Move late lint machanism in librustc_lint.

Author: cjgillot

src/librustc/lint/context.rs

@@ -17,23 +17,20 @@
 use self::TargetLint::*;
 
 use crate::hir;
-use crate::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
-use crate::hir::intravisit as hir_visit;
-use crate::hir::intravisit::Visitor;
+use crate::hir::def_id::{CrateNum, DefId};
 use crate::hir::map::{definitions::DisambiguatedDefPathData, DefPathData};
 use crate::lint::builtin::BuiltinLintDiagnostics;
 use crate::lint::levels::{LintLevelSets, LintLevelsBuilder};
-use crate::lint::{EarlyLintPassObject, LateLintPass, LateLintPassObject};
-use crate::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId, LintPass};
+use crate::lint::{EarlyLintPassObject, LateLintPassObject};
+use crate::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
 use crate::middle::privacy::AccessLevels;
 use crate::session::Session;
 use crate::ty::layout::{LayoutError, LayoutOf, TyLayout};
 use crate::ty::{self, print::Printer, subst::GenericArg, Ty, TyCtxt};
-use crate::util::common::time;
 use crate::util::nodemap::FxHashMap;
 
 use errors::DiagnosticBuilder;
-use rustc_data_structures::sync::{self, join, par_iter, ParallelIterator};
+use rustc_data_structures::sync;
 use rustc_span::{symbol::Symbol, MultiSpan, Span};
 use std::slice;
 use syntax::ast;
@@ -57,9 +54,9 @@ pub struct LintStore {
     /// necessarily in a sane manner. This is safe though.)
     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>>,
+    pub 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>>,
+    pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
 
     /// Lints indexed by name.
     by_name: FxHashMap<String, TargetLint>,
@@ -446,9 +443,9 @@ pub struct LateContext<'a, 'tcx> {
     pub access_levels: &'a AccessLevels,
 
     /// The store of registered lints and the lint levels.
-    lint_store: &'tcx LintStore,
+    pub lint_store: &'tcx LintStore,
 
-    last_node_with_lint_attrs: hir::HirId,
+    pub last_node_with_lint_attrs: hir::HirId,
 
     /// Generic type parameters in scope for the item we are in.
     pub generics: Option<&'tcx hir::Generics<'tcx>>,
@@ -457,11 +454,6 @@ pub struct LateContext<'a, 'tcx> {
     pub only_module: bool,
 }
 
-pub struct LateContextAndPass<'a, 'tcx, T: LateLintPass<'a, 'tcx>> {
-    context: LateContext<'a, 'tcx>,
-    pass: T,
-}
-
 /// Context for lint checking of the AST, after expansion, before lowering to
 /// HIR.
 pub struct EarlyContext<'a> {
@@ -578,10 +570,6 @@ impl<'a> EarlyContext<'a> {
     }
 }
 
-macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
-    $cx.pass.$f(&$cx.context, $($args),*);
-}) }
-
 impl LintContext for LateContext<'_, '_> {
     type PassObject = LateLintPassObject;
 
