compiler/rustc_errors/src/emitter.rs

   1 //! The current rustc diagnostics emitter.
   2 //!
   3 //! An `Emitter` takes care of generating the output from a `DiagnosticBuilder` struct.
   4 //!
   5 //! There are various `Emitter` implementations that generate different output formats such as
   6 //! JSON and human readable output.
   7 //!
   8 //! The output types are defined in `rustc_session::config::ErrorOutputType`.
   9
  10 use Destination::*;
  11
  12 use rustc_span::source_map::SourceMap;
  13 use rustc_span::{FileLines, SourceFile, Span};
  14
  15 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, Style, StyledString};
  16 use crate::styled_buffer::StyledBuffer;
  17 use crate::translation::{to_fluent_args, Translate};
  18 use crate::{
  19     diagnostic::DiagnosticLocation, CodeSuggestion, Diagnostic, DiagnosticId, DiagnosticMessage,
  20     FluentBundle, Handler, LazyFallbackBundle, Level, MultiSpan, SubDiagnostic,
  21     SubstitutionHighlight, SuggestionStyle,
  22 };
  23 use rustc_lint_defs::pluralize;
  24
  25 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
  26 use rustc_data_structures::sync::Lrc;
  27 use rustc_error_messages::{FluentArgs, SpanLabel};
  28 use rustc_span::hygiene::{ExpnKind, MacroKind};
  29 use std::borrow::Cow;
  30 use std::cmp::{max, min, Reverse};
  31 use std::io::prelude::*;
  32 use std::io::{self, IsTerminal};
  33 use std::iter;
  34 use std::path::Path;
  35 use termcolor::{Ansi, BufferWriter, ColorChoice, ColorSpec, StandardStream};
  36 use termcolor::{Buffer, Color, WriteColor};
  37
  38 /// Default column width, used in tests and when terminal dimensions cannot be determined.
  39 const DEFAULT_COLUMN_WIDTH: usize = 140;
  40
  41 /// Describes the way the content of the `rendered` field of the json output is generated
  42 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
  43 pub enum HumanReadableErrorType {
  44     Default(ColorConfig),
  45     AnnotateSnippet(ColorConfig),
  46     Short(ColorConfig),
  47 }
  48
  49 impl HumanReadableErrorType {
  50     /// Returns a (`short`, `color`) tuple
  51     pub fn unzip(self) -> (bool, ColorConfig) {
  52         match self {
  53             HumanReadableErrorType::Default(cc) => (false, cc),
  54             HumanReadableErrorType::Short(cc) => (true, cc),
  55             HumanReadableErrorType::AnnotateSnippet(cc) => (false, cc),
  56         }
  57     }
  58     pub fn new_emitter(
  59         self,
  60         dst: Box<dyn Write + Send>,
  61         source_map: Option<Lrc<SourceMap>>,
  62         bundle: Option<Lrc<FluentBundle>>,
  63         fallback_bundle: LazyFallbackBundle,
  64         teach: bool,
  65         diagnostic_width: Option<usize>,
  66         macro_backtrace: bool,
  67         track_diagnostics: bool,
  68     ) -> EmitterWriter {
  69         let (short, color_config) = self.unzip();
  70         let color = color_config.suggests_using_colors();
  71         EmitterWriter::new(
  72             dst,
  73             source_map,
  74             bundle,
  75             fallback_bundle,
  76             short,
  77             teach,
  78             color,
  79             diagnostic_width,
  80             macro_backtrace,
  81             track_diagnostics,
  82         )
  83     }
  84 }
  85
  86 #[derive(Clone, Copy, Debug)]
  87 struct Margin {
  88     /// The available whitespace in the left that can be consumed when centering.
  89     pub whitespace_left: usize,
  90     /// The column of the beginning of left-most span.
  91     pub span_left: usize,
  92     /// The column of the end of right-most span.
  93     pub span_right: usize,
  94     /// The beginning of the line to be displayed.
  95     pub computed_left: usize,
  96     /// The end of the line to be displayed.
  97     pub computed_right: usize,
  98     /// The current width of the terminal. Uses value of `DEFAULT_COLUMN_WIDTH` constant by default
  99     /// and in tests.
 100     pub column_width: usize,
 101     /// The end column of a span label, including the span. Doesn't account for labels not in the
 102     /// same line as the span.
 103     pub label_right: usize,
 104 }
 105
 106 impl Margin {
 107     fn new(
 108         whitespace_left: usize,
 109         span_left: usize,
 110         span_right: usize,
 111         label_right: usize,
 112         column_width: usize,
 113         max_line_len: usize,
 114     ) -> Self {
 115         // The 6 is padding to give a bit of room for `...` when displaying:
 116         // ```
 117         // error: message
 118         //   --> file.rs:16:58
 119         //    |
 120         // 16 | ... fn foo(self) -> Self::Bar {
 121         //    |                     ^^^^^^^^^
 122         // ```
 123
 124         let mut m = Margin {
 125             whitespace_left: whitespace_left.saturating_sub(6),
 126             span_left: span_left.saturating_sub(6),
 127             span_right: span_right + 6,
 128             computed_left: 0,
 129             computed_right: 0,
 130             column_width,
 131             label_right: label_right + 6,
 132         };
 133         m.compute(max_line_len);
 134         m
 135     }
 136
 137     fn was_cut_left(&self) -> bool {
 138         self.computed_left > 0
 139     }
 140
 141     fn was_cut_right(&self, line_len: usize) -> bool {
 142         let right =
 143             if self.computed_right == self.span_right || self.computed_right == self.label_right {
 144                 // Account for the "..." padding given above. Otherwise we end up with code lines that
 145                 // do fit but end in "..." as if they were trimmed.
 146                 self.computed_right - 6
 147             } else {
 148                 self.computed_right
 149             };
 150         right < line_len && self.computed_left + self.column_width < line_len
 151     }
 152
 153     fn compute(&mut self, max_line_len: usize) {
 154         // When there's a lot of whitespace (>20), we want to trim it as it is useless.
 155         self.computed_left = if self.whitespace_left > 20 {
 156             self.whitespace_left - 16 // We want some padding.
 157         } else {
 158             0
 159         };
 160         // We want to show as much as possible, max_line_len is the right-most boundary for the
 161         // relevant code.
 162         self.computed_right = max(max_line_len, self.computed_left);
 163
 164         if self.computed_right - self.computed_left > self.column_width {
 165             // Trimming only whitespace isn't enough, let's get craftier.
 166             if self.label_right - self.whitespace_left <= self.column_width {
 167                 // Attempt to fit the code window only trimming whitespace.
 168                 self.computed_left = self.whitespace_left;
 169                 self.computed_right = self.computed_left + self.column_width;
 170             } else if self.label_right - self.span_left <= self.column_width {
 171                 // Attempt to fit the code window considering only the spans and labels.
 172                 let padding_left = (self.column_width - (self.label_right - self.span_left)) / 2;
 173                 self.computed_left = self.span_left.saturating_sub(padding_left);
 174                 self.computed_right = self.computed_left + self.column_width;
 175             } else if self.span_right - self.span_left <= self.column_width {
 176                 // Attempt to fit the code window considering the spans and labels plus padding.
 177                 let padding_left = (self.column_width - (self.span_right - self.span_left)) / 5 * 2;
 178                 self.computed_left = self.span_left.saturating_sub(padding_left);
 179                 self.computed_right = self.computed_left + self.column_width;
 180             } else {
 181                 // Mostly give up but still don't show the full line.
 182                 self.computed_left = self.span_left;
 183                 self.computed_right = self.span_right;
 184             }
 185         }
 186     }
 187
 188     fn left(&self, line_len: usize) -> usize {
 189         min(self.computed_left, line_len)
 190     }
 191
 192     fn right(&self, line_len: usize) -> usize {
 193         if line_len.saturating_sub(self.computed_left) <= self.column_width {
 194             line_len
 195         } else {
 196             min(line_len, self.computed_right)
 197         }
 198     }
 199 }
 200
 201 const ANONYMIZED_LINE_NUM: &str = "LL";
 202
 203 /// Emitter trait for emitting errors.
 204 pub trait Emitter: Translate {
 205     /// Emit a structured diagnostic.
 206     fn emit_diagnostic(&mut self, diag: &Diagnostic);
 207
 208     /// Emit a notification that an artifact has been output.
 209     /// This is currently only supported for the JSON format,
 210     /// other formats can, and will, simply ignore it.
 211     fn emit_artifact_notification(&mut self, _path: &Path, _artifact_type: &str) {}
 212
 213     fn emit_future_breakage_report(&mut self, _diags: Vec<Diagnostic>) {}
 214
 215     /// Emit list of unused externs
 216     fn emit_unused_externs(
 217         &mut self,
 218         _lint_level: rustc_lint_defs::Level,
 219         _unused_externs: &[&str],
 220     ) {
 221     }
 222
 223     /// Checks if should show explanations about "rustc --explain"
 224     fn should_show_explain(&self) -> bool {
 225         true
 226     }
 227
 228     /// Checks if we can use colors in the current output stream.
 229     fn supports_color(&self) -> bool {
 230         false
 231     }
 232
 233     fn source_map(&self) -> Option<&Lrc<SourceMap>>;
 234
 235     /// Formats the substitutions of the primary_span
 236     ///
 237     /// There are a lot of conditions to this method, but in short:
 238     ///
 239     /// * If the current `Diagnostic` has only one visible `CodeSuggestion`,
 240     ///   we format the `help` suggestion depending on the content of the
 241     ///   substitutions. In that case, we return the modified span only.
 242     ///
 243     /// * If the current `Diagnostic` has multiple suggestions,
 244     ///   we return the original `primary_span` and the original suggestions.
 245     fn primary_span_formatted<'a>(
 246         &mut self,
 247         diag: &'a Diagnostic,
 248         fluent_args: &FluentArgs<'_>,
 249     ) -> (MultiSpan, &'a [CodeSuggestion]) {
 250         let mut primary_span = diag.span.clone();
 251         let suggestions = diag.suggestions.as_deref().unwrap_or(&[]);
 252         if let Some((sugg, rest)) = suggestions.split_first() {
 253             let msg = self.translate_message(&sugg.msg, fluent_args);
 254             if rest.is_empty() &&
 255                // ^ if there is only one suggestion
 256                // don't display multi-suggestions as labels
 257                sugg.substitutions.len() == 1 &&
 258                // don't display multipart suggestions as labels
 259                sugg.substitutions[0].parts.len() == 1 &&
 260                // don't display long messages as labels
 261                msg.split_whitespace().count() < 10 &&
 262                // don't display multiline suggestions as labels
 263                !sugg.substitutions[0].parts[0].snippet.contains('\n') &&
 264                ![
 265                     // when this style is set we want the suggestion to be a message, not inline
 266                     SuggestionStyle::HideCodeAlways,
 267                     // trivial suggestion for tooling's sake, never shown
 268                     SuggestionStyle::CompletelyHidden,
 269                     // subtle suggestion, never shown inline
 270                     SuggestionStyle::ShowAlways,
 271                ].contains(&sugg.style)
 272             {
 273                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
 274                 let msg = if substitution.is_empty() || sugg.style.hide_inline() {
 275                     // This substitution is only removal OR we explicitly don't want to show the
 276                     // code inline (`hide_inline`). Therefore, we don't show the substitution.
 277                     format!("help: {}", &msg)
 278                 } else {
 279                     // Show the default suggestion text with the substitution
 280                     format!(
 281                         "help: {}{}: `{}`",
 282                         &msg,
 283                         if self
 284                             .source_map()
 285                             .map(|sm| is_case_difference(
 286                                 sm,
 287                                 substitution,
 288                                 sugg.substitutions[0].parts[0].span,
 289                             ))
 290                             .unwrap_or(false)
 291                         {
 292                             " (notice the capitalization)"
 293                         } else {
 294                             ""
 295                         },
 296                         substitution,
 297                     )
 298                 };
 299                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
 300
 301                 // We return only the modified primary_span
 302                 (primary_span, &[])
 303             } else {
 304                 // if there are multiple suggestions, print them all in full
 305                 // to be consistent. We could try to figure out if we can
 306                 // make one (or the first one) inline, but that would give
 307                 // undue importance to a semi-random suggestion
 308                 (primary_span, suggestions)
 309             }
 310         } else {
 311             (primary_span, suggestions)
 312         }
 313     }
 314
 315     fn fix_multispans_in_extern_macros_and_render_macro_backtrace(
 316         &self,
 317         span: &mut MultiSpan,
 318         children: &mut Vec<SubDiagnostic>,
 319         level: &Level,
 320         backtrace: bool,
 321     ) {
 322         // Check for spans in macros, before `fix_multispans_in_extern_macros`
 323         // has a chance to replace them.
