src/librustc_lint/builtin.rs

   1 //! Lints in the Rust compiler.
   2 //!
   3 //! This contains lints which can feasibly be implemented as their own
   4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
   5 //! definitions of lints that are emitted directly inside the main compiler.
   6 //!
   7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
   8 //! Then add code to emit the new lint in the appropriate circumstances.
   9 //! You can do that in an existing `LintPass` if it makes sense, or in a
  10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  11 //! compiler. Only do the latter if the check can't be written cleanly as a
  12 //! `LintPass` (also, note that such lints will need to be defined in
  13 //! `rustc_session::lint::builtin`, not here).
  14 //!
  15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
  16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
  17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
  18 //! with a `pub fn new()`.
  19 //!
  20 //! If you define a new `LateLintPass`, you will also need to add it to the
  21 //! `late_lint_methods!` invocation in `lib.rs`.
  22
  23 use crate::{
  24     types::CItemKind, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
  25 };
  26 use rustc_ast::attr::{self, HasAttrs};
  27 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  28 use rustc_ast::visit::{FnCtxt, FnKind};
  29 use rustc_ast::{self as ast, *};
  30 use rustc_ast_pretty::pprust::{self, expr_to_string};
  31 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  32 use rustc_data_structures::stack::ensure_sufficient_stack;
  33 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
  34 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
  35 use rustc_feature::{GateIssue, Stability};
  36 use rustc_hir as hir;
  37 use rustc_hir::def::{DefKind, Res};
  38 use rustc_hir::def_id::DefId;
  39 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
  40 use rustc_hir::{HirId, HirIdSet, Node};
  41 use rustc_middle::lint::LintDiagnosticBuilder;
  42 use rustc_middle::ty::subst::{GenericArgKind, Subst};
  43 use rustc_middle::ty::{self, layout::LayoutError, Ty, TyCtxt};
  44 use rustc_session::lint::FutureIncompatibleInfo;
  45 use rustc_session::Session;
  46 use rustc_span::edition::Edition;
  47 use rustc_span::source_map::Spanned;
  48 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  49 use rustc_span::{BytePos, Span};
  50 use rustc_target::abi::{LayoutOf, VariantIdx};
  51 use rustc_trait_selection::traits::misc::can_type_implement_copy;
  52
  53 use crate::nonstandard_style::{method_context, MethodLateContext};
  54
  55 use std::fmt::Write;
  56 use tracing::{debug, trace};
  57
  58 // hardwired lints from librustc_middle
  59 pub use rustc_session::lint::builtin::*;
  60
  61 declare_lint! {
  62     WHILE_TRUE,
  63     Warn,
  64     "suggest using `loop { }` instead of `while true { }`"
  65 }
  66
  67 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  68
  69 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  70 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  71     while let ast::ExprKind::Paren(sub) = &expr.kind {
  72         expr = sub;
  73     }
  74     expr
  75 }
  76
  77 impl EarlyLintPass for WhileTrue {
  78     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
  79         if let ast::ExprKind::While(cond, ..) = &e.kind {
  80             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
  81                 if let ast::LitKind::Bool(true) = lit.kind {
  82                     if !lit.span.from_expansion() {
  83                         let msg = "denote infinite loops with `loop { ... }`";
  84                         let condition_span = cx.sess.source_map().guess_head_span(e.span);
  85                         cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
  86                             lint.build(msg)
  87                                 .span_suggestion_short(
  88                                     condition_span,
  89                                     "use `loop`",
  90                                     "loop".to_owned(),
  91                                     Applicability::MachineApplicable,
  92                                 )
  93                                 .emit();
  94                         })
  95                     }
  96                 }
  97             }
  98         }
  99     }
 100 }
 101
 102 declare_lint! {
 103     BOX_POINTERS,
 104     Allow,
 105     "use of owned (Box type) heap memory"
 106 }
 107
 108 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 109
 110 impl BoxPointers {
 111     fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
 112         for leaf in ty.walk() {
 113             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
 114                 if leaf_ty.is_box() {
 115                     cx.struct_span_lint(BOX_POINTERS, span, |lint| {
 116                         lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
 117                     });
 118                 }
 119             }
 120         }
 121     }
 122 }
 123
 124 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
 125     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 126         match it.kind {
 127             hir::ItemKind::Fn(..)
 128             | hir::ItemKind::TyAlias(..)
 129             | hir::ItemKind::Enum(..)
 130             | hir::ItemKind::Struct(..)
 131             | hir::ItemKind::Union(..) => {
 132                 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 133                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 134             }
 135             _ => (),
 136         }
 137
 138         // If it's a struct, we also have to check the fields' types
 139         match it.kind {
 140             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 141                 for struct_field in struct_def.fields() {
 142                     let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
 143                     self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
 144                 }
 145             }
 146             _ => (),
 147         }
 148     }
 149
 150     fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
 151         let ty = cx.typeck_results().node_type(e.hir_id);
 152         self.check_heap_type(cx, e.span, ty);
 153     }
 154 }
 155
 156 declare_lint! {
 157     NON_SHORTHAND_FIELD_PATTERNS,
 158     Warn,
 159     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 160 }
 161
 162 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 163
 164 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
 165     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
 166         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 167             let variant = cx
 168                 .typeck_results()
 169                 .pat_ty(pat)
 170                 .ty_adt_def()
 171                 .expect("struct pattern type is not an ADT")
 172                 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
 173             for fieldpat in field_pats {
 174                 if fieldpat.is_shorthand {
 175                     continue;
 176                 }
 177                 if fieldpat.span.from_expansion() {
 178                     // Don't lint if this is a macro expansion: macro authors
 179                     // shouldn't have to worry about this kind of style issue
 180                     // (Issue #49588)
 181                     continue;
 182                 }
 183                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 184                     if cx.tcx.find_field_index(ident, &variant)
 185                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
 186                     {
 187                         cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
 188                             let mut err = lint
 189                                 .build(&format!("the `{}:` in this pattern is redundant", ident));
 190                             let binding = match binding_annot {
 191                                 hir::BindingAnnotation::Unannotated => None,
 192                                 hir::BindingAnnotation::Mutable => Some("mut"),
 193                                 hir::BindingAnnotation::Ref => Some("ref"),
 194                                 hir::BindingAnnotation::RefMut => Some("ref mut"),
 195                             };
 196                             let ident = if let Some(binding) = binding {
 197                                 format!("{} {}", binding, ident)
 198                             } else {
 199                                 ident.to_string()
 200                             };
 201                             err.span_suggestion(
 202                                 fieldpat.span,
 203                                 "use shorthand field pattern",
 204                                 ident,
 205                                 Applicability::MachineApplicable,
 206                             );
 207                             err.emit();
 208                         });
 209                     }
 210                 }
 211             }
 212         }
 213     }
 214 }
 215
 216 declare_lint! {
 217     UNSAFE_CODE,
 218     Allow,
 219     "usage of `unsafe` code"
 220 }
 221
 222 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 223
 224 impl UnsafeCode {
 225     fn report_unsafe(
 226         &self,
 227         cx: &EarlyContext<'_>,
 228         span: Span,
 229         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 230     ) {
 231         // This comes from a macro that has `#[allow_internal_unsafe]`.
 232         if span.allows_unsafe() {
 233             return;
 234         }
 235
 236         cx.struct_span_lint(UNSAFE_CODE, span, decorate);
 237     }
 238 }
 239
 240 impl EarlyLintPass for UnsafeCode {
 241     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 242         if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
 243             self.report_unsafe(cx, attr.span, |lint| {
 244                 lint.build(
 245                     "`allow_internal_unsafe` allows defining \
 246                                                macros using unsafe without triggering \
 247                                                the `unsafe_code` lint at their call site",
 248                 )
 249                 .emit()
 250             });
 251         }
 252     }
 253
 254     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 255         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 256             // Don't warn about generated blocks; that'll just pollute the output.
 257             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 258                 self.report_unsafe(cx, blk.span, |lint| {
 259                     lint.build("usage of an `unsafe` block").emit()
 260                 });
 261             }
 262         }
 263     }
 264
 265     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 266         match it.kind {
 267             ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
 268                 self.report_unsafe(cx, it.span, |lint| {
 269                     lint.build("declaration of an `unsafe` trait").emit()
 270                 })
 271             }
 272
 273             ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
 274                 self.report_unsafe(cx, it.span, |lint| {
 275                     lint.build("implementation of an `unsafe` trait").emit()
 276                 })
 277             }
 278
 279             _ => {}
 280         }
 281     }
 282
 283     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
 284         if let FnKind::Fn(
 285             ctxt,
 286             _,
 287             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
 288             _,
 289             body,
 290         ) = fk
 291         {
 292             let msg = match ctxt {
 293                 FnCtxt::Foreign => return,
 294                 FnCtxt::Free => "declaration of an `unsafe` function",
 295                 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
 296                 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
 297             };
 298             self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
 299         }
 300     }
 301 }
 302
 303 declare_lint! {
 304     pub MISSING_DOCS,
 305     Allow,
 306     "detects missing documentation for public members",
 307     report_in_external_macro
 308 }
 309
 310 pub struct MissingDoc {
 311     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 312     doc_hidden_stack: Vec<bool>,
 313
 314     /// Private traits or trait items that leaked through. Don't check their methods.
