compiler/rustc_lint/src/builtin.rs

   1 //! Lints in the Rust compiler.
   2 //!
   3 //! This contains lints which can feasibly be implemented as their own
   4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
   5 //! definitions of lints that are emitted directly inside the main compiler.
   6 //!
   7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
   8 //! Then add code to emit the new lint in the appropriate circumstances.
   9 //! You can do that in an existing `LintPass` if it makes sense, or in a
  10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  11 //! compiler. Only do the latter if the check can't be written cleanly as a
  12 //! `LintPass` (also, note that such lints will need to be defined in
  13 //! `rustc_session::lint::builtin`, not here).
  14 //!
  15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
  16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
  17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
  18 //! with a `pub fn new()`.
  19 //!
  20 //! If you define a new `LateLintPass`, you will also need to add it to the
  21 //! `late_lint_methods!` invocation in `lib.rs`.
  22
  23 use crate::{
  24     errors::BuiltinEllpisisInclusiveRangePatterns,
  25     types::{transparent_newtype_field, CItemKind},
  26     EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
  27 };
  28 use rustc_ast::attr;
  29 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  30 use rustc_ast::visit::{FnCtxt, FnKind};
  31 use rustc_ast::{self as ast, *};
  32 use rustc_ast_pretty::pprust::{self, expr_to_string};
  33 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  34 use rustc_data_structures::stack::ensure_sufficient_stack;
  35 use rustc_errors::{
  36     fluent, Applicability, DelayDm, Diagnostic, DiagnosticBuilder, DiagnosticMessage,
  37     DiagnosticStyledString, MultiSpan,
  38 };
  39 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
  40 use rustc_hir as hir;
  41 use rustc_hir::def::{DefKind, Res};
  42 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
  43 use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, Node, PatKind, PredicateOrigin};
  44 use rustc_index::vec::Idx;
  45 use rustc_middle::lint::in_external_macro;
  46 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
  47 use rustc_middle::ty::print::with_no_trimmed_paths;
  48 use rustc_middle::ty::subst::GenericArgKind;
  49 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
  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
  62 // hardwired lints from librustc_middle
  63 pub use rustc_session::lint::builtin::*;
  64
  65 declare_lint! {
  66     /// The `while_true` lint detects `while true { }`.
  67     ///
  68     /// ### Example
  69     ///
  70     /// ```rust,no_run
  71     /// while true {
  72     ///
  73     /// }
  74     /// ```
  75     ///
  76     /// {{produces}}
  77     ///
  78     /// ### Explanation
  79     ///
  80     /// `while true` should be replaced with `loop`. A `loop` expression is
  81     /// the preferred way to write an infinite loop because it more directly
  82     /// expresses the intent of the loop.
  83     WHILE_TRUE,
  84     Warn,
  85     "suggest using `loop { }` instead of `while true { }`"
  86 }
  87
  88 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  89
  90 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  91 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  92     while let ast::ExprKind::Paren(sub) = &expr.kind {
  93         expr = sub;
  94     }
  95     expr
  96 }
  97
  98 impl EarlyLintPass for WhileTrue {
  99     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 100         if let ast::ExprKind::While(cond, _, label) = &e.kind
 101             && let cond = pierce_parens(cond)
 102             && let ast::ExprKind::Lit(token_lit) = cond.kind
 103             && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
 104             && !cond.span.from_expansion()
 105         {
 106             let condition_span = e.span.with_hi(cond.span.hi());
 107             cx.struct_span_lint(
 108                             WHILE_TRUE,
 109                             condition_span,
 110                 fluent::lint_builtin_while_true,
 111                             |lint| {
 112                     lint.span_suggestion_short(
 113                         condition_span,
 114                         fluent::suggestion,
 115                         format!(
 116                             "{}loop",
 117                             label.map_or_else(String::new, |label| format!(
 118                                 "{}: ",
 119                                 label.ident,
 120                             ))
 121                         ),
 122                         Applicability::MachineApplicable,
 123                     )
 124                 },
 125             )
 126         }
 127     }
 128 }
 129
 130 declare_lint! {
 131     /// The `box_pointers` lints use of the Box type.
 132     ///
 133     /// ### Example
 134     ///
 135     /// ```rust,compile_fail
 136     /// #![deny(box_pointers)]
 137     /// struct Foo {
 138     ///     x: Box<isize>,
 139     /// }
 140     /// ```
 141     ///
 142     /// {{produces}}
 143     ///
 144     /// ### Explanation
 145     ///
 146     /// This lint is mostly historical, and not particularly useful. `Box<T>`
 147     /// used to be built into the language, and the only way to do heap
 148     /// allocation. Today's Rust can call into other allocators, etc.
 149     BOX_POINTERS,
 150     Allow,
 151     "use of owned (Box type) heap memory"
 152 }
 153
 154 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 155
 156 impl BoxPointers {
 157     fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
 158         for leaf in ty.walk() {
 159             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
 160                 if leaf_ty.is_box() {
 161                     cx.struct_span_lint(
 162                         BOX_POINTERS,
 163                         span,
 164                         fluent::lint_builtin_box_pointers,
 165                         |lint| lint.set_arg("ty", ty),
 166                     );
 167                 }
 168             }
 169         }
 170     }
 171 }
 172
 173 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
 174     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 175         match it.kind {
 176             hir::ItemKind::Fn(..)
 177             | hir::ItemKind::TyAlias(..)
 178             | hir::ItemKind::Enum(..)
 179             | hir::ItemKind::Struct(..)
 180             | hir::ItemKind::Union(..) => {
 181                 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.owner_id))
 182             }
 183             _ => (),
 184         }
 185
 186         // If it's a struct, we also have to check the fields' types
 187         match it.kind {
 188             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 189                 for field in struct_def.fields() {
 190                     self.check_heap_type(cx, field.span, cx.tcx.type_of(field.def_id));
 191                 }
 192             }
 193             _ => (),
 194         }
 195     }
 196
 197     fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
 198         let ty = cx.typeck_results().node_type(e.hir_id);
 199         self.check_heap_type(cx, e.span, ty);
 200     }
 201 }
 202
 203 declare_lint! {
 204     /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
 205     /// instead of `Struct { x }` in a pattern.
 206     ///
 207     /// ### Example
 208     ///
 209     /// ```rust
 210     /// struct Point {
 211     ///     x: i32,
 212     ///     y: i32,
 213     /// }
 214     ///
 215     ///
 216     /// fn main() {
 217     ///     let p = Point {
 218     ///         x: 5,
 219     ///         y: 5,
 220     ///     };
 221     ///
 222     ///     match p {
 223     ///         Point { x: x, y: y } => (),
 224     ///     }
 225     /// }
 226     /// ```
 227     ///
 228     /// {{produces}}
 229     ///
 230     /// ### Explanation
 231     ///
 232     /// The preferred style is to avoid the repetition of specifying both the
 233     /// field name and the binding name if both identifiers are the same.
 234     NON_SHORTHAND_FIELD_PATTERNS,
 235     Warn,
 236     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 237 }
 238
 239 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 240
 241 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
 242     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
 243         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 244             let variant = cx
 245                 .typeck_results()
 246                 .pat_ty(pat)
 247                 .ty_adt_def()
 248                 .expect("struct pattern type is not an ADT")
 249                 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
 250             for fieldpat in field_pats {
 251                 if fieldpat.is_shorthand {
 252                     continue;
 253                 }
 254                 if fieldpat.span.from_expansion() {
 255                     // Don't lint if this is a macro expansion: macro authors
 256                     // shouldn't have to worry about this kind of style issue
 257                     // (Issue #49588)
 258                     continue;
 259                 }
 260                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 261                     if cx.tcx.find_field_index(ident, &variant)
 262                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
 263                     {
 264                         cx.struct_span_lint(
 265                             NON_SHORTHAND_FIELD_PATTERNS,
 266                             fieldpat.span,
 267                             fluent::lint_builtin_non_shorthand_field_patterns,
 268                             |lint| {
 269                                 let suggested_ident =
 270                                     format!("{}{}", binding_annot.prefix_str(), ident);
 271                                 lint.set_arg("ident", ident.clone()).span_suggestion(
 272                                     fieldpat.span,
 273                                     fluent::suggestion,
 274                                     suggested_ident,
 275                                     Applicability::MachineApplicable,
 276                                 )
 277                             },
 278                         );
 279                     }
 280                 }
 281             }
 282         }
 283     }
 284 }
 285
 286 declare_lint! {
 287     /// The `unsafe_code` lint catches usage of `unsafe` code.
 288     ///
 289     /// ### Example
 290     ///
 291     /// ```rust,compile_fail
 292     /// #![deny(unsafe_code)]
 293     /// fn main() {
 294     ///     unsafe {
 295     ///
 296     ///     }
 297     /// }
 298     /// ```
 299     ///
 300     /// {{produces}}
 301     ///
 302     /// ### Explanation
 303     ///
 304     /// This lint is intended to restrict the usage of `unsafe`, which can be
 305     /// difficult to use correctly.
 306     UNSAFE_CODE,
 307     Allow,
 308     "usage of `unsafe` code"
 309 }
 310
 311 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 312
 313 impl UnsafeCode {
 314     fn report_unsafe(
 315         &self,
 316         cx: &EarlyContext<'_>,
 317         span: Span,
 318         msg: impl Into<DiagnosticMessage>,
 319         decorate: impl for<'a, 'b> FnOnce(
 320             &'b mut DiagnosticBuilder<'a, ()>,
 321         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 322     ) {
 323         // This comes from a macro that has `#[allow_internal_unsafe]`.
 324         if span.allows_unsafe() {
 325             return;
 326         }
 327
 328         cx.struct_span_lint(UNSAFE_CODE, span, msg, decorate);
 329     }
 330
 331     fn report_overridden_symbol_name(
 332         &self,
 333         cx: &EarlyContext<'_>,
 334         span: Span,
 335         msg: DiagnosticMessage,
 336     ) {
 337         self.report_unsafe(cx, span, msg, |lint| {
 338             lint.note(fluent::lint_builtin_overridden_symbol_name)
 339         })
 340     }
 341
 342     fn report_overridden_symbol_section(
 343         &self,
 344         cx: &EarlyContext<'_>,
 345         span: Span,
 346         msg: DiagnosticMessage,
 347     ) {
 348         self.report_unsafe(cx, span, msg, |lint| {
 349             lint.note(fluent::lint_builtin_overridden_symbol_section)
 350         })
 351     }
 352 }
 353
 354 impl EarlyLintPass for UnsafeCode {
 355     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 356         if attr.has_name(sym::allow_internal_unsafe) {
 357             self.report_unsafe(cx, attr.span, fluent::lint_builtin_allow_internal_unsafe, |lint| {
 358                 lint
 359             });
 360         }
 361     }
 362
 363     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 364         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 365             // Don't warn about generated blocks; that'll just pollute the output.
 366             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 367                 self.report_unsafe(cx, blk.span, fluent::lint_builtin_unsafe_block, |lint| lint);
 368             }
 369         }
 370     }
 371
 372     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 373         match it.kind {
 374             ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => {
 375                 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_trait, |lint| lint)
 376             }
 377
 378             ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => {
 379                 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_impl, |lint| lint)
 380             }
 381
 382             ast::ItemKind::Fn(..) => {
 383                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 384                     self.report_overridden_symbol_name(
 385                         cx,
 386                         attr.span,
 387                         fluent::lint_builtin_no_mangle_fn,
 388                     );
 389                 }
 390
 391                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 392                     self.report_overridden_symbol_name(
 393                         cx,
 394                         attr.span,
 395                         fluent::lint_builtin_export_name_fn,
 396                     );
 397                 }
 398
 399                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
 400                     self.report_overridden_symbol_section(
 401                         cx,
 402                         attr.span,
 403                         fluent::lint_builtin_link_section_fn,
 404                     );
 405                 }
 406             }
 407
 408             ast::ItemKind::Static(..) => {
 409                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 410                     self.report_overridden_symbol_name(
 411                         cx,
 412                         attr.span,
 413                         fluent::lint_builtin_no_mangle_static,
 414                     );
 415                 }
 416
 417                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 418                     self.report_overridden_symbol_name(
 419                         cx,
 420                         attr.span,
 421                         fluent::lint_builtin_export_name_static,
 422                     );
 423                 }
 424
 425                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
 426                     self.report_overridden_symbol_section(
 427                         cx,
 428                         attr.span,
 429                         fluent::lint_builtin_link_section_static,
 430                     );
 431                 }
 432             }
 433
 434             _ => {}
 435         }
 436     }
 437
 438     fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 439         if let ast::AssocItemKind::Fn(..) = it.kind {
 440             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 441                 self.report_overridden_symbol_name(
 442                     cx,
 443                     attr.span,
 444                     fluent::lint_builtin_no_mangle_method,
 445                 );
 446             }
 447             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
 448                 self.report_overridden_symbol_name(
 449                     cx,
 450                     attr.span,
 451                     fluent::lint_builtin_export_name_method,
 452                 );
 453             }
 454         }
 455     }
 456
 457     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
 458         if let FnKind::Fn(
 459             ctxt,
 460             _,
 461             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
 462             _,
 463             _,
 464             body,
 465         ) = fk
 466         {
 467             let msg = match ctxt {
 468                 FnCtxt::Foreign => return,
 469                 FnCtxt::Free => fluent::lint_builtin_decl_unsafe_fn,
 470                 FnCtxt::Assoc(_) if body.is_none() => fluent::lint_builtin_decl_unsafe_method,
 471                 FnCtxt::Assoc(_) => fluent::lint_builtin_impl_unsafe_method,
 472             };
 473             self.report_unsafe(cx, span, msg, |lint| lint);
 474         }
 475     }
 476 }
 477
 478 declare_lint! {
 479     /// The `missing_docs` lint detects missing documentation for public items.
