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