compiler/rustc_lint/src/lib.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 [rustc_session::lint::builtin],
  12 //! which has further comments on how to add such a lint.
  13 //! rustc can also load user-defined lint plugins via the plugin mechanism.
  14 //!
  15 //! Some of rustc's lints are defined elsewhere in the compiler and work by
  16 //! calling `add_lint()` on the overall `Session` object. This works when
  17 //! it happens before the main lint pass, which emits the lints stored by
  18 //! `add_lint()`. To emit lints after the main lint pass (from codegen, for
  19 //! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
  20 //! in `context.rs`.
  21 //!
  22 //! Some code also exists in [rustc_session::lint], [rustc_middle::lint].
  23 //!
  24 //! ## Note
  25 //!
  26 //! This API is completely unstable and subject to change.
  27
  28 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
  29 #![cfg_attr(test, feature(test))]
  30 #![feature(array_windows)]
  31 #![feature(bool_to_option)]
  32 #![feature(box_syntax)]
  33 #![feature(box_patterns)]
  34 #![feature(crate_visibility_modifier)]
  35 #![feature(format_args_capture)]
  36 #![feature(iter_order_by)]
  37 #![feature(iter_zip)]
  38 #![feature(never_type)]
  39 #![feature(nll)]
  40 #![feature(control_flow_enum)]
  41 #![recursion_limit = "256"]
  42
  43 #[macro_use]
  44 extern crate rustc_middle;
  45 #[macro_use]
  46 extern crate rustc_session;
  47
  48 mod array_into_iter;
  49 pub mod builtin;
  50 mod context;
  51 mod early;
  52 mod internal;
  53 mod late;
  54 mod levels;
  55 mod methods;
  56 mod non_ascii_idents;
  57 mod non_fmt_panic;
  58 mod nonstandard_style;
  59 mod noop_method_call;
  60 mod passes;
  61 mod redundant_semicolon;
  62 mod traits;
  63 mod types;
  64 mod unused;
  65
  66 use rustc_ast as ast;
  67 use rustc_hir as hir;
  68 use rustc_hir::def_id::LocalDefId;
  69 use rustc_middle::ty::query::Providers;
  70 use rustc_middle::ty::TyCtxt;
  71 use rustc_session::lint::builtin::{
  72     BARE_TRAIT_OBJECTS, ELIDED_LIFETIMES_IN_PATHS, EXPLICIT_OUTLIVES_REQUIREMENTS,
  73 };
  74 use rustc_span::symbol::{Ident, Symbol};
  75 use rustc_span::Span;
  76
  77 use array_into_iter::ArrayIntoIter;
  78 use builtin::*;
  79 use internal::*;
  80 use methods::*;
  81 use non_ascii_idents::*;
  82 use non_fmt_panic::NonPanicFmt;
  83 use nonstandard_style::*;
  84 use noop_method_call::*;
  85 use redundant_semicolon::*;
  86 use traits::*;
  87 use types::*;
  88 use unused::*;
  89
  90 /// Useful for other parts of the compiler / Clippy.
  91 pub use builtin::SoftLints;
  92 pub use context::{CheckLintNameResult, EarlyContext, LateContext, LintContext, LintStore};
  93 pub use early::check_ast_crate;
  94 pub use late::check_crate;
  95 pub use passes::{EarlyLintPass, LateLintPass};
  96 pub use rustc_session::lint::Level::{self, *};
  97 pub use rustc_session::lint::{BufferedEarlyLint, FutureIncompatibleInfo, Lint, LintId};
  98 pub use rustc_session::lint::{LintArray, LintPass};
  99
 100 pub fn provide(providers: &mut Providers) {
 101     levels::provide(providers);
 102     *providers = Providers { lint_mod, ..*providers };
 103 }
 104
 105 fn lint_mod(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
 106     late::late_lint_mod(tcx, module_def_id, BuiltinCombinedModuleLateLintPass::new());
 107 }
 108
 109 macro_rules! pre_expansion_lint_passes {
 110     ($macro:path, $args:tt) => {
 111         $macro!($args, [KeywordIdents: KeywordIdents,]);
 112     };
 113 }
 114
 115 macro_rules! early_lint_passes {
 116     ($macro:path, $args:tt) => {
 117         $macro!(
 118             $args,
 119             [
 120                 UnusedParens: UnusedParens,
 121                 UnusedBraces: UnusedBraces,
 122                 UnusedImportBraces: UnusedImportBraces,
 123                 UnsafeCode: UnsafeCode,
 124                 AnonymousParameters: AnonymousParameters,
 125                 EllipsisInclusiveRangePatterns: EllipsisInclusiveRangePatterns::default(),
 126                 NonCamelCaseTypes: NonCamelCaseTypes,
 127                 DeprecatedAttr: DeprecatedAttr::new(),
 128                 WhileTrue: WhileTrue,
 129                 NonAsciiIdents: NonAsciiIdents,
 130                 IncompleteFeatures: IncompleteFeatures,
 131                 RedundantSemicolons: RedundantSemicolons,
 132                 UnusedDocComment: UnusedDocComment,
 133             ]
 134         );
 135     };
 136 }
 137
 138 macro_rules! declare_combined_early_pass {
 139     ([$name:ident], $passes:tt) => (
