compiler/rustc_errors/src/diagnostic_builder.rs

   1 use crate::diagnostic::IntoDiagnosticArg;
   2 use crate::{
   3     Diagnostic, DiagnosticId, DiagnosticMessage, DiagnosticStyledString, ErrorGuaranteed,
   4     SubdiagnosticMessage,
   5 };
   6 use crate::{Handler, Level, MultiSpan, StashKey};
   7 use rustc_lint_defs::Applicability;
   8
   9 use rustc_span::Span;
  10 use std::borrow::Cow;
  11 use std::fmt::{self, Debug};
  12 use std::marker::PhantomData;
  13 use std::ops::{Deref, DerefMut};
  14 use std::thread::panicking;
  15 use tracing::debug;
  16
  17 /// Used for emitting structured error messages and other diagnostic information.
  18 ///
  19 /// If there is some state in a downstream crate you would like to
  20 /// access in the methods of `DiagnosticBuilder` here, consider
  21 /// extending `HandlerFlags`, accessed via `self.handler.flags`.
  22 #[must_use]
  23 #[derive(Clone)]
  24 pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
  25     inner: DiagnosticBuilderInner<'a>,
  26     _marker: PhantomData<G>,
  27 }
  28
  29 /// This type exists only for `DiagnosticBuilder::forget_guarantee`, because it:
  30 /// 1. lacks the `G` parameter and therefore `DiagnosticBuilder<G1>` can be
  31 ///    converted into `DiagnosticBuilder<G2>` while reusing the `inner` field
  32 /// 2. can implement the `Drop` "bomb" instead of `DiagnosticBuilder`, as it
  33 ///    contains all of the data (`state` + `diagnostic`) of `DiagnosticBuilder`
  34 ///
  35 /// The `diagnostic` field is not `Copy` and can't be moved out of whichever
  36 /// type implements the `Drop` "bomb", but because of the above two facts, that
  37 /// never needs to happen - instead, the whole `inner: DiagnosticBuilderInner`
  38 /// can be moved out of a `DiagnosticBuilder` and into another.
  39 #[must_use]
  40 #[derive(Clone)]
  41 struct DiagnosticBuilderInner<'a> {
  42     state: DiagnosticBuilderState<'a>,
  43
  44     /// `Diagnostic` is a large type, and `DiagnosticBuilder` is often used as a
  45     /// return value, especially within the frequently-used `PResult` type.
  46     /// In theory, return value optimization (RVO) should avoid unnecessary
  47     /// copying. In practice, it does not (at the time of writing).
  48     diagnostic: Box<Diagnostic>,
  49 }
  50
  51 #[derive(Clone)]
  52 enum DiagnosticBuilderState<'a> {
  53     /// Initial state of a `DiagnosticBuilder`, before `.emit()` or `.cancel()`.
  54     ///
  55     /// The `Diagnostic` will be emitted through this `Handler`.
  56     Emittable(&'a Handler),
  57
  58     /// State of a `DiagnosticBuilder`, after `.emit()` or *during* `.cancel()`.
  59     ///
  60     /// The `Diagnostic` will be ignored when calling `.emit()`, and it can be
  61     /// assumed that `.emit()` was previously called, to end up in this state.
  62     ///
  63     /// While this is also used by `.cancel()`, this state is only observed by
  64     /// the `Drop` `impl` of `DiagnosticBuilderInner`, as `.cancel()` takes
  65     /// `self` by-value specifically to prevent any attempts to `.emit()`.
  66     ///
  67     // FIXME(eddyb) currently this doesn't prevent extending the `Diagnostic`,
  68     // despite that being potentially lossy, if important information is added
  69     // *after* the original `.emit()` call.
  70     AlreadyEmittedOrDuringCancellation,
  71 }
  72
  73 // `DiagnosticBuilderState` should be pointer-sized.
  74 rustc_data_structures::static_assert_size!(
  75     DiagnosticBuilderState<'_>,
  76     std::mem::size_of::<&Handler>()
  77 );
  78
  79 /// Trait for types that `DiagnosticBuilder::emit` can return as a "guarantee"
  80 /// (or "proof") token that the emission happened.
