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
  16 /// Used for emitting structured error messages and other diagnostic information.
  17 ///
  18 /// If there is some state in a downstream crate you would like to
  19 /// access in the methods of `DiagnosticBuilder` here, consider
  20 /// extending `HandlerFlags`, accessed via `self.handler.flags`.
  21 #[must_use]
  22 #[derive(Clone)]
  23 pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
  24     inner: DiagnosticBuilderInner<'a>,
  25     _marker: PhantomData<G>,
  26 }
  27
  28 /// This type exists only for `DiagnosticBuilder::forget_guarantee`, because it:
  29 /// 1. lacks the `G` parameter and therefore `DiagnosticBuilder<G1>` can be
  30 ///    converted into `DiagnosticBuilder<G2>` while reusing the `inner` field
  31 /// 2. can implement the `Drop` "bomb" instead of `DiagnosticBuilder`, as it
  32 ///    contains all of the data (`state` + `diagnostic`) of `DiagnosticBuilder`
  33 ///
  34 /// The `diagnostic` field is not `Copy` and can't be moved out of whichever
  35 /// type implements the `Drop` "bomb", but because of the above two facts, that
  36 /// never needs to happen - instead, the whole `inner: DiagnosticBuilderInner`
  37 /// can be moved out of a `DiagnosticBuilder` and into another.
  38 #[must_use]
  39 #[derive(Clone)]
  40 struct DiagnosticBuilderInner<'a> {
  41     state: DiagnosticBuilderState<'a>,
  42
  43     /// `Diagnostic` is a large type, and `DiagnosticBuilder` is often used as a
  44     /// return value, especially within the frequently-used `PResult` type.
  45     /// In theory, return value optimization (RVO) should avoid unnecessary
  46     /// copying. In practice, it does not (at the time of writing).
  47     diagnostic: Box<Diagnostic>,
  48 }
  49
  50 #[derive(Clone)]
  51 enum DiagnosticBuilderState<'a> {
  52     /// Initial state of a `DiagnosticBuilder`, before `.emit()` or `.cancel()`.
  53     ///
  54     /// The `Diagnostic` will be emitted through this `Handler`.
  55     Emittable(&'a Handler),
  56
  57     /// State of a `DiagnosticBuilder`, after `.emit()` or *during* `.cancel()`.
  58     ///
  59     /// The `Diagnostic` will be ignored when calling `.emit()`, and it can be
  60     /// assumed that `.emit()` was previously called, to end up in this state.
  61     ///
  62     /// While this is also used by `.cancel()`, this state is only observed by
  63     /// the `Drop` `impl` of `DiagnosticBuilderInner`, as `.cancel()` takes
  64     /// `self` by-value specifically to prevent any attempts to `.emit()`.
  65     ///
  66     // FIXME(eddyb) currently this doesn't prevent extending the `Diagnostic`,
  67     // despite that being potentially lossy, if important information is added
  68     // *after* the original `.emit()` call.
  69     AlreadyEmittedOrDuringCancellation,
  70 }
  71
  72 // `DiagnosticBuilderState` should be pointer-sized.
  73 rustc_data_structures::static_assert_size!(
  74     DiagnosticBuilderState<'_>,
  75     std::mem::size_of::<&Handler>()
  76 );
  77
  78 /// Trait for types that `DiagnosticBuilder::emit` can return as a "guarantee"
  79 /// (or "proof") token that the emission happened.
  80 pub trait EmissionGuarantee: Sized {
  81     /// Implementation of `DiagnosticBuilder::emit`, fully controlled by each
  82     /// `impl` of `EmissionGuarantee`, to make it impossible to create a value
  83     /// of `Self` without actually performing the emission.
  84     #[track_caller]
  85     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
  86
  87     /// Creates a new `DiagnosticBuilder` that will return this type of guarantee.
  88     #[track_caller]
  89     fn make_diagnostic_builder(
  90         handler: &Handler,
  91         msg: impl Into<DiagnosticMessage>,
  92     ) -> DiagnosticBuilder<'_, Self>;
  93 }
  94
  95 /// Private module for sealing the `IsError` helper trait.
  96 mod sealed_level_is_error {
  97     use crate::Level;
  98
  99     /// Sealed helper trait for statically checking that a `Level` is an error.
