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_session::lint::builtin`, which contains the
   5 //! definitions of lints that are emitted directly inside the main compiler.
   6 //!
   7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
   8 //! Then add code to emit the new lint in the appropriate circumstances.
   9 //! You can do that in an existing `LintPass` if it makes sense, or in a
  10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  11 //! compiler. Only do the latter if the check can't be written cleanly as a
  12 //! `LintPass` (also, note that such lints will need to be defined in
  13 //! `rustc_session::lint::builtin`, not here).
  14 //!
  15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
  16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
  17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
  18 //! with a `pub fn new()`.
  19 //!
  20 //! If you define a new `LateLintPass`, you will also need to add it to the
  21 //! `late_lint_methods!` invocation in `lib.rs`.
  22
  23 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
  24 use rustc_ast::ast::{self, Expr};
  25 use rustc_ast::attr::{self, HasAttrs};
  26 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  27 use rustc_ast::visit::{FnCtxt, FnKind};
  28 use rustc_ast_pretty::pprust::{self, expr_to_string};
  29 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  30 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
  31 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
  32 use rustc_feature::{GateIssue, Stability};
  33 use rustc_hir as hir;
  34 use rustc_hir::def::{DefKind, Res};
  35 use rustc_hir::def_id::DefId;
  36 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
  37 use rustc_hir::{HirId, HirIdSet, Node};
  38 use rustc_middle::lint::LintDiagnosticBuilder;
  39 use rustc_middle::ty::subst::GenericArgKind;
  40 use rustc_middle::ty::{self, Ty, TyCtxt};
  41 use rustc_session::lint::FutureIncompatibleInfo;
  42 use rustc_span::edition::Edition;
  43 use rustc_span::source_map::Spanned;
  44 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  45 use rustc_span::{BytePos, Span};
  46 use rustc_target::abi::VariantIdx;
  47 use rustc_trait_selection::traits::misc::can_type_implement_copy;
  48
  49 use crate::nonstandard_style::{method_context, MethodLateContext};
  50
  51 use log::{debug, trace};
  52 use std::fmt::Write;
  53
  54 // hardwired lints from librustc_middle
  55 pub use rustc_session::lint::builtin::*;
  56
  57 declare_lint! {
  58     WHILE_TRUE,
  59     Warn,
  60     "suggest using `loop { }` instead of `while true { }`"
  61 }
  62
  63 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  64
  65 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  66 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  67     while let ast::ExprKind::Paren(sub) = &expr.kind {
  68         expr = sub;
  69     }
  70     expr
  71 }
  72
  73 impl EarlyLintPass for WhileTrue {
  74     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
  75         if let ast::ExprKind::While(cond, ..) = &e.kind {
  76             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
  77                 if let ast::LitKind::Bool(true) = lit.kind {
  78                     if !lit.span.from_expansion() {
  79                         let msg = "denote infinite loops with `loop { ... }`";
  80                         let condition_span = cx.sess.source_map().guess_head_span(e.span);
  81                         cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
  82                             lint.build(msg)
  83                                 .span_suggestion_short(
  84                                     condition_span,
  85                                     "use `loop`",
  86                                     "loop".to_owned(),
  87                                     Applicability::MachineApplicable,
  88                                 )
  89                                 .emit();
  90                         })
  91                     }
  92                 }
  93             }
  94         }
  95     }
  96 }
  97
  98 declare_lint! {
  99     BOX_POINTERS,
 100     Allow,
 101     "use of owned (Box type) heap memory"
 102 }
 103
 104 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 105
 106 impl BoxPointers {
 107     fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
 108         for leaf in ty.walk() {
 109             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
 110                 if leaf_ty.is_box() {
 111                     cx.struct_span_lint(BOX_POINTERS, span, |lint| {
 112                         lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
 113                     });
 114                 }
 115             }
 116         }
 117     }
 118 }
 119
 120 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 121     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 122         match it.kind {
 123             hir::ItemKind::Fn(..)
 124             | hir::ItemKind::TyAlias(..)
 125             | hir::ItemKind::Enum(..)
 126             | hir::ItemKind::Struct(..)
 127             | hir::ItemKind::Union(..) => {
 128                 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 129                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 130             }
 131             _ => (),
 132         }
 133
 134         // If it's a struct, we also have to check the fields' types
 135         match it.kind {
 136             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 137                 for struct_field in struct_def.fields() {
 138                     let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
 139                     self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
 140                 }
 141             }
 142             _ => (),
 143         }
 144     }
 145
 146     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
 147         let ty = cx.tables.node_type(e.hir_id);
 148         self.check_heap_type(cx, e.span, ty);
 149     }
 150 }
 151
 152 declare_lint! {
 153     NON_SHORTHAND_FIELD_PATTERNS,
 154     Warn,
 155     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 156 }
 157
 158 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 159
 160 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 161     fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
 162         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 163             let variant = cx
 164                 .tables
 165                 .pat_ty(pat)
 166                 .ty_adt_def()
 167                 .expect("struct pattern type is not an ADT")
 168                 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
 169             for fieldpat in field_pats {
 170                 if fieldpat.is_shorthand {
 171                     continue;
 172                 }
 173                 if fieldpat.span.from_expansion() {
 174                     // Don't lint if this is a macro expansion: macro authors
 175                     // shouldn't have to worry about this kind of style issue
 176                     // (Issue #49588)
 177                     continue;
 178                 }
 179                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 180                     if cx.tcx.find_field_index(ident, &variant)
 181                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
 182                     {
 183                         cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
 184                             let mut err = lint
 185                                 .build(&format!("the `{}:` in this pattern is redundant", ident));
 186                             let binding = match binding_annot {
 187                                 hir::BindingAnnotation::Unannotated => None,
 188                                 hir::BindingAnnotation::Mutable => Some("mut"),
 189                                 hir::BindingAnnotation::Ref => Some("ref"),
 190                                 hir::BindingAnnotation::RefMut => Some("ref mut"),
 191                             };
 192                             let ident = if let Some(binding) = binding {
 193                                 format!("{} {}", binding, ident)
 194                             } else {
 195                                 ident.to_string()
 196                             };
 197                             err.span_suggestion(
 198                                 fieldpat.span,
 199                                 "use shorthand field pattern",
 200                                 ident,
 201                                 Applicability::MachineApplicable,
 202                             );
 203                             err.emit();
 204                         });
 205                     }
 206                 }
 207             }
 208         }
 209     }
 210 }
 211
 212 declare_lint! {
 213     UNSAFE_CODE,
 214     Allow,
 215     "usage of `unsafe` code"
 216 }
 217
 218 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 219
 220 impl UnsafeCode {
 221     fn report_unsafe(
 222         &self,
 223         cx: &EarlyContext<'_>,
 224         span: Span,
 225         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 226     ) {
 227         // This comes from a macro that has `#[allow_internal_unsafe]`.
 228         if span.allows_unsafe() {
 229             return;
 230         }
 231
 232         cx.struct_span_lint(UNSAFE_CODE, span, decorate);
 233     }
 234 }
 235
 236 impl EarlyLintPass for UnsafeCode {
 237     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 238         if attr.check_name(sym::allow_internal_unsafe) {
 239             self.report_unsafe(cx, attr.span, |lint| {
 240                 lint.build(
 241                     "`allow_internal_unsafe` allows defining \
 242                                                macros using unsafe without triggering \
 243                                                the `unsafe_code` lint at their call site",
 244                 )
 245                 .emit()
 246             });
 247         }
 248     }
 249
 250     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 251         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 252             // Don't warn about generated blocks; that'll just pollute the output.
 253             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 254                 self.report_unsafe(cx, blk.span, |lint| {
 255                     lint.build("usage of an `unsafe` block").emit()
 256                 });
 257             }
 258         }
 259     }
 260
 261     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 262         match it.kind {
 263             ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
 264                 self.report_unsafe(cx, it.span, |lint| {
 265                     lint.build("declaration of an `unsafe` trait").emit()
 266                 })
 267             }
 268
 269             ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
 270                 self.report_unsafe(cx, it.span, |lint| {
 271                     lint.build("implementation of an `unsafe` trait").emit()
 272                 })
 273             }
 274
 275             _ => {}
 276         }
 277     }
 278
 279     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
 280         if let FnKind::Fn(
 281             ctxt,
 282             _,
 283             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
 284             _,
 285             body,
 286         ) = fk
 287         {
 288             let msg = match ctxt {
 289                 FnCtxt::Foreign => return,
 290                 FnCtxt::Free => "declaration of an `unsafe` function",
 291                 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
 292                 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
 293             };
 294             self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
 295         }
 296     }
 297 }
 298
 299 declare_lint! {
 300     pub MISSING_DOCS,
 301     Allow,
 302     "detects missing documentation for public members",
 303     report_in_external_macro
 304 }
 305
 306 pub struct MissingDoc {
 307     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 308     doc_hidden_stack: Vec<bool>,
 309
 310     /// Private traits or trait items that leaked through. Don't check their methods.
