src/librustc_errors/emitter.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use self::Destination::*;
  12
  13 use syntax_pos::{FileMap, Span, MultiSpan};
  14
  15 use {Level, CodeSuggestion, DiagnosticBuilder, SubDiagnostic, CodeMapperDyn, DiagnosticId};
  16 use snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
  17 use styled_buffer::StyledBuffer;
  18
  19 use rustc_data_structures::sync::Lrc;
  20 use atty;
  21 use std::borrow::Cow;
  22 use std::io::prelude::*;
  23 use std::io;
  24 use std::collections::HashMap;
  25 use std::cmp::{min, Reverse};
  26 use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter};
  27 use termcolor::{WriteColor, Color, Buffer};
  28 use unicode_width;
  29
  30 const ANONYMIZED_LINE_NUM: &str = "LL";
  31
  32 /// Emitter trait for emitting errors.
  33 pub trait Emitter {
  34     /// Emit a structured diagnostic.
  35     fn emit(&mut self, db: &DiagnosticBuilder);
  36
  37     /// Check if should show explanations about "rustc --explain"
  38     fn should_show_explain(&self) -> bool {
  39         true
  40     }
  41 }
  42
  43 impl Emitter for EmitterWriter {
  44     fn emit(&mut self, db: &DiagnosticBuilder) {
  45         let mut primary_span = db.span.clone();
  46         let mut children = db.children.clone();
  47         let mut suggestions: &[_] = &[];
  48
  49         if let Some((sugg, rest)) = db.suggestions.split_first() {
  50             if rest.is_empty() &&
  51                // don't display multi-suggestions as labels
  52                sugg.substitutions.len() == 1 &&
  53                // don't display multipart suggestions as labels
  54                sugg.substitutions[0].parts.len() == 1 &&
  55                // don't display long messages as labels
  56                sugg.msg.split_whitespace().count() < 10 &&
  57                // don't display multiline suggestions as labels
  58                !sugg.substitutions[0].parts[0].snippet.contains('\n') {
  59                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
  60                 let msg = if substitution.len() == 0 || !sugg.show_code_when_inline {
  61                     // This substitution is only removal or we explicitly don't want to show the
  62                     // code inline, don't show it
  63                     format!("help: {}", sugg.msg)
  64                 } else {
  65                     format!("help: {}: `{}`", sugg.msg, substitution)
  66                 };
  67                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
  68             } else {
  69                 // if there are multiple suggestions, print them all in full
  70                 // to be consistent. We could try to figure out if we can
  71                 // make one (or the first one) inline, but that would give
  72                 // undue importance to a semi-random suggestion
  73                 suggestions = &db.suggestions;
  74             }
  75         }
  76
  77         self.fix_multispans_in_std_macros(&mut primary_span,
  78                                           &mut children,
  79                                           db.handler.flags.external_macro_backtrace);
  80
  81         self.emit_messages_default(&db.level,
  82                                    &db.styled_message(),
  83                                    &db.code,
  84                                    &primary_span,
  85                                    &children,
  86                                    &suggestions);
  87     }
  88
  89     fn should_show_explain(&self) -> bool {
  90         !self.short_message
  91     }
  92 }
  93
  94 /// maximum number of lines we will print for each error; arbitrary.
  95 pub const MAX_HIGHLIGHT_LINES: usize = 6;
  96 /// maximum number of suggestions to be shown
  97 ///
  98 /// Arbitrary, but taken from trait import suggestion limit
  99 pub const MAX_SUGGESTIONS: usize = 4;
 100
 101 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 102 pub enum ColorConfig {
 103     Auto,
 104     Always,
 105     Never,
 106 }
 107
 108 impl ColorConfig {
 109     fn to_color_choice(&self) -> ColorChoice {
 110         match *self {
 111             ColorConfig::Always => ColorChoice::Always,
 112             ColorConfig::Never => ColorChoice::Never,
 113             ColorConfig::Auto if atty::is(atty::Stream::Stderr) => {
 114                 ColorChoice::Auto
 115             }
 116             ColorConfig::Auto => ColorChoice::Never,
 117         }
 118     }
 119 }
 120
 121 pub struct EmitterWriter {
 122     dst: Destination,
 123     cm: Option<Lrc<CodeMapperDyn>>,
 124     short_message: bool,
 125     teach: bool,
 126     ui_testing: bool,
 127 }
 128
 129 struct FileWithAnnotatedLines {
 130     file: Lrc<FileMap>,
 131     lines: Vec<Line>,
 132     multiline_depth: usize,
 133 }
 134
 135 impl EmitterWriter {
 136     pub fn stderr(color_config: ColorConfig,
 137                   code_map: Option<Lrc<CodeMapperDyn>>,
 138                   short_message: bool,
 139                   teach: bool)
 140                   -> EmitterWriter {
 141         let dst = Destination::from_stderr(color_config);
 142         EmitterWriter {
 143             dst,
 144             cm: code_map,
 145             short_message,
 146             teach,
 147             ui_testing: false,
 148         }
 149     }
 150
 151     pub fn new(dst: Box<dyn Write + Send>,
 152                code_map: Option<Lrc<CodeMapperDyn>>,
 153                short_message: bool,
 154                teach: bool)
 155                -> EmitterWriter {
 156         EmitterWriter {
 157             dst: Raw(dst),
 158             cm: code_map,
 159             short_message,
 160             teach,
 161             ui_testing: false,
 162         }
 163     }
 164
 165     pub fn ui_testing(mut self, ui_testing: bool) -> Self {
 166         self.ui_testing = ui_testing;
 167         self
 168     }
 169
 170     fn maybe_anonymized(&self, line_num: usize) -> String {
 171         if self.ui_testing {
 172             ANONYMIZED_LINE_NUM.to_string()
 173         } else {
 174             line_num.to_string()
 175         }
 176     }
 177
 178     fn preprocess_annotations(&mut self, msp: &MultiSpan) -> Vec<FileWithAnnotatedLines> {
 179         fn add_annotation_to_file(file_vec: &mut Vec<FileWithAnnotatedLines>,
 180                                   file: Lrc<FileMap>,
 181                                   line_index: usize,
 182                                   ann: Annotation) {
 183
 184             for slot in file_vec.iter_mut() {
 185                 // Look through each of our files for the one we're adding to
 186                 if slot.file.name == file.name {
 187                     // See if we already have a line for it
 188                     for line_slot in &mut slot.lines {
 189                         if line_slot.line_index == line_index {
 190                             line_slot.annotations.push(ann);
 191                             return;
 192                         }
 193                     }
 194                     // We don't have a line yet, create one
 195                     slot.lines.push(Line {
 196                         line_index,
 197                         annotations: vec![ann],
 198                     });
 199                     slot.lines.sort();
 200                     return;
 201                 }
 202             }
 203             // This is the first time we're seeing the file
 204             file_vec.push(FileWithAnnotatedLines {
 205                 file,
 206                 lines: vec![Line {
 207                                 line_index,
 208                                 annotations: vec![ann],
 209                             }],
 210                 multiline_depth: 0,
 211             });
 212         }
 213
 214         let mut output = vec![];
 215         let mut multiline_annotations = vec![];
 216
 217         if let Some(ref cm) = self.cm {
 218             for span_label in msp.span_labels() {
 219                 if span_label.span.is_dummy() {
 220                     continue;
 221                 }
 222
 223                 let lo = cm.lookup_char_pos(span_label.span.lo());
 224                 let mut hi = cm.lookup_char_pos(span_label.span.hi());
 225
 226                 // Watch out for "empty spans". If we get a span like 6..6, we
 227                 // want to just display a `^` at 6, so convert that to
 228                 // 6..7. This is degenerate input, but it's best to degrade
 229                 // gracefully -- and the parser likes to supply a span like
 230                 // that for EOF, in particular.
