src/librustc/lint/mod.rs

   1 //! Lints, aka compiler warnings.
   2 //!
   3 //! A 'lint' check is a kind of miscellaneous constraint that a user _might_
   4 //! want to enforce, but might reasonably want to permit as well, on a
   5 //! module-by-module basis. They contrast with static constraints enforced by
   6 //! other phases of the compiler, which are generally required to hold in order
   7 //! to compile the program at all.
   8 //!
   9 //! Most lints can be written as `LintPass` instances. These run after
  10 //! all other analyses. The `LintPass`es built into rustc are defined
  11 //! within `builtin.rs`, which has further comments on how to add such a lint.
  12 //! rustc can also load user-defined lint plugins via the plugin mechanism.
  13 //!
  14 //! Some of rustc's lints are defined elsewhere in the compiler and work by
  15 //! calling `add_lint()` on the overall `Session` object. This works when
  16 //! it happens before the main lint pass, which emits the lints stored by
  17 //! `add_lint()`. To emit lints after the main lint pass (from codegen, for
  18 //! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
  19 //! in `context.rs`.
  20
  21 pub use self::Level::*;
  22 pub use self::LintSource::*;
  23
  24 use rustc_data_structures::sync;
  25
  26 use crate::hir::def_id::{CrateNum, LOCAL_CRATE};
  27 use crate::hir::intravisit;
  28 use crate::hir;
  29 use crate::lint::builtin::BuiltinLintDiagnostics;
  30 use crate::lint::builtin::parser::ILL_FORMED_ATTRIBUTE_INPUT;
  31 use crate::session::{Session, DiagnosticMessageId};
  32 use crate::ty::TyCtxt;
  33 use crate::ty::query::Providers;
  34 use crate::util::nodemap::NodeMap;
  35 use errors::{DiagnosticBuilder, DiagnosticId};
  36 use std::{hash, ptr};
  37 use syntax::ast;
  38 use syntax::source_map::{MultiSpan, ExpnFormat, CompilerDesugaringKind};
  39 use syntax::early_buffered_lints::BufferedEarlyLintId;
  40 use syntax::edition::Edition;
  41 use syntax::symbol::{Symbol, sym};
  42 use syntax_pos::Span;
  43
  44 pub use crate::lint::context::{LateContext, EarlyContext, LintContext, LintStore,
  45                         check_crate, check_ast_crate, late_lint_mod, CheckLintNameResult,
  46                         FutureIncompatibleInfo, BufferedEarlyLint,};
  47
  48 /// Specification of a single lint.
  49 #[derive(Copy, Clone, Debug)]
  50 pub struct Lint {
  51     /// A string identifier for the lint.
  52     ///
  53     /// This identifies the lint in attributes and in command-line arguments.
  54     /// In those contexts it is always lowercase, but this field is compared
  55     /// in a way which is case-insensitive for ASCII characters. This allows
  56     /// `declare_lint!()` invocations to follow the convention of upper-case
  57     /// statics without repeating the name.
  58     ///
  59     /// The name is written with underscores, e.g., "unused_imports".
  60     /// On the command line, underscores become dashes.
  61     pub name: &'static str,
  62
  63     /// Default level for the lint.
  64     pub default_level: Level,
  65
  66     /// Description of the lint or the issue it detects.
  67     ///
  68     /// e.g., "imports that are never used"
  69     pub desc: &'static str,
  70
  71     /// Starting at the given edition, default to the given lint level. If this is `None`, then use
  72     /// `default_level`.
  73     pub edition_lint_opts: Option<(Edition, Level)>,
  74
  75     /// `true` if this lint is reported even inside expansions of external macros.
  76     pub report_in_external_macro: bool,
  77 }
  78
  79 impl Lint {
  80     /// Returns the `rust::lint::Lint` for a `syntax::early_buffered_lints::BufferedEarlyLintId`.
  81     pub fn from_parser_lint_id(lint_id: BufferedEarlyLintId) -> &'static Self {
  82         match lint_id {
  83             BufferedEarlyLintId::IllFormedAttributeInput => ILL_FORMED_ATTRIBUTE_INPUT,
  84         }
  85     }
  86
  87     /// Gets the lint's name, with ASCII letters converted to lowercase.
  88     pub fn name_lower(&self) -> String {
  89         self.name.to_ascii_lowercase()
  90     }
  91
  92     pub fn default_level(&self, session: &Session) -> Level {
  93         self.edition_lint_opts
  94             .filter(|(e, _)| *e <= session.edition())
  95             .map(|(_, l)| l)
  96             .unwrap_or(self.default_level)
  97     }
  98 }
  99
 100 /// Declares a static item of type `&'static Lint`.
