src/librustc/lint/builtin.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Some lints that are built in to the compiler.
  12 //!
  13 //! These are the built-in lints that are emitted direct in the main
  14 //! compiler code, rather than using their own custom pass. Those
  15 //! lints are all available in `rustc_lint::builtin`.
  16
  17 use errors::{Applicability, DiagnosticBuilder};
  18 use lint::{LintPass, LateLintPass, LintArray};
  19 use session::Session;
  20 use syntax::ast;
  21 use syntax::source_map::Span;
  22
  23 declare_lint! {
  24     pub EXCEEDING_BITSHIFTS,
  25     Deny,
  26     "shift exceeds the type's number of bits"
  27 }
  28
  29 declare_lint! {
  30     pub CONST_ERR,
  31     Deny,
  32     "constant evaluation detected erroneous expression"
  33 }
  34
  35 declare_lint! {
  36     pub UNUSED_IMPORTS,
  37     Warn,
  38     "imports that are never used"
  39 }
  40
  41 declare_lint! {
  42     pub UNUSED_EXTERN_CRATES,
  43     Allow,
  44     "extern crates that are never used"
  45 }
  46
  47 declare_lint! {
  48     pub UNUSED_QUALIFICATIONS,
  49     Allow,
  50     "detects unnecessarily qualified names"
  51 }
  52
  53 declare_lint! {
  54     pub UNKNOWN_LINTS,
  55     Warn,
  56     "unrecognized lint attribute"
  57 }
  58
  59 declare_lint! {
  60     pub UNUSED_VARIABLES,
  61     Warn,
  62     "detect variables which are not used in any way"
  63 }
  64
  65 declare_lint! {
  66     pub UNUSED_ASSIGNMENTS,
  67     Warn,
  68     "detect assignments that will never be read"
  69 }
  70
  71 declare_lint! {
  72     pub DEAD_CODE,
  73     Warn,
  74     "detect unused, unexported items"
  75 }
  76
  77 declare_lint! {
  78     pub UNREACHABLE_CODE,
  79     Warn,
  80     "detects unreachable code paths",
  81     report_in_external_macro: true
  82 }
  83
  84 declare_lint! {
  85     pub UNREACHABLE_PATTERNS,
  86     Warn,
  87     "detects unreachable patterns"
  88 }
  89
  90 declare_lint! {
  91     pub UNUSED_MACROS,
  92     Warn,
  93     "detects macros that were not used"
  94 }
  95
  96 declare_lint! {
  97     pub WARNINGS,
  98     Warn,
  99     "mass-change the level for lints which produce warnings"
 100 }
 101
 102 declare_lint! {
 103     pub UNUSED_FEATURES,
 104     Warn,
 105     "unused features found in crate-level #[feature] directives"
 106 }
 107
 108 declare_lint! {
 109     pub STABLE_FEATURES,
 110     Warn,
 111     "stable features found in #[feature] directive"
 112 }
 113
 114 declare_lint! {
 115     pub UNKNOWN_CRATE_TYPES,
 116     Deny,
 117     "unknown crate type found in #[crate_type] directive"
 118 }
 119
 120 declare_lint! {
 121     pub TRIVIAL_CASTS,
 122     Allow,
 123     "detects trivial casts which could be removed"
 124 }
 125
 126 declare_lint! {
 127     pub TRIVIAL_NUMERIC_CASTS,
 128     Allow,
 129     "detects trivial casts of numeric types which could be removed"
 130 }
 131
 132 declare_lint! {
 133     pub PRIVATE_IN_PUBLIC,
 134     Warn,
 135     "detect private items in public interfaces not caught by the old implementation"
 136 }
 137
 138 declare_lint! {
 139     pub PUB_USE_OF_PRIVATE_EXTERN_CRATE,
 140     Deny,
 141     "detect public re-exports of private extern crates"
 142 }
 143
 144 declare_lint! {
 145     pub INVALID_TYPE_PARAM_DEFAULT,
 146     Deny,
 147     "type parameter default erroneously allowed in invalid location"
 148 }
 149
 150 declare_lint! {
 151     pub RENAMED_AND_REMOVED_LINTS,
 152     Warn,
 153     "lints that have been renamed or removed"
 154 }
 155
 156 declare_lint! {
 157     pub SAFE_EXTERN_STATICS,
 158     Deny,
 159     "safe access to extern statics was erroneously allowed"
 160 }
 161
 162 declare_lint! {
 163     pub SAFE_PACKED_BORROWS,
 164     Warn,
 165     "safe borrows of fields of packed structs were was erroneously allowed"
 166 }
 167
 168 declare_lint! {
 169     pub PATTERNS_IN_FNS_WITHOUT_BODY,
 170     Warn,
 171     "patterns in functions without body were erroneously allowed"
 172 }
 173
 174 declare_lint! {
 175     pub LEGACY_DIRECTORY_OWNERSHIP,
 176     Deny,
 177     "non-inline, non-`#[path]` modules (e.g. `mod foo;`) were erroneously allowed in some files \
 178      not named `mod.rs`"
 179 }
 180
 181 declare_lint! {
 182     pub LEGACY_CONSTRUCTOR_VISIBILITY,
 183     Deny,
