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 rustc::hir::def::Def;
  25 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  26 use rustc::ty::{self, Ty};
  27 use rustc::{lint, util};
  28 use hir::Node;
  29 use util::nodemap::HirIdSet;
  30 use lint::{LateContext, LintContext, LintArray};
  31 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
  32
  33 use rustc::util::nodemap::FxHashSet;
  34
  35 use syntax::tokenstream::{TokenTree, TokenStream};
  36 use syntax::ast;
  37 use syntax::ptr::P;
  38 use syntax::ast::Expr;
  39 use syntax::attr;
  40 use syntax::source_map::Spanned;
  41 use syntax::edition::Edition;
  42 use syntax::feature_gate::{AttributeGate, AttributeTemplate, AttributeType};
  43 use syntax::feature_gate::{Stability, deprecated_attributes};
  44 use syntax_pos::{BytePos, Span, SyntaxContext};
  45 use syntax::symbol::keywords;
  46 use syntax::errors::{Applicability, DiagnosticBuilder};
  47 use syntax::print::pprust::expr_to_string;
  48 use syntax::visit::FnKind;
  49 use syntax::struct_span_err;
  50
  51 use rustc::hir::{self, GenericParamKind, PatKind};
  52
  53 use crate::nonstandard_style::{MethodLateContext, method_context};
  54
  55 use log::debug;
  56
  57 // hardwired lints from librustc
  58 pub use lint::builtin::*;
  59
  60 declare_lint! {
  61     WHILE_TRUE,
  62     Warn,
  63     "suggest using `loop { }` instead of `while true { }`"
  64 }
  65
  66 #[derive(Copy, Clone)]
  67 pub struct WhileTrue;
  68
  69 impl LintPass for WhileTrue {
  70     fn name(&self) -> &'static str {
  71         "WhileTrue"
  72     }
  73
  74     fn get_lints(&self) -> LintArray {
  75         lint_array!(WHILE_TRUE)
  76     }
  77 }
  78
  79 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
  80     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
  81         if let hir::ExprKind::While(ref cond, ..) = e.node {
  82             if let hir::ExprKind::Lit(ref lit) = cond.node {
  83                 if let ast::LitKind::Bool(true) = lit.node {
  84                     if lit.span.ctxt() == SyntaxContext::empty() {
  85                         let msg = "denote infinite loops with `loop { ... }`";
  86                         let condition_span = cx.tcx.sess.source_map().def_span(e.span);
  87                         let mut err = cx.struct_span_lint(WHILE_TRUE, condition_span, msg);
  88                         err.span_suggestion_short(
  89                             condition_span,
  90                             "use `loop`",
  91                             "loop".to_owned(),
  92                             Applicability::MachineApplicable
  93                         );
  94                         err.emit();
  95                     }
  96                 }
  97             }
  98         }
  99     }
 100 }
 101
 102 declare_lint! {
 103     BOX_POINTERS,
 104     Allow,
 105     "use of owned (Box type) heap memory"
 106 }
 107
 108 #[derive(Copy, Clone)]
 109 pub struct BoxPointers;
 110
 111 impl BoxPointers {
 112     fn check_heap_type<'a, 'tcx>(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
 113         for leaf_ty in ty.walk() {
 114             if leaf_ty.is_box() {
 115                 let m = format!("type uses owned (Box type) pointers: {}", ty);
 116                 cx.span_lint(BOX_POINTERS, span, &m);
 117             }
 118         }
 119     }
 120 }
 121
 122 impl LintPass for BoxPointers {
 123     fn name(&self) -> &'static str {
 124         "BoxPointers"
 125     }
 126
 127     fn get_lints(&self) -> LintArray {
 128         lint_array!(BOX_POINTERS)
 129     }
 130 }
 131
 132 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 133     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 134         match it.node {
 135             hir::ItemKind::Fn(..) |
 136             hir::ItemKind::Ty(..) |
 137             hir::ItemKind::Enum(..) |
 138             hir::ItemKind::Struct(..) |
 139             hir::ItemKind::Union(..) => {
 140                 let def_id = cx.tcx.hir().local_def_id_from_hir_id(it.hir_id);
 141                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 142             }
 143             _ => ()
 144         }
 145
 146         // If it's a struct, we also have to check the fields' types
 147         match it.node {
 148             hir::ItemKind::Struct(ref struct_def, _) |
 149             hir::ItemKind::Union(ref struct_def, _) => {
 150                 for struct_field in struct_def.fields() {
 151                     let def_id = cx.tcx.hir().local_def_id_from_hir_id(struct_field.hir_id);
 152                     self.check_heap_type(cx, struct_field.span,
 153                                          cx.tcx.type_of(def_id));
 154                 }
 155             }
 156             _ => (),
 157         }
 158     }
 159
 160     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
 161         let ty = cx.tables.node_type(e.hir_id);
 162         self.check_heap_type(cx, e.span, ty);
 163     }
 164 }
 165
 166 declare_lint! {
 167     NON_SHORTHAND_FIELD_PATTERNS,
 168     Warn,
 169     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 170 }
 171
 172 #[derive(Copy, Clone)]
 173 pub struct NonShorthandFieldPatterns;
 174
 175 impl LintPass for NonShorthandFieldPatterns {
 176     fn name(&self) -> &'static str {
 177         "NonShorthandFieldPatterns"
 178     }
 179
 180     fn get_lints(&self) -> LintArray {
 181         lint_array!(NON_SHORTHAND_FIELD_PATTERNS)
 182     }
 183 }
 184
 185 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 186     fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat) {
 187         if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.node {
 188             let variant = cx.tables.pat_ty(pat).ty_adt_def()
 189                                    .expect("struct pattern type is not an ADT")
 190                                    .variant_of_def(cx.tables.qpath_def(qpath, pat.hir_id));
 191             for fieldpat in field_pats {
 192                 if fieldpat.node.is_shorthand {
 193                     continue;
 194                 }
 195                 if fieldpat.span.ctxt().outer().expn_info().is_some() {
 196                     // Don't lint if this is a macro expansion: macro authors
 197                     // shouldn't have to worry about this kind of style issue
 198                     // (Issue #49588)
 199                     continue;
 200                 }
 201                 if let PatKind::Binding(_, _, ident, None) = fieldpat.node.pat.node {
 202                     if cx.tcx.find_field_index(ident, &variant) ==
 203                        Some(cx.tcx.field_index(fieldpat.node.hir_id, cx.tables)) {
 204                         let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
 205                                      fieldpat.span,
 206                                      &format!("the `{}:` in this pattern is redundant", ident));
 207                         let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
 208                                                                                  ':');
 209                         err.span_suggestion_short(
 210                             subspan,
 211                             "remove this",
 212                             ident.to_string(),
 213                             Applicability::MachineApplicable
 214                         );
 215                         err.emit();
 216                     }
 217                 }
 218             }
 219         }
 220     }
 221 }
 222
 223 declare_lint! {
 224     UNSAFE_CODE,
 225     Allow,
 226     "usage of `unsafe` code"
 227 }
 228
 229 #[derive(Copy, Clone)]
 230 pub struct UnsafeCode;
 231
 232 impl LintPass for UnsafeCode {
 233     fn name(&self) -> &'static str {
 234         "UnsafeCode"
 235     }
 236
 237     fn get_lints(&self) -> LintArray {
 238         lint_array!(UNSAFE_CODE)
 239     }
 240 }
 241
 242 impl UnsafeCode {
 243     fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
 244         // This comes from a macro that has #[allow_internal_unsafe].
