Cannot implicitly convert in async method [duplicate]

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<Wrapper<IFoo>> or just a Wrapper<IFoo> — DLeh
– DLeh, Commented Jan 15, 2015 at 14:16
Also, it seems that serdar is right, you cannot implicitly convert from interfaces: stackoverflow.com/a/143567/526704 — DLeh
– DLeh, Commented Jan 15, 2015 at 14:18
Was also going to wield the dupehammer, but to this: stackoverflow.com/questions/1208796/… — spender
– spender, Commented Jan 15, 2015 at 14:21

Community · Accepted Answer · 2017-05-23 12:14:10Z

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, 2017 at 12:14

CommunityBot

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answered Jan 15, 2015 at 14:17

serdar

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2 Comments

Rawling Over a year ago

Yup, 6.4.4 in the C# spec. (Also if you remove the generics, you get an explicit 'User-defined conversion from interface' error.)

miniBill Over a year ago

I've modified the question

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