mv (mod) codemap source_map

1 files changed, 1235 insertions, 0 deletions

diff --git a/src/libsyntax/source_map.rs b/src/libsyntax/source_map.rs
new file mode 100644
index 00000000000..34cd026f7a0
--- /dev/null
+++ b/src/libsyntax/source_map.rs
@@ -0,0 +1,1235 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The SourceMap tracks all the source code used within a single crate, mapping
+//! from integer byte positions to the original source code location. Each bit
+//! of source parsed during crate parsing (typically files, in-memory strings,
+//! or various bits of macro expansion) cover a continuous range of bytes in the
+//! SourceMap and are represented by SourceFiles. Byte positions are stored in
+//! `spans` and used pervasively in the compiler. They are absolute positions
+//! within the SourceMap, which upon request can be converted to line and column
+//! information, source code snippets, etc.
+
+
+pub use syntax_pos::*;
+pub use syntax_pos::hygiene::{ExpnFormat, ExpnInfo};
+pub use self::ExpnFormat::*;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_hasher::StableHasher;
+use rustc_data_structures::sync::{Lrc, Lock, LockGuard};
+use std::cmp;
+use std::hash::Hash;
+use std::path::{Path, PathBuf};
+
+use std::env;
+use std::fs;
+use std::io::{self, Read};
+use errors::SourceMapper;
+
+/// Return the span itself if it doesn't come from a macro expansion,
+/// otherwise return the call site span up to the `enclosing_sp` by
+/// following the `expn_info` chain.
+pub fn original_sp(sp: Span, enclosing_sp: Span) -> Span {
+    let call_site1 = sp.ctxt().outer().expn_info().map(|ei| ei.call_site);
+    let call_site2 = enclosing_sp.ctxt().outer().expn_info().map(|ei| ei.call_site);
+    match (call_site1, call_site2) {
+        (None, _) => sp,
+        (Some(call_site1), Some(call_site2)) if call_site1 == call_site2 => sp,
+        (Some(call_site1), _) => original_sp(call_site1, enclosing_sp),
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
+pub struct Spanned<T> {
+    pub node: T,
+    pub span: Span,
+}
+
+pub fn respan<T>(sp: Span, t: T) -> Spanned<T> {
+    Spanned {node: t, span: sp}
+}
+
+pub fn dummy_spanned<T>(t: T) -> Spanned<T> {
+    respan(DUMMY_SP, t)
+}
+
+// _____________________________________________________________________________
+// SourceFile, MultiByteChar, FileName, FileLines
+//
+
+/// An abstraction over the fs operations used by the Parser.
+pub trait FileLoader {
+    /// Query the existence of a file.
+    fn file_exists(&self, path: &Path) -> bool;
+
+    /// Return an absolute path to a file, if possible.
+    fn abs_path(&self, path: &Path) -> Option<PathBuf>;
+
+    /// Read the contents of an UTF-8 file into memory.
+    fn read_file(&self, path: &Path) -> io::Result<String>;
+}
+
+/// A FileLoader that uses std::fs to load real files.
+pub struct RealFileLoader;
+
+impl FileLoader for RealFileLoader {
+    fn file_exists(&self, path: &Path) -> bool {
+        fs::metadata(path).is_ok()
+    }
+
+    fn abs_path(&self, path: &Path) -> Option<PathBuf> {
+        if path.is_absolute() {
+            Some(path.to_path_buf())
+        } else {
+            env::current_dir()
+                .ok()
+                .map(|cwd| cwd.join(path))
+        }
+    }
+
+    fn read_file(&self, path: &Path) -> io::Result<String> {
+        let mut src = String::new();
+        fs::File::open(path)?.read_to_string(&mut src)?;
+        Ok(src)
+    }
+}
+
+// This is a SourceFile identifier that is used to correlate SourceFiles between
+// subsequent compilation sessions (which is something we need to do during
+// incremental compilation).
+#[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
+pub struct StableFilemapId(u128);
+
+impl StableFilemapId {
+    pub fn new(source_file: &SourceFile) -> StableFilemapId {
+        let mut hasher = StableHasher::new();
+
+        source_file.name.hash(&mut hasher);
+        source_file.name_was_remapped.hash(&mut hasher);
+        source_file.unmapped_path.hash(&mut hasher);
+
+        StableFilemapId(hasher.finish())
+    }
+}
+
+// _____________________________________________________________________________
+// SourceMap
+//
+
+pub(super) struct SourceMapFiles {
+    pub(super) file_maps: Vec<Lrc<SourceFile>>,
+    stable_id_to_source_file: FxHashMap<StableFilemapId, Lrc<SourceFile>>
+}
+
+pub struct SourceMap {
+    pub(super) files: Lock<SourceMapFiles>,
+    file_loader: Box<dyn FileLoader + Sync + Send>,
+    // This is used to apply the file path remapping as specified via
+    // --remap-path-prefix to all SourceFiles allocated within this SourceMap.
