Merge remote-tracking branch 'upstream/master'

13 files changed, 257 insertions, 129 deletions

diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 830a457df74..b3d9cf9da36 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -158,29 +158,13 @@ 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, mut src: String) -> Rc<FileMap> {
+    pub fn new_filemap(&self, filename: FileName, src: String) -> Rc<FileMap> {
         let start_pos = self.next_start_pos();
         let mut files = self.files.borrow_mut();
 
-        // Remove utf-8 BOM if any.
-        if src.starts_with("\u{feff}") {
-            src.drain(..3);
-        }
-
-        let end_pos = start_pos + src.len();
-
         let (filename, was_remapped) = self.path_mapping.map_prefix(filename);
-
-        let filemap = Rc::new(FileMap {
-            name: filename,
-            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),
-            lines: RefCell::new(Vec::new()),
-            multibyte_chars: RefCell::new(Vec::new()),
-        });
+        let filemap =
+            Rc::new(FileMap::new(filename, was_remapped, src, Pos::from_usize(start_pos)));
 
         files.push(filemap.clone());
 
@@ -210,6 +194,7 @@ impl CodeMap {
                                 filename: FileName,
                                 name_was_remapped: bool,
                                 crate_of_origin: u32,
+                                src_hash: u128,
                                 source_len: usize,
                                 mut file_local_lines: Vec<BytePos>,
                                 mut file_local_multibyte_chars: Vec<MultiByteChar>)
@@ -233,6 +218,8 @@ impl CodeMap {
             name_was_remapped: name_was_remapped,
             crate_of_origin: crate_of_origin,
             src: None,
+            src_hash: src_hash,
+            external_src: RefCell::new(ExternalSource::AbsentOk),
             start_pos: start_pos,
             end_pos: end_pos,
             lines: RefCell::new(file_local_lines),
@@ -428,30 +415,31 @@ impl CodeMap {
                       local_end.fm.start_pos)
             }));
         } else {
-            match local_begin.fm.src {
-                Some(ref src) => {
-                    let start_index = local_begin.pos.to_usize();
-                    let end_index = local_end.pos.to_usize();
-                    let source_len = (local_begin.fm.end_pos -
-                                      local_begin.fm.start_pos).to_usize();
-
-                    if start_index > end_index || end_index > source_len {
-                        return Err(SpanSnippetError::MalformedForCodemap(
-                            MalformedCodemapPositions {
-                                name: local_begin.fm.name.clone(),
-                                source_len: source_len,
-                                begin_pos: local_begin.pos,
-                                end_pos: local_end.pos,
-                            }));
-                    }
-
-                    return Ok((&src[start_index..end_index]).to_string())
-                }
-                None => {
-                    return Err(SpanSnippetError::SourceNotAvailable {
-                        filename: local_begin.fm.name.clone()
-                    });
-                }
+            self.ensure_filemap_source_present(local_begin.fm.clone());
+
+            let start_index = local_begin.pos.to_usize();
+            let end_index = local_end.pos.to_usize();
+            let source_len = (local_begin.fm.end_pos -
+                              local_begin.fm.start_pos).to_usize();
+
+            if start_index > end_index || end_index > source_len {
+                return Err(SpanSnippetError::MalformedForCodemap(
+                    MalformedCodemapPositions {
+                        name: local_begin.fm.name.clone(),
+                        source_len: source_len,
+                        begin_pos: local_begin.pos,
+                        end_pos: local_end.pos,
+                    }));
+            }
+
+            if let Some(ref src) = local_begin.fm.src {
+                return Ok((&src[start_index..end_index]).to_string());
+            } else if let Some(src) = local_begin.fm.external_src.borrow().get_source() {
+                return Ok((&src[start_index..end_index]).to_string());
+            } else {
+                return Err(SpanSnippetError::SourceNotAvailable {
+                    filename: local_begin.fm.name.clone()
+                });
             }
         }
     }
@@ -572,6 +560,10 @@ impl CodeMapper for CodeMap {
         }
         sp
     }
+    fn ensure_filemap_source_present(&self, file_map: Rc<FileMap>) -> bool {
+        let src = self.file_loader.read_file(Path::new(&file_map.name)).ok();
+        return file_map.add_external_src(src)
+    }
 }
 
 #[derive(Clone)]
@@ -617,6 +609,7 @@ impl FilePathMapping {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::borrow::Cow;
     use std::rc::Rc;
 
