Stabilize in 1.19

39 files changed, 896 insertions, 789 deletions

diff --git a/src/libsyntax/Cargo.toml b/src/libsyntax/Cargo.toml
index 97d37266130..82e7cfa0032 100644
--- a/src/libsyntax/Cargo.toml
+++ b/src/libsyntax/Cargo.toml
@@ -11,7 +11,7 @@ crate-type = ["dylib"]
 [dependencies]
 serialize = { path = "../libserialize" }
 log = "0.3"
-rustc_bitflags = { path = "../librustc_bitflags" }
+bitflags = "0.8"
 syntax_pos = { path = "../libsyntax_pos" }
 rustc_errors = { path = "../librustc_errors" }
 rustc_data_structures = { path = "../librustc_data_structures" }
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 131adfe47af..24ce99208ed 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -715,7 +715,7 @@ impl Stmt {
             StmtKind::Mac(mac) => StmtKind::Mac(mac.map(|(mac, _style, attrs)| {
                 (mac, MacStmtStyle::Semicolon, attrs)
             })),
-            node @ _ => node,
+            node => node,
         };
         self
     }
@@ -1076,16 +1076,16 @@ impl LitKind {
     pub fn is_unsuffixed(&self) -> bool {
         match *self {
             // unsuffixed variants
-            LitKind::Str(..) => true,
-            LitKind::ByteStr(..) => true,
-            LitKind::Byte(..) => true,
-            LitKind::Char(..) => true,
-            LitKind::Int(_, LitIntType::Unsuffixed) => true,
-            LitKind::FloatUnsuffixed(..) => true,
+            LitKind::Str(..) |
+            LitKind::ByteStr(..) |
+            LitKind::Byte(..) |
+            LitKind::Char(..) |
+            LitKind::Int(_, LitIntType::Unsuffixed) |
+            LitKind::FloatUnsuffixed(..) |
             LitKind::Bool(..) => true,
             // suffixed variants
-            LitKind::Int(_, LitIntType::Signed(..)) => false,
-            LitKind::Int(_, LitIntType::Unsigned(..)) => false,
+            LitKind::Int(_, LitIntType::Signed(..)) |
+            LitKind::Int(_, LitIntType::Unsigned(..)) |
             LitKind::Float(..) => false,
         }
     }
@@ -1852,6 +1852,7 @@ pub enum ItemKind {
     /// E.g. `impl<A> Foo<A> { .. }` or `impl<A> Trait for Foo<A> { .. }`
     Impl(Unsafety,
              ImplPolarity,
+             Defaultness,
              Generics,
              Option<TraitRef>, // (optional) trait this impl implements
              P<Ty>, // self
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index 82492d97627..45f891d8dc5 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -112,7 +112,7 @@ impl NestedMetaItem {
     /// Returns the MetaItem if self is a NestedMetaItemKind::MetaItem.
     pub fn meta_item(&self) -> Option<&MetaItem> {
         match self.node {
-            NestedMetaItemKind::MetaItem(ref item) => Some(&item),
+            NestedMetaItemKind::MetaItem(ref item) => Some(item),
             _ => None
         }
     }
@@ -120,7 +120,7 @@ impl NestedMetaItem {
     /// Returns the Lit if self is a NestedMetaItemKind::Literal.
     pub fn literal(&self) -> Option<&Lit> {
         match self.node {
-            NestedMetaItemKind::Literal(ref lit) => Some(&lit),
+            NestedMetaItemKind::Literal(ref lit) => Some(lit),
             _ => None
         }
     }
@@ -259,7 +259,7 @@ impl MetaItem {
         match self.node {
             MetaItemKind::NameValue(ref v) => {
                 match v.node {
-                    LitKind::Str(ref s, _) => Some((*s).clone()),
+                    LitKind::Str(ref s, _) => Some(*s),
                     _ => None,
                 }
             },
@@ -511,8 +511,7 @@ pub fn find_export_name_attr(diag: &Handler, attrs: &[Attribute]) -> Option<Symb
             } else {
                 struct_span_err!(diag, attr.span, E0558,
                                  "export_name attribute has invalid format")
-                    .span_label(attr.span,
-                                &format!("did you mean #[export_name=\"*\"]?"))
+                    .span_label(attr.span, "did you mean #[export_name=\"*\"]?")
                     .emit();
                 None
             }
@@ -1218,9 +1217,10 @@ impl LitKind {
                 Token::Literal(token::Lit::Float(symbol), Some(Symbol::intern(ty.ty_to_string())))
             }
             LitKind::FloatUnsuffixed(symbol) => Token::Literal(token::Lit::Float(symbol), None),
-            LitKind::Bool(value) => Token::Ident(Ident::with_empty_ctxt(Symbol::intern(match value {
-                true => "true",
-                false => "false",
+            LitKind::Bool(value) => Token::Ident(Ident::with_empty_ctxt(Symbol::intern(if value {
+                "true"
+            } else {
+                "false"
             }))),
         }
     }
@@ -1262,7 +1262,7 @@ impl<T: HasAttrs> HasAttrs for Spanned<T> {
 
 impl HasAttrs for Vec<Attribute> {
     fn attrs(&self) -> &[Attribute] {
-        &self
+        self
     }
     fn map_attrs<F: FnOnce(Vec<Attribute>) -> Vec<Attribute>>(self, f: F) -> Self {
         f(self)
@@ -1271,7 +1271,7 @@ impl HasAttrs for Vec<Attribute> {
 
 impl HasAttrs for ThinVec<Attribute> {
     fn attrs(&self) -> &[Attribute] {
-        &self
+        self
     }
     fn map_attrs<F: FnOnce(Vec<Attribute>) -> Vec<Attribute>>(self, f: F) -> Self {
         f(self.into()).into()
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index da2d0a33d1a..d32c3ec5f46 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -21,8 +21,8 @@ pub use syntax_pos::*;
 pub use syntax_pos::hygiene::{ExpnFormat, ExpnInfo, NameAndSpan};
 pub use self::ExpnFormat::*;
 
-use std::cell::RefCell;
-use std::path::{Path,PathBuf};
+use std::cell::{RefCell, Ref};
+use std::path::{Path, PathBuf};
 use std::rc::Rc;
 
 use std::env;
@@ -103,33 +103,69 @@ impl FileLoader for RealFileLoader {
 //
 
 pub struct CodeMap {
-    pub files: RefCell<Vec<Rc<FileMap>>>,
-    file_loader: Box<FileLoader>
+    // The `files` field should not be visible outside of libsyntax so that we
+    // can do proper dependency tracking.
+    pub(super) files: RefCell<Vec<Rc<FileMap>>>,
+    file_loader: Box<FileLoader>,
+    // This is used to apply the file path remapping as specified via
+    // -Zremap-path-prefix to all FileMaps allocated within this CodeMap.
+    path_mapping: FilePathMapping,
+    // The CodeMap will invoke this callback whenever a specific FileMap is
+    // accessed. The callback starts out as a no-op but when the dependency
+    // graph becomes available later during the compilation process, it is
+    // be replaced with something that notifies the dep-tracking system.
+    dep_tracking_callback: RefCell<Box<Fn(&FileMap)>>,
 }
 
 impl CodeMap {
-    pub fn new() -> CodeMap {
+    pub fn new(path_mapping: FilePathMapping) -> CodeMap {
         CodeMap {
             files: RefCell::new(Vec::new()),
-            file_loader: Box::new(RealFileLoader)
+            file_loader: Box::new(RealFileLoader),
+            path_mapping: path_mapping,
+            dep_tracking_callback: RefCell::new(Box::new(|_| {})),
         }
     }
 
-    pub fn with_file_loader(file_loader: Box<FileLoader>) -> CodeMap {
+    pub fn with_file_loader(file_loader: Box<FileLoader>,
+                            path_mapping: FilePathMapping)
+                            -> CodeMap {
         CodeMap {
             files: RefCell::new(Vec::new()),
-            file_loader: file_loader
+            file_loader: file_loader,
+            path_mapping: path_mapping,
+            dep_tracking_callback: RefCell::new(Box::new(|_| {})),
         }
     }
 
+    pub fn path_mapping(&self) -> &FilePathMapping {
+        &self.path_mapping
+    }
+
+    pub fn set_dep_tracking_callback(&self, cb: Box<Fn(&FileMap)>) {
+        *self.dep_tracking_callback.borrow_mut() = cb;
+    }
+
     pub fn file_exists(&self, path: &Path) -> bool {
         self.file_loader.file_exists(path)
     }
 
     pub fn load_file(&self, path: &Path) -> io::Result<Rc<FileMap>> {
         let src = self.file_loader.read_file(path)?;
-        let abs_path = self.file_loader.abs_path(path).map(|p| p.to_str().unwrap().to_string());
-        Ok(self.new_filemap(path.to_str().unwrap().to_string(), abs_path, src))
+        Ok(self.new_filemap(path.to_str().unwrap().to_string(), src))
+    }
+
+    pub fn files(&self) -> Ref<Vec<Rc<FileMap>>> {
+        let files = self.files.borrow();
+        for file in files.iter() {
+            (self.dep_tracking_callback.borrow())(file);
+        }
+        files
+    }
+
+    /// Only use this if you do your own dependency tracking!
+    pub fn files_untracked(&self) -> Ref<Vec<Rc<FileMap>>> {
+        self.files.borrow()
     }
 
     fn next_start_pos(&self) -> usize {
@@ -144,8 +180,7 @@ impl CodeMap {
 
     /// Creates a new filemap without setting its line information. If you don't
     /// intend to set the line information yourself, you should use new_filemap_and_lines.
-    pub fn new_filemap(&self, filename: FileName, abs_path: Option<FileName>,
-                       mut src: String) -> Rc<FileMap> {
+    pub fn new_filemap(&self, filename: FileName, mut src: String) -> Rc<FileMap> {
         let start_pos = self.next_start_pos();
         let mut files = self.files.borrow_mut();
 
@@ -156,9 +191,12 @@ impl CodeMap {
 
         let end_pos = start_pos + src.len();
 
+        let (filename, was_remapped) = self.path_mapping.map_prefix(filename);
+
         let filemap = Rc::new(FileMap {
             name: filename,
-            abs_path: abs_path,
+            name_was_remapped: was_remapped,
+            crate_of_origin: 0,
             src: Some(Rc::new(src)),
             start_pos: Pos::from_usize(start_pos),
             end_pos: Pos::from_usize(end_pos),
@@ -172,11 +210,8 @@ impl CodeMap {
     }
 
     /// Creates a new filemap and sets its line information.
-    pub fn new_filemap_and_lines(&self, filename: &str, abs_path: Option<&str>,
-                                 src: &str) -> Rc<FileMap> {
-        let fm = self.new_filemap(filename.to_string(),
-                                  abs_path.map(|s| s.to_owned()),
-                                  src.to_owned());
+    pub fn new_filemap_and_lines(&self, filename: &str, src: &str) -> Rc<FileMap> {
+        let fm = self.new_filemap(filename.to_string(), src.to_owned());
         let mut byte_pos: u32 = fm.start_pos.0;
         for line in src.lines() {
             // register the start of this line
@@ -195,7 +230,8 @@ impl CodeMap {
     /// information for things inlined from other crates.
     pub fn new_imported_filemap(&self,
                                 filename: FileName,
-                                abs_path: Option<FileName>,
+                                name_was_remapped: bool,
+                                crate_of_origin: u32,
                                 source_len: usize,
                                 mut file_local_lines: Vec<BytePos>,
                                 mut file_local_multibyte_chars: Vec<MultiByteChar>)
@@ -216,7 +252,8 @@ impl CodeMap {
 
         let filemap = Rc::new(FileMap {
             name: filename,
-            abs_path: abs_path,
+            name_was_remapped: name_was_remapped,
+            crate_of_origin: crate_of_origin,
             src: None,
             start_pos: start_pos,
             end_pos: end_pos,
@@ -274,6 +311,8 @@ impl CodeMap {
         let files = self.files.borrow();
         let f = (*files)[idx].clone();
 
+        (self.dep_tracking_callback.borrow())(&f);
+
         match f.lookup_line(pos) {
             Some(line) => Ok(FileMapAndLine { fm: f, line: line }),
             None => Err(f)
@@ -446,7 +485,7 @@ impl CodeMap {
         match self.span_to_snippet(sp) {
             Ok(snippet) => {
                 let snippet = snippet.split(c).nth(0).unwrap_or("").trim_right();
-                if snippet.len() > 0 && !snippet.contains('\n') {
+                if !snippet.is_empty() && !snippet.contains('\n') {
                     Span { hi: BytePos(sp.lo.0 + snippet.len() as u32), ..sp }
                 } else {
                     sp
@@ -463,6 +502,7 @@ impl CodeMap {
     pub fn get_filemap(&self, filename: &str) -> Option<Rc<FileMap>> {
         for fm in self.files.borrow().iter() {
             if filename == fm.name {
+               (self.dep_tracking_callback.borrow())(fm);
                 return Some(fm.clone());
             }
         }
@@ -473,6 +513,7 @@ impl CodeMap {
     pub fn lookup_byte_offset(&self, bpos: BytePos) -> FileMapAndBytePos {
         let idx = self.lookup_filemap_idx(bpos);
         let fm = (*self.files.borrow())[idx].clone();
+        (self.dep_tracking_callback.borrow())(&fm);
         let offset = bpos - fm.start_pos;
         FileMapAndBytePos {fm: fm, pos: offset}
     }
@@ -483,6 +524,8 @@ impl CodeMap {
         let files = self.files.borrow();
         let map = &(*files)[idx];
 
+        (self.dep_tracking_callback.borrow())(map);
+
         // The number of extra bytes due to multibyte chars in the FileMap
         let mut total_extra_bytes = 0;
 
@@ -528,7 +571,7 @@ impl CodeMap {
     }
 
     pub fn count_lines(&self) -> usize {
-        self.files.borrow().iter().fold(0, |a, f| a + f.count_lines())
+        self.files().iter().fold(0, |a, f| a + f.count_lines())
     }
 }
 
@@ -550,6 +593,42 @@ impl CodeMapper for CodeMap {
     }
 }
 
+#[derive(Clone)]
+pub struct FilePathMapping {
+    mapping: Vec<(String, String)>,
+}
+
+impl FilePathMapping {
+    pub fn empty() -> FilePathMapping {
+        FilePathMapping {
+            mapping: vec![]
+        }
+    }
+
+    pub fn new(mapping: Vec<(String, String)>) -> FilePathMapping {
+        FilePathMapping {
+            mapping: mapping
+        }
+    }
+
+    /// Applies any path prefix substitution as defined by the mapping.
+    /// The return value is the remapped path and a boolean indicating whether
+    /// the path was affected by the mapping.
+    pub fn map_prefix(&self, path: String) -> (String, bool) {
+        // NOTE: We are iterating over the mapping entries from last to first
+        //       because entries specified later on the command line should
+        //       take precedence.
+        for &(ref from, ref to) in self.mapping.iter().rev() {
+            if path.starts_with(from) {
+                let mapped = path.replacen(from, to, 1);
+                return (mapped, true);
+            }
+        }
+
+        (path, false)
+    }
+}
+
 // _____________________________________________________________________________
 // Tests
 //
@@ -561,9 +640,8 @@ mod tests {
 
