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 }
 300
 301 pub struct MissingDoc {
 302     /// Stack of whether #[doc(hidden)] is set
 303     /// at each level which has lint attributes.
 304     doc_hidden_stack: Vec<bool>,
 305
 306     /// Private traits or trait items that leaked through. Don't check their methods.
 307     private_traits: HashSet<ast::NodeId>,
 308 }
 309
 310 impl MissingDoc {
 311     pub fn new() -> MissingDoc {
 312         MissingDoc {
 313             doc_hidden_stack: vec![false],
 314             private_traits: HashSet::new(),
 315         }
 316     }
 317
 318     fn doc_hidden(&self) -> bool {
 319         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 320     }
 321
 322     fn check_missing_docs_attrs(&self,
 323                                 cx: &LateContext,
 324                                 id: Option<ast::NodeId>,
 325                                 attrs: &[ast::Attribute],
 326                                 sp: Span,
 327                                 desc: &'static str) {
 328         // If we're building a test harness, then warning about
 329         // documentation is probably not really relevant right now.
 330         if cx.sess().opts.test {
 331             return;
 332         }
 333
 334         // `#[doc(hidden)]` disables missing_docs check.
 335         if self.doc_hidden() {
 336             return;
 337         }
 338
 339         // Only check publicly-visible items, using the result from the privacy pass.
 340         // It's an option so the crate root can also use this function (it doesn't
 341         // have a NodeId).
 342         if let Some(id) = id {
 343             if !cx.access_levels.is_exported(id) {
 344                 return;
 345             }
 346         }
 347
 348         fn has_doc(attr: &ast::Attribute) -> bool {
 349             if !attr.check_name("doc") {
 350                 return false;
 351             }
 352
 353             if attr.is_value_str() {
 354                 return true;
 355             }
 356
 357             if let Some(list) = attr.meta_item_list() {
 358                 for meta in list {
 359                     if meta.check_name("include") {
 360                         return true;
 361                     }
 362                 }
 363             }
 364
 365             false
 366         }
 367
 368         let has_doc = attrs.iter().any(|a| has_doc(a));
 369         if !has_doc {
 370             cx.span_lint(MISSING_DOCS,
 371                          cx.tcx.sess.source_map().def_span(sp),
 372                          &format!("missing documentation for {}", desc));
 373         }
 374     }
 375 }
 376
 377 impl LintPass for MissingDoc {
 378     fn get_lints(&self) -> LintArray {
 379         lint_array!(MISSING_DOCS)
 380     }
 381 }
 382
 383 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 384     fn enter_lint_attrs(&mut self, _: &LateContext, attrs: &[ast::Attribute]) {
 385         let doc_hidden = self.doc_hidden() ||
 386                          attrs.iter().any(|attr| {
 387             attr.check_name("doc") &&
 388             match attr.meta_item_list() {
 389                 None => false,
 390                 Some(l) => attr::list_contains_name(&l, "hidden"),
 391             }
 392         });
 393         self.doc_hidden_stack.push(doc_hidden);
 394     }
 395
 396     fn exit_lint_attrs(&mut self, _: &LateContext, _attrs: &[ast::Attribute]) {
 397         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 398     }
 399
 400     fn check_crate(&mut self, cx: &LateContext, krate: &hir::Crate) {
 401         self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
 402     }
 403
 404     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 405         let desc = match it.node {
 406             hir::ItemKind::Fn(..) => "a function",
 407             hir::ItemKind::Mod(..) => "a module",
 408             hir::ItemKind::Enum(..) => "an enum",
 409             hir::ItemKind::Struct(..) => "a struct",
 410             hir::ItemKind::Union(..) => "a union",
 411             hir::ItemKind::Trait(.., ref trait_item_refs) => {
 412                 // Issue #11592, traits are always considered exported, even when private.
 413                 if let hir::VisibilityKind::Inherited = it.vis.node {
 414                     self.private_traits.insert(it.id);
 415                     for trait_item_ref in trait_item_refs {
 416                         self.private_traits.insert(trait_item_ref.id.node_id);
 417                     }
 418                     return;
 419                 }
 420                 "a trait"
 421             }
 422             hir::ItemKind::Ty(..) => "a type alias",
 423             hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
 424                 // If the trait is private, add the impl items to private_traits so they don't get
 425                 // reported for missing docs.
 426                 let real_trait = trait_ref.path.def.def_id();
 427                 if let Some(node_id) = cx.tcx.hir.as_local_node_id(real_trait) {
 428                     match cx.tcx.hir.find(node_id) {
 429                         Some(hir_map::NodeItem(item)) => {
 430                             if let hir::VisibilityKind::Inherited = item.vis.node {
 431                                 for impl_item_ref in impl_item_refs {
 432                                     self.private_traits.insert(impl_item_ref.id.node_id);
 433                                 }
 434                             }
 435                         }
 436                         _ => {}
 437                     }
 438                 }
 439                 return;
 440             }
 441             hir::ItemKind::Const(..) => "a constant",
 442             hir::ItemKind::Static(..) => "a static",
 443             _ => return,
 444         };
 445
 446         self.check_missing_docs_attrs(cx, Some(it.id), &it.attrs, it.span, desc);
 447     }
 448
 449     fn check_trait_item(&mut self, cx: &LateContext, trait_item: &hir::TraitItem) {
 450         if self.private_traits.contains(&trait_item.id) {
 451             return;
 452         }
 453
 454         let desc = match trait_item.node {
 455             hir::TraitItemKind::Const(..) => "an associated constant",
 456             hir::TraitItemKind::Method(..) => "a trait method",
 457             hir::TraitItemKind::Type(..) => "an associated type",
 458         };
 459
 460         self.check_missing_docs_attrs(cx,
 461                                       Some(trait_item.id),
 462                                       &trait_item.attrs,
 463                                       trait_item.span,
 464                                       desc);
 465     }
 466
 467     fn check_impl_item(&mut self, cx: &LateContext, impl_item: &hir::ImplItem) {
 468         // If the method is an impl for a trait, don't doc.
