src/libsyntax_pos/lib.rs

   1 // Copyright 2012-2013 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 //! The source positions and related helper functions
  12 //!
  13 //! # Note
  14 //!
  15 //! This API is completely unstable and subject to change.
  16
  17 #![crate_name = "syntax_pos"]
  18 #![unstable(feature = "rustc_private", issue = "27812")]
  19 #![crate_type = "dylib"]
  20 #![crate_type = "rlib"]
  21 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  22       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  23       html_root_url = "https://doc.rust-lang.org/nightly/")]
  24 #![cfg_attr(not(stage0), deny(warnings))]
  25
  26 #![feature(custom_attribute)]
  27 #![allow(unused_attributes)]
  28 #![feature(rustc_private)]
  29 #![feature(staged_api)]
  30 #![cfg_attr(stage0, feature(question_mark))]
  31 #![feature(specialization)]
  32
  33 use std::cell::{Cell, RefCell};
  34 use std::ops::{Add, Sub};
  35 use std::rc::Rc;
  36 use std::cmp;
  37
  38 use std::fmt;
  39
  40 use serialize::{Encodable, Decodable, Encoder, Decoder};
  41
  42 extern crate serialize;
  43 extern crate serialize as rustc_serialize; // used by deriving
  44
  45 pub type FileName = String;
  46
  47 /// Spans represent a region of code, used for error reporting. Positions in spans
  48 /// are *absolute* positions from the beginning of the codemap, not positions
  49 /// relative to FileMaps. Methods on the CodeMap can be used to relate spans back
  50 /// to the original source.
  51 /// You must be careful if the span crosses more than one file - you will not be
  52 /// able to use many of the functions on spans in codemap and you cannot assume
  53 /// that the length of the span = hi - lo; there may be space in the BytePos
  54 /// range between files.
  55 #[derive(Clone, Copy, Hash, PartialEq, Eq)]
  56 pub struct Span {
  57     pub lo: BytePos,
  58     pub hi: BytePos,
  59     /// Information about where the macro came from, if this piece of
  60     /// code was created by a macro expansion.
  61     pub expn_id: ExpnId
  62 }
  63
  64 /// A collection of spans. Spans have two orthogonal attributes:
  65 ///
  66 /// - they can be *primary spans*. In this case they are the locus of
  67 ///   the error, and would be rendered with `^^^`.
  68 /// - they can have a *label*. In this case, the label is written next
  69 ///   to the mark in the snippet when we render.
  70 #[derive(Clone, Debug, PartialEq, Eq)]
  71 pub struct MultiSpan {
  72     primary_spans: Vec<Span>,
  73     span_labels: Vec<(Span, String)>,
  74 }
  75
  76 impl Span {
  77     /// Returns a new span representing just the end-point of this span
  78     pub fn end_point(self) -> Span {
  79         let lo = cmp::max(self.hi.0 - 1, self.lo.0);
  80         Span { lo: BytePos(lo), hi: self.hi, expn_id: self.expn_id}
  81     }
  82
  83     /// Returns `self` if `self` is not the dummy span, and `other` otherwise.
  84     pub fn substitute_dummy(self, other: Span) -> Span {
  85         if self.source_equal(&DUMMY_SP) { other } else { self }
  86     }
  87
  88     pub fn contains(self, other: Span) -> bool {
  89         self.lo <= other.lo && other.hi <= self.hi
  90     }
  91
  92     /// Return true if the spans are equal with regards to the source text.
  93     ///
  94     /// Use this instead of `==` when either span could be generated code,
  95     /// and you only care that they point to the same bytes of source text.
  96     pub fn source_equal(&self, other: &Span) -> bool {
  97         self.lo == other.lo && self.hi == other.hi
  98     }
  99
 100     /// Returns `Some(span)`, where the start is trimmed by the end of `other`
 101     pub fn trim_start(self, other: Span) -> Option<Span> {
 102         if self.hi > other.hi {
 103             Some(Span { lo: cmp::max(self.lo, other.hi), .. self })
 104         } else {
 105             None
 106         }
 107     }
 108 }
 109
 110 #[derive(Clone, Debug)]
 111 pub struct SpanLabel {
 112     /// The span we are going to include in the final snippet.
