rustc_hir_analysis/outlives/
mod.rs

1use rustc_hir::def::DefKind;
2use rustc_hir::def_id::LocalDefId;
3use rustc_middle::ty::{self, CratePredicatesMap, GenericArgKind, TyCtxt, Upcast};
4use rustc_span::Span;
5
6pub(crate) mod dump;
7mod explicit;
8mod implicit_infer;
9mod utils;
10
11pub(super) fn inferred_outlives_of(
12    tcx: TyCtxt<'_>,
13    item_def_id: LocalDefId,
14) -> &[(ty::Clause<'_>, Span)] {
15    match tcx.def_kind(item_def_id) {
16        DefKind::Struct | DefKind::Enum | DefKind::Union => {
17            let crate_map = tcx.inferred_outlives_crate(());
18            crate_map.predicates.get(&item_def_id.to_def_id()).copied().unwrap_or(&[])
19        }
20        DefKind::TyAlias if tcx.type_alias_is_lazy(item_def_id) => {
21            let crate_map = tcx.inferred_outlives_crate(());
22            crate_map.predicates.get(&item_def_id.to_def_id()).copied().unwrap_or(&[])
23        }
24        DefKind::AnonConst if tcx.features().generic_const_exprs() => {
25            let id = tcx.local_def_id_to_hir_id(item_def_id);
26            if tcx.hir_opt_const_param_default_param_def_id(id).is_some() {
27                // In `generics_of` we set the generics' parent to be our parent's parent which means that
28                // we lose out on the predicates of our actual parent if we dont return those predicates here.
29                // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
30                //
31                // struct Foo<'a, 'b, const N: usize = { ... }>(&'a &'b ());
32                //        ^^^                          ^^^^^^^ the def id we are calling
33                //        ^^^                                  inferred_outlives_of on
34                //        parent item we dont have set as the
35                //        parent of generics returned by `generics_of`
36                //
37                // In the above code we want the anon const to have predicates in its param env for `'b: 'a`
38                let item_def_id = tcx.hir_get_parent_item(id);
39                // In the above code example we would be calling `inferred_outlives_of(Foo)` here
40                tcx.inferred_outlives_of(item_def_id)
41            } else {
42                &[]
43            }
44        }
45        _ => &[],
46    }
47}
48
49pub(super) fn inferred_outlives_crate(tcx: TyCtxt<'_>, (): ()) -> CratePredicatesMap<'_> {
50    // Compute a map from each ADT (struct/enum/union) and lazy type alias to
51    // the **explicit** outlives predicates (`T: 'a`, `'a: 'b`) that the user wrote.
52    // Typically there won't be many of these, except in older code where
53    // they were mandatory. Nonetheless, we have to ensure that every such
54    // predicate is satisfied, so they form a kind of base set of requirements
55    // for the type.
56
57    // Compute the inferred predicates
58    let global_inferred_outlives = implicit_infer::infer_predicates(tcx);
59
60    // Convert the inferred predicates into the "collected" form the
61    // global data structure expects.
62    //
63    // FIXME -- consider correcting impedance mismatch in some way,
64    // probably by updating the global data structure.
65    let predicates = global_inferred_outlives
66        .iter()
67        .map(|(&def_id, set)| {
68            let predicates =
69                &*tcx.arena.alloc_from_iter(set.as_ref().skip_binder().iter().filter_map(
70                    |(ty::OutlivesPredicate(arg1, region2), &span)| {
71                        match arg1.kind() {
72                            GenericArgKind::Type(ty1) => Some((
73                                ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty1, *region2))
74                                    .upcast(tcx),
75                                span,
76                            )),
77                            GenericArgKind::Lifetime(region1) => Some((
78                                ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(
79                                    region1, *region2,
80                                ))
81                                .upcast(tcx),
82                                span,
83                            )),
84                            GenericArgKind::Const(_) => {
85                                // Generic consts don't impose any constraints.
86                                None
87                            }
88                        }
89                    },
90                ));
91            (def_id, predicates)
92        })
93        .collect();
94
95    ty::CratePredicatesMap { predicates }
96}
rustc_hir_analysis/outlives/mod.rs

rustc_hir_analysis/outlives/
mod.rs
