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         span: Span,
1368         vis_span: Span,
1369         exportable: bool,
1370     ) {
1371         let mut applicability = Applicability::MachineApplicable;
1372         if cx.tcx.visibility(def_id).is_public() && !cx.access_levels.is_reachable(def_id) {
1373             if vis_span.from_expansion() {
1374                 applicability = Applicability::MaybeIncorrect;
1375             }
1376             let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1377             cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1378                 let mut err = lint.build(fluent::lint::builtin_unreachable_pub);
1379                 err.set_arg("what", what);
1380
1381                 err.span_suggestion(
1382                     vis_span,
1383                     fluent::lint::suggestion,
1384                     "pub(crate)",
1385                     applicability,
1386                 );
1387                 if exportable {
1388                     err.help(fluent::lint::help);
1389                 }
1390                 err.emit();
1391             });
1392         }
1393     }
1394 }
1395
1396 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1397     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1398         // Do not warn for fake `use` statements.
1399         if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1400             return;
1401         }
1402         self.perform_lint(cx, "item", item.def_id, item.span, item.vis_span, true);
1403     }
1404
1405     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1406         self.perform_lint(
1407             cx,
1408             "item",
1409             foreign_item.def_id,
1410             foreign_item.span,
1411             foreign_item.vis_span,
1412             true,
1413         );
1414     }
1415
1416     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1417         let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1418         self.perform_lint(cx, "field", def_id, field.span, field.vis_span, false);
1419     }
1420
1421     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1422         // Only lint inherent impl items.
1423         if cx.tcx.associated_item(impl_item.def_id).trait_item_def_id.is_none() {
1424             self.perform_lint(
1425                 cx,
1426                 "item",
1427                 impl_item.def_id,
1428                 impl_item.span,
1429                 impl_item.vis_span,
1430                 false,
1431             );
1432         }
1433     }
1434 }
1435
1436 declare_lint! {
1437     /// The `type_alias_bounds` lint detects bounds in type aliases.
1438     ///
1439     /// ### Example
1440     ///
1441     /// ```rust
1442     /// type SendVec<T: Send> = Vec<T>;
1443     /// ```
1444     ///
1445     /// {{produces}}
1446     ///
1447     /// ### Explanation
1448     ///
1449     /// The trait bounds in a type alias are currently ignored, and should not
1450     /// be included to avoid confusion. This was previously allowed
1451     /// unintentionally; this may become a hard error in the future.
1452     TYPE_ALIAS_BOUNDS,
1453     Warn,
1454     "bounds in type aliases are not enforced"
1455 }
1456
1457 declare_lint_pass!(
1458     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1459     /// They are relevant when using associated types, but otherwise neither checked
1460     /// at definition site nor enforced at use site.
1461     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1462 );
1463
1464 impl TypeAliasBounds {
1465     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1466         match *qpath {
1467             hir::QPath::TypeRelative(ref ty, _) => {
1468                 // If this is a type variable, we found a `T::Assoc`.
1469                 match ty.kind {
1470                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1471                         matches!(path.res, Res::Def(DefKind::TyParam, _))
1472                     }
1473                     _ => false,
1474                 }
1475             }
1476             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1477         }
1478     }
1479
1480     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1481         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1482         // bound.  Let's see if this type does that.
1483
1484         // We use a HIR visitor to walk the type.
1485         use rustc_hir::intravisit::{self, Visitor};
1486         struct WalkAssocTypes<'a> {
1487             err: &'a mut Diagnostic,
1488         }
1489         impl Visitor<'_> for WalkAssocTypes<'_> {
1490             fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1491                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1492                     self.err.span_help(span, fluent::lint::builtin_type_alias_bounds_help);
1493                 }
1494                 intravisit::walk_qpath(self, qpath, id, span)
1495             }
1496         }
1497
1498         // Let's go for a walk!
1499         let mut visitor = WalkAssocTypes { err };
1500         visitor.visit_ty(ty);
1501     }
1502 }
1503
1504 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1505     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1506         let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1507             return
1508         };
1509         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1510             // Bounds are respected for `type X = impl Trait`
1511             return;
1512         }
1513         // There must not be a where clause
1514         if type_alias_generics.predicates.is_empty() {
1515             return;
1516         }
1517
1518         let mut where_spans = Vec::new();
1519         let mut inline_spans = Vec::new();
1520         let mut inline_sugg = Vec::new();
1521         for p in type_alias_generics.predicates {
1522             let span = p.span();
1523             if p.in_where_clause() {
1524                 where_spans.push(span);
1525             } else {
1526                 for b in p.bounds() {
1527                     inline_spans.push(b.span());
1528                 }
1529                 inline_sugg.push((span, String::new()));
1530             }
1531         }
1532
1533         let mut suggested_changing_assoc_types = false;
1534         if !where_spans.is_empty() {
1535             cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1536                 let mut err = lint.build(fluent::lint::builtin_type_alias_where_clause);
1537                 err.set_span(where_spans);
1538                 err.span_suggestion(
1539                     type_alias_generics.where_clause_span,
1540                     fluent::lint::suggestion,
1541                     "",
1542                     Applicability::MachineApplicable,
1543                 );
1544                 if !suggested_changing_assoc_types {
1545                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1546                     suggested_changing_assoc_types = true;
1547                 }
1548                 err.emit();
1549             });
1550         }
1551
1552         if !inline_spans.is_empty() {
1553             cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1554                 let mut err = lint.build(fluent::lint::builtin_type_alias_generic_bounds);
1555                 err.set_span(inline_spans);
1556                 err.multipart_suggestion(
1557                     fluent::lint::suggestion,
1558                     inline_sugg,
1559                     Applicability::MachineApplicable,
1560                 );
1561                 if !suggested_changing_assoc_types {
1562                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1563                 }
1564                 err.emit();
1565             });
1566         }
1567     }
1568 }
1569
1570 declare_lint_pass!(
1571     /// Lint constants that are erroneous.
1572     /// Without this lint, we might not get any diagnostic if the constant is
1573     /// unused within this crate, even though downstream crates can't use it
1574     /// without producing an error.
1575     UnusedBrokenConst => []
1576 );
1577
1578 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1579     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1580         match it.kind {
1581             hir::ItemKind::Const(_, body_id) => {
1582                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1583                 // trigger the query once for all constants since that will already report the errors
1584                 cx.tcx.ensure().const_eval_poly(def_id);
1585             }
1586             hir::ItemKind::Static(_, _, body_id) => {
1587                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1588                 cx.tcx.ensure().eval_static_initializer(def_id);
1589             }
1590             _ => {}
1591         }
1592     }
1593 }
1594
1595 declare_lint! {
1596     /// The `trivial_bounds` lint detects trait bounds that don't depend on
1597     /// any type parameters.
1598     ///
1599     /// ### Example
1600     ///
1601     /// ```rust
1602     /// #![feature(trivial_bounds)]
1603     /// pub struct A where i32: Copy;
1604     /// ```
1605     ///
1606     /// {{produces}}
1607     ///
1608     /// ### Explanation
1609     ///
1610     /// Usually you would not write a trait bound that you know is always
1611     /// true, or never true. However, when using macros, the macro may not
1612     /// know whether or not the constraint would hold or not at the time when
1613     /// generating the code. Currently, the compiler does not alert you if the
1614     /// constraint is always true, and generates an error if it is never true.
