src/librustc_errors/emitter.rs

   1 //! The current rustc diagnostics emitter.
   2 //!
   3 //! An `Emitter` takes care of generating the output from a `DiagnosticBuilder` struct.
   4 //!
   5 //! There are various `Emitter` implementations that generate different output formats such as
   6 //! JSON and human readable output.
   7 //!
   8 //! The output types are defined in `librustc::session::config::ErrorOutputType`.
   9
  10 use Destination::*;
  11
  12 use syntax_pos::{SourceFile, Span, MultiSpan};
  13
  14 use crate::{
  15     Level, CodeSuggestion, Diagnostic, SubDiagnostic, pluralise,
  16     SuggestionStyle, SourceMapper, SourceMapperDyn, DiagnosticId,
  17 };
  18 use crate::Level::Error;
  19 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
  20 use crate::styled_buffer::StyledBuffer;
  21
  22 use rustc_data_structures::fx::FxHashMap;
  23 use rustc_data_structures::sync::Lrc;
  24 use std::borrow::Cow;
  25 use std::io::prelude::*;
  26 use std::io;
  27 use std::cmp::{min, max, Reverse};
  28 use std::path::Path;
  29 use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter, Ansi};
  30 use termcolor::{WriteColor, Color, Buffer};
  31
  32 /// Describes the way the content of the `rendered` field of the json output is generated
  33 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
  34 pub enum HumanReadableErrorType {
  35     Default(ColorConfig),
  36     AnnotateSnippet(ColorConfig),
  37     Short(ColorConfig),
  38 }
  39
  40 impl HumanReadableErrorType {
  41     /// Returns a (`short`, `color`) tuple
  42     pub fn unzip(self) -> (bool, ColorConfig) {
  43         match self {
  44             HumanReadableErrorType::Default(cc) => (false, cc),
  45             HumanReadableErrorType::Short(cc) => (true, cc),
  46             HumanReadableErrorType::AnnotateSnippet(cc) => (false, cc),
  47         }
  48     }
  49     pub fn new_emitter(
  50         self,
  51         dst: Box<dyn Write + Send>,
  52         source_map: Option<Lrc<SourceMapperDyn>>,
  53         teach: bool,
  54         terminal_width: Option<usize>,
  55         external_macro_backtrace: bool,
  56     ) -> EmitterWriter {
  57         let (short, color_config) = self.unzip();
  58         let color = color_config.suggests_using_colors();
  59         EmitterWriter::new(dst, source_map, short, teach, color, terminal_width,
  60             external_macro_backtrace)
  61     }
  62 }
  63
  64 #[derive(Clone, Copy, Debug)]
  65 struct Margin {
  66     /// The available whitespace in the left that can be consumed when centering.
  67     pub whitespace_left: usize,
  68     /// The column of the beginning of left-most span.
  69     pub span_left: usize,
  70     /// The column of the end of right-most span.
  71     pub span_right: usize,
  72     /// The beginning of the line to be displayed.
  73     pub computed_left: usize,
  74     /// The end of the line to be displayed.
  75     pub computed_right: usize,
  76     /// The current width of the terminal. 140 by default and in tests.
  77     pub column_width: usize,
  78     /// The end column of a span label, including the span. Doesn't account for labels not in the
  79     /// same line as the span.
  80     pub label_right: usize,
  81 }
  82
  83 impl Margin {
  84     fn new(
  85         whitespace_left: usize,
  86         span_left: usize,
  87         span_right: usize,
  88         label_right: usize,
  89         column_width: usize,
  90         max_line_len: usize,
  91     ) -> Self {
  92         // The 6 is padding to give a bit of room for `...` when displaying:
  93         // ```
  94         // error: message
  95         //   --> file.rs:16:58
  96         //    |
  97         // 16 | ... fn foo(self) -> Self::Bar {
  98         //    |                     ^^^^^^^^^
  99         // ```
 100
 101         let mut m = Margin {
 102             whitespace_left: whitespace_left.saturating_sub(6),
 103             span_left: span_left.saturating_sub(6),
 104             span_right: span_right + 6,
 105             computed_left: 0,
 106             computed_right: 0,
 107             column_width,
 108             label_right: label_right + 6,
 109         };
 110         m.compute(max_line_len);
 111         m
 112     }
 113
 114     fn was_cut_left(&self) -> bool {
 115         self.computed_left > 0
 116     }
 117
 118     fn was_cut_right(&self, line_len: usize) -> bool {
 119         let right = if self.computed_right == self.span_right ||
 120             self.computed_right == self.label_right
 121         {
 122             // Account for the "..." padding given above. Otherwise we end up with code lines that
 123             // do fit but end in "..." as if they were trimmed.
 124             self.computed_right - 6
 125         } else {
 126             self.computed_right
 127         };
 128         right < line_len && self.computed_left + self.column_width < line_len
 129     }
 130
 131     fn compute(&mut self, max_line_len: usize) {
 132         // When there's a lot of whitespace (>20), we want to trim it as it is useless.
 133         self.computed_left = if self.whitespace_left > 20 {
 134             self.whitespace_left - 16 // We want some padding.
 135         } else {
 136             0
 137         };
 138         // We want to show as much as possible, max_line_len is the right-most boundary for the
 139         // relevant code.
 140         self.computed_right = max(max_line_len, self.computed_left);
 141
 142         if self.computed_right - self.computed_left > self.column_width {
 143             // Trimming only whitespace isn't enough, let's get craftier.
 144             if self.label_right - self.whitespace_left <= self.column_width {
 145                 // Attempt to fit the code window only trimming whitespace.
 146                 self.computed_left = self.whitespace_left;
 147                 self.computed_right = self.computed_left + self.column_width;
 148             } else if self.label_right - self.span_left <= self.column_width {
 149                 // Attempt to fit the code window considering only the spans and labels.
 150                 let padding_left = (self.column_width - (self.label_right - self.span_left)) / 2;
 151                 self.computed_left = self.span_left.saturating_sub(padding_left);
 152                 self.computed_right = self.computed_left + self.column_width;
 153             } else if self.span_right - self.span_left <= self.column_width {
 154                 // Attempt to fit the code window considering the spans and labels plus padding.
 155                 let padding_left = (self.column_width - (self.span_right - self.span_left)) / 5 * 2;
 156                 self.computed_left = self.span_left.saturating_sub(padding_left);
 157                 self.computed_right = self.computed_left + self.column_width;
 158             } else { // Mostly give up but still don't show the full line.
 159                 self.computed_left = self.span_left;
 160                 self.computed_right = self.span_right;
 161             }
 162         }
 163     }
 164
 165     fn left(&self, line_len: usize) -> usize {
 166         min(self.computed_left, line_len)
 167     }
 168
 169     fn right(&self, line_len: usize) -> usize {
 170         if line_len.saturating_sub(self.computed_left) <= self.column_width {
 171             line_len
 172         } else {
 173             min(line_len, self.computed_right)
 174         }
 175     }
 176 }
 177
 178 const ANONYMIZED_LINE_NUM: &str = "LL";
 179
 180 /// Emitter trait for emitting errors.
 181 pub trait Emitter {
 182     /// Emit a structured diagnostic.
 183     fn emit_diagnostic(&mut self, diag: &Diagnostic);
 184
 185     /// Emit a notification that an artifact has been output.
 186     /// This is currently only supported for the JSON format,
 187     /// other formats can, and will, simply ignore it.
 188     fn emit_artifact_notification(&mut self, _path: &Path, _artifact_type: &str) {}
 189
 190     /// Checks if should show explanations about "rustc --explain"
 191     fn should_show_explain(&self) -> bool {
 192         true
 193     }
 194
 195     fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>>;
 196
 197     /// Formats the substitutions of the primary_span
 198     ///
 199     /// The are a lot of conditions to this method, but in short:
 200     ///
 201     /// * If the current `Diagnostic` has only one visible `CodeSuggestion`,
 202     ///   we format the `help` suggestion depending on the content of the
 203     ///   substitutions. In that case, we return the modified span only.
 204     ///
 205     /// * If the current `Diagnostic` has multiple suggestions,
 206     ///   we return the original `primary_span` and the original suggestions.
 207     fn primary_span_formatted<'a>(
 208         &mut self,
 209         diag: &'a Diagnostic,
 210     ) -> (MultiSpan, &'a [CodeSuggestion]) {
 211         let mut primary_span = diag.span.clone();
 212         if let Some((sugg, rest)) = diag.suggestions.split_first() {
 213             if rest.is_empty() &&
 214                // ^ if there is only one suggestion
 215                // don't display multi-suggestions as labels
 216                sugg.substitutions.len() == 1 &&
 217                // don't display multipart suggestions as labels
 218                sugg.substitutions[0].parts.len() == 1 &&
 219                // don't display long messages as labels
 220                sugg.msg.split_whitespace().count() < 10 &&
 221                // don't display multiline suggestions as labels
 222                !sugg.substitutions[0].parts[0].snippet.contains('\n') &&
 223                ![
 224                     // when this style is set we want the suggestion to be a message, not inline
 225                     SuggestionStyle::HideCodeAlways,
 226                     // trivial suggestion for tooling's sake, never shown
 227                     SuggestionStyle::CompletelyHidden,
 228                     // subtle suggestion, never shown inline
 229                     SuggestionStyle::ShowAlways,
 230                ].contains(&sugg.style)
 231             {
 232                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
 233                 let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
 234                     // This substitution is only removal OR we explicitly don't want to show the
 235                     // code inline (`hide_inline`). Therefore, we don't show the substitution.
