diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index edc1e2f0b84d9..5bfc956aba198 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -1623,12 +1623,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     .lower_generic_params(bound_generic_params, hir::GenericParamSource::Binder),
                 bounded_ty: self
                     .lower_ty(bounded_ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Bound)),
-                bounds: self.arena.alloc_from_iter(bounds.iter().map(|bound| {
-                    self.lower_param_bound(
-                        bound,
-                        &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
-                    )
-                })),
+                bounds: self.lower_param_bounds(
+                    bounds,
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                ),
                 span: self.lower_span(*span),
                 origin: PredicateOrigin::WhereClause,
             }),
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index e426b937542ea..e506c150f7d39 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -56,7 +56,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // closure sooner rather than later, so first examine the expected
         // type, and see if can glean a closure kind from there.
         let (expected_sig, expected_kind) = match expected.to_option(self) {
-            Some(ty) => self.deduce_closure_signature(ty),
+            Some(ty) => {
+                self.deduce_closure_signature(self.try_structurally_resolve_type(expr_span, ty))
+            }
             None => (None, None),
         };
         let body = self.tcx.hir().body(closure.body);
@@ -688,8 +690,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             span_bug!(self.tcx.def_span(expr_def_id), "async fn generator outside of a fn")
         });
 
+        let closure_span = self.tcx.def_span(expr_def_id);
         let ret_ty = ret_coercion.borrow().expected_ty();
-        let ret_ty = self.inh.infcx.shallow_resolve(ret_ty);
+        let ret_ty = self.try_structurally_resolve_type(closure_span, ret_ty);
 
         let get_future_output = |predicate: ty::Predicate<'tcx>, span| {
             // Search for a pending obligation like
@@ -711,8 +714,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         };
 
-        let span = self.tcx.def_span(expr_def_id);
-
         let output_ty = match *ret_ty.kind() {
             ty::Infer(ty::TyVar(ret_vid)) => {
                 self.obligations_for_self_ty(ret_vid).find_map(|obligation| {
@@ -726,17 +727,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .find_map(|(p, s)| get_future_output(p.as_predicate(), s))?,
             ty::Error(_) => return None,
             _ => span_bug!(
-                span,
+                closure_span,
                 "async fn generator return type not an inference variable: {ret_ty}"
             ),
         };
 
-        let output_ty = self.normalize(span, output_ty);
+        let output_ty = self.normalize(closure_span, output_ty);
 
         // async fn that have opaque types in their return type need to redo the conversion to inference variables
         // as they fetch the still opaque version from the signature.
         let InferOk { value: output_ty, obligations } = self
-            .replace_opaque_types_with_inference_vars(output_ty, body_def_id, span, self.param_env);
+            .replace_opaque_types_with_inference_vars(
+                output_ty,
+                body_def_id,
+                closure_span,
+                self.param_env,
+            );
         self.register_predicates(obligations);
 
         Some(output_ty)
diff --git a/compiler/rustc_infer/src/infer/equate.rs b/compiler/rustc_infer/src/infer/equate.rs
index 665297da20f89..5d929394eb04c 100644
--- a/compiler/rustc_infer/src/infer/equate.rs
+++ b/compiler/rustc_infer/src/infer/equate.rs
@@ -56,7 +56,7 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
         // performing trait matching (which then performs equality
         // unification).
 
-        relate::relate_args(self, a_arg, b_arg)
+        relate::relate_args_invariantly(self, a_arg, b_arg)
     }
 
     fn relate_with_variance<T: Relate<'tcx>>(
diff --git a/compiler/rustc_infer/src/infer/generalize.rs b/compiler/rustc_infer/src/infer/generalize.rs
index dd7f8d3544155..c1e65ffe0a652 100644
--- a/compiler/rustc_infer/src/infer/generalize.rs
+++ b/compiler/rustc_infer/src/infer/generalize.rs
@@ -183,7 +183,7 @@ where
             // Avoid fetching the variance if we are in an invariant
             // context; no need, and it can induce dependency cycles
             // (e.g., #41849).
-            relate::relate_args(self, a_subst, b_subst)
+            relate::relate_args_invariantly(self, a_subst, b_subst)
         } else {
             let tcx = self.tcx();
             let opt_variances = tcx.variances_of(item_def_id);
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index e9d763afa68a0..96268006353cc 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -8,6 +8,7 @@ use crate::ty::error::{ExpectedFound, TypeError};
 use crate::ty::{self, Expr, ImplSubject, Term, TermKind, Ty, TyCtxt, TypeFoldable};
 use crate::ty::{GenericArg, GenericArgKind, GenericArgsRef};
 use rustc_hir as hir;
+use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
 use rustc_target::spec::abi;
 use std::iter;
@@ -134,7 +135,7 @@ pub fn relate_type_and_mut<'tcx, R: TypeRelation<'tcx>>(
 }
 
