Move early and late lint mechanisms to librustc_lint.

src/librustc/lint/levels.rs

@@ -155,7 +155,7 @@ pub struct LintLevelsBuilder<'a> {
 
 pub struct BuilderPush {
     prev: u32,
-    pub(super) changed: bool,
+    pub changed: bool,
 }
 
 impl<'a> LintLevelsBuilder<'a> {

src/librustc/lint/mod.rs

@@ -24,11 +24,8 @@ pub use self::LintSource::*;
 use rustc_data_structures::sync;
 
 use crate::hir;
-use crate::hir::def_id::{CrateNum, LOCAL_CRATE};
-use crate::hir::intravisit;
 use crate::lint::builtin::BuiltinLintDiagnostics;
 use crate::session::{DiagnosticMessageId, Session};
-use crate::ty::query::Providers;
 use crate::ty::TyCtxt;
 use crate::util::nodemap::NodeMap;
 use errors::{DiagnosticBuilder, DiagnosticId};
@@ -39,8 +36,7 @@ use syntax::source_map::{DesugaringKind, ExpnKind, MultiSpan};
 use syntax::symbol::Symbol;
 
 pub use crate::lint::context::{
-    check_ast_crate, check_crate, late_lint_mod, BufferedEarlyLint, CheckLintNameResult,
-    EarlyContext, LateContext, LintContext, LintStore,
+    BufferedEarlyLint, CheckLintNameResult, EarlyContext, LateContext, LintContext, LintStore,
 };
 
 pub use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintId};
@@ -376,11 +372,11 @@ mod context;
 pub mod internal;
 mod levels;
 
-pub use self::levels::{LintLevelMap, LintLevelSets};
+pub use self::levels::{LintLevelMap, LintLevelSets, LintLevelsBuilder};
 
 #[derive(Default)]
 pub struct LintBuffer {
-    map: NodeMap<Vec<BufferedEarlyLint>>,
+    pub map: NodeMap<Vec<BufferedEarlyLint>>,
 }
 
 impl LintBuffer {
@@ -405,7 +401,7 @@ impl LintBuffer {
         }
     }
 
-    fn take(&mut self, id: ast::NodeId) -> Vec<BufferedEarlyLint> {
+    pub fn take(&mut self, id: ast::NodeId) -> Vec<BufferedEarlyLint> {
         self.map.remove(&id).unwrap_or_default()
     }
 
@@ -564,122 +560,6 @@ pub fn maybe_lint_level_root(tcx: TyCtxt<'_>, id: hir::HirId) -> bool {
     attrs.iter().any(|attr| Level::from_symbol(attr.name_or_empty()).is_some())
 }
 
-fn lint_levels(tcx: TyCtxt<'_>, cnum: CrateNum) -> &LintLevelMap {
-    assert_eq!(cnum, LOCAL_CRATE);
-    let store = &tcx.lint_store;
-    let mut builder = LintLevelMapBuilder {
-        levels: LintLevelSets::builder(tcx.sess, false, &store),
-        tcx: tcx,
-        store: store,
-    };
-    let krate = tcx.hir().krate();
-
-    let push = builder.levels.push(&krate.attrs, &store);
-    builder.levels.register_id(hir::CRATE_HIR_ID);
-    for macro_def in krate.exported_macros {
-        builder.levels.register_id(macro_def.hir_id);
-    }
-    intravisit::walk_crate(&mut builder, krate);
-    builder.levels.pop(push);
-
-    tcx.arena.alloc(builder.levels.build_map())
-}
-
-struct LintLevelMapBuilder<'a, 'tcx> {
-    levels: levels::LintLevelsBuilder<'tcx>,
-    tcx: TyCtxt<'tcx>,
-    store: &'a LintStore,
-}
-
-impl LintLevelMapBuilder<'_, '_> {
-    fn with_lint_attrs<F>(&mut self, id: hir::HirId, attrs: &[ast::Attribute], f: F)
-    where
-        F: FnOnce(&mut Self),
-    {
-        let push = self.levels.push(attrs, self.store);
-        if push.changed {
-            self.levels.register_id(id);
-        }
-        f(self);
-        self.levels.pop(push);
-    }
-}
-
-impl intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
-        intravisit::NestedVisitorMap::All(&self.tcx.hir())
-    }
-
-    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
-        self.with_lint_attrs(param.hir_id, &param.attrs, |builder| {
-            intravisit::walk_param(builder, param);
-        });
-    }
-
-    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
-        self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
-            intravisit::walk_item(builder, it);
-        });
-    }
-
-    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
-        self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
-            intravisit::walk_foreign_item(builder, it);
-        })
-    }
-
-    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
-        self.with_lint_attrs(e.hir_id, &e.attrs, |builder| {
-            intravisit::walk_expr(builder, e);
-        })
-    }
-
-    fn visit_struct_field(&mut self, s: &'tcx hir::StructField<'tcx>) {
-        self.with_lint_attrs(s.hir_id, &s.attrs, |builder| {
-            intravisit::walk_struct_field(builder, s);
-        })
-    }
-
-    fn visit_variant(
-        &mut self,
-        v: &'tcx hir::Variant<'tcx>,
-        g: &'tcx hir::Generics<'tcx>,
-        item_id: hir::HirId,
-    ) {
-        self.with_lint_attrs(v.id, &v.attrs, |builder| {
-            intravisit::walk_variant(builder, v, g, item_id);
-        })
-    }
-
-    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
-        self.with_lint_attrs(l.hir_id, &l.attrs, |builder| {
-            intravisit::walk_local(builder, l);
-        })
-    }
-
-    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
-        self.with_lint_attrs(a.hir_id, &a.attrs, |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, &trait_item.attrs, |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, &impl_item.attrs, |builder| {
-            intravisit::walk_impl_item(builder, impl_item);
-        });
-    }
-}
-
-pub fn provide(providers: &mut Providers<'_>) {
-    providers.lint_levels = lint_levels;
-}
-
 /// Returns whether `span` originates in a foreign crate's external macro.
 ///
 /// This is used to test whether a lint should not even begin to figure out whether it should