 101 #[macro_export]
 102 macro_rules! declare_lint {
 103     ($vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
 104         declare_lint!{$vis $NAME, $Level, $desc, false}
 105     );
 106     ($vis: vis $NAME: ident, $Level: ident, $desc: expr, report_in_external_macro: $rep: expr) => (
 107         declare_lint!{$vis $NAME, $Level, $desc, $rep}
 108     );
 109     ($vis: vis $NAME: ident, $Level: ident, $desc: expr, $external: expr) => (
 110         $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
 111             name: stringify!($NAME),
 112             default_level: $crate::lint::$Level,
 113             desc: $desc,
 114             edition_lint_opts: None,
 115             report_in_external_macro: $external,
 116         };
 117     );
 118     ($vis: vis $NAME: ident, $Level: ident, $desc: expr,
 119      $lint_edition: expr => $edition_level: ident
 120     ) => (
 121         $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
 122             name: stringify!($NAME),
 123             default_level: $crate::lint::$Level,
 124             desc: $desc,
 125             edition_lint_opts: Some(($lint_edition, $crate::lint::Level::$edition_level)),
 126             report_in_external_macro: false,
 127         };
 128     );
 129 }
 130
 131 #[macro_export]
 132 macro_rules! declare_tool_lint {
 133     (
 134         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level: ident, $desc: expr
 135     ) => (
 136         declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, false}
 137     );
 138     (
 139         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level:ident, $desc:expr,
 140         report_in_external_macro: $rep:expr
 141     ) => (
 142          declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, $rep}
 143     );
 144     (
 145         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level:ident, $desc:expr,
 146         $external:expr
 147     ) => (
 148         $(#[$attr])*
 149         $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
 150             name: &concat!(stringify!($tool), "::", stringify!($NAME)),
 151             default_level: $crate::lint::$Level,
 152             desc: $desc,
 153             edition_lint_opts: None,
 154             report_in_external_macro: $external,
 155         };
 156     );
 157 }
 158
 159 /// Declares a static `LintArray` and return it as an expression.
 160 #[macro_export]
 161 macro_rules! lint_array {
 162     ($( $lint:expr ),* ,) => { lint_array!( $($lint),* ) };
 163     ($( $lint:expr ),*) => {{
 164         vec![$($lint),*]
 165     }}
 166 }
 167
 168 pub type LintArray = Vec<&'static Lint>;
 169
 170 pub trait LintPass {
 171     fn name(&self) -> &'static str;
 172
 173     /// Gets descriptions of the lints this `LintPass` object can emit.
 174     ///
 175     /// N.B., there is no enforcement that the object only emits lints it registered.
 176     /// And some `rustc` internal `LintPass`es register lints to be emitted by other
 177     /// parts of the compiler. If you want enforced access restrictions for your
 178     /// `Lint`, make it a private `static` item in its own module.
 179     fn get_lints(&self) -> LintArray;
 180 }
 181
 182 /// Implements `LintPass for $name` with the given list of `Lint` statics.
 183 #[macro_export]
 184 macro_rules! impl_lint_pass {
 185     ($name:ident => [$($lint:expr),* $(,)?]) => {
 186         impl LintPass for $name {
 187             fn name(&self) -> &'static str { stringify!($name) }
 188             fn get_lints(&self) -> LintArray { $crate::lint_array!($($lint),*) }
 189         }
 190     };
 191 }
 192
 193 /// Declares a type named `$name` which implements `LintPass`.
 194 /// To the right of `=>` a comma separated list of `Lint` statics is given.
