Comparers don't work for messy generic corner cases

[MichalStrehovsky]

Compile the repro below with/without optimizations.

Without optimizations, this prints:

Here
False
True

That's good.

With optimizations, this prints:

Here
False
Here
False

That's not so good.

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
{
    MyStruct<object, object> s1 = default;
    MyStruct<object, object> s2 = default;
    Console.WriteLine(Equals(s1, s2));
}

{
    MyStruct<object, string> s1 = default;
    MyStruct<object, string> s2 = default;
    Console.WriteLine(Equals(s1, s2));
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool Equals<T>(T x, T y)
{
    return EqualityComparer<T>.Default.Equals(x, y);
}

struct MyStruct<T, U> : IEquatable<MyStruct<U, U>>
{
    public bool Equals(MyStruct<U, U> other)
    {
        Console.WriteLine("Here");
        return false;
    }
}

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See info in area-owners.md if you want to be subscribed.

Issue Details

---

Compile the repro below with/without optimizations.

Without optimizations, this prints:

Here
False
True

That's good.

With optimizations, this prints:

Here
False
Here
False

That's not so good.

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
{
    MyStruct<object, object> s1 = default;
    MyStruct<object, object> s2 = default;
    Console.WriteLine(Equals(s1, s2));
}

{
    MyStruct<object, string> s1 = default;
    MyStruct<object, string> s2 = default;
    Console.WriteLine(Equals(s1, s2));
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool Equals<T>(T x, T y)
{
    return EqualityComparer<T>.Default.Equals(x, y);
}

struct MyStruct<T, U> : IEquatable<MyStruct<U, U>>
{
    public bool Equals(MyStruct<U, U> other)
    {
        Console.WriteLine("Here");
        return false;
    }
}

Author:	MichalStrehovsky
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[MichalStrehovsky]

(To be clear, this issue is not for Native AOT, it's broken for JIT scenarios. It's also broken on Native AOT but I'm going to wait until there's a defined behavior for this, defined by the JIT side.)

[jakobbotsch]

What is the non-NAOT repro case? This one doesn't seem to repro without NativeAOT for me.

[jakobbotsch]

(Seems like it was failing just recently until #88006. Also #88006 (comment) looks related.)

[JulieLeeMSFT]

@EgorBo PTAL. CC @jkotas.

Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Compile the repro below with/without optimizations.

Without optimizations, this prints:

Here
False
True

That's good.

With optimizations, this prints:

Here
False
Here
False

That's not so good.

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
{
    MyStruct<object, object> s1 = default;
    MyStruct<object, object> s2 = default;
    Console.WriteLine(Equals(s1, s2));
}

{
    MyStruct<object, string> s1 = default;
    MyStruct<object, string> s2 = default;
    Console.WriteLine(Equals(s1, s2));
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool Equals<T>(T x, T y)
{
    return EqualityComparer<T>.Default.Equals(x, y);
}

struct MyStruct<T, U> : IEquatable<MyStruct<U, U>>
{
    public bool Equals(MyStruct<U, U> other)
    {
        Console.WriteLine("Here");
        return false;
    }
}

Author:	MichalStrehovsky
Assignees:	-
Labels:	area-CodeGen-coreclr, untriaged, area-NativeAOT-coreclr
Milestone:	-

[jkotas]

This is a bug in native AOT implementation of JIT/EE interface. I will take a look.