     #[test]
@@ -626,12 +619,12 @@ mod tests {
                                 "first line.\nsecond line".to_string());
         fm.next_line(BytePos(0));
         // Test we can get lines with partial line info.
-        assert_eq!(fm.get_line(0), Some("first line."));
+        assert_eq!(fm.get_line(0), Some(Cow::from("first line.")));
         // TESTING BROKEN BEHAVIOR: line break declared before actual line break.
         fm.next_line(BytePos(10));
-        assert_eq!(fm.get_line(1), Some("."));
+        assert_eq!(fm.get_line(1), Some(Cow::from(".")));
         fm.next_line(BytePos(12));
-        assert_eq!(fm.get_line(2), Some("second line"));
+        assert_eq!(fm.get_line(2), Some(Cow::from("second line")));
     }
 
     #[test]
diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
index 2e98c7d9626..54e6dde41e6 100644
--- a/src/libsyntax/config.rs
+++ b/src/libsyntax/config.rs
@@ -223,7 +223,6 @@ impl<'a> StripUnconfigured<'a> {
             ast::ExprKind::Struct(path, fields, base) => {
                 let fields = fields.into_iter()
                     .filter_map(|field| {
-                        self.visit_struct_field_attrs(field.attrs());
                         self.configure(field)
                     })
                     .collect();
@@ -256,17 +255,6 @@ 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,
-                                          "struct_field_attributes",
-                                          field.span,
-                                          GateIssue::Language,
-                                          "attributes on struct literal fields are unstable");
-                err.emit();
-            }
-        }
-
         self.configure(field)
     }
 
@@ -275,7 +263,6 @@ impl<'a> StripUnconfigured<'a> {
             if let ast::PatKind::Struct(path, fields, etc) = pattern.node {
                 let fields = fields.into_iter()
                     .filter_map(|field| {
-                        self.visit_struct_field_attrs(field.attrs());
                         self.configure(field)
                     })
                     .collect();
@@ -284,21 +271,6 @@ impl<'a> StripUnconfigured<'a> {
             pattern
         })
     }
-
-    fn visit_struct_field_attrs(&mut self, attrs: &[ast::Attribute]) {
-        // flag the offending attributes
-        for attr in attrs.iter() {
-            if !self.features.map(|features| features.struct_field_attributes).unwrap_or(true) {
-                let mut err = feature_err(
-                    self.sess,
-                    "struct_field_attributes",
-                    attr.span,
-                    GateIssue::Language,
-                    "attributes on struct pattern or literal fields are unstable");
-                err.emit();
-            }
-        }
-    }
 }
 
 impl<'a> fold::Folder for StripUnconfigured<'a> {
diff --git a/src/libsyntax/diagnostics/macros.rs b/src/libsyntax/diagnostics/macros.rs
index 13016d72127..e8ecf58072a 100644
--- a/src/libsyntax/diagnostics/macros.rs
+++ b/src/libsyntax/diagnostics/macros.rs
@@ -75,6 +75,17 @@ macro_rules! struct_span_err {
 }
 
 #[macro_export]
+macro_rules! type_error_struct {
+    ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
+        if $typ.references_error() {
+            $session.diagnostic().struct_dummy()
+        } else {
+            struct_span_err!($session, $span, $code, $($message)*)
+        }
+    })
+}
+
+#[macro_export]
 macro_rules! struct_span_warn {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
         __diagnostic_used!($code);
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 0b6a2eb536a..61d8fc2941a 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -139,13 +139,20 @@ struct MatcherPos {
     sep: Option<Token>,
     idx: usize,
     up: Option<Box<MatcherPos>>,
-    matches: Vec<Vec<Rc<NamedMatch>>>,
+    matches: Vec<Rc<Vec<NamedMatch>>>,
     match_lo: usize,
     match_cur: usize,
     match_hi: usize,
     sp_lo: BytePos,
 }
 
+impl MatcherPos {
+    fn push_match(&mut self, idx: usize, m: NamedMatch) {
+        let matches = Rc::make_mut(&mut self.matches[idx]);
+        matches.push(m);
+    }
+}
+
 pub type NamedParseResult = ParseResult<HashMap<Ident, Rc<NamedMatch>>>;
 
 pub fn count_names(ms: &[TokenTree]) -> usize {
@@ -199,14 +206,15 @@ fn initial_matcher_pos(ms: Vec<TokenTree>, lo: BytePos) -> Box<MatcherPos> {
 /// only on the nesting depth of `ast::TTSeq`s in the originating
 /// token tree it was derived from.
 
