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1// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2// file at the top-level directory of this distribution and at
3// http://rust-lang.org/COPYRIGHT.
4//
5// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8// option. This file may not be copied, modified, or distributed
9// except according to those terms.
10
11// This implements the dead-code warning pass. It follows middle::reachable
12// closely. The idea is that all reachable symbols are live, codes called
13// from live codes are live, and everything else is dead.
14
9cc50fc6 15use dep_graph::DepNode;
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16use hir::map as ast_map;
17use hir::{self, pat_util, PatKind};
18use hir::intravisit::{self, Visitor};
19
20use middle::privacy;
21use ty::{self, TyCtxt};
22use hir::def::Def;
23use hir::def_id::{DefId};
1a4d82fc 24use lint;
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25
26use std::collections::HashSet;
62682a34 27use syntax::{ast, codemap};
b039eaaf 28use syntax::attr::{self, AttrMetaMethods};
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29
30// Any local node that may call something in its body block should be
31// explored. For example, if it's a live NodeItem that is a
32// function, then we should explore its block to check for codes that
33// may need to be marked as live.
54a0048b 34fn should_explore(tcx: &TyCtxt, node_id: ast::NodeId) -> bool {
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35 match tcx.map.find(node_id) {
36 Some(ast_map::NodeItem(..)) |
37 Some(ast_map::NodeImplItem(..)) |
38 Some(ast_map::NodeForeignItem(..)) |
39 Some(ast_map::NodeTraitItem(..)) =>
40 true,
41 _ =>
42 false
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43 }
44}
45
46struct MarkSymbolVisitor<'a, 'tcx: 'a> {
47 worklist: Vec<ast::NodeId>,
54a0048b 48 tcx: &'a TyCtxt<'tcx>,
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49 live_symbols: Box<HashSet<ast::NodeId>>,
50 struct_has_extern_repr: bool,
51 ignore_non_const_paths: bool,
52 inherited_pub_visibility: bool,
b039eaaf 53 ignore_variant_stack: Vec<DefId>,
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54}
55
56impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
54a0048b 57 fn new(tcx: &'a TyCtxt<'tcx>,
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58 worklist: Vec<ast::NodeId>) -> MarkSymbolVisitor<'a, 'tcx> {
59 MarkSymbolVisitor {
60 worklist: worklist,
61 tcx: tcx,
62 live_symbols: box HashSet::new(),
63 struct_has_extern_repr: false,
64 ignore_non_const_paths: false,
65 inherited_pub_visibility: false,
62682a34 66 ignore_variant_stack: vec![],
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67 }
68 }
69
e9174d1e 70 fn check_def_id(&mut self, def_id: DefId) {
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71 if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
72 if should_explore(self.tcx, node_id) {
73 self.worklist.push(node_id);
74 }
75 self.live_symbols.insert(node_id);
76 }
77 }
78
79 fn insert_def_id(&mut self, def_id: DefId) {
80 if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
81 debug_assert!(!should_explore(self.tcx, node_id));
82 self.live_symbols.insert(node_id);
1a4d82fc 83 }
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84 }
85
86 fn lookup_and_handle_definition(&mut self, id: &ast::NodeId) {
54a0048b 87 use ty::TypeVariants::{TyEnum, TyStruct};
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88
89 // If `bar` is a trait item, make sure to mark Foo as alive in `Foo::bar`
90 self.tcx.tables.borrow().item_substs.get(id)
91 .and_then(|substs| substs.substs.self_ty())
92 .map(|ty| match ty.sty {
93 TyEnum(tyid, _) | TyStruct(tyid, _) => self.check_def_id(tyid.did),
94 _ => (),
95 });
96
1a4d82fc 97 self.tcx.def_map.borrow().get(id).map(|def| {
c34b1796 98 match def.full_def() {
7453a54e 99 Def::Const(_) | Def::AssociatedConst(..) => {
b039eaaf 100 self.check_def_id(def.def_id());