1615     /// The `trivial_bounds` feature changes this to be a warning in both
1616     /// cases, giving macros more freedom and flexibility to generate code,
1617     /// while still providing a signal when writing non-macro code that
1618     /// something is amiss.
1619     ///
1620     /// See [RFC 2056] for more details. This feature is currently only
1621     /// available on the nightly channel, see [tracking issue #48214].
1622     ///
1623     /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1624     /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1625     TRIVIAL_BOUNDS,
1626     Warn,
1627     "these bounds don't depend on an type parameters"
1628 }
1629
1630 declare_lint_pass!(
1631     /// Lint for trait and lifetime bounds that don't depend on type parameters
1632     /// which either do nothing, or stop the item from being used.
1633     TrivialConstraints => [TRIVIAL_BOUNDS]
1634 );
1635
1636 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1637     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1638         use rustc_middle::ty::visit::TypeVisitable;
1639         use rustc_middle::ty::PredicateKind::*;
1640
1641         if cx.tcx.features().trivial_bounds {
1642             let predicates = cx.tcx.predicates_of(item.def_id);
1643             for &(predicate, span) in predicates.predicates {
1644                 let predicate_kind_name = match predicate.kind().skip_binder() {
1645                     Trait(..) => "trait",
1646                     TypeOutlives(..) |
1647                     RegionOutlives(..) => "lifetime",
1648
1649                     // Ignore projections, as they can only be global
1650                     // if the trait bound is global
1651                     Projection(..) |
1652                     // Ignore bounds that a user can't type
1653                     WellFormed(..) |
1654                     ObjectSafe(..) |
1655                     ClosureKind(..) |
1656                     Subtype(..) |
1657                     Coerce(..) |
1658                     ConstEvaluatable(..) |
1659                     ConstEquate(..) |
1660                     TypeWellFormedFromEnv(..) => continue,
1661                 };
1662                 if predicate.is_global() {
1663                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1664                         lint.build(fluent::lint::builtin_trivial_bounds)
1665                             .set_arg("predicate_kind_name", predicate_kind_name)
1666                             .set_arg("predicate", predicate)
1667                             .emit();
1668                     });
1669                 }
1670             }
1671         }
1672     }
1673 }
1674
1675 declare_lint_pass!(
1676     /// Does nothing as a lint pass, but registers some `Lint`s
1677     /// which are used by other parts of the compiler.
1678     SoftLints => [
1679         WHILE_TRUE,
1680         BOX_POINTERS,
1681         NON_SHORTHAND_FIELD_PATTERNS,
1682         UNSAFE_CODE,
1683         MISSING_DOCS,
1684         MISSING_COPY_IMPLEMENTATIONS,
1685         MISSING_DEBUG_IMPLEMENTATIONS,
1686         ANONYMOUS_PARAMETERS,
1687         UNUSED_DOC_COMMENTS,
1688         NO_MANGLE_CONST_ITEMS,
1689         NO_MANGLE_GENERIC_ITEMS,
1690         MUTABLE_TRANSMUTES,
1691         UNSTABLE_FEATURES,
1692         UNREACHABLE_PUB,
1693         TYPE_ALIAS_BOUNDS,
1694         TRIVIAL_BOUNDS
1695     ]
1696 );
1697
1698 declare_lint! {
1699     /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1700     /// pattern], which is deprecated.
1701     ///
1702     /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1703     ///
1704     /// ### Example
1705     ///
1706     /// ```rust,edition2018
1707     /// let x = 123;
1708     /// match x {
1709     ///     0...100 => {}
1710     ///     _ => {}
1711     /// }
1712     /// ```
1713     ///
1714     /// {{produces}}
1715     ///
1716     /// ### Explanation
1717     ///
1718     /// The `...` range pattern syntax was changed to `..=` to avoid potential
1719     /// confusion with the [`..` range expression]. Use the new form instead.
1720     ///
1721     /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1722     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1723     Warn,
1724     "`...` range patterns are deprecated",
1725     @future_incompatible = FutureIncompatibleInfo {
1726         reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1727         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1728     };
1729 }
1730
1731 #[derive(Default)]
1732 pub struct EllipsisInclusiveRangePatterns {
1733     /// If `Some(_)`, suppress all subsequent pattern
1734     /// warnings for better diagnostics.
1735     node_id: Option<ast::NodeId>,
1736 }
1737
1738 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1739
1740 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1741     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1742         if self.node_id.is_some() {
1743             // Don't recursively warn about patterns inside range endpoints.
1744             return;
1745         }
1746
1747         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1748
1749         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1750         /// corresponding to the ellipsis.
1751         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1752             match &pat.kind {
1753                 PatKind::Range(
1754                     a,
1755                     Some(b),
1756                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1757                 ) => Some((a.as_deref(), b, *span)),
1758                 _ => None,
1759             }
1760         }
1761
1762         let (parenthesise, endpoints) = match &pat.kind {
1763             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1764             _ => (false, matches_ellipsis_pat(pat)),
1765         };
1766
1767         if let Some((start, end, join)) = endpoints {
1768             let msg = fluent::lint::builtin_ellipsis_inclusive_range_patterns;
1769             let suggestion = fluent::lint::suggestion;
1770             if parenthesise {
1771                 self.node_id = Some(pat.id);
1772                 let end = expr_to_string(&end);
1773                 let replace = match start {
1774                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1775                     None => format!("&(..={})", end),
1776                 };
1777                 if join.edition() >= Edition::Edition2021 {
1778                     let mut err = cx.sess().struct_span_err_with_code(
1779                         pat.span,
1780                         msg,
1781                         rustc_errors::error_code!(E0783),
1782                     );
1783                     err.span_suggestion(
1784                         pat.span,
1785                         suggestion,
1786                         replace,
1787                         Applicability::MachineApplicable,
1788                     )
1789                     .emit();
1790                 } else {
1791                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1792                         lint.build(msg)
1793                             .span_suggestion(
1794                                 pat.span,
1795                                 suggestion,
1796                                 replace,
1797                                 Applicability::MachineApplicable,
1798                             )
1799                             .emit();
1800                     });
1801                 }
1802             } else {
1803                 let replace = "..=";
1804                 if join.edition() >= Edition::Edition2021 {
1805                     let mut err = cx.sess().struct_span_err_with_code(
1806                         pat.span,
1807                         msg,
1808                         rustc_errors::error_code!(E0783),
1809                     );
1810                     err.span_suggestion_short(
1811                         join,
1812                         suggestion,
1813                         replace,
1814                         Applicability::MachineApplicable,
1815                     )
1816                     .emit();
1817                 } else {
1818                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1819                         lint.build(msg)
1820                             .span_suggestion_short(
1821                                 join,
1822                                 suggestion,
1823                                 replace,
1824                                 Applicability::MachineApplicable,
1825                             )
1826                             .emit();
1827                     });
1828                 }
1829             };
1830         }
1831     }
1832
1833     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1834         if let Some(node_id) = self.node_id {
1835             if pat.id == node_id {
1836                 self.node_id = None
1837             }
1838         }
1839     }
1840 }
1841
1842 declare_lint! {
1843     /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1844     /// that are not able to be run by the test harness because they are in a
1845     /// position where they are not nameable.