 480     ///
 481     /// ### Example
 482     ///
 483     /// ```rust,compile_fail
 484     /// #![deny(missing_docs)]
 485     /// pub fn foo() {}
 486     /// ```
 487     ///
 488     /// {{produces}}
 489     ///
 490     /// ### Explanation
 491     ///
 492     /// This lint is intended to ensure that a library is well-documented.
 493     /// Items without documentation can be difficult for users to understand
 494     /// how to use properly.
 495     ///
 496     /// This lint is "allow" by default because it can be noisy, and not all
 497     /// projects may want to enforce everything to be documented.
 498     pub MISSING_DOCS,
 499     Allow,
 500     "detects missing documentation for public members",
 501     report_in_external_macro
 502 }
 503
 504 pub struct MissingDoc {
 505     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 506     doc_hidden_stack: Vec<bool>,
 507 }
 508
 509 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 510
 511 fn has_doc(attr: &ast::Attribute) -> bool {
 512     if attr.is_doc_comment() {
 513         return true;
 514     }
 515
 516     if !attr.has_name(sym::doc) {
 517         return false;
 518     }
 519
 520     if attr.value_str().is_some() {
 521         return true;
 522     }
 523
 524     if let Some(list) = attr.meta_item_list() {
 525         for meta in list {
 526             if meta.has_name(sym::hidden) {
 527                 return true;
 528             }
 529         }
 530     }
 531
 532     false
 533 }
 534
 535 impl MissingDoc {
 536     pub fn new() -> MissingDoc {
 537         MissingDoc { doc_hidden_stack: vec![false] }
 538     }
 539
 540     fn doc_hidden(&self) -> bool {
 541         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 542     }
 543
 544     fn check_missing_docs_attrs(
 545         &self,
 546         cx: &LateContext<'_>,
 547         def_id: LocalDefId,
 548         article: &'static str,
 549         desc: &'static str,
 550     ) {
 551         // If we're building a test harness, then warning about
 552         // documentation is probably not really relevant right now.
 553         if cx.sess().opts.test {
 554             return;
 555         }
 556
 557         // `#[doc(hidden)]` disables missing_docs check.
 558         if self.doc_hidden() {
 559             return;
 560         }
 561
 562         // Only check publicly-visible items, using the result from the privacy pass.
 563         // It's an option so the crate root can also use this function (it doesn't
 564         // have a `NodeId`).
 565         if def_id != CRATE_DEF_ID {
 566             if !cx.effective_visibilities.is_exported(def_id) {
 567                 return;
 568             }
 569         }
 570
 571         let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
 572         let has_doc = attrs.iter().any(has_doc);
 573         if !has_doc {
 574             cx.struct_span_lint(
 575                 MISSING_DOCS,
 576                 cx.tcx.def_span(def_id),
 577                 fluent::lint_builtin_missing_doc,
 578                 |lint| lint.set_arg("article", article).set_arg("desc", desc),
 579             );
 580         }
 581     }
 582 }
 583
 584 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 585     fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
 586         let doc_hidden = self.doc_hidden()
 587             || attrs.iter().any(|attr| {
 588                 attr.has_name(sym::doc)
 589                     && match attr.meta_item_list() {
 590                         None => false,
 591                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 592                     }
 593             });
 594         self.doc_hidden_stack.push(doc_hidden);
 595     }
 596
 597     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
 598         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 599     }
 600
 601     fn check_crate(&mut self, cx: &LateContext<'_>) {
 602         self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
 603     }
 604
 605     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 606         match it.kind {
 607             hir::ItemKind::Trait(..) => {
 608                 // Issue #11592: traits are always considered exported, even when private.
 609                 if cx.tcx.visibility(it.owner_id)
 610                     == ty::Visibility::Restricted(
 611                         cx.tcx.parent_module_from_def_id(it.owner_id.def_id).to_def_id(),
 612                     )
 613                 {
 614                     return;
 615                 }
 616             }
 617             hir::ItemKind::TyAlias(..)
 618             | hir::ItemKind::Fn(..)
 619             | hir::ItemKind::Macro(..)
 620             | hir::ItemKind::Mod(..)
 621             | hir::ItemKind::Enum(..)
 622             | hir::ItemKind::Struct(..)
 623             | hir::ItemKind::Union(..)
 624             | hir::ItemKind::Const(..)
 625             | hir::ItemKind::Static(..) => {}
 626
 627             _ => return,
 628         };
 629
 630         let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
 631
 632         self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
 633     }
 634
 635     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
 636         let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
 637
 638         self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
 639     }
 640
 641     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
 642         // If the method is an impl for a trait, don't doc.
 643         if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
 644             return;
 645         }
 646
 647         // If the method is an impl for an item with docs_hidden, don't doc.
 648         if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
 649             let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
 650             let impl_ty = cx.tcx.type_of(parent);
 651             let outerdef = match impl_ty.kind() {
 652                 ty::Adt(def, _) => Some(def.did()),
 653                 ty::Foreign(def_id) => Some(*def_id),
 654                 _ => None,
 655             };
 656             let is_hidden = match outerdef {
 657                 Some(id) => cx.tcx.is_doc_hidden(id),
 658                 None => false,
 659             };
 660             if is_hidden {
 661                 return;
 662             }
 663         }
 664
 665         let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
 666         self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
 667     }
 668
 669     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
 670         let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
 671         self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
 672     }
 673
 674     fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
 675         if !sf.is_positional() {
 676             self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
 677         }
 678     }
 679
 680     fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
 681         self.check_missing_docs_attrs(cx, v.def_id, "a", "variant");
 682     }
 683 }
 684
 685 declare_lint! {
 686     /// The `missing_copy_implementations` lint detects potentially-forgotten
 687     /// implementations of [`Copy`].
 688     ///
 689     /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
 690     ///
 691     /// ### Example
 692     ///
 693     /// ```rust,compile_fail
 694     /// #![deny(missing_copy_implementations)]
 695     /// pub struct Foo {
 696     ///     pub field: i32
 697     /// }
 698     /// # fn main() {}
 699     /// ```
 700     ///
 701     /// {{produces}}
 702     ///
 703     /// ### Explanation
 704     ///
 705     /// Historically (before 1.0), types were automatically marked as `Copy`
 706     /// if possible. This was changed so that it required an explicit opt-in
 707     /// by implementing the `Copy` trait. As part of this change, a lint was
 708     /// added to alert if a copyable type was not marked `Copy`.
 709     ///
 710     /// This lint is "allow" by default because this code isn't bad; it is
 711     /// common to write newtypes like this specifically so that a `Copy` type
 712     /// is no longer `Copy`. `Copy` types can result in unintended copies of
 713     /// large data which can impact performance.
 714     pub MISSING_COPY_IMPLEMENTATIONS,
 715     Allow,
 716     "detects potentially-forgotten implementations of `Copy`"
 717 }
 718
 719 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 720
 721 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
 722     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 723         if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
 724             return;
 725         }
 726         let (def, ty) = match item.kind {
 727             hir::ItemKind::Struct(_, ref ast_generics) => {
 728                 if !ast_generics.params.is_empty() {
 729                     return;
 730                 }
 731                 let def = cx.tcx.adt_def(item.owner_id);
 732                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 733             }
 734             hir::ItemKind::Union(_, ref ast_generics) => {
 735                 if !ast_generics.params.is_empty() {
 736                     return;
 737                 }
 738                 let def = cx.tcx.adt_def(item.owner_id);
 739                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 740             }
 741             hir::ItemKind::Enum(_, ref ast_generics) => {
 742                 if !ast_generics.params.is_empty() {
 743                     return;
 744                 }
 745                 let def = cx.tcx.adt_def(item.owner_id);
 746                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 747             }
 748             _ => return,
 749         };
 750         if def.has_dtor(cx.tcx) {
 751             return;
 752         }
 753         let param_env = ty::ParamEnv::empty();
 754         if ty.is_copy_modulo_regions(cx.tcx, param_env) {
 755             return;
 756         }
 757         if can_type_implement_copy(
 758             cx.tcx,
 759             param_env,
 760             ty,
 761             traits::ObligationCause::misc(item.span, item.hir_id()),
 762         )
 763         .is_ok()
 764         {
 765             cx.struct_span_lint(
 766                 MISSING_COPY_IMPLEMENTATIONS,
 767                 item.span,
 768                 fluent::lint_builtin_missing_copy_impl,
 769                 |lint| lint,
 770             )
 771         }
 772     }
 773 }
 774
 775 declare_lint! {
 776     /// The `missing_debug_implementations` lint detects missing
 777     /// implementations of [`fmt::Debug`].
 778     ///
 779     /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
 780     ///
 781     /// ### Example
 782     ///
 783     /// ```rust,compile_fail
 784     /// #![deny(missing_debug_implementations)]
 785     /// pub struct Foo;
 786     /// # fn main() {}
 787     /// ```
 788     ///
 789     /// {{produces}}
 790     ///
 791     /// ### Explanation
 792     ///
 793     /// Having a `Debug` implementation on all types can assist with
 794     /// debugging, as it provides a convenient way to format and display a
 795     /// value. Using the `#[derive(Debug)]` attribute will automatically
 796     /// generate a typical implementation, or a custom implementation can be
 797     /// added by manually implementing the `Debug` trait.
 798     ///
 799     /// This lint is "allow" by default because adding `Debug` to all types can
 800     /// have a negative impact on compile time and code size. It also requires
 801     /// boilerplate to be added to every type, which can be an impediment.
 802     MISSING_DEBUG_IMPLEMENTATIONS,
 803     Allow,
 804     "detects missing implementations of Debug"
 805 }
 806
 807 #[derive(Default)]
 808 pub struct MissingDebugImplementations {
 809     impling_types: Option<LocalDefIdSet>,
 810 }
 811
 812 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 813
 814 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 815     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 816         if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
 817             return;
 818         }
 819
 820         match item.kind {
 821             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 822             _ => return,
 823         }
 824
 825         let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
 826             return
 827         };
 828
 829         if self.impling_types.is_none() {
 830             let mut impls = LocalDefIdSet::default();
 831             cx.tcx.for_each_impl(debug, |d| {
 832                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 833                     if let Some(def_id) = ty_def.did().as_local() {
 834                         impls.insert(def_id);
 835                     }
 836                 }
 837             });
 838
 839             self.impling_types = Some(impls);
 840             debug!("{:?}", self.impling_types);
 841         }
 842
 843         if !self.impling_types.as_ref().unwrap().contains(&item.owner_id.def_id) {
 844             cx.struct_span_lint(
 845                 MISSING_DEBUG_IMPLEMENTATIONS,
 846                 item.span,
 847                 fluent::lint_builtin_missing_debug_impl,
 848                 |lint| lint.set_arg("debug", cx.tcx.def_path_str(debug)),
 849             );
 850         }
 851     }
 852 }
 853
 854 declare_lint! {
 855     /// The `anonymous_parameters` lint detects anonymous parameters in trait
 856     /// definitions.
 857     ///
 858     /// ### Example
 859     ///
 860     /// ```rust,edition2015,compile_fail
 861     /// #![deny(anonymous_parameters)]
 862     /// // edition 2015
 863     /// pub trait Foo {
 864     ///     fn foo(usize);
 865     /// }
 866     /// fn main() {}
 867     /// ```
 868     ///
 869     /// {{produces}}
 870     ///
 871     /// ### Explanation
 872     ///
 873     /// This syntax is mostly a historical accident, and can be worked around
 874     /// quite easily by adding an `_` pattern or a descriptive identifier:
 875     ///
 876     /// ```rust
 877     /// trait Foo {
 878     ///     fn foo(_: usize);
 879     /// }
 880     /// ```
 881     ///
 882     /// This syntax is now a hard error in the 2018 edition. In the 2015
 883     /// edition, this lint is "warn" by default. This lint
 884     /// enables the [`cargo fix`] tool with the `--edition` flag to
 885     /// automatically transition old code from the 2015 edition to 2018. The
 886     /// tool will run this lint and automatically apply the
 887     /// suggested fix from the compiler (which is to add `_` to each
 888     /// parameter). This provides a completely automated way to update old
 889     /// code for a new edition. See [issue #41686] for more details.
