compiler/rustc_middle/src/lint.rs

   1 use std::cmp;
   2
   3 use crate::ich::StableHashingContext;
   4 use rustc_data_structures::fx::FxHashMap;
   5 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
   6 use rustc_errors::{DiagnosticBuilder, DiagnosticId};
   7 use rustc_hir::HirId;
   8 use rustc_index::vec::IndexVec;
   9 use rustc_session::lint::{
  10     builtin::{self, FORBIDDEN_LINT_GROUPS},
  11     FutureIncompatibilityReason, Level, Lint, LintId,
  12 };
  13 use rustc_session::{DiagnosticMessageId, Session};
  14 use rustc_span::hygiene::MacroKind;
  15 use rustc_span::source_map::{DesugaringKind, ExpnKind, MultiSpan};
  16 use rustc_span::{symbol, Span, Symbol, DUMMY_SP};
  17
  18 /// How a lint level was set.
  19 #[derive(Clone, Copy, PartialEq, Eq, HashStable, Debug)]
  20 pub enum LintLevelSource {
  21     /// Lint is at the default level as declared
  22     /// in rustc or a plugin.
  23     Default,
  24
  25     /// Lint level was set by an attribute.
  26     Node(Symbol, Span, Option<Symbol> /* RFC 2383 reason */),
  27
  28     /// Lint level was set by a command-line flag.
  29     /// The provided `Level` is the level specified on the command line.
  30     /// (The actual level may be lower due to `--cap-lints`.)
  31     CommandLine(Symbol, Level),
  32 }
  33
  34 impl LintLevelSource {
  35     pub fn name(&self) -> Symbol {
  36         match *self {
  37             LintLevelSource::Default => symbol::kw::Default,
  38             LintLevelSource::Node(name, _, _) => name,
  39             LintLevelSource::CommandLine(name, _) => name,
  40         }
  41     }
  42
  43     pub fn span(&self) -> Span {
  44         match *self {
  45             LintLevelSource::Default => DUMMY_SP,
  46             LintLevelSource::Node(_, span, _) => span,
  47             LintLevelSource::CommandLine(_, _) => DUMMY_SP,
  48         }
  49     }
  50 }
  51
  52 /// A tuple of a lint level and its source.
  53 pub type LevelAndSource = (Level, LintLevelSource);
  54
  55 #[derive(Debug, HashStable)]
  56 pub struct LintLevelSets {
  57     pub list: IndexVec<LintStackIndex, LintSet>,
  58     pub lint_cap: Level,
  59 }
  60
  61 rustc_index::newtype_index! {
  62     #[derive(HashStable)]
  63     pub struct LintStackIndex {
  64         const COMMAND_LINE = 0,
  65     }
  66 }
  67
  68 #[derive(Debug, HashStable)]
  69 pub struct LintSet {
  70     // -A,-W,-D flags, a `Symbol` for the flag itself and `Level` for which
  71     // flag.
  72     pub specs: FxHashMap<LintId, LevelAndSource>,
  73
  74     pub parent: LintStackIndex,
  75 }
  76
  77 impl LintLevelSets {
  78     pub fn new() -> Self {
  79         LintLevelSets { list: IndexVec::new(), lint_cap: Level::Forbid }
  80     }
  81
  82     pub fn get_lint_level(
  83         &self,
  84         lint: &'static Lint,
  85         idx: LintStackIndex,
  86         aux: Option<&FxHashMap<LintId, LevelAndSource>>,
  87         sess: &Session,
  88     ) -> LevelAndSource {
  89         let (level, mut src) = self.get_lint_id_level(LintId::of(lint), idx, aux);
  90
  91         // If `level` is none then we actually assume the default level for this
  92         // lint.
  93         let mut level = level.unwrap_or_else(|| lint.default_level(sess.edition()));
  94
  95         // If we're about to issue a warning, check at the last minute for any
  96         // directives against the warnings "lint". If, for example, there's an
  97         // `allow(warnings)` in scope then we want to respect that instead.
  98         //
  99         // We exempt `FORBIDDEN_LINT_GROUPS` from this because it specifically
 100         // triggers in cases (like #80988) where you have `forbid(warnings)`,
 101         // and so if we turned that into an error, it'd defeat the purpose of the
 102         // future compatibility warning.
