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