 100     pub(crate) trait IsError<const L: Level> {}
 101
 102     impl IsError<{ Level::Bug }> for () {}
 103     impl IsError<{ Level::DelayedBug }> for () {}
 104     impl IsError<{ Level::Fatal }> for () {}
 105     // NOTE(eddyb) `Level::Error { lint: true }` is also an error, but lints
 106     // don't need error guarantees, as their levels are always dynamic.
 107     impl IsError<{ Level::Error { lint: false } }> for () {}
 108 }
 109
 110 impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
 111     /// Convenience function for internal use, clients should use one of the
 112     /// `struct_*` methods on [`Handler`].
 113     pub(crate) fn new_guaranteeing_error<M: Into<DiagnosticMessage>, const L: Level>(
 114         handler: &'a Handler,
 115         message: M,
 116     ) -> Self
 117     where
 118         (): sealed_level_is_error::IsError<L>,
 119     {
 120         Self {
 121             inner: DiagnosticBuilderInner {
 122                 state: DiagnosticBuilderState::Emittable(handler),
 123                 diagnostic: Box::new(Diagnostic::new_with_code(L, None, message)),
 124             },
 125             _marker: PhantomData,
 126         }
 127     }
 128
 129     /// Discard the guarantee `.emit()` would return, in favor of having the
 130     /// type `DiagnosticBuilder<'a, ()>`. This may be necessary whenever there
 131     /// is a common codepath handling both errors and warnings.
 132     pub fn forget_guarantee(self) -> DiagnosticBuilder<'a, ()> {
 133         DiagnosticBuilder { inner: self.inner, _marker: PhantomData }
 134     }
 135 }
 136
 137 // FIXME(eddyb) make `ErrorGuaranteed` impossible to create outside `.emit()`.
 138 impl EmissionGuarantee for ErrorGuaranteed {
 139     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 140         match db.inner.state {
 141             // First `.emit()` call, the `&Handler` is still available.
 142             DiagnosticBuilderState::Emittable(handler) => {
 143                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 144
 145                 let guar = handler.emit_diagnostic(&mut db.inner.diagnostic);
 146
 147                 // Only allow a guarantee if the `level` wasn't switched to a
 148                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
 149                 // can be overwritten with a new one, thanks to `DerefMut`.
 150                 assert!(
 151                     db.inner.diagnostic.is_error(),
 152                     "emitted non-error ({:?}) diagnostic \
 153                      from `DiagnosticBuilder<ErrorGuaranteed>`",
 154                     db.inner.diagnostic.level,
 155                 );
 156                 guar.unwrap()
 157             }
 158             // `.emit()` was previously called, disallowed from repeating it,
 159             // but can take advantage of the previous `.emit()`'s guarantee
 160             // still being applicable (i.e. as a form of idempotency).
 161             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
 162                 // Only allow a guarantee if the `level` wasn't switched to a
 163                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
 164                 // can be overwritten with a new one, thanks to `DerefMut`.
 165                 assert!(
 166                     db.inner.diagnostic.is_error(),
 167                     "`DiagnosticBuilder<ErrorGuaranteed>`'s diagnostic \
 168                      became non-error ({:?}), after original `.emit()`",
 169                     db.inner.diagnostic.level,
 170                 );
 171                 ErrorGuaranteed::unchecked_claim_error_was_emitted()
 172             }
 173         }
 174     }
 175
 176     fn make_diagnostic_builder(
 177         handler: &Handler,
 178         msg: impl Into<DiagnosticMessage>,
 179     ) -> DiagnosticBuilder<'_, Self> {
 180         DiagnosticBuilder::new_guaranteeing_error::<_, { Level::Error { lint: false } }>(
 181             handler, msg,
 182         )
 183     }
 184 }
 185
 186 impl<'a> DiagnosticBuilder<'a, ()> {
 187     /// Convenience function for internal use, clients should use one of the
 188     /// `struct_*` methods on [`Handler`].
 189     pub(crate) fn new<M: Into<DiagnosticMessage>>(
 190         handler: &'a Handler,
 191         level: Level,
 192         message: M,
 193     ) -> Self {
 194         let diagnostic = Diagnostic::new_with_code(level, None, message);
 195         Self::new_diagnostic(handler, diagnostic)
 196     }
 197
 198     /// Creates a new `DiagnosticBuilder` with an already constructed
 199     /// diagnostic.