 231                 if lo.col_display == hi.col_display && lo.line == hi.line {
 232                     hi.col_display += 1;
 233                 }
 234
 235                 let ann_type = if lo.line != hi.line {
 236                     let ml = MultilineAnnotation {
 237                         depth: 1,
 238                         line_start: lo.line,
 239                         line_end: hi.line,
 240                         start_col: lo.col_display,
 241                         end_col: hi.col_display,
 242                         is_primary: span_label.is_primary,
 243                         label: span_label.label.clone(),
 244                     };
 245                     multiline_annotations.push((lo.file.clone(), ml.clone()));
 246                     AnnotationType::Multiline(ml)
 247                 } else {
 248                     AnnotationType::Singleline
 249                 };
 250                 let ann = Annotation {
 251                     start_col: lo.col_display,
 252                     end_col: hi.col_display,
 253                     is_primary: span_label.is_primary,
 254                     label: span_label.label.clone(),
 255                     annotation_type: ann_type,
 256                 };
 257
 258                 if !ann.is_multiline() {
 259                     add_annotation_to_file(&mut output,
 260                                            lo.file,
 261                                            lo.line,
 262                                            ann);
 263                 }
 264             }
 265         }
 266
 267         // Find overlapping multiline annotations, put them at different depths
 268         multiline_annotations.sort_by_key(|&(_, ref ml)| (ml.line_start, ml.line_end));
 269         for item in multiline_annotations.clone() {
 270             let ann = item.1;
 271             for item in multiline_annotations.iter_mut() {
 272                 let ref mut a = item.1;
 273                 // Move all other multiline annotations overlapping with this one
 274                 // one level to the right.
 275                 if &ann != a &&
 276                     num_overlap(ann.line_start, ann.line_end, a.line_start, a.line_end, true)
 277                 {
 278                     a.increase_depth();
 279                 } else {
 280                     break;
 281                 }
 282             }
 283         }
 284
 285         let mut max_depth = 0;  // max overlapping multiline spans
 286         for (file, ann) in multiline_annotations {
 287             if ann.depth > max_depth {
 288                 max_depth = ann.depth;
 289             }
 290             add_annotation_to_file(&mut output, file.clone(), ann.line_start, ann.as_start());
 291             let middle = min(ann.line_start + 4, ann.line_end);
 292             for line in ann.line_start + 1..middle {
 293                 add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
 294             }
 295             if middle < ann.line_end - 1 {
 296                 for line in ann.line_end - 1..ann.line_end {
 297                     add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
 298                 }
 299             }
 300             add_annotation_to_file(&mut output, file, ann.line_end, ann.as_end());
 301         }
 302         for file_vec in output.iter_mut() {
 303             file_vec.multiline_depth = max_depth;
 304         }
 305         output
 306     }
 307
 308     fn render_source_line(&self,
 309                           buffer: &mut StyledBuffer,
 310                           file: Lrc<FileMap>,
 311                           line: &Line,
 312                           width_offset: usize,
 313                           code_offset: usize) -> Vec<(usize, Style)> {
 314         if line.line_index == 0 {
 315             return Vec::new();
 316         }
 317
 318         let source_string = match file.get_line(line.line_index - 1) {
 319             Some(s) => s,
 320             None => return Vec::new(),
 321         };
 322
 323         let line_offset = buffer.num_lines();
 324
 325         // First create the source line we will highlight.
 326         buffer.puts(line_offset, code_offset, &source_string, Style::Quotation);
 327         buffer.puts(line_offset,
 328                     0,
 329                     &self.maybe_anonymized(line.line_index),
 330                     Style::LineNumber);
 331
 332         draw_col_separator(buffer, line_offset, width_offset - 2);
 333
 334         // Special case when there's only one annotation involved, it is the start of a multiline
 335         // span and there's no text at the beginning of the code line. Instead of doing the whole
 336         // graph:
 337         //
 338         // 2 |   fn foo() {
 339         //   |  _^
 340         // 3 | |
 341         // 4 | | }
 342         //   | |_^ test
 343         //
 344         // we simplify the output to:
 345         //
 346         // 2 | / fn foo() {
 347         // 3 | |
 348         // 4 | | }
 349         //   | |_^ test
 350         if line.annotations.len() == 1 {
 351             if let Some(ref ann) = line.annotations.get(0) {
 352                 if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
 353                     if source_string.chars()
 354                                     .take(ann.start_col)
 355                                     .all(|c| c.is_whitespace()) {
 356                         let style = if ann.is_primary {
 357                             Style::UnderlinePrimary
 358                         } else {
 359                             Style::UnderlineSecondary
 360                         };
 361                         buffer.putc(line_offset,
 362                                     width_offset + depth - 1,
 363                                     '/',
 364                                     style);
 365                         return vec![(depth, style)];
 366                     }
 367                 }
 368             }
 369         }
 370
 371         // We want to display like this:
 372         //
 373         //      vec.push(vec.pop().unwrap());
 374         //      ---      ^^^               - previous borrow ends here
 375         //      |        |
 376         //      |        error occurs here
 377         //      previous borrow of `vec` occurs here
 378         //
 379         // But there are some weird edge cases to be aware of:
 380         //
 381         //      vec.push(vec.pop().unwrap());
 382         //      --------                    - previous borrow ends here
 383         //      ||
 384         //      |this makes no sense
 385         //      previous borrow of `vec` occurs here
 386         //
 387         // For this reason, we group the lines into "highlight lines"
 388         // and "annotations lines", where the highlight lines have the `^`.
 389
 390         // Sort the annotations by (start, end col)
 391         // The labels are reversed, sort and then reversed again.
 392         // Consider a list of annotations (A1, A2, C1, C2, B1, B2) where
 393         // the letter signifies the span. Here we are only sorting by the
 394         // span and hence, the order of the elements with the same span will
 395         // not change. On reversing the ordering (|a, b| but b.cmp(a)), you get
 396         // (C1, C2, B1, B2, A1, A2). All the elements with the same span are
 397         // still ordered first to last, but all the elements with different
 398         // spans are ordered by their spans in last to first order. Last to
 399         // first order is important, because the jiggly lines and | are on
 400         // the left, so the rightmost span needs to be rendered first,
 401         // otherwise the lines would end up needing to go over a message.
 402
 403         let mut annotations = line.annotations.clone();
 404         annotations.sort_by_key(|a| Reverse(a.start_col));
 405
 406         // First, figure out where each label will be positioned.
 407         //
 408         // In the case where you have the following annotations:
 409         //
 410         //      vec.push(vec.pop().unwrap());
 411         //      --------                    - previous borrow ends here [C]
 412         //      ||
 413         //      |this makes no sense [B]
 414         //      previous borrow of `vec` occurs here [A]
 415         //
 416         // `annotations_position` will hold [(2, A), (1, B), (0, C)].
