Resolve lifetimes using the regular logic for RPIT.

compiler/rustc_hir_analysis/src/collect/lifetimes.rs

@@ -452,7 +452,9 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     intravisit::walk_item(this, item)
                 });
             }
-            hir::ItemKind::OpaqueTy(hir::OpaqueTy { .. }) => {
+            hir::ItemKind::OpaqueTy(hir::OpaqueTy {
+                origin: hir::OpaqueTyOrigin::TyAlias, ..
+            }) => {
                 // Opaque types are visited when we visit the
                 // `TyKind::OpaqueDef`, so that they have the lifetimes from
                 // their parent opaque_ty in scope.
@@ -478,6 +480,37 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     });
                 }
             }
+            hir::ItemKind::OpaqueTy(hir::OpaqueTy {
+                origin: hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_),
+                generics,
+                ..
+            }) => {
+                // We want to start our early-bound indices at the end of the parent scope,
+                // not including any parent `impl Trait`s.
+                let mut lifetimes = FxIndexMap::default();
+                debug!(?generics.params);
+                for param in generics.params {
+                    match param.kind {
+                        GenericParamKind::Lifetime { .. } => {
+                            let (def_id, reg) = Region::early(self.tcx.hir(), &param);
+                            lifetimes.insert(def_id, reg);
+                        }
+                        GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {}
+                    }
+                }
+
+                let scope = Scope::Binder {
+                    hir_id: item.hir_id(),
+                    lifetimes,
+                    s: self.scope,
+                    scope_type: BinderScopeType::Normal,
+                    where_bound_origin: None,
+                };
+                self.with(scope, |this| {
+                    let scope = Scope::TraitRefBoundary { s: this.scope };
+                    this.with(scope, |this| intravisit::walk_item(this, item))
+                });
+            }
             hir::ItemKind::TyAlias(_, ref generics)
             | hir::ItemKind::Enum(_, ref generics)
             | hir::ItemKind::Struct(_, ref generics)
@@ -604,7 +637,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 //                 ^                  ^ this gets resolved in the scope of
                 //                                      the opaque_ty generics
                 let opaque_ty = self.tcx.hir().item(item_id);
-                let (generics, bounds) = match opaque_ty.kind {
+                match opaque_ty.kind {
                     hir::ItemKind::OpaqueTy(hir::OpaqueTy {
                         origin: hir::OpaqueTyOrigin::TyAlias,
                         ..
@@ -625,10 +658,8 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     }
                     hir::ItemKind::OpaqueTy(hir::OpaqueTy {
                         origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
-                        ref generics,
-                        bounds,
                         ..
-                    }) => (generics, bounds),
+                    }) => {}
                     ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),
                 };
 
@@ -681,38 +712,6 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         self.uninsert_lifetime_on_error(lifetime, def.unwrap());
                     }
                 }
-
-                // We want to start our early-bound indices at the end of the parent scope,
-                // not including any parent `impl Trait`s.
-                let mut lifetimes = FxIndexMap::default();
-                debug!(?generics.params);
-                for param in generics.params {
-                    match param.kind {
-                        GenericParamKind::Lifetime { .. } => {
-                            let (def_id, reg) = Region::early(self.tcx.hir(), &param);
-                            lifetimes.insert(def_id, reg);
-                        }
-                        GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {}
-                    }
-                }
-                self.record_late_bound_vars(ty.hir_id, vec![]);
-
-                let scope = Scope::Binder {
-                    hir_id: ty.hir_id,
-                    lifetimes,
-                    s: self.scope,
-                    scope_type: BinderScopeType::Normal,
-                    where_bound_origin: None,
-                };
-                self.with(scope, |this| {
-                    let scope = Scope::TraitRefBoundary { s: this.scope };
-                    this.with(scope, |this| {
-                        this.visit_generics(generics);
-                        for bound in bounds {
-                            this.visit_param_bound(bound);
-                        }
-                    })
-                });
             }
             _ => intravisit::walk_ty(self, ty),
         }

