868 lines
32 KiB
Rust
868 lines
32 KiB
Rust
// This implements the dead-code warning pass. It follows middle::reachable
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// closely. The idea is that all reachable symbols are live, codes called
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// from live codes are live, and everything else is dead.
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use itertools::Itertools;
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
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use rustc_errors::{pluralize, 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};
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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;
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::{self, DefIdTree, TyCtxt};
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use rustc_session::lint;
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use rustc_span::symbol::{sym, Symbol};
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use std::mem;
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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.hir().find_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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struct MarkSymbolVisitor<'tcx> {
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worklist: Vec<LocalDefId>,
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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: FxHashSet<LocalDefId>,
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repr_has_repr_c: 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: FxHashMap<LocalDefId, 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: FxHashMap<LocalDefId, 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);
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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::SelfTy { trait_: t, alias_to: i } => {
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if let Some(t) = t {
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self.check_def_id(t);
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}
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if let Some((i, _)) = i {
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self.check_def_id(i);
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}
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}
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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.tcx.field_index(hir_id, self.typeck_results());
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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.struct_span_lint_hir(
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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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|lint| {
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lint.build(&format!(
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"useless assignment of {} of type `{}` to itself",
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if is_field_assign { "field" } else { "variable" },
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self.typeck_results().expr_ty(lhs),
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))
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.emit();
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},
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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.tcx.field_index(pat.hir_id, self.typeck_results());
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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 mark_live_symbols(&mut self) {
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let mut scanned = FxHashSet::default();
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while let Some(id) = self.worklist.pop() {
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if !scanned.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.hir().find_by_def_id(id) {
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self.live_symbols.insert(id);
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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.has_attr(impl_of, sym::automatically_derived) {
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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();
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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 { def_id, .. }) = node
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&& self.should_ignore_item(def_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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self.repr_has_repr_c = 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.def_id);
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self.repr_has_repr_c = def.repr().c();
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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.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);
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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_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.tcx.field_index(field.hir_id, self.typeck_results());
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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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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(
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&mut self,
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def: &'tcx hir::VariantData<'tcx>,
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_: Symbol,
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_: &hir::Generics<'_>,
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_: hir::HirId,
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_: rustc_span::Span,
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) {
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let tcx = self.tcx;
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let has_repr_c = self.repr_has_repr_c;
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let live_fields = def.fields().iter().filter_map(|f| {
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let def_id = tcx.hir().local_def_id(f.hir_id);
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if has_repr_c {
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return Some(def_id);
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}
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if !tcx.visibility(f.hir_id.owner).is_public() {
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return None;
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}
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if tcx.visibility(def_id).is_public() { Some(def_id) } else { None }
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});
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self.live_symbols.extend(live_fields);
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intravisit::walk_struct_def(self, def);
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}
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fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
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match expr.kind {
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hir::ExprKind::Path(ref qpath @ hir::QPath::TypeRelative(..)) => {
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let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
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self.handle_res(res);
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}
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|
hir::ExprKind::MethodCall(..) => {
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self.lookup_and_handle_method(expr.hir_id);
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|
}
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|
hir::ExprKind::Field(ref lhs, ..) => {
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self.handle_field_access(&lhs, expr.hir_id);
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}
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|
hir::ExprKind::Struct(ref qpath, ref fields, _) => {
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let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
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self.handle_res(res);
|
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if let ty::Adt(adt, _) = self.typeck_results().expr_ty(expr).kind() {
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self.mark_as_used_if_union(*adt, fields);
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|
}
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|
}
|
|
_ => (),
|
|
}
|
|
|
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intravisit::walk_expr(self, expr);
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|
}
|
|
|
|
fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
|
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// 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());
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|
intravisit::walk_arm(self, arm);
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|
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, ref 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);
|
|
}
|
|
_ => (),
|
|
}
|
|
|
|
intravisit::walk_pat(self, pat);
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|
self.in_pat = false;
|
|
}
|
|
|
|
fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) {
|
|
self.handle_res(path.res);
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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(self.tcx.hir().local_def_id(c.hir_id));
|
|
intravisit::walk_anon_const(self, c);
|
|
|
|
self.in_pat = in_pat;
|
|
}
|
|
}
|
|
|
|
fn has_allow_dead_code_or_lang_attr(tcx: TyCtxt<'_>, id: hir::HirId) -> bool {
|
|
let attrs = tcx.hir().attrs(id);
|
|
if tcx.sess.contains_name(attrs, sym::lang) {
|
|
return true;
|
|
}
|
|
|
|
// Stable attribute for #[lang = "panic_impl"]
|
|
if tcx.sess.contains_name(attrs, sym::panic_handler) {
|
|
return true;
|
|
}
|
|
|
|
// (To be) stable attribute for #[lang = "oom"]
|
|
if tcx.sess.contains_name(attrs, sym::alloc_error_handler) {
|
|
return true;
|
|
}
|
|
|
|
let def_id = tcx.hir().local_def_id(id);
|
|
if 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.