 315     private_traits: FxHashSet<hir::HirId>,
 316 }
 317
 318 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 319
 320 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
 321     if attr.is_doc_comment() {
 322         return true;
 323     }
 324
 325     if !sess.check_name(attr, sym::doc) {
 326         return false;
 327     }
 328
 329     if attr.is_value_str() {
 330         return true;
 331     }
 332
 333     if let Some(list) = attr.meta_item_list() {
 334         for meta in list {
 335             if meta.has_name(sym::include) || meta.has_name(sym::hidden) {
 336                 return true;
 337             }
 338         }
 339     }
 340
 341     false
 342 }
 343
 344 impl MissingDoc {
 345     pub fn new() -> MissingDoc {
 346         MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
 347     }
 348
 349     fn doc_hidden(&self) -> bool {
 350         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 351     }
 352
 353     fn check_missing_docs_attrs(
 354         &self,
 355         cx: &LateContext<'_>,
 356         id: Option<hir::HirId>,
 357         attrs: &[ast::Attribute],
 358         sp: Span,
 359         article: &'static str,
 360         desc: &'static str,
 361     ) {
 362         // If we're building a test harness, then warning about
 363         // documentation is probably not really relevant right now.
 364         if cx.sess().opts.test {
 365             return;
 366         }
 367
 368         // `#[doc(hidden)]` disables missing_docs check.
 369         if self.doc_hidden() {
 370             return;
 371         }
 372
 373         // Only check publicly-visible items, using the result from the privacy pass.
 374         // It's an option so the crate root can also use this function (it doesn't
 375         // have a `NodeId`).
 376         if let Some(id) = id {
 377             if !cx.access_levels.is_exported(id) {
 378                 return;
 379             }
 380         }
 381
 382         let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
 383         if !has_doc {
 384             cx.struct_span_lint(
 385                 MISSING_DOCS,
 386                 cx.tcx.sess.source_map().guess_head_span(sp),
 387                 |lint| {
 388                     lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
 389                 },
 390             );
 391         }
 392     }
 393 }
 394
 395 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 396     fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
 397         let doc_hidden = self.doc_hidden()
 398             || attrs.iter().any(|attr| {
 399                 cx.sess().check_name(attr, sym::doc)
 400                     && match attr.meta_item_list() {
 401                         None => false,
 402                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 403                     }
 404             });
 405         self.doc_hidden_stack.push(doc_hidden);
 406     }
 407
 408     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
 409         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 410     }
 411
 412     fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
 413         self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
 414
 415         for macro_def in krate.exported_macros {
 416             let has_doc = macro_def.attrs.iter().any(|a| has_doc(cx.sess(), a));
 417             if !has_doc {
 418                 cx.struct_span_lint(
 419                     MISSING_DOCS,
 420                     cx.tcx.sess.source_map().guess_head_span(macro_def.span),
 421                     |lint| lint.build("missing documentation for macro").emit(),
 422                 );
 423             }
 424         }
 425     }
 426
 427     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 428         match it.kind {
 429             hir::ItemKind::Trait(.., trait_item_refs) => {
 430                 // Issue #11592: traits are always considered exported, even when private.
 431                 if let hir::VisibilityKind::Inherited = it.vis.node {
 432                     self.private_traits.insert(it.hir_id);
 433                     for trait_item_ref in trait_item_refs {
 434                         self.private_traits.insert(trait_item_ref.id.hir_id);
 435                     }
 436                     return;
 437                 }
 438             }
 439             hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
 440                 // If the trait is private, add the impl items to `private_traits` so they don't get
 441                 // reported for missing docs.
 442                 let real_trait = trait_ref.path.res.def_id();
 443                 if let Some(def_id) = real_trait.as_local() {
 444                     let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
 445                     if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
 446                         if let hir::VisibilityKind::Inherited = item.vis.node {
 447                             for impl_item_ref in items {
 448                                 self.private_traits.insert(impl_item_ref.id.hir_id);
 449                             }
 450                         }
 451                     }
 452                 }
 453                 return;
 454             }
 455
 456             hir::ItemKind::TyAlias(..)
 457             | hir::ItemKind::Fn(..)
 458             | hir::ItemKind::Mod(..)
 459             | hir::ItemKind::Enum(..)
 460             | hir::ItemKind::Struct(..)
 461             | hir::ItemKind::Union(..)
 462             | hir::ItemKind::Const(..)
 463             | hir::ItemKind::Static(..) => {}
 464
 465             _ => return,
 466         };
 467
 468         let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 469         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 470
 471         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
 472     }
 473
 474     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
 475         if self.private_traits.contains(&trait_item.hir_id) {
 476             return;
 477         }
 478
 479         let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
 480         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 481
 482         self.check_missing_docs_attrs(
 483             cx,
 484             Some(trait_item.hir_id),
 485             &trait_item.attrs,
 486             trait_item.span,
 487             article,
 488             desc,
 489         );
 490     }
 491
 492     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
 493         // If the method is an impl for a trait, don't doc.
 494         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 495             return;
 496         }
 497
 498         let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
 499         let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
 500         self.check_missing_docs_attrs(
 501             cx,
 502             Some(impl_item.hir_id),
 503             &impl_item.attrs,
 504             impl_item.span,
 505             article,
 506             desc,
 507         );
 508     }
 509
 510     fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
 511         if !sf.is_positional() {
 512             self.check_missing_docs_attrs(
 513                 cx,
 514                 Some(sf.hir_id),
 515                 &sf.attrs,
 516                 sf.span,
 517                 "a",
 518                 "struct field",
 519             )
 520         }
 521     }
 522
 523     fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
 524         self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
 525     }
 526 }
 527
 528 declare_lint! {
 529     pub MISSING_COPY_IMPLEMENTATIONS,
 530     Allow,
 531     "detects potentially-forgotten implementations of `Copy`"
 532 }
 533
 534 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 535
 536 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
 537     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 538         if !cx.access_levels.is_reachable(item.hir_id) {
 539             return;
 540         }
 541         let (def, ty) = match item.kind {
 542             hir::ItemKind::Struct(_, ref ast_generics) => {
 543                 if !ast_generics.params.is_empty() {
 544                     return;
 545                 }
 546                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 547                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 548             }
 549             hir::ItemKind::Union(_, ref ast_generics) => {
 550                 if !ast_generics.params.is_empty() {
 551                     return;
 552                 }
 553                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 554                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 555             }
 556             hir::ItemKind::Enum(_, ref ast_generics) => {
 557                 if !ast_generics.params.is_empty() {
 558                     return;
 559                 }
 560                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 561                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 562             }
 563             _ => return,
 564         };
 565         if def.has_dtor(cx.tcx) {
 566             return;
 567         }
 568         let param_env = ty::ParamEnv::empty();
 569         if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
 570             return;
 571         }
 572         if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
 573             cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
 574                 lint.build(
 575                     "type could implement `Copy`; consider adding `impl \
 576                           Copy`",
 577                 )
 578                 .emit()
 579             })
 580         }
 581     }
 582 }
 583
 584 declare_lint! {
 585     MISSING_DEBUG_IMPLEMENTATIONS,
 586     Allow,
 587     "detects missing implementations of Debug"
 588 }
 589
 590 #[derive(Default)]
 591 pub struct MissingDebugImplementations {
 592     impling_types: Option<HirIdSet>,
 593 }
 594
 595 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 596
 597 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 598     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
 599         if !cx.access_levels.is_reachable(item.hir_id) {
 600             return;
 601         }
 602
 603         match item.kind {
 604             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 605             _ => return,
 606         }
 607
 608         let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
 609             Some(debug) => debug,
 610             None => return,
 611         };
 612
 613         if self.impling_types.is_none() {
 614             let mut impls = HirIdSet::default();
 615             cx.tcx.for_each_impl(debug, |d| {
 616                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 617                     if let Some(def_id) = ty_def.did.as_local() {
 618                         impls.insert(cx.tcx.hir().local_def_id_to_hir_id(def_id));
 619                     }
 620                 }
 621             });
 622
 623             self.impling_types = Some(impls);
 624             debug!("{:?}", self.impling_types);
 625         }
 626
 627         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 628             cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
 629                 lint.build(&format!(
 630                     "type does not implement `{}`; consider adding `#[derive(Debug)]` \
 631                      or a manual implementation",
 632                     cx.tcx.def_path_str(debug)
 633                 ))
 634                 .emit()
 635             });
 636         }
 637     }
 638 }
 639
 640 declare_lint! {
 641     pub ANONYMOUS_PARAMETERS,
 642     Allow,
 643     "detects anonymous parameters",
 644     @future_incompatible = FutureIncompatibleInfo {
 645         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 646         edition: Some(Edition::Edition2018),
 647     };
 648 }
 649
 650 declare_lint_pass!(
 651     /// Checks for use of anonymous parameters (RFC 1685).
