Enum IfEnabled

pub(crate) enum IfEnabled<T> {
    Enabled(T, EnabledToken),
    Noop,
}

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.

We use this rather than just Option because we also have data structures (trackers, Accounts and so on) which have been torn down, or are “dummy” or “dangling”, which are supposed to return errors rather than no-op successes.

Variants

Enabled(T, EnabledToken)

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.

Noop

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

Implementations

impl<T> IfEnabled<T>

pub(crate) fn into_enabled(self) -> Option<T>

Convert to Option: return Some if this is Enabled

pub(crate) fn as_ref(&self) -> IfEnabled<&T>

Take reference; analogous to Option::as_ref

pub(crate) fn as_enabled(&self) -> Option<&T>

Take reference and convert to Option

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

pub(crate) fn enabled_or_bug(self) -> Result<T, Bug>

Return the contents of the Enabled, or declare it a Bug

Trait Implementations

impl<T: Clone> Clone for IfEnabled<T>

fn clone(&self) -> IfEnabled<T>

Returns a duplicate of the value.

const fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for IfEnabled<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: PartialEq> PartialEq for IfEnabled<T>

fn eq(&self, other: &IfEnabled<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

const fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: Eq> Eq for IfEnabled<T>

impl<T> StructuralPartialEq for IfEnabled<T>