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     types::{transparent_newtype_field, CItemKind},
  25     EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
  26 };
  27 use rustc_ast::attr;
  28 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  29 use rustc_ast::visit::{FnCtxt, FnKind};
  30 use rustc_ast::{self as ast, *};
  31 use rustc_ast_pretty::pprust::{self, expr_to_string};
  32 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  33 use rustc_data_structures::stack::ensure_sufficient_stack;
  34 use rustc_errors::{
  35     fluent, Applicability, Diagnostic, DiagnosticMessage, DiagnosticStyledString,
  36     LintDiagnosticBuilder, MultiSpan,
  37 };
  38 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
  39 use rustc_hir as hir;
  40 use rustc_hir::def::{DefKind, Res};
  41 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
  42 use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, PatKind, PredicateOrigin};
  43 use rustc_index::vec::Idx;
  44 use rustc_middle::lint::in_external_macro;
  45 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
  46 use rustc_middle::ty::print::with_no_trimmed_paths;
  47 use rustc_middle::ty::subst::GenericArgKind;
  48 use rustc_middle::ty::Instance;
  49 use rustc_middle::ty::{self, Ty, TyCtxt};
  50 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
  51 use rustc_span::edition::Edition;
  52 use rustc_span::source_map::Spanned;
  53 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  54 use rustc_span::{BytePos, InnerSpan, Span};
  55 use rustc_target::abi::VariantIdx;
  56 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
  57
  58 use crate::nonstandard_style::{method_context, MethodLateContext};
  59
  60 use std::fmt::Write;
  61 use tracing::{debug, trace};
  62
  63 // hardwired lints from librustc_middle
  64 pub use rustc_session::lint::builtin::*;
  65
  66 declare_lint! {
  67     /// The `while_true` lint detects `while true { }`.
  68     ///
  69     /// ### Example
  70     ///
  71     /// ```rust,no_run
  72     /// while true {
  73     ///
  74     /// }
  75     /// ```
  76     ///
  77     /// {{produces}}
  78     ///
  79     /// ### Explanation
  80     ///
  81     /// `while true` should be replaced with `loop`. A `loop` expression is
  82     /// the preferred way to write an infinite loop because it more directly
  83     /// expresses the intent of the loop.
  84     WHILE_TRUE,
  85     Warn,
  86     "suggest using `loop { }` instead of `while true { }`"
  87 }
  88
  89 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  90
  91 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  92 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  93     while let ast::ExprKind::Paren(sub) = &expr.kind {
  94         expr = sub;
  95     }
  96     expr
  97 }
  98
  99 impl EarlyLintPass for WhileTrue {
 100     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 101         if let ast::ExprKind::While(cond, _, label) = &e.kind {
 102             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
 103                 if let ast::LitKind::Bool(true) = lit.kind {
 104                     if !lit.span.from_expansion() {
 105                         let condition_span = e.span.with_hi(cond.span.hi());
 106                         cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
 107                             lint.build(fluent::lint::builtin_while_true)
 108                                 .span_suggestion_short(
 109                                     condition_span,
 110                                     fluent::lint::suggestion,
 111                                     format!(
 112                                         "{}loop",
 113                                         label.map_or_else(String::new, |label| format!(
 114                                             "{}: ",
 115                                             label.ident,
 116                                         ))
 117                                     ),
 118                                     Applicability::MachineApplicable,
 119                                 )
 120                                 .emit();
 121                         })
 122                     }
 123                 }
 124             }
 125         }
 126     }
 127 }
 128
 129 declare_lint! {
 130     /// The `box_pointers` lints use of the Box type.
 131     ///
 132     /// ### Example
 133     ///
 134     /// ```rust,compile_fail
 135     /// #![deny(box_pointers)]
 136     /// struct Foo {
 137     ///     x: Box<isize>,
 138     /// }
 139     /// ```
 140     ///
 141     /// {{produces}}
 142     ///
 143     /// ### Explanation
 144     ///
 145     /// This lint is mostly historical, and not particularly useful. `Box<T>`
 146     /// used to be built into the language, and the only way to do heap
 147     /// allocation. Today's Rust can call into other allocators, etc.
 148     BOX_POINTERS,
 149     Allow,
 150     "use of owned (Box type) heap memory"
 151 }
 152
 153 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 154
 155 impl BoxPointers {
 156     fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
 157         for leaf in ty.walk() {
 158             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
 159                 if leaf_ty.is_box() {
 160                     cx.struct_span_lint(BOX_POINTERS, span, |lint| {
 161                         lint.build(fluent::lint::builtin_box_pointers).set_arg("ty", ty).emit();
 162                     });
 163                 }
 164             }
 165         }
 166     }
 167 }
 168
 169 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
 170     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 171         match it.kind {
 172             hir::ItemKind::Fn(..)
 173             | hir::ItemKind::TyAlias(..)
 174             | hir::ItemKind::Enum(..)
 175             | hir::ItemKind::Struct(..)
 176             | hir::ItemKind::Union(..) => {
 177                 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
 178             }
 179             _ => (),
 180         }
 181
 182         // If it's a struct, we also have to check the fields' types
 183         match it.kind {
 184             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 185                 for struct_field in struct_def.fields() {
 186                     let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
 187                     self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
 188                 }
 189             }
 190             _ => (),
 191         }
 192     }
 193
 194     fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
 195         let ty = cx.typeck_results().node_type(e.hir_id);
 196         self.check_heap_type(cx, e.span, ty);
 197     }
 198 }
 199
 200 declare_lint! {
 201     /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
 202     /// instead of `Struct { x }` in a pattern.
 203     ///
 204     /// ### Example
 205     ///
 206     /// ```rust
 207     /// struct Point {
 208     ///     x: i32,
 209     ///     y: i32,
 210     /// }
 211     ///
 212     ///
 213     /// fn main() {
 214     ///     let p = Point {
 215     ///         x: 5,
 216     ///         y: 5,
 217     ///     };
 218     ///
 219     ///     match p {
 220     ///         Point { x: x, y: y } => (),
 221     ///     }
 222     /// }
 223     /// ```
 224     ///
 225     /// {{produces}}
 226     ///
 227     /// ### Explanation
 228     ///
 229     /// The preferred style is to avoid the repetition of specifying both the
 230     /// field name and the binding name if both identifiers are the same.
 231     NON_SHORTHAND_FIELD_PATTERNS,
 232     Warn,
 233     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 234 }
 235
 236 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 237
 238 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
 239     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
 240         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 241             let variant = cx
 242                 .typeck_results()
 243                 .pat_ty(pat)
 244                 .ty_adt_def()
 245                 .expect("struct pattern type is not an ADT")
 246                 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
 247             for fieldpat in field_pats {
 248                 if fieldpat.is_shorthand {
 249                     continue;
 250                 }
 251                 if fieldpat.span.from_expansion() {
 252                     // Don't lint if this is a macro expansion: macro authors
 253                     // shouldn't have to worry about this kind of style issue
 254                     // (Issue #49588)
 255                     continue;
 256                 }
 257                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 258                     if cx.tcx.find_field_index(ident, &variant)
 259                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
 260                     {
 261                         cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
 262                             let binding = match binding_annot {
 263                                 hir::BindingAnnotation::Unannotated => None,
 264                                 hir::BindingAnnotation::Mutable => Some("mut"),
 265                                 hir::BindingAnnotation::Ref => Some("ref"),
 266                                 hir::BindingAnnotation::RefMut => Some("ref mut"),
 267                             };
 268                             let suggested_ident = if let Some(binding) = binding {
 269                                 format!("{} {}", binding, ident)
 270                             } else {
 271                                 ident.to_string()
 272                             };
 273                             lint.build(fluent::lint::builtin_non_shorthand_field_patterns)
 274                                 .set_arg("ident", ident.clone())
 275                                 .span_suggestion(
 276                                     fieldpat.span,
 277                                     fluent::lint::suggestion,
 278                                     suggested_ident,
 279                                     Applicability::MachineApplicable,
 280                                 )
 281                                 .emit();
 282                         });
 283                     }
 284                 }
 285             }
 286         }
 287     }
 288 }
 289
 290 declare_lint! {
 291     /// The `unsafe_code` lint catches usage of `unsafe` code.
 292     ///
 293     /// ### Example
 294     ///
 295     /// ```rust,compile_fail
 296     /// #![deny(unsafe_code)]
 297     /// fn main() {
 298     ///     unsafe {
 299     ///
 300     ///     }
 301     /// }
 302     /// ```
 303     ///
 304     /// {{produces}}
 305     ///
 306     /// ### Explanation
 307     ///
 308     /// This lint is intended to restrict the usage of `unsafe`, which can be
 309     /// difficult to use correctly.
 310     UNSAFE_CODE,
 311     Allow,
 312     "usage of `unsafe` code"
 313 }
 314
 315 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 316
 317 impl UnsafeCode {
 318     fn report_unsafe(
 319         &self,
 320         cx: &EarlyContext<'_>,
 321         span: Span,
 322         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 323     ) {
 324         // This comes from a macro that has `#[allow_internal_unsafe]`.
 325         if span.allows_unsafe() {
 326             return;
 327         }
 328
 329         cx.struct_span_lint(UNSAFE_CODE, span, decorate);
 330     }
 331
 332     fn report_overridden_symbol_name(
 333         &self,
 334         cx: &EarlyContext<'_>,
 335         span: Span,
 336         msg: DiagnosticMessage,
 337     ) {
 338         self.report_unsafe(cx, span, |lint| {
 339             lint.build(msg).note(fluent::lint::builtin_overridden_symbol_name).emit();
 340         })
 341     }
 342
 343     fn report_overridden_symbol_section(
 344         &self,
 345         cx: &EarlyContext<'_>,
 346         span: Span,
 347         msg: DiagnosticMessage,
 348     ) {
 349         self.report_unsafe(cx, span, |lint| {
 350             lint.build(msg).note(fluent::lint::builtin_overridden_symbol_section).emit();
 351         })
 352     }
 353 }
 354
 355 impl EarlyLintPass for UnsafeCode {
 356     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 357         if attr.has_name(sym::allow_internal_unsafe) {
 358             self.report_unsafe(cx, attr.span, |lint| {
 359                 lint.build(fluent::lint::builtin_allow_internal_unsafe).emit();
 360             });
 361         }
 362     }
 363
 364     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 365         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 366             // Don't warn about generated blocks; that'll just pollute the output.
