1 use crate::diagnostic::DiagnosticArgValue;
2 use crate::{Diagnostic, DiagnosticId, DiagnosticMessage, DiagnosticStyledString, ErrorGuaranteed};
3 use crate::{Handler, Level, MultiSpan, StashKey};
4 use rustc_lint_defs::Applicability;
8 use std::fmt::{self, Debug};
9 use std::marker::PhantomData;
10 use std::ops::{Deref, DerefMut};
11 use std::thread::panicking;
14 /// Used for emitting structured error messages and other diagnostic information.
16 /// If there is some state in a downstream crate you would like to
17 /// access in the methods of `DiagnosticBuilder` here, consider
18 /// extending `HandlerFlags`, accessed via `self.handler.flags`.
21 pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
22 inner: DiagnosticBuilderInner<'a>,
23 _marker: PhantomData<G>,
26 /// This type exists only for `DiagnosticBuilder::forget_guarantee`, because it:
27 /// 1. lacks the `G` parameter and therefore `DiagnosticBuilder<G1>` can be
28 /// converted into `DiagnosticBuilder<G2>` while reusing the `inner` field
29 /// 2. can implement the `Drop` "bomb" instead of `DiagnosticBuilder`, as it
30 /// contains all of the data (`state` + `diagnostic`) of `DiagnosticBuilder`
32 /// The `diagnostic` field is not `Copy` and can't be moved out of whichever
33 /// type implements the `Drop` "bomb", but because of the above two facts, that
34 /// never needs to happen - instead, the whole `inner: DiagnosticBuilderInner`
35 /// can be moved out of a `DiagnosticBuilder` and into another.
38 struct DiagnosticBuilderInner<'a> {
39 state: DiagnosticBuilderState<'a>,
41 /// `Diagnostic` is a large type, and `DiagnosticBuilder` is often used as a
42 /// return value, especially within the frequently-used `PResult` type.
43 /// In theory, return value optimization (RVO) should avoid unnecessary
44 /// copying. In practice, it does not (at the time of writing).
45 diagnostic: Box<Diagnostic>,
49 enum DiagnosticBuilderState<'a> {
50 /// Initial state of a `DiagnosticBuilder`, before `.emit()` or `.cancel()`.
52 /// The `Diagnostic` will be emitted through this `Handler`.
53 Emittable(&'a Handler),
55 /// State of a `DiagnosticBuilder`, after `.emit()` or *during* `.cancel()`.
57 /// The `Diagnostic` will be ignored when calling `.emit()`, and it can be
58 /// assumed that `.emit()` was previously called, to end up in this state.
60 /// While this is also used by `.cancel()`, this state is only observed by
61 /// the `Drop` `impl` of `DiagnosticBuilderInner`, as `.cancel()` takes
62 /// `self` by-value specifically to prevent any attempts to `.emit()`.
64 // FIXME(eddyb) currently this doesn't prevent extending the `Diagnostic`,
65 // despite that being potentially lossy, if important information is added
66 // *after* the original `.emit()` call.
67 AlreadyEmittedOrDuringCancellation,
70 // `DiagnosticBuilderState` should be pointer-sized.
71 rustc_data_structures::static_assert_size!(
72 DiagnosticBuilderState<'_>,
73 std::mem::size_of::<&Handler>()
76 /// Trait for types that `DiagnosticBuilder::emit` can return as a "guarantee"
77 /// (or "proof") token that the emission happened.
78 pub trait EmissionGuarantee: Sized {
79 /// Implementation of `DiagnosticBuilder::emit`, fully controlled by each
80 /// `impl` of `EmissionGuarantee`, to make it impossible to create a value
81 /// of `Self` without actually performing the emission.
83 fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
86 /// Private module for sealing the `IsError` helper trait.
87 mod sealed_level_is_error {
90 /// Sealed helper trait for statically checking that a `Level` is an error.
91 crate trait IsError<const L: Level> {}
93 impl IsError<{ Level::Bug }> for () {}
94 impl IsError<{ Level::DelayedBug }> for () {}
95 impl IsError<{ Level::Fatal }> for () {}
96 // NOTE(eddyb) `Level::Error { lint: true }` is also an error, but lints
97 // don't need error guarantees, as their levels are always dynamic.
98 impl IsError<{ Level::Error { lint: false } }> for () {}
101 impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
102 /// Convenience function for internal use, clients should use one of the
103 /// `struct_*` methods on [`Handler`].
