src/librustc_lint/builtin.rs

   1 // Copyright 2012-2015 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 //! Lints in the Rust compiler.
  12 //!
  13 //! This contains lints which can feasibly be implemented as their own
  14 //! AST visitor. Also see `rustc::lint::builtin`, which contains the
  15 //! definitions of lints that are emitted directly inside the main
  16 //! compiler.
  17 //!
  18 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
  19 //! Then add code to emit the new lint in the appropriate circumstances.
  20 //! You can do that in an existing `LintPass` if it makes sense, or in a
  21 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  22 //! compiler. Only do the latter if the check can't be written cleanly as a
  23 //! `LintPass` (also, note that such lints will need to be defined in
  24 //! `rustc::lint::builtin`, not here).
  25 //!
  26 //! If you define a new `LintPass`, you will also need to add it to the
  27 //! `add_builtin!` or `add_builtin_with_new!` invocation in `lib.rs`.
  28 //! Use the former for unit-like structs and the latter for structs with
  29 //! a `pub fn new()`.
  30
  31 use rustc::hir::def::Def;
  32 use rustc::hir::def_id::DefId;
  33 use rustc::cfg;
  34 use rustc::ty::subst::Substs;
  35 use rustc::ty::{self, Ty};
  36 use rustc::traits;
  37 use rustc::hir::map as hir_map;
  38 use util::nodemap::NodeSet;
  39 use lint::{LateContext, LintContext, LintArray};
  40 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
  41
  42 use std::collections::HashSet;
  43 use rustc::util::nodemap::FxHashSet;
  44
  45 use syntax::tokenstream::{TokenTree, TokenStream};
  46 use syntax::ast;
  47 use syntax::attr;
  48 use syntax::source_map::Spanned;
  49 use syntax::edition::Edition;
  50 use syntax::feature_gate::{AttributeGate, AttributeType, Stability, deprecated_attributes};
  51 use syntax_pos::{BytePos, Span, SyntaxContext};
  52 use syntax::symbol::keywords;
  53 use syntax::errors::{Applicability, DiagnosticBuilder};
  54
  55 use rustc::hir::{self, GenericParamKind, PatKind};
  56 use rustc::hir::intravisit::FnKind;
  57
  58 use bad_style::{MethodLateContext, method_context};
  59
  60 // hardwired lints from librustc
  61 pub use lint::builtin::*;
  62
  63 declare_lint! {
  64     WHILE_TRUE,
  65     Warn,
  66     "suggest using `loop { }` instead of `while true { }`"
  67 }
  68
  69 #[derive(Copy, Clone)]
  70 pub struct WhileTrue;
  71
  72 impl LintPass for WhileTrue {
  73     fn get_lints(&self) -> LintArray {
  74         lint_array!(WHILE_TRUE)
  75     }
  76 }
  77
  78 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
  79     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
  80         if let hir::ExprKind::While(ref cond, ..) = e.node {
  81             if let hir::ExprKind::Lit(ref lit) = cond.node {
  82                 if let ast::LitKind::Bool(true) = lit.node {
  83                     if lit.span.ctxt() == SyntaxContext::empty() {
  84                         let msg = "denote infinite loops with `loop { ... }`";
  85                         let condition_span = cx.tcx.sess.source_map().def_span(e.span);
  86                         let mut err = cx.struct_span_lint(WHILE_TRUE, condition_span, msg);
  87                         err.span_suggestion_short_with_applicability(
  88                             condition_span,
  89                             "use `loop`",
  90                             "loop".to_owned(),
  91                             Applicability::MachineApplicable
  92                         );
  93                         err.emit();
  94                     }
  95                 }
  96             }
  97         }
  98     }
  99 }
 100
 101 declare_lint! {
 102     BOX_POINTERS,
 103     Allow,
 104     "use of owned (Box type) heap memory"
 105 }
 106
 107 #[derive(Copy, Clone)]
 108 pub struct BoxPointers;
 109
 110 impl BoxPointers {
 111     fn check_heap_type<'a, 'tcx>(&self, cx: &LateContext, span: Span, ty: Ty) {
 112         for leaf_ty in ty.walk() {
 113             if leaf_ty.is_box() {
 114                 let m = format!("type uses owned (Box type) pointers: {}", ty);
 115                 cx.span_lint(BOX_POINTERS, span, &m);
 116             }
 117         }
 118     }
 119 }
 120
 121 impl LintPass for BoxPointers {
 122     fn get_lints(&self) -> LintArray {
 123         lint_array!(BOX_POINTERS)
 124     }
 125 }
 126
 127 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 128     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 129         match it.node {
 130             hir::ItemKind::Fn(..) |
 131             hir::ItemKind::Ty(..) |
 132             hir::ItemKind::Enum(..) |
 133             hir::ItemKind::Struct(..) |
 134             hir::ItemKind::Union(..) => {
 135                 let def_id = cx.tcx.hir.local_def_id(it.id);
 136                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 137             }
 138             _ => ()
 139         }
 140
 141         // If it's a struct, we also have to check the fields' types
 142         match it.node {
 143             hir::ItemKind::Struct(ref struct_def, _) |
 144             hir::ItemKind::Union(ref struct_def, _) => {
 145                 for struct_field in struct_def.fields() {
 146                     let def_id = cx.tcx.hir.local_def_id(struct_field.id);
 147                     self.check_heap_type(cx, struct_field.span,
 148                                          cx.tcx.type_of(def_id));
 149                 }
 150             }
 151             _ => (),
 152         }
 153     }
 154
 155     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
 156         let ty = cx.tables.node_id_to_type(e.hir_id);
 157         self.check_heap_type(cx, e.span, ty);
 158     }
 159 }
 160
 161 declare_lint! {
 162     NON_SHORTHAND_FIELD_PATTERNS,
 163     Warn,
 164     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 165 }
 166
 167 #[derive(Copy, Clone)]
 168 pub struct NonShorthandFieldPatterns;
 169
 170 impl LintPass for NonShorthandFieldPatterns {
 171     fn get_lints(&self) -> LintArray {
 172         lint_array!(NON_SHORTHAND_FIELD_PATTERNS)
 173     }
 174 }
 175
 176 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 177     fn check_pat(&mut self, cx: &LateContext, pat: &hir::Pat) {
 178         if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.node {
 179             let variant = cx.tables.pat_ty(pat).ty_adt_def()
 180                                    .expect("struct pattern type is not an ADT")
 181                                    .variant_of_def(cx.tables.qpath_def(qpath, pat.hir_id));
 182             for fieldpat in field_pats {
 183                 if fieldpat.node.is_shorthand {
 184                     continue;
 185                 }
 186                 if fieldpat.span.ctxt().outer().expn_info().is_some() {
 187                     // Don't lint if this is a macro expansion: macro authors
 188                     // shouldn't have to worry about this kind of style issue
 189                     // (Issue #49588)
 190                     continue;
 191                 }
 192                 if let PatKind::Binding(_, _, ident, None) = fieldpat.node.pat.node {
 193                     if cx.tcx.find_field_index(ident, &variant) ==
 194                        Some(cx.tcx.field_index(fieldpat.node.id, cx.tables)) {
 195                         let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
 196                                      fieldpat.span,
 197                                      &format!("the `{}:` in this pattern is redundant", ident));
 198                         let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
 199                                                                                  ':');
 200                         err.span_suggestion_short_with_applicability(
 201                             subspan,
 202                             "remove this",
 203                             ident.to_string(),
 204                             Applicability::MachineApplicable
 205                         );
 206                         err.emit();
 207                     }
 208                 }
 209             }
 210         }
 211     }
 212 }
 213
 214 declare_lint! {
 215     UNSAFE_CODE,
 216     Allow,
 217     "usage of `unsafe` code"
 218 }
 219
 220 #[derive(Copy, Clone)]
 221 pub struct UnsafeCode;
 222
 223 impl LintPass for UnsafeCode {
 224     fn get_lints(&self) -> LintArray {
 225         lint_array!(UNSAFE_CODE)
 226     }
 227 }
 228
 229 impl UnsafeCode {
 230     fn report_unsafe(&self, cx: &LateContext, span: Span, desc: &'static str) {
 231         // This comes from a macro that has #[allow_internal_unsafe].
 232         if span.allows_unsafe() {
 233             return;
 234         }
 235
 236         cx.span_lint(UNSAFE_CODE, span, desc);
 237     }
 238 }
 239
 240 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnsafeCode {
 241     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
 242         if let hir::ExprKind::Block(ref blk, _) = e.node {
 243             // Don't warn about generated blocks, that'll just pollute the output.
