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