src/librustc_lint/builtin.rs

   1 //! Lints in the Rust compiler.
   2 //!
   3 //! This contains lints which can feasibly be implemented as their own
   4 //! AST visitor. Also see `rustc::lint::builtin`, which contains the
   5 //! definitions of lints that are emitted directly inside the main
   6 //! compiler.
   7 //!
   8 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
   9 //! Then add code to emit the new lint in the appropriate circumstances.
  10 //! You can do that in an existing `LintPass` if it makes sense, or in a
  11 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  12 //! compiler. Only do the latter if the check can't be written cleanly as a
  13 //! `LintPass` (also, note that such lints will need to be defined in
  14 //! `rustc::lint::builtin`, not here).
  15 //!
  16 //! If you define a new `EarlyLintPass`, you will also need to add it to the
  17 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
  18 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
  19 //! with a `pub fn new()`.
  20 //!
  21 //! If you define a new `LateLintPass`, you will also need to add it to the
  22 //! `late_lint_methods!` invocation in `lib.rs`.
  23
  24 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
  25 use rustc::hir::map::Map;
  26 use rustc::traits::misc::can_type_implement_copy;
  27 use rustc::ty::{self, layout::VariantIdx, Ty, TyCtxt};
  28 use rustc_data_structures::fx::FxHashSet;
  29 use rustc_errors::{Applicability, DiagnosticBuilder};
  30 use rustc_feature::Stability;
  31 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
  32 use rustc_hir as hir;
  33 use rustc_hir::def::{DefKind, Res};
  34 use rustc_hir::def_id::DefId;
  35 use rustc_hir::{GenericParamKind, PatKind};
  36 use rustc_hir::{HirIdSet, Node};
  37 use rustc_session::lint::FutureIncompatibleInfo;
  38 use rustc_span::edition::Edition;
  39 use rustc_span::source_map::Spanned;
  40 use rustc_span::symbol::{kw, sym, Symbol};
  41 use rustc_span::{BytePos, Span};
  42 use syntax::ast::{self, Expr};
  43 use syntax::attr::{self, HasAttrs};
  44 use syntax::print::pprust::{self, expr_to_string};
  45 use syntax::tokenstream::{TokenStream, TokenTree};
  46 use syntax::visit::FnKind;
  47
  48 use crate::nonstandard_style::{method_context, MethodLateContext};
  49
  50 use log::debug;
  51 use std::fmt::Write;
  52
  53 // hardwired lints from librustc
  54 pub use rustc_session::lint::builtin::*;
  55
  56 declare_lint! {
  57     WHILE_TRUE,
  58     Warn,
  59     "suggest using `loop { }` instead of `while true { }`"
  60 }
  61
  62 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  63
  64 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  65 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  66     while let ast::ExprKind::Paren(sub) = &expr.kind {
  67         expr = sub;
  68     }
  69     expr
  70 }
  71
  72 impl EarlyLintPass for WhileTrue {
  73     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
  74         if let ast::ExprKind::While(cond, ..) = &e.kind {
  75             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
  76                 if let ast::LitKind::Bool(true) = lit.kind {
  77                     if !lit.span.from_expansion() {
  78                         let msg = "denote infinite loops with `loop { ... }`";
  79                         let condition_span = cx.sess.source_map().def_span(e.span);
  80                         cx.struct_span_lint(WHILE_TRUE, condition_span, 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 declare_lint! {
  96     BOX_POINTERS,
  97     Allow,
  98     "use of owned (Box type) heap memory"
  99 }
 100
 101 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 102
 103 impl BoxPointers {
 104     fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
 105         for leaf_ty in ty.walk() {
 106             if leaf_ty.is_box() {
 107                 let m = format!("type uses owned (Box type) pointers: {}", ty);
 108                 cx.span_lint(BOX_POINTERS, span, &m);
 109             }
 110         }
 111     }
 112 }
 113
 114 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 115     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 116         match it.kind {
 117             hir::ItemKind::Fn(..)
 118             | hir::ItemKind::TyAlias(..)
 119             | hir::ItemKind::Enum(..)
 120             | hir::ItemKind::Struct(..)
 121             | hir::ItemKind::Union(..) => {
 122                 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 123                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 124             }
 125             _ => (),
 126         }
 127
 128         // If it's a struct, we also have to check the fields' types
 129         match it.kind {
 130             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 131                 for struct_field in struct_def.fields() {
 132                     let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
 133                     self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
 134                 }
 135             }
 136             _ => (),
 137         }
 138     }
 139
 140     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
 141         let ty = cx.tables.node_type(e.hir_id);
 142         self.check_heap_type(cx, e.span, ty);
 143     }
 144 }
 145
 146 declare_lint! {
 147     NON_SHORTHAND_FIELD_PATTERNS,
 148     Warn,
 149     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 150 }
 151
 152 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 153
 154 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 155     fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
 156         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
 157             let variant = cx
 158                 .tables
 159                 .pat_ty(pat)
 160                 .ty_adt_def()
 161                 .expect("struct pattern type is not an ADT")
 162                 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
 163             for fieldpat in field_pats {
 164                 if fieldpat.is_shorthand {
 165                     continue;
 166                 }
 167                 if fieldpat.span.from_expansion() {
 168                     // Don't lint if this is a macro expansion: macro authors
 169                     // shouldn't have to worry about this kind of style issue
 170                     // (Issue #49588)
 171                     continue;
 172                 }
 173                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
 174                     if cx.tcx.find_field_index(ident, &variant)
 175                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
 176                     {
 177                         let mut err = cx.struct_span_lint(
 178                             NON_SHORTHAND_FIELD_PATTERNS,
 179                             fieldpat.span,
 180                             &format!("the `{}:` in this pattern is redundant", ident),
 181                         );
 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 declare_lint! {
 208     UNSAFE_CODE,
 209     Allow,
 210     "usage of `unsafe` code"
 211 }
 212
 213 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 214
 215 impl UnsafeCode {
 216     fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
 217         // This comes from a macro that has `#[allow_internal_unsafe]`.
 218         if span.allows_unsafe() {
 219             return;
 220         }
 221
 222         cx.span_lint(UNSAFE_CODE, span, desc);
 223     }
 224 }
 225
 226 impl EarlyLintPass for UnsafeCode {
 227     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 228         if attr.check_name(sym::allow_internal_unsafe) {
 229             self.report_unsafe(
 230                 cx,
 231                 attr.span,
 232                 "`allow_internal_unsafe` allows defining \
 233                                                macros using unsafe without triggering \
 234                                                the `unsafe_code` lint at their call site",
 235             );
 236         }
 237     }
 238
 239     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 240         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 241             // Don't warn about generated blocks; that'll just pollute the output.
 242             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 243                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
 244             }
 245         }
 246     }
 247
 248     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 249         match it.kind {
 250             ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
 251                 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
 252             }
 253
 254             ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
 255                 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
 256             }
 257
 258             _ => return,
 259         }
 260     }
 261
 262     fn check_fn(
 263         &mut self,
 264         cx: &EarlyContext<'_>,
 265         fk: FnKind<'_>,
 266         _: &ast::FnDecl,
 267         span: Span,
 268         _: ast::NodeId,
 269     ) {
 270         match fk {
 271             FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
 272                 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
 273             }
 274
 275             FnKind::Method(_, sig, ..) => {
 276                 if sig.header.unsafety == ast::Unsafety::Unsafe {
 277                     self.report_unsafe(cx, span, "implementation of an `unsafe` method")
 278                 }
 279             }
 280
 281             _ => (),
 282         }
 283     }
 284
 285     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::AssocItem) {
 286         if let ast::AssocItemKind::Fn(ref sig, None) = item.kind {
 287             if sig.header.unsafety == ast::Unsafety::Unsafe {
 288                 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
 289             }
 290         }
 291     }
 292 }
 293
 294 declare_lint! {
 295     pub MISSING_DOCS,
 296     Allow,
 297     "detects missing documentation for public members",
 298     report_in_external_macro
 299 }
 300
 301 pub struct MissingDoc {
 302     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 303     doc_hidden_stack: Vec<bool>,
 304
 305     /// Private traits or trait items that leaked through. Don't check their methods.