 324         let has_macro_spans: Vec<_> = iter::once(&*span)
 325             .chain(children.iter().map(|child| &child.span))
 326             .flat_map(|span| span.primary_spans())
 327             .flat_map(|sp| sp.macro_backtrace())
 328             .filter_map(|expn_data| {
 329                 match expn_data.kind {
 330                     ExpnKind::Root => None,
 331
 332                     // Skip past non-macro entries, just in case there
 333                     // are some which do actually involve macros.
 334                     ExpnKind::Inlined | ExpnKind::Desugaring(..) | ExpnKind::AstPass(..) => None,
 335
 336                     ExpnKind::Macro(macro_kind, name) => Some((macro_kind, name)),
 337                 }
 338             })
 339             .collect();
 340
 341         if !backtrace {
 342             self.fix_multispans_in_extern_macros(span, children);
 343         }
 344
 345         self.render_multispans_macro_backtrace(span, children, backtrace);
 346
 347         if !backtrace {
 348             if let Some((macro_kind, name)) = has_macro_spans.first() {
 349                 // Mark the actual macro this originates from
 350                 let and_then = if let Some((macro_kind, last_name)) = has_macro_spans.last()
 351                     && last_name != name
 352                 {
 353                     let descr = macro_kind.descr();
 354                     format!(
 355                         " which comes from the expansion of the {descr} `{last_name}`",
 356                     )
 357                 } else {
 358                     "".to_string()
 359                 };
 360
 361                 let descr = macro_kind.descr();
 362                 let msg = format!(
 363                     "this {level} originates in the {descr} `{name}`{and_then} \
 364                     (in Nightly builds, run with -Z macro-backtrace for more info)",
 365                 );
 366
 367                 children.push(SubDiagnostic {
 368                     level: Level::Note,
 369                     message: vec![(DiagnosticMessage::Str(msg), Style::NoStyle)],
 370                     span: MultiSpan::new(),
 371                     render_span: None,
 372                 });
 373             }
 374         }
 375     }
 376
 377     fn render_multispans_macro_backtrace(
 378         &self,
 379         span: &mut MultiSpan,
 380         children: &mut Vec<SubDiagnostic>,
 381         backtrace: bool,
 382     ) {
 383         for span in iter::once(span).chain(children.iter_mut().map(|child| &mut child.span)) {
 384             self.render_multispan_macro_backtrace(span, backtrace);
 385         }
 386     }
 387
 388     fn render_multispan_macro_backtrace(&self, span: &mut MultiSpan, always_backtrace: bool) {
 389         let mut new_labels: Vec<(Span, String)> = vec![];
 390
 391         for &sp in span.primary_spans() {
 392             if sp.is_dummy() {
 393                 continue;
 394             }
 395
 396             // FIXME(eddyb) use `retain` on `macro_backtrace` to remove all the
 397             // entries we don't want to print, to make sure the indices being
 398             // printed are contiguous (or omitted if there's only one entry).
 399             let macro_backtrace: Vec<_> = sp.macro_backtrace().collect();
 400             for (i, trace) in macro_backtrace.iter().rev().enumerate() {
 401                 if trace.def_site.is_dummy() {
 402                     continue;
 403                 }
 404
 405                 if always_backtrace && !matches!(trace.kind, ExpnKind::Inlined) {
 406                     new_labels.push((
 407                         trace.def_site,
 408                         format!(
 409                             "in this expansion of `{}`{}",
 410                             trace.kind.descr(),
 411                             if macro_backtrace.len() > 1 {
 412                                 // if macro_backtrace.len() == 1 it'll be
 413                                 // pointed at by "in this macro invocation"
 414                                 format!(" (#{})", i + 1)
 415                             } else {
 416                                 String::new()
 417                             },
 418                         ),
 419                     ));
 420                 }
 421
 422                 // Don't add a label on the call site if the diagnostic itself
 423                 // already points to (a part of) that call site, as the label
 424                 // is meant for showing the relevant invocation when the actual
 425                 // diagnostic is pointing to some part of macro definition.
 426                 //
 427                 // This also handles the case where an external span got replaced
 428                 // with the call site span by `fix_multispans_in_extern_macros`.
 429                 //
 430                 // NB: `-Zmacro-backtrace` overrides this, for uniformity, as the
 431                 // "in this expansion of" label above is always added in that mode,
 432                 // and it needs an "in this macro invocation" label to match that.
 433                 let redundant_span = trace.call_site.contains(sp);
 434
 435                 if !redundant_span || always_backtrace {
 436                     let msg: Cow<'static, _> = match trace.kind {
 437                         ExpnKind::Macro(MacroKind::Attr, _) => {
 438                             "this procedural macro expansion".into()
 439                         }
 440                         ExpnKind::Macro(MacroKind::Derive, _) => {
 441                             "this derive macro expansion".into()
 442                         }
 443                         ExpnKind::Macro(MacroKind::Bang, _) => "this macro invocation".into(),
 444                         ExpnKind::Inlined => "this inlined function call".into(),
 445                         ExpnKind::Root => "the crate root".into(),
 446                         ExpnKind::AstPass(kind) => kind.descr().into(),
 447                         ExpnKind::Desugaring(kind) => {
 448                             format!("this {} desugaring", kind.descr()).into()
 449                         }
 450                     };
 451                     new_labels.push((
 452                         trace.call_site,
 453                         format!(
 454                             "in {}{}",
 455                             msg,
 456                             if macro_backtrace.len() > 1 && always_backtrace {
 457                                 // only specify order when the macro
 458                                 // backtrace is multiple levels deep
 459                                 format!(" (#{})", i + 1)
 460                             } else {
 461                                 String::new()
 462                             },
 463                         ),
 464                     ));
 465                 }
 466                 if !always_backtrace {
 467                     break;
 468                 }
 469             }
 470         }
 471
 472         for (label_span, label_text) in new_labels {
 473             span.push_span_label(label_span, label_text);
 474         }
 475     }
 476
 477     // This does a small "fix" for multispans by looking to see if it can find any that
 478     // point directly at external macros. Since these are often difficult to read,
 479     // this will change the span to point at the use site.
 480     fn fix_multispans_in_extern_macros(
 481         &self,
 482         span: &mut MultiSpan,
 483         children: &mut Vec<SubDiagnostic>,
 484     ) {
 485         debug!("fix_multispans_in_extern_macros: before: span={:?} children={:?}", span, children);
 486         self.fix_multispan_in_extern_macros(span);
 487         for child in children.iter_mut() {
 488             self.fix_multispan_in_extern_macros(&mut child.span);
 489         }
 490         debug!("fix_multispans_in_extern_macros: after: span={:?} children={:?}", span, children);
 491     }
 492
 493     // This "fixes" MultiSpans that contain `Span`s pointing to locations inside of external macros.
 494     // Since these locations are often difficult to read,
 495     // we move these spans from the external macros to their corresponding use site.
 496     fn fix_multispan_in_extern_macros(&self, span: &mut MultiSpan) {
 497         let Some(source_map) = self.source_map() else { return };
 498         // First, find all the spans in external macros and point instead at their use site.
 499         let replacements: Vec<(Span, Span)> = span
 500             .primary_spans()
 501             .iter()
 502             .copied()
 503             .chain(span.span_labels().iter().map(|sp_label| sp_label.span))
 504             .filter_map(|sp| {
 505                 if !sp.is_dummy() && source_map.is_imported(sp) {
 506                     let maybe_callsite = sp.source_callsite();
 507                     if sp != maybe_callsite {
 508                         return Some((sp, maybe_callsite));
 509                     }
 510                 }
 511                 None
 512             })
 513             .collect();
 514
 515         // After we have them, make sure we replace these 'bad' def sites with their use sites.
 516         for (from, to) in replacements {
 517             span.replace(from, to);
 518         }
 519     }
 520 }
 521
 522 impl Translate for EmitterWriter {
 523     fn fluent_bundle(&self) -> Option<&Lrc<FluentBundle>> {
 524         self.fluent_bundle.as_ref()
 525     }
 526
 527     fn fallback_fluent_bundle(&self) -> &FluentBundle {
 528         &self.fallback_bundle
 529     }
 530 }
 531
 532 impl Emitter for EmitterWriter {
 533     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
 534         self.sm.as_ref()
 535     }
 536
 537     fn emit_diagnostic(&mut self, diag: &Diagnostic) {
 538         let fluent_args = to_fluent_args(diag.args());
 539
 540         let mut children = diag.children.clone();
 541         let (mut primary_span, suggestions) = self.primary_span_formatted(diag, &fluent_args);
 542         debug!("emit_diagnostic: suggestions={:?}", suggestions);
 543
 544         self.fix_multispans_in_extern_macros_and_render_macro_backtrace(
 545             &mut primary_span,
 546             &mut children,
 547             &diag.level,
 548             self.macro_backtrace,
 549         );
 550
 551         self.emit_messages_default(
 552             &diag.level,
 553             &diag.message,
 554             &fluent_args,
 555             &diag.code,
 556             &primary_span,
 557             &children,
 558             suggestions,
 559             self.track_diagnostics.then_some(&diag.emitted_at),
 560         );
 561     }
 562
 563     fn should_show_explain(&self) -> bool {
 564         !self.short_message
 565     }
 566
 567     fn supports_color(&self) -> bool {
 568         self.dst.supports_color()
 569     }
 570 }
 571
 572 /// An emitter that does nothing when emitting a non-fatal diagnostic.
 573 /// Fatal diagnostics are forwarded to `fatal_handler` to avoid silent
 574 /// failures of rustc, as witnessed e.g. in issue #89358.
