compiler/rustc_lint/src/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     errors::BuiltinEllpisisInclusiveRangePatterns,
  25     types::{transparent_newtype_field, CItemKind},
  26     EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
  27 };
  28 use hir::IsAsync;
  29 use rustc_ast::attr;
  30 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  31 use rustc_ast::visit::{FnCtxt, FnKind};
  32 use rustc_ast::{self as ast, *};
  33 use rustc_ast_pretty::pprust::{self, expr_to_string};
  34 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  35 use rustc_data_structures::stack::ensure_sufficient_stack;
  36 use rustc_errors::{
  37     fluent, Applicability, DelayDm, Diagnostic, DiagnosticBuilder, DiagnosticMessage,
  38     DiagnosticStyledString, MultiSpan,
  39 };
  40 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
  41 use rustc_hir as hir;
  42 use rustc_hir::def::{DefKind, Res};
  43 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
  44 use rustc_hir::intravisit::FnKind as HirFnKind;
  45 use rustc_hir::{
  46     Body, FnDecl, ForeignItemKind, GenericParamKind, HirId, Node, PatKind, PredicateOrigin,
  47 };
  48 use rustc_index::vec::Idx;
  49 use rustc_middle::lint::in_external_macro;
  50 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
  51 use rustc_middle::ty::print::with_no_trimmed_paths;
  52 use rustc_middle::ty::subst::GenericArgKind;
  53 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
  54 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
  55 use rustc_span::edition::Edition;
  56 use rustc_span::source_map::Spanned;
  57 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  58 use rustc_span::{BytePos, InnerSpan, Span};
  59 use rustc_target::abi::{Abi, VariantIdx};
  60 use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
  61 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy, EvaluationResult};
  62
  63 use crate::nonstandard_style::{method_context, MethodLateContext};
  64
  65 use std::fmt::Write;
  66
  67 // hardwired lints from librustc_middle
  68 pub use rustc_session::lint::builtin::*;
  69
  70 declare_lint! {
  71     /// The `while_true` lint detects `while true { }`.
  72     ///
  73     /// ### Example
  74     ///
  75     /// ```rust,no_run
  76     /// while true {
  77     ///
  78     /// }
  79     /// ```
  80     ///
  81     /// {{produces}}
  82     ///
  83     /// ### Explanation
  84     ///
  85     /// `while true` should be replaced with `loop`. A `loop` expression is
  86     /// the preferred way to write an infinite loop because it more directly
  87     /// expresses the intent of the loop.
  88     WHILE_TRUE,
  89     Warn,
  90     "suggest using `loop { }` instead of `while true { }`"
  91 }
  92
  93 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  94
  95 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  96 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  97     while let ast::ExprKind::Paren(sub) = &expr.kind {
  98         expr = sub;
  99     }
 100     expr
 101 }
 102
 103 impl EarlyLintPass for WhileTrue {
 104     #[inline]
 105     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 106         if let ast::ExprKind::While(cond, _, label) = &e.kind
 107             && let cond = pierce_parens(cond)
 108             && let ast::ExprKind::Lit(token_lit) = cond.kind
 109             && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
 110             && !cond.span.from_expansion()
 111         {
 112             let condition_span = e.span.with_hi(cond.span.hi());
 113             cx.struct_span_lint(
 114                             WHILE_TRUE,
 115                             condition_span,
 116                 fluent::lint_builtin_while_true,
 117                             |lint| {
 118                     lint.span_suggestion_short(
 119                         condition_span,
 120                         fluent::suggestion,
 121                         format!(
 122                             "{}loop",
 123                             label.map_or_else(String::new, |label| format!(
 124                                 "{}: ",
 125                                 label.ident,
 126                             ))
 127                         ),
 128                         Applicability::MachineApplicable,
 129                     )
 130                 },
 131             )
 132         }
 133     }
 134 }
 135
 136 declare_lint! {
 137     /// The `box_pointers` lints use of the Box type.
 138     ///
 139     /// ### Example
 140     ///
 141     /// ```rust,compile_fail
 142     /// #![deny(box_pointers)]
 143     /// struct Foo {
 144     ///     x: Box<isize>,
 145     /// }
 146     /// ```
 147     ///
 148     /// {{produces}}
 149     ///
 150     /// ### Explanation
 151     ///
 152     /// This lint is mostly historical, and not particularly useful. `Box<T>`
 153     /// used to be built into the language, and the only way to do heap
 154     /// allocation. Today's Rust can call into other allocators, etc.
 155     BOX_POINTERS,
 156     Allow,
 157     "use of owned (Box type) heap memory"
 158 }
 159
 160 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 161
 162 impl BoxPointers {
 163     fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
 164         for leaf in ty.walk() {
 165             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
 166                 if leaf_ty.is_box() {
 167                     cx.struct_span_lint(
 168                         BOX_POINTERS,
 169                         span,
 170                         fluent::lint_builtin_box_pointers,
 171                         |lint| lint.set_arg("ty", ty),
 172                     );
 173                 }
 174             }
 175         }
 176     }
 177 }
 178
 179 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
 180     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 181         match it.kind {
 182             hir::ItemKind::Fn(..)
 183             | hir::ItemKind::TyAlias(..)
 184             | hir::ItemKind::Enum(..)
 185             | hir::ItemKind::Struct(..)
 186             | hir::ItemKind::Union(..) => {
 187                 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.owner_id))
 188             }
 189             _ => (),
 190         }
 191
 192         // If it's a struct, we also have to check the fields' types
 193         match it.kind {
 194             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 195                 for field in struct_def.fields() {
 196                     self.check_heap_type(cx, field.span, cx.tcx.type_of(field.def_id));
 197                 }
 198             }
 199             _ => (),
 200         }
 201     }
 202
 203     fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
 204         let ty = cx.typeck_results().node_type(e.hir_id);
 205         self.check_heap_type(cx, e.span, ty);
 206     }
 207 }
 208
 209 declare_lint! {
 210     /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
 211     /// instead of `Struct { x }` in a pattern.
 212     ///
 213     /// ### Example
 214     ///
 215     /// ```rust
 216     /// struct Point {
 217     ///     x: i32,
 218     ///     y: i32,
 219     /// }
 220     ///
 221     ///
 222     /// fn main() {
 223     ///     let p = Point {
 224     ///         x: 5,
 225     ///         y: 5,
 226     ///     };
 227     ///
 228     ///     match p {
 229     ///         Point { x: x, y: y } => (),
 230     ///     }
 231     /// }
 232     /// ```
 233     ///
 234     /// {{produces}}
 235     ///
 236     /// ### Explanation
 237     ///
 238     /// The preferred style is to avoid the repetition of specifying both the
 239     /// field name and the binding name if both identifiers are the same.
 240     NON_SHORTHAND_FIELD_PATTERNS,
 241     Warn,
 242     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 243 }
 244
 245 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 246
 247 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
 248     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
 249         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 250             let variant = cx
 251                 .typeck_results()
 252                 .pat_ty(pat)
 253                 .ty_adt_def()
 254                 .expect("struct pattern type is not an ADT")
 255                 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
 256             for fieldpat in field_pats {
 257                 if fieldpat.is_shorthand {
 258                     continue;
 259                 }
 260                 if fieldpat.span.from_expansion() {
 261                     // Don't lint if this is a macro expansion: macro authors
 262                     // shouldn't have to worry about this kind of style issue
 263                     // (Issue #49588)
 264                     continue;
 265                 }
 266                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 267                     if cx.tcx.find_field_index(ident, &variant)
 268                         == Some(cx.typeck_results().field_index(fieldpat.hir_id))
 269                     {
 270                         cx.struct_span_lint(
 271                             NON_SHORTHAND_FIELD_PATTERNS,
 272                             fieldpat.span,
 273                             fluent::lint_builtin_non_shorthand_field_patterns,
 274                             |lint| {
 275                                 let suggested_ident =
 276                                     format!("{}{}", binding_annot.prefix_str(), ident);
 277                                 lint.set_arg("ident", ident).span_suggestion(
 278                                     fieldpat.span,
 279                                     fluent::suggestion,
 280                                     suggested_ident,
 281                                     Applicability::MachineApplicable,
 282                                 )
 283                             },
 284                         );
 285                     }
 286                 }
 287             }
 288         }
 289     }
 290 }
 291
 292 declare_lint! {
 293     /// The `unsafe_code` lint catches usage of `unsafe` code.
 294     ///
 295     /// ### Example
 296     ///
 297     /// ```rust,compile_fail
 298     /// #![deny(unsafe_code)]
 299     /// fn main() {
 300     ///     unsafe {
 301     ///
 302     ///     }
 303     /// }
 304     /// ```
 305     ///
 306     /// {{produces}}
 307     ///
 308     /// ### Explanation
 309     ///
 310     /// This lint is intended to restrict the usage of `unsafe`, which can be
 311     /// difficult to use correctly.
 312     UNSAFE_CODE,
 313     Allow,
 314     "usage of `unsafe` code"
 315 }
 316
 317 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 318
 319 impl UnsafeCode {
 320     fn report_unsafe(
 321         &self,
 322         cx: &EarlyContext<'_>,
 323         span: Span,
 324         msg: impl Into<DiagnosticMessage>,
 325         decorate: impl for<'a, 'b> FnOnce(
 326             &'b mut DiagnosticBuilder<'a, ()>,
 327         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 328     ) {
 329         // This comes from a macro that has `#[allow_internal_unsafe]`.
 330         if span.allows_unsafe() {
 331             return;
 332         }
 333
 334         cx.struct_span_lint(UNSAFE_CODE, span, msg, decorate);
 335     }
 336
 337     fn report_overridden_symbol_name(
 338         &self,
 339         cx: &EarlyContext<'_>,
 340         span: Span,
 341         msg: DiagnosticMessage,
 342     ) {
 343         self.report_unsafe(cx, span, msg, |lint| {
 344             lint.note(fluent::lint_builtin_overridden_symbol_name)
 345         })
 346     }
 347
 348     fn report_overridden_symbol_section(
 349         &self,
 350         cx: &EarlyContext<'_>,
 351         span: Span,
 352         msg: DiagnosticMessage,
 353     ) {
 354         self.report_unsafe(cx, span, msg, |lint| {
 355             lint.note(fluent::lint_builtin_overridden_symbol_section)
 356         })
 357     }
 358 }
 359
 360 impl EarlyLintPass for UnsafeCode {
 361     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 362         if attr.has_name(sym::allow_internal_unsafe) {
 363             self.report_unsafe(cx, attr.span, fluent::lint_builtin_allow_internal_unsafe, |lint| {
 364                 lint
 365             });
 366         }
 367     }
 368
 369     #[inline]
 370     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 371         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 372             // Don't warn about generated blocks; that'll just pollute the output.
 373             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 374                 self.report_unsafe(cx, blk.span, fluent::lint_builtin_unsafe_block, |lint| lint);
 375             }
 376         }
 377     }
 378
 379     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 380         match it.kind {
 381             ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => {
 382                 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_trait, |lint| lint)
 383             }
 384
 385             ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => {
 386                 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_impl, |lint| lint)
 387             }
 388
 389             ast::ItemKind::Fn(..) => {
 390                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 391                     self.report_overridden_symbol_name(
 392                         cx,
 393                         attr.span,
 394                         fluent::lint_builtin_no_mangle_fn,
 395                     );
 396                 }
 397
 398                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 399                     self.report_overridden_symbol_name(
 400                         cx,
 401                         attr.span,
 402                         fluent::lint_builtin_export_name_fn,
 403                     );
 404                 }
 405
 406                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
 407                     self.report_overridden_symbol_section(
 408                         cx,
 409                         attr.span,
 410                         fluent::lint_builtin_link_section_fn,
 411                     );
 412                 }
 413             }
 414
 415             ast::ItemKind::Static(..) => {
 416                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 417                     self.report_overridden_symbol_name(
 418                         cx,
 419                         attr.span,
 420                         fluent::lint_builtin_no_mangle_static,
 421                     );
 422                 }
 423
 424                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 425                     self.report_overridden_symbol_name(
 426                         cx,
 427                         attr.span,
 428                         fluent::lint_builtin_export_name_static,
 429                     );
 430                 }
 431
 432                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
 433                     self.report_overridden_symbol_section(
 434                         cx,
 435                         attr.span,
 436                         fluent::lint_builtin_link_section_static,
 437                     );
 438                 }
 439             }
 440
 441             _ => {}
 442         }
 443     }
 444
 445     fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 446         if let ast::AssocItemKind::Fn(..) = it.kind {
 447             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 448                 self.report_overridden_symbol_name(
 449                     cx,
 450                     attr.span,
 451                     fluent::lint_builtin_no_mangle_method,
 452                 );
 453             }
 454             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 455                 self.report_overridden_symbol_name(
 456                     cx,
 457                     attr.span,
 458                     fluent::lint_builtin_export_name_method,
 459                 );
 460             }
 461         }
 462     }
 463
 464     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
 465         if let FnKind::Fn(
 466             ctxt,
 467             _,
 468             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
 469             _,
 470             _,
 471             body,
 472         ) = fk
 473         {
 474             let msg = match ctxt {
 475                 FnCtxt::Foreign => return,
 476                 FnCtxt::Free => fluent::lint_builtin_decl_unsafe_fn,
 477                 FnCtxt::Assoc(_) if body.is_none() => fluent::lint_builtin_decl_unsafe_method,
 478                 FnCtxt::Assoc(_) => fluent::lint_builtin_impl_unsafe_method,
 479             };
 480             self.report_unsafe(cx, span, msg, |lint| lint);
 481         }
 482     }
 483 }
 484
 485 declare_lint! {
 486     /// The `missing_docs` lint detects missing documentation for public items.
