1 files changed, 482 insertions, 0 deletions
diff --git a/compiler/rustc_lint/src/late.rs b/compiler/rustc_lint/src/late.rs
new file mode 100644
index 000000000..a329b3751
--- /dev/null
+++ b/compiler/rustc_lint/src/late.rs
@@ -0,0 +1,482 @@
+//! 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 crate::{passes::LateLintPassObject, LateContext, LateLintPass, LintStore};
+use rustc_ast as ast;
+use rustc_data_structures::sync::join;
+use rustc_hir as hir;
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::intravisit as hir_visit;
+use rustc_hir::intravisit::Visitor;
+use rustc_middle::hir::nested_filter;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_session::lint::LintPass;
+use rustc_span::symbol::Symbol;
+use rustc_span::Span;
+
+use std::any::Any;
+use std::cell::Cell;
+use std::slice;
+use tracing::debug;
+
+/// Extract the `LintStore` from the query context.
+/// This function exists because we've erased `LintStore` as `dyn Any` in the context.
+pub fn unerased_lint_store(tcx: TyCtxt<'_>) -> &LintStore {
+    let store: &dyn Any = &*tcx.lint_store;
+    store.downcast_ref().unwrap()
+}
+
+macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
+    $cx.pass.$f(&$cx.context, $($args),*);
+}) }
+
+struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
+    context: LateContext<'tcx>,
+    pass: T,
+}
+
+impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'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, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let attrs = self.context.tcx.hir().attrs(id);
+        let prev = self.context.last_node_with_lint_attrs;
+        self.context.last_node_with_lint_attrs = id;
+        debug!("late context: enter_attrs({:?})", attrs);
+        lint_callback!(self, enter_lint_attrs, attrs);
+        f(self);
+        debug!("late context: exit_attrs({:?})", attrs);
+        lint_callback!(self, exit_lint_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);
+    }
+}
+
+impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPass<'tcx, T> {
+    type NestedFilter = nested_filter::All;
+
+    /// 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(&mut self) -> Self::Map {
+        self.context.tcx.hir()
+    }
+
+    fn visit_nested_body(&mut self, body_id: hir::BodyId) {
+        let old_enclosing_body = self.context.enclosing_body.replace(body_id);
+        let old_cached_typeck_results = self.context.cached_typeck_results.get();
+
+        // HACK(eddyb) avoid trashing `cached_typeck_results` when we're
+        // nested in `visit_fn`, which may have already resulted in them
+        // being queried.
+        if old_enclosing_body != Some(body_id) {
+            self.context.cached_typeck_results.set(None);
+        }
+
+        let body = self.context.tcx.hir().body(body_id);
+        self.visit_body(body);
+        self.context.enclosing_body = old_enclosing_body;
+
+        // See HACK comment above.
+        if old_enclosing_body != Some(body_id) {
+            self.context.cached_typeck_results.set(old_cached_typeck_results);
+        }
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        self.with_lint_attrs(param.hir_id, |cx| {
+            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();
+        let old_cached_typeck_results = self.context.cached_typeck_results.take();
+        let old_enclosing_body = self.context.enclosing_body.take();
+        self.with_lint_attrs(it.hir_id(), |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.enclosing_body = old_enclosing_body;
+        self.context.cached_typeck_results.set(old_cached_typeck_results);
+        self.context.generics = generics;
+    }
+
+    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
+        self.with_lint_attrs(it.hir_id(), |cx| {
+            cx.with_param_env(it.hir_id(), |cx| {
+                lint_callback!(cx, check_foreign_item, it);
+                hir_visit::walk_foreign_item(cx, 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, |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>) {
+        // See `EarlyContextAndPass::visit_stmt` for an explanation
+        // of why we call `walk_stmt` outside of `with_lint_attrs`
+        self.with_lint_attrs(s.hir_id, |cx| {
+            lint_callback!(cx, 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 typeck results here, not just in visit_nested_body,
+        // in order for `check_fn` to be able to use them.