 311     private_traits: FxHashSet<hir::HirId>,
 312 }
 313
 314 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 315
 316 fn has_doc(attr: &ast::Attribute) -> bool {
 317     if attr.is_doc_comment() {
 318         return true;
 319     }
 320
 321     if !attr.check_name(sym::doc) {
 322         return false;
 323     }
 324
 325     if attr.is_value_str() {
 326         return true;
 327     }
 328
 329     if let Some(list) = attr.meta_item_list() {
 330         for meta in list {
 331             if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
 332                 return true;
 333             }
 334         }
 335     }
 336
 337     false
 338 }
 339
 340 impl MissingDoc {
 341     pub fn new() -> MissingDoc {
 342         MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
 343     }
 344
 345     fn doc_hidden(&self) -> bool {
 346         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 347     }
 348
 349     fn check_missing_docs_attrs(
 350         &self,
 351         cx: &LateContext<'_, '_>,
 352         id: Option<hir::HirId>,
 353         attrs: &[ast::Attribute],
 354         sp: Span,
 355         article: &'static str,
 356         desc: &'static str,
 357     ) {
 358         // If we're building a test harness, then warning about
 359         // documentation is probably not really relevant right now.
 360         if cx.sess().opts.test {
 361             return;
 362         }
 363
 364         // `#[doc(hidden)]` disables missing_docs check.
 365         if self.doc_hidden() {
 366             return;
 367         }
 368
 369         // Only check publicly-visible items, using the result from the privacy pass.
 370         // It's an option so the crate root can also use this function (it doesn't
 371         // have a `NodeId`).
 372         if let Some(id) = id {
 373             if !cx.access_levels.is_exported(id) {
 374                 return;
 375             }
 376         }
 377
 378         let has_doc = attrs.iter().any(|a| has_doc(a));
 379         if !has_doc {
 380             cx.struct_span_lint(
 381                 MISSING_DOCS,
 382                 cx.tcx.sess.source_map().guess_head_span(sp),
 383                 |lint| {
 384                     lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
 385                 },
 386             );
 387         }
 388     }
 389 }
 390
 391 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 392     fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
 393         let doc_hidden = self.doc_hidden()
 394             || attrs.iter().any(|attr| {
 395                 attr.check_name(sym::doc)
 396                     && match attr.meta_item_list() {
 397                         None => false,
 398                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 399                     }
 400             });
 401         self.doc_hidden_stack.push(doc_hidden);
 402     }
 403
 404     fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
 405         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 406     }
 407
 408     fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
 409         self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
 410
 411         for macro_def in krate.exported_macros {
 412             let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
 413             if !has_doc {
 414                 cx.struct_span_lint(
 415                     MISSING_DOCS,
 416                     cx.tcx.sess.source_map().guess_head_span(macro_def.span),
 417                     |lint| lint.build("missing documentation for macro").emit(),
 418                 );
 419             }
 420         }
 421     }
 422
 423     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 424         match it.kind {
 425             hir::ItemKind::Trait(.., trait_item_refs) => {
 426                 // Issue #11592: traits are always considered exported, even when private.
 427                 if let hir::VisibilityKind::Inherited = it.vis.node {
 428                     self.private_traits.insert(it.hir_id);
 429                     for trait_item_ref in trait_item_refs {
 430                         self.private_traits.insert(trait_item_ref.id.hir_id);
 431                     }
 432                     return;
 433                 }
 434             }
 435             hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
 436                 // If the trait is private, add the impl items to `private_traits` so they don't get
 437                 // reported for missing docs.
 438                 let real_trait = trait_ref.path.res.def_id();
 439                 if let Some(def_id) = real_trait.as_local() {
 440                     let hir_id = cx.tcx.hir().as_local_hir_id(def_id);
 441                     if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
 442                         if let hir::VisibilityKind::Inherited = item.vis.node {
 443                             for impl_item_ref in items {
 444                                 self.private_traits.insert(impl_item_ref.id.hir_id);
 445                             }
 446                         }
 447                     }
 448                 }
 449                 return;
 450             }
 451
 452             hir::ItemKind::TyAlias(..)
 453             | hir::ItemKind::Fn(..)
 454             | hir::ItemKind::Mod(..)
 455             | hir::ItemKind::Enum(..)
 456             | hir::ItemKind::Struct(..)
 457             | hir::ItemKind::Union(..)
 458             | hir::ItemKind::Const(..)
 459             | hir::ItemKind::Static(..) => {}
 460
 461             _ => return,
 462         };
 463
 464         let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 465         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 466
 467         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
 468     }
 469
 470     fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
 471         if self.private_traits.contains(&trait_item.hir_id) {
 472             return;
 473         }
 474
 475         let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
 476         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 477
 478         self.check_missing_docs_attrs(
 479             cx,
 480             Some(trait_item.hir_id),
 481             &trait_item.attrs,
 482             trait_item.span,
 483             article,
 484             desc,
 485         );
 486     }
 487
 488     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
 489         // If the method is an impl for a trait, don't doc.
 490         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 491             return;
 492         }
 493
 494         let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
 495         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 496         self.check_missing_docs_attrs(
 497             cx,
 498             Some(impl_item.hir_id),
 499             &impl_item.attrs,
 500             impl_item.span,
 501             article,
 502             desc,
 503         );
 504     }
 505
 506     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField<'_>) {
 507         if !sf.is_positional() {
 508             self.check_missing_docs_attrs(
 509                 cx,
 510                 Some(sf.hir_id),
 511                 &sf.attrs,
 512                 sf.span,
 513                 "a",
 514                 "struct field",
 515             )
 516         }
 517     }
 518
 519     fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
 520         self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
 521     }
 522 }
 523
 524 declare_lint! {
 525     pub MISSING_COPY_IMPLEMENTATIONS,
 526     Allow,
 527     "detects potentially-forgotten implementations of `Copy`"
 528 }
 529
 530 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 531
 532 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 533     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
 534         if !cx.access_levels.is_reachable(item.hir_id) {
 535             return;
 536         }
 537         let (def, ty) = match item.kind {
 538             hir::ItemKind::Struct(_, ref ast_generics) => {
 539                 if !ast_generics.params.is_empty() {
 540                     return;
 541                 }
 542                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 543                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 544             }
 545             hir::ItemKind::Union(_, ref ast_generics) => {
 546                 if !ast_generics.params.is_empty() {
 547                     return;
 548                 }
 549                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 550                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 551             }
 552             hir::ItemKind::Enum(_, ref ast_generics) => {
 553                 if !ast_generics.params.is_empty() {
 554                     return;
 555                 }
 556                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 557                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 558             }
 559             _ => return,
 560         };
 561         if def.has_dtor(cx.tcx) {
 562             return;
 563         }
 564         let param_env = ty::ParamEnv::empty();
 565         if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
 566             return;
 567         }
 568         if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
 569             cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
 570                 lint.build(
 571                     "type could implement `Copy`; consider adding `impl \
 572                           Copy`",
 573                 )
 574                 .emit()
 575             })
 576         }
 577     }
 578 }
 579
 580 declare_lint! {
 581     MISSING_DEBUG_IMPLEMENTATIONS,
 582     Allow,
 583     "detects missing implementations of Debug"
 584 }
 585
 586 #[derive(Default)]
 587 pub struct MissingDebugImplementations {
 588     impling_types: Option<HirIdSet>,
 589 }
 590
 591 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 592
 593 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 594     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
 595         if !cx.access_levels.is_reachable(item.hir_id) {
 596             return;
 597         }
 598
 599         match item.kind {
 600             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 601             _ => return,
 602         }
 603
 604         let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
 605             Some(debug) => debug,
 606             None => return,
 607         };
 608
 609         if self.impling_types.is_none() {
 610             let mut impls = HirIdSet::default();
 611             cx.tcx.for_each_impl(debug, |d| {
 612                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 613                     if let Some(def_id) = ty_def.did.as_local() {
 614                         impls.insert(cx.tcx.hir().as_local_hir_id(def_id));
 615                     }
 616                 }
 617             });
 618
 619             self.impling_types = Some(impls);
 620             debug!("{:?}", self.impling_types);
 621         }
 622
 623         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 624             cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
 625                 lint.build(&format!(
 626                     "type does not implement `{}`; consider adding `#[derive(Debug)]` \
 627                      or a manual implementation",
 628                     cx.tcx.def_path_str(debug)
 629                 ))
 630                 .emit()
 631             });
 632         }
 633     }
 634 }
 635
 636 declare_lint! {
 637     pub ANONYMOUS_PARAMETERS,
 638     Allow,
 639     "detects anonymous parameters",
 640     @future_incompatible = FutureIncompatibleInfo {
 641         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 642         edition: Some(Edition::Edition2018),
 643     };
 644 }
 645
 646 declare_lint_pass!(
 647     /// Checks for use of anonymous parameters (RFC 1685).
