src/librustc_lint/builtin.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Lints in the Rust compiler.
  12 //!
  13 //! This contains lints which can feasibly be implemented as their own
  14 //! AST visitor. Also see `rustc::lint::builtin`, which contains the
  15 //! definitions of lints that are emitted directly inside the main
  16 //! compiler.
  17 //!
  18 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
  19 //! Then add code to emit the new lint in the appropriate circumstances.
  20 //! You can do that in an existing `LintPass` if it makes sense, or in a
  21 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
  22 //! compiler. Only do the latter if the check can't be written cleanly as a
  23 //! `LintPass` (also, note that such lints will need to be defined in
  24 //! `rustc::lint::builtin`, not here).
  25 //!
  26 //! If you define a new `LintPass`, you will also need to add it to the
  27 //! `add_builtin!` or `add_builtin_with_new!` invocation in `lib.rs`.
  28 //! Use the former for unit-like structs and the latter for structs with
  29 //! a `pub fn new()`.
  30
  31 use rustc::hir::def::Def;
  32 use rustc::hir::def_id::DefId;
  33 use rustc::cfg;
  34 use rustc::ty::subst::Substs;
  35 use rustc::ty::{self, Ty};
  36 use rustc::traits;
  37 use hir::Node;
  38 use util::nodemap::NodeSet;
  39 use lint::{LateContext, LintContext, LintArray};
  40 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
  41
  42 use rustc::util::nodemap::FxHashSet;
  43
  44 use syntax::tokenstream::{TokenTree, TokenStream};
  45 use syntax::ast;
  46 use syntax::attr;
  47 use syntax::source_map::Spanned;
  48 use syntax::edition::Edition;
  49 use syntax::feature_gate::{AttributeGate, AttributeType, Stability, deprecated_attributes};
  50 use syntax_pos::{BytePos, Span, SyntaxContext};
  51 use syntax::symbol::keywords;
  52 use syntax::errors::{Applicability, DiagnosticBuilder};
  53
  54 use rustc::hir::{self, GenericParamKind, PatKind};
  55 use rustc::hir::intravisit::FnKind;
  56
  57 use nonstandard_style::{MethodLateContext, method_context};
  58
  59 // hardwired lints from librustc
  60 pub use lint::builtin::*;
  61
  62 declare_lint! {
  63     WHILE_TRUE,
  64     Warn,
  65     "suggest using `loop { }` instead of `while true { }`"
  66 }
  67
  68 #[derive(Copy, Clone)]
  69 pub struct WhileTrue;
  70
  71 impl LintPass for WhileTrue {
  72     fn get_lints(&self) -> LintArray {
  73         lint_array!(WHILE_TRUE)
  74     }
  75 }
  76
  77 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
  78     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
  79         if let hir::ExprKind::While(ref cond, ..) = e.node {
  80             if let hir::ExprKind::Lit(ref lit) = cond.node {
  81                 if let ast::LitKind::Bool(true) = lit.node {
  82                     if lit.span.ctxt() == SyntaxContext::empty() {
  83                         let msg = "denote infinite loops with `loop { ... }`";
  84                         let condition_span = cx.tcx.sess.source_map().def_span(e.span);
  85                         let mut err = cx.struct_span_lint(WHILE_TRUE, condition_span, msg);
  86                         err.span_suggestion_short_with_applicability(
  87                             condition_span,
  88                             "use `loop`",
  89                             "loop".to_owned(),
  90                             Applicability::MachineApplicable
  91                         );
  92                         err.emit();
  93                     }
  94                 }
  95             }
  96         }
  97     }
  98 }
  99
 100 declare_lint! {
 101     BOX_POINTERS,
 102     Allow,
 103     "use of owned (Box type) heap memory"
 104 }
 105
 106 #[derive(Copy, Clone)]
 107 pub struct BoxPointers;
 108
 109 impl BoxPointers {
 110     fn check_heap_type<'a, 'tcx>(&self, cx: &LateContext, span: Span, ty: Ty) {
 111         for leaf_ty in ty.walk() {
 112             if leaf_ty.is_box() {
 113                 let m = format!("type uses owned (Box type) pointers: {}", ty);
 114                 cx.span_lint(BOX_POINTERS, span, &m);
 115             }
 116         }
 117     }
 118 }
 119
 120 impl LintPass for BoxPointers {
 121     fn get_lints(&self) -> LintArray {
 122         lint_array!(BOX_POINTERS)
 123     }
 124 }
 125
 126 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 127     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 128         match it.node {
 129             hir::ItemKind::Fn(..) |
 130             hir::ItemKind::Ty(..) |
 131             hir::ItemKind::Enum(..) |
 132             hir::ItemKind::Struct(..) |
 133             hir::ItemKind::Union(..) => {
 134                 let def_id = cx.tcx.hir.local_def_id(it.id);
 135                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 136             }
 137             _ => ()
 138         }
 139
 140         // If it's a struct, we also have to check the fields' types
 141         match it.node {
 142             hir::ItemKind::Struct(ref struct_def, _) |
 143             hir::ItemKind::Union(ref struct_def, _) => {
 144                 for struct_field in struct_def.fields() {
 145                     let def_id = cx.tcx.hir.local_def_id(struct_field.id);
 146                     self.check_heap_type(cx, struct_field.span,
 147                                          cx.tcx.type_of(def_id));
 148                 }
 149             }
 150             _ => (),
 151         }
 152     }
 153
 154     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
 155         let ty = cx.tables.node_id_to_type(e.hir_id);
 156         self.check_heap_type(cx, e.span, ty);
 157     }
 158 }
 159
 160 declare_lint! {
 161     NON_SHORTHAND_FIELD_PATTERNS,
 162     Warn,
 163     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 164 }
 165
 166 #[derive(Copy, Clone)]
 167 pub struct NonShorthandFieldPatterns;
 168
 169 impl LintPass for NonShorthandFieldPatterns {
 170     fn get_lints(&self) -> LintArray {
 171         lint_array!(NON_SHORTHAND_FIELD_PATTERNS)
 172     }
 173 }
 174
 175 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 176     fn check_pat(&mut self, cx: &LateContext, pat: &hir::Pat) {
 177         if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.node {
 178             let variant = cx.tables.pat_ty(pat).ty_adt_def()
 179                                    .expect("struct pattern type is not an ADT")
 180                                    .variant_of_def(cx.tables.qpath_def(qpath, pat.hir_id));
 181             for fieldpat in field_pats {
 182                 if fieldpat.node.is_shorthand {
 183                     continue;
 184                 }
 185                 if fieldpat.span.ctxt().outer().expn_info().is_some() {
 186                     // Don't lint if this is a macro expansion: macro authors
 187                     // shouldn't have to worry about this kind of style issue
 188                     // (Issue #49588)
 189                     continue;
 190                 }
 191                 if let PatKind::Binding(_, _, ident, None) = fieldpat.node.pat.node {
 192                     if cx.tcx.find_field_index(ident, &variant) ==
 193                        Some(cx.tcx.field_index(fieldpat.node.id, cx.tables)) {
 194                         let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
 195                                      fieldpat.span,
 196                                      &format!("the `{}:` in this pattern is redundant", ident));
 197                         let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
 198                                                                                  ':');
 199                         err.span_suggestion_short_with_applicability(
 200                             subspan,
 201                             "remove this",
 202                             ident.to_string(),
 203                             Applicability::MachineApplicable
 204                         );
 205                         err.emit();
 206                     }
 207                 }
 208             }
 209         }
 210     }
 211 }
 212
 213 declare_lint! {
 214     UNSAFE_CODE,
 215     Allow,
 216     "usage of `unsafe` code"
 217 }
 218
 219 #[derive(Copy, Clone)]
 220 pub struct UnsafeCode;
 221
 222 impl LintPass for UnsafeCode {
 223     fn get_lints(&self) -> LintArray {
 224         lint_array!(UNSAFE_CODE)
 225     }
 226 }
 227
 228 impl UnsafeCode {
 229     fn report_unsafe(&self, cx: &LateContext, span: Span, desc: &'static str) {
 230         // This comes from a macro that has #[allow_internal_unsafe].
 231         if span.allows_unsafe() {
 232             return;
 233         }
 234
 235         cx.span_lint(UNSAFE_CODE, span, desc);
 236     }
 237 }
 238
 239 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnsafeCode {
 240     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
 241         if let hir::ExprKind::Block(ref blk, _) = e.node {
 242             // Don't warn about generated blocks, that'll just pollute the output.
 243             if blk.rules == hir::UnsafeBlock(hir::UserProvided) {
 244                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
 245             }
 246         }
 247     }
 248
 249     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 250         match it.node {
 251             hir::ItemKind::Trait(_, hir::Unsafety::Unsafe, ..) => {
 252                 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
 253             }
 254
 255             hir::ItemKind::Impl(hir::Unsafety::Unsafe, ..) => {
 256                 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
 257             }
 258
 259             _ => return,
 260         }
 261     }
 262
 263     fn check_fn(&mut self,
 264                 cx: &LateContext,
 265                 fk: FnKind<'tcx>,
 266                 _: &hir::FnDecl,
 267                 _: &hir::Body,
 268                 span: Span,
 269                 _: ast::NodeId) {
 270         match fk {
 271             FnKind::ItemFn(_, _, hir::FnHeader { unsafety: hir::Unsafety::Unsafe, .. }, ..) => {
 272                 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
 273             }
 274
 275             FnKind::Method(_, sig, ..) => {
 276                 if sig.header.unsafety == hir::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: &LateContext, item: &hir::TraitItem) {
 286         if let hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(_)) = item.node {
 287             if sig.header.unsafety == hir::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: true
 299 }
 300
 301 pub struct MissingDoc {
 302     /// Stack of whether #[doc(hidden)] is set
 303     /// at each level which has lint attributes.