 469         if method_context(cx, impl_item.id) == MethodLateContext::TraitImpl {
 470             return;
 471         }
 472
 473         let desc = match impl_item.node {
 474             hir::ImplItemKind::Const(..) => "an associated constant",
 475             hir::ImplItemKind::Method(..) => "a method",
 476             hir::ImplItemKind::Type(_) => "an associated type",
 477             hir::ImplItemKind::Existential(_) => "an associated existential type",
 478         };
 479         self.check_missing_docs_attrs(cx,
 480                                       Some(impl_item.id),
 481                                       &impl_item.attrs,
 482                                       impl_item.span,
 483                                       desc);
 484     }
 485
 486     fn check_struct_field(&mut self, cx: &LateContext, sf: &hir::StructField) {
 487         if !sf.is_positional() {
 488             self.check_missing_docs_attrs(cx,
 489                                           Some(sf.id),
 490                                           &sf.attrs,
 491                                           sf.span,
 492                                           "a struct field")
 493         }
 494     }
 495
 496     fn check_variant(&mut self, cx: &LateContext, v: &hir::Variant, _: &hir::Generics) {
 497         self.check_missing_docs_attrs(cx,
 498                                       Some(v.node.data.id()),
 499                                       &v.node.attrs,
 500                                       v.span,
 501                                       "a variant");
 502     }
 503 }
 504
 505 declare_lint! {
 506     pub MISSING_COPY_IMPLEMENTATIONS,
 507     Allow,
 508     "detects potentially-forgotten implementations of `Copy`"
 509 }
 510
 511 #[derive(Copy, Clone)]
 512 pub struct MissingCopyImplementations;
 513
 514 impl LintPass for MissingCopyImplementations {
 515     fn get_lints(&self) -> LintArray {
 516         lint_array!(MISSING_COPY_IMPLEMENTATIONS)
 517     }
 518 }
 519
 520 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 521     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
 522         if !cx.access_levels.is_reachable(item.id) {
 523             return;
 524         }
 525         let (def, ty) = match item.node {
 526             hir::ItemKind::Struct(_, ref ast_generics) => {
 527                 if !ast_generics.params.is_empty() {
 528                     return;
 529                 }
 530                 let def = cx.tcx.adt_def(cx.tcx.hir.local_def_id(item.id));
 531                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 532             }
 533             hir::ItemKind::Union(_, ref ast_generics) => {
 534                 if !ast_generics.params.is_empty() {
 535                     return;
 536                 }
 537                 let def = cx.tcx.adt_def(cx.tcx.hir.local_def_id(item.id));
 538                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 539             }
 540             hir::ItemKind::Enum(_, ref ast_generics) => {
 541                 if !ast_generics.params.is_empty() {
 542                     return;
 543                 }
 544                 let def = cx.tcx.adt_def(cx.tcx.hir.local_def_id(item.id));
 545                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 546             }
 547             _ => return,
 548         };
 549         if def.has_dtor(cx.tcx) {
 550             return;
 551         }
 552         let param_env = ty::ParamEnv::empty();
 553         if !ty.moves_by_default(cx.tcx, param_env, item.span) {
 554             return;
 555         }
 556         if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
 557             cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
 558                          item.span,
 559                          "type could implement `Copy`; consider adding `impl \
 560                           Copy`")
 561         }
 562     }
 563 }
 564
 565 declare_lint! {
 566     MISSING_DEBUG_IMPLEMENTATIONS,
 567     Allow,
 568     "detects missing implementations of fmt::Debug"
 569 }
 570
 571 pub struct MissingDebugImplementations {
 572     impling_types: Option<NodeSet>,
 573 }
 574
 575 impl MissingDebugImplementations {
 576     pub fn new() -> MissingDebugImplementations {
 577         MissingDebugImplementations { impling_types: None }
 578     }
 579 }
 580
 581 impl LintPass for MissingDebugImplementations {
 582     fn get_lints(&self) -> LintArray {
 583         lint_array!(MISSING_DEBUG_IMPLEMENTATIONS)
 584     }
 585 }
 586
 587 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 588     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
 589         if !cx.access_levels.is_reachable(item.id) {
 590             return;
 591         }
 592
 593         match item.node {
 594             hir::ItemKind::Struct(..) |
 595             hir::ItemKind::Union(..) |
 596             hir::ItemKind::Enum(..) => {}
 597             _ => return,
 598         }
 599
 600         let debug = match cx.tcx.lang_items().debug_trait() {
 601             Some(debug) => debug,
 602             None => return,
 603         };
 604
 605         if self.impling_types.is_none() {
 606             let mut impls = NodeSet();
 607             cx.tcx.for_each_impl(debug, |d| {
 608                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 609                     if let Some(node_id) = cx.tcx.hir.as_local_node_id(ty_def.did) {
 610                         impls.insert(node_id);
 611                     }
 612                 }
 613             });
 614
 615             self.impling_types = Some(impls);
 616             debug!("{:?}", self.impling_types);
 617         }
 618
 619         if !self.impling_types.as_ref().unwrap().contains(&item.id) {
 620             cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
 621                          item.span,
 622                          "type does not implement `fmt::Debug`; consider adding #[derive(Debug)] \
 623                           or a manual implementation")
 624         }
 625     }
 626 }
 627
 628 declare_lint! {
 629     pub ANONYMOUS_PARAMETERS,
 630     Allow,
 631     "detects anonymous parameters",
 632     Edition::Edition2018 => Warn
 633 }
 634
 635 /// Checks for use of anonymous parameters (RFC 1685)
 636 #[derive(Clone)]
 637 pub struct AnonymousParameters;
 638
 639 impl LintPass for AnonymousParameters {
 640     fn get_lints(&self) -> LintArray {
 641         lint_array!(ANONYMOUS_PARAMETERS)
 642     }
 643 }
 644
 645 impl EarlyLintPass for AnonymousParameters {
 646     fn check_trait_item(&mut self, cx: &EarlyContext, it: &ast::TraitItem) {
 647         match it.node {
 648             ast::TraitItemKind::Method(ref sig, _) => {
 649                 for arg in sig.decl.inputs.iter() {
 650                     match arg.pat.node {
 651                         ast::PatKind::Ident(_, ident, None) => {
 652                             if ident.name == keywords::Invalid.name() {
 653                                 let ty_snip = cx
 654                                     .sess
 655                                     .source_map()
 656                                     .span_to_snippet(arg.ty.span);
 657
 658                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 659                                     (snip, Applicability::MachineApplicable)
 660                                 } else {
 661                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 662                                 };
 663
 664                                 cx.struct_span_lint(
 665                                     ANONYMOUS_PARAMETERS,
 666                                     arg.pat.span,
 667                                     "anonymous parameters are deprecated and will be \
 668                                      removed in the next edition."
