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         sp: Span,
 556         article: &'static str,
 557         desc: &'static str,
 558     ) {
 559         // If we're building a test harness, then warning about
 560         // documentation is probably not really relevant right now.
 561         if cx.sess().opts.test {
 562             return;
 563         }
 564
 565         // `#[doc(hidden)]` disables missing_docs check.
 566         if self.doc_hidden() {
 567             return;
 568         }
 569
 570         // Only check publicly-visible items, using the result from the privacy pass.
 571         // It's an option so the crate root can also use this function (it doesn't
 572         // have a `NodeId`).
 573         if def_id != CRATE_DEF_ID {
 574             if !cx.access_levels.is_exported(def_id) {
 575                 return;
 576             }
 577         }
 578
 579         let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
 580         let has_doc = attrs.iter().any(has_doc);
 581         if !has_doc {
 582             cx.struct_span_lint(
 583                 MISSING_DOCS,
 584                 cx.tcx.sess.source_map().guess_head_span(sp),
 585                 |lint| {
 586                     lint.build(fluent::lint::builtin_missing_doc)
 587                         .set_arg("article", article)
 588                         .set_arg("desc", desc)
 589                         .emit();
 590                 },
 591             );
 592         }
 593     }
 594 }
 595
 596 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 597     fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
 598         let doc_hidden = self.doc_hidden()
 599             || attrs.iter().any(|attr| {
 600                 attr.has_name(sym::doc)
 601                     && match attr.meta_item_list() {
 602                         None => false,
 603                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 604                     }
 605             });
 606         self.doc_hidden_stack.push(doc_hidden);
 607     }
 608
 609     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
 610         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 611     }
 612
 613     fn check_crate(&mut self, cx: &LateContext<'_>) {
 614         self.check_missing_docs_attrs(
 615             cx,
 616             CRATE_DEF_ID,
 617             cx.tcx.def_span(CRATE_DEF_ID),
 618             "the",
 619             "crate",
 620         );
 621     }
 622
 623     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 624         match it.kind {
 625             hir::ItemKind::Trait(..) => {
 626                 // Issue #11592: traits are always considered exported, even when private.
 627                 if cx.tcx.visibility(it.def_id)
 628                     == ty::Visibility::Restricted(
 629                         cx.tcx.parent_module_from_def_id(it.def_id).to_def_id(),
 630                     )
 631                 {
 632                     return;
 633                 }
 634             }
 635             hir::ItemKind::TyAlias(..)
 636             | hir::ItemKind::Fn(..)
 637             | hir::ItemKind::Macro(..)
 638             | hir::ItemKind::Mod(..)
 639             | hir::ItemKind::Enum(..)
 640             | hir::ItemKind::Struct(..)
 641             | hir::ItemKind::Union(..)
 642             | hir::ItemKind::Const(..)
 643             | hir::ItemKind::Static(..) => {}
 644
 645             _ => return,
 646         };
 647
 648         let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
 649
 650         self.check_missing_docs_attrs(cx, it.def_id, it.span, article, desc);
 651     }
 652
 653     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
 654         let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
 655
 656         self.check_missing_docs_attrs(cx, trait_item.def_id, trait_item.span, article, desc);
 657     }
 658
 659     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
 660         // If the method is an impl for a trait, don't doc.
 661         if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
 662             return;
 663         }
 664
 665         // If the method is an impl for an item with docs_hidden, don't doc.
 666         if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
 667             let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
 668             let impl_ty = cx.tcx.type_of(parent);
 669             let outerdef = match impl_ty.kind() {
 670                 ty::Adt(def, _) => Some(def.did()),
 671                 ty::Foreign(def_id) => Some(*def_id),
 672                 _ => None,
 673             };
 674             let is_hidden = match outerdef {
 675                 Some(id) => cx.tcx.is_doc_hidden(id),
 676                 None => false,
 677             };
 678             if is_hidden {
 679                 return;
 680             }
 681         }
 682
 683         let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
 684         self.check_missing_docs_attrs(cx, impl_item.def_id, impl_item.span, article, desc);
 685     }
 686
 687     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
 688         let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
 689         self.check_missing_docs_attrs(cx, foreign_item.def_id, foreign_item.span, article, desc);
 690     }
 691
 692     fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
 693         if !sf.is_positional() {
 694             let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
 695             self.check_missing_docs_attrs(cx, def_id, sf.span, "a", "struct field")
 696         }
 697     }
 698
 699     fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
 700         self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), v.span, "a", "variant");
 701     }
 702 }
 703
 704 declare_lint! {
 705     /// The `missing_copy_implementations` lint detects potentially-forgotten
 706     /// implementations of [`Copy`].
 707     ///
 708     /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
 709     ///
 710     /// ### Example
 711     ///
 712     /// ```rust,compile_fail
 713     /// #![deny(missing_copy_implementations)]
 714     /// pub struct Foo {
 715     ///     pub field: i32
 716     /// }
 717     /// # fn main() {}
 718     /// ```
 719     ///
 720     /// {{produces}}
 721     ///
 722     /// ### Explanation
 723     ///
 724     /// Historically (before 1.0), types were automatically marked as `Copy`
 725     /// if possible. This was changed so that it required an explicit opt-in
 726     /// by implementing the `Copy` trait. As part of this change, a lint was
 727     /// added to alert if a copyable type was not marked `Copy`.
 728     ///
 729     /// This lint is "allow" by default because this code isn't bad; it is
 730     /// common to write newtypes like this specifically so that a `Copy` type
 731     /// is no longer `Copy`. `Copy` types can result in unintended copies of
 732     /// large data which can impact performance.
 733     pub MISSING_COPY_IMPLEMENTATIONS,
 734     Allow,
 735     "detects potentially-forgotten implementations of `Copy`"
 736 }
 737
 738 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 739
 740 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
 741     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 742         if !cx.access_levels.is_reachable(item.def_id) {
 743             return;
 744         }
 745         let (def, ty) = match item.kind {
 746             hir::ItemKind::Struct(_, ref ast_generics) => {
 747                 if !ast_generics.params.is_empty() {
 748                     return;
 749                 }
 750                 let def = cx.tcx.adt_def(item.def_id);
 751                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 752             }
 753             hir::ItemKind::Union(_, ref ast_generics) => {
 754                 if !ast_generics.params.is_empty() {
 755                     return;
 756                 }
 757                 let def = cx.tcx.adt_def(item.def_id);
 758                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 759             }
 760             hir::ItemKind::Enum(_, ref ast_generics) => {
 761                 if !ast_generics.params.is_empty() {
 762                     return;
 763                 }
 764                 let def = cx.tcx.adt_def(item.def_id);
 765                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 766             }
 767             _ => return,
 768         };
 769         if def.has_dtor(cx.tcx) {
 770             return;
 771         }
 772         let param_env = ty::ParamEnv::empty();
 773         if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
 774             return;
 775         }
 776         if can_type_implement_copy(
 777             cx.tcx,
 778             param_env,
 779             ty,
 780             traits::ObligationCause::misc(item.span, item.hir_id()),
 781         )
 782         .is_ok()
 783         {
 784             cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
 785                 lint.build(fluent::lint::builtin_missing_copy_impl).emit();
 786             })
 787         }
 788     }
 789 }
 790
 791 declare_lint! {
 792     /// The `missing_debug_implementations` lint detects missing
 793     /// implementations of [`fmt::Debug`].
 794     ///
 795     /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
 796     ///
 797     /// ### Example
 798     ///
 799     /// ```rust,compile_fail
 800     /// #![deny(missing_debug_implementations)]
 801     /// pub struct Foo;
 802     /// # fn main() {}
 803     /// ```
 804     ///
 805     /// {{produces}}
 806     ///
 807     /// ### Explanation
 808     ///
 809     /// Having a `Debug` implementation on all types can assist with
 810     /// debugging, as it provides a convenient way to format and display a
 811     /// value. Using the `#[derive(Debug)]` attribute will automatically
 812     /// generate a typical implementation, or a custom implementation can be
 813     /// added by manually implementing the `Debug` trait.
 814     ///
 815     /// This lint is "allow" by default because adding `Debug` to all types can
 816     /// have a negative impact on compile time and code size. It also requires
 817     /// boilerplate to be added to every type, which can be an impediment.
 818     MISSING_DEBUG_IMPLEMENTATIONS,
 819     Allow,
 820     "detects missing implementations of Debug"
 821 }
 822
 823 #[derive(Default)]
 824 pub struct MissingDebugImplementations {
 825     impling_types: Option<LocalDefIdSet>,
 826 }
 827
 828 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 829
 830 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 831     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 832         if !cx.access_levels.is_reachable(item.def_id) {
 833             return;
 834         }
 835
 836         match item.kind {
 837             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 838             _ => return,
 839         }
 840
 841         let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
 842             return
 843         };
 844
 845         if self.impling_types.is_none() {
 846             let mut impls = LocalDefIdSet::default();
 847             cx.tcx.for_each_impl(debug, |d| {
 848                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 849                     if let Some(def_id) = ty_def.did().as_local() {
 850                         impls.insert(def_id);
 851                     }
 852                 }
 853             });
 854
 855             self.impling_types = Some(impls);
 856             debug!("{:?}", self.impling_types);
 857         }
 858
 859         if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
 860             cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
 861                 lint.build(fluent::lint::builtin_missing_debug_impl)
 862                     .set_arg("debug", cx.tcx.def_path_str(debug))
 863                     .emit();
 864             });
 865         }
 866     }
 867 }
 868
 869 declare_lint! {
 870     /// The `anonymous_parameters` lint detects anonymous parameters in trait
 871     /// definitions.