 #[inline]
-pub fn relate_args<'tcx, R: TypeRelation<'tcx>>(
+pub fn relate_args_invariantly<'tcx, R: TypeRelation<'tcx>>(
     relation: &mut R,
     a_arg: GenericArgsRef<'tcx>,
     b_arg: GenericArgsRef<'tcx>,
@@ -273,7 +274,20 @@ impl<'tcx> Relate<'tcx> for ty::AliasTy<'tcx> {
         if a.def_id != b.def_id {
             Err(TypeError::ProjectionMismatched(expected_found(relation, a.def_id, b.def_id)))
         } else {
-            let args = relation.relate(a.args, b.args)?;
+            let args = match relation.tcx().def_kind(a.def_id) {
+                DefKind::OpaqueTy => relate_args_with_variances(
+                    relation,
+                    a.def_id,
+                    relation.tcx().variances_of(a.def_id),
+                    a.args,
+                    b.args,
+                    false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle
+                )?,
+                DefKind::AssocTy | DefKind::AssocConst | DefKind::TyAlias => {
+                    relate_args_invariantly(relation, a.args, b.args)?
+                }
+                def => bug!("unknown alias DefKind: {def:?}"),
+            };
             Ok(relation.tcx().mk_alias_ty(a.def_id, args))
         }
     }
@@ -315,7 +329,7 @@ impl<'tcx> Relate<'tcx> for ty::TraitRef<'tcx> {
         if a.def_id != b.def_id {
             Err(TypeError::Traits(expected_found(relation, a.def_id, b.def_id)))
         } else {
-            let args = relate_args(relation, a.args, b.args)?;
+            let args = relate_args_invariantly(relation, a.args, b.args)?;
             Ok(ty::TraitRef::new(relation.tcx(), a.def_id, args))
         }
     }
@@ -331,7 +345,7 @@ impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> {
         if a.def_id != b.def_id {
             Err(TypeError::Traits(expected_found(relation, a.def_id, b.def_id)))
         } else {
-            let args = relate_args(relation, a.args, b.args)?;
+            let args = relate_args_invariantly(relation, a.args, b.args)?;
             Ok(ty::ExistentialTraitRef { def_id: a.def_id, args })
         }
     }
@@ -449,7 +463,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             // All Generator types with the same id represent
             // the (anonymous) type of the same generator expression. So
             // all of their regions should be equated.
-            let args = relation.relate(a_args, b_args)?;
+            let args = relate_args_invariantly(relation, a_args, b_args)?;
             Ok(Ty::new_generator(tcx, a_id, args, movability))
         }
 
@@ -459,7 +473,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             // All GeneratorWitness types with the same id represent
             // the (anonymous) type of the same generator expression. So
             // all of their regions should be equated.
-            let args = relation.relate(a_args, b_args)?;
+            let args = relate_args_invariantly(relation, a_args, b_args)?;
             Ok(Ty::new_generator_witness(tcx, a_id, args))
         }
 
@@ -467,7 +481,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             // All Closure types with the same id represent
             // the (anonymous) type of the same closure expression. So
             // all of their regions should be equated.
-            let args = relation.relate(a_args, b_args)?;
+            let args = relate_args_invariantly(relation, a_args, b_args)?;
             Ok(Ty::new_closure(tcx, a_id, &args))
         }
 
@@ -536,24 +550,6 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             Ok(Ty::new_fn_ptr(tcx, fty))
         }
 