 113     pub span: Span,
 114
 115     /// Is this a primary span? This is the "locus" of the message,
 116     /// and is indicated with a `^^^^` underline, versus `----`.
 117     pub is_primary: bool,
 118
 119     /// What label should we attach to this span (if any)?
 120     pub label: Option<String>,
 121 }
 122
 123 impl serialize::UseSpecializedEncodable for Span {
 124     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 125         s.emit_struct("Span", 2, |s| {
 126             s.emit_struct_field("lo", 0, |s| {
 127                 self.lo.encode(s)
 128             })?;
 129
 130             s.emit_struct_field("hi", 1, |s| {
 131                 self.hi.encode(s)
 132             })
 133         })
 134     }
 135 }
 136
 137 impl serialize::UseSpecializedDecodable for Span {
 138     fn default_decode<D: Decoder>(d: &mut D) -> Result<Span, D::Error> {
 139         d.read_struct("Span", 2, |d| {
 140             let lo = d.read_struct_field("lo", 0, Decodable::decode)?;
 141             let hi = d.read_struct_field("hi", 1, Decodable::decode)?;
 142             Ok(mk_sp(lo, hi))
 143         })
 144     }
 145 }
 146
 147 fn default_span_debug(span: Span, f: &mut fmt::Formatter) -> fmt::Result {
 148     write!(f, "Span {{ lo: {:?}, hi: {:?}, expn_id: {:?} }}",
 149            span.lo, span.hi, span.expn_id)
 150 }
 151
 152 impl fmt::Debug for Span {
 153     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 154         SPAN_DEBUG.with(|span_debug| span_debug.get()(*self, f))
 155     }
 156 }
 157
 158 pub const DUMMY_SP: Span = Span { lo: BytePos(0), hi: BytePos(0), expn_id: NO_EXPANSION };
 159
 160 // Generic span to be used for code originating from the command line
 161 pub const COMMAND_LINE_SP: Span = Span { lo: BytePos(0),
 162                                          hi: BytePos(0),
 163                                          expn_id: COMMAND_LINE_EXPN };
 164
 165 impl MultiSpan {
 166     pub fn new() -> MultiSpan {
 167         MultiSpan {
 168             primary_spans: vec![],
 169             span_labels: vec![]
 170         }
 171     }
 172
 173     pub fn from_span(primary_span: Span) -> MultiSpan {
 174         MultiSpan {
 175             primary_spans: vec![primary_span],
 176             span_labels: vec![]
 177         }
 178     }
 179
 180     pub fn from_spans(vec: Vec<Span>) -> MultiSpan {
 181         MultiSpan {
 182             primary_spans: vec,
 183             span_labels: vec![]
 184         }
 185     }
 186
 187     pub fn push_span_label(&mut self, span: Span, label: String) {
 188         self.span_labels.push((span, label));
 189     }
 190
 191     /// Selects the first primary span (if any)
 192     pub fn primary_span(&self) -> Option<Span> {
 193         self.primary_spans.first().cloned()
 194     }
 195
 196     /// Returns all primary spans.
 197     pub fn primary_spans(&self) -> &[Span] {
 198         &self.primary_spans
 199     }
 200
 201     /// Replaces all occurances of one Span with another. Used to move Spans in areas that don't
 202     /// display well (like std macros). Returns true if replacements occurred.