 487     ///
 488     /// ### Example
 489     ///
 490     /// ```rust,compile_fail
 491     /// #![deny(missing_docs)]
 492     /// pub fn foo() {}
 493     /// ```
 494     ///
 495     /// {{produces}}
 496     ///
 497     /// ### Explanation
 498     ///
 499     /// This lint is intended to ensure that a library is well-documented.
 500     /// Items without documentation can be difficult for users to understand
 501     /// how to use properly.
 502     ///
 503     /// This lint is "allow" by default because it can be noisy, and not all
 504     /// projects may want to enforce everything to be documented.
 505     pub MISSING_DOCS,
 506     Allow,
 507     "detects missing documentation for public members",
 508     report_in_external_macro
 509 }
 510
 511 pub struct MissingDoc {
 512     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 513     doc_hidden_stack: Vec<bool>,
 514 }
 515
 516 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 517
 518 fn has_doc(attr: &ast::Attribute) -> bool {
 519     if attr.is_doc_comment() {
 520         return true;
 521     }
 522
 523     if !attr.has_name(sym::doc) {
 524         return false;
 525     }
 526
 527     if attr.value_str().is_some() {
 528         return true;
 529     }
 530
 531     if let Some(list) = attr.meta_item_list() {
 532         for meta in list {
 533             if meta.has_name(sym::hidden) {
 534                 return true;
 535             }
 536         }
 537     }
 538
 539     false
 540 }
 541
 542 impl MissingDoc {
 543     pub fn new() -> MissingDoc {
 544         MissingDoc { doc_hidden_stack: vec![false] }
 545     }
 546
 547     fn doc_hidden(&self) -> bool {
 548         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 549     }
 550
 551     fn check_missing_docs_attrs(
 552         &self,
 553         cx: &LateContext<'_>,
 554         def_id: LocalDefId,
 555         article: &'static str,
 556         desc: &'static str,
 557     ) {
 558         // If we're building a test harness, then warning about
 559         // documentation is probably not really relevant right now.
 560         if cx.sess().opts.test {
 561             return;
 562         }
 563
 564         // `#[doc(hidden)]` disables missing_docs check.
 565         if self.doc_hidden() {
 566             return;
 567         }
 568
 569         // Only check publicly-visible items, using the result from the privacy pass.
 570         // It's an option so the crate root can also use this function (it doesn't
 571         // have a `NodeId`).
 572         if def_id != CRATE_DEF_ID {
 573             if !cx.effective_visibilities.is_exported(def_id) {
 574                 return;
 575             }
 576         }
 577
 578         let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
 579         let has_doc = attrs.iter().any(has_doc);
 580         if !has_doc {
 581             cx.struct_span_lint(
 582                 MISSING_DOCS,
 583                 cx.tcx.def_span(def_id),
 584                 fluent::lint_builtin_missing_doc,
 585                 |lint| lint.set_arg("article", article).set_arg("desc", desc),
 586             );
 587         }
 588     }
 589 }
 590
 591 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 592     #[inline]
 593     fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
 594         let doc_hidden = self.doc_hidden()
 595             || attrs.iter().any(|attr| {
 596                 attr.has_name(sym::doc)
 597                     && match attr.meta_item_list() {
 598                         None => false,
 599                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 600                     }
 601             });
 602         self.doc_hidden_stack.push(doc_hidden);
 603     }
 604
 605     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
 606         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 607     }
 608
 609     fn check_crate(&mut self, cx: &LateContext<'_>) {
 610         self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
 611     }
 612
 613     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 614         match it.kind {
 615             hir::ItemKind::Trait(..) => {
 616                 // Issue #11592: traits are always considered exported, even when private.
 617                 if cx.tcx.visibility(it.owner_id)
 618                     == ty::Visibility::Restricted(
 619                         cx.tcx.parent_module_from_def_id(it.owner_id.def_id).to_def_id(),
 620                     )
 621                 {
 622                     return;
 623                 }
 624             }
 625             hir::ItemKind::TyAlias(..)
 626             | hir::ItemKind::Fn(..)
 627             | hir::ItemKind::Macro(..)
 628             | hir::ItemKind::Mod(..)
 629             | hir::ItemKind::Enum(..)
 630             | hir::ItemKind::Struct(..)
 631             | hir::ItemKind::Union(..)
 632             | hir::ItemKind::Const(..)
 633             | hir::ItemKind::Static(..) => {}
 634
 635             _ => return,
 636         };
 637
 638         let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
 639
 640         self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
 641     }
 642
 643     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
 644         let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
 645
 646         self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
 647     }
 648
 649     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
 650         // If the method is an impl for a trait, don't doc.
 651         if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
 652             return;
 653         }
 654
 655         // If the method is an impl for an item with docs_hidden, don't doc.
 656         if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
 657             let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
 658             let impl_ty = cx.tcx.type_of(parent);
 659             let outerdef = match impl_ty.kind() {
 660                 ty::Adt(def, _) => Some(def.did()),
 661                 ty::Foreign(def_id) => Some(*def_id),
 662                 _ => None,
 663             };
 664             let is_hidden = match outerdef {
 665                 Some(id) => cx.tcx.is_doc_hidden(id),
 666                 None => false,
 667             };
 668             if is_hidden {
 669                 return;
 670             }
 671         }
 672
 673         let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
 674         self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
 675     }
 676
 677     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
 678         let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
 679         self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
 680     }
 681
 682     fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
 683         if !sf.is_positional() {
 684             self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
 685         }
 686     }
 687
 688     fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
 689         self.check_missing_docs_attrs(cx, v.def_id, "a", "variant");
 690     }
 691 }
 692
 693 declare_lint! {
 694     /// The `missing_copy_implementations` lint detects potentially-forgotten
 695     /// implementations of [`Copy`].
 696     ///
 697     /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
 698     ///
 699     /// ### Example
 700     ///
 701     /// ```rust,compile_fail
 702     /// #![deny(missing_copy_implementations)]
 703     /// pub struct Foo {
 704     ///     pub field: i32
 705     /// }
 706     /// # fn main() {}
 707     /// ```
 708     ///
 709     /// {{produces}}
 710     ///
 711     /// ### Explanation
 712     ///
 713     /// Historically (before 1.0), types were automatically marked as `Copy`
 714     /// if possible. This was changed so that it required an explicit opt-in
 715     /// by implementing the `Copy` trait. As part of this change, a lint was
 716     /// added to alert if a copyable type was not marked `Copy`.
 717     ///
 718     /// This lint is "allow" by default because this code isn't bad; it is
 719     /// common to write newtypes like this specifically so that a `Copy` type
 720     /// is no longer `Copy`. `Copy` types can result in unintended copies of
 721     /// large data which can impact performance.
 722     pub MISSING_COPY_IMPLEMENTATIONS,
 723     Allow,
 724     "detects potentially-forgotten implementations of `Copy`"
 725 }
 726
 727 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 728
 729 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
 730     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 731         if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
 732             return;
 733         }
 734         let (def, ty) = match item.kind {
 735             hir::ItemKind::Struct(_, ref ast_generics) => {
 736                 if !ast_generics.params.is_empty() {
 737                     return;
 738                 }
 739                 let def = cx.tcx.adt_def(item.owner_id);
 740                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 741             }
 742             hir::ItemKind::Union(_, ref ast_generics) => {
 743                 if !ast_generics.params.is_empty() {
 744                     return;
 745                 }
 746                 let def = cx.tcx.adt_def(item.owner_id);
 747                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 748             }
 749             hir::ItemKind::Enum(_, ref ast_generics) => {
 750                 if !ast_generics.params.is_empty() {
 751                     return;
 752                 }
 753                 let def = cx.tcx.adt_def(item.owner_id);
 754                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 755             }
 756             _ => return,
 757         };
 758         if def.has_dtor(cx.tcx) {
 759             return;
 760         }
 761
 762         // If the type contains a raw pointer, it may represent something like a handle,
 763         // and recommending Copy might be a bad idea.
 764         for field in def.all_fields() {
 765             let did = field.did;
 766             if cx.tcx.type_of(did).is_unsafe_ptr() {
 767                 return;
 768             }
 769         }
 770         let param_env = ty::ParamEnv::empty();
 771         if ty.is_copy_modulo_regions(cx.tcx, param_env) {
 772             return;
 773         }
 774
 775         // We shouldn't recommend implementing `Copy` on stateful things,
 776         // such as iterators.
 777         if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator) {
 778             if cx.tcx.infer_ctxt().build().type_implements_trait(iter_trait, [ty], param_env)
 779                 == EvaluationResult::EvaluatedToOk
 780             {
 781                 return;
 782             }
 783         }
 784
 785         // Default value of clippy::trivially_copy_pass_by_ref
 786         const MAX_SIZE: u64 = 256;
 787
 788         if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
 789             if size > MAX_SIZE {
 790                 return;
 791             }
 792         }
 793
 794         if can_type_implement_copy(
 795             cx.tcx,
 796             param_env,
 797             ty,
 798             traits::ObligationCause::misc(item.span, item.hir_id()),
 799         )
 800         .is_ok()
 801         {
 802             cx.struct_span_lint(
 803                 MISSING_COPY_IMPLEMENTATIONS,
 804                 item.span,
 805                 fluent::lint_builtin_missing_copy_impl,
 806                 |lint| lint,
 807             )
 808         }
 809     }
 810 }
 811
 812 declare_lint! {
 813     /// The `missing_debug_implementations` lint detects missing
 814     /// implementations of [`fmt::Debug`].
 815     ///
 816     /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
 817     ///
 818     /// ### Example
 819     ///
 820     /// ```rust,compile_fail
 821     /// #![deny(missing_debug_implementations)]
 822     /// pub struct Foo;
 823     /// # fn main() {}
 824     /// ```
 825     ///
 826     /// {{produces}}
 827     ///
 828     /// ### Explanation
 829     ///
 830     /// Having a `Debug` implementation on all types can assist with
 831     /// debugging, as it provides a convenient way to format and display a
 832     /// value. Using the `#[derive(Debug)]` attribute will automatically
 833     /// generate a typical implementation, or a custom implementation can be
 834     /// added by manually implementing the `Debug` trait.
 835     ///
 836     /// This lint is "allow" by default because adding `Debug` to all types can
 837     /// have a negative impact on compile time and code size. It also requires
 838     /// boilerplate to be added to every type, which can be an impediment.
 839     MISSING_DEBUG_IMPLEMENTATIONS,
 840     Allow,
 841     "detects missing implementations of Debug"
 842 }
 843
 844 #[derive(Default)]
 845 pub struct MissingDebugImplementations {
 846     impling_types: Option<LocalDefIdSet>,
 847 }
 848
 849 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 850
 851 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 852     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 853         if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
 854             return;
 855         }
 856
 857         match item.kind {
 858             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 859             _ => return,
 860         }
 861
 862         let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
 863             return
 864         };
 865
 866         if self.impling_types.is_none() {
 867             let mut impls = LocalDefIdSet::default();
 868             cx.tcx.for_each_impl(debug, |d| {
 869                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 870                     if let Some(def_id) = ty_def.did().as_local() {
 871                         impls.insert(def_id);
 872                     }
 873                 }
 874             });
 875
 876             self.impling_types = Some(impls);
 877             debug!("{:?}", self.impling_types);
 878         }
 879
 880         if !self.impling_types.as_ref().unwrap().contains(&item.owner_id.def_id) {
 881             cx.struct_span_lint(
 882                 MISSING_DEBUG_IMPLEMENTATIONS,
 883                 item.span,
 884                 fluent::lint_builtin_missing_debug_impl,
 885                 |lint| lint.set_arg("debug", cx.tcx.def_path_str(debug)),
 886             );
 887         }
 888     }
 889 }
 890
 891 declare_lint! {
 892     /// The `anonymous_parameters` lint detects anonymous parameters in trait
 893     /// definitions.
 894     ///
 895     /// ### Example
 896     ///
 897     /// ```rust,edition2015,compile_fail
 898     /// #![deny(anonymous_parameters)]
 899     /// // edition 2015
 900     /// pub trait Foo {
 901     ///     fn foo(usize);
 902     /// }
 903     /// fn main() {}
 904     /// ```
 905     ///
 906     /// {{produces}}
 907     ///
 908     /// ### Explanation
 909     ///
 910     /// This syntax is mostly a historical accident, and can be worked around
 911     /// quite easily by adding an `_` pattern or a descriptive identifier:
 912     ///
 913     /// ```rust
 914     /// trait Foo {
 915     ///     fn foo(_: usize);
 916     /// }
 917     /// ```
 918     ///
 919     /// This syntax is now a hard error in the 2018 edition. In the 2015
 920     /// edition, this lint is "warn" by default. This lint
 921     /// enables the [`cargo fix`] tool with the `--edition` flag to
 922     /// automatically transition old code from the 2015 edition to 2018. The
 923     /// tool will run this lint and automatically apply the
 924     /// suggested fix from the compiler (which is to add `_` to each
 925     /// parameter). This provides a completely automated way to update old
 926     /// code for a new edition. See [issue #41686] for more details.
 927     ///
 928     /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
 929     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
 930     pub ANONYMOUS_PARAMETERS,
 931     Warn,
 932     "detects anonymous parameters",
 933     @future_incompatible = FutureIncompatibleInfo {
 934         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 935         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
 936     };
 937 }
 938
 939 declare_lint_pass!(
 940     /// Checks for use of anonymous parameters (RFC 1685).
