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::{
  24     types::CItemKind, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
  25 };
  26 use rustc_ast::ast::{self, Expr};
  27 use rustc_ast::attr::{self, HasAttrs};
  28 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  29 use rustc_ast::visit::{FnCtxt, FnKind};
  30 use rustc_ast_pretty::pprust::{self, expr_to_string};
  31 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  32 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
  33 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
  34 use rustc_feature::{GateIssue, Stability};
  35 use rustc_hir as hir;
  36 use rustc_hir::def::{DefKind, Res};
  37 use rustc_hir::def_id::DefId;
  38 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
  39 use rustc_hir::{HirId, HirIdSet, Node};
  40 use rustc_middle::lint::LintDiagnosticBuilder;
  41 use rustc_middle::ty::subst::{GenericArgKind, Subst};
  42 use rustc_middle::ty::{self, Ty, TyCtxt};
  43 use rustc_session::lint::FutureIncompatibleInfo;
  44 use rustc_session::Session;
  45 use rustc_span::edition::Edition;
  46 use rustc_span::source_map::Spanned;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{BytePos, Span};
  49 use rustc_target::abi::{LayoutOf, VariantIdx};
  50 use rustc_trait_selection::traits::misc::can_type_implement_copy;
  51
  52 use crate::nonstandard_style::{method_context, MethodLateContext};
  53
  54 use log::{debug, trace};
  55 use std::fmt::Write;
  56
  57 // hardwired lints from librustc_middle
  58 pub use rustc_session::lint::builtin::*;
  59
  60 declare_lint! {
  61     WHILE_TRUE,
  62     Warn,
  63     "suggest using `loop { }` instead of `while true { }`"
  64 }
  65
  66 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  67
  68 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  69 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  70     while let ast::ExprKind::Paren(sub) = &expr.kind {
  71         expr = sub;
  72     }
  73     expr
  74 }
  75
  76 impl EarlyLintPass for WhileTrue {
  77     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
  78         if let ast::ExprKind::While(cond, ..) = &e.kind {
  79             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
  80                 if let ast::LitKind::Bool(true) = lit.kind {
  81                     if !lit.span.from_expansion() {
  82                         let msg = "denote infinite loops with `loop { ... }`";
  83                         let condition_span = cx.sess.source_map().guess_head_span(e.span);
  84                         cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
  85                             lint.build(msg)
  86                                 .span_suggestion_short(
  87                                     condition_span,
  88                                     "use `loop`",
  89                                     "loop".to_owned(),
  90                                     Applicability::MachineApplicable,
  91                                 )
  92                                 .emit();
  93                         })
  94                     }
  95                 }
  96             }
  97         }
  98     }
  99 }
 100
 101 declare_lint! {
 102     BOX_POINTERS,
 103     Allow,
 104     "use of owned (Box type) heap memory"
 105 }
 106
 107 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 108
 109 impl BoxPointers {
 110     fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
 111         for leaf in ty.walk() {
 112             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
 113                 if leaf_ty.is_box() {
 114                     cx.struct_span_lint(BOX_POINTERS, span, |lint| {
 115                         lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
 116                     });
 117                 }
 118             }
 119         }
 120     }
 121 }
 122
 123 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
 124     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 125         match it.kind {
 126             hir::ItemKind::Fn(..)
 127             | hir::ItemKind::TyAlias(..)
 128             | hir::ItemKind::Enum(..)
 129             | hir::ItemKind::Struct(..)
 130             | hir::ItemKind::Union(..) => {
 131                 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 132                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 133             }
 134             _ => (),
 135         }
 136
 137         // If it's a struct, we also have to check the fields' types
 138         match it.kind {
 139             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 140                 for struct_field in struct_def.fields() {
 141                     let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
 142                     self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
 143                 }
 144             }
 145             _ => (),
 146         }
 147     }
 148
 149     fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
 150         let ty = cx.typeck_results().node_type(e.hir_id);
 151         self.check_heap_type(cx, e.span, ty);
 152     }
 153 }
 154
 155 declare_lint! {
 156     NON_SHORTHAND_FIELD_PATTERNS,
 157     Warn,
 158     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 159 }
 160
 161 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 162
 163 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
 164     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
 165         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 166             let variant = cx
 167                 .typeck_results()
 168                 .pat_ty(pat)
 169                 .ty_adt_def()
 170                 .expect("struct pattern type is not an ADT")
 171                 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
 172             for fieldpat in field_pats {
 173                 if fieldpat.is_shorthand {
 174                     continue;
 175                 }
 176                 if fieldpat.span.from_expansion() {
 177                     // Don't lint if this is a macro expansion: macro authors
 178                     // shouldn't have to worry about this kind of style issue
 179                     // (Issue #49588)
 180                     continue;
 181                 }
 182                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 183                     if cx.tcx.find_field_index(ident, &variant)
 184                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
 185                     {
 186                         cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
 187                             let mut err = lint
 188                                 .build(&format!("the `{}:` in this pattern is redundant", ident));
 189                             let binding = match binding_annot {
 190                                 hir::BindingAnnotation::Unannotated => None,
 191                                 hir::BindingAnnotation::Mutable => Some("mut"),
 192                                 hir::BindingAnnotation::Ref => Some("ref"),
 193                                 hir::BindingAnnotation::RefMut => Some("ref mut"),
 194                             };
 195                             let ident = if let Some(binding) = binding {
 196                                 format!("{} {}", binding, ident)
 197                             } else {
 198                                 ident.to_string()
 199                             };
 200                             err.span_suggestion(
 201                                 fieldpat.span,
 202                                 "use shorthand field pattern",
 203                                 ident,
 204                                 Applicability::MachineApplicable,
 205                             );
 206                             err.emit();
 207                         });
 208                     }
 209                 }
 210             }
 211         }
 212     }
 213 }
 214
 215 declare_lint! {
 216     UNSAFE_CODE,
 217     Allow,
 218     "usage of `unsafe` code"
 219 }
 220
 221 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 222
 223 impl UnsafeCode {
 224     fn report_unsafe(
 225         &self,
 226         cx: &EarlyContext<'_>,
 227         span: Span,
 228         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 229     ) {
 230         // This comes from a macro that has `#[allow_internal_unsafe]`.
 231         if span.allows_unsafe() {
 232             return;
 233         }
 234
 235         cx.struct_span_lint(UNSAFE_CODE, span, decorate);
 236     }
 237 }
 238
 239 impl EarlyLintPass for UnsafeCode {
 240     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 241         if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
 242             self.report_unsafe(cx, attr.span, |lint| {
 243                 lint.build(
 244                     "`allow_internal_unsafe` allows defining \
 245                                                macros using unsafe without triggering \
 246                                                the `unsafe_code` lint at their call site",
 247                 )
 248                 .emit()
 249             });
 250         }
 251     }
 252
 253     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 254         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 255             // Don't warn about generated blocks; that'll just pollute the output.
 256             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 257                 self.report_unsafe(cx, blk.span, |lint| {
 258                     lint.build("usage of an `unsafe` block").emit()
 259                 });
 260             }
 261         }
 262     }
 263
 264     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 265         match it.kind {
 266             ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
 267                 self.report_unsafe(cx, it.span, |lint| {
 268                     lint.build("declaration of an `unsafe` trait").emit()
 269                 })
 270             }
 271
 272             ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
 273                 self.report_unsafe(cx, it.span, |lint| {
 274                     lint.build("implementation of an `unsafe` trait").emit()
 275                 })
 276             }
 277
 278             _ => {}
 279         }
 280     }
 281
 282     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
 283         if let FnKind::Fn(
 284             ctxt,
 285             _,
 286             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
 287             _,
 288             body,
 289         ) = fk
 290         {
 291             let msg = match ctxt {
 292                 FnCtxt::Foreign => return,
 293                 FnCtxt::Free => "declaration of an `unsafe` function",
 294                 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
 295                 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
 296             };
 297             self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
 298         }
 299     }
 300 }
 301
 302 declare_lint! {
 303     pub MISSING_DOCS,
 304     Allow,
 305     "detects missing documentation for public members",
 306     report_in_external_macro
 307 }
 308
 309 pub struct MissingDoc {
 310     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 311     doc_hidden_stack: Vec<bool>,
 312
 313     /// Private traits or trait items that leaked through. Don't check their methods.