 245         if span.allows_unsafe() {
 246             return;
 247         }
 248
 249         cx.span_lint(UNSAFE_CODE, span, desc);
 250     }
 251 }
 252
 253 impl EarlyLintPass for UnsafeCode {
 254     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 255         if attr.check_name("allow_internal_unsafe") {
 256             self.report_unsafe(cx, attr.span, "`allow_internal_unsafe` allows defining \
 257                                                macros using unsafe without triggering \
 258                                                the `unsafe_code` lint at their call site");
 259         }
 260     }
 261
 262     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 263         if let ast::ExprKind::Block(ref blk, _) = e.node {
 264             // Don't warn about generated blocks, that'll just pollute the output.
 265             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 266                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
 267             }
 268         }
 269     }
 270
 271     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 272         match it.node {
 273             ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
 274                 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
 275             }
 276
 277             ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
 278                 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
 279             }
 280
 281             _ => return,
 282         }
 283     }
 284
 285     fn check_fn(&mut self,
 286                 cx: &EarlyContext<'_>,
 287                 fk: FnKind<'_>,
 288                 _: &ast::FnDecl,
 289                 span: Span,
 290                 _: ast::NodeId) {
 291         match fk {
 292             FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
 293                 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
 294             }
 295
 296             FnKind::Method(_, sig, ..) => {
 297                 if sig.header.unsafety == ast::Unsafety::Unsafe {
 298                     self.report_unsafe(cx, span, "implementation of an `unsafe` method")
 299                 }
 300             }
 301
 302             _ => (),
 303         }
 304     }
 305
 306     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::TraitItem) {
 307         if let ast::TraitItemKind::Method(ref sig, None) = item.node {
 308             if sig.header.unsafety == ast::Unsafety::Unsafe {
 309                 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
 310             }
 311         }
 312     }
 313 }
 314
 315 declare_lint! {
 316     pub MISSING_DOCS,
 317     Allow,
 318     "detects missing documentation for public members",
 319     report_in_external_macro: true
 320 }
 321
 322 pub struct MissingDoc {
 323     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 324     doc_hidden_stack: Vec<bool>,
 325
 326     /// Private traits or trait items that leaked through. Don't check their methods.
 327     private_traits: FxHashSet<hir::HirId>,
 328 }
 329
 330 fn has_doc(attr: &ast::Attribute) -> bool {
 331     if !attr.check_name("doc") {
 332         return false;
 333     }
 334
 335     if attr.is_value_str() {
 336         return true;
 337     }
 338
 339     if let Some(list) = attr.meta_item_list() {
 340         for meta in list {
 341             if meta.check_name("include") || meta.check_name("hidden") {
 342                 return true;
 343             }
 344         }
 345     }
 346
 347     false
 348 }
 349
 350 impl MissingDoc {
 351     pub fn new() -> MissingDoc {
 352         MissingDoc {
 353             doc_hidden_stack: vec![false],
 354             private_traits: FxHashSet::default(),
 355         }
 356     }
 357
 358     fn doc_hidden(&self) -> bool {
 359         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 360     }
 361
 362     fn check_missing_docs_attrs(&self,
 363                                 cx: &LateContext<'_, '_>,
 364                                 id: Option<hir::HirId>,
 365                                 attrs: &[ast::Attribute],
 366                                 sp: Span,
 367                                 desc: &'static str) {
 368         // If we're building a test harness, then warning about
 369         // documentation is probably not really relevant right now.
 370         if cx.sess().opts.test {
 371             return;
 372         }
 373
 374         // `#[doc(hidden)]` disables missing_docs check.
 375         if self.doc_hidden() {
 376             return;
 377         }
 378
 379         // Only check publicly-visible items, using the result from the privacy pass.
 380         // It's an option so the crate root can also use this function (it doesn't
 381         // have a NodeId).
 382         if let Some(id) = id {
 383             let node_id = cx.tcx.hir().hir_to_node_id(id);
 384             if !cx.access_levels.is_exported(node_id) {
 385                 return;
 386             }
 387         }
 388
 389         let has_doc = attrs.iter().any(|a| has_doc(a));
 390         if !has_doc {
 391             cx.span_lint(MISSING_DOCS,
 392                          cx.tcx.sess.source_map().def_span(sp),
 393                          &format!("missing documentation for {}", desc));
 394         }
 395     }
 396 }
 397
 398 impl LintPass for MissingDoc {
 399     fn name(&self) -> &'static str {
 400         "MissingDoc"
 401     }
 402
 403     fn get_lints(&self) -> LintArray {
 404         lint_array!(MISSING_DOCS)
 405     }
 406 }
 407
 408 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 409     fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
 410         let doc_hidden = self.doc_hidden() ||
 411                          attrs.iter().any(|attr| {
 412             attr.check_name("doc") &&
 413             match attr.meta_item_list() {
 414                 None => false,
 415                 Some(l) => attr::list_contains_name(&l, "hidden"),
 416             }
 417         });
 418         self.doc_hidden_stack.push(doc_hidden);
 419     }
 420
 421     fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
 422         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 423     }
 424
 425     fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate) {
 426         self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
 427
 428         for macro_def in &krate.exported_macros {
 429             let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
 430             if !has_doc {
 431                 cx.span_lint(MISSING_DOCS,
 432                              cx.tcx.sess.source_map().def_span(macro_def.span),
 433                              "missing documentation for macro");
 434             }
 435         }
 436     }
 437
 438     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 439         let desc = match it.node {
 440             hir::ItemKind::Fn(..) => "a function",
 441             hir::ItemKind::Mod(..) => "a module",
 442             hir::ItemKind::Enum(..) => "an enum",
 443             hir::ItemKind::Struct(..) => "a struct",
 444             hir::ItemKind::Union(..) => "a union",
 445             hir::ItemKind::Trait(.., ref trait_item_refs) => {
 446                 // Issue #11592, traits are always considered exported, even when private.
 447                 if let hir::VisibilityKind::Inherited = it.vis.node {
 448                     self.private_traits.insert(it.hir_id);
 449                     for trait_item_ref in trait_item_refs {
 450                         self.private_traits.insert(trait_item_ref.id.hir_id);
 451                     }
 452                     return;
 453                 }
 454                 "a trait"
 455             }
 456             hir::ItemKind::Ty(..) => "a type alias",
 457             hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
 458                 // If the trait is private, add the impl items to private_traits so they don't get
 459                 // reported for missing docs.
 460                 let real_trait = trait_ref.path.def.def_id();
 461                 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
 462                     match cx.tcx.hir().find_by_hir_id(hir_id) {
 463                         Some(Node::Item(item)) => {
 464                             if let hir::VisibilityKind::Inherited = item.vis.node {
 465                                 for impl_item_ref in impl_item_refs {
 466                                     self.private_traits.insert(impl_item_ref.id.hir_id);
 467                                 }
 468                             }
 469                         }
 470                         _ => {}
 471                     }
 472                 }
 473                 return;
 474             }
 475             hir::ItemKind::Const(..) => "a constant",
 476             hir::ItemKind::Static(..) => "a static",
 477             _ => return,
 478         };
 479
 480         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
 481     }
 482
 483     fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem) {
 484         if self.private_traits.contains(&trait_item.hir_id) {
 485             return;
 486         }
 487
 488         let desc = match trait_item.node {
 489             hir::TraitItemKind::Const(..) => "an associated constant",
 490             hir::TraitItemKind::Method(..) => "a trait method",
 491             hir::TraitItemKind::Type(..) => "an associated type",
 492         };
 493
 494         self.check_missing_docs_attrs(cx,
 495                                       Some(trait_item.hir_id),
 496                                       &trait_item.attrs,
 497                                       trait_item.span,
 498                                       desc);
 499     }
 500
 501     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
 502         // If the method is an impl for a trait, don't doc.