 200     pub(crate) fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
 201         debug!("Created new diagnostic");
 202         Self {
 203             inner: DiagnosticBuilderInner {
 204                 state: DiagnosticBuilderState::Emittable(handler),
 205                 diagnostic: Box::new(diagnostic),
 206             },
 207             _marker: PhantomData,
 208         }
 209     }
 210 }
 211
 212 // FIXME(eddyb) should there be a `Option<ErrorGuaranteed>` impl as well?
 213 impl EmissionGuarantee for () {
 214     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 215         match db.inner.state {
 216             // First `.emit()` call, the `&Handler` is still available.
 217             DiagnosticBuilderState::Emittable(handler) => {
 218                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 219
 220                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 221             }
 222             // `.emit()` was previously called, disallowed from repeating it.
 223             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 224         }
 225     }
 226
 227     fn make_diagnostic_builder(
 228         handler: &Handler,
 229         msg: impl Into<DiagnosticMessage>,
 230     ) -> DiagnosticBuilder<'_, Self> {
 231         DiagnosticBuilder::new(handler, Level::Warning(None), msg)
 232     }
 233 }
 234
 235 impl<'a> DiagnosticBuilder<'a, !> {
 236     /// Convenience function for internal use, clients should use one of the
 237     /// `struct_*` methods on [`Handler`].
 238     pub(crate) fn new_fatal(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
 239         let diagnostic = Diagnostic::new_with_code(Level::Fatal, None, message);
 240         Self::new_diagnostic_fatal(handler, diagnostic)
 241     }
 242
 243     /// Creates a new `DiagnosticBuilder` with an already constructed
 244     /// diagnostic.
 245     pub(crate) fn new_diagnostic_fatal(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
 246         debug!("Created new diagnostic");
 247         Self {
 248             inner: DiagnosticBuilderInner {
 249                 state: DiagnosticBuilderState::Emittable(handler),
 250                 diagnostic: Box::new(diagnostic),
 251             },
 252             _marker: PhantomData,
 253         }
 254     }
 255 }
 256
 257 impl EmissionGuarantee for ! {
 258     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
 259         match db.inner.state {
 260             // First `.emit()` call, the `&Handler` is still available.
 261             DiagnosticBuilderState::Emittable(handler) => {
 262                 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 263
 264                 handler.emit_diagnostic(&mut db.inner.diagnostic);
 265             }
 266             // `.emit()` was previously called, disallowed from repeating it.
 267             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 268         }
 269         // Then fatally error, returning `!`
 270         crate::FatalError.raise()
 271     }
 272
 273     fn make_diagnostic_builder(
 274         handler: &Handler,
 275         msg: impl Into<DiagnosticMessage>,
 276     ) -> DiagnosticBuilder<'_, Self> {
 277         DiagnosticBuilder::new_fatal(handler, msg)
 278     }
 279 }
 280
 281 /// In general, the `DiagnosticBuilder` uses deref to allow access to
 282 /// the fields and methods of the embedded `diagnostic` in a
 283 /// transparent way. *However,* many of the methods are intended to
 284 /// be used in a chained way, and hence ought to return `self`. In
 285 /// that case, we can't just naively forward to the method on the
 286 /// `diagnostic`, because the return type would be a `&Diagnostic`
 287 /// instead of a `&DiagnosticBuilder<'a>`. This `forward!` macro makes
 288 /// it easy to declare such methods on the builder.
 289 macro_rules! forward {
 290     // Forward pattern for &mut self -> &mut Self
 291     (
 292         $(#[$attrs:meta])*
 293         pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
 294     ) => {
 295         $(#[$attrs])*
 296         #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
 297         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
 298             self.inner.diagnostic.$n($($name),*);
 299             self
 300         }
 301     };
 302 }
 303
 304 impl<G: EmissionGuarantee> Deref for DiagnosticBuilder<'_, G> {
 305     type Target = Diagnostic;
 306
 307     fn deref(&self) -> &Diagnostic {
 308         &self.inner.diagnostic
 309     }
 310 }
 311
 312 impl<G: EmissionGuarantee> DerefMut for DiagnosticBuilder<'_, G> {
 313     fn deref_mut(&mut self) -> &mut Diagnostic {
 314         &mut self.inner.diagnostic
 315     }
 316 }
 317
 318 impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
 319     /// Emit the diagnostic.