1846     ///
1847     /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1848     ///
1849     /// ### Example
1850     ///
1851     /// ```rust,test
1852     /// fn main() {
1853     ///     #[test]
1854     ///     fn foo() {
1855     ///         // This test will not fail because it does not run.
1856     ///         assert_eq!(1, 2);
1857     ///     }
1858     /// }
1859     /// ```
1860     ///
1861     /// {{produces}}
1862     ///
1863     /// ### Explanation
1864     ///
1865     /// In order for the test harness to run a test, the test function must be
1866     /// located in a position where it can be accessed from the crate root.
1867     /// This generally means it must be defined in a module, and not anywhere
1868     /// else such as inside another function. The compiler previously allowed
1869     /// this without an error, so a lint was added as an alert that a test is
1870     /// not being used. Whether or not this should be allowed has not yet been
1871     /// decided, see [RFC 2471] and [issue #36629].
1872     ///
1873     /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1874     /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1875     UNNAMEABLE_TEST_ITEMS,
1876     Warn,
1877     "detects an item that cannot be named being marked as `#[test_case]`",
1878     report_in_external_macro
1879 }
1880
1881 pub struct UnnameableTestItems {
1882     boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1883     items_nameable: bool,
1884 }
1885
1886 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1887
1888 impl UnnameableTestItems {
1889     pub fn new() -> Self {
1890         Self { boundary: None, items_nameable: true }
1891     }
1892 }
1893
1894 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1895     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1896         if self.items_nameable {
1897             if let hir::ItemKind::Mod(..) = it.kind {
1898             } else {
1899                 self.items_nameable = false;
1900                 self.boundary = Some(it.def_id);
1901             }
1902             return;
1903         }
1904
1905         let attrs = cx.tcx.hir().attrs(it.hir_id());
1906         if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1907             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1908                 lint.build(fluent::lint::builtin_unnameable_test_items).emit();
1909             });
1910         }
1911     }
1912
1913     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1914         if !self.items_nameable && self.boundary == Some(it.def_id) {
1915             self.items_nameable = true;
1916         }
1917     }
1918 }
1919
1920 declare_lint! {
1921     /// The `keyword_idents` lint detects edition keywords being used as an
1922     /// identifier.
1923     ///
1924     /// ### Example
1925     ///
1926     /// ```rust,edition2015,compile_fail
1927     /// #![deny(keyword_idents)]
1928     /// // edition 2015
1929     /// fn dyn() {}
1930     /// ```
1931     ///
1932     /// {{produces}}
1933     ///
1934     /// ### Explanation
1935     ///
1936     /// Rust [editions] allow the language to evolve without breaking
1937     /// backwards compatibility. This lint catches code that uses new keywords
1938     /// that are added to the language that are used as identifiers (such as a
1939     /// variable name, function name, etc.). If you switch the compiler to a
1940     /// new edition without updating the code, then it will fail to compile if
1941     /// you are using a new keyword as an identifier.
1942     ///
1943     /// You can manually change the identifiers to a non-keyword, or use a
1944     /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1945     ///
1946     /// This lint solves the problem automatically. It is "allow" by default
1947     /// because the code is perfectly valid in older editions. The [`cargo
1948     /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1949     /// and automatically apply the suggested fix from the compiler (which is
1950     /// to use a raw identifier). This provides a completely automated way to
1951     /// update old code for a new edition.
1952     ///
1953     /// [editions]: https://doc.rust-lang.org/edition-guide/
1954     /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1955     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1956     pub KEYWORD_IDENTS,
1957     Allow,
1958     "detects edition keywords being used as an identifier",
1959     @future_incompatible = FutureIncompatibleInfo {
1960         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1961         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1962     };
1963 }
1964
1965 declare_lint_pass!(
1966     /// Check for uses of edition keywords used as an identifier.
1967     KeywordIdents => [KEYWORD_IDENTS]
1968 );
1969
1970 struct UnderMacro(bool);
1971
1972 impl KeywordIdents {
1973     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1974         for tt in tokens.into_trees() {
1975             match tt {
1976                 // Only report non-raw idents.
1977                 TokenTree::Token(token) => {
1978                     if let Some((ident, false)) = token.ident() {
1979                         self.check_ident_token(cx, UnderMacro(true), ident);
1980                     }
1981                 }
1982                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1983             }
1984         }
1985     }
1986
1987     fn check_ident_token(
1988         &mut self,
1989         cx: &EarlyContext<'_>,
1990         UnderMacro(under_macro): UnderMacro,
1991         ident: Ident,
1992     ) {
1993         let next_edition = match cx.sess().edition() {
1994             Edition::Edition2015 => {
1995                 match ident.name {
1996                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1997
1998                     // rust-lang/rust#56327: Conservatively do not
1999                     // attempt to report occurrences of `dyn` within
2000                     // macro definitions or invocations, because `dyn`
2001                     // can legitimately occur as a contextual keyword
2002                     // in 2015 code denoting its 2018 meaning, and we
2003                     // do not want rustfix to inject bugs into working
2004                     // code by rewriting such occurrences.
2005                     //
2006                     // But if we see `dyn` outside of a macro, we know
2007                     // its precise role in the parsed AST and thus are
2008                     // assured this is truly an attempt to use it as
2009                     // an identifier.
2010                     kw::Dyn if !under_macro => Edition::Edition2018,
2011
2012                     _ => return,
2013                 }
2014             }
2015
2016             // There are no new keywords yet for the 2018 edition and beyond.
2017             _ => return,
2018         };
2019
2020         // Don't lint `r#foo`.