 575 pub struct SilentEmitter {
 576     pub fatal_handler: Handler,
 577     pub fatal_note: Option<String>,
 578 }
 579
 580 impl Translate for SilentEmitter {
 581     fn fluent_bundle(&self) -> Option<&Lrc<FluentBundle>> {
 582         None
 583     }
 584
 585     fn fallback_fluent_bundle(&self) -> &FluentBundle {
 586         panic!("silent emitter attempted to translate message")
 587     }
 588 }
 589
 590 impl Emitter for SilentEmitter {
 591     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
 592         None
 593     }
 594
 595     fn emit_diagnostic(&mut self, d: &Diagnostic) {
 596         if d.level == Level::Fatal {
 597             let mut d = d.clone();
 598             if let Some(ref note) = self.fatal_note {
 599                 d.note(note);
 600             }
 601             self.fatal_handler.emit_diagnostic(&mut d);
 602         }
 603     }
 604 }
 605
 606 /// Maximum number of suggestions to be shown
 607 ///
 608 /// Arbitrary, but taken from trait import suggestion limit
 609 pub const MAX_SUGGESTIONS: usize = 4;
 610
 611 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 612 pub enum ColorConfig {
 613     Auto,
 614     Always,
 615     Never,
 616 }
 617
 618 impl ColorConfig {
 619     fn to_color_choice(self) -> ColorChoice {
 620         match self {
 621             ColorConfig::Always => {
 622                 if io::stderr().is_terminal() {
 623                     ColorChoice::Always
 624                 } else {
 625                     ColorChoice::AlwaysAnsi
 626                 }
 627             }
 628             ColorConfig::Never => ColorChoice::Never,
 629             ColorConfig::Auto if io::stderr().is_terminal() => ColorChoice::Auto,
 630             ColorConfig::Auto => ColorChoice::Never,
 631         }
 632     }
 633     fn suggests_using_colors(self) -> bool {
 634         match self {
 635             ColorConfig::Always | ColorConfig::Auto => true,
 636             ColorConfig::Never => false,
 637         }
 638     }
 639 }
 640
 641 /// Handles the writing of `HumanReadableErrorType::Default` and `HumanReadableErrorType::Short`
 642 pub struct EmitterWriter {
 643     dst: Destination,
 644     sm: Option<Lrc<SourceMap>>,
 645     fluent_bundle: Option<Lrc<FluentBundle>>,
 646     fallback_bundle: LazyFallbackBundle,
 647     short_message: bool,
 648     teach: bool,
 649     ui_testing: bool,
 650     diagnostic_width: Option<usize>,
 651
 652     macro_backtrace: bool,
 653     track_diagnostics: bool,
 654 }
 655
 656 #[derive(Debug)]
 657 pub struct FileWithAnnotatedLines {
 658     pub file: Lrc<SourceFile>,
 659     pub lines: Vec<Line>,
 660     multiline_depth: usize,
 661 }
 662
 663 impl EmitterWriter {
 664     pub fn stderr(
 665         color_config: ColorConfig,
 666         source_map: Option<Lrc<SourceMap>>,
 667         fluent_bundle: Option<Lrc<FluentBundle>>,
 668         fallback_bundle: LazyFallbackBundle,
 669         short_message: bool,
 670         teach: bool,
 671         diagnostic_width: Option<usize>,
 672         macro_backtrace: bool,
 673         track_diagnostics: bool,
 674     ) -> EmitterWriter {
 675         let dst = Destination::from_stderr(color_config);
 676         EmitterWriter {
 677             dst,
 678             sm: source_map,
 679             fluent_bundle,
 680             fallback_bundle,
 681             short_message,
 682             teach,
 683             ui_testing: false,
 684             diagnostic_width,
 685             macro_backtrace,
 686             track_diagnostics,
 687         }
 688     }
 689
 690     pub fn new(
 691         dst: Box<dyn Write + Send>,
 692         source_map: Option<Lrc<SourceMap>>,
 693         fluent_bundle: Option<Lrc<FluentBundle>>,
 694         fallback_bundle: LazyFallbackBundle,
 695         short_message: bool,
 696         teach: bool,
 697         colored: bool,
 698         diagnostic_width: Option<usize>,
 699         macro_backtrace: bool,
 700         track_diagnostics: bool,
 701     ) -> EmitterWriter {
 702         EmitterWriter {
 703             dst: Raw(dst, colored),
 704             sm: source_map,
 705             fluent_bundle,
 706             fallback_bundle,
 707             short_message,
 708             teach,
 709             ui_testing: false,
 710             diagnostic_width,
 711             macro_backtrace,
 712             track_diagnostics,
 713         }
 714     }
 715
 716     pub fn ui_testing(mut self, ui_testing: bool) -> Self {
 717         self.ui_testing = ui_testing;
 718         self
 719     }
 720
 721     fn maybe_anonymized(&self, line_num: usize) -> Cow<'static, str> {
 722         if self.ui_testing {
 723             Cow::Borrowed(ANONYMIZED_LINE_NUM)
 724         } else {
 725             Cow::Owned(line_num.to_string())
 726         }
 727     }
 728
 729     fn draw_line(
 730         &self,
 731         buffer: &mut StyledBuffer,
 732         source_string: &str,
 733         line_index: usize,
 734         line_offset: usize,
 735         width_offset: usize,
 736         code_offset: usize,
 737         margin: Margin,
 738     ) {
 739         // Tabs are assumed to have been replaced by spaces in calling code.
 740         debug_assert!(!source_string.contains('\t'));
 741         let line_len = source_string.len();
 742         // Create the source line we will highlight.
 743         let left = margin.left(line_len);
 744         let right = margin.right(line_len);
 745         // On long lines, we strip the source line, accounting for unicode.
 746         let mut taken = 0;
 747         let code: String = source_string
 748             .chars()
 749             .skip(left)
 750             .take_while(|ch| {
 751                 // Make sure that the trimming on the right will fall within the terminal width.
 752                 // FIXME: `unicode_width` sometimes disagrees with terminals on how wide a `char` is.
 753                 // For now, just accept that sometimes the code line will be longer than desired.
 754                 let next = unicode_width::UnicodeWidthChar::width(*ch).unwrap_or(1);
 755                 if taken + next > right - left {
 756                     return false;
 757                 }
 758                 taken += next;
 759                 true
 760             })
 761             .collect();
 762         buffer.puts(line_offset, code_offset, &code, Style::Quotation);
 763         if margin.was_cut_left() {
 764             // We have stripped some code/whitespace from the beginning, make it clear.
 765             buffer.puts(line_offset, code_offset, "...", Style::LineNumber);
 766         }
 767         if margin.was_cut_right(line_len) {
 768             // We have stripped some code after the right-most span end, make it clear we did so.
 769             buffer.puts(line_offset, code_offset + taken - 3, "...", Style::LineNumber);
 770         }
 771         buffer.puts(line_offset, 0, &self.maybe_anonymized(line_index), Style::LineNumber);
 772
 773         draw_col_separator_no_space(buffer, line_offset, width_offset - 2);
 774     }
 775
 776     #[instrument(level = "trace", skip(self), ret)]
 777     fn render_source_line(
 778         &self,
 779         buffer: &mut StyledBuffer,
 780         file: Lrc<SourceFile>,
 781         line: &Line,
 782         width_offset: usize,
 783         code_offset: usize,
 784         margin: Margin,
 785     ) -> Vec<(usize, Style)> {
 786         // Draw:
 787         //
 788         //   LL | ... code ...
 789         //      |     ^^-^ span label
 790         //      |       |
 791         //      |       secondary span label
 792         //
 793         //   ^^ ^ ^^^ ^^^^ ^^^ we don't care about code too far to the right of a span, we trim it
 794         //   |  | |   |
 795         //   |  | |   actual code found in your source code and the spans we use to mark it
 796         //   |  | when there's too much wasted space to the left, trim it
 797         //   |  vertical divider between the column number and the code
 798         //   column number
 799
 800         if line.line_index == 0 {
 801             return Vec::new();
 802         }
 803
 804         let source_string = match file.get_line(line.line_index - 1) {
 805             Some(s) => normalize_whitespace(&s),
 806             None => return Vec::new(),
 807         };
 808         trace!(?source_string);
 809
 810         let line_offset = buffer.num_lines();
 811
 812         // Left trim
 813         let left = margin.left(source_string.len());
 814
 815         // Account for unicode characters of width !=0 that were removed.
 816         let left = source_string
 817             .chars()
 818             .take(left)
 819             .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
 820             .sum();
 821
 822         self.draw_line(
 823             buffer,
 824             &source_string,
 825             line.line_index,
 826             line_offset,
 827             width_offset,
 828             code_offset,
 829             margin,
 830         );
 831
 832         // Special case when there's only one annotation involved, it is the start of a multiline
 833         // span and there's no text at the beginning of the code line. Instead of doing the whole
 834         // graph:
 835         //
 836         // 2 |   fn foo() {
 837         //   |  _^
 838         // 3 | |
 839         // 4 | | }
 840         //   | |_^ test
 841         //
 842         // we simplify the output to:
 843         //
 844         // 2 | / fn foo() {
 845         // 3 | |
 846         // 4 | | }
 847         //   | |_^ test
 848         if let [ann] = &line.annotations[..] {
 849             if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
 850                 if source_string.chars().take(ann.start_col).all(|c| c.is_whitespace()) {
 851                     let style = if ann.is_primary {
 852                         Style::UnderlinePrimary
 853                     } else {
 854                         Style::UnderlineSecondary
 855                     };
 856                     buffer.putc(line_offset, width_offset + depth - 1, '/', style);
 857                     return vec![(depth, style)];
 858                 }
 859             }
 860         }
 861
 862         // We want to display like this:
 863         //
 864         //      vec.push(vec.pop().unwrap());
 865         //      ---      ^^^               - previous borrow ends here
 866         //      |        |
 867         //      |        error occurs here
 868         //      previous borrow of `vec` occurs here
 869         //
 870         // But there are some weird edge cases to be aware of:
 871         //
 872         //      vec.push(vec.pop().unwrap());
 873         //      --------                    - previous borrow ends here
 874         //      ||
 875         //      |this makes no sense
 876         //      previous borrow of `vec` occurs here
 877         //
 878         // For this reason, we group the lines into "highlight lines"
 879         // and "annotations lines", where the highlight lines have the `^`.
 880
 881         // Sort the annotations by (start, end col)
 882         // The labels are reversed, sort and then reversed again.
 883         // Consider a list of annotations (A1, A2, C1, C2, B1, B2) where
 884         // the letter signifies the span. Here we are only sorting by the
 885         // span and hence, the order of the elements with the same span will
 886         // not change. On reversing the ordering (|a, b| but b.cmp(a)), you get
 887         // (C1, C2, B1, B2, A1, A2). All the elements with the same span are
 888         // still ordered first to last, but all the elements with different
 889         // spans are ordered by their spans in last to first order. Last to
 890         // first order is important, because the jiggly lines and | are on
 891         // the left, so the rightmost span needs to be rendered first,
 892         // otherwise the lines would end up needing to go over a message.
 893
 894         let mut annotations = line.annotations.clone();
 895         annotations.sort_by_key(|a| Reverse(a.start_col));
 896
 897         // First, figure out where each label will be positioned.
 898         //
 899         // In the case where you have the following annotations:
 900         //
 901         //      vec.push(vec.pop().unwrap());
 902         //      --------                    - previous borrow ends here [C]
 903         //      ||
 904         //      |this makes no sense [B]
 905         //      previous borrow of `vec` occurs here [A]
 906         //
 907         // `annotations_position` will hold [(2, A), (1, B), (0, C)].
 908         //
 909         // We try, when possible, to stick the rightmost annotation at the end
 910         // of the highlight line:
 911         //
 912         //      vec.push(vec.pop().unwrap());
 913         //      ---      ---               - previous borrow ends here
 914         //
 915         // But sometimes that's not possible because one of the other
 916         // annotations overlaps it. For example, from the test
 917         // `span_overlap_label`, we have the following annotations
 918         // (written on distinct lines for clarity):
 919         //
 920         //      fn foo(x: u32) {
 921         //      --------------
 922         //             -
 923         //
 924         // In this case, we can't stick the rightmost-most label on
 925         // the highlight line, or we would get:
 926         //
 927         //      fn foo(x: u32) {
 928         //      -------- x_span
 929         //      |
 930         //      fn_span
 931         //
 932         // which is totally weird. Instead we want:
 933         //
 934         //      fn foo(x: u32) {
 935         //      --------------
 936         //      |      |
 937         //      |      x_span
 938         //      fn_span
 939         //
 940         // which is...less weird, at least. In fact, in general, if
 941         // the rightmost span overlaps with any other span, we should
 942         // use the "hang below" version, so we can at least make it
 943         // clear where the span *starts*. There's an exception for this
 944         // logic, when the labels do not have a message:
 945         //
 946         //      fn foo(x: u32) {
 947         //      --------------
 948         //             |
 949         //             x_span
 950         //
 951         // instead of:
 952         //
 953         //      fn foo(x: u32) {
 954         //      --------------
 955         //      |      |
 956         //      |      x_span
 957         //      <EMPTY LINE>
 958         //
 959         let mut annotations_position = vec![];
 960         let mut line_len = 0;
 961         let mut p = 0;
 962         for (i, annotation) in annotations.iter().enumerate() {
 963             for (j, next) in annotations.iter().enumerate() {
 964                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
 965                     && annotation.has_label()     // take space (they have text and are not
 966                     && j > i                      // multiline lines).
 967                     && p == 0
 968                 // We're currently on the first line, move the label one line down
 969                 {
 970                     // If we're overlapping with an un-labelled annotation with the same span
 971                     // we can just merge them in the output
 972                     if next.start_col == annotation.start_col
 973                         && next.end_col == annotation.end_col
 974                         && !next.has_label()
 975                     {
 976                         continue;
 977                     }
 978
 979                     // This annotation needs a new line in the output.
 980                     p += 1;
 981                     break;
 982                 }
 983             }
 984             annotations_position.push((p, annotation));
 985             for (j, next) in annotations.iter().enumerate() {
 986                 if j > i {
 987                     let l = next.label.as_ref().map_or(0, |label| label.len() + 2);
 988                     if (overlaps(next, annotation, l) // Do not allow two labels to be in the same
 989                                                      // line if they overlap including padding, to
 990                                                      // avoid situations like:
 991                                                      //
 992                                                      //      fn foo(x: u32) {
 993                                                      //      -------^------
 994                                                      //      |      |
 995                                                      //      fn_spanx_span
 996                                                      //
 997                         && annotation.has_label()    // Both labels must have some text, otherwise
 998                         && next.has_label())         // they are not overlapping.
 999                                                      // Do not add a new line if this annotation
1000                                                      // or the next are vertical line placeholders.
1001                         || (annotation.takes_space() // If either this or the next annotation is
1002                             && next.has_label())     // multiline start/end, move it to a new line
1003                         || (annotation.has_label()   // so as not to overlap the horizontal lines.