 367             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 368                 self.report_unsafe(cx, blk.span, |lint| {
 369                     lint.build(fluent::lint::builtin_unsafe_block).emit();
 370                 });
 371             }
 372         }
 373     }
 374
 375     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 376         match it.kind {
 377             ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => self
 378                 .report_unsafe(cx, it.span, |lint| {
 379                     lint.build(fluent::lint::builtin_unsafe_trait).emit();
 380                 }),
 381
 382             ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => self
 383                 .report_unsafe(cx, it.span, |lint| {
 384                     lint.build(fluent::lint::builtin_unsafe_impl).emit();
 385                 }),
 386
 387             ast::ItemKind::Fn(..) => {
 388                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 389                     self.report_overridden_symbol_name(
 390                         cx,
 391                         attr.span,
 392                         fluent::lint::builtin_no_mangle_fn,
 393                     );
 394                 }
 395
 396                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 397                     self.report_overridden_symbol_name(
 398                         cx,
 399                         attr.span,
 400                         fluent::lint::builtin_export_name_fn,
 401                     );
 402                 }
 403
 404                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
 405                     self.report_overridden_symbol_section(
 406                         cx,
 407                         attr.span,
 408                         fluent::lint::builtin_link_section_fn,
 409                     );
 410                 }
 411             }
 412
 413             ast::ItemKind::Static(..) => {
 414                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 415                     self.report_overridden_symbol_name(
 416                         cx,
 417                         attr.span,
 418                         fluent::lint::builtin_no_mangle_static,
 419                     );
 420                 }
 421
 422                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 423                     self.report_overridden_symbol_name(
 424                         cx,
 425                         attr.span,
 426                         fluent::lint::builtin_export_name_static,
 427                     );
 428                 }
 429
 430                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
 431                     self.report_overridden_symbol_section(
 432                         cx,
 433                         attr.span,
 434                         fluent::lint::builtin_link_section_static,
 435                     );
 436                 }
 437             }
 438
 439             _ => {}
 440         }
 441     }
 442
 443     fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 444         if let ast::AssocItemKind::Fn(..) = it.kind {
 445             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 446                 self.report_overridden_symbol_name(
 447                     cx,
 448                     attr.span,
 449                     fluent::lint::builtin_no_mangle_method,
 450                 );
 451             }
 452             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 453                 self.report_overridden_symbol_name(
 454                     cx,
 455                     attr.span,
 456                     fluent::lint::builtin_export_name_method,
 457                 );
 458             }
 459         }
 460     }
 461
 462     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
 463         if let FnKind::Fn(
 464             ctxt,
 465             _,
 466             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
 467             _,
 468             _,
 469             body,
 470         ) = fk
 471         {
 472             let msg = match ctxt {
 473                 FnCtxt::Foreign => return,
 474                 FnCtxt::Free => fluent::lint::builtin_decl_unsafe_fn,
 475                 FnCtxt::Assoc(_) if body.is_none() => fluent::lint::builtin_decl_unsafe_method,
 476                 FnCtxt::Assoc(_) => fluent::lint::builtin_impl_unsafe_method,
 477             };
 478             self.report_unsafe(cx, span, |lint| {
 479                 lint.build(msg).emit();
 480             });
 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.access_levels.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(MISSING_DOCS, cx.tcx.def_span(def_id), |lint| {
 582                 lint.build(fluent::lint::builtin_missing_doc)
 583                     .set_arg("article", article)
 584                     .set_arg("desc", desc)
 585                     .emit();
 586             });
 587         }
 588     }
 589 }
 590
 591 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 592     fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
 593         let doc_hidden = self.doc_hidden()
 594             || attrs.iter().any(|attr| {
 595                 attr.has_name(sym::doc)
 596                     && match attr.meta_item_list() {
 597                         None => false,
 598                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 599                     }
 600             });
 601         self.doc_hidden_stack.push(doc_hidden);
 602     }
 603
 604     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
 605         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 606     }
 607
 608     fn check_crate(&mut self, cx: &LateContext<'_>) {
 609         self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
 610     }
 611
 612     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 613         match it.kind {
 614             hir::ItemKind::Trait(..) => {
 615                 // Issue #11592: traits are always considered exported, even when private.
 616                 if cx.tcx.visibility(it.def_id)
 617                     == ty::Visibility::Restricted(
 618                         cx.tcx.parent_module_from_def_id(it.def_id).to_def_id(),
 619                     )
 620                 {
 621                     return;
 622                 }
 623             }
 624             hir::ItemKind::TyAlias(..)
 625             | hir::ItemKind::Fn(..)
 626             | hir::ItemKind::Macro(..)
 627             | hir::ItemKind::Mod(..)
 628             | hir::ItemKind::Enum(..)
 629             | hir::ItemKind::Struct(..)
 630             | hir::ItemKind::Union(..)
 631             | hir::ItemKind::Const(..)
 632             | hir::ItemKind::Static(..) => {}
 633
 634             _ => return,
 635         };
 636
 637         let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
 638
 639         self.check_missing_docs_attrs(cx, it.def_id, article, desc);
 640     }
 641
 642     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
 643         let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
 644
 645         self.check_missing_docs_attrs(cx, trait_item.def_id, article, desc);
 646     }
 647
 648     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
 649         // If the method is an impl for a trait, don't doc.
 650         if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
 651             return;
 652         }
 653
 654         // If the method is an impl for an item with docs_hidden, don't doc.
 655         if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
 656             let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
 657             let impl_ty = cx.tcx.type_of(parent);
 658             let outerdef = match impl_ty.kind() {
 659                 ty::Adt(def, _) => Some(def.did()),
 660                 ty::Foreign(def_id) => Some(*def_id),
 661                 _ => None,
 662             };
 663             let is_hidden = match outerdef {
 664                 Some(id) => cx.tcx.is_doc_hidden(id),
 665                 None => false,
 666             };
 667             if is_hidden {
 668                 return;
 669             }
 670         }
 671
 672         let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
 673         self.check_missing_docs_attrs(cx, impl_item.def_id, article, desc);
 674     }
 675
 676     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
 677         let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
 678         self.check_missing_docs_attrs(cx, foreign_item.def_id, article, desc);
 679     }
 680
 681     fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
 682         if !sf.is_positional() {
 683             let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
 684             self.check_missing_docs_attrs(cx, 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, cx.tcx.hir().local_def_id(v.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.access_levels.is_reachable(item.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.def_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.def_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.def_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         let param_env = ty::ParamEnv::empty();
 762         if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
 763             return;
 764         }
 765         if can_type_implement_copy(
 766             cx.tcx,
 767             param_env,
 768             ty,
 769             traits::ObligationCause::misc(item.span, item.hir_id()),
 770         )
 771         .is_ok()
 772         {
 773             cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
 774                 lint.build(fluent::lint::builtin_missing_copy_impl).emit();
 775             })
 776         }
 777     }
 778 }
 779
 780 declare_lint! {
 781     /// The `missing_debug_implementations` lint detects missing
 782     /// implementations of [`fmt::Debug`].
 783     ///
 784     /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
 785     ///
 786     /// ### Example
 787     ///
 788     /// ```rust,compile_fail
 789     /// #![deny(missing_debug_implementations)]
 790     /// pub struct Foo;
 791     /// # fn main() {}
 792     /// ```
 793     ///
 794     /// {{produces}}
 795     ///
 796     /// ### Explanation
 797     ///
 798     /// Having a `Debug` implementation on all types can assist with
 799     /// debugging, as it provides a convenient way to format and display a
 800     /// value. Using the `#[derive(Debug)]` attribute will automatically
 801     /// generate a typical implementation, or a custom implementation can be
 802     /// added by manually implementing the `Debug` trait.
 803     ///
 804     /// This lint is "allow" by default because adding `Debug` to all types can
 805     /// have a negative impact on compile time and code size. It also requires
 806     /// boilerplate to be added to every type, which can be an impediment.
 807     MISSING_DEBUG_IMPLEMENTATIONS,
 808     Allow,
 809     "detects missing implementations of Debug"
 810 }
 811
 812 #[derive(Default)]
 813 pub struct MissingDebugImplementations {
 814     impling_types: Option<LocalDefIdSet>,
 815 }
 816
 817 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 818
 819 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 820     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 821         if !cx.access_levels.is_reachable(item.def_id) {
 822             return;
 823         }
 824
 825         match item.kind {
 826             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 827             _ => return,
 828         }
 829
 830         let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
 831             return
 832         };
 833
 834         if self.impling_types.is_none() {
 835             let mut impls = LocalDefIdSet::default();
 836             cx.tcx.for_each_impl(debug, |d| {
 837                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 838                     if let Some(def_id) = ty_def.did().as_local() {
 839                         impls.insert(def_id);
 840                     }
 841                 }
 842             });
 843
 844             self.impling_types = Some(impls);
 845             debug!("{:?}", self.impling_types);
 846         }
 847
 848         if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
 849             cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
 850                 lint.build(fluent::lint::builtin_missing_debug_impl)
 851                     .set_arg("debug", cx.tcx.def_path_str(debug))
 852                     .emit();
 853             });
 854         }
 855     }
 856 }
 857
 858 declare_lint! {
 859     /// The `anonymous_parameters` lint detects anonymous parameters in trait
 860     /// definitions.
 861     ///
 862     /// ### Example
 863     ///
 864     /// ```rust,edition2015,compile_fail
 865     /// #![deny(anonymous_parameters)]
 866     /// // edition 2015
 867     /// pub trait Foo {
 868     ///     fn foo(usize);
 869     /// }
 870     /// fn main() {}
 871     /// ```
 872     ///
 873     /// {{produces}}
 874     ///
 875     /// ### Explanation
 876     ///
 877     /// This syntax is mostly a historical accident, and can be worked around
 878     /// quite easily by adding an `_` pattern or a descriptive identifier:
 879     ///
 880     /// ```rust
 881     /// trait Foo {
 882     ///     fn foo(_: usize);
 883     /// }
 884     /// ```
 885     ///
 886     /// This syntax is now a hard error in the 2018 edition. In the 2015
 887     /// edition, this lint is "warn" by default. This lint
 888     /// enables the [`cargo fix`] tool with the `--edition` flag to
 889     /// automatically transition old code from the 2015 edition to 2018. The
 890     /// tool will run this lint and automatically apply the
 891     /// suggested fix from the compiler (which is to add `_` to each
 892     /// parameter). This provides a completely automated way to update old
 893     /// code for a new edition. See [issue #41686] for more details.
 894     ///
 895     /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
 896     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
 897     pub ANONYMOUS_PARAMETERS,
 898     Warn,
 899     "detects anonymous parameters",
 900     @future_incompatible = FutureIncompatibleInfo {
 901         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 902         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
 903     };
 904 }
 905
 906 declare_lint_pass!(
 907     /// Checks for use of anonymous parameters (RFC 1685).
 908     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 909 );
 910
 911 impl EarlyLintPass for AnonymousParameters {
 912     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 913         if cx.sess().edition() != Edition::Edition2015 {
 914             // This is a hard error in future editions; avoid linting and erroring
 915             return;
 916         }
 917         if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
 918             for arg in sig.decl.inputs.iter() {
 919                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 920                     if ident.name == kw::Empty {
 921                         cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
 922                             let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
 923
 924                             let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 925                                 (snip.as_str(), Applicability::MachineApplicable)
 926                             } else {
 927                                 ("<type>", Applicability::HasPlaceholders)
 928                             };
 929
 930                             lint.build(fluent::lint::builtin_anonymous_params)
 931                                 .span_suggestion(
 932                                     arg.pat.span,
 933                                     fluent::lint::suggestion,
 934                                     format!("_: {}", ty_snip),
 935                                     appl,
 936                                 )
 937                                 .emit();
 938                         })
 939                     }
 940                 }
 941             }
 942         }
 943     }
 944 }
 945
 946 /// Check for use of attributes which have been deprecated.
 947 #[derive(Clone)]
 948 pub struct DeprecatedAttr {
 949     // This is not free to compute, so we want to keep it around, rather than
 950     // compute it for every attribute.
