src/librustc_errors/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 `librustc::session::config::ErrorOutputType`.
   9
  10 use Destination::*;
  11
  12 use syntax_pos::{SourceFile, Span, MultiSpan};
  13
  14 use crate::{
  15     Level, CodeSuggestion, Diagnostic, SubDiagnostic,
  16     SuggestionStyle, SourceMapperDyn, DiagnosticId,
  17 };
  18 use crate::Level::Error;
  19 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
  20 use crate::styled_buffer::StyledBuffer;
  21
  22 use rustc_data_structures::fx::FxHashMap;
  23 use rustc_data_structures::sync::Lrc;
  24 use std::borrow::Cow;
  25 use std::io::prelude::*;
  26 use std::io;
  27 use std::cmp::{min, max, Reverse};
  28 use std::path::Path;
  29 use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter, Ansi};
  30 use termcolor::{WriteColor, Color, Buffer};
  31
  32 /// Describes the way the content of the `rendered` field of the json output is generated
  33 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
  34 pub enum HumanReadableErrorType {
  35     Default(ColorConfig),
  36     AnnotateSnippet(ColorConfig),
  37     Short(ColorConfig),
  38 }
  39
  40 impl HumanReadableErrorType {
  41     /// Returns a (`short`, `color`) tuple
  42     pub fn unzip(self) -> (bool, ColorConfig) {
  43         match self {
  44             HumanReadableErrorType::Default(cc) => (false, cc),
  45             HumanReadableErrorType::Short(cc) => (true, cc),
  46             HumanReadableErrorType::AnnotateSnippet(cc) => (false, cc),
  47         }
  48     }
  49     pub fn new_emitter(
  50         self,
  51         dst: Box<dyn Write + Send>,
  52         source_map: Option<Lrc<SourceMapperDyn>>,
  53         teach: bool,
  54         terminal_width: Option<usize>,
  55         external_macro_backtrace: bool,
  56     ) -> EmitterWriter {
  57         let (short, color_config) = self.unzip();
  58         let color = color_config.suggests_using_colors();
  59         EmitterWriter::new(dst, source_map, short, teach, color, terminal_width,
  60             external_macro_backtrace)
  61     }
  62 }
  63
  64 #[derive(Clone, Copy, Debug)]
  65 struct Margin {
  66     /// The available whitespace in the left that can be consumed when centering.
  67     pub whitespace_left: usize,
  68     /// The column of the beginning of left-most span.
  69     pub span_left: usize,
  70     /// The column of the end of right-most span.
  71     pub span_right: usize,
  72     /// The beginning of the line to be displayed.
  73     pub computed_left: usize,
  74     /// The end of the line to be displayed.
  75     pub computed_right: usize,
  76     /// The current width of the terminal. 140 by default and in tests.
  77     pub column_width: usize,
  78     /// The end column of a span label, including the span. Doesn't account for labels not in the
  79     /// same line as the span.
  80     pub label_right: usize,
  81 }
  82
  83 impl Margin {
  84     fn new(
  85         whitespace_left: usize,
  86         span_left: usize,
  87         span_right: usize,
  88         label_right: usize,
  89         column_width: usize,
  90         max_line_len: usize,
  91     ) -> Self {
  92         // The 6 is padding to give a bit of room for `...` when displaying:
  93         // ```
  94         // error: message
  95         //   --> file.rs:16:58
  96         //    |
  97         // 16 | ... fn foo(self) -> Self::Bar {
  98         //    |                     ^^^^^^^^^
  99         // ```
 100
 101         let mut m = Margin {
 102             whitespace_left: if whitespace_left >= 6 { whitespace_left - 6 } else { 0 },
 103             span_left: if span_left >= 6 { span_left - 6 } else { 0 },
 104             span_right: span_right + 6,
 105             computed_left: 0,
 106             computed_right: 0,
 107             column_width,
 108             label_right: label_right + 6,
 109         };
 110         m.compute(max_line_len);
 111         m
 112     }
 113
 114     fn was_cut_left(&self) -> bool {
 115         self.computed_left > 0
 116     }
 117
 118     fn was_cut_right(&self, line_len: usize) -> bool {
 119         let right = if self.computed_right == self.span_right ||
 120             self.computed_right == self.label_right
 121         {
 122             // Account for the "..." padding given above. Otherwise we end up with code lines that
 123             // do fit but end in "..." as if they were trimmed.
 124             self.computed_right - 6
 125         } else {
 126             self.computed_right
 127         };
 128         right < line_len && line_len > self.computed_left + self.column_width
 129     }
 130
 131     fn compute(&mut self, max_line_len: usize) {
 132         // When there's a lot of whitespace (>20), we want to trim it as it is useless.
 133         self.computed_left = if self.whitespace_left > 20 {
 134             self.whitespace_left - 16 // We want some padding.
 135         } else {
 136             0
 137         };
 138         // We want to show as much as possible, max_line_len is the right-most boundary for the
 139         // relevant code.
 140         self.computed_right = max(max_line_len, self.computed_left);
 141
 142         if self.computed_right - self.computed_left > self.column_width {
 143             // Trimming only whitespace isn't enough, let's get craftier.
 144             if self.label_right - self.whitespace_left <= self.column_width {
 145                 // Attempt to fit the code window only trimming whitespace.
 146                 self.computed_left = self.whitespace_left;
 147                 self.computed_right = self.computed_left + self.column_width;
 148             } else if self.label_right - self.span_left <= self.column_width {
 149                 // Attempt to fit the code window considering only the spans and labels.
 150                 let padding_left = (self.column_width - (self.label_right - self.span_left)) / 2;
 151                 self.computed_left = self.span_left.saturating_sub(padding_left);
 152                 self.computed_right = self.computed_left + self.column_width;
 153             } else if self.span_right - self.span_left <= self.column_width {
 154                 // Attempt to fit the code window considering the spans and labels plus padding.
 155                 let padding_left = (self.column_width - (self.span_right - self.span_left)) / 5 * 2;
 156                 self.computed_left = self.span_left.saturating_sub(padding_left);
 157                 self.computed_right = self.computed_left + self.column_width;
 158             } else { // Mostly give up but still don't show the full line.
 159                 self.computed_left = self.span_left;
 160                 self.computed_right = self.span_right;
 161             }
 162         }
 163     }
 164
 165     fn left(&self, line_len: usize) -> usize {
 166         min(self.computed_left, line_len)
 167     }
 168
 169     fn right(&self, line_len: usize) -> usize {
 170         if max(line_len, self.computed_left) - self.computed_left <= self.column_width {
 171             line_len
 172         } else if self.computed_right > line_len {
 173             line_len
 174         } else {
 175             self.computed_right
 176         }
 177     }
 178 }
 179
 180 const ANONYMIZED_LINE_NUM: &str = "LL";
 181
 182 /// Emitter trait for emitting errors.
 183 pub trait Emitter {
 184     /// Emit a structured diagnostic.
 185     fn emit_diagnostic(&mut self, db: &Diagnostic);
 186
 187     /// Emit a notification that an artifact has been output.
 188     /// This is currently only supported for the JSON format,
 189     /// other formats can, and will, simply ignore it.
 190     fn emit_artifact_notification(&mut self, _path: &Path, _artifact_type: &str) {}
 191
 192     /// Checks if should show explanations about "rustc --explain"
 193     fn should_show_explain(&self) -> bool {
 194         true
 195     }
 196
 197     /// Formats the substitutions of the primary_span
 198     ///
 199     /// The are a lot of conditions to this method, but in short:
 200     ///
 201     /// * If the current `Diagnostic` has only one visible `CodeSuggestion`,
 202     ///   we format the `help` suggestion depending on the content of the
 203     ///   substitutions. In that case, we return the modified span only.
 204     ///
 205     /// * If the current `Diagnostic` has multiple suggestions,
 206     ///   we return the original `primary_span` and the original suggestions.
 207     fn primary_span_formatted<'a>(
 208         &mut self,
 209         db: &'a Diagnostic
 210     ) -> (MultiSpan, &'a [CodeSuggestion]) {
 211         let mut primary_span = db.span.clone();
 212         if let Some((sugg, rest)) = db.suggestions.split_first() {
 213             if rest.is_empty() &&
 214                // ^ if there is only one suggestion
 215                // don't display multi-suggestions as labels
 216                sugg.substitutions.len() == 1 &&
 217                // don't display multipart suggestions as labels
 218                sugg.substitutions[0].parts.len() == 1 &&
 219                // don't display long messages as labels
 220                sugg.msg.split_whitespace().count() < 10 &&
 221                // don't display multiline suggestions as labels
 222                !sugg.substitutions[0].parts[0].snippet.contains('\n') &&
 223                // when this style is set we want the suggestion to be a message, not inline
 224                sugg.style != SuggestionStyle::HideCodeAlways &&
 225                // trivial suggestion for tooling's sake, never shown
 226                sugg.style != SuggestionStyle::CompletelyHidden
 227             {
 228                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
 229                 let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
 230                     // This substitution is only removal OR we explicitly don't want to show the
 231                     // code inline (`hide_inline`). Therefore, we don't show the substitution.
