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