 872     ///
 873     /// ### Example
 874     ///
 875     /// ```rust,edition2015,compile_fail
 876     /// #![deny(anonymous_parameters)]
 877     /// // edition 2015
 878     /// pub trait Foo {
 879     ///     fn foo(usize);
 880     /// }
 881     /// fn main() {}
 882     /// ```
 883     ///
 884     /// {{produces}}
 885     ///
 886     /// ### Explanation
 887     ///
 888     /// This syntax is mostly a historical accident, and can be worked around
 889     /// quite easily by adding an `_` pattern or a descriptive identifier:
 890     ///
 891     /// ```rust
 892     /// trait Foo {
 893     ///     fn foo(_: usize);
 894     /// }
 895     /// ```
 896     ///
 897     /// This syntax is now a hard error in the 2018 edition. In the 2015
 898     /// edition, this lint is "warn" by default. This lint
 899     /// enables the [`cargo fix`] tool with the `--edition` flag to
 900     /// automatically transition old code from the 2015 edition to 2018. The
 901     /// tool will run this lint and automatically apply the
 902     /// suggested fix from the compiler (which is to add `_` to each
 903     /// parameter). This provides a completely automated way to update old
 904     /// code for a new edition. See [issue #41686] for more details.
 905     ///
 906     /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
 907     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
 908     pub ANONYMOUS_PARAMETERS,
 909     Warn,
 910     "detects anonymous parameters",
 911     @future_incompatible = FutureIncompatibleInfo {
 912         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 913         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
 914     };
 915 }
 916
 917 declare_lint_pass!(
 918     /// Checks for use of anonymous parameters (RFC 1685).
 919     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 920 );
 921
 922 impl EarlyLintPass for AnonymousParameters {
 923     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 924         if cx.sess().edition() != Edition::Edition2015 {
 925             // This is a hard error in future editions; avoid linting and erroring
 926             return;
 927         }
 928         if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
 929             for arg in sig.decl.inputs.iter() {
 930                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 931                     if ident.name == kw::Empty {
 932                         cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
 933                             let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
 934
 935                             let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 936                                 (snip.as_str(), Applicability::MachineApplicable)
 937                             } else {
 938                                 ("<type>", Applicability::HasPlaceholders)
 939                             };
 940
 941                             lint.build(fluent::lint::builtin_anonymous_params)
 942                                 .span_suggestion(
 943                                     arg.pat.span,
 944                                     fluent::lint::suggestion,
 945                                     format!("_: {}", ty_snip),
 946                                     appl,
 947                                 )
 948                                 .emit();
 949                         })
 950                     }
 951                 }
 952             }
 953         }
 954     }
 955 }
 956
 957 /// Check for use of attributes which have been deprecated.
 958 #[derive(Clone)]
 959 pub struct DeprecatedAttr {
 960     // This is not free to compute, so we want to keep it around, rather than
 961     // compute it for every attribute.
 962     depr_attrs: Vec<&'static BuiltinAttribute>,
 963 }
 964
 965 impl_lint_pass!(DeprecatedAttr => []);
 966
 967 impl DeprecatedAttr {
 968     pub fn new() -> DeprecatedAttr {
 969         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 970     }
 971 }
 972
 973 impl EarlyLintPass for DeprecatedAttr {
 974     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 975         for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
 976             if attr.ident().map(|ident| ident.name) == Some(*name) {
 977                 if let &AttributeGate::Gated(
 978                     Stability::Deprecated(link, suggestion),
 979                     name,
 980                     reason,
 981                     _,
 982                 ) = gate
 983                 {
 984                     cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
 985                         // FIXME(davidtwco) translatable deprecated attr
 986                         lint.build(fluent::lint::builtin_deprecated_attr_link)
 987                             .set_arg("name", name)
 988                             .set_arg("reason", reason)
 989                             .set_arg("link", link)
 990                             .span_suggestion_short(
 991                                 attr.span,
 992                                 suggestion.map(|s| s.into()).unwrap_or(
 993                                     fluent::lint::builtin_deprecated_attr_default_suggestion,
 994                                 ),
 995                                 "",
 996                                 Applicability::MachineApplicable,
 997                             )
 998                             .emit();
 999                     });
1000                 }
1001                 return;
1002             }
1003         }
1004         if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1005             cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
1006                 lint.build(fluent::lint::builtin_deprecated_attr_used)
1007                     .set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
1008                     .span_suggestion_short(
1009                         attr.span,
1010                         fluent::lint::builtin_deprecated_attr_default_suggestion,
1011                         "",
1012                         Applicability::MachineApplicable,
1013                     )
1014                     .emit();
1015             });
1016         }
1017     }
1018 }
1019
1020 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1021     use rustc_ast::token::CommentKind;
1022
1023     let mut attrs = attrs.iter().peekable();
1024
1025     // Accumulate a single span for sugared doc comments.
1026     let mut sugared_span: Option<Span> = None;
1027
1028     while let Some(attr) = attrs.next() {
1029         let is_doc_comment = attr.is_doc_comment();
1030         if is_doc_comment {
1031             sugared_span =
1032                 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1033         }
1034
1035         if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1036             continue;
1037         }
1038
1039         let span = sugared_span.take().unwrap_or(attr.span);
1040
1041         if is_doc_comment || attr.has_name(sym::doc) {
1042             cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1043                 let mut err = lint.build(fluent::lint::builtin_unused_doc_comment);
1044                 err.set_arg("kind", node_kind);
1045                 err.span_label(node_span, fluent::lint::label);
1046                 match attr.kind {
1047                     AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1048                         err.help(fluent::lint::plain_help);
1049                     }
1050                     AttrKind::DocComment(CommentKind::Block, _) => {
1051                         err.help(fluent::lint::block_help);
1052                     }
1053                 }
1054                 err.emit();
1055             });
1056         }
1057     }
1058 }
1059
1060 impl EarlyLintPass for UnusedDocComment {
1061     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1062         let kind = match stmt.kind {
1063             ast::StmtKind::Local(..) => "statements",
1064             // Disabled pending discussion in #78306
1065             ast::StmtKind::Item(..) => return,
1066             // expressions will be reported by `check_expr`.
1067             ast::StmtKind::Empty
1068             | ast::StmtKind::Semi(_)
1069             | ast::StmtKind::Expr(_)
1070             | ast::StmtKind::MacCall(_) => return,
1071         };
1072
1073         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1074     }
1075
1076     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1077         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1078         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1079     }
1080
1081     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1082         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1083     }
1084
1085     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1086         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
1087     }
1088
1089     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1090         warn_if_doc(cx, block.span, "blocks", &block.attrs());
1091     }
1092
1093     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1094         if let ast::ItemKind::ForeignMod(_) = item.kind {
1095             warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1096         }
1097     }
1098 }
1099
1100 declare_lint! {
1101     /// The `no_mangle_const_items` lint detects any `const` items with the
1102     /// [`no_mangle` attribute].
1103     ///
1104     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1105     ///
1106     /// ### Example
1107     ///
1108     /// ```rust,compile_fail
1109     /// #[no_mangle]
1110     /// const FOO: i32 = 5;
1111     /// ```
1112     ///
1113     /// {{produces}}
1114     ///
1115     /// ### Explanation
1116     ///
1117     /// Constants do not have their symbols exported, and therefore, this
1118     /// probably means you meant to use a [`static`], not a [`const`].
1119     ///
1120     /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1121     /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1122     NO_MANGLE_CONST_ITEMS,
1123     Deny,
1124     "const items will not have their symbols exported"
1125 }
1126
1127 declare_lint! {
1128     /// The `no_mangle_generic_items` lint detects generic items that must be
1129     /// mangled.
1130     ///
1131     /// ### Example
1132     ///
1133     /// ```rust
1134     /// #[no_mangle]
1135     /// fn foo<T>(t: T) {
1136     ///
1137     /// }
1138     /// ```
1139     ///
1140     /// {{produces}}
1141     ///
1142     /// ### Explanation
1143     ///
1144     /// A function with generics must have its symbol mangled to accommodate
1145     /// the generic parameter. The [`no_mangle` attribute] has no effect in
1146     /// this situation, and should be removed.
1147     ///
1148     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1149     NO_MANGLE_GENERIC_ITEMS,
1150     Warn,
1151     "generic items must be mangled"
1152 }
1153
1154 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1155
1156 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1157     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1158         let attrs = cx.tcx.hir().attrs(it.hir_id());
1159         let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1160                                              impl_generics: Option<&hir::Generics<'_>>,
1161                                              generics: &hir::Generics<'_>,
1162                                              span| {
1163             for param in
1164                 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1165             {
1166                 match param.kind {
1167                     GenericParamKind::Lifetime { .. } => {}
1168                     GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1169                         cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1170                             lint.build(fluent::lint::builtin_no_mangle_generic)
1171                                 .span_suggestion_short(
1172                                     no_mangle_attr.span,
1173                                     fluent::lint::suggestion,
1174                                     "",
1175                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1176                                     // fix may be to monomorphize source by hand
1177                                     Applicability::MaybeIncorrect,
1178                                 )
1179                                 .emit();
1180                         });
1181                         break;
1182                     }
1183                 }
1184             }
1185         };
1186         match it.kind {
1187             hir::ItemKind::Fn(.., ref generics, _) => {
1188                 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1189                     check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1190                 }
1191             }
1192             hir::ItemKind::Const(..) => {
1193                 if cx.sess().contains_name(attrs, sym::no_mangle) {
1194                     // Const items do not refer to a particular location in memory, and therefore
1195                     // don't have anything to attach a symbol to
1196                     cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1197                         let mut err = lint.build(fluent::lint::builtin_const_no_mangle);
1198
1199                         // account for "pub const" (#45562)
1200                         let start = cx
1201                             .tcx
1202                             .sess
1203                             .source_map()
1204                             .span_to_snippet(it.span)
1205                             .map(|snippet| snippet.find("const").unwrap_or(0))
1206                             .unwrap_or(0) as u32;
1207                         // `const` is 5 chars
1208                         let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1209                         err.span_suggestion(
1210                             const_span,
1211                             fluent::lint::suggestion,
1212                             "pub static",
1213                             Applicability::MachineApplicable,
1214                         );
1215                         err.emit();
1216                     });
1217                 }
1218             }
1219             hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1220                 for it in *items {
1221                     if let hir::AssocItemKind::Fn { .. } = it.kind {
1222                         if let Some(no_mangle_attr) = cx
1223                             .sess()
1224                             .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1225                         {
1226                             check_no_mangle_on_generic_fn(
1227                                 no_mangle_attr,
1228                                 Some(generics),
1229                                 cx.tcx.hir().get_generics(it.id.def_id).unwrap(),
1230                                 it.span,
1231                             );
1232                         }
1233                     }
1234                 }
1235             }
1236             _ => {}
1237         }
1238     }
1239 }
1240
1241 declare_lint! {
1242     /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1243     /// T` because it is [undefined behavior].