+#[derive(Debug, Clone)]
 pub enum NamedMatch {
-    MatchedSeq(Vec<Rc<NamedMatch>>, syntax_pos::Span),
+    MatchedSeq(Rc<Vec<NamedMatch>>, syntax_pos::Span),
     MatchedNonterminal(Rc<Nonterminal>)
 }
 
-fn nameize<I: Iterator<Item=Rc<NamedMatch>>>(sess: &ParseSess, ms: &[TokenTree], mut res: I)
+fn nameize<I: Iterator<Item=NamedMatch>>(sess: &ParseSess, ms: &[TokenTree], mut res: I)
                                              -> NamedParseResult {
-    fn n_rec<I: Iterator<Item=Rc<NamedMatch>>>(sess: &ParseSess, m: &TokenTree, mut res: &mut I,
+    fn n_rec<I: Iterator<Item=NamedMatch>>(sess: &ParseSess, m: &TokenTree, mut res: &mut I,
              ret_val: &mut HashMap<Ident, Rc<NamedMatch>>)
              -> Result<(), (syntax_pos::Span, String)> {
         match *m {
@@ -228,7 +236,8 @@ fn nameize<I: Iterator<Item=Rc<NamedMatch>>>(sess: &ParseSess, ms: &[TokenTree],
             TokenTree::MetaVarDecl(sp, bind_name, _) => {
                 match ret_val.entry(bind_name) {
                     Vacant(spot) => {
-                        spot.insert(res.next().unwrap());
+                        // FIXME(simulacrum): Don't construct Rc here
+                        spot.insert(Rc::new(res.next().unwrap()));
                     }
                     Occupied(..) => {
                         return Err((sp, format!("duplicated bind name: {}", bind_name)))
@@ -280,8 +289,8 @@ fn token_name_eq(t1 : &Token, t2 : &Token) -> bool {
     }
 }
 
-fn create_matches(len: usize) -> Vec<Vec<Rc<NamedMatch>>> {
-    (0..len).into_iter().map(|_| Vec::new()).collect()
+fn create_matches(len: usize) -> Vec<Rc<Vec<NamedMatch>>> {
+    (0..len).into_iter().map(|_| Rc::new(Vec::new())).collect()
 }
 
 fn inner_parse_loop(sess: &ParseSess,
@@ -320,15 +329,10 @@ fn inner_parse_loop(sess: &ParseSess,
                     // update matches (the MBE "parse tree") by appending
                     // each tree as a subtree.
 
-                    // I bet this is a perf problem: we're preemptively
-                    // doing a lot of array work that will get thrown away
-                    // most of the time.
-
                     // Only touch the binders we have actually bound
                     for idx in ei.match_lo..ei.match_hi {
                         let sub = ei.matches[idx].clone();
-                        new_pos.matches[idx]
-                            .push(Rc::new(MatchedSeq(sub, Span { lo: ei.sp_lo, ..span })));
+                        new_pos.push_match(idx, MatchedSeq(sub, Span { lo: ei.sp_lo, ..span }));
                     }
 
