618 lines
22 KiB
Rust
618 lines
22 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// 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 front::map as ast_map;
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use rustc_front::hir;
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use rustc_front::visit::{self, Visitor};
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use middle::{def, pat_util, privacy, ty};
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use middle::def_id::{DefId};
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use lint;
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use util::nodemap::NodeSet;
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use std::collections::HashSet;
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use syntax::{ast, codemap};
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use syntax::attr::{self, AttrMetaMethods};
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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 NodeItem 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: &ty::ctxt, node_id: ast::NodeId) -> bool {
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match tcx.map.find(node_id) {
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Some(ast_map::NodeItem(..)) |
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Some(ast_map::NodeImplItem(..)) |
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Some(ast_map::NodeForeignItem(..)) |
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Some(ast_map::NodeTraitItem(..)) =>
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true,
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_ =>
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false
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}
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}
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struct MarkSymbolVisitor<'a, 'tcx: 'a> {
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worklist: Vec<ast::NodeId>,
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tcx: &'a ty::ctxt<'tcx>,
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live_symbols: Box<HashSet<ast::NodeId>>,
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struct_has_extern_repr: bool,
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ignore_non_const_paths: bool,
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inherited_pub_visibility: bool,
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ignore_variant_stack: Vec<DefId>,
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}
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impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
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fn new(tcx: &'a ty::ctxt<'tcx>,
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worklist: Vec<ast::NodeId>) -> MarkSymbolVisitor<'a, 'tcx> {
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MarkSymbolVisitor {
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worklist: worklist,
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tcx: tcx,
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live_symbols: box HashSet::new(),
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struct_has_extern_repr: false,
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ignore_non_const_paths: false,
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inherited_pub_visibility: false,
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ignore_variant_stack: vec![],
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}
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}
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fn check_def_id(&mut self, def_id: DefId) {
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if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
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if should_explore(self.tcx, node_id) {
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self.worklist.push(node_id);
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}
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self.live_symbols.insert(node_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(node_id) = self.tcx.map.as_local_node_id(def_id) {
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debug_assert!(!should_explore(self.tcx, node_id));
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self.live_symbols.insert(node_id);
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}
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}
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fn lookup_and_handle_definition(&mut self, id: &ast::NodeId) {
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use middle::ty::TypeVariants::{TyEnum, TyStruct};
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// If `bar` is a trait item, make sure to mark Foo as alive in `Foo::bar`
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self.tcx.tables.borrow().item_substs.get(id)
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.and_then(|substs| substs.substs.self_ty())
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.map(|ty| match ty.sty {
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TyEnum(tyid, _) | TyStruct(tyid, _) => self.check_def_id(tyid.did),
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_ => (),
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});
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self.tcx.def_map.borrow().get(id).map(|def| {
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match def.full_def() {
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def::DefConst(_) | def::DefAssociatedConst(..) => {
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self.check_def_id(def.def_id());
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}
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_ if self.ignore_non_const_paths => (),
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def::DefPrimTy(_) => (),
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def::DefSelfTy(..) => (),
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def::DefVariant(enum_id, 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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_ => {
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self.check_def_id(def.def_id());
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}
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}
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});
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}
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fn lookup_and_handle_method(&mut self, id: ast::NodeId) {
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let method_call = ty::MethodCall::expr(id);
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let method = self.tcx.tables.borrow().method_map[&method_call];
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self.check_def_id(method.def_id);
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}
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fn handle_field_access(&mut self, lhs: &hir::Expr, name: ast::Name) {
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if let ty::TyStruct(def, _) = self.tcx.expr_ty_adjusted(lhs).sty {
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self.insert_def_id(def.struct_variant().field_named(name).did);
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} else {
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self.tcx.sess.span_bug(lhs.span, "named field access on non-struct")
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}
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}
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fn handle_tup_field_access(&mut self, lhs: &hir::Expr, idx: usize) {
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if let ty::TyStruct(def, _) = self.tcx.expr_ty_adjusted(lhs).sty {
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self.insert_def_id(def.struct_variant().fields[idx].did);
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}
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}
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fn handle_field_pattern_match(&mut self, lhs: &hir::Pat,
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pats: &[codemap::Spanned<hir::FieldPat>]) {
