Fix some compiler errors that can occur with specific project setups

contributing.md

@@ -192,7 +192,7 @@ Example:
 
 #pragma warning disable
 
-#if TASKSEXTENSIONSREFERENCED && (NETFRAMEWORK || NETSTANDARD2_0 || NETCOREAPP2_0)
+#if TASKSEXTENSIONSREFERENCED && MEMORYREFERENCED && (NETFRAMEWORK || NETSTANDARD2_0 || NETCOREAPP2_0)
 
 using System;
 using System.Buffers;

src/Consume/Consume.cs

@@ -98,6 +98,10 @@ class Consume
         var split = "a b".Split(' ', StringSplitOptions.RemoveEmptyEntries);
         split = "a b".Split(' ', 2, StringSplitOptions.RemoveEmptyEntries);
         var contains = "a b".Contains(' ');
+
+        // Test to make sure there are no clashes in the Polyfill code with classes that
+        // might be defined in user code. See comments in Debug.cs for more details.
+        Debug.Log("Test log to make sure this is working");
     }
 
 #if HTTPREFERENCED

src/Consume/Debug.cs

@@ -0,0 +1,29 @@
+using System;
+
+// Test to make sure there are no clashes in the Polyfill code with classes that might be defined in user code.
+//
+// Some codebases, for better or for worse, define classes with names that match common classes in the base
+// .NET libraries, like "Debug". This works find in those codebases because they are usually contained in the
+// same namespace, or are guarded in some other way. But if a Polyfill attribute is imported and uses code like:
+//     Debug.Assert(genericParameter.IsGenericParameter);
+// instead of a fully qualified name like:
+//     System.Debug.Assert(genericParameter.IsGenericParameter);
+// then users of Polyfill will get errors like the following, which they can't easily fix:
+//     'Debug' does not contain a definition for 'Assert'
+//
+// So, this file defines a custom Debug class to make sure that Polyfill code doesn't clash with user code.
+
+class Debug
+{
+    public static void Log(string content) => Console.WriteLine(content);
+
+    public static void Log(ConsoleColor color, string content)
+    {
+        Console.ForegroundColor = color;
+        Console.WriteLine(content);
+        Console.ResetColor();
+    }
+
+    public static void LogWarning(string content) => Log(ConsoleColor.Yellow, content);
+    public static void LogError(string content) => Log(ConsoleColor.Red, content);
+}

src/ConsumeTasksWithNoMemory/ConsumeTasksWithNoMemory.csproj

@@ -0,0 +1,31 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
+  </PropertyGroup>
+  <ItemGroup>
+    <!-- This project is specifically designed to guard against a miscompile where System.Threading.Tasks.Extensions is referenced, but System.Memory is not. -->
+    <!-- <PackageReference Include="System.Memory" Version="4.5.5" Condition="$(TargetFramework) != '.NETStandard' or $(TargetFrameworkIdentifier) == '.NETFramework' or $(TargetFramework.StartsWith('netcoreapp'))" /> -->
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" Condition="$(TargetFramework) == 'netstandard2.0' or $(TargetFramework) == 'netcoreapp2.0' or $(TargetFrameworkIdentifier) == '.NETFramework'" />
+    <Compile Include="..\Polyfill\*.cs">
+      <Link>Pollyfill\%(RecursiveDir)%(Filename).cs</Link>
+    </Compile>
+    <Compile Include="..\Polyfill\Nullable\*.cs">
+      <Link>Pollyfill\Nullable\%(RecursiveDir)%(Filename).cs</Link>
+    </Compile>
+    <Compile Include="..\Polyfill\Nullability\*.cs">
+      <Link>Pollyfill\Nullability\%(RecursiveDir)%(Filename).cs</Link>
+    </Compile>
+    <Compile Include="..\Polyfill\IndexRange\*.cs">
+      <Link>Pollyfill\IndexRange\%(RecursiveDir)%(Filename).cs</Link>
+    </Compile>
+    <Compile Include="..\Polyfill\Trimming\*.cs">
+      <Link>Pollyfill\Trimming\%(RecursiveDir)%(Filename).cs</Link>
+    </Compile>
+    <Compile Include="..\Polyfill\PlatformCompatibility\*.cs">
+      <Link>Pollyfill\PlatformCompatibility\%(RecursiveDir)%(Filename).cs</Link>
+    </Compile>
+  </ItemGroup>
+  <Import Project="$(ProjectDir)..\Polyfill\Polyfill.props" />
+  <Import Project="$(ProjectDir)..\Polyfill\Polyfill.targets" />
+</Project>

