src/librustc_lint/builtin.rs

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