Auto merge of #101895 - GuillaumeGomez:rollup-ured85q, r=GuillaumeGomez

Rollup of 7 pull requests

Successful merges:

 - #101494 (rustdoc mobile: move notable traits to return type)
 - #101813 (Extend CSS check to CSS variables)
 - #101825 (Fix back RPIT changes)
 - #101843 (Suggest associated const for incorrect use of let in traits)
 - #101859 (Slight vertical formatting)
 - #101868 (rustdoc: use more precise URLs for jump-to-definition links)
 - #101877 (rustdoc: remove no-op CSS `.block { padding: 0 }`)

Failed merges:

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

20 files changed, 542 insertions, 453 deletions

diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 90bb01aa216..24672efc63c 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -220,7 +220,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 &sym.qself,
                                 &sym.path,
                                 ParamMode::Optional,
-                                &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                                &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                             );
                             hir::InlineAsmOperand::SymStatic { path, def_id }
                         } else {
diff --git a/compiler/rustc_ast_lowering/src/block.rs b/compiler/rustc_ast_lowering/src/block.rs
index 7465706d1a9..e0869bb1063 100644
--- a/compiler/rustc_ast_lowering/src/block.rs
+++ b/compiler/rustc_ast_lowering/src/block.rs
@@ -84,9 +84,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_local(&mut self, l: &Local) -> &'hir hir::Local<'hir> {
-        let ty = l.ty.as_ref().map(|t| {
-            self.lower_ty(t, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Variable))
-        });
+        let ty = l
+            .ty
+            .as_ref()
+            .map(|t| self.lower_ty(t, &ImplTraitContext::Disallowed(ImplTraitPosition::Variable)));
         let init = l.kind.init().map(|init| self.lower_expr(init));
         let hir_id = self.lower_node_id(l.id);
         let pat = self.lower_pat(&l.pat);
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 7f5e09938cb..6c09269352c 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -66,7 +66,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         seg,
                         ParamMode::Optional,
                         ParenthesizedGenericArgs::Err,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                        &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                     ));
                     let receiver = self.lower_expr(receiver);
                     let args =
@@ -89,14 +89,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
                 ExprKind::Cast(ref expr, ref ty) => {
                     let expr = self.lower_expr(expr);
-                    let ty = self
-                        .lower_ty(ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+                    let ty =
+                        self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                     hir::ExprKind::Cast(expr, ty)
                 }
                 ExprKind::Type(ref expr, ref ty) => {
                     let expr = self.lower_expr(expr);
-                    let ty = self
-                        .lower_ty(ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+                    let ty =
+                        self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                     hir::ExprKind::Type(expr, ty)
                 }
                 ExprKind::AddrOf(k, m, ref ohs) => {
@@ -225,7 +225,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         qself,
                         path,
                         ParamMode::Optional,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                        &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                     );
                     hir::ExprKind::Path(qpath)
                 }
@@ -259,7 +259,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                             &se.qself,
                             &se.path,
                             ParamMode::Optional,
-                            &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                            &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                         )),
                         self.arena
                             .alloc_from_iter(se.fields.iter().map(|x| self.lower_expr_field(x))),
@@ -556,14 +556,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
         async_gen_kind: hir::AsyncGeneratorKind,
         body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
     ) -> hir::ExprKind<'hir> {
-        let output =
-            match ret_ty {
-                Some(ty) => hir::FnRetTy::Return(self.lower_ty(
-                    &ty,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::AsyncBlock),
-                )),
-                None => hir::FnRetTy::DefaultReturn(self.lower_span(span)),
-            };
+        let output = match ret_ty {
+            Some(ty) => hir::FnRetTy::Return(
+                self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::AsyncBlock)),
+            ),
+            None => hir::FnRetTy::DefaultReturn(self.lower_span(span)),
+        };
 
         // Resume argument type. We let the compiler infer this to simplify the lowering. It is
         // fully constrained by `future::from_generator`.
@@ -855,22 +853,21 @@ impl<'hir> LoweringContext<'_, 'hir> {
             (body_id, generator_option)
         });
 
-        self.lower_lifetime_binder(closure_id, generic_params, |lctx, bound_generic_params| {
-            // Lower outside new scope to preserve `is_in_loop_condition`.
-            let fn_decl = lctx.lower_fn_decl(decl, None, fn_decl_span, FnDeclKind::Closure, None);
-
-            let c = lctx.arena.alloc(hir::Closure {
-                binder: binder_clause,
-                capture_clause,
-                bound_generic_params,
-                fn_decl,
-                body: body_id,
-                fn_decl_span: lctx.lower_span(fn_decl_span),
-                movability: generator_option,
-            });
+        let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params);
+        // Lower outside new scope to preserve `is_in_loop_condition`.
+        let fn_decl = self.lower_fn_decl(decl, None, fn_decl_span, FnDeclKind::Closure, None);
+
+        let c = self.arena.alloc(hir::Closure {
+            binder: binder_clause,
+            capture_clause,
+            bound_generic_params,
+            fn_decl,
+            body: body_id,
+            fn_decl_span: self.lower_span(fn_decl_span),
+            movability: generator_option,
+        });
 
-            hir::ExprKind::Closure(c)
-        })
+        hir::ExprKind::Closure(c)
     }
 
     fn generator_movability_for_fn(
@@ -957,24 +954,23 @@ impl<'hir> LoweringContext<'_, 'hir> {
             body_id
         });
 
-        self.lower_lifetime_binder(closure_id, generic_params, |lctx, bound_generic_params| {
-            // We need to lower the declaration outside the new scope, because we
-            // have to conserve the state of being inside a loop condition for the
-            // closure argument types.
-            let fn_decl =
-                lctx.lower_fn_decl(&outer_decl, None, fn_decl_span, FnDeclKind::Closure, None);
-
-            let c = lctx.arena.alloc(hir::Closure {
-                binder: binder_clause,
-                capture_clause,
-                bound_generic_params,
-                fn_decl,
-                body,
-                fn_decl_span: lctx.lower_span(fn_decl_span),
-                movability: None,
-            });
-            hir::ExprKind::Closure(c)
-        })
+        let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params);
+        // We need to lower the declaration outside the new scope, because we
+        // have to conserve the state of being inside a loop condition for the
+        // closure argument types.
+        let fn_decl =
+            self.lower_fn_decl(&outer_decl, None, fn_decl_span, FnDeclKind::Closure, None);
+
+        let c = self.arena.alloc(hir::Closure {
+            binder: binder_clause,
+            capture_clause,
+            bound_generic_params,
+            fn_decl,
+            body,
+            fn_decl_span: self.lower_span(fn_decl_span),
+            movability: None,
+        });
+        hir::ExprKind::Closure(c)
     }
 
     /// Destructure the LHS of complex assignments.
@@ -1133,7 +1129,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         qself,
                         path,
                         ParamMode::Optional,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                        &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                     );
                     // Destructure like a tuple struct.
                     let tuple_struct_pat = hir::PatKind::TupleStruct(
@@ -1152,7 +1148,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         qself,
                         path,
                         ParamMode::Optional,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                        &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                     );
                     // Destructure like a unit struct.
                     let unit_struct_pat = hir::PatKind::Path(qpath);
@@ -1176,7 +1172,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     &se.qself,
                     &se.path,
                     ParamMode::Optional,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                 );
                 let fields_omitted = match &se.rest {
                     StructRest::Base(e) => {
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 52273778dcc..550833275e4 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -313,8 +313,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, ty) = self.lower_generics(
                     &generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
-                    |this| this.lower_ty(ty, &mut ImplTraitContext::TypeAliasesOpaqueTy),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    |this| this.lower_ty(ty, &ImplTraitContext::TypeAliasesOpaqueTy),
                 );
                 hir::ItemKind::TyAlias(ty, generics)
             }
@@ -326,7 +326,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, ty) = self.lower_generics(
                     &generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| this.arena.alloc(this.ty(span, hir::TyKind::Err)),
                 );
                 hir::ItemKind::TyAlias(ty, generics)
@@ -335,7 +335,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, variants) = self.lower_generics(
                     generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| {
                         this.arena.alloc_from_iter(
                             enum_definition.variants.iter().map(|x| this.lower_variant(x)),
@@ -348,7 +348,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, struct_def) = self.lower_generics(
                     generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| this.lower_variant_data(hir_id, struct_def),
                 );
                 hir::ItemKind::Struct(struct_def, generics)
@@ -357,7 +357,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, vdata) = self.lower_generics(
                     generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| this.lower_variant_data(hir_id, vdata),
                 );
                 hir::ItemKind::Union(vdata, generics)
@@ -391,14 +391,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         let trait_ref = trait_ref.as_ref().map(|trait_ref| {
                             this.lower_trait_ref(
                                 trait_ref,
-                                &mut ImplTraitContext::Disallowed(ImplTraitPosition::Trait),
+                                &ImplTraitContext::Disallowed(ImplTraitPosition::Trait),
                             )
                         });
 