 314     private_traits: FxHashSet<hir::HirId>,
 315 }
 316
 317 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 318
 319 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
 320     if attr.is_doc_comment() {
 321         return true;
 322     }
 323
 324     if !sess.check_name(attr, sym::doc) {
 325         return false;
 326     }
 327
 328     if attr.is_value_str() {
 329         return true;
 330     }
 331
 332     if let Some(list) = attr.meta_item_list() {
 333         for meta in list {
 334             if meta.has_name(sym::include) || meta.has_name(sym::hidden) {
 335                 return true;
 336             }
 337         }
 338     }
 339
 340     false
 341 }
 342
 343 impl MissingDoc {
 344     pub fn new() -> MissingDoc {
 345         MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
 346     }
 347
 348     fn doc_hidden(&self) -> bool {
 349         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 350     }
 351
 352     fn check_missing_docs_attrs(
 353         &self,
 354         cx: &LateContext<'_>,
 355         id: Option<hir::HirId>,
 356         attrs: &[ast::Attribute],
 357         sp: Span,
 358         article: &'static str,
 359         desc: &'static str,
 360     ) {
 361         // If we're building a test harness, then warning about
 362         // documentation is probably not really relevant right now.
 363         if cx.sess().opts.test {
 364             return;
 365         }
 366
 367         // `#[doc(hidden)]` disables missing_docs check.
 368         if self.doc_hidden() {
 369             return;
 370         }
 371
 372         // Only check publicly-visible items, using the result from the privacy pass.
 373         // It's an option so the crate root can also use this function (it doesn't
 374         // have a `NodeId`).
 375         if let Some(id) = id {
 376             if !cx.access_levels.is_exported(id) {
 377                 return;
 378             }
 379         }
 380
 381         let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
 382         if !has_doc {
 383             cx.struct_span_lint(
 384                 MISSING_DOCS,
 385                 cx.tcx.sess.source_map().guess_head_span(sp),
 386                 |lint| {
 387                     lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
 388                 },
 389             );
 390         }
 391     }
 392 }
 393
 394 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 395     fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
 396         let doc_hidden = self.doc_hidden()
 397             || attrs.iter().any(|attr| {
 398                 cx.sess().check_name(attr, sym::doc)
 399                     && match attr.meta_item_list() {
 400                         None => false,
 401                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 402                     }
 403             });
 404         self.doc_hidden_stack.push(doc_hidden);
 405     }
 406
 407     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
 408         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 409     }
 410
 411     fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
 412         self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
 413
 414         for macro_def in krate.exported_macros {
 415             let has_doc = macro_def.attrs.iter().any(|a| has_doc(cx.sess(), a));
 416             if !has_doc {
 417                 cx.struct_span_lint(
 418                     MISSING_DOCS,
 419                     cx.tcx.sess.source_map().guess_head_span(macro_def.span),
 420                     |lint| lint.build("missing documentation for macro").emit(),
 421                 );
 422             }
 423         }
 424     }
 425
 426     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 427         match it.kind {
 428             hir::ItemKind::Trait(.., trait_item_refs) => {
 429                 // Issue #11592: traits are always considered exported, even when private.
 430                 if let hir::VisibilityKind::Inherited = it.vis.node {
 431                     self.private_traits.insert(it.hir_id);
 432                     for trait_item_ref in trait_item_refs {
 433                         self.private_traits.insert(trait_item_ref.id.hir_id);
 434                     }
 435                     return;
 436                 }
 437             }
 438             hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
 439                 // If the trait is private, add the impl items to `private_traits` so they don't get
 440                 // reported for missing docs.
 441                 let real_trait = trait_ref.path.res.def_id();
 442                 if let Some(def_id) = real_trait.as_local() {
 443                     let hir_id = cx.tcx.hir().as_local_hir_id(def_id);
 444                     if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
 445                         if let hir::VisibilityKind::Inherited = item.vis.node {
 446                             for impl_item_ref in items {
 447                                 self.private_traits.insert(impl_item_ref.id.hir_id);
 448                             }
 449                         }
 450                     }
 451                 }
 452                 return;
 453             }
 454
 455             hir::ItemKind::TyAlias(..)
 456             | hir::ItemKind::Fn(..)
 457             | hir::ItemKind::Mod(..)
 458             | hir::ItemKind::Enum(..)
 459             | hir::ItemKind::Struct(..)
 460             | hir::ItemKind::Union(..)
 461             | hir::ItemKind::Const(..)
 462             | hir::ItemKind::Static(..) => {}
 463
 464             _ => return,
 465         };
 466
 467         let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 468         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 469
 470         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
 471     }
 472
 473     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
 474         if self.private_traits.contains(&trait_item.hir_id) {
 475             return;
 476         }
 477
 478         let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
 479         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 480
 481         self.check_missing_docs_attrs(
 482             cx,
 483             Some(trait_item.hir_id),
 484             &trait_item.attrs,
 485             trait_item.span,
 486             article,
 487             desc,
 488         );
 489     }
 490
 491     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
 492         // If the method is an impl for a trait, don't doc.
 493         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 494             return;
 495         }
 496
 497         let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
 498         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 499         self.check_missing_docs_attrs(
 500             cx,
 501             Some(impl_item.hir_id),
 502             &impl_item.attrs,
 503             impl_item.span,
 504             article,
 505             desc,
 506         );
 507     }
 508
 509     fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
 510         if !sf.is_positional() {
 511             self.check_missing_docs_attrs(
 512                 cx,
 513                 Some(sf.hir_id),
 514                 &sf.attrs,
 515                 sf.span,
 516                 "a",
 517                 "struct field",
 518             )
 519         }
 520     }
 521
 522     fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
 523         self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
 524     }
 525 }
 526
 527 declare_lint! {
 528     pub MISSING_COPY_IMPLEMENTATIONS,
 529     Allow,
 530     "detects potentially-forgotten implementations of `Copy`"
 531 }
 532
 533 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 534
 535 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
 536     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 537         if !cx.access_levels.is_reachable(item.hir_id) {
 538             return;
 539         }
 540         let (def, ty) = match item.kind {
 541             hir::ItemKind::Struct(_, ref ast_generics) => {
 542                 if !ast_generics.params.is_empty() {
 543                     return;
 544                 }
 545                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 546                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 547             }
 548             hir::ItemKind::Union(_, ref ast_generics) => {
 549                 if !ast_generics.params.is_empty() {
 550                     return;
 551                 }
 552                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 553                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 554             }
 555             hir::ItemKind::Enum(_, ref ast_generics) => {
 556                 if !ast_generics.params.is_empty() {
 557                     return;
 558                 }
 559                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 560                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 561             }
 562             _ => return,
 563         };
 564         if def.has_dtor(cx.tcx) {
 565             return;
 566         }
 567         let param_env = ty::ParamEnv::empty();
 568         if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
 569             return;
 570         }
 571         if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
 572             cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
 573                 lint.build(
 574                     "type could implement `Copy`; consider adding `impl \
 575                           Copy`",
 576                 )
 577                 .emit()
 578             })
 579         }
 580     }
 581 }
 582
 583 declare_lint! {
 584     MISSING_DEBUG_IMPLEMENTATIONS,
 585     Allow,
 586     "detects missing implementations of Debug"
 587 }
 588
 589 #[derive(Default)]
 590 pub struct MissingDebugImplementations {
 591     impling_types: Option<HirIdSet>,
 592 }
 593
 594 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 595
 596 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 597     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 598         if !cx.access_levels.is_reachable(item.hir_id) {
 599             return;
 600         }
 601
 602         match item.kind {
 603             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 604             _ => return,
 605         }
 606
 607         let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
 608             Some(debug) => debug,
 609             None => return,
 610         };
 611
 612         if self.impling_types.is_none() {
 613             let mut impls = HirIdSet::default();
 614             cx.tcx.for_each_impl(debug, |d| {
 615                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 616                     if let Some(def_id) = ty_def.did.as_local() {
 617                         impls.insert(cx.tcx.hir().as_local_hir_id(def_id));
 618                     }
 619                 }
 620             });
 621
 622             self.impling_types = Some(impls);
 623             debug!("{:?}", self.impling_types);
 624         }
 625
 626         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 627             cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
 628                 lint.build(&format!(
 629                     "type does not implement `{}`; consider adding `#[derive(Debug)]` \
 630                      or a manual implementation",
 631                     cx.tcx.def_path_str(debug)
 632                 ))
 633                 .emit()
 634             });
 635         }
 636     }
 637 }
 638
 639 declare_lint! {
 640     pub ANONYMOUS_PARAMETERS,
 641     Allow,
 642     "detects anonymous parameters",
 643     @future_incompatible = FutureIncompatibleInfo {
 644         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 645         edition: Some(Edition::Edition2018),
 646     };
 647 }
 648
 649 declare_lint_pass!(
 650     /// Checks for use of anonymous parameters (RFC 1685).