 648     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 649 );
 650
 651 impl EarlyLintPass for AnonymousParameters {
 652     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 653         if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
 654             for arg in sig.decl.inputs.iter() {
 655                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 656                     if ident.name == kw::Invalid {
 657                         cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
 658                             let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
 659
 660                             let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 661                                 (snip.as_str(), Applicability::MachineApplicable)
 662                             } else {
 663                                 ("<type>", Applicability::HasPlaceholders)
 664                             };
 665
 666                             lint.build(
 667                                 "anonymous parameters are deprecated and will be \
 668                                      removed in the next edition.",
 669                             )
 670                             .span_suggestion(
 671                                 arg.pat.span,
 672                                 "try naming the parameter or explicitly \
 673                                             ignoring it",
 674                                 format!("_: {}", ty_snip),
 675                                 appl,
 676                             )
 677                             .emit();
 678                         })
 679                     }
 680                 }
 681             }
 682         }
 683     }
 684 }
 685
 686 /// Check for use of attributes which have been deprecated.
 687 #[derive(Clone)]
 688 pub struct DeprecatedAttr {
 689     // This is not free to compute, so we want to keep it around, rather than
 690     // compute it for every attribute.
 691     depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
 692 }
 693
 694 impl_lint_pass!(DeprecatedAttr => []);
 695
 696 impl DeprecatedAttr {
 697     pub fn new() -> DeprecatedAttr {
 698         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 699     }
 700 }
 701
 702 fn lint_deprecated_attr(
 703     cx: &EarlyContext<'_>,
 704     attr: &ast::Attribute,
 705     msg: &str,
 706     suggestion: Option<&str>,
 707 ) {
 708     cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
 709         lint.build(msg)
 710             .span_suggestion_short(
 711                 attr.span,
 712                 suggestion.unwrap_or("remove this attribute"),
 713                 String::new(),
 714                 Applicability::MachineApplicable,
 715             )
 716             .emit();
 717     })
 718 }
 719
 720 impl EarlyLintPass for DeprecatedAttr {
 721     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 722         for &&(n, _, _, ref g) in &self.depr_attrs {
 723             if attr.ident().map(|ident| ident.name) == Some(n) {
 724                 if let &AttributeGate::Gated(
 725                     Stability::Deprecated(link, suggestion),
 726                     ref name,
 727                     ref reason,
 728                     _,
 729                 ) = g
 730                 {
 731                     let msg =
 732                         format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
 733                     lint_deprecated_attr(cx, attr, &msg, suggestion);
 734                 }
 735                 return;
 736             }
 737         }
 738         if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
 739             let path_str = pprust::path_to_string(&attr.get_normal_item().path);
 740             let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
 741             lint_deprecated_attr(cx, attr, &msg, None);
 742         }
 743     }
 744 }
 745
 746 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
 747     let mut attrs = attrs.iter().peekable();
 748
 749     // Accumulate a single span for sugared doc comments.
 750     let mut sugared_span: Option<Span> = None;
 751
 752     while let Some(attr) = attrs.next() {
 753         if attr.is_doc_comment() {
 754             sugared_span =
 755                 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
 756         }
 757
 758         if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
 759             continue;
 760         }
 761
 762         let span = sugared_span.take().unwrap_or_else(|| attr.span);
 763
 764         if attr.is_doc_comment() || attr.check_name(sym::doc) {
 765             cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
 766                 let mut err = lint.build("unused doc comment");
 767                 err.span_label(
 768                     node_span,
 769                     format!("rustdoc does not generate documentation for {}", node_kind),
 770                 );
 771                 err.emit();
 772             });
 773         }
 774     }
 775 }
 776
 777 impl EarlyLintPass for UnusedDocComment {
 778     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 779         let kind = match stmt.kind {
 780             ast::StmtKind::Local(..) => "statements",
 781             ast::StmtKind::Item(..) => "inner items",
 782             // expressions will be reported by `check_expr`.
 783             ast::StmtKind::Empty
 784             | ast::StmtKind::Semi(_)
 785             | ast::StmtKind::Expr(_)
 786             | ast::StmtKind::MacCall(_) => return,
 787         };
 788
 789         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
 790     }
 791
 792     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 793         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
 794         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
 795     }
 796
 797     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 798         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
 799     }
 800 }
 801
 802 declare_lint! {
 803     NO_MANGLE_CONST_ITEMS,
 804     Deny,
 805     "const items will not have their symbols exported"
 806 }
 807
 808 declare_lint! {
 809     NO_MANGLE_GENERIC_ITEMS,
 810     Warn,
 811     "generic items must be mangled"
 812 }
 813
 814 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
 815
 816 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
 817     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 818         match it.kind {
 819             hir::ItemKind::Fn(.., ref generics, _) => {
 820                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
 821                     for param in generics.params {
 822                         match param.kind {
 823                             GenericParamKind::Lifetime { .. } => {}
 824                             GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
 825                                 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
 826                                     lint.build(
 827                                         "functions generic over types or consts must be mangled",
 828                                     )
 829                                     .span_suggestion_short(
 830                                         no_mangle_attr.span,
 831                                         "remove this attribute",
 832                                         String::new(),
 833                                         // Use of `#[no_mangle]` suggests FFI intent; correct
 834                                         // fix may be to monomorphize source by hand
 835                                         Applicability::MaybeIncorrect,
 836                                     )
 837                                     .emit();
 838                                 });
 839                                 break;
 840                             }
 841                         }
 842                     }
 843                 }
 844             }
 845             hir::ItemKind::Const(..) => {
 846                 if attr::contains_name(&it.attrs, sym::no_mangle) {
 847                     // Const items do not refer to a particular location in memory, and therefore
 848                     // don't have anything to attach a symbol to
 849                     cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
 850                         let msg = "const items should never be `#[no_mangle]`";
 851                         let mut err = lint.build(msg);
 852
 853                         // account for "pub const" (#45562)
 854                         let start = cx
 855                             .tcx
 856                             .sess
 857                             .source_map()
 858                             .span_to_snippet(it.span)
 859                             .map(|snippet| snippet.find("const").unwrap_or(0))
 860                             .unwrap_or(0) as u32;
 861                         // `const` is 5 chars
 862                         let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 863                         err.span_suggestion(
 864                             const_span,
 865                             "try a static value",
 866                             "pub static".to_owned(),
 867                             Applicability::MachineApplicable,
 868                         );
 869                         err.emit();
 870                     });
 871                 }
 872             }
 873             _ => {}
 874         }
 875     }
 876 }
 877
 878 declare_lint! {
 879     MUTABLE_TRANSMUTES,
 880     Deny,
 881     "mutating transmuted &mut T from &T may cause undefined behavior"
 882 }
 883
 884 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
 885
 886 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
 887     fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
 888         use rustc_target::spec::abi::Abi::RustIntrinsic;
 889         if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
 890             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
 891         {
 892             if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
 893                 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 894                                consider instead using an UnsafeCell";
 895                 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
 896             }
 897         }
 898
 899         fn get_transmute_from_to<'a, 'tcx>(
 900             cx: &LateContext<'a, 'tcx>,
 901             expr: &hir::Expr<'_>,
 902         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
 903             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
 904                 cx.tables.qpath_res(qpath, expr.hir_id)
 905             } else {
 906                 return None;
 907             };
 908             if let Res::Def(DefKind::Fn, did) = def {
 909                 if !def_id_is_transmute(cx, did) {
 910                     return None;
 911                 }
 912                 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
 913                 let from = sig.inputs().skip_binder()[0];
 914                 let to = *sig.output().skip_binder();
 915                 return Some((from, to));
 916             }
 917             None
 918         }
 919
 920         fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
 921             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
 922                 && cx.tcx.item_name(def_id) == sym::transmute
 923         }
 924     }
 925 }
 926
 927 declare_lint! {
 928     UNSTABLE_FEATURES,
 929     Allow,
 930     "enabling unstable features (deprecated. do not use)"
 931 }
 932
 933 declare_lint_pass!(
 934     /// Forbids using the `#[feature(...)]` attribute
 935     UnstableFeatures => [UNSTABLE_FEATURES]
 936 );
 937
 938 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
 939     fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
 940         if attr.check_name(sym::feature) {
 941             if let Some(items) = attr.meta_item_list() {
 942                 for item in items {
 943                     ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
 944                         lint.build("unstable feature").emit()
 945                     });
 946                 }
 947             }
 948         }
 949     }
 950 }
 951
 952 declare_lint! {
 953     pub UNREACHABLE_PUB,
 954     Allow,
 955     "`pub` items not reachable from crate root"
 956 }
 957
 958 declare_lint_pass!(
 959     /// Lint for items marked `pub` that aren't reachable from other crates.