+    path_mapping: FilePathMapping,
+    /// In case we are in a doctest, replace all file names with the PathBuf,
+    /// and add the given offsets to the line info
+    doctest_offset: Option<(FileName, isize)>,
+}
+
+impl SourceMap {
+    pub fn new(path_mapping: FilePathMapping) -> SourceMap {
+        SourceMap {
+            files: Lock::new(SourceMapFiles {
+                file_maps: Vec::new(),
+                stable_id_to_source_file: FxHashMap(),
+            }),
+            file_loader: Box::new(RealFileLoader),
+            path_mapping,
+            doctest_offset: None,
+        }
+    }
+
+    pub fn new_doctest(path_mapping: FilePathMapping,
+                       file: FileName, line: isize) -> SourceMap {
+        SourceMap {
+            doctest_offset: Some((file, line)),
+            ..SourceMap::new(path_mapping)
+        }
+
+    }
+
+    pub fn with_file_loader(file_loader: Box<dyn FileLoader + Sync + Send>,
+                            path_mapping: FilePathMapping)
+                            -> SourceMap {
+        SourceMap {
+            files: Lock::new(SourceMapFiles {
+                file_maps: Vec::new(),
+                stable_id_to_source_file: FxHashMap(),
+            }),
+            file_loader: file_loader,
+            path_mapping,
+            doctest_offset: None,
+        }
+    }
+
+    pub fn path_mapping(&self) -> &FilePathMapping {
+        &self.path_mapping
+    }
+
+    pub fn file_exists(&self, path: &Path) -> bool {
+        self.file_loader.file_exists(path)
+    }
+
+    pub fn load_file(&self, path: &Path) -> io::Result<Lrc<SourceFile>> {
+        let src = self.file_loader.read_file(path)?;
+        let filename = if let Some((ref name, _)) = self.doctest_offset {
+            name.clone()
+        } else {
+            path.to_owned().into()
+        };
+        Ok(self.new_source_file(filename, src))
+    }
+
+    pub fn files(&self) -> LockGuard<Vec<Lrc<SourceFile>>> {
+        LockGuard::map(self.files.borrow(), |files| &mut files.file_maps)
+    }
+
+    pub fn source_file_by_stable_id(&self, stable_id: StableFilemapId) -> Option<Lrc<SourceFile>> {
+        self.files.borrow().stable_id_to_source_file.get(&stable_id).map(|fm| fm.clone())
+    }
+
+    fn next_start_pos(&self) -> usize {
+        match self.files.borrow().file_maps.last() {
+            None => 0,
+            // Add one so there is some space between files. This lets us distinguish
+            // positions in the codemap, even in the presence of zero-length files.
+            Some(last) => last.end_pos.to_usize() + 1,
+        }
+    }
+
+    /// Creates a new source_file.
+    /// This does not ensure that only one SourceFile exists per file name.
+    pub fn new_source_file(&self, filename: FileName, src: String) -> Lrc<SourceFile> {
+        let start_pos = self.next_start_pos();
+
+        // The path is used to determine the directory for loading submodules and
+        // include files, so it must be before remapping.
+        // Note that filename may not be a valid path, eg it may be `<anon>` etc,
+        // but this is okay because the directory determined by `path.pop()` will
+        // be empty, so the working directory will be used.
+        let unmapped_path = filename.clone();
+
+        let (filename, was_remapped) = match filename {
+            FileName::Real(filename) => {
+                let (filename, was_remapped) = self.path_mapping.map_prefix(filename);
+                (FileName::Real(filename), was_remapped)
+            },
+            other => (other, false),
+        };
+        let source_file = Lrc::new(SourceFile::new(
+            filename,
+            was_remapped,
+            unmapped_path,
+            src,
+            Pos::from_usize(start_pos),
+        ));
+
+        let mut files = self.files.borrow_mut();
+
+        files.file_maps.push(source_file.clone());
+        files.stable_id_to_source_file.insert(StableFilemapId::new(&source_file), source_file.clone());
+
+        source_file
+    }
+
+    /// Allocates a new SourceFile representing a source file from an external
+    /// crate. The source code of such an "imported source_file" is not available,
+    /// but we still know enough to generate accurate debuginfo location
+    /// information for things inlined from other crates.
+    pub fn new_imported_source_file(&self,
+                                filename: FileName,
+                                name_was_remapped: bool,
+                                crate_of_origin: u32,
+                                src_hash: u128,
+                                name_hash: u128,
+                                source_len: usize,
+                                mut file_local_lines: Vec<BytePos>,
+                                mut file_local_multibyte_chars: Vec<MultiByteChar>,
+                                mut file_local_non_narrow_chars: Vec<NonNarrowChar>)
+                                -> Lrc<SourceFile> {
+        let start_pos = self.next_start_pos();
+
+        let end_pos = Pos::from_usize(start_pos + source_len);
+        let start_pos = Pos::from_usize(start_pos);
+
+        for pos in &mut file_local_lines {
+            *pos = *pos + start_pos;
+        }
+
+        for mbc in &mut file_local_multibyte_chars {
+            mbc.pos = mbc.pos + start_pos;
+        }
+
+        for swc in &mut file_local_non_narrow_chars {
+            *swc = *swc + start_pos;
+        }
+
+        let source_file = Lrc::new(SourceFile {
+            name: filename,
+            name_was_remapped,
+            unmapped_path: None,
+            crate_of_origin,
+            src: None,
+            src_hash,
+            external_src: Lock::new(ExternalSource::AbsentOk),
+            start_pos,
+            end_pos,
+            lines: file_local_lines,
+            multibyte_chars: file_local_multibyte_chars,
+            non_narrow_chars: file_local_non_narrow_chars,
+            name_hash,
+        });
+
+        let mut files = self.files.borrow_mut();
+
+        files.file_maps.push(source_file.clone());
+        files.stable_id_to_source_file.insert(StableFilemapId::new(&source_file), source_file.clone());
+
+        source_file
+    }
+
+    pub fn mk_substr_filename(&self, sp: Span) -> String {
+        let pos = self.lookup_char_pos(sp.lo());
+        format!("<{}:{}:{}>",
+                 pos.file.name,
+                 pos.line,
+                 pos.col.to_usize() + 1)
+    }
+
+    // If there is a doctest_offset, apply it to the line
+    pub fn doctest_offset_line(&self, mut orig: usize) -> usize {
+        if let Some((_, line)) = self.doctest_offset {
+            if line >= 0 {
+                orig = orig + line as usize;