 951     depr_attrs: Vec<&'static BuiltinAttribute>,
 952 }
 953
 954 impl_lint_pass!(DeprecatedAttr => []);
 955
 956 impl DeprecatedAttr {
 957     pub fn new() -> DeprecatedAttr {
 958         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 959     }
 960 }
 961
 962 impl EarlyLintPass for DeprecatedAttr {
 963     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 964         for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
 965             if attr.ident().map(|ident| ident.name) == Some(*name) {
 966                 if let &AttributeGate::Gated(
 967                     Stability::Deprecated(link, suggestion),
 968                     name,
 969                     reason,
 970                     _,
 971                 ) = gate
 972                 {
 973                     cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
 974                         // FIXME(davidtwco) translatable deprecated attr
 975                         lint.build(fluent::lint::builtin_deprecated_attr_link)
 976                             .set_arg("name", name)
 977                             .set_arg("reason", reason)
 978                             .set_arg("link", link)
 979                             .span_suggestion_short(
 980                                 attr.span,
 981                                 suggestion.map(|s| s.into()).unwrap_or(
 982                                     fluent::lint::builtin_deprecated_attr_default_suggestion,
 983                                 ),
 984                                 "",
 985                                 Applicability::MachineApplicable,
 986                             )
 987                             .emit();
 988                     });
 989                 }
 990                 return;
 991             }
 992         }
 993         if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
 994             cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
 995                 lint.build(fluent::lint::builtin_deprecated_attr_used)
 996                     .set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
 997                     .span_suggestion_short(
 998                         attr.span,
 999                         fluent::lint::builtin_deprecated_attr_default_suggestion,
1000                         "",
1001                         Applicability::MachineApplicable,
1002                     )
1003                     .emit();
1004             });
1005         }
1006     }
1007 }
1008
1009 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1010     use rustc_ast::token::CommentKind;
1011
1012     let mut attrs = attrs.iter().peekable();
1013
1014     // Accumulate a single span for sugared doc comments.
1015     let mut sugared_span: Option<Span> = None;
1016
1017     while let Some(attr) = attrs.next() {
1018         let is_doc_comment = attr.is_doc_comment();
1019         if is_doc_comment {
1020             sugared_span =
1021                 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1022         }
1023
1024         if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1025             continue;
1026         }
1027
1028         let span = sugared_span.take().unwrap_or(attr.span);
1029
1030         if is_doc_comment || attr.has_name(sym::doc) {
1031             cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1032                 let mut err = lint.build(fluent::lint::builtin_unused_doc_comment);
1033                 err.set_arg("kind", node_kind);
1034                 err.span_label(node_span, fluent::lint::label);
1035                 match attr.kind {
1036                     AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1037                         err.help(fluent::lint::plain_help);
1038                     }
1039                     AttrKind::DocComment(CommentKind::Block, _) => {
1040                         err.help(fluent::lint::block_help);
1041                     }
1042                 }
1043                 err.emit();
1044             });
1045         }
1046     }
1047 }
1048
1049 impl EarlyLintPass for UnusedDocComment {
1050     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1051         let kind = match stmt.kind {
1052             ast::StmtKind::Local(..) => "statements",
1053             // Disabled pending discussion in #78306
1054             ast::StmtKind::Item(..) => return,
1055             // expressions will be reported by `check_expr`.
1056             ast::StmtKind::Empty
1057             | ast::StmtKind::Semi(_)
1058             | ast::StmtKind::Expr(_)
1059             | ast::StmtKind::MacCall(_) => return,
1060         };
1061
1062         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1063     }
1064
1065     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1066         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1067         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1068     }
1069
1070     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1071         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1072     }
1073
1074     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1075         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
1076     }
1077
1078     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1079         warn_if_doc(cx, block.span, "blocks", &block.attrs());
1080     }
1081
1082     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1083         if let ast::ItemKind::ForeignMod(_) = item.kind {
1084             warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1085         }
1086     }
1087 }
1088
1089 declare_lint! {
1090     /// The `no_mangle_const_items` lint detects any `const` items with the
1091     /// [`no_mangle` attribute].
1092     ///
1093     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1094     ///
1095     /// ### Example
1096     ///
1097     /// ```rust,compile_fail
1098     /// #[no_mangle]
1099     /// const FOO: i32 = 5;
1100     /// ```
1101     ///
1102     /// {{produces}}
1103     ///
1104     /// ### Explanation
1105     ///
1106     /// Constants do not have their symbols exported, and therefore, this
1107     /// probably means you meant to use a [`static`], not a [`const`].
1108     ///
1109     /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1110     /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1111     NO_MANGLE_CONST_ITEMS,
1112     Deny,
1113     "const items will not have their symbols exported"
1114 }
1115
1116 declare_lint! {
1117     /// The `no_mangle_generic_items` lint detects generic items that must be
1118     /// mangled.
1119     ///
1120     /// ### Example
1121     ///
1122     /// ```rust
1123     /// #[no_mangle]
1124     /// fn foo<T>(t: T) {
1125     ///
1126     /// }
1127     /// ```
1128     ///
1129     /// {{produces}}
1130     ///
1131     /// ### Explanation
1132     ///
1133     /// A function with generics must have its symbol mangled to accommodate
1134     /// the generic parameter. The [`no_mangle` attribute] has no effect in
1135     /// this situation, and should be removed.
1136     ///
1137     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1138     NO_MANGLE_GENERIC_ITEMS,
1139     Warn,
1140     "generic items must be mangled"
1141 }
1142
1143 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1144
1145 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1146     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1147         let attrs = cx.tcx.hir().attrs(it.hir_id());
1148         let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1149                                              impl_generics: Option<&hir::Generics<'_>>,
1150                                              generics: &hir::Generics<'_>,
1151                                              span| {
1152             for param in
1153                 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1154             {
1155                 match param.kind {
1156                     GenericParamKind::Lifetime { .. } => {}
1157                     GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1158                         cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1159                             lint.build(fluent::lint::builtin_no_mangle_generic)
1160                                 .span_suggestion_short(
1161                                     no_mangle_attr.span,
1162                                     fluent::lint::suggestion,
1163                                     "",
1164                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1165                                     // fix may be to monomorphize source by hand
1166                                     Applicability::MaybeIncorrect,
1167                                 )
1168                                 .emit();
1169                         });
1170                         break;
1171                     }
1172                 }
1173             }
1174         };
1175         match it.kind {
1176             hir::ItemKind::Fn(.., ref generics, _) => {
1177                 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1178                     check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1179                 }
1180             }
1181             hir::ItemKind::Const(..) => {
1182                 if cx.sess().contains_name(attrs, sym::no_mangle) {
1183                     // Const items do not refer to a particular location in memory, and therefore
1184                     // don't have anything to attach a symbol to
1185                     cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1186                         let mut err = lint.build(fluent::lint::builtin_const_no_mangle);
1187
1188                         // account for "pub const" (#45562)
1189                         let start = cx
1190                             .tcx
1191                             .sess
1192                             .source_map()
1193                             .span_to_snippet(it.span)
1194                             .map(|snippet| snippet.find("const").unwrap_or(0))
1195                             .unwrap_or(0) as u32;
1196                         // `const` is 5 chars
1197                         let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1198                         err.span_suggestion(
1199                             const_span,
1200                             fluent::lint::suggestion,
1201                             "pub static",
1202                             Applicability::MachineApplicable,
1203                         );
1204                         err.emit();
1205                     });
1206                 }
1207             }
1208             hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1209                 for it in *items {
1210                     if let hir::AssocItemKind::Fn { .. } = it.kind {
1211                         if let Some(no_mangle_attr) = cx
1212                             .sess()
1213                             .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1214                         {
1215                             check_no_mangle_on_generic_fn(
1216                                 no_mangle_attr,
1217                                 Some(generics),
1218                                 cx.tcx.hir().get_generics(it.id.def_id).unwrap(),
1219                                 it.span,
1220                             );
1221                         }
1222                     }
1223                 }
1224             }
1225             _ => {}
1226         }
1227     }
1228 }
1229
1230 declare_lint! {
1231     /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1232     /// T` because it is [undefined behavior].
1233     ///
1234     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1235     ///
1236     /// ### Example
1237     ///
1238     /// ```rust,compile_fail
1239     /// unsafe {
1240     ///     let y = std::mem::transmute::<&i32, &mut i32>(&5);
1241     /// }
1242     /// ```
1243     ///
1244     /// {{produces}}
1245     ///
1246     /// ### Explanation
1247     ///
1248     /// Certain assumptions are made about aliasing of data, and this transmute
1249     /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1250     ///
1251     /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1252     MUTABLE_TRANSMUTES,
1253     Deny,
1254     "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1255 }
1256
1257 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1258
1259 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1260     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1261         if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1262             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1263         {
1264             if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1265                 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
1266                     lint.build(fluent::lint::builtin_mutable_transmutes).emit();
1267                 });
1268             }
1269         }
1270
1271         fn get_transmute_from_to<'tcx>(
1272             cx: &LateContext<'tcx>,
1273             expr: &hir::Expr<'_>,
1274         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1275             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1276                 cx.qpath_res(qpath, expr.hir_id)
1277             } else {
1278                 return None;
1279             };
1280             if let Res::Def(DefKind::Fn, did) = def {
1281                 if !def_id_is_transmute(cx, did) {
1282                     return None;
1283                 }
1284                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1285                 let from = sig.inputs().skip_binder()[0];
1286                 let to = sig.output().skip_binder();
1287                 return Some((from, to));
1288             }
1289             None
1290         }
1291
1292         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1293             cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1294         }
1295     }
1296 }
1297
1298 declare_lint! {
1299     /// The `unstable_features` is deprecated and should no longer be used.
1300     UNSTABLE_FEATURES,
1301     Allow,
1302     "enabling unstable features (deprecated. do not use)"
1303 }
1304
1305 declare_lint_pass!(
1306     /// Forbids using the `#[feature(...)]` attribute
1307     UnstableFeatures => [UNSTABLE_FEATURES]
1308 );
1309
1310 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1311     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1312         if attr.has_name(sym::feature) {
1313             if let Some(items) = attr.meta_item_list() {
1314                 for item in items {
1315                     cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1316                         lint.build(fluent::lint::builtin_unstable_features).emit();
1317                     });
1318                 }
1319             }
1320         }
1321     }
1322 }
1323
1324 declare_lint! {
1325     /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1326     /// the crate root.
1327     ///
1328     /// ### Example
1329     ///
1330     /// ```rust,compile_fail
1331     /// #![deny(unreachable_pub)]
1332     /// mod foo {
1333     ///     pub mod bar {
1334     ///
1335     ///     }
1336     /// }
1337     /// ```
1338     ///
1339     /// {{produces}}
1340     ///
1341     /// ### Explanation
1342     ///
1343     /// A bare `pub` visibility may be misleading if the item is not actually
1344     /// publicly exported from the crate. The `pub(crate)` visibility is
1345     /// recommended to be used instead, which more clearly expresses the intent
1346     /// that the item is only visible within its own crate.
1347     ///
1348     /// This lint is "allow" by default because it will trigger for a large
1349     /// amount existing Rust code, and has some false-positives. Eventually it
1350     /// is desired for this to become warn-by-default.
1351     pub UNREACHABLE_PUB,
1352     Allow,
1353     "`pub` items not reachable from crate root"
1354 }
1355
1356 declare_lint_pass!(
1357     /// Lint for items marked `pub` that aren't reachable from other crates.
