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 declare_lint! {
 742     pub UNUSED_DOC_COMMENTS,
 743     Warn,
 744     "detects doc comments that aren't used by rustdoc"
 745 }
 746
 747 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
 748
 749 impl UnusedDocComment {
 750     fn warn_if_doc(
 751         &self,
 752         cx: &EarlyContext<'_>,
 753         node_span: Span,
 754         node_kind: &str,
 755         is_macro_expansion: bool,
 756         attrs: &[ast::Attribute],
 757     ) {
 758         let mut attrs = attrs.into_iter().peekable();
 759
 760         // Accumulate a single span for sugared doc comments.
 761         let mut sugared_span: Option<Span> = None;
 762
 763         while let Some(attr) = attrs.next() {
 764             if attr.is_doc_comment() {
 765                 sugared_span = Some(
 766                     sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())),
 767                 );
 768             }
 769
 770             if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
 771                 continue;
 772             }
 773
 774             let span = sugared_span.take().unwrap_or_else(|| attr.span);
 775
 776             if attr.is_doc_comment() || attr.check_name(sym::doc) {
 777                 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
 778                     let mut err = lint.build("unused doc comment");
 779                     err.span_label(
 780                         node_span,
 781                         format!("rustdoc does not generate documentation for {}", node_kind),
 782                     );
 783                     if is_macro_expansion {
 784                         err.help(
 785                             "to document an item produced by a macro, \
 786                                   the macro must produce the documentation as part of its expansion",
 787                         );
 788                     }
 789                     err.emit();
 790                 });
 791             }
 792         }
 793     }
 794 }
 795
 796 impl EarlyLintPass for UnusedDocComment {
 797     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 798         if let ast::ItemKind::Mac(..) = item.kind {
 799             self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
 800         }
 801     }
 802
 803     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 804         let (kind, is_macro_expansion) = match stmt.kind {
 805             ast::StmtKind::Local(..) => ("statements", false),
 806             ast::StmtKind::Item(..) => ("inner items", false),
 807             ast::StmtKind::Mac(..) => ("macro expansions", true),
 808             // expressions will be reported by `check_expr`.
 809             ast::StmtKind::Semi(..) | ast::StmtKind::Expr(..) => return,
 810         };
 811
 812         self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.kind.attrs());
 813     }
 814
 815     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 816         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
 817         self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
 818     }
 819
 820     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 821         self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
 822     }
 823 }
 824
 825 declare_lint! {
 826     NO_MANGLE_CONST_ITEMS,
 827     Deny,
 828     "const items will not have their symbols exported"
 829 }
 830
 831 declare_lint! {
 832     NO_MANGLE_GENERIC_ITEMS,
 833     Warn,
 834     "generic items must be mangled"
 835 }
 836
 837 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
 838
 839 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
 840     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 841         match it.kind {
 842             hir::ItemKind::Fn(.., ref generics, _) => {
 843                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
 844                     for param in generics.params {
 845                         match param.kind {
 846                             GenericParamKind::Lifetime { .. } => {}
 847                             GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
 848                                 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
 849                                     lint.build(
 850                                         "functions generic over types or consts must be mangled",
 851                                     )
 852                                     .span_suggestion_short(
 853                                         no_mangle_attr.span,
 854                                         "remove this attribute",
 855                                         String::new(),
 856                                         // Use of `#[no_mangle]` suggests FFI intent; correct
 857                                         // fix may be to monomorphize source by hand
 858                                         Applicability::MaybeIncorrect,
 859                                     )
 860                                     .emit();
 861                                 });
 862                                 break;
 863                             }
 864                         }
 865                     }
 866                 }
 867             }
 868             hir::ItemKind::Const(..) => {
 869                 if attr::contains_name(&it.attrs, sym::no_mangle) {
 870                     // Const items do not refer to a particular location in memory, and therefore
 871                     // don't have anything to attach a symbol to
 872                     cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
 873                         let msg = "const items should never be `#[no_mangle]`";
 874                         let mut err = lint.build(msg);
 875
 876                         // account for "pub const" (#45562)
 877                         let start = cx
 878                             .tcx
 879                             .sess
 880                             .source_map()
 881                             .span_to_snippet(it.span)
 882                             .map(|snippet| snippet.find("const").unwrap_or(0))
 883                             .unwrap_or(0) as u32;
 884                         // `const` is 5 chars
 885                         let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 886                         err.span_suggestion(
 887                             const_span,
 888                             "try a static value",
 889                             "pub static".to_owned(),
 890                             Applicability::MachineApplicable,
 891                         );
 892                         err.emit();
 893                     });
 894                 }
 895             }
 896             _ => {}
 897         }
 898     }
 899 }
 900
 901 declare_lint! {
 902     MUTABLE_TRANSMUTES,
 903     Deny,
 904     "mutating transmuted &mut T from &T may cause undefined behavior"
 905 }
 906
