Auto merge of #108145 - matthiaskrgr:rollup-bgadak1, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #104068 (rustdoc: Add PartialOrd trait to doc comment explanation)
 - #107489 (Implement partial support for non-lifetime binders)
 - #107905 (Pass arguments to `x` subcommands with `--`)
 - #108009 (Move some tests)
 - #108086 (wasm: Register the `relaxed-simd` target feature)
 - #108104 (don't into self)
 - #108133 (Small cleanups around `EarlyBinder`)
 - #108136 (Do not ICE on unmet trait alias impl bounds)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

95 files changed, 822 insertions, 370 deletions

diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 1535837fd05..d1ae8c1fdbd 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -294,27 +294,6 @@ impl<'a> AstValidator<'a> {
         }
     }
 
-    fn check_late_bound_lifetime_defs(&self, params: &[GenericParam]) {
-        // Check only lifetime parameters are present and that the lifetime
-        // parameters that are present have no bounds.
-        let non_lt_param_spans: Vec<_> = params
-            .iter()
-            .filter_map(|param| match param.kind {
-                GenericParamKind::Lifetime { .. } => {
-                    if !param.bounds.is_empty() {
-                        let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
-                        self.session.emit_err(ForbiddenLifetimeBound { spans });
-                    }
-                    None
-                }
-                _ => Some(param.ident.span),
-            })
-            .collect();
-        if !non_lt_param_spans.is_empty() {
-            self.session.emit_err(ForbiddenNonLifetimeParam { spans: non_lt_param_spans });
-        }
-    }
-
     fn check_fn_decl(&self, fn_decl: &FnDecl, self_semantic: SelfSemantic) {
         self.check_decl_num_args(fn_decl);
         self.check_decl_cvaradic_pos(fn_decl);
@@ -745,7 +724,6 @@ impl<'a> AstValidator<'a> {
                     )
                     .emit();
                 });
-                self.check_late_bound_lifetime_defs(&bfty.generic_params);
                 if let Extern::Implicit(_) = bfty.ext {
                     let sig_span = self.session.source_map().next_point(ty.span.shrink_to_lo());
                     self.maybe_lint_missing_abi(sig_span, ty.id);
@@ -1318,9 +1296,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         for predicate in &generics.where_clause.predicates {
             match predicate {
                 WherePredicate::BoundPredicate(bound_pred) => {
-                    // A type binding, eg `for<'c> Foo: Send+Clone+'c`
-                    self.check_late_bound_lifetime_defs(&bound_pred.bound_generic_params);
-
                     // This is slightly complicated. Our representation for poly-trait-refs contains a single
                     // binder and thus we only allow a single level of quantification. However,
                     // the syntax of Rust permits quantification in two places in where clauses,
@@ -1396,11 +1371,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         visit::walk_param_bound(self, bound)
     }
 
-    fn visit_poly_trait_ref(&mut self, t: &'a PolyTraitRef) {
-        self.check_late_bound_lifetime_defs(&t.bound_generic_params);
-        visit::walk_poly_trait_ref(self, t);
-    }
-
     fn visit_variant_data(&mut self, s: &'a VariantData) {
         self.with_banned_assoc_ty_bound(|this| visit::walk_struct_def(this, s))
     }
@@ -1437,10 +1407,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 .emit();
         }
 
-        if let FnKind::Closure(ClosureBinder::For { generic_params, .. }, ..) = fk {
-            self.check_late_bound_lifetime_defs(generic_params);
-        }
-
         if let FnKind::Fn(
             _,
             _,
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 89ba6f936d1..3af2ef4e727 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -11,6 +11,8 @@ use rustc_span::symbol::sym;
 use rustc_span::Span;
 use rustc_target::spec::abi;
 
+use crate::errors::ForbiddenLifetimeBound;
+
 macro_rules! gate_feature_fn {
     ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $help: expr) => {{
         let (visitor, has_feature, span, name, explain, help) =
@@ -136,6 +138,34 @@ impl<'a> PostExpansionVisitor<'a> {
         }
         ImplTraitVisitor { vis: self }.visit_ty(ty);
     }
+
+    fn check_late_bound_lifetime_defs(&self, params: &[ast::GenericParam]) {
+        // Check only lifetime parameters are present and that the lifetime
+        // parameters that are present have no bounds.
+        let non_lt_param_spans: Vec<_> = params
+            .iter()
+            .filter_map(|param| match param.kind {
+                ast::GenericParamKind::Lifetime { .. } => None,
+                _ => Some(param.ident.span),
+            })
+            .collect();
+        // FIXME: gate_feature_post doesn't really handle multispans...
+        if !non_lt_param_spans.is_empty() && !self.features.non_lifetime_binders {
+            feature_err(
+                &self.sess.parse_sess,
+                sym::non_lifetime_binders,
+                non_lt_param_spans,
+                rustc_errors::fluent::ast_passes_forbidden_non_lifetime_param,
+            )
+            .emit();
+        }
+        for param in params {
+            if !param.bounds.is_empty() {
+                let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
+                self.sess.emit_err(ForbiddenLifetimeBound { spans });
+            }
+        }
+    }
 }
 
 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
@@ -147,7 +177,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ..
         }) = attr_info
         {
-            gate_feature_fn!(self, has_feature, attr.span, *name, descr);
+            gate_feature_fn!(self, has_feature, attr.span, *name, *descr);
         }
         // Check unstable flavors of the `#[doc]` attribute.
         if attr.has_name(sym::doc) {
@@ -306,6 +336,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::TyKind::BareFn(bare_fn_ty) => {
                 // Function pointers cannot be `const`
                 self.check_extern(bare_fn_ty.ext, ast::Const::No);
+                self.check_late_bound_lifetime_defs(&bare_fn_ty.generic_params);
             }
             ast::TyKind::Never => {
                 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
@@ -318,6 +349,19 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         visit::walk_ty(self, ty)
     }
 
+    fn visit_generics(&mut self, g: &'a ast::Generics) {
+        for predicate in &g.where_clause.predicates {
+            match predicate {
+                ast::WherePredicate::BoundPredicate(bound_pred) => {
+                    // A type binding, eg `for<'c> Foo: Send+Clone+'c`
+                    self.check_late_bound_lifetime_defs(&bound_pred.bound_generic_params);
+                }
+                _ => {}
+            }
+        }
+        visit::walk_generics(self, g);
+    }
+
     fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
         if let ast::FnRetTy::Ty(output_ty) = ret_ty {
             if let ast::TyKind::Never = output_ty.kind {
@@ -437,12 +481,21 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         visit::walk_pat(self, pattern)
     }
 
+    fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef) {
+        self.check_late_bound_lifetime_defs(&t.bound_generic_params);
+        visit::walk_poly_trait_ref(self, t);
+    }
+
     fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
         if let Some(header) = fn_kind.header() {
             // Stability of const fn methods are covered in `visit_assoc_item` below.
             self.check_extern(header.ext, header.constness);
         }
 
+        if let FnKind::Closure(ast::ClosureBinder::For { generic_params, .. }, ..) = fn_kind {
+            self.check_late_bound_lifetime_defs(generic_params);
+        }
+
         if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
             gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
         }
diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index 40531c1c164..3d240108b4a 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -731,7 +731,7 @@ pub fn eval_condition(
                             sess,
                             sym::cfg_target_compact,
                             cfg.span,
-                            &"compact `cfg(target(..))` is experimental and subject to change"
+                            "compact `cfg(target(..))` is experimental and subject to change"
                         ).emit();
                     }
 
diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index a6afbad5b24..0432a9c5a12 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -286,6 +286,7 @@ const WASM_ALLOWED_FEATURES: &[(&str, Option<Symbol>)] = &[
     ("mutable-globals", Some(sym::wasm_target_feature)),
     ("nontrapping-fptoint", Some(sym::wasm_target_feature)),
     ("reference-types", Some(sym::wasm_target_feature)),
+    ("relaxed-simd", Some(sym::wasm_target_feature)),
     ("sign-ext", Some(sym::wasm_target_feature)),
     ("simd128", None),
     // tidy-alphabetical-end
diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 5267f73efc8..7122ccdcd2e 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -473,6 +473,8 @@ declare_features! (
     (active, no_sanitize, "1.42.0", Some(39699), None),
     /// Allows using the `non_exhaustive_omitted_patterns` lint.
     (active, non_exhaustive_omitted_patterns_lint, "1.57.0", Some(89554), None),
+    /// Allows `for<T>` binders in where-clauses
+    (incomplete, non_lifetime_binders, "CURRENT_RUSTC_VERSION", Some(1), None),
     /// Allows making `dyn Trait` well-formed even if `Trait` is not object safe.
     /// In that case, `dyn Trait: Trait` does not hold. Moreover, coercions and
     /// casts in safe Rust to `dyn Trait` for such a `Trait` is also forbidden.
diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index e5c176f19ea..221721f5909 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -14,7 +14,7 @@ use crate::errors::{
     AmbiguousLifetimeBound, MultipleRelaxedDefaultBounds, TraitObjectDeclaredWithNoTraits,
     TypeofReservedKeywordUsed, ValueOfAssociatedStructAlreadySpecified,
 };
-use crate::middle::resolve_lifetime as rl;
+use crate::middle::resolve_bound_vars as rbv;
 use crate::require_c_abi_if_c_variadic;
 use rustc_ast::TraitObjectSyntax;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -225,10 +225,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let tcx = self.tcx();
         let lifetime_name = |def_id| tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id));
 
-        match tcx.named_region(lifetime.hir_id) {
-            Some(rl::Region::Static) => tcx.lifetimes.re_static,
+        match tcx.named_bound_var(lifetime.hir_id) {
+            Some(rbv::ResolvedArg::StaticLifetime) => tcx.lifetimes.re_static,
 
-            Some(rl::Region::LateBound(debruijn, index, def_id)) => {
+            Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
                 let name = lifetime_name(def_id.expect_local());
                 let br = ty::BoundRegion {
                     var: ty::BoundVar::from_u32(index),
@@ -237,7 +237,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 tcx.mk_re_late_bound(debruijn, br)
             }
 
-            Some(rl::Region::EarlyBound(def_id)) => {
+            Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
                 let name = tcx.hir().ty_param_name(def_id.expect_local());
                 let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
                 let generics = tcx.generics_of(item_def_id);
@@ -245,7 +245,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 tcx.mk_re_early_bound(ty::EarlyBoundRegion { def_id, index, name })
             }
 
-            Some(rl::Region::Free(scope, id)) => {
+            Some(rbv::ResolvedArg::Free(scope, id)) => {
                 let name = lifetime_name(id.expect_local());
                 tcx.mk_re_free(scope, ty::BrNamed(id, name))
 
@@ -1607,7 +1607,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             self.ast_region_to_region(lifetime, None)
         } else {
             self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
-                if tcx.named_region(lifetime.hir_id).is_some() {
+                if tcx.named_bound_var(lifetime.hir_id).is_some() {
                     self.ast_region_to_region(lifetime, None)
                 } else {
                     self.re_infer(None, span).unwrap_or_else(|| {
@@ -2600,6 +2600,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         &self,
         opt_self_ty: Option<Ty<'tcx>>,
         path: &hir::Path<'_>,
+        hir_id: hir::HirId,
         permit_variants: bool,
     ) -> Ty<'tcx> {
         let tcx = self.tcx();
@@ -2663,11 +2664,25 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     }
                 });
 
-                let def_id = def_id.expect_local();
-                let item_def_id = tcx.hir().ty_param_owner(def_id);
-                let generics = tcx.generics_of(item_def_id);
-                let index = generics.param_def_id_to_index[&def_id.to_def_id()];
-                tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id))
+                match tcx.named_bound_var(hir_id) {
+                    Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
+                        let name =
+                            tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local()));
+                        let br = ty::BoundTy {
+                            var: ty::BoundVar::from_u32(index),
+                            kind: ty::BoundTyKind::Param(def_id, name),
+                        };
+                        tcx.mk_ty(ty::Bound(debruijn, br))
+                    }
+                    Some(rbv::ResolvedArg::EarlyBound(_)) => {
+                        let def_id = def_id.expect_local();
+                        let item_def_id = tcx.hir().ty_param_owner(def_id);
+                        let generics = tcx.generics_of(item_def_id);
+                        let index = generics.param_def_id_to_index[&def_id.to_def_id()];
+                        tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id))
+                    }
+                    arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"),
+                }
             }
             Res::SelfTyParam { .. } => {
                 // `Self` in trait or type alias.
@@ -2870,14 +2885,22 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             hir::TyKind::BareFn(bf) => {
                 require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, ast_ty.span);
 