1244     ///
1245     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1246     ///
1247     /// ### Example
1248     ///
1249     /// ```rust,compile_fail
1250     /// unsafe {
1251     ///     let y = std::mem::transmute::<&i32, &mut i32>(&5);
1252     /// }
1253     /// ```
1254     ///
1255     /// {{produces}}
1256     ///
1257     /// ### Explanation
1258     ///
1259     /// Certain assumptions are made about aliasing of data, and this transmute
1260     /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1261     ///
1262     /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1263     MUTABLE_TRANSMUTES,
1264     Deny,
1265     "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1266 }
1267
1268 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1269
1270 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1271     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1272         if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1273             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1274         {
1275             if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1276                 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
1277                     lint.build(fluent::lint::builtin_mutable_transmutes).emit();
1278                 });
1279             }
1280         }
1281
1282         fn get_transmute_from_to<'tcx>(
1283             cx: &LateContext<'tcx>,
1284             expr: &hir::Expr<'_>,
1285         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1286             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1287                 cx.qpath_res(qpath, expr.hir_id)
1288             } else {
1289                 return None;
1290             };
1291             if let Res::Def(DefKind::Fn, did) = def {
1292                 if !def_id_is_transmute(cx, did) {
1293                     return None;
1294                 }
1295                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1296                 let from = sig.inputs().skip_binder()[0];
1297                 let to = sig.output().skip_binder();
1298                 return Some((from, to));
1299             }
1300             None
1301         }
1302
1303         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1304             cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1305         }
1306     }
1307 }
1308
1309 declare_lint! {
1310     /// The `unstable_features` is deprecated and should no longer be used.
1311     UNSTABLE_FEATURES,
1312     Allow,
1313     "enabling unstable features (deprecated. do not use)"
1314 }
1315
1316 declare_lint_pass!(
1317     /// Forbids using the `#[feature(...)]` attribute
1318     UnstableFeatures => [UNSTABLE_FEATURES]
1319 );
1320
1321 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1322     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1323         if attr.has_name(sym::feature) {
1324             if let Some(items) = attr.meta_item_list() {
1325                 for item in items {
1326                     cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1327                         lint.build(fluent::lint::builtin_unstable_features).emit();
1328                     });
1329                 }
1330             }
1331         }
1332     }
1333 }
1334
1335 declare_lint! {
1336     /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1337     /// the crate root.
1338     ///
1339     /// ### Example
1340     ///
1341     /// ```rust,compile_fail
1342     /// #![deny(unreachable_pub)]
1343     /// mod foo {
1344     ///     pub mod bar {
1345     ///
1346     ///     }
1347     /// }
1348     /// ```
1349     ///
1350     /// {{produces}}
1351     ///
1352     /// ### Explanation
1353     ///
1354     /// A bare `pub` visibility may be misleading if the item is not actually
1355     /// publicly exported from the crate. The `pub(crate)` visibility is
1356     /// recommended to be used instead, which more clearly expresses the intent
1357     /// that the item is only visible within its own crate.
1358     ///
1359     /// This lint is "allow" by default because it will trigger for a large
1360     /// amount existing Rust code, and has some false-positives. Eventually it
1361     /// is desired for this to become warn-by-default.
1362     pub UNREACHABLE_PUB,
1363     Allow,
1364     "`pub` items not reachable from crate root"
1365 }
1366
1367 declare_lint_pass!(
1368     /// Lint for items marked `pub` that aren't reachable from other crates.
1369     UnreachablePub => [UNREACHABLE_PUB]
1370 );
1371
1372 impl UnreachablePub {
1373     fn perform_lint(
1374         &self,
1375         cx: &LateContext<'_>,
1376         what: &str,
1377         def_id: LocalDefId,
1378         span: Span,
1379         vis_span: Span,
1380         exportable: bool,
1381     ) {
1382         let mut applicability = Applicability::MachineApplicable;
1383         if cx.tcx.visibility(def_id).is_public() && !cx.access_levels.is_reachable(def_id) {
1384             if vis_span.from_expansion() {
1385                 applicability = Applicability::MaybeIncorrect;
1386             }
1387             let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1388             cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1389                 let mut err = lint.build(fluent::lint::builtin_unreachable_pub);
1390                 err.set_arg("what", what);
1391
1392                 err.span_suggestion(
1393                     vis_span,
1394                     fluent::lint::suggestion,
1395                     "pub(crate)",
1396                     applicability,
1397                 );
1398                 if exportable {
1399                     err.help(fluent::lint::help);
1400                 }
1401                 err.emit();
1402             });
1403         }
1404     }
1405 }
1406
1407 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1408     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1409         // Do not warn for fake `use` statements.
1410         if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1411             return;
1412         }
1413         self.perform_lint(cx, "item", item.def_id, item.span, item.vis_span, true);
1414     }
1415
1416     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1417         self.perform_lint(
1418             cx,
1419             "item",
1420             foreign_item.def_id,
1421             foreign_item.span,
1422             foreign_item.vis_span,
1423             true,
1424         );
1425     }
1426
1427     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1428         let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1429         self.perform_lint(cx, "field", def_id, field.span, field.vis_span, false);
1430     }
1431
1432     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1433         // Only lint inherent impl items.
1434         if cx.tcx.associated_item(impl_item.def_id).trait_item_def_id.is_none() {
1435             self.perform_lint(
1436                 cx,
1437                 "item",
1438                 impl_item.def_id,
1439                 impl_item.span,
1440                 impl_item.vis_span,
1441                 false,
1442             );
1443         }
1444     }
1445 }
1446
1447 declare_lint! {
1448     /// The `type_alias_bounds` lint detects bounds in type aliases.
1449     ///
1450     /// ### Example
1451     ///
1452     /// ```rust
1453     /// type SendVec<T: Send> = Vec<T>;
1454     /// ```
1455     ///
1456     /// {{produces}}
1457     ///
1458     /// ### Explanation
1459     ///
1460     /// The trait bounds in a type alias are currently ignored, and should not
1461     /// be included to avoid confusion. This was previously allowed
1462     /// unintentionally; this may become a hard error in the future.
1463     TYPE_ALIAS_BOUNDS,
1464     Warn,
1465     "bounds in type aliases are not enforced"
1466 }
1467
1468 declare_lint_pass!(
1469     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1470     /// They are relevant when using associated types, but otherwise neither checked
1471     /// at definition site nor enforced at use site.
1472     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1473 );
1474
1475 impl TypeAliasBounds {
1476     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1477         match *qpath {
1478             hir::QPath::TypeRelative(ref ty, _) => {
1479                 // If this is a type variable, we found a `T::Assoc`.
1480                 match ty.kind {
1481                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1482                         matches!(path.res, Res::Def(DefKind::TyParam, _))
1483                     }
1484                     _ => false,
1485                 }
1486             }
1487             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1488         }
1489     }
1490
1491     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1492         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1493         // bound.  Let's see if this type does that.
1494
1495         // We use a HIR visitor to walk the type.
1496         use rustc_hir::intravisit::{self, Visitor};
1497         struct WalkAssocTypes<'a> {
1498             err: &'a mut Diagnostic,
1499         }
1500         impl Visitor<'_> for WalkAssocTypes<'_> {
1501             fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1502                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1503                     self.err.span_help(span, fluent::lint::builtin_type_alias_bounds_help);
1504                 }
1505                 intravisit::walk_qpath(self, qpath, id, span)
1506             }
1507         }
1508
1509         // Let's go for a walk!
1510         let mut visitor = WalkAssocTypes { err };
1511         visitor.visit_ty(ty);
1512     }
1513 }
1514
1515 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1516     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1517         let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1518             return
1519         };
1520         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1521             // Bounds are respected for `type X = impl Trait`
1522             return;
1523         }
1524         // There must not be a where clause
1525         if type_alias_generics.predicates.is_empty() {
1526             return;
1527         }
1528
1529         let mut where_spans = Vec::new();
1530         let mut inline_spans = Vec::new();
1531         let mut inline_sugg = Vec::new();
1532         for p in type_alias_generics.predicates {
1533             let span = p.span();
1534             if p.in_where_clause() {
1535                 where_spans.push(span);
1536             } else {
1537                 for b in p.bounds() {
1538                     inline_spans.push(b.span());
1539                 }
1540                 inline_sugg.push((span, String::new()));
1541             }
1542         }
1543
1544         let mut suggested_changing_assoc_types = false;
1545         if !where_spans.is_empty() {
1546             cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1547                 let mut err = lint.build(fluent::lint::builtin_type_alias_where_clause);
1548                 err.set_span(where_spans);
1549                 err.span_suggestion(
1550                     type_alias_generics.where_clause_span,
1551                     fluent::lint::suggestion,
1552                     "",
1553                     Applicability::MachineApplicable,
1554                 );
1555                 if !suggested_changing_assoc_types {
1556                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1557                     suggested_changing_assoc_types = true;
1558                 }
1559                 err.emit();
1560             });
1561         }
1562
1563         if !inline_spans.is_empty() {
1564             cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1565                 let mut err = lint.build(fluent::lint::builtin_type_alias_generic_bounds);
1566                 err.set_span(inline_spans);
1567                 err.multipart_suggestion(
1568                     fluent::lint::suggestion,
1569                     inline_sugg,
1570                     Applicability::MachineApplicable,
1571                 );
1572                 if !suggested_changing_assoc_types {
1573                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1574                 }
1575                 err.emit();
1576             });
1577         }
1578     }
1579 }
1580
1581 declare_lint_pass!(
1582     /// Lint constants that are erroneous.
1583     /// Without this lint, we might not get any diagnostic if the constant is
1584     /// unused within this crate, even though downstream crates can't use it
1585     /// without producing an error.