 320     #[track_caller]
 321     pub fn emit(&mut self) -> G {
 322         G::diagnostic_builder_emit_producing_guarantee(self)
 323     }
 324
 325     /// Emit the diagnostic unless `delay` is true,
 326     /// in which case the emission will be delayed as a bug.
 327     ///
 328     /// See `emit` and `delay_as_bug` for details.
 329     #[track_caller]
 330     pub fn emit_unless(&mut self, delay: bool) -> G {
 331         if delay {
 332             self.downgrade_to_delayed_bug();
 333         }
 334         self.emit()
 335     }
 336
 337     /// Cancel the diagnostic (a structured diagnostic must either be emitted or
 338     /// cancelled or it will panic when dropped).
 339     ///
 340     /// This method takes `self` by-value to disallow calling `.emit()` on it,
 341     /// which may be expected to *guarantee* the emission of an error, either
 342     /// at the time of the call, or through a prior `.emit()` call.
 343     pub fn cancel(mut self) {
 344         self.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
 345         drop(self);
 346     }
 347
 348     /// Stashes diagnostic for possible later improvement in a different,
 349     /// later stage of the compiler. The diagnostic can be accessed with
 350     /// the provided `span` and `key` through [`Handler::steal_diagnostic()`].
 351     ///
 352     /// As with `buffer`, this is unless the handler has disabled such buffering.
 353     pub fn stash(self, span: Span, key: StashKey) {
 354         if let Some((diag, handler)) = self.into_diagnostic() {
 355             handler.stash_diagnostic(span, key, diag);
 356         }
 357     }
 358
 359     /// Converts the builder to a `Diagnostic` for later emission,
 360     /// unless handler has disabled such buffering, or `.emit()` was called.
 361     pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
 362         let handler = match self.inner.state {
 363             // No `.emit()` calls, the `&Handler` is still available.
 364             DiagnosticBuilderState::Emittable(handler) => handler,
 365             // `.emit()` was previously called, nothing we can do.
 366             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
 367                 return None;
 368             }
 369         };
 370
 371         if handler.flags.dont_buffer_diagnostics || handler.flags.treat_err_as_bug.is_some() {
 372             self.emit();
 373             return None;
 374         }
 375
 376         // Take the `Diagnostic` by replacing it with a dummy.
 377         let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
 378         let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
 379
 380         // Disable the ICE on `Drop`.
 381         self.cancel();
 382
 383         // Logging here is useful to help track down where in logs an error was
 384         // actually emitted.
 385         debug!("buffer: diagnostic={:?}", diagnostic);
 386
 387         Some((diagnostic, handler))
 388     }
 389
 390     /// Buffers the diagnostic for later emission,
 391     /// unless handler has disabled such buffering.
 392     pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
 393         buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
 394     }
 395
 396     /// Delay emission of this diagnostic as a bug.
 397     ///
 398     /// This can be useful in contexts where an error indicates a bug but
 399     /// typically this only happens when other compilation errors have already
 400     /// happened. In those cases this can be used to defer emission of this
 401     /// diagnostic as a bug in the compiler only if no other errors have been
 402     /// emitted.
 403     ///
 404     /// In the meantime, though, callsites are required to deal with the "bug"
 405     /// locally in whichever way makes the most sense.
 406     #[track_caller]
 407     pub fn delay_as_bug(&mut self) {
 408         self.downgrade_to_delayed_bug();
 409         self.emit();
 410     }
 411
 412     forward!(
 413         #[track_caller]
 414         pub fn downgrade_to_delayed_bug(&mut self,) -> &mut Self
 415     );
 416
 417     forward!(
 418     /// Appends a labeled span to the diagnostic.
 419     ///
 420     /// Labels are used to convey additional context for the diagnostic's primary span. They will
 421     /// be shown together with the original diagnostic's span, *not* with spans added by
 422     /// `span_note`, `span_help`, etc. Therefore, if the primary span is not displayable (because
 423     /// the span is `DUMMY_SP` or the source code isn't found), labels will not be displayed
 424     /// either.
 425     ///
 426     /// Implementation-wise, the label span is pushed onto the [`MultiSpan`] that was created when
 427     /// the diagnostic was constructed. However, the label span is *not* considered a
 428     /// ["primary span"][`MultiSpan`]; only the `Span` supplied when creating the diagnostic is
 429     /// primary.
