     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49

    use {Future, IntoFuture, Poll};
    use core::fmt;
    use super::chain::Chain;

    /// Future for the `flatten` combinator, flattening a future-of-a-future to get just
    /// the result of the final future.
    ///
    /// This is created by the `Future::flatten` method.
    #[must_use = "futures do nothing unless polled"]
    pub struct Flatten<A> where A: Future, A::Item: IntoFuture {
        state: Chain<A, <A::Item as IntoFuture>::Future, ()>,
    }

    impl<A> fmt::Debug for Flatten<A>
        where A: Future + fmt::Debug,
              A::Item: IntoFuture,
              <<A as IntoFuture>::Item as IntoFuture>::Future: fmt::Debug,
    {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_struct("Flatten")
                .field("state", &self.state)
                .finish()
        }
    }

    pub fn new<A>(future: A) -> Flatten<A>
        where A: Future,
              A::Item: IntoFuture,
    {
        Flatten {
            state: Chain::new(future, ()),
        }
    }

    impl<A> Future for Flatten<A>
        where A: Future,
              A::Item: IntoFuture,
              <<A as Future>::Item as IntoFuture>::Error: From<<A as Future>::Error>
    {
        type Item = <<A as Future>::Item as IntoFuture>::Item;
        type Error = <<A as Future>::Item as IntoFuture>::Error;

        fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
            self.state.poll(|a, ()| {
                let future = a?.into_future();
                Ok(Err(future))
            })
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)