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 use rustc_span::source_map::Spanned;
   9
  10 use rustc_span::Span;
  11 use std::borrow::Cow;
  12 use std::fmt::{self, Debug};
  13 use std::marker::PhantomData;
  14 use std::ops::{Deref, DerefMut};
  15 use std::thread::panicking;
  16
  17 /// Trait implemented by error types. This should not be implemented manually. Instead, use
  18 /// `#[derive(Diagnostic)]` -- see [rustc_macros::Diagnostic].
  19 #[cfg_attr(bootstrap, rustc_diagnostic_item = "SessionDiagnostic")]
  20 #[cfg_attr(not(bootstrap), rustc_diagnostic_item = "IntoDiagnostic")]
  21 pub trait IntoDiagnostic<'a, T: EmissionGuarantee = ErrorGuaranteed> {
  22     /// Write out as a diagnostic out of `Handler`.
  23     #[must_use]
  24     fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, T>;
  25 }
  26
  27 impl<'a, T, E> IntoDiagnostic<'a, E> for Spanned<T>
  28 where
  29     T: IntoDiagnostic<'a, E>,
  30     E: EmissionGuarantee,
  31 {
  32     fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, E> {
  33         let mut diag = self.node.into_diagnostic(handler);
  34         diag.set_span(self.span);
  35         diag
  36     }
  37 }
  38
  39 /// Used for emitting structured error messages and other diagnostic information.
  40 ///
  41 /// If there is some state in a downstream crate you would like to
  42 /// access in the methods of `DiagnosticBuilder` here, consider
  43 /// extending `HandlerFlags`, accessed via `self.handler.flags`.
  44 #[must_use]
  45 #[derive(Clone)]
  46 pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
  47     inner: DiagnosticBuilderInner<'a>,
  48     _marker: PhantomData<G>,
  49 }
  50
  51 /// This type exists only for `DiagnosticBuilder::forget_guarantee`, because it:
  52 /// 1. lacks the `G` parameter and therefore `DiagnosticBuilder<G1>` can be
  53 ///    converted into `DiagnosticBuilder<G2>` while reusing the `inner` field
  54 /// 2. can implement the `Drop` "bomb" instead of `DiagnosticBuilder`, as it
  55 ///    contains all of the data (`state` + `diagnostic`) of `DiagnosticBuilder`
  56 ///
  57 /// The `diagnostic` field is not `Copy` and can't be moved out of whichever
  58 /// type implements the `Drop` "bomb", but because of the above two facts, that
  59 /// never needs to happen - instead, the whole `inner: DiagnosticBuilderInner`
  60 /// can be moved out of a `DiagnosticBuilder` and into another.
  61 #[must_use]
  62 #[derive(Clone)]
  63 struct DiagnosticBuilderInner<'a> {
  64     state: DiagnosticBuilderState<'a>,
  65
  66     /// `Diagnostic` is a large type, and `DiagnosticBuilder` is often used as a
  67     /// return value, especially within the frequently-used `PResult` type.
  68     /// In theory, return value optimization (RVO) should avoid unnecessary
  69     /// copying. In practice, it does not (at the time of writing).
  70     diagnostic: Box<Diagnostic>,
  71 }
  72
  73 #[derive(Clone)]
  74 enum DiagnosticBuilderState<'a> {
  75     /// Initial state of a `DiagnosticBuilder`, before `.emit()` or `.cancel()`.
  76     ///
  77     /// The `Diagnostic` will be emitted through this `Handler`.
  78     Emittable(&'a Handler),
  79
  80     /// State of a `DiagnosticBuilder`, after `.emit()` or *during* `.cancel()`.
  81     ///
  82     /// The `Diagnostic` will be ignored when calling `.emit()`, and it can be
  83     /// assumed that `.emit()` was previously called, to end up in this state.