 195 #[macro_export]
 196 macro_rules! declare_lint_pass {
 197     ($(#[$m:meta])* $name:ident => [$($lint:expr),* $(,)?]) => {
 198         $(#[$m])* #[derive(Copy, Clone)] pub struct $name;
 199         $crate::impl_lint_pass!($name => [$($lint),*]);
 200     };
 201 }
 202
 203 #[macro_export]
 204 macro_rules! late_lint_methods {
 205     ($macro:path, $args:tt, [$hir:tt]) => (
 206         $macro!($args, [$hir], [
 207             fn check_body(a: &$hir hir::Body);
 208             fn check_body_post(a: &$hir hir::Body);
 209             fn check_name(a: Span, b: ast::Name);
 210             fn check_crate(a: &$hir hir::Crate);
 211             fn check_crate_post(a: &$hir hir::Crate);
 212             fn check_mod(a: &$hir hir::Mod, b: Span, c: hir::HirId);
 213             fn check_mod_post(a: &$hir hir::Mod, b: Span, c: hir::HirId);
 214             fn check_foreign_item(a: &$hir hir::ForeignItem);
 215             fn check_foreign_item_post(a: &$hir hir::ForeignItem);
 216             fn check_item(a: &$hir hir::Item);
 217             fn check_item_post(a: &$hir hir::Item);
 218             fn check_local(a: &$hir hir::Local);
 219             fn check_block(a: &$hir hir::Block);
 220             fn check_block_post(a: &$hir hir::Block);
 221             fn check_stmt(a: &$hir hir::Stmt);
 222             fn check_arm(a: &$hir hir::Arm);
 223             fn check_pat(a: &$hir hir::Pat);
 224             fn check_expr(a: &$hir hir::Expr);
 225             fn check_expr_post(a: &$hir hir::Expr);
 226             fn check_ty(a: &$hir hir::Ty);
 227             fn check_generic_param(a: &$hir hir::GenericParam);
 228             fn check_generics(a: &$hir hir::Generics);
 229             fn check_where_predicate(a: &$hir hir::WherePredicate);
 230             fn check_poly_trait_ref(a: &$hir hir::PolyTraitRef, b: hir::TraitBoundModifier);
 231             fn check_fn(
 232                 a: hir::intravisit::FnKind<$hir>,
 233                 b: &$hir hir::FnDecl,
 234                 c: &$hir hir::Body,
 235                 d: Span,
 236                 e: hir::HirId);
 237             fn check_fn_post(
 238                 a: hir::intravisit::FnKind<$hir>,
 239                 b: &$hir hir::FnDecl,
 240                 c: &$hir hir::Body,
 241                 d: Span,
 242                 e: hir::HirId
 243             );
 244             fn check_trait_item(a: &$hir hir::TraitItem);
 245             fn check_trait_item_post(a: &$hir hir::TraitItem);
 246             fn check_impl_item(a: &$hir hir::ImplItem);
 247             fn check_impl_item_post(a: &$hir hir::ImplItem);
 248             fn check_struct_def(
 249                 a: &$hir hir::VariantData,
 250                 b: ast::Name,
 251                 c: &$hir hir::Generics,
 252                 d: hir::HirId
 253             );
 254             fn check_struct_def_post(
 255                 a: &$hir hir::VariantData,
 256                 b: ast::Name,
 257                 c: &$hir hir::Generics,
 258                 d: hir::HirId
 259             );
 260             fn check_struct_field(a: &$hir hir::StructField);
 261             fn check_variant(a: &$hir hir::Variant, b: &$hir hir::Generics);
 262             fn check_variant_post(a: &$hir hir::Variant, b: &$hir hir::Generics);
 263             fn check_lifetime(a: &$hir hir::Lifetime);
 264             fn check_path(a: &$hir hir::Path, b: hir::HirId);
 265             fn check_attribute(a: &$hir ast::Attribute);
 266
 267             /// Called when entering a syntax node that can have lint attributes such
 268             /// as `#[allow(...)]`. Called with *all* the attributes of that node.
 269             fn enter_lint_attrs(a: &$hir [ast::Attribute]);
 270
 271             /// Counterpart to `enter_lint_attrs`.
 272             fn exit_lint_attrs(a: &$hir [ast::Attribute]);
 273         ]);
 274     )
 275 }
 276
 277 /// Trait for types providing lint checks.
 278 ///
 279 /// Each `check` method checks a single syntax node, and should not
 280 /// invoke methods recursively (unlike `Visitor`). By default they
 281 /// do nothing.
 282 //
 283 // FIXME: eliminate the duplication with `Visitor`. But this also
 284 // contains a few lint-specific methods with no equivalent in `Visitor`.