 941     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 942 );
 943
 944 impl EarlyLintPass for AnonymousParameters {
 945     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 946         if cx.sess().edition() != Edition::Edition2015 {
 947             // This is a hard error in future editions; avoid linting and erroring
 948             return;
 949         }
 950         if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
 951             for arg in sig.decl.inputs.iter() {
 952                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 953                     if ident.name == kw::Empty {
 954                         let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
 955
 956                         let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 957                             (snip.as_str(), Applicability::MachineApplicable)
 958                         } else {
 959                             ("<type>", Applicability::HasPlaceholders)
 960                         };
 961                         cx.struct_span_lint(
 962                             ANONYMOUS_PARAMETERS,
 963                             arg.pat.span,
 964                             fluent::lint_builtin_anonymous_params,
 965                             |lint| {
 966                                 lint.span_suggestion(
 967                                     arg.pat.span,
 968                                     fluent::suggestion,
 969                                     format!("_: {}", ty_snip),
 970                                     appl,
 971                                 )
 972                             },
 973                         )
 974                     }
 975                 }
 976             }
 977         }
 978     }
 979 }
 980
 981 /// Check for use of attributes which have been deprecated.
 982 #[derive(Clone)]
 983 pub struct DeprecatedAttr {
 984     // This is not free to compute, so we want to keep it around, rather than
 985     // compute it for every attribute.
 986     depr_attrs: Vec<&'static BuiltinAttribute>,
 987 }
 988
 989 impl_lint_pass!(DeprecatedAttr => []);
 990
 991 impl DeprecatedAttr {
 992     pub fn new() -> DeprecatedAttr {
 993         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 994     }
 995 }
 996
 997 impl EarlyLintPass for DeprecatedAttr {
 998     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 999         for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
1000             if attr.ident().map(|ident| ident.name) == Some(*name) {
1001                 if let &AttributeGate::Gated(
1002                     Stability::Deprecated(link, suggestion),
1003                     name,
1004                     reason,
1005                     _,
1006                 ) = gate
1007                 {
1008                     // FIXME(davidtwco) translatable deprecated attr
1009                     cx.struct_span_lint(
1010                         DEPRECATED,
1011                         attr.span,
1012                         fluent::lint_builtin_deprecated_attr_link,
1013                         |lint| {
1014                             lint.set_arg("name", name)
1015                                 .set_arg("reason", reason)
1016                                 .set_arg("link", link)
1017                                 .span_suggestion_short(
1018                                     attr.span,
1019                                     suggestion.map(|s| s.into()).unwrap_or(
1020                                         fluent::lint_builtin_deprecated_attr_default_suggestion,
1021                                     ),
1022                                     "",
1023                                     Applicability::MachineApplicable,
1024                                 )
1025                         },
1026                     );
1027                 }
1028                 return;
1029             }
1030         }
1031         if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1032             cx.struct_span_lint(
1033                 DEPRECATED,
1034                 attr.span,
1035                 fluent::lint_builtin_deprecated_attr_used,
1036                 |lint| {
1037                     lint.set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
1038                         .span_suggestion_short(
1039                             attr.span,
1040                             fluent::lint_builtin_deprecated_attr_default_suggestion,
1041                             "",
1042                             Applicability::MachineApplicable,
1043                         )
1044                 },
1045             );
1046         }
1047     }
1048 }
1049
1050 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1051     use rustc_ast::token::CommentKind;
1052
1053     let mut attrs = attrs.iter().peekable();
1054
1055     // Accumulate a single span for sugared doc comments.
1056     let mut sugared_span: Option<Span> = None;
1057
1058     while let Some(attr) = attrs.next() {
1059         let is_doc_comment = attr.is_doc_comment();
1060         if is_doc_comment {
1061             sugared_span =
1062                 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1063         }
1064
1065         if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1066             continue;
1067         }
1068
1069         let span = sugared_span.take().unwrap_or(attr.span);
1070
1071         if is_doc_comment || attr.has_name(sym::doc) {
1072             cx.struct_span_lint(
1073                 UNUSED_DOC_COMMENTS,
1074                 span,
1075                 fluent::lint_builtin_unused_doc_comment,
1076                 |lint| {
1077                     lint.set_arg("kind", node_kind).span_label(node_span, fluent::label).help(
1078                         match attr.kind {
1079                             AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1080                                 fluent::plain_help
1081                             }
1082                             AttrKind::DocComment(CommentKind::Block, _) => fluent::block_help,
1083                         },
1084                     )
1085                 },
1086             );
1087         }
1088     }
1089 }
1090
1091 impl EarlyLintPass for UnusedDocComment {
1092     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1093         let kind = match stmt.kind {
1094             ast::StmtKind::Local(..) => "statements",
1095             // Disabled pending discussion in #78306
1096             ast::StmtKind::Item(..) => return,
1097             // expressions will be reported by `check_expr`.
1098             ast::StmtKind::Empty
1099             | ast::StmtKind::Semi(_)
1100             | ast::StmtKind::Expr(_)
1101             | ast::StmtKind::MacCall(_) => return,
1102         };
1103
1104         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1105     }
1106
1107     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1108         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1109         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1110     }
1111
1112     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1113         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1114     }
1115
1116     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1117         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
1118     }
1119
1120     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1121         warn_if_doc(cx, block.span, "blocks", &block.attrs());
1122     }
1123
1124     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1125         if let ast::ItemKind::ForeignMod(_) = item.kind {
1126             warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1127         }
1128     }
1129 }
1130
1131 declare_lint! {
1132     /// The `no_mangle_const_items` lint detects any `const` items with the
1133     /// [`no_mangle` attribute].
1134     ///
1135     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1136     ///
1137     /// ### Example
1138     ///
1139     /// ```rust,compile_fail
1140     /// #[no_mangle]
1141     /// const FOO: i32 = 5;
1142     /// ```
1143     ///
1144     /// {{produces}}
1145     ///
1146     /// ### Explanation
1147     ///
1148     /// Constants do not have their symbols exported, and therefore, this
1149     /// probably means you meant to use a [`static`], not a [`const`].
1150     ///
1151     /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1152     /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1153     NO_MANGLE_CONST_ITEMS,
1154     Deny,
1155     "const items will not have their symbols exported"
1156 }
1157
1158 declare_lint! {
1159     /// The `no_mangle_generic_items` lint detects generic items that must be
1160     /// mangled.
1161     ///
1162     /// ### Example
1163     ///
1164     /// ```rust
1165     /// #[no_mangle]
1166     /// fn foo<T>(t: T) {
1167     ///
1168     /// }
1169     /// ```
1170     ///
1171     /// {{produces}}
1172     ///
1173     /// ### Explanation
1174     ///
1175     /// A function with generics must have its symbol mangled to accommodate
1176     /// the generic parameter. The [`no_mangle` attribute] has no effect in
1177     /// this situation, and should be removed.
1178     ///
1179     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1180     NO_MANGLE_GENERIC_ITEMS,
1181     Warn,
1182     "generic items must be mangled"
1183 }
1184
1185 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1186
1187 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1188     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1189         let attrs = cx.tcx.hir().attrs(it.hir_id());
1190         let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1191                                              impl_generics: Option<&hir::Generics<'_>>,
1192                                              generics: &hir::Generics<'_>,
1193                                              span| {
1194             for param in
1195                 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1196             {
1197                 match param.kind {
1198                     GenericParamKind::Lifetime { .. } => {}
1199                     GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1200                         cx.struct_span_lint(
1201                             NO_MANGLE_GENERIC_ITEMS,
1202                             span,
1203                             fluent::lint_builtin_no_mangle_generic,
1204                             |lint| {
1205                                 lint.span_suggestion_short(
1206                                     no_mangle_attr.span,
1207                                     fluent::suggestion,
1208                                     "",
1209                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1210                                     // fix may be to monomorphize source by hand
1211                                     Applicability::MaybeIncorrect,
1212                                 )
1213                             },
1214                         );
1215                         break;
1216                     }
1217                 }
1218             }
1219         };
1220         match it.kind {
1221             hir::ItemKind::Fn(.., ref generics, _) => {
1222                 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1223                     check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1224                 }
1225             }
1226             hir::ItemKind::Const(..) => {
1227                 if cx.sess().contains_name(attrs, sym::no_mangle) {
1228                     // Const items do not refer to a particular location in memory, and therefore
1229                     // don't have anything to attach a symbol to
1230                     cx.struct_span_lint(
1231                         NO_MANGLE_CONST_ITEMS,
1232                         it.span,
1233                         fluent::lint_builtin_const_no_mangle,
1234                         |lint| {
1235                             // account for "pub const" (#45562)
1236                             let start = cx
1237                                 .tcx
1238                                 .sess
1239                                 .source_map()
1240                                 .span_to_snippet(it.span)
1241                                 .map(|snippet| snippet.find("const").unwrap_or(0))
1242                                 .unwrap_or(0) as u32;
1243                             // `const` is 5 chars
1244                             let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1245                             lint.span_suggestion(
1246                                 const_span,
1247                                 fluent::suggestion,
1248                                 "pub static",
1249                                 Applicability::MachineApplicable,
1250                             )
1251                         },
1252                     );
1253                 }
1254             }
1255             hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1256                 for it in *items {
1257                     if let hir::AssocItemKind::Fn { .. } = it.kind {
1258                         if let Some(no_mangle_attr) = cx
1259                             .sess()
1260                             .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1261                         {
1262                             check_no_mangle_on_generic_fn(
1263                                 no_mangle_attr,
1264                                 Some(generics),
1265                                 cx.tcx.hir().get_generics(it.id.owner_id.def_id).unwrap(),
1266                                 it.span,
1267                             );
1268                         }
1269                     }
1270                 }
1271             }
1272             _ => {}
1273         }
1274     }
1275 }
1276
1277 declare_lint! {
1278     /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1279     /// T` because it is [undefined behavior].
1280     ///
1281     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1282     ///
1283     /// ### Example
1284     ///
1285     /// ```rust,compile_fail
1286     /// unsafe {
1287     ///     let y = std::mem::transmute::<&i32, &mut i32>(&5);
1288     /// }
1289     /// ```
1290     ///
1291     /// {{produces}}
1292     ///
1293     /// ### Explanation
1294     ///
1295     /// Certain assumptions are made about aliasing of data, and this transmute
1296     /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1297     ///
1298     /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1299     MUTABLE_TRANSMUTES,
1300     Deny,
1301     "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1302 }
1303
1304 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1305
1306 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1307     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1308         if let Some((&ty::Ref(_, _, from_mutbl), &ty::Ref(_, _, to_mutbl))) =
1309             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1310         {
1311             if from_mutbl < to_mutbl {
1312                 cx.struct_span_lint(
1313                     MUTABLE_TRANSMUTES,
1314                     expr.span,
1315                     fluent::lint_builtin_mutable_transmutes,
1316                     |lint| lint,
1317                 );
1318             }
1319         }
1320
1321         fn get_transmute_from_to<'tcx>(
1322             cx: &LateContext<'tcx>,
1323             expr: &hir::Expr<'_>,
1324         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1325             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1326                 cx.qpath_res(qpath, expr.hir_id)
1327             } else {
1328                 return None;
1329             };
1330             if let Res::Def(DefKind::Fn, did) = def {
1331                 if !def_id_is_transmute(cx, did) {
1332                     return None;
1333                 }
1334                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1335                 let from = sig.inputs().skip_binder()[0];
1336                 let to = sig.output().skip_binder();
1337                 return Some((from, to));
1338             }
1339             None
1340         }
1341
1342         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1343             cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1344         }
1345     }
1346 }
1347
1348 declare_lint! {
1349     /// The `unstable_features` is deprecated and should no longer be used.
1350     UNSTABLE_FEATURES,
1351     Allow,
1352     "enabling unstable features (deprecated. do not use)"
1353 }
1354
1355 declare_lint_pass!(
1356     /// Forbids using the `#[feature(...)]` attribute
1357     UnstableFeatures => [UNSTABLE_FEATURES]
1358 );
1359
1360 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1361     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1362         if attr.has_name(sym::feature) {
1363             if let Some(items) = attr.meta_item_list() {
1364                 for item in items {
1365                     cx.struct_span_lint(
1366                         UNSTABLE_FEATURES,
1367                         item.span(),
1368                         fluent::lint_builtin_unstable_features,
1369                         |lint| lint,
1370                     );
1371                 }
1372             }
1373         }
1374     }
1375 }
1376
1377 declare_lint! {
1378     /// The `ungated_async_fn_track_caller` lint warns when the
1379     /// `#[track_caller]` attribute is used on an async function, method, or
1380     /// closure, without enabling the corresponding unstable feature flag.
1381     ///
1382     /// ### Example
1383     ///
1384     /// ```rust
1385     /// #[track_caller]
1386     /// async fn foo() {}
1387     /// ```
1388     ///
1389     /// {{produces}}
1390     ///
1391     /// ### Explanation
1392     ///
1393     /// The attribute must be used in conjunction with the
1394     /// [`closure_track_caller` feature flag]. Otherwise, the `#[track_caller]`
1395     /// annotation will function as a no-op.
