src/librustc_errors/diagnostic_builder.rs

   1 use crate::{Diagnostic, DiagnosticId, DiagnosticStyledString};
   2 use crate::{Applicability, Level, Handler, StashKey};
   3
   4 use std::fmt::{self, Debug};
   5 use std::ops::{Deref, DerefMut};
   6 use std::thread::panicking;
   7 use syntax_pos::{MultiSpan, Span};
   8 use log::debug;
   9
  10 /// Used for emitting structured error messages and other diagnostic information.
  11 ///
  12 /// If there is some state in a downstream crate you would like to
  13 /// access in the methods of `DiagnosticBuilder` here, consider
  14 /// extending `HandlerFlags`, accessed via `self.handler.flags`.
  15 #[must_use]
  16 #[derive(Clone)]
  17 pub struct DiagnosticBuilder<'a>(Box<DiagnosticBuilderInner<'a>>);
  18
  19 /// This is a large type, and often used as a return value, especially within
  20 /// the frequently-used `PResult` type. In theory, return value optimization
  21 /// (RVO) should avoid unnecessary copying. In practice, it does not (at the
  22 /// time of writing). The split between `DiagnosticBuilder` and
  23 /// `DiagnosticBuilderInner` exists to avoid many `memcpy` calls.
  24 #[must_use]
  25 #[derive(Clone)]
  26 struct DiagnosticBuilderInner<'a> {
  27     handler: &'a Handler,
  28     diagnostic: Diagnostic,
  29     allow_suggestions: bool,
  30 }
  31
  32 /// In general, the `DiagnosticBuilder` uses deref to allow access to
  33 /// the fields and methods of the embedded `diagnostic` in a
  34 /// transparent way. *However,* many of the methods are intended to
  35 /// be used in a chained way, and hence ought to return `self`. In
  36 /// that case, we can't just naively forward to the method on the
  37 /// `diagnostic`, because the return type would be a `&Diagnostic`
  38 /// instead of a `&DiagnosticBuilder<'a>`. This `forward!` macro makes
  39 /// it easy to declare such methods on the builder.
  40 macro_rules! forward {
  41     // Forward pattern for &self -> &Self
  42     (
  43         $(#[$attrs:meta])*
  44         pub fn $n:ident(&self, $($name:ident: $ty:ty),* $(,)?) -> &Self
  45     ) => {
  46         $(#[$attrs])*
  47         pub fn $n(&self, $($name: $ty),*) -> &Self {
  48             self.diagnostic.$n($($name),*);
  49             self
  50         }
  51     };
  52
  53     // Forward pattern for &mut self -> &mut Self
  54     (
  55         $(#[$attrs:meta])*
  56         pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
  57     ) => {
  58         $(#[$attrs])*
  59         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
  60             self.0.diagnostic.$n($($name),*);
  61             self
  62         }
  63     };
  64
  65     // Forward pattern for &mut self -> &mut Self, with S: Into<MultiSpan>
  66     // type parameter. No obvious way to make this more generic.
  67     (
  68         $(#[$attrs:meta])*
  69         pub fn $n:ident<S: Into<MultiSpan>>(
  70             &mut self,
  71             $($name:ident: $ty:ty),*
  72             $(,)?
  73         ) -> &mut Self
  74     ) => {
  75         $(#[$attrs])*
  76         pub fn $n<S: Into<MultiSpan>>(&mut self, $($name: $ty),*) -> &mut Self {
  77             self.0.diagnostic.$n($($name),*);
  78             self
  79         }
  80     };
  81 }
  82
  83 impl<'a> Deref for DiagnosticBuilder<'a> {
  84     type Target = Diagnostic;
  85
  86     fn deref(&self) -> &Diagnostic {
  87         &self.0.diagnostic
  88     }
  89 }
  90
  91 impl<'a> DerefMut for DiagnosticBuilder<'a> {
  92     fn deref_mut(&mut self) -> &mut Diagnostic {
  93         &mut self.0.diagnostic
  94     }
  95 }
  96
  97 impl<'a> DiagnosticBuilder<'a> {
  98     /// Emit the diagnostic.
  99     pub fn emit(&mut self) {
 100         self.0.handler.emit_diagnostic(&self);
 101         self.cancel();
 102     }
 103
 104     /// Emit the diagnostic unless `delay` is true,
 105     /// in which case the emission will be delayed as a bug.
 106     ///
 107     /// See `emit` and `delay_as_bug` for details.
 108     pub fn emit_unless(&mut self, delay: bool) {
 109         if delay {
 110             self.delay_as_bug()
 111         } else {
 112             self.emit()
 113         }
 114     }
 115
 116     /// Stashes diagnostic for possible later improvement in a different,
 117     /// later stage of the compiler. The diagnostic can be accessed with
 118     /// the provided `span` and `key` through `.steal_diagnostic` on `Handler`.
 119     ///
 120     /// As with `buffer`, this is unless the handler has disabled such buffering.