 306     private_traits: FxHashSet<hir::HirId>,
 307 }
 308
 309 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 310
 311 fn has_doc(attr: &ast::Attribute) -> bool {
 312     if attr.is_doc_comment() {
 313         return true;
 314     }
 315
 316     if !attr.check_name(sym::doc) {
 317         return false;
 318     }
 319
 320     if attr.is_value_str() {
 321         return true;
 322     }
 323
 324     if let Some(list) = attr.meta_item_list() {
 325         for meta in list {
 326             if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
 327                 return true;
 328             }
 329         }
 330     }
 331
 332     false
 333 }
 334
 335 impl MissingDoc {
 336     pub fn new() -> MissingDoc {
 337         MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
 338     }
 339
 340     fn doc_hidden(&self) -> bool {
 341         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 342     }
 343
 344     fn check_missing_docs_attrs(
 345         &self,
 346         cx: &LateContext<'_, '_>,
 347         id: Option<hir::HirId>,
 348         attrs: &[ast::Attribute],
 349         sp: Span,
 350         desc: &'static str,
 351     ) {
 352         // If we're building a test harness, then warning about
 353         // documentation is probably not really relevant right now.
 354         if cx.sess().opts.test {
 355             return;
 356         }
 357
 358         // `#[doc(hidden)]` disables missing_docs check.
 359         if self.doc_hidden() {
 360             return;
 361         }
 362
 363         // Only check publicly-visible items, using the result from the privacy pass.
 364         // It's an option so the crate root can also use this function (it doesn't
 365         // have a `NodeId`).
 366         if let Some(id) = id {
 367             if !cx.access_levels.is_exported(id) {
 368                 return;
 369             }
 370         }
 371
 372         let has_doc = attrs.iter().any(|a| has_doc(a));
 373         if !has_doc {
 374             cx.span_lint(
 375                 MISSING_DOCS,
 376                 cx.tcx.sess.source_map().def_span(sp),
 377                 &format!("missing documentation for {}", desc),
 378             );
 379         }
 380     }
 381 }
 382
 383 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 384     fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
 385         let doc_hidden = self.doc_hidden()
 386             || attrs.iter().any(|attr| {
 387                 attr.check_name(sym::doc)
 388                     && match attr.meta_item_list() {
 389                         None => false,
 390                         Some(l) => attr::list_contains_name(&l, sym::hidden),
 391                     }
 392             });
 393         self.doc_hidden_stack.push(doc_hidden);
 394     }
 395
 396     fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
 397         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 398     }
 399
 400     fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
 401         self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
 402
 403         for macro_def in krate.exported_macros {
 404             let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
 405             if !has_doc {
 406                 cx.span_lint(
 407                     MISSING_DOCS,
 408                     cx.tcx.sess.source_map().def_span(macro_def.span),
 409                     "missing documentation for macro",
 410                 );
 411             }
 412         }
 413     }
 414
 415     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 416         let desc = match it.kind {
 417             hir::ItemKind::Fn(..) => "a function",
 418             hir::ItemKind::Mod(..) => "a module",
 419             hir::ItemKind::Enum(..) => "an enum",
 420             hir::ItemKind::Struct(..) => "a struct",
 421             hir::ItemKind::Union(..) => "a union",
 422             hir::ItemKind::Trait(.., trait_item_refs) => {
 423                 // Issue #11592: traits are always considered exported, even when private.
 424                 if let hir::VisibilityKind::Inherited = it.vis.node {
 425                     self.private_traits.insert(it.hir_id);
 426                     for trait_item_ref in trait_item_refs {
 427                         self.private_traits.insert(trait_item_ref.id.hir_id);
 428                     }
 429                     return;
 430                 }
 431                 "a trait"
 432             }
 433             hir::ItemKind::TyAlias(..) => "a type alias",
 434             hir::ItemKind::Impl(.., Some(ref trait_ref), _, impl_item_refs) => {
 435                 // If the trait is private, add the impl items to `private_traits` so they don't get
 436                 // reported for missing docs.
 437                 let real_trait = trait_ref.path.res.def_id();
 438                 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
 439                     match cx.tcx.hir().find(hir_id) {
 440                         Some(Node::Item(item)) => {
 441                             if let hir::VisibilityKind::Inherited = item.vis.node {
 442                                 for impl_item_ref in impl_item_refs {
 443                                     self.private_traits.insert(impl_item_ref.id.hir_id);
 444                                 }
 445                             }
 446                         }
 447                         _ => {}
 448                     }
 449                 }
 450                 return;
 451             }
 452             hir::ItemKind::Const(..) => "a constant",
 453             hir::ItemKind::Static(..) => "a static",
 454             _ => return,
 455         };
 456
 457         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
 458     }
 459
 460     fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
 461         if self.private_traits.contains(&trait_item.hir_id) {
 462             return;
 463         }
 464
 465         let desc = match trait_item.kind {
 466             hir::TraitItemKind::Const(..) => "an associated constant",
 467             hir::TraitItemKind::Method(..) => "a trait method",
 468             hir::TraitItemKind::Type(..) => "an associated type",
 469         };
 470
 471         self.check_missing_docs_attrs(
 472             cx,
 473             Some(trait_item.hir_id),
 474             &trait_item.attrs,
 475             trait_item.span,
 476             desc,
 477         );
 478     }
 479
 480     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
 481         // If the method is an impl for a trait, don't doc.
