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-rw-r--r--compiler/rustc_resolve/Cargo.toml1
-rw-r--r--compiler/rustc_resolve/messages.ftl2
-rw-r--r--compiler/rustc_resolve/src/build_reduced_graph.rs165
-rw-r--r--compiler/rustc_resolve/src/check_unused.rs4
-rw-r--r--compiler/rustc_resolve/src/diagnostics.rs48
-rw-r--r--compiler/rustc_resolve/src/effective_visibilities.rs4
-rw-r--r--compiler/rustc_resolve/src/errors.rs59
-rw-r--r--compiler/rustc_resolve/src/ident.rs81
-rw-r--r--compiler/rustc_resolve/src/imports.rs98
-rw-r--r--compiler/rustc_resolve/src/late.rs147
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs228
-rw-r--r--compiler/rustc_resolve/src/lib.rs91
-rw-r--r--compiler/rustc_resolve/src/macros.rs77
-rw-r--r--compiler/rustc_resolve/src/rustdoc.rs17
14 files changed, 512 insertions, 510 deletions
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index 1238ce0125a..9ea9c58cfd1 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -11,7 +11,6 @@ pulldown-cmark = { version = "0.11", features = ["html"], default-features = fal
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_resolve/messages.ftl b/compiler/rustc_resolve/messages.ftl
index aa818cc9c46..39e9a9cc58a 100644
--- a/compiler/rustc_resolve/messages.ftl
+++ b/compiler/rustc_resolve/messages.ftl
@@ -41,8 +41,6 @@ resolve_attempt_to_use_non_constant_value_in_constant_without_suggestion =
 resolve_attributes_starting_with_rustc_are_reserved =
     attributes starting with `rustc` are reserved for use by the `rustc` compiler
 
-resolve_bad_macro_import = bad macro import
-
 resolve_binding_in_never_pattern =
     never patterns cannot contain variable bindings
     .suggestion = use a wildcard `_` instead
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index c3bfd759f4c..82eae088803 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -11,20 +11,24 @@ use std::sync::Arc;
 use rustc_ast::visit::{self, AssocCtxt, Visitor, WalkItemKind};
 use rustc_ast::{
     self as ast, AssocItem, AssocItemKind, Block, ConstItem, Delegation, Fn, ForeignItem,
-    ForeignItemKind, Impl, Item, ItemKind, MetaItemKind, NodeId, StaticItem, StmtKind, TyAlias,
+    ForeignItemKind, Impl, Item, ItemKind, NodeId, StaticItem, StmtKind, TyAlias,
 };
 use rustc_attr_parsing as attr;
+use rustc_attr_parsing::AttributeParser;
 use rustc_expand::base::ResolverExpand;
 use rustc_expand::expand::AstFragment;
+use rustc_hir::Attribute;
+use rustc_hir::attrs::{AttributeKind, MacroUseArgs};
 use rustc_hir::def::{self, *};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_index::bit_set::DenseBitSet;
 use rustc_metadata::creader::LoadedMacro;
-use rustc_middle::bug;
 use rustc_middle::metadata::ModChild;
 use rustc_middle::ty::{Feed, Visibility};
+use rustc_middle::{bug, span_bug};
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind};
 use rustc_span::{Ident, Span, Symbol, kw, sym};
+use thin_vec::ThinVec;
 use tracing::debug;
 
 use crate::Namespace::{MacroNS, TypeNS, ValueNS};
@@ -42,30 +46,59 @@ type Res = def::Res<NodeId>;
 impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
     /// otherwise, reports an error.
-    pub(crate) fn define_binding(
+    pub(crate) fn define_binding_local(
         &mut self,
         parent: Module<'ra>,
         ident: Ident,
         ns: Namespace,
         binding: NameBinding<'ra>,
     ) {
-        if let Err(old_binding) = self.try_define(parent, ident, ns, binding, false) {
+        if let Err(old_binding) = self.try_define_local(parent, ident, ns, binding, false) {
             self.report_conflict(parent, ident, ns, old_binding, binding);
         }
     }
 
-    fn define(
+    fn define_local(
         &mut self,
         parent: Module<'ra>,
         ident: Ident,
         ns: Namespace,
         res: Res,
-        vis: Visibility<impl Into<DefId>>,
+        vis: Visibility,
         span: Span,
         expn_id: LocalExpnId,
     ) {
         let binding = self.arenas.new_res_binding(res, vis.to_def_id(), span, expn_id);
-        self.define_binding(parent, ident, ns, binding)
+        self.define_binding_local(parent, ident, ns, binding);
+    }
+
+    fn define_extern(
+        &self,
+        parent: Module<'ra>,
+        ident: Ident,
+        ns: Namespace,
+        res: Res,
+        vis: Visibility<DefId>,
+        span: Span,
+        expn_id: LocalExpnId,
+    ) {
+        let binding = self.arenas.new_res_binding(res, vis, span, expn_id);
+        // Even if underscore names cannot be looked up, we still need to add them to modules,
+        // because they can be fetched by glob imports from those modules, and bring traits
+        // into scope both directly and through glob imports.
+        let key = BindingKey::new_disambiguated(ident, ns, || {
+            parent.underscore_disambiguator.update(|d| d + 1);
+            parent.underscore_disambiguator.get()
+        });
+        if self
+            .resolution_or_default(parent, key)
+            .borrow_mut()
+            .non_glob_binding
+            .replace(binding)
+            .is_some()
+        {
+            span_bug!(span, "an external binding was already defined");
+        }
     }
 
     /// Walks up the tree of definitions starting at `def_id`,
@@ -188,7 +221,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         visitor.parent_scope.macro_rules
     }
 
-    pub(crate) fn build_reduced_graph_external(&mut self, module: Module<'ra>) {
+    pub(crate) fn build_reduced_graph_external(&self, module: Module<'ra>) {
         for child in self.tcx.module_children(module.def_id()) {
             let parent_scope = ParentScope::module(module, self);
             self.build_reduced_graph_for_external_crate_res(child, parent_scope)
@@ -197,7 +230,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
     /// Builds the reduced graph for a single item in an external crate.
     fn build_reduced_graph_for_external_crate_res(
-        &mut self,
+        &self,
         child: &ModChild,
         parent_scope: ParentScope<'ra>,
     ) {
@@ -228,7 +261,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 _,
             )
             | Res::PrimTy(..)
-            | Res::ToolMod => self.define(parent, ident, TypeNS, res, vis, span, expansion),
+            | Res::ToolMod => self.define_extern(parent, ident, TypeNS, res, vis, span, expansion),
             Res::Def(
                 DefKind::Fn
                 | DefKind::AssocFn
@@ -237,9 +270,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 | DefKind::AssocConst
                 | DefKind::Ctor(..),
                 _,
-            ) => self.define(parent, ident, ValueNS, res, vis, span, expansion),
+            ) => self.define_extern(parent, ident, ValueNS, res, vis, span, expansion),
             Res::Def(DefKind::Macro(..), _) | Res::NonMacroAttr(..) => {
-                self.define(parent, ident, MacroNS, res, vis, span, expansion)
+                self.define_extern(parent, ident, MacroNS, res, vis, span, expansion)
             }
             Res::Def(
                 DefKind::TyParam
@@ -448,8 +481,10 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     self.r.per_ns(|this, ns| {
                         if !type_ns_only || ns == TypeNS {
                             let key = BindingKey::new(target, ns);
-                            let mut resolution = this.resolution(current_module, key).borrow_mut();
-                            resolution.single_imports.insert(import);
+                            this.resolution_or_default(current_module, key)
+                                .borrow_mut()
+                                .single_imports
+                                .insert(import);
                         }
                     });
                 }
@@ -705,7 +740,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         let expansion = parent_scope.expansion;
 
         // Define a name in the type namespace if it is not anonymous.
-        self.r.define(parent, ident, TypeNS, adt_res, adt_vis, adt_span, expansion);
+        self.r.define_local(parent, ident, TypeNS, adt_res, adt_vis, adt_span, expansion);
         self.r.feed_visibility(feed, adt_vis);
         let def_id = feed.key();
 
@@ -757,7 +792,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             }
 
             ItemKind::Mod(_, ident, ref mod_kind) => {
-                self.r.define(parent, ident, TypeNS, res, vis, sp, expansion);
+                self.r.define_local(parent, ident, TypeNS, res, vis, sp, expansion);
 
                 if let ast::ModKind::Loaded(_, _, _, Err(_)) = mod_kind {
                     self.r.mods_with_parse_errors.insert(def_id);
@@ -776,10 +811,10 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             ItemKind::Const(box ConstItem { ident, .. })
             | ItemKind::Delegation(box Delegation { ident, .. })
             | ItemKind::Static(box StaticItem { ident, .. }) => {
-                self.r.define(parent, ident, ValueNS, res, vis, sp, expansion);
+                self.r.define_local(parent, ident, ValueNS, res, vis, sp, expansion);
             }
             ItemKind::Fn(box Fn { ident, .. }) => {
-                self.r.define(parent, ident, ValueNS, res, vis, sp, expansion);
+                self.r.define_local(parent, ident, ValueNS, res, vis, sp, expansion);
 
                 // Functions introducing procedural macros reserve a slot
                 // in the macro namespace as well (see #52225).
@@ -788,11 +823,11 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
 
             // These items live in the type namespace.
             ItemKind::TyAlias(box TyAlias { ident, .. }) | ItemKind::TraitAlias(ident, ..) => {
-                self.r.define(parent, ident, TypeNS, res, vis, sp, expansion);
+                self.r.define_local(parent, ident, TypeNS, res, vis, sp, expansion);
             }
 