 244             if blk.rules == hir::UnsafeBlock(hir::UserProvided) {
 245                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
 246             }
 247         }
 248     }
 249
 250     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 251         match it.node {
 252             hir::ItemKind::Trait(_, hir::Unsafety::Unsafe, ..) => {
 253                 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
 254             }
 255
 256             hir::ItemKind::Impl(hir::Unsafety::Unsafe, ..) => {
 257                 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
 258             }
 259
 260             _ => return,
 261         }
 262     }
 263
 264     fn check_fn(&mut self,
 265                 cx: &LateContext,
 266                 fk: FnKind<'tcx>,
 267                 _: &hir::FnDecl,
 268                 _: &hir::Body,
 269                 span: Span,
 270                 _: ast::NodeId) {
 271         match fk {
 272             FnKind::ItemFn(_, _, hir::FnHeader { unsafety: hir::Unsafety::Unsafe, .. }, ..) => {
 273                 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
 274             }
 275
 276             FnKind::Method(_, sig, ..) => {
 277                 if sig.header.unsafety == hir::Unsafety::Unsafe {
 278                     self.report_unsafe(cx, span, "implementation of an `unsafe` method")
 279                 }
 280             }
 281
 282             _ => (),
 283         }
 284     }
 285
 286     fn check_trait_item(&mut self, cx: &LateContext, item: &hir::TraitItem) {
 287         if let hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(_)) = item.node {
 288             if sig.header.unsafety == hir::Unsafety::Unsafe {
 289                 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
 290             }
 291         }
 292     }
 293 }
 294
 295 declare_lint! {
 296     pub MISSING_DOCS,
 297     Allow,
 298     "detects missing documentation for public members",
 299     report_in_external_macro: true
 300 }
 301
 302 pub struct MissingDoc {
 303     /// Stack of whether #[doc(hidden)] is set
 304     /// at each level which has lint attributes.
 305     doc_hidden_stack: Vec<bool>,
 306
 307     /// Private traits or trait items that leaked through. Don't check their methods.
 308     private_traits: HashSet<ast::NodeId>,
 309 }
 310
 311 impl MissingDoc {
 312     pub fn new() -> MissingDoc {
 313         MissingDoc {
 314             doc_hidden_stack: vec![false],
 315             private_traits: HashSet::new(),
 316         }
 317     }
 318
 319     fn doc_hidden(&self) -> bool {
 320         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 321     }
 322
 323     fn check_missing_docs_attrs(&self,
 324                                 cx: &LateContext,
 325                                 id: Option<ast::NodeId>,
 326                                 attrs: &[ast::Attribute],
 327                                 sp: Span,
 328                                 desc: &'static str) {
 329         // If we're building a test harness, then warning about
 330         // documentation is probably not really relevant right now.
 331         if cx.sess().opts.test {
 332             return;
 333         }
 334
 335         // `#[doc(hidden)]` disables missing_docs check.
 336         if self.doc_hidden() {
 337             return;
 338         }
 339
 340         // Only check publicly-visible items, using the result from the privacy pass.
 341         // It's an option so the crate root can also use this function (it doesn't
 342         // have a NodeId).
 343         if let Some(id) = id {
 344             if !cx.access_levels.is_exported(id) {
 345                 return;
 346             }
 347         }
 348
 349         fn has_doc(attr: &ast::Attribute) -> bool {
 350             if !attr.check_name("doc") {
 351                 return false;
 352             }
 353
 354             if attr.is_value_str() {
 355                 return true;
 356             }
 357
 358             if let Some(list) = attr.meta_item_list() {
 359                 for meta in list {
 360                     if meta.check_name("include") {
 361                         return true;
 362                     }
 363                 }
 364             }
 365
 366             false
 367         }
 368
 369         let has_doc = attrs.iter().any(|a| has_doc(a));
 370         if !has_doc {
 371             cx.span_lint(MISSING_DOCS,
 372                          cx.tcx.sess.source_map().def_span(sp),
 373                          &format!("missing documentation for {}", desc));
 374         }
 375     }
 376 }
 377
 378 impl LintPass for MissingDoc {
 379     fn get_lints(&self) -> LintArray {
 380         lint_array!(MISSING_DOCS)
 381     }
 382 }
 383
 384 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 385     fn enter_lint_attrs(&mut self, _: &LateContext, attrs: &[ast::Attribute]) {
 386         let doc_hidden = self.doc_hidden() ||
 387                          attrs.iter().any(|attr| {
 388             attr.check_name("doc") &&
 389             match attr.meta_item_list() {
 390                 None => false,
 391                 Some(l) => attr::list_contains_name(&l, "hidden"),
 392             }
 393         });
 394         self.doc_hidden_stack.push(doc_hidden);
 395     }
 396
 397     fn exit_lint_attrs(&mut self, _: &LateContext, _attrs: &[ast::Attribute]) {
 398         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 399     }
 400
 401     fn check_crate(&mut self, cx: &LateContext, krate: &hir::Crate) {
 402         self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
 403     }
 404
 405     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 406         let desc = match it.node {
 407             hir::ItemKind::Fn(..) => "a function",
 408             hir::ItemKind::Mod(..) => "a module",
 409             hir::ItemKind::Enum(..) => "an enum",
 410             hir::ItemKind::Struct(..) => "a struct",
 411             hir::ItemKind::Union(..) => "a union",
 412             hir::ItemKind::Trait(.., ref trait_item_refs) => {
 413                 // Issue #11592, traits are always considered exported, even when private.
 414                 if let hir::VisibilityKind::Inherited = it.vis.node {
 415                     self.private_traits.insert(it.id);
 416                     for trait_item_ref in trait_item_refs {
 417                         self.private_traits.insert(trait_item_ref.id.node_id);
 418                     }
 419                     return;
 420                 }
 421                 "a trait"
 422             }
 423             hir::ItemKind::Ty(..) => "a type alias",
 424             hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
 425                 // If the trait is private, add the impl items to private_traits so they don't get
 426                 // reported for missing docs.
 427                 let real_trait = trait_ref.path.def.def_id();
 428                 if let Some(node_id) = cx.tcx.hir.as_local_node_id(real_trait) {
 429                     match cx.tcx.hir.find(node_id) {
 430                         Some(hir_map::NodeItem(item)) => {
 431                             if let hir::VisibilityKind::Inherited = item.vis.node {
 432                                 for impl_item_ref in impl_item_refs {
 433                                     self.private_traits.insert(impl_item_ref.id.node_id);
 434                                 }
 435                             }
 436                         }
 437                         _ => {}
 438                     }
 439                 }
 440                 return;
 441             }
 442             hir::ItemKind::Const(..) => "a constant",
 443             hir::ItemKind::Static(..) => "a static",
 444             _ => return,
 445         };
 446
 447         self.check_missing_docs_attrs(cx, Some(it.id), &it.attrs, it.span, desc);
 448     }
 449
 450     fn check_trait_item(&mut self, cx: &LateContext, trait_item: &hir::TraitItem) {
 451         if self.private_traits.contains(&trait_item.id) {
 452             return;
 453         }
 454
 455         let desc = match trait_item.node {
 456             hir::TraitItemKind::Const(..) => "an associated constant",
 457             hir::TraitItemKind::Method(..) => "a trait method",
 458             hir::TraitItemKind::Type(..) => "an associated type",
 459         };
 460
 461         self.check_missing_docs_attrs(cx,
 462                                       Some(trait_item.id),
 463                                       &trait_item.attrs,
 464                                       trait_item.span,
 465                                       desc);
 466     }
 467
 468     fn check_impl_item(&mut self, cx: &LateContext, impl_item: &hir::ImplItem) {
 469         // If the method is an impl for a trait, don't doc.
