src/librustc_errors/lib.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  12       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  13       html_root_url = "https://doc.rust-lang.org/nightly/")]
  14 #![deny(warnings)]
  15
  16 #![feature(custom_attribute)]
  17 #![allow(unused_attributes)]
  18 #![feature(range_contains)]
  19 #![cfg_attr(unix, feature(libc))]
  20 #![feature(conservative_impl_trait)]
  21 #![feature(i128_type)]
  22
  23 extern crate term;
  24 #[cfg(unix)]
  25 extern crate libc;
  26 extern crate rustc_data_structures;
  27 extern crate serialize as rustc_serialize;
  28 extern crate syntax_pos;
  29
  30 pub use emitter::ColorConfig;
  31
  32 use self::Level::*;
  33
  34 use emitter::{Emitter, EmitterWriter};
  35
  36 use rustc_data_structures::fx::FxHashSet;
  37 use rustc_data_structures::stable_hasher::StableHasher;
  38
  39 use std::borrow::Cow;
  40 use std::cell::{RefCell, Cell};
  41 use std::mem;
  42 use std::rc::Rc;
  43 use std::{error, fmt};
  44
  45 mod diagnostic;
  46 mod diagnostic_builder;
  47 pub mod emitter;
  48 mod snippet;
  49 pub mod registry;
  50 mod styled_buffer;
  51 mod lock;
  52
  53 use syntax_pos::{BytePos, Loc, FileLinesResult, FileMap, FileName, MultiSpan, Span, NO_EXPANSION};
  54
  55 #[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
  56 pub struct CodeSuggestion {
  57     /// Each substitute can have multiple variants due to multiple
  58     /// applicable suggestions
  59     ///
  60     /// `foo.bar` might be replaced with `a.b` or `x.y` by replacing
  61     /// `foo` and `bar` on their own:
  62     ///
  63     /// ```
  64     /// vec![
  65     ///     Substitution { parts: vec![(0..3, "a"), (4..7, "b")] },
  66     ///     Substitution { parts: vec![(0..3, "x"), (4..7, "y")] },
  67     /// ]
  68     /// ```
  69     ///
  70     /// or by replacing the entire span:
  71     ///
  72     /// ```
  73     /// vec![
  74     ///     Substitution { parts: vec![(0..7, "a.b")] },
  75     ///     Substitution { parts: vec![(0..7, "x.y")] },
  76     /// ]
  77     /// ```
  78     pub substitutions: Vec<Substitution>,
  79     pub msg: String,
  80     pub show_code_when_inline: bool,
  81 }
  82
  83 #[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
  84 /// See the docs on `CodeSuggestion::substitutions`
  85 pub struct Substitution {
  86     pub parts: Vec<SubstitutionPart>,
  87 }
  88
  89 #[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
  90 pub struct SubstitutionPart {
  91     pub span: Span,
  92     pub snippet: String,
  93 }
  94
  95 pub trait CodeMapper {
  96     fn lookup_char_pos(&self, pos: BytePos) -> Loc;
  97     fn span_to_lines(&self, sp: Span) -> FileLinesResult;
  98     fn span_to_string(&self, sp: Span) -> String;
  99     fn span_to_filename(&self, sp: Span) -> FileName;
 100     fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span>;
 101     fn call_span_if_macro(&self, sp: Span) -> Span;
 102     fn ensure_filemap_source_present(&self, file_map: Rc<FileMap>) -> bool;
 103 }
 104
 105 impl CodeSuggestion {
 106     /// Returns the assembled code suggestions and whether they should be shown with an underline.