 890     ///
 891     /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
 892     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
 893     pub ANONYMOUS_PARAMETERS,
 894     Warn,
 895     "detects anonymous parameters",
 896     @future_incompatible = FutureIncompatibleInfo {
 897         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 898         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
 899     };
 900 }
 901
 902 declare_lint_pass!(
 903     /// Checks for use of anonymous parameters (RFC 1685).
 904     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 905 );
 906
 907 impl EarlyLintPass for AnonymousParameters {
 908     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 909         if cx.sess().edition() != Edition::Edition2015 {
 910             // This is a hard error in future editions; avoid linting and erroring
 911             return;
 912         }
 913         if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
 914             for arg in sig.decl.inputs.iter() {
 915                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 916                     if ident.name == kw::Empty {
 917                         let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
 918
 919                         let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 920                             (snip.as_str(), Applicability::MachineApplicable)
 921                         } else {
 922                             ("<type>", Applicability::HasPlaceholders)
 923                         };
 924                         cx.struct_span_lint(
 925                             ANONYMOUS_PARAMETERS,
 926                             arg.pat.span,
 927                             fluent::lint_builtin_anonymous_params,
 928                             |lint| {
 929                                 lint.span_suggestion(
 930                                     arg.pat.span,
 931                                     fluent::suggestion,
 932                                     format!("_: {}", ty_snip),
 933                                     appl,
 934                                 )
 935                             },
 936                         )
 937                     }
 938                 }
 939             }
 940         }
 941     }
 942 }
 943
 944 /// Check for use of attributes which have been deprecated.
 945 #[derive(Clone)]
 946 pub struct DeprecatedAttr {
 947     // This is not free to compute, so we want to keep it around, rather than
 948     // compute it for every attribute.
 949     depr_attrs: Vec<&'static BuiltinAttribute>,
 950 }
 951
 952 impl_lint_pass!(DeprecatedAttr => []);
 953
 954 impl DeprecatedAttr {
 955     pub fn new() -> DeprecatedAttr {
 956         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 957     }
 958 }
 959
 960 impl EarlyLintPass for DeprecatedAttr {
 961     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 962         for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
 963             if attr.ident().map(|ident| ident.name) == Some(*name) {
 964                 if let &AttributeGate::Gated(
 965                     Stability::Deprecated(link, suggestion),
 966                     name,
 967                     reason,
 968                     _,
 969                 ) = gate
 970                 {
 971                     // FIXME(davidtwco) translatable deprecated attr
 972                     cx.struct_span_lint(
 973                         DEPRECATED,
 974                         attr.span,
 975                         fluent::lint_builtin_deprecated_attr_link,
 976                         |lint| {
 977                             lint.set_arg("name", name)
 978                                 .set_arg("reason", reason)
 979                                 .set_arg("link", link)
 980                                 .span_suggestion_short(
 981                                     attr.span,
 982                                     suggestion.map(|s| s.into()).unwrap_or(
 983                                         fluent::lint_builtin_deprecated_attr_default_suggestion,
 984                                     ),
 985                                     "",
 986                                     Applicability::MachineApplicable,
 987                                 )
 988                         },
 989                     );
 990                 }
 991                 return;
 992             }
 993         }
 994         if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
 995             cx.struct_span_lint(
 996                 DEPRECATED,
 997                 attr.span,
 998                 fluent::lint_builtin_deprecated_attr_used,
 999                 |lint| {
1000                     lint.set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
1001                         .span_suggestion_short(
1002                             attr.span,
1003                             fluent::lint_builtin_deprecated_attr_default_suggestion,
1004                             "",
1005                             Applicability::MachineApplicable,
1006                         )
1007                 },
1008             );
1009         }
1010     }
1011 }
1012
1013 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1014     use rustc_ast::token::CommentKind;
1015
1016     let mut attrs = attrs.iter().peekable();
1017
1018     // Accumulate a single span for sugared doc comments.
1019     let mut sugared_span: Option<Span> = None;
1020
1021     while let Some(attr) = attrs.next() {
1022         let is_doc_comment = attr.is_doc_comment();
1023         if is_doc_comment {
1024             sugared_span =
1025                 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1026         }
1027
1028         if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1029             continue;
1030         }
1031
1032         let span = sugared_span.take().unwrap_or(attr.span);
1033
1034         if is_doc_comment || attr.has_name(sym::doc) {
1035             cx.struct_span_lint(
1036                 UNUSED_DOC_COMMENTS,
1037                 span,
1038                 fluent::lint_builtin_unused_doc_comment,
1039                 |lint| {
1040                     lint.set_arg("kind", node_kind).span_label(node_span, fluent::label).help(
1041                         match attr.kind {
1042                             AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1043                                 fluent::plain_help
1044                             }
1045                             AttrKind::DocComment(CommentKind::Block, _) => fluent::block_help,
1046                         },
1047                     )
1048                 },
1049             );
1050         }
1051     }
1052 }
1053
1054 impl EarlyLintPass for UnusedDocComment {
1055     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1056         let kind = match stmt.kind {
1057             ast::StmtKind::Local(..) => "statements",
1058             // Disabled pending discussion in #78306
1059             ast::StmtKind::Item(..) => return,
1060             // expressions will be reported by `check_expr`.
1061             ast::StmtKind::Empty
1062             | ast::StmtKind::Semi(_)
1063             | ast::StmtKind::Expr(_)
1064             | ast::StmtKind::MacCall(_) => return,
1065         };
1066
1067         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1068     }
1069
1070     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1071         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1072         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1073     }
1074
1075     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1076         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1077     }
1078
1079     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1080         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
1081     }
1082
1083     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1084         warn_if_doc(cx, block.span, "blocks", &block.attrs());
1085     }
1086
1087     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1088         if let ast::ItemKind::ForeignMod(_) = item.kind {
1089             warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1090         }
1091     }
1092 }
1093
1094 declare_lint! {
1095     /// The `no_mangle_const_items` lint detects any `const` items with the
1096     /// [`no_mangle` attribute].
1097     ///
1098     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1099     ///
1100     /// ### Example
1101     ///
1102     /// ```rust,compile_fail
1103     /// #[no_mangle]
1104     /// const FOO: i32 = 5;
1105     /// ```
1106     ///
1107     /// {{produces}}
1108     ///
1109     /// ### Explanation
1110     ///
1111     /// Constants do not have their symbols exported, and therefore, this
1112     /// probably means you meant to use a [`static`], not a [`const`].
1113     ///
1114     /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1115     /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1116     NO_MANGLE_CONST_ITEMS,
1117     Deny,
1118     "const items will not have their symbols exported"
1119 }
1120
1121 declare_lint! {
1122     /// The `no_mangle_generic_items` lint detects generic items that must be
1123     /// mangled.
1124     ///
1125     /// ### Example
1126     ///
1127     /// ```rust
1128     /// #[no_mangle]
1129     /// fn foo<T>(t: T) {
1130     ///
1131     /// }
1132     /// ```
1133     ///
1134     /// {{produces}}
1135     ///
1136     /// ### Explanation
1137     ///
1138     /// A function with generics must have its symbol mangled to accommodate
1139     /// the generic parameter. The [`no_mangle` attribute] has no effect in
1140     /// this situation, and should be removed.
1141     ///
1142     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1143     NO_MANGLE_GENERIC_ITEMS,
1144     Warn,
1145     "generic items must be mangled"
1146 }
1147
1148 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1149
1150 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1151     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1152         let attrs = cx.tcx.hir().attrs(it.hir_id());
1153         let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1154                                              impl_generics: Option<&hir::Generics<'_>>,
1155                                              generics: &hir::Generics<'_>,
1156                                              span| {
1157             for param in
1158                 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1159             {
1160                 match param.kind {
1161                     GenericParamKind::Lifetime { .. } => {}
1162                     GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1163                         cx.struct_span_lint(
1164                             NO_MANGLE_GENERIC_ITEMS,
1165                             span,
1166                             fluent::lint_builtin_no_mangle_generic,
1167                             |lint| {
1168                                 lint.span_suggestion_short(
1169                                     no_mangle_attr.span,
1170                                     fluent::suggestion,
1171                                     "",
1172                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1173                                     // fix may be to monomorphize source by hand
1174                                     Applicability::MaybeIncorrect,
1175                                 )
1176                             },
1177                         );
1178                         break;
1179                     }
1180                 }
1181             }
1182         };
1183         match it.kind {
1184             hir::ItemKind::Fn(.., ref generics, _) => {
1185                 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1186                     check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1187                 }
1188             }
1189             hir::ItemKind::Const(..) => {
1190                 if cx.sess().contains_name(attrs, sym::no_mangle) {
1191                     // Const items do not refer to a particular location in memory, and therefore
1192                     // don't have anything to attach a symbol to
1193                     cx.struct_span_lint(
1194                         NO_MANGLE_CONST_ITEMS,
1195                         it.span,
1196                         fluent::lint_builtin_const_no_mangle,
1197                         |lint| {
1198                             // account for "pub const" (#45562)
1199                             let start = cx
1200                                 .tcx
1201                                 .sess
1202                                 .source_map()
1203                                 .span_to_snippet(it.span)
1204                                 .map(|snippet| snippet.find("const").unwrap_or(0))
1205                                 .unwrap_or(0) as u32;
1206                             // `const` is 5 chars
1207                             let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1208                             lint.span_suggestion(
1209                                 const_span,
1210                                 fluent::suggestion,
1211                                 "pub static",
1212                                 Applicability::MachineApplicable,
1213                             )
1214                         },
1215                     );
1216                 }
1217             }
1218             hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1219                 for it in *items {
1220                     if let hir::AssocItemKind::Fn { .. } = it.kind {
1221                         if let Some(no_mangle_attr) = cx
1222                             .sess()
1223                             .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1224                         {
1225                             check_no_mangle_on_generic_fn(
1226                                 no_mangle_attr,
1227                                 Some(generics),
1228                                 cx.tcx.hir().get_generics(it.id.owner_id.def_id).unwrap(),
1229                                 it.span,
1230                             );
1231                         }
1232                     }
1233                 }
1234             }
1235             _ => {}
1236         }
1237     }
1238 }
1239
1240 declare_lint! {
1241     /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1242     /// T` because it is [undefined behavior].
1243     ///
1244     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1245     ///
1246     /// ### Example
1247     ///
1248     /// ```rust,compile_fail
1249     /// unsafe {
1250     ///     let y = std::mem::transmute::<&i32, &mut i32>(&5);
1251     /// }
1252     /// ```
1253     ///
1254     /// {{produces}}
1255     ///
1256     /// ### Explanation
1257     ///
1258     /// Certain assumptions are made about aliasing of data, and this transmute
1259     /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1260     ///
1261     /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1262     MUTABLE_TRANSMUTES,
1263     Deny,
1264     "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1265 }
1266
1267 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1268
1269 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1270     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1271         if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1272             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1273         {
1274             if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1275                 cx.struct_span_lint(
1276                     MUTABLE_TRANSMUTES,
1277                     expr.span,
1278                     fluent::lint_builtin_mutable_transmutes,
1279                     |lint| lint,
1280                 );
1281             }
1282         }
1283
1284         fn get_transmute_from_to<'tcx>(
1285             cx: &LateContext<'tcx>,
1286             expr: &hir::Expr<'_>,
1287         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1288             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1289                 cx.qpath_res(qpath, expr.hir_id)
1290             } else {
1291                 return None;
1292             };
1293             if let Res::Def(DefKind::Fn, did) = def {
1294                 if !def_id_is_transmute(cx, did) {
1295                     return None;
1296                 }
1297                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1298                 let from = sig.inputs().skip_binder()[0];
1299                 let to = sig.output().skip_binder();
1300                 return Some((from, to));
1301             }
1302             None
1303         }
1304
1305         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1306             cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1307         }
1308     }
1309 }
1310
1311 declare_lint! {
1312     /// The `unstable_features` is deprecated and should no longer be used.
1313     UNSTABLE_FEATURES,
1314     Allow,
1315     "enabling unstable features (deprecated. do not use)"
1316 }
1317
1318 declare_lint_pass!(
1319     /// Forbids using the `#[feature(...)]` attribute
1320     UnstableFeatures => [UNSTABLE_FEATURES]
1321 );
1322
1323 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1324     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1325         if attr.has_name(sym::feature) {
1326             if let Some(items) = attr.meta_item_list() {
1327                 for item in items {
1328                     cx.struct_span_lint(
1329                         UNSTABLE_FEATURES,
1330                         item.span(),
1331                         fluent::lint_builtin_unstable_features,
1332                         |lint| lint,
1333                     );
1334                 }
1335             }
1336         }
1337     }
1338 }
1339
1340 declare_lint! {
1341     /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1342     /// the crate root.