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101 }
102 _ if self.ignore_non_const_paths => (),
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103 Def::PrimTy(_) => (),
104 Def::SelfTy(..) => (),
105 Def::Variant(enum_id, variant_id) => {
1a4d82fc 106 self.check_def_id(enum_id);
b039eaaf 107 if !self.ignore_variant_stack.contains(&variant_id) {
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108 self.check_def_id(variant_id);
109 }
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110 }
111 _ => {
112 self.check_def_id(def.def_id());
113 }
114 }
115 });
116 }
117
c1a9b12d 118 fn lookup_and_handle_method(&mut self, id: ast::NodeId) {
1a4d82fc 119 let method_call = ty::MethodCall::expr(id);
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120 let method = self.tcx.tables.borrow().method_map[&method_call];
121 self.check_def_id(method.def_id);
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122 }
123
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124 fn handle_field_access(&mut self, lhs: &hir::Expr, name: ast::Name) {
125 if let ty::TyStruct(def, _) = self.tcx.expr_ty_adjusted(lhs).sty {
b039eaaf 126 self.insert_def_id(def.struct_variant().field_named(name).did);
e9174d1e 127 } else {
54a0048b 128 span_bug!(lhs.span, "named field access on non-struct")
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129 }
130 }
131
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132 fn handle_tup_field_access(&mut self, lhs: &hir::Expr, idx: usize) {
133 if let ty::TyStruct(def, _) = self.tcx.expr_ty_adjusted(lhs).sty {
b039eaaf 134 self.insert_def_id(def.struct_variant().fields[idx].did);
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135 }
136 }
137
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138 fn handle_field_pattern_match(&mut self, lhs: &hir::Pat,
139 pats: &[codemap::Spanned<hir::FieldPat>]) {
140 let def = self.tcx.def_map.borrow().get(&lhs.id).unwrap().full_def();
141 let pat_ty = self.tcx.node_id_to_type(lhs.id);
142 let variant = match pat_ty.sty {
143 ty::TyStruct(adt, _) | ty::TyEnum(adt, _) => adt.variant_of_def(def),
54a0048b 144 _ => span_bug!(lhs.span, "non-ADT in struct pattern")
1a4d82fc 145 };
85aaf69f 146 for pat in pats {
7453a54e 147 if let PatKind::Wild = pat.node.pat.node {
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148 continue;
149 }
b039eaaf 150 self.insert_def_id(variant.field_named(pat.node.name).did);
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151 }
152 }
153
154 fn mark_live_symbols(&mut self) {
155 let mut scanned = HashSet::new();
9346a6ac 156 while !self.worklist.is_empty() {
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157 let id = self.worklist.pop().unwrap();
158 if scanned.contains(&id) {
159 continue
160 }
161 scanned.insert(id);
162
163 match self.tcx.map.find(id) {
164 Some(ref node) => {
165 self.live_symbols.insert(id);
166 self.visit_node(node);
167 }
168 None => (),
169 }
170 }
171 }
172
173 fn visit_node(&mut self, node: &ast_map::Node) {
174 let had_extern_repr = self.struct_has_extern_repr;
175 self.struct_has_extern_repr = false;
176 let had_inherited_pub_visibility = self.inherited_pub_visibility;
177 self.inherited_pub_visibility = false;
178 match *node {
179 ast_map::NodeItem(item) => {
180 match item.node {
e9174d1e 181 hir::ItemStruct(..) => {
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182 self.struct_has_extern_repr = item.attrs.iter().any(|attr| {
183 attr::find_repr_attrs(self.tcx.sess.diagnostic(), attr)
184 .contains(&attr::ReprExtern)
185 });
186
7453a54e 187 intravisit::walk_item(self, &item);
1a4d82fc 188 }
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189 hir::ItemEnum(..) => {
190 self.inherited_pub_visibility = item.vis == hir::Public;
7453a54e 191 intravisit::walk_item(self, &item);
1a4d82fc 192 }
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193 hir::ItemFn(..)
194 | hir::ItemTy(..)
195 | hir::ItemStatic(..)