     #[test]
     fn t1 () {
-        let cm = CodeMap::new();
+        let cm = CodeMap::new(FilePathMapping::empty());
         let fm = cm.new_filemap("blork.rs".to_string(),
-                                None,
                                 "first line.\nsecond line".to_string());
         fm.next_line(BytePos(0));
         // Test we can get lines with partial line info.
@@ -578,9 +656,8 @@ mod tests {
     #[test]
     #[should_panic]
     fn t2 () {
-        let cm = CodeMap::new();
+        let cm = CodeMap::new(FilePathMapping::empty());
         let fm = cm.new_filemap("blork.rs".to_string(),
-                                None,
                                 "first line.\nsecond line".to_string());
         // TESTING *REALLY* BROKEN BEHAVIOR:
         fm.next_line(BytePos(0));
@@ -589,15 +666,12 @@ mod tests {
     }
 
     fn init_code_map() -> CodeMap {
-        let cm = CodeMap::new();
+        let cm = CodeMap::new(FilePathMapping::empty());
         let fm1 = cm.new_filemap("blork.rs".to_string(),
-                                 None,
                                  "first line.\nsecond line".to_string());
         let fm2 = cm.new_filemap("empty.rs".to_string(),
-                                 None,
                                  "".to_string());
         let fm3 = cm.new_filemap("blork2.rs".to_string(),
-                                 None,
                                  "first line.\nsecond line".to_string());
 
         fm1.next_line(BytePos(0));
@@ -656,14 +730,12 @@ mod tests {
     }
 
     fn init_code_map_mbc() -> CodeMap {
-        let cm = CodeMap::new();
+        let cm = CodeMap::new(FilePathMapping::empty());
         // € is a three byte utf8 char.
         let fm1 =
             cm.new_filemap("blork.rs".to_string(),
-                           None,
                            "fir€st €€€€ line.\nsecond line".to_string());
         let fm2 = cm.new_filemap("blork2.rs".to_string(),
-                                 None,
                                  "first line€€.\n€ second line".to_string());
 
         fm1.next_line(BytePos(0));
@@ -728,10 +800,10 @@ mod tests {
     /// lines in the middle of a file.
     #[test]
     fn span_to_snippet_and_lines_spanning_multiple_lines() {
-        let cm = CodeMap::new();
+        let cm = CodeMap::new(FilePathMapping::empty());
         let inputtext = "aaaaa\nbbbbBB\nCCC\nDDDDDddddd\neee\n";
         let selection = "     \n    ~~\n~~~\n~~~~~     \n   \n";
-        cm.new_filemap_and_lines("blork.rs", None, inputtext);
+        cm.new_filemap_and_lines("blork.rs", inputtext);
         let span = span_from_selection(inputtext, selection);
 
         // check that we are extracting the text we thought we were extracting
@@ -770,11 +842,11 @@ mod tests {
     /// Test failing to merge two spans on different lines
     #[test]
     fn span_merging_fail() {
-        let cm = CodeMap::new();
+        let cm = CodeMap::new(FilePathMapping::empty());
         let inputtext  = "bbbb BB\ncc CCC\n";
         let selection1 = "     ~~\n      \n";
         let selection2 = "       \n   ~~~\n";
-        cm.new_filemap_and_lines("blork.rs", None, inputtext);
+        cm.new_filemap_and_lines("blork.rs", inputtext);
         let span1 = span_from_selection(inputtext, selection1);
         let span2 = span_from_selection(inputtext, selection2);
 
diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
index ede8a33df65..2e98c7d9626 100644
--- a/src/libsyntax/config.rs
+++ b/src/libsyntax/config.rs
@@ -123,7 +123,7 @@ impl<'a> StripUnconfigured<'a> {
                 return false;
             }
 
-            let mis = if !is_cfg(&attr) {
+            let mis = if !is_cfg(attr) {
                 return true;
             } else if let Some(mis) = attr.meta_item_list() {
                 mis
@@ -150,7 +150,7 @@ impl<'a> StripUnconfigured<'a> {
         // flag the offending attributes
         for attr in attrs.iter() {
             if !self.features.map(|features| features.stmt_expr_attributes).unwrap_or(true) {
-                let mut err = feature_err(&self.sess,
+                let mut err = feature_err(self.sess,
                                           "stmt_expr_attributes",
                                           attr.span,
                                           GateIssue::Language,
@@ -258,7 +258,7 @@ impl<'a> StripUnconfigured<'a> {
     pub fn configure_struct_expr_field(&mut self, field: ast::Field) -> Option<ast::Field> {
         if !self.features.map(|features| features.struct_field_attributes).unwrap_or(true) {
             if !field.attrs.is_empty() {
-                let mut err = feature_err(&self.sess,
+                let mut err = feature_err(self.sess,
                                           "struct_field_attributes",
                                           field.span,
                                           GateIssue::Language,
@@ -290,7 +290,7 @@ impl<'a> StripUnconfigured<'a> {
         for attr in attrs.iter() {
             if !self.features.map(|features| features.struct_field_attributes).unwrap_or(true) {
                 let mut err = feature_err(
-                    &self.sess,
+                    self.sess,
                     "struct_field_attributes",
                     attr.span,
                     GateIssue::Language,
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
index fe5cb87ad59..73aeb40df84 100644
--- a/src/libsyntax/diagnostics/plugin.rs
+++ b/src/libsyntax/diagnostics/plugin.rs
@@ -120,7 +120,7 @@ pub fn expand_register_diagnostic<'cx>(ecx: &'cx mut ExtCtxt,
 
         // URLs can be unavoidably longer than the line limit, so we allow them.
         // Allowed format is: `[name]: https://www.rust-lang.org/`
-        let is_url = |l: &str| l.starts_with('[') && l.contains("]:") && l.contains("http");
+        let is_url = |l: &str| l.starts_with("[") && l.contains("]:") && l.contains("http");
 
         if msg.lines().any(|line| line.len() > MAX_DESCRIPTION_WIDTH && !is_url(line)) {
             ecx.span_err(span, &format!(
@@ -177,7 +177,7 @@ pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt,
             if let Err(e) = output_metadata(ecx,
                                             &target_triple,
                                             &crate_name.name.as_str(),
-                                            &diagnostics) {
+                                            diagnostics) {
                 ecx.span_bug(span, &format!(
                     "error writing metadata for triple `{}` and crate `{}`, error: {}, \
                      cause: {:?}",
@@ -227,7 +227,7 @@ pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt,
 
     MacEager::items(SmallVector::many(vec![
         P(ast::Item {
-            ident: name.clone(),
+            ident: *name,
             attrs: Vec::new(),
             id: ast::DUMMY_NODE_ID,
             node: ast::ItemKind::Const(
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index fda026fec64..1930f61121b 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -24,6 +24,7 @@ use ptr::P;
 use symbol::Symbol;
 use util::small_vector::SmallVector;
 
+use std::collections::HashMap;
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::default::Default;
@@ -534,7 +535,7 @@ pub enum SyntaxExtension {
     ///
     /// The `bool` dictates whether the contents of the macro can
     /// directly use `#[unstable]` things (true == yes).
-    NormalTT(Box<TTMacroExpander>, Option<Span>, bool),
+    NormalTT(Box<TTMacroExpander>, Option<(ast::NodeId, Span)>, bool),
 
     /// A function-like syntax extension that has an extra ident before
     /// the block.
@@ -588,6 +589,7 @@ pub trait Resolver {
                      -> Result<Option<Rc<SyntaxExtension>>, Determinacy>;
     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
                      -> Result<Rc<SyntaxExtension>, Determinacy>;
+    fn check_unused_macros(&self);
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -617,6 +619,7 @@ impl Resolver for DummyResolver {
                      _force: bool) -> Result<Rc<SyntaxExtension>, Determinacy> {
         Err(Determinacy::Determined)
     }
+    fn check_unused_macros(&self) {}
 }
 
 #[derive(Clone)]
@@ -634,8 +637,8 @@ pub struct ExpansionData {
 }
 
 /// One of these is made during expansion and incrementally updated as we go;
-/// when a macro expansion occurs, the resulting nodes have the backtrace()
-/// -> expn_info of their expansion context stored into their span.
+/// when a macro expansion occurs, the resulting nodes have the `backtrace()
+/// -> expn_info` of their expansion context stored into their span.
 pub struct ExtCtxt<'a> {
     pub parse_sess: &'a parse::ParseSess,
     pub ecfg: expand::ExpansionConfig<'a>,
@@ -643,6 +646,7 @@ pub struct ExtCtxt<'a> {
     pub resolver: &'a mut Resolver,
     pub resolve_err_count: usize,
     pub current_expansion: ExpansionData,
+    pub expansions: HashMap<Span, Vec<String>>,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -662,6 +666,7 @@ impl<'a> ExtCtxt<'a> {
                 module: Rc::new(ModuleData { mod_path: Vec::new(), directory: PathBuf::new() }),
                 directory_ownership: DirectoryOwnership::Owned,
             },
+            expansions: HashMap::new(),
         }
     }
 
@@ -695,7 +700,7 @@ impl<'a> ExtCtxt<'a> {
     /// Returns span for the macro which originally caused the current expansion to happen.
     ///
     /// Stops backtracing at include! boundary.
-    pub fn expansion_cause(&self) -> Span {
+    pub fn expansion_cause(&self) -> Option<Span> {
         let mut ctxt = self.backtrace();
         let mut last_macro = None;
         loop {
@@ -706,12 +711,12 @@ impl<'a> ExtCtxt<'a> {
                 }
                 ctxt = info.call_site.ctxt;
                 last_macro = Some(info.call_site);
-                return Some(());
+                Some(())
             }).is_none() {
                 break
             }
         }
-        last_macro.expect("missing expansion backtrace")
+        last_macro
     }
 
     pub fn struct_span_warn(&self,
@@ -765,6 +770,15 @@ impl<'a> ExtCtxt<'a> {
     pub fn span_bug(&self, sp: Span, msg: &str) -> ! {
         self.parse_sess.span_diagnostic.span_bug(sp, msg);
     }
+    pub fn trace_macros_diag(&self) {
+        for (sp, notes) in self.expansions.iter() {
+            let mut db = self.parse_sess.span_diagnostic.span_note_diag(*sp, "trace_macro");
+            for note in notes {
+                db.note(note);
+            }
+            db.emit();
+        }
+    }
     pub fn bug(&self, msg: &str) -> ! {
         self.parse_sess.span_diagnostic.bug(msg);
     }
@@ -783,11 +797,15 @@ impl<'a> ExtCtxt<'a> {
             v.push(self.ident_of(s));
         }
         v.extend(components.iter().map(|s| self.ident_of(s)));
-        return v
+        v
     }
     pub fn name_of(&self, st: &str) -> ast::Name {
         Symbol::intern(st)
     }
+
+    pub fn check_unused_macros(&self) {
+        self.resolver.check_unused_macros();
+    }
 }
 
 /// Extract a string literal from the macro expanded version of `expr`,
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index e0fb46ff5eb..09f22e8691e 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -52,7 +52,7 @@ pub trait AstBuilder {
     fn ty_mt(&self, ty: P<ast::Ty>, mutbl: ast::Mutability) -> ast::MutTy;
 
     fn ty(&self, span: Span, ty: ast::TyKind) -> P<ast::Ty>;
-    fn ty_path(&self, ast::Path) -> P<ast::Ty>;
+    fn ty_path(&self, path: ast::Path) -> P<ast::Ty>;
     fn ty_ident(&self, span: Span, idents: ast::Ident) -> P<ast::Ty>;
 
     fn ty_rptr(&self, span: Span,
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 842398ea02b..25e0aed220a 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -231,7 +231,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             },
             _ => unreachable!(),
         };
-
+        self.cx.trace_macros_diag();
         krate
     }
 
@@ -415,19 +415,19 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
 
         match *ext {
             MultiModifier(ref mac) => {
-                let meta = panictry!(attr.parse_meta(&self.cx.parse_sess));
+                let meta = panictry!(attr.parse_meta(self.cx.parse_sess));
                 let item = mac.expand(self.cx, attr.span, &meta, item);
                 kind.expect_from_annotatables(item)
             }
             MultiDecorator(ref mac) => {
                 let mut items = Vec::new();
-                let meta = panictry!(attr.parse_meta(&self.cx.parse_sess));
+                let meta = panictry!(attr.parse_meta(self.cx.parse_sess));
                 mac.expand(self.cx, attr.span, &meta, &item, &mut |item| items.push(item));
                 items.push(item);
                 kind.expect_from_annotatables(items)
             }
             SyntaxExtension::AttrProcMacro(ref mac) => {
-                let item_toks = stream_for_item(&item, &self.cx.parse_sess);
+                let item_toks = stream_for_item(&item, self.cx.parse_sess);
 
                 let span = Span { ctxt: self.cx.backtrace(), ..attr.span };
                 let tok_result = mac.expand(self.cx, attr.span, attr.tokens, item_toks);
@@ -439,7 +439,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             }
             _ => {
                 let msg = &format!("macro `{}` may not be used in attributes", attr.path);
-                self.cx.span_err(attr.span, &msg);
+                self.cx.span_err(attr.span, msg);
                 kind.dummy(attr.span)
             }
         }
@@ -454,7 +454,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         };
         let path = &mac.node.path;
 
-        let ident = ident.unwrap_or(keywords::Invalid.ident());
+        let ident = ident.unwrap_or_else(|| keywords::Invalid.ident());
         let marked_tts = noop_fold_tts(mac.node.stream(), &mut Marker(mark));
         let opt_expanded = match *ext {
             NormalTT(ref expandfun, exp_span, allow_internal_unstable) => {
@@ -469,7 +469,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     call_site: span,
                     callee: NameAndSpan {
                         format: MacroBang(Symbol::intern(&format!("{}", path))),
-                        span: exp_span,
+                        span: exp_span.map(|(_, s)| s),
                         allow_internal_unstable: allow_internal_unstable,
                     },
                 });
@@ -591,7 +591,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             }
             _ => {
                 let msg = &format!("macro `{}` may not be used for derive attributes", attr.path);
-                self.cx.span_err(span, &msg);
+                self.cx.span_err(span, msg);
                 kind.dummy(span)
             }
         }
@@ -749,19 +749,15 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
         let features = self.cx.ecfg.features.unwrap();
         for attr in attrs.iter() {
-            feature_gate::check_attribute(&attr, &self.cx.parse_sess, features);
+            feature_gate::check_attribute(attr, self.cx.parse_sess, features);
         }
     }
 }
 
 pub fn find_attr_invoc(attrs: &mut Vec<ast::Attribute>) -> Option<ast::Attribute> {
-    for i in 0 .. attrs.len() {
-        if !attr::is_known(&attrs[i]) && !is_builtin_attr(&attrs[i]) {
-             return Some(attrs.remove(i));
-        }
-    }
-
-    None
+    attrs.iter()
+         .position(|a| !attr::is_known(a) && !is_builtin_attr(a))
+         .map(|i| attrs.remove(i))
 }
 
