UnsafeAccessor does not work for generic constructors, .NET 9

[mgravell]

Description

This ticket suggests that this should work from 9.0 Preview 4, however this fails in 9.0 GA:

using System.Runtime.CompilerServices;

// this works fine
Console.WriteLine(Hack.CreateFoo());

// this doesn't work
Console.WriteLine(Hack.CreateBar<int>());

// this doesn't work
Bar<int> evil = (Bar<int>)RuntimeHelpers.GetUninitializedObject(typeof(Bar<int>));
Hack.HacketyHackHack(evil);
Console.WriteLine(evil);

static class Hack
{
    [UnsafeAccessor(UnsafeAccessorKind.Constructor)]
    internal static extern Foo CreateFoo();

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = ".ctor")]
    internal extern static void HacketyHackHack<T>(Bar<T> obj);

    [UnsafeAccessor(UnsafeAccessorKind.Constructor)]
    internal static extern Bar<T> CreateBar<T>();
}
class Foo
{
    private readonly string s = ".ctor has run";
    public override string ToString() => s;
    private Foo() { }
}
class Bar<T>
{
    private readonly string s = ".ctor has run; " + typeof(T).Name;
    public override string ToString() => s;
    private Bar() { }
}

Reproduction Steps

as above

Expected behavior

it works

Actual behavior

Unhandled exception. System.InvalidProgramException: Generic type constraints do not match.
   at Hack.CreateBar[T]()
   at Program.<Main>$(String[] args) in C:\Users\marcg\source\repos\ConsoleApp4\ConsoleApp4\Program.cs:line 7

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[vcsjones]

Where T is declared seems to matter. This works:

using System;
using System;
using System.Runtime.CompilerServices;

Hack<int>.CreateBar();

Bar<int> evil = (Bar<int>)RuntimeHelpers.GetUninitializedObject(typeof(Bar<int>));
Console.WriteLine(Hack<short>.CreateBar());
Hack<int>.HacketyHackHack(evil);
Console.WriteLine(evil);

static class Hack<T>
{

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = ".ctor")]
    internal extern static void HacketyHackHack(Bar<T> obj);

    [UnsafeAccessor(UnsafeAccessorKind.Constructor)]
    internal static extern Bar<T> CreateBar();
}

class Bar<T>
{
    private readonly string s = ".ctor has run; " + typeof(T).Name;
    public override string ToString() => s;
    private Bar() { }
}

[mgravell]

Useful workaround @vcsjones ! (I haven't verified, but will do tomorrow)

[jkotas]

cc @AaronRobinsonMSFT