196 | hir::ItemConst(..) => {
7453a54e 197 intravisit::walk_item(self, &item);
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198 }
199 _ => ()
200 }
201 }
c34b1796 202 ast_map::NodeTraitItem(trait_item) => {
92a42be0 203 intravisit::walk_trait_item(self, trait_item);
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204 }
205 ast_map::NodeImplItem(impl_item) => {
92a42be0 206 intravisit::walk_impl_item(self, impl_item);
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207 }
208 ast_map::NodeForeignItem(foreign_item) => {
7453a54e 209 intravisit::walk_foreign_item(self, &foreign_item);
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210 }
211 _ => ()
212 }
213 self.struct_has_extern_repr = had_extern_repr;
214 self.inherited_pub_visibility = had_inherited_pub_visibility;
215 }
216}
217
218impl<'a, 'tcx, 'v> Visitor<'v> for MarkSymbolVisitor<'a, 'tcx> {
219
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220 fn visit_variant_data(&mut self, def: &hir::VariantData, _: ast::Name,
221 _: &hir::Generics, _: ast::NodeId, _: codemap::Span) {
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222 let has_extern_repr = self.struct_has_extern_repr;
223 let inherited_pub_visibility = self.inherited_pub_visibility;
b039eaaf 224 let live_fields = def.fields().iter().filter(|f| {
54a0048b 225 has_extern_repr || inherited_pub_visibility || f.vis == hir::Public
1a4d82fc 226 });
54a0048b 227 self.live_symbols.extend(live_fields.map(|f| f.id));
1a4d82fc 228
92a42be0 229 intravisit::walk_struct_def(self, def);
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230 }
231
e9174d1e 232 fn visit_expr(&mut self, expr: &hir::Expr) {
1a4d82fc 233 match expr.node {
e9174d1e 234 hir::ExprMethodCall(..) => {
c1a9b12d 235 self.lookup_and_handle_method(expr.id);
1a4d82fc 236 }
b039eaaf 237 hir::ExprField(ref lhs, ref name) => {
7453a54e 238 self.handle_field_access(&lhs, name.node);
1a4d82fc 239 }
e9174d1e 240 hir::ExprTupField(ref lhs, idx) => {
7453a54e 241 self.handle_tup_field_access(&lhs, idx.node);
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242 }
243 _ => ()
244 }
245
92a42be0 246 intravisit::walk_expr(self, expr);
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247 }
248
e9174d1e 249 fn visit_arm(&mut self, arm: &hir::Arm) {
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250 if arm.pats.len() == 1 {
251 let pat = &*arm.pats[0];
92a42be0 252 let variants = pat_util::necessary_variants(&self.tcx.def_map.borrow(), pat);
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253
254 // Inside the body, ignore constructions of variants
255 // necessary for the pattern to match. Those construction sites
256 // can't be reached unless the variant is constructed elsewhere.
257 let len = self.ignore_variant_stack.len();
7453a54e 258 self.ignore_variant_stack.extend_from_slice(&variants);
92a42be0 259 intravisit::walk_arm(self, arm);
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260 self.ignore_variant_stack.truncate(len);
261 } else {
92a42be0 262 intravisit::walk_arm(self, arm);
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263 }
264 }
265
e9174d1e 266 fn visit_pat(&mut self, pat: &hir::Pat) {
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267 let def_map = &self.tcx.def_map;
268 match pat.node {
7453a54e 269 PatKind::Struct(_, ref fields, _) => {
85aaf69f 270 self.handle_field_pattern_match(pat, fields);
1a4d82fc 271 }
92a42be0 272 _ if pat_util::pat_is_const(&def_map.borrow(), pat) => {
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273 // it might be the only use of a const
274 self.lookup_and_handle_definition(&pat.id)
275 }
276 _ => ()
277 }
278
279 self.ignore_non_const_paths = true;
92a42be0 280 intravisit::walk_pat(self, pat);
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281 self.ignore_non_const_paths = false;
282 }
283
e9174d1e 284 fn visit_path(&mut self, path: &hir::Path, id: ast::NodeId) {
1a4d82fc 285 self.lookup_and_handle_definition(&id);
92a42be0 286 intravisit::walk_path(self, path);
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287 }
288
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289 fn visit_path_list_item(&mut self, path: &hir::Path, item: &hir::PathListItem) {
290 self.lookup_and_handle_definition(&item.node.id());
92a42be0 291 intravisit::walk_path_list_item(self, path, item);
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292 }
293}
294
b039eaaf 295fn has_allow_dead_code_or_lang_attr(attrs: &[ast::Attribute]) -> bool {
85aaf69f 296 if attr::contains_name(attrs, "lang") {
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297 return true;
298 }
299
300 let dead_code = lint::builtin::DEAD_CODE.name_lower();
b039eaaf 301 for attr in lint::gather_attrs(attrs) {
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302 match attr {
303 Ok((ref name, lint::Allow, _))
85aaf69f 304 if &name[..] == dead_code => return true,
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305 _ => (),
306 }
307 }
308 false
309}
310
311// This visitor seeds items that
312// 1) We want to explicitly consider as live:
313// * Item annotated with #[allow(dead_code)]
314// - This is done so that if we want to suppress warnings for a
315// group of dead functions, we only have to annotate the "root".