2021         if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2022             return;
2023         }
2024
2025         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2026             lint.build(fluent::lint::builtin_keyword_idents)
2027                 .set_arg("kw", ident.clone())
2028                 .set_arg("next", next_edition)
2029                 .span_suggestion(
2030                     ident.span,
2031                     fluent::lint::suggestion,
2032                     format!("r#{}", ident),
2033                     Applicability::MachineApplicable,
2034                 )
2035                 .emit();
2036         });
2037     }
2038 }
2039
2040 impl EarlyLintPass for KeywordIdents {
2041     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2042         self.check_tokens(cx, mac_def.body.inner_tokens());
2043     }
2044     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2045         self.check_tokens(cx, mac.args.inner_tokens());
2046     }
2047     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2048         self.check_ident_token(cx, UnderMacro(false), ident);
2049     }
2050 }
2051
2052 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2053
2054 impl ExplicitOutlivesRequirements {
2055     fn lifetimes_outliving_lifetime<'tcx>(
2056         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2057         index: u32,
2058     ) -> Vec<ty::Region<'tcx>> {
2059         inferred_outlives
2060             .iter()
2061             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2062                 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2063                     ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2064                     _ => None,
2065                 },
2066                 _ => None,
2067             })
2068             .collect()
2069     }
2070
2071     fn lifetimes_outliving_type<'tcx>(
2072         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2073         index: u32,
2074     ) -> Vec<ty::Region<'tcx>> {
2075         inferred_outlives
2076             .iter()
2077             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2078                 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2079                     a.is_param(index).then_some(b)
2080                 }
2081                 _ => None,
2082             })
2083             .collect()
2084     }
2085
2086     fn collect_outlives_bound_spans<'tcx>(
2087         &self,
2088         tcx: TyCtxt<'tcx>,
2089         bounds: &hir::GenericBounds<'_>,
2090         inferred_outlives: &[ty::Region<'tcx>],
2091     ) -> Vec<(usize, Span)> {
2092         use rustc_middle::middle::resolve_lifetime::Region;
2093
2094         bounds
2095             .iter()
2096             .enumerate()
2097             .filter_map(|(i, bound)| {
2098                 if let hir::GenericBound::Outlives(lifetime) = bound {
2099                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
2100                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2101                             if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
2102                         }),
2103                         _ => false,
2104                     };
2105                     is_inferred.then_some((i, bound.span()))
2106                 } else {
2107                     None
2108                 }
2109             })
2110             .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2111             .collect()
2112     }
2113
2114     fn consolidate_outlives_bound_spans(
2115         &self,
2116         lo: Span,
2117         bounds: &hir::GenericBounds<'_>,
2118         bound_spans: Vec<(usize, Span)>,
2119     ) -> Vec<Span> {
2120         if bounds.is_empty() {
2121             return Vec::new();
2122         }
2123         if bound_spans.len() == bounds.len() {
2124             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2125             // If all bounds are inferable, we want to delete the colon, so
2126             // start from just after the parameter (span passed as argument)
2127             vec![lo.to(last_bound_span)]
2128         } else {
2129             let mut merged = Vec::new();
2130             let mut last_merged_i = None;
2131
2132             let mut from_start = true;
2133             for (i, bound_span) in bound_spans {
2134                 match last_merged_i {
2135                     // If the first bound is inferable, our span should also eat the leading `+`.
2136                     None if i == 0 => {
2137                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2138                         last_merged_i = Some(0);
2139                     }
2140                     // If consecutive bounds are inferable, merge their spans
2141                     Some(h) if i == h + 1 => {
2142                         if let Some(tail) = merged.last_mut() {
2143                             // Also eat the trailing `+` if the first
2144                             // more-than-one bound is inferable
2145                             let to_span = if from_start && i < bounds.len() {
2146                                 bounds[i + 1].span().shrink_to_lo()
2147                             } else {
2148                                 bound_span
2149                             };
2150                             *tail = tail.to(to_span);
2151                             last_merged_i = Some(i);
2152                         } else {
2153                             bug!("another bound-span visited earlier");
2154                         }
2155                     }
2156                     _ => {
2157                         // When we find a non-inferable bound, subsequent inferable bounds
2158                         // won't be consecutive from the start (and we'll eat the leading
2159                         // `+` rather than the trailing one)
2160                         from_start = false;
2161                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2162                         last_merged_i = Some(i);
2163                     }
2164                 }
2165             }
2166             merged
2167         }
2168     }
2169 }
2170
2171 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2172     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2173         use rustc_middle::middle::resolve_lifetime::Region;
2174
2175         let def_id = item.def_id;
2176         if let hir::ItemKind::Struct(_, ref hir_generics)
2177         | hir::ItemKind::Enum(_, ref hir_generics)
2178         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2179         {
2180             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2181             if inferred_outlives.is_empty() {
2182                 return;
2183             }
2184
2185             let ty_generics = cx.tcx.generics_of(def_id);
2186
2187             let mut bound_count = 0;
2188             let mut lint_spans = Vec::new();
2189             let mut where_lint_spans = Vec::new();
2190             let mut dropped_predicate_count = 0;
2191             let num_predicates = hir_generics.predicates.len();
2192             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2193                 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2194                     hir::WherePredicate::RegionPredicate(predicate) => {
2195                         if let Some(Region::EarlyBound(index, ..)) =
2196                             cx.tcx.named_region(predicate.lifetime.hir_id)
2197                         {
2198                             (
2199                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2200                                 &predicate.bounds,
2201                                 predicate.span,
2202                                 predicate.in_where_clause,
2203                             )
2204                         } else {
2205                             continue;
2206                         }
2207                     }
2208                     hir::WherePredicate::BoundPredicate(predicate) => {
2209                         // FIXME we can also infer bounds on associated types,
2210                         // and should check for them here.
2211                         match predicate.bounded_ty.kind {
2212                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2213                                 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2214                                     continue
2215                                 };
2216                                 let index = ty_generics.param_def_id_to_index[&def_id];
2217                                 (
2218                                     Self::lifetimes_outliving_type(inferred_outlives, index),
2219                                     &predicate.bounds,
2220                                     predicate.span,
2221                                     predicate.origin == PredicateOrigin::WhereClause,
2222                                 )
2223                             }
2224                             _ => {
2225                                 continue;
2226                             }
2227                         }
2228                     }
2229                     _ => continue,
2230                 };
2231                 if relevant_lifetimes.is_empty() {
2232                     continue;
2233                 }
2234
2235                 let bound_spans =
2236                     self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2237                 bound_count += bound_spans.len();
2238
2239                 let drop_predicate = bound_spans.len() == bounds.len();
2240                 if drop_predicate {
2241                     dropped_predicate_count += 1;
2242                 }
2243
2244                 if drop_predicate && !in_where_clause {
2245                     lint_spans.push(span);
2246                 } else if drop_predicate && i + 1 < num_predicates {
2247                     // If all the bounds on a predicate were inferable and there are
2248                     // further predicates, we want to eat the trailing comma.
2249                     let next_predicate_span = hir_generics.predicates[i + 1].span();
2250                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2251                 } else {
2252                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2253                         span.shrink_to_lo(),
2254                         bounds,
2255                         bound_spans,
2256                     ));
2257                 }
2258             }
2259
2260             // If all predicates are inferable, drop the entire clause
2261             // (including the `where`)
2262             if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2263             {
2264                 let where_span = hir_generics.where_clause_span;
2265                 // Extend the where clause back to the closing `>` of the
2266                 // generics, except for tuple struct, which have the `where`
2267                 // after the fields of the struct.
2268                 let full_where_span =
2269                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2270                         where_span
2271                     } else {
2272                         hir_generics.span.shrink_to_hi().to(where_span)
2273                     };
2274                 lint_spans.push(full_where_span);
2275             } else {
2276                 lint_spans.extend(where_lint_spans);
2277             }
2278
2279             if !lint_spans.is_empty() {
2280                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2281                     lint.build(fluent::lint::builtin_explicit_outlives)
2282                         .set_arg("count", bound_count)
2283                         .multipart_suggestion(
2284                             fluent::lint::suggestion,
2285                             lint_spans
2286                                 .into_iter()
2287                                 .map(|span| (span, String::new()))
2288                                 .collect::<Vec<_>>(),
2289                             Applicability::MachineApplicable,
2290                         )
2291                         .emit();
2292                 });
2293             }
2294         }
2295     }
2296 }
2297
2298 declare_lint! {
2299     /// The `incomplete_features` lint detects unstable features enabled with
2300     /// the [`feature` attribute] that may function improperly in some or all
2301     /// cases.