 482         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 483             return;
 484         }
 485
 486         let desc = match impl_item.kind {
 487             hir::ImplItemKind::Const(..) => "an associated constant",
 488             hir::ImplItemKind::Method(..) => "a method",
 489             hir::ImplItemKind::TyAlias(_) => "an associated type",
 490             hir::ImplItemKind::OpaqueTy(_) => "an associated `impl Trait` type",
 491         };
 492         self.check_missing_docs_attrs(
 493             cx,
 494             Some(impl_item.hir_id),
 495             &impl_item.attrs,
 496             impl_item.span,
 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(cx, Some(sf.hir_id), &sf.attrs, sf.span, "a struct field")
 504         }
 505     }
 506
 507     fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
 508         self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a variant");
 509     }
 510 }
 511
 512 declare_lint! {
 513     pub MISSING_COPY_IMPLEMENTATIONS,
 514     Allow,
 515     "detects potentially-forgotten implementations of `Copy`"
 516 }
 517
 518 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 519
 520 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 521     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
 522         if !cx.access_levels.is_reachable(item.hir_id) {
 523             return;
 524         }
 525         let (def, ty) = match item.kind {
 526             hir::ItemKind::Struct(_, ref ast_generics) => {
 527                 if !ast_generics.params.is_empty() {
 528                     return;
 529                 }
 530                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 531                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 532             }
 533             hir::ItemKind::Union(_, 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::Enum(_, 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             _ => return,
 548         };
 549         if def.has_dtor(cx.tcx) {
 550             return;
 551         }
 552         let param_env = ty::ParamEnv::empty();
 553         if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
 554             return;
 555         }
 556         if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
 557             cx.span_lint(
 558                 MISSING_COPY_IMPLEMENTATIONS,
 559                 item.span,
 560                 "type could implement `Copy`; consider adding `impl \
 561                           Copy`",
 562             )
 563         }
 564     }
 565 }
 566
 567 declare_lint! {
 568     MISSING_DEBUG_IMPLEMENTATIONS,
 569     Allow,
 570     "detects missing implementations of fmt::Debug"
 571 }
 572
 573 #[derive(Default)]
 574 pub struct MissingDebugImplementations {
 575     impling_types: Option<HirIdSet>,
 576 }
 577
 578 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 579
 580 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 581     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
 582         if !cx.access_levels.is_reachable(item.hir_id) {
 583             return;
 584         }
 585
 586         match item.kind {
 587             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
 588             _ => return,
 589         }
 590
 591         let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
 592             Some(debug) => debug,
 593             None => return,
 594         };
 595
 596         if self.impling_types.is_none() {
 597             let mut impls = HirIdSet::default();
 598             cx.tcx.for_each_impl(debug, |d| {
 599                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 600                     if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
 601                         impls.insert(hir_id);
 602                     }
 603                 }
 604             });
 605
 606             self.impling_types = Some(impls);
 607             debug!("{:?}", self.impling_types);
 608         }
 609
 610         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 611             cx.span_lint(
 612                 MISSING_DEBUG_IMPLEMENTATIONS,
 613                 item.span,
 614                 "type does not implement `fmt::Debug`; consider adding `#[derive(Debug)]` \
 615                           or a manual implementation",
 616             )
 617         }
 618     }
 619 }
 620
 621 declare_lint! {
 622     pub ANONYMOUS_PARAMETERS,
 623     Allow,
 624     "detects anonymous parameters",
 625     @future_incompatible = FutureIncompatibleInfo {
 626         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
 627         edition: Some(Edition::Edition2018),
 628     };
 629 }
 630
 631 declare_lint_pass!(
 632     /// Checks for use of anonymous parameters (RFC 1685).
 633     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 634 );
 635
 636 impl EarlyLintPass for AnonymousParameters {
 637     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
 638         match it.kind {
 639             ast::AssocItemKind::Fn(ref sig, _) => {
 640                 for arg in sig.decl.inputs.iter() {
 641                     match arg.pat.kind {
 642                         ast::PatKind::Ident(_, ident, None) => {
 643                             if ident.name == kw::Invalid {
 644                                 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
 645
 646                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 647                                     (snip, Applicability::MachineApplicable)
 648                                 } else {
 649                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 650                                 };
 651
 652                                 cx.struct_span_lint(
 653                                     ANONYMOUS_PARAMETERS,
 654                                     arg.pat.span,
 655                                     "anonymous parameters are deprecated and will be \
 656                                      removed in the next edition.",
 657                                 )
 658                                 .span_suggestion(
 659                                     arg.pat.span,
 660                                     "Try naming the parameter or explicitly \
 661                                     ignoring it",
 662                                     format!("_: {}", ty_snip),
 663                                     appl,
 664                                 )
 665                                 .emit();
 666                             }
 667                         }
 668                         _ => (),
 669                     }
 670                 }
 671             }
 672             _ => (),
 673         }
 674     }
 675 }
 676
 677 /// Check for use of attributes which have been deprecated.
 678 #[derive(Clone)]
 679 pub struct DeprecatedAttr {
 680     // This is not free to compute, so we want to keep it around, rather than
 681     // compute it for every attribute.
 682     depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
 683 }
 684
 685 impl_lint_pass!(DeprecatedAttr => []);
 686
 687 impl DeprecatedAttr {
 688     pub fn new() -> DeprecatedAttr {
 689         DeprecatedAttr { depr_attrs: deprecated_attributes() }
 690     }
 691 }
 692
 693 fn lint_deprecated_attr(
 694     cx: &EarlyContext<'_>,
 695     attr: &ast::Attribute,
 696     msg: &str,
 697     suggestion: Option<&str>,
 698 ) {
 699     cx.struct_span_lint(DEPRECATED, attr.span, &msg)
 700         .span_suggestion_short(
 701             attr.span,
 702             suggestion.unwrap_or("remove this attribute"),
 703             String::new(),
 704             Applicability::MachineApplicable,
 705         )
 706         .emit();
 707 }
 708
 709 impl EarlyLintPass for DeprecatedAttr {
 710     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 711         for &&(n, _, _, ref g) in &self.depr_attrs {
 712             if attr.ident().map(|ident| ident.name) == Some(n) {
 713                 if let &AttributeGate::Gated(
 714                     Stability::Deprecated(link, suggestion),
 715                     ref name,
 716                     ref reason,
 717                     _,
 718                 ) = g
 719                 {
 720                     let msg =
 721                         format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
 722                     lint_deprecated_attr(cx, attr, &msg, suggestion);
 723                 }
 724                 return;
 725             }
 726         }
 727         if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
 728             let path_str = pprust::path_to_string(&attr.get_normal_item().path);
 729             let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
 730             lint_deprecated_attr(cx, attr, &msg, None);
 731         }
 732     }
 733 }
 734
 735 declare_lint! {
 736     pub UNUSED_DOC_COMMENTS,
 737     Warn,
 738     "detects doc comments that aren't used by rustdoc"
 739 }
 740
 741 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
 742
 743 impl UnusedDocComment {
 744     fn warn_if_doc(
 745         &self,
 746         cx: &EarlyContext<'_>,
 747         node_span: Span,
 748         node_kind: &str,
 749         is_macro_expansion: bool,
 750         attrs: &[ast::Attribute],
 751     ) {
 752         let mut attrs = attrs.into_iter().peekable();
 753
 754         // Accumulate a single span for sugared doc comments.
 755         let mut sugared_span: Option<Span> = None;
 756
 757         while let Some(attr) = attrs.next() {
 758             if attr.is_doc_comment() {
 759                 sugared_span = Some(
 760                     sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())),
 761                 );
 762             }
 763
 764             if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
 765                 continue;
 766             }
 767
 768             let span = sugared_span.take().unwrap_or_else(|| attr.span);
 769
 770             if attr.is_doc_comment() || attr.check_name(sym::doc) {
 771                 let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
 772
 773                 err.span_label(
 774                     node_span,
 775                     format!("rustdoc does not generate documentation for {}", node_kind),
 776                 );
 777
 778                 if is_macro_expansion {
 779                     err.help(
 780                         "to document an item produced by a macro, \
 781                               the macro must produce the documentation as part of its expansion",
 782                     );
 783                 }
 784
 785                 err.emit();
 786             }
 787         }
 788     }
 789 }
 790
 791 impl EarlyLintPass for UnusedDocComment {
 792     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 793         if let ast::ItemKind::Mac(..) = item.kind {
 794             self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
 795         }
 796     }
 797
 798     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 799         let (kind, is_macro_expansion) = match stmt.kind {
 800             ast::StmtKind::Local(..) => ("statements", false),
 801             ast::StmtKind::Item(..) => ("inner items", false),
 802             ast::StmtKind::Mac(..) => ("macro expansions", true),
 803             // expressions will be reported by `check_expr`.