 470         if method_context(cx, impl_item.id) == MethodLateContext::TraitImpl {
 471             return;
 472         }
 473
 474         let desc = match impl_item.node {
 475             hir::ImplItemKind::Const(..) => "an associated constant",
 476             hir::ImplItemKind::Method(..) => "a method",
 477             hir::ImplItemKind::Type(_) => "an associated type",
 478             hir::ImplItemKind::Existential(_) => "an associated existential type",
 479         };
 480         self.check_missing_docs_attrs(cx,
 481                                       Some(impl_item.id),
 482                                       &impl_item.attrs,
 483                                       impl_item.span,
 484                                       desc);
 485     }
 486
 487     fn check_struct_field(&mut self, cx: &LateContext, sf: &hir::StructField) {
 488         if !sf.is_positional() {
 489             self.check_missing_docs_attrs(cx,
 490                                           Some(sf.id),
 491                                           &sf.attrs,
 492                                           sf.span,
 493                                           "a struct field")
 494         }
 495     }
 496
 497     fn check_variant(&mut self, cx: &LateContext, v: &hir::Variant, _: &hir::Generics) {
 498         self.check_missing_docs_attrs(cx,
 499                                       Some(v.node.data.id()),
 500                                       &v.node.attrs,
 501                                       v.span,
 502                                       "a variant");
 503     }
 504 }
 505
 506 declare_lint! {
 507     pub MISSING_COPY_IMPLEMENTATIONS,
 508     Allow,
 509     "detects potentially-forgotten implementations of `Copy`"
 510 }
 511
 512 #[derive(Copy, Clone)]
 513 pub struct MissingCopyImplementations;
 514
 515 impl LintPass for MissingCopyImplementations {
 516     fn get_lints(&self) -> LintArray {
 517         lint_array!(MISSING_COPY_IMPLEMENTATIONS)
 518     }
 519 }
 520
 521 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 522     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
 523         if !cx.access_levels.is_reachable(item.id) {
 524             return;
 525         }
 526         let (def, ty) = match item.node {
 527             hir::ItemKind::Struct(_, ref ast_generics) => {
 528                 if !ast_generics.params.is_empty() {
 529                     return;
 530                 }
 531                 let def = cx.tcx.adt_def(cx.tcx.hir.local_def_id(item.id));
 532                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 533             }
 534             hir::ItemKind::Union(_, ref ast_generics) => {
 535                 if !ast_generics.params.is_empty() {
 536                     return;
 537                 }
 538                 let def = cx.tcx.adt_def(cx.tcx.hir.local_def_id(item.id));
 539                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 540             }
 541             hir::ItemKind::Enum(_, ref ast_generics) => {
 542                 if !ast_generics.params.is_empty() {
 543                     return;
 544                 }
 545                 let def = cx.tcx.adt_def(cx.tcx.hir.local_def_id(item.id));
 546                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 547             }
 548             _ => return,
 549         };
 550         if def.has_dtor(cx.tcx) {
 551             return;
 552         }
 553         let param_env = ty::ParamEnv::empty();
 554         if !ty.moves_by_default(cx.tcx, param_env, item.span) {
 555             return;
 556         }
 557         if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
 558             cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
 559                          item.span,
 560                          "type could implement `Copy`; consider adding `impl \
 561                           Copy`")
 562         }
 563     }
 564 }
 565
 566 declare_lint! {
 567     MISSING_DEBUG_IMPLEMENTATIONS,
 568     Allow,
 569     "detects missing implementations of fmt::Debug"
 570 }
 571
 572 pub struct MissingDebugImplementations {
 573     impling_types: Option<NodeSet>,
 574 }
 575
 576 impl MissingDebugImplementations {
 577     pub fn new() -> MissingDebugImplementations {
 578         MissingDebugImplementations { impling_types: None }
 579     }
 580 }
 581
 582 impl LintPass for MissingDebugImplementations {
 583     fn get_lints(&self) -> LintArray {
 584         lint_array!(MISSING_DEBUG_IMPLEMENTATIONS)
 585     }
 586 }
 587
 588 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 589     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
 590         if !cx.access_levels.is_reachable(item.id) {
 591             return;
 592         }
 593
 594         match item.node {
 595             hir::ItemKind::Struct(..) |
 596             hir::ItemKind::Union(..) |
 597             hir::ItemKind::Enum(..) => {}
 598             _ => return,
 599         }
 600
 601         let debug = match cx.tcx.lang_items().debug_trait() {
 602             Some(debug) => debug,
 603             None => return,
 604         };
 605
 606         if self.impling_types.is_none() {
 607             let mut impls = NodeSet();
 608             cx.tcx.for_each_impl(debug, |d| {
 609                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 610                     if let Some(node_id) = cx.tcx.hir.as_local_node_id(ty_def.did) {
 611                         impls.insert(node_id);
 612                     }
 613                 }
 614             });
 615
 616             self.impling_types = Some(impls);
 617             debug!("{:?}", self.impling_types);
 618         }
 619
 620         if !self.impling_types.as_ref().unwrap().contains(&item.id) {
 621             cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
 622                          item.span,
 623                          "type does not implement `fmt::Debug`; consider adding #[derive(Debug)] \
 624                           or a manual implementation")
 625         }
 626     }
 627 }
 628
 629 declare_lint! {
 630     pub ANONYMOUS_PARAMETERS,
 631     Allow,
 632     "detects anonymous parameters",
 633     Edition::Edition2018 => Warn
 634 }
 635
 636 /// Checks for use of anonymous parameters (RFC 1685)
 637 #[derive(Clone)]
 638 pub struct AnonymousParameters;
 639
 640 impl LintPass for AnonymousParameters {
 641     fn get_lints(&self) -> LintArray {
 642         lint_array!(ANONYMOUS_PARAMETERS)
 643     }
 644 }
 645
 646 impl EarlyLintPass for AnonymousParameters {
 647     fn check_trait_item(&mut self, cx: &EarlyContext, it: &ast::TraitItem) {
 648         match it.node {
 649             ast::TraitItemKind::Method(ref sig, _) => {
 650                 for arg in sig.decl.inputs.iter() {
 651                     match arg.pat.node {
 652                         ast::PatKind::Ident(_, ident, None) => {
 653                             if ident.name == keywords::Invalid.name() {
 654                                 let ty_snip = cx
 655                                     .sess
 656                                     .source_map()
 657                                     .span_to_snippet(arg.ty.span);
 658
 659                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 660                                     (snip, Applicability::MachineApplicable)
 661                                 } else {
 662                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 663                                 };
 664
 665                                 cx.struct_span_lint(
 666                                     ANONYMOUS_PARAMETERS,
 667                                     arg.pat.span,
 668                                     "anonymous parameters are deprecated and will be \
 669                                      removed in the next edition."
 670                                 ).span_suggestion_with_applicability(
 671                                     arg.pat.span,
 672                                     "Try naming the parameter or explicitly \
 673                                     ignoring it",
 674                                     format!("_: {}", ty_snip),
 675                                     appl
 676                                 ).emit();
 677                             }
 678                         }
 679                         _ => (),
 680                     }
 681                 }
 682             },
 683             _ => (),
 684         }
 685     }
 686 }
 687
 688 /// Checks for incorrect use use of `repr` attributes.
 689 #[derive(Clone)]
 690 pub struct BadRepr;
 691
 692 impl LintPass for BadRepr {
 693     fn get_lints(&self) -> LintArray {
 694         lint_array!()
 695     }
 696 }
 697
 698 impl EarlyLintPass for BadRepr {
 699     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
 700         if attr.name() == "repr" {
 701             let list = attr.meta_item_list();
 702
 703             let repr_str = |lit: &str| { format!("#[repr({})]", lit) };
 704
 705             // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
 706             // no hints (``#[repr]`)
 707             let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
 708             if !has_hints {
 709                 let mut suggested = false;
 710                 let mut warn = if let Some(ref lit) = attr.value_str() {
 711                     // avoid warning about empty `repr` on `#[repr = "foo"]`
 712                     let mut warn = cx.struct_span_lint(
 713                         BAD_REPR,
 714                         attr.span,
 715                         "`repr` attribute isn't configurable with a literal",
 716                     );
 717                     match lit.to_string().as_ref() {
 718                         | "C" | "packed" | "rust" | "transparent"
 719                         | "u8" | "u16" | "u32" | "u64" | "u128" | "usize"
 720                         | "i8" | "i16" | "i32" | "i64" | "i128" | "isize" => {
 721                             // if the literal could have been a valid `repr` arg,
 722                             // suggest the correct syntax
 723                             warn.span_suggestion_with_applicability(
 724                                 attr.span,
 725                                 "give `repr` a hint",
 726                                 repr_str(&lit.as_str()),
 727                                 Applicability::MachineApplicable
 728                             );
 729                             suggested = true;
 730                         }
 731                         _ => {  // the literal wasn't a valid `repr` arg
 732                             warn.span_label(attr.span, "needs a hint");
 733                         }
 734                     };
 735                     warn
 736                 } else {
 737                     let mut warn = cx.struct_span_lint(
 738                         BAD_REPR,
 739                         attr.span,
 740                         "`repr` attribute must have a hint",
 741                     );
 742                     warn.span_label(attr.span, "needs a hint");
 743                     warn
 744                 };
 745                 if !suggested {
 746                     warn.help(&format!(
 747                         "valid hints include `{}`, `{}`, `{}` and `{}`",
 748                         repr_str("C"),
 749                         repr_str("packed"),
 750                         repr_str("rust"),
 751                         repr_str("transparent"),
 752                     ));
 753                     warn.note("for more information, visit \
 754                                <https://doc.rust-lang.org/reference/type-layout.html>");
 755                 }
 756                 warn.emit();
 757             }
 758         }
 759     }
 760 }
 761
 762 /// Checks for use of attributes which have been deprecated.
