Trait rustc_data_structures::undo_log::UndoLogs

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pub trait UndoLogs<T> {
    // Required methods
    fn num_open_snapshots(&self) -> usize;
    fn push(&mut self, undo: T);
    fn clear(&mut self);

    // Provided methods
    fn in_snapshot(&self) -> bool { ... }
    fn extend<I>(&mut self, undos: I)
       where Self: Sized,
             I: IntoIterator<Item = T> { ... }
}

Expand description

A trait which allows undo actions (T) to be pushed which can be used to rollback actions at a later time if needed.

The undo actions themselves are opaque to UndoLogs, only specified Rollback implementations need to know what an action is and how to reverse it.

Required Methods§

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fn num_open_snapshots(&self) -> usize

How many open snapshots this undo log currently has

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fn push(&mut self, undo: T)

Pushes a new “undo item” onto the undo log. This method is invoked when some action is taken (e.g., a variable is unified). It records the info needed to reverse that action should an enclosing snapshot be rolled back.

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