 960     UnreachablePub => [UNREACHABLE_PUB]
 961 );
 962
 963 impl UnreachablePub {
 964     fn perform_lint(
 965         &self,
 966         cx: &LateContext<'_, '_>,
 967         what: &str,
 968         id: hir::HirId,
 969         vis: &hir::Visibility<'_>,
 970         span: Span,
 971         exportable: bool,
 972     ) {
 973         let mut applicability = Applicability::MachineApplicable;
 974         match vis.node {
 975             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
 976                 if span.from_expansion() {
 977                     applicability = Applicability::MaybeIncorrect;
 978                 }
 979                 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
 980                 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
 981                     let mut err = lint.build(&format!("unreachable `pub` {}", what));
 982                     let replacement = if cx.tcx.features().crate_visibility_modifier {
 983                         "crate"
 984                     } else {
 985                         "pub(crate)"
 986                     }
 987                     .to_owned();
 988
 989                     err.span_suggestion(
 990                         vis.span,
 991                         "consider restricting its visibility",
 992                         replacement,
 993                         applicability,
 994                     );
 995                     if exportable {
 996                         err.help("or consider exporting it for use by other crates");
 997                     }
 998                     err.emit();
 999                 });
1000             }
1001             _ => {}
1002         }
1003     }
1004 }
1005
1006 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1007     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1008         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1009     }
1010
1011     fn check_foreign_item(
1012         &mut self,
1013         cx: &LateContext<'_, '_>,
1014         foreign_item: &hir::ForeignItem<'tcx>,
1015     ) {
1016         self.perform_lint(
1017             cx,
1018             "item",
1019             foreign_item.hir_id,
1020             &foreign_item.vis,
1021             foreign_item.span,
1022             true,
1023         );
1024     }
1025
1026     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1027         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1028     }
1029
1030     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1031         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1032     }
1033 }
1034
1035 declare_lint! {
1036     TYPE_ALIAS_BOUNDS,
1037     Warn,
1038     "bounds in type aliases are not enforced"
1039 }
1040
1041 declare_lint_pass!(
1042     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1043     /// They are relevant when using associated types, but otherwise neither checked
1044     /// at definition site nor enforced at use site.
1045     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1046 );
1047
1048 impl TypeAliasBounds {
1049     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1050         match *qpath {
1051             hir::QPath::TypeRelative(ref ty, _) => {
1052                 // If this is a type variable, we found a `T::Assoc`.
1053                 match ty.kind {
1054                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1055                         Res::Def(DefKind::TyParam, _) => true,
1056                         _ => false,
1057                     },
1058                     _ => false,
1059                 }
1060             }
1061             hir::QPath::Resolved(..) => false,
1062         }
1063     }
1064
1065     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1066         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1067         // bound.  Let's see if this type does that.
1068
1069         // We use a HIR visitor to walk the type.
1070         use rustc_hir::intravisit::{self, Visitor};
1071         struct WalkAssocTypes<'a, 'db> {
1072             err: &'a mut DiagnosticBuilder<'db>,
1073         }
1074         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1075             type Map = intravisit::ErasedMap<'v>;
1076
1077             fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1078                 intravisit::NestedVisitorMap::None
1079             }
1080
1081             fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1082                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1083                     self.err.span_help(
1084                         span,
1085                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1086                          associated types in type aliases",
1087                     );
1088                 }
1089                 intravisit::walk_qpath(self, qpath, id, span)
1090             }
1091         }
1092
1093         // Let's go for a walk!
1094         let mut visitor = WalkAssocTypes { err };
1095         visitor.visit_ty(ty);
1096     }
1097 }
1098
1099 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1100     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1101         let (ty, type_alias_generics) = match item.kind {
1102             hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1103             _ => return,
1104         };
1105         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1106             // Bounds are respected for `type X = impl Trait`
1107             return;
1108         }
1109         let mut suggested_changing_assoc_types = false;
1110         // There must not be a where clause
1111         if !type_alias_generics.where_clause.predicates.is_empty() {
1112             cx.lint(
1113                 TYPE_ALIAS_BOUNDS,
1114                 |lint| {
1115                     let mut err = lint.build("where clauses are not enforced in type aliases");
1116                     let spans: Vec<_> = type_alias_generics
1117                         .where_clause
1118                         .predicates
1119                         .iter()
1120                         .map(|pred| pred.span())
1121                         .collect();
1122                     err.set_span(spans);
1123                     err.span_suggestion(
1124                         type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1125                         "the clause will not be checked when the type alias is used, and should be removed",
1126                         String::new(),
1127                         Applicability::MachineApplicable,
1128                     );
1129                     if !suggested_changing_assoc_types {
1130                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1131                         suggested_changing_assoc_types = true;
1132                     }
1133                     err.emit();
1134                 },
1135             );
1136         }
1137         // The parameters must not have bounds
1138         for param in type_alias_generics.params.iter() {
1139             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1140             let suggestion = spans
1141                 .iter()
1142                 .map(|sp| {
1143                     let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1144                     (start.to(*sp), String::new())
1145                 })
1146                 .collect();
1147             if !spans.is_empty() {
1148                 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1149                     let mut err =
1150                         lint.build("bounds on generic parameters are not enforced in type aliases");
1151                     let msg = "the bound will not be checked when the type alias is used, \
1152                                    and should be removed";
1153                     err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1154                     if !suggested_changing_assoc_types {
1155                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1156                         suggested_changing_assoc_types = true;
1157                     }
1158                     err.emit();
1159                 });
1160             }
1161         }
1162     }
1163 }
1164
1165 declare_lint_pass!(
1166     /// Lint constants that are erroneous.
1167     /// Without this lint, we might not get any diagnostic if the constant is
1168     /// unused within this crate, even though downstream crates can't use it
1169     /// without producing an error.
1170     UnusedBrokenConst => []
1171 );
1172
1173 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1174     let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1175     // trigger the query once for all constants since that will already report the errors
1176     // FIXME: Use ensure here
1177     let _ = cx.tcx.const_eval_poly(def_id);
1178 }
1179
1180 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1181     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1182         match it.kind {
1183             hir::ItemKind::Const(_, body_id) => {
1184                 check_const(cx, body_id);
1185             }
1186             hir::ItemKind::Static(_, _, body_id) => {
1187                 check_const(cx, body_id);
1188             }
1189             _ => {}
1190         }
1191     }
1192 }
1193
1194 declare_lint! {
1195     TRIVIAL_BOUNDS,
1196     Warn,
1197     "these bounds don't depend on an type parameters"
1198 }
1199
1200 declare_lint_pass!(
1201     /// Lint for trait and lifetime bounds that don't depend on type parameters
1202     /// which either do nothing, or stop the item from being used.