 651     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 652 );
 653
 654 impl EarlyLintPass for AnonymousParameters {
 655     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 656         if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
 657             for arg in sig.decl.inputs.iter() {
 658                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 659                     if ident.name == kw::Invalid {
 660                         cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
 661                             let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
 662
 663                             let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 664                                 (snip.as_str(), Applicability::MachineApplicable)
 665                             } else {
 666                                 ("<type>", Applicability::HasPlaceholders)
 667                             };
 668
 669                             lint.build(
 670                                 "anonymous parameters are deprecated and will be \
 671                                      removed in the next edition.",
 672                             )
 673                             .span_suggestion(
 674                                 arg.pat.span,
 675                                 "try naming the parameter or explicitly \
 676                                             ignoring it",
 677                                 format!("_: {}", ty_snip),
 678                                 appl,
 679                             )
 680                             .emit();
 681                         })
 682                     }
 683                 }
 684             }
 685         }
 686     }
 687 }
 688
 689 /// Check for use of attributes which have been deprecated.
 690 #[derive(Clone)]
 691 pub struct DeprecatedAttr {
 692     // This is not free to compute, so we want to keep it around, rather than
 693     // compute it for every attribute.
 694     depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
 695 }
 696
 697 impl_lint_pass!(DeprecatedAttr => []);
 698
 699 impl DeprecatedAttr {
 700     pub fn new() -> DeprecatedAttr {
 701         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 702     }
 703 }
 704
 705 fn lint_deprecated_attr(
 706     cx: &EarlyContext<'_>,
 707     attr: &ast::Attribute,
 708     msg: &str,
 709     suggestion: Option<&str>,
 710 ) {
 711     cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
 712         lint.build(msg)
 713             .span_suggestion_short(
 714                 attr.span,
 715                 suggestion.unwrap_or("remove this attribute"),
 716                 String::new(),
 717                 Applicability::MachineApplicable,
 718             )
 719             .emit();
 720     })
 721 }
 722
 723 impl EarlyLintPass for DeprecatedAttr {
 724     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 725         for &&(n, _, _, ref g) in &self.depr_attrs {
 726             if attr.ident().map(|ident| ident.name) == Some(n) {
 727                 if let &AttributeGate::Gated(
 728                     Stability::Deprecated(link, suggestion),
 729                     ref name,
 730                     ref reason,
 731                     _,
 732                 ) = g
 733                 {
 734                     let msg =
 735                         format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
 736                     lint_deprecated_attr(cx, attr, &msg, suggestion);
 737                 }
 738                 return;
 739             }
 740         }
 741         if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
 742             let path_str = pprust::path_to_string(&attr.get_normal_item().path);
 743             let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
 744             lint_deprecated_attr(cx, attr, &msg, None);
 745         }
 746     }
 747 }
 748
 749 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
 750     let mut attrs = attrs.iter().peekable();
 751
 752     // Accumulate a single span for sugared doc comments.
 753     let mut sugared_span: Option<Span> = None;
 754
 755     while let Some(attr) = attrs.next() {
 756         if attr.is_doc_comment() {
 757             sugared_span =
 758                 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
 759         }
 760
 761         if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
 762             continue;
 763         }
 764
 765         let span = sugared_span.take().unwrap_or_else(|| attr.span);
 766
 767         if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
 768             cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
 769                 let mut err = lint.build("unused doc comment");
 770                 err.span_label(
 771                     node_span,
 772                     format!("rustdoc does not generate documentation for {}", node_kind),
 773                 );
 774                 err.emit();
 775             });
 776         }
 777     }
 778 }
 779
 780 impl EarlyLintPass for UnusedDocComment {
 781     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 782         let kind = match stmt.kind {
 783             ast::StmtKind::Local(..) => "statements",
 784             ast::StmtKind::Item(..) => "inner items",
 785             // expressions will be reported by `check_expr`.
 786             ast::StmtKind::Empty
 787             | ast::StmtKind::Semi(_)
 788             | ast::StmtKind::Expr(_)
 789             | ast::StmtKind::MacCall(_) => return,
 790         };
 791
 792         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
 793     }
 794
 795     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 796         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
 797         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
 798     }
 799
 800     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 801         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
 802     }
 803 }
 804
 805 declare_lint! {
 806     NO_MANGLE_CONST_ITEMS,
 807     Deny,
 808     "const items will not have their symbols exported"
 809 }
 810
 811 declare_lint! {
 812     NO_MANGLE_GENERIC_ITEMS,
 813     Warn,
 814     "generic items must be mangled"
 815 }
 816
 817 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
 818
 819 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
 820     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 821         match it.kind {
 822             hir::ItemKind::Fn(.., ref generics, _) => {
 823                 if let Some(no_mangle_attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 824                     for param in generics.params {
 825                         match param.kind {
 826                             GenericParamKind::Lifetime { .. } => {}
 827                             GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
 828                                 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
 829                                     lint.build(
 830                                         "functions generic over types or consts must be mangled",
 831                                     )
 832                                     .span_suggestion_short(
 833                                         no_mangle_attr.span,
 834                                         "remove this attribute",
 835                                         String::new(),
 836                                         // Use of `#[no_mangle]` suggests FFI intent; correct
 837                                         // fix may be to monomorphize source by hand
 838                                         Applicability::MaybeIncorrect,
 839                                     )
 840                                     .emit();
 841                                 });
 842                                 break;
 843                             }
 844                         }
 845                     }
 846                 }
 847             }
 848             hir::ItemKind::Const(..) => {
 849                 if cx.sess().contains_name(&it.attrs, sym::no_mangle) {
 850                     // Const items do not refer to a particular location in memory, and therefore
 851                     // don't have anything to attach a symbol to
 852                     cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
 853                         let msg = "const items should never be `#[no_mangle]`";
 854                         let mut err = lint.build(msg);
 855
 856                         // account for "pub const" (#45562)
 857                         let start = cx
 858                             .tcx
 859                             .sess
 860                             .source_map()
 861                             .span_to_snippet(it.span)
 862                             .map(|snippet| snippet.find("const").unwrap_or(0))
 863                             .unwrap_or(0) as u32;
 864                         // `const` is 5 chars
 865                         let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 866                         err.span_suggestion(
 867                             const_span,
 868                             "try a static value",
 869                             "pub static".to_owned(),
 870                             Applicability::MachineApplicable,
 871                         );
 872                         err.emit();
 873                     });
 874                 }
 875             }
 876             _ => {}
 877         }
 878     }
 879 }
 880
 881 declare_lint! {
 882     MUTABLE_TRANSMUTES,
 883     Deny,
 884     "mutating transmuted &mut T from &T may cause undefined behavior"
 885 }
 886
 887 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
 888
 889 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
 890     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
 891         use rustc_target::spec::abi::Abi::RustIntrinsic;
 892         if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
 893             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
 894         {
 895             if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
 896                 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 897                                consider instead using an UnsafeCell";
 898                 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
 899             }
 900         }
 901
 902         fn get_transmute_from_to<'tcx>(
 903             cx: &LateContext<'tcx>,
 904             expr: &hir::Expr<'_>,
 905         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
 906             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
 907                 cx.qpath_res(qpath, expr.hir_id)
 908             } else {
 909                 return None;
 910             };
 911             if let Res::Def(DefKind::Fn, did) = def {
 912                 if !def_id_is_transmute(cx, did) {
 913                     return None;
 914                 }
 915                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
 916                 let from = sig.inputs().skip_binder()[0];
 917                 let to = sig.output().skip_binder();
 918                 return Some((from, to));
 919             }
 920             None
 921         }
 922
 923         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
 924             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
 925                 && cx.tcx.item_name(def_id) == sym::transmute
 926         }
 927     }
 928 }
 929
 930 declare_lint! {
 931     UNSTABLE_FEATURES,
 932     Allow,
 933     "enabling unstable features (deprecated. do not use)"
 934 }
 935
 936 declare_lint_pass!(
 937     /// Forbids using the `#[feature(...)]` attribute
 938     UnstableFeatures => [UNSTABLE_FEATURES]
 939 );
 940
 941 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
 942     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
 943         if cx.sess().check_name(attr, sym::feature) {
 944             if let Some(items) = attr.meta_item_list() {
 945                 for item in items {
 946                     cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
 947                         lint.build("unstable feature").emit()
 948                     });
 949                 }
 950             }
 951         }
 952     }
 953 }
 954
 955 declare_lint! {
 956     pub UNREACHABLE_PUB,
 957     Allow,
 958     "`pub` items not reachable from crate root"
 959 }
 960
 961 declare_lint_pass!(
 962     /// Lint for items marked `pub` that aren't reachable from other crates.