@@ -783,434 +771,3 @@ impl<'a, 'tcx> LayoutOf for LateContext<'a, 'tcx> {
         self.tcx.layout_of(self.param_env.and(ty))
     }
 }
-
-impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> LateContextAndPass<'a, 'tcx, T> {
-    /// 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: hir::HirId, attrs: &'tcx [ast::Attribute], f: F)
-    where
-        F: FnOnce(&mut Self),
-    {
-        let prev = self.context.last_node_with_lint_attrs;
-        self.context.last_node_with_lint_attrs = id;
-        self.enter_attrs(attrs);
-        f(self);
-        self.exit_attrs(attrs);
-        self.context.last_node_with_lint_attrs = prev;
-    }
-
-    fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
-    where
-        F: FnOnce(&mut Self),
-    {
-        let old_param_env = self.context.param_env;
-        self.context.param_env =
-            self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
-        f(self);
-        self.context.param_env = old_param_env;
-    }
-
-    fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
-        lint_callback!(self, check_mod, m, s, n);
-        hir_visit::walk_mod(self, m, n);
-        lint_callback!(self, check_mod_post, m, s, n);
-    }
-
-    fn enter_attrs(&mut self, attrs: &'tcx [ast::Attribute]) {
-        debug!("late context: enter_attrs({:?})", attrs);
-        lint_callback!(self, enter_lint_attrs, attrs);
-    }
-
-    fn exit_attrs(&mut self, attrs: &'tcx [ast::Attribute]) {
-        debug!("late context: exit_attrs({:?})", attrs);
-        lint_callback!(self, exit_lint_attrs, attrs);
-    }
-}
-
-impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> hir_visit::Visitor<'tcx>
-    for LateContextAndPass<'a, 'tcx, T>
-{
-    /// Because lints are scoped lexically, we want to walk nested
-    /// items in the context of the outer item, so enable
-    /// deep-walking.
-    fn nested_visit_map<'this>(&'this mut self) -> hir_visit::NestedVisitorMap<'this, 'tcx> {
-        hir_visit::NestedVisitorMap::All(&self.context.tcx.hir())
-    }
-
-    fn visit_nested_body(&mut self, body: hir::BodyId) {
-        let old_tables = self.context.tables;
-        self.context.tables = self.context.tcx.body_tables(body);
-        let body = self.context.tcx.hir().body(body);
-        self.visit_body(body);
-        self.context.tables = old_tables;
-    }
-
-    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
-        self.with_lint_attrs(param.hir_id, &param.attrs, |cx| {
-            lint_callback!(cx, check_param, param);
-            hir_visit::walk_param(cx, param);
-        });
-    }
-
-    fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
-        lint_callback!(self, check_body, body);
-        hir_visit::walk_body(self, body);
-        lint_callback!(self, check_body_post, body);
-    }
-
-    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
-        let generics = self.context.generics.take();
-        self.context.generics = it.kind.generics();
-        self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
-            cx.with_param_env(it.hir_id, |cx| {
-                lint_callback!(cx, check_item, it);
-                hir_visit::walk_item(cx, it);
-                lint_callback!(cx, check_item_post, it);
-            });
-        });
-        self.context.generics = generics;
-    }
-
-    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
-        self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
-            cx.with_param_env(it.hir_id, |cx| {
-                lint_callback!(cx, check_foreign_item, it);
-                hir_visit::walk_foreign_item(cx, it);
-                lint_callback!(cx, check_foreign_item_post, it);
-            });
-        })
-    }
-
-    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
-        lint_callback!(self, check_pat, p);
-        hir_visit::walk_pat(self, p);
-    }
-
-    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
-        self.with_lint_attrs(e.hir_id, &e.attrs, |cx| {
-            lint_callback!(cx, check_expr, e);
-            hir_visit::walk_expr(cx, e);
-            lint_callback!(cx, check_expr_post, e);
-        })
-    }
-
-    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
-        // statement attributes are actually just attributes on one of
-        // - item
-        // - local
-        // - expression
-        // so we keep track of lint levels there
-        lint_callback!(self, check_stmt, s);
-        hir_visit::walk_stmt(self, s);
-    }
-
-    fn visit_fn(
-        &mut self,
-        fk: hir_visit::FnKind<'tcx>,
-        decl: &'tcx hir::FnDecl<'tcx>,
-        body_id: hir::BodyId,
-        span: Span,
-        id: hir::HirId,
-    ) {
-        // Wrap in tables here, not just in visit_nested_body,
-        // in order for `check_fn` to be able to use them.
