Stabilize in 1.19

9 files changed, 319 insertions, 294 deletions

diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index 92cec462ffb..082930777e5 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -62,7 +62,7 @@ impl<'a> Parser<'a> {
                 _ => break,
             }
         }
-        return Ok(attrs);
+        Ok(attrs)
     }
 
     /// Matches `attribute = # ! [ meta_item ]`
@@ -182,7 +182,7 @@ impl<'a> Parser<'a> {
                     }
 
                     let attr = self.parse_attribute(true)?;
-                    assert!(attr.style == ast::AttrStyle::Inner);
+                    assert_eq!(attr.style, ast::AttrStyle::Inner);
                     attrs.push(attr);
                 }
                 token::DocComment(s) => {
diff --git a/src/libsyntax/parse/classify.rs b/src/libsyntax/parse/classify.rs
index 4fe4ec7e4c0..0c6f09ba766 100644
--- a/src/libsyntax/parse/classify.rs
+++ b/src/libsyntax/parse/classify.rs
@@ -43,14 +43,14 @@ pub fn expr_is_simple_block(e: &ast::Expr) -> bool {
 }
 
 /// this statement requires a semicolon after it.
-/// note that in one case (stmt_semi), we've already
+/// note that in one case (`stmt_semi`), we've already
 /// seen the semicolon, and thus don't need another.
 pub fn stmt_ends_with_semi(stmt: &ast::StmtKind) -> bool {
     match *stmt {
         ast::StmtKind::Local(_) => true,
-        ast::StmtKind::Item(_) => false,
         ast::StmtKind::Expr(ref e) => expr_requires_semi_to_be_stmt(e),
-        ast::StmtKind::Semi(..) => false,
+        ast::StmtKind::Item(_) |
+        ast::StmtKind::Semi(..) |
         ast::StmtKind::Mac(..) => false,
     }
 }
diff --git a/src/libsyntax/parse/common.rs b/src/libsyntax/parse/common.rs
index b57708f9193..fe931f7cf6a 100644
--- a/src/libsyntax/parse/common.rs
+++ b/src/libsyntax/parse/common.rs
@@ -12,7 +12,7 @@
 
 use parse::token;
 
-/// SeqSep : a sequence separator (token)
+/// `SeqSep` : a sequence separator (token)
 /// and whether a trailing separator is allowed.
 pub struct SeqSep {
     pub sep: Option<token::Token>,
diff --git a/src/libsyntax/parse/lexer/comments.rs b/src/libsyntax/parse/lexer/comments.rs
index c97b8ddf919..8b545d3b909 100644
--- a/src/libsyntax/parse/lexer/comments.rs
+++ b/src/libsyntax/parse/lexer/comments.rs
@@ -77,7 +77,7 @@ pub fn strip_doc_comment_decoration(comment: &str) -> String {
         while j > i && lines[j - 1].trim().is_empty() {
             j -= 1;
         }
-        lines[i..j].iter().cloned().collect()
+        lines[i..j].to_vec()
     }
 
     /// remove a "[ \t]*\*" block from each line, if possible
@@ -348,8 +348,8 @@ pub fn gather_comments_and_literals(sess: &ParseSess, path: String, srdr: &mut R
     let mut src = Vec::new();
     srdr.read_to_end(&mut src).unwrap();
     let src = String::from_utf8(src).unwrap();
-    let cm = CodeMap::new();
-    let filemap = cm.new_filemap(path, None, src);
+    let cm = CodeMap::new(sess.codemap().path_mapping().clone());
+    let filemap = cm.new_filemap(path, src);
     let mut rdr = lexer::StringReader::new_raw(sess, filemap);
 
     let mut comments: Vec<Comment> = Vec::new();
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 920b2c401e2..0bcd4578518 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -10,7 +10,7 @@
 
 use ast::{self, Ident};
 use syntax_pos::{self, BytePos, CharPos, Pos, Span, NO_EXPANSION};
-use codemap::CodeMap;
+use codemap::{CodeMap, FilePathMapping};
 use errors::{FatalError, DiagnosticBuilder};
 use parse::{token, ParseSess};
 use str::char_at;
@@ -73,7 +73,7 @@ fn mk_sp(lo: BytePos, hi: BytePos) -> Span {
 }
 
 impl<'a> StringReader<'a> {
-    fn next_token(&mut self) -> TokenAndSpan where Self: Sized {
+    fn next_token(&mut self) -> TokenAndSpan {
         let res = self.try_next_token();
         self.unwrap_or_abort(res)
     }
@@ -144,7 +144,7 @@ impl<'a> StringReader<'a> {
 
 impl<'a> StringReader<'a> {
     /// For comments.rs, which hackily pokes into next_pos and ch
-    pub fn new_raw<'b>(sess: &'a ParseSess, filemap: Rc<syntax_pos::FileMap>) -> Self {
+    pub fn new_raw(sess: &'a ParseSess, filemap: Rc<syntax_pos::FileMap>) -> Self {
         let mut sr = StringReader::new_raw_internal(sess, filemap);
         sr.bump();
         sr
@@ -180,7 +180,7 @@ impl<'a> StringReader<'a> {
 
     pub fn new(sess: &'a ParseSess, filemap: Rc<syntax_pos::FileMap>) -> Self {
         let mut sr = StringReader::new_raw(sess, filemap);
-        if let Err(_) = sr.advance_token() {
+        if sr.advance_token().is_err() {
             sr.emit_fatal_errors();
             panic!(FatalError);
         }
@@ -205,7 +205,7 @@ impl<'a> StringReader<'a> {
 
         sr.bump();
 
-        if let Err(_) = sr.advance_token() {
+        if sr.advance_token().is_err() {
             sr.emit_fatal_errors();
             panic!(FatalError);
         }
@@ -504,7 +504,7 @@ impl<'a> StringReader<'a> {
                     self.bump();
 
                     // line comments starting with "///" or "//!" are doc-comments
-                    let doc_comment = self.ch_is('/') || self.ch_is('!');
+                    let doc_comment = (self.ch_is('/') && !self.nextch_is('/')) || self.ch_is('!');
                     let start_bpos = self.pos - BytePos(2);
 
                     while !self.is_eof() {
@@ -525,7 +525,7 @@ impl<'a> StringReader<'a> {
                         self.bump();
                     }
 
-                    return if doc_comment {
+                    if doc_comment {
                         self.with_str_from(start_bpos, |string| {
                             // comments with only more "/"s are not doc comments
                             let tok = if is_doc_comment(string) {
@@ -544,7 +544,7 @@ impl<'a> StringReader<'a> {
                             tok: token::Comment,
                             sp: mk_sp(start_bpos, self.pos),
                         })
-                    };
+                    }
                 }
                 Some('*') => {
                     self.bump();
@@ -563,7 +563,7 @@ impl<'a> StringReader<'a> {
 
                 // I guess this is the only way to figure out if
                 // we're at the beginning of the file...
-                let cmap = CodeMap::new();
+                let cmap = CodeMap::new(FilePathMapping::empty());
                 cmap.files.borrow_mut().push(self.filemap.clone());
                 let loc = cmap.lookup_char_pos_adj(self.pos);
                 debug!("Skipping a shebang");
@@ -754,9 +754,7 @@ impl<'a> StringReader<'a> {
         // integer literal followed by field/method access or a range pattern
         // (`0..2` and `12.foo()`)
         if self.ch_is('.') && !self.nextch_is('.') &&
-           !self.nextch()
-                .unwrap_or('\0')
-                .is_xid_start() {
+           !ident_start(self.nextch()) {
             // might have stuff after the ., and if it does, it needs to start
             // with a number
             self.bump();
@@ -766,7 +764,7 @@ impl<'a> StringReader<'a> {
             }
             let pos = self.pos;
             self.check_float_base(start_bpos, pos, base);
-            return token::Float(self.name_from(start_bpos));
+            token::Float(self.name_from(start_bpos))
         } else {
             // it might be a float if it has an exponent
             if self.ch_is('e') || self.ch_is('E') {
@@ -776,7 +774,7 @@ impl<'a> StringReader<'a> {
                 return token::Float(self.name_from(start_bpos));
             }
             // but we certainly have an integer!
-            return token::Integer(self.name_from(start_bpos));
+            token::Integer(self.name_from(start_bpos))
         }
     }
 