 304     doc_hidden_stack: Vec<bool>,
 305
 306     /// Private traits or trait items that leaked through. Don't check their methods.
 307     private_traits: FxHashSet<ast::NodeId>,
 308 }
 309
 310 impl MissingDoc {
 311     pub fn new() -> MissingDoc {
 312         MissingDoc {
 313             doc_hidden_stack: vec![false],
 314             private_traits: FxHashSet::default(),
 315         }
 316     }
 317
 318     fn doc_hidden(&self) -> bool {
 319         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 320     }
 321
 322     fn check_missing_docs_attrs(&self,
 323                                 cx: &LateContext,
 324                                 id: Option<ast::NodeId>,
 325                                 attrs: &[ast::Attribute],
 326                                 sp: Span,
 327                                 desc: &'static str) {
 328         // If we're building a test harness, then warning about
 329         // documentation is probably not really relevant right now.
 330         if cx.sess().opts.test {
 331             return;
 332         }
 333
 334         // `#[doc(hidden)]` disables missing_docs check.
 335         if self.doc_hidden() {
 336             return;
 337         }
 338
 339         // Only check publicly-visible items, using the result from the privacy pass.
 340         // It's an option so the crate root can also use this function (it doesn't
 341         // have a NodeId).
 342         if let Some(id) = id {
 343             if !cx.access_levels.is_exported(id) {
 344                 return;
 345             }
 346         }
 347
 348         fn has_doc(attr: &ast::Attribute) -> bool {
 349             if !attr.check_name("doc") {
 350                 return false;
 351             }
 352
 353             if attr.is_value_str() {
 354                 return true;
 355             }
 356
 357             if let Some(list) = attr.meta_item_list() {
 358                 for meta in list {
 359                     if meta.check_name("include") {
 360                         return true;
 361                     }
 362                 }
 363             }
 364
 365             false
 366         }
 367
 368         let has_doc = attrs.iter().any(|a| has_doc(a));
 369         if !has_doc {
 370             cx.span_lint(MISSING_DOCS,
 371                          cx.tcx.sess.source_map().def_span(sp),
 372                          &format!("missing documentation for {}", desc));
 373         }
 374     }
 375 }
 376
 377 impl LintPass for MissingDoc {
 378     fn get_lints(&self) -> LintArray {
 379         lint_array!(MISSING_DOCS)
 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("doc") &&
 388             match attr.meta_item_list() {
 389                 None => false,
 390                 Some(l) => attr::list_contains_name(&l, "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
 404     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
 405         let desc = match it.node {
 406             hir::ItemKind::Fn(..) => "a function",
 407             hir::ItemKind::Mod(..) => "a module",
 408             hir::ItemKind::Enum(..) => "an enum",
 409             hir::ItemKind::Struct(..) => "a struct",
 410             hir::ItemKind::Union(..) => "a union",
 411             hir::ItemKind::Trait(.., ref trait_item_refs) => {
 412                 // Issue #11592, traits are always considered exported, even when private.
 413                 if let hir::VisibilityKind::Inherited = it.vis.node {
 414                     self.private_traits.insert(it.id);
 415                     for trait_item_ref in trait_item_refs {
 416                         self.private_traits.insert(trait_item_ref.id.node_id);
 417                     }
 418                     return;
 419                 }
 420                 "a trait"
 421             }
 422             hir::ItemKind::Ty(..) => "a type alias",
 423             hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
 424                 // If the trait is private, add the impl items to private_traits so they don't get
 425                 // reported for missing docs.
 426                 let real_trait = trait_ref.path.def.def_id();
 427                 if let Some(node_id) = cx.tcx.hir.as_local_node_id(real_trait) {
 428                     match cx.tcx.hir.find(node_id) {
 429                         Some(Node::Item(item)) => {
 430                             if let hir::VisibilityKind::Inherited = item.vis.node {
 431                                 for impl_item_ref in impl_item_refs {
 432                                     self.private_traits.insert(impl_item_ref.id.node_id);
 433                                 }
 434                             }
 435                         }
 436                         _ => {}
 437                     }
 438                 }
 439                 return;
 440             }
 441             hir::ItemKind::Const(..) => "a constant",
 442             hir::ItemKind::Static(..) => "a static",
 443             _ => return,
 444         };
 445
 446         self.check_missing_docs_attrs(cx, Some(it.id), &it.attrs, it.span, desc);
 447     }
 448
 449     fn check_trait_item(&mut self, cx: &LateContext, trait_item: &hir::TraitItem) {
 450         if self.private_traits.contains(&trait_item.id) {
 451             return;
 452         }
 453
 454         let desc = match trait_item.node {
 455             hir::TraitItemKind::Const(..) => "an associated constant",
 456             hir::TraitItemKind::Method(..) => "a trait method",
 457             hir::TraitItemKind::Type(..) => "an associated type",
 458         };
 459
 460         self.check_missing_docs_attrs(cx,
 461                                       Some(trait_item.id),
 462                                       &trait_item.attrs,
 463                                       trait_item.span,
 464                                       desc);
 465     }
 466
 467     fn check_impl_item(&mut self, cx: &LateContext, impl_item: &hir::ImplItem) {
 468         // If the method is an impl for a trait, don't doc.
 469         if method_context(cx, impl_item.id) == MethodLateContext::TraitImpl {
 470             return;
 471         }
 472
 473         let desc = match impl_item.node {
 474             hir::ImplItemKind::Const(..) => "an associated constant",
 475             hir::ImplItemKind::Method(..) => "a method",
 476             hir::ImplItemKind::Type(_) => "an associated type",
 477             hir::ImplItemKind::Existential(_) => "an associated existential type",
 478         };
 479         self.check_missing_docs_attrs(cx,
 480                                       Some(impl_item.id),
 481                                       &impl_item.attrs,
 482                                       impl_item.span,
 483                                       desc);
 484     }
 485
 486     fn check_struct_field(&mut self, cx: &LateContext, sf: &hir::StructField) {
 487         if !sf.is_positional() {
 488             self.check_missing_docs_attrs(cx,
 489                                           Some(sf.id),
 490                                           &sf.attrs,
 491                                           sf.span,
 492                                           "a struct field")
 493         }
 494     }
 495
 496     fn check_variant(&mut self, cx: &LateContext, v: &hir::Variant, _: &hir::Generics) {
 497         self.check_missing_docs_attrs(cx,
 498                                       Some(v.node.data.id()),
 499                                       &v.node.attrs,
 500                                       v.span,
 501                                       "a variant");
 502     }
 503 }
 504
 505 declare_lint! {
 506     pub MISSING_COPY_IMPLEMENTATIONS,
 507     Allow,
 508     "detects potentially-forgotten implementations of `Copy`"
 509 }
 510
 511 #[derive(Copy, Clone)]
 512 pub struct MissingCopyImplementations;
 513
 514 impl LintPass for MissingCopyImplementations {
 515     fn get_lints(&self) -> LintArray {
 516         lint_array!(MISSING_COPY_IMPLEMENTATIONS)
 517     }
 518 }
 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.id) {
 523             return;
 524         }
 525         let (def, ty) = match item.node {
 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.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.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.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.moves_by_default(cx.tcx, param_env, item.span) {
 554             return;
 555         }
 556         if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
 557             cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
 558                          item.span,
 559                          "type could implement `Copy`; consider adding `impl \
 560                           Copy`")
 561         }
 562     }
 563 }
 564
 565 declare_lint! {
 566     MISSING_DEBUG_IMPLEMENTATIONS,
 567     Allow,
 568     "detects missing implementations of fmt::Debug"
 569 }
 570
 571 pub struct MissingDebugImplementations {
 572     impling_types: Option<NodeSet>,
 573 }
 574
 575 impl MissingDebugImplementations {
 576     pub fn new() -> MissingDebugImplementations {
 577         MissingDebugImplementations { impling_types: None }
 578     }
 579 }
 580
 581 impl LintPass for MissingDebugImplementations {
 582     fn get_lints(&self) -> LintArray {
 583         lint_array!(MISSING_DEBUG_IMPLEMENTATIONS)
 584     }
 585 }
 586
 587 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 588     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
 589         if !cx.access_levels.is_reachable(item.id) {
 590             return;
 591         }
 592
 593         match item.node {
 594             hir::ItemKind::Struct(..) |
 595             hir::ItemKind::Union(..) |
 596             hir::ItemKind::Enum(..) => {}
 597             _ => return,
 598         }
 599
 600         let debug = match cx.tcx.lang_items().debug_trait() {
 601             Some(debug) => debug,
 602             None => return,
 603         };
 604
 605         if self.impling_types.is_none() {
 606             let mut impls = NodeSet();
 607             cx.tcx.for_each_impl(debug, |d| {
 608                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 609                     if let Some(node_id) = cx.tcx.hir.as_local_node_id(ty_def.did) {
 610                         impls.insert(node_id);
 611                     }
 612                 }
 613             });
 614
 615             self.impling_types = Some(impls);
 616             debug!("{:?}", self.impling_types);
 617         }
 618
 619         if !self.impling_types.as_ref().unwrap().contains(&item.id) {
 620             cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
 621                          item.span,
 622                          "type does not implement `fmt::Debug`; consider adding #[derive(Debug)] \
 623                           or a manual implementation")
 624         }
 625     }
 626 }
 627
 628 declare_lint! {
 629     pub ANONYMOUS_PARAMETERS,
 630     Allow,
 631     "detects anonymous parameters"
 632 }
 633
 634 /// Checks for use of anonymous parameters (RFC 1685)
 635 #[derive(Clone)]
 636 pub struct AnonymousParameters;
 637
 638 impl LintPass for AnonymousParameters {
 639     fn get_lints(&self) -> LintArray {
 640         lint_array!(ANONYMOUS_PARAMETERS)
 641     }
 642 }
 643
 644 impl EarlyLintPass for AnonymousParameters {
 645     fn check_trait_item(&mut self, cx: &EarlyContext, it: &ast::TraitItem) {
 646         match it.node {
 647             ast::TraitItemKind::Method(ref sig, _) => {
 648                 for arg in sig.decl.inputs.iter() {
 649                     match arg.pat.node {
 650                         ast::PatKind::Ident(_, ident, None) => {
 651                             if ident.name == keywords::Invalid.name() {
 652                                 let ty_snip = cx
 653                                     .sess
 654                                     .source_map()
 655                                     .span_to_snippet(arg.ty.span);
 656
 657                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 658                                     (snip, Applicability::MachineApplicable)
 659                                 } else {
 660                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 661                                 };
 662
 663                                 cx.struct_span_lint(
 664                                     ANONYMOUS_PARAMETERS,
 665                                     arg.pat.span,
 666                                     "anonymous parameters are deprecated and will be \
 667                                      removed in the next edition."