1203     TrivialConstraints => [TRIVIAL_BOUNDS]
1204 );
1205
1206 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1207     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1208         use rustc_middle::ty::fold::TypeFoldable;
1209         use rustc_middle::ty::PredicateKind::*;
1210
1211         if cx.tcx.features().trivial_bounds {
1212             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1213             let predicates = cx.tcx.predicates_of(def_id);
1214             for &(predicate, span) in predicates.predicates {
1215                 let predicate_kind_name = match predicate.kind() {
1216                     Trait(..) => "Trait",
1217                     TypeOutlives(..) |
1218                     RegionOutlives(..) => "Lifetime",
1219
1220                     // Ignore projections, as they can only be global
1221                     // if the trait bound is global
1222                     Projection(..) |
1223                     // Ignore bounds that a user can't type
1224                     WellFormed(..) |
1225                     ObjectSafe(..) |
1226                     ClosureKind(..) |
1227                     Subtype(..) |
1228                     ConstEvaluatable(..) |
1229                     ConstEquate(..) => continue,
1230                 };
1231                 if predicate.is_global() {
1232                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1233                         lint.build(&format!(
1234                             "{} bound {} does not depend on any type \
1235                                 or lifetime parameters",
1236                             predicate_kind_name, predicate
1237                         ))
1238                         .emit()
1239                     });
1240                 }
1241             }
1242         }
1243     }
1244 }
1245
1246 declare_lint_pass!(
1247     /// Does nothing as a lint pass, but registers some `Lint`s
1248     /// which are used by other parts of the compiler.
1249     SoftLints => [
1250         WHILE_TRUE,
1251         BOX_POINTERS,
1252         NON_SHORTHAND_FIELD_PATTERNS,
1253         UNSAFE_CODE,
1254         MISSING_DOCS,
1255         MISSING_COPY_IMPLEMENTATIONS,
1256         MISSING_DEBUG_IMPLEMENTATIONS,
1257         ANONYMOUS_PARAMETERS,
1258         UNUSED_DOC_COMMENTS,
1259         NO_MANGLE_CONST_ITEMS,
1260         NO_MANGLE_GENERIC_ITEMS,
1261         MUTABLE_TRANSMUTES,
1262         UNSTABLE_FEATURES,
1263         UNREACHABLE_PUB,
1264         TYPE_ALIAS_BOUNDS,
1265         TRIVIAL_BOUNDS
1266     ]
1267 );
1268
1269 declare_lint! {
1270     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1271     Warn,
1272     "`...` range patterns are deprecated"
1273 }
1274
1275 #[derive(Default)]
1276 pub struct EllipsisInclusiveRangePatterns {
1277     /// If `Some(_)`, suppress all subsequent pattern
1278     /// warnings for better diagnostics.
1279     node_id: Option<ast::NodeId>,
1280 }
1281
1282 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1283
1284 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1285     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1286         if self.node_id.is_some() {
1287             // Don't recursively warn about patterns inside range endpoints.
1288             return;
1289         }
1290
1291         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1292
1293         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1294         /// corresponding to the ellipsis.
1295         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1296             match &pat.kind {
1297                 PatKind::Range(
1298                     a,
1299                     Some(b),
1300                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1301                 ) => Some((a.as_deref(), b, *span)),
1302                 _ => None,
1303             }
1304         }
1305
1306         let (parenthesise, endpoints) = match &pat.kind {
1307             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1308             _ => (false, matches_ellipsis_pat(pat)),
1309         };
1310
1311         if let Some((start, end, join)) = endpoints {
1312             let msg = "`...` range patterns are deprecated";
1313             let suggestion = "use `..=` for an inclusive range";
1314             if parenthesise {
1315                 self.node_id = Some(pat.id);
1316                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1317                     let end = expr_to_string(&end);
1318                     let replace = match start {
1319                         Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1320                         None => format!("&(..={})", end),
1321                     };
1322                     lint.build(msg)
1323                         .span_suggestion(
1324                             pat.span,
1325                             suggestion,
1326                             replace,
1327                             Applicability::MachineApplicable,
1328                         )
1329                         .emit();
1330                 });
1331             } else {
1332                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1333                     lint.build(msg)
1334                         .span_suggestion_short(
1335                             join,
1336                             suggestion,
1337                             "..=".to_owned(),
1338                             Applicability::MachineApplicable,
1339                         )
1340                         .emit();
1341                 });
1342             };
1343         }
1344     }
1345
1346     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1347         if let Some(node_id) = self.node_id {
1348             if pat.id == node_id {
1349                 self.node_id = None
1350             }
1351         }
1352     }
1353 }
1354
1355 declare_lint! {
1356     UNNAMEABLE_TEST_ITEMS,
1357     Warn,
1358     "detects an item that cannot be named being marked as `#[test_case]`",
1359     report_in_external_macro
1360 }
1361
1362 pub struct UnnameableTestItems {
1363     boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1364     items_nameable: bool,
1365 }
1366
1367 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1368
1369 impl UnnameableTestItems {
1370     pub fn new() -> Self {
1371         Self { boundary: None, items_nameable: true }
1372     }
1373 }
1374
1375 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1376     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1377         if self.items_nameable {
1378             if let hir::ItemKind::Mod(..) = it.kind {
1379             } else {
1380                 self.items_nameable = false;
1381                 self.boundary = Some(it.hir_id);
1382             }
1383             return;
1384         }
1385
1386         if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1387             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1388                 lint.build("cannot test inner items").emit()
1389             });
1390         }
1391     }
1392
1393     fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1394         if !self.items_nameable && self.boundary == Some(it.hir_id) {
1395             self.items_nameable = true;
1396         }
1397     }
1398 }
1399
1400 declare_lint! {
1401     pub KEYWORD_IDENTS,
1402     Allow,
1403     "detects edition keywords being used as an identifier",
1404     @future_incompatible = FutureIncompatibleInfo {
1405         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1406         edition: Some(Edition::Edition2018),
1407     };
1408 }
1409
1410 declare_lint_pass!(
1411     /// Check for uses of edition keywords used as an identifier.
1412     KeywordIdents => [KEYWORD_IDENTS]
1413 );
1414
1415 struct UnderMacro(bool);
1416
1417 impl KeywordIdents {
1418     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1419         for tt in tokens.into_trees() {
1420             match tt {
1421                 // Only report non-raw idents.
1422                 TokenTree::Token(token) => {
1423                     if let Some((ident, false)) = token.ident() {
1424                         self.check_ident_token(cx, UnderMacro(true), ident);
1425                     }
1426                 }
1427                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1428             }
1429         }
1430     }
1431
1432     fn check_ident_token(
1433         &mut self,
1434         cx: &EarlyContext<'_>,
1435         UnderMacro(under_macro): UnderMacro,
1436         ident: Ident,
1437     ) {
1438         let next_edition = match cx.sess.edition() {
1439             Edition::Edition2015 => {
1440                 match ident.name {
1441                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1442
1443                     // rust-lang/rust#56327: Conservatively do not
1444                     // attempt to report occurrences of `dyn` within
1445                     // macro definitions or invocations, because `dyn`
1446                     // can legitimately occur as a contextual keyword
1447                     // in 2015 code denoting its 2018 meaning, and we
1448                     // do not want rustfix to inject bugs into working
1449                     // code by rewriting such occurrences.
1450                     //
1451                     // But if we see `dyn` outside of a macro, we know
1452                     // its precise role in the parsed AST and thus are
1453                     // assured this is truly an attempt to use it as
1454                     // an identifier.
1455                     kw::Dyn if !under_macro => Edition::Edition2018,
1456
1457                     _ => return,
1458                 }
1459             }
1460
1461             // There are no new keywords yet for the 2018 edition and beyond.
1462             _ => return,
1463         };
1464
1465         // Don't lint `r#foo`.