@@ -1053,9 +1051,9 @@ impl<'a> StringReader<'a> {
         self.bump();
         if self.ch_is('=') {
             self.bump();
-            return token::BinOpEq(op);
+            token::BinOpEq(op)
         } else {
-            return token::BinOp(op);
+            token::BinOp(op)
         }
     }
 
@@ -1102,15 +1100,15 @@ impl<'a> StringReader<'a> {
             // One-byte tokens.
             ';' => {
                 self.bump();
-                return Ok(token::Semi);
+                Ok(token::Semi)
             }
             ',' => {
                 self.bump();
-                return Ok(token::Comma);
+                Ok(token::Comma)
             }
             '.' => {
                 self.bump();
-                return if self.ch_is('.') {
+                if self.ch_is('.') {
                     self.bump();
                     if self.ch_is('.') {
                         self.bump();
@@ -1120,61 +1118,61 @@ impl<'a> StringReader<'a> {
                     }
                 } else {
                     Ok(token::Dot)
-                };
+                }
             }
             '(' => {
                 self.bump();
-                return Ok(token::OpenDelim(token::Paren));
+                Ok(token::OpenDelim(token::Paren))
             }
             ')' => {
                 self.bump();
-                return Ok(token::CloseDelim(token::Paren));
+                Ok(token::CloseDelim(token::Paren))
             }
             '{' => {
                 self.bump();
-                return Ok(token::OpenDelim(token::Brace));
+                Ok(token::OpenDelim(token::Brace))
             }
             '}' => {
                 self.bump();
-                return Ok(token::CloseDelim(token::Brace));
+                Ok(token::CloseDelim(token::Brace))
             }
             '[' => {
                 self.bump();
-                return Ok(token::OpenDelim(token::Bracket));
+                Ok(token::OpenDelim(token::Bracket))
             }
             ']' => {
                 self.bump();
-                return Ok(token::CloseDelim(token::Bracket));
+                Ok(token::CloseDelim(token::Bracket))
             }
             '@' => {
                 self.bump();
-                return Ok(token::At);
+                Ok(token::At)
             }
             '#' => {
                 self.bump();
-                return Ok(token::Pound);
+                Ok(token::Pound)
             }
             '~' => {
                 self.bump();
-                return Ok(token::Tilde);
+                Ok(token::Tilde)
             }
             '?' => {
                 self.bump();
-                return Ok(token::Question);
+                Ok(token::Question)
             }
             ':' => {
                 self.bump();
                 if self.ch_is(':') {
                     self.bump();
-                    return Ok(token::ModSep);
+                    Ok(token::ModSep)
                 } else {
-                    return Ok(token::Colon);
+                    Ok(token::Colon)
                 }
             }
 
             '$' => {
                 self.bump();
-                return Ok(token::Dollar);
+                Ok(token::Dollar)
             }
 
             // Multi-byte tokens.
@@ -1182,21 +1180,21 @@ impl<'a> StringReader<'a> {
                 self.bump();
                 if self.ch_is('=') {
                     self.bump();
-                    return Ok(token::EqEq);
+                    Ok(token::EqEq)
                 } else if self.ch_is('>') {
                     self.bump();
-                    return Ok(token::FatArrow);
+                    Ok(token::FatArrow)
                 } else {
-                    return Ok(token::Eq);
+                    Ok(token::Eq)
                 }
             }
             '!' => {
                 self.bump();
                 if self.ch_is('=') {
                     self.bump();
-                    return Ok(token::Ne);
+                    Ok(token::Ne)
                 } else {
-                    return Ok(token::Not);
+                    Ok(token::Not)
                 }
             }
             '<' => {
@@ -1204,21 +1202,21 @@ impl<'a> StringReader<'a> {
                 match self.ch.unwrap_or('\x00') {
                     '=' => {
                         self.bump();
-                        return Ok(token::Le);
+                        Ok(token::Le)
                     }
                     '<' => {
-                        return Ok(self.binop(token::Shl));
+                        Ok(self.binop(token::Shl))
                     }
                     '-' => {
                         self.bump();
                         match self.ch.unwrap_or('\x00') {
                             _ => {
-                                return Ok(token::LArrow);
+                                Ok(token::LArrow)
                             }
                         }
                     }
                     _ => {
-                        return Ok(token::Lt);
+                        Ok(token::Lt)
                     }
                 }
             }
@@ -1227,13 +1225,13 @@ impl<'a> StringReader<'a> {
                 match self.ch.unwrap_or('\x00') {
                     '=' => {
                         self.bump();
-                        return Ok(token::Ge);
+                        Ok(token::Ge)
                     }
                     '>' => {
-                        return Ok(self.binop(token::Shr));
+                        Ok(self.binop(token::Shr))
                     }
                     _ => {
-                        return Ok(token::Gt);
+                        Ok(token::Gt)
                     }
                 }
             }
@@ -1303,7 +1301,7 @@ impl<'a> StringReader<'a> {
                 };
                 self.bump(); // advance ch past token
                 let suffix = self.scan_optional_raw_name();
-                return Ok(token::Literal(token::Char(id), suffix));
+                Ok(token::Literal(token::Char(id), suffix))
             }
             'b' => {
                 self.bump();
@@ -1314,7 +1312,7 @@ impl<'a> StringReader<'a> {
                     _ => unreachable!(),  // Should have been a token::Ident above.
                 };
                 let suffix = self.scan_optional_raw_name();
-                return Ok(token::Literal(lit, suffix));
+                Ok(token::Literal(lit, suffix))
             }
             '"' => {
                 let start_bpos = self.pos;
@@ -1345,7 +1343,7 @@ impl<'a> StringReader<'a> {
                 };
                 self.bump();
                 let suffix = self.scan_optional_raw_name();
-                return Ok(token::Literal(token::Str_(id), suffix));
+                Ok(token::Literal(token::Str_(id), suffix))
             }
             'r' => {
                 let start_bpos = self.pos;
@@ -1416,24 +1414,24 @@ impl<'a> StringReader<'a> {
                     Symbol::intern("??")
                 };
                 let suffix = self.scan_optional_raw_name();
-                return Ok(token::Literal(token::StrRaw(id, hash_count), suffix));
+                Ok(token::Literal(token::StrRaw(id, hash_count), suffix))
             }
             '-' => {
                 if self.nextch_is('>') {
                     self.bump();
                     self.bump();
-                    return Ok(token::RArrow);
+                    Ok(token::RArrow)
                 } else {
-                    return Ok(self.binop(token::Minus));
+                    Ok(self.binop(token::Minus))
                 }
             }
             '&' => {
                 if self.nextch_is('&') {
                     self.bump();
                     self.bump();
-                    return Ok(token::AndAnd);
+                    Ok(token::AndAnd)
                 } else {
-                    return Ok(self.binop(token::And));
+                    Ok(self.binop(token::And))
                 }
             }
             '|' => {
@@ -1441,27 +1439,27 @@ impl<'a> StringReader<'a> {
                     Some('|') => {
                         self.bump();
                         self.bump();
-                        return Ok(token::OrOr);
+                        Ok(token::OrOr)
                     }
                     _ => {
-                        return Ok(self.binop(token::Or));
+                        Ok(self.binop(token::Or))
                     }
                 }
             }
             '+' => {
-                return Ok(self.binop(token::Plus));
+                Ok(self.binop(token::Plus))
             }
             '*' => {
-                return Ok(self.binop(token::Star));
+                Ok(self.binop(token::Star))
             }
             '/' => {
-                return Ok(self.binop(token::Slash));
+                Ok(self.binop(token::Slash))
             }
             '^' => {
-                return Ok(self.binop(token::Caret));
+                Ok(self.binop(token::Caret))
             }
             '%' => {
-                return Ok(self.binop(token::Percent));
+                Ok(self.binop(token::Percent))
             }
             c => {
                 let last_bpos = self.pos;
@@ -1470,7 +1468,7 @@ impl<'a> StringReader<'a> {
                                                           bpos,
                                                           "unknown start of token",
                                                           c);
-                unicode_chars::check_for_substitution(&self, c, &mut err);
+                unicode_chars::check_for_substitution(self, c, &mut err);
                 self.fatal_errs.push(err);
                 Err(())
             }
@@ -1492,14 +1490,14 @@ impl<'a> StringReader<'a> {
         if self.ch_is('\n') {
             self.bump();
         }
-        return val;
+        val
     }
 
