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 use syntax_pos::source_map::SourceMap;
  14
  15 use crate::{
  16     Level, CodeSuggestion, Diagnostic, SubDiagnostic, pluralize,
  17     SuggestionStyle, DiagnosticId,
  18 };
  19 use crate::Level::Error;
  20 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
  21 use crate::styled_buffer::StyledBuffer;
  22
  23 use rustc_data_structures::fx::FxHashMap;
  24 use rustc_data_structures::sync::Lrc;
  25 use std::borrow::Cow;
  26 use std::io::prelude::*;
  27 use std::io;
  28 use std::cmp::{min, max, Reverse};
  29 use std::path::Path;
  30 use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter, Ansi};
  31 use termcolor::{WriteColor, Color, Buffer};
  32
  33 /// Describes the way the content of the `rendered` field of the json output is generated
  34 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
  35 pub enum HumanReadableErrorType {
  36     Default(ColorConfig),
  37     AnnotateSnippet(ColorConfig),
  38     Short(ColorConfig),
  39 }
  40
  41 impl HumanReadableErrorType {
  42     /// Returns a (`short`, `color`) tuple
  43     pub fn unzip(self) -> (bool, ColorConfig) {
  44         match self {
  45             HumanReadableErrorType::Default(cc) => (false, cc),
  46             HumanReadableErrorType::Short(cc) => (true, cc),
  47             HumanReadableErrorType::AnnotateSnippet(cc) => (false, cc),
  48         }
  49     }
  50     pub fn new_emitter(
  51         self,
  52         dst: Box<dyn Write + Send>,
  53         source_map: Option<Lrc<SourceMap>>,
  54         teach: bool,
  55         terminal_width: Option<usize>,
  56         external_macro_backtrace: bool,
  57     ) -> EmitterWriter {
  58         let (short, color_config) = self.unzip();
  59         let color = color_config.suggests_using_colors();
  60         EmitterWriter::new(dst, source_map, short, teach, color, terminal_width,
  61             external_macro_backtrace)
  62     }
  63 }
  64
  65 #[derive(Clone, Copy, Debug)]
  66 struct Margin {
  67     /// The available whitespace in the left that can be consumed when centering.
  68     pub whitespace_left: usize,
  69     /// The column of the beginning of left-most span.
  70     pub span_left: usize,
  71     /// The column of the end of right-most span.
  72     pub span_right: usize,
  73     /// The beginning of the line to be displayed.
  74     pub computed_left: usize,
  75     /// The end of the line to be displayed.
  76     pub computed_right: usize,
  77     /// The current width of the terminal. 140 by default and in tests.
  78     pub column_width: usize,
  79     /// The end column of a span label, including the span. Doesn't account for labels not in the
  80     /// same line as the span.
  81     pub label_right: usize,
  82 }
  83
  84 impl Margin {
  85     fn new(
  86         whitespace_left: usize,
  87         span_left: usize,
  88         span_right: usize,
  89         label_right: usize,
  90         column_width: usize,
  91         max_line_len: usize,
  92     ) -> Self {
  93         // The 6 is padding to give a bit of room for `...` when displaying:
  94         // ```
  95         // error: message
  96         //   --> file.rs:16:58
  97         //    |
  98         // 16 | ... fn foo(self) -> Self::Bar {
  99         //    |                     ^^^^^^^^^
 100         // ```
 101
 102         let mut m = Margin {
 103             whitespace_left: whitespace_left.saturating_sub(6),
 104             span_left: span_left.saturating_sub(6),
 105             span_right: span_right + 6,
 106             computed_left: 0,
 107             computed_right: 0,
 108             column_width,
 109             label_right: label_right + 6,
 110         };
 111         m.compute(max_line_len);
 112         m
 113     }
 114
 115     fn was_cut_left(&self) -> bool {
 116         self.computed_left > 0
 117     }
 118
 119     fn was_cut_right(&self, line_len: usize) -> bool {
 120         let right = if self.computed_right == self.span_right ||
 121             self.computed_right == self.label_right
 122         {
 123             // Account for the "..." padding given above. Otherwise we end up with code lines that
 124             // do fit but end in "..." as if they were trimmed.
 125             self.computed_right - 6
 126         } else {
 127             self.computed_right
 128         };
 129         right < line_len && self.computed_left + self.column_width < line_len
 130     }
 131
 132     fn compute(&mut self, max_line_len: usize) {
 133         // When there's a lot of whitespace (>20), we want to trim it as it is useless.
 134         self.computed_left = if self.whitespace_left > 20 {
 135             self.whitespace_left - 16 // We want some padding.
 136         } else {
 137             0
 138         };
 139         // We want to show as much as possible, max_line_len is the right-most boundary for the
 140         // relevant code.
 141         self.computed_right = max(max_line_len, self.computed_left);
 142
 143         if self.computed_right - self.computed_left > self.column_width {
 144             // Trimming only whitespace isn't enough, let's get craftier.
 145             if self.label_right - self.whitespace_left <= self.column_width {
 146                 // Attempt to fit the code window only trimming whitespace.
 147                 self.computed_left = self.whitespace_left;
 148                 self.computed_right = self.computed_left + self.column_width;
 149             } else if self.label_right - self.span_left <= self.column_width {
 150                 // Attempt to fit the code window considering only the spans and labels.
 151                 let padding_left = (self.column_width - (self.label_right - self.span_left)) / 2;
 152                 self.computed_left = self.span_left.saturating_sub(padding_left);
 153                 self.computed_right = self.computed_left + self.column_width;
 154             } else if self.span_right - self.span_left <= self.column_width {
 155                 // Attempt to fit the code window considering the spans and labels plus padding.
 156                 let padding_left = (self.column_width - (self.span_right - self.span_left)) / 5 * 2;
 157                 self.computed_left = self.span_left.saturating_sub(padding_left);
 158                 self.computed_right = self.computed_left + self.column_width;
 159             } else { // Mostly give up but still don't show the full line.
 160                 self.computed_left = self.span_left;
 161                 self.computed_right = self.span_right;
 162             }
 163         }
 164     }
 165
 166     fn left(&self, line_len: usize) -> usize {
 167         min(self.computed_left, line_len)
 168     }
 169
 170     fn right(&self, line_len: usize) -> usize {
 171         if line_len.saturating_sub(self.computed_left) <= self.column_width {
 172             line_len
 173         } else {
 174             min(line_len, self.computed_right)
 175         }
 176     }
 177 }
 178
 179 const ANONYMIZED_LINE_NUM: &str = "LL";
 180
 181 /// Emitter trait for emitting errors.
 182 pub trait Emitter {
 183     /// Emit a structured diagnostic.
 184     fn emit_diagnostic(&mut self, diag: &Diagnostic);
 185
 186     /// Emit a notification that an artifact has been output.
 187     /// This is currently only supported for the JSON format,
 188     /// other formats can, and will, simply ignore it.
 189     fn emit_artifact_notification(&mut self, _path: &Path, _artifact_type: &str) {}
 190
 191     /// Checks if should show explanations about "rustc --explain"
 192     fn should_show_explain(&self) -> bool {
 193         true
 194     }
 195
 196     fn source_map(&self) -> Option<&Lrc<SourceMap>>;
 197
 198     /// Formats the substitutions of the primary_span
 199     ///
 200     /// The are a lot of conditions to this method, but in short:
 201     ///
 202     /// * If the current `Diagnostic` has only one visible `CodeSuggestion`,
 203     ///   we format the `help` suggestion depending on the content of the
 204     ///   substitutions. In that case, we return the modified span only.
 205     ///
 206     /// * If the current `Diagnostic` has multiple suggestions,
 207     ///   we return the original `primary_span` and the original suggestions.
 208     fn primary_span_formatted<'a>(
 209         &mut self,
 210         diag: &'a Diagnostic,
 211     ) -> (MultiSpan, &'a [CodeSuggestion]) {
 212         let mut primary_span = diag.span.clone();
 213         if let Some((sugg, rest)) = diag.suggestions.split_first() {
 214             if rest.is_empty() &&
 215                // ^ if there is only one suggestion
 216                // don't display multi-suggestions as labels
 217                sugg.substitutions.len() == 1 &&
 218                // don't display multipart suggestions as labels
 219                sugg.substitutions[0].parts.len() == 1 &&
 220                // don't display long messages as labels
 221                sugg.msg.split_whitespace().count() < 10 &&
 222                // don't display multiline suggestions as labels
 223                !sugg.substitutions[0].parts[0].snippet.contains('\n') &&
 224                ![
 225                     // when this style is set we want the suggestion to be a message, not inline
 226                     SuggestionStyle::HideCodeAlways,
 227                     // trivial suggestion for tooling's sake, never shown
 228                     SuggestionStyle::CompletelyHidden,
 229                     // subtle suggestion, never shown inline
 230                     SuggestionStyle::ShowAlways,
 231                ].contains(&sugg.style)
 232             {
 233                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
 234                 let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
 235                     // This substitution is only removal OR we explicitly don't want to show the
 236                     // code inline (`hide_inline`). Therefore, we don't show the substitution.