 // These are pretty nasty. Ideally, we would keep the tokens around, linked from
@@ -783,7 +779,7 @@ fn stream_for_item(item: &Annotatable, parse_sess: &ParseSess) -> TokenStream {
 
 fn string_to_stream(text: String, parse_sess: &ParseSess) -> TokenStream {
     let filename = String::from("<macro expansion>");
-    filemap_to_stream(parse_sess, parse_sess.codemap().new_filemap(filename, None, text))
+    filemap_to_stream(parse_sess, parse_sess.codemap().new_filemap(filename, text))
 }
 
 impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
@@ -923,7 +919,7 @@ impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
                 let result = noop_fold_item(item, self);
                 self.cx.current_expansion.module = orig_module;
                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
-                return result;
+                result
             }
             // Ensure that test functions are accessible from the test harness.
             ast::ItemKind::Fn(..) if self.cx.ecfg.should_test => {
@@ -1038,7 +1034,7 @@ impl<'feat> ExpansionConfig<'feat> {
         ExpansionConfig {
             crate_name: crate_name,
             features: None,
-            recursion_limit: 64,
+            recursion_limit: 1024,
             trace_mac: false,
             should_test: false,
             single_step: false,
diff --git a/src/libsyntax/ext/quote.rs b/src/libsyntax/ext/quote.rs
index d7a85baa3ff..f8fac847a05 100644
--- a/src/libsyntax/ext/quote.rs
+++ b/src/libsyntax/ext/quote.rs
@@ -23,7 +23,7 @@ use tokenstream::{TokenStream, TokenTree};
 ///
 /// This is registered as a set of expression syntax extension called quote!
 /// that lifts its argument token-tree to an AST representing the
-/// construction of the same token tree, with token::SubstNt interpreted
+/// construction of the same token tree, with `token::SubstNt` interpreted
 /// as antiquotes (splices).
 
 pub mod rt {
@@ -389,7 +389,7 @@ pub fn unflatten(tts: Vec<TokenTree>) -> Vec<TokenTree> {
                 result = results.pop().unwrap();
                 result.push(tree);
             }
-            tree @ _ => result.push(tree),
+            tree => result.push(tree),
         }
     }
     result
@@ -612,8 +612,11 @@ fn mk_delim(cx: &ExtCtxt, sp: Span, delim: token::DelimToken) -> P<ast::Expr> {
 #[allow(non_upper_case_globals)]
 fn expr_mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
     macro_rules! mk_lit {
-        ($name: expr, $suffix: expr, $($args: expr),*) => {{
-            let inner = cx.expr_call(sp, mk_token_path(cx, sp, $name), vec![$($args),*]);
+        ($name: expr, $suffix: expr, $content: expr $(, $count: expr)*) => {{
+            let name = mk_name(cx, sp, ast::Ident::with_empty_ctxt($content));
+            let inner = cx.expr_call(sp, mk_token_path(cx, sp, $name), vec![
+                name $(, cx.expr_usize(sp, $count))*
+            ]);
             let suffix = match $suffix {
                 Some(name) => cx.expr_some(sp, mk_name(cx, sp, ast::Ident::with_empty_ctxt(name))),
                 None => cx.expr_none(sp)
@@ -621,7 +624,8 @@ fn expr_mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
             cx.expr_call(sp, mk_token_path(cx, sp, "Literal"), vec![inner, suffix])
         }}
     }
-    match *tok {
+
+    let name = match *tok {
         token::BinOp(binop) => {
             return cx.expr_call(sp, mk_token_path(cx, sp, "BinOp"), vec![mk_binop(cx, sp, binop)]);
         }
@@ -639,34 +643,14 @@ fn expr_mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
                                 vec![mk_delim(cx, sp, delim)]);
         }
 
-        token::Literal(token::Byte(i), suf) => {
-            let e_byte = mk_name(cx, sp, ast::Ident::with_empty_ctxt(i));
-            return mk_lit!("Byte", suf, e_byte);
-        }
-
-        token::Literal(token::Char(i), suf) => {
-            let e_char = mk_name(cx, sp, ast::Ident::with_empty_ctxt(i));
-            return mk_lit!("Char", suf, e_char);
-        }
-
-        token::Literal(token::Integer(i), suf) => {
-            let e_int = mk_name(cx, sp, ast::Ident::with_empty_ctxt(i));
-            return mk_lit!("Integer", suf, e_int);
-        }
-
-        token::Literal(token::Float(fident), suf) => {
-            let e_fident = mk_name(cx, sp, ast::Ident::with_empty_ctxt(fident));
-            return mk_lit!("Float", suf, e_fident);
-        }
-
-        token::Literal(token::Str_(ident), suf) => {
-            return mk_lit!("Str_", suf, mk_name(cx, sp, ast::Ident::with_empty_ctxt(ident)))
-        }
-
-        token::Literal(token::StrRaw(ident, n), suf) => {
-            return mk_lit!("StrRaw", suf, mk_name(cx, sp, ast::Ident::with_empty_ctxt(ident)),
-                           cx.expr_usize(sp, n))
-        }
+        token::Literal(token::Byte(i), suf) => return mk_lit!("Byte", suf, i),
+        token::Literal(token::Char(i), suf) => return mk_lit!("Char", suf, i),
+        token::Literal(token::Integer(i), suf) => return mk_lit!("Integer", suf, i),
+        token::Literal(token::Float(i), suf) => return mk_lit!("Float", suf, i),
+        token::Literal(token::Str_(i), suf) => return mk_lit!("Str_", suf, i),
+        token::Literal(token::StrRaw(i, n), suf) => return mk_lit!("StrRaw", suf, i, n),
+        token::Literal(token::ByteStr(i), suf) => return mk_lit!("ByteStr", suf, i),
+        token::Literal(token::ByteStrRaw(i, n), suf) => return mk_lit!("ByteStrRaw", suf, i, n),
 
         token::Ident(ident) => {
             return cx.expr_call(sp,
@@ -688,10 +672,6 @@ fn expr_mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
 
         token::Interpolated(_) => panic!("quote! with interpolated token"),
 
-        _ => ()
-    }
-
-    let name = match *tok {
         token::Eq           => "Eq",
         token::Lt           => "Lt",
         token::Le           => "Le",
@@ -706,6 +686,7 @@ fn expr_mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
         token::At           => "At",
         token::Dot          => "Dot",
         token::DotDot       => "DotDot",
+        token::DotDotDot    => "DotDotDot",
         token::Comma        => "Comma",
         token::Semi         => "Semi",
         token::Colon        => "Colon",
@@ -718,7 +699,10 @@ fn expr_mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
         token::Question     => "Question",
         token::Underscore   => "Underscore",
         token::Eof          => "Eof",
-        _                   => panic!("unhandled token in quote!"),
+
+        token::Whitespace | token::SubstNt(_) | token::Comment | token::Shebang(_) => {
+            panic!("unhandled token in quote!");
+        }
     };
     mk_token_path(cx, sp, name)
 }
diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index 0103d6ea959..3cdd3a4b2c3 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -35,7 +35,7 @@ pub fn expand_line(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                    -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "line!");
 
-    let topmost = cx.expansion_cause();
+    let topmost = cx.expansion_cause().unwrap_or(sp);
     let loc = cx.codemap().lookup_char_pos(topmost.lo);
 
     base::MacEager::expr(cx.expr_u32(topmost, loc.line as u32))
@@ -46,7 +46,7 @@ pub fn expand_column(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                   -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "column!");
 
-    let topmost = cx.expansion_cause();
+    let topmost = cx.expansion_cause().unwrap_or(sp);
     let loc = cx.codemap().lookup_char_pos(topmost.lo);
 
     base::MacEager::expr(cx.expr_u32(topmost, loc.col.to_usize() as u32))
@@ -59,7 +59,7 @@ pub fn expand_file(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                    -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "file!");
 
-    let topmost = cx.expansion_cause();
+    let topmost = cx.expansion_cause().unwrap_or(sp);
     let loc = cx.codemap().lookup_char_pos(topmost.lo);
     base::MacEager::expr(cx.expr_str(topmost, Symbol::intern(&loc.file.name)))
 }
@@ -142,7 +142,7 @@ pub fn expand_include_str(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenT
             // Add this input file to the code map to make it available as
             // dependency information
             let filename = format!("{}", file.display());
-            cx.codemap().new_filemap_and_lines(&filename, None, &src);
+            cx.codemap().new_filemap_and_lines(&filename, &src);
 
             base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&src)))
         }
@@ -150,7 +150,7 @@ pub fn expand_include_str(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenT
             cx.span_err(sp,
                         &format!("{} wasn't a utf-8 file",
                                 file.display()));
-            return DummyResult::expr(sp);
+            DummyResult::expr(sp)
         }
     }
 }
@@ -167,13 +167,13 @@ pub fn expand_include_bytes(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::Toke
         Err(e) => {
             cx.span_err(sp,
                         &format!("couldn't read {}: {}", file.display(), e));
-            return DummyResult::expr(sp);
+            DummyResult::expr(sp)
         }
         Ok(..) => {
             // Add this input file to the code map to make it available as
             // dependency information, but don't enter it's contents
             let filename = format!("{}", file.display());
-            cx.codemap().new_filemap_and_lines(&filename, None, "");
+            cx.codemap().new_filemap_and_lines(&filename, "");
 
             base::MacEager::expr(cx.expr_lit(sp, ast::LitKind::ByteStr(Rc::new(bytes))))
         }
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index eb0b7c29f8d..bf66aa0f00b 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -36,43 +36,47 @@
 //! repetitions indicated by Kleene stars. It only advances or calls out to the
 //! real Rust parser when no `cur_eis` items remain
 //!
-//! Example: Start parsing `a a a a b` against [· a $( a )* a b].
+//! Example:
 //!
-//! Remaining input: `a a a a b`
+//! ```text, ignore
+//! Start parsing a a a a b against [· a $( a )* a b].
+//!
+//! Remaining input: a a a a b
 //! next_eis: [· a $( a )* a b]
 //!
-//! - - - Advance over an `a`. - - -
+//! - - - Advance over an a. - - -
 //!
-//! Remaining input: `a a a b`
+//! Remaining input: a a a b
 //! cur: [a · $( a )* a b]
 //! Descend/Skip (first item).
 //! next: [a $( · a )* a b]  [a $( a )* · a b].
 //!
-//! - - - Advance over an `a`. - - -
+//! - - - Advance over an a. - - -
 //!
-//! Remaining input: `a a b`
+//! Remaining input: a a b
 //! cur: [a $( a · )* a b]  next: [a $( a )* a · b]
 //! Finish/Repeat (first item)
 //! next: [a $( a )* · a b]  [a $( · a )* a b]  [a $( a )* a · b]
 //!
-//! - - - Advance over an `a`. - - - (this looks exactly like the last step)
+//! - - - Advance over an a. - - - (this looks exactly like the last step)
 //!
-//! Remaining input: `a b`
+//! Remaining input: a b
 //! cur: [a $( a · )* a b]  next: [a $( a )* a · b]
 //! Finish/Repeat (first item)
 //! next: [a $( a )* · a b]  [a $( · a )* a b]  [a $( a )* a · b]
 //!
-//! - - - Advance over an `a`. - - - (this looks exactly like the last step)
+//! - - - Advance over an a. - - - (this looks exactly like the last step)
 //!
-//! Remaining input: `b`
+//! Remaining input: b
 //! cur: [a $( a · )* a b]  next: [a $( a )* a · b]
 //! Finish/Repeat (first item)
 //! next: [a $( a )* · a b]  [a $( · a )* a b]
 //!
-//! - - - Advance over a `b`. - - -
+//! - - - Advance over a b. - - -
 //!
-//! Remaining input: ``
+//! Remaining input: ''
 //! eof: [a $( a )* a b ·]
+//! ```
 
 pub use self::NamedMatch::*;
 pub use self::ParseResult::*;
@@ -178,20 +182,20 @@ fn initial_matcher_pos(ms: Vec<TokenTree>, lo: BytePos) -> Box<MatcherPos> {
     })
 }
 
-/// NamedMatch is a pattern-match result for a single token::MATCH_NONTERMINAL:
+/// `NamedMatch` is a pattern-match result for a single `token::MATCH_NONTERMINAL`:
 /// so it is associated with a single ident in a parse, and all
-/// `MatchedNonterminal`s in the NamedMatch have the same nonterminal type
-/// (expr, item, etc). Each leaf in a single NamedMatch corresponds to a
-/// single token::MATCH_NONTERMINAL in the TokenTree that produced it.
+/// `MatchedNonterminal`s in the `NamedMatch` have the same nonterminal type
+/// (expr, item, etc). Each leaf in a single `NamedMatch` corresponds to a
+/// single `token::MATCH_NONTERMINAL` in the `TokenTree` that produced it.
 ///
-/// The in-memory structure of a particular NamedMatch represents the match
+/// The in-memory structure of a particular `NamedMatch` represents the match
 /// that occurred when a particular subset of a matcher was applied to a
 /// particular token tree.
 ///
-/// The width of each MatchedSeq in the NamedMatch, and the identity of the
-/// `MatchedNonterminal`s, will depend on the token tree it was applied to:
-/// each MatchedSeq corresponds to a single TTSeq in the originating
-/// token tree. The depth of the NamedMatch structure will therefore depend
+/// The width of each `MatchedSeq` in the `NamedMatch`, and the identity of
+/// the `MatchedNonterminal`s, will depend on the token tree it was applied
+/// to: each `MatchedSeq` corresponds to a single `TTSeq` in the originating
+/// token tree. The depth of the `NamedMatch` structure will therefore depend
 /// only on the nesting depth of `ast::TTSeq`s in the originating
 /// token tree it was derived from.
 
@@ -267,11 +271,12 @@ pub fn parse_failure_msg(tok: Token) -> String {
 
 /// Perform a token equality check, ignoring syntax context (that is, an unhygienic comparison)
 fn token_name_eq(t1 : &Token, t2 : &Token) -> bool {
-    match (t1,t2) {
-        (&token::Ident(id1),&token::Ident(id2))
-        | (&token::Lifetime(id1),&token::Lifetime(id2)) =>
-            id1.name == id2.name,
-        _ => *t1 == *t2
+    if let (Some(id1), Some(id2)) = (t1.ident(), t2.ident()) {
+        id1.name == id2.name
+    } else if let (&token::Lifetime(id1), &token::Lifetime(id2)) = (t1, t2) {
+        id1.name == id2.name
+    } else {
+        *t1 == *t2
     }
 }
 
@@ -334,7 +339,7 @@ fn inner_parse_loop(sess: &ParseSess,
                 // Check if we need a separator
                 if idx == len && ei.sep.is_some() {
                     // We have a separator, and it is the current token.
-                    if ei.sep.as_ref().map(|ref sep| token_name_eq(&token, sep)).unwrap_or(false) {
+                    if ei.sep.as_ref().map(|sep| token_name_eq(token, sep)).unwrap_or(false) {
                         ei.idx += 1;
                         next_eis.push(ei);
                     }
@@ -401,7 +406,7 @@ fn inner_parse_loop(sess: &ParseSess,
                     cur_eis.push(ei);
                 }
                 TokenTree::Token(_, ref t) => {
-                    if token_name_eq(t, &token) {
+                    if token_name_eq(t, token) {
                         ei.idx += 1;
                         next_eis.push(ei);
                     }
@@ -485,11 +490,8 @@ pub fn parse(sess: &ParseSess, tts: TokenStream, ms: &[TokenTree], directory: Op
 }
 
 fn parse_nt<'a>(p: &mut Parser<'a>, sp: Span, name: &str) -> Nonterminal {
-    match name {
-        "tt" => {
-            return token::NtTT(p.parse_token_tree());
-        }
-        _ => {}
+    if name == "tt" {
+        return token::NtTT(p.parse_token_tree());
     }
     // check at the beginning and the parser checks after each bump
     p.process_potential_macro_variable();
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index be979960725..a208f530602 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -27,8 +27,8 @@ use symbol::Symbol;
 use tokenstream::{TokenStream, TokenTree};
 
 use std::cell::RefCell;
-use std::collections::{HashMap};
-use std::collections::hash_map::{Entry};
+use std::collections::HashMap;
+use std::collections::hash_map::Entry;
 use std::rc::Rc;
 
 pub struct ParserAnyMacro<'a> {
@@ -85,7 +85,7 @@ impl TTMacroExpander for MacroRulesMacroExpander {
 }
 