1396     ///
1397     /// [`closure_track_caller` feature flag]: https://doc.rust-lang.org/beta/unstable-book/language-features/closure-track-caller.html
1398     UNGATED_ASYNC_FN_TRACK_CALLER,
1399     Warn,
1400     "enabling track_caller on an async fn is a no-op unless the closure_track_caller feature is enabled"
1401 }
1402
1403 declare_lint_pass!(
1404     /// Explains corresponding feature flag must be enabled for the `#[track_caller] attribute to
1405     /// do anything
1406     UngatedAsyncFnTrackCaller => [UNGATED_ASYNC_FN_TRACK_CALLER]
1407 );
1408
1409 impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
1410     fn check_fn(
1411         &mut self,
1412         cx: &LateContext<'_>,
1413         fn_kind: HirFnKind<'_>,
1414         _: &'tcx FnDecl<'_>,
1415         _: &'tcx Body<'_>,
1416         span: Span,
1417         hir_id: HirId,
1418     ) {
1419         if fn_kind.asyncness() == IsAsync::Async
1420             && !cx.tcx.features().closure_track_caller
1421             && let attrs = cx.tcx.hir().attrs(hir_id)
1422             // Now, check if the function has the `#[track_caller]` attribute
1423             && let Some(attr) = attrs.iter().find(|attr| attr.has_name(sym::track_caller))
1424             {
1425                 cx.struct_span_lint(
1426                     UNGATED_ASYNC_FN_TRACK_CALLER,
1427                     attr.span,
1428                     fluent::lint_ungated_async_fn_track_caller,
1429                     |lint| {
1430                         lint.span_label(span, fluent::label);
1431                         rustc_session::parse::add_feature_diagnostics(
1432                             lint,
1433                             &cx.tcx.sess.parse_sess,
1434                             sym::closure_track_caller,
1435                         );
1436                         lint
1437                     },
1438                 );
1439             }
1440     }
1441 }
1442
1443 declare_lint! {
1444     /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1445     /// the crate root.
1446     ///
1447     /// ### Example
1448     ///
1449     /// ```rust,compile_fail
1450     /// #![deny(unreachable_pub)]
1451     /// mod foo {
1452     ///     pub mod bar {
1453     ///
1454     ///     }
1455     /// }
1456     /// ```
1457     ///
1458     /// {{produces}}
1459     ///
1460     /// ### Explanation
1461     ///
1462     /// A bare `pub` visibility may be misleading if the item is not actually
1463     /// publicly exported from the crate. The `pub(crate)` visibility is
1464     /// recommended to be used instead, which more clearly expresses the intent
1465     /// that the item is only visible within its own crate.
1466     ///
1467     /// This lint is "allow" by default because it will trigger for a large
1468     /// amount existing Rust code, and has some false-positives. Eventually it
1469     /// is desired for this to become warn-by-default.
1470     pub UNREACHABLE_PUB,
1471     Allow,
1472     "`pub` items not reachable from crate root"
1473 }
1474
1475 declare_lint_pass!(
1476     /// Lint for items marked `pub` that aren't reachable from other crates.
1477     UnreachablePub => [UNREACHABLE_PUB]
1478 );
1479
1480 impl UnreachablePub {
1481     fn perform_lint(
1482         &self,
1483         cx: &LateContext<'_>,
1484         what: &str,
1485         def_id: LocalDefId,
1486         vis_span: Span,
1487         exportable: bool,
1488     ) {
1489         let mut applicability = Applicability::MachineApplicable;
1490         if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
1491         {
1492             if vis_span.from_expansion() {
1493                 applicability = Applicability::MaybeIncorrect;
1494             }
1495             let def_span = cx.tcx.def_span(def_id);
1496             cx.struct_span_lint(
1497                 UNREACHABLE_PUB,
1498                 def_span,
1499                 fluent::lint_builtin_unreachable_pub,
1500                 |lint| {
1501                     lint.set_arg("what", what);
1502
1503                     lint.span_suggestion(vis_span, fluent::suggestion, "pub(crate)", applicability);
1504                     if exportable {
1505                         lint.help(fluent::help);
1506                     }
1507                     lint
1508                 },
1509             );
1510         }
1511     }
1512 }
1513
1514 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1515     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1516         // Do not warn for fake `use` statements.
1517         if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1518             return;
1519         }
1520         self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
1521     }
1522
1523     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1524         self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
1525     }
1526
1527     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1528         let map = cx.tcx.hir();
1529         if matches!(map.get_parent(field.hir_id), Node::Variant(_)) {
1530             return;
1531         }
1532         self.perform_lint(cx, "field", field.def_id, field.vis_span, false);
1533     }
1534
1535     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1536         // Only lint inherent impl items.
1537         if cx.tcx.associated_item(impl_item.owner_id).trait_item_def_id.is_none() {
1538             self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
1539         }
1540     }
1541 }
1542
1543 declare_lint! {
1544     /// The `type_alias_bounds` lint detects bounds in type aliases.
1545     ///
1546     /// ### Example
1547     ///
1548     /// ```rust
1549     /// type SendVec<T: Send> = Vec<T>;
1550     /// ```
1551     ///
1552     /// {{produces}}
1553     ///
1554     /// ### Explanation
1555     ///
1556     /// The trait bounds in a type alias are currently ignored, and should not
1557     /// be included to avoid confusion. This was previously allowed
1558     /// unintentionally; this may become a hard error in the future.
1559     TYPE_ALIAS_BOUNDS,
1560     Warn,
1561     "bounds in type aliases are not enforced"
1562 }
1563
1564 declare_lint_pass!(
1565     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1566     /// They are relevant when using associated types, but otherwise neither checked
1567     /// at definition site nor enforced at use site.
1568     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1569 );
1570
1571 impl TypeAliasBounds {
1572     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1573         match *qpath {
1574             hir::QPath::TypeRelative(ref ty, _) => {
1575                 // If this is a type variable, we found a `T::Assoc`.
1576                 match ty.kind {
1577                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1578                         matches!(path.res, Res::Def(DefKind::TyParam, _))
1579                     }
1580                     _ => false,
1581                 }
1582             }
1583             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1584         }
1585     }
1586
1587     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1588         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1589         // bound.  Let's see if this type does that.
1590
1591         // We use a HIR visitor to walk the type.
1592         use rustc_hir::intravisit::{self, Visitor};
1593         struct WalkAssocTypes<'a> {
1594             err: &'a mut Diagnostic,
1595         }
1596         impl Visitor<'_> for WalkAssocTypes<'_> {
1597             fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1598                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1599                     self.err.span_help(span, fluent::lint_builtin_type_alias_bounds_help);
1600                 }
1601                 intravisit::walk_qpath(self, qpath, id)
1602             }
1603         }
1604
1605         // Let's go for a walk!
1606         let mut visitor = WalkAssocTypes { err };
1607         visitor.visit_ty(ty);
1608     }
1609 }
1610
1611 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1612     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1613         let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1614             return
1615         };
1616         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1617             // Bounds are respected for `type X = impl Trait`
1618             return;
1619         }
1620         // There must not be a where clause
1621         if type_alias_generics.predicates.is_empty() {
1622             return;
1623         }
1624
1625         let mut where_spans = Vec::new();
1626         let mut inline_spans = Vec::new();
1627         let mut inline_sugg = Vec::new();
1628         for p in type_alias_generics.predicates {
1629             let span = p.span();
1630             if p.in_where_clause() {
1631                 where_spans.push(span);
1632             } else {
1633                 for b in p.bounds() {
1634                     inline_spans.push(b.span());
1635                 }
1636                 inline_sugg.push((span, String::new()));
1637             }
1638         }
1639
1640         let mut suggested_changing_assoc_types = false;
1641         if !where_spans.is_empty() {
1642             cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_where_clause, |lint| {
1643                 lint.set_span(where_spans);
1644                 lint.span_suggestion(
1645                     type_alias_generics.where_clause_span,
1646                     fluent::suggestion,
1647                     "",
1648                     Applicability::MachineApplicable,
1649                 );
1650                 if !suggested_changing_assoc_types {
1651                     TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1652                     suggested_changing_assoc_types = true;
1653                 }
1654                 lint
1655             });
1656         }
1657
1658         if !inline_spans.is_empty() {
1659             cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_generic_bounds, |lint| {
1660                 lint.set_span(inline_spans);
1661                 lint.multipart_suggestion(
1662                     fluent::suggestion,
1663                     inline_sugg,
1664                     Applicability::MachineApplicable,
1665                 );
1666                 if !suggested_changing_assoc_types {
1667                     TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1668                 }
1669                 lint
1670             });
1671         }
1672     }
1673 }
1674
1675 declare_lint_pass!(
1676     /// Lint constants that are erroneous.
1677     /// Without this lint, we might not get any diagnostic if the constant is
1678     /// unused within this crate, even though downstream crates can't use it
1679     /// without producing an error.
1680     UnusedBrokenConst => []
1681 );
1682
1683 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1684     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1685         match it.kind {
1686             hir::ItemKind::Const(_, body_id) => {
1687                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1688                 // trigger the query once for all constants since that will already report the errors
1689                 cx.tcx.ensure().const_eval_poly(def_id);
1690             }
1691             hir::ItemKind::Static(_, _, body_id) => {
1692                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1693                 cx.tcx.ensure().eval_static_initializer(def_id);
1694             }
1695             _ => {}
1696         }
1697     }
1698 }
1699
1700 declare_lint! {
1701     /// The `trivial_bounds` lint detects trait bounds that don't depend on
1702     /// any type parameters.
1703     ///
1704     /// ### Example
1705     ///
1706     /// ```rust
1707     /// #![feature(trivial_bounds)]
1708     /// pub struct A where i32: Copy;
1709     /// ```
1710     ///
1711     /// {{produces}}
1712     ///
1713     /// ### Explanation
1714     ///
1715     /// Usually you would not write a trait bound that you know is always
1716     /// true, or never true. However, when using macros, the macro may not
1717     /// know whether or not the constraint would hold or not at the time when
1718     /// generating the code. Currently, the compiler does not alert you if the
1719     /// constraint is always true, and generates an error if it is never true.
1720     /// The `trivial_bounds` feature changes this to be a warning in both
1721     /// cases, giving macros more freedom and flexibility to generate code,
1722     /// while still providing a signal when writing non-macro code that
1723     /// something is amiss.
1724     ///
1725     /// See [RFC 2056] for more details. This feature is currently only
1726     /// available on the nightly channel, see [tracking issue #48214].
1727     ///
1728     /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1729     /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1730     TRIVIAL_BOUNDS,
1731     Warn,
1732     "these bounds don't depend on an type parameters"
1733 }
1734
1735 declare_lint_pass!(
1736     /// Lint for trait and lifetime bounds that don't depend on type parameters
1737     /// which either do nothing, or stop the item from being used.
1738     TrivialConstraints => [TRIVIAL_BOUNDS]
1739 );
1740
1741 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1742     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1743         use rustc_middle::ty::visit::TypeVisitable;
1744         use rustc_middle::ty::Clause;
1745         use rustc_middle::ty::PredicateKind::*;
1746
1747         if cx.tcx.features().trivial_bounds {
1748             let predicates = cx.tcx.predicates_of(item.owner_id);
1749             for &(predicate, span) in predicates.predicates {
1750                 let predicate_kind_name = match predicate.kind().skip_binder() {
1751                     Clause(Clause::Trait(..)) => "trait",
1752                     Clause(Clause::TypeOutlives(..)) |
1753                     Clause(Clause::RegionOutlives(..)) => "lifetime",
1754
1755                     // Ignore projections, as they can only be global
1756                     // if the trait bound is global
1757                     Clause(Clause::Projection(..)) |
1758                     // Ignore bounds that a user can't type
1759                     WellFormed(..) |
1760                     ObjectSafe(..) |
1761                     ClosureKind(..) |
1762                     Subtype(..) |
1763                     Coerce(..) |
1764                     ConstEvaluatable(..) |
1765                     ConstEquate(..) |
1766                     Ambiguous |
1767                     TypeWellFormedFromEnv(..) => continue,
1768                 };
1769                 if predicate.is_global() {
1770                     cx.struct_span_lint(
1771                         TRIVIAL_BOUNDS,
1772                         span,
1773                         fluent::lint_builtin_trivial_bounds,
1774                         |lint| {
1775                             lint.set_arg("predicate_kind_name", predicate_kind_name)
1776                                 .set_arg("predicate", predicate)
1777                         },
1778                     );
1779                 }
1780             }
1781         }
1782     }
1783 }
1784
1785 declare_lint_pass!(
1786     /// Does nothing as a lint pass, but registers some `Lint`s
1787     /// which are used by other parts of the compiler.
1788     SoftLints => [
1789         WHILE_TRUE,
1790         BOX_POINTERS,
1791         NON_SHORTHAND_FIELD_PATTERNS,
1792         UNSAFE_CODE,
1793         MISSING_DOCS,
1794         MISSING_COPY_IMPLEMENTATIONS,
1795         MISSING_DEBUG_IMPLEMENTATIONS,
1796         ANONYMOUS_PARAMETERS,
1797         UNUSED_DOC_COMMENTS,
1798         NO_MANGLE_CONST_ITEMS,
1799         NO_MANGLE_GENERIC_ITEMS,
1800         MUTABLE_TRANSMUTES,
1801         UNSTABLE_FEATURES,
1802         UNREACHABLE_PUB,
1803         TYPE_ALIAS_BOUNDS,
1804         TRIVIAL_BOUNDS
1805     ]
1806 );
1807
1808 declare_lint! {
1809     /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1810     /// pattern], which is deprecated.
1811     ///
1812     /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1813     ///
1814     /// ### Example
1815     ///
1816     /// ```rust,edition2018
1817     /// let x = 123;
1818     /// match x {
1819     ///     0...100 => {}
1820     ///     _ => {}
1821     /// }
1822     /// ```
1823     ///
1824     /// {{produces}}
1825     ///
1826     /// ### Explanation
1827     ///
1828     /// The `...` range pattern syntax was changed to `..=` to avoid potential
1829     /// confusion with the [`..` range expression]. Use the new form instead.