 203     pub fn replace(&mut self, before: Span, after: Span) -> bool {
 204         let mut replacements_occurred = false;
 205         for primary_span in &mut self.primary_spans {
 206             if *primary_span == before {
 207                 *primary_span = after;
 208                 replacements_occurred = true;
 209             }
 210         }
 211         for span_label in &mut self.span_labels {
 212             if span_label.0 == before {
 213                 span_label.0 = after;
 214                 replacements_occurred = true;
 215             }
 216         }
 217         replacements_occurred
 218     }
 219
 220     /// Returns the strings to highlight. We always ensure that there
 221     /// is an entry for each of the primary spans -- for each primary
 222     /// span P, if there is at least one label with span P, we return
 223     /// those labels (marked as primary). But otherwise we return
 224     /// `SpanLabel` instances with empty labels.
 225     pub fn span_labels(&self) -> Vec<SpanLabel> {
 226         let is_primary = |span| self.primary_spans.contains(&span);
 227         let mut span_labels = vec![];
 228
 229         for &(span, ref label) in &self.span_labels {
 230             span_labels.push(SpanLabel {
 231                 span: span,
 232                 is_primary: is_primary(span),
 233                 label: Some(label.clone())
 234             });
 235         }
 236
 237         for &span in &self.primary_spans {
 238             if !span_labels.iter().any(|sl| sl.span == span) {
 239                 span_labels.push(SpanLabel {
 240                     span: span,
 241                     is_primary: true,
 242                     label: None
 243                 });
 244             }
 245         }
 246
 247         span_labels
 248     }
 249 }
 250
 251 impl From<Span> for MultiSpan {
 252     fn from(span: Span) -> MultiSpan {
 253         MultiSpan::from_span(span)
 254     }
 255 }
 256
 257 #[derive(PartialEq, Eq, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Copy)]
 258 pub struct ExpnId(pub u32);
 259
 260 pub const NO_EXPANSION: ExpnId = ExpnId(!0);
 261 // For code appearing from the command line
 262 pub const COMMAND_LINE_EXPN: ExpnId = ExpnId(!1);
 263
 264 // For code generated by a procedural macro, without knowing which
 265 // Used in `qquote!`
 266 pub const PROC_EXPN: ExpnId = ExpnId(!2);
 267
 268 impl ExpnId {
 269     pub fn from_u32(id: u32) -> ExpnId {
 270         ExpnId(id)
 271     }
 272
 273     pub fn into_u32(self) -> u32 {
 274         self.0
 275     }
 276 }
 277
 278 /// Identifies an offset of a multi-byte character in a FileMap
 279 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Eq, PartialEq)]
 280 pub struct MultiByteChar {
 281     /// The absolute offset of the character in the CodeMap
 282     pub pos: BytePos,
 283     /// The number of bytes, >=2
 284     pub bytes: usize,
 285 }
 286
 287 /// A single source in the CodeMap.
 288 pub struct FileMap {
 289     /// The name of the file that the source came from, source that doesn't
 290     /// originate from files has names between angle brackets by convention,
 291     /// e.g. `<anon>`
 292     pub name: FileName,
 293     /// The absolute path of the file that the source came from.
 294     pub abs_path: Option<FileName>,
 295     /// The complete source code
 296     pub src: Option<Rc<String>>,
 297     /// The start position of this source in the CodeMap
 298     pub start_pos: BytePos,
 299     /// The end position of this source in the CodeMap
 300     pub end_pos: BytePos,
 301     /// Locations of lines beginnings in the source code
 302     pub lines: RefCell<Vec<BytePos>>,
 303     /// Locations of multi-byte characters in the source code
 304     pub multibyte_chars: RefCell<Vec<MultiByteChar>>,
 305 }
 306
 307 impl Encodable for FileMap {
 308     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 309         s.emit_struct("FileMap", 6, |s| {
 310             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 311             s.emit_struct_field("abs_path", 1, |s| self.abs_path.encode(s))?;
 312             s.emit_struct_field("start_pos", 2, |s| self.start_pos.encode(s))?;
 313             s.emit_struct_field("end_pos", 3, |s| self.end_pos.encode(s))?;
 314             s.emit_struct_field("lines", 4, |s| {
 315                 let lines = self.lines.borrow();
 316                 // store the length
 317                 s.emit_u32(lines.len() as u32)?;
 318
 319                 if !lines.is_empty() {
 320                     // In order to preserve some space, we exploit the fact that
 321                     // the lines list is sorted and individual lines are
 322                     // probably not that long. Because of that we can store lines
 323                     // as a difference list, using as little space as possible
 324                     // for the differences.
