1 use crate::diagnostic::IntoDiagnosticArg;
3 Diagnostic, DiagnosticId, DiagnosticMessage, DiagnosticStyledString, ErrorGuaranteed,
6 use crate::{Handler, Level, MultiSpan, StashKey};
7 use rustc_lint_defs::Applicability;
8 use rustc_span::source_map::Spanned;
12 use std::fmt::{self, Debug};
13 use std::marker::PhantomData;
14 use std::ops::{Deref, DerefMut};
15 use std::thread::panicking;
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`.
24 fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, T>;
27 impl<'a, T, E> IntoDiagnostic<'a, E> for Spanned<T>
29 T: IntoDiagnostic<'a, E>,
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);
39 /// Used for emitting structured error messages and other diagnostic information.
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`.
46 pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
47 inner: DiagnosticBuilderInner<'a>,
48 _marker: PhantomData<G>,
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`
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.
63 struct DiagnosticBuilderInner<'a> {
64 state: DiagnosticBuilderState<'a>,
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>,
74 enum DiagnosticBuilderState<'a> {
75 /// Initial state of a `DiagnosticBuilder`, before `.emit()` or `.cancel()`.
77 /// The `Diagnostic` will be emitted through this `Handler`.
78 Emittable(&'a Handler),
80 /// State of a `DiagnosticBuilder`, after `.emit()` or *during* `.cancel()`.
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.
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()`.
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,
95 // `DiagnosticBuilderState` should be pointer-sized.
96 rustc_data_structures::static_assert_size!(
97 DiagnosticBuilderState<'_>,
98 std::mem::size_of::<&Handler>()
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.
108 fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
110 /// Creates a new `DiagnosticBuilder` that will return this type of guarantee.
112 fn make_diagnostic_builder(
114 msg: impl Into<DiagnosticMessage>,
115 ) -> DiagnosticBuilder<'_, Self>;
118 /// Private module for sealing the `IsError` helper trait.
119 mod sealed_level_is_error {
122 /// Sealed helper trait for statically checking that a `Level` is an error.
123 pub(crate) trait IsError<const L: Level> {}
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 () {}
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,
141 (): sealed_level_is_error::IsError<L>,
144 inner: DiagnosticBuilderInner {
145 state: DiagnosticBuilderState::Emittable(handler),
146 diagnostic: Box::new(Diagnostic::new_with_code(L, None, message)),
148 _marker: PhantomData,
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 }
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;
168 let guar = handler.emit_diagnostic(&mut db.inner.diagnostic);
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`.
174 db.inner.diagnostic.is_error(),
175 "emitted non-error ({:?}) diagnostic \
176 from `DiagnosticBuilder<ErrorGuaranteed>`",
177 db.inner.diagnostic.level,
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`.
189 db.inner.diagnostic.is_error(),
190 "`DiagnosticBuilder<ErrorGuaranteed>`'s diagnostic \
191 became non-error ({:?}), after original `.emit()`",
192 db.inner.diagnostic.level,
194 ErrorGuaranteed::unchecked_claim_error_was_emitted()
199 fn make_diagnostic_builder(
201 msg: impl Into<DiagnosticMessage>,
202 ) -> DiagnosticBuilder<'_, Self> {
203 DiagnosticBuilder::new_guaranteeing_error::<_, { Level::Error { lint: false } }>(
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,
217 let diagnostic = Diagnostic::new_with_code(level, None, message);
218 Self::new_diagnostic(handler, diagnostic)
221 /// Creates a new `DiagnosticBuilder` with an already constructed
223 pub(crate) fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
224 debug!("Created new diagnostic");
226 inner: DiagnosticBuilderInner {
227 state: DiagnosticBuilderState::Emittable(handler),
228 diagnostic: Box::new(diagnostic),
230 _marker: PhantomData,
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;
243 handler.emit_diagnostic(&mut db.inner.diagnostic);
245 // `.emit()` was previously called, disallowed from repeating it.
246 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
250 fn make_diagnostic_builder(
252 msg: impl Into<DiagnosticMessage>,
253 ) -> DiagnosticBuilder<'_, Self> {
254 DiagnosticBuilder::new(handler, Level::Warning(None), msg)
258 impl<'a> DiagnosticBuilder<'a, !> {
259 /// Convenience function for internal use, clients should use one of the
260 /// `struct_*` methods on [`Handler`].
261 pub(crate) fn new_fatal(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
262 let diagnostic = Diagnostic::new_with_code(Level::Fatal, None, message);
263 Self::new_diagnostic_fatal(handler, diagnostic)
266 /// Creates a new `DiagnosticBuilder` with an already constructed
268 pub(crate) fn new_diagnostic_fatal(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
269 debug!("Created new diagnostic");
271 inner: DiagnosticBuilderInner {
272 state: DiagnosticBuilderState::Emittable(handler),
273 diagnostic: Box::new(diagnostic),
275 _marker: PhantomData,
280 impl EmissionGuarantee for ! {
281 fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
282 match db.inner.state {
283 // First `.emit()` call, the `&Handler` is still available.
