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         let mut buffer_ops = vec![];
 849         let mut annotations = vec![];
 850         let mut short_start = true;
 851         for ann in &line.annotations {
 852             if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
 853                 if source_string.chars().take(ann.start_col).all(|c| c.is_whitespace()) {
 854                     let style = if ann.is_primary {
 855                         Style::UnderlinePrimary
 856                     } else {
 857                         Style::UnderlineSecondary
 858                     };
 859                     annotations.push((depth, style));
 860                     buffer_ops.push((line_offset, width_offset + depth - 1, '/', style));
 861                 } else {
 862                     short_start = false;
 863                     break;
 864                 }
 865             } else if let AnnotationType::MultilineLine(_) = ann.annotation_type {
 866             } else {
 867                 short_start = false;
 868                 break;
 869             }
 870         }
 871         if short_start {
 872             for (y, x, c, s) in buffer_ops {
 873                 buffer.putc(y, x, c, s);
 874             }
 875             return annotations;
 876         }
 877
 878         // We want to display like this:
 879         //
 880         //      vec.push(vec.pop().unwrap());
 881         //      ---      ^^^               - previous borrow ends here
 882         //      |        |
 883         //      |        error occurs here
 884         //      previous borrow of `vec` occurs here
 885         //
 886         // But there are some weird edge cases to be aware of:
 887         //
 888         //      vec.push(vec.pop().unwrap());
 889         //      --------                    - previous borrow ends here
 890         //      ||
 891         //      |this makes no sense
 892         //      previous borrow of `vec` occurs here
 893         //
 894         // For this reason, we group the lines into "highlight lines"
 895         // and "annotations lines", where the highlight lines have the `^`.
 896
 897         // Sort the annotations by (start, end col)
 898         // The labels are reversed, sort and then reversed again.
 899         // Consider a list of annotations (A1, A2, C1, C2, B1, B2) where
 900         // the letter signifies the span. Here we are only sorting by the
 901         // span and hence, the order of the elements with the same span will
 902         // not change. On reversing the ordering (|a, b| but b.cmp(a)), you get
 903         // (C1, C2, B1, B2, A1, A2). All the elements with the same span are
 904         // still ordered first to last, but all the elements with different
 905         // spans are ordered by their spans in last to first order. Last to
 906         // first order is important, because the jiggly lines and | are on
 907         // the left, so the rightmost span needs to be rendered first,
 908         // otherwise the lines would end up needing to go over a message.
 909
 910         let mut annotations = line.annotations.clone();
 911         annotations.sort_by_key(|a| Reverse(a.start_col));
 912
 913         // First, figure out where each label will be positioned.
 914         //
 915         // In the case where you have the following annotations:
 916         //
 917         //      vec.push(vec.pop().unwrap());
 918         //      --------                    - previous borrow ends here [C]
 919         //      ||
 920         //      |this makes no sense [B]
 921         //      previous borrow of `vec` occurs here [A]
 922         //
 923         // `annotations_position` will hold [(2, A), (1, B), (0, C)].
 924         //
 925         // We try, when possible, to stick the rightmost annotation at the end
 926         // of the highlight line:
 927         //
 928         //      vec.push(vec.pop().unwrap());
 929         //      ---      ---               - previous borrow ends here
 930         //
 931         // But sometimes that's not possible because one of the other
 932         // annotations overlaps it. For example, from the test
 933         // `span_overlap_label`, we have the following annotations
 934         // (written on distinct lines for clarity):
 935         //
 936         //      fn foo(x: u32) {
 937         //      --------------
 938         //             -
 939         //
 940         // In this case, we can't stick the rightmost-most label on
 941         // the highlight line, or we would get:
 942         //
 943         //      fn foo(x: u32) {
 944         //      -------- x_span
 945         //      |
 946         //      fn_span
 947         //
 948         // which is totally weird. Instead we want:
 949         //
 950         //      fn foo(x: u32) {
 951         //      --------------
 952         //      |      |
 953         //      |      x_span
 954         //      fn_span
 955         //
 956         // which is...less weird, at least. In fact, in general, if
 957         // the rightmost span overlaps with any other span, we should
 958         // use the "hang below" version, so we can at least make it
 959         // clear where the span *starts*. There's an exception for this
 960         // logic, when the labels do not have a message:
 961         //
 962         //      fn foo(x: u32) {
 963         //      --------------
 964         //             |
 965         //             x_span
 966         //
 967         // instead of:
 968         //
 969         //      fn foo(x: u32) {
 970         //      --------------
 971         //      |      |
 972         //      |      x_span
 973         //      <EMPTY LINE>
 974         //
 975         let mut annotations_position = vec![];
 976         let mut line_len = 0;
 977         let mut p = 0;
 978         for (i, annotation) in annotations.iter().enumerate() {
 979             for (j, next) in annotations.iter().enumerate() {
 980                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
 981                     && annotation.has_label()     // take space (they have text and are not
 982                     && j > i                      // multiline lines).
 983                     && p == 0
 984                 // We're currently on the first line, move the label one line down
 985                 {
 986                     // If we're overlapping with an un-labelled annotation with the same span
 987                     // we can just merge them in the output
 988                     if next.start_col == annotation.start_col
 989                         && next.end_col == annotation.end_col
 990                         && !next.has_label()
 991                     {
 992                         continue;
 993                     }
 994
 995                     // This annotation needs a new line in the output.
 996                     p += 1;
 997                     break;
 998                 }
 999             }
1000             annotations_position.push((p, annotation));
1001             for (j, next) in annotations.iter().enumerate() {
1002                 if j > i {
1003                     let l = next.label.as_ref().map_or(0, |label| label.len() + 2);
1004                     if (overlaps(next, annotation, l) // Do not allow two labels to be in the same
1005                                                      // line if they overlap including padding, to
1006                                                      // avoid situations like:
1007                                                      //
1008                                                      //      fn foo(x: u32) {
1009                                                      //      -------^------
1010                                                      //      |      |
1011                                                      //      fn_spanx_span
1012                                                      //
1013                         && annotation.has_label()    // Both labels must have some text, otherwise
1014                         && next.has_label())         // they are not overlapping.
1015                                                      // Do not add a new line if this annotation
1016                                                      // or the next are vertical line placeholders.
1017                         || (annotation.takes_space() // If either this or the next annotation is
1018                             && next.has_label())     // multiline start/end, move it to a new line
1019                         || (annotation.has_label()   // so as not to overlap the horizontal lines.
1020                             && next.takes_space())
1021                         || (annotation.takes_space() && next.takes_space())
1022                         || (overlaps(next, annotation, l)
1023                             && next.end_col <= annotation.end_col
1024                             && next.has_label()
1025                             && p == 0)
1026                     // Avoid #42595.
1027                     {
1028                         // This annotation needs a new line in the output.
1029                         p += 1;
1030                         break;
1031                     }
1032                 }
1033             }
1034             line_len = max(line_len, p);
1035         }
1036
1037         if line_len != 0 {
1038             line_len += 1;
1039         }
1040
1041         // If there are no annotations or the only annotations on this line are
1042         // MultilineLine, then there's only code being shown, stop processing.
1043         if line.annotations.iter().all(|a| a.is_line()) {
1044             return vec![];
1045         }
1046
1047         // Write the column separator.
1048         //
1049         // After this we will have:
1050         //
1051         // 2 |   fn foo() {
1052         //   |
1053         //   |
1054         //   |
1055         // 3 |
1056         // 4 |   }
1057         //   |
1058         for pos in 0..=line_len {
1059             draw_col_separator(buffer, line_offset + pos + 1, width_offset - 2);
1060         }
1061
1062         // Write the horizontal lines for multiline annotations
1063         // (only the first and last lines need this).
1064         //
1065         // After this we will have:
1066         //
1067         // 2 |   fn foo() {
1068         //   |  __________
1069         //   |
1070         //   |
1071         // 3 |
1072         // 4 |   }
1073         //   |  _
1074         for &(pos, annotation) in &annotations_position {
1075             let style = if annotation.is_primary {
1076                 Style::UnderlinePrimary
1077             } else {
1078                 Style::UnderlineSecondary
1079             };
1080             let pos = pos + 1;
1081             match annotation.annotation_type {
1082                 AnnotationType::MultilineStart(depth) | AnnotationType::MultilineEnd(depth) => {
1083                     draw_range(
1084                         buffer,
1085                         '_',
1086                         line_offset + pos,
1087                         width_offset + depth,
1088                         (code_offset + annotation.start_col).saturating_sub(left),
1089                         style,
1090                     );
1091                 }
1092                 _ if self.teach => {
1093                     buffer.set_style_range(
1094                         line_offset,
1095                         (code_offset + annotation.start_col).saturating_sub(left),
1096                         (code_offset + annotation.end_col).saturating_sub(left),
1097                         style,
1098                         annotation.is_primary,
1099                     );
1100                 }
1101                 _ => {}
1102             }
1103         }
1104
1105         // Write the vertical lines for labels that are on a different line as the underline.
