Revert "Auto merge of #101620 - cjgillot:compute_lint_levels_by_def, r=oli-obk"

This reverts commit 2cb9a65684dba47c52de8fa938febf97a73e70a9, reversing
changes made to 750bd1a7ff3e010611b97ee75d30b7cbf5f3a03c.

5 files changed, 286 insertions, 402 deletions

diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 34506c84cb8..7ca6ec5d962 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -560,7 +560,7 @@ pub struct LateContext<'tcx> {
 
 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 pub struct EarlyContext<'a> {
-    pub builder: LintLevelsBuilder<'a, crate::levels::TopDown>,
+    pub builder: LintLevelsBuilder<'a>,
     pub buffered: LintBuffer,
 }
 
diff --git a/compiler/rustc_lint/src/early.rs b/compiler/rustc_lint/src/early.rs
index 45f54cfed2d..96ecd79a69c 100644
--- a/compiler/rustc_lint/src/early.rs
+++ b/compiler/rustc_lint/src/early.rs
@@ -59,7 +59,6 @@ impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
         F: FnOnce(&mut Self),
     {
         let is_crate_node = id == ast::CRATE_NODE_ID;
-        debug!(?id);
         let push = self.context.builder.push(attrs, is_crate_node, None);
 
         self.check_id(id);
diff --git a/compiler/rustc_lint/src/expect.rs b/compiler/rustc_lint/src/expect.rs
index b9a3d52ca9b..699e8154318 100644
--- a/compiler/rustc_lint/src/expect.rs
+++ b/compiler/rustc_lint/src/expect.rs
@@ -16,10 +16,8 @@ fn check_expectations(tcx: TyCtxt<'_>, tool_filter: Option<Symbol>) {
         return;
     }
 
-    let lint_expectations = tcx.lint_expectations(());
     let fulfilled_expectations = tcx.sess.diagnostic().steal_fulfilled_expectation_ids();
-
-    tracing::debug!(?lint_expectations, ?fulfilled_expectations);
+    let lint_expectations = &tcx.lint_levels(()).lint_expectations;
 
     for (id, expectation) in lint_expectations {
         // This check will always be true, since `lint_expectations` only
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index a9ba2ad1d10..1e16ac51e9e 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -6,11 +6,10 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, Diagnostic, LintDiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::{intravisit, HirId};
-use rustc_index::vec::IndexVec;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::lint::{
-    reveal_actual_level, struct_lint_level, LevelAndSource, LintExpectation, LintLevelSource,
-    ShallowLintLevelMap,
+    struct_lint_level, LevelAndSource, LintExpectation, LintLevelMap, LintLevelSets,
+    LintLevelSource, LintSet, LintStackIndex, COMMAND_LINE,
 };
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{RegisteredTools, TyCtxt};
@@ -28,292 +27,47 @@ use crate::errors::{
     UnknownToolInScopedLint,
 };
 
