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 std::fmt::Write;
  25
  26 use rustc::hir::def::{Res, DefKind};
  27 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  28 use rustc::ty::{self, Ty, TyCtxt, layout::VariantIdx};
  29 use rustc::{lint, util};
  30 use hir::Node;
  31 use util::nodemap::HirIdSet;
  32 use lint::{LateContext, LintContext, LintArray};
  33 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
  34
  35 use rustc::util::nodemap::FxHashSet;
  36
  37 use syntax::tokenstream::{TokenTree, TokenStream};
  38 use syntax::ast::{self, Expr};
  39 use syntax::ptr::P;
  40 use syntax::attr::{self, HasAttrs, AttributeTemplate};
  41 use syntax::source_map::Spanned;
  42 use syntax::edition::Edition;
  43 use syntax::feature_gate::{self, AttributeGate, AttributeType};
  44 use syntax::feature_gate::{Stability, deprecated_attributes};
  45 use syntax_pos::{BytePos, Span};
  46 use syntax::symbol::{Symbol, kw, sym};
  47 use syntax::errors::{Applicability, DiagnosticBuilder};
  48 use syntax::print::pprust::expr_to_string;
  49 use syntax::visit::FnKind;
  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 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
  67
  68 /// Traverse through any amount of parenthesis and return the first non-parens expression.
  69 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
  70     while let ast::ExprKind::Paren(sub) = &expr.kind {
  71         expr = sub;
  72     }
  73     expr
  74 }
  75
  76 impl EarlyLintPass for WhileTrue {
  77     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
  78         if let ast::ExprKind::While(cond, ..) = &e.kind {
  79             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
  80                 if let ast::LitKind::Bool(true) = lit.kind {
  81                     if !lit.span.from_expansion() {
  82                         let msg = "denote infinite loops with `loop { ... }`";
  83                         let condition_span = cx.sess.source_map().def_span(e.span);
  84                         cx.struct_span_lint(WHILE_TRUE, condition_span, msg)
  85                             .span_suggestion_short(
  86                                 condition_span,
  87                                 "use `loop`",
  88                                 "loop".to_owned(),
  89                                 Applicability::MachineApplicable
  90                             )
  91                             .emit();
  92                     }
  93                 }
  94             }
  95         }
  96     }
  97 }
  98
  99 declare_lint! {
 100     BOX_POINTERS,
 101     Allow,
 102     "use of owned (Box type) heap memory"
 103 }
 104
 105 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
 106
 107 impl BoxPointers {
 108     fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
 109         for leaf_ty in ty.walk() {
 110             if leaf_ty.is_box() {
 111                 let m = format!("type uses owned (Box type) pointers: {}", ty);
 112                 cx.span_lint(BOX_POINTERS, span, &m);
 113             }
 114         }
 115     }
 116 }
 117
 118 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
 119     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 120         match it.node {
 121             hir::ItemKind::Fn(..) |
 122             hir::ItemKind::TyAlias(..) |
 123             hir::ItemKind::Enum(..) |
 124             hir::ItemKind::Struct(..) |
 125             hir::ItemKind::Union(..) => {
 126                 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 127                 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
 128             }
 129             _ => ()
 130         }
 131
 132         // If it's a struct, we also have to check the fields' types
 133         match it.node {
 134             hir::ItemKind::Struct(ref struct_def, _) |
 135             hir::ItemKind::Union(ref struct_def, _) => {
 136                 for struct_field in struct_def.fields() {
 137                     let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
 138                     self.check_heap_type(cx, struct_field.span,
 139                                          cx.tcx.type_of(def_id));
 140                 }
 141             }
 142             _ => (),
 143         }
 144     }
 145
 146     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
 147         let ty = cx.tables.node_type(e.hir_id);
 148         self.check_heap_type(cx, e.span, ty);
 149     }
 150 }
 151
 152 declare_lint! {
 153     NON_SHORTHAND_FIELD_PATTERNS,
 154     Warn,
 155     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
 156 }
 157
 158 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
 159
 160 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
 161     fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat) {
 162         if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.kind {
 163             let variant = cx.tables.pat_ty(pat).ty_adt_def()
 164                                    .expect("struct pattern type is not an ADT")
 165                                    .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
 166             for fieldpat in field_pats {
 167                 if fieldpat.is_shorthand {
 168                     continue;
 169                 }
 170                 if fieldpat.span.from_expansion() {
 171                     // Don't lint if this is a macro expansion: macro authors
 172                     // shouldn't have to worry about this kind of style issue
 173                     // (Issue #49588)
 174                     continue;
 175                 }
 176                 if let PatKind::Binding(_, _, ident, None) = fieldpat.pat.kind {
 177                     if cx.tcx.find_field_index(ident, &variant) ==
 178                        Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables)) {
 179                         let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
 180                                      fieldpat.span,
 181                                      &format!("the `{}:` in this pattern is redundant", ident));
 182                         let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
 183                                                                                  ':');
 184                         err.span_suggestion_short(
 185                             subspan,
 186                             "remove this",
 187                             ident.to_string(),
 188                             Applicability::MachineApplicable
 189                         );
 190                         err.emit();
 191                     }
 192                 }
 193             }
 194         }
 195     }
 196 }
 197
 198 declare_lint! {
 199     UNSAFE_CODE,
 200     Allow,
 201     "usage of `unsafe` code"
 202 }
 203
 204 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
 205
 206 impl UnsafeCode {
 207     fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
 208         // This comes from a macro that has `#[allow_internal_unsafe]`.
 209         if span.allows_unsafe() {
 210             return;
 211         }
 212
 213         cx.span_lint(UNSAFE_CODE, span, desc);
 214     }
 215 }
 216
 217 impl EarlyLintPass for UnsafeCode {
 218     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 219         if attr.check_name(sym::allow_internal_unsafe) {
 220             self.report_unsafe(cx, attr.span, "`allow_internal_unsafe` allows defining \
 221                                                macros using unsafe without triggering \
 222                                                the `unsafe_code` lint at their call site");
 223         }
 224     }
 225
 226     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
 227         if let ast::ExprKind::Block(ref blk, _) = e.kind {
 228             // Don't warn about generated blocks; that'll just pollute the output.
 229             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
 230                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
 231             }
 232         }
 233     }
 234
 235     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
 236         match it.node {
 237             ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
 238                 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
 239             }
 240
 241             ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
 242                 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
 243             }
 244
 245             _ => return,
 246         }
 247     }
 248
 249     fn check_fn(&mut self,
 250                 cx: &EarlyContext<'_>,
 251                 fk: FnKind<'_>,
 252                 _: &ast::FnDecl,
 253                 span: Span,
 254                 _: ast::NodeId) {
 255         match fk {
 256             FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
 257                 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
 258             }
 259
 260             FnKind::Method(_, sig, ..) => {
 261                 if sig.header.unsafety == ast::Unsafety::Unsafe {
 262                     self.report_unsafe(cx, span, "implementation of an `unsafe` method")
 263                 }
 264             }
 265
 266             _ => (),
 267         }
 268     }
 269
 270     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::TraitItem) {
 271         if let ast::TraitItemKind::Method(ref sig, None) = item.kind {
 272             if sig.header.unsafety == ast::Unsafety::Unsafe {
 273                 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
 274             }
 275         }
 276     }
 277 }
 278
 279 declare_lint! {
 280     pub MISSING_DOCS,
 281     Allow,
 282     "detects missing documentation for public members",
 283     report_in_external_macro: true
 284 }
 285
 286 pub struct MissingDoc {
 287     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
 288     doc_hidden_stack: Vec<bool>,
 289
 290     /// Private traits or trait items that leaked through. Don't check their methods.