 963     UnreachablePub => [UNREACHABLE_PUB]
 964 );
 965
 966 impl UnreachablePub {
 967     fn perform_lint(
 968         &self,
 969         cx: &LateContext<'_>,
 970         what: &str,
 971         id: hir::HirId,
 972         vis: &hir::Visibility<'_>,
 973         span: Span,
 974         exportable: bool,
 975     ) {
 976         let mut applicability = Applicability::MachineApplicable;
 977         match vis.node {
 978             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
 979                 if span.from_expansion() {
 980                     applicability = Applicability::MaybeIncorrect;
 981                 }
 982                 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
 983                 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
 984                     let mut err = lint.build(&format!("unreachable `pub` {}", what));
 985                     let replacement = if cx.tcx.features().crate_visibility_modifier {
 986                         "crate"
 987                     } else {
 988                         "pub(crate)"
 989                     }
 990                     .to_owned();
 991
 992                     err.span_suggestion(
 993                         vis.span,
 994                         "consider restricting its visibility",
 995                         replacement,
 996                         applicability,
 997                     );
 998                     if exportable {
 999                         err.help("or consider exporting it for use by other crates");
1000                     }
1001                     err.emit();
1002                 });
1003             }
1004             _ => {}
1005         }
1006     }
1007 }
1008
1009 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1010     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1011         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1012     }
1013
1014     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1015         self.perform_lint(
1016             cx,
1017             "item",
1018             foreign_item.hir_id,
1019             &foreign_item.vis,
1020             foreign_item.span,
1021             true,
1022         );
1023     }
1024
1025     fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
1026         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1027     }
1028
1029     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1030         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1031     }
1032 }
1033
1034 declare_lint! {
1035     TYPE_ALIAS_BOUNDS,
1036     Warn,
1037     "bounds in type aliases are not enforced"
1038 }
1039
1040 declare_lint_pass!(
1041     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1042     /// They are relevant when using associated types, but otherwise neither checked
1043     /// at definition site nor enforced at use site.
1044     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1045 );
1046
1047 impl TypeAliasBounds {
1048     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1049         match *qpath {
1050             hir::QPath::TypeRelative(ref ty, _) => {
1051                 // If this is a type variable, we found a `T::Assoc`.
1052                 match ty.kind {
1053                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1054                         Res::Def(DefKind::TyParam, _) => true,
1055                         _ => false,
1056                     },
1057                     _ => false,
1058                 }
1059             }
1060             hir::QPath::Resolved(..) => false,
1061         }
1062     }
1063
1064     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1065         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1066         // bound.  Let's see if this type does that.
1067
1068         // We use a HIR visitor to walk the type.
1069         use rustc_hir::intravisit::{self, Visitor};
1070         struct WalkAssocTypes<'a, 'db> {
1071             err: &'a mut DiagnosticBuilder<'db>,
1072         }
1073         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1074             type Map = intravisit::ErasedMap<'v>;
1075
1076             fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1077                 intravisit::NestedVisitorMap::None
1078             }
1079
1080             fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1081                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1082                     self.err.span_help(
1083                         span,
1084                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1085                          associated types in type aliases",
1086                     );
1087                 }
1088                 intravisit::walk_qpath(self, qpath, id, span)
1089             }
1090         }
1091
1092         // Let's go for a walk!
1093         let mut visitor = WalkAssocTypes { err };
1094         visitor.visit_ty(ty);
1095     }
1096 }
1097
1098 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1099     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1100         let (ty, type_alias_generics) = match item.kind {
1101             hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1102             _ => return,
1103         };
1104         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1105             // Bounds are respected for `type X = impl Trait`
1106             return;
1107         }
1108         let mut suggested_changing_assoc_types = false;
1109         // There must not be a where clause
1110         if !type_alias_generics.where_clause.predicates.is_empty() {
1111             cx.lint(
1112                 TYPE_ALIAS_BOUNDS,
1113                 |lint| {
1114                     let mut err = lint.build("where clauses are not enforced in type aliases");
1115                     let spans: Vec<_> = type_alias_generics
1116                         .where_clause
1117                         .predicates
1118                         .iter()
1119                         .map(|pred| pred.span())
1120                         .collect();
1121                     err.set_span(spans);
1122                     err.span_suggestion(
1123                         type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1124                         "the clause will not be checked when the type alias is used, and should be removed",
1125                         String::new(),
1126                         Applicability::MachineApplicable,
1127                     );
1128                     if !suggested_changing_assoc_types {
1129                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1130                         suggested_changing_assoc_types = true;
1131                     }
1132                     err.emit();
1133                 },
1134             );
1135         }
1136         // The parameters must not have bounds
1137         for param in type_alias_generics.params.iter() {
1138             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1139             let suggestion = spans
1140                 .iter()
1141                 .map(|sp| {
1142                     let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1143                     (start.to(*sp), String::new())
1144                 })
1145                 .collect();
1146             if !spans.is_empty() {
1147                 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1148                     let mut err =
1149                         lint.build("bounds on generic parameters are not enforced in type aliases");
1150                     let msg = "the bound will not be checked when the type alias is used, \
1151                                    and should be removed";
1152                     err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1153                     if !suggested_changing_assoc_types {
1154                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1155                         suggested_changing_assoc_types = true;
1156                     }
1157                     err.emit();
1158                 });
1159             }
1160         }
1161     }
1162 }
1163
1164 declare_lint_pass!(
1165     /// Lint constants that are erroneous.
1166     /// Without this lint, we might not get any diagnostic if the constant is
1167     /// unused within this crate, even though downstream crates can't use it
1168     /// without producing an error.
1169     UnusedBrokenConst => []
1170 );
1171
1172 fn check_const(cx: &LateContext<'_>, body_id: hir::BodyId) {
1173     let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1174     // trigger the query once for all constants since that will already report the errors
1175     // FIXME: Use ensure here
1176     let _ = cx.tcx.const_eval_poly(def_id);
1177 }
1178
1179 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1180     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1181         match it.kind {
1182             hir::ItemKind::Const(_, body_id) => {
1183                 check_const(cx, body_id);
1184             }
1185             hir::ItemKind::Static(_, _, body_id) => {
1186                 check_const(cx, body_id);
1187             }
1188             _ => {}
1189         }
1190     }
1191 }
1192
1193 declare_lint! {
1194     TRIVIAL_BOUNDS,
1195     Warn,
1196     "these bounds don't depend on an type parameters"
1197 }
1198
1199 declare_lint_pass!(
1200     /// Lint for trait and lifetime bounds that don't depend on type parameters
1201     /// which either do nothing, or stop the item from being used.
1202     TrivialConstraints => [TRIVIAL_BOUNDS]
1203 );
1204
1205 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1206     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1207         use rustc_middle::ty::fold::TypeFoldable;
1208         use rustc_middle::ty::PredicateAtom::*;
1209
1210         if cx.tcx.features().trivial_bounds {
1211             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1212             let predicates = cx.tcx.predicates_of(def_id);
1213             for &(predicate, span) in predicates.predicates {
1214                 let predicate_kind_name = match predicate.skip_binders() {
1215                     Trait(..) => "Trait",
1216                     TypeOutlives(..) |
1217                     RegionOutlives(..) => "Lifetime",
1218
1219                     // Ignore projections, as they can only be global
1220                     // if the trait bound is global
1221                     Projection(..) |
1222                     // Ignore bounds that a user can't type
1223                     WellFormed(..) |
1224                     ObjectSafe(..) |
1225                     ClosureKind(..) |
1226                     Subtype(..) |
1227                     ConstEvaluatable(..) |
1228                     ConstEquate(..) => continue,
1229                 };
1230                 if predicate.is_global() {
1231                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1232                         lint.build(&format!(
1233                             "{} bound {} does not depend on any type \
1234                                 or lifetime parameters",
1235                             predicate_kind_name, predicate
1236                         ))
1237                         .emit()
1238                     });
1239                 }
1240             }
1241         }
1242     }
1243 }
1244
1245 declare_lint_pass!(
1246     /// Does nothing as a lint pass, but registers some `Lint`s
1247     /// which are used by other parts of the compiler.