  84     ///
  85     /// While this is also used by `.cancel()`, this state is only observed by
  86     /// the `Drop` `impl` of `DiagnosticBuilderInner`, as `.cancel()` takes
  87     /// `self` by-value specifically to prevent any attempts to `.emit()`.
  88     ///
  89     // FIXME(eddyb) currently this doesn't prevent extending the `Diagnostic`,
  90     // despite that being potentially lossy, if important information is added
  91     // *after* the original `.emit()` call.
  92     AlreadyEmittedOrDuringCancellation,
  93 }
  94
  95 // `DiagnosticBuilderState` should be pointer-sized.
  96 rustc_data_structures::static_assert_size!(
  97     DiagnosticBuilderState<'_>,
  98     std::mem::size_of::<&Handler>()
  99 );
 100
 101 /// Trait for types that `DiagnosticBuilder::emit` can return as a "guarantee"
 102 /// (or "proof") token that the emission happened.
 103 pub trait EmissionGuarantee: Sized {
 104     /// Implementation of `DiagnosticBuilder::emit`, fully controlled by each
 105     /// `impl` of `EmissionGuarantee`, to make it impossible to create a value
 106     /// of `Self` without actually performing the emission.
 107     #[track_caller]
 108     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
 109
 110     /// Creates a new `DiagnosticBuilder` that will return this type of guarantee.
 111     #[track_caller]
 112     fn make_diagnostic_builder(
 113         handler: &Handler,
 114         msg: impl Into<DiagnosticMessage>,
 115     ) -> DiagnosticBuilder<'_, Self>;
 116 }
 117
 118 /// Private module for sealing the `IsError` helper trait.
 119 mod sealed_level_is_error {
 120     use crate::Level;
 121
 122     /// Sealed helper trait for statically checking that a `Level` is an error.
 123     pub(crate) trait IsError<const L: Level> {}
 124
 125     impl IsError<{ Level::Bug }> for () {}
 126     impl IsError<{ Level::DelayedBug }> for () {}
 127     impl IsError<{ Level::Fatal }> for () {}
 128     // NOTE(eddyb) `Level::Error { lint: true }` is also an error, but lints
 129     // don't need error guarantees, as their levels are always dynamic.
 130     impl IsError<{ Level::Error { lint: false } }> for () {}
 131 }
 132
 133 impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
 134     /// Convenience function for internal use, clients should use one of the
 135     /// `struct_*` methods on [`Handler`].
 136     pub(crate) fn new_guaranteeing_error<M: Into<DiagnosticMessage>, const L: Level>(
 137         handler: &'a Handler,
 138         message: M,
 139     ) -> Self
 140     where
 141         (): sealed_level_is_error::IsError<L>,
 142     {
 143         Self {
 144             inner: DiagnosticBuilderInner {
 145                 state: DiagnosticBuilderState::Emittable(handler),
 146                 diagnostic: Box::new(Diagnostic::new_with_code(L, None, message)),
 147             },
 148             _marker: PhantomData,
 149         }
 150     }
 151
 152     /// Discard the guarantee `.emit()` would return, in favor of having the
 153     /// type `DiagnosticBuilder<'a, ()>`. This may be necessary whenever there
 154     /// is a common codepath handling both errors and warnings.
 155     pub fn forget_guarantee(self) -> DiagnosticBuilder<'a, ()> {
 156         DiagnosticBuilder { inner: self.inner, _marker: PhantomData }
 157     }
 158 }
 159
 160 // FIXME(eddyb) make `ErrorGuaranteed` impossible to create outside `.emit()`.
 161 impl EmissionGuarantee for ErrorGuaranteed {
 162     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 163         match db.inner.state {
 164             // First `.emit()` call, the `&Handler` is still available.
 165             DiagnosticBuilderState::Emittable(handler) => {
 166                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 167
 168                 let guar = handler.emit_diagnostic(&mut db.inner.diagnostic);
 169
 170                 // Only allow a guarantee if the `level` wasn't switched to a
 171                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
 172                 // can be overwritten with a new one, thanks to `DerefMut`.