 652     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 653 );
 654
 655 impl EarlyLintPass for AnonymousParameters {
 656     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 657         if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
 658             for arg in sig.decl.inputs.iter() {
 659                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
 660                     if ident.name == kw::Invalid {
 661                         cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
 662                             let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
 663
 664                             let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
 665                                 (snip.as_str(), Applicability::MachineApplicable)
 666                             } else {
 667                                 ("<type>", Applicability::HasPlaceholders)
 668                             };
 669
 670                             lint.build(
 671                                 "anonymous parameters are deprecated and will be \
 672                                      removed in the next edition.",
 673                             )
 674                             .span_suggestion(
 675                                 arg.pat.span,
 676                                 "try naming the parameter or explicitly \
 677                                             ignoring it",
 678                                 format!("_: {}", ty_snip),
 679                                 appl,
 680                             )
 681                             .emit();
 682                         })
 683                     }
 684                 }
 685             }
 686         }
 687     }
 688 }
 689
 690 /// Check for use of attributes which have been deprecated.
 691 #[derive(Clone)]
 692 pub struct DeprecatedAttr {
 693     // This is not free to compute, so we want to keep it around, rather than
 694     // compute it for every attribute.
 695     depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
 696 }
 697
 698 impl_lint_pass!(DeprecatedAttr => []);
 699
 700 impl DeprecatedAttr {
 701     pub fn new() -> DeprecatedAttr {
 702         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 703     }
 704 }
 705
 706 fn lint_deprecated_attr(
 707     cx: &EarlyContext<'_>,
 708     attr: &ast::Attribute,
 709     msg: &str,
 710     suggestion: Option<&str>,
 711 ) {
 712     cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
 713         lint.build(msg)
 714             .span_suggestion_short(
 715                 attr.span,
 716                 suggestion.unwrap_or("remove this attribute"),
 717                 String::new(),
 718                 Applicability::MachineApplicable,
 719             )
 720             .emit();
 721     })
 722 }
 723
 724 impl EarlyLintPass for DeprecatedAttr {
 725     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 726         for &&(n, _, _, ref g) in &self.depr_attrs {
 727             if attr.ident().map(|ident| ident.name) == Some(n) {
 728                 if let &AttributeGate::Gated(
 729                     Stability::Deprecated(link, suggestion),
 730                     ref name,
 731                     ref reason,
 732                     _,
 733                 ) = g
 734                 {
 735                     let msg =
 736                         format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
 737                     lint_deprecated_attr(cx, attr, &msg, suggestion);
 738                 }
 739                 return;
 740             }
 741         }
 742         if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
 743             let path_str = pprust::path_to_string(&attr.get_normal_item().path);
 744             let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
 745             lint_deprecated_attr(cx, attr, &msg, None);
 746         }
 747     }
 748 }
 749
 750 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
 751     let mut attrs = attrs.iter().peekable();
 752
 753     // Accumulate a single span for sugared doc comments.
 754     let mut sugared_span: Option<Span> = None;
 755
 756     while let Some(attr) = attrs.next() {
 757         if attr.is_doc_comment() {
 758             sugared_span =
 759                 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
 760         }
 761
 762         if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
 763             continue;
 764         }
 765
 766         let span = sugared_span.take().unwrap_or_else(|| attr.span);
 767
 768         if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
 769             cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
 770                 let mut err = lint.build("unused doc comment");
 771                 err.span_label(
 772                     node_span,
 773                     format!("rustdoc does not generate documentation for {}", node_kind),
 774                 );
 775                 err.emit();
 776             });
 777         }
 778     }
 779 }
 780
 781 impl EarlyLintPass for UnusedDocComment {
 782     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 783         let kind = match stmt.kind {
 784             ast::StmtKind::Local(..) => "statements",
 785             ast::StmtKind::Item(..) => "inner items",
 786             // expressions will be reported by `check_expr`.
 787             ast::StmtKind::Empty
 788             | ast::StmtKind::Semi(_)
 789             | ast::StmtKind::Expr(_)
 790             | ast::StmtKind::MacCall(_) => return,
 791         };
 792
 793         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
 794     }
 795
 796     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 797         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
 798         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
 799     }
 800
 801     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 802         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
 803     }
 804 }
 805
 806 declare_lint! {
 807     NO_MANGLE_CONST_ITEMS,
 808     Deny,
 809     "const items will not have their symbols exported"
 810 }
 811
 812 declare_lint! {
 813     NO_MANGLE_GENERIC_ITEMS,
 814     Warn,
 815     "generic items must be mangled"
 816 }
 817
 818 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
 819
 820 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
 821     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
 822         match it.kind {
 823             hir::ItemKind::Fn(.., ref generics, _) => {
 824                 if let Some(no_mangle_attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
 825                     for param in generics.params {
 826                         match param.kind {
 827                             GenericParamKind::Lifetime { .. } => {}
 828                             GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
 829                                 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
 830                                     lint.build(
 831                                         "functions generic over types or consts must be mangled",
 832                                     )
 833                                     .span_suggestion_short(
 834                                         no_mangle_attr.span,
 835                                         "remove this attribute",
 836                                         String::new(),
 837                                         // Use of `#[no_mangle]` suggests FFI intent; correct
 838                                         // fix may be to monomorphize source by hand
 839                                         Applicability::MaybeIncorrect,
 840                                     )
 841                                     .emit();
 842                                 });
 843                                 break;
 844                             }
 845                         }
 846                     }
 847                 }
 848             }
 849             hir::ItemKind::Const(..) => {
 850                 if cx.sess().contains_name(&it.attrs, sym::no_mangle) {
 851                     // Const items do not refer to a particular location in memory, and therefore
 852                     // don't have anything to attach a symbol to
 853                     cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
 854                         let msg = "const items should never be `#[no_mangle]`";
 855                         let mut err = lint.build(msg);
 856
 857                         // account for "pub const" (#45562)
 858                         let start = cx
 859                             .tcx
 860                             .sess
 861                             .source_map()
 862                             .span_to_snippet(it.span)
 863                             .map(|snippet| snippet.find("const").unwrap_or(0))
 864                             .unwrap_or(0) as u32;
 865                         // `const` is 5 chars
 866                         let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 867                         err.span_suggestion(
 868                             const_span,
 869                             "try a static value",
 870                             "pub static".to_owned(),
 871                             Applicability::MachineApplicable,
 872                         );
 873                         err.emit();
 874                     });
 875                 }
 876             }
 877             _ => {}
 878         }
 879     }
 880 }
 881
 882 declare_lint! {
 883     MUTABLE_TRANSMUTES,
 884     Deny,
 885     "mutating transmuted &mut T from &T may cause undefined behavior"
 886 }
 887
 888 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
 889
 890 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
 891     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
 892         use rustc_target::spec::abi::Abi::RustIntrinsic;
 893         if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
 894             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
 895         {
 896             if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
 897                 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 898                                consider instead using an UnsafeCell";
 899                 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
 900             }
 901         }
 902
 903         fn get_transmute_from_to<'tcx>(
 904             cx: &LateContext<'tcx>,
 905             expr: &hir::Expr<'_>,
 906         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
 907             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
 908                 cx.qpath_res(qpath, expr.hir_id)
 909             } else {
 910                 return None;
 911             };
 912             if let Res::Def(DefKind::Fn, did) = def {
 913                 if !def_id_is_transmute(cx, did) {
 914                     return None;
 915                 }
 916                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
 917                 let from = sig.inputs().skip_binder()[0];
 918                 let to = sig.output().skip_binder();
 919                 return Some((from, to));
 920             }
 921             None
 922         }
 923
 924         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
 925             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
 926                 && cx.tcx.item_name(def_id) == sym::transmute
 927         }
 928     }
 929 }
 930
 931 declare_lint! {
 932     UNSTABLE_FEATURES,
 933     Allow,
 934     "enabling unstable features (deprecated. do not use)"
 935 }
 936
 937 declare_lint_pass!(
 938     /// Forbids using the `#[feature(...)]` attribute
 939     UnstableFeatures => [UNSTABLE_FEATURES]
 940 );
 941
 942 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
 943     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
 944         if cx.sess().check_name(attr, sym::feature) {
 945             if let Some(items) = attr.meta_item_list() {
 946                 for item in items {
 947                     cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
 948                         lint.build("unstable feature").emit()
 949                     });
 950                 }
 951             }
 952         }
 953     }
 954 }
 955
 956 declare_lint! {
 957     pub UNREACHABLE_PUB,
 958     Allow,
 959     "`pub` items not reachable from crate root"
 960 }
 961
 962 declare_lint_pass!(
 963     /// Lint for items marked `pub` that aren't reachable from other crates.