 417         //
 418         // We try, when possible, to stick the rightmost annotation at the end
 419         // of the highlight line:
 420         //
 421         //      vec.push(vec.pop().unwrap());
 422         //      ---      ---               - previous borrow ends here
 423         //
 424         // But sometimes that's not possible because one of the other
 425         // annotations overlaps it. For example, from the test
 426         // `span_overlap_label`, we have the following annotations
 427         // (written on distinct lines for clarity):
 428         //
 429         //      fn foo(x: u32) {
 430         //      --------------
 431         //             -
 432         //
 433         // In this case, we can't stick the rightmost-most label on
 434         // the highlight line, or we would get:
 435         //
 436         //      fn foo(x: u32) {
 437         //      -------- x_span
 438         //      |
 439         //      fn_span
 440         //
 441         // which is totally weird. Instead we want:
 442         //
 443         //      fn foo(x: u32) {
 444         //      --------------
 445         //      |      |
 446         //      |      x_span
 447         //      fn_span
 448         //
 449         // which is...less weird, at least. In fact, in general, if
 450         // the rightmost span overlaps with any other span, we should
 451         // use the "hang below" version, so we can at least make it
 452         // clear where the span *starts*. There's an exception for this
 453         // logic, when the labels do not have a message:
 454         //
 455         //      fn foo(x: u32) {
 456         //      --------------
 457         //             |
 458         //             x_span
 459         //
 460         // instead of:
 461         //
 462         //      fn foo(x: u32) {
 463         //      --------------
 464         //      |      |
 465         //      |      x_span
 466         //      <EMPTY LINE>
 467         //
 468         let mut annotations_position = vec![];
 469         let mut line_len = 0;
 470         let mut p = 0;
 471         for (i, annotation) in annotations.iter().enumerate() {
 472             for (j, next) in annotations.iter().enumerate() {
 473                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
 474                     && annotation.has_label()     // take space (they have text and are not
 475                     && j > i                      // multiline lines).
 476                     && p == 0  // We're currently on the first line, move the label one line down
 477                 {
 478                     // This annotation needs a new line in the output.
 479                     p += 1;
 480                     break;
 481                 }
 482             }
 483             annotations_position.push((p, annotation));
 484             for (j, next) in annotations.iter().enumerate() {
 485                 if j > i  {
 486                     let l = if let Some(ref label) = next.label {
 487                         label.len() + 2
 488                     } else {
 489                         0
 490                     };
 491                     if (overlaps(next, annotation, l) // Do not allow two labels to be in the same
 492                                                      // line if they overlap including padding, to
 493                                                      // avoid situations like:
 494                                                      //
 495                                                      //      fn foo(x: u32) {
 496                                                      //      -------^------
 497                                                      //      |      |
 498                                                      //      fn_spanx_span
 499                                                      //
 500                         && annotation.has_label()    // Both labels must have some text, otherwise
 501                         && next.has_label())         // they are not overlapping.
 502                                                      // Do not add a new line if this annotation
 503                                                      // or the next are vertical line placeholders.
 504                         || (annotation.takes_space() // If either this or the next annotation is
 505                             && next.has_label())     // multiline start/end, move it to a new line
 506                         || (annotation.has_label()   // so as not to overlap the orizontal lines.
 507                             && next.takes_space())
 508                         || (annotation.takes_space() && next.takes_space())
 509                         || (overlaps(next, annotation, l)
 510                             && next.end_col <= annotation.end_col
 511                             && next.has_label()
 512                             && p == 0)  // Avoid #42595.
 513                     {
 514                         // This annotation needs a new line in the output.
 515                         p += 1;
 516                         break;
 517                     }
 518                 }
 519             }
 520             if line_len < p {
 521                 line_len = p;
 522             }
 523         }
 524
 525         if line_len != 0 {
 526             line_len += 1;
 527         }
 528
 529         // If there are no annotations or the only annotations on this line are
 530         // MultilineLine, then there's only code being shown, stop processing.
 531         if line.annotations.iter().all(|a| a.is_line()) {
 532             return vec![];
 533         }
 534
 535         // Write the colunmn separator.
 536         //
 537         // After this we will have:
 538         //
 539         // 2 |   fn foo() {
 540         //   |
 541         //   |
 542         //   |
 543         // 3 |
 544         // 4 |   }
 545         //   |
 546         for pos in 0..line_len + 1 {
 547             draw_col_separator(buffer, line_offset + pos + 1, width_offset - 2);
 548             buffer.putc(line_offset + pos + 1,
 549                         width_offset - 2,
 550                         '|',
 551                         Style::LineNumber);
 552         }
 553
 554         // Write the horizontal lines for multiline annotations
 555         // (only the first and last lines need this).
 556         //
 557         // After this we will have:
 558         //
 559         // 2 |   fn foo() {
 560         //   |  __________
 561         //   |
 562         //   |
 563         // 3 |
 564         // 4 |   }
 565         //   |  _
 566         for &(pos, annotation) in &annotations_position {
 567             let style = if annotation.is_primary {
 568                 Style::UnderlinePrimary
 569             } else {
 570                 Style::UnderlineSecondary
 571             };
 572             let pos = pos + 1;
 573             match annotation.annotation_type {
 574                 AnnotationType::MultilineStart(depth) |
 575                 AnnotationType::MultilineEnd(depth) => {
 576                     draw_range(buffer,
 577                                '_',
 578                                line_offset + pos,
 579                                width_offset + depth,
 580                                code_offset + annotation.start_col,
 581                                style);
 582                 }
 583                 _ if self.teach => {
 584                     buffer.set_style_range(line_offset,
 585                                            code_offset + annotation.start_col,
 586                                            code_offset + annotation.end_col,
 587                                            style,
 588                                            annotation.is_primary);
 589                 }
 590                 _ => {}
 591             }
 592         }
 593
 594         // Write the vertical lines for labels that are on a different line as the underline.
 595         //
 596         // After this we will have:
 597         //
 598         // 2 |   fn foo() {
 599         //   |  __________
 600         //   | |    |
 601         //   | |
 602         // 3 |
 603         // 4 | | }
 604         //   | |_
 605         for &(pos, annotation) in &annotations_position {
 606             let style = if annotation.is_primary {
 607                 Style::UnderlinePrimary
 608             } else {
 609                 Style::UnderlineSecondary
 610             };
 611             let pos = pos + 1;
 612
 613             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
 614                 for p in line_offset + 1..line_offset + pos + 1 {
 615                     buffer.putc(p,
 616                                 code_offset + annotation.start_col,
 617                                 '|',
 618                                 style);
 619                 }
 620             }
 621             match annotation.annotation_type {
 622                 AnnotationType::MultilineStart(depth) => {
 623                     for p in line_offset + pos + 1..line_offset + line_len + 2 {
 624                         buffer.putc(p,
 625                                     width_offset + depth - 1,
 626                                     '|',
 627                                     style);
 628                     }
 629                 }
 630                 AnnotationType::MultilineEnd(depth) => {
 631                     for p in line_offset..line_offset + pos + 1 {
 632                         buffer.putc(p,
 633                                     width_offset + depth - 1,
 634                                     '|',
 635                                     style);
 636                     }
 637                 }
 638                 _ => (),
 639             }
 640         }
 641
 642         // Write the labels on the annotations that actually have a label.