-                        let lowered_ty = this.lower_ty(
-                            ty,
-                            &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type),
-                        );
+                        let lowered_ty = this
+                            .lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
 
                         (trait_ref, lowered_ty)
                     });
@@ -437,11 +435,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, (unsafety, items, bounds)) = self.lower_generics(
                     generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| {
                         let bounds = this.lower_param_bounds(
                             bounds,
-                            &mut ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                            &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
                         );
                         let items = this.arena.alloc_from_iter(
                             items.iter().map(|item| this.lower_trait_item_ref(item)),
@@ -456,11 +454,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, bounds) = self.lower_generics(
                     generics,
                     id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| {
                         this.lower_param_bounds(
                             bounds,
-                            &mut ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                            &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
                         )
                     },
                 );
@@ -483,7 +481,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         span: Span,
         body: Option<&Expr>,
     ) -> (&'hir hir::Ty<'hir>, hir::BodyId) {
-        let ty = self.lower_ty(ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+        let ty = self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
         (ty, self.lower_const_body(span, body))
     }
 
@@ -675,8 +673,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
                 }
                 ForeignItemKind::Static(ref t, m, _) => {
-                    let ty = self
-                        .lower_ty(t, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+                    let ty =
+                        self.lower_ty(t, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                     hir::ForeignItemKind::Static(ty, m)
                 }
                 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
@@ -744,11 +742,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 qself,
                 path,
                 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
-                &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
             );
             self.arena.alloc(t)
         } else {
-            self.lower_ty(&f.ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type))
+            self.lower_ty(&f.ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type))
         };
         let hir_id = self.lower_node_id(f.id);
         self.lower_attrs(hir_id, &f.attrs);
@@ -771,8 +769,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         let (generics, kind, has_default) = match i.kind {
             AssocItemKind::Const(_, ref ty, ref default) => {
-                let ty =
-                    self.lower_ty(ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+                let ty = self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                 let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x)));
                 (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body), body.is_some())
             }
@@ -813,18 +810,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, kind) = self.lower_generics(
                     &generics,
                     i.id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| {
                         let ty = ty.as_ref().map(|x| {
-                            this.lower_ty(
-                                x,
-                                &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type),
-                            )
+                            this.lower_ty(x, &ImplTraitContext::Disallowed(ImplTraitPosition::Type))
                         });
                         hir::TraitItemKind::Type(
                             this.lower_param_bounds(
                                 bounds,
-                                &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                                &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                             ),
                             ty,
                         )
@@ -877,8 +871,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         let (generics, kind) = match &i.kind {
             AssocItemKind::Const(_, ty, expr) => {
-                let ty =
-                    self.lower_ty(ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+                let ty = self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                 (
                     hir::Generics::empty(),
                     hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
@@ -905,14 +898,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 self.lower_generics(
                     &generics,
                     i.id,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
                     |this| match ty {
                         None => {
                             let ty = this.arena.alloc(this.ty(i.span, hir::TyKind::Err));
                             hir::ImplItemKind::TyAlias(ty)
                         }
                         Some(ty) => {
-                            let ty = this.lower_ty(ty, &mut ImplTraitContext::TypeAliasesOpaqueTy);
+                            let ty = this.lower_ty(ty, &ImplTraitContext::TypeAliasesOpaqueTy);
                             hir::ImplItemKind::TyAlias(ty)
                         }
                     },
@@ -1322,7 +1315,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         generics: &Generics,
         parent_node_id: NodeId,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
         f: impl FnOnce(&mut Self) -> T,
     ) -> (&'hir hir::Generics<'hir>, T) {
         debug_assert!(self.impl_trait_defs.is_empty());
@@ -1427,7 +1420,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         id: NodeId,
         kind: &GenericParamKind,
         bounds: &[GenericBound],
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
         origin: PredicateOrigin,
     ) -> Option<hir::WherePredicate<'hir>> {
         // Do not create a clause if we do not have anything inside it.
@@ -1502,14 +1495,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 span,
             }) => hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
                 bound_generic_params: self.lower_generic_params(bound_generic_params),
-                bounded_ty: self.lower_ty(
-                    bounded_ty,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type),
-                ),
+                bounded_ty: self
+                    .lower_ty(bounded_ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type)),
                 bounds: self.arena.alloc_from_iter(bounds.iter().map(|bound| {
                     self.lower_param_bound(
                         bound,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                        &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
                     )
                 })),
                 span: self.lower_span(span),
@@ -1524,20 +1515,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 lifetime: self.lower_lifetime(lifetime),
                 bounds: self.lower_param_bounds(
                     bounds,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
                 ),
                 in_where_clause: true,
             }),
             WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, span }) => {
                 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
-                    lhs_ty: self.lower_ty(
-                        lhs_ty,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type),
-                    ),
-                    rhs_ty: self.lower_ty(
-                        rhs_ty,
-                        &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type),
-                    ),
+                    lhs_ty: self
+                        .lower_ty(lhs_ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type)),
+                    rhs_ty: self
+                        .lower_ty(rhs_ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type)),
                     span: self.lower_span(span),
                 })
             }
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 409ee55268c..cb6bf0863b3 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -839,31 +839,23 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// name resolver owing to lifetime elision; this also populates the resolver's node-id->def-id
     /// map, so that later calls to `opt_node_id_to_def_id` that refer to these extra lifetime
     /// parameters will be successful.
-    #[instrument(level = "debug", skip(self, in_binder))]
+    #[instrument(level = "debug", skip(self))]
     #[inline]
-    fn lower_lifetime_binder<R>(
+    fn lower_lifetime_binder(
         &mut self,
         binder: NodeId,
         generic_params: &[GenericParam],
-        in_binder: impl FnOnce(&mut Self, &'hir [hir::GenericParam<'hir>]) -> R,
-    ) -> R {
+    ) -> &'hir [hir::GenericParam<'hir>] {
+        let mut generic_params: Vec<_> = self.lower_generic_params_mut(generic_params).collect();
         let extra_lifetimes = self.resolver.take_extra_lifetime_params(binder);
         debug!(?extra_lifetimes);
-        let extra_lifetimes: Vec<_> = extra_lifetimes
-            .into_iter()
-            .filter_map(|(ident, node_id, res)| {
-                self.lifetime_res_to_generic_param(ident, node_id, res)
-            })
-            .collect();
-
-        let generic_params: Vec<_> = self
-            .lower_generic_params_mut(generic_params)
-            .chain(extra_lifetimes.into_iter())
-            .collect();
+        generic_params.extend(extra_lifetimes.into_iter().filter_map(|(ident, node_id, res)| {
+            self.lifetime_res_to_generic_param(ident, node_id, res)
+        }));
         let generic_params = self.arena.alloc_from_iter(generic_params);
         debug!(?generic_params);
 
