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Use FxIndexMap instead FxHashMap to stabilize iteration order in EffectiveVisibilities #121851

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Mar 31, 2024
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Use FxIndexMap instead FxHashMap to stabilize iteration order in EffectiveVisibilities #121851

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a50490c
Use FxIndexMap instead FxHashMap to stabilize iteration order in Effe…
michaelwoerister Mar 1, 2024
7e4bc4a
Remove and disallow HashStable impl of HashMap.
michaelwoerister Mar 27, 2024
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48 changes: 2 additions & 46 deletions compiler/rustc_data_structures/src/stable_hasher.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -684,26 +684,11 @@ where
impl_stable_traits_for_trivial_type!(::std::path::Path);
impl_stable_traits_for_trivial_type!(::std::path::PathBuf);

impl<K, V, R, HCX> HashStable<HCX> for ::std::collections::HashMap<K, V, R>
where
K: ToStableHashKey<HCX> + Eq,
V: HashStable<HCX>,
R: BuildHasher,
{
#[inline]
fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
stable_hash_reduce(hcx, hasher, self.iter(), self.len(), |hasher, hcx, (key, value)| {
let key = key.to_stable_hash_key(hcx);
key.hash_stable(hcx, hasher);
value.hash_stable(hcx, hasher);
});
}
}

// It is not safe to implement HashStable for HashSet or any other collection type
// It is not safe to implement HashStable for HashSet, HashMap or any other collection type
// with unstable but observable iteration order.
// See https://github.com/rust-lang/compiler-team/issues/533 for further information.
impl<V, HCX> !HashStable<HCX> for std::collections::HashSet<V> {}
impl<K, V, HCX> !HashStable<HCX> for std::collections::HashMap<K, V> {}

impl<K, V, HCX> HashStable<HCX> for ::std::collections::BTreeMap<K, V>
where
Expand All @@ -730,35 +715,6 @@ where
}
}

fn stable_hash_reduce<HCX, I, C, F>(
hcx: &mut HCX,
hasher: &mut StableHasher,
mut collection: C,
length: usize,
hash_function: F,
) where
C: Iterator<Item = I>,
F: Fn(&mut StableHasher, &mut HCX, I),
{
length.hash_stable(hcx, hasher);

match length {
1 => {
hash_function(hasher, hcx, collection.next().unwrap());
}
_ => {
let hash = collection
.map(|value| {
let mut hasher = StableHasher::new();
hash_function(&mut hasher, hcx, value);
hasher.finish::<Hash128>()
})
.reduce(|accum, value| accum.wrapping_add(value));
hash.hash_stable(hcx, hasher);
}
}
}

/// Controls what data we do or do not hash.
/// Whenever a `HashStable` implementation caches its
/// result, it needs to include `HashingControls` as part
Expand Down
9 changes: 4 additions & 5 deletions compiler/rustc_middle/src/middle/privacy.rs
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Expand Up @@ -2,7 +2,7 @@
//! outside their scopes. This pass will also generate a set of exported items
//! which are available for use externally when compiled as a library.
use crate::ty::{TyCtxt, Visibility};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::fx::{FxIndexMap, IndexEntry};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_hir::def::DefKind;
use rustc_macros::HashStable;
Expand Down Expand Up @@ -90,7 +90,7 @@ impl EffectiveVisibility {
/// Holds a map of effective visibilities for reachable HIR nodes.
#[derive(Clone, Debug)]
pub struct EffectiveVisibilities<Id = LocalDefId> {
map: FxHashMap<Id, EffectiveVisibility>,
map: FxIndexMap<Id, EffectiveVisibility>,
}

impl EffectiveVisibilities {
Expand Down Expand Up @@ -130,9 +130,8 @@ impl EffectiveVisibilities {
eff_vis: &EffectiveVisibility,
tcx: TyCtxt<'_>,
) {
use std::collections::hash_map::Entry;
match self.map.entry(def_id) {
Entry::Occupied(mut occupied) => {
IndexEntry::Occupied(mut occupied) => {
let old_eff_vis = occupied.get_mut();
for l in Level::all_levels() {
let vis_at_level = eff_vis.at_level(l);
Expand All @@ -145,7 +144,7 @@ impl EffectiveVisibilities {
}
old_eff_vis
}
Entry::Vacant(vacant) => vacant.insert(*eff_vis),
IndexEntry::Vacant(vacant) => vacant.insert(*eff_vis),
};
}

Expand Down
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