1106         //
1107         // After this we will have:
1108         //
1109         // 2 |   fn foo() {
1110         //   |  __________
1111         //   | |    |
1112         //   | |
1113         // 3 | |
1114         // 4 | | }
1115         //   | |_
1116         for &(pos, annotation) in &annotations_position {
1117             let style = if annotation.is_primary {
1118                 Style::UnderlinePrimary
1119             } else {
1120                 Style::UnderlineSecondary
1121             };
1122             let pos = pos + 1;
1123
1124             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
1125                 for p in line_offset + 1..=line_offset + pos {
1126                     buffer.putc(
1127                         p,
1128                         (code_offset + annotation.start_col).saturating_sub(left),
1129                         '|',
1130                         style,
1131                     );
1132                 }
1133             }
1134             match annotation.annotation_type {
1135                 AnnotationType::MultilineStart(depth) => {
1136                     for p in line_offset + pos + 1..line_offset + line_len + 2 {
1137                         buffer.putc(p, width_offset + depth - 1, '|', style);
1138                     }
1139                 }
1140                 AnnotationType::MultilineEnd(depth) => {
1141                     for p in line_offset..=line_offset + pos {
1142                         buffer.putc(p, width_offset + depth - 1, '|', style);
1143                     }
1144                 }
1145                 _ => (),
1146             }
1147         }
1148
1149         // Write the labels on the annotations that actually have a label.
1150         //
1151         // After this we will have:
1152         //
1153         // 2 |   fn foo() {
1154         //   |  __________
1155         //   |      |
1156         //   |      something about `foo`
1157         // 3 |
1158         // 4 |   }
1159         //   |  _  test
1160         for &(pos, annotation) in &annotations_position {
1161             let style =
1162                 if annotation.is_primary { Style::LabelPrimary } else { Style::LabelSecondary };
1163             let (pos, col) = if pos == 0 {
1164                 (pos + 1, (annotation.end_col + 1).saturating_sub(left))
1165             } else {
1166                 (pos + 2, annotation.start_col.saturating_sub(left))
1167             };
1168             if let Some(ref label) = annotation.label {
1169                 buffer.puts(line_offset + pos, code_offset + col, label, style);
1170             }
1171         }
1172
1173         // Sort from biggest span to smallest span so that smaller spans are
1174         // represented in the output:
1175         //
1176         // x | fn foo()
1177         //   | ^^^---^^
1178         //   | |  |
1179         //   | |  something about `foo`
1180         //   | something about `fn foo()`
1181         annotations_position.sort_by_key(|(_, ann)| {
1182             // Decreasing order. When annotations share the same length, prefer `Primary`.
1183             (Reverse(ann.len()), ann.is_primary)
1184         });
1185
1186         // Write the underlines.
1187         //
1188         // After this we will have:
1189         //
1190         // 2 |   fn foo() {
1191         //   |  ____-_____^
1192         //   |      |
1193         //   |      something about `foo`
1194         // 3 |
1195         // 4 |   }
1196         //   |  _^  test
1197         for &(_, annotation) in &annotations_position {
1198             let (underline, style) = if annotation.is_primary {
1199                 ('^', Style::UnderlinePrimary)
1200             } else {
1201                 ('-', Style::UnderlineSecondary)
1202             };
1203             for p in annotation.start_col..annotation.end_col {
1204                 buffer.putc(
1205                     line_offset + 1,
1206                     (code_offset + p).saturating_sub(left),
1207                     underline,
1208                     style,
1209                 );
1210             }
1211         }
1212         annotations_position
1213             .iter()
1214             .filter_map(|&(_, annotation)| match annotation.annotation_type {
1215                 AnnotationType::MultilineStart(p) | AnnotationType::MultilineEnd(p) => {
1216                     let style = if annotation.is_primary {
1217                         Style::LabelPrimary
1218                     } else {
1219                         Style::LabelSecondary
1220                     };
1221                     Some((p, style))
1222                 }
1223                 _ => None,
1224             })
1225             .collect::<Vec<_>>()
1226     }
1227
1228     fn get_multispan_max_line_num(&mut self, msp: &MultiSpan) -> usize {
1229         let Some(ref sm) = self.sm else {
1230             return 0;
1231         };
1232
1233         let will_be_emitted = |span: Span| {
1234             !span.is_dummy() && {
1235                 let file = sm.lookup_source_file(span.hi());
1236                 sm.ensure_source_file_source_present(file)
1237             }
1238         };
1239
1240         let mut max = 0;
1241         for primary_span in msp.primary_spans() {
1242             if will_be_emitted(*primary_span) {
1243                 let hi = sm.lookup_char_pos(primary_span.hi());
1244                 max = (hi.line).max(max);
1245             }
1246         }
1247         if !self.short_message {
1248             for span_label in msp.span_labels() {
1249                 if will_be_emitted(span_label.span) {
1250                     let hi = sm.lookup_char_pos(span_label.span.hi());
1251                     max = (hi.line).max(max);
1252                 }
1253             }
1254         }
1255
1256         max
1257     }
1258
1259     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
1260         let primary = self.get_multispan_max_line_num(span);
1261         children
1262             .iter()
1263             .map(|sub| self.get_multispan_max_line_num(&sub.span))
1264             .max()
1265             .unwrap_or(0)
1266             .max(primary)
1267     }
1268
1269     /// Adds a left margin to every line but the first, given a padding length and the label being
1270     /// displayed, keeping the provided highlighting.
1271     fn msg_to_buffer(
1272         &self,
1273         buffer: &mut StyledBuffer,
1274         msg: &[(DiagnosticMessage, Style)],
1275         args: &FluentArgs<'_>,
1276         padding: usize,
1277         label: &str,
1278         override_style: Option<Style>,
1279     ) {
1280         // The extra 5 ` ` is padding that's always needed to align to the `note: `:
1281         //
1282         //   error: message
1283         //     --> file.rs:13:20
1284         //      |
1285         //   13 |     <CODE>
1286         //      |      ^^^^
1287         //      |
1288         //      = note: multiline
1289         //              message
1290         //   ++^^^----xx
1291         //    |  |   | |
1292         //    |  |   | magic `2`
1293         //    |  |   length of label
1294         //    |  magic `3`
1295         //    `max_line_num_len`
1296         let padding = " ".repeat(padding + label.len() + 5);
1297
1298         /// Returns `override` if it is present and `style` is `NoStyle` or `style` otherwise
1299         fn style_or_override(style: Style, override_: Option<Style>) -> Style {
1300             match (style, override_) {
1301                 (Style::NoStyle, Some(override_)) => override_,
1302                 _ => style,
1303             }
1304         }
1305
1306         let mut line_number = 0;
1307
1308         // Provided the following diagnostic message:
1309         //
1310         //     let msg = vec![
1311         //       ("
1312         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
1313         //       ("looks", Style::Highlight),
1314         //       ("with\nvery ", Style::NoStyle),
1315         //       ("weird", Style::Highlight),
1316         //       (" formats\n", Style::NoStyle),
1317         //       ("see?", Style::Highlight),
1318         //     ];
1319         //
1320         // the expected output on a note is (* surround the highlighted text)
1321         //
1322         //        = note: highlighted multiline
1323         //                string to
1324         //                see how it *looks* with
1325         //                very *weird* formats
1326         //                see?