-        in_binder(self, generic_params)
+        generic_params
     }
 
     fn with_dyn_type_scope<T>(&mut self, in_scope: bool, f: impl FnOnce(&mut Self) -> T) -> T {
@@ -992,7 +984,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_assoc_ty_constraint(
         &mut self,
         constraint: &AssocConstraint,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::TypeBinding<'hir> {
         debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
         // lower generic arguments of identifier in constraint
@@ -1011,7 +1003,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         } else {
             self.arena.alloc(hir::GenericArgs::none())
         };
-        let mut itctx_tait = ImplTraitContext::TypeAliasesOpaqueTy;
+        let itctx_tait = &ImplTraitContext::TypeAliasesOpaqueTy;
 
         let kind = match constraint.kind {
             AssocConstraintKind::Equality { ref term } => {
@@ -1049,9 +1041,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     // then to an opaque type).
                     //
                     // FIXME: this is only needed until `impl Trait` is allowed in type aliases.
-                    ImplTraitContext::Disallowed(_) if self.is_in_dyn_type => {
-                        (true, &mut itctx_tait)
-                    }
+                    ImplTraitContext::Disallowed(_) if self.is_in_dyn_type => (true, itctx_tait),
 
                     // We are in the parameter position, but not within a dyn type:
                     //
@@ -1130,7 +1120,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_generic_arg(
         &mut self,
         arg: &ast::GenericArg,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::GenericArg<'hir> {
         match arg {
             ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(&lt)),
@@ -1192,7 +1182,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     #[instrument(level = "debug", skip(self))]
-    fn lower_ty(&mut self, t: &Ty, itctx: &mut ImplTraitContext) -> &'hir hir::Ty<'hir> {
+    fn lower_ty(&mut self, t: &Ty, itctx: &ImplTraitContext) -> &'hir hir::Ty<'hir> {
         self.arena.alloc(self.lower_ty_direct(t, itctx))
     }
 
@@ -1202,7 +1192,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         qself: &Option<QSelf>,
         path: &Path,
         param_mode: ParamMode,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::Ty<'hir> {
         // Check whether we should interpret this as a bare trait object.
         // This check mirrors the one in late resolution.  We only introduce this special case in
@@ -1245,7 +1235,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.ty(span, hir::TyKind::Tup(tys))
     }
 
-    fn lower_ty_direct(&mut self, t: &Ty, itctx: &mut ImplTraitContext) -> hir::Ty<'hir> {
+    fn lower_ty_direct(&mut self, t: &Ty, itctx: &ImplTraitContext) -> hir::Ty<'hir> {
         let kind = match t.kind {
             TyKind::Infer => hir::TyKind::Infer,
             TyKind::Err => hir::TyKind::Err,
@@ -1268,15 +1258,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
             }
             TyKind::BareFn(ref f) => {
-                self.lower_lifetime_binder(t.id, &f.generic_params, |lctx, generic_params| {
-                    hir::TyKind::BareFn(lctx.arena.alloc(hir::BareFnTy {
-                        generic_params,
-                        unsafety: lctx.lower_unsafety(f.unsafety),
-                        abi: lctx.lower_extern(f.ext),
-                        decl: lctx.lower_fn_decl(&f.decl, None, t.span, FnDeclKind::Pointer, None),
-                        param_names: lctx.lower_fn_params_to_names(&f.decl),
-                    }))
-                })
+                let generic_params = self.lower_lifetime_binder(t.id, &f.generic_params);
+                hir::TyKind::BareFn(self.arena.alloc(hir::BareFnTy {
+                    generic_params,
+                    unsafety: self.lower_unsafety(f.unsafety),
+                    abi: self.lower_extern(f.ext),
+                    decl: self.lower_fn_decl(&f.decl, None, t.span, FnDeclKind::Pointer, None),
+                    param_names: self.lower_fn_params_to_names(&f.decl),
+                }))
             }
             TyKind::Never => hir::TyKind::Never,
             TyKind::Tup(ref tys) => hir::TyKind::Tup(
@@ -1357,7 +1346,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         def_node_id,
                         bounds,
                         false,
-                        &mut ImplTraitContext::TypeAliasesOpaqueTy,
+                        &ImplTraitContext::TypeAliasesOpaqueTy,
                     ),
                     ImplTraitContext::Universal => {
                         let span = t.span;
@@ -1444,7 +1433,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         opaque_ty_node_id: NodeId,
         bounds: &GenericBounds,
         in_trait: bool,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::TyKind<'hir> {
         // Make sure we know that some funky desugaring has been going on here.
         // This is a first: there is code in other places like for loop
@@ -1690,11 +1679,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
         let inputs = self.arena.alloc_from_iter(inputs.iter().map(|param| {
             if fn_node_id.is_some() {
-                self.lower_ty_direct(&param.ty, &mut ImplTraitContext::Universal)
+                self.lower_ty_direct(&param.ty, &ImplTraitContext::Universal)
             } else {
                 self.lower_ty_direct(
                     &param.ty,
-                    &mut ImplTraitContext::Disallowed(match kind {
+                    &ImplTraitContext::Disallowed(match kind {
                         FnDeclKind::Fn | FnDeclKind::Inherent => {
                             unreachable!("fn should allow in-band lifetimes")
                         }
@@ -2093,7 +2082,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_param_bound(
         &mut self,
         tpb: &GenericBound,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::GenericBound<'hir> {
         match tpb {
             GenericBound::Trait(p, modifier) => hir::GenericBound::Trait(
@@ -2209,7 +2198,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             GenericParamKind::Type { ref default, .. } => {
                 let kind = hir::GenericParamKind::Type {
                     default: default.as_ref().map(|x| {
-                        self.lower_ty(x, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type))
+                        self.lower_ty(x, &ImplTraitContext::Disallowed(ImplTraitPosition::Type))
                     }),
                     synthetic: false,
                 };
@@ -2217,8 +2206,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 (hir::ParamName::Plain(self.lower_ident(param.ident)), kind)
             }
             GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
-                let ty =
-                    self.lower_ty(&ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::Type));
+                let ty = self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                 let default = default.as_ref().map(|def| self.lower_anon_const(def));
                 (
                     hir::ParamName::Plain(self.lower_ident(param.ident)),
@@ -2228,11 +2216,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_trait_ref(
-        &mut self,
-        p: &TraitRef,
-        itctx: &mut ImplTraitContext,
-    ) -> hir::TraitRef<'hir> {
+    fn lower_trait_ref(&mut self, p: &TraitRef, itctx: &ImplTraitContext) -> hir::TraitRef<'hir> {
         let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
             hir::QPath::Resolved(None, path) => path,
             qpath => panic!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
@@ -2244,19 +2228,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_poly_trait_ref(
         &mut self,
         p: &PolyTraitRef,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::PolyTraitRef<'hir> {
-        self.lower_lifetime_binder(
-            p.trait_ref.ref_id,
-            &p.bound_generic_params,
-            |lctx, bound_generic_params| {
-                let trait_ref = lctx.lower_trait_ref(&p.trait_ref, itctx);
-                hir::PolyTraitRef { bound_generic_params, trait_ref, span: lctx.lower_span(p.span) }
-            },
-        )
+        let bound_generic_params =
+            self.lower_lifetime_binder(p.trait_ref.ref_id, &p.bound_generic_params);
+        let trait_ref = self.lower_trait_ref(&p.trait_ref, itctx);
+        hir::PolyTraitRef { bound_generic_params, trait_ref, span: self.lower_span(p.span) }
     }
 
-    fn lower_mt(&mut self, mt: &MutTy, itctx: &mut ImplTraitContext) -> hir::MutTy<'hir> {
+    fn lower_mt(&mut self, mt: &MutTy, itctx: &ImplTraitContext) -> hir::MutTy<'hir> {
         hir::MutTy { ty: self.lower_ty(&mt.ty, itctx), mutbl: mt.mutbl }
     }
 
@@ -2264,17 +2244,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_param_bounds(
         &mut self,
         bounds: &[GenericBound],
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::GenericBounds<'hir> {
         self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, itctx))
     }
 