-        let old_tables = self.context.tables;
-        self.context.tables = self.context.tcx.body_tables(body_id);
-        let body = self.context.tcx.hir().body(body_id);
-        lint_callback!(self, check_fn, fk, decl, body, span, id);
-        hir_visit::walk_fn(self, fk, decl, body_id, span, id);
-        lint_callback!(self, check_fn_post, fk, decl, body, span, id);
-        self.context.tables = old_tables;
-    }
-
-    fn visit_variant_data(
-        &mut self,
-        s: &'tcx hir::VariantData<'tcx>,
-        _: ast::Name,
-        _: &'tcx hir::Generics<'tcx>,
-        _: hir::HirId,
-        _: Span,
-    ) {
-        lint_callback!(self, check_struct_def, s);
-        hir_visit::walk_struct_def(self, s);
-        lint_callback!(self, check_struct_def_post, s);
-    }
-
-    fn visit_struct_field(&mut self, s: &'tcx hir::StructField<'tcx>) {
-        self.with_lint_attrs(s.hir_id, &s.attrs, |cx| {
-            lint_callback!(cx, check_struct_field, s);
-            hir_visit::walk_struct_field(cx, 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, |cx| {
-            lint_callback!(cx, check_variant, v);
-            hir_visit::walk_variant(cx, v, g, item_id);
-            lint_callback!(cx, check_variant_post, v);
-        })
-    }
-
-    fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
-        lint_callback!(self, check_ty, t);
-        hir_visit::walk_ty(self, t);
-    }
-
-    fn visit_name(&mut self, sp: Span, name: ast::Name) {
-        lint_callback!(self, check_name, sp, name);
-    }
-
-    fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
-        if !self.context.only_module {
-            self.process_mod(m, s, n);
-        }
-    }
-
-    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
-        self.with_lint_attrs(l.hir_id, &l.attrs, |cx| {
-            lint_callback!(cx, check_local, l);
-            hir_visit::walk_local(cx, l);
-        })
-    }
-
-    fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
-        lint_callback!(self, check_block, b);
-        hir_visit::walk_block(self, b);
-        lint_callback!(self, check_block_post, b);
-    }
-
-    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
-        lint_callback!(self, check_arm, a);
-        hir_visit::walk_arm(self, a);
-    }
-
-    fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
-        lint_callback!(self, check_generic_param, p);
-        hir_visit::walk_generic_param(self, p);
-    }
-
-    fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
-        lint_callback!(self, check_generics, g);
-        hir_visit::walk_generics(self, g);
-    }
-
-    fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
-        lint_callback!(self, check_where_predicate, p);
-        hir_visit::walk_where_predicate(self, p);
-    }
-
-    fn visit_poly_trait_ref(
-        &mut self,
-        t: &'tcx hir::PolyTraitRef<'tcx>,
-        m: hir::TraitBoundModifier,
-    ) {
-        lint_callback!(self, check_poly_trait_ref, t, m);
-        hir_visit::walk_poly_trait_ref(self, t, m);
-    }
-
-    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
-        let generics = self.context.generics.take();
-        self.context.generics = Some(&trait_item.generics);
-        self.with_lint_attrs(trait_item.hir_id, &trait_item.attrs, |cx| {
-            cx.with_param_env(trait_item.hir_id, |cx| {
-                lint_callback!(cx, check_trait_item, trait_item);
-                hir_visit::walk_trait_item(cx, trait_item);
-                lint_callback!(cx, check_trait_item_post, trait_item);
-            });
-        });
-        self.context.generics = generics;
-    }
-
-    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
-        let generics = self.context.generics.take();
-        self.context.generics = Some(&impl_item.generics);
-        self.with_lint_attrs(impl_item.hir_id, &impl_item.attrs, |cx| {
-            cx.with_param_env(impl_item.hir_id, |cx| {
-                lint_callback!(cx, check_impl_item, impl_item);
-                hir_visit::walk_impl_item(cx, impl_item);
-                lint_callback!(cx, check_impl_item_post, impl_item);
-            });
-        });
-        self.context.generics = generics;
-    }
-
-    fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
-        lint_callback!(self, check_lifetime, lt);
-        hir_visit::walk_lifetime(self, lt);
-    }
-
-    fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
-        lint_callback!(self, check_path, p, id);
-        hir_visit::walk_path(self, p);
-    }
-
-    fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
-        lint_callback!(self, check_attribute, attr);
-    }
-}
-
-struct LateLintPassObjects<'a> {
-    lints: &'a mut [LateLintPassObject],
-}
-
-#[allow(rustc::lint_pass_impl_without_macro)]
-impl LintPass for LateLintPassObjects<'_> {