+            } else {
+                orig = orig - (-line) as usize;
+            }
+        }
+        orig
+    }
+
+    /// Lookup source information about a BytePos
+    pub fn lookup_char_pos(&self, pos: BytePos) -> Loc {
+        let chpos = self.bytepos_to_file_charpos(pos);
+        match self.lookup_line(pos) {
+            Ok(SourceFileAndLine { fm: f, line: a }) => {
+                let line = a + 1; // Line numbers start at 1
+                let linebpos = f.lines[a];
+                let linechpos = self.bytepos_to_file_charpos(linebpos);
+                let col = chpos - linechpos;
+
+                let col_display = {
+                    let start_width_idx = f
+                        .non_narrow_chars
+                        .binary_search_by_key(&linebpos, |x| x.pos())
+                        .unwrap_or_else(|x| x);
+                    let end_width_idx = f
+                        .non_narrow_chars
+                        .binary_search_by_key(&pos, |x| x.pos())
+                        .unwrap_or_else(|x| x);
+                    let special_chars = end_width_idx - start_width_idx;
+                    let non_narrow: usize = f
+                        .non_narrow_chars[start_width_idx..end_width_idx]
+                        .into_iter()
+                        .map(|x| x.width())
+                        .sum();
+                    col.0 - special_chars + non_narrow
+                };
+                debug!("byte pos {:?} is on the line at byte pos {:?}",
+                       pos, linebpos);
+                debug!("char pos {:?} is on the line at char pos {:?}",
+                       chpos, linechpos);
+                debug!("byte is on line: {}", line);
+                assert!(chpos >= linechpos);
+                Loc {
+                    file: f,
+                    line,
+                    col,
+                    col_display,
+                }
+            }
+            Err(f) => {
+                let col_display = {
+                    let end_width_idx = f
+                        .non_narrow_chars
+                        .binary_search_by_key(&pos, |x| x.pos())
+                        .unwrap_or_else(|x| x);
+                    let non_narrow: usize = f
+                        .non_narrow_chars[0..end_width_idx]
+                        .into_iter()
+                        .map(|x| x.width())
+                        .sum();
+                    chpos.0 - end_width_idx + non_narrow
+                };
+                Loc {
+                    file: f,
+                    line: 0,
+                    col: chpos,
+                    col_display,
+                }
+            }
+        }
+    }
+
+    // If the relevant source_file is empty, we don't return a line number.
+    pub fn lookup_line(&self, pos: BytePos) -> Result<SourceFileAndLine, Lrc<SourceFile>> {
+        let idx = self.lookup_source_file_idx(pos);
+
+        let f = (*self.files.borrow().file_maps)[idx].clone();
+
+        match f.lookup_line(pos) {
+            Some(line) => Ok(SourceFileAndLine { fm: f, line: line }),
+            None => Err(f)
+        }
+    }
+
+    pub fn lookup_char_pos_adj(&self, pos: BytePos) -> LocWithOpt {
+        let loc = self.lookup_char_pos(pos);
+        LocWithOpt {
+            filename: loc.file.name.clone(),
+            line: loc.line,
+            col: loc.col,
+            file: Some(loc.file)
+        }
+    }
+
+    /// Returns `Some(span)`, a union of the lhs and rhs span.  The lhs must precede the rhs. If
+    /// there are gaps between lhs and rhs, the resulting union will cross these gaps.
+    /// For this to work, the spans have to be:
+    ///
+    ///    * the ctxt of both spans much match
+    ///    * the lhs span needs to end on the same line the rhs span begins
+    ///    * the lhs span must start at or before the rhs span
+    pub fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
+        // make sure we're at the same expansion id
+        if sp_lhs.ctxt() != sp_rhs.ctxt() {
+            return None;
+        }
+
+        let lhs_end = match self.lookup_line(sp_lhs.hi()) {
+            Ok(x) => x,
+            Err(_) => return None
+        };
+        let rhs_begin = match self.lookup_line(sp_rhs.lo()) {
+            Ok(x) => x,
+            Err(_) => return None
+        };
+
+        // if we must cross lines to merge, don't merge
+        if lhs_end.line != rhs_begin.line {
+            return None;
+        }
+
+        // ensure these follow the expected order and we don't overlap
+        if (sp_lhs.lo() <= sp_rhs.lo()) && (sp_lhs.hi() <= sp_rhs.lo()) {
+            Some(sp_lhs.to(sp_rhs))
+        } else {
+            None
+        }
+    }
+
+    pub fn span_to_string(&self, sp: Span) -> String {
+        if self.files.borrow().file_maps.is_empty() && sp.is_dummy() {
+            return "no-location".to_string();
+        }
+
+        let lo = self.lookup_char_pos_adj(sp.lo());
+        let hi = self.lookup_char_pos_adj(sp.hi());
+        format!("{}:{}:{}: {}:{}",
+                        lo.filename,
+                        lo.line,
+                        lo.col.to_usize() + 1,
+                        hi.line,
+                        hi.col.to_usize() + 1)
+    }
+
+    pub fn span_to_filename(&self, sp: Span) -> FileName {
+        self.lookup_char_pos(sp.lo()).file.name.clone()
+    }
+
+    pub fn span_to_unmapped_path(&self, sp: Span) -> FileName {
+        self.lookup_char_pos(sp.lo()).file.unmapped_path.clone()
+            .expect("SourceMap::span_to_unmapped_path called for imported SourceFile?")
+    }
+
+    pub fn is_multiline(&self, sp: Span) -> bool {
+        let lo = self.lookup_char_pos(sp.lo());
+        let hi = self.lookup_char_pos(sp.hi());
+        lo.line != hi.line
+    }
+
+    pub fn span_to_lines(&self, sp: Span) -> FileLinesResult {
+        debug!("span_to_lines(sp={:?})", sp);
+
+        if sp.lo() > sp.hi() {
+            return Err(SpanLinesError::IllFormedSpan(sp));
+        }
+
+        let lo = self.lookup_char_pos(sp.lo());
+        debug!("span_to_lines: lo={:?}", lo);
+        let hi = self.lookup_char_pos(sp.hi());
+        debug!("span_to_lines: hi={:?}", hi);
+
+        if lo.file.start_pos != hi.file.start_pos {
+            return Err(SpanLinesError::DistinctSources(DistinctSources {
+                begin: (lo.file.name.clone(), lo.file.start_pos),
+                end: (hi.file.name.clone(), hi.file.start_pos),
+            }));
+        }
+        assert!(hi.line >= lo.line);
+
+        let mut lines = Vec::with_capacity(hi.line - lo.line + 1);
+
+        // The span starts partway through the first line,
+        // but after that it starts from offset 0.