284 DiagnosticBuilderState::Emittable(handler) => {
285 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
287 handler.emit_diagnostic(&mut db.inner.diagnostic);
289 // `.emit()` was previously called, disallowed from repeating it.
290 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
292 // Then fatally error, returning `!`
293 crate::FatalError.raise()
296 fn make_diagnostic_builder(
298 msg: impl Into<DiagnosticMessage>,
299 ) -> DiagnosticBuilder<'_, Self> {
300 DiagnosticBuilder::new_fatal(handler, msg)
304 /// In general, the `DiagnosticBuilder` uses deref to allow access to
305 /// the fields and methods of the embedded `diagnostic` in a
306 /// transparent way. *However,* many of the methods are intended to
307 /// be used in a chained way, and hence ought to return `self`. In
308 /// that case, we can't just naively forward to the method on the
309 /// `diagnostic`, because the return type would be a `&Diagnostic`
310 /// instead of a `&DiagnosticBuilder<'a>`. This `forward!` macro makes
311 /// it easy to declare such methods on the builder.
312 macro_rules! forward {
313 // Forward pattern for &mut self -> &mut Self
316 pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
319 #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
320 pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
321 self.inner.diagnostic.$n($($name),*);
327 impl<G: EmissionGuarantee> Deref for DiagnosticBuilder<'_, G> {
328 type Target = Diagnostic;
330 fn deref(&self) -> &Diagnostic {
331 &self.inner.diagnostic
335 impl<G: EmissionGuarantee> DerefMut for DiagnosticBuilder<'_, G> {
336 fn deref_mut(&mut self) -> &mut Diagnostic {
337 &mut self.inner.diagnostic
341 impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
342 /// Emit the diagnostic.
344 pub fn emit(&mut self) -> G {
345 G::diagnostic_builder_emit_producing_guarantee(self)
348 /// Emit the diagnostic unless `delay` is true,
349 /// in which case the emission will be delayed as a bug.
351 /// See `emit` and `delay_as_bug` for details.
353 pub fn emit_unless(&mut self, delay: bool) -> G {
355 self.downgrade_to_delayed_bug();
360 /// Cancel the diagnostic (a structured diagnostic must either be emitted or
361 /// cancelled or it will panic when dropped).
363 /// This method takes `self` by-value to disallow calling `.emit()` on it,
364 /// which may be expected to *guarantee* the emission of an error, either
365 /// at the time of the call, or through a prior `.emit()` call.
366 pub fn cancel(mut self) {
367 self.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
371 /// Stashes diagnostic for possible later improvement in a different,
372 /// later stage of the compiler. The diagnostic can be accessed with
373 /// the provided `span` and `key` through [`Handler::steal_diagnostic()`].
375 /// As with `buffer`, this is unless the handler has disabled such buffering.
376 pub fn stash(self, span: Span, key: StashKey) {
377 if let Some((diag, handler)) = self.into_diagnostic() {
378 handler.stash_diagnostic(span, key, diag);
382 /// Converts the builder to a `Diagnostic` for later emission,
383 /// unless handler has disabled such buffering, or `.emit()` was called.
384 pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
385 let handler = match self.inner.state {
386 // No `.emit()` calls, the `&Handler` is still available.
387 DiagnosticBuilderState::Emittable(handler) => handler,
388 // `.emit()` was previously called, nothing we can do.
389 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
394 if handler.flags.dont_buffer_diagnostics || handler.flags.treat_err_as_bug.is_some() {
399 // Take the `Diagnostic` by replacing it with a dummy.
400 let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
401 let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
403 // Disable the ICE on `Drop`.
406 // Logging here is useful to help track down where in logs an error was
408 debug!("buffer: diagnostic={:?}", diagnostic);
410 Some((diagnostic, handler))
413 /// Buffers the diagnostic for later emission,
414 /// unless handler has disabled such buffering.
415 pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
416 buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
419 /// Delay emission of this diagnostic as a bug.
421 /// This can be useful in contexts where an error indicates a bug but
422 /// typically this only happens when other compilation errors have already
423 /// happened. In those cases this can be used to defer emission of this
424 /// diagnostic as a bug in the compiler only if no other errors have been
427 /// In the meantime, though, callsites are required to deal with the "bug"
428 /// locally in whichever way makes the most sense.
430 pub fn delay_as_bug(&mut self) {
431 self.downgrade_to_delayed_bug();
437 pub fn downgrade_to_delayed_bug(&mut self,) -> &mut Self
441 /// Appends a labeled span to the diagnostic.
443 /// Labels are used to convey additional context for the diagnostic's primary span. They will
444 /// be shown together with the original diagnostic's span, *not* with spans added by
445 /// `span_note`, `span_help`, etc. Therefore, if the primary span is not displayable (because
446 /// the span is `DUMMY_SP` or the source code isn't found), labels will not be displayed
449 /// Implementation-wise, the label span is pushed onto the [`MultiSpan`] that was created when
450 /// the diagnostic was constructed. However, the label span is *not* considered a
451 /// ["primary span"][`MultiSpan`]; only the `Span` supplied when creating the diagnostic is
453 pub fn span_label(&mut self, span: Span, label: impl Into<SubdiagnosticMessage>) -> &mut Self);
456 /// Labels all the given spans with the provided label.