 236                     format!("help: {}", sugg.msg)
 237                 } else {
 238                     // Show the default suggestion text with the substitution
 239                     format!(
 240                         "help: {}{}: `{}`",
 241                         sugg.msg,
 242                         if self.source_map().map(|sm| is_case_difference(
 243                             &**sm,
 244                             substitution,
 245                             sugg.substitutions[0].parts[0].span,
 246                         )).unwrap_or(false) {
 247                             " (notice the capitalization)"
 248                         } else {
 249                             ""
 250                         },
 251                         substitution,
 252                     )
 253                 };
 254                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
 255
 256                 // We return only the modified primary_span
 257                 (primary_span, &[])
 258             } else {
 259                 // if there are multiple suggestions, print them all in full
 260                 // to be consistent. We could try to figure out if we can
 261                 // make one (or the first one) inline, but that would give
 262                 // undue importance to a semi-random suggestion
 263                 (primary_span, &diag.suggestions)
 264             }
 265         } else {
 266             (primary_span, &diag.suggestions)
 267         }
 268     }
 269
 270     // This does a small "fix" for multispans by looking to see if it can find any that
 271     // point directly at <*macros>. Since these are often difficult to read, this
 272     // will change the span to point at the use site.
 273     fn fix_multispans_in_std_macros(&self,
 274                                     source_map: &Option<Lrc<SourceMapperDyn>>,
 275                                     span: &mut MultiSpan,
 276                                     children: &mut Vec<SubDiagnostic>,
 277                                     level: &Level,
 278                                     backtrace: bool) {
 279         let mut spans_updated = self.fix_multispan_in_std_macros(source_map, span, backtrace);
 280         for child in children.iter_mut() {
 281             spans_updated |= self.fix_multispan_in_std_macros(
 282                                  source_map,
 283                                  &mut child.span,
 284                                  backtrace
 285                              );
 286         }
 287         let msg = if level == &Error {
 288             "this error originates in a macro outside of the current crate \
 289              (in Nightly builds, run with -Z external-macro-backtrace \
 290               for more info)".to_string()
 291         } else {
 292             "this warning originates in a macro outside of the current crate \
 293              (in Nightly builds, run with -Z external-macro-backtrace \
 294               for more info)".to_string()
 295         };
 296
 297         if spans_updated {
 298             children.push(SubDiagnostic {
 299                 level: Level::Note,
 300                 message: vec![
 301                     (msg,
 302                      Style::NoStyle),
 303                 ],
 304                 span: MultiSpan::new(),
 305                 render_span: None,
 306             });
 307         }
 308     }
 309
 310     // This "fixes" MultiSpans that contain Spans that are pointing to locations inside of
 311     // <*macros>. Since these locations are often difficult to read, we move these Spans from
 312     // <*macros> to their corresponding use site.
 313     fn fix_multispan_in_std_macros(&self,
 314                                    source_map: &Option<Lrc<SourceMapperDyn>>,
 315                                    span: &mut MultiSpan,
 316                                    always_backtrace: bool) -> bool {
 317         let sm = match source_map {
 318             Some(ref sm) => sm,
 319             None => return false,
 320         };
 321
 322         let mut before_after: Vec<(Span, Span)> = vec![];
 323         let mut new_labels: Vec<(Span, String)> = vec![];
 324
 325         // First, find all the spans in <*macros> and point instead at their use site
 326         for sp in span.primary_spans() {
 327             if sp.is_dummy() {
 328                 continue;
 329             }
 330             let call_sp = sm.call_span_if_macro(*sp);
 331             if call_sp != *sp && !always_backtrace {
 332                 before_after.push((*sp, call_sp));
 333             }
 334             let backtrace_len = sp.macro_backtrace().len();
 335             for (i, trace) in sp.macro_backtrace().iter().rev().enumerate() {
 336                 // Only show macro locations that are local
 337                 // and display them like a span_note
 338                 if trace.def_site_span.is_dummy() {
 339                     continue;
 340                 }
 341                 if always_backtrace {
 342                     new_labels.push((trace.def_site_span,
 343                                         format!("in this expansion of `{}`{}",
 344                                                 trace.macro_decl_name,
 345                                                 if backtrace_len > 2 {
 346                                                     // if backtrace_len == 1 it'll be pointed
 347                                                     // at by "in this macro invocation"
 348                                                     format!(" (#{})", i + 1)
 349                                                 } else {
 350                                                     String::new()
 351                                                 })));
 352                 }
 353                 // Check to make sure we're not in any <*macros>
 354                 if !sm.span_to_filename(trace.def_site_span).is_macros() &&
 355                     !trace.macro_decl_name.starts_with("desugaring of ") &&
 356                     !trace.macro_decl_name.starts_with("#[") ||
 357                     always_backtrace {
 358                     new_labels.push((trace.call_site,
 359                                         format!("in this macro invocation{}",
 360                                                 if backtrace_len > 2 && always_backtrace {
 361                                                     // only specify order when the macro
 362                                                     // backtrace is multiple levels deep
 363                                                     format!(" (#{})", i + 1)
 364                                                 } else {
 365                                                     String::new()
 366                                                 })));
 367                     if !always_backtrace {
 368                         break;
 369                     }
 370                 }
 371             }
 372         }
 373         for (label_span, label_text) in new_labels {
 374             span.push_span_label(label_span, label_text);
 375         }
 376         for sp_label in span.span_labels() {
 377             if sp_label.span.is_dummy() {
 378                 continue;
 379             }
 380             if sm.span_to_filename(sp_label.span.clone()).is_macros() &&
 381                 !always_backtrace
 382             {
 383                 let v = sp_label.span.macro_backtrace();
 384                 if let Some(use_site) = v.last() {
 385                     before_after.push((sp_label.span.clone(), use_site.call_site.clone()));
 386                 }
 387             }
 388         }
 389         // After we have them, make sure we replace these 'bad' def sites with their use sites
 390         let spans_updated = !before_after.is_empty();
 391         for (before, after) in before_after {
 392             span.replace(before, after);
 393         }
 394
 395         spans_updated
 396     }
 397 }
 398
 399 impl Emitter for EmitterWriter {
 400     fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>> {
 401         self.sm.as_ref()
 402     }
 403
 404     fn emit_diagnostic(&mut self, diag: &Diagnostic) {
 405         let mut children = diag.children.clone();
 406         let (mut primary_span, suggestions) = self.primary_span_formatted(&diag);
 407
 408         self.fix_multispans_in_std_macros(&self.sm,
 409                                           &mut primary_span,
 410                                           &mut children,
 411                                           &diag.level,
 412                                           self.external_macro_backtrace);
 413
 414         self.emit_messages_default(&diag.level,
 415                                    &diag.styled_message(),
 416                                    &diag.code,
 417                                    &primary_span,
 418                                    &children,
 419                                    &suggestions);
 420     }
 421
 422     fn should_show_explain(&self) -> bool {
 423         !self.short_message
 424     }
 425 }
 426
 427 /// maximum number of lines we will print for each error; arbitrary.
 428 pub const MAX_HIGHLIGHT_LINES: usize = 6;
 429 /// maximum number of suggestions to be shown
 430 ///
 431 /// Arbitrary, but taken from trait import suggestion limit
 432 pub const MAX_SUGGESTIONS: usize = 4;
 433
 434 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 435 pub enum ColorConfig {
 436     Auto,
 437     Always,
 438     Never,
 439 }
 440
 441 impl ColorConfig {
 442     fn to_color_choice(self) -> ColorChoice {
 443         match self {
 444             ColorConfig::Always => {
 445                 if atty::is(atty::Stream::Stderr) {
 446                     ColorChoice::Always
 447                 } else {
 448                     ColorChoice::AlwaysAnsi
 449                 }
 450             }
 451             ColorConfig::Never => ColorChoice::Never,
 452             ColorConfig::Auto if atty::is(atty::Stream::Stderr) => {
 453                 ColorChoice::Auto
 454             }
 455             ColorConfig::Auto => ColorChoice::Never,
 456         }
 457     }
 458     fn suggests_using_colors(self) -> bool {
 459         match self {
 460             | ColorConfig::Always
 461             | ColorConfig::Auto
 462             => true,
 463             ColorConfig::Never => false,
 464         }
 465     }
 466 }
 467
 468 /// Handles the writing of `HumanReadableErrorType::Default` and `HumanReadableErrorType::Short`
 469 pub struct EmitterWriter {
 470     dst: Destination,
 471     sm: Option<Lrc<SourceMapperDyn>>,
 472     short_message: bool,
 473     teach: bool,
 474     ui_testing: bool,
 475     terminal_width: Option<usize>,
 476
 477     external_macro_backtrace: bool,
 478 }
 479
 480 #[derive(Debug)]
 481 pub struct FileWithAnnotatedLines {
 482     pub file: Lrc<SourceFile>,
 483     pub lines: Vec<Line>,
 484     multiline_depth: usize,
 485 }
 486
 487 impl EmitterWriter {
 488     pub fn stderr(
 489         color_config: ColorConfig,
 490         source_map: Option<Lrc<SourceMapperDyn>>,
 491         short_message: bool,
 492         teach: bool,
 493         terminal_width: Option<usize>,
 494         external_macro_backtrace: bool,
 495     ) -> EmitterWriter {
 496         let dst = Destination::from_stderr(color_config);
 497         EmitterWriter {
 498             dst,
 499             sm: source_map,
 500             short_message,
 501             teach,
 502             ui_testing: false,
 503             terminal_width,
 504             external_macro_backtrace,
 505         }
 506     }
 507
 508     pub fn new(
 509         dst: Box<dyn Write + Send>,
 510         source_map: Option<Lrc<SourceMapperDyn>>,
 511         short_message: bool,
 512         teach: bool,
 513         colored: bool,
 514         terminal_width: Option<usize>,
 515         external_macro_backtrace: bool,
 516     ) -> EmitterWriter {
 517         EmitterWriter {
 518             dst: Raw(dst, colored),
 519             sm: source_map,
 520             short_message,
 521             teach,
 522             ui_testing: false,
 523             terminal_width,
 524             external_macro_backtrace,
 525         }
 526     }
 527
 528     pub fn ui_testing(mut self, ui_testing: bool) -> Self {
 529         self.ui_testing = ui_testing;
 530         self
 531     }
 532
 533     fn maybe_anonymized(&self, line_num: usize) -> String {
 534         if self.ui_testing {
 535             ANONYMIZED_LINE_NUM.to_string()
 536         } else {
 537             line_num.to_string()
 538         }
 539     }
 540
 541     fn draw_line(
 542         &self,
 543         buffer: &mut StyledBuffer,
 544         source_string: &str,
 545         line_index: usize,
 546         line_offset: usize,
 547         width_offset: usize,
 548         code_offset: usize,
 549         margin: Margin,
 550     ) {
 551         let line_len = source_string.len();
 552         // Create the source line we will highlight.