 668                                 ).span_suggestion_with_applicability(
 669                                     arg.pat.span,
 670                                     "Try naming the parameter or explicitly \
 671                                     ignoring it",
 672                                     format!("_: {}", ty_snip),
 673                                     appl
 674                                 ).emit();
 675                             }
 676                         }
 677                         _ => (),
 678                     }
 679                 }
 680             },
 681             _ => (),
 682         }
 683     }
 684 }
 685
 686 /// Checks for incorrect use use of `repr` attributes.
 687 #[derive(Clone)]
 688 pub struct BadRepr;
 689
 690 impl LintPass for BadRepr {
 691     fn get_lints(&self) -> LintArray {
 692         lint_array!()
 693     }
 694 }
 695
 696 impl EarlyLintPass for BadRepr {
 697     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
 698         if attr.name() == "repr" {
 699             let list = attr.meta_item_list();
 700
 701             let repr_str = |lit: &str| { format!("#[repr({})]", lit) };
 702
 703             // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
 704             // no hints (``#[repr]`)
 705             let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
 706             if !has_hints {
 707                 let mut suggested = false;
 708                 let mut warn = if let Some(ref lit) = attr.value_str() {
 709                     // avoid warning about empty `repr` on `#[repr = "foo"]`
 710                     let mut warn = cx.struct_span_lint(
 711                         BAD_REPR,
 712                         attr.span,
 713                         "`repr` attribute isn't configurable with a literal",
 714                     );
 715                     match lit.to_string().as_ref() {
 716                         | "C" | "packed" | "rust" | "transparent"
 717                         | "u8" | "u16" | "u32" | "u64" | "u128" | "usize"
 718                         | "i8" | "i16" | "i32" | "i64" | "i128" | "isize" => {
 719                             // if the literal could have been a valid `repr` arg,
 720                             // suggest the correct syntax
 721                             warn.span_suggestion_with_applicability(
 722                                 attr.span,
 723                                 "give `repr` a hint",
 724                                 repr_str(&lit.as_str()),
 725                                 Applicability::MachineApplicable
 726                             );
 727                             suggested = true;
 728                         }
 729                         _ => {  // the literal wasn't a valid `repr` arg
 730                             warn.span_label(attr.span, "needs a hint");
 731                         }
 732                     };
 733                     warn
 734                 } else {
 735                     let mut warn = cx.struct_span_lint(
 736                         BAD_REPR,
 737                         attr.span,
 738                         "`repr` attribute must have a hint",
 739                     );
 740                     warn.span_label(attr.span, "needs a hint");
 741                     warn
 742                 };
 743                 if !suggested {
 744                     warn.help(&format!(
 745                         "valid hints include `{}`, `{}`, `{}` and `{}`",
 746                         repr_str("C"),
 747                         repr_str("packed"),
 748                         repr_str("rust"),
 749                         repr_str("transparent"),
 750                     ));
 751                     warn.note("for more information, visit \
 752                                <https://doc.rust-lang.org/reference/type-layout.html>");
 753                 }
 754                 warn.emit();
 755             }
 756         }
 757     }
 758 }
 759
 760 /// Checks for use of attributes which have been deprecated.
 761 #[derive(Clone)]
 762 pub struct DeprecatedAttr {
 763     // This is not free to compute, so we want to keep it around, rather than
 764     // compute it for every attribute.
 765     depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeGate)>,
 766 }
 767
 768 impl DeprecatedAttr {
 769     pub fn new() -> DeprecatedAttr {
 770         DeprecatedAttr {
 771             depr_attrs: deprecated_attributes(),
 772         }
 773     }
 774 }
 775
 776 impl LintPass for DeprecatedAttr {
 777     fn get_lints(&self) -> LintArray {
 778         lint_array!()
 779     }
 780 }
 781
 782 impl EarlyLintPass for DeprecatedAttr {
 783     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
 784         for &&(n, _, ref g) in &self.depr_attrs {
 785             if attr.name() == n {
 786                 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
 787                                              ref name,
 788                                              ref reason,
 789                                              _) = g {
 790                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
 791                                       name, reason, link);
 792                     let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
 793                     err.span_suggestion_short_with_applicability(
 794                         attr.span,
 795                         suggestion.unwrap_or("remove this attribute"),
 796                         String::new(),
 797                         Applicability::MachineApplicable
 798                     );
 799                     err.emit();
 800                 }
 801                 return;
 802             }
 803         }
 804     }
 805 }
 806
 807 declare_lint! {
 808     pub UNUSED_DOC_COMMENTS,
 809     Warn,
 810     "detects doc comments that aren't used by rustdoc"
 811 }
 812
 813 #[derive(Copy, Clone)]
 814 pub struct UnusedDocComment;
 815
 816 impl LintPass for UnusedDocComment {
 817     fn get_lints(&self) -> LintArray {
 818         lint_array![UNUSED_DOC_COMMENTS]
 819     }
 820 }
 821
 822 impl UnusedDocComment {
 823     fn warn_if_doc<'a, 'tcx,
 824                    I: Iterator<Item=&'a ast::Attribute>,
 825                    C: LintContext<'tcx>>(&self, mut attrs: I, cx: &C) {
 826         if let Some(attr) = attrs.find(|a| a.is_value_str() && a.check_name("doc")) {
 827             cx.struct_span_lint(UNUSED_DOC_COMMENTS, attr.span, "doc comment not used by rustdoc")
 828               .emit();
 829         }
 830     }
 831 }
 832
 833 impl EarlyLintPass for UnusedDocComment {
 834     fn check_local(&mut self, cx: &EarlyContext, decl: &ast::Local) {
 835         self.warn_if_doc(decl.attrs.iter(), cx);
 836     }
 837
 838     fn check_arm(&mut self, cx: &EarlyContext, arm: &ast::Arm) {
 839         self.warn_if_doc(arm.attrs.iter(), cx);
 840     }
 841
 842     fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
 843         self.warn_if_doc(expr.attrs.iter(), cx);
 844     }
 845 }
 846
 847 declare_lint! {
 848     pub UNCONDITIONAL_RECURSION,
 849     Warn,
 850     "functions that cannot return without calling themselves"
 851 }
 852
 853 #[derive(Copy, Clone)]
 854 pub struct UnconditionalRecursion;
 855
 856
 857 impl LintPass for UnconditionalRecursion {
 858     fn get_lints(&self) -> LintArray {
 859         lint_array![UNCONDITIONAL_RECURSION]
 860     }
 861 }
 862
 863 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnconditionalRecursion {
 864     fn check_fn(&mut self,
 865                 cx: &LateContext,
 866                 fn_kind: FnKind,
 867                 _: &hir::FnDecl,
 868                 body: &hir::Body,
 869                 sp: Span,
 870                 id: ast::NodeId) {
 871         let method = match fn_kind {
 872             FnKind::ItemFn(..) => None,
 873             FnKind::Method(..) => {
 874                 Some(cx.tcx.associated_item(cx.tcx.hir.local_def_id(id)))
 875             }
 876             // closures can't recur, so they don't matter.