-    fn lower_param_bounds_mut<'s, 'b>(
+    fn lower_param_bounds_mut<'s>(
         &'s mut self,
         bounds: &'s [GenericBound],
-        itctx: &'b mut ImplTraitContext,
-    ) -> impl Iterator<Item = hir::GenericBound<'hir>> + Captures<'s> + Captures<'a> + Captures<'b>
-    {
+        itctx: &'s ImplTraitContext,
+    ) -> impl Iterator<Item = hir::GenericBound<'hir>> + Captures<'s> + Captures<'a> {
         bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx))
     }
 
@@ -2304,7 +2283,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             node_id,
             &GenericParamKind::Type { default: None },
             bounds,
-            &mut ImplTraitContext::Universal,
+            &ImplTraitContext::Universal,
             hir::PredicateOrigin::ImplTrait,
         );
 
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index a3d864023a9..6bb1bb9eace 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -22,7 +22,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         qself: &Option<QSelf>,
         p: &Path,
         param_mode: ParamMode,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::QPath<'hir> {
         let qself_position = qself.as_ref().map(|q| q.position);
         let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
@@ -156,7 +156,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     segment,
                     param_mode,
                     ParenthesizedGenericArgs::Err,
-                    &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                    &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                 )
             })),
             span: self.lower_span(p.span),
@@ -180,7 +180,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         segment: &PathSegment,
         param_mode: ParamMode,
         parenthesized_generic_args: ParenthesizedGenericArgs,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> hir::PathSegment<'hir> {
         debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment,);
         let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
@@ -316,7 +316,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         data: &AngleBracketedArgs,
         param_mode: ParamMode,
-        itctx: &mut ImplTraitContext,
+        itctx: &ImplTraitContext,
     ) -> (GenericArgsCtor<'hir>, bool) {
         let has_non_lt_args = data.args.iter().any(|arg| match arg {
             AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
@@ -350,14 +350,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // we generally don't permit such things (see #51008).
         let ParenthesizedArgs { span, inputs, inputs_span, output } = data;
         let inputs = self.arena.alloc_from_iter(inputs.iter().map(|ty| {
-            self.lower_ty_direct(
-                ty,
-                &mut ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam),
-            )
+            self.lower_ty_direct(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam))
         }));
         let output_ty = match output {
-            FnRetTy::Ty(ty) => self
-                .lower_ty(&ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn)),
+            FnRetTy::Ty(ty) => {
+                self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn))
+            }
             FnRetTy::Default(_) => self.arena.alloc(self.ty_tup(*span, &[])),
         };
         let args = smallvec![GenericArg::Type(self.arena.alloc(self.ty_tup(*inputs_span, inputs)))];
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index b190a7062de..e55b5ce71cd 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -698,11 +698,22 @@ impl<'a> Parser<'a> {
                     let semicolon_span = self.token.span;
                     // We have to bail or we'll potentially never make progress.
                     let non_item_span = self.token.span;
-                    self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                    let is_let = self.token.is_keyword(kw::Let);
+
                     let mut err = self.struct_span_err(non_item_span, "non-item in item list");
-                    err.span_label(open_brace_span, "item list starts here")
-                        .span_label(non_item_span, "non-item starts here")
-                        .span_label(self.prev_token.span, "item list ends here");
+                    self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                    if is_let {
+                        err.span_suggestion(
+                            non_item_span,
+                            "consider using `const` instead of `let` for associated const",
+                            "const",
+                            Applicability::MachineApplicable,
+                        );
+                    } else {
+                        err.span_label(open_brace_span, "item list starts here")
+                            .span_label(non_item_span, "non-item starts here")
+                            .span_label(self.prev_token.span, "item list ends here");
+                    }
                     if is_unnecessary_semicolon {
                         err.span_suggestion(
                             semicolon_span,
diff --git a/compiler/rustc_parse/src/parser/nonterminal.rs b/compiler/rustc_parse/src/parser/nonterminal.rs
index e215b6872bf..103dd801257 100644
--- a/compiler/rustc_parse/src/parser/nonterminal.rs
+++ b/compiler/rustc_parse/src/parser/nonterminal.rs
@@ -66,18 +66,18 @@ impl<'a> Parser<'a> {
             },
             NonterminalKind::PatParam { .. } | NonterminalKind::PatWithOr { .. } => {
                 match token.kind {
-                token::Ident(..) |                  // box, ref, mut, and other identifiers (can stricten)
-                token::OpenDelim(Delimiter::Parenthesis) |    // tuple pattern
-                token::OpenDelim(Delimiter::Bracket) |  // slice pattern
-                token::BinOp(token::And) |          // reference
-                token::BinOp(token::Minus) |        // negative literal
-                token::AndAnd |                     // double reference
-                token::Literal(..) |                // literal
-                token::DotDot |                     // range pattern (future compat)
-                token::DotDotDot |                  // range pattern (future compat)
-                token::ModSep |                     // path
-                token::Lt |                         // path (UFCS constant)
-                token::BinOp(token::Shl) => true,   // path (double UFCS)
+                token::Ident(..) |                          // box, ref, mut, and other identifiers (can stricten)
+                token::OpenDelim(Delimiter::Parenthesis) |  // tuple pattern
+                token::OpenDelim(Delimiter::Bracket) |      // slice pattern
+                token::BinOp(token::And) |                  // reference
+                token::BinOp(token::Minus) |                // negative literal
+                token::AndAnd |                             // double reference
+                token::Literal(..) |                        // literal
+                token::DotDot |                             // range pattern (future compat)
+                token::DotDotDot |                          // range pattern (future compat)
+                token::ModSep |                             // path
+                token::Lt |                                 // path (UFCS constant)
+                token::BinOp(token::Shl) => true,           // path (double UFCS)
                 // leading vert `|` or-pattern
                 token::BinOp(token::Or) =>  matches!(kind, NonterminalKind::PatWithOr {..}),
                 token::Interpolated(ref nt) => may_be_ident(nt),
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 8a8cc272e81..932533db05c 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -412,7 +412,13 @@ impl Options {
 
         let to_check = matches.opt_strs("check-theme");
         if !to_check.is_empty() {
-            let paths = theme::load_css_paths(static_files::themes::LIGHT.as_bytes());
+            let paths = match theme::load_css_paths(static_files::themes::LIGHT) {
+                Ok(p) => p,
+                Err(e) => {
+                    diag.struct_err(&e.to_string()).emit();
+                    return Err(1);
+                }
+            };
             let mut errors = 0;
 
             println!("rustdoc: [check-theme] Starting tests! (Ignoring all other arguments)");
@@ -547,7 +553,13 @@ impl Options {
 
         let mut themes = Vec::new();
         if matches.opt_present("theme") {
-            let paths = theme::load_css_paths(static_files::themes::LIGHT.as_bytes());
+            let paths = match theme::load_css_paths(static_files::themes::LIGHT) {
+                Ok(p) => p,
+                Err(e) => {
+                    diag.struct_err(&e.to_string()).emit();
+                    return Err(1);
+                }
+            };
 
             for (theme_file, theme_s) in
                 matches.opt_strs("theme").iter().map(|s| (PathBuf::from(&s), s.to_owned()))
diff --git a/src/librustdoc/html/highlight.rs b/src/librustdoc/html/highlight.rs
index 1e6cab8fcd3..8922bf37785 100644
--- a/src/librustdoc/html/highlight.rs
+++ b/src/librustdoc/html/highlight.rs
@@ -29,6 +29,8 @@ pub(crate) struct HrefContext<'a, 'b, 'c> {
     /// This field is used to know "how far" from the top of the directory we are to link to either
     /// documentation pages or other source pages.
     pub(crate) root_path: &'c str,
+    /// This field is used to calculate precise local URLs.
+    pub(crate) current_href: &'c str,
 }
 