1248     SoftLints => [
1249         WHILE_TRUE,
1250         BOX_POINTERS,
1251         NON_SHORTHAND_FIELD_PATTERNS,
1252         UNSAFE_CODE,
1253         MISSING_DOCS,
1254         MISSING_COPY_IMPLEMENTATIONS,
1255         MISSING_DEBUG_IMPLEMENTATIONS,
1256         ANONYMOUS_PARAMETERS,
1257         UNUSED_DOC_COMMENTS,
1258         NO_MANGLE_CONST_ITEMS,
1259         NO_MANGLE_GENERIC_ITEMS,
1260         MUTABLE_TRANSMUTES,
1261         UNSTABLE_FEATURES,
1262         UNREACHABLE_PUB,
1263         TYPE_ALIAS_BOUNDS,
1264         TRIVIAL_BOUNDS
1265     ]
1266 );
1267
1268 declare_lint! {
1269     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1270     Warn,
1271     "`...` range patterns are deprecated"
1272 }
1273
1274 #[derive(Default)]
1275 pub struct EllipsisInclusiveRangePatterns {
1276     /// If `Some(_)`, suppress all subsequent pattern
1277     /// warnings for better diagnostics.
1278     node_id: Option<ast::NodeId>,
1279 }
1280
1281 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1282
1283 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1284     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1285         if self.node_id.is_some() {
1286             // Don't recursively warn about patterns inside range endpoints.
1287             return;
1288         }
1289
1290         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1291
1292         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1293         /// corresponding to the ellipsis.
1294         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1295             match &pat.kind {
1296                 PatKind::Range(
1297                     a,
1298                     Some(b),
1299                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1300                 ) => Some((a.as_deref(), b, *span)),
1301                 _ => None,
1302             }
1303         }
1304
1305         let (parenthesise, endpoints) = match &pat.kind {
1306             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1307             _ => (false, matches_ellipsis_pat(pat)),
1308         };
1309
1310         if let Some((start, end, join)) = endpoints {
1311             let msg = "`...` range patterns are deprecated";
1312             let suggestion = "use `..=` for an inclusive range";
1313             if parenthesise {
1314                 self.node_id = Some(pat.id);
1315                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1316                     let end = expr_to_string(&end);
1317                     let replace = match start {
1318                         Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1319                         None => format!("&(..={})", end),
1320                     };
1321                     lint.build(msg)
1322                         .span_suggestion(
1323                             pat.span,
1324                             suggestion,
1325                             replace,
1326                             Applicability::MachineApplicable,
1327                         )
1328                         .emit();
1329                 });
1330             } else {
1331                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1332                     lint.build(msg)
1333                         .span_suggestion_short(
1334                             join,
1335                             suggestion,
1336                             "..=".to_owned(),
1337                             Applicability::MachineApplicable,
1338                         )
1339                         .emit();
1340                 });
1341             };
1342         }
1343     }
1344
1345     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1346         if let Some(node_id) = self.node_id {
1347             if pat.id == node_id {
1348                 self.node_id = None
1349             }
1350         }
1351     }
1352 }
1353
1354 declare_lint! {
1355     UNNAMEABLE_TEST_ITEMS,
1356     Warn,
1357     "detects an item that cannot be named being marked as `#[test_case]`",
1358     report_in_external_macro
1359 }
1360
1361 pub struct UnnameableTestItems {
1362     boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1363     items_nameable: bool,
1364 }
1365
1366 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1367
1368 impl UnnameableTestItems {
1369     pub fn new() -> Self {
1370         Self { boundary: None, items_nameable: true }
1371     }
1372 }
1373
1374 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1375     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1376         if self.items_nameable {
1377             if let hir::ItemKind::Mod(..) = it.kind {
1378             } else {
1379                 self.items_nameable = false;
1380                 self.boundary = Some(it.hir_id);
1381             }
1382             return;
1383         }
1384
1385         if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::rustc_test_marker) {
1386             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1387                 lint.build("cannot test inner items").emit()
1388             });
1389         }
1390     }
1391
1392     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1393         if !self.items_nameable && self.boundary == Some(it.hir_id) {
1394             self.items_nameable = true;
1395         }
1396     }
1397 }
1398
1399 declare_lint! {
1400     pub KEYWORD_IDENTS,
1401     Allow,
1402     "detects edition keywords being used as an identifier",
1403     @future_incompatible = FutureIncompatibleInfo {
1404         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1405         edition: Some(Edition::Edition2018),
1406     };
1407 }
1408
1409 declare_lint_pass!(
1410     /// Check for uses of edition keywords used as an identifier.
1411     KeywordIdents => [KEYWORD_IDENTS]
1412 );
1413
1414 struct UnderMacro(bool);
1415
1416 impl KeywordIdents {
1417     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1418         for tt in tokens.into_trees() {
1419             match tt {
1420                 // Only report non-raw idents.
1421                 TokenTree::Token(token) => {
1422                     if let Some((ident, false)) = token.ident() {
1423                         self.check_ident_token(cx, UnderMacro(true), ident);
1424                     }
1425                 }
1426                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1427             }
1428         }
1429     }
1430
1431     fn check_ident_token(
1432         &mut self,
1433         cx: &EarlyContext<'_>,
1434         UnderMacro(under_macro): UnderMacro,
1435         ident: Ident,
1436     ) {
1437         let next_edition = match cx.sess.edition() {
1438             Edition::Edition2015 => {
1439                 match ident.name {
1440                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1441
1442                     // rust-lang/rust#56327: Conservatively do not
1443                     // attempt to report occurrences of `dyn` within
1444                     // macro definitions or invocations, because `dyn`
1445                     // can legitimately occur as a contextual keyword
1446                     // in 2015 code denoting its 2018 meaning, and we
1447                     // do not want rustfix to inject bugs into working
1448                     // code by rewriting such occurrences.
1449                     //
1450                     // But if we see `dyn` outside of a macro, we know
1451                     // its precise role in the parsed AST and thus are
1452                     // assured this is truly an attempt to use it as
1453                     // an identifier.
1454                     kw::Dyn if !under_macro => Edition::Edition2018,
1455
1456                     _ => return,
1457                 }
1458             }
1459
1460             // There are no new keywords yet for the 2018 edition and beyond.
1461             _ => return,
1462         };
1463
1464         // Don't lint `r#foo`.
1465         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1466             return;
1467         }
1468
1469         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1470             lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1471                 .span_suggestion(
1472                     ident.span,
1473                     "you can use a raw identifier to stay compatible",
1474                     format!("r#{}", ident),
1475                     Applicability::MachineApplicable,
1476                 )
1477                 .emit()
1478         });
1479     }
1480 }
1481
1482 impl EarlyLintPass for KeywordIdents {
1483     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1484         self.check_tokens(cx, mac_def.body.inner_tokens());
1485     }
1486     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1487         self.check_tokens(cx, mac.args.inner_tokens());
1488     }
1489     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1490         self.check_ident_token(cx, UnderMacro(false), ident);
1491     }
1492 }
1493
1494 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1495
1496 impl ExplicitOutlivesRequirements {
1497     fn lifetimes_outliving_lifetime<'tcx>(
1498         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1499         index: u32,
1500     ) -> Vec<ty::Region<'tcx>> {
1501         inferred_outlives
1502             .iter()
1503             .filter_map(|(pred, _)| match pred.skip_binders() {
1504                 ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1505                     ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
1506                     _ => None,
1507                 },
1508                 _ => None,
1509             })
1510             .collect()
1511     }
1512
1513     fn lifetimes_outliving_type<'tcx>(
1514         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1515         index: u32,
1516     ) -> Vec<ty::Region<'tcx>> {
1517         inferred_outlives
1518             .iter()
1519             .filter_map(|(pred, _)| match pred.skip_binders() {
1520                 ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1521                     a.is_param(index).then_some(b)
1522                 }
1523                 _ => None,
1524             })
1525             .collect()
1526     }
1527
1528     fn collect_outlived_lifetimes<'tcx>(
1529         &self,
1530         param: &'tcx hir::GenericParam<'tcx>,
1531         tcx: TyCtxt<'tcx>,
1532         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1533         ty_generics: &'tcx ty::Generics,
1534     ) -> Vec<ty::Region<'tcx>> {
1535         let index =
1536             ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1537
1538         match param.kind {
1539             hir::GenericParamKind::Lifetime { .. } => {
1540                 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1541             }
1542             hir::GenericParamKind::Type { .. } => {
1543                 Self::lifetimes_outliving_type(inferred_outlives, index)
1544             }
1545             hir::GenericParamKind::Const { .. } => Vec::new(),
1546         }
1547     }
1548
1549     fn collect_outlives_bound_spans<'tcx>(
1550         &self,
1551         tcx: TyCtxt<'tcx>,
1552         bounds: &hir::GenericBounds<'_>,
1553         inferred_outlives: &[ty::Region<'tcx>],
1554         infer_static: bool,
1555     ) -> Vec<(usize, Span)> {
1556         use rustc_middle::middle::resolve_lifetime::Region;
1557
1558         bounds
1559             .iter()
1560             .enumerate()
1561             .filter_map(|(i, bound)| {
1562                 if let hir::GenericBound::Outlives(lifetime) = bound {
1563                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
1564                         Some(Region::Static) if infer_static => inferred_outlives
1565                             .iter()
1566                             .any(|r| if let ty::ReStatic = r { true } else { false }),
1567                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1568                             if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1569                         }),
1570                         _ => false,
1571                     };
1572                     is_inferred.then_some((i, bound.span()))
1573                 } else {
1574                     None
1575                 }
1576             })
1577             .collect()
1578     }
1579
1580     fn consolidate_outlives_bound_spans(
1581         &self,
1582         lo: Span,
1583         bounds: &hir::GenericBounds<'_>,
1584         bound_spans: Vec<(usize, Span)>,
1585     ) -> Vec<Span> {
1586         if bounds.is_empty() {
1587             return Vec::new();
1588         }
1589         if bound_spans.len() == bounds.len() {
1590             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1591             // If all bounds are inferable, we want to delete the colon, so
1592             // start from just after the parameter (span passed as argument)
1593             vec![lo.to(last_bound_span)]
1594         } else {
1595             let mut merged = Vec::new();
1596             let mut last_merged_i = None;
1597
1598             let mut from_start = true;
1599             for (i, bound_span) in bound_spans {
1600                 match last_merged_i {
1601                     // If the first bound is inferable, our span should also eat the leading `+`.