1586     UnusedBrokenConst => []
1587 );
1588
1589 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1590     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1591         match it.kind {
1592             hir::ItemKind::Const(_, body_id) => {
1593                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1594                 // trigger the query once for all constants since that will already report the errors
1595                 cx.tcx.ensure().const_eval_poly(def_id);
1596             }
1597             hir::ItemKind::Static(_, _, body_id) => {
1598                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1599                 cx.tcx.ensure().eval_static_initializer(def_id);
1600             }
1601             _ => {}
1602         }
1603     }
1604 }
1605
1606 declare_lint! {
1607     /// The `trivial_bounds` lint detects trait bounds that don't depend on
1608     /// any type parameters.
1609     ///
1610     /// ### Example
1611     ///
1612     /// ```rust
1613     /// #![feature(trivial_bounds)]
1614     /// pub struct A where i32: Copy;
1615     /// ```
1616     ///
1617     /// {{produces}}
1618     ///
1619     /// ### Explanation
1620     ///
1621     /// Usually you would not write a trait bound that you know is always
1622     /// true, or never true. However, when using macros, the macro may not
1623     /// know whether or not the constraint would hold or not at the time when
1624     /// generating the code. Currently, the compiler does not alert you if the
1625     /// constraint is always true, and generates an error if it is never true.
1626     /// The `trivial_bounds` feature changes this to be a warning in both
1627     /// cases, giving macros more freedom and flexibility to generate code,
1628     /// while still providing a signal when writing non-macro code that
1629     /// something is amiss.
1630     ///
1631     /// See [RFC 2056] for more details. This feature is currently only
1632     /// available on the nightly channel, see [tracking issue #48214].
1633     ///
1634     /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1635     /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1636     TRIVIAL_BOUNDS,
1637     Warn,
1638     "these bounds don't depend on an type parameters"
1639 }
1640
1641 declare_lint_pass!(
1642     /// Lint for trait and lifetime bounds that don't depend on type parameters
1643     /// which either do nothing, or stop the item from being used.
1644     TrivialConstraints => [TRIVIAL_BOUNDS]
1645 );
1646
1647 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1648     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1649         use rustc_middle::ty::visit::TypeVisitable;
1650         use rustc_middle::ty::PredicateKind::*;
1651
1652         if cx.tcx.features().trivial_bounds {
1653             let predicates = cx.tcx.predicates_of(item.def_id);
1654             for &(predicate, span) in predicates.predicates {
1655                 let predicate_kind_name = match predicate.kind().skip_binder() {
1656                     Trait(..) => "trait",
1657                     TypeOutlives(..) |
1658                     RegionOutlives(..) => "lifetime",
1659
1660                     // Ignore projections, as they can only be global
1661                     // if the trait bound is global
1662                     Projection(..) |
1663                     // Ignore bounds that a user can't type
1664                     WellFormed(..) |
1665                     ObjectSafe(..) |
1666                     ClosureKind(..) |
1667                     Subtype(..) |
1668                     Coerce(..) |
1669                     ConstEvaluatable(..) |
1670                     ConstEquate(..) |
1671                     TypeWellFormedFromEnv(..) => continue,
1672                 };
1673                 if predicate.is_global() {
1674                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1675                         lint.build(fluent::lint::builtin_trivial_bounds)
1676                             .set_arg("predicate_kind_name", predicate_kind_name)
1677                             .set_arg("predicate", predicate)
1678                             .emit();
1679                     });
1680                 }
1681             }
1682         }
1683     }
1684 }
1685
1686 declare_lint_pass!(
1687     /// Does nothing as a lint pass, but registers some `Lint`s
1688     /// which are used by other parts of the compiler.
1689     SoftLints => [
1690         WHILE_TRUE,
1691         BOX_POINTERS,
1692         NON_SHORTHAND_FIELD_PATTERNS,
1693         UNSAFE_CODE,
1694         MISSING_DOCS,
1695         MISSING_COPY_IMPLEMENTATIONS,
1696         MISSING_DEBUG_IMPLEMENTATIONS,
1697         ANONYMOUS_PARAMETERS,
1698         UNUSED_DOC_COMMENTS,
1699         NO_MANGLE_CONST_ITEMS,
1700         NO_MANGLE_GENERIC_ITEMS,
1701         MUTABLE_TRANSMUTES,
1702         UNSTABLE_FEATURES,
1703         UNREACHABLE_PUB,
1704         TYPE_ALIAS_BOUNDS,
1705         TRIVIAL_BOUNDS
1706     ]
1707 );
1708
1709 declare_lint! {
1710     /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1711     /// pattern], which is deprecated.
1712     ///
1713     /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1714     ///
1715     /// ### Example
1716     ///
1717     /// ```rust,edition2018
1718     /// let x = 123;
1719     /// match x {
1720     ///     0...100 => {}
1721     ///     _ => {}
1722     /// }
1723     /// ```
1724     ///
1725     /// {{produces}}
1726     ///
1727     /// ### Explanation
1728     ///
1729     /// The `...` range pattern syntax was changed to `..=` to avoid potential
1730     /// confusion with the [`..` range expression]. Use the new form instead.
1731     ///
1732     /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1733     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1734     Warn,
1735     "`...` range patterns are deprecated",
1736     @future_incompatible = FutureIncompatibleInfo {
1737         reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1738         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1739     };
1740 }
1741
1742 #[derive(Default)]
1743 pub struct EllipsisInclusiveRangePatterns {
1744     /// If `Some(_)`, suppress all subsequent pattern
1745     /// warnings for better diagnostics.
1746     node_id: Option<ast::NodeId>,
1747 }
1748
1749 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1750
1751 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1752     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1753         if self.node_id.is_some() {
1754             // Don't recursively warn about patterns inside range endpoints.
1755             return;
1756         }
1757
1758         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1759
1760         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1761         /// corresponding to the ellipsis.
1762         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1763             match &pat.kind {
1764                 PatKind::Range(
1765                     a,
1766                     Some(b),
1767                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1768                 ) => Some((a.as_deref(), b, *span)),
1769                 _ => None,
1770             }
1771         }
1772
1773         let (parenthesise, endpoints) = match &pat.kind {
1774             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1775             _ => (false, matches_ellipsis_pat(pat)),
1776         };
1777
1778         if let Some((start, end, join)) = endpoints {
1779             let msg = fluent::lint::builtin_ellipsis_inclusive_range_patterns;
1780             let suggestion = fluent::lint::suggestion;
1781             if parenthesise {
1782                 self.node_id = Some(pat.id);
1783                 let end = expr_to_string(&end);
1784                 let replace = match start {
1785                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1786                     None => format!("&(..={})", end),
1787                 };
1788                 if join.edition() >= Edition::Edition2021 {
1789                     let mut err = cx.sess().struct_span_err_with_code(
1790                         pat.span,
1791                         msg,
1792                         rustc_errors::error_code!(E0783),
1793                     );
1794                     err.span_suggestion(
1795                         pat.span,
1796                         suggestion,
1797                         replace,
1798                         Applicability::MachineApplicable,
1799                     )
1800                     .emit();
1801                 } else {
1802                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1803                         lint.build(msg)
1804                             .span_suggestion(
1805                                 pat.span,
1806                                 suggestion,
1807                                 replace,
1808                                 Applicability::MachineApplicable,
1809                             )
1810                             .emit();
1811                     });
1812                 }
1813             } else {
1814                 let replace = "..=";
1815                 if join.edition() >= Edition::Edition2021 {
1816                     let mut err = cx.sess().struct_span_err_with_code(
1817                         pat.span,
1818                         msg,
1819                         rustc_errors::error_code!(E0783),
1820                     );
1821                     err.span_suggestion_short(
1822                         join,
1823                         suggestion,
1824                         replace,
1825                         Applicability::MachineApplicable,
1826                     )
1827                     .emit();
1828                 } else {
1829                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1830                         lint.build(msg)
1831                             .span_suggestion_short(
1832                                 join,
1833                                 suggestion,
1834                                 replace,
1835                                 Applicability::MachineApplicable,
1836                             )
1837                             .emit();
1838                     });
1839                 }
1840             };
1841         }
1842     }
1843
1844     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1845         if let Some(node_id) = self.node_id {
1846             if pat.id == node_id {
1847                 self.node_id = None
1848             }
1849         }
1850     }
1851 }
1852
1853 declare_lint! {
1854     /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1855     /// that are not able to be run by the test harness because they are in a
1856     /// position where they are not nameable.
1857     ///
1858     /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1859     ///
1860     /// ### Example
1861     ///
1862     /// ```rust,test
1863     /// fn main() {
1864     ///     #[test]
1865     ///     fn foo() {
1866     ///         // This test will not fail because it does not run.
1867     ///         assert_eq!(1, 2);
1868     ///     }
1869     /// }
1870     /// ```
1871     ///
1872     /// {{produces}}
1873     ///
1874     /// ### Explanation
1875     ///
1876     /// In order for the test harness to run a test, the test function must be
1877     /// located in a position where it can be accessed from the crate root.
1878     /// This generally means it must be defined in a module, and not anywhere
1879     /// else such as inside another function. The compiler previously allowed
1880     /// this without an error, so a lint was added as an alert that a test is
1881     /// not being used. Whether or not this should be allowed has not yet been
1882     /// decided, see [RFC 2471] and [issue #36629].
1883     ///
1884     /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1885     /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1886     UNNAMEABLE_TEST_ITEMS,
1887     Warn,
1888     "detects an item that cannot be named being marked as `#[test_case]`",
1889     report_in_external_macro
1890 }
1891
1892 pub struct UnnameableTestItems {
1893     boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1894     items_nameable: bool,
1895 }
1896
1897 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1898
1899 impl UnnameableTestItems {
1900     pub fn new() -> Self {
1901         Self { boundary: None, items_nameable: true }
1902     }
1903 }
1904
1905 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1906     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1907         if self.items_nameable {
1908             if let hir::ItemKind::Mod(..) = it.kind {
1909             } else {
1910                 self.items_nameable = false;
1911                 self.boundary = Some(it.def_id);
1912             }
1913             return;
1914         }
1915
1916         let attrs = cx.tcx.hir().attrs(it.hir_id());
1917         if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1918             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1919                 lint.build(fluent::lint::builtin_unnameable_test_items).emit();
1920             });
1921         }
1922     }
1923
1924     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1925         if !self.items_nameable && self.boundary == Some(it.def_id) {
1926             self.items_nameable = true;
1927         }
1928     }
1929 }
1930
1931 declare_lint! {
1932     /// The `keyword_idents` lint detects edition keywords being used as an
1933     /// identifier.