1830     ///
1831     /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1832     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1833     Warn,
1834     "`...` range patterns are deprecated",
1835     @future_incompatible = FutureIncompatibleInfo {
1836         reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1837         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1838     };
1839 }
1840
1841 #[derive(Default)]
1842 pub struct EllipsisInclusiveRangePatterns {
1843     /// If `Some(_)`, suppress all subsequent pattern
1844     /// warnings for better diagnostics.
1845     node_id: Option<ast::NodeId>,
1846 }
1847
1848 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1849
1850 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1851     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1852         if self.node_id.is_some() {
1853             // Don't recursively warn about patterns inside range endpoints.
1854             return;
1855         }
1856
1857         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1858
1859         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1860         /// corresponding to the ellipsis.
1861         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1862             match &pat.kind {
1863                 PatKind::Range(
1864                     a,
1865                     Some(b),
1866                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1867                 ) => Some((a.as_deref(), b, *span)),
1868                 _ => None,
1869             }
1870         }
1871
1872         let (parenthesise, endpoints) = match &pat.kind {
1873             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1874             _ => (false, matches_ellipsis_pat(pat)),
1875         };
1876
1877         if let Some((start, end, join)) = endpoints {
1878             let msg = fluent::lint_builtin_ellipsis_inclusive_range_patterns;
1879             let suggestion = fluent::suggestion;
1880             if parenthesise {
1881                 self.node_id = Some(pat.id);
1882                 let end = expr_to_string(&end);
1883                 let replace = match start {
1884                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1885                     None => format!("&(..={})", end),
1886                 };
1887                 if join.edition() >= Edition::Edition2021 {
1888                     cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1889                         span: pat.span,
1890                         suggestion: pat.span,
1891                         replace,
1892                     });
1893                 } else {
1894                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg, |lint| {
1895                         lint.span_suggestion(
1896                             pat.span,
1897                             suggestion,
1898                             replace,
1899                             Applicability::MachineApplicable,
1900                         )
1901                     });
1902                 }
1903             } else {
1904                 let replace = "..=";
1905                 if join.edition() >= Edition::Edition2021 {
1906                     cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1907                         span: pat.span,
1908                         suggestion: join,
1909                         replace: replace.to_string(),
1910                     });
1911                 } else {
1912                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg, |lint| {
1913                         lint.span_suggestion_short(
1914                             join,
1915                             suggestion,
1916                             replace,
1917                             Applicability::MachineApplicable,
1918                         )
1919                     });
1920                 }
1921             };
1922         }
1923     }
1924
1925     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1926         if let Some(node_id) = self.node_id {
1927             if pat.id == node_id {
1928                 self.node_id = None
1929             }
1930         }
1931     }
1932 }
1933
1934 declare_lint! {
1935     /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1936     /// that are not able to be run by the test harness because they are in a
1937     /// position where they are not nameable.
1938     ///
1939     /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1940     ///
1941     /// ### Example
1942     ///
1943     /// ```rust,test
1944     /// fn main() {
1945     ///     #[test]
1946     ///     fn foo() {
1947     ///         // This test will not fail because it does not run.
1948     ///         assert_eq!(1, 2);
1949     ///     }
1950     /// }
1951     /// ```
1952     ///
1953     /// {{produces}}
1954     ///
1955     /// ### Explanation
1956     ///
1957     /// In order for the test harness to run a test, the test function must be
1958     /// located in a position where it can be accessed from the crate root.
1959     /// This generally means it must be defined in a module, and not anywhere
1960     /// else such as inside another function. The compiler previously allowed
1961     /// this without an error, so a lint was added as an alert that a test is
1962     /// not being used. Whether or not this should be allowed has not yet been
1963     /// decided, see [RFC 2471] and [issue #36629].
1964     ///
1965     /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1966     /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1967     UNNAMEABLE_TEST_ITEMS,
1968     Warn,
1969     "detects an item that cannot be named being marked as `#[test_case]`",
1970     report_in_external_macro
1971 }
1972
1973 pub struct UnnameableTestItems {
1974     boundary: Option<hir::OwnerId>, // Id of the item under which things are not nameable
1975     items_nameable: bool,
1976 }
1977
1978 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1979
1980 impl UnnameableTestItems {
1981     pub fn new() -> Self {
1982         Self { boundary: None, items_nameable: true }
1983     }
1984 }
1985
1986 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1987     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1988         if self.items_nameable {
1989             if let hir::ItemKind::Mod(..) = it.kind {
1990             } else {
1991                 self.items_nameable = false;
1992                 self.boundary = Some(it.owner_id);
1993             }
1994             return;
1995         }
1996
1997         let attrs = cx.tcx.hir().attrs(it.hir_id());
1998         if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1999             cx.struct_span_lint(
2000                 UNNAMEABLE_TEST_ITEMS,
2001                 attr.span,
2002                 fluent::lint_builtin_unnameable_test_items,
2003                 |lint| lint,
2004             );
2005         }
2006     }
2007
2008     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
2009         if !self.items_nameable && self.boundary == Some(it.owner_id) {
2010             self.items_nameable = true;
2011         }
2012     }
2013 }
2014
2015 declare_lint! {
2016     /// The `keyword_idents` lint detects edition keywords being used as an
2017     /// identifier.
2018     ///
2019     /// ### Example
2020     ///
2021     /// ```rust,edition2015,compile_fail
2022     /// #![deny(keyword_idents)]
2023     /// // edition 2015
2024     /// fn dyn() {}
2025     /// ```
2026     ///
2027     /// {{produces}}
2028     ///
2029     /// ### Explanation
2030     ///
2031     /// Rust [editions] allow the language to evolve without breaking
2032     /// backwards compatibility. This lint catches code that uses new keywords
2033     /// that are added to the language that are used as identifiers (such as a
2034     /// variable name, function name, etc.). If you switch the compiler to a
2035     /// new edition without updating the code, then it will fail to compile if
2036     /// you are using a new keyword as an identifier.
2037     ///
2038     /// You can manually change the identifiers to a non-keyword, or use a
2039     /// [raw identifier], for example `r#dyn`, to transition to a new edition.
2040     ///
2041     /// This lint solves the problem automatically. It is "allow" by default
2042     /// because the code is perfectly valid in older editions. The [`cargo
2043     /// fix`] tool with the `--edition` flag will switch this lint to "warn"
2044     /// and automatically apply the suggested fix from the compiler (which is
2045     /// to use a raw identifier). This provides a completely automated way to
2046     /// update old code for a new edition.
2047     ///
2048     /// [editions]: https://doc.rust-lang.org/edition-guide/
2049     /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
2050     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
2051     pub KEYWORD_IDENTS,
2052     Allow,
2053     "detects edition keywords being used as an identifier",
2054     @future_incompatible = FutureIncompatibleInfo {
2055         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
2056         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
2057     };
2058 }
2059
2060 declare_lint_pass!(
2061     /// Check for uses of edition keywords used as an identifier.
2062     KeywordIdents => [KEYWORD_IDENTS]
2063 );
2064
2065 struct UnderMacro(bool);
2066
2067 impl KeywordIdents {
2068     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
2069         for tt in tokens.into_trees() {
2070             match tt {
2071                 // Only report non-raw idents.
2072                 TokenTree::Token(token, _) => {
2073                     if let Some((ident, false)) = token.ident() {
2074                         self.check_ident_token(cx, UnderMacro(true), ident);
2075                     }
2076                 }
2077                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
2078             }
2079         }
2080     }
2081
2082     fn check_ident_token(
2083         &mut self,
2084         cx: &EarlyContext<'_>,
2085         UnderMacro(under_macro): UnderMacro,
2086         ident: Ident,
2087     ) {
2088         let next_edition = match cx.sess().edition() {
2089             Edition::Edition2015 => {
2090                 match ident.name {
2091                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
2092
2093                     // rust-lang/rust#56327: Conservatively do not
2094                     // attempt to report occurrences of `dyn` within
2095                     // macro definitions or invocations, because `dyn`
2096                     // can legitimately occur as a contextual keyword
2097                     // in 2015 code denoting its 2018 meaning, and we
2098                     // do not want rustfix to inject bugs into working
2099                     // code by rewriting such occurrences.
2100                     //
2101                     // But if we see `dyn` outside of a macro, we know
2102                     // its precise role in the parsed AST and thus are
2103                     // assured this is truly an attempt to use it as
2104                     // an identifier.
2105                     kw::Dyn if !under_macro => Edition::Edition2018,
2106
2107                     _ => return,
2108                 }
2109             }
2110
2111             // There are no new keywords yet for the 2018 edition and beyond.
2112             _ => return,
2113         };
2114
2115         // Don't lint `r#foo`.
2116         if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2117             return;
2118         }
2119
2120         cx.struct_span_lint(
2121             KEYWORD_IDENTS,
2122             ident.span,
2123             fluent::lint_builtin_keyword_idents,
2124             |lint| {
2125                 lint.set_arg("kw", ident).set_arg("next", next_edition).span_suggestion(
2126                     ident.span,
2127                     fluent::suggestion,
2128                     format!("r#{}", ident),
2129                     Applicability::MachineApplicable,
2130                 )
2131             },
2132         );
2133     }
2134 }
2135
2136 impl EarlyLintPass for KeywordIdents {
2137     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
2138         self.check_tokens(cx, mac_def.body.tokens.clone());
2139     }
2140     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2141         self.check_tokens(cx, mac.args.tokens.clone());
2142     }
2143     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2144         self.check_ident_token(cx, UnderMacro(false), ident);
2145     }
2146 }
2147
2148 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2149
2150 impl ExplicitOutlivesRequirements {
2151     fn lifetimes_outliving_lifetime<'tcx>(
2152         inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
2153         def_id: DefId,
2154     ) -> Vec<ty::Region<'tcx>> {
2155         inferred_outlives
2156             .iter()
2157             .filter_map(|(clause, _)| match *clause {
2158                 ty::Clause::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2159                     ty::ReEarlyBound(ebr) if ebr.def_id == def_id => Some(b),
2160                     _ => None,
2161                 },
2162                 _ => None,
2163             })
2164             .collect()
2165     }
2166
2167     fn lifetimes_outliving_type<'tcx>(
2168         inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
2169         index: u32,
2170     ) -> Vec<ty::Region<'tcx>> {
2171         inferred_outlives
2172             .iter()
2173             .filter_map(|(clause, _)| match *clause {
2174                 ty::Clause::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2175                     a.is_param(index).then_some(b)
2176                 }
2177                 _ => None,
2178             })
2179             .collect()
2180     }
2181
2182     fn collect_outlives_bound_spans<'tcx>(
2183         &self,
2184         tcx: TyCtxt<'tcx>,
2185         bounds: &hir::GenericBounds<'_>,
2186         inferred_outlives: &[ty::Region<'tcx>],
2187         predicate_span: Span,
2188     ) -> Vec<(usize, Span)> {
2189         use rustc_middle::middle::resolve_lifetime::Region;
2190
2191         bounds
2192             .iter()
2193             .enumerate()
2194             .filter_map(|(i, bound)| {
2195                 let hir::GenericBound::Outlives(lifetime) = bound else {
2196                     return None;
2197                 };
2198
2199                 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2200                     Some(Region::EarlyBound(def_id)) => inferred_outlives
2201                         .iter()
2202                         .any(|r| matches!(**r, ty::ReEarlyBound(ebr) if { ebr.def_id == def_id })),
2203                     _ => false,
2204                 };
2205
2206                 if !is_inferred {
2207                     return None;
2208                 }
2209
2210                 let span = bound.span().find_ancestor_inside(predicate_span)?;
2211                 if in_external_macro(tcx.sess, span) {
2212                     return None;
2213                 }
2214
2215                 Some((i, span))
2216             })
2217             .collect()
2218     }
2219
2220     fn consolidate_outlives_bound_spans(
2221         &self,
2222         lo: Span,
2223         bounds: &hir::GenericBounds<'_>,
2224         bound_spans: Vec<(usize, Span)>,
2225     ) -> Vec<Span> {
2226         if bounds.is_empty() {
2227             return Vec::new();
2228         }
2229         if bound_spans.len() == bounds.len() {
2230             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2231             // If all bounds are inferable, we want to delete the colon, so
2232             // start from just after the parameter (span passed as argument)
2233             vec![lo.to(last_bound_span)]
2234         } else {
2235             let mut merged = Vec::new();
2236             let mut last_merged_i = None;
2237
2238             let mut from_start = true;
2239             for (i, bound_span) in bound_spans {
2240                 match last_merged_i {
2241                     // If the first bound is inferable, our span should also eat the leading `+`.
