mirror of
https://github.com/rust-lang/rust.git
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1034 lines
39 KiB
Rust
1034 lines
39 KiB
Rust
// This implements the dead-code warning pass.
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// All reachable symbols are live, code called from live code is live, code with certain lint
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// expectations such as `#[expect(unused)]` and `#[expect(dead_code)]` is live, and everything else
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// is dead.
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use hir::def_id::{LocalDefIdMap, LocalDefIdSet};
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use rustc_data_structures::unord::UnordSet;
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use rustc_errors::MultiSpan;
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use rustc_hir as hir;
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use rustc_hir::def::{CtorOf, DefKind, Res};
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use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
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use rustc_hir::intravisit::{self, Visitor};
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use rustc_hir::{Node, PatKind, TyKind};
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use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
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use rustc_middle::middle::privacy::Level;
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use rustc_middle::query::Providers;
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_session::lint::builtin::{DEAD_CODE, UNUSED_TUPLE_STRUCT_FIELDS};
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use rustc_session::lint::{self, Lint, LintId};
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use rustc_span::symbol::{sym, Symbol};
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use rustc_target::abi::FieldIdx;
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use std::mem;
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use crate::errors::{
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ChangeFieldsToBeOfUnitType, IgnoredDerivedImpls, MultipleDeadCodes, ParentInfo,
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UselessAssignment,
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};
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// Any local node that may call something in its body block should be
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// explored. For example, if it's a live Node::Item that is a
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// function, then we should explore its block to check for codes that
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// may need to be marked as live.
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fn should_explore(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
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matches!(
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tcx.opt_hir_node_by_def_id(def_id),
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Some(
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Node::Item(..)
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| Node::ImplItem(..)
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| Node::ForeignItem(..)
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| Node::TraitItem(..)
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| Node::Variant(..)
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| Node::AnonConst(..)
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)
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)
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}
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/// Determine if a work from the worklist is coming from the a `#[allow]`
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/// or a `#[expect]` of `dead_code`
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#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
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enum ComesFromAllowExpect {
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Yes,
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No,
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}
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struct MarkSymbolVisitor<'tcx> {
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worklist: Vec<(LocalDefId, ComesFromAllowExpect)>,
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tcx: TyCtxt<'tcx>,
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maybe_typeck_results: Option<&'tcx ty::TypeckResults<'tcx>>,
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live_symbols: LocalDefIdSet,
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repr_has_repr_c: bool,
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repr_has_repr_simd: bool,
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in_pat: bool,
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ignore_variant_stack: Vec<DefId>,
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// maps from tuple struct constructors to tuple struct items
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struct_constructors: LocalDefIdMap<LocalDefId>,
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// maps from ADTs to ignored derived traits (e.g. Debug and Clone)
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// and the span of their respective impl (i.e., part of the derive
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// macro)
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ignored_derived_traits: LocalDefIdMap<Vec<(DefId, DefId)>>,
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}
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impl<'tcx> MarkSymbolVisitor<'tcx> {
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/// Gets the type-checking results for the current body.
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/// As this will ICE if called outside bodies, only call when working with
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/// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
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#[track_caller]
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fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
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self.maybe_typeck_results
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.expect("`MarkSymbolVisitor::typeck_results` called outside of body")
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}
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fn check_def_id(&mut self, def_id: DefId) {
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if let Some(def_id) = def_id.as_local() {
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if should_explore(self.tcx, def_id) || self.struct_constructors.contains_key(&def_id) {
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self.worklist.push((def_id, ComesFromAllowExpect::No));
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}
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self.live_symbols.insert(def_id);
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}
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}
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fn insert_def_id(&mut self, def_id: DefId) {
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if let Some(def_id) = def_id.as_local() {
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debug_assert!(!should_explore(self.tcx, def_id));
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self.live_symbols.insert(def_id);
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}
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}
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fn handle_res(&mut self, res: Res) {
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match res {
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Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::TyAlias, def_id) => {
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self.check_def_id(def_id);
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}
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_ if self.in_pat => {}
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Res::PrimTy(..) | Res::SelfCtor(..) | Res::Local(..) => {}
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Res::Def(DefKind::Ctor(CtorOf::Variant, ..), ctor_def_id) => {
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let variant_id = self.tcx.parent(ctor_def_id);
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let enum_id = self.tcx.parent(variant_id);
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self.check_def_id(enum_id);
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if !self.ignore_variant_stack.contains(&ctor_def_id) {
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self.check_def_id(variant_id);
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}
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}
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Res::Def(DefKind::Variant, variant_id) => {
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let enum_id = self.tcx.parent(variant_id);
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self.check_def_id(enum_id);
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if !self.ignore_variant_stack.contains(&variant_id) {
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self.check_def_id(variant_id);
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}
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}
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Res::Def(_, def_id) => self.check_def_id(def_id),
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Res::SelfTyParam { trait_: t } => self.check_def_id(t),
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Res::SelfTyAlias { alias_to: i, .. } => self.check_def_id(i),
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Res::ToolMod | Res::NonMacroAttr(..) | Res::Err => {}
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}
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}
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fn lookup_and_handle_method(&mut self, id: hir::HirId) {
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if let Some(def_id) = self.typeck_results().type_dependent_def_id(id) {
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self.check_def_id(def_id);
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} else {
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bug!("no type-dependent def for method");
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}
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}
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fn handle_field_access(&mut self, lhs: &hir::Expr<'_>, hir_id: hir::HirId) {
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match self.typeck_results().expr_ty_adjusted(lhs).kind() {
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ty::Adt(def, _) => {
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let index = self.typeck_results().field_index(hir_id);
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self.insert_def_id(def.non_enum_variant().fields[index].did);
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}
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ty::Tuple(..) => {}
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_ => span_bug!(lhs.span, "named field access on non-ADT"),
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}
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}
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#[allow(dead_code)] // FIXME(81658): should be used + lint reinstated after #83171 relands.