|
|
if cg_attrs.contains_extern_indicator()
|
|
|| cg_attrs.flags.contains(CodegenFnAttrFlags::USED)
|
|
|| cg_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
|
|
{
|
|
return true;
|
|
}
|
|
}
|
|
|
|
tcx.lint_level_at_node(lint::builtin::DEAD_CODE, id).0 == lint::Allow
|
|
}
|
|
|
|
// 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>,
|
|
struct_constructors: &mut FxHashMap<LocalDefId, LocalDefId>,
|
|
id: hir::ItemId,
|
|
) {
|
|
let allow_dead_code = has_allow_dead_code_or_lang_attr(tcx, id.hir_id());
|
|
if allow_dead_code {
|
|
worklist.push(id.def_id);
|
|
}
|
|
|
|
match tcx.def_kind(id.def_id) {
|
|
DefKind::Enum => {
|
|
let item = tcx.hir().item(id);
|
|
if let hir::ItemKind::Enum(ref enum_def, _) = item.kind {
|
|
let hir = tcx.hir();
|
|
if allow_dead_code {
|
|
worklist.extend(
|
|
enum_def.variants.iter().map(|variant| hir.local_def_id(variant.id)),
|
|
);
|
|
}
|
|
|
|
for variant in enum_def.variants {
|
|
if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
|
|
struct_constructors
|
|
.insert(hir.local_def_id(ctor_hir_id), hir.local_def_id(variant.id));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
DefKind::Impl => {
|
|
let of_trait = tcx.impl_trait_ref(id.def_id);
|
|
|
|
if of_trait.is_some() {
|
|
worklist.push(id.def_id);
|
|
}
|
|
|
|
// get DefIds from another query
|
|
let local_def_ids = tcx
|
|
.associated_item_def_ids(id.def_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.is_some()
|
|
|| has_allow_dead_code_or_lang_attr(tcx, tcx.hir().local_def_id_to_hir_id(id))
|
|
{
|
|
worklist.push(id);
|
|
}
|
|
}
|
|
}
|
|
DefKind::Struct => {
|
|
let item = tcx.hir().item(id);
|
|
if let hir::ItemKind::Struct(ref variant_data, _) = item.kind
|
|
&& let Some(ctor_hir_id) = variant_data.ctor_hir_id()
|
|
{
|
|
struct_constructors.insert(tcx.hir().local_def_id(ctor_hir_id), item.def_id);
|
|
}
|
|
}
|
|
DefKind::GlobalAsm => {
|
|
// global_asm! is always live.
|
|
worklist.push(id.def_id);
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
|
|
fn check_trait_item<'tcx>(tcx: TyCtxt<'tcx>, worklist: &mut Vec<LocalDefId>, id: hir::TraitItemId) {
|
|
use hir::TraitItemKind::{Const, Fn};
|
|
if matches!(tcx.def_kind(id.def_id), DefKind::AssocConst | DefKind::AssocFn) {
|
|
let trait_item = tcx.hir().trait_item(id);
|
|
if matches!(trait_item.kind, Const(_, Some(_)) | Fn(_, hir::TraitFn::Provided(_)))
|
|
&& has_allow_dead_code_or_lang_attr(tcx, trait_item.hir_id())
|
|
{
|
|
worklist.push(trait_item.def_id);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_foreign_item<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
worklist: &mut Vec<LocalDefId>,
|
|
id: hir::ForeignItemId,
|
|
) {
|
|
if matches!(tcx.def_kind(id.def_id), DefKind::Static(_) | DefKind::Fn)
|
|
&& has_allow_dead_code_or_lang_attr(tcx, id.hir_id())
|
|
{
|
|
worklist.push(id.def_id);
|
|
}
|
|
}
|
|
|
|
fn create_and_seed_worklist<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
) -> (Vec<LocalDefId>, FxHashMap<LocalDefId, LocalDefId>) {
|
|
let access_levels = &tcx.privacy_access_levels(());
|
|
// see `MarkSymbolVisitor::struct_constructors`
|
|
let mut struct_constructors = Default::default();
|
|
let mut worklist = access_levels
|
|
.map
|
|
.iter()
|
|
.filter_map(
|
|
|(&id, &level)| {
|
|
if level >= privacy::AccessLevel::Reachable { Some(id) } else { None }