-                tcx.mk_fn_ptr(self.ty_of_fn(
+                let fn_ptr_ty = tcx.mk_fn_ptr(self.ty_of_fn(
                     ast_ty.hir_id,
                     bf.unsafety,
                     bf.abi,
                     bf.decl,
                     None,
                     Some(ast_ty),
-                ))
+                ));
+
+                if let Some(guar) =
+                    deny_non_region_late_bound(tcx, bf.generic_params, "function pointer")
+                {
+                    tcx.ty_error_with_guaranteed(guar)
+                } else {
+                    fn_ptr_ty
+                }
             }
             hir::TyKind::TraitObject(bounds, lifetime, repr) => {
                 self.maybe_lint_bare_trait(ast_ty, in_path);
@@ -2885,12 +2908,27 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn,
                     TraitObjectSyntax::DynStar => ty::DynStar,
                 };
-                self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime, borrowed, repr)
+
+                let object_ty = self.conv_object_ty_poly_trait_ref(
+                    ast_ty.span,
+                    bounds,
+                    lifetime,
+                    borrowed,
+                    repr,
+                );
+
+                if let Some(guar) = bounds.iter().find_map(|trait_ref| {
+                    deny_non_region_late_bound(tcx, trait_ref.bound_generic_params, "trait object")
+                }) {
+                    tcx.ty_error_with_guaranteed(guar)
+                } else {
+                    object_ty
+                }
             }
             hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => {
                 debug!(?maybe_qself, ?path);
                 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself));
-                self.res_to_ty(opt_self_ty, path, false)
+                self.res_to_ty(opt_self_ty, path, ast_ty.hir_id, false)
             }
             &hir::TyKind::OpaqueDef(item_id, lifetimes, in_trait) => {
                 let opaque_ty = tcx.hir().item(item_id);
@@ -3346,3 +3384,24 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         }
     }
 }
+
+fn deny_non_region_late_bound(
+    tcx: TyCtxt<'_>,
+    params: &[hir::GenericParam<'_>],
+    where_: &str,
+) -> Option<ErrorGuaranteed> {
+    params.iter().find_map(|bad_param| {
+        let what = match bad_param.kind {
+            hir::GenericParamKind::Type { .. } => "type",
+            hir::GenericParamKind::Const { .. } => "const",
+            hir::GenericParamKind::Lifetime { .. } => return None,
+        };
+
+        let mut diag = tcx.sess.struct_span_err(
+            bad_param.span,
+            format!("late-bound {what} parameter not allowed on {where_} types"),
+        );
+
+        Some(if tcx.features().non_lifetime_binders { diag.emit() } else { diag.delay_as_bug() })
+    })
+}
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 456c5bc99b7..8ebe576a224 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -41,8 +41,8 @@ use std::iter;
 
 mod generics_of;
 mod item_bounds;
-mod lifetimes;
 mod predicates_of;
+mod resolve_bound_vars;
 mod type_of;
 
 ///////////////////////////////////////////////////////////////////////////
@@ -53,7 +53,7 @@ fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
 }
 
 pub fn provide(providers: &mut Providers) {
-    lifetimes::provide(providers);
+    resolve_bound_vars::provide(providers);
     *providers = Providers {
         opt_const_param_of: type_of::opt_const_param_of,
         type_of: type_of::type_of,
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index 014ee9fcc20..7bcaeadbcf6 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -1,4 +1,4 @@
-use crate::middle::resolve_lifetime as rl;
+use crate::middle::resolve_bound_vars as rbv;
 use hir::{
     intravisit::{self, Visitor},
     GenericParamKind, HirId, Node,
@@ -394,10 +394,11 @@ fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<S
                 return;
             }
 
-            match self.tcx.named_region(lt.hir_id) {
-                Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
-                Some(rl::Region::LateBound(debruijn, _, _)) if debruijn < self.outer_index => {}
-                Some(rl::Region::LateBound(..) | rl::Region::Free(..)) | None => {
+            match self.tcx.named_bound_var(lt.hir_id) {
+                Some(rbv::ResolvedArg::StaticLifetime | rbv::ResolvedArg::EarlyBound(..)) => {}
+                Some(rbv::ResolvedArg::LateBound(debruijn, _, _))
+                    if debruijn < self.outer_index => {}
+                Some(rbv::ResolvedArg::LateBound(..) | rbv::ResolvedArg::Free(..)) | None => {
                     self.has_late_bound_regions = Some(lt.ident.span);
                 }
             }
diff --git a/compiler/rustc_hir_analysis/src/collect/lifetimes.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index d8606f759b2..8c388040fbf 100644
--- a/compiler/rustc_hir_analysis/src/collect/lifetimes.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -16,7 +16,7 @@ use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirIdMap, LifetimeName, Node};
 use rustc_middle::bug;
 use rustc_middle::hir::nested_filter;
-use rustc_middle::middle::resolve_lifetime::*;
+use rustc_middle::middle::resolve_bound_vars::*;
 use rustc_middle::ty::{self, ir::TypeVisitor, DefIdTree, TyCtxt, TypeSuperVisitable};
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{sym, Ident};
@@ -24,59 +24,61 @@ use rustc_span::Span;
 use std::fmt;
 
 trait RegionExt {
-    fn early(param: &GenericParam<'_>) -> (LocalDefId, Region);
+    fn early(param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg);
 
-    fn late(index: u32, param: &GenericParam<'_>) -> (LocalDefId, Region);
+    fn late(index: u32, param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg);
 
     fn id(&self) -> Option<DefId>;
 
-    fn shifted(self, amount: u32) -> Region;
+    fn shifted(self, amount: u32) -> ResolvedArg;
 }
 
-impl RegionExt for Region {
-    fn early(param: &GenericParam<'_>) -> (LocalDefId, Region) {
-        debug!("Region::early: def_id={:?}", param.def_id);
-        (param.def_id, Region::EarlyBound(param.def_id.to_def_id()))
+impl RegionExt for ResolvedArg {
+    fn early(param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
+        debug!("ResolvedArg::early: def_id={:?}", param.def_id);
+        (param.def_id, ResolvedArg::EarlyBound(param.def_id.to_def_id()))
     }
 
-    fn late(idx: u32, param: &GenericParam<'_>) -> (LocalDefId, Region) {
+    fn late(idx: u32, param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
         let depth = ty::INNERMOST;
         debug!(
-            "Region::late: idx={:?}, param={:?} depth={:?} def_id={:?}",
+            "ResolvedArg::late: idx={:?}, param={:?} depth={:?} def_id={:?}",
             idx, param, depth, param.def_id,
         );
-        (param.def_id, Region::LateBound(depth, idx, param.def_id.to_def_id()))
+        (param.def_id, ResolvedArg::LateBound(depth, idx, param.def_id.to_def_id()))
     }
 
     fn id(&self) -> Option<DefId> {
         match *self {
-            Region::Static => None,
+            ResolvedArg::StaticLifetime => None,
 
-            Region::EarlyBound(id) | Region::LateBound(_, _, id) | Region::Free(_, id) => Some(id),
+            ResolvedArg::EarlyBound(id)
+            | ResolvedArg::LateBound(_, _, id)
+            | ResolvedArg::Free(_, id) => Some(id),
         }
     }
 
-    fn shifted(self, amount: u32) -> Region {
+    fn shifted(self, amount: u32) -> ResolvedArg {
         match self {
-            Region::LateBound(debruijn, idx, id) => {
-                Region::LateBound(debruijn.shifted_in(amount), idx, id)
+            ResolvedArg::LateBound(debruijn, idx, id) => {
+                ResolvedArg::LateBound(debruijn.shifted_in(amount), idx, id)
             }
             _ => self,
         }
     }
 }
 
-/// Maps the id of each lifetime reference to the lifetime decl
+/// Maps the id of each bound variable reference to the variable decl
 /// that it corresponds to.
 ///
-/// FIXME. This struct gets converted to a `ResolveLifetimes` for
+/// FIXME. This struct gets converted to a `ResolveBoundVars` for
 /// actual use. It has the same data, but indexed by `LocalDefId`. This
 /// is silly.
 #[derive(Debug, Default)]
-struct NamedRegionMap {
-    // maps from every use of a named (not anonymous) lifetime to a
-    // `Region` describing how that region is bound
-    defs: HirIdMap<Region>,
+struct NamedVarMap {
+    // maps from every use of a named (not anonymous) bound var to a
+    // `ResolvedArg` describing how that variable is bound
+    defs: HirIdMap<ResolvedArg>,
 
     // Maps relevant hir items to the bound vars on them. These include:
     // - function defs
@@ -87,9 +89,9 @@ struct NamedRegionMap {
     late_bound_vars: HirIdMap<Vec<ty::BoundVariableKind>>,
 }
 
-struct LifetimeContext<'a, 'tcx> {
+struct BoundVarContext<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    map: &'a mut NamedRegionMap,
+    map: &'a mut NamedVarMap,
     scope: ScopeRef<'a>,
 }
 
@@ -102,7 +104,7 @@ enum Scope<'a> {
     Binder {
         /// We use an IndexMap here because we want these lifetimes in order
         /// for diagnostics.
-        lifetimes: FxIndexMap<LocalDefId, Region>,
+        bound_vars: FxIndexMap<LocalDefId, ResolvedArg>,
 
         scope_type: BinderScopeType,
 
@@ -141,7 +143,7 @@ enum Scope<'a> {
     /// inferred in a function body or potentially error outside one),
     /// for the default choice of lifetime in a trait object type.
     ObjectLifetimeDefault {
-        lifetime: Option<Region>,
+        lifetime: Option<ResolvedArg>,
         s: ScopeRef<'a>,
     },
 
@@ -150,7 +152,7 @@ enum Scope<'a> {
     /// lifetimes encountered when identifying the trait that an associated type
     /// is declared on.
     Supertrait {
-        lifetimes: Vec<ty::BoundVariableKind>,
+        bound_vars: Vec<ty::BoundVariableKind>,
         s: ScopeRef<'a>,
     },
 
@@ -185,9 +187,9 @@ struct TruncatedScopeDebug<'a>(&'a Scope<'a>);
 impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.0 {
-            Scope::Binder { lifetimes, scope_type, hir_id, where_bound_origin, s: _ } => f
+            Scope::Binder { bound_vars, scope_type, hir_id, where_bound_origin, s: _ } => f
                 .debug_struct("Binder")
-                .field("lifetimes", lifetimes)
+                .field("bound_vars", bound_vars)
                 .field("scope_type", scope_type)
                 .field("hir_id", hir_id)
                 .field("where_bound_origin", where_bound_origin)
@@ -202,9 +204,9 @@ impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
                 .field("lifetime", lifetime)
                 .field("s", &"..")
                 .finish(),
-            Scope::Supertrait { lifetimes, s: _ } => f
+            Scope::Supertrait { bound_vars, s: _ } => f
                 .debug_struct("Supertrait")
-                .field("lifetimes", lifetimes)
+                .field("bound_vars", bound_vars)
                 .field("s", &"..")
                 .finish(),
             Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(),
@@ -219,27 +221,27 @@ type ScopeRef<'a> = &'a Scope<'a>;
 
 pub(crate) fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers {
-        resolve_lifetimes,
+        resolve_bound_vars,
 
-        named_region_map: |tcx, id| tcx.resolve_lifetimes(id).defs.get(&id),
+        named_variable_map: |tcx, id| tcx.resolve_bound_vars(id).defs.get(&id),
         is_late_bound_map,
         object_lifetime_default,
-        late_bound_vars_map: |tcx, id| tcx.resolve_lifetimes(id).late_bound_vars.get(&id),
+        late_bound_vars_map: |tcx, id| tcx.resolve_bound_vars(id).late_bound_vars.get(&id),
 
         ..*providers
     };
 }
 
-/// Computes the `ResolveLifetimes` map that contains data for an entire `Item`.
+/// Computes the `ResolveBoundVars` map that contains data for an entire `Item`.
 /// You should not read the result of this query directly, but rather use
-/// `named_region_map`, `is_late_bound_map`, etc.
+/// `named_variable_map`, `is_late_bound_map`, etc.
 #[instrument(level = "debug", skip(tcx))]
-fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: hir::OwnerId) -> ResolveLifetimes {
-    let mut named_region_map =
-        NamedRegionMap { defs: Default::default(), late_bound_vars: Default::default() };
-    let mut visitor = LifetimeContext {
+fn resolve_bound_vars(tcx: TyCtxt<'_>, local_def_id: hir::OwnerId) -> ResolveBoundVars {
+    let mut named_variable_map =
+        NamedVarMap { defs: Default::default(), late_bound_vars: Default::default() };
+    let mut visitor = BoundVarContext {
         tcx,
-        map: &mut named_region_map,
+        map: &mut named_variable_map,
         scope: &Scope::Root { opt_parent_item: None },
     };
     match tcx.hir().owner(local_def_id) {
@@ -260,13 +262,13 @@ fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: hir::OwnerId) -> ResolveLife
         hir::OwnerNode::Crate(_) => {}
     }
 
-    let mut rl = ResolveLifetimes::default();
+    let mut rl = ResolveBoundVars::default();
 
-    for (hir_id, v) in named_region_map.defs {
+    for (hir_id, v) in named_variable_map.defs {
         let map = rl.defs.entry(hir_id.owner).or_default();
         map.insert(hir_id.local_id, v);
     }
-    for (hir_id, v) in named_region_map.late_bound_vars {
+    for (hir_id, v) in named_variable_map.late_bound_vars {
         let map = rl.late_bound_vars.entry(hir_id.owner).or_default();
         map.insert(hir_id.local_id, v);
     }
@@ -276,21 +278,33 @@ fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: hir::OwnerId) -> ResolveLife
     rl
 }
 
-fn late_region_as_bound_region(tcx: TyCtxt<'_>, region: &Region) -> ty::BoundVariableKind {
-    match region {
-        Region::LateBound(_, _, def_id) => {
+fn late_arg_as_bound_arg<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    arg: &ResolvedArg,
+    param: &GenericParam<'tcx>,
+) -> ty::BoundVariableKind {
+    match arg {
+        ResolvedArg::LateBound(_, _, def_id) => {
             let name = tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local()));
-            ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name))
+            match param.kind {
+                GenericParamKind::Lifetime { .. } => {
+                    ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name))
+                }
+                GenericParamKind::Type { .. } => {
+                    ty::BoundVariableKind::Ty(ty::BoundTyKind::Param(*def_id, name))
+                }
+                GenericParamKind::Const { .. } => ty::BoundVariableKind::Const,
+            }
         }
-        _ => bug!("{:?} is not a late region", region),
+        _ => bug!("{:?} is not a late argument", arg),
     }
 }
 
-impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
+impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
     /// Returns the binders in scope and the type of `Binder` that should be created for a poly trait ref.
     fn poly_trait_ref_binder_info(&mut self) -> (Vec<ty::BoundVariableKind>, BinderScopeType) {
         let mut scope = self.scope;
-        let mut supertrait_lifetimes = vec![];
+        let mut supertrait_bound_vars = vec![];
         loop {
             match scope {
                 Scope::Body { .. } | Scope::Root { .. } => {
@@ -301,14 +315,14 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     scope = s;
                 }
 