2302     ///
2303     /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2304     ///
2305     /// ### Example
2306     ///
2307     /// ```rust
2308     /// #![feature(generic_const_exprs)]
2309     /// ```
2310     ///
2311     /// {{produces}}
2312     ///
2313     /// ### Explanation
2314     ///
2315     /// Although it is encouraged for people to experiment with unstable
2316     /// features, some of them are known to be incomplete or faulty. This lint
2317     /// is a signal that the feature has not yet been finished, and you may
2318     /// experience problems with it.
2319     pub INCOMPLETE_FEATURES,
2320     Warn,
2321     "incomplete features that may function improperly in some or all cases"
2322 }
2323
2324 declare_lint_pass!(
2325     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2326     IncompleteFeatures => [INCOMPLETE_FEATURES]
2327 );
2328
2329 impl EarlyLintPass for IncompleteFeatures {
2330     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2331         let features = cx.sess().features_untracked();
2332         features
2333             .declared_lang_features
2334             .iter()
2335             .map(|(name, span, _)| (name, span))
2336             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2337             .filter(|(&name, _)| features.incomplete(name))
2338             .for_each(|(&name, &span)| {
2339                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2340                     let mut builder = lint.build(fluent::lint::builtin_incomplete_features);
2341                     builder.set_arg("name", name);
2342                     if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2343                         builder.set_arg("n", n);
2344                         builder.note(fluent::lint::note);
2345                     }
2346                     if HAS_MIN_FEATURES.contains(&name) {
2347                         builder.help(fluent::lint::help);
2348                     }
2349                     builder.emit();
2350                 })
2351             });
2352     }
2353 }
2354
2355 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2356
2357 declare_lint! {
2358     /// The `invalid_value` lint detects creating a value that is not valid,
2359     /// such as a null reference.
2360     ///
2361     /// ### Example
2362     ///
2363     /// ```rust,no_run
2364     /// # #![allow(unused)]
2365     /// unsafe {
2366     ///     let x: &'static i32 = std::mem::zeroed();
2367     /// }
2368     /// ```
2369     ///
2370     /// {{produces}}
2371     ///
2372     /// ### Explanation
2373     ///
2374     /// In some situations the compiler can detect that the code is creating
2375     /// an invalid value, which should be avoided.
2376     ///
2377     /// In particular, this lint will check for improper use of
2378     /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2379     /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2380     /// lint should provide extra information to indicate what the problem is
2381     /// and a possible solution.
2382     ///
2383     /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2384     /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2385     /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2386     /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2387     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2388     pub INVALID_VALUE,
2389     Warn,
2390     "an invalid value is being created (such as a null reference)"
2391 }
2392
2393 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2394
2395 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2396     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2397         #[derive(Debug, Copy, Clone, PartialEq)]
2398         enum InitKind {
2399             Zeroed,
2400             Uninit,
2401         }
2402
2403         /// Information about why a type cannot be initialized this way.
2404         /// Contains an error message and optionally a span to point at.
2405         type InitError = (String, Option<Span>);
2406
2407         /// Test if this constant is all-0.
2408         fn is_zero(expr: &hir::Expr<'_>) -> bool {
2409             use hir::ExprKind::*;
2410             use rustc_ast::LitKind::*;
2411             match &expr.kind {
2412                 Lit(lit) => {
2413                     if let Int(i, _) = lit.node {
2414                         i == 0
2415                     } else {
2416                         false
2417                     }
2418                 }
2419                 Tup(tup) => tup.iter().all(is_zero),
2420                 _ => false,
2421             }
2422         }
2423
2424         /// Determine if this expression is a "dangerous initialization".
2425         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2426             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2427                 // Find calls to `mem::{uninitialized,zeroed}` methods.
2428                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2429                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2430                     match cx.tcx.get_diagnostic_name(def_id) {
2431                         Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2432                         Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2433                         Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2434                         _ => {}
2435                     }
2436                 }
2437             } else if let hir::ExprKind::MethodCall(_, ref args, _) = expr.kind {
2438                 // Find problematic calls to `MaybeUninit::assume_init`.
2439                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2440                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2441                     // This is a call to *some* method named `assume_init`.
2442                     // See if the `self` parameter is one of the dangerous constructors.
2443                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2444                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2445                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2446                             match cx.tcx.get_diagnostic_name(def_id) {
2447                                 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2448                                 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2449                                 _ => {}
2450                             }
2451                         }
2452                     }
2453                 }
2454             }
2455
2456             None
2457         }
2458
2459         /// Test if this enum has several actually "existing" variants.
2460         /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2461         fn is_multi_variant<'tcx>(adt: ty::AdtDef<'tcx>) -> bool {
2462             // As an approximation, we only count dataless variants. Those are definitely inhabited.
2463             let existing_variants = adt.variants().iter().filter(|v| v.fields.is_empty()).count();
2464             existing_variants > 1
2465         }
2466
2467         /// Return `Some` only if we are sure this type does *not*
2468         /// allow zero initialization.
2469         fn ty_find_init_error<'tcx>(
2470             cx: &LateContext<'tcx>,
2471             ty: Ty<'tcx>,
2472             init: InitKind,
2473         ) -> Option<InitError> {
2474             use rustc_type_ir::sty::TyKind::*;
2475             match ty.kind() {
2476                 // Primitive types that don't like 0 as a value.
2477                 Ref(..) => Some(("references must be non-null".to_string(), None)),
2478                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2479                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2480                 Never => Some(("the `!` type has no valid value".to_string(), None)),
2481                 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2482                 // raw ptr to dyn Trait
2483                 {
2484                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2485                 }
2486                 // Primitive types with other constraints.
2487                 Bool if init == InitKind::Uninit => {
2488                     Some(("booleans must be either `true` or `false`".to_string(), None))
2489                 }
2490                 Char if init == InitKind::Uninit => {
2491                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
2492                 }
2493                 // Recurse and checks for some compound types.
2494                 Adt(adt_def, substs) if !adt_def.is_union() => {
2495                     // First check if this ADT has a layout attribute (like `NonNull` and friends).
2496                     use std::ops::Bound;
2497                     match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
2498                         // We exploit here that `layout_scalar_valid_range` will never
2499                         // return `Bound::Excluded`.  (And we have tests checking that we
2500                         // handle the attribute correctly.)
2501                         (Bound::Included(lo), _) if lo > 0 => {
2502                             return Some((format!("`{}` must be non-null", ty), None));
2503                         }
2504                         (Bound::Included(_), _) | (_, Bound::Included(_))
2505                             if init == InitKind::Uninit =>
2506                         {
2507                             return Some((
2508                                 format!(
2509                                     "`{}` must be initialized inside its custom valid range",
2510                                     ty,
2511                                 ),
2512                                 None,
2513                             ));
2514                         }
2515                         _ => {}
2516                     }
2517                     // Now, recurse.
2518                     match adt_def.variants().len() {
2519                         0 => Some(("enums with no variants have no valid value".to_string(), None)),
2520                         1 => {
2521                             // Struct, or enum with exactly one variant.