-        // The args of opaque types may not all be invariant, so we have
-        // to treat them separately from other aliases.
-        (
-            &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, args: a_args, .. }),
-            &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, args: b_args, .. }),
-        ) if a_def_id == b_def_id => {
-            let opt_variances = tcx.variances_of(a_def_id);
-            let args = relate_args_with_variances(
-                relation,
-                a_def_id,
-                opt_variances,
-                a_args,
-                b_args,
-                false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle
-            )?;
-            Ok(Ty::new_opaque(tcx, a_def_id, args))
-        }
-
         // Alias tend to mostly already be handled downstream due to normalization.
         (&ty::Alias(a_kind, a_data), &ty::Alias(b_kind, b_data)) => {
             let alias_ty = relation.relate(a_data, b_data)?;
@@ -709,7 +705,7 @@ impl<'tcx> Relate<'tcx> for ty::ClosureArgs<'tcx> {
         a: ty::ClosureArgs<'tcx>,
         b: ty::ClosureArgs<'tcx>,
     ) -> RelateResult<'tcx, ty::ClosureArgs<'tcx>> {
-        let args = relate_args(relation, a.args, b.args)?;
+        let args = relate_args_invariantly(relation, a.args, b.args)?;
         Ok(ty::ClosureArgs { args })
     }
 }
@@ -720,7 +716,7 @@ impl<'tcx> Relate<'tcx> for ty::GeneratorArgs<'tcx> {
         a: ty::GeneratorArgs<'tcx>,
         b: ty::GeneratorArgs<'tcx>,
     ) -> RelateResult<'tcx, ty::GeneratorArgs<'tcx>> {
-        let args = relate_args(relation, a.args, b.args)?;
+        let args = relate_args_invariantly(relation, a.args, b.args)?;
         Ok(ty::GeneratorArgs { args })
     }
 }
@@ -731,7 +727,7 @@ impl<'tcx> Relate<'tcx> for GenericArgsRef<'tcx> {
         a: GenericArgsRef<'tcx>,
         b: GenericArgsRef<'tcx>,
     ) -> RelateResult<'tcx, GenericArgsRef<'tcx>> {
-        relate_args(relation, a, b)
+        relate_args_invariantly(relation, a, b)
     }
 }
 
@@ -835,19 +831,6 @@ impl<'tcx> Relate<'tcx> for Term<'tcx> {
     }
 }
 
-impl<'tcx> Relate<'tcx> for ty::ProjectionPredicate<'tcx> {
-    fn relate<R: TypeRelation<'tcx>>(
-        relation: &mut R,
-        a: ty::ProjectionPredicate<'tcx>,
-        b: ty::ProjectionPredicate<'tcx>,
-    ) -> RelateResult<'tcx, ty::ProjectionPredicate<'tcx>> {
-        Ok(ty::ProjectionPredicate {
-            projection_ty: relation.relate(a.projection_ty, b.projection_ty)?,
-            term: relation.relate(a.term, b.term)?,
-        })
-    }
-}
-
 ///////////////////////////////////////////////////////////////////////////
 // Error handling
 
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs
index 64e262c6c9359..b51bfe8c6ab1f 100644
--- a/compiler/rustc_mir_transform/src/const_prop_lint.rs
+++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs
@@ -22,7 +22,6 @@ use rustc_middle::ty::{
 };
 use rustc_span::Span;
 use rustc_target::abi::{HasDataLayout, Size, TargetDataLayout};
-use rustc_trait_selection::traits;
 
 use crate::const_prop::CanConstProp;
 use crate::const_prop::ConstPropMachine;
@@ -35,9 +34,9 @@ use crate::MirLint;
 /// Severely regress performance.
 const MAX_ALLOC_LIMIT: u64 = 1024;
 
-pub struct ConstProp;
+pub struct ConstPropLint;
 
-impl<'tcx> MirLint<'tcx> for ConstProp {
+impl<'tcx> MirLint<'tcx> for ConstPropLint {
     fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
         if body.tainted_by_errors.is_some() {
             return;
@@ -49,61 +48,25 @@ impl<'tcx> MirLint<'tcx> for ConstProp {
         }
 
         let def_id = body.source.def_id().expect_local();
-        let is_fn_like = tcx.def_kind(def_id).is_fn_like();
-        let is_assoc_const = tcx.def_kind(def_id) == DefKind::AssocConst;
+        let def_kind = tcx.def_kind(def_id);
+        let is_fn_like = def_kind.is_fn_like();
+        let is_assoc_const = def_kind == DefKind::AssocConst;
 
         // Only run const prop on functions, methods, closures and associated constants
         if !is_fn_like && !is_assoc_const {
             // skip anon_const/statics/consts because they'll be evaluated by miri anyway
-            trace!("ConstProp skipped for {:?}", def_id);
+            trace!("ConstPropLint skipped for {:?}", def_id);
             return;
         }
 