 /// Given `lhses` and `rhses`, this is the new macro we create
-fn generic_extension<'cx>(cx: &'cx ExtCtxt,
+fn generic_extension<'cx>(cx: &'cx mut ExtCtxt,
                           sp: Span,
                           name: ast::Ident,
                           arg: TokenStream,
@@ -93,7 +93,9 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,
                           rhses: &[quoted::TokenTree])
                           -> Box<MacResult+'cx> {
     if cx.trace_macros() {
-        println!("{}! {{ {} }}", name, arg);
+        let sp = sp.macro_backtrace().last().map(|trace| trace.call_site).unwrap_or(sp);
+        let mut values: &mut Vec<String> = cx.expansions.entry(sp).or_insert_with(Vec::new);
+        values.push(format!("expands to `{}! {{ {} }}`", name, arg));
     }
 
     // Which arm's failure should we report? (the one furthest along)
@@ -204,7 +206,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
     let mut valid = true;
 
     // Extract the arguments:
-    let lhses = match **argument_map.get(&lhs_nm).unwrap() {
+    let lhses = match *argument_map[&lhs_nm] {
         MatchedSeq(ref s, _) => {
             s.iter().map(|m| {
                 if let MatchedNonterminal(ref nt) = **m {
@@ -220,7 +222,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
         _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
     };
 
-    let rhses = match **argument_map.get(&rhs_nm).unwrap() {
+    let rhses = match *argument_map[&rhs_nm] {
         MatchedSeq(ref s, _) => {
             s.iter().map(|m| {
                 if let MatchedNonterminal(ref nt) = **m {
@@ -250,7 +252,9 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
         valid: valid,
     });
 
-    NormalTT(exp, Some(def.span), attr::contains_name(&def.attrs, "allow_internal_unstable"))
+    NormalTT(exp,
+             Some((def.id, def.span)),
+             attr::contains_name(&def.attrs, "allow_internal_unstable"))
 }
 
 fn check_lhs_nt_follows(sess: &ParseSess,
@@ -258,13 +262,12 @@ fn check_lhs_nt_follows(sess: &ParseSess,
                         lhs: &quoted::TokenTree) -> bool {
     // lhs is going to be like TokenTree::Delimited(...), where the
     // entire lhs is those tts. Or, it can be a "bare sequence", not wrapped in parens.
-    match lhs {
-        &quoted::TokenTree::Delimited(_, ref tts) => check_matcher(sess, features, &tts.tts),
-        _ => {
-            let msg = "invalid macro matcher; matchers must be contained in balanced delimiters";
-            sess.span_diagnostic.span_err(lhs.span(), msg);
-            false
-        }
+    if let quoted::TokenTree::Delimited(_, ref tts) = *lhs {
+        check_matcher(sess, features, &tts.tts)
+    } else {
+        let msg = "invalid macro matcher; matchers must be contained in balanced delimiters";
+        sess.span_diagnostic.span_err(lhs.span(), msg);
+        false
     }
     // we don't abort on errors on rejection, the driver will do that for us
     // after parsing/expansion. we can report every error in every macro this way.
@@ -281,17 +284,15 @@ fn check_lhs_no_empty_seq(sess: &ParseSess, tts: &[quoted::TokenTree]) -> bool {
                 return false;
             },
             TokenTree::Sequence(span, ref seq) => {
-                if seq.separator.is_none() {
-                    if seq.tts.iter().all(|seq_tt| {
-                        match *seq_tt {
-                            TokenTree::Sequence(_, ref sub_seq) =>
-                                sub_seq.op == quoted::KleeneOp::ZeroOrMore,
-                            _ => false,
-                        }
-                    }) {
-                        sess.span_diagnostic.span_err(span, "repetition matches empty token tree");
-                        return false;
+                if seq.separator.is_none() && seq.tts.iter().all(|seq_tt| {
+                    match *seq_tt {
+                        TokenTree::Sequence(_, ref sub_seq) =>
+                            sub_seq.op == quoted::KleeneOp::ZeroOrMore,
+                        _ => false,
                     }
+                }) {
+                    sess.span_diagnostic.span_err(span, "repetition matches empty token tree");
+                    return false;
                 }
                 if !check_lhs_no_empty_seq(sess, &seq.tts) {
                     return false;
@@ -405,7 +406,7 @@ impl FirstSets {
                 }
             }
 
-            return first;
+            first
         }
     }
 
@@ -467,7 +468,7 @@ impl FirstSets {
         // we only exit the loop if `tts` was empty or if every
         // element of `tts` matches the empty sequence.
         assert!(first.maybe_empty);
-        return first;
+        first
     }
 }
 
@@ -577,7 +578,7 @@ fn check_matcher_core(sess: &ParseSess,
         let build_suffix_first = || {
             let mut s = first_sets.first(suffix);
             if s.maybe_empty { s.add_all(follow); }
-            return s;
+            s
         };
 
         // (we build `suffix_first` on demand below; you can tell
@@ -859,6 +860,7 @@ fn quoted_tt_to_string(tt: &quoted::TokenTree) -> String {
     match *tt {
         quoted::TokenTree::Token(_, ref tok) => ::print::pprust::token_to_string(tok),
         quoted::TokenTree::MetaVarDecl(_, name, kind) => format!("${}:{}", name, kind),
-        _ => panic!("unexpected quoted::TokenTree::{Sequence or Delimited} in follow set checker"),
+        _ => panic!("unexpected quoted::TokenTree::{{Sequence or Delimited}} \
+                     in follow set checker"),
     }
 }
diff --git a/src/libsyntax/ext/tt/quoted.rs b/src/libsyntax/ext/tt/quoted.rs
index d216effbd45..fa65e9501c2 100644
--- a/src/libsyntax/ext/tt/quoted.rs
+++ b/src/libsyntax/ext/tt/quoted.rs
@@ -96,6 +96,17 @@ impl TokenTree {
         }
     }
 
+    pub fn is_empty(&self) -> bool {
+        match *self {
+            TokenTree::Delimited(_, ref delimed) => match delimed.delim {
+                token::NoDelim => delimed.tts.is_empty(),
+                _ => false,
+            },
+            TokenTree::Sequence(_, ref seq) => seq.tts.is_empty(),
+            _ => true,
+        }
+    }
+
     pub fn get_tt(&self, index: usize) -> TokenTree {
         match (self, index) {
             (&TokenTree::Delimited(_, ref delimed), _) if delimed.delim == token::NoDelim => {
@@ -144,9 +155,9 @@ pub fn parse(input: tokenstream::TokenStream, expect_matchers: bool, sess: &Pars
                             }
                             _ => end_sp,
                         },
-                        tree @ _ => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+                        tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
                     },
-                    tree @ _ => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(start_sp),
+                    tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(start_sp),
                 };
                 sess.missing_fragment_specifiers.borrow_mut().insert(span);
                 result.push(TokenTree::MetaVarDecl(span, ident, keywords::Invalid.ident()));
@@ -228,10 +239,10 @@ fn parse_sep_and_kleene_op<I>(input: &mut I, span: Span, sess: &ParseSess)
                     Some(op) => return (Some(tok), op),
                     None => span,
                 },
-                tree @ _ => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+                tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
             }
         },
-        tree @ _ => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+        tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
     };
 
     sess.span_diagnostic.span_err(span, "expected `*` or `+`");
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 947089b0b9a..2a435bdea10 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -121,20 +121,20 @@ pub fn transcribe(sp_diag: &Handler,
                                          &repeats) {
                     LockstepIterSize::Unconstrained => {
                         panic!(sp_diag.span_fatal(
-                            sp.clone(), /* blame macro writer */
+                            sp, /* blame macro writer */
                             "attempted to repeat an expression \
                              containing no syntax \
                              variables matched as repeating at this depth"));
                     }
                     LockstepIterSize::Contradiction(ref msg) => {
                         // FIXME #2887 blame macro invoker instead
-                        panic!(sp_diag.span_fatal(sp.clone(), &msg[..]));
+                        panic!(sp_diag.span_fatal(sp, &msg[..]));
                     }
                     LockstepIterSize::Constraint(len, _) => {
                         if len == 0 {
                             if seq.op == quoted::KleeneOp::OneOrMore {
                                 // FIXME #2887 blame invoker
-                                panic!(sp_diag.span_fatal(sp.clone(),
+                                panic!(sp_diag.span_fatal(sp,
                                                           "this must repeat at least once"));
                             }
                         } else {
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index fa0e45194dc..6acf27f314a 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -294,9 +294,6 @@ declare_features! (
 
     (active, use_extern_macros, "1.15.0", Some(35896)),
 
-    // Allows `break {expr}` with a value inside `loop`s.
-    (active, loop_break_value, "1.14.0", Some(37339)),
-
     // Allows #[target_feature(...)]
     (active, target_feature, "1.15.0", None),
 
@@ -407,7 +404,7 @@ declare_features! (
     (accepted, question_mark, "1.13.0", Some(31436)),
     // Allows `..` in tuple (struct) patterns
     (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627)),
-    (accepted, item_like_imports, "1.14.0", Some(35120)),
+    (accepted, item_like_imports, "1.15.0", Some(35120)),
     // Allows using `Self` and associated types in struct expressions and patterns.
     (accepted, more_struct_aliases, "1.16.0", Some(37544)),
     // elide `'static` lifetimes in `static`s and `const`s
@@ -420,8 +417,10 @@ declare_features! (
     (accepted, pub_restricted, "1.18.0", Some(32409)),
     // The #![windows_subsystem] attribute
     (accepted, windows_subsystem, "1.18.0", Some(37499)),
+    // Allows `break {expr}` with a value inside `loop`s.
+    (accepted, loop_break_value, "1.19.0", Some(37339)),
     // Permits numeric fields in struct expressions and patterns.
-    (accepted, relaxed_adts, "1.18.0", Some(35626)),
+    (accepted, relaxed_adts, "1.19.0", Some(35626)),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must
@@ -472,7 +471,7 @@ pub enum Stability {
 impl ::std::fmt::Debug for AttributeGate {
     fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
         match *self {
-            Gated(ref stab, ref name, ref expl, _) =>
+            Gated(ref stab, name, expl, _) =>
                 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
             Ungated => write!(fmt, "Ungated")
         }
@@ -816,7 +815,7 @@ pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeG
 ];
 
 // cfg(...)'s that are feature gated
-const GATED_CFGS: &'static [(&'static str, &'static str, fn(&Features) -> bool)] = &[
+const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
     // (name in cfg, feature, function to check if the feature is enabled)
     ("target_feature", "cfg_target_feature", cfg_fn!(cfg_target_feature)),
     ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
@@ -881,7 +880,7 @@ impl<'a> Context<'a> {
         let name = unwrap_or!(attr.name(), return).as_str();
         for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
             if name == n {
-                if let &Gated(_, ref name, ref desc, ref has_feature) = gateage {
+                if let Gated(_, name, desc, ref has_feature) = *gateage {
                     gate_feature_fn!(self, has_feature, attr.span, name, desc);
                 }
                 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
@@ -1098,7 +1097,7 @@ fn contains_novel_literal(item: &ast::MetaItem) -> bool {
         NameValue(ref lit) => !lit.node.is_str(),
         List(ref list) => list.iter().any(|li| {
             match li.node {
-                MetaItem(ref mi) => contains_novel_literal(&mi),
+                MetaItem(ref mi) => contains_novel_literal(mi),
                 Literal(_) => true,
             }
         }),
@@ -1116,7 +1115,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             return
         }
 
-        let meta = panictry!(attr.parse_meta(&self.context.parse_sess));
+        let meta = panictry!(attr.parse_meta(self.context.parse_sess));
         if contains_novel_literal(&meta) {
             gate_feature_post!(&self, attr_literals, attr.span,
                                "non-string literals in attributes, or string \
@@ -1211,15 +1210,18 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                                     and possibly buggy");
             }
 
-            ast::ItemKind::Impl(_, polarity, _, _, _, _) => {
-                match polarity {
-                    ast::ImplPolarity::Negative => {
-                        gate_feature_post!(&self, optin_builtin_traits,
-                                           i.span,
-                                           "negative trait bounds are not yet fully implemented; \
-                                            use marker types for now");
-                    },
-                    _ => {}
+            ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
+                if polarity == ast::ImplPolarity::Negative {
+                    gate_feature_post!(&self, optin_builtin_traits,
+                                       i.span,
+                                       "negative trait bounds are not yet fully implemented; \
+                                        use marker types for now");
+                }
+
+                if let ast::Defaultness::Default = defaultness {
+                    gate_feature_post!(&self, specialization,
+                                       i.span,
+                                       "specialization is unstable");
                 }
             }
 
@@ -1262,11 +1264,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 
     fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
         if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
-            match output_ty.node {
-                ast::TyKind::Never => return,
-                _ => (),
-            };
-            self.visit_ty(output_ty)
+            if output_ty.node != ast::TyKind::Never {
+                self.visit_ty(output_ty)
+            }
         }
     }
 
@@ -1287,10 +1287,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::ExprKind::InPlace(..) => {
                 gate_feature_post!(&self, placement_in_syntax, e.span, EXPLAIN_PLACEMENT_IN);
             }
-            ast::ExprKind::Break(_, Some(_)) => {
-                gate_feature_post!(&self, loop_break_value, e.span,
-                                   "`break` with a value is experimental");
-            }
             ast::ExprKind::Lit(ref lit) => {
                 if let ast::LitKind::Int(_, ref ty) = lit.node {
                     match *ty {
@@ -1345,17 +1341,14 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 span: Span,
                 _node_id: NodeId) {
         // check for const fn declarations
-        match fn_kind {
-            FnKind::ItemFn(_, _, _, Spanned { node: ast::Constness::Const, .. }, _, _, _) => {
-                gate_feature_post!(&self, const_fn, span, "const fn is unstable");
-            }
-            _ => {
-                // stability of const fn methods are covered in
-                // visit_trait_item and visit_impl_item below; this is
-                // because default methods don't pass through this
-                // point.
-            }
+        if let FnKind::ItemFn(_, _, _, Spanned { node: ast::Constness::Const, .. }, _, _, _) =
+            fn_kind {
+            gate_feature_post!(&self, const_fn, span, "const fn is unstable");
         }
+        // stability of const fn methods are covered in
+        // visit_trait_item and visit_impl_item below; this is
+        // because default methods don't pass through this
+        // point.
 
         match fn_kind {
             FnKind::ItemFn(_, _, _, _, abi, _, _) |
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index f39399a62e8..58cf50cdc00 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -897,9 +897,16 @@ pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
         ItemKind::DefaultImpl(unsafety, ref trait_ref) => {
             ItemKind::DefaultImpl(unsafety, folder.fold_trait_ref((*trait_ref).clone()))
         }
-        ItemKind::Impl(unsafety, polarity, generics, ifce, ty, impl_items) => ItemKind::Impl(
+        ItemKind::Impl(unsafety,
+                       polarity,
+                       defaultness,
+                       generics,
+                       ifce,
+                       ty,
+                       impl_items) => ItemKind::Impl(
             unsafety,
             polarity,
+            defaultness,
             folder.fold_generics(generics),
             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref.clone())),
             folder.fold_ty(ty),
diff --git a/src/libsyntax/json.rs b/src/libsyntax/json.rs
index dec1b7d1d87..f37dcfdde89 100644
--- a/src/libsyntax/json.rs
+++ b/src/libsyntax/json.rs
@@ -19,7 +19,7 @@
 
 // FIXME spec the JSON output properly.
 