     fn read_one_line_comment(&mut self) -> String {
         let val = self.read_to_eol();
         assert!((val.as_bytes()[0] == b'/' && val.as_bytes()[1] == b'/') ||
                 (val.as_bytes()[0] == b'#' && val.as_bytes()[1] == b'!'));
-        return val;
+        val
     }
 
     fn consume_non_eol_whitespace(&mut self) {
@@ -1543,7 +1541,7 @@ impl<'a> StringReader<'a> {
             Symbol::intern("?")
         };
         self.bump(); // advance ch past token
-        return token::Byte(id);
+        token::Byte(id)
     }
 
     fn scan_byte_escape(&mut self, delim: char, below_0x7f_only: bool) -> bool {
@@ -1576,7 +1574,7 @@ impl<'a> StringReader<'a> {
             Symbol::intern("??")
         };
         self.bump();
-        return token::ByteStr(id);
+        token::ByteStr(id)
     }
 
     fn scan_raw_byte_string(&mut self) -> token::Lit {
@@ -1629,8 +1627,8 @@ impl<'a> StringReader<'a> {
             self.bump();
         }
         self.bump();
-        return token::ByteStrRaw(self.name_from_to(content_start_bpos, content_end_bpos),
-                                 hash_count);
+        token::ByteStrRaw(self.name_from_to(content_start_bpos, content_end_bpos),
+                                 hash_count)
     }
 }
 
@@ -1648,7 +1646,7 @@ fn in_range(c: Option<char>, lo: char, hi: char) -> bool {
 }
 
 fn is_dec_digit(c: Option<char>) -> bool {
-    return in_range(c, '0', '9');
+    in_range(c, '0', '9')
 }
 
 pub fn is_doc_comment(s: &str) -> bool {
@@ -1718,13 +1716,13 @@ mod tests {
                  sess: &'a ParseSess,
                  teststr: String)
                  -> StringReader<'a> {
-        let fm = cm.new_filemap("zebra.rs".to_string(), None, teststr);
+        let fm = cm.new_filemap("zebra.rs".to_string(), teststr);
         StringReader::new(sess, fm)
     }
 
     #[test]
     fn t1() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         let mut string_reader = setup(&cm,
                                       &sh,
@@ -1776,7 +1774,7 @@ mod tests {
 
     #[test]
     fn doublecolonparsing() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         check_tokenization(setup(&cm, &sh, "a b".to_string()),
                            vec![mk_ident("a"), token::Whitespace, mk_ident("b")]);
@@ -1784,7 +1782,7 @@ mod tests {
 
     #[test]
     fn dcparsing_2() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         check_tokenization(setup(&cm, &sh, "a::b".to_string()),
                            vec![mk_ident("a"), token::ModSep, mk_ident("b")]);
@@ -1792,7 +1790,7 @@ mod tests {
 
     #[test]
     fn dcparsing_3() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         check_tokenization(setup(&cm, &sh, "a ::b".to_string()),
                            vec![mk_ident("a"), token::Whitespace, token::ModSep, mk_ident("b")]);
@@ -1800,7 +1798,7 @@ mod tests {
 
     #[test]
     fn dcparsing_4() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         check_tokenization(setup(&cm, &sh, "a:: b".to_string()),
                            vec![mk_ident("a"), token::ModSep, token::Whitespace, mk_ident("b")]);
@@ -1808,7 +1806,7 @@ mod tests {
 
     #[test]
     fn character_a() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         assert_eq!(setup(&cm, &sh, "'a'".to_string()).next_token().tok,
                    token::Literal(token::Char(Symbol::intern("a")), None));
@@ -1816,7 +1814,7 @@ mod tests {
 
     #[test]
     fn character_space() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         assert_eq!(setup(&cm, &sh, "' '".to_string()).next_token().tok,
                    token::Literal(token::Char(Symbol::intern(" ")), None));
@@ -1824,7 +1822,7 @@ mod tests {
 
     #[test]
     fn character_escaped() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         assert_eq!(setup(&cm, &sh, "'\\n'".to_string()).next_token().tok,
                    token::Literal(token::Char(Symbol::intern("\\n")), None));
@@ -1832,7 +1830,7 @@ mod tests {
 
     #[test]
     fn lifetime_name() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         assert_eq!(setup(&cm, &sh, "'abc".to_string()).next_token().tok,
                    token::Lifetime(Ident::from_str("'abc")));
@@ -1840,7 +1838,7 @@ mod tests {
 
     #[test]
     fn raw_string() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         assert_eq!(setup(&cm, &sh, "r###\"\"#a\\b\x00c\"\"###".to_string())
                        .next_token()
@@ -1850,7 +1848,7 @@ mod tests {
 
     #[test]
     fn literal_suffixes() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         macro_rules! test {
             ($input: expr, $tok_type: ident, $tok_contents: expr) => {{
@@ -1894,7 +1892,7 @@ mod tests {
 
     #[test]
     fn nested_block_comments() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         let mut lexer = setup(&cm, &sh, "/* /* */ */'a'".to_string());
         match lexer.next_token().tok {
@@ -1907,7 +1905,7 @@ mod tests {
 
     #[test]
     fn crlf_comments() {
-        let cm = Rc::new(CodeMap::new());
+        let cm = Rc::new(CodeMap::new(FilePathMapping::empty()));
         let sh = mk_sess(cm.clone());
         let mut lexer = setup(&cm, &sh, "// test\r\n/// test\r\n".to_string());
         let comment = lexer.next_token();
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index c63a6524f74..1eff819d755 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -11,7 +11,7 @@
 //! The main parser interface
 
 use ast::{self, CrateConfig};
-use codemap::CodeMap;
+use codemap::{CodeMap, FilePathMapping};
 use syntax_pos::{self, Span, FileMap, NO_EXPANSION};
 use errors::{Handler, ColorConfig, DiagnosticBuilder};
 use feature_gate::UnstableFeatures;
@@ -53,8 +53,8 @@ pub struct ParseSess {
 }
 
 impl ParseSess {
-    pub fn new() -> Self {
-        let cm = Rc::new(CodeMap::new());
+    pub fn new(file_path_mapping: FilePathMapping) -> Self {
+        let cm = Rc::new(CodeMap::new(file_path_mapping));
         let handler = Handler::with_tty_emitter(ColorConfig::Auto,
                                                 true,
                                                 false,
@@ -107,18 +107,18 @@ pub fn parse_crate_attrs_from_file<'a>(input: &Path, sess: &'a ParseSess)
     parser.parse_inner_attributes()
 }
 
-pub fn parse_crate_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
-                                       -> PResult<'a, ast::Crate> {
+pub fn parse_crate_from_source_str(name: String, source: String, sess: &ParseSess)
+                                       -> PResult<ast::Crate> {
     new_parser_from_source_str(sess, name, source).parse_crate_mod()
 }
 
