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@@ -485,6 +485,309 @@ impl<S> MemoryLocation<S> {
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_marker: PhantomData,
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}
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}
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+
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+ #[track_caller]
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+ fn try_borrow<T: Any>(
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+ &self,
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+ #[cfg(any(debug_assertions, feature = "debug_ownership"))]
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+ created_at: &'static std::panic::Location<'static>,
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+ ) -> Result<GenerationalRef<T>, BorrowError> {
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ self.0
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+ .borrowed_at
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+ .borrow_mut()
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+ .push(std::panic::Location::caller());
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+ match self.0.data.try_borrow() {
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+ Ok(borrow) => match Ref::filter_map(borrow, |any| any.as_ref()?.downcast_ref::<T>()) {
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+ Ok(reference) => Ok(GenerationalRef {
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+ inner: reference,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: GenerationalRefBorrowInfo {
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+ borrowed_at: std::panic::Location::caller(),
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+ borrowed_from: self.0,
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+ },
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+ }),
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+ Err(_) => Err(BorrowError::Dropped(ValueDroppedError {
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+ #[cfg(any(debug_assertions, feature = "debug_ownership"))]
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+ created_at,
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+ })),
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+ },
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+ Err(_) => Err(BorrowError::AlreadyBorrowedMut(AlreadyBorrowedMutError {
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrowed_mut_at: self.0.borrowed_mut_at.get().unwrap(),
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+ })),
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+ }
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+ }
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+
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+ #[track_caller]
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+ fn try_borrow_mut<T: Any>(
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+ &self,
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+ #[cfg(any(debug_assertions, feature = "debug_ownership"))]
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+ created_at: &'static std::panic::Location<'static>,
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+ ) -> Result<GenerationalRefMut<T>, BorrowMutError> {
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ {
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+ self.0
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+ .borrowed_mut_at
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+ .set(Some(std::panic::Location::caller()));
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+ }
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+ match self.0.data.try_borrow_mut() {
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+ Ok(borrow_mut) => {
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+ match RefMut::filter_map(borrow_mut, |any| any.as_mut()?.downcast_mut::<T>()) {
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+ Ok(reference) => Ok(GenerationalRefMut {
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+ inner: reference,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: GenerationalRefMutBorrowInfo {
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+ borrowed_from: self.0,
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+ },
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+ }),
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+ Err(_) => Err(BorrowMutError::Dropped(ValueDroppedError {
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+ #[cfg(any(debug_assertions, feature = "debug_ownership"))]
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+ created_at,
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+ })),
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+ }
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+ }
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+ Err(_) => Err(BorrowMutError::AlreadyBorrowed(AlreadyBorrowedError {
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrowed_at: self.0.borrowed_at.borrow().clone(),
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+ })),
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+ }
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+ }
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+}
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+
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+#[derive(Debug, Clone)]
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+/// An error that can occur when trying to borrow a value.
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+pub enum BorrowError {
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+ /// The value was dropped.
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+ Dropped(ValueDroppedError),
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+ /// The value was already borrowed mutably.
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+ AlreadyBorrowedMut(AlreadyBorrowedMutError),
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+}
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+
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+impl Display for BorrowError {
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+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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+ match self {
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+ BorrowError::Dropped(error) => Display::fmt(error, f),
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+ BorrowError::AlreadyBorrowedMut(error) => Display::fmt(error, f),
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+ }
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+ }
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+}
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+
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+impl Error for BorrowError {}
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+
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+#[derive(Debug, Clone)]
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+/// An error that can occur when trying to borrow a value mutably.
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+pub enum BorrowMutError {
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+ /// The value was dropped.
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+ Dropped(ValueDroppedError),
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+ /// The value was already borrowed.
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+ AlreadyBorrowed(AlreadyBorrowedError),
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+ /// The value was already borrowed mutably.
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+ AlreadyBorrowedMut(AlreadyBorrowedMutError),
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+}
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+
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+impl Display for BorrowMutError {
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+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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+ match self {
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+ BorrowMutError::Dropped(error) => Display::fmt(error, f),
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+ BorrowMutError::AlreadyBorrowedMut(error) => Display::fmt(error, f),
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+ BorrowMutError::AlreadyBorrowed(error) => Display::fmt(error, f),
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+ }
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+ }
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+}
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+
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+impl Error for BorrowMutError {}
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+
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+/// An error that can occur when trying to use a value that has been dropped.
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+#[derive(Debug, Copy, Clone)]
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+pub struct ValueDroppedError {
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+ #[cfg(any(debug_assertions, feature = "debug_ownership"))]
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+ created_at: &'static std::panic::Location<'static>,
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+}
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+
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+impl Display for ValueDroppedError {
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+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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+ f.write_str("Failed to borrow because the value was dropped.")?;
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+ #[cfg(any(debug_assertions, feature = "debug_ownership"))]
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+ f.write_fmt(format_args!("created_at: {}", self.created_at))?;
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+ Ok(())
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+ }
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+}
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+
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+impl std::error::Error for ValueDroppedError {}
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+
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+/// An error that can occur when trying to borrow a value that has already been borrowed mutably.