+        let mut start_col = lo.col;
+
+        // For every line but the last, it extends from `start_col`
+        // and to the end of the line. Be careful because the line
+        // numbers in Loc are 1-based, so we subtract 1 to get 0-based
+        // lines.
+        for line_index in lo.line-1 .. hi.line-1 {
+            let line_len = lo.file.get_line(line_index)
+                                  .map(|s| s.chars().count())
+                                  .unwrap_or(0);
+            lines.push(LineInfo { line_index,
+                                  start_col,
+                                  end_col: CharPos::from_usize(line_len) });
+            start_col = CharPos::from_usize(0);
+        }
+
+        // For the last line, it extends from `start_col` to `hi.col`:
+        lines.push(LineInfo { line_index: hi.line - 1,
+                              start_col,
+                              end_col: hi.col });
+
+        Ok(FileLines {file: lo.file, lines: lines})
+    }
+
+    /// Extract the source surrounding the given `Span` using the `extract_source` function. The
+    /// extract function takes three arguments: a string slice containing the source, an index in
+    /// the slice for the beginning of the span and an index in the slice for the end of the span.
+    fn span_to_source<F>(&self, sp: Span, extract_source: F) -> Result<String, SpanSnippetError>
+        where F: Fn(&str, usize, usize) -> String
+    {
+        if sp.lo() > sp.hi() {
+            return Err(SpanSnippetError::IllFormedSpan(sp));
+        }
+
+        let local_begin = self.lookup_byte_offset(sp.lo());
+        let local_end = self.lookup_byte_offset(sp.hi());
+
+        if local_begin.fm.start_pos != local_end.fm.start_pos {
+            return Err(SpanSnippetError::DistinctSources(DistinctSources {
+                begin: (local_begin.fm.name.clone(),
+                        local_begin.fm.start_pos),
+                end: (local_end.fm.name.clone(),
+                      local_end.fm.start_pos)
+            }));
+        } else {
+            self.ensure_source_file_source_present(local_begin.fm.clone());
+
+            let start_index = local_begin.pos.to_usize();
+            let end_index = local_end.pos.to_usize();
+            let source_len = (local_begin.fm.end_pos -
+                              local_begin.fm.start_pos).to_usize();
+
+            if start_index > end_index || end_index > source_len {
+                return Err(SpanSnippetError::MalformedForCodemap(
+                    MalformedCodemapPositions {
+                        name: local_begin.fm.name.clone(),
+                        source_len,
+                        begin_pos: local_begin.pos,
+                        end_pos: local_end.pos,
+                    }));
+            }
+
+            if let Some(ref src) = local_begin.fm.src {
+                return Ok(extract_source(src, start_index, end_index));
+            } else if let Some(src) = local_begin.fm.external_src.borrow().get_source() {
+                return Ok(extract_source(src, start_index, end_index));
+            } else {
+                return Err(SpanSnippetError::SourceNotAvailable {
+                    filename: local_begin.fm.name.clone()
+                });
+            }
+        }
+    }
+
+    /// Return the source snippet as `String` corresponding to the given `Span`
+    pub fn span_to_snippet(&self, sp: Span) -> Result<String, SpanSnippetError> {
+        self.span_to_source(sp, |src, start_index, end_index| src[start_index..end_index]
+                                                                .to_string())
+    }
+
+    /// Return the source snippet as `String` before the given `Span`
+    pub fn span_to_prev_source(&self, sp: Span) -> Result<String, SpanSnippetError> {
+        self.span_to_source(sp, |src, start_index, _| src[..start_index].to_string())
+    }
+
+    /// Extend the given `Span` to just after the previous occurrence of `c`. Return the same span
+    /// if no character could be found or if an error occurred while retrieving the code snippet.
+    pub fn span_extend_to_prev_char(&self, sp: Span, c: char) -> Span {
+        if let Ok(prev_source) = self.span_to_prev_source(sp) {
+            let prev_source = prev_source.rsplit(c).nth(0).unwrap_or("").trim_left();
+            if !prev_source.is_empty() && !prev_source.contains('\n') {
+                return sp.with_lo(BytePos(sp.lo().0 - prev_source.len() as u32));
+            }
+        }
+
+        sp
+    }
+
+    /// Extend the given `Span` to just after the previous occurrence of `pat` when surrounded by
+    /// whitespace. Return the same span if no character could be found or if an error occurred
+    /// while retrieving the code snippet.
+    pub fn span_extend_to_prev_str(&self, sp: Span, pat: &str, accept_newlines: bool) -> Span {
+        // assure that the pattern is delimited, to avoid the following
+        //     fn my_fn()
+        //           ^^^^ returned span without the check
+        //     ---------- correct span
+        for ws in &[" ", "\t", "\n"] {
+            let pat = pat.to_owned() + ws;
+            if let Ok(prev_source) = self.span_to_prev_source(sp) {
+                let prev_source = prev_source.rsplit(&pat).nth(0).unwrap_or("").trim_left();
+                if !prev_source.is_empty() && (!prev_source.contains('\n') || accept_newlines) {
+                    return sp.with_lo(BytePos(sp.lo().0 - prev_source.len() as u32));
+                }
+            }
+        }
+
+        sp
+    }
+
+    /// Given a `Span`, try to get a shorter span ending before the first occurrence of `c` `char`
+    pub fn span_until_char(&self, sp: Span, c: char) -> Span {
+        match self.span_to_snippet(sp) {
+            Ok(snippet) => {
+                let snippet = snippet.split(c).nth(0).unwrap_or("").trim_right();
+                if !snippet.is_empty() && !snippet.contains('\n') {
+                    sp.with_hi(BytePos(sp.lo().0 + snippet.len() as u32))
+                } else {
+                    sp
+                }
+            }
+            _ => sp,
+        }
+    }
+
+    /// Given a `Span`, try to get a shorter span ending just after the first occurrence of `char`
+    /// `c`.
