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rustdoc: heavily simplify the synthesis of auto trait impls #123340

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Apr 2, 2024
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rustdoc: heavily simplify the synthesis of auto trait impls #123340

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cbd593e
rustdoc: synthetic impls: auto traits: Fx{Hash↦Index}{Map,Set}
fmease Apr 1, 2024
069e7f2
rustdoc: heavily simplify synthesis of auto trait impls
fmease Mar 31, 2024
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62 changes: 22 additions & 40 deletions compiler/rustc_trait_selection/src/traits/auto_trait.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,13 @@ use super::*;
use crate::errors::UnableToConstructConstantValue;
use crate::infer::region_constraints::{Constraint, RegionConstraintData};
use crate::traits::project::ProjectAndUnifyResult;

use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
use rustc_data_structures::unord::UnordSet;
use rustc_infer::infer::DefineOpaqueTypes;
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::ty::{Region, RegionVid};

use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};

use std::collections::hash_map::Entry;
use std::collections::VecDeque;
use std::iter;

Expand All @@ -25,8 +25,8 @@ pub enum RegionTarget<'tcx> {

#[derive(Default, Debug, Clone)]
pub struct RegionDeps<'tcx> {
larger: FxIndexSet<RegionTarget<'tcx>>,
smaller: FxIndexSet<RegionTarget<'tcx>>,
pub larger: FxIndexSet<RegionTarget<'tcx>>,
pub smaller: FxIndexSet<RegionTarget<'tcx>>,
}

pub enum AutoTraitResult<A> {
Expand All @@ -35,17 +35,10 @@ pub enum AutoTraitResult<A> {
NegativeImpl,
}

#[allow(dead_code)]
impl<A> AutoTraitResult<A> {
fn is_auto(&self) -> bool {
matches!(self, AutoTraitResult::PositiveImpl(_) | AutoTraitResult::NegativeImpl)
}
}

pub struct AutoTraitInfo<'cx> {
pub full_user_env: ty::ParamEnv<'cx>,
pub region_data: RegionConstraintData<'cx>,
pub vid_to_region: FxHashMap<ty::RegionVid, ty::Region<'cx>>,
pub vid_to_region: FxIndexMap<ty::RegionVid, ty::Region<'cx>>,
}

pub struct AutoTraitFinder<'tcx> {
Expand Down Expand Up @@ -88,19 +81,12 @@ impl<'tcx> AutoTraitFinder<'tcx> {

let infcx = tcx.infer_ctxt().build();
let mut selcx = SelectionContext::new(&infcx);
for polarity in [true, false] {
for polarity in [ty::PredicatePolarity::Positive, ty::PredicatePolarity::Negative] {
let result = selcx.select(&Obligation::new(
tcx,
ObligationCause::dummy(),
orig_env,
ty::TraitPredicate {
trait_ref,
polarity: if polarity {
ty::PredicatePolarity::Positive
} else {
ty::PredicatePolarity::Negative
},
},
ty::TraitPredicate { trait_ref, polarity },
));
if let Ok(Some(ImplSource::UserDefined(_))) = result {
debug!(
Expand All @@ -114,7 +100,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
}

let infcx = tcx.infer_ctxt().build();
let mut fresh_preds = FxHashSet::default();
let mut fresh_preds = FxIndexSet::default();

// Due to the way projections are handled by SelectionContext, we need to run
// evaluate_predicates twice: once on the original param env, and once on the result of
Expand Down Expand Up @@ -239,7 +225,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
user_env: ty::ParamEnv<'tcx>,
fresh_preds: &mut FxHashSet<ty::Predicate<'tcx>>,
fresh_preds: &mut FxIndexSet<ty::Predicate<'tcx>>,
) -> Option<(ty::ParamEnv<'tcx>, ty::ParamEnv<'tcx>)> {
let tcx = infcx.tcx;

Expand All @@ -252,7 +238,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {

let mut select = SelectionContext::new(infcx);

let mut already_visited = FxHashSet::default();
let mut already_visited = UnordSet::new();
let mut predicates = VecDeque::new();
predicates.push_back(ty::Binder::dummy(ty::TraitPredicate {
trait_ref: ty::TraitRef::new(infcx.tcx, trait_did, [ty]),
Expand Down Expand Up @@ -473,9 +459,9 @@ impl<'tcx> AutoTraitFinder<'tcx> {
fn map_vid_to_region<'cx>(
&self,
regions: &RegionConstraintData<'cx>,
) -> FxHashMap<ty::RegionVid, ty::Region<'cx>> {
let mut vid_map: FxHashMap<RegionTarget<'cx>, RegionDeps<'cx>> = FxHashMap::default();
let mut finished_map = FxHashMap::default();
) -> FxIndexMap<ty::RegionVid, ty::Region<'cx>> {
let mut vid_map = FxIndexMap::<RegionTarget<'cx>, RegionDeps<'cx>>::default();
let mut finished_map = FxIndexMap::default();

for (constraint, _) in &regions.constraints {
match constraint {
Expand Down Expand Up @@ -513,25 +499,22 @@ impl<'tcx> AutoTraitFinder<'tcx> {
}

while !vid_map.is_empty() {
#[allow(rustc::potential_query_instability)]
let target = *vid_map.keys().next().expect("Keys somehow empty");
let deps = vid_map.remove(&target).expect("Entry somehow missing");
let target = *vid_map.keys().next().unwrap();
let deps = vid_map.swap_remove(&target).unwrap();

for smaller in deps.smaller.iter() {
for larger in deps.larger.iter() {
match (smaller, larger) {
(&RegionTarget::Region(_), &RegionTarget::Region(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*smaller) {
if let IndexEntry::Occupied(v) = vid_map.entry(*smaller) {
let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger);
// FIXME(#120456) - is `swap_remove` correct?
smaller_deps.larger.swap_remove(&target);
}

if let Entry::Occupied(v) = vid_map.entry(*larger) {
if let IndexEntry::Occupied(v) = vid_map.entry(*larger) {
let larger_deps = v.into_mut();
larger_deps.smaller.insert(*smaller);
// FIXME(#120456) - is `swap_remove` correct?
larger_deps.smaller.swap_remove(&target);
}
}
Expand All @@ -542,24 +525,23 @@ impl<'tcx> AutoTraitFinder<'tcx> {
// Do nothing; we don't care about regions that are smaller than vids.
}
(&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*smaller) {
if let IndexEntry::Occupied(v) = vid_map.entry(*smaller) {
let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger);
// FIXME(#120456) - is `swap_remove` correct?
smaller_deps.larger.swap_remove(&target);
}

if let Entry::Occupied(v) = vid_map.entry(*larger) {
if let IndexEntry::Occupied(v) = vid_map.entry(*larger) {
let larger_deps = v.into_mut();
larger_deps.smaller.insert(*smaller);
// FIXME(#120456) - is `swap_remove` correct?
larger_deps.smaller.swap_remove(&target);
}
}
}
}
}
}

finished_map
}

Expand Down Expand Up @@ -588,7 +570,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
ty: Ty<'_>,
nested: impl Iterator<Item = PredicateObligation<'tcx>>,
computed_preds: &mut FxIndexSet<ty::Predicate<'tcx>>,
fresh_preds: &mut FxHashSet<ty::Predicate<'tcx>>,
fresh_preds: &mut FxIndexSet<ty::Predicate<'tcx>>,
predicates: &mut VecDeque<ty::PolyTraitPredicate<'tcx>>,
selcx: &mut SelectionContext<'_, 'tcx>,
) -> bool {
Expand Down
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