1327         for (text, style) in msg.iter() {
1328             let text = self.translate_message(text, args);
1329             let lines = text.split('\n').collect::<Vec<_>>();
1330             if lines.len() > 1 {
1331                 for (i, line) in lines.iter().enumerate() {
1332                     if i != 0 {
1333                         line_number += 1;
1334                         buffer.append(line_number, &padding, Style::NoStyle);
1335                     }
1336                     buffer.append(line_number, line, style_or_override(*style, override_style));
1337                 }
1338             } else {
1339                 buffer.append(line_number, &text, style_or_override(*style, override_style));
1340             }
1341         }
1342     }
1343
1344     #[instrument(level = "trace", skip(self, args), ret)]
1345     fn emit_message_default(
1346         &mut self,
1347         msp: &MultiSpan,
1348         msg: &[(DiagnosticMessage, Style)],
1349         args: &FluentArgs<'_>,
1350         code: &Option<DiagnosticId>,
1351         level: &Level,
1352         max_line_num_len: usize,
1353         is_secondary: bool,
1354         emitted_at: Option<&DiagnosticLocation>,
1355     ) -> io::Result<()> {
1356         let mut buffer = StyledBuffer::new();
1357
1358         if !msp.has_primary_spans() && !msp.has_span_labels() && is_secondary && !self.short_message
1359         {
1360             // This is a secondary message with no span info
1361             for _ in 0..max_line_num_len {
1362                 buffer.prepend(0, " ", Style::NoStyle);
1363             }
1364             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
1365             if *level != Level::FailureNote {
1366                 buffer.append(0, level.to_str(), Style::MainHeaderMsg);
1367                 buffer.append(0, ": ", Style::NoStyle);
1368             }
1369             self.msg_to_buffer(&mut buffer, msg, args, max_line_num_len, "note", None);
1370         } else {
1371             let mut label_width = 0;
1372             // The failure note level itself does not provide any useful diagnostic information
1373             if *level != Level::FailureNote {
1374                 buffer.append(0, level.to_str(), Style::Level(*level));
1375                 label_width += level.to_str().len();
1376             }
1377             // only render error codes, not lint codes
1378             if let Some(DiagnosticId::Error(ref code)) = *code {
1379                 buffer.append(0, "[", Style::Level(*level));
1380                 buffer.append(0, code, Style::Level(*level));
1381                 buffer.append(0, "]", Style::Level(*level));
1382                 label_width += 2 + code.len();
1383             }
1384             let header_style = if is_secondary { Style::HeaderMsg } else { Style::MainHeaderMsg };
1385             if *level != Level::FailureNote {
1386                 buffer.append(0, ": ", header_style);
1387                 label_width += 2;
1388             }
1389             for (text, _) in msg.iter() {
1390                 let text = self.translate_message(text, args);
1391                 // Account for newlines to align output to its label.
1392                 for (line, text) in normalize_whitespace(&text).lines().enumerate() {
1393                     buffer.append(
1394                         0 + line,
1395                         &format!(
1396                             "{}{}",
1397                             if line == 0 { String::new() } else { " ".repeat(label_width) },
1398                             text
1399                         ),
1400                         header_style,
1401                     );
1402                 }
1403             }
1404         }
1405         let mut annotated_files = FileWithAnnotatedLines::collect_annotations(self, args, msp);
1406         trace!("{annotated_files:#?}");
1407
1408         // Make sure our primary file comes first
1409         let primary_span = msp.primary_span().unwrap_or_default();
1410         let (Some(sm), false) = (self.sm.as_ref(), primary_span.is_dummy()) else {
1411             // If we don't have span information, emit and exit
1412             return emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message);
1413         };
1414         let primary_lo = sm.lookup_char_pos(primary_span.lo());
1415         if let Ok(pos) =
1416             annotated_files.binary_search_by(|x| x.file.name.cmp(&primary_lo.file.name))
1417         {
1418             annotated_files.swap(0, pos);
1419         }
1420
1421         // Print out the annotate source lines that correspond with the error
1422         for annotated_file in annotated_files {
1423             // we can't annotate anything if the source is unavailable.
1424             if !sm.ensure_source_file_source_present(annotated_file.file.clone()) {
1425                 if !self.short_message {
1426                     // We'll just print an unannotated message.
1427                     for (annotation_id, line) in annotated_file.lines.iter().enumerate() {
1428                         let mut annotations = line.annotations.clone();
1429                         annotations.sort_by_key(|a| Reverse(a.start_col));
1430                         let mut line_idx = buffer.num_lines();
1431
1432                         let labels: Vec<_> = annotations
1433                             .iter()
1434                             .filter_map(|a| Some((a.label.as_ref()?, a.is_primary)))
1435                             .filter(|(l, _)| !l.is_empty())
1436                             .collect();
1437
1438                         if annotation_id == 0 || !labels.is_empty() {
1439                             buffer.append(
1440                                 line_idx,
1441                                 &format!(
1442                                     "{}:{}:{}",
1443                                     sm.filename_for_diagnostics(&annotated_file.file.name),
1444                                     sm.doctest_offset_line(
1445                                         &annotated_file.file.name,
1446                                         line.line_index
1447                                     ),
1448                                     annotations[0].start_col + 1,
1449                                 ),
1450                                 Style::LineAndColumn,
1451                             );
1452                             if annotation_id == 0 {
1453                                 buffer.prepend(line_idx, "--> ", Style::LineNumber);
1454                             } else {
1455                                 buffer.prepend(line_idx, "::: ", Style::LineNumber);
1456                             }
1457                             for _ in 0..max_line_num_len {
1458                                 buffer.prepend(line_idx, " ", Style::NoStyle);
1459                             }
1460                             line_idx += 1;
1461                         }
1462                         for (label, is_primary) in labels.into_iter() {
1463                             let style = if is_primary {
1464                                 Style::LabelPrimary
1465                             } else {
1466                                 Style::LabelSecondary
1467                             };
1468                             buffer.prepend(line_idx, " |", Style::LineNumber);
1469                             for _ in 0..max_line_num_len {
1470                                 buffer.prepend(line_idx, " ", Style::NoStyle);
1471                             }
1472                             line_idx += 1;
1473                             buffer.append(line_idx, " = note: ", style);
1474                             for _ in 0..max_line_num_len {
1475                                 buffer.prepend(line_idx, " ", Style::NoStyle);
1476                             }
1477                             buffer.append(line_idx, label, style);
1478                             line_idx += 1;
1479                         }
1480                     }
1481                 }
1482                 continue;
1483             }
1484
1485             // print out the span location and spacer before we print the annotated source
1486             // to do this, we need to know if this span will be primary
1487             let is_primary = primary_lo.file.name == annotated_file.file.name;
1488             if is_primary {
1489                 let loc = primary_lo.clone();
1490                 if !self.short_message {
1491                     // remember where we are in the output buffer for easy reference
1492                     let buffer_msg_line_offset = buffer.num_lines();
1493
1494                     buffer.prepend(buffer_msg_line_offset, "--> ", Style::LineNumber);
1495                     buffer.append(
1496                         buffer_msg_line_offset,
1497                         &format!(
1498                             "{}:{}:{}",
1499                             sm.filename_for_diagnostics(&loc.file.name),
1500                             sm.doctest_offset_line(&loc.file.name, loc.line),
1501                             loc.col.0 + 1,
1502                         ),
1503                         Style::LineAndColumn,
1504                     );
1505                     for _ in 0..max_line_num_len {
1506                         buffer.prepend(buffer_msg_line_offset, " ", Style::NoStyle);
1507                     }
1508                 } else {
1509                     buffer.prepend(
1510                         0,
1511                         &format!(
1512                             "{}:{}:{}: ",
1513                             sm.filename_for_diagnostics(&loc.file.name),
1514                             sm.doctest_offset_line(&loc.file.name, loc.line),
1515                             loc.col.0 + 1,
1516                         ),
1517                         Style::LineAndColumn,
1518                     );
1519                 }
1520             } else if !self.short_message {
1521                 // remember where we are in the output buffer for easy reference
1522                 let buffer_msg_line_offset = buffer.num_lines();
1523
1524                 // Add spacing line
1525                 draw_col_separator_no_space(
1526                     &mut buffer,
1527                     buffer_msg_line_offset,
1528                     max_line_num_len + 1,
1529                 );
1530
1531                 // Then, the secondary file indicator
1532                 buffer.prepend(buffer_msg_line_offset + 1, "::: ", Style::LineNumber);
1533                 let loc = if let Some(first_line) = annotated_file.lines.first() {
1534                     let col = if let Some(first_annotation) = first_line.annotations.first() {
1535                         format!(":{}", first_annotation.start_col + 1)
1536                     } else {
1537                         String::new()
1538                     };
1539                     format!(
1540                         "{}:{}{}",
1541                         sm.filename_for_diagnostics(&annotated_file.file.name),
1542                         sm.doctest_offset_line(&annotated_file.file.name, first_line.line_index),
1543                         col
1544                     )
1545                 } else {
1546                     format!("{}", sm.filename_for_diagnostics(&annotated_file.file.name))
1547                 };
1548                 buffer.append(buffer_msg_line_offset + 1, &loc, Style::LineAndColumn);
1549                 for _ in 0..max_line_num_len {
1550                     buffer.prepend(buffer_msg_line_offset + 1, " ", Style::NoStyle);
1551                 }
1552             }
1553
1554             if !self.short_message {
1555                 // Put in the spacer between the location and annotated source
1556                 let buffer_msg_line_offset = buffer.num_lines();
1557                 draw_col_separator_no_space(
1558                     &mut buffer,
1559                     buffer_msg_line_offset,
1560                     max_line_num_len + 1,
1561                 );
1562
1563                 // Contains the vertical lines' positions for active multiline annotations
1564                 let mut multilines = FxIndexMap::default();
1565
1566                 // Get the left-side margin to remove it
1567                 let mut whitespace_margin = usize::MAX;
1568                 for line_idx in 0..annotated_file.lines.len() {
1569                     let file = annotated_file.file.clone();
1570                     let line = &annotated_file.lines[line_idx];
1571                     if let Some(source_string) = file.get_line(line.line_index - 1) {
1572                         let leading_whitespace = source_string
1573                             .chars()
1574                             .take_while(|c| c.is_whitespace())
1575                             .map(|c| {
1576                                 match c {
1577                                     // Tabs are displayed as 4 spaces
1578                                     '\t' => 4,
1579                                     _ => 1,
1580                                 }
1581                             })
1582                             .sum();
1583                         if source_string.chars().any(|c| !c.is_whitespace()) {
1584                             whitespace_margin = min(whitespace_margin, leading_whitespace);
1585                         }
1586                     }
1587                 }
1588                 if whitespace_margin == usize::MAX {
1589                     whitespace_margin = 0;
1590                 }
1591
1592                 // Left-most column any visible span points at.