 503         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 504             return;
 505         }
 506
 507         let desc = match impl_item.node {
 508             hir::ImplItemKind::Const(..) => "an associated constant",
 509             hir::ImplItemKind::Method(..) => "a method",
 510             hir::ImplItemKind::Type(_) => "an associated type",
 511             hir::ImplItemKind::Existential(_) => "an associated existential type",
 512         };
 513         self.check_missing_docs_attrs(cx,
 514                                       Some(impl_item.hir_id),
 515                                       &impl_item.attrs,
 516                                       impl_item.span,
 517                                       desc);
 518     }
 519
 520     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField) {
 521         if !sf.is_positional() {
 522             self.check_missing_docs_attrs(cx,
 523                                           Some(sf.hir_id),
 524                                           &sf.attrs,
 525                                           sf.span,
 526                                           "a struct field")
 527         }
 528     }
 529
 530     fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant, _: &hir::Generics) {
 531         self.check_missing_docs_attrs(cx,
 532                                       Some(v.node.data.hir_id()),
 533                                       &v.node.attrs,
 534                                       v.span,
 535                                       "a variant");
 536     }
 537 }
 538
 539 declare_lint! {
 540     pub MISSING_COPY_IMPLEMENTATIONS,
 541     Allow,
 542     "detects potentially-forgotten implementations of `Copy`"
 543 }
 544
 545 #[derive(Copy, Clone)]
 546 pub struct MissingCopyImplementations;
 547
 548 impl LintPass for MissingCopyImplementations {
 549     fn name(&self) -> &'static str {
 550         "MissingCopyImplementations"
 551     }
 552
 553     fn get_lints(&self) -> LintArray {
 554         lint_array!(MISSING_COPY_IMPLEMENTATIONS)
 555     }
 556 }
 557
 558 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 559     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
 560         let node_id = cx.tcx.hir().hir_to_node_id(item.hir_id);
 561         if !cx.access_levels.is_reachable(node_id) {
 562             return;
 563         }
 564         let (def, ty) = match item.node {
 565             hir::ItemKind::Struct(_, ref ast_generics) => {
 566                 if !ast_generics.params.is_empty() {
 567                     return;
 568                 }
 569                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id_from_hir_id(item.hir_id));
 570                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 571             }
 572             hir::ItemKind::Union(_, ref ast_generics) => {
 573                 if !ast_generics.params.is_empty() {
 574                     return;
 575                 }
 576                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id_from_hir_id(item.hir_id));
 577                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 578             }
 579             hir::ItemKind::Enum(_, ref ast_generics) => {
 580                 if !ast_generics.params.is_empty() {
 581                     return;
 582                 }
 583                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id_from_hir_id(item.hir_id));
 584                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 585             }
 586             _ => return,
 587         };
 588         if def.has_dtor(cx.tcx) {
 589             return;
 590         }
 591         let param_env = ty::ParamEnv::empty();
 592         if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
 593             return;
 594         }
 595         if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
 596             cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
 597                          item.span,
 598                          "type could implement `Copy`; consider adding `impl \
 599                           Copy`")
 600         }
 601     }
 602 }
 603
 604 declare_lint! {
 605     MISSING_DEBUG_IMPLEMENTATIONS,
 606     Allow,
 607     "detects missing implementations of fmt::Debug"
 608 }
 609
 610 pub struct MissingDebugImplementations {
 611     impling_types: Option<HirIdSet>,
 612 }
 613
 614 impl MissingDebugImplementations {
 615     pub fn new() -> MissingDebugImplementations {
 616         MissingDebugImplementations { impling_types: None }
 617     }
 618 }
 619
 620 impl LintPass for MissingDebugImplementations {
 621     fn name(&self) -> &'static str {
 622         "MissingDebugImplementations"
 623     }
 624
 625     fn get_lints(&self) -> LintArray {
 626         lint_array!(MISSING_DEBUG_IMPLEMENTATIONS)
 627     }
 628 }
 629
 630 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 631     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
 632         let node_id = cx.tcx.hir().hir_to_node_id(item.hir_id);
 633         if !cx.access_levels.is_reachable(node_id) {
 634             return;
 635         }
 636
 637         match item.node {
 638             hir::ItemKind::Struct(..) |
 639             hir::ItemKind::Union(..) |
 640             hir::ItemKind::Enum(..) => {}
 641             _ => return,
 642         }
 643
 644         let debug = match cx.tcx.lang_items().debug_trait() {
 645             Some(debug) => debug,
 646             None => return,
 647         };
 648
 649         if self.impling_types.is_none() {
 650             let mut impls = HirIdSet::default();
 651             cx.tcx.for_each_impl(debug, |d| {
 652                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 653                     if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
 654                         impls.insert(hir_id);
 655                     }
 656                 }
 657             });
 658
 659             self.impling_types = Some(impls);
 660             debug!("{:?}", self.impling_types);
 661         }
 662
 663         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 664             cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
 665                          item.span,
 666                          "type does not implement `fmt::Debug`; consider adding #[derive(Debug)] \
 667                           or a manual implementation")
 668         }
 669     }
 670 }
 671
 672 declare_lint! {
 673     pub ANONYMOUS_PARAMETERS,
 674     Allow,
 675     "detects anonymous parameters"
 676 }
 677
 678 /// Checks for use of anonymous parameters (RFC 1685).
 679 #[derive(Copy, Clone)]
 680 pub struct AnonymousParameters;
 681
 682 impl LintPass for AnonymousParameters {
 683     fn name(&self) -> &'static str {
 684         "AnonymousParameters"
 685     }
 686
 687     fn get_lints(&self) -> LintArray {
 688         lint_array!(ANONYMOUS_PARAMETERS)
 689     }
 690 }
 691
 692 impl EarlyLintPass for AnonymousParameters {
 693     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::TraitItem) {
 694         match it.node {
 695             ast::TraitItemKind::Method(ref sig, _) => {
 696                 for arg in sig.decl.inputs.iter() {
 697                     match arg.pat.node {
 698                         ast::PatKind::Ident(_, ident, None) => {
 699                             if ident.name == keywords::Invalid.name() {
 700                                 let ty_snip = cx
 701                                     .sess
 702                                     .source_map()
 703                                     .span_to_snippet(arg.ty.span);
 704
 705                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 706                                     (snip, Applicability::MachineApplicable)
 707                                 } else {
 708                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 709                                 };
 710
 711                                 cx.struct_span_lint(
 712                                     ANONYMOUS_PARAMETERS,
 713                                     arg.pat.span,
 714                                     "anonymous parameters are deprecated and will be \
 715                                      removed in the next edition."
 716                                 ).span_suggestion(
 717                                     arg.pat.span,
 718                                     "Try naming the parameter or explicitly \
 719                                     ignoring it",
 720                                     format!("_: {}", ty_snip),
 721                                     appl
 722                                 ).emit();
 723                             }
 724                         }
 725                         _ => (),
 726                     }
 727                 }
 728             },
 729             _ => (),
 730         }
 731     }
 732 }
 733
 734 /// Check for use of attributes which have been deprecated.
 735 #[derive(Clone)]
 736 pub struct DeprecatedAttr {
 737     // This is not free to compute, so we want to keep it around, rather than
 738     // compute it for every attribute.