1004                             && next.takes_space())
1005                         || (annotation.takes_space() && next.takes_space())
1006                         || (overlaps(next, annotation, l)
1007                             && next.end_col <= annotation.end_col
1008                             && next.has_label()
1009                             && p == 0)
1010                     // Avoid #42595.
1011                     {
1012                         // This annotation needs a new line in the output.
1013                         p += 1;
1014                         break;
1015                     }
1016                 }
1017             }
1018             line_len = max(line_len, p);
1019         }
1020
1021         if line_len != 0 {
1022             line_len += 1;
1023         }
1024
1025         // If there are no annotations or the only annotations on this line are
1026         // MultilineLine, then there's only code being shown, stop processing.
1027         if line.annotations.iter().all(|a| a.is_line()) {
1028             return vec![];
1029         }
1030
1031         // Write the column separator.
1032         //
1033         // After this we will have:
1034         //
1035         // 2 |   fn foo() {
1036         //   |
1037         //   |
1038         //   |
1039         // 3 |
1040         // 4 |   }
1041         //   |
1042         for pos in 0..=line_len {
1043             draw_col_separator(buffer, line_offset + pos + 1, width_offset - 2);
1044         }
1045
1046         // Write the horizontal lines for multiline annotations
1047         // (only the first and last lines need this).
1048         //
1049         // After this we will have:
1050         //
1051         // 2 |   fn foo() {
1052         //   |  __________
1053         //   |
1054         //   |
1055         // 3 |
1056         // 4 |   }
1057         //   |  _
1058         for &(pos, annotation) in &annotations_position {
1059             let style = if annotation.is_primary {
1060                 Style::UnderlinePrimary
1061             } else {
1062                 Style::UnderlineSecondary
1063             };
1064             let pos = pos + 1;
1065             match annotation.annotation_type {
1066                 AnnotationType::MultilineStart(depth) | AnnotationType::MultilineEnd(depth) => {
1067                     draw_range(
1068                         buffer,
1069                         '_',
1070                         line_offset + pos,
1071                         width_offset + depth,
1072                         (code_offset + annotation.start_col).saturating_sub(left),
1073                         style,
1074                     );
1075                 }
1076                 _ if self.teach => {
1077                     buffer.set_style_range(
1078                         line_offset,
1079                         (code_offset + annotation.start_col).saturating_sub(left),
1080                         (code_offset + annotation.end_col).saturating_sub(left),
1081                         style,
1082                         annotation.is_primary,
1083                     );
1084                 }
1085                 _ => {}
1086             }
1087         }
1088
1089         // Write the vertical lines for labels that are on a different line as the underline.
1090         //
1091         // After this we will have:
1092         //
1093         // 2 |   fn foo() {
1094         //   |  __________
1095         //   | |    |
1096         //   | |
1097         // 3 | |
1098         // 4 | | }
1099         //   | |_
1100         for &(pos, annotation) in &annotations_position {
1101             let style = if annotation.is_primary {
1102                 Style::UnderlinePrimary
1103             } else {
1104                 Style::UnderlineSecondary
1105             };
1106             let pos = pos + 1;
1107
1108             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
1109                 for p in line_offset + 1..=line_offset + pos {
1110                     buffer.putc(
1111                         p,
1112                         (code_offset + annotation.start_col).saturating_sub(left),
1113                         '|',
1114                         style,
1115                     );
1116                 }
1117             }
1118             match annotation.annotation_type {
1119                 AnnotationType::MultilineStart(depth) => {
1120                     for p in line_offset + pos + 1..line_offset + line_len + 2 {
1121                         buffer.putc(p, width_offset + depth - 1, '|', style);
1122                     }
1123                 }
1124                 AnnotationType::MultilineEnd(depth) => {
1125                     for p in line_offset..=line_offset + pos {
1126                         buffer.putc(p, width_offset + depth - 1, '|', style);
1127                     }
1128                 }
1129                 _ => (),
1130             }
1131         }
1132
1133         // Write the labels on the annotations that actually have a label.
1134         //
1135         // After this we will have:
1136         //
1137         // 2 |   fn foo() {
1138         //   |  __________
1139         //   |      |
1140         //   |      something about `foo`
1141         // 3 |
1142         // 4 |   }
1143         //   |  _  test
1144         for &(pos, annotation) in &annotations_position {
1145             let style =
1146                 if annotation.is_primary { Style::LabelPrimary } else { Style::LabelSecondary };
1147             let (pos, col) = if pos == 0 {
1148                 (pos + 1, (annotation.end_col + 1).saturating_sub(left))
1149             } else {
1150                 (pos + 2, annotation.start_col.saturating_sub(left))
1151             };
1152             if let Some(ref label) = annotation.label {
1153                 buffer.puts(line_offset + pos, code_offset + col, label, style);
1154             }
1155         }
1156
1157         // Sort from biggest span to smallest span so that smaller spans are
1158         // represented in the output:
1159         //
1160         // x | fn foo()
1161         //   | ^^^---^^
1162         //   | |  |
1163         //   | |  something about `foo`
1164         //   | something about `fn foo()`
1165         annotations_position.sort_by_key(|(_, ann)| {
1166             // Decreasing order. When annotations share the same length, prefer `Primary`.
1167             (Reverse(ann.len()), ann.is_primary)
1168         });
1169
1170         // Write the underlines.
1171         //
1172         // After this we will have:
1173         //
1174         // 2 |   fn foo() {
1175         //   |  ____-_____^
1176         //   |      |
1177         //   |      something about `foo`
1178         // 3 |
1179         // 4 |   }
1180         //   |  _^  test
1181         for &(_, annotation) in &annotations_position {
1182             let (underline, style) = if annotation.is_primary {
1183                 ('^', Style::UnderlinePrimary)
1184             } else {
1185                 ('-', Style::UnderlineSecondary)
1186             };
1187             for p in annotation.start_col..annotation.end_col {
1188                 buffer.putc(
1189                     line_offset + 1,
1190                     (code_offset + p).saturating_sub(left),
1191                     underline,
1192                     style,
1193                 );
1194             }
1195         }
1196         annotations_position
1197             .iter()
1198             .filter_map(|&(_, annotation)| match annotation.annotation_type {
1199                 AnnotationType::MultilineStart(p) | AnnotationType::MultilineEnd(p) => {
1200                     let style = if annotation.is_primary {
1201                         Style::LabelPrimary
1202                     } else {
1203                         Style::LabelSecondary
1204                     };
1205                     Some((p, style))
1206                 }
1207                 _ => None,
1208             })
1209             .collect::<Vec<_>>()
1210     }
1211
1212     fn get_multispan_max_line_num(&mut self, msp: &MultiSpan) -> usize {
1213         let Some(ref sm) = self.sm else {
1214             return 0;
1215         };
1216
1217         let will_be_emitted = |span: Span| {
1218             !span.is_dummy() && {
1219                 let file = sm.lookup_source_file(span.hi());
1220                 sm.ensure_source_file_source_present(file)
1221             }
1222         };
1223
1224         let mut max = 0;
1225         for primary_span in msp.primary_spans() {
1226             if will_be_emitted(*primary_span) {
1227                 let hi = sm.lookup_char_pos(primary_span.hi());
1228                 max = (hi.line).max(max);
1229             }
1230         }
1231         if !self.short_message {
1232             for span_label in msp.span_labels() {
1233                 if will_be_emitted(span_label.span) {
1234                     let hi = sm.lookup_char_pos(span_label.span.hi());
1235                     max = (hi.line).max(max);
1236                 }
1237             }
1238         }
1239
1240         max
1241     }
1242
1243     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
1244         let primary = self.get_multispan_max_line_num(span);
1245         children
1246             .iter()
1247             .map(|sub| self.get_multispan_max_line_num(&sub.span))
1248             .max()
1249             .unwrap_or(0)
1250             .max(primary)
1251     }
1252
1253     /// Adds a left margin to every line but the first, given a padding length and the label being
1254     /// displayed, keeping the provided highlighting.
1255     fn msg_to_buffer(
1256         &self,
1257         buffer: &mut StyledBuffer,
1258         msg: &[(DiagnosticMessage, Style)],
1259         args: &FluentArgs<'_>,
1260         padding: usize,
1261         label: &str,
1262         override_style: Option<Style>,
1263     ) {
1264         // The extra 5 ` ` is padding that's always needed to align to the `note: `:
1265         //
1266         //   error: message
1267         //     --> file.rs:13:20
1268         //      |
1269         //   13 |     <CODE>
1270         //      |      ^^^^
1271         //      |
1272         //      = note: multiline
1273         //              message
1274         //   ++^^^----xx
1275         //    |  |   | |
1276         //    |  |   | magic `2`
1277         //    |  |   length of label
1278         //    |  magic `3`
1279         //    `max_line_num_len`
1280         let padding = " ".repeat(padding + label.len() + 5);
1281
1282         /// Returns `override` if it is present and `style` is `NoStyle` or `style` otherwise
1283         fn style_or_override(style: Style, override_: Option<Style>) -> Style {
1284             match (style, override_) {
1285                 (Style::NoStyle, Some(override_)) => override_,
1286                 _ => style,
1287             }
1288         }
1289
1290         let mut line_number = 0;
1291
1292         // Provided the following diagnostic message:
1293         //
1294         //     let msg = vec![
1295         //       ("
1296         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
1297         //       ("looks", Style::Highlight),
1298         //       ("with\nvery ", Style::NoStyle),
1299         //       ("weird", Style::Highlight),
1300         //       (" formats\n", Style::NoStyle),
1301         //       ("see?", Style::Highlight),
1302         //     ];
1303         //
1304         // the expected output on a note is (* surround the highlighted text)
1305         //
1306         //        = note: highlighted multiline
1307         //                string to
1308         //                see how it *looks* with
1309         //                very *weird* formats
1310         //                see?
1311         for &(ref text, ref style) in msg.iter() {
1312             let text = self.translate_message(text, args);
1313             let lines = text.split('\n').collect::<Vec<_>>();
1314             if lines.len() > 1 {
1315                 for (i, line) in lines.iter().enumerate() {
1316                     if i != 0 {
1317                         line_number += 1;
1318                         buffer.append(line_number, &padding, Style::NoStyle);
1319                     }
1320                     buffer.append(line_number, line, style_or_override(*style, override_style));
1321                 }
1322             } else {
1323                 buffer.append(line_number, &text, style_or_override(*style, override_style));
1324             }
1325         }
1326     }
1327
1328     #[instrument(level = "trace", skip(self, args), ret)]
1329     fn emit_message_default(
1330         &mut self,
1331         msp: &MultiSpan,
1332         msg: &[(DiagnosticMessage, Style)],
1333         args: &FluentArgs<'_>,
1334         code: &Option<DiagnosticId>,
1335         level: &Level,
1336         max_line_num_len: usize,
1337         is_secondary: bool,
1338         emitted_at: Option<&DiagnosticLocation>,
1339     ) -> io::Result<()> {
1340         let mut buffer = StyledBuffer::new();
1341
1342         if !msp.has_primary_spans() && !msp.has_span_labels() && is_secondary && !self.short_message
1343         {
1344             // This is a secondary message with no span info
1345             for _ in 0..max_line_num_len {
1346                 buffer.prepend(0, " ", Style::NoStyle);
1347             }
1348             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
1349             if *level != Level::FailureNote {
1350                 buffer.append(0, level.to_str(), Style::MainHeaderMsg);
1351                 buffer.append(0, ": ", Style::NoStyle);
1352             }
1353             self.msg_to_buffer(&mut buffer, msg, args, max_line_num_len, "note", None);
1354         } else {
1355             let mut label_width = 0;
1356             // The failure note level itself does not provide any useful diagnostic information
1357             if *level != Level::FailureNote {
1358                 buffer.append(0, level.to_str(), Style::Level(*level));
1359                 label_width += level.to_str().len();
1360             }
1361             // only render error codes, not lint codes
1362             if let Some(DiagnosticId::Error(ref code)) = *code {
1363                 buffer.append(0, "[", Style::Level(*level));
1364                 buffer.append(0, code, Style::Level(*level));
1365                 buffer.append(0, "]", Style::Level(*level));
1366                 label_width += 2 + code.len();
1367             }
1368             let header_style = if is_secondary { Style::HeaderMsg } else { Style::MainHeaderMsg };
1369             if *level != Level::FailureNote {
1370                 buffer.append(0, ": ", header_style);
1371                 label_width += 2;
1372             }
1373             for &(ref text, _) in msg.iter() {
1374                 let text = self.translate_message(text, args);
1375                 // Account for newlines to align output to its label.