 291     private_traits: FxHashSet<hir::HirId>,
 292 }
 293
 294 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 295
 296 fn has_doc(attr: &ast::Attribute) -> bool {
 297     if !attr.check_name(sym::doc) {
 298         return false;
 299     }
 300
 301     if attr.is_value_str() {
 302         return true;
 303     }
 304
 305     if let Some(list) = attr.meta_item_list() {
 306         for meta in list {
 307             if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
 308                 return true;
 309             }
 310         }
 311     }
 312
 313     false
 314 }
 315
 316 impl MissingDoc {
 317     pub fn new() -> MissingDoc {
 318         MissingDoc {
 319             doc_hidden_stack: vec![false],
 320             private_traits: FxHashSet::default(),
 321         }
 322     }
 323
 324     fn doc_hidden(&self) -> bool {
 325         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
 326     }
 327
 328     fn check_missing_docs_attrs(&self,
 329                                 cx: &LateContext<'_, '_>,
 330                                 id: Option<hir::HirId>,
 331                                 attrs: &[ast::Attribute],
 332                                 sp: Span,
 333                                 desc: &'static str) {
 334         // If we're building a test harness, then warning about
 335         // documentation is probably not really relevant right now.
 336         if cx.sess().opts.test {
 337             return;
 338         }
 339
 340         // `#[doc(hidden)]` disables missing_docs check.
 341         if self.doc_hidden() {
 342             return;
 343         }
 344
 345         // Only check publicly-visible items, using the result from the privacy pass.
 346         // It's an option so the crate root can also use this function (it doesn't
 347         // have a `NodeId`).
 348         if let Some(id) = id {
 349             if !cx.access_levels.is_exported(id) {
 350                 return;
 351             }
 352         }
 353
 354         let has_doc = attrs.iter().any(|a| has_doc(a));
 355         if !has_doc {
 356             cx.span_lint(MISSING_DOCS,
 357                          cx.tcx.sess.source_map().def_span(sp),
 358                          &format!("missing documentation for {}", desc));
 359         }
 360     }
 361 }
 362
 363 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
 364     fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
 365         let doc_hidden = self.doc_hidden() ||
 366                          attrs.iter().any(|attr| {
 367             attr.check_name(sym::doc) &&
 368             match attr.meta_item_list() {
 369                 None => false,
 370                 Some(l) => attr::list_contains_name(&l, sym::hidden),
 371             }
 372         });
 373         self.doc_hidden_stack.push(doc_hidden);
 374     }
 375
 376     fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
 377         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
 378     }
 379
 380     fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate) {
 381         self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
 382
 383         for macro_def in &krate.exported_macros {
 384             let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
 385             if !has_doc {
 386                 cx.span_lint(MISSING_DOCS,
 387                              cx.tcx.sess.source_map().def_span(macro_def.span),
 388                              "missing documentation for macro");
 389             }
 390         }
 391     }
 392
 393     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 394         let desc = match it.node {
 395             hir::ItemKind::Fn(..) => "a function",
 396             hir::ItemKind::Mod(..) => "a module",
 397             hir::ItemKind::Enum(..) => "an enum",
 398             hir::ItemKind::Struct(..) => "a struct",
 399             hir::ItemKind::Union(..) => "a union",
 400             hir::ItemKind::Trait(.., ref trait_item_refs) => {
 401                 // Issue #11592: traits are always considered exported, even when private.
 402                 if let hir::VisibilityKind::Inherited = it.vis.node {
 403                     self.private_traits.insert(it.hir_id);
 404                     for trait_item_ref in trait_item_refs {
 405                         self.private_traits.insert(trait_item_ref.id.hir_id);
 406                     }
 407                     return;
 408                 }
 409                 "a trait"
 410             }
 411             hir::ItemKind::TyAlias(..) => "a type alias",
 412             hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
 413                 // If the trait is private, add the impl items to `private_traits` so they don't get
 414                 // reported for missing docs.
 415                 let real_trait = trait_ref.path.res.def_id();
 416                 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
 417                     match cx.tcx.hir().find(hir_id) {
 418                         Some(Node::Item(item)) => {
 419                             if let hir::VisibilityKind::Inherited = item.vis.node {
 420                                 for impl_item_ref in impl_item_refs {
 421                                     self.private_traits.insert(impl_item_ref.id.hir_id);
 422                                 }
 423                             }
 424                         }
 425                         _ => {}
 426                     }
 427                 }
 428                 return;
 429             }
 430             hir::ItemKind::Const(..) => "a constant",
 431             hir::ItemKind::Static(..) => "a static",
 432             _ => return,
 433         };
 434
 435         self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
 436     }
 437
 438     fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem) {
 439         if self.private_traits.contains(&trait_item.hir_id) {
 440             return;
 441         }
 442
 443         let desc = match trait_item.kind {
 444             hir::TraitItemKind::Const(..) => "an associated constant",
 445             hir::TraitItemKind::Method(..) => "a trait method",
 446             hir::TraitItemKind::Type(..) => "an associated type",
 447         };
 448
 449         self.check_missing_docs_attrs(cx,
 450                                       Some(trait_item.hir_id),
 451                                       &trait_item.attrs,
 452                                       trait_item.span,
 453                                       desc);
 454     }
 455
 456     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
 457         // If the method is an impl for a trait, don't doc.
 458         if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
 459             return;
 460         }
 461
 462         let desc = match impl_item.kind {
 463             hir::ImplItemKind::Const(..) => "an associated constant",
 464             hir::ImplItemKind::Method(..) => "a method",
 465             hir::ImplItemKind::TyAlias(_) => "an associated type",
 466             hir::ImplItemKind::OpaqueTy(_) => "an associated `impl Trait` type",
 467         };
 468         self.check_missing_docs_attrs(cx,
 469                                       Some(impl_item.hir_id),
 470                                       &impl_item.attrs,
 471                                       impl_item.span,
 472                                       desc);
 473     }
 474
 475     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField) {
 476         if !sf.is_positional() {
 477             self.check_missing_docs_attrs(cx,
 478                                           Some(sf.hir_id),
 479                                           &sf.attrs,
 480                                           sf.span,
 481                                           "a struct field")
 482         }
 483     }
 484
 485     fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant) {
 486         self.check_missing_docs_attrs(cx,
 487                                       Some(v.id),
 488                                       &v.attrs,
 489                                       v.span,
 490                                       "a variant");
 491     }
 492 }
 493
 494 declare_lint! {
 495     pub MISSING_COPY_IMPLEMENTATIONS,
 496     Allow,
 497     "detects potentially-forgotten implementations of `Copy`"
 498 }
 499
 500 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
 501
 502 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
 503     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
 504         if !cx.access_levels.is_reachable(item.hir_id) {
 505             return;
 506         }
 507         let (def, ty) = match item.node {
 508             hir::ItemKind::Struct(_, ref ast_generics) => {
 509                 if !ast_generics.params.is_empty() {
 510                     return;
 511                 }
 512                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 513                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 514             }
 515             hir::ItemKind::Union(_, ref ast_generics) => {
 516                 if !ast_generics.params.is_empty() {
 517                     return;
 518                 }
 519                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 520                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 521             }
 522             hir::ItemKind::Enum(_, ref ast_generics) => {
 523                 if !ast_generics.params.is_empty() {
 524                     return;
 525                 }
 526                 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
 527                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
 528             }
 529             _ => return,
 530         };
 531         if def.has_dtor(cx.tcx) {
 532             return;
 533         }
 534         let param_env = ty::ParamEnv::empty();
 535         if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
 536             return;
 537         }
 538         if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
 539             cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
 540                          item.span,
 541                          "type could implement `Copy`; consider adding `impl \
 542                           Copy`")
 543         }
 544     }
 545 }
 546
 547 declare_lint! {
 548     MISSING_DEBUG_IMPLEMENTATIONS,
 549     Allow,
 550     "detects missing implementations of fmt::Debug"
 551 }
 552
 553 #[derive(Default)]
 554 pub struct MissingDebugImplementations {
 555     impling_types: Option<HirIdSet>,
 556 }
 557
 558 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 559
 560 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 561     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
 562         if !cx.access_levels.is_reachable(item.hir_id) {
 563             return;
 564         }
 565
 566         match item.node {
 567             hir::ItemKind::Struct(..) |
 568             hir::ItemKind::Union(..) |
 569             hir::ItemKind::Enum(..) => {}
 570             _ => return,
 571         }
 572
 573         let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
 574             Some(debug) => debug,
 575             None => return,
 576         };
 577
 578         if self.impling_types.is_none() {
 579             let mut impls = HirIdSet::default();
 580             cx.tcx.for_each_impl(debug, |d| {
 581                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
 582                     if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
 583                         impls.insert(hir_id);
 584                     }
 585                 }
 586             });
 587
 588             self.impling_types = Some(impls);
 589             debug!("{:?}", self.impling_types);
 590         }
 591
 592         if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
 593             cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
 594                          item.span,
 595                          "type does not implement `fmt::Debug`; consider adding `#[derive(Debug)]` \
 596                           or a manual implementation")
 597         }
 598     }
 599 }
 600
 601 declare_lint! {
 602     pub ANONYMOUS_PARAMETERS,
 603     Allow,
 604     "detects anonymous parameters"
 605 }
 606
 607 declare_lint_pass!(
 608     /// Checks for use of anonymous parameters (RFC 1685).