 739     depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeTemplate, AttributeGate)>,
 740 }
 741
 742 impl DeprecatedAttr {
 743     pub fn new() -> DeprecatedAttr {
 744         DeprecatedAttr {
 745             depr_attrs: deprecated_attributes(),
 746         }
 747     }
 748 }
 749
 750 impl LintPass for DeprecatedAttr {
 751     fn name(&self) -> &'static str {
 752         "DeprecatedAttr"
 753     }
 754
 755     fn get_lints(&self) -> LintArray {
 756         lint_array!()
 757     }
 758 }
 759
 760 impl EarlyLintPass for DeprecatedAttr {
 761     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 762         for &&(n, _, _, ref g) in &self.depr_attrs {
 763             if attr.name() == n {
 764                 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
 765                                              ref name,
 766                                              ref reason,
 767                                              _) = g {
 768                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
 769                                       name, reason, link);
 770                     let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
 771                     err.span_suggestion_short(
 772                         attr.span,
 773                         suggestion.unwrap_or("remove this attribute"),
 774                         String::new(),
 775                         Applicability::MachineApplicable
 776                     );
 777                     err.emit();
 778                 }
 779                 return;
 780             }
 781         }
 782     }
 783 }
 784
 785 declare_lint! {
 786     pub UNUSED_DOC_COMMENTS,
 787     Warn,
 788     "detects doc comments that aren't used by rustdoc"
 789 }
 790
 791 #[derive(Copy, Clone)]
 792 pub struct UnusedDocComment;
 793
 794 impl LintPass for UnusedDocComment {
 795     fn name(&self) -> &'static str {
 796         "UnusedDocComment"
 797     }
 798
 799     fn get_lints(&self) -> LintArray {
 800         lint_array![UNUSED_DOC_COMMENTS]
 801     }
 802 }
 803
 804 impl UnusedDocComment {
 805     fn warn_if_doc<'a, 'tcx,
 806                    I: Iterator<Item=&'a ast::Attribute>,
 807                    C: LintContext<'tcx>>(&self, mut attrs: I, cx: &C) {
 808         if let Some(attr) = attrs.find(|a| a.is_value_str() && a.check_name("doc")) {
 809             cx.struct_span_lint(UNUSED_DOC_COMMENTS, attr.span, "doc comment not used by rustdoc")
 810               .emit();
 811         }
 812     }
 813 }
 814
 815 impl EarlyLintPass for UnusedDocComment {
 816     fn check_local(&mut self, cx: &EarlyContext<'_>, decl: &ast::Local) {
 817         self.warn_if_doc(decl.attrs.iter(), cx);
 818     }
 819
 820     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 821         self.warn_if_doc(arm.attrs.iter(), cx);
 822     }
 823
 824     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 825         self.warn_if_doc(expr.attrs.iter(), cx);
 826     }
 827 }
 828
 829 declare_lint! {
 830     PLUGIN_AS_LIBRARY,
 831     Warn,
 832     "compiler plugin used as ordinary library in non-plugin crate"
 833 }
 834
 835 #[derive(Copy, Clone)]
 836 pub struct PluginAsLibrary;
 837
 838 impl LintPass for PluginAsLibrary {
 839     fn name(&self) -> &'static str {
 840         "PluginAsLibrary"
 841     }
 842
 843     fn get_lints(&self) -> LintArray {
 844         lint_array![PLUGIN_AS_LIBRARY]
 845     }
 846 }
 847
 848 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
 849     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 850         if cx.tcx.plugin_registrar_fn(LOCAL_CRATE).is_some() {
 851             // We're compiling a plugin; it's fine to link other plugins.
 852             return;
 853         }
 854
 855         match it.node {
 856             hir::ItemKind::ExternCrate(..) => (),
 857             _ => return,
 858         };
 859
 860         let def_id = cx.tcx.hir().local_def_id_from_hir_id(it.hir_id);
 861         let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
 862             Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
 863             None => {
 864                 // Probably means we aren't linking the crate for some reason.
 865                 //
 866                 // Not sure if / when this could happen.
 867                 return;
 868             }
 869         };
 870
 871         if prfn.is_some() {
 872             cx.span_lint(PLUGIN_AS_LIBRARY,
 873                          it.span,
 874                          "compiler plugin used as an ordinary library");
 875         }
 876     }
 877 }
 878
 879 declare_lint! {
 880     NO_MANGLE_CONST_ITEMS,
 881     Deny,
 882     "const items will not have their symbols exported"
 883 }
 884
 885 declare_lint! {
 886     NO_MANGLE_GENERIC_ITEMS,
 887     Warn,
 888     "generic items must be mangled"
 889 }
 890
 891 #[derive(Copy, Clone)]
 892 pub struct InvalidNoMangleItems;
 893
 894 impl LintPass for InvalidNoMangleItems {
 895     fn name(&self) -> &'static str {
 896         "InvalidNoMangleItems"
 897     }
 898
 899     fn get_lints(&self) -> LintArray {
 900         lint_array!(NO_MANGLE_CONST_ITEMS,
 901                     NO_MANGLE_GENERIC_ITEMS)
 902     }
 903 }
 904
 905 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
 906     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 907         match it.node {
 908             hir::ItemKind::Fn(.., ref generics, _) => {
 909                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, "no_mangle") {
 910                     for param in &generics.params {
 911                         match param.kind {
 912                             GenericParamKind::Lifetime { .. } => {}
 913                             GenericParamKind::Type { .. } |
 914                             GenericParamKind::Const { .. } => {
 915                                 let mut err = cx.struct_span_lint(
 916                                     NO_MANGLE_GENERIC_ITEMS,
 917                                     it.span,
 918                                     "functions generic over types or consts must be mangled",
 919                                 );
 920                                 err.span_suggestion_short(
 921                                     no_mangle_attr.span,
 922                                     "remove this attribute",
 923                                     String::new(),
 924                                     // Use of `#[no_mangle]` suggests FFI intent; correct
 925                                     // fix may be to monomorphize source by hand
 926                                     Applicability::MaybeIncorrect
 927                                 );
 928                                 err.emit();
 929                                 break;
 930                             }
 931                         }
 932                     }
 933                 }
 934             }
 935             hir::ItemKind::Const(..) => {
 936                 if attr::contains_name(&it.attrs, "no_mangle") {
 937                     // Const items do not refer to a particular location in memory, and therefore
 938                     // don't have anything to attach a symbol to
 939                     let msg = "const items should never be #[no_mangle]";
 940                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
 941
 942                     // account for "pub const" (#45562)
 943                     let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
 944                         .map(|snippet| snippet.find("const").unwrap_or(0))
 945                         .unwrap_or(0) as u32;
 946                     // `const` is 5 chars
 947                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 948                     err.span_suggestion(
 949                         const_span,
 950                         "try a static value",
 951                         "pub static".to_owned(),
 952                         Applicability::MachineApplicable
 953                     );
 954                     err.emit();
 955                 }
 956             }
 957             _ => {}
 958         }
 959     }
 960 }
 961
 962 #[derive(Clone, Copy)]
 963 pub struct MutableTransmutes;
 964
 965 declare_lint! {
 966     MUTABLE_TRANSMUTES,
 967     Deny,
 968     "mutating transmuted &mut T from &T may cause undefined behavior"
 969 }
 970
 971 impl LintPass for MutableTransmutes {
 972     fn name(&self) -> &'static str {
 973         "MutableTransmutes"
 974     }
 975
 976     fn get_lints(&self) -> LintArray {
 977         lint_array!(MUTABLE_TRANSMUTES)
 978     }
 979 }
 980
 981 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
 982     fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr) {
 983         use rustc_target::spec::abi::Abi::RustIntrinsic;
 984
 985         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 986                    consider instead using an UnsafeCell";
 987         match get_transmute_from_to(cx, expr) {
 988             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