 669                                 ).span_suggestion_with_applicability(
 670                                     arg.pat.span,
 671                                     "Try naming the parameter or explicitly \
 672                                     ignoring it",
 673                                     format!("_: {}", ty_snip),
 674                                     appl
 675                                 ).emit();
 676                             }
 677                         }
 678                         _ => (),
 679                     }
 680                 }
 681             },
 682             _ => (),
 683         }
 684     }
 685 }
 686
 687 /// Checks for incorrect use use of `repr` attributes.
 688 #[derive(Clone)]
 689 pub struct BadRepr;
 690
 691 impl LintPass for BadRepr {
 692     fn get_lints(&self) -> LintArray {
 693         lint_array!()
 694     }
 695 }
 696
 697 impl EarlyLintPass for BadRepr {
 698     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
 699         if attr.name() == "repr" {
 700             let list = attr.meta_item_list();
 701
 702             let repr_str = |lit: &str| { format!("#[repr({})]", lit) };
 703
 704             // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
 705             // no hints (``#[repr]`)
 706             let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
 707             if !has_hints {
 708                 let mut suggested = false;
 709                 let mut warn = if let Some(ref lit) = attr.value_str() {
 710                     // avoid warning about empty `repr` on `#[repr = "foo"]`
 711                     let mut warn = cx.struct_span_lint(
 712                         BAD_REPR,
 713                         attr.span,
 714                         "`repr` attribute isn't configurable with a literal",
 715                     );
 716                     match lit.to_string().as_ref() {
 717                         | "C" | "packed" | "rust" | "transparent"
 718                         | "u8" | "u16" | "u32" | "u64" | "u128" | "usize"
 719                         | "i8" | "i16" | "i32" | "i64" | "i128" | "isize" => {
 720                             // if the literal could have been a valid `repr` arg,
 721                             // suggest the correct syntax
 722                             warn.span_suggestion_with_applicability(
 723                                 attr.span,
 724                                 "give `repr` a hint",
 725                                 repr_str(&lit.as_str()),
 726                                 Applicability::MachineApplicable
 727                             );
 728                             suggested = true;
 729                         }
 730                         _ => {  // the literal wasn't a valid `repr` arg
 731                             warn.span_label(attr.span, "needs a hint");
 732                         }
 733                     };
 734                     warn
 735                 } else {
 736                     let mut warn = cx.struct_span_lint(
 737                         BAD_REPR,
 738                         attr.span,
 739                         "`repr` attribute must have a hint",
 740                     );
 741                     warn.span_label(attr.span, "needs a hint");
 742                     warn
 743                 };
 744                 if !suggested {
 745                     warn.help(&format!(
 746                         "valid hints include `{}`, `{}`, `{}` and `{}`",
 747                         repr_str("C"),
 748                         repr_str("packed"),
 749                         repr_str("rust"),
 750                         repr_str("transparent"),
 751                     ));
 752                     warn.note("for more information, visit \
 753                                <https://doc.rust-lang.org/reference/type-layout.html>");
 754                 }
 755                 warn.emit();
 756             }
 757         }
 758     }
 759 }
 760
 761 /// Checks for use of attributes which have been deprecated.
 762 #[derive(Clone)]
 763 pub struct DeprecatedAttr {
 764     // This is not free to compute, so we want to keep it around, rather than
 765     // compute it for every attribute.