-use codemap::CodeMap;
+use codemap::{CodeMap, FilePathMapping};
 use syntax_pos::{self, MacroBacktrace, Span, SpanLabel, MultiSpan};
 use errors::registry::Registry;
 use errors::{DiagnosticBuilder, SubDiagnostic, RenderSpan, CodeSuggestion, CodeMapper};
@@ -48,7 +48,8 @@ impl JsonEmitter {
     }
 
     pub fn basic() -> JsonEmitter {
-        JsonEmitter::stderr(None, Rc::new(CodeMap::new()))
+        let file_path_mapping = FilePathMapping::empty();
+        JsonEmitter::stderr(None, Rc::new(CodeMap::new(file_path_mapping)))
     }
 
     pub fn new(dst: Box<Write + Send>,
@@ -152,6 +153,18 @@ impl Diagnostic {
     fn from_diagnostic_builder(db: &DiagnosticBuilder,
                                je: &JsonEmitter)
                                -> Diagnostic {
+        let sugg = db.suggestions.iter().flat_map(|sugg| {
+            je.render(sugg).into_iter().map(move |rendered| {
+                Diagnostic {
+                    message: sugg.msg.clone(),
+                    code: None,
+                    level: "help",
+                    spans: DiagnosticSpan::from_suggestion(sugg, je),
+                    children: vec![],
+                    rendered: Some(rendered),
+                }
+            })
+        });
         Diagnostic {
             message: db.message(),
             code: DiagnosticCode::map_opt_string(db.code.clone(), je),
@@ -159,7 +172,7 @@ impl Diagnostic {
             spans: DiagnosticSpan::from_multispan(&db.span, je),
             children: db.children.iter().map(|c| {
                 Diagnostic::from_sub_diagnostic(c, je)
-            }).collect(),
+            }).chain(sugg).collect(),
             rendered: None,
         }
     }
@@ -173,8 +186,7 @@ impl Diagnostic {
                      .map(|sp| DiagnosticSpan::from_render_span(sp, je))
                      .unwrap_or_else(|| DiagnosticSpan::from_multispan(&db.span, je)),
             children: vec![],
-            rendered: db.render_span.as_ref()
-                                    .and_then(|rsp| je.render(rsp)),
+            rendered: None,
         }
     }
 }
@@ -267,14 +279,19 @@ impl DiagnosticSpan {
 
     fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter)
                        -> Vec<DiagnosticSpan> {
-        assert_eq!(suggestion.msp.span_labels().len(), suggestion.substitutes.len());
-        suggestion.msp.span_labels()
-                      .into_iter()
-                      .zip(&suggestion.substitutes)
-                      .map(|(span_label, suggestion)| {
-                          DiagnosticSpan::from_span_label(span_label,
-                                                          Some(suggestion),
-                                                          je)
+        suggestion.substitution_parts
+                      .iter()
+                      .flat_map(|substitution| {
+                          substitution.substitutions.iter().map(move |suggestion| {
+                              let span_label = SpanLabel {
+                                  span: substitution.span,
+                                  is_primary: true,
+                                  label: None,
+                              };
+                              DiagnosticSpan::from_span_label(span_label,
+                                                              Some(suggestion),
+                                                              je)
+                          })
                       })
                       .collect()
     }
@@ -283,8 +300,9 @@ impl DiagnosticSpan {
         match *rsp {
             RenderSpan::FullSpan(ref msp) =>
                 DiagnosticSpan::from_multispan(msp, je),
-            RenderSpan::Suggestion(ref suggestion) =>
-                DiagnosticSpan::from_suggestion(suggestion, je),
+            // regular diagnostics don't produce this anymore
+            // FIXME(oli_obk): remove it entirely
+            RenderSpan::Suggestion(_) => unreachable!(),
         }
     }
 }
@@ -319,7 +337,7 @@ impl DiagnosticSpanLine {
                       })
                      .collect()
              })
-            .unwrap_or(vec![])
+            .unwrap_or_else(|_| vec![])
     }
 }
 
@@ -340,17 +358,8 @@ impl DiagnosticCode {
 }
 
 impl JsonEmitter {
-    fn render(&self, render_span: &RenderSpan) -> Option<String> {
-        use std::borrow::Borrow;
-
-        match *render_span {
-            RenderSpan::FullSpan(_) => {
-                None
-            }
-            RenderSpan::Suggestion(ref suggestion) => {
-                Some(suggestion.splice_lines(self.cm.borrow()))
-            }
-        }
+    fn render(&self, suggestion: &CodeSuggestion) -> Vec<String> {
+        suggestion.splice_lines(&*self.cm)
     }
 }
 
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 86ee1c5336d..32dafcdb582 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -15,7 +15,6 @@
 //! This API is completely unstable and subject to change.
 
 #![crate_name = "syntax"]
-#![unstable(feature = "rustc_private", issue = "27812")]
 #![crate_type = "dylib"]
 #![crate_type = "rlib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -24,20 +23,17 @@
        test(attr(deny(warnings))))]
 #![deny(warnings)]
 
-#![feature(associated_consts)]
-#![feature(const_fn)]
-#![feature(optin_builtin_traits)]
-#![feature(rustc_private)]
-#![feature(staged_api)]
-#![feature(str_escape)]
 #![feature(unicode)]
 #![feature(rustc_diagnostic_macros)]
-#![feature(specialization)]
 #![feature(i128_type)]
 
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
+#![cfg_attr(stage0, feature(rustc_private))]
+#![cfg_attr(stage0, feature(staged_api))]
+
 extern crate serialize;
 #[macro_use] extern crate log;
-#[macro_use] #[no_link] extern crate rustc_bitflags;
+#[macro_use] extern crate bitflags;
 extern crate std_unicode;
 pub extern crate rustc_errors as errors;
 extern crate syntax_pos;
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,
diff --git a/src/libsyntax/print/pp.rs b/src/libsyntax/print/pp.rs
index 1d67c2a2c2b..e893c859247 100644
--- a/src/libsyntax/print/pp.rs
+++ b/src/libsyntax/print/pp.rs
@@ -113,22 +113,22 @@
 //! between using 'left' and 'right' terms to denote the wrapped-to-ring-buffer
 //! and point-in-infinite-stream senses freely.
 //!
-//! There is a parallel ring buffer, 'size', that holds the calculated size of
+//! There is a parallel ring buffer, `size`, that holds the calculated size of
 //! each token. Why calculated? Because for Begin/End pairs, the "size"
 //! includes everything between the pair. That is, the "size" of Begin is
 //! actually the sum of the sizes of everything between Begin and the paired
-//! End that follows. Since that is arbitrarily far in the future, 'size' is
+//! End that follows. Since that is arbitrarily far in the future, `size` is
 //! being rewritten regularly while the printer runs; in fact most of the
-//! machinery is here to work out 'size' entries on the fly (and give up when
+//! machinery is here to work out `size` entries on the fly (and give up when
 //! they're so obviously over-long that "infinity" is a good enough
 //! approximation for purposes of line breaking).
 //!
 //! The "input side" of the printer is managed as an abstract process called
-//! SCAN, which uses 'scan_stack', to manage calculating 'size'. SCAN is, in
+//! SCAN, which uses `scan_stack`, to manage calculating `size`. SCAN is, in
 //! other words, the process of calculating 'size' entries.
 //!
 //! The "output side" of the printer is managed by an abstract process called
-//! PRINT, which uses 'print_stack', 'margin' and 'space' to figure out what to
+//! PRINT, which uses `print_stack`, `margin` and `space` to figure out what to
 //! do with each token/size pair it consumes as it goes. It's trying to consume
 //! the entire buffered window, but can't output anything until the size is >=
 //! 0 (sizes are set to negative while they're pending calculation).
@@ -409,7 +409,7 @@ impl<'a> Printer<'a> {
     pub fn advance_right(&mut self) {
         self.right += 1;
         self.right %= self.buf_len;
-        assert!(self.right != self.left);
+        assert_ne!(self.right, self.left);
     }
     pub fn advance_left(&mut self) -> io::Result<()> {
         debug!("advance_left Vec<{},{}>, sizeof({})={}", self.left, self.right,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index be1d26f8fe4..83c289ff80b 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -233,7 +233,7 @@ pub fn token_to_string(tok: &Token) -> String {
         token::CloseDelim(token::Bracket) => "]".to_string(),
         token::OpenDelim(token::Brace) => "{".to_string(),
         token::CloseDelim(token::Brace) => "}".to_string(),
-        token::OpenDelim(token::NoDelim) => " ".to_string(),
+        token::OpenDelim(token::NoDelim) |
         token::CloseDelim(token::NoDelim) => " ".to_string(),
         token::Pound                => "#".to_string(),
         token::Dollar               => "$".to_string(),
@@ -244,7 +244,7 @@ pub fn token_to_string(tok: &Token) -> String {
             let mut out = match lit {
                 token::Byte(b)           => format!("b'{}'", b),
                 token::Char(c)           => format!("'{}'", c),
-                token::Float(c)          => c.to_string(),
+                token::Float(c)          |
                 token::Integer(c)        => c.to_string(),
                 token::Str_(s)           => format!("\"{}\"", s),
                 token::StrRaw(s, n)      => format!("r{delim}\"{string}\"{delim}",
@@ -277,23 +277,23 @@ pub fn token_to_string(tok: &Token) -> String {
         token::Shebang(s)           => format!("/* shebang: {}*/", s),
 
         token::Interpolated(ref nt) => match **nt {
-            token::NtExpr(ref e)        => expr_to_string(&e),
-            token::NtMeta(ref e)        => meta_item_to_string(&e),
-            token::NtTy(ref e)          => ty_to_string(&e),
-            token::NtPath(ref e)        => path_to_string(&e),
-            token::NtItem(ref e)        => item_to_string(&e),
-            token::NtBlock(ref e)       => block_to_string(&e),
-            token::NtStmt(ref e)        => stmt_to_string(&e),
-            token::NtPat(ref e)         => pat_to_string(&e),
+            token::NtExpr(ref e)        => expr_to_string(e),
+            token::NtMeta(ref e)        => meta_item_to_string(e),
+            token::NtTy(ref e)          => ty_to_string(e),
+            token::NtPath(ref e)        => path_to_string(e),
+            token::NtItem(ref e)        => item_to_string(e),
+            token::NtBlock(ref e)       => block_to_string(e),
+            token::NtStmt(ref e)        => stmt_to_string(e),
+            token::NtPat(ref e)         => pat_to_string(e),
             token::NtIdent(ref e)       => ident_to_string(e.node),
             token::NtTT(ref tree)       => tt_to_string(tree.clone()),
-            token::NtArm(ref e)         => arm_to_string(&e),
-            token::NtImplItem(ref e)    => impl_item_to_string(&e),
-            token::NtTraitItem(ref e)   => trait_item_to_string(&e),
-            token::NtGenerics(ref e)    => generics_to_string(&e),
-            token::NtWhereClause(ref e) => where_clause_to_string(&e),
-            token::NtArg(ref e)         => arg_to_string(&e),
-            token::NtVis(ref e)         => vis_to_string(&e),
+            token::NtArm(ref e)         => arm_to_string(e),
+            token::NtImplItem(ref e)    => impl_item_to_string(e),
+            token::NtTraitItem(ref e)   => trait_item_to_string(e),
+            token::NtGenerics(ref e)    => generics_to_string(e),
+            token::NtWhereClause(ref e) => where_clause_to_string(e),
+            token::NtArg(ref e)         => arg_to_string(e),
+            token::NtVis(ref e)         => vis_to_string(e),
         }
     }
 }
@@ -520,8 +520,7 @@ pub trait PrintState<'a> {
 
         let mut result = None;
 
-        if let &Some(ref lits) = self.literals()
-        {
+        if let Some(ref lits) = *self.literals() {
             while cur_lit < lits.len() {
                 let ltrl = (*lits)[cur_lit].clone();
                 if ltrl.pos > pos { break; }
@@ -618,11 +617,8 @@ pub trait PrintState<'a> {
 
     fn print_literal(&mut self, lit: &ast::Lit) -> io::Result<()> {
         self.maybe_print_comment(lit.span.lo)?;
-        match self.next_lit(lit.span.lo) {
-            Some(ref ltrl) => {
-                return word(self.writer(), &(*ltrl).lit);
-            }
-            _ => ()
+        if let Some(ref ltrl) = self.next_lit(lit.span.lo) {
+            return word(self.writer(), &(*ltrl).lit);
         }
         match lit.node {
             ast::LitKind::Str(st, style) => self.print_string(&st.as_str(), style),
@@ -677,7 +673,7 @@ pub trait PrintState<'a> {
                     style: ast::StrStyle) -> io::Result<()> {
         let st = match style {
             ast::StrStyle::Cooked => {
-                (format!("\"{}\"", st.escape_default()))
+                (format!("\"{}\"", parse::escape_default(st)))
             }
             ast::StrStyle::Raw(n) => {
                 (format!("r{delim}\"{string}\"{delim}",
@@ -799,7 +795,7 @@ pub trait PrintState<'a> {
                 self.popen()?;
                 self.commasep(Consistent,
                               &items[..],
-                              |s, i| s.print_meta_list_item(&i))?;
+                              |s, i| s.print_meta_list_item(i))?;
                 self.pclose()?;
             }
         }
@@ -982,14 +978,14 @@ impl<'a> State<'a> {
 
     pub fn commasep_exprs(&mut self, b: Breaks,
                           exprs: &[P<ast::Expr>]) -> io::Result<()> {
-        self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&e), |e| e.span)
+        self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
     }
 
     pub fn print_mod(&mut self, _mod: &ast::Mod,
                      attrs: &[ast::Attribute]) -> io::Result<()> {
         self.print_inner_attributes(attrs)?;
         for item in &_mod.items {
-            self.print_item(&item)?;
+            self.print_item(item)?;
         }
         Ok(())
     }
@@ -1018,7 +1014,7 @@ impl<'a> State<'a> {
         match ty.node {
             ast::TyKind::Slice(ref ty) => {
                 word(&mut self.s, "[")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 word(&mut self.s, "]")?;
             }
             ast::TyKind::Ptr(ref mt) => {
@@ -1040,7 +1036,7 @@ impl<'a> State<'a> {
             ast::TyKind::Tup(ref elts) => {
                 self.popen()?;
                 self.commasep(Inconsistent, &elts[..],
-                              |s, ty| s.print_type(&ty))?;
+                              |s, ty| s.print_type(ty))?;
                 if elts.len() == 1 {
                     word(&mut self.s, ",")?;
                 }
@@ -1048,7 +1044,7 @@ impl<'a> State<'a> {
             }
             ast::TyKind::Paren(ref typ) => {
                 self.popen()?;
-                self.print_type(&typ)?;
+                self.print_type(typ)?;
                 self.pclose()?;
             }
             ast::TyKind::BareFn(ref f) => {
@@ -1081,14 +1077,14 @@ impl<'a> State<'a> {
             }
             ast::TyKind::Array(ref ty, ref v) => {
                 word(&mut self.s, "[")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 word(&mut self.s, "; ")?;
-                self.print_expr(&v)?;
+                self.print_expr(v)?;
                 word(&mut self.s, "]")?;
             }
             ast::TyKind::Typeof(ref e) => {
                 word(&mut self.s, "typeof(")?;
-                self.print_expr(&e)?;
+                self.print_expr(e)?;
                 word(&mut self.s, ")")?;
             }
             ast::TyKind::Infer => {
@@ -1130,7 +1126,7 @@ impl<'a> State<'a> {
                 }
                 self.print_ident(item.ident)?;
                 self.word_space(":")?;
-                self.print_type(&t)?;
+                self.print_type(t)?;
                 word(&mut self.s, ";")?;
                 self.end()?; // end the head-ibox
                 self.end() // end the outer cbox
@@ -1187,7 +1183,7 @@ impl<'a> State<'a> {
                 self.head(&visibility_qualified(&item.vis, "extern crate"))?;
                 if let Some(p) = *optional_path {
                     let val = p.as_str();
-                    if val.contains("-") {
+                    if val.contains('-') {
                         self.print_string(&val, ast::StrStyle::Cooked)?;
                     } else {
                         self.print_name(p)?;
@@ -1203,7 +1199,7 @@ impl<'a> State<'a> {
             }
             ast::ItemKind::Use(ref vp) => {
                 self.head(&visibility_qualified(&item.vis, "use"))?;
-                self.print_view_path(&vp)?;
+                self.print_view_path(vp)?;
                 word(&mut self.s, ";")?;
                 self.end()?; // end inner head-block
                 self.end()?; // end outer head-block
@@ -1215,12 +1211,12 @@ impl<'a> State<'a> {
                 }
                 self.print_ident(item.ident)?;
                 self.word_space(":")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 space(&mut self.s)?;
                 self.end()?; // end the head-ibox
 