 121     pub fn stash(self, span: Span, key: StashKey) {
 122         if let Some((diag, handler)) = self.into_diagnostic() {
 123             handler.stash_diagnostic(span, key, diag);
 124         }
 125     }
 126
 127     /// Converts the builder to a `Diagnostic` for later emission,
 128     /// unless handler has disabled such buffering.
 129     pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
 130         if self.0.handler.flags.dont_buffer_diagnostics ||
 131             self.0.handler.flags.treat_err_as_bug.is_some()
 132         {
 133             self.emit();
 134             return None;
 135         }
 136
 137         let handler = self.0.handler;
 138
 139         // We need to use `ptr::read` because `DiagnosticBuilder` implements `Drop`.
 140         let diagnostic;
 141         unsafe {
 142             diagnostic = std::ptr::read(&self.0.diagnostic);
 143             std::mem::forget(self);
 144         };
 145         // Logging here is useful to help track down where in logs an error was
 146         // actually emitted.
 147         debug!("buffer: diagnostic={:?}", diagnostic);
 148
 149         Some((diagnostic, handler))
 150     }
 151
 152     /// Buffers the diagnostic for later emission,
 153     /// unless handler has disabled such buffering.
 154     pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
 155         buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
 156     }
 157
 158     /// Convenience function for internal use, clients should use one of the
 159     /// span_* methods instead.
 160     pub fn sub<S: Into<MultiSpan>>(
 161         &mut self,
 162         level: Level,
 163         message: &str,
 164         span: Option<S>,
 165     ) -> &mut Self {
 166         let span = span.map(|s| s.into()).unwrap_or_else(|| MultiSpan::new());
 167         self.0.diagnostic.sub(level, message, span, None);
 168         self
 169     }
 170
 171     /// Delay emission of this diagnostic as a bug.
 172     ///
 173     /// This can be useful in contexts where an error indicates a bug but
 174     /// typically this only happens when other compilation errors have already
 175     /// happened. In those cases this can be used to defer emission of this
 176     /// diagnostic as a bug in the compiler only if no other errors have been
 177     /// emitted.
 178     ///
 179     /// In the meantime, though, callsites are required to deal with the "bug"
 180     /// locally in whichever way makes the most sense.
 181     pub fn delay_as_bug(&mut self) {
 182         self.level = Level::Bug;
 183         self.0.handler.delay_as_bug(self.0.diagnostic.clone());
 184         self.cancel();
 185     }
 186
 187     /// Adds a span/label to be included in the resulting snippet.
 188     /// This is pushed onto the `MultiSpan` that was created when the
 189     /// diagnostic was first built. If you don't call this function at
 190     /// all, and you just supplied a `Span` to create the diagnostic,
 191     /// then the snippet will just include that `Span`, which is
 192     /// called the primary span.
 193     pub fn span_label<T: Into<String>>(&mut self, span: Span, label: T) -> &mut Self {
 194         self.0.diagnostic.span_label(span, label);
 195         self
 196     }
 197
 198     forward!(pub fn note_expected_found(&mut self,
 199                                         label: &dyn fmt::Display,
 200                                         expected: DiagnosticStyledString,
 201                                         found: DiagnosticStyledString,
 202                                         ) -> &mut Self);
 203
 204     forward!(pub fn note_expected_found_extra(&mut self,
 205                                               label: &dyn fmt::Display,
 206                                               expected: DiagnosticStyledString,
 207                                               found: DiagnosticStyledString,
 208                                               expected_extra: &dyn fmt::Display,
 209                                               found_extra: &dyn fmt::Display,
 210                                               ) -> &mut Self);
 211
 212     forward!(pub fn note(&mut self, msg: &str) -> &mut Self);
 213     forward!(pub fn span_note<S: Into<MultiSpan>>(&mut self,
 214                                                   sp: S,
 215                                                   msg: &str,
 216                                                   ) -> &mut Self);
 217     forward!(pub fn warn(&mut self, msg: &str) -> &mut Self);
 218     forward!(pub fn span_warn<S: Into<MultiSpan>>(&mut self, sp: S, msg: &str) -> &mut Self);
 219     forward!(pub fn help(&mut self, msg: &str) -> &mut Self);
 220     forward!(pub fn span_help<S: Into<MultiSpan>>(&mut self,
 221                                                   sp: S,
 222                                                   msg: &str,
 223                                                   ) -> &mut Self);
 224
 225     pub fn multipart_suggestion(
 226         &mut self,
 227         msg: &str,
 228         suggestion: Vec<(Span, String)>,
 229         applicability: Applicability,
 230     ) -> &mut Self {
 231         if !self.0.allow_suggestions {
 232             return self
 233         }
 234         self.0.diagnostic.multipart_suggestion(
 235             msg,
 236             suggestion,
 237             applicability,