104 crate fn new_guaranteeing_error<M: Into<DiagnosticMessage>, const L: Level>(
105 handler: &'a Handler,
109 (): sealed_level_is_error::IsError<L>,
112 inner: DiagnosticBuilderInner {
113 state: DiagnosticBuilderState::Emittable(handler),
114 diagnostic: Box::new(Diagnostic::new_with_code(L, None, message)),
116 _marker: PhantomData,
120 /// Discard the guarantee `.emit()` would return, in favor of having the
121 /// type `DiagnosticBuilder<'a, ()>`. This may be necessary whenever there
122 /// is a common codepath handling both errors and warnings.
123 pub fn forget_guarantee(self) -> DiagnosticBuilder<'a, ()> {
124 DiagnosticBuilder { inner: self.inner, _marker: PhantomData }
128 // FIXME(eddyb) make `ErrorGuaranteed` impossible to create outside `.emit()`.
129 impl EmissionGuarantee for ErrorGuaranteed {
130 fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
131 match db.inner.state {
132 // First `.emit()` call, the `&Handler` is still available.
133 DiagnosticBuilderState::Emittable(handler) => {
134 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
136 let guar = handler.emit_diagnostic(&mut db.inner.diagnostic);
138 // Only allow a guarantee if the `level` wasn't switched to a
139 // non-error - the field isn't `pub`, but the whole `Diagnostic`
140 // can be overwritten with a new one, thanks to `DerefMut`.
142 db.inner.diagnostic.is_error(),
143 "emitted non-error ({:?}) diagnostic \
144 from `DiagnosticBuilder<ErrorGuaranteed>`",
145 db.inner.diagnostic.level,
149 // `.emit()` was previously called, disallowed from repeating it,
150 // but can take advantage of the previous `.emit()`'s guarantee
151 // still being applicable (i.e. as a form of idempotency).
152 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
153 // Only allow a guarantee if the `level` wasn't switched to a
154 // non-error - the field isn't `pub`, but the whole `Diagnostic`
155 // can be overwritten with a new one, thanks to `DerefMut`.
157 db.inner.diagnostic.is_error(),
158 "`DiagnosticBuilder<ErrorGuaranteed>`'s diagnostic \
159 became non-error ({:?}), after original `.emit()`",
160 db.inner.diagnostic.level,
162 ErrorGuaranteed::unchecked_claim_error_was_emitted()
168 impl<'a> DiagnosticBuilder<'a, ()> {
169 /// Convenience function for internal use, clients should use one of the
170 /// `struct_*` methods on [`Handler`].
171 crate fn new<M: Into<DiagnosticMessage>>(
172 handler: &'a Handler,
176 let diagnostic = Diagnostic::new_with_code(level, None, message);
177 Self::new_diagnostic(handler, diagnostic)
180 /// Creates a new `DiagnosticBuilder` with an already constructed
182 crate fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
183 debug!("Created new diagnostic");
185 inner: DiagnosticBuilderInner {
186 state: DiagnosticBuilderState::Emittable(handler),
187 diagnostic: Box::new(diagnostic),
189 _marker: PhantomData,
194 // FIXME(eddyb) should there be a `Option<ErrorGuaranteed>` impl as well?
195 impl EmissionGuarantee for () {
196 fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
197 match db.inner.state {
198 // First `.emit()` call, the `&Handler` is still available.
199 DiagnosticBuilderState::Emittable(handler) => {
200 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
202 handler.emit_diagnostic(&mut db.inner.diagnostic);
204 // `.emit()` was previously called, disallowed from repeating it.
205 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
210 impl<'a> DiagnosticBuilder<'a, !> {
211 /// Convenience function for internal use, clients should use one of the
212 /// `struct_*` methods on [`Handler`].
213 crate fn new_fatal(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
214 let diagnostic = Diagnostic::new_with_code(Level::Fatal, None, message);
215 Self::new_diagnostic_fatal(handler, diagnostic)
218 /// Creates a new `DiagnosticBuilder` with an already constructed
220 crate fn new_diagnostic_fatal(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
221 debug!("Created new diagnostic");
223 inner: DiagnosticBuilderInner {
224 state: DiagnosticBuilderState::Emittable(handler),
225 diagnostic: Box::new(diagnostic),
227 _marker: PhantomData,
232 impl EmissionGuarantee for ! {
233 fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
234 match db.inner.state {
235 // First `.emit()` call, the `&Handler` is still available.
236 DiagnosticBuilderState::Emittable(handler) => {
237 db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
239 handler.emit_diagnostic(&mut db.inner.diagnostic);
241 // `.emit()` was previously called, disallowed from repeating it.