 184     "detects use of struct constructors that would be invisible with new visibility rules"
 185 }
 186
 187 declare_lint! {
 188     pub MISSING_FRAGMENT_SPECIFIER,
 189     Deny,
 190     "detects missing fragment specifiers in unused `macro_rules!` patterns"
 191 }
 192
 193 declare_lint! {
 194     pub PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
 195     Deny,
 196     "detects parenthesized generic parameters in type and module names"
 197 }
 198
 199 declare_lint! {
 200     pub LATE_BOUND_LIFETIME_ARGUMENTS,
 201     Warn,
 202     "detects generic lifetime arguments in path segments with late bound lifetime parameters"
 203 }
 204
 205 declare_lint! {
 206     pub INCOHERENT_FUNDAMENTAL_IMPLS,
 207     Deny,
 208     "potentially-conflicting impls were erroneously allowed"
 209 }
 210
 211 declare_lint! {
 212     pub BAD_REPR,
 213     Warn,
 214     "detects incorrect use of `repr` attribute"
 215 }
 216
 217 declare_lint! {
 218     pub DEPRECATED,
 219     Warn,
 220     "detects use of deprecated items",
 221     report_in_external_macro: true
 222 }
 223
 224 declare_lint! {
 225     pub UNUSED_UNSAFE,
 226     Warn,
 227     "unnecessary use of an `unsafe` block"
 228 }
 229
 230 declare_lint! {
 231     pub UNUSED_MUT,
 232     Warn,
 233     "detect mut variables which don't need to be mutable"
 234 }
 235
 236 declare_lint! {
 237     pub SINGLE_USE_LIFETIMES,
 238     Allow,
 239     "detects lifetime parameters that are only used once"
 240 }
 241
 242 declare_lint! {
 243     pub UNUSED_LIFETIMES,
 244     Allow,
 245     "detects lifetime parameters that are never used"
 246 }
 247
 248 declare_lint! {
 249     pub TYVAR_BEHIND_RAW_POINTER,
 250     Warn,
 251     "raw pointer to an inference variable"
 252 }
 253
 254 declare_lint! {
 255     pub ELIDED_LIFETIMES_IN_PATHS,
 256     Allow,
 257     "hidden lifetime parameters in types are deprecated"
 258 }
 259
 260 declare_lint! {
 261     pub BARE_TRAIT_OBJECTS,
 262     Allow,
 263     "suggest using `dyn Trait` for trait objects"
 264 }
 265
 266 declare_lint! {
 267     pub ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
 268     Allow,
 269     "fully qualified paths that start with a module name \
 270      instead of `crate`, `self`, or an extern crate name"
 271 }
 272
 273 declare_lint! {
 274     pub ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
 275     Warn,
 276     "floating-point literals cannot be used in patterns"
 277 }
 278
 279 declare_lint! {
 280     pub UNSTABLE_NAME_COLLISIONS,
 281     Warn,
 282     "detects name collision with an existing but unstable method"
 283 }
 284
 285 declare_lint! {
 286     pub IRREFUTABLE_LET_PATTERNS,
 287     Deny,
 288     "detects irrefutable patterns in if-let and while-let statements"
 289 }
 290
 291 declare_lint! {
 292     pub UNUSED_LABELS,
 293     Allow,
 294     "detects labels that are never used"
 295 }
 296
 297 declare_lint! {
 298     pub DUPLICATE_ASSOCIATED_TYPE_BINDINGS,
 299     Warn,
 300     "warns about duplicate associated type bindings in generics"
 301 }
 302
 303 declare_lint! {
 304     pub DUPLICATE_MACRO_EXPORTS,
 305     Deny,
 306     "detects duplicate macro exports"
 307 }
 308
 309 declare_lint! {
 310     pub INTRA_DOC_LINK_RESOLUTION_FAILURE,
 311     Warn,
 312     "warn about documentation intra links resolution failure"
 313 }
 314
 315 declare_lint! {
 316     pub MISSING_DOC_ITEM_CODE_EXAMPLE,
 317     Allow,
 318     "warn about missing code example in an item's documentation"
 319 }
 320
 321 declare_lint! {
 322     pub WHERE_CLAUSES_OBJECT_SAFETY,
 323     Warn,
 324     "checks the object safety of where clauses"
 325 }
 326
 327 declare_lint! {
 328     pub PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
 329     Warn,
 330     "detects proc macro derives using inaccessible names from parent modules"
 331 }
 332
 333 declare_lint! {
 334     pub MACRO_USE_EXTERN_CRATE,
 335     Allow,
 336     "the `#[macro_use]` attribute is now deprecated in favor of using macros \
 337      via the module system"
 338 }
 339
 340 declare_lint! {
 341     pub MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
 342     Deny,
 343     "macro-expanded `macro_export` macros from the current crate \
 344      cannot be referred to by absolute paths"
 345 }
