src/librustc_lint/builtin.rs

   1 //! Lints in the Rust compiler.
   2 //!
   3 //! This contains lints which can feasibly be implemented as their own
   4 //! AST visitor. Also see `rustc::lint::builtin`, which contains the
   5 //! definitions of lints that are emitted directly inside the main
   6 //! compiler.
   7 //!
   8 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
   9 //! Then add code to emit the new lint in the appropriate circumstances.
  10 //! You can do that in an existing `LintPass` if it makes sense, or in a
  11 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  12 //! compiler. Only do the latter if the check can't be written cleanly as a
  13 //! `LintPass` (also, note that such lints will need to be defined in
  14 //! `rustc::lint::builtin`, not here).
  15 //!
  16 //! If you define a new `EarlyLintPass`, you will also need to add it to the
  17 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
  18 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
  19 //! with a `pub fn new()`.
  20 //!
  21 //! If you define a new `LateLintPass`, you will also need to add it to the
  22 //! `late_lint_methods!` invocation in `lib.rs`.
  23
  24 use rustc::hir::def::Def;
  25 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  26 use rustc::ty::{self, Ty};
  27 use rustc::{lint, util};
  28 use hir::Node;
  29 use util::nodemap::HirIdSet;
  30 use lint::{LateContext, LintContext, LintArray};
  31 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
  32
  33 use rustc::util::nodemap::FxHashSet;
  34
  35 use syntax::tokenstream::{TokenTree, TokenStream};
  36 use syntax::ast;
  37 use syntax::ptr::P;
  38 use syntax::ast::Expr;
  39 use syntax::attr::{self, HasAttrs};
  40 use syntax::source_map::Spanned;
  41 use syntax::edition::Edition;
  42 use syntax::feature_gate::{AttributeGate, AttributeTemplate, AttributeType};
  43 use syntax::feature_gate::{Stability, deprecated_attributes};
  44 use syntax_pos::{BytePos, Span, SyntaxContext};
  45 use syntax::symbol::keywords;
  46 use syntax::errors::{Applicability, DiagnosticBuilder};
  47 use syntax::print::pprust::expr_to_string;
  48 use syntax::visit::FnKind;
  49 use syntax::struct_span_err;
  50
  51 use rustc::hir::{self, GenericParamKind, PatKind};
  52
  53 use crate::nonstandard_style::{MethodLateContext, method_context};
  54
  55 use log::debug;
  56
  57 // hardwired lints from librustc
  58 pub use lint::builtin::*;
  59
  60 declare_lint! {
  61     WHILE_TRUE,
  62     Warn,
  63     "suggest using `loop { }` instead of `while true { }`"
  64 }
  65
  66 #[derive(Copy, Clone)]
  67 pub struct WhileTrue;
  68
  69 impl LintPass for WhileTrue {
  70     fn name(&self) -> &'static str {
  71         "WhileTrue"
  72     }
  73
  74     fn get_lints(&self) -> LintArray {
  75         lint_array!(WHILE_TRUE)
  76     }
  77 }
  78
  79 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
  80     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
  81         if let hir::ExprKind::While(ref cond, ..) = e.node {
  82             if let hir::ExprKind::Lit(ref lit) = cond.node {
  83                 if let ast::LitKind::Bool(true) = lit.node {
  84                     if lit.span.ctxt() == SyntaxContext::empty() {
  85                         let msg = "denote infinite loops with `loop { ... }`";
  86                         let condition_span = cx.tcx.sess.source_map().def_span(e.span);
  87                         let mut err = cx.struct_span_lint(WHILE_TRUE, condition_span, msg);
  88                         err.span_suggestion_short(
  89                             condition_span,
  90                             "use `loop`",
  91                             "loop".to_owned(),
  92                             Applicability::MachineApplicable
  93                         );
  94                         err.emit();
  95                     }
  96                 }
  97             }
  98         }
  99     }
 100 }
 101
 102 declare_lint! {
 103     BOX_POINTERS,
 104     Allow,
 105     "use of owned (Box type) heap memory"
 106 }
 107
 108 #[derive(Copy, Clone)]
 109 pub struct BoxPointers;
 110
 111 impl BoxPointers {
 112     fn check_heap_type<'a, 'tcx>(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
 113         for leaf_ty in ty.walk() {
 114             if leaf_ty.is_box() {
 115                 let m = format!("type uses owned (Box type) pointers: {}", ty);
 116                 cx.span_lint(BOX_POINTERS, span, &m);
 117             }
 118         }
 119     }
 120 }
 121
 122 impl LintPass for BoxPointers {
 123     fn name(&self) -> &'static str {
 124         "BoxPointers"
 125     }
 126
 127     fn get_lints(&self) -> LintArray {
 128         lint_array!(BOX_POINTERS)
 129     }
 130 }
 131
 132 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 133     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 134         match it.node {
 135             hir::ItemKind::Fn(..) |
 136             hir::ItemKind::Ty(..) |
 137             hir::ItemKind::Enum(..) |
 138             hir::ItemKind::Struct(..) |
 139             hir::ItemKind::Union(..) => {
 140                 let def_id = cx.tcx.hir().local_def_id_from_hir_id(it.hir_id);
 141                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 142             }
 143             _ => ()
 144         }
 145
 146         // If it's a struct, we also have to check the fields' types
 147         match it.node {
 148             hir::ItemKind::Struct(ref struct_def, _) |
 149             hir::ItemKind::Union(ref struct_def, _) => {
 150                 for struct_field in struct_def.fields() {
 151                     let def_id = cx.tcx.hir().local_def_id_from_hir_id(struct_field.hir_id);
 152                     self.check_heap_type(cx, struct_field.span,
 153                                          cx.tcx.type_of(def_id));
 154                 }
 155             }
 156             _ => (),
 157         }
 158     }
 159
 160     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
 161         let ty = cx.tables.node_type(e.hir_id);
 162         self.check_heap_type(cx, e.span, ty);
 163     }
 164 }
 165
 166 declare_lint! {
 167     NON_SHORTHAND_FIELD_PATTERNS,
 168     Warn,
 169     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 170 }
 171
 172 #[derive(Copy, Clone)]
 173 pub struct NonShorthandFieldPatterns;
 174
 175 impl LintPass for NonShorthandFieldPatterns {
 176     fn name(&self) -> &'static str {
 177         "NonShorthandFieldPatterns"
 178     }
 179
 180     fn get_lints(&self) -> LintArray {
 181         lint_array!(NON_SHORTHAND_FIELD_PATTERNS)
 182     }
 183 }
 184
 185 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 186     fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat) {
 187         if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.node {
 188             let variant = cx.tables.pat_ty(pat).ty_adt_def()
 189                                    .expect("struct pattern type is not an ADT")
 190                                    .variant_of_def(cx.tables.qpath_def(qpath, pat.hir_id));
 191             for fieldpat in field_pats {
 192                 if fieldpat.node.is_shorthand {
 193                     continue;
 194                 }
 195                 if fieldpat.span.ctxt().outer().expn_info().is_some() {
 196                     // Don't lint if this is a macro expansion: macro authors
 197                     // shouldn't have to worry about this kind of style issue
 198                     // (Issue #49588)
 199                     continue;
 200                 }
 201                 if let PatKind::Binding(_, _, ident, None) = fieldpat.node.pat.node {
 202                     if cx.tcx.find_field_index(ident, &variant) ==
 203                        Some(cx.tcx.field_index(fieldpat.node.hir_id, cx.tables)) {
 204                         let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
 205                                      fieldpat.span,
 206                                      &format!("the `{}:` in this pattern is redundant", ident));
 207                         let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
 208                                                                                  ':');
 209                         err.span_suggestion_short(
 210                             subspan,
 211                             "remove this",
 212                             ident.to_string(),
 213                             Applicability::MachineApplicable
 214                         );
 215                         err.emit();
 216                     }
 217                 }
 218             }
 219         }
 220     }
 221 }
 222
 223 declare_lint! {
 224     UNSAFE_CODE,
 225     Allow,
 226     "usage of `unsafe` code"
 227 }
 228
 229 #[derive(Copy, Clone)]
 230 pub struct UnsafeCode;
 231
 232 impl LintPass for UnsafeCode {
 233     fn name(&self) -> &'static str {
 234         "UnsafeCode"
 235     }
 236
 237     fn get_lints(&self) -> LintArray {
 238         lint_array!(UNSAFE_CODE)
 239     }
 240 }
 241
 242 impl UnsafeCode {
 243     fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
 244         // This comes from a macro that has #[allow_internal_unsafe].
