rustc_traits/
coroutine_witnesses.rs

1use rustc_infer::infer::TyCtxtInferExt;
2use rustc_infer::infer::canonical::QueryRegionConstraint;
3use rustc_infer::infer::canonical::query_response::make_query_region_constraints;
4use rustc_infer::infer::resolve::OpportunisticRegionResolver;
5use rustc_infer::traits::{Obligation, ObligationCause};
6use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, fold_regions};
7use rustc_span::def_id::DefId;
8use rustc_trait_selection::traits::{ObligationCtxt, with_replaced_escaping_bound_vars};
9
10/// Return the set of types that should be taken into account when checking
11/// trait bounds on a coroutine's internal state. This properly replaces
12/// `ReErased` with new existential bound lifetimes.
13pub(crate) fn coroutine_hidden_types<'tcx>(
14    tcx: TyCtxt<'tcx>,
15    def_id: DefId,
16) -> ty::EarlyBinder<'tcx, ty::Binder<'tcx, ty::CoroutineWitnessTypes<TyCtxt<'tcx>>>> {
17    let coroutine_layout = tcx.mir_coroutine_witnesses(def_id);
18    let mut vars = ::alloc::vec::Vec::new()vec![];
19    let bound_tys = tcx.mk_type_list_from_iter(
20        coroutine_layout
21            .as_ref()
22            .map_or_else(|| [].iter(), |l| l.field_tys.iter())
23            .filter(|decl| !decl.ignore_for_traits)
24            .map(|decl| {
25                let ty = fold_regions(tcx, decl.ty, |re, debruijn| {
26                    match (&re, &tcx.lifetimes.re_erased) {
    (left_val, right_val) => {
        if !(*left_val == *right_val) {
            let kind = ::core::panicking::AssertKind::Eq;
            ::core::panicking::assert_failed(kind, &*left_val, &*right_val,
                ::core::option::Option::None);
        }
    }
};assert_eq!(re, tcx.lifetimes.re_erased);
27                    let var = ty::BoundVar::from_usize(vars.len());
28                    vars.push(ty::BoundVariableKind::Region(ty::BoundRegionKind::Anon));
29                    ty::Region::new_bound(
30                        tcx,
31                        debruijn,
32                        ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon },
33                    )
34                });
35                ty
36            }),
37    );
38
39    let assumptions = compute_assumptions(tcx, def_id, bound_tys);
40
41    ty::EarlyBinder::bind(ty::Binder::bind_with_vars(
42        ty::CoroutineWitnessTypes { types: bound_tys, assumptions },
43        tcx.mk_bound_variable_kinds(&vars),
44    ))
45}
46
47fn compute_assumptions<'tcx>(
48    tcx: TyCtxt<'tcx>,
49    def_id: DefId,
50    bound_tys: &'tcx ty::List<Ty<'tcx>>,
51) -> &'tcx ty::List<ty::ArgOutlivesPredicate<'tcx>> {
52    let infcx = tcx.infer_ctxt().build(ty::TypingMode::Analysis {
53        defining_opaque_types_and_generators: ty::List::empty(),
54    });
55    with_replaced_escaping_bound_vars(&infcx, &mut ::alloc::boxed::box_assume_init_into_vec_unsafe(::alloc::intrinsics::write_box_via_move(::alloc::boxed::Box::new_uninit(),
        [None]))vec![None], bound_tys, |bound_tys| {
56        let param_env = tcx.param_env(def_id);
57        let ocx = ObligationCtxt::new(&infcx);
58
59        ocx.register_obligations(bound_tys.iter().map(|ty| {
60            Obligation::new(
61                tcx,
62                ObligationCause::dummy(),
63                param_env,
64                ty::ClauseKind::WellFormed(ty.into()),
65            )
66        }));
67        let _errors = ocx.evaluate_obligations_error_on_ambiguity();
68
69        let region_obligations = infcx.take_registered_region_obligations();
70        let region_assumptions = infcx.take_registered_region_assumptions();
71        let region_constraints = infcx.take_and_reset_region_constraints();
72
73        let constraints = make_query_region_constraints(
74            region_obligations,
75            &region_constraints,
76            region_assumptions,
77        )
78        .constraints
79        .fold_with(&mut OpportunisticRegionResolver::new(&infcx));
80
81        tcx.mk_outlives_from_iter(
82            constraints
83                .into_iter()
84                .flat_map(|QueryRegionConstraint { constraint, .. }| constraint.iter_outlives())
85                // FIXME(higher_ranked_auto): We probably should deeply resolve these before
86                // filtering out infers which only correspond to unconstrained infer regions
87                // which we can sometimes get.
88                .filter(|o| !o.has_infer()),
89        )
90    })
91}
rustc_traits/coroutine_witnesses.rs

rustc_traits/
coroutine_witnesses.rs