 346
 347 declare_lint! {
 348     pub EXPLICIT_OUTLIVES_REQUIREMENTS,
 349     Allow,
 350     "outlives requirements can be inferred"
 351 }
 352
 353 /// Some lints that are buffered from `libsyntax`. See `syntax::early_buffered_lints`.
 354 pub mod parser {
 355     declare_lint! {
 356         pub QUESTION_MARK_MACRO_SEP,
 357         Allow,
 358         "detects the use of `?` as a macro separator"
 359     }
 360 }
 361
 362 /// Does nothing as a lint pass, but registers some `Lint`s
 363 /// which are used by other parts of the compiler.
 364 #[derive(Copy, Clone)]
 365 pub struct HardwiredLints;
 366
 367 impl LintPass for HardwiredLints {
 368     fn get_lints(&self) -> LintArray {
 369         lint_array!(
 370             ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
 371             EXCEEDING_BITSHIFTS,
 372             UNUSED_IMPORTS,
 373             UNUSED_EXTERN_CRATES,
 374             UNUSED_QUALIFICATIONS,
 375             UNKNOWN_LINTS,
 376             UNUSED_VARIABLES,
 377             UNUSED_ASSIGNMENTS,
 378             DEAD_CODE,
 379             UNREACHABLE_CODE,
 380             UNREACHABLE_PATTERNS,
 381             UNUSED_MACROS,
 382             WARNINGS,
 383             UNUSED_FEATURES,
 384             STABLE_FEATURES,
 385             UNKNOWN_CRATE_TYPES,
 386             TRIVIAL_CASTS,
 387             TRIVIAL_NUMERIC_CASTS,
 388             PRIVATE_IN_PUBLIC,
 389             PUB_USE_OF_PRIVATE_EXTERN_CRATE,
 390             INVALID_TYPE_PARAM_DEFAULT,
 391             CONST_ERR,
 392             RENAMED_AND_REMOVED_LINTS,
 393             SAFE_EXTERN_STATICS,
 394             SAFE_PACKED_BORROWS,
 395             PATTERNS_IN_FNS_WITHOUT_BODY,
 396             LEGACY_DIRECTORY_OWNERSHIP,
 397             LEGACY_CONSTRUCTOR_VISIBILITY,
 398             MISSING_FRAGMENT_SPECIFIER,
 399             PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
 400             LATE_BOUND_LIFETIME_ARGUMENTS,
 401             INCOHERENT_FUNDAMENTAL_IMPLS,
 402             DEPRECATED,
 403             UNUSED_UNSAFE,
 404             UNUSED_MUT,
 405             SINGLE_USE_LIFETIMES,
 406             UNUSED_LIFETIMES,
 407             UNUSED_LABELS,
 408             TYVAR_BEHIND_RAW_POINTER,
 409             ELIDED_LIFETIMES_IN_PATHS,
 410             BARE_TRAIT_OBJECTS,
 411             ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
 412             UNSTABLE_NAME_COLLISIONS,
 413             IRREFUTABLE_LET_PATTERNS,
 414             DUPLICATE_ASSOCIATED_TYPE_BINDINGS,
 415             DUPLICATE_MACRO_EXPORTS,
 416             INTRA_DOC_LINK_RESOLUTION_FAILURE,
 417             MISSING_DOC_CODE_EXAMPLES,
 418             WHERE_CLAUSES_OBJECT_SAFETY,
 419             PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
 420             MACRO_USE_EXTERN_CRATE,
 421             MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
 422             parser::QUESTION_MARK_MACRO_SEP,
 423         )
 424     }
 425 }
 426
 427 // this could be a closure, but then implementing derive traits
 428 // becomes hacky (and it gets allocated)
 429 #[derive(PartialEq, RustcEncodable, RustcDecodable, Debug)]
 430 pub enum BuiltinLintDiagnostics {
 431     Normal,
 432     BareTraitObject(Span, /* is_global */ bool),
 433     AbsPathWithModule(Span),
 434     DuplicatedMacroExports(ast::Ident, Span, Span),
 435     ProcMacroDeriveResolutionFallback(Span),
 436     MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
 437     ElidedLifetimesInPaths(usize, Span, bool, Span, String),
 438     UnknownCrateTypes(Span, String, String),
 439 }
 440
 441 impl BuiltinLintDiagnostics {
 442     pub fn run(self, sess: &Session, db: &mut DiagnosticBuilder<'_>) {
 443         match self {
 444             BuiltinLintDiagnostics::Normal => (),
 445             BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 446                 let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 447                     Ok(ref s) if is_global => (format!("dyn ({})", s),
 448                                                Applicability::MachineApplicable),
 449                     Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 450                     Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders)
 451                 };