 766     depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeGate)>,
 767 }
 768
 769 impl DeprecatedAttr {
 770     pub fn new() -> DeprecatedAttr {
 771         DeprecatedAttr {
 772             depr_attrs: deprecated_attributes(),
 773         }
 774     }
 775 }
 776
 777 impl LintPass for DeprecatedAttr {
 778     fn get_lints(&self) -> LintArray {
 779         lint_array!()
 780     }
 781 }
 782
 783 impl EarlyLintPass for DeprecatedAttr {
 784     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
 785         for &&(n, _, ref g) in &self.depr_attrs {
 786             if attr.name() == n {
 787                 if let &AttributeGate::Gated(Stability::Deprecated(link),
 788                                              ref name,
 789                                              ref reason,
 790                                              _) = g {
 791                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
 792                                       name, reason, link);
 793                     let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
 794                     err.span_suggestion_short_with_applicability(
 795                         attr.span,
 796                         "remove this attribute",
 797                         "".to_owned(),
 798                         Applicability::MachineApplicable
 799                     );
 800                     err.emit();
 801                 }
 802                 return;
 803             }
 804         }
 805     }
 806 }
 807
 808 declare_lint! {
 809     pub UNUSED_DOC_COMMENTS,
 810     Warn,
 811     "detects doc comments that aren't used by rustdoc"
 812 }
 813
 814 #[derive(Copy, Clone)]
 815 pub struct UnusedDocComment;
 816
 817 impl LintPass for UnusedDocComment {
 818     fn get_lints(&self) -> LintArray {
 819         lint_array![UNUSED_DOC_COMMENTS]
 820     }
 821 }
 822
 823 impl UnusedDocComment {
 824     fn warn_if_doc<'a, 'tcx,
 825                    I: Iterator<Item=&'a ast::Attribute>,
 826                    C: LintContext<'tcx>>(&self, mut attrs: I, cx: &C) {
 827         if let Some(attr) = attrs.find(|a| a.is_value_str() && a.check_name("doc")) {
 828             cx.struct_span_lint(UNUSED_DOC_COMMENTS, attr.span, "doc comment not used by rustdoc")
 829               .emit();
 830         }
 831     }
 832 }
 833
 834 impl EarlyLintPass for UnusedDocComment {
 835     fn check_local(&mut self, cx: &EarlyContext, decl: &ast::Local) {
 836         self.warn_if_doc(decl.attrs.iter(), cx);
 837     }
 838
 839     fn check_arm(&mut self, cx: &EarlyContext, arm: &ast::Arm) {
 840         self.warn_if_doc(arm.attrs.iter(), cx);
 841     }
 842
 843     fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
 844         self.warn_if_doc(expr.attrs.iter(), cx);
 845     }
 846 }
 847
 848 declare_lint! {
 849     pub UNCONDITIONAL_RECURSION,
 850     Warn,
 851     "functions that cannot return without calling themselves"
 852 }
 853
 854 #[derive(Copy, Clone)]
 855 pub struct UnconditionalRecursion;
 856
 857
 858 impl LintPass for UnconditionalRecursion {
 859     fn get_lints(&self) -> LintArray {
 860         lint_array![UNCONDITIONAL_RECURSION]
 861     }
 862 }
 863
 864 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnconditionalRecursion {
 865     fn check_fn(&mut self,
 866                 cx: &LateContext,
 867                 fn_kind: FnKind,
 868                 _: &hir::FnDecl,
 869                 body: &hir::Body,
 870                 sp: Span,
 871                 id: ast::NodeId) {
 872         let method = match fn_kind {
 873             FnKind::ItemFn(..) => None,
 874             FnKind::Method(..) => {
 875                 Some(cx.tcx.associated_item(cx.tcx.hir.local_def_id(id)))
 876             }
 877             // closures can't recur, so they don't matter.
 878             FnKind::Closure(_) => return,
 879         };
 880
 881         // Walk through this function (say `f`) looking to see if
 882         // every possible path references itself, i.e. the function is
 883         // called recursively unconditionally. This is done by trying
 884         // to find a path from the entry node to the exit node that
 885         // *doesn't* call `f` by traversing from the entry while
 886         // pretending that calls of `f` are sinks (i.e. ignoring any
 887         // exit edges from them).
 888         //
 889         // NB. this has an edge case with non-returning statements,
 890         // like `loop {}` or `panic!()`: control flow never reaches
 891         // the exit node through these, so one can have a function
 892         // that never actually calls itselfs but is still picked up by
 893         // this lint:
 894         //
 895         //     fn f(cond: bool) {
 896         //         if !cond { panic!() } // could come from `assert!(cond)`
 897         //         f(false)
 898         //     }
 899         //
 900         // In general, functions of that form may be able to call
 901         // itself a finite number of times and then diverge. The lint
 902         // considers this to be an error for two reasons, (a) it is
 903         // easier to implement, and (b) it seems rare to actually want
 904         // to have behaviour like the above, rather than
 905         // e.g. accidentally recurring after an assert.
 906
 907         let cfg = cfg::CFG::new(cx.tcx, &body);
 908
 909         let mut work_queue = vec![cfg.entry];
 910         let mut reached_exit_without_self_call = false;
 911         let mut self_call_spans = vec![];
 912         let mut visited = HashSet::new();
 913
 914         while let Some(idx) = work_queue.pop() {
 915             if idx == cfg.exit {
 916                 // found a path!
 917                 reached_exit_without_self_call = true;
 918                 break;
 919             }
 920
 921             let cfg_id = idx.node_id();
 922             if visited.contains(&cfg_id) {
 923                 // already done
 924                 continue;
 925             }
 926             visited.insert(cfg_id);
 927
 928             // is this a recursive call?
 929             let local_id = cfg.graph.node_data(idx).id();
 930             if local_id != hir::DUMMY_ITEM_LOCAL_ID {
 931                 let node_id = cx.tcx.hir.hir_to_node_id(hir::HirId {
 932                     owner: body.value.hir_id.owner,
 933                     local_id
 934                 });
 935                 let self_recursive = match method {
 936                     Some(ref method) => expr_refers_to_this_method(cx, method, node_id),
 937                     None => expr_refers_to_this_fn(cx, id, node_id),
 938                 };
 939                 if self_recursive {
 940                     self_call_spans.push(cx.tcx.hir.span(node_id));
 941                     // this is a self call, so we shouldn't explore past
 942                     // this node in the CFG.