 804             ast::StmtKind::Semi(..) | ast::StmtKind::Expr(..) => return,
 805         };
 806
 807         self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.kind.attrs());
 808     }
 809
 810     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 811         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
 812         self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
 813     }
 814
 815     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 816         self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
 817     }
 818 }
 819
 820 declare_lint! {
 821     NO_MANGLE_CONST_ITEMS,
 822     Deny,
 823     "const items will not have their symbols exported"
 824 }
 825
 826 declare_lint! {
 827     NO_MANGLE_GENERIC_ITEMS,
 828     Warn,
 829     "generic items must be mangled"
 830 }
 831
 832 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
 833
 834 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
 835     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
 836         match it.kind {
 837             hir::ItemKind::Fn(.., ref generics, _) => {
 838                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
 839                     for param in generics.params {
 840                         match param.kind {
 841                             GenericParamKind::Lifetime { .. } => {}
 842                             GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
 843                                 let mut err = cx.struct_span_lint(
 844                                     NO_MANGLE_GENERIC_ITEMS,
 845                                     it.span,
 846                                     "functions generic over types or consts must be mangled",
 847                                 );
 848                                 err.span_suggestion_short(
 849                                     no_mangle_attr.span,
 850                                     "remove this attribute",
 851                                     String::new(),
 852                                     // Use of `#[no_mangle]` suggests FFI intent; correct
 853                                     // fix may be to monomorphize source by hand
 854                                     Applicability::MaybeIncorrect,
 855                                 );
 856                                 err.emit();
 857                                 break;
 858                             }
 859                         }
 860                     }
 861                 }
 862             }
 863             hir::ItemKind::Const(..) => {
 864                 if attr::contains_name(&it.attrs, sym::no_mangle) {
 865                     // Const items do not refer to a particular location in memory, and therefore
 866                     // don't have anything to attach a symbol to
 867                     let msg = "const items should never be `#[no_mangle]`";
 868                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
 869
 870                     // account for "pub const" (#45562)
 871                     let start = cx
 872                         .tcx
 873                         .sess
 874                         .source_map()
 875                         .span_to_snippet(it.span)
 876                         .map(|snippet| snippet.find("const").unwrap_or(0))
 877                         .unwrap_or(0) as u32;
 878                     // `const` is 5 chars
 879                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 880                     err.span_suggestion(
 881                         const_span,
 882                         "try a static value",
 883                         "pub static".to_owned(),
 884                         Applicability::MachineApplicable,
 885                     );
 886                     err.emit();
 887                 }
 888             }
 889             _ => {}
 890         }
 891     }
 892 }
 893
 894 declare_lint! {
 895     MUTABLE_TRANSMUTES,
 896     Deny,
 897     "mutating transmuted &mut T from &T may cause undefined behavior"
 898 }
 899
 900 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
 901
 902 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
 903     fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
 904         use rustc_target::spec::abi::Abi::RustIntrinsic;
 905
 906         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 907                    consider instead using an UnsafeCell";
 908         match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
 909             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
 910                 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
 911                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
 912                 }
 913             }
 914             _ => (),
 915         }
 916
 917         fn get_transmute_from_to<'a, 'tcx>(
 918             cx: &LateContext<'a, 'tcx>,
 919             expr: &hir::Expr<'_>,
 920         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
 921             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
 922                 cx.tables.qpath_res(qpath, expr.hir_id)
 923             } else {
 924                 return None;
 925             };
 926             if let Res::Def(DefKind::Fn, did) = def {
 927                 if !def_id_is_transmute(cx, did) {
 928                     return None;
 929                 }
 930                 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
 931                 let from = sig.inputs().skip_binder()[0];
 932                 let to = *sig.output().skip_binder();
 933                 return Some((from, to));
 934             }
 935             None
 936         }
 937
 938         fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
 939             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
 940                 && cx.tcx.item_name(def_id) == sym::transmute
 941         }
 942     }
 943 }
 944
 945 declare_lint! {
 946     UNSTABLE_FEATURES,
 947     Allow,
 948     "enabling unstable features (deprecated. do not use)"
 949 }
 950
 951 declare_lint_pass!(
 952     /// Forbids using the `#[feature(...)]` attribute
 953     UnstableFeatures => [UNSTABLE_FEATURES]
 954 );
 955
 956 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
 957     fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
 958         if attr.check_name(sym::feature) {
 959             if let Some(items) = attr.meta_item_list() {
 960                 for item in items {
 961                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
 962                 }
 963             }
 964         }
 965     }
 966 }
 967
 968 declare_lint! {
 969     pub UNREACHABLE_PUB,
 970     Allow,
 971     "`pub` items not reachable from crate root"
 972 }
 973
 974 declare_lint_pass!(
 975     /// Lint for items marked `pub` that aren't reachable from other crates.
 976     UnreachablePub => [UNREACHABLE_PUB]
 977 );
 978
 979 impl UnreachablePub {
 980     fn perform_lint(
 981         &self,
 982         cx: &LateContext<'_, '_>,
 983         what: &str,
 984         id: hir::HirId,
 985         vis: &hir::Visibility<'_>,
 986         span: Span,
 987         exportable: bool,
 988     ) {
 989         let mut applicability = Applicability::MachineApplicable;
 990         match vis.node {
 991             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
 992                 if span.from_expansion() {
 993                     applicability = Applicability::MaybeIncorrect;
 994                 }
 995                 let def_span = cx.tcx.sess.source_map().def_span(span);
 996                 let mut err = cx.struct_span_lint(
 997                     UNREACHABLE_PUB,
 998                     def_span,
 999                     &format!("unreachable `pub` {}", what),
1000                 );
1001                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1002                     "crate"
1003                 } else {
1004                     "pub(crate)"
1005                 }
1006                 .to_owned();
1007
1008                 err.span_suggestion(
1009                     vis.span,
1010                     "consider restricting its visibility",
1011                     replacement,
1012                     applicability,
1013                 );
1014                 if exportable {
1015                     err.help("or consider exporting it for use by other crates");
1016                 }
1017                 err.emit();
1018             }
1019             _ => {}
1020         }
1021     }
1022 }
1023
1024 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1025     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1026         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1027     }
1028
1029     fn check_foreign_item(
1030         &mut self,
1031         cx: &LateContext<'_, '_>,
1032         foreign_item: &hir::ForeignItem<'tcx>,
1033     ) {
1034         self.perform_lint(
1035             cx,
1036             "item",
1037             foreign_item.hir_id,
1038             &foreign_item.vis,
1039             foreign_item.span,
1040             true,
1041         );
1042     }
1043
1044     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1045         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1046     }
1047
1048     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1049         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1050     }
1051 }
1052
1053 declare_lint! {
1054     TYPE_ALIAS_BOUNDS,
1055     Warn,
1056     "bounds in type aliases are not enforced"
1057 }
1058
1059 declare_lint_pass!(
1060     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1061     /// They are relevant when using associated types, but otherwise neither checked
1062     /// at definition site nor enforced at use site.
1063     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1064 );
1065
1066 impl TypeAliasBounds {
1067     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1068         match *qpath {
1069             hir::QPath::TypeRelative(ref ty, _) => {
1070                 // If this is a type variable, we found a `T::Assoc`.
1071                 match ty.kind {
1072                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1073                         Res::Def(DefKind::TyParam, _) => true,
1074                         _ => false,
1075                     },
1076                     _ => false,
1077                 }
1078             }
1079             hir::QPath::Resolved(..) => false,
1080         }
1081     }
1082
1083     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1084         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1085         // bound.  Let's see if this type does that.
1086
1087         // We use a HIR visitor to walk the type.