+    pub fn span_through_char(&self, sp: Span, c: char) -> Span {
+        if let Ok(snippet) = self.span_to_snippet(sp) {
+            if let Some(offset) = snippet.find(c) {
+                return sp.with_hi(BytePos(sp.lo().0 + (offset + c.len_utf8()) as u32));
+            }
+        }
+        sp
+    }
+
+    /// Given a `Span`, get a new `Span` covering the first token and all its trailing whitespace or
+    /// the original `Span`.
+    ///
+    /// If `sp` points to `"let mut x"`, then a span pointing at `"let "` will be returned.
+    pub fn span_until_non_whitespace(&self, sp: Span) -> Span {
+        let mut whitespace_found = false;
+
+        self.span_take_while(sp, |c| {
+            if !whitespace_found && c.is_whitespace() {
+                whitespace_found = true;
+            }
+
+            if whitespace_found && !c.is_whitespace() {
+                false
+            } else {
+                true
+            }
+        })
+    }
+
+    /// Given a `Span`, get a new `Span` covering the first token without its trailing whitespace or
+    /// the original `Span` in case of error.
+    ///
+    /// If `sp` points to `"let mut x"`, then a span pointing at `"let"` will be returned.
+    pub fn span_until_whitespace(&self, sp: Span) -> Span {
+        self.span_take_while(sp, |c| !c.is_whitespace())
+    }
+
+    /// Given a `Span`, get a shorter one until `predicate` yields false.
+    pub fn span_take_while<P>(&self, sp: Span, predicate: P) -> Span
+        where P: for <'r> FnMut(&'r char) -> bool
+    {
+        if let Ok(snippet) = self.span_to_snippet(sp) {
+            let offset = snippet.chars()
+                .take_while(predicate)
+                .map(|c| c.len_utf8())
+                .sum::<usize>();
+
+            sp.with_hi(BytePos(sp.lo().0 + (offset as u32)))
+        } else {
+            sp
+        }
+    }
+
+    pub fn def_span(&self, sp: Span) -> Span {
+        self.span_until_char(sp, '{')
+    }
+
+    /// Returns a new span representing just the start-point of this span
+    pub fn start_point(&self, sp: Span) -> Span {
+        let pos = sp.lo().0;
+        let width = self.find_width_of_character_at_span(sp, false);
+        let corrected_start_position = pos.checked_add(width).unwrap_or(pos);
+        let end_point = BytePos(cmp::max(corrected_start_position, sp.lo().0));
+        sp.with_hi(end_point)
+    }
+
+    /// Returns a new span representing just the end-point of this span
+    pub fn end_point(&self, sp: Span) -> Span {
+        let pos = sp.hi().0;
+
+        let width = self.find_width_of_character_at_span(sp, false);
+        let corrected_end_position = pos.checked_sub(width).unwrap_or(pos);
+
+        let end_point = BytePos(cmp::max(corrected_end_position, sp.lo().0));
+        sp.with_lo(end_point)
+    }
+
+    /// Returns a new span representing the next character after the end-point of this span
+    pub fn next_point(&self, sp: Span) -> Span {
+        let start_of_next_point = sp.hi().0;
+
+        let width = self.find_width_of_character_at_span(sp, true);
+        // If the width is 1, then the next span should point to the same `lo` and `hi`. However,
+        // in the case of a multibyte character, where the width != 1, the next span should
+        // span multiple bytes to include the whole character.
+        let end_of_next_point = start_of_next_point.checked_add(
+            width - 1).unwrap_or(start_of_next_point);
+
+        let end_of_next_point = BytePos(cmp::max(sp.lo().0 + 1, end_of_next_point));
+        Span::new(BytePos(start_of_next_point), end_of_next_point, sp.ctxt())
+    }
+
+    /// Finds the width of a character, either before or after the provided span.
+    fn find_width_of_character_at_span(&self, sp: Span, forwards: bool) -> u32 {
+        // Disregard malformed spans and assume a one-byte wide character.
+        if sp.lo() >= sp.hi() {
+            debug!("find_width_of_character_at_span: early return malformed span");
+            return 1;
+        }
+
+        let local_begin = self.lookup_byte_offset(sp.lo());
+        let local_end = self.lookup_byte_offset(sp.hi());
+        debug!("find_width_of_character_at_span: local_begin=`{:?}`, local_end=`{:?}`",
+               local_begin, local_end);
+
+        let start_index = local_begin.pos.to_usize();
+        let end_index = local_end.pos.to_usize();
+        debug!("find_width_of_character_at_span: start_index=`{:?}`, end_index=`{:?}`",
+               start_index, end_index);
+
+        // Disregard indexes that are at the start or end of their spans, they can't fit bigger
+        // characters.
+        if (!forwards && end_index == usize::min_value()) ||
+            (forwards && start_index == usize::max_value()) {
+            debug!("find_width_of_character_at_span: start or end of span, cannot be multibyte");
+            return 1;
+        }
+
+        let source_len = (local_begin.fm.end_pos - local_begin.fm.start_pos).to_usize();
+        debug!("find_width_of_character_at_span: source_len=`{:?}`", source_len);
+        // Ensure indexes are also not malformed.
+        if start_index > end_index || end_index > source_len {
+            debug!("find_width_of_character_at_span: source indexes are malformed");
+            return 1;
+        }
+
+        let src = local_begin.fm.external_src.borrow();
+
+        // We need to extend the snippet to the end of the src rather than to end_index so when
+        // searching forwards for boundaries we've got somewhere to search.