 964     UnreachablePub => [UNREACHABLE_PUB]
 965 );
 966
 967 impl UnreachablePub {
 968     fn perform_lint(
 969         &self,
 970         cx: &LateContext<'_>,
 971         what: &str,
 972         id: hir::HirId,
 973         vis: &hir::Visibility<'_>,
 974         span: Span,
 975         exportable: bool,
 976     ) {
 977         let mut applicability = Applicability::MachineApplicable;
 978         match vis.node {
 979             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
 980                 if span.from_expansion() {
 981                     applicability = Applicability::MaybeIncorrect;
 982                 }
 983                 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
 984                 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
 985                     let mut err = lint.build(&format!("unreachable `pub` {}", what));
 986                     let replacement = if cx.tcx.features().crate_visibility_modifier {
 987                         "crate"
 988                     } else {
 989                         "pub(crate)"
 990                     }
 991                     .to_owned();
 992
 993                     err.span_suggestion(
 994                         vis.span,
 995                         "consider restricting its visibility",
 996                         replacement,
 997                         applicability,
 998                     );
 999                     if exportable {
1000                         err.help("or consider exporting it for use by other crates");
1001                     }
1002                     err.emit();
1003                 });
1004             }
1005             _ => {}
1006         }
1007     }
1008 }
1009
1010 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1011     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1012         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1013     }
1014
1015     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1016         self.perform_lint(
1017             cx,
1018             "item",
1019             foreign_item.hir_id,
1020             &foreign_item.vis,
1021             foreign_item.span,
1022             true,
1023         );
1024     }
1025
1026     fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
1027         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1028     }
1029
1030     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1031         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1032     }
1033 }
1034
1035 declare_lint! {
1036     TYPE_ALIAS_BOUNDS,
1037     Warn,
1038     "bounds in type aliases are not enforced"
1039 }
1040
1041 declare_lint_pass!(
1042     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1043     /// They are relevant when using associated types, but otherwise neither checked
1044     /// at definition site nor enforced at use site.
1045     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1046 );
1047
1048 impl TypeAliasBounds {
1049     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1050         match *qpath {
1051             hir::QPath::TypeRelative(ref ty, _) => {
1052                 // If this is a type variable, we found a `T::Assoc`.
1053                 match ty.kind {
1054                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1055                         Res::Def(DefKind::TyParam, _) => true,
1056                         _ => false,
1057                     },
1058                     _ => false,
1059                 }
1060             }
1061             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1062         }
1063     }
1064
1065     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1066         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1067         // bound.  Let's see if this type does that.
1068
1069         // We use a HIR visitor to walk the type.
1070         use rustc_hir::intravisit::{self, Visitor};
1071         struct WalkAssocTypes<'a, 'db> {
1072             err: &'a mut DiagnosticBuilder<'db>,
1073         }
1074         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1075             type Map = intravisit::ErasedMap<'v>;
1076
1077             fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1078                 intravisit::NestedVisitorMap::None
1079             }
1080
1081             fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1082                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1083                     self.err.span_help(
1084                         span,
1085                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1086                          associated types in type aliases",
1087                     );
1088                 }
1089                 intravisit::walk_qpath(self, qpath, id, span)
1090             }
1091         }
1092
1093         // Let's go for a walk!
1094         let mut visitor = WalkAssocTypes { err };
1095         visitor.visit_ty(ty);
1096     }
1097 }
1098
1099 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1100     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1101         let (ty, type_alias_generics) = match item.kind {
1102             hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1103             _ => return,
1104         };
1105         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1106             // Bounds are respected for `type X = impl Trait`
1107             return;
1108         }
1109         let mut suggested_changing_assoc_types = false;
1110         // There must not be a where clause
1111         if !type_alias_generics.where_clause.predicates.is_empty() {
1112             cx.lint(
1113                 TYPE_ALIAS_BOUNDS,
1114                 |lint| {
1115                     let mut err = lint.build("where clauses are not enforced in type aliases");
1116                     let spans: Vec<_> = type_alias_generics
1117                         .where_clause
1118                         .predicates
1119                         .iter()
1120                         .map(|pred| pred.span())
1121                         .collect();
1122                     err.set_span(spans);
1123                     err.span_suggestion(
1124                         type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1125                         "the clause will not be checked when the type alias is used, and should be removed",
1126                         String::new(),
1127                         Applicability::MachineApplicable,
1128                     );
1129                     if !suggested_changing_assoc_types {
1130                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1131                         suggested_changing_assoc_types = true;
1132                     }
1133                     err.emit();
1134                 },
1135             );
1136         }
1137         // The parameters must not have bounds
1138         for param in type_alias_generics.params.iter() {
1139             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1140             let suggestion = spans
1141                 .iter()
1142                 .map(|sp| {
1143                     let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1144                     (start.to(*sp), String::new())
1145                 })
1146                 .collect();
1147             if !spans.is_empty() {
1148                 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1149                     let mut err =
1150                         lint.build("bounds on generic parameters are not enforced in type aliases");
1151                     let msg = "the bound will not be checked when the type alias is used, \
1152                                    and should be removed";
1153                     err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1154                     if !suggested_changing_assoc_types {
1155                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1156                         suggested_changing_assoc_types = true;
1157                     }
1158                     err.emit();
1159                 });
1160             }
1161         }
1162     }
1163 }
1164
1165 declare_lint_pass!(
1166     /// Lint constants that are erroneous.
1167     /// Without this lint, we might not get any diagnostic if the constant is
1168     /// unused within this crate, even though downstream crates can't use it
1169     /// without producing an error.
1170     UnusedBrokenConst => []
1171 );
1172
1173 fn check_const(cx: &LateContext<'_>, body_id: hir::BodyId) {
1174     let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1175     // trigger the query once for all constants since that will already report the errors
1176     // FIXME: Use ensure here
1177     let _ = cx.tcx.const_eval_poly(def_id);
1178 }
1179
1180 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1181     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1182         match it.kind {
1183             hir::ItemKind::Const(_, body_id) => {
1184                 check_const(cx, body_id);
1185             }
1186             hir::ItemKind::Static(_, _, body_id) => {
1187                 check_const(cx, body_id);
1188             }
1189             _ => {}
1190         }
1191     }
1192 }
1193
1194 declare_lint! {
1195     TRIVIAL_BOUNDS,
1196     Warn,
1197     "these bounds don't depend on an type parameters"
1198 }
1199
1200 declare_lint_pass!(
1201     /// Lint for trait and lifetime bounds that don't depend on type parameters
1202     /// which either do nothing, or stop the item from being used.
1203     TrivialConstraints => [TRIVIAL_BOUNDS]
1204 );
1205
1206 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1207     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1208         use rustc_middle::ty::fold::TypeFoldable;
1209         use rustc_middle::ty::PredicateAtom::*;
1210
1211         if cx.tcx.features().trivial_bounds {
1212             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1213             let predicates = cx.tcx.predicates_of(def_id);
1214             for &(predicate, span) in predicates.predicates {
1215                 let predicate_kind_name = match predicate.skip_binders() {
1216                     Trait(..) => "Trait",
1217                     TypeOutlives(..) |
1218                     RegionOutlives(..) => "Lifetime",
1219
1220                     // Ignore projections, as they can only be global
1221                     // if the trait bound is global
1222                     Projection(..) |
1223                     // Ignore bounds that a user can't type
1224                     WellFormed(..) |
1225                     ObjectSafe(..) |
1226                     ClosureKind(..) |
1227                     Subtype(..) |
1228                     ConstEvaluatable(..) |
1229                     ConstEquate(..) => continue,
1230                 };
1231                 if predicate.is_global() {
1232                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1233                         lint.build(&format!(
1234                             "{} bound {} does not depend on any type \
1235                                 or lifetime parameters",
1236                             predicate_kind_name, predicate
1237                         ))
1238                         .emit()
1239                     });
1240                 }
1241             }
1242         }
1243     }
1244 }
1245
1246 declare_lint_pass!(
1247     /// Does nothing as a lint pass, but registers some `Lint`s
1248     /// which are used by other parts of the compiler.