 /// Decorations are represented as a map from CSS class to vector of character ranges.
@@ -977,9 +979,9 @@ fn string_without_closing_tag<T: Display>(
                 // a link to their definition can be generated using this:
                 // https://github.com/rust-lang/rust/blob/60f1a2fc4b535ead9c85ce085fdce49b1b097531/src/librustdoc/html/render/context.rs#L315-L338
                 match href {
-                    LinkFromSrc::Local(span) => context
-                        .href_from_span(*span, true)
-                        .map(|s| format!("{}{}", href_context.root_path, s)),
+                    LinkFromSrc::Local(span) => {
+                        context.href_from_span_relative(*span, href_context.current_href)
+                    }
                     LinkFromSrc::External(def_id) => {
                         format::href_with_root_path(*def_id, context, Some(href_context.root_path))
                             .ok()
diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
index 01b96dc7215..62def4a94e8 100644
--- a/src/librustdoc/html/render/context.rs
+++ b/src/librustdoc/html/render/context.rs
@@ -31,6 +31,7 @@ use crate::formats::FormatRenderer;
 use crate::html::escape::Escape;
 use crate::html::format::{join_with_double_colon, Buffer};
 use crate::html::markdown::{self, plain_text_summary, ErrorCodes, IdMap};
+use crate::html::url_parts_builder::UrlPartsBuilder;
 use crate::html::{layout, sources};
 use crate::scrape_examples::AllCallLocations;
 use crate::try_err;
@@ -370,6 +371,35 @@ impl<'tcx> Context<'tcx> {
             anchor = anchor
         ))
     }
+
+    pub(crate) fn href_from_span_relative(
+        &self,
+        span: clean::Span,
+        relative_to: &str,
+    ) -> Option<String> {
+        self.href_from_span(span, false).map(|s| {
+            let mut url = UrlPartsBuilder::new();
+            let mut dest_href_parts = s.split('/');
+            let mut cur_href_parts = relative_to.split('/');
+            for (cur_href_part, dest_href_part) in (&mut cur_href_parts).zip(&mut dest_href_parts) {
+                if cur_href_part != dest_href_part {
+                    url.push(dest_href_part);
+                    break;
+                }
+            }
+            for dest_href_part in dest_href_parts {
+                url.push(dest_href_part);
+            }
+            let loline = span.lo(self.sess()).line;
+            let hiline = span.hi(self.sess()).line;
+            format!(
+                "{}{}#{}",
+                "../".repeat(cur_href_parts.count()),
+                url.finish(),
+                if loline == hiline { loline.to_string() } else { format!("{loline}-{hiline}") }
+            )
+        })
+    }
 }
 
 /// Generates the documentation for `crate` into the directory `dst`
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index f37c54e4298..2e2bee78b95 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -288,11 +288,14 @@ pub(crate) fn print_src(
         }
     }
     line_numbers.write_str("</pre>");
+    let current_href = &context
+        .href_from_span(clean::Span::new(file_span), false)
+        .expect("only local crates should have sources emitted");
     highlight::render_source_with_highlighting(
         s,
         buf,
         line_numbers,
-        highlight::HrefContext { context, file_span, root_path },
+        highlight::HrefContext { context, file_span, root_path, current_href },
         decoration_info,
     );
 }
diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index b0dcd36d6b3..ccb30262060 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -497,9 +497,6 @@ img {
 	font-weight: 500;
 }
 
-.block {
-	padding: 0;
-}
 .block ul, .block li {
 	padding: 0;
 	margin: 0;
@@ -1865,12 +1862,6 @@ in storage.js plus the media query with (min-width: 701px)
 		display: none !important;
 	}
 
-	.notable-traits {
-		position: absolute;
-		left: -22px;
-		top: 24px;
-	}
-
 	#titles > button > div.count {
 		display: block;
 	}
diff --git a/src/librustdoc/theme.rs b/src/librustdoc/theme.rs
index 0118d7dd207..e7a26cb346e 100644
--- a/src/librustdoc/theme.rs
+++ b/src/librustdoc/theme.rs
@@ -1,271 +1,252 @@
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxHashMap;
+use std::collections::hash_map::Entry;
 use std::fs;
-use std::hash::{Hash, Hasher};
+use std::iter::Peekable;
 use std::path::Path;
+use std::str::Chars;
 
 use rustc_errors::Handler;
 
 #[cfg(test)]
 mod tests;
 
-#[derive(Debug, Clone, Eq)]
+#[derive(Debug)]
 pub(crate) struct CssPath {
-    pub(crate) name: String,
-    pub(crate) children: FxHashSet<CssPath>,
-}
-
-// This PartialEq implementation IS NOT COMMUTATIVE!!!
-//
-// The order is very important: the second object must have all first's rules.
-// However, the first is not required to have all of the second's rules.
-impl PartialEq for CssPath {
-    fn eq(&self, other: &CssPath) -> bool {
-        if self.name != other.name {
-            false
-        } else {
-            for child in &self.children {
-                if !other.children.iter().any(|c| child == c) {
-                    return false;
-                }
-            }
-            true
+    pub(crate) rules: FxHashMap<String, String>,
+    pub(crate) children: FxHashMap<String, CssPath>,
+}
+
+/// When encountering a `"` or a `'`, returns the whole string, including the quote characters.
+fn get_string(iter: &mut Peekable<Chars<'_>>, string_start: char, buffer: &mut String) {
+    buffer.push(string_start);
+    while let Some(c) = iter.next() {
+        buffer.push(c);
+        if c == '\\' {
+            iter.next();
+        } else if c == string_start {
+            break;
         }
     }
 }
 
-impl Hash for CssPath {
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.name.hash(state);
-        for x in &self.children {
-            x.hash(state);
+fn get_inside_paren(
+    iter: &mut Peekable<Chars<'_>>,
+    paren_start: char,
+    paren_end: char,
+    buffer: &mut String,
+) {
+    buffer.push(paren_start);
+    while let Some(c) = iter.next() {
+        handle_common_chars(c, buffer, iter);
+        if c == paren_end {
+            break;
         }
     }
 }
 
-impl CssPath {
-    fn new(name: String) -> CssPath {
-        CssPath { name, children: FxHashSet::default() }
+/// Skips a `/*` comment.
+fn skip_comment(iter: &mut Peekable<Chars<'_>>) {
+    while let Some(c) = iter.next() {
+        if c == '*' && iter.next() == Some('/') {
+            break;
+        }
     }
 }
 
-/// All variants contain the position they occur.
-#[derive(Debug, Clone, Copy)]
-enum Events {
-    StartLineComment(usize),
-    StartComment(usize),
-    EndComment(usize),
-    InBlock(usize),
-    OutBlock(usize),
-}
-
-impl Events {
-    fn get_pos(&self) -> usize {
-        match *self {
-            Events::StartLineComment(p)
-            | Events::StartComment(p)
-            | Events::EndComment(p)
-            | Events::InBlock(p)
-            | Events::OutBlock(p) => p,
+/// Skips a line comment (`//`).
+fn skip_line_comment(iter: &mut Peekable<Chars<'_>>) {
+    while let Some(c) = iter.next() {
+        if c == '\n' {
+            break;
         }
     }
-
-    fn is_comment(&self) -> bool {
-        matches!(
-            self,
-            Events::StartLineComment(_) | Events::StartComment(_) | Events::EndComment(_)
-        )
-    }
 }
 
-fn previous_is_line_comment(events: &[Events]) -> bool {
-    matches!(events.last(), Some(&Events::StartLineComment(_)))
-}
-
-fn is_line_comment(pos: usize, v: &[u8], events: &[Events]) -> bool {
-    if let Some(&Events::StartComment(_)) = events.last() {
-        return false;
+fn handle_common_chars(c: char, buffer: &mut String, iter: &mut Peekable<Chars<'_>>) {
+    match c {
+        '"' | '\'' => get_string(iter, c, buffer),
+        '/' if iter.peek() == Some(&'*') => skip_comment(iter),
+        '/' if iter.peek() == Some(&'/') => skip_line_comment(iter),
+        '(' => get_inside_paren(iter, c, ')', buffer),
+        '[' => get_inside_paren(iter, c, ']', buffer),
+        _ => buffer.push(c),
     }
-    v[pos + 1] == b'/'
 }
 