-pub fn parse_crate_attrs_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
-                                             -> PResult<'a, Vec<ast::Attribute>> {
+pub fn parse_crate_attrs_from_source_str(name: String, source: String, sess: &ParseSess)
+                                             -> PResult<Vec<ast::Attribute>> {
     new_parser_from_source_str(sess, name, source).parse_inner_attributes()
 }
 
-pub fn parse_expr_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
-                                      -> PResult<'a, P<ast::Expr>> {
+pub fn parse_expr_from_source_str(name: String, source: String, sess: &ParseSess)
+                                      -> PResult<P<ast::Expr>> {
     new_parser_from_source_str(sess, name, source).parse_expr()
 }
 
@@ -126,30 +126,30 @@ pub fn parse_expr_from_source_str<'a>(name: String, source: String, sess: &'a Pa
 ///
 /// Returns `Ok(Some(item))` when successful, `Ok(None)` when no item was found, and`Err`
 /// when a syntax error occurred.
-pub fn parse_item_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
-                                      -> PResult<'a, Option<P<ast::Item>>> {
+pub fn parse_item_from_source_str(name: String, source: String, sess: &ParseSess)
+                                      -> PResult<Option<P<ast::Item>>> {
     new_parser_from_source_str(sess, name, source).parse_item()
 }
 
-pub fn parse_meta_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
-                                      -> PResult<'a, ast::MetaItem> {
+pub fn parse_meta_from_source_str(name: String, source: String, sess: &ParseSess)
+                                      -> PResult<ast::MetaItem> {
     new_parser_from_source_str(sess, name, source).parse_meta_item()
 }
 
-pub fn parse_stmt_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
-                                      -> PResult<'a, Option<ast::Stmt>> {
+pub fn parse_stmt_from_source_str(name: String, source: String, sess: &ParseSess)
+                                      -> PResult<Option<ast::Stmt>> {
     new_parser_from_source_str(sess, name, source).parse_stmt()
 }
 
-pub fn parse_stream_from_source_str<'a>(name: String, source: String, sess: &'a ParseSess)
+pub fn parse_stream_from_source_str(name: String, source: String, sess: &ParseSess)
                                         -> TokenStream {
-    filemap_to_stream(sess, sess.codemap().new_filemap(name, None, source))
+    filemap_to_stream(sess, sess.codemap().new_filemap(name, source))
 }
 
 // Create a new parser from a source string
-pub fn new_parser_from_source_str<'a>(sess: &'a ParseSess, name: String, source: String)
-                                      -> Parser<'a> {
-    filemap_to_parser(sess, sess.codemap().new_filemap(name, None, source))
+pub fn new_parser_from_source_str(sess: &ParseSess, name: String, source: String)
+                                      -> Parser {
+    filemap_to_parser(sess, sess.codemap().new_filemap(name, source))
 }
 
 /// Create a new parser, handling errors as appropriate
@@ -173,7 +173,7 @@ pub fn new_sub_parser_from_file<'a>(sess: &'a ParseSess,
 }
 
 /// Given a filemap and config, return a parser
-pub fn filemap_to_parser<'a>(sess: &'a ParseSess, filemap: Rc<FileMap>, ) -> Parser<'a> {
+pub fn filemap_to_parser(sess: & ParseSess, filemap: Rc<FileMap>, ) -> Parser {
     let end_pos = filemap.end_pos;
     let mut parser = stream_to_parser(sess, filemap_to_stream(sess, filemap));
 
@@ -186,7 +186,7 @@ pub fn filemap_to_parser<'a>(sess: &'a ParseSess, filemap: Rc<FileMap>, ) -> Par
 
 // must preserve old name for now, because quote! from the *existing*
 // compiler expands into it
-pub fn new_parser_from_tts<'a>(sess: &'a ParseSess, tts: Vec<TokenTree>) -> Parser<'a> {
+pub fn new_parser_from_tts(sess: &ParseSess, tts: Vec<TokenTree>) -> Parser {
     stream_to_parser(sess, tts.into_iter().collect())
 }
 
@@ -216,8 +216,8 @@ pub fn filemap_to_stream(sess: &ParseSess, filemap: Rc<FileMap>) -> TokenStream
     panictry!(srdr.parse_all_token_trees())
 }
 
-/// Given stream and the ParseSess, produce a parser
-pub fn stream_to_parser<'a>(sess: &'a ParseSess, stream: TokenStream) -> Parser<'a> {
+/// Given stream and the `ParseSess`, produce a parser
+pub fn stream_to_parser(sess: &ParseSess, stream: TokenStream) -> Parser {
     Parser::new(sess, stream, None, false)
 }
 
@@ -251,7 +251,7 @@ pub fn char_lit(lit: &str) -> (char, isize) {
             (c, 4)
         }
         'u' => {
-            assert!(lit.as_bytes()[2] == b'{');
+            assert_eq!(lit.as_bytes()[2], b'{');
             let idx = lit.find('}').unwrap();
             let v = u32::from_str_radix(&lit[3..idx], 16).unwrap();
             let c = char::from_u32(v).unwrap();
@@ -261,10 +261,14 @@ pub fn char_lit(lit: &str) -> (char, isize) {
     }
 }
 
+pub fn escape_default(s: &str) -> String {
+    s.chars().map(char::escape_default).flat_map(|x| x).collect()
+}
+
 /// Parse a string representing a string literal into its final form. Does
 /// unescaping.
 pub fn str_lit(lit: &str) -> String {
-    debug!("parse_str_lit: given {}", lit.escape_default());
+    debug!("parse_str_lit: given {}", escape_default(lit));
     let mut res = String::with_capacity(lit.len());
 
     // FIXME #8372: This could be a for-loop if it didn't borrow the iterator
@@ -283,51 +287,46 @@ pub fn str_lit(lit: &str) -> String {
     }
 
     let mut chars = lit.char_indices().peekable();
-    loop {
-        match chars.next() {
-            Some((i, c)) => {
-                match c {
-                    '\\' => {
-                        let ch = chars.peek().unwrap_or_else(|| {
-                            panic!("{}", error(i))
-                        }).1;
-
-                        if ch == '\n' {
-                            eat(&mut chars);
-                        } else if ch == '\r' {
-                            chars.next();
-                            let ch = chars.peek().unwrap_or_else(|| {
-                                panic!("{}", error(i))
-                            }).1;
-
-                            if ch != '\n' {
-                                panic!("lexer accepted bare CR");
-                            }
-                            eat(&mut chars);
-                        } else {
-                            // otherwise, a normal escape
-                            let (c, n) = char_lit(&lit[i..]);
-                            for _ in 0..n - 1 { // we don't need to move past the first \
-                                chars.next();
-                            }
-                            res.push(c);
-                        }
-                    },
-                    '\r' => {
-                        let ch = chars.peek().unwrap_or_else(|| {
-                            panic!("{}", error(i))
-                        }).1;
+    while let Some((i, c)) = chars.next() {
+        match c {
+            '\\' => {
+                let ch = chars.peek().unwrap_or_else(|| {
+                    panic!("{}", error(i))
+                }).1;
+
+                if ch == '\n' {
+                    eat(&mut chars);
+                } else if ch == '\r' {
+                    chars.next();
+                    let ch = chars.peek().unwrap_or_else(|| {
+                        panic!("{}", error(i))
+                    }).1;
 