src/librustc_interface/passes.rs

@@ -231,7 +231,7 @@ fn configure_and_expand_inner<'a>(
     metadata_loader: &'a MetadataLoaderDyn,
 ) -> Result<(ast::Crate, Resolver<'a>)> {
     time(sess, "pre-AST-expansion lint checks", || {
-        lint::check_ast_crate(
+        rustc_lint::check_ast_crate(
             sess,
             lint_store,
             &krate,
@@ -458,7 +458,7 @@ pub fn lower_to_hir<'res, 'tcx>(
     });
 
     time(sess, "early lint checks", || {
-        lint::check_ast_crate(
+        rustc_lint::check_ast_crate(
             sess,
             lint_store,
             &krate,
@@ -692,7 +692,6 @@ pub fn default_provide(providers: &mut ty::query::Providers<'_>) {
     rustc_resolve::provide(providers);
     rustc_traits::provide(providers);
     rustc_metadata::provide(providers);
-    lint::provide(providers);
     rustc_lint::provide(providers);
     rustc_codegen_utils::provide(providers);
     rustc_codegen_ssa::provide(providers);
@@ -886,7 +885,7 @@ fn analysis(tcx: TyCtxt<'_>, cnum: CrateNum) -> Result<()> {
                     },
                     {
                         time(sess, "lint checking", || {
-                            lint::check_crate(tcx, || {
+                            rustc_lint::check_crate(tcx, || {
                                 rustc_lint::BuiltinCombinedLateLintPass::new()
                             });
                         });