-fn load_css_events(v: &[u8]) -> Vec<Events> {
-    let mut pos = 0;
-    let mut events = Vec::with_capacity(100);
-
-    while pos + 1 < v.len() {
-        match v[pos] {
-            b'/' if v[pos + 1] == b'*' => {
-                events.push(Events::StartComment(pos));
-                pos += 1;
-            }
-            b'/' if is_line_comment(pos, v, &events) => {
-                events.push(Events::StartLineComment(pos));
-                pos += 1;
-            }
-            b'\n' if previous_is_line_comment(&events) => {
-                events.push(Events::EndComment(pos));
-            }
-            b'*' if v[pos + 1] == b'/' => {
-                events.push(Events::EndComment(pos + 2));
-                pos += 1;
-            }
-            b'{' if !previous_is_line_comment(&events) => {
-                if let Some(&Events::StartComment(_)) = events.last() {
-                    pos += 1;
-                    continue;
-                }
-                events.push(Events::InBlock(pos + 1));
-            }
-            b'}' if !previous_is_line_comment(&events) => {
-                if let Some(&Events::StartComment(_)) = events.last() {
-                    pos += 1;
-                    continue;
-                }
-                events.push(Events::OutBlock(pos + 1));
-            }
-            _ => {}
+/// Returns a CSS property name. Ends when encountering a `:` character.
+///
+/// If the `:` character isn't found, returns `None`.
+///
+/// If a `{` character is encountered, returns an error.
+fn parse_property_name(iter: &mut Peekable<Chars<'_>>) -> Result<Option<String>, String> {
+    let mut content = String::new();
+
+    while let Some(c) = iter.next() {
+        match c {
+            ':' => return Ok(Some(content.trim().to_owned())),
+            '{' => return Err("Unexpected `{` in a `{}` block".to_owned()),
+            '}' => break,
+            _ => handle_common_chars(c, &mut content, iter),
         }
-        pos += 1;
     }
-    events
-}
-
-fn get_useful_next(events: &[Events], pos: &mut usize) -> Option<Events> {
-    while *pos < events.len() {
-        if !events[*pos].is_comment() {
-            return Some(events[*pos]);
+    Ok(None)
+}
+
+/// Try to get the value of a CSS property (the `#fff` in `color: #fff`). It'll stop when it
+/// encounters a `{` or a `;` character.
+///
+/// It returns the value string and a boolean set to `true` if the value is ended with a `}` because
+/// it means that the parent block is done and that we should notify the parent caller.
+fn parse_property_value(iter: &mut Peekable<Chars<'_>>) -> (String, bool) {
+    let mut value = String::new();
+    let mut out_block = false;
+
+    while let Some(c) = iter.next() {
+        match c {
+            ';' => break,
+            '}' => {
+                out_block = true;
+                break;
+            }
+            _ => handle_common_chars(c, &mut value, iter),
         }
-        *pos += 1;
     }
-    None
+    (value.trim().to_owned(), out_block)
 }
 
-fn get_previous_positions(events: &[Events], mut pos: usize) -> Vec<usize> {
-    let mut ret = Vec::with_capacity(3);
+/// This is used to parse inside a CSS `{}` block. If we encounter a new `{` inside it, we consider
+/// it as a new block and therefore recurse into `parse_rules`.
+fn parse_rules(
+    content: &str,
+    selector: String,
+    iter: &mut Peekable<Chars<'_>>,
+    paths: &mut FxHashMap<String, CssPath>,
+) -> Result<(), String> {
+    let mut rules = FxHashMap::default();
+    let mut children = FxHashMap::default();
 
-    ret.push(events[pos].get_pos());
-    if pos > 0 {
-        pos -= 1;
-    }
     loop {
-        if pos < 1 || !events[pos].is_comment() {
-            let x = events[pos].get_pos();
-            if *ret.last().unwrap() != x {
-                ret.push(x);
-            } else {
-                ret.push(0);
+        // If the parent isn't a "normal" CSS selector, we only expect sub-selectors and not CSS
+        // properties.
+        if selector.starts_with('@') {
+            parse_selectors(content, iter, &mut children)?;
+            break;
+        }
+        let rule = match parse_property_name(iter)? {
+            Some(r) => {
+                if r.is_empty() {
+                    return Err(format!("Found empty rule in selector `{selector}`"));
+                }
+                r
+            }
+            None => break,
+        };
+        let (value, out_block) = parse_property_value(iter);
+        if value.is_empty() {
+            return Err(format!("Found empty value for rule `{rule}` in selector `{selector}`"));
+        }
+        match rules.entry(rule) {
+            Entry::Occupied(mut o) => {
+                *o.get_mut() = value;
+            }
+            Entry::Vacant(v) => {
+                v.insert(value);
             }
+        }
+        if out_block {
             break;
         }
-        ret.push(events[pos].get_pos());
-        pos -= 1;
-    }
-    if ret.len() & 1 != 0 && events[pos].is_comment() {
-        ret.push(0);
     }
-    ret.iter().rev().cloned().collect()
-}
-
-fn build_rule(v: &[u8], positions: &[usize]) -> String {
-    minifier::css::minify(
-        &positions
-            .chunks(2)
-            .map(|x| ::std::str::from_utf8(&v[x[0]..x[1]]).unwrap_or(""))
-            .collect::<String>()
-            .trim()
-            .chars()
-            .filter_map(|c| match c {
-                '\n' | '\t' => Some(' '),
-                '/' | '{' | '}' => None,
-                c => Some(c),
-            })
-            .collect::<String>()
-            .split(' ')
-            .filter(|s| !s.is_empty())
-            .intersperse(" ")
-            .collect::<String>(),
-    )
-    .map(|css| css.to_string())
-    .unwrap_or_else(|_| String::new())
-}
-
-fn inner(v: &[u8], events: &[Events], pos: &mut usize) -> FxHashSet<CssPath> {
-    let mut paths = Vec::with_capacity(50);
 
