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/// Represents the result of a non-blocking read from a [DashMap](crate::DashMap).
#[derive(Debug)]
pub enum TryResult<R> {
    /// The value was present in the map, and the lock for the shard was successfully obtained.
    Present(R),
    /// The shard wasn't locked, and the value wasn't present in the map.
    Absent,
    /// The shard was locked.
    Locked,
}

impl<R> TryResult<R> {
    /// Returns `true` if the value was present in the map, and the lock for the shard was successfully obtained.
    pub fn is_present(&self) -> bool {
        matches!(self, TryResult::Present(_))
    }

    /// Returns `true` if the shard wasn't locked, and the value wasn't present in the map.
    pub fn is_absent(&self) -> bool {
        matches!(self, TryResult::Absent)
    }

    /// Returns `true` if the shard was locked.
    pub fn is_locked(&self) -> bool {
        matches!(self, TryResult::Locked)
    }

    /// If `self` is [Present](TryResult::Present), returns the reference to the value in the map.
    /// Panics if `self` is not [Present](TryResult::Present).
    pub fn unwrap(self) -> R {
        match self {
            TryResult::Present(r) => r,
            TryResult::Locked => panic!("Called unwrap() on TryResult::Locked"),
            TryResult::Absent => panic!("Called unwrap() on TryResult::Absent"),
        }
    }

    /// If `self` is [Present](TryResult::Present), returns the reference to the value in the map.
    /// If `self` is not [Present](TryResult::Present), returns `None`.
    pub fn try_unwrap(self) -> Option<R> {
        match self {
            TryResult::Present(r) => Some(r),
            _ => None,
        }
    }
}