  81 pub trait EmissionGuarantee: Sized {
  82     /// Implementation of `DiagnosticBuilder::emit`, fully controlled by each
  83     /// `impl` of `EmissionGuarantee`, to make it impossible to create a value
  84     /// of `Self` without actually performing the emission.
  85     #[track_caller]
  86     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
  87 }
  88
  89 /// Private module for sealing the `IsError` helper trait.
  90 mod sealed_level_is_error {
  91     use crate::Level;
  92
  93     /// Sealed helper trait for statically checking that a `Level` is an error.
  94     pub(crate) trait IsError<const L: Level> {}
  95
  96     impl IsError<{ Level::Bug }> for () {}
  97     impl IsError<{ Level::DelayedBug }> for () {}
  98     impl IsError<{ Level::Fatal }> for () {}
  99     // NOTE(eddyb) `Level::Error { lint: true }` is also an error, but lints
 100     // don't need error guarantees, as their levels are always dynamic.
 101     impl IsError<{ Level::Error { lint: false } }> for () {}
 102 }
 103
 104 impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
 105     /// Convenience function for internal use, clients should use one of the
 106     /// `struct_*` methods on [`Handler`].
 107     pub(crate) fn new_guaranteeing_error<M: Into<DiagnosticMessage>, const L: Level>(
 108         handler: &'a Handler,
 109         message: M,
 110     ) -> Self
 111     where
 112         (): sealed_level_is_error::IsError<L>,
 113     {
 114         Self {
 115             inner: DiagnosticBuilderInner {
 116                 state: DiagnosticBuilderState::Emittable(handler),
 117                 diagnostic: Box::new(Diagnostic::new_with_code(L, None, message)),
 118             },
 119             _marker: PhantomData,
 120         }
 121     }
 122
 123     /// Discard the guarantee `.emit()` would return, in favor of having the
 124     /// type `DiagnosticBuilder<'a, ()>`. This may be necessary whenever there
 125     /// is a common codepath handling both errors and warnings.
 126     pub fn forget_guarantee(self) -> DiagnosticBuilder<'a, ()> {
 127         DiagnosticBuilder { inner: self.inner, _marker: PhantomData }
 128     }
 129 }
 130
 131 // FIXME(eddyb) make `ErrorGuaranteed` impossible to create outside `.emit()`.
 132 impl EmissionGuarantee for ErrorGuaranteed {
 133     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 134         match db.inner.state {
 135             // First `.emit()` call, the `&Handler` is still available.
 136             DiagnosticBuilderState::Emittable(handler) => {
 137                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 138
 139                 let guar = handler.emit_diagnostic(&mut db.inner.diagnostic);
 140
 141                 // Only allow a guarantee if the `level` wasn't switched to a
 142                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
 143                 // can be overwritten with a new one, thanks to `DerefMut`.
 144                 assert!(
 145                     db.inner.diagnostic.is_error(),
 146                     "emitted non-error ({:?}) diagnostic \
 147                      from `DiagnosticBuilder<ErrorGuaranteed>`",
 148                     db.inner.diagnostic.level,
 149                 );
 150                 guar.unwrap()
 151             }
 152             // `.emit()` was previously called, disallowed from repeating it,
 153             // but can take advantage of the previous `.emit()`'s guarantee
 154             // still being applicable (i.e. as a form of idempotency).
 155             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
 156                 // Only allow a guarantee if the `level` wasn't switched to a
 157                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
 158                 // can be overwritten with a new one, thanks to `DerefMut`.
 159                 assert!(
 160                     db.inner.diagnostic.is_error(),
 161                     "`DiagnosticBuilder<ErrorGuaranteed>`'s diagnostic \
 162                      became non-error ({:?}), after original `.emit()`",
 163                     db.inner.diagnostic.level,
 164                 );
 165                 ErrorGuaranteed::unchecked_claim_error_was_emitted()
 166             }
 167         }
 168     }
 169 }
 170
 171 impl<'a> DiagnosticBuilder<'a, ()> {
 172     /// Convenience function for internal use, clients should use one of the
 173     /// `struct_*` methods on [`Handler`].