1088         use rustc_hir::intravisit::{self, Visitor};
1089         struct WalkAssocTypes<'a, 'db> {
1090             err: &'a mut DiagnosticBuilder<'db>,
1091         }
1092         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1093             type Map = Map<'v>;
1094
1095             fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1096                 intravisit::NestedVisitorMap::None
1097             }
1098
1099             fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1100                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1101                     self.err.span_help(
1102                         span,
1103                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1104                          associated types in type aliases",
1105                     );
1106                 }
1107                 intravisit::walk_qpath(self, qpath, id, span)
1108             }
1109         }
1110
1111         // Let's go for a walk!
1112         let mut visitor = WalkAssocTypes { err };
1113         visitor.visit_ty(ty);
1114     }
1115 }
1116
1117 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1118     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1119         let (ty, type_alias_generics) = match item.kind {
1120             hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1121             _ => return,
1122         };
1123         let mut suggested_changing_assoc_types = false;
1124         // There must not be a where clause
1125         if !type_alias_generics.where_clause.predicates.is_empty() {
1126             let spans: Vec<_> = type_alias_generics
1127                 .where_clause
1128                 .predicates
1129                 .iter()
1130                 .map(|pred| pred.span())
1131                 .collect();
1132             let mut err = cx.struct_span_lint(
1133                 TYPE_ALIAS_BOUNDS,
1134                 spans,
1135                 "where clauses are not enforced in type aliases",
1136             );
1137             err.span_suggestion(
1138                 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1139                 "the clause will not be checked when the type alias is used, and should be removed",
1140                 String::new(),
1141                 Applicability::MachineApplicable,
1142             );
1143             if !suggested_changing_assoc_types {
1144                 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1145                 suggested_changing_assoc_types = true;
1146             }
1147             err.emit();
1148         }
1149         // The parameters must not have bounds
1150         for param in type_alias_generics.params.iter() {
1151             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1152             let suggestion = spans
1153                 .iter()
1154                 .map(|sp| {
1155                     let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1156                     (start.to(*sp), String::new())
1157                 })
1158                 .collect();
1159             if !spans.is_empty() {
1160                 let mut err = cx.struct_span_lint(
1161                     TYPE_ALIAS_BOUNDS,
1162                     spans,
1163                     "bounds on generic parameters are not enforced in type aliases",
1164                 );
1165                 let msg = "the bound will not be checked when the type alias is used, \
1166                            and should be removed";
1167                 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1168                 if !suggested_changing_assoc_types {
1169                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1170                     suggested_changing_assoc_types = true;
1171                 }
1172                 err.emit();
1173             }
1174         }
1175     }
1176 }
1177
1178 declare_lint_pass!(
1179     /// Lint constants that are erroneous.
1180     /// Without this lint, we might not get any diagnostic if the constant is
1181     /// unused within this crate, even though downstream crates can't use it
1182     /// without producing an error.
1183     UnusedBrokenConst => []
1184 );
1185
1186 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1187     let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1188     // trigger the query once for all constants since that will already report the errors
1189     // FIXME: Use ensure here
1190     let _ = cx.tcx.const_eval_poly(def_id);
1191 }
1192
1193 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1194     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1195         match it.kind {
1196             hir::ItemKind::Const(_, body_id) => {
1197                 check_const(cx, body_id);
1198             }
1199             hir::ItemKind::Static(_, _, body_id) => {
1200                 check_const(cx, body_id);
1201             }
1202             _ => {}
1203         }
1204     }
1205 }
1206
1207 declare_lint! {
1208     TRIVIAL_BOUNDS,
1209     Warn,
1210     "these bounds don't depend on an type parameters"
1211 }
1212
1213 declare_lint_pass!(
1214     /// Lint for trait and lifetime bounds that don't depend on type parameters
1215     /// which either do nothing, or stop the item from being used.
1216     TrivialConstraints => [TRIVIAL_BOUNDS]
1217 );
1218
1219 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1220     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1221         use rustc::ty::fold::TypeFoldable;
1222         use rustc::ty::Predicate::*;
1223
1224         if cx.tcx.features().trivial_bounds {
1225             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1226             let predicates = cx.tcx.predicates_of(def_id);
1227             for &(predicate, span) in predicates.predicates {
1228                 let predicate_kind_name = match predicate {
1229                     Trait(..) => "Trait",
1230                     TypeOutlives(..) |
1231                     RegionOutlives(..) => "Lifetime",
1232
1233                     // Ignore projections, as they can only be global
1234                     // if the trait bound is global
1235                     Projection(..) |
1236                     // Ignore bounds that a user can't type
1237                     WellFormed(..) |
1238                     ObjectSafe(..) |
1239                     ClosureKind(..) |
1240                     Subtype(..) |
1241                     ConstEvaluatable(..) => continue,
1242                 };
1243                 if predicate.is_global() {
1244                     cx.span_lint(
1245                         TRIVIAL_BOUNDS,
1246                         span,
1247                         &format!(
1248                             "{} bound {} does not depend on any type \
1249                                 or lifetime parameters",
1250                             predicate_kind_name, predicate
1251                         ),
1252                     );
1253                 }
1254             }
1255         }
1256     }
1257 }
1258
1259 declare_lint_pass!(
1260     /// Does nothing as a lint pass, but registers some `Lint`s
1261     /// which are used by other parts of the compiler.
1262     SoftLints => [
1263         WHILE_TRUE,
1264         BOX_POINTERS,
1265         NON_SHORTHAND_FIELD_PATTERNS,
1266         UNSAFE_CODE,
1267         MISSING_DOCS,
1268         MISSING_COPY_IMPLEMENTATIONS,
1269         MISSING_DEBUG_IMPLEMENTATIONS,
1270         ANONYMOUS_PARAMETERS,
1271         UNUSED_DOC_COMMENTS,
1272         NO_MANGLE_CONST_ITEMS,
1273         NO_MANGLE_GENERIC_ITEMS,
1274         MUTABLE_TRANSMUTES,
1275         UNSTABLE_FEATURES,
1276         UNREACHABLE_PUB,
1277         TYPE_ALIAS_BOUNDS,
1278         TRIVIAL_BOUNDS
1279     ]
1280 );
1281
1282 declare_lint! {
1283     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1284     Warn,
1285     "`...` range patterns are deprecated"
1286 }
1287
1288 #[derive(Default)]
1289 pub struct EllipsisInclusiveRangePatterns {
1290     /// If `Some(_)`, suppress all subsequent pattern
1291     /// warnings for better diagnostics.
1292     node_id: Option<ast::NodeId>,
1293 }
1294
1295 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1296
1297 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1298     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1299         if self.node_id.is_some() {
1300             // Don't recursively warn about patterns inside range endpoints.
1301             return;
1302         }
1303
1304         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1305
1306         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1307         /// corresponding to the ellipsis.