1376                 for (line, text) in normalize_whitespace(&text).lines().enumerate() {
1377                     buffer.append(
1378                         0 + line,
1379                         &format!(
1380                             "{}{}",
1381                             if line == 0 { String::new() } else { " ".repeat(label_width) },
1382                             text
1383                         ),
1384                         header_style,
1385                     );
1386                 }
1387             }
1388         }
1389         let mut annotated_files = FileWithAnnotatedLines::collect_annotations(self, args, msp);
1390         trace!("{annotated_files:#?}");
1391
1392         // Make sure our primary file comes first
1393         let primary_span = msp.primary_span().unwrap_or_default();
1394         let (Some(sm), false) = (self.sm.as_ref(), primary_span.is_dummy()) else {
1395             // If we don't have span information, emit and exit
1396             return emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message);
1397         };
1398         let primary_lo = sm.lookup_char_pos(primary_span.lo());
1399         if let Ok(pos) =
1400             annotated_files.binary_search_by(|x| x.file.name.cmp(&primary_lo.file.name))
1401         {
1402             annotated_files.swap(0, pos);
1403         }
1404
1405         // Print out the annotate source lines that correspond with the error
1406         for annotated_file in annotated_files {
1407             // we can't annotate anything if the source is unavailable.
1408             if !sm.ensure_source_file_source_present(annotated_file.file.clone()) {
1409                 if !self.short_message {
1410                     // We'll just print an unannotated message.
1411                     for (annotation_id, line) in annotated_file.lines.into_iter().enumerate() {
1412                         let mut annotations = line.annotations.clone();
1413                         annotations.sort_by_key(|a| Reverse(a.start_col));
1414                         let mut line_idx = buffer.num_lines();
1415                         buffer.append(
1416                             line_idx,
1417                             &format!(
1418                                 "{}:{}:{}",
1419                                 sm.filename_for_diagnostics(&annotated_file.file.name),
1420                                 sm.doctest_offset_line(&annotated_file.file.name, line.line_index),
1421                                 annotations[0].start_col + 1,
1422                             ),
1423                             Style::LineAndColumn,
1424                         );
1425                         if annotation_id == 0 {
1426                             buffer.prepend(line_idx, "--> ", Style::LineNumber);
1427                             for _ in 0..max_line_num_len {
1428                                 buffer.prepend(line_idx, " ", Style::NoStyle);
1429                             }
1430                             line_idx += 1;
1431                         };
1432                         for (i, annotation) in annotations.into_iter().enumerate() {
1433                             if let Some(label) = &annotation.label {
1434                                 let style = if annotation.is_primary {
1435                                     Style::LabelPrimary
1436                                 } else {
1437                                     Style::LabelSecondary
1438                                 };
1439                                 if annotation_id == 0 {
1440                                     buffer.prepend(line_idx, " |", Style::LineNumber);
1441                                     for _ in 0..max_line_num_len {
1442                                         buffer.prepend(line_idx, " ", Style::NoStyle);
1443                                     }
1444                                     line_idx += 1;
1445                                     buffer.append(line_idx + i, " = note: ", style);
1446                                     for _ in 0..max_line_num_len {
1447                                         buffer.prepend(line_idx, " ", Style::NoStyle);
1448                                     }
1449                                 } else {
1450                                     buffer.append(line_idx + i, ": ", style);
1451                                 }
1452                                 buffer.append(line_idx + i, label, style);
1453                             }
1454                         }
1455                     }
1456                 }
1457                 continue;
1458             }
1459
1460             // print out the span location and spacer before we print the annotated source
1461             // to do this, we need to know if this span will be primary
1462             let is_primary = primary_lo.file.name == annotated_file.file.name;
1463             if is_primary {
1464                 let loc = primary_lo.clone();
1465                 if !self.short_message {
1466                     // remember where we are in the output buffer for easy reference
1467                     let buffer_msg_line_offset = buffer.num_lines();
1468
1469                     buffer.prepend(buffer_msg_line_offset, "--> ", Style::LineNumber);
1470                     buffer.append(
1471                         buffer_msg_line_offset,
1472                         &format!(
1473                             "{}:{}:{}",
1474                             sm.filename_for_diagnostics(&loc.file.name),
1475                             sm.doctest_offset_line(&loc.file.name, loc.line),
1476                             loc.col.0 + 1,
1477                         ),
1478                         Style::LineAndColumn,
1479                     );
1480                     for _ in 0..max_line_num_len {
1481                         buffer.prepend(buffer_msg_line_offset, " ", Style::NoStyle);
1482                     }
1483                 } else {
1484                     buffer.prepend(
1485                         0,
1486                         &format!(
1487                             "{}:{}:{}: ",
1488                             sm.filename_for_diagnostics(&loc.file.name),
1489                             sm.doctest_offset_line(&loc.file.name, loc.line),
1490                             loc.col.0 + 1,
1491                         ),
1492                         Style::LineAndColumn,
1493                     );
1494                 }
1495             } else if !self.short_message {
1496                 // remember where we are in the output buffer for easy reference
1497                 let buffer_msg_line_offset = buffer.num_lines();
1498
1499                 // Add spacing line
1500                 draw_col_separator_no_space(
1501                     &mut buffer,
1502                     buffer_msg_line_offset,
1503                     max_line_num_len + 1,
1504                 );
1505
1506                 // Then, the secondary file indicator
1507                 buffer.prepend(buffer_msg_line_offset + 1, "::: ", Style::LineNumber);
1508                 let loc = if let Some(first_line) = annotated_file.lines.first() {
1509                     let col = if let Some(first_annotation) = first_line.annotations.first() {
1510                         format!(":{}", first_annotation.start_col + 1)
1511                     } else {
1512                         String::new()
1513                     };
1514                     format!(
1515                         "{}:{}{}",
1516                         sm.filename_for_diagnostics(&annotated_file.file.name),
1517                         sm.doctest_offset_line(&annotated_file.file.name, first_line.line_index),
1518                         col
1519                     )
1520                 } else {
1521                     format!("{}", sm.filename_for_diagnostics(&annotated_file.file.name))
1522                 };
1523                 buffer.append(buffer_msg_line_offset + 1, &loc, Style::LineAndColumn);
1524                 for _ in 0..max_line_num_len {
1525                     buffer.prepend(buffer_msg_line_offset + 1, " ", Style::NoStyle);
1526                 }
1527             }
1528
1529             if !self.short_message {
1530                 // Put in the spacer between the location and annotated source
1531                 let buffer_msg_line_offset = buffer.num_lines();
1532                 draw_col_separator_no_space(
1533                     &mut buffer,
1534                     buffer_msg_line_offset,
1535                     max_line_num_len + 1,
1536                 );
1537
1538                 // Contains the vertical lines' positions for active multiline annotations
1539                 let mut multilines = FxIndexMap::default();
1540
1541                 // Get the left-side margin to remove it
1542                 let mut whitespace_margin = usize::MAX;
1543                 for line_idx in 0..annotated_file.lines.len() {
1544                     let file = annotated_file.file.clone();
1545                     let line = &annotated_file.lines[line_idx];
1546                     if let Some(source_string) = file.get_line(line.line_index - 1) {
1547                         let leading_whitespace = source_string
1548                             .chars()
1549                             .take_while(|c| c.is_whitespace())
1550                             .map(|c| {
1551                                 match c {
1552                                     // Tabs are displayed as 4 spaces
1553                                     '\t' => 4,
1554                                     _ => 1,
1555                                 }
1556                             })
1557                             .sum();
1558                         if source_string.chars().any(|c| !c.is_whitespace()) {
1559                             whitespace_margin = min(whitespace_margin, leading_whitespace);
1560                         }
1561                     }
1562                 }
1563                 if whitespace_margin == usize::MAX {
1564                     whitespace_margin = 0;
1565                 }
1566
1567                 // Left-most column any visible span points at.
1568                 let mut span_left_margin = usize::MAX;
1569                 for line in &annotated_file.lines {
1570                     for ann in &line.annotations {
1571                         span_left_margin = min(span_left_margin, ann.start_col);
1572                         span_left_margin = min(span_left_margin, ann.end_col);
1573                     }
1574                 }
1575                 if span_left_margin == usize::MAX {
1576                     span_left_margin = 0;
1577                 }
1578
1579                 // Right-most column any visible span points at.
1580                 let mut span_right_margin = 0;
1581                 let mut label_right_margin = 0;
1582                 let mut max_line_len = 0;
1583                 for line in &annotated_file.lines {
1584                     max_line_len = max(
1585                         max_line_len,
1586                         annotated_file.file.get_line(line.line_index - 1).map_or(0, |s| s.len()),
1587                     );
1588                     for ann in &line.annotations {
1589                         span_right_margin = max(span_right_margin, ann.start_col);
1590                         span_right_margin = max(span_right_margin, ann.end_col);
1591                         // FIXME: account for labels not in the same line
1592                         let label_right = ann.label.as_ref().map_or(0, |l| l.len() + 1);
1593                         label_right_margin = max(label_right_margin, ann.end_col + label_right);
1594                     }
1595                 }
1596
1597                 let width_offset = 3 + max_line_num_len;
1598                 let code_offset = if annotated_file.multiline_depth == 0 {
1599                     width_offset
1600                 } else {
1601                     width_offset + annotated_file.multiline_depth + 1
1602                 };
1603
1604                 let column_width = if let Some(width) = self.diagnostic_width {
1605                     width.saturating_sub(code_offset)
1606                 } else if self.ui_testing {
1607                     DEFAULT_COLUMN_WIDTH
1608                 } else {
1609                     termize::dimensions()
1610                         .map(|(w, _)| w.saturating_sub(code_offset))
1611                         .unwrap_or(DEFAULT_COLUMN_WIDTH)
1612                 };
1613
1614                 let margin = Margin::new(
1615                     whitespace_margin,
1616                     span_left_margin,
1617                     span_right_margin,
1618                     label_right_margin,
1619                     column_width,
1620                     max_line_len,
1621                 );
1622
1623                 // Next, output the annotate source for this file
1624                 for line_idx in 0..annotated_file.lines.len() {
1625                     let previous_buffer_line = buffer.num_lines();
1626
1627                     let depths = self.render_source_line(
1628                         &mut buffer,
1629                         annotated_file.file.clone(),
1630                         &annotated_file.lines[line_idx],
1631                         width_offset,
1632                         code_offset,
1633                         margin,
1634                     );
1635
1636                     let mut to_add = FxHashMap::default();
1637
1638                     for (depth, style) in depths {
1639                         if multilines.remove(&depth).is_none() {
1640                             to_add.insert(depth, style);
1641                         }
1642                     }
1643
1644                     // Set the multiline annotation vertical lines to the left of
1645                     // the code in this line.
1646                     for (depth, style) in &multilines {
1647                         for line in previous_buffer_line..buffer.num_lines() {
1648                             draw_multiline_line(&mut buffer, line, width_offset, *depth, *style);
1649                         }
1650                     }
1651                     // check to see if we need to print out or elide lines that come between
1652                     // this annotated line and the next one.
1653                     if line_idx < (annotated_file.lines.len() - 1) {
1654                         let line_idx_delta = annotated_file.lines[line_idx + 1].line_index
1655                             - annotated_file.lines[line_idx].line_index;
1656                         if line_idx_delta > 2 {
1657                             let last_buffer_line_num = buffer.num_lines();
1658                             buffer.puts(last_buffer_line_num, 0, "...", Style::LineNumber);
1659
1660                             // Set the multiline annotation vertical lines on `...` bridging line.