 763 #[derive(Clone)]
 764 pub struct DeprecatedAttr {
 765     // This is not free to compute, so we want to keep it around, rather than
 766     // compute it for every attribute.
 767     depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeGate)>,
 768 }
 769
 770 impl DeprecatedAttr {
 771     pub fn new() -> DeprecatedAttr {
 772         DeprecatedAttr {
 773             depr_attrs: deprecated_attributes(),
 774         }
 775     }
 776 }
 777
 778 impl LintPass for DeprecatedAttr {
 779     fn get_lints(&self) -> LintArray {
 780         lint_array!()
 781     }
 782 }
 783
 784 impl EarlyLintPass for DeprecatedAttr {
 785     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
 786         for &&(n, _, ref g) in &self.depr_attrs {
 787             if attr.name() == n {
 788                 if let &AttributeGate::Gated(Stability::Deprecated(link),
 789                                              ref name,
 790                                              ref reason,
 791                                              _) = g {
 792                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
 793                                       name, reason, link);
 794                     let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
 795                     err.span_suggestion_short_with_applicability(
 796                         attr.span,
 797                         "remove this attribute",
 798                         "".to_owned(),
 799                         Applicability::MachineApplicable
 800                     );
 801                     err.emit();
 802                 }
 803                 return;
 804             }
 805         }
 806     }
 807 }
 808
 809 declare_lint! {
 810     pub UNUSED_DOC_COMMENTS,
 811     Warn,
 812     "detects doc comments that aren't used by rustdoc"
 813 }
 814
 815 #[derive(Copy, Clone)]
 816 pub struct UnusedDocComment;
 817
 818 impl LintPass for UnusedDocComment {
 819     fn get_lints(&self) -> LintArray {
 820         lint_array![UNUSED_DOC_COMMENTS]
 821     }
 822 }
 823
 824 impl UnusedDocComment {
 825     fn warn_if_doc<'a, 'tcx,
 826                    I: Iterator<Item=&'a ast::Attribute>,
 827                    C: LintContext<'tcx>>(&self, mut attrs: I, cx: &C) {
 828         if let Some(attr) = attrs.find(|a| a.is_value_str() && a.check_name("doc")) {
 829             cx.struct_span_lint(UNUSED_DOC_COMMENTS, attr.span, "doc comment not used by rustdoc")
 830               .emit();
 831         }
 832     }
 833 }
 834
 835 impl EarlyLintPass for UnusedDocComment {
 836     fn check_local(&mut self, cx: &EarlyContext, decl: &ast::Local) {
 837         self.warn_if_doc(decl.attrs.iter(), cx);
 838     }
 839
 840     fn check_arm(&mut self, cx: &EarlyContext, arm: &ast::Arm) {
 841         self.warn_if_doc(arm.attrs.iter(), cx);
 842     }
 843
 844     fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
 845         self.warn_if_doc(expr.attrs.iter(), cx);
 846     }
 847 }
 848
 849 declare_lint! {
 850     pub UNCONDITIONAL_RECURSION,
 851     Warn,
 852     "functions that cannot return without calling themselves"
 853 }
 854
 855 #[derive(Copy, Clone)]
 856 pub struct UnconditionalRecursion;
 857
 858
 859 impl LintPass for UnconditionalRecursion {
 860     fn get_lints(&self) -> LintArray {
 861         lint_array![UNCONDITIONAL_RECURSION]
 862     }
 863 }
 864
 865 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnconditionalRecursion {
 866     fn check_fn(&mut self,
 867                 cx: &LateContext,
 868                 fn_kind: FnKind,
 869                 _: &hir::FnDecl,
 870                 body: &hir::Body,
 871                 sp: Span,
 872                 id: ast::NodeId) {
 873         let method = match fn_kind {
 874             FnKind::ItemFn(..) => None,
 875             FnKind::Method(..) => {
 876                 Some(cx.tcx.associated_item(cx.tcx.hir.local_def_id(id)))
 877             }
 878             // closures can't recur, so they don't matter.
 879             FnKind::Closure(_) => return,
 880         };
 881
 882         // Walk through this function (say `f`) looking to see if
 883         // every possible path references itself, i.e. the function is
 884         // called recursively unconditionally. This is done by trying
 885         // to find a path from the entry node to the exit node that
 886         // *doesn't* call `f` by traversing from the entry while
 887         // pretending that calls of `f` are sinks (i.e. ignoring any
 888         // exit edges from them).
 889         //
 890         // NB. this has an edge case with non-returning statements,
 891         // like `loop {}` or `panic!()`: control flow never reaches
 892         // the exit node through these, so one can have a function
 893         // that never actually calls itself but is still picked up by
 894         // this lint:
 895         //
 896         //     fn f(cond: bool) {
 897         //         if !cond { panic!() } // could come from `assert!(cond)`
 898         //         f(false)
 899         //     }
 900         //
 901         // In general, functions of that form may be able to call
 902         // itself a finite number of times and then diverge. The lint
 903         // considers this to be an error for two reasons, (a) it is
 904         // easier to implement, and (b) it seems rare to actually want
 905         // to have behaviour like the above, rather than
 906         // e.g. accidentally recurring after an assert.
 907
 908         let cfg = cfg::CFG::new(cx.tcx, &body);
 909
 910         let mut work_queue = vec![cfg.entry];
 911         let mut reached_exit_without_self_call = false;
 912         let mut self_call_spans = vec![];
 913         let mut visited = HashSet::new();
 914
 915         while let Some(idx) = work_queue.pop() {
 916             if idx == cfg.exit {
 917                 // found a path!
 918                 reached_exit_without_self_call = true;
 919                 break;
 920             }
 921
 922             let cfg_id = idx.node_id();
 923             if visited.contains(&cfg_id) {
 924                 // already done
 925                 continue;
 926             }
 927             visited.insert(cfg_id);
 928
 929             // is this a recursive call?
 930             let local_id = cfg.graph.node_data(idx).id();
 931             if local_id != hir::DUMMY_ITEM_LOCAL_ID {
 932                 let node_id = cx.tcx.hir.hir_to_node_id(hir::HirId {
 933                     owner: body.value.hir_id.owner,
 934                     local_id
 935                 });
 936                 let self_recursive = match method {
 937                     Some(ref method) => expr_refers_to_this_method(cx, method, node_id),
 938                     None => expr_refers_to_this_fn(cx, id, node_id),
 939                 };
 940                 if self_recursive {
 941                     self_call_spans.push(cx.tcx.hir.span(node_id));
 942                     // this is a self call, so we shouldn't explore past
 943                     // this node in the CFG.
 944                     continue;
 945                 }
 946             }
 947
 948             // add the successors of this node to explore the graph further.
 949             for (_, edge) in cfg.graph.outgoing_edges(idx) {
 950                 let target_idx = edge.target();
 951                 let target_cfg_id = target_idx.node_id();
 952                 if !visited.contains(&target_cfg_id) {
 953                     work_queue.push(target_idx)
 954                 }
 955             }
 956         }
 957
 958         // Check the number of self calls because a function that
 959         // doesn't return (e.g. calls a `-> !` function or `loop { /*
 960         // no break */ }`) shouldn't be linted unless it actually
 961         // recurs.
 962         if !reached_exit_without_self_call && !self_call_spans.is_empty() {
 963             let sp = cx.tcx.sess.source_map().def_span(sp);
 964             let mut db = cx.struct_span_lint(UNCONDITIONAL_RECURSION,
 965                                              sp,
 966                                              "function cannot return without recurring");
 967             db.span_label(sp, "cannot return without recurring");
 968             // offer some help to the programmer.
 969             for call in &self_call_spans {
 970                 db.span_label(*call, "recursive call site");
 971             }
 972             db.help("a `loop` may express intention better if this is on purpose");
 973             db.emit();
 974         }
 975
 976         // all done
 977         return;
 978
 979         // Functions for identifying if the given Expr NodeId `id`
 980         // represents a call to the function `fn_id`/method `method`.