 907 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
 908
 909 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
 910     fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
 911         use rustc_target::spec::abi::Abi::RustIntrinsic;
 912
 913         match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
 914             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
 915                 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
 916                     let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 917                                consider instead using an UnsafeCell";
 918                     cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
 919                         lint.build(msg).emit()
 920                     });
 921                 }
 922             }
 923             _ => (),
 924         }
 925
 926         fn get_transmute_from_to<'a, 'tcx>(
 927             cx: &LateContext<'a, 'tcx>,
 928             expr: &hir::Expr<'_>,
 929         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
 930             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
 931                 cx.tables.qpath_res(qpath, expr.hir_id)
 932             } else {
 933                 return None;
 934             };
 935             if let Res::Def(DefKind::Fn, did) = def {
 936                 if !def_id_is_transmute(cx, did) {
 937                     return None;
 938                 }
 939                 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
 940                 let from = sig.inputs().skip_binder()[0];
 941                 let to = *sig.output().skip_binder();
 942                 return Some((from, to));
 943             }
 944             None
 945         }
 946
 947         fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
 948             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
 949                 && cx.tcx.item_name(def_id) == sym::transmute
 950         }
 951     }
 952 }
 953
 954 declare_lint! {
 955     UNSTABLE_FEATURES,
 956     Allow,
 957     "enabling unstable features (deprecated. do not use)"
 958 }
 959
 960 declare_lint_pass!(
 961     /// Forbids using the `#[feature(...)]` attribute
 962     UnstableFeatures => [UNSTABLE_FEATURES]
 963 );
 964
 965 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
 966     fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
 967         if attr.check_name(sym::feature) {
 968             if let Some(items) = attr.meta_item_list() {
 969                 for item in items {
 970                     ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
 971                         lint.build("unstable feature").emit()
 972                     });
 973                 }
 974             }
 975         }
 976     }
 977 }
 978
 979 declare_lint! {
 980     pub UNREACHABLE_PUB,
 981     Allow,
 982     "`pub` items not reachable from crate root"
 983 }
 984
 985 declare_lint_pass!(
 986     /// Lint for items marked `pub` that aren't reachable from other crates.
 987     UnreachablePub => [UNREACHABLE_PUB]
 988 );
 989
 990 impl UnreachablePub {
 991     fn perform_lint(
 992         &self,
 993         cx: &LateContext<'_, '_>,
 994         what: &str,
 995         id: hir::HirId,
 996         vis: &hir::Visibility<'_>,
 997         span: Span,
 998         exportable: bool,
 999     ) {
1000         let mut applicability = Applicability::MachineApplicable;
1001         match vis.node {
1002             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1003                 if span.from_expansion() {
1004                     applicability = Applicability::MaybeIncorrect;
1005                 }
1006                 let def_span = cx.tcx.sess.source_map().def_span(span);
1007                 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1008                     let mut err = lint.build(&format!("unreachable `pub` {}", what));
1009                     let replacement = if cx.tcx.features().crate_visibility_modifier {
1010                         "crate"
1011                     } else {
1012                         "pub(crate)"
1013                     }
1014                     .to_owned();
1015
1016                     err.span_suggestion(
1017                         vis.span,
1018                         "consider restricting its visibility",
1019                         replacement,
1020                         applicability,
1021                     );
1022                     if exportable {
1023                         err.help("or consider exporting it for use by other crates");
1024                     }
1025                     err.emit();
1026                 });
1027             }
1028             _ => {}
1029         }
1030     }
1031 }
1032
1033 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1034     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1035         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1036     }
1037
1038     fn check_foreign_item(
1039         &mut self,
1040         cx: &LateContext<'_, '_>,
1041         foreign_item: &hir::ForeignItem<'tcx>,
1042     ) {
1043         self.perform_lint(
1044             cx,
1045             "item",
1046             foreign_item.hir_id,
1047             &foreign_item.vis,
1048             foreign_item.span,
1049             true,
1050         );
1051     }
1052
1053     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1054         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1055     }
1056
1057     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1058         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1059     }
1060 }
1061
1062 declare_lint! {
1063     TYPE_ALIAS_BOUNDS,
1064     Warn,
1065     "bounds in type aliases are not enforced"
1066 }
1067
1068 declare_lint_pass!(
1069     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1070     /// They are relevant when using associated types, but otherwise neither checked
1071     /// at definition site nor enforced at use site.
1072     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1073 );
1074
1075 impl TypeAliasBounds {
1076     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1077         match *qpath {
1078             hir::QPath::TypeRelative(ref ty, _) => {
1079                 // If this is a type variable, we found a `T::Assoc`.
1080                 match ty.kind {
1081                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1082                         Res::Def(DefKind::TyParam, _) => true,
1083                         _ => false,
1084                     },
1085                     _ => false,
1086                 }
1087             }
1088             hir::QPath::Resolved(..) => false,
1089         }
1090     }
1091
1092     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1093         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1094         // bound.  Let's see if this type does that.
1095
1096         // We use a HIR visitor to walk the type.