             ItemKind::Enum(ident, _, _) | ItemKind::Trait(box ast::Trait { ident, .. }) => {
-                self.r.define(parent, ident, TypeNS, res, vis, sp, expansion);
+                self.r.define_local(parent, ident, TypeNS, res, vis, sp, expansion);
 
                 self.parent_scope.module = self.r.new_local_module(
                     Some(parent),
@@ -844,7 +879,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     let feed = self.r.feed(ctor_node_id);
                     let ctor_def_id = feed.key();
                     let ctor_res = self.res(ctor_def_id);
-                    self.r.define(parent, ident, ValueNS, ctor_res, ctor_vis, sp, expansion);
+                    self.r.define_local(parent, ident, ValueNS, ctor_res, ctor_vis, sp, expansion);
                     self.r.feed_visibility(feed, ctor_vis);
                     // We need the field visibility spans also for the constructor for E0603.
                     self.insert_field_visibilities_local(ctor_def_id.to_def_id(), vdata.fields());
@@ -949,18 +984,17 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 // more details: https://github.com/rust-lang/rust/pull/111761
                 return;
             }
-            let entry = self
-                .r
-                .extern_prelude
-                .entry(ident)
-                .or_insert(ExternPreludeEntry { binding: None, introduced_by_item: true });
+            let entry = self.r.extern_prelude.entry(ident).or_insert(ExternPreludeEntry {
+                binding: Cell::new(None),
+                introduced_by_item: true,
+            });
             if orig_name.is_some() {
                 entry.introduced_by_item = true;
             }
             // Binding from `extern crate` item in source code can replace
             // a binding from `--extern` on command line here.
             if !entry.is_import() {
-                entry.binding = Some(imported_binding)
+                entry.binding.set(Some(imported_binding));
             } else if ident.name != kw::Underscore {
                 self.r.dcx().span_delayed_bug(
                     item.span,
@@ -968,7 +1002,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 );
             }
         }
-        self.r.define_binding(parent, ident, TypeNS, imported_binding);
+        self.r.define_binding_local(parent, ident, TypeNS, imported_binding);
     }
 
     /// Constructs the reduced graph for one foreign item.
@@ -985,7 +1019,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         let parent = self.parent_scope.module;
         let expansion = self.parent_scope.expansion;
         let vis = self.resolve_visibility(&item.vis);
-        self.r.define(parent, ident, ns, self.res(def_id), vis, item.span, expansion);
+        self.r.define_local(parent, ident, ns, self.res(def_id), vis, item.span, expansion);
         self.r.feed_visibility(feed, vis);
     }
 
@@ -1020,42 +1054,31 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
     /// Returns `true` if we should consider the underlying `extern crate` to be used.
     fn process_macro_use_imports(&mut self, item: &Item, module: Module<'ra>) -> bool {
         let mut import_all = None;
-        let mut single_imports = Vec::new();
-        for attr in &item.attrs {
-            if attr.has_name(sym::macro_use) {
-                if self.parent_scope.module.parent.is_some() {
-                    self.r.dcx().emit_err(errors::ExternCrateLoadingMacroNotAtCrateRoot {
-                        span: item.span,
-                    });
-                }
-                if let ItemKind::ExternCrate(Some(orig_name), _) = item.kind
-                    && orig_name == kw::SelfLower
-                {
-                    self.r.dcx().emit_err(errors::MacroUseExternCrateSelf { span: attr.span });
-                }
-                let ill_formed = |span| {
-                    self.r.dcx().emit_err(errors::BadMacroImport { span });
-                };
-                match attr.meta() {
-                    Some(meta) => match meta.kind {
-                        MetaItemKind::Word => {
-                            import_all = Some(meta.span);
-                            break;
-                        }
-                        MetaItemKind::List(meta_item_inners) => {
-                            for meta_item_inner in meta_item_inners {
-                                match meta_item_inner.ident() {
-                                    Some(ident) if meta_item_inner.is_word() => {
-                                        single_imports.push(ident)
-                                    }
-                                    _ => ill_formed(meta_item_inner.span()),
-                                }
-                            }
-                        }
-                        MetaItemKind::NameValue(..) => ill_formed(meta.span),
-                    },
-                    None => ill_formed(attr.span),
-                }
+        let mut single_imports = ThinVec::new();
+        if let Some(Attribute::Parsed(AttributeKind::MacroUse { span, arguments })) =
+            AttributeParser::parse_limited(
+                self.r.tcx.sess,
+                &item.attrs,
+                sym::macro_use,
+                item.span,
+                item.id,
+                None,
+            )
+        {
+            if self.parent_scope.module.parent.is_some() {
+                self.r
+                    .dcx()
+                    .emit_err(errors::ExternCrateLoadingMacroNotAtCrateRoot { span: item.span });
+            }
+            if let ItemKind::ExternCrate(Some(orig_name), _) = item.kind
+                && orig_name == kw::SelfLower
+            {
+                self.r.dcx().emit_err(errors::MacroUseExternCrateSelf { span });
+            }
+
+            match arguments {
+                MacroUseArgs::UseAll => import_all = Some(span),
+                MacroUseArgs::UseSpecific(imports) => single_imports = imports,
             }
         }
 
@@ -1079,7 +1102,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         if let Some(span) = import_all {
             let import = macro_use_import(self, span, false);
             self.r.potentially_unused_imports.push(import);
-            module.for_each_child(self, |this, ident, ns, binding| {
+            module.for_each_child_mut(self, |this, ident, ns, binding| {
                 if ns == MacroNS {
                     let import = if this.r.is_accessible_from(binding.vis, this.parent_scope.module)
                     {
@@ -1244,7 +1267,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 });
                 self.r.import_use_map.insert(import, Used::Other);
                 let import_binding = self.r.import(binding, import);
-                self.r.define_binding(self.r.graph_root, ident, MacroNS, import_binding);
+                self.r.define_binding_local(self.r.graph_root, ident, MacroNS, import_binding);
             } else {
                 self.r.check_reserved_macro_name(ident, res);
                 self.insert_unused_macro(ident, def_id, item.id);
@@ -1272,7 +1295,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             if !vis.is_public() {
                 self.insert_unused_macro(ident, def_id, item.id);
             }
-            self.r.define(module, ident, MacroNS, res, vis, span, expansion);
+            self.r.define_local(module, ident, MacroNS, res, vis, span, expansion);
             self.r.feed_visibility(feed, vis);
             self.parent_scope.macro_rules
         }
@@ -1408,7 +1431,7 @@ impl<'a, 'ra, 'tcx> Visitor<'a> for BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         if ctxt == AssocCtxt::Trait {
             let parent = self.parent_scope.module;
             let expansion = self.parent_scope.expansion;
-            self.r.define(parent, ident, ns, self.res(def_id), vis, item.span, expansion);
+            self.r.define_local(parent, ident, ns, self.res(def_id), vis, item.span, expansion);
         } else if !matches!(&item.kind, AssocItemKind::Delegation(deleg) if deleg.from_glob)
             && ident.name != kw::Underscore
         {
@@ -1496,7 +1519,7 @@ impl<'a, 'ra, 'tcx> Visitor<'a> for BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         let feed = self.r.feed(variant.id);
         let def_id = feed.key();
         let vis = self.resolve_visibility(&variant.vis);
-        self.r.define(parent, ident, TypeNS, self.res(def_id), vis, variant.span, expn_id);
+        self.r.define_local(parent, ident, TypeNS, self.res(def_id), vis, variant.span, expn_id);
         self.r.feed_visibility(feed, vis);
 
         // If the variant is marked as non_exhaustive then lower the visibility to within the crate.
@@ -1512,7 +1535,7 @@ impl<'a, 'ra, 'tcx> Visitor<'a> for BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             let feed = self.r.feed(ctor_node_id);
             let ctor_def_id = feed.key();
             let ctor_res = self.res(ctor_def_id);
-            self.r.define(parent, ident, ValueNS, ctor_res, ctor_vis, variant.span, expn_id);
+            self.r.define_local(parent, ident, ValueNS, ctor_res, ctor_vis, variant.span, expn_id);
             self.r.feed_visibility(feed, ctor_vis);
         }
 
diff --git a/compiler/rustc_resolve/src/check_unused.rs b/compiler/rustc_resolve/src/check_unused.rs
index 81ee02ac3c7..b85a814776a 100644
--- a/compiler/rustc_resolve/src/check_unused.rs
+++ b/compiler/rustc_resolve/src/check_unused.rs
@@ -509,9 +509,7 @@ impl Resolver<'_, '_> {
         let mut check_redundant_imports = FxIndexSet::default();
         for module in self.arenas.local_modules().iter() {
             for (_key, resolution) in self.resolutions(*module).borrow().iter() {
-                let resolution = resolution.borrow();
-
-                if let Some(binding) = resolution.best_binding()
+                if let Some(binding) = resolution.borrow().best_binding()
                     && let NameBindingKind::Import { import, .. } = binding.kind
                     && let ImportKind::Single { id, .. } = import.kind
                 {
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index d72fbc189e7..3b57f6e883a 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -4,9 +4,6 @@ use rustc_ast::{
     self as ast, CRATE_NODE_ID, Crate, ItemKind, ModKind, NodeId, Path, join_path_idents,
 };
 use rustc_ast_pretty::pprust;
-use rustc_attr_data_structures::{
-    self as attr, AttributeKind, CfgEntry, Stability, StrippedCfgItem, find_attr,
-};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
@@ -15,10 +12,11 @@ use rustc_errors::{
     report_ambiguity_error, struct_span_code_err,
 };
 use rustc_feature::BUILTIN_ATTRIBUTES;
-use rustc_hir::PrimTy;
+use rustc_hir::attrs::{AttributeKind, CfgEntry, StrippedCfgItem};
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind, PerNS};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
+use rustc_hir::{PrimTy, Stability, StabilityLevel, find_attr};
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
@@ -523,7 +521,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     pub(crate) fn add_module_candidates(
-        &mut self,
+        &self,
         module: Module<'ra>,
         names: &mut Vec<TypoSuggestion>,
         filter_fn: &impl Fn(Res) -> bool,
@@ -803,10 +801,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     err.multipart_suggestion(msg, suggestions, applicability);
                 }
-                if let Some(ModuleOrUniformRoot::Module(module)) = module
-                    && let Some(module) = module.opt_def_id()
-                    && let Some(segment) = segment
-                {
+
+                if let Some(segment) = segment {
+                    let module = match module {
+                        Some(ModuleOrUniformRoot::Module(m)) if let Some(id) = m.opt_def_id() => id,
+                        _ => CRATE_DEF_ID.to_def_id(),
+                    };
                     self.find_cfg_stripped(&mut err, &segment, module);
                 }
 