src/librustc_lint/early.rs

@@ -0,0 +1,383 @@
+//! Implementation of lint checking.
+//!
+//! The lint checking is mostly consolidated into one pass which runs
+//! after all other analyses. Throughout compilation, lint warnings
+//! can be added via the `add_lint` method on the Session structure. This
+//! requires a span and an ID of the node that the lint is being added to. The
+//! lint isn't actually emitted at that time because it is unknown what the
+//! actual lint level at that location is.
+//!
+//! To actually emit lint warnings/errors, a separate pass is used.
+//! A context keeps track of the current state of all lint levels.
+//! Upon entering a node of the ast which can modify the lint settings, the
+//! previous lint state is pushed onto a stack and the ast is then recursed
+//! upon. As the ast is traversed, this keeps track of the current lint level
+//! for all lint attributes.
+
+use rustc::lint::{EarlyContext, LintStore};
+use rustc::lint::{EarlyLintPass, EarlyLintPassObject};
+use rustc::lint::{LintBuffer, LintContext, LintPass};
+use rustc::session::Session;
+use rustc::util::common::time;
+
+use rustc_span::Span;
+use std::slice;
+use syntax::ast;
+use syntax::visit as ast_visit;
+
+use log::debug;
+
+macro_rules! run_early_pass { ($cx:expr, $f:ident, $($args:expr),*) => ({
+    $cx.pass.$f(&$cx.context, $($args),*);
+}) }
+
+struct EarlyContextAndPass<'a, T: EarlyLintPass> {
+    context: EarlyContext<'a>,
+    pass: T,
+}
+
+impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
+    fn check_id(&mut self, id: ast::NodeId) {
+        for early_lint in self.context.buffered.take(id) {
+            self.context.lookup_and_emit_with_diagnostics(
+                early_lint.lint_id.lint,
+                Some(early_lint.span.clone()),
+                &early_lint.msg,
+                early_lint.diagnostic,
+            );
+        }
+    }
+
+    /// Merge the lints specified by any lint attributes into the
+    /// current lint context, call the provided function, then reset the
+    /// lints in effect to their previous state.
+    fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'a [ast::Attribute], f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let push = self.context.builder.push(attrs, &self.context.lint_store);
+        self.check_id(id);
+        self.enter_attrs(attrs);
+        f(self);
+        self.exit_attrs(attrs);
+        self.context.builder.pop(push);
+    }
+
+    fn enter_attrs(&mut self, attrs: &'a [ast::Attribute]) {
+        debug!("early context: enter_attrs({:?})", attrs);
+        run_early_pass!(self, enter_lint_attrs, attrs);
+    }
+
+    fn exit_attrs(&mut self, attrs: &'a [ast::Attribute]) {
+        debug!("early context: exit_attrs({:?})", attrs);
+        run_early_pass!(self, exit_lint_attrs, attrs);
+    }
+}
+
+impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T> {
+    fn visit_param(&mut self, param: &'a ast::Param) {
+        self.with_lint_attrs(param.id, &param.attrs, |cx| {
+            run_early_pass!(cx, check_param, param);
+            ast_visit::walk_param(cx, param);
+        });
+    }
+
+    fn visit_item(&mut self, it: &'a ast::Item) {
+        self.with_lint_attrs(it.id, &it.attrs, |cx| {
+            run_early_pass!(cx, check_item, it);
+            ast_visit::walk_item(cx, it);
+            run_early_pass!(cx, check_item_post, it);
+        })
+    }
+
+    fn visit_foreign_item(&mut self, it: &'a ast::ForeignItem) {
+        self.with_lint_attrs(it.id, &it.attrs, |cx| {
+            run_early_pass!(cx, check_foreign_item, it);
+            ast_visit::walk_foreign_item(cx, it);
+            run_early_pass!(cx, check_foreign_item_post, it);
+        })
+    }
+
+    fn visit_pat(&mut self, p: &'a ast::Pat) {
+        run_early_pass!(self, check_pat, p);
+        self.check_id(p.id);
+        ast_visit::walk_pat(self, p);
+        run_early_pass!(self, check_pat_post, p);
+    }
+
+    fn visit_expr(&mut self, e: &'a ast::Expr) {
+        self.with_lint_attrs(e.id, &e.attrs, |cx| {
+            run_early_pass!(cx, check_expr, e);
+            ast_visit::walk_expr(cx, e);
+        })
+    }
+
+    fn visit_stmt(&mut self, s: &'a ast::Stmt) {
+        run_early_pass!(self, check_stmt, s);
+        self.check_id(s.id);
+        ast_visit::walk_stmt(self, s);
+    }
+
+    fn visit_fn(
+        &mut self,
+        fk: ast_visit::FnKind<'a>,