 981
 982         fn expr_refers_to_this_fn(cx: &LateContext, fn_id: ast::NodeId, id: ast::NodeId) -> bool {
 983             match cx.tcx.hir.get(id) {
 984                 hir_map::NodeExpr(&hir::Expr { node: hir::ExprKind::Call(ref callee, _), .. }) => {
 985                     let def = if let hir::ExprKind::Path(ref qpath) = callee.node {
 986                         cx.tables.qpath_def(qpath, callee.hir_id)
 987                     } else {
 988                         return false;
 989                     };
 990                     match def {
 991                         Def::Local(..) | Def::Upvar(..) => false,
 992                         _ => def.def_id() == cx.tcx.hir.local_def_id(fn_id)
 993                     }
 994                 }
 995                 _ => false,
 996             }
 997         }
 998
 999         // Check if the expression `id` performs a call to `method`.
1000         fn expr_refers_to_this_method(cx: &LateContext,
1001                                       method: &ty::AssociatedItem,
1002                                       id: ast::NodeId)
1003                                       -> bool {
1004             use rustc::ty::adjustment::*;
1005
1006             // Ignore non-expressions.
1007             let expr = if let hir_map::NodeExpr(e) = cx.tcx.hir.get(id) {
1008                 e
1009             } else {
1010                 return false;
1011             };
1012
1013             // Check for overloaded autoderef method calls.
1014             let mut source = cx.tables.expr_ty(expr);
1015             for adjustment in cx.tables.expr_adjustments(expr) {
1016                 if let Adjust::Deref(Some(deref)) = adjustment.kind {
1017                     let (def_id, substs) = deref.method_call(cx.tcx, source);
1018                     if method_call_refers_to_method(cx, method, def_id, substs, id) {
1019                         return true;
1020                     }
1021                 }
1022                 source = adjustment.target;
1023             }
1024
1025             // Check for method calls and overloaded operators.
1026             if cx.tables.is_method_call(expr) {
1027                 let hir_id = cx.tcx.hir.definitions().node_to_hir_id(id);
1028                 if let Some(def) = cx.tables.type_dependent_defs().get(hir_id) {
1029                     let def_id = def.def_id();
1030                     let substs = cx.tables.node_substs(hir_id);
1031                     if method_call_refers_to_method(cx, method, def_id, substs, id) {
1032                         return true;
1033                     }
1034                 } else {
1035                     cx.tcx.sess.delay_span_bug(expr.span,
1036                                                "no type-dependent def for method call");
1037                 }
1038             }
1039
1040             // Check for calls to methods via explicit paths (e.g. `T::method()`).
1041             match expr.node {
1042                 hir::ExprKind::Call(ref callee, _) => {
1043                     let def = if let hir::ExprKind::Path(ref qpath) = callee.node {
1044                         cx.tables.qpath_def(qpath, callee.hir_id)
1045                     } else {
1046                         return false;
1047                     };
1048                     match def {
1049                         Def::Method(def_id) => {
1050                             let substs = cx.tables.node_substs(callee.hir_id);
1051                             method_call_refers_to_method(cx, method, def_id, substs, id)
1052                         }
1053                         _ => false,
1054                     }
1055                 }
1056                 _ => false,
1057             }
1058         }
1059
1060         // Check if the method call to the method with the ID `callee_id`
1061         // and instantiated with `callee_substs` refers to method `method`.
1062         fn method_call_refers_to_method<'a, 'tcx>(cx: &LateContext<'a, 'tcx>,
1063                                                   method: &ty::AssociatedItem,
1064                                                   callee_id: DefId,
1065                                                   callee_substs: &Substs<'tcx>,
1066                                                   expr_id: ast::NodeId)
1067                                                   -> bool {
1068             let tcx = cx.tcx;
1069             let callee_item = tcx.associated_item(callee_id);
1070
1071             match callee_item.container {
1072                 // This is an inherent method, so the `def_id` refers
1073                 // directly to the method definition.
1074                 ty::ImplContainer(_) => callee_id == method.def_id,
1075
1076                 // A trait method, from any number of possible sources.
1077                 // Attempt to select a concrete impl before checking.
1078                 ty::TraitContainer(trait_def_id) => {
1079                     let trait_ref = ty::TraitRef::from_method(tcx, trait_def_id, callee_substs);
1080                     let trait_ref = ty::Binder::bind(trait_ref);
1081                     let span = tcx.hir.span(expr_id);
1082                     let obligation =
1083                         traits::Obligation::new(traits::ObligationCause::misc(span, expr_id),
1084                                                 cx.param_env,
1085                                                 trait_ref.to_poly_trait_predicate());
1086
1087                     tcx.infer_ctxt().enter(|infcx| {
1088                         let mut selcx = traits::SelectionContext::new(&infcx);
1089                         match selcx.select(&obligation) {
1090                             // The method comes from a `T: Trait` bound.
1091                             // If `T` is `Self`, then this call is inside
1092                             // a default method definition.
1093                             Ok(Some(traits::VtableParam(_))) => {
1094                                 let on_self = trait_ref.self_ty().is_self();
1095                                 // We can only be recurring in a default
1096                                 // method if we're being called literally
1097                                 // on the `Self` type.
1098                                 on_self && callee_id == method.def_id
1099                             }
1100
1101                             // The `impl` is known, so we check that with a
1102                             // special case:
1103                             Ok(Some(traits::VtableImpl(vtable_impl))) => {
1104                                 let container = ty::ImplContainer(vtable_impl.impl_def_id);
1105                                 // It matches if it comes from the same impl,
1106                                 // and has the same method name.
1107                                 container == method.container &&
1108                                 callee_item.ident.name == method.ident.name
1109                             }
1110
1111                             // There's no way to know if this call is
1112                             // recursive, so we assume it's not.
1113                             _ => false,
1114                         }
1115                     })
1116                 }
1117             }
1118         }
1119     }
1120 }
1121
1122 declare_lint! {
1123     PLUGIN_AS_LIBRARY,
1124     Warn,
1125     "compiler plugin used as ordinary library in non-plugin crate"
1126 }
1127
1128 #[derive(Copy, Clone)]
1129 pub struct PluginAsLibrary;
1130
1131 impl LintPass for PluginAsLibrary {
1132     fn get_lints(&self) -> LintArray {
1133         lint_array![PLUGIN_AS_LIBRARY]
1134     }
1135 }
1136
1137 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
1138     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1139         if cx.sess().plugin_registrar_fn.get().is_some() {
1140             // We're compiling a plugin; it's fine to link other plugins.
1141             return;
1142         }
1143
1144         match it.node {
1145             hir::ItemKind::ExternCrate(..) => (),
1146             _ => return,
1147         };
1148
1149         let def_id = cx.tcx.hir.local_def_id(it.id);
1150         let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
1151             Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
1152             None => {
1153                 // Probably means we aren't linking the crate for some reason.
1154                 //
1155                 // Not sure if / when this could happen.