 877             FnKind::Closure(_) => return,
 878         };
 879
 880         // Walk through this function (say `f`) looking to see if
 881         // every possible path references itself, i.e. the function is
 882         // called recursively unconditionally. This is done by trying
 883         // to find a path from the entry node to the exit node that
 884         // *doesn't* call `f` by traversing from the entry while
 885         // pretending that calls of `f` are sinks (i.e. ignoring any
 886         // exit edges from them).
 887         //
 888         // NB. this has an edge case with non-returning statements,
 889         // like `loop {}` or `panic!()`: control flow never reaches
 890         // the exit node through these, so one can have a function
 891         // that never actually calls itself but is still picked up by
 892         // this lint:
 893         //
 894         //     fn f(cond: bool) {
 895         //         if !cond { panic!() } // could come from `assert!(cond)`
 896         //         f(false)
 897         //     }
 898         //
 899         // In general, functions of that form may be able to call
 900         // itself a finite number of times and then diverge. The lint
 901         // considers this to be an error for two reasons, (a) it is
 902         // easier to implement, and (b) it seems rare to actually want
 903         // to have behaviour like the above, rather than
 904         // e.g. accidentally recursing after an assert.
 905
 906         let cfg = cfg::CFG::new(cx.tcx, &body);
 907
 908         let mut work_queue = vec![cfg.entry];
 909         let mut reached_exit_without_self_call = false;
 910         let mut self_call_spans = vec![];
 911         let mut visited = FxHashSet::default();
 912
 913         while let Some(idx) = work_queue.pop() {
 914             if idx == cfg.exit {
 915                 // found a path!
 916                 reached_exit_without_self_call = true;
 917                 break;
 918             }
 919
 920             let cfg_id = idx.node_id();
 921             if visited.contains(&cfg_id) {
 922                 // already done
 923                 continue;
 924             }
 925             visited.insert(cfg_id);
 926
 927             // is this a recursive call?
 928             let local_id = cfg.graph.node_data(idx).id();
 929             if local_id != hir::DUMMY_ITEM_LOCAL_ID {
 930                 let node_id = cx.tcx.hir.hir_to_node_id(hir::HirId {
 931                     owner: body.value.hir_id.owner,
 932                     local_id
 933                 });
 934                 let self_recursive = match method {
 935                     Some(ref method) => expr_refers_to_this_method(cx, method, node_id),
 936                     None => expr_refers_to_this_fn(cx, id, node_id),
 937                 };
 938                 if self_recursive {
 939                     self_call_spans.push(cx.tcx.hir.span(node_id));
 940                     // this is a self call, so we shouldn't explore past
 941                     // this node in the CFG.
 942                     continue;
 943                 }
 944             }
 945
 946             // add the successors of this node to explore the graph further.
 947             for (_, edge) in cfg.graph.outgoing_edges(idx) {
 948                 let target_idx = edge.target();
 949                 let target_cfg_id = target_idx.node_id();
 950                 if !visited.contains(&target_cfg_id) {
 951                     work_queue.push(target_idx)
 952                 }
 953             }
 954         }
 955
 956         // Check the number of self calls because a function that
 957         // doesn't return (e.g. calls a `-> !` function or `loop { /*
 958         // no break */ }`) shouldn't be linted unless it actually
 959         // recurs.
 960         if !reached_exit_without_self_call && !self_call_spans.is_empty() {
 961             let sp = cx.tcx.sess.source_map().def_span(sp);
 962             let mut db = cx.struct_span_lint(UNCONDITIONAL_RECURSION,
 963                                              sp,
 964                                              "function cannot return without recursing");
 965             db.span_label(sp, "cannot return without recursing");
 966             // offer some help to the programmer.
 967             for call in &self_call_spans {
 968                 db.span_label(*call, "recursive call site");
 969             }
 970             db.help("a `loop` may express intention better if this is on purpose");
 971             db.emit();
 972         }
 973
 974         // all done
 975         return;
 976
 977         // Functions for identifying if the given Expr NodeId `id`
 978         // represents a call to the function `fn_id`/method `method`.
 979
 980         fn expr_refers_to_this_fn(cx: &LateContext, fn_id: ast::NodeId, id: ast::NodeId) -> bool {
 981             match cx.tcx.hir.get(id) {
 982                 Node::Expr(&hir::Expr { node: hir::ExprKind::Call(ref callee, _), .. }) => {
 983                     let def = if let hir::ExprKind::Path(ref qpath) = callee.node {
 984                         cx.tables.qpath_def(qpath, callee.hir_id)
 985                     } else {
 986                         return false;
 987                     };
 988                     match def {
 989                         Def::Local(..) | Def::Upvar(..) => false,
 990                         _ => def.def_id() == cx.tcx.hir.local_def_id(fn_id)
 991                     }
 992                 }
 993                 _ => false,
 994             }
 995         }
 996
 997         // Check if the expression `id` performs a call to `method`.
 998         fn expr_refers_to_this_method(cx: &LateContext,
 999                                       method: &ty::AssociatedItem,
1000                                       id: ast::NodeId)
1001                                       -> bool {
1002             use rustc::ty::adjustment::*;
1003
1004             // Ignore non-expressions.
1005             let expr = if let Node::Expr(e) = cx.tcx.hir.get(id) {
1006                 e
1007             } else {
1008                 return false;
1009             };
1010
1011             // Check for overloaded autoderef method calls.
1012             let mut source = cx.tables.expr_ty(expr);
1013             for adjustment in cx.tables.expr_adjustments(expr) {
1014                 if let Adjust::Deref(Some(deref)) = adjustment.kind {
1015                     let (def_id, substs) = deref.method_call(cx.tcx, source);
1016                     if method_call_refers_to_method(cx, method, def_id, substs, id) {
1017                         return true;
1018                     }
1019                 }
1020                 source = adjustment.target;
1021             }
1022
1023             // Check for method calls and overloaded operators.
1024             if cx.tables.is_method_call(expr) {
1025                 let hir_id = cx.tcx.hir.definitions().node_to_hir_id(id);
1026                 if let Some(def) = cx.tables.type_dependent_defs().get(hir_id) {
1027                     let def_id = def.def_id();
1028                     let substs = cx.tables.node_substs(hir_id);
1029                     if method_call_refers_to_method(cx, method, def_id, substs, id) {
1030                         return true;
1031                     }
1032                 } else {
1033                     cx.tcx.sess.delay_span_bug(expr.span,
1034                                                "no type-dependent def for method call");
1035                 }
1036             }
1037
1038             // Check for calls to methods via explicit paths (e.g. `T::method()`).
1039             match expr.node {
1040                 hir::ExprKind::Call(ref callee, _) => {
1041                     let def = if let hir::ExprKind::Path(ref qpath) = callee.node {
1042                         cx.tables.qpath_def(qpath, callee.hir_id)
1043                     } else {
1044                         return false;
1045                     };
1046                     match def {
1047                         Def::Method(def_id) => {
1048                             let substs = cx.tables.node_substs(callee.hir_id);
1049                             method_call_refers_to_method(cx, method, def_id, substs, id)
1050                         }
1051                         _ => false,
1052                     }
1053                 }
1054                 _ => false,
1055             }
1056         }
1057
1058         // Check if the method call to the method with the ID `callee_id`
1059         // and instantiated with `callee_substs` refers to method `method`.
1060         fn method_call_refers_to_method<'a, 'tcx>(cx: &LateContext<'a, 'tcx>,
1061                                                   method: &ty::AssociatedItem,
1062                                                   callee_id: DefId,
1063                                                   callee_substs: &Substs<'tcx>,
1064                                                   expr_id: ast::NodeId)
1065                                                   -> bool {
1066             let tcx = cx.tcx;
1067             let callee_item = tcx.associated_item(callee_id);
1068
1069             match callee_item.container {
1070                 // This is an inherent method, so the `def_id` refers
1071                 // directly to the method definition.
1072                 ty::ImplContainer(_) => callee_id == method.def_id,
1073
1074                 // A trait method, from any number of possible sources.
1075                 // Attempt to select a concrete impl before checking.
1076                 ty::TraitContainer(trait_def_id) => {
1077                     let trait_ref = ty::TraitRef::from_method(tcx, trait_def_id, callee_substs);
1078                     let trait_ref = ty::Binder::bind(trait_ref);
1079                     let span = tcx.hir.span(expr_id);
1080                     let obligation =
1081                         traits::Obligation::new(traits::ObligationCause::misc(span, expr_id),
1082                                                 cx.param_env,
1083                                                 trait_ref.to_poly_trait_predicate());
1084
1085                     tcx.infer_ctxt().enter(|infcx| {
1086                         let mut selcx = traits::SelectionContext::new(&infcx);
1087                         match selcx.select(&obligation) {
1088                             // The method comes from a `T: Trait` bound.
1089                             // If `T` is `Self`, then this call is inside
1090                             // a default method definition.
1091                             Ok(Some(traits::VtableParam(_))) => {
1092                                 let on_self = trait_ref.self_ty().is_self();
1093                                 // We can only be recursing in a default
1094                                 // method if we're being called literally
1095                                 // on the `Self` type.
1096                                 on_self && callee_id == method.def_id
1097                             }
1098
1099                             // The `impl` is known, so we check that with a
1100                             // special case:
1101                             Ok(Some(traits::VtableImpl(vtable_impl))) => {
1102                                 let container = ty::ImplContainer(vtable_impl.impl_def_id);
1103                                 // It matches if it comes from the same impl,
1104                                 // and has the same method name.