1934     ///
1935     /// ### Example
1936     ///
1937     /// ```rust,edition2015,compile_fail
1938     /// #![deny(keyword_idents)]
1939     /// // edition 2015
1940     /// fn dyn() {}
1941     /// ```
1942     ///
1943     /// {{produces}}
1944     ///
1945     /// ### Explanation
1946     ///
1947     /// Rust [editions] allow the language to evolve without breaking
1948     /// backwards compatibility. This lint catches code that uses new keywords
1949     /// that are added to the language that are used as identifiers (such as a
1950     /// variable name, function name, etc.). If you switch the compiler to a
1951     /// new edition without updating the code, then it will fail to compile if
1952     /// you are using a new keyword as an identifier.
1953     ///
1954     /// You can manually change the identifiers to a non-keyword, or use a
1955     /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1956     ///
1957     /// This lint solves the problem automatically. It is "allow" by default
1958     /// because the code is perfectly valid in older editions. The [`cargo
1959     /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1960     /// and automatically apply the suggested fix from the compiler (which is
1961     /// to use a raw identifier). This provides a completely automated way to
1962     /// update old code for a new edition.
1963     ///
1964     /// [editions]: https://doc.rust-lang.org/edition-guide/
1965     /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1966     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1967     pub KEYWORD_IDENTS,
1968     Allow,
1969     "detects edition keywords being used as an identifier",
1970     @future_incompatible = FutureIncompatibleInfo {
1971         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1972         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1973     };
1974 }
1975
1976 declare_lint_pass!(
1977     /// Check for uses of edition keywords used as an identifier.
1978     KeywordIdents => [KEYWORD_IDENTS]
1979 );
1980
1981 struct UnderMacro(bool);
1982
1983 impl KeywordIdents {
1984     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1985         for tt in tokens.into_trees() {
1986             match tt {
1987                 // Only report non-raw idents.
1988                 TokenTree::Token(token) => {
1989                     if let Some((ident, false)) = token.ident() {
1990                         self.check_ident_token(cx, UnderMacro(true), ident);
1991                     }
1992                 }
1993                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1994             }
1995         }
1996     }
1997
1998     fn check_ident_token(
1999         &mut self,
2000         cx: &EarlyContext<'_>,
2001         UnderMacro(under_macro): UnderMacro,
2002         ident: Ident,
2003     ) {
2004         let next_edition = match cx.sess().edition() {
2005             Edition::Edition2015 => {
2006                 match ident.name {
2007                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
2008
2009                     // rust-lang/rust#56327: Conservatively do not
2010                     // attempt to report occurrences of `dyn` within
2011                     // macro definitions or invocations, because `dyn`
2012                     // can legitimately occur as a contextual keyword
2013                     // in 2015 code denoting its 2018 meaning, and we
2014                     // do not want rustfix to inject bugs into working
2015                     // code by rewriting such occurrences.
2016                     //
2017                     // But if we see `dyn` outside of a macro, we know
2018                     // its precise role in the parsed AST and thus are
2019                     // assured this is truly an attempt to use it as
2020                     // an identifier.
2021                     kw::Dyn if !under_macro => Edition::Edition2018,
2022
2023                     _ => return,
2024                 }
2025             }
2026
2027             // There are no new keywords yet for the 2018 edition and beyond.
2028             _ => return,
2029         };
2030
2031         // Don't lint `r#foo`.
2032         if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2033             return;
2034         }
2035
2036         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2037             lint.build(fluent::lint::builtin_keyword_idents)
2038                 .set_arg("kw", ident.clone())
2039                 .set_arg("next", next_edition)
2040                 .span_suggestion(
2041                     ident.span,
2042                     fluent::lint::suggestion,
2043                     format!("r#{}", ident),
2044                     Applicability::MachineApplicable,
2045                 )
2046                 .emit();
2047         });
2048     }
2049 }
2050
2051 impl EarlyLintPass for KeywordIdents {
2052     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2053         self.check_tokens(cx, mac_def.body.inner_tokens());
2054     }
2055     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2056         self.check_tokens(cx, mac.args.inner_tokens());
2057     }
2058     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2059         self.check_ident_token(cx, UnderMacro(false), ident);
2060     }
2061 }
2062
2063 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2064
2065 impl ExplicitOutlivesRequirements {
2066     fn lifetimes_outliving_lifetime<'tcx>(
2067         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2068         index: u32,
2069     ) -> Vec<ty::Region<'tcx>> {
2070         inferred_outlives
2071             .iter()
2072             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2073                 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2074                     ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2075                     _ => None,
2076                 },
2077                 _ => None,
2078             })
2079             .collect()
2080     }
2081
2082     fn lifetimes_outliving_type<'tcx>(
2083         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2084         index: u32,
2085     ) -> Vec<ty::Region<'tcx>> {
2086         inferred_outlives
2087             .iter()
2088             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2089                 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2090                     a.is_param(index).then_some(b)
2091                 }
2092                 _ => None,
2093             })
2094             .collect()
2095     }
2096
2097     fn collect_outlives_bound_spans<'tcx>(
2098         &self,
2099         tcx: TyCtxt<'tcx>,
2100         bounds: &hir::GenericBounds<'_>,
2101         inferred_outlives: &[ty::Region<'tcx>],
2102     ) -> Vec<(usize, Span)> {
2103         use rustc_middle::middle::resolve_lifetime::Region;
2104
2105         bounds
2106             .iter()
2107             .enumerate()
2108             .filter_map(|(i, bound)| {
2109                 if let hir::GenericBound::Outlives(lifetime) = bound {
2110                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
2111                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2112                             if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
2113                         }),
2114                         _ => false,
2115                     };
2116                     is_inferred.then_some((i, bound.span()))
2117                 } else {
2118                     None
2119                 }
2120             })
2121             .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2122             .collect()
2123     }
2124
2125     fn consolidate_outlives_bound_spans(
2126         &self,
2127         lo: Span,
2128         bounds: &hir::GenericBounds<'_>,
2129         bound_spans: Vec<(usize, Span)>,
2130     ) -> Vec<Span> {
2131         if bounds.is_empty() {
2132             return Vec::new();
2133         }
2134         if bound_spans.len() == bounds.len() {
2135             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2136             // If all bounds are inferable, we want to delete the colon, so
2137             // start from just after the parameter (span passed as argument)
2138             vec![lo.to(last_bound_span)]
2139         } else {
2140             let mut merged = Vec::new();
2141             let mut last_merged_i = None;
2142
2143             let mut from_start = true;
2144             for (i, bound_span) in bound_spans {
2145                 match last_merged_i {
2146                     // If the first bound is inferable, our span should also eat the leading `+`.
2147                     None if i == 0 => {
2148                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2149                         last_merged_i = Some(0);
2150                     }
2151                     // If consecutive bounds are inferable, merge their spans
2152                     Some(h) if i == h + 1 => {
2153                         if let Some(tail) = merged.last_mut() {
2154                             // Also eat the trailing `+` if the first
2155                             // more-than-one bound is inferable
2156                             let to_span = if from_start && i < bounds.len() {
2157                                 bounds[i + 1].span().shrink_to_lo()
2158                             } else {
2159                                 bound_span
2160                             };
2161                             *tail = tail.to(to_span);
2162                             last_merged_i = Some(i);
2163                         } else {
2164                             bug!("another bound-span visited earlier");
2165                         }
2166                     }
2167                     _ => {
2168                         // When we find a non-inferable bound, subsequent inferable bounds
2169                         // won't be consecutive from the start (and we'll eat the leading
2170                         // `+` rather than the trailing one)
2171                         from_start = false;
2172                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2173                         last_merged_i = Some(i);
2174                     }
2175                 }
2176             }
2177             merged
2178         }
2179     }
2180 }
2181
2182 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2183     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2184         use rustc_middle::middle::resolve_lifetime::Region;
2185
2186         let def_id = item.def_id;
2187         if let hir::ItemKind::Struct(_, ref hir_generics)
2188         | hir::ItemKind::Enum(_, ref hir_generics)
2189         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2190         {
2191             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2192             if inferred_outlives.is_empty() {
2193                 return;
2194             }
2195
2196             let ty_generics = cx.tcx.generics_of(def_id);
2197
2198             let mut bound_count = 0;
2199             let mut lint_spans = Vec::new();
2200             let mut where_lint_spans = Vec::new();
2201             let mut dropped_predicate_count = 0;
2202             let num_predicates = hir_generics.predicates.len();
2203             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2204                 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2205                     hir::WherePredicate::RegionPredicate(predicate) => {
2206                         if let Some(Region::EarlyBound(index, ..)) =
2207                             cx.tcx.named_region(predicate.lifetime.hir_id)
2208                         {
2209                             (
2210                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2211                                 &predicate.bounds,
2212                                 predicate.span,
2213                                 predicate.in_where_clause,
2214                             )
2215                         } else {
2216                             continue;
2217                         }
2218                     }
2219                     hir::WherePredicate::BoundPredicate(predicate) => {
2220                         // FIXME we can also infer bounds on associated types,
2221                         // and should check for them here.
2222                         match predicate.bounded_ty.kind {
2223                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2224                                 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2225                                     continue
2226                                 };
2227                                 let index = ty_generics.param_def_id_to_index[&def_id];
2228                                 (
2229                                     Self::lifetimes_outliving_type(inferred_outlives, index),
2230                                     &predicate.bounds,
2231                                     predicate.span,
2232                                     predicate.origin == PredicateOrigin::WhereClause,
2233                                 )
2234                             }
2235                             _ => {
2236                                 continue;
2237                             }
2238                         }
2239                     }
2240                     _ => continue,
2241                 };
2242                 if relevant_lifetimes.is_empty() {
2243                     continue;
2244                 }
2245
2246                 let bound_spans =
2247                     self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2248                 bound_count += bound_spans.len();
2249
2250                 let drop_predicate = bound_spans.len() == bounds.len();
2251                 if drop_predicate {
2252                     dropped_predicate_count += 1;
2253                 }
2254
2255                 if drop_predicate && !in_where_clause {
2256                     lint_spans.push(span);
2257                 } else if drop_predicate && i + 1 < num_predicates {
2258                     // If all the bounds on a predicate were inferable and there are
2259                     // further predicates, we want to eat the trailing comma.