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let def = self.tcx.def_map.borrow().get(&lhs.id).unwrap().full_def();
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let pat_ty = self.tcx.node_id_to_type(lhs.id);
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let variant = match pat_ty.sty {
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ty::TyStruct(adt, _) | ty::TyEnum(adt, _) => adt.variant_of_def(def),
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_ => self.tcx.sess.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 hir::PatWild(hir::PatWildSingle) = pat.node.pat.node {
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continue;
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}
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self.insert_def_id(variant.field_named(pat.node.name).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 = HashSet::new();
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while !self.worklist.is_empty() {
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let id = self.worklist.pop().unwrap();
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if scanned.contains(&id) {
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continue
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}
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scanned.insert(id);
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match self.tcx.map.find(id) {
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Some(ref node) => {
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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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None => (),
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}
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}
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}
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fn visit_node(&mut self, node: &ast_map::Node) {
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let had_extern_repr = self.struct_has_extern_repr;
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self.struct_has_extern_repr = false;
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let had_inherited_pub_visibility = self.inherited_pub_visibility;
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self.inherited_pub_visibility = false;
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match *node {
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ast_map::NodeItem(item) => {
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match item.node {
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hir::ItemStruct(..) => {
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self.struct_has_extern_repr = item.attrs.iter().any(|attr| {
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attr::find_repr_attrs(self.tcx.sess.diagnostic(), attr)
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.contains(&attr::ReprExtern)
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});
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visit::walk_item(self, &*item);
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}
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hir::ItemEnum(..) => {
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self.inherited_pub_visibility = item.vis == hir::Public;
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visit::walk_item(self, &*item);
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}
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hir::ItemFn(..)
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| hir::ItemTy(..)
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| hir::ItemStatic(..)
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| hir::ItemConst(..) => {
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visit::walk_item(self, &*item);
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}
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_ => ()
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}
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}
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ast_map::NodeTraitItem(trait_item) => {
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visit::walk_trait_item(self, trait_item);
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}
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ast_map::NodeImplItem(impl_item) => {
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visit::walk_impl_item(self, impl_item);
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}
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ast_map::NodeForeignItem(foreign_item) => {
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visit::walk_foreign_item(self, &*foreign_item);
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}
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_ => ()
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}
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self.struct_has_extern_repr = had_extern_repr;
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self.inherited_pub_visibility = had_inherited_pub_visibility;
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}
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}
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impl<'a, 'tcx, 'v> Visitor<'v> for MarkSymbolVisitor<'a, 'tcx> {
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fn visit_variant_data(&mut self, def: &hir::VariantData, _: ast::Name,
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_: &hir::Generics, _: ast::NodeId, _: codemap::Span) {
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let has_extern_repr = self.struct_has_extern_repr;
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let inherited_pub_visibility = self.inherited_pub_visibility;
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let live_fields = def.fields().filter(|f| {
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has_extern_repr || inherited_pub_visibility || match f.node.kind {
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hir::NamedField(_, hir::Public) => true,
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_ => false
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}
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});
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self.live_symbols.extend(live_fields.map(|f| f.node.id));
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visit::walk_struct_def(self, def);
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}
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fn visit_expr(&mut self, expr: &hir::Expr) {
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match expr.node {
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hir::ExprMethodCall(..) => {
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self.lookup_and_handle_method(expr.id);
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}
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hir::ExprField(ref lhs, ref name) => {
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self.handle_field_access(&**lhs, name.node);
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}
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hir::ExprTupField(ref lhs, idx) => {
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self.handle_tup_field_access(&**lhs, idx.node);
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}
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_ => ()
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}
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visit::walk_expr(self, expr);
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}
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fn visit_arm(&mut self, arm: &hir::Arm) {
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if arm.pats.len() == 1 {
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let pat = &*arm.pats[0];
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let variants = pat_util::necessary_variants(&self.tcx.def_map, pat);
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// Inside the body, ignore constructions of variants
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// necessary for the pattern to match. Those construction sites
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// can't be reached unless the variant is constructed elsewhere.
