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store fn to create Arc<dyn Any> instead of drop

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This will allow us to invoke callbacks when deleting
a memo with `Arc<dyn Any>` values.
This commit is contained in:
Niko Matsakis 2024-08-15 10:57:36 +03:00
parent d8ae590428
commit f12874fe62
1 changed files with 11 additions and 9 deletions
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20
src/table/memo.rs
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@ -43,7 +43,7 @@ struct MemoEntryData {
type_id: TypeId,
/// A pointer to `std::mem::drop::<Arc<M>>` for the erased memo type `M`
drop_fn: fn(Arc<DummyMemo>),
to_dyn_any_fn: fn(Arc<DummyMemo>) -> Arc<dyn Any>,
/// An [`ArcSwap`][] to a `Arc<M>` for the erased memo type `M`
arc_swap: ArcSwap<DummyMemo>,
@ -61,9 +61,11 @@ impl MemoTable {
unsafe { std::mem::transmute::<Arc<DummyMemo>, Arc<M>>(memo) }
}
fn drop_fn<M>() -> fn(Arc<DummyMemo>) {
let f: fn(Arc<M>) = std::mem::drop::<Arc<M>>;
unsafe { std::mem::transmute::<fn(Arc<M>), fn(Arc<DummyMemo>)>(f) }
fn to_dyn_any_fn<M: Any>() -> fn(Arc<DummyMemo>) -> Arc<dyn Any> {
let f: fn(Arc<M>) -> Arc<dyn Any> = |x| x;
unsafe {
std::mem::transmute::<fn(Arc<M>) -> Arc<dyn Any>, fn(Arc<DummyMemo>) -> Arc<dyn Any>>(f)
}
}
pub(crate) fn insert<M: Any + Send + Sync>(
@ -77,7 +79,7 @@ impl MemoTable {
data:
Some(MemoEntryData {
type_id,
drop_fn: _,
to_dyn_any_fn: _,
arc_swap,
}),
}) = self.memos.read().get(memo_ingredient_index.as_usize())
@ -106,7 +108,7 @@ impl MemoTable {
memos[memo_ingredient_index] = MemoEntry {
data: Some(MemoEntryData {
type_id: TypeId::of::<M>(),
drop_fn: Self::drop_fn::<M>(),
to_dyn_any_fn: Self::to_dyn_any_fn::<M>(),
arc_swap: ArcSwap::new(Self::to_dummy(memo)),
}),
};
@ -122,7 +124,7 @@ impl MemoTable {
data:
Some(MemoEntryData {
type_id,
drop_fn: _,
to_dyn_any_fn: _,
arc_swap,
}),
}) = memos.get(memo_ingredient_index.as_usize())
@ -145,12 +147,12 @@ impl Drop for MemoEntry {
fn drop(&mut self) {
if let Some(MemoEntryData {
type_id: _,
drop_fn,
to_dyn_any_fn,
arc_swap,
}) = self.data.take()
{
let arc = arc_swap.into_inner();
drop_fn(arc);
std::mem::drop(to_dyn_any_fn(arc));
}
}
}