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Remove HybridBitSet::dummy

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This commit is contained in:
ljedrz 2018-10-16 18:36:44 +02:00
parent 5ea8eb55cd
commit 1dd92c4a70
1 changed files with 14 additions and 36 deletions
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50
src/librustc_data_structures/bit_set.rs
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@ -423,15 +423,6 @@ pub enum HybridBitSet<T: Idx> {
}
impl<T: Idx> HybridBitSet<T> {
// FIXME: This function is used in conjunction with `mem::replace()` in
// several pieces of awful code below. I can't work out how else to appease
// the borrow checker.
fn dummy() -> Self {
// The cheapest HybridBitSet to construct, which is only used to get
// around the borrow checker.
HybridBitSet::Sparse(SparseBitSet::new_empty(0))
}
pub fn new_empty(domain_size: usize) -> Self {
HybridBitSet::Sparse(SparseBitSet::new_empty(domain_size))
}
@ -487,20 +478,14 @@ impl<T: Idx> HybridBitSet<T> {
// that doesn't matter because `elem` is already present.
false
}
HybridBitSet::Sparse(_) => {
HybridBitSet::Sparse(sparse) => {
// The set is sparse and full. Convert to a dense set.
match mem::replace(self, HybridBitSet::dummy()) {
HybridBitSet::Sparse(sparse) => {
let mut dense = sparse.to_dense();
let changed = dense.insert(elem);
assert!(changed);
*self = HybridBitSet::Dense(dense);
changed
}
_ => unreachable!()
}
let mut dense = sparse.to_dense();
let changed = dense.insert(elem);
assert!(changed);
*self = HybridBitSet::Dense(dense);
changed
}
HybridBitSet::Dense(dense) => dense.insert(elem),
}
}
@ -525,33 +510,26 @@ impl<T: Idx> HybridBitSet<T> {
pub fn union(&mut self, other: &HybridBitSet<T>) -> bool {
match self {
HybridBitSet::Sparse(_) => {
HybridBitSet::Sparse(self_sparse) => {
match other {
HybridBitSet::Sparse(other_sparse) => {
// Both sets are sparse. Add the elements in
// `other_sparse` to `self_hybrid` one at a time. This
// may or may not cause `self_hybrid` to be densified.
// `other_sparse` to `self` one at a time. This
// may or may not cause `self` to be densified.
assert_eq!(self.domain_size(), other.domain_size());
let mut self_hybrid = mem::replace(self, HybridBitSet::dummy());
let mut changed = false;
for elem in other_sparse.iter() {
changed |= self_hybrid.insert(*elem);
changed |= self.insert(*elem);
}
*self = self_hybrid;
changed
}
HybridBitSet::Dense(other_dense) => {
// `self` is sparse and `other` is dense. Densify
// `self` and then do the bitwise union.
match mem::replace(self, HybridBitSet::dummy()) {
HybridBitSet::Sparse(self_sparse) => {
let mut new_dense = self_sparse.to_dense();
let changed = new_dense.union(other_dense);
*self = HybridBitSet::Dense(new_dense);
changed
}
_ => unreachable!()
}
let mut new_dense = self_sparse.to_dense();
let changed = new_dense.union(other_dense);
*self = HybridBitSet::Dense(new_dense);
changed
}
}
}