1593                 let mut span_left_margin = usize::MAX;
1594                 for line in &annotated_file.lines {
1595                     for ann in &line.annotations {
1596                         span_left_margin = min(span_left_margin, ann.start_col);
1597                         span_left_margin = min(span_left_margin, ann.end_col);
1598                     }
1599                 }
1600                 if span_left_margin == usize::MAX {
1601                     span_left_margin = 0;
1602                 }
1603
1604                 // Right-most column any visible span points at.
1605                 let mut span_right_margin = 0;
1606                 let mut label_right_margin = 0;
1607                 let mut max_line_len = 0;
1608                 for line in &annotated_file.lines {
1609                     max_line_len = max(
1610                         max_line_len,
1611                         annotated_file.file.get_line(line.line_index - 1).map_or(0, |s| s.len()),
1612                     );
1613                     for ann in &line.annotations {
1614                         span_right_margin = max(span_right_margin, ann.start_col);
1615                         span_right_margin = max(span_right_margin, ann.end_col);
1616                         // FIXME: account for labels not in the same line
1617                         let label_right = ann.label.as_ref().map_or(0, |l| l.len() + 1);
1618                         label_right_margin = max(label_right_margin, ann.end_col + label_right);
1619                     }
1620                 }
1621
1622                 let width_offset = 3 + max_line_num_len;
1623                 let code_offset = if annotated_file.multiline_depth == 0 {
1624                     width_offset
1625                 } else {
1626                     width_offset + annotated_file.multiline_depth + 1
1627                 };
1628
1629                 let column_width = if let Some(width) = self.diagnostic_width {
1630                     width.saturating_sub(code_offset)
1631                 } else if self.ui_testing {
1632                     DEFAULT_COLUMN_WIDTH
1633                 } else {
1634                     termize::dimensions()
1635                         .map(|(w, _)| w.saturating_sub(code_offset))
1636                         .unwrap_or(DEFAULT_COLUMN_WIDTH)
1637                 };
1638
1639                 let margin = Margin::new(
1640                     whitespace_margin,
1641                     span_left_margin,
1642                     span_right_margin,
1643                     label_right_margin,
1644                     column_width,
1645                     max_line_len,
1646                 );
1647
1648                 // Next, output the annotate source for this file
1649                 for line_idx in 0..annotated_file.lines.len() {
1650                     let previous_buffer_line = buffer.num_lines();
1651
1652                     let depths = self.render_source_line(
1653                         &mut buffer,
1654                         annotated_file.file.clone(),
1655                         &annotated_file.lines[line_idx],
1656                         width_offset,
1657                         code_offset,
1658                         margin,
1659                     );
1660
1661                     let mut to_add = FxHashMap::default();
1662
1663                     for (depth, style) in depths {
1664                         if multilines.remove(&depth).is_none() {
1665                             to_add.insert(depth, style);
1666                         }
1667                     }
1668
1669                     // Set the multiline annotation vertical lines to the left of
1670                     // the code in this line.
1671                     for (depth, style) in &multilines {
1672                         for line in previous_buffer_line..buffer.num_lines() {
1673                             draw_multiline_line(&mut buffer, line, width_offset, *depth, *style);
1674                         }
1675                     }
1676                     // check to see if we need to print out or elide lines that come between
1677                     // this annotated line and the next one.
1678                     if line_idx < (annotated_file.lines.len() - 1) {
1679                         let line_idx_delta = annotated_file.lines[line_idx + 1].line_index
1680                             - annotated_file.lines[line_idx].line_index;
1681                         if line_idx_delta > 2 {
1682                             let last_buffer_line_num = buffer.num_lines();
1683                             buffer.puts(last_buffer_line_num, 0, "...", Style::LineNumber);
1684
1685                             // Set the multiline annotation vertical lines on `...` bridging line.
1686                             for (depth, style) in &multilines {
1687                                 draw_multiline_line(
1688                                     &mut buffer,
1689                                     last_buffer_line_num,
1690                                     width_offset,
1691                                     *depth,
1692                                     *style,
1693                                 );
1694                             }
1695                         } else if line_idx_delta == 2 {
1696                             let unannotated_line = annotated_file
1697                                 .file
1698                                 .get_line(annotated_file.lines[line_idx].line_index)
1699                                 .unwrap_or_else(|| Cow::from(""));
1700
1701                             let last_buffer_line_num = buffer.num_lines();
1702
1703                             self.draw_line(
1704                                 &mut buffer,
1705                                 &normalize_whitespace(&unannotated_line),
1706                                 annotated_file.lines[line_idx + 1].line_index - 1,
1707                                 last_buffer_line_num,
1708                                 width_offset,
1709                                 code_offset,
1710                                 margin,
1711                             );
1712
1713                             for (depth, style) in &multilines {
1714                                 draw_multiline_line(
1715                                     &mut buffer,
1716                                     last_buffer_line_num,
1717                                     width_offset,
1718                                     *depth,
1719                                     *style,
1720                                 );
1721                             }
1722                         }
1723                     }
1724
1725                     multilines.extend(&to_add);
1726                 }
1727             }
1728             trace!("buffer: {:#?}", buffer.render());
1729         }
1730
1731         if let Some(tracked) = emitted_at {
1732             let track = format!("-Ztrack-diagnostics: created at {tracked}");
1733             let len = buffer.num_lines();
1734             buffer.append(len, &track, Style::NoStyle);
1735         }
1736
1737         // final step: take our styled buffer, render it, then output it
1738         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1739
1740         Ok(())
1741     }
1742
1743     fn emit_suggestion_default(
1744         &mut self,
1745         span: &MultiSpan,
1746         suggestion: &CodeSuggestion,
1747         args: &FluentArgs<'_>,
1748         level: &Level,
1749         max_line_num_len: usize,
1750     ) -> io::Result<()> {
1751         let Some(ref sm) = self.sm else {
1752             return Ok(());
1753         };
1754
1755         // Render the replacements for each suggestion
1756         let suggestions = suggestion.splice_lines(sm);
1757         debug!("emit_suggestion_default: suggestions={:?}", suggestions);
1758
1759         if suggestions.is_empty() {
1760             // Suggestions coming from macros can have malformed spans. This is a heavy handed
1761             // approach to avoid ICEs by ignoring the suggestion outright.
1762             return Ok(());
1763         }
1764
1765         let mut buffer = StyledBuffer::new();
1766
1767         // Render the suggestion message
1768         buffer.append(0, level.to_str(), Style::Level(*level));
1769         buffer.append(0, ": ", Style::HeaderMsg);
1770
1771         self.msg_to_buffer(
1772             &mut buffer,
1773             &[(suggestion.msg.to_owned(), Style::NoStyle)],
1774             args,
1775             max_line_num_len,
1776             "suggestion",
1777             Some(Style::HeaderMsg),
1778         );
1779
1780         let mut row_num = 2;
1781         draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
1782         let mut notice_capitalization = false;
1783         for (complete, parts, highlights, only_capitalization) in
1784             suggestions.iter().take(MAX_SUGGESTIONS)
1785         {
1786             notice_capitalization |= only_capitalization;
1787
1788             let has_deletion = parts.iter().any(|p| p.is_deletion(sm));
1789             let is_multiline = complete.lines().count() > 1;
1790
1791             if let Some(span) = span.primary_span() {
1792                 // Compare the primary span of the diagnostic with the span of the suggestion
1793                 // being emitted.  If they belong to the same file, we don't *need* to show the
1794                 // file name, saving in verbosity, but if it *isn't* we do need it, otherwise we're
1795                 // telling users to make a change but not clarifying *where*.
