis.InteractiveHost.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Compile Include="..\..\Compilers\Core\Portable\InternalUtilities\PlatformAttributes.cs" Link="Utilities\PlatformAttributes.cs" />
+  </ItemGroup>
+
   <Target Name="PublishProjectOutputGroup" DependsOnTargets="Publish" Returns="@(_PublishedFiles)">
     <ItemGroup>
       <!-- Need to include and then update items (https://github.com/microsoft/msbuild/issues/1053) -->

src/Interactive/HostProcess/InteractiveHostEntryPoint.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Windows.Forms;
@@ -13,6 +14,7 @@ namespace Microsoft.CodeAnalysis.Interactive
 {
     internal static class InteractiveHostEntryPoint
     {
+        [SupportedOSPlatform("windows")]
         private static async Task<int> Main(string[] args)
         {
             FatalError.Handler = FailFast.OnFatalException;
@@ -51,9 +53,11 @@ private static async Task<int> Main(string[] args)
             }
         }
 
+        [SupportedOSPlatform("windows")]
         [DllImport("kernel32", PreserveSig = true)]
         internal static extern ErrorMode SetErrorMode(ErrorMode mode);
 
+        [SupportedOSPlatform("windows")]
         [DllImport("kernel32", PreserveSig = true)]
         internal static extern ErrorMode GetErrorMode();