 232                     format!("help: {}", sugg.msg)
 233                 } else {
 234                     // Show the default suggestion text with the substitution
 235                     format!("help: {}: `{}`", sugg.msg, substitution)
 236                 };
 237                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
 238
 239                 // We return only the modified primary_span
 240                 (primary_span, &[])
 241             } else {
 242                 // if there are multiple suggestions, print them all in full
 243                 // to be consistent. We could try to figure out if we can
 244                 // make one (or the first one) inline, but that would give
 245                 // undue importance to a semi-random suggestion
 246                 (primary_span, &db.suggestions)
 247             }
 248         } else {
 249             (primary_span, &db.suggestions)
 250         }
 251     }
 252
 253     // This does a small "fix" for multispans by looking to see if it can find any that
 254     // point directly at <*macros>. Since these are often difficult to read, this
 255     // will change the span to point at the use site.
 256     fn fix_multispans_in_std_macros(&self,
 257                                     source_map: &Option<Lrc<SourceMapperDyn>>,
 258                                     span: &mut MultiSpan,
 259                                     children: &mut Vec<SubDiagnostic>,
 260                                     level: &Level,
 261                                     backtrace: bool) {
 262         let mut spans_updated = self.fix_multispan_in_std_macros(source_map, span, backtrace);
 263         for child in children.iter_mut() {
 264             spans_updated |= self.fix_multispan_in_std_macros(
 265                                  source_map,
 266                                  &mut child.span,
 267                                  backtrace
 268                              );
 269         }
 270         let msg = if level == &Error {
 271             "this error originates in a macro outside of the current crate \
 272              (in Nightly builds, run with -Z external-macro-backtrace \
 273               for more info)".to_string()
 274         } else {
 275             "this warning originates in a macro outside of the current crate \
 276              (in Nightly builds, run with -Z external-macro-backtrace \
 277               for more info)".to_string()
 278         };
 279
 280         if spans_updated {
 281             children.push(SubDiagnostic {
 282                 level: Level::Note,
 283                 message: vec![
 284                     (msg,
 285                      Style::NoStyle),
 286                 ],
 287                 span: MultiSpan::new(),
 288                 render_span: None,
 289             });
 290         }
 291     }
 292
 293     // This "fixes" MultiSpans that contain Spans that are pointing to locations inside of
 294     // <*macros>. Since these locations are often difficult to read, we move these Spans from
 295     // <*macros> to their corresponding use site.
 296     fn fix_multispan_in_std_macros(&self,
 297                                    source_map: &Option<Lrc<SourceMapperDyn>>,
 298                                    span: &mut MultiSpan,
 299                                    always_backtrace: bool) -> bool {
 300         let mut spans_updated = false;
 301
 302         if let Some(ref sm) = source_map {
 303             let mut before_after: Vec<(Span, Span)> = vec![];
 304             let mut new_labels: Vec<(Span, String)> = vec![];
 305
 306             // First, find all the spans in <*macros> and point instead at their use site
 307             for sp in span.primary_spans() {
 308                 if sp.is_dummy() {
 309                     continue;
 310                 }
 311                 let call_sp = sm.call_span_if_macro(*sp);
 312                 if call_sp != *sp && !always_backtrace {
 313                     before_after.push((*sp, call_sp));
 314                 }
 315                 let backtrace_len = sp.macro_backtrace().len();
 316                 for (i, trace) in sp.macro_backtrace().iter().rev().enumerate() {
 317                     // Only show macro locations that are local
 318                     // and display them like a span_note
 319                     if trace.def_site_span.is_dummy() {
 320                         continue;
 321                     }
 322                     if always_backtrace {
 323                         new_labels.push((trace.def_site_span,
 324                                             format!("in this expansion of `{}`{}",
 325                                                     trace.macro_decl_name,
 326                                                     if backtrace_len > 2 {
 327                                                         // if backtrace_len == 1 it'll be pointed
 328                                                         // at by "in this macro invocation"
 329                                                         format!(" (#{})", i + 1)
 330                                                     } else {
 331                                                         String::new()
 332                                                     })));
 333                     }
 334                     // Check to make sure we're not in any <*macros>
 335                     if !sm.span_to_filename(trace.def_site_span).is_macros() &&
 336                         !trace.macro_decl_name.starts_with("desugaring of ") &&
 337                         !trace.macro_decl_name.starts_with("#[") ||
 338                         always_backtrace {
 339                         new_labels.push((trace.call_site,
 340                                             format!("in this macro invocation{}",
 341                                                     if backtrace_len > 2 && always_backtrace {
 342                                                         // only specify order when the macro
 343                                                         // backtrace is multiple levels deep
 344                                                         format!(" (#{})", i + 1)
 345                                                     } else {
 346                                                         String::new()
 347                                                     })));
 348                         if !always_backtrace {
 349                             break;
 350                         }
 351                     }
 352                 }
 353             }
 354             for (label_span, label_text) in new_labels {
 355                 span.push_span_label(label_span, label_text);
 356             }
 357             for sp_label in span.span_labels() {
 358                 if sp_label.span.is_dummy() {
 359                     continue;
 360                 }
 361                 if sm.span_to_filename(sp_label.span.clone()).is_macros() &&
 362                     !always_backtrace
 363                 {
 364                     let v = sp_label.span.macro_backtrace();
 365                     if let Some(use_site) = v.last() {
 366                         before_after.push((sp_label.span.clone(), use_site.call_site.clone()));
 367                     }
 368                 }
 369             }
 370             // After we have them, make sure we replace these 'bad' def sites with their use sites
 371             for (before, after) in before_after {
 372                 span.replace(before, after);
 373                 spans_updated = true;
 374             }
 375         }
 376
 377         spans_updated
 378     }
 379 }
 380
 381 impl Emitter for EmitterWriter {
 382     fn emit_diagnostic(&mut self, db: &Diagnostic) {
 383         let mut children = db.children.clone();
 384         let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
 385
 386         self.fix_multispans_in_std_macros(&self.sm,
 387                                           &mut primary_span,
 388                                           &mut children,
 389                                           &db.level,
 390                                           self.external_macro_backtrace);
 391
 392         self.emit_messages_default(&db.level,
 393                                    &db.styled_message(),
 394                                    &db.code,
 395                                    &primary_span,
 396                                    &children,
 397                                    &suggestions);
 398     }
 399
 400     fn should_show_explain(&self) -> bool {
 401         !self.short_message
 402     }
 403 }
 404
 405 /// maximum number of lines we will print for each error; arbitrary.
 406 pub const MAX_HIGHLIGHT_LINES: usize = 6;
 407 /// maximum number of suggestions to be shown
 408 ///
 409 /// Arbitrary, but taken from trait import suggestion limit
 410 pub const MAX_SUGGESTIONS: usize = 4;
 411
 412 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 413 pub enum ColorConfig {
 414     Auto,
 415     Always,
 416     Never,
 417 }
 418
 419 impl ColorConfig {
 420     fn to_color_choice(self) -> ColorChoice {
 421         match self {
 422             ColorConfig::Always => {
 423                 if atty::is(atty::Stream::Stderr) {
 424                     ColorChoice::Always
 425                 } else {
 426                     ColorChoice::AlwaysAnsi
 427                 }
 428             }
 429             ColorConfig::Never => ColorChoice::Never,
 430             ColorConfig::Auto if atty::is(atty::Stream::Stderr) => {
 431                 ColorChoice::Auto
 432             }
 433             ColorConfig::Auto => ColorChoice::Never,
 434         }
 435     }
 436     fn suggests_using_colors(self) -> bool {
 437         match self {
 438             | ColorConfig::Always
 439             | ColorConfig::Auto
 440             => true,
 441             ColorConfig::Never => false,
 442         }
 443     }
 444 }
 445
 446 /// Handles the writing of `HumanReadableErrorType::Default` and `HumanReadableErrorType::Short`
 447 pub struct EmitterWriter {
 448     dst: Destination,
 449     sm: Option<Lrc<SourceMapperDyn>>,
 450     short_message: bool,
 451     teach: bool,
 452     ui_testing: bool,
 453     terminal_width: Option<usize>,
 454
 455     external_macro_backtrace: bool,
 456 }
 457
 458 #[derive(Debug)]
 459 pub struct FileWithAnnotatedLines {
 460     pub file: Lrc<SourceFile>,
 461     pub lines: Vec<Line>,
 462     multiline_depth: usize,
 463 }
 464
 465 impl EmitterWriter {
 466     pub fn stderr(
 467         color_config: ColorConfig,
 468         source_map: Option<Lrc<SourceMapperDyn>>,
 469         short_message: bool,
 470         teach: bool,
 471         terminal_width: Option<usize>,
 472         external_macro_backtrace: bool,
 473     ) -> EmitterWriter {
 474         let dst = Destination::from_stderr(color_config);
 475         EmitterWriter {
 476             dst,
 477             sm: source_map,
 478             short_message,
 479             teach,
 480             ui_testing: false,
 481             terminal_width,
 482             external_macro_backtrace,
 483         }
 484     }
 485
 486     pub fn new(
 487         dst: Box<dyn Write + Send>,
 488         source_map: Option<Lrc<SourceMapperDyn>>,
 489         short_message: bool,
 490         teach: bool,
 491         colored: bool,
 492         terminal_width: Option<usize>,
 493         external_macro_backtrace: bool,
 494     ) -> EmitterWriter {
 495         EmitterWriter {
 496             dst: Raw(dst, colored),
 497             sm: source_map,
 498             short_message,
 499             teach,
 500             ui_testing: false,
 501             terminal_width,
 502             external_macro_backtrace,
 503         }
 504     }
 505
 506     pub fn ui_testing(mut self, ui_testing: bool) -> Self {
 507         self.ui_testing = ui_testing;
 508         self
 509     }
 510
 511     fn maybe_anonymized(&self, line_num: usize) -> String {
 512         if self.ui_testing {
 513             ANONYMIZED_LINE_NUM.to_string()
 514         } else {
 515             line_num.to_string()
 516         }
 517     }
 518
 519     fn draw_line(
 520         &self,
 521         buffer: &mut StyledBuffer,
 522         source_string: &str,
 523         line_index: usize,
 524         line_offset: usize,
 525         width_offset: usize,
 526         code_offset: usize,
 527         margin: Margin,
 528     ) {
 529         let line_len = source_string.len();
 530         // Create the source line we will highlight.