+        let old_enclosing_body = self.context.enclosing_body.replace(body_id);
+        let old_cached_typeck_results = self.context.cached_typeck_results.take();
+        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);
+        self.context.enclosing_body = old_enclosing_body;
+        self.context.cached_typeck_results.set(old_cached_typeck_results);
+    }
+
+    fn visit_variant_data(
+        &mut self,
+        s: &'tcx hir::VariantData<'tcx>,
+        _: Symbol,
+        _: &'tcx hir::Generics<'tcx>,
+        _: hir::HirId,
+        _: Span,
+    ) {
+        lint_callback!(self, check_struct_def, s);
+        hir_visit::walk_struct_def(self, s);
+    }
+
+    fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
+        self.with_lint_attrs(s.hir_id, |cx| {
+            lint_callback!(cx, check_field_def, s);
+            hir_visit::walk_field_def(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, |cx| {
+            lint_callback!(cx, check_variant, v);
+            hir_visit::walk_variant(cx, v, g, item_id);
+        })
+    }
+
+    fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
+        lint_callback!(self, check_ty, t);
+        hir_visit::walk_ty(self, t);
+    }
+
+    fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
+        hir_visit::walk_inf(self, inf);
+    }
+
+    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, |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>) {
+        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(), |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);
+            });
+        });
+        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(), |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) {
+        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 {
+    ([$hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &LateContext<$hir>, $($param: $arg),*) {
+            for obj in self.lints.iter_mut() {
+                obj.$name(context, $($param),*);
+            }
+        })*
+    )
+}
+
+macro_rules! late_lint_pass_impl {
+    ([], [$hir:tt], $methods:tt) => {
+        impl<$hir> LateLintPass<$hir> for LateLintPassObjects<'_> {
+            expand_late_lint_pass_impl_methods!([$hir], $methods);
+        }
+    };
+}
+
+crate::late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
+
+fn late_lint_mod_pass<'tcx, T: LateLintPass<'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    module_def_id: LocalDefId,
+    pass: T,
+) {
+    let access_levels = &tcx.privacy_access_levels(());
+
+    let context = LateContext {
+        tcx,
+        enclosing_body: None,
+        cached_typeck_results: Cell::new(None),
+        param_env: ty::ParamEnv::empty(),
+        access_levels,
+        lint_store: unerased_lint_store(tcx),
+        last_node_with_lint_attrs: tcx.hir().local_def_id_to_hir_id(module_def_id),
+        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 {
+        for attr in tcx.hir().attrs(hir::CRATE_HIR_ID).iter() {
+            cx.visit_attribute(attr)
+        }
+    }
+}
+
+pub fn late_lint_mod<'tcx, T: LateLintPass<'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    module_def_id: LocalDefId,
+    builtin_lints: T,
+) {
+    if tcx.sess.opts.unstable_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<_> =
+        unerased_lint_store(tcx).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: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
+    let access_levels = &tcx.privacy_access_levels(());
+
+    let context = LateContext {
+        tcx,
+        enclosing_body: None,
+        cached_typeck_results: Cell::new(None),
+        param_env: ty::ParamEnv::empty(),
+        access_levels,
+        lint_store: unerased_lint_store(tcx),
+        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, |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,);
+        tcx.hir().walk_toplevel_module(cx);
+        tcx.hir().walk_attributes(cx);
+        lint_callback!(cx, check_crate_post,);
+    })
+}
+
+fn late_lint_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
+    let mut passes = unerased_lint_store(tcx).late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
+
+    if !tcx.sess.opts.unstable_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 {
+            tcx.sess.prof.extra_verbose_generic_activity("run_late_lint", pass.name()).run(|| {
+                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+            });
+        }
+
+        let mut passes: Vec<_> =
+            unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
+
+        for pass in &mut passes {
+            tcx.sess.prof.extra_verbose_generic_activity("run_late_module_lint", pass.name()).run(
+                || {
+                    late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+                },
+            );
+        }
+    }
+}
+
+/// Performs lint checking on a crate.
+pub fn check_crate<'tcx, T: LateLintPass<'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    builtin_lints: impl FnOnce() -> T + Send,
+) {
+    join(
+        || {
+            tcx.sess.time("crate_lints", || {
+                // Run whole crate non-incremental lints
+                late_lint_crate(tcx, builtin_lints());
+            });
+        },
+        || {
+            tcx.sess.time("module_lints", || {
+                // Run per-module lints
+                tcx.hir().par_for_each_module(|module| tcx.ensure().lint_mod(module));
+            });
+        },
+    );
+}