compiler/rustc_span/src/source_map/tests.rs - toolchain/rustc - Git at Google

 use super::*;

 use rustc_data_structures::sync::Lrc;

 fn init_source_map() -> SourceMap {
     let sm = SourceMap::new(FilePathMapping::empty());
     sm.new_source_file(PathBuf::from("blork.rs").into(), "first line.\nsecond line".to_string());
     sm.new_source_file(PathBuf::from("empty.rs").into(), String::new());
     sm.new_source_file(PathBuf::from("blork2.rs").into(), "first line.\nsecond line".to_string());
     sm
 }

 impl SourceMap {
     /// 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 syntax contexts 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.
     fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
         // Ensure 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 that 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
         }
     }

     /// Converts an absolute `BytePos` to a `CharPos` relative to the `SourceFile`.
     fn bytepos_to_file_charpos(&self, bpos: BytePos) -> CharPos {
         let idx = self.lookup_source_file_idx(bpos);
         let sf = &(*self.files.borrow().source_files)[idx];
         sf.bytepos_to_file_charpos(bpos)
     }
 }

 /// Tests `lookup_byte_offset`.
 #[test]
 fn t3() {
     let sm = init_source_map();

     let srcfbp1 = sm.lookup_byte_offset(BytePos(23));
     assert_eq!(srcfbp1.sf.name, PathBuf::from("blork.rs").into());
     assert_eq!(srcfbp1.pos, BytePos(23));

     let srcfbp1 = sm.lookup_byte_offset(BytePos(24));
     assert_eq!(srcfbp1.sf.name, PathBuf::from("empty.rs").into());
     assert_eq!(srcfbp1.pos, BytePos(0));

     let srcfbp2 = sm.lookup_byte_offset(BytePos(25));
     assert_eq!(srcfbp2.sf.name, PathBuf::from("blork2.rs").into());
     assert_eq!(srcfbp2.pos, BytePos(0));
 }

 /// Tests `bytepos_to_file_charpos`.
 #[test]
 fn t4() {
     let sm = init_source_map();

     let cp1 = sm.bytepos_to_file_charpos(BytePos(22));
     assert_eq!(cp1, CharPos(22));

     let cp2 = sm.bytepos_to_file_charpos(BytePos(25));
     assert_eq!(cp2, CharPos(0));
 }

 /// Tests zero-length `SourceFile`s.
 #[test]
 fn t5() {
     let sm = init_source_map();

     let loc1 = sm.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 = sm.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_source_map_mbc() -> SourceMap {
     let sm = SourceMap::new(FilePathMapping::empty());
     // "€" is a three-byte UTF8 char.
     sm.new_source_file(
         PathBuf::from("blork.rs").into(),
         "fir€st €€€€ line.\nsecond line".to_string(),
     );
     sm.new_source_file(
         PathBuf::from("blork2.rs").into(),
         "first line€€.\n€ second line".to_string(),
     );
     sm
 }

 /// Tests `bytepos_to_file_charpos` in the presence of multi-byte chars.
 #[test]
 fn t6() {
     let sm = init_source_map_mbc();

     let cp1 = sm.bytepos_to_file_charpos(BytePos(3));
     assert_eq!(cp1, CharPos(3));

     let cp2 = sm.bytepos_to_file_charpos(BytePos(6));
     assert_eq!(cp2, CharPos(4));

     let cp3 = sm.bytepos_to_file_charpos(BytePos(56));
     assert_eq!(cp3, CharPos(12));

     let cp4 = sm.bytepos_to_file_charpos(BytePos(61));
     assert_eq!(cp4, CharPos(15));
 }

 /// Test `span_to_lines` for a span ending at the end of a `SourceFile`.
 #[test]
 fn t7() {
     let sm = init_source_map();
     let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let file_lines = sm.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_or(left_index, |x| x as u32);
     Span::with_root_ctxt(BytePos(left_index), BytePos(right_index + 1))
 }

