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use rustc_hir as hir;
use rustc_infer::infer::canonical::{self, Canonical};
use rustc_infer::infer::outlives::components::{push_outlives_components, Component};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::traits::query::OutlivesBound;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable};
use rustc_span::source_map::DUMMY_SP;
use rustc_trait_selection::infer::InferCtxtBuilderExt;
use rustc_trait_selection::traits::query::{CanonicalTyGoal, Fallible, NoSolution};
use rustc_trait_selection::traits::wf;
use rustc_trait_selection::traits::ObligationCtxt;
use smallvec::{smallvec, SmallVec};
pub(crate) fn provide(p: &mut Providers) {
*p = Providers { implied_outlives_bounds, ..*p };
}
fn implied_outlives_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
goal: CanonicalTyGoal<'tcx>,
) -> Result<
&'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
NoSolution,
> {
tcx.infer_ctxt().enter_canonical_trait_query(&goal, |ocx, key| {
let (param_env, ty) = key.into_parts();
compute_implied_outlives_bounds(ocx, param_env, ty)
})
}
fn compute_implied_outlives_bounds<'tcx>(
ocx: &ObligationCtxt<'_, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
ty: Ty<'tcx>,
) -> Fallible<Vec<OutlivesBound<'tcx>>> {
let tcx = ocx.infcx.tcx;
let mut checked_wf_args = rustc_data_structures::fx::FxHashSet::default();
let mut wf_args = vec![ty.into()];
let mut outlives_bounds: Vec<ty::OutlivesPredicate<ty::GenericArg<'tcx>, ty::Region<'tcx>>> =
vec![];
while let Some(arg) = wf_args.pop() {
if !checked_wf_args.insert(arg) {
continue;
}
let obligations =
wf::obligations(ocx.infcx, param_env, hir::CRATE_HIR_ID, 0, arg, DUMMY_SP)
.unwrap_or_default();
ocx.register_obligations(
obligations.iter().filter(|o| o.predicate.has_non_region_infer()).cloned(),
);
outlives_bounds.extend(obligations.into_iter().filter_map(|obligation| {
assert!(!obligation.has_escaping_bound_vars());
match obligation.predicate.kind().no_bound_vars() {
None => None,
Some(pred) => match pred {
ty::PredicateKind::Clause(ty::Clause::Trait(..))
| ty::PredicateKind::Subtype(..)
| ty::PredicateKind::Coerce(..)
| ty::PredicateKind::Clause(ty::Clause::Projection(..))
| ty::PredicateKind::ClosureKind(..)
| ty::PredicateKind::ObjectSafe(..)
| ty::PredicateKind::ConstEvaluatable(..)
| ty::PredicateKind::ConstEquate(..)
| ty::PredicateKind::Ambiguous
| ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
ty::PredicateKind::WellFormed(arg) => {
wf_args.push(arg);
None
}
ty::PredicateKind::Clause(ty::Clause::RegionOutlives(
ty::OutlivesPredicate(r_a, r_b),
)) => Some(ty::OutlivesPredicate(r_a.into(), r_b)),
ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
ty_a,
r_b,
))) => Some(ty::OutlivesPredicate(ty_a.into(), r_b)),
},
}
}));
}
match ocx.select_all_or_error().as_slice() {
[] => (),
_ => return Err(NoSolution),
}
let implied_bounds = outlives_bounds
.into_iter()
.flat_map(|ty::OutlivesPredicate(a, r_b)| match a.unpack() {
ty::GenericArgKind::Lifetime(r_a) => vec![OutlivesBound::RegionSubRegion(r_b, r_a)],
ty::GenericArgKind::Type(ty_a) => {
let ty_a = ocx.infcx.resolve_vars_if_possible(ty_a);
let mut components = smallvec![];
push_outlives_components(tcx, ty_a, &mut components);
implied_bounds_from_components(r_b, components)
}
ty::GenericArgKind::Const(_) => unreachable!(),
})
.collect();
Ok(implied_bounds)
}
fn implied_bounds_from_components<'tcx>(
sub_region: ty::Region<'tcx>,
sup_components: SmallVec<[Component<'tcx>; 4]>,
) -> Vec<OutlivesBound<'tcx>> {
sup_components
.into_iter()
.filter_map(|component| {
match component {
Component::Region(r) => Some(OutlivesBound::RegionSubRegion(sub_region, r)),
Component::Param(p) => Some(OutlivesBound::RegionSubParam(sub_region, p)),
Component::Projection(p) => Some(OutlivesBound::RegionSubProjection(sub_region, p)),
Component::Opaque(def_id, substs) => {
Some(OutlivesBound::RegionSubOpaque(sub_region, def_id, substs))
}
Component::EscapingProjection(_) =>
{
None
}
Component::UnresolvedInferenceVariable(..) => None,
}
})
.collect()
}