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Elaboration tweaks #127388

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merged 2 commits into from
Jul 6, 2024
Merged

Elaboration tweaks #127388

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e5412da
Supertrait elaboration doesn't need to use Predicates
compiler-errors Jul 5, 2024
99429a6
Split out transitive_bounds_that_define_assoc_item
compiler-errors Jul 5, 2024
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47 changes: 29 additions & 18 deletions compiler/rustc_infer/src/traits/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ use smallvec::smallvec;
use crate::infer::outlives::components::{push_outlives_components, Component};
use crate::traits::{self, Obligation, ObligationCauseCode, PredicateObligation};
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::ty::ToPolyTraitRef;
use rustc_middle::ty::{self, Ty, TyCtxt, Upcast};
use rustc_span::symbol::Ident;
use rustc_span::Span;
Expand Down Expand Up @@ -82,7 +83,6 @@ pub struct Elaborator<'tcx, O> {
enum Filter {
All,
OnlySelf,
OnlySelfThatDefines(Ident),
}

/// Describes how to elaborate an obligation into a sub-obligation.
Expand Down Expand Up @@ -252,12 +252,6 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
self
}

/// Filter to only the supertraits of trait predicates that define the assoc_ty.
pub fn filter_only_self_that_defines(mut self, assoc_ty: Ident) -> Self {
self.mode = Filter::OnlySelfThatDefines(assoc_ty);
self
}

fn elaborate(&mut self, elaboratable: &O) {
let tcx = self.visited.tcx;

Expand All @@ -277,9 +271,6 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
let predicates = match self.mode {
Filter::All => tcx.explicit_implied_predicates_of(data.def_id()),
Filter::OnlySelf => tcx.explicit_super_predicates_of(data.def_id()),
Filter::OnlySelfThatDefines(ident) => {
tcx.explicit_supertraits_containing_assoc_item((data.def_id(), ident))
}
};

let obligations =
Expand Down Expand Up @@ -405,14 +396,14 @@ impl<'tcx, O: Elaboratable<'tcx>> Iterator for Elaborator<'tcx, O> {
pub fn supertraits<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>,
) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
) -> FilterToTraits<Elaborator<'tcx, ty::Clause<'tcx>>> {
elaborate(tcx, [trait_ref.upcast(tcx)]).filter_only_self().filter_to_traits()
}

pub fn transitive_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
) -> FilterToTraits<Elaborator<'tcx, ty::Clause<'tcx>>> {
elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.upcast(tcx)))
.filter_only_self()
.filter_to_traits()
Expand All @@ -427,17 +418,37 @@ pub fn transitive_bounds_that_define_assoc_item<'tcx>(
tcx: TyCtxt<'tcx>,
trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
assoc_name: Ident,
) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.upcast(tcx)))
.filter_only_self_that_defines(assoc_name)
.filter_to_traits()
) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> {
let mut seen = FxHashSet::default();
let mut stack: Vec<_> = trait_refs.collect();

std::iter::from_fn(move || {
while let Some(trait_ref) = stack.pop() {
if !seen.insert(tcx.anonymize_bound_vars(trait_ref)) {
continue;
}

stack.extend(
tcx.explicit_supertraits_containing_assoc_item((trait_ref.def_id(), assoc_name))
.instantiate_own_identity()
.map(|(clause, _)| clause.instantiate_supertrait(tcx, trait_ref))
.filter_map(|clause| clause.as_trait_clause())
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// FIXME: Negative supertraits are elaborated here lol
.map(|trait_pred| trait_pred.to_poly_trait_ref()),
);

return Some(trait_ref);
}

None
})
}

///////////////////////////////////////////////////////////////////////////
// Other
///////////////////////////////////////////////////////////////////////////

impl<'tcx> Elaborator<'tcx, ty::Predicate<'tcx>> {
impl<'tcx> Elaborator<'tcx, ty::Clause<'tcx>> {
fn filter_to_traits(self) -> FilterToTraits<Self> {
FilterToTraits { base_iterator: self }
}
Expand All @@ -449,7 +460,7 @@ pub struct FilterToTraits<I> {
base_iterator: I,
}

impl<'tcx, I: Iterator<Item = ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
impl<'tcx, I: Iterator<Item = ty::Clause<'tcx>>> Iterator for FilterToTraits<I> {
type Item = ty::PolyTraitRef<'tcx>;

fn next(&mut self) -> Option<ty::PolyTraitRef<'tcx>> {
Expand Down
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