 553         let left = margin.left(line_len);
 554         let right = margin.right(line_len);
 555         // On long lines, we strip the source line, accounting for unicode.
 556         let mut taken = 0;
 557         let code: String = source_string.chars().skip(left).take_while(|ch| {
 558             // Make sure that the trimming on the right will fall within the terminal width.
 559             // FIXME: `unicode_width` sometimes disagrees with terminals on how wide a `char` is.
 560             // For now, just accept that sometimes the code line will be longer than desired.
 561             let next = unicode_width::UnicodeWidthChar::width(*ch).unwrap_or(1);
 562             if taken + next > right - left {
 563                 return false;
 564             }
 565             taken += next;
 566             true
 567         }).collect();
 568         buffer.puts(line_offset, code_offset, &code, Style::Quotation);
 569         if margin.was_cut_left() {
 570             // We have stripped some code/whitespace from the beginning, make it clear.
 571             buffer.puts(line_offset, code_offset, "...", Style::LineNumber);
 572         }
 573         if margin.was_cut_right(line_len) {
 574             // We have stripped some code after the right-most span end, make it clear we did so.
 575             buffer.puts(line_offset, code_offset + taken - 3, "...", Style::LineNumber);
 576         }
 577         buffer.puts(line_offset, 0, &self.maybe_anonymized(line_index), Style::LineNumber);
 578
 579         draw_col_separator(buffer, line_offset, width_offset - 2);
 580     }
 581
 582     fn render_source_line(
 583         &self,
 584         buffer: &mut StyledBuffer,
 585         file: Lrc<SourceFile>,
 586         line: &Line,
 587         width_offset: usize,
 588         code_offset: usize,
 589         margin: Margin,
 590     ) -> Vec<(usize, Style)> {
 591         // Draw:
 592         //
 593         //   LL | ... code ...
 594         //      |     ^^-^ span label
 595         //      |       |
 596         //      |       secondary span label
 597         //
 598         //   ^^ ^ ^^^ ^^^^ ^^^ we don't care about code too far to the right of a span, we trim it
 599         //   |  | |   |
 600         //   |  | |   actual code found in your source code and the spans we use to mark it
 601         //   |  | when there's too much wasted space to the left, trim it
 602         //   |  vertical divider between the column number and the code
 603         //   column number
 604
 605         if line.line_index == 0 {
 606             return Vec::new();
 607         }
 608
 609         let source_string = match file.get_line(line.line_index - 1) {
 610             Some(s) => s,
 611             None => return Vec::new(),
 612         };
 613
 614         let line_offset = buffer.num_lines();
 615
 616         let left = margin.left(source_string.len()); // Left trim
 617         // Account for unicode characters of width !=0 that were removed.
 618         let left = source_string.chars().take(left)
 619             .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
 620             .sum();
 621
 622         self.draw_line(
 623             buffer,
 624             &source_string,
 625             line.line_index,
 626             line_offset,
 627             width_offset,
 628             code_offset,
 629             margin,
 630         );
 631
 632         // Special case when there's only one annotation involved, it is the start of a multiline
 633         // span and there's no text at the beginning of the code line. Instead of doing the whole
 634         // graph:
 635         //
 636         // 2 |   fn foo() {
 637         //   |  _^
 638         // 3 | |
 639         // 4 | | }
 640         //   | |_^ test
 641         //
 642         // we simplify the output to:
 643         //
 644         // 2 | / fn foo() {
 645         // 3 | |
 646         // 4 | | }
 647         //   | |_^ test
 648         if let [ann] = &line.annotations[..] {
 649             if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
 650                 if source_string.chars().take(ann.start_col).all(|c| c.is_whitespace()) {
 651                     let style = if ann.is_primary {
 652                         Style::UnderlinePrimary
 653                     } else {
 654                         Style::UnderlineSecondary
 655                     };
 656                     buffer.putc(line_offset, width_offset + depth - 1, '/', style);
 657                     return vec![(depth, style)];
 658                 }
 659             }
 660         }
 661
 662         // We want to display like this:
 663         //
 664         //      vec.push(vec.pop().unwrap());
 665         //      ---      ^^^               - previous borrow ends here
 666         //      |        |
 667         //      |        error occurs here
 668         //      previous borrow of `vec` occurs here
 669         //
 670         // But there are some weird edge cases to be aware of:
 671         //
 672         //      vec.push(vec.pop().unwrap());
 673         //      --------                    - previous borrow ends here
 674         //      ||
 675         //      |this makes no sense
 676         //      previous borrow of `vec` occurs here
 677         //
 678         // For this reason, we group the lines into "highlight lines"
 679         // and "annotations lines", where the highlight lines have the `^`.
 680
 681         // Sort the annotations by (start, end col)
 682         // The labels are reversed, sort and then reversed again.
 683         // Consider a list of annotations (A1, A2, C1, C2, B1, B2) where
 684         // the letter signifies the span. Here we are only sorting by the
 685         // span and hence, the order of the elements with the same span will
 686         // not change. On reversing the ordering (|a, b| but b.cmp(a)), you get
 687         // (C1, C2, B1, B2, A1, A2). All the elements with the same span are
 688         // still ordered first to last, but all the elements with different
 689         // spans are ordered by their spans in last to first order. Last to
 690         // first order is important, because the jiggly lines and | are on
 691         // the left, so the rightmost span needs to be rendered first,
 692         // otherwise the lines would end up needing to go over a message.
 693
 694         let mut annotations = line.annotations.clone();
 695         annotations.sort_by_key(|a| Reverse(a.start_col));
 696
 697         // First, figure out where each label will be positioned.
 698         //
 699         // In the case where you have the following annotations:
 700         //
 701         //      vec.push(vec.pop().unwrap());
 702         //      --------                    - previous borrow ends here [C]
 703         //      ||
 704         //      |this makes no sense [B]
 705         //      previous borrow of `vec` occurs here [A]
 706         //
 707         // `annotations_position` will hold [(2, A), (1, B), (0, C)].
 708         //
 709         // We try, when possible, to stick the rightmost annotation at the end
 710         // of the highlight line:
 711         //
 712         //      vec.push(vec.pop().unwrap());
 713         //      ---      ---               - previous borrow ends here
 714         //
 715         // But sometimes that's not possible because one of the other
 716         // annotations overlaps it. For example, from the test
 717         // `span_overlap_label`, we have the following annotations
 718         // (written on distinct lines for clarity):
 719         //
 720         //      fn foo(x: u32) {
 721         //      --------------
 722         //             -
 723         //
 724         // In this case, we can't stick the rightmost-most label on
 725         // the highlight line, or we would get:
 726         //
 727         //      fn foo(x: u32) {
 728         //      -------- x_span
 729         //      |
 730         //      fn_span
 731         //
 732         // which is totally weird. Instead we want:
 733         //
 734         //      fn foo(x: u32) {
 735         //      --------------
 736         //      |      |
 737         //      |      x_span
 738         //      fn_span
 739         //
 740         // which is...less weird, at least. In fact, in general, if
 741         // the rightmost span overlaps with any other span, we should
 742         // use the "hang below" version, so we can at least make it
 743         // clear where the span *starts*. There's an exception for this
 744         // logic, when the labels do not have a message:
 745         //
 746         //      fn foo(x: u32) {
 747         //      --------------
 748         //             |
 749         //             x_span
 750         //
 751         // instead of:
 752         //
 753         //      fn foo(x: u32) {
 754         //      --------------
 755         //      |      |
 756         //      |      x_span
 757         //      <EMPTY LINE>
 758         //
 759         let mut annotations_position = vec![];
 760         let mut line_len = 0;
 761         let mut p = 0;
 762         for (i, annotation) in annotations.iter().enumerate() {
 763             for (j, next) in annotations.iter().enumerate() {
 764                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
 765                     && annotation.has_label()     // take space (they have text and are not
 766                     && j > i                      // multiline lines).