1308         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1309             match &pat.kind {
1310                 PatKind::Range(
1311                     a,
1312                     Some(b),
1313                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1314                 ) => Some((a.as_deref(), b, *span)),
1315                 _ => None,
1316             }
1317         }
1318
1319         let (parenthesise, endpoints) = match &pat.kind {
1320             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1321             _ => (false, matches_ellipsis_pat(pat)),
1322         };
1323
1324         if let Some((start, end, join)) = endpoints {
1325             let msg = "`...` range patterns are deprecated";
1326             let suggestion = "use `..=` for an inclusive range";
1327             if parenthesise {
1328                 self.node_id = Some(pat.id);
1329                 let end = expr_to_string(&end);
1330                 let replace = match start {
1331                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1332                     None => format!("&(..={})", end),
1333                 };
1334                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1335                 err.span_suggestion(
1336                     pat.span,
1337                     suggestion,
1338                     replace,
1339                     Applicability::MachineApplicable,
1340                 );
1341                 err.emit();
1342             } else {
1343                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1344                 err.span_suggestion_short(
1345                     join,
1346                     suggestion,
1347                     "..=".to_owned(),
1348                     Applicability::MachineApplicable,
1349                 );
1350                 err.emit();
1351             };
1352         }
1353     }
1354
1355     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1356         if let Some(node_id) = self.node_id {
1357             if pat.id == node_id {
1358                 self.node_id = None
1359             }
1360         }
1361     }
1362 }
1363
1364 declare_lint! {
1365     UNNAMEABLE_TEST_ITEMS,
1366     Warn,
1367     "detects an item that cannot be named being marked as `#[test_case]`",
1368     report_in_external_macro
1369 }
1370
1371 pub struct UnnameableTestItems {
1372     boundary: hir::HirId, // HirId of the item under which things are not nameable
1373     items_nameable: bool,
1374 }
1375
1376 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1377
1378 impl UnnameableTestItems {
1379     pub fn new() -> Self {
1380         Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1381     }
1382 }
1383
1384 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1385     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1386         if self.items_nameable {
1387             if let hir::ItemKind::Mod(..) = it.kind {
1388             } else {
1389                 self.items_nameable = false;
1390                 self.boundary = it.hir_id;
1391             }
1392             return;
1393         }
1394
1395         if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1396             cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, "cannot test inner items").emit();
1397         }
1398     }
1399
1400     fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1401         if !self.items_nameable && self.boundary == it.hir_id {
1402             self.items_nameable = true;
1403         }
1404     }
1405 }
1406
1407 declare_lint! {
1408     pub KEYWORD_IDENTS,
1409     Allow,
1410     "detects edition keywords being used as an identifier",
1411     @future_incompatible = FutureIncompatibleInfo {
1412         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1413         edition: Some(Edition::Edition2018),
1414     };
1415 }
1416
1417 declare_lint_pass!(
1418     /// Check for uses of edition keywords used as an identifier.
1419     KeywordIdents => [KEYWORD_IDENTS]
1420 );
1421
1422 struct UnderMacro(bool);
1423
1424 impl KeywordIdents {
1425     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1426         for tt in tokens.into_trees() {
1427             match tt {
1428                 // Only report non-raw idents.
1429                 TokenTree::Token(token) => {
1430                     if let Some((ident, false)) = token.ident() {
1431                         self.check_ident_token(cx, UnderMacro(true), ident);
1432                     }
1433                 }
1434                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1435             }
1436         }
1437     }
1438
1439     fn check_ident_token(
1440         &mut self,
1441         cx: &EarlyContext<'_>,
1442         UnderMacro(under_macro): UnderMacro,
1443         ident: ast::Ident,
1444     ) {
1445         let next_edition = match cx.sess.edition() {
1446             Edition::Edition2015 => {
1447                 match ident.name {
1448                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1449
1450                     // rust-lang/rust#56327: Conservatively do not
1451                     // attempt to report occurrences of `dyn` within
1452                     // macro definitions or invocations, because `dyn`
1453                     // can legitimately occur as a contextual keyword
1454                     // in 2015 code denoting its 2018 meaning, and we
1455                     // do not want rustfix to inject bugs into working
1456                     // code by rewriting such occurrences.
1457                     //
1458                     // But if we see `dyn` outside of a macro, we know
1459                     // its precise role in the parsed AST and thus are
1460                     // assured this is truly an attempt to use it as
1461                     // an identifier.
1462                     kw::Dyn if !under_macro => Edition::Edition2018,
1463
1464                     _ => return,
1465                 }
1466             }
1467
1468             // There are no new keywords yet for the 2018 edition and beyond.
1469             _ => return,
1470         };
1471
1472         // Don't lint `r#foo`.
1473         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1474             return;
1475         }
1476
1477         let mut lint = cx.struct_span_lint(
1478             KEYWORD_IDENTS,
1479             ident.span,
1480             &format!("`{}` is a keyword in the {} edition", ident, next_edition),
1481         );
1482         lint.span_suggestion(
1483             ident.span,
1484             "you can use a raw identifier to stay compatible",
1485             format!("r#{}", ident),
1486             Applicability::MachineApplicable,
1487         );
1488         lint.emit()
1489     }
1490 }
1491
1492 impl EarlyLintPass for KeywordIdents {
1493     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1494         self.check_tokens(cx, mac_def.body.inner_tokens());
1495     }
1496     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1497         self.check_tokens(cx, mac.args.inner_tokens());
1498     }
1499     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1500         self.check_ident_token(cx, UnderMacro(false), ident);
1501     }
1502 }
1503
1504 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1505
1506 impl ExplicitOutlivesRequirements {
1507     fn lifetimes_outliving_lifetime<'tcx>(
1508         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1509         index: u32,
1510     ) -> Vec<ty::Region<'tcx>> {
1511         inferred_outlives
1512             .iter()
1513             .filter_map(|(pred, _)| match pred {
1514                 ty::Predicate::RegionOutlives(outlives) => {
1515                     let outlives = outlives.skip_binder();
1516                     match outlives.0 {
1517                         ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1518                         _ => None,
1519                     }
1520                 }
1521                 _ => None,
1522             })
1523             .collect()
1524     }
1525
1526     fn lifetimes_outliving_type<'tcx>(
1527         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1528         index: u32,
1529     ) -> Vec<ty::Region<'tcx>> {
1530         inferred_outlives
1531             .iter()
1532             .filter_map(|(pred, _)| match pred {
1533                 ty::Predicate::TypeOutlives(outlives) => {
1534                     let outlives = outlives.skip_binder();
1535                     outlives.0.is_param(index).then_some(outlives.1)
1536                 }
1537                 _ => None,
1538             })
1539             .collect()
1540     }
1541
1542     fn collect_outlived_lifetimes<'tcx>(
1543         &self,
1544         param: &'tcx hir::GenericParam<'tcx>,
1545         tcx: TyCtxt<'tcx>,
1546         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1547         ty_generics: &'tcx ty::Generics,
1548     ) -> Vec<ty::Region<'tcx>> {
1549         let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1550
1551         match param.kind {
1552             hir::GenericParamKind::Lifetime { .. } => {
1553                 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1554             }
1555             hir::GenericParamKind::Type { .. } => {
1556                 Self::lifetimes_outliving_type(inferred_outlives, index)
1557             }
1558             hir::GenericParamKind::Const { .. } => Vec::new(),
1559         }
1560     }
1561
1562     fn collect_outlives_bound_spans<'tcx>(
1563         &self,
1564         tcx: TyCtxt<'tcx>,
1565         bounds: &hir::GenericBounds<'_>,
1566         inferred_outlives: &[ty::Region<'tcx>],
1567         infer_static: bool,
1568     ) -> Vec<(usize, Span)> {
1569         use rustc::middle::resolve_lifetime::Region;
1570
1571         bounds
1572             .iter()
1573             .enumerate()
1574             .filter_map(|(i, bound)| {
1575                 if let hir::GenericBound::Outlives(lifetime) = bound {
1576                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
1577                         Some(Region::Static) if infer_static => inferred_outlives
1578                             .iter()
1579                             .any(|r| if let ty::ReStatic = r { true } else { false }),
1580                         Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1581                             if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1582                         }),
1583                         _ => false,
1584                     };
1585                     is_inferred.then_some((i, bound.span()))
1586                 } else {
1587                     None
1588                 }
1589             })
1590             .collect()
1591     }
1592
1593     fn consolidate_outlives_bound_spans(
1594         &self,
1595         lo: Span,
1596         bounds: &hir::GenericBounds<'_>,
1597         bound_spans: Vec<(usize, Span)>,
1598     ) -> Vec<Span> {
1599         if bounds.is_empty() {
1600             return Vec::new();
1601         }
1602         if bound_spans.len() == bounds.len() {
1603             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1604             // If all bounds are inferable, we want to delete the colon, so
1605             // start from just after the parameter (span passed as argument)
1606             vec![lo.to(last_bound_span)]
1607         } else {
1608             let mut merged = Vec::new();
1609             let mut last_merged_i = None;
1610
1611             let mut from_start = true;
1612             for (i, bound_span) in bound_spans {
1613                 match last_merged_i {
1614                     // If the first bound is inferable, our span should also eat the leading `+`.