-    fn name(&self) -> &'static str {
-        panic!()
-    }
-}
-
-macro_rules! expand_late_lint_pass_impl_methods {
-    ([$a:tt, $hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
-        $(fn $name(&mut self, context: &LateContext<$a, $hir>, $($param: $arg),*) {
-            for obj in self.lints.iter_mut() {
-                obj.$name(context, $($param),*);
-            }
-        })*
-    )
-}
-
-macro_rules! late_lint_pass_impl {
-    ([], [$hir:tt], $methods:tt) => (
-        impl LateLintPass<'a, $hir> for LateLintPassObjects<'_> {
-            expand_late_lint_pass_impl_methods!(['a, $hir], $methods);
-        }
-    )
-}
-
-late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
-
-fn late_lint_mod_pass<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
-    tcx: TyCtxt<'tcx>,
-    module_def_id: DefId,
-    pass: T,
-) {
-    let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
-
-    let context = LateContext {
-        tcx,
-        tables: &ty::TypeckTables::empty(None),
-        param_env: ty::ParamEnv::empty(),
-        access_levels,
-        lint_store: &tcx.lint_store,
-        last_node_with_lint_attrs: tcx.hir().as_local_hir_id(module_def_id).unwrap(),
-        generics: None,
-        only_module: true,
-    };
-
-    let mut cx = LateContextAndPass { context, pass };
-
-    let (module, span, hir_id) = tcx.hir().get_module(module_def_id);
-    cx.process_mod(module, span, hir_id);
-
-    // Visit the crate attributes
-    if hir_id == hir::CRATE_HIR_ID {
-        walk_list!(cx, visit_attribute, tcx.hir().attrs(hir::CRATE_HIR_ID));
-    }
-}
-
-pub fn late_lint_mod<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
-    tcx: TyCtxt<'tcx>,
-    module_def_id: DefId,
-    builtin_lints: T,
-) {
-    if tcx.sess.opts.debugging_opts.no_interleave_lints {
-        // These passes runs in late_lint_crate with -Z no_interleave_lints
-        return;
-    }
-
-    late_lint_mod_pass(tcx, module_def_id, builtin_lints);
-
-    let mut passes: Vec<_> =
-        tcx.lint_store.late_module_passes.iter().map(|pass| (pass)()).collect();
-
-    if !passes.is_empty() {
-        late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
-    }
-}
-
-fn late_lint_pass_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
-    let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
-
-    let krate = tcx.hir().krate();
-
-    let context = LateContext {
-        tcx,
-        tables: &ty::TypeckTables::empty(None),
-        param_env: ty::ParamEnv::empty(),
-        access_levels,
-        lint_store: &tcx.lint_store,
-        last_node_with_lint_attrs: hir::CRATE_HIR_ID,
-        generics: None,
-        only_module: false,
-    };
-
-    let mut cx = LateContextAndPass { context, pass };
-
-    // Visit the whole crate.
-    cx.with_lint_attrs(hir::CRATE_HIR_ID, &krate.attrs, |cx| {
-        // since the root module isn't visited as an item (because it isn't an
-        // item), warn for it here.
-        lint_callback!(cx, check_crate, krate);
-
-        hir_visit::walk_crate(cx, krate);
-
-        lint_callback!(cx, check_crate_post, krate);
-    })
-}
-
-fn late_lint_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
-    let mut passes = tcx.lint_store.late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
-
-    if !tcx.sess.opts.debugging_opts.no_interleave_lints {
-        if !passes.is_empty() {
-            late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
-        }
-
-        late_lint_pass_crate(tcx, builtin_lints);
-    } else {
-        for pass in &mut passes {
-            time(tcx.sess, &format!("running late lint: {}", pass.name()), || {
-                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
-            });
-        }
-
-        let mut passes: Vec<_> =
-            tcx.lint_store.late_module_passes.iter().map(|pass| (pass)()).collect();
-
-        for pass in &mut passes {
-            time(tcx.sess, &format!("running late module lint: {}", pass.name()), || {
-                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
-            });
-        }
-    }
-}
-
-/// Performs lint checking on a crate.
-pub fn check_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
-    tcx: TyCtxt<'tcx>,
-    builtin_lints: impl FnOnce() -> T + Send,
-) {
-    join(
-        || {
-            time(tcx.sess, "crate lints", || {
-                // Run whole crate non-incremental lints
-                late_lint_crate(tcx, builtin_lints());
-            });
-        },
-        || {
-            time(tcx.sess, "module lints", || {
-                // Run per-module lints
-                par_iter(&tcx.hir().krate().modules).for_each(|(&module, _)| {
-                    tcx.ensure().lint_mod(tcx.hir().local_def_id(module));
-                });
-            });
-        },
-    );
-}