 173                 assert!(
 174                     db.inner.diagnostic.is_error(),
 175                     "emitted non-error ({:?}) diagnostic \
 176                      from `DiagnosticBuilder<ErrorGuaranteed>`",
 177                     db.inner.diagnostic.level,
 178                 );
 179                 guar.unwrap()
 180             }
 181             // `.emit()` was previously called, disallowed from repeating it,
 182             // but can take advantage of the previous `.emit()`'s guarantee
 183             // still being applicable (i.e. as a form of idempotency).
 184             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
 185                 // Only allow a guarantee if the `level` wasn't switched to a
 186                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
 187                 // can be overwritten with a new one, thanks to `DerefMut`.
 188                 assert!(
 189                     db.inner.diagnostic.is_error(),
 190                     "`DiagnosticBuilder<ErrorGuaranteed>`'s diagnostic \
 191                      became non-error ({:?}), after original `.emit()`",
 192                     db.inner.diagnostic.level,
 193                 );
 194                 ErrorGuaranteed::unchecked_claim_error_was_emitted()
 195             }
 196         }
 197     }
 198
 199     fn make_diagnostic_builder(
 200         handler: &Handler,
 201         msg: impl Into<DiagnosticMessage>,
 202     ) -> DiagnosticBuilder<'_, Self> {
 203         DiagnosticBuilder::new_guaranteeing_error::<_, { Level::Error { lint: false } }>(
 204             handler, msg,
 205         )
 206     }
 207 }
 208
 209 impl<'a> DiagnosticBuilder<'a, ()> {
 210     /// Convenience function for internal use, clients should use one of the
 211     /// `struct_*` methods on [`Handler`].
 212     pub(crate) fn new<M: Into<DiagnosticMessage>>(
 213         handler: &'a Handler,
 214         level: Level,
 215         message: M,
 216     ) -> Self {
 217         let diagnostic = Diagnostic::new_with_code(level, None, message);
 218         Self::new_diagnostic(handler, diagnostic)
 219     }
 220
 221     /// Creates a new `DiagnosticBuilder` with an already constructed
 222     /// diagnostic.
 223     pub(crate) fn new_diagnostic(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 // FIXME(eddyb) should there be a `Option<ErrorGuaranteed>` impl as well?
 236 impl EmissionGuarantee for () {
 237     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 238         match db.inner.state {
 239             // First `.emit()` call, the `&Handler` is still available.
 240             DiagnosticBuilderState::Emittable(handler) => {
 241                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 242
 243                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 244             }
 245             // `.emit()` was previously called, disallowed from repeating it.
 246             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 247         }
 248     }
 249
 250     fn make_diagnostic_builder(
 251         handler: &Handler,
 252         msg: impl Into<DiagnosticMessage>,
 253     ) -> DiagnosticBuilder<'_, Self> {
 254         DiagnosticBuilder::new(handler, Level::Warning(None), msg)
 255     }
 256 }
 257
 258 /// Marker type which enables implementation of `create_note` and `emit_note` functions for
 259 /// note-without-error struct diagnostics.
 260 #[derive(Copy, Clone)]
 261 pub struct Noted;
 262
 263 impl<'a> DiagnosticBuilder<'a, Noted> {
 264     /// Convenience function for internal use, clients should use one of the
 265     /// `struct_*` methods on [`Handler`].
 266     pub(crate) fn new_note(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
 267         let diagnostic = Diagnostic::new_with_code(Level::Note, None, message);
 268         Self::new_diagnostic_note(handler, diagnostic)
 269     }
 270
 271     /// Creates a new `DiagnosticBuilder` with an already constructed
 272     /// diagnostic.