 174     pub(crate) fn new<M: Into<DiagnosticMessage>>(
 175         handler: &'a Handler,
 176         level: Level,
 177         message: M,
 178     ) -> Self {
 179         let diagnostic = Diagnostic::new_with_code(level, None, message);
 180         Self::new_diagnostic(handler, diagnostic)
 181     }
 182
 183     /// Creates a new `DiagnosticBuilder` with an already constructed
 184     /// diagnostic.
 185     pub(crate) fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
 186         debug!("Created new diagnostic");
 187         Self {
 188             inner: DiagnosticBuilderInner {
 189                 state: DiagnosticBuilderState::Emittable(handler),
 190                 diagnostic: Box::new(diagnostic),
 191             },
 192             _marker: PhantomData,
 193         }
 194     }
 195 }
 196
 197 // FIXME(eddyb) should there be a `Option<ErrorGuaranteed>` impl as well?
 198 impl EmissionGuarantee for () {
 199     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 200         match db.inner.state {
 201             // First `.emit()` call, the `&Handler` is still available.
 202             DiagnosticBuilderState::Emittable(handler) => {
 203                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 204
 205                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 206             }
 207             // `.emit()` was previously called, disallowed from repeating it.
 208             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 209         }
 210     }
 211 }
 212
 213 impl<'a> DiagnosticBuilder<'a, !> {
 214     /// Convenience function for internal use, clients should use one of the
 215     /// `struct_*` methods on [`Handler`].
 216     pub(crate) fn new_fatal(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
 217         let diagnostic = Diagnostic::new_with_code(Level::Fatal, None, message);
 218         Self::new_diagnostic_fatal(handler, diagnostic)
 219     }
 220
 221     /// Creates a new `DiagnosticBuilder` with an already constructed
 222     /// diagnostic.
 223     pub(crate) fn new_diagnostic_fatal(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
 224         debug!("Created new diagnostic");
 225         Self {
 226             inner: DiagnosticBuilderInner {
 227                 state: DiagnosticBuilderState::Emittable(handler),
 228                 diagnostic: Box::new(diagnostic),
 229             },
 230             _marker: PhantomData,
 231         }
 232     }
 233 }
 234
 235 impl EmissionGuarantee for ! {
 236     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 237         match db.inner.state {
 238             // First `.emit()` call, the `&Handler` is still available.
 239             DiagnosticBuilderState::Emittable(handler) => {
 240                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 241
 242                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 243             }
 244             // `.emit()` was previously called, disallowed from repeating it.
 245             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 246         }
 247         // Then fatally error, returning `!`
 248         crate::FatalError.raise()
 249     }
 250 }
 251
 252 /// In general, the `DiagnosticBuilder` uses deref to allow access to
 253 /// the fields and methods of the embedded `diagnostic` in a
 254 /// transparent way. *However,* many of the methods are intended to
 255 /// be used in a chained way, and hence ought to return `self`. In
 256 /// that case, we can't just naively forward to the method on the
 257 /// `diagnostic`, because the return type would be a `&Diagnostic`
 258 /// instead of a `&DiagnosticBuilder<'a>`. This `forward!` macro makes
 259 /// it easy to declare such methods on the builder.
 260 macro_rules! forward {
 261     // Forward pattern for &mut self -> &mut Self
 262     (
 263         $(#[$attrs:meta])*
 264         pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
 265     ) => {
 266         $(#[$attrs])*
 267         #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
 268         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
 269             self.inner.diagnostic.$n($($name),*);
 270             self
 271         }
 272     };
 273 }
 274
 275 impl<G: EmissionGuarantee> Deref for DiagnosticBuilder<'_, G> {
 276     type Target = Diagnostic;
 277
 278     fn deref(&self) -> &Diagnostic {
 279         &self.inner.diagnostic
 280     }
 281 }
 282
 283 impl<G: EmissionGuarantee> DerefMut for DiagnosticBuilder<'_, G> {
 284     fn deref_mut(&mut self) -> &mut Diagnostic {
 285         &mut self.inner.diagnostic
 286     }
 287 }
 288
 289 impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
 290     /// Emit the diagnostic.
 291     #[track_caller]
 292     pub fn emit(&mut self) -> G {
 293         G::diagnostic_builder_emit_producing_guarantee(self)
 294     }
 295
 296     /// Emit the diagnostic unless `delay` is true,
 297     /// in which case the emission will be delayed as a bug.