                     new_pos.match_cur = ei.match_hi;
@@ -362,7 +366,7 @@ fn inner_parse_loop(sess: &ParseSess,
                         new_ei.match_cur += seq.num_captures;
                         new_ei.idx += 1;
                         for idx in ei.match_cur..ei.match_cur + seq.num_captures {
-                            new_ei.matches[idx].push(Rc::new(MatchedSeq(vec![], sp)));
+                            new_ei.push_match(idx, MatchedSeq(Rc::new(vec![]), sp));
                         }
                         cur_eis.push(new_ei);
                     }
@@ -446,7 +450,9 @@ pub fn parse(sess: &ParseSess,
         /* error messages here could be improved with links to orig. rules */
         if token_name_eq(&parser.token, &token::Eof) {
             if eof_eis.len() == 1 {
-                let matches = eof_eis[0].matches.iter_mut().map(|mut dv| dv.pop().unwrap());
+                let matches = eof_eis[0].matches.iter_mut().map(|mut dv| {
+                    Rc::make_mut(dv).pop().unwrap()
+                });
                 return nameize(sess, ms, matches);
             } else if eof_eis.len() > 1 {
                 return Error(parser.span, "ambiguity: multiple successful parses".to_string());
@@ -479,8 +485,8 @@ pub fn parse(sess: &ParseSess,
             let mut ei = bb_eis.pop().unwrap();
             if let TokenTree::MetaVarDecl(span, _, ident) = ei.top_elts.get_tt(ei.idx) {
                 let match_cur = ei.match_cur;
-                ei.matches[match_cur].push(Rc::new(MatchedNonterminal(
-                            Rc::new(parse_nt(&mut parser, span, &ident.name.as_str())))));
+                ei.push_match(match_cur,
+                    MatchedNonterminal(Rc::new(parse_nt(&mut parser, span, &ident.name.as_str()))));
                 ei.idx += 1;
                 ei.match_cur += 1;
             } else {
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 0472a94e0ce..9c728c9f2eb 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -219,7 +219,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
     let lhses = match *argument_map[&lhs_nm] {
         MatchedSeq(ref s, _) => {
             s.iter().map(|m| {
-                if let MatchedNonterminal(ref nt) = **m {
+                if let MatchedNonterminal(ref nt) = *m {
                     if let NtTT(ref tt) = **nt {
                         let tt = quoted::parse(tt.clone().into(), true, sess).pop().unwrap();
                         valid &= check_lhs_nt_follows(sess, features, &tt);
@@ -235,7 +235,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
     let rhses = match *argument_map[&rhs_nm] {
         MatchedSeq(ref s, _) => {
             s.iter().map(|m| {
-                if let MatchedNonterminal(ref nt) = **m {
+                if let MatchedNonterminal(ref nt) = *m {
                     if let NtTT(ref tt) = **nt {
                         return quoted::parse(tt.clone().into(), false, sess).pop().unwrap();
                     }
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 2a435bdea10..78e755e73fa 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -182,15 +182,16 @@ fn lookup_cur_matched(ident: Ident,
                       repeats: &[(usize, usize)])
                       -> Option<Rc<NamedMatch>> {
     interpolations.get(&ident).map(|matched| {
-        repeats.iter().fold(matched.clone(), |ad, &(idx, _)| {
-            match *ad {
-                MatchedNonterminal(_) => {
-                    // end of the line; duplicate henceforth
-                    ad.clone()
-                }
-                MatchedSeq(ref ads, _) => ads[idx].clone()
+        let mut matched = matched.clone();
+        for &(idx, _) in repeats {
+            let m = matched.clone();
+            match *m {
+                MatchedNonterminal(_) => break,
+                MatchedSeq(ref ads, _) => matched = Rc::new(ads[idx].clone()),
             }
-        })
+        }
+
+        matched
     })
 }
 
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index b2f52d11db2..4543378789d 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -312,9 +312,6 @@ declare_features! (
     // Declarative macros 2.0 (`macro`).
     (active, decl_macro, "1.17.0", Some(39412)),
 
-    // Allows attributes on struct literal fields.
-    (active, struct_field_attributes, "1.16.0", Some(38814)),
-
     // Allows #[link(kind="static-nobundle"...]
     (active, static_nobundle, "1.16.0", Some(37403)),
 
@@ -325,6 +322,10 @@ declare_features! (
     // rustc internal
     (active, sanitizer_runtime, "1.17.0", None),
 
+    // Used to identify crates that contain the profiler runtime
+    // rustc internal
+    (active, profiler_runtime, "1.18.0", None),
+
     // `extern "x86-interrupt" fn()`
     (active, abi_x86_interrupt, "1.17.0", Some(40180)),
 
@@ -426,6 +427,8 @@ declare_features! (
     (accepted, relaxed_adts, "1.19.0", Some(35626)),
     // Coerces non capturing closures to function pointers
     (accepted, closure_to_fn_coercion, "1.19.0", Some(39817)),
+    // Allows attributes on struct literal fields.
+    (accepted, struct_field_attributes, "1.20.0", Some(38814)),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must
@@ -691,6 +694,13 @@ pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeG
                                               identify crates that contain the runtime of a \
                                               sanitizer and will never be stable",
                                              cfg_fn!(sanitizer_runtime))),
+    ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
+                                             "profiler_runtime",
+                                             "the `#[profiler_runtime]` attribute is used to \
+                                              identify the `profiler_builtins` crate which \
+                                              contains the profiler runtime and will never be \
+                                              stable",
+                                             cfg_fn!(profiler_runtime))),
 
     ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
                                               "allow_internal_unstable",
diff --git a/src/libsyntax/json.rs b/src/libsyntax/json.rs
index f37dcfdde89..e60edafe4ee 100644
--- a/src/libsyntax/json.rs
+++ b/src/libsyntax/json.rs
@@ -314,7 +314,7 @@ impl DiagnosticSpanLine {
                          h_end: usize)
                          -> DiagnosticSpanLine {
         DiagnosticSpanLine {
-            text: fm.get_line(index).unwrap_or("").to_owned(),
+            text: fm.get_line(index).map_or(String::new(), |l| l.into_owned()),
             highlight_start: h_start,
             highlight_end: h_end,
         }
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index d9cb2b4ab7d..0b145c54f61 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -150,7 +150,7 @@ fn maybe_append(mut lhs: Vec<Attribute>, rhs: Option<Vec<Attribute>>)
     lhs
 }
 
-#[derive(PartialEq)]
+#[derive(Clone, PartialEq)]
 enum PrevTokenKind {
     DocComment,
     Comma,
@@ -162,6 +162,7 @@ enum PrevTokenKind {
 
 /* ident is handled by common.rs */
 
+#[derive(Clone)]
 pub struct Parser<'a> {
     pub sess: &'a ParseSess,
     /// the current token:
@@ -193,11 +194,13 @@ pub struct Parser<'a> {
 }
 
 
+#[derive(Clone)]
 struct TokenCursor {
     frame: TokenCursorFrame,
     stack: Vec<TokenCursorFrame>,
 }
 
+#[derive(Clone)]
 struct TokenCursorFrame {
     delim: token::DelimToken,
     span: Span,
@@ -397,6 +400,7 @@ impl Error {
     }
 }
 
+#[derive(Debug)]
 pub enum LhsExpr {
     NotYetParsed,
     AttributesParsed(ThinVec<Attribute>),
@@ -1249,10 +1253,7 @@ impl<'a> Parser<'a> {
             let mac = respan(lo.to(self.prev_span), Mac_ { path: pth, tts: tts });
             (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac))
         } else {
-            let (constness, unsafety, abi) = match self.parse_fn_front_matter() {
-                Ok(cua) => cua,
-                Err(e) => return Err(e),
-            };
+            let (constness, unsafety, abi) = self.parse_fn_front_matter()?;
 
             let ident = self.parse_ident()?;
             let mut generics = self.parse_generics()?;
@@ -1724,7 +1725,7 @@ impl<'a> Parser<'a> {
 
         let segments = match mode {
             PathStyle::Type => {
-                self.parse_path_segments_without_colons()?
+                self.parse_path_segments_without_colons(true)?
             }
             PathStyle::Expr => {
                 self.parse_path_segments_with_colons()?
@@ -1745,6 +1746,16 @@ impl<'a> Parser<'a> {
     /// bounds are permitted and whether `::` must precede type parameter
     /// groups.
     pub fn parse_path(&mut self, mode: PathStyle) -> PResult<'a, ast::Path> {
+        self.parse_path_common(mode, true)
+    }
+
+    pub fn parse_path_without_generics(&mut self, mode: PathStyle) -> PResult<'a, ast::Path> {
+        self.parse_path_common(mode, false)
+    }
+
+    fn parse_path_common(&mut self, mode: PathStyle, parse_generics: bool)
+        -> PResult<'a, ast::Path>
+    {
         maybe_whole!(self, NtPath, |x| x);
 
         let lo = self.meta_var_span.unwrap_or(self.span);
@@ -1755,7 +1766,7 @@ impl<'a> Parser<'a> {
         // A bound set is a set of type parameter bounds.
         let mut segments = match mode {
             PathStyle::Type => {
-                self.parse_path_segments_without_colons()?
+                self.parse_path_segments_without_colons(parse_generics)?
             }
             PathStyle::Expr => {
                 self.parse_path_segments_with_colons()?
@@ -1800,7 +1811,9 @@ impl<'a> Parser<'a> {
     /// - `a::b<T,U>::c<V,W>`
     /// - `a::b<T,U>::c(V) -> W`
     /// - `a::b<T,U>::c(V)`
-    pub fn parse_path_segments_without_colons(&mut self) -> PResult<'a, Vec<PathSegment>> {
+    pub fn parse_path_segments_without_colons(&mut self, parse_generics: bool)
+        -> PResult<'a, Vec<PathSegment>>
+    {
         let mut segments = Vec::new();
         loop {
             // First, parse an identifier.
@@ -1819,7 +1832,7 @@ impl<'a> Parser<'a> {
             }
 