@@ -1076,11 +1076,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         }
                     }
                 }
-                Scope::CrateRoot => {
-                    let root_ident = Ident::new(kw::PathRoot, ident.span);
-                    let root_module = this.resolve_crate_root(root_ident);
-                    this.add_module_candidates(root_module, &mut suggestions, filter_fn, None);
-                }
                 Scope::Module(module, _) => {
                     this.add_module_candidates(module, &mut suggestions, filter_fn, None);
                 }
@@ -1155,7 +1150,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     fn lookup_import_candidates_from_module<FilterFn>(
-        &mut self,
+        &self,
         lookup_ident: Ident,
         namespace: Namespace,
         parent_scope: &ParentScope<'ra>,
@@ -1367,9 +1362,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         match self.tcx.lookup_stability(did) {
             Some(Stability {
-                level: attr::StabilityLevel::Unstable { implied_by, .. },
-                feature,
-                ..
+                level: StabilityLevel::Unstable { implied_by, .. }, feature, ..
             }) => {
                 if span.allows_unstable(feature) {
                     true
@@ -2664,10 +2657,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             return None;
         }
 
-        let resolutions = self.resolutions(crate_module).borrow();
         let binding_key = BindingKey::new(ident, MacroNS);
-        let resolution = resolutions.get(&binding_key)?;
-        let binding = resolution.borrow().binding()?;
+        let binding = self.resolution(crate_module, binding_key)?.binding()?;
         let Res::Def(DefKind::Macro(MacroKind::Bang), _) = binding.res() else {
             return None;
         };
@@ -2850,16 +2841,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 continue;
             }
 
-            let note = errors::FoundItemConfigureOut { span: ident.span };
-            err.subdiagnostic(note);
-
-            if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
-                let note = errors::ItemWasBehindFeature { feature, span: cfg.1 };
-                err.subdiagnostic(note);
+            let item_was = if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
+                errors::ItemWas::BehindFeature { feature, span: cfg.1 }
             } else {
-                let note = errors::ItemWasCfgOut { span: cfg.1 };
-                err.subdiagnostic(note);
-            }
+                errors::ItemWas::CfgOut { span: cfg.1 }
+            };
+            let note = errors::FoundItemConfigureOut { span: ident.span, item_was };
+            err.subdiagnostic(note);
         }
     }
 }
diff --git a/compiler/rustc_resolve/src/effective_visibilities.rs b/compiler/rustc_resolve/src/effective_visibilities.rs
index 34d1e9552fd..fe6e5b8e6eb 100644
--- a/compiler/rustc_resolve/src/effective_visibilities.rs
+++ b/compiler/rustc_resolve/src/effective_visibilities.rs
@@ -114,9 +114,7 @@ impl<'a, 'ra, 'tcx> EffectiveVisibilitiesVisitor<'a, 'ra, 'tcx> {
     /// including their whole reexport chains.
     fn set_bindings_effective_visibilities(&mut self, module_id: LocalDefId) {
         let module = self.r.expect_module(module_id.to_def_id());
-        let resolutions = self.r.resolutions(module);
-
-        for (_, name_resolution) in resolutions.borrow().iter() {
+        for (_, name_resolution) in self.r.resolutions(module).borrow().iter() {
             let Some(mut binding) = name_resolution.borrow().binding() else {
                 continue;
             };
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index b34bcb38f84..2747ba135ed 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -1,10 +1,13 @@
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, ElidedLifetimeInPathSubdiag, MultiSpan};
+use rustc_errors::{
+    Applicability, Diag, ElidedLifetimeInPathSubdiag, EmissionGuarantee, IntoDiagArg, MultiSpan,
+    Subdiagnostic,
+};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
 
-use crate::Res;
 use crate::late::PatternSource;
+use crate::{Res, fluent_generated as fluent};
 
 #[derive(Diagnostic)]
 #[diag(resolve_generic_params_from_outer_item, code = E0401)]
@@ -816,13 +819,6 @@ pub(crate) struct ExternCrateLoadingMacroNotAtCrateRoot {
 }
 
 #[derive(Diagnostic)]
-#[diag(resolve_bad_macro_import, code = E0466)]
-pub(crate) struct BadMacroImport {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(resolve_extern_crate_self_requires_renaming)]
 pub(crate) struct ExternCrateSelfRequiresRenaming {
     #[primary_span]
@@ -1208,26 +1204,35 @@ pub(crate) struct IdentInScopeButItIsDesc<'a> {
     pub(crate) imported_ident_desc: &'a str,
 }
 
-#[derive(Subdiagnostic)]
-#[note(resolve_found_an_item_configured_out)]
 pub(crate) struct FoundItemConfigureOut {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(resolve_item_was_behind_feature)]
-pub(crate) struct ItemWasBehindFeature {
-    pub(crate) feature: Symbol,
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(resolve_item_was_cfg_out)]
-pub(crate) struct ItemWasCfgOut {
-    #[primary_span]
     pub(crate) span: Span,
+    pub(crate) item_was: ItemWas,
+}
+
+pub(crate) enum ItemWas {
+    BehindFeature { feature: Symbol, span: Span },
+    CfgOut { span: Span },
+}
+
+impl Subdiagnostic for FoundItemConfigureOut {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        let mut multispan: MultiSpan = self.span.into();
+        match self.item_was {
+            ItemWas::BehindFeature { feature, span } => {
+                let key = "feature".into();
+                let value = feature.into_diag_arg(&mut None);
+                let msg = diag.dcx.eagerly_translate_to_string(
+                    fluent::resolve_item_was_behind_feature,
+                    [(&key, &value)].into_iter(),
+                );
+                multispan.push_span_label(span, msg);
+            }
+            ItemWas::CfgOut { span } => {
+                multispan.push_span_label(span, fluent::resolve_item_was_cfg_out);
+            }
+        }
+        diag.span_note(multispan, fluent::resolve_found_an_item_configured_out);
+    }
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index 34941398a2b..f5bc46bf053 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -93,20 +93,21 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // 6. Language prelude: builtin attributes (closed, controlled).
 
         let rust_2015 = ctxt.edition().is_rust_2015();
-        let (ns, macro_kind, is_absolute_path) = match scope_set {
-            ScopeSet::All(ns) => (ns, None, false),
-            ScopeSet::AbsolutePath(ns) => (ns, None, true),
-            ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
-            ScopeSet::Late(ns, ..) => (ns, None, false),
+        let (ns, macro_kind) = match scope_set {
+            ScopeSet::All(ns)
+            | ScopeSet::ModuleAndExternPrelude(ns, _)
+            | ScopeSet::Late(ns, ..) => (ns, None),
+            ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind)),
         };
         let module = match scope_set {
             // Start with the specified module.
-            ScopeSet::Late(_, module, _) => module,
+            ScopeSet::Late(_, module, _) | ScopeSet::ModuleAndExternPrelude(_, module) => module,
             // Jump out of trait or enum modules, they do not act as scopes.
             _ => parent_scope.module.nearest_item_scope(),
         };
+        let module_and_extern_prelude = matches!(scope_set, ScopeSet::ModuleAndExternPrelude(..));
         let mut scope = match ns {
-            _ if is_absolute_path => Scope::CrateRoot,
+            _ if module_and_extern_prelude => Scope::Module(module, None),
             TypeNS | ValueNS => Scope::Module(module, None),
             MacroNS => Scope::DeriveHelpers(parent_scope.expansion),
         };
@@ -134,11 +135,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     true
                 }
-                Scope::CrateRoot => true,
                 Scope::Module(..) => true,
                 Scope::MacroUsePrelude => use_prelude || rust_2015,
                 Scope::BuiltinAttrs => true,
-                Scope::ExternPrelude => use_prelude || is_absolute_path,
+                Scope::ExternPrelude => use_prelude || module_and_extern_prelude,
                 Scope::ToolPrelude => use_prelude,
                 Scope::StdLibPrelude => use_prelude || ns == MacroNS,
                 Scope::BuiltinTypes => true,
@@ -174,7 +174,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     MacroRulesScope::Empty => Scope::Module(module, None),
                 },
-                Scope::CrateRoot => match ns {
+                Scope::Module(..) if module_and_extern_prelude => match ns {
                     TypeNS => {
                         ctxt.adjust(ExpnId::root());
                         Scope::ExternPrelude
@@ -203,7 +203,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 }
                 Scope::MacroUsePrelude => Scope::StdLibPrelude,
                 Scope::BuiltinAttrs => break, // nowhere else to search
-                Scope::ExternPrelude if is_absolute_path => break,
+                Scope::ExternPrelude if module_and_extern_prelude => break,
                 Scope::ExternPrelude => Scope::ToolPrelude,
                 Scope::ToolPrelude => Scope::StdLibPrelude,
                 Scope::StdLibPrelude => match ns {
@@ -404,10 +404,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
 
         let (ns, macro_kind) = match scope_set {
-            ScopeSet::All(ns) => (ns, None),
-            ScopeSet::AbsolutePath(ns) => (ns, None),
+            ScopeSet::All(ns)
+            | ScopeSet::ModuleAndExternPrelude(ns, _)
+            | ScopeSet::Late(ns, ..) => (ns, None),
             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind)),
-            ScopeSet::Late(ns, ..) => (ns, None),
         };
 