 245         if span.allows_unsafe() {
 246             return;
 247         }
 248
 249         cx.span_lint(UNSAFE_CODE, span, desc);
 250     }
 251 }
 252
 253 impl EarlyLintPass for UnsafeCode {
 254     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 255         if attr.check_name("allow_internal_unsafe") {
 256             self.report_unsafe(cx, attr.span, "`allow_internal_unsafe` allows defining \
 257                                                macros using unsafe without triggering \
 258                                                the `unsafe_code` lint at their call site");
 259         }
 260     }
 261
 262     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 263         if let ast::ExprKind::Block(ref blk, _) = e.node {
 264             // Don't warn about generated blocks, that'll just pollute the output.
 265             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 266                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
 267             }
 268         }
 269     }
 270
 271     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 272         match it.node {
 273             ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
 274                 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
 275             }
 276
 277             ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
 278                 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
 279             }
 280
 281             _ => return,
 282         }
 283     }
 284
 285     fn check_fn(&mut self,
 286                 cx: &EarlyContext<'_>,
 287                 fk: FnKind<'_>,
 288                 _: &ast::FnDecl,
 289                 span: Span,
 290                 _: ast::NodeId) {
 291         match fk {
 292             FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
 293                 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
 294             }
 295
 296             FnKind::Method(_, sig, ..) => {
 297                 if sig.header.unsafety == ast::Unsafety::Unsafe {
 298                     self.report_unsafe(cx, span, "implementation of an `unsafe` method")
 299                 }
 300             }
 301
 302             _ => (),
 303         }
 304     }
 305
 306     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::TraitItem) {
 307         if let ast::TraitItemKind::Method(ref sig, None) = item.node {
 308             if sig.header.unsafety == ast::Unsafety::Unsafe {
 309                 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
 310             }
 311         }
 312     }
 313 }
 314
 315 declare_lint! {
 316     pub MISSING_DOCS,
 317     Allow,
 318     "detects missing documentation for public members",
 319     report_in_external_macro: true
 320 }
 321
 322 pub struct MissingDoc {
 323     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 324     doc_hidden_stack: Vec<bool>,
 325
 326     /// Private traits or trait items that leaked through. Don't check their methods.
 327     private_traits: FxHashSet<hir::HirId>,
 328 }
 329
 330 fn has_doc(attr: &ast::Attribute) -> bool {
 331     if !attr.check_name("doc") {
 332         return false;
 333     }
 334
 335     if attr.is_value_str() {
 336         return true;
 337     }
 338
 339     if let Some(list) = attr.meta_item_list() {
 340         for meta in list {
 341             if meta.check_name("include") || meta.check_name("hidden") {
 342                 return true;
 343             }
 344         }
 345     }
 346
 347     false
 348 }
 349
 350 impl MissingDoc {
 351     pub fn new() -> MissingDoc {
 352         MissingDoc {
 353             doc_hidden_stack: vec![false],
 354             private_traits: FxHashSet::default(),
 355         }
 356     }
 357
 358     fn doc_hidden(&self) -> bool {
 359         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 360     }
 361
 362     fn check_missing_docs_attrs(&self,
 363                                 cx: &LateContext<'_, '_>,
 364                                 id: Option<hir::HirId>,
 365                                 attrs: &[ast::Attribute],
 366                                 sp: Span,
 367                                 desc: &'static str) {
 368         // If we're building a test harness, then warning about
 369         // documentation is probably not really relevant right now.
 370         if cx.sess().opts.test {
 371             return;
 372         }
 373
 374         // `#[doc(hidden)]` disables missing_docs check.
 375         if self.doc_hidden() {
 376             return;
 377         }
 378
 379         // Only check publicly-visible items, using the result from the privacy pass.
 380         // It's an option so the crate root can also use this function (it doesn't
 381         // have a NodeId).
 382         if let Some(id) = id {
 383             if !cx.access_levels.is_exported(id) {
 384                 return;
 385             }
 386         }
 387
 388         let has_doc = attrs.iter().any(|a| has_doc(a));
 389         if !has_doc {
 390             cx.span_lint(MISSING_DOCS,
 391                          cx.tcx.sess.source_map().def_span(sp),
 392                          &format!("missing documentation for {}", desc));
 393         }
 394     }
 395 }
 396
 397 impl LintPass for MissingDoc {
 398     fn name(&self) -> &'static str {
 399         "MissingDoc"
 400     }
 401
 402     fn get_lints(&self) -> LintArray {
 403         lint_array!(MISSING_DOCS)
 404     }
 405 }
 406
 407 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 408     fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
 409         let doc_hidden = self.doc_hidden() ||
 410                          attrs.iter().any(|attr| {
 411             attr.check_name("doc") &&
 412             match attr.meta_item_list() {
 413                 None => false,
 414                 Some(l) => attr::list_contains_name(&l, "hidden"),
 415             }
 416         });
 417         self.doc_hidden_stack.push(doc_hidden);
 418     }
 419
 420     fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
 421         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 422     }
 423
 424     fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate) {
 425         self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
 426
 427         for macro_def in &krate.exported_macros {
 428             let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
 429             if !has_doc {
 430                 cx.span_lint(MISSING_DOCS,
 431                              cx.tcx.sess.source_map().def_span(macro_def.span),
 432                              "missing documentation for macro");
 433             }
 434         }
 435     }
 436
 437     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 438         let desc = match it.node {
 439             hir::ItemKind::Fn(..) => "a function",
 440             hir::ItemKind::Mod(..) => "a module",
 441             hir::ItemKind::Enum(..) => "an enum",
 442             hir::ItemKind::Struct(..) => "a struct",
 443             hir::ItemKind::Union(..) => "a union",
 444             hir::ItemKind::Trait(.., ref trait_item_refs) => {
 445                 // Issue #11592, traits are always considered exported, even when private.
 446                 if let hir::VisibilityKind::Inherited = it.vis.node {
 447                     self.private_traits.insert(it.hir_id);
 448                     for trait_item_ref in trait_item_refs {
 449                         self.private_traits.insert(trait_item_ref.id.hir_id);
 450                     }
 451                     return;
 452                 }
 453                 "a trait"
 454             }
 455             hir::ItemKind::Ty(..) => "a type alias",
 456             hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
 457                 // If the trait is private, add the impl items to private_traits so they don't get
 458                 // reported for missing docs.
 459                 let real_trait = trait_ref.path.def.def_id();
 460                 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
 461                     match cx.tcx.hir().find_by_hir_id(hir_id) {
 462                         Some(Node::Item(item)) => {
 463                             if let hir::VisibilityKind::Inherited = item.vis.node {
 464                                 for impl_item_ref in impl_item_refs {
 465                                     self.private_traits.insert(impl_item_ref.id.hir_id);
 466                                 }
 467                             }
 468                         }
 469                         _ => {}
 470                     }
 471                 }
 472                 return;
 473             }
 474             hir::ItemKind::Const(..) => "a constant",
 475             hir::ItemKind::Static(..) => "a static",
 476             _ => return,
 477         };
 478
 479         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
 480     }
 481
 482     fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem) {
 483         if self.private_traits.contains(&trait_item.hir_id) {
 484             return;
 485         }
 486
 487         let desc = match trait_item.node {
 488             hir::TraitItemKind::Const(..) => "an associated constant",
 489             hir::TraitItemKind::Method(..) => "a trait method",
 490             hir::TraitItemKind::Type(..) => "an associated type",
 491         };
 492
 493         self.check_missing_docs_attrs(cx,
 494                                       Some(trait_item.hir_id),
 495                                       &trait_item.attrs,
 496                                       trait_item.span,
 497                                       desc);
 498     }
 499
 500     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
 501         // If the method is an impl for a trait, don't doc.