 103         if level == Level::Warn && LintId::of(lint) != LintId::of(FORBIDDEN_LINT_GROUPS) {
 104             let (warnings_level, warnings_src) =
 105                 self.get_lint_id_level(LintId::of(builtin::WARNINGS), idx, aux);
 106             if let Some(configured_warning_level) = warnings_level {
 107                 if configured_warning_level != Level::Warn {
 108                     level = configured_warning_level;
 109                     src = warnings_src;
 110                 }
 111             }
 112         }
 113
 114         // Ensure that we never exceed the `--cap-lints` argument
 115         // unless the source is a --force-warn
 116         level = if let LintLevelSource::CommandLine(_, Level::ForceWarn) = src {
 117             level
 118         } else {
 119             cmp::min(level, self.lint_cap)
 120         };
 121
 122         if let Some(driver_level) = sess.driver_lint_caps.get(&LintId::of(lint)) {
 123             // Ensure that we never exceed driver level.
 124             level = cmp::min(*driver_level, level);
 125         }
 126
 127         (level, src)
 128     }
 129
 130     pub fn get_lint_id_level(
 131         &self,
 132         id: LintId,
 133         mut idx: LintStackIndex,
 134         aux: Option<&FxHashMap<LintId, LevelAndSource>>,
 135     ) -> (Option<Level>, LintLevelSource) {
 136         if let Some(specs) = aux {
 137             if let Some(&(level, src)) = specs.get(&id) {
 138                 return (Some(level), src);
 139             }
 140         }
 141         loop {
 142             let LintSet { ref specs, parent } = self.list[idx];
 143             if let Some(&(level, src)) = specs.get(&id) {
 144                 return (Some(level), src);
 145             }
 146             if idx == COMMAND_LINE {
 147                 return (None, LintLevelSource::Default);
 148             }
 149             idx = parent;
 150         }
 151     }
 152 }
 153
 154 #[derive(Debug)]
 155 pub struct LintLevelMap {
 156     pub sets: LintLevelSets,
 157     pub id_to_set: FxHashMap<HirId, LintStackIndex>,
 158 }
 159
 160 impl LintLevelMap {
 161     /// If the `id` was previously registered with `register_id` when building
 162     /// this `LintLevelMap` this returns the corresponding lint level and source
 163     /// of the lint level for the lint provided.
 164     ///
 165     /// If the `id` was not previously registered, returns `None`. If `None` is
 166     /// returned then the parent of `id` should be acquired and this function
 167     /// should be called again.
 168     pub fn level_and_source(
 169         &self,
 170         lint: &'static Lint,
 171         id: HirId,
 172         session: &Session,
 173     ) -> Option<LevelAndSource> {
 174         self.id_to_set.get(&id).map(|idx| self.sets.get_lint_level(lint, *idx, None, session))
 175     }
 176 }
 177
 178 impl<'a> HashStable<StableHashingContext<'a>> for LintLevelMap {
 179     #[inline]
 180     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
 181         let LintLevelMap { ref sets, ref id_to_set } = *self;
 182
 183         id_to_set.hash_stable(hcx, hasher);
 184
 185         hcx.while_hashing_spans(true, |hcx| sets.hash_stable(hcx, hasher))
 186     }
 187 }
 188
 189 pub struct LintDiagnosticBuilder<'a>(DiagnosticBuilder<'a>);
 190
 191 impl<'a> LintDiagnosticBuilder<'a> {
 192     /// Return the inner DiagnosticBuilder, first setting the primary message to `msg`.
 193     pub fn build(mut self, msg: &str) -> DiagnosticBuilder<'a> {
 194         self.0.set_primary_message(msg);
 195         self.0
 196     }
 197
 198     /// Create a LintDiagnosticBuilder from some existing DiagnosticBuilder.
 199     pub fn new(err: DiagnosticBuilder<'a>) -> LintDiagnosticBuilder<'a> {
 200         LintDiagnosticBuilder(err)
 201     }
 202 }
 203
 204 pub fn struct_lint_level<'s, 'd>(
 205     sess: &'s Session,
 206     lint: &'static Lint,
 207     level: Level,
 208     src: LintLevelSource,
 209     span: Option<MultiSpan>,
 210     decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>) + 'd,
 211 ) {
 212     // Avoid codegen bloat from monomorphization by immediately doing dyn dispatch of `decorate` to
 213     // the "real" work.