1796                 let loc = sm.lookup_char_pos(parts[0].span.lo());
1797                 if loc.file.name != sm.span_to_filename(span) && loc.file.name.is_real() {
1798                     buffer.puts(row_num - 1, 0, "--> ", Style::LineNumber);
1799                     buffer.append(
1800                         row_num - 1,
1801                         &format!(
1802                             "{}:{}:{}",
1803                             sm.filename_for_diagnostics(&loc.file.name),
1804                             sm.doctest_offset_line(&loc.file.name, loc.line),
1805                             loc.col.0 + 1,
1806                         ),
1807                         Style::LineAndColumn,
1808                     );
1809                     for _ in 0..max_line_num_len {
1810                         buffer.prepend(row_num - 1, " ", Style::NoStyle);
1811                     }
1812                     row_num += 1;
1813                 }
1814             }
1815             let show_code_change = if has_deletion && !is_multiline {
1816                 DisplaySuggestion::Diff
1817             } else if (parts.len() != 1 || parts[0].snippet.trim() != complete.trim())
1818                 && !is_multiline
1819             {
1820                 DisplaySuggestion::Underline
1821             } else {
1822                 DisplaySuggestion::None
1823             };
1824
1825             if let DisplaySuggestion::Diff = show_code_change {
1826                 row_num += 1;
1827             }
1828
1829             let file_lines = sm
1830                 .span_to_lines(parts[0].span)
1831                 .expect("span_to_lines failed when emitting suggestion");
1832
1833             assert!(!file_lines.lines.is_empty() || parts[0].span.is_dummy());
1834
1835             let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
1836             draw_col_separator_no_space(&mut buffer, row_num - 1, max_line_num_len + 1);
1837             let mut lines = complete.lines();
1838             if lines.clone().next().is_none() {
1839                 // Account for a suggestion to completely remove a line(s) with whitespace (#94192).
1840                 let line_end = sm.lookup_char_pos(parts[0].span.hi()).line;
1841                 for line in line_start..=line_end {
1842                     buffer.puts(
1843                         row_num - 1 + line - line_start,
1844                         0,
1845                         &self.maybe_anonymized(line),
1846                         Style::LineNumber,
1847                     );
1848                     buffer.puts(
1849                         row_num - 1 + line - line_start,
1850                         max_line_num_len + 1,
1851                         "- ",
1852                         Style::Removal,
1853                     );
1854                     buffer.puts(
1855                         row_num - 1 + line - line_start,
1856                         max_line_num_len + 3,
1857                         &normalize_whitespace(&file_lines.file.get_line(line - 1).unwrap()),
1858                         Style::Removal,
1859                     );
1860                 }
1861                 row_num += line_end - line_start;
1862             }
1863             let mut unhighlighted_lines = Vec::new();
1864             for (line_pos, (line, highlight_parts)) in lines.by_ref().zip(highlights).enumerate() {
1865                 debug!(%line_pos, %line, ?highlight_parts);
1866
1867                 // Remember lines that are not highlighted to hide them if needed
1868                 if highlight_parts.is_empty() {
1869                     unhighlighted_lines.push((line_pos, line));
1870                     continue;
1871                 }
1872
1873                 match unhighlighted_lines.len() {
1874                     0 => (),
1875                     // Since we show first line, "..." line and last line,
1876                     // There is no reason to hide if there are 3 or less lines
1877                     // (because then we just replace a line with ... which is
1878                     // not helpful)
1879                     n if n <= 3 => unhighlighted_lines.drain(..).for_each(|(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                     // Print first unhighlighted line, "..." and last unhighlighted line, like so:
1894                     //
1895                     // LL | this line was highlighted
1896                     // LL | this line is just for context
1897                     //   ...
1898                     // LL | this line is just for context
1899                     // LL | this line was highlighted
1900                     _ => {
1901                         let last_line = unhighlighted_lines.pop();
1902                         let first_line = unhighlighted_lines.drain(..).next();
1903
1904                         first_line.map(|(p, l)| {
1905                             self.draw_code_line(
1906                                 &mut buffer,
1907                                 &mut row_num,
1908                                 &Vec::new(),
1909                                 p,
1910                                 l,
1911                                 line_start,
1912                                 show_code_change,
1913                                 max_line_num_len,
1914                                 &file_lines,
1915                                 is_multiline,
1916                             )
1917                         });
1918
1919                         buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
1920                         row_num += 1;
1921
1922                         last_line.map(|(p, l)| {
1923                             self.draw_code_line(
1924                                 &mut buffer,
1925                                 &mut row_num,
1926                                 &Vec::new(),
1927                                 p,
1928                                 l,
1929                                 line_start,
1930                                 show_code_change,
1931                                 max_line_num_len,
1932                                 &file_lines,
1933                                 is_multiline,
1934                             )
1935                         });
1936                     }
1937                 }
1938
1939                 self.draw_code_line(
1940                     &mut buffer,
1941                     &mut row_num,
1942                     highlight_parts,
1943                     line_pos,
1944                     line,
1945                     line_start,
1946                     show_code_change,
1947                     max_line_num_len,
1948                     &file_lines,
1949                     is_multiline,
1950                 )
1951             }
1952
1953             // This offset and the ones below need to be signed to account for replacement code
1954             // that is shorter than the original code.
1955             let mut offsets: Vec<(usize, isize)> = Vec::new();
1956             // Only show an underline in the suggestions if the suggestion is not the
1957             // entirety of the code being shown and the displayed code is not multiline.
1958             if let DisplaySuggestion::Diff | DisplaySuggestion::Underline = show_code_change {
1959                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
1960                 for part in parts {
1961                     let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
1962                     let span_end_pos = sm.lookup_char_pos(part.span.hi()).col_display;
1963
1964                     // If this addition is _only_ whitespace, then don't trim it,
1965                     // or else we're just not rendering anything.
1966                     let is_whitespace_addition = part.snippet.trim().is_empty();
1967
1968                     // Do not underline the leading...
1969                     let start = if is_whitespace_addition {
1970                         0
1971                     } else {
1972                         part.snippet.len().saturating_sub(part.snippet.trim_start().len())
1973                     };
1974                     // ...or trailing spaces. Account for substitutions containing unicode
1975                     // characters.
1976                     let sub_len: usize =
1977                         if is_whitespace_addition { &part.snippet } else { part.snippet.trim() }
1978                             .chars()
1979                             .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1980                             .sum();
1981
1982                     let offset: isize = offsets
1983                         .iter()
1984                         .filter_map(
1985                             |(start, v)| if span_start_pos <= *start { None } else { Some(v) },
1986                         )
1987                         .sum();
1988                     let underline_start = (span_start_pos + start) as isize + offset;
1989                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
1990                     assert!(underline_start >= 0 && underline_end >= 0);
1991                     let padding: usize = max_line_num_len + 3;
1992                     for p in underline_start..underline_end {
1993                         if let DisplaySuggestion::Underline = show_code_change {
1994                             // If this is a replacement, underline with `^`, if this is an addition
1995                             // underline with `+`.
1996                             buffer.putc(
1997                                 row_num,
1998                                 (padding as isize + p) as usize,
1999                                 if part.is_addition(sm) { '+' } else { '~' },
2000                                 Style::Addition,
2001                             );
2002                         }
2003                     }
2004                     if let DisplaySuggestion::Diff = show_code_change {
2005                         // Colorize removal with red in diff format.
2006                         buffer.set_style_range(
2007                             row_num - 2,
2008                             (padding as isize + span_start_pos as isize) as usize,
2009                             (padding as isize + span_end_pos as isize) as usize,
2010                             Style::Removal,
2011                             true,
2012                         );
2013                     }
2014
2015                     // length of the code after substitution
2016                     let full_sub_len = part
2017                         .snippet
2018                         .chars()
2019                         .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
2020                         .sum::<usize>() as isize;
2021
2022                     // length of the code to be substituted
2023                     let snippet_len = span_end_pos as isize - span_start_pos as isize;
2024                     // For multiple substitutions, use the position *after* the previous
2025                     // substitutions have happened, only when further substitutions are
2026                     // located strictly after.