1249     SoftLints => [
1250         WHILE_TRUE,
1251         BOX_POINTERS,
1252         NON_SHORTHAND_FIELD_PATTERNS,
1253         UNSAFE_CODE,
1254         MISSING_DOCS,
1255         MISSING_COPY_IMPLEMENTATIONS,
1256         MISSING_DEBUG_IMPLEMENTATIONS,
1257         ANONYMOUS_PARAMETERS,
1258         UNUSED_DOC_COMMENTS,
1259         NO_MANGLE_CONST_ITEMS,
1260         NO_MANGLE_GENERIC_ITEMS,
1261         MUTABLE_TRANSMUTES,
1262         UNSTABLE_FEATURES,
1263         UNREACHABLE_PUB,
1264         TYPE_ALIAS_BOUNDS,
1265         TRIVIAL_BOUNDS
1266     ]
1267 );
1268
1269 declare_lint! {
1270     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1271     Warn,
1272     "`...` range patterns are deprecated"
1273 }
1274
1275 #[derive(Default)]
1276 pub struct EllipsisInclusiveRangePatterns {
1277     /// If `Some(_)`, suppress all subsequent pattern
1278     /// warnings for better diagnostics.
1279     node_id: Option<ast::NodeId>,
1280 }
1281
1282 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1283
1284 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1285     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1286         if self.node_id.is_some() {
1287             // Don't recursively warn about patterns inside range endpoints.
1288             return;
1289         }
1290
1291         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1292
1293         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1294         /// corresponding to the ellipsis.
1295         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1296             match &pat.kind {
1297                 PatKind::Range(
1298                     a,
1299                     Some(b),
1300                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1301                 ) => Some((a.as_deref(), b, *span)),
1302                 _ => None,
1303             }
1304         }
1305
1306         let (parenthesise, endpoints) = match &pat.kind {
1307             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1308             _ => (false, matches_ellipsis_pat(pat)),
1309         };
1310
1311         if let Some((start, end, join)) = endpoints {
1312             let msg = "`...` range patterns are deprecated";
1313             let suggestion = "use `..=` for an inclusive range";
1314             if parenthesise {
1315                 self.node_id = Some(pat.id);
1316                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1317                     let end = expr_to_string(&end);
1318                     let replace = match start {
1319                         Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1320                         None => format!("&(..={})", end),
1321                     };
1322                     lint.build(msg)
1323                         .span_suggestion(
1324                             pat.span,
1325                             suggestion,
1326                             replace,
1327                             Applicability::MachineApplicable,
1328                         )
1329                         .emit();
1330                 });
1331             } else {
1332                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1333                     lint.build(msg)
1334                         .span_suggestion_short(
1335                             join,
1336                             suggestion,
1337                             "..=".to_owned(),
1338                             Applicability::MachineApplicable,
1339                         )
1340                         .emit();
1341                 });
1342             };
1343         }
1344     }
1345
1346     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1347         if let Some(node_id) = self.node_id {
1348             if pat.id == node_id {
1349                 self.node_id = None
1350             }
1351         }
1352     }
1353 }
1354
1355 declare_lint! {
1356     UNNAMEABLE_TEST_ITEMS,
1357     Warn,
1358     "detects an item that cannot be named being marked as `#[test_case]`",
1359     report_in_external_macro
1360 }
1361
1362 pub struct UnnameableTestItems {
1363     boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1364     items_nameable: bool,
1365 }
1366
1367 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1368
1369 impl UnnameableTestItems {
1370     pub fn new() -> Self {
1371         Self { boundary: None, items_nameable: true }
1372     }
1373 }
1374
1375 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1376     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1377         if self.items_nameable {
1378             if let hir::ItemKind::Mod(..) = it.kind {
1379             } else {
1380                 self.items_nameable = false;
1381                 self.boundary = Some(it.hir_id);
1382             }
1383             return;
1384         }
1385
1386         if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::rustc_test_marker) {
1387             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1388                 lint.build("cannot test inner items").emit()
1389             });
1390         }
1391     }
1392
1393     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1394         if !self.items_nameable && self.boundary == Some(it.hir_id) {
1395             self.items_nameable = true;
1396         }
1397     }
1398 }
1399
1400 declare_lint! {
1401     pub KEYWORD_IDENTS,
1402     Allow,
1403     "detects edition keywords being used as an identifier",
1404     @future_incompatible = FutureIncompatibleInfo {
1405         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1406         edition: Some(Edition::Edition2018),
1407     };
1408 }
1409
1410 declare_lint_pass!(
1411     /// Check for uses of edition keywords used as an identifier.
1412     KeywordIdents => [KEYWORD_IDENTS]
1413 );
1414
1415 struct UnderMacro(bool);
1416
1417 impl KeywordIdents {
1418     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1419         for tt in tokens.into_trees() {
1420             match tt {
1421                 // Only report non-raw idents.
1422                 TokenTree::Token(token) => {
1423                     if let Some((ident, false)) = token.ident() {
1424                         self.check_ident_token(cx, UnderMacro(true), ident);
1425                     }
1426                 }
1427                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1428             }
1429         }
1430     }
1431
1432     fn check_ident_token(
1433         &mut self,
1434         cx: &EarlyContext<'_>,
1435         UnderMacro(under_macro): UnderMacro,
1436         ident: Ident,
1437     ) {
1438         let next_edition = match cx.sess.edition() {
1439             Edition::Edition2015 => {
1440                 match ident.name {
1441                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1442
1443                     // rust-lang/rust#56327: Conservatively do not
1444                     // attempt to report occurrences of `dyn` within
1445                     // macro definitions or invocations, because `dyn`
1446                     // can legitimately occur as a contextual keyword
1447                     // in 2015 code denoting its 2018 meaning, and we
1448                     // do not want rustfix to inject bugs into working
1449                     // code by rewriting such occurrences.
1450                     //
1451                     // But if we see `dyn` outside of a macro, we know
1452                     // its precise role in the parsed AST and thus are
1453                     // assured this is truly an attempt to use it as
1454                     // an identifier.
1455                     kw::Dyn if !under_macro => Edition::Edition2018,
1456
1457                     _ => return,
1458                 }
1459             }
1460
1461             // There are no new keywords yet for the 2018 edition and beyond.
1462             _ => return,
1463         };
1464
1465         // Don't lint `r#foo`.
1466         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1467             return;
1468         }
1469
1470         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1471             lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1472                 .span_suggestion(
1473                     ident.span,
1474                     "you can use a raw identifier to stay compatible",
1475                     format!("r#{}", ident),
1476                     Applicability::MachineApplicable,
1477                 )
1478                 .emit()
1479         });
1480     }
1481 }
1482
1483 impl EarlyLintPass for KeywordIdents {
1484     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1485         self.check_tokens(cx, mac_def.body.inner_tokens());
1486     }
1487     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1488         self.check_tokens(cx, mac.args.inner_tokens());
1489     }
1490     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1491         self.check_ident_token(cx, UnderMacro(false), ident);
1492     }
1493 }
1494
1495 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1496
1497 impl ExplicitOutlivesRequirements {
1498     fn lifetimes_outliving_lifetime<'tcx>(
1499         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1500         index: u32,
1501     ) -> Vec<ty::Region<'tcx>> {
1502         inferred_outlives
1503             .iter()
1504             .filter_map(|(pred, _)| match pred.skip_binders() {
1505                 ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1506                     ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
1507                     _ => None,
1508                 },
1509                 _ => None,
1510             })
1511             .collect()
1512     }
1513
1514     fn lifetimes_outliving_type<'tcx>(
1515         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1516         index: u32,
1517     ) -> Vec<ty::Region<'tcx>> {
1518         inferred_outlives
1519             .iter()
1520             .filter_map(|(pred, _)| match pred.skip_binders() {
1521                 ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1522                     a.is_param(index).then_some(b)
1523                 }
1524                 _ => None,
1525             })
1526             .collect()
1527     }
1528
1529     fn collect_outlived_lifetimes<'tcx>(
1530         &self,
1531         param: &'tcx hir::GenericParam<'tcx>,
1532         tcx: TyCtxt<'tcx>,
1533         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1534         ty_generics: &'tcx ty::Generics,
1535     ) -> Vec<ty::Region<'tcx>> {
1536         let index =
1537             ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1538
1539         match param.kind {
1540             hir::GenericParamKind::Lifetime { .. } => {
1541                 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1542             }
1543             hir::GenericParamKind::Type { .. } => {
1544                 Self::lifetimes_outliving_type(inferred_outlives, index)
1545             }
1546             hir::GenericParamKind::Const { .. } => Vec::new(),
1547         }
1548     }
1549
1550     fn collect_outlives_bound_spans<'tcx>(
1551         &self,
1552         tcx: TyCtxt<'tcx>,
1553         bounds: &hir::GenericBounds<'_>,
1554         inferred_outlives: &[ty::Region<'tcx>],
1555         infer_static: bool,
1556     ) -> Vec<(usize, Span)> {
1557         use rustc_middle::middle::resolve_lifetime::Region;
1558
1559         bounds
1560             .iter()
1561             .enumerate()
1562             .filter_map(|(i, bound)| {
1563                 if let hir::GenericBound::Outlives(lifetime) = bound {
1564                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
1565                         Some(Region::Static) if infer_static => inferred_outlives
1566                             .iter()
1567                             .any(|r| if let ty::ReStatic = r { true } else { false }),
1568                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1569                             if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1570                         }),
1571                         _ => false,
1572                     };
1573                     is_inferred.then_some((i, bound.span()))
1574                 } else {
1575                     None
1576                 }
1577             })
1578             .collect()
1579     }
1580
1581     fn consolidate_outlives_bound_spans(
1582         &self,
1583         lo: Span,
1584         bounds: &hir::GenericBounds<'_>,
1585         bound_spans: Vec<(usize, Span)>,
1586     ) -> Vec<Span> {
1587         if bounds.is_empty() {
1588             return Vec::new();
1589         }
1590         if bound_spans.len() == bounds.len() {
1591             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1592             // If all bounds are inferable, we want to delete the colon, so
1593             // start from just after the parameter (span passed as argument)
1594             vec![lo.to(last_bound_span)]
1595         } else {
1596             let mut merged = Vec::new();
1597             let mut last_merged_i = None;
1598
1599             let mut from_start = true;
1600             for (i, bound_span) in bound_spans {
1601                 match last_merged_i {
1602                     // If the first bound is inferable, our span should also eat the leading `+`.