 502         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 503             return;
 504         }
 505
 506         let desc = match impl_item.node {
 507             hir::ImplItemKind::Const(..) => "an associated constant",
 508             hir::ImplItemKind::Method(..) => "a method",
 509             hir::ImplItemKind::Type(_) => "an associated type",
 510             hir::ImplItemKind::Existential(_) => "an associated existential type",
 511         };
 512         self.check_missing_docs_attrs(cx,
 513                                       Some(impl_item.hir_id),
 514                                       &impl_item.attrs,
 515                                       impl_item.span,
 516                                       desc);
 517     }
 518
 519     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField) {
 520         if !sf.is_positional() {
 521             self.check_missing_docs_attrs(cx,
 522                                           Some(sf.hir_id),
 523                                           &sf.attrs,
 524                                           sf.span,
 525                                           "a struct field")
 526         }
 527     }
 528
 529     fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant, _: &hir::Generics) {
 530         self.check_missing_docs_attrs(cx,
 531                                       Some(v.node.data.hir_id()),
 532                                       &v.node.attrs,
 533                                       v.span,
 534                                       "a variant");
 535     }
 536 }
 537
 538 declare_lint! {
 539     pub MISSING_COPY_IMPLEMENTATIONS,
 540     Allow,
 541     "detects potentially-forgotten implementations of `Copy`"
 542 }
 543
 544 #[derive(Copy, Clone)]
 545 pub struct MissingCopyImplementations;
 546
 547 impl LintPass for MissingCopyImplementations {
 548     fn name(&self) -> &'static str {
 549         "MissingCopyImplementations"
 550     }
 551
 552     fn get_lints(&self) -> LintArray {
 553         lint_array!(MISSING_COPY_IMPLEMENTATIONS)
 554     }
 555 }
 556
 557 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 558     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
 559         if !cx.access_levels.is_reachable(item.hir_id) {
 560             return;
 561         }
 562         let (def, ty) = match item.node {
 563             hir::ItemKind::Struct(_, ref ast_generics) => {
 564                 if !ast_generics.params.is_empty() {
 565                     return;
 566                 }
 567                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id_from_hir_id(item.hir_id));
 568                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 569             }
 570             hir::ItemKind::Union(_, ref ast_generics) => {
 571                 if !ast_generics.params.is_empty() {
 572                     return;
 573                 }
 574                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id_from_hir_id(item.hir_id));
 575                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 576             }
 577             hir::ItemKind::Enum(_, ref ast_generics) => {
 578                 if !ast_generics.params.is_empty() {
 579                     return;
 580                 }
 581                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id_from_hir_id(item.hir_id));
 582                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 583             }
 584             _ => return,
 585         };
 586         if def.has_dtor(cx.tcx) {
 587             return;
 588         }
 589         let param_env = ty::ParamEnv::empty();
 590         if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
 591             return;
 592         }
 593         if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
 594             cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
 595                          item.span,
 596                          "type could implement `Copy`; consider adding `impl \
 597                           Copy`")
 598         }
 599     }
 600 }
 601
 602 declare_lint! {
 603     MISSING_DEBUG_IMPLEMENTATIONS,
 604     Allow,
 605     "detects missing implementations of fmt::Debug"
 606 }
 607
 608 pub struct MissingDebugImplementations {
 609     impling_types: Option<HirIdSet>,
 610 }
 611
 612 impl MissingDebugImplementations {
 613     pub fn new() -> MissingDebugImplementations {
 614         MissingDebugImplementations { impling_types: None }
 615     }
 616 }
 617
 618 impl LintPass for MissingDebugImplementations {
 619     fn name(&self) -> &'static str {
 620         "MissingDebugImplementations"
 621     }
 622
 623     fn get_lints(&self) -> LintArray {
 624         lint_array!(MISSING_DEBUG_IMPLEMENTATIONS)
 625     }
 626 }
 627
 628 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 629     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
 630         if !cx.access_levels.is_reachable(item.hir_id) {
 631             return;
 632         }
 633
 634         match item.node {
 635             hir::ItemKind::Struct(..) |
 636             hir::ItemKind::Union(..) |
 637             hir::ItemKind::Enum(..) => {}
 638             _ => return,
 639         }
 640
 641         let debug = match cx.tcx.lang_items().debug_trait() {
 642             Some(debug) => debug,
 643             None => return,
 644         };
 645
 646         if self.impling_types.is_none() {
 647             let mut impls = HirIdSet::default();
 648             cx.tcx.for_each_impl(debug, |d| {
 649                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 650                     if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
 651                         impls.insert(hir_id);
 652                     }
 653                 }
 654             });
 655
 656             self.impling_types = Some(impls);
 657             debug!("{:?}", self.impling_types);
 658         }
 659
 660         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 661             cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
 662                          item.span,
 663                          "type does not implement `fmt::Debug`; consider adding #[derive(Debug)] \
 664                           or a manual implementation")
 665         }
 666     }
 667 }
 668
 669 declare_lint! {
 670     pub ANONYMOUS_PARAMETERS,
 671     Allow,
 672     "detects anonymous parameters"
 673 }
 674
 675 /// Checks for use of anonymous parameters (RFC 1685).
 676 #[derive(Copy, Clone)]
 677 pub struct AnonymousParameters;
 678
 679 impl LintPass for AnonymousParameters {
 680     fn name(&self) -> &'static str {
 681         "AnonymousParameters"
 682     }
 683
 684     fn get_lints(&self) -> LintArray {
 685         lint_array!(ANONYMOUS_PARAMETERS)
 686     }
 687 }
 688
 689 impl EarlyLintPass for AnonymousParameters {
 690     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::TraitItem) {
 691         match it.node {
 692             ast::TraitItemKind::Method(ref sig, _) => {
 693                 for arg in sig.decl.inputs.iter() {
 694                     match arg.pat.node {
 695                         ast::PatKind::Ident(_, ident, None) => {
 696                             if ident.name == keywords::Invalid.name() {
 697                                 let ty_snip = cx
 698                                     .sess
 699                                     .source_map()
 700                                     .span_to_snippet(arg.ty.span);
 701
 702                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 703                                     (snip, Applicability::MachineApplicable)
 704                                 } else {
 705                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 706                                 };
 707
 708                                 cx.struct_span_lint(
 709                                     ANONYMOUS_PARAMETERS,
 710                                     arg.pat.span,
 711                                     "anonymous parameters are deprecated and will be \
 712                                      removed in the next edition."
 713                                 ).span_suggestion(
 714                                     arg.pat.span,
 715                                     "Try naming the parameter or explicitly \
 716                                     ignoring it",
 717                                     format!("_: {}", ty_snip),
 718                                     appl
 719                                 ).emit();
 720                             }
 721                         }
 722                         _ => (),
 723                     }
 724                 }
 725             },
 726             _ => (),
 727         }
 728     }
 729 }
 730
 731 /// Check for use of attributes which have been deprecated.
 732 #[derive(Clone)]
 733 pub struct DeprecatedAttr {
 734     // This is not free to compute, so we want to keep it around, rather than
 735     // compute it for every attribute.