 643         //
 644         // After this we will have:
 645         //
 646         // 2 |   fn foo() {
 647         //   |  __________
 648         //   |      |
 649         //   |      something about `foo`
 650         // 3 |
 651         // 4 |   }
 652         //   |  _  test
 653         for &(pos, annotation) in &annotations_position {
 654             let style = if annotation.is_primary {
 655                 Style::LabelPrimary
 656             } else {
 657                 Style::LabelSecondary
 658             };
 659             let (pos, col) = if pos == 0 {
 660                 (pos + 1, annotation.end_col + 1)
 661             } else {
 662                 (pos + 2, annotation.start_col)
 663             };
 664             if let Some(ref label) = annotation.label {
 665                 buffer.puts(line_offset + pos,
 666                             code_offset + col,
 667                             &label,
 668                             style);
 669             }
 670         }
 671
 672         // Sort from biggest span to smallest span so that smaller spans are
 673         // represented in the output:
 674         //
 675         // x | fn foo()
 676         //   | ^^^---^^
 677         //   | |  |
 678         //   | |  something about `foo`
 679         //   | something about `fn foo()`
 680         annotations_position.sort_by(|a, b| {
 681             // Decreasing order
 682             a.1.len().cmp(&b.1.len()).reverse()
 683         });
 684
 685         // Write the underlines.
 686         //
 687         // After this we will have:
 688         //
 689         // 2 |   fn foo() {
 690         //   |  ____-_____^
 691         //   |      |
 692         //   |      something about `foo`
 693         // 3 |
 694         // 4 |   }
 695         //   |  _^  test
 696         for &(_, annotation) in &annotations_position {
 697             let (underline, style) = if annotation.is_primary {
 698                 ('^', Style::UnderlinePrimary)
 699             } else {
 700                 ('-', Style::UnderlineSecondary)
 701             };
 702             for p in annotation.start_col..annotation.end_col {
 703                 buffer.putc(line_offset + 1,
 704                             code_offset + p,
 705                             underline,
 706                             style);
 707             }
 708         }
 709         annotations_position.iter().filter_map(|&(_, annotation)| {
 710             match annotation.annotation_type {
 711                 AnnotationType::MultilineStart(p) | AnnotationType::MultilineEnd(p) => {
 712                     let style = if annotation.is_primary {
 713                         Style::LabelPrimary
 714                     } else {
 715                         Style::LabelSecondary
 716                     };
 717                     Some((p, style))
 718                 }
 719                 _ => None
 720             }
 721
 722         }).collect::<Vec<_>>()
 723     }
 724
 725     fn get_multispan_max_line_num(&mut self, msp: &MultiSpan) -> usize {
 726         let mut max = 0;
 727         if let Some(ref cm) = self.cm {
 728             for primary_span in msp.primary_spans() {
 729                 if !primary_span.is_dummy() {
 730                     let hi = cm.lookup_char_pos(primary_span.hi());
 731                     if hi.line > max {
 732                         max = hi.line;
 733                     }
 734                 }
 735             }
 736             if !self.short_message {
 737                 for span_label in msp.span_labels() {
 738                     if !span_label.span.is_dummy() {
 739                         let hi = cm.lookup_char_pos(span_label.span.hi());
 740                         if hi.line > max {
 741                             max = hi.line;
 742                         }
 743                     }
 744                 }
 745             }
 746         }
 747         max
 748     }
 749
 750     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
 751         let mut max = 0;
 752
 753         let primary = self.get_multispan_max_line_num(span);
 754         max = if primary > max { primary } else { max };
 755
 756         for sub in children {
 757             let sub_result = self.get_multispan_max_line_num(&sub.span);
 758             max = if sub_result > max { primary } else { max };
 759         }
 760         max
 761     }
 762
 763     // This "fixes" MultiSpans that contain Spans that are pointing to locations inside of
 764     // <*macros>. Since these locations are often difficult to read, we move these Spans from
 765     // <*macros> to their corresponding use site.
 766     fn fix_multispan_in_std_macros(&mut self,
 767                                    span: &mut MultiSpan,
 768                                    always_backtrace: bool) -> bool {
 769         let mut spans_updated = false;
 770
 771         if let Some(ref cm) = self.cm {
 772             let mut before_after: Vec<(Span, Span)> = vec![];
 773             let mut new_labels: Vec<(Span, String)> = vec![];
 774
 775             // First, find all the spans in <*macros> and point instead at their use site
 776             for sp in span.primary_spans() {
 777                 if sp.is_dummy() {
 778                     continue;
 779                 }
 780                 let call_sp = cm.call_span_if_macro(*sp);
 781                 if call_sp != *sp && !always_backtrace {
 782                     before_after.push((*sp, call_sp));
 783                 }
 784                 let backtrace_len = sp.macro_backtrace().len();
 785                 for (i, trace) in sp.macro_backtrace().iter().rev().enumerate() {
 786                     // Only show macro locations that are local
 787                     // and display them like a span_note
 788                     if let Some(def_site) = trace.def_site_span {
 789                         if def_site.is_dummy() {
 790                             continue;
 791                         }
 792                         if always_backtrace {
 793                             new_labels.push((def_site,
 794                                              format!("in this expansion of `{}`{}",
 795                                                      trace.macro_decl_name,
 796                                                      if backtrace_len > 2 {
 797                                                          // if backtrace_len == 1 it'll be pointed
 798                                                          // at by "in this macro invocation"
 799                                                          format!(" (#{})", i + 1)
 800                                                      } else {
 801                                                          "".to_string()
 802                                                      })));
 803                         }
 804                         // Check to make sure we're not in any <*macros>
 805                         if !cm.span_to_filename(def_site).is_macros() &&
 806                            !trace.macro_decl_name.starts_with("desugaring of ") &&
 807                            !trace.macro_decl_name.starts_with("#[") ||
 808                            always_backtrace {
 809                             new_labels.push((trace.call_site,
 810                                              format!("in this macro invocation{}",
 811                                                      if backtrace_len > 2 && always_backtrace {
 812                                                          // only specify order when the macro
 813                                                          // backtrace is multiple levels deep
 814                                                          format!(" (#{})", i + 1)
 815                                                      } else {
 816                                                          "".to_string()
 817                                                      })));
 818                             if !always_backtrace {
 819                                 break;
 820                             }
 821                         }
 822                     }
 823                 }
 824             }
 825             for (label_span, label_text) in new_labels {
 826                 span.push_span_label(label_span, label_text);
 827             }
 828             for sp_label in span.span_labels() {
 829                 if sp_label.span.is_dummy() {
 830                     continue;
 831                 }
 832                 if cm.span_to_filename(sp_label.span.clone()).is_macros() &&
 833                     !always_backtrace
 834                 {
 835                     let v = sp_label.span.macro_backtrace();
 836                     if let Some(use_site) = v.last() {
 837                         before_after.push((sp_label.span.clone(), use_site.call_site.clone()));
 838                     }
 839                 }
 840             }
 841             // After we have them, make sure we replace these 'bad' def sites with their use sites
 842             for (before, after) in before_after {
 843                 span.replace(before, after);
 844                 spans_updated = true;
 845             }
 846         }
 847
 848         spans_updated
 849     }
 850
 851     // This does a small "fix" for multispans by looking to see if it can find any that
 852     // point directly at <*macros>. Since these are often difficult to read, this
 853     // will change the span to point at the use site.