1097         use rustc_hir::intravisit::{self, Visitor};
1098         struct WalkAssocTypes<'a, 'db> {
1099             err: &'a mut DiagnosticBuilder<'db>,
1100         }
1101         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1102             type Map = Map<'v>;
1103
1104             fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1105                 intravisit::NestedVisitorMap::None
1106             }
1107
1108             fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1109                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1110                     self.err.span_help(
1111                         span,
1112                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1113                          associated types in type aliases",
1114                     );
1115                 }
1116                 intravisit::walk_qpath(self, qpath, id, span)
1117             }
1118         }
1119
1120         // Let's go for a walk!
1121         let mut visitor = WalkAssocTypes { err };
1122         visitor.visit_ty(ty);
1123     }
1124 }
1125
1126 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1127     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1128         let (ty, type_alias_generics) = match item.kind {
1129             hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1130             _ => return,
1131         };
1132         let mut suggested_changing_assoc_types = false;
1133         // There must not be a where clause
1134         if !type_alias_generics.where_clause.predicates.is_empty() {
1135             cx.lint(
1136                 TYPE_ALIAS_BOUNDS,
1137                 |lint| {
1138                     let mut err = lint.build("where clauses are not enforced in type aliases");
1139                     let spans: Vec<_> = type_alias_generics
1140                         .where_clause
1141                         .predicates
1142                         .iter()
1143                         .map(|pred| pred.span())
1144                         .collect();
1145                     err.set_span(spans);
1146                     err.span_suggestion(
1147                         type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1148                         "the clause will not be checked when the type alias is used, and should be removed",
1149                         String::new(),
1150                         Applicability::MachineApplicable,
1151                     );
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         // The parameters must not have bounds
1161         for param in type_alias_generics.params.iter() {
1162             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1163             let suggestion = spans
1164                 .iter()
1165                 .map(|sp| {
1166                     let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1167                     (start.to(*sp), String::new())
1168                 })
1169                 .collect();
1170             if !spans.is_empty() {
1171                 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1172                     let mut err =
1173                         lint.build("bounds on generic parameters are not enforced in type aliases");
1174                     let msg = "the bound will not be checked when the type alias is used, \
1175                                    and should be removed";
1176                     err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1177                     if !suggested_changing_assoc_types {
1178                         TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1179                         suggested_changing_assoc_types = true;
1180                     }
1181                     err.emit();
1182                 });
1183             }
1184         }
1185     }
1186 }
1187
1188 declare_lint_pass!(
1189     /// Lint constants that are erroneous.
1190     /// Without this lint, we might not get any diagnostic if the constant is
1191     /// unused within this crate, even though downstream crates can't use it
1192     /// without producing an error.
1193     UnusedBrokenConst => []
1194 );
1195
1196 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1197     let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1198     // trigger the query once for all constants since that will already report the errors
1199     // FIXME: Use ensure here
1200     let _ = cx.tcx.const_eval_poly(def_id);
1201 }
1202
1203 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1204     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1205         match it.kind {
1206             hir::ItemKind::Const(_, body_id) => {
1207                 check_const(cx, body_id);
1208             }
1209             hir::ItemKind::Static(_, _, body_id) => {
1210                 check_const(cx, body_id);
1211             }
1212             _ => {}
1213         }
1214     }
1215 }
1216
1217 declare_lint! {
1218     TRIVIAL_BOUNDS,
1219     Warn,
1220     "these bounds don't depend on an type parameters"
1221 }
1222
1223 declare_lint_pass!(
1224     /// Lint for trait and lifetime bounds that don't depend on type parameters
1225     /// which either do nothing, or stop the item from being used.
1226     TrivialConstraints => [TRIVIAL_BOUNDS]
1227 );
1228
1229 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1230     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1231         use rustc::ty::fold::TypeFoldable;
1232         use rustc::ty::Predicate::*;
1233
1234         if cx.tcx.features().trivial_bounds {
1235             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1236             let predicates = cx.tcx.predicates_of(def_id);
1237             for &(predicate, span) in predicates.predicates {
1238                 let predicate_kind_name = match predicate {
1239                     Trait(..) => "Trait",
1240                     TypeOutlives(..) |
1241                     RegionOutlives(..) => "Lifetime",
1242
1243                     // Ignore projections, as they can only be global
1244                     // if the trait bound is global
1245                     Projection(..) |
1246                     // Ignore bounds that a user can't type
1247                     WellFormed(..) |
1248                     ObjectSafe(..) |
1249                     ClosureKind(..) |
1250                     Subtype(..) |
1251                     ConstEvaluatable(..) => continue,
1252                 };
1253                 if predicate.is_global() {
1254                     cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1255                         lint.build(&format!(
1256                             "{} bound {} does not depend on any type \
1257                                 or lifetime parameters",
1258                             predicate_kind_name, predicate
1259                         ))
1260                         .emit()
1261                     });
1262                 }
1263             }
1264         }
1265     }
1266 }
1267
1268 declare_lint_pass!(
1269     /// Does nothing as a lint pass, but registers some `Lint`s
1270     /// which are used by other parts of the compiler.
