It seems that in most cases the C# compiler could call Dispose() automatically. Like most cases of the using pattern look like:

public void SomeMethod()
{
    ...

    using (var foo = new Foo())
    {
        ...
    }

    // Foo isn't use after here (obviously).
    ...
}

Since foo isn't used (that's a very simple detection) and since its not provided as argument to another method (that's a supposition that applies to many use cases and can be extended), the compiler could automatically call Dispose() without the developper requiring to do it.

This means that in most cases the using is pretty useless if the compiler does some smart job. IDisposable seem low level enough to me to be taken in account by a compiler.

Now why isn't this done? Wouldn't that improve the performances (if the developpers are... dirty).