 107     pub fn splice_lines(&self, cm: &CodeMapper) -> Vec<(String, Vec<SubstitutionPart>)> {
 108         use syntax_pos::{CharPos, Loc, Pos};
 109
 110         fn push_trailing(buf: &mut String,
 111                          line_opt: Option<&Cow<str>>,
 112                          lo: &Loc,
 113                          hi_opt: Option<&Loc>) {
 114             let (lo, hi_opt) = (lo.col.to_usize(), hi_opt.map(|hi| hi.col.to_usize()));
 115             if let Some(line) = line_opt {
 116                 if let Some(lo) = line.char_indices().map(|(i, _)| i).nth(lo) {
 117                     let hi_opt = hi_opt.and_then(|hi| line.char_indices().map(|(i, _)| i).nth(hi));
 118                     buf.push_str(match hi_opt {
 119                         Some(hi) => &line[lo..hi],
 120                         None => &line[lo..],
 121                     });
 122                 }
 123                 if let None = hi_opt {
 124                     buf.push('\n');
 125                 }
 126             }
 127         }
 128
 129         assert!(!self.substitutions.is_empty());
 130
 131         self.substitutions.iter().cloned().map(|mut substitution| {
 132             // Assumption: all spans are in the same file, and all spans
 133             // are disjoint. Sort in ascending order.
 134             substitution.parts.sort_by_key(|part| part.span.lo());
 135
 136             // Find the bounding span.
 137             let lo = substitution.parts.iter().map(|part| part.span.lo()).min().unwrap();
 138             let hi = substitution.parts.iter().map(|part| part.span.hi()).min().unwrap();
 139             let bounding_span = Span::new(lo, hi, NO_EXPANSION);
 140             let lines = cm.span_to_lines(bounding_span).unwrap();
 141             assert!(!lines.lines.is_empty());
 142
 143             // To build up the result, we do this for each span:
 144             // - push the line segment trailing the previous span
 145             //   (at the beginning a "phantom" span pointing at the start of the line)
 146             // - push lines between the previous and current span (if any)
 147             // - if the previous and current span are not on the same line
 148             //   push the line segment leading up to the current span
 149             // - splice in the span substitution
 150             //
 151             // Finally push the trailing line segment of the last span
 152             let fm = &lines.file;
 153             let mut prev_hi = cm.lookup_char_pos(bounding_span.lo());
 154             prev_hi.col = CharPos::from_usize(0);
 155
 156             let mut prev_line = fm.get_line(lines.lines[0].line_index);
 157             let mut buf = String::new();
 158
 159             for part in &substitution.parts {
 160                 let cur_lo = cm.lookup_char_pos(part.span.lo());
 161                 if prev_hi.line == cur_lo.line {
 162                     push_trailing(&mut buf, prev_line.as_ref(), &prev_hi, Some(&cur_lo));
 163                 } else {
 164                     push_trailing(&mut buf, prev_line.as_ref(), &prev_hi, None);
 165                     // push lines between the previous and current span (if any)
 166                     for idx in prev_hi.line..(cur_lo.line - 1) {
 167                         if let Some(line) = fm.get_line(idx) {
 168                             buf.push_str(line.as_ref());
 169                             buf.push('\n');
 170                         }
 171                     }
 172                     if let Some(cur_line) = fm.get_line(cur_lo.line - 1) {
 173                         buf.push_str(&cur_line[..cur_lo.col.to_usize()]);
 174                     }
 175                 }
 176                 buf.push_str(&part.snippet);
 177                 prev_hi = cm.lookup_char_pos(part.span.hi());
 178                 prev_line = fm.get_line(prev_hi.line - 1);
 179             }
 180             // if the replacement already ends with a newline, don't print the next line
 181             if !buf.ends_with('\n') {
 182                 push_trailing(&mut buf, prev_line.as_ref(), &prev_hi, None);
 183             }
 184             // remove trailing newlines
 185             while buf.ends_with('\n') {
 186                 buf.pop();
 187             }
 188             (buf, substitution.parts)
 189         }).collect()
 190     }
 191 }
 192
 193 /// Used as a return value to signify a fatal error occurred. (It is also
 194 /// used as the argument to panic at the moment, but that will eventually
 195 /// not be true.)