1105                                 container == method.container &&
1106                                 callee_item.ident.name == method.ident.name
1107                             }
1108
1109                             // There's no way to know if this call is
1110                             // recursive, so we assume it's not.
1111                             _ => false,
1112                         }
1113                     })
1114                 }
1115             }
1116         }
1117     }
1118 }
1119
1120 declare_lint! {
1121     PLUGIN_AS_LIBRARY,
1122     Warn,
1123     "compiler plugin used as ordinary library in non-plugin crate"
1124 }
1125
1126 #[derive(Copy, Clone)]
1127 pub struct PluginAsLibrary;
1128
1129 impl LintPass for PluginAsLibrary {
1130     fn get_lints(&self) -> LintArray {
1131         lint_array![PLUGIN_AS_LIBRARY]
1132     }
1133 }
1134
1135 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
1136     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1137         if cx.sess().plugin_registrar_fn.get().is_some() {
1138             // We're compiling a plugin; it's fine to link other plugins.
1139             return;
1140         }
1141
1142         match it.node {
1143             hir::ItemKind::ExternCrate(..) => (),
1144             _ => return,
1145         };
1146
1147         let def_id = cx.tcx.hir.local_def_id(it.id);
1148         let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
1149             Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
1150             None => {
1151                 // Probably means we aren't linking the crate for some reason.
1152                 //
1153                 // Not sure if / when this could happen.
1154                 return;
1155             }
1156         };
1157
1158         if prfn.is_some() {
1159             cx.span_lint(PLUGIN_AS_LIBRARY,
1160                          it.span,
1161                          "compiler plugin used as an ordinary library");
1162         }
1163     }
1164 }
1165
1166 declare_lint! {
1167     NO_MANGLE_CONST_ITEMS,
1168     Deny,
1169     "const items will not have their symbols exported"
1170 }
1171
1172 declare_lint! {
1173     NO_MANGLE_GENERIC_ITEMS,
1174     Warn,
1175     "generic items must be mangled"
1176 }
1177
1178 #[derive(Copy, Clone)]
1179 pub struct InvalidNoMangleItems;
1180
1181 impl LintPass for InvalidNoMangleItems {
1182     fn get_lints(&self) -> LintArray {
1183         lint_array!(NO_MANGLE_CONST_ITEMS,
1184                     NO_MANGLE_GENERIC_ITEMS)
1185     }
1186 }
1187
1188 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
1189     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1190         match it.node {
1191             hir::ItemKind::Fn(.., ref generics, _) => {
1192                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, "no_mangle") {
1193                     for param in &generics.params {
1194                         match param.kind {
1195                             GenericParamKind::Lifetime { .. } => {}
1196                             GenericParamKind::Type { .. } => {
1197                                 let mut err = cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS,
1198                                                                   it.span,
1199                                                                   "functions generic over \
1200                                                                    types must be mangled");
1201                                 err.span_suggestion_short_with_applicability(
1202                                     no_mangle_attr.span,
1203                                     "remove this attribute",
1204                                     String::new(),
1205                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1206                                     // fix may be to monomorphize source by hand
1207                                     Applicability::MaybeIncorrect
1208                                 );
1209                                 err.emit();
1210                                 break;
1211                             }
1212                         }
1213                     }
1214                 }
1215             }
1216             hir::ItemKind::Const(..) => {
1217                 if attr::contains_name(&it.attrs, "no_mangle") {
1218                     // Const items do not refer to a particular location in memory, and therefore
1219                     // don't have anything to attach a symbol to
1220                     let msg = "const items should never be #[no_mangle]";
1221                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
1222
1223                     // account for "pub const" (#45562)
1224                     let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
1225                         .map(|snippet| snippet.find("const").unwrap_or(0))
1226                         .unwrap_or(0) as u32;
1227                     // `const` is 5 chars
1228                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1229                     err.span_suggestion_with_applicability(
1230                         const_span,
1231                         "try a static value",
1232                         "pub static".to_owned(),
1233                         Applicability::MachineApplicable
1234                     );
1235                     err.emit();
1236                 }
1237             }
1238             _ => {}
1239         }
1240     }
1241 }
1242
1243 #[derive(Clone, Copy)]
1244 pub struct MutableTransmutes;
1245
1246 declare_lint! {
1247     MUTABLE_TRANSMUTES,
1248     Deny,
1249     "mutating transmuted &mut T from &T may cause undefined behavior"
1250 }
1251
1252 impl LintPass for MutableTransmutes {
1253     fn get_lints(&self) -> LintArray {
1254         lint_array!(MUTABLE_TRANSMUTES)
1255     }
1256 }
1257
1258 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
1259     fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
1260         use rustc_target::spec::abi::Abi::RustIntrinsic;
1261
1262         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1263                    consider instead using an UnsafeCell";
1264         match get_transmute_from_to(cx, expr) {
1265             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
1266                 if to_mt == hir::Mutability::MutMutable &&
1267                    from_mt == hir::Mutability::MutImmutable {
1268                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
1269                 }
1270             }
1271             _ => (),
1272         }
1273
1274         fn get_transmute_from_to<'a, 'tcx>
1275             (cx: &LateContext<'a, 'tcx>,
1276              expr: &hir::Expr)
1277              -> Option<(&'tcx ty::TyKind<'tcx>, &'tcx ty::TyKind<'tcx>)> {
1278             let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
1279                 cx.tables.qpath_def(qpath, expr.hir_id)
1280             } else {
1281                 return None;
1282             };
1283             if let Def::Fn(did) = def {
1284                 if !def_id_is_transmute(cx, did) {
1285                     return None;
1286                 }
1287                 let sig = cx.tables.node_id_to_type(expr.hir_id).fn_sig(cx.tcx);
1288                 let from = sig.inputs().skip_binder()[0];
1289                 let to = *sig.output().skip_binder();
1290                 return Some((&from.sty, &to.sty));
1291             }
1292             None
1293         }
1294
1295         fn def_id_is_transmute(cx: &LateContext, def_id: DefId) -> bool {
1296             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
1297             cx.tcx.item_name(def_id) == "transmute"
1298         }
1299     }
1300 }
1301
1302 /// Forbids using the `#[feature(...)]` attribute
1303 #[derive(Copy, Clone)]
1304 pub struct UnstableFeatures;
1305
1306 declare_lint! {
1307     UNSTABLE_FEATURES,
1308     Allow,
1309     "enabling unstable features (deprecated. do not use)"
1310 }
1311
1312 impl LintPass for UnstableFeatures {
1313     fn get_lints(&self) -> LintArray {
1314         lint_array!(UNSTABLE_FEATURES)
1315     }
1316 }
1317
1318 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
1319     fn check_attribute(&mut self, ctx: &LateContext, attr: &ast::Attribute) {
1320         if attr.check_name("feature") {
1321             if let Some(items) = attr.meta_item_list() {
1322                 for item in items {
1323                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
1324                 }
1325             }
1326         }
1327     }
1328 }
1329
1330 /// Lint for unions that contain fields with possibly non-trivial destructors.
1331 pub struct UnionsWithDropFields;
1332
1333 declare_lint! {
1334     UNIONS_WITH_DROP_FIELDS,
1335     Warn,
1336     "use of unions that contain fields with possibly non-trivial drop code"
1337 }
1338
1339 impl LintPass for UnionsWithDropFields {
1340     fn get_lints(&self) -> LintArray {
1341         lint_array!(UNIONS_WITH_DROP_FIELDS)
1342     }
1343 }
1344
1345 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
1346     fn check_item(&mut self, ctx: &LateContext, item: &hir::Item) {
1347         if let hir::ItemKind::Union(ref vdata, _) = item.node {
1348             for field in vdata.fields() {
1349                 let field_ty = ctx.tcx.type_of(ctx.tcx.hir.local_def_id(field.id));
1350                 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1351                     ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1352                                   field.span,
1353                                   "union contains a field with possibly non-trivial drop code, \
1354                                    drop code of union fields is ignored when dropping the union");
1355                     return;
1356                 }
1357             }
1358         }
1359     }
1360 }
1361
1362 /// Lint for items marked `pub` that aren't reachable from other crates
1363 pub struct UnreachablePub;
1364
1365 declare_lint! {
1366     pub UNREACHABLE_PUB,
1367     Allow,
1368     "`pub` items not reachable from crate root"
1369 }
1370
1371 impl LintPass for UnreachablePub {
1372     fn get_lints(&self) -> LintArray {
1373         lint_array!(UNREACHABLE_PUB)
1374     }
1375 }
1376
1377 impl UnreachablePub {
1378     fn perform_lint(&self, cx: &LateContext, what: &str, id: ast::NodeId,
1379                     vis: &hir::Visibility, span: Span, exportable: bool) {
1380         let mut applicability = Applicability::MachineApplicable;
1381         match vis.node {
1382             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1383                 if span.ctxt().outer().expn_info().is_some() {
1384                     applicability = Applicability::MaybeIncorrect;
1385                 }
1386                 let def_span = cx.tcx.sess.source_map().def_span(span);
1387                 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1388                                                   &format!("unreachable `pub` {}", what));
1389                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1390                     "crate"
1391                 } else {
1392                     "pub(crate)"
1393                 }.to_owned();
1394
1395                 err.span_suggestion_with_applicability(vis.span,
1396                                                        "consider restricting its visibility",
1397                                                        replacement,
1398                                                        applicability);
1399                 if exportable {
1400                     err.help("or consider exporting it for use by other crates");
1401                 }
1402                 err.emit();
1403             },
1404             _ => {}
1405         }
1406     }
1407 }
1408
1409
1410 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1411     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
1412         self.perform_lint(cx, "item", item.id, &item.vis, item.span, true);
1413     }
1414
1415     fn check_foreign_item(&mut self, cx: &LateContext, foreign_item: &hir::ForeignItem) {
1416         self.perform_lint(cx, "item", foreign_item.id, &foreign_item.vis,
1417                           foreign_item.span, true);
1418     }
1419
1420     fn check_struct_field(&mut self, cx: &LateContext, field: &hir::StructField) {
1421         self.perform_lint(cx, "field", field.id, &field.vis, field.span, false);
1422     }
1423
1424     fn check_impl_item(&mut self, cx: &LateContext, impl_item: &hir::ImplItem) {
1425         self.perform_lint(cx, "item", impl_item.id, &impl_item.vis, impl_item.span, false);
1426     }
1427 }
1428
1429 /// Lint for trait and lifetime bounds in type aliases being mostly ignored:
1430 /// They are relevant when using associated types, but otherwise neither checked
1431 /// at definition site nor enforced at use site.