 214     fn struct_lint_level_impl(
 215         sess: &'s Session,
 216         lint: &'static Lint,
 217         level: Level,
 218         src: LintLevelSource,
 219         span: Option<MultiSpan>,
 220         decorate: Box<dyn for<'b> FnOnce(LintDiagnosticBuilder<'b>) + 'd>,
 221     ) {
 222         // Check for future incompatibility lints and issue a stronger warning.
 223         let lint_id = LintId::of(lint);
 224         let future_incompatible = lint.future_incompatible;
 225
 226         let has_future_breakage = future_incompatible.map_or(
 227             // Default allow lints trigger too often for testing.
 228             sess.opts.debugging_opts.future_incompat_test && lint.default_level != Level::Allow,
 229             |incompat| {
 230                 matches!(incompat.reason, FutureIncompatibilityReason::FutureReleaseErrorReportNow)
 231             },
 232         );
 233
 234         let mut err = match (level, span) {
 235             (Level::Allow, span) => {
 236                 if has_future_breakage {
 237                     if let Some(span) = span {
 238                         sess.struct_span_allow(span, "")
 239                     } else {
 240                         sess.struct_allow("")
 241                     }
 242                 } else {
 243                     return;
 244                 }
 245             }
 246             (Level::Warn, Some(span)) => sess.struct_span_warn(span, ""),
 247             (Level::Warn, None) => sess.struct_warn(""),
 248             (Level::ForceWarn, Some(span)) => sess.struct_span_force_warn(span, ""),
 249             (Level::ForceWarn, None) => sess.struct_force_warn(""),
 250             (Level::Deny | Level::Forbid, Some(span)) => sess.struct_span_err(span, ""),
 251             (Level::Deny | Level::Forbid, None) => sess.struct_err(""),
 252         };
 253
 254         // If this code originates in a foreign macro, aka something that this crate
 255         // did not itself author, then it's likely that there's nothing this crate
 256         // can do about it. We probably want to skip the lint entirely.
 257         if err.span.primary_spans().iter().any(|s| in_external_macro(sess, *s)) {
 258             // Any suggestions made here are likely to be incorrect, so anything we
 259             // emit shouldn't be automatically fixed by rustfix.
 260             err.allow_suggestions(false);
 261
 262             // If this is a future incompatible that is not an edition fixing lint
 263             // it'll become a hard error, so we have to emit *something*. Also,
 264             // if this lint occurs in the expansion of a macro from an external crate,
 265             // allow individual lints to opt-out from being reported.
 266             let not_future_incompatible =
 267                 future_incompatible.map(|f| f.reason.edition().is_some()).unwrap_or(true);
 268             if not_future_incompatible && !lint.report_in_external_macro {
 269                 err.cancel();
 270                 // Don't continue further, since we don't want to have
 271                 // `diag_span_note_once` called for a diagnostic that isn't emitted.