316// For example, if both `f` and `g` are dead and `f` calls `g`,
317// then annotating `f` with `#[allow(dead_code)]` will suppress
318// warning for both `f` and `g`.
319// * Item annotated with #[lang=".."]
320// - This is because lang items are always callable from elsewhere.
321// or
322// 2) We are not sure to be live or not
323// * Implementation of a trait method
324struct LifeSeeder {
325 worklist: Vec<ast::NodeId>
326}
327
328impl<'v> Visitor<'v> for LifeSeeder {
e9174d1e 329 fn visit_item(&mut self, item: &hir::Item) {
85aaf69f 330 let allow_dead_code = has_allow_dead_code_or_lang_attr(&item.attrs);
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331 if allow_dead_code {
332 self.worklist.push(item.id);
333 }
334 match item.node {
e9174d1e 335 hir::ItemEnum(ref enum_def, _) if allow_dead_code => {
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336 self.worklist.extend(enum_def.variants.iter()
337 .map(|variant| variant.node.data.id()));
1a4d82fc 338 }
e9174d1e 339 hir::ItemTrait(_, _, _, ref trait_items) => {
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340 for trait_item in trait_items {
341 match trait_item.node {
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342 hir::ConstTraitItem(_, Some(_)) |
343 hir::MethodTraitItem(_, Some(_)) => {
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344 if has_allow_dead_code_or_lang_attr(&trait_item.attrs) {
345 self.worklist.push(trait_item.id);
346 }
347 }
348 _ => {}
349 }
350 }
351 }
e9174d1e 352 hir::ItemImpl(_, _, _, ref opt_trait, _, ref impl_items) => {
85aaf69f 353 for impl_item in impl_items {
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354 if opt_trait.is_some() ||
355 has_allow_dead_code_or_lang_attr(&impl_item.attrs) {
356 self.worklist.push(impl_item.id);
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357 }
358 }
359 }
360 _ => ()
361 }
1a4d82fc 362 }
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363}
364
54a0048b 365fn create_and_seed_worklist(tcx: &TyCtxt,
92a42be0 366 access_levels: &privacy::AccessLevels,
e9174d1e 367 krate: &hir::Crate) -> Vec<ast::NodeId> {
1a4d82fc 368 let mut worklist = Vec::new();
92a42be0 369 for (id, _) in &access_levels.map {
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370 worklist.push(*id);
371 }
372
373 // Seed entry point
374 match *tcx.sess.entry_fn.borrow() {
375 Some((id, _)) => worklist.push(id),
376 None => ()
377 }
378
d9579d0f 379 // Seed implemented trait items
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380 let mut life_seeder = LifeSeeder {
381 worklist: worklist
382 };
92a42be0 383 krate.visit_all_items(&mut life_seeder);
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384
385 return life_seeder.worklist;
386}
387
54a0048b 388fn find_live(tcx: &TyCtxt,
92a42be0 389 access_levels: &privacy::AccessLevels,
e9174d1e 390 krate: &hir::Crate)
1a4d82fc 391 -> Box<HashSet<ast::NodeId>> {
92a42be0 392 let worklist = create_and_seed_worklist(tcx, access_levels, krate);
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393 let mut symbol_visitor = MarkSymbolVisitor::new(tcx, worklist);
394 symbol_visitor.mark_live_symbols();
395 symbol_visitor.live_symbols
396}
397
e9174d1e 398fn get_struct_ctor_id(item: &hir::Item) -> Option<ast::NodeId> {
1a4d82fc 399 match item.node {
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400 hir::ItemStruct(ref struct_def, _) if !struct_def.is_struct() => {
401 Some(struct_def.id())
402 }
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403 _ => None
404 }
405}
406
407struct DeadVisitor<'a, 'tcx: 'a> {
54a0048b 408 tcx: &'a TyCtxt<'tcx>,
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409 live_symbols: Box<HashSet<ast::NodeId>>,
410}
411
412impl<'a, 'tcx> DeadVisitor<'a, 'tcx> {
e9174d1e 413 fn should_warn_about_item(&mut self, item: &hir::Item) -> bool {
1a4d82fc 414 let should_warn = match item.node {
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415 hir::ItemStatic(..)
