604 lines
22 KiB
Rust
604 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 middle::{def, pat_util, privacy, ty};
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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, ast_map, codemap};
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use syntax::ast_util::{local_def, is_local, PostExpansionMethod};
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use syntax::attr::{self, AttrMetaMethods};
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use syntax::visit::{self, Visitor};
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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, def_id: ast::DefId) -> bool {
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if !is_local(def_id) {
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return false;
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}
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match tcx.map.find(def_id.node) {
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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(..)) => true,
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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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}
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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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}
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}
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fn check_def_id(&mut self, def_id: ast::DefId) {
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if should_explore(self.tcx, def_id) {
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self.worklist.push(def_id.node);
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}
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self.live_symbols.insert(def_id.node);
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}
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fn lookup_and_handle_definition(&mut self, id: &ast::NodeId) {
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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(_) => {
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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::DefVariant(enum_id, variant_id, _) => {
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self.check_def_id(enum_id);
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self.check_def_id(variant_id);
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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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span: codemap::Span) {
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let method_call = ty::MethodCall::expr(id);
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match self.tcx.method_map.borrow().get(&method_call) {
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Some(method) => {
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match method.origin {
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ty::MethodStatic(def_id) => {
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match ty::provided_source(self.tcx, def_id) {
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Some(p_did) => self.check_def_id(p_did),
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None => self.check_def_id(def_id)
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}
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}
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ty::MethodStaticClosure(_) => {}
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ty::MethodTypeParam(ty::MethodParam {
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ref trait_ref,
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method_num: index,
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..
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}) |
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ty::MethodTraitObject(ty::MethodObject {
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ref trait_ref,
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method_num: index,
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..
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}) => {
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let trait_item = ty::trait_item(self.tcx,
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trait_ref.def_id,
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index);
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match trait_item {
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ty::MethodTraitItem(method) => {
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self.check_def_id(method.def_id);
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}
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ty::TypeTraitItem(typedef) => {
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self.check_def_id(typedef.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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None => {
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self.tcx.sess.span_bug(span,
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"method call expression not \
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in method map?!")
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}
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}
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}
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fn handle_field_access(&mut self, lhs: &ast::Expr, name: &ast::Ident) {
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match ty::expr_ty_adjusted(self.tcx, lhs).sty {
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ty::ty_struct(id, _) => {
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let fields = ty::lookup_struct_fields(self.tcx, id);
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let field_id = fields.iter()
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.find(|field| field.name == name.name).unwrap().id;
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self.live_symbols.insert(field_id.node);
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},
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_ => ()
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}
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}
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fn handle_tup_field_access(&mut self, lhs: &ast::Expr, idx: uint) {
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match ty::expr_ty_adjusted(self.tcx, lhs).sty {
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ty::ty_struct(id, _) => {
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let fields = ty::lookup_struct_fields(self.tcx, id);
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let field_id = fields[idx].id;
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self.live_symbols.insert(field_id.node);
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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(&mut self, lhs: &ast::Pat,
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pats: &[codemap::Spanned<ast::FieldPat>]) {
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let id = match self.tcx.def_map.borrow()[lhs.id].full_def() {
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def::DefVariant(_, id, _) => id,
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_ => {
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match ty::ty_to_def_id(ty::node_id_to_type(self.tcx,
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lhs.id)) {
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None => {
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self.tcx.sess.span_bug(lhs.span,
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"struct pattern wasn't of a \
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type with a def ID?!")
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}
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Some(def_id) => def_id,
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}
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}
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};
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let fields = ty::lookup_struct_fields(self.tcx, id);
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for pat in pats {
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let field_id = fields.iter()
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.find(|field| field.name == pat.node.ident.name).unwrap().id;
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self.live_symbols.insert(field_id.node);
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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.len() > 0 {
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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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ast::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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ast::ItemEnum(..) => {
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self.inherited_pub_visibility = item.vis == ast::Public;
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visit::walk_item(self, &*item);
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}
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ast::ItemFn(..)
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| ast::ItemTy(..)
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| ast::ItemStatic(..)