src/test/ui/impl-trait/impl-fn-hrtb-bounds.rs

@@ -4,16 +4,19 @@ use std::fmt::Debug;
 fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
     //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     |x| x
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
     //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     |x| x
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
     //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     |x| x
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn d() -> impl Fn() -> (impl Debug + '_) {

src/test/ui/impl-trait/impl-fn-hrtb-bounds.stderr

@@ -1,5 +1,5 @@
 error[E0106]: missing lifetime specifier
-  --> $DIR/impl-fn-hrtb-bounds.rs:19:38
+  --> $DIR/impl-fn-hrtb-bounds.rs:22:38
    |
 LL | fn d() -> impl Fn() -> (impl Debug + '_) {
    |                                      ^^ expected named lifetime parameter
@@ -22,30 +22,57 @@ note: lifetime declared here
 LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
    |                   ^
 
+error: lifetime may not live long enough
+  --> $DIR/impl-fn-hrtb-bounds.rs:6:9
+   |
+LL |     |x| x
+   |      -- ^ returning this value requires that `'1` must outlive `'2`
+   |      ||
+   |      |return type of closure is impl Debug + '2
+   |      has type `&'1 u8`
+
 error: higher kinded lifetime bounds on nested opaque types are not supported yet
-  --> $DIR/impl-fn-hrtb-bounds.rs:9:52
+  --> $DIR/impl-fn-hrtb-bounds.rs:10:52
    |
 LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
    |                                                    ^^
    |
 note: lifetime declared here
-  --> $DIR/impl-fn-hrtb-bounds.rs:9:20
+  --> $DIR/impl-fn-hrtb-bounds.rs:10:20
    |
 LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
    |                    ^^
 
+error: lifetime may not live long enough
+  --> $DIR/impl-fn-hrtb-bounds.rs:12:9
+   |
+LL |     |x| x
+   |      -- ^ returning this value requires that `'1` must outlive `'2`
+   |      ||
+   |      |return type of closure is impl Debug + '2
+   |      has type `&'1 u8`
+
 error: higher kinded lifetime bounds on nested opaque types are not supported yet
-  --> $DIR/impl-fn-hrtb-bounds.rs:14:52
+  --> $DIR/impl-fn-hrtb-bounds.rs:16:52
    |
 LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
    |                                                    ^^
    |
 note: lifetime declared here
-  --> $DIR/impl-fn-hrtb-bounds.rs:14:20
+  --> $DIR/impl-fn-hrtb-bounds.rs:16:20
    |
 LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
    |                    ^^
 
-error: aborting due to 4 previous errors
+error: lifetime may not live long enough
+  --> $DIR/impl-fn-hrtb-bounds.rs:18:9
+   |
+LL |     |x| x
+   |      -- ^ returning this value requires that `'1` must outlive `'2`
+   |      ||
+   |      |return type of closure is impl Debug + '2
+   |      has type `&'1 u8`
+
+error: aborting due to 7 previous errors
 
 For more information about this error, try `rustc --explain E0106`.

src/test/ui/impl-trait/impl-fn-parsing-ambiguities.rs

@@ -3,8 +3,9 @@ use std::fmt::Debug;
 
 fn a() -> impl Fn(&u8) -> impl Debug + '_ {
     //~^ ERROR ambiguous `+` in a type
-    //~^^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+    //~| ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     |x| x
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn b() -> impl Fn() -> impl Debug + Send {

src/test/ui/impl-trait/impl-fn-parsing-ambiguities.stderr

@@ -5,7 +5,7 @@ LL | fn a() -> impl Fn(&u8) -> impl Debug + '_ {
    |                           ^^^^^^^^^^^^^^^ help: use parentheses to disambiguate: `(impl Debug + '_)`
 
 error: ambiguous `+` in a type
-  --> $DIR/impl-fn-parsing-ambiguities.rs:10:24
+  --> $DIR/impl-fn-parsing-ambiguities.rs:11:24
    |
 LL | fn b() -> impl Fn() -> impl Debug + Send {
    |                        ^^^^^^^^^^^^^^^^^ help: use parentheses to disambiguate: `(impl Debug + Send)`
@@ -22,5 +22,14 @@ note: lifetime declared here
 LL | fn a() -> impl Fn(&u8) -> impl Debug + '_ {
    |                   ^
 