2522                             // Proceed recursively, check all fields.
2523                             let variant = &adt_def.variant(VariantIdx::from_u32(0));
2524                             variant.fields.iter().find_map(|field| {
2525                                 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(
2526                                     |(mut msg, span)| {
2527                                         if span.is_none() {
2528                                             // Point to this field, should be helpful for figuring
2529                                             // out where the source of the error is.
2530                                             let span = cx.tcx.def_span(field.did);
2531                                             write!(
2532                                                 &mut msg,
2533                                                 " (in this {} field)",
2534                                                 adt_def.descr()
2535                                             )
2536                                             .unwrap();
2537                                             (msg, Some(span))
2538                                         } else {
2539                                             // Just forward.
2540                                             (msg, span)
2541                                         }
2542                                     },
2543                                 )
2544                             })
2545                         }
2546                         // Multi-variant enum.
2547                         _ => {
2548                             if init == InitKind::Uninit && is_multi_variant(*adt_def) {
2549                                 let span = cx.tcx.def_span(adt_def.did());
2550                                 Some((
2551                                     "enums have to be initialized to a variant".to_string(),
2552                                     Some(span),
2553                                 ))
2554                             } else {
2555                                 // In principle, for zero-initialization we could figure out which variant corresponds
2556                                 // to tag 0, and check that... but for now we just accept all zero-initializations.
2557                                 None
2558                             }
2559                         }
2560                     }
2561                 }
2562                 Tuple(..) => {
2563                     // Proceed recursively, check all fields.
2564                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2565                 }
2566                 Array(ty, len) => {
2567                     if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2568                         // Array length known at array non-empty -- recurse.
2569                         ty_find_init_error(cx, *ty, init)
2570                     } else {
2571                         // Empty array or size unknown.
2572                         None
2573                     }
2574                 }
2575                 // Conservative fallback.
2576                 _ => None,
2577             }
2578         }
2579
2580         if let Some(init) = is_dangerous_init(cx, expr) {
2581             // This conjures an instance of a type out of nothing,
2582             // using zeroed or uninitialized memory.
2583             // We are extremely conservative with what we warn about.
2584             let conjured_ty = cx.typeck_results().expr_ty(expr);
2585             if let Some((msg, span)) =
2586                 with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2587             {
2588                 // FIXME(davidtwco): make translatable
2589                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2590                     let mut err = lint.build(&format!(
2591                         "the type `{}` does not permit {}",
2592                         conjured_ty,
2593                         match init {
2594                             InitKind::Zeroed => "zero-initialization",
2595                             InitKind::Uninit => "being left uninitialized",
2596                         },
2597                     ));
2598                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2599                     err.span_label(
2600                         expr.span,
2601                         "help: use `MaybeUninit<T>` instead, \
2602                             and only call `assume_init` after initialization is done",
2603                     );
2604                     if let Some(span) = span {
2605                         err.span_note(span, &msg);
2606                     } else {
2607                         err.note(&msg);
2608                     }
2609                     err.emit();
2610                 });
2611             }
2612         }
2613     }
2614 }
2615
2616 declare_lint! {
2617     /// The `clashing_extern_declarations` lint detects when an `extern fn`
2618     /// has been declared with the same name but different types.
2619     ///
2620     /// ### Example
2621     ///
2622     /// ```rust
2623     /// mod m {
2624     ///     extern "C" {
2625     ///         fn foo();
2626     ///     }
2627     /// }
2628     ///
2629     /// extern "C" {
2630     ///     fn foo(_: u32);
2631     /// }
2632     /// ```
2633     ///
2634     /// {{produces}}
2635     ///
2636     /// ### Explanation
2637     ///
2638     /// Because two symbols of the same name cannot be resolved to two
2639     /// different functions at link time, and one function cannot possibly
2640     /// have two types, a clashing extern declaration is almost certainly a
2641     /// mistake. Check to make sure that the `extern` definitions are correct
2642     /// and equivalent, and possibly consider unifying them in one location.
2643     ///
2644     /// This lint does not run between crates because a project may have
2645     /// dependencies which both rely on the same extern function, but declare
2646     /// it in a different (but valid) way. For example, they may both declare
2647     /// an opaque type for one or more of the arguments (which would end up
2648     /// distinct types), or use types that are valid conversions in the
2649     /// language the `extern fn` is defined in. In these cases, the compiler
2650     /// can't say that the clashing declaration is incorrect.
2651     pub CLASHING_EXTERN_DECLARATIONS,
2652     Warn,
2653     "detects when an extern fn has been declared with the same name but different types"
2654 }
2655
2656 pub struct ClashingExternDeclarations {
2657     /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2658     /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2659     /// the symbol should be reported as a clashing declaration.
2660     // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2661     // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2662     seen_decls: FxHashMap<Symbol, HirId>,
2663 }
2664
2665 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2666 /// just from declaration itself. This is important because we don't want to report clashes on
2667 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2668 /// different name.
2669 enum SymbolName {
2670     /// The name of the symbol + the span of the annotation which introduced the link name.
2671     Link(Symbol, Span),
2672     /// No link name, so just the name of the symbol.
2673     Normal(Symbol),
2674 }
2675
2676 impl SymbolName {
2677     fn get_name(&self) -> Symbol {
2678         match self {
2679             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2680         }
2681     }
2682 }
2683
2684 impl ClashingExternDeclarations {
2685     pub(crate) fn new() -> Self {
2686         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2687     }
2688     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2689     /// for the item, return its HirId without updating the set.
2690     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2691         let did = fi.def_id.to_def_id();
2692         let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2693         let name = Symbol::intern(tcx.symbol_name(instance).name);
2694         if let Some(&hir_id) = self.seen_decls.get(&name) {
2695             // Avoid updating the map with the new entry when we do find a collision. We want to
2696             // make sure we're always pointing to the first definition as the previous declaration.
2697             // This lets us avoid emitting "knock-on" diagnostics.
2698             Some(hir_id)
2699         } else {
2700             self.seen_decls.insert(name, fi.hir_id())
2701         }
2702     }
2703
2704     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2705     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2706     /// symbol's name.
2707     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2708         if let Some((overridden_link_name, overridden_link_name_span)) =
2709             tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2710                 // FIXME: Instead of searching through the attributes again to get span
2711                 // information, we could have codegen_fn_attrs also give span information back for
2712                 // where the attribute was defined. However, until this is found to be a
2713                 // bottleneck, this does just fine.
2714                 (
2715                     overridden_link_name,
2716                     tcx.get_attr(fi.def_id.to_def_id(), sym::link_name).unwrap().span,
2717                 )
2718             })
2719         {
2720             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2721         } else {
2722             SymbolName::Normal(fi.ident.name)
2723         }
2724     }
2725
2726     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2727     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2728     /// with the same members (as the declarations shouldn't clash).