|
|
},
|
|
)
|
|
// Seed entry point
|
|
.chain(tcx.entry_fn(()).and_then(|(def_id, _)| def_id.as_local()))
|
|
.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>(
|
|
tcx: TyCtxt<'tcx>,
|
|
(): (),
|
|
) -> (FxHashSet<LocalDefId>, FxHashMap<LocalDefId, 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,
|
|
in_pat: false,
|
|
ignore_variant_stack: vec![],
|
|
struct_constructors,
|
|
ignored_derived_traits: FxHashMap::default(),
|
|
};
|
|
symbol_visitor.mark_live_symbols();
|
|
(symbol_visitor.live_symbols, symbol_visitor.ignored_derived_traits)
|
|
}
|
|
|
|
struct DeadVariant {
|
|
def_id: LocalDefId,
|
|
name: Symbol,
|
|
level: lint::Level,
|
|
}
|
|
|
|
struct DeadVisitor<'tcx> {
|
|
tcx: TyCtxt<'tcx>,
|
|
live_symbols: &'tcx FxHashSet<LocalDefId>,
|
|
ignored_derived_traits: &'tcx FxHashMap<LocalDefId, Vec<(DefId, DefId)>>,
|
|
}
|
|
|
|
impl<'tcx> DeadVisitor<'tcx> {
|
|
fn should_warn_about_field(&mut self, field: &ty::FieldDef) -> bool {
|
|
if self.live_symbols.contains(&field.did.expect_local()) {
|
|
return false;
|
|
}
|
|
let is_positional = field.name.as_str().starts_with(|c: char| c.is_ascii_digit());
|
|
if is_positional {
|
|
return false;
|
|
}
|
|
let field_type = self.tcx.type_of(field.did);
|
|
!field_type.is_phantom_data()
|
|
}
|
|
|
|
fn warn_multiple_dead_codes(
|
|
&self,
|
|
dead_codes: &[LocalDefId],
|
|
participle: &str,
|
|
parent_item: Option<LocalDefId>,
|
|
) {
|
|
if let Some(&first_id) = dead_codes.first() {
|
|
let tcx = self.tcx;
|
|
let names: Vec<_> = dead_codes
|
|
.iter()
|
|
.map(|&def_id| tcx.item_name(def_id.to_def_id()).to_string())
|
|
.collect();
|
|
let spans = dead_codes
|
|
.iter()
|
|
.map(|&def_id| match tcx.def_ident_span(def_id) {
|
|
Some(s) => s.with_ctxt(tcx.def_span(def_id).ctxt()),
|
|
None => tcx.def_span(def_id),
|
|
})
|
|
.collect();
|
|
|
|
tcx.struct_span_lint_hir(
|
|
lint::builtin::DEAD_CODE,
|
|
tcx.hir().local_def_id_to_hir_id(first_id),
|
|
MultiSpan::from_spans(spans),
|
|
|lint| {
|
|
let descr = tcx.def_kind(first_id).descr(first_id.to_def_id());
|
|
let span_len = dead_codes.len();
|
|
let names = match &names[..] {
|
|
_ if span_len > 6 => String::new(),
|
|
[name] => format!("`{name}` "),
|
|
[names @ .., last] => {
|
|
format!(
|
|
"{} and `{last}` ",
|
|
names.iter().map(|name| format!("`{name}`")).join(", ")
|
|
)
|
|
}
|
|
[] => unreachable!(),
|
|
};
|
|
let mut err = lint.build(&format!(
|
|
"{these}{descr}{s} {names}{are} never {participle}",
|
|
these = if span_len > 6 { "multiple " } else { "" },
|
|
s = pluralize!(span_len),
|
|
are = pluralize!("is", span_len),
|
|
));
|
|
|
|
if let Some(parent_item) = parent_item {
|
|
let parent_descr = tcx.def_kind(parent_item).descr(parent_item.to_def_id());
|
|
err.span_label(
|
|
tcx.def_ident_span(parent_item).unwrap(),
|
|
format!("{descr}{s} in this {parent_descr}", s = pluralize!(span_len)),
|
|
);
|
|
}
|
|
|
|
let encl_def_id = parent_item.unwrap_or(first_id);
|
|
if let Some(ign_traits) = self.ignored_derived_traits.get(&encl_def_id) {
|
|
let traits_str = ign_traits
|
|
.iter()
|
|
.map(|(trait_id, _)| format!("`{}`", self.tcx.item_name(*trait_id)))
|
|
.collect::<Vec<_>>()
|
|
.join(" and ");
|
|
let plural_s = pluralize!(ign_traits.len());
|
|
let article = if ign_traits.len() > 1 { "" } else { "a " };