 238         );
 239         self
 240     }
 241
 242     pub fn tool_only_multipart_suggestion(
 243         &mut self,
 244         msg: &str,
 245         suggestion: Vec<(Span, String)>,
 246         applicability: Applicability,
 247     ) -> &mut Self {
 248         if !self.0.allow_suggestions {
 249             return self
 250         }
 251         self.0.diagnostic.tool_only_multipart_suggestion(
 252             msg,
 253             suggestion,
 254             applicability,
 255         );
 256         self
 257     }
 258
 259     pub fn span_suggestion(
 260         &mut self,
 261         sp: Span,
 262         msg: &str,
 263         suggestion: String,
 264         applicability: Applicability,
 265     ) -> &mut Self {
 266         if !self.0.allow_suggestions {
 267             return self
 268         }
 269         self.0.diagnostic.span_suggestion(
 270             sp,
 271             msg,
 272             suggestion,
 273             applicability,
 274         );
 275         self
 276     }
 277
 278     pub fn span_suggestions(
 279         &mut self,
 280         sp: Span,
 281         msg: &str,
 282         suggestions: impl Iterator<Item = String>,
 283         applicability: Applicability,
 284     ) -> &mut Self {
 285         if !self.0.allow_suggestions {
 286             return self
 287         }
 288         self.0.diagnostic.span_suggestions(
 289             sp,
 290             msg,
 291             suggestions,
 292             applicability,
 293         );
 294         self
 295     }
 296
 297     pub fn span_suggestion_short(
 298         &mut self,
 299         sp: Span,
 300         msg: &str,
 301         suggestion: String,
 302         applicability: Applicability,
 303     ) -> &mut Self {
 304         if !self.0.allow_suggestions {
 305             return self
 306         }
 307         self.0.diagnostic.span_suggestion_short(
 308             sp,
 309             msg,
 310             suggestion,
 311             applicability,
 312         );
 313         self
 314     }
 315
 316     pub fn span_suggestion_hidden(
 317         &mut self,
 318         sp: Span,
 319         msg: &str,
 320         suggestion: String,
 321         applicability: Applicability,
 322     ) -> &mut Self {
 323         if !self.0.allow_suggestions {
 324             return self
 325         }
 326         self.0.diagnostic.span_suggestion_hidden(
 327             sp,
 328             msg,
 329             suggestion,
 330             applicability,
 331         );
 332         self
 333     }
 334
 335     pub fn tool_only_span_suggestion(
 336         &mut self,
 337         sp: Span,
 338         msg: &str,
 339         suggestion: String,
 340         applicability: Applicability,
 341     ) -> &mut Self {
 342         if !self.0.allow_suggestions {
 343             return self
 344         }
 345         self.0.diagnostic.tool_only_span_suggestion(
 346             sp,
 347             msg,
 348             suggestion,
 349             applicability,
 350         );
 351         self
 352     }
 353
 354     forward!(pub fn set_span<S: Into<MultiSpan>>(&mut self, sp: S) -> &mut Self);
 355     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 356
 357     pub fn allow_suggestions(&mut self, allow: bool) -> &mut Self {
 358         self.0.allow_suggestions = allow;
 359         self
 360     }
 361
 362     /// Convenience function for internal use, clients should use one of the
 363     /// struct_* methods on Handler.
 364     crate fn new(handler: &'a Handler, level: Level, message: &str) -> DiagnosticBuilder<'a> {
 365         DiagnosticBuilder::new_with_code(handler, level, None, message)
 366     }
 367
 368     /// Convenience function for internal use, clients should use one of the
 369     /// struct_* methods on Handler.
 370     crate fn new_with_code(handler: &'a Handler,
 371                          level: Level,
 372                          code: Option<DiagnosticId>,
 373                          message: &str)
 374                          -> DiagnosticBuilder<'a> {
 375         let diagnostic = Diagnostic::new_with_code(level, code, message);
 376         DiagnosticBuilder::new_diagnostic(handler, diagnostic)
 377     }
 378
 379     /// Creates a new `DiagnosticBuilder` with an already constructed
 380     /// diagnostic.
 381     crate fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic)
 382                          -> DiagnosticBuilder<'a> {
 383         DiagnosticBuilder(Box::new(DiagnosticBuilderInner {
 384             handler,
 385             diagnostic,
 386             allow_suggestions: true,
 387         }))
 388     }
 389 }
 390
 391 impl<'a> Debug for DiagnosticBuilder<'a> {
 392     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 393         self.0.diagnostic.fmt(f)
 394     }
 395 }
 396
 397 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or canceled
 398 /// or we emit a bug.
 399 impl<'a> Drop for DiagnosticBuilder<'a> {
 400     fn drop(&mut self) {
 401         if !panicking() && !self.cancelled() {
 402             let mut db = DiagnosticBuilder::new(
 403                 self.0.handler,
 404                 Level::Bug,
 405                 "the following error was constructed but not emitted",
 406             );
 407             db.emit();
 408             self.emit();
 409             panic!();
 410         }
 411     }
 412 }