1358     UnreachablePub => [UNREACHABLE_PUB]
1359 );
1360
1361 impl UnreachablePub {
1362     fn perform_lint(
1363         &self,
1364         cx: &LateContext<'_>,
1365         what: &str,
1366         def_id: LocalDefId,
1367         vis_span: Span,
1368         exportable: bool,
1369     ) {
1370         let mut applicability = Applicability::MachineApplicable;
1371         if cx.tcx.visibility(def_id).is_public() && !cx.access_levels.is_reachable(def_id) {
1372             if vis_span.from_expansion() {
1373                 applicability = Applicability::MaybeIncorrect;
1374             }
1375             let def_span = cx.tcx.def_span(def_id);
1376             cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1377                 let mut err = lint.build(fluent::lint::builtin_unreachable_pub);
1378                 err.set_arg("what", what);
1379
1380                 err.span_suggestion(
1381                     vis_span,
1382                     fluent::lint::suggestion,
1383                     "pub(crate)",
1384                     applicability,
1385                 );
1386                 if exportable {
1387                     err.help(fluent::lint::help);
1388                 }
1389                 err.emit();
1390             });
1391         }
1392     }
1393 }
1394
1395 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1396     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1397         // Do not warn for fake `use` statements.
1398         if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1399             return;
1400         }
1401         self.perform_lint(cx, "item", item.def_id, item.vis_span, true);
1402     }
1403
1404     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1405         self.perform_lint(cx, "item", foreign_item.def_id, foreign_item.vis_span, true);
1406     }
1407
1408     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1409         let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1410         self.perform_lint(cx, "field", def_id, field.vis_span, false);
1411     }
1412
1413     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1414         // Only lint inherent impl items.
1415         if cx.tcx.associated_item(impl_item.def_id).trait_item_def_id.is_none() {
1416             self.perform_lint(cx, "item", impl_item.def_id, impl_item.vis_span, false);
1417         }
1418     }
1419 }
1420
1421 declare_lint! {
1422     /// The `type_alias_bounds` lint detects bounds in type aliases.
1423     ///
1424     /// ### Example
1425     ///
1426     /// ```rust
1427     /// type SendVec<T: Send> = Vec<T>;
1428     /// ```
1429     ///
1430     /// {{produces}}
1431     ///
1432     /// ### Explanation
1433     ///
1434     /// The trait bounds in a type alias are currently ignored, and should not
1435     /// be included to avoid confusion. This was previously allowed
1436     /// unintentionally; this may become a hard error in the future.
1437     TYPE_ALIAS_BOUNDS,
1438     Warn,
1439     "bounds in type aliases are not enforced"
1440 }
1441
1442 declare_lint_pass!(
1443     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1444     /// They are relevant when using associated types, but otherwise neither checked
1445     /// at definition site nor enforced at use site.
1446     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1447 );
1448
1449 impl TypeAliasBounds {
1450     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1451         match *qpath {
1452             hir::QPath::TypeRelative(ref ty, _) => {
1453                 // If this is a type variable, we found a `T::Assoc`.
1454                 match ty.kind {
1455                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1456                         matches!(path.res, Res::Def(DefKind::TyParam, _))
1457                     }
1458                     _ => false,
1459                 }
1460             }
1461             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1462         }
1463     }
1464
1465     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1466         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1467         // bound.  Let's see if this type does that.
1468
1469         // We use a HIR visitor to walk the type.
1470         use rustc_hir::intravisit::{self, Visitor};
1471         struct WalkAssocTypes<'a> {
1472             err: &'a mut Diagnostic,
1473         }
1474         impl Visitor<'_> for WalkAssocTypes<'_> {
1475             fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1476                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1477                     self.err.span_help(span, fluent::lint::builtin_type_alias_bounds_help);
1478                 }
1479                 intravisit::walk_qpath(self, qpath, id, span)
1480             }
1481         }
1482
1483         // Let's go for a walk!
1484         let mut visitor = WalkAssocTypes { err };
1485         visitor.visit_ty(ty);
1486     }
1487 }
1488
1489 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1490     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1491         let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1492             return
1493         };
1494         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1495             // Bounds are respected for `type X = impl Trait`
1496             return;
1497         }
1498         // There must not be a where clause
1499         if type_alias_generics.predicates.is_empty() {
1500             return;
1501         }
1502
1503         let mut where_spans = Vec::new();
1504         let mut inline_spans = Vec::new();
1505         let mut inline_sugg = Vec::new();
1506         for p in type_alias_generics.predicates {
1507             let span = p.span();
1508             if p.in_where_clause() {
1509                 where_spans.push(span);
1510             } else {
1511                 for b in p.bounds() {
1512                     inline_spans.push(b.span());
1513                 }
1514                 inline_sugg.push((span, String::new()));
1515             }
1516         }
1517
1518         let mut suggested_changing_assoc_types = false;
1519         if !where_spans.is_empty() {
1520             cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1521                 let mut err = lint.build(fluent::lint::builtin_type_alias_where_clause);
1522                 err.set_span(where_spans);
1523                 err.span_suggestion(
1524                     type_alias_generics.where_clause_span,
1525                     fluent::lint::suggestion,
1526                     "",
1527                     Applicability::MachineApplicable,
1528                 );
1529                 if !suggested_changing_assoc_types {
1530                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1531                     suggested_changing_assoc_types = true;
1532                 }
1533                 err.emit();
1534             });
1535         }
1536
1537         if !inline_spans.is_empty() {
1538             cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1539                 let mut err = lint.build(fluent::lint::builtin_type_alias_generic_bounds);
1540                 err.set_span(inline_spans);
1541                 err.multipart_suggestion(
1542                     fluent::lint::suggestion,
1543                     inline_sugg,
1544                     Applicability::MachineApplicable,
1545                 );
1546                 if !suggested_changing_assoc_types {
1547                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1548                 }
1549                 err.emit();
1550             });
1551         }
1552     }
1553 }
1554
1555 declare_lint_pass!(
1556     /// Lint constants that are erroneous.
1557     /// Without this lint, we might not get any diagnostic if the constant is
1558     /// unused within this crate, even though downstream crates can't use it
1559     /// without producing an error.
1560     UnusedBrokenConst => []
1561 );
1562
1563 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1564     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1565         match it.kind {
1566             hir::ItemKind::Const(_, body_id) => {
1567                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1568                 // trigger the query once for all constants since that will already report the errors
1569                 cx.tcx.ensure().const_eval_poly(def_id);
1570             }
1571             hir::ItemKind::Static(_, _, body_id) => {
1572                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1573                 cx.tcx.ensure().eval_static_initializer(def_id);
1574             }
1575             _ => {}
1576         }
1577     }
1578 }
1579
1580 declare_lint! {
1581     /// The `trivial_bounds` lint detects trait bounds that don't depend on
1582     /// any type parameters.
1583     ///
1584     /// ### Example
1585     ///
1586     /// ```rust
1587     /// #![feature(trivial_bounds)]
1588     /// pub struct A where i32: Copy;
1589     /// ```
1590     ///
1591     /// {{produces}}
1592     ///
1593     /// ### Explanation
1594     ///
1595     /// Usually you would not write a trait bound that you know is always
1596     /// true, or never true. However, when using macros, the macro may not
1597     /// know whether or not the constraint would hold or not at the time when
1598     /// generating the code. Currently, the compiler does not alert you if the
1599     /// constraint is always true, and generates an error if it is never true.
1600     /// The `trivial_bounds` feature changes this to be a warning in both
1601     /// cases, giving macros more freedom and flexibility to generate code,
1602     /// while still providing a signal when writing non-macro code that
1603     /// something is amiss.
1604     ///
1605     /// See [RFC 2056] for more details. This feature is currently only
1606     /// available on the nightly channel, see [tracking issue #48214].
1607     ///
1608     /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1609     /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1610     TRIVIAL_BOUNDS,
1611     Warn,
1612     "these bounds don't depend on an type parameters"
1613 }
1614
1615 declare_lint_pass!(
1616     /// Lint for trait and lifetime bounds that don't depend on type parameters
1617     /// which either do nothing, or stop the item from being used.
1618     TrivialConstraints => [TRIVIAL_BOUNDS]
1619 );
1620
1621 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1622     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1623         use rustc_middle::ty::visit::TypeVisitable;
1624         use rustc_middle::ty::PredicateKind::*;
1625
1626         if cx.tcx.features().trivial_bounds {
1627             let predicates = cx.tcx.predicates_of(item.def_id);
1628             for &(predicate, span) in predicates.predicates {
1629                 let predicate_kind_name = match predicate.kind().skip_binder() {
1630                     Trait(..) => "trait",
1631                     TypeOutlives(..) |
1632                     RegionOutlives(..) => "lifetime",
1633
1634                     // Ignore projections, as they can only be global
1635                     // if the trait bound is global
1636                     Projection(..) |
1637                     // Ignore bounds that a user can't type
1638                     WellFormed(..) |
1639                     ObjectSafe(..) |
1640                     ClosureKind(..) |
1641                     Subtype(..) |
1642                     Coerce(..) |
1643                     ConstEvaluatable(..) |
1644                     ConstEquate(..) |
1645                     TypeWellFormedFromEnv(..) => continue,
1646                 };
1647                 if predicate.is_global() {
1648                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1649                         lint.build(fluent::lint::builtin_trivial_bounds)
1650                             .set_arg("predicate_kind_name", predicate_kind_name)
1651                             .set_arg("predicate", predicate)
1652                             .emit();
1653                     });
1654                 }
1655             }
1656         }
1657     }
1658 }
1659
1660 declare_lint_pass!(
1661     /// Does nothing as a lint pass, but registers some `Lint`s
1662     /// which are used by other parts of the compiler.
1663     SoftLints => [
1664         WHILE_TRUE,
1665         BOX_POINTERS,
1666         NON_SHORTHAND_FIELD_PATTERNS,
1667         UNSAFE_CODE,
1668         MISSING_DOCS,
1669         MISSING_COPY_IMPLEMENTATIONS,
1670         MISSING_DEBUG_IMPLEMENTATIONS,
1671         ANONYMOUS_PARAMETERS,
1672         UNUSED_DOC_COMMENTS,
1673         NO_MANGLE_CONST_ITEMS,
1674         NO_MANGLE_GENERIC_ITEMS,
1675         MUTABLE_TRANSMUTES,
1676         UNSTABLE_FEATURES,
1677         UNREACHABLE_PUB,
1678         TYPE_ALIAS_BOUNDS,
1679         TRIVIAL_BOUNDS
1680     ]
1681 );
1682
1683 declare_lint! {
1684     /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1685     /// pattern], which is deprecated.
1686     ///
1687     /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1688     ///
1689     /// ### Example
1690     ///
1691     /// ```rust,edition2018
1692     /// let x = 123;
1693     /// match x {
1694     ///     0...100 => {}
1695     ///     _ => {}
1696     /// }
1697     /// ```
1698     ///
1699     /// {{produces}}
1700     ///
1701     /// ### Explanation
1702     ///
1703     /// The `...` range pattern syntax was changed to `..=` to avoid potential
1704     /// confusion with the [`..` range expression]. Use the new form instead.