                 self.word_space("=")?;
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 word(&mut self.s, ";")?;
                 self.end()?; // end the outer cbox
             }
@@ -1228,12 +1224,12 @@ impl<'a> State<'a> {
                 self.head(&visibility_qualified(&item.vis, "const"))?;
                 self.print_ident(item.ident)?;
                 self.word_space(":")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 space(&mut self.s)?;
                 self.end()?; // end the head-ibox
 
                 self.word_space("=")?;
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 word(&mut self.s, ";")?;
                 self.end()?; // end the outer cbox
             }
@@ -1249,7 +1245,7 @@ impl<'a> State<'a> {
                     &item.vis
                 )?;
                 word(&mut self.s, " ")?;
-                self.print_block_with_attrs(&body, &item.attrs)?;
+                self.print_block_with_attrs(body, &item.attrs)?;
             }
             ast::ItemKind::Mod(ref _mod) => {
                 self.head(&visibility_qualified(&item.vis, "mod"))?;
@@ -1282,7 +1278,7 @@ impl<'a> State<'a> {
                 self.print_where_clause(&params.where_clause)?;
                 space(&mut self.s)?;
                 self.word_space("=")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 word(&mut self.s, ";")?;
                 self.end()?; // end the outer ibox
             }
@@ -1297,11 +1293,11 @@ impl<'a> State<'a> {
             }
             ast::ItemKind::Struct(ref struct_def, ref generics) => {
                 self.head(&visibility_qualified(&item.vis, "struct"))?;
-                self.print_struct(&struct_def, generics, item.ident, item.span, true)?;
+                self.print_struct(struct_def, generics, item.ident, item.span, true)?;
             }
             ast::ItemKind::Union(ref struct_def, ref generics) => {
                 self.head(&visibility_qualified(&item.vis, "union"))?;
-                self.print_struct(&struct_def, generics, item.ident, item.span, true)?;
+                self.print_struct(struct_def, generics, item.ident, item.span, true)?;
             }
             ast::ItemKind::DefaultImpl(unsafety, ref trait_ref) => {
                 self.head("")?;
@@ -1317,12 +1313,14 @@ impl<'a> State<'a> {
             }
             ast::ItemKind::Impl(unsafety,
                           polarity,
+                          defaultness,
                           ref generics,
                           ref opt_trait,
                           ref ty,
                           ref impl_items) => {
                 self.head("")?;
                 self.print_visibility(&item.vis)?;
+                self.print_defaultness(defaultness)?;
                 self.print_unsafety(unsafety)?;
                 self.word_nbsp("impl")?;
 
@@ -1331,11 +1329,8 @@ impl<'a> State<'a> {
                     space(&mut self.s)?;
                 }
 
-                match polarity {
-                    ast::ImplPolarity::Negative => {
-                        word(&mut self.s, "!")?;
-                    },
-                    _ => {}
+                if polarity == ast::ImplPolarity::Negative {
+                    word(&mut self.s, "!")?;
                 }
 
                 if let Some(ref t) = *opt_trait {
@@ -1344,7 +1339,7 @@ impl<'a> State<'a> {
                     self.word_space("for")?;
                 }
 
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 self.print_where_clause(&generics.where_clause)?;
 
                 space(&mut self.s)?;
@@ -1477,6 +1472,13 @@ impl<'a> State<'a> {
         }
     }
 
+    pub fn print_defaultness(&mut self, defatulness: ast::Defaultness) -> io::Result<()> {
+        if let ast::Defaultness::Default = defatulness {
+            try!(self.word_nbsp("default"));
+        }
+        Ok(())
+    }
+
     pub fn print_struct(&mut self,
                         struct_def: &ast::VariantData,
                         generics: &ast::Generics,
@@ -1534,7 +1536,7 @@ impl<'a> State<'a> {
             Some(ref d) => {
                 space(&mut self.s)?;
                 self.word_space("=")?;
-                self.print_expr(&d)
+                self.print_expr(d)
             }
             _ => Ok(())
         }
@@ -1562,7 +1564,7 @@ impl<'a> State<'a> {
         self.print_outer_attributes(&ti.attrs)?;
         match ti.node {
             ast::TraitItemKind::Const(ref ty, ref default) => {
-                self.print_associated_const(ti.ident, &ty,
+                self.print_associated_const(ti.ident, ty,
                                             default.as_ref().map(|expr| &**expr),
                                             &ast::Visibility::Inherited)?;
             }
@@ -1602,12 +1604,10 @@ impl<'a> State<'a> {
         self.hardbreak_if_not_bol()?;
         self.maybe_print_comment(ii.span.lo)?;
         self.print_outer_attributes(&ii.attrs)?;
-        if let ast::Defaultness::Default = ii.defaultness {
-            self.word_nbsp("default")?;
-        }
+        self.print_defaultness(ii.defaultness)?;
         match ii.node {
             ast::ImplItemKind::Const(ref ty, ref expr) => {
-                self.print_associated_const(ii.ident, &ty, Some(&expr), &ii.vis)?;
+                self.print_associated_const(ii.ident, ty, Some(expr), &ii.vis)?;
             }
             ast::ImplItemKind::Method(ref sig, ref body) => {
                 self.head("")?;
@@ -1643,38 +1643,38 @@ impl<'a> State<'a> {
                 self.word_nbsp("let")?;
 
                 self.ibox(INDENT_UNIT)?;
-                self.print_local_decl(&loc)?;
+                self.print_local_decl(loc)?;
                 self.end()?;
                 if let Some(ref init) = loc.init {
                     self.nbsp()?;
                     self.word_space("=")?;
-                    self.print_expr(&init)?;
+                    self.print_expr(init)?;
                 }
                 word(&mut self.s, ";")?;
                 self.end()?;
             }
-            ast::StmtKind::Item(ref item) => self.print_item(&item)?,
+            ast::StmtKind::Item(ref item) => self.print_item(item)?,
             ast::StmtKind::Expr(ref expr) => {
                 self.space_if_not_bol()?;
-                self.print_expr_outer_attr_style(&expr, false)?;
+                self.print_expr_outer_attr_style(expr, false)?;
                 if parse::classify::expr_requires_semi_to_be_stmt(expr) {
                     word(&mut self.s, ";")?;
                 }
             }
             ast::StmtKind::Semi(ref expr) => {
                 self.space_if_not_bol()?;
-                self.print_expr_outer_attr_style(&expr, false)?;
+                self.print_expr_outer_attr_style(expr, false)?;
                 word(&mut self.s, ";")?;
             }
             ast::StmtKind::Mac(ref mac) => {
                 let (ref mac, style, ref attrs) = **mac;
                 self.space_if_not_bol()?;
-                self.print_outer_attributes(&attrs)?;
+                self.print_outer_attributes(attrs)?;
                 let delim = match style {
                     ast::MacStmtStyle::Braces => token::Brace,
                     _ => token::Paren
                 };
-                self.print_mac(&mac, delim)?;
+                self.print_mac(mac, delim)?;
                 if style == ast::MacStmtStyle::Semicolon {
                     word(&mut self.s, ";")?;
                 }
@@ -1728,7 +1728,7 @@ impl<'a> State<'a> {
                 ast::StmtKind::Expr(ref expr) if i == blk.stmts.len() - 1 => {
                     self.maybe_print_comment(st.span.lo)?;
                     self.space_if_not_bol()?;
-                    self.print_expr_outer_attr_style(&expr, false)?;
+                    self.print_expr_outer_attr_style(expr, false)?;
                     self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi))?;
                 }
                 _ => self.print_stmt(st)?,
@@ -1748,9 +1748,9 @@ impl<'a> State<'a> {
                         self.cbox(INDENT_UNIT - 1)?;
                         self.ibox(0)?;
                         word(&mut self.s, " else if ")?;
-                        self.print_expr(&i)?;
+                        self.print_expr(i)?;
                         space(&mut self.s)?;
-                        self.print_block(&then)?;
+                        self.print_block(then)?;
                         self.print_else(e.as_ref().map(|e| &**e))
                     }
                     // "another else-if-let"
@@ -1758,12 +1758,12 @@ impl<'a> State<'a> {
                         self.cbox(INDENT_UNIT - 1)?;
                         self.ibox(0)?;
                         word(&mut self.s, " else if let ")?;
-                        self.print_pat(&pat)?;
+                        self.print_pat(pat)?;
                         space(&mut self.s)?;
                         self.word_space("=")?;
-                        self.print_expr(&expr)?;
+                        self.print_expr(expr)?;
                         space(&mut self.s)?;
-                        self.print_block(&then)?;
+                        self.print_block(then)?;
                         self.print_else(e.as_ref().map(|e| &**e))
                     }
                     // "final else"
@@ -1771,7 +1771,7 @@ impl<'a> State<'a> {
                         self.cbox(INDENT_UNIT - 1)?;
                         self.ibox(0)?;
                         word(&mut self.s, " else ")?;
-                        self.print_block(&b)
+                        self.print_block(b)
                     }
                     // BLEAH, constraints would be great here
                     _ => {
@@ -1837,12 +1837,8 @@ impl<'a> State<'a> {
                                       binop: ast::BinOp) -> bool {
         match sub_expr.node {
             ast::ExprKind::Binary(ref sub_op, _, _) => {
-                if AssocOp::from_ast_binop(sub_op.node).precedence() <
-                    AssocOp::from_ast_binop(binop.node).precedence() {
-                    true
-                } else {
-                    false
-                }
+                AssocOp::from_ast_binop(sub_op.node).precedence() <
+                    AssocOp::from_ast_binop(binop.node).precedence()
             }
             _ => true
         }
@@ -1922,7 +1918,7 @@ impl<'a> State<'a> {
                     space(&mut self.s)?;
                 }
                 word(&mut self.s, "..")?;
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 self.end()?;
             }
             _ => if !fields.is_empty() {
@@ -1962,7 +1958,7 @@ impl<'a> State<'a> {
         if !tys.is_empty() {
             word(&mut self.s, "::<")?;
             self.commasep(Inconsistent, tys,
-                          |s, ty| s.print_type(&ty))?;
+                          |s, ty| s.print_type(ty))?;
             word(&mut self.s, ">")?;
         }
         self.print_call_post(base_args)
@@ -2031,7 +2027,7 @@ impl<'a> State<'a> {
                 self.print_expr_vec(&exprs[..], attrs)?;
             }
             ast::ExprKind::Repeat(ref element, ref count) => {
-                self.print_expr_repeat(&element, &count, attrs)?;
+                self.print_expr_repeat(element, count, attrs)?;
             }
             ast::ExprKind::Struct(ref path, ref fields, ref wth) => {
                 self.print_expr_struct(path, &fields[..], wth, attrs)?;
@@ -2040,43 +2036,43 @@ impl<'a> State<'a> {
                 self.print_expr_tup(&exprs[..], attrs)?;
             }
             ast::ExprKind::Call(ref func, ref args) => {
-                self.print_expr_call(&func, &args[..])?;
+                self.print_expr_call(func, &args[..])?;
             }
             ast::ExprKind::MethodCall(ident, ref tys, ref args) => {
                 self.print_expr_method_call(ident, &tys[..], &args[..])?;
             }
             ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
-                self.print_expr_binary(op, &lhs, &rhs)?;
+                self.print_expr_binary(op, lhs, rhs)?;
             }
             ast::ExprKind::Unary(op, ref expr) => {
-                self.print_expr_unary(op, &expr)?;
+                self.print_expr_unary(op, expr)?;
             }
             ast::ExprKind::AddrOf(m, ref expr) => {
-                self.print_expr_addr_of(m, &expr)?;
+                self.print_expr_addr_of(m, expr)?;
             }
             ast::ExprKind::Lit(ref lit) => {
-                self.print_literal(&lit)?;
+                self.print_literal(lit)?;
             }
             ast::ExprKind::Cast(ref expr, ref ty) => {
                 if let ast::ExprKind::Cast(..) = expr.node {
-                    self.print_expr(&expr)?;
+                    self.print_expr(expr)?;
                 } else {
-                    self.print_expr_maybe_paren(&expr)?;
+                    self.print_expr_maybe_paren(expr)?;
                 }
                 space(&mut self.s)?;
                 self.word_space("as")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
             }
             ast::ExprKind::Type(ref expr, ref ty) => {
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 self.word_space(":")?;
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
             }
             ast::ExprKind::If(ref test, ref blk, ref elseopt) => {
-                self.print_if(&test, &blk, elseopt.as_ref().map(|e| &**e))?;
+                self.print_if(test, blk, elseopt.as_ref().map(|e| &**e))?;
             }
             ast::ExprKind::IfLet(ref pat, ref expr, ref blk, ref elseopt) => {
-                self.print_if_let(&pat, &expr, &blk, elseopt.as_ref().map(|e| &**e))?;
+                self.print_if_let(pat, expr, blk, elseopt.as_ref().map(|e| &**e))?;
             }
             ast::ExprKind::While(ref test, ref blk, opt_ident) => {
                 if let Some(ident) = opt_ident {
@@ -2084,9 +2080,9 @@ impl<'a> State<'a> {
                     self.word_space(":")?;
                 }
                 self.head("while")?;
-                self.print_expr(&test)?;
+                self.print_expr(test)?;
                 space(&mut self.s)?;
-                self.print_block_with_attrs(&blk, attrs)?;
+                self.print_block_with_attrs(blk, attrs)?;
             }
             ast::ExprKind::WhileLet(ref pat, ref expr, ref blk, opt_ident) => {
                 if let Some(ident) = opt_ident {
@@ -2094,12 +2090,12 @@ impl<'a> State<'a> {
                     self.word_space(":")?;
                 }
                 self.head("while let")?;
-                self.print_pat(&pat)?;
+                self.print_pat(pat)?;
                 space(&mut self.s)?;
                 self.word_space("=")?;
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 space(&mut self.s)?;
-                self.print_block_with_attrs(&blk, attrs)?;
+                self.print_block_with_attrs(blk, attrs)?;
             }
             ast::ExprKind::ForLoop(ref pat, ref iter, ref blk, opt_ident) => {
                 if let Some(ident) = opt_ident {
@@ -2107,12 +2103,12 @@ impl<'a> State<'a> {
                     self.word_space(":")?;
                 }
                 self.head("for")?;
-                self.print_pat(&pat)?;
+                self.print_pat(pat)?;
                 space(&mut self.s)?;
                 self.word_space("in")?;
-                self.print_expr(&iter)?;
+                self.print_expr(iter)?;
                 space(&mut self.s)?;
-                self.print_block_with_attrs(&blk, attrs)?;
+                self.print_block_with_attrs(blk, attrs)?;
             }
             ast::ExprKind::Loop(ref blk, opt_ident) => {
                 if let Some(ident) = opt_ident {
@@ -2121,13 +2117,13 @@ impl<'a> State<'a> {
                 }
                 self.head("loop")?;
                 space(&mut self.s)?;
-                self.print_block_with_attrs(&blk, attrs)?;
+                self.print_block_with_attrs(blk, attrs)?;
             }
             ast::ExprKind::Match(ref expr, ref arms) => {
                 self.cbox(INDENT_UNIT)?;
                 self.ibox(4)?;
                 self.word_nbsp("match")?;
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 space(&mut self.s)?;
                 self.bopen()?;
                 self.print_inner_attributes_no_trailing_hardbreak(attrs)?;
@@ -2139,7 +2135,7 @@ impl<'a> State<'a> {
             ast::ExprKind::Closure(capture_clause, ref decl, ref body, _) => {
                 self.print_capture_clause(capture_clause)?;
 