1156                 return;
1157             }
1158         };
1159
1160         if prfn.is_some() {
1161             cx.span_lint(PLUGIN_AS_LIBRARY,
1162                          it.span,
1163                          "compiler plugin used as an ordinary library");
1164         }
1165     }
1166 }
1167
1168 declare_lint! {
1169     PRIVATE_NO_MANGLE_FNS,
1170     Warn,
1171     "functions marked #[no_mangle] should be exported"
1172 }
1173
1174 declare_lint! {
1175     PRIVATE_NO_MANGLE_STATICS,
1176     Warn,
1177     "statics marked #[no_mangle] should be exported"
1178 }
1179
1180 declare_lint! {
1181     NO_MANGLE_CONST_ITEMS,
1182     Deny,
1183     "const items will not have their symbols exported"
1184 }
1185
1186 declare_lint! {
1187     NO_MANGLE_GENERIC_ITEMS,
1188     Warn,
1189     "generic items must be mangled"
1190 }
1191
1192 #[derive(Copy, Clone)]
1193 pub struct InvalidNoMangleItems;
1194
1195 impl LintPass for InvalidNoMangleItems {
1196     fn get_lints(&self) -> LintArray {
1197         lint_array!(PRIVATE_NO_MANGLE_FNS,
1198                     PRIVATE_NO_MANGLE_STATICS,
1199                     NO_MANGLE_CONST_ITEMS,
1200                     NO_MANGLE_GENERIC_ITEMS)
1201     }
1202 }
1203
1204 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
1205     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1206         let suggest_export = |vis: &hir::Visibility, err: &mut DiagnosticBuilder| {
1207             let suggestion = match vis.node {
1208                 hir::VisibilityKind::Inherited => {
1209                     // inherited visibility is empty span at item start; need an extra space
1210                     Some("pub ".to_owned())
1211                 },
1212                 hir::VisibilityKind::Restricted { .. } |
1213                 hir::VisibilityKind::Crate(_) => {
1214                     Some("pub".to_owned())
1215                 },
1216                 hir::VisibilityKind::Public => {
1217                     err.help("try exporting the item with a `pub use` statement");
1218                     None
1219                 }
1220             };
1221             if let Some(replacement) = suggestion {
1222                 err.span_suggestion_with_applicability(
1223                     vis.span,
1224                     "try making it public",
1225                     replacement,
1226                     Applicability::MachineApplicable
1227                 );
1228             }
1229         };
1230
1231         match it.node {
1232             hir::ItemKind::Fn(.., ref generics, _) => {
1233                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, "no_mangle") {
1234                     if attr::contains_name(&it.attrs, "linkage") {
1235                         return;
1236                     }
1237                     if !cx.access_levels.is_reachable(it.id) {
1238                         let msg = "function is marked #[no_mangle], but not exported";
1239                         let mut err = cx.struct_span_lint(PRIVATE_NO_MANGLE_FNS, it.span, msg);
1240                         suggest_export(&it.vis, &mut err);
1241                         err.emit();
1242                     }
1243                     for param in &generics.params {
1244                         match param.kind {
1245                             GenericParamKind::Lifetime { .. } => {}
1246                             GenericParamKind::Type { .. } => {
1247                                 let mut err = cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS,
1248                                                                   it.span,
1249                                                                   "functions generic over \
1250                                                                    types must be mangled");
1251                                 err.span_suggestion_short_with_applicability(
1252                                     no_mangle_attr.span,
1253                                     "remove this attribute",
1254                                     "".to_owned(),
1255                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1256                                     // fix may be to monomorphize source by hand
1257                                     Applicability::MaybeIncorrect
1258                                 );
1259                                 err.emit();
1260                                 break;
1261                             }
1262                         }
1263                     }
1264                 }
1265             }
1266             hir::ItemKind::Static(..) => {
1267                 if attr::contains_name(&it.attrs, "no_mangle") &&
1268                     !cx.access_levels.is_reachable(it.id) {
1269                         let msg = "static is marked #[no_mangle], but not exported";
1270                         let mut err = cx.struct_span_lint(PRIVATE_NO_MANGLE_STATICS, it.span, msg);
1271                         suggest_export(&it.vis, &mut err);
1272                         err.emit();
1273                     }
1274             }
1275             hir::ItemKind::Const(..) => {
1276                 if attr::contains_name(&it.attrs, "no_mangle") {
1277                     // Const items do not refer to a particular location in memory, and therefore
1278                     // don't have anything to attach a symbol to
1279                     let msg = "const items should never be #[no_mangle]";
1280                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
1281
1282                     // account for "pub const" (#45562)
1283                     let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
1284                         .map(|snippet| snippet.find("const").unwrap_or(0))
1285                         .unwrap_or(0) as u32;
1286                     // `const` is 5 chars
1287                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1288                     err.span_suggestion_with_applicability(
1289                         const_span,
1290                         "try a static value",
1291                         "pub static".to_owned(),
1292                         Applicability::MachineApplicable
1293                     );
1294                     err.emit();
1295                 }
1296             }
1297             _ => {}
1298         }
1299     }
1300 }
1301
1302 #[derive(Clone, Copy)]
1303 pub struct MutableTransmutes;
1304
1305 declare_lint! {
1306     MUTABLE_TRANSMUTES,
1307     Deny,
1308     "mutating transmuted &mut T from &T may cause undefined behavior"
1309 }
1310
1311 impl LintPass for MutableTransmutes {
1312     fn get_lints(&self) -> LintArray {
1313         lint_array!(MUTABLE_TRANSMUTES)
1314     }
1315 }
1316
1317 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
1318     fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
1319         use rustc_target::spec::abi::Abi::RustIntrinsic;
1320
1321         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1322                    consider instead using an UnsafeCell";
1323         match get_transmute_from_to(cx, expr) {
1324             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
1325                 if to_mt == hir::Mutability::MutMutable &&
1326                    from_mt == hir::Mutability::MutImmutable {
1327                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
1328                 }
1329             }
1330             _ => (),
1331         }
1332
1333         fn get_transmute_from_to<'a, 'tcx>
1334             (cx: &LateContext<'a, 'tcx>,
1335              expr: &hir::Expr)
1336              -> Option<(&'tcx ty::TyKind<'tcx>, &'tcx ty::TyKind<'tcx>)> {
1337             let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
1338                 cx.tables.qpath_def(qpath, expr.hir_id)
1339             } else {
1340                 return None;
1341             };
1342             if let Def::Fn(did) = def {
1343                 if !def_id_is_transmute(cx, did) {
1344                     return None;
1345                 }
1346                 let sig = cx.tables.node_id_to_type(expr.hir_id).fn_sig(cx.tcx);
1347                 let from = sig.inputs().skip_binder()[0];
1348                 let to = *sig.output().skip_binder();
1349                 return Some((&from.sty, &to.sty));
1350             }
1351             None
1352         }
1353
1354         fn def_id_is_transmute(cx: &LateContext, def_id: DefId) -> bool {
1355             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
1356             cx.tcx.item_name(def_id) == "transmute"
1357         }
1358     }
1359 }
1360
1361 /// Forbids using the `#[feature(...)]` attribute
1362 #[derive(Copy, Clone)]
1363 pub struct UnstableFeatures;
1364
1365 declare_lint! {
1366     UNSTABLE_FEATURES,
1367     Allow,
1368     "enabling unstable features (deprecated. do not use)"
1369 }
1370
1371 impl LintPass for UnstableFeatures {
1372     fn get_lints(&self) -> LintArray {
1373         lint_array!(UNSTABLE_FEATURES)
1374     }
1375 }
1376
1377 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
1378     fn check_attribute(&mut self, ctx: &LateContext, attr: &ast::Attribute) {
1379         if attr.check_name("feature") {
1380             if let Some(items) = attr.meta_item_list() {
1381                 for item in items {
1382                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
1383                 }
1384             }
1385         }
1386     }
1387 }
1388
1389 /// Lint for unions that contain fields with possibly non-trivial destructors.
1390 pub struct UnionsWithDropFields;
1391
1392 declare_lint! {
1393     UNIONS_WITH_DROP_FIELDS,
1394     Warn,
1395     "use of unions that contain fields with possibly non-trivial drop code"
1396 }
1397
1398 impl LintPass for UnionsWithDropFields {
1399     fn get_lints(&self) -> LintArray {
1400         lint_array!(UNIONS_WITH_DROP_FIELDS)
1401     }
1402 }
1403
1404 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
1405     fn check_item(&mut self, ctx: &LateContext, item: &hir::Item) {
1406         if let hir::ItemKind::Union(ref vdata, _) = item.node {
1407             for field in vdata.fields() {
1408                 let field_ty = ctx.tcx.type_of(ctx.tcx.hir.local_def_id(field.id));
1409                 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1410                     ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1411                                   field.span,
1412                                   "union contains a field with possibly non-trivial drop code, \
1413                                    drop code of union fields is ignored when dropping the union");
1414                     return;
1415                 }
1416             }
1417         }
1418     }
1419 }
1420
1421 /// Lint for items marked `pub` that aren't reachable from other crates
1422 pub struct UnreachablePub;
1423
1424 declare_lint! {
1425     pub UNREACHABLE_PUB,
1426     Allow,
1427     "`pub` items not reachable from crate root"
1428 }
1429
1430 impl LintPass for UnreachablePub {
1431     fn get_lints(&self) -> LintArray {
1432         lint_array!(UNREACHABLE_PUB)
1433     }
1434 }
1435
1436 impl UnreachablePub {
1437     fn perform_lint(&self, cx: &LateContext, what: &str, id: ast::NodeId,
1438                     vis: &hir::Visibility, span: Span, exportable: bool) {
1439         let mut applicability = Applicability::MachineApplicable;
1440         match vis.node {
1441             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1442                 if span.ctxt().outer().expn_info().is_some() {
1443                     applicability = Applicability::MaybeIncorrect;
1444                 }
1445                 let def_span = cx.tcx.sess.source_map().def_span(span);
1446                 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1447                                                   &format!("unreachable `pub` {}", what));
1448                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1449                     "crate"
1450                 } else {
1451                     "pub(crate)"
1452                 }.to_owned();
1453
1454                 err.span_suggestion_with_applicability(vis.span,
1455                                                        "consider restricting its visibility",
1456                                                        replacement,
1457                                                        applicability);
1458                 if exportable {
1459                     err.help("or consider exporting it for use by other crates");
1460                 }
1461                 err.emit();
1462             },
1463             _ => {}
1464         }
1465     }
1466 }
1467
1468
1469 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1470     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
1471         self.perform_lint(cx, "item", item.id, &item.vis, item.span, true);
1472     }
1473
1474     fn check_foreign_item(&mut self, cx: &LateContext, foreign_item: &hir::ForeignItem) {
1475         self.perform_lint(cx, "item", foreign_item.id, &foreign_item.vis,
1476                           foreign_item.span, true);
1477     }
1478
1479     fn check_struct_field(&mut self, cx: &LateContext, field: &hir::StructField) {
1480         self.perform_lint(cx, "field", field.id, &field.vis, field.span, false);
1481     }
1482
1483     fn check_impl_item(&mut self, cx: &LateContext, impl_item: &hir::ImplItem) {
1484         self.perform_lint(cx, "item", impl_item.id, &impl_item.vis, impl_item.span, false);
1485     }
1486 }
1487
1488 /// Lint for trait and lifetime bounds in type aliases being mostly ignored:
1489 /// They are relevant when using associated types, but otherwise neither checked
1490 /// at definition site nor enforced at use site.