1343     ///
1344     /// ### Example
1345     ///
1346     /// ```rust,compile_fail
1347     /// #![deny(unreachable_pub)]
1348     /// mod foo {
1349     ///     pub mod bar {
1350     ///
1351     ///     }
1352     /// }
1353     /// ```
1354     ///
1355     /// {{produces}}
1356     ///
1357     /// ### Explanation
1358     ///
1359     /// A bare `pub` visibility may be misleading if the item is not actually
1360     /// publicly exported from the crate. The `pub(crate)` visibility is
1361     /// recommended to be used instead, which more clearly expresses the intent
1362     /// that the item is only visible within its own crate.
1363     ///
1364     /// This lint is "allow" by default because it will trigger for a large
1365     /// amount existing Rust code, and has some false-positives. Eventually it
1366     /// is desired for this to become warn-by-default.
1367     pub UNREACHABLE_PUB,
1368     Allow,
1369     "`pub` items not reachable from crate root"
1370 }
1371
1372 declare_lint_pass!(
1373     /// Lint for items marked `pub` that aren't reachable from other crates.
1374     UnreachablePub => [UNREACHABLE_PUB]
1375 );
1376
1377 impl UnreachablePub {
1378     fn perform_lint(
1379         &self,
1380         cx: &LateContext<'_>,
1381         what: &str,
1382         def_id: LocalDefId,
1383         vis_span: Span,
1384         exportable: bool,
1385     ) {
1386         let mut applicability = Applicability::MachineApplicable;
1387         if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
1388         {
1389             if vis_span.from_expansion() {
1390                 applicability = Applicability::MaybeIncorrect;
1391             }
1392             let def_span = cx.tcx.def_span(def_id);
1393             cx.struct_span_lint(
1394                 UNREACHABLE_PUB,
1395                 def_span,
1396                 fluent::lint_builtin_unreachable_pub,
1397                 |lint| {
1398                     lint.set_arg("what", what);
1399
1400                     lint.span_suggestion(vis_span, fluent::suggestion, "pub(crate)", applicability);
1401                     if exportable {
1402                         lint.help(fluent::help);
1403                     }
1404                     lint
1405                 },
1406             );
1407         }
1408     }
1409 }
1410
1411 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1412     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1413         // Do not warn for fake `use` statements.
1414         if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1415             return;
1416         }
1417         self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
1418     }
1419
1420     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1421         self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
1422     }
1423
1424     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1425         let map = cx.tcx.hir();
1426         if matches!(map.get(map.get_parent_node(field.hir_id)), Node::Variant(_)) {
1427             return;
1428         }
1429         self.perform_lint(cx, "field", field.def_id, 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.owner_id).trait_item_def_id.is_none() {
1435             self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
1436         }
1437     }
1438 }
1439
1440 declare_lint! {
1441     /// The `type_alias_bounds` lint detects bounds in type aliases.
1442     ///
1443     /// ### Example
1444     ///
1445     /// ```rust
1446     /// type SendVec<T: Send> = Vec<T>;
1447     /// ```
1448     ///
1449     /// {{produces}}
1450     ///
1451     /// ### Explanation
1452     ///
1453     /// The trait bounds in a type alias are currently ignored, and should not
1454     /// be included to avoid confusion. This was previously allowed
1455     /// unintentionally; this may become a hard error in the future.
1456     TYPE_ALIAS_BOUNDS,
1457     Warn,
1458     "bounds in type aliases are not enforced"
1459 }
1460
1461 declare_lint_pass!(
1462     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1463     /// They are relevant when using associated types, but otherwise neither checked
1464     /// at definition site nor enforced at use site.
1465     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1466 );
1467
1468 impl TypeAliasBounds {
1469     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1470         match *qpath {
1471             hir::QPath::TypeRelative(ref ty, _) => {
1472                 // If this is a type variable, we found a `T::Assoc`.
1473                 match ty.kind {
1474                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1475                         matches!(path.res, Res::Def(DefKind::TyParam, _))
1476                     }
1477                     _ => false,
1478                 }
1479             }
1480             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1481         }
1482     }
1483
1484     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1485         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1486         // bound.  Let's see if this type does that.
1487
1488         // We use a HIR visitor to walk the type.
1489         use rustc_hir::intravisit::{self, Visitor};
1490         struct WalkAssocTypes<'a> {
1491             err: &'a mut Diagnostic,
1492         }
1493         impl Visitor<'_> for WalkAssocTypes<'_> {
1494             fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1495                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1496                     self.err.span_help(span, fluent::lint_builtin_type_alias_bounds_help);
1497                 }
1498                 intravisit::walk_qpath(self, qpath, id)
1499             }
1500         }
1501
1502         // Let's go for a walk!
1503         let mut visitor = WalkAssocTypes { err };
1504         visitor.visit_ty(ty);
1505     }
1506 }
1507
1508 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1509     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1510         let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1511             return
1512         };
1513         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1514             // Bounds are respected for `type X = impl Trait`
1515             return;
1516         }
1517         // There must not be a where clause
1518         if type_alias_generics.predicates.is_empty() {
1519             return;
1520         }
1521
1522         let mut where_spans = Vec::new();
1523         let mut inline_spans = Vec::new();
1524         let mut inline_sugg = Vec::new();
1525         for p in type_alias_generics.predicates {
1526             let span = p.span();
1527             if p.in_where_clause() {
1528                 where_spans.push(span);
1529             } else {
1530                 for b in p.bounds() {
1531                     inline_spans.push(b.span());
1532                 }
1533                 inline_sugg.push((span, String::new()));
1534             }
1535         }
1536
1537         let mut suggested_changing_assoc_types = false;
1538         if !where_spans.is_empty() {
1539             cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_where_clause, |lint| {
1540                 lint.set_span(where_spans);
1541                 lint.span_suggestion(
1542                     type_alias_generics.where_clause_span,
1543                     fluent::suggestion,
1544                     "",
1545                     Applicability::MachineApplicable,
1546                 );
1547                 if !suggested_changing_assoc_types {
1548                     TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1549                     suggested_changing_assoc_types = true;
1550                 }
1551                 lint
1552             });
1553         }
1554
1555         if !inline_spans.is_empty() {
1556             cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_generic_bounds, |lint| {
1557                 lint.set_span(inline_spans);
1558                 lint.multipart_suggestion(
1559                     fluent::suggestion,
1560                     inline_sugg,
1561                     Applicability::MachineApplicable,
1562                 );
1563                 if !suggested_changing_assoc_types {
1564                     TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1565                 }
1566                 lint
1567             });
1568         }
1569     }
1570 }
1571
1572 declare_lint_pass!(
1573     /// Lint constants that are erroneous.
1574     /// Without this lint, we might not get any diagnostic if the constant is
1575     /// unused within this crate, even though downstream crates can't use it
1576     /// without producing an error.
1577     UnusedBrokenConst => []
1578 );
1579
1580 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1581     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1582         match it.kind {
1583             hir::ItemKind::Const(_, body_id) => {
1584                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1585                 // trigger the query once for all constants since that will already report the errors
1586                 cx.tcx.ensure().const_eval_poly(def_id);
1587             }
1588             hir::ItemKind::Static(_, _, body_id) => {
1589                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1590                 cx.tcx.ensure().eval_static_initializer(def_id);
1591             }
1592             _ => {}
1593         }
1594     }
1595 }
1596
1597 declare_lint! {
1598     /// The `trivial_bounds` lint detects trait bounds that don't depend on
1599     /// any type parameters.
1600     ///
1601     /// ### Example
1602     ///
1603     /// ```rust
1604     /// #![feature(trivial_bounds)]
1605     /// pub struct A where i32: Copy;
1606     /// ```
1607     ///
1608     /// {{produces}}
1609     ///
1610     /// ### Explanation
1611     ///
1612     /// Usually you would not write a trait bound that you know is always
1613     /// true, or never true. However, when using macros, the macro may not
1614     /// know whether or not the constraint would hold or not at the time when
1615     /// generating the code. Currently, the compiler does not alert you if the
1616     /// constraint is always true, and generates an error if it is never true.
1617     /// The `trivial_bounds` feature changes this to be a warning in both
1618     /// cases, giving macros more freedom and flexibility to generate code,
1619     /// while still providing a signal when writing non-macro code that
1620     /// something is amiss.
1621     ///
1622     /// See [RFC 2056] for more details. This feature is currently only
1623     /// available on the nightly channel, see [tracking issue #48214].
1624     ///
1625     /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1626     /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1627     TRIVIAL_BOUNDS,
1628     Warn,
1629     "these bounds don't depend on an type parameters"
1630 }
1631
1632 declare_lint_pass!(
1633     /// Lint for trait and lifetime bounds that don't depend on type parameters
1634     /// which either do nothing, or stop the item from being used.
1635     TrivialConstraints => [TRIVIAL_BOUNDS]
1636 );
1637
1638 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1639     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1640         use rustc_middle::ty::visit::TypeVisitable;
1641         use rustc_middle::ty::PredicateKind::*;
1642
1643         if cx.tcx.features().trivial_bounds {
1644             let predicates = cx.tcx.predicates_of(item.owner_id);
1645             for &(predicate, span) in predicates.predicates {
1646                 let predicate_kind_name = match predicate.kind().skip_binder() {
1647                     Trait(..) => "trait",
1648                     TypeOutlives(..) |
1649                     RegionOutlives(..) => "lifetime",
1650
1651                     // Ignore projections, as they can only be global
1652                     // if the trait bound is global
1653                     Projection(..) |
1654                     // Ignore bounds that a user can't type
1655                     WellFormed(..) |
1656                     ObjectSafe(..) |
1657                     ClosureKind(..) |
1658                     Subtype(..) |
1659                     Coerce(..) |
1660                     ConstEvaluatable(..) |
1661                     ConstEquate(..) |
1662                     Ambiguous |
1663                     TypeWellFormedFromEnv(..) => continue,
1664                 };
1665                 if predicate.is_global() {
1666                     cx.struct_span_lint(
1667                         TRIVIAL_BOUNDS,
1668                         span,
1669                         fluent::lint_builtin_trivial_bounds,
1670                         |lint| {
1671                             lint.set_arg("predicate_kind_name", predicate_kind_name)
1672                                 .set_arg("predicate", predicate)
1673                         },
1674                     );
1675                 }
1676             }
1677         }
1678     }
1679 }
1680
1681 declare_lint_pass!(
1682     /// Does nothing as a lint pass, but registers some `Lint`s
1683     /// which are used by other parts of the compiler.
1684     SoftLints => [
1685         WHILE_TRUE,
1686         BOX_POINTERS,
1687         NON_SHORTHAND_FIELD_PATTERNS,
1688         UNSAFE_CODE,
1689         MISSING_DOCS,
1690         MISSING_COPY_IMPLEMENTATIONS,
1691         MISSING_DEBUG_IMPLEMENTATIONS,
1692         ANONYMOUS_PARAMETERS,
1693         UNUSED_DOC_COMMENTS,
1694         NO_MANGLE_CONST_ITEMS,
1695         NO_MANGLE_GENERIC_ITEMS,
1696         MUTABLE_TRANSMUTES,
1697         UNSTABLE_FEATURES,
1698         UNREACHABLE_PUB,
1699         TYPE_ALIAS_BOUNDS,
1700         TRIVIAL_BOUNDS
1701     ]
1702 );
1703
1704 declare_lint! {
1705     /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1706     /// pattern], which is deprecated.
1707     ///
1708     /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1709     ///
1710     /// ### Example
1711     ///
1712     /// ```rust,edition2018
1713     /// let x = 123;
1714     /// match x {
1715     ///     0...100 => {}
1716     ///     _ => {}
1717     /// }
1718     /// ```
1719     ///
1720     /// {{produces}}
1721     ///
1722     /// ### Explanation
1723     ///
1724     /// The `...` range pattern syntax was changed to `..=` to avoid potential
1725     /// confusion with the [`..` range expression]. Use the new form instead.
1726     ///
1727     /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1728     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1729     Warn,
1730     "`...` range patterns are deprecated",
1731     @future_incompatible = FutureIncompatibleInfo {
1732         reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1733         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1734     };
1735 }
1736
1737 #[derive(Default)]
1738 pub struct EllipsisInclusiveRangePatterns {
1739     /// If `Some(_)`, suppress all subsequent pattern
1740     /// warnings for better diagnostics.