 531         let left = margin.left(line_len);
 532         let right = margin.right(line_len);
 533         // On long lines, we strip the source line, accounting for unicode.
 534         let mut taken = 0;
 535         let code: String = source_string.chars().skip(left).take_while(|ch| {
 536             // Make sure that the trimming on the right will fall within the terminal width.
 537             // FIXME: `unicode_width` sometimes disagrees with terminals on how wide a `char` is.
 538             // For now, just accept that sometimes the code line will be longer than desired.
 539             let next = unicode_width::UnicodeWidthChar::width(*ch).unwrap_or(1);
 540             if taken + next > right - left {
 541                 return false;
 542             }
 543             taken += next;
 544             true
 545         }).collect();
 546         buffer.puts(line_offset, code_offset, &code, Style::Quotation);
 547         if margin.was_cut_left() {
 548             // We have stripped some code/whitespace from the beginning, make it clear.
 549             buffer.puts(line_offset, code_offset, "...", Style::LineNumber);
 550         }
 551         if margin.was_cut_right(line_len) {
 552             // We have stripped some code after the right-most span end, make it clear we did so.
 553             buffer.puts(line_offset, code_offset + taken - 3, "...", Style::LineNumber);
 554         }
 555         buffer.puts(line_offset, 0, &self.maybe_anonymized(line_index), Style::LineNumber);
 556
 557         draw_col_separator(buffer, line_offset, width_offset - 2);
 558     }
 559
 560     fn render_source_line(
 561         &self,
 562         buffer: &mut StyledBuffer,
 563         file: Lrc<SourceFile>,
 564         line: &Line,
 565         width_offset: usize,
 566         code_offset: usize,
 567         margin: Margin,
 568     ) -> Vec<(usize, Style)> {
 569         // Draw:
 570         //
 571         //   LL | ... code ...
 572         //      |     ^^-^ span label
 573         //      |       |
 574         //      |       secondary span label
 575         //
 576         //   ^^ ^ ^^^ ^^^^ ^^^ we don't care about code too far to the right of a span, we trim it
 577         //   |  | |   |
 578         //   |  | |   actual code found in your source code and the spans we use to mark it
 579         //   |  | when there's too much wasted space to the left, trim it
 580         //   |  vertical divider between the column number and the code
 581         //   column number
 582
 583         if line.line_index == 0 {
 584             return Vec::new();
 585         }
 586
 587         let source_string = match file.get_line(line.line_index - 1) {
 588             Some(s) => s,
 589             None => return Vec::new(),
 590         };
 591
 592         let line_offset = buffer.num_lines();
 593
 594         let left = margin.left(source_string.len()); // Left trim
 595         // Account for unicode characters of width !=0 that were removed.
 596         let left = source_string.chars().take(left).fold(0, |acc, ch| {
 597             acc + unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1)
 598         });
 599
 600         self.draw_line(
 601             buffer,
 602             &source_string,
 603             line.line_index,
 604             line_offset,
 605             width_offset,
 606             code_offset,
 607             margin,
 608         );
 609
 610         // Special case when there's only one annotation involved, it is the start of a multiline
 611         // span and there's no text at the beginning of the code line. Instead of doing the whole
 612         // graph:
 613         //
 614         // 2 |   fn foo() {
 615         //   |  _^
 616         // 3 | |
 617         // 4 | | }
 618         //   | |_^ test
 619         //
 620         // we simplify the output to:
 621         //
 622         // 2 | / fn foo() {
 623         // 3 | |
 624         // 4 | | }
 625         //   | |_^ test
 626         if line.annotations.len() == 1 {
 627             if let Some(ref ann) = line.annotations.get(0) {
 628                 if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
 629                     if source_string.chars().take(ann.start_col).all(|c| c.is_whitespace()) {
 630                         let style = if ann.is_primary {
 631                             Style::UnderlinePrimary
 632                         } else {
 633                             Style::UnderlineSecondary
 634                         };
 635                         buffer.putc(line_offset, width_offset + depth - 1, '/', style);
 636                         return vec![(depth, style)];
 637                     }
 638                 }
 639             }
 640         }
 641
 642         // We want to display like this:
 643         //
 644         //      vec.push(vec.pop().unwrap());
 645         //      ---      ^^^               - previous borrow ends here
 646         //      |        |
 647         //      |        error occurs here
 648         //      previous borrow of `vec` occurs here
 649         //
 650         // But there are some weird edge cases to be aware of:
 651         //
 652         //      vec.push(vec.pop().unwrap());
 653         //      --------                    - previous borrow ends here
 654         //      ||
 655         //      |this makes no sense
 656         //      previous borrow of `vec` occurs here
 657         //
 658         // For this reason, we group the lines into "highlight lines"
 659         // and "annotations lines", where the highlight lines have the `^`.
 660
 661         // Sort the annotations by (start, end col)
 662         // The labels are reversed, sort and then reversed again.
 663         // Consider a list of annotations (A1, A2, C1, C2, B1, B2) where
 664         // the letter signifies the span. Here we are only sorting by the
 665         // span and hence, the order of the elements with the same span will
 666         // not change. On reversing the ordering (|a, b| but b.cmp(a)), you get
 667         // (C1, C2, B1, B2, A1, A2). All the elements with the same span are
 668         // still ordered first to last, but all the elements with different
 669         // spans are ordered by their spans in last to first order. Last to
 670         // first order is important, because the jiggly lines and | are on
 671         // the left, so the rightmost span needs to be rendered first,
 672         // otherwise the lines would end up needing to go over a message.
 673
 674         let mut annotations = line.annotations.clone();
 675         annotations.sort_by_key(|a| Reverse(a.start_col));
 676
 677         // First, figure out where each label will be positioned.
 678         //
 679         // In the case where you have the following annotations:
 680         //
 681         //      vec.push(vec.pop().unwrap());
 682         //      --------                    - previous borrow ends here [C]
 683         //      ||
 684         //      |this makes no sense [B]
 685         //      previous borrow of `vec` occurs here [A]
 686         //
 687         // `annotations_position` will hold [(2, A), (1, B), (0, C)].
 688         //
 689         // We try, when possible, to stick the rightmost annotation at the end
 690         // of the highlight line:
 691         //
 692         //      vec.push(vec.pop().unwrap());
 693         //      ---      ---               - previous borrow ends here
 694         //
 695         // But sometimes that's not possible because one of the other
 696         // annotations overlaps it. For example, from the test
 697         // `span_overlap_label`, we have the following annotations
 698         // (written on distinct lines for clarity):
 699         //
 700         //      fn foo(x: u32) {
 701         //      --------------
 702         //             -
 703         //
 704         // In this case, we can't stick the rightmost-most label on
 705         // the highlight line, or we would get:
 706         //
 707         //      fn foo(x: u32) {
 708         //      -------- x_span
 709         //      |
 710         //      fn_span
 711         //
 712         // which is totally weird. Instead we want:
 713         //
 714         //      fn foo(x: u32) {
 715         //      --------------
 716         //      |      |
 717         //      |      x_span
 718         //      fn_span
 719         //
 720         // which is...less weird, at least. In fact, in general, if
 721         // the rightmost span overlaps with any other span, we should
 722         // use the "hang below" version, so we can at least make it
 723         // clear where the span *starts*. There's an exception for this
 724         // logic, when the labels do not have a message:
 725         //
 726         //      fn foo(x: u32) {
 727         //      --------------
 728         //             |
 729         //             x_span
 730         //
 731         // instead of:
 732         //
 733         //      fn foo(x: u32) {
 734         //      --------------
 735         //      |      |
 736         //      |      x_span
 737         //      <EMPTY LINE>
 738         //
 739         let mut annotations_position = vec![];
 740         let mut line_len = 0;
 741         let mut p = 0;
 742         for (i, annotation) in annotations.iter().enumerate() {
 743             for (j, next) in annotations.iter().enumerate() {
 744                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
 745                     && annotation.has_label()     // take space (they have text and are not
 746                     && j > i                      // multiline lines).
 747                     && p == 0  // We're currently on the first line, move the label one line down
 748                 {
 749                     // If we're overlapping with an un-labelled annotation with the same span
 750                     // we can just merge them in the output
 751                     if next.start_col == annotation.start_col
 752                     && next.end_col == annotation.end_col
 753                     && !next.has_label()
 754                     {
 755                         continue;
 756                     }
 757
 758                     // This annotation needs a new line in the output.