 196 #[derive(Copy, Clone, Debug)]
 197 #[must_use]
 198 pub struct FatalError;
 199
 200 impl fmt::Display for FatalError {
 201     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 202         write!(f, "parser fatal error")
 203     }
 204 }
 205
 206 impl error::Error for FatalError {
 207     fn description(&self) -> &str {
 208         "The parser has encountered a fatal error"
 209     }
 210 }
 211
 212 /// Signifies that the compiler died with an explicit call to `.bug`
 213 /// or `.span_bug` rather than a failed assertion, etc.
 214 #[derive(Copy, Clone, Debug)]
 215 pub struct ExplicitBug;
 216
 217 impl fmt::Display for ExplicitBug {
 218     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 219         write!(f, "parser internal bug")
 220     }
 221 }
 222
 223 impl error::Error for ExplicitBug {
 224     fn description(&self) -> &str {
 225         "The parser has encountered an internal bug"
 226     }
 227 }
 228
 229 pub use diagnostic::{Diagnostic, SubDiagnostic, DiagnosticStyledString, DiagnosticId};
 230 pub use diagnostic_builder::DiagnosticBuilder;
 231
 232 /// A handler deals with errors; certain errors
 233 /// (fatal, bug, unimpl) may cause immediate exit,
 234 /// others log errors for later reporting.
 235 pub struct Handler {
 236     err_count: Cell<usize>,
 237     emitter: RefCell<Box<Emitter>>,
 238     pub can_emit_warnings: bool,
 239     treat_err_as_bug: bool,
 240     continue_after_error: Cell<bool>,
 241     delayed_span_bug: RefCell<Option<Diagnostic>>,
 242     tracked_diagnostics: RefCell<Option<Vec<Diagnostic>>>,
 243
 244     // This set contains a hash of every diagnostic that has been emitted by
 245     // this handler. These hashes is used to avoid emitting the same error
 246     // twice.
 247     emitted_diagnostics: RefCell<FxHashSet<u128>>,
 248 }
 249
 250 impl Handler {
 251     pub fn with_tty_emitter(color_config: ColorConfig,
 252                             can_emit_warnings: bool,
 253                             treat_err_as_bug: bool,
 254                             cm: Option<Rc<CodeMapper>>)
 255                             -> Handler {
 256         let emitter = Box::new(EmitterWriter::stderr(color_config, cm, false));
 257         Handler::with_emitter(can_emit_warnings, treat_err_as_bug, emitter)
 258     }
 259
 260     pub fn with_emitter(can_emit_warnings: bool,
 261                         treat_err_as_bug: bool,
 262                         e: Box<Emitter>)
 263                         -> Handler {
 264         Handler {
 265             err_count: Cell::new(0),
 266             emitter: RefCell::new(e),
 267             can_emit_warnings,
 268             treat_err_as_bug,
 269             continue_after_error: Cell::new(true),
 270             delayed_span_bug: RefCell::new(None),
 271             tracked_diagnostics: RefCell::new(None),
 272             emitted_diagnostics: RefCell::new(FxHashSet()),
 273         }
 274     }
 275
 276     pub fn set_continue_after_error(&self, continue_after_error: bool) {
 277         self.continue_after_error.set(continue_after_error);
 278     }
 279
 280     // NOTE: DO NOT call this function from rustc, as it relies on `err_count` being non-zero
 281     // if an error happened to avoid ICEs. This function should only be called from tools.