 298     ///
 299     /// See `emit` and `delay_as_bug` for details.
 300     #[track_caller]
 301     pub fn emit_unless(&mut self, delay: bool) -> G {
 302         if delay {
 303             self.downgrade_to_delayed_bug();
 304         }
 305         self.emit()
 306     }
 307
 308     /// Cancel the diagnostic (a structured diagnostic must either be emitted or
 309     /// cancelled or it will panic when dropped).
 310     ///
 311     /// This method takes `self` by-value to disallow calling `.emit()` on it,
 312     /// which may be expected to *guarantee* the emission of an error, either
 313     /// at the time of the call, or through a prior `.emit()` call.
 314     pub fn cancel(mut self) {
 315         self.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 316         drop(self);
 317     }
 318
 319     /// Stashes diagnostic for possible later improvement in a different,
 320     /// later stage of the compiler. The diagnostic can be accessed with
 321     /// the provided `span` and `key` through [`Handler::steal_diagnostic()`].
 322     ///
 323     /// As with `buffer`, this is unless the handler has disabled such buffering.
 324     pub fn stash(self, span: Span, key: StashKey) {
 325         if let Some((diag, handler)) = self.into_diagnostic() {
 326             handler.stash_diagnostic(span, key, diag);
 327         }
 328     }
 329
 330     /// Converts the builder to a `Diagnostic` for later emission,
 331     /// unless handler has disabled such buffering, or `.emit()` was called.
 332     pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
 333         let handler = match self.inner.state {
 334             // No `.emit()` calls, the `&Handler` is still available.
 335             DiagnosticBuilderState::Emittable(handler) => handler,
 336             // `.emit()` was previously called, nothing we can do.
 337             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
 338                 return None;
 339             }
 340         };
 341
 342         if handler.flags.dont_buffer_diagnostics || handler.flags.treat_err_as_bug.is_some() {
 343             self.emit();
 344             return None;
 345         }
 346
 347         // Take the `Diagnostic` by replacing it with a dummy.
 348         let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
 349         let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
 350
 351         // Disable the ICE on `Drop`.
 352         self.cancel();
 353
 354         // Logging here is useful to help track down where in logs an error was
 355         // actually emitted.
 356         debug!("buffer: diagnostic={:?}", diagnostic);
 357
 358         Some((diagnostic, handler))
 359     }
 360
 361     /// Buffers the diagnostic for later emission,
 362     /// unless handler has disabled such buffering.
 363     pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
 364         buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
 365     }
 366
 367     /// Delay emission of this diagnostic as a bug.
 368     ///
 369     /// This can be useful in contexts where an error indicates a bug but
 370     /// typically this only happens when other compilation errors have already
 371     /// happened. In those cases this can be used to defer emission of this
 372     /// diagnostic as a bug in the compiler only if no other errors have been
 373     /// emitted.
 374     ///
 375     /// In the meantime, though, callsites are required to deal with the "bug"
 376     /// locally in whichever way makes the most sense.
 377     #[track_caller]
 378     pub fn delay_as_bug(&mut self) {
 379         self.downgrade_to_delayed_bug();
 380         self.emit();
 381     }
 382
 383     forward!(
 384         #[track_caller]
 385         pub fn downgrade_to_delayed_bug(&mut self,) -> &mut Self
 386     );
 387
 388     forward!(
 389     /// Appends a labeled span to the diagnostic.
 390     ///
 391     /// Labels are used to convey additional context for the diagnostic's primary span. They will
 392     /// be shown together with the original diagnostic's span, *not* with spans added by
 393     /// `span_note`, `span_help`, etc. Therefore, if the primary span is not displayable (because
 394     /// the span is `DUMMY_SP` or the source code isn't found), labels will not be displayed
 395     /// either.
 396     ///
 397     /// Implementation-wise, the label span is pushed onto the [`MultiSpan`] that was created when
 398     /// the diagnostic was constructed. However, the label span is *not* considered a
 399     /// ["primary span"][`MultiSpan`]; only the `Span` supplied when creating the diagnostic is
 400     /// primary.