2027                     offsets.push((span_end_pos, full_sub_len - snippet_len));
2028                 }
2029                 row_num += 1;
2030             }
2031
2032             // if we elided some lines, add an ellipsis
2033             if lines.next().is_some() {
2034                 buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
2035             } else if let DisplaySuggestion::None = show_code_change {
2036                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
2037                 row_num += 1;
2038             }
2039         }
2040         if suggestions.len() > MAX_SUGGESTIONS {
2041             let others = suggestions.len() - MAX_SUGGESTIONS;
2042             let msg = format!("and {} other candidate{}", others, pluralize!(others));
2043             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
2044         } else if notice_capitalization {
2045             let msg = "notice the capitalization difference";
2046             buffer.puts(row_num, max_line_num_len + 3, msg, Style::NoStyle);
2047         }
2048         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
2049         Ok(())
2050     }
2051
2052     #[instrument(level = "trace", skip(self, args, code, children, suggestions))]
2053     fn emit_messages_default(
2054         &mut self,
2055         level: &Level,
2056         message: &[(DiagnosticMessage, Style)],
2057         args: &FluentArgs<'_>,
2058         code: &Option<DiagnosticId>,
2059         span: &MultiSpan,
2060         children: &[SubDiagnostic],
2061         suggestions: &[CodeSuggestion],
2062         emitted_at: Option<&DiagnosticLocation>,
2063     ) {
2064         let max_line_num_len = if self.ui_testing {
2065             ANONYMIZED_LINE_NUM.len()
2066         } else {
2067             let n = self.get_max_line_num(span, children);
2068             num_decimal_digits(n)
2069         };
2070
2071         match self.emit_message_default(
2072             span,
2073             message,
2074             args,
2075             code,
2076             level,
2077             max_line_num_len,
2078             false,
2079             emitted_at,
2080         ) {
2081             Ok(()) => {
2082                 if !children.is_empty()
2083                     || suggestions.iter().any(|s| s.style != SuggestionStyle::CompletelyHidden)
2084                 {
2085                     let mut buffer = StyledBuffer::new();
2086                     if !self.short_message {
2087                         draw_col_separator_no_space(&mut buffer, 0, max_line_num_len + 1);
2088                     }
2089                     if let Err(e) = emit_to_destination(
2090                         &buffer.render(),
2091                         level,
2092                         &mut self.dst,
2093                         self.short_message,
2094                     ) {
2095                         panic!("failed to emit error: {}", e)
2096                     }
2097                 }
2098                 if !self.short_message {
2099                     for child in children {
2100                         let span = child.render_span.as_ref().unwrap_or(&child.span);
2101                         if let Err(err) = self.emit_message_default(
2102                             span,
2103                             &child.message,
2104                             args,
2105                             &None,
2106                             &child.level,
2107                             max_line_num_len,
2108                             true,
2109                             None,
2110                         ) {
2111                             panic!("failed to emit error: {}", err);
2112                         }
2113                     }
2114                     for sugg in suggestions {
2115                         if sugg.style == SuggestionStyle::CompletelyHidden {
2116                             // do not display this suggestion, it is meant only for tools
2117                         } else if sugg.style == SuggestionStyle::HideCodeAlways {
2118                             if let Err(e) = self.emit_message_default(
2119                                 &MultiSpan::new(),
2120                                 &[(sugg.msg.to_owned(), Style::HeaderMsg)],
2121                                 args,
2122                                 &None,
2123                                 &Level::Help,
2124                                 max_line_num_len,
2125                                 true,
2126                                 None,
2127                             ) {
2128                                 panic!("failed to emit error: {}", e);
2129                             }
2130                         } else if let Err(e) = self.emit_suggestion_default(
2131                             span,
2132                             sugg,
2133                             args,
2134                             &Level::Help,
2135                             max_line_num_len,
2136                         ) {
2137                             panic!("failed to emit error: {}", e);
2138                         };
2139                     }
2140                 }
2141             }
2142             Err(e) => panic!("failed to emit error: {}", e),
2143         }
2144
2145         let mut dst = self.dst.writable();
2146         match writeln!(dst) {
2147             Err(e) => panic!("failed to emit error: {}", e),
2148             _ => {
2149                 if let Err(e) = dst.flush() {
2150                     panic!("failed to emit error: {}", e)
2151                 }
2152             }
2153         }
2154     }
2155
2156     fn draw_code_line(
2157         &self,
2158         buffer: &mut StyledBuffer,
2159         row_num: &mut usize,
2160         highlight_parts: &Vec<SubstitutionHighlight>,
2161         line_pos: usize,
2162         line: &str,
2163         line_start: usize,
2164         show_code_change: DisplaySuggestion,
2165         max_line_num_len: usize,
2166         file_lines: &FileLines,
2167         is_multiline: bool,
2168     ) {
2169         // Print the span column to avoid confusion
2170         buffer.puts(*row_num, 0, &self.maybe_anonymized(line_start + line_pos), Style::LineNumber);
2171         if let DisplaySuggestion::Diff = show_code_change {
2172             // Add the line number for both addition and removal to drive the point home.
2173             //
2174             // N - fn foo<A: T>(bar: A) {
2175             // N + fn foo(bar: impl T) {
2176             buffer.puts(
2177                 *row_num - 1,
2178                 0,
2179                 &self.maybe_anonymized(line_start + line_pos),
2180                 Style::LineNumber,
2181             );
2182             buffer.puts(*row_num - 1, max_line_num_len + 1, "- ", Style::Removal);
2183             buffer.puts(
2184                 *row_num - 1,
2185                 max_line_num_len + 3,
2186                 &normalize_whitespace(
2187                     &file_lines.file.get_line(file_lines.lines[line_pos].line_index).unwrap(),
2188                 ),
2189                 Style::NoStyle,
2190             );
2191             buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
2192         } else if is_multiline {
2193             match &highlight_parts[..] {
2194                 [SubstitutionHighlight { start: 0, end }] if *end == line.len() => {
2195                     buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
2196                 }
2197                 [] => {
2198                     draw_col_separator(buffer, *row_num, max_line_num_len + 1);
2199                 }
2200                 _ => {
2201                     buffer.puts(*row_num, max_line_num_len + 1, "~ ", Style::Addition);
2202                 }
2203             }
2204         } else {
2205             draw_col_separator(buffer, *row_num, max_line_num_len + 1);
2206         }
2207
2208         // print the suggestion
2209         buffer.append(*row_num, &normalize_whitespace(line), Style::NoStyle);
2210
2211         // Colorize addition/replacements with green.
2212         for &SubstitutionHighlight { start, end } in highlight_parts {
2213             // Account for tabs when highlighting (#87972).
2214             let tabs: usize = line
2215                 .chars()
2216                 .take(start)
2217                 .map(|ch| match ch {
2218                     '\t' => 3,
2219                     _ => 0,
2220                 })
2221                 .sum();
2222             buffer.set_style_range(
2223                 *row_num,
2224                 max_line_num_len + 3 + start + tabs,
2225                 max_line_num_len + 3 + end + tabs,
2226                 Style::Addition,
2227                 true,
2228             );
2229         }
2230         *row_num += 1;
2231     }
2232 }
2233
2234 #[derive(Clone, Copy, Debug)]
2235 enum DisplaySuggestion {
2236     Underline,
2237     Diff,
2238     None,
2239 }
2240
2241 impl FileWithAnnotatedLines {
2242     /// Preprocess all the annotations so that they are grouped by file and by line number
2243     /// This helps us quickly iterate over the whole message (including secondary file spans)
2244     pub fn collect_annotations(
2245         emitter: &dyn Emitter,
2246         args: &FluentArgs<'_>,
2247         msp: &MultiSpan,
2248     ) -> Vec<FileWithAnnotatedLines> {
2249         fn add_annotation_to_file(
2250             file_vec: &mut Vec<FileWithAnnotatedLines>,
2251             file: Lrc<SourceFile>,
2252             line_index: usize,
2253             ann: Annotation,
2254         ) {
2255             for slot in file_vec.iter_mut() {
2256                 // Look through each of our files for the one we're adding to
2257                 if slot.file.name == file.name {
2258                     // See if we already have a line for it
2259                     for line_slot in &mut slot.lines {
2260                         if line_slot.line_index == line_index {
2261                             line_slot.annotations.push(ann);
2262                             return;
2263                         }
2264                     }
2265                     // We don't have a line yet, create one
2266                     slot.lines.push(Line { line_index, annotations: vec![ann] });
2267                     slot.lines.sort();
2268                     return;
2269                 }
2270             }
2271             // This is the first time we're seeing the file
2272             file_vec.push(FileWithAnnotatedLines {
2273                 file,
2274                 lines: vec![Line { line_index, annotations: vec![ann] }],
2275                 multiline_depth: 0,
2276             });
2277         }
2278
2279         let mut output = vec![];
2280         let mut multiline_annotations = vec![];
2281
2282         if let Some(ref sm) = emitter.source_map() {
2283             for SpanLabel { span, is_primary, label } in msp.span_labels() {
2284                 // If we don't have a useful span, pick the primary span if that exists.