 943                     continue;
 944                 }
 945             }
 946
 947             // add the successors of this node to explore the graph further.
 948             for (_, edge) in cfg.graph.outgoing_edges(idx) {
 949                 let target_idx = edge.target();
 950                 let target_cfg_id = target_idx.node_id();
 951                 if !visited.contains(&target_cfg_id) {
 952                     work_queue.push(target_idx)
 953                 }
 954             }
 955         }
 956
 957         // Check the number of self calls because a function that
 958         // doesn't return (e.g. calls a `-> !` function or `loop { /*
 959         // no break */ }`) shouldn't be linted unless it actually
 960         // recurs.
 961         if !reached_exit_without_self_call && !self_call_spans.is_empty() {
 962             let sp = cx.tcx.sess.source_map().def_span(sp);
 963             let mut db = cx.struct_span_lint(UNCONDITIONAL_RECURSION,
 964                                              sp,
 965                                              "function cannot return without recurring");
 966             db.span_label(sp, "cannot return without recurring");
 967             // offer some help to the programmer.
 968             for call in &self_call_spans {
 969                 db.span_label(*call, "recursive call site");
 970             }
 971             db.help("a `loop` may express intention better if this is on purpose");
 972             db.emit();
 973         }
 974
 975         // all done
 976         return;
 977
 978         // Functions for identifying if the given Expr NodeId `id`
 979         // represents a call to the function `fn_id`/method `method`.
 980
 981         fn expr_refers_to_this_fn(cx: &LateContext, fn_id: ast::NodeId, id: ast::NodeId) -> bool {
 982             match cx.tcx.hir.get(id) {
 983                 hir_map::NodeExpr(&hir::Expr { node: hir::ExprKind::Call(ref callee, _), .. }) => {
 984                     let def = if let hir::ExprKind::Path(ref qpath) = callee.node {
 985                         cx.tables.qpath_def(qpath, callee.hir_id)
 986                     } else {
 987                         return false;
 988                     };
 989                     match def {
 990                         Def::Local(..) | Def::Upvar(..) => false,
 991                         _ => def.def_id() == cx.tcx.hir.local_def_id(fn_id)
 992                     }
 993                 }
 994                 _ => false,
 995             }
 996         }
 997
 998         // Check if the expression `id` performs a call to `method`.
 999         fn expr_refers_to_this_method(cx: &LateContext,
1000                                       method: &ty::AssociatedItem,
1001                                       id: ast::NodeId)
1002                                       -> bool {
1003             use rustc::ty::adjustment::*;
1004
1005             // Ignore non-expressions.
1006             let expr = if let hir_map::NodeExpr(e) = cx.tcx.hir.get(id) {
1007                 e
1008             } else {
1009                 return false;
1010             };
1011
1012             // Check for overloaded autoderef method calls.
1013             let mut source = cx.tables.expr_ty(expr);
1014             for adjustment in cx.tables.expr_adjustments(expr) {
1015                 if let Adjust::Deref(Some(deref)) = adjustment.kind {
1016                     let (def_id, substs) = deref.method_call(cx.tcx, source);
1017                     if method_call_refers_to_method(cx, method, def_id, substs, id) {
1018                         return true;
1019                     }
1020                 }
1021                 source = adjustment.target;
1022             }
1023
1024             // Check for method calls and overloaded operators.
1025             if cx.tables.is_method_call(expr) {
1026                 let hir_id = cx.tcx.hir.definitions().node_to_hir_id(id);
1027                 if let Some(def) = cx.tables.type_dependent_defs().get(hir_id) {
1028                     let def_id = def.def_id();
1029                     let substs = cx.tables.node_substs(hir_id);
1030                     if method_call_refers_to_method(cx, method, def_id, substs, id) {
1031                         return true;
1032                     }
1033                 } else {
1034                     cx.tcx.sess.delay_span_bug(expr.span,
1035                                                "no type-dependent def for method call");
1036                 }
1037             }
1038
1039             // Check for calls to methods via explicit paths (e.g. `T::method()`).
1040             match expr.node {
1041                 hir::ExprKind::Call(ref callee, _) => {
1042                     let def = if let hir::ExprKind::Path(ref qpath) = callee.node {
1043                         cx.tables.qpath_def(qpath, callee.hir_id)
1044                     } else {
1045                         return false;
1046                     };
1047                     match def {
1048                         Def::Method(def_id) => {
1049                             let substs = cx.tables.node_substs(callee.hir_id);
1050                             method_call_refers_to_method(cx, method, def_id, substs, id)
1051                         }
1052                         _ => false,
1053                     }
1054                 }
1055                 _ => false,
1056             }
1057         }
1058
1059         // Check if the method call to the method with the ID `callee_id`
1060         // and instantiated with `callee_substs` refers to method `method`.
1061         fn method_call_refers_to_method<'a, 'tcx>(cx: &LateContext<'a, 'tcx>,
1062                                                   method: &ty::AssociatedItem,
1063                                                   callee_id: DefId,
1064                                                   callee_substs: &Substs<'tcx>,
1065                                                   expr_id: ast::NodeId)
1066                                                   -> bool {
1067             let tcx = cx.tcx;
1068             let callee_item = tcx.associated_item(callee_id);
1069
1070             match callee_item.container {
1071                 // This is an inherent method, so the `def_id` refers
1072                 // directly to the method definition.
1073                 ty::ImplContainer(_) => callee_id == method.def_id,
1074
1075                 // A trait method, from any number of possible sources.