-                        if ch != '\n' {
-                            panic!("lexer accepted bare CR");
-                        }
+                    if ch != '\n' {
+                        panic!("lexer accepted bare CR");
+                    }
+                    eat(&mut chars);
+                } else {
+                    // otherwise, a normal escape
+                    let (c, n) = char_lit(&lit[i..]);
+                    for _ in 0..n - 1 { // we don't need to move past the first \
                         chars.next();
-                        res.push('\n');
                     }
-                    c => res.push(c),
+                    res.push(c);
                 }
             },
-            None => break
+            '\r' => {
+                let ch = chars.peek().unwrap_or_else(|| {
+                    panic!("{}", error(i))
+                }).1;
+
+                if ch != '\n' {
+                    panic!("lexer accepted bare CR");
+                }
+                chars.next();
+                res.push('\n');
+            }
+            c => res.push(c),
         }
     }
 
@@ -339,25 +338,19 @@ pub fn str_lit(lit: &str) -> String {
 /// Parse a string representing a raw string literal into its final form. The
 /// only operation this does is convert embedded CRLF into a single LF.
 pub fn raw_str_lit(lit: &str) -> String {
-    debug!("raw_str_lit: given {}", lit.escape_default());
+    debug!("raw_str_lit: given {}", escape_default(lit));
     let mut res = String::with_capacity(lit.len());
 
-    // FIXME #8372: This could be a for-loop if it didn't borrow the iterator
     let mut chars = lit.chars().peekable();
-    loop {
-        match chars.next() {
-            Some(c) => {
-                if c == '\r' {
-                    if *chars.peek().unwrap() != '\n' {
-                        panic!("lexer accepted bare CR");
-                    }
-                    chars.next();
-                    res.push('\n');
-                } else {
-                    res.push(c);
-                }
-            },
-            None => break
+    while let Some(c) = chars.next() {
+        if c == '\r' {
+            if *chars.peek().unwrap() != '\n' {
+                panic!("lexer accepted bare CR");
+            }
+            chars.next();
+            res.push('\n');
+        } else {
+            res.push(c);
         }
     }
 
@@ -455,7 +448,7 @@ pub fn byte_lit(lit: &str) -> (u8, usize) {
     if lit.len() == 1 {
         (lit.as_bytes()[0], 1)
     } else {
-        assert!(lit.as_bytes()[0] == b'\\', err(0));
+        assert_eq!(lit.as_bytes()[0], b'\\', "{}", err(0));
         let b = match lit.as_bytes()[1] {
             b'"' => b'"',
             b'n' => b'\n',
@@ -476,7 +469,7 @@ pub fn byte_lit(lit: &str) -> (u8, usize) {
                 }
             }
         };
-        return (b, 2);
+        (b, 2)
     }
 }
 
@@ -487,7 +480,7 @@ pub fn byte_str_lit(lit: &str) -> Rc<Vec<u8>> {
     let error = |i| format!("lexer should have rejected {} at {}", lit, i);
 
     /// Eat everything up to a non-whitespace
-    fn eat<'a, I: Iterator<Item=(usize, u8)>>(it: &mut iter::Peekable<I>) {
+    fn eat<I: Iterator<Item=(usize, u8)>>(it: &mut iter::Peekable<I>) {
         loop {
             match it.peek().map(|x| x.1) {
                 Some(b' ') | Some(b'\n') | Some(b'\r') | Some(b'\t') => {
@@ -574,7 +567,7 @@ pub fn integer_lit(s: &str, suffix: Option<Symbol>, diag: Option<(Span, &Handler
             if let Some(err) = err {
                 err!(diag, |span, diag| diag.span_err(span, err));
             }
-            return filtered_float_lit(Symbol::intern(&s), Some(suf), diag)
+            return filtered_float_lit(Symbol::intern(s), Some(suf), diag)
         }
     }
 
@@ -828,7 +821,7 @@ mod tests {
     }
 
     #[test] fn parse_ident_pat () {
-        let sess = ParseSess::new();
+        let sess = ParseSess::new(FilePathMapping::empty());
         let mut parser = string_to_parser(&sess, "b".to_string());
         assert!(panictry!(parser.parse_pat())
                 == P(ast::Pat{
@@ -998,7 +991,7 @@ mod tests {
     }
 
     #[test] fn crlf_doc_comments() {
-        let sess = ParseSess::new();
+        let sess = ParseSess::new(FilePathMapping::empty());
 
         let name = "<source>".to_string();
         let source = "/// doc comment\r\nfn foo() {}".to_string();
@@ -1023,7 +1016,7 @@ mod tests {
 
     #[test]
     fn ttdelim_span() {
-        let sess = ParseSess::new();
+        let sess = ParseSess::new(FilePathMapping::empty());
         let expr = parse::parse_expr_from_source_str("foo".to_string(),
             "foo!( fn main() { body } )".to_string(), &sess).unwrap();
 
diff --git a/src/libsyntax/parse/obsolete.rs b/src/libsyntax/parse/obsolete.rs
index d5baec675e4..078e86aa294 100644
--- a/src/libsyntax/parse/obsolete.rs
+++ b/src/libsyntax/parse/obsolete.rs
@@ -59,7 +59,7 @@ impl<'a> ParserObsoleteMethods for parser::Parser<'a> {
 
         if !self.obsolete_set.contains(&kind) &&
             (error || self.sess.span_diagnostic.can_emit_warnings) {
-            err.note(&format!("{}", desc));
+            err.note(desc);
             self.obsolete_set.insert(kind);
         }
         err.emit();
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 1baf0d1b54c..4741f896d3c 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -57,12 +57,14 @@ use tokenstream::{self, Delimited, ThinTokenStream, TokenTree, TokenStream};
 use symbol::{Symbol, keywords};
 use util::ThinVec;
 
+use std::cmp;
 use std::collections::HashSet;
-use std::{cmp, mem, slice};
+use std::mem;
 use std::path::{self, Path, PathBuf};
+use std::slice;
 
 bitflags! {
-    flags Restrictions: u8 {
+    pub flags Restrictions: u8 {
         const RESTRICTION_STMT_EXPR         = 1 << 0,
         const RESTRICTION_NO_STRUCT_LITERAL = 1 << 1,
     }
@@ -246,7 +248,7 @@ impl TokenCursor {
     fn next_desugared(&mut self) -> TokenAndSpan {
         let (sp, name) = match self.next() {
             TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
-            tok @ _ => return tok,
+            tok => return tok,
         };
 
         let stripped = strip_doc_comment_decoration(&name.as_str());
@@ -352,7 +354,7 @@ pub enum Error {
 }
 
 impl Error {
-    pub fn span_err<'a>(self, sp: Span, handler: &'a errors::Handler) -> DiagnosticBuilder<'a> {
+    pub fn span_err(self, sp: Span, handler: &errors::Handler) -> DiagnosticBuilder {
         match self {
             Error::FileNotFoundForModule { ref mod_name,
                                            ref default_path,
@@ -476,9 +478,10 @@ impl<'a> Parser<'a> {
     }
 