 989                 if to_mt == hir::Mutability::MutMutable &&
 990                    from_mt == hir::Mutability::MutImmutable {
 991                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
 992                 }
 993             }
 994             _ => (),
 995         }
 996
 997         fn get_transmute_from_to<'a, 'tcx>
 998             (cx: &LateContext<'a, 'tcx>,
 999              expr: &hir::Expr)
1000              -> Option<(&'tcx ty::TyKind<'tcx>, &'tcx ty::TyKind<'tcx>)> {
1001             let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
1002                 cx.tables.qpath_def(qpath, expr.hir_id)
1003             } else {
1004                 return None;
1005             };
1006             if let Def::Fn(did) = def {
1007                 if !def_id_is_transmute(cx, did) {
1008                     return None;
1009                 }
1010                 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
1011                 let from = sig.inputs().skip_binder()[0];
1012                 let to = *sig.output().skip_binder();
1013                 return Some((&from.sty, &to.sty));
1014             }
1015             None
1016         }
1017
1018         fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
1019             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
1020             cx.tcx.item_name(def_id) == "transmute"
1021         }
1022     }
1023 }
1024
1025 /// Forbids using the `#[feature(...)]` attribute
1026 #[derive(Copy, Clone)]
1027 pub struct UnstableFeatures;
1028
1029 declare_lint! {
1030     UNSTABLE_FEATURES,
1031     Allow,
1032     "enabling unstable features (deprecated. do not use)"
1033 }
1034
1035 impl LintPass for UnstableFeatures {
1036     fn name(&self) -> &'static str {
1037         "UnstableFeatures"
1038     }
1039
1040     fn get_lints(&self) -> LintArray {
1041         lint_array!(UNSTABLE_FEATURES)
1042     }
1043 }
1044
1045 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
1046     fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
1047         if attr.check_name("feature") {
1048             if let Some(items) = attr.meta_item_list() {
1049                 for item in items {
1050                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
1051                 }
1052             }
1053         }
1054     }
1055 }
1056
1057 /// Lint for unions that contain fields with possibly non-trivial destructors.
1058 pub struct UnionsWithDropFields;
1059
1060 declare_lint! {
1061     UNIONS_WITH_DROP_FIELDS,
1062     Warn,
1063     "use of unions that contain fields with possibly non-trivial drop code"
1064 }
1065
1066 impl LintPass for UnionsWithDropFields {
1067     fn name(&self) -> &'static str {
1068         "UnionsWithDropFields"
1069     }
1070
1071     fn get_lints(&self) -> LintArray {
1072         lint_array!(UNIONS_WITH_DROP_FIELDS)
1073     }
1074 }
1075
1076 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
1077     fn check_item(&mut self, ctx: &LateContext<'_, '_>, item: &hir::Item) {
1078         if let hir::ItemKind::Union(ref vdata, _) = item.node {
1079             for field in vdata.fields() {
1080                 let field_ty = ctx.tcx.type_of(
1081                     ctx.tcx.hir().local_def_id_from_hir_id(field.hir_id));
1082                 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1083                     ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1084                                   field.span,
1085                                   "union contains a field with possibly non-trivial drop code, \
1086                                    drop code of union fields is ignored when dropping the union");
1087                     return;
1088                 }
1089             }
1090         }
1091     }
1092 }
1093
1094 /// Lint for items marked `pub` that aren't reachable from other crates.
1095 #[derive(Copy, Clone)]
1096 pub struct UnreachablePub;
1097
1098 declare_lint! {
1099     pub UNREACHABLE_PUB,
1100     Allow,
1101     "`pub` items not reachable from crate root"
1102 }
1103
1104 impl LintPass for UnreachablePub {
1105     fn name(&self) -> &'static str {
1106         "UnreachablePub"
1107     }
1108
1109     fn get_lints(&self) -> LintArray {
1110         lint_array!(UNREACHABLE_PUB)
1111     }
1112 }
1113
1114 impl UnreachablePub {
1115     fn perform_lint(&self, cx: &LateContext<'_, '_>, what: &str, id: hir::HirId,
1116                     vis: &hir::Visibility, span: Span, exportable: bool) {
1117         let mut applicability = Applicability::MachineApplicable;
1118         let node_id = cx.tcx.hir().hir_to_node_id(id);
1119         match vis.node {
1120             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(node_id) => {
1121                 if span.ctxt().outer().expn_info().is_some() {
1122                     applicability = Applicability::MaybeIncorrect;
1123                 }
1124                 let def_span = cx.tcx.sess.source_map().def_span(span);
1125                 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1126                                                   &format!("unreachable `pub` {}", what));
1127                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1128                     "crate"
1129                 } else {
1130                     "pub(crate)"
1131                 }.to_owned();
1132
1133                 err.span_suggestion(
1134                     vis.span,
1135                     "consider restricting its visibility",
1136                     replacement,
1137                     applicability,
1138                 );
1139                 if exportable {
1140                     err.help("or consider exporting it for use by other crates");
1141                 }
1142                 err.emit();
1143             },
1144             _ => {}
1145         }
1146     }
1147 }
1148
1149
1150 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1151     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1152         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1153     }
1154
1155     fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, foreign_item: &hir::ForeignItem) {
1156         self.perform_lint(cx, "item", foreign_item.hir_id, &foreign_item.vis,
1157                           foreign_item.span, true);
1158     }
1159
1160     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
1161         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1162     }
1163
1164     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
1165         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1166     }
1167 }
1168
1169 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1170 /// They are relevant when using associated types, but otherwise neither checked
1171 /// at definition site nor enforced at use site.
1172
1173 pub struct TypeAliasBounds;
1174
1175 declare_lint! {
1176     TYPE_ALIAS_BOUNDS,
1177     Warn,
1178     "bounds in type aliases are not enforced"
1179 }
1180
1181 impl LintPass for TypeAliasBounds {
1182     fn name(&self) -> &'static str {
1183         "TypeAliasBounds"
1184     }
1185
1186     fn get_lints(&self) -> LintArray {
1187         lint_array!(TYPE_ALIAS_BOUNDS)
1188     }
1189 }
1190
1191 impl TypeAliasBounds {
1192     fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1193         match *qpath {
1194             hir::QPath::TypeRelative(ref ty, _) => {
1195                 // If this is a type variable, we found a `T::Assoc`.
1196                 match ty.node {
1197                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1198                         match path.def {
1199                             Def::TyParam(_) => true,
1200                             _ => false
1201                         }
1202                     }
1203                     _ => false
1204                 }
1205             }
1206             hir::QPath::Resolved(..) => false,
1207         }
1208     }
1209
1210     fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder<'_>) {
1211         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1212         // bound.  Let's see if this type does that.
1213
1214         // We use a HIR visitor to walk the type.
1215         use rustc::hir::intravisit::{self, Visitor};
1216         struct WalkAssocTypes<'a, 'db> where 'db: 'a {
1217             err: &'a mut DiagnosticBuilder<'db>
1218         }
1219         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1220             fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1221             {
1222                 intravisit::NestedVisitorMap::None
1223             }
1224
1225             fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1226                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1227                     self.err.span_help(span,
1228                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1229                          associated types in type aliases");
1230                 }
1231                 intravisit::walk_qpath(self, qpath, id, span)
1232             }
1233         }
1234
1235         // Let's go for a walk!
