Why 'await' causing compiler error when that in an interpolated string?

[Connect-a]

The following code cannot be compiled:

        private static async Task Main()
        {
            // compiler error CS0103 : The name 'await' does not exist in the current context
            var z = $"{await (Task.FromResult(string.Empty))}";

            // allowed
            var a = await Task.FromResult(string.Empty);
            var b = await (Task.FromResult(string.Empty));
            var c = $"{await Task.FromResult(string.Empty)}";

            Console.ReadLine();
        }

[spydacarnage]

If you get rid of the brackets, so it is just:

var z = $"{await Task.FromResult(string.Empty)}";

Then it works. I assume that the parentheses around the Task.FromResult(...) confuse the compiler (in the same way that a ? : expression inside an interpolated string needs to be surrounded by parentheses).

[ronnygunawan]

I assume that the parentheses around the Task.FromResult(...) confuse the compiler (in the same way that a ? : expression inside an interpolated string needs to be surrounded by parentheses).

It's not the same. ? : must be parenthesized because : would end the interpolation, since : is used as delimiter between expression and its format string.

[CyrusNajmabadi]

Sounds like a bug to me. Likely a compiler issue where the lexer/parser get confused as to what's inside the interpolation.

[HaloFour]

Sounds like a bug? Maybe open on the Roslyn repo?

[Connect-a]

Should I open the same issue on the Roslyn repo?
I heard that it is possible to transfer issues, but unfortunately I don't have permission.