rust-libp2p/core/src/upgrade/error.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
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use multistream_select::ProtocolChoiceError;
use std::fmt;

/// Error that can happen when upgrading a connection or substream to use a protocol.
#[derive(Debug)]
pub enum UpgradeError<E> {
    /// Error during the negotiation process.
    Select(ProtocolChoiceError),
    /// Error during the post-negotiation handshake.
    Apply(E),
}

impl<E> UpgradeError<E> {
    pub fn map_err<F, T>(self, f: F) -> UpgradeError<T>
    where
        F: FnOnce(E) -> T
    {
        match self {
            UpgradeError::Select(e) => UpgradeError::Select(e),
            UpgradeError::Apply(e) => UpgradeError::Apply(f(e)),
        }
    }

    pub fn into_err<T>(self) -> UpgradeError<T>
    where
        T: From<E>
    {
        self.map_err(Into::into)
    }
}

impl<E> fmt::Display for UpgradeError<E>
where
    E: fmt::Display
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            UpgradeError::Select(e) => write!(f, "select error: {}", e),
            UpgradeError::Apply(e) => write!(f, "upgrade apply error: {}", e),
        }
    }
}

impl<E> std::error::Error for UpgradeError<E>
where
    E: std::error::Error + 'static
{
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            UpgradeError::Select(e) => Some(e),
            UpgradeError::Apply(e) => Some(e),
        }
    }
}

impl<E> From<ProtocolChoiceError> for UpgradeError<E> {
    fn from(e: ProtocolChoiceError) -> Self {
        UpgradeError::Select(e)
    }
}