1466         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1467             return;
1468         }
1469
1470         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1471             lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1472                 .span_suggestion(
1473                     ident.span,
1474                     "you can use a raw identifier to stay compatible",
1475                     format!("r#{}", ident),
1476                     Applicability::MachineApplicable,
1477                 )
1478                 .emit()
1479         });
1480     }
1481 }
1482
1483 impl EarlyLintPass for KeywordIdents {
1484     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1485         self.check_tokens(cx, mac_def.body.inner_tokens());
1486     }
1487     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1488         self.check_tokens(cx, mac.args.inner_tokens());
1489     }
1490     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1491         self.check_ident_token(cx, UnderMacro(false), ident);
1492     }
1493 }
1494
1495 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1496
1497 impl ExplicitOutlivesRequirements {
1498     fn lifetimes_outliving_lifetime<'tcx>(
1499         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1500         index: u32,
1501     ) -> Vec<ty::Region<'tcx>> {
1502         inferred_outlives
1503             .iter()
1504             .filter_map(|(pred, _)| match pred.kind() {
1505                 ty::PredicateKind::RegionOutlives(outlives) => {
1506                     let outlives = outlives.skip_binder();
1507                     match outlives.0 {
1508                         ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1509                         _ => None,
1510                     }
1511                 }
1512                 _ => None,
1513             })
1514             .collect()
1515     }
1516
1517     fn lifetimes_outliving_type<'tcx>(
1518         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1519         index: u32,
1520     ) -> Vec<ty::Region<'tcx>> {
1521         inferred_outlives
1522             .iter()
1523             .filter_map(|(pred, _)| match pred.kind() {
1524                 ty::PredicateKind::TypeOutlives(outlives) => {
1525                     let outlives = outlives.skip_binder();
1526                     outlives.0.is_param(index).then_some(outlives.1)
1527                 }
1528                 _ => None,
1529             })
1530             .collect()
1531     }
1532
1533     fn collect_outlived_lifetimes<'tcx>(
1534         &self,
1535         param: &'tcx hir::GenericParam<'tcx>,
1536         tcx: TyCtxt<'tcx>,
1537         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1538         ty_generics: &'tcx ty::Generics,
1539     ) -> Vec<ty::Region<'tcx>> {
1540         let index =
1541             ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1542
1543         match param.kind {
1544             hir::GenericParamKind::Lifetime { .. } => {
1545                 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1546             }
1547             hir::GenericParamKind::Type { .. } => {
1548                 Self::lifetimes_outliving_type(inferred_outlives, index)
1549             }
1550             hir::GenericParamKind::Const { .. } => Vec::new(),
1551         }
1552     }
1553
1554     fn collect_outlives_bound_spans<'tcx>(
1555         &self,
1556         tcx: TyCtxt<'tcx>,
1557         bounds: &hir::GenericBounds<'_>,
1558         inferred_outlives: &[ty::Region<'tcx>],
1559         infer_static: bool,
1560     ) -> Vec<(usize, Span)> {
1561         use rustc_middle::middle::resolve_lifetime::Region;
1562
1563         bounds
1564             .iter()
1565             .enumerate()
1566             .filter_map(|(i, bound)| {
1567                 if let hir::GenericBound::Outlives(lifetime) = bound {
1568                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
1569                         Some(Region::Static) if infer_static => inferred_outlives
1570                             .iter()
1571                             .any(|r| if let ty::ReStatic = r { true } else { false }),
1572                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1573                             if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1574                         }),
1575                         _ => false,
1576                     };
1577                     is_inferred.then_some((i, bound.span()))
1578                 } else {
1579                     None
1580                 }
1581             })
1582             .collect()
1583     }
1584
1585     fn consolidate_outlives_bound_spans(
1586         &self,
1587         lo: Span,
1588         bounds: &hir::GenericBounds<'_>,
1589         bound_spans: Vec<(usize, Span)>,
1590     ) -> Vec<Span> {
1591         if bounds.is_empty() {
1592             return Vec::new();
1593         }
1594         if bound_spans.len() == bounds.len() {
1595             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1596             // If all bounds are inferable, we want to delete the colon, so
1597             // start from just after the parameter (span passed as argument)
1598             vec![lo.to(last_bound_span)]
1599         } else {
1600             let mut merged = Vec::new();
1601             let mut last_merged_i = None;
1602
1603             let mut from_start = true;
1604             for (i, bound_span) in bound_spans {
1605                 match last_merged_i {
1606                     // If the first bound is inferable, our span should also eat the leading `+`.
1607                     None if i == 0 => {
1608                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1609                         last_merged_i = Some(0);
1610                     }
1611                     // If consecutive bounds are inferable, merge their spans
1612                     Some(h) if i == h + 1 => {
1613                         if let Some(tail) = merged.last_mut() {
1614                             // Also eat the trailing `+` if the first
1615                             // more-than-one bound is inferable
1616                             let to_span = if from_start && i < bounds.len() {
1617                                 bounds[i + 1].span().shrink_to_lo()
1618                             } else {
1619                                 bound_span
1620                             };
1621                             *tail = tail.to(to_span);
1622                             last_merged_i = Some(i);
1623                         } else {
1624                             bug!("another bound-span visited earlier");
1625                         }
1626                     }
1627                     _ => {
1628                         // When we find a non-inferable bound, subsequent inferable bounds
1629                         // won't be consecutive from the start (and we'll eat the leading
1630                         // `+` rather than the trailing one)
1631                         from_start = false;
1632                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1633                         last_merged_i = Some(i);
1634                     }
1635                 }
1636             }
1637             merged
1638         }
1639     }
1640 }
1641
1642 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1643     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1644         use rustc_middle::middle::resolve_lifetime::Region;
1645
1646         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1647         let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1648         if let hir::ItemKind::Struct(_, ref hir_generics)
1649         | hir::ItemKind::Enum(_, ref hir_generics)
1650         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1651         {
1652             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1653             if inferred_outlives.is_empty() {
1654                 return;
1655             }
1656
1657             let ty_generics = cx.tcx.generics_of(def_id);
1658
1659             let mut bound_count = 0;
1660             let mut lint_spans = Vec::new();
1661
1662             for param in hir_generics.params {
1663                 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1664                     if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1665                 });
1666                 if !has_lifetime_bounds {
1667                     continue;
1668                 }
1669
1670                 let relevant_lifetimes =
1671                     self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1672                 if relevant_lifetimes.is_empty() {
1673                     continue;
1674                 }
1675
1676                 let bound_spans = self.collect_outlives_bound_spans(
1677                     cx.tcx,
1678                     &param.bounds,
1679                     &relevant_lifetimes,
1680                     infer_static,
1681                 );
1682                 bound_count += bound_spans.len();
1683                 lint_spans.extend(self.consolidate_outlives_bound_spans(
1684                     param.span.shrink_to_hi(),
1685                     &param.bounds,
1686                     bound_spans,
1687                 ));
1688             }
1689
1690             let mut where_lint_spans = Vec::new();
1691             let mut dropped_predicate_count = 0;
1692             let num_predicates = hir_generics.where_clause.predicates.len();
1693             for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1694                 let (relevant_lifetimes, bounds, span) = match where_predicate {
1695                     hir::WherePredicate::RegionPredicate(predicate) => {
1696                         if let Some(Region::EarlyBound(index, ..)) =
1697                             cx.tcx.named_region(predicate.lifetime.hir_id)
1698                         {
1699                             (
1700                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1701                                 &predicate.bounds,
1702                                 predicate.span,
1703                             )
1704                         } else {
1705                             continue;
1706                         }
1707                     }
1708                     hir::WherePredicate::BoundPredicate(predicate) => {
1709                         // FIXME we can also infer bounds on associated types,
1710                         // and should check for them here.
1711                         match predicate.bounded_ty.kind {
1712                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1713                                 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1714                                     let index = ty_generics.param_def_id_to_index[&def_id];
1715                                     (
1716                                         Self::lifetimes_outliving_type(inferred_outlives, index),
1717                                         &predicate.bounds,
1718                                         predicate.span,
1719                                     )
1720                                 } else {
1721                                     continue;
1722                                 }
1723                             }
1724                             _ => {
1725                                 continue;
1726                             }
1727                         }
1728                     }
1729                     _ => continue,
1730                 };
1731                 if relevant_lifetimes.is_empty() {
1732                     continue;
1733                 }
1734
1735                 let bound_spans = self.collect_outlives_bound_spans(
1736                     cx.tcx,
1737                     bounds,
1738                     &relevant_lifetimes,
1739                     infer_static,
1740                 );
1741                 bound_count += bound_spans.len();
1742
1743                 let drop_predicate = bound_spans.len() == bounds.len();
1744                 if drop_predicate {
1745                     dropped_predicate_count += 1;
1746                 }
1747
1748                 // If all the bounds on a predicate were inferable and there are
1749                 // further predicates, we want to eat the trailing comma.
1750                 if drop_predicate && i + 1 < num_predicates {
1751                     let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1752                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1753                 } else {
1754                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1755                         span.shrink_to_lo(),
1756                         bounds,
1757                         bound_spans,
1758                     ));
1759                 }
1760             }
1761
1762             // If all predicates are inferable, drop the entire clause
1763             // (including the `where`)
1764             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1765                 let where_span = hir_generics
1766                     .where_clause
1767                     .span()
1768                     .expect("span of (nonempty) where clause should exist");
1769                 // Extend the where clause back to the closing `>` of the
1770                 // generics, except for tuple struct, which have the `where`
1771                 // after the fields of the struct.