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let len = self.ignore_variant_stack.len();
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self.ignore_variant_stack.push_all(&*variants);
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visit::walk_arm(self, arm);
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self.ignore_variant_stack.truncate(len);
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} else {
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visit::walk_arm(self, arm);
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}
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}
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fn visit_pat(&mut self, pat: &hir::Pat) {
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let def_map = &self.tcx.def_map;
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match pat.node {
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hir::PatStruct(_, ref fields, _) => {
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self.handle_field_pattern_match(pat, fields);
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}
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_ if pat_util::pat_is_const(def_map, pat) => {
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// it might be the only use of a const
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self.lookup_and_handle_definition(&pat.id)
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}
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_ => ()
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}
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self.ignore_non_const_paths = true;
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visit::walk_pat(self, pat);
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self.ignore_non_const_paths = false;
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}
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fn visit_path(&mut self, path: &hir::Path, id: ast::NodeId) {
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self.lookup_and_handle_definition(&id);
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visit::walk_path(self, path);
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}
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fn visit_path_list_item(&mut self, path: &hir::Path, item: &hir::PathListItem) {
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self.lookup_and_handle_definition(&item.node.id());
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visit::walk_path_list_item(self, path, item);
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}
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fn visit_item(&mut self, _: &hir::Item) {
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// Do not recurse into items. These items will be added to the
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// worklist and recursed into manually if necessary.
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}
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}
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fn has_allow_dead_code_or_lang_attr(attrs: &[ast::Attribute]) -> bool {
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if attr::contains_name(attrs, "lang") {
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return true;
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}
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let dead_code = lint::builtin::DEAD_CODE.name_lower();
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for attr in lint::gather_attrs(attrs) {
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match attr {
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Ok((ref name, lint::Allow, _))
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if &name[..] == dead_code => return true,
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_ => (),
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}
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}
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false
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}
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// This visitor seeds items that
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// 1) We want to explicitly consider as live:
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// * Item annotated with #[allow(dead_code)]
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// - This is done so that if we want to suppress warnings for a
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// group of dead functions, we only have to annotate the "root".
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// For example, if both `f` and `g` are dead and `f` calls `g`,
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// then annotating `f` with `#[allow(dead_code)]` will suppress
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// warning for both `f` and `g`.
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// * Item annotated with #[lang=".."]
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// - This is because lang items are always callable from elsewhere.
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// or
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// 2) We are not sure to be live or not
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// * Implementation of a trait method
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struct LifeSeeder {
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worklist: Vec<ast::NodeId>
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}
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impl<'v> Visitor<'v> for LifeSeeder {
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fn visit_item(&mut self, item: &hir::Item) {
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let allow_dead_code = has_allow_dead_code_or_lang_attr(&item.attrs);
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if allow_dead_code {
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self.worklist.push(item.id);
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}
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match item.node {
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hir::ItemEnum(ref enum_def, _) if allow_dead_code => {
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self.worklist.extend(enum_def.variants.iter()
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.map(|variant| variant.node.data.id()));
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}
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hir::ItemTrait(_, _, _, ref trait_items) => {
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for trait_item in trait_items {
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match trait_item.node {
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hir::ConstTraitItem(_, Some(_)) |
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hir::MethodTraitItem(_, Some(_)) => {
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if has_allow_dead_code_or_lang_attr(&trait_item.attrs) {
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self.worklist.push(trait_item.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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}
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hir::ItemImpl(_, _, _, ref opt_trait, _, ref impl_items) => {
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for impl_item in impl_items {
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match impl_item.node {
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hir::ConstImplItem(..) |
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hir::MethodImplItem(..) => {
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if opt_trait.is_some() ||
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has_allow_dead_code_or_lang_attr(&impl_item.attrs) {
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self.worklist.push(impl_item.id);
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}
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}
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hir::TypeImplItem(_) => {}
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}
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}
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}
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_ => ()
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}
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visit::walk_item(self, item);
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}
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}
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fn create_and_seed_worklist(tcx: &ty::ctxt,
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exported_items: &privacy::ExportedItems,
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reachable_symbols: &NodeSet,
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krate: &hir::Crate) -> Vec<ast::NodeId> {
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let mut worklist = Vec::new();
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// Preferably, we would only need to seed the worklist with reachable
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// symbols. However, since the set of reachable symbols differs
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// depending on whether a crate is built as bin or lib, and we want
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// the warning to be consistent, we also seed the worklist with
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// exported symbols.
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for id in exported_items {
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worklist.push(*id);
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}
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for id in reachable_symbols {
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// Reachable variants can be dead, because we warn about
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// variants never constructed, not variants never used.