 609     AnonymousParameters => [ANONYMOUS_PARAMETERS]
 610 );
 611
 612 impl EarlyLintPass for AnonymousParameters {
 613     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::TraitItem) {
 614         match it.kind {
 615             ast::TraitItemKind::Method(ref sig, _) => {
 616                 for arg in sig.decl.inputs.iter() {
 617                     match arg.pat.kind {
 618                         ast::PatKind::Ident(_, ident, None) => {
 619                             if ident.name == kw::Invalid {
 620                                 let ty_snip = cx
 621                                     .sess
 622                                     .source_map()
 623                                     .span_to_snippet(arg.ty.span);
 624
 625                                 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
 626                                     (snip, Applicability::MachineApplicable)
 627                                 } else {
 628                                     ("<type>".to_owned(), Applicability::HasPlaceholders)
 629                                 };
 630
 631                                 cx.struct_span_lint(
 632                                     ANONYMOUS_PARAMETERS,
 633                                     arg.pat.span,
 634                                     "anonymous parameters are deprecated and will be \
 635                                      removed in the next edition."
 636                                 ).span_suggestion(
 637                                     arg.pat.span,
 638                                     "Try naming the parameter or explicitly \
 639                                     ignoring it",
 640                                     format!("_: {}", ty_snip),
 641                                     appl
 642                                 ).emit();
 643                             }
 644                         }
 645                         _ => (),
 646                     }
 647                 }
 648             },
 649             _ => (),
 650         }
 651     }
 652 }
 653
 654 /// Check for use of attributes which have been deprecated.
 655 #[derive(Clone)]
 656 pub struct DeprecatedAttr {
 657     // This is not free to compute, so we want to keep it around, rather than
 658     // compute it for every attribute.
 659     depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
 660 }
 661
 662 impl_lint_pass!(DeprecatedAttr => []);
 663
 664 impl DeprecatedAttr {
 665     pub fn new() -> DeprecatedAttr {
 666         DeprecatedAttr {
 667             depr_attrs: deprecated_attributes(),
 668         }
 669     }
 670 }
 671
 672 fn lint_deprecated_attr(
 673     cx: &EarlyContext<'_>,
 674     attr: &ast::Attribute,
 675     msg: &str,
 676     suggestion: Option<&str>,
 677 ) {
 678     cx.struct_span_lint(DEPRECATED, attr.span, &msg)
 679         .span_suggestion_short(
 680             attr.span,
 681             suggestion.unwrap_or("remove this attribute"),
 682             String::new(),
 683             Applicability::MachineApplicable
 684         )
 685         .emit();
 686 }
 687
 688 impl EarlyLintPass for DeprecatedAttr {
 689     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
 690         for &&(n, _, _, ref g) in &self.depr_attrs {
 691             if attr.ident().map(|ident| ident.name) == Some(n) {
 692                 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
 693                                              ref name,
 694                                              ref reason,
 695                                              _) = g {
 696                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
 697                                       name, reason, link);
 698                     lint_deprecated_attr(cx, attr, &msg, suggestion);
 699                 }
 700                 return;
 701             }
 702         }
 703         if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
 704             let msg = format!("use of deprecated attribute `{}`: no longer used.", attr.path);
 705             lint_deprecated_attr(cx, attr, &msg, None);
 706         }
 707     }
 708 }
 709
 710 declare_lint! {
 711     pub UNUSED_DOC_COMMENTS,
 712     Warn,
 713     "detects doc comments that aren't used by rustdoc"
 714 }
 715
 716 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
 717
 718 impl UnusedDocComment {
 719     fn warn_if_doc(
 720         &self,
 721         cx: &EarlyContext<'_>,
 722         node_span: Span,
 723         node_kind: &str,
 724         is_macro_expansion: bool,
 725         attrs: &[ast::Attribute]
 726     ) {
 727         let mut attrs = attrs.into_iter().peekable();
 728
 729         // Accumulate a single span for sugared doc comments.
 730         let mut sugared_span: Option<Span> = None;
 731
 732         while let Some(attr) = attrs.next() {
 733             if attr.is_sugared_doc {
 734                 sugared_span = Some(
 735                     sugared_span.map_or_else(
 736                         || attr.span,
 737                         |span| span.with_hi(attr.span.hi()),
 738                     ),
 739                 );
 740             }
 741
 742             if attrs.peek().map(|next_attr| next_attr.is_sugared_doc).unwrap_or_default() {
 743                 continue;
 744             }
 745
 746             let span = sugared_span.take().unwrap_or_else(|| attr.span);
 747
 748             if attr.check_name(sym::doc) {
 749                 let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
 750
 751                 err.span_label(
 752                     node_span,
 753                     format!("rustdoc does not generate documentation for {}", node_kind)
 754                 );
 755
 756                 if is_macro_expansion {
 757                     err.help("to document an item produced by a macro, \
 758                               the macro must produce the documentation as part of its expansion");
 759                 }
 760
 761                 err.emit();
 762             }
 763         }
 764     }
 765 }
 766
 767 impl EarlyLintPass for UnusedDocComment {
 768     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 769         if let ast::ItemKind::Mac(..) = item.node {
 770             self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
 771         }
 772     }
 773
 774     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
 775         let (kind, is_macro_expansion) = match stmt.kind {
 776             ast::StmtKind::Local(..) => ("statements", false),
 777             ast::StmtKind::Item(..) => ("inner items", false),
 778             ast::StmtKind::Mac(..) => ("macro expansions", true),
 779             // expressions will be reported by `check_expr`.
 780             ast::StmtKind::Semi(..) |
 781             ast::StmtKind::Expr(..) => return,
 782         };
 783
 784         self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.kind.attrs());
 785     }
 786
 787     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
 788         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
 789         self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
 790     }
 791
 792     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
 793         self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
 794     }
 795 }
 796
 797 declare_lint! {
 798     PLUGIN_AS_LIBRARY,
 799     Warn,
 800     "compiler plugin used as ordinary library in non-plugin crate"
 801 }
 802
 803 declare_lint_pass!(PluginAsLibrary => [PLUGIN_AS_LIBRARY]);
 804
 805 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
 806     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 807         if cx.tcx.plugin_registrar_fn(LOCAL_CRATE).is_some() {
 808             // We're compiling a plugin; it's fine to link other plugins.
 809             return;
 810         }
 811
 812         match it.node {
 813             hir::ItemKind::ExternCrate(..) => (),
 814             _ => return,
 815         };
 816
 817         let def_id = cx.tcx.hir().local_def_id(it.hir_id);
 818         let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
 819             Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
 820             None => {
 821                 // Probably means we aren't linking the crate for some reason.
 822                 //
 823                 // Not sure if / when this could happen.