 759                     p += 1;
 760                     break;
 761                 }
 762             }
 763             annotations_position.push((p, annotation));
 764             for (j, next) in annotations.iter().enumerate() {
 765                 if j > i  {
 766                     let l = if let Some(ref label) = next.label {
 767                         label.len() + 2
 768                     } else {
 769                         0
 770                     };
 771                     if (overlaps(next, annotation, l) // Do not allow two labels to be in the same
 772                                                      // line if they overlap including padding, to
 773                                                      // avoid situations like:
 774                                                      //
 775                                                      //      fn foo(x: u32) {
 776                                                      //      -------^------
 777                                                      //      |      |
 778                                                      //      fn_spanx_span
 779                                                      //
 780                         && annotation.has_label()    // Both labels must have some text, otherwise
 781                         && next.has_label())         // they are not overlapping.
 782                                                      // Do not add a new line if this annotation
 783                                                      // or the next are vertical line placeholders.
 784                         || (annotation.takes_space() // If either this or the next annotation is
 785                             && next.has_label())     // multiline start/end, move it to a new line
 786                         || (annotation.has_label()   // so as not to overlap the orizontal lines.
 787                             && next.takes_space())
 788                         || (annotation.takes_space() && next.takes_space())
 789                         || (overlaps(next, annotation, l)
 790                             && next.end_col <= annotation.end_col
 791                             && next.has_label()
 792                             && p == 0)  // Avoid #42595.
 793                     {
 794                         // This annotation needs a new line in the output.
 795                         p += 1;
 796                         break;
 797                     }
 798                 }
 799             }
 800             if line_len < p {
 801                 line_len = p;
 802             }
 803         }
 804
 805         if line_len != 0 {
 806             line_len += 1;
 807         }
 808
 809         // If there are no annotations or the only annotations on this line are
 810         // MultilineLine, then there's only code being shown, stop processing.
 811         if line.annotations.iter().all(|a| a.is_line()) {
 812             return vec![];
 813         }
 814
 815         // Write the colunmn separator.
 816         //
 817         // After this we will have:
 818         //
 819         // 2 |   fn foo() {
 820         //   |
 821         //   |
 822         //   |
 823         // 3 |
 824         // 4 |   }
 825         //   |
 826         for pos in 0..=line_len {
 827             draw_col_separator(buffer, line_offset + pos + 1, width_offset - 2);
 828             buffer.putc(line_offset + pos + 1,
 829                         width_offset - 2,
 830                         '|',
 831                         Style::LineNumber);
 832         }
 833
 834         // Write the horizontal lines for multiline annotations
 835         // (only the first and last lines need this).
 836         //
 837         // After this we will have:
 838         //
 839         // 2 |   fn foo() {
 840         //   |  __________
 841         //   |
 842         //   |
 843         // 3 |
 844         // 4 |   }
 845         //   |  _
 846         for &(pos, annotation) in &annotations_position {
 847             let style = if annotation.is_primary {
 848                 Style::UnderlinePrimary
 849             } else {
 850                 Style::UnderlineSecondary
 851             };
 852             let pos = pos + 1;
 853             match annotation.annotation_type {
 854                 AnnotationType::MultilineStart(depth) |
 855                 AnnotationType::MultilineEnd(depth) => {
 856                     draw_range(
 857                         buffer,
 858                         '_',
 859                         line_offset + pos,
 860                         width_offset + depth,
 861                         code_offset + annotation.start_col - left,
 862                         style,
 863                     );
 864                 }
 865                 _ if self.teach => {
 866                     buffer.set_style_range(
 867                         line_offset,
 868                         code_offset + annotation.start_col - left,
 869                         code_offset + annotation.end_col - left,
 870                         style,
 871                         annotation.is_primary,
 872                     );
 873                 }
 874                 _ => {}
 875             }
 876         }
 877
 878         // Write the vertical lines for labels that are on a different line as the underline.
 879         //
 880         // After this we will have:
 881         //
 882         // 2 |   fn foo() {
 883         //   |  __________
 884         //   | |    |
 885         //   | |
 886         // 3 |
 887         // 4 | | }
 888         //   | |_
 889         for &(pos, annotation) in &annotations_position {
 890             let style = if annotation.is_primary {
 891                 Style::UnderlinePrimary
 892             } else {
 893                 Style::UnderlineSecondary
 894             };
 895             let pos = pos + 1;
 896
 897             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
 898                 for p in line_offset + 1..=line_offset + pos {
 899                     buffer.putc(p,
 900                                 code_offset + annotation.start_col - margin.computed_left,
 901                                 '|',
 902                                 style);
 903                 }
 904             }
 905             match annotation.annotation_type {
 906                 AnnotationType::MultilineStart(depth) => {
 907                     for p in line_offset + pos + 1..line_offset + line_len + 2 {
 908                         buffer.putc(p,
 909                                     width_offset + depth - 1,
 910                                     '|',
 911                                     style);
 912                     }
 913                 }
 914                 AnnotationType::MultilineEnd(depth) => {
 915                     for p in line_offset..=line_offset + pos {
 916                         buffer.putc(p,
 917                                     width_offset + depth - 1,
 918                                     '|',
 919                                     style);
 920                     }
 921                 }
 922                 _ => (),
 923             }
 924         }
 925
 926         // Write the labels on the annotations that actually have a label.
 927         //
 928         // After this we will have:
 929         //
 930         // 2 |   fn foo() {
 931         //   |  __________
 932         //   |      |
 933         //   |      something about `foo`
 934         // 3 |
 935         // 4 |   }
 936         //   |  _  test
 937         for &(pos, annotation) in &annotations_position {
 938             let style = if annotation.is_primary {
 939                 Style::LabelPrimary
 940             } else {
 941                 Style::LabelSecondary
 942             };
 943             let (pos, col) = if pos == 0 {
 944                 (pos + 1, if annotation.end_col + 1 > left {
 945                     annotation.end_col + 1 - left
 946                 } else {
 947                     0
 948                 })
 949             } else {
 950                 (pos + 2, if annotation.start_col > left {
 951                     annotation.start_col - left
 952                 } else {
 953                     0
 954                 })
 955             };
 956             if let Some(ref label) = annotation.label {
 957                 buffer.puts(line_offset + pos, code_offset + col, &label, style);
 958             }
 959         }
 960
 961         // Sort from biggest span to smallest span so that smaller spans are
 962         // represented in the output:
 963         //
 964         // x | fn foo()
 965         //   | ^^^---^^
 966         //   | |  |
 967         //   | |  something about `foo`
 968         //   | something about `fn foo()`
 969         annotations_position.sort_by(|a, b| {
 970             // Decreasing order. When `a` and `b` are the same length, prefer `Primary`.
 971             (a.1.len(), !a.1.is_primary).cmp(&(b.1.len(), !b.1.is_primary)).reverse()
 972         });
 973
 974         // Write the underlines.
 975         //
 976         // After this we will have:
 977         //
 978         // 2 |   fn foo() {
 979         //   |  ____-_____^
 980         //   |      |
 981         //   |      something about `foo`
 982         // 3 |
 983         // 4 |   }
 984         //   |  _^  test
 985         for &(_, annotation) in &annotations_position {
 986             let (underline, style) = if annotation.is_primary {
 987                 ('^', Style::UnderlinePrimary)
 988             } else {
 989                 ('-', Style::UnderlineSecondary)
 990             };
 991             for p in annotation.start_col..annotation.end_col {
 992                 buffer.putc(
 993                     line_offset + 1,
 994                     if code_offset + p > left {
 995                         code_offset + p - left
 996                     } else {
 997                         0
 998                     },
 999                     underline,
1000                     style,
1001                 );
1002             }
1003         }
1004         annotations_position.iter().filter_map(|&(_, annotation)| {
1005             match annotation.annotation_type {
1006                 AnnotationType::MultilineStart(p) | AnnotationType::MultilineEnd(p) => {
1007                     let style = if annotation.is_primary {
1008                         Style::LabelPrimary
1009                     } else {
1010                         Style::LabelSecondary
1011                     };
1012                     Some((p, style))
1013                 }
1014                 _ => None
1015             }
1016
1017         }).collect::<Vec<_>>()
1018     }
1019
1020     fn get_multispan_max_line_num(&mut self, msp: &MultiSpan) -> usize {
1021         let mut max = 0;
1022         if let Some(ref sm) = self.sm {
1023             for primary_span in msp.primary_spans() {
1024                 if !primary_span.is_dummy() {
1025                     let hi = sm.lookup_char_pos(primary_span.hi());
1026                     if hi.line > max {
1027                         max = hi.line;
1028                     }
1029                 }
1030             }
1031             if !self.short_message {
1032                 for span_label in msp.span_labels() {
1033                     if !span_label.span.is_dummy() {
1034                         let hi = sm.lookup_char_pos(span_label.span.hi());
1035                         if hi.line > max {
1036                             max = hi.line;
1037                         }
1038                     }
1039                 }
1040             }
1041         }
1042         max
1043     }
1044
1045     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
1046
1047         let primary = self.get_multispan_max_line_num(span);
1048         let mut max = primary;
1049
1050         for sub in children {
1051             let sub_result = self.get_multispan_max_line_num(&sub.span);
1052             max = std::cmp::max(sub_result, max);
1053         }
1054         max
1055     }
1056
1057     /// Adds a left margin to every line but the first, given a padding length and the label being
1058     /// displayed, keeping the provided highlighting.
