     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
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70

    use core::fmt::Display;

    use {Fail, Compat, Context};

    /// Extension methods for `Result`.
    pub trait ResultExt<T, E> {
        /// Wraps the error in `Compat` to make it compatible with older error
        /// handling APIs that expect `std::error::Error`.
        fn compat(self) -> Result<T, Compat<E>>;

        /// Wraps the error type in a context type.
        fn context<D>(self, context: D) -> Result<T, Context<D>> where
            D: Display + Send + Sync + 'static;

        /// Wraps the error type in a context type generated by looking at the
        /// error value.
        fn with_context<F, D>(self, f: F) -> Result<T, Context<D>> where
            F: FnOnce(&E) -> D,
            D: Display + Send + Sync + 'static;
    }

    impl<T, E> ResultExt<T, E> for Result<T, E> where
        E: Fail,
    {
        fn compat(self) -> Result<T, Compat<E>> {
            self.map_err(|err| err.compat())
        }

        fn context<D>(self, context: D) -> Result<T, Context<D>> where
            D: Display + Send + Sync + 'static
        {
            self.map_err(|failure| failure.context(context))
        }

        fn with_context<F, D>(self, f: F) -> Result<T, Context<D>> where
            F: FnOnce(&E) -> D,
            D: Display + Send + Sync + 'static
        {
            self.map_err(|failure| {
                let context = f(&failure);
                failure.context(context)
            })
        }
    }

    with_std! {
        use Error;

        impl<T> ResultExt<T, Error> for Result<T, Error> {
            fn compat(self) -> Result<T, Compat<Error>> {
                self.map_err(|err| err.compat())
            }

            fn context<D>(self, context: D) -> Result<T, Context<D>> where
                D: Display + Send + Sync + 'static
            {
                self.map_err(|failure| failure.context(context))
            }

            fn with_context<F, D>(self, f: F) -> Result<T, Context<D>> where
                F: FnOnce(&Error) -> D,
                D: Display + Send + Sync + 'static
            {
                self.map_err(|failure| {
                    let context = f(&failure);
                    failure.context(context)
                })
            }
        }
    }

# 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`)