2260                     let next_predicate_span = hir_generics.predicates[i + 1].span();
2261                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2262                 } else {
2263                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2264                         span.shrink_to_lo(),
2265                         bounds,
2266                         bound_spans,
2267                     ));
2268                 }
2269             }
2270
2271             // If all predicates are inferable, drop the entire clause
2272             // (including the `where`)
2273             if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2274             {
2275                 let where_span = hir_generics.where_clause_span;
2276                 // Extend the where clause back to the closing `>` of the
2277                 // generics, except for tuple struct, which have the `where`
2278                 // after the fields of the struct.
2279                 let full_where_span =
2280                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2281                         where_span
2282                     } else {
2283                         hir_generics.span.shrink_to_hi().to(where_span)
2284                     };
2285                 lint_spans.push(full_where_span);
2286             } else {
2287                 lint_spans.extend(where_lint_spans);
2288             }
2289
2290             if !lint_spans.is_empty() {
2291                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2292                     lint.build(fluent::lint::builtin_explicit_outlives)
2293                         .set_arg("count", bound_count)
2294                         .multipart_suggestion(
2295                             fluent::lint::suggestion,
2296                             lint_spans
2297                                 .into_iter()
2298                                 .map(|span| (span, String::new()))
2299                                 .collect::<Vec<_>>(),
2300                             Applicability::MachineApplicable,
2301                         )
2302                         .emit();
2303                 });
2304             }
2305         }
2306     }
2307 }
2308
2309 declare_lint! {
2310     /// The `incomplete_features` lint detects unstable features enabled with
2311     /// the [`feature` attribute] that may function improperly in some or all
2312     /// cases.
2313     ///
2314     /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2315     ///
2316     /// ### Example
2317     ///
2318     /// ```rust
2319     /// #![feature(generic_const_exprs)]
2320     /// ```
2321     ///
2322     /// {{produces}}
2323     ///
2324     /// ### Explanation
2325     ///
2326     /// Although it is encouraged for people to experiment with unstable
2327     /// features, some of them are known to be incomplete or faulty. This lint
2328     /// is a signal that the feature has not yet been finished, and you may
2329     /// experience problems with it.
2330     pub INCOMPLETE_FEATURES,
2331     Warn,
2332     "incomplete features that may function improperly in some or all cases"
2333 }
2334
2335 declare_lint_pass!(
2336     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2337     IncompleteFeatures => [INCOMPLETE_FEATURES]
2338 );
2339
2340 impl EarlyLintPass for IncompleteFeatures {
2341     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2342         let features = cx.sess().features_untracked();
2343         features
2344             .declared_lang_features
2345             .iter()
2346             .map(|(name, span, _)| (name, span))
2347             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2348             .filter(|(&name, _)| features.incomplete(name))
2349             .for_each(|(&name, &span)| {
2350                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2351                     let mut builder = lint.build(fluent::lint::builtin_incomplete_features);
2352                     builder.set_arg("name", name);
2353                     if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2354                         builder.set_arg("n", n);
2355                         builder.note(fluent::lint::note);
2356                     }
2357                     if HAS_MIN_FEATURES.contains(&name) {
2358                         builder.help(fluent::lint::help);
2359                     }
2360                     builder.emit();
2361                 })
2362             });
2363     }
2364 }
2365
2366 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2367
2368 declare_lint! {
2369     /// The `invalid_value` lint detects creating a value that is not valid,
2370     /// such as a null reference.
2371     ///
2372     /// ### Example
2373     ///
2374     /// ```rust,no_run
2375     /// # #![allow(unused)]
2376     /// unsafe {
2377     ///     let x: &'static i32 = std::mem::zeroed();
2378     /// }
2379     /// ```
2380     ///
2381     /// {{produces}}
2382     ///
2383     /// ### Explanation
2384     ///
2385     /// In some situations the compiler can detect that the code is creating
2386     /// an invalid value, which should be avoided.
2387     ///
2388     /// In particular, this lint will check for improper use of
2389     /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2390     /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2391     /// lint should provide extra information to indicate what the problem is
2392     /// and a possible solution.
2393     ///
2394     /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2395     /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2396     /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2397     /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2398     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2399     pub INVALID_VALUE,
2400     Warn,
2401     "an invalid value is being created (such as a null reference)"
2402 }
2403
2404 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2405
2406 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2407     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2408         #[derive(Debug, Copy, Clone, PartialEq)]
2409         enum InitKind {
2410             Zeroed,
2411             Uninit,
2412         }
2413
2414         /// Information about why a type cannot be initialized this way.
2415         /// Contains an error message and optionally a span to point at.
2416         type InitError = (String, Option<Span>);
2417
2418         /// Test if this constant is all-0.
2419         fn is_zero(expr: &hir::Expr<'_>) -> bool {
2420             use hir::ExprKind::*;
2421             use rustc_ast::LitKind::*;
2422             match &expr.kind {
2423                 Lit(lit) => {
2424                     if let Int(i, _) = lit.node {
2425                         i == 0
2426                     } else {
2427                         false
2428                     }
2429                 }
2430                 Tup(tup) => tup.iter().all(is_zero),
2431                 _ => false,
2432             }
2433         }
2434
2435         /// Determine if this expression is a "dangerous initialization".
2436         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2437             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2438                 // Find calls to `mem::{uninitialized,zeroed}` methods.
2439                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2440                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2441                     match cx.tcx.get_diagnostic_name(def_id) {
2442                         Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2443                         Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2444                         Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2445                         _ => {}
2446                     }
2447                 }
2448             } else if let hir::ExprKind::MethodCall(_, ref args, _) = expr.kind {
2449                 // Find problematic calls to `MaybeUninit::assume_init`.
2450                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2451                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2452                     // This is a call to *some* method named `assume_init`.
2453                     // See if the `self` parameter is one of the dangerous constructors.
2454                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2455                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2456                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2457                             match cx.tcx.get_diagnostic_name(def_id) {
2458                                 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2459                                 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2460                                 _ => {}
2461                             }
2462                         }
2463                     }
2464                 }
2465             }
2466
2467             None
2468         }
2469
2470         /// Test if this enum has several actually "existing" variants.
2471         /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2472         fn is_multi_variant<'tcx>(adt: ty::AdtDef<'tcx>) -> bool {
2473             // As an approximation, we only count dataless variants. Those are definitely inhabited.
2474             let existing_variants = adt.variants().iter().filter(|v| v.fields.is_empty()).count();
2475             existing_variants > 1
2476         }
2477
2478         /// Return `Some` only if we are sure this type does *not*
2479         /// allow zero initialization.
2480         fn ty_find_init_error<'tcx>(
2481             cx: &LateContext<'tcx>,
2482             ty: Ty<'tcx>,
2483             init: InitKind,
2484         ) -> Option<InitError> {
2485             use rustc_type_ir::sty::TyKind::*;
2486             match ty.kind() {
2487                 // Primitive types that don't like 0 as a value.
2488                 Ref(..) => Some(("references must be non-null".to_string(), None)),
2489                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2490                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2491                 Never => Some(("the `!` type has no valid value".to_string(), None)),
2492                 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2493                 // raw ptr to dyn Trait
2494                 {
2495                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2496                 }
2497                 // Primitive types with other constraints.
2498                 Bool if init == InitKind::Uninit => {
2499                     Some(("booleans must be either `true` or `false`".to_string(), None))
2500                 }
2501                 Char if init == InitKind::Uninit => {
2502                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
2503                 }
2504                 // Recurse and checks for some compound types.
2505                 Adt(adt_def, substs) if !adt_def.is_union() => {
2506                     // First check if this ADT has a layout attribute (like `NonNull` and friends).
2507                     use std::ops::Bound;
2508                     match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
2509                         // We exploit here that `layout_scalar_valid_range` will never
2510                         // return `Bound::Excluded`.  (And we have tests checking that we
2511                         // handle the attribute correctly.)
2512                         (Bound::Included(lo), _) if lo > 0 => {
2513                             return Some((format!("`{}` must be non-null", ty), None));
2514                         }
2515                         (Bound::Included(_), _) | (_, Bound::Included(_))
2516                             if init == InitKind::Uninit =>
2517                         {
2518                             return Some((
2519                                 format!(
2520                                     "`{}` must be initialized inside its custom valid range",
2521                                     ty,
2522                                 ),
2523                                 None,
2524                             ));
2525                         }
2526                         _ => {}
2527                     }
2528                     // Now, recurse.
2529                     match adt_def.variants().len() {
2530                         0 => Some(("enums with no variants have no valid value".to_string(), None)),
2531                         1 => {
2532                             // Struct, or enum with exactly one variant.
2533                             // Proceed recursively, check all fields.
2534                             let variant = &adt_def.variant(VariantIdx::from_u32(0));
2535                             variant.fields.iter().find_map(|field| {
2536                                 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(
2537                                     |(mut msg, span)| {
2538                                         if span.is_none() {
2539                                             // Point to this field, should be helpful for figuring
2540                                             // out where the source of the error is.
2541                                             let span = cx.tcx.def_span(field.did);
2542                                             write!(
2543                                                 &mut msg,
2544                                                 " (in this {} field)",
2545                                                 adt_def.descr()
2546                                             )
2547                                             .unwrap();
2548                                             (msg, Some(span))
2549                                         } else {
2550                                             // Just forward.
2551                                             (msg, span)
2552                                         }
2553                                     },
2554                                 )
2555                             })
2556                         }
2557                         // Multi-variant enum.