-/// Collection of lint levels for the whole crate.
-/// This is used by AST-based lints, which do not
-/// wait until we have built HIR to be emitted.
-#[derive(Debug)]
-struct LintLevelSets {
-    /// Linked list of specifications.
-    list: IndexVec<LintStackIndex, LintSet>,
-}
-
-rustc_index::newtype_index! {
-    struct LintStackIndex {
-        ENCODABLE = custom, // we don't need encoding
-        const COMMAND_LINE = 0,
-    }
-}
-
-/// Specifications found at this position in the stack.  This map only represents the lints
-/// found for one set of attributes (like `shallow_lint_levels_on` does).
-///
-/// We store the level specifications as a linked list.
-/// Each `LintSet` represents a set of attributes on the same AST node.
-/// The `parent` forms a linked list that matches the AST tree.
-/// This way, walking the linked list is equivalent to walking the AST bottom-up
-/// to find the specifications for a given lint.
-#[derive(Debug)]
-struct LintSet {
-    // -A,-W,-D flags, a `Symbol` for the flag itself and `Level` for which
-    // flag.
-    specs: FxHashMap<LintId, LevelAndSource>,
-    parent: LintStackIndex,
-}
-
-impl LintLevelSets {
-    fn new() -> Self {
-        LintLevelSets { list: IndexVec::new() }
-    }
-
-    fn get_lint_level(
-        &self,
-        lint: &'static Lint,
-        idx: LintStackIndex,
-        aux: Option<&FxHashMap<LintId, LevelAndSource>>,
-        sess: &Session,
-    ) -> LevelAndSource {
-        let lint = LintId::of(lint);
-        let (level, mut src) = self.raw_lint_id_level(lint, idx, aux);
-        let level = reveal_actual_level(level, &mut src, sess, lint, |id| {
-            self.raw_lint_id_level(id, idx, aux)
-        });
-        (level, src)
-    }
-
-    fn raw_lint_id_level(
-        &self,
-        id: LintId,
-        mut idx: LintStackIndex,
-        aux: Option<&FxHashMap<LintId, LevelAndSource>>,
-    ) -> (Option<Level>, LintLevelSource) {
-        if let Some(specs) = aux {
-            if let Some(&(level, src)) = specs.get(&id) {
-                return (Some(level), src);
-            }
-        }
-        loop {
-            let LintSet { ref specs, parent } = self.list[idx];
-            if let Some(&(level, src)) = specs.get(&id) {
-                return (Some(level), src);
-            }
-            if idx == COMMAND_LINE {
-                return (None, LintLevelSource::Default);
-            }
-            idx = parent;
-        }
-    }
-}
-
-fn lint_expectations(tcx: TyCtxt<'_>, (): ()) -> Vec<(LintExpectationId, LintExpectation)> {
+fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
     let store = unerased_lint_store(tcx);
+    let levels =
+        LintLevelsBuilder::new(tcx.sess, false, &store, &tcx.resolutions(()).registered_tools);
+    let mut builder = LintLevelMapBuilder { levels, tcx };
+    let krate = tcx.hir().krate();
 
-    let mut builder = LintLevelsBuilder {
-        sess: tcx.sess,
-        provider: QueryMapExpectationsWrapper {
-            tcx,
-            cur: hir::CRATE_HIR_ID,
-            specs: ShallowLintLevelMap::default(),
-            expectations: Vec::new(),
-            unstable_to_stable_ids: FxHashMap::default(),
-        },
-        warn_about_weird_lints: false,
-        store,
-        registered_tools: &tcx.resolutions(()).registered_tools,
-    };
-
-    builder.add_command_line();
-    builder.add_id(hir::CRATE_HIR_ID);
-    tcx.hir().walk_toplevel_module(&mut builder);
-
-    tcx.sess.diagnostic().update_unstable_expectation_id(&builder.provider.unstable_to_stable_ids);
+    builder.levels.id_to_set.reserve(krate.owners.len() + 1);
 
-    builder.provider.expectations
-}
+    let push =
+        builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), true, Some(hir::CRATE_HIR_ID));
 
-fn shallow_lint_levels_on(tcx: TyCtxt<'_>, hir_id: HirId) -> ShallowLintLevelMap {
-    let store = unerased_lint_store(tcx);
-
-    let mut levels = LintLevelsBuilder {
-        sess: tcx.sess,
-        provider: LintLevelQueryMap { tcx, cur: hir_id, specs: ShallowLintLevelMap::default() },
-        warn_about_weird_lints: false,
-        store,
-        registered_tools: &tcx.resolutions(()).registered_tools,
-    };
-
-    let is_crate = hir::CRATE_HIR_ID == hir_id;
-    if is_crate {
-        levels.add_command_line();
-    }
-    debug!(?hir_id);
-    levels.add(tcx.hir().attrs(hir_id), is_crate, Some(hir_id));
+    builder.levels.register_id(hir::CRATE_HIR_ID);
+    tcx.hir().walk_toplevel_module(&mut builder);
+    builder.levels.pop(push);
 
-    levels.provider.specs
+    builder.levels.update_unstable_expectation_ids();
+    builder.levels.build_map()
 }
 