1603                     None if i == 0 => {
1604                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1605                         last_merged_i = Some(0);
1606                     }
1607                     // If consecutive bounds are inferable, merge their spans
1608                     Some(h) if i == h + 1 => {
1609                         if let Some(tail) = merged.last_mut() {
1610                             // Also eat the trailing `+` if the first
1611                             // more-than-one bound is inferable
1612                             let to_span = if from_start && i < bounds.len() {
1613                                 bounds[i + 1].span().shrink_to_lo()
1614                             } else {
1615                                 bound_span
1616                             };
1617                             *tail = tail.to(to_span);
1618                             last_merged_i = Some(i);
1619                         } else {
1620                             bug!("another bound-span visited earlier");
1621                         }
1622                     }
1623                     _ => {
1624                         // When we find a non-inferable bound, subsequent inferable bounds
1625                         // won't be consecutive from the start (and we'll eat the leading
1626                         // `+` rather than the trailing one)
1627                         from_start = false;
1628                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1629                         last_merged_i = Some(i);
1630                     }
1631                 }
1632             }
1633             merged
1634         }
1635     }
1636 }
1637
1638 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
1639     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
1640         use rustc_middle::middle::resolve_lifetime::Region;
1641
1642         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1643         let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1644         if let hir::ItemKind::Struct(_, ref hir_generics)
1645         | hir::ItemKind::Enum(_, ref hir_generics)
1646         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1647         {
1648             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1649             if inferred_outlives.is_empty() {
1650                 return;
1651             }
1652
1653             let ty_generics = cx.tcx.generics_of(def_id);
1654
1655             let mut bound_count = 0;
1656             let mut lint_spans = Vec::new();
1657
1658             for param in hir_generics.params {
1659                 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1660                     if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1661                 });
1662                 if !has_lifetime_bounds {
1663                     continue;
1664                 }
1665
1666                 let relevant_lifetimes =
1667                     self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1668                 if relevant_lifetimes.is_empty() {
1669                     continue;
1670                 }
1671
1672                 let bound_spans = self.collect_outlives_bound_spans(
1673                     cx.tcx,
1674                     &param.bounds,
1675                     &relevant_lifetimes,
1676                     infer_static,
1677                 );
1678                 bound_count += bound_spans.len();
1679                 lint_spans.extend(self.consolidate_outlives_bound_spans(
1680                     param.span.shrink_to_hi(),
1681                     &param.bounds,
1682                     bound_spans,
1683                 ));
1684             }
1685
1686             let mut where_lint_spans = Vec::new();
1687             let mut dropped_predicate_count = 0;
1688             let num_predicates = hir_generics.where_clause.predicates.len();
1689             for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1690                 let (relevant_lifetimes, bounds, span) = match where_predicate {
1691                     hir::WherePredicate::RegionPredicate(predicate) => {
1692                         if let Some(Region::EarlyBound(index, ..)) =
1693                             cx.tcx.named_region(predicate.lifetime.hir_id)
1694                         {
1695                             (
1696                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1697                                 &predicate.bounds,
1698                                 predicate.span,
1699                             )
1700                         } else {
1701                             continue;
1702                         }
1703                     }
1704                     hir::WherePredicate::BoundPredicate(predicate) => {
1705                         // FIXME we can also infer bounds on associated types,
1706                         // and should check for them here.
1707                         match predicate.bounded_ty.kind {
1708                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1709                                 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1710                                     let index = ty_generics.param_def_id_to_index[&def_id];
1711                                     (
1712                                         Self::lifetimes_outliving_type(inferred_outlives, index),
1713                                         &predicate.bounds,
1714                                         predicate.span,
1715                                     )
1716                                 } else {
1717                                     continue;
1718                                 }
1719                             }
1720                             _ => {
1721                                 continue;
1722                             }
1723                         }
1724                     }
1725                     _ => continue,
1726                 };
1727                 if relevant_lifetimes.is_empty() {
1728                     continue;
1729                 }
1730
1731                 let bound_spans = self.collect_outlives_bound_spans(
1732                     cx.tcx,
1733                     bounds,
1734                     &relevant_lifetimes,
1735                     infer_static,
1736                 );
1737                 bound_count += bound_spans.len();
1738
1739                 let drop_predicate = bound_spans.len() == bounds.len();
1740                 if drop_predicate {
1741                     dropped_predicate_count += 1;
1742                 }
1743
1744                 // If all the bounds on a predicate were inferable and there are
1745                 // further predicates, we want to eat the trailing comma.
1746                 if drop_predicate && i + 1 < num_predicates {
1747                     let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1748                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1749                 } else {
1750                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1751                         span.shrink_to_lo(),
1752                         bounds,
1753                         bound_spans,
1754                     ));
1755                 }
1756             }
1757
1758             // If all predicates are inferable, drop the entire clause
1759             // (including the `where`)
1760             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1761                 let where_span = hir_generics
1762                     .where_clause
1763                     .span()
1764                     .expect("span of (nonempty) where clause should exist");
1765                 // Extend the where clause back to the closing `>` of the
1766                 // generics, except for tuple struct, which have the `where`
1767                 // after the fields of the struct.
1768                 let full_where_span =
1769                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1770                         where_span
1771                     } else {
1772                         hir_generics.span.shrink_to_hi().to(where_span)
1773                     };
1774                 lint_spans.push(full_where_span);
1775             } else {
1776                 lint_spans.extend(where_lint_spans);
1777             }
1778
1779             if !lint_spans.is_empty() {
1780                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1781                     lint.build("outlives requirements can be inferred")
1782                         .multipart_suggestion(
1783                             if bound_count == 1 {
1784                                 "remove this bound"
1785                             } else {
1786                                 "remove these bounds"
1787                             },
1788                             lint_spans
1789                                 .into_iter()
1790                                 .map(|span| (span, "".to_owned()))
1791                                 .collect::<Vec<_>>(),
1792                             Applicability::MachineApplicable,
1793                         )
1794                         .emit();
1795                 });
1796             }
1797         }
1798     }
1799 }
1800
1801 declare_lint! {
1802     pub INCOMPLETE_FEATURES,
1803     Warn,
1804     "incomplete features that may function improperly in some or all cases"
1805 }
1806
1807 declare_lint_pass!(
1808     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1809     IncompleteFeatures => [INCOMPLETE_FEATURES]
1810 );
1811
1812 impl EarlyLintPass for IncompleteFeatures {
1813     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1814         let features = cx.sess.features_untracked();
1815         features
1816             .declared_lang_features
1817             .iter()
1818             .map(|(name, span, _)| (name, span))
1819             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1820             .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1821             .for_each(|(&name, &span)| {
1822                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1823                     let mut builder = lint.build(&format!(
1824                         "the feature `{}` is incomplete and may not be safe to use \
1825                          and/or cause compiler crashes",
1826                         name,
1827                     ));
1828                     if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1829                         builder.note(&format!(
1830                             "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1831                              for more information",
1832                             n, n,
1833                         ));
1834                     }
1835                     builder.emit();
1836                 })
1837             });
1838     }
1839 }
1840
1841 declare_lint! {
1842     pub INVALID_VALUE,
1843     Warn,
1844     "an invalid value is being created (such as a NULL reference)"
1845 }
1846
1847 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1848
1849 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
1850     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
1851         #[derive(Debug, Copy, Clone, PartialEq)]
1852         enum InitKind {
1853             Zeroed,
1854             Uninit,
1855         };
1856
1857         /// Information about why a type cannot be initialized this way.