         // This is *the* result, resolution from the scope closest to the resolved identifier.
@@ -487,31 +487,16 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         MacroRulesScope::Invocation(_) => Err(Determinacy::Undetermined),
                         _ => Err(Determinacy::Determined),
                     },
-                    Scope::CrateRoot => {
-                        let root_ident = Ident::new(kw::PathRoot, ident.span);
-                        let root_module = this.resolve_crate_root(root_ident);
-                        let binding = this.resolve_ident_in_module(
-                            ModuleOrUniformRoot::Module(root_module),
-                            ident,
-                            ns,
-                            parent_scope,
-                            finalize,
-                            ignore_binding,
-                            ignore_import,
-                        );
-                        match binding {
-                            Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
-                            Err((Determinacy::Undetermined, Weak::No)) => {
-                                return Some(Err(Determinacy::determined(force)));
-                            }
-                            Err((Determinacy::Undetermined, Weak::Yes)) => {
-                                Err(Determinacy::Undetermined)
-                            }
-                            Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
-                        }
-                    }
                     Scope::Module(module, derive_fallback_lint_id) => {
-                        let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
+                        let (adjusted_parent_scope, finalize) =
+                            if matches!(scope_set, ScopeSet::ModuleAndExternPrelude(..)) {
+                                (parent_scope, finalize)
+                            } else {
+                                (
+                                    &ParentScope { module, ..*parent_scope },
+                                    finalize.map(|f| Finalize { used: Used::Scope, ..f }),
+                                )
+                            };
                         let binding = this.resolve_ident_in_module_unadjusted(
                             ModuleOrUniformRoot::Module(module),
                             ident,
@@ -522,7 +507,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                             } else {
                                 Shadowing::Restricted
                             },
-                            finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
+                            finalize,
                             ignore_binding,
                             ignore_import,
                         );
@@ -776,7 +761,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             ModuleOrUniformRoot::ExternPrelude => {
                 ident.span.normalize_to_macros_2_0_and_adjust(ExpnId::root());
             }
-            ModuleOrUniformRoot::CrateRootAndExternPrelude | ModuleOrUniformRoot::CurrentScope => {
+            ModuleOrUniformRoot::ModuleAndExternPrelude(..) | ModuleOrUniformRoot::CurrentScope => {
                 // No adjustments
             }
         }
@@ -810,11 +795,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     ) -> Result<NameBinding<'ra>, (Determinacy, Weak)> {
         let module = match module {
             ModuleOrUniformRoot::Module(module) => module,
-            ModuleOrUniformRoot::CrateRootAndExternPrelude => {
+            ModuleOrUniformRoot::ModuleAndExternPrelude(module) => {
                 assert_eq!(shadowing, Shadowing::Unrestricted);
                 let binding = self.early_resolve_ident_in_lexical_scope(
                     ident,
-                    ScopeSet::AbsolutePath(ns),
+                    ScopeSet::ModuleAndExternPrelude(ns, module),
                     parent_scope,
                     finalize,
                     finalize.is_some(),
@@ -863,8 +848,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         };
 
         let key = BindingKey::new(ident, ns);
-        let resolution =
-            self.resolution(module, key).try_borrow_mut().map_err(|_| (Determined, Weak::No))?; // This happens when there is a cycle of imports.
+        // `try_borrow_mut` is required to ensure exclusive access, even if the resulting binding
+        // doesn't need to be mutable. It will fail when there is a cycle of imports, and without
+        // the exclusive access infinite recursion will crash the compiler with stack overflow.
+        let resolution = &*self
+            .resolution_or_default(module, key)
+            .try_borrow_mut()
+            .map_err(|_| (Determined, Weak::No))?;
 
         // If the primary binding is unusable, search further and return the shadowed glob
         // binding if it exists. What we really want here is having two separate scopes in
@@ -1531,7 +1521,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         && self.tcx.sess.at_least_rust_2018()
                     {
                         // `::a::b` from 2015 macro on 2018 global edition
-                        module = Some(ModuleOrUniformRoot::CrateRootAndExternPrelude);
+                        let crate_root = self.resolve_crate_root(ident);
+                        module = Some(ModuleOrUniformRoot::ModuleAndExternPrelude(crate_root));
                         continue;
                     }
                     if name == kw::PathRoot || name == kw::Crate || name == kw::DollarCrate {
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index b4c15ed1ca7..156df45147f 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -181,10 +181,10 @@ pub(crate) struct ImportData<'ra> {
     ///
     /// | `module_path` | `imported_module` | remark |
     /// |-|-|-|
-    /// |`use prefix::foo`| `ModuleOrUniformRoot::Module(prefix)`               | - |
-    /// |`use ::foo`      | `ModuleOrUniformRoot::ExternPrelude`                | 2018+ editions |
-    /// |`use ::foo`      | `ModuleOrUniformRoot::CrateRootAndExternPrelude`    | a special case in 2015 edition |
-    /// |`use foo`        | `ModuleOrUniformRoot::CurrentScope`                 | - |
+    /// |`use prefix::foo`| `ModuleOrUniformRoot::Module(prefix)`         | - |
+    /// |`use ::foo`      | `ModuleOrUniformRoot::ExternPrelude`          | 2018+ editions |
+    /// |`use ::foo`      | `ModuleOrUniformRoot::ModuleAndExternPrelude` | a special case in 2015 edition |
+    /// |`use foo`        | `ModuleOrUniformRoot::CurrentScope`           | - |
     pub imported_module: Cell<Option<ModuleOrUniformRoot<'ra>>>,
     pub vis: Visibility,
 }
@@ -334,8 +334,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     /// Define the name or return the existing binding if there is a collision.
-    /// `update` indicates if the definition is a redefinition of an existing binding.
-    pub(crate) fn try_define(
+    pub(crate) fn try_define_local(
         &mut self,
         module: Module<'ra>,
         ident: Ident,
@@ -350,9 +349,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // because they can be fetched by glob imports from those modules, and bring traits
         // into scope both directly and through glob imports.
         let key = BindingKey::new_disambiguated(ident, ns, || {
-            (module.0.0.lazy_resolutions.borrow().len() + 1).try_into().unwrap()
+            module.underscore_disambiguator.update(|d| d + 1);
+            module.underscore_disambiguator.get()
         });
-        self.update_resolution(module, key, warn_ambiguity, |this, resolution| {
+        self.update_local_resolution(module, key, warn_ambiguity, |this, resolution| {
             if let Some(old_binding) = resolution.best_binding() {
                 if res == Res::Err && old_binding.res() != Res::Err {
                     // Do not override real bindings with `Res::Err`s from error recovery.
@@ -455,7 +455,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
     // Use `f` to mutate the resolution of the name in the module.
     // If the resolution becomes a success, define it in the module's glob importers.
-    fn update_resolution<T, F>(
+    fn update_local_resolution<T, F>(
         &mut self,
         module: Module<'ra>,
         key: BindingKey,
@@ -468,7 +468,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
         // during which the resolution might end up getting re-defined via a glob cycle.
         let (binding, t, warn_ambiguity) = {
-            let resolution = &mut *self.resolution(module, key).borrow_mut();
+            let resolution = &mut *self.resolution_or_default(module, key).borrow_mut();
             let old_binding = resolution.binding();
 
             let t = f(self, resolution);
@@ -496,7 +496,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             };
             if self.is_accessible_from(binding.vis, scope) {
                 let imported_binding = self.import(binding, *import);
-                let _ = self.try_define(
+                let _ = self.try_define_local(
                     import.parent_scope.module,
                     ident,
                     key.ns,
@@ -522,11 +522,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             let dummy_binding = self.import(dummy_binding, import);
             self.per_ns(|this, ns| {
                 let module = import.parent_scope.module;
-                let _ = this.try_define(module, target, ns, dummy_binding, false);
+                let _ = this.try_define_local(module, target, ns, dummy_binding, false);
                 // Don't remove underscores from `single_imports`, they were never added.
                 if target.name != kw::Underscore {
                     let key = BindingKey::new(target, ns);
-                    this.update_resolution(module, key, false, |_, resolution| {
+                    this.update_local_resolution(module, key, false, |_, resolution| {
                         resolution.single_imports.swap_remove(&import);
                     })
                 }
@@ -650,7 +650,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         for module in self.arenas.local_modules().iter() {
             for (key, resolution) in self.resolutions(*module).borrow().iter() {
                 let resolution = resolution.borrow();
-
                 let Some(binding) = resolution.best_binding() else { continue };
 
                 if let NameBindingKind::Import { import, .. } = binding.kind
@@ -902,14 +901,14 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         }
                         // We need the `target`, `source` can be extracted.
                         let imported_binding = this.import(binding, import);
-                        this.define_binding(parent, target, ns, imported_binding);
+                        this.define_binding_local(parent, target, ns, imported_binding);
                         PendingBinding::Ready(Some(imported_binding))
                     }
                     Err(Determinacy::Determined) => {
                         // Don't remove underscores from `single_imports`, they were never added.
                         if target.name != kw::Underscore {
                             let key = BindingKey::new(target, ns);
-                            this.update_resolution(parent, key, false, |_, resolution| {
+                            this.update_local_resolution(parent, key, false, |_, resolution| {
                                 resolution.single_imports.swap_remove(&import);
                             });
                         }
@@ -1201,41 +1200,39 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             });
 