 140         early_lint_methods!(declare_combined_early_lint_pass, [pub $name, $passes]);
 141     )
 142 }
 143
 144 pre_expansion_lint_passes!(declare_combined_early_pass, [BuiltinCombinedPreExpansionLintPass]);
 145 early_lint_passes!(declare_combined_early_pass, [BuiltinCombinedEarlyLintPass]);
 146
 147 macro_rules! late_lint_passes {
 148     ($macro:path, $args:tt) => {
 149         $macro!(
 150             $args,
 151             [
 152                 // FIXME: Look into regression when this is used as a module lint
 153                 // May Depend on constants elsewhere
 154                 UnusedBrokenConst: UnusedBrokenConst,
 155                 // Uses attr::is_used which is untracked, can't be an incremental module pass.
 156                 UnusedAttributes: UnusedAttributes::new(),
 157                 // Needs to run after UnusedAttributes as it marks all `feature` attributes as used.
 158                 UnstableFeatures: UnstableFeatures,
 159                 // Tracks state across modules
 160                 UnnameableTestItems: UnnameableTestItems::new(),
 161                 // Tracks attributes of parents
 162                 MissingDoc: MissingDoc::new(),
 163                 // Depends on access levels
 164                 // FIXME: Turn the computation of types which implement Debug into a query
 165                 // and change this to a module lint pass
 166                 MissingDebugImplementations: MissingDebugImplementations::default(),
 167                 ArrayIntoIter: ArrayIntoIter::default(),
 168                 ClashingExternDeclarations: ClashingExternDeclarations::new(),
 169                 DropTraitConstraints: DropTraitConstraints,
 170                 TemporaryCStringAsPtr: TemporaryCStringAsPtr,
 171                 NonPanicFmt: NonPanicFmt,
 172                 NoopMethodCall: NoopMethodCall,
 173             ]
 174         );
 175     };
 176 }
 177
 178 macro_rules! late_lint_mod_passes {
 179     ($macro:path, $args:tt) => {
 180         $macro!(
 181             $args,
 182             [
 183                 HardwiredLints: HardwiredLints,
 184                 ImproperCTypesDeclarations: ImproperCTypesDeclarations,
 185                 ImproperCTypesDefinitions: ImproperCTypesDefinitions,
 186                 VariantSizeDifferences: VariantSizeDifferences,
 187                 BoxPointers: BoxPointers,
 188                 PathStatements: PathStatements,
 189                 // Depends on referenced function signatures in expressions
 190                 UnusedResults: UnusedResults,
 191                 NonUpperCaseGlobals: NonUpperCaseGlobals,
 192                 NonShorthandFieldPatterns: NonShorthandFieldPatterns,
 193                 UnusedAllocation: UnusedAllocation,
 194                 // Depends on types used in type definitions
 195                 MissingCopyImplementations: MissingCopyImplementations,
 196                 // Depends on referenced function signatures in expressions
 197                 MutableTransmutes: MutableTransmutes,
 198                 TypeAliasBounds: TypeAliasBounds,
 199                 TrivialConstraints: TrivialConstraints,
 200                 TypeLimits: TypeLimits::new(),
 201                 NonSnakeCase: NonSnakeCase,
 202                 InvalidNoMangleItems: InvalidNoMangleItems,
 203                 // Depends on access levels
 204                 UnreachablePub: UnreachablePub,
 205                 ExplicitOutlivesRequirements: ExplicitOutlivesRequirements,
 206                 InvalidValue: InvalidValue,
 207                 DerefNullPtr: DerefNullPtr,
 208             ]
 209         );
 210     };
 211 }
 212
 213 macro_rules! declare_combined_late_pass {
 214     ([$v:vis $name:ident], $passes:tt) => (
 215         late_lint_methods!(declare_combined_late_lint_pass, [$v $name, $passes], ['tcx]);
 216     )
 217 }
 218
 219 // FIXME: Make a separate lint type which do not require typeck tables
 220 late_lint_passes!(declare_combined_late_pass, [pub BuiltinCombinedLateLintPass]);
 221
 222 late_lint_mod_passes!(declare_combined_late_pass, [BuiltinCombinedModuleLateLintPass]);
 223
 224 pub fn new_lint_store(no_interleave_lints: bool, internal_lints: bool) -> LintStore {
 225     let mut lint_store = LintStore::new();
 226
 227     register_builtins(&mut lint_store, no_interleave_lints);
 228     if internal_lints {
 229         register_internals(&mut lint_store);
 230     }
 231
 232     lint_store
 233 }
 234
 235 /// Tell the `LintStore` about all the built-in lints (the ones
 236 /// defined in this crate and the ones defined in
 237 /// `rustc_session::lint::builtin`).