1059     fn msg_to_buffer(&self,
1060                      buffer: &mut StyledBuffer,
1061                      msg: &[(String, Style)],
1062                      padding: usize,
1063                      label: &str,
1064                      override_style: Option<Style>) {
1065
1066         // The extra 5 ` ` is padding that's always needed to align to the `note: `:
1067         //
1068         //   error: message
1069         //     --> file.rs:13:20
1070         //      |
1071         //   13 |     <CODE>
1072         //      |      ^^^^
1073         //      |
1074         //      = note: multiline
1075         //              message
1076         //   ++^^^----xx
1077         //    |  |   | |
1078         //    |  |   | magic `2`
1079         //    |  |   length of label
1080         //    |  magic `3`
1081         //    `max_line_num_len`
1082         let padding = " ".repeat(padding + label.len() + 5);
1083
1084         /// Returns `true` if `style`, or the override if present and the style is `NoStyle`.
1085         fn style_or_override(style: Style, override_style: Option<Style>) -> Style {
1086             if let Some(o) = override_style {
1087                 if style == Style::NoStyle {
1088                     return o;
1089                 }
1090             }
1091             style
1092         }
1093
1094         let mut line_number = 0;
1095
1096         // Provided the following diagnostic message:
1097         //
1098         //     let msg = vec![
1099         //       ("
1100         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
1101         //       ("looks", Style::Highlight),
1102         //       ("with\nvery ", Style::NoStyle),
1103         //       ("weird", Style::Highlight),
1104         //       (" formats\n", Style::NoStyle),
1105         //       ("see?", Style::Highlight),
1106         //     ];
1107         //
1108         // the expected output on a note is (* surround the highlighted text)
1109         //
1110         //        = note: highlighted multiline
1111         //                string to
1112         //                see how it *looks* with
1113         //                very *weird* formats
1114         //                see?
1115         for &(ref text, ref style) in msg.iter() {
1116             let lines = text.split('\n').collect::<Vec<_>>();
1117             if lines.len() > 1 {
1118                 for (i, line) in lines.iter().enumerate() {
1119                     if i != 0 {
1120                         line_number += 1;
1121                         buffer.append(line_number, &padding, Style::NoStyle);
1122                     }
1123                     buffer.append(line_number, line, style_or_override(*style, override_style));
1124                 }
1125             } else {
1126                 buffer.append(line_number, text, style_or_override(*style, override_style));
1127             }
1128         }
1129     }
1130
1131     fn emit_message_default(
1132         &mut self,
1133         msp: &MultiSpan,
1134         msg: &[(String, Style)],
1135         code: &Option<DiagnosticId>,
1136         level: &Level,
1137         max_line_num_len: usize,
1138         is_secondary: bool,
1139     ) -> io::Result<()> {
1140         let mut buffer = StyledBuffer::new();
1141         let header_style = if is_secondary {
1142             Style::HeaderMsg
1143         } else {
1144             Style::MainHeaderMsg
1145         };
1146
1147         if !msp.has_primary_spans() && !msp.has_span_labels() && is_secondary
1148            && !self.short_message {
1149             // This is a secondary message with no span info
1150             for _ in 0..max_line_num_len {
1151                 buffer.prepend(0, " ", Style::NoStyle);
1152             }
1153             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
1154             if *level != Level::FailureNote {
1155                 let level_str = level.to_string();
1156                 if !level_str.is_empty() {
1157                     buffer.append(0, &level_str, Style::MainHeaderMsg);
1158                     buffer.append(0, ": ", Style::NoStyle);
1159                 }
1160             }
1161             self.msg_to_buffer(&mut buffer, msg, max_line_num_len, "note", None);
1162         } else {
1163             let level_str = level.to_string();
1164             // The failure note level itself does not provide any useful diagnostic information
1165             if *level != Level::FailureNote && !level_str.is_empty() {
1166                 buffer.append(0, &level_str, Style::Level(level.clone()));
1167             }
1168             // only render error codes, not lint codes
1169             if let Some(DiagnosticId::Error(ref code)) = *code {
1170                 buffer.append(0, "[", Style::Level(level.clone()));
1171                 buffer.append(0, &code, Style::Level(level.clone()));
1172                 buffer.append(0, "]", Style::Level(level.clone()));
1173             }
1174             if *level != Level::FailureNote && !level_str.is_empty() {
1175                 buffer.append(0, ": ", header_style);
1176             }
1177             for &(ref text, _) in msg.iter() {
1178                 buffer.append(0, text, header_style);
1179             }
1180         }
1181
1182         let mut annotated_files = FileWithAnnotatedLines::collect_annotations(msp, &self.sm);
1183
1184         // Make sure our primary file comes first
1185         let (primary_lo, sm) = if let (Some(sm), Some(ref primary_span)) =
1186             (self.sm.as_ref(), msp.primary_span().as_ref()) {
1187             if !primary_span.is_dummy() {
1188                 (sm.lookup_char_pos(primary_span.lo()), sm)
1189             } else {
1190                 emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1191                 return Ok(());
1192             }
1193         } else {
1194             // If we don't have span information, emit and exit
1195             emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1196             return Ok(());
1197         };
1198         if let Ok(pos) =
1199             annotated_files.binary_search_by(|x| x.file.name.cmp(&primary_lo.file.name)) {
1200             annotated_files.swap(0, pos);
1201         }
1202
1203         // Print out the annotate source lines that correspond with the error
1204         for annotated_file in annotated_files {
1205             // we can't annotate anything if the source is unavailable.
1206             if !sm.ensure_source_file_source_present(annotated_file.file.clone()) {
1207                 continue;
1208             }
1209
1210             // print out the span location and spacer before we print the annotated source
1211             // to do this, we need to know if this span will be primary
1212             let is_primary = primary_lo.file.name == annotated_file.file.name;
1213             if is_primary {
1214                 let loc = primary_lo.clone();
1215                 if !self.short_message {
1216                     // remember where we are in the output buffer for easy reference
1217                     let buffer_msg_line_offset = buffer.num_lines();
1218
1219                     buffer.prepend(buffer_msg_line_offset, "--> ", Style::LineNumber);
1220                     buffer.append(
1221                         buffer_msg_line_offset,
1222                         &format!(
1223                             "{}:{}:{}",
1224                             loc.file.name,
1225                             sm.doctest_offset_line(&loc.file.name, loc.line),
1226                             loc.col.0 + 1,
1227                         ),
1228                         Style::LineAndColumn,
1229                     );
1230                     for _ in 0..max_line_num_len {
1231                         buffer.prepend(buffer_msg_line_offset, " ", Style::NoStyle);
1232                     }
1233                 } else {
1234                     buffer.prepend(
1235                         0,
1236                         &format!(
1237                             "{}:{}:{}: ",
1238                             loc.file.name,
1239                             sm.doctest_offset_line(&loc.file.name, loc.line),
1240                             loc.col.0 + 1,
1241                         ),
1242                         Style::LineAndColumn,
1243                     );
1244                 }
1245             } else if !self.short_message {
1246                 // remember where we are in the output buffer for easy reference
1247                 let buffer_msg_line_offset = buffer.num_lines();
1248
1249                 // Add spacing line
1250                 draw_col_separator(&mut buffer, buffer_msg_line_offset, max_line_num_len + 1);
1251
1252                 // Then, the secondary file indicator
1253                 buffer.prepend(buffer_msg_line_offset + 1, "::: ", Style::LineNumber);
1254                 let loc = if let Some(first_line) = annotated_file.lines.first() {
1255                     let col = if let Some(first_annotation) = first_line.annotations.first() {
1256                         format!(":{}", first_annotation.start_col + 1)
1257                     } else {
1258                         String::new()
1259                     };
1260                     format!("{}:{}{}",
1261                             annotated_file.file.name,
1262                             sm.doctest_offset_line(
1263                                 &annotated_file.file.name, first_line.line_index),
1264                             col)
1265                 } else {
1266                     annotated_file.file.name.to_string()
1267                 };
1268                 buffer.append(buffer_msg_line_offset + 1,
1269                               &loc,
1270                               Style::LineAndColumn);
1271                 for _ in 0..max_line_num_len {
1272                     buffer.prepend(buffer_msg_line_offset + 1, " ", Style::NoStyle);
1273                 }
1274             }
1275
1276             if !self.short_message {
1277                 // Put in the spacer between the location and annotated source
1278                 let buffer_msg_line_offset = buffer.num_lines();
1279                 draw_col_separator_no_space(&mut buffer,
1280                                             buffer_msg_line_offset,
1281                                             max_line_num_len + 1);
1282
1283                 // Contains the vertical lines' positions for active multiline annotations
1284                 let mut multilines = FxHashMap::default();
1285
1286                 // Get the left-side margin to remove it
1287                 let mut whitespace_margin = std::usize::MAX;
1288                 for line_idx in 0..annotated_file.lines.len() {
1289                     let file = annotated_file.file.clone();
1290                     let line = &annotated_file.lines[line_idx];
1291                     if let Some(source_string) = file.get_line(line.line_index - 1) {
1292                         let leading_whitespace = source_string
1293                             .chars()
1294                             .take_while(|c| c.is_whitespace())
1295                             .count();
1296                         if source_string.chars().any(|c| !c.is_whitespace()) {
1297                             whitespace_margin = min(
1298                                 whitespace_margin,
1299                                 leading_whitespace,
1300                             );
1301                         }
1302                     }
1303                 }
1304                 if whitespace_margin == std::usize::MAX {
1305                     whitespace_margin = 0;
1306                 }
1307
1308                 // Left-most column any visible span points at.