 767                     && p == 0  // We're currently on the first line, move the label one line down
 768                 {
 769                     // If we're overlapping with an un-labelled annotation with the same span
 770                     // we can just merge them in the output
 771                     if next.start_col == annotation.start_col
 772                     && next.end_col == annotation.end_col
 773                     && !next.has_label()
 774                     {
 775                         continue;
 776                     }
 777
 778                     // This annotation needs a new line in the output.
 779                     p += 1;
 780                     break;
 781                 }
 782             }
 783             annotations_position.push((p, annotation));
 784             for (j, next) in annotations.iter().enumerate() {
 785                 if j > i  {
 786                     let l = next.label.as_ref().map_or(0, |label| label.len() + 2);
 787                     if (overlaps(next, annotation, l) // Do not allow two labels to be in the same
 788                                                      // line if they overlap including padding, to
 789                                                      // avoid situations like:
 790                                                      //
 791                                                      //      fn foo(x: u32) {
 792                                                      //      -------^------
 793                                                      //      |      |
 794                                                      //      fn_spanx_span
 795                                                      //
 796                         && annotation.has_label()    // Both labels must have some text, otherwise
 797                         && next.has_label())         // they are not overlapping.
 798                                                      // Do not add a new line if this annotation
 799                                                      // or the next are vertical line placeholders.
 800                         || (annotation.takes_space() // If either this or the next annotation is
 801                             && next.has_label())     // multiline start/end, move it to a new line
 802                         || (annotation.has_label()   // so as not to overlap the orizontal lines.
 803                             && next.takes_space())
 804                         || (annotation.takes_space() && next.takes_space())
 805                         || (overlaps(next, annotation, l)
 806                             && next.end_col <= annotation.end_col
 807                             && next.has_label()
 808                             && p == 0)  // Avoid #42595.
 809                     {
 810                         // This annotation needs a new line in the output.
 811                         p += 1;
 812                         break;
 813                     }
 814                 }
 815             }
 816             line_len = max(line_len, p);
 817         }
 818
 819         if line_len != 0 {
 820             line_len += 1;
 821         }
 822
 823         // If there are no annotations or the only annotations on this line are
 824         // MultilineLine, then there's only code being shown, stop processing.
 825         if line.annotations.iter().all(|a| a.is_line()) {
 826             return vec![];
 827         }
 828
 829         // Write the colunmn separator.
 830         //
 831         // After this we will have:
 832         //
 833         // 2 |   fn foo() {
 834         //   |
 835         //   |
 836         //   |
 837         // 3 |
 838         // 4 |   }
 839         //   |
 840         for pos in 0..=line_len {
 841             draw_col_separator(buffer, line_offset + pos + 1, width_offset - 2);
 842             buffer.putc(line_offset + pos + 1,
 843                         width_offset - 2,
 844                         '|',
 845                         Style::LineNumber);
 846         }
 847
 848         // Write the horizontal lines for multiline annotations
 849         // (only the first and last lines need this).
 850         //
 851         // After this we will have:
 852         //
 853         // 2 |   fn foo() {
 854         //   |  __________
 855         //   |
 856         //   |
 857         // 3 |
 858         // 4 |   }
 859         //   |  _
 860         for &(pos, annotation) in &annotations_position {
 861             let style = if annotation.is_primary {
 862                 Style::UnderlinePrimary
 863             } else {
 864                 Style::UnderlineSecondary
 865             };
 866             let pos = pos + 1;
 867             match annotation.annotation_type {
 868                 AnnotationType::MultilineStart(depth) |
 869                 AnnotationType::MultilineEnd(depth) => {
 870                     draw_range(
 871                         buffer,
 872                         '_',
 873                         line_offset + pos,
 874                         width_offset + depth,
 875                         code_offset + annotation.start_col - left,
 876                         style,
 877                     );
 878                 }
 879                 _ if self.teach => {
 880                     buffer.set_style_range(
 881                         line_offset,
 882                         code_offset + annotation.start_col - left,
 883                         code_offset + annotation.end_col - left,
 884                         style,
 885                         annotation.is_primary,
 886                     );
 887                 }
 888                 _ => {}
 889             }
 890         }
 891
 892         // Write the vertical lines for labels that are on a different line as the underline.
 893         //
 894         // After this we will have:
 895         //
 896         // 2 |   fn foo() {
 897         //   |  __________
 898         //   | |    |
 899         //   | |
 900         // 3 |
 901         // 4 | | }
 902         //   | |_
 903         for &(pos, annotation) in &annotations_position {
 904             let style = if annotation.is_primary {
 905                 Style::UnderlinePrimary
 906             } else {
 907                 Style::UnderlineSecondary
 908             };
 909             let pos = pos + 1;
 910
 911             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
 912                 for p in line_offset + 1..=line_offset + pos {
 913                     buffer.putc(p,
 914                                 code_offset + annotation.start_col - margin.computed_left,
 915                                 '|',
 916                                 style);
 917                 }
 918             }
 919             match annotation.annotation_type {
 920                 AnnotationType::MultilineStart(depth) => {
 921                     for p in line_offset + pos + 1..line_offset + line_len + 2 {
 922                         buffer.putc(p,
 923                                     width_offset + depth - 1,
 924                                     '|',
 925                                     style);
 926                     }
 927                 }
 928                 AnnotationType::MultilineEnd(depth) => {
 929                     for p in line_offset..=line_offset + pos {
 930                         buffer.putc(p,
 931                                     width_offset + depth - 1,
 932                                     '|',
 933                                     style);
 934                     }
 935                 }
 936                 _ => (),
 937             }
 938         }
 939
 940         // Write the labels on the annotations that actually have a label.
 941         //
 942         // After this we will have:
 943         //
 944         // 2 |   fn foo() {
 945         //   |  __________
 946         //   |      |
 947         //   |      something about `foo`
 948         // 3 |
 949         // 4 |   }
 950         //   |  _  test
 951         for &(pos, annotation) in &annotations_position {
 952             let style = if annotation.is_primary {
 953                 Style::LabelPrimary
 954             } else {
 955                 Style::LabelSecondary
 956             };
 957             let (pos, col) = if pos == 0 {
 958                 (pos + 1, (annotation.end_col + 1).saturating_sub(left))
 959             } else {
 960                 (pos + 2, annotation.start_col.saturating_sub(left))
 961             };
 962             if let Some(ref label) = annotation.label {
 963                 buffer.puts(line_offset + pos, code_offset + col, &label, style);
 964             }
 965         }
 966
 967         // Sort from biggest span to smallest span so that smaller spans are
 968         // represented in the output:
 969         //
 970         // x | fn foo()
 971         //   | ^^^---^^
 972         //   | |  |
 973         //   | |  something about `foo`
 974         //   | something about `fn foo()`
 975         annotations_position.sort_by_key(|(_, ann)| {
 976             // Decreasing order. When annotations share the same length, prefer `Primary`.
 977             (Reverse(ann.len()), ann.is_primary)
 978         });
 979
 980         // Write the underlines.
 981         //
 982         // After this we will have:
 983         //
 984         // 2 |   fn foo() {
 985         //   |  ____-_____^
 986         //   |      |
 987         //   |      something about `foo`
 988         // 3 |
 989         // 4 |   }
 990         //   |  _^  test
 991         for &(_, annotation) in &annotations_position {
 992             let (underline, style) = if annotation.is_primary {
 993                 ('^', Style::UnderlinePrimary)
 994             } else {
 995                 ('-', Style::UnderlineSecondary)
 996             };
 997             for p in annotation.start_col..annotation.end_col {
 998                 buffer.putc(
 999                     line_offset + 1,
1000                     (code_offset + p).saturating_sub(left),
1001                     underline,
1002                     style,
1003                 );
1004             }
1005         }
1006         annotations_position.iter().filter_map(|&(_, annotation)| {
1007             match annotation.annotation_type {
1008                 AnnotationType::MultilineStart(p) | AnnotationType::MultilineEnd(p) => {
1009                     let style = if annotation.is_primary {
1010                         Style::LabelPrimary
1011                     } else {
1012                         Style::LabelSecondary
1013                     };
1014                     Some((p, style))
1015                 }
1016                 _ => None
1017             }
1018
1019         }).collect::<Vec<_>>()
1020     }
1021
1022     fn get_multispan_max_line_num(&mut self, msp: &MultiSpan) -> usize {
1023         let sm = match self.sm {
1024             Some(ref sm) => sm,
1025             None => return 0,
1026         };
1027
1028         let mut max = 0;
1029         for primary_span in msp.primary_spans() {
1030             if !primary_span.is_dummy() {
1031                 let hi = sm.lookup_char_pos(primary_span.hi());
1032                 max = (hi.line).max(max);
1033             }
1034         }
1035         if !self.short_message {
1036             for span_label in msp.span_labels() {
1037                 if !span_label.span.is_dummy() {
1038                     let hi = sm.lookup_char_pos(span_label.span.hi());
1039                     max = (hi.line).max(max);
1040                 }
1041             }
1042         }
1043
1044         max
1045     }
1046
1047     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
1048         let primary = self.get_multispan_max_line_num(span);
1049         children.iter()
1050             .map(|sub| self.get_multispan_max_line_num(&sub.span))
1051             .max()
1052             .unwrap_or(0)
1053             .max(primary)
1054     }
1055
1056     /// Adds a left margin to every line but the first, given a padding length and the label being
1057     /// displayed, keeping the provided highlighting.