 237                     format!("help: {}", sugg.msg)
 238                 } else {
 239                     // Show the default suggestion text with the substitution
 240                     format!(
 241                         "help: {}{}: `{}`",
 242                         sugg.msg,
 243                         if self.source_map().map(|sm| is_case_difference(
 244                             &**sm,
 245                             substitution,
 246                             sugg.substitutions[0].parts[0].span,
 247                         )).unwrap_or(false) {
 248                             " (notice the capitalization)"
 249                         } else {
 250                             ""
 251                         },
 252                         substitution,
 253                     )
 254                 };
 255                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
 256
 257                 // We return only the modified primary_span
 258                 (primary_span, &[])
 259             } else {
 260                 // if there are multiple suggestions, print them all in full
 261                 // to be consistent. We could try to figure out if we can
 262                 // make one (or the first one) inline, but that would give
 263                 // undue importance to a semi-random suggestion
 264                 (primary_span, &diag.suggestions)
 265             }
 266         } else {
 267             (primary_span, &diag.suggestions)
 268         }
 269     }
 270
 271     // This does a small "fix" for multispans by looking to see if it can find any that
 272     // point directly at <*macros>. Since these are often difficult to read, this
 273     // will change the span to point at the use site.
 274     fn fix_multispans_in_std_macros(&self,
 275                                     source_map: &Option<Lrc<SourceMap>>,
 276                                     span: &mut MultiSpan,
 277                                     children: &mut Vec<SubDiagnostic>,
 278                                     level: &Level,
 279                                     backtrace: bool) {
 280         let mut spans_updated = self.fix_multispan_in_std_macros(source_map, span, backtrace);
 281         for child in children.iter_mut() {
 282             spans_updated |= self.fix_multispan_in_std_macros(
 283                                  source_map,
 284                                  &mut child.span,
 285                                  backtrace
 286                              );
 287         }
 288         let msg = if level == &Error {
 289             "this error originates in a macro outside of the current crate \
 290              (in Nightly builds, run with -Z external-macro-backtrace \
 291               for more info)".to_string()
 292         } else {
 293             "this warning originates in a macro outside of the current crate \
 294              (in Nightly builds, run with -Z external-macro-backtrace \
 295               for more info)".to_string()
 296         };
 297
 298         if spans_updated {
 299             children.push(SubDiagnostic {
 300                 level: Level::Note,
 301                 message: vec![
 302                     (msg,
 303                      Style::NoStyle),
 304                 ],
 305                 span: MultiSpan::new(),
 306                 render_span: None,
 307             });
 308         }
 309     }
 310
 311     // This "fixes" MultiSpans that contain Spans that are pointing to locations inside of
 312     // <*macros>. Since these locations are often difficult to read, we move these Spans from
 313     // <*macros> to their corresponding use site.
 314     fn fix_multispan_in_std_macros(&self,
 315                                    source_map: &Option<Lrc<SourceMap>>,
 316                                    span: &mut MultiSpan,
 317                                    always_backtrace: bool) -> bool {
 318         let sm = match source_map {
 319             Some(ref sm) => sm,
 320             None => return false,
 321         };
 322
 323         let mut before_after: Vec<(Span, Span)> = vec![];
 324         let mut new_labels: Vec<(Span, String)> = vec![];
 325
 326         // First, find all the spans in <*macros> and point instead at their use site
 327         for sp in span.primary_spans() {
 328             if sp.is_dummy() {
 329                 continue;
 330             }
 331             let call_sp = sm.call_span_if_macro(*sp);
 332             if call_sp != *sp && !always_backtrace {
 333                 before_after.push((*sp, call_sp));
 334             }
 335             let backtrace_len = sp.macro_backtrace().len();
 336             for (i, trace) in sp.macro_backtrace().iter().rev().enumerate() {
 337                 // Only show macro locations that are local
 338                 // and display them like a span_note
 339                 if trace.def_site_span.is_dummy() {
 340                     continue;
 341                 }
 342                 if always_backtrace {
 343                     new_labels.push((trace.def_site_span,
 344                                         format!("in this expansion of `{}`{}",
 345                                                 trace.macro_decl_name,
 346                                                 if backtrace_len > 2 {
 347                                                     // if backtrace_len == 1 it'll be pointed
 348                                                     // at by "in this macro invocation"
 349                                                     format!(" (#{})", i + 1)
 350                                                 } else {
 351                                                     String::new()
 352                                                 })));
 353                 }
 354                 // Check to make sure we're not in any <*macros>
 355                 if !sm.span_to_filename(trace.def_site_span).is_macros() &&
 356                     !trace.macro_decl_name.starts_with("desugaring of ") &&
 357                     !trace.macro_decl_name.starts_with("#[") ||
 358                     always_backtrace {
 359                     new_labels.push((trace.call_site,
 360                                         format!("in this macro invocation{}",
 361                                                 if backtrace_len > 2 && always_backtrace {
 362                                                     // only specify order when the macro
 363                                                     // backtrace is multiple levels deep
 364                                                     format!(" (#{})", i + 1)
 365                                                 } else {
 366                                                     String::new()
 367                                                 })));
 368                     if !always_backtrace {
 369                         break;
 370                     }
 371                 }
 372             }
 373         }
 374         for (label_span, label_text) in new_labels {
 375             span.push_span_label(label_span, label_text);
 376         }
 377         for sp_label in span.span_labels() {
 378             if sp_label.span.is_dummy() {
 379                 continue;
 380             }
 381             if sm.span_to_filename(sp_label.span.clone()).is_macros() &&
 382                 !always_backtrace
 383             {
 384                 let v = sp_label.span.macro_backtrace();
 385                 if let Some(use_site) = v.last() {
 386                     before_after.push((sp_label.span.clone(), use_site.call_site.clone()));
 387                 }
 388             }
 389         }
 390         // After we have them, make sure we replace these 'bad' def sites with their use sites
 391         let spans_updated = !before_after.is_empty();
 392         for (before, after) in before_after {
 393             span.replace(before, after);
 394         }
 395
 396         spans_updated
 397     }
 398 }
 399
 400 impl Emitter for EmitterWriter {
 401     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
 402         self.sm.as_ref()
 403     }
 404
 405     fn emit_diagnostic(&mut self, diag: &Diagnostic) {
 406         let mut children = diag.children.clone();
 407         let (mut primary_span, suggestions) = self.primary_span_formatted(&diag);
 408
 409         self.fix_multispans_in_std_macros(&self.sm,
 410                                           &mut primary_span,
 411                                           &mut children,
 412                                           &diag.level,
 413                                           self.external_macro_backtrace);
 414
 415         self.emit_messages_default(&diag.level,
 416                                    &diag.styled_message(),
 417                                    &diag.code,
 418                                    &primary_span,
 419                                    &children,
 420                                    &suggestions);
 421     }
 422
 423     fn should_show_explain(&self) -> bool {
 424         !self.short_message
 425     }
 426 }
 427
 428 /// An emitter that does nothing when emitting a diagnostic.
 429 pub struct SilentEmitter;
 430
 431 impl Emitter for SilentEmitter {
 432     fn source_map(&self) -> Option<&Lrc<SourceMap>> { None }
 433     fn emit_diagnostic(&mut self, _: &Diagnostic) {}
 434 }
 435
 436 /// maximum number of lines we will print for each error; arbitrary.
 437 pub const MAX_HIGHLIGHT_LINES: usize = 6;
 438 /// maximum number of suggestions to be shown
 439 ///
 440 /// Arbitrary, but taken from trait import suggestion limit
 441 pub const MAX_SUGGESTIONS: usize = 4;
 442
 443 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 444 pub enum ColorConfig {
 445     Auto,
 446     Always,
 447     Never,
 448 }
 449
 450 impl ColorConfig {
 451     fn to_color_choice(self) -> ColorChoice {
 452         match self {
 453             ColorConfig::Always => {
 454                 if atty::is(atty::Stream::Stderr) {
 455                     ColorChoice::Always
 456                 } else {
 457                     ColorChoice::AlwaysAnsi
 458                 }
 459             }
 460             ColorConfig::Never => ColorChoice::Never,
 461             ColorConfig::Auto if atty::is(atty::Stream::Stderr) => {
 462                 ColorChoice::Auto
 463             }
 464             ColorConfig::Auto => ColorChoice::Never,
 465         }
 466     }
 467     fn suggests_using_colors(self) -> bool {
 468         match self {
 469             | ColorConfig::Always
 470             | ColorConfig::Auto
 471             => true,
 472             ColorConfig::Never => false,
 473         }
 474     }
 475 }
 476
 477 /// Handles the writing of `HumanReadableErrorType::Default` and `HumanReadableErrorType::Short`
 478 pub struct EmitterWriter {
 479     dst: Destination,
 480     sm: Option<Lrc<SourceMap>>,
 481     short_message: bool,
 482     teach: bool,
 483     ui_testing: bool,
 484     terminal_width: Option<usize>,
 485
 486     external_macro_backtrace: bool,
 487 }
 488
 489 #[derive(Debug)]
 490 pub struct FileWithAnnotatedLines {
 491     pub file: Lrc<SourceFile>,
 492     pub lines: Vec<Line>,
 493     multiline_depth: usize,
 494 }
 495
 496 impl EmitterWriter {
 497     pub fn stderr(
 498         color_config: ColorConfig,
 499         source_map: Option<Lrc<SourceMap>>,
 500         short_message: bool,
 501         teach: bool,
 502         terminal_width: Option<usize>,
 503         external_macro_backtrace: bool,
 504     ) -> EmitterWriter {
 505         let dst = Destination::from_stderr(color_config);
 506         EmitterWriter {
 507             dst,
 508             sm: source_map,
 509             short_message,
 510             teach,
 511             ui_testing: false,
 512             terminal_width,
 513             external_macro_backtrace,
 514         }
 515     }
 516
 517     pub fn new(
 518         dst: Box<dyn Write + Send>,
 519         source_map: Option<Lrc<SourceMap>>,
 520         short_message: bool,
 521         teach: bool,
 522         colored: bool,
 523         terminal_width: Option<usize>,
 524         external_macro_backtrace: bool,
 525     ) -> EmitterWriter {
 526         EmitterWriter {
 527             dst: Raw(dst, colored),
 528             sm: source_map,
 529             short_message,
 530             teach,
 531             ui_testing: false,
 532             terminal_width,
 533             external_macro_backtrace,
 534         }
 535     }
 536
 537     pub fn ui_testing(mut self, ui_testing: bool) -> Self {
 538         self.ui_testing = ui_testing;
 539         self
 540     }
 541
 542     fn maybe_anonymized(&self, line_num: usize) -> String {
 543         if self.ui_testing {
 544             ANONYMIZED_LINE_NUM.to_string()
 545         } else {
 546             line_num.to_string()
 547         }
 548     }
 549
 550     fn draw_line(
 551         &self,
 552         buffer: &mut StyledBuffer,
 553         source_string: &str,
 554         line_index: usize,
 555         line_offset: usize,
 556         width_offset: usize,
 557         code_offset: usize,
 558         margin: Margin,
 559     ) {
 560         let line_len = source_string.len();
 561         // Create the source line we will highlight.