 401     pub fn span_label(&mut self, span: Span, label: impl Into<SubdiagnosticMessage>) -> &mut Self);
 402
 403     forward!(
 404     /// Labels all the given spans with the provided label.
 405     /// See [`Diagnostic::span_label()`] for more information.
 406     pub fn span_labels(
 407         &mut self,
 408         spans: impl IntoIterator<Item = Span>,
 409         label: impl AsRef<str>,
 410     ) -> &mut Self);
 411
 412     forward!(pub fn note_expected_found(
 413         &mut self,
 414         expected_label: &dyn fmt::Display,
 415         expected: DiagnosticStyledString,
 416         found_label: &dyn fmt::Display,
 417         found: DiagnosticStyledString,
 418     ) -> &mut Self);
 419
 420     forward!(pub fn note_expected_found_extra(
 421         &mut self,
 422         expected_label: &dyn fmt::Display,
 423         expected: DiagnosticStyledString,
 424         found_label: &dyn fmt::Display,
 425         found: DiagnosticStyledString,
 426         expected_extra: &dyn fmt::Display,
 427         found_extra: &dyn fmt::Display,
 428     ) -> &mut Self);
 429
 430     forward!(pub fn note_unsuccessful_coercion(
 431         &mut self,
 432         expected: DiagnosticStyledString,
 433         found: DiagnosticStyledString,
 434     ) -> &mut Self);
 435
 436     forward!(pub fn note(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 437     forward!(pub fn note_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 438     forward!(pub fn span_note(
 439         &mut self,
 440         sp: impl Into<MultiSpan>,
 441         msg: impl Into<SubdiagnosticMessage>,
 442     ) -> &mut Self);
 443     forward!(pub fn span_note_once(
 444         &mut self,
 445         sp: impl Into<MultiSpan>,
 446         msg: impl Into<SubdiagnosticMessage>,
 447     ) -> &mut Self);
 448     forward!(pub fn warn(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 449     forward!(pub fn span_warn(
 450         &mut self,
 451         sp: impl Into<MultiSpan>,
 452         msg: impl Into<SubdiagnosticMessage>,
 453     ) -> &mut Self);
 454     forward!(pub fn help(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 455     forward!(pub fn span_help(
 456         &mut self,
 457         sp: impl Into<MultiSpan>,
 458         msg: impl Into<SubdiagnosticMessage>,
 459     ) -> &mut Self);
 460     forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
 461     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 462
 463     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
 464     forward!(pub fn clear_suggestions(&mut self,) -> &mut Self);
 465
 466     forward!(pub fn multipart_suggestion(
 467         &mut self,
 468         msg: impl Into<SubdiagnosticMessage>,
 469         suggestion: Vec<(Span, String)>,
 470         applicability: Applicability,
 471     ) -> &mut Self);
 472     forward!(pub fn multipart_suggestion_verbose(
 473         &mut self,
 474         msg: impl Into<SubdiagnosticMessage>,
 475         suggestion: Vec<(Span, String)>,
 476         applicability: Applicability,
 477     ) -> &mut Self);
 478     forward!(pub fn tool_only_multipart_suggestion(
 479         &mut self,
 480         msg: impl Into<SubdiagnosticMessage>,
 481         suggestion: Vec<(Span, String)>,
 482         applicability: Applicability,
 483     ) -> &mut Self);
 484     forward!(pub fn span_suggestion(
 485         &mut self,
 486         sp: Span,
 487         msg: impl Into<SubdiagnosticMessage>,
 488         suggestion: impl ToString,
 489         applicability: Applicability,
 490     ) -> &mut Self);
 491     forward!(pub fn span_suggestions(
 492         &mut self,
 493         sp: Span,
 494         msg: impl Into<SubdiagnosticMessage>,
 495         suggestions: impl Iterator<Item = String>,
 496         applicability: Applicability,
 497     ) -> &mut Self);
 498     forward!(pub fn multipart_suggestions(
 499         &mut self,
 500         msg: impl Into<SubdiagnosticMessage>,
 501         suggestions: impl Iterator<Item = Vec<(Span, String)>>,
 502         applicability: Applicability,
 503     ) -> &mut Self);
 504     forward!(pub fn span_suggestion_short(
 505         &mut self,
 506         sp: Span,
