Question: IL Metadata for optional parameter of type DateTime

[HaloFour]

https://github.com/dotnet/corefx/issues/26164

The following currently causes a System.FormatException due to a bug in the CLR:

public class SomeType
{
    public void Method(DateTime timestamp = default(DateTime)) { }
}

class Program
{
    static void Main()
    {
        var parameter = typeof(SomeType).GetMethod("Method").GetParameters()[0];
        var defaultValue = parameter.DefaultValue; // exception thrown here
    }
}

This is caused by a bug that has been located here where the CLR expects to see optional DateTime parameters with optional values annotated with the System.Runtime.CompilerServices.DateTimeConstantAttribute attribute.

This is obviously a bug in the CLR and should be fixed. The question would be should the C# compiler also emit this attribute to "smooth over" the bug on existing frameworks? Would that require a change to the language specification or would that be considered an implementation detail?

[jnm2]

Yeah, I ran into this too.

[stakx]

FYI, I've submitted a bugfix for the CoreCLR (dotnet/coreclr#17877). If this gets merged, I'll try to see whether the fix can be backported to the CLR as well.