1772                 let full_where_span =
1773                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1774                         where_span
1775                     } else {
1776                         hir_generics.span.shrink_to_hi().to(where_span)
1777                     };
1778                 lint_spans.push(full_where_span);
1779             } else {
1780                 lint_spans.extend(where_lint_spans);
1781             }
1782
1783             if !lint_spans.is_empty() {
1784                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1785                     lint.build("outlives requirements can be inferred")
1786                         .multipart_suggestion(
1787                             if bound_count == 1 {
1788                                 "remove this bound"
1789                             } else {
1790                                 "remove these bounds"
1791                             },
1792                             lint_spans
1793                                 .into_iter()
1794                                 .map(|span| (span, "".to_owned()))
1795                                 .collect::<Vec<_>>(),
1796                             Applicability::MachineApplicable,
1797                         )
1798                         .emit();
1799                 });
1800             }
1801         }
1802     }
1803 }
1804
1805 declare_lint! {
1806     pub INCOMPLETE_FEATURES,
1807     Warn,
1808     "incomplete features that may function improperly in some or all cases"
1809 }
1810
1811 declare_lint_pass!(
1812     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1813     IncompleteFeatures => [INCOMPLETE_FEATURES]
1814 );
1815
1816 impl EarlyLintPass for IncompleteFeatures {
1817     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1818         let features = cx.sess.features_untracked();
1819         features
1820             .declared_lang_features
1821             .iter()
1822             .map(|(name, span, _)| (name, span))
1823             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1824             .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1825             .for_each(|(&name, &span)| {
1826                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1827                     let mut builder = lint.build(&format!(
1828                         "the feature `{}` is incomplete and may not be safe to use \
1829                          and/or cause compiler crashes",
1830                         name,
1831                     ));
1832                     if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1833                         builder.note(&format!(
1834                             "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1835                              for more information",
1836                             n, n,
1837                         ));
1838                     }
1839                     builder.emit();
1840                 })
1841             });
1842     }
1843 }
1844
1845 declare_lint! {
1846     pub INVALID_VALUE,
1847     Warn,
1848     "an invalid value is being created (such as a NULL reference)"
1849 }
1850
1851 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1852
1853 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1854     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1855         #[derive(Debug, Copy, Clone, PartialEq)]
1856         enum InitKind {
1857             Zeroed,
1858             Uninit,
1859         };
1860
1861         /// Information about why a type cannot be initialized this way.
1862         /// Contains an error message and optionally a span to point at.
1863         type InitError = (String, Option<Span>);
1864
1865         /// Test if this constant is all-0.
1866         fn is_zero(expr: &hir::Expr<'_>) -> bool {
1867             use hir::ExprKind::*;
1868             use rustc_ast::ast::LitKind::*;
1869             match &expr.kind {
1870                 Lit(lit) => {
1871                     if let Int(i, _) = lit.node {
1872                         i == 0
1873                     } else {
1874                         false
1875                     }
1876                 }
1877                 Tup(tup) => tup.iter().all(is_zero),
1878                 _ => false,
1879             }
1880         }
1881
1882         /// Determine if this expression is a "dangerous initialization".
1883         fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1884             // `transmute` is inside an anonymous module (the `extern` block?);
1885             // `Invalid` represents the empty string and matches that.
1886             // FIXME(#66075): use diagnostic items.  Somehow, that does not seem to work
1887             // on intrinsics right now.
1888             const TRANSMUTE_PATH: &[Symbol] =
1889                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1890
1891             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1892                 // Find calls to `mem::{uninitialized,zeroed}` methods.
1893                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1894                     let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1895
1896                     if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1897                         return Some(InitKind::Zeroed);
1898                     } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1899                         return Some(InitKind::Uninit);
1900                     } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1901                         if is_zero(&args[0]) {
1902                             return Some(InitKind::Zeroed);
1903                         }
1904                     }
1905                 }
1906             } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1907                 // Find problematic calls to `MaybeUninit::assume_init`.
1908                 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1909                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1910                     // This is a call to *some* method named `assume_init`.
1911                     // See if the `self` parameter is one of the dangerous constructors.
1912                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1913                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1914                             let def_id =
1915                                 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1916
1917                             if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1918                                 return Some(InitKind::Zeroed);
1919                             } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1920                                 return Some(InitKind::Uninit);
1921                             }
1922                         }
1923                     }
1924                 }
1925             }
1926
1927             None
1928         }
1929
1930         /// Return `Some` only if we are sure this type does *not*
1931         /// allow zero initialization.
1932         fn ty_find_init_error<'tcx>(
1933             tcx: TyCtxt<'tcx>,
1934             ty: Ty<'tcx>,
1935             init: InitKind,
1936         ) -> Option<InitError> {
1937             use rustc_middle::ty::TyKind::*;
1938             match ty.kind {
1939                 // Primitive types that don't like 0 as a value.
1940                 Ref(..) => Some(("references must be non-null".to_string(), None)),
1941                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1942                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1943                 Never => Some(("the `!` type has no valid value".to_string(), None)),
1944                 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1945                 // raw ptr to dyn Trait
1946                 {
1947                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1948                 }
1949                 // Primitive types with other constraints.
1950                 Bool if init == InitKind::Uninit => {
1951                     Some(("booleans must be either `true` or `false`".to_string(), None))
1952                 }
1953                 Char if init == InitKind::Uninit => {
1954                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
1955                 }
1956                 // Recurse and checks for some compound types.
1957                 Adt(adt_def, substs) if !adt_def.is_union() => {
1958                     // First check f this ADT has a layout attribute (like `NonNull` and friends).
1959                     use std::ops::Bound;
1960                     match tcx.layout_scalar_valid_range(adt_def.did) {
1961                         // We exploit here that `layout_scalar_valid_range` will never
1962                         // return `Bound::Excluded`.  (And we have tests checking that we
1963                         // handle the attribute correctly.)
1964                         (Bound::Included(lo), _) if lo > 0 => {
1965                             return Some((format!("`{}` must be non-null", ty), None));
1966                         }
1967                         (Bound::Included(_), _) | (_, Bound::Included(_))
1968                             if init == InitKind::Uninit =>
1969                         {
1970                             return Some((
1971                                 format!(
1972                                     "`{}` must be initialized inside its custom valid range",
1973                                     ty,
1974                                 ),
1975                                 None,
1976                             ));
1977                         }
1978                         _ => {}
1979                     }
1980                     // Now, recurse.
1981                     match adt_def.variants.len() {
1982                         0 => Some(("enums with no variants have no valid value".to_string(), None)),
1983                         1 => {
1984                             // Struct, or enum with exactly one variant.
1985                             // Proceed recursively, check all fields.
1986                             let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1987                             variant.fields.iter().find_map(|field| {
1988                                 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1989                                     |(mut msg, span)| {
1990                                         if span.is_none() {
1991                                             // Point to this field, should be helpful for figuring
1992                                             // out where the source of the error is.
1993                                             let span = tcx.def_span(field.did);
1994                                             write!(
1995                                                 &mut msg,
1996                                                 " (in this {} field)",
1997                                                 adt_def.descr()
1998                                             )
1999                                             .unwrap();
2000                                             (msg, Some(span))
2001                                         } else {
2002                                             // Just forward.
2003                                             (msg, span)
2004                                         }
2005                                     },
2006                                 )
2007                             })
2008                         }
2009                         // Multi-variant enums are tricky: if all but one variant are
2010                         // uninhabited, we might actually do layout like for a single-variant
2011                         // enum, and then even leaving them uninitialized could be okay.
2012                         _ => None, // Conservative fallback for multi-variant enum.
2013                     }
2014                 }
2015                 Tuple(..) => {
2016                     // Proceed recursively, check all fields.
2017                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2018                 }
2019                 // Conservative fallback.
2020                 _ => None,
2021             }
2022         }
2023
2024         if let Some(init) = is_dangerous_init(cx, expr) {
2025             // This conjures an instance of a type out of nothing,
2026             // using zeroed or uninitialized memory.
2027             // We are extremely conservative with what we warn about.
