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