1705     ///
1706     /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1707     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1708     Warn,
1709     "`...` range patterns are deprecated",
1710     @future_incompatible = FutureIncompatibleInfo {
1711         reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1712         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1713     };
1714 }
1715
1716 #[derive(Default)]
1717 pub struct EllipsisInclusiveRangePatterns {
1718     /// If `Some(_)`, suppress all subsequent pattern
1719     /// warnings for better diagnostics.
1720     node_id: Option<ast::NodeId>,
1721 }
1722
1723 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1724
1725 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1726     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1727         if self.node_id.is_some() {
1728             // Don't recursively warn about patterns inside range endpoints.
1729             return;
1730         }
1731
1732         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1733
1734         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1735         /// corresponding to the ellipsis.
1736         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1737             match &pat.kind {
1738                 PatKind::Range(
1739                     a,
1740                     Some(b),
1741                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1742                 ) => Some((a.as_deref(), b, *span)),
1743                 _ => None,
1744             }
1745         }
1746
1747         let (parenthesise, endpoints) = match &pat.kind {
1748             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1749             _ => (false, matches_ellipsis_pat(pat)),
1750         };
1751
1752         if let Some((start, end, join)) = endpoints {
1753             let msg = fluent::lint::builtin_ellipsis_inclusive_range_patterns;
1754             let suggestion = fluent::lint::suggestion;
1755             if parenthesise {
1756                 self.node_id = Some(pat.id);
1757                 let end = expr_to_string(&end);
1758                 let replace = match start {
1759                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1760                     None => format!("&(..={})", end),
1761                 };
1762                 if join.edition() >= Edition::Edition2021 {
1763                     let mut err = cx.sess().struct_span_err_with_code(
1764                         pat.span,
1765                         msg,
1766                         rustc_errors::error_code!(E0783),
1767                     );
1768                     err.span_suggestion(
1769                         pat.span,
1770                         suggestion,
1771                         replace,
1772                         Applicability::MachineApplicable,
1773                     )
1774                     .emit();
1775                 } else {
1776                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1777                         lint.build(msg)
1778                             .span_suggestion(
1779                                 pat.span,
1780                                 suggestion,
1781                                 replace,
1782                                 Applicability::MachineApplicable,
1783                             )
1784                             .emit();
1785                     });
1786                 }
1787             } else {
1788                 let replace = "..=";
1789                 if join.edition() >= Edition::Edition2021 {
1790                     let mut err = cx.sess().struct_span_err_with_code(
1791                         pat.span,
1792                         msg,
1793                         rustc_errors::error_code!(E0783),
1794                     );
1795                     err.span_suggestion_short(
1796                         join,
1797                         suggestion,
1798                         replace,
1799                         Applicability::MachineApplicable,
1800                     )
1801                     .emit();
1802                 } else {
1803                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1804                         lint.build(msg)
1805                             .span_suggestion_short(
1806                                 join,
1807                                 suggestion,
1808                                 replace,
1809                                 Applicability::MachineApplicable,
1810                             )
1811                             .emit();
1812                     });
1813                 }
1814             };
1815         }
1816     }
1817
1818     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1819         if let Some(node_id) = self.node_id {
1820             if pat.id == node_id {
1821                 self.node_id = None
1822             }
1823         }
1824     }
1825 }
1826
1827 declare_lint! {
1828     /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1829     /// that are not able to be run by the test harness because they are in a
1830     /// position where they are not nameable.
1831     ///
1832     /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1833     ///
1834     /// ### Example
1835     ///
1836     /// ```rust,test
1837     /// fn main() {
1838     ///     #[test]
1839     ///     fn foo() {
1840     ///         // This test will not fail because it does not run.
1841     ///         assert_eq!(1, 2);
1842     ///     }
1843     /// }
1844     /// ```
1845     ///
1846     /// {{produces}}
1847     ///
1848     /// ### Explanation
1849     ///
1850     /// In order for the test harness to run a test, the test function must be
1851     /// located in a position where it can be accessed from the crate root.
1852     /// This generally means it must be defined in a module, and not anywhere
1853     /// else such as inside another function. The compiler previously allowed
1854     /// this without an error, so a lint was added as an alert that a test is
1855     /// not being used. Whether or not this should be allowed has not yet been
1856     /// decided, see [RFC 2471] and [issue #36629].
1857     ///
1858     /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1859     /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1860     UNNAMEABLE_TEST_ITEMS,
1861     Warn,
1862     "detects an item that cannot be named being marked as `#[test_case]`",
1863     report_in_external_macro
1864 }
1865
1866 pub struct UnnameableTestItems {
1867     boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1868     items_nameable: bool,
1869 }
1870
1871 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1872
1873 impl UnnameableTestItems {
1874     pub fn new() -> Self {
1875         Self { boundary: None, items_nameable: true }
1876     }
1877 }
1878
1879 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1880     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1881         if self.items_nameable {
1882             if let hir::ItemKind::Mod(..) = it.kind {
1883             } else {
1884                 self.items_nameable = false;
1885                 self.boundary = Some(it.def_id);
1886             }
1887             return;
1888         }
1889
1890         let attrs = cx.tcx.hir().attrs(it.hir_id());
1891         if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1892             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1893                 lint.build(fluent::lint::builtin_unnameable_test_items).emit();
1894             });
1895         }
1896     }
1897
1898     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1899         if !self.items_nameable && self.boundary == Some(it.def_id) {
1900             self.items_nameable = true;
1901         }
1902     }
1903 }
1904
1905 declare_lint! {
1906     /// The `keyword_idents` lint detects edition keywords being used as an
1907     /// identifier.
1908     ///
1909     /// ### Example
1910     ///
1911     /// ```rust,edition2015,compile_fail
1912     /// #![deny(keyword_idents)]
1913     /// // edition 2015
1914     /// fn dyn() {}
1915     /// ```
1916     ///
1917     /// {{produces}}
1918     ///
1919     /// ### Explanation
1920     ///
1921     /// Rust [editions] allow the language to evolve without breaking
1922     /// backwards compatibility. This lint catches code that uses new keywords
1923     /// that are added to the language that are used as identifiers (such as a
1924     /// variable name, function name, etc.). If you switch the compiler to a
1925     /// new edition without updating the code, then it will fail to compile if
1926     /// you are using a new keyword as an identifier.
1927     ///
1928     /// You can manually change the identifiers to a non-keyword, or use a
1929     /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1930     ///
1931     /// This lint solves the problem automatically. It is "allow" by default
1932     /// because the code is perfectly valid in older editions. The [`cargo
1933     /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1934     /// and automatically apply the suggested fix from the compiler (which is
1935     /// to use a raw identifier). This provides a completely automated way to
1936     /// update old code for a new edition.
1937     ///
1938     /// [editions]: https://doc.rust-lang.org/edition-guide/
1939     /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1940     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1941     pub KEYWORD_IDENTS,
1942     Allow,
1943     "detects edition keywords being used as an identifier",
1944     @future_incompatible = FutureIncompatibleInfo {
1945         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1946         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1947     };
1948 }
1949
1950 declare_lint_pass!(
1951     /// Check for uses of edition keywords used as an identifier.
1952     KeywordIdents => [KEYWORD_IDENTS]
1953 );
1954
1955 struct UnderMacro(bool);
1956
1957 impl KeywordIdents {
1958     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1959         for tt in tokens.into_trees() {
1960             match tt {
1961                 // Only report non-raw idents.
1962                 TokenTree::Token(token, _) => {
1963                     if let Some((ident, false)) = token.ident() {
1964                         self.check_ident_token(cx, UnderMacro(true), ident);
1965                     }
1966                 }
1967                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1968             }
1969         }
1970     }
1971
1972     fn check_ident_token(
1973         &mut self,
1974         cx: &EarlyContext<'_>,
1975         UnderMacro(under_macro): UnderMacro,
1976         ident: Ident,
1977     ) {
1978         let next_edition = match cx.sess().edition() {
1979             Edition::Edition2015 => {
1980                 match ident.name {
1981                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1982
1983                     // rust-lang/rust#56327: Conservatively do not
1984                     // attempt to report occurrences of `dyn` within
1985                     // macro definitions or invocations, because `dyn`
1986                     // can legitimately occur as a contextual keyword
1987                     // in 2015 code denoting its 2018 meaning, and we
1988                     // do not want rustfix to inject bugs into working
1989                     // code by rewriting such occurrences.
1990                     //
1991                     // But if we see `dyn` outside of a macro, we know
1992                     // its precise role in the parsed AST and thus are
1993                     // assured this is truly an attempt to use it as
1994                     // an identifier.
1995                     kw::Dyn if !under_macro => Edition::Edition2018,
1996
1997                     _ => return,
1998                 }
1999             }
2000
2001             // There are no new keywords yet for the 2018 edition and beyond.
2002             _ => return,
2003         };
2004
2005         // Don't lint `r#foo`.
2006         if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2007             return;
2008         }
2009
2010         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2011             lint.build(fluent::lint::builtin_keyword_idents)
2012                 .set_arg("kw", ident.clone())
2013                 .set_arg("next", next_edition)
2014                 .span_suggestion(
2015                     ident.span,
2016                     fluent::lint::suggestion,
2017                     format!("r#{}", ident),
2018                     Applicability::MachineApplicable,
2019                 )
2020                 .emit();
2021         });
2022     }
2023 }
2024
2025 impl EarlyLintPass for KeywordIdents {
2026     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2027         self.check_tokens(cx, mac_def.body.inner_tokens());
2028     }
2029     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2030         self.check_tokens(cx, mac.args.inner_tokens());
2031     }
2032     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2033         self.check_ident_token(cx, UnderMacro(false), ident);
2034     }
2035 }
2036
2037 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2038
2039 impl ExplicitOutlivesRequirements {
2040     fn lifetimes_outliving_lifetime<'tcx>(
2041         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2042         index: u32,
2043     ) -> Vec<ty::Region<'tcx>> {
2044         inferred_outlives
2045             .iter()
2046             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2047                 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2048                     ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2049                     _ => None,
2050                 },
2051                 _ => None,
2052             })
2053             .collect()
2054     }
2055
2056     fn lifetimes_outliving_type<'tcx>(
2057         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2058         index: u32,
2059     ) -> Vec<ty::Region<'tcx>> {
2060         inferred_outlives
2061             .iter()
2062             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2063                 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2064                     a.is_param(index).then_some(b)
2065                 }
2066                 _ => None,
2067             })
2068             .collect()
2069     }
2070
2071     fn collect_outlives_bound_spans<'tcx>(
2072         &self,
2073         tcx: TyCtxt<'tcx>,
2074         bounds: &hir::GenericBounds<'_>,
2075         inferred_outlives: &[ty::Region<'tcx>],
2076     ) -> Vec<(usize, Span)> {
2077         use rustc_middle::middle::resolve_lifetime::Region;
2078
2079         bounds
2080             .iter()
2081             .enumerate()
2082             .filter_map(|(i, bound)| {
2083                 if let hir::GenericBound::Outlives(lifetime) = bound {
2084                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
2085                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2086                             if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
2087                         }),
2088                         _ => false,
2089                     };
2090                     is_inferred.then_some((i, bound.span()))
2091                 } else {
2092                     None
2093                 }
2094             })
2095             .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2096             .collect()
2097     }
2098
2099     fn consolidate_outlives_bound_spans(
2100         &self,
2101         lo: Span,
2102         bounds: &hir::GenericBounds<'_>,
2103         bound_spans: Vec<(usize, Span)>,
2104     ) -> Vec<Span> {
2105         if bounds.is_empty() {
2106             return Vec::new();
2107         }
2108         if bound_spans.len() == bounds.len() {
2109             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2110             // If all bounds are inferable, we want to delete the colon, so
2111             // start from just after the parameter (span passed as argument)
2112             vec![lo.to(last_bound_span)]
2113         } else {
2114             let mut merged = Vec::new();
2115             let mut last_merged_i = None;
2116
2117             let mut from_start = true;
2118             for (i, bound_span) in bound_spans {
2119                 match last_merged_i {
2120                     // If the first bound is inferable, our span should also eat the leading `+`.