             return if all_ns_failed {
-                let resolutions = match module {
-                    ModuleOrUniformRoot::Module(module) => Some(self.resolutions(module).borrow()),
-                    _ => None,
-                };
-                let resolutions = resolutions.as_ref().into_iter().flat_map(|r| r.iter());
-                let names = resolutions
-                    .filter_map(|(BindingKey { ident: i, .. }, resolution)| {
-                        if i.name == ident.name {
-                            return None;
-                        } // Never suggest the same name
-                        match *resolution.borrow() {
-                            ref resolution
-                                if let Some(name_binding) = resolution.best_binding() =>
-                            {
-                                match name_binding.kind {
-                                    NameBindingKind::Import { binding, .. } => {
-                                        match binding.kind {
-                                            // Never suggest the name that has binding error
-                                            // i.e., the name that cannot be previously resolved
-                                            NameBindingKind::Res(Res::Err) => None,
-                                            _ => Some(i.name),
+                let names = match module {
+                    ModuleOrUniformRoot::Module(module) => {
+                        self.resolutions(module)
+                            .borrow()
+                            .iter()
+                            .filter_map(|(BindingKey { ident: i, .. }, resolution)| {
+                                if i.name == ident.name {
+                                    return None;
+                                } // Never suggest the same name
+
+                                let resolution = resolution.borrow();
+                                if let Some(name_binding) = resolution.best_binding() {
+                                    match name_binding.kind {
+                                        NameBindingKind::Import { binding, .. } => {
+                                            match binding.kind {
+                                                // Never suggest the name that has binding error
+                                                // i.e., the name that cannot be previously resolved
+                                                NameBindingKind::Res(Res::Err) => None,
+                                                _ => Some(i.name),
+                                            }
                                         }
+                                        _ => Some(i.name),
                                     }
-                                    _ => Some(i.name),
+                                } else if resolution.single_imports.is_empty() {
+                                    None
+                                } else {
+                                    Some(i.name)
                                 }
-                            }
-                            NameResolution { ref single_imports, .. }
-                                if single_imports.is_empty() =>
-                            {
-                                None
-                            }
-                            _ => Some(i.name),
-                        }
-                    })
-                    .collect::<Vec<Symbol>>();
+                            })
+                            .collect()
+                    }
+                    _ => Vec::new(),
+                };
 
                 let lev_suggestion =
                     find_best_match_for_name(&names, ident.name, None).map(|suggestion| {
@@ -1516,10 +1513,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 let imported_binding = self.import(binding, import);
                 let warn_ambiguity = self
                     .resolution(import.parent_scope.module, key)
-                    .borrow()
-                    .binding()
+                    .and_then(|r| r.binding())
                     .is_some_and(|binding| binding.warn_ambiguity_recursive());
-                let _ = self.try_define(
+                let _ = self.try_define_local(
                     import.parent_scope.module,
                     key.ident,
                     key.ns,
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 93cec8daa5a..163e4b5b7a9 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -910,22 +910,15 @@ impl<'ast, 'ra, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'ra, 'tc
                     span,
                     |this| {
                         this.visit_generic_params(&fn_ptr.generic_params, false);
-                        this.with_lifetime_rib(
-                            LifetimeRibKind::AnonymousCreateParameter {
-                                binder: ty.id,
-                                report_in_path: false,
-                            },
-                            |this| {
-                                this.resolve_fn_signature(
-                                    ty.id,
-                                    false,
-                                    // We don't need to deal with patterns in parameters, because
-                                    // they are not possible for foreign or bodiless functions.
-                                    fn_ptr.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
-                                    &fn_ptr.decl.output,
-                                )
-                            },
-                        );
+                        this.resolve_fn_signature(
+                            ty.id,
+                            false,
+                            // We don't need to deal with patterns in parameters, because
+                            // they are not possible for foreign or bodiless functions.
+                            fn_ptr.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
+                            &fn_ptr.decl.output,
+                            false,
+                        )
                     },
                 )
             }
@@ -1042,19 +1035,12 @@ impl<'ast, 'ra, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'ra, 'tc
                 self.visit_fn_header(&sig.header);
                 self.visit_ident(ident);
                 self.visit_generics(generics);
-                self.with_lifetime_rib(
-                    LifetimeRibKind::AnonymousCreateParameter {
-                        binder: fn_id,
-                        report_in_path: false,
-                    },
-                    |this| {
-                        this.resolve_fn_signature(
-                            fn_id,
-                            sig.decl.has_self(),
-                            sig.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
-                            &sig.decl.output,
-                        );
-                    },
+                self.resolve_fn_signature(
+                    fn_id,
+                    sig.decl.has_self(),
+                    sig.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
+                    &sig.decl.output,
+                    false,
                 );
                 return;
             }
@@ -1080,22 +1066,15 @@ impl<'ast, 'ra, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'ra, 'tc
                             .coroutine_kind
                             .map(|coroutine_kind| coroutine_kind.return_id());
 
-                        this.with_lifetime_rib(
-                            LifetimeRibKind::AnonymousCreateParameter {
-                                binder: fn_id,
-                                report_in_path: coro_node_id.is_some(),
-                            },
-                            |this| {
-                                this.resolve_fn_signature(
-                                    fn_id,
-                                    declaration.has_self(),
-                                    declaration
-                                        .inputs
-                                        .iter()
-                                        .map(|Param { pat, ty, .. }| (Some(&**pat), &**ty)),
-                                    &declaration.output,
-                                );
-                            },
+                        this.resolve_fn_signature(
+                            fn_id,
+                            declaration.has_self(),
+                            declaration
+                                .inputs
+                                .iter()
+                                .map(|Param { pat, ty, .. }| (Some(&**pat), &**ty)),
+                            &declaration.output,
+                            coro_node_id.is_some(),
                         );
 
                         if let Some(contract) = contract {
@@ -1307,19 +1286,12 @@ impl<'ast, 'ra, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'ra, 'tc
                             kind: LifetimeBinderKind::PolyTrait,
                             ..
                         } => {
-                            self.with_lifetime_rib(
-                                LifetimeRibKind::AnonymousCreateParameter {
-                                    binder,
-                                    report_in_path: false,
-                                },
-                                |this| {
-                                    this.resolve_fn_signature(
-                                        binder,
-                                        false,
-                                        p_args.inputs.iter().map(|ty| (None, &**ty)),
-                                        &p_args.output,
-                                    )
-                                },
+                            self.resolve_fn_signature(
+                                binder,
+                                false,
+                                p_args.inputs.iter().map(|ty| (None, &**ty)),
+                                &p_args.output,
+                                false,
                             );
                             break;
                         }
@@ -2236,25 +2208,32 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         has_self: bool,
         inputs: impl Iterator<Item = (Option<&'ast Pat>, &'ast Ty)> + Clone,
         output_ty: &'ast FnRetTy,
+        report_elided_lifetimes_in_path: bool,
     ) {
-        // Add each argument to the rib.
-        let elision_lifetime = self.resolve_fn_params(has_self, inputs);
-        debug!(?elision_lifetime);
-
-        let outer_failures = take(&mut self.diag_metadata.current_elision_failures);
-        let output_rib = if let Ok(res) = elision_lifetime.as_ref() {
-            self.r.lifetime_elision_allowed.insert(fn_id);
-            LifetimeRibKind::Elided(*res)
-        } else {
-            LifetimeRibKind::ElisionFailure
+        let rib = LifetimeRibKind::AnonymousCreateParameter {
+            binder: fn_id,
+            report_in_path: report_elided_lifetimes_in_path,
         };
-        self.with_lifetime_rib(output_rib, |this| visit::walk_fn_ret_ty(this, output_ty));
-        let elision_failures =
-            replace(&mut self.diag_metadata.current_elision_failures, outer_failures);
-        if !elision_failures.is_empty() {
-            let Err(failure_info) = elision_lifetime else { bug!() };
-            self.report_missing_lifetime_specifiers(elision_failures, Some(failure_info));
-        }
+        self.with_lifetime_rib(rib, |this| {
+            // Add each argument to the rib.
+            let elision_lifetime = this.resolve_fn_params(has_self, inputs);
+            debug!(?elision_lifetime);
+
+            let outer_failures = take(&mut this.diag_metadata.current_elision_failures);
+            let output_rib = if let Ok(res) = elision_lifetime.as_ref() {
+                this.r.lifetime_elision_allowed.insert(fn_id);
+                LifetimeRibKind::Elided(*res)
+            } else {
+                LifetimeRibKind::ElisionFailure
+            };
+            this.with_lifetime_rib(output_rib, |this| visit::walk_fn_ret_ty(this, output_ty));
+            let elision_failures =
+                replace(&mut this.diag_metadata.current_elision_failures, outer_failures);
+            if !elision_failures.is_empty() {
+                let Err(failure_info) = elision_lifetime else { bug!() };
+                this.report_missing_lifetime_specifiers(elision_failures, Some(failure_info));
+            }
+        });
     }
 
     /// Resolve inside function parameters and parameter types.
@@ -2913,7 +2892,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                     self.r
                         .dcx()
                         .create_err(errors::UnderscoreLifetimeIsReserved { span: param.ident.span })
-                        .emit_unless(is_raw_underscore_lifetime);
+                        .emit_unless_delay(is_raw_underscore_lifetime);
                     // Record lifetime res, so lowering knows there is something fishy.
                     self.record_lifetime_param(param.id, LifetimeRes::Error);
                     continue;
@@ -3449,8 +3428,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         };
         ident.span.normalize_to_macros_2_0_and_adjust(module.expansion);
         let key = BindingKey::new(ident, ns);
-        let mut binding =
-            self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.best_binding());
+        let mut binding = self.r.resolution(module, key).and_then(|r| r.best_binding());
         debug!(?binding);
         if binding.is_none() {
             // We could not find the trait item in the correct namespace.
@@ -3461,8 +3439,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 _ => ns,
             };
             let key = BindingKey::new(ident, ns);
-            binding =
-                self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.best_binding());
+            binding = self.r.resolution(module, key).and_then(|r| r.best_binding());
             debug!(?binding);
         }
 
@@ -4254,13 +4231,21 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 //
                 // And that's what happens below - we're just mixing both messages
                 // into a single one.
+                let failed_to_resolve = match parent_err.node {
+                    ResolutionError::FailedToResolve { .. } => true,
+                    _ => false,
+                };
                 let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
 