242 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
244 // Then fatally error, returning `!`
245 crate::FatalError.raise()
249 /// In general, the `DiagnosticBuilder` uses deref to allow access to
250 /// the fields and methods of the embedded `diagnostic` in a
251 /// transparent way. *However,* many of the methods are intended to
252 /// be used in a chained way, and hence ought to return `self`. In
253 /// that case, we can't just naively forward to the method on the
254 /// `diagnostic`, because the return type would be a `&Diagnostic`
255 /// instead of a `&DiagnosticBuilder<'a>`. This `forward!` macro makes
256 /// it easy to declare such methods on the builder.
257 macro_rules! forward {
258 // Forward pattern for &mut self -> &mut Self
261 pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
264 #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
265 pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
266 self.inner.diagnostic.$n($($name),*);
272 impl<G: EmissionGuarantee> Deref for DiagnosticBuilder<'_, G> {
273 type Target = Diagnostic;
275 fn deref(&self) -> &Diagnostic {
276 &self.inner.diagnostic
280 impl<G: EmissionGuarantee> DerefMut for DiagnosticBuilder<'_, G> {
281 fn deref_mut(&mut self) -> &mut Diagnostic {
282 &mut self.inner.diagnostic
286 impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
287 /// Emit the diagnostic.
289 pub fn emit(&mut self) -> G {
290 G::diagnostic_builder_emit_producing_guarantee(self)
293 /// Emit the diagnostic unless `delay` is true,
294 /// in which case the emission will be delayed as a bug.
296 /// See `emit` and `delay_as_bug` for details.
298 pub fn emit_unless(&mut self, delay: bool) -> G {
300 self.downgrade_to_delayed_bug();
305 /// Cancel the diagnostic (a structured diagnostic must either be emitted or
306 /// cancelled or it will panic when dropped).
308 /// This method takes `self` by-value to disallow calling `.emit()` on it,
309 /// which may be expected to *guarantee* the emission of an error, either
310 /// at the time of the call, or through a prior `.emit()` call.
311 pub fn cancel(mut self) {
312 self.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
316 /// Stashes diagnostic for possible later improvement in a different,
317 /// later stage of the compiler. The diagnostic can be accessed with
318 /// the provided `span` and `key` through [`Handler::steal_diagnostic()`].
320 /// As with `buffer`, this is unless the handler has disabled such buffering.
321 pub fn stash(self, span: Span, key: StashKey) {
322 if let Some((diag, handler)) = self.into_diagnostic() {
323 handler.stash_diagnostic(span, key, diag);
327 /// Converts the builder to a `Diagnostic` for later emission,
328 /// unless handler has disabled such buffering, or `.emit()` was called.
329 pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
330 let handler = match self.inner.state {
331 // No `.emit()` calls, the `&Handler` is still available.
332 DiagnosticBuilderState::Emittable(handler) => handler,
333 // `.emit()` was previously called, nothing we can do.
334 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {
339 if handler.flags.dont_buffer_diagnostics || handler.flags.treat_err_as_bug.is_some() {
344 // Take the `Diagnostic` by replacing it with a dummy.
345 let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
346 let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
348 // Disable the ICE on `Drop`.
351 // Logging here is useful to help track down where in logs an error was
353 debug!("buffer: diagnostic={:?}", diagnostic);
355 Some((diagnostic, handler))
358 /// Buffers the diagnostic for later emission,
359 /// unless handler has disabled such buffering.
360 pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
361 buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
364 /// Delay emission of this diagnostic as a bug.
366 /// This can be useful in contexts where an error indicates a bug but
367 /// typically this only happens when other compilation errors have already
368 /// happened. In those cases this can be used to defer emission of this
369 /// diagnostic as a bug in the compiler only if no other errors have been
372 /// In the meantime, though, callsites are required to deal with the "bug"
373 /// locally in whichever way makes the most sense.
375 pub fn delay_as_bug(&mut self) {
376 self.downgrade_to_delayed_bug();
382 pub fn downgrade_to_delayed_bug(&mut self,) -> &mut Self
386 /// Appends a labeled span to the diagnostic.
388 /// Labels are used to convey additional context for the diagnostic's primary span. They will
389 /// be shown together with the original diagnostic's span, *not* with spans added by
390 /// `span_note`, `span_help`, etc. Therefore, if the primary span is not displayable (because
391 /// the span is `DUMMY_SP` or the source code isn't found), labels will not be displayed
394 /// Implementation-wise, the label span is pushed onto the [`MultiSpan`] that was created when
395 /// the diagnostic was constructed. However, the label span is *not* considered a
396 /// ["primary span"][`MultiSpan`]; only the `Span` supplied when creating the diagnostic is
398 pub fn span_label(&mut self, span: Span, label: impl Into<DiagnosticMessage>) -> &mut Self);
401 /// Labels all the given spans with the provided label.
402 /// See [`Diagnostic::span_label()`] for more information.