2285                 // Worst case we'll just print an error at the top of the main file.
2286                 let span = match (span.is_dummy(), msp.primary_span()) {
2287                     (_, None) | (false, _) => span,
2288                     (true, Some(span)) => span,
2289                 };
2290
2291                 let lo = sm.lookup_char_pos(span.lo());
2292                 let mut hi = sm.lookup_char_pos(span.hi());
2293
2294                 // Watch out for "empty spans". If we get a span like 6..6, we
2295                 // want to just display a `^` at 6, so convert that to
2296                 // 6..7. This is degenerate input, but it's best to degrade
2297                 // gracefully -- and the parser likes to supply a span like
2298                 // that for EOF, in particular.
2299
2300                 if lo.col_display == hi.col_display && lo.line == hi.line {
2301                     hi.col_display += 1;
2302                 }
2303
2304                 let label = label.as_ref().map(|m| emitter.translate_message(m, args).to_string());
2305
2306                 if lo.line != hi.line {
2307                     let ml = MultilineAnnotation {
2308                         depth: 1,
2309                         line_start: lo.line,
2310                         line_end: hi.line,
2311                         start_col: lo.col_display,
2312                         end_col: hi.col_display,
2313                         is_primary,
2314                         label,
2315                         overlaps_exactly: false,
2316                     };
2317                     multiline_annotations.push((lo.file, ml));
2318                 } else {
2319                     let ann = Annotation {
2320                         start_col: lo.col_display,
2321                         end_col: hi.col_display,
2322                         is_primary,
2323                         label,
2324                         annotation_type: AnnotationType::Singleline,
2325                     };
2326                     add_annotation_to_file(&mut output, lo.file, lo.line, ann);
2327                 };
2328             }
2329         }
2330
2331         // Find overlapping multiline annotations, put them at different depths
2332         multiline_annotations.sort_by_key(|(_, ml)| (ml.line_start, usize::MAX - ml.line_end));
2333         for (_, ann) in multiline_annotations.clone() {
2334             for (_, a) in multiline_annotations.iter_mut() {
2335                 // Move all other multiline annotations overlapping with this one
2336                 // one level to the right.
2337                 if !(ann.same_span(a))
2338                     && num_overlap(ann.line_start, ann.line_end, a.line_start, a.line_end, true)
2339                 {
2340                     a.increase_depth();
2341                 } else if ann.same_span(a) && &ann != a {
2342                     a.overlaps_exactly = true;
2343                 } else {
2344                     break;
2345                 }
2346             }
2347         }
2348
2349         let mut max_depth = 0; // max overlapping multiline spans
2350         for (_, ann) in &multiline_annotations {
2351             max_depth = max(max_depth, ann.depth);
2352         }
2353         // Change order of multispan depth to minimize the number of overlaps in the ASCII art.
2354         for (_, a) in multiline_annotations.iter_mut() {
2355             a.depth = max_depth - a.depth + 1;
2356         }
2357         for (file, ann) in multiline_annotations {
2358             let mut end_ann = ann.as_end();
2359             if !ann.overlaps_exactly {
2360                 // avoid output like
2361                 //
2362                 //  |        foo(
2363                 //  |   _____^
2364                 //  |  |_____|
2365                 //  | ||         bar,
2366                 //  | ||     );
2367                 //  | ||      ^
2368                 //  | ||______|
2369                 //  |  |______foo
2370                 //  |         baz
2371                 //
2372                 // and instead get
2373                 //
2374                 //  |       foo(
2375                 //  |  _____^
2376                 //  | |         bar,
2377                 //  | |     );
2378                 //  | |      ^
2379                 //  | |      |
2380                 //  | |______foo
2381                 //  |        baz
2382                 add_annotation_to_file(&mut output, file.clone(), ann.line_start, ann.as_start());
2383                 // 4 is the minimum vertical length of a multiline span when presented: two lines
2384                 // of code and two lines of underline. This is not true for the special case where
2385                 // the beginning doesn't have an underline, but the current logic seems to be
2386                 // working correctly.
2387                 let middle = min(ann.line_start + 4, ann.line_end);
2388                 for line in ann.line_start + 1..middle {
2389                     // Every `|` that joins the beginning of the span (`___^`) to the end (`|__^`).
2390                     add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
2391                 }
2392                 let line_end = ann.line_end - 1;
2393                 if middle < line_end {
2394                     add_annotation_to_file(&mut output, file.clone(), line_end, ann.as_line());
2395                 }
2396             } else {
2397                 end_ann.annotation_type = AnnotationType::Singleline;
2398             }
2399             add_annotation_to_file(&mut output, file, ann.line_end, end_ann);
2400         }
2401         for file_vec in output.iter_mut() {
2402             file_vec.multiline_depth = max_depth;
2403         }
2404         output
2405     }
2406 }
2407
2408 // instead of taking the String length or dividing by 10 while > 0, we multiply a limit by 10 until
2409 // we're higher. If the loop isn't exited by the `return`, the last multiplication will wrap, which
2410 // is OK, because while we cannot fit a higher power of 10 in a usize, the loop will end anyway.
2411 // This is also why we need the max number of decimal digits within a `usize`.
2412 fn num_decimal_digits(num: usize) -> usize {
2413     #[cfg(target_pointer_width = "64")]
2414     const MAX_DIGITS: usize = 20;
2415
2416     #[cfg(target_pointer_width = "32")]
2417     const MAX_DIGITS: usize = 10;
2418
2419     #[cfg(target_pointer_width = "16")]
2420     const MAX_DIGITS: usize = 5;
2421
2422     let mut lim = 10;
2423     for num_digits in 1..MAX_DIGITS {
2424         if num < lim {
2425             return num_digits;
2426         }
2427         lim = lim.wrapping_mul(10);
2428     }
2429     MAX_DIGITS
2430 }
2431
2432 // We replace some characters so the CLI output is always consistent and underlines aligned.
2433 const OUTPUT_REPLACEMENTS: &[(char, &str)] = &[
2434     ('\t', "    "),   // We do our own tab replacement
2435     ('\u{200D}', ""), // Replace ZWJ with nothing for consistent terminal output of grapheme clusters.
2436     ('\u{202A}', ""), // The following unicode text flow control characters are inconsistently
2437     ('\u{202B}', ""), // supported across CLIs and can cause confusion due to the bytes on disk
2438     ('\u{202D}', ""), // not corresponding to the visible source code, so we replace them always.
2439     ('\u{202E}', ""),
2440     ('\u{2066}', ""),
2441     ('\u{2067}', ""),
2442     ('\u{2068}', ""),
2443     ('\u{202C}', ""),
2444     ('\u{2069}', ""),
2445 ];
2446
2447 fn normalize_whitespace(str: &str) -> String {
2448     let mut s = str.to_string();
2449     for (c, replacement) in OUTPUT_REPLACEMENTS {
2450         s = s.replace(*c, replacement);
2451     }
2452     s
2453 }
2454
2455 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
2456     buffer.puts(line, col, "| ", Style::LineNumber);
2457 }
2458
2459 fn draw_col_separator_no_space(buffer: &mut StyledBuffer, line: usize, col: usize) {
2460     draw_col_separator_no_space_with_style(buffer, line, col, Style::LineNumber);
2461 }
2462
2463 fn draw_col_separator_no_space_with_style(
2464     buffer: &mut StyledBuffer,
2465     line: usize,
2466     col: usize,
2467     style: Style,
2468 ) {
2469     buffer.putc(line, col, '|', style);
2470 }
2471
2472 fn draw_range(
2473     buffer: &mut StyledBuffer,
2474     symbol: char,
2475     line: usize,
2476     col_from: usize,
2477     col_to: usize,
2478     style: Style,
2479 ) {
2480     for col in col_from..col_to {
2481         buffer.putc(line, col, symbol, style);
2482     }
2483 }
2484
2485 fn draw_note_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
2486     buffer.puts(line, col, "= ", Style::LineNumber);
2487 }
2488
2489 fn draw_multiline_line(
2490     buffer: &mut StyledBuffer,
2491     line: usize,
2492     offset: usize,
2493     depth: usize,
2494     style: Style,
2495 ) {
2496     buffer.putc(line, offset + depth - 1, '|', style);
2497 }
2498
2499 fn num_overlap(
2500     a_start: usize,
2501     a_end: usize,
2502     b_start: usize,
2503     b_end: usize,
2504     inclusive: bool,
2505 ) -> bool {
2506     let extra = if inclusive { 1 } else { 0 };
2507     (b_start..b_end + extra).contains(&a_start) || (a_start..a_end + extra).contains(&b_start)
2508 }
2509 fn overlaps(a1: &Annotation, a2: &Annotation, padding: usize) -> bool {
2510     num_overlap(a1.start_col, a1.end_col + padding, a2.start_col, a2.end_col, false)
2511 }
2512
2513 fn emit_to_destination(
2514     rendered_buffer: &[Vec<StyledString>],
2515     lvl: &Level,
2516     dst: &mut Destination,
2517     short_message: bool,
2518 ) -> io::Result<()> {
2519     use crate::lock;
2520
2521     let mut dst = dst.writable();
2522
2523     // In order to prevent error message interleaving, where multiple error lines get intermixed
2524     // when multiple compiler processes error simultaneously, we emit errors with additional
2525     // steps.