 736     depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeTemplate, AttributeGate)>,
 737 }
 738
 739 impl DeprecatedAttr {
 740     pub fn new() -> DeprecatedAttr {
 741         DeprecatedAttr {
 742             depr_attrs: deprecated_attributes(),
 743         }
 744     }
 745 }
 746
 747 impl LintPass for DeprecatedAttr {
 748     fn name(&self) -> &'static str {
 749         "DeprecatedAttr"
 750     }
 751
 752     fn get_lints(&self) -> LintArray {
 753         lint_array!()
 754     }
 755 }
 756
 757 impl EarlyLintPass for DeprecatedAttr {
 758     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 759         for &&(n, _, _, ref g) in &self.depr_attrs {
 760             if attr.ident_str() == Some(n) {
 761                 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
 762                                              ref name,
 763                                              ref reason,
 764                                              _) = g {
 765                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
 766                                       name, reason, link);
 767                     let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
 768                     err.span_suggestion_short(
 769                         attr.span,
 770                         suggestion.unwrap_or("remove this attribute"),
 771                         String::new(),
 772                         Applicability::MachineApplicable
 773                     );
 774                     err.emit();
 775                 }
 776                 return;
 777             }
 778         }
 779     }
 780 }
 781
 782 declare_lint! {
 783     pub UNUSED_DOC_COMMENTS,
 784     Warn,
 785     "detects doc comments that aren't used by rustdoc"
 786 }
 787
 788 #[derive(Copy, Clone)]
 789 pub struct UnusedDocComment;
 790
 791 impl LintPass for UnusedDocComment {
 792     fn name(&self) -> &'static str {
 793         "UnusedDocComment"
 794     }
 795
 796     fn get_lints(&self) -> LintArray {
 797         lint_array![UNUSED_DOC_COMMENTS]
 798     }
 799 }
 800
 801 impl UnusedDocComment {
 802     fn warn_if_doc(
 803         &self,
 804         cx: &EarlyContext<'_>,
 805         node_span: Span,
 806         node_kind: &str,
 807         is_macro_expansion: bool,
 808         attrs: &[ast::Attribute]
 809     ) {
 810         let mut attrs = attrs.into_iter().peekable();
 811
 812         // Accumulate a single span for sugared doc comments.
 813         let mut sugared_span: Option<Span> = None;
 814
 815         while let Some(attr) = attrs.next() {
 816             if attr.is_sugared_doc {
 817                 sugared_span = Some(
 818                     sugared_span.map_or_else(
 819                         || attr.span,
 820                         |span| span.with_hi(attr.span.hi()),
 821                     ),
 822                 );
 823             }
 824
 825             if attrs.peek().map(|next_attr| next_attr.is_sugared_doc).unwrap_or_default() {
 826                 continue;
 827             }
 828
 829             let span = sugared_span.take().unwrap_or_else(|| attr.span);
 830
 831             if attr.check_name("doc") {
 832                 let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
 833
 834                 err.span_label(
 835                     node_span,
 836                     format!("rustdoc does not generate documentation for {}", node_kind)
 837                 );
 838
 839                 if is_macro_expansion {
 840                     err.help("to document an item produced by a macro, \
 841                               the macro must produce the documentation as part of its expansion");
 842                 }
 843
 844                 err.emit();
 845             }
 846         }
 847     }
 848 }
 849
 850 impl EarlyLintPass for UnusedDocComment {
 851     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 852         if let ast::ItemKind::Mac(..) = item.node {
 853             self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
 854         }
 855     }
 856
 857     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 858         let (kind, is_macro_expansion) = match stmt.node {
 859             ast::StmtKind::Local(..) => ("statements", false),
 860             ast::StmtKind::Item(..) => ("inner items", false),
 861             ast::StmtKind::Mac(..) => ("macro expansions", true),
 862             // expressions will be reported by `check_expr`.
 863             ast::StmtKind::Semi(..) |
 864             ast::StmtKind::Expr(..) => return,
 865         };
 866
 867         self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.node.attrs());
 868     }
 869
 870     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 871         let arm_span = arm.pats[0].span.with_hi(arm.body.span.hi());
 872         self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
 873     }
 874
 875     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 876         self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
 877     }
 878 }
 879
 880 declare_lint! {
 881     PLUGIN_AS_LIBRARY,
 882     Warn,
 883     "compiler plugin used as ordinary library in non-plugin crate"
 884 }
 885
 886 #[derive(Copy, Clone)]
 887 pub struct PluginAsLibrary;
 888
 889 impl LintPass for PluginAsLibrary {
 890     fn name(&self) -> &'static str {
 891         "PluginAsLibrary"
 892     }
 893
 894     fn get_lints(&self) -> LintArray {
 895         lint_array![PLUGIN_AS_LIBRARY]
 896     }
 897 }
 898
 899 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
 900     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 901         if cx.tcx.plugin_registrar_fn(LOCAL_CRATE).is_some() {
 902             // We're compiling a plugin; it's fine to link other plugins.
 903             return;
 904         }
 905
 906         match it.node {
 907             hir::ItemKind::ExternCrate(..) => (),
 908             _ => return,
 909         };
 910
 911         let def_id = cx.tcx.hir().local_def_id_from_hir_id(it.hir_id);
 912         let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
 913             Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
 914             None => {
 915                 // Probably means we aren't linking the crate for some reason.
 916                 //
 917                 // Not sure if / when this could happen.
 918                 return;
 919             }
 920         };
 921
 922         if prfn.is_some() {
 923             cx.span_lint(PLUGIN_AS_LIBRARY,
 924                          it.span,
 925                          "compiler plugin used as an ordinary library");
 926         }
 927     }
 928 }
 929
 930 declare_lint! {
 931     NO_MANGLE_CONST_ITEMS,
 932     Deny,
 933     "const items will not have their symbols exported"
 934 }
 935
 936 declare_lint! {
 937     NO_MANGLE_GENERIC_ITEMS,
 938     Warn,
 939     "generic items must be mangled"
 940 }
 941
 942 #[derive(Copy, Clone)]
 943 pub struct InvalidNoMangleItems;
 944
 945 impl LintPass for InvalidNoMangleItems {
 946     fn name(&self) -> &'static str {
 947         "InvalidNoMangleItems"
 948     }
 949
 950     fn get_lints(&self) -> LintArray {
 951         lint_array!(NO_MANGLE_CONST_ITEMS,
 952                     NO_MANGLE_GENERIC_ITEMS)
 953     }
 954 }
 955
 956 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
 957     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 958         match it.node {
 959             hir::ItemKind::Fn(.., ref generics, _) => {
 960                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, "no_mangle") {
 961                     for param in &generics.params {
 962                         match param.kind {
 963                             GenericParamKind::Lifetime { .. } => {}
 964                             GenericParamKind::Type { .. } |
 965                             GenericParamKind::Const { .. } => {
 966                                 let mut err = cx.struct_span_lint(
 967                                     NO_MANGLE_GENERIC_ITEMS,
 968                                     it.span,
 969                                     "functions generic over types or consts must be mangled",
 970                                 );
 971                                 err.span_suggestion_short(
 972                                     no_mangle_attr.span,
 973                                     "remove this attribute",
 974                                     String::new(),
 975                                     // Use of `#[no_mangle]` suggests FFI intent; correct
 976                                     // fix may be to monomorphize source by hand
 977                                     Applicability::MaybeIncorrect
 978                                 );
 979                                 err.emit();
 980                                 break;
 981                             }
 982                         }
 983                     }
 984                 }
 985             }
 986             hir::ItemKind::Const(..) => {
 987                 if attr::contains_name(&it.attrs, "no_mangle") {
 988                     // Const items do not refer to a particular location in memory, and therefore
 989                     // don't have anything to attach a symbol to
 990                     let msg = "const items should never be #[no_mangle]";
 991                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
 992
 993                     // account for "pub const" (#45562)
 994                     let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