 /// Tests `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 sm = SourceMap::new(FilePathMapping::empty());
     let inputtext = "aaaaa\nbbbbBB\nCCC\nDDDDDddddd\neee\n";
     let selection = "     \n    ~~\n~~~\n~~~~~     \n   \n";
     sm.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!(&sm.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 = sm.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 span_to_snippet for a span ending at the end of a `SourceFile`.
 #[test]
 fn t8() {
     let sm = init_source_map();
     let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let snippet = sm.span_to_snippet(span);

     assert_eq!(snippet, Ok("second line".to_string()));
 }

 /// Test `span_to_str` for a span ending at the end of a `SourceFile`.
 #[test]
 fn t9() {
     let sm = init_source_map();
     let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let sstr = sm.span_to_diagnostic_string(span);

     assert_eq!(sstr, "blork.rs:2:1: 2:12");
 }

 /// Tests failing to merge two spans on different lines.
 #[test]
 fn span_merging_fail() {
     let sm = SourceMap::new(FilePathMapping::empty());
     let inputtext = "bbbb BB\ncc CCC\n";
     let selection1 = "     ~~\n      \n";
     let selection2 = "       \n   ~~~\n";
     sm.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!(sm.merge_spans(span1, span2).is_none());
 }

 /// Tests loading an external source file that requires normalization.
 #[test]
 fn t10() {
     let sm = SourceMap::new(FilePathMapping::empty());
     let unnormalized = "first line.\r\nsecond line";
     let normalized = "first line.\nsecond line";

     let src_file = sm.new_source_file(PathBuf::from("blork.rs").into(), unnormalized.to_string());

     assert_eq!(src_file.src.as_ref().unwrap().as_ref(), normalized);
     assert!(
         src_file.src_hash.matches(unnormalized),
         "src_hash should use the source before normalization"
     );

     let SourceFile {
         name,
         src_hash,
         start_pos,
         end_pos,
         lines,
         multibyte_chars,
         non_narrow_chars,
         normalized_pos,
         name_hash,
         ..
     } = (*src_file).clone();

     let imported_src_file = sm.new_imported_source_file(
         name,
         src_hash,
         name_hash,
         (end_pos - start_pos).to_usize(),
         CrateNum::new(0),
         lines,
         multibyte_chars,
         non_narrow_chars,
         normalized_pos,
         start_pos,
         end_pos,
     );

     assert!(
         imported_src_file.external_src.borrow().get_source().is_none(),
         "imported source file should not have source yet"
     );
     imported_src_file.add_external_src(|| Some(unnormalized.to_string()));
     assert_eq!(
         imported_src_file.external_src.borrow().get_source().unwrap().as_ref(),
         normalized,
         "imported source file should be normalized"
     );
 }

 /// 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 {
         eprintln!(
             "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::with_root_ctxt(
                     BytePos(lo as u32 + file.start_pos.0),
                     BytePos(hi as u32 + file.start_pos.0),
                 );
                 assert_eq!(&self.span_to_snippet(span).unwrap()[..], substring);
                 return span;
             }
             i += 1;
         }
     }
 }

 fn map_path_prefix(mapping: &FilePathMapping, path: &str) -> String {
     // It's important that we convert to a string here because that's what
     // later stages do too (e.g. in the backend), and comparing `Path` values
     // won't catch some differences at the string level, e.g. "abc" and "abc/"
     // compare as equal.
     mapping.map_prefix(path.into()).0.to_string_lossy().to_string()
 }

 #[cfg(unix)]
 #[test]
 fn path_prefix_remapping() {
     // Relative to relative
     {
         let mapping = &FilePathMapping::new(vec![("abc/def".into(), "foo".into())]);

         assert_eq!(map_path_prefix(mapping, "abc/def/src/main.rs"), "foo/src/main.rs");
         assert_eq!(map_path_prefix(mapping, "abc/def"), "foo");
     }

     // Relative to absolute
     {
         let mapping = &FilePathMapping::new(vec![("abc/def".into(), "/foo".into())]);

         assert_eq!(map_path_prefix(mapping, "abc/def/src/main.rs"), "/foo/src/main.rs");
         assert_eq!(map_path_prefix(mapping, "abc/def"), "/foo");
     }

     // Absolute to relative
     {
         let mapping = &FilePathMapping::new(vec![("/abc/def".into(), "foo".into())]);

         assert_eq!(map_path_prefix(mapping, "/abc/def/src/main.rs"), "foo/src/main.rs");
         assert_eq!(map_path_prefix(mapping, "/abc/def"), "foo");
     }