 562         let left = margin.left(line_len);
 563         let right = margin.right(line_len);
 564         // On long lines, we strip the source line, accounting for unicode.
 565         let mut taken = 0;
 566         let code: String = source_string.chars().skip(left).take_while(|ch| {
 567             // Make sure that the trimming on the right will fall within the terminal width.
 568             // FIXME: `unicode_width` sometimes disagrees with terminals on how wide a `char` is.
 569             // For now, just accept that sometimes the code line will be longer than desired.
 570             let next = unicode_width::UnicodeWidthChar::width(*ch).unwrap_or(1);
 571             if taken + next > right - left {
 572                 return false;
 573             }
 574             taken += next;
 575             true
 576         }).collect();
 577         buffer.puts(line_offset, code_offset, &code, Style::Quotation);
 578         if margin.was_cut_left() {
 579             // We have stripped some code/whitespace from the beginning, make it clear.
 580             buffer.puts(line_offset, code_offset, "...", Style::LineNumber);
 581         }
 582         if margin.was_cut_right(line_len) {
 583             // We have stripped some code after the right-most span end, make it clear we did so.
 584             buffer.puts(line_offset, code_offset + taken - 3, "...", Style::LineNumber);
 585         }
 586         buffer.puts(line_offset, 0, &self.maybe_anonymized(line_index), Style::LineNumber);
 587
 588         draw_col_separator(buffer, line_offset, width_offset - 2);
 589     }
 590
 591     fn render_source_line(
 592         &self,
 593         buffer: &mut StyledBuffer,
 594         file: Lrc<SourceFile>,
 595         line: &Line,
 596         width_offset: usize,
 597         code_offset: usize,
 598         margin: Margin,
 599     ) -> Vec<(usize, Style)> {
 600         // Draw:
 601         //
 602         //   LL | ... code ...
 603         //      |     ^^-^ span label
 604         //      |       |
 605         //      |       secondary span label
 606         //
 607         //   ^^ ^ ^^^ ^^^^ ^^^ we don't care about code too far to the right of a span, we trim it
 608         //   |  | |   |
 609         //   |  | |   actual code found in your source code and the spans we use to mark it
 610         //   |  | when there's too much wasted space to the left, trim it
 611         //   |  vertical divider between the column number and the code
 612         //   column number
 613
 614         if line.line_index == 0 {
 615             return Vec::new();
 616         }
 617
 618         let source_string = match file.get_line(line.line_index - 1) {
 619             Some(s) => s,
 620             None => return Vec::new(),
 621         };
 622
 623         let line_offset = buffer.num_lines();
 624
 625         let left = margin.left(source_string.len()); // Left trim
 626         // Account for unicode characters of width !=0 that were removed.
 627         let left = source_string.chars().take(left)
 628             .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
 629             .sum();
 630
 631         self.draw_line(
 632             buffer,
 633             &source_string,
 634             line.line_index,
 635             line_offset,
 636             width_offset,
 637             code_offset,
 638             margin,
 639         );
 640
 641         // Special case when there's only one annotation involved, it is the start of a multiline
 642         // span and there's no text at the beginning of the code line. Instead of doing the whole
 643         // graph:
 644         //
 645         // 2 |   fn foo() {
 646         //   |  _^
 647         // 3 | |
 648         // 4 | | }
 649         //   | |_^ test
 650         //
 651         // we simplify the output to:
 652         //
 653         // 2 | / fn foo() {
 654         // 3 | |
 655         // 4 | | }
 656         //   | |_^ test
 657         if let [ann] = &line.annotations[..] {
 658             if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
 659                 if source_string.chars().take(ann.start_col).all(|c| c.is_whitespace()) {
 660                     let style = if ann.is_primary {
 661                         Style::UnderlinePrimary
 662                     } else {
 663                         Style::UnderlineSecondary
 664                     };
 665                     buffer.putc(line_offset, width_offset + depth - 1, '/', style);
 666                     return vec![(depth, style)];
 667                 }
 668             }
 669         }
 670
 671         // We want to display like this:
 672         //
 673         //      vec.push(vec.pop().unwrap());
 674         //      ---      ^^^               - previous borrow ends here
 675         //      |        |
 676         //      |        error occurs here
 677         //      previous borrow of `vec` occurs here
 678         //
 679         // But there are some weird edge cases to be aware of:
 680         //
 681         //      vec.push(vec.pop().unwrap());
 682         //      --------                    - previous borrow ends here
 683         //      ||
 684         //      |this makes no sense
 685         //      previous borrow of `vec` occurs here
 686         //
 687         // For this reason, we group the lines into "highlight lines"
 688         // and "annotations lines", where the highlight lines have the `^`.
 689
 690         // Sort the annotations by (start, end col)
 691         // The labels are reversed, sort and then reversed again.
 692         // Consider a list of annotations (A1, A2, C1, C2, B1, B2) where
 693         // the letter signifies the span. Here we are only sorting by the
 694         // span and hence, the order of the elements with the same span will
 695         // not change. On reversing the ordering (|a, b| but b.cmp(a)), you get
 696         // (C1, C2, B1, B2, A1, A2). All the elements with the same span are
 697         // still ordered first to last, but all the elements with different
 698         // spans are ordered by their spans in last to first order. Last to
 699         // first order is important, because the jiggly lines and | are on
 700         // the left, so the rightmost span needs to be rendered first,
 701         // otherwise the lines would end up needing to go over a message.
 702
 703         let mut annotations = line.annotations.clone();
 704         annotations.sort_by_key(|a| Reverse(a.start_col));
 705
 706         // First, figure out where each label will be positioned.
 707         //
 708         // In the case where you have the following annotations:
 709         //
 710         //      vec.push(vec.pop().unwrap());
 711         //      --------                    - previous borrow ends here [C]
 712         //      ||
 713         //      |this makes no sense [B]
 714         //      previous borrow of `vec` occurs here [A]
 715         //
 716         // `annotations_position` will hold [(2, A), (1, B), (0, C)].
 717         //
 718         // We try, when possible, to stick the rightmost annotation at the end
 719         // of the highlight line:
 720         //
 721         //      vec.push(vec.pop().unwrap());
 722         //      ---      ---               - previous borrow ends here
 723         //
 724         // But sometimes that's not possible because one of the other
 725         // annotations overlaps it. For example, from the test
 726         // `span_overlap_label`, we have the following annotations
 727         // (written on distinct lines for clarity):
 728         //
 729         //      fn foo(x: u32) {
 730         //      --------------
 731         //             -
 732         //
 733         // In this case, we can't stick the rightmost-most label on
 734         // the highlight line, or we would get:
 735         //
 736         //      fn foo(x: u32) {
 737         //      -------- x_span
 738         //      |
 739         //      fn_span
 740         //
 741         // which is totally weird. Instead we want:
 742         //
 743         //      fn foo(x: u32) {
 744         //      --------------
 745         //      |      |
 746         //      |      x_span
 747         //      fn_span
 748         //
 749         // which is...less weird, at least. In fact, in general, if
 750         // the rightmost span overlaps with any other span, we should
 751         // use the "hang below" version, so we can at least make it
 752         // clear where the span *starts*. There's an exception for this
 753         // logic, when the labels do not have a message:
 754         //
 755         //      fn foo(x: u32) {
 756         //      --------------
 757         //             |
 758         //             x_span
 759         //
 760         // instead of:
 761         //
 762         //      fn foo(x: u32) {
 763         //      --------------
 764         //      |      |
 765         //      |      x_span
 766         //      <EMPTY LINE>
 767         //
 768         let mut annotations_position = vec![];
 769         let mut line_len = 0;
 770         let mut p = 0;
 771         for (i, annotation) in annotations.iter().enumerate() {
 772             for (j, next) in annotations.iter().enumerate() {
 773                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
 774                     && annotation.has_label()     // take space (they have text and are not
 775                     && j > i                      // multiline lines).
 776                     && p == 0  // We're currently on the first line, move the label one line down
 777                 {
 778                     // If we're overlapping with an un-labelled annotation with the same span
 779                     // we can just merge them in the output
 780                     if next.start_col == annotation.start_col
 781                     && next.end_col == annotation.end_col
 782                     && !next.has_label()
 783                     {
 784                         continue;
 785                     }
 786
 787                     // This annotation needs a new line in the output.