 995                         .map(|snippet| snippet.find("const").unwrap_or(0))
 996                         .unwrap_or(0) as u32;
 997                     // `const` is 5 chars
 998                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 999                     err.span_suggestion(
1000                         const_span,
1001                         "try a static value",
1002                         "pub static".to_owned(),
1003                         Applicability::MachineApplicable
1004                     );
1005                     err.emit();
1006                 }
1007             }
1008             _ => {}
1009         }
1010     }
1011 }
1012
1013 #[derive(Clone, Copy)]
1014 pub struct MutableTransmutes;
1015
1016 declare_lint! {
1017     MUTABLE_TRANSMUTES,
1018     Deny,
1019     "mutating transmuted &mut T from &T may cause undefined behavior"
1020 }
1021
1022 impl LintPass for MutableTransmutes {
1023     fn name(&self) -> &'static str {
1024         "MutableTransmutes"
1025     }
1026
1027     fn get_lints(&self) -> LintArray {
1028         lint_array!(MUTABLE_TRANSMUTES)
1029     }
1030 }
1031
1032 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
1033     fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1034         use rustc_target::spec::abi::Abi::RustIntrinsic;
1035
1036         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1037                    consider instead using an UnsafeCell";
1038         match get_transmute_from_to(cx, expr) {
1039             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
1040                 if to_mt == hir::Mutability::MutMutable &&
1041                    from_mt == hir::Mutability::MutImmutable {
1042                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
1043                 }
1044             }
1045             _ => (),
1046         }
1047
1048         fn get_transmute_from_to<'a, 'tcx>
1049             (cx: &LateContext<'a, 'tcx>,
1050              expr: &hir::Expr)
1051              -> Option<(&'tcx ty::TyKind<'tcx>, &'tcx ty::TyKind<'tcx>)> {
1052             let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
1053                 cx.tables.qpath_def(qpath, expr.hir_id)
1054             } else {
1055                 return None;
1056             };
1057             if let Def::Fn(did) = def {
1058                 if !def_id_is_transmute(cx, did) {
1059                     return None;
1060                 }
1061                 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
1062                 let from = sig.inputs().skip_binder()[0];
1063                 let to = *sig.output().skip_binder();
1064                 return Some((&from.sty, &to.sty));
1065             }
1066             None
1067         }
1068
1069         fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
1070             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
1071             cx.tcx.item_name(def_id) == "transmute"
1072         }
1073     }
1074 }
1075
1076 /// Forbids using the `#[feature(...)]` attribute
1077 #[derive(Copy, Clone)]
1078 pub struct UnstableFeatures;
1079
1080 declare_lint! {
1081     UNSTABLE_FEATURES,
1082     Allow,
1083     "enabling unstable features (deprecated. do not use)"
1084 }
1085
1086 impl LintPass for UnstableFeatures {
1087     fn name(&self) -> &'static str {
1088         "UnstableFeatures"
1089     }
1090
1091     fn get_lints(&self) -> LintArray {
1092         lint_array!(UNSTABLE_FEATURES)
1093     }
1094 }
1095
1096 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
1097     fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
1098         if attr.check_name("feature") {
1099             if let Some(items) = attr.meta_item_list() {
1100                 for item in items {
1101                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
1102                 }
1103             }
1104         }
1105     }
1106 }
1107
1108 /// Lint for unions that contain fields with possibly non-trivial destructors.
1109 pub struct UnionsWithDropFields;
1110
1111 declare_lint! {
1112     UNIONS_WITH_DROP_FIELDS,
1113     Warn,
1114     "use of unions that contain fields with possibly non-trivial drop code"
1115 }
1116
1117 impl LintPass for UnionsWithDropFields {
1118     fn name(&self) -> &'static str {
1119         "UnionsWithDropFields"
1120     }
1121
1122     fn get_lints(&self) -> LintArray {
1123         lint_array!(UNIONS_WITH_DROP_FIELDS)
1124     }
1125 }
1126
1127 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
1128     fn check_item(&mut self, ctx: &LateContext<'_, '_>, item: &hir::Item) {
1129         if let hir::ItemKind::Union(ref vdata, _) = item.node {
1130             for field in vdata.fields() {
1131                 let field_ty = ctx.tcx.type_of(
1132                     ctx.tcx.hir().local_def_id_from_hir_id(field.hir_id));
1133                 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1134                     ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1135                                   field.span,
1136                                   "union contains a field with possibly non-trivial drop code, \
1137                                    drop code of union fields is ignored when dropping the union");
1138                     return;
1139                 }
1140             }
1141         }
1142     }
1143 }
1144
1145 /// Lint for items marked `pub` that aren't reachable from other crates.
1146 #[derive(Copy, Clone)]
1147 pub struct UnreachablePub;
1148
1149 declare_lint! {
1150     pub UNREACHABLE_PUB,
1151     Allow,
1152     "`pub` items not reachable from crate root"
1153 }
1154
1155 impl LintPass for UnreachablePub {
1156     fn name(&self) -> &'static str {
1157         "UnreachablePub"
1158     }
1159
1160     fn get_lints(&self) -> LintArray {
1161         lint_array!(UNREACHABLE_PUB)
1162     }
1163 }
1164
1165 impl UnreachablePub {
1166     fn perform_lint(&self, cx: &LateContext<'_, '_>, what: &str, id: hir::HirId,
1167                     vis: &hir::Visibility, span: Span, exportable: bool) {
1168         let mut applicability = Applicability::MachineApplicable;
1169         match vis.node {
1170             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1171                 if span.ctxt().outer().expn_info().is_some() {
1172                     applicability = Applicability::MaybeIncorrect;
1173                 }
1174                 let def_span = cx.tcx.sess.source_map().def_span(span);
1175                 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1176                                                   &format!("unreachable `pub` {}", what));
1177                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1178                     "crate"
1179                 } else {
1180                     "pub(crate)"
1181                 }.to_owned();
1182
1183                 err.span_suggestion(
1184                     vis.span,
1185                     "consider restricting its visibility",
1186                     replacement,
1187                     applicability,
1188                 );
1189                 if exportable {
1190                     err.help("or consider exporting it for use by other crates");
1191                 }
1192                 err.emit();
1193             },
1194             _ => {}
1195         }
1196     }
1197 }
1198
1199
1200 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1201     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1202         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1203     }
1204
1205     fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, foreign_item: &hir::ForeignItem) {
1206         self.perform_lint(cx, "item", foreign_item.hir_id, &foreign_item.vis,
1207                           foreign_item.span, true);
1208     }
1209
1210     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
1211         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1212     }
1213
1214     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
1215         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1216     }
1217 }
1218
1219 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1220 /// They are relevant when using associated types, but otherwise neither checked
1221 /// at definition site nor enforced at use site.
1222
1223 pub struct TypeAliasBounds;
1224
1225 declare_lint! {
1226     TYPE_ALIAS_BOUNDS,
1227     Warn,
1228     "bounds in type aliases are not enforced"
1229 }
1230
1231 impl LintPass for TypeAliasBounds {
1232     fn name(&self) -> &'static str {
1233         "TypeAliasBounds"
1234     }
1235
1236     fn get_lints(&self) -> LintArray {
1237         lint_array!(TYPE_ALIAS_BOUNDS)
1238     }
1239 }
1240
1241 impl TypeAliasBounds {
1242     fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1243         match *qpath {
1244             hir::QPath::TypeRelative(ref ty, _) => {
1245                 // If this is a type variable, we found a `T::Assoc`.
1246                 match ty.node {
1247                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1248                         match path.def {
1249                             Def::TyParam(_) => true,
1250                             _ => false
1251                         }
1252                     }
1253                     _ => false
1254                 }
1255             }
1256             hir::QPath::Resolved(..) => false,
1257         }
1258     }
1259
1260     fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder<'_>) {
1261         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1262         // bound.  Let's see if this type does that.