 282     pub fn reset_err_count(&self) {
 283         self.err_count.set(0);
 284     }
 285
 286     pub fn struct_dummy<'a>(&'a self) -> DiagnosticBuilder<'a> {
 287         DiagnosticBuilder::new(self, Level::Cancelled, "")
 288     }
 289
 290     pub fn struct_span_warn<'a, S: Into<MultiSpan>>(&'a self,
 291                                                     sp: S,
 292                                                     msg: &str)
 293                                                     -> DiagnosticBuilder<'a> {
 294         let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
 295         result.set_span(sp);
 296         if !self.can_emit_warnings {
 297             result.cancel();
 298         }
 299         result
 300     }
 301     pub fn struct_span_warn_with_code<'a, S: Into<MultiSpan>>(&'a self,
 302                                                               sp: S,
 303                                                               msg: &str,
 304                                                               code: DiagnosticId)
 305                                                               -> DiagnosticBuilder<'a> {
 306         let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
 307         result.set_span(sp);
 308         result.code(code);
 309         if !self.can_emit_warnings {
 310             result.cancel();
 311         }
 312         result
 313     }
 314     pub fn struct_warn<'a>(&'a self, msg: &str) -> DiagnosticBuilder<'a> {
 315         let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
 316         if !self.can_emit_warnings {
 317             result.cancel();
 318         }
 319         result
 320     }
 321     pub fn struct_span_err<'a, S: Into<MultiSpan>>(&'a self,
 322                                                    sp: S,
 323                                                    msg: &str)
 324                                                    -> DiagnosticBuilder<'a> {
 325         let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
 326         result.set_span(sp);
 327         result
 328     }
 329     pub fn struct_span_err_with_code<'a, S: Into<MultiSpan>>(&'a self,
 330                                                              sp: S,
 331                                                              msg: &str,
 332                                                              code: DiagnosticId)
 333                                                              -> DiagnosticBuilder<'a> {
 334         let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
 335         result.set_span(sp);
 336         result.code(code);
 337         result
 338     }
 339     // FIXME: This method should be removed (every error should have an associated error code).
 340     pub fn struct_err<'a>(&'a self, msg: &str) -> DiagnosticBuilder<'a> {
 341         DiagnosticBuilder::new(self, Level::Error, msg)
 342     }
 343     pub fn struct_err_with_code<'a>(
 344         &'a self,
 345         msg: &str,
 346         code: DiagnosticId,
 347     ) -> DiagnosticBuilder<'a> {
 348         let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
 349         result.code(code);
 350         result
 351     }
 352     pub fn struct_span_fatal<'a, S: Into<MultiSpan>>(&'a self,
 353                                                      sp: S,
 354                                                      msg: &str)
 355                                                      -> DiagnosticBuilder<'a> {
 356         let mut result = DiagnosticBuilder::new(self, Level::Fatal, msg);
 357         result.set_span(sp);
 358         result
 359     }
 360     pub fn struct_span_fatal_with_code<'a, S: Into<MultiSpan>>(&'a self,
 361                                                                sp: S,
 362                                                                msg: &str,
 363                                                                code: DiagnosticId)
 364                                                                -> DiagnosticBuilder<'a> {
 365         let mut result = DiagnosticBuilder::new(self, Level::Fatal, msg);
 366         result.set_span(sp);
 367         result.code(code);
 368         result
 369     }
 370     pub fn struct_fatal<'a>(&'a self, msg: &str) -> DiagnosticBuilder<'a> {
 371         DiagnosticBuilder::new(self, Level::Fatal, msg)
 372     }
 373
 374     pub fn cancel(&self, err: &mut DiagnosticBuilder) {