2242                     None if i == 0 => {
2243                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2244                         last_merged_i = Some(0);
2245                     }
2246                     // If consecutive bounds are inferable, merge their spans
2247                     Some(h) if i == h + 1 => {
2248                         if let Some(tail) = merged.last_mut() {
2249                             // Also eat the trailing `+` if the first
2250                             // more-than-one bound is inferable
2251                             let to_span = if from_start && i < bounds.len() {
2252                                 bounds[i + 1].span().shrink_to_lo()
2253                             } else {
2254                                 bound_span
2255                             };
2256                             *tail = tail.to(to_span);
2257                             last_merged_i = Some(i);
2258                         } else {
2259                             bug!("another bound-span visited earlier");
2260                         }
2261                     }
2262                     _ => {
2263                         // When we find a non-inferable bound, subsequent inferable bounds
2264                         // won't be consecutive from the start (and we'll eat the leading
2265                         // `+` rather than the trailing one)
2266                         from_start = false;
2267                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2268                         last_merged_i = Some(i);
2269                     }
2270                 }
2271             }
2272             merged
2273         }
2274     }
2275 }
2276
2277 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2278     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2279         use rustc_middle::middle::resolve_lifetime::Region;
2280
2281         let def_id = item.owner_id.def_id;
2282         if let hir::ItemKind::Struct(_, hir_generics)
2283         | hir::ItemKind::Enum(_, hir_generics)
2284         | hir::ItemKind::Union(_, hir_generics) = item.kind
2285         {
2286             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2287             if inferred_outlives.is_empty() {
2288                 return;
2289             }
2290
2291             let ty_generics = cx.tcx.generics_of(def_id);
2292
2293             let mut bound_count = 0;
2294             let mut lint_spans = Vec::new();
2295             let mut where_lint_spans = Vec::new();
2296             let mut dropped_predicate_count = 0;
2297             let num_predicates = hir_generics.predicates.len();
2298             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2299                 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
2300                     match where_predicate {
2301                         hir::WherePredicate::RegionPredicate(predicate) => {
2302                             if let Some(Region::EarlyBound(region_def_id)) =
2303                                 cx.tcx.named_region(predicate.lifetime.hir_id)
2304                             {
2305                                 (
2306                                     Self::lifetimes_outliving_lifetime(
2307                                         inferred_outlives,
2308                                         region_def_id,
2309                                     ),
2310                                     &predicate.bounds,
2311                                     predicate.span,
2312                                     predicate.in_where_clause,
2313                                 )
2314                             } else {
2315                                 continue;
2316                             }
2317                         }
2318                         hir::WherePredicate::BoundPredicate(predicate) => {
2319                             // FIXME we can also infer bounds on associated types,
2320                             // and should check for them here.
2321                             match predicate.bounded_ty.kind {
2322                                 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => {
2323                                     let Res::Def(DefKind::TyParam, def_id) = path.res else {
2324                                     continue;
2325                                 };
2326                                     let index = ty_generics.param_def_id_to_index[&def_id];
2327                                     (
2328                                         Self::lifetimes_outliving_type(inferred_outlives, index),
2329                                         &predicate.bounds,
2330                                         predicate.span,
2331                                         predicate.origin == PredicateOrigin::WhereClause,
2332                                     )
2333                                 }
2334                                 _ => {
2335                                     continue;
2336                                 }
2337                             }
2338                         }
2339                         _ => continue,
2340                     };
2341                 if relevant_lifetimes.is_empty() {
2342                     continue;
2343                 }
2344
2345                 let bound_spans = self.collect_outlives_bound_spans(
2346                     cx.tcx,
2347                     bounds,
2348                     &relevant_lifetimes,
2349                     predicate_span,
2350                 );
2351                 bound_count += bound_spans.len();
2352
2353                 let drop_predicate = bound_spans.len() == bounds.len();
2354                 if drop_predicate {
2355                     dropped_predicate_count += 1;
2356                 }
2357
2358                 if drop_predicate && !in_where_clause {
2359                     lint_spans.push(predicate_span);
2360                 } else if drop_predicate && i + 1 < num_predicates {
2361                     // If all the bounds on a predicate were inferable and there are
2362                     // further predicates, we want to eat the trailing comma.
2363                     let next_predicate_span = hir_generics.predicates[i + 1].span();
2364                     where_lint_spans.push(predicate_span.to(next_predicate_span.shrink_to_lo()));
2365                 } else {
2366                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2367                         predicate_span.shrink_to_lo(),
2368                         bounds,
2369                         bound_spans,
2370                     ));
2371                 }
2372             }
2373
2374             // If all predicates are inferable, drop the entire clause
2375             // (including the `where`)
2376             if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2377             {
2378                 let where_span = hir_generics.where_clause_span;
2379                 // Extend the where clause back to the closing `>` of the
2380                 // generics, except for tuple struct, which have the `where`
2381                 // after the fields of the struct.
2382                 let full_where_span =
2383                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2384                         where_span
2385                     } else {
2386                         hir_generics.span.shrink_to_hi().to(where_span)
2387                     };
2388
2389                 // Due to macro expansions, the `full_where_span` might not actually contain all predicates.
2390                 if where_lint_spans.iter().all(|&sp| full_where_span.contains(sp)) {
2391                     lint_spans.push(full_where_span);
2392                 } else {
2393                     lint_spans.extend(where_lint_spans);
2394                 }
2395             } else {
2396                 lint_spans.extend(where_lint_spans);
2397             }
2398
2399             if !lint_spans.is_empty() {
2400                 // Do not automatically delete outlives requirements from macros.
2401                 let applicability = if lint_spans.iter().all(|sp| sp.can_be_used_for_suggestions())
2402                 {
2403                     Applicability::MachineApplicable
2404                 } else {
2405                     Applicability::MaybeIncorrect
2406                 };
2407
2408                 cx.struct_span_lint(
2409                     EXPLICIT_OUTLIVES_REQUIREMENTS,
2410                     lint_spans.clone(),
2411                     fluent::lint_builtin_explicit_outlives,
2412                     |lint| {
2413                         lint.set_arg("count", bound_count).multipart_suggestion(
2414                             fluent::suggestion,
2415                             lint_spans.into_iter().map(|span| (span, String::new())).collect(),
2416                             applicability,
2417                         )
2418                     },
2419                 );
2420             }
2421         }
2422     }
2423 }
2424
2425 declare_lint! {
2426     /// The `incomplete_features` lint detects unstable features enabled with
2427     /// the [`feature` attribute] that may function improperly in some or all
2428     /// cases.
2429     ///
2430     /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2431     ///
2432     /// ### Example
2433     ///
2434     /// ```rust
2435     /// #![feature(generic_const_exprs)]
2436     /// ```
2437     ///
2438     /// {{produces}}
2439     ///
2440     /// ### Explanation
2441     ///
2442     /// Although it is encouraged for people to experiment with unstable
2443     /// features, some of them are known to be incomplete or faulty. This lint
2444     /// is a signal that the feature has not yet been finished, and you may
2445     /// experience problems with it.
2446     pub INCOMPLETE_FEATURES,
2447     Warn,
2448     "incomplete features that may function improperly in some or all cases"
2449 }
2450
2451 declare_lint_pass!(
2452     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2453     IncompleteFeatures => [INCOMPLETE_FEATURES]
2454 );
2455
2456 impl EarlyLintPass for IncompleteFeatures {
2457     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2458         let features = cx.sess().features_untracked();
2459         features
2460             .declared_lang_features
2461             .iter()
2462             .map(|(name, span, _)| (name, span))
2463             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2464             .filter(|(&name, _)| features.incomplete(name))
2465             .for_each(|(&name, &span)| {
2466                 cx.struct_span_lint(
2467                     INCOMPLETE_FEATURES,
2468                     span,
2469                     fluent::lint_builtin_incomplete_features,
2470                     |lint| {
2471                         lint.set_arg("name", name);
2472                         if let Some(n) =
2473                             rustc_feature::find_feature_issue(name, GateIssue::Language)
2474                         {
2475                             lint.set_arg("n", n);
2476                             lint.note(fluent::note);
2477                         }
2478                         if HAS_MIN_FEATURES.contains(&name) {
2479                             lint.help(fluent::help);
2480                         }
2481                         lint
2482                     },
2483                 )
2484             });
2485     }
2486 }
2487
2488 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2489
2490 declare_lint! {
2491     /// The `invalid_value` lint detects creating a value that is not valid,
2492     /// such as a null reference.
2493     ///
2494     /// ### Example
2495     ///
2496     /// ```rust,no_run
2497     /// # #![allow(unused)]
2498     /// unsafe {
2499     ///     let x: &'static i32 = std::mem::zeroed();
2500     /// }
2501     /// ```
2502     ///
2503     /// {{produces}}
2504     ///
2505     /// ### Explanation
2506     ///
2507     /// In some situations the compiler can detect that the code is creating
2508     /// an invalid value, which should be avoided.
2509     ///
2510     /// In particular, this lint will check for improper use of
2511     /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2512     /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2513     /// lint should provide extra information to indicate what the problem is
2514     /// and a possible solution.
2515     ///
2516     /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2517     /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2518     /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2519     /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2520     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2521     pub INVALID_VALUE,
2522     Warn,
2523     "an invalid value is being created (such as a null reference)"
2524 }
2525
2526 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2527
2528 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2529     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2530         #[derive(Debug, Copy, Clone, PartialEq)]
2531         enum InitKind {
2532             Zeroed,
2533             Uninit,
2534         }
2535
2536         /// Information about why a type cannot be initialized this way.
2537         struct InitError {
2538             message: String,
2539             /// Spans from struct fields and similar that can be obtained from just the type.
2540             span: Option<Span>,
2541             /// Used to report a trace through adts.
2542             nested: Option<Box<InitError>>,
2543         }
2544         impl InitError {
2545             fn spanned(self, span: Span) -> InitError {
2546                 Self { span: Some(span), ..self }
2547             }
2548
2549             fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
2550                 assert!(self.nested.is_none());
2551                 Self { nested: nested.into().map(Box::new), ..self }
2552             }
2553         }
2554
2555         impl<'a> From<&'a str> for InitError {
2556             fn from(s: &'a str) -> Self {
2557                 s.to_owned().into()
2558             }
2559         }
2560         impl From<String> for InitError {
2561             fn from(message: String) -> Self {
2562                 Self { message, span: None, nested: None }
2563             }
2564         }
2565
2566         /// Test if this constant is all-0.
2567         fn is_zero(expr: &hir::Expr<'_>) -> bool {
2568             use hir::ExprKind::*;
2569             use rustc_ast::LitKind::*;
2570             match &expr.kind {
2571                 Lit(lit) => {
2572                     if let Int(i, _) = lit.node {
2573                         i == 0
2574                     } else {
2575                         false
2576                     }
2577                 }
2578                 Tup(tup) => tup.iter().all(is_zero),
2579                 _ => false,
2580             }
2581         }
2582
2583         /// Determine if this expression is a "dangerous initialization".
2584         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2585             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2586                 // Find calls to `mem::{uninitialized,zeroed}` methods.
2587                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2588                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2589                     match cx.tcx.get_diagnostic_name(def_id) {
2590                         Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2591                         Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2592                         Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2593                         _ => {}
2594                     }
2595                 }
2596             } else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
2597                 // Find problematic calls to `MaybeUninit::assume_init`.
2598                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2599                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2600                     // This is a call to *some* method named `assume_init`.
2601                     // See if the `self` parameter is one of the dangerous constructors.
2602                     if let hir::ExprKind::Call(ref path_expr, _) = receiver.kind {
2603                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2604                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2605                             match cx.tcx.get_diagnostic_name(def_id) {
2606                                 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2607                                 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2608                                 _ => {}
2609                             }
2610                         }
2611                     }
2612                 }
2613             }
2614
2615             None
2616         }
2617
2618         fn variant_find_init_error<'tcx>(
2619             cx: &LateContext<'tcx>,
2620             ty: Ty<'tcx>,
2621             variant: &VariantDef,
2622             substs: ty::SubstsRef<'tcx>,
2623             descr: &str,
2624             init: InitKind,
2625         ) -> Option<InitError> {
2626             let mut field_err = variant.fields.iter().find_map(|field| {
2627                 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|mut err| {
2628                     if !field.did.is_local() {
2629                         err
2630                     } else if err.span.is_none() {
2631                         err.span = Some(cx.tcx.def_span(field.did));
2632                         write!(&mut err.message, " (in this {descr})").unwrap();
2633                         err
2634                     } else {
2635                         InitError::from(format!("in this {descr}"))
2636                             .spanned(cx.tcx.def_span(field.did))
2637                             .nested(err)
2638                     }
2639                 })
2640             });
2641
2642             // Check if this ADT has a constrained layout (like `NonNull` and friends).
2643             if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty)) {
2644                 if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &layout.abi {
2645                     let range = scalar.valid_range(cx);
2646                     let msg = if !range.contains(0) {
2647                         "must be non-null"
2648                     } else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
2649                         // Prefer reporting on the fields over the entire struct for uninit,
2650                         // as the information bubbles out and it may be unclear why the type can't
2651                         // be null from just its outside signature.
2652
2653                         "must be initialized inside its custom valid range"
2654                     } else {
2655                         return field_err;
2656                     };
2657                     if let Some(field_err) = &mut field_err {
2658                         // Most of the time, if the field error is the same as the struct error,
2659                         // the struct error only happens because of the field error.
2660                         if field_err.message.contains(msg) {
2661                             field_err.message = format!("because {}", field_err.message);
2662                         }
2663                     }
2664                     return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
2665                 }
2666             }
2667             field_err
2668         }
2669
2670         /// Return `Some` only if we are sure this type does *not*
2671         /// allow zero initialization.
2672         fn ty_find_init_error<'tcx>(
2673             cx: &LateContext<'tcx>,
2674             ty: Ty<'tcx>,
2675             init: InitKind,
2676         ) -> Option<InitError> {
2677             use rustc_type_ir::sty::TyKind::*;
2678             match ty.kind() {
2679                 // Primitive types that don't like 0 as a value.
2680                 Ref(..) => Some("references must be non-null".into()),
2681                 Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
2682                 FnPtr(..) => Some("function pointers must be non-null".into()),
2683                 Never => Some("the `!` type has no valid value".into()),
2684                 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2685                 // raw ptr to dyn Trait
2686                 {
2687                     Some("the vtable of a wide raw pointer must be non-null".into())
2688                 }
2689                 // Primitive types with other constraints.