-pub struct TopDown {
+pub struct LintLevelsBuilder<'s> {
+    sess: &'s Session,
+    lint_expectations: Vec<(LintExpectationId, LintExpectation)>,
+    /// Each expectation has a stable and an unstable identifier. This map
+    /// is used to map from unstable to stable [`LintExpectationId`]s.
+    expectation_id_map: FxHashMap<LintExpectationId, LintExpectationId>,
     sets: LintLevelSets,
+    id_to_set: FxHashMap<HirId, LintStackIndex>,
     cur: LintStackIndex,
-}
-
-pub trait LintLevelsProvider {
-    fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource>;
-    fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource>;
-    fn get_lint_level(&self, lint: &'static Lint, sess: &Session) -> LevelAndSource;
-    fn push_expectation(&mut self, _id: LintExpectationId, _expectation: LintExpectation) {}
-}
-
-impl LintLevelsProvider for TopDown {
-    fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource> {
-        &self.sets.list[self.cur].specs
-    }
-
-    fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource> {
-        &mut self.sets.list[self.cur].specs
-    }
-
-    fn get_lint_level(&self, lint: &'static Lint, sess: &Session) -> LevelAndSource {
-        self.sets.get_lint_level(lint, self.cur, Some(self.current_specs()), sess)
-    }
-}
-
-struct LintLevelQueryMap<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    cur: HirId,
-    specs: ShallowLintLevelMap,
-}
-
-impl LintLevelsProvider for LintLevelQueryMap<'_> {
-    fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource> {
-        &self.specs.specs
-    }
-    fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource> {
-        &mut self.specs.specs
-    }
-    fn get_lint_level(&self, lint: &'static Lint, _: &Session) -> LevelAndSource {
-        self.specs.lint_level_id_at_node(self.tcx, LintId::of(lint), self.cur)
-    }
-}
-
-struct QueryMapExpectationsWrapper<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    cur: HirId,
-    specs: ShallowLintLevelMap,
-    expectations: Vec<(LintExpectationId, LintExpectation)>,
-    unstable_to_stable_ids: FxHashMap<LintExpectationId, LintExpectationId>,
-}
-
-impl LintLevelsProvider for QueryMapExpectationsWrapper<'_> {
-    fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource> {
-        &self.specs.specs
-    }
-    fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource> {
-        self.specs.specs.clear();
-        &mut self.specs.specs
-    }
-    fn get_lint_level(&self, lint: &'static Lint, _: &Session) -> LevelAndSource {
-        self.specs.lint_level_id_at_node(self.tcx, LintId::of(lint), self.cur)
-    }
-    fn push_expectation(&mut self, id: LintExpectationId, expectation: LintExpectation) {
-        let LintExpectationId::Stable { attr_id: Some(attr_id), hir_id, attr_index, .. } = id else { bug!("unstable expectation id should already be mapped") };
-        let key = LintExpectationId::Unstable { attr_id, lint_index: None };
-
-        if !self.unstable_to_stable_ids.contains_key(&key) {
-            self.unstable_to_stable_ids.insert(
-                key,
-                LintExpectationId::Stable { hir_id, attr_index, lint_index: None, attr_id: None },
-            );
-        }
-
-        self.expectations.push((id.normalize(), expectation));
-    }
-}
-
-impl<'tcx> LintLevelsBuilder<'_, QueryMapExpectationsWrapper<'tcx>> {
-    fn add_id(&mut self, hir_id: HirId) {
-        self.add(self.provider.tcx.hir().attrs(hir_id), hir_id == hir::CRATE_HIR_ID, Some(hir_id));
-    }
-}
-
-impl<'tcx> intravisit::Visitor<'tcx> for LintLevelsBuilder<'_, QueryMapExpectationsWrapper<'tcx>> {
-    type NestedFilter = nested_filter::All;
-
-    fn nested_visit_map(&mut self) -> Self::Map {
-        self.provider.tcx.hir()
-    }
-
-    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
-        self.add_id(param.hir_id);
-        intravisit::walk_param(self, param);
-    }
-
-    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
-        self.add_id(it.hir_id());
-        intravisit::walk_item(self, it);
-    }
-
-    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
-        self.add_id(it.hir_id());
-        intravisit::walk_foreign_item(self, it);
-    }
-
-    fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
-        // We will call `add_id` when we walk
-        // the `StmtKind`. The outer statement itself doesn't
-        // define the lint levels.
-        intravisit::walk_stmt(self, e);
-    }
-
-    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
-        self.add_id(e.hir_id);
-        intravisit::walk_expr(self, e);
-    }
-
-    fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
-        self.add_id(s.hir_id);
-        intravisit::walk_field_def(self, s);
-    }
-
-    fn visit_variant(&mut self, v: &'tcx hir::Variant<'tcx>) {
-        self.add_id(v.id);
-        intravisit::walk_variant(self, v);
-    }
-
-    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
-        self.add_id(l.hir_id);
-        intravisit::walk_local(self, l);
-    }
-
-    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
-        self.add_id(a.hir_id);
-        intravisit::walk_arm(self, a);
-    }
-
-    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
-        self.add_id(trait_item.hir_id());
-        intravisit::walk_trait_item(self, trait_item);
-    }
-
-    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
-        self.add_id(impl_item.hir_id());
-        intravisit::walk_impl_item(self, impl_item);
-    }
-}
-
-pub struct LintLevelsBuilder<'s, P> {
-    sess: &'s Session,
-    provider: P,
     warn_about_weird_lints: bool,
     store: &'s LintStore,
     registered_tools: &'s RegisteredTools,
 }
 