 430     pub fn span_label(&mut self, span: Span, label: impl Into<SubdiagnosticMessage>) -> &mut Self);
 431
 432     forward!(
 433     /// Labels all the given spans with the provided label.
 434     /// See [`Diagnostic::span_label()`] for more information.
 435     pub fn span_labels(
 436         &mut self,
 437         spans: impl IntoIterator<Item = Span>,
 438         label: impl AsRef<str>,
 439     ) -> &mut Self);
 440
 441     forward!(pub fn note_expected_found(
 442         &mut self,
 443         expected_label: &dyn fmt::Display,
 444         expected: DiagnosticStyledString,
 445         found_label: &dyn fmt::Display,
 446         found: DiagnosticStyledString,
 447     ) -> &mut Self);
 448
 449     forward!(pub fn note_expected_found_extra(
 450         &mut self,
 451         expected_label: &dyn fmt::Display,
 452         expected: DiagnosticStyledString,
 453         found_label: &dyn fmt::Display,
 454         found: DiagnosticStyledString,
 455         expected_extra: &dyn fmt::Display,
 456         found_extra: &dyn fmt::Display,
 457     ) -> &mut Self);
 458
 459     forward!(pub fn note_unsuccessful_coercion(
 460         &mut self,
 461         expected: DiagnosticStyledString,
 462         found: DiagnosticStyledString,
 463     ) -> &mut Self);
 464
 465     forward!(pub fn note(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 466     forward!(pub fn note_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 467     forward!(pub fn span_note(
 468         &mut self,
 469         sp: impl Into<MultiSpan>,
 470         msg: impl Into<SubdiagnosticMessage>,
 471     ) -> &mut Self);
 472     forward!(pub fn span_note_once(
 473         &mut self,
 474         sp: impl Into<MultiSpan>,
 475         msg: impl Into<SubdiagnosticMessage>,
 476     ) -> &mut Self);
 477     forward!(pub fn warn(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 478     forward!(pub fn span_warn(
 479         &mut self,
 480         sp: impl Into<MultiSpan>,
 481         msg: impl Into<SubdiagnosticMessage>,
 482     ) -> &mut Self);
 483     forward!(pub fn help(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
 484     forward!(pub fn span_help(
 485         &mut self,
 486         sp: impl Into<MultiSpan>,
 487         msg: impl Into<SubdiagnosticMessage>,
 488     ) -> &mut Self);
 489     forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
 490     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 491
 492     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
 493     forward!(pub fn clear_suggestions(&mut self,) -> &mut Self);
 494
 495     forward!(pub fn multipart_suggestion(
 496         &mut self,
 497         msg: impl Into<SubdiagnosticMessage>,
 498         suggestion: Vec<(Span, String)>,
 499         applicability: Applicability,
 500     ) -> &mut Self);
 501     forward!(pub fn multipart_suggestion_verbose(
 502         &mut self,
 503         msg: impl Into<SubdiagnosticMessage>,
 504         suggestion: Vec<(Span, String)>,
 505         applicability: Applicability,
 506     ) -> &mut Self);
 507     forward!(pub fn tool_only_multipart_suggestion(
 508         &mut self,
 509         msg: impl Into<SubdiagnosticMessage>,
 510         suggestion: Vec<(Span, String)>,
 511         applicability: Applicability,
 512     ) -> &mut Self);
 513     forward!(pub fn span_suggestion(
 514         &mut self,
 515         sp: Span,
 516         msg: impl Into<SubdiagnosticMessage>,
 517         suggestion: impl ToString,
 518         applicability: Applicability,
 519     ) -> &mut Self);
 520     forward!(pub fn span_suggestions(
 521         &mut self,
 522         sp: Span,
 523         msg: impl Into<SubdiagnosticMessage>,
 524         suggestions: impl Iterator<Item = String>,
 525         applicability: Applicability,
 526     ) -> &mut Self);
 527     forward!(pub fn multipart_suggestions(
 528         &mut self,
 529         msg: impl Into<SubdiagnosticMessage>,
 530         suggestions: impl Iterator<Item = Vec<(Span, String)>>,
 531         applicability: Applicability,
 532     ) -> &mut Self);
 533     forward!(pub fn span_suggestion_short(
 534         &mut self,
 535         sp: Span,
