The proposal to add a similar method from std [`map_while`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map_while) for stream. This would be convenient to reduce this: ```rust stream.map(|x| u32::checked_div(16, x)) .take_while(|x| future::ready(x.is_some())) .map(|x| x.unwrap()) ``` to this: ```rust stream.map_while(|x| future::ready(u32::checked_div(16, x))) ```