-error: aborting due to 3 previous errors
+error: lifetime may not live long enough
+  --> $DIR/impl-fn-parsing-ambiguities.rs:7:9
+   |
+LL |     |x| x
+   |      -- ^ returning this value requires that `'1` must outlive `'2`
+   |      ||
+   |      |return type of closure is impl Debug + '2
+   |      has type `&'1 u8`
+
+error: aborting due to 4 previous errors
 

src/test/ui/impl-trait/issues/issue-67830.rs

@@ -21,6 +21,8 @@ struct A;
 fn test() -> impl for<'a> MyFn<&'a A, Output=impl Iterator + 'a> {
     //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     Wrap(|a| Some(a).into_iter())
+    //~^ ERROR implementation of `FnOnce` is not general enough
+    //~| ERROR implementation of `FnOnce` is not general enough
 }
 
 fn main() {}

src/test/ui/impl-trait/issues/issue-67830.stderr

@@ -10,5 +10,23 @@ note: lifetime declared here
 LL | fn test() -> impl for<'a> MyFn<&'a A, Output=impl Iterator + 'a> {
    |                       ^^
 
-error: aborting due to previous error
+error: implementation of `FnOnce` is not general enough
+  --> $DIR/issue-67830.rs:23:5
+   |
+LL |     Wrap(|a| Some(a).into_iter())
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
+   |
+   = note: closure with signature `fn(&'2 A) -> std::option::IntoIter<&A>` must implement `FnOnce<(&'1 A,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `FnOnce<(&'2 A,)>`, for some specific lifetime `'2`
+
+error: implementation of `FnOnce` is not general enough
+  --> $DIR/issue-67830.rs:23:5
+   |
+LL |     Wrap(|a| Some(a).into_iter())
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
+   |
+   = note: closure with signature `fn(&'2 A) -> std::option::IntoIter<&A>` must implement `FnOnce<(&'1 A,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `FnOnce<(&'2 A,)>`, for some specific lifetime `'2`
+
+error: aborting due to 3 previous errors
 

src/test/ui/impl-trait/issues/issue-88236-2.rs

@@ -18,11 +18,16 @@ fn make_impl() -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {}
 fn make_weird_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
     //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     &()
+    //~^ ERROR implementation of `Hrtb` is not general enough
+    //~| ERROR implementation of `Hrtb` is not general enough
 }
 
 fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
     //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
     x
+    //~^ ERROR implementation of `Hrtb` is not general enough
+    //~| ERROR implementation of `Hrtb` is not general enough
+    //~| ERROR lifetime may not live long enough
 }
 
 fn main() {}

src/test/ui/impl-trait/issues/issue-88236-2.stderr

@@ -22,17 +22,71 @@ note: lifetime declared here
 LL | fn make_weird_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
    |                                               ^^
 
+error: implementation of `Hrtb` is not general enough
+  --> $DIR/issue-88236-2.rs:20:5
+   |
+LL |     &()
+   |     ^^^ implementation of `Hrtb` is not general enough
+   |
+   = note: `Hrtb<'0>` would have to be implemented for the type `&()`, for any lifetime `'0`...
+   = note: ...but `Hrtb<'1>` is actually implemented for the type `&'1 ()`, for some specific lifetime `'1`
+
+error: implementation of `Hrtb` is not general enough
+  --> $DIR/issue-88236-2.rs:20:5
+   |
+LL |     &()
+   |     ^^^ implementation of `Hrtb` is not general enough
+   |
+   = note: `Hrtb<'0>` would have to be implemented for the type `&()`, for any lifetime `'0`...
+   = note: ...but `Hrtb<'1>` is actually implemented for the type `&'1 ()`, for some specific lifetime `'1`
+
 error: higher kinded lifetime bounds on nested opaque types are not supported yet
-  --> $DIR/issue-88236-2.rs:23:78
+  --> $DIR/issue-88236-2.rs:25:78
    |
 LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
    |                                                                              ^^
    |
 note: lifetime declared here
-  --> $DIR/issue-88236-2.rs:23:45
+  --> $DIR/issue-88236-2.rs:25:45
    |
 LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
    |                                             ^^
 