                 // overwrite all properties with the parent's error message
                 err.messages = take(&mut parent_err.messages);
                 err.code = take(&mut parent_err.code);
                 swap(&mut err.span, &mut parent_err.span);
-                err.children = take(&mut parent_err.children);
+                if failed_to_resolve {
+                    err.children = take(&mut parent_err.children);
+                } else {
+                    err.children.append(&mut parent_err.children);
+                }
                 err.sort_span = parent_err.sort_span;
                 err.is_lint = parent_err.is_lint.clone();
 
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 69095942f52..236b1404eeb 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -525,9 +525,8 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         }
         self.err_code_special_cases(&mut err, source, path, span);
 
-        if let Some(module) = base_error.module {
-            self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
-        }
+        let module = base_error.module.unwrap_or_else(|| CRATE_DEF_ID.to_def_id());
+        self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
 
         (err, candidates)
     }
@@ -818,10 +817,10 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             // If the first argument in call is `self` suggest calling a method.
             if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
                 let mut args_snippet = String::new();
-                if let Some(args_span) = args_span {
-                    if let Ok(snippet) = self.r.tcx.sess.source_map().span_to_snippet(args_span) {
-                        args_snippet = snippet;
-                    }
+                if let Some(args_span) = args_span
+                    && let Ok(snippet) = self.r.tcx.sess.source_map().span_to_snippet(args_span)
+                {
+                    args_snippet = snippet;
                 }
 
                 err.span_suggestion(
@@ -955,59 +954,57 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)),
             false,
         ) = (source, res, is_macro)
-        {
-            if let Some(bounds @ [first_bound, .., last_bound]) =
+            && let Some(bounds @ [first_bound, .., last_bound]) =
                 self.diag_metadata.current_trait_object
-            {
-                fallback = true;
-                let spans: Vec<Span> = bounds
-                    .iter()
-                    .map(|bound| bound.span())
-                    .filter(|&sp| sp != base_error.span)
-                    .collect();
+        {
+            fallback = true;
+            let spans: Vec<Span> = bounds
+                .iter()
+                .map(|bound| bound.span())
+                .filter(|&sp| sp != base_error.span)
+                .collect();
 
-                let start_span = first_bound.span();
-                // `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
-                let end_span = last_bound.span();
-                // `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
-                let last_bound_span = spans.last().cloned().unwrap();
-                let mut multi_span: MultiSpan = spans.clone().into();
-                for sp in spans {
-                    let msg = if sp == last_bound_span {
-                        format!(
-                            "...because of {these} bound{s}",
-                            these = pluralize!("this", bounds.len() - 1),
-                            s = pluralize!(bounds.len() - 1),
-                        )
-                    } else {
-                        String::new()
-                    };
-                    multi_span.push_span_label(sp, msg);
-                }
-                multi_span.push_span_label(base_error.span, "expected this type to be a trait...");
-                err.span_help(
-                    multi_span,
-                    "`+` is used to constrain a \"trait object\" type with lifetimes or \
+            let start_span = first_bound.span();
+            // `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
+            let end_span = last_bound.span();
+            // `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
+            let last_bound_span = spans.last().cloned().unwrap();
+            let mut multi_span: MultiSpan = spans.clone().into();
+            for sp in spans {
+                let msg = if sp == last_bound_span {
+                    format!(
+                        "...because of {these} bound{s}",
+                        these = pluralize!("this", bounds.len() - 1),
+                        s = pluralize!(bounds.len() - 1),
+                    )
+                } else {
+                    String::new()
+                };
+                multi_span.push_span_label(sp, msg);
+            }
+            multi_span.push_span_label(base_error.span, "expected this type to be a trait...");
+            err.span_help(
+                multi_span,
+                "`+` is used to constrain a \"trait object\" type with lifetimes or \
                         auto-traits; structs and enums can't be bound in that way",
-                );
-                if bounds.iter().all(|bound| match bound {
-                    ast::GenericBound::Outlives(_) | ast::GenericBound::Use(..) => true,
-                    ast::GenericBound::Trait(tr) => tr.span == base_error.span,
-                }) {
-                    let mut sugg = vec![];
-                    if base_error.span != start_span {
-                        sugg.push((start_span.until(base_error.span), String::new()));
-                    }
-                    if base_error.span != end_span {
-                        sugg.push((base_error.span.shrink_to_hi().to(end_span), String::new()));
-                    }
-
-                    err.multipart_suggestion(
-                        "if you meant to use a type and not a trait here, remove the bounds",
-                        sugg,
-                        Applicability::MaybeIncorrect,
-                    );
+            );
+            if bounds.iter().all(|bound| match bound {
+                ast::GenericBound::Outlives(_) | ast::GenericBound::Use(..) => true,
+                ast::GenericBound::Trait(tr) => tr.span == base_error.span,
+            }) {
+                let mut sugg = vec![];
+                if base_error.span != start_span {
+                    sugg.push((start_span.until(base_error.span), String::new()));
+                }
+                if base_error.span != end_span {
+                    sugg.push((base_error.span.shrink_to_hi().to(end_span), String::new()));
                 }
+
+                err.multipart_suggestion(
+                    "if you meant to use a type and not a trait here, remove the bounds",
+                    sugg,
+                    Applicability::MaybeIncorrect,
+                );
             }
         }
 
@@ -1151,13 +1148,13 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         }
         err.code(E0411);
         err.span_label(span, "`Self` is only available in impls, traits, and type definitions");
-        if let Some(item) = self.diag_metadata.current_item {
-            if let Some(ident) = item.kind.ident() {
-                err.span_label(
-                    ident.span,
-                    format!("`Self` not allowed in {} {}", item.kind.article(), item.kind.descr()),
-                );
-            }
+        if let Some(item) = self.diag_metadata.current_item
+            && let Some(ident) = item.kind.ident()
+        {
+            err.span_label(
+                ident.span,
+                format!("`Self` not allowed in {} {}", item.kind.article(), item.kind.descr()),
+            );
         }
         true
     }
@@ -1461,15 +1458,17 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
                 self.resolve_path(mod_path, None, None)
             {
-                let resolutions = self.r.resolutions(module).borrow();
-                let targets: Vec<_> = resolutions
+                let targets: Vec<_> = self
+                    .r
+                    .resolutions(module)
+                    .borrow()
                     .iter()
                     .filter_map(|(key, resolution)| {
                         resolution
                             .borrow()
                             .best_binding()
                             .map(|binding| binding.res())
-                            .and_then(|res| if filter_fn(res) { Some((key, res)) } else { None })
+                            .and_then(|res| if filter_fn(res) { Some((*key, res)) } else { None })
                     })
                     .collect();
                 if let [target] = targets.as_slice() {
@@ -1932,11 +1931,11 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 };
 
                 let (ctor_def, ctor_vis, fields) = if let Some(struct_ctor) = struct_ctor {
-                    if let PathSource::Expr(Some(parent)) = source {
-                        if let ExprKind::Field(..) | ExprKind::MethodCall(..) = parent.kind {
-                            bad_struct_syntax_suggestion(self, err, def_id);
-                            return true;
-                        }
+                    if let PathSource::Expr(Some(parent)) = source
+                        && let ExprKind::Field(..) | ExprKind::MethodCall(..) = parent.kind
+                    {
+                        bad_struct_syntax_suggestion(self, err, def_id);
+                        return true;
                     }
                     struct_ctor
                 } else {
@@ -2300,8 +2299,9 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             return None;
         }
 
-        let resolutions = self.r.resolutions(*module);
-        let targets = resolutions
+        let targets = self
+            .r
+            .resolutions(*module)
             .borrow()
             .iter()
             .filter_map(|(key, res)| {
@@ -2344,19 +2344,13 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
             if let Some(node_id) =
                 self.diag_metadata.current_self_type.as_ref().and_then(extract_node_id)
+                && let Some(resolution) = self.r.partial_res_map.get(&node_id)
+                && let Some(Res::Def(DefKind::Struct | DefKind::Union, did)) = resolution.full_res()
+                && let Some(fields) = self.r.field_idents(did)
+                && let Some(field) = fields.iter().find(|id| ident.name == id.name)
             {
                 // Look for a field with the same name in the current self_type.
-                if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
-                    if let Some(Res::Def(DefKind::Struct | DefKind::Union, did)) =
-                        resolution.full_res()
-                    {
-                        if let Some(fields) = self.r.field_idents(did) {
-                            if let Some(field) = fields.iter().find(|id| ident.name == id.name) {
-                                return Some(AssocSuggestion::Field(field.span));
-                            }
-                        }
-                    }
-                }
+                return Some(AssocSuggestion::Field(field.span));
             }
         }
 
@@ -2391,44 +2385,44 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         }
 