 325                     let max_line_length = if lines.len() == 1 {
 326                         0
 327                     } else {
 328                         lines.windows(2)
 329                              .map(|w| w[1] - w[0])
 330                              .map(|bp| bp.to_usize())
 331                              .max()
 332                              .unwrap()
 333                     };
 334
 335                     let bytes_per_diff: u8 = match max_line_length {
 336                         0 ... 0xFF => 1,
 337                         0x100 ... 0xFFFF => 2,
 338                         _ => 4
 339                     };
 340
 341                     // Encode the number of bytes used per diff.
 342                     bytes_per_diff.encode(s)?;
 343
 344                     // Encode the first element.
 345                     lines[0].encode(s)?;
 346
 347                     let diff_iter = (&lines[..]).windows(2)
 348                                                 .map(|w| (w[1] - w[0]));
 349
 350                     match bytes_per_diff {
 351                         1 => for diff in diff_iter { (diff.0 as u8).encode(s)? },
 352                         2 => for diff in diff_iter { (diff.0 as u16).encode(s)? },
 353                         4 => for diff in diff_iter { diff.0.encode(s)? },
 354                         _ => unreachable!()
 355                     }
 356                 }
 357
 358                 Ok(())
 359             })?;
 360             s.emit_struct_field("multibyte_chars", 5, |s| {
 361                 (*self.multibyte_chars.borrow()).encode(s)
 362             })
 363         })
 364     }
 365 }
 366
 367 impl Decodable for FileMap {
 368     fn decode<D: Decoder>(d: &mut D) -> Result<FileMap, D::Error> {
 369
 370         d.read_struct("FileMap", 6, |d| {
 371             let name: String = d.read_struct_field("name", 0, |d| Decodable::decode(d))?;
 372             let abs_path: Option<String> =
 373                 d.read_struct_field("abs_path", 1, |d| Decodable::decode(d))?;
 374             let start_pos: BytePos = d.read_struct_field("start_pos", 2, |d| Decodable::decode(d))?;
 375             let end_pos: BytePos = d.read_struct_field("end_pos", 3, |d| Decodable::decode(d))?;
 376             let lines: Vec<BytePos> = d.read_struct_field("lines", 4, |d| {
 377                 let num_lines: u32 = Decodable::decode(d)?;
 378                 let mut lines = Vec::with_capacity(num_lines as usize);
 379
 380                 if num_lines > 0 {
 381                     // Read the number of bytes used per diff.
 382                     let bytes_per_diff: u8 = Decodable::decode(d)?;
 383
 384                     // Read the first element.
 385                     let mut line_start: BytePos = Decodable::decode(d)?;
 386                     lines.push(line_start);
 387
 388                     for _ in 1..num_lines {
 389                         let diff = match bytes_per_diff {
 390                             1 => d.read_u8()? as u32,
 391                             2 => d.read_u16()? as u32,
 392                             4 => d.read_u32()?,
 393                             _ => unreachable!()
 394                         };
 395
 396                         line_start = line_start + BytePos(diff);
 397
 398                         lines.push(line_start);
 399                     }
 400                 }
 401
 402                 Ok(lines)
 403             })?;
 404             let multibyte_chars: Vec<MultiByteChar> =
 405                 d.read_struct_field("multibyte_chars", 5, |d| Decodable::decode(d))?;
 406             Ok(FileMap {
 407                 name: name,
 408                 abs_path: abs_path,
 409                 start_pos: start_pos,
 410                 end_pos: end_pos,
 411                 src: None,
 412                 lines: RefCell::new(lines),
 413                 multibyte_chars: RefCell::new(multibyte_chars)
 414             })
 415         })
 416     }
 417 }
 418
 419 impl fmt::Debug for FileMap {
 420     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
 421         write!(fmt, "FileMap({})", self.name)
 422     }
 423 }
 424
 425 impl FileMap {
 426     /// EFFECT: register a start-of-line offset in the
 427     /// table of line-beginnings.