1661                             for (depth, style) in &multilines {
1662                                 draw_multiline_line(
1663                                     &mut buffer,
1664                                     last_buffer_line_num,
1665                                     width_offset,
1666                                     *depth,
1667                                     *style,
1668                                 );
1669                             }
1670                         } else if line_idx_delta == 2 {
1671                             let unannotated_line = annotated_file
1672                                 .file
1673                                 .get_line(annotated_file.lines[line_idx].line_index)
1674                                 .unwrap_or_else(|| Cow::from(""));
1675
1676                             let last_buffer_line_num = buffer.num_lines();
1677
1678                             self.draw_line(
1679                                 &mut buffer,
1680                                 &normalize_whitespace(&unannotated_line),
1681                                 annotated_file.lines[line_idx + 1].line_index - 1,
1682                                 last_buffer_line_num,
1683                                 width_offset,
1684                                 code_offset,
1685                                 margin,
1686                             );
1687
1688                             for (depth, style) in &multilines {
1689                                 draw_multiline_line(
1690                                     &mut buffer,
1691                                     last_buffer_line_num,
1692                                     width_offset,
1693                                     *depth,
1694                                     *style,
1695                                 );
1696                             }
1697                         }
1698                     }
1699
1700                     multilines.extend(&to_add);
1701                 }
1702             }
1703             trace!("buffer: {:#?}", buffer.render());
1704         }
1705
1706         if let Some(tracked) = emitted_at {
1707             let track = format!("-Ztrack-diagnostics: created at {tracked}");
1708             let len = buffer.num_lines();
1709             buffer.append(len, &track, Style::NoStyle);
1710         }
1711
1712         // final step: take our styled buffer, render it, then output it
1713         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1714
1715         Ok(())
1716     }
1717
1718     fn emit_suggestion_default(
1719         &mut self,
1720         span: &MultiSpan,
1721         suggestion: &CodeSuggestion,
1722         args: &FluentArgs<'_>,
1723         level: &Level,
1724         max_line_num_len: usize,
1725     ) -> io::Result<()> {
1726         let Some(ref sm) = self.sm else {
1727             return Ok(());
1728         };
1729
1730         // Render the replacements for each suggestion
1731         let suggestions = suggestion.splice_lines(sm);
1732         debug!("emit_suggestion_default: suggestions={:?}", suggestions);
1733
1734         if suggestions.is_empty() {
1735             // Suggestions coming from macros can have malformed spans. This is a heavy handed
1736             // approach to avoid ICEs by ignoring the suggestion outright.
1737             return Ok(());
1738         }
1739
1740         let mut buffer = StyledBuffer::new();
1741
1742         // Render the suggestion message
1743         buffer.append(0, level.to_str(), Style::Level(*level));
1744         buffer.append(0, ": ", Style::HeaderMsg);
1745
1746         self.msg_to_buffer(
1747             &mut buffer,
1748             &[(suggestion.msg.to_owned(), Style::NoStyle)],
1749             args,
1750             max_line_num_len,
1751             "suggestion",
1752             Some(Style::HeaderMsg),
1753         );
1754
1755         let mut row_num = 2;
1756         draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
1757         let mut notice_capitalization = false;
1758         for (complete, parts, highlights, only_capitalization) in
1759             suggestions.iter().take(MAX_SUGGESTIONS)
1760         {
1761             notice_capitalization |= only_capitalization;
1762
1763             let has_deletion = parts.iter().any(|p| p.is_deletion(sm));
1764             let is_multiline = complete.lines().count() > 1;
1765
1766             if let Some(span) = span.primary_span() {
1767                 // Compare the primary span of the diagnostic with the span of the suggestion
1768                 // being emitted.  If they belong to the same file, we don't *need* to show the
1769                 // file name, saving in verbosity, but if it *isn't* we do need it, otherwise we're
1770                 // telling users to make a change but not clarifying *where*.
1771                 let loc = sm.lookup_char_pos(parts[0].span.lo());
1772                 if loc.file.name != sm.span_to_filename(span) && loc.file.name.is_real() {
1773                     buffer.puts(row_num - 1, 0, "--> ", Style::LineNumber);
1774                     buffer.append(
1775                         row_num - 1,
1776                         &format!(
1777                             "{}:{}:{}",
1778                             sm.filename_for_diagnostics(&loc.file.name),
1779                             sm.doctest_offset_line(&loc.file.name, loc.line),
1780                             loc.col.0 + 1,
1781                         ),
1782                         Style::LineAndColumn,
1783                     );
1784                     for _ in 0..max_line_num_len {
1785                         buffer.prepend(row_num - 1, " ", Style::NoStyle);
1786                     }
1787                     row_num += 1;
1788                 }
1789             }
1790             let show_code_change = if has_deletion && !is_multiline {
1791                 DisplaySuggestion::Diff
1792             } else if (parts.len() != 1 || parts[0].snippet.trim() != complete.trim())
1793                 && !is_multiline
1794             {
1795                 DisplaySuggestion::Underline
1796             } else {
1797                 DisplaySuggestion::None
1798             };
1799
1800             if let DisplaySuggestion::Diff = show_code_change {
1801                 row_num += 1;
1802             }
1803
1804             let file_lines = sm
1805                 .span_to_lines(parts[0].span)
1806                 .expect("span_to_lines failed when emitting suggestion");
1807
1808             assert!(!file_lines.lines.is_empty() || parts[0].span.is_dummy());
1809
1810             let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
1811             draw_col_separator_no_space(&mut buffer, row_num - 1, max_line_num_len + 1);
1812             let mut lines = complete.lines();
1813             if lines.clone().next().is_none() {
1814                 // Account for a suggestion to completely remove a line(s) with whitespace (#94192).
1815                 let line_end = sm.lookup_char_pos(parts[0].span.hi()).line;
1816                 for line in line_start..=line_end {
1817                     buffer.puts(
1818                         row_num - 1 + line - line_start,
1819                         0,
1820                         &self.maybe_anonymized(line),
1821                         Style::LineNumber,
1822                     );
1823                     buffer.puts(
1824                         row_num - 1 + line - line_start,
1825                         max_line_num_len + 1,
1826                         "- ",
1827                         Style::Removal,
1828                     );
1829                     buffer.puts(
1830                         row_num - 1 + line - line_start,
1831                         max_line_num_len + 3,
1832                         &normalize_whitespace(&file_lines.file.get_line(line - 1).unwrap()),
1833                         Style::Removal,
1834                     );
1835                 }
1836                 row_num += line_end - line_start;
1837             }
1838             let mut unhighlighted_lines = Vec::new();
1839             for (line_pos, (line, highlight_parts)) in lines.by_ref().zip(highlights).enumerate() {
1840                 debug!(%line_pos, %line, ?highlight_parts);
1841
1842                 // Remember lines that are not highlighted to hide them if needed
1843                 if highlight_parts.is_empty() {
1844                     unhighlighted_lines.push((line_pos, line));
1845                     continue;
1846                 }
1847
1848                 match unhighlighted_lines.len() {
1849                     0 => (),
1850                     // Since we show first line, "..." line and last line,
1851                     // There is no reason to hide if there are 3 or less lines
1852                     // (because then we just replace a line with ... which is
1853                     // not helpful)
1854                     n if n <= 3 => unhighlighted_lines.drain(..).for_each(|(p, l)| {
1855                         self.draw_code_line(
1856                             &mut buffer,
1857                             &mut row_num,
1858                             &Vec::new(),
1859                             p,
1860                             l,
1861                             line_start,
1862                             show_code_change,
1863                             max_line_num_len,
1864                             &file_lines,
1865                             is_multiline,
1866                         )
1867                     }),
1868                     // Print first unhighlighted line, "..." and last unhighlighted line, like so:
1869                     //
1870                     // LL | this line was highlighted
1871                     // LL | this line is just for context
1872                     //   ...
1873                     // LL | this line is just for context
1874                     // LL | this line was highlighted
1875                     _ => {
1876                         let last_line = unhighlighted_lines.pop();
1877                         let first_line = unhighlighted_lines.drain(..).next();
1878
1879                         first_line.map(|(p, l)| {
1880                             self.draw_code_line(
1881                                 &mut buffer,
1882                                 &mut row_num,
1883                                 &Vec::new(),
1884                                 p,
1885                                 l,
1886                                 line_start,
1887                                 show_code_change,
1888                                 max_line_num_len,
1889                                 &file_lines,
1890                                 is_multiline,
1891                             )
1892                         });
1893
1894                         buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
1895                         row_num += 1;
1896
1897                         last_line.map(|(p, l)| {
1898                             self.draw_code_line(
1899                                 &mut buffer,
1900                                 &mut row_num,
1901                                 &Vec::new(),
1902                                 p,
1903                                 l,
1904                                 line_start,
1905                                 show_code_change,
1906                                 max_line_num_len,
1907                                 &file_lines,
1908                                 is_multiline,
1909                             )
1910                         });
1911                     }
1912                 }
1913
1914                 self.draw_code_line(
1915                     &mut buffer,
1916                     &mut row_num,
1917                     highlight_parts,
1918                     line_pos,
1919                     line,
1920                     line_start,
1921                     show_code_change,
1922                     max_line_num_len,
1923                     &file_lines,
1924                     is_multiline,
1925                 )
1926             }
1927
1928             // This offset and the ones below need to be signed to account for replacement code
1929             // that is shorter than the original code.
1930             let mut offsets: Vec<(usize, isize)> = Vec::new();
1931             // Only show an underline in the suggestions if the suggestion is not the
1932             // entirety of the code being shown and the displayed code is not multiline.
1933             if let DisplaySuggestion::Diff | DisplaySuggestion::Underline = show_code_change {
1934                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
1935                 for part in parts {
1936                     let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
1937                     let span_end_pos = sm.lookup_char_pos(part.span.hi()).col_display;
1938
1939                     // If this addition is _only_ whitespace, then don't trim it,
1940                     // or else we're just not rendering anything.
1941                     let is_whitespace_addition = part.snippet.trim().is_empty();
1942
1943                     // Do not underline the leading...
1944                     let start = if is_whitespace_addition {
1945                         0
1946                     } else {
1947                         part.snippet.len().saturating_sub(part.snippet.trim_start().len())
1948                     };
1949                     // ...or trailing spaces. Account for substitutions containing unicode
1950                     // characters.
1951                     let sub_len: usize =
1952                         if is_whitespace_addition { &part.snippet } else { part.snippet.trim() }
1953                             .chars()
1954                             .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1955                             .sum();
1956
1957                     let offset: isize = offsets
1958                         .iter()
1959                         .filter_map(
1960                             |(start, v)| if span_start_pos <= *start { None } else { Some(v) },
1961                         )
1962                         .sum();
1963                     let underline_start = (span_start_pos + start) as isize + offset;
1964                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
1965                     assert!(underline_start >= 0 && underline_end >= 0);
1966                     let padding: usize = max_line_num_len + 3;
1967                     for p in underline_start..underline_end {
1968                         if let DisplaySuggestion::Underline = show_code_change {
1969                             // If this is a replacement, underline with `^`, if this is an addition
1970                             // underline with `+`.
1971                             buffer.putc(
1972                                 row_num,
1973                                 (padding as isize + p) as usize,
1974                                 if part.is_addition(sm) { '+' } else { '~' },
1975                                 Style::Addition,
1976                             );
1977                         }
1978                     }
1979                     if let DisplaySuggestion::Diff = show_code_change {
1980                         // Colorize removal with red in diff format.
1981                         buffer.set_style_range(
1982                             row_num - 2,
1983                             (padding as isize + span_start_pos as isize) as usize,
1984                             (padding as isize + span_end_pos as isize) as usize,
1985                             Style::Removal,
1986                             true,
1987                         );
1988                     }
1989
1990                     // length of the code after substitution
1991                     let full_sub_len = part
1992                         .snippet
1993                         .chars()
1994                         .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1995                         .sum::<usize>() as isize;
1996
1997                     // length of the code to be substituted
1998                     let snippet_len = span_end_pos as isize - span_start_pos as isize;
1999                     // For multiple substitutions, use the position *after* the previous
2000                     // substitutions have happened, only when further substitutions are
2001                     // located strictly after.