1058     fn msg_to_buffer(&self,
1059                      buffer: &mut StyledBuffer,
1060                      msg: &[(String, Style)],
1061                      padding: usize,
1062                      label: &str,
1063                      override_style: Option<Style>) {
1064
1065         // The extra 5 ` ` is padding that's always needed to align to the `note: `:
1066         //
1067         //   error: message
1068         //     --> file.rs:13:20
1069         //      |
1070         //   13 |     <CODE>
1071         //      |      ^^^^
1072         //      |
1073         //      = note: multiline
1074         //              message
1075         //   ++^^^----xx
1076         //    |  |   | |
1077         //    |  |   | magic `2`
1078         //    |  |   length of label
1079         //    |  magic `3`
1080         //    `max_line_num_len`
1081         let padding = " ".repeat(padding + label.len() + 5);
1082
1083         /// Returns `override` if it is present and `style` is `NoStyle` or `style` otherwise
1084         fn style_or_override(style: Style, override_: Option<Style>) -> Style {
1085             match (style, override_) {
1086                 (Style::NoStyle, Some(override_)) => override_,
1087                 _ => style,
1088             }
1089         }
1090
1091         let mut line_number = 0;
1092
1093         // Provided the following diagnostic message:
1094         //
1095         //     let msg = vec![
1096         //       ("
1097         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
1098         //       ("looks", Style::Highlight),
1099         //       ("with\nvery ", Style::NoStyle),
1100         //       ("weird", Style::Highlight),
1101         //       (" formats\n", Style::NoStyle),
1102         //       ("see?", Style::Highlight),
1103         //     ];
1104         //
1105         // the expected output on a note is (* surround the highlighted text)
1106         //
1107         //        = note: highlighted multiline
1108         //                string to
1109         //                see how it *looks* with
1110         //                very *weird* formats
1111         //                see?
1112         for &(ref text, ref style) in msg.iter() {
1113             let lines = text.split('\n').collect::<Vec<_>>();
1114             if lines.len() > 1 {
1115                 for (i, line) in lines.iter().enumerate() {
1116                     if i != 0 {
1117                         line_number += 1;
1118                         buffer.append(line_number, &padding, Style::NoStyle);
1119                     }
1120                     buffer.append(line_number, line, style_or_override(*style, override_style));
1121                 }
1122             } else {
1123                 buffer.append(line_number, text, style_or_override(*style, override_style));
1124             }
1125         }
1126     }
1127
1128     fn emit_message_default(
1129         &mut self,
1130         msp: &MultiSpan,
1131         msg: &[(String, Style)],
1132         code: &Option<DiagnosticId>,
1133         level: &Level,
1134         max_line_num_len: usize,
1135         is_secondary: bool,
1136     ) -> io::Result<()> {
1137         let mut buffer = StyledBuffer::new();
1138         let header_style = if is_secondary {
1139             Style::HeaderMsg
1140         } else {
1141             Style::MainHeaderMsg
1142         };
1143
1144         if !msp.has_primary_spans() && !msp.has_span_labels() && is_secondary
1145            && !self.short_message {
1146             // This is a secondary message with no span info
1147             for _ in 0..max_line_num_len {
1148                 buffer.prepend(0, " ", Style::NoStyle);
1149             }
1150             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
1151             if *level != Level::FailureNote {
1152                 let level_str = level.to_string();
1153                 if !level_str.is_empty() {
1154                     buffer.append(0, &level_str, Style::MainHeaderMsg);
1155                     buffer.append(0, ": ", Style::NoStyle);
1156                 }
1157             }
1158             self.msg_to_buffer(&mut buffer, msg, max_line_num_len, "note", None);
1159         } else {
1160             let level_str = level.to_string();
1161             // The failure note level itself does not provide any useful diagnostic information
1162             if *level != Level::FailureNote && !level_str.is_empty() {
1163                 buffer.append(0, &level_str, Style::Level(level.clone()));
1164             }
1165             // only render error codes, not lint codes
1166             if let Some(DiagnosticId::Error(ref code)) = *code {
1167                 buffer.append(0, "[", Style::Level(level.clone()));
1168                 buffer.append(0, &code, Style::Level(level.clone()));
1169                 buffer.append(0, "]", Style::Level(level.clone()));
1170             }
1171             if *level != Level::FailureNote && !level_str.is_empty() {
1172                 buffer.append(0, ": ", header_style);
1173             }
1174             for &(ref text, _) in msg.iter() {
1175                 buffer.append(0, text, header_style);
1176             }
1177         }
1178
1179         let mut annotated_files = FileWithAnnotatedLines::collect_annotations(msp, &self.sm);
1180
1181         // Make sure our primary file comes first
1182         let (primary_lo, sm) = if let (Some(sm), Some(ref primary_span)) =
1183             (self.sm.as_ref(), msp.primary_span().as_ref()) {
1184             if !primary_span.is_dummy() {
1185                 (sm.lookup_char_pos(primary_span.lo()), sm)
1186             } else {
1187                 emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1188                 return Ok(());
1189             }
1190         } else {
1191             // If we don't have span information, emit and exit
1192             emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1193             return Ok(());
1194         };
1195         if let Ok(pos) =
1196             annotated_files.binary_search_by(|x| x.file.name.cmp(&primary_lo.file.name)) {
1197             annotated_files.swap(0, pos);
1198         }
1199
1200         // Print out the annotate source lines that correspond with the error
1201         for annotated_file in annotated_files {
1202             // we can't annotate anything if the source is unavailable.
1203             if !sm.ensure_source_file_source_present(annotated_file.file.clone()) {
1204                 continue;
1205             }
1206
1207             // print out the span location and spacer before we print the annotated source
1208             // to do this, we need to know if this span will be primary
1209             let is_primary = primary_lo.file.name == annotated_file.file.name;
1210             if is_primary {
1211                 let loc = primary_lo.clone();
1212                 if !self.short_message {
1213                     // remember where we are in the output buffer for easy reference
1214                     let buffer_msg_line_offset = buffer.num_lines();
1215
1216                     buffer.prepend(buffer_msg_line_offset, "--> ", Style::LineNumber);
1217                     buffer.append(
1218                         buffer_msg_line_offset,
1219                         &format!(
1220                             "{}:{}:{}",
1221                             loc.file.name,
1222                             sm.doctest_offset_line(&loc.file.name, loc.line),
1223                             loc.col.0 + 1,
1224                         ),
1225                         Style::LineAndColumn,
1226                     );
1227                     for _ in 0..max_line_num_len {
1228                         buffer.prepend(buffer_msg_line_offset, " ", Style::NoStyle);
1229                     }
1230                 } else {
1231                     buffer.prepend(
1232                         0,
1233                         &format!(
1234                             "{}:{}:{}: ",
1235                             loc.file.name,
1236                             sm.doctest_offset_line(&loc.file.name, loc.line),
1237                             loc.col.0 + 1,
1238                         ),
1239                         Style::LineAndColumn,
1240                     );
1241                 }
1242             } else if !self.short_message {
1243                 // remember where we are in the output buffer for easy reference
1244                 let buffer_msg_line_offset = buffer.num_lines();
1245
1246                 // Add spacing line
1247                 draw_col_separator(&mut buffer, buffer_msg_line_offset, max_line_num_len + 1);
1248
1249                 // Then, the secondary file indicator
1250                 buffer.prepend(buffer_msg_line_offset + 1, "::: ", Style::LineNumber);
1251                 let loc = if let Some(first_line) = annotated_file.lines.first() {
1252                     let col = if let Some(first_annotation) = first_line.annotations.first() {
1253                         format!(":{}", first_annotation.start_col + 1)
1254                     } else {
1255                         String::new()
1256                     };
1257                     format!("{}:{}{}",
1258                             annotated_file.file.name,
1259                             sm.doctest_offset_line(
1260                                 &annotated_file.file.name, first_line.line_index),
1261                             col)
1262                 } else {
1263                     annotated_file.file.name.to_string()
1264                 };
1265                 buffer.append(buffer_msg_line_offset + 1,
1266                               &loc,
1267                               Style::LineAndColumn);
1268                 for _ in 0..max_line_num_len {
1269                     buffer.prepend(buffer_msg_line_offset + 1, " ", Style::NoStyle);
1270                 }
1271             }
1272
1273             if !self.short_message {
1274                 // Put in the spacer between the location and annotated source
1275                 let buffer_msg_line_offset = buffer.num_lines();
1276                 draw_col_separator_no_space(&mut buffer,
1277                                             buffer_msg_line_offset,
1278                                             max_line_num_len + 1);
1279
1280                 // Contains the vertical lines' positions for active multiline annotations
1281                 let mut multilines = FxHashMap::default();
1282
1283                 // Get the left-side margin to remove it
1284                 let mut whitespace_margin = std::usize::MAX;
1285                 for line_idx in 0..annotated_file.lines.len() {
1286                     let file = annotated_file.file.clone();
1287                     let line = &annotated_file.lines[line_idx];
1288                     if let Some(source_string) = file.get_line(line.line_index - 1) {
1289                         let leading_whitespace = source_string
1290                             .chars()
1291                             .take_while(|c| c.is_whitespace())
1292                             .count();
1293                         if source_string.chars().any(|c| !c.is_whitespace()) {
1294                             whitespace_margin = min(
1295                                 whitespace_margin,
1296                                 leading_whitespace,
1297                             );
1298                         }
1299                     }
1300                 }
1301                 if whitespace_margin == std::usize::MAX {
1302                     whitespace_margin = 0;
1303                 }
1304
1305                 // Left-most column any visible span points at.