-pub(crate) struct BuilderPush {
+pub struct BuilderPush {
     prev: LintStackIndex,
+    pub changed: bool,
 }
 
-impl<'s> LintLevelsBuilder<'s, TopDown> {
-    pub(crate) fn new(
+impl<'s> LintLevelsBuilder<'s> {
+    pub fn new(
         sess: &'s Session,
         warn_about_weird_lints: bool,
         store: &'s LintStore,
@@ -321,66 +75,20 @@ impl<'s> LintLevelsBuilder<'s, TopDown> {
     ) -> Self {
         let mut builder = LintLevelsBuilder {
             sess,
-            provider: TopDown { sets: LintLevelSets::new(), cur: COMMAND_LINE },
+            lint_expectations: Default::default(),
+            expectation_id_map: Default::default(),
+            sets: LintLevelSets::new(),
+            cur: COMMAND_LINE,
+            id_to_set: Default::default(),
             warn_about_weird_lints,
             store,
             registered_tools,
         };
-        builder.process_command_line();
-        assert_eq!(builder.provider.sets.list.len(), 1);
+        builder.process_command_line(sess, store);
+        assert_eq!(builder.sets.list.len(), 1);
         builder
     }
 
-    fn process_command_line(&mut self) {
-        self.provider.cur = self
-            .provider
-            .sets
-            .list
-            .push(LintSet { specs: FxHashMap::default(), parent: COMMAND_LINE });
-        self.add_command_line();
-    }
-
-    /// Pushes a list of AST lint attributes onto this context.
-    ///
-    /// This function will return a `BuilderPush` object which should be passed
-    /// to `pop` when this scope for the attributes provided is exited.
-    ///
-    /// This function will perform a number of tasks:
-    ///
-    /// * It'll validate all lint-related attributes in `attrs`
-    /// * It'll mark all lint-related attributes as used
-    /// * Lint levels will be updated based on the attributes provided
-    /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
-    ///   `#[allow]`
-    ///
-    /// Don't forget to call `pop`!
-    pub(crate) fn push(
-        &mut self,
-        attrs: &[ast::Attribute],
-        is_crate_node: bool,
-        source_hir_id: Option<HirId>,
-    ) -> BuilderPush {
-        let prev = self.provider.cur;
-        self.provider.cur =
-            self.provider.sets.list.push(LintSet { specs: FxHashMap::default(), parent: prev });
-
-        self.add(attrs, is_crate_node, source_hir_id);
-
-        if self.provider.current_specs().is_empty() {
-            self.provider.sets.list.pop();
-            self.provider.cur = prev;
-        }
-
-        BuilderPush { prev }
-    }
-
-    /// Called after `push` when the scope of a set of attributes are exited.
-    pub(crate) fn pop(&mut self, push: BuilderPush) {
-        self.provider.cur = push.prev;
-    }
-}
-
-impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     pub(crate) fn sess(&self) -> &Session {
         self.sess
     }
@@ -390,20 +98,24 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     }
 
     fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource> {
-        self.provider.current_specs()
+        &self.sets.list[self.cur].specs
     }
 
     fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource> {
-        self.provider.current_specs_mut()
+        &mut self.sets.list[self.cur].specs
     }
 