2121                     None if i == 0 => {
2122                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2123                         last_merged_i = Some(0);
2124                     }
2125                     // If consecutive bounds are inferable, merge their spans
2126                     Some(h) if i == h + 1 => {
2127                         if let Some(tail) = merged.last_mut() {
2128                             // Also eat the trailing `+` if the first
2129                             // more-than-one bound is inferable
2130                             let to_span = if from_start && i < bounds.len() {
2131                                 bounds[i + 1].span().shrink_to_lo()
2132                             } else {
2133                                 bound_span
2134                             };
2135                             *tail = tail.to(to_span);
2136                             last_merged_i = Some(i);
2137                         } else {
2138                             bug!("another bound-span visited earlier");
2139                         }
2140                     }
2141                     _ => {
2142                         // When we find a non-inferable bound, subsequent inferable bounds
2143                         // won't be consecutive from the start (and we'll eat the leading
2144                         // `+` rather than the trailing one)
2145                         from_start = false;
2146                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2147                         last_merged_i = Some(i);
2148                     }
2149                 }
2150             }
2151             merged
2152         }
2153     }
2154 }
2155
2156 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2157     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2158         use rustc_middle::middle::resolve_lifetime::Region;
2159
2160         let def_id = item.def_id;
2161         if let hir::ItemKind::Struct(_, ref hir_generics)
2162         | hir::ItemKind::Enum(_, ref hir_generics)
2163         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2164         {
2165             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2166             if inferred_outlives.is_empty() {
2167                 return;
2168             }
2169
2170             let ty_generics = cx.tcx.generics_of(def_id);
2171
2172             let mut bound_count = 0;
2173             let mut lint_spans = Vec::new();
2174             let mut where_lint_spans = Vec::new();
2175             let mut dropped_predicate_count = 0;
2176             let num_predicates = hir_generics.predicates.len();
2177             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2178                 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2179                     hir::WherePredicate::RegionPredicate(predicate) => {
2180                         if let Some(Region::EarlyBound(index, ..)) =
2181                             cx.tcx.named_region(predicate.lifetime.hir_id)
2182                         {
2183                             (
2184                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2185                                 &predicate.bounds,
2186                                 predicate.span,
2187                                 predicate.in_where_clause,
2188                             )
2189                         } else {
2190                             continue;
2191                         }
2192                     }
2193                     hir::WherePredicate::BoundPredicate(predicate) => {
2194                         // FIXME we can also infer bounds on associated types,
2195                         // and should check for them here.
2196                         match predicate.bounded_ty.kind {
2197                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2198                                 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2199                                     continue
2200                                 };
2201                                 let index = ty_generics.param_def_id_to_index[&def_id];
2202                                 (
2203                                     Self::lifetimes_outliving_type(inferred_outlives, index),
2204                                     &predicate.bounds,
2205                                     predicate.span,
2206                                     predicate.origin == PredicateOrigin::WhereClause,
2207                                 )
2208                             }
2209                             _ => {
2210                                 continue;
2211                             }
2212                         }
2213                     }
2214                     _ => continue,
2215                 };
2216                 if relevant_lifetimes.is_empty() {
2217                     continue;
2218                 }
2219
2220                 let bound_spans =
2221                     self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2222                 bound_count += bound_spans.len();
2223
2224                 let drop_predicate = bound_spans.len() == bounds.len();
2225                 if drop_predicate {
2226                     dropped_predicate_count += 1;
2227                 }
2228
2229                 if drop_predicate && !in_where_clause {
2230                     lint_spans.push(span);
2231                 } else if drop_predicate && i + 1 < num_predicates {
2232                     // If all the bounds on a predicate were inferable and there are
2233                     // further predicates, we want to eat the trailing comma.
2234                     let next_predicate_span = hir_generics.predicates[i + 1].span();
2235                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2236                 } else {
2237                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2238                         span.shrink_to_lo(),
2239                         bounds,
2240                         bound_spans,
2241                     ));
2242                 }
2243             }
2244
2245             // If all predicates are inferable, drop the entire clause
2246             // (including the `where`)
2247             if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2248             {
2249                 let where_span = hir_generics.where_clause_span;
2250                 // Extend the where clause back to the closing `>` of the
2251                 // generics, except for tuple struct, which have the `where`
2252                 // after the fields of the struct.
2253                 let full_where_span =
2254                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2255                         where_span
2256                     } else {
2257                         hir_generics.span.shrink_to_hi().to(where_span)
2258                     };
2259                 lint_spans.push(full_where_span);
2260             } else {
2261                 lint_spans.extend(where_lint_spans);
2262             }
2263
2264             if !lint_spans.is_empty() {
2265                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2266                     lint.build(fluent::lint::builtin_explicit_outlives)
2267                         .set_arg("count", bound_count)
2268                         .multipart_suggestion(
2269                             fluent::lint::suggestion,
2270                             lint_spans
2271                                 .into_iter()
2272                                 .map(|span| (span, String::new()))
2273                                 .collect::<Vec<_>>(),
2274                             Applicability::MachineApplicable,
2275                         )
2276                         .emit();
2277                 });
2278             }
2279         }
2280     }
2281 }
2282
2283 declare_lint! {
2284     /// The `incomplete_features` lint detects unstable features enabled with
2285     /// the [`feature` attribute] that may function improperly in some or all
2286     /// cases.
2287     ///
2288     /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2289     ///
2290     /// ### Example
2291     ///
2292     /// ```rust
2293     /// #![feature(generic_const_exprs)]
2294     /// ```
2295     ///
2296     /// {{produces}}
2297     ///
2298     /// ### Explanation
2299     ///
2300     /// Although it is encouraged for people to experiment with unstable
2301     /// features, some of them are known to be incomplete or faulty. This lint
2302     /// is a signal that the feature has not yet been finished, and you may
2303     /// experience problems with it.
2304     pub INCOMPLETE_FEATURES,
2305     Warn,
2306     "incomplete features that may function improperly in some or all cases"
2307 }
2308
2309 declare_lint_pass!(
2310     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2311     IncompleteFeatures => [INCOMPLETE_FEATURES]
2312 );
2313
2314 impl EarlyLintPass for IncompleteFeatures {
2315     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2316         let features = cx.sess().features_untracked();
2317         features
2318             .declared_lang_features
2319             .iter()
2320             .map(|(name, span, _)| (name, span))
2321             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2322             .filter(|(&name, _)| features.incomplete(name))
2323             .for_each(|(&name, &span)| {
2324                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2325                     let mut builder = lint.build(fluent::lint::builtin_incomplete_features);
2326                     builder.set_arg("name", name);
2327                     if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2328                         builder.set_arg("n", n);
2329                         builder.note(fluent::lint::note);
2330                     }
2331                     if HAS_MIN_FEATURES.contains(&name) {
2332                         builder.help(fluent::lint::help);
2333                     }
2334                     builder.emit();
2335                 })
2336             });
2337     }
2338 }
2339
2340 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2341
2342 declare_lint! {
2343     /// The `invalid_value` lint detects creating a value that is not valid,
2344     /// such as a null reference.
2345     ///
2346     /// ### Example
2347     ///
2348     /// ```rust,no_run
2349     /// # #![allow(unused)]
2350     /// unsafe {
2351     ///     let x: &'static i32 = std::mem::zeroed();
2352     /// }
2353     /// ```
2354     ///
2355     /// {{produces}}
2356     ///
2357     /// ### Explanation
2358     ///
2359     /// In some situations the compiler can detect that the code is creating
2360     /// an invalid value, which should be avoided.
2361     ///
2362     /// In particular, this lint will check for improper use of
2363     /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2364     /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2365     /// lint should provide extra information to indicate what the problem is
2366     /// and a possible solution.
2367     ///
2368     /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2369     /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2370     /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2371     /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2372     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2373     pub INVALID_VALUE,
2374     Warn,
2375     "an invalid value is being created (such as a null reference)"
2376 }
2377
2378 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2379
2380 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2381     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2382         #[derive(Debug, Copy, Clone, PartialEq)]
2383         enum InitKind {
2384             Zeroed,
2385             Uninit,
2386         }
2387
2388         /// Information about why a type cannot be initialized this way.
2389         /// Contains an error message and optionally a span to point at.
2390         type InitError = (String, Option<Span>);
2391
2392         /// Test if this constant is all-0.
2393         fn is_zero(expr: &hir::Expr<'_>) -> bool {
2394             use hir::ExprKind::*;
2395             use rustc_ast::LitKind::*;
2396             match &expr.kind {
2397                 Lit(lit) => {
2398                     if let Int(i, _) = lit.node {
2399                         i == 0
2400                     } else {
2401                         false
2402                     }
2403                 }
2404                 Tup(tup) => tup.iter().all(is_zero),
2405                 _ => false,
2406             }
2407         }
2408
2409         /// Determine if this expression is a "dangerous initialization".
2410         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2411             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2412                 // Find calls to `mem::{uninitialized,zeroed}` methods.
2413                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2414                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2415                     match cx.tcx.get_diagnostic_name(def_id) {
2416                         Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2417                         Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2418                         Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2419                         _ => {}
2420                     }
2421                 }
2422             } else if let hir::ExprKind::MethodCall(_, ref args, _) = expr.kind {
2423                 // Find problematic calls to `MaybeUninit::assume_init`.
2424                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2425                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2426                     // This is a call to *some* method named `assume_init`.
2427                     // See if the `self` parameter is one of the dangerous constructors.
2428                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2429                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2430                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2431                             match cx.tcx.get_diagnostic_name(def_id) {
2432                                 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2433                                 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2434                                 _ => {}
2435                             }
2436                         }
2437                     }
2438                 }
2439             }
2440
2441             None
2442         }
2443
2444         /// Test if this enum has several actually "existing" variants.
2445         /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2446         fn is_multi_variant<'tcx>(adt: ty::AdtDef<'tcx>) -> bool {
2447             // As an approximation, we only count dataless variants. Those are definitely inhabited.
2448             let existing_variants = adt.variants().iter().filter(|v| v.fields.is_empty()).count();
2449             existing_variants > 1
2450         }
2451
2452         /// Return `Some` only if we are sure this type does *not*
2453         /// allow zero initialization.
2454         fn ty_find_init_error<'tcx>(
2455             cx: &LateContext<'tcx>,
2456             ty: Ty<'tcx>,
2457             init: InitKind,
2458         ) -> Option<InitError> {
2459             use rustc_type_ir::sty::TyKind::*;
2460             match ty.kind() {
2461                 // Primitive types that don't like 0 as a value.
2462                 Ref(..) => Some(("references must be non-null".to_string(), None)),
2463                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2464                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2465                 Never => Some(("the `!` type has no valid value".to_string(), None)),
2466                 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2467                 // raw ptr to dyn Trait
2468                 {
2469                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2470                 }
2471                 // Primitive types with other constraints.