src/librustc/lint/mod.rs

@@ -39,8 +39,7 @@ use syntax::source_map::{DesugaringKind, ExpnKind, MultiSpan};
 use syntax::symbol::Symbol;
 
 pub use crate::lint::context::{
-    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};

src/librustc_interface/passes.rs

@@ -886,7 +886,7 @@ 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/late.rs

@@ -0,0 +1,473 @@
+//! 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::hir;
+use rustc::hir::def_id::{DefId, LOCAL_CRATE};
+use rustc::hir::intravisit as hir_visit;
+use rustc::hir::intravisit::Visitor;
+use rustc::lint::LateContext;
+use rustc::lint::LintPass;
+use rustc::lint::{LateLintPass, LateLintPassObject};
+use rustc::ty::{self, TyCtxt};
+use rustc::util::common::time;
+
+use rustc_data_structures::sync::{join, par_iter, ParallelIterator};
+use rustc_span::Span;
+use std::slice;
+use syntax::ast;
+
+use log::debug;
+use syntax::walk_list;
+
+macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
+    $cx.pass.$f(&$cx.context, $($args),*);
+}) }
+
+struct LateContextAndPass<'a, 'tcx, T: LateLintPass<'a, 'tcx>> {
+    context: LateContext<'a, 'tcx>,
+    pass: T,
+}
+
+impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> LateContextAndPass<'a, 'tcx, T> {
+    /// 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: hir::HirId, attrs: &'tcx [ast::Attribute], f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let prev = self.context.last_node_with_lint_attrs;
+        self.context.last_node_with_lint_attrs = id;
+        self.enter_attrs(attrs);
+        f(self);
+        self.exit_attrs(attrs);
+        self.context.last_node_with_lint_attrs = prev;
+    }
+
+    fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let old_param_env = self.context.param_env;
+        self.context.param_env =
+            self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
+        f(self);
+        self.context.param_env = old_param_env;
+    }
+
+    fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
+        lint_callback!(self, check_mod, m, s, n);
+        hir_visit::walk_mod(self, m, n);
+        lint_callback!(self, check_mod_post, m, s, n);
+    }
+
+    fn enter_attrs(&mut self, attrs: &'tcx [ast::Attribute]) {
+        debug!("late context: enter_attrs({:?})", attrs);
+        lint_callback!(self, enter_lint_attrs, attrs);
+    }
+
+    fn exit_attrs(&mut self, attrs: &'tcx [ast::Attribute]) {
+        debug!("late context: exit_attrs({:?})", attrs);
+        lint_callback!(self, exit_lint_attrs, attrs);
+    }
+}
+
+impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> hir_visit::Visitor<'tcx>
+    for LateContextAndPass<'a, 'tcx, T>
+{
+    /// Because lints are scoped lexically, we want to walk nested
+    /// items in the context of the outer item, so enable
+    /// deep-walking.
+    fn nested_visit_map<'this>(&'this mut self) -> hir_visit::NestedVisitorMap<'this, 'tcx> {
+        hir_visit::NestedVisitorMap::All(&self.context.tcx.hir())
+    }
+
+    fn visit_nested_body(&mut self, body: hir::BodyId) {
+        let old_tables = self.context.tables;
+        self.context.tables = self.context.tcx.body_tables(body);
+        let body = self.context.tcx.hir().body(body);
+        self.visit_body(body);
+        self.context.tables = old_tables;
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        self.with_lint_attrs(param.hir_id, &param.attrs, |cx| {
+            lint_callback!(cx, check_param, param);
+            hir_visit::walk_param(cx, param);
+        });
+    }
+
+    fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
+        lint_callback!(self, check_body, body);
+        hir_visit::walk_body(self, body);
+        lint_callback!(self, check_body_post, body);
+    }
+
+    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
+        let generics = self.context.generics.take();
+        self.context.generics = it.kind.generics();