-    fn add_command_line(&mut self) {
-        for &(ref lint_name, level) in &self.sess.opts.lint_opts {
-            self.store.check_lint_name_cmdline(self.sess, &lint_name, level, self.registered_tools);
+    fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
+        self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
+
+        self.cur =
+            self.sets.list.push(LintSet { specs: FxHashMap::default(), parent: COMMAND_LINE });
+        for &(ref lint_name, level) in &sess.opts.lint_opts {
+            store.check_lint_name_cmdline(sess, &lint_name, level, self.registered_tools);
             let orig_level = level;
             let lint_flag_val = Symbol::intern(lint_name);
 
-            let Ok(ids) = self.store.find_lints(&lint_name) else {
+            let Ok(ids) = store.find_lints(&lint_name) else {
                 // errors handled in check_lint_name_cmdline above
                 continue
             };
@@ -426,11 +138,9 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
     /// (e.g. if a forbid was already inserted on the same scope), then emits a
     /// diagnostic with no change to `specs`.
-    fn insert_spec(&mut self, id: LintId, (mut level, src): LevelAndSource) {
-        let (old_level, old_src) = self.provider.get_lint_level(id.lint, &self.sess);
-        if let Level::Expect(id) = &mut level && let LintExpectationId::Stable { .. } = id {
-            *id = id.normalize();
-        }
+    fn insert_spec(&mut self, id: LintId, (level, src): LevelAndSource) {
+        let (old_level, old_src) =
+            self.sets.get_lint_level(id.lint, self.cur, Some(self.current_specs()), &self.sess);
         // Setting to a non-forbid level is an error if the lint previously had
         // a forbid level. Note that this is not necessarily true even with a
         // `#[forbid(..)]` attribute present, as that is overridden by `--cap-lints`.
@@ -448,7 +158,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                 let id_name = id.lint.name_lower();
                 let fcw_warning = match old_src {
                     LintLevelSource::Default => false,
-                    LintLevelSource::Node { name, .. } => self.store.is_lint_group(name),
+                    LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
                 };
                 debug!(
@@ -468,8 +178,8 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                                 id.to_string()
                             ));
                         }
-                        LintLevelSource::Node { span, reason, .. } => {
-                            diag.span_label(span, "`forbid` level set here");
+                        LintLevelSource::Node(_, forbid_source_span, reason) => {
+                            diag.span_label(forbid_source_span, "`forbid` level set here");
                             if let Some(rationale) = reason {
                                 diag.note(rationale.as_str());
                             }
@@ -489,8 +199,11 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                             LintLevelSource::Default => {
                                 OverruledAttributeSub::DefaultSource { id: id.to_string() }
                             }
-                            LintLevelSource::Node { span, reason, .. } => {
-                                OverruledAttributeSub::NodeSource { span, reason }
+                            LintLevelSource::Node(_, forbid_source_span, reason) => {
+                                OverruledAttributeSub::NodeSource {
+                                    span: forbid_source_span,
+                                    reason,
+                                }
                             }
                             LintLevelSource::CommandLine(_, _) => {
                                 OverruledAttributeSub::CommandLineSource
@@ -543,7 +256,29 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         };
     }
 
-    fn add(&mut self, attrs: &[ast::Attribute], is_crate_node: bool, source_hir_id: Option<HirId>) {
+    /// Pushes a list of AST lint attributes onto this context.
+    ///
+    /// This function will return a `BuilderPush` object which should be passed
+    /// to `pop` when this scope for the attributes provided is exited.
+    ///
+    /// This function will perform a number of tasks:
+    ///
+    /// * It'll validate all lint-related attributes in `attrs`
+    /// * It'll mark all lint-related attributes as used
+    /// * Lint levels will be updated based on the attributes provided
+    /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
+    ///   `#[allow]`
+    ///
+    /// Don't forget to call `pop`!
+    pub(crate) fn push(
+        &mut self,
+        attrs: &[ast::Attribute],
+        is_crate_node: bool,
+        source_hir_id: Option<HirId>,
+    ) -> BuilderPush {
+        let prev = self.cur;
+        self.cur = self.sets.list.push(LintSet { specs: FxHashMap::default(), parent: prev });
+
         let sess = self.sess;
         for (attr_index, attr) in attrs.iter().enumerate() {
             if attr.has_name(sym::automatically_derived) {
@@ -558,17 +293,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                 None => continue,
                 // This is the only lint level with a `LintExpectationId` that can be created from an attribute
                 Some(Level::Expect(unstable_id)) if let Some(hir_id) = source_hir_id => {
-                    let LintExpectationId::Unstable { attr_id, lint_index } = unstable_id
-                        else { bug!("stable id Level::from_attr") };
-
-                    let stable_id = LintExpectationId::Stable {
-                        hir_id,
-                        attr_index: attr_index.try_into().unwrap(),
-                        lint_index,
-                        // we pass the previous unstable attr_id such that we can trace the ast id when building a map
-                        // to go from unstable to stable id.
-                        attr_id: Some(attr_id),
-                    };
+                    let stable_id = self.create_stable_id(unstable_id, hir_id, attr_index);
 