1271     SoftLints => [
1272         WHILE_TRUE,
1273         BOX_POINTERS,
1274         NON_SHORTHAND_FIELD_PATTERNS,
1275         UNSAFE_CODE,
1276         MISSING_DOCS,
1277         MISSING_COPY_IMPLEMENTATIONS,
1278         MISSING_DEBUG_IMPLEMENTATIONS,
1279         ANONYMOUS_PARAMETERS,
1280         UNUSED_DOC_COMMENTS,
1281         NO_MANGLE_CONST_ITEMS,
1282         NO_MANGLE_GENERIC_ITEMS,
1283         MUTABLE_TRANSMUTES,
1284         UNSTABLE_FEATURES,
1285         UNREACHABLE_PUB,
1286         TYPE_ALIAS_BOUNDS,
1287         TRIVIAL_BOUNDS
1288     ]
1289 );
1290
1291 declare_lint! {
1292     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1293     Warn,
1294     "`...` range patterns are deprecated"
1295 }
1296
1297 #[derive(Default)]
1298 pub struct EllipsisInclusiveRangePatterns {
1299     /// If `Some(_)`, suppress all subsequent pattern
1300     /// warnings for better diagnostics.
1301     node_id: Option<ast::NodeId>,
1302 }
1303
1304 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1305
1306 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1307     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1308         if self.node_id.is_some() {
1309             // Don't recursively warn about patterns inside range endpoints.
1310             return;
1311         }
1312
1313         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1314
1315         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1316         /// corresponding to the ellipsis.
1317         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1318             match &pat.kind {
1319                 PatKind::Range(
1320                     a,
1321                     Some(b),
1322                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1323                 ) => Some((a.as_deref(), b, *span)),
1324                 _ => None,
1325             }
1326         }
1327
1328         let (parenthesise, endpoints) = match &pat.kind {
1329             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1330             _ => (false, matches_ellipsis_pat(pat)),
1331         };
1332
1333         if let Some((start, end, join)) = endpoints {
1334             let msg = "`...` range patterns are deprecated";
1335             let suggestion = "use `..=` for an inclusive range";
1336             if parenthesise {
1337                 self.node_id = Some(pat.id);
1338                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1339                     let end = expr_to_string(&end);
1340                     let replace = match start {
1341                         Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1342                         None => format!("&(..={})", end),
1343                     };
1344                     lint.build(msg)
1345                         .span_suggestion(
1346                             pat.span,
1347                             suggestion,
1348                             replace,
1349                             Applicability::MachineApplicable,
1350                         )
1351                         .emit();
1352                 });
1353             } else {
1354                 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1355                     lint.build(msg)
1356                         .span_suggestion_short(
1357                             join,
1358                             suggestion,
1359                             "..=".to_owned(),
1360                             Applicability::MachineApplicable,
1361                         )
1362                         .emit();
1363                 });
1364             };
1365         }
1366     }
1367
1368     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1369         if let Some(node_id) = self.node_id {
1370             if pat.id == node_id {
1371                 self.node_id = None
1372             }
1373         }
1374     }
1375 }
1376
1377 declare_lint! {
1378     UNNAMEABLE_TEST_ITEMS,
1379     Warn,
1380     "detects an item that cannot be named being marked as `#[test_case]`",
1381     report_in_external_macro
1382 }
1383
1384 pub struct UnnameableTestItems {
1385     boundary: hir::HirId, // HirId of the item under which things are not nameable
1386     items_nameable: bool,
1387 }
1388
1389 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1390
1391 impl UnnameableTestItems {
1392     pub fn new() -> Self {
1393         Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1394     }
1395 }
1396
1397 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1398     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1399         if self.items_nameable {
1400             if let hir::ItemKind::Mod(..) = it.kind {
1401             } else {
1402                 self.items_nameable = false;
1403                 self.boundary = it.hir_id;
1404             }
1405             return;
1406         }
1407
1408         if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1409             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1410                 lint.build("cannot test inner items").emit()
1411             });
1412         }
1413     }
1414
1415     fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1416         if !self.items_nameable && self.boundary == it.hir_id {
1417             self.items_nameable = true;
1418         }
1419     }
1420 }
1421
1422 declare_lint! {
1423     pub KEYWORD_IDENTS,
1424     Allow,
1425     "detects edition keywords being used as an identifier",
1426     @future_incompatible = FutureIncompatibleInfo {
1427         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1428         edition: Some(Edition::Edition2018),
1429     };
1430 }
1431
1432 declare_lint_pass!(
1433     /// Check for uses of edition keywords used as an identifier.
1434     KeywordIdents => [KEYWORD_IDENTS]
1435 );
1436
1437 struct UnderMacro(bool);
1438
1439 impl KeywordIdents {
1440     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1441         for tt in tokens.into_trees() {
1442             match tt {
1443                 // Only report non-raw idents.