416 | hir::ItemConst(..)
417 | hir::ItemFn(..)
418 | hir::ItemEnum(..)
419 | hir::ItemStruct(..) => true,
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420 _ => false
421 };
422 let ctor_id = get_struct_ctor_id(item);
423 should_warn && !self.symbol_is_live(item.id, ctor_id)
424 }
425
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426 fn should_warn_about_field(&mut self, field: &hir::StructField) -> bool {
427 let field_type = self.tcx.node_id_to_type(field.id);
c1a9b12d 428 let is_marker_field = match field_type.ty_to_def_id() {
7453a54e 429 Some(def_id) => self.tcx.lang_items.items().iter().any(|item| *item == Some(def_id)),
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430 _ => false
431 };
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432 !field.is_positional()
433 && !self.symbol_is_live(field.id, None)
1a4d82fc 434 && !is_marker_field
54a0048b 435 && !has_allow_dead_code_or_lang_attr(&field.attrs)
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436 }
437
e9174d1e 438 fn should_warn_about_variant(&mut self, variant: &hir::Variant_) -> bool {
b039eaaf 439 !self.symbol_is_live(variant.data.id(), None)
85aaf69f 440 && !has_allow_dead_code_or_lang_attr(&variant.attrs)
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441 }
442
443 // id := node id of an item's definition.
444 // ctor_id := `Some` if the item is a struct_ctor (tuple struct),
445 // `None` otherwise.
446 // If the item is a struct_ctor, then either its `id` or
447 // `ctor_id` (unwrapped) is in the live_symbols set. More specifically,
448 // DefMap maps the ExprPath of a struct_ctor to the node referred by
449 // `ctor_id`. On the other hand, in a statement like
450 // `type <ident> <generics> = <ty>;` where <ty> refers to a struct_ctor,
451 // DefMap maps <ty> to `id` instead.
b039eaaf
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452 fn symbol_is_live(&mut self,
453 id: ast::NodeId,
454 ctor_id: Option<ast::NodeId>)
455 -> bool {
1a4d82fc
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456 if self.live_symbols.contains(&id)
457 || ctor_id.map_or(false,
458 |ctor| self.live_symbols.contains(&ctor)) {
459 return true;
460 }
d9579d0f 461 // If it's a type whose items are live, then it's live, too.
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462 // This is done to handle the case where, for example, the static
463 // method of a private type is used, but the type itself is never
464 // called directly.
465 let impl_items = self.tcx.impl_items.borrow();
b039eaaf 466 match self.tcx.inherent_impls.borrow().get(&self.tcx.map.local_def_id(id)) {
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467 None => (),
468 Some(impl_list) => {
62682a34
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469 for impl_did in impl_list.iter() {
470 for item_did in impl_items.get(impl_did).unwrap().iter() {
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471 if let Some(item_node_id) =
472 self.tcx.map.as_local_node_id(item_did.def_id()) {
473 if self.live_symbols.contains(&item_node_id) {
474 return true;
475 }
1a4d82fc
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476 }
477 }
478 }
479 }
480 }
481 false
482 }
483
484 fn warn_dead_code(&mut self,
485 id: ast::NodeId,
486 span: codemap::Span,
9346a6ac 487 name: ast::Name,
1a4d82fc 488 node_type: &str) {
9346a6ac 489 let name = name.as_str();
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490 if !name.starts_with("_") {
491 self.tcx
492 .sess
493 .add_lint(lint::builtin::DEAD_CODE,
494 id,
495 span,
496 format!("{} is never used: `{}`", node_type, name));
497 }
498 }
499}
500
501impl<'a, 'tcx, 'v> Visitor<'v> for DeadVisitor<'a, 'tcx> {
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502 /// Walk nested items in place so that we don't report dead-code
503 /// on inner functions when the outer function is already getting
504 /// an error. We could do this also by checking the parents, but
505 /// this is how the code is setup and it seems harmless enough.