 238 fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
 239     macro_rules! add_lint_group {
 240         ($name:expr, $($lint:ident),*) => (
 241             store.register_group(false, $name, None, vec![$(LintId::of($lint)),*]);
 242         )
 243     }
 244
 245     macro_rules! register_pass {
 246         ($method:ident, $ty:ident, $constructor:expr) => {
 247             store.register_lints(&$ty::get_lints());
 248             store.$method(|| box $constructor);
 249         };
 250     }
 251
 252     macro_rules! register_passes {
 253         ($method:ident, [$($passes:ident: $constructor:expr,)*]) => (
 254             $(
 255                 register_pass!($method, $passes, $constructor);
 256             )*
 257         )
 258     }
 259
 260     if no_interleave_lints {
 261         pre_expansion_lint_passes!(register_passes, register_pre_expansion_pass);
 262         early_lint_passes!(register_passes, register_early_pass);
 263         late_lint_passes!(register_passes, register_late_pass);
 264         late_lint_mod_passes!(register_passes, register_late_mod_pass);
 265     } else {
 266         store.register_lints(&BuiltinCombinedPreExpansionLintPass::get_lints());
 267         store.register_lints(&BuiltinCombinedEarlyLintPass::get_lints());
 268         store.register_lints(&BuiltinCombinedModuleLateLintPass::get_lints());
 269         store.register_lints(&BuiltinCombinedLateLintPass::get_lints());
 270     }
 271
 272     add_lint_group!(
 273         "nonstandard_style",
 274         NON_CAMEL_CASE_TYPES,
 275         NON_SNAKE_CASE,
 276         NON_UPPER_CASE_GLOBALS
 277     );
 278
 279     add_lint_group!(
 280         "unused",
 281         UNUSED_IMPORTS,
 282         UNUSED_VARIABLES,
 283         UNUSED_ASSIGNMENTS,
 284         DEAD_CODE,
 285         UNUSED_MUT,
 286         UNREACHABLE_CODE,
 287         UNREACHABLE_PATTERNS,
 288         UNUSED_MUST_USE,
 289         UNUSED_UNSAFE,
 290         PATH_STATEMENTS,
 291         UNUSED_ATTRIBUTES,
 292         UNUSED_MACROS,
 293         UNUSED_ALLOCATION,
 294         UNUSED_DOC_COMMENTS,
 295         UNUSED_EXTERN_CRATES,
 296         UNUSED_FEATURES,
 297         UNUSED_LABELS,
 298         UNUSED_PARENS,
 299         UNUSED_BRACES,
 300         REDUNDANT_SEMICOLONS
 301     );
 302
 303     add_lint_group!(
 304         "rust_2018_idioms",
 305         BARE_TRAIT_OBJECTS,
 306         UNUSED_EXTERN_CRATES,
 307         ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
 308         ELIDED_LIFETIMES_IN_PATHS,
 309         EXPLICIT_OUTLIVES_REQUIREMENTS // FIXME(#52665, #47816) not always applicable and not all
 310                                        // macros are ready for this yet.
 311                                        // UNREACHABLE_PUB,
 312
 313                                        // FIXME macro crates are not up for this yet, too much
 314                                        // breakage is seen if we try to encourage this lint.