 788                     p += 1;
 789                     break;
 790                 }
 791             }
 792             annotations_position.push((p, annotation));
 793             for (j, next) in annotations.iter().enumerate() {
 794                 if j > i  {
 795                     let l = next.label.as_ref().map_or(0, |label| label.len() + 2);
 796                     if (overlaps(next, annotation, l) // Do not allow two labels to be in the same
 797                                                      // line if they overlap including padding, to
 798                                                      // avoid situations like:
 799                                                      //
 800                                                      //      fn foo(x: u32) {
 801                                                      //      -------^------
 802                                                      //      |      |
 803                                                      //      fn_spanx_span
 804                                                      //
 805                         && annotation.has_label()    // Both labels must have some text, otherwise
 806                         && next.has_label())         // they are not overlapping.
 807                                                      // Do not add a new line if this annotation
 808                                                      // or the next are vertical line placeholders.
 809                         || (annotation.takes_space() // If either this or the next annotation is
 810                             && next.has_label())     // multiline start/end, move it to a new line
 811                         || (annotation.has_label()   // so as not to overlap the orizontal lines.
 812                             && next.takes_space())
 813                         || (annotation.takes_space() && next.takes_space())
 814                         || (overlaps(next, annotation, l)
 815                             && next.end_col <= annotation.end_col
 816                             && next.has_label()
 817                             && p == 0)  // Avoid #42595.
 818                     {
 819                         // This annotation needs a new line in the output.
 820                         p += 1;
 821                         break;
 822                     }
 823                 }
 824             }
 825             line_len = max(line_len, p);
 826         }
 827
 828         if line_len != 0 {
 829             line_len += 1;
 830         }
 831
 832         // If there are no annotations or the only annotations on this line are
 833         // MultilineLine, then there's only code being shown, stop processing.
 834         if line.annotations.iter().all(|a| a.is_line()) {
 835             return vec![];
 836         }
 837
 838         // Write the column separator.
 839         //
 840         // After this we will have:
 841         //
 842         // 2 |   fn foo() {
 843         //   |
 844         //   |
 845         //   |
 846         // 3 |
 847         // 4 |   }
 848         //   |
 849         for pos in 0..=line_len {
 850             draw_col_separator(buffer, line_offset + pos + 1, width_offset - 2);
 851             buffer.putc(line_offset + pos + 1,
 852                         width_offset - 2,
 853                         '|',
 854                         Style::LineNumber);
 855         }
 856
 857         // Write the horizontal lines for multiline annotations
 858         // (only the first and last lines need this).
 859         //
 860         // After this we will have:
 861         //
 862         // 2 |   fn foo() {
 863         //   |  __________
 864         //   |
 865         //   |
 866         // 3 |
 867         // 4 |   }
 868         //   |  _
 869         for &(pos, annotation) in &annotations_position {
 870             let style = if annotation.is_primary {
 871                 Style::UnderlinePrimary
 872             } else {
 873                 Style::UnderlineSecondary
 874             };
 875             let pos = pos + 1;
 876             match annotation.annotation_type {
 877                 AnnotationType::MultilineStart(depth) |
 878                 AnnotationType::MultilineEnd(depth) => {
 879                     draw_range(
 880                         buffer,
 881                         '_',
 882                         line_offset + pos,
 883                         width_offset + depth,
 884                         code_offset + annotation.start_col - left,
 885                         style,
 886                     );
 887                 }
 888                 _ if self.teach => {
 889                     buffer.set_style_range(
 890                         line_offset,
 891                         code_offset + annotation.start_col - left,
 892                         code_offset + annotation.end_col - left,
 893                         style,
 894                         annotation.is_primary,
 895                     );
 896                 }
 897                 _ => {}
 898             }
 899         }
 900
 901         // Write the vertical lines for labels that are on a different line as the underline.
 902         //
 903         // After this we will have:
 904         //
 905         // 2 |   fn foo() {
 906         //   |  __________
 907         //   | |    |
 908         //   | |
 909         // 3 | |
 910         // 4 | | }
 911         //   | |_
 912         for &(pos, annotation) in &annotations_position {
 913             let style = if annotation.is_primary {
 914                 Style::UnderlinePrimary
 915             } else {
 916                 Style::UnderlineSecondary
 917             };
 918             let pos = pos + 1;
 919
 920             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
 921                 for p in line_offset + 1..=line_offset + pos {
 922                     buffer.putc(p,
 923                                 (code_offset + annotation.start_col).saturating_sub(left),
 924                                 '|',
 925                                 style);
 926                 }
 927             }
 928             match annotation.annotation_type {
 929                 AnnotationType::MultilineStart(depth) => {
 930                     for p in line_offset + pos + 1..line_offset + line_len + 2 {
 931                         buffer.putc(p,
 932                                     width_offset + depth - 1,
 933                                     '|',
 934                                     style);
 935                     }
 936                 }
 937                 AnnotationType::MultilineEnd(depth) => {
 938                     for p in line_offset..=line_offset + pos {
 939                         buffer.putc(p,
 940                                     width_offset + depth - 1,
 941                                     '|',
 942                                     style);
 943                     }
 944                 }
 945                 _ => (),
 946             }
 947         }
 948
 949         // Write the labels on the annotations that actually have a label.
 950         //
 951         // After this we will have:
 952         //
 953         // 2 |   fn foo() {
 954         //   |  __________
 955         //   |      |
 956         //   |      something about `foo`
 957         // 3 |
 958         // 4 |   }
 959         //   |  _  test
 960         for &(pos, annotation) in &annotations_position {
 961             let style = if annotation.is_primary {
 962                 Style::LabelPrimary
 963             } else {
 964                 Style::LabelSecondary
 965             };
 966             let (pos, col) = if pos == 0 {
 967                 (pos + 1, (annotation.end_col + 1).saturating_sub(left))
 968             } else {
 969                 (pos + 2, annotation.start_col.saturating_sub(left))
 970             };
 971             if let Some(ref label) = annotation.label {
 972                 buffer.puts(line_offset + pos, code_offset + col, &label, style);
 973             }
 974         }
 975
 976         // Sort from biggest span to smallest span so that smaller spans are
 977         // represented in the output:
 978         //
 979         // x | fn foo()
 980         //   | ^^^---^^
 981         //   | |  |
 982         //   | |  something about `foo`
 983         //   | something about `fn foo()`
 984         annotations_position.sort_by_key(|(_, ann)| {
 985             // Decreasing order. When annotations share the same length, prefer `Primary`.
 986             (Reverse(ann.len()), ann.is_primary)
 987         });
 988
 989         // Write the underlines.
 990         //
 991         // After this we will have:
 992         //
 993         // 2 |   fn foo() {
 994         //   |  ____-_____^
 995         //   |      |
 996         //   |      something about `foo`
 997         // 3 |
 998         // 4 |   }
 999         //   |  _^  test
1000         for &(_, annotation) in &annotations_position {
1001             let (underline, style) = if annotation.is_primary {
1002                 ('^', Style::UnderlinePrimary)
1003             } else {
1004                 ('-', Style::UnderlineSecondary)
1005             };
1006             for p in annotation.start_col..annotation.end_col {
1007                 buffer.putc(
1008                     line_offset + 1,
1009                     (code_offset + p).saturating_sub(left),
1010                     underline,
1011                     style,
1012                 );
1013             }
1014         }
1015         annotations_position.iter().filter_map(|&(_, annotation)| {
1016             match annotation.annotation_type {
1017                 AnnotationType::MultilineStart(p) | AnnotationType::MultilineEnd(p) => {
1018                     let style = if annotation.is_primary {
1019                         Style::LabelPrimary
1020                     } else {
1021                         Style::LabelSecondary
1022                     };
1023                     Some((p, style))
1024                 }
1025                 _ => None
1026             }
1027
1028         }).collect::<Vec<_>>()
1029     }
1030
1031     fn get_multispan_max_line_num(&mut self, msp: &MultiSpan) -> usize {
1032         let sm = match self.sm {
1033             Some(ref sm) => sm,
1034             None => return 0,
1035         };
1036
1037         let mut max = 0;
1038         for primary_span in msp.primary_spans() {
1039             if !primary_span.is_dummy() {
1040                 let hi = sm.lookup_char_pos(primary_span.hi());
1041                 max = (hi.line).max(max);
1042             }
1043         }
1044         if !self.short_message {
1045             for span_label in msp.span_labels() {
1046                 if !span_label.span.is_dummy() {
1047                     let hi = sm.lookup_char_pos(span_label.span.hi());
1048                     max = (hi.line).max(max);
1049                 }
1050             }
1051         }
1052
1053         max
1054     }
1055
1056     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
1057         let primary = self.get_multispan_max_line_num(span);
1058         children.iter()
1059             .map(|sub| self.get_multispan_max_line_num(&sub.span))
1060             .max()
1061             .unwrap_or(0)
1062             .max(primary)
1063     }
1064
1065     /// Adds a left margin to every line but the first, given a padding length and the label being
1066     /// displayed, keeping the provided highlighting.