1615                     None if i == 0 => {
1616                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1617                         last_merged_i = Some(0);
1618                     }
1619                     // If consecutive bounds are inferable, merge their spans
1620                     Some(h) if i == h + 1 => {
1621                         if let Some(tail) = merged.last_mut() {
1622                             // Also eat the trailing `+` if the first
1623                             // more-than-one bound is inferable
1624                             let to_span = if from_start && i < bounds.len() {
1625                                 bounds[i + 1].span().shrink_to_lo()
1626                             } else {
1627                                 bound_span
1628                             };
1629                             *tail = tail.to(to_span);
1630                             last_merged_i = Some(i);
1631                         } else {
1632                             bug!("another bound-span visited earlier");
1633                         }
1634                     }
1635                     _ => {
1636                         // When we find a non-inferable bound, subsequent inferable bounds
1637                         // won't be consecutive from the start (and we'll eat the leading
1638                         // `+` rather than the trailing one)
1639                         from_start = false;
1640                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1641                         last_merged_i = Some(i);
1642                     }
1643                 }
1644             }
1645             merged
1646         }
1647     }
1648 }
1649
1650 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1651     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1652         use rustc::middle::resolve_lifetime::Region;
1653
1654         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1655         let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1656         if let hir::ItemKind::Struct(_, ref hir_generics)
1657         | hir::ItemKind::Enum(_, ref hir_generics)
1658         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1659         {
1660             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1661             if inferred_outlives.is_empty() {
1662                 return;
1663             }
1664
1665             let ty_generics = cx.tcx.generics_of(def_id);
1666
1667             let mut bound_count = 0;
1668             let mut lint_spans = Vec::new();
1669
1670             for param in hir_generics.params {
1671                 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1672                     if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1673                 });
1674                 if !has_lifetime_bounds {
1675                     continue;
1676                 }
1677
1678                 let relevant_lifetimes =
1679                     self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1680                 if relevant_lifetimes.is_empty() {
1681                     continue;
1682                 }
1683
1684                 let bound_spans = self.collect_outlives_bound_spans(
1685                     cx.tcx,
1686                     &param.bounds,
1687                     &relevant_lifetimes,
1688                     infer_static,
1689                 );
1690                 bound_count += bound_spans.len();
1691                 lint_spans.extend(self.consolidate_outlives_bound_spans(
1692                     param.span.shrink_to_hi(),
1693                     &param.bounds,
1694                     bound_spans,
1695                 ));
1696             }
1697
1698             let mut where_lint_spans = Vec::new();
1699             let mut dropped_predicate_count = 0;
1700             let num_predicates = hir_generics.where_clause.predicates.len();
1701             for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1702                 let (relevant_lifetimes, bounds, span) = match where_predicate {
1703                     hir::WherePredicate::RegionPredicate(predicate) => {
1704                         if let Some(Region::EarlyBound(index, ..)) =
1705                             cx.tcx.named_region(predicate.lifetime.hir_id)
1706                         {
1707                             (
1708                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1709                                 &predicate.bounds,
1710                                 predicate.span,
1711                             )
1712                         } else {
1713                             continue;
1714                         }
1715                     }
1716                     hir::WherePredicate::BoundPredicate(predicate) => {
1717                         // FIXME we can also infer bounds on associated types,
1718                         // and should check for them here.
1719                         match predicate.bounded_ty.kind {
1720                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1721                                 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1722                                     let index = ty_generics.param_def_id_to_index[&def_id];
1723                                     (
1724                                         Self::lifetimes_outliving_type(inferred_outlives, index),
1725                                         &predicate.bounds,
1726                                         predicate.span,
1727                                     )
1728                                 } else {
1729                                     continue;
1730                                 }
1731                             }
1732                             _ => {
1733                                 continue;
1734                             }
1735                         }
1736                     }
1737                     _ => continue,
1738                 };
1739                 if relevant_lifetimes.is_empty() {
1740                     continue;
1741                 }
1742
1743                 let bound_spans = self.collect_outlives_bound_spans(
1744                     cx.tcx,
1745                     bounds,
1746                     &relevant_lifetimes,
1747                     infer_static,
1748                 );
1749                 bound_count += bound_spans.len();
1750
1751                 let drop_predicate = bound_spans.len() == bounds.len();
1752                 if drop_predicate {
1753                     dropped_predicate_count += 1;
1754                 }
1755
1756                 // If all the bounds on a predicate were inferable and there are
1757                 // further predicates, we want to eat the trailing comma.
1758                 if drop_predicate && i + 1 < num_predicates {
1759                     let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1760                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1761                 } else {
1762                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1763                         span.shrink_to_lo(),
1764                         bounds,
1765                         bound_spans,
1766                     ));
1767                 }
1768             }
1769
1770             // If all predicates are inferable, drop the entire clause
1771             // (including the `where`)
1772             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1773                 let where_span = hir_generics
1774                     .where_clause
1775                     .span()
1776                     .expect("span of (nonempty) where clause should exist");
1777                 // Extend the where clause back to the closing `>` of the
1778                 // generics, except for tuple struct, which have the `where`
1779                 // after the fields of the struct.
1780                 let full_where_span =
1781                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1782                         where_span
1783                     } else {
1784                         hir_generics.span.shrink_to_hi().to(where_span)
1785                     };
1786                 lint_spans.push(full_where_span);
1787             } else {
1788                 lint_spans.extend(where_lint_spans);
1789             }
1790
1791             if !lint_spans.is_empty() {
1792                 let mut err = cx.struct_span_lint(
1793                     EXPLICIT_OUTLIVES_REQUIREMENTS,
1794                     lint_spans.clone(),
1795                     "outlives requirements can be inferred",
1796                 );
1797                 err.multipart_suggestion(
1798                     if bound_count == 1 { "remove this bound" } else { "remove these bounds" },
1799                     lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1800                     Applicability::MachineApplicable,
1801                 );
1802                 err.emit();
1803             }
1804         }
1805     }
1806 }
1807
1808 declare_lint! {
1809     pub INCOMPLETE_FEATURES,
1810     Warn,
1811     "incomplete features that may function improperly in some or all cases"
1812 }
1813
1814 declare_lint_pass!(
1815     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `feature_gate.rs`.