     fn next_tok(&mut self) -> TokenAndSpan {
-        let mut next = match self.desugar_doc_comments {
-            true => self.token_cursor.next_desugared(),
-            false => self.token_cursor.next(),
+        let mut next = if self.desugar_doc_comments {
+            self.token_cursor.next_desugared()
+        } else {
+            self.token_cursor.next()
         };
         if next.sp == syntax_pos::DUMMY_SP {
             next.sp = self.prev_span;
@@ -549,7 +552,7 @@ impl<'a> Parser<'a> {
             // This might be a sign we need a connect method on Iterator.
             let b = i.next()
                      .map_or("".to_string(), |t| t.to_string());
-            i.enumerate().fold(b, |mut b, (i, ref a)| {
+            i.enumerate().fold(b, |mut b, (i, a)| {
                 if tokens.len() > 2 && i == tokens.len() - 2 {
                     b.push_str(", or ");
                 } else if tokens.len() == 2 && i == tokens.len() - 2 {
@@ -600,10 +603,10 @@ impl<'a> Parser<'a> {
                 label_sp
             };
             if self.span.contains(sp) {
-                err.span_label(self.span, &label_exp);
+                err.span_label(self.span, label_exp);
             } else {
-                err.span_label(sp, &label_exp);
-                err.span_label(self.span, &"unexpected token");
+                err.span_label(sp, label_exp);
+                err.span_label(self.span, "unexpected token");
             }
             Err(err)
         }
@@ -983,18 +986,15 @@ impl<'a> Parser<'a> {
                 token::CloseDelim(..) | token::Eof => break,
                 _ => {}
             };
-            match sep.sep {
-                Some(ref t) => {
-                    if first {
-                        first = false;
-                    } else {
-                        if let Err(e) = self.expect(t) {
-                            fe(e);
-                            break;
-                        }
+            if let Some(ref t) = sep.sep {
+                if first {
+                    first = false;
+                } else {
+                    if let Err(e) = self.expect(t) {
+                        fe(e);
+                        break;
                     }
                 }
-                _ => ()
             }
             if sep.trailing_sep_allowed && kets.iter().any(|k| self.check(k)) {
                 break;
@@ -1451,9 +1451,9 @@ impl<'a> Parser<'a> {
         } else if self.eat_keyword(keywords::Impl) {
             // FIXME: figure out priority of `+` in `impl Trait1 + Trait2` (#34511).
             TyKind::ImplTrait(self.parse_ty_param_bounds()?)
-        } else if self.check(&token::Question) {
+        } else if self.check(&token::Question) ||
+                  self.check_lifetime() && self.look_ahead(1, |t| t == &token::BinOp(token::Plus)){
             // Bound list (trait object type)
-            // Bound lists starting with `'lt` are not currently supported (#40043)
             TyKind::TraitObject(self.parse_ty_param_bounds_common(allow_plus)?)
         } else {
             let msg = format!("expected type, found {}", self.this_token_descr());
@@ -1490,9 +1490,8 @@ impl<'a> Parser<'a> {
         let bounds = self.parse_ty_param_bounds()?;
         let sum_span = ty.span.to(self.prev_span);
 
-        let mut err = struct_span_err!(self.sess.span_diagnostic, ty.span, E0178,
-            "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(&ty));
-        err.span_label(ty.span, &format!("expected a path"));
+        let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
+            "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
 
         match ty.node {
             TyKind::Rptr(ref lifetime, ref mut_ty) => {
@@ -1511,9 +1510,11 @@ impl<'a> Parser<'a> {
                 err.span_suggestion(sum_span, "try adding parentheses:", sum_with_parens);
             }
             TyKind::Ptr(..) | TyKind::BareFn(..) => {
-                help!(&mut err, "perhaps you forgot parentheses?");
+                err.span_label(sum_span, "perhaps you forgot parentheses?");
             }
-            _ => {}
+            _ => {
+                err.span_label(sum_span, "expected a path");
+            },
         }
         err.emit();
         Ok(())
@@ -1544,7 +1545,7 @@ impl<'a> Parser<'a> {
 
     pub fn is_named_argument(&mut self) -> bool {
         let offset = match self.token {
-            token::BinOp(token::And) => 1,
+            token::BinOp(token::And) |
             token::AndAnd => 1,
             _ if self.token.is_keyword(keywords::Mut) => 1,
             _ => 0
@@ -2288,7 +2289,7 @@ impl<'a> Parser<'a> {
                     let e = if self.token.can_begin_expr()
                                && !(self.token == token::OpenDelim(token::Brace)
                                     && self.restrictions.contains(
-                                           Restrictions::RESTRICTION_NO_STRUCT_LITERAL)) {
+                                           RESTRICTION_NO_STRUCT_LITERAL)) {
                         Some(self.parse_expr()?)
                     } else {
                         None
@@ -2315,7 +2316,7 @@ impl<'a> Parser<'a> {
                         // This is a struct literal, unless we're prohibited
                         // from parsing struct literals here.
                         let prohibited = self.restrictions.contains(
-                            Restrictions::RESTRICTION_NO_STRUCT_LITERAL
+                            RESTRICTION_NO_STRUCT_LITERAL
                         );
                         if !prohibited {
                             return self.parse_struct_expr(lo, pth, attrs);
@@ -2553,7 +2554,7 @@ impl<'a> Parser<'a> {
                     let fstr = n.as_str();
                     let mut err = self.diagnostic().struct_span_err(self.prev_span,
                         &format!("unexpected token: `{}`", n));
-                    err.span_label(self.prev_span, &"unexpected token");
+                    err.span_label(self.prev_span, "unexpected token");
                     if fstr.chars().all(|x| "0123456789.".contains(x)) {
                         let float = match fstr.parse::<f64>().ok() {
                             Some(f) => f,
@@ -2697,6 +2698,19 @@ impl<'a> Parser<'a> {
                 let (span, e) = self.interpolated_or_expr_span(e)?;
                 (span, self.mk_unary(UnOp::Not, e))
             }
+            // Suggest `!` for bitwise negation when encountering a `~`
+            token::Tilde => {
+                self.bump();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                let span_of_tilde = lo;
+                let mut err = self.diagnostic().struct_span_err(span_of_tilde,
+                        "`~` can not be used as a unary operator");
+                err.span_label(span_of_tilde, "did you mean `!`?");
+                err.help("use `!` instead of `~` if you meant to perform bitwise negation");
+                err.emit();
+                (span, self.mk_unary(UnOp::Not, e))
+            }
             token::BinOp(token::Minus) => {
                 self.bump();
                 let e = self.parse_prefix_expr(None);
@@ -2719,7 +2733,7 @@ impl<'a> Parser<'a> {
             token::Ident(..) if self.token.is_keyword(keywords::In) => {
                 self.bump();
                 let place = self.parse_expr_res(
-                    Restrictions::RESTRICTION_NO_STRUCT_LITERAL,
+                    RESTRICTION_NO_STRUCT_LITERAL,
                     None,
                 )?;
                 let blk = self.parse_block()?;
@@ -2782,7 +2796,7 @@ impl<'a> Parser<'a> {
 
             let cur_op_span = self.span;
             let restrictions = if op.is_assign_like() {
-                self.restrictions & Restrictions::RESTRICTION_NO_STRUCT_LITERAL
+                self.restrictions & RESTRICTION_NO_STRUCT_LITERAL
             } else {
                 self.restrictions
             };
@@ -2832,13 +2846,13 @@ impl<'a> Parser<'a> {
 
             let rhs = match op.fixity() {
                 Fixity::Right => self.with_res(
-                    restrictions - Restrictions::RESTRICTION_STMT_EXPR,
+                    restrictions - RESTRICTION_STMT_EXPR,
                     |this| {
                         this.parse_assoc_expr_with(op.precedence(),
                             LhsExpr::NotYetParsed)
                 }),
                 Fixity::Left => self.with_res(
-                    restrictions - Restrictions::RESTRICTION_STMT_EXPR,
+                    restrictions - RESTRICTION_STMT_EXPR,
                     |this| {
                         this.parse_assoc_expr_with(op.precedence() + 1,
                             LhsExpr::NotYetParsed)
@@ -2846,7 +2860,7 @@ impl<'a> Parser<'a> {
                 // We currently have no non-associative operators that are not handled above by
                 // the special cases. The code is here only for future convenience.
                 Fixity::None => self.with_res(
-                    restrictions - Restrictions::RESTRICTION_STMT_EXPR,
+                    restrictions - RESTRICTION_STMT_EXPR,
                     |this| {
                         this.parse_assoc_expr_with(op.precedence() + 1,
                             LhsExpr::NotYetParsed)
@@ -2956,7 +2970,7 @@ impl<'a> Parser<'a> {
         if self.token.can_begin_expr() {
             // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
             if self.token == token::OpenDelim(token::Brace) {
-                return !self.restrictions.contains(Restrictions::RESTRICTION_NO_STRUCT_LITERAL);
+                return !self.restrictions.contains(RESTRICTION_NO_STRUCT_LITERAL);
             }
             true
         } else {
@@ -2970,7 +2984,7 @@ impl<'a> Parser<'a> {
             return self.parse_if_let_expr(attrs);
         }
         let lo = self.prev_span;
-        let cond = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None)?;
+        let cond = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL, None)?;
         let thn = self.parse_block()?;
         let mut els: Option<P<Expr>> = None;
         let mut hi = thn.span;
@@ -2989,7 +3003,7 @@ impl<'a> Parser<'a> {
         self.expect_keyword(keywords::Let)?;
         let pat = self.parse_pat()?;
         self.expect(&token::Eq)?;
-        let expr = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None)?;
+        let expr = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL, None)?;
         let thn = self.parse_block()?;
         let (hi, els) = if self.eat_keyword(keywords::Else) {
             let expr = self.parse_else_expr()?;
@@ -3043,7 +3057,7 @@ impl<'a> Parser<'a> {
 
         let pat = self.parse_pat()?;
         self.expect_keyword(keywords::In)?;
-        let expr = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None)?;
+        let expr = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL, None)?;
         let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
         attrs.extend(iattrs);
 
