3 files changed, 33 insertions, 15 deletions
diff --git a/compiler/rustc_typeck/src/outlives/outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
index 229a64650..3008dfcad 100644
--- a/compiler/rustc_typeck/src/outlives/outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
@@ -1,22 +1,32 @@
+use crate::infer::InferCtxt;
+use crate::traits::query::type_op::{self, TypeOp, TypeOpOutput};
+use crate::traits::query::NoSolution;
+use crate::traits::{ObligationCause, TraitEngine, TraitEngineExt};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
-use rustc_middle::ty::{self, Ty};
-use rustc_trait_selection::infer::InferCtxt;
-use rustc_trait_selection::traits::query::type_op::{self, TypeOp, TypeOpOutput};
-use rustc_trait_selection::traits::query::NoSolution;
-use rustc_trait_selection::traits::{ObligationCause, TraitEngine, TraitEngineExt};
+use rustc_hir::HirId;
+use rustc_middle::ty::{self, ParamEnv, Ty};
 
 pub use rustc_middle::traits::query::OutlivesBound;
 
-pub trait InferCtxtExt<'tcx> {
+type Bounds<'a, 'tcx: 'a> = impl Iterator<Item = OutlivesBound<'tcx>> + 'a;
+pub trait InferCtxtExt<'a, 'tcx> {
     fn implied_outlives_bounds(
         &self,
         param_env: ty::ParamEnv<'tcx>,
         body_id: hir::HirId,
         ty: Ty<'tcx>,
     ) -> Vec<OutlivesBound<'tcx>>;
+
+    fn implied_bounds_tys(
+        &'a self,
+        param_env: ty::ParamEnv<'tcx>,
+        body_id: hir::HirId,
+        tys: FxHashSet<Ty<'tcx>>,
+    ) -> Bounds<'a, 'tcx>;
 }
 
-impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
+impl<'a, 'cx, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'cx, 'tcx> {
     /// Implied bounds are region relationships that we deduce
     /// automatically. The idea is that (e.g.) a caller must check that a
     /// function's argument types are well-formed immediately before
@@ -36,7 +46,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
     ///   Note that this may cause outlives obligations to be injected
     ///   into the inference context with this body-id.
     /// - `ty`, the type that we are supposed to assume is WF.
-    #[instrument(level = "debug", skip(self, param_env, body_id))]
+    #[instrument(level = "debug", skip(self, param_env, body_id), ret)]
     fn implied_outlives_bounds(
         &self,
         param_env: ty::ParamEnv<'tcx>,
@@ -61,6 +71,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
         let TypeOpOutput { output, constraints, .. } = result;
 
         if let Some(constraints) = constraints {
+            debug!(?constraints);
             // Instantiation may have produced new inference variables and constraints on those
             // variables. Process these constraints.
             let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(self.tcx);
@@ -87,4 +98,18 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
 
         output
     }
+
+    fn implied_bounds_tys(
+        &'a self,
+        param_env: ParamEnv<'tcx>,
+        body_id: HirId,
+        tys: FxHashSet<Ty<'tcx>>,
+    ) -> Bounds<'a, 'tcx> {
+        tys.into_iter()
+            .map(move |ty| {
+                let ty = self.resolve_vars_if_possible(ty);
+                self.implied_outlives_bounds(param_env, body_id, ty)
+            })
+            .flatten()
+    }
 }
diff --git a/compiler/rustc_typeck/src/outlives/mod.rs b/compiler/rustc_typeck/src/outlives/mod.rs
index 8fa65d51e..e50c26765 100644
--- a/compiler/rustc_typeck/src/outlives/mod.rs
+++ b/compiler/rustc_typeck/src/outlives/mod.rs
@@ -9,7 +9,6 @@ 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;
diff --git a/compiler/rustc_typeck/src/outlives/utils.rs b/compiler/rustc_typeck/src/outlives/utils.rs
index b718ca942..3e8d023fb 100644
--- a/compiler/rustc_typeck/src/outlives/utils.rs
+++ b/compiler/rustc_typeck/src/outlives/utils.rs
@@ -161,12 +161,6 @@ fn is_free_region(region: Region<'_>) -> bool {
         // ignore it.  We can't put it on the struct header anyway.
         ty::ReLateBound(..) => false,
 
-        // This can appear in `where Self: ` bounds (#64855):
-        //
-        //     struct Bar<T>(<Self as Foo>::Type) where Self: ;
-        //     struct Baz<'a>(&'a Self) where Self: ;
-        ty::ReEmpty(_) => false,
-
         // These regions don't appear in types from type declarations:
         ty::ReErased | ty::ReVar(..) | ty::RePlaceholder(..) | ty::ReFree(..) => {
             bug!("unexpected region in outlives inference: {:?}", region);