 452                 db.span_suggestion_with_applicability(span, "use `dyn`", sugg, app);
 453             }
 454             BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 455                 let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 456                     Ok(ref s) => {
 457                         // FIXME(Manishearth) ideally the emitting code
 458                         // can tell us whether or not this is global
 459                         let opt_colon = if s.trim_left().starts_with("::") {
 460                             ""
 461                         } else {
 462                             "::"
 463                         };
 464
 465                         (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 466                     }
 467                     Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders)
 468                 };
 469                 db.span_suggestion_with_applicability(span, "use `crate`", sugg, app);
 470             }
 471             BuiltinLintDiagnostics::DuplicatedMacroExports(ident, earlier_span, later_span) => {
 472                 db.span_label(later_span, format!("`{}` already exported", ident));
 473                 db.span_note(earlier_span, "previous macro export is now shadowed");
 474             }
 475             BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 476                 db.span_label(span, "names from parent modules are not \
 477                                      accessible without an explicit import");
 478             }
 479             BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(span_def) => {
 480                 db.span_note(span_def, "the macro is defined here");
 481             }
 482             BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 483                 n, path_span, incl_angl_brckt, insertion_span, anon_lts
 484             ) => {
 485                 let (replace_span, suggestion) = if incl_angl_brckt {
 486                     (insertion_span, anon_lts)
 487                 } else {
 488                     // When possible, prefer a suggestion that replaces the whole
 489                     // `Path<T>` expression with `Path<'_, T>`, rather than inserting `'_, `
 490                     // at a point (which makes for an ugly/confusing label)
 491                     if let Ok(snippet) = sess.source_map().span_to_snippet(path_span) {
 492                         // But our spans can get out of whack due to macros; if the place we think
 493                         // we want to insert `'_` isn't even within the path expression's span, we
 494                         // should bail out of making any suggestion rather than panicking on a
 495                         // subtract-with-overflow or string-slice-out-out-bounds (!)
 496                         // FIXME: can we do better?
 497                         if insertion_span.lo().0 < path_span.lo().0 {
 498                             return;
 499                         }
 500                         let insertion_index = (insertion_span.lo().0 - path_span.lo().0) as usize;
 501                         if insertion_index > snippet.len() {
 502                             return;
 503                         }
 504                         let (before, after) = snippet.split_at(insertion_index);
 505                         (path_span, format!("{}{}{}", before, anon_lts, after))
 506                     } else {
 507                         (insertion_span, anon_lts)
 508                     }
 509                 };
 510                 db.span_suggestion_with_applicability(
 511                     replace_span,
 512                     &format!("indicate the anonymous lifetime{}", if n >= 2 { "s" } else { "" }),
 513                     suggestion,
 514                     Applicability::MachineApplicable
 515                 );
 516             }
 517             BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 518                 db.span_suggestion_with_applicability(
 519                     span,
 520                     &note,
 521                     sugg,
 522                     Applicability::MaybeIncorrect
 523                 );
 524             }
 525         }
 526     }
 527 }
 528
 529 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HardwiredLints {}