2472                 Bool if init == InitKind::Uninit => {
2473                     Some(("booleans must be either `true` or `false`".to_string(), None))
2474                 }
2475                 Char if init == InitKind::Uninit => {
2476                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
2477                 }
2478                 // Recurse and checks for some compound types.
2479                 Adt(adt_def, substs) if !adt_def.is_union() => {
2480                     // First check if this ADT has a layout attribute (like `NonNull` and friends).
2481                     use std::ops::Bound;
2482                     match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
2483                         // We exploit here that `layout_scalar_valid_range` will never
2484                         // return `Bound::Excluded`.  (And we have tests checking that we
2485                         // handle the attribute correctly.)
2486                         (Bound::Included(lo), _) if lo > 0 => {
2487                             return Some((format!("`{}` must be non-null", ty), None));
2488                         }
2489                         (Bound::Included(_), _) | (_, Bound::Included(_))
2490                             if init == InitKind::Uninit =>
2491                         {
2492                             return Some((
2493                                 format!(
2494                                     "`{}` must be initialized inside its custom valid range",
2495                                     ty,
2496                                 ),
2497                                 None,
2498                             ));
2499                         }
2500                         _ => {}
2501                     }
2502                     // Now, recurse.
2503                     match adt_def.variants().len() {
2504                         0 => Some(("enums with no variants have no valid value".to_string(), None)),
2505                         1 => {
2506                             // Struct, or enum with exactly one variant.
2507                             // Proceed recursively, check all fields.
2508                             let variant = &adt_def.variant(VariantIdx::from_u32(0));
2509                             variant.fields.iter().find_map(|field| {
2510                                 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(
2511                                     |(mut msg, span)| {
2512                                         if span.is_none() {
2513                                             // Point to this field, should be helpful for figuring
2514                                             // out where the source of the error is.
2515                                             let span = cx.tcx.def_span(field.did);
2516                                             write!(
2517                                                 &mut msg,
2518                                                 " (in this {} field)",
2519                                                 adt_def.descr()
2520                                             )
2521                                             .unwrap();
2522                                             (msg, Some(span))
2523                                         } else {
2524                                             // Just forward.
2525                                             (msg, span)
2526                                         }
2527                                     },
2528                                 )
2529                             })
2530                         }
2531                         // Multi-variant enum.
2532                         _ => {
2533                             if init == InitKind::Uninit && is_multi_variant(*adt_def) {
2534                                 let span = cx.tcx.def_span(adt_def.did());
2535                                 Some((
2536                                     "enums have to be initialized to a variant".to_string(),
2537                                     Some(span),
2538                                 ))
2539                             } else {
2540                                 // In principle, for zero-initialization we could figure out which variant corresponds
2541                                 // to tag 0, and check that... but for now we just accept all zero-initializations.
2542                                 None
2543                             }
2544                         }
2545                     }
2546                 }
2547                 Tuple(..) => {
2548                     // Proceed recursively, check all fields.
2549                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2550                 }
2551                 Array(ty, len) => {
2552                     if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2553                         // Array length known at array non-empty -- recurse.
2554                         ty_find_init_error(cx, *ty, init)
2555                     } else {
2556                         // Empty array or size unknown.
2557                         None
2558                     }
2559                 }
2560                 // Conservative fallback.
2561                 _ => None,
2562             }
2563         }
2564
2565         if let Some(init) = is_dangerous_init(cx, expr) {
2566             // This conjures an instance of a type out of nothing,
2567             // using zeroed or uninitialized memory.
2568             // We are extremely conservative with what we warn about.
2569             let conjured_ty = cx.typeck_results().expr_ty(expr);
2570             if let Some((msg, span)) =
2571                 with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2572             {
2573                 // FIXME(davidtwco): make translatable
2574                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2575                     let mut err = lint.build(&format!(
2576                         "the type `{}` does not permit {}",
2577                         conjured_ty,
2578                         match init {
2579                             InitKind::Zeroed => "zero-initialization",
2580                             InitKind::Uninit => "being left uninitialized",
2581                         },
2582                     ));
2583                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2584                     err.span_label(
2585                         expr.span,
2586                         "help: use `MaybeUninit<T>` instead, \
2587                             and only call `assume_init` after initialization is done",
2588                     );
2589                     if let Some(span) = span {
2590                         err.span_note(span, &msg);
2591                     } else {
2592                         err.note(&msg);
2593                     }
2594                     err.emit();
2595                 });
2596             }
2597         }
2598     }
2599 }
2600
2601 declare_lint! {
2602     /// The `clashing_extern_declarations` lint detects when an `extern fn`
2603     /// has been declared with the same name but different types.
2604     ///
2605     /// ### Example
2606     ///
2607     /// ```rust
2608     /// mod m {
2609     ///     extern "C" {
2610     ///         fn foo();
2611     ///     }
2612     /// }
2613     ///
2614     /// extern "C" {
2615     ///     fn foo(_: u32);
2616     /// }
2617     /// ```
2618     ///
2619     /// {{produces}}
2620     ///
2621     /// ### Explanation
2622     ///
2623     /// Because two symbols of the same name cannot be resolved to two
2624     /// different functions at link time, and one function cannot possibly
2625     /// have two types, a clashing extern declaration is almost certainly a
2626     /// mistake. Check to make sure that the `extern` definitions are correct
2627     /// and equivalent, and possibly consider unifying them in one location.
2628     ///
2629     /// This lint does not run between crates because a project may have
2630     /// dependencies which both rely on the same extern function, but declare
2631     /// it in a different (but valid) way. For example, they may both declare
2632     /// an opaque type for one or more of the arguments (which would end up
2633     /// distinct types), or use types that are valid conversions in the
2634     /// language the `extern fn` is defined in. In these cases, the compiler
2635     /// can't say that the clashing declaration is incorrect.
2636     pub CLASHING_EXTERN_DECLARATIONS,
2637     Warn,
2638     "detects when an extern fn has been declared with the same name but different types"
2639 }
2640
2641 pub struct ClashingExternDeclarations {
2642     /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2643     /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2644     /// the symbol should be reported as a clashing declaration.
2645     // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2646     // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2647     seen_decls: FxHashMap<Symbol, HirId>,
2648 }
2649
2650 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2651 /// just from declaration itself. This is important because we don't want to report clashes on
2652 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2653 /// different name.
2654 enum SymbolName {
2655     /// The name of the symbol + the span of the annotation which introduced the link name.
2656     Link(Symbol, Span),
2657     /// No link name, so just the name of the symbol.
2658     Normal(Symbol),
2659 }
2660
2661 impl SymbolName {
2662     fn get_name(&self) -> Symbol {
2663         match self {
2664             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2665         }
2666     }
2667 }
2668
2669 impl ClashingExternDeclarations {
2670     pub(crate) fn new() -> Self {
2671         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2672     }
2673     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2674     /// for the item, return its HirId without updating the set.
2675     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2676         let did = fi.def_id.to_def_id();
2677         let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2678         let name = Symbol::intern(tcx.symbol_name(instance).name);
2679         if let Some(&hir_id) = self.seen_decls.get(&name) {
2680             // Avoid updating the map with the new entry when we do find a collision. We want to
2681             // make sure we're always pointing to the first definition as the previous declaration.
2682             // This lets us avoid emitting "knock-on" diagnostics.
2683             Some(hir_id)
2684         } else {
2685             self.seen_decls.insert(name, fi.hir_id())
2686         }
2687     }
2688
2689     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2690     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2691     /// symbol's name.
2692     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2693         if let Some((overridden_link_name, overridden_link_name_span)) =
2694             tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2695                 // FIXME: Instead of searching through the attributes again to get span
2696                 // information, we could have codegen_fn_attrs also give span information back for
2697                 // where the attribute was defined. However, until this is found to be a
2698                 // bottleneck, this does just fine.
2699                 (
2700                     overridden_link_name,
2701                     tcx.get_attr(fi.def_id.to_def_id(), sym::link_name).unwrap().span,
2702                 )
2703             })
2704         {
2705             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2706         } else {
2707             SymbolName::Normal(fi.ident.name)
2708         }
2709     }
2710
2711     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2712     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2713     /// with the same members (as the declarations shouldn't clash).
2714     fn structurally_same_type<'tcx>(
2715         cx: &LateContext<'tcx>,
2716         a: Ty<'tcx>,
2717         b: Ty<'tcx>,
2718         ckind: CItemKind,
2719     ) -> bool {
2720         fn structurally_same_type_impl<'tcx>(
2721             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2722             cx: &LateContext<'tcx>,
2723             a: Ty<'tcx>,
2724             b: Ty<'tcx>,
2725             ckind: CItemKind,
2726         ) -> bool {
2727             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2728             let tcx = cx.tcx;
2729
2730             // Given a transparent newtype, reach through and grab the inner
2731             // type unless the newtype makes the type non-null.
2732             let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2733                 let mut ty = ty;
2734                 loop {
2735                     if let ty::Adt(def, substs) = *ty.kind() {
2736                         let is_transparent = def.repr().transparent();
2737                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2738                         debug!(
2739                             "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2740                             ty, is_transparent, is_non_null
2741                         );
2742                         if is_transparent && !is_non_null {
2743                             debug_assert!(def.variants().len() == 1);
2744                             let v = &def.variant(VariantIdx::new(0));
2745                             ty = transparent_newtype_field(tcx, v)
2746                                 .expect(
2747                                     "single-variant transparent structure with zero-sized field",
2748                                 )
2749                                 .ty(tcx, substs);
2750                             continue;
2751                         }
2752                     }
2753                     debug!("non_transparent_ty -> {:?}", ty);
2754                     return ty;
2755                 }
2756             };
2757
2758             let a = non_transparent_ty(a);
2759             let b = non_transparent_ty(b);
2760
2761             if !seen_types.insert((a, b)) {
2762                 // We've encountered a cycle. There's no point going any further -- the types are
2763                 // structurally the same.
2764                 return true;
2765             }
2766             let tcx = cx.tcx;
2767             if a == b {
2768                 // All nominally-same types are structurally same, too.
2769                 true
2770             } else {
2771                 // Do a full, depth-first comparison between the two.
2772                 use rustc_type_ir::sty::TyKind::*;
2773                 let a_kind = a.kind();
2774                 let b_kind = b.kind();
2775
2776                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2777                     debug!("compare_layouts({:?}, {:?})", a, b);
2778                     let a_layout = &cx.layout_of(a)?.layout.abi();
2779                     let b_layout = &cx.layout_of(b)?.layout.abi();
2780                     debug!(
2781                         "comparing layouts: {:?} == {:?} = {}",
2782                         a_layout,
2783                         b_layout,
2784                         a_layout == b_layout
2785                     );
2786                     Ok(a_layout == b_layout)
2787                 };
2788
2789                 #[allow(rustc::usage_of_ty_tykind)]
2790                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2791                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2792                 };
2793
2794                 ensure_sufficient_stack(|| {
2795                     match (a_kind, b_kind) {
2796                         (Adt(a_def, _), Adt(b_def, _)) => {
2797                             // We can immediately rule out these types as structurally same if
2798                             // their layouts differ.