1491
1492 pub struct TypeAliasBounds;
1493
1494 declare_lint! {
1495     TYPE_ALIAS_BOUNDS,
1496     Warn,
1497     "bounds in type aliases are not enforced"
1498 }
1499
1500 impl LintPass for TypeAliasBounds {
1501     fn get_lints(&self) -> LintArray {
1502         lint_array!(TYPE_ALIAS_BOUNDS)
1503     }
1504 }
1505
1506 impl TypeAliasBounds {
1507     fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1508         match *qpath {
1509             hir::QPath::TypeRelative(ref ty, _) => {
1510                 // If this is a type variable, we found a `T::Assoc`.
1511                 match ty.node {
1512                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1513                         match path.def {
1514                             Def::TyParam(_) => true,
1515                             _ => false
1516                         }
1517                     }
1518                     _ => false
1519                 }
1520             }
1521             hir::QPath::Resolved(..) => false,
1522         }
1523     }
1524
1525     fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder) {
1526         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1527         // bound.  Let's see if this type does that.
1528
1529         // We use a HIR visitor to walk the type.
1530         use rustc::hir::intravisit::{self, Visitor};
1531         struct WalkAssocTypes<'a, 'db> where 'db: 'a {
1532             err: &'a mut DiagnosticBuilder<'db>
1533         }
1534         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1535             fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1536             {
1537                 intravisit::NestedVisitorMap::None
1538             }
1539
1540             fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1541                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1542                     self.err.span_help(span,
1543                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1544                          associated types in type aliases");
1545                 }
1546                 intravisit::walk_qpath(self, qpath, id, span)
1547             }
1548         }
1549
1550         // Let's go for a walk!
1551         let mut visitor = WalkAssocTypes { err };
1552         visitor.visit_ty(ty);
1553     }
1554 }
1555
1556 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1557     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
1558         let (ty, type_alias_generics) = match item.node {
1559             hir::ItemKind::Ty(ref ty, ref generics) => (&*ty, generics),
1560             _ => return,
1561         };
1562         let mut suggested_changing_assoc_types = false;
1563         // There must not be a where clause
1564         if !type_alias_generics.where_clause.predicates.is_empty() {
1565             let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1566                 .map(|pred| pred.span()).collect();
1567             let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1568                 "where clauses are not enforced in type aliases");
1569             err.help("the clause will not be checked when the type alias is used, \
1570                       and should be removed");
1571             if !suggested_changing_assoc_types {
1572                 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1573                 suggested_changing_assoc_types = true;
1574             }
1575             err.emit();
1576         }
1577         // The parameters must not have bounds
1578         for param in type_alias_generics.params.iter() {
1579             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1580             if !spans.is_empty() {
1581                 let mut err = cx.struct_span_lint(
1582                     TYPE_ALIAS_BOUNDS,
1583                     spans,
1584                     "bounds on generic parameters are not enforced in type aliases",
1585                 );
1586                 err.help("the bound will not be checked when the type alias is used, \
1587                           and should be removed");
1588                 if !suggested_changing_assoc_types {
1589                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1590                     suggested_changing_assoc_types = true;
1591                 }
1592                 err.emit();
1593             }
1594         }
1595     }
1596 }
1597
1598 /// Lint constants that are erroneous.
1599 /// Without this lint, we might not get any diagnostic if the constant is
1600 /// unused within this crate, even though downstream crates can't use it
1601 /// without producing an error.
1602 pub struct UnusedBrokenConst;
1603
1604 impl LintPass for UnusedBrokenConst {
1605     fn get_lints(&self) -> LintArray {
1606         lint_array!()
1607     }
1608 }
1609
1610 fn validate_const<'a, 'tcx>(
1611     tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
1612     constant: &ty::Const<'tcx>,
1613     param_env: ty::ParamEnv<'tcx>,
1614     gid: ::rustc::mir::interpret::GlobalId<'tcx>,
1615     what: &str,
1616 ) {
1617     let mut ecx = ::rustc_mir::interpret::mk_eval_cx(tcx, gid.instance, param_env).unwrap();
1618     let result = (|| {
1619         use rustc_target::abi::LayoutOf;
1620         use rustc_mir::interpret::OpTy;
1621
1622         let op = ecx.const_value_to_op(constant.val)?;
1623         let layout = ecx.layout_of(constant.ty)?;
1624         let place = ecx.allocate_op(OpTy { op, layout })?.into();
1625
1626         let mut todo = vec![(place, Vec::new())];
1627         let mut seen = FxHashSet();
1628         seen.insert(place);
1629         while let Some((place, mut path)) = todo.pop() {
1630             ecx.validate_mplace(
1631                 place,
1632                 &mut path,
1633                 &mut seen,
1634                 &mut todo,
1635             )?;
1636         }
1637         Ok(())
1638     })();
1639     if let Err(err) = result {
1640         let (trace, span) = ecx.generate_stacktrace(None);
1641         let err = ::rustc::mir::interpret::ConstEvalErr {
1642             error: err,
1643             stacktrace: trace,
1644             span,
1645         };
1646         let err = err.struct_error(
1647             tcx.at(span),
1648             &format!("this {} likely exhibits undefined behavior", what),
1649         );
1650         if let Some(mut err) = err {
1651             err.note("The rules on what exactly is undefined behavior aren't clear, \
1652                 so this check might be overzealous. Please open an issue on the rust compiler \
1653                 repository if you believe it should not be considered undefined behavior",
1654             );
1655             err.emit();
1656         }
1657     }
1658 }
1659
1660 fn check_const(cx: &LateContext, body_id: hir::BodyId, what: &str) {
1661     let def_id = cx.tcx.hir.body_owner_def_id(body_id);
1662     let is_static = cx.tcx.is_static(def_id).is_some();
1663     let param_env = if is_static {
1664         // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1665         ty::ParamEnv::reveal_all()
1666     } else {
1667         cx.tcx.param_env(def_id)
1668     };
1669     let cid = ::rustc::mir::interpret::GlobalId {
1670         instance: ty::Instance::mono(cx.tcx, def_id),
1671         promoted: None
1672     };
1673     match cx.tcx.const_eval(param_env.and(cid)) {
1674         Ok(val) => validate_const(cx.tcx, val, param_env, cid, what),
1675         Err(err) => {
1676             // errors for statics are already reported directly in the query, avoid duplicates
1677             if !is_static {
1678                 let span = cx.tcx.def_span(def_id);
1679                 err.report_as_lint(
1680                     cx.tcx.at(span),
1681                     &format!("this {} cannot be used", what),
1682                     cx.current_lint_root(),
1683                 );
1684             }
1685         },
1686     }
1687 }
1688
1689 struct UnusedBrokenConstVisitor<'a, 'tcx: 'a>(&'a LateContext<'a, 'tcx>);
1690
1691 impl<'a, 'tcx, 'v> hir::intravisit::Visitor<'v> for UnusedBrokenConstVisitor<'a, 'tcx> {
1692     fn visit_nested_body(&mut self, id: hir::BodyId) {
1693         check_const(self.0, id, "array length");
1694     }
1695     fn nested_visit_map<'this>(&'this mut self) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1696         hir::intravisit::NestedVisitorMap::None
1697     }
1698 }
1699
1700 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1701     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1702         match it.node {
1703             hir::ItemKind::Const(_, body_id) => {
1704                 check_const(cx, body_id, "constant");
1705             },
1706             hir::ItemKind::Static(_, _, body_id) => {
1707                 check_const(cx, body_id, "static");
1708             },
1709             hir::ItemKind::Ty(ref ty, _) => hir::intravisit::walk_ty(
1710                 &mut UnusedBrokenConstVisitor(cx),
1711                 ty
1712             ),
1713             _ => {},
1714         }
1715     }
1716 }
1717
1718 /// Lint for trait and lifetime bounds that don't depend on type parameters
1719 /// which either do nothing, or stop the item from being used.