 428     /// UNCHECKED INVARIANT: these offsets must be added in the right
 429     /// order and must be in the right places; there is shared knowledge
 430     /// about what ends a line between this file and parse.rs
 431     /// WARNING: pos param here is the offset relative to start of CodeMap,
 432     /// and CodeMap will append a newline when adding a filemap without a newline at the end,
 433     /// so the safe way to call this is with value calculated as
 434     /// filemap.start_pos + newline_offset_relative_to_the_start_of_filemap.
 435     pub fn next_line(&self, pos: BytePos) {
 436         // the new charpos must be > the last one (or it's the first one).
 437         let mut lines = self.lines.borrow_mut();
 438         let line_len = lines.len();
 439         assert!(line_len == 0 || ((*lines)[line_len - 1] < pos));
 440         lines.push(pos);
 441     }
 442
 443     /// get a line from the list of pre-computed line-beginnings.
 444     /// line-number here is 0-based.
 445     pub fn get_line(&self, line_number: usize) -> Option<&str> {
 446         match self.src {
 447             Some(ref src) => {
 448                 let lines = self.lines.borrow();
 449                 lines.get(line_number).map(|&line| {
 450                     let begin: BytePos = line - self.start_pos;
 451                     let begin = begin.to_usize();
 452                     // We can't use `lines.get(line_number+1)` because we might
 453                     // be parsing when we call this function and thus the current
 454                     // line is the last one we have line info for.
 455                     let slice = &src[begin..];
 456                     match slice.find('\n') {
 457                         Some(e) => &slice[..e],
 458                         None => slice
 459                     }
 460                 })
 461             }
 462             None => None
 463         }
 464     }
 465
 466     pub fn record_multibyte_char(&self, pos: BytePos, bytes: usize) {
 467         assert!(bytes >=2 && bytes <= 4);
 468         let mbc = MultiByteChar {
 469             pos: pos,
 470             bytes: bytes,
 471         };
 472         self.multibyte_chars.borrow_mut().push(mbc);
 473     }
 474
 475     pub fn is_real_file(&self) -> bool {
 476         !(self.name.starts_with("<") &&
 477           self.name.ends_with(">"))
 478     }
 479
 480     pub fn is_imported(&self) -> bool {
 481         self.src.is_none()
 482     }
 483
 484     pub fn byte_length(&self) -> u32 {
 485         self.end_pos.0 - self.start_pos.0
 486     }
 487     pub fn count_lines(&self) -> usize {
 488         self.lines.borrow().len()
 489     }
 490
 491     /// Find the line containing the given position. The return value is the
 492     /// index into the `lines` array of this FileMap, not the 1-based line
 493     /// number. If the filemap is empty or the position is located before the
 494     /// first line, None is returned.
 495     pub fn lookup_line(&self, pos: BytePos) -> Option<usize> {
 496         let lines = self.lines.borrow();
 497         if lines.len() == 0 {
 498             return None;
 499         }
 500
 501         let line_index = lookup_line(&lines[..], pos);
 502         assert!(line_index < lines.len() as isize);
 503         if line_index >= 0 {
 504             Some(line_index as usize)
 505         } else {
 506             None
 507         }
 508     }
 509
 510     pub fn line_bounds(&self, line_index: usize) -> (BytePos, BytePos) {
 511         if self.start_pos == self.end_pos {
 512             return (self.start_pos, self.end_pos);
 513         }
 514
 515         let lines = self.lines.borrow();
 516         assert!(line_index < lines.len());
 517         if line_index == (lines.len() - 1) {
 518             (lines[line_index], self.end_pos)
 519         } else {
 520             (lines[line_index], lines[line_index + 1])
 521         }
 522     }
 523 }
 524
 525 // _____________________________________________________________________________
 526 // Pos, BytePos, CharPos
 527 //
 528
 529 pub trait Pos {
 530     fn from_usize(n: usize) -> Self;
 531     fn to_usize(&self) -> usize;
 532 }
 533
 534 /// A byte offset. Keep this small (currently 32-bits), as AST contains
 535 /// a lot of them.