 824                 return;
 825             }
 826         };
 827
 828         if prfn.is_some() {
 829             cx.span_lint(PLUGIN_AS_LIBRARY,
 830                          it.span,
 831                          "compiler plugin used as an ordinary library");
 832         }
 833     }
 834 }
 835
 836 declare_lint! {
 837     NO_MANGLE_CONST_ITEMS,
 838     Deny,
 839     "const items will not have their symbols exported"
 840 }
 841
 842 declare_lint! {
 843     NO_MANGLE_GENERIC_ITEMS,
 844     Warn,
 845     "generic items must be mangled"
 846 }
 847
 848 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
 849
 850 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
 851     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
 852         match it.node {
 853             hir::ItemKind::Fn(.., ref generics, _) => {
 854                 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
 855                     for param in &generics.params {
 856                         match param.kind {
 857                             GenericParamKind::Lifetime { .. } => {}
 858                             GenericParamKind::Type { .. } |
 859                             GenericParamKind::Const { .. } => {
 860                                 let mut err = cx.struct_span_lint(
 861                                     NO_MANGLE_GENERIC_ITEMS,
 862                                     it.span,
 863                                     "functions generic over types or consts must be mangled",
 864                                 );
 865                                 err.span_suggestion_short(
 866                                     no_mangle_attr.span,
 867                                     "remove this attribute",
 868                                     String::new(),
 869                                     // Use of `#[no_mangle]` suggests FFI intent; correct
 870                                     // fix may be to monomorphize source by hand
 871                                     Applicability::MaybeIncorrect
 872                                 );
 873                                 err.emit();
 874                                 break;
 875                             }
 876                         }
 877                     }
 878                 }
 879             }
 880             hir::ItemKind::Const(..) => {
 881                 if attr::contains_name(&it.attrs, sym::no_mangle) {
 882                     // Const items do not refer to a particular location in memory, and therefore
 883                     // don't have anything to attach a symbol to
 884                     let msg = "const items should never be `#[no_mangle]`";
 885                     let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
 886
 887                     // account for "pub const" (#45562)
 888                     let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
 889                         .map(|snippet| snippet.find("const").unwrap_or(0))
 890                         .unwrap_or(0) as u32;
 891                     // `const` is 5 chars
 892                     let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
 893                     err.span_suggestion(
 894                         const_span,
 895                         "try a static value",
 896                         "pub static".to_owned(),
 897                         Applicability::MachineApplicable
 898                     );
 899                     err.emit();
 900                 }
 901             }
 902             _ => {}
 903         }
 904     }
 905 }
 906
 907 declare_lint! {
 908     MUTABLE_TRANSMUTES,
 909     Deny,
 910     "mutating transmuted &mut T from &T may cause undefined behavior"
 911 }
 912
 913 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
 914
 915 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
 916     fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr) {
 917         use rustc_target::spec::abi::Abi::RustIntrinsic;
 918
 919         let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
 920                    consider instead using an UnsafeCell";
 921         match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
 922             Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
 923                 if to_mt == hir::Mutability::MutMutable &&
 924                    from_mt == hir::Mutability::MutImmutable {
 925                     cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
 926                 }
 927             }
 928             _ => (),
 929         }
 930
 931         fn get_transmute_from_to<'a, 'tcx>
 932             (cx: &LateContext<'a, 'tcx>,
 933              expr: &hir::Expr)
 934              -> Option<(Ty<'tcx>, Ty<'tcx>)> {
 935             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
 936                 cx.tables.qpath_res(qpath, expr.hir_id)
 937             } else {
 938                 return None;
 939             };
 940             if let Res::Def(DefKind::Fn, did) = def {
 941                 if !def_id_is_transmute(cx, did) {
 942                     return None;
 943                 }
 944                 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
 945                 let from = sig.inputs().skip_binder()[0];
 946                 let to = *sig.output().skip_binder();
 947                 return Some((from, to));
 948             }
 949             None
 950         }
 951
 952         fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
 953             cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
 954             cx.tcx.item_name(def_id) == sym::transmute
 955         }
 956     }
 957 }
 958
 959 declare_lint! {
 960     UNSTABLE_FEATURES,
 961     Allow,
 962     "enabling unstable features (deprecated. do not use)"
 963 }
 964
 965 declare_lint_pass!(
 966     /// Forbids using the `#[feature(...)]` attribute
 967     UnstableFeatures => [UNSTABLE_FEATURES]
 968 );
 969
 970 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
 971     fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
 972         if attr.check_name(sym::feature) {
 973             if let Some(items) = attr.meta_item_list() {
 974                 for item in items {
 975                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
 976                 }
 977             }
 978         }
 979     }
 980 }
 981
 982 declare_lint! {
 983     UNIONS_WITH_DROP_FIELDS,
 984     Warn,
 985     "use of unions that contain fields with possibly non-trivial drop code"
 986 }
 987
 988 declare_lint_pass!(
 989     /// Lint for unions that contain fields with possibly non-trivial destructors.
 990     UnionsWithDropFields => [UNIONS_WITH_DROP_FIELDS]
 991 );
 992
 993 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
 994     fn check_item(&mut self, ctx: &LateContext<'_, '_>, item: &hir::Item) {
 995         if let hir::ItemKind::Union(ref vdata, _) = item.node {
 996             for field in vdata.fields() {
 997                 let field_ty = ctx.tcx.type_of(
 998                     ctx.tcx.hir().local_def_id(field.hir_id));
 999                 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1000                     ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1001                                   field.span,
1002                                   "union contains a field with possibly non-trivial drop code, \
1003                                    drop code of union fields is ignored when dropping the union");
1004                     return;
1005                 }
1006             }
1007         }
1008     }
1009 }
1010
1011 declare_lint! {
1012     pub UNREACHABLE_PUB,
1013     Allow,
1014     "`pub` items not reachable from crate root"
1015 }
1016
1017 declare_lint_pass!(
1018     /// Lint for items marked `pub` that aren't reachable from other crates.
1019     UnreachablePub => [UNREACHABLE_PUB]
1020 );
1021
1022 impl UnreachablePub {
1023     fn perform_lint(&self, cx: &LateContext<'_, '_>, what: &str, id: hir::HirId,
1024                     vis: &hir::Visibility, span: Span, exportable: bool) {
1025         let mut applicability = Applicability::MachineApplicable;
1026         match vis.node {
1027             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1028                 if span.from_expansion() {
1029                     applicability = Applicability::MaybeIncorrect;
1030                 }
1031                 let def_span = cx.tcx.sess.source_map().def_span(span);
1032                 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1033                                                   &format!("unreachable `pub` {}", what));
1034                 let replacement = if cx.tcx.features().crate_visibility_modifier {
1035                     "crate"
1036                 } else {
1037                     "pub(crate)"
1038                 }.to_owned();
1039
1040                 err.span_suggestion(
1041                     vis.span,
1042                     "consider restricting its visibility",
1043                     replacement,
1044                     applicability,
1045                 );
1046                 if exportable {
1047                     err.help("or consider exporting it for use by other crates");
1048                 }
1049                 err.emit();
1050             },
1051             _ => {}
1052         }
1053     }
1054 }
1055
1056 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1057     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1058         self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1059     }
1060
1061     fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, foreign_item: &hir::ForeignItem) {
1062         self.perform_lint(cx, "item", foreign_item.hir_id, &foreign_item.vis,
1063                           foreign_item.span, true);
1064     }
1065
1066     fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
1067         self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1068     }
1069
1070     fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
1071         self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1072     }
1073 }
1074
1075 declare_lint! {
1076     TYPE_ALIAS_BOUNDS,
1077     Warn,
1078     "bounds in type aliases are not enforced"
1079 }
1080
1081 declare_lint_pass!(
1082     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1083     /// They are relevant when using associated types, but otherwise neither checked
1084     /// at definition site nor enforced at use site.
1085     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1086 );
1087
1088 impl TypeAliasBounds {
1089     fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1090         match *qpath {
1091             hir::QPath::TypeRelative(ref ty, _) => {
1092                 // If this is a type variable, we found a `T::Assoc`.