1067     fn msg_to_buffer(&self,
1068                      buffer: &mut StyledBuffer,
1069                      msg: &[(String, Style)],
1070                      padding: usize,
1071                      label: &str,
1072                      override_style: Option<Style>) {
1073
1074         // The extra 5 ` ` is padding that's always needed to align to the `note: `:
1075         //
1076         //   error: message
1077         //     --> file.rs:13:20
1078         //      |
1079         //   13 |     <CODE>
1080         //      |      ^^^^
1081         //      |
1082         //      = note: multiline
1083         //              message
1084         //   ++^^^----xx
1085         //    |  |   | |
1086         //    |  |   | magic `2`
1087         //    |  |   length of label
1088         //    |  magic `3`
1089         //    `max_line_num_len`
1090         let padding = " ".repeat(padding + label.len() + 5);
1091
1092         /// Returns `override` if it is present and `style` is `NoStyle` or `style` otherwise
1093         fn style_or_override(style: Style, override_: Option<Style>) -> Style {
1094             match (style, override_) {
1095                 (Style::NoStyle, Some(override_)) => override_,
1096                 _ => style,
1097             }
1098         }
1099
1100         let mut line_number = 0;
1101
1102         // Provided the following diagnostic message:
1103         //
1104         //     let msg = vec![
1105         //       ("
1106         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
1107         //       ("looks", Style::Highlight),
1108         //       ("with\nvery ", Style::NoStyle),
1109         //       ("weird", Style::Highlight),
1110         //       (" formats\n", Style::NoStyle),
1111         //       ("see?", Style::Highlight),
1112         //     ];
1113         //
1114         // the expected output on a note is (* surround the highlighted text)
1115         //
1116         //        = note: highlighted multiline
1117         //                string to
1118         //                see how it *looks* with
1119         //                very *weird* formats
1120         //                see?
1121         for &(ref text, ref style) in msg.iter() {
1122             let lines = text.split('\n').collect::<Vec<_>>();
1123             if lines.len() > 1 {
1124                 for (i, line) in lines.iter().enumerate() {
1125                     if i != 0 {
1126                         line_number += 1;
1127                         buffer.append(line_number, &padding, Style::NoStyle);
1128                     }
1129                     buffer.append(line_number, line, style_or_override(*style, override_style));
1130                 }
1131             } else {
1132                 buffer.append(line_number, text, style_or_override(*style, override_style));
1133             }
1134         }
1135     }
1136
1137     fn emit_message_default(
1138         &mut self,
1139         msp: &MultiSpan,
1140         msg: &[(String, Style)],
1141         code: &Option<DiagnosticId>,
1142         level: &Level,
1143         max_line_num_len: usize,
1144         is_secondary: bool,
1145     ) -> io::Result<()> {
1146         let mut buffer = StyledBuffer::new();
1147         let header_style = if is_secondary {
1148             Style::HeaderMsg
1149         } else {
1150             Style::MainHeaderMsg
1151         };
1152
1153         if !msp.has_primary_spans() && !msp.has_span_labels() && is_secondary
1154            && !self.short_message {
1155             // This is a secondary message with no span info
1156             for _ in 0..max_line_num_len {
1157                 buffer.prepend(0, " ", Style::NoStyle);
1158             }
1159             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
1160             if *level != Level::FailureNote {
1161                 let level_str = level.to_string();
1162                 if !level_str.is_empty() {
1163                     buffer.append(0, &level_str, Style::MainHeaderMsg);
1164                     buffer.append(0, ": ", Style::NoStyle);
1165                 }
1166             }
1167             self.msg_to_buffer(&mut buffer, msg, max_line_num_len, "note", None);
1168         } else {
1169             let level_str = level.to_string();
1170             // The failure note level itself does not provide any useful diagnostic information
1171             if *level != Level::FailureNote && !level_str.is_empty() {
1172                 buffer.append(0, &level_str, Style::Level(level.clone()));
1173             }
1174             // only render error codes, not lint codes
1175             if let Some(DiagnosticId::Error(ref code)) = *code {
1176                 buffer.append(0, "[", Style::Level(level.clone()));
1177                 buffer.append(0, &code, Style::Level(level.clone()));
1178                 buffer.append(0, "]", Style::Level(level.clone()));
1179             }
1180             if *level != Level::FailureNote && !level_str.is_empty() {
1181                 buffer.append(0, ": ", header_style);
1182             }
1183             for &(ref text, _) in msg.iter() {
1184                 buffer.append(0, text, header_style);
1185             }
1186         }
1187
1188         let mut annotated_files = FileWithAnnotatedLines::collect_annotations(msp, &self.sm);
1189
1190         // Make sure our primary file comes first
1191         let (primary_lo, sm) = if let (Some(sm), Some(ref primary_span)) =
1192             (self.sm.as_ref(), msp.primary_span().as_ref()) {
1193             if !primary_span.is_dummy() {
1194                 (sm.lookup_char_pos(primary_span.lo()), sm)
1195             } else {
1196                 emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1197                 return Ok(());
1198             }
1199         } else {
1200             // If we don't have span information, emit and exit
1201             emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1202             return Ok(());
1203         };
1204         if let Ok(pos) =
1205             annotated_files.binary_search_by(|x| x.file.name.cmp(&primary_lo.file.name)) {
1206             annotated_files.swap(0, pos);
1207         }
1208
1209         // Print out the annotate source lines that correspond with the error
1210         for annotated_file in annotated_files {
1211             // we can't annotate anything if the source is unavailable.
1212             if !sm.ensure_source_file_source_present(annotated_file.file.clone()) {
1213                 continue;
1214             }
1215
1216             // print out the span location and spacer before we print the annotated source
1217             // to do this, we need to know if this span will be primary
1218             let is_primary = primary_lo.file.name == annotated_file.file.name;
1219             if is_primary {
1220                 let loc = primary_lo.clone();
1221                 if !self.short_message {
1222                     // remember where we are in the output buffer for easy reference
1223                     let buffer_msg_line_offset = buffer.num_lines();
1224
1225                     buffer.prepend(buffer_msg_line_offset, "--> ", Style::LineNumber);
1226                     buffer.append(
1227                         buffer_msg_line_offset,
1228                         &format!(
1229                             "{}:{}:{}",
1230                             loc.file.name,
1231                             sm.doctest_offset_line(&loc.file.name, loc.line),
1232                             loc.col.0 + 1,
1233                         ),
1234                         Style::LineAndColumn,
1235                     );
1236                     for _ in 0..max_line_num_len {
1237                         buffer.prepend(buffer_msg_line_offset, " ", Style::NoStyle);
1238                     }
1239                 } else {
1240                     buffer.prepend(
1241                         0,
1242                         &format!(
1243                             "{}:{}:{}: ",
1244                             loc.file.name,
1245                             sm.doctest_offset_line(&loc.file.name, loc.line),
1246                             loc.col.0 + 1,
1247                         ),
1248                         Style::LineAndColumn,
1249                     );
1250                 }
1251             } else if !self.short_message {
1252                 // remember where we are in the output buffer for easy reference
1253                 let buffer_msg_line_offset = buffer.num_lines();
1254
1255                 // Add spacing line
1256                 draw_col_separator(&mut buffer, buffer_msg_line_offset, max_line_num_len + 1);
1257
1258                 // Then, the secondary file indicator
1259                 buffer.prepend(buffer_msg_line_offset + 1, "::: ", Style::LineNumber);
1260                 let loc = if let Some(first_line) = annotated_file.lines.first() {
1261                     let col = if let Some(first_annotation) = first_line.annotations.first() {
1262                         format!(":{}", first_annotation.start_col + 1)
1263                     } else {
1264                         String::new()
1265                     };
1266                     format!("{}:{}{}",
1267                             annotated_file.file.name,
1268                             sm.doctest_offset_line(
1269                                 &annotated_file.file.name, first_line.line_index),
1270                             col)
1271                 } else {
1272                     annotated_file.file.name.to_string()
1273                 };
1274                 buffer.append(buffer_msg_line_offset + 1,
1275                               &loc,
1276                               Style::LineAndColumn);
1277                 for _ in 0..max_line_num_len {
1278                     buffer.prepend(buffer_msg_line_offset + 1, " ", Style::NoStyle);
1279                 }
1280             }
1281
1282             if !self.short_message {
1283                 // Put in the spacer between the location and annotated source
1284                 let buffer_msg_line_offset = buffer.num_lines();
1285                 draw_col_separator_no_space(&mut buffer,
1286                                             buffer_msg_line_offset,
1287                                             max_line_num_len + 1);
1288
1289                 // Contains the vertical lines' positions for active multiline annotations
1290                 let mut multilines = FxHashMap::default();
1291
1292                 // Get the left-side margin to remove it
1293                 let mut whitespace_margin = std::usize::MAX;
1294                 for line_idx in 0..annotated_file.lines.len() {
1295                     let file = annotated_file.file.clone();
1296                     let line = &annotated_file.lines[line_idx];
1297                     if let Some(source_string) = file.get_line(line.line_index - 1) {
1298                         let leading_whitespace = source_string
1299                             .chars()
1300                             .take_while(|c| c.is_whitespace())
1301                             .count();
1302                         if source_string.chars().any(|c| !c.is_whitespace()) {
1303                             whitespace_margin = min(
1304                                 whitespace_margin,
1305                                 leading_whitespace,
1306                             );
1307                         }
1308                     }
1309                 }
1310                 if whitespace_margin == std::usize::MAX {
1311                     whitespace_margin = 0;
1312                 }
1313
1314                 // Left-most column any visible span points at.