                     Level::Expect(stable_id)
                 }
@@ -683,7 +408,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                                 [lint] => *lint == LintId::of(UNFULFILLED_LINT_EXPECTATIONS),
                                 _ => false,
                             };
-                            self.provider.push_expectation(
+                            self.lint_expectations.push((
                                 expect_id,
                                 LintExpectation::new(
                                     reason,
@@ -691,19 +416,13 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                                     is_unfulfilled_lint_expectations,
                                     tool_name,
                                 ),
-                            );
+                            ));
                         }
-                        let src = LintLevelSource::Node {
-                            name: meta_item
-                                .path
-                                .segments
-                                .last()
-                                .expect("empty lint name")
-                                .ident
-                                .name,
-                            span: sp,
+                        let src = LintLevelSource::Node(
+                            meta_item.path.segments.last().expect("empty lint name").ident.name,
+                            sp,
                             reason,
-                        };
+                        );
                         for &id in *ids {
                             if self.check_gated_lint(id, attr.span) {
                                 self.insert_spec(id, (level, src));
@@ -716,26 +435,31 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                             Ok(ids) => {
                                 let complete_name =
                                     &format!("{}::{}", tool_ident.unwrap().name, name);
-                                let src = LintLevelSource::Node {
-                                    name: Symbol::intern(complete_name),
-                                    span: sp,
+                                let src = LintLevelSource::Node(
+                                    Symbol::intern(complete_name),
+                                    sp,
                                     reason,
-                                };
+                                );
                                 for &id in ids {
                                     if self.check_gated_lint(id, attr.span) {
                                         self.insert_spec(id, (level, src));
                                     }
                                 }
                                 if let Level::Expect(expect_id) = level {
-                                    self.provider.push_expectation(
+                                    self.lint_expectations.push((
                                         expect_id,
                                         LintExpectation::new(reason, sp, false, tool_name),
-                                    );
+                                    ));
                                 }
                             }
                             Err((Some(ids), ref new_lint_name)) => {
                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
-                                let (lvl, src) = self.provider.get_lint_level(lint, &sess);
+                                let (lvl, src) = self.sets.get_lint_level(
+                                    lint,
+                                    self.cur,
+                                    Some(self.current_specs()),
+                                    &sess,
+                                );
                                 struct_lint_level(
                                     self.sess,
                                     lint,
@@ -759,19 +483,19 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                                     },
                                 );
 
-                                let src = LintLevelSource::Node {
-                                    name: Symbol::intern(&new_lint_name),
-                                    span: sp,
+                                let src = LintLevelSource::Node(
+                                    Symbol::intern(&new_lint_name),
+                                    sp,
                                     reason,
-                                };
+                                );
                                 for id in ids {
                                     self.insert_spec(*id, (level, src));
                                 }
                                 if let Level::Expect(expect_id) = level {
-                                    self.provider.push_expectation(
+                                    self.lint_expectations.push((
                                         expect_id,
                                         LintExpectation::new(reason, sp, false, tool_name),
-                                    );
+                                    ));
                                 }
                             }
                             Err((None, _)) => {
@@ -797,7 +521,12 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
 