1093                 match ty.kind {
1094                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1095                         match path.res {
1096                             Res::Def(DefKind::TyParam, _) => true,
1097                             _ => false
1098                         }
1099                     }
1100                     _ => false
1101                 }
1102             }
1103             hir::QPath::Resolved(..) => false,
1104         }
1105     }
1106
1107     fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder<'_>) {
1108         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1109         // bound.  Let's see if this type does that.
1110
1111         // We use a HIR visitor to walk the type.
1112         use rustc::hir::intravisit::{self, Visitor};
1113         struct WalkAssocTypes<'a, 'db> {
1114             err: &'a mut DiagnosticBuilder<'db>
1115         }
1116         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1117             fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1118             {
1119                 intravisit::NestedVisitorMap::None
1120             }
1121
1122             fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1123                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1124                     self.err.span_help(span,
1125                         "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1126                          associated types in type aliases");
1127                 }
1128                 intravisit::walk_qpath(self, qpath, id, span)
1129             }
1130         }
1131
1132         // Let's go for a walk!
1133         let mut visitor = WalkAssocTypes { err };
1134         visitor.visit_ty(ty);
1135     }
1136 }
1137
1138 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1139     fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1140         let (ty, type_alias_generics) = match item.node {
1141             hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1142             _ => return,
1143         };
1144         let mut suggested_changing_assoc_types = false;
1145         // There must not be a where clause
1146         if !type_alias_generics.where_clause.predicates.is_empty() {
1147             let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1148                 .map(|pred| pred.span()).collect();
1149             let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1150                 "where clauses are not enforced in type aliases");
1151             err.help("the clause will not be checked when the type alias is used, \
1152                       and should be removed");
1153             if !suggested_changing_assoc_types {
1154                 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1155                 suggested_changing_assoc_types = true;
1156             }
1157             err.emit();
1158         }
1159         // The parameters must not have bounds
1160         for param in type_alias_generics.params.iter() {
1161             let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1162             if !spans.is_empty() {
1163                 let mut err = cx.struct_span_lint(
1164                     TYPE_ALIAS_BOUNDS,
1165                     spans,
1166                     "bounds on generic parameters are not enforced in type aliases",
1167                 );
1168                 err.help("the bound will not be checked when the type alias is used, \
1169                           and should be removed");
1170                 if !suggested_changing_assoc_types {
1171                     TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1172                     suggested_changing_assoc_types = true;
1173                 }
1174                 err.emit();
1175             }
1176         }
1177     }
1178 }
1179
1180 declare_lint_pass!(
1181     /// Lint constants that are erroneous.
1182     /// Without this lint, we might not get any diagnostic if the constant is
1183     /// unused within this crate, even though downstream crates can't use it
1184     /// without producing an error.
1185     UnusedBrokenConst => []
1186 );
1187
1188 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1189     let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1190     let param_env = if cx.tcx.is_static(def_id) {
1191         // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1192         ty::ParamEnv::reveal_all()
1193     } else {
1194         cx.tcx.param_env(def_id)
1195     };
1196     let cid = ::rustc::mir::interpret::GlobalId {
1197         instance: ty::Instance::mono(cx.tcx, def_id),
1198         promoted: None
1199     };
1200     // trigger the query once for all constants since that will already report the errors
1201     // FIXME: Use ensure here
1202     let _ = cx.tcx.const_eval(param_env.and(cid));
1203 }
1204
1205 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1206     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1207         match it.node {
1208             hir::ItemKind::Const(_, body_id) => {
1209                 check_const(cx, body_id);
1210             },
1211             hir::ItemKind::Static(_, _, body_id) => {
1212                 check_const(cx, body_id);
1213             },
1214             _ => {},
1215         }
1216     }
1217 }
1218
1219 declare_lint! {
1220     TRIVIAL_BOUNDS,
1221     Warn,
1222     "these bounds don't depend on an type parameters"
1223 }
1224
1225 declare_lint_pass!(
1226     /// Lint for trait and lifetime bounds that don't depend on type parameters
1227     /// which either do nothing, or stop the item from being used.
1228     TrivialConstraints => [TRIVIAL_BOUNDS]
1229 );
1230
1231 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1232     fn check_item(
1233         &mut self,
1234         cx: &LateContext<'a, 'tcx>,
1235         item: &'tcx hir::Item,
1236     ) {
1237         use rustc::ty::fold::TypeFoldable;
1238         use rustc::ty::Predicate::*;
1239
1240         if cx.tcx.features().trivial_bounds {
1241             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1242             let predicates = cx.tcx.predicates_of(def_id);
1243             for &(predicate, span) in &predicates.predicates {
1244                 let predicate_kind_name = match predicate {
1245                     Trait(..) => "Trait",
1246                     TypeOutlives(..) |
1247                     RegionOutlives(..) => "Lifetime",
1248
1249                     // Ignore projections, as they can only be global
1250                     // if the trait bound is global
1251                     Projection(..) |
1252                     // Ignore bounds that a user can't type
1253                     WellFormed(..) |
1254                     ObjectSafe(..) |
1255                     ClosureKind(..) |
1256                     Subtype(..) |
1257                     ConstEvaluatable(..) => continue,
1258                 };
1259                 if predicate.is_global() {
1260                     cx.span_lint(
1261                         TRIVIAL_BOUNDS,
1262                         span,
1263                         &format!("{} bound {} does not depend on any type \
1264                                 or lifetime parameters", predicate_kind_name, predicate),
1265                     );
1266                 }
1267             }
1268         }
1269     }
1270 }
1271
1272 declare_lint_pass!(
1273     /// Does nothing as a lint pass, but registers some `Lint`s
1274     /// which are used by other parts of the compiler.
1275     SoftLints => [
1276         WHILE_TRUE,
1277         BOX_POINTERS,
1278         NON_SHORTHAND_FIELD_PATTERNS,
1279         UNSAFE_CODE,
1280         MISSING_DOCS,
1281         MISSING_COPY_IMPLEMENTATIONS,
1282         MISSING_DEBUG_IMPLEMENTATIONS,
1283         ANONYMOUS_PARAMETERS,
1284         UNUSED_DOC_COMMENTS,
1285         PLUGIN_AS_LIBRARY,
1286         NO_MANGLE_CONST_ITEMS,
1287         NO_MANGLE_GENERIC_ITEMS,
1288         MUTABLE_TRANSMUTES,
1289         UNSTABLE_FEATURES,
1290         UNIONS_WITH_DROP_FIELDS,
1291         UNREACHABLE_PUB,
1292         TYPE_ALIAS_BOUNDS,
1293         TRIVIAL_BOUNDS
1294     ]
1295 );
1296
1297 declare_lint! {
1298     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1299     Warn,
1300     "`...` range patterns are deprecated"
1301 }
1302
1303 #[derive(Default)]
1304 pub struct EllipsisInclusiveRangePatterns {
1305     /// If `Some(_)`, suppress all subsequent pattern
1306     /// warnings for better diagnostics.
1307     node_id: Option<ast::NodeId>,
1308 }
1309
1310 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1311
1312 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1313     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1314         if self.node_id.is_some() {
1315             // Don't recursively warn about patterns inside range endpoints.
1316             return
1317         }
1318
1319         use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1320
1321         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1322         /// corresponding to the ellipsis.