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fn handle_assign(&mut self, expr: &'tcx hir::Expr<'tcx>) {
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if self
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.typeck_results()
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.expr_adjustments(expr)
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.iter()
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.any(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(_)))
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{
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self.visit_expr(expr);
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} else if let hir::ExprKind::Field(base, ..) = expr.kind {
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// Ignore write to field
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self.handle_assign(base);
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} else {
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self.visit_expr(expr);
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}
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}
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#[allow(dead_code)] // FIXME(81658): should be used + lint reinstated after #83171 relands.
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fn check_for_self_assign(&mut self, assign: &'tcx hir::Expr<'tcx>) {
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fn check_for_self_assign_helper<'tcx>(
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typeck_results: &'tcx ty::TypeckResults<'tcx>,
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lhs: &'tcx hir::Expr<'tcx>,
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rhs: &'tcx hir::Expr<'tcx>,
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) -> bool {
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match (&lhs.kind, &rhs.kind) {
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(hir::ExprKind::Path(ref qpath_l), hir::ExprKind::Path(ref qpath_r)) => {
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if let (Res::Local(id_l), Res::Local(id_r)) = (
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typeck_results.qpath_res(qpath_l, lhs.hir_id),
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typeck_results.qpath_res(qpath_r, rhs.hir_id),
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) {
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if id_l == id_r {
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return true;
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}
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}
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return false;
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}
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(hir::ExprKind::Field(lhs_l, ident_l), hir::ExprKind::Field(lhs_r, ident_r)) => {
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if ident_l == ident_r {
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return check_for_self_assign_helper(typeck_results, lhs_l, lhs_r);
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}
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return false;
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}
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_ => {
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return false;
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}
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}
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}
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if let hir::ExprKind::Assign(lhs, rhs, _) = assign.kind
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&& check_for_self_assign_helper(self.typeck_results(), lhs, rhs)
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&& !assign.span.from_expansion()
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{
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let is_field_assign = matches!(lhs.kind, hir::ExprKind::Field(..));
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self.tcx.emit_spanned_lint(
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lint::builtin::DEAD_CODE,
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assign.hir_id,
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assign.span,
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UselessAssignment { is_field_assign, ty: self.typeck_results().expr_ty(lhs) },
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)
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}
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}
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fn handle_field_pattern_match(
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&mut self,
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lhs: &hir::Pat<'_>,
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res: Res,
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pats: &[hir::PatField<'_>],
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) {
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let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
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ty::Adt(adt, _) => adt.variant_of_res(res),
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_ => span_bug!(lhs.span, "non-ADT in struct pattern"),
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};
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for pat in pats {
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if let PatKind::Wild = pat.pat.kind {
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continue;
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}
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let index = self.typeck_results().field_index(pat.hir_id);
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self.insert_def_id(variant.fields[index].did);
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}
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}
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fn handle_tuple_field_pattern_match(
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&mut self,
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lhs: &hir::Pat<'_>,
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res: Res,
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pats: &[hir::Pat<'_>],
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dotdot: hir::DotDotPos,
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) {
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let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
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ty::Adt(adt, _) => adt.variant_of_res(res),
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_ => span_bug!(lhs.span, "non-ADT in tuple struct pattern"),
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};
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let dotdot = dotdot.as_opt_usize().unwrap_or(pats.len());
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let first_n = pats.iter().enumerate().take(dotdot);
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let missing = variant.fields.len() - pats.len();
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let last_n = pats.iter().enumerate().skip(dotdot).map(|(idx, pat)| (idx + missing, pat));
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for (idx, pat) in first_n.chain(last_n) {
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if let PatKind::Wild = pat.kind {
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continue;
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}
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self.insert_def_id(variant.fields[FieldIdx::from_usize(idx)].did);
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}
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}
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fn handle_offset_of(&mut self, expr: &'tcx hir::Expr<'tcx>) {
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let data = self.typeck_results().offset_of_data();
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let &(container, ref indices) =
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data.get(expr.hir_id).expect("no offset_of_data for offset_of");
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let body_did = self.typeck_results().hir_owner.to_def_id();
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let param_env = self.tcx.param_env(body_did);
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let mut current_ty = container;
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for &(variant, field) in indices {
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match current_ty.kind() {
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ty::Adt(def, subst) => {
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let field = &def.variant(variant).fields[field];
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self.insert_def_id(field.did);
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let field_ty = field.ty(self.tcx, subst);
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current_ty = self.tcx.normalize_erasing_regions(param_env, field_ty);
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}
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// we don't need to mark tuple fields as live,
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// but we may need to mark subfields
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ty::Tuple(tys) => {
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current_ty =
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self.tcx.normalize_erasing_regions(param_env, tys[field.as_usize()]);
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}
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_ => span_bug!(expr.span, "named field access on non-ADT"),
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}
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}
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}
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fn mark_live_symbols(&mut self) {
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let mut scanned = UnordSet::default();
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while let Some(work) = self.worklist.pop() {
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if !scanned.insert(work) {
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continue;
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}
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let (id, comes_from_allow_expect) = work;
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// Avoid accessing the HIR for the synthesized associated type generated for RPITITs.