2002                     offsets.push((span_end_pos, full_sub_len - snippet_len));
2003                 }
2004                 row_num += 1;
2005             }
2006
2007             // if we elided some lines, add an ellipsis
2008             if lines.next().is_some() {
2009                 buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
2010             } else if let DisplaySuggestion::None = show_code_change {
2011                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
2012                 row_num += 1;
2013             }
2014         }
2015         if suggestions.len() > MAX_SUGGESTIONS {
2016             let others = suggestions.len() - MAX_SUGGESTIONS;
2017             let msg = format!("and {} other candidate{}", others, pluralize!(others));
2018             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
2019         } else if notice_capitalization {
2020             let msg = "notice the capitalization difference";
2021             buffer.puts(row_num, max_line_num_len + 3, msg, Style::NoStyle);
2022         }
2023         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
2024         Ok(())
2025     }
2026
2027     #[instrument(level = "trace", skip(self, args, code, children, suggestions))]
2028     fn emit_messages_default(
2029         &mut self,
2030         level: &Level,
2031         message: &[(DiagnosticMessage, Style)],
2032         args: &FluentArgs<'_>,
2033         code: &Option<DiagnosticId>,
2034         span: &MultiSpan,
2035         children: &[SubDiagnostic],
2036         suggestions: &[CodeSuggestion],
2037         emitted_at: Option<&DiagnosticLocation>,
2038     ) {
2039         let max_line_num_len = if self.ui_testing {
2040             ANONYMIZED_LINE_NUM.len()
2041         } else {
2042             let n = self.get_max_line_num(span, children);
2043             num_decimal_digits(n)
2044         };
2045
2046         match self.emit_message_default(
2047             span,
2048             message,
2049             args,
2050             code,
2051             level,
2052             max_line_num_len,
2053             false,
2054             emitted_at,
2055         ) {
2056             Ok(()) => {
2057                 if !children.is_empty()
2058                     || suggestions.iter().any(|s| s.style != SuggestionStyle::CompletelyHidden)
2059                 {
2060                     let mut buffer = StyledBuffer::new();
2061                     if !self.short_message {
2062                         draw_col_separator_no_space(&mut buffer, 0, max_line_num_len + 1);
2063                     }
2064                     if let Err(e) = emit_to_destination(
2065                         &buffer.render(),
2066                         level,
2067                         &mut self.dst,
2068                         self.short_message,
2069                     ) {
2070                         panic!("failed to emit error: {}", e)
2071                     }
2072                 }
2073                 if !self.short_message {
2074                     for child in children {
2075                         let span = child.render_span.as_ref().unwrap_or(&child.span);
2076                         if let Err(err) = self.emit_message_default(
2077                             span,
2078                             &child.message,
2079                             args,
2080                             &None,
2081                             &child.level,
2082                             max_line_num_len,
2083                             true,
2084                             None,
2085                         ) {
2086                             panic!("failed to emit error: {}", err);
2087                         }
2088                     }
2089                     for sugg in suggestions {
2090                         if sugg.style == SuggestionStyle::CompletelyHidden {
2091                             // do not display this suggestion, it is meant only for tools
2092                         } else if sugg.style == SuggestionStyle::HideCodeAlways {
2093                             if let Err(e) = self.emit_message_default(
2094                                 &MultiSpan::new(),
2095                                 &[(sugg.msg.to_owned(), Style::HeaderMsg)],
2096                                 args,
2097                                 &None,
2098                                 &Level::Help,
2099                                 max_line_num_len,
2100                                 true,
2101                                 None,
2102                             ) {
2103                                 panic!("failed to emit error: {}", e);
2104                             }
2105                         } else if let Err(e) = self.emit_suggestion_default(
2106                             span,
2107                             sugg,
2108                             args,
2109                             &Level::Help,
2110                             max_line_num_len,
2111                         ) {
2112                             panic!("failed to emit error: {}", e);
2113                         };
2114                     }
2115                 }
2116             }
2117             Err(e) => panic!("failed to emit error: {}", e),
2118         }
2119
2120         let mut dst = self.dst.writable();
2121         match writeln!(dst) {
2122             Err(e) => panic!("failed to emit error: {}", e),
2123             _ => {
2124                 if let Err(e) = dst.flush() {
2125                     panic!("failed to emit error: {}", e)
2126                 }
2127             }
2128         }
2129     }
2130
2131     fn draw_code_line(
2132         &self,
2133         buffer: &mut StyledBuffer,
2134         row_num: &mut usize,
2135         highlight_parts: &Vec<SubstitutionHighlight>,
2136         line_pos: usize,
2137         line: &str,
2138         line_start: usize,
2139         show_code_change: DisplaySuggestion,
2140         max_line_num_len: usize,
2141         file_lines: &FileLines,
2142         is_multiline: bool,
2143     ) {
2144         // Print the span column to avoid confusion
2145         buffer.puts(*row_num, 0, &self.maybe_anonymized(line_start + line_pos), Style::LineNumber);
2146         if let DisplaySuggestion::Diff = show_code_change {
2147             // Add the line number for both addition and removal to drive the point home.
2148             //
2149             // N - fn foo<A: T>(bar: A) {
2150             // N + fn foo(bar: impl T) {
2151             buffer.puts(
2152                 *row_num - 1,
2153                 0,
2154                 &self.maybe_anonymized(line_start + line_pos),
2155                 Style::LineNumber,
2156             );
2157             buffer.puts(*row_num - 1, max_line_num_len + 1, "- ", Style::Removal);
2158             buffer.puts(
2159                 *row_num - 1,
2160                 max_line_num_len + 3,
2161                 &normalize_whitespace(
2162                     &file_lines.file.get_line(file_lines.lines[line_pos].line_index).unwrap(),
2163                 ),
2164                 Style::NoStyle,
2165             );
2166             buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
2167         } else if is_multiline {
2168             match &highlight_parts[..] {
2169                 [SubstitutionHighlight { start: 0, end }] if *end == line.len() => {
2170                     buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
2171                 }
2172                 [] => {
2173                     draw_col_separator(buffer, *row_num, max_line_num_len + 1);
2174                 }
2175                 _ => {
2176                     buffer.puts(*row_num, max_line_num_len + 1, "~ ", Style::Addition);
2177                 }
2178             }
2179         } else {
2180             draw_col_separator(buffer, *row_num, max_line_num_len + 1);
2181         }
2182
2183         // print the suggestion
2184         buffer.append(*row_num, &normalize_whitespace(line), Style::NoStyle);
2185
2186         // Colorize addition/replacements with green.
2187         for &SubstitutionHighlight { start, end } in highlight_parts {
2188             // Account for tabs when highlighting (#87972).
2189             let tabs: usize = line
2190                 .chars()
2191                 .take(start)
2192                 .map(|ch| match ch {
2193                     '\t' => 3,
2194                     _ => 0,
2195                 })
2196                 .sum();
2197             buffer.set_style_range(
2198                 *row_num,
2199                 max_line_num_len + 3 + start + tabs,
2200                 max_line_num_len + 3 + end + tabs,
2201                 Style::Addition,
2202                 true,
2203             );
2204         }
2205         *row_num += 1;
2206     }
2207 }
2208
2209 #[derive(Clone, Copy, Debug)]
2210 enum DisplaySuggestion {
2211     Underline,
2212     Diff,
2213     None,
2214 }
2215
2216 impl FileWithAnnotatedLines {
2217     /// Preprocess all the annotations so that they are grouped by file and by line number
2218     /// This helps us quickly iterate over the whole message (including secondary file spans)
2219     pub fn collect_annotations(
2220         emitter: &dyn Emitter,
2221         args: &FluentArgs<'_>,
2222         msp: &MultiSpan,
2223     ) -> Vec<FileWithAnnotatedLines> {
2224         fn add_annotation_to_file(
2225             file_vec: &mut Vec<FileWithAnnotatedLines>,
2226             file: Lrc<SourceFile>,
2227             line_index: usize,
2228             ann: Annotation,
2229         ) {
2230             for slot in file_vec.iter_mut() {
2231                 // Look through each of our files for the one we're adding to
2232                 if slot.file.name == file.name {
2233                     // See if we already have a line for it
2234                     for line_slot in &mut slot.lines {
2235                         if line_slot.line_index == line_index {
2236                             line_slot.annotations.push(ann);
2237                             return;
2238                         }
2239                     }
2240                     // We don't have a line yet, create one
2241                     slot.lines.push(Line { line_index, annotations: vec![ann] });
2242                     slot.lines.sort();
2243                     return;
2244                 }
2245             }
2246             // This is the first time we're seeing the file
2247             file_vec.push(FileWithAnnotatedLines {
2248                 file,
2249                 lines: vec![Line { line_index, annotations: vec![ann] }],
2250                 multiline_depth: 0,
2251             });
2252         }
2253
2254         let mut output = vec![];
2255         let mut multiline_annotations = vec![];
2256
2257         if let Some(ref sm) = emitter.source_map() {
2258             for SpanLabel { span, is_primary, label } in msp.span_labels() {
2259                 // If we don't have a useful span, pick the primary span if that exists.
2260                 // Worst case we'll just print an error at the top of the main file.
2261                 let span = match (span.is_dummy(), msp.primary_span()) {
2262                     (_, None) | (false, _) => span,
2263                     (true, Some(span)) => span,
2264                 };
2265
2266                 let lo = sm.lookup_char_pos(span.lo());
2267                 let mut hi = sm.lookup_char_pos(span.hi());
2268
2269                 // Watch out for "empty spans". If we get a span like 6..6, we
2270                 // want to just display a `^` at 6, so convert that to
2271                 // 6..7. This is degenerate input, but it's best to degrade
2272                 // gracefully -- and the parser likes to supply a span like
2273                 // that for EOF, in particular.
2274
2275                 if lo.col_display == hi.col_display && lo.line == hi.line {
2276                     hi.col_display += 1;
2277                 }
2278
2279                 let label = label.as_ref().map(|m| emitter.translate_message(m, args).to_string());
2280
2281                 if lo.line != hi.line {
2282                     let ml = MultilineAnnotation {
2283                         depth: 1,
2284                         line_start: lo.line,
2285                         line_end: hi.line,
2286                         start_col: lo.col_display,
2287                         end_col: hi.col_display,
2288                         is_primary,
2289                         label,
2290                         overlaps_exactly: false,
2291                     };
2292                     multiline_annotations.push((lo.file, ml));
2293                 } else {
2294                     let ann = Annotation {
2295                         start_col: lo.col_display,
2296                         end_col: hi.col_display,
2297                         is_primary,
2298                         label,
2299                         annotation_type: AnnotationType::Singleline,
2300                     };
2301                     add_annotation_to_file(&mut output, lo.file, lo.line, ann);
2302                 };
2303             }
2304         }
2305
2306         // Find overlapping multiline annotations, put them at different depths
2307         multiline_annotations.sort_by_key(|&(_, ref ml)| (ml.line_start, usize::MAX - ml.line_end));
2308         for (_, ann) in multiline_annotations.clone() {
2309             for (_, a) in multiline_annotations.iter_mut() {
2310                 // Move all other multiline annotations overlapping with this one
2311                 // one level to the right.
2312                 if !(ann.same_span(a))
2313                     && num_overlap(ann.line_start, ann.line_end, a.line_start, a.line_end, true)
2314                 {
2315                     a.increase_depth();
2316                 } else if ann.same_span(a) && &ann != a {
2317                     a.overlaps_exactly = true;
2318                 } else {
2319                     break;
2320                 }
2321             }
2322         }
2323
2324         let mut max_depth = 0; // max overlapping multiline spans
2325         for (_, ann) in &multiline_annotations {
2326             max_depth = max(max_depth, ann.depth);
2327         }
2328         // Change order of multispan depth to minimize the number of overlaps in the ASCII art.
2329         for (_, a) in multiline_annotations.iter_mut() {
2330             a.depth = max_depth - a.depth + 1;
2331         }
2332         for (file, ann) in multiline_annotations {
2333             let mut end_ann = ann.as_end();
2334             if !ann.overlaps_exactly {
2335                 // avoid output like
2336                 //
2337                 //  |        foo(
2338                 //  |   _____^
2339                 //  |  |_____|
2340                 //  | ||         bar,
2341                 //  | ||     );
2342                 //  | ||      ^
2343                 //  | ||______|
2344                 //  |  |______foo
2345                 //  |         baz
2346                 //
2347                 // and instead get
2348                 //
2349                 //  |       foo(
2350                 //  |  _____^
2351                 //  | |         bar,
2352                 //  | |     );
2353                 //  | |      ^
2354                 //  | |      |
2355                 //  | |______foo
2356                 //  |        baz
2357                 add_annotation_to_file(&mut output, file.clone(), ann.line_start, ann.as_start());
2358                 // 4 is the minimum vertical length of a multiline span when presented: two lines
2359                 // of code and two lines of underline. This is not true for the special case where
2360                 // the beginning doesn't have an underline, but the current logic seems to be
2361                 // working correctly.
2362                 let middle = min(ann.line_start + 4, ann.line_end);
2363                 for line in ann.line_start + 1..middle {
2364                     // Every `|` that joins the beginning of the span (`___^`) to the end (`|__^`).
