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Rollup merge of #109641 - compiler-errors:dont-elaborate-non-obl, r=oli-obk

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Don't elaborate non-obligations into obligations

It's suspicious to elaborate a `PolyTraitRef` or `Predicate` into an `Obligation`, since the former does not have a param-env associated with it, but the latter does. This is a footgun that, while not being misused *currently* in the compiler, easily could be misused by someone less familiar with the elaborator's inner workings.

This PR just changes the API -- ideally, the elaborator wouldn't even have to deal with obligations if we're not elaborating obligations, but that would require a bit more abstraction than I could be bothered with today.
This commit is contained in:
Matthias Krüger 2023-03-27 08:46:55 +02:00 • committed by GitHub
commit 6535e66fa5
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20 changed files with 112 additions and 131 deletions
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78
compiler/rustc_infer/src/traits/util.rs
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@ -74,44 +74,58 @@ pub struct Elaborator<'tcx> {
pub fn elaborate_trait_ref<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>,
) -> Elaborator<'tcx> {
) -> impl Iterator<Item = ty::Predicate<'tcx>> {
elaborate_predicates(tcx, std::iter::once(trait_ref.without_const().to_predicate(tcx)))
}
pub fn elaborate_trait_refs<'tcx>(
tcx: TyCtxt<'tcx>,
trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
) -> Elaborator<'tcx> {
let predicates = trait_refs.map(|trait_ref| trait_ref.without_const().to_predicate(tcx));
) -> impl Iterator<Item = ty::Predicate<'tcx>> {
let predicates = trait_refs.map(move |trait_ref| trait_ref.without_const().to_predicate(tcx));
elaborate_predicates(tcx, predicates)
}
pub fn elaborate_predicates<'tcx>(
tcx: TyCtxt<'tcx>,
predicates: impl Iterator<Item = ty::Predicate<'tcx>>,
) -> Elaborator<'tcx> {
let obligations = predicates
.map(|predicate| {
predicate_obligation(predicate, ty::ParamEnv::empty(), ObligationCause::dummy())
})
.collect();
elaborate_obligations(tcx, obligations)
) -> impl Iterator<Item = ty::Predicate<'tcx>> {
elaborate_obligations(
tcx,
predicates
.map(|predicate| {
Obligation::new(
tcx,
// We'll dump the cause/param-env later
ObligationCause::dummy(),
ty::ParamEnv::empty(),
predicate,
)
})
.collect(),
)
.map(|obl| obl.predicate)
}
pub fn elaborate_predicates_with_span<'tcx>(
tcx: TyCtxt<'tcx>,
predicates: impl Iterator<Item = (ty::Predicate<'tcx>, Span)>,
) -> Elaborator<'tcx> {
let obligations = predicates
.map(|(predicate, span)| {
predicate_obligation(
predicate,
ty::ParamEnv::empty(),
ObligationCause::dummy_with_span(span),
)
})
.collect();
elaborate_obligations(tcx, obligations)
) -> impl Iterator<Item = (ty::Predicate<'tcx>, Span)> {
elaborate_obligations(
tcx,
predicates
.map(|(predicate, span)| {
Obligation::new(
tcx,
// We'll dump the cause/param-env later
ObligationCause::dummy_with_span(span),
ty::ParamEnv::empty(),
predicate,
)
})
.collect(),
)
.map(|obl| (obl.predicate, obl.cause.span))
}
pub fn elaborate_obligations<'tcx>(
@ -141,10 +155,6 @@ impl<'tcx> Elaborator<'tcx> {
self.stack.extend(obligations.into_iter().filter(|o| self.visited.insert(o.predicate)));
}
pub fn filter_to_traits(self) -> FilterToTraits<Self> {
FilterToTraits::new(self)
}
fn elaborate(&mut self, obligation: &PredicateObligation<'tcx>) {
let tcx = self.visited.tcx;
@ -325,20 +335,18 @@ impl<'tcx> Iterator for Elaborator<'tcx> {
// Supertrait iterator
///////////////////////////////////////////////////////////////////////////
pub type Supertraits<'tcx> = FilterToTraits<Elaborator<'tcx>>;
pub fn supertraits<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>,
) -> Supertraits<'tcx> {
elaborate_trait_ref(tcx, trait_ref).filter_to_traits()
) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> {
FilterToTraits::new(elaborate_trait_ref(tcx, trait_ref))
}
pub fn transitive_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
) -> Supertraits<'tcx> {
elaborate_trait_refs(tcx, bounds).filter_to_traits()
trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> {
FilterToTraits::new(elaborate_trait_refs(tcx, trait_refs))
}
/// A specialized variant of `elaborate_trait_refs` that only elaborates trait references that may
@ -393,12 +401,12 @@ impl<I> FilterToTraits<I> {
}
}
impl<'tcx, I: Iterator<Item = PredicateObligation<'tcx>>> Iterator for FilterToTraits<I> {
impl<'tcx, I: Iterator<Item = ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
type Item = ty::PolyTraitRef<'tcx>;
fn next(&mut self) -> Option<ty::PolyTraitRef<'tcx>> {
while let Some(obligation) = self.base_iterator.next() {
if let Some(data) = obligation.predicate.to_opt_poly_trait_pred() {
while let Some(pred) = self.base_iterator.next() {
if let Some(data) = pred.to_opt_poly_trait_pred() {
return Some(data.map_bound(|t| t.trait_ref));
}
}