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