2690                 Bool if init == InitKind::Uninit => {
2691                     Some("booleans must be either `true` or `false`".into())
2692                 }
2693                 Char if init == InitKind::Uninit => {
2694                     Some("characters must be a valid Unicode codepoint".into())
2695                 }
2696                 Int(_) | Uint(_) if init == InitKind::Uninit => {
2697                     Some("integers must be initialized".into())
2698                 }
2699                 Float(_) if init == InitKind::Uninit => Some("floats must be initialized".into()),
2700                 RawPtr(_) if init == InitKind::Uninit => {
2701                     Some("raw pointers must be initialized".into())
2702                 }
2703                 // Recurse and checks for some compound types. (but not unions)
2704                 Adt(adt_def, substs) if !adt_def.is_union() => {
2705                     // Handle structs.
2706                     if adt_def.is_struct() {
2707                         return variant_find_init_error(
2708                             cx,
2709                             ty,
2710                             adt_def.non_enum_variant(),
2711                             substs,
2712                             "struct field",
2713                             init,
2714                         );
2715                     }
2716                     // And now, enums.
2717                     let span = cx.tcx.def_span(adt_def.did());
2718                     let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
2719                         let definitely_inhabited = match variant
2720                             .inhabited_predicate(cx.tcx, *adt_def)
2721                             .subst(cx.tcx, substs)
2722                             .apply_any_module(cx.tcx, cx.param_env)
2723                         {
2724                             // Entirely skip uninhbaited variants.
2725                             Some(false) => return None,
2726                             // Forward the others, but remember which ones are definitely inhabited.
2727                             Some(true) => true,
2728                             None => false,
2729                         };
2730                         Some((variant, definitely_inhabited))
2731                     });
2732                     let Some(first_variant) = potential_variants.next() else {
2733                         return Some(InitError::from("enums with no inhabited variants have no valid value").spanned(span));
2734                     };
2735                     // So we have at least one potentially inhabited variant. Might we have two?
2736                     let Some(second_variant) = potential_variants.next() else {
2737                         // There is only one potentially inhabited variant. So we can recursively check that variant!
2738                         return variant_find_init_error(
2739                             cx,
2740                             ty,
2741                             &first_variant.0,
2742                             substs,
2743                             "field of the only potentially inhabited enum variant",
2744                             init,
2745                         );
2746                     };
2747                     // So we have at least two potentially inhabited variants.
2748                     // If we can prove that we have at least two *definitely* inhabited variants,
2749                     // then we have a tag and hence leaving this uninit is definitely disallowed.
2750                     // (Leaving it zeroed could be okay, depending on which variant is encoded as zero tag.)
2751                     if init == InitKind::Uninit {
2752                         let definitely_inhabited = (first_variant.1 as usize)
2753                             + (second_variant.1 as usize)
2754                             + potential_variants
2755                                 .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
2756                                 .count();
2757                         if definitely_inhabited > 1 {
2758                             return Some(InitError::from(
2759                                 "enums with multiple inhabited variants have to be initialized to a variant",
2760                             ).spanned(span));
2761                         }
2762                     }
2763                     // We couldn't find anything wrong here.
2764                     None
2765                 }
2766                 Tuple(..) => {
2767                     // Proceed recursively, check all fields.
2768                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2769                 }
2770                 Array(ty, len) => {
2771                     if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2772                         // Array length known at array non-empty -- recurse.
2773                         ty_find_init_error(cx, *ty, init)
2774                     } else {
2775                         // Empty array or size unknown.
2776                         None
2777                     }
2778                 }
2779                 // Conservative fallback.
2780                 _ => None,
2781             }
2782         }
2783
2784         if let Some(init) = is_dangerous_init(cx, expr) {
2785             // This conjures an instance of a type out of nothing,
2786             // using zeroed or uninitialized memory.
2787             // We are extremely conservative with what we warn about.
2788             let conjured_ty = cx.typeck_results().expr_ty(expr);
2789             if let Some(mut err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2790             {
2791                 // FIXME(davidtwco): make translatable
2792                 cx.struct_span_lint(
2793                     INVALID_VALUE,
2794                     expr.span,
2795                     DelayDm(|| {
2796                         format!(
2797                             "the type `{}` does not permit {}",
2798                             conjured_ty,
2799                             match init {
2800                                 InitKind::Zeroed => "zero-initialization",
2801                                 InitKind::Uninit => "being left uninitialized",
2802                             },
2803                         )
2804                     }),
2805                     |lint| {
2806                         lint.span_label(
2807                             expr.span,
2808                             "this code causes undefined behavior when executed",
2809                         );
2810                         lint.span_label(
2811                             expr.span,
2812                             "help: use `MaybeUninit<T>` instead, \
2813                             and only call `assume_init` after initialization is done",
2814                         );
2815                         loop {
2816                             if let Some(span) = err.span {
2817                                 lint.span_note(span, &err.message);
2818                             } else {
2819                                 lint.note(&err.message);
2820                             }
2821                             if let Some(e) = err.nested {
2822                                 err = *e;
2823                             } else {
2824                                 break;
2825                             }
2826                         }
2827                         lint
2828                     },
2829                 );
2830             }
2831         }
2832     }
2833 }
2834
2835 declare_lint! {
2836     /// The `clashing_extern_declarations` lint detects when an `extern fn`
2837     /// has been declared with the same name but different types.
2838     ///
2839     /// ### Example
2840     ///
2841     /// ```rust
2842     /// mod m {
2843     ///     extern "C" {
2844     ///         fn foo();
2845     ///     }
2846     /// }
2847     ///
2848     /// extern "C" {
2849     ///     fn foo(_: u32);
2850     /// }
2851     /// ```
2852     ///
2853     /// {{produces}}
2854     ///
2855     /// ### Explanation
2856     ///
2857     /// Because two symbols of the same name cannot be resolved to two
2858     /// different functions at link time, and one function cannot possibly
2859     /// have two types, a clashing extern declaration is almost certainly a
2860     /// mistake. Check to make sure that the `extern` definitions are correct
2861     /// and equivalent, and possibly consider unifying them in one location.
2862     ///
2863     /// This lint does not run between crates because a project may have
2864     /// dependencies which both rely on the same extern function, but declare
2865     /// it in a different (but valid) way. For example, they may both declare
2866     /// an opaque type for one or more of the arguments (which would end up
2867     /// distinct types), or use types that are valid conversions in the
2868     /// language the `extern fn` is defined in. In these cases, the compiler
2869     /// can't say that the clashing declaration is incorrect.
2870     pub CLASHING_EXTERN_DECLARATIONS,
2871     Warn,
2872     "detects when an extern fn has been declared with the same name but different types"
2873 }
2874
2875 pub struct ClashingExternDeclarations {
2876     /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2877     /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2878     /// the symbol should be reported as a clashing declaration.
2879     // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2880     // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2881     seen_decls: FxHashMap<Symbol, HirId>,
2882 }
2883
2884 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2885 /// just from declaration itself. This is important because we don't want to report clashes on
2886 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2887 /// different name.
2888 enum SymbolName {
2889     /// The name of the symbol + the span of the annotation which introduced the link name.
2890     Link(Symbol, Span),
2891     /// No link name, so just the name of the symbol.
2892     Normal(Symbol),
2893 }
2894
2895 impl SymbolName {
2896     fn get_name(&self) -> Symbol {
2897         match self {
2898             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2899         }
2900     }
2901 }
2902
2903 impl ClashingExternDeclarations {
2904     pub(crate) fn new() -> Self {
2905         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2906     }
2907     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2908     /// for the item, return its HirId without updating the set.
2909     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2910         let did = fi.owner_id.to_def_id();
2911         let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2912         let name = Symbol::intern(tcx.symbol_name(instance).name);
2913         if let Some(&hir_id) = self.seen_decls.get(&name) {
2914             // Avoid updating the map with the new entry when we do find a collision. We want to
2915             // make sure we're always pointing to the first definition as the previous declaration.
2916             // This lets us avoid emitting "knock-on" diagnostics.
2917             Some(hir_id)
2918         } else {
2919             self.seen_decls.insert(name, fi.hir_id())
2920         }
2921     }
2922
2923     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2924     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2925     /// symbol's name.
2926     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2927         if let Some((overridden_link_name, overridden_link_name_span)) =
2928             tcx.codegen_fn_attrs(fi.owner_id).link_name.map(|overridden_link_name| {
2929                 // FIXME: Instead of searching through the attributes again to get span
2930                 // information, we could have codegen_fn_attrs also give span information back for
2931                 // where the attribute was defined. However, until this is found to be a
2932                 // bottleneck, this does just fine.
2933                 (
2934                     overridden_link_name,
2935                     tcx.get_attr(fi.owner_id.to_def_id(), sym::link_name).unwrap().span,
2936                 )
2937             })
2938         {
2939             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2940         } else {
2941             SymbolName::Normal(fi.ident.name)
2942         }
2943     }
2944
2945     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2946     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2947     /// with the same members (as the declarations shouldn't clash).
2948     fn structurally_same_type<'tcx>(
2949         cx: &LateContext<'tcx>,
2950         a: Ty<'tcx>,
2951         b: Ty<'tcx>,
2952         ckind: CItemKind,
2953     ) -> bool {
2954         fn structurally_same_type_impl<'tcx>(
2955             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2956             cx: &LateContext<'tcx>,
2957             a: Ty<'tcx>,
2958             b: Ty<'tcx>,
2959             ckind: CItemKind,
2960         ) -> bool {
2961             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2962             let tcx = cx.tcx;
2963
2964             // Given a transparent newtype, reach through and grab the inner
2965             // type unless the newtype makes the type non-null.
2966             let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2967                 let mut ty = ty;
2968                 loop {
2969                     if let ty::Adt(def, substs) = *ty.kind() {
2970                         let is_transparent = def.repr().transparent();
2971                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2972                         debug!(
2973                             "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2974                             ty, is_transparent, is_non_null
2975                         );
2976                         if is_transparent && !is_non_null {
2977                             debug_assert!(def.variants().len() == 1);
2978                             let v = &def.variant(VariantIdx::new(0));
2979                             ty = transparent_newtype_field(tcx, v)
2980                                 .expect(
2981                                     "single-variant transparent structure with zero-sized field",
2982                                 )
2983                                 .ty(tcx, substs);
2984                             continue;
2985                         }
2986                     }
2987                     debug!("non_transparent_ty -> {:?}", ty);
2988                     return ty;
2989                 }
2990             };
2991
2992             let a = non_transparent_ty(a);
2993             let b = non_transparent_ty(b);
2994
2995             if !seen_types.insert((a, b)) {
2996                 // We've encountered a cycle. There's no point going any further -- the types are
2997                 // structurally the same.
2998                 return true;
2999             }
3000             let tcx = cx.tcx;
3001             if a == b {
3002                 // All nominally-same types are structurally same, too.
3003                 true
3004             } else {
3005                 // Do a full, depth-first comparison between the two.
3006                 use rustc_type_ir::sty::TyKind::*;
3007                 let a_kind = a.kind();
3008                 let b_kind = b.kind();
3009
3010                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
3011                     debug!("compare_layouts({:?}, {:?})", a, b);
3012                     let a_layout = &cx.layout_of(a)?.layout.abi();
3013                     let b_layout = &cx.layout_of(b)?.layout.abi();
3014                     debug!(
3015                         "comparing layouts: {:?} == {:?} = {}",
3016                         a_layout,
3017                         b_layout,
3018                         a_layout == b_layout
3019                     );
3020                     Ok(a_layout == b_layout)
3021                 };
3022
3023                 #[allow(rustc::usage_of_ty_tykind)]
3024                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
3025                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
3026                 };
3027
3028                 ensure_sufficient_stack(|| {
3029                     match (a_kind, b_kind) {
3030                         (Adt(a_def, _), Adt(b_def, _)) => {
3031                             // We can immediately rule out these types as structurally same if
3032                             // their layouts differ.
3033                             match compare_layouts(a, b) {
3034                                 Ok(false) => return false,
3035                                 _ => (), // otherwise, continue onto the full, fields comparison
3036                             }
3037
3038                             // Grab a flattened representation of all fields.
3039                             let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
3040                             let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
3041
3042                             // Perform a structural comparison for each field.
3043                             a_fields.eq_by(
3044                                 b_fields,
3045                                 |&ty::FieldDef { did: a_did, .. },
3046                                  &ty::FieldDef { did: b_did, .. }| {
3047                                     structurally_same_type_impl(
3048                                         seen_types,
3049                                         cx,
3050                                         tcx.type_of(a_did),
3051                                         tcx.type_of(b_did),
3052                                         ckind,
3053                                     )
3054                                 },
3055                             )
3056                         }
3057                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
3058                             // For arrays, we also check the constness of the type.
3059                             a_const.kind() == b_const.kind()
3060                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
3061                         }
3062                         (Slice(a_ty), Slice(b_ty)) => {
3063                             structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
3064                         }
3065                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
3066                             a_tymut.mutbl == b_tymut.mutbl
3067                                 && structurally_same_type_impl(
3068                                     seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
3069                                 )
3070                         }
3071                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
3072                             // For structural sameness, we don't need the region to be same.
3073                             a_mut == b_mut
3074                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
3075                         }
3076                         (FnDef(..), FnDef(..)) => {
3077                             let a_poly_sig = a.fn_sig(tcx);
3078                             let b_poly_sig = b.fn_sig(tcx);
3079
3080                             // We don't compare regions, but leaving bound regions around ICEs, so
3081                             // we erase them.