 273     pub(crate) fn new_diagnostic_note(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
 274         debug!("Created new diagnostic");
 275         Self {
 276             inner: DiagnosticBuilderInner {
 277                 state: DiagnosticBuilderState::Emittable(handler),
 278                 diagnostic: Box::new(diagnostic),
 279             },
 280             _marker: PhantomData,
 281         }
 282     }
 283 }
 284
 285 impl EmissionGuarantee for Noted {
 286     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 287         match db.inner.state {
 288             // First `.emit()` call, the `&Handler` is still available.
 289             DiagnosticBuilderState::Emittable(handler) => {
 290                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 291                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 292             }
 293             // `.emit()` was previously called, disallowed from repeating it.
 294             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 295         }
 296
 297         Noted
 298     }
 299
 300     fn make_diagnostic_builder(
 301         handler: &Handler,
 302         msg: impl Into<DiagnosticMessage>,
 303     ) -> DiagnosticBuilder<'_, Self> {
 304         DiagnosticBuilder::new_note(handler, msg)
 305     }
 306 }
 307
 308 impl<'a> DiagnosticBuilder<'a, !> {
 309     /// Convenience function for internal use, clients should use one of the
 310     /// `struct_*` methods on [`Handler`].
 311     pub(crate) fn new_fatal(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
 312         let diagnostic = Diagnostic::new_with_code(Level::Fatal, None, message);
 313         Self::new_diagnostic_fatal(handler, diagnostic)
 314     }
 315
 316     /// Creates a new `DiagnosticBuilder` with an already constructed
 317     /// diagnostic.
 318     pub(crate) fn new_diagnostic_fatal(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
 319         debug!("Created new diagnostic");
 320         Self {
 321             inner: DiagnosticBuilderInner {
 322                 state: DiagnosticBuilderState::Emittable(handler),
 323                 diagnostic: Box::new(diagnostic),
 324             },
 325             _marker: PhantomData,
 326         }
 327     }
 328 }
 329
 330 impl EmissionGuarantee for ! {
 331     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 332         match db.inner.state {
 333             // First `.emit()` call, the `&Handler` is still available.
 334             DiagnosticBuilderState::Emittable(handler) => {
 335                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 336
 337                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 338             }
 339             // `.emit()` was previously called, disallowed from repeating it.
 340             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 341         }
 342         // Then fatally error, returning `!`
 343         crate::FatalError.raise()
 344     }
 345
 346     fn make_diagnostic_builder(
 347         handler: &Handler,
 348         msg: impl Into<DiagnosticMessage>,
 349     ) -> DiagnosticBuilder<'_, Self> {
 350         DiagnosticBuilder::new_fatal(handler, msg)
 351     }
 352 }
 353
 354 /// In general, the `DiagnosticBuilder` uses deref to allow access to
 355 /// the fields and methods of the embedded `diagnostic` in a
 356 /// transparent way. *However,* many of the methods are intended to
 357 /// be used in a chained way, and hence ought to return `self`. In
 358 /// that case, we can't just naively forward to the method on the
 359 /// `diagnostic`, because the return type would be a `&Diagnostic`
 360 /// instead of a `&DiagnosticBuilder<'a>`. This `forward!` macro makes
 361 /// it easy to declare such methods on the builder.
 362 macro_rules! forward {
 363     // Forward pattern for &mut self -> &mut Self
 364     (
 365         $(#[$attrs:meta])*
 366         pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
 367     ) => {
 368         $(#[$attrs])*
 369         #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
 370         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
 371             self.inner.diagnostic.$n($($name),*);
 372             self
 373         }
 374     };
 375 }
 376
 377 impl<G: EmissionGuarantee> Deref for DiagnosticBuilder<'_, G> {
 378     type Target = Diagnostic;
 379
 380     fn deref(&self) -> &Diagnostic {
 381         &self.inner.diagnostic
 382     }
 383 }
 384
 385 impl<G: EmissionGuarantee> DerefMut for DiagnosticBuilder<'_, G> {
 386     fn deref_mut(&mut self) -> &mut Diagnostic {
 387         &mut self.inner.diagnostic
 388     }
 389 }
 390
 391 impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
 392     /// Emit the diagnostic.