 285
 286 macro_rules! expand_lint_pass_methods {
 287     ($context:ty, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 288         $(#[inline(always)] fn $name(&mut self, _: $context, $(_: $arg),*) {})*
 289     )
 290 }
 291
 292 macro_rules! declare_late_lint_pass {
 293     ([], [$hir:tt], [$($methods:tt)*]) => (
 294         pub trait LateLintPass<'a, $hir>: LintPass {
 295             fn fresh_late_pass(&self) -> LateLintPassObject {
 296                 panic!()
 297             }
 298             expand_lint_pass_methods!(&LateContext<'a, $hir>, [$($methods)*]);
 299         }
 300     )
 301 }
 302
 303 late_lint_methods!(declare_late_lint_pass, [], ['tcx]);
 304
 305 #[macro_export]
 306 macro_rules! expand_combined_late_lint_pass_method {
 307     ([$($passes:ident),*], $self: ident, $name: ident, $params:tt) => ({
 308         $($self.$passes.$name $params;)*
 309     })
 310 }
 311
 312 #[macro_export]
 313 macro_rules! expand_combined_late_lint_pass_methods {
 314     ($passes:tt, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 315         $(fn $name(&mut self, context: &LateContext<'a, 'tcx>, $($param: $arg),*) {
 316             expand_combined_late_lint_pass_method!($passes, self, $name, (context, $($param),*));
 317         })*
 318     )
 319 }
 320
 321 #[macro_export]
 322 macro_rules! declare_combined_late_lint_pass {
 323     ([$v:vis $name:ident, [$($passes:ident: $constructor:expr,)*]], [$hir:tt], $methods:tt) => (
 324         #[allow(non_snake_case)]
 325         $v struct $name {
 326             $($passes: $passes,)*
 327         }
 328
 329         impl $name {
 330             $v fn new() -> Self {
 331                 Self {
 332                     $($passes: $constructor,)*
 333                 }
 334             }
 335         }
 336
 337         impl<'a, 'tcx> LateLintPass<'a, 'tcx> for $name {
 338             expand_combined_late_lint_pass_methods!([$($passes),*], $methods);
 339         }
 340
 341         impl LintPass for $name {
 342             fn name(&self) -> &'static str {
 343                 panic!()
 344             }
 345
 346             fn get_lints(&self) -> LintArray {
 347                 let mut lints = Vec::new();
 348                 $(lints.extend_from_slice(&self.$passes.get_lints());)*
 349                 lints
 350             }
 351         }
 352     )
 353 }
 354
 355 #[macro_export]
 356 macro_rules! early_lint_methods {
 357     ($macro:path, $args:tt) => (
 358         $macro!($args, [
 359             fn check_ident(a: ast::Ident);
 360             fn check_crate(a: &ast::Crate);
 361             fn check_crate_post(a: &ast::Crate);
 362             fn check_mod(a: &ast::Mod, b: Span, c: ast::NodeId);
 363             fn check_mod_post(a: &ast::Mod, b: Span, c: ast::NodeId);
 364             fn check_foreign_item(a: &ast::ForeignItem);
 365             fn check_foreign_item_post(a: &ast::ForeignItem);
 366             fn check_item(a: &ast::Item);
 367             fn check_item_post(a: &ast::Item);
 368             fn check_local(a: &ast::Local);
 369             fn check_block(a: &ast::Block);
 370             fn check_block_post(a: &ast::Block);
 371             fn check_stmt(a: &ast::Stmt);
 372             fn check_arm(a: &ast::Arm);
 373             fn check_pat(a: &ast::Pat);
 374             fn check_pat_post(a: &ast::Pat);
 375             fn check_expr(a: &ast::Expr);
 376             fn check_expr_post(a: &ast::Expr);
 377             fn check_ty(a: &ast::Ty);
 378             fn check_generic_param(a: &ast::GenericParam);
 379             fn check_generics(a: &ast::Generics);
 380             fn check_where_predicate(a: &ast::WherePredicate);
 381             fn check_poly_trait_ref(a: &ast::PolyTraitRef,
 382                                     b: &ast::TraitBoundModifier);
 383             fn check_fn(a: syntax::visit::FnKind<'_>, b: &ast::FnDecl, c: Span, d_: ast::NodeId);
 384             fn check_fn_post(
 385                 a: syntax::visit::FnKind<'_>,
 386                 b: &ast::FnDecl,
 387                 c: Span,
 388                 d: ast::NodeId
 389             );
 390             fn check_trait_item(a: &ast::TraitItem);
 391             fn check_trait_item_post(a: &ast::TraitItem);
 392             fn check_impl_item(a: &ast::ImplItem);
 393             fn check_impl_item_post(a: &ast::ImplItem);
 394             fn check_struct_def(
 395                 a: &ast::VariantData,
 396                 b: ast::Ident,
 397                 c: &ast::Generics,
 398                 d: ast::NodeId
 399             );
 400             fn check_struct_def_post(
 401                 a: &ast::VariantData,
 402                 b: ast::Ident,
 403                 c: &ast::Generics,
 404                 d: ast::NodeId
 405             );
 406             fn check_struct_field(a: &ast::StructField);
 407             fn check_variant(a: &ast::Variant, b: &ast::Generics);
 408             fn check_variant_post(a: &ast::Variant, b: &ast::Generics);
 409             fn check_lifetime(a: &ast::Lifetime);
 410             fn check_path(a: &ast::Path, b: ast::NodeId);
 411             fn check_attribute(a: &ast::Attribute);
 412             fn check_mac_def(a: &ast::MacroDef, b: ast::NodeId);
 413             fn check_mac(a: &ast::Mac);
 414
 415             /// Called when entering a syntax node that can have lint attributes such
 416             /// as `#[allow(...)]`. Called with *all* the attributes of that node.