 375         err.cancel();
 376     }
 377
 378     fn panic_if_treat_err_as_bug(&self) {
 379         if self.treat_err_as_bug {
 380             panic!("encountered error with `-Z treat_err_as_bug");
 381         }
 382     }
 383
 384     pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, msg: &str) -> FatalError {
 385         self.emit(&sp.into(), msg, Fatal);
 386         FatalError
 387     }
 388     pub fn span_fatal_with_code<S: Into<MultiSpan>>(&self,
 389                                                     sp: S,
 390                                                     msg: &str,
 391                                                     code: DiagnosticId)
 392                                                     -> FatalError {
 393         self.emit_with_code(&sp.into(), msg, code, Fatal);
 394         FatalError
 395     }
 396     pub fn span_err<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
 397         self.emit(&sp.into(), msg, Error);
 398     }
 399     pub fn mut_span_err<'a, S: Into<MultiSpan>>(&'a self,
 400                                                 sp: S,
 401                                                 msg: &str)
 402                                                 -> DiagnosticBuilder<'a> {
 403         let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
 404         result.set_span(sp);
 405         result
 406     }
 407     pub fn span_err_with_code<S: Into<MultiSpan>>(&self, sp: S, msg: &str, code: DiagnosticId) {
 408         self.emit_with_code(&sp.into(), msg, code, Error);
 409     }
 410     pub fn span_warn<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
 411         self.emit(&sp.into(), msg, Warning);
 412     }
 413     pub fn span_warn_with_code<S: Into<MultiSpan>>(&self, sp: S, msg: &str, code: DiagnosticId) {
 414         self.emit_with_code(&sp.into(), msg, code, Warning);
 415     }
 416     pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, msg: &str) -> ! {
 417         self.emit(&sp.into(), msg, Bug);
 418         panic!(ExplicitBug);
 419     }
 420     pub fn delay_span_bug<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
 421         if self.treat_err_as_bug {
 422             self.span_bug(sp, msg);
 423         }
 424         let mut diagnostic = Diagnostic::new(Level::Bug, msg);
 425         diagnostic.set_span(sp.into());
 426         *self.delayed_span_bug.borrow_mut() = Some(diagnostic);
 427     }
 428     pub fn span_bug_no_panic<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
 429         self.emit(&sp.into(), msg, Bug);
 430     }
 431     pub fn span_note_without_error<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
 432         self.emit(&sp.into(), msg, Note);
 433     }
 434     pub fn span_note_diag<'a>(&'a self,
 435                               sp: Span,
 436                               msg: &str)
 437                               -> DiagnosticBuilder<'a> {
 438         let mut db = DiagnosticBuilder::new(self, Note, msg);
 439         db.set_span(sp);
 440         db
 441     }
 442     pub fn span_unimpl<S: Into<MultiSpan>>(&self, sp: S, msg: &str) -> ! {
 443         self.span_bug(sp, &format!("unimplemented {}", msg));
 444     }
 445     pub fn fatal(&self, msg: &str) -> FatalError {
 446         if self.treat_err_as_bug {
 447             self.bug(msg);
 448         }
 449         let mut db = DiagnosticBuilder::new(self, Fatal, msg);
 450         db.emit();
 451         FatalError
 452     }
 453     pub fn err(&self, msg: &str) {
 454         if self.treat_err_as_bug {
 455             self.bug(msg);
 456         }
 457         let mut db = DiagnosticBuilder::new(self, Error, msg);
 458         db.emit();
 459     }
 460     pub fn warn(&self, msg: &str) {
 461         let mut db = DiagnosticBuilder::new(self, Warning, msg);
 462         db.emit();
 463     }
 464     pub fn note_without_error(&self, msg: &str) {
 465         let mut db = DiagnosticBuilder::new(self, Note, msg);
 466         db.emit();
 467     }
 468     pub fn bug(&self, msg: &str) -> ! {
 469         let mut db = DiagnosticBuilder::new(self, Bug, msg);
 470         db.emit();
 471         panic!(ExplicitBug);
 472     }
 473     pub fn unimpl(&self, msg: &str) -> ! {
 474         self.bug(&format!("unimplemented {}", msg));
 475     }
 476
 477     fn bump_err_count(&self) {
 478         self.panic_if_treat_err_as_bug();
 479         self.err_count.set(self.err_count.get() + 1);
 480     }