405 spans: impl IntoIterator<Item = Span>,
406 label: impl AsRef<str>,
409 forward!(pub fn note_expected_found(
411 expected_label: &dyn fmt::Display,
412 expected: DiagnosticStyledString,
413 found_label: &dyn fmt::Display,
414 found: DiagnosticStyledString,
417 forward!(pub fn note_expected_found_extra(
419 expected_label: &dyn fmt::Display,
420 expected: DiagnosticStyledString,
421 found_label: &dyn fmt::Display,
422 found: DiagnosticStyledString,
423 expected_extra: &dyn fmt::Display,
424 found_extra: &dyn fmt::Display,
427 forward!(pub fn note_unsuccessful_coercion(
429 expected: DiagnosticStyledString,
430 found: DiagnosticStyledString,
433 forward!(pub fn note(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
434 forward!(pub fn note_once(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
435 forward!(pub fn span_note(
437 sp: impl Into<MultiSpan>,
438 msg: impl Into<DiagnosticMessage>,
440 forward!(pub fn span_note_once(
442 sp: impl Into<MultiSpan>,
443 msg: impl Into<DiagnosticMessage>,
445 forward!(pub fn warn(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
446 forward!(pub fn span_warn(&mut self, sp: impl Into<MultiSpan>, msg: &str) -> &mut Self);
447 forward!(pub fn help(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self);
448 forward!(pub fn span_help(
450 sp: impl Into<MultiSpan>,
451 msg: impl Into<DiagnosticMessage>,
453 forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
454 forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
456 forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
458 forward!(pub fn multipart_suggestion(
460 msg: impl Into<DiagnosticMessage>,
461 suggestion: Vec<(Span, String)>,
462 applicability: Applicability,
464 forward!(pub fn multipart_suggestion_verbose(
466 msg: impl Into<DiagnosticMessage>,
467 suggestion: Vec<(Span, String)>,
468 applicability: Applicability,
470 forward!(pub fn tool_only_multipart_suggestion(
472 msg: impl Into<DiagnosticMessage>,
473 suggestion: Vec<(Span, String)>,
474 applicability: Applicability,
476 forward!(pub fn span_suggestion(
479 msg: impl Into<DiagnosticMessage>,
480 suggestion: impl ToString,
481 applicability: Applicability,
483 forward!(pub fn span_suggestions(
486 msg: impl Into<DiagnosticMessage>,
487 suggestions: impl Iterator<Item = String>,
488 applicability: Applicability,
490 forward!(pub fn multipart_suggestions(
492 msg: impl Into<DiagnosticMessage>,
493 suggestions: impl Iterator<Item = Vec<(Span, String)>>,
494 applicability: Applicability,
496 forward!(pub fn span_suggestion_short(
499 msg: impl Into<DiagnosticMessage>,
500 suggestion: impl ToString,
501 applicability: Applicability,
503 forward!(pub fn span_suggestion_verbose(
506 msg: impl Into<DiagnosticMessage>,
507 suggestion: impl ToString,
508 applicability: Applicability,
510 forward!(pub fn span_suggestion_hidden(
513 msg: impl Into<DiagnosticMessage>,
514 suggestion: impl ToString,
515 applicability: Applicability,
517 forward!(pub fn tool_only_span_suggestion(
520 msg: impl Into<DiagnosticMessage>,
521 suggestion: impl ToString,
522 applicability: Applicability,
525 forward!(pub fn set_primary_message(&mut self, msg: impl Into<String>) -> &mut Self);
526 forward!(pub fn set_span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self);
527 forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
528 forward!(pub fn set_arg(
530 name: impl Into<Cow<'static, str>>,
531 arg: DiagnosticArgValue<'static>,
534 forward!(pub fn subdiagnostic(
536 subdiagnostic: impl crate::AddSubdiagnostic
540 impl<G: EmissionGuarantee> Debug for DiagnosticBuilder<'_, G> {
541 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
542 self.inner.diagnostic.fmt(f)
546 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or cancelled
547 /// or we emit a bug.
548 impl Drop for DiagnosticBuilderInner<'_> {
551 // No `.emit()` or `.cancel()` calls.
552 DiagnosticBuilderState::Emittable(handler) => {
554 handler.emit_diagnostic(&mut Diagnostic::new(
556 DiagnosticMessage::Str(
557 "the following error was constructed but not emitted".to_string(),
560 handler.emit_diagnostic(&mut self.diagnostic);
564 // `.emit()` was previously called, or maybe we're during `.cancel()`.
565 DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
571 macro_rules! struct_span_err {
572 ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
573 $session.struct_span_err_with_code(
575 &format!($($message)*),
576 $crate::error_code!($code),
582 macro_rules! error_code {
583 ($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};