-                Scope::Supertrait { s, lifetimes } => {
-                    supertrait_lifetimes = lifetimes.clone();
+                Scope::Supertrait { s, bound_vars } => {
+                    supertrait_bound_vars = bound_vars.clone();
                     scope = s;
                 }
 
                 Scope::TraitRefBoundary { .. } => {
                     // We should only see super trait lifetimes if there is a `Binder` above
-                    assert!(supertrait_lifetimes.is_empty());
+                    assert!(supertrait_bound_vars.is_empty());
                     break (vec![], BinderScopeType::Normal);
                 }
 
@@ -316,14 +330,14 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     // Nested poly trait refs have the binders concatenated
                     let mut full_binders =
                         self.map.late_bound_vars.entry(*hir_id).or_default().clone();
-                    full_binders.extend(supertrait_lifetimes.into_iter());
+                    full_binders.extend(supertrait_bound_vars.into_iter());
                     break (full_binders, BinderScopeType::Concatenating);
                 }
             }
         }
     }
 }
-impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
+impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
     type NestedFilter = nested_filter::OnlyBodies;
 
     fn nested_visit_map(&mut self) -> Self::Map {
@@ -386,14 +400,13 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 }
             }
 
-            let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) =
+            let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
                 bound_generic_params
                     .iter()
-                    .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. }))
                     .enumerate()
                     .map(|(late_bound_idx, param)| {
-                        let pair = Region::late(late_bound_idx as u32, param);
-                        let r = late_region_as_bound_region(self.tcx, &pair.1);
+                        let pair = ResolvedArg::late(late_bound_idx as u32, param);
+                        let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
                         (pair, r)
                     })
                     .unzip();
@@ -401,7 +414,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
             self.record_late_bound_vars(e.hir_id, binders);
             let scope = Scope::Binder {
                 hir_id: e.hir_id,
-                lifetimes,
+                bound_vars,
                 s: self.scope,
                 scope_type: BinderScopeType::Normal,
                 where_bound_origin: None,
@@ -461,7 +474,8 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 // conservatively add all resolved lifetimes. Otherwise we run into problems in
                 // cases like `type Foo<'a> = impl Bar<As = impl Baz + 'a>`.
                 let parent_item = self.tcx.hir().get_parent_item(item.hir_id());
-                let resolved_lifetimes: &ResolveLifetimes = self.tcx.resolve_lifetimes(parent_item);
+                let resolved_lifetimes: &ResolveBoundVars =
+                    self.tcx.resolve_bound_vars(parent_item);
                 // We need to add *all* deps, since opaque tys may want them from *us*
                 for (&owner, defs) in resolved_lifetimes.defs.iter() {
                     defs.iter().for_each(|(&local_id, region)| {
@@ -478,35 +492,33 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 }
             }
             hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-                origin: hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_),
+                origin: hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent),
                 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();
+                let mut bound_vars = FxIndexMap::default();
                 debug!(?generics.params);
                 for param in generics.params {
-                    match param.kind {
-                        GenericParamKind::Lifetime { .. } => {
-                            let (def_id, reg) = Region::early(&param);
-                            lifetimes.insert(def_id, reg);
-                        }
-                        GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {}
-                    }
+                    let (def_id, reg) = ResolvedArg::early(&param);
+                    bound_vars.insert(def_id, reg);
                 }
 
-                let scope = Scope::Binder {
-                    hir_id: item.hir_id(),
-                    lifetimes,
-                    s: self.scope,
-                    scope_type: BinderScopeType::Normal,
-                    where_bound_origin: None,
-                };
+                let scope = Scope::Root { opt_parent_item: Some(parent) };
                 self.with(scope, |this| {
-                    let scope = Scope::TraitRefBoundary { s: this.scope };
-                    this.with(scope, |this| intravisit::walk_item(this, item))
-                });
+                    let scope = Scope::Binder {
+                        hir_id: item.hir_id(),
+                        bound_vars,
+                        s: this.scope,
+                        scope_type: BinderScopeType::Normal,
+                        where_bound_origin: None,
+                    };
+                    this.with(scope, |this| {
+                        let scope = Scope::TraitRefBoundary { s: this.scope };
+                        this.with(scope, |this| intravisit::walk_item(this, item))
+                    });
+                })
             }
             hir::ItemKind::TyAlias(_, generics)
             | hir::ItemKind::Enum(_, generics)
@@ -516,18 +528,11 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
             | hir::ItemKind::TraitAlias(generics, ..)
             | hir::ItemKind::Impl(&hir::Impl { generics, .. }) => {
                 // These kinds of items have only early-bound lifetime parameters.
-                let lifetimes = generics
-                    .params
-                    .iter()
-                    .filter_map(|param| match param.kind {
-                        GenericParamKind::Lifetime { .. } => Some(Region::early(param)),
-                        GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => None,
-                    })
-                    .collect();
+                let bound_vars = generics.params.iter().map(ResolvedArg::early).collect();
                 self.record_late_bound_vars(item.hir_id(), vec![]);
                 let scope = Scope::Binder {
                     hir_id: item.hir_id(),
-                    lifetimes,
+                    bound_vars,
                     scope_type: BinderScopeType::Normal,
                     s: self.scope,
                     where_bound_origin: None,
@@ -562,21 +567,20 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
     fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
         match ty.kind {
             hir::TyKind::BareFn(c) => {
-                let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = c
+                let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) = c
                     .generic_params
                     .iter()
-                    .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. }))
                     .enumerate()
                     .map(|(late_bound_idx, param)| {
-                        let pair = Region::late(late_bound_idx as u32, param);
-                        let r = late_region_as_bound_region(self.tcx, &pair.1);
+                        let pair = ResolvedArg::late(late_bound_idx as u32, param);
+                        let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
                         (pair, r)
                     })
                     .unzip();
                 self.record_late_bound_vars(ty.hir_id, binders);
                 let scope = Scope::Binder {
                     hir_id: ty.hir_id,
-                    lifetimes,
+                    bound_vars,
                     s: self.scope,
                     scope_type: BinderScopeType::Normal,
                     where_bound_origin: None,
@@ -674,7 +678,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     // well-supported at the moment, so this doesn't work.
                     // In the future, this should be fixed and this error should be removed.
                     let def = self.map.defs.get(&lifetime.hir_id).cloned();
-                    let Some(Region::LateBound(_, _, def_id)) = def else {
+                    let Some(ResolvedArg::LateBound(_, _, def_id)) = def else {
                         continue
                     };
                     let Some(def_id) = def_id.as_local() else {
@@ -722,18 +726,11 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
             }
             Type(bounds, ty) => {
                 let generics = &trait_item.generics;
-                let lifetimes = generics
-                    .params
-                    .iter()
-                    .filter_map(|param| match param.kind {
-                        GenericParamKind::Lifetime { .. } => Some(Region::early(param)),
-                        GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => None,
-                    })
-                    .collect();
+                let bound_vars = generics.params.iter().map(ResolvedArg::early).collect();
                 self.record_late_bound_vars(trait_item.hir_id(), vec![]);
                 let scope = Scope::Binder {
                     hir_id: trait_item.hir_id(),
-                    lifetimes,
+                    bound_vars,
                     s: self.scope,
                     scope_type: BinderScopeType::Normal,
                     where_bound_origin: None,
@@ -768,18 +765,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
             }),
             Type(ty) => {
                 let generics = &impl_item.generics;
-                let lifetimes: FxIndexMap<LocalDefId, Region> = generics
-                    .params
-                    .iter()
-                    .filter_map(|param| match param.kind {
-                        GenericParamKind::Lifetime { .. } => Some(Region::early(param)),
-                        GenericParamKind::Const { .. } | GenericParamKind::Type { .. } => None,
-                    })
-                    .collect();
+                let bound_vars: FxIndexMap<LocalDefId, ResolvedArg> =
+                    generics.params.iter().map(ResolvedArg::early).collect();
                 self.record_late_bound_vars(impl_item.hir_id(), vec![]);
                 let scope = Scope::Binder {
                     hir_id: impl_item.hir_id(),
-                    lifetimes,
+                    bound_vars,
                     s: self.scope,
                     scope_type: BinderScopeType::Normal,
                     where_bound_origin: None,
@@ -803,7 +794,9 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
     #[instrument(level = "debug", skip(self))]
     fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
         match lifetime_ref.res {
-            hir::LifetimeName::Static => self.insert_lifetime(lifetime_ref, Region::Static),
+            hir::LifetimeName::Static => {
+                self.insert_lifetime(lifetime_ref, ResolvedArg::StaticLifetime)
+            }
             hir::LifetimeName::Param(param_def_id) => {
                 self.resolve_lifetime_ref(param_def_id, lifetime_ref)
             }
@@ -814,13 +807,16 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
         }
     }
 
-    fn visit_path(&mut self, path: &hir::Path<'tcx>, _: hir::HirId) {
+    fn visit_path(&mut self, path: &hir::Path<'tcx>, hir_id: hir::HirId) {
         for (i, segment) in path.segments.iter().enumerate() {
             let depth = path.segments.len() - i - 1;
             if let Some(args) = segment.args {
                 self.visit_segment_args(path.res, depth, args);
             }
         }
+        if let Res::Def(DefKind::TyParam | DefKind::ConstParam, param_def_id) = path.res {
+            self.resolve_type_ref(param_def_id.expect_local(), hir_id);
+        }
     }
 
     fn visit_fn(
@@ -869,24 +865,17 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         origin,
                         ..
                     }) => {
-                        let lifetimes: FxIndexMap<LocalDefId, Region> =
+
+                        let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
                             bound_generic_params
-                                .iter()
-                                .filter(|param| {
-                                    matches!(param.kind, GenericParamKind::Lifetime { .. })
-                                })
-                                .enumerate()
-                                .map(|(late_bound_idx, param)| {
-                                        Region::late(late_bound_idx as u32, param)
-                                })
-                                .collect();
-                        let binders: Vec<_> =
-                            lifetimes
-                                .iter()
-                                .map(|(_, region)| {
-                                     late_region_as_bound_region(this.tcx, region)
-                                })
-                                .collect();
+                            .iter()
+                            .enumerate()
+                            .map(|(late_bound_idx, param)| {
+                                let pair = ResolvedArg::late(late_bound_idx as u32, param);
+                                let r = late_arg_as_bound_arg(this.tcx, &pair.1, param);
+                                (pair, r)
+                            })
+                            .unzip();
                         this.record_late_bound_vars(hir_id, binders.clone());
                         // Even if there are no lifetimes defined here, we still wrap it in a binder
                         // scope. If there happens to be a nested poly trait ref (an error), that
@@ -894,7 +883,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         // being wrong.
                         let scope = Scope::Binder {
                             hir_id,
-                            lifetimes,
+                            bound_vars,
                             s: this.scope,
                             scope_type: BinderScopeType::Normal,
                             where_bound_origin: Some(origin),
@@ -920,7 +909,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                                 if lt.res != hir::LifetimeName::Static {
                                     continue;
                                 }
-                                this.insert_lifetime(lt, Region::Static);
+                                this.insert_lifetime(lt, ResolvedArg::StaticLifetime);
                                 this.tcx
                                     .sess
                                     .struct_span_warn(
@@ -964,7 +953,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 self.record_late_bound_vars(*hir_id, binders);
                 let scope = Scope::Binder {
                     hir_id: *hir_id,
-                    lifetimes: FxIndexMap::default(),
+                    bound_vars: FxIndexMap::default(),
                     s: self.scope,
                     scope_type,
                     where_bound_origin: None,
@@ -983,16 +972,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
         let (mut binders, scope_type) = self.poly_trait_ref_binder_info();
 
         let initial_bound_vars = binders.len() as u32;
-        let mut lifetimes: FxIndexMap<LocalDefId, Region> = FxIndexMap::default();
-        let binders_iter = trait_ref
-            .bound_generic_params
-            .iter()
-            .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. }))
-            .enumerate()
-            .map(|(late_bound_idx, param)| {
-                let pair = Region::late(initial_bound_vars + late_bound_idx as u32, param);
-                let r = late_region_as_bound_region(self.tcx, &pair.1);
-                lifetimes.insert(pair.0, pair.1);
+        let mut bound_vars: FxIndexMap<LocalDefId, ResolvedArg> = FxIndexMap::default();
+        let binders_iter =
+            trait_ref.bound_generic_params.iter().enumerate().map(|(late_bound_idx, param)| {
+                let pair = ResolvedArg::late(initial_bound_vars + late_bound_idx as u32, param);
+                let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
+                bound_vars.insert(pair.0, pair.1);
                 r
             });
         binders.extend(binders_iter);
@@ -1006,7 +991,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
         // refs.
         let scope = Scope::Binder {
             hir_id: trait_ref.trait_ref.hir_ref_id,
-            lifetimes,
+            bound_vars,
             s: self.scope,
             scope_type,
             where_bound_origin: None,
@@ -1063,13 +1048,13 @@ fn object_lifetime_default(tcx: TyCtxt<'_>, param_def_id: DefId) -> ObjectLifeti
     }
 }
 
-impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
+impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
     fn with<F>(&mut self, wrap_scope: Scope<'_>, f: F)
     where
-        F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>),
+        F: for<'b> FnOnce(&mut BoundVarContext<'b, 'tcx>),
     {
-        let LifetimeContext { tcx, map, .. } = self;
-        let mut this = LifetimeContext { tcx: *tcx, map, scope: &wrap_scope };
+        let BoundVarContext { tcx, map, .. } = self;
+        let mut this = BoundVarContext { tcx: *tcx, map, scope: &wrap_scope };
         let span = debug_span!("scope", scope = ?TruncatedScopeDebug(&this.scope));
         {
             let _enter = span.enter();
@@ -1110,23 +1095,25 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         generics: &'tcx hir::Generics<'tcx>,
         walk: F,
     ) where
-        F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),
+        F: for<'b, 'c> FnOnce(&'b mut BoundVarContext<'c, 'tcx>),
     {
         let mut named_late_bound_vars = 0;
-        let lifetimes: FxIndexMap<LocalDefId, Region> = generics
+        let bound_vars: FxIndexMap<LocalDefId, ResolvedArg> = generics
             .params
             .iter()
-            .filter_map(|param| match param.kind {
+            .map(|param| match param.kind {
                 GenericParamKind::Lifetime { .. } => {
                     if self.tcx.is_late_bound(param.hir_id) {
                         let late_bound_idx = named_late_bound_vars;
                         named_late_bound_vars += 1;
-                        Some(Region::late(late_bound_idx, param))
+                        ResolvedArg::late(late_bound_idx, param)
                     } else {
-                        Some(Region::early(param))
+                        ResolvedArg::early(param)
                     }
                 }
-                GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => None,
+                GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
+                    ResolvedArg::early(param)
+                }
             })
             .collect();
 