1315                 let mut span_left_margin = std::usize::MAX;
1316                 for line in &annotated_file.lines {
1317                     for ann in &line.annotations {
1318                         span_left_margin = min(span_left_margin, ann.start_col);
1319                         span_left_margin = min(span_left_margin, ann.end_col);
1320                     }
1321                 }
1322                 if span_left_margin == std::usize::MAX {
1323                     span_left_margin = 0;
1324                 }
1325
1326                 // Right-most column any visible span points at.
1327                 let mut span_right_margin = 0;
1328                 let mut label_right_margin = 0;
1329                 let mut max_line_len = 0;
1330                 for line in &annotated_file.lines {
1331                     max_line_len = max(max_line_len, annotated_file.file
1332                         .get_line(line.line_index - 1)
1333                         .map_or(0, |s| s.len()));
1334                     for ann in &line.annotations {
1335                         span_right_margin = max(span_right_margin, ann.start_col);
1336                         span_right_margin = max(span_right_margin, ann.end_col);
1337                         // FIXME: account for labels not in the same line
1338                         let label_right = ann.label.as_ref().map_or(0, |l| l.len() + 1);
1339                         label_right_margin = max(label_right_margin, ann.end_col + label_right);
1340                     }
1341                 }
1342
1343                 let width_offset = 3 + max_line_num_len;
1344                 let code_offset = if annotated_file.multiline_depth == 0 {
1345                     width_offset
1346                 } else {
1347                     width_offset + annotated_file.multiline_depth + 1
1348                 };
1349
1350                 let column_width = if let Some(width) = self.terminal_width {
1351                     width.saturating_sub(code_offset)
1352                 } else if self.ui_testing {
1353                     140
1354                 } else {
1355                     term_size::dimensions()
1356                         .map(|(w, _)| w.saturating_sub(code_offset))
1357                         .unwrap_or(std::usize::MAX)
1358                 };
1359
1360                 let margin = Margin::new(
1361                     whitespace_margin,
1362                     span_left_margin,
1363                     span_right_margin,
1364                     label_right_margin,
1365                     column_width,
1366                     max_line_len,
1367                 );
1368
1369                 // Next, output the annotate source for this file
1370                 for line_idx in 0..annotated_file.lines.len() {
1371                     let previous_buffer_line = buffer.num_lines();
1372
1373                     let depths = self.render_source_line(
1374                         &mut buffer,
1375                         annotated_file.file.clone(),
1376                         &annotated_file.lines[line_idx],
1377                         width_offset,
1378                         code_offset,
1379                         margin,
1380                     );
1381
1382                     let mut to_add = FxHashMap::default();
1383
1384                     for (depth, style) in depths {
1385                         if multilines.get(&depth).is_some() {
1386                             multilines.remove(&depth);
1387                         } else {
1388                             to_add.insert(depth, style);
1389                         }
1390                     }
1391
1392                     // Set the multiline annotation vertical lines to the left of
1393                     // the code in this line.
1394                     for (depth, style) in &multilines {
1395                         for line in previous_buffer_line..buffer.num_lines() {
1396                             draw_multiline_line(&mut buffer,
1397                                                 line,
1398                                                 width_offset,
1399                                                 *depth,
1400                                                 *style);
1401                         }
1402                     }
1403                     // check to see if we need to print out or elide lines that come between
1404                     // this annotated line and the next one.
1405                     if line_idx < (annotated_file.lines.len() - 1) {
1406                         let line_idx_delta = annotated_file.lines[line_idx + 1].line_index -
1407                                              annotated_file.lines[line_idx].line_index;
1408                         if line_idx_delta > 2 {
1409                             let last_buffer_line_num = buffer.num_lines();
1410                             buffer.puts(last_buffer_line_num, 0, "...", Style::LineNumber);
1411
1412                             // Set the multiline annotation vertical lines on `...` bridging line.
1413                             for (depth, style) in &multilines {
1414                                 draw_multiline_line(&mut buffer,
1415                                                     last_buffer_line_num,
1416                                                     width_offset,
1417                                                     *depth,
1418                                                     *style);
1419                             }
1420                         } else if line_idx_delta == 2 {
1421                             let unannotated_line = annotated_file.file
1422                                 .get_line(annotated_file.lines[line_idx].line_index)
1423                                 .unwrap_or_else(|| Cow::from(""));
1424
1425                             let last_buffer_line_num = buffer.num_lines();
1426
1427                             self.draw_line(
1428                                 &mut buffer,
1429                                 &unannotated_line,
1430                                 annotated_file.lines[line_idx + 1].line_index - 1,
1431                                 last_buffer_line_num,
1432                                 width_offset,
1433                                 code_offset,
1434                                 margin,
1435                             );
1436
1437                             for (depth, style) in &multilines {
1438                                 draw_multiline_line(
1439                                     &mut buffer,
1440                                     last_buffer_line_num,
1441                                     width_offset,
1442                                     *depth,
1443                                     *style,
1444                                 );
1445                             }
1446                         }
1447                     }
1448
1449                     multilines.extend(&to_add);
1450                 }
1451             }
1452         }
1453
1454         // final step: take our styled buffer, render it, then output it
1455         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1456
1457         Ok(())
1458
1459     }
1460
1461     fn emit_suggestion_default(
1462         &mut self,
1463         suggestion: &CodeSuggestion,
1464         level: &Level,
1465         max_line_num_len: usize,
1466     ) -> io::Result<()> {
1467         let sm = match self.sm {
1468             Some(ref sm) => sm,
1469             None => return Ok(())
1470         };
1471
1472         let mut buffer = StyledBuffer::new();
1473
1474         // Render the suggestion message
1475         let level_str = level.to_string();
1476         if !level_str.is_empty() {
1477             buffer.append(0, &level_str, Style::Level(level.clone()));
1478             buffer.append(0, ": ", Style::HeaderMsg);
1479         }
1480         self.msg_to_buffer(
1481             &mut buffer,
1482             &[(suggestion.msg.to_owned(), Style::NoStyle)],
1483             max_line_num_len,
1484             "suggestion",
1485             Some(Style::HeaderMsg),
1486         );
1487
1488         // Render the replacements for each suggestion
1489         let suggestions = suggestion.splice_lines(&**sm);
1490
1491         let mut row_num = 2;
1492         let mut notice_capitalization = false;
1493         for (complete, parts, only_capitalization) in suggestions.iter().take(MAX_SUGGESTIONS) {
1494             notice_capitalization |= only_capitalization;
1495             // Only show underline if the suggestion spans a single line and doesn't cover the
1496             // entirety of the code output. If you have multiple replacements in the same line
1497             // of code, show the underline.
1498             let show_underline = !(parts.len() == 1
1499                 && parts[0].snippet.trim() == complete.trim())
1500                 && complete.lines().count() == 1;
1501
1502             let lines = sm.span_to_lines(parts[0].span).unwrap();
1503
1504             assert!(!lines.lines.is_empty());
1505
1506             let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
1507             draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
1508             let mut line_pos = 0;
1509             let mut lines = complete.lines();
1510             for line in lines.by_ref().take(MAX_HIGHLIGHT_LINES) {
1511                 // Print the span column to avoid confusion
1512                 buffer.puts(row_num,
1513                             0,
1514                             &self.maybe_anonymized(line_start + line_pos),
1515                             Style::LineNumber);
1516                 // print the suggestion
1517                 draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1518                 buffer.append(row_num, line, Style::NoStyle);
1519                 line_pos += 1;
1520                 row_num += 1;
1521             }
1522
1523             // This offset and the ones below need to be signed to account for replacement code
1524             // that is shorter than the original code.
1525             let mut offset: isize = 0;
1526             // Only show an underline in the suggestions if the suggestion is not the
1527             // entirety of the code being shown and the displayed code is not multiline.
1528             if show_underline {
1529                 draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1530                 for part in parts {
1531                     let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
1532                     let span_end_pos = sm.lookup_char_pos(part.span.hi()).col_display;
1533
1534                     // Do not underline the leading...
1535                     let start = part.snippet.len()
1536                         .saturating_sub(part.snippet.trim_start().len());
1537                     // ...or trailing spaces. Account for substitutions containing unicode
1538                     // characters.
1539                     let sub_len: usize = part.snippet.trim().chars()
1540                         .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1541                         .sum();
1542
1543                     let underline_start = (span_start_pos + start) as isize + offset;
1544                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
1545                     for p in underline_start..underline_end {
1546                         buffer.putc(row_num,
1547                                     max_line_num_len + 3 + p as usize,
1548                                     '^',
1549                                     Style::UnderlinePrimary);
1550                     }
1551                     // underline removals too
1552                     if underline_start == underline_end {
1553                         for p in underline_start-1..underline_start+1 {
1554                             buffer.putc(row_num,
1555                                         max_line_num_len + 3 + p as usize,
1556                                         '-',
1557                                         Style::UnderlineSecondary);
1558                         }
1559                     }
1560
1561                     // length of the code after substitution
1562                     let full_sub_len = part.snippet.chars()
1563                         .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1564                         .sum::<usize>() as isize;
1565
1566                     // length of the code to be substituted
1567                     let snippet_len = span_end_pos as isize - span_start_pos as isize;
1568                     // For multiple substitutions, use the position *after* the previous
1569                     // substitutions have happened.
