MutatingMethods_MutationsAffectOriginal test fails (imported from CoreFX)

[EgorBo]

Steps to Reproduce

The following test imported from CoreFX fails on mono (and works fine on .NET Core 2.1):

using System;

namespace ConsoleApplication11
{
    internal class Program
    {
        public static void Main()
        {
            MutatingStruct? ms = new MutatingStruct() { Value = 1 };

            for (int i = 1; i <= 4; i++)
            {
                AssertEqual(i.ToString(), ms.Value.ToString());
                AssertEqual(i, ms.Value.Value);

                AssertEqual(i.ToString(), ms.ToString());
                AssertEqual(i + 1, ms.Value.Value);
            }

            for (int i = 5; i <= 6; i++)
            {
                ms.Value.Equals(new object());
                AssertEqual(i, ms.Value.Value);

                ms.Equals(new object());
                AssertEqual(i + 1, ms.Value.Value);
            }
        }

        private static void AssertEqual(object o1, object o2)
        {
            if (!o1.Equals(o2))
                throw new Exception($"{o1} != {o2}");
        }

        private struct MutatingStruct
        {
            public int Value;
            public override string ToString() => Value++.ToString();
            public override bool Equals(object obj) => Value++.Equals(null);
            public override int GetHashCode() => Value++.GetHashCode();
        }
    }   
}

Current Behavior

Unhandled Exception:
System.Exception: 6 != 5

Expected Behavior

Exception is not thrown (.NET Core 2.1)

On which platforms did you notice this

[x] macOS
[ ] Linux
[ ] Windows

[marek-safar]

@vargaz please add it to your bugs week list

[vargaz]

            ms.Equals(new object());

doesn't seem to call MutatingStruct.Equals ().

[vargaz]

2 problems here:
ms.Equals(new object());
returns false without calling ms.Value.Equals, since object () is not the same type.

it should be changed to:
ms.Equals(new MutatingStruct() { Value = 1 });

Also, Nullable.Equals () does:
return other.value.Equals (value);
this should be changed to
return value.Equals (other.value);

[lewurm]

FWIW, the interp has the same result. it's a problem in the BCL imho.

[jaykrell]

Mono BCL that is?

[vargaz]

Should we enable the original test ?

[marek-safar]

@vargaz @lewurm added the test in his commit