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+#[derive(Debug, Copy, Clone)]
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+pub struct AlreadyBorrowedMutError {
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrowed_mut_at: &'static std::panic::Location<'static>,
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+}
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+
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+impl Display for AlreadyBorrowedMutError {
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+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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+ f.write_str("Failed to borrow because the value was already borrowed mutably.")?;
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ f.write_fmt(format_args!("borrowed_mut_at: {}", self.borrowed_mut_at))?;
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+ Ok(())
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+ }
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+}
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+
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+impl std::error::Error for AlreadyBorrowedMutError {}
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+
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+/// An error that can occur when trying to borrow a value mutably that has already been borrowed immutably.
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+#[derive(Debug, Clone)]
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+pub struct AlreadyBorrowedError {
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrowed_at: Vec<&'static std::panic::Location<'static>>,
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+}
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+
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+impl Display for AlreadyBorrowedError {
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+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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+ f.write_str("Failed to borrow mutably because the value was already borrowed immutably.")?;
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ f.write_str("borrowed_at:")?;
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ for location in self.borrowed_at.iter() {
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+ f.write_fmt(format_args!("\t{}", location))?;
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+ }
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+ Ok(())
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+ }
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+}
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+
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+impl std::error::Error for AlreadyBorrowedError {}
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+
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+/// A reference to a value in a generational box.
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+pub struct GenerationalRef<T: 'static> {
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+ inner: Ref<'static, T>,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: GenerationalRefBorrowInfo,
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+}
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+
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+impl<T: 'static> GenerationalRef<T> {
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+ /// Map one ref type to another.
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+ pub fn map<U, F>(orig: GenerationalRef<T>, f: F) -> GenerationalRef<U>
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+ where
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+ F: FnOnce(&T) -> &U,
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+ {
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+ GenerationalRef {
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+ inner: Ref::map(orig.inner, f),
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: GenerationalRefBorrowInfo {
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+ borrowed_at: orig.borrow.borrowed_at,
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+ borrowed_from: orig.borrow.borrowed_from,
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+ },
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+ }
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+ }
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+
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+ /// Filter one ref type to another.
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+ pub fn filter_map<U, F>(orig: GenerationalRef<T>, f: F) -> Option<GenerationalRef<U>>
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+ where
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+ F: FnOnce(&T) -> Option<&U>,
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+ {
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+ let Self {
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+ inner,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow,
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+ } = orig;
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+ Ref::filter_map(inner, f).ok().map(|inner| GenerationalRef {
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+ inner,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: GenerationalRefBorrowInfo {
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+ borrowed_at: borrow.borrowed_at,
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+ borrowed_from: borrow.borrowed_from,
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+ },
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+ })
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+ }
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+}
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+
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+impl<T: 'static> Deref for GenerationalRef<T> {
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+ type Target = T;
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+
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+ fn deref(&self) -> &Self::Target {
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+ self.inner.deref()
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+ }
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+}
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+
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+#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+struct GenerationalRefBorrowInfo {
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+ borrowed_at: &'static std::panic::Location<'static>,
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+ borrowed_from: &'static MemoryLocationInner,
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+}
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+
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+#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+impl Drop for GenerationalRefBorrowInfo {
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+ fn drop(&mut self) {
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+ self.borrowed_from
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+ .borrowed_at
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+ .borrow_mut()
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+ .retain(|location| std::ptr::eq(*location, self.borrowed_at as *const _));
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+ }
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+}
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+
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+/// A mutable reference to a value in a generational box.
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+pub struct GenerationalRefMut<T: 'static> {
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+ inner: RefMut<'static, T>,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: GenerationalRefMutBorrowInfo,
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+}
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+
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+impl<T: 'static> GenerationalRefMut<T> {
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+ /// Map one ref type to another.
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+ pub fn map<U, F>(orig: GenerationalRefMut<T>, f: F) -> GenerationalRefMut<U>
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+ where
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+ F: FnOnce(&mut T) -> &mut U,
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+ {
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+ GenerationalRefMut {
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+ inner: RefMut::map(orig.inner, f),
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow: orig.borrow,
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+ }
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+ }
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+
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+ /// Filter one ref type to another.
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+ pub fn filter_map<U, F>(orig: GenerationalRefMut<T>, f: F) -> Option<GenerationalRefMut<U>>
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+ where
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+ F: FnOnce(&mut T) -> Option<&mut U>,
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+ {
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+ let Self {
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+ inner,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow,
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+ } = orig;
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+ RefMut::filter_map(inner, f)
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+ .ok()
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+ .map(|inner| GenerationalRefMut {
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+ inner,
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+ #[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+ borrow,
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+ })
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+ }
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+}
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+
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+impl<T: 'static> Deref for GenerationalRefMut<T> {
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+ type Target = T;
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+
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+ fn deref(&self) -> &Self::Target {
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+ self.inner.deref()
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+ }
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+}
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+
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+impl<T: 'static> DerefMut for GenerationalRefMut<T> {
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+ fn deref_mut(&mut self) -> &mut Self::Target {
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+ self.inner.deref_mut()
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+ }
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+}
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+
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+#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+struct GenerationalRefMutBorrowInfo {
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+ borrowed_from: &'static MemoryLocationInner,
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+}
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+
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+#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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+impl Drop for GenerationalRefMutBorrowInfo {
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+ fn drop(&mut self) {
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+ self.borrowed_from.borrowed_mut_at.take();
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+ }
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}
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/// Owner: Handles dropping generational boxes. The owner acts like a runtime lifetime guard. Any states that you create with an owner will be dropped when that owner is dropped.
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