1263
1264         // We use a HIR visitor to walk the type.
1265         use rustc::hir::intravisit::{self, Visitor};
1266         struct WalkAssocTypes<'a, 'db> where 'db: 'a {
1267             err: &'a mut DiagnosticBuilder<'db>
1268         }
1269         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1270             fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1271             {
1272                 intravisit::NestedVisitorMap::None
1273             }
1274
1275             fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1276                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1277                     self.err.span_help(span,
1278                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1279                          associated types in type aliases");
1280                 }
1281                 intravisit::walk_qpath(self, qpath, id, span)
1282             }
1283         }
1284
1285         // Let's go for a walk!
1286         let mut visitor = WalkAssocTypes { err };
1287         visitor.visit_ty(ty);
1288     }
1289 }
1290
1291 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1292     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1293         let (ty, type_alias_generics) = match item.node {
1294             hir::ItemKind::Ty(ref ty, ref generics) => (&*ty, generics),
1295             _ => return,
1296         };
1297         let mut suggested_changing_assoc_types = false;
1298         // There must not be a where clause
1299         if !type_alias_generics.where_clause.predicates.is_empty() {
1300             let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1301                 .map(|pred| pred.span()).collect();
1302             let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1303                 "where clauses are not enforced in type aliases");
1304             err.help("the clause will not be checked when the type alias is used, \
1305                       and should be removed");
1306             if !suggested_changing_assoc_types {
1307                 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1308                 suggested_changing_assoc_types = true;
1309             }
1310             err.emit();
1311         }
1312         // The parameters must not have bounds
1313         for param in type_alias_generics.params.iter() {
1314             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1315             if !spans.is_empty() {
1316                 let mut err = cx.struct_span_lint(
1317                     TYPE_ALIAS_BOUNDS,
1318                     spans,
1319                     "bounds on generic parameters are not enforced in type aliases",
1320                 );
1321                 err.help("the bound will not be checked when the type alias is used, \
1322                           and should be removed");
1323                 if !suggested_changing_assoc_types {
1324                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1325                     suggested_changing_assoc_types = true;
1326                 }
1327                 err.emit();
1328             }
1329         }
1330     }
1331 }
1332
1333 /// Lint constants that are erroneous.
1334 /// Without this lint, we might not get any diagnostic if the constant is
1335 /// unused within this crate, even though downstream crates can't use it
1336 /// without producing an error.
1337 pub struct UnusedBrokenConst;
1338
1339 impl LintPass for UnusedBrokenConst {
1340     fn name(&self) -> &'static str {
1341         "UnusedBrokenConst"
1342     }
1343
1344     fn get_lints(&self) -> LintArray {
1345         lint_array!()
1346     }
1347 }
1348 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1349     let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1350     let is_static = cx.tcx.is_static(def_id).is_some();
1351     let param_env = if is_static {
1352         // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1353         ty::ParamEnv::reveal_all()
1354     } else {
1355         cx.tcx.param_env(def_id)
1356     };
1357     let cid = ::rustc::mir::interpret::GlobalId {
1358         instance: ty::Instance::mono(cx.tcx, def_id),
1359         promoted: None
1360     };
1361     // trigger the query once for all constants since that will already report the errors
1362     let _ = cx.tcx.const_eval(param_env.and(cid));
1363 }
1364
1365 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1366     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1367         match it.node {
1368             hir::ItemKind::Const(_, body_id) => {
1369                 check_const(cx, body_id);
1370             },
1371             hir::ItemKind::Static(_, _, body_id) => {
1372                 check_const(cx, body_id);
1373             },
1374             _ => {},
1375         }
1376     }
1377 }
1378
1379 /// Lint for trait and lifetime bounds that don't depend on type parameters
1380 /// which either do nothing, or stop the item from being used.
1381 pub struct TrivialConstraints;
1382
1383 declare_lint! {
1384     TRIVIAL_BOUNDS,
1385     Warn,
1386     "these bounds don't depend on an type parameters"
1387 }
1388
1389 impl LintPass for TrivialConstraints {
1390     fn name(&self) -> &'static str {
1391         "TrivialConstraints"
1392     }
1393
1394     fn get_lints(&self) -> LintArray {
1395         lint_array!(TRIVIAL_BOUNDS)
1396     }
1397 }
1398
1399 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1400     fn check_item(
1401         &mut self,
1402         cx: &LateContext<'a, 'tcx>,
1403         item: &'tcx hir::Item,
1404     ) {
1405         use rustc::ty::fold::TypeFoldable;
1406         use rustc::ty::Predicate::*;
1407
1408
1409         if cx.tcx.features().trivial_bounds {
1410             let def_id = cx.tcx.hir().local_def_id_from_hir_id(item.hir_id);
1411             let predicates = cx.tcx.predicates_of(def_id);
1412             for &(predicate, span) in &predicates.predicates {
1413                 let predicate_kind_name = match predicate {
1414                     Trait(..) => "Trait",
1415                     TypeOutlives(..) |
1416                     RegionOutlives(..) => "Lifetime",
1417
1418                     // Ignore projections, as they can only be global
1419                     // if the trait bound is global
1420                     Projection(..) |
1421                     // Ignore bounds that a user can't type
1422                     WellFormed(..) |
1423                     ObjectSafe(..) |
1424                     ClosureKind(..) |
1425                     Subtype(..) |
1426                     ConstEvaluatable(..) => continue,
1427                 };
1428                 if predicate.is_global() {
1429                     cx.span_lint(
1430                         TRIVIAL_BOUNDS,
1431                         span,
1432                         &format!("{} bound {} does not depend on any type \
1433                                 or lifetime parameters", predicate_kind_name, predicate),
1434                     );
1435                 }
1436             }
1437         }
1438     }
1439 }
1440
1441
1442 /// Does nothing as a lint pass, but registers some `Lint`s
1443 /// which are used by other parts of the compiler.
1444 #[derive(Copy, Clone)]
1445 pub struct SoftLints;
1446
1447 impl LintPass for SoftLints {
1448     fn name(&self) -> &'static str {
1449         "SoftLints"
1450     }
1451
1452     fn get_lints(&self) -> LintArray {
1453         lint_array!(
1454             WHILE_TRUE,
1455             BOX_POINTERS,
1456             NON_SHORTHAND_FIELD_PATTERNS,
1457             UNSAFE_CODE,
1458             MISSING_DOCS,
1459             MISSING_COPY_IMPLEMENTATIONS,
1460             MISSING_DEBUG_IMPLEMENTATIONS,
1461             ANONYMOUS_PARAMETERS,
1462             UNUSED_DOC_COMMENTS,
1463             PLUGIN_AS_LIBRARY,
1464             NO_MANGLE_CONST_ITEMS,
1465             NO_MANGLE_GENERIC_ITEMS,
1466             MUTABLE_TRANSMUTES,
1467             UNSTABLE_FEATURES,
1468             UNIONS_WITH_DROP_FIELDS,
1469             UNREACHABLE_PUB,
1470             TYPE_ALIAS_BOUNDS,
1471             TRIVIAL_BOUNDS
1472         )
1473     }
1474 }
1475
1476 declare_lint! {
1477     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1478     Allow,
1479     "`...` range patterns are deprecated"
1480 }
1481
1482
1483 pub struct EllipsisInclusiveRangePatterns;
1484
1485 impl LintPass for EllipsisInclusiveRangePatterns {
1486     fn name(&self) -> &'static str {
1487         "EllipsisInclusiveRangePatterns"
1488     }
1489
1490     fn get_lints(&self) -> LintArray {
1491         lint_array!(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS)
1492     }
1493 }
1494
1495 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1496     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat, visit_subpats: &mut bool) {
1497         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1498
1499         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1500         /// corresponding to the ellipsis.