1306                 let mut span_left_margin = std::usize::MAX;
1307                 for line in &annotated_file.lines {
1308                     for ann in &line.annotations {
1309                         span_left_margin = min(span_left_margin, ann.start_col);
1310                         span_left_margin = min(span_left_margin, ann.end_col);
1311                     }
1312                 }
1313                 if span_left_margin == std::usize::MAX {
1314                     span_left_margin = 0;
1315                 }
1316
1317                 // Right-most column any visible span points at.
1318                 let mut span_right_margin = 0;
1319                 let mut label_right_margin = 0;
1320                 let mut max_line_len = 0;
1321                 for line in &annotated_file.lines {
1322                     max_line_len = max(max_line_len, annotated_file.file
1323                         .get_line(line.line_index - 1)
1324                         .map_or(0, |s| s.len()));
1325                     for ann in &line.annotations {
1326                         span_right_margin = max(span_right_margin, ann.start_col);
1327                         span_right_margin = max(span_right_margin, ann.end_col);
1328                         // FIXME: account for labels not in the same line
1329                         let label_right = ann.label.as_ref().map_or(0, |l| l.len() + 1);
1330                         label_right_margin = max(label_right_margin, ann.end_col + label_right);
1331                     }
1332                 }
1333
1334                 let width_offset = 3 + max_line_num_len;
1335                 let code_offset = if annotated_file.multiline_depth == 0 {
1336                     width_offset
1337                 } else {
1338                     width_offset + annotated_file.multiline_depth + 1
1339                 };
1340
1341                 let column_width = if let Some(width) = self.terminal_width {
1342                     width.saturating_sub(code_offset)
1343                 } else if self.ui_testing {
1344                     140
1345                 } else {
1346                     term_size::dimensions()
1347                         .map(|(w, _)| w.saturating_sub(code_offset))
1348                         .unwrap_or(std::usize::MAX)
1349                 };
1350
1351                 let margin = Margin::new(
1352                     whitespace_margin,
1353                     span_left_margin,
1354                     span_right_margin,
1355                     label_right_margin,
1356                     column_width,
1357                     max_line_len,
1358                 );
1359
1360                 // Next, output the annotate source for this file
1361                 for line_idx in 0..annotated_file.lines.len() {
1362                     let previous_buffer_line = buffer.num_lines();
1363
1364                     let depths = self.render_source_line(
1365                         &mut buffer,
1366                         annotated_file.file.clone(),
1367                         &annotated_file.lines[line_idx],
1368                         width_offset,
1369                         code_offset,
1370                         margin,
1371                     );
1372
1373                     let mut to_add = FxHashMap::default();
1374
1375                     for (depth, style) in depths {
1376                         if multilines.get(&depth).is_some() {
1377                             multilines.remove(&depth);
1378                         } else {
1379                             to_add.insert(depth, style);
1380                         }
1381                     }
1382
1383                     // Set the multiline annotation vertical lines to the left of
1384                     // the code in this line.
1385                     for (depth, style) in &multilines {
1386                         for line in previous_buffer_line..buffer.num_lines() {
1387                             draw_multiline_line(&mut buffer,
1388                                                 line,
1389                                                 width_offset,
1390                                                 *depth,
1391                                                 *style);
1392                         }
1393                     }
1394                     // check to see if we need to print out or elide lines that come between
1395                     // this annotated line and the next one.
1396                     if line_idx < (annotated_file.lines.len() - 1) {
1397                         let line_idx_delta = annotated_file.lines[line_idx + 1].line_index -
1398                                              annotated_file.lines[line_idx].line_index;
1399                         if line_idx_delta > 2 {
1400                             let last_buffer_line_num = buffer.num_lines();
1401                             buffer.puts(last_buffer_line_num, 0, "...", Style::LineNumber);
1402
1403                             // Set the multiline annotation vertical lines on `...` bridging line.
1404                             for (depth, style) in &multilines {
1405                                 draw_multiline_line(&mut buffer,
1406                                                     last_buffer_line_num,
1407                                                     width_offset,
1408                                                     *depth,
1409                                                     *style);
1410                             }
1411                         } else if line_idx_delta == 2 {
1412                             let unannotated_line = annotated_file.file
1413                                 .get_line(annotated_file.lines[line_idx].line_index)
1414                                 .unwrap_or_else(|| Cow::from(""));
1415
1416                             let last_buffer_line_num = buffer.num_lines();
1417
1418                             self.draw_line(
1419                                 &mut buffer,
1420                                 &unannotated_line,
1421                                 annotated_file.lines[line_idx + 1].line_index - 1,
1422                                 last_buffer_line_num,
1423                                 width_offset,
1424                                 code_offset,
1425                                 margin,
1426                             );
1427
1428                             for (depth, style) in &multilines {
1429                                 draw_multiline_line(
1430                                     &mut buffer,
1431                                     last_buffer_line_num,
1432                                     width_offset,
1433                                     *depth,
1434                                     *style,
1435                                 );
1436                             }
1437                         }
1438                     }
1439
1440                     multilines.extend(&to_add);
1441                 }
1442             }
1443         }
1444
1445         // final step: take our styled buffer, render it, then output it
1446         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1447
1448         Ok(())
1449
1450     }
1451
1452     fn emit_suggestion_default(
1453         &mut self,
1454         suggestion: &CodeSuggestion,
1455         level: &Level,
1456         max_line_num_len: usize,
1457     ) -> io::Result<()> {
1458         let sm = match self.sm {
1459             Some(ref sm) => sm,
1460             None => return Ok(())
1461         };
1462
1463         let mut buffer = StyledBuffer::new();
1464
1465         // Render the suggestion message
1466         let level_str = level.to_string();
1467         if !level_str.is_empty() {
1468             buffer.append(0, &level_str, Style::Level(level.clone()));
1469             buffer.append(0, ": ", Style::HeaderMsg);
1470         }
1471         self.msg_to_buffer(
1472             &mut buffer,
1473             &[(suggestion.msg.to_owned(), Style::NoStyle)],
1474             max_line_num_len,
1475             "suggestion",
1476             Some(Style::HeaderMsg),
1477         );
1478
1479         // Render the replacements for each suggestion
1480         let suggestions = suggestion.splice_lines(&**sm);
1481
1482         let mut row_num = 2;
1483         let mut notice_capitalization = false;
1484         for (complete, parts, only_capitalization) in suggestions.iter().take(MAX_SUGGESTIONS) {
1485             notice_capitalization |= only_capitalization;
1486             // Only show underline if the suggestion spans a single line and doesn't cover the
1487             // entirety of the code output. If you have multiple replacements in the same line
1488             // of code, show the underline.
1489             let show_underline = !(parts.len() == 1
1490                 && parts[0].snippet.trim() == complete.trim())
1491                 && complete.lines().count() == 1;
1492
1493             let lines = sm.span_to_lines(parts[0].span).unwrap();
1494
1495             assert!(!lines.lines.is_empty());
1496
1497             let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
1498             draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
1499             let mut line_pos = 0;
1500             let mut lines = complete.lines();
1501             for line in lines.by_ref().take(MAX_HIGHLIGHT_LINES) {
1502                 // Print the span column to avoid confusion
1503                 buffer.puts(row_num,
1504                             0,
1505                             &self.maybe_anonymized(line_start + line_pos),
1506                             Style::LineNumber);
1507                 // print the suggestion
1508                 draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1509                 buffer.append(row_num, line, Style::NoStyle);
1510                 line_pos += 1;
1511                 row_num += 1;
1512             }
1513
1514             // This offset and the ones below need to be signed to account for replacement code
1515             // that is shorter than the original code.
1516             let mut offset: isize = 0;
1517             // Only show an underline in the suggestions if the suggestion is not the
1518             // entirety of the code being shown and the displayed code is not multiline.
1519             if show_underline {
1520                 draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
1521                 for part in parts {
1522                     let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
1523                     let span_end_pos = sm.lookup_char_pos(part.span.hi()).col_display;
1524
1525                     // Do not underline the leading...
1526                     let start = part.snippet.len()
1527                         .saturating_sub(part.snippet.trim_start().len());
1528                     // ...or trailing spaces. Account for substitutions containing unicode
1529                     // characters.
1530                     let sub_len: usize = part.snippet.trim().chars()
1531                         .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1532                         .sum();
1533
1534                     let underline_start = (span_start_pos + start) as isize + offset;
1535                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
1536                     for p in underline_start..underline_end {
1537                         buffer.putc(row_num,
1538                                     max_line_num_len + 3 + p as usize,
1539                                     '^',
1540                                     Style::UnderlinePrimary);
1541                     }
1542                     // underline removals too
1543                     if underline_start == underline_end {
1544                         for p in underline_start-1..underline_start+1 {
1545                             buffer.putc(row_num,
1546                                         max_line_num_len + 3 + p as usize,
1547                                         '-',
1548                                         Style::UnderlineSecondary);
1549                         }
1550                     }
1551
1552                     // length of the code after substitution
1553                     let full_sub_len = part.snippet.chars()
1554                         .map(|ch| unicode_width::UnicodeWidthChar::width(ch).unwrap_or(1))
1555                         .sum::<usize>() as isize;
1556
1557                     // length of the code to be substituted
1558                     let snippet_len = span_end_pos as isize - span_start_pos as isize;
1559                     // For multiple substitutions, use the position *after* the previous
1560                     // substitutions have happened.
