src/librustc_errors/emitter.rs

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