Why does compiler emit async state machine for async methods with only synchronous code?

[voroninp]

I can mark a method as async and do not use await, I get a warning from the compiler:

public async Task Foo()
{
}

When I look at IL (at least in LinqPad) I see that compiler emits code for state machine.

Why not just wrapping the result with the task? In this case it would be return Task.CompltedTaks

[YairHalberstadt]

This has been discussed on roslyn at dotnet/roslyn#3659

In short, they would take this, but you would have to be careful to keep semantics exactly the same.