1561                     offset += full_sub_len - snippet_len;
1562                 }
1563                 row_num += 1;
1564             }
1565
1566             // if we elided some lines, add an ellipsis
1567             if lines.next().is_some() {
1568                 buffer.puts(row_num, max_line_num_len - 1, "...", Style::LineNumber);
1569             } else if !show_underline {
1570                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
1571                 row_num += 1;
1572             }
1573         }
1574         if suggestions.len() > MAX_SUGGESTIONS {
1575             let others = suggestions.len() - MAX_SUGGESTIONS;
1576             let msg = format!("and {} other candidate{}", others, pluralise!(others));
1577             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
1578         } else if notice_capitalization {
1579             let msg = "notice the capitalization difference";
1580             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
1581         }
1582         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
1583         Ok(())
1584     }
1585
1586     fn emit_messages_default(
1587         &mut self,
1588         level: &Level,
1589         message: &[(String, Style)],
1590         code: &Option<DiagnosticId>,
1591         span: &MultiSpan,
1592         children: &[SubDiagnostic],
1593         suggestions: &[CodeSuggestion],
1594     ) {
1595         let max_line_num_len = if self.ui_testing {
1596             ANONYMIZED_LINE_NUM.len()
1597         } else {
1598             self.get_max_line_num(span, children).to_string().len()
1599         };
1600
1601         match self.emit_message_default(span, message, code, level, max_line_num_len, false) {
1602             Ok(()) => {
1603                 if !children.is_empty() || suggestions.iter().any(|s| {
1604                     s.style != SuggestionStyle::CompletelyHidden
1605                 }) {
1606                     let mut buffer = StyledBuffer::new();
1607                     if !self.short_message {
1608                         draw_col_separator_no_space(&mut buffer, 0, max_line_num_len + 1);
1609                     }
1610                     match emit_to_destination(&buffer.render(), level, &mut self.dst,
1611                                               self.short_message) {
1612                         Ok(()) => (),
1613                         Err(e) => panic!("failed to emit error: {}", e)
1614                     }
1615                 }
1616                 if !self.short_message {
1617                     for child in children {
1618                         let span = child.render_span.as_ref().unwrap_or(&child.span);
1619                         match self.emit_message_default(
1620                             &span,
1621                             &child.styled_message(),
1622                             &None,
1623                             &child.level,
1624                             max_line_num_len,
1625                             true,
1626                         ) {
1627                             Err(e) => panic!("failed to emit error: {}", e),
1628                             _ => ()
1629                         }
1630                     }
1631                     for sugg in suggestions {
1632                         if sugg.style == SuggestionStyle::CompletelyHidden {
1633                             // do not display this suggestion, it is meant only for tools
1634                         } else if sugg.style == SuggestionStyle::HideCodeAlways {
1635                             match self.emit_message_default(
1636                                 &MultiSpan::new(),
1637                                 &[(sugg.msg.to_owned(), Style::HeaderMsg)],
1638                                 &None,
1639                                 &Level::Help,
1640                                 max_line_num_len,
1641                                 true,
1642                             ) {
1643                                 Err(e) => panic!("failed to emit error: {}", e),
1644                                 _ => ()
1645                             }
1646                         } else {
1647                             match self.emit_suggestion_default(
1648                                 sugg,
1649                                 &Level::Help,
1650                                 max_line_num_len,
1651                             ) {
1652                                 Err(e) => panic!("failed to emit error: {}", e),
1653                                 _ => ()
1654                             }
1655                         }
1656                     }
1657                 }
1658             }
1659             Err(e) => panic!("failed to emit error: {}", e),
1660         }
1661
1662         let mut dst = self.dst.writable();
1663         match writeln!(dst) {
1664             Err(e) => panic!("failed to emit error: {}", e),
1665             _ => {
1666                 match dst.flush() {
1667                     Err(e) => panic!("failed to emit error: {}", e),
1668                     _ => (),
1669                 }
1670             }
1671         }
1672     }
1673 }
1674
1675 impl FileWithAnnotatedLines {
1676     /// Preprocess all the annotations so that they are grouped by file and by line number
1677     /// This helps us quickly iterate over the whole message (including secondary file spans)
1678     pub fn collect_annotations(
1679         msp: &MultiSpan,
1680         source_map: &Option<Lrc<SourceMapperDyn>>
1681     ) -> Vec<FileWithAnnotatedLines> {
1682         fn add_annotation_to_file(file_vec: &mut Vec<FileWithAnnotatedLines>,
1683                                   file: Lrc<SourceFile>,
1684                                   line_index: usize,
1685                                   ann: Annotation) {
1686
1687             for slot in file_vec.iter_mut() {
1688                 // Look through each of our files for the one we're adding to
1689                 if slot.file.name == file.name {
1690                     // See if we already have a line for it
1691                     for line_slot in &mut slot.lines {
1692                         if line_slot.line_index == line_index {
1693                             line_slot.annotations.push(ann);
1694                             return;
1695                         }
1696                     }
1697                     // We don't have a line yet, create one
1698                     slot.lines.push(Line {
1699                         line_index,
1700                         annotations: vec![ann],
1701                     });
1702                     slot.lines.sort();
1703                     return;
1704                 }
1705             }
1706             // This is the first time we're seeing the file
1707             file_vec.push(FileWithAnnotatedLines {
1708                 file,
1709                 lines: vec![Line {
1710                                 line_index,
1711                                 annotations: vec![ann],
1712                             }],
1713                 multiline_depth: 0,
1714             });
1715         }
1716
1717         let mut output = vec![];
1718         let mut multiline_annotations = vec![];
1719
1720         if let Some(ref sm) = source_map {
1721             for span_label in msp.span_labels() {
1722                 if span_label.span.is_dummy() {
1723                     continue;
1724                 }
1725
1726                 let lo = sm.lookup_char_pos(span_label.span.lo());
1727                 let mut hi = sm.lookup_char_pos(span_label.span.hi());
1728
1729                 // Watch out for "empty spans". If we get a span like 6..6, we
1730                 // want to just display a `^` at 6, so convert that to
1731                 // 6..7. This is degenerate input, but it's best to degrade
1732                 // gracefully -- and the parser likes to supply a span like
1733                 // that for EOF, in particular.
1734
1735                 if lo.col_display == hi.col_display && lo.line == hi.line {
1736                     hi.col_display += 1;
1737                 }
1738
1739                 if lo.line != hi.line {
1740                     let ml = MultilineAnnotation {
1741                         depth: 1,
1742                         line_start: lo.line,
1743                         line_end: hi.line,
1744                         start_col: lo.col_display,
1745                         end_col: hi.col_display,
1746                         is_primary: span_label.is_primary,
1747                         label: span_label.label,
1748                         overlaps_exactly: false,
1749                     };
1750                     multiline_annotations.push((lo.file, ml));
1751                 } else {
1752                     let ann = Annotation {
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                         annotation_type: AnnotationType::Singleline,
1758                     };
1759                     add_annotation_to_file(&mut output, lo.file, lo.line, ann);
1760                 };
1761             }
1762         }
1763
1764         // Find overlapping multiline annotations, put them at different depths
1765         multiline_annotations.sort_by_key(|&(_, ref ml)| (ml.line_start, ml.line_end));
1766         for (_, ann) in multiline_annotations.clone() {
1767             for (_, a) in multiline_annotations.iter_mut() {
1768                 // Move all other multiline annotations overlapping with this one
1769                 // one level to the right.
1770                 if !(ann.same_span(a)) &&
1771                     num_overlap(ann.line_start, ann.line_end, a.line_start, a.line_end, true)
1772                 {
1773                     a.increase_depth();
1774                 } else if ann.same_span(a) && &ann != a {
1775                     a.overlaps_exactly = true;
1776                 } else {
1777                     break;
1778                 }
1779             }
1780         }
1781
1782         let mut max_depth = 0;  // max overlapping multiline spans
1783         for (file, ann) in multiline_annotations {
1784             max_depth = max(max_depth, ann.depth);
1785             let mut end_ann = ann.as_end();
1786             if !ann.overlaps_exactly {
1787                 // avoid output like
1788                 //
1789                 //  |        foo(
1790                 //  |   _____^
1791                 //  |  |_____|
1792                 //  | ||         bar,
1793                 //  | ||     );
1794                 //  | ||      ^
1795                 //  | ||______|
1796                 //  |  |______foo
1797                 //  |         baz
1798                 //
1799                 // and instead get
1800                 //
1801                 //  |       foo(
1802                 //  |  _____^
1803                 //  | |         bar,
1804                 //  | |     );
1805                 //  | |      ^
1806                 //  | |      |
1807                 //  | |______foo
1808                 //  |        baz
1809                 add_annotation_to_file(&mut output, file.clone(), ann.line_start, ann.as_start());
1810                 // 4 is the minimum vertical length of a multiline span when presented: two lines
1811                 // of code and two lines of underline. This is not true for the special case where
1812                 // the beginning doesn't have an underline, but the current logic seems to be
1813                 // working correctly.
1814                 let middle = min(ann.line_start + 4, ann.line_end);
1815                 for line in ann.line_start + 1..middle {
1816                     // Every `|` that joins the beginning of the span (`___^`) to the end (`|__^`).