2729     fn structurally_same_type<'tcx>(
2730         cx: &LateContext<'tcx>,
2731         a: Ty<'tcx>,
2732         b: Ty<'tcx>,
2733         ckind: CItemKind,
2734     ) -> bool {
2735         fn structurally_same_type_impl<'tcx>(
2736             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2737             cx: &LateContext<'tcx>,
2738             a: Ty<'tcx>,
2739             b: Ty<'tcx>,
2740             ckind: CItemKind,
2741         ) -> bool {
2742             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2743             let tcx = cx.tcx;
2744
2745             // Given a transparent newtype, reach through and grab the inner
2746             // type unless the newtype makes the type non-null.
2747             let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2748                 let mut ty = ty;
2749                 loop {
2750                     if let ty::Adt(def, substs) = *ty.kind() {
2751                         let is_transparent = def.repr().transparent();
2752                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2753                         debug!(
2754                             "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2755                             ty, is_transparent, is_non_null
2756                         );
2757                         if is_transparent && !is_non_null {
2758                             debug_assert!(def.variants().len() == 1);
2759                             let v = &def.variant(VariantIdx::new(0));
2760                             ty = transparent_newtype_field(tcx, v)
2761                                 .expect(
2762                                     "single-variant transparent structure with zero-sized field",
2763                                 )
2764                                 .ty(tcx, substs);
2765                             continue;
2766                         }
2767                     }
2768                     debug!("non_transparent_ty -> {:?}", ty);
2769                     return ty;
2770                 }
2771             };
2772
2773             let a = non_transparent_ty(a);
2774             let b = non_transparent_ty(b);
2775
2776             if !seen_types.insert((a, b)) {
2777                 // We've encountered a cycle. There's no point going any further -- the types are
2778                 // structurally the same.
2779                 return true;
2780             }
2781             let tcx = cx.tcx;
2782             if a == b {
2783                 // All nominally-same types are structurally same, too.
2784                 true
2785             } else {
2786                 // Do a full, depth-first comparison between the two.
2787                 use rustc_type_ir::sty::TyKind::*;
2788                 let a_kind = a.kind();
2789                 let b_kind = b.kind();
2790
2791                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2792                     debug!("compare_layouts({:?}, {:?})", a, b);
2793                     let a_layout = &cx.layout_of(a)?.layout.abi();
2794                     let b_layout = &cx.layout_of(b)?.layout.abi();
2795                     debug!(
2796                         "comparing layouts: {:?} == {:?} = {}",
2797                         a_layout,
2798                         b_layout,
2799                         a_layout == b_layout
2800                     );
2801                     Ok(a_layout == b_layout)
2802                 };
2803
2804                 #[allow(rustc::usage_of_ty_tykind)]
2805                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2806                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2807                 };
2808
2809                 ensure_sufficient_stack(|| {
2810                     match (a_kind, b_kind) {
2811                         (Adt(a_def, _), Adt(b_def, _)) => {
2812                             // We can immediately rule out these types as structurally same if
2813                             // their layouts differ.
2814                             match compare_layouts(a, b) {
2815                                 Ok(false) => return false,
2816                                 _ => (), // otherwise, continue onto the full, fields comparison
2817                             }
2818
2819                             // Grab a flattened representation of all fields.
2820                             let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2821                             let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2822
2823                             // Perform a structural comparison for each field.
2824                             a_fields.eq_by(
2825                                 b_fields,
2826                                 |&ty::FieldDef { did: a_did, .. },
2827                                  &ty::FieldDef { did: b_did, .. }| {
2828                                     structurally_same_type_impl(
2829                                         seen_types,
2830                                         cx,
2831                                         tcx.type_of(a_did),
2832                                         tcx.type_of(b_did),
2833                                         ckind,
2834                                     )
2835                                 },
2836                             )
2837                         }
2838                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2839                             // For arrays, we also check the constness of the type.
2840                             a_const.kind() == b_const.kind()
2841                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2842                         }
2843                         (Slice(a_ty), Slice(b_ty)) => {
2844                             structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2845                         }
2846                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2847                             a_tymut.mutbl == b_tymut.mutbl
2848                                 && structurally_same_type_impl(
2849                                     seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2850                                 )
2851                         }
2852                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2853                             // For structural sameness, we don't need the region to be same.
2854                             a_mut == b_mut
2855                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2856                         }
2857                         (FnDef(..), FnDef(..)) => {
2858                             let a_poly_sig = a.fn_sig(tcx);
2859                             let b_poly_sig = b.fn_sig(tcx);
2860
2861                             // As we don't compare regions, skip_binder is fine.
2862                             let a_sig = a_poly_sig.skip_binder();
2863                             let b_sig = b_poly_sig.skip_binder();
2864
2865                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2866                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2867                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2868                                     structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2869                                 })
2870                                 && structurally_same_type_impl(
2871                                     seen_types,
2872                                     cx,
2873                                     a_sig.output(),
2874                                     b_sig.output(),
2875                                     ckind,
2876                                 )
2877                         }
2878                         (Tuple(a_substs), Tuple(b_substs)) => {
2879                             a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2880                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2881                             })
2882                         }
2883                         // For these, it's not quite as easy to define structural-sameness quite so easily.
2884                         // For the purposes of this lint, take the conservative approach and mark them as
2885                         // not structurally same.
2886                         (Dynamic(..), Dynamic(..))
2887                         | (Error(..), Error(..))
2888                         | (Closure(..), Closure(..))
2889                         | (Generator(..), Generator(..))
2890                         | (GeneratorWitness(..), GeneratorWitness(..))
2891                         | (Projection(..), Projection(..))
2892                         | (Opaque(..), Opaque(..)) => false,
2893
2894                         // These definitely should have been caught above.
2895                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2896
2897                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2898                         // enum layout optimisation is being applied.
2899                         (Adt(..), other_kind) | (other_kind, Adt(..))
2900                             if is_primitive_or_pointer(other_kind) =>
2901                         {
2902                             let (primitive, adt) =
2903                                 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2904                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2905                                 ty == primitive
2906                             } else {
2907                                 compare_layouts(a, b).unwrap_or(false)
2908                             }
2909                         }
2910                         // Otherwise, just compare the layouts. This may fail to lint for some
2911                         // incompatible types, but at the very least, will stop reads into
2912                         // uninitialised memory.
2913                         _ => compare_layouts(a, b).unwrap_or(false),
2914                     }
2915                 })
2916             }
2917         }
2918         let mut seen_types = FxHashSet::default();
2919         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2920     }
2921 }
2922
2923 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2924
2925 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2926     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2927         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2928         if let ForeignItemKind::Fn(..) = this_fi.kind {
2929             let tcx = cx.tcx;
2930             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2931                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2932                 let this_decl_ty = tcx.type_of(this_fi.def_id);
2933                 debug!(
2934                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2935                     existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2936                 );
2937                 // Check that the declarations match.
2938                 if !Self::structurally_same_type(
2939                     cx,
2940                     existing_decl_ty,
2941                     this_decl_ty,
2942                     CItemKind::Declaration,
2943                 ) {
2944                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
2945                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
2946
2947                     // We want to ensure that we use spans for both decls that include where the
2948                     // name was defined, whether that was from the link_name attribute or not.
2949                     let get_relevant_span =
2950                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2951                             SymbolName::Normal(_) => fi.span,
2952                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2953                         };
2954                     // Finally, emit the diagnostic.