2028             let conjured_ty = cx.tables.expr_ty(expr);
2029             if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2030                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2031                     let mut err = lint.build(&format!(
2032                         "the type `{}` does not permit {}",
2033                         conjured_ty,
2034                         match init {
2035                             InitKind::Zeroed => "zero-initialization",
2036                             InitKind::Uninit => "being left uninitialized",
2037                         },
2038                     ));
2039                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2040                     err.span_label(
2041                         expr.span,
2042                         "help: use `MaybeUninit<T>` instead, \
2043                             and only call `assume_init` after initialization is done",
2044                     );
2045                     if let Some(span) = span {
2046                         err.span_note(span, &msg);
2047                     } else {
2048                         err.note(&msg);
2049                     }
2050                     err.emit();
2051                 });
2052             }
2053         }
2054     }
2055 }
2056
2057 declare_lint! {
2058     pub CLASHING_EXTERN_DECL,
2059     Warn,
2060     "detects when an extern fn has been declared with the same name but different types"
2061 }
2062
2063 pub struct ClashingExternDecl {
2064     seen_decls: FxHashMap<Symbol, HirId>,
2065 }
2066
2067 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2068 /// just from declaration itself. This is important because we don't want to report clashes on
2069 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2070 /// different name.
2071 enum SymbolName {
2072     /// The name of the symbol + the span of the annotation which introduced the link name.
2073     Link(Symbol, Span),
2074     /// No link name, so just the name of the symbol.
2075     Normal(Symbol),
2076 }
2077
2078 impl SymbolName {
2079     fn get_name(&self) -> Symbol {
2080         match self {
2081             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2082         }
2083     }
2084 }
2085
2086 impl ClashingExternDecl {
2087     crate fn new() -> Self {
2088         ClashingExternDecl { seen_decls: FxHashMap::default() }
2089     }
2090     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2091     /// for the item, return its HirId without updating the set.
2092     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2093         let hid = fi.hir_id;
2094
2095         let name =
2096             &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2097
2098         if self.seen_decls.contains_key(name) {
2099             // Avoid updating the map with the new entry when we do find a collision. We want to
2100             // make sure we're always pointing to the first definition as the previous declaration.
2101             // This lets us avoid emitting "knock-on" diagnostics.
2102             Some(*self.seen_decls.get(name).unwrap())
2103         } else {
2104             self.seen_decls.insert(*name, hid)
2105         }
2106     }
2107
2108     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2109     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2110     /// symbol's name.
2111     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2112         let did = tcx.hir().local_def_id(fi.hir_id);
2113         if let Some((overridden_link_name, overridden_link_name_span)) =
2114             tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2115                 // FIXME: Instead of searching through the attributes again to get span
2116                 // information, we could have codegen_fn_attrs also give span information back for
2117                 // where the attribute was defined. However, until this is found to be a
2118                 // bottleneck, this does just fine.
2119                 (
2120                     overridden_link_name,
2121                     tcx.get_attrs(did.to_def_id())
2122                         .iter()
2123                         .find(|at| at.check_name(sym::link_name))
2124                         .unwrap()
2125                         .span,
2126                 )
2127             })
2128         {
2129             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2130         } else {
2131             SymbolName::Normal(fi.ident.name)
2132         }
2133     }
2134
2135     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2136     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2137     /// with the same members (as the declarations shouldn't clash).
2138     fn structurally_same_type<'a, 'tcx>(
2139         cx: &LateContext<'a, 'tcx>,
2140         a: Ty<'tcx>,
2141         b: Ty<'tcx>,
2142     ) -> bool {
2143         let tcx = cx.tcx;
2144         if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2145             // All nominally-same types are structurally same, too.
2146             true
2147         } else {
2148             // Do a full, depth-first comparison between the two.
2149             use rustc_middle::ty::TyKind::*;
2150             let a_kind = &a.kind;
2151             let b_kind = &b.kind;
2152
2153             match (a_kind, b_kind) {
2154                 (Adt(..), Adt(..)) => {
2155                     // Adts are pretty straightforward: just compare the layouts.
2156                     use rustc_target::abi::LayoutOf;
2157                     let a_layout = cx.layout_of(a).unwrap().layout;
2158                     let b_layout = cx.layout_of(b).unwrap().layout;
2159                     a_layout == b_layout
2160                 }
2161                 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2162                     // For arrays, we also check the constness of the type.
2163                     a_const.val == b_const.val
2164                         && Self::structurally_same_type(cx, a_const.ty, b_const.ty)
2165                         && Self::structurally_same_type(cx, a_ty, b_ty)
2166                 }
2167                 (Slice(a_ty), Slice(b_ty)) => Self::structurally_same_type(cx, a_ty, b_ty),
2168                 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2169                     a_tymut.mutbl == a_tymut.mutbl
2170                         && Self::structurally_same_type(cx, &a_tymut.ty, &b_tymut.ty)
2171                 }
2172                 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2173                     // For structural sameness, we don't need the region to be same.
2174                     a_mut == b_mut && Self::structurally_same_type(cx, a_ty, b_ty)
2175                 }
2176                 (FnDef(..), FnDef(..)) => {
2177                     // As we don't compare regions, skip_binder is fine.
2178                     let a_poly_sig = a.fn_sig(tcx);
2179                     let b_poly_sig = b.fn_sig(tcx);
2180
2181                     let a_sig = a_poly_sig.skip_binder();
2182                     let b_sig = b_poly_sig.skip_binder();
2183
2184                     (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2185                         == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2186                         && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2187                             Self::structurally_same_type(cx, a, b)
2188                         })
2189                         && Self::structurally_same_type(cx, a_sig.output(), b_sig.output())
2190                 }
2191                 (Tuple(a_substs), Tuple(b_substs)) => {
2192                     a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2193                         Self::structurally_same_type(cx, a_ty, b_ty)
2194                     })
2195                 }
2196                 // For these, it's not quite as easy to define structural-sameness quite so easily.
2197                 // For the purposes of this lint, take the conservative approach and mark them as
2198                 // not structurally same.
2199                 (Dynamic(..), Dynamic(..))
2200                 | (Error(..), Error(..))
2201                 | (Closure(..), Closure(..))
2202                 | (Generator(..), Generator(..))
2203                 | (GeneratorWitness(..), GeneratorWitness(..))
2204                 | (Projection(..), Projection(..))
2205                 | (Opaque(..), Opaque(..)) => false,
2206                 // These definitely should have been caught above.
2207                 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2208                 _ => false,
2209             }
2210         }
2211     }
2212 }
2213
2214 impl_lint_pass!(ClashingExternDecl => [CLASHING_EXTERN_DECL]);
2215
2216 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ClashingExternDecl {
2217     fn check_foreign_item(&mut self, cx: &LateContext<'a, 'tcx>, this_fi: &hir::ForeignItem<'_>) {
2218         trace!("ClashingExternDecl: check_foreign_item: {:?}", this_fi);
2219         if let ForeignItemKind::Fn(..) = this_fi.kind {
2220             let tcx = *&cx.tcx;
2221             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2222                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2223                 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2224                 debug!(
2225                     "ClashingExternDecl: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2226                     existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2227                 );
2228                 // Check that the declarations match.
2229                 if !Self::structurally_same_type(cx, existing_decl_ty, this_decl_ty) {
2230                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2231                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
2232
2233                     // We want to ensure that we use spans for both decls that include where the
2234                     // name was defined, whether that was from the link_name attribute or not.
2235                     let get_relevant_span =
2236                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2237                             SymbolName::Normal(_) => fi.span,
2238                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2239                         };
2240                     // Finally, emit the diagnostic.
2241                     tcx.struct_span_lint_hir(
2242                         CLASHING_EXTERN_DECL,
2243                         this_fi.hir_id,
2244                         get_relevant_span(this_fi),
2245                         |lint| {
2246                             let mut expected_str = DiagnosticStyledString::new();
2247                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2248                             let mut found_str = DiagnosticStyledString::new();
2249                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2250
2251                             lint.build(&format!(
2252                                 "`{}` redeclare{} with a different signature",
2253                                 this_fi.ident.name,
2254                                 if orig.get_name() == this_fi.ident.name {
2255                                     "d".to_string()
2256                                 } else {
2257                                     format!("s `{}`", orig.get_name())
2258                                 }
2259                             ))
2260                             .span_label(
2261                                 get_relevant_span(orig_fi),
2262                                 &format!("`{}` previously declared here", orig.get_name()),
2263                             )
2264                             .span_label(
2265                                 get_relevant_span(this_fi),
2266                                 "this signature doesn't match the previous declaration",
2267                             )
2268                             .note_expected_found(&"", expected_str, &"", found_str)
2269                             .emit()
2270                         },
2271                     );
2272                 }
2273             }
2274         }
2275     }
2276 }