506 fn visit_nested_item(&mut self, item: hir::ItemId) {
507 self.visit_item(self.tcx.map.expect_item(item.id))
508 }
509
e9174d1e 510 fn visit_item(&mut self, item: &hir::Item) {
1a4d82fc 511 if self.should_warn_about_item(item) {
9346a6ac
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512 self.warn_dead_code(
513 item.id,
514 item.span,
b039eaaf 515 item.name,
9346a6ac
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516 item.node.descriptive_variant()
517 );
1a4d82fc 518 } else {
92a42be0
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519 // Only continue if we didn't warn
520 intravisit::walk_item(self, item);
521 }
522 }
523
524 fn visit_variant(&mut self, variant: &hir::Variant, g: &hir::Generics, id: ast::NodeId) {
525 if self.should_warn_about_variant(&variant.node) {
526 self.warn_dead_code(variant.node.data.id(), variant.span,
527 variant.node.name, "variant");
528 } else {
529 intravisit::walk_variant(self, variant, g, id);
1a4d82fc 530 }
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531 }
532
e9174d1e 533 fn visit_foreign_item(&mut self, fi: &hir::ForeignItem) {
1a4d82fc 534 if !self.symbol_is_live(fi.id, None) {
b039eaaf 535 self.warn_dead_code(fi.id, fi.span, fi.name, fi.node.descriptive_variant());
1a4d82fc 536 }
92a42be0 537 intravisit::walk_foreign_item(self, fi);
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538 }
539
e9174d1e 540 fn visit_struct_field(&mut self, field: &hir::StructField) {
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541 if self.should_warn_about_field(&field) {
542 self.warn_dead_code(field.id, field.span,
543 field.name, "struct field");
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544 }
545
92a42be0 546 intravisit::walk_struct_field(self, field);
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547 }
548
e9174d1e 549 fn visit_impl_item(&mut self, impl_item: &hir::ImplItem) {
d9579d0f 550 match impl_item.node {
92a42be0 551 hir::ImplItemKind::Const(_, ref expr) => {
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552 if !self.symbol_is_live(impl_item.id, None) {
553 self.warn_dead_code(impl_item.id, impl_item.span,
b039eaaf 554 impl_item.name, "associated const");
d9579d0f 555 }
92a42be0 556 intravisit::walk_expr(self, expr)
d9579d0f 557 }
92a42be0 558 hir::ImplItemKind::Method(_, ref body) => {
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559 if !self.symbol_is_live(impl_item.id, None) {
560 self.warn_dead_code(impl_item.id, impl_item.span,
b039eaaf 561 impl_item.name, "method");
d9579d0f 562 }
92a42be0 563 intravisit::walk_block(self, body)
d9579d0f 564 }
92a42be0 565 hir::ImplItemKind::Type(..) => {}
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566 }
567 }
568
569 // Overwrite so that we don't warn the trait item itself.
e9174d1e 570 fn visit_trait_item(&mut self, trait_item: &hir::TraitItem) {
d9579d0f 571 match trait_item.node {
e9174d1e 572 hir::ConstTraitItem(_, Some(ref expr)) => {
92a42be0 573 intravisit::walk_expr(self, expr)
d9579d0f 574 }
e9174d1e 575 hir::MethodTraitItem(_, Some(ref body)) => {
92a42be0 576 intravisit::walk_block(self, body)
1a4d82fc 577 }
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578 hir::ConstTraitItem(_, None) |
579 hir::MethodTraitItem(_, None) |
580 hir::TypeTraitItem(..) => {}
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581 }
582 }
583}
584
54a0048b 585pub fn check_crate(tcx: &TyCtxt, access_levels: &privacy::AccessLevels) {
9cc50fc6 586 let _task = tcx.dep_graph.in_task(DepNode::DeadCheck);
1a4d82fc 587 let krate = tcx.map.krate();
92a42be0 588 let live_symbols = find_live(tcx, access_levels, krate);
1a4d82fc 589 let mut visitor = DeadVisitor { tcx: tcx, live_symbols: live_symbols };
92a42be0 590 intravisit::walk_crate(&mut visitor, krate);
1a4d82fc 591}