 393     #[track_caller]
 394     pub fn emit(&mut self) -> G {
 395         G::diagnostic_builder_emit_producing_guarantee(self)
 396     }
 397
 398     /// Emit the diagnostic unless `delay` is true,
 399     /// in which case the emission will be delayed as a bug.
 400     ///
 401     /// See `emit` and `delay_as_bug` for details.
 402     #[track_caller]
 403     pub fn emit_unless(&mut self, delay: bool) -> G {
 404         if delay {
 405             self.downgrade_to_delayed_bug();
 406         }
 407         self.emit()
 408     }
 409
 410     /// Cancel the diagnostic (a structured diagnostic must either be emitted or
 411     /// cancelled or it will panic when dropped).
 412     ///
 413     /// This method takes `self` by-value to disallow calling `.emit()` on it,
 414     /// which may be expected to *guarantee* the emission of an error, either
 415     /// at the time of the call, or through a prior `.emit()` call.
 416     pub fn cancel(mut self) {
 417         self.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 418         drop(self);
 419     }
 420
 421     /// Stashes diagnostic for possible later improvement in a different,
 422     /// later stage of the compiler. The diagnostic can be accessed with
 423     /// the provided `span` and `key` through [`Handler::steal_diagnostic()`].
 424     ///
 425     /// As with `buffer`, this is unless the handler has disabled such buffering.
 426     pub fn stash(self, span: Span, key: StashKey) {
 427         if let Some((diag, handler)) = self.into_diagnostic() {
 428             handler.stash_diagnostic(span, key, diag);
 429         }
 430     }
 431
 432     /// Converts the builder to a `Diagnostic` for later emission,
 433     /// unless handler has disabled such buffering, or `.emit()` was called.
 434     pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
 435         let handler = match self.inner.state {
 436             // No `.emit()` calls, the `&Handler` is still available.
 437             DiagnosticBuilderState::Emittable(handler) => handler,
 438             // `.emit()` was previously called, nothing we can do.
 439             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
 440                 return None;
 441             }
 442         };
 443
 444         if handler.flags.dont_buffer_diagnostics || handler.flags.treat_err_as_bug.is_some() {
 445             self.emit();
 446             return None;
 447         }
 448
 449         // Take the `Diagnostic` by replacing it with a dummy.
 450         let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
 451         let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
 452
 453         // Disable the ICE on `Drop`.
 454         self.cancel();
 455
 456         // Logging here is useful to help track down where in logs an error was
 457         // actually emitted.
 458         debug!("buffer: diagnostic={:?}", diagnostic);
 459
 460         Some((diagnostic, handler))
 461     }
 462
 463     /// Buffers the diagnostic for later emission,
 464     /// unless handler has disabled such buffering.
 465     pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
 466         buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
 467     }
 468
 469     /// Delay emission of this diagnostic as a bug.
 470     ///
 471     /// This can be useful in contexts where an error indicates a bug but
 472     /// typically this only happens when other compilation errors have already
 473     /// happened. In those cases this can be used to defer emission of this
 474     /// diagnostic as a bug in the compiler only if no other errors have been
 475     /// emitted.
 476     ///
 477     /// In the meantime, though, callsites are required to deal with the "bug"
 478     /// locally in whichever way makes the most sense.
 479     #[track_caller]
 480     pub fn delay_as_bug(&mut self) {
 481         self.downgrade_to_delayed_bug();
 482         self.emit();
 483     }
 484
 485     forward!(
 486         #[track_caller]
 487         pub fn downgrade_to_delayed_bug(&mut self,) -> &mut Self
 488     );
 489
 490     forward!(
 491     /// Appends a labeled span to the diagnostic.