1309                 let mut span_left_margin = std::usize::MAX;
1310                 for line in &annotated_file.lines {
1311                     for ann in &line.annotations {
1312                         span_left_margin = min(span_left_margin, ann.start_col);
1313                         span_left_margin = min(span_left_margin, ann.end_col);
1314                     }
1315                 }
1316                 if span_left_margin == std::usize::MAX {
1317                     span_left_margin = 0;
1318                 }
1319
1320                 // Right-most column any visible span points at.
1321                 let mut span_right_margin = 0;
1322                 let mut label_right_margin = 0;
1323                 let mut max_line_len = 0;
1324                 for line in &annotated_file.lines {
1325                     max_line_len = max(max_line_len, annotated_file.file
1326                         .get_line(line.line_index - 1)
1327                         .map(|s| s.len())
1328                         .unwrap_or(0));
1329                     for ann in &line.annotations {
1330                         span_right_margin = max(span_right_margin, ann.start_col);
1331                         span_right_margin = max(span_right_margin, ann.end_col);
1332                         // FIXME: account for labels not in the same line
1333                         let label_right = ann.label.as_ref().map(|l| l.len() + 1).unwrap_or(0);
1334                         label_right_margin = max(label_right_margin, ann.end_col + label_right);
1335                     }
1336                 }
1337
1338                 let width_offset = 3 + max_line_num_len;
1339                 let code_offset = if annotated_file.multiline_depth == 0 {
1340                     width_offset
1341                 } else {
1342                     width_offset + annotated_file.multiline_depth + 1
1343                 };
1344
1345                 let column_width = if let Some(width) = self.terminal_width {
1346                     width.saturating_sub(code_offset)
1347                 } else if self.ui_testing {
1348                     140
1349                 } else {
1350                     term_size::dimensions()
1351                         .map(|(w, _)| w.saturating_sub(code_offset))
1352                         .unwrap_or(std::usize::MAX)
1353                 };
1354
1355                 let margin = Margin::new(
1356                     whitespace_margin,
1357                     span_left_margin,
1358                     span_right_margin,
1359                     label_right_margin,
1360                     column_width,
1361                     max_line_len,
1362                 );
1363
1364                 // Next, output the annotate source for this file
1365                 for line_idx in 0..annotated_file.lines.len() {
1366                     let previous_buffer_line = buffer.num_lines();
1367
1368                     let depths = self.render_source_line(
1369                         &mut buffer,
1370                         annotated_file.file.clone(),
1371                         &annotated_file.lines[line_idx],
1372                         width_offset,
1373                         code_offset,
1374                         margin,
1375                     );
1376
1377                     let mut to_add = FxHashMap::default();
1378
1379                     for (depth, style) in depths {
1380                         if multilines.get(&depth).is_some() {
1381                             multilines.remove(&depth);
1382                         } else {
1383                             to_add.insert(depth, style);
1384                         }
1385                     }
1386
1387                     // Set the multiline annotation vertical lines to the left of
1388                     // the code in this line.
1389                     for (depth, style) in &multilines {
1390                         for line in previous_buffer_line..buffer.num_lines() {
1391                             draw_multiline_line(&mut buffer,
1392                                                 line,
1393                                                 width_offset,
1394                                                 *depth,
1395                                                 *style);
1396                         }
1397                     }
1398                     // check to see if we need to print out or elide lines that come between
1399                     // this annotated line and the next one.
1400                     if line_idx < (annotated_file.lines.len() - 1) {
1401                         let line_idx_delta = annotated_file.lines[line_idx + 1].line_index -
1402                                              annotated_file.lines[line_idx].line_index;
1403                         if line_idx_delta > 2 {
1404                             let last_buffer_line_num = buffer.num_lines();
1405                             buffer.puts(last_buffer_line_num, 0, "...", Style::LineNumber);
1406
1407                             // Set the multiline annotation vertical lines on `...` bridging line.
1408                             for (depth, style) in &multilines {
1409                                 draw_multiline_line(&mut buffer,
1410                                                     last_buffer_line_num,
1411                                                     width_offset,
1412                                                     *depth,
1413                                                     *style);
1414                             }
1415                         } else if line_idx_delta == 2 {
1416                             let unannotated_line = annotated_file.file
1417                                 .get_line(annotated_file.lines[line_idx].line_index)
1418                                 .unwrap_or_else(|| Cow::from(""));
1419
1420                             let last_buffer_line_num = buffer.num_lines();
1421
1422                             self.draw_line(
1423                                 &mut buffer,
1424                                 &unannotated_line,
1425                                 annotated_file.lines[line_idx + 1].line_index - 1,
1426                                 last_buffer_line_num,
1427                                 width_offset,
1428                                 code_offset,
1429                                 margin,
1430                             );
1431
1432                             for (depth, style) in &multilines {
1433                                 draw_multiline_line(
1434                                     &mut buffer,
1435                                     last_buffer_line_num,
1436                                     width_offset,
1437                                     *depth,
1438                                     *style,
1439                                 );
1440                             }
1441                         }
1442                     }
1443
1444                     multilines.extend(&to_add);
1445                 }
1446             }
1447         }
1448
1449         // final step: take our styled buffer, render it, then output it
1450         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1451
1452         Ok(())
1453
1454     }
1455
1456     fn emit_suggestion_default(
1457         &mut self,
1458         suggestion: &CodeSuggestion,
1459         level: &Level,
1460         max_line_num_len: usize,
1461     ) -> io::Result<()> {
1462         if let Some(ref sm) = self.sm {
1463             let mut buffer = StyledBuffer::new();
1464
1465             // Render the suggestion message
1466             let level_str = level.to_string();
1467             if !level_str.is_empty() {
1468                 buffer.append(0, &level_str, Style::Level(level.clone()));
1469                 buffer.append(0, ": ", Style::HeaderMsg);
1470             }
1471             self.msg_to_buffer(
1472                 &mut buffer,
1473                 &[(suggestion.msg.to_owned(), Style::NoStyle)],
1474                 max_line_num_len,
1475                 "suggestion",
1476                 Some(Style::HeaderMsg),
1477             );
1478
1479             // Render the replacements for each suggestion
1480             let suggestions = suggestion.splice_lines(&**sm);
1481
1482             let mut row_num = 2;
1483             for &(ref complete, ref parts) in suggestions.iter().take(MAX_SUGGESTIONS) {
1484                 // Only show underline if the suggestion spans a single line and doesn't cover the
1485                 // entirety of the code output. If you have multiple replacements in the same line
1486                 // of code, show the underline.
1487                 let show_underline = !(parts.len() == 1
1488                     && parts[0].snippet.trim() == complete.trim())
1489                     && complete.lines().count() == 1;
1490
1491                 let lines = sm.span_to_lines(parts[0].span).unwrap();
1492
1493                 assert!(!lines.lines.is_empty());
1494
1495                 let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
1496                 draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
1497                 let mut line_pos = 0;
1498                 let mut lines = complete.lines();
1499                 for line in lines.by_ref().take(MAX_HIGHLIGHT_LINES) {
1500                     // Print the span column to avoid confusion
1501                     buffer.puts(row_num,
1502                                 0,
1503                                 &self.maybe_anonymized(line_start + line_pos),
1504                                 Style::LineNumber);
1505                     // print the suggestion
1506                     draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1507                     buffer.append(row_num, line, Style::NoStyle);
1508                     line_pos += 1;
1509                     row_num += 1;
1510                 }
1511
1512                 // This offset and the ones below need to be signed to account for replacement code
1513                 // that is shorter than the original code.
1514                 let mut offset: isize = 0;
1515                 // Only show an underline in the suggestions if the suggestion is not the
1516                 // entirety of the code being shown and the displayed code is not multiline.
1517                 if show_underline {
1518                     draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1519                     for part in parts {
1520                         let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
1521                         let span_end_pos = sm.lookup_char_pos(part.span.hi()).col_display;
1522
1523                         // Do not underline the leading...
1524                         let start = part.snippet.len()
1525                             .saturating_sub(part.snippet.trim_start().len());
1526                         // ...or trailing spaces. Account for substitutions containing unicode
1527                         // characters.
1528                         let sub_len = part.snippet.trim().chars().fold(0, |acc, ch| {
1529                             acc + unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1)
1530                         });
1531
1532                         let underline_start = (span_start_pos + start) as isize + offset;
1533                         let underline_end = (span_start_pos + start + sub_len) as isize + offset;
1534                         for p in underline_start..underline_end {
1535                             buffer.putc(row_num,
1536                                         max_line_num_len + 3 + p as usize,
1537                                         '^',
1538                                         Style::UnderlinePrimary);
1539                         }
1540                         // underline removals too
1541                         if underline_start == underline_end {
1542                             for p in underline_start-1..underline_start+1 {
1543                                 buffer.putc(row_num,
1544                                             max_line_num_len + 3 + p as usize,
1545                                             '-',
1546                                             Style::UnderlineSecondary);
1547                             }
1548                         }
1549
1550                         // length of the code after substitution
1551                         let full_sub_len = part.snippet.chars().fold(0, |acc, ch| {
1552                             acc + unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1) as isize
1553                         });
1554
1555                         // length of the code to be substituted
1556                         let snippet_len = span_end_pos as isize - span_start_pos as isize;
1557                         // For multiple substitutions, use the position *after* the previous
1558                         // substitutions have happened.