@@ -3058,7 +3072,7 @@ impl<'a> Parser<'a> {
         if self.token.is_keyword(keywords::Let) {
             return self.parse_while_let_expr(opt_ident, span_lo, attrs);
         }
-        let cond = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None)?;
+        let cond = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL, None)?;
         let (iattrs, body) = self.parse_inner_attrs_and_block()?;
         attrs.extend(iattrs);
         let span = span_lo.to(body.span);
@@ -3072,7 +3086,7 @@ impl<'a> Parser<'a> {
         self.expect_keyword(keywords::Let)?;
         let pat = self.parse_pat()?;
         self.expect(&token::Eq)?;
-        let expr = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None)?;
+        let expr = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL, None)?;
         let (iattrs, body) = self.parse_inner_attrs_and_block()?;
         attrs.extend(iattrs);
         let span = span_lo.to(body.span);
@@ -3102,7 +3116,7 @@ impl<'a> Parser<'a> {
     fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
         let match_span = self.prev_span;
         let lo = self.prev_span;
-        let discriminant = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL,
+        let discriminant = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL,
                                                None)?;
         if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
             if self.token == token::Token::Semi {
@@ -3138,12 +3152,13 @@ impl<'a> Parser<'a> {
 
         let attrs = self.parse_outer_attributes()?;
         let pats = self.parse_pats()?;
-        let mut guard = None;
-        if self.eat_keyword(keywords::If) {
-            guard = Some(self.parse_expr()?);
-        }
+        let guard = if self.eat_keyword(keywords::If) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
         self.expect(&token::FatArrow)?;
-        let expr = self.parse_expr_res(Restrictions::RESTRICTION_STMT_EXPR, None)?;
+        let expr = self.parse_expr_res(RESTRICTION_STMT_EXPR, None)?;
 
         let require_comma =
             !classify::expr_is_simple_block(&expr)
@@ -3584,10 +3599,11 @@ impl<'a> Parser<'a> {
         let lo = self.span;
         let pat = self.parse_pat()?;
 
-        let mut ty = None;
-        if self.eat(&token::Colon) {
-            ty = Some(self.parse_ty()?);
-        }
+        let ty = if self.eat(&token::Colon) {
+            Some(self.parse_ty()?)
+        } else {
+            None
+        };
         let init = self.parse_initializer()?;
         Ok(P(ast::Local {
             ty: ty,
@@ -3724,7 +3740,7 @@ impl<'a> Parser<'a> {
         self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
 
         // prevent `while catch {} {}`, `if catch {} {} else {}`, etc.
-        !self.restrictions.contains(Restrictions::RESTRICTION_NO_STRUCT_LITERAL)
+        !self.restrictions.contains(RESTRICTION_NO_STRUCT_LITERAL)
     }
 
     fn is_union_item(&self) -> bool {
@@ -3796,7 +3812,7 @@ impl<'a> Parser<'a> {
                     self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
                 };
 
-                let expr = self.with_res(Restrictions::RESTRICTION_STMT_EXPR, |this| {
+                let expr = self.with_res(RESTRICTION_STMT_EXPR, |this| {
                     let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
                     this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
                 })?;
@@ -3913,7 +3929,7 @@ impl<'a> Parser<'a> {
                 },
                 None => {
                     let unused_attrs = |attrs: &[_], s: &mut Self| {
-                        if attrs.len() > 0 {
+                        if !attrs.is_empty() {
                             if s.prev_token_kind == PrevTokenKind::DocComment {
                                 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
                             } else {
@@ -3936,7 +3952,7 @@ impl<'a> Parser<'a> {
 
                     // Remainder are line-expr stmts.
                     let e = self.parse_expr_res(
-                        Restrictions::RESTRICTION_STMT_EXPR, Some(attrs.into()))?;
+                        RESTRICTION_STMT_EXPR, Some(attrs.into()))?;
                     Stmt {
                         id: ast::DUMMY_NODE_ID,
                         span: lo.to(e.span),
@@ -3949,7 +3965,7 @@ impl<'a> Parser<'a> {
 
     /// Is this expression a successfully-parsed statement?
     fn expr_is_complete(&mut self, e: &Expr) -> bool {
-        self.restrictions.contains(Restrictions::RESTRICTION_STMT_EXPR) &&
+        self.restrictions.contains(RESTRICTION_STMT_EXPR) &&
             !classify::expr_requires_semi_to_be_stmt(e)
     }
 
@@ -4776,7 +4792,7 @@ impl<'a> Parser<'a> {
             sp,
             &format!("missing `fn`, `type`, or `const` for {}-item declaration",
                      item_type));
-        err.span_label(sp, &"missing `fn`, `type`, or `const`");
+        err.span_label(sp, "missing `fn`, `type`, or `const`");
         err
     }
 
@@ -4799,7 +4815,7 @@ impl<'a> Parser<'a> {
                 self.expect(&token::Not)?;
             }
 
-            self.complain_if_pub_macro(&vis, prev_span);
+            self.complain_if_pub_macro(vis, prev_span);
 
             // eat a matched-delimiter token tree:
             *at_end = true;
@@ -4863,7 +4879,9 @@ impl<'a> Parser<'a> {
     ///    impl<T> Foo { ... }
     ///    impl<T> ToString for &'static T { ... }
     ///    impl Send for .. {}
-    fn parse_item_impl(&mut self, unsafety: ast::Unsafety) -> PResult<'a, ItemInfo> {
+    fn parse_item_impl(&mut self,
+                       unsafety: ast::Unsafety,
+                       defaultness: Defaultness) -> PResult<'a, ItemInfo> {
         let impl_span = self.span;
 
         // First, parse type parameters if necessary.
@@ -4899,13 +4917,10 @@ impl<'a> Parser<'a> {
                 }
             }
         } else {
-            match polarity {
-                ast::ImplPolarity::Negative => {
-                    // This is a negated type implementation
-                    // `impl !MyType {}`, which is not allowed.
-                    self.span_err(neg_span, "inherent implementation can't be negated");
-                },
-                _ => {}
+            if polarity == ast::ImplPolarity::Negative {
+                // This is a negated type implementation
+                // `impl !MyType {}`, which is not allowed.
+                self.span_err(neg_span, "inherent implementation can't be negated");
             }
             None
         };
@@ -4916,6 +4931,11 @@ impl<'a> Parser<'a> {
                                           allowed to have generics");
             }
 
+            if let ast::Defaultness::Default = defaultness {
+                self.span_err(impl_span, "`default impl` is not allowed for \
+                                         default trait implementations");
+            }
+
             self.expect(&token::OpenDelim(token::Brace))?;
             self.expect(&token::CloseDelim(token::Brace))?;
             Ok((keywords::Invalid.ident(),
@@ -4944,7 +4964,7 @@ impl<'a> Parser<'a> {
             }
 