1323         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(&P<Expr>, &P<Expr>, Span)> {
1324             match &pat.kind {
1325                 PatKind::Range(a, b, Spanned { span, node: RangeEnd::Included(DotDotDot), .. }) => {
1326                     Some((a, b, *span))
1327                 }
1328                 _ => None,
1329             }
1330         }
1331
1332         let (parenthesise, endpoints) = match &pat.kind {
1333             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1334             _ => (false, matches_ellipsis_pat(pat)),
1335         };
1336
1337         if let Some((start, end, join)) = endpoints {
1338             let msg = "`...` range patterns are deprecated";
1339             let suggestion = "use `..=` for an inclusive range";
1340             if parenthesise {
1341                 self.node_id = Some(pat.id);
1342                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1343                 err.span_suggestion(
1344                     pat.span,
1345                     suggestion,
1346                     format!("&({}..={})", expr_to_string(&start), expr_to_string(&end)),
1347                     Applicability::MachineApplicable,
1348                 );
1349                 err.emit();
1350             } else {
1351                 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1352                 err.span_suggestion_short(
1353                     join,
1354                     suggestion,
1355                     "..=".to_owned(),
1356                     Applicability::MachineApplicable,
1357                 );
1358                 err.emit();
1359             };
1360         }
1361     }
1362
1363     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1364         if let Some(node_id) = self.node_id {
1365             if pat.id == node_id {
1366                 self.node_id = None
1367             }
1368         }
1369     }
1370 }
1371
1372 declare_lint! {
1373     UNNAMEABLE_TEST_ITEMS,
1374     Warn,
1375     "detects an item that cannot be named being marked as `#[test_case]`",
1376     report_in_external_macro: true
1377 }
1378
1379 pub struct UnnameableTestItems {
1380     boundary: hir::HirId, // HirId of the item under which things are not nameable
1381     items_nameable: bool,
1382 }
1383
1384 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1385
1386 impl UnnameableTestItems {
1387     pub fn new() -> Self {
1388         Self {
1389             boundary: hir::DUMMY_HIR_ID,
1390             items_nameable: true
1391         }
1392     }
1393 }
1394
1395 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1396     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1397         if self.items_nameable {
1398             if let hir::ItemKind::Mod(..) = it.node {}
1399             else {
1400                 self.items_nameable = false;
1401                 self.boundary = it.hir_id;
1402             }
1403             return;
1404         }
1405
1406         if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1407             cx.struct_span_lint(
1408                 UNNAMEABLE_TEST_ITEMS,
1409                 attr.span,
1410                 "cannot test inner items",
1411             ).emit();
1412         }
1413     }
1414
1415     fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item) {
1416         if !self.items_nameable && self.boundary == it.hir_id {
1417             self.items_nameable = true;
1418         }
1419     }
1420 }
1421
1422 declare_lint! {
1423     pub KEYWORD_IDENTS,
1424     Allow,
1425     "detects edition keywords being used as an identifier"
1426 }
1427
1428 declare_lint_pass!(
1429     /// Check for uses of edition keywords used as an identifier.
1430     KeywordIdents => [KEYWORD_IDENTS]
1431 );
1432
1433 struct UnderMacro(bool);
1434
1435 impl KeywordIdents {
1436     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1437         for tt in tokens.into_trees() {
1438             match tt {
1439                 // Only report non-raw idents.
1440                 TokenTree::Token(token) => if let Some((ident, false)) = token.ident() {
1441                     self.check_ident_token(cx, UnderMacro(true), ident);
1442                 }
1443                 TokenTree::Delimited(_, _, tts) => {
1444                     self.check_tokens(cx, tts)
1445                 },
1446             }
1447         }
1448     }
1449
1450     fn check_ident_token(&mut self,
1451                          cx: &EarlyContext<'_>,
1452                          UnderMacro(under_macro): UnderMacro,
1453                          ident: ast::Ident)
1454     {
1455         let next_edition = match cx.sess.edition() {
1456             Edition::Edition2015 => {
1457                 match ident.name {
1458                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1459
1460                     // rust-lang/rust#56327: Conservatively do not
1461                     // attempt to report occurrences of `dyn` within
1462                     // macro definitions or invocations, because `dyn`
1463                     // can legitimately occur as a contextual keyword
1464                     // in 2015 code denoting its 2018 meaning, and we
1465                     // do not want rustfix to inject bugs into working
1466                     // code by rewriting such occurrences.
1467                     //
1468                     // But if we see `dyn` outside of a macro, we know
1469                     // its precise role in the parsed AST and thus are
1470                     // assured this is truly an attempt to use it as
1471                     // an identifier.
1472                     kw::Dyn if !under_macro => Edition::Edition2018,
1473
1474                     _ => return,
1475                 }
1476             }
1477
1478             // There are no new keywords yet for the 2018 edition and beyond.
1479             _ => return,
1480         };
1481
1482         // Don't lint `r#foo`.
1483         if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1484             return;
1485         }
1486
1487         let mut lint = cx.struct_span_lint(
1488             KEYWORD_IDENTS,
1489             ident.span,
1490             &format!("`{}` is a keyword in the {} edition",
1491                      ident.as_str(),
1492                      next_edition),
1493         );
1494         lint.span_suggestion(
1495             ident.span,
1496             "you can use a raw identifier to stay compatible",
1497             format!("r#{}", ident.as_str()),
1498             Applicability::MachineApplicable,
1499         );
1500         lint.emit()
1501     }
1502 }
1503
1504 impl EarlyLintPass for KeywordIdents {
1505     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1506         self.check_tokens(cx, mac_def.stream());
1507     }
1508     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1509         self.check_tokens(cx, mac.tts.clone().into());
1510     }
1511     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1512         self.check_ident_token(cx, UnderMacro(false), ident);
1513     }
1514 }
1515
1516 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1517
1518 impl ExplicitOutlivesRequirements {
1519     fn lifetimes_outliving_lifetime<'tcx>(
1520         inferred_outlives: &'tcx [ty::Predicate<'tcx>],
1521         index: u32,
1522     ) -> Vec<ty::Region<'tcx>> {
1523         inferred_outlives.iter().filter_map(|pred| {
1524             match pred {
1525                 ty::Predicate::RegionOutlives(outlives) => {
1526                     let outlives = outlives.skip_binder();
1527                     match outlives.0 {
1528                         ty::ReEarlyBound(ebr) if ebr.index == index => {
1529                             Some(outlives.1)
1530                         }
1531                         _ => None,
1532                     }
1533                 }
1534                 _ => None
1535             }
1536         }).collect()
1537     }
1538
1539     fn lifetimes_outliving_type<'tcx>(
1540         inferred_outlives: &'tcx [ty::Predicate<'tcx>],
1541         index: u32,
1542     ) -> Vec<ty::Region<'tcx>> {
1543         inferred_outlives.iter().filter_map(|pred| {
1544             match pred {
1545                 ty::Predicate::TypeOutlives(outlives) => {
1546                     let outlives = outlives.skip_binder();
1547                     if outlives.0.is_param(index) {
1548                         Some(outlives.1)
1549                     } else {
1550                         None
1551                     }
1552                 }
1553                 _ => None
1554             }
1555         }).collect()
1556     }
1557
1558     fn collect_outlived_lifetimes<'tcx>(
1559         &self,
1560         param: &'tcx hir::GenericParam,
1561         tcx: TyCtxt<'tcx>,
1562         inferred_outlives: &'tcx [ty::Predicate<'tcx>],
1563         ty_generics: &'tcx ty::Generics,
1564     ) -> Vec<ty::Region<'tcx>> {
1565         let index = ty_generics.param_def_id_to_index[
1566             &tcx.hir().local_def_id(param.hir_id)];
1567
1568         match param.kind {
1569             hir::GenericParamKind::Lifetime { .. } => {
1570                 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1571             }
1572             hir::GenericParamKind::Type { .. } => {
1573                 Self::lifetimes_outliving_type(inferred_outlives, index)
1574             }
1575             hir::GenericParamKind::Const { .. } => Vec::new(),
1576         }
1577     }
1578
1579
1580     fn collect_outlives_bound_spans<'tcx>(
1581         &self,
1582         tcx: TyCtxt<'tcx>,
1583         bounds: &hir::GenericBounds,
1584         inferred_outlives: &[ty::Region<'tcx>],
1585         infer_static: bool,
1586     ) -> Vec<(usize, Span)> {
1587         use rustc::middle::resolve_lifetime::Region;
1588
1589         bounds
1590             .iter()
1591             .enumerate()
1592             .filter_map(|(i, bound)| {
1593                 if let hir::GenericBound::Outlives(lifetime) = bound {
1594                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
1595                         Some(Region::Static) if infer_static => {
1596                             inferred_outlives.iter()
1597                                 .any(|r| if let ty::ReStatic = r { true } else { false })
1598                         }
1599                         Some(Region::EarlyBound(index, ..)) => inferred_outlives
1600                             .iter()
1601                             .any(|r| {
1602                                 if let ty::ReEarlyBound(ebr) = r {
1603                                     ebr.index == index
1604                                 } else {
1605                                     false
1606                                 }
1607                             }),
1608                         _ => false,
1609                     };
1610                     if is_inferred {
1611                         Some((i, bound.span()))
1612                     } else {
1613                         None
1614                     }
1615                 } else {
1616                     None
1617                 }
1618             })
1619             .collect()
1620     }
1621
1622     fn consolidate_outlives_bound_spans(
1623         &self,
1624         lo: Span,
1625         bounds: &hir::GenericBounds,
1626         bound_spans: Vec<(usize, Span)>
1627     ) -> Vec<Span> {
1628         if bounds.is_empty() {
1629             return Vec::new();
1630         }
1631         if bound_spans.len() == bounds.len() {
1632             let (_, last_bound_span) = bound_spans[bound_spans.len()-1];
1633             // If all bounds are inferable, we want to delete the colon, so
1634             // start from just after the parameter (span passed as argument)
1635             vec![lo.to(last_bound_span)]
1636         } else {
1637             let mut merged = Vec::new();
1638             let mut last_merged_i = None;
1639
1640             let mut from_start = true;
1641             for (i, bound_span) in bound_spans {
1642                 match last_merged_i {
1643                     // If the first bound is inferable, our span should also eat the leading `+`.