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if self.tcx.is_impl_trait_in_trait(id.to_def_id()) {
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self.live_symbols.insert(id);
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continue;
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}
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// in the case of tuple struct constructors we want to check the item, not the generated
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// tuple struct constructor function
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let id = self.struct_constructors.get(&id).copied().unwrap_or(id);
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if let Some(node) = self.tcx.opt_hir_node_by_def_id(id) {
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// When using `#[allow]` or `#[expect]` of `dead_code`, we do a QOL improvement
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// by declaring fn calls, statics, ... within said items as live, as well as
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// the item itself, although technically this is not the case.
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//
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// This means that the lint for said items will never be fired.
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//
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// This doesn't make any difference for the item declared with `#[allow]`, as
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// the lint firing will be a nop, as it will be silenced by the `#[allow]` of
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// the item.
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//
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// However, for `#[expect]`, the presence or absence of the lint is relevant,
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// so we don't add it to the list of live symbols when it comes from a
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// `#[expect]`. This means that we will correctly report an item as live or not
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// for the `#[expect]` case.
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//
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// Note that an item can and will be duplicated on the worklist with different
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// `ComesFromAllowExpect`, particularly if it was added from the
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// `effective_visibilities` query or from the `#[allow]`/`#[expect]` checks,
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// this "duplication" is essential as otherwise a function with `#[expect]`
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// called from a `pub fn` may be falsely reported as not live, falsely
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// triggering the `unfulfilled_lint_expectations` lint.
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if comes_from_allow_expect != ComesFromAllowExpect::Yes {
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self.live_symbols.insert(id);
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}
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self.visit_node(node);
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}
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}
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}
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/// Automatically generated items marked with `rustc_trivial_field_reads`
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/// will be ignored for the purposes of dead code analysis (see PR #85200
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/// for discussion).
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fn should_ignore_item(&mut self, def_id: DefId) -> bool {
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if let Some(impl_of) = self.tcx.impl_of_method(def_id) {
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if !self.tcx.is_automatically_derived(impl_of) {
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return false;
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}
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if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of)
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&& self.tcx.has_attr(trait_of, sym::rustc_trivial_field_reads)
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{
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let trait_ref = self.tcx.impl_trait_ref(impl_of).unwrap().instantiate_identity();
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if let ty::Adt(adt_def, _) = trait_ref.self_ty().kind()
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&& let Some(adt_def_id) = adt_def.did().as_local()
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{
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self.ignored_derived_traits
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.entry(adt_def_id)
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.or_default()
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.push((trait_of, impl_of));
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}
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return true;
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}
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}
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return false;
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}
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fn visit_node(&mut self, node: Node<'tcx>) {
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if let Node::ImplItem(hir::ImplItem { owner_id, .. }) = node
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&& self.should_ignore_item(owner_id.to_def_id())
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{
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return;
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}
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let had_repr_c = self.repr_has_repr_c;
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let had_repr_simd = self.repr_has_repr_simd;
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self.repr_has_repr_c = false;
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self.repr_has_repr_simd = false;
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match node {
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Node::Item(item) => match item.kind {
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hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) => {
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let def = self.tcx.adt_def(item.owner_id);
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self.repr_has_repr_c = def.repr().c();
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self.repr_has_repr_simd = def.repr().simd();
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intravisit::walk_item(self, item)
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}
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hir::ItemKind::ForeignMod { .. } => {}
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_ => intravisit::walk_item(self, item),
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},
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Node::TraitItem(trait_item) => {
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intravisit::walk_trait_item(self, trait_item);
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}
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Node::ImplItem(impl_item) => {
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let item = self.tcx.local_parent(impl_item.owner_id.def_id);
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if self.tcx.impl_trait_ref(item).is_none() {
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//// If it's a type whose items are live, then it's live, too.
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//// This is done to handle the case where, for example, the static
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//// method of a private type is used, but the type itself is never
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//// called directly.