1741     node_id: Option<ast::NodeId>,
1742 }
1743
1744 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1745
1746 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1747     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1748         if self.node_id.is_some() {
1749             // Don't recursively warn about patterns inside range endpoints.
1750             return;
1751         }
1752
1753         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1754
1755         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1756         /// corresponding to the ellipsis.
1757         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1758             match &pat.kind {
1759                 PatKind::Range(
1760                     a,
1761                     Some(b),
1762                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1763                 ) => Some((a.as_deref(), b, *span)),
1764                 _ => None,
1765             }
1766         }
1767
1768         let (parenthesise, endpoints) = match &pat.kind {
1769             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1770             _ => (false, matches_ellipsis_pat(pat)),
1771         };
1772
1773         if let Some((start, end, join)) = endpoints {
1774             let msg = fluent::lint_builtin_ellipsis_inclusive_range_patterns;
1775             let suggestion = fluent::suggestion;
1776             if parenthesise {
1777                 self.node_id = Some(pat.id);
1778                 let end = expr_to_string(&end);
1779                 let replace = match start {
1780                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1781                     None => format!("&(..={})", end),
1782                 };
1783                 if join.edition() >= Edition::Edition2021 {
1784                     cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1785                         span: pat.span,
1786                         suggestion: pat.span,
1787                         replace,
1788                     });
1789                 } else {
1790                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg, |lint| {
1791                         lint.span_suggestion(
1792                             pat.span,
1793                             suggestion,
1794                             replace,
1795                             Applicability::MachineApplicable,
1796                         )
1797                     });
1798                 }
1799             } else {
1800                 let replace = "..=";
1801                 if join.edition() >= Edition::Edition2021 {
1802                     cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1803                         span: pat.span,
1804                         suggestion: join,
1805                         replace: replace.to_string(),
1806                     });
1807                 } else {
1808                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg, |lint| {
1809                         lint.span_suggestion_short(
1810                             join,
1811                             suggestion,
1812                             replace,
1813                             Applicability::MachineApplicable,
1814                         )
1815                     });
1816                 }
1817             };
1818         }
1819     }
1820
1821     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1822         if let Some(node_id) = self.node_id {
1823             if pat.id == node_id {
1824                 self.node_id = None
1825             }
1826         }
1827     }
1828 }
1829
1830 declare_lint! {
1831     /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1832     /// that are not able to be run by the test harness because they are in a
1833     /// position where they are not nameable.
1834     ///
1835     /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1836     ///
1837     /// ### Example
1838     ///
1839     /// ```rust,test
1840     /// fn main() {
1841     ///     #[test]
1842     ///     fn foo() {
1843     ///         // This test will not fail because it does not run.
1844     ///         assert_eq!(1, 2);
1845     ///     }
1846     /// }
1847     /// ```
1848     ///
1849     /// {{produces}}
1850     ///
1851     /// ### Explanation
1852     ///
1853     /// In order for the test harness to run a test, the test function must be
1854     /// located in a position where it can be accessed from the crate root.
1855     /// This generally means it must be defined in a module, and not anywhere
1856     /// else such as inside another function. The compiler previously allowed
1857     /// this without an error, so a lint was added as an alert that a test is
1858     /// not being used. Whether or not this should be allowed has not yet been
1859     /// decided, see [RFC 2471] and [issue #36629].
1860     ///
1861     /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1862     /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1863     UNNAMEABLE_TEST_ITEMS,
1864     Warn,
1865     "detects an item that cannot be named being marked as `#[test_case]`",
1866     report_in_external_macro
1867 }
1868
1869 pub struct UnnameableTestItems {
1870     boundary: Option<hir::OwnerId>, // Id of the item under which things are not nameable
1871     items_nameable: bool,
1872 }
1873
1874 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1875
1876 impl UnnameableTestItems {
1877     pub fn new() -> Self {
1878         Self { boundary: None, items_nameable: true }
1879     }
1880 }
1881
1882 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1883     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1884         if self.items_nameable {
1885             if let hir::ItemKind::Mod(..) = it.kind {
1886             } else {
1887                 self.items_nameable = false;
1888                 self.boundary = Some(it.owner_id);
1889             }
1890             return;
1891         }
1892
1893         let attrs = cx.tcx.hir().attrs(it.hir_id());
1894         if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1895             cx.struct_span_lint(
1896                 UNNAMEABLE_TEST_ITEMS,
1897                 attr.span,
1898                 fluent::lint_builtin_unnameable_test_items,
1899                 |lint| lint,
1900             );
1901         }
1902     }
1903
1904     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1905         if !self.items_nameable && self.boundary == Some(it.owner_id) {
1906             self.items_nameable = true;
1907         }
1908     }
1909 }
1910
1911 declare_lint! {
1912     /// The `keyword_idents` lint detects edition keywords being used as an
1913     /// identifier.
1914     ///
1915     /// ### Example
1916     ///
1917     /// ```rust,edition2015,compile_fail
1918     /// #![deny(keyword_idents)]
1919     /// // edition 2015
1920     /// fn dyn() {}
1921     /// ```
1922     ///
1923     /// {{produces}}
1924     ///
1925     /// ### Explanation
1926     ///
1927     /// Rust [editions] allow the language to evolve without breaking
1928     /// backwards compatibility. This lint catches code that uses new keywords
1929     /// that are added to the language that are used as identifiers (such as a
1930     /// variable name, function name, etc.). If you switch the compiler to a
1931     /// new edition without updating the code, then it will fail to compile if
1932     /// you are using a new keyword as an identifier.
1933     ///
1934     /// You can manually change the identifiers to a non-keyword, or use a
1935     /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1936     ///
1937     /// This lint solves the problem automatically. It is "allow" by default
1938     /// because the code is perfectly valid in older editions. The [`cargo
1939     /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1940     /// and automatically apply the suggested fix from the compiler (which is
1941     /// to use a raw identifier). This provides a completely automated way to
1942     /// update old code for a new edition.
1943     ///
1944     /// [editions]: https://doc.rust-lang.org/edition-guide/
1945     /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1946     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1947     pub KEYWORD_IDENTS,
1948     Allow,
1949     "detects edition keywords being used as an identifier",
1950     @future_incompatible = FutureIncompatibleInfo {
1951         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1952         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1953     };
1954 }
1955
1956 declare_lint_pass!(
1957     /// Check for uses of edition keywords used as an identifier.
1958     KeywordIdents => [KEYWORD_IDENTS]
1959 );
1960
1961 struct UnderMacro(bool);
1962
1963 impl KeywordIdents {
1964     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1965         for tt in tokens.into_trees() {
1966             match tt {
1967                 // Only report non-raw idents.
1968                 TokenTree::Token(token, _) => {
1969                     if let Some((ident, false)) = token.ident() {
1970                         self.check_ident_token(cx, UnderMacro(true), ident);
1971                     }
1972                 }
1973                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1974             }
1975         }
1976     }
1977
1978     fn check_ident_token(
1979         &mut self,
1980         cx: &EarlyContext<'_>,
1981         UnderMacro(under_macro): UnderMacro,
1982         ident: Ident,
1983     ) {
1984         let next_edition = match cx.sess().edition() {
1985             Edition::Edition2015 => {
1986                 match ident.name {
1987                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1988
1989                     // rust-lang/rust#56327: Conservatively do not
1990                     // attempt to report occurrences of `dyn` within
1991                     // macro definitions or invocations, because `dyn`
1992                     // can legitimately occur as a contextual keyword
1993                     // in 2015 code denoting its 2018 meaning, and we
1994                     // do not want rustfix to inject bugs into working
1995                     // code by rewriting such occurrences.
1996                     //
1997                     // But if we see `dyn` outside of a macro, we know
1998                     // its precise role in the parsed AST and thus are
1999                     // assured this is truly an attempt to use it as
2000                     // an identifier.
2001                     kw::Dyn if !under_macro => Edition::Edition2018,
2002
2003                     _ => return,
2004                 }
2005             }
2006
2007             // There are no new keywords yet for the 2018 edition and beyond.
2008             _ => return,
2009         };
2010
2011         // Don't lint `r#foo`.
2012         if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2013             return;
2014         }
2015
2016         cx.struct_span_lint(
2017             KEYWORD_IDENTS,
2018             ident.span,
2019             fluent::lint_builtin_keyword_idents,
2020             |lint| {
2021                 lint.set_arg("kw", ident.clone()).set_arg("next", next_edition).span_suggestion(
2022                     ident.span,
2023                     fluent::suggestion,
2024                     format!("r#{}", ident),
2025                     Applicability::MachineApplicable,
2026                 )
2027             },
2028         );
2029     }
2030 }
2031
2032 impl EarlyLintPass for KeywordIdents {
2033     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
2034         self.check_tokens(cx, mac_def.body.tokens.clone());
2035     }
2036     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2037         self.check_tokens(cx, mac.args.tokens.clone());
2038     }
2039     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2040         self.check_ident_token(cx, UnderMacro(false), ident);
2041     }
2042 }
2043
2044 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2045
2046 impl ExplicitOutlivesRequirements {
2047     fn lifetimes_outliving_lifetime<'tcx>(
2048         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2049         def_id: DefId,
2050     ) -> Vec<ty::Region<'tcx>> {
2051         inferred_outlives
2052             .iter()
2053             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2054                 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2055                     ty::ReEarlyBound(ebr) if ebr.def_id == def_id => Some(b),
2056                     _ => None,
2057                 },
2058                 _ => None,
2059             })
2060             .collect()
2061     }
2062
2063     fn lifetimes_outliving_type<'tcx>(
2064         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2065         index: u32,
2066     ) -> Vec<ty::Region<'tcx>> {
2067         inferred_outlives
2068             .iter()
2069             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2070                 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2071                     a.is_param(index).then_some(b)
2072                 }
2073                 _ => None,
2074             })
2075             .collect()
2076     }
2077
2078     fn collect_outlives_bound_spans<'tcx>(
2079         &self,
2080         tcx: TyCtxt<'tcx>,
2081         bounds: &hir::GenericBounds<'_>,
2082         inferred_outlives: &[ty::Region<'tcx>],
2083     ) -> Vec<(usize, Span)> {
2084         use rustc_middle::middle::resolve_lifetime::Region;
2085
2086         bounds
2087             .iter()
2088             .enumerate()
2089             .filter_map(|(i, bound)| {
2090                 if let hir::GenericBound::Outlives(lifetime) = bound {
2091                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
2092                         Some(Region::EarlyBound(def_id)) => inferred_outlives.iter().any(|r| {
2093                             if let ty::ReEarlyBound(ebr) = **r {
2094                                 ebr.def_id == def_id
2095                             } else {
2096                                 false
2097                             }
2098                         }),
2099                         _ => false,
2100                     };
2101                     is_inferred.then_some((i, bound.span()))
2102                 } else {
2103                     None
2104                 }
2105             })
2106             .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2107             .collect()
2108     }
2109
2110     fn consolidate_outlives_bound_spans(
2111         &self,
2112         lo: Span,
2113         bounds: &hir::GenericBounds<'_>,
2114         bound_spans: Vec<(usize, Span)>,
2115     ) -> Vec<Span> {
2116         if bounds.is_empty() {
2117             return Vec::new();
2118         }
2119         if bound_spans.len() == bounds.len() {
2120             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2121             // If all bounds are inferable, we want to delete the colon, so
2122             // start from just after the parameter (span passed as argument)
2123             vec![lo.to(last_bound_span)]
2124         } else {
2125             let mut merged = Vec::new();
2126             let mut last_merged_i = None;
2127
2128             let mut from_start = true;
2129             for (i, bound_span) in bound_spans {
2130                 match last_merged_i {
2131                     // If the first bound is inferable, our span should also eat the leading `+`.