 536 #[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
 537 pub struct BytePos(pub u32);
 538
 539 /// A character offset. Because of multibyte utf8 characters, a byte offset
 540 /// is not equivalent to a character offset. The CodeMap will convert BytePos
 541 /// values to CharPos values as necessary.
 542 #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
 543 pub struct CharPos(pub usize);
 544
 545 // FIXME: Lots of boilerplate in these impls, but so far my attempts to fix
 546 // have been unsuccessful
 547
 548 impl Pos for BytePos {
 549     fn from_usize(n: usize) -> BytePos { BytePos(n as u32) }
 550     fn to_usize(&self) -> usize { let BytePos(n) = *self; n as usize }
 551 }
 552
 553 impl Add for BytePos {
 554     type Output = BytePos;
 555
 556     fn add(self, rhs: BytePos) -> BytePos {
 557         BytePos((self.to_usize() + rhs.to_usize()) as u32)
 558     }
 559 }
 560
 561 impl Sub for BytePos {
 562     type Output = BytePos;
 563
 564     fn sub(self, rhs: BytePos) -> BytePos {
 565         BytePos((self.to_usize() - rhs.to_usize()) as u32)
 566     }
 567 }
 568
 569 impl Encodable for BytePos {
 570     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 571         s.emit_u32(self.0)
 572     }
 573 }
 574
 575 impl Decodable for BytePos {
 576     fn decode<D: Decoder>(d: &mut D) -> Result<BytePos, D::Error> {
 577         Ok(BytePos(d.read_u32()?))
 578     }
 579 }
 580
 581 impl Pos for CharPos {
 582     fn from_usize(n: usize) -> CharPos { CharPos(n) }
 583     fn to_usize(&self) -> usize { let CharPos(n) = *self; n }
 584 }
 585
 586 impl Add for CharPos {
 587     type Output = CharPos;
 588
 589     fn add(self, rhs: CharPos) -> CharPos {
 590         CharPos(self.to_usize() + rhs.to_usize())
 591     }
 592 }
 593
 594 impl Sub for CharPos {
 595     type Output = CharPos;
 596
 597     fn sub(self, rhs: CharPos) -> CharPos {
 598         CharPos(self.to_usize() - rhs.to_usize())
 599     }
 600 }
 601
 602 // _____________________________________________________________________________
 603 // Loc, LocWithOpt, FileMapAndLine, FileMapAndBytePos
 604 //
 605
 606 /// A source code location used for error reporting
 607 #[derive(Debug, Clone)]
 608 pub struct Loc {
 609     /// Information about the original source
 610     pub file: Rc<FileMap>,
 611     /// The (1-based) line number
 612     pub line: usize,
 613     /// The (0-based) column offset
 614     pub col: CharPos
 615 }
 616
 617 /// A source code location used as the result of lookup_char_pos_adj
 618 // Actually, *none* of the clients use the filename *or* file field;
 619 // perhaps they should just be removed.
 620 #[derive(Debug)]
 621 pub struct LocWithOpt {
 622     pub filename: FileName,
 623     pub line: usize,
 624     pub col: CharPos,
 625     pub file: Option<Rc<FileMap>>,
 626 }
 627
 628 // used to be structural records. Better names, anyone?
 629 #[derive(Debug)]
 630 pub struct FileMapAndLine { pub fm: Rc<FileMap>, pub line: usize }
 631 #[derive(Debug)]
 632 pub struct FileMapAndBytePos { pub fm: Rc<FileMap>, pub pos: BytePos }
 633
 634 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 635 pub struct LineInfo {
 636     /// Index of line, starting from 0.