 417             fn enter_lint_attrs(a: &[ast::Attribute]);
 418
 419             /// Counterpart to `enter_lint_attrs`.
 420             fn exit_lint_attrs(a: &[ast::Attribute]);
 421         ]);
 422     )
 423 }
 424
 425 macro_rules! expand_early_lint_pass_methods {
 426     ($context:ty, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 427         $(#[inline(always)] fn $name(&mut self, _: $context, $(_: $arg),*) {})*
 428     )
 429 }
 430
 431 macro_rules! declare_early_lint_pass {
 432     ([], [$($methods:tt)*]) => (
 433         pub trait EarlyLintPass: LintPass {
 434             expand_early_lint_pass_methods!(&EarlyContext<'_>, [$($methods)*]);
 435         }
 436     )
 437 }
 438
 439 early_lint_methods!(declare_early_lint_pass, []);
 440
 441 #[macro_export]
 442 macro_rules! expand_combined_early_lint_pass_method {
 443     ([$($passes:ident),*], $self: ident, $name: ident, $params:tt) => ({
 444         $($self.$passes.$name $params;)*
 445     })
 446 }
 447
 448 #[macro_export]
 449 macro_rules! expand_combined_early_lint_pass_methods {
 450     ($passes:tt, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 451         $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
 452             expand_combined_early_lint_pass_method!($passes, self, $name, (context, $($param),*));
 453         })*
 454     )
 455 }
 456
 457 #[macro_export]
 458 macro_rules! declare_combined_early_lint_pass {
 459     ([$v:vis $name:ident, [$($passes:ident: $constructor:expr,)*]], $methods:tt) => (
 460         #[allow(non_snake_case)]
 461         $v struct $name {
 462             $($passes: $passes,)*
 463         }
 464
 465         impl $name {
 466             $v fn new() -> Self {
 467                 Self {
 468                     $($passes: $constructor,)*
 469                 }
 470             }
 471         }
 472
 473         impl EarlyLintPass for $name {
 474             expand_combined_early_lint_pass_methods!([$($passes),*], $methods);
 475         }
 476
 477         impl LintPass for $name {
 478             fn name(&self) -> &'static str {
 479                 panic!()
 480             }
 481
 482             fn get_lints(&self) -> LintArray {
 483                 let mut lints = Vec::new();
 484                 $(lints.extend_from_slice(&self.$passes.get_lints());)*
 485                 lints
 486             }
 487         }
 488     )
 489 }
 490
 491 /// A lint pass boxed up as a trait object.
 492 pub type EarlyLintPassObject = Box<dyn EarlyLintPass + sync::Send + sync::Sync + 'static>;
 493 pub type LateLintPassObject = Box<dyn for<'a, 'tcx> LateLintPass<'a, 'tcx> + sync::Send
 494                                                                            + sync::Sync + 'static>;
 495
 496
 497
 498 /// Identifies a lint known to the compiler.
 499 #[derive(Clone, Copy, Debug)]
 500 pub struct LintId {
 501     // Identity is based on pointer equality of this field.
 502     lint: &'static Lint,
 503 }
 504
 505 impl PartialEq for LintId {
 506     fn eq(&self, other: &LintId) -> bool {
 507         ptr::eq(self.lint, other.lint)
 508     }
 509 }
 510
 511 impl Eq for LintId { }
 512
 513 impl hash::Hash for LintId {
 514     fn hash<H: hash::Hasher>(&self, state: &mut H) {
 515         let ptr = self.lint as *const Lint;
 516         ptr.hash(state);
 517     }
 518 }
 519
 520 impl LintId {
 521     /// Gets the `LintId` for a `Lint`.
 522     pub fn of(lint: &'static Lint) -> LintId {
 523         LintId {
 524             lint,
 525         }
 526     }
 527
 528     pub fn lint_name_raw(&self) -> &'static str {
 529         self.lint.name
 530     }
 531
 532     /// Gets the name of the lint.
 533     pub fn to_string(&self) -> String {
 534         self.lint.name_lower()
 535     }
 536 }
 537
 538 /// Setting for how to handle a lint.
 539 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 540 pub enum Level {
 541     Allow, Warn, Deny, Forbid,
 542 }
 543
 544 impl_stable_hash_for!(enum self::Level {
 545     Allow,
 546     Warn,
 547     Deny,
 548     Forbid
 549 });
 550
 551 impl Level {
 552     /// Converts a level to a lower-case string.
 553     pub fn as_str(self) -> &'static str {
 554         match self {
 555             Allow => "allow",
 556             Warn => "warn",
 557             Deny => "deny",
 558             Forbid => "forbid",
 559         }
 560     }
 561
 562     /// Converts a lower-case string to a level.