@@ -1139,14 +1126,14 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             })
             .enumerate()
             .map(|(late_bound_idx, param)| {
-                let pair = Region::late(late_bound_idx as u32, param);
-                late_region_as_bound_region(self.tcx, &pair.1)
+                let pair = ResolvedArg::late(late_bound_idx as u32, param);
+                late_arg_as_bound_arg(self.tcx, &pair.1, param)
             })
             .collect();
         self.record_late_bound_vars(hir_id, binders);
         let scope = Scope::Binder {
             hir_id,
-            lifetimes,
+            bound_vars,
             s: self.scope,
             scope_type: BinderScopeType::Normal,
             where_bound_origin: None,
@@ -1177,15 +1164,15 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                 Scope::Root { opt_parent_item } => {
                     if let Some(parent_item) = opt_parent_item
                         && let parent_generics = self.tcx.generics_of(parent_item)
-                        && parent_generics.param_def_id_to_index.contains_key(&region_def_id.to_def_id())
+                        && parent_generics.param_def_id_to_index(self.tcx, region_def_id.to_def_id()).is_some()
                     {
-                        break Some(Region::EarlyBound(region_def_id.to_def_id()));
+                        break Some(ResolvedArg::EarlyBound(region_def_id.to_def_id()));
                     }
                     break None;
                 }
 
-                Scope::Binder { ref lifetimes, scope_type, s, where_bound_origin, .. } => {
-                    if let Some(&def) = lifetimes.get(&region_def_id) {
+                Scope::Binder { ref bound_vars, scope_type, s, where_bound_origin, .. } => {
+                    if let Some(&def) = bound_vars.get(&region_def_id) {
                         break Some(def.shifted(late_depth));
                     }
                     match scope_type {
@@ -1259,7 +1246,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         };
 
         if let Some(mut def) = result {
-            if let Region::EarlyBound(..) = def {
+            if let ResolvedArg::EarlyBound(..) = def {
                 // Do not free early-bound regions, only late-bound ones.
             } else if let Some(body_id) = outermost_body {
                 let fn_id = self.tcx.hir().body_owner(body_id);
@@ -1275,10 +1262,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                         kind: hir::ImplItemKind::Fn(..),
                         ..
                     }) => {
-                        def = Region::Free(owner_id.to_def_id(), def.id().unwrap());
+                        def = ResolvedArg::Free(owner_id.to_def_id(), def.id().unwrap());
                     }
                     Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(closure), .. }) => {
-                        def = Region::Free(closure.def_id.to_def_id(), def.id().unwrap());
+                        def = ResolvedArg::Free(closure.def_id.to_def_id(), def.id().unwrap());
                     }
                     _ => {}
                 }
@@ -1329,6 +1316,57 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         );
     }
 
+    fn resolve_type_ref(&mut self, param_def_id: LocalDefId, hir_id: hir::HirId) {
+        // Walk up the scope chain, tracking the number of fn scopes
+        // that we pass through, until we find a lifetime with the
+        // given name or we run out of scopes.
+        // search.
+        let mut late_depth = 0;
+        let mut scope = self.scope;
+        let result = loop {
+            match *scope {
+                Scope::Body { s, .. } => {
+                    scope = s;
+                }
+
+                Scope::Root { opt_parent_item } => {
+                    if let Some(parent_item) = opt_parent_item
+                        && let parent_generics = self.tcx.generics_of(parent_item)
+                        && parent_generics.param_def_id_to_index(self.tcx, param_def_id.to_def_id()).is_some()
+                    {
+                        break Some(ResolvedArg::EarlyBound(param_def_id.to_def_id()));
+                    }
+                    break None;
+                }
+
+                Scope::Binder { ref bound_vars, scope_type, s, .. } => {
+                    if let Some(&def) = bound_vars.get(&param_def_id) {
+                        break Some(def.shifted(late_depth));
+                    }
+                    match scope_type {
+                        BinderScopeType::Normal => late_depth += 1,
+                        BinderScopeType::Concatenating => {}
+                    }
+                    scope = s;
+                }
+
+                Scope::Elision { s, .. }
+                | Scope::ObjectLifetimeDefault { s, .. }
+                | Scope::Supertrait { s, .. }
+                | Scope::TraitRefBoundary { s, .. } => {
+                    scope = s;
+                }
+            }
+        };
+
+        if let Some(def) = result {
+            self.map.defs.insert(hir_id, def);
+            return;
+        }
+
+        span_bug!(self.tcx.hir().span(hir_id), "could not resolve {param_def_id:?}",);
+    }
+
     #[instrument(level = "debug", skip(self))]
     fn visit_segment_args(
         &mut self,
@@ -1415,10 +1453,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     if in_body {
                         None
                     } else {
-                        Some(Region::Static)
+                        Some(ResolvedArg::StaticLifetime)
                     }
                 }
-                ObjectLifetimeDefault::Static => Some(Region::Static),
+                ObjectLifetimeDefault::Static => Some(ResolvedArg::StaticLifetime),
                 ObjectLifetimeDefault::Param(param_def_id) => {
                     // This index can be used with `generic_args` since `parent_count == 0`.
                     let index = generics.param_def_id_to_index[&param_def_id] as usize;
@@ -1507,18 +1545,19 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         // in the trait ref `YY<...>` in `Item: YY<...>`.
         for binding in generic_args.bindings {
             let scope = Scope::ObjectLifetimeDefault {
-                lifetime: if has_lifetime_parameter { None } else { Some(Region::Static) },
+                lifetime: if has_lifetime_parameter {
+                    None
+                } else {
+                    Some(ResolvedArg::StaticLifetime)
+                },
                 s: self.scope,
             };
             if let Some(type_def_id) = type_def_id {
-                let lifetimes = LifetimeContext::supertrait_hrtb_lifetimes(
-                    self.tcx,
-                    type_def_id,
-                    binding.ident,
-                );
+                let bound_vars =
+                    BoundVarContext::supertrait_hrtb_vars(self.tcx, type_def_id, binding.ident);
                 self.with(scope, |this| {
                     let scope = Scope::Supertrait {
-                        lifetimes: lifetimes.unwrap_or_default(),
+                        bound_vars: bound_vars.unwrap_or_default(),
                         s: this.scope,
                     };
                     this.with(scope, |this| this.visit_assoc_type_binding(binding));
@@ -1541,7 +1580,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     /// ```
     /// In this case, if we wanted to the supertrait HRTB lifetimes for `As` on
     /// the starting trait `Bar`, we would return `Some(['b, 'a])`.
-    fn supertrait_hrtb_lifetimes(
+    fn supertrait_hrtb_vars(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
         assoc_name: Ident,
@@ -1626,7 +1665,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     scope = s;
                 }
 
-                Scope::Root { .. } | Scope::Elision { .. } => break Region::Static,
+                Scope::Root { .. } | Scope::Elision { .. } => break ResolvedArg::StaticLifetime,
 
                 Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return,
 
@@ -1641,7 +1680,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     }
 
     #[instrument(level = "debug", skip(self))]
-    fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region) {
+    fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: ResolvedArg) {
         debug!(span = ?lifetime_ref.ident.span);
         self.map.defs.insert(lifetime_ref.hir_id, def);
     }
@@ -1649,7 +1688,11 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     /// Sometimes we resolve a lifetime, but later find that it is an
     /// error (esp. around impl trait). In that case, we remove the
     /// entry into `map.defs` so as not to confuse later code.
-    fn uninsert_lifetime_on_error(&mut self, lifetime_ref: &'tcx hir::Lifetime, bad_def: Region) {
+    fn uninsert_lifetime_on_error(
+        &mut self,
+        lifetime_ref: &'tcx hir::Lifetime,
+        bad_def: ResolvedArg,
+    ) {
         let old_value = self.map.defs.remove(&lifetime_ref.hir_id);
         assert_eq!(old_value, Some(bad_def));
     }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index d13d8ff8270..0aa5b075d19 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -477,14 +477,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // This is the "trait" (meaning, the predicate "proved" by this `impl`) which provides the `Self` type we care about.
         // For the purposes of this function, we hope that it is a `struct` type, and that our current `expr` is a literal of
         // that struct type.
-        let impl_trait_self_ref = if self.tcx.is_trait_alias(obligation.impl_def_id) {
+        let impl_trait_self_ref = if self.tcx.is_trait_alias(obligation.impl_or_alias_def_id) {
             self.tcx.mk_trait_ref(
-                obligation.impl_def_id,
-                ty::InternalSubsts::identity_for_item(self.tcx, obligation.impl_def_id),
+                obligation.impl_or_alias_def_id,
+                ty::InternalSubsts::identity_for_item(self.tcx, obligation.impl_or_alias_def_id),
             )
         } else {
             self.tcx
-                .impl_trait_ref(obligation.impl_def_id)
+                .impl_trait_ref(obligation.impl_or_alias_def_id)
                 .map(|impl_def| impl_def.skip_binder())
                 // It is possible that this is absent. In this case, we make no progress.
                 .ok_or(expr)?
@@ -494,7 +494,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let impl_self_ty: Ty<'tcx> = impl_trait_self_ref.self_ty();
 
         let impl_predicates: ty::GenericPredicates<'tcx> =
-            self.tcx.predicates_of(obligation.impl_def_id);
+            self.tcx.predicates_of(obligation.impl_or_alias_def_id);
         let Some(impl_predicate_index) = obligation.impl_def_predicate_index else {
             // We don't have the index, so we can only guess.
             return Err(expr);
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 63b170a3c63..69a7235802b 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -1740,7 +1740,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match *qpath {
             QPath::Resolved(ref maybe_qself, ref path) => {
                 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself).raw);
-                let ty = self.astconv().res_to_ty(self_ty, path, true);
+                let ty = self.astconv().res_to_ty(self_ty, path, hir_id, true);
                 (path.res, self.handle_raw_ty(path_span, ty))
             }
             QPath::TypeRelative(ref qself, ref segment) => {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index a35fa008a95..a805dad062e 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1576,7 +1576,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                                 traits::ImplDerivedObligation(Box::new(
                                     traits::ImplDerivedObligationCause {
                                         derived,
-                                        impl_def_id,
+                                        impl_or_alias_def_id: impl_def_id,
                                         impl_def_predicate_index: None,
                                         span,
                                     },
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 54890489f8b..ef30cd55c0e 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -616,7 +616,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     ObligationCauseCode::ImplDerivedObligation(data)
                         if matches!(p.kind().skip_binder(), ty::PredicateKind::Clause(_)) =>
                     {
-                        Some((p, parent, data.impl_def_id, data))
+                        Some((p, parent, data.impl_or_alias_def_id, data))
                     }
                     _ => None,
                 })
@@ -714,7 +714,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         );
                     }
                     Some(Node::Item(hir::Item {
-                        ident, kind: hir::ItemKind::Trait(..), ..
+                        ident,
+                        kind: hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..),
+                        ..
                     })) => {
                         skip_list.insert(p);
                         let entry = spanned_predicates.entry(ident.span);
diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
index 964222307bc..f5504b05dc4 100644
--- a/compiler/rustc_infer/src/infer/combine.rs
+++ b/compiler/rustc_infer/src/infer/combine.rs
@@ -125,11 +125,11 @@ impl<'tcx> InferCtxt<'tcx> {
             }
 
             (ty::Alias(AliasKind::Projection, _), _) if self.tcx.trait_solver_next() => {
-                relation.register_type_equate_obligation(a.into(), b.into());
+                relation.register_type_equate_obligation(a, b);
                 Ok(b)
             }
             (_, ty::Alias(AliasKind::Projection, _)) if self.tcx.trait_solver_next() => {
-                relation.register_type_equate_obligation(b.into(), a.into());
+                relation.register_type_equate_obligation(b, a);
                 Ok(a)
             }
 
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs
index 39f4d502259..4fe6c6618f6 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs
@@ -2,7 +2,7 @@ use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
-use rustc_middle::middle::resolve_lifetime as rl;
+use rustc_middle::middle::resolve_bound_vars as rbv;
 use rustc_middle::ty::{self, Region, TyCtxt};
 
 /// This function calls the `visit_ty` method for the parameters
@@ -99,11 +99,11 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
             hir::TyKind::Ref(ref lifetime, _) => {
                 // the lifetime of the Ref
                 let hir_id = lifetime.hir_id;
-                match (self.tcx.named_region(hir_id), self.bound_region) {
+                match (self.tcx.named_bound_var(hir_id), self.bound_region) {
                     // Find the index of the named region that was part of the
                     // error. We will then search the function parameters for a bound
                     // region at the right depth with the same index
-                    (Some(rl::Region::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
+                    (Some(rbv::ResolvedArg::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
                         debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
                         if id == def_id {
                             self.found_type = Some(arg);
@@ -115,7 +115,7 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                     // error. We will then search the function parameters for a bound
                     // region at the right depth with the same index
                     (
-                        Some(rl::Region::LateBound(debruijn_index, _, id)),
+                        Some(rbv::ResolvedArg::LateBound(debruijn_index, _, id)),
                         ty::BrNamed(def_id, _),
                     ) => {
                         debug!(
@@ -131,10 +131,10 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
 