         // Look for associated items in the current trait.
-        if let Some((module, _)) = self.current_trait_ref {
-            if let Ok(binding) = self.r.maybe_resolve_ident_in_module(
+        if let Some((module, _)) = self.current_trait_ref
+            && let Ok(binding) = self.r.maybe_resolve_ident_in_module(
                 ModuleOrUniformRoot::Module(module),
                 ident,
                 ns,
                 &self.parent_scope,
                 None,
-            ) {
-                let res = binding.res();
-                if filter_fn(res) {
-                    match res {
-                        Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => {
-                            let has_self = match def_id.as_local() {
-                                Some(def_id) => self
-                                    .r
-                                    .delegation_fn_sigs
-                                    .get(&def_id)
-                                    .is_some_and(|sig| sig.has_self),
-                                None => {
-                                    self.r.tcx.fn_arg_idents(def_id).first().is_some_and(|&ident| {
-                                        matches!(ident, Some(Ident { name: kw::SelfLower, .. }))
-                                    })
-                                }
-                            };
-                            if has_self {
-                                return Some(AssocSuggestion::MethodWithSelf { called });
-                            } else {
-                                return Some(AssocSuggestion::AssocFn { called });
+            )
+        {
+            let res = binding.res();
+            if filter_fn(res) {
+                match res {
+                    Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => {
+                        let has_self = match def_id.as_local() {
+                            Some(def_id) => self
+                                .r
+                                .delegation_fn_sigs
+                                .get(&def_id)
+                                .is_some_and(|sig| sig.has_self),
+                            None => {
+                                self.r.tcx.fn_arg_idents(def_id).first().is_some_and(|&ident| {
+                                    matches!(ident, Some(Ident { name: kw::SelfLower, .. }))
+                                })
                             }
+                        };
+                        if has_self {
+                            return Some(AssocSuggestion::MethodWithSelf { called });
+                        } else {
+                            return Some(AssocSuggestion::AssocFn { called });
                         }
-                        Res::Def(DefKind::AssocConst, _) => {
-                            return Some(AssocSuggestion::AssocConst);
-                        }
-                        Res::Def(DefKind::AssocTy, _) => {
-                            return Some(AssocSuggestion::AssocType);
-                        }
-                        _ => {}
                     }
+                    Res::Def(DefKind::AssocConst, _) => {
+                        return Some(AssocSuggestion::AssocConst);
+                    }
+                    Res::Def(DefKind::AssocTy, _) => {
+                        return Some(AssocSuggestion::AssocType);
+                    }
+                    _ => {}
                 }
             }
         }
@@ -2630,7 +2624,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         false
     }
 
-    fn find_module(&mut self, def_id: DefId) -> Option<(Module<'ra>, ImportSuggestion)> {
+    fn find_module(&self, def_id: DefId) -> Option<(Module<'ra>, ImportSuggestion)> {
         let mut result = None;
         let mut seen_modules = FxHashSet::default();
         let root_did = self.r.graph_root.def_id();
@@ -2687,7 +2681,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         result
     }
 
-    fn collect_enum_ctors(&mut self, def_id: DefId) -> Option<Vec<(Path, DefId, CtorKind)>> {
+    fn collect_enum_ctors(&self, def_id: DefId) -> Option<Vec<(Path, DefId, CtorKind)>> {
         self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
             let mut variants = Vec::new();
             enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
@@ -2704,7 +2698,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
 
     /// Adds a suggestion for using an enum's variant when an enum is used instead.
     fn suggest_using_enum_variant(
-        &mut self,
+        &self,
         err: &mut Diag<'_>,
         source: PathSource<'_, '_, '_>,
         def_id: DefId,
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 948b67a3798..dbde6f7cfd7 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -21,7 +21,7 @@
 #![recursion_limit = "256"]
 // tidy-alphabetical-end
 
-use std::cell::{Cell, RefCell};
+use std::cell::{Cell, Ref, RefCell};
 use std::collections::BTreeSet;
 use std::fmt;
 use std::sync::Arc;
@@ -41,7 +41,6 @@ use rustc_ast::{
     self as ast, AngleBracketedArg, CRATE_NODE_ID, Crate, Expr, ExprKind, GenericArg, GenericArgs,
     LitKind, NodeId, Path, attr,
 };
-use rustc_attr_data_structures::StrippedCfgItem;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::steal::Steal;
@@ -50,6 +49,7 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::{Applicability, Diag, ErrCode, ErrorGuaranteed};
 use rustc_expand::base::{DeriveResolution, SyntaxExtension, SyntaxExtensionKind};
 use rustc_feature::BUILTIN_ATTRIBUTES;
+use rustc_hir::attrs::StrippedCfgItem;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{
     self, CtorOf, DefKind, DocLinkResMap, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS,
@@ -64,8 +64,8 @@ use rustc_middle::middle::privacy::EffectiveVisibilities;
 use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{
-    self, DelegationFnSig, Feed, MainDefinition, RegisteredTools, ResolverGlobalCtxt,
-    ResolverOutputs, TyCtxt, TyCtxtFeed, Visibility,
+    self, DelegationFnSig, Feed, MainDefinition, RegisteredTools, ResolverAstLowering,
+    ResolverGlobalCtxt, TyCtxt, TyCtxtFeed, Visibility,
 };
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::lint::builtin::PRIVATE_MACRO_USE;
@@ -119,7 +119,6 @@ enum Scope<'ra> {
     DeriveHelpers(LocalExpnId),
     DeriveHelpersCompat,
     MacroRules(MacroRulesScopeRef<'ra>),
-    CrateRoot,
     // The node ID is for reporting the `PROC_MACRO_DERIVE_RESOLUTION_FALLBACK`
     // lint if it should be reported.
     Module(Module<'ra>, Option<NodeId>),
@@ -139,8 +138,8 @@ enum Scope<'ra> {
 enum ScopeSet<'ra> {
     /// All scopes with the given namespace.
     All(Namespace),
-    /// Crate root, then extern prelude (used for mixed 2015-2018 mode in macros).
-    AbsolutePath(Namespace),
+    /// A module, then extern prelude (used for mixed 2015-2018 mode in macros).
+    ModuleAndExternPrelude(Namespace, Module<'ra>),
     /// All scopes with macro namespace and the given macro kind restriction.
     Macro(MacroKind),
     /// All scopes with the given namespace, used for partially performing late resolution.
@@ -419,8 +418,10 @@ enum ModuleOrUniformRoot<'ra> {
     /// Regular module.
     Module(Module<'ra>),
 
-    /// Virtual module that denotes resolution in crate root with fallback to extern prelude.
-    CrateRootAndExternPrelude,
+    /// Virtual module that denotes resolution in a module with fallback to extern prelude.
+    /// Used for paths starting with `::` coming from 2015 edition macros
+    /// used in 2018+ edition crates.
+    ModuleAndExternPrelude(Module<'ra>),
 
     /// Virtual module that denotes resolution in extern prelude.
     /// Used for paths starting with `::` on 2018 edition.
@@ -579,6 +580,8 @@ struct ModuleData<'ra> {
     lazy_resolutions: Resolutions<'ra>,
     /// True if this is a module from other crate that needs to be populated on access.
     populate_on_access: Cell<bool>,
+    /// Used to disambiguate underscore items (`const _: T = ...`) in the module.
+    underscore_disambiguator: Cell<u32>,
 
     /// Macro invocations that can expand into items in this module.
     unexpanded_invocations: RefCell<FxHashSet<LocalExpnId>>,
@@ -639,6 +642,7 @@ impl<'ra> ModuleData<'ra> {
             kind,
             lazy_resolutions: Default::default(),
             populate_on_access: Cell::new(is_foreign),
+            underscore_disambiguator: Cell::new(0),
             unexpanded_invocations: Default::default(),
             no_implicit_prelude,
             glob_importers: RefCell::new(Vec::new()),
@@ -652,11 +656,23 @@ impl<'ra> ModuleData<'ra> {
 }
 
 impl<'ra> Module<'ra> {
-    fn for_each_child<'tcx, R, F>(self, resolver: &mut R, mut f: F)
-    where
-        R: AsMut<Resolver<'ra, 'tcx>>,
-        F: FnMut(&mut R, Ident, Namespace, NameBinding<'ra>),
-    {
+    fn for_each_child<'tcx, R: AsRef<Resolver<'ra, 'tcx>>>(
+        self,
+        resolver: &R,
+        mut f: impl FnMut(&R, Ident, Namespace, NameBinding<'ra>),
+    ) {
+        for (key, name_resolution) in resolver.as_ref().resolutions(self).borrow().iter() {
+            if let Some(binding) = name_resolution.borrow().best_binding() {
+                f(resolver, key.ident, key.ns, binding);
+            }
+        }
+    }
+
+    fn for_each_child_mut<'tcx, R: AsMut<Resolver<'ra, 'tcx>>>(
+        self,
+        resolver: &mut R,
+        mut f: impl FnMut(&mut R, Ident, Namespace, NameBinding<'ra>),
+    ) {
         for (key, name_resolution) in resolver.as_mut().resolutions(self).borrow().iter() {
             if let Some(binding) = name_resolution.borrow().best_binding() {
                 f(resolver, key.ident, key.ns, binding);
@@ -665,10 +681,7 @@ impl<'ra> Module<'ra> {
     }
 
     /// This modifies `self` in place. The traits will be stored in `self.traits`.
-    fn ensure_traits<'tcx, R>(self, resolver: &mut R)
-    where
-        R: AsMut<Resolver<'ra, 'tcx>>,
-    {
+    fn ensure_traits<'tcx>(self, resolver: &impl AsRef<Resolver<'ra, 'tcx>>) {
         let mut traits = self.traits.borrow_mut();
         if traits.is_none() {
             let mut collected_traits = Vec::new();
@@ -677,7 +690,7 @@ impl<'ra> Module<'ra> {
                     return;
                 }
                 if let Res::Def(DefKind::Trait | DefKind::TraitAlias, def_id) = binding.res() {
-                    collected_traits.push((name, binding, r.as_mut().get_module(def_id)))
+                    collected_traits.push((name, binding, r.as_ref().get_module(def_id)))
                 }
             });
             *traits = Some(collected_traits.into_boxed_slice());
@@ -996,13 +1009,13 @@ impl<'ra> NameBindingData<'ra> {
 
 #[derive(Default, Clone)]
 struct ExternPreludeEntry<'ra> {
-    binding: Option<NameBinding<'ra>>,
+    binding: Cell<Option<NameBinding<'ra>>>,
     introduced_by_item: bool,
 }
 
 impl ExternPreludeEntry<'_> {
     fn is_import(&self) -> bool {
-        self.binding.is_some_and(|binding| binding.is_import())
+        self.binding.get().is_some_and(|binding| binding.is_import())
     }
 }
 