-                self.print_fn_block_args(&decl)?;
+                self.print_fn_block_args(decl)?;
                 space(&mut self.s)?;
                 self.print_expr(body)?;
                 self.end()?; // need to close a box
@@ -2154,48 +2150,48 @@ impl<'a> State<'a> {
                 self.cbox(INDENT_UNIT)?;
                 // head-box, will be closed by print-block after {
                 self.ibox(0)?;
-                self.print_block_with_attrs(&blk, attrs)?;
+                self.print_block_with_attrs(blk, attrs)?;
             }
             ast::ExprKind::Assign(ref lhs, ref rhs) => {
-                self.print_expr(&lhs)?;
+                self.print_expr(lhs)?;
                 space(&mut self.s)?;
                 self.word_space("=")?;
-                self.print_expr(&rhs)?;
+                self.print_expr(rhs)?;
             }
             ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
-                self.print_expr(&lhs)?;
+                self.print_expr(lhs)?;
                 space(&mut self.s)?;
                 word(&mut self.s, op.node.to_string())?;
                 self.word_space("=")?;
-                self.print_expr(&rhs)?;
+                self.print_expr(rhs)?;
             }
             ast::ExprKind::Field(ref expr, id) => {
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 word(&mut self.s, ".")?;
                 self.print_ident(id.node)?;
             }
             ast::ExprKind::TupField(ref expr, id) => {
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 word(&mut self.s, ".")?;
                 self.print_usize(id.node)?;
             }
             ast::ExprKind::Index(ref expr, ref index) => {
-                self.print_expr(&expr)?;
+                self.print_expr(expr)?;
                 word(&mut self.s, "[")?;
-                self.print_expr(&index)?;
+                self.print_expr(index)?;
                 word(&mut self.s, "]")?;
             }
             ast::ExprKind::Range(ref start, ref end, limits) => {
-                if let &Some(ref e) = start {
-                    self.print_expr(&e)?;
+                if let Some(ref e) = *start {
+                    self.print_expr(e)?;
                 }
                 if limits == ast::RangeLimits::HalfOpen {
                     word(&mut self.s, "..")?;
                 } else {
                     word(&mut self.s, "...")?;
                 }
-                if let &Some(ref e) = end {
-                    self.print_expr(&e)?;
+                if let Some(ref e) = *end {
+                    self.print_expr(e)?;
                 }
             }
             ast::ExprKind::Path(None, ref path) => {
@@ -2226,12 +2222,9 @@ impl<'a> State<'a> {
             }
             ast::ExprKind::Ret(ref result) => {
                 word(&mut self.s, "return")?;
-                match *result {
-                    Some(ref expr) => {
-                        word(&mut self.s, " ")?;
-                        self.print_expr(&expr)?;
-                    }
-                    _ => ()
+                if let Some(ref expr) = *result {
+                    word(&mut self.s, " ")?;
+                    self.print_expr(expr)?;
                 }
             }
             ast::ExprKind::InlineAsm(ref a) => {
@@ -2261,7 +2254,7 @@ impl<'a> State<'a> {
                 self.commasep(Inconsistent, &a.inputs, |s, &(co, ref o)| {
                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
                     s.popen()?;
-                    s.print_expr(&o)?;
+                    s.print_expr(o)?;
                     s.pclose()?;
                     Ok(())
                 })?;
@@ -2301,7 +2294,7 @@ impl<'a> State<'a> {
             ast::ExprKind::Paren(ref e) => {
                 self.popen()?;
                 self.print_inner_attributes_inline(attrs)?;
-                self.print_expr(&e)?;
+                self.print_expr(e)?;
                 self.pclose()?;
             },
             ast::ExprKind::Try(ref e) => {
@@ -2311,7 +2304,7 @@ impl<'a> State<'a> {
             ast::ExprKind::Catch(ref blk) => {
                 self.head("do catch")?;
                 space(&mut self.s)?;
-                self.print_block_with_attrs(&blk, attrs)?
+                self.print_block_with_attrs(blk, attrs)?
             }
         }
         self.ann.post(self, NodeExpr(expr))?;
@@ -2322,7 +2315,7 @@ impl<'a> State<'a> {
         self.print_pat(&loc.pat)?;
         if let Some(ref ty) = loc.ty {
             self.word_space(":")?;
-            self.print_type(&ty)?;
+            self.print_type(ty)?;
         }
         Ok(())
     }
@@ -2390,7 +2383,7 @@ impl<'a> State<'a> {
             space(&mut self.s)?;
             self.word_space("as")?;
             let depth = path.segments.len() - qself.position;
-            self.print_path(&path, false, depth, false)?;
+            self.print_path(path, false, depth, false)?;
         }
         word(&mut self.s, ">")?;
         word(&mut self.s, "::")?;
@@ -2431,7 +2424,7 @@ impl<'a> State<'a> {
                     self.commasep(
                         Inconsistent,
                         &data.types,
-                        |s, ty| s.print_type(&ty))?;
+                        |s, ty| s.print_type(ty))?;
                         comma = true;
                 }
 
@@ -2454,13 +2447,13 @@ impl<'a> State<'a> {
                 self.commasep(
                     Inconsistent,
                     &data.inputs,
-                    |s, ty| s.print_type(&ty))?;
+                    |s, ty| s.print_type(ty))?;
                 word(&mut self.s, ")")?;
 
                 if let Some(ref ty) = data.output {
                     self.space_if_not_bol()?;
                     self.word_space("->")?;
-                    self.print_type(&ty)?;
+                    self.print_type(ty)?;
                 }
             }
         }
@@ -2489,24 +2482,24 @@ impl<'a> State<'a> {
                 self.print_ident(path1.node)?;
                 if let Some(ref p) = *sub {
                     word(&mut self.s, "@")?;
-                    self.print_pat(&p)?;
+                    self.print_pat(p)?;
                 }
             }
             PatKind::TupleStruct(ref path, ref elts, ddpos) => {
                 self.print_path(path, true, 0, false)?;
                 self.popen()?;
                 if let Some(ddpos) = ddpos {
-                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p))?;
                     if ddpos != 0 {
                         self.word_space(",")?;
                     }
                     word(&mut self.s, "..")?;
                     if ddpos != elts.len() {
                         word(&mut self.s, ",")?;
-                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p))?;
                     }
                 } else {
-                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
+                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p))?;
                 }
                 self.pclose()?;
             }
@@ -2542,17 +2535,17 @@ impl<'a> State<'a> {
             PatKind::Tuple(ref elts, ddpos) => {
                 self.popen()?;
                 if let Some(ddpos) = ddpos {
-                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p))?;
                     if ddpos != 0 {
                         self.word_space(",")?;
                     }
                     word(&mut self.s, "..")?;
                     if ddpos != elts.len() {
                         word(&mut self.s, ",")?;
-                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p))?;
                     }
                 } else {
-                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
+                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p))?;
                     if elts.len() == 1 {
                         word(&mut self.s, ",")?;
                     }
@@ -2561,41 +2554,41 @@ impl<'a> State<'a> {
             }
             PatKind::Box(ref inner) => {
                 word(&mut self.s, "box ")?;
-                self.print_pat(&inner)?;
+                self.print_pat(inner)?;
             }
             PatKind::Ref(ref inner, mutbl) => {
                 word(&mut self.s, "&")?;
                 if mutbl == ast::Mutability::Mutable {
                     word(&mut self.s, "mut ")?;
                 }
-                self.print_pat(&inner)?;
+                self.print_pat(inner)?;
             }
             PatKind::Lit(ref e) => self.print_expr(&**e)?,
             PatKind::Range(ref begin, ref end, ref end_kind) => {
-                self.print_expr(&begin)?;
+                self.print_expr(begin)?;
                 space(&mut self.s)?;
                 match *end_kind {
                     RangeEnd::Included => word(&mut self.s, "...")?,
                     RangeEnd::Excluded => word(&mut self.s, "..")?,
                 }
-                self.print_expr(&end)?;
+                self.print_expr(end)?;
             }
             PatKind::Slice(ref before, ref slice, ref after) => {
                 word(&mut self.s, "[")?;
                 self.commasep(Inconsistent,
                                    &before[..],
-                                   |s, p| s.print_pat(&p))?;
+                                   |s, p| s.print_pat(p))?;
                 if let Some(ref p) = *slice {
                     if !before.is_empty() { self.word_space(",")?; }
                     if p.node != PatKind::Wild {
-                        self.print_pat(&p)?;
+                        self.print_pat(p)?;
                     }
                     word(&mut self.s, "..")?;
                     if !after.is_empty() { self.word_space(",")?; }
                 }
                 self.commasep(Inconsistent,
                                    &after[..],
-                                   |s, p| s.print_pat(&p))?;
+                                   |s, p| s.print_pat(p))?;
                 word(&mut self.s, "]")?;
             }
             PatKind::Mac(ref m) => self.print_mac(m, token::Paren)?,
@@ -2621,12 +2614,12 @@ impl<'a> State<'a> {
                 space(&mut self.s)?;
                 self.word_space("|")?;
             }
-            self.print_pat(&p)?;
+            self.print_pat(p)?;
         }
         space(&mut self.s)?;
         if let Some(ref e) = arm.guard {
             self.word_space("if")?;
-            self.print_expr(&e)?;
+            self.print_expr(e)?;
             space(&mut self.s)?;
         }
         self.word_space("=>")?;
@@ -2634,7 +2627,7 @@ impl<'a> State<'a> {
         match arm.body.node {
             ast::ExprKind::Block(ref blk) => {
                 // the block will close the pattern's ibox
-                self.print_block_unclosed_indent(&blk, INDENT_UNIT)?;
+                self.print_block_unclosed_indent(blk, INDENT_UNIT)?;
 
                 // If it is a user-provided unsafe block, print a comma after it
                 if let BlockCheckMode::Unsafe(ast::UserProvided) = blk.rules {
@@ -2666,7 +2659,7 @@ impl<'a> State<'a> {
                 self.print_mutability(m)?;
                 word(&mut self.s, "self")?;
                 self.word_space(":")?;
-                self.print_type(&typ)
+                self.print_type(typ)
             }
         }
     }
@@ -2718,7 +2711,7 @@ impl<'a> State<'a> {
         self.word_space("->")?;
         match decl.output {
             ast::FunctionRetTy::Ty(ref ty) => {
-                self.print_type(&ty)?;
+                self.print_type(ty)?;
                 self.maybe_print_comment(ty.span.lo)
             }
             ast::FunctionRetTy::Default(..) => unreachable!(),
@@ -2832,7 +2825,7 @@ impl<'a> State<'a> {
             Some(ref default) => {
                 space(&mut self.s)?;
                 self.word_space("=")?;
-                self.print_type(&default)
+                self.print_type(default)
             }
             _ => Ok(())
         }
@@ -2858,7 +2851,7 @@ impl<'a> State<'a> {
                                                                              ref bounds,
                                                                              ..}) => {
                     self.print_formal_lifetime_list(bound_lifetimes)?;
-                    self.print_type(&bounded_ty)?;
+                    self.print_type(bounded_ty)?;
                     self.print_bounds(":", bounds)?;
                 }
                 ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{ref lifetime,
@@ -2970,7 +2963,7 @@ impl<'a> State<'a> {
         match decl.output {
             ast::FunctionRetTy::Default(..) => unreachable!(),
             ast::FunctionRetTy::Ty(ref ty) =>
-                self.print_type(&ty)?
+                self.print_type(ty)?
         }
         self.end()?;
 
@@ -3037,14 +3030,9 @@ impl<'a> State<'a> {
         if self.next_comment().is_none() {
             hardbreak(&mut self.s)?;
         }
-        loop {
-            match self.next_comment() {
-                Some(ref cmnt) => {
-                    self.print_comment(cmnt)?;
-                    self.cur_cmnt_and_lit.cur_cmnt += 1;
-                }
-                _ => break
-            }
+        while let Some(ref cmnt) = self.next_comment() {
+            self.print_comment(cmnt)?;
+            self.cur_cmnt_and_lit.cur_cmnt += 1;
         }
         Ok(())
     }
diff --git a/src/libsyntax/std_inject.rs b/src/libsyntax/std_inject.rs
index c7820a15fb3..8e257102e1c 100644
--- a/src/libsyntax/std_inject.rs
+++ b/src/libsyntax/std_inject.rs
@@ -18,7 +18,7 @@ use ptr::P;
 use tokenstream::TokenStream;
 
 /// Craft a span that will be ignored by the stability lint's
-/// call to codemap's is_internal check.
+/// call to codemap's `is_internal` check.
 /// The expanded code uses the unstable `#[prelude_import]` attribute.
 fn ignored_span(sp: Span) -> Span {
     let mark = Mark::fresh();
@@ -49,7 +49,7 @@ pub fn maybe_inject_crates_ref(mut krate: ast::Crate, alt_std_name: Option<Strin
         None => return krate,
     };
 
-    let crate_name = Symbol::intern(&alt_std_name.unwrap_or(name.to_string()));
+    let crate_name = Symbol::intern(&alt_std_name.unwrap_or_else(|| name.to_string()));
 
     krate.module.items.insert(0, P(ast::Item {
         attrs: vec![attr::mk_attr_outer(DUMMY_SP,
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index 50380626d7f..bb1a6ff65a5 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -106,9 +106,8 @@ impl<'a> fold::Folder for TestHarnessGenerator<'a> {
         // Add a special __test module to the crate that will contain code
         // generated for the test harness
         let (mod_, reexport) = mk_test_module(&mut self.cx);
-        match reexport {
-            Some(re) => folded.module.items.push(re),
-            None => {}
+        if let Some(re) = reexport {
+            folded.module.items.push(re)
         }
         folded.module.items.push(mod_);
         folded
@@ -257,7 +256,7 @@ fn mk_reexport_mod(cx: &mut TestCtxt,
     let parent = if parent == ast::DUMMY_NODE_ID { ast::CRATE_NODE_ID } else { parent };
     cx.ext_cx.current_expansion.mark = cx.ext_cx.resolver.get_module_scope(parent);
     let it = cx.ext_cx.monotonic_expander().fold_item(P(ast::Item {
-        ident: sym.clone(),
+        ident: sym,
         attrs: Vec::new(),
         id: ast::DUMMY_NODE_ID,
         node: ast::ItemKind::Mod(reexport_mod),
@@ -308,7 +307,7 @@ fn generate_test_harness(sess: &ParseSess,
 }
 