1720 pub struct TrivialConstraints;
1721
1722 declare_lint! {
1723     TRIVIAL_BOUNDS,
1724     Warn,
1725     "these bounds don't depend on an type parameters"
1726 }
1727
1728 impl LintPass for TrivialConstraints {
1729     fn get_lints(&self) -> LintArray {
1730         lint_array!(TRIVIAL_BOUNDS)
1731     }
1732 }
1733
1734 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1735     fn check_item(
1736         &mut self,
1737         cx: &LateContext<'a, 'tcx>,
1738         item: &'tcx hir::Item,
1739     ) {
1740         use rustc::ty::fold::TypeFoldable;
1741         use rustc::ty::Predicate::*;
1742
1743
1744         if cx.tcx.features().trivial_bounds {
1745             let def_id = cx.tcx.hir.local_def_id(item.id);
1746             let predicates = cx.tcx.predicates_of(def_id);
1747             for predicate in &predicates.predicates {
1748                 let predicate_kind_name = match *predicate {
1749                     Trait(..) => "Trait",
1750                     TypeOutlives(..) |
1751                     RegionOutlives(..) => "Lifetime",
1752
1753                     // Ignore projections, as they can only be global
1754                     // if the trait bound is global
1755                     Projection(..) |
1756                     // Ignore bounds that a user can't type
1757                     WellFormed(..) |
1758                     ObjectSafe(..) |
1759                     ClosureKind(..) |
1760                     Subtype(..) |
1761                     ConstEvaluatable(..) => continue,
1762                 };
1763                 if predicate.is_global() {
1764                     cx.span_lint(
1765                         TRIVIAL_BOUNDS,
1766                         item.span,
1767                         &format!("{} bound {} does not depend on any type \
1768                                 or lifetime parameters", predicate_kind_name, predicate),
1769                     );
1770                 }
1771             }
1772         }
1773     }
1774 }
1775
1776
1777 /// Does nothing as a lint pass, but registers some `Lint`s
1778 /// which are used by other parts of the compiler.
1779 #[derive(Copy, Clone)]
1780 pub struct SoftLints;
1781
1782 impl LintPass for SoftLints {
1783     fn get_lints(&self) -> LintArray {
1784         lint_array!(
1785             WHILE_TRUE,
1786             BOX_POINTERS,
1787             NON_SHORTHAND_FIELD_PATTERNS,
1788             UNSAFE_CODE,
1789             MISSING_DOCS,
1790             MISSING_COPY_IMPLEMENTATIONS,
1791             MISSING_DEBUG_IMPLEMENTATIONS,
1792             ANONYMOUS_PARAMETERS,
1793             UNUSED_DOC_COMMENTS,
1794             UNCONDITIONAL_RECURSION,
1795             PLUGIN_AS_LIBRARY,
1796             PRIVATE_NO_MANGLE_FNS,
1797             PRIVATE_NO_MANGLE_STATICS,
1798             NO_MANGLE_CONST_ITEMS,
1799             NO_MANGLE_GENERIC_ITEMS,
1800             MUTABLE_TRANSMUTES,
1801             UNSTABLE_FEATURES,
1802             UNIONS_WITH_DROP_FIELDS,
1803             UNREACHABLE_PUB,
1804             TYPE_ALIAS_BOUNDS,
1805             TRIVIAL_BOUNDS
1806         )
1807     }
1808 }
1809
1810 declare_lint! {
1811     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1812     Allow,
1813     "`...` range patterns are deprecated"
1814 }
1815
1816
1817 pub struct EllipsisInclusiveRangePatterns;
1818
1819 impl LintPass for EllipsisInclusiveRangePatterns {
1820     fn get_lints(&self) -> LintArray {
1821         lint_array!(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS)
1822     }
1823 }
1824
1825 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1826     fn check_pat(&mut self, cx: &EarlyContext, pat: &ast::Pat) {
1827         use self::ast::{PatKind, RangeEnd, RangeSyntax};
1828
1829         if let PatKind::Range(
1830             _, _, Spanned { span, node: RangeEnd::Included(RangeSyntax::DotDotDot) }
1831         ) = pat.node {
1832             let msg = "`...` range patterns are deprecated";
1833             let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, span, msg);
1834             err.span_suggestion_short_with_applicability(
1835                 span, "use `..=` for an inclusive range", "..=".to_owned(),
1836                 // FIXME: outstanding problem with precedence in ref patterns:
1837                 // https://github.com/rust-lang/rust/issues/51043#issuecomment-392252285
1838                 Applicability::MaybeIncorrect
1839             );
1840             err.emit()
1841         }
1842     }
1843 }
1844
1845 declare_lint! {
1846     UNNAMEABLE_TEST_FUNCTIONS,
1847     Warn,
1848     "detects an function that cannot be named being marked as #[test]"
1849 }
1850
1851 pub struct UnnameableTestFunctions;
1852
1853 impl LintPass for UnnameableTestFunctions {
1854     fn get_lints(&self) -> LintArray {
1855         lint_array!(UNNAMEABLE_TEST_FUNCTIONS)
1856     }
1857 }
1858
1859 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestFunctions {
1860     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1861         match it.node {
1862             hir::ItemKind::Fn(..) => {
1863                 for attr in &it.attrs {
1864                     if attr.name() == "test" {
1865                         let parent = cx.tcx.hir.get_parent(it.id);
1866                         match cx.tcx.hir.find(parent) {
1867                             Some(hir_map::NodeItem(hir::Item {node: hir::ItemKind::Mod(_), ..})) |
1868                             None => {}
1869                             _ => {
1870                                 cx.struct_span_lint(
1871                                     UNNAMEABLE_TEST_FUNCTIONS,
1872                                     attr.span,
1873                                     "cannot test inner function",
1874                                 ).emit();
1875                             }
1876                         }
1877                         break;
1878                     }
1879                 }
1880             }
1881             _ => return,
1882         };
1883     }
1884 }
1885
1886 declare_lint! {
1887     pub ASYNC_IDENTS,
1888     Allow,
1889     "detects `async` being used as an identifier"
1890 }
1891
1892 /// Checks for uses of `async` as an identifier
1893 #[derive(Clone)]
1894 pub struct Async2018;
1895
1896 impl LintPass for Async2018 {
1897     fn get_lints(&self) -> LintArray {
1898         lint_array!(ASYNC_IDENTS)
1899     }
1900 }
1901
1902 impl Async2018 {
1903     fn check_tokens(&mut self, cx: &EarlyContext, tokens: TokenStream) {
1904         for tt in tokens.into_trees() {
1905             match tt {
1906                 TokenTree::Token(span, tok) => match tok.ident() {
1907                     // only report non-raw idents
1908                     Some((ident, false)) if ident.as_str() == "async" => {
1909                         self.report(cx, span.substitute_dummy(ident.span))
1910                     },
1911                     _ => {},
1912                 }
1913                 TokenTree::Delimited(_, ref delim) => {
1914                     self.check_tokens(cx, delim.tts.clone().into())
1915                 },
1916             }
1917         }
1918     }
1919     fn report(&mut self, cx: &EarlyContext, span: Span) {
1920         // don't lint `r#async`
1921         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&span) {
1922             return;
1923         }
1924         let mut lint = cx.struct_span_lint(
1925             ASYNC_IDENTS,
1926             span,
1927             "`async` is a keyword in the 2018 edition",
1928         );
1929
1930         // Don't suggest about raw identifiers if the feature isn't active
1931         lint.span_suggestion_with_applicability(
1932             span,
1933             "you can use a raw identifier to stay compatible",
1934             "r#async".to_string(),
1935             Applicability::MachineApplicable,
1936         );
1937         lint.emit()
1938     }
1939 }
1940
1941 impl EarlyLintPass for Async2018 {
1942     fn check_mac_def(&mut self, cx: &EarlyContext, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1943         self.check_tokens(cx, mac_def.stream());
1944     }
1945     fn check_mac(&mut self, cx: &EarlyContext, mac: &ast::Mac) {
1946         self.check_tokens(cx, mac.node.tts.clone().into());
1947     }
1948     fn check_ident(&mut self, cx: &EarlyContext, ident: ast::Ident) {
1949         if ident.as_str() == "async" {
1950             self.report(cx, ident.span);
1951         }
1952     }
1953 }