2132                     None if i == 0 => {
2133                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2134                         last_merged_i = Some(0);
2135                     }
2136                     // If consecutive bounds are inferable, merge their spans
2137                     Some(h) if i == h + 1 => {
2138                         if let Some(tail) = merged.last_mut() {
2139                             // Also eat the trailing `+` if the first
2140                             // more-than-one bound is inferable
2141                             let to_span = if from_start && i < bounds.len() {
2142                                 bounds[i + 1].span().shrink_to_lo()
2143                             } else {
2144                                 bound_span
2145                             };
2146                             *tail = tail.to(to_span);
2147                             last_merged_i = Some(i);
2148                         } else {
2149                             bug!("another bound-span visited earlier");
2150                         }
2151                     }
2152                     _ => {
2153                         // When we find a non-inferable bound, subsequent inferable bounds
2154                         // won't be consecutive from the start (and we'll eat the leading
2155                         // `+` rather than the trailing one)
2156                         from_start = false;
2157                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2158                         last_merged_i = Some(i);
2159                     }
2160                 }
2161             }
2162             merged
2163         }
2164     }
2165 }
2166
2167 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2168     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2169         use rustc_middle::middle::resolve_lifetime::Region;
2170
2171         let def_id = item.owner_id.def_id;
2172         if let hir::ItemKind::Struct(_, ref hir_generics)
2173         | hir::ItemKind::Enum(_, ref hir_generics)
2174         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2175         {
2176             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2177             if inferred_outlives.is_empty() {
2178                 return;
2179             }
2180
2181             let ty_generics = cx.tcx.generics_of(def_id);
2182
2183             let mut bound_count = 0;
2184             let mut lint_spans = Vec::new();
2185             let mut where_lint_spans = Vec::new();
2186             let mut dropped_predicate_count = 0;
2187             let num_predicates = hir_generics.predicates.len();
2188             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2189                 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2190                     hir::WherePredicate::RegionPredicate(predicate) => {
2191                         if let Some(Region::EarlyBound(region_def_id)) =
2192                             cx.tcx.named_region(predicate.lifetime.hir_id)
2193                         {
2194                             (
2195                                 Self::lifetimes_outliving_lifetime(
2196                                     inferred_outlives,
2197                                     region_def_id,
2198                                 ),
2199                                 &predicate.bounds,
2200                                 predicate.span,
2201                                 predicate.in_where_clause,
2202                             )
2203                         } else {
2204                             continue;
2205                         }
2206                     }
2207                     hir::WherePredicate::BoundPredicate(predicate) => {
2208                         // FIXME we can also infer bounds on associated types,
2209                         // and should check for them here.
2210                         match predicate.bounded_ty.kind {
2211                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2212                                 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2213                                     continue
2214                                 };
2215                                 let index = ty_generics.param_def_id_to_index[&def_id];
2216                                 (
2217                                     Self::lifetimes_outliving_type(inferred_outlives, index),
2218                                     &predicate.bounds,
2219                                     predicate.span,
2220                                     predicate.origin == PredicateOrigin::WhereClause,
2221                                 )
2222                             }
2223                             _ => {
2224                                 continue;
2225                             }
2226                         }
2227                     }
2228                     _ => continue,
2229                 };
2230                 if relevant_lifetimes.is_empty() {
2231                     continue;
2232                 }
2233
2234                 let bound_spans =
2235                     self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2236                 bound_count += bound_spans.len();
2237
2238                 let drop_predicate = bound_spans.len() == bounds.len();
2239                 if drop_predicate {
2240                     dropped_predicate_count += 1;
2241                 }
2242
2243                 if drop_predicate && !in_where_clause {
2244                     lint_spans.push(span);
2245                 } else if drop_predicate && i + 1 < num_predicates {
2246                     // If all the bounds on a predicate were inferable and there are
2247                     // further predicates, we want to eat the trailing comma.
2248                     let next_predicate_span = hir_generics.predicates[i + 1].span();
2249                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2250                 } else {
2251                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2252                         span.shrink_to_lo(),
2253                         bounds,
2254                         bound_spans,
2255                     ));
2256                 }
2257             }
2258
2259             // If all predicates are inferable, drop the entire clause
2260             // (including the `where`)
2261             if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2262             {
2263                 let where_span = hir_generics.where_clause_span;
2264                 // Extend the where clause back to the closing `>` of the
2265                 // generics, except for tuple struct, which have the `where`
2266                 // after the fields of the struct.
2267                 let full_where_span =
2268                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2269                         where_span
2270                     } else {
2271                         hir_generics.span.shrink_to_hi().to(where_span)
2272                     };
2273                 lint_spans.push(full_where_span);
2274             } else {
2275                 lint_spans.extend(where_lint_spans);
2276             }
2277
2278             if !lint_spans.is_empty() {
2279                 cx.struct_span_lint(
2280                     EXPLICIT_OUTLIVES_REQUIREMENTS,
2281                     lint_spans.clone(),
2282                     fluent::lint_builtin_explicit_outlives,
2283                     |lint| {
2284                         lint.set_arg("count", bound_count).multipart_suggestion(
2285                             fluent::suggestion,
2286                             lint_spans
2287                                 .into_iter()
2288                                 .map(|span| (span, String::new()))
2289                                 .collect::<Vec<_>>(),
2290                             Applicability::MachineApplicable,
2291                         )
2292                     },
2293                 );
2294             }
2295         }
2296     }
2297 }
2298
2299 declare_lint! {
2300     /// The `incomplete_features` lint detects unstable features enabled with
2301     /// the [`feature` attribute] that may function improperly in some or all
2302     /// cases.
2303     ///
2304     /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2305     ///
2306     /// ### Example
2307     ///
2308     /// ```rust
2309     /// #![feature(generic_const_exprs)]
2310     /// ```
2311     ///
2312     /// {{produces}}
2313     ///
2314     /// ### Explanation
2315     ///
2316     /// Although it is encouraged for people to experiment with unstable
2317     /// features, some of them are known to be incomplete or faulty. This lint
2318     /// is a signal that the feature has not yet been finished, and you may
2319     /// experience problems with it.
2320     pub INCOMPLETE_FEATURES,
2321     Warn,
2322     "incomplete features that may function improperly in some or all cases"
2323 }
2324
2325 declare_lint_pass!(
2326     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2327     IncompleteFeatures => [INCOMPLETE_FEATURES]
2328 );
2329
2330 impl EarlyLintPass for IncompleteFeatures {
2331     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2332         let features = cx.sess().features_untracked();
2333         features
2334             .declared_lang_features
2335             .iter()
2336             .map(|(name, span, _)| (name, span))
2337             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2338             .filter(|(&name, _)| features.incomplete(name))
2339             .for_each(|(&name, &span)| {
2340                 cx.struct_span_lint(
2341                     INCOMPLETE_FEATURES,
2342                     span,
2343                     fluent::lint_builtin_incomplete_features,
2344                     |lint| {
2345                         lint.set_arg("name", name);
2346                         if let Some(n) =
2347                             rustc_feature::find_feature_issue(name, GateIssue::Language)
2348                         {
2349                             lint.set_arg("n", n);
2350                             lint.note(fluent::note);
2351                         }
2352                         if HAS_MIN_FEATURES.contains(&name) {
2353                             lint.help(fluent::help);
2354                         }
2355                         lint
2356                     },
2357                 )
2358             });
2359     }
2360 }
2361
2362 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2363
2364 declare_lint! {
2365     /// The `invalid_value` lint detects creating a value that is not valid,
2366     /// such as a null reference.
2367     ///
2368     /// ### Example
2369     ///
2370     /// ```rust,no_run
2371     /// # #![allow(unused)]
2372     /// unsafe {
2373     ///     let x: &'static i32 = std::mem::zeroed();
2374     /// }
2375     /// ```
2376     ///
2377     /// {{produces}}
2378     ///
2379     /// ### Explanation
2380     ///
2381     /// In some situations the compiler can detect that the code is creating
2382     /// an invalid value, which should be avoided.
2383     ///
2384     /// In particular, this lint will check for improper use of
2385     /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2386     /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2387     /// lint should provide extra information to indicate what the problem is
2388     /// and a possible solution.
2389     ///
2390     /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2391     /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2392     /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2393     /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2394     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2395     pub INVALID_VALUE,
2396     Warn,
2397     "an invalid value is being created (such as a null reference)"
2398 }
2399
2400 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2401
2402 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2403     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2404         #[derive(Debug, Copy, Clone, PartialEq)]
2405         enum InitKind {
2406             Zeroed,
2407             Uninit,
2408         }
2409
2410         /// Information about why a type cannot be initialized this way.
2411         /// Contains an error message and optionally a span to point at.
2412         type InitError = (String, Option<Span>);
2413
2414         /// Test if this constant is all-0.
2415         fn is_zero(expr: &hir::Expr<'_>) -> bool {
2416             use hir::ExprKind::*;
2417             use rustc_ast::LitKind::*;
2418             match &expr.kind {
2419                 Lit(lit) => {
2420                     if let Int(i, _) = lit.node {
2421                         i == 0
2422                     } else {
2423                         false
2424                     }
2425                 }
2426                 Tup(tup) => tup.iter().all(is_zero),
2427                 _ => false,
2428             }
2429         }
2430
2431         /// Determine if this expression is a "dangerous initialization".
2432         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2433             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2434                 // Find calls to `mem::{uninitialized,zeroed}` methods.
2435                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2436                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2437                     match cx.tcx.get_diagnostic_name(def_id) {
2438                         Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2439                         Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2440                         Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2441                         _ => {}
2442                     }
2443                 }
2444             } else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
2445                 // Find problematic calls to `MaybeUninit::assume_init`.
2446                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2447                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2448                     // This is a call to *some* method named `assume_init`.
2449                     // See if the `self` parameter is one of the dangerous constructors.
2450                     if let hir::ExprKind::Call(ref path_expr, _) = receiver.kind {
2451                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2452                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2453                             match cx.tcx.get_diagnostic_name(def_id) {
2454                                 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2455                                 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2456                                 _ => {}
2457                             }
2458                         }
2459                     }
2460                 }
2461             }
2462
2463             None
2464         }
2465
2466         fn variant_find_init_error<'tcx>(
2467             cx: &LateContext<'tcx>,
2468             variant: &VariantDef,
2469             substs: ty::SubstsRef<'tcx>,
2470             descr: &str,
2471             init: InitKind,
2472         ) -> Option<InitError> {
2473             variant.fields.iter().find_map(|field| {
2474                 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|(mut msg, span)| {
2475                     if span.is_none() {
2476                         // Point to this field, should be helpful for figuring
2477                         // out where the source of the error is.
2478                         let span = cx.tcx.def_span(field.did);
2479                         write!(&mut msg, " (in this {descr})").unwrap();
2480                         (msg, Some(span))
2481                     } else {
2482                         // Just forward.
2483                         (msg, span)
2484                     }
2485                 })
2486             })
2487         }
2488
2489         /// Return `Some` only if we are sure this type does *not*
2490         /// allow zero initialization.
2491         fn ty_find_init_error<'tcx>(
2492             cx: &LateContext<'tcx>,
2493             ty: Ty<'tcx>,
2494             init: InitKind,
2495         ) -> Option<InitError> {
2496             use rustc_type_ir::sty::TyKind::*;
2497             match ty.kind() {
2498                 // Primitive types that don't like 0 as a value.
2499                 Ref(..) => Some(("references must be non-null".to_string(), None)),
2500                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2501                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2502                 Never => Some(("the `!` type has no valid value".to_string(), None)),
2503                 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2504                 // raw ptr to dyn Trait
2505                 {
2506                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2507                 }
2508                 // Primitive types with other constraints.
2509                 Bool if init == InitKind::Uninit => {
2510                     Some(("booleans must be either `true` or `false`".to_string(), None))
2511                 }
2512                 Char if init == InitKind::Uninit => {
2513                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
2514                 }
2515                 Int(_) | Uint(_) if init == InitKind::Uninit => {
2516                     Some(("integers must not be uninitialized".to_string(), None))
2517                 }
2518                 Float(_) if init == InitKind::Uninit => {
2519                     Some(("floats must not be uninitialized".to_string(), None))
2520                 }
2521                 RawPtr(_) if init == InitKind::Uninit => {
2522                     Some(("raw pointers must not be uninitialized".to_string(), None))
2523                 }
2524                 // Recurse and checks for some compound types. (but not unions)
2525                 Adt(adt_def, substs) if !adt_def.is_union() => {
2526                     // First check if this ADT has a layout attribute (like `NonNull` and friends).
2527                     use std::ops::Bound;
2528                     match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
2529                         // We exploit here that `layout_scalar_valid_range` will never
2530                         // return `Bound::Excluded`.  (And we have tests checking that we
2531                         // handle the attribute correctly.)
2532                         // We don't add a span since users cannot declare such types anyway.
2533                         (Bound::Included(lo), Bound::Included(hi)) if 0 < lo && lo < hi => {
2534                             return Some((format!("`{}` must be non-null", ty), None));
2535                         }
2536                         (Bound::Included(lo), Bound::Unbounded) if 0 < lo => {
2537                             return Some((format!("`{}` must be non-null", ty), None));
2538                         }
2539                         (Bound::Included(_), _) | (_, Bound::Included(_))
2540                             if init == InitKind::Uninit =>
2541                         {
2542                             return Some((
2543                                 format!(
2544                                     "`{}` must be initialized inside its custom valid range",
2545                                     ty,
2546                                 ),
2547                                 None,
2548                             ));
2549                         }
2550                         _ => {}
2551                     }
2552                     // Handle structs.
2553                     if adt_def.is_struct() {
2554                         return variant_find_init_error(
2555                             cx,
2556                             adt_def.non_enum_variant(),
2557                             substs,
2558                             "struct field",
2559                             init,
2560                         );
2561                     }
2562                     // And now, enums.