-    while *pos < events.len() {
-        if let Some(Events::OutBlock(_)) = get_useful_next(events, pos) {
-            *pos += 1;
-            break;
+    match paths.entry(selector) {
+        Entry::Occupied(mut o) => {
+            let v = o.get_mut();
+            for (key, value) in rules.into_iter() {
+                v.rules.insert(key, value);
+            }
+            for (sel, child) in children.into_iter() {
+                v.children.insert(sel, child);
+            }
         }
-        if let Some(Events::InBlock(_)) = get_useful_next(events, pos) {
-            paths.push(CssPath::new(build_rule(v, &get_previous_positions(events, *pos))));
-            *pos += 1;
+        Entry::Vacant(v) => {
+            v.insert(CssPath { rules, children });
         }
-        while let Some(Events::InBlock(_)) = get_useful_next(events, pos) {
-            if let Some(ref mut path) = paths.last_mut() {
-                for entry in inner(v, events, pos).iter() {
-                    path.children.insert(entry.clone());
-                }
+    }
+    Ok(())
+}
+
+pub(crate) fn parse_selectors(
+    content: &str,
+    iter: &mut Peekable<Chars<'_>>,
+    paths: &mut FxHashMap<String, CssPath>,
+) -> Result<(), String> {
+    let mut selector = String::new();
+
+    while let Some(c) = iter.next() {
+        match c {
+            '{' => {
+                let s = minifier::css::minify(selector.trim()).map(|s| s.to_string())?;
+                parse_rules(content, s, iter, paths)?;
+                selector.clear();
             }
-        }
-        if let Some(Events::OutBlock(_)) = get_useful_next(events, pos) {
-            *pos += 1;
+            '}' => break,
+            ';' => selector.clear(), // We don't handle inline selectors like `@import`.
+            _ => handle_common_chars(c, &mut selector, iter),
         }
     }
-    paths.iter().cloned().collect()
-}
-
-pub(crate) fn load_css_paths(v: &[u8]) -> CssPath {
-    let events = load_css_events(v);
-    let mut pos = 0;
-
-    let mut parent = CssPath::new("parent".to_owned());
-    parent.children = inner(v, &events, &mut pos);
-    parent
-}
-
-pub(crate) fn get_differences(against: &CssPath, other: &CssPath, v: &mut Vec<String>) {
-    if against.name == other.name {
-        for child in &against.children {
-            let mut found = false;
-            let mut found_working = false;
-            let mut tmp = Vec::new();
-
-            for other_child in &other.children {
-                if child.name == other_child.name {
-                    if child != other_child {
-                        get_differences(child, other_child, &mut tmp);
-                    } else {
-                        found_working = true;
+    Ok(())
+}
+
+/// The entry point to parse the CSS rules. Every time we encounter a `{`, we then parse the rules
+/// inside it.
+pub(crate) fn load_css_paths(content: &str) -> Result<FxHashMap<String, CssPath>, String> {
+    let mut iter = content.chars().peekable();
+    let mut paths = FxHashMap::default();
+
+    parse_selectors(content, &mut iter, &mut paths)?;
+    Ok(paths)
+}
+
+pub(crate) fn get_differences(
+    origin: &FxHashMap<String, CssPath>,
+    against: &FxHashMap<String, CssPath>,
+    v: &mut Vec<String>,
+) {
+    for (selector, entry) in origin.iter() {
+        match against.get(selector) {
+            Some(a) => {
+                get_differences(&entry.children, &a.children, v);
+                if selector == ":root" {
+                    // We need to check that all variables have been set.
+                    for rule in entry.rules.keys() {
+                        if !a.rules.contains_key(rule) {
+                            v.push(format!("  Missing CSS variable `{rule}` in `:root`"));
+                        }
                     }
-                    found = true;
-                    break;
                 }
             }
-            if !found {
-                v.push(format!("  Missing \"{}\" rule", child.name));
-            } else if !found_working {
-                v.extend(tmp.iter().cloned());
-            }
+            None => v.push(format!("  Missing rule `{selector}`")),
         }
     }
 }
 
 pub(crate) fn test_theme_against<P: AsRef<Path>>(
     f: &P,
-    against: &CssPath,
+    origin: &FxHashMap<String, CssPath>,
     diag: &Handler,
 ) -> (bool, Vec<String>) {
-    let data = match fs::read(f) {
+    let against = match fs::read_to_string(f)
+        .map_err(|e| e.to_string())
+        .and_then(|data| load_css_paths(&data))
+    {
         Ok(c) => c,
         Err(e) => {
-            diag.struct_err(&e.to_string()).emit();
+            diag.struct_err(&e).emit();
             return (false, vec![]);
         }
     };
 
-    let paths = load_css_paths(&data);
     let mut ret = vec![];
-    get_differences(against, &paths, &mut ret);
+    get_differences(origin, &against, &mut ret);
     (true, ret)
 }
diff --git a/src/librustdoc/theme/tests.rs b/src/librustdoc/theme/tests.rs
index ae8f43c6d55..08a174d27d3 100644
--- a/src/librustdoc/theme/tests.rs
+++ b/src/librustdoc/theme/tests.rs
@@ -44,11 +44,7 @@ rule j end {}
 "#;
 
     let mut ret = Vec::new();
-    get_differences(
-        &load_css_paths(against.as_bytes()),
-        &load_css_paths(text.as_bytes()),
-        &mut ret,
-    );
+    get_differences(&load_css_paths(against).unwrap(), &load_css_paths(text).unwrap(), &mut ret);
     assert!(ret.is_empty());
 }
 
@@ -61,46 +57,45 @@ a
 c // sdf
 d {}
 "#;
-    let paths = load_css_paths(text.as_bytes());
-    assert!(paths.children.contains(&CssPath::new("a b c d".to_owned())));
+    let paths = load_css_paths(text).unwrap();
+    assert!(paths.contains_key(&"a b c d".to_owned()));
 }
 
 #[test]
 fn test_comparison() {
-    let x = r#"
-a {
-    b {
-        c {}
-    }
+    let origin = r#"
+@a {
+    b {}
+    c {}
 }
 "#;
 
-    let y = r#"
-a {
+    let against = r#"
+@a {
     b {}
 }
 "#;
 
-    let against = load_css_paths(y.as_bytes());
-    let other = load_css_paths(x.as_bytes());
+    let origin = load_css_paths(origin).unwrap();
+    let against = load_css_paths(against).unwrap();
 
     let mut ret = Vec::new();
-    get_differences(&against, &other, &mut ret);
+    get_differences(&against, &origin, &mut ret);
     assert!(ret.is_empty());
-    get_differences(&other, &against, &mut ret);
-    assert_eq!(ret, vec!["  Missing \"c\" rule".to_owned()]);
+    get_differences(&origin, &against, &mut ret);
+    assert_eq!(ret, vec!["  Missing rule `c`".to_owned()]);
 }
 
 #[test]
 fn check_empty_css() {
-    let events = load_css_events(&[]);
-    assert_eq!(events.len(), 0);
+    let paths = load_css_paths("").unwrap();
+    assert_eq!(paths.len(), 0);
 }
 
 #[test]
 fn check_invalid_css() {
-    let events = load_css_events(b"*");
-    assert_eq!(events.len(), 0);
+    let paths = load_css_paths("*").unwrap();
+    assert_eq!(paths.len(), 0);
 }
 
 #[test]
@@ -108,10 +103,85 @@ fn test_with_minification() {
     let text = include_str!("../html/static/css/themes/dark.css");
     let minified = minifier::css::minify(&text).expect("CSS minification failed").to_string();
 
-    let against = load_css_paths(text.as_bytes());
-    let other = load_css_paths(minified.as_bytes());
+    let against = load_css_paths(text).unwrap();
+    let other = load_css_paths(&minified).unwrap();
+
+    let mut ret = Vec::new();
+    get_differences(&against, &other, &mut ret);
+    assert!(ret.is_empty());
+}
+
+#[test]
+fn test_media() {
+    let text = r#"
+@media (min-width: 701px) {
+    a:hover {
+        color: #fff;
+    }
+
+    b {
+        x: y;
+    }
+}
+
+@media (max-width: 1001px) {
+    b {
+        x: y;
+    }
+}
+"#;
+
+    let paths = load_css_paths(text).unwrap();
+    let p = paths.get("@media (min-width:701px)");
+    assert!(p.is_some());
+    let p = p.unwrap();
+    assert!(p.children.get("a:hover").is_some());
+    assert!(p.children.get("b").is_some());
+
+    let p = paths.get("@media (max-width:1001px)");
+    assert!(p.is_some());
+    let p = p.unwrap();
+    assert!(p.children.get("b").is_some());
+}
+
+#[test]
+fn test_css_variables() {
+    let x = r#"
+:root {
+    --a: #fff;
+}
+"#;
+
+    let y = r#"
+:root {
+    --a: #fff;
+    --b: #fff;
+}
+"#;
+
+    let against = load_css_paths(x).unwrap();
+    let other = load_css_paths(y).unwrap();
 