             // Parse types, optionally.
-            let parameters = if self.eat_lt() {
+            let parameters = if parse_generics && self.eat_lt() {
                 let (lifetimes, types, bindings) = self.parse_generic_args()?;
                 self.expect_gt()?;
                 ast::AngleBracketedParameterData {
@@ -2798,8 +2811,9 @@ impl<'a> Parser<'a> {
             }
             // Special cases:
             if op == AssocOp::As {
-                let rhs = self.parse_ty_no_plus()?;
-                lhs = self.mk_expr(lhs_span.to(rhs.span), ExprKind::Cast(lhs, rhs), ThinVec::new());
+                // Save the state of the parser before parsing type normally, in case there is a
+                // LessThan comparison after this cast.
+                lhs = self.parse_assoc_op_as(lhs, lhs_span)?;
                 continue
             } else if op == AssocOp::Colon {
                 let rhs = self.parse_ty_no_plus()?;
@@ -2897,11 +2911,74 @@ impl<'a> Parser<'a> {
         Ok(lhs)
     }
 
+    fn parse_assoc_op_as(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
+        let rp = self.clone();
+        match self.parse_ty_no_plus() {
+            Ok(rhs) => {
+                Ok(self.mk_expr(lhs_span.to(rhs.span),
+                                ExprKind::Cast(lhs, rhs),
+                                ThinVec::new()))
+            }
+            Err(mut err) => {
+                let rp_err = self.clone();
+                let sp = rp_err.span.clone();
+
+                // Rewind to before attempting to parse the type with generics, to get
+                // arround #22644.
+                mem::replace(self, rp);
+                let lo = self.span;
+                match self.parse_path_without_generics(PathStyle::Type) {
+                    Ok(path) => {
+                        // Successfully parsed the type leaving a `<` yet to parse
+                        err.cancel();
+                        let codemap = self.sess.codemap();
+                        let suggestion_span = lhs_span.to(self.prev_span);
+                        let suggestion = match codemap.span_to_snippet(suggestion_span) {
+                            Ok(lstring) => format!("({})", lstring),
+                            _ => format!("(<expression> as <type>)")
+                        };
+                        let warn_message = match codemap.span_to_snippet(self.prev_span) {
+                            Ok(lstring) => format!("`{}`", lstring),
+                            _ => "a type".to_string(),
+                        };
+                        let msg = format!("`<` is interpreted as a start of generic \
+                                           arguments for {}, not a comparison",
+                                          warn_message);
+                        let mut err = self.sess.span_diagnostic.struct_span_err(sp, &msg);
+                        err.span_label(sp, "interpreted as generic argument");
+                        err.span_label(self.span, "not interpreted as comparison");
+                        err.span_suggestion(suggestion_span,
+                                            "if you want to compare the casted value then write:",
+                                            suggestion);
+                        err.emit();
+
+                        let path = TyKind::Path(None, path);
+                        let span = lo.to(self.prev_span);
+                        let rhs = P(Ty { node: path, span: span, id: ast::DUMMY_NODE_ID });
+                        // Letting the parser accept the recovered type to avoid further errors,
+                        // but the code will still not compile due to the error emitted above.
+                        Ok(self.mk_expr(lhs_span.to(rhs.span),
+                                        ExprKind::Cast(lhs, rhs),
+                                        ThinVec::new()))
+                    }
+                    Err(mut path_err) => {
+                        // Still couldn't parse, return original error and parser state
+                        path_err.cancel();
+                        mem::replace(self, rp_err);
+                        Err(err)
+                    }
+                }
+            }
+        }
+    }
+
     /// Produce an error if comparison operators are chained (RFC #558).
     /// We only need to check lhs, not rhs, because all comparison ops
     /// have same precedence and are left-associative
     fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
-        debug_assert!(outer_op.is_comparison());
+        debug_assert!(outer_op.is_comparison(),
+                      "check_no_chained_comparison: {:?} is not comparison",
+                      outer_op);
         match lhs.node {
             ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
                 // respan to include both operators
@@ -2925,7 +3002,9 @@ impl<'a> Parser<'a> {
     fn parse_prefix_range_expr(&mut self,
                                already_parsed_attrs: Option<ThinVec<Attribute>>)
                                -> PResult<'a, P<Expr>> {
-        debug_assert!(self.token == token::DotDot || self.token == token::DotDotDot);
+        debug_assert!(self.token == token::DotDot || self.token == token::DotDotDot,
+                      "parse_prefix_range_expr: token {:?} is not DotDot or DotDotDot",
+                      self.token);
         let tok = self.token.clone();
         let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
         let lo = self.span;
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 073ededcb0c..34cda433d52 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -370,6 +370,10 @@ pub fn path_to_string(p: &ast::Path) -> String {
     to_string(|s| s.print_path(p, false, 0, false))
 }
 
