nameof(@object) == "@object" while [CallerArgumentExpression] injects "object"

[r-pankevicius]

Hi,

I'd like to believe it's .net runtime issue but would like to check here first, maybe it's language specific.

Here is how I found this subtle difference: r-pankevicius/EnsureArg6@9fc6856

/r

PS: The method under test (with CallerArgumentExpressionAttribute) is:
https://github.com/r-pankevicius/EnsureArg6/blob/main/src/EnsureArg6/EnsureArg6.Types.cs#L92

[CyrusNajmabadi]

Can you provide a clearer repro that includes all referencedd symbols. I have no idea where [CallerArgumentExpression] is even used in the code you linked to.

[r-pankevicius]

Look below: #7224 (comment)

[r-pankevicius]

Oh, Okay, I see, I updated the topic:
https://github.com/r-pankevicius/EnsureArg6/blob/main/src/EnsureArg6/EnsureArg6.Types.cs#L92

[HaloFour]

This?

using System;
using System.Runtime.CompilerServices;

object @object = "foo";
M(nameof(@object));

void M(string x, [CallerArgumentExpression("x")] string? y = null) {
    Console.WriteLine(x); // prints "object"
    Console.WriteLine(y); // prints "nameof(@object)"
}

[CyrusNajmabadi]

If so, that's by design. nameof gives you the name of the thing (which is just object). Whereas CallerArgument gives you the actual syntactic argument passed along. in this case nameof(@object).

[r-pankevicius]

I think it's opposite, look at examples from me and @HaloFour.

[CyrusNajmabadi]

In the examples you have posted, things work as I would expect them to.

[r-pankevicius]

@HaloFour Yes, it's my case:

using System;

namespace CallerArgumentExpressionVsNameoff
{
	internal class Program
	{
		internal static void Main(string[] args)
		{
			object @object = "foo";
			M(nameof(@object));
		}

		private static void M(object x, [CallerArgumentExpression("x")] string? y = null)
		{
			Console.WriteLine(x); // prints "object"
			Console.WriteLine(y); // prints "nameof(@object)"
		}
	}
}