2558                         _ => {
2559                             if init == InitKind::Uninit && is_multi_variant(*adt_def) {
2560                                 let span = cx.tcx.def_span(adt_def.did());
2561                                 Some((
2562                                     "enums have to be initialized to a variant".to_string(),
2563                                     Some(span),
2564                                 ))
2565                             } else {
2566                                 // In principle, for zero-initialization we could figure out which variant corresponds
2567                                 // to tag 0, and check that... but for now we just accept all zero-initializations.
2568                                 None
2569                             }
2570                         }
2571                     }
2572                 }
2573                 Tuple(..) => {
2574                     // Proceed recursively, check all fields.
2575                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2576                 }
2577                 Array(ty, len) => {
2578                     if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2579                         // Array length known at array non-empty -- recurse.
2580                         ty_find_init_error(cx, *ty, init)
2581                     } else {
2582                         // Empty array or size unknown.
2583                         None
2584                     }
2585                 }
2586                 // Conservative fallback.
2587                 _ => None,
2588             }
2589         }
2590
2591         if let Some(init) = is_dangerous_init(cx, expr) {
2592             // This conjures an instance of a type out of nothing,
2593             // using zeroed or uninitialized memory.
2594             // We are extremely conservative with what we warn about.
2595             let conjured_ty = cx.typeck_results().expr_ty(expr);
2596             if let Some((msg, span)) =
2597                 with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2598             {
2599                 // FIXME(davidtwco): make translatable
2600                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2601                     let mut err = lint.build(&format!(
2602                         "the type `{}` does not permit {}",
2603                         conjured_ty,
2604                         match init {
2605                             InitKind::Zeroed => "zero-initialization",
2606                             InitKind::Uninit => "being left uninitialized",
2607                         },
2608                     ));
2609                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2610                     err.span_label(
2611                         expr.span,
2612                         "help: use `MaybeUninit<T>` instead, \
2613                             and only call `assume_init` after initialization is done",
2614                     );
2615                     if let Some(span) = span {
2616                         err.span_note(span, &msg);
2617                     } else {
2618                         err.note(&msg);
2619                     }
2620                     err.emit();
2621                 });
2622             }
2623         }
2624     }
2625 }
2626
2627 declare_lint! {
2628     /// The `clashing_extern_declarations` lint detects when an `extern fn`
2629     /// has been declared with the same name but different types.
2630     ///
2631     /// ### Example
2632     ///
2633     /// ```rust
2634     /// mod m {
2635     ///     extern "C" {
2636     ///         fn foo();
2637     ///     }
2638     /// }
2639     ///
2640     /// extern "C" {
2641     ///     fn foo(_: u32);
2642     /// }
2643     /// ```
2644     ///
2645     /// {{produces}}
2646     ///
2647     /// ### Explanation
2648     ///
2649     /// Because two symbols of the same name cannot be resolved to two
2650     /// different functions at link time, and one function cannot possibly
2651     /// have two types, a clashing extern declaration is almost certainly a
2652     /// mistake. Check to make sure that the `extern` definitions are correct
2653     /// and equivalent, and possibly consider unifying them in one location.
2654     ///
2655     /// This lint does not run between crates because a project may have
2656     /// dependencies which both rely on the same extern function, but declare
2657     /// it in a different (but valid) way. For example, they may both declare
2658     /// an opaque type for one or more of the arguments (which would end up
2659     /// distinct types), or use types that are valid conversions in the
2660     /// language the `extern fn` is defined in. In these cases, the compiler
2661     /// can't say that the clashing declaration is incorrect.
2662     pub CLASHING_EXTERN_DECLARATIONS,
2663     Warn,
2664     "detects when an extern fn has been declared with the same name but different types"
2665 }
2666
2667 pub struct ClashingExternDeclarations {
2668     /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2669     /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2670     /// the symbol should be reported as a clashing declaration.
2671     // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2672     // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2673     seen_decls: FxHashMap<Symbol, HirId>,
2674 }
2675
2676 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2677 /// just from declaration itself. This is important because we don't want to report clashes on
2678 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2679 /// different name.
2680 enum SymbolName {
2681     /// The name of the symbol + the span of the annotation which introduced the link name.
2682     Link(Symbol, Span),
2683     /// No link name, so just the name of the symbol.
2684     Normal(Symbol),
2685 }
2686
2687 impl SymbolName {
2688     fn get_name(&self) -> Symbol {
2689         match self {
2690             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2691         }
2692     }
2693 }
2694
2695 impl ClashingExternDeclarations {
2696     pub(crate) fn new() -> Self {
2697         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2698     }
2699     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2700     /// for the item, return its HirId without updating the set.
2701     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2702         let did = fi.def_id.to_def_id();
2703         let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2704         let name = Symbol::intern(tcx.symbol_name(instance).name);
2705         if let Some(&hir_id) = self.seen_decls.get(&name) {
2706             // Avoid updating the map with the new entry when we do find a collision. We want to
2707             // make sure we're always pointing to the first definition as the previous declaration.
2708             // This lets us avoid emitting "knock-on" diagnostics.
2709             Some(hir_id)
2710         } else {
2711             self.seen_decls.insert(name, fi.hir_id())
2712         }
2713     }
2714
2715     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2716     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2717     /// symbol's name.
2718     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2719         if let Some((overridden_link_name, overridden_link_name_span)) =
2720             tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2721                 // FIXME: Instead of searching through the attributes again to get span
2722                 // information, we could have codegen_fn_attrs also give span information back for
2723                 // where the attribute was defined. However, until this is found to be a
2724                 // bottleneck, this does just fine.
2725                 (
2726                     overridden_link_name,
2727                     tcx.get_attr(fi.def_id.to_def_id(), sym::link_name).unwrap().span,
2728                 )
2729             })
2730         {
2731             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2732         } else {
2733             SymbolName::Normal(fi.ident.name)
2734         }
2735     }
2736
2737     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2738     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2739     /// with the same members (as the declarations shouldn't clash).
2740     fn structurally_same_type<'tcx>(
2741         cx: &LateContext<'tcx>,
2742         a: Ty<'tcx>,
2743         b: Ty<'tcx>,
2744         ckind: CItemKind,
2745     ) -> bool {
2746         fn structurally_same_type_impl<'tcx>(
2747             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2748             cx: &LateContext<'tcx>,
2749             a: Ty<'tcx>,
2750             b: Ty<'tcx>,
2751             ckind: CItemKind,
2752         ) -> bool {
2753             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2754             let tcx = cx.tcx;
2755
2756             // Given a transparent newtype, reach through and grab the inner
2757             // type unless the newtype makes the type non-null.
2758             let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2759                 let mut ty = ty;
2760                 loop {
2761                     if let ty::Adt(def, substs) = *ty.kind() {
2762                         let is_transparent = def.repr().transparent();
2763                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2764                         debug!(
2765                             "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2766                             ty, is_transparent, is_non_null
2767                         );
2768                         if is_transparent && !is_non_null {
2769                             debug_assert!(def.variants().len() == 1);
2770                             let v = &def.variant(VariantIdx::new(0));
2771                             ty = transparent_newtype_field(tcx, v)
2772                                 .expect(
2773                                     "single-variant transparent structure with zero-sized field",
2774                                 )
2775                                 .ty(tcx, substs);
2776                             continue;
2777                         }
2778                     }
2779                     debug!("non_transparent_ty -> {:?}", ty);
2780                     return ty;
2781                 }
2782             };
2783
2784             let a = non_transparent_ty(a);
2785             let b = non_transparent_ty(b);
2786
2787             if !seen_types.insert((a, b)) {
2788                 // We've encountered a cycle. There's no point going any further -- the types are
2789                 // structurally the same.
2790                 return true;
2791             }
2792             let tcx = cx.tcx;
2793             if a == b {
2794                 // All nominally-same types are structurally same, too.
2795                 true
2796             } else {
2797                 // Do a full, depth-first comparison between the two.
2798                 use rustc_type_ir::sty::TyKind::*;
2799                 let a_kind = a.kind();
2800                 let b_kind = b.kind();
2801
2802                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2803                     debug!("compare_layouts({:?}, {:?})", a, b);
2804                     let a_layout = &cx.layout_of(a)?.layout.abi();
2805                     let b_layout = &cx.layout_of(b)?.layout.abi();
2806                     debug!(
2807                         "comparing layouts: {:?} == {:?} = {}",
2808                         a_layout,
2809                         b_layout,
2810                         a_layout == b_layout
2811                     );
2812                     Ok(a_layout == b_layout)
2813                 };
2814
2815                 #[allow(rustc::usage_of_ty_tykind)]
2816                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2817                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2818                 };
2819
2820                 ensure_sufficient_stack(|| {
2821                     match (a_kind, b_kind) {
2822                         (Adt(a_def, _), Adt(b_def, _)) => {
2823                             // We can immediately rule out these types as structurally same if
2824                             // their layouts differ.
2825                             match compare_layouts(a, b) {
2826                                 Ok(false) => return false,
2827                                 _ => (), // otherwise, continue onto the full, fields comparison
2828                             }
2829
2830                             // Grab a flattened representation of all fields.
2831                             let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2832                             let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2833
2834                             // Perform a structural comparison for each field.
2835                             a_fields.eq_by(
2836                                 b_fields,
2837                                 |&ty::FieldDef { did: a_did, .. },
2838                                  &ty::FieldDef { did: b_did, .. }| {
2839                                     structurally_same_type_impl(
2840                                         seen_types,
2841                                         cx,
2842                                         tcx.type_of(a_did),
2843                                         tcx.type_of(b_did),
2844                                         ckind,
2845                                     )
2846                                 },
2847                             )
2848                         }
2849                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2850                             // For arrays, we also check the constness of the type.
2851                             a_const.kind() == b_const.kind()
2852                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2853                         }
2854                         (Slice(a_ty), Slice(b_ty)) => {
2855                             structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2856                         }
2857                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2858                             a_tymut.mutbl == b_tymut.mutbl
2859                                 && structurally_same_type_impl(
2860                                     seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2861                                 )
2862                         }
2863                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2864                             // For structural sameness, we don't need the region to be same.