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let self_ty = self.tcx.type_of(item).instantiate_identity();
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match *self_ty.kind() {
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ty::Adt(def, _) => self.check_def_id(def.did()),
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ty::Foreign(did) => self.check_def_id(did),
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ty::Dynamic(data, ..) => {
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if let Some(def_id) = data.principal_def_id() {
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self.check_def_id(def_id)
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}
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}
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_ => {}
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}
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}
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intravisit::walk_impl_item(self, impl_item);
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}
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Node::ForeignItem(foreign_item) => {
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intravisit::walk_foreign_item(self, foreign_item);
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}
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_ => {}
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}
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self.repr_has_repr_simd = had_repr_simd;
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self.repr_has_repr_c = had_repr_c;
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}
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fn mark_as_used_if_union(&mut self, adt: ty::AdtDef<'tcx>, fields: &[hir::ExprField<'_>]) {
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if adt.is_union() && adt.non_enum_variant().fields.len() > 1 && adt.did().is_local() {
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for field in fields {
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let index = self.typeck_results().field_index(field.hir_id);
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self.insert_def_id(adt.non_enum_variant().fields[index].did);
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}
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}
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}
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}
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|
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impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
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fn visit_nested_body(&mut self, body: hir::BodyId) {
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let old_maybe_typeck_results =
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self.maybe_typeck_results.replace(self.tcx.typeck_body(body));
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let body = self.tcx.hir().body(body);
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self.visit_body(body);
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self.maybe_typeck_results = old_maybe_typeck_results;
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}
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|
|
fn visit_variant_data(&mut self, def: &'tcx hir::VariantData<'tcx>) {
|
|
let tcx = self.tcx;
|
|
let has_repr_c = self.repr_has_repr_c;
|
|
let has_repr_simd = self.repr_has_repr_simd;
|
|
let live_fields = def.fields().iter().filter_map(|f| {
|
|
let def_id = f.def_id;
|
|
if has_repr_c || (f.is_positional() && has_repr_simd) {
|
|
return Some(def_id);
|
|
}
|
|
if !tcx.visibility(f.hir_id.owner.def_id).is_public() {
|
|
return None;
|
|
}
|
|
if tcx.visibility(def_id).is_public() { Some(def_id) } else { None }
|
|
});
|
|
self.live_symbols.extend(live_fields);
|
|
|
|
intravisit::walk_struct_def(self, def);
|
|
}
|
|
|
|
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
|
|
match expr.kind {
|
|
hir::ExprKind::Path(ref qpath @ hir::QPath::TypeRelative(..)) => {
|
|
let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
|
|
self.handle_res(res);
|
|
}
|
|
hir::ExprKind::MethodCall(..) => {
|
|
self.lookup_and_handle_method(expr.hir_id);
|
|
}
|
|
hir::ExprKind::Field(ref lhs, ..) => {
|
|
self.handle_field_access(lhs, expr.hir_id);
|
|
}
|
|
hir::ExprKind::Struct(qpath, fields, _) => {
|
|
let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
|
|
self.handle_res(res);
|
|
if let ty::Adt(adt, _) = self.typeck_results().expr_ty(expr).kind() {
|
|
self.mark_as_used_if_union(*adt, fields);
|
|
}
|
|
}
|
|
hir::ExprKind::Closure(cls) => {
|
|
self.insert_def_id(cls.def_id.to_def_id());
|
|
}
|
|
hir::ExprKind::OffsetOf(..) => {
|
|
self.handle_offset_of(expr);
|
|
}
|
|
_ => (),
|
|
}
|
|
|
|
intravisit::walk_expr(self, expr);
|
|
}
|
|
|
|
fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
|
|
// Inside the body, ignore constructions of variants
|
|
// necessary for the pattern to match. Those construction sites
|
|
// can't be reached unless the variant is constructed elsewhere.
|
|
let len = self.ignore_variant_stack.len();
|
|
self.ignore_variant_stack.extend(arm.pat.necessary_variants());
|
|
intravisit::walk_arm(self, arm);
|
|
self.ignore_variant_stack.truncate(len);
|
|
}
|
|
|
|
fn visit_pat(&mut self, pat: &'tcx hir::Pat<'tcx>) {
|
|
self.in_pat = true;
|
|
match pat.kind {
|
|
PatKind::Struct(ref path, fields, _) => {
|
|
let res = self.typeck_results().qpath_res(path, pat.hir_id);
|
|
self.handle_field_pattern_match(pat, res, fields);
|
|
}
|
|
PatKind::Path(ref qpath) => {
|
|
let res = self.typeck_results().qpath_res(qpath, pat.hir_id);
|
|
self.handle_res(res);
|
|
}
|
|
PatKind::TupleStruct(ref qpath, fields, dotdot) => {
|
|
let res = self.typeck_results().qpath_res(qpath, pat.hir_id);
|
|
self.handle_tuple_field_pattern_match(pat, res, fields, dotdot);
|
|
}
|
|
_ => (),
|
|
}
|
|
|
|
intravisit::walk_pat(self, pat);
|
|
self.in_pat = false;
|
|
}
|
|
|
|
fn visit_path(&mut self, path: &hir::Path<'tcx>, _: hir::HirId) {
|
|
self.handle_res(path.res);
|
|
intravisit::walk_path(self, path);
|
|
}
|
|
|
|
fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
|
|
if let TyKind::OpaqueDef(item_id, _, _) = ty.kind {
|
|
let item = self.tcx.hir().item(item_id);
|
|
intravisit::walk_item(self, item);
|
|
}
|
|
intravisit::walk_ty(self, ty);
|
|
}
|
|
|
|
fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
|
|
// When inline const blocks are used in pattern position, paths
|
|
// referenced by it should be considered as used.
|
|
let in_pat = mem::replace(&mut self.in_pat, false);
|
|
|
|
self.live_symbols.insert(c.def_id);
|
|
intravisit::walk_anon_const(self, c);
|
|
|
|
self.in_pat = in_pat;
|
|
}
|
|
|
|
fn visit_inline_const(&mut self, c: &'tcx hir::ConstBlock) {
|
|
// When inline const blocks are used in pattern position, paths
|
|
// referenced by it should be considered as used.
