aterm 0.13.0

Implementation of the Annotated Terms data structure
Documentation 
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#![allow(unknown_lints)]

use interface;
use interface::Term;
use utils::insert_or_get;
use rc::ATerm;

use std::cell::UnsafeCell;
use std::rc::Rc;
use std::collections::HashSet;
use std::hash::Hash;
use std::marker::PhantomData;

#[derive(Default, Debug)]
pub struct ATermFactory<B: Hash + Eq> {
    arena: UnsafeCell<HashSet<Rc<ATerm<B>>>>,
    _nothing: PhantomData<B>,
}

impl<B: Hash + Eq> ATermFactory<B> {
    pub fn new() -> Self {
        ATermFactory {
            arena: UnsafeCell::new(HashSet::new()),
            _nothing: PhantomData,
        }
    }

    pub fn with_capacity(capacity: usize) -> Self {
        ATermFactory {
            arena: UnsafeCell::new(HashSet::with_capacity(capacity)),
            _nothing: PhantomData,
        }
    }

    // Yes this is evil and unsafe, but that's why it's private!
    #[allow(mut_from_ref)]
    fn get_arena(&self) -> &mut HashSet<Rc<ATerm<B>>> {
        unsafe { &mut *self.arena.get() }
    }
}

impl<B: Clone + Hash + Eq> interface::ATermFactory<B> for ATermFactory<B> {
    type ATerm = ATerm<B>;
    type ATermRef = Rc<ATerm<B>>;

    fn no_annos(&self, term: Term<Rc<ATerm<B>>, B>) -> Self::ATermRef {
        insert_or_get(self.get_arena(), Rc::new(ATerm::no_annos(term))).clone()
    }

    fn with_annos<A>(&self, term: Term<Rc<ATerm<B>>, B>, annos: A) -> Self::ATermRef
        where A: IntoIterator<Item = Self::ATermRef>
    {
        insert_or_get(self.get_arena(), Rc::new(ATerm::with_annos(term, annos))).clone()
    }
}

impl<B: Clone + Hash + Eq> interface::SharedATermFactory<B> for ATermFactory<B> {
    fn get_shared(&self, value: Self::ATermRef) -> Self::ATermRef
        where Self::ATermRef: Clone
    {
        insert_or_get(self.get_arena(), value.clone()).clone()
    }
}