1076                 // Attempt to select a concrete impl before checking.
1077                 ty::TraitContainer(trait_def_id) => {
1078                     let trait_ref = ty::TraitRef::from_method(tcx, trait_def_id, callee_substs);
1079                     let trait_ref = ty::Binder::bind(trait_ref);
1080                     let span = tcx.hir.span(expr_id);
1081                     let obligation =
1082                         traits::Obligation::new(traits::ObligationCause::misc(span, expr_id),
1083                                                 cx.param_env,
1084                                                 trait_ref.to_poly_trait_predicate());
1085
1086                     tcx.infer_ctxt().enter(|infcx| {
1087                         let mut selcx = traits::SelectionContext::new(&infcx);
1088                         match selcx.select(&obligation) {
1089                             // The method comes from a `T: Trait` bound.
1090                             // If `T` is `Self`, then this call is inside
1091                             // a default method definition.
1092                             Ok(Some(traits::VtableParam(_))) => {
1093                                 let on_self = trait_ref.self_ty().is_self();
1094                                 // We can only be recurring in a default
1095                                 // method if we're being called literally
1096                                 // on the `Self` type.
1097                                 on_self && callee_id == method.def_id
1098                             }
1099
1100                             // The `impl` is known, so we check that with a
1101                             // special case:
1102                             Ok(Some(traits::VtableImpl(vtable_impl))) => {
1103                                 let container = ty::ImplContainer(vtable_impl.impl_def_id);
1104                                 // It matches if it comes from the same impl,
1105                                 // and has the same method name.
1106                                 container == method.container &&
1107                                 callee_item.ident.name == method.ident.name
1108                             }
1109
1110                             // There's no way to know if this call is
1111                             // recursive, so we assume it's not.
1112                             _ => false,
1113                         }
1114                     })
1115                 }
1116             }
1117         }
1118     }
1119 }
1120
1121 declare_lint! {
1122     PLUGIN_AS_LIBRARY,
1123     Warn,
1124     "compiler plugin used as ordinary library in non-plugin crate"
1125 }
1126
1127 #[derive(Copy, Clone)]
1128 pub struct PluginAsLibrary;
1129
1130 impl LintPass for PluginAsLibrary {
1131     fn get_lints(&self) -> LintArray {
1132         lint_array![PLUGIN_AS_LIBRARY]
1133     }
1134 }
1135
1136 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
1137     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1138         if cx.sess().plugin_registrar_fn.get().is_some() {
1139             // We're compiling a plugin; it's fine to link other plugins.
1140             return;
1141         }
1142
1143         match it.node {
1144             hir::ItemKind::ExternCrate(..) => (),
1145             _ => return,
1146         };
1147
1148         let def_id = cx.tcx.hir.local_def_id(it.id);
1149         let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
1150             Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
1151             None => {
1152                 // Probably means we aren't linking the crate for some reason.
1153                 //
1154                 // Not sure if / when this could happen.
1155                 return;
1156             }
1157         };
1158
1159         if prfn.is_some() {
1160             cx.span_lint(PLUGIN_AS_LIBRARY,
1161                          it.span,
1162                          "compiler plugin used as an ordinary library");
1163         }
1164     }
1165 }
1166
1167 declare_lint! {
1168     PRIVATE_NO_MANGLE_FNS,
1169     Warn,
1170     "functions marked #[no_mangle] should be exported"
1171 }
1172
1173 declare_lint! {
1174     PRIVATE_NO_MANGLE_STATICS,
1175     Warn,
1176     "statics marked #[no_mangle] should be exported"
1177 }
1178
1179 declare_lint! {
1180     NO_MANGLE_CONST_ITEMS,
1181     Deny,
1182     "const items will not have their symbols exported"
1183 }
1184
1185 declare_lint! {
1186     NO_MANGLE_GENERIC_ITEMS,
1187     Warn,
1188     "generic items must be mangled"
1189 }
1190
1191 #[derive(Copy, Clone)]
1192 pub struct InvalidNoMangleItems;
1193
1194 impl LintPass for InvalidNoMangleItems {
1195     fn get_lints(&self) -> LintArray {
1196         lint_array!(PRIVATE_NO_MANGLE_FNS,
1197                     PRIVATE_NO_MANGLE_STATICS,
1198                     NO_MANGLE_CONST_ITEMS,
1199                     NO_MANGLE_GENERIC_ITEMS)
1200     }
1201 }
1202
1203 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
1204     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1205         let suggest_export = |vis: &hir::Visibility, err: &mut DiagnosticBuilder| {
1206             let suggestion = match vis.node {
1207                 hir::VisibilityKind::Inherited => {
1208                     // inherited visibility is empty span at item start; need an extra space
1209                     Some("pub ".to_owned())
1210                 },
1211                 hir::VisibilityKind::Restricted { .. } |
1212                 hir::VisibilityKind::Crate(_) => {
1213                     Some("pub".to_owned())
1214                 },
1215                 hir::VisibilityKind::Public => {
1216                     err.help("try exporting the item with a `pub use` statement");
1217                     None
1218                 }
1219             };
1220             if let Some(replacement) = suggestion {
1221                 err.span_suggestion_with_applicability(
1222                     vis.span,
1223                     "try making it public",
1224                     replacement,
1225                     Applicability::MachineApplicable
1226                 );
1227             }
1228         };
1229
1230         match it.node {
1231             hir::ItemKind::Fn(.., ref generics, _) => {
1232                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, "no_mangle") {
1233                     if attr::contains_name(&it.attrs, "linkage") {
1234                         return;
1235                     }
1236                     if !cx.access_levels.is_reachable(it.id) {
1237                         let msg = "function is marked #[no_mangle], but not exported";