1858         /// Contains an error message and optionally a span to point at.
1859         type InitError = (String, Option<Span>);
1860
1861         /// Test if this constant is all-0.
1862         fn is_zero(expr: &hir::Expr<'_>) -> bool {
1863             use hir::ExprKind::*;
1864             use rustc_ast::LitKind::*;
1865             match &expr.kind {
1866                 Lit(lit) => {
1867                     if let Int(i, _) = lit.node {
1868                         i == 0
1869                     } else {
1870                         false
1871                     }
1872                 }
1873                 Tup(tup) => tup.iter().all(is_zero),
1874                 _ => false,
1875             }
1876         }
1877
1878         /// Determine if this expression is a "dangerous initialization".
1879         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1880             // `transmute` is inside an anonymous module (the `extern` block?);
1881             // `Invalid` represents the empty string and matches that.
1882             // FIXME(#66075): use diagnostic items.  Somehow, that does not seem to work
1883             // on intrinsics right now.
1884             const TRANSMUTE_PATH: &[Symbol] =
1885                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1886
1887             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1888                 // Find calls to `mem::{uninitialized,zeroed}` methods.
1889                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1890                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1891
1892                     if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1893                         return Some(InitKind::Zeroed);
1894                     } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1895                         return Some(InitKind::Uninit);
1896                     } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1897                         if is_zero(&args[0]) {
1898                             return Some(InitKind::Zeroed);
1899                         }
1900                     }
1901                 }
1902             } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1903                 // Find problematic calls to `MaybeUninit::assume_init`.
1904                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
1905                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1906                     // This is a call to *some* method named `assume_init`.
1907                     // See if the `self` parameter is one of the dangerous constructors.
1908                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1909                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1910                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1911
1912                             if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1913                                 return Some(InitKind::Zeroed);
1914                             } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1915                                 return Some(InitKind::Uninit);
1916                             }
1917                         }
1918                     }
1919                 }
1920             }
1921
1922             None
1923         }
1924
1925         /// Test if this enum has several actually "existing" variants.
1926         /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
1927         fn is_multi_variant(adt: &ty::AdtDef) -> bool {
1928             // As an approximation, we only count dataless variants. Those are definitely inhabited.
1929             let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
1930             existing_variants > 1
1931         }
1932
1933         /// Return `Some` only if we are sure this type does *not*
1934         /// allow zero initialization.
1935         fn ty_find_init_error<'tcx>(
1936             tcx: TyCtxt<'tcx>,
1937             ty: Ty<'tcx>,
1938             init: InitKind,
1939         ) -> Option<InitError> {
1940             use rustc_middle::ty::TyKind::*;
1941             match ty.kind {
1942                 // Primitive types that don't like 0 as a value.
1943                 Ref(..) => Some(("references must be non-null".to_string(), None)),
1944                 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1945                 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1946                 Never => Some(("the `!` type has no valid value".to_string(), None)),
1947                 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1948                 // raw ptr to dyn Trait
1949                 {
1950                     Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1951                 }
1952                 // Primitive types with other constraints.
1953                 Bool if init == InitKind::Uninit => {
1954                     Some(("booleans must be either `true` or `false`".to_string(), None))
1955                 }
1956                 Char if init == InitKind::Uninit => {
1957                     Some(("characters must be a valid Unicode codepoint".to_string(), None))
1958                 }
1959                 // Recurse and checks for some compound types.
1960                 Adt(adt_def, substs) if !adt_def.is_union() => {
1961                     // First check if this ADT has a layout attribute (like `NonNull` and friends).
1962                     use std::ops::Bound;
1963                     match tcx.layout_scalar_valid_range(adt_def.did) {
1964                         // We exploit here that `layout_scalar_valid_range` will never
1965                         // return `Bound::Excluded`.  (And we have tests checking that we
1966                         // handle the attribute correctly.)
1967                         (Bound::Included(lo), _) if lo > 0 => {
1968                             return Some((format!("`{}` must be non-null", ty), None));
1969                         }
1970                         (Bound::Included(_), _) | (_, Bound::Included(_))
1971                             if init == InitKind::Uninit =>
1972                         {
1973                             return Some((
1974                                 format!(
1975                                     "`{}` must be initialized inside its custom valid range",
1976                                     ty,
1977                                 ),
1978                                 None,
1979                             ));
1980                         }
1981                         _ => {}
1982                     }
1983                     // Now, recurse.
1984                     match adt_def.variants.len() {
1985                         0 => Some(("enums with no variants have no valid value".to_string(), None)),
1986                         1 => {
1987                             // Struct, or enum with exactly one variant.
1988                             // Proceed recursively, check all fields.
1989                             let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1990                             variant.fields.iter().find_map(|field| {
1991                                 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1992                                     |(mut msg, span)| {
1993                                         if span.is_none() {
1994                                             // Point to this field, should be helpful for figuring
1995                                             // out where the source of the error is.
1996                                             let span = tcx.def_span(field.did);
1997                                             write!(
1998                                                 &mut msg,
1999                                                 " (in this {} field)",
2000                                                 adt_def.descr()
2001                                             )
2002                                             .unwrap();
2003                                             (msg, Some(span))
2004                                         } else {
2005                                             // Just forward.
2006                                             (msg, span)
2007                                         }
2008                                     },
2009                                 )
2010                             })
2011                         }
2012                         // Multi-variant enum.
2013                         _ => {
2014                             if init == InitKind::Uninit && is_multi_variant(adt_def) {
2015                                 let span = tcx.def_span(adt_def.did);
2016                                 Some((
2017                                     "enums have to be initialized to a variant".to_string(),
2018                                     Some(span),
2019                                 ))
2020                             } else {
2021                                 // In principle, for zero-initialization we could figure out which variant corresponds
2022                                 // to tag 0, and check that... but for now we just accept all zero-initializations.
2023                                 None
2024                             }
2025                         }
2026                     }
2027                 }
2028                 Tuple(..) => {
2029                     // Proceed recursively, check all fields.
2030                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2031                 }
2032                 // Conservative fallback.
2033                 _ => None,
2034             }
2035         }
2036
2037         if let Some(init) = is_dangerous_init(cx, expr) {
2038             // This conjures an instance of a type out of nothing,
2039             // using zeroed or uninitialized memory.
2040             // We are extremely conservative with what we warn about.
2041             let conjured_ty = cx.typeck_results().expr_ty(expr);
2042             if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2043                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2044                     let mut err = lint.build(&format!(
2045                         "the type `{}` does not permit {}",
2046                         conjured_ty,
2047                         match init {
2048                             InitKind::Zeroed => "zero-initialization",
2049                             InitKind::Uninit => "being left uninitialized",
2050                         },
2051                     ));
2052                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2053                     err.span_label(
2054                         expr.span,
2055                         "help: use `MaybeUninit<T>` instead, \
2056                             and only call `assume_init` after initialization is done",
2057                     );
2058                     if let Some(span) = span {
2059                         err.span_note(span, &msg);
2060                     } else {
2061                         err.note(&msg);
2062                     }
2063                     err.emit();
2064                 });
2065             }
2066         }
2067     }
2068 }
2069
2070 declare_lint! {
2071     pub CLASHING_EXTERN_DECLARATIONS,
2072     Warn,
2073     "detects when an extern fn has been declared with the same name but different types"
2074 }
2075
2076 pub struct ClashingExternDeclarations {
2077     seen_decls: FxHashMap<Symbol, HirId>,
2078 }
2079
2080 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2081 /// just from declaration itself. This is important because we don't want to report clashes on
2082 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2083 /// different name.
2084 enum SymbolName {
2085     /// The name of the symbol + the span of the annotation which introduced the link name.
2086     Link(Symbol, Span),
2087     /// No link name, so just the name of the symbol.
2088     Normal(Symbol),
2089 }
2090
2091 impl SymbolName {
2092     fn get_name(&self) -> Symbol {
2093         match self {
2094             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2095         }
2096     }
2097 }
2098
2099 impl ClashingExternDeclarations {
2100     crate fn new() -> Self {
2101         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2102     }
2103     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2104     /// for the item, return its HirId without updating the set.
2105     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2106         let hid = fi.hir_id;
2107
2108         let name =
2109             &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2110
2111         if self.seen_decls.contains_key(name) {
2112             // Avoid updating the map with the new entry when we do find a collision. We want to
2113             // make sure we're always pointing to the first definition as the previous declaration.
2114             // This lets us avoid emitting "knock-on" diagnostics.
2115             Some(*self.seen_decls.get(name).unwrap())
2116         } else {
2117             self.seen_decls.insert(*name, hid)
2118         }
2119     }
2120
2121     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2122     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2123     /// symbol's name.