+        let snippet = if let Some(ref src) = local_begin.fm.src {
+            let len = src.len();
+            (&src[start_index..len])
+        } else if let Some(src) = src.get_source() {
+            let len = src.len();
+            (&src[start_index..len])
+        } else {
+            return 1;
+        };
+        debug!("find_width_of_character_at_span: snippet=`{:?}`", snippet);
+
+        let mut target = if forwards { end_index + 1 } else { end_index - 1 };
+        debug!("find_width_of_character_at_span: initial target=`{:?}`", target);
+
+        while !snippet.is_char_boundary(target - start_index) && target < source_len {
+            target = if forwards {
+                target + 1
+            } else {
+                match target.checked_sub(1) {
+                    Some(target) => target,
+                    None => {
+                        break;
+                    }
+                }
+            };
+            debug!("find_width_of_character_at_span: target=`{:?}`", target);
+        }
+        debug!("find_width_of_character_at_span: final target=`{:?}`", target);
+
+        if forwards {
+            (target - end_index) as u32
+        } else {
+            (end_index - target) as u32
+        }
+    }
+
+    pub fn get_source_file(&self, filename: &FileName) -> Option<Lrc<SourceFile>> {
+        for fm in self.files.borrow().file_maps.iter() {
+            if *filename == fm.name {
+                return Some(fm.clone());
+            }
+        }
+        None
+    }
+
+    /// For a global BytePos compute the local offset within the containing SourceFile
+    pub fn lookup_byte_offset(&self, bpos: BytePos) -> SourceFileAndBytePos {
+        let idx = self.lookup_source_file_idx(bpos);
+        let fm = (*self.files.borrow().file_maps)[idx].clone();
+        let offset = bpos - fm.start_pos;
+        SourceFileAndBytePos {fm: fm, pos: offset}
+    }
+
+    /// Converts an absolute BytePos to a CharPos relative to the source_file.
+    pub fn bytepos_to_file_charpos(&self, bpos: BytePos) -> CharPos {
+        let idx = self.lookup_source_file_idx(bpos);
+        let map = &(*self.files.borrow().file_maps)[idx];
+
+        // The number of extra bytes due to multibyte chars in the SourceFile
+        let mut total_extra_bytes = 0;
+
+        for mbc in map.multibyte_chars.iter() {
+            debug!("{}-byte char at {:?}", mbc.bytes, mbc.pos);
+            if mbc.pos < bpos {
+                // every character is at least one byte, so we only
+                // count the actual extra bytes.
+                total_extra_bytes += mbc.bytes as u32 - 1;
+                // We should never see a byte position in the middle of a
+                // character
+                assert!(bpos.to_u32() >= mbc.pos.to_u32() + mbc.bytes as u32);
+            } else {
+                break;
+            }
+        }
+
+        assert!(map.start_pos.to_u32() + total_extra_bytes <= bpos.to_u32());
+        CharPos(bpos.to_usize() - map.start_pos.to_usize() - total_extra_bytes as usize)
+    }
+
+    // Return the index of the source_file (in self.files) which contains pos.
+    pub fn lookup_source_file_idx(&self, pos: BytePos) -> usize {
+        let files = self.files.borrow();
+        let files = &files.file_maps;
+        let count = files.len();
+
+        // Binary search for the source_file.
+        let mut a = 0;
+        let mut b = count;
+        while b - a > 1 {
+            let m = (a + b) / 2;
+            if files[m].start_pos > pos {
+                b = m;
+            } else {
+                a = m;
+            }
+        }
+
+        assert!(a < count, "position {} does not resolve to a source location", pos.to_usize());
+
+        return a;
+    }
+
+    pub fn count_lines(&self) -> usize {
+        self.files().iter().fold(0, |a, f| a + f.count_lines())
+    }
+
+
+    pub fn generate_fn_name_span(&self, span: Span) -> Option<Span> {
+        let prev_span = self.span_extend_to_prev_str(span, "fn", true);
+        self.span_to_snippet(prev_span).map(|snippet| {
+            let len = snippet.find(|c: char| !c.is_alphanumeric() && c != '_')
+                .expect("no label after fn");
+            prev_span.with_hi(BytePos(prev_span.lo().0 + len as u32))
+        }).ok()
+    }
+
+    /// Take the span of a type parameter in a function signature and try to generate a span for the
+    /// function name (with generics) and a new snippet for this span with the pointed type
+    /// parameter as a new local type parameter.
+    ///
+    /// For instance:
+    /// ```rust,ignore (pseudo-Rust)
+    /// // Given span
+    /// fn my_function(param: T)
+    /// //                    ^ Original span
+    ///
+    /// // Result
+    /// fn my_function(param: T)
+    /// // ^^^^^^^^^^^ Generated span with snippet `my_function<T>`
+    /// ```
+    ///
+    /// Attention: The method used is very fragile since it essentially duplicates the work of the
+    /// parser. If you need to use this function or something similar, please consider updating the
+    /// codemap functions and this function to something more robust.