1238                         let mut err = cx.struct_span_lint(PRIVATE_NO_MANGLE_FNS, it.span, msg);
1239                         suggest_export(&it.vis, &mut err);
1240                         err.emit();
1241                     }
1242                     for param in &generics.params {
1243                         match param.kind {
1244                             GenericParamKind::Lifetime { .. } => {}
1245                             GenericParamKind::Type { .. } => {
1246                                 let mut err = cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS,
1247                                                                   it.span,
1248                                                                   "functions generic over \
1249                                                                    types must be mangled");
1250                                 err.span_suggestion_short_with_applicability(
1251                                     no_mangle_attr.span,
1252                                     "remove this attribute",
1253                                     "".to_owned(),
1254                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1255                                     // fix may be to monomorphize source by hand
1256                                     Applicability::MaybeIncorrect
1257                                 );
1258                                 err.emit();
1259                                 break;
1260                             }
1261                         }
1262                     }
1263                 }
1264             }
1265             hir::ItemKind::Static(..) => {
1266                 if attr::contains_name(&it.attrs, "no_mangle") &&
1267                     !cx.access_levels.is_reachable(it.id) {
1268                         let msg = "static is marked #[no_mangle], but not exported";
1269                         let mut err = cx.struct_span_lint(PRIVATE_NO_MANGLE_STATICS, it.span, msg);
1270                         suggest_export(&it.vis, &mut err);
1271                         err.emit();
1272                     }
1273             }
1274             hir::ItemKind::Const(..) => {
1275                 if attr::contains_name(&it.attrs, "no_mangle") {
1276                     // Const items do not refer to a particular location in memory, and therefore
1277                     // don't have anything to attach a symbol to
1278                     let msg = "const items should never be #[no_mangle]";
1279                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
1280
1281                     // account for "pub const" (#45562)
1282                     let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
1283                         .map(|snippet| snippet.find("const").unwrap_or(0))
1284                         .unwrap_or(0) as u32;
1285                     // `const` is 5 chars
1286                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1287                     err.span_suggestion_with_applicability(
1288                         const_span,
1289                         "try a static value",
1290                         "pub static".to_owned(),
1291                         Applicability::MachineApplicable
1292                     );
1293                     err.emit();
1294                 }
1295             }
1296             _ => {}
1297         }
1298     }
1299 }
1300
1301 #[derive(Clone, Copy)]
1302 pub struct MutableTransmutes;
1303
1304 declare_lint! {
1305     MUTABLE_TRANSMUTES,
1306     Deny,
1307     "mutating transmuted &mut T from &T may cause undefined behavior"
1308 }
1309
1310 impl LintPass for MutableTransmutes {
1311     fn get_lints(&self) -> LintArray {
1312         lint_array!(MUTABLE_TRANSMUTES)
1313     }
1314 }
1315
1316 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
1317     fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
1318         use rustc_target::spec::abi::Abi::RustIntrinsic;
1319
1320         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1321                    consider instead using an UnsafeCell";
1322         match get_transmute_from_to(cx, expr) {
1323             Some((&ty::TyRef(_, _, from_mt), &ty::TyRef(_, _, to_mt))) => {
1324                 if to_mt == hir::Mutability::MutMutable &&
1325                    from_mt == hir::Mutability::MutImmutable {
1326                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
1327                 }
1328             }
1329             _ => (),
1330         }
1331
1332         fn get_transmute_from_to<'a, 'tcx>
1333             (cx: &LateContext<'a, 'tcx>,
1334              expr: &hir::Expr)
1335              -> Option<(&'tcx ty::TypeVariants<'tcx>, &'tcx ty::TypeVariants<'tcx>)> {
1336             let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
1337                 cx.tables.qpath_def(qpath, expr.hir_id)
1338             } else {
1339                 return None;
1340             };
1341             if let Def::Fn(did) = def {
1342                 if !def_id_is_transmute(cx, did) {
1343                     return None;
1344                 }
1345                 let sig = cx.tables.node_id_to_type(expr.hir_id).fn_sig(cx.tcx);
1346                 let from = sig.inputs().skip_binder()[0];
1347                 let to = *sig.output().skip_binder();
1348                 return Some((&from.sty, &to.sty));
1349             }
1350             None
1351         }
1352
1353         fn def_id_is_transmute(cx: &LateContext, def_id: DefId) -> bool {
1354             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
1355             cx.tcx.item_name(def_id) == "transmute"
1356         }
1357     }
1358 }
1359
1360 /// Forbids using the `#[feature(...)]` attribute
1361 #[derive(Copy, Clone)]
1362 pub struct UnstableFeatures;
1363
1364 declare_lint! {
1365     UNSTABLE_FEATURES,
1366     Allow,
1367     "enabling unstable features (deprecated. do not use)"
1368 }
1369
1370 impl LintPass for UnstableFeatures {
1371     fn get_lints(&self) -> LintArray {
1372         lint_array!(UNSTABLE_FEATURES)
1373     }
1374 }
1375
1376 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
1377     fn check_attribute(&mut self, ctx: &LateContext, attr: &ast::Attribute) {
1378         if attr.check_name("feature") {
1379             if let Some(items) = attr.meta_item_list() {
1380                 for item in items {
1381                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
1382                 }
1383             }
1384         }
1385     }
1386 }
1387
1388 /// Lint for unions that contain fields with possibly non-trivial destructors.