1644                     None if i == 0 => {
1645                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1646                         last_merged_i = Some(0);
1647                     },
1648                     // If consecutive bounds are inferable, merge their spans
1649                     Some(h) if i == h+1 => {
1650                         if let Some(tail) = merged.last_mut() {
1651                             // Also eat the trailing `+` if the first
1652                             // more-than-one bound is inferable
1653                             let to_span = if from_start && i < bounds.len() {
1654                                 bounds[i+1].span().shrink_to_lo()
1655                             } else {
1656                                 bound_span
1657                             };
1658                             *tail = tail.to(to_span);
1659                             last_merged_i = Some(i);
1660                         } else {
1661                             bug!("another bound-span visited earlier");
1662                         }
1663                     },
1664                     _ => {
1665                         // When we find a non-inferable bound, subsequent inferable bounds
1666                         // won't be consecutive from the start (and we'll eat the leading
1667                         // `+` rather than the trailing one)
1668                         from_start = false;
1669                         merged.push(bounds[i-1].span().shrink_to_hi().to(bound_span));
1670                         last_merged_i = Some(i);
1671                     }
1672                 }
1673             }
1674             merged
1675         }
1676     }
1677 }
1678
1679 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1680     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
1681         use rustc::middle::resolve_lifetime::Region;
1682
1683         let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1684         let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1685         if let hir::ItemKind::Struct(_, ref hir_generics)
1686             | hir::ItemKind::Enum(_, ref hir_generics)
1687             | hir::ItemKind::Union(_, ref hir_generics) = item.node
1688         {
1689             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1690             if inferred_outlives.is_empty() {
1691                 return;
1692             }
1693
1694             let ty_generics = cx.tcx.generics_of(def_id);
1695
1696             let mut bound_count = 0;
1697             let mut lint_spans = Vec::new();
1698
1699             for param in &hir_generics.params {
1700                 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1701                     if let hir::GenericBound::Outlives(_) = bound {
1702                         true
1703                     } else {
1704                         false
1705                     }
1706                 });
1707                 if !has_lifetime_bounds {
1708                     continue;
1709                 }
1710
1711                 let relevant_lifetimes = self.collect_outlived_lifetimes(
1712                     param,
1713                     cx.tcx,
1714                     inferred_outlives,
1715                     ty_generics,
1716                 );
1717                 if relevant_lifetimes.is_empty() {
1718                     continue;
1719                 }
1720
1721                 let bound_spans = self.collect_outlives_bound_spans(
1722                     cx.tcx, &param.bounds, &relevant_lifetimes, infer_static,
1723                 );
1724                 bound_count += bound_spans.len();
1725                 lint_spans.extend(
1726                     self.consolidate_outlives_bound_spans(
1727                         param.span.shrink_to_hi(), &param.bounds, bound_spans
1728                     )
1729                 );
1730             }
1731
1732             let mut where_lint_spans = Vec::new();
1733             let mut dropped_predicate_count = 0;
1734             let num_predicates = hir_generics.where_clause.predicates.len();
1735             for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1736                 let (relevant_lifetimes, bounds, span) = match where_predicate {
1737                     hir::WherePredicate::RegionPredicate(predicate) => {
1738                         if let Some(Region::EarlyBound(index, ..))
1739                             = cx.tcx.named_region(predicate.lifetime.hir_id)
1740                         {
1741                             (
1742                                 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1743                                 &predicate.bounds,
1744                                 predicate.span,
1745                             )
1746                         } else {
1747                             continue;
1748                         }
1749                     }
1750                     hir::WherePredicate::BoundPredicate(predicate) => {
1751                         // FIXME we can also infer bounds on associated types,
1752                         // and should check for them here.
1753                         match predicate.bounded_ty.kind {
1754                             hir::TyKind::Path(hir::QPath::Resolved(
1755                                 None,
1756                                 ref path,
1757                             )) => {
1758                                 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1759                                     let index = ty_generics.param_def_id_to_index[&def_id];
1760                                     (
1761                                         Self::lifetimes_outliving_type(inferred_outlives, index),
1762                                         &predicate.bounds,
1763                                         predicate.span,
1764                                     )
1765                                 } else {
1766                                     continue;
1767                                 }
1768                             },
1769                             _ => { continue; }
1770                         }
1771                     }
1772                     _ => continue,
1773                 };
1774                 if relevant_lifetimes.is_empty() {
1775                     continue;
1776                 }
1777
1778                 let bound_spans = self.collect_outlives_bound_spans(
1779                     cx.tcx, bounds, &relevant_lifetimes, infer_static,
1780                 );
1781                 bound_count += bound_spans.len();
1782
1783                 let drop_predicate = bound_spans.len() == bounds.len();
1784                 if drop_predicate {
1785                     dropped_predicate_count += 1;
1786                 }
1787
1788                 // If all the bounds on a predicate were inferable and there are
1789                 // further predicates, we want to eat the trailing comma.
1790                 if drop_predicate && i + 1 < num_predicates {
1791                     let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1792                     where_lint_spans.push(
1793                         span.to(next_predicate_span.shrink_to_lo())
1794                     );
1795                 } else {
1796                     where_lint_spans.extend(
1797                         self.consolidate_outlives_bound_spans(
1798                             span.shrink_to_lo(),
1799                             bounds,
1800                             bound_spans
1801                         )
1802                     );
1803                 }
1804             }
1805
1806             // If all predicates are inferable, drop the entire clause
1807             // (including the `where`)
1808             if num_predicates > 0 && dropped_predicate_count == num_predicates {
1809                 let where_span = hir_generics.where_clause.span()
1810                     .expect("span of (nonempty) where clause should exist");
1811                 // Extend the where clause back to the closing `>` of the
1812                 // generics, except for tuple struct, which have the `where`
1813                 // after the fields of the struct.
1814                 let full_where_span = if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _)
1815                         = item.node
1816                 {
1817                     where_span
1818                 } else {
1819                     hir_generics.span.shrink_to_hi().to(where_span)
1820                 };
1821                 lint_spans.push(
1822                     full_where_span
1823                 );
1824             } else {
1825                 lint_spans.extend(where_lint_spans);
1826             }
1827
1828             if !lint_spans.is_empty() {
1829                 let mut err = cx.struct_span_lint(
1830                     EXPLICIT_OUTLIVES_REQUIREMENTS,
1831                     lint_spans.clone(),
1832                     "outlives requirements can be inferred"
1833                 );
1834                 err.multipart_suggestion(
1835                     if bound_count == 1 {
1836                         "remove this bound"
1837                     } else {
1838                         "remove these bounds"
1839                     },
1840                     lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1841                     Applicability::MachineApplicable
1842                 );
1843                 err.emit();
1844             }
1845         }
1846     }
1847 }
1848
1849 declare_lint! {
1850     pub INCOMPLETE_FEATURES,
1851     Warn,
1852     "incomplete features that may function improperly in some or all cases"
1853 }
1854
1855 declare_lint_pass!(
1856     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `feature_gate.rs`.