2563                     let span = cx.tcx.def_span(adt_def.did());
2564                     let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
2565                         let definitely_inhabited = match variant
2566                             .inhabited_predicate(cx.tcx, *adt_def)
2567                             .subst(cx.tcx, substs)
2568                             .apply_any_module(cx.tcx, cx.param_env)
2569                         {
2570                             // Entirely skip uninhbaited variants.
2571                             Some(false) => return None,
2572                             // Forward the others, but remember which ones are definitely inhabited.
2573                             Some(true) => true,
2574                             None => false,
2575                         };
2576                         Some((variant, definitely_inhabited))
2577                     });
2578                     let Some(first_variant) = potential_variants.next() else {
2579                         return Some(("enums with no inhabited variants have no valid value".to_string(), Some(span)));
2580                     };
2581                     // So we have at least one potentially inhabited variant. Might we have two?
2582                     let Some(second_variant) = potential_variants.next() else {
2583                         // There is only one potentially inhabited variant. So we can recursively check that variant!
2584                         return variant_find_init_error(
2585                             cx,
2586                             &first_variant.0,
2587                             substs,
2588                             "field of the only potentially inhabited enum variant",
2589                             init,
2590                         );
2591                     };
2592                     // So we have at least two potentially inhabited variants.
2593                     // If we can prove that we have at least two *definitely* inhabited variants,
2594                     // then we have a tag and hence leaving this uninit is definitely disallowed.
2595                     // (Leaving it zeroed could be okay, depending on which variant is encoded as zero tag.)
2596                     if init == InitKind::Uninit {
2597                         let definitely_inhabited = (first_variant.1 as usize)
2598                             + (second_variant.1 as usize)
2599                             + potential_variants
2600                                 .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
2601                                 .count();
2602                         if definitely_inhabited > 1 {
2603                             return Some((
2604                                 "enums with multiple inhabited variants have to be initialized to a variant".to_string(),
2605                                 Some(span),
2606                             ));
2607                         }
2608                     }
2609                     // We couldn't find anything wrong here.
2610                     None
2611                 }
2612                 Tuple(..) => {
2613                     // Proceed recursively, check all fields.
2614                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2615                 }
2616                 Array(ty, len) => {
2617                     if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2618                         // Array length known at array non-empty -- recurse.
2619                         ty_find_init_error(cx, *ty, init)
2620                     } else {
2621                         // Empty array or size unknown.
2622                         None
2623                     }
2624                 }
2625                 // Conservative fallback.
2626                 _ => None,
2627             }
2628         }
2629
2630         if let Some(init) = is_dangerous_init(cx, expr) {
2631             // This conjures an instance of a type out of nothing,
2632             // using zeroed or uninitialized memory.
2633             // We are extremely conservative with what we warn about.
2634             let conjured_ty = cx.typeck_results().expr_ty(expr);
2635             if let Some((msg, span)) =
2636                 with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2637             {
2638                 // FIXME(davidtwco): make translatable
2639                 cx.struct_span_lint(
2640                     INVALID_VALUE,
2641                     expr.span,
2642                     DelayDm(|| {
2643                         format!(
2644                             "the type `{}` does not permit {}",
2645                             conjured_ty,
2646                             match init {
2647                                 InitKind::Zeroed => "zero-initialization",
2648                                 InitKind::Uninit => "being left uninitialized",
2649                             },
2650                         )
2651                     }),
2652                     |lint| {
2653                         lint.span_label(
2654                             expr.span,
2655                             "this code causes undefined behavior when executed",
2656                         );
2657                         lint.span_label(
2658                             expr.span,
2659                             "help: use `MaybeUninit<T>` instead, \
2660                             and only call `assume_init` after initialization is done",
2661                         );
2662                         if let Some(span) = span {
2663                             lint.span_note(span, &msg);
2664                         } else {
2665                             lint.note(&msg);
2666                         }
2667                         lint
2668                     },
2669                 );
2670             }
2671         }
2672     }
2673 }
2674
2675 declare_lint! {
2676     /// The `clashing_extern_declarations` lint detects when an `extern fn`
2677     /// has been declared with the same name but different types.
2678     ///
2679     /// ### Example
2680     ///
2681     /// ```rust
2682     /// mod m {
2683     ///     extern "C" {
2684     ///         fn foo();
2685     ///     }
2686     /// }
2687     ///
2688     /// extern "C" {
2689     ///     fn foo(_: u32);
2690     /// }
2691     /// ```
2692     ///
2693     /// {{produces}}
2694     ///
2695     /// ### Explanation
2696     ///
2697     /// Because two symbols of the same name cannot be resolved to two
2698     /// different functions at link time, and one function cannot possibly
2699     /// have two types, a clashing extern declaration is almost certainly a
2700     /// mistake. Check to make sure that the `extern` definitions are correct
2701     /// and equivalent, and possibly consider unifying them in one location.
2702     ///
2703     /// This lint does not run between crates because a project may have
2704     /// dependencies which both rely on the same extern function, but declare
2705     /// it in a different (but valid) way. For example, they may both declare
2706     /// an opaque type for one or more of the arguments (which would end up
2707     /// distinct types), or use types that are valid conversions in the
2708     /// language the `extern fn` is defined in. In these cases, the compiler
2709     /// can't say that the clashing declaration is incorrect.
2710     pub CLASHING_EXTERN_DECLARATIONS,
2711     Warn,
2712     "detects when an extern fn has been declared with the same name but different types"
2713 }
2714
2715 pub struct ClashingExternDeclarations {
2716     /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2717     /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2718     /// the symbol should be reported as a clashing declaration.
2719     // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2720     // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2721     seen_decls: FxHashMap<Symbol, HirId>,
2722 }
2723
2724 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2725 /// just from declaration itself. This is important because we don't want to report clashes on
2726 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2727 /// different name.
2728 enum SymbolName {
2729     /// The name of the symbol + the span of the annotation which introduced the link name.
2730     Link(Symbol, Span),
2731     /// No link name, so just the name of the symbol.
2732     Normal(Symbol),
2733 }
2734
2735 impl SymbolName {
2736     fn get_name(&self) -> Symbol {
2737         match self {
2738             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2739         }
2740     }
2741 }
2742
2743 impl ClashingExternDeclarations {
2744     pub(crate) fn new() -> Self {
2745         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2746     }
2747     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2748     /// for the item, return its HirId without updating the set.
2749     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2750         let did = fi.owner_id.to_def_id();
2751         let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2752         let name = Symbol::intern(tcx.symbol_name(instance).name);
2753         if let Some(&hir_id) = self.seen_decls.get(&name) {
2754             // Avoid updating the map with the new entry when we do find a collision. We want to
2755             // make sure we're always pointing to the first definition as the previous declaration.
2756             // This lets us avoid emitting "knock-on" diagnostics.
2757             Some(hir_id)
2758         } else {
2759             self.seen_decls.insert(name, fi.hir_id())
2760         }
2761     }
2762
2763     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2764     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2765     /// symbol's name.
2766     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2767         if let Some((overridden_link_name, overridden_link_name_span)) =
2768             tcx.codegen_fn_attrs(fi.owner_id).link_name.map(|overridden_link_name| {
2769                 // FIXME: Instead of searching through the attributes again to get span
2770                 // information, we could have codegen_fn_attrs also give span information back for
2771                 // where the attribute was defined. However, until this is found to be a
2772                 // bottleneck, this does just fine.
2773                 (
2774                     overridden_link_name,
2775                     tcx.get_attr(fi.owner_id.to_def_id(), sym::link_name).unwrap().span,
2776                 )
2777             })
2778         {
2779             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2780         } else {
2781             SymbolName::Normal(fi.ident.name)
2782         }
2783     }
2784
2785     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2786     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2787     /// with the same members (as the declarations shouldn't clash).
2788     fn structurally_same_type<'tcx>(
2789         cx: &LateContext<'tcx>,
2790         a: Ty<'tcx>,
2791         b: Ty<'tcx>,
2792         ckind: CItemKind,
2793     ) -> bool {
2794         fn structurally_same_type_impl<'tcx>(
2795             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2796             cx: &LateContext<'tcx>,
2797             a: Ty<'tcx>,
2798             b: Ty<'tcx>,
2799             ckind: CItemKind,
2800         ) -> bool {
2801             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2802             let tcx = cx.tcx;
2803
2804             // Given a transparent newtype, reach through and grab the inner
2805             // type unless the newtype makes the type non-null.
2806             let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2807                 let mut ty = ty;
2808                 loop {
2809                     if let ty::Adt(def, substs) = *ty.kind() {
2810                         let is_transparent = def.repr().transparent();
2811                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2812                         debug!(
2813                             "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2814                             ty, is_transparent, is_non_null
2815                         );
2816                         if is_transparent && !is_non_null {
2817                             debug_assert!(def.variants().len() == 1);
2818                             let v = &def.variant(VariantIdx::new(0));
2819                             ty = transparent_newtype_field(tcx, v)
2820                                 .expect(
2821                                     "single-variant transparent structure with zero-sized field",
2822                                 )
2823                                 .ty(tcx, substs);
2824                             continue;
2825                         }
2826                     }
2827                     debug!("non_transparent_ty -> {:?}", ty);
2828                     return ty;
2829                 }
2830             };
2831
2832             let a = non_transparent_ty(a);
2833             let b = non_transparent_ty(b);
2834
2835             if !seen_types.insert((a, b)) {
2836                 // We've encountered a cycle. There's no point going any further -- the types are
2837                 // structurally the same.
2838                 return true;
2839             }
2840             let tcx = cx.tcx;
2841             if a == b {
2842                 // All nominally-same types are structurally same, too.
2843                 true
2844             } else {
2845                 // Do a full, depth-first comparison between the two.
2846                 use rustc_type_ir::sty::TyKind::*;
2847                 let a_kind = a.kind();
2848                 let b_kind = b.kind();
2849
2850                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2851                     debug!("compare_layouts({:?}, {:?})", a, b);
2852                     let a_layout = &cx.layout_of(a)?.layout.abi();
2853                     let b_layout = &cx.layout_of(b)?.layout.abi();
2854                     debug!(
2855                         "comparing layouts: {:?} == {:?} = {}",
2856                         a_layout,
2857                         b_layout,
2858                         a_layout == b_layout
2859                     );
2860                     Ok(a_layout == b_layout)
2861                 };
2862
2863                 #[allow(rustc::usage_of_ty_tykind)]
2864                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2865                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2866                 };
2867
2868                 ensure_sufficient_stack(|| {
2869                     match (a_kind, b_kind) {
2870                         (Adt(a_def, _), Adt(b_def, _)) => {
2871                             // We can immediately rule out these types as structurally same if
2872                             // their layouts differ.
2873                             match compare_layouts(a, b) {
2874                                 Ok(false) => return false,
2875                                 _ => (), // otherwise, continue onto the full, fields comparison
2876                             }
2877
2878                             // Grab a flattened representation of all fields.
2879                             let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2880                             let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2881
2882                             // Perform a structural comparison for each field.
2883                             a_fields.eq_by(
2884                                 b_fields,
2885                                 |&ty::FieldDef { did: a_did, .. },
2886                                  &ty::FieldDef { did: b_did, .. }| {
2887                                     structurally_same_type_impl(
2888                                         seen_types,
2889                                         cx,
2890                                         tcx.type_of(a_did),
2891                                         tcx.type_of(b_did),
2892                                         ckind,
2893                                     )
2894                                 },
2895                             )
2896                         }
2897                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2898                             // For arrays, we also check the constness of the type.
2899                             a_const.kind() == b_const.kind()
2900                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2901                         }
2902                         (Slice(a_ty), Slice(b_ty)) => {
2903                             structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2904                         }
2905                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2906                             a_tymut.mutbl == b_tymut.mutbl
2907                                 && structurally_same_type_impl(
2908                                     seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2909                                 )
2910                         }
2911                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2912                             // For structural sameness, we don't need the region to be same.
2913                             a_mut == b_mut
2914                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2915                         }
2916                         (FnDef(..), FnDef(..)) => {
2917                             let a_poly_sig = a.fn_sig(tcx);
2918                             let b_poly_sig = b.fn_sig(tcx);
2919
2920                             // We don't compare regions, but leaving bound regions around ICEs, so
2921                             // we erase them.
2922                             let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
2923                             let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
2924
2925                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2926                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2927                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2928                                     structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2929                                 })
2930                                 && structurally_same_type_impl(
2931                                     seen_types,
2932                                     cx,
2933                                     a_sig.output(),
2934                                     b_sig.output(),
2935                                     ckind,
2936                                 )
2937                         }
2938                         (Tuple(a_substs), Tuple(b_substs)) => {
2939                             a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2940                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2941                             })
2942                         }
2943                         // For these, it's not quite as easy to define structural-sameness quite so easily.