1559                         offset += full_sub_len - snippet_len;
1560                     }
1561                     row_num += 1;
1562                 }
1563
1564                 // if we elided some lines, add an ellipsis
1565                 if lines.next().is_some() {
1566                     buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
1567                 } else if !show_underline {
1568                     draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
1569                     row_num += 1;
1570                 }
1571             }
1572             if suggestions.len() > MAX_SUGGESTIONS {
1573                 let msg = format!("and {} other candidates", suggestions.len() - MAX_SUGGESTIONS);
1574                 buffer.puts(row_num, 0, &msg, Style::NoStyle);
1575             }
1576             emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1577         }
1578         Ok(())
1579     }
1580
1581     fn emit_messages_default(&mut self,
1582                              level: &Level,
1583                              message: &[(String, Style)],
1584                              code: &Option<DiagnosticId>,
1585                              span: &MultiSpan,
1586                              children: &[SubDiagnostic],
1587                              suggestions: &[CodeSuggestion]) {
1588         let max_line_num_len = if self.ui_testing {
1589             ANONYMIZED_LINE_NUM.len()
1590         } else {
1591             self.get_max_line_num(span, children).to_string().len()
1592         };
1593
1594         match self.emit_message_default(span,
1595                                         message,
1596                                         code,
1597                                         level,
1598                                         max_line_num_len,
1599                                         false) {
1600             Ok(()) => {
1601                 if !children.is_empty() {
1602                     let mut buffer = StyledBuffer::new();
1603                     if !self.short_message {
1604                         draw_col_separator_no_space(&mut buffer, 0, max_line_num_len + 1);
1605                     }
1606                     match emit_to_destination(&buffer.render(), level, &mut self.dst,
1607                                               self.short_message) {
1608                         Ok(()) => (),
1609                         Err(e) => panic!("failed to emit error: {}", e)
1610                     }
1611                 }
1612                 if !self.short_message {
1613                     for child in children {
1614                         let span = child.render_span.as_ref().unwrap_or(&child.span);
1615                         match self.emit_message_default(
1616                             &span,
1617                             &child.styled_message(),
1618                             &None,
1619                             &child.level,
1620                             max_line_num_len,
1621                             true,
1622                         ) {
1623                             Err(e) => panic!("failed to emit error: {}", e),
1624                             _ => ()
1625                         }
1626                     }
1627                     for sugg in suggestions {
1628                         if sugg.style == SuggestionStyle::CompletelyHidden {
1629                             // do not display this suggestion, it is meant only for tools
1630                         } else if sugg.style == SuggestionStyle::HideCodeAlways {
1631                             match self.emit_message_default(
1632                                 &MultiSpan::new(),
1633                                 &[(sugg.msg.to_owned(), Style::HeaderMsg)],
1634                                 &None,
1635                                 &Level::Help,
1636                                 max_line_num_len,
1637                                 true,
1638                             ) {
1639                                 Err(e) => panic!("failed to emit error: {}", e),
1640                                 _ => ()
1641                             }
1642                         } else {
1643                             match self.emit_suggestion_default(
1644                                 sugg,
1645                                 &Level::Help,
1646                                 max_line_num_len,
1647                             ) {
1648                                 Err(e) => panic!("failed to emit error: {}", e),
1649                                 _ => ()
1650                             }
1651                         }
1652                     }
1653                 }
1654             }
1655             Err(e) => panic!("failed to emit error: {}", e),
1656         }
1657
1658         let mut dst = self.dst.writable();
1659         match writeln!(dst) {
1660             Err(e) => panic!("failed to emit error: {}", e),
1661             _ => {
1662                 match dst.flush() {
1663                     Err(e) => panic!("failed to emit error: {}", e),
1664                     _ => (),
1665                 }
1666             }
1667         }
1668     }
1669 }
1670
1671 impl FileWithAnnotatedLines {
1672     /// Preprocess all the annotations so that they are grouped by file and by line number
1673     /// This helps us quickly iterate over the whole message (including secondary file spans)
1674     pub fn collect_annotations(
1675         msp: &MultiSpan,
1676         source_map: &Option<Lrc<SourceMapperDyn>>
1677     ) -> Vec<FileWithAnnotatedLines> {
1678         fn add_annotation_to_file(file_vec: &mut Vec<FileWithAnnotatedLines>,
1679                                   file: Lrc<SourceFile>,
1680                                   line_index: usize,
1681                                   ann: Annotation) {
1682
1683             for slot in file_vec.iter_mut() {
1684                 // Look through each of our files for the one we're adding to
1685                 if slot.file.name == file.name {
1686                     // See if we already have a line for it
1687                     for line_slot in &mut slot.lines {
1688                         if line_slot.line_index == line_index {
1689                             line_slot.annotations.push(ann);
1690                             return;
1691                         }
1692                     }
1693                     // We don't have a line yet, create one
1694                     slot.lines.push(Line {
1695                         line_index,
1696                         annotations: vec![ann],
1697                     });
1698                     slot.lines.sort();
1699                     return;
1700                 }
1701             }
1702             // This is the first time we're seeing the file
1703             file_vec.push(FileWithAnnotatedLines {
1704                 file,
1705                 lines: vec![Line {
1706                                 line_index,
1707                                 annotations: vec![ann],
1708                             }],
1709                 multiline_depth: 0,
1710             });
1711         }
1712
1713         let mut output = vec![];
1714         let mut multiline_annotations = vec![];
1715
1716         if let Some(ref sm) = source_map {
1717             for span_label in msp.span_labels() {
1718                 if span_label.span.is_dummy() {
1719                     continue;
1720                 }
1721
1722                 let lo = sm.lookup_char_pos(span_label.span.lo());
1723                 let mut hi = sm.lookup_char_pos(span_label.span.hi());
1724
1725                 // Watch out for "empty spans". If we get a span like 6..6, we
1726                 // want to just display a `^` at 6, so convert that to
1727                 // 6..7. This is degenerate input, but it's best to degrade
1728                 // gracefully -- and the parser likes to supply a span like
1729                 // that for EOF, in particular.
1730
1731                 if lo.col_display == hi.col_display && lo.line == hi.line {
1732                     hi.col_display += 1;
1733                 }
1734
1735                 let ann_type = if lo.line != hi.line {
1736                     let ml = MultilineAnnotation {
1737                         depth: 1,
1738                         line_start: lo.line,
1739                         line_end: hi.line,
1740                         start_col: lo.col_display,
1741                         end_col: hi.col_display,
1742                         is_primary: span_label.is_primary,
1743                         label: span_label.label.clone(),
1744                         overlaps_exactly: false,
1745                     };
1746                     multiline_annotations.push((lo.file.clone(), ml.clone()));
1747                     AnnotationType::Multiline(ml)
1748                 } else {
1749                     AnnotationType::Singleline
1750                 };
1751                 let ann = Annotation {
1752                     start_col: lo.col_display,
1753                     end_col: hi.col_display,
1754                     is_primary: span_label.is_primary,
1755                     label: span_label.label.clone(),
1756                     annotation_type: ann_type,
1757                 };
1758
1759                 if !ann.is_multiline() {
1760                     add_annotation_to_file(&mut output, lo.file, lo.line, ann);
1761                 }
1762             }
1763         }
1764
1765         // Find overlapping multiline annotations, put them at different depths
1766         multiline_annotations.sort_by_key(|&(_, ref ml)| (ml.line_start, ml.line_end));
1767         for item in multiline_annotations.clone() {
1768             let ann = item.1;
1769             for item in multiline_annotations.iter_mut() {
1770                 let ref mut a = item.1;
1771                 // Move all other multiline annotations overlapping with this one
1772                 // one level to the right.
1773                 if !(ann.same_span(a)) &&
1774                     num_overlap(ann.line_start, ann.line_end, a.line_start, a.line_end, true)
1775                 {
1776                     a.increase_depth();
1777                 } else if ann.same_span(a) && &ann != a {
1778                     a.overlaps_exactly = true;
1779                 } else {
1780                     break;
1781                 }
1782             }
1783         }
1784
1785         let mut max_depth = 0;  // max overlapping multiline spans
1786         for (file, ann) in multiline_annotations {
1787             if ann.depth > max_depth {
1788                 max_depth = ann.depth;
1789             }
1790             let mut end_ann = ann.as_end();
1791             if !ann.overlaps_exactly {
1792                 // avoid output like
1793                 //
1794                 //  |        foo(
1795                 //  |   _____^
1796                 //  |  |_____|
1797                 //  | ||         bar,
1798                 //  | ||     );
1799                 //  | ||      ^
1800                 //  | ||______|
1801                 //  |  |______foo
1802                 //  |         baz
1803                 //
1804                 // and instead get
1805                 //
1806                 //  |       foo(
1807                 //  |  _____^
1808                 //  | |         bar,
1809                 //  | |     );
1810                 //  | |      ^
1811                 //  | |      |
1812                 //  | |______foo
1813                 //  |        baz
1814                 add_annotation_to_file(&mut output, file.clone(), ann.line_start, ann.as_start());
1815                 // 4 is the minimum vertical length of a multiline span when presented: two lines
1816                 // of code and two lines of underline. This is not true for the special case where
1817                 // the beginning doesn't have an underline, but the current logic seems to be
1818                 // working correctly.