+        decl: &'a ast::FnDecl,
+        span: Span,
+        id: ast::NodeId,
+    ) {
+        run_early_pass!(self, check_fn, fk, decl, span, id);
+        self.check_id(id);
+        ast_visit::walk_fn(self, fk, decl, span);
+        run_early_pass!(self, check_fn_post, fk, decl, span, id);
+    }
+
+    fn visit_variant_data(&mut self, s: &'a ast::VariantData) {
+        run_early_pass!(self, check_struct_def, s);
+        if let Some(ctor_hir_id) = s.ctor_id() {
+            self.check_id(ctor_hir_id);
+        }
+        ast_visit::walk_struct_def(self, s);
+        run_early_pass!(self, check_struct_def_post, s);
+    }
+
+    fn visit_struct_field(&mut self, s: &'a ast::StructField) {
+        self.with_lint_attrs(s.id, &s.attrs, |cx| {
+            run_early_pass!(cx, check_struct_field, s);
+            ast_visit::walk_struct_field(cx, s);
+        })
+    }
+
+    fn visit_variant(&mut self, v: &'a ast::Variant) {
+        self.with_lint_attrs(v.id, &v.attrs, |cx| {
+            run_early_pass!(cx, check_variant, v);
+            ast_visit::walk_variant(cx, v);
+            run_early_pass!(cx, check_variant_post, v);
+        })
+    }
+
+    fn visit_ty(&mut self, t: &'a ast::Ty) {
+        run_early_pass!(self, check_ty, t);
+        self.check_id(t.id);
+        ast_visit::walk_ty(self, t);
+    }
+
+    fn visit_ident(&mut self, ident: ast::Ident) {
+        run_early_pass!(self, check_ident, ident);
+    }
+
+    fn visit_mod(&mut self, m: &'a ast::Mod, s: Span, _a: &[ast::Attribute], n: ast::NodeId) {
+        run_early_pass!(self, check_mod, m, s, n);
+        self.check_id(n);
+        ast_visit::walk_mod(self, m);
+        run_early_pass!(self, check_mod_post, m, s, n);
+    }
+
+    fn visit_local(&mut self, l: &'a ast::Local) {
+        self.with_lint_attrs(l.id, &l.attrs, |cx| {
+            run_early_pass!(cx, check_local, l);
+            ast_visit::walk_local(cx, l);
+        })
+    }
+
+    fn visit_block(&mut self, b: &'a ast::Block) {
+        run_early_pass!(self, check_block, b);
+        self.check_id(b.id);
+        ast_visit::walk_block(self, b);
+        run_early_pass!(self, check_block_post, b);
+    }
+
+    fn visit_arm(&mut self, a: &'a ast::Arm) {
+        run_early_pass!(self, check_arm, a);
+        ast_visit::walk_arm(self, a);
+    }
+
+    fn visit_expr_post(&mut self, e: &'a ast::Expr) {
+        run_early_pass!(self, check_expr_post, e);
+    }
+
+    fn visit_generic_param(&mut self, param: &'a ast::GenericParam) {
+        run_early_pass!(self, check_generic_param, param);
+        ast_visit::walk_generic_param(self, param);
+    }
+
+    fn visit_generics(&mut self, g: &'a ast::Generics) {
+        run_early_pass!(self, check_generics, g);
+        ast_visit::walk_generics(self, g);
+    }
+
+    fn visit_where_predicate(&mut self, p: &'a ast::WherePredicate) {
+        run_early_pass!(self, check_where_predicate, p);
+        ast_visit::walk_where_predicate(self, p);
+    }
+
+    fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef, m: &'a ast::TraitBoundModifier) {
+        run_early_pass!(self, check_poly_trait_ref, t, m);
+        ast_visit::walk_poly_trait_ref(self, t, m);
+    }
+
+    fn visit_trait_item(&mut self, trait_item: &'a ast::AssocItem) {
+        self.with_lint_attrs(trait_item.id, &trait_item.attrs, |cx| {
+            run_early_pass!(cx, check_trait_item, trait_item);
+            ast_visit::walk_trait_item(cx, trait_item);
+            run_early_pass!(cx, check_trait_item_post, trait_item);
+        });
+    }
+
+    fn visit_impl_item(&mut self, impl_item: &'a ast::AssocItem) {
+        self.with_lint_attrs(impl_item.id, &impl_item.attrs, |cx| {
+            run_early_pass!(cx, check_impl_item, impl_item);
+            ast_visit::walk_impl_item(cx, impl_item);
+            run_early_pass!(cx, check_impl_item_post, impl_item);
+        });
+    }
+
+    fn visit_lifetime(&mut self, lt: &'a ast::Lifetime) {
+        run_early_pass!(self, check_lifetime, lt);
+        self.check_id(lt.id);
+    }
+
+    fn visit_path(&mut self, p: &'a ast::Path, id: ast::NodeId) {
+        run_early_pass!(self, check_path, p, id);
+        self.check_id(id);
+        ast_visit::walk_path(self, p);
+    }
+
+    fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
+        run_early_pass!(self, check_attribute, attr);
+    }
+