 563     pub fn from_str(x: &str) -> Option<Level> {
 564         match x {
 565             "allow" => Some(Allow),
 566             "warn" => Some(Warn),
 567             "deny" => Some(Deny),
 568             "forbid" => Some(Forbid),
 569             _ => None,
 570         }
 571     }
 572
 573     /// Converts a symbol to a level.
 574     pub fn from_symbol(x: Symbol) -> Option<Level> {
 575         match x {
 576             sym::allow => Some(Allow),
 577             sym::warn => Some(Warn),
 578             sym::deny => Some(Deny),
 579             sym::forbid => Some(Forbid),
 580             _ => None,
 581         }
 582     }
 583 }
 584
 585 /// How a lint level was set.
 586 #[derive(Clone, Copy, PartialEq, Eq)]
 587 pub enum LintSource {
 588     /// Lint is at the default level as declared
 589     /// in rustc or a plugin.
 590     Default,
 591
 592     /// Lint level was set by an attribute.
 593     Node(ast::Name, Span, Option<Symbol> /* RFC 2383 reason */),
 594
 595     /// Lint level was set by a command-line flag.
 596     CommandLine(Symbol),
 597 }
 598
 599 impl_stable_hash_for!(enum self::LintSource {
 600     Default,
 601     Node(name, span, reason),
 602     CommandLine(text)
 603 });
 604
 605 pub type LevelSource = (Level, LintSource);
 606
 607 pub mod builtin;
 608 pub mod internal;
 609 mod context;
 610 mod levels;
 611
 612 pub use self::levels::{LintLevelSets, LintLevelMap};
 613
 614 #[derive(Default)]
 615 pub struct LintBuffer {
 616     map: NodeMap<Vec<BufferedEarlyLint>>,
 617 }
 618
 619 impl LintBuffer {
 620     pub fn add_lint(&mut self,
 621                     lint: &'static Lint,
 622                     id: ast::NodeId,
 623                     sp: MultiSpan,
 624                     msg: &str,
 625                     diagnostic: BuiltinLintDiagnostics) {
 626         let early_lint = BufferedEarlyLint {
 627             lint_id: LintId::of(lint),
 628             ast_id: id,
 629             span: sp,
 630             msg: msg.to_string(),
 631             diagnostic
 632         };
 633         let arr = self.map.entry(id).or_default();
 634         if !arr.contains(&early_lint) {
 635             arr.push(early_lint);
 636         }
 637     }
 638
 639     pub fn take(&mut self, id: ast::NodeId) -> Vec<BufferedEarlyLint> {
 640         self.map.remove(&id).unwrap_or_default()
 641     }
 642
 643     pub fn get_any(&self) -> Option<&[BufferedEarlyLint]> {
 644         let key = self.map.keys().next().map(|k| *k);
 645         key.map(|k| &self.map[&k][..])
 646     }
 647 }
 648
 649 pub fn struct_lint_level<'a>(sess: &'a Session,
 650                              lint: &'static Lint,
 651                              level: Level,
 652                              src: LintSource,
 653                              span: Option<MultiSpan>,
 654                              msg: &str)
 655     -> DiagnosticBuilder<'a>
 656 {
 657     let mut err = match (level, span) {
 658         (Level::Allow, _) => return sess.diagnostic().struct_dummy(),
 659         (Level::Warn, Some(span)) => sess.struct_span_warn(span, msg),
 660         (Level::Warn, None) => sess.struct_warn(msg),
 661         (Level::Deny, Some(span)) |
 662         (Level::Forbid, Some(span)) => sess.struct_span_err(span, msg),
 663         (Level::Deny, None) |
 664         (Level::Forbid, None) => sess.struct_err(msg),
 665     };
 666
 667     let name = lint.name_lower();
 668     match src {
 669         LintSource::Default => {
 670             sess.diag_note_once(
 671                 &mut err,
 672                 DiagnosticMessageId::from(lint),
 673                 &format!("#[{}({})] on by default", level.as_str(), name));
 674         }
 675         LintSource::CommandLine(lint_flag_val) => {
 676             let flag = match level {
 677                 Level::Warn => "-W",
 678                 Level::Deny => "-D",
 679                 Level::Forbid => "-F",
 680                 Level::Allow => panic!(),
 681             };
 682             let hyphen_case_lint_name = name.replace("_", "-");
 683             if lint_flag_val.as_str() == name {
 684                 sess.diag_note_once(
 685                     &mut err,
 686                     DiagnosticMessageId::from(lint),
 687                     &format!("requested on the command line with `{} {}`",
 688                              flag, hyphen_case_lint_name));
 689             } else {
 690                 let hyphen_case_flag_val = lint_flag_val.as_str().replace("_", "-");
 691                 sess.diag_note_once(
 692                     &mut err,
 693                     DiagnosticMessageId::from(lint),
 694                     &format!("`{} {}` implied by `{} {}`",
 695                              flag, hyphen_case_lint_name, flag,
 696                              hyphen_case_flag_val));
 697             }
 698         }
 699         LintSource::Node(lint_attr_name, src, reason) => {
 700             if let Some(rationale) = reason {
 701                 err.note(&rationale.as_str());
 702             }
 703             sess.diag_span_note_once(&mut err, DiagnosticMessageId::from(lint),
 704                                      src, "lint level defined here");
 705             if lint_attr_name.as_str() != name {
 706                 let level_str = level.as_str();
 707                 sess.diag_note_once(&mut err, DiagnosticMessageId::from(lint),
 708                                     &format!("#[{}({})] implied by #[{}({})]",
 709                                              level_str, name, level_str, lint_attr_name));
 710             }
 711         }
 712     }
 713
 714     err.code(DiagnosticId::Lint(name));
 715
 716     // Check for future incompatibility lints and issue a stronger warning.