 854     fn fix_multispans_in_std_macros(&mut self,
 855                                     span: &mut MultiSpan,
 856                                     children: &mut Vec<SubDiagnostic>,
 857                                     backtrace: bool) {
 858         let mut spans_updated = self.fix_multispan_in_std_macros(span, backtrace);
 859         for child in children.iter_mut() {
 860             spans_updated |= self.fix_multispan_in_std_macros(&mut child.span, backtrace);
 861         }
 862         if spans_updated {
 863             children.push(SubDiagnostic {
 864                 level: Level::Note,
 865                 message: vec![
 866                     ("this error originates in a macro outside of the current crate \
 867                       (in Nightly builds, run with -Z external-macro-backtrace \
 868                        for more info)".to_string(),
 869                      Style::NoStyle),
 870                 ],
 871                 span: MultiSpan::new(),
 872                 render_span: None,
 873             });
 874         }
 875     }
 876
 877     /// Add a left margin to every line but the first, given a padding length and the label being
 878     /// displayed, keeping the provided highlighting.
 879     fn msg_to_buffer(&self,
 880                      buffer: &mut StyledBuffer,
 881                      msg: &[(String, Style)],
 882                      padding: usize,
 883                      label: &str,
 884                      override_style: Option<Style>) {
 885
 886         // The extra 5 ` ` is padding that's always needed to align to the `note: `:
 887         //
 888         //   error: message
 889         //     --> file.rs:13:20
 890         //      |
 891         //   13 |     <CODE>
 892         //      |      ^^^^
 893         //      |
 894         //      = note: multiline
 895         //              message
 896         //   ++^^^----xx
 897         //    |  |   | |
 898         //    |  |   | magic `2`
 899         //    |  |   length of label
 900         //    |  magic `3`
 901         //    `max_line_num_len`
 902         let padding = " ".repeat(padding + label.len() + 5);
 903
 904         /// Return whether `style`, or the override if present and the style is `NoStyle`.
 905         fn style_or_override(style: Style, override_style: Option<Style>) -> Style {
 906             if let Some(o) = override_style {
 907                 if style == Style::NoStyle {
 908                     return o;
 909                 }
 910             }
 911             style
 912         }
 913
 914         let mut line_number = 0;
 915
 916         // Provided the following diagnostic message:
 917         //
 918         //     let msg = vec![
 919         //       ("
 920         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
 921         //       ("looks", Style::Highlight),
 922         //       ("with\nvery ", Style::NoStyle),
 923         //       ("weird", Style::Highlight),
 924         //       (" formats\n", Style::NoStyle),
 925         //       ("see?", Style::Highlight),
 926         //     ];
 927         //
 928         // the expected output on a note is (* surround the highlighted text)
 929         //
 930         //        = note: highlighted multiline
 931         //                string to
 932         //                see how it *looks* with
 933         //                very *weird* formats
 934         //                see?
 935         for &(ref text, ref style) in msg.iter() {
 936             let lines = text.split('\n').collect::<Vec<_>>();
 937             if lines.len() > 1 {
 938                 for (i, line) in lines.iter().enumerate() {
 939                     if i != 0 {
 940                         line_number += 1;
 941                         buffer.append(line_number, &padding, Style::NoStyle);
 942                     }
 943                     buffer.append(line_number, line, style_or_override(*style, override_style));
 944                 }
 945             } else {
 946                 buffer.append(line_number, text, style_or_override(*style, override_style));
 947             }
 948         }
 949     }
 950
 951     fn emit_message_default(&mut self,
 952                             msp: &MultiSpan,
 953                             msg: &[(String, Style)],
 954                             code: &Option<DiagnosticId>,
 955                             level: &Level,
 956                             max_line_num_len: usize,
 957                             is_secondary: bool)
 958                             -> io::Result<()> {
 959         let mut buffer = StyledBuffer::new();
 960         let header_style = if is_secondary {
 961             Style::HeaderMsg
 962         } else {
 963             Style::MainHeaderMsg
 964         };
 965
 966         if msp.primary_spans().is_empty() && msp.span_labels().is_empty() && is_secondary
 967            && !self.short_message {
 968             // This is a secondary message with no span info
 969             for _ in 0..max_line_num_len {
 970                 buffer.prepend(0, " ", Style::NoStyle);
 971             }
 972             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
 973             let level_str = level.to_string();
 974             if !level_str.is_empty() {
 975                 buffer.append(0, &level_str, Style::MainHeaderMsg);
 976                 buffer.append(0, ": ", Style::NoStyle);
 977             }
 978             self.msg_to_buffer(&mut buffer, msg, max_line_num_len, "note", None);
 979         } else {
 980             let level_str = level.to_string();
 981             if !level_str.is_empty() {
 982                 buffer.append(0, &level_str, Style::Level(level.clone()));
 983             }
 984             // only render error codes, not lint codes
 985             if let Some(DiagnosticId::Error(ref code)) = *code {
 986                 buffer.append(0, "[", Style::Level(level.clone()));
 987                 buffer.append(0, &code, Style::Level(level.clone()));
 988                 buffer.append(0, "]", Style::Level(level.clone()));
 989             }
 990             if !level_str.is_empty() {
 991                 buffer.append(0, ": ", header_style);
 992             }
 993             for &(ref text, _) in msg.iter() {
 994                 buffer.append(0, text, header_style);
 995             }
 996         }
 997
 998         // Preprocess all the annotations so that they are grouped by file and by line number
 999         // This helps us quickly iterate over the whole message (including secondary file spans)
1000         let mut annotated_files = self.preprocess_annotations(msp);
1001
1002         // Make sure our primary file comes first
1003         let (primary_lo, cm) = if let (Some(cm), Some(ref primary_span)) =
1004             (self.cm.as_ref(), msp.primary_span().as_ref()) {
1005             if !primary_span.is_dummy() {
1006                 (cm.lookup_char_pos(primary_span.lo()), cm)
1007             } else {
1008                 emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1009                 return Ok(());
1010             }
1011         } else {
1012             // If we don't have span information, emit and exit
1013             emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1014             return Ok(());
1015         };
1016         if let Ok(pos) =
1017             annotated_files.binary_search_by(|x| x.file.name.cmp(&primary_lo.file.name)) {
1018             annotated_files.swap(0, pos);
1019         }
1020
1021         // Print out the annotate source lines that correspond with the error
1022         for annotated_file in annotated_files {
1023             // we can't annotate anything if the source is unavailable.