             Ok((keywords::Invalid.ident(),
-             ItemKind::Impl(unsafety, polarity, generics, opt_trait, ty, impl_items),
+             ItemKind::Impl(unsafety, polarity, defaultness, generics, opt_trait, ty, impl_items),
              Some(attrs)))
         }
     }
@@ -5122,7 +5142,6 @@ impl<'a> Parser<'a> {
         }
 
         if self.check(&token::OpenDelim(token::Paren)) {
-            let start_span = self.span;
             // We don't `self.bump()` the `(` yet because this might be a struct definition where
             // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
             // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
@@ -5161,12 +5180,9 @@ impl<'a> Parser<'a> {
 `pub(in path::to::module)`: visible only on the specified path"##;
                 let path = self.parse_path(PathStyle::Mod)?;
                 let path_span = self.prev_span;
-                let help_msg = format!("to make this visible only to module `{}`, add `in` before \
-                                       the path:",
-                                       path);
+                let help_msg = format!("make this visible only to module `{}` with `in`:", path);
                 self.expect(&token::CloseDelim(token::Paren))?;  // `)`
-                let sp = start_span.to(self.prev_span);
-                let mut err = self.span_fatal_help(sp, &msg, &suggestion);
+                let mut err = self.span_fatal_help(path_span, msg, suggestion);
                 err.span_suggestion(path_span, &help_msg, format!("in {}", path));
                 err.emit();  // emit diagnostic, but continue with public visibility
             }
@@ -5363,24 +5379,25 @@ impl<'a> Parser<'a> {
             }
             let mut err = self.diagnostic().struct_span_err(id_sp,
                 "cannot declare a new module at this location");
-            let this_module = match self.directory.path.file_name() {
-                Some(file_name) => file_name.to_str().unwrap().to_owned(),
-                None => self.root_module_name.as_ref().unwrap().clone(),
-            };
-            err.span_note(id_sp,
-                          &format!("maybe move this module `{0}` to its own directory \
-                                    via `{0}{1}mod.rs`",
-                                   this_module,
-                                   path::MAIN_SEPARATOR));
+            if id_sp != syntax_pos::DUMMY_SP {
+                let src_path = PathBuf::from(self.sess.codemap().span_to_filename(id_sp));
+                if let Some(stem) = src_path.file_stem() {
+                    let mut dest_path = src_path.clone();
+                    dest_path.set_file_name(stem);
+                    dest_path.push("mod.rs");
+                    err.span_note(id_sp,
+                                  &format!("maybe move this module `{}` to its own \
+                                            directory via `{}`", src_path.to_string_lossy(),
+                                           dest_path.to_string_lossy()));
+                }
+            }
             if paths.path_exists {
                 err.span_note(id_sp,
                               &format!("... or maybe `use` the module `{}` instead \
                                         of possibly redeclaring it",
                                        paths.name));
-                Err(err)
-            } else {
-                Err(err)
             }
+            Err(err)
         } else {
             paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
         }
@@ -5756,13 +5773,19 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.check_keyword(keywords::Unsafe) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Impl))
+        if (self.check_keyword(keywords::Unsafe) &&
+            self.look_ahead(1, |t| t.is_keyword(keywords::Impl))) ||
+           (self.check_keyword(keywords::Default) &&
+            self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) &&
+            self.look_ahead(2, |t| t.is_keyword(keywords::Impl)))
         {
             // IMPL ITEM
+            let defaultness = self.parse_defaultness()?;
             self.expect_keyword(keywords::Unsafe)?;
             self.expect_keyword(keywords::Impl)?;
-            let (ident, item_, extra_attrs) = self.parse_item_impl(ast::Unsafety::Unsafe)?;
+            let (ident,
+                 item_,
+                 extra_attrs) = self.parse_item_impl(ast::Unsafety::Unsafe, defaultness)?;
             let prev_span = self.prev_span;
             let item = self.mk_item(lo.to(prev_span),
                                     ident,
@@ -5856,9 +5879,16 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.eat_keyword(keywords::Impl) {
+        if (self.check_keyword(keywords::Impl)) ||
+           (self.check_keyword(keywords::Default) &&
+            self.look_ahead(1, |t| t.is_keyword(keywords::Impl)))
+        {
             // IMPL ITEM
-            let (ident, item_, extra_attrs) = self.parse_item_impl(ast::Unsafety::Normal)?;
+            let defaultness = self.parse_defaultness()?;
+            self.expect_keyword(keywords::Impl)?;
+            let (ident,
+                 item_,
+                 extra_attrs) = self.parse_item_impl(ast::Unsafety::Normal, defaultness)?;
             let prev_span = self.prev_span;
             let item = self.mk_item(lo.to(prev_span),
                                     ident,
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 25cabef70c1..77db604c56e 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -53,6 +53,10 @@ impl DelimToken {
     pub fn len(self) -> usize {
         if self == NoDelim { 0 } else { 1 }
     }
+
+    pub fn is_empty(self) -> bool {
+        self == NoDelim
+    }
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
@@ -198,17 +202,17 @@ impl Token {
     pub fn can_begin_expr(&self) -> bool {
         match *self {
             Ident(ident)                => ident_can_begin_expr(ident), // value name or keyword
-            OpenDelim(..)               => true, // tuple, array or block
-            Literal(..)                 => true, // literal
-            Not                         => true, // operator not
-            BinOp(Minus)                => true, // unary minus
-            BinOp(Star)                 => true, // dereference
-            BinOp(Or) | OrOr            => true, // closure
-            BinOp(And)                  => true, // reference
-            AndAnd                      => true, // double reference
-            DotDot | DotDotDot          => true, // range notation
-            Lt | BinOp(Shl)             => true, // associated path
-            ModSep                      => true, // global path
+            OpenDelim(..)               | // tuple, array or block
+            Literal(..)                 | // literal
+            Not                         | // operator not
+            BinOp(Minus)                | // unary minus
+            BinOp(Star)                 | // dereference
+            BinOp(Or) | OrOr            | // closure
+            BinOp(And)                  | // reference
+            AndAnd                      | // double reference
+            DotDot | DotDotDot          | // range notation
+            Lt | BinOp(Shl)             | // associated path
+            ModSep                      | // global path
             Pound                       => true, // expression attributes
             Interpolated(ref nt) => match **nt {
                 NtIdent(..) | NtExpr(..) | NtBlock(..) | NtPath(..) => true,
@@ -222,16 +226,16 @@ impl Token {
     pub fn can_begin_type(&self) -> bool {
         match *self {
             Ident(ident)                => ident_can_begin_type(ident), // type name or keyword
-            OpenDelim(Paren)            => true, // tuple
-            OpenDelim(Bracket)          => true, // array
-            Underscore                  => true, // placeholder
-            Not                         => true, // never
-            BinOp(Star)                 => true, // raw pointer
-            BinOp(And)                  => true, // reference
-            AndAnd                      => true, // double reference
-            Question                    => true, // maybe bound in trait object
-            Lifetime(..)                => true, // lifetime bound in trait object
-            Lt | BinOp(Shl)             => true, // associated path
+            OpenDelim(Paren)            | // tuple
+            OpenDelim(Bracket)          | // array
+            Underscore                  | // placeholder
+            Not                         | // never
+            BinOp(Star)                 | // raw pointer
+            BinOp(And)                  | // reference
+            AndAnd                      | // double reference
+            Question                    | // maybe bound in trait object
+            Lifetime(..)                | // lifetime bound in trait object
+            Lt | BinOp(Shl)             | // associated path
             ModSep                      => true, // global path
             Interpolated(ref nt) => match **nt {
                 NtIdent(..) | NtTy(..) | NtPath(..) => true,