1236         let mut visitor = WalkAssocTypes { err };
1237         visitor.visit_ty(ty);
1238     }
1239 }
1240
1241 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1242     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1243         let (ty, type_alias_generics) = match item.node {
1244             hir::ItemKind::Ty(ref ty, ref generics) => (&*ty, generics),
1245             _ => return,
1246         };
1247         let mut suggested_changing_assoc_types = false;
1248         // There must not be a where clause
1249         if !type_alias_generics.where_clause.predicates.is_empty() {
1250             let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1251                 .map(|pred| pred.span()).collect();
1252             let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1253                 "where clauses are not enforced in type aliases");
1254             err.help("the clause will not be checked when the type alias is used, \
1255                       and should be removed");
1256             if !suggested_changing_assoc_types {
1257                 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1258                 suggested_changing_assoc_types = true;
1259             }
1260             err.emit();
1261         }
1262         // The parameters must not have bounds
1263         for param in type_alias_generics.params.iter() {
1264             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1265             if !spans.is_empty() {
1266                 let mut err = cx.struct_span_lint(
1267                     TYPE_ALIAS_BOUNDS,
1268                     spans,
1269                     "bounds on generic parameters are not enforced in type aliases",
1270                 );
1271                 err.help("the bound will not be checked when the type alias is used, \
1272                           and should be removed");
1273                 if !suggested_changing_assoc_types {
1274                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1275                     suggested_changing_assoc_types = true;
1276                 }
1277                 err.emit();
1278             }
1279         }
1280     }
1281 }
1282
1283 /// Lint constants that are erroneous.
1284 /// Without this lint, we might not get any diagnostic if the constant is
1285 /// unused within this crate, even though downstream crates can't use it
1286 /// without producing an error.
1287 pub struct UnusedBrokenConst;
1288
1289 impl LintPass for UnusedBrokenConst {
1290     fn name(&self) -> &'static str {
1291         "UnusedBrokenConst"
1292     }
1293
1294     fn get_lints(&self) -> LintArray {
1295         lint_array!()
1296     }
1297 }
1298 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1299     let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1300     let is_static = cx.tcx.is_static(def_id).is_some();
1301     let param_env = if is_static {
1302         // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1303         ty::ParamEnv::reveal_all()
1304     } else {
1305         cx.tcx.param_env(def_id)
1306     };
1307     let cid = ::rustc::mir::interpret::GlobalId {
1308         instance: ty::Instance::mono(cx.tcx, def_id),
1309         promoted: None
1310     };
1311     // trigger the query once for all constants since that will already report the errors
1312     let _ = cx.tcx.const_eval(param_env.and(cid));
1313 }
1314
1315 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1316     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1317         match it.node {
1318             hir::ItemKind::Const(_, body_id) => {
1319                 check_const(cx, body_id);
1320             },
1321             hir::ItemKind::Static(_, _, body_id) => {
1322                 check_const(cx, body_id);
1323             },
1324             _ => {},
1325         }
1326     }
1327 }
1328
1329 /// Lint for trait and lifetime bounds that don't depend on type parameters
1330 /// which either do nothing, or stop the item from being used.
1331 pub struct TrivialConstraints;
1332
1333 declare_lint! {
1334     TRIVIAL_BOUNDS,
1335     Warn,
1336     "these bounds don't depend on an type parameters"
1337 }
1338
1339 impl LintPass for TrivialConstraints {
1340     fn name(&self) -> &'static str {
1341         "TrivialConstraints"
1342     }
1343
1344     fn get_lints(&self) -> LintArray {
1345         lint_array!(TRIVIAL_BOUNDS)
1346     }
1347 }
1348
1349 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1350     fn check_item(
1351         &mut self,
1352         cx: &LateContext<'a, 'tcx>,
1353         item: &'tcx hir::Item,
1354     ) {
1355         use rustc::ty::fold::TypeFoldable;
1356         use rustc::ty::Predicate::*;
1357
1358
1359         if cx.tcx.features().trivial_bounds {
1360             let def_id = cx.tcx.hir().local_def_id_from_hir_id(item.hir_id);
1361             let predicates = cx.tcx.predicates_of(def_id);
1362             for &(predicate, span) in &predicates.predicates {
1363                 let predicate_kind_name = match predicate {
1364                     Trait(..) => "Trait",
1365                     TypeOutlives(..) |
1366                     RegionOutlives(..) => "Lifetime",
1367
1368                     // Ignore projections, as they can only be global
1369                     // if the trait bound is global
1370                     Projection(..) |
1371                     // Ignore bounds that a user can't type
1372                     WellFormed(..) |
1373                     ObjectSafe(..) |
1374                     ClosureKind(..) |
1375                     Subtype(..) |
1376                     ConstEvaluatable(..) => continue,
1377                 };
1378                 if predicate.is_global() {
1379                     cx.span_lint(
1380                         TRIVIAL_BOUNDS,
1381                         span,
1382                         &format!("{} bound {} does not depend on any type \
1383                                 or lifetime parameters", predicate_kind_name, predicate),
1384                     );
1385                 }
1386             }
1387         }
1388     }
1389 }
1390
1391
1392 /// Does nothing as a lint pass, but registers some `Lint`s
1393 /// which are used by other parts of the compiler.
1394 #[derive(Copy, Clone)]
1395 pub struct SoftLints;
1396
1397 impl LintPass for SoftLints {
1398     fn name(&self) -> &'static str {
1399         "SoftLints"
1400     }
1401
1402     fn get_lints(&self) -> LintArray {
1403         lint_array!(
1404             WHILE_TRUE,
1405             BOX_POINTERS,
1406             NON_SHORTHAND_FIELD_PATTERNS,
1407             UNSAFE_CODE,
1408             MISSING_DOCS,
1409             MISSING_COPY_IMPLEMENTATIONS,
1410             MISSING_DEBUG_IMPLEMENTATIONS,
1411             ANONYMOUS_PARAMETERS,
1412             UNUSED_DOC_COMMENTS,
1413             PLUGIN_AS_LIBRARY,
1414             NO_MANGLE_CONST_ITEMS,
1415             NO_MANGLE_GENERIC_ITEMS,
1416             MUTABLE_TRANSMUTES,
1417             UNSTABLE_FEATURES,
1418             UNIONS_WITH_DROP_FIELDS,
1419             UNREACHABLE_PUB,
1420             TYPE_ALIAS_BOUNDS,
1421             TRIVIAL_BOUNDS
1422         )
1423     }
1424 }
1425
1426 declare_lint! {
1427     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1428     Allow,
1429     "`...` range patterns are deprecated"
1430 }
1431
1432
1433 pub struct EllipsisInclusiveRangePatterns;
1434
1435 impl LintPass for EllipsisInclusiveRangePatterns {
1436     fn name(&self) -> &'static str {
1437         "EllipsisInclusiveRangePatterns"
1438     }
1439
1440     fn get_lints(&self) -> LintArray {
1441         lint_array!(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS)
1442     }
1443 }
1444
1445 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1446     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat, visit_subpats: &mut bool) {
1447         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1448
1449         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1450         /// corresponding to the ellipsis.