src/Polyfill.sln

@@ -33,6 +33,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NoRefsTests", "NoRefsTests\
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ConsumeNoRefs", "ConsumeNoRefs\ConsumeNoRefs.csproj", "{B4DC96CA-C700-499F-A9A2-0C767DCF8C30}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ConsumeTasksWithNoMemory", "ConsumeTasksWithNoMemory\ConsumeTasksWithNoMemory.csproj", "{96EF1E04-5862-4D9E-B800-A6402F1ADF7A}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -75,6 +77,10 @@ Global
 		{B4DC96CA-C700-499F-A9A2-0C767DCF8C30}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{B4DC96CA-C700-499F-A9A2-0C767DCF8C30}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{B4DC96CA-C700-499F-A9A2-0C767DCF8C30}.Release|Any CPU.Build.0 = Release|Any CPU
+		{96EF1E04-5862-4D9E-B800-A6402F1ADF7A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{96EF1E04-5862-4D9E-B800-A6402F1ADF7A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{96EF1E04-5862-4D9E-B800-A6402F1ADF7A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{96EF1E04-5862-4D9E-B800-A6402F1ADF7A}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

src/Polyfill/Nullability/NullabilityInfo.cs

@@ -6,6 +6,7 @@
 
 using System.Linq;
 using System.Diagnostics.CodeAnalysis;
+
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 

src/Polyfill/Nullability/NullabilityInfoContext.cs

@@ -6,6 +6,7 @@
 
 using System.Linq;
 using System.Diagnostics.CodeAnalysis;
+
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
@@ -15,6 +16,10 @@
 
 namespace System.Reflection
 {
+    // Some codebases define their own Debug class, which can cause clashes and compile errors if we aren't explicit here.
+    // See comments in Debug.cs in Consume project for more details.
+    using Debug = System.Diagnostics.Debug;
+
     /// <summary>
     /// Provides APIs for populating nullability information/context from reflection members:
     /// <see cref="ParameterInfo"/>, <see cref="FieldInfo"/>, <see cref="PropertyInfo"/> and <see cref="EventInfo"/>.

src/Polyfill/PolyfillExtensions_Stream.cs

@@ -13,6 +13,8 @@
 
 static partial class PolyfillExtensions
 {
+#if MEMORYREFERENCED
+
     /// <summary>
     /// Asynchronously reads a sequence of bytes from the current stream, advances the position within the stream by
     /// the number of bytes read, and monitors cancellation requests.
@@ -64,6 +66,8 @@ public static ValueTask WriteAsync(
         return new(target.WriteAsync(segment.Array!, segment.Offset, segment.Count, cancellationToken));
     }
 
+#endif
+
     /// <summary>
     /// Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified
     /// cancellation token. Both streams positions are advanced by the number of bytes copied.

src/Polyfill/PolyfillExtensions_TextReader.cs

@@ -11,7 +11,7 @@
 
 static partial class PolyfillExtensions
 {
-#if TASKSEXTENSIONSREFERENCED && (NETFRAMEWORK || NETSTANDARD2_0 || NETCOREAPP2_0)
+#if TASKSEXTENSIONSREFERENCED && MEMORYREFERENCED && (NETFRAMEWORK || NETSTANDARD2_0 || NETCOREAPP2_0)
     /// <summary>
     /// Asynchronously reads the characters from the current stream into a memory block.
     /// </summary>

src/Polyfill/PolyfillExtensions_TextWriter.cs

@@ -2,7 +2,7 @@
 
 #pragma warning disable
 
-#if TASKSEXTENSIONSREFERENCED && (NETFRAMEWORK || NETSTANDARD2_0 || NETCOREAPP2_0)
+#if TASKSEXTENSIONSREFERENCED && MEMORYREFERENCED && (NETFRAMEWORK || NETSTANDARD2_0 || NETCOREAPP2_0)
 
 using System;
 using System.Buffers;

src/Tests/NullabilitySync.cs

@@ -50,6 +50,7 @@ public async Task Run()
                      using System.Linq;
                      using System.Diagnostics.CodeAnalysis;
 
+
                      """;
 
         var suffix = """
@@ -60,6 +61,7 @@ public async Task Run()
 
         infoContext = prefix + infoContext + suffix;
         infoContext = MakeInternal(infoContext);
+        infoContext = AddDebugClassFix(infoContext);
         OverWrite(infoContext, "NullabilityInfoContext.cs");
 
         info = prefix + info + suffix;
@@ -87,6 +89,19 @@ static string MakeInternal(string source) =>
                     sealed class
                     """);
 
+    static string AddDebugClassFix(string source) =>
+        source
+            .Replace(
+                "namespace System.Reflection\r\n{",
+                """
+                    namespace System.Reflection
+                    {
+                        // Some codebases define their own Debug class, which can cause clashes and compile errors if we aren't explicit here.
+                        // See comments in Debug.cs in Consume project for more details.
+                        using Debug = System.Diagnostics.Debug;
+                    
+                    """);
+
     static void OverWrite(string content, string file)
     {
         var path = Path.Combine(dir, file);