457 /// See [`Diagnostic::span_label()`] for more information.
460 spans: impl IntoIterator<Item = Span>,
461 label: impl AsRef<str>,
464 forward!(pub fn note_expected_found(
466 expected_label: &dyn fmt::Display,
467 expected: DiagnosticStyledString,
468 found_label: &dyn fmt::Display,
469 found: DiagnosticStyledString,
472 forward!(pub fn note_expected_found_extra(
474 expected_label: &dyn fmt::Display,
475 expected: DiagnosticStyledString,
476 found_label: &dyn fmt::Display,
477 found: DiagnosticStyledString,
478 expected_extra: &dyn fmt::Display,
479 found_extra: &dyn fmt::Display,
482 forward!(pub fn note_unsuccessful_coercion(
484 expected: DiagnosticStyledString,
485 found: DiagnosticStyledString,
488 forward!(pub fn note(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
489 forward!(pub fn note_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
490 forward!(pub fn span_note(
492 sp: impl Into<MultiSpan>,
493 msg: impl Into<SubdiagnosticMessage>,
495 forward!(pub fn span_note_once(
497 sp: impl Into<MultiSpan>,
498 msg: impl Into<SubdiagnosticMessage>,
500 forward!(pub fn warn(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
501 forward!(pub fn span_warn(
503 sp: impl Into<MultiSpan>,
504 msg: impl Into<SubdiagnosticMessage>,
506 forward!(pub fn help(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
507 forward!(pub fn span_help(
509 sp: impl Into<MultiSpan>,
510 msg: impl Into<SubdiagnosticMessage>,
512 forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
513 forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
515 forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
516 forward!(pub fn clear_suggestions(&mut self,) -> &mut Self);
518 forward!(pub fn multipart_suggestion(
520 msg: impl Into<SubdiagnosticMessage>,
521 suggestion: Vec<(Span, String)>,
522 applicability: Applicability,
524 forward!(pub fn multipart_suggestion_verbose(
526 msg: impl Into<SubdiagnosticMessage>,
527 suggestion: Vec<(Span, String)>,
528 applicability: Applicability,
530 forward!(pub fn tool_only_multipart_suggestion(
532 msg: impl Into<SubdiagnosticMessage>,
533 suggestion: Vec<(Span, String)>,
534 applicability: Applicability,
536 forward!(pub fn span_suggestion(
539 msg: impl Into<SubdiagnosticMessage>,
540 suggestion: impl ToString,
541 applicability: Applicability,
543 forward!(pub fn span_suggestions(
546 msg: impl Into<SubdiagnosticMessage>,
547 suggestions: impl Iterator<Item = String>,
548 applicability: Applicability,
550 forward!(pub fn multipart_suggestions(
552 msg: impl Into<SubdiagnosticMessage>,
553 suggestions: impl Iterator<Item = Vec<(Span, String)>>,
554 applicability: Applicability,
556 forward!(pub fn span_suggestion_short(
559 msg: impl Into<SubdiagnosticMessage>,
560 suggestion: impl ToString,
561 applicability: Applicability,
563 forward!(pub fn span_suggestion_verbose(
566 msg: impl Into<SubdiagnosticMessage>,
567 suggestion: impl ToString,
568 applicability: Applicability,
570 forward!(pub fn span_suggestion_hidden(
573 msg: impl Into<SubdiagnosticMessage>,
574 suggestion: impl ToString,
575 applicability: Applicability,
577 forward!(pub fn tool_only_span_suggestion(
580 msg: impl Into<SubdiagnosticMessage>,
581 suggestion: impl ToString,
582 applicability: Applicability,
585 forward!(pub fn set_primary_message(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
586 forward!(pub fn set_span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self);
587 forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
588 forward!(pub fn set_arg(
590 name: impl Into<Cow<'static, str>>,
591 arg: impl IntoDiagnosticArg,
594 forward!(pub fn subdiagnostic(
596 subdiagnostic: impl crate::AddToDiagnostic
600 impl<G: EmissionGuarantee> Debug for DiagnosticBuilder<'_, G> {
601 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
602 self.inner.diagnostic.fmt(f)
606 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or cancelled
607 /// or we emit a bug.
608 impl Drop for DiagnosticBuilderInner<'_> {
611 // No `.emit()` or `.cancel()` calls.
612 DiagnosticBuilderState::Emittable(handler) => {
614 handler.emit_diagnostic(&mut Diagnostic::new(
616 DiagnosticMessage::Str(
617 "the following error was constructed but not emitted".to_string(),
620 handler.emit_diagnostic(&mut self.diagnostic);
621 panic!("error was constructed but not emitted");
624 // `.emit()` was previously called, or maybe we're during `.cancel()`.
625 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
631 macro_rules! struct_span_err {
632 ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
633 $session.struct_span_err_with_code(
635 &format!($($message)*),
636 $crate::error_code!($code),
642 macro_rules! error_code {
643 ($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};