1451         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(&P<Expr>, &P<Expr>, Span)> {
1452             match &pat.node {
1453                 PatKind::Range(a, b, Spanned { span, node: RangeEnd::Included(DotDotDot), .. }) => {
1454                     Some((a, b, *span))
1455                 }
1456                 _ => None,
1457             }
1458         }
1459
1460         let (parenthesise, endpoints) = match &pat.node {
1461             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1462             _ => (false, matches_ellipsis_pat(pat)),
1463         };
1464
1465         if let Some((start, end, join)) = endpoints {
1466             let msg = "`...` range patterns are deprecated";
1467             let suggestion = "use `..=` for an inclusive range";
1468             if parenthesise {
1469                 *visit_subpats = false;
1470                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1471                 err.span_suggestion(
1472                     pat.span,
1473                     suggestion,
1474                     format!("&({}..={})", expr_to_string(&start), expr_to_string(&end)),
1475                     Applicability::MachineApplicable,
1476                 );
1477                 err.emit();
1478             } else {
1479                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1480                 err.span_suggestion_short(
1481                     join,
1482                     suggestion,
1483                     "..=".to_owned(),
1484                     Applicability::MachineApplicable,
1485                 );
1486                 err.emit();
1487             };
1488         }
1489     }
1490 }
1491
1492 declare_lint! {
1493     UNNAMEABLE_TEST_ITEMS,
1494     Warn,
1495     "detects an item that cannot be named being marked as #[test_case]",
1496     report_in_external_macro: true
1497 }
1498
1499 pub struct UnnameableTestItems {
1500     boundary: hir::HirId, // HirId of the item under which things are not nameable
1501     items_nameable: bool,
1502 }
1503
1504 impl UnnameableTestItems {
1505     pub fn new() -> Self {
1506         Self {
1507             boundary: hir::DUMMY_HIR_ID,
1508             items_nameable: true
1509         }
1510     }
1511 }
1512
1513 impl LintPass for UnnameableTestItems {
1514     fn name(&self) -> &'static str {
1515         "UnnameableTestItems"
1516     }
1517
1518     fn get_lints(&self) -> LintArray {
1519         lint_array!(UNNAMEABLE_TEST_ITEMS)
1520     }
1521 }
1522
1523 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1524     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1525         if self.items_nameable {
1526             if let hir::ItemKind::Mod(..) = it.node {}
1527             else {
1528                 self.items_nameable = false;
1529                 self.boundary = it.hir_id;
1530             }
1531             return;
1532         }
1533
1534         if let Some(attr) = attr::find_by_name(&it.attrs, "rustc_test_marker") {
1535             cx.struct_span_lint(
1536                 UNNAMEABLE_TEST_ITEMS,
1537                 attr.span,
1538                 "cannot test inner items",
1539             ).emit();
1540         }
1541     }
1542
1543     fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item) {
1544         if !self.items_nameable && self.boundary == it.hir_id {
1545             self.items_nameable = true;
1546         }
1547     }
1548 }
1549
1550 declare_lint! {
1551     pub KEYWORD_IDENTS,
1552     Allow,
1553     "detects edition keywords being used as an identifier"
1554 }
1555
1556 /// Check for uses of edition keywords used as an identifier.
1557 #[derive(Copy, Clone)]
1558 pub struct KeywordIdents;
1559
1560 impl LintPass for KeywordIdents {
1561     fn name(&self) -> &'static str {
1562         "KeywordIdents"
1563     }
1564
1565     fn get_lints(&self) -> LintArray {
1566         lint_array!(KEYWORD_IDENTS)
1567     }
1568 }
1569
1570 impl KeywordIdents {
1571     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1572         for tt in tokens.into_trees() {
1573             match tt {
1574                 TokenTree::Token(span, tok) => match tok.ident() {
1575                     // only report non-raw idents
1576                     Some((ident, false)) => {
1577                         self.check_ident(cx, ast::Ident {
1578                             span: span.substitute_dummy(ident.span),
1579                             ..ident
1580                         });
1581                     }
1582                     _ => {},
1583                 }
1584                 TokenTree::Delimited(_, _, tts) => {
1585                     self.check_tokens(cx, tts)
1586                 },
1587             }
1588         }
1589     }
1590 }
1591
1592 impl EarlyLintPass for KeywordIdents {
1593     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1594         self.check_tokens(cx, mac_def.stream());
1595     }
1596     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1597         self.check_tokens(cx, mac.node.tts.clone().into());
1598     }
1599     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1600         let ident_str = &ident.as_str()[..];
1601         let cur_edition = cx.sess.edition();
1602         let is_raw_ident = |ident: ast::Ident| {
1603             cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span)
1604         };
1605         let next_edition = match cur_edition {
1606             Edition::Edition2015 => {
1607                 match ident_str {
1608                     "async" | "try" | "dyn" => Edition::Edition2018,
1609                     // Only issue warnings for `await` if the `async_await`
1610                     // feature isn't being used. Otherwise, users need
1611                     // to keep using `await` for the macro exposed by std.
1612                     "await" if !cx.sess.features_untracked().async_await => Edition::Edition2018,
1613                     _ => return,
1614                 }
1615             }
1616
1617             // There are no new keywords yet for the 2018 edition and beyond.
1618             // However, `await` is a "false" keyword in the 2018 edition,
1619             // and can only be used if the `async_await` feature is enabled.
1620             // Otherwise, we emit an error.
1621             _ => {
1622                 if "await" == ident_str
1623                     && !cx.sess.features_untracked().async_await
1624                     && !is_raw_ident(ident)
1625                 {
1626                     let mut err = struct_span_err!(
1627                         cx.sess,
1628                         ident.span,
1629                         E0721,
1630                         "`await` is a keyword in the {} edition", cur_edition,
1631                     );
1632                     err.span_suggestion(
1633                         ident.span,
1634                         "you can use a raw identifier to stay compatible",
1635                         "r#await".to_string(),
1636                         Applicability::MachineApplicable,
1637                     );
1638                     err.emit();
1639                 }
1640                 return
1641             },
1642         };
1643
1644         // don't lint `r#foo`
1645         if is_raw_ident(ident) {
1646             return;
1647         }
1648
1649         let mut lint = cx.struct_span_lint(
1650             KEYWORD_IDENTS,
1651             ident.span,
1652             &format!("`{}` is a keyword in the {} edition",
1653                      ident.as_str(),
1654                      next_edition),
1655         );
1656         lint.span_suggestion(
1657             ident.span,
1658             "you can use a raw identifier to stay compatible",
1659             format!("r#{}", ident.as_str()),
1660             Applicability::MachineApplicable,
1661         );
1662         lint.emit()
1663     }
1664 }
1665
1666
1667 pub struct ExplicitOutlivesRequirements;
1668
1669 impl LintPass for ExplicitOutlivesRequirements {
1670     fn name(&self) -> &'static str {
1671         "ExplicitOutlivesRequirements"
1672     }
1673
1674     fn get_lints(&self) -> LintArray {
1675         lint_array![EXPLICIT_OUTLIVES_REQUIREMENTS]
1676     }
1677 }
1678
1679 impl ExplicitOutlivesRequirements {
1680     fn collect_outlives_bound_spans(
1681         &self,
1682         cx: &LateContext<'_, '_>,
1683         item_def_id: DefId,
1684         param_name: &str,
1685         bounds: &hir::GenericBounds,
1686         infer_static: bool
1687     ) -> Vec<(usize, Span)> {
1688         // For lack of a more elegant strategy for comparing the `ty::Predicate`s
1689         // returned by this query with the params/bounds grabbed from the HIR—and
1690         // with some regrets—we're going to covert the param/lifetime names to
1691         // strings
1692         let inferred_outlives = cx.tcx.inferred_outlives_of(item_def_id);
1693
1694         let ty_lt_names = inferred_outlives.iter().filter_map(|pred| {
1695             let binder = match pred {
1696                 ty::Predicate::TypeOutlives(binder) => binder,
1697                 _ => { return None; }
1698             };
1699             let ty_outlives_pred = binder.skip_binder();
1700             let ty_name = match ty_outlives_pred.0.sty {
1701                 ty::Param(param) => param.name.to_string(),