 717     let lints = sess.lint_store.borrow();
 718     let lint_id = LintId::of(lint);
 719     let future_incompatible = lints.future_incompatible(lint_id);
 720     if let Some(future_incompatible) = future_incompatible {
 721         const STANDARD_MESSAGE: &str =
 722             "this was previously accepted by the compiler but is being phased out; \
 723              it will become a hard error";
 724
 725         let explanation = if lint_id == LintId::of(builtin::UNSTABLE_NAME_COLLISIONS) {
 726             "once this method is added to the standard library, \
 727              the ambiguity may cause an error or change in behavior!"
 728                 .to_owned()
 729         } else if lint_id == LintId::of(builtin::MUTABLE_BORROW_RESERVATION_CONFLICT) {
 730             "this borrowing pattern was not meant to be accepted, \
 731              and may become a hard error in the future"
 732                 .to_owned()
 733         } else if let Some(edition) = future_incompatible.edition {
 734             format!("{} in the {} edition!", STANDARD_MESSAGE, edition)
 735         } else {
 736             format!("{} in a future release!", STANDARD_MESSAGE)
 737         };
 738         let citation = format!("for more information, see {}",
 739                                future_incompatible.reference);
 740         err.warn(&explanation);
 741         err.note(&citation);
 742     }
 743
 744     // If this code originates in a foreign macro, aka something that this crate
 745     // did not itself author, then it's likely that there's nothing this crate
 746     // can do about it. We probably want to skip the lint entirely.
 747     if err.span.primary_spans().iter().any(|s| in_external_macro(sess, *s)) {
 748         // Any suggestions made here are likely to be incorrect, so anything we
 749         // emit shouldn't be automatically fixed by rustfix.
 750         err.allow_suggestions(false);
 751
 752         // If this is a future incompatible lint it'll become a hard error, so
 753         // we have to emit *something*. Also allow lints to whitelist themselves
 754         // on a case-by-case basis for emission in a foreign macro.
 755         if future_incompatible.is_none() && !lint.report_in_external_macro {
 756             err.cancel()
 757         }
 758     }
 759
 760     return err
 761 }
 762
 763 pub fn maybe_lint_level_root(tcx: TyCtxt<'_>, id: hir::HirId) -> bool {
 764     let attrs = tcx.hir().attrs(id);
 765     attrs.iter().any(|attr| Level::from_symbol(attr.name_or_empty()).is_some())
 766 }
 767
 768 fn lint_levels<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> &'tcx LintLevelMap {
 769     assert_eq!(cnum, LOCAL_CRATE);
 770     let mut builder = LintLevelMapBuilder {
 771         levels: LintLevelSets::builder(tcx.sess),
 772         tcx: tcx,
 773     };
 774     let krate = tcx.hir().krate();
 775
 776     let push = builder.levels.push(&krate.attrs);
 777     builder.levels.register_id(hir::CRATE_HIR_ID);
 778     for macro_def in &krate.exported_macros {
 779        builder.levels.register_id(macro_def.hir_id);
 780     }
 781     intravisit::walk_crate(&mut builder, krate);
 782     builder.levels.pop(push);
 783
 784     tcx.arena.alloc(builder.levels.build_map())
 785 }
 786
 787 struct LintLevelMapBuilder<'tcx> {
 788     levels: levels::LintLevelsBuilder<'tcx>,
 789     tcx: TyCtxt<'tcx>,
 790 }
 791
 792 impl LintLevelMapBuilder<'tcx> {
 793     fn with_lint_attrs<F>(&mut self,
 794                           id: hir::HirId,
 795                           attrs: &[ast::Attribute],
 796                           f: F)
 797         where F: FnOnce(&mut Self)
 798     {
 799         let push = self.levels.push(attrs);
 800         if push.changed {
 801             self.levels.register_id(id);
 802         }
 803         f(self);
 804         self.levels.pop(push);
 805     }
 806 }
 807
 808 impl intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
 809     fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
 810         intravisit::NestedVisitorMap::All(&self.tcx.hir())
 811     }
 812