1444                 TokenTree::Token(token) => {
1445                     if let Some((ident, false)) = token.ident() {
1446                         self.check_ident_token(cx, UnderMacro(true), ident);
1447                     }
1448                 }
1449                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1450             }
1451         }
1452     }
1453
1454     fn check_ident_token(
1455         &mut self,
1456         cx: &EarlyContext<'_>,
1457         UnderMacro(under_macro): UnderMacro,
1458         ident: ast::Ident,
1459     ) {
1460         let next_edition = match cx.sess.edition() {
1461             Edition::Edition2015 => {
1462                 match ident.name {
1463                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1464
1465                     // rust-lang/rust#56327: Conservatively do not
1466                     // attempt to report occurrences of `dyn` within
1467                     // macro definitions or invocations, because `dyn`
1468                     // can legitimately occur as a contextual keyword
1469                     // in 2015 code denoting its 2018 meaning, and we
1470                     // do not want rustfix to inject bugs into working
1471                     // code by rewriting such occurrences.
1472                     //
1473                     // But if we see `dyn` outside of a macro, we know
1474                     // its precise role in the parsed AST and thus are
1475                     // assured this is truly an attempt to use it as
1476                     // an identifier.
1477                     kw::Dyn if !under_macro => Edition::Edition2018,
1478
1479                     _ => return,
1480                 }
1481             }
1482
1483             // There are no new keywords yet for the 2018 edition and beyond.
1484             _ => return,
1485         };
1486
1487         // Don't lint `r#foo`.
1488         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1489             return;
1490         }
1491
1492         cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1493             lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1494                 .span_suggestion(
1495                     ident.span,
1496                     "you can use a raw identifier to stay compatible",
1497                     format!("r#{}", ident),
1498                     Applicability::MachineApplicable,
1499                 )
1500                 .emit()
1501         });
1502     }
1503 }
1504
1505 impl EarlyLintPass for KeywordIdents {
1506     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1507         self.check_tokens(cx, mac_def.body.inner_tokens());
1508     }
1509     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1510         self.check_tokens(cx, mac.args.inner_tokens());
1511     }
1512     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1513         self.check_ident_token(cx, UnderMacro(false), ident);
1514     }
1515 }
1516
1517 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1518
1519 impl ExplicitOutlivesRequirements {
1520     fn lifetimes_outliving_lifetime<'tcx>(
1521         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1522         index: u32,
1523     ) -> Vec<ty::Region<'tcx>> {
1524         inferred_outlives
1525             .iter()
1526             .filter_map(|(pred, _)| match pred {
1527                 ty::Predicate::RegionOutlives(outlives) => {
1528                     let outlives = outlives.skip_binder();
1529                     match outlives.0 {
1530                         ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1531                         _ => None,
1532                     }
1533                 }
1534                 _ => None,
1535             })
1536             .collect()
1537     }
1538
1539     fn lifetimes_outliving_type<'tcx>(
1540         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1541         index: u32,
1542     ) -> Vec<ty::Region<'tcx>> {
1543         inferred_outlives
1544             .iter()
1545             .filter_map(|(pred, _)| match pred {
1546                 ty::Predicate::TypeOutlives(outlives) => {
1547                     let outlives = outlives.skip_binder();
1548                     outlives.0.is_param(index).then_some(outlives.1)
1549                 }
1550                 _ => None,
1551             })
1552             .collect()
1553     }
1554
1555     fn collect_outlived_lifetimes<'tcx>(
1556         &self,
1557         param: &'tcx hir::GenericParam<'tcx>,
1558         tcx: TyCtxt<'tcx>,
1559         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1560         ty_generics: &'tcx ty::Generics,
1561     ) -> Vec<ty::Region<'tcx>> {
1562         let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1563
1564         match param.kind {
1565             hir::GenericParamKind::Lifetime { .. } => {
1566                 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1567             }
1568             hir::GenericParamKind::Type { .. } => {
1569                 Self::lifetimes_outliving_type(inferred_outlives, index)
1570             }
1571             hir::GenericParamKind::Const { .. } => Vec::new(),
1572         }
1573     }
1574
1575     fn collect_outlives_bound_spans<'tcx>(
1576         &self,
1577         tcx: TyCtxt<'tcx>,
1578         bounds: &hir::GenericBounds<'_>,
1579         inferred_outlives: &[ty::Region<'tcx>],
1580         infer_static: bool,
1581     ) -> Vec<(usize, Span)> {
1582         use rustc::middle::resolve_lifetime::Region;
1583
1584         bounds
1585             .iter()
1586             .enumerate()
1587             .filter_map(|(i, bound)| {
1588                 if let hir::GenericBound::Outlives(lifetime) = bound {
1589                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
1590                         Some(Region::Static) if infer_static => inferred_outlives
1591                             .iter()
1592                             .any(|r| if let ty::ReStatic = r { true } else { false }),
1593                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1594                             if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1595                         }),
1596                         _ => false,
1597                     };
1598                     is_inferred.then_some((i, bound.span()))
1599                 } else {
1600                     None
1601                 }
1602             })
1603             .collect()
1604     }
1605
1606     fn consolidate_outlives_bound_spans(
1607         &self,
1608         lo: Span,
1609         bounds: &hir::GenericBounds<'_>,
1610         bound_spans: Vec<(usize, Span)>,
1611     ) -> Vec<Span> {
1612         if bounds.is_empty() {
1613             return Vec::new();
1614         }
1615         if bound_spans.len() == bounds.len() {
1616             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1617             // If all bounds are inferable, we want to delete the colon, so
1618             // start from just after the parameter (span passed as argument)
1619             vec![lo.to(last_bound_span)]
1620         } else {
1621             let mut merged = Vec::new();
1622             let mut last_merged_i = None;
1623
1624             let mut from_start = true;
1625             for (i, bound_span) in bound_spans {
1626                 match last_merged_i {
1627                     // If the first bound is inferable, our span should also eat the leading `+`.