 492     ///
 493     /// Labels are used to convey additional context for the diagnostic's primary span. They will
 494     /// be shown together with the original diagnostic's span, *not* with spans added by
 495     /// `span_note`, `span_help`, etc. Therefore, if the primary span is not displayable (because
 496     /// the span is `DUMMY_SP` or the source code isn't found), labels will not be displayed
 497     /// either.
 498     ///
 499     /// Implementation-wise, the label span is pushed onto the [`MultiSpan`] that was created when
 500     /// the diagnostic was constructed. However, the label span is *not* considered a
 501     /// ["primary span"][`MultiSpan`]; only the `Span` supplied when creating the diagnostic is
 502     /// primary.
 503     pub fn span_label(&mut self, span: Span, label: impl Into<SubdiagnosticMessage>) -> &mut Self);
 504
 505     forward!(
 506     /// Labels all the given spans with the provided label.
 507     /// See [`Diagnostic::span_label()`] for more information.
 508     pub fn span_labels(
 509         &mut self,
 510         spans: impl IntoIterator<Item = Span>,
 511         label: impl AsRef<str>,
 512     ) -> &mut Self);
 513
 514     forward!(pub fn note_expected_found(
 515         &mut self,
 516         expected_label: &dyn fmt::Display,
 517         expected: DiagnosticStyledString,
 518         found_label: &dyn fmt::Display,
 519         found: DiagnosticStyledString,
 520     ) -> &mut Self);
 521
 522     forward!(pub fn note_expected_found_extra(
 523         &mut self,
 524         expected_label: &dyn fmt::Display,
 525         expected: DiagnosticStyledString,
 526         found_label: &dyn fmt::Display,
 527         found: DiagnosticStyledString,
 528         expected_extra: &dyn fmt::Display,
 529         found_extra: &dyn fmt::Display,
 530     ) -> &mut Self);
 531
 532     forward!(pub fn note_unsuccessful_coercion(
 533         &mut self,
 534         expected: DiagnosticStyledString,
 535         found: DiagnosticStyledString,
 536     ) -> &mut Self);
 537
 538     forward!(pub fn note(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 539     forward!(pub fn note_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 540     forward!(pub fn span_note(
 541         &mut self,
 542         sp: impl Into<MultiSpan>,
 543         msg: impl Into<SubdiagnosticMessage>,
 544     ) -> &mut Self);
 545     forward!(pub fn span_note_once(
 546         &mut self,
 547         sp: impl Into<MultiSpan>,
 548         msg: impl Into<SubdiagnosticMessage>,
 549     ) -> &mut Self);
 550     forward!(pub fn warn(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 551     forward!(pub fn span_warn(
 552         &mut self,
 553         sp: impl Into<MultiSpan>,
 554         msg: impl Into<SubdiagnosticMessage>,
 555     ) -> &mut Self);
 556     forward!(pub fn help(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 557     forward!(pub fn span_help(
 558         &mut self,
 559         sp: impl Into<MultiSpan>,
 560         msg: impl Into<SubdiagnosticMessage>,
 561     ) -> &mut Self);
 562     forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
 563     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 564
 565     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
 566     forward!(pub fn clear_suggestions(&mut self,) -> &mut Self);
 567
 568     forward!(pub fn multipart_suggestion(
 569         &mut self,
 570         msg: impl Into<SubdiagnosticMessage>,
 571         suggestion: Vec<(Span, String)>,
 572         applicability: Applicability,
 573     ) -> &mut Self);
 574     forward!(pub fn multipart_suggestion_verbose(
 575         &mut self,
 576         msg: impl Into<SubdiagnosticMessage>,
 577         suggestion: Vec<(Span, String)>,
 578         applicability: Applicability,
 579     ) -> &mut Self);
 580     forward!(pub fn tool_only_multipart_suggestion(
 581         &mut self,
 582         msg: impl Into<SubdiagnosticMessage>,
 583         suggestion: Vec<(Span, String)>,
 584         applicability: Applicability,
 585     ) -> &mut Self);