+    pub fn generate_local_type_param_snippet(&self, span: Span) -> Option<(Span, String)> {
+        // Try to extend the span to the previous "fn" keyword to retrieve the function
+        // signature
+        let sugg_span = self.span_extend_to_prev_str(span, "fn", false);
+        if sugg_span != span {
+            if let Ok(snippet) = self.span_to_snippet(sugg_span) {
+                // Consume the function name
+                let mut offset = snippet.find(|c: char| !c.is_alphanumeric() && c != '_')
+                    .expect("no label after fn");
+
+                // Consume the generics part of the function signature
+                let mut bracket_counter = 0;
+                let mut last_char = None;
+                for c in snippet[offset..].chars() {
+                    match c {
+                        '<' => bracket_counter += 1,
+                        '>' => bracket_counter -= 1,
+                        '(' => if bracket_counter == 0 { break; }
+                        _ => {}
+                    }
+                    offset += c.len_utf8();
+                    last_char = Some(c);
+                }
+
+                // Adjust the suggestion span to encompass the function name with its generics
+                let sugg_span = sugg_span.with_hi(BytePos(sugg_span.lo().0 + offset as u32));
+
+                // Prepare the new suggested snippet to append the type parameter that triggered
+                // the error in the generics of the function signature
+                let mut new_snippet = if last_char == Some('>') {
+                    format!("{}, ", &snippet[..(offset - '>'.len_utf8())])
+                } else {
+                    format!("{}<", &snippet[..offset])
+                };
+                new_snippet.push_str(&self.span_to_snippet(span).unwrap_or("T".to_string()));
+                new_snippet.push('>');
+
+                return Some((sugg_span, new_snippet));
+            }
+        }
+
+        None
+    }
+}
+
+impl SourceMapper for SourceMap {
+    fn lookup_char_pos(&self, pos: BytePos) -> Loc {
+        self.lookup_char_pos(pos)
+    }
+    fn span_to_lines(&self, sp: Span) -> FileLinesResult {
+        self.span_to_lines(sp)
+    }
+    fn span_to_string(&self, sp: Span) -> String {
+        self.span_to_string(sp)
+    }
+    fn span_to_filename(&self, sp: Span) -> FileName {
+        self.span_to_filename(sp)
+    }
+    fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
+        self.merge_spans(sp_lhs, sp_rhs)
+    }
+    fn call_span_if_macro(&self, sp: Span) -> Span {
+        if self.span_to_filename(sp.clone()).is_macros() {
+            let v = sp.macro_backtrace();
+            if let Some(use_site) = v.last() {
+                return use_site.call_site;
+            }
+        }
+        sp
+    }
+    fn ensure_source_file_source_present(&self, file_map: Lrc<SourceFile>) -> bool {
+        file_map.add_external_src(
+            || match file_map.name {
+                FileName::Real(ref name) => self.file_loader.read_file(name).ok(),
+                _ => None,
+            }
+        )
+    }
+    fn doctest_offset_line(&self, line: usize) -> usize {
+        self.doctest_offset_line(line)
+    }
+}
+
+#[derive(Clone)]
+pub struct FilePathMapping {
+    mapping: Vec<(PathBuf, PathBuf)>,
+}
+
+impl FilePathMapping {
+    pub fn empty() -> FilePathMapping {
+        FilePathMapping {
+            mapping: vec![]
+        }
+    }
+
+    pub fn new(mapping: Vec<(PathBuf, PathBuf)>) -> FilePathMapping {
+        FilePathMapping {
+            mapping,
+        }
+    }
+
+    /// Applies any path prefix substitution as defined by the mapping.
+    /// The return value is the remapped path and a boolean indicating whether
+    /// the path was affected by the mapping.
+    pub fn map_prefix(&self, path: PathBuf) -> (PathBuf, bool) {
+        // NOTE: We are iterating over the mapping entries from last to first
+        //       because entries specified later on the command line should
+        //       take precedence.
+        for &(ref from, ref to) in self.mapping.iter().rev() {
+            if let Ok(rest) = path.strip_prefix(from) {
+                return (to.join(rest), true);
+            }
+        }
+
+        (path, false)
+    }
+}
+
+// _____________________________________________________________________________
+// Tests
+//
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rustc_data_structures::sync::Lrc;
+
+    fn init_code_map() -> SourceMap {
+        let cm = SourceMap::new(FilePathMapping::empty());
+        cm.new_source_file(PathBuf::from("blork.rs").into(),
+                       "first line.\nsecond line".to_string());
+        cm.new_source_file(PathBuf::from("empty.rs").into(),
+                       "".to_string());
+        cm.new_source_file(PathBuf::from("blork2.rs").into(),
+                       "first line.\nsecond line".to_string());
+        cm
+    }
+
+    #[test]
+    fn t3() {
+        // Test lookup_byte_offset
+        let cm = init_code_map();
+
+        let fmabp1 = cm.lookup_byte_offset(BytePos(23));
+        assert_eq!(fmabp1.fm.name, PathBuf::from("blork.rs").into());
+        assert_eq!(fmabp1.pos, BytePos(23));
+
+        let fmabp1 = cm.lookup_byte_offset(BytePos(24));
+        assert_eq!(fmabp1.fm.name, PathBuf::from("empty.rs").into());
+        assert_eq!(fmabp1.pos, BytePos(0));
+
+        let fmabp2 = cm.lookup_byte_offset(BytePos(25));
+        assert_eq!(fmabp2.fm.name, PathBuf::from("blork2.rs").into());
+        assert_eq!(fmabp2.pos, BytePos(0));
+    }
+
+    #[test]
+    fn t4() {
+        // Test bytepos_to_file_charpos
+        let cm = init_code_map();
+
+        let cp1 = cm.bytepos_to_file_charpos(BytePos(22));
+        assert_eq!(cp1, CharPos(22));
+
+        let cp2 = cm.bytepos_to_file_charpos(BytePos(25));
+        assert_eq!(cp2, CharPos(0));
+    }
+
+    #[test]
+    fn t5() {
+        // Test zero-length source_files.
+        let cm = init_code_map();
+
+        let loc1 = cm.lookup_char_pos(BytePos(22));
+        assert_eq!(loc1.file.name, PathBuf::from("blork.rs").into());
+        assert_eq!(loc1.line, 2);
+        assert_eq!(loc1.col, CharPos(10));
+
+        let loc2 = cm.lookup_char_pos(BytePos(25));
+        assert_eq!(loc2.file.name, PathBuf::from("blork2.rs").into());
+        assert_eq!(loc2.line, 1);
+        assert_eq!(loc2.col, CharPos(0));
+    }
+
+    fn init_code_map_mbc() -> SourceMap {
+        let cm = SourceMap::new(FilePathMapping::empty());
+        // € is a three byte utf8 char.