1628                     None if i == 0 => {
1629                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1630                         last_merged_i = Some(0);
1631                     }
1632                     // If consecutive bounds are inferable, merge their spans
1633                     Some(h) if i == h + 1 => {
1634                         if let Some(tail) = merged.last_mut() {
1635                             // Also eat the trailing `+` if the first
1636                             // more-than-one bound is inferable
1637                             let to_span = if from_start && i < bounds.len() {
1638                                 bounds[i + 1].span().shrink_to_lo()
1639                             } else {
1640                                 bound_span
1641                             };
1642                             *tail = tail.to(to_span);
1643                             last_merged_i = Some(i);
1644                         } else {
1645                             bug!("another bound-span visited earlier");
1646                         }
1647                     }
1648                     _ => {
1649                         // When we find a non-inferable bound, subsequent inferable bounds
1650                         // won't be consecutive from the start (and we'll eat the leading
1651                         // `+` rather than the trailing one)
1652                         from_start = false;
1653                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1654                         last_merged_i = Some(i);
1655                     }
1656                 }
1657             }
1658             merged
1659         }
1660     }
1661 }
1662
1663 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1664     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1665         use rustc::middle::resolve_lifetime::Region;
1666
1667         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1668         let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1669         if let hir::ItemKind::Struct(_, ref hir_generics)
1670         | hir::ItemKind::Enum(_, ref hir_generics)
1671         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1672         {
1673             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1674             if inferred_outlives.is_empty() {
1675                 return;
1676             }
1677
1678             let ty_generics = cx.tcx.generics_of(def_id);
1679
1680             let mut bound_count = 0;
1681             let mut lint_spans = Vec::new();
1682
1683             for param in hir_generics.params {
1684                 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1685                     if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1686                 });
1687                 if !has_lifetime_bounds {
1688                     continue;
1689                 }
1690
1691                 let relevant_lifetimes =
1692                     self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1693                 if relevant_lifetimes.is_empty() {
1694                     continue;
1695                 }
1696
1697                 let bound_spans = self.collect_outlives_bound_spans(
1698                     cx.tcx,
1699                     &param.bounds,
1700                     &relevant_lifetimes,
1701                     infer_static,
1702                 );
1703                 bound_count += bound_spans.len();
1704                 lint_spans.extend(self.consolidate_outlives_bound_spans(
1705                     param.span.shrink_to_hi(),
1706                     &param.bounds,
1707                     bound_spans,
1708                 ));
1709             }
1710
1711             let mut where_lint_spans = Vec::new();
1712             let mut dropped_predicate_count = 0;
1713             let num_predicates = hir_generics.where_clause.predicates.len();
1714             for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1715                 let (relevant_lifetimes, bounds, span) = match where_predicate {
1716                     hir::WherePredicate::RegionPredicate(predicate) => {
1717                         if let Some(Region::EarlyBound(index, ..)) =
1718                             cx.tcx.named_region(predicate.lifetime.hir_id)
1719                         {
1720                             (
1721                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1722                                 &predicate.bounds,
1723                                 predicate.span,
1724                             )
1725                         } else {
1726                             continue;
1727                         }
1728                     }
1729                     hir::WherePredicate::BoundPredicate(predicate) => {
1730                         // FIXME we can also infer bounds on associated types,
1731                         // and should check for them here.
1732                         match predicate.bounded_ty.kind {
1733                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1734                                 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1735                                     let index = ty_generics.param_def_id_to_index[&def_id];
1736                                     (
1737                                         Self::lifetimes_outliving_type(inferred_outlives, index),
1738                                         &predicate.bounds,
1739                                         predicate.span,
1740                                     )
1741                                 } else {
1742                                     continue;
1743                                 }
1744                             }
1745                             _ => {
1746                                 continue;
1747                             }
1748                         }
1749                     }
1750                     _ => continue,
1751                 };
1752                 if relevant_lifetimes.is_empty() {
1753                     continue;
1754                 }
1755
1756                 let bound_spans = self.collect_outlives_bound_spans(
1757                     cx.tcx,
1758                     bounds,
1759                     &relevant_lifetimes,
1760                     infer_static,
1761                 );
1762                 bound_count += bound_spans.len();
1763
1764                 let drop_predicate = bound_spans.len() == bounds.len();
1765                 if drop_predicate {
1766                     dropped_predicate_count += 1;
1767                 }
1768
1769                 // If all the bounds on a predicate were inferable and there are
1770                 // further predicates, we want to eat the trailing comma.
