IsAwaitable 1.1.0

using System.Threading.Tasks;

// Checks if it's awaitable
bool IsAwaitable(this object? instance);
bool IsAwaitable(this Type type);
// await x;

// Check if it's awaitable and returns a result
bool IsAwaitableWithResult(this object? instance);
bool IsAwaitableWithResult(this Type type);
// var foo = await x;

Samples

// On instances
Task doAsync = DoSomethingAsync();
_ = doAsync.IsAwaitable(); // true

// Returing a result
Task<int> promise = GetSomethingAsync();
_ = promise.IsAwaitable(); // true
_ = promise.IsAwaitableWithResult(); // true

// On types
_ = typeof(Task).IsAwaitable(); // true

// On value tasks
_ = typeof(ValueTask).IsAwaitable(); // true
_ = typeof(ValueTask<>).IsAwaitableWithResult(); // true

// On custom awaitables!
class CustomDelay
{
    private readonly TimeSpan _delay;

    public CustomDelay(TimeSpan delay) =>
        _delay = delay;

    public TaskAwaiter GetAwaiter() =>
        Task.Delay(_delay).GetAwaiter();
}

var delay = new CustomDelay(TimeSpan.FromSeconds(2));
_ = delay.IsAwaitable(); // true
_ = delay.IsAwaitableWithResult(); // false