2955                     tcx.struct_span_lint_hir(
2956                         CLASHING_EXTERN_DECLARATIONS,
2957                         this_fi.hir_id(),
2958                         get_relevant_span(this_fi),
2959                         |lint| {
2960                             let mut expected_str = DiagnosticStyledString::new();
2961                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2962                             let mut found_str = DiagnosticStyledString::new();
2963                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2964
2965                             lint.build(if orig.get_name() == this_fi.ident.name {
2966                                 fluent::lint::builtin_clashing_extern_same_name
2967                             } else {
2968                                 fluent::lint::builtin_clashing_extern_diff_name
2969                             })
2970                             .set_arg("this_fi", this_fi.ident.name)
2971                             .set_arg("orig", orig.get_name())
2972                             .span_label(
2973                                 get_relevant_span(orig_fi),
2974                                 fluent::lint::previous_decl_label,
2975                             )
2976                             .span_label(get_relevant_span(this_fi), fluent::lint::mismatch_label)
2977                             // FIXME(davidtwco): translatable expected/found
2978                             .note_expected_found(&"", expected_str, &"", found_str)
2979                             .emit();
2980                         },
2981                     );
2982                 }
2983             }
2984         }
2985     }
2986 }
2987
2988 declare_lint! {
2989     /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
2990     /// which causes [undefined behavior].
2991     ///
2992     /// ### Example
2993     ///
2994     /// ```rust,no_run
2995     /// # #![allow(unused)]
2996     /// use std::ptr;
2997     /// unsafe {
2998     ///     let x = &*ptr::null::<i32>();
2999     ///     let x = ptr::addr_of!(*ptr::null::<i32>());
3000     ///     let x = *(0 as *const i32);
3001     /// }
3002     /// ```
3003     ///
3004     /// {{produces}}
3005     ///
3006     /// ### Explanation
3007     ///
3008     /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3009     /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3010     ///
3011     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3012     pub DEREF_NULLPTR,
3013     Warn,
3014     "detects when an null pointer is dereferenced"
3015 }
3016
3017 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3018
3019 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3020     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3021         /// test if expression is a null ptr
3022         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3023             match &expr.kind {
3024                 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3025                     if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3026                         return is_zero(expr) || is_null_ptr(cx, expr);
3027                     }
3028                 }
3029                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3030                 rustc_hir::ExprKind::Call(ref path, _) => {
3031                     if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3032                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3033                             return matches!(
3034                                 cx.tcx.get_diagnostic_name(def_id),
3035                                 Some(sym::ptr_null | sym::ptr_null_mut)
3036                             );
3037                         }
3038                     }
3039                 }
3040                 _ => {}
3041             }
3042             false
3043         }
3044
3045         /// test if expression is the literal `0`
3046         fn is_zero(expr: &hir::Expr<'_>) -> bool {
3047             match &expr.kind {
3048                 rustc_hir::ExprKind::Lit(ref lit) => {
3049                     if let LitKind::Int(a, _) = lit.node {
3050                         return a == 0;
3051                     }
3052                 }
3053                 _ => {}
3054             }
3055             false
3056         }
3057
3058         if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3059             if is_null_ptr(cx, expr_deref) {
3060                 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3061                     let mut err = lint.build(fluent::lint::builtin_deref_nullptr);
3062                     err.span_label(expr.span, fluent::lint::label);
3063                     err.emit();
3064                 });
3065             }
3066         }
3067     }
3068 }
3069
3070 declare_lint! {
3071     /// The `named_asm_labels` lint detects the use of named labels in the
3072     /// inline `asm!` macro.
3073     ///
3074     /// ### Example
3075     ///
3076     /// ```rust,compile_fail
3077     /// use std::arch::asm;
3078     ///
3079     /// fn main() {
3080     ///     unsafe {
3081     ///         asm!("foo: bar");
3082     ///     }
3083     /// }
3084     /// ```
3085     ///
3086     /// {{produces}}
3087     ///
3088     /// ### Explanation
3089     ///
3090     /// LLVM is allowed to duplicate inline assembly blocks for any
3091     /// reason, for example when it is in a function that gets inlined. Because
3092     /// of this, GNU assembler [local labels] *must* be used instead of labels
3093     /// with a name. Using named labels might cause assembler or linker errors.
3094     ///
3095     /// See the explanation in [Rust By Example] for more details.
3096     ///
3097     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3098     /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3099     pub NAMED_ASM_LABELS,
3100     Deny,
3101     "named labels in inline assembly",
3102 }
3103
3104 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3105
3106 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3107     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3108         if let hir::Expr {
3109             kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3110             ..
3111         } = expr
3112         {
3113             for (template_sym, template_snippet, template_span) in template_strs.iter() {
3114                 let template_str = template_sym.as_str();
3115                 let find_label_span = |needle: &str| -> Option<Span> {
3116                     if let Some(template_snippet) = template_snippet {
3117                         let snippet = template_snippet.as_str();
3118                         if let Some(pos) = snippet.find(needle) {
3119                             let end = pos
3120                                 + snippet[pos..]
3121                                     .find(|c| c == ':')
3122                                     .unwrap_or(snippet[pos..].len() - 1);
3123                             let inner = InnerSpan::new(pos, end);
3124                             return Some(template_span.from_inner(inner));
3125                         }
3126                     }
3127
3128                     None
3129                 };
3130
3131                 let mut found_labels = Vec::new();
3132
3133                 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3134                 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3135                 for statement in statements {
3136                     // If there's a comment, trim it from the statement
3137                     let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3138                     let mut start_idx = 0;
3139                     for (idx, _) in statement.match_indices(':') {
3140                         let possible_label = statement[start_idx..idx].trim();
3141                         let mut chars = possible_label.chars();
3142                         let Some(c) = chars.next() else {
3143                             // Empty string means a leading ':' in this section, which is not a label
3144                             break
3145                         };
3146                         // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3147                         if (c.is_alphabetic() || matches!(c, '.' | '_'))
3148                             && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3149                         {
3150                             found_labels.push(possible_label);
3151                         } else {
3152                             // If we encounter a non-label, there cannot be any further labels, so stop checking
3153                             break;
3154                         }
3155
3156                         start_idx = idx + 1;
3157                     }
3158                 }
3159
3160                 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3161
3162                 if found_labels.len() > 0 {
3163                     let spans = found_labels
3164                         .into_iter()
3165                         .filter_map(|label| find_label_span(label))
3166                         .collect::<Vec<Span>>();
3167                     // If there were labels but we couldn't find a span, combine the warnings and use the template span
3168                     let target_spans: MultiSpan =
3169                         if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3170
3171                     cx.lookup_with_diagnostics(
3172                             NAMED_ASM_LABELS,
3173                             Some(target_spans),
3174                             |diag| {
3175                                 diag.build(fluent::lint::builtin_asm_labels).emit();
3176                             },
3177                             BuiltinLintDiagnostics::NamedAsmLabel(
3178                                 "only local labels of the form `<number>:` should be used in inline asm"
3179                                     .to_string(),
3180                             ),
3181                         );
3182                 }
3183             }
3184         }
3185     }
3186 }