                     (
                         Some(
-                            rl::Region::Static
-                            | rl::Region::Free(_, _)
-                            | rl::Region::EarlyBound(_)
-                            | rl::Region::LateBound(_, _, _),
+                            rbv::ResolvedArg::StaticLifetime
+                            | rbv::ResolvedArg::Free(_, _)
+                            | rbv::ResolvedArg::EarlyBound(_)
+                            | rbv::ResolvedArg::LateBound(_, _, _),
                         )
                         | None,
                         _,
@@ -186,9 +186,9 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
     }
 
     fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) {
-        match (self.tcx.named_region(lifetime.hir_id), self.bound_region) {
+        match (self.tcx.named_bound_var(lifetime.hir_id), self.bound_region) {
             // the lifetime of the TyPath!
-            (Some(rl::Region::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
+            (Some(rbv::ResolvedArg::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
                 debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
                 if id == def_id {
                     self.found_it = true;
@@ -196,7 +196,7 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
                 }
             }
 
-            (Some(rl::Region::LateBound(debruijn_index, _, id)), ty::BrNamed(def_id, _)) => {
+            (Some(rbv::ResolvedArg::LateBound(debruijn_index, _, id)), ty::BrNamed(def_id, _)) => {
                 debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,);
                 debug!("id={:?}", id);
                 debug!("def_id={:?}", def_id);
@@ -208,10 +208,10 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
 
             (
                 Some(
-                    rl::Region::Static
-                    | rl::Region::EarlyBound(_)
-                    | rl::Region::LateBound(_, _, _)
-                    | rl::Region::Free(_, _),
+                    rbv::ResolvedArg::StaticLifetime
+                    | rbv::ResolvedArg::EarlyBound(_)
+                    | rbv::ResolvedArg::LateBound(_, _, _)
+                    | rbv::ResolvedArg::Free(_, _),
                 )
                 | None,
                 _,
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index e617eb68d47..68b39c5f00f 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -158,7 +158,7 @@ impl<'tcx> Elaborator<'tcx> {
                                 traits::ImplDerivedObligation(Box::new(
                                     traits::ImplDerivedObligationCause {
                                         derived,
-                                        impl_def_id: data.def_id(),
+                                        impl_or_alias_def_id: data.def_id(),
                                         impl_def_predicate_index: Some(index),
                                         span,
                                     },
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 34cf17d25a9..cd793d36de6 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -2007,7 +2007,7 @@ impl ExplicitOutlivesRequirements {
         inferred_outlives: &[ty::Region<'tcx>],
         predicate_span: Span,
     ) -> Vec<(usize, Span)> {
-        use rustc_middle::middle::resolve_lifetime::Region;
+        use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
 
         bounds
             .iter()
@@ -2017,8 +2017,8 @@ impl ExplicitOutlivesRequirements {
                     return None;
                 };
 
-                let is_inferred = match tcx.named_region(lifetime.hir_id) {
-                    Some(Region::EarlyBound(def_id)) => inferred_outlives
+                let is_inferred = match tcx.named_bound_var(lifetime.hir_id) {
+                    Some(ResolvedArg::EarlyBound(def_id)) => inferred_outlives
                         .iter()
                         .any(|r| matches!(**r, ty::ReEarlyBound(ebr) if { ebr.def_id == def_id })),
                     _ => false,
@@ -2097,7 +2097,7 @@ impl ExplicitOutlivesRequirements {
 
 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
-        use rustc_middle::middle::resolve_lifetime::Region;
+        use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
 
         let def_id = item.owner_id.def_id;
         if let hir::ItemKind::Struct(_, hir_generics)
@@ -2120,8 +2120,8 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
                     match where_predicate {
                         hir::WherePredicate::RegionPredicate(predicate) => {
-                            if let Some(Region::EarlyBound(region_def_id)) =
-                                cx.tcx.named_region(predicate.lifetime.hir_id)
+                            if let Some(ResolvedArg::EarlyBound(region_def_id)) =
+                                cx.tcx.named_bound_var(predicate.lifetime.hir_id)
                             {
                                 (
                                     Self::lifetimes_outliving_lifetime(
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 43047051f0f..e941dd45688 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1541,8 +1541,9 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 self.tables.impl_defaultness.set_some(def_id.index, *defaultness);
                 self.tables.constness.set_some(def_id.index, *constness);
 
-                let trait_ref = self.tcx.impl_trait_ref(def_id).map(ty::EarlyBinder::skip_binder);
+                let trait_ref = self.tcx.impl_trait_ref(def_id);
                 if let Some(trait_ref) = trait_ref {
+                    let trait_ref = trait_ref.skip_binder();
                     let trait_def = self.tcx.trait_def(trait_ref.def_id);
                     if let Ok(mut an) = trait_def.ancestors(self.tcx, def_id) {
                         if let Some(specialization_graph::Node::Impl(parent)) = an.nth(1) {
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 9227609cc8b..a9fb8b246c6 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -18,7 +18,7 @@ use rustc_index::vec::IndexVec;
 use rustc_middle::metadata::ModChild;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
-use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
+use rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault;
 use rustc_middle::mir;
 use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::query::Providers;
diff --git a/compiler/rustc_middle/src/middle/mod.rs b/compiler/rustc_middle/src/middle/mod.rs
index 8dc68b1f5a8..0b6774f1b1f 100644
--- a/compiler/rustc_middle/src/middle/mod.rs
+++ b/compiler/rustc_middle/src/middle/mod.rs
@@ -29,7 +29,7 @@ pub mod lib_features {
 pub mod limits;
 pub mod privacy;
 pub mod region;
-pub mod resolve_lifetime;
+pub mod resolve_bound_vars;
 pub mod stability;
 
 pub fn provide(providers: &mut crate::ty::query::Providers) {
diff --git a/compiler/rustc_middle/src/middle/resolve_lifetime.rs b/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
index c3bf1c717d9..b96d07e7dc8 100644
--- a/compiler/rustc_middle/src/middle/resolve_lifetime.rs
+++ b/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
@@ -1,4 +1,4 @@
-//! Name resolution for lifetimes: type declarations.
+//! Name resolution for lifetimes and late-bound type and const variables: type declarations.
 
 use crate::ty;
 
@@ -8,10 +8,10 @@ use rustc_hir::{ItemLocalId, OwnerId};
 use rustc_macros::HashStable;
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
-pub enum Region {
-    Static,
-    EarlyBound(/* lifetime decl */ DefId),
-    LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* lifetime decl */ DefId),
+pub enum ResolvedArg {
+    StaticLifetime,
+    EarlyBound(/* decl */ DefId),
+    LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* decl */ DefId),
     Free(DefId, /* lifetime decl */ DefId),
 }
 
@@ -46,10 +46,10 @@ pub enum ObjectLifetimeDefault {
 /// Maps the id of each lifetime reference to the lifetime decl
 /// that it corresponds to.
 #[derive(Default, HashStable, Debug)]
-pub struct ResolveLifetimes {
+pub struct ResolveBoundVars {
     /// Maps from every use of a named (not anonymous) lifetime to a
     /// `Region` describing how that region is bound
-    pub defs: FxHashMap<OwnerId, FxHashMap<ItemLocalId, Region>>,
+    pub defs: FxHashMap<OwnerId, FxHashMap<ItemLocalId, ResolvedArg>>,
 
     pub late_bound_vars: FxHashMap<OwnerId, FxHashMap<ItemLocalId, Vec<ty::BoundVariableKind>>>,
 }
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 4b34f6b4881..6f878a955fa 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -781,7 +781,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query issue33140_self_ty(key: DefId) -> Option<ty::Ty<'tcx>> {
+    query issue33140_self_ty(key: DefId) -> Option<ty::EarlyBinder<ty::Ty<'tcx>>> {
         desc { |tcx| "computing Self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
     }
 
@@ -1641,12 +1641,12 @@ rustc_queries! {
     /// Does lifetime resolution on items. Importantly, we can't resolve
     /// lifetimes directly on things like trait methods, because of trait params.
     /// See `rustc_resolve::late::lifetimes for details.
-    query resolve_lifetimes(_: hir::OwnerId) -> &'tcx ResolveLifetimes {
+    query resolve_bound_vars(_: hir::OwnerId) -> &'tcx ResolveBoundVars {
         arena_cache
         desc { "resolving lifetimes" }
     }
-    query named_region_map(_: hir::OwnerId) ->
-        Option<&'tcx FxHashMap<ItemLocalId, Region>> {
+    query named_variable_map(_: hir::OwnerId) ->
+        Option<&'tcx FxHashMap<ItemLocalId, ResolvedArg>> {
         desc { "looking up a named region" }
     }
     query is_late_bound_map(_: hir::OwnerId) -> Option<&'tcx FxIndexSet<ItemLocalId>> {
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index c528929e756..6231dd9b6f5 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -474,7 +474,11 @@ pub enum WellFormedLoc {
 #[derive(TypeVisitable, TypeFoldable)]
 pub struct ImplDerivedObligationCause<'tcx> {
     pub derived: DerivedObligationCause<'tcx>,
-    pub impl_def_id: DefId,
+    /// The `DefId` of the `impl` that gave rise to the `derived` obligation.
+    /// If the `derived` obligation arose from a trait alias, which conceptually has a synthetic impl,
+    /// then this will be the `DefId` of that trait alias. Care should therefore be taken to handle
+    /// that exceptional case where appropriate.
+    pub impl_or_alias_def_id: DefId,
     /// The index of the derived predicate in the parent impl's predicates.
     pub impl_def_predicate_index: Option<usize>,
     pub span: Span,
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 927f18f59b9..c7268d561e5 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -1,7 +1,9 @@
+use crate::middle::resolve_bound_vars as rbv;
 use crate::mir::interpret::LitToConstInput;
 use crate::ty::{self, DefIdTree, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt};
 use rustc_data_structures::intern::Interned;
 use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_macros::HashStable;
 use std::fmt;
@@ -125,16 +127,27 @@ impl<'tcx> Const<'tcx> {
             }
         }
 
-        use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
         match expr.kind {
-            ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
-                // Find the name and index of the const parameter by indexing the generics of
-                // the parent item and construct a `ParamConst`.
-                let item_def_id = tcx.parent(def_id);
-                let generics = tcx.generics_of(item_def_id);
-                let index = generics.param_def_id_to_index[&def_id];
-                let name = tcx.item_name(def_id);
-                Some(tcx.mk_const(ty::ParamConst::new(index, name), ty))
+            hir::ExprKind::Path(hir::QPath::Resolved(
+                _,
+                &hir::Path { res: Res::Def(DefKind::ConstParam, def_id), .. },
+            )) => {
+                match tcx.named_bound_var(expr.hir_id) {
+                    Some(rbv::ResolvedArg::EarlyBound(_)) => {
+                        // Find the name and index of the const parameter by indexing the generics of
+                        // the parent item and construct a `ParamConst`.
+                        let item_def_id = tcx.parent(def_id);
+                        let generics = tcx.generics_of(item_def_id);
+                        let index = generics.param_def_id_to_index[&def_id];
+                        let name = tcx.item_name(def_id);
+                        Some(tcx.mk_const(ty::ParamConst::new(index, name), ty))
+                    }
+                    Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => Some(tcx.mk_const(
+                        ty::ConstKind::Bound(debruijn, ty::BoundVar::from_u32(index)),
+                        ty,
+                    )),
+                    arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id),
+                }
             }
             _ => None,
         }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index b37c3e5cf2c..d5be23d2b98 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -9,7 +9,7 @@ use crate::dep_graph::{DepGraph, DepKindStruct};
 use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
 use crate::lint::struct_lint_level;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
-use crate::middle::resolve_lifetime;
+use crate::middle::resolve_bound_vars;
 use crate::middle::stability;
 use crate::mir::interpret::{self, Allocation, ConstAllocation};
 use crate::mir::{
@@ -2368,9 +2368,9 @@ impl<'tcx> TyCtxt<'tcx> {
         Some(&*candidates)
     }
 
-    pub fn named_region(self, id: HirId) -> Option<resolve_lifetime::Region> {
+    pub fn named_bound_var(self, id: HirId) -> Option<resolve_bound_vars::ResolvedArg> {
         debug!(?id, "named_region");
-        self.named_region_map(id.owner).and_then(|map| map.get(&id.local_id).cloned())
+        self.named_variable_map(id.owner).and_then(|map| map.get(&id.local_id).cloned())
     }
 
     pub fn is_late_bound(self, id: HirId) -> bool {
diff --git a/compiler/rustc_middle/src/ty/fast_reject.rs b/compiler/rustc_middle/src/ty/fast_reject.rs
index 9afa37e9ef3..106ce9990e1 100644
--- a/compiler/rustc_middle/src/ty/fast_reject.rs
+++ b/compiler/rustc_middle/src/ty/fast_reject.rs
@@ -290,7 +290,7 @@ impl DeepRejectCtxt {
             // Impls cannot contain these types as these cannot be named directly.
             ty::FnDef(..) | ty::Closure(..) | ty::Generator(..) => false,
 
-            ty::Placeholder(..) => false,
+            ty::Placeholder(..) | ty::Bound(..) => false,
 