1024             if !cm.ensure_filemap_source_present(annotated_file.file.clone()) {
1025                 continue;
1026             }
1027
1028             // print out the span location and spacer before we print the annotated source
1029             // to do this, we need to know if this span will be primary
1030             let is_primary = primary_lo.file.name == annotated_file.file.name;
1031             if is_primary {
1032                 let loc = primary_lo.clone();
1033                 if !self.short_message {
1034                     // remember where we are in the output buffer for easy reference
1035                     let buffer_msg_line_offset = buffer.num_lines();
1036
1037                     buffer.prepend(buffer_msg_line_offset, "--> ", Style::LineNumber);
1038                     buffer.append(buffer_msg_line_offset,
1039                                   &format!("{}:{}:{}",
1040                                            loc.file.name,
1041                                            cm.doctest_offset_line(loc.line),
1042                                            loc.col.0 + 1),
1043                                   Style::LineAndColumn);
1044                     for _ in 0..max_line_num_len {
1045                         buffer.prepend(buffer_msg_line_offset, " ", Style::NoStyle);
1046                     }
1047                 } else {
1048                     buffer.prepend(0,
1049                                    &format!("{}:{}:{}: ",
1050                                             loc.file.name,
1051                                             cm.doctest_offset_line(loc.line),
1052                                             loc.col.0 + 1),
1053                                    Style::LineAndColumn);
1054                 }
1055             } else if !self.short_message {
1056                 // remember where we are in the output buffer for easy reference
1057                 let buffer_msg_line_offset = buffer.num_lines();
1058
1059                 // Add spacing line
1060                 draw_col_separator(&mut buffer, buffer_msg_line_offset, max_line_num_len + 1);
1061
1062                 // Then, the secondary file indicator
1063                 buffer.prepend(buffer_msg_line_offset + 1, "::: ", Style::LineNumber);
1064                 let loc = if let Some(first_line) = annotated_file.lines.first() {
1065                     let col = if let Some(first_annotation) = first_line.annotations.first() {
1066                         format!(":{}", first_annotation.start_col + 1)
1067                     } else {
1068                         "".to_string()
1069                     };
1070                     format!("{}:{}{}",
1071                             annotated_file.file.name,
1072                             cm.doctest_offset_line(first_line.line_index),
1073                             col)
1074                 } else {
1075                     annotated_file.file.name.to_string()
1076                 };
1077                 buffer.append(buffer_msg_line_offset + 1,
1078                               &loc,
1079                               Style::LineAndColumn);
1080                 for _ in 0..max_line_num_len {
1081                     buffer.prepend(buffer_msg_line_offset + 1, " ", Style::NoStyle);
1082                 }
1083             }
1084
1085             if !self.short_message {
1086                 // Put in the spacer between the location and annotated source
1087                 let buffer_msg_line_offset = buffer.num_lines();
1088                 draw_col_separator_no_space(&mut buffer,
1089                                             buffer_msg_line_offset,
1090                                             max_line_num_len + 1);
1091
1092                 // Contains the vertical lines' positions for active multiline annotations
1093                 let mut multilines = HashMap::new();
1094
1095                 // Next, output the annotate source for this file
1096                 for line_idx in 0..annotated_file.lines.len() {
1097                     let previous_buffer_line = buffer.num_lines();
1098
1099                     let width_offset = 3 + max_line_num_len;
1100                     let code_offset = if annotated_file.multiline_depth == 0 {
1101                         width_offset
1102                     } else {
1103                         width_offset + annotated_file.multiline_depth + 1
1104                     };
1105
1106                     let depths = self.render_source_line(&mut buffer,
1107                                                          annotated_file.file.clone(),
1108                                                          &annotated_file.lines[line_idx],
1109                                                          width_offset,
1110                                                          code_offset);
1111
1112                     let mut to_add = HashMap::new();
1113
1114                     for (depth, style) in depths {
1115                         if multilines.get(&depth).is_some() {
1116                             multilines.remove(&depth);
1117                         } else {
1118                             to_add.insert(depth, style);
1119                         }
1120                     }
1121
1122                     // Set the multiline annotation vertical lines to the left of
1123                     // the code in this line.
1124                     for (depth, style) in &multilines {
1125                         for line in previous_buffer_line..buffer.num_lines() {
1126                             draw_multiline_line(&mut buffer,
1127                                                 line,
1128                                                 width_offset,
1129                                                 *depth,
1130                                                 *style);
1131                         }
1132                     }
1133                     // check to see if we need to print out or elide lines that come between
1134                     // this annotated line and the next one.
1135                     if line_idx < (annotated_file.lines.len() - 1) {
1136                         let line_idx_delta = annotated_file.lines[line_idx + 1].line_index -
1137                                              annotated_file.lines[line_idx].line_index;
1138                         if line_idx_delta > 2 {
1139                             let last_buffer_line_num = buffer.num_lines();
1140                             buffer.puts(last_buffer_line_num, 0, "...", Style::LineNumber);
1141
1142                             // Set the multiline annotation vertical lines on `...` bridging line.
1143                             for (depth, style) in &multilines {
1144                                 draw_multiline_line(&mut buffer,
1145                                                     last_buffer_line_num,
1146                                                     width_offset,
1147                                                     *depth,
1148                                                     *style);
1149                             }
1150                         } else if line_idx_delta == 2 {
1151                             let unannotated_line = annotated_file.file
1152                                 .get_line(annotated_file.lines[line_idx].line_index)
1153                                 .unwrap_or_else(|| Cow::from(""));
1154
1155                             let last_buffer_line_num = buffer.num_lines();
1156
1157                             buffer.puts(last_buffer_line_num,
1158                                         0,
1159                                         &self.maybe_anonymized(annotated_file.lines[line_idx + 1]
1160                                                                              .line_index - 1),
1161                                         Style::LineNumber);
1162                             draw_col_separator(&mut buffer,
1163                                                last_buffer_line_num,
1164                                                1 + max_line_num_len);
1165                             buffer.puts(last_buffer_line_num,
1166                                         code_offset,
1167                                         &unannotated_line,
1168                                         Style::Quotation);
1169
1170                             for (depth, style) in &multilines {
1171                                 draw_multiline_line(&mut buffer,
1172                                                     last_buffer_line_num,
1173                                                     width_offset,
1174                                                     *depth,
1175                                                     *style);
1176                             }
1177                         }
1178                     }
1179
1180                     multilines.extend(&to_add);
1181                 }
1182             }
1183         }
1184
1185         // final step: take our styled buffer, render it, then output it
1186         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1187
1188         Ok(())
1189
1190     }
1191
1192     fn emit_suggestion_default(&mut self,
1193                                suggestion: &CodeSuggestion,
1194                                level: &Level,
1195                                max_line_num_len: usize)
1196                                -> io::Result<()> {
1197         if let Some(ref cm) = self.cm {
1198             let mut buffer = StyledBuffer::new();
1199
1200             // Render the suggestion message
1201             let level_str = level.to_string();
1202             if !level_str.is_empty() {
1203                 buffer.append(0, &level_str, Style::Level(level.clone()));
1204                 buffer.append(0, ": ", Style::HeaderMsg);
1205             }
1206             self.msg_to_buffer(&mut buffer,
1207                                &[(suggestion.msg.to_owned(), Style::NoStyle)],
1208                                max_line_num_len,
1209                                "suggestion",
1210                                Some(Style::HeaderMsg));
1211
1212             // Render the replacements for each suggestion
1213             let suggestions = suggestion.splice_lines(&**cm);
1214
1215             let mut row_num = 2;
1216             for &(ref complete, ref parts) in suggestions.iter().take(MAX_SUGGESTIONS) {
1217                 // Only show underline if the suggestion spans a single line and doesn't cover the
1218                 // entirety of the code output. If you have multiple replacements in the same line
1219                 // of code, show the underline.