2944                         // For the purposes of this lint, take the conservative approach and mark them as
2945                         // not structurally same.
2946                         (Dynamic(..), Dynamic(..))
2947                         | (Error(..), Error(..))
2948                         | (Closure(..), Closure(..))
2949                         | (Generator(..), Generator(..))
2950                         | (GeneratorWitness(..), GeneratorWitness(..))
2951                         | (Projection(..), Projection(..))
2952                         | (Opaque(..), Opaque(..)) => false,
2953
2954                         // These definitely should have been caught above.
2955                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2956
2957                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2958                         // enum layout optimisation is being applied.
2959                         (Adt(..), other_kind) | (other_kind, Adt(..))
2960                             if is_primitive_or_pointer(other_kind) =>
2961                         {
2962                             let (primitive, adt) =
2963                                 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2964                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2965                                 ty == primitive
2966                             } else {
2967                                 compare_layouts(a, b).unwrap_or(false)
2968                             }
2969                         }
2970                         // Otherwise, just compare the layouts. This may fail to lint for some
2971                         // incompatible types, but at the very least, will stop reads into
2972                         // uninitialised memory.
2973                         _ => compare_layouts(a, b).unwrap_or(false),
2974                     }
2975                 })
2976             }
2977         }
2978         let mut seen_types = FxHashSet::default();
2979         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2980     }
2981 }
2982
2983 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2984
2985 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2986     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2987         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2988         if let ForeignItemKind::Fn(..) = this_fi.kind {
2989             let tcx = cx.tcx;
2990             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2991                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2992                 let this_decl_ty = tcx.type_of(this_fi.owner_id);
2993                 debug!(
2994                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2995                     existing_hid, existing_decl_ty, this_fi.owner_id, this_decl_ty
2996                 );
2997                 // Check that the declarations match.
2998                 if !Self::structurally_same_type(
2999                     cx,
3000                     existing_decl_ty,
3001                     this_decl_ty,
3002                     CItemKind::Declaration,
3003                 ) {
3004                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
3005                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
3006
3007                     // We want to ensure that we use spans for both decls that include where the
3008                     // name was defined, whether that was from the link_name attribute or not.
3009                     let get_relevant_span =
3010                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3011                             SymbolName::Normal(_) => fi.span,
3012                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3013                         };
3014                     // Finally, emit the diagnostic.
3015
3016                     let msg = if orig.get_name() == this_fi.ident.name {
3017                         fluent::lint_builtin_clashing_extern_same_name
3018                     } else {
3019                         fluent::lint_builtin_clashing_extern_diff_name
3020                     };
3021                     tcx.struct_span_lint_hir(
3022                         CLASHING_EXTERN_DECLARATIONS,
3023                         this_fi.hir_id(),
3024                         get_relevant_span(this_fi),
3025                         msg,
3026                         |lint| {
3027                             let mut expected_str = DiagnosticStyledString::new();
3028                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3029                             let mut found_str = DiagnosticStyledString::new();
3030                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3031
3032                             lint.set_arg("this_fi", this_fi.ident.name)
3033                                 .set_arg("orig", orig.get_name())
3034                                 .span_label(get_relevant_span(orig_fi), fluent::previous_decl_label)
3035                                 .span_label(get_relevant_span(this_fi), fluent::mismatch_label)
3036                                 // FIXME(davidtwco): translatable expected/found
3037                                 .note_expected_found(&"", expected_str, &"", found_str)
3038                         },
3039                     );
3040                 }
3041             }
3042         }
3043     }
3044 }
3045
3046 declare_lint! {
3047     /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3048     /// which causes [undefined behavior].
3049     ///
3050     /// ### Example
3051     ///
3052     /// ```rust,no_run
3053     /// # #![allow(unused)]
3054     /// use std::ptr;
3055     /// unsafe {
3056     ///     let x = &*ptr::null::<i32>();
3057     ///     let x = ptr::addr_of!(*ptr::null::<i32>());
3058     ///     let x = *(0 as *const i32);
3059     /// }
3060     /// ```
3061     ///
3062     /// {{produces}}
3063     ///
3064     /// ### Explanation
3065     ///
3066     /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3067     /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3068     ///
3069     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3070     pub DEREF_NULLPTR,
3071     Warn,
3072     "detects when an null pointer is dereferenced"
3073 }
3074
3075 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3076
3077 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3078     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3079         /// test if expression is a null ptr
3080         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3081             match &expr.kind {
3082                 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3083                     if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3084                         return is_zero(expr) || is_null_ptr(cx, expr);
3085                     }
3086                 }
3087                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3088                 rustc_hir::ExprKind::Call(ref path, _) => {
3089                     if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3090                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3091                             return matches!(
3092                                 cx.tcx.get_diagnostic_name(def_id),
3093                                 Some(sym::ptr_null | sym::ptr_null_mut)
3094                             );
3095                         }
3096                     }
3097                 }
3098                 _ => {}
3099             }
3100             false
3101         }
3102
3103         /// test if expression is the literal `0`
3104         fn is_zero(expr: &hir::Expr<'_>) -> bool {
3105             match &expr.kind {
3106                 rustc_hir::ExprKind::Lit(ref lit) => {
3107                     if let LitKind::Int(a, _) = lit.node {
3108                         return a == 0;
3109                     }
3110                 }
3111                 _ => {}
3112             }
3113             false
3114         }
3115
3116         if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3117             if is_null_ptr(cx, expr_deref) {
3118                 cx.struct_span_lint(
3119                     DEREF_NULLPTR,
3120                     expr.span,
3121                     fluent::lint_builtin_deref_nullptr,
3122                     |lint| lint.span_label(expr.span, fluent::label),
3123                 );
3124             }
3125         }
3126     }
3127 }
3128
3129 declare_lint! {
3130     /// The `named_asm_labels` lint detects the use of named labels in the
3131     /// inline `asm!` macro.
3132     ///
3133     /// ### Example
3134     ///
3135     /// ```rust,compile_fail
3136     /// # #![feature(asm_experimental_arch)]
3137     /// use std::arch::asm;
3138     ///
3139     /// fn main() {
3140     ///     unsafe {
3141     ///         asm!("foo: bar");
3142     ///     }
3143     /// }
3144     /// ```
3145     ///
3146     /// {{produces}}
3147     ///
3148     /// ### Explanation
3149     ///
3150     /// LLVM is allowed to duplicate inline assembly blocks for any
3151     /// reason, for example when it is in a function that gets inlined. Because
3152     /// of this, GNU assembler [local labels] *must* be used instead of labels
3153     /// with a name. Using named labels might cause assembler or linker errors.
3154     ///
3155     /// See the explanation in [Rust By Example] for more details.
3156     ///
3157     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3158     /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3159     pub NAMED_ASM_LABELS,
3160     Deny,
3161     "named labels in inline assembly",
3162 }
3163
3164 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3165
3166 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3167     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3168         if let hir::Expr {
3169             kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3170             ..
3171         } = expr
3172         {
3173             for (template_sym, template_snippet, template_span) in template_strs.iter() {
3174                 let template_str = template_sym.as_str();
3175                 let find_label_span = |needle: &str| -> Option<Span> {
3176                     if let Some(template_snippet) = template_snippet {
3177                         let snippet = template_snippet.as_str();
3178                         if let Some(pos) = snippet.find(needle) {
3179                             let end = pos
3180                                 + snippet[pos..]
3181                                     .find(|c| c == ':')
3182                                     .unwrap_or(snippet[pos..].len() - 1);
3183                             let inner = InnerSpan::new(pos, end);
3184                             return Some(template_span.from_inner(inner));
3185                         }
3186                     }
3187
3188                     None
3189                 };
3190
3191                 let mut found_labels = Vec::new();
3192
3193                 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3194                 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3195                 for statement in statements {
3196                     // If there's a comment, trim it from the statement
3197                     let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3198                     let mut start_idx = 0;
3199                     for (idx, _) in statement.match_indices(':') {
3200                         let possible_label = statement[start_idx..idx].trim();
3201                         let mut chars = possible_label.chars();
3202                         let Some(c) = chars.next() else {
3203                             // Empty string means a leading ':' in this section, which is not a label
3204                             break
3205                         };
3206                         // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3207                         if (c.is_alphabetic() || matches!(c, '.' | '_'))
3208                             && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3209                         {
3210                             found_labels.push(possible_label);
3211                         } else {
3212                             // If we encounter a non-label, there cannot be any further labels, so stop checking
3213                             break;
3214                         }
3215
3216                         start_idx = idx + 1;
3217                     }
3218                 }
3219
3220                 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3221
3222                 if found_labels.len() > 0 {
3223                     let spans = found_labels
3224                         .into_iter()
3225                         .filter_map(|label| find_label_span(label))
3226                         .collect::<Vec<Span>>();
3227                     // If there were labels but we couldn't find a span, combine the warnings and use the template span
3228                     let target_spans: MultiSpan =
3229                         if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3230
3231                     cx.lookup_with_diagnostics(
3232                             NAMED_ASM_LABELS,
3233                             Some(target_spans),
3234                             fluent::lint_builtin_asm_labels,
3235                             |lint| lint,
3236                             BuiltinLintDiagnostics::NamedAsmLabel(
3237                                 "only local labels of the form `<number>:` should be used in inline asm"
3238                                     .to_string(),
3239                             ),
3240                         );
3241                 }
3242             }
3243         }
3244     }
3245 }
3246
3247 declare_lint! {
3248     /// The `special_module_name` lint detects module
3249     /// declarations for files that have a special meaning.
3250     ///
3251     /// ### Example
3252     ///
3253     /// ```rust,compile_fail
3254     /// mod lib;
3255     ///
3256     /// fn main() {
3257     ///     lib::run();
3258     /// }
3259     /// ```
3260     ///
3261     /// {{produces}}
3262     ///
3263     /// ### Explanation
3264     ///
3265     /// Cargo recognizes `lib.rs` and `main.rs` as the root of a
3266     /// library or binary crate, so declaring them as modules
3267     /// will lead to miscompilation of the crate unless configured
3268     /// explicitly.
3269     ///
3270     /// To access a library from a binary target within the same crate,
3271     /// use `your_crate_name::` as the path instead of `lib::`:
3272     ///
3273     /// ```rust,compile_fail
3274     /// // bar/src/lib.rs
3275     /// fn run() {
3276     ///     // ...
3277     /// }
3278     ///
3279     /// // bar/src/main.rs
3280     /// fn main() {
3281     ///     bar::run();
3282     /// }
3283     /// ```
3284     ///
3285     /// Binary targets cannot be used as libraries and so declaring
3286     /// one as a module is not allowed.
3287     pub SPECIAL_MODULE_NAME,
3288     Warn,
3289     "module declarations for files with a special meaning",
3290 }
3291
3292 declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
3293
3294 impl EarlyLintPass for SpecialModuleName {
3295     fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
3296         for item in &krate.items {
3297             if let ast::ItemKind::Mod(
3298                 _,
3299                 ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _),
3300             ) = item.kind
3301             {
3302                 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
3303                     continue;
3304                 }
3305
3306                 match item.ident.name.as_str() {
3307                     "lib" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for lib.rs", |lint| {
3308                         lint
3309                             .note("lib.rs is the root of this crate's library target")
3310                             .help("to refer to it from other targets, use the library's name as the path")
3311                     }),
3312                     "main" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for main.rs", |lint| {
3313                         lint
3314                             .note("a binary crate cannot be used as library")
3315                     }),
3316                     _ => continue
3317                 }
3318             }
3319         }
3320     }
3321 }
3322
3323 pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
3324
3325 declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
3326
3327 impl EarlyLintPass for UnexpectedCfgs {
3328     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
3329         let cfg = &cx.sess().parse_sess.config;
3330         let check_cfg = &cx.sess().parse_sess.check_config;
3331         for &(name, value) in cfg {
3332             if let Some(names_valid) = &check_cfg.names_valid {
3333                 if !names_valid.contains(&name) {
3334                     cx.lookup(
3335                         UNEXPECTED_CFGS,
3336                         None::<MultiSpan>,
3337                         fluent::lint_builtin_unexpected_cli_config_name,
3338                         |diag| diag.help(fluent::help).set_arg("name", name),
3339                     );
3340                 }
3341             }
3342             if let Some(value) = value {
3343                 if let Some(values) = &check_cfg.values_valid.get(&name) {
3344                     if !values.contains(&value) {
3345                         cx.lookup(
3346                             UNEXPECTED_CFGS,
3347                             None::<MultiSpan>,
3348                             fluent::lint_builtin_unexpected_cli_config_value,
3349                             |diag| {
3350                                 diag.help(fluent::help)
3351                                     .set_arg("name", name)
3352                                     .set_arg("value", value)
3353                             },
3354                         );
3355                     }
3356                 }
3357             }
3358         }
3359     }
3360 }