2124     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2125         let did = tcx.hir().local_def_id(fi.hir_id);
2126         if let Some((overridden_link_name, overridden_link_name_span)) =
2127             tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2128                 // FIXME: Instead of searching through the attributes again to get span
2129                 // information, we could have codegen_fn_attrs also give span information back for
2130                 // where the attribute was defined. However, until this is found to be a
2131                 // bottleneck, this does just fine.
2132                 (
2133                     overridden_link_name,
2134                     tcx.get_attrs(did.to_def_id())
2135                         .iter()
2136                         .find(|at| tcx.sess.check_name(at, sym::link_name))
2137                         .unwrap()
2138                         .span,
2139                 )
2140             })
2141         {
2142             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2143         } else {
2144             SymbolName::Normal(fi.ident.name)
2145         }
2146     }
2147
2148     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2149     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2150     /// with the same members (as the declarations shouldn't clash).
2151     fn structurally_same_type<'tcx>(
2152         cx: &LateContext<'tcx>,
2153         a: Ty<'tcx>,
2154         b: Ty<'tcx>,
2155         ckind: CItemKind,
2156     ) -> bool {
2157         fn structurally_same_type_impl<'tcx>(
2158             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2159             cx: &LateContext<'tcx>,
2160             a: Ty<'tcx>,
2161             b: Ty<'tcx>,
2162             ckind: CItemKind,
2163         ) -> bool {
2164             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2165             if !seen_types.insert((a, b)) {
2166                 // We've encountered a cycle. There's no point going any further -- the types are
2167                 // structurally the same.
2168                 return true;
2169             }
2170             let tcx = cx.tcx;
2171             if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2172                 // All nominally-same types are structurally same, too.
2173                 true
2174             } else {
2175                 // Do a full, depth-first comparison between the two.
2176                 use rustc_middle::ty::TyKind::*;
2177                 let a_kind = &a.kind;
2178                 let b_kind = &b.kind;
2179
2180                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2181                     debug!("compare_layouts({:?}, {:?})", a, b);
2182                     let a_layout = &cx.layout_of(a)?.layout.abi;
2183                     let b_layout = &cx.layout_of(b)?.layout.abi;
2184                     debug!(
2185                         "comparing layouts: {:?} == {:?} = {}",
2186                         a_layout,
2187                         b_layout,
2188                         a_layout == b_layout
2189                     );
2190                     Ok(a_layout == b_layout)
2191                 };
2192
2193                 #[allow(rustc::usage_of_ty_tykind)]
2194                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2195                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2196                 };
2197
2198                 ensure_sufficient_stack(|| {
2199                     match (a_kind, b_kind) {
2200                         (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2201                             let a = a.subst(cx.tcx, a_substs);
2202                             let b = b.subst(cx.tcx, b_substs);
2203                             debug!("Comparing {:?} and {:?}", a, b);
2204
2205                             // We can immediately rule out these types as structurally same if
2206                             // their layouts differ.
2207                             match compare_layouts(a, b) {
2208                                 Ok(false) => return false,
2209                                 _ => (), // otherwise, continue onto the full, fields comparison
2210                             }
2211
2212                             // Grab a flattened representation of all fields.
2213                             let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2214                             let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2215
2216                             // Perform a structural comparison for each field.
2217                             a_fields.eq_by(
2218                                 b_fields,
2219                                 |&ty::FieldDef { did: a_did, .. },
2220                                  &ty::FieldDef { did: b_did, .. }| {
2221                                     structurally_same_type_impl(
2222                                         seen_types,
2223                                         cx,
2224                                         tcx.type_of(a_did),
2225                                         tcx.type_of(b_did),
2226                                         ckind,
2227                                     )
2228                                 },
2229                             )
2230                         }
2231                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2232                             // For arrays, we also check the constness of the type.
2233                             a_const.val == b_const.val
2234                                 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2235                         }
2236                         (Slice(a_ty), Slice(b_ty)) => {
2237                             structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2238                         }
2239                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2240                             a_tymut.mutbl == b_tymut.mutbl
2241                                 && structurally_same_type_impl(
2242                                     seen_types,
2243                                     cx,
2244                                     &a_tymut.ty,
2245                                     &b_tymut.ty,
2246                                     ckind,
2247                                 )
2248                         }
2249                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2250                             // For structural sameness, we don't need the region to be same.
2251                             a_mut == b_mut
2252                                 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2253                         }
2254                         (FnDef(..), FnDef(..)) => {
2255                             let a_poly_sig = a.fn_sig(tcx);
2256                             let b_poly_sig = b.fn_sig(tcx);
2257
2258                             // As we don't compare regions, skip_binder is fine.
2259                             let a_sig = a_poly_sig.skip_binder();
2260                             let b_sig = b_poly_sig.skip_binder();
2261
2262                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2263                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2264                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2265                                     structurally_same_type_impl(seen_types, cx, a, b, ckind)
2266                                 })
2267                                 && structurally_same_type_impl(
2268                                     seen_types,
2269                                     cx,
2270                                     a_sig.output(),
2271                                     b_sig.output(),
2272                                     ckind,
2273                                 )
2274                         }
2275                         (Tuple(a_substs), Tuple(b_substs)) => {
2276                             a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2277                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2278                             })
2279                         }
2280                         // For these, it's not quite as easy to define structural-sameness quite so easily.
2281                         // For the purposes of this lint, take the conservative approach and mark them as
2282                         // not structurally same.
2283                         (Dynamic(..), Dynamic(..))
2284                         | (Error(..), Error(..))
2285                         | (Closure(..), Closure(..))
2286                         | (Generator(..), Generator(..))
2287                         | (GeneratorWitness(..), GeneratorWitness(..))
2288                         | (Projection(..), Projection(..))
2289                         | (Opaque(..), Opaque(..)) => false,
2290
2291                         // These definitely should have been caught above.
2292                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2293
2294                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2295                         // enum layout optimisation is being applied.
2296                         (Adt(..), other_kind) | (other_kind, Adt(..))
2297                             if is_primitive_or_pointer(other_kind) =>
2298                         {
2299                             let (primitive, adt) =
2300                                 if is_primitive_or_pointer(&a.kind) { (a, b) } else { (b, a) };
2301                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2302                                 ty == primitive
2303                             } else {
2304                                 compare_layouts(a, b).unwrap_or(false)
2305                             }
2306                         }
2307                         // Otherwise, just compare the layouts. This may fail to lint for some
2308                         // incompatible types, but at the very least, will stop reads into
2309                         // uninitialised memory.
2310                         _ => compare_layouts(a, b).unwrap_or(false),
2311                     }
2312                 })
2313             }
2314         }
2315         let mut seen_types = FxHashSet::default();
2316         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2317     }
2318 }
2319
2320 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2321
2322 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2323     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2324         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2325         if let ForeignItemKind::Fn(..) = this_fi.kind {
2326             let tcx = *&cx.tcx;
2327             if let Some(existing_hid) = self.insert(tcx, this_fi) {
2328                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2329                 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2330                 debug!(
2331                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2332                     existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2333                 );
2334                 // Check that the declarations match.
2335                 if !Self::structurally_same_type(
2336                     cx,
2337                     existing_decl_ty,
2338                     this_decl_ty,
2339                     CItemKind::Declaration,
2340                 ) {
2341                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2342                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
2343
2344                     // We want to ensure that we use spans for both decls that include where the
2345                     // name was defined, whether that was from the link_name attribute or not.
2346                     let get_relevant_span =
2347                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2348                             SymbolName::Normal(_) => fi.span,
2349                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2350                         };
2351                     // Finally, emit the diagnostic.
2352                     tcx.struct_span_lint_hir(
2353                         CLASHING_EXTERN_DECLARATIONS,
2354                         this_fi.hir_id,
2355                         get_relevant_span(this_fi),
2356                         |lint| {
2357                             let mut expected_str = DiagnosticStyledString::new();
2358                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2359                             let mut found_str = DiagnosticStyledString::new();
2360                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2361
2362                             lint.build(&format!(
2363                                 "`{}` redeclare{} with a different signature",
2364                                 this_fi.ident.name,
2365                                 if orig.get_name() == this_fi.ident.name {
2366                                     "d".to_string()
2367                                 } else {
2368                                     format!("s `{}`", orig.get_name())
2369                                 }
2370                             ))
2371                             .span_label(
2372                                 get_relevant_span(orig_fi),
2373                                 &format!("`{}` previously declared here", orig.get_name()),
2374                             )
2375                             .span_label(
2376                                 get_relevant_span(this_fi),
2377                                 "this signature doesn't match the previous declaration",
2378                             )
2379                             .note_expected_found(&"", expected_str, &"", found_str)
2380                             .emit()
2381                         },
2382                     );
2383                 }
2384             }
2385         }
2386     }
2387 }