1220                 let show_underline = !(parts.len() == 1
1221                     && parts[0].snippet.trim() == complete.trim())
1222                     && complete.lines().count() == 1;
1223
1224                 let lines = cm.span_to_lines(parts[0].span).unwrap();
1225
1226                 assert!(!lines.lines.is_empty());
1227
1228                 let line_start = cm.lookup_char_pos(parts[0].span.lo()).line;
1229                 draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
1230                 let mut line_pos = 0;
1231                 let mut lines = complete.lines();
1232                 for line in lines.by_ref().take(MAX_HIGHLIGHT_LINES) {
1233                     // Print the span column to avoid confusion
1234                     buffer.puts(row_num,
1235                                 0,
1236                                 &self.maybe_anonymized(line_start + line_pos),
1237                                 Style::LineNumber);
1238                     // print the suggestion
1239                     draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1240                     buffer.append(row_num, line, Style::NoStyle);
1241                     line_pos += 1;
1242                     row_num += 1;
1243                 }
1244
1245                 // This offset and the ones below need to be signed to account for replacement code
1246                 // that is shorter than the original code.
1247                 let mut offset: isize = 0;
1248                 // Only show an underline in the suggestions if the suggestion is not the
1249                 // entirety of the code being shown and the displayed code is not multiline.
1250                 if show_underline {
1251                     draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1252                     for part in parts {
1253                         let span_start_pos = cm.lookup_char_pos(part.span.lo()).col_display;
1254                         let span_end_pos = cm.lookup_char_pos(part.span.hi()).col_display;
1255
1256                         // Do not underline the leading...
1257                         let start = part.snippet.len()
1258                             .saturating_sub(part.snippet.trim_left().len());
1259                         // ...or trailing spaces. Account for substitutions containing unicode
1260                         // characters.
1261                         let sub_len = part.snippet.trim().chars().fold(0, |acc, ch| {
1262                             acc + unicode_width::UnicodeWidthChar::width(ch).unwrap_or(0)
1263                         });
1264
1265                         let underline_start = (span_start_pos + start) as isize + offset;
1266                         let underline_end = (span_start_pos + start + sub_len) as isize + offset;
1267                         for p in underline_start..underline_end {
1268                             buffer.putc(row_num,
1269                                         max_line_num_len + 3 + p as usize,
1270                                         '^',
1271                                         Style::UnderlinePrimary);
1272                         }
1273                         // underline removals too
1274                         if underline_start == underline_end {
1275                             for p in underline_start-1..underline_start+1 {
1276                                 buffer.putc(row_num,
1277                                             max_line_num_len + 3 + p as usize,
1278                                             '-',
1279                                             Style::UnderlineSecondary);
1280                             }
1281                         }
1282
1283                         // length of the code after substitution
1284                         let full_sub_len = part.snippet.chars().fold(0, |acc, ch| {
1285                             acc + unicode_width::UnicodeWidthChar::width(ch).unwrap_or(0) as isize
1286                         });
1287
1288                         // length of the code to be substituted
1289                         let snippet_len = span_end_pos as isize - span_start_pos as isize;
1290                         // For multiple substitutions, use the position *after* the previous
1291                         // substitutions have happened.
1292                         offset += full_sub_len - snippet_len;
1293                     }
1294                     row_num += 1;
1295                 }
1296
1297                 // if we elided some lines, add an ellipsis
1298                 if lines.next().is_some() {
1299                     buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
1300                 } else if !show_underline {
1301                     draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
1302                     row_num += 1;
1303                 }
1304             }
1305             if suggestions.len() > MAX_SUGGESTIONS {
1306                 let msg = format!("and {} other candidates", suggestions.len() - MAX_SUGGESTIONS);
1307                 buffer.puts(row_num, 0, &msg, Style::NoStyle);
1308             }
1309             emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1310         }
1311         Ok(())
1312     }
1313
1314     fn emit_messages_default(&mut self,
1315                              level: &Level,
1316                              message: &[(String, Style)],
1317                              code: &Option<DiagnosticId>,
1318                              span: &MultiSpan,
1319                              children: &[SubDiagnostic],
1320                              suggestions: &[CodeSuggestion]) {
1321         let max_line_num_len = if self.ui_testing {
1322             ANONYMIZED_LINE_NUM.len()
1323         } else {
1324             self.get_max_line_num(span, children).to_string().len()
1325         };
1326
1327         match self.emit_message_default(span,
1328                                         message,
1329                                         code,
1330                                         level,
1331                                         max_line_num_len,
1332                                         false) {
1333             Ok(()) => {
1334                 if !children.is_empty() {
1335                     let mut buffer = StyledBuffer::new();
1336                     if !self.short_message {
1337                         draw_col_separator_no_space(&mut buffer, 0, max_line_num_len + 1);
1338                     }
1339                     match emit_to_destination(&buffer.render(), level, &mut self.dst,
1340                                               self.short_message) {
1341                         Ok(()) => (),
1342                         Err(e) => panic!("failed to emit error: {}", e)
1343                     }
1344                 }
1345                 if !self.short_message {
1346                     for child in children {
1347                         let span = child.render_span.as_ref().unwrap_or(&child.span);
1348                         match self.emit_message_default(&span,
1349                                                         &child.styled_message(),
1350                                                         &None,
1351                                                         &child.level,
1352                                                         max_line_num_len,
1353                                                         true) {
1354                             Err(e) => panic!("failed to emit error: {}", e),
1355                             _ => ()
1356                         }
1357                     }
1358                     for sugg in suggestions {
1359                         match self.emit_suggestion_default(sugg,
1360                                                            &Level::Help,
1361                                                            max_line_num_len) {
1362                             Err(e) => panic!("failed to emit error: {}", e),
1363                             _ => ()
1364                         }
1365                     }
1366                 }
1367             }
1368             Err(e) => panic!("failed to emit error: {}", e),
1369         }
1370
1371         let mut dst = self.dst.writable();
1372         match write!(dst, "\n") {
1373             Err(e) => panic!("failed to emit error: {}", e),
1374             _ => {
1375                 match dst.flush() {
1376                     Err(e) => panic!("failed to emit error: {}", e),
1377                     _ => (),
1378                 }
1379             }
1380         }
1381     }
1382 }
1383
1384 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1385     buffer.puts(line, col, "| ", Style::LineNumber);
1386 }
1387
1388 fn draw_col_separator_no_space(buffer: &mut StyledBuffer, line: usize, col: usize) {
1389     draw_col_separator_no_space_with_style(buffer, line, col, Style::LineNumber);
1390 }
1391
1392 fn draw_col_separator_no_space_with_style(buffer: &mut StyledBuffer,
1393                                           line: usize,
1394                                           col: usize,
1395                                           style: Style) {
1396     buffer.putc(line, col, '|', style);
1397 }
1398
1399 fn draw_range(buffer: &mut StyledBuffer, symbol: char, line: usize,
1400               col_from: usize, col_to: usize, style: Style) {
1401     for col in col_from..col_to {
1402         buffer.putc(line, col, symbol, style);
1403     }
1404 }
1405
1406 fn draw_note_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1407     buffer.puts(line, col, "= ", Style::LineNumber);
1408 }
1409
1410 fn draw_multiline_line(buffer: &mut StyledBuffer,
1411                        line: usize,
1412                        offset: usize,
1413                        depth: usize,
1414                        style: Style)
1415 {
1416     buffer.putc(line, offset + depth - 1, '|', style);
1417 }
1418
1419 fn num_overlap(a_start: usize, a_end: usize, b_start: usize, b_end:usize, inclusive: bool) -> bool {
1420     let extra = if inclusive {
1421         1
1422     } else {
1423         0
1424     };
1425     (b_start..b_end + extra).contains(&a_start) ||
1426     (a_start..a_end + extra).contains(&b_start)
1427 }
1428 fn overlaps(a1: &Annotation, a2: &Annotation, padding: usize) -> bool {
1429     num_overlap(a1.start_col, a1.end_col + padding, a2.start_col, a2.end_col, false)
1430 }
1431
1432 fn emit_to_destination(rendered_buffer: &[Vec<StyledString>],
1433                        lvl: &Level,
1434                        dst: &mut Destination,
1435                        short_message: bool)
1436                        -> io::Result<()> {
1437     use lock;
1438
1439     let mut dst = dst.writable();
1440
1441     // In order to prevent error message interleaving, where multiple error lines get intermixed
1442     // when multiple compiler processes error simultaneously, we emit errors with additional
1443     // steps.