     let mut ret = Vec::new();
     get_differences(&against, &other, &mut ret);
     assert!(ret.is_empty());
+    get_differences(&other, &against, &mut ret);
+    assert_eq!(ret, vec!["  Missing CSS variable `--b` in `:root`".to_owned()]);
+}
+
+#[test]
+fn test_weird_rule_value() {
+    let x = r#"
+a[text=("a")] {
+    b: url({;}.png);
+    c: #fff
+}
+"#;
+
+    let paths = load_css_paths(&x).unwrap();
+    let p = paths.get("a[text=(\"a\")]");
+    assert!(p.is_some());
+    let p = p.unwrap();
+    assert_eq!(p.rules.get("b"), Some(&"url({;}.png)".to_owned()));
+    assert_eq!(p.rules.get("c"), Some(&"#fff".to_owned()));
 }
diff --git a/src/test/rustdoc/check-source-code-urls-to-def-std.rs b/src/test/rustdoc/check-source-code-urls-to-def-std.rs
index 3396b234a77..e12d8445f4f 100644
--- a/src/test/rustdoc/check-source-code-urls-to-def-std.rs
+++ b/src/test/rustdoc/check-source-code-urls-to-def-std.rs
@@ -9,7 +9,7 @@ fn babar() {}
 // @has - '//a[@href="{{channel}}/std/primitive.u32.html"]' 'u32'
 // @has - '//a[@href="{{channel}}/std/primitive.str.html"]' 'str'
 // @has - '//a[@href="{{channel}}/std/primitive.bool.html"]' 'bool'
-// @has - '//a[@href="../../src/foo/check-source-code-urls-to-def-std.rs.html#7"]' 'babar'
+// @has - '//a[@href="#7"]' 'babar'
 pub fn foo(a: u32, b: &str, c: String) {
     let x = 12;
     let y: bool = true;
@@ -31,12 +31,12 @@ macro_rules! data {
 pub fn another_foo() {
     // This is known limitation: if the macro doesn't generate anything, the visitor
     // can't find any item or anything that could tell us that it comes from expansion.
-    // @!has - '//a[@href="../../src/foo/check-source-code-urls-to-def-std.rs.html#19"]' 'yolo!'
+    // @!has - '//a[@href="#19"]' 'yolo!'
     yolo!();
     // @has - '//a[@href="{{channel}}/std/macro.eprintln.html"]' 'eprintln!'
     eprintln!();
-    // @has - '//a[@href="../../src/foo/check-source-code-urls-to-def-std.rs.html#27-29"]' 'data!'
+    // @has - '//a[@href="#27-29"]' 'data!'
     let x = data!(4);
-    // @has - '//a[@href="../../src/foo/check-source-code-urls-to-def-std.rs.html#23-25"]' 'bar!'
+    // @has - '//a[@href="#23-25"]' 'bar!'
     bar!(x);
 }
diff --git a/src/test/rustdoc/check-source-code-urls-to-def.rs b/src/test/rustdoc/check-source-code-urls-to-def.rs
index ec44e1bc65c..d00a3e35519 100644
--- a/src/test/rustdoc/check-source-code-urls-to-def.rs
+++ b/src/test/rustdoc/check-source-code-urls-to-def.rs
@@ -10,14 +10,14 @@ extern crate source_code;
 
 // @has 'src/foo/check-source-code-urls-to-def.rs.html'
 
-// @has - '//a[@href="../../src/foo/auxiliary/source-code-bar.rs.html#1-17"]' 'bar'
+// @has - '//a[@href="auxiliary/source-code-bar.rs.html#1-17"]' 'bar'
 #[path = "auxiliary/source-code-bar.rs"]
 pub mod bar;
 
-// @count - '//a[@href="../../src/foo/auxiliary/source-code-bar.rs.html#5"]' 4
+// @count - '//a[@href="auxiliary/source-code-bar.rs.html#5"]' 4
 use bar::Bar;
-// @has - '//a[@href="../../src/foo/auxiliary/source-code-bar.rs.html#13"]' 'self'
-// @has - '//a[@href="../../src/foo/auxiliary/source-code-bar.rs.html#14"]' 'Trait'
+// @has - '//a[@href="auxiliary/source-code-bar.rs.html#13"]' 'self'
+// @has - '//a[@href="auxiliary/source-code-bar.rs.html#14"]' 'Trait'
 use bar::sub::{self, Trait};
 
 pub struct Foo;
@@ -31,26 +31,26 @@ fn babar() {}
 // @has - '//a/@href' '/struct.String.html'
 // @has - '//a/@href' '/primitive.u32.html'
 // @has - '//a/@href' '/primitive.str.html'
-// @count - '//a[@href="../../src/foo/check-source-code-urls-to-def.rs.html#23"]' 5
+// @count - '//a[@href="#23"]' 5
 // @has - '//a[@href="../../source_code/struct.SourceCode.html"]' 'source_code::SourceCode'
 pub fn foo(a: u32, b: &str, c: String, d: Foo, e: bar::Bar, f: source_code::SourceCode) {
     let x = 12;
     let y: Foo = Foo;
     let z: Bar = bar::Bar { field: Foo };
     babar();
-    // @has - '//a[@href="../../src/foo/check-source-code-urls-to-def.rs.html#26"]' 'hello'
+    // @has - '//a[@href="#26"]' 'hello'
     y.hello();
 }
 
-// @has - '//a[@href="../../src/foo/auxiliary/source-code-bar.rs.html#14"]' 'bar::sub::Trait'
-// @has - '//a[@href="../../src/foo/auxiliary/source-code-bar.rs.html#14"]' 'Trait'
+// @has - '//a[@href="auxiliary/source-code-bar.rs.html#14"]' 'bar::sub::Trait'
+// @has - '//a[@href="auxiliary/source-code-bar.rs.html#14"]' 'Trait'
 pub fn foo2<T: bar::sub::Trait, V: Trait>(t: &T, v: &V, b: bool) {}
 
 pub trait AnotherTrait {}
 pub trait WhyNot {}
 
-// @has - '//a[@href="../../src/foo/check-source-code-urls-to-def.rs.html#49"]' 'AnotherTrait'
-// @has - '//a[@href="../../src/foo/check-source-code-urls-to-def.rs.html#50"]' 'WhyNot'
+// @has - '//a[@href="#49"]' 'AnotherTrait'
+// @has - '//a[@href="#50"]' 'WhyNot'
 pub fn foo3<T, V>(t: &T, v: &V)
 where
     T: AnotherTrait,
@@ -59,7 +59,7 @@ where
 
 pub trait AnotherTrait2 {}
 
-// @has - '//a[@href="../../src/foo/check-source-code-urls-to-def.rs.html#60"]' 'AnotherTrait2'
+// @has - '//a[@href="#60"]' 'AnotherTrait2'
 pub fn foo4() {
     let x: Vec<AnotherTrait2> = Vec::new();
 }
diff --git a/src/test/ui/parser/suggest-assoc-const.fixed b/src/test/ui/parser/suggest-assoc-const.fixed
new file mode 100644
index 00000000000..259f37b23a5
--- /dev/null
+++ b/src/test/ui/parser/suggest-assoc-const.fixed
@@ -0,0 +1,10 @@
+// Issue: 101797, Suggest associated const for incorrect use of let in traits
+// run-rustfix
+trait Trait {
+    const _X: i32;
+    //~^ ERROR non-item in item list
+}
+
+fn main() {
+
+}
diff --git a/src/test/ui/parser/suggest-assoc-const.rs b/src/test/ui/parser/suggest-assoc-const.rs
new file mode 100644
index 00000000000..c7be712ec07
--- /dev/null
+++ b/src/test/ui/parser/suggest-assoc-const.rs
@@ -0,0 +1,10 @@
+// Issue: 101797, Suggest associated const for incorrect use of let in traits
+// run-rustfix
+trait Trait {
+    let _X: i32;
+    //~^ ERROR non-item in item list
+}
+
+fn main() {
+
+}
diff --git a/src/test/ui/parser/suggest-assoc-const.stderr b/src/test/ui/parser/suggest-assoc-const.stderr
new file mode 100644
index 00000000000..2ddfa07c5be
--- /dev/null
+++ b/src/test/ui/parser/suggest-assoc-const.stderr
@@ -0,0 +1,8 @@
+error: non-item in item list
+  --> $DIR/suggest-assoc-const.rs:4:5
+   |
+LL |     let _X: i32;
+   |     ^^^ help: consider using `const` instead of `let` for associated const: `const`
+
+error: aborting due to previous error
+