+        self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
+            cx.with_param_env(it.hir_id, |cx| {
+                lint_callback!(cx, check_item, it);
+                hir_visit::walk_item(cx, it);
+                lint_callback!(cx, check_item_post, it);
+            });
+        });
+        self.context.generics = generics;
+    }
+
+    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
+        self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
+            cx.with_param_env(it.hir_id, |cx| {
+                lint_callback!(cx, check_foreign_item, it);
+                hir_visit::walk_foreign_item(cx, it);
+                lint_callback!(cx, check_foreign_item_post, it);
+            });
+        })
+    }
+
+    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
+        lint_callback!(self, check_pat, p);
+        hir_visit::walk_pat(self, p);
+    }
+
+    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
+        self.with_lint_attrs(e.hir_id, &e.attrs, |cx| {
+            lint_callback!(cx, check_expr, e);
+            hir_visit::walk_expr(cx, e);
+            lint_callback!(cx, check_expr_post, e);
+        })
+    }
+
+    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
+        // statement attributes are actually just attributes on one of
+        // - item
+        // - local
+        // - expression
+        // so we keep track of lint levels there
+        lint_callback!(self, check_stmt, s);
+        hir_visit::walk_stmt(self, s);
+    }
+
+    fn visit_fn(
+        &mut self,
+        fk: hir_visit::FnKind<'tcx>,
+        decl: &'tcx hir::FnDecl<'tcx>,
+        body_id: hir::BodyId,
+        span: Span,
+        id: hir::HirId,
+    ) {
+        // Wrap in tables here, not just in visit_nested_body,
+        // in order for `check_fn` to be able to use them.
+        let old_tables = self.context.tables;
+        self.context.tables = self.context.tcx.body_tables(body_id);
+        let body = self.context.tcx.hir().body(body_id);
+        lint_callback!(self, check_fn, fk, decl, body, span, id);
+        hir_visit::walk_fn(self, fk, decl, body_id, span, id);
+        lint_callback!(self, check_fn_post, fk, decl, body, span, id);
+        self.context.tables = old_tables;
+    }
+
+    fn visit_variant_data(
+        &mut self,
+        s: &'tcx hir::VariantData<'tcx>,
+        _: ast::Name,
+        _: &'tcx hir::Generics<'tcx>,
+        _: hir::HirId,
+        _: Span,
+    ) {
+        lint_callback!(self, check_struct_def, s);
+        hir_visit::walk_struct_def(self, s);
+        lint_callback!(self, check_struct_def_post, s);
+    }
+
+    fn visit_struct_field(&mut self, s: &'tcx hir::StructField<'tcx>) {
+        self.with_lint_attrs(s.hir_id, &s.attrs, |cx| {
+            lint_callback!(cx, check_struct_field, s);
+            hir_visit::walk_struct_field(cx, 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, |cx| {
+            lint_callback!(cx, check_variant, v);
+            hir_visit::walk_variant(cx, v, g, item_id);
+            lint_callback!(cx, check_variant_post, v);
+        })
+    }
+
+    fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
+        lint_callback!(self, check_ty, t);
+        hir_visit::walk_ty(self, t);
+    }
+
+    fn visit_name(&mut self, sp: Span, name: ast::Name) {
+        lint_callback!(self, check_name, sp, name);
+    }
+
+    fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
+        if !self.context.only_module {
+            self.process_mod(m, s, n);
+        }
+    }
+
+    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
+        self.with_lint_attrs(l.hir_id, &l.attrs, |cx| {
+            lint_callback!(cx, check_local, l);
+            hir_visit::walk_local(cx, l);
+        })
+    }
+
+    fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
+        lint_callback!(self, check_block, b);
+        hir_visit::walk_block(self, b);