1432
1433 pub struct TypeAliasBounds;
1434
1435 declare_lint! {
1436     TYPE_ALIAS_BOUNDS,
1437     Warn,
1438     "bounds in type aliases are not enforced"
1439 }
1440
1441 impl LintPass for TypeAliasBounds {
1442     fn get_lints(&self) -> LintArray {
1443         lint_array!(TYPE_ALIAS_BOUNDS)
1444     }
1445 }
1446
1447 impl TypeAliasBounds {
1448     fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1449         match *qpath {
1450             hir::QPath::TypeRelative(ref ty, _) => {
1451                 // If this is a type variable, we found a `T::Assoc`.
1452                 match ty.node {
1453                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1454                         match path.def {
1455                             Def::TyParam(_) => true,
1456                             _ => false
1457                         }
1458                     }
1459                     _ => false
1460                 }
1461             }
1462             hir::QPath::Resolved(..) => false,
1463         }
1464     }
1465
1466     fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder) {
1467         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1468         // bound.  Let's see if this type does that.
1469
1470         // We use a HIR visitor to walk the type.
1471         use rustc::hir::intravisit::{self, Visitor};
1472         struct WalkAssocTypes<'a, 'db> where 'db: 'a {
1473             err: &'a mut DiagnosticBuilder<'db>
1474         }
1475         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1476             fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1477             {
1478                 intravisit::NestedVisitorMap::None
1479             }
1480
1481             fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1482                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1483                     self.err.span_help(span,
1484                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1485                          associated types in type aliases");
1486                 }
1487                 intravisit::walk_qpath(self, qpath, id, span)
1488             }
1489         }
1490
1491         // Let's go for a walk!
1492         let mut visitor = WalkAssocTypes { err };
1493         visitor.visit_ty(ty);
1494     }
1495 }
1496
1497 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1498     fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
1499         let (ty, type_alias_generics) = match item.node {
1500             hir::ItemKind::Ty(ref ty, ref generics) => (&*ty, generics),
1501             _ => return,
1502         };
1503         let mut suggested_changing_assoc_types = false;
1504         // There must not be a where clause
1505         if !type_alias_generics.where_clause.predicates.is_empty() {
1506             let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1507                 .map(|pred| pred.span()).collect();
1508             let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1509                 "where clauses are not enforced in type aliases");
1510             err.help("the clause will not be checked when the type alias is used, \
1511                       and should be removed");
1512             if !suggested_changing_assoc_types {
1513                 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1514                 suggested_changing_assoc_types = true;
1515             }
1516             err.emit();
1517         }
1518         // The parameters must not have bounds
1519         for param in type_alias_generics.params.iter() {
1520             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1521             if !spans.is_empty() {
1522                 let mut err = cx.struct_span_lint(
1523                     TYPE_ALIAS_BOUNDS,
1524                     spans,
1525                     "bounds on generic parameters are not enforced in type aliases",
1526                 );
1527                 err.help("the bound will not be checked when the type alias is used, \
1528                           and should be removed");
1529                 if !suggested_changing_assoc_types {
1530                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1531                     suggested_changing_assoc_types = true;
1532                 }
1533                 err.emit();
1534             }
1535         }
1536     }
1537 }
1538
1539 /// Lint constants that are erroneous.
1540 /// Without this lint, we might not get any diagnostic if the constant is
1541 /// unused within this crate, even though downstream crates can't use it
1542 /// without producing an error.
1543 pub struct UnusedBrokenConst;
1544
1545 impl LintPass for UnusedBrokenConst {
1546     fn get_lints(&self) -> LintArray {
1547         lint_array!()
1548     }
1549 }
1550
1551 fn validate_const<'a, 'tcx>(
1552     tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
1553     constant: &ty::Const<'tcx>,
1554     param_env: ty::ParamEnv<'tcx>,
1555     gid: ::rustc::mir::interpret::GlobalId<'tcx>,
1556     what: &str,
1557 ) {
1558     let ecx = ::rustc_mir::const_eval::mk_eval_cx(tcx, gid.instance, param_env).unwrap();
1559     let result = (|| {
1560         let op = ecx.const_to_op(constant)?;
1561         let mut ref_tracking = ::rustc_mir::interpret::RefTracking::new(op);
1562         while let Some((op, mut path)) = ref_tracking.todo.pop() {
1563             ecx.validate_operand(
1564                 op,
1565                 &mut path,
1566                 Some(&mut ref_tracking),
1567                 /* const_mode */ true,
1568             )?;
1569         }
1570         Ok(())
1571     })();
1572     if let Err(err) = result {
1573         let (trace, span) = ecx.generate_stacktrace(None);
1574         let err = ::rustc::mir::interpret::ConstEvalErr {
1575             error: err,
1576             stacktrace: trace,
1577             span,
1578         };
1579         let err = err.struct_error(
1580             tcx.at(span),
1581             &format!("this {} likely exhibits undefined behavior", what),
1582         );
1583         if let Some(mut err) = err {
1584             err.note("The rules on what exactly is undefined behavior aren't clear, \
1585                 so this check might be overzealous. Please open an issue on the rust compiler \
1586                 repository if you believe it should not be considered undefined behavior",
1587             );
1588             err.emit();
1589         }
1590     }
1591 }
1592
1593 fn check_const(cx: &LateContext, body_id: hir::BodyId, what: &str) {
1594     let def_id = cx.tcx.hir.body_owner_def_id(body_id);
1595     let is_static = cx.tcx.is_static(def_id).is_some();
1596     let param_env = if is_static {
1597         // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1598         ty::ParamEnv::reveal_all()
1599     } else {
1600         cx.tcx.param_env(def_id)
1601     };
1602     let cid = ::rustc::mir::interpret::GlobalId {
1603         instance: ty::Instance::mono(cx.tcx, def_id),
1604         promoted: None
1605     };
1606     match cx.tcx.const_eval(param_env.and(cid)) {
1607         Ok(val) => validate_const(cx.tcx, val, param_env, cid, what),
1608         Err(err) => {
1609             // errors for statics are already reported directly in the query, avoid duplicates
1610             if !is_static {
1611                 let span = cx.tcx.def_span(def_id);
1612                 err.report_as_lint(
1613                     cx.tcx.at(span),
1614                     &format!("this {} cannot be used", what),
1615                     cx.current_lint_root(),
1616                 );
1617             }
1618         },
1619     }
1620 }
1621
1622 struct UnusedBrokenConstVisitor<'a, 'tcx: 'a>(&'a LateContext<'a, 'tcx>);
1623
1624 impl<'a, 'tcx, 'v> hir::intravisit::Visitor<'v> for UnusedBrokenConstVisitor<'a, 'tcx> {
1625     fn visit_nested_body(&mut self, id: hir::BodyId) {
1626         check_const(self.0, id, "array length");
1627     }
1628     fn nested_visit_map<'this>(&'this mut self) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1629         hir::intravisit::NestedVisitorMap::None
1630     }
1631 }
1632
1633 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1634     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1635         match it.node {
1636             hir::ItemKind::Const(_, body_id) => {
1637                 check_const(cx, body_id, "constant");
1638             },
1639             hir::ItemKind::Static(_, _, body_id) => {
1640                 check_const(cx, body_id, "static");
1641             },
1642             hir::ItemKind::Ty(ref ty, _) => hir::intravisit::walk_ty(
1643                 &mut UnusedBrokenConstVisitor(cx),
1644                 ty
1645             ),
1646             _ => {},
1647         }
1648     }
1649 }
1650
1651 /// Lint for trait and lifetime bounds that don't depend on type parameters
1652 /// which either do nothing, or stop the item from being used.
