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