|
|
let in_pat = mem::replace(&mut self.in_pat, false);
|
|
|
|
self.live_symbols.insert(c.def_id);
|
|
intravisit::walk_inline_const(self, c);
|
|
|
|
self.in_pat = in_pat;
|
|
}
|
|
}
|
|
|
|
fn has_allow_dead_code_or_lang_attr(
|
|
tcx: TyCtxt<'_>,
|
|
def_id: LocalDefId,
|
|
) -> Option<ComesFromAllowExpect> {
|
|
fn has_lang_attr(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
|
|
tcx.has_attr(def_id, sym::lang)
|
|
// Stable attribute for #[lang = "panic_impl"]
|
|
|| tcx.has_attr(def_id, sym::panic_handler)
|
|
}
|
|
|
|
fn has_allow_expect_dead_code(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
|
|
let hir_id = tcx.local_def_id_to_hir_id(def_id);
|
|
let lint_level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, hir_id).0;
|
|
matches!(lint_level, lint::Allow | lint::Expect(_))
|
|
}
|
|
|
|
fn has_used_like_attr(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
|
|
tcx.def_kind(def_id).has_codegen_attrs() && {
|
|
let cg_attrs = tcx.codegen_fn_attrs(def_id);
|
|
|
|
// #[used], #[no_mangle], #[export_name], etc also keeps the item alive
|
|
// forcefully, e.g., for placing it in a specific section.
|
|
cg_attrs.contains_extern_indicator()
|
|
|| cg_attrs.flags.contains(CodegenFnAttrFlags::USED)
|
|
|| cg_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
|
|
}
|
|
}
|
|
|
|
if has_allow_expect_dead_code(tcx, def_id) {
|
|
Some(ComesFromAllowExpect::Yes)
|
|
} else if has_used_like_attr(tcx, def_id) || has_lang_attr(tcx, def_id) {
|
|
Some(ComesFromAllowExpect::No)
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
// These check_* functions seeds items that
|
|
// 1) We want to explicitly consider as live:
|
|
// * Item annotated with #[allow(dead_code)]
|
|
// - This is done so that if we want to suppress warnings for a
|
|
// group of dead functions, we only have to annotate the "root".
|
|
// For example, if both `f` and `g` are dead and `f` calls `g`,
|
|
// then annotating `f` with `#[allow(dead_code)]` will suppress
|
|
// warning for both `f` and `g`.
|
|
// * Item annotated with #[lang=".."]
|
|
// - This is because lang items are always callable from elsewhere.
|
|
// or
|
|
// 2) We are not sure to be live or not
|
|
// * Implementations of traits and trait methods
|
|
fn check_item<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
|
|
struct_constructors: &mut LocalDefIdMap<LocalDefId>,
|
|
id: hir::ItemId,
|
|
) {
|
|
let allow_dead_code = has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id);
|
|
if let Some(comes_from_allow) = allow_dead_code {
|
|
worklist.push((id.owner_id.def_id, comes_from_allow));
|
|
}
|
|
|
|
match tcx.def_kind(id.owner_id) {
|
|
DefKind::Enum => {
|
|
let item = tcx.hir().item(id);
|
|
if let hir::ItemKind::Enum(ref enum_def, _) = item.kind {
|
|
if let Some(comes_from_allow) = allow_dead_code {
|
|
worklist.extend(
|
|
enum_def.variants.iter().map(|variant| (variant.def_id, comes_from_allow)),
|
|
);
|
|
}
|
|
|
|
for variant in enum_def.variants {
|
|
if let Some(ctor_def_id) = variant.data.ctor_def_id() {
|
|
struct_constructors.insert(ctor_def_id, variant.def_id);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
DefKind::Impl { of_trait } => {
|
|
if of_trait {
|
|
worklist.push((id.owner_id.def_id, ComesFromAllowExpect::No));
|
|
}
|
|
|
|
// get DefIds from another query
|
|
let local_def_ids = tcx
|
|
.associated_item_def_ids(id.owner_id)
|
|
.iter()
|
|
.filter_map(|def_id| def_id.as_local());
|
|
|
|
// And we access the Map here to get HirId from LocalDefId
|
|
for id in local_def_ids {
|
|
if of_trait {
|
|
worklist.push((id, ComesFromAllowExpect::No));
|
|
} else if let Some(comes_from_allow) = has_allow_dead_code_or_lang_attr(tcx, id) {
|
|
worklist.push((id, comes_from_allow));
|
|
}
|
|
}
|
|
}
|
|
DefKind::Struct => {
|
|
let item = tcx.hir().item(id);
|
|
if let hir::ItemKind::Struct(ref variant_data, _) = item.kind
|
|
&& let Some(ctor_def_id) = variant_data.ctor_def_id()
|
|
{
|
|
struct_constructors.insert(ctor_def_id, item.owner_id.def_id);
|
|
}
|
|
}
|
|
DefKind::GlobalAsm => {
|
|
// global_asm! is always live.