+    fn visit_mac_def(&mut self, mac: &'a ast::MacroDef, id: ast::NodeId) {
+        run_early_pass!(self, check_mac_def, mac, id);
+        self.check_id(id);
+    }
+
+    fn visit_mac(&mut self, mac: &'a ast::Mac) {
+        // FIXME(#54110): So, this setup isn't really right. I think
+        // that (a) the libsyntax visitor ought to be doing this as
+        // part of `walk_mac`, and (b) we should be calling
+        // `visit_path`, *but* that would require a `NodeId`, and I
+        // want to get #53686 fixed quickly. -nmatsakis
+        ast_visit::walk_path(self, &mac.path);
+
+        run_early_pass!(self, check_mac, mac);
+    }
+}
+
+struct EarlyLintPassObjects<'a> {
+    lints: &'a mut [EarlyLintPassObject],
+}
+
+#[allow(rustc::lint_pass_impl_without_macro)]
+impl LintPass for EarlyLintPassObjects<'_> {
+    fn name(&self) -> &'static str {
+        panic!()
+    }
+}
+
+macro_rules! expand_early_lint_pass_impl_methods {
+    ([$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
+            for obj in self.lints.iter_mut() {
+                obj.$name(context, $($param),*);
+            }
+        })*
+    )
+}
+
+macro_rules! early_lint_pass_impl {
+    ([], [$($methods:tt)*]) => (
+        impl EarlyLintPass for EarlyLintPassObjects<'_> {
+            expand_early_lint_pass_impl_methods!([$($methods)*]);
+        }
+    )
+}
+
+early_lint_methods!(early_lint_pass_impl, []);
+
+fn early_lint_crate<T: EarlyLintPass>(
+    sess: &Session,
+    lint_store: &LintStore,
+    krate: &ast::Crate,
+    pass: T,
+    buffered: LintBuffer,
+    warn_about_weird_lints: bool,
+) -> LintBuffer {
+    let mut cx = EarlyContextAndPass {
+        context: EarlyContext::new(sess, lint_store, krate, buffered, warn_about_weird_lints),
+        pass,
+    };
+
+    // Visit the whole crate.
+    cx.with_lint_attrs(ast::CRATE_NODE_ID, &krate.attrs, |cx| {
+        // since the root module isn't visited as an item (because it isn't an
+        // item), warn for it here.
+        run_early_pass!(cx, check_crate, krate);
+
+        ast_visit::walk_crate(cx, krate);
+
+        run_early_pass!(cx, check_crate_post, krate);
+    });
+    cx.context.buffered
+}
+
+pub fn check_ast_crate<T: EarlyLintPass>(
+    sess: &Session,
+    lint_store: &LintStore,
+    krate: &ast::Crate,
+    pre_expansion: bool,
+    lint_buffer: Option<LintBuffer>,
+    builtin_lints: T,
+) {
+    let mut passes: Vec<_> = if pre_expansion {
+        lint_store.pre_expansion_passes.iter().map(|p| (p)()).collect()
+    } else {
+        lint_store.early_passes.iter().map(|p| (p)()).collect()
+    };
+    let mut buffered = lint_buffer.unwrap_or_default();
+
+    if !sess.opts.debugging_opts.no_interleave_lints {
+        buffered =
+            early_lint_crate(sess, lint_store, krate, builtin_lints, buffered, pre_expansion);
+
+        if !passes.is_empty() {
+            buffered = early_lint_crate(
+                sess,
+                lint_store,
+                krate,
+                EarlyLintPassObjects { lints: &mut passes[..] },
+                buffered,
+                pre_expansion,
+            );
+        }
+    } else {
+        for pass in &mut passes {
+            buffered = time(sess, &format!("running lint: {}", pass.name()), || {
+                early_lint_crate(
+                    sess,
+                    lint_store,
+                    krate,
+                    EarlyLintPassObjects { lints: slice::from_mut(pass) },
+                    buffered,
+                    pre_expansion,
+                )
+            });
+        }
+    }
+
+    // All of the buffered lints should have been emitted at this point.
+    // If not, that means that we somehow buffered a lint for a node id
+    // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
+    //
+    // Rustdoc runs everybody-loops before the early lints and removes
+    // function bodies, so it's totally possible for linted
+    // node ids to not exist (e.g., macros defined within functions for the
+    // unused_macro lint) anymore. So we only run this check
+    // when we're not in rustdoc mode. (see issue #47639)
+    if !sess.opts.actually_rustdoc {
+        for (_id, lints) in buffered.map {
+            for early_lint in lints {
+                sess.delay_span_bug(early_lint.span, "failed to process buffered lint here");
+            }
+        }
+    }
+}