1389 pub struct UnionsWithDropFields;
1390
1391 declare_lint! {
1392     UNIONS_WITH_DROP_FIELDS,
1393     Warn,
1394     "use of unions that contain fields with possibly non-trivial drop code"
1395 }
1396
1397 impl LintPass for UnionsWithDropFields {
1398     fn get_lints(&self) -> LintArray {
1399         lint_array!(UNIONS_WITH_DROP_FIELDS)
1400     }
1401 }
1402
1403 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
1404     fn check_item(&mut self, ctx: &LateContext, item: &hir::Item) {
1405         if let hir::ItemKind::Union(ref vdata, _) = item.node {
1406             for field in vdata.fields() {
1407                 let field_ty = ctx.tcx.type_of(ctx.tcx.hir.local_def_id(field.id));
1408                 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1409                     ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1410                                   field.span,
1411                                   "union contains a field with possibly non-trivial drop code, \
1412                                    drop code of union fields is ignored when dropping the union");
1413                     return;
1414                 }
1415             }
1416         }
1417     }
1418 }
1419
1420 /// Lint for items marked `pub` that aren't reachable from other crates
1421 pub struct UnreachablePub;
1422
1423 declare_lint! {
1424     pub UNREACHABLE_PUB,
1425     Allow,
1426     "`pub` items not reachable from crate root"
1427 }
1428
1429 impl LintPass for UnreachablePub {
1430     fn get_lints(&self) -> LintArray {
1431         lint_array!(UNREACHABLE_PUB)
1432     }
1433 }
1434
1435 impl UnreachablePub {
1436     fn perform_lint(&self, cx: &LateContext, what: &str, id: ast::NodeId,
1437                     vis: &hir::Visibility, span: Span, exportable: bool) {
1438         let mut applicability = Applicability::MachineApplicable;
1439         match vis.node {
1440             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1441                 if span.ctxt().outer().expn_info().is_some() {
1442                     applicability = Applicability::MaybeIncorrect;
1443                 }
1444                 let def_span = cx.tcx.sess.source_map().def_span(span);
1445                 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1446                                                   &format!("unreachable `pub` {}", what));
1447                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1448                     "crate"
1449                 } else {
1450                     "pub(crate)"
1451                 }.to_owned();
1452
1453                 err.span_suggestion_with_applicability(vis.span,
1454                                                        "consider restricting its visibility",
1455                                                        replacement,
1456                                                        applicability);
1457                 if exportable {
1458                     err.help("or consider exporting it for use by other crates");
1459                 }
1460                 err.emit();
1461             },
1462             _ => {}
1463         }
1464     }
1465 }
1466
1467
1468 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1469     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
1470         self.perform_lint(cx, "item", item.id, &item.vis, item.span, true);
1471     }
1472
1473     fn check_foreign_item(&mut self, cx: &LateContext, foreign_item: &hir::ForeignItem) {
1474         self.perform_lint(cx, "item", foreign_item.id, &foreign_item.vis,
1475                           foreign_item.span, true);
1476     }
1477
1478     fn check_struct_field(&mut self, cx: &LateContext, field: &hir::StructField) {
1479         self.perform_lint(cx, "field", field.id, &field.vis, field.span, false);
1480     }
1481
1482     fn check_impl_item(&mut self, cx: &LateContext, impl_item: &hir::ImplItem) {
1483         self.perform_lint(cx, "item", impl_item.id, &impl_item.vis, impl_item.span, false);
1484     }
1485 }
1486
1487 /// Lint for trait and lifetime bounds in type aliases being mostly ignored:
1488 /// They are relevant when using associated types, but otherwise neither checked
1489 /// at definition site nor enforced at use site.
1490
1491 pub struct TypeAliasBounds;
1492
1493 declare_lint! {
1494     TYPE_ALIAS_BOUNDS,
1495     Warn,
1496     "bounds in type aliases are not enforced"
1497 }
1498
1499 impl LintPass for TypeAliasBounds {
1500     fn get_lints(&self) -> LintArray {
1501         lint_array!(TYPE_ALIAS_BOUNDS)
1502     }
1503 }
1504
1505 impl TypeAliasBounds {
1506     fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1507         match *qpath {
1508             hir::QPath::TypeRelative(ref ty, _) => {
1509                 // If this is a type variable, we found a `T::Assoc`.
1510                 match ty.node {
1511                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1512                         match path.def {
1513                             Def::TyParam(_) => true,
1514                             _ => false
1515                         }
1516                     }
1517                     _ => false
1518                 }
1519             }
1520             hir::QPath::Resolved(..) => false,
1521         }
1522     }
1523
1524     fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder) {
1525         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1526         // bound.  Let's see if this type does that.
1527
1528         // We use a HIR visitor to walk the type.
1529         use rustc::hir::intravisit::{self, Visitor};
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: hir::HirId, 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 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         if cx.sess.features_untracked().raw_identifiers {
1932             lint.span_suggestion_with_applicability(
1933                 span,
1934                 "you can use a raw identifier to stay compatible",
1935                 "r#async".to_string(),
1936                 Applicability::MachineApplicable,
1937             );
1938         }
1939         lint.emit()
1940     }
1941 }
1942
1943 impl EarlyLintPass for Async2018 {
1944     fn check_mac_def(&mut self, cx: &EarlyContext, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1945         self.check_tokens(cx, mac_def.stream());
1946     }
1947     fn check_mac(&mut self, cx: &EarlyContext, mac: &ast::Mac) {
1948         self.check_tokens(cx, mac.node.tts.clone().into());
1949     }
1950     fn check_ident(&mut self, cx: &EarlyContext, ident: ast::Ident) {
1951         if ident.as_str() == "async" {
1952             self.report(cx, ident.span);
1953         }
1954     }
1955 }