+        lint_callback!(self, check_block_post, b);
+    }
+
+    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
+        lint_callback!(self, check_arm, a);
+        hir_visit::walk_arm(self, a);
+    }
+
+    fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
+        lint_callback!(self, check_generic_param, p);
+        hir_visit::walk_generic_param(self, p);
+    }
+
+    fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
+        lint_callback!(self, check_generics, g);
+        hir_visit::walk_generics(self, g);
+    }
+
+    fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
+        lint_callback!(self, check_where_predicate, p);
+        hir_visit::walk_where_predicate(self, p);
+    }
+
+    fn visit_poly_trait_ref(
+        &mut self,
+        t: &'tcx hir::PolyTraitRef<'tcx>,
+        m: hir::TraitBoundModifier,
+    ) {
+        lint_callback!(self, check_poly_trait_ref, t, m);
+        hir_visit::walk_poly_trait_ref(self, t, m);
+    }
+
+    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
+        let generics = self.context.generics.take();
+        self.context.generics = Some(&trait_item.generics);
+        self.with_lint_attrs(trait_item.hir_id, &trait_item.attrs, |cx| {
+            cx.with_param_env(trait_item.hir_id, |cx| {
+                lint_callback!(cx, check_trait_item, trait_item);
+                hir_visit::walk_trait_item(cx, trait_item);
+                lint_callback!(cx, check_trait_item_post, trait_item);
+            });
+        });
+        self.context.generics = generics;
+    }
+
+    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
+        let generics = self.context.generics.take();
+        self.context.generics = Some(&impl_item.generics);
+        self.with_lint_attrs(impl_item.hir_id, &impl_item.attrs, |cx| {
+            cx.with_param_env(impl_item.hir_id, |cx| {
+                lint_callback!(cx, check_impl_item, impl_item);
+                hir_visit::walk_impl_item(cx, impl_item);
+                lint_callback!(cx, check_impl_item_post, impl_item);
+            });
+        });
+        self.context.generics = generics;
+    }
+
+    fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
+        lint_callback!(self, check_lifetime, lt);
+        hir_visit::walk_lifetime(self, lt);
+    }
+
+    fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
+        lint_callback!(self, check_path, p, id);
+        hir_visit::walk_path(self, p);
+    }
+
+    fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
+        lint_callback!(self, check_attribute, attr);
+    }
+}
+
+struct LateLintPassObjects<'a> {
+    lints: &'a mut [LateLintPassObject],
+}
+
+#[allow(rustc::lint_pass_impl_without_macro)]
+impl LintPass for LateLintPassObjects<'_> {
+    fn name(&self) -> &'static str {
+        panic!()
+    }
+}
+
+macro_rules! expand_late_lint_pass_impl_methods {
+    ([$a:tt, $hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &LateContext<$a, $hir>, $($param: $arg),*) {
+            for obj in self.lints.iter_mut() {
+                obj.$name(context, $($param),*);
+            }
+        })*
+    )
+}
+
+macro_rules! late_lint_pass_impl {
+    ([], [$hir:tt], $methods:tt) => (
+        impl<'a, $hir> LateLintPass<'a, $hir> for LateLintPassObjects<'_> {
+            expand_late_lint_pass_impl_methods!(['a, $hir], $methods);
+        }
+    )
+}
+
+late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
+
+fn late_lint_mod_pass<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    module_def_id: DefId,
+    pass: T,
+) {
+    let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
+
+    let context = LateContext {
+        tcx,
+        tables: &ty::TypeckTables::empty(None),
+        param_env: ty::ParamEnv::empty(),
+        access_levels,
+        lint_store: &tcx.lint_store,
+        last_node_with_lint_attrs: tcx.hir().as_local_hir_id(module_def_id).unwrap(),