2526     //
2527     // On Unix systems, we write into a buffered terminal rather than directly to a terminal. When
2528     // the .flush() is called we take the buffer created from the buffered writes and write it at
2529     // one shot.  Because the Unix systems use ANSI for the colors, which is a text-based styling
2530     // scheme, this buffered approach works and maintains the styling.
2531     //
2532     // On Windows, styling happens through calls to a terminal API. This prevents us from using the
2533     // same buffering approach.  Instead, we use a global Windows mutex, which we acquire long
2534     // enough to output the full error message, then we release.
2535     let _buffer_lock = lock::acquire_global_lock("rustc_errors");
2536     for (pos, line) in rendered_buffer.iter().enumerate() {
2537         for part in line {
2538             dst.apply_style(*lvl, part.style)?;
2539             write!(dst, "{}", part.text)?;
2540             dst.reset()?;
2541         }
2542         if !short_message && (!lvl.is_failure_note() || pos != rendered_buffer.len() - 1) {
2543             writeln!(dst)?;
2544         }
2545     }
2546     dst.flush()?;
2547     Ok(())
2548 }
2549
2550 pub enum Destination {
2551     Terminal(StandardStream),
2552     Buffered(BufferWriter),
2553     // The bool denotes whether we should be emitting ansi color codes or not
2554     Raw(Box<(dyn Write + Send)>, bool),
2555 }
2556
2557 pub enum WritableDst<'a> {
2558     Terminal(&'a mut StandardStream),
2559     Buffered(&'a mut BufferWriter, Buffer),
2560     Raw(&'a mut (dyn Write + Send)),
2561     ColoredRaw(Ansi<&'a mut (dyn Write + Send)>),
2562 }
2563
2564 impl Destination {
2565     fn from_stderr(color: ColorConfig) -> Destination {
2566         let choice = color.to_color_choice();
2567         // On Windows we'll be performing global synchronization on the entire
2568         // system for emitting rustc errors, so there's no need to buffer
2569         // anything.
2570         //
2571         // On non-Windows we rely on the atomicity of `write` to ensure errors
2572         // don't get all jumbled up.
2573         if cfg!(windows) {
2574             Terminal(StandardStream::stderr(choice))
2575         } else {
2576             Buffered(BufferWriter::stderr(choice))
2577         }
2578     }
2579
2580     fn writable(&mut self) -> WritableDst<'_> {
2581         match *self {
2582             Destination::Terminal(ref mut t) => WritableDst::Terminal(t),
2583             Destination::Buffered(ref mut t) => {
2584                 let buf = t.buffer();
2585                 WritableDst::Buffered(t, buf)
2586             }
2587             Destination::Raw(ref mut t, false) => WritableDst::Raw(t),
2588             Destination::Raw(ref mut t, true) => WritableDst::ColoredRaw(Ansi::new(t)),
2589         }
2590     }
2591
2592     fn supports_color(&self) -> bool {
2593         match *self {
2594             Self::Terminal(ref stream) => stream.supports_color(),
2595             Self::Buffered(ref buffer) => buffer.buffer().supports_color(),
2596             Self::Raw(_, supports_color) => supports_color,
2597         }
2598     }
2599 }
2600
2601 impl<'a> WritableDst<'a> {
2602     fn apply_style(&mut self, lvl: Level, style: Style) -> io::Result<()> {
2603         let mut spec = ColorSpec::new();
2604         match style {
2605             Style::Addition => {
2606                 spec.set_fg(Some(Color::Green)).set_intense(true);
2607             }
2608             Style::Removal => {
2609                 spec.set_fg(Some(Color::Red)).set_intense(true);
2610             }
2611             Style::LineAndColumn => {}
2612             Style::LineNumber => {
2613                 spec.set_bold(true);
2614                 spec.set_intense(true);
2615                 if cfg!(windows) {
2616                     spec.set_fg(Some(Color::Cyan));
2617                 } else {
2618                     spec.set_fg(Some(Color::Blue));
2619                 }
2620             }
2621             Style::Quotation => {}
2622             Style::MainHeaderMsg => {
2623                 spec.set_bold(true);
2624                 if cfg!(windows) {
2625                     spec.set_intense(true).set_fg(Some(Color::White));
2626                 }
2627             }
2628             Style::UnderlinePrimary | Style::LabelPrimary => {
2629                 spec = lvl.color();
2630                 spec.set_bold(true);
2631             }
2632             Style::UnderlineSecondary | Style::LabelSecondary => {
2633                 spec.set_bold(true).set_intense(true);
2634                 if cfg!(windows) {
2635                     spec.set_fg(Some(Color::Cyan));
2636                 } else {
2637                     spec.set_fg(Some(Color::Blue));
2638                 }
2639             }
2640             Style::HeaderMsg | Style::NoStyle => {}
2641             Style::Level(lvl) => {
2642                 spec = lvl.color();
2643                 spec.set_bold(true);
2644             }
2645             Style::Highlight => {
2646                 spec.set_bold(true);
2647             }
2648         }
2649         self.set_color(&spec)
2650     }
2651
2652     fn set_color(&mut self, color: &ColorSpec) -> io::Result<()> {
2653         match *self {
2654             WritableDst::Terminal(ref mut t) => t.set_color(color),
2655             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
2656             WritableDst::ColoredRaw(ref mut t) => t.set_color(color),
2657             WritableDst::Raw(_) => Ok(()),
2658         }
2659     }
2660
2661     fn reset(&mut self) -> io::Result<()> {
2662         match *self {
2663             WritableDst::Terminal(ref mut t) => t.reset(),
2664             WritableDst::Buffered(_, ref mut t) => t.reset(),
2665             WritableDst::ColoredRaw(ref mut t) => t.reset(),
2666             WritableDst::Raw(_) => Ok(()),
2667         }
2668     }
2669 }
2670
2671 impl<'a> Write for WritableDst<'a> {
2672     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
2673         match *self {
2674             WritableDst::Terminal(ref mut t) => t.write(bytes),
2675             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
2676             WritableDst::Raw(ref mut w) => w.write(bytes),
2677             WritableDst::ColoredRaw(ref mut t) => t.write(bytes),
2678         }
2679     }
2680
2681     fn flush(&mut self) -> io::Result<()> {
2682         match *self {
2683             WritableDst::Terminal(ref mut t) => t.flush(),
2684             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
2685             WritableDst::Raw(ref mut w) => w.flush(),
2686             WritableDst::ColoredRaw(ref mut w) => w.flush(),
2687         }
2688     }
2689 }
2690
2691 impl<'a> Drop for WritableDst<'a> {
2692     fn drop(&mut self) {
2693         if let WritableDst::Buffered(ref mut dst, ref mut buf) = self {
2694             drop(dst.print(buf));
2695         }
2696     }
2697 }
2698
2699 /// Whether the original and suggested code are visually similar enough to warrant extra wording.
2700 pub fn is_case_difference(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
2701     // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
2702     let found = match sm.span_to_snippet(sp) {
2703         Ok(snippet) => snippet,
2704         Err(e) => {
2705             warn!(error = ?e, "Invalid span {:?}", sp);
2706             return false;
2707         }
2708     };
2709     let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
2710     // All the chars that differ in capitalization are confusable (above):
2711     let confusable = iter::zip(found.chars(), suggested.chars())
2712         .filter(|(f, s)| f != s)
2713         .all(|(f, s)| (ascii_confusables.contains(&f) || ascii_confusables.contains(&s)));
2714     confusable && found.to_lowercase() == suggested.to_lowercase()
2715             // FIXME: We sometimes suggest the same thing we already have, which is a
2716             //        bug, but be defensive against that here.
2717             && found != suggested
2718 }