-error: aborting due to 3 previous errors
+error: lifetime may not live long enough
+  --> $DIR/issue-88236-2.rs:27:5
+   |
+LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
+   |                  -- lifetime `'b` defined here
+LL |
+LL |     x
+   |     ^ returning this value requires that `'b` must outlive `'static`
+   |
+help: to declare that `impl for<'a> Hrtb<'a, Assoc = impl Send + 'static>` captures data from argument `x`, you can add an explicit `'b` lifetime bound
+   |
+LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> + 'b {
+   |                                                                                  ++++
+help: to declare that `impl Send + 'a` captures data from argument `x`, you can add an explicit `'b` lifetime bound
+   |
+LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a + 'b> {
+   |                                                                                 ++++
+
+error: implementation of `Hrtb` is not general enough
+  --> $DIR/issue-88236-2.rs:27:5
+   |
+LL |     x
+   |     ^ implementation of `Hrtb` is not general enough
+   |
+   = note: `Hrtb<'0>` would have to be implemented for the type `&()`, for any lifetime `'0`...
+   = note: ...but `Hrtb<'1>` is actually implemented for the type `&'1 ()`, for some specific lifetime `'1`
+
+error: implementation of `Hrtb` is not general enough
+  --> $DIR/issue-88236-2.rs:27:5
+   |
+LL |     x
+   |     ^ implementation of `Hrtb` is not general enough
+   |
+   = note: `Hrtb<'0>` would have to be implemented for the type `&()`, for any lifetime `'0`...
+   = note: ...but `Hrtb<'1>` is actually implemented for the type `&'1 ()`, for some specific lifetime `'1`
+
+error: aborting due to 8 previous errors
 

src/test/ui/impl-trait/nested-rpit-hrtb.rs

@@ -31,34 +31,40 @@ fn one_hrtb_trait_param() -> impl for<'a> Foo<'a, Assoc = impl Qux<'a>> {}
 
 fn one_hrtb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'a> {}
 //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+//~| ERROR implementation of `Bar` is not general enough
 
 fn one_hrtb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl Qux<'a>> {}
 //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+//~| ERROR the trait bound `&(): Qux<'static>` is not satisfied
 
-// This should pass.
+// This should resolve.
 fn one_hrtb_mention_fn_trait_param<'b>() -> impl for<'a> Foo<'a, Assoc = impl Qux<'b>> {}
 
-// This should pass.
+// This should resolve.
 fn one_hrtb_mention_fn_outlives<'b>() -> impl for<'a> Foo<'a, Assoc = impl Sized + 'b> {}
 
-// This should pass.
+// This should resolve.
 fn one_hrtb_mention_fn_trait_param_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl Qux<'b>> {}
+//~^ ERROR the trait bound `&(): Qux<'b>` is not satisfied
 
-// This should pass.
+// This should resolve.
 fn one_hrtb_mention_fn_outlives_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'b> {}
+//~^ ERROR implementation of `Bar` is not general enough
 
-// This should pass.
+// This should resolve.
 fn two_htrb_trait_param() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Qux<'b>> {}
 
 // `'b` is not in scope for the outlives bound.
 fn two_htrb_outlives() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Sized + 'b> {}
 //~^ ERROR use of undeclared lifetime name `'b` [E0261]
 
-// This should pass.
+// This should resolve.
 fn two_htrb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Qux<'b>> {}
+//~^ ERROR the trait bound `for<'b> &(): Qux<'b>` is not satisfied
 
 // `'b` is not in scope for the outlives bound.
 fn two_htrb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Sized + 'b> {}
 //~^ ERROR use of undeclared lifetime name `'b` [E0261]
+//~| ERROR implementation of `Bar` is not general enough
 
 fn main() {}

src/test/ui/impl-trait/nested-rpit-hrtb.stderr

@@ -1,5 +1,5 @@
 error[E0261]: use of undeclared lifetime name `'b`
-  --> $DIR/nested-rpit-hrtb.rs:54:77
+  --> $DIR/nested-rpit-hrtb.rs:58:77
    |
 LL | fn two_htrb_outlives() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Sized + 'b> {}
    |                                                                             ^^ undeclared lifetime
@@ -15,7 +15,7 @@ LL | fn two_htrb_outlives<'b>() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Siz
    |                     ++++
 