2799                             match compare_layouts(a, b) {
2800                                 Ok(false) => return false,
2801                                 _ => (), // otherwise, continue onto the full, fields comparison
2802                             }
2803
2804                             // Grab a flattened representation of all fields.
2805                             let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2806                             let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2807
2808                             // Perform a structural comparison for each field.
2809                             a_fields.eq_by(
2810                                 b_fields,
2811                                 |&ty::FieldDef { did: a_did, .. },
2812                                  &ty::FieldDef { did: b_did, .. }| {
2813                                     structurally_same_type_impl(
2814                                         seen_types,
2815                                         cx,
2816                                         tcx.type_of(a_did),
2817                                         tcx.type_of(b_did),
2818                                         ckind,
2819                                     )
2820                                 },
2821                             )
2822                         }
2823                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2824                             // For arrays, we also check the constness of the type.
2825                             a_const.kind() == b_const.kind()
2826                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2827                         }
2828                         (Slice(a_ty), Slice(b_ty)) => {
2829                             structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2830                         }
2831                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2832                             a_tymut.mutbl == b_tymut.mutbl
2833                                 && structurally_same_type_impl(
2834                                     seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2835                                 )
2836                         }
2837                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2838                             // For structural sameness, we don't need the region to be same.
2839                             a_mut == b_mut
2840                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2841                         }
2842                         (FnDef(..), FnDef(..)) => {
2843                             let a_poly_sig = a.fn_sig(tcx);
2844                             let b_poly_sig = b.fn_sig(tcx);
2845
2846                             // We don't compare regions, but leaving bound regions around ICEs, so
2847                             // we erase them.
2848                             let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
2849                             let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
2850
2851                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2852                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2853                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2854                                     structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2855                                 })
2856                                 && structurally_same_type_impl(
2857                                     seen_types,
2858                                     cx,
2859                                     a_sig.output(),
2860                                     b_sig.output(),
2861                                     ckind,
2862                                 )
2863                         }
2864                         (Tuple(a_substs), Tuple(b_substs)) => {
2865                             a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2866                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2867                             })
2868                         }
2869                         // For these, it's not quite as easy to define structural-sameness quite so easily.
2870                         // For the purposes of this lint, take the conservative approach and mark them as
2871                         // not structurally same.
2872                         (Dynamic(..), Dynamic(..))
2873                         | (Error(..), Error(..))
2874                         | (Closure(..), Closure(..))
2875                         | (Generator(..), Generator(..))
2876                         | (GeneratorWitness(..), GeneratorWitness(..))
2877                         | (Projection(..), Projection(..))
2878                         | (Opaque(..), Opaque(..)) => false,
2879
2880                         // These definitely should have been caught above.
2881                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2882
2883                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2884                         // enum layout optimisation is being applied.
2885                         (Adt(..), other_kind) | (other_kind, Adt(..))
2886                             if is_primitive_or_pointer(other_kind) =>
2887                         {
2888                             let (primitive, adt) =
2889                                 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2890                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2891                                 ty == primitive
2892                             } else {
2893                                 compare_layouts(a, b).unwrap_or(false)
2894                             }
2895                         }
2896                         // Otherwise, just compare the layouts. This may fail to lint for some
2897                         // incompatible types, but at the very least, will stop reads into
2898                         // uninitialised memory.
2899                         _ => compare_layouts(a, b).unwrap_or(false),
2900                     }
2901                 })
2902             }
2903         }
2904         let mut seen_types = FxHashSet::default();
2905         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2906     }
2907 }
2908
2909 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2910
2911 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2912     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2913         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2914         if let ForeignItemKind::Fn(..) = this_fi.kind {
2915             let tcx = cx.tcx;
2916             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2917                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2918                 let this_decl_ty = tcx.type_of(this_fi.def_id);
2919                 debug!(
2920                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2921                     existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2922                 );
2923                 // Check that the declarations match.
2924                 if !Self::structurally_same_type(
2925                     cx,
2926                     existing_decl_ty,
2927                     this_decl_ty,
2928                     CItemKind::Declaration,
2929                 ) {
2930                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
2931                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
2932
2933                     // We want to ensure that we use spans for both decls that include where the
2934                     // name was defined, whether that was from the link_name attribute or not.
2935                     let get_relevant_span =
2936                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2937                             SymbolName::Normal(_) => fi.span,
2938                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2939                         };
2940                     // Finally, emit the diagnostic.
2941                     tcx.struct_span_lint_hir(
2942                         CLASHING_EXTERN_DECLARATIONS,
2943                         this_fi.hir_id(),
2944                         get_relevant_span(this_fi),
2945                         |lint| {
2946                             let mut expected_str = DiagnosticStyledString::new();
2947                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2948                             let mut found_str = DiagnosticStyledString::new();
2949                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2950
2951                             lint.build(if orig.get_name() == this_fi.ident.name {
2952                                 fluent::lint::builtin_clashing_extern_same_name
2953                             } else {
2954                                 fluent::lint::builtin_clashing_extern_diff_name
2955                             })
2956                             .set_arg("this_fi", this_fi.ident.name)
2957                             .set_arg("orig", orig.get_name())
2958                             .span_label(
2959                                 get_relevant_span(orig_fi),
2960                                 fluent::lint::previous_decl_label,
2961                             )
2962                             .span_label(get_relevant_span(this_fi), fluent::lint::mismatch_label)
2963                             // FIXME(davidtwco): translatable expected/found
2964                             .note_expected_found(&"", expected_str, &"", found_str)
2965                             .emit();
2966                         },
2967                     );
2968                 }
2969             }
2970         }
2971     }
2972 }
2973
2974 declare_lint! {
2975     /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
2976     /// which causes [undefined behavior].
2977     ///
2978     /// ### Example
2979     ///
2980     /// ```rust,no_run
2981     /// # #![allow(unused)]
2982     /// use std::ptr;
2983     /// unsafe {
2984     ///     let x = &*ptr::null::<i32>();
2985     ///     let x = ptr::addr_of!(*ptr::null::<i32>());
2986     ///     let x = *(0 as *const i32);
2987     /// }
2988     /// ```
2989     ///
2990     /// {{produces}}
2991     ///
2992     /// ### Explanation
2993     ///
2994     /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
2995     /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
2996     ///
2997     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2998     pub DEREF_NULLPTR,
2999     Warn,
3000     "detects when an null pointer is dereferenced"
3001 }
3002
3003 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3004
3005 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3006     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3007         /// test if expression is a null ptr
3008         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3009             match &expr.kind {
3010                 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3011                     if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3012                         return is_zero(expr) || is_null_ptr(cx, expr);
3013                     }
3014                 }
3015                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3016                 rustc_hir::ExprKind::Call(ref path, _) => {
3017                     if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3018                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3019                             return matches!(
3020                                 cx.tcx.get_diagnostic_name(def_id),
3021                                 Some(sym::ptr_null | sym::ptr_null_mut)
3022                             );
3023                         }
3024                     }
3025                 }
3026                 _ => {}
3027             }
3028             false
3029         }
3030
3031         /// test if expression is the literal `0`
3032         fn is_zero(expr: &hir::Expr<'_>) -> bool {
3033             match &expr.kind {
3034                 rustc_hir::ExprKind::Lit(ref lit) => {
3035                     if let LitKind::Int(a, _) = lit.node {
3036                         return a == 0;
3037                     }
3038                 }
3039                 _ => {}
3040             }
3041             false
3042         }
3043
3044         if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3045             if is_null_ptr(cx, expr_deref) {
3046                 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3047                     let mut err = lint.build(fluent::lint::builtin_deref_nullptr);
3048                     err.span_label(expr.span, fluent::lint::label);
3049                     err.emit();
3050                 });
3051             }
3052         }
3053     }
3054 }
3055
3056 declare_lint! {
3057     /// The `named_asm_labels` lint detects the use of named labels in the
3058     /// inline `asm!` macro.
3059     ///
3060     /// ### Example
3061     ///
3062     /// ```rust,compile_fail
3063     /// use std::arch::asm;
3064     ///
3065     /// fn main() {
3066     ///     unsafe {
3067     ///         asm!("foo: bar");
3068     ///     }
3069     /// }
3070     /// ```
3071     ///
3072     /// {{produces}}
3073     ///
3074     /// ### Explanation
3075     ///
3076     /// LLVM is allowed to duplicate inline assembly blocks for any
3077     /// reason, for example when it is in a function that gets inlined. Because
3078     /// of this, GNU assembler [local labels] *must* be used instead of labels
3079     /// with a name. Using named labels might cause assembler or linker errors.
3080     ///
3081     /// See the explanation in [Rust By Example] for more details.
3082     ///
3083     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3084     /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3085     pub NAMED_ASM_LABELS,
3086     Deny,
3087     "named labels in inline assembly",
3088 }
3089
3090 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3091
3092 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3093     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3094         if let hir::Expr {
3095             kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3096             ..
3097         } = expr
3098         {
3099             for (template_sym, template_snippet, template_span) in template_strs.iter() {
3100                 let template_str = template_sym.as_str();
3101                 let find_label_span = |needle: &str| -> Option<Span> {
3102                     if let Some(template_snippet) = template_snippet {
3103                         let snippet = template_snippet.as_str();
3104                         if let Some(pos) = snippet.find(needle) {
3105                             let end = pos
3106                                 + snippet[pos..]
3107                                     .find(|c| c == ':')
3108                                     .unwrap_or(snippet[pos..].len() - 1);
3109                             let inner = InnerSpan::new(pos, end);
3110                             return Some(template_span.from_inner(inner));
3111                         }
3112                     }
3113
3114                     None
3115                 };
3116
3117                 let mut found_labels = Vec::new();
3118
3119                 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3120                 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3121                 for statement in statements {
3122                     // If there's a comment, trim it from the statement
3123                     let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3124                     let mut start_idx = 0;
3125                     for (idx, _) in statement.match_indices(':') {
3126                         let possible_label = statement[start_idx..idx].trim();
3127                         let mut chars = possible_label.chars();
3128                         let Some(c) = chars.next() else {
3129                             // Empty string means a leading ':' in this section, which is not a label
3130                             break
3131                         };
3132                         // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3133                         if (c.is_alphabetic() || matches!(c, '.' | '_'))
3134                             && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3135                         {
3136                             found_labels.push(possible_label);
3137                         } else {
3138                             // If we encounter a non-label, there cannot be any further labels, so stop checking
3139                             break;
3140                         }
3141
3142                         start_idx = idx + 1;
3143                     }
3144                 }
3145
3146                 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3147
3148                 if found_labels.len() > 0 {
3149                     let spans = found_labels
3150                         .into_iter()
3151                         .filter_map(|label| find_label_span(label))
3152                         .collect::<Vec<Span>>();
3153                     // If there were labels but we couldn't find a span, combine the warnings and use the template span
3154                     let target_spans: MultiSpan =
3155                         if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3156
3157                     cx.lookup_with_diagnostics(
3158                             NAMED_ASM_LABELS,
3159                             Some(target_spans),
3160                             |diag| {
3161                                 diag.build(fluent::lint::builtin_asm_labels).emit();
3162                             },
3163                             BuiltinLintDiagnostics::NamedAsmLabel(
3164                                 "only local labels of the form `<number>:` should be used in inline asm"
3165                                     .to_string(),
3166                             ),
3167                         );
3168                 }
3169             }
3170         }
3171     }
3172 }