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if let Some(ast_map::NodeVariant(..)) = tcx.map.find(*id) {
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continue;
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}
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worklist.push(*id);
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}
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// Seed entry point
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match *tcx.sess.entry_fn.borrow() {
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Some((id, _)) => worklist.push(id),
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None => ()
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}
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// Seed implemented trait items
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let mut life_seeder = LifeSeeder {
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worklist: worklist
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};
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visit::walk_crate(&mut life_seeder, krate);
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return life_seeder.worklist;
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}
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fn find_live(tcx: &ty::ctxt,
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exported_items: &privacy::ExportedItems,
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reachable_symbols: &NodeSet,
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krate: &hir::Crate)
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-> Box<HashSet<ast::NodeId>> {
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let worklist = create_and_seed_worklist(tcx, exported_items,
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reachable_symbols, krate);
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let mut symbol_visitor = MarkSymbolVisitor::new(tcx, worklist);
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symbol_visitor.mark_live_symbols();
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symbol_visitor.live_symbols
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}
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fn get_struct_ctor_id(item: &hir::Item) -> Option<ast::NodeId> {
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match item.node {
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hir::ItemStruct(ref struct_def, _) if !struct_def.is_struct() => {
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Some(struct_def.id())
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}
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_ => None
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}
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}
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struct DeadVisitor<'a, 'tcx: 'a> {
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tcx: &'a ty::ctxt<'tcx>,
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live_symbols: Box<HashSet<ast::NodeId>>,
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}
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impl<'a, 'tcx> DeadVisitor<'a, 'tcx> {
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fn should_warn_about_item(&mut self, item: &hir::Item) -> bool {
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let should_warn = match item.node {
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hir::ItemStatic(..)
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| hir::ItemConst(..)
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| hir::ItemFn(..)
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| hir::ItemEnum(..)
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| hir::ItemStruct(..) => true,
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_ => false
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};
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let ctor_id = get_struct_ctor_id(item);
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should_warn && !self.symbol_is_live(item.id, ctor_id)
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}
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fn should_warn_about_field(&mut self, node: &hir::StructField_) -> bool {
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let is_named = node.name().is_some();
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let field_type = self.tcx.node_id_to_type(node.id);
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let is_marker_field = match field_type.ty_to_def_id() {
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Some(def_id) => self.tcx.lang_items.items().any(|(_, item)| *item == Some(def_id)),
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_ => false
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};
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is_named
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&& !self.symbol_is_live(node.id, None)
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&& !is_marker_field
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&& !has_allow_dead_code_or_lang_attr(&node.attrs)
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}
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fn should_warn_about_variant(&mut self, variant: &hir::Variant_) -> bool {
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!self.symbol_is_live(variant.data.id(), None)
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&& !has_allow_dead_code_or_lang_attr(&variant.attrs)
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}
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// id := node id of an item's definition.
|
|
// ctor_id := `Some` if the item is a struct_ctor (tuple struct),
|
|
// `None` otherwise.
|
|
// If the item is a struct_ctor, then either its `id` or
|
|
// `ctor_id` (unwrapped) is in the live_symbols set. More specifically,
|
|
// DefMap maps the ExprPath of a struct_ctor to the node referred by
|
|
// `ctor_id`. On the other hand, in a statement like
|
|
// `type <ident> <generics> = <ty>;` where <ty> refers to a struct_ctor,
|
|
// DefMap maps <ty> to `id` instead.
|
|
fn symbol_is_live(&mut self,
|
|
id: ast::NodeId,
|
|
ctor_id: Option<ast::NodeId>)
|
|
-> bool {
|
|
if self.live_symbols.contains(&id)
|
|
|| ctor_id.map_or(false,
|
|
|ctor| self.live_symbols.contains(&ctor)) {
|
|
return true;
|
|
}
|
|
// If it's a type whose items are live, then it's live, too.
|
|
// This is done to handle the case where, for example, the static
|
|
// method of a private type is used, but the type itself is never
|
|
// called directly.