1816     IncompleteFeatures => [INCOMPLETE_FEATURES]
1817 );
1818
1819 impl EarlyLintPass for IncompleteFeatures {
1820     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1821         let features = cx.sess.features_untracked();
1822         features
1823             .declared_lang_features
1824             .iter()
1825             .map(|(name, span, _)| (name, span))
1826             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1827             .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1828             .for_each(|(name, &span)| {
1829                 cx.struct_span_lint(
1830                     INCOMPLETE_FEATURES,
1831                     span,
1832                     &format!(
1833                         "the feature `{}` is incomplete and may cause the compiler to crash",
1834                         name,
1835                     ),
1836                 )
1837                 .emit();
1838             });
1839     }
1840 }
1841
1842 declare_lint! {
1843     pub INVALID_VALUE,
1844     Warn,
1845     "an invalid value is being created (such as a NULL reference)"
1846 }
1847
1848 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1849
1850 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1851     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1852         #[derive(Debug, Copy, Clone, PartialEq)]
1853         enum InitKind {
1854             Zeroed,
1855             Uninit,
1856         };
1857
1858         /// Information about why a type cannot be initialized this way.
1859         /// Contains an error message and optionally a span to point at.
1860         type InitError = (String, Option<Span>);
1861
1862         /// Test if this constant is all-0.
1863         fn is_zero(expr: &hir::Expr<'_>) -> bool {
1864             use hir::ExprKind::*;
1865             use syntax::ast::LitKind::*;
1866             match &expr.kind {
1867                 Lit(lit) => {
1868                     if let Int(i, _) = lit.node {
1869                         i == 0
1870                     } else {
1871                         false
1872                     }
1873                 }
1874                 Tup(tup) => tup.iter().all(is_zero),
1875                 _ => false,
1876             }
1877         }
1878
1879         /// Determine if this expression is a "dangerous initialization".
1880         fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1881             // `transmute` is inside an anonymous module (the `extern` block?);
1882             // `Invalid` represents the empty string and matches that.
1883             // FIXME(#66075): use diagnostic items.  Somehow, that does not seem to work
1884             // on intrinsics right now.
1885             const TRANSMUTE_PATH: &[Symbol] =
1886                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1887
1888             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1889                 // Find calls to `mem::{uninitialized,zeroed}` methods.
1890                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1891                     let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1892
1893                     if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1894                         return Some(InitKind::Zeroed);
1895                     } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1896                         return Some(InitKind::Uninit);
1897                     } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1898                         if is_zero(&args[0]) {
1899                             return Some(InitKind::Zeroed);
1900                         }
1901                     }
1902                 }
1903             } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1904                 // Find problematic calls to `MaybeUninit::assume_init`.
1905                 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1906                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1907                     // This is a call to *some* method named `assume_init`.
1908                     // See if the `self` parameter is one of the dangerous constructors.
1909                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1910                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1911                             let def_id =
1912                                 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1913
1914                             if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1915                                 return Some(InitKind::Zeroed);
1916                             } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1917                                 return Some(InitKind::Uninit);
1918                             }
1919                         }
1920                     }
1921                 }
1922             }
1923
1924             None
1925         }
1926
1927         /// Return `Some` only if we are sure this type does *not*
1928         /// allow zero initialization.
1929         fn ty_find_init_error<'tcx>(
1930             tcx: TyCtxt<'tcx>,
1931             ty: Ty<'tcx>,
1932             init: InitKind,
1933         ) -> Option<InitError> {
1934             use rustc::ty::TyKind::*;
1935             match ty.kind {
1936                 // Primitive types that don't like 0 as a value.
1937                 Ref(..) => Some((format!("References must be non-null"), None)),
1938                 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
1939                 FnPtr(..) => Some((format!("Function pointers must be non-null"), None)),
1940                 Never => Some((format!("The never type (`!`) has no valid value"), None)),
1941                 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1942                 // raw ptr to dyn Trait
1943                 {
1944                     Some((format!("The vtable of a wide raw pointer must be non-null"), None))
1945                 }
1946                 // Primitive types with other constraints.
1947                 Bool if init == InitKind::Uninit => {
1948                     Some((format!("Booleans must be `true` or `false`"), None))
1949                 }
1950                 Char if init == InitKind::Uninit => {
1951                     Some((format!("Characters must be a valid unicode codepoint"), None))
1952                 }
1953                 // Recurse and checks for some compound types.
1954                 Adt(adt_def, substs) if !adt_def.is_union() => {
1955                     // First check f this ADT has a layout attribute (like `NonNull` and friends).
1956                     use std::ops::Bound;
1957                     match tcx.layout_scalar_valid_range(adt_def.did) {
1958                         // We exploit here that `layout_scalar_valid_range` will never
1959                         // return `Bound::Excluded`.  (And we have tests checking that we
1960                         // handle the attribute correctly.)
1961                         (Bound::Included(lo), _) if lo > 0 => {
1962                             return Some((format!("{} must be non-null", ty), None));
1963                         }
1964                         (Bound::Included(_), _) | (_, Bound::Included(_))
1965                             if init == InitKind::Uninit =>
1966                         {
1967                             return Some((
1968                                 format!("{} must be initialized inside its custom valid range", ty),
1969                                 None,
1970                             ));
1971                         }
1972                         _ => {}
1973                     }
1974                     // Now, recurse.
1975                     match adt_def.variants.len() {
1976                         0 => Some((format!("0-variant enums have no valid value"), None)),
1977                         1 => {
1978                             // Struct, or enum with exactly one variant.
1979                             // Proceed recursively, check all fields.
1980                             let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1981                             variant.fields.iter().find_map(|field| {
1982                                 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1983                                     |(mut msg, span)| {
1984                                         if span.is_none() {
1985                                             // Point to this field, should be helpful for figuring
1986                                             // out where the source of the error is.
1987                                             let span = tcx.def_span(field.did);
1988                                             write!(
1989                                                 &mut msg,
1990                                                 " (in this {} field)",
1991                                                 adt_def.descr()
1992                                             )
1993                                             .unwrap();
1994                                             (msg, Some(span))
1995                                         } else {
1996                                             // Just forward.
1997                                             (msg, span)
1998                                         }
1999                                     },
2000                                 )
2001                             })
2002                         }
2003                         // Multi-variant enums are tricky: if all but one variant are
2004                         // uninhabited, we might actually do layout like for a single-variant
2005                         // enum, and then even leaving them uninitialized could be okay.
2006                         _ => None, // Conservative fallback for multi-variant enum.
2007                     }
2008                 }
2009                 Tuple(..) => {
2010                     // Proceed recursively, check all fields.
2011                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2012                 }
2013                 // Conservative fallback.
2014                 _ => None,
2015             }
2016         }
2017
2018         if let Some(init) = is_dangerous_init(cx, expr) {
2019             // This conjures an instance of a type out of nothing,
2020             // using zeroed or uninitialized memory.
2021             // We are extremely conservative with what we warn about.
2022             let conjured_ty = cx.tables.expr_ty(expr);
2023             if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2024                 let mut err = cx.struct_span_lint(
2025                     INVALID_VALUE,
2026                     expr.span,
2027                     &format!(
2028                         "the type `{}` does not permit {}",
2029                         conjured_ty,
2030                         match init {
2031                             InitKind::Zeroed => "zero-initialization",
2032                             InitKind::Uninit => "being left uninitialized",
2033                         },
2034                     ),
2035                 );
2036                 err.span_label(expr.span, "this code causes undefined behavior when executed");
2037                 err.span_label(
2038                     expr.span,
2039                     "help: use `MaybeUninit<T>` instead, \
2040                     and only call `assume_init` after initialization is done",
2041                 );
2042                 if let Some(span) = span {
2043                     err.span_note(span, &msg);
2044                 } else {
2045                     err.note(&msg);
2046                 }
2047                 err.emit();
2048             }
2049         }
2050     }
2051 }