|
|
worklist.push((id.owner_id.def_id, ComesFromAllowExpect::No));
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
|
|
fn check_trait_item(
|
|
tcx: TyCtxt<'_>,
|
|
worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
|
|
id: hir::TraitItemId,
|
|
) {
|
|
use hir::TraitItemKind::{Const, Fn};
|
|
if matches!(tcx.def_kind(id.owner_id), DefKind::AssocConst | DefKind::AssocFn) {
|
|
let trait_item = tcx.hir().trait_item(id);
|
|
if matches!(trait_item.kind, Const(_, Some(_)) | Fn(_, hir::TraitFn::Provided(_)))
|
|
&& let Some(comes_from_allow) =
|
|
has_allow_dead_code_or_lang_attr(tcx, trait_item.owner_id.def_id)
|
|
{
|
|
worklist.push((trait_item.owner_id.def_id, comes_from_allow));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_foreign_item(
|
|
tcx: TyCtxt<'_>,
|
|
worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
|
|
id: hir::ForeignItemId,
|
|
) {
|
|
if matches!(tcx.def_kind(id.owner_id), DefKind::Static(_) | DefKind::Fn)
|
|
&& let Some(comes_from_allow) = has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id)
|
|
{
|
|
worklist.push((id.owner_id.def_id, comes_from_allow));
|
|
}
|
|
}
|
|
|
|
fn create_and_seed_worklist(
|
|
tcx: TyCtxt<'_>,
|
|
) -> (Vec<(LocalDefId, ComesFromAllowExpect)>, LocalDefIdMap<LocalDefId>) {
|
|
let effective_visibilities = &tcx.effective_visibilities(());
|
|
// see `MarkSymbolVisitor::struct_constructors`
|
|
let mut struct_constructors = Default::default();
|
|
let mut worklist = effective_visibilities
|
|
.iter()
|
|
.filter_map(|(&id, effective_vis)| {
|
|
effective_vis
|
|
.is_public_at_level(Level::Reachable)
|
|
.then_some(id)
|
|
.map(|id| (id, ComesFromAllowExpect::No))
|
|
})
|
|
// Seed entry point
|
|
.chain(
|
|
tcx.entry_fn(())
|
|
.and_then(|(def_id, _)| def_id.as_local().map(|id| (id, ComesFromAllowExpect::No))),
|
|
)
|
|
.collect::<Vec<_>>();
|
|
|
|
let crate_items = tcx.hir_crate_items(());
|
|
for id in crate_items.items() {
|
|
check_item(tcx, &mut worklist, &mut struct_constructors, id);
|
|
}
|
|
|
|
for id in crate_items.trait_items() {
|
|
check_trait_item(tcx, &mut worklist, id);
|
|
}
|
|
|
|
for id in crate_items.foreign_items() {
|
|
check_foreign_item(tcx, &mut worklist, id);
|
|
}
|
|
|
|
(worklist, struct_constructors)
|
|
}
|
|
|
|
fn live_symbols_and_ignored_derived_traits(
|
|
tcx: TyCtxt<'_>,
|
|
(): (),
|
|
) -> (LocalDefIdSet, LocalDefIdMap<Vec<(DefId, DefId)>>) {
|
|
let (worklist, struct_constructors) = create_and_seed_worklist(tcx);
|
|
let mut symbol_visitor = MarkSymbolVisitor {
|
|
worklist,
|
|
tcx,
|
|
maybe_typeck_results: None,
|
|
live_symbols: Default::default(),
|
|
repr_has_repr_c: false,
|
|
repr_has_repr_simd: false,
|
|
in_pat: false,
|
|
ignore_variant_stack: vec![],
|
|
struct_constructors,
|
|
ignored_derived_traits: Default::default(),
|
|
};
|
|
symbol_visitor.mark_live_symbols();
|
|
(symbol_visitor.live_symbols, symbol_visitor.ignored_derived_traits)
|
|
}
|
|
|
|
struct DeadItem {
|
|
def_id: LocalDefId,
|
|
name: Symbol,
|
|
level: lint::Level,
|
|
}
|
|
|
|
struct DeadVisitor<'tcx> {
|
|
tcx: TyCtxt<'tcx>,
|
|
live_symbols: &'tcx LocalDefIdSet,
|
|
ignored_derived_traits: &'tcx LocalDefIdMap<Vec<(DefId, DefId)>>,
|
|
}
|
|
|
|
enum ShouldWarnAboutField {
|
|
Yes,
|
|
No,
|
|
}
|
|
|
|
impl<'tcx> DeadVisitor<'tcx> {
|
|
fn should_warn_about_field(&mut self, field: &ty::FieldDef) -> ShouldWarnAboutField {
|
|
if self.live_symbols.contains(&field.did.expect_local()) {
|
|
return ShouldWarnAboutField::No;
|
|
}
|
|
let field_type = self.tcx.type_of(field.did).instantiate_identity();
|
|
if field_type.is_phantom_data() {
|
|
return ShouldWarnAboutField::No;
|
|
}
|
|
let is_positional = field.name.as_str().starts_with(|c: char| c.is_ascii_digit());
|
|
if is_positional
|
|
&& self
|
|
.tcx
|
|
.layout_of(self.tcx.param_env(field.did).and(field_type))
|
|
.map_or(true, |layout| layout.is_zst())
|
|
{
|
|
return ShouldWarnAboutField::No;
|
|
}
|
|
ShouldWarnAboutField::Yes
|
|
}
|
|
|
|
fn def_lint_level(&self, lint: &'static Lint, id: LocalDefId) -> lint::Level {
|
|
let hir_id = self.tcx.local_def_id_to_hir_id(id);
|
|
self.tcx.lint_level_at_node(lint, hir_id).0
|
|
}
|
|
|
|
// # Panics
|
|
// All `dead_codes` must have the same lint level, otherwise we will intentionally ICE.
