Error CS4007 is not visible in the editor

[vsfeedback]

This issue has been moved from a ticket on Developer Community.

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[severity:It's more difficult to complete my work]
with this code

namespace ConsoleApp3
{
	internal class Program
	{
		static void Main(string[] args)
		{
			Console.WriteLine(M(). Count(i => i == 0));
		}

static IEnumerable<int> M()
		{
			Span<int> ints = stackalloc int[5];
			foreach (var i in ints)
				yield return i;
		}
	}
}

you will not get a visible error on the foreach in the editor. The error also isn't in the error list. You'll be shown the error as late as when building, and it'll appear only in the error list.

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Original Comments

Feedback Bot on 3/1/2025, 11:48 AM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

[jjonescz]

Yes, currently the error

error CS4007: Instance of type 'System.Span<int>' cannot be preserved across 'await' or 'yield' boundary.

is a "build-only diagnostic", i.e., it is reported during later stages of the compiler which don't run in the IDE, they run only during full builds.

I agree it's not an ideal development experience and we could think about changing that.