1602                     None if i == 0 => {
1603                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1604                         last_merged_i = Some(0);
1605                     }
1606                     // If consecutive bounds are inferable, merge their spans
1607                     Some(h) if i == h + 1 => {
1608                         if let Some(tail) = merged.last_mut() {
1609                             // Also eat the trailing `+` if the first
1610                             // more-than-one bound is inferable
1611                             let to_span = if from_start && i < bounds.len() {
1612                                 bounds[i + 1].span().shrink_to_lo()
1613                             } else {
1614                                 bound_span
1615                             };
1616                             *tail = tail.to(to_span);
1617                             last_merged_i = Some(i);
1618                         } else {
1619                             bug!("another bound-span visited earlier");
1620                         }
1621                     }
1622                     _ => {
1623                         // When we find a non-inferable bound, subsequent inferable bounds
1624                         // won't be consecutive from the start (and we'll eat the leading
1625                         // `+` rather than the trailing one)
1626                         from_start = false;
1627                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1628                         last_merged_i = Some(i);
1629                     }
1630                 }
1631             }
1632             merged
1633         }
1634     }
1635 }
1636
1637 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
1638     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
1639         use rustc_middle::middle::resolve_lifetime::Region;
1640
1641         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1642         let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1643         if let hir::ItemKind::Struct(_, ref hir_generics)
1644         | hir::ItemKind::Enum(_, ref hir_generics)
1645         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1646         {
1647             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1648             if inferred_outlives.is_empty() {
1649                 return;
1650             }
1651
1652             let ty_generics = cx.tcx.generics_of(def_id);
1653
1654             let mut bound_count = 0;
1655             let mut lint_spans = Vec::new();
1656
1657             for param in hir_generics.params {
1658                 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1659                     if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1660                 });
1661                 if !has_lifetime_bounds {
1662                     continue;
1663                 }
1664
1665                 let relevant_lifetimes =
1666                     self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1667                 if relevant_lifetimes.is_empty() {
1668                     continue;
1669                 }
1670
1671                 let bound_spans = self.collect_outlives_bound_spans(
1672                     cx.tcx,
1673                     &param.bounds,
1674                     &relevant_lifetimes,
1675                     infer_static,
1676                 );
1677                 bound_count += bound_spans.len();
1678                 lint_spans.extend(self.consolidate_outlives_bound_spans(
1679                     param.span.shrink_to_hi(),
1680                     &param.bounds,
1681                     bound_spans,
1682                 ));
1683             }
1684
1685             let mut where_lint_spans = Vec::new();
1686             let mut dropped_predicate_count = 0;
1687             let num_predicates = hir_generics.where_clause.predicates.len();
1688             for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1689                 let (relevant_lifetimes, bounds, span) = match where_predicate {
1690                     hir::WherePredicate::RegionPredicate(predicate) => {
1691                         if let Some(Region::EarlyBound(index, ..)) =
1692                             cx.tcx.named_region(predicate.lifetime.hir_id)
1693                         {
1694                             (
1695                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1696                                 &predicate.bounds,
1697                                 predicate.span,
1698                             )
1699                         } else {
1700                             continue;
1701                         }
1702                     }
1703                     hir::WherePredicate::BoundPredicate(predicate) => {
1704                         // FIXME we can also infer bounds on associated types,
1705                         // and should check for them here.
1706                         match predicate.bounded_ty.kind {
1707                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1708                                 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1709                                     let index = ty_generics.param_def_id_to_index[&def_id];
1710                                     (
1711                                         Self::lifetimes_outliving_type(inferred_outlives, index),
1712                                         &predicate.bounds,
1713                                         predicate.span,
1714                                     )
1715                                 } else {
1716                                     continue;
1717                                 }
1718                             }
1719                             _ => {
1720                                 continue;
1721                             }
1722                         }
1723                     }
1724                     _ => continue,
1725                 };
1726                 if relevant_lifetimes.is_empty() {
1727                     continue;
1728                 }
1729
1730                 let bound_spans = self.collect_outlives_bound_spans(
1731                     cx.tcx,
1732                     bounds,
1733                     &relevant_lifetimes,
1734                     infer_static,
1735                 );
1736                 bound_count += bound_spans.len();
1737
1738                 let drop_predicate = bound_spans.len() == bounds.len();
1739                 if drop_predicate {
1740                     dropped_predicate_count += 1;
1741                 }
1742
1743                 // If all the bounds on a predicate were inferable and there are
1744                 // further predicates, we want to eat the trailing comma.
1745                 if drop_predicate && i + 1 < num_predicates {
1746                     let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1747                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1748                 } else {
1749                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1750                         span.shrink_to_lo(),
1751                         bounds,
1752                         bound_spans,
1753                     ));
1754                 }
1755             }
1756
1757             // If all predicates are inferable, drop the entire clause
1758             // (including the `where`)
1759             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1760                 let where_span = hir_generics
1761                     .where_clause
1762                     .span()
1763                     .expect("span of (nonempty) where clause should exist");
1764                 // Extend the where clause back to the closing `>` of the
1765                 // generics, except for tuple struct, which have the `where`
1766                 // after the fields of the struct.
1767                 let full_where_span =
1768                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1769                         where_span
1770                     } else {
1771                         hir_generics.span.shrink_to_hi().to(where_span)
1772                     };
1773                 lint_spans.push(full_where_span);
1774             } else {
1775                 lint_spans.extend(where_lint_spans);
1776             }
1777
1778             if !lint_spans.is_empty() {
1779                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1780                     lint.build("outlives requirements can be inferred")
1781                         .multipart_suggestion(
1782                             if bound_count == 1 {
1783                                 "remove this bound"
1784                             } else {
1785                                 "remove these bounds"
1786                             },
1787                             lint_spans
1788                                 .into_iter()
1789                                 .map(|span| (span, "".to_owned()))
1790                                 .collect::<Vec<_>>(),
1791                             Applicability::MachineApplicable,
1792                         )
1793                         .emit();
1794                 });
1795             }
1796         }
1797     }
1798 }
1799
1800 declare_lint! {
1801     pub INCOMPLETE_FEATURES,
1802     Warn,
1803     "incomplete features that may function improperly in some or all cases"
1804 }
1805
1806 declare_lint_pass!(
1807     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1808     IncompleteFeatures => [INCOMPLETE_FEATURES]
1809 );
1810
1811 impl EarlyLintPass for IncompleteFeatures {
1812     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1813         let features = cx.sess.features_untracked();
1814         features
1815             .declared_lang_features
1816             .iter()
1817             .map(|(name, span, _)| (name, span))
1818             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1819             .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1820             .for_each(|(&name, &span)| {
1821                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1822                     let mut builder = lint.build(&format!(
1823                         "the feature `{}` is incomplete and may not be safe to use \
1824                          and/or cause compiler crashes",
1825                         name,
1826                     ));
1827                     if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1828                         builder.note(&format!(
1829                             "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1830                              for more information",
1831                             n, n,
1832                         ));
1833                     }
1834                     builder.emit();
1835                 })
1836             });
1837     }
1838 }
1839
1840 declare_lint! {
1841     pub INVALID_VALUE,
1842     Warn,
1843     "an invalid value is being created (such as a NULL reference)"
1844 }
1845
1846 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1847
1848 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
1849     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
1850         #[derive(Debug, Copy, Clone, PartialEq)]
1851         enum InitKind {
1852             Zeroed,
1853             Uninit,
1854         };
1855
1856         /// Information about why a type cannot be initialized this way.