2365                     add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
2366                 }
2367                 let line_end = ann.line_end - 1;
2368                 if middle < line_end {
2369                     add_annotation_to_file(&mut output, file.clone(), line_end, ann.as_line());
2370                 }
2371             } else {
2372                 end_ann.annotation_type = AnnotationType::Singleline;
2373             }
2374             add_annotation_to_file(&mut output, file, ann.line_end, end_ann);
2375         }
2376         for file_vec in output.iter_mut() {
2377             file_vec.multiline_depth = max_depth;
2378         }
2379         output
2380     }
2381 }
2382
2383 // instead of taking the String length or dividing by 10 while > 0, we multiply a limit by 10 until
2384 // we're higher. If the loop isn't exited by the `return`, the last multiplication will wrap, which
2385 // is OK, because while we cannot fit a higher power of 10 in a usize, the loop will end anyway.
2386 // This is also why we need the max number of decimal digits within a `usize`.
2387 fn num_decimal_digits(num: usize) -> usize {
2388     #[cfg(target_pointer_width = "64")]
2389     const MAX_DIGITS: usize = 20;
2390
2391     #[cfg(target_pointer_width = "32")]
2392     const MAX_DIGITS: usize = 10;
2393
2394     #[cfg(target_pointer_width = "16")]
2395     const MAX_DIGITS: usize = 5;
2396
2397     let mut lim = 10;
2398     for num_digits in 1..MAX_DIGITS {
2399         if num < lim {
2400             return num_digits;
2401         }
2402         lim = lim.wrapping_mul(10);
2403     }
2404     MAX_DIGITS
2405 }
2406
2407 // We replace some characters so the CLI output is always consistent and underlines aligned.
2408 const OUTPUT_REPLACEMENTS: &[(char, &str)] = &[
2409     ('\t', "    "),   // We do our own tab replacement
2410     ('\u{200D}', ""), // Replace ZWJ with nothing for consistent terminal output of grapheme clusters.
2411     ('\u{202A}', ""), // The following unicode text flow control characters are inconsistently
2412     ('\u{202B}', ""), // supported across CLIs and can cause confusion due to the bytes on disk
2413     ('\u{202D}', ""), // not corresponding to the visible source code, so we replace them always.
2414     ('\u{202E}', ""),
2415     ('\u{2066}', ""),
2416     ('\u{2067}', ""),
2417     ('\u{2068}', ""),
2418     ('\u{202C}', ""),
2419     ('\u{2069}', ""),
2420 ];
2421
2422 fn normalize_whitespace(str: &str) -> String {
2423     let mut s = str.to_string();
2424     for (c, replacement) in OUTPUT_REPLACEMENTS {
2425         s = s.replace(*c, replacement);
2426     }
2427     s
2428 }
2429
2430 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
2431     buffer.puts(line, col, "| ", Style::LineNumber);
2432 }
2433
2434 fn draw_col_separator_no_space(buffer: &mut StyledBuffer, line: usize, col: usize) {
2435     draw_col_separator_no_space_with_style(buffer, line, col, Style::LineNumber);
2436 }
2437
2438 fn draw_col_separator_no_space_with_style(
2439     buffer: &mut StyledBuffer,
2440     line: usize,
2441     col: usize,
2442     style: Style,
2443 ) {
2444     buffer.putc(line, col, '|', style);
2445 }
2446
2447 fn draw_range(
2448     buffer: &mut StyledBuffer,
2449     symbol: char,
2450     line: usize,
2451     col_from: usize,
2452     col_to: usize,
2453     style: Style,
2454 ) {
2455     for col in col_from..col_to {
2456         buffer.putc(line, col, symbol, style);
2457     }
2458 }
2459
2460 fn draw_note_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
2461     buffer.puts(line, col, "= ", Style::LineNumber);
2462 }
2463
2464 fn draw_multiline_line(
2465     buffer: &mut StyledBuffer,
2466     line: usize,
2467     offset: usize,
2468     depth: usize,
2469     style: Style,
2470 ) {
2471     buffer.putc(line, offset + depth - 1, '|', style);
2472 }
2473
2474 fn num_overlap(
2475     a_start: usize,
2476     a_end: usize,
2477     b_start: usize,
2478     b_end: usize,
2479     inclusive: bool,
2480 ) -> bool {
2481     let extra = if inclusive { 1 } else { 0 };
2482     (b_start..b_end + extra).contains(&a_start) || (a_start..a_end + extra).contains(&b_start)
2483 }
2484 fn overlaps(a1: &Annotation, a2: &Annotation, padding: usize) -> bool {
2485     num_overlap(a1.start_col, a1.end_col + padding, a2.start_col, a2.end_col, false)
2486 }
2487
2488 fn emit_to_destination(
2489     rendered_buffer: &[Vec<StyledString>],
2490     lvl: &Level,
2491     dst: &mut Destination,
2492     short_message: bool,
2493 ) -> io::Result<()> {
2494     use crate::lock;
2495
2496     let mut dst = dst.writable();
2497
2498     // In order to prevent error message interleaving, where multiple error lines get intermixed
2499     // when multiple compiler processes error simultaneously, we emit errors with additional
2500     // steps.
2501     //
2502     // On Unix systems, we write into a buffered terminal rather than directly to a terminal. When
2503     // the .flush() is called we take the buffer created from the buffered writes and write it at
2504     // one shot.  Because the Unix systems use ANSI for the colors, which is a text-based styling
2505     // scheme, this buffered approach works and maintains the styling.
2506     //
2507     // On Windows, styling happens through calls to a terminal API. This prevents us from using the
2508     // same buffering approach.  Instead, we use a global Windows mutex, which we acquire long
2509     // enough to output the full error message, then we release.
2510     let _buffer_lock = lock::acquire_global_lock("rustc_errors");
2511     for (pos, line) in rendered_buffer.iter().enumerate() {
2512         for part in line {
2513             dst.apply_style(*lvl, part.style)?;
2514             write!(dst, "{}", part.text)?;
2515             dst.reset()?;
2516         }
2517         if !short_message && (!lvl.is_failure_note() || pos != rendered_buffer.len() - 1) {
2518             writeln!(dst)?;
2519         }
2520     }
2521     dst.flush()?;
2522     Ok(())
2523 }
2524
2525 pub enum Destination {
2526     Terminal(StandardStream),
2527     Buffered(BufferWriter),
2528     // The bool denotes whether we should be emitting ansi color codes or not
2529     Raw(Box<(dyn Write + Send)>, bool),
2530 }
2531
2532 pub enum WritableDst<'a> {
2533     Terminal(&'a mut StandardStream),
2534     Buffered(&'a mut BufferWriter, Buffer),
2535     Raw(&'a mut (dyn Write + Send)),
2536     ColoredRaw(Ansi<&'a mut (dyn Write + Send)>),
2537 }
2538
2539 impl Destination {
2540     fn from_stderr(color: ColorConfig) -> Destination {
2541         let choice = color.to_color_choice();
2542         // On Windows we'll be performing global synchronization on the entire
2543         // system for emitting rustc errors, so there's no need to buffer
2544         // anything.
2545         //
2546         // On non-Windows we rely on the atomicity of `write` to ensure errors
2547         // don't get all jumbled up.
2548         if cfg!(windows) {
2549             Terminal(StandardStream::stderr(choice))
2550         } else {
2551             Buffered(BufferWriter::stderr(choice))
2552         }
2553     }
2554
2555     fn writable(&mut self) -> WritableDst<'_> {
2556         match *self {
2557             Destination::Terminal(ref mut t) => WritableDst::Terminal(t),
2558             Destination::Buffered(ref mut t) => {
2559                 let buf = t.buffer();
2560                 WritableDst::Buffered(t, buf)
2561             }
2562             Destination::Raw(ref mut t, false) => WritableDst::Raw(t),
2563             Destination::Raw(ref mut t, true) => WritableDst::ColoredRaw(Ansi::new(t)),
2564         }
2565     }
2566
2567     fn supports_color(&self) -> bool {
2568         match *self {
2569             Self::Terminal(ref stream) => stream.supports_color(),
2570             Self::Buffered(ref buffer) => buffer.buffer().supports_color(),
2571             Self::Raw(_, supports_color) => supports_color,
2572         }
2573     }
2574 }
2575
2576 impl<'a> WritableDst<'a> {
2577     fn apply_style(&mut self, lvl: Level, style: Style) -> io::Result<()> {
2578         let mut spec = ColorSpec::new();
2579         match style {
2580             Style::Addition => {
2581                 spec.set_fg(Some(Color::Green)).set_intense(true);
2582             }
2583             Style::Removal => {
2584                 spec.set_fg(Some(Color::Red)).set_intense(true);
2585             }
2586             Style::LineAndColumn => {}
2587             Style::LineNumber => {
2588                 spec.set_bold(true);
2589                 spec.set_intense(true);
2590                 if cfg!(windows) {
2591                     spec.set_fg(Some(Color::Cyan));
2592                 } else {
2593                     spec.set_fg(Some(Color::Blue));
2594                 }
2595             }
2596             Style::Quotation => {}
2597             Style::MainHeaderMsg => {
2598                 spec.set_bold(true);
2599                 if cfg!(windows) {
2600                     spec.set_intense(true).set_fg(Some(Color::White));
2601                 }
2602             }
2603             Style::UnderlinePrimary | Style::LabelPrimary => {
2604                 spec = lvl.color();
2605                 spec.set_bold(true);
2606             }
2607             Style::UnderlineSecondary | Style::LabelSecondary => {
2608                 spec.set_bold(true).set_intense(true);
2609                 if cfg!(windows) {
2610                     spec.set_fg(Some(Color::Cyan));
2611                 } else {
2612                     spec.set_fg(Some(Color::Blue));
2613                 }
2614             }
2615             Style::HeaderMsg | Style::NoStyle => {}
2616             Style::Level(lvl) => {
2617                 spec = lvl.color();
2618                 spec.set_bold(true);
2619             }
2620             Style::Highlight => {
2621                 spec.set_bold(true);
2622             }
2623         }
2624         self.set_color(&spec)
2625     }
2626
2627     fn set_color(&mut self, color: &ColorSpec) -> io::Result<()> {
2628         match *self {
2629             WritableDst::Terminal(ref mut t) => t.set_color(color),
2630             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
2631             WritableDst::ColoredRaw(ref mut t) => t.set_color(color),
2632             WritableDst::Raw(_) => Ok(()),
2633         }
2634     }
2635
2636     fn reset(&mut self) -> io::Result<()> {
2637         match *self {
2638             WritableDst::Terminal(ref mut t) => t.reset(),
2639             WritableDst::Buffered(_, ref mut t) => t.reset(),
2640             WritableDst::ColoredRaw(ref mut t) => t.reset(),
2641             WritableDst::Raw(_) => Ok(()),
2642         }
2643     }
2644 }
2645
2646 impl<'a> Write for WritableDst<'a> {
2647     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
2648         match *self {
2649             WritableDst::Terminal(ref mut t) => t.write(bytes),
2650             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
2651             WritableDst::Raw(ref mut w) => w.write(bytes),
2652             WritableDst::ColoredRaw(ref mut t) => t.write(bytes),
2653         }
2654     }
2655
2656     fn flush(&mut self) -> io::Result<()> {
2657         match *self {
2658             WritableDst::Terminal(ref mut t) => t.flush(),
2659             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
2660             WritableDst::Raw(ref mut w) => w.flush(),
2661             WritableDst::ColoredRaw(ref mut w) => w.flush(),
2662         }
2663     }
2664 }
2665
2666 impl<'a> Drop for WritableDst<'a> {
2667     fn drop(&mut self) {
2668         if let WritableDst::Buffered(ref mut dst, ref mut buf) = self {
2669             drop(dst.print(buf));
2670         }
2671     }
2672 }
2673
2674 /// Whether the original and suggested code are visually similar enough to warrant extra wording.
2675 pub fn is_case_difference(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
2676     // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
2677     let found = match sm.span_to_snippet(sp) {
2678         Ok(snippet) => snippet,
2679         Err(e) => {
2680             warn!(error = ?e, "Invalid span {:?}", sp);
2681             return false;
2682         }
2683     };
2684     let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
2685     // All the chars that differ in capitalization are confusable (above):
2686     let confusable = iter::zip(found.chars(), suggested.chars())
2687         .filter(|(f, s)| f != s)
2688         .all(|(f, s)| (ascii_confusables.contains(&f) || ascii_confusables.contains(&s)));
2689     confusable && found.to_lowercase() == suggested.to_lowercase()
2690             // FIXME: We sometimes suggest the same thing we already have, which is a
2691             //        bug, but be defensive against that here.
2692             && found != suggested
2693 }