1501         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(&P<Expr>, &P<Expr>, Span)> {
1502             match &pat.node {
1503                 PatKind::Range(a, b, Spanned { span, node: RangeEnd::Included(DotDotDot), .. }) => {
1504                     Some((a, b, *span))
1505                 }
1506                 _ => None,
1507             }
1508         }
1509
1510         let (parenthesise, endpoints) = match &pat.node {
1511             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1512             _ => (false, matches_ellipsis_pat(pat)),
1513         };
1514
1515         if let Some((start, end, join)) = endpoints {
1516             let msg = "`...` range patterns are deprecated";
1517             let suggestion = "use `..=` for an inclusive range";
1518             if parenthesise {
1519                 *visit_subpats = false;
1520                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1521                 err.span_suggestion(
1522                     pat.span,
1523                     suggestion,
1524                     format!("&({}..={})", expr_to_string(&start), expr_to_string(&end)),
1525                     Applicability::MachineApplicable,
1526                 );
1527                 err.emit();
1528             } else {
1529                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1530                 err.span_suggestion_short(
1531                     join,
1532                     suggestion,
1533                     "..=".to_owned(),
1534                     Applicability::MachineApplicable,
1535                 );
1536                 err.emit();
1537             };
1538         }
1539     }
1540 }
1541
1542 declare_lint! {
1543     UNNAMEABLE_TEST_ITEMS,
1544     Warn,
1545     "detects an item that cannot be named being marked as #[test_case]",
1546     report_in_external_macro: true
1547 }
1548
1549 pub struct UnnameableTestItems {
1550     boundary: hir::HirId, // HirId of the item under which things are not nameable
1551     items_nameable: bool,
1552 }
1553
1554 impl UnnameableTestItems {
1555     pub fn new() -> Self {
1556         Self {
1557             boundary: hir::DUMMY_HIR_ID,
1558             items_nameable: true
1559         }
1560     }
1561 }
1562
1563 impl LintPass for UnnameableTestItems {
1564     fn name(&self) -> &'static str {
1565         "UnnameableTestItems"
1566     }
1567
1568     fn get_lints(&self) -> LintArray {
1569         lint_array!(UNNAMEABLE_TEST_ITEMS)
1570     }
1571 }
1572
1573 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1574     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1575         if self.items_nameable {
1576             if let hir::ItemKind::Mod(..) = it.node {}
1577             else {
1578                 self.items_nameable = false;
1579                 self.boundary = it.hir_id;
1580             }
1581             return;
1582         }
1583
1584         if let Some(attr) = attr::find_by_name(&it.attrs, "rustc_test_marker") {
1585             cx.struct_span_lint(
1586                 UNNAMEABLE_TEST_ITEMS,
1587                 attr.span,
1588                 "cannot test inner items",
1589             ).emit();
1590         }
1591     }
1592
1593     fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item) {
1594         if !self.items_nameable && self.boundary == it.hir_id {
1595             self.items_nameable = true;
1596         }
1597     }
1598 }
1599
1600 declare_lint! {
1601     pub KEYWORD_IDENTS,
1602     Allow,
1603     "detects edition keywords being used as an identifier"
1604 }
1605
1606 /// Check for uses of edition keywords used as an identifier.
1607 #[derive(Copy, Clone)]
1608 pub struct KeywordIdents;
1609
1610 impl LintPass for KeywordIdents {
1611     fn name(&self) -> &'static str {
1612         "KeywordIdents"
1613     }
1614
1615     fn get_lints(&self) -> LintArray {
1616         lint_array!(KEYWORD_IDENTS)
1617     }
1618 }
1619
1620 impl KeywordIdents {
1621     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1622         for tt in tokens.into_trees() {
1623             match tt {
1624                 TokenTree::Token(span, tok) => match tok.ident() {
1625                     // only report non-raw idents
1626                     Some((ident, false)) => {
1627                         self.check_ident(cx, ast::Ident {
1628                             span: span.substitute_dummy(ident.span),
1629                             ..ident
1630                         });
1631                     }
1632                     _ => {},
1633                 }
1634                 TokenTree::Delimited(_, _, tts) => {
1635                     self.check_tokens(cx, tts)
1636                 },
1637             }
1638         }
1639     }
1640 }
1641
1642 impl EarlyLintPass for KeywordIdents {
1643     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1644         self.check_tokens(cx, mac_def.stream());
1645     }
1646     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1647         self.check_tokens(cx, mac.node.tts.clone().into());
1648     }
1649     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1650         let ident_str = &ident.as_str()[..];
1651         let cur_edition = cx.sess.edition();
1652         let is_raw_ident = |ident: ast::Ident| {
1653             cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span)
1654         };
1655         let next_edition = match cur_edition {
1656             Edition::Edition2015 => {
1657                 match ident_str {
1658                     "async" | "try" | "dyn" => Edition::Edition2018,
1659                     // Only issue warnings for `await` if the `async_await`
1660                     // feature isn't being used. Otherwise, users need
1661                     // to keep using `await` for the macro exposed by std.
1662                     "await" if !cx.sess.features_untracked().async_await => Edition::Edition2018,
1663                     _ => return,
1664                 }
1665             }
1666
1667             // There are no new keywords yet for the 2018 edition and beyond.
1668             // However, `await` is a "false" keyword in the 2018 edition,
1669             // and can only be used if the `async_await` feature is enabled.
1670             // Otherwise, we emit an error.