1653 pub struct TrivialConstraints;
1654
1655 declare_lint! {
1656     TRIVIAL_BOUNDS,
1657     Warn,
1658     "these bounds don't depend on an type parameters"
1659 }
1660
1661 impl LintPass for TrivialConstraints {
1662     fn get_lints(&self) -> LintArray {
1663         lint_array!(TRIVIAL_BOUNDS)
1664     }
1665 }
1666
1667 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1668     fn check_item(
1669         &mut self,
1670         cx: &LateContext<'a, 'tcx>,
1671         item: &'tcx hir::Item,
1672     ) {
1673         use rustc::ty::fold::TypeFoldable;
1674         use rustc::ty::Predicate::*;
1675
1676
1677         if cx.tcx.features().trivial_bounds {
1678             let def_id = cx.tcx.hir.local_def_id(item.id);
1679             let predicates = cx.tcx.predicates_of(def_id);
1680             for &(predicate, span) in &predicates.predicates {
1681                 let predicate_kind_name = match predicate {
1682                     Trait(..) => "Trait",
1683                     TypeOutlives(..) |
1684                     RegionOutlives(..) => "Lifetime",
1685
1686                     // Ignore projections, as they can only be global
1687                     // if the trait bound is global
1688                     Projection(..) |
1689                     // Ignore bounds that a user can't type
1690                     WellFormed(..) |
1691                     ObjectSafe(..) |
1692                     ClosureKind(..) |
1693                     Subtype(..) |
1694                     ConstEvaluatable(..) => continue,
1695                 };
1696                 if predicate.is_global() {
1697                     cx.span_lint(
1698                         TRIVIAL_BOUNDS,
1699                         span,
1700                         &format!("{} bound {} does not depend on any type \
1701                                 or lifetime parameters", predicate_kind_name, predicate),
1702                     );
1703                 }
1704             }
1705         }
1706     }
1707 }
1708
1709
1710 /// Does nothing as a lint pass, but registers some `Lint`s
1711 /// which are used by other parts of the compiler.
1712 #[derive(Copy, Clone)]
1713 pub struct SoftLints;
1714
1715 impl LintPass for SoftLints {
1716     fn get_lints(&self) -> LintArray {
1717         lint_array!(
1718             WHILE_TRUE,
1719             BOX_POINTERS,
1720             NON_SHORTHAND_FIELD_PATTERNS,
1721             UNSAFE_CODE,
1722             MISSING_DOCS,
1723             MISSING_COPY_IMPLEMENTATIONS,
1724             MISSING_DEBUG_IMPLEMENTATIONS,
1725             ANONYMOUS_PARAMETERS,
1726             UNUSED_DOC_COMMENTS,
1727             UNCONDITIONAL_RECURSION,
1728             PLUGIN_AS_LIBRARY,
1729             NO_MANGLE_CONST_ITEMS,
1730             NO_MANGLE_GENERIC_ITEMS,
1731             MUTABLE_TRANSMUTES,
1732             UNSTABLE_FEATURES,
1733             UNIONS_WITH_DROP_FIELDS,
1734             UNREACHABLE_PUB,
1735             TYPE_ALIAS_BOUNDS,
1736             TRIVIAL_BOUNDS
1737         )
1738     }
1739 }
1740
1741 declare_lint! {
1742     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1743     Allow,
1744     "`...` range patterns are deprecated"
1745 }
1746
1747
1748 pub struct EllipsisInclusiveRangePatterns;
1749
1750 impl LintPass for EllipsisInclusiveRangePatterns {
1751     fn get_lints(&self) -> LintArray {
1752         lint_array!(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS)
1753     }
1754 }
1755
1756 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1757     fn check_pat(&mut self, cx: &EarlyContext, pat: &ast::Pat) {
1758         use self::ast::{PatKind, RangeEnd, RangeSyntax};
1759
1760         if let PatKind::Range(
1761             _, _, Spanned { span, node: RangeEnd::Included(RangeSyntax::DotDotDot) }
1762         ) = pat.node {
1763             let msg = "`...` range patterns are deprecated";
1764             let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, span, msg);
1765             err.span_suggestion_short_with_applicability(
1766                 span, "use `..=` for an inclusive range", "..=".to_owned(),
1767                 // FIXME: outstanding problem with precedence in ref patterns:
1768                 // https://github.com/rust-lang/rust/issues/51043#issuecomment-392252285
1769                 Applicability::MaybeIncorrect
1770             );
1771             err.emit()
1772         }
1773     }
1774 }
1775
1776 declare_lint! {
1777     UNNAMEABLE_TEST_ITEMS,
1778     Warn,
1779     "detects an item that cannot be named being marked as #[test_case]",
1780     report_in_external_macro: true
1781 }
1782
1783 pub struct UnnameableTestItems {
1784     boundary: ast::NodeId, // NodeId of the item under which things are not nameable
1785     items_nameable: bool,
1786 }
1787
1788 impl UnnameableTestItems {
1789     pub fn new() -> Self {
1790         Self {
1791             boundary: ast::DUMMY_NODE_ID,
1792             items_nameable: true
1793         }
1794     }
1795 }
1796
1797 impl LintPass for UnnameableTestItems {
1798     fn get_lints(&self) -> LintArray {
1799         lint_array!(UNNAMEABLE_TEST_ITEMS)
1800     }
1801 }
1802
1803 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1804     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
1805         if self.items_nameable {
1806             if let hir::ItemKind::Mod(..) = it.node {}
1807             else {
1808                 self.items_nameable = false;
1809                 self.boundary = it.id;
1810             }
1811             return;
1812         }
1813
1814         if let Some(attr) = attr::find_by_name(&it.attrs, "rustc_test_marker") {
1815             cx.struct_span_lint(
1816                 UNNAMEABLE_TEST_ITEMS,
1817                 attr.span,
1818                 "cannot test inner items",
1819             ).emit();
1820         }
1821     }
1822
1823     fn check_item_post(&mut self, _cx: &LateContext, it: &hir::Item) {
1824         if !self.items_nameable && self.boundary == it.id {
1825             self.items_nameable = true;
1826         }
1827     }
1828 }
1829
1830 declare_lint! {
1831     pub KEYWORD_IDENTS,
1832     Allow,
1833     "detects edition keywords being used as an identifier"
1834 }
1835
1836 /// Checks for uses of edtion keywords used as an identifier
1837 #[derive(Clone)]
1838 pub struct KeywordIdents;
1839
1840 impl LintPass for KeywordIdents {
1841     fn get_lints(&self) -> LintArray {
1842         lint_array!(KEYWORD_IDENTS)
1843     }
1844 }
1845
1846 impl KeywordIdents {
1847     fn check_tokens(&mut self, cx: &EarlyContext, tokens: TokenStream) {
1848         for tt in tokens.into_trees() {
1849             match tt {
1850                 TokenTree::Token(span, tok) => match tok.ident() {
1851                     // only report non-raw idents
1852                     Some((ident, false)) => {
1853                         self.check_ident(cx, ast::Ident {
1854                             span: span.substitute_dummy(ident.span),
1855                             ..ident
1856                         });
1857                     }
1858                     _ => {},
1859                 }
1860                 TokenTree::Delimited(_, ref delim) => {
1861                     self.check_tokens(cx, delim.tts.clone().into())
1862                 },
1863             }
1864         }
1865     }
1866 }
1867
1868 impl EarlyLintPass for KeywordIdents {
1869     fn check_mac_def(&mut self, cx: &EarlyContext, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1870         self.check_tokens(cx, mac_def.stream());
1871     }
1872     fn check_mac(&mut self, cx: &EarlyContext, mac: &ast::Mac) {
1873         self.check_tokens(cx, mac.node.tts.clone().into());
1874     }
1875     fn check_ident(&mut self, cx: &EarlyContext, ident: ast::Ident) {
1876         let ident_str = &ident.as_str()[..];
1877         let cur_edition = cx.sess.edition();
1878         let is_raw_ident = |ident: ast::Ident| {
1879             cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span)
1880         };
1881         let next_edition = match cur_edition {
1882             Edition::Edition2015 => {
1883                 match ident_str {
1884                     "async" | "try" | "dyn" => Edition::Edition2018,
1885                     // Only issue warnings for `await` if the `async_await`
1886                     // feature isn't being used. Otherwise, users need
1887                     // to keep using `await` for the macro exposed by std.
1888                     "await" if !cx.sess.features_untracked().async_await => Edition::Edition2018,
1889                     _ => return,
1890                 }
1891             }
1892
1893             // no new keywords yet for 2018 edition and beyond
1894             // However, `await` is a "false" keyword in the 2018 edition,
1895             // and can only be used if the `async_await` feature is enabled.
1896             // Otherwise, we emit an error.