 481
 482     pub fn err_count(&self) -> usize {
 483         self.err_count.get()
 484     }
 485
 486     pub fn has_errors(&self) -> bool {
 487         self.err_count.get() > 0
 488     }
 489     pub fn abort_if_errors(&self) {
 490         let s;
 491         match self.err_count.get() {
 492             0 => {
 493                 if let Some(bug) = self.delayed_span_bug.borrow_mut().take() {
 494                     DiagnosticBuilder::new_diagnostic(self, bug).emit();
 495                 }
 496                 return;
 497             }
 498             1 => s = "aborting due to previous error".to_string(),
 499             _ => {
 500                 s = format!("aborting due to {} previous errors", self.err_count.get());
 501             }
 502         }
 503
 504         panic!(self.fatal(&s));
 505     }
 506     pub fn emit(&self, msp: &MultiSpan, msg: &str, lvl: Level) {
 507         if lvl == Warning && !self.can_emit_warnings {
 508             return;
 509         }
 510         let mut db = DiagnosticBuilder::new(self, lvl, msg);
 511         db.set_span(msp.clone());
 512         db.emit();
 513         if !self.continue_after_error.get() {
 514             self.abort_if_errors();
 515         }
 516     }
 517     pub fn emit_with_code(&self, msp: &MultiSpan, msg: &str, code: DiagnosticId, lvl: Level) {
 518         if lvl == Warning && !self.can_emit_warnings {
 519             return;
 520         }
 521         let mut db = DiagnosticBuilder::new_with_code(self, lvl, Some(code), msg);
 522         db.set_span(msp.clone());
 523         db.emit();
 524         if !self.continue_after_error.get() {
 525             self.abort_if_errors();
 526         }
 527     }
 528
 529     pub fn track_diagnostics<F, R>(&self, f: F) -> (R, Vec<Diagnostic>)
 530         where F: FnOnce() -> R
 531     {
 532         let prev = mem::replace(&mut *self.tracked_diagnostics.borrow_mut(),
 533                                 Some(Vec::new()));
 534         let ret = f();
 535         let diagnostics = mem::replace(&mut *self.tracked_diagnostics.borrow_mut(), prev)
 536             .unwrap();
 537         (ret, diagnostics)
 538     }
 539
 540     fn emit_db(&self, db: &DiagnosticBuilder) {
 541         let diagnostic = &**db;
 542
 543         if let Some(ref mut list) = *self.tracked_diagnostics.borrow_mut() {
 544             list.push(diagnostic.clone());
 545         }
 546
 547         let diagnostic_hash = {
 548             use std::hash::Hash;
 549             let mut hasher = StableHasher::new();
 550             diagnostic.hash(&mut hasher);
 551             hasher.finish()
 552         };
 553
 554         // Only emit the diagnostic if we haven't already emitted an equivalent
 555         // one:
 556         if self.emitted_diagnostics.borrow_mut().insert(diagnostic_hash) {
 557             self.emitter.borrow_mut().emit(db);
 558         }
 559     }
 560 }
 561
 562
 563 #[derive(Copy, PartialEq, Clone, Hash, Debug, RustcEncodable, RustcDecodable)]
 564 pub enum Level {
 565     Bug,
 566     Fatal,
 567     // An error which while not immediately fatal, should stop the compiler
 568     // progressing beyond the current phase.
 569     PhaseFatal,
 570     Error,
 571     Warning,
 572     Note,
 573     Help,
 574     Cancelled,
 575 }
 576
 577 impl fmt::Display for Level {
 578     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 579         self.to_str().fmt(f)
 580     }
 581 }
 582
 583 impl Level {
 584     fn color(self) -> term::color::Color {
 585         match self {
 586             Bug | Fatal | PhaseFatal | Error => term::color::BRIGHT_RED,
 587             Warning => {
 588                 if cfg!(windows) {
 589                     term::color::BRIGHT_YELLOW
 590                 } else {
 591                     term::color::YELLOW
 592                 }
 593             }
 594             Note => term::color::BRIGHT_GREEN,
 595             Help => term::color::BRIGHT_CYAN,
 596             Cancelled => unreachable!(),
 597         }
 598     }
 599
 600     pub fn to_str(self) -> &'static str {
 601         match self {
 602             Bug => "error: internal compiler error",
 603             Fatal | PhaseFatal | Error => "error",
 604             Warning => "warning",
 605             Note => "note",
 606             Help => "help",
 607             Cancelled => panic!("Shouldn't call on cancelled error"),
 608         }
 609     }
 610 }