+pub fn path_segment_to_string(p: &ast::PathSegment) -> String {
+    to_string(|s| s.print_path_segment(p, false))
+}
+
 pub fn ident_to_string(id: ast::Ident) -> String {
     to_string(|s| s.print_ident(id))
 }
@@ -2359,18 +2363,27 @@ impl<'a> State<'a> {
             if i > 0 {
                 word(&mut self.s, "::")?
             }
-            if segment.identifier.name != keywords::CrateRoot.name() &&
-               segment.identifier.name != "$crate" {
-                self.print_ident(segment.identifier)?;
-                if let Some(ref parameters) = segment.parameters {
-                    self.print_path_parameters(parameters, colons_before_params)?;
-                }
-            }
+            self.print_path_segment(segment, colons_before_params)?;
         }
 
         Ok(())
     }
 
+    fn print_path_segment(&mut self,
+                          segment: &ast::PathSegment,
+                          colons_before_params: bool)
+                          -> io::Result<()>
+    {
+        if segment.identifier.name != keywords::CrateRoot.name() &&
+           segment.identifier.name != "$crate" {
+            self.print_ident(segment.identifier)?;
+            if let Some(ref parameters) = segment.parameters {
+                self.print_path_parameters(parameters, colons_before_params)?;
+            }
+        }
+        Ok(())
+    }
+
     fn print_qpath(&mut self,
                    path: &ast::Path,
                    qself: &ast::QSelf,
diff --git a/src/libsyntax/ptr.rs b/src/libsyntax/ptr.rs
index 15111bbba0a..d51ff9860ac 100644
--- a/src/libsyntax/ptr.rs
+++ b/src/libsyntax/ptr.rs
@@ -211,10 +211,7 @@ impl<T: Encodable> Encodable for P<[T]> {
 
 impl<T: Decodable> Decodable for P<[T]> {
     fn decode<D: Decoder>(d: &mut D) -> Result<P<[T]>, D::Error> {
-        Ok(P::from_vec(match Decodable::decode(d) {
-            Ok(t) => t,
-            Err(e) => return Err(e)
-        }))
+        Ok(P::from_vec(Decodable::decode(d)?))
     }
 }
 
diff --git a/src/libsyntax/test_snippet.rs b/src/libsyntax/test_snippet.rs
index b3fa1e97376..4fae2ff9814 100644
--- a/src/libsyntax/test_snippet.rs
+++ b/src/libsyntax/test_snippet.rs
@@ -736,6 +736,49 @@ error: foo
 }
 
 #[test]
+fn multiple_labels_secondary_without_message_3() {
+    test_harness(r#"
+fn foo() {
+  a  bc  d
+}
+"#,
+    vec![
+        SpanLabel {
+            start: Position {
+                string: "a",
+                count: 1,
+            },
+            end: Position {
+                string: "b",
+                count: 1,
+            },
+            label: "`a` is a good letter",
+        },
+        SpanLabel {
+            start: Position {
+                string: "c",
+                count: 1,
+            },
+            end: Position {
+                string: "d",
+                count: 1,
+            },
+            label: "",
+        },
+    ],
+    r#"
+error: foo
+ --> test.rs:3:3
+  |
+3 |   a  bc  d
+  |   ^^^^----
+  |   |
+  |   `a` is a good letter
+
+"#);
+}
+
+#[test]
 fn multiple_labels_without_message() {
     test_harness(r#"
 fn foo() {
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 339e7c0b628..963482fc223 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -227,14 +227,17 @@ impl TokenStream {
     }
 }
 
+#[derive(Clone)]
 pub struct Cursor(CursorKind);
 
+#[derive(Clone)]
 enum CursorKind {
     Empty,
     Tree(TokenTree, bool /* consumed? */),
     Stream(StreamCursor),
 }
 
+#[derive(Clone)]
 struct StreamCursor {
     stream: RcSlice<TokenStream>,
     index: usize,