+        cm.new_source_file(PathBuf::from("blork.rs").into(),
+                       "fir€st €€€€ line.\nsecond line".to_string());
+        cm.new_source_file(PathBuf::from("blork2.rs").into(),
+                       "first line€€.\n€ second line".to_string());
+        cm
+    }
+
+    #[test]
+    fn t6() {
+        // Test bytepos_to_file_charpos in the presence of multi-byte chars
+        let cm = init_code_map_mbc();
+
+        let cp1 = cm.bytepos_to_file_charpos(BytePos(3));
+        assert_eq!(cp1, CharPos(3));
+
+        let cp2 = cm.bytepos_to_file_charpos(BytePos(6));
+        assert_eq!(cp2, CharPos(4));
+
+        let cp3 = cm.bytepos_to_file_charpos(BytePos(56));
+        assert_eq!(cp3, CharPos(12));
+
+        let cp4 = cm.bytepos_to_file_charpos(BytePos(61));
+        assert_eq!(cp4, CharPos(15));
+    }
+
+    #[test]
+    fn t7() {
+        // Test span_to_lines for a span ending at the end of source_file
+        let cm = init_code_map();
+        let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
+        let file_lines = cm.span_to_lines(span).unwrap();
+
+        assert_eq!(file_lines.file.name, PathBuf::from("blork.rs").into());
+        assert_eq!(file_lines.lines.len(), 1);
+        assert_eq!(file_lines.lines[0].line_index, 1);
+    }
+
+    /// Given a string like " ~~~~~~~~~~~~ ", produces a span
+    /// converting that range. The idea is that the string has the same
+    /// length as the input, and we uncover the byte positions.  Note
+    /// that this can span lines and so on.
+    fn span_from_selection(input: &str, selection: &str) -> Span {
+        assert_eq!(input.len(), selection.len());
+        let left_index = selection.find('~').unwrap() as u32;
+        let right_index = selection.rfind('~').map(|x|x as u32).unwrap_or(left_index);
+        Span::new(BytePos(left_index), BytePos(right_index + 1), NO_EXPANSION)
+    }
+
+    /// Test span_to_snippet and span_to_lines for a span converting 3
+    /// lines in the middle of a file.
+    #[test]
+    fn span_to_snippet_and_lines_spanning_multiple_lines() {
+        let cm = SourceMap::new(FilePathMapping::empty());
+        let inputtext = "aaaaa\nbbbbBB\nCCC\nDDDDDddddd\neee\n";
+        let selection = "     \n    ~~\n~~~\n~~~~~     \n   \n";
+        cm.new_source_file(Path::new("blork.rs").to_owned().into(), inputtext.to_string());
+        let span = span_from_selection(inputtext, selection);
+
+        // check that we are extracting the text we thought we were extracting
+        assert_eq!(&cm.span_to_snippet(span).unwrap(), "BB\nCCC\nDDDDD");
+
+        // check that span_to_lines gives us the complete result with the lines/cols we expected
+        let lines = cm.span_to_lines(span).unwrap();
+        let expected = vec![
+            LineInfo { line_index: 1, start_col: CharPos(4), end_col: CharPos(6) },
+            LineInfo { line_index: 2, start_col: CharPos(0), end_col: CharPos(3) },
+            LineInfo { line_index: 3, start_col: CharPos(0), end_col: CharPos(5) }
+            ];
+        assert_eq!(lines.lines, expected);
+    }
+
+    #[test]
+    fn t8() {
+        // Test span_to_snippet for a span ending at the end of source_file
+        let cm = init_code_map();
+        let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
+        let snippet = cm.span_to_snippet(span);
+
+        assert_eq!(snippet, Ok("second line".to_string()));
+    }
+
+    #[test]
+    fn t9() {
+        // Test span_to_str for a span ending at the end of source_file
+        let cm = init_code_map();
+        let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
+        let sstr =  cm.span_to_string(span);
+
+        assert_eq!(sstr, "blork.rs:2:1: 2:12");
+    }
+
+    /// Test failing to merge two spans on different lines
+    #[test]
+    fn span_merging_fail() {
+        let cm = SourceMap::new(FilePathMapping::empty());
+        let inputtext  = "bbbb BB\ncc CCC\n";
+        let selection1 = "     ~~\n      \n";
+        let selection2 = "       \n   ~~~\n";
+        cm.new_source_file(Path::new("blork.rs").to_owned().into(), inputtext.to_owned());
+        let span1 = span_from_selection(inputtext, selection1);
+        let span2 = span_from_selection(inputtext, selection2);
+
+        assert!(cm.merge_spans(span1, span2).is_none());
+    }
+
+    /// Returns the span corresponding to the `n`th occurrence of
+    /// `substring` in `source_text`.
+    trait SourceMapExtension {
+        fn span_substr(&self,
+                    file: &Lrc<SourceFile>,
+                    source_text: &str,
+                    substring: &str,
+                    n: usize)
+                    -> Span;
+    }
+
+    impl SourceMapExtension for SourceMap {
+        fn span_substr(&self,
+                    file: &Lrc<SourceFile>,
+                    source_text: &str,
+                    substring: &str,
+                    n: usize)
+                    -> Span
+        {
+            println!("span_substr(file={:?}/{:?}, substring={:?}, n={})",
+                    file.name, file.start_pos, substring, n);
+            let mut i = 0;
+            let mut hi = 0;
+            loop {
+                let offset = source_text[hi..].find(substring).unwrap_or_else(|| {
+                    panic!("source_text `{}` does not have {} occurrences of `{}`, only {}",
+                        source_text, n, substring, i);
+                });
+                let lo = hi + offset;
+                hi = lo + substring.len();
+                if i == n {
+                    let span = Span::new(
+                        BytePos(lo as u32 + file.start_pos.0),
+                        BytePos(hi as u32 + file.start_pos.0),
+                        NO_EXPANSION,
+                    );
+                    assert_eq!(&self.span_to_snippet(span).unwrap()[..],
+                            substring);
+                    return span;
+                }
+                i += 1;
+            }
+        }
+    }
+}