|
|
// This is because we emit a multi-spanned lint using the lint level of the `dead_codes`'s
|
|
// first local def id.
|
|
// Prefer calling `Self.warn_dead_code` or `Self.warn_dead_code_grouped_by_lint_level`
|
|
// since those methods group by lint level before calling this method.
|
|
fn lint_at_single_level(
|
|
&self,
|
|
dead_codes: &[&DeadItem],
|
|
participle: &str,
|
|
parent_item: Option<LocalDefId>,
|
|
lint: &'static Lint,
|
|
) {
|
|
let Some(&first_item) = dead_codes.first() else {
|
|
return;
|
|
};
|
|
let tcx = self.tcx;
|
|
|
|
let first_lint_level = first_item.level;
|
|
assert!(dead_codes.iter().skip(1).all(|item| item.level == first_lint_level));
|
|
|
|
let names: Vec<_> = dead_codes.iter().map(|item| item.name).collect();
|
|
let spans: Vec<_> = dead_codes
|
|
.iter()
|
|
.map(|item| match tcx.def_ident_span(item.def_id) {
|
|
Some(s) => s.with_ctxt(tcx.def_span(item.def_id).ctxt()),
|
|
None => tcx.def_span(item.def_id),
|
|
})
|
|
.collect();
|
|
|
|
let descr = tcx.def_descr(first_item.def_id.to_def_id());
|
|
// `impl` blocks are "batched" and (unlike other batching) might
|
|
// contain different kinds of associated items.
|
|
let descr = if dead_codes.iter().any(|item| tcx.def_descr(item.def_id.to_def_id()) != descr)
|
|
{
|
|
"associated item"
|
|
} else {
|
|
descr
|
|
};
|
|
let num = dead_codes.len();
|
|
let multiple = num > 6;
|
|
let name_list = names.into();
|
|
|
|
let parent_info = if let Some(parent_item) = parent_item {
|
|
let parent_descr = tcx.def_descr(parent_item.to_def_id());
|
|
let span = if let DefKind::Impl { .. } = tcx.def_kind(parent_item) {
|
|
tcx.def_span(parent_item)
|
|
} else {
|
|
tcx.def_ident_span(parent_item).unwrap()
|
|
};
|
|
Some(ParentInfo { num, descr, parent_descr, span })
|
|
} else {
|
|
None
|
|
};
|
|
|
|
let encl_def_id = parent_item.unwrap_or(first_item.def_id);
|
|
let ignored_derived_impls =
|
|
if let Some(ign_traits) = self.ignored_derived_traits.get(&encl_def_id) {
|
|
let trait_list = ign_traits
|
|
.iter()
|
|
.map(|(trait_id, _)| self.tcx.item_name(*trait_id))
|
|
.collect::<Vec<_>>();
|
|
let trait_list_len = trait_list.len();
|
|
Some(IgnoredDerivedImpls {
|
|
name: self.tcx.item_name(encl_def_id.to_def_id()),
|
|
trait_list: trait_list.into(),
|
|
trait_list_len,
|
|
})
|
|
} else {
|
|
None
|
|
};
|
|
|
|
let diag = if LintId::of(lint) == LintId::of(UNUSED_TUPLE_STRUCT_FIELDS) {
|
|
MultipleDeadCodes::UnusedTupleStructFields {
|
|
multiple,
|
|
num,
|
|
descr,
|
|
participle,
|
|
name_list,
|
|
change_fields_suggestion: ChangeFieldsToBeOfUnitType { num, spans: spans.clone() },
|
|
parent_info,
|
|
ignored_derived_impls,
|
|
}
|
|
} else {
|
|
MultipleDeadCodes::DeadCodes {
|
|
multiple,
|
|
num,
|
|
descr,
|
|
participle,
|
|
name_list,
|
|
parent_info,
|
|
ignored_derived_impls,
|
|
}
|
|
};
|
|
|
|
let hir_id = tcx.local_def_id_to_hir_id(first_item.def_id);
|
|
self.tcx.emit_spanned_lint(lint, hir_id, MultiSpan::from_spans(spans), diag);
|
|
}
|
|
|
|
fn warn_multiple(
|
|
&self,
|
|
def_id: LocalDefId,
|
|
participle: &str,
|
|
dead_codes: Vec<DeadItem>,
|
|
lint: &'static Lint,
|
|
) {
|
|
let mut dead_codes = dead_codes
|
|
.iter()
|
|
.filter(|v| !v.name.as_str().starts_with('_'))
|
|
.collect::<Vec<&DeadItem>>();
|
|
if dead_codes.is_empty() {
|
|
return;
|
|
}
|
|
dead_codes.sort_by_key(|v| v.level);
|
|
for group in dead_codes[..].group_by(|a, b| a.level == b.level) {
|
|
self.lint_at_single_level(&group, participle, Some(def_id), lint);
|
|
}
|
|
}
|
|
|
|
fn warn_dead_code(&mut self, id: LocalDefId, participle: &str) {
|
|
let item = DeadItem {
|
|
def_id: id,
|
|
name: self.tcx.item_name(id.to_def_id()),
|
|
level: self.def_lint_level(DEAD_CODE, id),
|
|
};
|
|
self.lint_at_single_level(&[&item], participle, None, DEAD_CODE);
|
|
}
|
|
|
|
fn check_definition(&mut self, def_id: LocalDefId) {
|
|
if self.is_live_code(def_id) {
|
|
return;
|
|
}
|
|
match self.tcx.def_kind(def_id) {
|
|
DefKind::AssocConst
|
|
| DefKind::AssocFn
|
|
| DefKind::Fn
|
|
| DefKind::Static(_)
|
|
| DefKind::Const
|
|
| DefKind::TyAlias
|
|
| DefKind::Enum
|
|
| DefKind::Union
|
|
| DefKind::ForeignTy => self.warn_dead_code(def_id, "used"),
|
|
DefKind::Struct => self.warn_dead_code(def_id, "constructed"),
|
|
DefKind::Variant | DefKind::Field => bug!("should be handled specially"),
|
|
_ => {}
|
|
}
|
|
}
|
|
|
|
fn is_live_code(&self, def_id: LocalDefId) -> bool {
|
|
// if we cannot get a name for the item, then we just assume that it is
|
|
// live. I mean, we can't really emit a lint.