@@ -1024,6 +1037,11 @@ impl MacroData {
     }
 }
 
+pub struct ResolverOutputs {
+    pub global_ctxt: ResolverGlobalCtxt,
+    pub ast_lowering: ResolverAstLowering,
+}
+
 /// The main resolver class.
 ///
 /// This is the visitor that walks the whole crate.
@@ -1336,6 +1354,12 @@ impl<'ra, 'tcx> AsMut<Resolver<'ra, 'tcx>> for Resolver<'ra, 'tcx> {
     }
 }
 
+impl<'ra, 'tcx> AsRef<Resolver<'ra, 'tcx>> for Resolver<'ra, 'tcx> {
+    fn as_ref(&self) -> &Resolver<'ra, 'tcx> {
+        self
+    }
+}
+
 impl<'tcx> Resolver<'_, 'tcx> {
     fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId> {
         self.opt_feed(node).map(|f| f.key())
@@ -1857,7 +1881,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     // We don't reject trait aliases (`trait_module == None`) because we don't have access to their
     // associated items.
     fn trait_may_have_item(
-        &mut self,
+        &self,
         trait_module: Option<Module<'ra>>,
         assoc_item: Option<(Symbol, Namespace)>,
     ) -> bool {
@@ -1889,7 +1913,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         import_ids
     }
 
-    fn resolutions(&mut self, module: Module<'ra>) -> &'ra Resolutions<'ra> {
+    fn resolutions(&self, module: Module<'ra>) -> &'ra Resolutions<'ra> {
         if module.populate_on_access.get() {
             module.populate_on_access.set(false);
             self.build_reduced_graph_external(module);
@@ -1898,12 +1922,19 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     fn resolution(
-        &mut self,
+        &self,
+        module: Module<'ra>,
+        key: BindingKey,
+    ) -> Option<Ref<'ra, NameResolution<'ra>>> {
+        self.resolutions(module).borrow().get(&key).map(|resolution| resolution.borrow())
+    }
+
+    fn resolution_or_default(
+        &self,
         module: Module<'ra>,
         key: BindingKey,
     ) -> &'ra RefCell<NameResolution<'ra>> {
-        *self
-            .resolutions(module)
+        self.resolutions(module)
             .borrow_mut()
             .entry(key)
             .or_insert_with(|| self.arenas.alloc_name_resolution())
@@ -1980,7 +2011,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             // but not introduce it, as used if they are accessed from lexical scope.
             if used == Used::Scope {
                 if let Some(entry) = self.extern_prelude.get(&ident.normalize_to_macros_2_0()) {
-                    if !entry.introduced_by_item && entry.binding == Some(used_binding) {
+                    if !entry.introduced_by_item && entry.binding.get() == Some(used_binding) {
                         return;
                     }
                 }
@@ -2144,7 +2175,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         let norm_ident = ident.normalize_to_macros_2_0();
         let binding = self.extern_prelude.get(&norm_ident).cloned().and_then(|entry| {
-            Some(if let Some(binding) = entry.binding {
+            Some(if let Some(binding) = entry.binding.get() {
                 if finalize {
                     if !entry.is_import() {
                         self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span);
@@ -2169,8 +2200,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             })
         });
 
-        if let Some(entry) = self.extern_prelude.get_mut(&norm_ident) {
-            entry.binding = binding;
+        if let Some(entry) = self.extern_prelude.get(&norm_ident) {
+            entry.binding.set(binding);
         }
 
         binding
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 0e8904a7dea..4e3c0cd5bc0 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -1,22 +1,24 @@
 //! A bunch of methods and structures more or less related to resolving macros and
 //! interface provided by `Resolver` to macro expander.
 
+use std::any::Any;
 use std::cell::Cell;
 use std::mem;
 use std::sync::Arc;
 
 use rustc_ast::{self as ast, Crate, NodeId, attr};
 use rustc_ast_pretty::pprust;
-use rustc_attr_data_structures::{CfgEntry, StabilityLevel, StrippedCfgItem};
 use rustc_errors::{Applicability, DiagCtxtHandle, StashKey};
 use rustc_expand::base::{
     Annotatable, DeriveResolution, Indeterminate, ResolverExpand, SyntaxExtension,
     SyntaxExtensionKind,
 };
-use rustc_expand::compile_declarative_macro;
 use rustc_expand::expand::{
     AstFragment, AstFragmentKind, Invocation, InvocationKind, SupportsMacroExpansion,
 };
+use rustc_expand::{MacroRulesMacroExpander, compile_declarative_macro};
+use rustc_hir::StabilityLevel;
+use rustc_hir::attrs::{CfgEntry, StrippedCfgItem};
 use rustc_hir::def::{self, DefKind, Namespace, NonMacroAttrKind};
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_middle::middle::stability;
@@ -357,8 +359,12 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
             let SyntaxExtensionKind::LegacyBang(ref ext) = m.ext.kind else {
                 continue;
             };
+            let ext: &dyn Any = ext.as_ref();
+            let Some(m) = ext.downcast_ref::<MacroRulesMacroExpander>() else {
+                continue;
+            };
             for arm_i in unused_arms.iter() {
-                if let Some((ident, rule_span)) = ext.get_unused_rule(arm_i) {
+                if let Some((ident, rule_span)) = m.get_unused_rule(arm_i) {
                     self.lint_buffer.buffer_lint(
                         UNUSED_MACRO_RULES,
                         node_id,
@@ -506,7 +512,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
     }
 
     fn glob_delegation_suffixes(
-        &mut self,
+        &self,
         trait_def_id: DefId,
         impl_def_id: LocalDefId,
     ) -> Result<Vec<(Ident, Option<Ident>)>, Indeterminate> {
@@ -1018,40 +1024,39 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         node_id: NodeId,
     ) {
         let span = path.span;
-        if let Some(stability) = &ext.stability {
-            if let StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. } =
+        if let Some(stability) = &ext.stability
+            && let StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. } =
                 stability.level
-            {
-                let feature = stability.feature;
-
-                let is_allowed =
-                    |feature| self.tcx.features().enabled(feature) || span.allows_unstable(feature);
-                let allowed_by_implication = implied_by.is_some_and(|feature| is_allowed(feature));
-                if !is_allowed(feature) && !allowed_by_implication {
-                    let lint_buffer = &mut self.lint_buffer;
-                    let soft_handler = |lint, span, msg: String| {
-                        lint_buffer.buffer_lint(
-                            lint,
-                            node_id,
-                            span,
-                            BuiltinLintDiag::UnstableFeature(
-                                // FIXME make this translatable
-                                msg.into(),
-                            ),
-                        )
-                    };
-                    stability::report_unstable(
-                        self.tcx.sess,
-                        feature,
-                        reason.to_opt_reason(),
-                        issue,
-                        None,
-                        is_soft,
+        {
+            let feature = stability.feature;
+
+            let is_allowed =
+                |feature| self.tcx.features().enabled(feature) || span.allows_unstable(feature);
+            let allowed_by_implication = implied_by.is_some_and(|feature| is_allowed(feature));
+            if !is_allowed(feature) && !allowed_by_implication {
+                let lint_buffer = &mut self.lint_buffer;
+                let soft_handler = |lint, span, msg: String| {
+                    lint_buffer.buffer_lint(
+                        lint,
+                        node_id,
                         span,
-                        soft_handler,
-                        stability::UnstableKind::Regular,
-                    );
-                }
+                        BuiltinLintDiag::UnstableFeature(
+                            // FIXME make this translatable
+                            msg.into(),
+                        ),
+                    )
+                };
+                stability::report_unstable(
+                    self.tcx.sess,
+                    feature,
+                    reason.to_opt_reason(),
+                    issue,
+                    None,
+                    is_soft,
+                    span,
+                    soft_handler,
+                    stability::UnstableKind::Regular,
+                );
             }
         }
         if let Some(depr) = &ext.deprecation {
diff --git a/compiler/rustc_resolve/src/rustdoc.rs b/compiler/rustc_resolve/src/rustdoc.rs
index 24e15ded94f..6450f63472c 100644
--- a/compiler/rustc_resolve/src/rustdoc.rs
+++ b/compiler/rustc_resolve/src/rustdoc.rs
@@ -509,9 +509,8 @@ fn collect_link_data<'input, F: BrokenLinkCallback<'input>>(
     display_text.map(String::into_boxed_str)
 }
 
-/// Returns a tuple containing a span encompassing all the document fragments and a boolean that is
-/// `true` if any of the fragments are from a macro expansion.
-pub fn span_of_fragments_with_expansion(fragments: &[DocFragment]) -> Option<(Span, bool)> {
+/// Returns a span encompassing all the document fragments.
+pub fn span_of_fragments(fragments: &[DocFragment]) -> Option<Span> {
     let (first_fragment, last_fragment) = match fragments {
         [] => return None,
         [first, .., last] => (first, last),
@@ -520,15 +519,7 @@ pub fn span_of_fragments_with_expansion(fragments: &[DocFragment]) -> Option<(Sp
     if first_fragment.span == DUMMY_SP {
         return None;
     }
-    Some((
-        first_fragment.span.to(last_fragment.span),
-        fragments.iter().any(|frag| frag.from_expansion),
-    ))
-}
-
-/// Returns a span encompassing all the document fragments.
-pub fn span_of_fragments(fragments: &[DocFragment]) -> Option<Span> {
-    span_of_fragments_with_expansion(fragments).map(|(sp, _)| sp)
+    Some(first_fragment.span.to(last_fragment.span))
 }
 
 /// Attempts to match a range of bytes from parsed markdown to a `Span` in the source code.
@@ -686,7 +677,7 @@ pub fn source_span_for_markdown_range_inner(
         }
     }
 
-    let (span, _) = span_of_fragments_with_expansion(fragments)?;
+    let span = span_of_fragments(fragments)?;
     let src_span = span.from_inner(InnerSpan::new(
         md_range.start + start_bytes,
         md_range.end + start_bytes + end_bytes,