1857         /// Contains an error message and optionally a span to point at.
1858         type InitError = (String, Option<Span>);
1859
1860         /// Test if this constant is all-0.
1861         fn is_zero(expr: &hir::Expr<'_>) -> bool {
1862             use hir::ExprKind::*;
1863             use rustc_ast::ast::LitKind::*;
1864             match &expr.kind {
1865                 Lit(lit) => {
1866                     if let Int(i, _) = lit.node {
1867                         i == 0
1868                     } else {
1869                         false
1870                     }
1871                 }
1872                 Tup(tup) => tup.iter().all(is_zero),
1873                 _ => false,
1874             }
1875         }
1876
1877         /// Determine if this expression is a "dangerous initialization".
1878         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1879             // `transmute` is inside an anonymous module (the `extern` block?);
1880             // `Invalid` represents the empty string and matches that.
1881             // FIXME(#66075): use diagnostic items.  Somehow, that does not seem to work
1882             // on intrinsics right now.
1883             const TRANSMUTE_PATH: &[Symbol] =
1884                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1885
1886             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1887                 // Find calls to `mem::{uninitialized,zeroed}` methods.
1888                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1889                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1890
1891                     if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1892                         return Some(InitKind::Zeroed);
1893                     } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1894                         return Some(InitKind::Uninit);
1895                     } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1896                         if is_zero(&args[0]) {
1897                             return Some(InitKind::Zeroed);
1898                         }
1899                     }
1900                 }
1901             } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1902                 // Find problematic calls to `MaybeUninit::assume_init`.
1903                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
1904                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1905                     // This is a call to *some* method named `assume_init`.
1906                     // See if the `self` parameter is one of the dangerous constructors.
1907                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1908                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1909                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1910
1911                             if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1912                                 return Some(InitKind::Zeroed);
1913                             } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1914                                 return Some(InitKind::Uninit);
1915                             }
1916                         }
1917                     }
1918                 }
1919             }
1920
1921             None
1922         }
1923
1924         /// Test if this enum has several actually "existing" variants.
1925         /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
1926         fn is_multi_variant(adt: &ty::AdtDef) -> bool {
1927             // As an approximation, we only count dataless variants. Those are definitely inhabited.
1928             let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
1929             existing_variants > 1
1930         }
1931
1932         /// Return `Some` only if we are sure this type does *not*
1933         /// allow zero initialization.
1934         fn ty_find_init_error<'tcx>(
1935             tcx: TyCtxt<'tcx>,
1936             ty: Ty<'tcx>,
1937             init: InitKind,
1938         ) -> Option<InitError> {
1939             use rustc_middle::ty::TyKind::*;
1940             match ty.kind {
1941                 // Primitive types that don't like 0 as a value.
1942                 Ref(..) => Some(("references must be non-null".to_string(), None)),
1943                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1944                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1945                 Never => Some(("the `!` type has no valid value".to_string(), None)),
1946                 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1947                 // raw ptr to dyn Trait
1948                 {
1949                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1950                 }
1951                 // Primitive types with other constraints.
1952                 Bool if init == InitKind::Uninit => {
1953                     Some(("booleans must be either `true` or `false`".to_string(), None))
1954                 }
1955                 Char if init == InitKind::Uninit => {
1956                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
1957                 }
1958                 // Recurse and checks for some compound types.
1959                 Adt(adt_def, substs) if !adt_def.is_union() => {
1960                     // First check if this ADT has a layout attribute (like `NonNull` and friends).
1961                     use std::ops::Bound;
1962                     match tcx.layout_scalar_valid_range(adt_def.did) {
1963                         // We exploit here that `layout_scalar_valid_range` will never
1964                         // return `Bound::Excluded`.  (And we have tests checking that we
1965                         // handle the attribute correctly.)
1966                         (Bound::Included(lo), _) if lo > 0 => {
1967                             return Some((format!("`{}` must be non-null", ty), None));
1968                         }
1969                         (Bound::Included(_), _) | (_, Bound::Included(_))
1970                             if init == InitKind::Uninit =>
1971                         {
1972                             return Some((
1973                                 format!(
1974                                     "`{}` must be initialized inside its custom valid range",
1975                                     ty,
1976                                 ),
1977                                 None,
1978                             ));
1979                         }
1980                         _ => {}
1981                     }
1982                     // Now, recurse.
1983                     match adt_def.variants.len() {
1984                         0 => Some(("enums with no variants have no valid value".to_string(), None)),
1985                         1 => {
1986                             // Struct, or enum with exactly one variant.
1987                             // Proceed recursively, check all fields.
1988                             let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1989                             variant.fields.iter().find_map(|field| {
1990                                 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1991                                     |(mut msg, span)| {
1992                                         if span.is_none() {
1993                                             // Point to this field, should be helpful for figuring
1994                                             // out where the source of the error is.
1995                                             let span = tcx.def_span(field.did);
1996                                             write!(
1997                                                 &mut msg,
1998                                                 " (in this {} field)",
1999                                                 adt_def.descr()
2000                                             )
2001                                             .unwrap();
2002                                             (msg, Some(span))
2003                                         } else {
2004                                             // Just forward.
2005                                             (msg, span)
2006                                         }
2007                                     },
2008                                 )
2009                             })
2010                         }
2011                         // Multi-variant enum.
2012                         _ => {
2013                             if init == InitKind::Uninit && is_multi_variant(adt_def) {
2014                                 let span = tcx.def_span(adt_def.did);
2015                                 Some((
2016                                     "enums have to be initialized to a variant".to_string(),
2017                                     Some(span),
2018                                 ))
2019                             } else {
2020                                 // In principle, for zero-initialization we could figure out which variant corresponds
2021                                 // to tag 0, and check that... but for now we just accept all zero-initializations.
2022                                 None
2023                             }
2024                         }
2025                     }
2026                 }
2027                 Tuple(..) => {
2028                     // Proceed recursively, check all fields.
2029                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2030                 }
2031                 // Conservative fallback.
2032                 _ => None,
2033             }
2034         }
2035
2036         if let Some(init) = is_dangerous_init(cx, expr) {
2037             // This conjures an instance of a type out of nothing,
2038             // using zeroed or uninitialized memory.
2039             // We are extremely conservative with what we warn about.
2040             let conjured_ty = cx.typeck_results().expr_ty(expr);
2041             if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2042                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2043                     let mut err = lint.build(&format!(
2044                         "the type `{}` does not permit {}",
2045                         conjured_ty,
2046                         match init {
2047                             InitKind::Zeroed => "zero-initialization",
2048                             InitKind::Uninit => "being left uninitialized",
2049                         },
2050                     ));
2051                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2052                     err.span_label(
2053                         expr.span,
2054                         "help: use `MaybeUninit<T>` instead, \
2055                             and only call `assume_init` after initialization is done",
2056                     );
2057                     if let Some(span) = span {
2058                         err.span_note(span, &msg);
2059                     } else {
2060                         err.note(&msg);
2061                     }
2062                     err.emit();
2063                 });
2064             }
2065         }
2066     }
2067 }
2068
2069 declare_lint! {
2070     pub CLASHING_EXTERN_DECLARATIONS,
2071     Warn,
2072     "detects when an extern fn has been declared with the same name but different types"
2073 }
2074
2075 pub struct ClashingExternDeclarations {
2076     seen_decls: FxHashMap<Symbol, HirId>,
2077 }
2078
2079 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2080 /// just from declaration itself. This is important because we don't want to report clashes on
2081 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2082 /// different name.
2083 enum SymbolName {
2084     /// The name of the symbol + the span of the annotation which introduced the link name.
2085     Link(Symbol, Span),
2086     /// No link name, so just the name of the symbol.
2087     Normal(Symbol),
2088 }
2089
2090 impl SymbolName {
2091     fn get_name(&self) -> Symbol {
2092         match self {
2093             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2094         }
2095     }
2096 }
2097
2098 impl ClashingExternDeclarations {
2099     crate fn new() -> Self {
2100         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2101     }
2102     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2103     /// for the item, return its HirId without updating the set.