 536         msg: impl Into<SubdiagnosticMessage>,
 537         suggestion: impl ToString,
 538         applicability: Applicability,
 539     ) -> &mut Self);
 540     forward!(pub fn span_suggestion_verbose(
 541         &mut self,
 542         sp: Span,
 543         msg: impl Into<SubdiagnosticMessage>,
 544         suggestion: impl ToString,
 545         applicability: Applicability,
 546     ) -> &mut Self);
 547     forward!(pub fn span_suggestion_hidden(
 548         &mut self,
 549         sp: Span,
 550         msg: impl Into<SubdiagnosticMessage>,
 551         suggestion: impl ToString,
 552         applicability: Applicability,
 553     ) -> &mut Self);
 554     forward!(pub fn tool_only_span_suggestion(
 555         &mut self,
 556         sp: Span,
 557         msg: impl Into<SubdiagnosticMessage>,
 558         suggestion: impl ToString,
 559         applicability: Applicability,
 560     ) -> &mut Self);
 561
 562     forward!(pub fn set_primary_message(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
 563     forward!(pub fn set_span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self);
 564     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 565     forward!(pub fn set_arg(
 566         &mut self,
 567         name: impl Into<Cow<'static, str>>,
 568         arg: impl IntoDiagnosticArg,
 569     ) -> &mut Self);
 570
 571     forward!(pub fn subdiagnostic(
 572         &mut self,
 573         subdiagnostic: impl crate::AddSubdiagnostic
 574     ) -> &mut Self);
 575 }
 576
 577 impl<G: EmissionGuarantee> Debug for DiagnosticBuilder<'_, G> {
 578     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 579         self.inner.diagnostic.fmt(f)
 580     }
 581 }
 582
 583 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or cancelled
 584 /// or we emit a bug.
 585 impl Drop for DiagnosticBuilderInner<'_> {
 586     fn drop(&mut self) {
 587         match self.state {
 588             // No `.emit()` or `.cancel()` calls.
 589             DiagnosticBuilderState::Emittable(handler) => {
 590                 if !panicking() {
 591                     handler.emit_diagnostic(&mut Diagnostic::new(
 592                         Level::Bug,
 593                         DiagnosticMessage::Str(
 594                             "the following error was constructed but not emitted".to_string(),
 595                         ),
 596                     ));
 597                     handler.emit_diagnostic(&mut self.diagnostic);
 598                     panic!("error was constructed but not emitted");
 599                 }
 600             }
 601             // `.emit()` was previously called, or maybe we're during `.cancel()`.
 602             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
 603         }
 604     }
 605 }
 606
 607 #[macro_export]
 608 macro_rules! struct_span_err {
 609     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
 610         $session.struct_span_err_with_code(
 611             $span,
 612             &format!($($message)*),
 613             $crate::error_code!($code),
 614         )
 615     })
 616 }
 617
 618 #[macro_export]
 619 macro_rules! error_code {
 620     ($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};
 621 }
 622
 623 /// Wrapper around a `DiagnosticBuilder` for creating lints.
 624 pub struct LintDiagnosticBuilder<'a, G: EmissionGuarantee>(DiagnosticBuilder<'a, G>);
 625
 626 impl<'a, G: EmissionGuarantee> LintDiagnosticBuilder<'a, G> {
 627     #[rustc_lint_diagnostics]
 628     /// Return the inner `DiagnosticBuilder`, first setting the primary message to `msg`.
 629     pub fn build(mut self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'a, G> {
 630         self.0.set_primary_message(msg);
 631         self.0.set_is_lint();
 632         self.0
 633     }
 634
 635     /// Create a `LintDiagnosticBuilder` from some existing `DiagnosticBuilder`.
 636     pub fn new(err: DiagnosticBuilder<'a, G>) -> LintDiagnosticBuilder<'a, G> {
 637         LintDiagnosticBuilder(err)
 638     }
 639 }
 640
 641 impl<'a> LintDiagnosticBuilder<'a, ErrorGuaranteed> {
 642     pub fn forget_guarantee(self) -> LintDiagnosticBuilder<'a, ()> {
 643         LintDiagnosticBuilder(self.0.forget_guarantee())
 644     }
 645 }