 315                                        // MACRO_USE_EXTERN_CRATE
 316     );
 317
 318     // Register renamed and removed lints.
 319     store.register_renamed("single_use_lifetime", "single_use_lifetimes");
 320     store.register_renamed("elided_lifetime_in_path", "elided_lifetimes_in_paths");
 321     store.register_renamed("bare_trait_object", "bare_trait_objects");
 322     store.register_renamed("unstable_name_collision", "unstable_name_collisions");
 323     store.register_renamed("unused_doc_comment", "unused_doc_comments");
 324     store.register_renamed("async_idents", "keyword_idents");
 325     store.register_renamed("exceeding_bitshifts", "arithmetic_overflow");
 326     store.register_renamed("redundant_semicolon", "redundant_semicolons");
 327     store.register_renamed("overlapping_patterns", "overlapping_range_endpoints");
 328     store.register_renamed("safe_packed_borrows", "unaligned_references");
 329     store.register_renamed("disjoint_capture_migration", "rust_2021_incompatible_closure_captures");
 330     store.register_renamed("or_patterns_back_compat", "rust_2021_incompatible_or_patterns");
 331     store.register_renamed("non_fmt_panic", "non_fmt_panics");
 332
 333     // These were moved to tool lints, but rustc still sees them when compiling normally, before
 334     // tool lints are registered, so `check_tool_name_for_backwards_compat` doesn't work. Use
 335     // `register_removed` explicitly.
 336     const RUSTDOC_LINTS: &[&str] = &[
 337         "broken_intra_doc_links",
 338         "private_intra_doc_links",
 339         "missing_crate_level_docs",
 340         "missing_doc_code_examples",
 341         "private_doc_tests",
 342         "invalid_codeblock_attributes",
 343         "invalid_html_tags",
 344         "non_autolinks",
 345     ];
 346     for rustdoc_lint in RUSTDOC_LINTS {
 347         store.register_ignored(rustdoc_lint);
 348     }
 349     store.register_removed(
 350         "intra_doc_link_resolution_failure",
 351         "use `rustdoc::broken_intra_doc_links` instead",
 352     );
 353     store.register_removed("rustdoc", "use `rustdoc::all` instead");
 354
 355     store.register_removed("unknown_features", "replaced by an error");
 356     store.register_removed("unsigned_negation", "replaced by negate_unsigned feature gate");
 357     store.register_removed("negate_unsigned", "cast a signed value instead");
 358     store.register_removed("raw_pointer_derive", "using derive with raw pointers is ok");
 359     // Register lint group aliases.
 360     store.register_group_alias("nonstandard_style", "bad_style");
 361     // This was renamed to `raw_pointer_derive`, which was then removed,
 362     // so it is also considered removed.
 363     store.register_removed("raw_pointer_deriving", "using derive with raw pointers is ok");
 364     store.register_removed("drop_with_repr_extern", "drop flags have been removed");
 365     store.register_removed("fat_ptr_transmutes", "was accidentally removed back in 2014");
 366     store.register_removed("deprecated_attr", "use `deprecated` instead");
 367     store.register_removed(
 368         "transmute_from_fn_item_types",
 369         "always cast functions before transmuting them",
 370     );
 371     store.register_removed(
 372         "hr_lifetime_in_assoc_type",
 373         "converted into hard error, see issue #33685 \
 374          <https://github.com/rust-lang/rust/issues/33685> for more information",
 375     );
 376     store.register_removed(
 377         "inaccessible_extern_crate",
 378         "converted into hard error, see issue #36886 \
 379          <https://github.com/rust-lang/rust/issues/36886> for more information",
 380     );
 381     store.register_removed(
 382         "super_or_self_in_global_path",
 383         "converted into hard error, see issue #36888 \
 384          <https://github.com/rust-lang/rust/issues/36888> for more information",
 385     );
 386     store.register_removed(
 387         "overlapping_inherent_impls",
 388         "converted into hard error, see issue #36889 \
 389          <https://github.com/rust-lang/rust/issues/36889> for more information",
 390     );
 391     store.register_removed(
 392         "illegal_floating_point_constant_pattern",
 393         "converted into hard error, see issue #36890 \
 394          <https://github.com/rust-lang/rust/issues/36890> for more information",
 395     );
 396     store.register_removed(
 397         "illegal_struct_or_enum_constant_pattern",
 398         "converted into hard error, see issue #36891 \