 813     fn visit_item(&mut self, it: &'tcx hir::Item) {
 814         self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
 815             intravisit::walk_item(builder, it);
 816         });
 817     }
 818
 819     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem) {
 820         self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
 821             intravisit::walk_foreign_item(builder, it);
 822         })
 823     }
 824
 825     fn visit_expr(&mut self, e: &'tcx hir::Expr) {
 826         self.with_lint_attrs(e.hir_id, &e.attrs, |builder| {
 827             intravisit::walk_expr(builder, e);
 828         })
 829     }
 830
 831     fn visit_struct_field(&mut self, s: &'tcx hir::StructField) {
 832         self.with_lint_attrs(s.hir_id, &s.attrs, |builder| {
 833             intravisit::walk_struct_field(builder, s);
 834         })
 835     }
 836
 837     fn visit_variant(&mut self,
 838                      v: &'tcx hir::Variant,
 839                      g: &'tcx hir::Generics,
 840                      item_id: hir::HirId) {
 841         self.with_lint_attrs(v.node.id, &v.node.attrs, |builder| {
 842             intravisit::walk_variant(builder, v, g, item_id);
 843         })
 844     }
 845
 846     fn visit_local(&mut self, l: &'tcx hir::Local) {
 847         self.with_lint_attrs(l.hir_id, &l.attrs, |builder| {
 848             intravisit::walk_local(builder, l);
 849         })
 850     }
 851
 852     fn visit_arm(&mut self, a: &'tcx hir::Arm) {
 853         self.with_lint_attrs(a.hir_id, &a.attrs, |builder| {
 854             intravisit::walk_arm(builder, a);
 855         })
 856     }
 857
 858     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
 859         self.with_lint_attrs(trait_item.hir_id, &trait_item.attrs, |builder| {
 860             intravisit::walk_trait_item(builder, trait_item);
 861         });
 862     }
 863
 864     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
 865         self.with_lint_attrs(impl_item.hir_id, &impl_item.attrs, |builder| {
 866             intravisit::walk_impl_item(builder, impl_item);
 867         });
 868     }
 869 }
 870
 871 pub fn provide(providers: &mut Providers<'_>) {
 872     providers.lint_levels = lint_levels;
 873 }
 874
 875 /// Returns whether `span` originates in a foreign crate's external macro.
 876 ///
 877 /// This is used to test whether a lint should not even begin to figure out whether it should
 878 /// be reported on the current node.
 879 pub fn in_external_macro(sess: &Session, span: Span) -> bool {
 880     let info = match span.ctxt().outer_expn_info() {
 881         Some(info) => info,
 882         // no ExpnInfo means this span doesn't come from a macro
 883         None => return false,
 884     };
 885
 886     match info.format {
 887         ExpnFormat::MacroAttribute(..) => true, // definitely a plugin
 888         ExpnFormat::CompilerDesugaring(CompilerDesugaringKind::ForLoop) => false,
 889         ExpnFormat::CompilerDesugaring(_) => true, // well, it's "external"
 890         ExpnFormat::MacroBang(..) => {
 891             let def_site = match info.def_site {
 892                 Some(span) => span,
 893                 // no span for the def_site means it's an external macro
 894                 None => return true,
 895             };
 896
 897             match sess.source_map().span_to_snippet(def_site) {
 898                 Ok(code) => !code.starts_with("macro_rules"),
 899                 // no snippet = external macro or compiler-builtin expansion
 900                 Err(_) => true,
 901             }
 902         }
 903     }
 904 }
 905
 906 /// Returns whether `span` originates in a derive macro's expansion
 907 pub fn in_derive_expansion(span: Span) -> bool {
 908     let info = match span.ctxt().outer_expn_info() {
 909         Some(info) => info,
 910         // no ExpnInfo means this span doesn't come from a macro
 911         None => return false,
 912     };
 913
 914     match info.format {
 915         ExpnFormat::MacroAttribute(symbol) => symbol.as_str().starts_with("derive("),
 916         _ => false,
 917     }
 918 }