1771                 if drop_predicate && i + 1 < num_predicates {
1772                     let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1773                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1774                 } else {
1775                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1776                         span.shrink_to_lo(),
1777                         bounds,
1778                         bound_spans,
1779                     ));
1780                 }
1781             }
1782
1783             // If all predicates are inferable, drop the entire clause
1784             // (including the `where`)
1785             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1786                 let where_span = hir_generics
1787                     .where_clause
1788                     .span()
1789                     .expect("span of (nonempty) where clause should exist");
1790                 // Extend the where clause back to the closing `>` of the
1791                 // generics, except for tuple struct, which have the `where`
1792                 // after the fields of the struct.
1793                 let full_where_span =
1794                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1795                         where_span
1796                     } else {
1797                         hir_generics.span.shrink_to_hi().to(where_span)
1798                     };
1799                 lint_spans.push(full_where_span);
1800             } else {
1801                 lint_spans.extend(where_lint_spans);
1802             }
1803
1804             if !lint_spans.is_empty() {
1805                 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1806                     lint.build("outlives requirements can be inferred")
1807                         .multipart_suggestion(
1808                             if bound_count == 1 {
1809                                 "remove this bound"
1810                             } else {
1811                                 "remove these bounds"
1812                             },
1813                             lint_spans
1814                                 .into_iter()
1815                                 .map(|span| (span, "".to_owned()))
1816                                 .collect::<Vec<_>>(),
1817                             Applicability::MachineApplicable,
1818                         )
1819                         .emit();
1820                 });
1821             }
1822         }
1823     }
1824 }
1825
1826 declare_lint! {
1827     pub INCOMPLETE_FEATURES,
1828     Warn,
1829     "incomplete features that may function improperly in some or all cases"
1830 }
1831
1832 declare_lint_pass!(
1833     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1834     IncompleteFeatures => [INCOMPLETE_FEATURES]
1835 );
1836
1837 impl EarlyLintPass for IncompleteFeatures {
1838     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1839         let features = cx.sess.features_untracked();
1840         features
1841             .declared_lang_features
1842             .iter()
1843             .map(|(name, span, _)| (name, span))
1844             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1845             .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1846             .for_each(|(name, &span)| {
1847                 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1848                     lint.build(&format!(
1849                         "the feature `{}` is incomplete and may cause the compiler to crash",
1850                         name,
1851                     ))
1852                     .emit()
1853                 })
1854             });
1855     }
1856 }
1857
1858 declare_lint! {
1859     pub INVALID_VALUE,
1860     Warn,
1861     "an invalid value is being created (such as a NULL reference)"
1862 }
1863
1864 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1865
1866 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1867     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1868         #[derive(Debug, Copy, Clone, PartialEq)]
1869         enum InitKind {
1870             Zeroed,
1871             Uninit,
1872         };
1873
1874         /// Information about why a type cannot be initialized this way.
1875         /// Contains an error message and optionally a span to point at.
1876         type InitError = (String, Option<Span>);
1877
1878         /// Test if this constant is all-0.
1879         fn is_zero(expr: &hir::Expr<'_>) -> bool {
1880             use hir::ExprKind::*;
1881             use syntax::ast::LitKind::*;
1882             match &expr.kind {
1883                 Lit(lit) => {
1884                     if let Int(i, _) = lit.node {
1885                         i == 0
1886                     } else {
1887                         false
1888                     }
1889                 }
1890                 Tup(tup) => tup.iter().all(is_zero),
1891                 _ => false,
1892             }
1893         }
1894
1895         /// Determine if this expression is a "dangerous initialization".
1896         fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1897             // `transmute` is inside an anonymous module (the `extern` block?);
1898             // `Invalid` represents the empty string and matches that.
1899             // FIXME(#66075): use diagnostic items.  Somehow, that does not seem to work
1900             // on intrinsics right now.
1901             const TRANSMUTE_PATH: &[Symbol] =
1902                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1903
1904             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1905                 // Find calls to `mem::{uninitialized,zeroed}` methods.
1906                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1907                     let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1908
1909                     if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1910                         return Some(InitKind::Zeroed);
1911                     } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1912                         return Some(InitKind::Uninit);
1913                     } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1914                         if is_zero(&args[0]) {
1915                             return Some(InitKind::Zeroed);
1916                         }
1917                     }
1918                 }
1919             } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1920                 // Find problematic calls to `MaybeUninit::assume_init`.
1921                 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1922                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1923                     // This is a call to *some* method named `assume_init`.
1924                     // See if the `self` parameter is one of the dangerous constructors.