 /// Craft a span that will be ignored by the stability lint's
-/// call to codemap's is_internal check.
+/// call to codemap's `is_internal` check.
 /// The expanded code calls some unstable functions in the test crate.
 fn ignored_span(cx: &TestCtxt, sp: Span) -> Span {
     Span { ctxt: cx.ctxt, ..sp }
@@ -354,7 +353,7 @@ fn is_test_fn(cx: &TestCtxt, i: &ast::Item) -> bool {
         }
     }
 
-    return has_test_attr && has_test_signature(i) == Yes;
+    has_test_attr && has_test_signature(i) == Yes
 }
 
 fn is_bench_fn(cx: &TestCtxt, i: &ast::Item) -> bool {
@@ -385,7 +384,7 @@ fn is_bench_fn(cx: &TestCtxt, i: &ast::Item) -> bool {
                       `fn(&mut Bencher) -> ()`");
     }
 
-    return has_bench_attr && has_test_signature(i);
+    has_bench_attr && has_test_signature(i)
 }
 
 fn is_ignored(i: &ast::Item) -> bool {
@@ -442,7 +441,7 @@ We're going to be building a module that looks more or less like:
 mod __test {
   extern crate test (name = "test", vers = "...");
   fn main() {
-    test::test_main_static(&::os::args()[], tests)
+    test::test_main_static(&::os::args()[], tests, test::Options::new())
   }
 
   static tests : &'static [test::TestDescAndFn] = &[
@@ -478,7 +477,7 @@ fn mk_main(cx: &mut TestCtxt) -> P<ast::Item> {
     //        pub fn main() {
     //            #![main]
     //            use std::slice::AsSlice;
-    //            test::test_main_static(::std::os::args().as_slice(), TESTS);
+    //            test::test_main_static(::std::os::args().as_slice(), TESTS, test::Options::new());
     //        }
 
     let sp = ignored_span(cx, DUMMY_SP);
@@ -504,16 +503,14 @@ fn mk_main(cx: &mut TestCtxt) -> P<ast::Item> {
                            ast::Unsafety::Normal,
                            dummy_spanned(ast::Constness::NotConst),
                            ::abi::Abi::Rust, ast::Generics::default(), main_body);
-    let main = P(ast::Item {
+    P(ast::Item {
         ident: Ident::from_str("main"),
         attrs: vec![main_attr],
         id: ast::DUMMY_NODE_ID,
         node: main,
         vis: ast::Visibility::Public,
         span: sp
-    });
-
-    return main;
+    })
 }
 
 fn mk_test_module(cx: &mut TestCtxt) -> (P<ast::Item>, Option<P<ast::Item>>) {
diff --git a/src/libsyntax/test_snippet.rs b/src/libsyntax/test_snippet.rs
index dc9b22c37e2..b3fa1e97376 100644
--- a/src/libsyntax/test_snippet.rs
+++ b/src/libsyntax/test_snippet.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use codemap::CodeMap;
+use codemap::{CodeMap, FilePathMapping};
 use errors::Handler;
 use errors::emitter::EmitterWriter;
 use std::io;
@@ -47,8 +47,8 @@ impl<T: Write> Write for Shared<T> {
 fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &str) {
     let output = Arc::new(Mutex::new(Vec::new()));
 
-    let code_map = Rc::new(CodeMap::new());
-    code_map.new_filemap_and_lines("test.rs", None, &file_text);
+    let code_map = Rc::new(CodeMap::new(FilePathMapping::empty()));
+    code_map.new_filemap_and_lines("test.rs", &file_text);
 
     let primary_span = make_span(&file_text, &span_labels[0].start, &span_labels[0].end);
     let mut msp = MultiSpan::from_span(primary_span);
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 86bfdebe42b..9c1371a31fe 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -10,16 +10,16 @@
 
 //! # Token Streams
 //!
-//! TokenStreams represent syntactic objects before they are converted into ASTs.
+//! `TokenStream`s represent syntactic objects before they are converted into ASTs.
 //! A `TokenStream` is, roughly speaking, a sequence (eg stream) of `TokenTree`s,
 //! which are themselves a single `Token` or a `Delimited` subsequence of tokens.
 //!
 //! ## Ownership
-//! TokenStreams are persistent data structures constructed as ropes with reference
-//! counted-children. In general, this means that calling an operation on a TokenStream
-//! (such as `slice`) produces an entirely new TokenStream from the borrowed reference to
-//! the original. This essentially coerces TokenStreams into 'views' of their subparts,
-//! and a borrowed TokenStream is sufficient to build an owned TokenStream without taking
+//! `TokenStreams` are persistent data structures constructed as ropes with reference
+//! counted-children. In general, this means that calling an operation on a `TokenStream`
+//! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
+//! the original. This essentially coerces `TokenStream`s into 'views' of their subparts,
+//! and a borrowed `TokenStream` is sufficient to build an owned `TokenStream` without taking
 //! ownership of the original.
 
 use syntax_pos::{BytePos, Span, DUMMY_SP};
@@ -88,7 +88,7 @@ impl Delimited {
 /// If the syntax extension is an MBE macro, it will attempt to match its
 /// LHS token tree against the provided token tree, and if it finds a
 /// match, will transcribe the RHS token tree, splicing in any captured
-/// macro_parser::matched_nonterminals into the `SubstNt`s it finds.
+/// `macro_parser::matched_nonterminals` into the `SubstNt`s it finds.
 ///
 /// The RHS of an MBE macro is the only place `SubstNt`s are substituted.
 /// Nothing special happens to misnamed or misplaced `SubstNt`s.
diff --git a/src/libsyntax/util/lev_distance.rs b/src/libsyntax/util/lev_distance.rs
index a6fff2d7074..9307f3c58d4 100644
--- a/src/libsyntax/util/lev_distance.rs
+++ b/src/libsyntax/util/lev_distance.rs
@@ -53,9 +53,10 @@ pub fn find_best_match_for_name<'a, T>(iter_names: T,
     iter_names
     .filter_map(|&name| {
         let dist = lev_distance(lookup, &name.as_str());
-        match dist <= max_dist {    // filter the unwanted cases
-            true => Some((name, dist)),
-            false => None,
+        if dist <= max_dist {    // filter the unwanted cases
+            Some((name, dist))
+        } else {
+            None
         }
     })
     .min_by_key(|&(_, val)| val)    // extract the tuple containing the minimum edit distance
diff --git a/src/libsyntax/util/move_map.rs b/src/libsyntax/util/move_map.rs
index fe05e2958b3..8cc37afa354 100644
--- a/src/libsyntax/util/move_map.rs
+++ b/src/libsyntax/util/move_map.rs
@@ -37,10 +37,10 @@ impl<T> MoveMap<T> for Vec<T> {
                 // move the read_i'th item out of the vector and map it
                 // to an iterator
                 let e = ptr::read(self.get_unchecked(read_i));
-                let mut iter = f(e).into_iter();
+                let iter = f(e).into_iter();
                 read_i += 1;
 
-                while let Some(e) = iter.next() {
+                for e in iter {
                     if write_i < read_i {
                         ptr::write(self.get_unchecked_mut(write_i), e);
                         write_i += 1;
@@ -93,10 +93,10 @@ impl<T> MoveMap<T> for SmallVector<T> {
                 // move the read_i'th item out of the vector and map it
                 // to an iterator
                 let e = ptr::read(self.get_unchecked(read_i));
-                let mut iter = f(e).into_iter();
+                let iter = f(e).into_iter();
                 read_i += 1;
 
-                while let Some(e) = iter.next() {
+                for e in iter {
                     if write_i < read_i {
                         ptr::write(self.get_unchecked_mut(write_i), e);
                         write_i += 1;
diff --git a/src/libsyntax/util/node_count.rs b/src/libsyntax/util/node_count.rs
index 9d9957a0f45..0a5d0c2e7fe 100644
--- a/src/libsyntax/util/node_count.rs
+++ b/src/libsyntax/util/node_count.rs
@@ -31,7 +31,7 @@ impl<'ast> Visitor<'ast> for NodeCounter {
         self.count += 1;
         walk_ident(self, span, ident);
     }
-    fn visit_mod(&mut self, m: &Mod, _s: Span, _n: NodeId) {
+    fn visit_mod(&mut self, m: &Mod, _s: Span, _a: &[Attribute], _n: NodeId) {
         self.count += 1;
         walk_mod(self, m)
     }
diff --git a/src/libsyntax/util/parser_testing.rs b/src/libsyntax/util/parser_testing.rs
index 51eb295b502..2727ab79ebf 100644
--- a/src/libsyntax/util/parser_testing.rs
+++ b/src/libsyntax/util/parser_testing.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 use ast::{self, Ident};
+use codemap::FilePathMapping;
 use parse::{ParseSess, PResult, filemap_to_stream};
 use parse::{lexer, new_parser_from_source_str};
 use parse::parser::Parser;
@@ -18,8 +19,8 @@ use std::iter::Peekable;
 
 /// Map a string to tts, using a made-up filename:
 pub fn string_to_stream(source_str: String) -> TokenStream {
-    let ps = ParseSess::new();
-    filemap_to_stream(&ps, ps.codemap().new_filemap("bogofile".to_string(), None, source_str))
+    let ps = ParseSess::new(FilePathMapping::empty());
+    filemap_to_stream(&ps, ps.codemap().new_filemap("bogofile".to_string(), source_str))
 }
 
 /// Map string to parser (via tts)
@@ -38,7 +39,7 @@ fn with_error_checking_parse<'a, T, F>(s: String, ps: &'a ParseSess, f: F) -> T
 
 /// Parse a string, return a crate.
 pub fn string_to_crate (source_str : String) -> ast::Crate {
-    let ps = ParseSess::new();
+    let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
         p.parse_crate_mod()
     })
@@ -46,7 +47,7 @@ pub fn string_to_crate (source_str : String) -> ast::Crate {
 
 /// Parse a string, return an expr
 pub fn string_to_expr (source_str : String) -> P<ast::Expr> {
-    let ps = ParseSess::new();
+    let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
         p.parse_expr()
     })
@@ -54,7 +55,7 @@ pub fn string_to_expr (source_str : String) -> P<ast::Expr> {
 
 /// Parse a string, return an item
 pub fn string_to_item (source_str : String) -> Option<P<ast::Item>> {
-    let ps = ParseSess::new();
+    let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
         p.parse_item()
     })
@@ -62,7 +63,7 @@ pub fn string_to_item (source_str : String) -> Option<P<ast::Item>> {
 
 /// Parse a string, return a stmt
 pub fn string_to_stmt(source_str : String) -> Option<ast::Stmt> {
-    let ps = ParseSess::new();
+    let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
         p.parse_stmt()
     })
@@ -71,7 +72,7 @@ pub fn string_to_stmt(source_str : String) -> Option<ast::Stmt> {
 /// Parse a string, return a pat. Uses "irrefutable"... which doesn't
 /// (currently) affect parsing.
 pub fn string_to_pat(source_str: String) -> P<ast::Pat> {
-    let ps = ParseSess::new();
+    let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
         p.parse_pat()
     })
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index bae1c56db00..0fa0753b22c 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -27,6 +27,7 @@ use abi::Abi;
 use ast::*;
 use syntax_pos::Span;
 use codemap::Spanned;
+use tokenstream::ThinTokenStream;
 
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum FnKind<'a> {
@@ -56,7 +57,9 @@ pub trait Visitor<'ast>: Sized {
     fn visit_ident(&mut self, span: Span, ident: Ident) {
         walk_ident(self, span, ident);
     }
-    fn visit_mod(&mut self, m: &'ast Mod, _s: Span, _n: NodeId) { walk_mod(self, m) }
+    fn visit_mod(&mut self, m: &'ast Mod, _s: Span, _attrs: &[Attribute], _n: NodeId) {
+        walk_mod(self, m);
+    }
     fn visit_foreign_item(&mut self, i: &'ast ForeignItem) { walk_foreign_item(self, i) }
     fn visit_global_asm(&mut self, ga: &'ast GlobalAsm) { walk_global_asm(self, ga) }
     fn visit_item(&mut self, i: &'ast Item) { walk_item(self, i) }
@@ -110,6 +113,9 @@ pub trait Visitor<'ast>: Sized {
         // definition in your trait impl:
         // visit::walk_mac(self, _mac)
     }
+    fn visit_mac_def(&mut self, _mac: &'ast ThinTokenStream, _id: NodeId) {
+        // Nothing to do
+    }
     fn visit_path(&mut self, path: &'ast Path, _id: NodeId) {
         walk_path(self, path)
     }
@@ -172,7 +178,7 @@ pub fn walk_ident<'a, V: Visitor<'a>>(visitor: &mut V, span: Span, ident: Ident)
 }
 
 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) {
-    visitor.visit_mod(&krate.module, krate.span, CRATE_NODE_ID);
+    visitor.visit_mod(&krate.module, krate.span, &krate.attrs, CRATE_NODE_ID);
     walk_list!(visitor, visit_attribute, &krate.attrs);
 }
 
@@ -249,7 +255,7 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
                              item.id)
         }
         ItemKind::Mod(ref module) => {
-            visitor.visit_mod(module, item.span, item.id)
+            visitor.visit_mod(module, item.span, &item.attrs, item.id)
         }
         ItemKind::ForeignMod(ref foreign_module) => {
             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
@@ -266,7 +272,7 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
         ItemKind::DefaultImpl(_, ref trait_ref) => {
             visitor.visit_trait_ref(trait_ref)
         }
-        ItemKind::Impl(_, _,
+        ItemKind::Impl(_, _, _,
                  ref type_parameters,
                  ref opt_trait_reference,
                  ref typ,
@@ -288,7 +294,7 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
             walk_list!(visitor, visit_trait_item, methods);
         }
         ItemKind::Mac(ref mac) => visitor.visit_mac(mac),
-        ItemKind::MacroDef(..) => {},
+        ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
     }
     walk_list!(visitor, visit_attribute, &item.attrs);
 }
@@ -343,9 +349,7 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
             visitor.visit_ty(ty);
             visitor.visit_expr(expression)
         }
-        TyKind::TraitObject(ref bounds) => {
-            walk_list!(visitor, visit_ty_param_bound, bounds);
-        }
+        TyKind::TraitObject(ref bounds) |
         TyKind::ImplTrait(ref bounds) => {
             walk_list!(visitor, visit_ty_param_bound, bounds);
         }
@@ -540,7 +544,7 @@ pub fn walk_fn<'a, V>(visitor: &mut V, kind: FnKind<'a>, declaration: &'a FnDecl
             walk_fn_decl(visitor, declaration);
             visitor.visit_block(body);
         }
-        FnKind::Method(_, ref sig, _, body) => {
+        FnKind::Method(_, sig, _, body) => {
             visitor.visit_generics(&sig.generics);
             walk_fn_decl(visitor, declaration);
             visitor.visit_block(body);
@@ -776,7 +780,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
         }
         ExprKind::InlineAsm(ref ia) => {
             for &(_, ref input) in &ia.inputs {
-                visitor.visit_expr(&input)
+                visitor.visit_expr(input)
             }
             for output in &ia.outputs {
                 visitor.visit_expr(&output.expr)