1570                     offset += full_sub_len - snippet_len;
1571                 }
1572                 row_num += 1;
1573             }
1574
1575             // if we elided some lines, add an ellipsis
1576             if lines.next().is_some() {
1577                 buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
1578             } else if !show_underline {
1579                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
1580                 row_num += 1;
1581             }
1582         }
1583         if suggestions.len() > MAX_SUGGESTIONS {
1584             let others = suggestions.len() - MAX_SUGGESTIONS;
1585             let msg = format!("and {} other candidate{}", others, pluralize!(others));
1586             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
1587         } else if notice_capitalization {
1588             let msg = "notice the capitalization difference";
1589             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
1590         }
1591         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1592         Ok(())
1593     }
1594
1595     fn emit_messages_default(
1596         &mut self,
1597         level: &Level,
1598         message: &[(String, Style)],
1599         code: &Option<DiagnosticId>,
1600         span: &MultiSpan,
1601         children: &[SubDiagnostic],
1602         suggestions: &[CodeSuggestion],
1603     ) {
1604         let max_line_num_len = if self.ui_testing {
1605             ANONYMIZED_LINE_NUM.len()
1606         } else {
1607             self.get_max_line_num(span, children).to_string().len()
1608         };
1609
1610         match self.emit_message_default(span, message, code, level, max_line_num_len, false) {
1611             Ok(()) => {
1612                 if !children.is_empty() || suggestions.iter().any(|s| {
1613                     s.style != SuggestionStyle::CompletelyHidden
1614                 }) {
1615                     let mut buffer = StyledBuffer::new();
1616                     if !self.short_message {
1617                         draw_col_separator_no_space(&mut buffer, 0, max_line_num_len + 1);
1618                     }
1619                     match emit_to_destination(&buffer.render(), level, &mut self.dst,
1620                                               self.short_message) {
1621                         Ok(()) => (),
1622                         Err(e) => panic!("failed to emit error: {}", e)
1623                     }
1624                 }
1625                 if !self.short_message {
1626                     for child in children {
1627                         let span = child.render_span.as_ref().unwrap_or(&child.span);
1628                         match self.emit_message_default(
1629                             &span,
1630                             &child.styled_message(),
1631                             &None,
1632                             &child.level,
1633                             max_line_num_len,
1634                             true,
1635                         ) {
1636                             Err(e) => panic!("failed to emit error: {}", e),
1637                             _ => ()
1638                         }
1639                     }
1640                     for sugg in suggestions {
1641                         if sugg.style == SuggestionStyle::CompletelyHidden {
1642                             // do not display this suggestion, it is meant only for tools
1643                         } else if sugg.style == SuggestionStyle::HideCodeAlways {
1644                             match self.emit_message_default(
1645                                 &MultiSpan::new(),
1646                                 &[(sugg.msg.to_owned(), Style::HeaderMsg)],
1647                                 &None,
1648                                 &Level::Help,
1649                                 max_line_num_len,
1650                                 true,
1651                             ) {
1652                                 Err(e) => panic!("failed to emit error: {}", e),
1653                                 _ => ()
1654                             }
1655                         } else {
1656                             match self.emit_suggestion_default(
1657                                 sugg,
1658                                 &Level::Help,
1659                                 max_line_num_len,
1660                             ) {
1661                                 Err(e) => panic!("failed to emit error: {}", e),
1662                                 _ => ()
1663                             }
1664                         }
1665                     }
1666                 }
1667             }
1668             Err(e) => panic!("failed to emit error: {}", e),
1669         }
1670
1671         let mut dst = self.dst.writable();
1672         match writeln!(dst) {
1673             Err(e) => panic!("failed to emit error: {}", e),
1674             _ => {
1675                 match dst.flush() {
1676                     Err(e) => panic!("failed to emit error: {}", e),
1677                     _ => (),
1678                 }
1679             }
1680         }
1681     }
1682 }
1683
1684 impl FileWithAnnotatedLines {
1685     /// Preprocess all the annotations so that they are grouped by file and by line number
1686     /// This helps us quickly iterate over the whole message (including secondary file spans)
1687     pub fn collect_annotations(
1688         msp: &MultiSpan,
1689         source_map: &Option<Lrc<SourceMap>>
1690     ) -> Vec<FileWithAnnotatedLines> {
1691         fn add_annotation_to_file(file_vec: &mut Vec<FileWithAnnotatedLines>,
1692                                   file: Lrc<SourceFile>,
1693                                   line_index: usize,
1694                                   ann: Annotation) {
1695
1696             for slot in file_vec.iter_mut() {
1697                 // Look through each of our files for the one we're adding to
1698                 if slot.file.name == file.name {
1699                     // See if we already have a line for it
1700                     for line_slot in &mut slot.lines {
1701                         if line_slot.line_index == line_index {
1702                             line_slot.annotations.push(ann);
1703                             return;
1704                         }
1705                     }
1706                     // We don't have a line yet, create one
1707                     slot.lines.push(Line {
1708                         line_index,
1709                         annotations: vec![ann],
1710                     });
1711                     slot.lines.sort();
1712                     return;
1713                 }
1714             }
1715             // This is the first time we're seeing the file
1716             file_vec.push(FileWithAnnotatedLines {
1717                 file,
1718                 lines: vec![Line {
1719                                 line_index,
1720                                 annotations: vec![ann],
1721                             }],
1722                 multiline_depth: 0,
1723             });
1724         }
1725
1726         let mut output = vec![];
1727         let mut multiline_annotations = vec![];
1728
1729         if let Some(ref sm) = source_map {
1730             for span_label in msp.span_labels() {
1731                 if span_label.span.is_dummy() {
1732                     continue;
1733                 }
1734
1735                 let lo = sm.lookup_char_pos(span_label.span.lo());
1736                 let mut hi = sm.lookup_char_pos(span_label.span.hi());
1737
1738                 // Watch out for "empty spans". If we get a span like 6..6, we
1739                 // want to just display a `^` at 6, so convert that to
1740                 // 6..7. This is degenerate input, but it's best to degrade
1741                 // gracefully -- and the parser likes to supply a span like
1742                 // that for EOF, in particular.
1743
1744                 if lo.col_display == hi.col_display && lo.line == hi.line {
1745                     hi.col_display += 1;
1746                 }
1747
1748                 if lo.line != hi.line {
1749                     let ml = MultilineAnnotation {
1750                         depth: 1,
1751                         line_start: lo.line,
1752                         line_end: hi.line,
1753                         start_col: lo.col_display,
1754                         end_col: hi.col_display,
1755                         is_primary: span_label.is_primary,
1756                         label: span_label.label,
1757                         overlaps_exactly: false,
1758                     };
1759                     multiline_annotations.push((lo.file, ml));
1760                 } else {
1761                     let ann = Annotation {
1762                         start_col: lo.col_display,
1763                         end_col: hi.col_display,
1764                         is_primary: span_label.is_primary,
1765                         label: span_label.label,
1766                         annotation_type: AnnotationType::Singleline,
1767                     };
1768                     add_annotation_to_file(&mut output, lo.file, lo.line, ann);
1769                 };
1770             }
1771         }
1772
1773         // Find overlapping multiline annotations, put them at different depths
1774         multiline_annotations.sort_by_key(|&(_, ref ml)| (ml.line_start, ml.line_end));
1775         for (_, ann) in multiline_annotations.clone() {
1776             for (_, a) in multiline_annotations.iter_mut() {
1777                 // Move all other multiline annotations overlapping with this one
1778                 // one level to the right.
1779                 if !(ann.same_span(a)) &&
1780                     num_overlap(ann.line_start, ann.line_end, a.line_start, a.line_end, true)
1781                 {
1782                     a.increase_depth();
1783                 } else if ann.same_span(a) && &ann != a {
1784                     a.overlaps_exactly = true;
1785                 } else {
1786                     break;
1787                 }
1788             }
1789         }
1790
1791         let mut max_depth = 0;  // max overlapping multiline spans
1792         for (file, ann) in multiline_annotations {
1793             max_depth = max(max_depth, ann.depth);
1794             let mut end_ann = ann.as_end();
1795             if !ann.overlaps_exactly {
1796                 // avoid output like
1797                 //
1798                 //  |        foo(
1799                 //  |   _____^
1800                 //  |  |_____|
1801                 //  | ||         bar,
1802                 //  | ||     );
1803                 //  | ||      ^
1804                 //  | ||______|
1805                 //  |  |______foo
1806                 //  |         baz
1807                 //
1808                 // and instead get
1809                 //
1810                 //  |       foo(
1811                 //  |  _____^
1812                 //  | |         bar,
1813                 //  | |     );
1814                 //  | |      ^
1815                 //  | |      |
1816                 //  | |______foo
1817                 //  |        baz
1818                 add_annotation_to_file(&mut output, file.clone(), ann.line_start, ann.as_start());
1819                 // 4 is the minimum vertical length of a multiline span when presented: two lines
1820                 // of code and two lines of underline. This is not true for the special case where
1821                 // the beginning doesn't have an underline, but the current logic seems to be
1822                 // working correctly.
1823                 let middle = min(ann.line_start + 4, ann.line_end);
1824                 for line in ann.line_start + 1..middle {
1825                     // Every `|` that joins the beginning of the span (`___^`) to the end (`|__^`).
