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use rustc::infer::InferCtxt;
use rustc::infer::canonical::{self, Canonical};
use rustc::traits::{TraitEngine, TraitEngineExt};
use rustc::traits::query::outlives_bounds::OutlivesBound;
use rustc::traits::query::{CanonicalTyGoal, Fallible, NoSolution};
use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc::ty::outlives::Component;
use rustc::ty::query::Providers;
use rustc::ty::wf;
use syntax::ast::DUMMY_NODE_ID;
use syntax::source_map::DUMMY_SP;
use rustc::traits::FulfillmentContext;
use rustc_data_structures::sync::Lrc;
crate fn provide(p: &mut Providers) {
*p = Providers {
implied_outlives_bounds,
..*p
};
}
fn implied_outlives_bounds<'tcx>(
tcx: TyCtxt<'_, 'tcx, 'tcx>,
goal: CanonicalTyGoal<'tcx>,
) -> Result<
Lrc<Canonical<'tcx, canonical::QueryResult<'tcx, Vec<OutlivesBound<'tcx>>>>>,
NoSolution,
> {
tcx.infer_ctxt()
.enter_canonical_trait_query(&goal, |infcx, _fulfill_cx, key| {
let (param_env, ty) = key.into_parts();
compute_implied_outlives_bounds(&infcx, param_env, ty)
})
}
fn compute_implied_outlives_bounds<'tcx>(
infcx: &InferCtxt<'_, '_, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
ty: Ty<'tcx>
) -> Fallible<Vec<OutlivesBound<'tcx>>> {
let tcx = infcx.tcx;
let mut wf_types = vec![ty];
let mut implied_bounds = vec![];
let mut fulfill_cx = FulfillmentContext::new();
while let Some(ty) = wf_types.pop() {
let obligations =
wf::obligations(infcx, param_env, DUMMY_NODE_ID, ty, DUMMY_SP).unwrap_or(vec![]);
fulfill_cx.register_predicate_obligations(
infcx,
obligations
.iter()
.filter(|o| o.predicate.has_infer_types())
.cloned(),
);
implied_bounds.extend(obligations.into_iter().flat_map(|obligation| {
assert!(!obligation.has_escaping_regions());
match obligation.predicate {
ty::Predicate::Trait(..) |
ty::Predicate::Subtype(..) |
ty::Predicate::Projection(..) |
ty::Predicate::ClosureKind(..) |
ty::Predicate::ObjectSafe(..) |
ty::Predicate::ConstEvaluatable(..) => vec![],
ty::Predicate::WellFormed(subty) => {
wf_types.push(subty);
vec![]
}
ty::Predicate::RegionOutlives(ref data) => match data.no_late_bound_regions() {
None => vec![],
Some(ty::OutlivesPredicate(r_a, r_b)) => {
vec![OutlivesBound::RegionSubRegion(r_b, r_a)]
}
},
ty::Predicate::TypeOutlives(ref data) => match data.no_late_bound_regions() {
None => vec![],
Some(ty::OutlivesPredicate(ty_a, r_b)) => {
let ty_a = infcx.resolve_type_vars_if_possible(&ty_a);
let components = tcx.outlives_components(ty_a);
implied_bounds_from_components(r_b, components)
}
},
}
}));
}
match fulfill_cx.select_all_or_error(infcx) {
Ok(()) => Ok(implied_bounds),
Err(_) => Err(NoSolution),
}
}
fn implied_bounds_from_components(
sub_region: ty::Region<'tcx>,
sup_components: Vec<Component<'tcx>>,
) -> Vec<OutlivesBound<'tcx>> {
sup_components
.into_iter()
.flat_map(|component| {
match component {
Component::Region(r) =>
vec![OutlivesBound::RegionSubRegion(sub_region, r)],
Component::Param(p) =>
vec![OutlivesBound::RegionSubParam(sub_region, p)],
Component::Projection(p) =>
vec![OutlivesBound::RegionSubProjection(sub_region, p)],
Component::EscapingProjection(_) =>
vec![],
Component::UnresolvedInferenceVariable(..) =>
vec![],
}
})
.collect()
}