-        let is_generator = tcx.type_of(def_id.to_def_id()).instantiate_identity().is_generator();
         // FIXME(welseywiser) const prop doesn't work on generators because of query cycles
         // computing their layout.
-        if is_generator {
-            trace!("ConstProp skipped for generator {:?}", def_id);
+        if let DefKind::Generator = def_kind {
+            trace!("ConstPropLint skipped for generator {:?}", def_id);
             return;
         }
 
-        // Check if it's even possible to satisfy the 'where' clauses
-        // for this item.
-        // This branch will never be taken for any normal function.
-        // However, it's possible to `#!feature(trivial_bounds)]` to write
-        // a function with impossible to satisfy clauses, e.g.:
-        // `fn foo() where String: Copy {}`
-        //
-        // We don't usually need to worry about this kind of case,
-        // since we would get a compilation error if the user tried
-        // to call it. However, since we can do const propagation
-        // even without any calls to the function, we need to make
-        // sure that it even makes sense to try to evaluate the body.
-        // If there are unsatisfiable where clauses, then all bets are
-        // off, and we just give up.
-        //
-        // We manually filter the predicates, skipping anything that's not
-        // "global". We are in a potentially generic context
-        // (e.g. we are evaluating a function without substituting generic
-        // parameters, so this filtering serves two purposes:
-        //
-        // 1. We skip evaluating any predicates that we would
-        // never be able prove are unsatisfiable (e.g. `<T as Foo>`
-        // 2. We avoid trying to normalize predicates involving generic
-        // parameters (e.g. `<T as Foo>::MyItem`). This can confuse
-        // the normalization code (leading to cycle errors), since
-        // it's usually never invoked in this way.
-        let predicates = tcx
-            .predicates_of(def_id.to_def_id())
-            .predicates
-            .iter()
-            .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None });
-        if traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect()) {
-            trace!("ConstProp skipped for {:?}: found unsatisfiable predicates", def_id);
-            return;
-        }
-
-        trace!("ConstProp starting for {:?}", def_id);
+        trace!("ConstPropLint starting for {:?}", def_id);
 
         // FIXME(oli-obk, eddyb) Optimize locals (or even local paths) to hold
         // constants, instead of just checking for const-folding succeeding.
@@ -112,7 +75,7 @@ impl<'tcx> MirLint<'tcx> for ConstProp {
         let mut linter = ConstPropagator::new(body, tcx);
         linter.visit_body(body);
 
-        trace!("ConstProp done for {:?}", def_id);
+        trace!("ConstPropLint done for {:?}", def_id);
     }
 }
 
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index c42888d8791e9..9ee2f6dcea00f 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -496,7 +496,7 @@ fn run_runtime_lowering_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         &elaborate_box_derefs::ElaborateBoxDerefs,
         &generator::StateTransform,
         &add_retag::AddRetag,
-        &Lint(const_prop_lint::ConstProp),
+        &Lint(const_prop_lint::ConstPropLint),
     ];
     pm::run_passes_no_validate(tcx, body, passes, Some(MirPhase::Runtime(RuntimePhase::Initial)));
 }
@@ -554,8 +554,6 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &const_prop::ConstProp,
             &gvn::GVN,
             &dataflow_const_prop::DataflowConstProp,
-            //
-            // Const-prop runs unconditionally, but doesn't mutate the MIR at mir-opt-level=0.
             &const_debuginfo::ConstDebugInfo,
             &o1(simplify_branches::SimplifyConstCondition::AfterConstProp),
             &early_otherwise_branch::EarlyOtherwiseBranch,
diff --git a/src/librustdoc/formats/cache.rs b/src/librustdoc/formats/cache.rs
index b916baecc1407..4ccb5f2be346b 100644
--- a/src/librustdoc/formats/cache.rs
+++ b/src/librustdoc/formats/cache.rs
@@ -221,16 +221,23 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
             _ => self.cache.stripped_mod,
         };
 