src/librustc_lint/levels.rs

@@ -0,0 +1,125 @@
+use rustc::hir;
+use rustc::hir::def_id::{CrateNum, LOCAL_CRATE};
+use rustc::hir::intravisit;
+use rustc::lint::{LintLevelMap, LintLevelSets, LintLevelsBuilder, LintStore};
+use rustc::ty::query::Providers;
+use rustc::ty::TyCtxt;
+use syntax::ast;
+
+pub use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintId};
+
+fn lint_levels(tcx: TyCtxt<'_>, cnum: CrateNum) -> &LintLevelMap {
+    assert_eq!(cnum, LOCAL_CRATE);
+    let store = &tcx.lint_store;
+    let mut builder = LintLevelMapBuilder {
+        levels: LintLevelSets::builder(tcx.sess, false, &store),
+        tcx: tcx,
+        store: store,
+    };
+    let krate = tcx.hir().krate();
+
+    let push = builder.levels.push(&krate.attrs, &store);
+    builder.levels.register_id(hir::CRATE_HIR_ID);
+    for macro_def in krate.exported_macros {
+        builder.levels.register_id(macro_def.hir_id);
+    }
+    intravisit::walk_crate(&mut builder, krate);
+    builder.levels.pop(push);
+
+    tcx.arena.alloc(builder.levels.build_map())
+}
+
+struct LintLevelMapBuilder<'a, 'tcx> {
+    levels: LintLevelsBuilder<'tcx>,
+    tcx: TyCtxt<'tcx>,
+    store: &'a LintStore,
+}
+
+impl LintLevelMapBuilder<'_, '_> {
+    fn with_lint_attrs<F>(&mut self, id: hir::HirId, attrs: &[ast::Attribute], f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let push = self.levels.push(attrs, self.store);
+        if push.changed {
+            self.levels.register_id(id);
+        }
+        f(self);
+        self.levels.pop(push);
+    }
+}
+
+impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
+    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
+        intravisit::NestedVisitorMap::All(&self.tcx.hir())
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        self.with_lint_attrs(param.hir_id, &param.attrs, |builder| {
+            intravisit::walk_param(builder, param);
+        });
+    }
+
+    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
+        self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
+            intravisit::walk_item(builder, it);
+        });
+    }
+
+    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
+        self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
+            intravisit::walk_foreign_item(builder, it);
+        })
+    }
+
+    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
+        self.with_lint_attrs(e.hir_id, &e.attrs, |builder| {
+            intravisit::walk_expr(builder, e);
+        })
+    }
+
+    fn visit_struct_field(&mut self, s: &'tcx hir::StructField<'tcx>) {
+        self.with_lint_attrs(s.hir_id, &s.attrs, |builder| {
+            intravisit::walk_struct_field(builder, s);
+        })
+    }
+
+    fn visit_variant(
+        &mut self,
+        v: &'tcx hir::Variant<'tcx>,
+        g: &'tcx hir::Generics<'tcx>,
+        item_id: hir::HirId,
+    ) {
+        self.with_lint_attrs(v.id, &v.attrs, |builder| {
+            intravisit::walk_variant(builder, v, g, item_id);
+        })
+    }
+
+    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
+        self.with_lint_attrs(l.hir_id, &l.attrs, |builder| {
+            intravisit::walk_local(builder, l);
+        })
+    }
+
+    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
+        self.with_lint_attrs(a.hir_id, &a.attrs, |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, &trait_item.attrs, |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, &impl_item.attrs, |builder| {
+            intravisit::walk_impl_item(builder, impl_item);
+        });
+    }
+}
+
+pub fn provide(providers: &mut Providers<'_>) {
+    providers.lint_levels = lint_levels;
+}

src/librustc_lint/lib.rs

@@ -24,6 +24,9 @@ extern crate rustc_session;
 
 mod array_into_iter;
 pub mod builtin;
+mod early;
+mod late;
+mod levels;
 mod non_ascii_idents;
 mod nonstandard_style;
 mod redundant_semicolon;
@@ -57,13 +60,16 @@ use unused::*;
 
 /// Useful for other parts of the compiler.
 pub use builtin::SoftLints;
+pub use early::check_ast_crate;
+pub use late::check_crate;
 
 pub fn provide(providers: &mut Providers<'_>) {
+    levels::provide(providers);
     *providers = Providers { lint_mod, ..*providers };
 }
 
 fn lint_mod(tcx: TyCtxt<'_>, module_def_id: DefId) {
-    lint::late_lint_mod(tcx, module_def_id, BuiltinCombinedModuleLateLintPass::new());
+    late::late_lint_mod(tcx, module_def_id, BuiltinCombinedModuleLateLintPass::new());
 }
 
 macro_rules! pre_expansion_lint_passes {