|
|
let is_are = if ign_traits.len() > 1 { "these are" } else { "this is" };
|
|
let msg = format!(
|
|
"`{}` has {}derived impl{} for the trait{} {}, but {} \
|
|
intentionally ignored during dead code analysis",
|
|
self.tcx.item_name(encl_def_id.to_def_id()),
|
|
article,
|
|
plural_s,
|
|
plural_s,
|
|
traits_str,
|
|
is_are
|
|
);
|
|
err.note(&msg);
|
|
}
|
|
err.emit();
|
|
},
|
|
);
|
|
}
|
|
}
|
|
|
|
fn warn_dead_fields_and_variants(
|
|
&self,
|
|
def_id: LocalDefId,
|
|
participle: &str,
|
|
dead_codes: Vec<DeadVariant>,
|
|
) {
|
|
let mut dead_codes = dead_codes
|
|
.iter()
|
|
.filter(|v| !v.name.as_str().starts_with('_'))
|
|
.map(|v| v)
|
|
.collect::<Vec<&DeadVariant>>();
|
|
if dead_codes.is_empty() {
|
|
return;
|
|
}
|
|
dead_codes.sort_by_key(|v| v.level);
|
|
for (_, group) in &dead_codes.into_iter().group_by(|v| v.level) {
|
|
self.warn_multiple_dead_codes(
|
|
&group.map(|v| v.def_id).collect::<Vec<_>>(),
|
|
participle,
|
|
Some(def_id),
|
|
);
|
|
}
|
|
}
|
|
|
|
fn warn_dead_code(&mut self, id: LocalDefId, participle: &str) {
|
|
self.warn_multiple_dead_codes(&[id], participle, None);
|
|
}
|
|
|
|
fn check_definition(&mut self, def_id: LocalDefId) {
|
|
if self.live_symbols.contains(&def_id) {
|
|
return;
|
|
}
|
|
let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
|
|
if has_allow_dead_code_or_lang_attr(self.tcx, hir_id) {
|
|
return;
|
|
}
|
|
let Some(name) = self.tcx.opt_item_name(def_id.to_def_id()) else {
|
|
return
|
|
};
|
|
if name.as_str().starts_with('_') {
|
|
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 check_mod_deathness(tcx: TyCtxt<'_>, module: LocalDefId) {
|
|
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 !live_symbols.contains(&item.def_id) {
|
|
let parent = tcx.local_parent(item.def_id);
|
|
if parent != module && !live_symbols.contains(&parent) {
|
|
// We already have diagnosed something.
|
|
continue;
|
|
}
|
|
visitor.check_definition(item.def_id);
|
|
continue;
|
|
}
|
|
|
|
let def_kind = tcx.def_kind(item.def_id);
|
|
if let DefKind::Struct | DefKind::Union | DefKind::Enum = def_kind {
|
|
let adt = tcx.adt_def(item.def_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 hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
|
|
let level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, hir_id).0;
|
|
dead_variants.push(DeadVariant { def_id, name: variant.name, level });
|
|
continue;
|
|
}
|
|
|
|
let dead_fields = variant
|
|
.fields
|
|
.iter()
|
|
.filter_map(|field| {
|
|
let def_id = field.did.expect_local();
|
|
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
|
|
if visitor.should_warn_about_field(&field) {
|
|
let level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, hir_id).0;
|
|
Some(DeadVariant { def_id, name: field.name, level })
|
|
} else {
|
|
None
|
|
}
|
|
})
|
|
.collect();
|
|
visitor.warn_dead_fields_and_variants(def_id, "read", dead_fields)
|
|
}
|
|
|
|
visitor.warn_dead_fields_and_variants(item.def_id, "constructed", dead_variants);
|
|
}
|
|
}
|
|
|
|
for impl_item in module_items.impl_items() {
|
|
visitor.check_definition(impl_item.def_id);
|
|
}
|
|
|
|
for foreign_item in module_items.foreign_items() {
|
|
visitor.check_definition(foreign_item.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 };
|
|
}
|