     // Absolute to absolute
     {
         let mapping = &FilePathMapping::new(vec![("/abc/def".into(), "/foo".into())]);

         assert_eq!(map_path_prefix(mapping, "/abc/def/src/main.rs"), "/foo/src/main.rs");
         assert_eq!(map_path_prefix(mapping, "/abc/def"), "/foo");
     }
 }

 #[cfg(windows)]
 #[test]
 fn path_prefix_remapping_from_relative2() {
     // Relative to relative
     {
         let mapping = &FilePathMapping::new(vec![("abc\\def".into(), "foo".into())]);

         assert_eq!(map_path_prefix(mapping, "abc\\def\\src\\main.rs"), "foo\\src\\main.rs");
         assert_eq!(map_path_prefix(mapping, "abc\\def"), "foo");
     }

     // Relative to absolute
     {
         let mapping = &FilePathMapping::new(vec![("abc\\def".into(), "X:\\foo".into())]);

         assert_eq!(map_path_prefix(mapping, "abc\\def\\src\\main.rs"), "X:\\foo\\src\\main.rs");
         assert_eq!(map_path_prefix(mapping, "abc\\def"), "X:\\foo");
     }

     // Absolute to relative
     {
         let mapping = &FilePathMapping::new(vec![("X:\\abc\\def".into(), "foo".into())]);

         assert_eq!(map_path_prefix(mapping, "X:\\abc\\def\\src\\main.rs"), "foo\\src\\main.rs");
         assert_eq!(map_path_prefix(mapping, "X:\\abc\\def"), "foo");
     }

     // Absolute to absolute
     {
         let mapping = &FilePathMapping::new(vec![("X:\\abc\\def".into(), "X:\\foo".into())]);

         assert_eq!(map_path_prefix(mapping, "X:\\abc\\def\\src\\main.rs"), "X:\\foo\\src\\main.rs");
         assert_eq!(map_path_prefix(mapping, "X:\\abc\\def"), "X:\\foo");
     }
 }
	use super::*;

	use rustc_data_structures::sync::Lrc;

	fn init_source_map() -> SourceMap {
	let sm = SourceMap::new(FilePathMapping::empty());
	sm.new_source_file(PathBuf::from("blork.rs").into(), "first line.\nsecond line".to_string());
	sm.new_source_file(PathBuf::from("empty.rs").into(), String::new());
	sm.new_source_file(PathBuf::from("blork2.rs").into(), "first line.\nsecond line".to_string());
	sm
	}

	impl SourceMap {
	/// 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 syntax contexts 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.
	fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
	// Ensure 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 that 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
	}
	}

	/// Converts an absolute `BytePos` to a `CharPos` relative to the `SourceFile`.
	fn bytepos_to_file_charpos(&self, bpos: BytePos) -> CharPos {
	let idx = self.lookup_source_file_idx(bpos);
	let sf = &(*self.files.borrow().source_files)[idx];
	sf.bytepos_to_file_charpos(bpos)
	}
	}

	/// Tests `lookup_byte_offset`.
	#[test]
	fn t3() {
	let sm = init_source_map();

	let srcfbp1 = sm.lookup_byte_offset(BytePos(23));
	assert_eq!(srcfbp1.sf.name, PathBuf::from("blork.rs").into());
	assert_eq!(srcfbp1.pos, BytePos(23));

	let srcfbp1 = sm.lookup_byte_offset(BytePos(24));
	assert_eq!(srcfbp1.sf.name, PathBuf::from("empty.rs").into());
	assert_eq!(srcfbp1.pos, BytePos(0));

	let srcfbp2 = sm.lookup_byte_offset(BytePos(25));
	assert_eq!(srcfbp2.sf.name, PathBuf::from("blork2.rs").into());
	assert_eq!(srcfbp2.pos, BytePos(0));
	}

	/// Tests `bytepos_to_file_charpos`.
	#[test]
	fn t4() {
	let sm = init_source_map();

	let cp1 = sm.bytepos_to_file_charpos(BytePos(22));
	assert_eq!(cp1, CharPos(22));

	let cp2 = sm.bytepos_to_file_charpos(BytePos(25));
	assert_eq!(cp2, CharPos(0));
	}