             // Depending on the value of `treat_obligation_params`, we either
             // treat generic parameters like placeholders or like inference variables.
@@ -310,7 +310,7 @@ impl DeepRejectCtxt {
 
             ty::Error(_) => true,
 
-            ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) | ty::Bound(..) => {
+            ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) => {
                 bug!("unexpected obligation type: {:?}", obligation_ty)
             }
         }
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 303675d3ca5..8849e7eab33 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -57,7 +57,7 @@ trivially_parameterized_over_tcx! {
     crate::metadata::ModChild,
     crate::middle::codegen_fn_attrs::CodegenFnAttrs,
     crate::middle::exported_symbols::SymbolExportInfo,
-    crate::middle::resolve_lifetime::ObjectLifetimeDefault,
+    crate::middle::resolve_bound_vars::ObjectLifetimeDefault,
     crate::mir::ConstQualifs,
     ty::AssocItemContainer,
     ty::DeducedParamAttrs,
diff --git a/compiler/rustc_middle/src/ty/query.rs b/compiler/rustc_middle/src/ty/query.rs
index 5c45cc389ee..431f3a5a000 100644
--- a/compiler/rustc_middle/src/ty/query.rs
+++ b/compiler/rustc_middle/src/ty/query.rs
@@ -8,7 +8,7 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
 use crate::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
 use crate::middle::lib_features::LibFeatures;
 use crate::middle::privacy::EffectiveVisibilities;
-use crate::middle::resolve_lifetime::{ObjectLifetimeDefault, Region, ResolveLifetimes};
+use crate::middle::resolve_bound_vars::{ObjectLifetimeDefault, ResolveBoundVars, ResolvedArg};
 use crate::middle::stability::{self, DeprecationEntry};
 use crate::mir;
 use crate::mir::interpret::GlobalId;
diff --git a/compiler/rustc_mir_transform/src/ctfe_limit.rs b/compiler/rustc_mir_transform/src/ctfe_limit.rs
index 7d127032179..1b3ac78fbc6 100644
--- a/compiler/rustc_mir_transform/src/ctfe_limit.rs
+++ b/compiler/rustc_mir_transform/src/ctfe_limit.rs
@@ -47,8 +47,7 @@ fn has_back_edge(
         return false;
     }
     // Check if any of the dominators of the node are also the node's successor.
-    doms.dominators(node)
-        .any(|dom| node_data.terminator().successors().into_iter().any(|succ| succ == dom))
+    doms.dominators(node).any(|dom| node_data.terminator().successors().any(|succ| succ == dom))
 }
 
 fn insert_counter(basic_block_data: &mut BasicBlockData<'_>) {
diff --git a/compiler/rustc_mir_transform/src/ssa.rs b/compiler/rustc_mir_transform/src/ssa.rs
index 65c15d9c674..c1e7f62dea5 100644
--- a/compiler/rustc_mir_transform/src/ssa.rs
+++ b/compiler/rustc_mir_transform/src/ssa.rs
@@ -2,7 +2,7 @@ use either::Either;
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_index::bit_set::BitSet;
 use rustc_index::vec::IndexVec;
-use rustc_middle::middle::resolve_lifetime::Set1;
+use rustc_middle::middle::resolve_bound_vars::Set1;
 use rustc_middle::mir::visit::*;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{ParamEnv, TyCtxt};
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 225095948af..7cff8996d24 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -18,7 +18,7 @@ use rustc_hir::{
 };
 use rustc_hir::{MethodKind, Target, Unsafety};
 use rustc_middle::hir::nested_filter;
-use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
+use rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault;
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{ParamEnv, TyCtxt};
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 4675bd79c46..0a0c94e1dfb 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -270,10 +270,11 @@ where
             | ty::Ref(..)
             | ty::FnPtr(..)
             | ty::Param(..)
+            | ty::Bound(..)
             | ty::Error(_)
             | ty::GeneratorWitness(..)
             | ty::GeneratorWitnessMIR(..) => {}
-            ty::Bound(..) | ty::Placeholder(..) | ty::Infer(..) => {
+            ty::Placeholder(..) | ty::Infer(..) => {
                 bug!("unexpected type: {:?}", ty)
             }
         }
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index d3bcbbabf55..324de7461cd 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -21,7 +21,7 @@ use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, PartialRes, PerNS};
 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::{BindingAnnotation, PrimTy, TraitCandidate};
-use rustc_middle::middle::resolve_lifetime::Set1;
+use rustc_middle::middle::resolve_bound_vars::Set1;
 use rustc_middle::ty::DefIdTree;
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::{CrateType, ResolveDocLinks};
@@ -2505,7 +2505,13 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
 
             let res = match kind {
                 ItemRibKind(..) | AssocItemRibKind => Res::Def(def_kind, def_id.to_def_id()),
-                NormalRibKind => Res::Err,
+                NormalRibKind => {
+                    if self.r.session.features_untracked().non_lifetime_binders {
+                        Res::Def(def_kind, def_id.to_def_id())
+                    } else {
+                        Res::Err
+                    }
+                }
                 _ => span_bug!(param.ident.span, "Unexpected rib kind {:?}", kind),
             };
             self.r.record_partial_res(param.id, PartialRes::new(res));
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 093698f3b35..bd32adbbdbb 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -4,7 +4,7 @@ use crate::cgu_reuse_tracker::CguReuse;
 use crate::parse::ParseSess;
 use rustc_ast::token;
 use rustc_ast::util::literal::LitError;
-use rustc_errors::MultiSpan;
+use rustc_errors::{error_code, DiagnosticMessage, EmissionGuarantee, IntoDiagnostic, MultiSpan};
 use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
 use rustc_target::spec::{SplitDebuginfo, StackProtector, TargetTriple};
@@ -27,12 +27,22 @@ pub struct CguNotRecorded<'a> {
     pub cgu_name: &'a str,
 }
 
-#[derive(Diagnostic)]
-#[diag(session_feature_gate_error, code = "E0658")]
-pub struct FeatureGateError<'a> {
-    #[primary_span]
+pub struct FeatureGateError {
     pub span: MultiSpan,
-    pub explain: &'a str,
+    pub explain: DiagnosticMessage,
+}
+
+impl<'a, T: EmissionGuarantee> IntoDiagnostic<'a, T> for FeatureGateError {
+    #[track_caller]
+    fn into_diagnostic(
+        self,
+        handler: &'a rustc_errors::Handler,
+    ) -> rustc_errors::DiagnosticBuilder<'a, T> {
+        let mut diag = handler.struct_diagnostic(self.explain);
+        diag.set_span(self.span);
+        diag.code(error_code!(E0658));
+        diag
+    }
 }
 
 #[derive(Subdiagnostic)]
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 2aa8ca9e4a9..cbdcc5581e5 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -88,7 +88,7 @@ pub fn feature_err<'a>(
     sess: &'a ParseSess,
     feature: Symbol,
     span: impl Into<MultiSpan>,
-    explain: &str,
+    explain: impl Into<DiagnosticMessage>,
 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
     feature_err_issue(sess, feature, span, GateIssue::Language, explain)
 }
@@ -103,7 +103,7 @@ pub fn feature_err_issue<'a>(
     feature: Symbol,
     span: impl Into<MultiSpan>,
     issue: GateIssue,
-    explain: &str,
+    explain: impl Into<DiagnosticMessage>,
 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
     let span = span.into();
 
@@ -114,7 +114,7 @@ pub fn feature_err_issue<'a>(
             .map(|err| err.cancel());
     }
 
-    let mut err = sess.create_err(FeatureGateError { span, explain });
+    let mut err = sess.create_err(FeatureGateError { span, explain: explain.into() });
     add_feature_diagnostics_for_issue(&mut err, sess, feature, issue);
     err
 }
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 56835a2466a..37d2aea42ad 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1016,6 +1016,7 @@ symbols! {
         non_ascii_idents,
         non_exhaustive,
         non_exhaustive_omitted_patterns_lint,
+        non_lifetime_binders,
         non_modrs_mods,
         nontemporal_store,
         noop_method_borrow,
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
index 52ed64868c0..91d96655b64 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
@@ -60,7 +60,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
     ) -> Option<(DefId, SubstsRef<'tcx>)> {
         let tcx = self.tcx;
         let param_env = obligation.param_env;
-        let trait_ref = tcx.erase_late_bound_regions(trait_ref);
+        let trait_ref = self.instantiate_binder_with_placeholders(trait_ref);
         let trait_self_ty = trait_ref.self_ty();
 
         let mut self_match_impls = vec![];
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 8041066d5d5..a0c67f480d0 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -1056,7 +1056,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> bool {
         let self_ty = self.resolve_vars_if_possible(trait_pred.self_ty());
-        let ty = self.tcx.erase_late_bound_regions(self_ty);
+        let ty = self.instantiate_binder_with_placeholders(self_ty);
         let Some(generics) = self.tcx.hir().get_generics(obligation.cause.body_id) else { return false };
         let ty::Ref(_, inner_ty, hir::Mutability::Not) = ty.kind() else { return false };
         let ty::Param(param) = inner_ty.kind() else { return false };
@@ -3143,7 +3143,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     parent_trait_pred.print_modifiers_and_trait_path()
                 );
                 let mut is_auto_trait = false;
-                match self.tcx.hir().get_if_local(data.impl_def_id) {
+                match self.tcx.hir().get_if_local(data.impl_or_alias_def_id) {
                     Some(Node::Item(hir::Item {
                         kind: hir::ItemKind::Trait(is_auto, ..),
                         ident,
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index e9f7c3bc4cc..dae602908a3 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -396,7 +396,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // still be provided by a manual implementation for
                     // this trait and type.
                 }
-                ty::Param(..) | ty::Alias(ty::Projection, ..) => {
+                ty::Param(..)
+                | ty::Alias(ty::Projection, ..)
+                | ty::Placeholder(..)
+                | ty::Bound(..) => {
                     // In these cases, we don't know what the actual
                     // type is. Therefore, we cannot break it down
                     // into its constituent types. So we don't
@@ -448,6 +451,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         );
 
         self.infcx.probe(|_snapshot| {
+            if obligation.has_non_region_late_bound() {
+                return;
+            }
+
             // The code below doesn't care about regions, and the
             // self-ty here doesn't escape this probe, so just erase
             // any LBR.
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 9770813e86d..0167f402610 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -1189,7 +1189,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             let cause = obligation.derived_cause(|derived| {
                 ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
                     derived,
-                    impl_def_id,
+                    impl_or_alias_def_id: impl_def_id,
                     impl_def_predicate_index: None,
                     span: obligation.cause.span,
                 }))
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 27feedc48be..26f869ac1fe 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2657,7 +2657,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             let cause = cause.clone().derived_cause(parent_trait_pred, |derived| {
                 ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
                     derived,
-                    impl_def_id: def_id,
+                    impl_or_alias_def_id: def_id,
                     impl_def_predicate_index: Some(index),
                     span,
                 }))
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 41e837e8b75..fc3d9fb067d 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -1,7 +1,9 @@
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
 use rustc_index::bit_set::BitSet;
-use rustc_middle::ty::{self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{
+    self, Binder, EarlyBinder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt,
+};
 use rustc_session::config::TraitSolver;
 use rustc_span::def_id::{DefId, CRATE_DEF_ID};
 use rustc_trait_selection::traits;
@@ -355,7 +357,7 @@ fn instance_def_size_estimate<'tcx>(
 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
 ///
 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
-fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
+fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<EarlyBinder<Ty<'_>>> {
     debug!("issue33140_self_ty({:?})", def_id);
 
     let trait_ref = tcx
@@ -394,7 +396,7 @@ fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
 
     if self_ty_matches {
         debug!("issue33140_self_ty - MATCHES!");
-        Some(self_ty)
+        Some(EarlyBinder(self_ty))
     } else {
         debug!("issue33140_self_ty - non-matching self type");
         None
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index 5a0b8594104..9e3e13e7004 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -3502,8 +3502,10 @@ pub trait Iterator {
         }
     }
 
-    /// [Lexicographically](Ord#lexicographical-comparison) compares the elements of this [`Iterator`] with those
-    /// of another.
+    /// [Lexicographically](Ord#lexicographical-comparison) compares the [`PartialOrd`] elements of
+    /// this [`Iterator`] with those of another. The comparison works like short-circuit
+    /// evaluation, returning a result without comparing the remaining elements.
+    /// As soon as an order can be determined, the evaluation stops and a result is returned.
     ///
     /// # Examples
     ///
@@ -3513,9 +3515,25 @@ pub trait Iterator {
     /// assert_eq!([1.].iter().partial_cmp([1.].iter()), Some(Ordering::Equal));
     /// assert_eq!([1.].iter().partial_cmp([1., 2.].iter()), Some(Ordering::Less));
     /// assert_eq!([1., 2.].iter().partial_cmp([1.].iter()), Some(Ordering::Greater));
+    /// ```
     ///
+    /// For floating-point numbers, NaN does not have a total order and will result
+    /// in `None` when compared:
+    ///
+    /// ```
     /// assert_eq!([f64::NAN].iter().partial_cmp([1.].iter()), None);
     /// ```
+    ///
+    /// The results are determined by the order of evaluation.
+    ///
+    /// ```
+    /// use std::cmp::Ordering;
+    ///
+    /// assert_eq!([1.0, f64::NAN].iter().partial_cmp([2.0, f64::NAN].iter()), Some(Ordering::Less));
+    /// assert_eq!([2.0, f64::NAN].iter().partial_cmp([1.0, f64::NAN].iter()), Some(Ordering::Greater));
+    /// assert_eq!([f64::NAN, 1.0].iter().partial_cmp([f64::NAN, 2.0].iter()), None);
+    /// ```
+    ///
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn partial_cmp<I>(self, other: I) -> Option<Ordering>
     where
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index 1675ed158c9..ff7821fb9ff 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -58,9 +58,10 @@ fn args(builder: &Builder<'_>) -> Vec<String> {
         clippy_lint_warn.iter().for_each(|v| clippy_lint_levels.push(format!("-W{}", v)));
         clippy_lint_forbid.iter().for_each(|v| clippy_lint_levels.push(format!("-F{}", v)));
         args.extend(clippy_lint_levels);
+        args.extend(builder.config.free_args.clone());
         args
     } else {
-        vec![]
+        builder.config.free_args.clone()
     }
 }
 
