//! Helper type for disabling memory tracking when not wanted

use crate::internal_prelude::*;

/// Either `T`, if we're enabled, or nothing if we're no-op

///

/// Used for runtime control of whether the memory quota is enabled:

/// we support explicitly creating a no-op tracker

/// with [`MemoryQuotaTracker::new_noop`](crate::MemoryQuotaTracker::new_noop).

///

/// We use this rather than just `Option` because we also have data structures

/// (trackers, `Account`s and so on)

/// which have been torn down, or are "dummy" or "dangling",

/// which are supposed to return errors rather than no-op successes.

#[derive(Clone, Debug, Eq, PartialEq)]

pub(crate) enum IfEnabled<T> {

    /// We're enabled, and supposed to be tracking memory

    ///

    /// The 2nd member causes this variant to prove that tracking is enabled.

    /// If tracking is disabled at compile time, this variant is uninhabited

    /// and the whole `IfEnabled` becomes a unit.

    Enabled(T, EnabledToken),

    /// We're inenabled and everything should be a lightweight no-op

    Noop,

}

use IfEnabled::*;

impl<T> IfEnabled<T> {

    /// Convert to `Option`: return `Some` if this is `Enabled`

        }

    /// Take reference; analogous to `Option::as_ref`

        }

    /// Take reference and convert to `Option`

    ///

    /// Convenience helper equivalent to `.as_ref().into_enabled()`.

    /// Return the contents of the `Enabled`, or declare it a [`Bug`]

    #[track_caller]

        }

}