	/// Tests zero-length `SourceFile`s.
	#[test]
	fn t5() {
	let sm = init_source_map();

	let loc1 = sm.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 = sm.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_source_map_mbc() -> SourceMap {
	let sm = SourceMap::new(FilePathMapping::empty());
	// "€" is a three-byte UTF8 char.
	sm.new_source_file(
	PathBuf::from("blork.rs").into(),
	"fir€st €€€€ line.\nsecond line".to_string(),
	);
	sm.new_source_file(
	PathBuf::from("blork2.rs").into(),
	"first line€€.\n€ second line".to_string(),
	);
	sm
	}

	/// Tests `bytepos_to_file_charpos` in the presence of multi-byte chars.
	#[test]
	fn t6() {
	let sm = init_source_map_mbc();

	let cp1 = sm.bytepos_to_file_charpos(BytePos(3));
	assert_eq!(cp1, CharPos(3));

	let cp2 = sm.bytepos_to_file_charpos(BytePos(6));
	assert_eq!(cp2, CharPos(4));

	let cp3 = sm.bytepos_to_file_charpos(BytePos(56));
	assert_eq!(cp3, CharPos(12));

	let cp4 = sm.bytepos_to_file_charpos(BytePos(61));
	assert_eq!(cp4, CharPos(15));
	}

	/// Test `span_to_lines` for a span ending at the end of a `SourceFile`.
	#[test]
	fn t7() {
	let sm = init_source_map();
	let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
	let file_lines = sm.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_or(left_index, \|x\| x as u32);
	Span::with_root_ctxt(BytePos(left_index), BytePos(right_index + 1))
	}

	/// Tests `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 sm = SourceMap::new(FilePathMapping::empty());
	let inputtext = "aaaaa\nbbbbBB\nCCC\nDDDDDddddd\neee\n";
	let selection = " \n ~~\n~~~\n~~~~~ \n \n";
	sm.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!(&sm.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 = sm.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 span_to_snippet for a span ending at the end of a `SourceFile`.
	#[test]
	fn t8() {
	let sm = init_source_map();
	let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
	let snippet = sm.span_to_snippet(span);

	assert_eq!(snippet, Ok("second line".to_string()));
	}

	/// Test `span_to_str` for a span ending at the end of a `SourceFile`.
	#[test]
	fn t9() {
	let sm = init_source_map();
	let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
	let sstr = sm.span_to_diagnostic_string(span);

	assert_eq!(sstr, "blork.rs:2:1: 2:12");
	}

	/// Tests failing to merge two spans on different lines.
	#[test]
	fn span_merging_fail() {
	let sm = SourceMap::new(FilePathMapping::empty());
	let inputtext = "bbbb BB\ncc CCC\n";
	let selection1 = " ~~\n \n";
	let selection2 = " \n ~~~\n";
	sm.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!(sm.merge_spans(span1, span2).is_none());
	}

	/// Tests loading an external source file that requires normalization.
	#[test]
	fn t10() {
	let sm = SourceMap::new(FilePathMapping::empty());
	let unnormalized = "first line.\r\nsecond line";
	let normalized = "first line.\nsecond line";

	let src_file = sm.new_source_file(PathBuf::from("blork.rs").into(), unnormalized.to_string());

	assert_eq!(src_file.src.as_ref().unwrap().as_ref(), normalized);
	assert!(
	src_file.src_hash.matches(unnormalized),
	"src_hash should use the source before normalization"
	);

	let SourceFile {
	name,
	src_hash,
	start_pos,
	end_pos,
	lines,
	multibyte_chars,
	non_narrow_chars,
	normalized_pos,
	name_hash,
	..
	} = (*src_file).clone();

	let imported_src_file = sm.new_imported_source_file(
	name,
	src_hash,
	name_hash,
	(end_pos - start_pos).to_usize(),
	CrateNum::new(0),
	lines,
	multibyte_chars,
	non_narrow_chars,
	normalized_pos,
	start_pos,
	end_pos,
	);

	assert!(
	imported_src_file.external_src.borrow().get_source().is_none(),
	"imported source file should not have source yet"
	);
	imported_src_file.add_external_src(\|\| Some(unnormalized.to_string()));
	assert_eq!(
	imported_src_file.external_src.borrow().get_source().unwrap().as_ref(),
	normalized,
	"imported source file should be normalized"
	);
	}