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index e5fad538969..cd027a4abb7 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -97,6 +97,10 @@ pub struct Config {
     pub cmd: Subcommand,
     pub incremental: bool,
     pub dry_run: DryRun,
+    /// Arguments appearing after `--` to be forwarded to tools,
+    /// e.g. `--fix-broken` or test arguments.
+    pub free_args: Vec<String>,
+
     /// `None` if we shouldn't download CI compiler artifacts, or the commit to download if we should.
     #[cfg(not(test))]
     download_rustc_commit: Option<String>,
@@ -866,6 +870,7 @@ impl Config {
         config.keep_stage = flags.keep_stage;
         config.keep_stage_std = flags.keep_stage_std;
         config.color = flags.color;
+        config.free_args = flags.free_args.clone().unwrap_or_default();
         if let Some(value) = flags.deny_warnings {
             config.deny_warnings = value;
         }
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index ff927ed561b..f07e710a9e6 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -80,6 +80,10 @@ pub struct Flags {
     pub llvm_profile_generate: bool,
     pub llvm_bolt_profile_generate: bool,
     pub llvm_bolt_profile_use: Option<String>,
+
+    /// Arguments appearing after `--` to be forwarded to tools,
+    /// e.g. `--fix-broken` or test arguments.
+    pub free_args: Option<Vec<String>>,
 }
 
 #[derive(Debug)]
@@ -157,6 +161,12 @@ impl Default for Subcommand {
 
 impl Flags {
     pub fn parse(args: &[String]) -> Flags {
+        let (args, free_args) = if let Some(pos) = args.iter().position(|s| s == "--") {
+            let (args, free) = args.split_at(pos);
+            (args, Some(free[1..].to_vec()))
+        } else {
+            (args, None)
+        };
         let mut subcommand_help = String::from(
             "\
 Usage: x.py <subcommand> [options] [<paths>...]
@@ -709,6 +719,7 @@ Arguments:
             llvm_profile_generate: matches.opt_present("llvm-profile-generate"),
             llvm_bolt_profile_generate: matches.opt_present("llvm-bolt-profile-generate"),
             llvm_bolt_profile_use: matches.opt_str("llvm-bolt-profile-use"),
+            free_args,
         }
     }
 }
diff --git a/src/bootstrap/run.rs b/src/bootstrap/run.rs
index e0280854541..e14440f57a8 100644
--- a/src/bootstrap/run.rs
+++ b/src/bootstrap/run.rs
@@ -183,6 +183,7 @@ impl Step for Miri {
         // Forward arguments.
         miri.arg("--").arg("--target").arg(target.rustc_target_arg());
         miri.args(builder.config.cmd.args());
+        miri.args(&builder.config.free_args);
 
         // miri tests need to know about the stage sysroot
         miri.env("MIRI_SYSROOT", &miri_sysroot);
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index f8835fe11a8..9cd6107b43a 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1588,6 +1588,7 @@ note: if you're sure you want to do this, please open an issue as to why. In the
             .collect();
 
         test_args.append(&mut builder.config.cmd.test_args());
+        test_args.extend(builder.config.free_args.iter().map(|s| s.as_str()));
 
         // On Windows, replace forward slashes in test-args by backslashes
         // so the correct filters are passed to libtest
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 54c8f156f9d..10af968e34f 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -21,7 +21,7 @@ use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LocalDefId, LOCAL_CRATE};
 use rustc_hir::PredicateOrigin;
 use rustc_hir_analysis::hir_ty_to_ty;
 use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
-use rustc_middle::middle::resolve_lifetime as rl;
+use rustc_middle::middle::resolve_bound_vars as rbv;
 use rustc_middle::ty::fold::ir::TypeFolder;
 use rustc_middle::ty::InternalSubsts;
 use rustc_middle::ty::TypeVisitable;
@@ -200,11 +200,11 @@ fn clean_poly_trait_ref_with_bindings<'tcx>(
 }
 
 fn clean_lifetime<'tcx>(lifetime: &hir::Lifetime, cx: &mut DocContext<'tcx>) -> Lifetime {
-    let def = cx.tcx.named_region(lifetime.hir_id);
+    let def = cx.tcx.named_bound_var(lifetime.hir_id);
     if let Some(
-        rl::Region::EarlyBound(node_id)
-        | rl::Region::LateBound(_, _, node_id)
-        | rl::Region::Free(_, node_id),
+        rbv::ResolvedArg::EarlyBound(node_id)
+        | rbv::ResolvedArg::LateBound(_, _, node_id)
+        | rbv::ResolvedArg::Free(_, node_id),
     ) = def
     {
         if let Some(lt) = cx.substs.get(&node_id).and_then(|p| p.as_lt()).cloned() {
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 4d8ce54dc5c..6fe665d7e40 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -129,7 +129,7 @@ fn external_generic_args<'tcx>(
         });
         GenericArgs::Parenthesized { inputs, output }
     } else {
-        GenericArgs::AngleBracketed { args: args.into(), bindings: bindings.into() }
+        GenericArgs::AngleBracketed { args: args.into(), bindings }
     }
 }
 
diff --git a/src/tools/clippy/clippy_lints/src/ptr.rs b/src/tools/clippy/clippy_lints/src/ptr.rs
index d88409c356e..fc550936165 100644
--- a/src/tools/clippy/clippy_lints/src/ptr.rs
+++ b/src/tools/clippy/clippy_lints/src/ptr.rs
@@ -505,13 +505,13 @@ fn check_mut_from_ref<'tcx>(cx: &LateContext<'tcx>, sig: &FnSig<'_>, body: Optio
     if let FnRetTy::Return(ty) = sig.decl.output
         && let Some((out, Mutability::Mut, _)) = get_ref_lm(ty)
     {
-        let out_region = cx.tcx.named_region(out.hir_id);
+        let out_region = cx.tcx.named_bound_var(out.hir_id);
         let args: Option<Vec<_>> = sig
             .decl
             .inputs
             .iter()
             .filter_map(get_ref_lm)
-            .filter(|&(lt, _, _)| cx.tcx.named_region(lt.hir_id) == out_region)
+            .filter(|&(lt, _, _)| cx.tcx.named_bound_var(lt.hir_id) == out_region)
             .map(|(_, mutability, span)| (mutability == Mutability::Not).then_some(span))
             .collect();
         if let Some(args) = args
diff --git a/src/tools/tidy/src/ui_tests.rs b/src/tools/tidy/src/ui_tests.rs
index ef3abb9514f..409f7563184 100644
--- a/src/tools/tidy/src/ui_tests.rs
+++ b/src/tools/tidy/src/ui_tests.rs
@@ -10,7 +10,7 @@ use std::path::Path;
 const ENTRY_LIMIT: usize = 1000;
 // FIXME: The following limits should be reduced eventually.
 const ROOT_ENTRY_LIMIT: usize = 940;
-const ISSUES_ENTRY_LIMIT: usize = 2001;
+const ISSUES_ENTRY_LIMIT: usize = 1978;
 
 fn check_entries(path: &Path, bad: &mut bool) {
     for dir in Walk::new(&path.join("ui")) {
diff --git a/tests/ui/issues/issue-38821.rs b/tests/ui/associated-types/issue-38821.rs
index 6753860e9ff..6753860e9ff 100644
--- a/tests/ui/issues/issue-38821.rs
+++ b/tests/ui/associated-types/issue-38821.rs
diff --git a/tests/ui/issues/issue-38821.stderr b/tests/ui/associated-types/issue-38821.stderr
index a52a9c138f1..a52a9c138f1 100644
--- a/tests/ui/issues/issue-38821.stderr
+++ b/tests/ui/associated-types/issue-38821.stderr
diff --git a/tests/ui/issues/issue-83924.fixed b/tests/ui/borrowck/issue-83924.fixed
index aa40da12b87..aa40da12b87 100644
--- a/tests/ui/issues/issue-83924.fixed
+++ b/tests/ui/borrowck/issue-83924.fixed
diff --git a/tests/ui/issues/issue-83924.rs b/tests/ui/borrowck/issue-83924.rs
index 22b80fe2f38..22b80fe2f38 100644
--- a/tests/ui/issues/issue-83924.rs
+++ b/tests/ui/borrowck/issue-83924.rs
diff --git a/tests/ui/issues/issue-83924.stderr b/tests/ui/borrowck/issue-83924.stderr
index 572414df2bf..572414df2bf 100644
--- a/tests/ui/issues/issue-83924.stderr
+++ b/tests/ui/borrowck/issue-83924.stderr
diff --git a/tests/ui/bounds-lifetime.stderr b/tests/ui/bounds-lifetime.stderr
index a0395ed4904..a3427e21cde 100644
--- a/tests/ui/bounds-lifetime.stderr
+++ b/tests/ui/bounds-lifetime.stderr
@@ -16,17 +16,24 @@ error: lifetime bounds cannot be used in this context
 LL | type C = for<'b, 'a: 'b +> fn();
    |                      ^^
 
-error: only lifetime parameters can be used in this context
+error[E0658]: only lifetime parameters can be used in this context
   --> $DIR/bounds-lifetime.rs:4:18
    |
 LL | type D = for<'a, T> fn();
    |                  ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
-error: only lifetime parameters can be used in this context
+error[E0658]: only lifetime parameters can be used in this context
   --> $DIR/bounds-lifetime.rs:5:18
    |
 LL | type E = dyn for<T> Fn();
    |                  ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/closures/binder/disallow-const.stderr b/tests/ui/closures/binder/disallow-const.stderr
index 3c3b43d8cf3..9f4deaa774d 100644
--- a/tests/ui/closures/binder/disallow-const.stderr
+++ b/tests/ui/closures/binder/disallow-const.stderr
@@ -1,8 +1,12 @@
-error: only lifetime parameters can be used in this context
+error[E0658]: only lifetime parameters can be used in this context
   --> $DIR/disallow-const.rs:4:15
    |
 LL |     for<const N: i32> || -> () {};
    |               ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/closures/binder/disallow-ty.stderr b/tests/ui/closures/binder/disallow-ty.stderr
index 51b6773edea..22882ca2ba6 100644
--- a/tests/ui/closures/binder/disallow-ty.stderr
+++ b/tests/ui/closures/binder/disallow-ty.stderr
@@ -1,8 +1,12 @@
-error: only lifetime parameters can be used in this context
+error[E0658]: only lifetime parameters can be used in this context
   --> $DIR/disallow-ty.rs:4:9
    |
 LL |     for<T> || -> () {};
    |         ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/conditional-compilation/cfg-generic-params.stderr b/tests/ui/conditional-compilation/cfg-generic-params.stderr
index 4d6560e96e5..69b0f741156 100644
--- a/tests/ui/conditional-compilation/cfg-generic-params.stderr
+++ b/tests/ui/conditional-compilation/cfg-generic-params.stderr
@@ -1,21 +1,3 @@
-error: only lifetime parameters can be used in this context
-  --> $DIR/cfg-generic-params.rs:7:45
-   |
-LL | type FnBad = for<#[cfg(no)] 'a, #[cfg(yes)] T> fn();
-   |                                             ^
-
-error: only lifetime parameters can be used in this context
-  --> $DIR/cfg-generic-params.rs:11:51
-   |
-LL | type PolyBad = dyn for<#[cfg(no)] 'a, #[cfg(yes)] T> Copy;
-   |                                                   ^
-
-error: only lifetime parameters can be used in this context
-  --> $DIR/cfg-generic-params.rs:15:54
-   |
-LL | struct WhereBad where for<#[cfg(no)] 'a, #[cfg(yes)] T> u8: Copy;
-   |                                                      ^
-
 error: cannot find attribute `unknown` in this scope
   --> $DIR/cfg-generic-params.rs:19:29
    |
@@ -46,5 +28,33 @@ error: cannot find attribute `unknown` in this scope
 LL | struct WhereYes where for<#[cfg_attr(yes, unknown)] 'a> u8: Copy;
    |                                           ^^^^^^^
 
+error[E0658]: only lifetime parameters can be used in this context
+  --> $DIR/cfg-generic-params.rs:7:45
+   |
+LL | type FnBad = for<#[cfg(no)] 'a, #[cfg(yes)] T> fn();
+   |                                             ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
+
+error[E0658]: only lifetime parameters can be used in this context
+  --> $DIR/cfg-generic-params.rs:11:51
+   |
+LL | type PolyBad = dyn for<#[cfg(no)] 'a, #[cfg(yes)] T> Copy;
+   |                                                   ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
+
+error[E0658]: only lifetime parameters can be used in this context
+  --> $DIR/cfg-generic-params.rs:15:54
+   |
+LL | struct WhereBad where for<#[cfg(no)] 'a, #[cfg(yes)] T> u8: Copy;
+   |                                                      ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
+
 error: aborting due to 8 previous errors
 