|
|
let impl_items = self.tcx.impl_items.borrow();
|
|
match self.tcx.inherent_impls.borrow().get(&self.tcx.map.local_def_id(id)) {
|
|
None => (),
|
|
Some(impl_list) => {
|
|
for impl_did in impl_list.iter() {
|
|
for item_did in impl_items.get(impl_did).unwrap().iter() {
|
|
if let Some(item_node_id) =
|
|
self.tcx.map.as_local_node_id(item_did.def_id()) {
|
|
if self.live_symbols.contains(&item_node_id) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
false
|
|
}
|
|
|
|
fn warn_dead_code(&mut self,
|
|
id: ast::NodeId,
|
|
span: codemap::Span,
|
|
name: ast::Name,
|
|
node_type: &str) {
|
|
let name = name.as_str();
|
|
if !name.starts_with("_") {
|
|
self.tcx
|
|
.sess
|
|
.add_lint(lint::builtin::DEAD_CODE,
|
|
id,
|
|
span,
|
|
format!("{} is never used: `{}`", node_type, name));
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx, 'v> Visitor<'v> for DeadVisitor<'a, 'tcx> {
|
|
fn visit_item(&mut self, item: &hir::Item) {
|
|
if self.should_warn_about_item(item) {
|
|
self.warn_dead_code(
|
|
item.id,
|
|
item.span,
|
|
item.name,
|
|
item.node.descriptive_variant()
|
|
);
|
|
} else {
|
|
match item.node {
|
|
hir::ItemEnum(ref enum_def, _) => {
|
|
for variant in &enum_def.variants {
|
|
if self.should_warn_about_variant(&variant.node) {
|
|
self.warn_dead_code(variant.node.data.id(), variant.span,
|
|
variant.node.name, "variant");
|
|
}
|
|
}
|
|
},
|
|
_ => ()
|
|
}
|
|
}
|
|
visit::walk_item(self, item);
|
|
}
|
|
|
|
fn visit_foreign_item(&mut self, fi: &hir::ForeignItem) {
|
|
if !self.symbol_is_live(fi.id, None) {
|
|
self.warn_dead_code(fi.id, fi.span, fi.name, fi.node.descriptive_variant());
|
|
}
|
|
visit::walk_foreign_item(self, fi);
|
|
}
|
|
|
|
fn visit_struct_field(&mut self, field: &hir::StructField) {
|
|
if self.should_warn_about_field(&field.node) {
|
|
self.warn_dead_code(field.node.id, field.span,
|
|
field.node.name().unwrap(), "struct field");
|
|
}
|
|
|
|
visit::walk_struct_field(self, field);
|
|
}
|
|
|
|
fn visit_impl_item(&mut self, impl_item: &hir::ImplItem) {
|
|
match impl_item.node {
|
|
hir::ConstImplItem(_, ref expr) => {
|
|
if !self.symbol_is_live(impl_item.id, None) {
|
|
self.warn_dead_code(impl_item.id, impl_item.span,
|
|
impl_item.name, "associated const");
|
|
}
|
|
visit::walk_expr(self, expr)
|
|
}
|
|
hir::MethodImplItem(_, ref body) => {
|
|
if !self.symbol_is_live(impl_item.id, None) {
|
|
self.warn_dead_code(impl_item.id, impl_item.span,
|
|
impl_item.name, "method");
|
|
}
|
|
visit::walk_block(self, body)
|
|
}
|
|
hir::TypeImplItem(..) => {}
|
|
}
|
|
}
|
|
|
|
// Overwrite so that we don't warn the trait item itself.
|
|
fn visit_trait_item(&mut self, trait_item: &hir::TraitItem) {
|
|
match trait_item.node {
|
|
hir::ConstTraitItem(_, Some(ref expr)) => {
|
|
visit::walk_expr(self, expr)
|
|
}
|
|
hir::MethodTraitItem(_, Some(ref body)) => {
|
|
visit::walk_block(self, body)
|
|
}
|
|
hir::ConstTraitItem(_, None) |
|
|
hir::MethodTraitItem(_, None) |
|
|
hir::TypeTraitItem(..) => {}
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn check_crate(tcx: &ty::ctxt,
|
|
exported_items: &privacy::ExportedItems,
|
|
reachable_symbols: &NodeSet) {
|
|
let krate = tcx.map.krate();
|
|
let live_symbols = find_live(tcx, exported_items,
|
|
reachable_symbols, krate);
|
|
let mut visitor = DeadVisitor { tcx: tcx, live_symbols: live_symbols };
|
|
visit::walk_crate(&mut visitor, krate);
|
|
}
|