Cannot implicitly convert in async method

Question

The following code doesn't compile, and I fail to understand why

namespace ImplicitConversion
{
    struct Wrapper<T>
    {
        public static implicit operator Wrapper<T> (T input)
        {
            return new Wrapper<T> ();
        }
    }

    interface IFoo
    {
    }

    class Foo:IFoo
    {
    }

    class MainClass
    {
        public static void Main (string[] args)
        {       
        }

        static Wrapper<IFoo> Test ()
        {
            IFoo foo = new Foo ();
            return foo; // Cannot implicitly convert type 'ImplicitConversion.IFoo' to 'ImplicitConversion.Wrapper<ImplicitConversion.IFoo>' (CS0029) (ImplicitConversion)
        }
    }
}

Why can't I use the implicit conversion?

this doesn't really have anything to do with it being an async method btw. this conversion fails whether it's a `Task>` or just a `Wrapper` — DLeh, Jan 15 '15 at 14:16
Also, it seems that serdar is right, you cannot implicitly convert from interfaces: http://stackoverflow.com/a/143567/526704 — DLeh, Jan 15 '15 at 14:18
Was also going to wield the dupehammer, but to this: http://stackoverflow.com/questions/1208796/c-sharp-compiler-bug-why-doesnt-this-implicit-user-defined-conversion-compile — spender, Jan 15 '15 at 14:21

score 2 · Accepted Answer · edited May 23 '17 at 12:14

2

As DLeh mentioned it is not about async.

AFAIK interfaces can not be converted(either implicit or explicit).

See this answer for details: https://stackoverflow.com/a/143567/526704

edited May 23 '17 at 12:14

Community

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answered Jan 15 '15 at 14:17

serdar

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Yup, 6.4.4 in the C# spec. (Also if you remove the generics, you get an explicit 'User-defined conversion from interface' error.) – Rawling Jan 15 '15 at 14:19
I've modified the question – miniBill Jan 15 '15 at 14:20

Cannot implicitly convert in async method

1 Answers1