Failing tests for using nullability attributes in WPF codebehind

appveyor.yml

@@ -41,6 +41,8 @@ test_script:
 - msbuild /restore tests/SingleTFM /p:TestFramework=netcoreapp3.0 /warnaserror /nr:false /v:m
 - git clean -dxf tests
 - msbuild /restore tests/SingleTFM /p:TestFramework=netcoreapp3.1 /warnaserror /nr:false /v:m
+- git clean -dxf tests
+- msbuild /restore tests/WPF /warnaserror /nr:false /v:m
 
 - git clean -dxf tests
 - dotnet msbuild -restore tests/MultiTFM -warnaserror -nr:false -v:m
@@ -70,5 +72,7 @@ test_script:
 - dotnet msbuild -restore tests/SingleTFM -p:TestFramework=netcoreapp3.0 -warnaserror -nr:false -v:m
 - git clean -dxf tests
 - dotnet msbuild -restore tests/SingleTFM -p:TestFramework=netcoreapp3.1 -warnaserror -nr:false -v:m
+- git clean -dxf tests
+- dotnet msbuild -restore tests/WPF -warnaserror -nr:false -v:m
 artifacts:
 - path: 'TunnelVisionLabs.ReferenceAssemblyAnnotator\**\*.nupkg'

tests/WPF/UserControl1.xaml

@@ -0,0 +1,12 @@
+<UserControl x:Class="WPF.UserControl1"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
+             xmlns:local="clr-namespace:WPF"
+             mc:Ignorable="d" 
+             d:DesignHeight="450" d:DesignWidth="800">
+    <Grid>
+
+    </Grid>
+</UserControl>

tests/WPF/UserControl1.xaml.cs

@@ -0,0 +1,25 @@
+using System.Collections.Generic;
+using System.Data.SqlClient;
+using System.Diagnostics.CodeAnalysis;
+using System.Windows.Controls;
+
+namespace WPF
+{
+    public partial class UserControl1 : UserControl
+    {
+        public UserControl1()
+        {
+            InitializeComponent();
+        }
+
+        public static void M(SqlConnection connection, [AllowNull] string? x)
+        {
+            if (!string.IsNullOrEmpty(x))
+            {
+                x.ToString();
+            }
+
+            _ = EqualityComparer<string?>.Default.GetHashCode(x);
+        }
+    }
+}

tests/WPF/WPF.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
+
+  <PropertyGroup>
+    <!-- Using net40 instead of net35. jnm2.ReferenceAssemblies.net35 isn't automatically referenced by the .NET Core SDK like
+         Microsoft.NETFramework.ReferenceAssemblies is, and therefore it doesn't provide assemblies to the WPF temp assembly project. -->
+    <TargetFrameworks>net40;net48;netcoreapp3.0;netcoreapp3.1</TargetFrameworks>
+    <UseWPF>true</UseWPF>
+    <LangVersion>8</LangVersion>
+    <Nullable>enable</Nullable>
+    <NoWarn>RA1000</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Condition="'$(TargetFramework)' != 'net40'" Include="System.Data.SqlClient" Version="4.8.0" />
+    <PackageReference Include="TunnelVisionLabs.ReferenceAssemblyAnnotator" Version="1.0.0-alpha.*" PrivateAssets="all" />
+    <PackageDownload Include="Microsoft.NETCore.App.Ref" Version="[3.1.0]" />
+  </ItemGroup>
+
+</Project>