 586     forward!(pub fn span_suggestion(
 587         &mut self,
 588         sp: Span,
 589         msg: impl Into<SubdiagnosticMessage>,
 590         suggestion: impl ToString,
 591         applicability: Applicability,
 592     ) -> &mut Self);
 593     forward!(pub fn span_suggestions(
 594         &mut self,
 595         sp: Span,
 596         msg: impl Into<SubdiagnosticMessage>,
 597         suggestions: impl Iterator<Item = String>,
 598         applicability: Applicability,
 599     ) -> &mut Self);
 600     forward!(pub fn multipart_suggestions(
 601         &mut self,
 602         msg: impl Into<SubdiagnosticMessage>,
 603         suggestions: impl Iterator<Item = Vec<(Span, String)>>,
 604         applicability: Applicability,
 605     ) -> &mut Self);
 606     forward!(pub fn span_suggestion_short(
 607         &mut self,
 608         sp: Span,
 609         msg: impl Into<SubdiagnosticMessage>,
 610         suggestion: impl ToString,
 611         applicability: Applicability,
 612     ) -> &mut Self);
 613     forward!(pub fn span_suggestion_verbose(
 614         &mut self,
 615         sp: Span,
 616         msg: impl Into<SubdiagnosticMessage>,
 617         suggestion: impl ToString,
 618         applicability: Applicability,
 619     ) -> &mut Self);
 620     forward!(pub fn span_suggestion_hidden(
 621         &mut self,
 622         sp: Span,
 623         msg: impl Into<SubdiagnosticMessage>,
 624         suggestion: impl ToString,
 625         applicability: Applicability,
 626     ) -> &mut Self);
 627     forward!(pub fn tool_only_span_suggestion(
 628         &mut self,
 629         sp: Span,
 630         msg: impl Into<SubdiagnosticMessage>,
 631         suggestion: impl ToString,
 632         applicability: Applicability,
 633     ) -> &mut Self);
 634
 635     forward!(pub fn set_primary_message(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
 636     forward!(pub fn set_span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self);
 637     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 638     forward!(pub fn set_arg(
 639         &mut self,
 640         name: impl Into<Cow<'static, str>>,
 641         arg: impl IntoDiagnosticArg,
 642     ) -> &mut Self);
 643
 644     forward!(pub fn subdiagnostic(
 645         &mut self,
 646         subdiagnostic: impl crate::AddToDiagnostic
 647     ) -> &mut Self);
 648 }
 649
 650 impl<G: EmissionGuarantee> Debug for DiagnosticBuilder<'_, G> {
 651     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 652         self.inner.diagnostic.fmt(f)
 653     }
 654 }
 655
 656 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or cancelled
 657 /// or we emit a bug.
 658 impl Drop for DiagnosticBuilderInner<'_> {
 659     fn drop(&mut self) {
 660         match self.state {
 661             // No `.emit()` or `.cancel()` calls.
 662             DiagnosticBuilderState::Emittable(handler) => {
 663                 if !panicking() {
 664                     handler.emit_diagnostic(&mut Diagnostic::new(
 665                         Level::Bug,
 666                         DiagnosticMessage::Str(
 667                             "the following error was constructed but not emitted".to_string(),
 668                         ),
 669                     ));
 670                     handler.emit_diagnostic(&mut self.diagnostic);
 671                     panic!("error was constructed but not emitted");
 672                 }
 673             }
 674             // `.emit()` was previously called, or maybe we're during `.cancel()`.
 675             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 676         }
 677     }
 678 }
 679
 680 #[macro_export]
 681 macro_rules! struct_span_err {
 682     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
 683         $session.struct_span_err_with_code(
 684             $span,
 685             &format!($($message)*),
 686             $crate::error_code!($code),
 687         )
 688     })
 689 }
 690
 691 #[macro_export]
 692 macro_rules! error_code {
 693     ($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};
 694 }