1819                 let middle = min(ann.line_start + 4, ann.line_end);
1820                 for line in ann.line_start + 1..middle {
1821                     // Every `|` that joins the beginning of the span (`___^`) to the end (`|__^`).
1822                     add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
1823                 }
1824                 if middle < ann.line_end - 1 {
1825                     for line in ann.line_end - 1..ann.line_end {
1826                         add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
1827                     }
1828                 }
1829             } else {
1830                 end_ann.annotation_type = AnnotationType::Singleline;
1831             }
1832             add_annotation_to_file(&mut output, file, ann.line_end, end_ann);
1833         }
1834         for file_vec in output.iter_mut() {
1835             file_vec.multiline_depth = max_depth;
1836         }
1837         output
1838     }
1839 }
1840
1841 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1842     buffer.puts(line, col, "| ", Style::LineNumber);
1843 }
1844
1845 fn draw_col_separator_no_space(buffer: &mut StyledBuffer, line: usize, col: usize) {
1846     draw_col_separator_no_space_with_style(buffer, line, col, Style::LineNumber);
1847 }
1848
1849 fn draw_col_separator_no_space_with_style(buffer: &mut StyledBuffer,
1850                                           line: usize,
1851                                           col: usize,
1852                                           style: Style) {
1853     buffer.putc(line, col, '|', style);
1854 }
1855
1856 fn draw_range(buffer: &mut StyledBuffer, symbol: char, line: usize,
1857               col_from: usize, col_to: usize, style: Style) {
1858     for col in col_from..col_to {
1859         buffer.putc(line, col, symbol, style);
1860     }
1861 }
1862
1863 fn draw_note_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1864     buffer.puts(line, col, "= ", Style::LineNumber);
1865 }
1866
1867 fn draw_multiline_line(buffer: &mut StyledBuffer,
1868                        line: usize,
1869                        offset: usize,
1870                        depth: usize,
1871                        style: Style)
1872 {
1873     buffer.putc(line, offset + depth - 1, '|', style);
1874 }
1875
1876 fn num_overlap(a_start: usize, a_end: usize, b_start: usize, b_end:usize, inclusive: bool) -> bool {
1877     let extra = if inclusive {
1878         1
1879     } else {
1880         0
1881     };
1882     (b_start..b_end + extra).contains(&a_start) ||
1883     (a_start..a_end + extra).contains(&b_start)
1884 }
1885 fn overlaps(a1: &Annotation, a2: &Annotation, padding: usize) -> bool {
1886     num_overlap(a1.start_col, a1.end_col + padding, a2.start_col, a2.end_col, false)
1887 }
1888
1889 fn emit_to_destination(rendered_buffer: &[Vec<StyledString>],
1890                        lvl: &Level,
1891                        dst: &mut Destination,
1892                        short_message: bool)
1893                        -> io::Result<()> {
1894     use crate::lock;
1895
1896     let mut dst = dst.writable();
1897
1898     // In order to prevent error message interleaving, where multiple error lines get intermixed
1899     // when multiple compiler processes error simultaneously, we emit errors with additional
1900     // steps.
1901     //
1902     // On Unix systems, we write into a buffered terminal rather than directly to a terminal. When
1903     // the .flush() is called we take the buffer created from the buffered writes and write it at
1904     // one shot.  Because the Unix systems use ANSI for the colors, which is a text-based styling
1905     // scheme, this buffered approach works and maintains the styling.
1906     //
1907     // On Windows, styling happens through calls to a terminal API. This prevents us from using the
1908     // same buffering approach.  Instead, we use a global Windows mutex, which we acquire long
1909     // enough to output the full error message, then we release.
1910     let _buffer_lock = lock::acquire_global_lock("rustc_errors");
1911     for (pos, line) in rendered_buffer.iter().enumerate() {
1912         for part in line {
1913             dst.apply_style(lvl.clone(), part.style)?;
1914             write!(dst, "{}", part.text)?;
1915             dst.reset()?;
1916         }
1917         if !short_message && (!lvl.is_failure_note() || pos != rendered_buffer.len() - 1) {
1918             writeln!(dst)?;
1919         }
1920     }
1921     dst.flush()?;
1922     Ok(())
1923 }
1924
1925 pub enum Destination {
1926     Terminal(StandardStream),
1927     Buffered(BufferWriter),
1928     // The bool denotes whether we should be emitting ansi color codes or not
1929     Raw(Box<(dyn Write + Send)>, bool),
1930 }
1931
1932 pub enum WritableDst<'a> {
1933     Terminal(&'a mut StandardStream),
1934     Buffered(&'a mut BufferWriter, Buffer),
1935     Raw(&'a mut (dyn Write + Send)),
1936     ColoredRaw(Ansi<&'a mut (dyn Write + Send)>),
1937 }
1938
1939 impl Destination {
1940     fn from_stderr(color: ColorConfig) -> Destination {
1941         let choice = color.to_color_choice();
1942         // On Windows we'll be performing global synchronization on the entire
1943         // system for emitting rustc errors, so there's no need to buffer
1944         // anything.
1945         //
1946         // On non-Windows we rely on the atomicity of `write` to ensure errors
1947         // don't get all jumbled up.
1948         if cfg!(windows) {
1949             Terminal(StandardStream::stderr(choice))
1950         } else {
1951             Buffered(BufferWriter::stderr(choice))
1952         }
1953     }
1954
1955     fn writable(&mut self) -> WritableDst<'_> {
1956         match *self {
1957             Destination::Terminal(ref mut t) => WritableDst::Terminal(t),
1958             Destination::Buffered(ref mut t) => {
1959                 let buf = t.buffer();
1960                 WritableDst::Buffered(t, buf)
1961             }
1962             Destination::Raw(ref mut t, false) => WritableDst::Raw(t),
1963             Destination::Raw(ref mut t, true) => WritableDst::ColoredRaw(Ansi::new(t)),
1964         }
1965     }
1966 }
1967
1968 impl<'a> WritableDst<'a> {
1969     fn apply_style(&mut self, lvl: Level, style: Style) -> io::Result<()> {
1970         let mut spec = ColorSpec::new();
1971         match style {
1972             Style::LineAndColumn => {}
1973             Style::LineNumber => {
1974                 spec.set_bold(true);
1975                 spec.set_intense(true);
1976                 if cfg!(windows) {
1977                     spec.set_fg(Some(Color::Cyan));
1978                 } else {
1979                     spec.set_fg(Some(Color::Blue));
1980                 }
1981             }
1982             Style::Quotation => {}
1983             Style::MainHeaderMsg => {
1984                 spec.set_bold(true);
1985                 if cfg!(windows) {
1986                     spec.set_intense(true)
1987                         .set_fg(Some(Color::White));
1988                 }
1989             }
1990             Style::UnderlinePrimary | Style::LabelPrimary => {
1991                 spec = lvl.color();
1992                 spec.set_bold(true);
1993             }
1994             Style::UnderlineSecondary |
1995             Style::LabelSecondary => {
1996                 spec.set_bold(true)
1997                     .set_intense(true);
1998                 if cfg!(windows) {
1999                     spec.set_fg(Some(Color::Cyan));
2000                 } else {
2001                     spec.set_fg(Some(Color::Blue));
2002                 }
2003             }
2004             Style::HeaderMsg |
2005             Style::NoStyle => {}
2006             Style::Level(lvl) => {
2007                 spec = lvl.color();
2008                 spec.set_bold(true);
2009             }
2010             Style::Highlight => {
2011                 spec.set_bold(true);
2012             }
2013         }
2014         self.set_color(&spec)
2015     }
2016
2017     fn set_color(&mut self, color: &ColorSpec) -> io::Result<()> {
2018         match *self {
2019             WritableDst::Terminal(ref mut t) => t.set_color(color),
2020             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
2021             WritableDst::ColoredRaw(ref mut t) => t.set_color(color),
2022             WritableDst::Raw(_) => Ok(())
2023         }
2024     }
2025
2026     fn reset(&mut self) -> io::Result<()> {
2027         match *self {
2028             WritableDst::Terminal(ref mut t) => t.reset(),
2029             WritableDst::Buffered(_, ref mut t) => t.reset(),
2030             WritableDst::ColoredRaw(ref mut t) => t.reset(),
2031             WritableDst::Raw(_) => Ok(()),
2032         }
2033     }
2034 }
2035
2036 impl<'a> Write for WritableDst<'a> {
2037     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
2038         match *self {
2039             WritableDst::Terminal(ref mut t) => t.write(bytes),
2040             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
2041             WritableDst::Raw(ref mut w) => w.write(bytes),
2042             WritableDst::ColoredRaw(ref mut t) => t.write(bytes),
2043         }
2044     }
2045
2046     fn flush(&mut self) -> io::Result<()> {
2047         match *self {
2048             WritableDst::Terminal(ref mut t) => t.flush(),
2049             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
2050             WritableDst::Raw(ref mut w) => w.flush(),
2051             WritableDst::ColoredRaw(ref mut w) => w.flush(),
2052         }
2053     }
2054 }
2055
2056 impl<'a> Drop for WritableDst<'a> {
2057     fn drop(&mut self) {
2058         match *self {
2059             WritableDst::Buffered(ref mut dst, ref mut buf) => {
2060                 drop(dst.print(buf));
2061             }
2062             _ => {}
2063         }
2064     }
2065 }