                     CheckLintNameResult::Warning(msg, renamed) => {
                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
-                        let (renamed_lint_level, src) = self.provider.get_lint_level(lint, &sess);
+                        let (renamed_lint_level, src) = self.sets.get_lint_level(
+                            lint,
+                            self.cur,
+                            Some(self.current_specs()),
+                            &sess,
+                        );
                         struct_lint_level(
                             self.sess,
                             lint,
@@ -820,7 +549,12 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                     }
                     CheckLintNameResult::NoLint(suggestion) => {
                         let lint = builtin::UNKNOWN_LINTS;
-                        let (level, src) = self.provider.get_lint_level(lint, self.sess);
+                        let (level, src) = self.sets.get_lint_level(
+                            lint,
+                            self.cur,
+                            Some(self.current_specs()),
+                            self.sess,
+                        );
                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
                             let name = if let Some(tool_ident) = tool_ident {
                                 format!("{}::{}", tool_ident.name, name)
@@ -849,21 +583,17 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                     if let CheckLintNameResult::Ok(ids) =
                         self.store.check_lint_name(&new_name, None, self.registered_tools)
                     {
-                        let src = LintLevelSource::Node {
-                            name: Symbol::intern(&new_name),
-                            span: sp,
-                            reason,
-                        };
+                        let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
                         for &id in ids {
                             if self.check_gated_lint(id, attr.span) {
                                 self.insert_spec(id, (level, src));
                             }
                         }
                         if let Level::Expect(expect_id) = level {
-                            self.provider.push_expectation(
+                            self.lint_expectations.push((
                                 expect_id,
                                 LintExpectation::new(reason, sp, false, tool_name),
-                            );
+                            ));
                         }
                     } else {
                         panic!("renamed lint does not exist: {}", new_name);
@@ -878,12 +608,13 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                     continue;
                 }
 
-                let LintLevelSource::Node { name: lint_attr_name, span: lint_attr_span, .. } = *src else {
+                let LintLevelSource::Node(lint_attr_name, lint_attr_span, _) = *src else {
                     continue
                 };
 
                 let lint = builtin::UNUSED_ATTRIBUTES;
-                let (lint_level, lint_src) = self.provider.get_lint_level(lint, &self.sess);
+                let (lint_level, lint_src) =
+                    self.sets.get_lint_level(lint, self.cur, Some(self.current_specs()), self.sess);
                 struct_lint_level(
                     self.sess,
                     lint,
@@ -903,13 +634,32 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                 break;
             }
         }
+
+        if self.current_specs().is_empty() {
+            self.sets.list.pop();
+            self.cur = prev;
+        }
+
+        BuilderPush { prev, changed: prev != self.cur }
+    }
+
+    fn create_stable_id(
+        &mut self,
+        unstable_id: LintExpectationId,
+        hir_id: HirId,
+        attr_index: usize,
+    ) -> LintExpectationId {
+        let stable_id =
+            LintExpectationId::Stable { hir_id, attr_index: attr_index as u16, lint_index: None };
+
+        self.expectation_id_map.insert(unstable_id, stable_id);
+
+        stable_id
     }
 
     /// Checks if the lint is gated on a feature that is not enabled.
     ///
     /// Returns `true` if the lint's feature is enabled.
-    // FIXME only emit this once for each attribute, instead of repeating it 4 times for
-    // pre-expansion lints, post-expansion lints, `shallow_lint_levels_on` and `lint_expectations`.
     fn check_gated_lint(&self, lint_id: LintId, span: Span) -> bool {
         if let Some(feature) = lint_id.lint.feature_gate {
             if !self.sess.features_untracked().enabled(feature) {
@@ -928,14 +678,19 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         true
     }
 
+    /// Called after `push` when the scope of a set of attributes are exited.
+    pub fn pop(&mut self, push: BuilderPush) {
+        self.cur = push.prev;
+    }
+
     /// Find the lint level for a lint.
-    pub fn lint_level(&self, lint: &'static Lint) -> LevelAndSource {
-        self.provider.get_lint_level(lint, self.sess)
+    pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
+        self.sets.get_lint_level(lint, self.cur, None, self.sess)
     }
 