+        generics: None,
+        only_module: true,
+    };
+
+    let mut cx = LateContextAndPass { context, pass };
+
+    let (module, span, hir_id) = tcx.hir().get_module(module_def_id);
+    cx.process_mod(module, span, hir_id);
+
+    // Visit the crate attributes
+    if hir_id == hir::CRATE_HIR_ID {
+        walk_list!(cx, visit_attribute, tcx.hir().attrs(hir::CRATE_HIR_ID));
+    }
+}
+
+pub fn late_lint_mod<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    module_def_id: DefId,
+    builtin_lints: T,
+) {
+    if tcx.sess.opts.debugging_opts.no_interleave_lints {
+        // These passes runs in late_lint_crate with -Z no_interleave_lints
+        return;
+    }
+
+    late_lint_mod_pass(tcx, module_def_id, builtin_lints);
+
+    let mut passes: Vec<_> =
+        tcx.lint_store.late_module_passes.iter().map(|pass| (pass)()).collect();
+
+    if !passes.is_empty() {
+        late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
+    }
+}
+
+fn late_lint_pass_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
+    let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
+
+    let krate = tcx.hir().krate();
+
+    let context = LateContext {
+        tcx,
+        tables: &ty::TypeckTables::empty(None),
+        param_env: ty::ParamEnv::empty(),
+        access_levels,
+        lint_store: &tcx.lint_store,
+        last_node_with_lint_attrs: hir::CRATE_HIR_ID,
+        generics: None,
+        only_module: false,
+    };
+
+    let mut cx = LateContextAndPass { context, pass };
+
+    // Visit the whole crate.
+    cx.with_lint_attrs(hir::CRATE_HIR_ID, &krate.attrs, |cx| {
+        // since the root module isn't visited as an item (because it isn't an
+        // item), warn for it here.
+        lint_callback!(cx, check_crate, krate);
+
+        hir_visit::walk_crate(cx, krate);
+
+        lint_callback!(cx, check_crate_post, krate);
+    })
+}
+
+fn late_lint_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
+    let mut passes = tcx.lint_store.late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
+
+    if !tcx.sess.opts.debugging_opts.no_interleave_lints {
+        if !passes.is_empty() {
+            late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
+        }
+
+        late_lint_pass_crate(tcx, builtin_lints);
+    } else {
+        for pass in &mut passes {
+            time(tcx.sess, &format!("running late lint: {}", pass.name()), || {
+                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+            });
+        }
+
+        let mut passes: Vec<_> =
+            tcx.lint_store.late_module_passes.iter().map(|pass| (pass)()).collect();
+
+        for pass in &mut passes {
+            time(tcx.sess, &format!("running late module lint: {}", pass.name()), || {
+                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+            });
+        }
+    }
+}
+
+/// Performs lint checking on a crate.
+pub fn check_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    builtin_lints: impl FnOnce() -> T + Send,
+) {
+    join(
+        || {
+            time(tcx.sess, "crate lints", || {
+                // Run whole crate non-incremental lints
+                late_lint_crate(tcx, builtin_lints());
+            });
+        },
+        || {
+            time(tcx.sess, "module lints", || {
+                // Run per-module lints
+                par_iter(&tcx.hir().krate().modules).for_each(|(&module, _)| {
+                    tcx.ensure().lint_mod(tcx.hir().local_def_id(module));
+                });
+            });
+        },
+    );
+}

src/librustc_lint/lib.rs

@@ -25,6 +25,7 @@ extern crate rustc_session;
 mod array_into_iter;
 pub mod builtin;
 mod early;
+mod late;
 mod non_ascii_idents;
 mod nonstandard_style;
 mod redundant_semicolon;
@@ -59,13 +60,14 @@ 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<'_>) {
     *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 {