1857     IncompleteFeatures => [INCOMPLETE_FEATURES]
1858 );
1859
1860 impl EarlyLintPass for IncompleteFeatures {
1861     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1862         let features = cx.sess.features_untracked();
1863         features.declared_lang_features
1864             .iter().map(|(name, span, _)| (name, span))
1865             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1866             .filter(|(name, _)| feature_gate::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1867             .for_each(|(name, &span)| {
1868                 cx.struct_span_lint(
1869                     INCOMPLETE_FEATURES,
1870                     span,
1871                     &format!(
1872                         "the feature `{}` is incomplete and may cause the compiler to crash",
1873                         name,
1874                     )
1875                 )
1876                 .emit();
1877             });
1878     }
1879 }
1880
1881 declare_lint! {
1882     pub INVALID_VALUE,
1883     Warn,
1884     "an invalid value is being created (such as a NULL reference)"
1885 }
1886
1887 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1888
1889 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1890     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr) {
1891
1892         #[derive(Debug, Copy, Clone, PartialEq)]
1893         enum InitKind { Zeroed, Uninit };
1894
1895         /// Information about why a type cannot be initialized this way.
1896         /// Contains an error message and optionally a span to point at.
1897         type InitError = (String, Option<Span>);
1898
1899         /// Test if this constant is all-0.
1900         fn is_zero(expr: &hir::Expr) -> bool {
1901             use hir::ExprKind::*;
1902             use syntax::ast::LitKind::*;
1903             match &expr.kind {
1904                 Lit(lit) =>
1905                     if let Int(i, _) = lit.node {
1906                         i == 0
1907                     } else {
1908                         false
1909                     },
1910                 Tup(tup) =>
1911                     tup.iter().all(is_zero),
1912                 _ =>
1913                     false
1914             }
1915         }
1916
1917         /// Determine if this expression is a "dangerous initialization".
1918         fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<InitKind> {
1919             const ZEROED_PATH: &[Symbol] = &[sym::core, sym::mem, sym::zeroed];
1920             const UININIT_PATH: &[Symbol] = &[sym::core, sym::mem, sym::uninitialized];
1921             // `transmute` is inside an anonymous module (the `extern` block?);
1922             // `Invalid` represents the empty string and matches that.
1923             const TRANSMUTE_PATH: &[Symbol] =
1924                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1925
1926             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1927                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1928                     let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1929
1930                     if cx.match_def_path(def_id, ZEROED_PATH) {
1931                         return Some(InitKind::Zeroed);
1932                     }
1933                     if cx.match_def_path(def_id, UININIT_PATH) {
1934                         return Some(InitKind::Uninit);
1935                     }
1936                     if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1937                         if is_zero(&args[0]) {
1938                             return Some(InitKind::Zeroed);
1939                         }
1940                     }
1941                     // FIXME: Also detect `MaybeUninit::zeroed().assume_init()` and
1942                     // `MaybeUninit::uninit().assume_init()`.
1943                 }
1944             }
1945
1946             None
1947         }
1948
1949         /// Return `Some` only if we are sure this type does *not*
1950         /// allow zero initialization.
1951         fn ty_find_init_error<'tcx>(
1952             tcx: TyCtxt<'tcx>,
1953             ty: Ty<'tcx>,
1954             init: InitKind,
1955         ) -> Option<InitError> {
1956             use rustc::ty::TyKind::*;
1957             match ty.kind {
1958                 // Primitive types that don't like 0 as a value.
1959                 Ref(..) => Some((format!("References must be non-null"), None)),
1960                 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
1961                 FnPtr(..) => Some((format!("Function pointers must be non-null"), None)),
1962                 Never => Some((format!("The never type (`!`) has no valid value"), None)),
1963                 // Primitive types with other constraints.
1964                 Bool if init == InitKind::Uninit =>
1965                     Some((format!("Booleans must be `true` or `false`"), None)),
1966                 Char if init == InitKind::Uninit =>
1967                     Some((format!("Characters must be a valid unicode codepoint"), None)),
1968                 // Recurse and checks for some compound types.
1969                 Adt(adt_def, substs) if !adt_def.is_union() => {
1970                     // First check f this ADT has a layout attribute (like `NonNull` and friends).
1971                     use std::ops::Bound;
1972                     match tcx.layout_scalar_valid_range(adt_def.did) {
1973                         // We exploit here that `layout_scalar_valid_range` will never
1974                         // return `Bound::Excluded`.  (And we have tests checking that we
1975                         // handle the attribute correctly.)
1976                         (Bound::Included(lo), _) if lo > 0 =>
1977                             return Some((format!("{} must be non-null", ty), None)),
1978                         (Bound::Included(_), _) | (_, Bound::Included(_))
1979                         if init == InitKind::Uninit =>
1980                             return Some((
1981                                 format!("{} must be initialized inside its custom valid range", ty),
1982                                 None,
1983                             )),
1984                         _ => {}
1985                     }
1986                     // Now, recurse.
1987                     match adt_def.variants.len() {
1988                         0 => Some((format!("0-variant enums have no valid value"), None)),
1989                         1 => {
1990                             // Struct, or enum with exactly one variant.
1991                             // Proceed recursively, check all fields.
1992                             let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1993                             variant.fields.iter().find_map(|field| {
1994                                 ty_find_init_error(
1995                                     tcx,
1996                                     field.ty(tcx, substs),
1997                                     init,
1998                                 ).map(|(mut msg, span)| if span.is_none() {
1999                                     // Point to this field, should be helpful for figuring
2000                                     // out where the source of the error is.
2001                                     let span = tcx.def_span(field.did);
2002                                     write!(&mut msg, " (in this {} field)", adt_def.descr())
2003                                         .unwrap();
2004                                     (msg, Some(span))
2005                                 } else {
2006                                     // Just forward.
2007                                     (msg, span)
2008                                 })
2009                             })
2010                         }
2011                         // Multi-variant enums are tricky: if all but one variant are
2012                         // uninhabited, we might actually do layout like for a single-variant
2013                         // enum, and then even leaving them uninitialized could be okay.
2014                         _ => None, // Conservative fallback for multi-variant enum.
2015                     }
2016                 }
2017                 Tuple(..) => {
2018                     // Proceed recursively, check all fields.
2019                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2020                 }
2021                 // Conservative fallback.
2022                 _ => None,
2023             }
2024         }
2025
2026         if let Some(init) = is_dangerous_init(cx, expr) {
2027             // This conjures an instance of a type out of nothing,
2028             // using zeroed or uninitialized memory.
2029             // We are extremely conservative with what we warn about.
2030             let conjured_ty = cx.tables.expr_ty(expr);
2031             if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2032                 let mut err = cx.struct_span_lint(
2033                     INVALID_VALUE,
2034                     expr.span,
2035                     &format!(
2036                         "the type `{}` does not permit {}",
2037                         conjured_ty,
2038                         match init {
2039                             InitKind::Zeroed => "zero-initialization",
2040                             InitKind::Uninit => "being left uninitialized",
2041                         },
2042                     ),
2043                 );
2044                 err.span_label(expr.span,
2045                     "this code causes undefined behavior when executed");
2046                 err.span_label(expr.span, "help: use `MaybeUninit<T>` instead");
2047                 if let Some(span) = span {
2048                     err.span_note(span, &msg);
2049                 } else {
2050                     err.note(&msg);
2051                 }
2052                 err.emit();
2053             }
2054         }
2055     }
2056 }