 error[E0261]: use of undeclared lifetime name `'b`
-  --> $DIR/nested-rpit-hrtb.rs:61:82
+  --> $DIR/nested-rpit-hrtb.rs:66:82
    |
 LL | fn two_htrb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Sized + 'b> {}
    |                                                                                  ^^ undeclared lifetime
@@ -65,18 +65,70 @@ note: lifetime declared here
 LL | fn one_hrtb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'a> {}
    |                                         ^^
 
+error: implementation of `Bar` is not general enough
+  --> $DIR/nested-rpit-hrtb.rs:32:78
+   |
+LL | fn one_hrtb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'a> {}
+   |                                                                              ^^ implementation of `Bar` is not general enough
+   |
+   = note: `()` must implement `Bar<'0>`, for any lifetime `'0`...
+   = note: ...but it actually implements `Bar<'1>`, for some specific lifetime `'1`
+
 error: higher kinded lifetime bounds on nested opaque types are not supported yet
-  --> $DIR/nested-rpit-hrtb.rs:35:73
+  --> $DIR/nested-rpit-hrtb.rs:36:73
    |
 LL | fn one_hrtb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl Qux<'a>> {}
    |                                                                         ^^
    |
 note: lifetime declared here
-  --> $DIR/nested-rpit-hrtb.rs:35:44
+  --> $DIR/nested-rpit-hrtb.rs:36:44
    |
 LL | fn one_hrtb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl Qux<'a>> {}
    |                                            ^^
 
-error: aborting due to 6 previous errors
+error[E0277]: the trait bound `&(): Qux<'static>` is not satisfied
+  --> $DIR/nested-rpit-hrtb.rs:36:64
+   |
+LL | fn one_hrtb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl Qux<'a>> {}
+   |                                                                ^^^^^^^^^^^^ the trait `Qux<'static>` is not implemented for `&()`
+   |
+   = help: the trait `Qux<'_>` is implemented for `()`
 
-For more information about this error, try `rustc --explain E0261`.
+error[E0277]: the trait bound `&(): Qux<'b>` is not satisfied
+  --> $DIR/nested-rpit-hrtb.rs:47:79
+   |
+LL | fn one_hrtb_mention_fn_trait_param_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl Qux<'b>> {}
+   |                                                                               ^^^^^^^^^^^^ the trait `Qux<'b>` is not implemented for `&()`
+   |
+   = help: the trait `Qux<'_>` is implemented for `()`
+
+error: implementation of `Bar` is not general enough
+  --> $DIR/nested-rpit-hrtb.rs:51:93
+   |
+LL | fn one_hrtb_mention_fn_outlives_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'b> {}
+   |                                                                                             ^^ implementation of `Bar` is not general enough
+   |
+   = note: `()` must implement `Bar<'0>`, for any lifetime `'0`...
+   = note: ...but it actually implements `Bar<'1>`, for some specific lifetime `'1`
+
+error[E0277]: the trait bound `for<'b> &(): Qux<'b>` is not satisfied
+  --> $DIR/nested-rpit-hrtb.rs:62:64
+   |
+LL | fn two_htrb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Qux<'b>> {}
+   |                                                                ^^^^^^^^^^^^^^^^^^^^ the trait `for<'b> Qux<'b>` is not implemented for `&()`
+   |
+   = help: the trait `Qux<'_>` is implemented for `()`
+
+error: implementation of `Bar` is not general enough
+  --> $DIR/nested-rpit-hrtb.rs:66:86
+   |
+LL | fn two_htrb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Sized + 'b> {}
+   |                                                                                      ^^ implementation of `Bar` is not general enough
+   |
+   = note: `()` must implement `Bar<'0>`, for any lifetime `'0`...
+   = note: ...but it actually implements `Bar<'1>`, for some specific lifetime `'1`
+
+error: aborting due to 12 previous errors
+
+Some errors have detailed explanations: E0261, E0277.
+For more information about an error, try `rustc --explain E0261`.