 637     pub line_index: usize,
 638
 639     /// Column in line where span begins, starting from 0.
 640     pub start_col: CharPos,
 641
 642     /// Column in line where span ends, starting from 0, exclusive.
 643     pub end_col: CharPos,
 644 }
 645
 646 pub struct FileLines {
 647     pub file: Rc<FileMap>,
 648     pub lines: Vec<LineInfo>
 649 }
 650
 651 thread_local!(pub static SPAN_DEBUG: Cell<fn(Span, &mut fmt::Formatter) -> fmt::Result> =
 652                 Cell::new(default_span_debug));
 653
 654 /* assuming that we're not in macro expansion */
 655 pub fn mk_sp(lo: BytePos, hi: BytePos) -> Span {
 656     Span {lo: lo, hi: hi, expn_id: NO_EXPANSION}
 657 }
 658
 659 pub struct MacroBacktrace {
 660     /// span where macro was applied to generate this code
 661     pub call_site: Span,
 662
 663     /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
 664     pub macro_decl_name: String,
 665
 666     /// span where macro was defined (if known)
 667     pub def_site_span: Option<Span>,
 668 }
 669
 670 // _____________________________________________________________________________
 671 // SpanLinesError, SpanSnippetError, DistinctSources, MalformedCodemapPositions
 672 //
 673
 674 pub type FileLinesResult = Result<FileLines, SpanLinesError>;
 675
 676 #[derive(Clone, PartialEq, Eq, Debug)]
 677 pub enum SpanLinesError {
 678     IllFormedSpan(Span),
 679     DistinctSources(DistinctSources),
 680 }
 681
 682 #[derive(Clone, PartialEq, Eq, Debug)]
 683 pub enum SpanSnippetError {
 684     IllFormedSpan(Span),
 685     DistinctSources(DistinctSources),
 686     MalformedForCodemap(MalformedCodemapPositions),
 687     SourceNotAvailable { filename: String }
 688 }
 689
 690 #[derive(Clone, PartialEq, Eq, Debug)]
 691 pub struct DistinctSources {
 692     pub begin: (String, BytePos),
 693     pub end: (String, BytePos)
 694 }
 695
 696 #[derive(Clone, PartialEq, Eq, Debug)]
 697 pub struct MalformedCodemapPositions {
 698     pub name: String,
 699     pub source_len: usize,
 700     pub begin_pos: BytePos,
 701     pub end_pos: BytePos
 702 }
 703
 704 // Given a slice of line start positions and a position, returns the index of
 705 // the line the position is on. Returns -1 if the position is located before
 706 // the first line.
 707 fn lookup_line(lines: &[BytePos], pos: BytePos) -> isize {
 708     match lines.binary_search(&pos) {
 709         Ok(line) => line as isize,
 710         Err(line) => line as isize - 1
 711     }
 712 }
 713
 714 #[cfg(test)]
 715 mod tests {
 716     use super::{lookup_line, BytePos};
 717
 718     #[test]
 719     fn test_lookup_line() {
 720
 721         let lines = &[BytePos(3), BytePos(17), BytePos(28)];
 722
 723         assert_eq!(lookup_line(lines, BytePos(0)), -1);
 724         assert_eq!(lookup_line(lines, BytePos(3)),  0);
 725         assert_eq!(lookup_line(lines, BytePos(4)),  0);
 726
 727         assert_eq!(lookup_line(lines, BytePos(16)), 0);
 728         assert_eq!(lookup_line(lines, BytePos(17)), 1);
 729         assert_eq!(lookup_line(lines, BytePos(18)), 1);
 730
 731         assert_eq!(lookup_line(lines, BytePos(28)), 2);
 732         assert_eq!(lookup_line(lines, BytePos(29)), 2);
 733     }
 734 }