2865                             a_mut == b_mut
2866                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2867                         }
2868                         (FnDef(..), FnDef(..)) => {
2869                             let a_poly_sig = a.fn_sig(tcx);
2870                             let b_poly_sig = b.fn_sig(tcx);
2871
2872                             // As we don't compare regions, skip_binder is fine.
2873                             let a_sig = a_poly_sig.skip_binder();
2874                             let b_sig = b_poly_sig.skip_binder();
2875
2876                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2877                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2878                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2879                                     structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2880                                 })
2881                                 && structurally_same_type_impl(
2882                                     seen_types,
2883                                     cx,
2884                                     a_sig.output(),
2885                                     b_sig.output(),
2886                                     ckind,
2887                                 )
2888                         }
2889                         (Tuple(a_substs), Tuple(b_substs)) => {
2890                             a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2891                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2892                             })
2893                         }
2894                         // For these, it's not quite as easy to define structural-sameness quite so easily.
2895                         // For the purposes of this lint, take the conservative approach and mark them as
2896                         // not structurally same.
2897                         (Dynamic(..), Dynamic(..))
2898                         | (Error(..), Error(..))
2899                         | (Closure(..), Closure(..))
2900                         | (Generator(..), Generator(..))
2901                         | (GeneratorWitness(..), GeneratorWitness(..))
2902                         | (Projection(..), Projection(..))
2903                         | (Opaque(..), Opaque(..)) => false,
2904
2905                         // These definitely should have been caught above.
2906                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2907
2908                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2909                         // enum layout optimisation is being applied.
2910                         (Adt(..), other_kind) | (other_kind, Adt(..))
2911                             if is_primitive_or_pointer(other_kind) =>
2912                         {
2913                             let (primitive, adt) =
2914                                 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2915                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2916                                 ty == primitive
2917                             } else {
2918                                 compare_layouts(a, b).unwrap_or(false)
2919                             }
2920                         }
2921                         // Otherwise, just compare the layouts. This may fail to lint for some
2922                         // incompatible types, but at the very least, will stop reads into
2923                         // uninitialised memory.
2924                         _ => compare_layouts(a, b).unwrap_or(false),
2925                     }
2926                 })
2927             }
2928         }
2929         let mut seen_types = FxHashSet::default();
2930         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2931     }
2932 }
2933
2934 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2935
2936 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2937     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2938         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2939         if let ForeignItemKind::Fn(..) = this_fi.kind {
2940             let tcx = cx.tcx;
2941             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2942                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2943                 let this_decl_ty = tcx.type_of(this_fi.def_id);
2944                 debug!(
2945                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2946                     existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2947                 );
2948                 // Check that the declarations match.
2949                 if !Self::structurally_same_type(
2950                     cx,
2951                     existing_decl_ty,
2952                     this_decl_ty,
2953                     CItemKind::Declaration,
2954                 ) {
2955                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
2956                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
2957
2958                     // We want to ensure that we use spans for both decls that include where the
2959                     // name was defined, whether that was from the link_name attribute or not.
2960                     let get_relevant_span =
2961                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2962                             SymbolName::Normal(_) => fi.span,
2963                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2964                         };
2965                     // Finally, emit the diagnostic.
2966                     tcx.struct_span_lint_hir(
2967                         CLASHING_EXTERN_DECLARATIONS,
2968                         this_fi.hir_id(),
2969                         get_relevant_span(this_fi),
2970                         |lint| {
2971                             let mut expected_str = DiagnosticStyledString::new();
2972                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2973                             let mut found_str = DiagnosticStyledString::new();
2974                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2975
2976                             lint.build(if orig.get_name() == this_fi.ident.name {
2977                                 fluent::lint::builtin_clashing_extern_same_name
2978                             } else {
2979                                 fluent::lint::builtin_clashing_extern_diff_name
2980                             })
2981                             .set_arg("this_fi", this_fi.ident.name)
2982                             .set_arg("orig", orig.get_name())
2983                             .span_label(
2984                                 get_relevant_span(orig_fi),
2985                                 fluent::lint::previous_decl_label,
2986                             )
2987                             .span_label(get_relevant_span(this_fi), fluent::lint::mismatch_label)
2988                             // FIXME(davidtwco): translatable expected/found
2989                             .note_expected_found(&"", expected_str, &"", found_str)
2990                             .emit();
2991                         },
2992                     );
2993                 }
2994             }
2995         }
2996     }
2997 }
2998
2999 declare_lint! {
3000     /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3001     /// which causes [undefined behavior].
3002     ///
3003     /// ### Example
3004     ///
3005     /// ```rust,no_run
3006     /// # #![allow(unused)]
3007     /// use std::ptr;
3008     /// unsafe {
3009     ///     let x = &*ptr::null::<i32>();
3010     ///     let x = ptr::addr_of!(*ptr::null::<i32>());
3011     ///     let x = *(0 as *const i32);
3012     /// }
3013     /// ```
3014     ///
3015     /// {{produces}}
3016     ///
3017     /// ### Explanation
3018     ///
3019     /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3020     /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3021     ///
3022     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3023     pub DEREF_NULLPTR,
3024     Warn,
3025     "detects when an null pointer is dereferenced"
3026 }
3027
3028 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3029
3030 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3031     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3032         /// test if expression is a null ptr
3033         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3034             match &expr.kind {
3035                 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3036                     if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3037                         return is_zero(expr) || is_null_ptr(cx, expr);
3038                     }
3039                 }
3040                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3041                 rustc_hir::ExprKind::Call(ref path, _) => {
3042                     if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3043                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3044                             return matches!(
3045                                 cx.tcx.get_diagnostic_name(def_id),
3046                                 Some(sym::ptr_null | sym::ptr_null_mut)
3047                             );
3048                         }
3049                     }
3050                 }
3051                 _ => {}
3052             }
3053             false
3054         }
3055
3056         /// test if expression is the literal `0`
3057         fn is_zero(expr: &hir::Expr<'_>) -> bool {
3058             match &expr.kind {
3059                 rustc_hir::ExprKind::Lit(ref lit) => {
3060                     if let LitKind::Int(a, _) = lit.node {
3061                         return a == 0;
3062                     }
3063                 }
3064                 _ => {}
3065             }
3066             false
3067         }
3068
3069         if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3070             if is_null_ptr(cx, expr_deref) {
3071                 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3072                     let mut err = lint.build(fluent::lint::builtin_deref_nullptr);
3073                     err.span_label(expr.span, fluent::lint::label);
3074                     err.emit();
3075                 });
3076             }
3077         }
3078     }
3079 }
3080
3081 declare_lint! {
3082     /// The `named_asm_labels` lint detects the use of named labels in the
3083     /// inline `asm!` macro.
3084     ///
3085     /// ### Example
3086     ///
3087     /// ```rust,compile_fail
3088     /// use std::arch::asm;
3089     ///
3090     /// fn main() {
3091     ///     unsafe {
3092     ///         asm!("foo: bar");
3093     ///     }
3094     /// }
3095     /// ```
3096     ///
3097     /// {{produces}}
3098     ///
3099     /// ### Explanation
3100     ///
3101     /// LLVM is allowed to duplicate inline assembly blocks for any
3102     /// reason, for example when it is in a function that gets inlined. Because
3103     /// of this, GNU assembler [local labels] *must* be used instead of labels
3104     /// with a name. Using named labels might cause assembler or linker errors.
3105     ///
3106     /// See the explanation in [Rust By Example] for more details.
3107     ///
3108     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3109     /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3110     pub NAMED_ASM_LABELS,
3111     Deny,
3112     "named labels in inline assembly",
3113 }
3114
3115 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3116
3117 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3118     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3119         if let hir::Expr {
3120             kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3121             ..
3122         } = expr
3123         {
3124             for (template_sym, template_snippet, template_span) in template_strs.iter() {
3125                 let template_str = template_sym.as_str();
3126                 let find_label_span = |needle: &str| -> Option<Span> {
3127                     if let Some(template_snippet) = template_snippet {
3128                         let snippet = template_snippet.as_str();
3129                         if let Some(pos) = snippet.find(needle) {
3130                             let end = pos
3131                                 + snippet[pos..]
3132                                     .find(|c| c == ':')
3133                                     .unwrap_or(snippet[pos..].len() - 1);
3134                             let inner = InnerSpan::new(pos, end);
3135                             return Some(template_span.from_inner(inner));
3136                         }
3137                     }
3138
3139                     None
3140                 };
3141
3142                 let mut found_labels = Vec::new();
3143
3144                 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3145                 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3146                 for statement in statements {
3147                     // If there's a comment, trim it from the statement
3148                     let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3149                     let mut start_idx = 0;
3150                     for (idx, _) in statement.match_indices(':') {
3151                         let possible_label = statement[start_idx..idx].trim();
3152                         let mut chars = possible_label.chars();
3153                         let Some(c) = chars.next() else {
3154                             // Empty string means a leading ':' in this section, which is not a label
3155                             break
3156                         };
3157                         // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3158                         if (c.is_alphabetic() || matches!(c, '.' | '_'))
3159                             && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3160                         {
3161                             found_labels.push(possible_label);
3162                         } else {
3163                             // If we encounter a non-label, there cannot be any further labels, so stop checking
3164                             break;
3165                         }
3166
3167                         start_idx = idx + 1;
3168                     }
3169                 }
3170
3171                 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3172
3173                 if found_labels.len() > 0 {
3174                     let spans = found_labels
3175                         .into_iter()
3176                         .filter_map(|label| find_label_span(label))
3177                         .collect::<Vec<Span>>();
3178                     // If there were labels but we couldn't find a span, combine the warnings and use the template span
3179                     let target_spans: MultiSpan =
3180                         if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3181
3182                     cx.lookup_with_diagnostics(
3183                             NAMED_ASM_LABELS,
3184                             Some(target_spans),
3185                             |diag| {
3186                                 diag.build(fluent::lint::builtin_asm_labels).emit();
3187                             },
3188                             BuiltinLintDiagnostics::NamedAsmLabel(
3189                                 "only local labels of the form `<number>:` should be used in inline asm"
3190                                     .to_string(),
3191                             ),
3192                         );
3193                 }
3194             }
3195         }
3196     }
3197 }