1444     //
1445     // On Unix systems, we write into a buffered terminal rather than directly to a terminal. When
1446     // the .flush() is called we take the buffer created from the buffered writes and write it at
1447     // one shot.  Because the Unix systems use ANSI for the colors, which is a text-based styling
1448     // scheme, this buffered approach works and maintains the styling.
1449     //
1450     // On Windows, styling happens through calls to a terminal API. This prevents us from using the
1451     // same buffering approach.  Instead, we use a global Windows mutex, which we acquire long
1452     // enough to output the full error message, then we release.
1453     let _buffer_lock = lock::acquire_global_lock("rustc_errors");
1454     for (pos, line) in rendered_buffer.iter().enumerate() {
1455         for part in line {
1456             dst.apply_style(lvl.clone(), part.style)?;
1457             write!(dst, "{}", part.text)?;
1458             dst.reset()?;
1459         }
1460         if !short_message && (!lvl.is_failure_note() || pos != rendered_buffer.len() - 1) {
1461             write!(dst, "\n")?;
1462         }
1463     }
1464     dst.flush()?;
1465     Ok(())
1466 }
1467
1468 pub enum Destination {
1469     Terminal(StandardStream),
1470     Buffered(BufferWriter),
1471     Raw(Box<dyn Write + Send>),
1472 }
1473
1474 pub enum WritableDst<'a> {
1475     Terminal(&'a mut StandardStream),
1476     Buffered(&'a mut BufferWriter, Buffer),
1477     Raw(&'a mut Box<dyn Write + Send>),
1478 }
1479
1480 impl Destination {
1481     fn from_stderr(color: ColorConfig) -> Destination {
1482         let choice = color.to_color_choice();
1483         // On Windows we'll be performing global synchronization on the entire
1484         // system for emitting rustc errors, so there's no need to buffer
1485         // anything.
1486         //
1487         // On non-Windows we rely on the atomicity of `write` to ensure errors
1488         // don't get all jumbled up.
1489         if cfg!(windows) {
1490             Terminal(StandardStream::stderr(choice))
1491         } else {
1492             Buffered(BufferWriter::stderr(choice))
1493         }
1494     }
1495
1496     fn writable<'a>(&'a mut self) -> WritableDst<'a> {
1497         match *self {
1498             Destination::Terminal(ref mut t) => WritableDst::Terminal(t),
1499             Destination::Buffered(ref mut t) => {
1500                 let buf = t.buffer();
1501                 WritableDst::Buffered(t, buf)
1502             }
1503             Destination::Raw(ref mut t) => WritableDst::Raw(t),
1504         }
1505     }
1506 }
1507
1508 impl<'a> WritableDst<'a> {
1509     fn apply_style(&mut self, lvl: Level, style: Style) -> io::Result<()> {
1510         let mut spec = ColorSpec::new();
1511         match style {
1512             Style::LineAndColumn => {}
1513             Style::LineNumber => {
1514                 spec.set_bold(true);
1515                 spec.set_intense(true);
1516                 if cfg!(windows) {
1517                     spec.set_fg(Some(Color::Cyan));
1518                 } else {
1519                     spec.set_fg(Some(Color::Blue));
1520                 }
1521             }
1522             Style::Quotation => {}
1523             Style::OldSchoolNoteText | Style::MainHeaderMsg => {
1524                 spec.set_bold(true);
1525                 if cfg!(windows) {
1526                     spec.set_intense(true)
1527                         .set_fg(Some(Color::White));
1528                 }
1529             }
1530             Style::UnderlinePrimary | Style::LabelPrimary => {
1531                 spec = lvl.color();
1532                 spec.set_bold(true);
1533             }
1534             Style::UnderlineSecondary |
1535             Style::LabelSecondary => {
1536                 spec.set_bold(true)
1537                     .set_intense(true);
1538                 if cfg!(windows) {
1539                     spec.set_fg(Some(Color::Cyan));
1540                 } else {
1541                     spec.set_fg(Some(Color::Blue));
1542                 }
1543             }
1544             Style::HeaderMsg |
1545             Style::NoStyle => {}
1546             Style::Level(lvl) => {
1547                 spec = lvl.color();
1548                 spec.set_bold(true);
1549             }
1550             Style::Highlight => {
1551                 spec.set_bold(true);
1552             }
1553         }
1554         self.set_color(&spec)
1555     }
1556
1557     fn set_color(&mut self, color: &ColorSpec) -> io::Result<()> {
1558         match *self {
1559             WritableDst::Terminal(ref mut t) => t.set_color(color),
1560             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
1561             WritableDst::Raw(_) => Ok(())
1562         }
1563     }
1564
1565     fn reset(&mut self) -> io::Result<()> {
1566         match *self {
1567             WritableDst::Terminal(ref mut t) => t.reset(),
1568             WritableDst::Buffered(_, ref mut t) => t.reset(),
1569             WritableDst::Raw(_) => Ok(()),
1570         }
1571     }
1572 }
1573
1574 impl<'a> Write for WritableDst<'a> {
1575     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
1576         match *self {
1577             WritableDst::Terminal(ref mut t) => t.write(bytes),
1578             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
1579             WritableDst::Raw(ref mut w) => w.write(bytes),
1580         }
1581     }
1582
1583     fn flush(&mut self) -> io::Result<()> {
1584         match *self {
1585             WritableDst::Terminal(ref mut t) => t.flush(),
1586             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
1587             WritableDst::Raw(ref mut w) => w.flush(),
1588         }
1589     }
1590 }
1591
1592 impl<'a> Drop for WritableDst<'a> {
1593     fn drop(&mut self) {
1594         match *self {
1595             WritableDst::Buffered(ref mut dst, ref mut buf) => {
1596                 drop(dst.print(buf));
1597             }
1598             _ => {}
1599         }
1600     }
1601 }