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