1817                     add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
1818                 }
1819                 if middle < ann.line_end - 1 {
1820                     for line in ann.line_end - 1..ann.line_end {
1821                         add_annotation_to_file(&mut output, file.clone(), line, ann.as_line());
1822                     }
1823                 }
1824             } else {
1825                 end_ann.annotation_type = AnnotationType::Singleline;
1826             }
1827             add_annotation_to_file(&mut output, file, ann.line_end, end_ann);
1828         }
1829         for file_vec in output.iter_mut() {
1830             file_vec.multiline_depth = max_depth;
1831         }
1832         output
1833     }
1834 }
1835
1836 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1837     buffer.puts(line, col, "| ", Style::LineNumber);
1838 }
1839
1840 fn draw_col_separator_no_space(buffer: &mut StyledBuffer, line: usize, col: usize) {
1841     draw_col_separator_no_space_with_style(buffer, line, col, Style::LineNumber);
1842 }
1843
1844 fn draw_col_separator_no_space_with_style(buffer: &mut StyledBuffer,
1845                                           line: usize,
1846                                           col: usize,
1847                                           style: Style) {
1848     buffer.putc(line, col, '|', style);
1849 }
1850
1851 fn draw_range(buffer: &mut StyledBuffer, symbol: char, line: usize,
1852               col_from: usize, col_to: usize, style: Style) {
1853     for col in col_from..col_to {
1854         buffer.putc(line, col, symbol, style);
1855     }
1856 }
1857
1858 fn draw_note_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
1859     buffer.puts(line, col, "= ", Style::LineNumber);
1860 }
1861
1862 fn draw_multiline_line(buffer: &mut StyledBuffer,
1863                        line: usize,
1864                        offset: usize,
1865                        depth: usize,
1866                        style: Style)
1867 {
1868     buffer.putc(line, offset + depth - 1, '|', style);
1869 }
1870
1871 fn num_overlap(a_start: usize, a_end: usize, b_start: usize, b_end:usize, inclusive: bool) -> bool {
1872     let extra = if inclusive {
1873         1
1874     } else {
1875         0
1876     };
1877     (b_start..b_end + extra).contains(&a_start) ||
1878     (a_start..a_end + extra).contains(&b_start)
1879 }
1880 fn overlaps(a1: &Annotation, a2: &Annotation, padding: usize) -> bool {
1881     num_overlap(a1.start_col, a1.end_col + padding, a2.start_col, a2.end_col, false)
1882 }
1883
1884 fn emit_to_destination(rendered_buffer: &[Vec<StyledString>],
1885                        lvl: &Level,
1886                        dst: &mut Destination,
1887                        short_message: bool)
1888                        -> io::Result<()> {
1889     use crate::lock;
1890
1891     let mut dst = dst.writable();
1892
1893     // In order to prevent error message interleaving, where multiple error lines get intermixed
1894     // when multiple compiler processes error simultaneously, we emit errors with additional
1895     // steps.
1896     //
1897     // On Unix systems, we write into a buffered terminal rather than directly to a terminal. When
1898     // the .flush() is called we take the buffer created from the buffered writes and write it at
1899     // one shot.  Because the Unix systems use ANSI for the colors, which is a text-based styling
1900     // scheme, this buffered approach works and maintains the styling.
1901     //
1902     // On Windows, styling happens through calls to a terminal API. This prevents us from using the
1903     // same buffering approach.  Instead, we use a global Windows mutex, which we acquire long
1904     // enough to output the full error message, then we release.
1905     let _buffer_lock = lock::acquire_global_lock("rustc_errors");
1906     for (pos, line) in rendered_buffer.iter().enumerate() {
1907         for part in line {
1908             dst.apply_style(lvl.clone(), part.style)?;
1909             write!(dst, "{}", part.text)?;
1910             dst.reset()?;
1911         }
1912         if !short_message && (!lvl.is_failure_note() || pos != rendered_buffer.len() - 1) {
1913             writeln!(dst)?;
1914         }
1915     }
1916     dst.flush()?;
1917     Ok(())
1918 }
1919
1920 pub enum Destination {
1921     Terminal(StandardStream),
1922     Buffered(BufferWriter),
1923     // The bool denotes whether we should be emitting ansi color codes or not
1924     Raw(Box<(dyn Write + Send)>, bool),
1925 }
1926
1927 pub enum WritableDst<'a> {
1928     Terminal(&'a mut StandardStream),
1929     Buffered(&'a mut BufferWriter, Buffer),
1930     Raw(&'a mut (dyn Write + Send)),
1931     ColoredRaw(Ansi<&'a mut (dyn Write + Send)>),
1932 }
1933
1934 impl Destination {
1935     fn from_stderr(color: ColorConfig) -> Destination {
1936         let choice = color.to_color_choice();
1937         // On Windows we'll be performing global synchronization on the entire
1938         // system for emitting rustc errors, so there's no need to buffer
1939         // anything.
1940         //
1941         // On non-Windows we rely on the atomicity of `write` to ensure errors
1942         // don't get all jumbled up.
1943         if cfg!(windows) {
1944             Terminal(StandardStream::stderr(choice))
1945         } else {
1946             Buffered(BufferWriter::stderr(choice))
1947         }
1948     }
1949
1950     fn writable(&mut self) -> WritableDst<'_> {
1951         match *self {
1952             Destination::Terminal(ref mut t) => WritableDst::Terminal(t),
1953             Destination::Buffered(ref mut t) => {
1954                 let buf = t.buffer();
1955                 WritableDst::Buffered(t, buf)
1956             }
1957             Destination::Raw(ref mut t, false) => WritableDst::Raw(t),
1958             Destination::Raw(ref mut t, true) => WritableDst::ColoredRaw(Ansi::new(t)),
1959         }
1960     }
1961 }
1962
1963 impl<'a> WritableDst<'a> {
1964     fn apply_style(&mut self, lvl: Level, style: Style) -> io::Result<()> {
1965         let mut spec = ColorSpec::new();
1966         match style {
1967             Style::LineAndColumn => {}
1968             Style::LineNumber => {
1969                 spec.set_bold(true);
1970                 spec.set_intense(true);
1971                 if cfg!(windows) {
1972                     spec.set_fg(Some(Color::Cyan));
1973                 } else {
1974                     spec.set_fg(Some(Color::Blue));
1975                 }
1976             }
1977             Style::Quotation => {}
1978             Style::MainHeaderMsg => {
1979                 spec.set_bold(true);
1980                 if cfg!(windows) {
1981                     spec.set_intense(true)
1982                         .set_fg(Some(Color::White));
1983                 }
1984             }
1985             Style::UnderlinePrimary | Style::LabelPrimary => {
1986                 spec = lvl.color();
1987                 spec.set_bold(true);
1988             }
1989             Style::UnderlineSecondary |
1990             Style::LabelSecondary => {
1991                 spec.set_bold(true)
1992                     .set_intense(true);
1993                 if cfg!(windows) {
1994                     spec.set_fg(Some(Color::Cyan));
1995                 } else {
1996                     spec.set_fg(Some(Color::Blue));
1997                 }
1998             }
1999             Style::HeaderMsg |
2000             Style::NoStyle => {}
2001             Style::Level(lvl) => {
2002                 spec = lvl.color();
2003                 spec.set_bold(true);
2004             }
2005             Style::Highlight => {
2006                 spec.set_bold(true);
2007             }
2008         }
2009         self.set_color(&spec)
2010     }
2011
2012     fn set_color(&mut self, color: &ColorSpec) -> io::Result<()> {
2013         match *self {
2014             WritableDst::Terminal(ref mut t) => t.set_color(color),
2015             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
2016             WritableDst::ColoredRaw(ref mut t) => t.set_color(color),
2017             WritableDst::Raw(_) => Ok(())
2018         }
2019     }
2020
2021     fn reset(&mut self) -> io::Result<()> {
2022         match *self {
2023             WritableDst::Terminal(ref mut t) => t.reset(),
2024             WritableDst::Buffered(_, ref mut t) => t.reset(),
2025             WritableDst::ColoredRaw(ref mut t) => t.reset(),
2026             WritableDst::Raw(_) => Ok(()),
2027         }
2028     }
2029 }
2030
2031 impl<'a> Write for WritableDst<'a> {
2032     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
2033         match *self {
2034             WritableDst::Terminal(ref mut t) => t.write(bytes),
2035             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
2036             WritableDst::Raw(ref mut w) => w.write(bytes),
2037             WritableDst::ColoredRaw(ref mut t) => t.write(bytes),
2038         }
2039     }
2040
2041     fn flush(&mut self) -> io::Result<()> {
2042         match *self {
2043             WritableDst::Terminal(ref mut t) => t.flush(),
2044             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
2045             WritableDst::Raw(ref mut w) => w.flush(),
2046             WritableDst::ColoredRaw(ref mut w) => w.flush(),
2047         }
2048     }
2049 }
2050
2051 impl<'a> Drop for WritableDst<'a> {
2052     fn drop(&mut self) {
2053         match *self {
2054             WritableDst::Buffered(ref mut dst, ref mut buf) => {
2055                 drop(dst.print(buf));
2056             }
2057             _ => {}
2058         }
2059     }
2060 }
2061
2062 /// Whether the original and suggested code are visually similar enough to warrant extra wording.
2063 pub fn is_case_difference(sm: &dyn SourceMapper, suggested: &str, sp: Span) -> bool {
2064     // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
2065     let found = sm.span_to_snippet(sp).unwrap();
2066     let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
2067     // All the chars that differ in capitalization are confusable (above):
2068     let confusable = found.chars().zip(suggested.chars()).filter(|(f, s)| f != s).all(|(f, s)| {
2069         (ascii_confusables.contains(&f) || ascii_confusables.contains(&s))
2070     });
2071     confusable && found.to_lowercase() == suggested.to_lowercase()
2072             // FIXME: We sometimes suggest the same thing we already have, which is a
2073             //        bug, but be defensive against that here.
2074             && found != suggested
2075 }