     /// Used to emit a lint-related diagnostic based on the current state of
     /// this lint context.
-    pub(crate) fn struct_lint(
+    pub fn struct_lint(
         &self,
         lint: &'static Lint,
         span: Option<MultiSpan>,
@@ -944,8 +699,141 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         let (level, src) = self.lint_level(lint);
         struct_lint_level(self.sess, lint, level, src, span, decorate)
     }
+
+    /// Registers the ID provided with the current set of lints stored in
+    /// this context.
+    pub fn register_id(&mut self, id: HirId) {
+        self.id_to_set.insert(id, self.cur);
+    }
+
+    fn update_unstable_expectation_ids(&self) {
+        self.sess.diagnostic().update_unstable_expectation_id(&self.expectation_id_map);
+    }
+
+    pub fn build_map(self) -> LintLevelMap {
+        LintLevelMap {
+            sets: self.sets,
+            id_to_set: self.id_to_set,
+            lint_expectations: self.lint_expectations,
+        }
+    }
+}
+
+struct LintLevelMapBuilder<'tcx> {
+    levels: LintLevelsBuilder<'tcx>,
+    tcx: TyCtxt<'tcx>,
+}
+
+impl LintLevelMapBuilder<'_> {
+    fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let is_crate_hir = id == hir::CRATE_HIR_ID;
+        let attrs = self.tcx.hir().attrs(id);
+        let push = self.levels.push(attrs, is_crate_hir, Some(id));
+
+        if push.changed {
+            self.levels.register_id(id);
+        }
+        f(self);
+        self.levels.pop(push);
+    }
+}
+
+impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
+    type NestedFilter = nested_filter::All;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.tcx.hir()
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        self.with_lint_attrs(param.hir_id, |builder| {
+            intravisit::walk_param(builder, param);
+        });
+    }
+
+    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
+        self.with_lint_attrs(it.hir_id(), |builder| {
+            intravisit::walk_item(builder, it);
+        });
+    }
+
+    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
+        self.with_lint_attrs(it.hir_id(), |builder| {
+            intravisit::walk_foreign_item(builder, it);
+        })
+    }
+
+    fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
+        // We will call `with_lint_attrs` when we walk
+        // the `StmtKind`. The outer statement itself doesn't
+        // define the lint levels.
+        intravisit::walk_stmt(self, e);
+    }
+
+    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
+        self.with_lint_attrs(e.hir_id, |builder| {
+            intravisit::walk_expr(builder, e);
+        })
+    }
+
+    fn visit_expr_field(&mut self, field: &'tcx hir::ExprField<'tcx>) {
+        self.with_lint_attrs(field.hir_id, |builder| {
+            intravisit::walk_expr_field(builder, field);
+        })
+    }
+
+    fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
+        self.with_lint_attrs(s.hir_id, |builder| {
+            intravisit::walk_field_def(builder, s);
+        })
+    }
+
+    fn visit_variant(&mut self, v: &'tcx hir::Variant<'tcx>) {
+        self.with_lint_attrs(v.id, |builder| {
+            intravisit::walk_variant(builder, v);
+        })
+    }
+
+    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
+        self.with_lint_attrs(l.hir_id, |builder| {
+            intravisit::walk_local(builder, l);
+        })
+    }
+
+    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
+        self.with_lint_attrs(a.hir_id, |builder| {
+            intravisit::walk_arm(builder, a);
+        })
+    }
+
+    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
+        self.with_lint_attrs(trait_item.hir_id(), |builder| {
+            intravisit::walk_trait_item(builder, trait_item);
+        });
+    }
+
+    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
+        self.with_lint_attrs(impl_item.hir_id(), |builder| {
+            intravisit::walk_impl_item(builder, impl_item);
+        });
+    }
+
+    fn visit_pat_field(&mut self, field: &'tcx hir::PatField<'tcx>) {
+        self.with_lint_attrs(field.hir_id, |builder| {
+            intravisit::walk_pat_field(builder, field);
+        })
+    }
+
+    fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
+        self.with_lint_attrs(p.hir_id, |builder| {
+            intravisit::walk_generic_param(builder, p);
+        });
+    }
 }
 
-pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { shallow_lint_levels_on, lint_expectations, ..*providers };
+pub fn provide(providers: &mut Providers) {
+    providers.lint_levels = lint_levels;
 }
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index c760e435699..752a751f6bc 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -35,7 +35,6 @@
 #![feature(iter_order_by)]
 #![feature(let_chains)]
 #![cfg_attr(bootstrap, feature(let_else))]
-#![feature(min_specialization)]
 #![feature(never_type)]
 #![recursion_limit = "256"]