|
|
let Some(name) = self.tcx.opt_item_name(def_id.to_def_id()) else {
|
|
return true;
|
|
};
|
|
|
|
self.live_symbols.contains(&def_id) || name.as_str().starts_with('_')
|
|
}
|
|
}
|
|
|
|
fn check_mod_deathness(tcx: TyCtxt<'_>, module: LocalModDefId) {
|
|
let (live_symbols, ignored_derived_traits) = tcx.live_symbols_and_ignored_derived_traits(());
|
|
let mut visitor = DeadVisitor { tcx, live_symbols, ignored_derived_traits };
|
|
|
|
let module_items = tcx.hir_module_items(module);
|
|
|
|
for item in module_items.items() {
|
|
if let hir::ItemKind::Impl(impl_item) = tcx.hir().item(item).kind {
|
|
let mut dead_items = Vec::new();
|
|
for item in impl_item.items {
|
|
let def_id = item.id.owner_id.def_id;
|
|
if !visitor.is_live_code(def_id) {
|
|
let name = tcx.item_name(def_id.to_def_id());
|
|
let level = visitor.def_lint_level(DEAD_CODE, def_id);
|
|
|
|
dead_items.push(DeadItem { def_id, name, level })
|
|
}
|
|
}
|
|
visitor.warn_multiple(item.owner_id.def_id, "used", dead_items, DEAD_CODE);
|
|
}
|
|
|
|
if !live_symbols.contains(&item.owner_id.def_id) {
|
|
let parent = tcx.local_parent(item.owner_id.def_id);
|
|
if parent != module.to_local_def_id() && !live_symbols.contains(&parent) {
|
|
// We already have diagnosed something.
|
|
continue;
|
|
}
|
|
visitor.check_definition(item.owner_id.def_id);
|
|
continue;
|
|
}
|
|
|
|
let def_kind = tcx.def_kind(item.owner_id);
|
|
if let DefKind::Struct | DefKind::Union | DefKind::Enum = def_kind {
|
|
let adt = tcx.adt_def(item.owner_id);
|
|
let mut dead_variants = Vec::new();
|
|
|
|
for variant in adt.variants() {
|
|
let def_id = variant.def_id.expect_local();
|
|
if !live_symbols.contains(&def_id) {
|
|
// Record to group diagnostics.
|
|
let level = visitor.def_lint_level(DEAD_CODE, def_id);
|
|
dead_variants.push(DeadItem { def_id, name: variant.name, level });
|
|
continue;
|
|
}
|
|
|
|
let is_positional = variant.fields.raw.first().map_or(false, |field| {
|
|
field.name.as_str().starts_with(|c: char| c.is_ascii_digit())
|
|
});
|
|
let lint = if is_positional { UNUSED_TUPLE_STRUCT_FIELDS } else { DEAD_CODE };
|
|
let dead_fields = variant
|
|
.fields
|
|
.iter()
|
|
.filter_map(|field| {
|
|
let def_id = field.did.expect_local();
|
|
if let ShouldWarnAboutField::Yes = visitor.should_warn_about_field(field) {
|
|
let level = visitor.def_lint_level(lint, def_id);
|
|
Some(DeadItem { def_id, name: field.name, level })
|
|
} else {
|
|
None
|
|
}
|
|
})
|
|
.collect();
|
|
visitor.warn_multiple(def_id, "read", dead_fields, lint);
|
|
}
|
|
|
|
visitor.warn_multiple(item.owner_id.def_id, "constructed", dead_variants, DEAD_CODE);
|
|
}
|
|
}
|
|
|
|
for foreign_item in module_items.foreign_items() {
|
|
visitor.check_definition(foreign_item.owner_id.def_id);
|
|
}
|
|
|
|
// We do not warn trait items.
|
|
}
|
|
|
|
pub(crate) fn provide(providers: &mut Providers) {
|
|
*providers =
|
|
Providers { live_symbols_and_ignored_derived_traits, check_mod_deathness, ..*providers };
|
|
}
|