 272                 return;
 273             }
 274         }
 275
 276         let name = lint.name_lower();
 277         match src {
 278             LintLevelSource::Default => {
 279                 sess.diag_note_once(
 280                     &mut err,
 281                     DiagnosticMessageId::from(lint),
 282                     &format!("`#[{}({})]` on by default", level.as_str(), name),
 283                 );
 284             }
 285             LintLevelSource::CommandLine(lint_flag_val, orig_level) => {
 286                 let flag = match orig_level {
 287                     Level::Warn => "-W",
 288                     Level::Deny => "-D",
 289                     Level::Forbid => "-F",
 290                     Level::Allow => "-A",
 291                     Level::ForceWarn => "--force-warn",
 292                 };
 293                 let hyphen_case_lint_name = name.replace("_", "-");
 294                 if lint_flag_val.as_str() == name {
 295                     sess.diag_note_once(
 296                         &mut err,
 297                         DiagnosticMessageId::from(lint),
 298                         &format!(
 299                             "requested on the command line with `{} {}`",
 300                             flag, hyphen_case_lint_name
 301                         ),
 302                     );
 303                 } else {
 304                     let hyphen_case_flag_val = lint_flag_val.as_str().replace("_", "-");
 305                     sess.diag_note_once(
 306                         &mut err,
 307                         DiagnosticMessageId::from(lint),
 308                         &format!(
 309                             "`{} {}` implied by `{} {}`",
 310                             flag, hyphen_case_lint_name, flag, hyphen_case_flag_val
 311                         ),
 312                     );
 313                 }
 314             }
 315             LintLevelSource::Node(lint_attr_name, src, reason) => {
 316                 if let Some(rationale) = reason {
 317                     err.note(&rationale.as_str());
 318                 }
 319                 sess.diag_span_note_once(
 320                     &mut err,
 321                     DiagnosticMessageId::from(lint),
 322                     src,
 323                     "the lint level is defined here",
 324                 );
 325                 if lint_attr_name.as_str() != name {
 326                     let level_str = level.as_str();
 327                     sess.diag_note_once(
 328                         &mut err,
 329                         DiagnosticMessageId::from(lint),
 330                         &format!(
 331                             "`#[{}({})]` implied by `#[{}({})]`",
 332                             level_str, name, level_str, lint_attr_name
 333                         ),
 334                     );
 335                 }
 336             }
 337         }
 338
 339         let is_force_warn = matches!(level, Level::ForceWarn);
 340         err.code(DiagnosticId::Lint { name, has_future_breakage, is_force_warn });
 341
 342         if let Some(future_incompatible) = future_incompatible {
 343             let explanation = if lint_id == LintId::of(builtin::UNSTABLE_NAME_COLLISIONS) {
 344                 "once this associated item is added to the standard library, the ambiguity may \
 345                  cause an error or change in behavior!"
 346                     .to_owned()
 347             } else if lint_id == LintId::of(builtin::MUTABLE_BORROW_RESERVATION_CONFLICT) {
 348                 "this borrowing pattern was not meant to be accepted, and may become a hard error \
 349                  in the future"
 350                     .to_owned()
 351             } else if let FutureIncompatibilityReason::EditionError(edition) =
 352                 future_incompatible.reason
 353             {
 354                 let current_edition = sess.edition();
 355                 format!(
 356                     "this is accepted in the current edition (Rust {}) but is a hard error in Rust {}!",
 357                     current_edition, edition
 358                 )
 359             } else if let FutureIncompatibilityReason::EditionSemanticsChange(edition) =
 360                 future_incompatible.reason
 361             {
 362                 format!("this changes meaning in Rust {}", edition)
 363             } else {
 364                 "this was previously accepted by the compiler but is being phased out; \
 365                  it will become a hard error in a future release!"
 366                     .to_owned()
 367             };
 368             if future_incompatible.explain_reason {
 369                 err.warn(&explanation);
 370             }
 371             if !future_incompatible.reference.is_empty() {
 372                 let citation =
 373                     format!("for more information, see {}", future_incompatible.reference);
 374                 err.note(&citation);
 375             }
 376         }
 377
 378         // Finally, run `decorate`. This function is also responsible for emitting the diagnostic.
 379         decorate(LintDiagnosticBuilder::new(err));
 380     }
 381     struct_lint_level_impl(sess, lint, level, src, span, Box::new(decorate))
 382 }
 383
 384 /// Returns whether `span` originates in a foreign crate's external macro.
 385 ///
 386 /// This is used to test whether a lint should not even begin to figure out whether it should
 387 /// be reported on the current node.
 388 pub fn in_external_macro(sess: &Session, span: Span) -> bool {
 389     let expn_data = span.ctxt().outer_expn_data();
 390     match expn_data.kind {
 391         ExpnKind::Inlined | ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop(_)) => {
 392             false
 393         }
 394         ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => true, // well, it's "external"
 395         ExpnKind::Macro(MacroKind::Bang, _) => {
 396             // Dummy span for the `def_site` means it's an external macro.
 397             expn_data.def_site.is_dummy() || sess.source_map().is_imported(expn_data.def_site)
 398         }
 399         ExpnKind::Macro { .. } => true, // definitely a plugin
 400     }
 401 }