 399          <https://github.com/rust-lang/rust/issues/36891> for more information",
 400     );
 401     store.register_removed(
 402         "lifetime_underscore",
 403         "converted into hard error, see issue #36892 \
 404          <https://github.com/rust-lang/rust/issues/36892> for more information",
 405     );
 406     store.register_removed(
 407         "extra_requirement_in_impl",
 408         "converted into hard error, see issue #37166 \
 409          <https://github.com/rust-lang/rust/issues/37166> for more information",
 410     );
 411     store.register_removed(
 412         "legacy_imports",
 413         "converted into hard error, see issue #38260 \
 414          <https://github.com/rust-lang/rust/issues/38260> for more information",
 415     );
 416     store.register_removed(
 417         "coerce_never",
 418         "converted into hard error, see issue #48950 \
 419          <https://github.com/rust-lang/rust/issues/48950> for more information",
 420     );
 421     store.register_removed(
 422         "resolve_trait_on_defaulted_unit",
 423         "converted into hard error, see issue #48950 \
 424          <https://github.com/rust-lang/rust/issues/48950> for more information",
 425     );
 426     store.register_removed(
 427         "private_no_mangle_fns",
 428         "no longer a warning, `#[no_mangle]` functions always exported",
 429     );
 430     store.register_removed(
 431         "private_no_mangle_statics",
 432         "no longer a warning, `#[no_mangle]` statics always exported",
 433     );
 434     store.register_removed("bad_repr", "replaced with a generic attribute input check");
 435     store.register_removed(
 436         "duplicate_matcher_binding_name",
 437         "converted into hard error, see issue #57742 \
 438          <https://github.com/rust-lang/rust/issues/57742> for more information",
 439     );
 440     store.register_removed(
 441         "incoherent_fundamental_impls",
 442         "converted into hard error, see issue #46205 \
 443          <https://github.com/rust-lang/rust/issues/46205> for more information",
 444     );
 445     store.register_removed(
 446         "legacy_constructor_visibility",
 447         "converted into hard error, see issue #39207 \
 448          <https://github.com/rust-lang/rust/issues/39207> for more information",
 449     );
 450     store.register_removed(
 451         "legacy_directory_ownership",
 452         "converted into hard error, see issue #37872 \
 453          <https://github.com/rust-lang/rust/issues/37872> for more information",
 454     );
 455     store.register_removed(
 456         "safe_extern_statics",
 457         "converted into hard error, see issue #36247 \
 458          <https://github.com/rust-lang/rust/issues/36247> for more information",
 459     );
 460     store.register_removed(
 461         "parenthesized_params_in_types_and_modules",
 462         "converted into hard error, see issue #42238 \
 463          <https://github.com/rust-lang/rust/issues/42238> for more information",
 464     );
 465     store.register_removed(
 466         "duplicate_macro_exports",
 467         "converted into hard error, see issue #35896 \
 468          <https://github.com/rust-lang/rust/issues/35896> for more information",
 469     );
 470     store.register_removed(
 471         "nested_impl_trait",
 472         "converted into hard error, see issue #59014 \
 473          <https://github.com/rust-lang/rust/issues/59014> for more information",
 474     );
 475     store.register_removed("plugin_as_library", "plugins have been deprecated and retired");
 476 }
 477
 478 fn register_internals(store: &mut LintStore) {
 479     store.register_lints(&LintPassImpl::get_lints());
 480     store.register_early_pass(|| box LintPassImpl);
 481     store.register_lints(&DefaultHashTypes::get_lints());
 482     store.register_late_pass(|| box DefaultHashTypes);
 483     store.register_lints(&ExistingDocKeyword::get_lints());
 484     store.register_late_pass(|| box ExistingDocKeyword);
 485     store.register_lints(&TyTyKind::get_lints());
 486     store.register_late_pass(|| box TyTyKind);
 487     store.register_group(
 488         false,
 489         "rustc::internal",
 490         None,
 491         vec![
 492             LintId::of(DEFAULT_HASH_TYPES),
 493             LintId::of(USAGE_OF_TY_TYKIND),
 494             LintId::of(LINT_PASS_IMPL_WITHOUT_MACRO),
 495             LintId::of(TY_PASS_BY_REFERENCE),
 496             LintId::of(USAGE_OF_QUALIFIED_TY),
 497             LintId::of(EXISTING_DOC_KEYWORD),
 498         ],
 499     );
 500 }
 501
 502 #[cfg(test)]
 503 mod tests;