1 files changed, 130 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/outlives/mod.rs b/compiler/rustc_typeck/src/outlives/mod.rs
new file mode 100644
index 000000000..8fa65d51e
--- /dev/null
+++ b/compiler/rustc_typeck/src/outlives/mod.rs
@@ -0,0 +1,130 @@
+use hir::Node;
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::{self, CratePredicatesMap, ToPredicate, TyCtxt};
+use rustc_span::symbol::sym;
+use rustc_span::Span;
+
+mod explicit;
+mod implicit_infer;
+pub(crate) mod outlives_bounds;
+/// Code to write unit test for outlives.
+pub mod test;
+mod utils;
+
+pub fn provide(providers: &mut Providers) {
+    *providers = Providers { inferred_outlives_of, inferred_outlives_crate, ..*providers };
+}
+
+fn inferred_outlives_of(tcx: TyCtxt<'_>, item_def_id: DefId) -> &[(ty::Predicate<'_>, Span)] {
+    let id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
+
+    if matches!(tcx.def_kind(item_def_id), hir::def::DefKind::AnonConst) && tcx.lazy_normalization()
+    {
+        if tcx.hir().opt_const_param_default_param_hir_id(id).is_some() {
+            // In `generics_of` we set the generics' parent to be our parent's parent which means that
+            // we lose out on the predicates of our actual parent if we dont return those predicates here.
+            // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
+            //
+            // struct Foo<'a, 'b, const N: usize = { ... }>(&'a &'b ());
+            //        ^^^                          ^^^^^^^ the def id we are calling
+            //        ^^^                                  inferred_outlives_of on
+            //        parent item we dont have set as the
+            //        parent of generics returned by `generics_of`
+            //
+            // In the above code we want the anon const to have predicates in its param env for `'b: 'a`
+            let item_def_id = tcx.hir().get_parent_item(id);
+            // In the above code example we would be calling `inferred_outlives_of(Foo)` here
+            return tcx.inferred_outlives_of(item_def_id);
+        }
+    }
+
+    match tcx.hir().get(id) {
+        Node::Item(item) => match item.kind {
+            hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..) => {
+                let crate_map = tcx.inferred_outlives_crate(());
+
+                let predicates = crate_map.predicates.get(&item_def_id).copied().unwrap_or(&[]);
+
+                if tcx.has_attr(item_def_id, sym::rustc_outlives) {
+                    let mut pred: Vec<String> = predicates
+                        .iter()
+                        .map(|(out_pred, _)| match out_pred.kind().skip_binder() {
+                            ty::PredicateKind::RegionOutlives(p) => p.to_string(),
+                            ty::PredicateKind::TypeOutlives(p) => p.to_string(),
+                            err => bug!("unexpected predicate {:?}", err),
+                        })
+                        .collect();
+                    pred.sort();
+
+                    let span = tcx.def_span(item_def_id);
+                    let mut err = tcx.sess.struct_span_err(span, "rustc_outlives");
+                    for p in &pred {
+                        err.note(p);
+                    }
+                    err.emit();
+                }
+
+                debug!("inferred_outlives_of({:?}) = {:?}", item_def_id, predicates);
+
+                predicates
+            }
+
+            _ => &[],
+        },
+
+        _ => &[],
+    }
+}
+
+fn inferred_outlives_crate(tcx: TyCtxt<'_>, (): ()) -> CratePredicatesMap<'_> {
+    // Compute a map from each struct/enum/union S to the **explicit**
+    // outlives predicates (`T: 'a`, `'a: 'b`) that the user wrote.
+    // Typically there won't be many of these, except in older code where
+    // they were mandatory. Nonetheless, we have to ensure that every such
+    // predicate is satisfied, so they form a kind of base set of requirements
+    // for the type.
+
+    // Compute the inferred predicates
+    let global_inferred_outlives = implicit_infer::infer_predicates(tcx);
+
+    // Convert the inferred predicates into the "collected" form the
+    // global data structure expects.
+    //
+    // FIXME -- consider correcting impedance mismatch in some way,
+    // probably by updating the global data structure.
+    let predicates = global_inferred_outlives
+        .iter()
+        .map(|(&def_id, set)| {
+            let predicates = &*tcx.arena.alloc_from_iter(set.0.iter().filter_map(
+                |(ty::OutlivesPredicate(kind1, region2), &span)| {
+                    match kind1.unpack() {
+                        GenericArgKind::Type(ty1) => Some((
+                            ty::Binder::dummy(ty::PredicateKind::TypeOutlives(
+                                ty::OutlivesPredicate(ty1, *region2),
+                            ))
+                            .to_predicate(tcx),
+                            span,
+                        )),
+                        GenericArgKind::Lifetime(region1) => Some((
+                            ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
+                                ty::OutlivesPredicate(region1, *region2),
+                            ))
+                            .to_predicate(tcx),
+                            span,
+                        )),
+                        GenericArgKind::Const(_) => {
+                            // Generic consts don't impose any constraints.
+                            None
+                        }
+                    }
+                },
+            ));
+            (def_id, predicates)
+        })
+        .collect();
+
+    ty::CratePredicatesMap { predicates }
+}