1925                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1926                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1927                             let def_id =
1928                                 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1929
1930                             if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1931                                 return Some(InitKind::Zeroed);
1932                             } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1933                                 return Some(InitKind::Uninit);
1934                             }
1935                         }
1936                     }
1937                 }
1938             }
1939
1940             None
1941         }
1942
1943         /// Return `Some` only if we are sure this type does *not*
1944         /// allow zero initialization.
1945         fn ty_find_init_error<'tcx>(
1946             tcx: TyCtxt<'tcx>,
1947             ty: Ty<'tcx>,
1948             init: InitKind,
1949         ) -> Option<InitError> {
1950             use rustc::ty::TyKind::*;
1951             match ty.kind {
1952                 // Primitive types that don't like 0 as a value.
1953                 Ref(..) => Some((format!("references must be non-null"), None)),
1954                 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
1955                 FnPtr(..) => Some((format!("function pointers must be non-null"), None)),
1956                 Never => Some((format!("the `!` type has no valid value"), None)),
1957                 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1958                 // raw ptr to dyn Trait
1959                 {
1960                     Some((format!("the vtable of a wide raw pointer must be non-null"), None))
1961                 }
1962                 // Primitive types with other constraints.
1963                 Bool if init == InitKind::Uninit => {
1964                     Some((format!("booleans must be either `true` or `false`"), None))
1965                 }
1966                 Char if init == InitKind::Uninit => {
1967                     Some((format!("characters must be a valid Unicode codepoint"), None))
1968                 }
1969                 // Recurse and checks for some compound types.
1970                 Adt(adt_def, substs) if !adt_def.is_union() => {
1971                     // First check f this ADT has a layout attribute (like `NonNull` and friends).
1972                     use std::ops::Bound;
1973                     match tcx.layout_scalar_valid_range(adt_def.did) {
1974                         // We exploit here that `layout_scalar_valid_range` will never
1975                         // return `Bound::Excluded`.  (And we have tests checking that we
1976                         // handle the attribute correctly.)
1977                         (Bound::Included(lo), _) if lo > 0 => {
1978                             return Some((format!("`{}` must be non-null", ty), None));
1979                         }
1980                         (Bound::Included(_), _) | (_, Bound::Included(_))
1981                             if init == InitKind::Uninit =>
1982                         {
1983                             return Some((
1984                                 format!(
1985                                     "`{}` must be initialized inside its custom valid range",
1986                                     ty,
1987                                 ),
1988                                 None,
1989                             ));
1990                         }
1991                         _ => {}
1992                     }
1993                     // Now, recurse.
1994                     match adt_def.variants.len() {
1995                         0 => Some((format!("enums with no variants have no valid value"), None)),
1996                         1 => {
1997                             // Struct, or enum with exactly one variant.
1998                             // Proceed recursively, check all fields.
1999                             let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2000                             variant.fields.iter().find_map(|field| {
2001                                 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2002                                     |(mut msg, span)| {
2003                                         if span.is_none() {
2004                                             // Point to this field, should be helpful for figuring
2005                                             // out where the source of the error is.
2006                                             let span = tcx.def_span(field.did);
2007                                             write!(
2008                                                 &mut msg,
2009                                                 " (in this {} field)",
2010                                                 adt_def.descr()
2011                                             )
2012                                             .unwrap();
2013                                             (msg, Some(span))
2014                                         } else {
2015                                             // Just forward.
2016                                             (msg, span)
2017                                         }
2018                                     },
2019                                 )
2020                             })
2021                         }
2022                         // Multi-variant enums are tricky: if all but one variant are
2023                         // uninhabited, we might actually do layout like for a single-variant
2024                         // enum, and then even leaving them uninitialized could be okay.
2025                         _ => None, // Conservative fallback for multi-variant enum.
2026                     }
2027                 }
2028                 Tuple(..) => {
2029                     // Proceed recursively, check all fields.
2030                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2031                 }
2032                 // Conservative fallback.
2033                 _ => None,
2034             }
2035         }
2036
2037         if let Some(init) = is_dangerous_init(cx, expr) {
2038             // This conjures an instance of a type out of nothing,
2039             // using zeroed or uninitialized memory.
2040             // We are extremely conservative with what we warn about.
2041             let conjured_ty = cx.tables.expr_ty(expr);
2042             if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2043                 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2044                     let mut err = lint.build(&format!(
2045                         "the type `{}` does not permit {}",
2046                         conjured_ty,
2047                         match init {
2048                             InitKind::Zeroed => "zero-initialization",
2049                             InitKind::Uninit => "being left uninitialized",
2050                         },
2051                     ));
2052                     err.span_label(expr.span, "this code causes undefined behavior when executed");
2053                     err.span_label(
2054                         expr.span,
2055                         "help: use `MaybeUninit<T>` instead, \
2056                             and only call `assume_init` after initialization is done",
2057                     );
2058                     if let Some(span) = span {
2059                         err.span_note(span, &msg);
2060                     } else {
2061                         err.note(&msg);
2062                     }
2063                     err.emit();
2064                 });
2065             }
2066         }
2067     }
2068 }