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/issues/issue-33903.rs b/tests/ui/consts/issue-33903.rs
index 613aa121a47..613aa121a47 100644
--- a/tests/ui/issues/issue-33903.rs
+++ b/tests/ui/consts/issue-33903.rs
diff --git a/tests/ui/issues/issue-54582.rs b/tests/ui/consts/issue-54582.rs
index 8c50cac67f8..8c50cac67f8 100644
--- a/tests/ui/issues/issue-54582.rs
+++ b/tests/ui/consts/issue-54582.rs
diff --git a/tests/ui/issues/issue-2735-2.rs b/tests/ui/drop/issue-2735-2.rs
index 70ebce9d35a..70ebce9d35a 100644
--- a/tests/ui/issues/issue-2735-2.rs
+++ b/tests/ui/drop/issue-2735-2.rs
diff --git a/tests/ui/issues/issue-2735-3.rs b/tests/ui/drop/issue-2735-3.rs
index 23301537835..23301537835 100644
--- a/tests/ui/issues/issue-2735-3.rs
+++ b/tests/ui/drop/issue-2735-3.rs
diff --git a/tests/ui/issues/issue-2735.rs b/tests/ui/drop/issue-2735.rs
index 20d3949a9f9..20d3949a9f9 100644
--- a/tests/ui/issues/issue-2735.rs
+++ b/tests/ui/drop/issue-2735.rs
diff --git a/tests/ui/feature-gates/feature-gate-non_lifetime_binders.rs b/tests/ui/feature-gates/feature-gate-non_lifetime_binders.rs
new file mode 100644
index 00000000000..221e9133fcc
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-non_lifetime_binders.rs
@@ -0,0 +1,4 @@
+fn foo() where for<T> T:, {}
+//~^ ERROR only lifetime parameters can be used in this context
+
+fn main() {}
diff --git a/tests/ui/feature-gates/feature-gate-non_lifetime_binders.stderr b/tests/ui/feature-gates/feature-gate-non_lifetime_binders.stderr
new file mode 100644
index 00000000000..75645e32401
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-non_lifetime_binders.stderr
@@ -0,0 +1,12 @@
+error[E0658]: only lifetime parameters can be used in this context
+  --> $DIR/feature-gate-non_lifetime_binders.rs:1:20
+   |
+LL | fn foo() where for<T> T:, {}
+   |                    ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/issues/issue-75307.rs b/tests/ui/fmt/issue-75307.rs
index cffa6bea8ed..cffa6bea8ed 100644
--- a/tests/ui/issues/issue-75307.rs
+++ b/tests/ui/fmt/issue-75307.rs
diff --git a/tests/ui/issues/issue-75307.stderr b/tests/ui/fmt/issue-75307.stderr
index c5b0b11e7d0..c5b0b11e7d0 100644
--- a/tests/ui/issues/issue-75307.stderr
+++ b/tests/ui/fmt/issue-75307.stderr
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-wrong-kind.stderr b/tests/ui/higher-rank-trait-bounds/hrtb-wrong-kind.stderr
index f31aa554634..d605c9e0df7 100644
--- a/tests/ui/higher-rank-trait-bounds/hrtb-wrong-kind.stderr
+++ b/tests/ui/higher-rank-trait-bounds/hrtb-wrong-kind.stderr
@@ -1,14 +1,21 @@
-error: only lifetime parameters can be used in this context
+error[E0658]: only lifetime parameters can be used in this context
   --> $DIR/hrtb-wrong-kind.rs:1:18
    |
 LL | fn a() where for<T> T: Copy {}
    |                  ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
-error: only lifetime parameters can be used in this context
+error[E0658]: only lifetime parameters can be used in this context
   --> $DIR/hrtb-wrong-kind.rs:4:24
    |
 LL | fn b() where for<const C: usize> [(); C]: Copy {}
    |                        ^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/issues/issue-39292.rs b/tests/ui/higher-rank-trait-bounds/issue-39292.rs
index 968cf08916f..968cf08916f 100644
--- a/tests/ui/issues/issue-39292.rs
+++ b/tests/ui/higher-rank-trait-bounds/issue-39292.rs
diff --git a/tests/ui/issues/issue-50576.rs b/tests/ui/loops/issue-50576.rs
index e0c36b8273a..e0c36b8273a 100644
--- a/tests/ui/issues/issue-50576.rs
+++ b/tests/ui/loops/issue-50576.rs
diff --git a/tests/ui/issues/issue-50576.stderr b/tests/ui/loops/issue-50576.stderr
index 4ec22fde910..4ec22fde910 100644
--- a/tests/ui/issues/issue-50576.stderr
+++ b/tests/ui/loops/issue-50576.stderr
diff --git a/tests/ui/issues/issue-22536-copy-mustnt-zero.rs b/tests/ui/moves/issue-22536-copy-mustnt-zero.rs
index 017f36484c1..017f36484c1 100644
--- a/tests/ui/issues/issue-22536-copy-mustnt-zero.rs
+++ b/tests/ui/moves/issue-22536-copy-mustnt-zero.rs
diff --git a/tests/ui/issues/issue-27583.rs b/tests/ui/nll/issue-27583.rs
index 84c94c7c905..84c94c7c905 100644
--- a/tests/ui/issues/issue-27583.rs
+++ b/tests/ui/nll/issue-27583.rs
diff --git a/tests/ui/issues/issue-48179.rs b/tests/ui/nll/issue-48179.rs
index f81203dc412..f81203dc412 100644
--- a/tests/ui/issues/issue-48179.rs
+++ b/tests/ui/nll/issue-48179.rs
diff --git a/tests/ui/issues/issue-75777.rs b/tests/ui/nll/issue-75777.rs
index a1e438bc617..a1e438bc617 100644
--- a/tests/ui/issues/issue-75777.rs
+++ b/tests/ui/nll/issue-75777.rs
diff --git a/tests/ui/issues/issue-75777.stderr b/tests/ui/nll/issue-75777.stderr
index 370cd72fd55..370cd72fd55 100644
--- a/tests/ui/issues/issue-75777.stderr
+++ b/tests/ui/nll/issue-75777.stderr
diff --git a/tests/ui/parser/recover-fn-ptr-with-generics.stderr b/tests/ui/parser/recover-fn-ptr-with-generics.stderr
index 1da9c18571b..069fcffe9a0 100644
--- a/tests/ui/parser/recover-fn-ptr-with-generics.stderr
+++ b/tests/ui/parser/recover-fn-ptr-with-generics.stderr
@@ -88,12 +88,6 @@ error: expected identifier, found `>`
 LL |     type QuiteBroken = fn<const>();
    |                                ^ expected identifier
 
-error: lifetime bounds cannot be used in this context
-  --> $DIR/recover-fn-ptr-with-generics.rs:22:26
-   |
-LL |     let _: extern fn<'a: 'static>();
-   |                          ^^^^^^^
-
 error[E0412]: cannot find type `T` in this scope
   --> $DIR/recover-fn-ptr-with-generics.rs:5:27
    |
@@ -106,6 +100,12 @@ error[E0412]: cannot find type `T` in this scope
 LL |     type Identity = fn<T>(T) -> T;
    |                                 ^ not found in this scope
 
+error: lifetime bounds cannot be used in this context
+  --> $DIR/recover-fn-ptr-with-generics.rs:22:26
+   |
+LL |     let _: extern fn<'a: 'static>();
+   |                          ^^^^^^^
+
 error: aborting due to 12 previous errors
 
 For more information about this error, try `rustc --explain E0412`.
diff --git a/tests/ui/issues/issue-40003.rs b/tests/ui/recursion_limit/issue-40003.rs
index 5e61361f987..5e61361f987 100644
--- a/tests/ui/issues/issue-40003.rs
+++ b/tests/ui/recursion_limit/issue-40003.rs
diff --git a/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs
new file mode 100644
index 00000000000..0b1f9ab57c9
--- /dev/null
+++ b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs
@@ -0,0 +1,15 @@
+// Regression test for #108132: do not ICE upon unmet trait alias constraint in generic impl
+
+#![feature(trait_alias)]
+
+trait IteratorAlias = Iterator;
+
+struct Foo<I>(I);
+
+impl<I: IteratorAlias> Foo<I> {
+    fn f() {}
+}
+
+fn main() {
+    Foo::<()>::f() //~ trait bounds were not satisfied
+}
diff --git a/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.stderr b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.stderr
new file mode 100644
index 00000000000..f1b259d5a65
--- /dev/null
+++ b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.stderr
@@ -0,0 +1,25 @@
+error[E0599]: the function or associated item `f` exists for struct `Foo<()>`, but its trait bounds were not satisfied
+  --> $DIR/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs:14:16
+   |
+LL | struct Foo<I>(I);
+   | ------------- function or associated item `f` not found for this struct
+...
+LL |     Foo::<()>::f()
+   |                ^ function or associated item cannot be called on `Foo<()>` due to unsatisfied trait bounds
+   |
+note: trait bound `(): Iterator` was not satisfied
+  --> $DIR/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs:5:23
+   |
+LL | trait IteratorAlias = Iterator;
+   |       -------------   ^^^^^^^^ unsatisfied trait bound introduced here
+note: trait bound `(): IteratorAlias` was not satisfied
+  --> $DIR/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs:9:9
+   |
+LL | impl<I: IteratorAlias> Foo<I> {
+   |         ^^^^^^^^^^^^^  ------
+   |         |
+   |         unsatisfied trait bound introduced here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0599`.
diff --git a/tests/ui/traits/non_lifetime_binders/basic.rs b/tests/ui/traits/non_lifetime_binders/basic.rs
new file mode 100644
index 00000000000..a797aae65db
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/basic.rs
@@ -0,0 +1,19 @@
+// check-pass
+// Basic test that show's we can succesfully typeck a `for<T>` where clause.
+
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+trait Trait {}
+
+impl<T: ?Sized> Trait for T {}
+
+fn foo()
+where
+    for<T> T: Trait,
+{
+}
+
+fn main() {
+    foo();
+}
diff --git a/tests/ui/traits/non_lifetime_binders/basic.stderr b/tests/ui/traits/non_lifetime_binders/basic.stderr
new file mode 100644
index 00000000000..fddc5d9fc25
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/basic.stderr
@@ -0,0 +1,11 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/basic.rs:4:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/traits/non_lifetime_binders/fail.rs b/tests/ui/traits/non_lifetime_binders/fail.rs
new file mode 100644
index 00000000000..460f68907e8
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/fail.rs
@@ -0,0 +1,23 @@
+// Error reporting for where `for<T> T: Trait` doesn't hold
+
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+trait Trait {}
+
+fn fail()
+where
+    for<T> T: Trait,
+{}
+
+fn auto_trait()
+where
+    for<T> T: Send,
+{}
+
+fn main() {
+    fail();
+    //~^ ERROR the trait bound `T: Trait` is not satisfied
+    auto_trait();
+    //~^ ERROR `T` cannot be sent between threads safely
+}
diff --git a/tests/ui/traits/non_lifetime_binders/fail.stderr b/tests/ui/traits/non_lifetime_binders/fail.stderr
new file mode 100644
index 00000000000..ba5953193a4
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/fail.stderr
@@ -0,0 +1,43 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/fail.rs:3:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0277]: the trait bound `T: Trait` is not satisfied
+  --> $DIR/fail.rs:19:5
+   |
+LL |     fail();
+   |     ^^^^ the trait `Trait` is not implemented for `T`
+   |
+note: required by a bound in `fail`
+  --> $DIR/fail.rs:10:15
+   |
+LL | fn fail()
+   |    ---- required by a bound in this
+LL | where
+LL |     for<T> T: Trait,
+   |               ^^^^^ required by this bound in `fail`
+
+error[E0277]: `T` cannot be sent between threads safely
+  --> $DIR/fail.rs:21:5
+   |
+LL |     auto_trait();
+   |     ^^^^^^^^^^ `T` cannot be sent between threads safely
+   |
+   = help: the trait `Send` is not implemented for `T`
+note: required by a bound in `auto_trait`
+  --> $DIR/fail.rs:15:15
+   |
+LL | fn auto_trait()
+   |    ---------- required by a bound in this
+LL | where
+LL |     for<T> T: Send,
+   |               ^^^^ required by this bound in `auto_trait`
+
+error: aborting due to 2 previous errors; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/traits/non_lifetime_binders/on-dyn.rs b/tests/ui/traits/non_lifetime_binders/on-dyn.rs
new file mode 100644
index 00000000000..8fb7dd27605
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/on-dyn.rs
@@ -0,0 +1,13 @@
+// Tests to make sure that we reject polymorphic dyn trait.
+
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+trait Test<T> {}
+
+fn foo() -> &'static dyn for<T> Test<T> {
+    //~^ ERROR late-bound type parameter not allowed on trait object types
+    todo!()
+}
+
+fn main() {}
diff --git a/tests/ui/traits/non_lifetime_binders/on-dyn.stderr b/tests/ui/traits/non_lifetime_binders/on-dyn.stderr
new file mode 100644
index 00000000000..44071107de4
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/on-dyn.stderr
@@ -0,0 +1,17 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/on-dyn.rs:3:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: late-bound type parameter not allowed on trait object types
+  --> $DIR/on-dyn.rs:8:30
+   |
+LL | fn foo() -> &'static dyn for<T> Test<T> {
+   |                              ^
+
+error: aborting due to previous error; 1 warning emitted
+
diff --git a/tests/ui/traits/non_lifetime_binders/on-ptr.rs b/tests/ui/traits/non_lifetime_binders/on-ptr.rs
new file mode 100644
index 00000000000..0aaff52b6d8
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/on-ptr.rs
@@ -0,0 +1,13 @@
+// Tests to make sure that we reject polymorphic fn ptrs.
+
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+fn foo() -> for<T> fn(T) {
+    //~^ ERROR late-bound type parameter not allowed on function pointer types
+    todo!()
+}
+
+fn main() {
+    foo()(1i32);
+}
diff --git a/tests/ui/traits/non_lifetime_binders/on-ptr.stderr b/tests/ui/traits/non_lifetime_binders/on-ptr.stderr
new file mode 100644
index 00000000000..bb7dccaf07d
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/on-ptr.stderr
@@ -0,0 +1,17 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/on-ptr.rs:3:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: late-bound type parameter not allowed on function pointer types
+  --> $DIR/on-ptr.rs:6:17
+   |
+LL | fn foo() -> for<T> fn(T) {
+   |                 ^
+
+error: aborting due to previous error; 1 warning emitted
+
diff --git a/tests/ui/issues/issue-53712.rs b/tests/ui/typeck/issue-53712.rs
index 2353904d79d..2353904d79d 100644
--- a/tests/ui/issues/issue-53712.rs
+++ b/tests/ui/typeck/issue-53712.rs
diff --git a/tests/ui/issues/issue-53712.stderr b/tests/ui/typeck/issue-53712.stderr
index db85919afcb..db85919afcb 100644
--- a/tests/ui/issues/issue-53712.stderr
+++ b/tests/ui/typeck/issue-53712.stderr
diff --git a/tests/ui/issues/issue-7813.rs b/tests/ui/typeck/issue-7813.rs
index ce549bde601..ce549bde601 100644
--- a/tests/ui/issues/issue-7813.rs
+++ b/tests/ui/typeck/issue-7813.rs
diff --git a/tests/ui/issues/issue-7813.stderr b/tests/ui/typeck/issue-7813.stderr
index 2a747f679a8..2a747f679a8 100644
--- a/tests/ui/issues/issue-7813.stderr
+++ b/tests/ui/typeck/issue-7813.stderr