1897             _ => {
1898                 if "await" == ident_str
1899                     && !cx.sess.features_untracked().async_await
1900                     && !is_raw_ident(ident)
1901                 {
1902                     let mut err = struct_span_err!(
1903                         cx.sess,
1904                         ident.span,
1905                         E0721,
1906                         "`await` is a keyword in the {} edition", cur_edition,
1907                     );
1908                     err.span_suggestion_with_applicability(
1909                         ident.span,
1910                         "you can use a raw identifier to stay compatible",
1911                         "r#await".to_string(),
1912                         Applicability::MachineApplicable,
1913                     );
1914                     err.emit();
1915                 }
1916                 return
1917             },
1918         };
1919
1920         // don't lint `r#foo`
1921         if is_raw_ident(ident) {
1922             return;
1923         }
1924
1925         let mut lint = cx.struct_span_lint(
1926             KEYWORD_IDENTS,
1927             ident.span,
1928             &format!("`{}` is a keyword in the {} edition",
1929                      ident.as_str(),
1930                      next_edition),
1931         );
1932         lint.span_suggestion_with_applicability(
1933             ident.span,
1934             "you can use a raw identifier to stay compatible",
1935             format!("r#{}", ident.as_str()),
1936             Applicability::MachineApplicable,
1937         );
1938         lint.emit()
1939     }
1940 }
1941
1942
1943 pub struct ExplicitOutlivesRequirements;
1944
1945 impl LintPass for ExplicitOutlivesRequirements {
1946     fn get_lints(&self) -> LintArray {
1947         lint_array![EXPLICIT_OUTLIVES_REQUIREMENTS]
1948     }
1949 }
1950
1951 impl ExplicitOutlivesRequirements {
1952     fn collect_outlives_bound_spans(
1953         &self,
1954         cx: &LateContext,
1955         item_def_id: DefId,
1956         param_name: &str,
1957         bounds: &hir::GenericBounds,
1958         infer_static: bool
1959     ) -> Vec<(usize, Span)> {
1960         // For lack of a more elegant strategy for comparing the `ty::Predicate`s
1961         // returned by this query with the params/bounds grabbed from the HIR—and
1962         // with some regrets—we're going to covert the param/lifetime names to
1963         // strings
1964         let inferred_outlives = cx.tcx.inferred_outlives_of(item_def_id);
1965
1966         let ty_lt_names = inferred_outlives.iter().filter_map(|pred| {
1967             let binder = match pred {
1968                 ty::Predicate::TypeOutlives(binder) => binder,
1969                 _ => { return None; }
1970             };
1971             let ty_outlives_pred = binder.skip_binder();
1972             let ty_name = match ty_outlives_pred.0.sty {
1973                 ty::Param(param) => param.name.to_string(),
1974                 _ => { return None; }
1975             };
1976             let lt_name = match ty_outlives_pred.1 {
1977                 ty::RegionKind::ReEarlyBound(region) => {
1978                     region.name.to_string()
1979                 },
1980                 _ => { return None; }
1981             };
1982             Some((ty_name, lt_name))
1983         }).collect::<Vec<_>>();
1984
1985         let mut bound_spans = Vec::new();
1986         for (i, bound) in bounds.iter().enumerate() {
1987             if let hir::GenericBound::Outlives(lifetime) = bound {
1988                 let is_static = match lifetime.name {
1989                     hir::LifetimeName::Static => true,
1990                     _ => false
1991                 };
1992                 if is_static && !infer_static {
1993                     // infer-outlives for 'static is still feature-gated (tracking issue #44493)
1994                     continue;
1995                 }
1996
1997                 let lt_name = &lifetime.name.ident().to_string();
1998                 if ty_lt_names.contains(&(param_name.to_owned(), lt_name.to_owned())) {
1999                     bound_spans.push((i, bound.span()));
2000                 }
2001             }
2002         }
2003         bound_spans
2004     }
2005
2006     fn consolidate_outlives_bound_spans(
2007         &self,
2008         lo: Span,
2009         bounds: &hir::GenericBounds,
2010         bound_spans: Vec<(usize, Span)>
2011     ) -> Vec<Span> {
2012         if bounds.is_empty() {
2013             return Vec::new();
2014         }
2015         if bound_spans.len() == bounds.len() {
2016             let (_, last_bound_span) = bound_spans[bound_spans.len()-1];
2017             // If all bounds are inferable, we want to delete the colon, so
2018             // start from just after the parameter (span passed as argument)
2019             vec![lo.to(last_bound_span)]
2020         } else {
2021             let mut merged = Vec::new();
2022             let mut last_merged_i = None;
2023
2024             let mut from_start = true;
2025             for (i, bound_span) in bound_spans {
2026                 match last_merged_i {
2027                     // If the first bound is inferable, our span should also eat the trailing `+`
2028                     None if i == 0 => {
2029                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2030                         last_merged_i = Some(0);
2031                     },
2032                     // If consecutive bounds are inferable, merge their spans
2033                     Some(h) if i == h+1 => {
2034                         if let Some(tail) = merged.last_mut() {
2035                             // Also eat the trailing `+` if the first
2036                             // more-than-one bound is inferable
2037                             let to_span = if from_start && i < bounds.len() {
2038                                 bounds[i+1].span().shrink_to_lo()
2039                             } else {
2040                                 bound_span
2041                             };
2042                             *tail = tail.to(to_span);
2043                             last_merged_i = Some(i);
2044                         } else {
2045                             bug!("another bound-span visited earlier");
2046                         }
2047                     },
2048                     _ => {
2049                         // When we find a non-inferable bound, subsequent inferable bounds
2050                         // won't be consecutive from the start (and we'll eat the leading
2051                         // `+` rather than the trailing one)
2052                         from_start = false;
2053                         merged.push(bounds[i-1].span().shrink_to_hi().to(bound_span));
2054                         last_merged_i = Some(i);
2055                     }
2056                 }
2057             }
2058             merged
2059         }
2060     }
2061 }
2062
2063 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
2064     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
2065         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2066         let def_id = cx.tcx.hir.local_def_id(item.id);
2067         if let hir::ItemKind::Struct(_, ref generics) = item.node {
2068             let mut bound_count = 0;
2069             let mut lint_spans = Vec::new();
2070
2071             for param in &generics.params {
2072                 let param_name = match param.kind {
2073                     hir::GenericParamKind::Lifetime { .. } => { continue; },
2074                     hir::GenericParamKind::Type { .. } => {
2075                         match param.name {
2076                             hir::ParamName::Fresh(_) => { continue; },
2077                             hir::ParamName::Error => { continue; },
2078                             hir::ParamName::Plain(name) => name.to_string()
2079                         }
2080                     }
2081                 };
2082                 let bound_spans = self.collect_outlives_bound_spans(
2083                     cx, def_id, &param_name, &param.bounds, infer_static
2084                 );
2085                 bound_count += bound_spans.len();
2086                 lint_spans.extend(
2087                     self.consolidate_outlives_bound_spans(
2088                         param.span.shrink_to_hi(), &param.bounds, bound_spans
2089                     )
2090                 );
2091             }
2092
2093             let mut where_lint_spans = Vec::new();
2094             let mut dropped_predicate_count = 0;
2095             let num_predicates = generics.where_clause.predicates.len();
2096             for (i, where_predicate) in generics.where_clause.predicates.iter().enumerate() {
2097                 if let hir::WherePredicate::BoundPredicate(predicate) = where_predicate {
2098                     let param_name = match predicate.bounded_ty.node {
2099                         hir::TyKind::Path(ref qpath) => {
2100                             if let hir::QPath::Resolved(None, ty_param_path) = qpath {
2101                                 ty_param_path.segments[0].ident.to_string()
2102                             } else {
2103                                 continue;
2104                             }
2105                         },
2106                         _ => { continue; }
2107                     };
2108                     let bound_spans = self.collect_outlives_bound_spans(
2109                         cx, def_id, &param_name, &predicate.bounds, infer_static
2110                     );
2111                     bound_count += bound_spans.len();
2112
2113                     let drop_predicate = bound_spans.len() == predicate.bounds.len();
2114                     if drop_predicate {
2115                         dropped_predicate_count += 1;
2116                     }
2117
2118                     // If all the bounds on a predicate were inferable and there are
2119                     // further predicates, we want to eat the trailing comma
2120                     if drop_predicate && i + 1 < num_predicates {
2121                         let next_predicate_span = generics.where_clause.predicates[i+1].span();
2122                         where_lint_spans.push(
2123                             predicate.span.to(next_predicate_span.shrink_to_lo())
2124                         );
2125                     } else {
2126                         where_lint_spans.extend(
2127                             self.consolidate_outlives_bound_spans(
2128                                 predicate.span.shrink_to_lo(),
2129                                 &predicate.bounds,
2130                                 bound_spans
2131                             )
2132                         );
2133                     }
2134                 }
2135             }
2136
2137             // If all predicates are inferable, drop the entire clause
2138             // (including the `where`)
2139             if num_predicates > 0 && dropped_predicate_count == num_predicates {
2140                 let full_where_span = generics.span.shrink_to_hi()
2141                     .to(generics.where_clause.span()
2142                     .expect("span of (nonempty) where clause should exist"));
2143                 lint_spans.push(
2144                     full_where_span
2145                 );
2146             } else {
2147                 lint_spans.extend(where_lint_spans);
2148             }
2149
2150             if !lint_spans.is_empty() {
2151                 let mut err = cx.struct_span_lint(
2152                     EXPLICIT_OUTLIVES_REQUIREMENTS,
2153                     lint_spans.clone(),
2154                     "outlives requirements can be inferred"
2155                 );
2156                 err.multipart_suggestion_with_applicability(
2157                     if bound_count == 1 {
2158                         "remove this bound"
2159                     } else {
2160                         "remove these bounds"
2161                     },
2162                     lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
2163                     Applicability::MachineApplicable
2164                 );
2165                 err.emit();
2166             }
2167
2168         }
2169     }
2170
2171 }