3082                             let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
3083                             let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
3084
3085                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
3086                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
3087                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
3088                                     structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
3089                                 })
3090                                 && structurally_same_type_impl(
3091                                     seen_types,
3092                                     cx,
3093                                     a_sig.output(),
3094                                     b_sig.output(),
3095                                     ckind,
3096                                 )
3097                         }
3098                         (Tuple(a_substs), Tuple(b_substs)) => {
3099                             a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
3100                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
3101                             })
3102                         }
3103                         // For these, it's not quite as easy to define structural-sameness quite so easily.
3104                         // For the purposes of this lint, take the conservative approach and mark them as
3105                         // not structurally same.
3106                         (Dynamic(..), Dynamic(..))
3107                         | (Error(..), Error(..))
3108                         | (Closure(..), Closure(..))
3109                         | (Generator(..), Generator(..))
3110                         | (GeneratorWitness(..), GeneratorWitness(..))
3111                         | (Alias(ty::Projection, ..), Alias(ty::Projection, ..))
3112                         | (Alias(ty::Opaque, ..), Alias(ty::Opaque, ..)) => false,
3113
3114                         // These definitely should have been caught above.
3115                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
3116
3117                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
3118                         // enum layout optimisation is being applied.
3119                         (Adt(..), other_kind) | (other_kind, Adt(..))
3120                             if is_primitive_or_pointer(other_kind) =>
3121                         {
3122                             let (primitive, adt) =
3123                                 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
3124                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
3125                                 ty == primitive
3126                             } else {
3127                                 compare_layouts(a, b).unwrap_or(false)
3128                             }
3129                         }
3130                         // Otherwise, just compare the layouts. This may fail to lint for some
3131                         // incompatible types, but at the very least, will stop reads into
3132                         // uninitialised memory.
3133                         _ => compare_layouts(a, b).unwrap_or(false),
3134                     }
3135                 })
3136             }
3137         }
3138         let mut seen_types = FxHashSet::default();
3139         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
3140     }
3141 }
3142
3143 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
3144
3145 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
3146     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
3147         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
3148         if let ForeignItemKind::Fn(..) = this_fi.kind {
3149             let tcx = cx.tcx;
3150             if let Some(existing_hid) = self.insert(tcx, this_fi) {
3151                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
3152                 let this_decl_ty = tcx.type_of(this_fi.owner_id);
3153                 debug!(
3154                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
3155                     existing_hid, existing_decl_ty, this_fi.owner_id, this_decl_ty
3156                 );
3157                 // Check that the declarations match.
3158                 if !Self::structurally_same_type(
3159                     cx,
3160                     existing_decl_ty,
3161                     this_decl_ty,
3162                     CItemKind::Declaration,
3163                 ) {
3164                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
3165                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
3166
3167                     // We want to ensure that we use spans for both decls that include where the
3168                     // name was defined, whether that was from the link_name attribute or not.
3169                     let get_relevant_span =
3170                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3171                             SymbolName::Normal(_) => fi.span,
3172                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3173                         };
3174                     // Finally, emit the diagnostic.
3175
3176                     let msg = if orig.get_name() == this_fi.ident.name {
3177                         fluent::lint_builtin_clashing_extern_same_name
3178                     } else {
3179                         fluent::lint_builtin_clashing_extern_diff_name
3180                     };
3181                     tcx.struct_span_lint_hir(
3182                         CLASHING_EXTERN_DECLARATIONS,
3183                         this_fi.hir_id(),
3184                         get_relevant_span(this_fi),
3185                         msg,
3186                         |lint| {
3187                             let mut expected_str = DiagnosticStyledString::new();
3188                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3189                             let mut found_str = DiagnosticStyledString::new();
3190                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3191
3192                             lint.set_arg("this_fi", this_fi.ident.name)
3193                                 .set_arg("orig", orig.get_name())
3194                                 .span_label(get_relevant_span(orig_fi), fluent::previous_decl_label)
3195                                 .span_label(get_relevant_span(this_fi), fluent::mismatch_label)
3196                                 // FIXME(davidtwco): translatable expected/found
3197                                 .note_expected_found(&"", expected_str, &"", found_str)
3198                         },
3199                     );
3200                 }
3201             }
3202         }
3203     }
3204 }
3205
3206 declare_lint! {
3207     /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3208     /// which causes [undefined behavior].
3209     ///
3210     /// ### Example
3211     ///
3212     /// ```rust,no_run
3213     /// # #![allow(unused)]
3214     /// use std::ptr;
3215     /// unsafe {
3216     ///     let x = &*ptr::null::<i32>();
3217     ///     let x = ptr::addr_of!(*ptr::null::<i32>());
3218     ///     let x = *(0 as *const i32);
3219     /// }
3220     /// ```
3221     ///
3222     /// {{produces}}
3223     ///
3224     /// ### Explanation
3225     ///
3226     /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3227     /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3228     ///
3229     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3230     pub DEREF_NULLPTR,
3231     Warn,
3232     "detects when an null pointer is dereferenced"
3233 }
3234
3235 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3236
3237 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3238     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3239         /// test if expression is a null ptr
3240         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3241             match &expr.kind {
3242                 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3243                     if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3244                         return is_zero(expr) || is_null_ptr(cx, expr);
3245                     }
3246                 }
3247                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3248                 rustc_hir::ExprKind::Call(ref path, _) => {
3249                     if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3250                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3251                             return matches!(
3252                                 cx.tcx.get_diagnostic_name(def_id),
3253                                 Some(sym::ptr_null | sym::ptr_null_mut)
3254                             );
3255                         }
3256                     }
3257                 }
3258                 _ => {}
3259             }
3260             false
3261         }
3262
3263         /// test if expression is the literal `0`
3264         fn is_zero(expr: &hir::Expr<'_>) -> bool {
3265             match &expr.kind {
3266                 rustc_hir::ExprKind::Lit(ref lit) => {
3267                     if let LitKind::Int(a, _) = lit.node {
3268                         return a == 0;
3269                     }
3270                 }
3271                 _ => {}
3272             }
3273             false
3274         }
3275
3276         if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3277             if is_null_ptr(cx, expr_deref) {
3278                 cx.struct_span_lint(
3279                     DEREF_NULLPTR,
3280                     expr.span,
3281                     fluent::lint_builtin_deref_nullptr,
3282                     |lint| lint.span_label(expr.span, fluent::label),
3283                 );
3284             }
3285         }
3286     }
3287 }
3288
3289 declare_lint! {
3290     /// The `named_asm_labels` lint detects the use of named labels in the
3291     /// inline `asm!` macro.
3292     ///
3293     /// ### Example
3294     ///
3295     /// ```rust,compile_fail
3296     /// # #![feature(asm_experimental_arch)]
3297     /// use std::arch::asm;
3298     ///
3299     /// fn main() {
3300     ///     unsafe {
3301     ///         asm!("foo: bar");
3302     ///     }
3303     /// }
3304     /// ```
3305     ///
3306     /// {{produces}}
3307     ///
3308     /// ### Explanation
3309     ///
3310     /// LLVM is allowed to duplicate inline assembly blocks for any
3311     /// reason, for example when it is in a function that gets inlined. Because
3312     /// of this, GNU assembler [local labels] *must* be used instead of labels
3313     /// with a name. Using named labels might cause assembler or linker errors.
3314     ///
3315     /// See the explanation in [Rust By Example] for more details.
3316     ///
3317     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3318     /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3319     pub NAMED_ASM_LABELS,
3320     Deny,
3321     "named labels in inline assembly",
3322 }
3323
3324 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3325
3326 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3327     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3328         if let hir::Expr {
3329             kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3330             ..
3331         } = expr
3332         {
3333             for (template_sym, template_snippet, template_span) in template_strs.iter() {
3334                 let template_str = template_sym.as_str();
3335                 let find_label_span = |needle: &str| -> Option<Span> {
3336                     if let Some(template_snippet) = template_snippet {
3337                         let snippet = template_snippet.as_str();
3338                         if let Some(pos) = snippet.find(needle) {
3339                             let end = pos
3340                                 + snippet[pos..]
3341                                     .find(|c| c == ':')
3342                                     .unwrap_or(snippet[pos..].len() - 1);
3343                             let inner = InnerSpan::new(pos, end);
3344                             return Some(template_span.from_inner(inner));
3345                         }
3346                     }
3347
3348                     None
3349                 };
3350
3351                 let mut found_labels = Vec::new();
3352
3353                 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3354                 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3355                 for statement in statements {
3356                     // If there's a comment, trim it from the statement
3357                     let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3358                     let mut start_idx = 0;
3359                     for (idx, _) in statement.match_indices(':') {
3360                         let possible_label = statement[start_idx..idx].trim();
3361                         let mut chars = possible_label.chars();
3362                         let Some(c) = chars.next() else {
3363                             // Empty string means a leading ':' in this section, which is not a label
3364                             break
3365                         };
3366                         // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3367                         if (c.is_alphabetic() || matches!(c, '.' | '_'))
3368                             && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3369                         {
3370                             found_labels.push(possible_label);
3371                         } else {
3372                             // If we encounter a non-label, there cannot be any further labels, so stop checking
3373                             break;
3374                         }
3375
3376                         start_idx = idx + 1;
3377                     }
3378                 }
3379
3380                 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3381
3382                 if found_labels.len() > 0 {
3383                     let spans = found_labels
3384                         .into_iter()
3385                         .filter_map(|label| find_label_span(label))
3386                         .collect::<Vec<Span>>();
3387                     // If there were labels but we couldn't find a span, combine the warnings and use the template span
3388                     let target_spans: MultiSpan =
3389                         if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3390
3391                     cx.lookup_with_diagnostics(
3392                             NAMED_ASM_LABELS,
3393                             Some(target_spans),
3394                             fluent::lint_builtin_asm_labels,
3395                             |lint| lint,
3396                             BuiltinLintDiagnostics::NamedAsmLabel(
3397                                 "only local labels of the form `<number>:` should be used in inline asm"
3398                                     .to_string(),
3399                             ),
3400                         );
3401                 }
3402             }
3403         }
3404     }
3405 }
3406
3407 declare_lint! {
3408     /// The `special_module_name` lint detects module
3409     /// declarations for files that have a special meaning.
3410     ///
3411     /// ### Example
3412     ///
3413     /// ```rust,compile_fail
3414     /// mod lib;
3415     ///
3416     /// fn main() {
3417     ///     lib::run();
3418     /// }
3419     /// ```
3420     ///
3421     /// {{produces}}
3422     ///
3423     /// ### Explanation
3424     ///
3425     /// Cargo recognizes `lib.rs` and `main.rs` as the root of a
3426     /// library or binary crate, so declaring them as modules
3427     /// will lead to miscompilation of the crate unless configured
3428     /// explicitly.
3429     ///
3430     /// To access a library from a binary target within the same crate,
3431     /// use `your_crate_name::` as the path instead of `lib::`:
3432     ///
3433     /// ```rust,compile_fail
3434     /// // bar/src/lib.rs
3435     /// fn run() {
3436     ///     // ...
3437     /// }
3438     ///
3439     /// // bar/src/main.rs
3440     /// fn main() {
3441     ///     bar::run();
3442     /// }
3443     /// ```
3444     ///
3445     /// Binary targets cannot be used as libraries and so declaring
3446     /// one as a module is not allowed.
3447     pub SPECIAL_MODULE_NAME,
3448     Warn,
3449     "module declarations for files with a special meaning",
3450 }
3451
3452 declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
3453
3454 impl EarlyLintPass for SpecialModuleName {
3455     fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
3456         for item in &krate.items {
3457             if let ast::ItemKind::Mod(
3458                 _,
3459                 ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _),
3460             ) = item.kind
3461             {
3462                 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
3463                     continue;
3464                 }
3465
3466                 match item.ident.name.as_str() {
3467                     "lib" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for lib.rs", |lint| {
3468                         lint
3469                             .note("lib.rs is the root of this crate's library target")
3470                             .help("to refer to it from other targets, use the library's name as the path")
3471                     }),
3472                     "main" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for main.rs", |lint| {
3473                         lint
3474                             .note("a binary crate cannot be used as library")
3475                     }),
3476                     _ => continue
3477                 }
3478             }
3479         }
3480     }
3481 }
3482
3483 pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
3484
3485 declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
3486
3487 impl EarlyLintPass for UnexpectedCfgs {
3488     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
3489         let cfg = &cx.sess().parse_sess.config;
3490         let check_cfg = &cx.sess().parse_sess.check_config;
3491         for &(name, value) in cfg {
3492             if let Some(names_valid) = &check_cfg.names_valid {
3493                 if !names_valid.contains(&name) {
3494                     cx.lookup(
3495                         UNEXPECTED_CFGS,
3496                         None::<MultiSpan>,
3497                         fluent::lint_builtin_unexpected_cli_config_name,
3498                         |diag| diag.help(fluent::help).set_arg("name", name),
3499                     );
3500                 }
3501             }
3502             if let Some(value) = value {
3503                 if let Some(values) = &check_cfg.values_valid.get(&name) {
3504                     if !values.contains(&value) {
3505                         cx.lookup(
3506                             UNEXPECTED_CFGS,
3507                             None::<MultiSpan>,
3508                             fluent::lint_builtin_unexpected_cli_config_value,
3509                             |diag| {
3510                                 diag.help(fluent::help)
3511                                     .set_arg("name", name)
3512                                     .set_arg("value", value)
3513                             },
3514                         );
3515                     }
3516                 }
3517             }
3518         }
3519     }
3520 }