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| ast::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_method) => {
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visit::walk_trait_item(self, trait_method);
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}
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ast_map::NodeImplItem(impl_item) => {
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match *impl_item {
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ast::MethodImplItem(ref method) => {
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visit::walk_method_helper(self, method);
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}
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ast::TypeImplItem(_) => {}
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}
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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_struct_def(&mut self, def: &ast::StructDef, _: ast::Ident,
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_: &ast::Generics, _: ast::NodeId) {
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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.iter().filter(|f| {
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has_extern_repr || inherited_pub_visibility || match f.node.kind {
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ast::NamedField(_, ast::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: &ast::Expr) {
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match expr.node {
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ast::ExprMethodCall(..) => {
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self.lookup_and_handle_method(expr.id, expr.span);
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}
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ast::ExprField(ref lhs, ref ident) => {
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self.handle_field_access(&**lhs, &ident.node);
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}
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ast::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_pat(&mut self, pat: &ast::Pat) {
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let def_map = &self.tcx.def_map;
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match pat.node {
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ast::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: &ast::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_item(&mut self, _: &ast::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: &ast::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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ast::ItemEnum(ref enum_def, _) if allow_dead_code => {
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self.worklist.extend(enum_def.variants.iter().map(|variant| variant.node.id));
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}
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ast::ItemImpl(_, _, _, Some(ref _trait_ref), _, ref impl_items) => {
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for impl_item in impl_items {
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match *impl_item {
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ast::MethodImplItem(ref method) => {
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self.worklist.push(method.id);
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}
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ast::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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fn visit_fn(&mut self, fk: visit::FnKind<'v>,
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_: &'v ast::FnDecl, block: &'v ast::Block,
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_: codemap::Span, id: ast::NodeId) {
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// Check for method here because methods are not ast::Item
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match fk {
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visit::FkMethod(_, _, method) => {
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if has_allow_dead_code_or_lang_attr(&method.attrs) {
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self.worklist.push(id);
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}
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}
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_ => ()
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}
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visit::walk_block(self, block);
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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: &ast::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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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 methods
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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: &ast::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: &ast::Item) -> Option<ast::NodeId> {
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match item.node {
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ast::ItemStruct(ref struct_def, _) => struct_def.ctor_id,
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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: &ast::Item) -> bool {
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let should_warn = match item.node {
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ast::ItemStatic(..)
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| ast::ItemConst(..)
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| ast::ItemFn(..)
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| ast::ItemEnum(..)
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| ast::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: &ast::StructField_) -> bool {
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let is_named = node.ident().is_some();
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let field_type = ty::node_id_to_type(self.tcx, node.id);
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let is_marker_field = match ty::ty_to_def_id(field_type) {
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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: &ast::Variant_) -> bool {
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!self.symbol_is_live(variant.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.
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// ctor_id := `Some` if the item is a struct_ctor (tuple struct),
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// `None` otherwise.
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// If the item is a struct_ctor, then either its `id` or
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// `ctor_id` (unwrapped) is in the live_symbols set. More specifically,
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// DefMap maps the ExprPath of a struct_ctor to the node referred by
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// `ctor_id`. On the other hand, in a statement like
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// `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 methods 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(&local_def(id)) {
|
|
None => (),
|
|
Some(impl_list) => {
|
|
for impl_did in &**impl_list {
|
|
for item_did in &(*impl_items)[*impl_did] {
|
|
if self.live_symbols.contains(&item_did.def_id()
|
|
.node) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
false
|
|
}
|
|
|
|
fn warn_dead_code(&mut self,
|
|
id: ast::NodeId,
|
|
span: codemap::Span,
|
|
ident: ast::Ident,
|
|
node_type: &str) {
|
|
let name = ident.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: &ast::Item) {
|
|
if self.should_warn_about_item(item) {
|
|
self.warn_dead_code(item.id, item.span, item.ident, item.node.descriptive_variant());
|
|
} else {
|
|
match item.node {
|
|
ast::ItemEnum(ref enum_def, _) => {
|
|
for variant in &enum_def.variants {
|
|
if self.should_warn_about_variant(&variant.node) {
|
|
self.warn_dead_code(variant.node.id, variant.span,
|
|
variant.node.name, "variant");
|
|
}
|
|
}
|
|
},
|
|
_ => ()
|
|
}
|
|
}
|
|
visit::walk_item(self, item);
|
|
}
|
|
|
|
fn visit_foreign_item(&mut self, fi: &ast::ForeignItem) {
|
|
if !self.symbol_is_live(fi.id, None) {
|
|
self.warn_dead_code(fi.id, fi.span, fi.ident, fi.node.descriptive_variant());
|
|
}
|
|
visit::walk_foreign_item(self, fi);
|
|
}
|
|
|
|
fn visit_fn(&mut self, fk: visit::FnKind<'v>,
|
|
_: &'v ast::FnDecl, block: &'v ast::Block,
|
|
span: codemap::Span, id: ast::NodeId) {
|
|
// Have to warn method here because methods are not ast::Item
|
|
match fk {
|
|
visit::FkMethod(name, _, _) => {
|
|
if !self.symbol_is_live(id, None) {
|
|
self.warn_dead_code(id, span, name, "method");
|
|
}
|
|
}
|
|
_ => ()
|
|
}
|
|
visit::walk_block(self, block);
|
|
}
|
|
|
|
fn visit_struct_field(&mut self, field: &ast::StructField) {
|
|
if self.should_warn_about_field(&field.node) {
|
|
self.warn_dead_code(field.node.id, field.span,
|
|
field.node.ident().unwrap(), "struct field");
|
|
}
|
|
|
|
visit::walk_struct_field(self, field);
|
|
}
|
|
|
|
// Overwrite so that we don't warn the trait method itself.
|
|
fn visit_trait_item(&mut self, trait_method: &ast::TraitItem) {
|
|
match *trait_method {
|
|
ast::ProvidedMethod(ref method) => {
|
|
visit::walk_block(self, &*method.pe_body())
|
|
}
|
|
ast::RequiredMethod(_) => {}
|
|
ast::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);
|
|
}
|