1671             _ => {
1672                 if "await" == ident_str
1673                     && !cx.sess.features_untracked().async_await
1674                     && !is_raw_ident(ident)
1675                 {
1676                     let mut err = struct_span_err!(
1677                         cx.sess,
1678                         ident.span,
1679                         E0721,
1680                         "`await` is a keyword in the {} edition", cur_edition,
1681                     );
1682                     err.span_suggestion(
1683                         ident.span,
1684                         "you can use a raw identifier to stay compatible",
1685                         "r#await".to_string(),
1686                         Applicability::MachineApplicable,
1687                     );
1688                     err.emit();
1689                 }
1690                 return
1691             },
1692         };
1693
1694         // don't lint `r#foo`
1695         if is_raw_ident(ident) {
1696             return;
1697         }
1698
1699         let mut lint = cx.struct_span_lint(
1700             KEYWORD_IDENTS,
1701             ident.span,
1702             &format!("`{}` is a keyword in the {} edition",
1703                      ident.as_str(),
1704                      next_edition),
1705         );
1706         lint.span_suggestion(
1707             ident.span,
1708             "you can use a raw identifier to stay compatible",
1709             format!("r#{}", ident.as_str()),
1710             Applicability::MachineApplicable,
1711         );
1712         lint.emit()
1713     }
1714 }
1715
1716
1717 pub struct ExplicitOutlivesRequirements;
1718
1719 impl LintPass for ExplicitOutlivesRequirements {
1720     fn name(&self) -> &'static str {
1721         "ExplicitOutlivesRequirements"
1722     }
1723
1724     fn get_lints(&self) -> LintArray {
1725         lint_array![EXPLICIT_OUTLIVES_REQUIREMENTS]
1726     }
1727 }
1728
1729 impl ExplicitOutlivesRequirements {
1730     fn collect_outlives_bound_spans(
1731         &self,
1732         cx: &LateContext<'_, '_>,
1733         item_def_id: DefId,
1734         param_name: &str,
1735         bounds: &hir::GenericBounds,
1736         infer_static: bool
1737     ) -> Vec<(usize, Span)> {
1738         // For lack of a more elegant strategy for comparing the `ty::Predicate`s
1739         // returned by this query with the params/bounds grabbed from the HIR—and
1740         // with some regrets—we're going to covert the param/lifetime names to
1741         // strings
1742         let inferred_outlives = cx.tcx.inferred_outlives_of(item_def_id);
1743
1744         let ty_lt_names = inferred_outlives.iter().filter_map(|pred| {
1745             let binder = match pred {
1746                 ty::Predicate::TypeOutlives(binder) => binder,
1747                 _ => { return None; }
1748             };
1749             let ty_outlives_pred = binder.skip_binder();
1750             let ty_name = match ty_outlives_pred.0.sty {
1751                 ty::Param(param) => param.name.to_string(),
1752                 _ => { return None; }
1753             };
1754             let lt_name = match ty_outlives_pred.1 {
1755                 ty::RegionKind::ReEarlyBound(region) => {
1756                     region.name.to_string()
1757                 },
1758                 _ => { return None; }
1759             };
1760             Some((ty_name, lt_name))
1761         }).collect::<Vec<_>>();
1762
1763         let mut bound_spans = Vec::new();
1764         for (i, bound) in bounds.iter().enumerate() {
1765             if let hir::GenericBound::Outlives(lifetime) = bound {
1766                 let is_static = match lifetime.name {
1767                     hir::LifetimeName::Static => true,
1768                     _ => false
1769                 };
1770                 if is_static && !infer_static {
1771                     // infer-outlives for 'static is still feature-gated (tracking issue #44493)
1772                     continue;
1773                 }
1774
1775                 let lt_name = &lifetime.name.ident().to_string();
1776                 if ty_lt_names.contains(&(param_name.to_owned(), lt_name.to_owned())) {
1777                     bound_spans.push((i, bound.span()));
1778                 }
1779             }
1780         }
1781         bound_spans
1782     }
1783
1784     fn consolidate_outlives_bound_spans(
1785         &self,
1786         lo: Span,
1787         bounds: &hir::GenericBounds,
1788         bound_spans: Vec<(usize, Span)>
1789     ) -> Vec<Span> {
1790         if bounds.is_empty() {
1791             return Vec::new();
1792         }
1793         if bound_spans.len() == bounds.len() {
1794             let (_, last_bound_span) = bound_spans[bound_spans.len()-1];
1795             // If all bounds are inferable, we want to delete the colon, so
1796             // start from just after the parameter (span passed as argument)
1797             vec![lo.to(last_bound_span)]
1798         } else {
1799             let mut merged = Vec::new();
1800             let mut last_merged_i = None;
1801
1802             let mut from_start = true;
1803             for (i, bound_span) in bound_spans {
1804                 match last_merged_i {
1805                     // If the first bound is inferable, our span should also eat the trailing `+`
1806                     None if i == 0 => {
1807                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1808                         last_merged_i = Some(0);
1809                     },
1810                     // If consecutive bounds are inferable, merge their spans
1811                     Some(h) if i == h+1 => {
1812                         if let Some(tail) = merged.last_mut() {
1813                             // Also eat the trailing `+` if the first
1814                             // more-than-one bound is inferable
1815                             let to_span = if from_start && i < bounds.len() {
1816                                 bounds[i+1].span().shrink_to_lo()
1817                             } else {
1818                                 bound_span
1819                             };
1820                             *tail = tail.to(to_span);
1821                             last_merged_i = Some(i);
1822                         } else {
1823                             bug!("another bound-span visited earlier");
1824                         }
1825                     },
1826                     _ => {
1827                         // When we find a non-inferable bound, subsequent inferable bounds
1828                         // won't be consecutive from the start (and we'll eat the leading
1829                         // `+` rather than the trailing one)
1830                         from_start = false;
1831                         merged.push(bounds[i-1].span().shrink_to_hi().to(bound_span));
1832                         last_merged_i = Some(i);
1833                     }
1834                 }
1835             }
1836             merged
1837         }
1838     }
1839 }
1840
1841 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1842     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
1843         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1844         let def_id = cx.tcx.hir().local_def_id_from_hir_id(item.hir_id);
1845         if let hir::ItemKind::Struct(_, ref generics) = item.node {
1846             let mut bound_count = 0;
1847             let mut lint_spans = Vec::new();
1848
1849             for param in &generics.params {
1850                 let param_name = match param.kind {
1851                     hir::GenericParamKind::Lifetime { .. } => continue,
1852                     hir::GenericParamKind::Type { .. } => {
1853                         match param.name {
1854                             hir::ParamName::Fresh(_) => continue,
1855                             hir::ParamName::Error => continue,
1856                             hir::ParamName::Plain(name) => name.to_string(),
1857                         }
1858                     }
1859                     hir::GenericParamKind::Const { .. } => continue,
1860                 };
1861                 let bound_spans = self.collect_outlives_bound_spans(
1862                     cx, def_id, &param_name, &param.bounds, infer_static
1863                 );
1864                 bound_count += bound_spans.len();
1865                 lint_spans.extend(
1866                     self.consolidate_outlives_bound_spans(
1867                         param.span.shrink_to_hi(), &param.bounds, bound_spans
1868                     )
1869                 );
1870             }
1871
1872             let mut where_lint_spans = Vec::new();
1873             let mut dropped_predicate_count = 0;
1874             let num_predicates = generics.where_clause.predicates.len();
1875             for (i, where_predicate) in generics.where_clause.predicates.iter().enumerate() {
1876                 if let hir::WherePredicate::BoundPredicate(predicate) = where_predicate {
1877                     let param_name = match predicate.bounded_ty.node {
1878                         hir::TyKind::Path(ref qpath) => {
1879                             if let hir::QPath::Resolved(None, ty_param_path) = qpath {
1880                                 ty_param_path.segments[0].ident.to_string()
1881                             } else {
1882                                 continue;
1883                             }
1884                         },
1885                         _ => { continue; }
1886                     };
1887                     let bound_spans = self.collect_outlives_bound_spans(
1888                         cx, def_id, &param_name, &predicate.bounds, infer_static
1889                     );
1890                     bound_count += bound_spans.len();
1891
1892                     let drop_predicate = bound_spans.len() == predicate.bounds.len();
1893                     if drop_predicate {
1894                         dropped_predicate_count += 1;
1895                     }
1896
1897                     // If all the bounds on a predicate were inferable and there are
1898                     // further predicates, we want to eat the trailing comma
1899                     if drop_predicate && i + 1 < num_predicates {
1900                         let next_predicate_span = generics.where_clause.predicates[i+1].span();
1901                         where_lint_spans.push(
1902                             predicate.span.to(next_predicate_span.shrink_to_lo())
1903                         );
1904                     } else {
1905                         where_lint_spans.extend(
1906                             self.consolidate_outlives_bound_spans(
1907                                 predicate.span.shrink_to_lo(),
1908                                 &predicate.bounds,
1909                                 bound_spans
1910                             )
1911                         );
1912                     }
1913                 }
1914             }
1915
1916             // If all predicates are inferable, drop the entire clause
1917             // (including the `where`)
1918             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1919                 let full_where_span = generics.span.shrink_to_hi()
1920                     .to(generics.where_clause.span()
1921                     .expect("span of (nonempty) where clause should exist"));
1922                 lint_spans.push(
1923                     full_where_span
1924                 );
1925             } else {
1926                 lint_spans.extend(where_lint_spans);
1927             }
1928
1929             if !lint_spans.is_empty() {
1930                 let mut err = cx.struct_span_lint(
1931                     EXPLICIT_OUTLIVES_REQUIREMENTS,
1932                     lint_spans.clone(),
1933                     "outlives requirements can be inferred"
1934                 );
1935                 err.multipart_suggestion(
1936                     if bound_count == 1 {
1937                         "remove this bound"
1938                     } else {
1939                         "remove these bounds"
1940                     },
1941                     lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1942                     Applicability::MachineApplicable
1943                 );
1944                 err.emit();
1945             }
1946
1947         }
1948     }
1949
1950 }