 507         msg: impl Into<SubdiagnosticMessage>,
 508         suggestion: impl ToString,
 509         applicability: Applicability,
 510     ) -> &mut Self);
 511     forward!(pub fn span_suggestion_verbose(
 512         &mut self,
 513         sp: Span,
 514         msg: impl Into<SubdiagnosticMessage>,
 515         suggestion: impl ToString,
 516         applicability: Applicability,
 517     ) -> &mut Self);
 518     forward!(pub fn span_suggestion_hidden(
 519         &mut self,
 520         sp: Span,
 521         msg: impl Into<SubdiagnosticMessage>,
 522         suggestion: impl ToString,
 523         applicability: Applicability,
 524     ) -> &mut Self);
 525     forward!(pub fn tool_only_span_suggestion(
 526         &mut self,
 527         sp: Span,
 528         msg: impl Into<SubdiagnosticMessage>,
 529         suggestion: impl ToString,
 530         applicability: Applicability,
 531     ) -> &mut Self);
 532
 533     forward!(pub fn set_primary_message(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
 534     forward!(pub fn set_span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self);
 535     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 536     forward!(pub fn set_arg(
 537         &mut self,
 538         name: impl Into<Cow<'static, str>>,
 539         arg: impl IntoDiagnosticArg,
 540     ) -> &mut Self);
 541
 542     forward!(pub fn subdiagnostic(
 543         &mut self,
 544         subdiagnostic: impl crate::AddSubdiagnostic
 545     ) -> &mut Self);
 546 }
 547
 548 impl<G: EmissionGuarantee> Debug for DiagnosticBuilder<'_, G> {
 549     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 550         self.inner.diagnostic.fmt(f)
 551     }
 552 }
 553
 554 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or cancelled
 555 /// or we emit a bug.
 556 impl Drop for DiagnosticBuilderInner<'_> {
 557     fn drop(&mut self) {
 558         match self.state {
 559             // No `.emit()` or `.cancel()` calls.
 560             DiagnosticBuilderState::Emittable(handler) => {
 561                 if !panicking() {
 562                     handler.emit_diagnostic(&mut Diagnostic::new(
 563                         Level::Bug,
 564                         DiagnosticMessage::Str(
 565                             "the following error was constructed but not emitted".to_string(),
 566                         ),
 567                     ));
 568                     handler.emit_diagnostic(&mut self.diagnostic);
 569                     panic!();
 570                 }
 571             }
 572             // `.emit()` was previously called, or maybe we're during `.cancel()`.
 573             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 574         }
 575     }
 576 }
 577
 578 #[macro_export]
 579 macro_rules! struct_span_err {
 580     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
 581         $session.struct_span_err_with_code(
 582             $span,
 583             &format!($($message)*),
 584             $crate::error_code!($code),
 585         )
 586     })
 587 }
 588
 589 #[macro_export]
 590 macro_rules! error_code {
 591     ($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};
 592 }
 593
 594 /// Wrapper around a `DiagnosticBuilder` for creating lints.
 595 pub struct LintDiagnosticBuilder<'a, G: EmissionGuarantee>(DiagnosticBuilder<'a, G>);
 596
 597 impl<'a, G: EmissionGuarantee> LintDiagnosticBuilder<'a, G> {
 598     #[rustc_lint_diagnostics]
 599     /// Return the inner `DiagnosticBuilder`, first setting the primary message to `msg`.
 600     pub fn build(mut self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'a, G> {
 601         self.0.set_primary_message(msg);
 602         self.0.set_is_lint();
 603         self.0
 604     }
 605
 606     /// Create a `LintDiagnosticBuilder` from some existing `DiagnosticBuilder`.
 607     pub fn new(err: DiagnosticBuilder<'a, G>) -> LintDiagnosticBuilder<'a, G> {
 608         LintDiagnosticBuilder(err)
 609     }
 610 }
 611
 612 impl<'a> LintDiagnosticBuilder<'a, ErrorGuaranteed> {
 613     pub fn forget_guarantee(self) -> LintDiagnosticBuilder<'a, ()> {
 614         LintDiagnosticBuilder(self.0.forget_guarantee())
 615     }
 616 }