+        #[inline]
+        fn is_from_private_dep(tcx: TyCtxt<'_>, cache: &Cache, def_id: DefId) -> bool {
+            let krate = def_id.krate;
+
+            cache.masked_crates.contains(&krate) || tcx.is_private_dep(krate)
+        }
+
         // If the impl is from a masked crate or references something from a
         // masked crate then remove it completely.
         if let clean::ImplItem(ref i) = *item.kind &&
             (self.cache.masked_crates.contains(&item.item_id.krate())
                 || i.trait_
                     .as_ref()
-                    .map_or(false, |t| self.cache.masked_crates.contains(&t.def_id().krate))
+                    .map_or(false, |t| is_from_private_dep(self.tcx, self.cache, t.def_id()))
                 || i.for_
                     .def_id(self.cache)
-                    .map_or(false, |d| self.cache.masked_crates.contains(&d.krate)))
+                    .map_or(false, |d| is_from_private_dep(self.tcx, self.cache, d)))
         {
             return None;
         }
diff --git a/tests/rustdoc-js/auxiliary/equivalent.rs b/tests/rustdoc-js/auxiliary/equivalent.rs
new file mode 100644
index 0000000000000..a19b5a2d44df2
--- /dev/null
+++ b/tests/rustdoc-js/auxiliary/equivalent.rs
@@ -0,0 +1,15 @@
+use std::borrow::Borrow;
+
+pub trait Equivalent<K: ?Sized> {
+    fn equivalent(&self, key: &K) -> bool;
+}
+
+impl<Q: ?Sized, K: ?Sized> Equivalent<K> for Q
+where
+    Q: Eq,
+    K: Borrow<Q>,
+{
+    fn equivalent(&self, key: &K) -> bool {
+        PartialEq::eq(self, key.borrow())
+    }
+}
diff --git a/tests/rustdoc-js/search-non-local-trait-impl.js b/tests/rustdoc-js/search-non-local-trait-impl.js
new file mode 100644
index 0000000000000..9ebeceb69f902
--- /dev/null
+++ b/tests/rustdoc-js/search-non-local-trait-impl.js
@@ -0,0 +1,9 @@
+// exact-check
+
+// This test ensures that methods from blanket impls of not available foreign traits
+// don't show up in the search results.
+
+const EXPECTED = {
+    'query': 'equivalent',
+    'others': [],
+};
diff --git a/tests/rustdoc-js/search-non-local-trait-impl.rs b/tests/rustdoc-js/search-non-local-trait-impl.rs
new file mode 100644
index 0000000000000..462b75b0b1326
--- /dev/null
+++ b/tests/rustdoc-js/search-non-local-trait-impl.rs
@@ -0,0 +1,8 @@
+// aux-crate:priv:equivalent=equivalent.rs
+// compile-flags: -Zunstable-options --extern equivalent
+// edition:2018
+
+extern crate equivalent;
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct LayoutError;
diff --git a/tests/ui/impl-trait/in-trait/opaque-variances.rs b/tests/ui/impl-trait/in-trait/opaque-variances.rs
new file mode 100644
index 0000000000000..60bfab0deb582
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/opaque-variances.rs
@@ -0,0 +1,14 @@
+// check-pass
+// compile-flags: -Ztrait-solver=next
+
+fn foo<'a: 'a>(x: &'a Vec<i32>) -> impl Sized {
+    ()
+}
+
+fn main() {
+    // in NLL, we want to make sure that the `'a` subst of `foo` does not get
+    // related between `x` and the RHS of the assignment. That would require
+    // that the temp is live for the lifetime of the variable `x`, which of
+    // course is not necessary since `'a` is not captured by the RPIT.
+    let x = foo(&Vec::new());
+}
diff --git a/tests/ui/traits/new-solver/deduce-closure-signature-after-normalization.rs b/tests/ui/traits/new-solver/deduce-closure-signature-after-normalization.rs
new file mode 100644
index 0000000000000..d67fc65032ca7
--- /dev/null
+++ b/tests/ui/traits/new-solver/deduce-closure-signature-after-normalization.rs
@@ -0,0 +1,12 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+#![feature(return_position_impl_trait_in_trait)]
+
+trait Foo {
+    fn test() -> impl Fn(u32) -> u32 {
+        |x| x.count_ones()
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/traits/new-solver/normalize-async-closure-in-trait.rs b/tests/ui/traits/new-solver/normalize-async-closure-in-trait.rs
new file mode 100644
index 0000000000000..b6200096a8921
--- /dev/null
+++ b/tests/ui/traits/new-solver/normalize-async-closure-in-trait.rs
@@ -0,0 +1,11 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+// edition:2021
+
+#![feature(async_fn_in_trait)]
+
+trait Foo {
+    async fn bar() {}
+}
+
+fn main() {}