1826                     add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
1827                 }
1828                 let line_end = ann.line_end - 1;
1829                 if middle < line_end {
1830                     add_annotation_to_file(&mut output, file.clone(), line_end, ann.as_line());
1831                 }
1832             } else {
1833                 end_ann.annotation_type = AnnotationType::Singleline;
1834             }
1835             add_annotation_to_file(&mut output, file, ann.line_end, end_ann);
1836         }
1837         for file_vec in output.iter_mut() {
1838             file_vec.multiline_depth = max_depth;
1839         }
1840         output
1841     }
1842 }
1843
1844 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1845     buffer.puts(line, col, "| ", Style::LineNumber);
1846 }
1847
1848 fn draw_col_separator_no_space(buffer: &mut StyledBuffer, line: usize, col: usize) {
1849     draw_col_separator_no_space_with_style(buffer, line, col, Style::LineNumber);
1850 }
1851
1852 fn draw_col_separator_no_space_with_style(buffer: &mut StyledBuffer,
1853                                           line: usize,
1854                                           col: usize,
1855                                           style: Style) {
1856     buffer.putc(line, col, '|', style);
1857 }
1858
1859 fn draw_range(buffer: &mut StyledBuffer, symbol: char, line: usize,
1860               col_from: usize, col_to: usize, style: Style) {
1861     for col in col_from..col_to {
1862         buffer.putc(line, col, symbol, style);
1863     }
1864 }
1865
1866 fn draw_note_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1867     buffer.puts(line, col, "= ", Style::LineNumber);
1868 }
1869
1870 fn draw_multiline_line(buffer: &mut StyledBuffer,
1871                        line: usize,
1872                        offset: usize,
1873                        depth: usize,
1874                        style: Style)
1875 {
1876     buffer.putc(line, offset + depth - 1, '|', style);
1877 }
1878
1879 fn num_overlap(a_start: usize, a_end: usize, b_start: usize, b_end:usize, inclusive: bool) -> bool {
1880     let extra = if inclusive {
1881         1
1882     } else {
1883         0
1884     };
1885     (b_start..b_end + extra).contains(&a_start) ||
1886     (a_start..a_end + extra).contains(&b_start)
1887 }
1888 fn overlaps(a1: &Annotation, a2: &Annotation, padding: usize) -> bool {
1889     num_overlap(a1.start_col, a1.end_col + padding, a2.start_col, a2.end_col, false)
1890 }
1891
1892 fn emit_to_destination(rendered_buffer: &[Vec<StyledString>],
1893                        lvl: &Level,
1894                        dst: &mut Destination,
1895                        short_message: bool)
1896                        -> io::Result<()> {
1897     use crate::lock;
1898
1899     let mut dst = dst.writable();
1900
1901     // In order to prevent error message interleaving, where multiple error lines get intermixed
1902     // when multiple compiler processes error simultaneously, we emit errors with additional
1903     // steps.
1904     //
1905     // On Unix systems, we write into a buffered terminal rather than directly to a terminal. When
1906     // the .flush() is called we take the buffer created from the buffered writes and write it at
1907     // one shot.  Because the Unix systems use ANSI for the colors, which is a text-based styling
1908     // scheme, this buffered approach works and maintains the styling.
1909     //
1910     // On Windows, styling happens through calls to a terminal API. This prevents us from using the
1911     // same buffering approach.  Instead, we use a global Windows mutex, which we acquire long
1912     // enough to output the full error message, then we release.
1913     let _buffer_lock = lock::acquire_global_lock("rustc_errors");
1914     for (pos, line) in rendered_buffer.iter().enumerate() {
1915         for part in line {
1916             dst.apply_style(lvl.clone(), part.style)?;
1917             write!(dst, "{}", part.text)?;
1918             dst.reset()?;
1919         }
1920         if !short_message && (!lvl.is_failure_note() || pos != rendered_buffer.len() - 1) {
1921             writeln!(dst)?;
1922         }
1923     }
1924     dst.flush()?;
1925     Ok(())
1926 }
1927
1928 pub enum Destination {
1929     Terminal(StandardStream),
1930     Buffered(BufferWriter),
1931     // The bool denotes whether we should be emitting ansi color codes or not
1932     Raw(Box<(dyn Write + Send)>, bool),
1933 }
1934
1935 pub enum WritableDst<'a> {
1936     Terminal(&'a mut StandardStream),
1937     Buffered(&'a mut BufferWriter, Buffer),
1938     Raw(&'a mut (dyn Write + Send)),
1939     ColoredRaw(Ansi<&'a mut (dyn Write + Send)>),
1940 }
1941
1942 impl Destination {
1943     fn from_stderr(color: ColorConfig) -> Destination {
1944         let choice = color.to_color_choice();
1945         // On Windows we'll be performing global synchronization on the entire
1946         // system for emitting rustc errors, so there's no need to buffer
1947         // anything.
1948         //
1949         // On non-Windows we rely on the atomicity of `write` to ensure errors
1950         // don't get all jumbled up.
1951         if cfg!(windows) {
1952             Terminal(StandardStream::stderr(choice))
1953         } else {
1954             Buffered(BufferWriter::stderr(choice))
1955         }
1956     }
1957
1958     fn writable(&mut self) -> WritableDst<'_> {
1959         match *self {
1960             Destination::Terminal(ref mut t) => WritableDst::Terminal(t),
1961             Destination::Buffered(ref mut t) => {
1962                 let buf = t.buffer();
1963                 WritableDst::Buffered(t, buf)
1964             }
1965             Destination::Raw(ref mut t, false) => WritableDst::Raw(t),
1966             Destination::Raw(ref mut t, true) => WritableDst::ColoredRaw(Ansi::new(t)),
1967         }
1968     }
1969 }
1970
1971 impl<'a> WritableDst<'a> {
1972     fn apply_style(&mut self, lvl: Level, style: Style) -> io::Result<()> {
1973         let mut spec = ColorSpec::new();
1974         match style {
1975             Style::LineAndColumn => {}
1976             Style::LineNumber => {
1977                 spec.set_bold(true);
1978                 spec.set_intense(true);
1979                 if cfg!(windows) {
1980                     spec.set_fg(Some(Color::Cyan));
1981                 } else {
1982                     spec.set_fg(Some(Color::Blue));
1983                 }
1984             }
1985             Style::Quotation => {}
1986             Style::MainHeaderMsg => {
1987                 spec.set_bold(true);
1988                 if cfg!(windows) {
1989                     spec.set_intense(true)
1990                         .set_fg(Some(Color::White));
1991                 }
1992             }
1993             Style::UnderlinePrimary | Style::LabelPrimary => {
1994                 spec = lvl.color();
1995                 spec.set_bold(true);
1996             }
1997             Style::UnderlineSecondary |
1998             Style::LabelSecondary => {
1999                 spec.set_bold(true)
2000                     .set_intense(true);
2001                 if cfg!(windows) {
2002                     spec.set_fg(Some(Color::Cyan));
2003                 } else {
2004                     spec.set_fg(Some(Color::Blue));
2005                 }
2006             }
2007             Style::HeaderMsg |
2008             Style::NoStyle => {}
2009             Style::Level(lvl) => {
2010                 spec = lvl.color();
2011                 spec.set_bold(true);
2012             }
2013             Style::Highlight => {
2014                 spec.set_bold(true);
2015             }
2016         }
2017         self.set_color(&spec)
2018     }
2019
2020     fn set_color(&mut self, color: &ColorSpec) -> io::Result<()> {
2021         match *self {
2022             WritableDst::Terminal(ref mut t) => t.set_color(color),
2023             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
2024             WritableDst::ColoredRaw(ref mut t) => t.set_color(color),
2025             WritableDst::Raw(_) => Ok(())
2026         }
2027     }
2028
2029     fn reset(&mut self) -> io::Result<()> {
2030         match *self {
2031             WritableDst::Terminal(ref mut t) => t.reset(),
2032             WritableDst::Buffered(_, ref mut t) => t.reset(),
2033             WritableDst::ColoredRaw(ref mut t) => t.reset(),
2034             WritableDst::Raw(_) => Ok(()),
2035         }
2036     }
2037 }
2038
2039 impl<'a> Write for WritableDst<'a> {
2040     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
2041         match *self {
2042             WritableDst::Terminal(ref mut t) => t.write(bytes),
2043             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
2044             WritableDst::Raw(ref mut w) => w.write(bytes),
2045             WritableDst::ColoredRaw(ref mut t) => t.write(bytes),
2046         }
2047     }
2048
2049     fn flush(&mut self) -> io::Result<()> {
2050         match *self {
2051             WritableDst::Terminal(ref mut t) => t.flush(),
2052             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
2053             WritableDst::Raw(ref mut w) => w.flush(),
2054             WritableDst::ColoredRaw(ref mut w) => w.flush(),
2055         }
2056     }
2057 }
2058
2059 impl<'a> Drop for WritableDst<'a> {
2060     fn drop(&mut self) {
2061         match *self {
2062             WritableDst::Buffered(ref mut dst, ref mut buf) => {
2063                 drop(dst.print(buf));
2064             }
2065             _ => {}
2066         }
2067     }
2068 }
2069
2070 /// Whether the original and suggested code are visually similar enough to warrant extra wording.
2071 pub fn is_case_difference(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
2072     // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
2073     let found = sm.span_to_snippet(sp).unwrap();
2074     let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
2075     // All the chars that differ in capitalization are confusable (above):
2076     let confusable = found.chars().zip(suggested.chars()).filter(|(f, s)| f != s).all(|(f, s)| {
2077         (ascii_confusables.contains(&f) || ascii_confusables.contains(&s))
2078     });
2079     confusable && found.to_lowercase() == suggested.to_lowercase()
2080             // FIXME: We sometimes suggest the same thing we already have, which is a
2081             //        bug, but be defensive against that here.
2082             && found != suggested
2083 }