1702                 _ => { return None; }
1703             };
1704             let lt_name = match ty_outlives_pred.1 {
1705                 ty::RegionKind::ReEarlyBound(region) => {
1706                     region.name.to_string()
1707                 },
1708                 _ => { return None; }
1709             };
1710             Some((ty_name, lt_name))
1711         }).collect::<Vec<_>>();
1712
1713         let mut bound_spans = Vec::new();
1714         for (i, bound) in bounds.iter().enumerate() {
1715             if let hir::GenericBound::Outlives(lifetime) = bound {
1716                 let is_static = match lifetime.name {
1717                     hir::LifetimeName::Static => true,
1718                     _ => false
1719                 };
1720                 if is_static && !infer_static {
1721                     // infer-outlives for 'static is still feature-gated (tracking issue #44493)
1722                     continue;
1723                 }
1724
1725                 let lt_name = &lifetime.name.ident().to_string();
1726                 if ty_lt_names.contains(&(param_name.to_owned(), lt_name.to_owned())) {
1727                     bound_spans.push((i, bound.span()));
1728                 }
1729             }
1730         }
1731         bound_spans
1732     }
1733
1734     fn consolidate_outlives_bound_spans(
1735         &self,
1736         lo: Span,
1737         bounds: &hir::GenericBounds,
1738         bound_spans: Vec<(usize, Span)>
1739     ) -> Vec<Span> {
1740         if bounds.is_empty() {
1741             return Vec::new();
1742         }
1743         if bound_spans.len() == bounds.len() {
1744             let (_, last_bound_span) = bound_spans[bound_spans.len()-1];
1745             // If all bounds are inferable, we want to delete the colon, so
1746             // start from just after the parameter (span passed as argument)
1747             vec![lo.to(last_bound_span)]
1748         } else {
1749             let mut merged = Vec::new();
1750             let mut last_merged_i = None;
1751
1752             let mut from_start = true;
1753             for (i, bound_span) in bound_spans {
1754                 match last_merged_i {
1755                     // If the first bound is inferable, our span should also eat the trailing `+`
1756                     None if i == 0 => {
1757                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1758                         last_merged_i = Some(0);
1759                     },
1760                     // If consecutive bounds are inferable, merge their spans
1761                     Some(h) if i == h+1 => {
1762                         if let Some(tail) = merged.last_mut() {
1763                             // Also eat the trailing `+` if the first
1764                             // more-than-one bound is inferable
1765                             let to_span = if from_start && i < bounds.len() {
1766                                 bounds[i+1].span().shrink_to_lo()
1767                             } else {
1768                                 bound_span
1769                             };
1770                             *tail = tail.to(to_span);
1771                             last_merged_i = Some(i);
1772                         } else {
1773                             bug!("another bound-span visited earlier");
1774                         }
1775                     },
1776                     _ => {
1777                         // When we find a non-inferable bound, subsequent inferable bounds
1778                         // won't be consecutive from the start (and we'll eat the leading
1779                         // `+` rather than the trailing one)
1780                         from_start = false;
1781                         merged.push(bounds[i-1].span().shrink_to_hi().to(bound_span));
1782                         last_merged_i = Some(i);
1783                     }
1784                 }
1785             }
1786             merged
1787         }
1788     }
1789 }
1790
1791 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1792     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
1793         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1794         let def_id = cx.tcx.hir().local_def_id_from_hir_id(item.hir_id);
1795         if let hir::ItemKind::Struct(_, ref generics) = item.node {
1796             let mut bound_count = 0;
1797             let mut lint_spans = Vec::new();
1798
1799             for param in &generics.params {
1800                 let param_name = match param.kind {
1801                     hir::GenericParamKind::Lifetime { .. } => continue,
1802                     hir::GenericParamKind::Type { .. } => {
1803                         match param.name {
1804                             hir::ParamName::Fresh(_) => continue,
1805                             hir::ParamName::Error => continue,
1806                             hir::ParamName::Plain(name) => name.to_string(),
1807                         }
1808                     }
1809                     hir::GenericParamKind::Const { .. } => continue,
1810                 };
1811                 let bound_spans = self.collect_outlives_bound_spans(
1812                     cx, def_id, &param_name, &param.bounds, infer_static
1813                 );
1814                 bound_count += bound_spans.len();
1815                 lint_spans.extend(
1816                     self.consolidate_outlives_bound_spans(
1817                         param.span.shrink_to_hi(), &param.bounds, bound_spans
1818                     )
1819                 );
1820             }
1821
1822             let mut where_lint_spans = Vec::new();
1823             let mut dropped_predicate_count = 0;
1824             let num_predicates = generics.where_clause.predicates.len();
1825             for (i, where_predicate) in generics.where_clause.predicates.iter().enumerate() {
1826                 if let hir::WherePredicate::BoundPredicate(predicate) = where_predicate {
1827                     let param_name = match predicate.bounded_ty.node {
1828                         hir::TyKind::Path(ref qpath) => {
1829                             if let hir::QPath::Resolved(None, ty_param_path) = qpath {
1830                                 ty_param_path.segments[0].ident.to_string()
1831                             } else {
1832                                 continue;
1833                             }
1834                         },
1835                         _ => { continue; }
1836                     };
1837                     let bound_spans = self.collect_outlives_bound_spans(
1838                         cx, def_id, &param_name, &predicate.bounds, infer_static
1839                     );
1840                     bound_count += bound_spans.len();
1841
1842                     let drop_predicate = bound_spans.len() == predicate.bounds.len();
1843                     if drop_predicate {
1844                         dropped_predicate_count += 1;
1845                     }
1846
1847                     // If all the bounds on a predicate were inferable and there are
1848                     // further predicates, we want to eat the trailing comma
1849                     if drop_predicate && i + 1 < num_predicates {
1850                         let next_predicate_span = generics.where_clause.predicates[i+1].span();
1851                         where_lint_spans.push(
1852                             predicate.span.to(next_predicate_span.shrink_to_lo())
1853                         );
1854                     } else {
1855                         where_lint_spans.extend(
1856                             self.consolidate_outlives_bound_spans(
1857                                 predicate.span.shrink_to_lo(),
1858                                 &predicate.bounds,
1859                                 bound_spans
1860                             )
1861                         );
1862                     }
1863                 }
1864             }
1865
1866             // If all predicates are inferable, drop the entire clause
1867             // (including the `where`)
1868             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1869                 let full_where_span = generics.span.shrink_to_hi()
1870                     .to(generics.where_clause.span()
1871                     .expect("span of (nonempty) where clause should exist"));
1872                 lint_spans.push(
1873                     full_where_span
1874                 );
1875             } else {
1876                 lint_spans.extend(where_lint_spans);
1877             }
1878
1879             if !lint_spans.is_empty() {
1880                 let mut err = cx.struct_span_lint(
1881                     EXPLICIT_OUTLIVES_REQUIREMENTS,
1882                     lint_spans.clone(),
1883                     "outlives requirements can be inferred"
1884                 );
1885                 err.multipart_suggestion(
1886                     if bound_count == 1 {
1887                         "remove this bound"
1888                     } else {
1889                         "remove these bounds"
1890                     },
1891                     lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1892                     Applicability::MachineApplicable
1893                 );
1894                 err.emit();
1895             }
1896
1897         }
1898     }
1899
1900 }