src/librustc_errors/emitter.rs

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