Move early lint machanism in librustc_lint.

5 files changed, 399 insertions, 370 deletions

diff --git a/src/librustc/lint/context.rs b/src/librustc/lint/context.rs
index 6e0bb3a2a2b..ad6bdae1697 100644
--- a/src/librustc/lint/context.rs
+++ b/src/librustc/lint/context.rs
@@ -23,7 +23,7 @@ use crate::hir::intravisit::Visitor;
 use crate::hir::map::{definitions::DisambiguatedDefPathData, DefPathData};
 use crate::lint::builtin::BuiltinLintDiagnostics;
 use crate::lint::levels::{LintLevelSets, LintLevelsBuilder};
-use crate::lint::{EarlyLintPass, EarlyLintPassObject, LateLintPass, LateLintPassObject};
+use crate::lint::{EarlyLintPassObject, LateLintPass, LateLintPassObject};
 use crate::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId, LintPass};
 use crate::middle::privacy::AccessLevels;
 use crate::session::Session;
@@ -38,7 +38,6 @@ use rustc_span::{symbol::Symbol, MultiSpan, Span};
 use std::slice;
 use syntax::ast;
 use syntax::util::lev_distance::find_best_match_for_name;
-use syntax::visit as ast_visit;
 
 use rustc_error_codes::*;
 
@@ -56,8 +55,8 @@ pub struct LintStore {
     /// interior mutability, we don't enforce this (and lints should, in theory,
     /// be compatible with being constructed more than once, though not
     /// necessarily in a sane manner. This is safe though.)
-    pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
-    early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
+    pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
+    pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
     late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
     /// This is unique in that we construct them per-module, so not once.
     late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
@@ -455,7 +454,7 @@ pub struct LateContext<'a, 'tcx> {
     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 
     /// We are only looking at one module
-    only_module: bool,
+    pub only_module: bool,
 }
 
 pub struct LateContextAndPass<'a, 'tcx, T: LateLintPass<'a, 'tcx>> {
@@ -472,17 +471,12 @@ pub struct EarlyContext<'a> {
     /// The crate being checked.
     pub krate: &'a ast::Crate,
 
-    builder: LintLevelsBuilder<'a>,
+    pub builder: LintLevelsBuilder<'a>,
 
     /// The store of registered lints and the lint levels.
-    lint_store: &'a LintStore,
+    pub lint_store: &'a LintStore,
 
-    buffered: LintBuffer,
-}
-
-pub struct EarlyContextAndPass<'a, T: EarlyLintPass> {
-    context: EarlyContext<'a>,
-    pass: T,
+    pub buffered: LintBuffer,
 }
 
 pub trait LintPassObject: Sized {}
@@ -567,7 +561,7 @@ pub trait LintContext: Sized {
 }
 
 impl<'a> EarlyContext<'a> {
-    fn new(
+    pub fn new(
         sess: &'a Session,
         lint_store: &'a LintStore,
         krate: &'a ast::Crate,
@@ -588,48 +582,6 @@ macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
     $cx.pass.$f(&$cx.context, $($args),*);
 }) }
 
-macro_rules! run_early_pass { ($cx:expr, $f:ident, $($args:expr),*) => ({
-    $cx.pass.$f(&$cx.context, $($args),*);
-}) }
-
-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 LintContext for LateContext<'_, '_> {
     type PassObject = LateLintPassObject;
 
@@ -1103,195 +1055,6 @@ impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> hir_visit::Visitor<'tcx>
     }
 }
 
-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 LateLintPassObjects<'a> {
     lints: &'a mut [LateLintPassObject],
 }
@@ -1451,122 +1214,3 @@ pub fn check_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
         },
     );
 }
-
-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");
-            }
-        }
-    }
-}
diff --git a/src/librustc/lint/mod.rs b/src/librustc/lint/mod.rs
index 7e433f50db2..f2d7d72360d 100644
--- a/src/librustc/lint/mod.rs
+++ b/src/librustc/lint/mod.rs
@@ -39,8 +39,8 @@ 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,
+    check_crate, late_lint_mod, BufferedEarlyLint, CheckLintNameResult, EarlyContext, LateContext,
+    LintContext, LintStore,
 };
 
 pub use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintId};
@@ -380,7 +380,7 @@ pub use self::levels::{LintLevelMap, LintLevelSets};
 
 #[derive(Default)]
 pub struct LintBuffer {
-    map: NodeMap<Vec<BufferedEarlyLint>>,
+    pub map: NodeMap<Vec<BufferedEarlyLint>>,
 }
 
 impl LintBuffer {
@@ -405,7 +405,7 @@ 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()
     }
 
diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 4d15424112e..35d6d3abdd8 100644
--- a/src/librustc_interface/passes.rs
+++ b/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,
diff --git a/src/librustc_lint/early.rs b/src/librustc_lint/early.rs
new file mode 100644
index 00000000000..482a7822b76
--- /dev/null
+++ b/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");
+            }
+        }
+    }
+}
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index 099f154d4c8..57f260e758d 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -24,6 +24,7 @@ extern crate rustc_session;
 
 mod array_into_iter;
 pub mod builtin;
+mod early;
 mod non_ascii_idents;
 mod nonstandard_style;
 mod redundant_semicolon;
@@ -57,6 +58,7 @@ use unused::*;
 
 /// Useful for other parts of the compiler.
 pub use builtin::SoftLints;
+pub use early::check_ast_crate;
 
 pub fn provide(providers: &mut Providers<'_>) {
     *providers = Providers { lint_mod, ..*providers };