	/// 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 {
	eprintln!(
	"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::with_root_ctxt(
	BytePos(lo as u32 + file.start_pos.0),
	BytePos(hi as u32 + file.start_pos.0),
	);
	assert_eq!(&self.span_to_snippet(span).unwrap()[..], substring);
	return span;
	}
	i += 1;
	}
	}
	}

	fn map_path_prefix(mapping: &FilePathMapping, path: &str) -> String {
	// It's important that we convert to a string here because that's what
	// later stages do too (e.g. in the backend), and comparing `Path` values
	// won't catch some differences at the string level, e.g. "abc" and "abc/"
	// compare as equal.
	mapping.map_prefix(path.into()).0.to_string_lossy().to_string()
	}

	#[cfg(unix)]
	#[test]
	fn path_prefix_remapping() {
	// Relative to relative
	{
	let mapping = &FilePathMapping::new(vec![("abc/def".into(), "foo".into())]);

	assert_eq!(map_path_prefix(mapping, "abc/def/src/main.rs"), "foo/src/main.rs");
	assert_eq!(map_path_prefix(mapping, "abc/def"), "foo");
	}

	// Relative to absolute
	{
	let mapping = &FilePathMapping::new(vec![("abc/def".into(), "/foo".into())]);

	assert_eq!(map_path_prefix(mapping, "abc/def/src/main.rs"), "/foo/src/main.rs");
	assert_eq!(map_path_prefix(mapping, "abc/def"), "/foo");
	}

	// Absolute to relative
	{
	let mapping = &FilePathMapping::new(vec![("/abc/def".into(), "foo".into())]);

	assert_eq!(map_path_prefix(mapping, "/abc/def/src/main.rs"), "foo/src/main.rs");
	assert_eq!(map_path_prefix(mapping, "/abc/def"), "foo");
	}

	// Absolute to absolute
	{
	let mapping = &FilePathMapping::new(vec![("/abc/def".into(), "/foo".into())]);

	assert_eq!(map_path_prefix(mapping, "/abc/def/src/main.rs"), "/foo/src/main.rs");
	assert_eq!(map_path_prefix(mapping, "/abc/def"), "/foo");
	}
	}

	#[cfg(windows)]
	#[test]
	fn path_prefix_remapping_from_relative2() {
	// Relative to relative
	{
	let mapping = &FilePathMapping::new(vec![("abc\\def".into(), "foo".into())]);

	assert_eq!(map_path_prefix(mapping, "abc\\def\\src\\main.rs"), "foo\\src\\main.rs");
	assert_eq!(map_path_prefix(mapping, "abc\\def"), "foo");
	}

	// Relative to absolute
	{
	let mapping = &FilePathMapping::new(vec![("abc\\def".into(), "X:\\foo".into())]);

	assert_eq!(map_path_prefix(mapping, "abc\\def\\src\\main.rs"), "X:\\foo\\src\\main.rs");
	assert_eq!(map_path_prefix(mapping, "abc\\def"), "X:\\foo");
	}

	// Absolute to relative
	{
	let mapping = &FilePathMapping::new(vec![("X:\\abc\\def".into(), "foo".into())]);

	assert_eq!(map_path_prefix(mapping, "X:\\abc\\def\\src\\main.rs"), "foo\\src\\main.rs");
	assert_eq!(map_path_prefix(mapping, "X:\\abc\\def"), "foo");
	}

	// Absolute to absolute
	{
	let mapping = &FilePathMapping::new(vec![("X:\\abc\\def".into(), "X:\\foo".into())]);

	assert_eq!(map_path_prefix(mapping, "X:\\abc\\def\\src\\main.rs"), "X:\\foo\\src\\main.rs");
	assert_eq!(map_path_prefix(mapping, "X:\\abc\\def"), "X:\\foo");
	}
	}