2104     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2105         let hid = fi.hir_id;
2106
2107         let name =
2108             &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2109
2110         if self.seen_decls.contains_key(name) {
2111             // Avoid updating the map with the new entry when we do find a collision. We want to
2112             // make sure we're always pointing to the first definition as the previous declaration.
2113             // This lets us avoid emitting "knock-on" diagnostics.
2114             Some(*self.seen_decls.get(name).unwrap())
2115         } else {
2116             self.seen_decls.insert(*name, hid)
2117         }
2118     }
2119
2120     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2121     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2122     /// symbol's name.
2123     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2124         let did = tcx.hir().local_def_id(fi.hir_id);
2125         if let Some((overridden_link_name, overridden_link_name_span)) =
2126             tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2127                 // FIXME: Instead of searching through the attributes again to get span
2128                 // information, we could have codegen_fn_attrs also give span information back for
2129                 // where the attribute was defined. However, until this is found to be a
2130                 // bottleneck, this does just fine.
2131                 (
2132                     overridden_link_name,
2133                     tcx.get_attrs(did.to_def_id())
2134                         .iter()
2135                         .find(|at| tcx.sess.check_name(at, sym::link_name))
2136                         .unwrap()
2137                         .span,
2138                 )
2139             })
2140         {
2141             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2142         } else {
2143             SymbolName::Normal(fi.ident.name)
2144         }
2145     }
2146
2147     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2148     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2149     /// with the same members (as the declarations shouldn't clash).
2150     fn structurally_same_type<'tcx>(
2151         cx: &LateContext<'tcx>,
2152         a: Ty<'tcx>,
2153         b: Ty<'tcx>,
2154         ckind: CItemKind,
2155     ) -> bool {
2156         debug!("structurally_same_type(cx, a = {:?}, b = {:?})", a, b);
2157         let tcx = cx.tcx;
2158         if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2159             // All nominally-same types are structurally same, too.
2160             true
2161         } else {
2162             // Do a full, depth-first comparison between the two.
2163             use rustc_middle::ty::TyKind::*;
2164             let a_kind = &a.kind;
2165             let b_kind = &b.kind;
2166
2167             let compare_layouts = |a, b| -> bool {
2168                 let a_layout = &cx.layout_of(a).unwrap().layout.abi;
2169                 let b_layout = &cx.layout_of(b).unwrap().layout.abi;
2170                 debug!("{:?} == {:?} = {}", a_layout, b_layout, a_layout == b_layout);
2171                 a_layout == b_layout
2172             };
2173
2174             #[allow(rustc::usage_of_ty_tykind)]
2175             let is_primitive_or_pointer =
2176                 |kind: &ty::TyKind<'_>| kind.is_primitive() || matches!(kind, RawPtr(..));
2177
2178             match (a_kind, b_kind) {
2179                 (Adt(_, a_substs), Adt(_, b_substs)) => {
2180                     let a = a.subst(cx.tcx, a_substs);
2181                     let b = b.subst(cx.tcx, b_substs);
2182                     debug!("Comparing {:?} and {:?}", a, b);
2183
2184                     if let (Adt(a_def, ..), Adt(b_def, ..)) = (&a.kind, &b.kind) {
2185                         // Grab a flattened representation of all fields.
2186                         let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2187                         let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2188                         compare_layouts(a, b)
2189                             && a_fields.eq_by(
2190                                 b_fields,
2191                                 |&ty::FieldDef { did: a_did, .. },
2192                                  &ty::FieldDef { did: b_did, .. }| {
2193                                     Self::structurally_same_type(
2194                                         cx,
2195                                         tcx.type_of(a_did),
2196                                         tcx.type_of(b_did),
2197                                         ckind,
2198                                     )
2199                                 },
2200                             )
2201                     } else {
2202                         unreachable!()
2203                     }
2204                 }
2205                 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2206                     // For arrays, we also check the constness of the type.
2207                     a_const.val == b_const.val
2208                         && Self::structurally_same_type(cx, a_const.ty, b_const.ty, ckind)
2209                         && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2210                 }
2211                 (Slice(a_ty), Slice(b_ty)) => Self::structurally_same_type(cx, a_ty, b_ty, ckind),
2212                 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2213                     a_tymut.mutbl == b_tymut.mutbl
2214                         && Self::structurally_same_type(cx, &a_tymut.ty, &b_tymut.ty, ckind)
2215                 }
2216                 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2217                     // For structural sameness, we don't need the region to be same.
2218                     a_mut == b_mut && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2219                 }
2220                 (FnDef(..), FnDef(..)) => {
2221                     let a_poly_sig = a.fn_sig(tcx);
2222                     let b_poly_sig = b.fn_sig(tcx);
2223
2224                     // As we don't compare regions, skip_binder is fine.
2225                     let a_sig = a_poly_sig.skip_binder();
2226                     let b_sig = b_poly_sig.skip_binder();
2227
2228                     (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2229                         == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2230                         && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2231                             Self::structurally_same_type(cx, a, b, ckind)
2232                         })
2233                         && Self::structurally_same_type(cx, a_sig.output(), b_sig.output(), ckind)
2234                 }
2235                 (Tuple(a_substs), Tuple(b_substs)) => {
2236                     a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2237                         Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2238                     })
2239                 }
2240                 // For these, it's not quite as easy to define structural-sameness quite so easily.
2241                 // For the purposes of this lint, take the conservative approach and mark them as
2242                 // not structurally same.
2243                 (Dynamic(..), Dynamic(..))
2244                 | (Error(..), Error(..))
2245                 | (Closure(..), Closure(..))
2246                 | (Generator(..), Generator(..))
2247                 | (GeneratorWitness(..), GeneratorWitness(..))
2248                 | (Projection(..), Projection(..))
2249                 | (Opaque(..), Opaque(..)) => false,
2250
2251                 // These definitely should have been caught above.
2252                 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2253
2254                 // An Adt and a primitive type. This can be FFI-safe is the ADT is an enum with a
2255                 // non-null field.
2256                 (Adt(..), other_kind) | (other_kind, Adt(..))
2257                     if is_primitive_or_pointer(other_kind) =>
2258                 {
2259                     let (primitive, adt) =
2260                         if is_primitive_or_pointer(&a.kind) { (a, b) } else { (b, a) };
2261                     if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2262                         ty == primitive
2263                     } else {
2264                         compare_layouts(a, b)
2265                     }
2266                 }
2267                 // Otherwise, just compare the layouts. This may fail to lint for some
2268                 // incompatible types, but at the very least, will stop reads into
2269                 // uninitialised memory.
2270                 _ => compare_layouts(a, b),
2271             }
2272         }
2273     }
2274 }
2275
2276 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2277
2278 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2279     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2280         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2281         if let ForeignItemKind::Fn(..) = this_fi.kind {
2282             let tcx = *&cx.tcx;
2283             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2284                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2285                 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2286                 debug!(
2287                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2288                     existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2289                 );
2290                 // Check that the declarations match.
2291                 if !Self::structurally_same_type(
2292                     cx,
2293                     existing_decl_ty,
2294                     this_decl_ty,
2295                     CItemKind::Declaration,
2296                 ) {
2297                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2298                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
2299
2300                     // We want to ensure that we use spans for both decls that include where the
2301                     // name was defined, whether that was from the link_name attribute or not.
2302                     let get_relevant_span =
2303                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2304                             SymbolName::Normal(_) => fi.span,
2305                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2306                         };
2307                     // Finally, emit the diagnostic.
2308                     tcx.struct_span_lint_hir(
2309                         CLASHING_EXTERN_DECLARATIONS,
2310                         this_fi.hir_id,
2311                         get_relevant_span(this_fi),
2312                         |lint| {
2313                             let mut expected_str = DiagnosticStyledString::new();
2314                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2315                             let mut found_str = DiagnosticStyledString::new();
2316                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2317
2318                             lint.build(&format!(
2319                                 "`{}` redeclare{} with a different signature",
2320                                 this_fi.ident.name,
2321                                 if orig.get_name() == this_fi.ident.name {
2322                                     "d".to_string()
2323                                 } else {
2324                                     format!("s `{}`", orig.get_name())
2325                                 }
2326                             ))
2327                             .span_label(
2328                                 get_relevant_span(orig_fi),
2329                                 &format!("`{}` previously declared here", orig.get_name()),
2330                             )
2331                             .span_label(
2332                                 get_relevant_span(this_fi),
2333                                 "this signature doesn't match the previous declaration",
2334                             )
2335                             .note_expected_found(&"", expected_str, &"", found_str)
2336                             .emit()
2337                         },
2338                     );
2339                 }
2340             }
2341         }
2342     }
2343 }