Rollup of 14 pull requests

src/bootstrap/check.rs

@@ -246,8 +246,11 @@ impl Step for Rls {
         let compiler = builder.compiler(stage, host);
 
         builder.ensure(tool::Rls { compiler, target: self.host });
-        let mut cargo = builder.cargo(compiler, Mode::Tool, host, "test");
-        cargo.arg("--manifest-path").arg(build.src.join("src/tools/rls/Cargo.toml"));
+        let mut cargo = tool::prepare_tool_cargo(builder,
+                                                 compiler,
+                                                 host,
+                                                 "test",
+                                                 "src/tools/rls");
 
         // Don't build tests dynamically, just a pain to work with
         cargo.env("RUSTC_NO_PREFER_DYNAMIC", "1");
@@ -291,8 +294,11 @@ impl Step for Rustfmt {
         let compiler = builder.compiler(stage, host);
 
         builder.ensure(tool::Rustfmt { compiler, target: self.host });
-        let mut cargo = builder.cargo(compiler, Mode::Tool, host, "test");
-        cargo.arg("--manifest-path").arg(build.src.join("src/tools/rustfmt/Cargo.toml"));
+        let mut cargo = tool::prepare_tool_cargo(builder,
+                                                 compiler,
+                                                 host,
+                                                 "test",
+                                                 "src/tools/rustfmt");
 
         // Don't build tests dynamically, just a pain to work with
         cargo.env("RUSTC_NO_PREFER_DYNAMIC", "1");

src/bootstrap/native.rs

@@ -352,34 +352,51 @@ impl Step for Openssl {
             // originally from https://www.openssl.org/source/...
             let url = format!("https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/{}",
                               name);
-            let mut ok = false;
+            let mut last_error = None;
             for _ in 0..3 {
                 let status = Command::new("curl")
                                 .arg("-o").arg(&tmp)
+                                .arg("-f")  // make curl fail if the URL does not return HTTP 200
                                 .arg(&url)
                                 .status()
                                 .expect("failed to spawn curl");
-                if status.success() {
-                    ok = true;
-                    break
+
+                // Retry if download failed.
+                if !status.success() {
+                    last_error = Some(status.to_string());
+                    continue;
                 }
+
+                // Ensure the hash is correct.
+                let mut shasum = if target.contains("apple") || build.build.contains("netbsd") {
+                    let mut cmd = Command::new("shasum");
+                    cmd.arg("-a").arg("256");
+                    cmd
+                } else {
+                    Command::new("sha256sum")
+                };
+                let output = output(&mut shasum.arg(&tmp));
+                let found = output.split_whitespace().next().unwrap();
+
+                // If the hash is wrong, probably the download is incomplete or S3 served an error
+                // page. In any case, retry.
+                if found != OPENSSL_SHA256 {
+                    last_error = Some(format!(
+                        "downloaded openssl sha256 different\n\
+                         expected: {}\n\
+                         found:    {}\n",
+                        OPENSSL_SHA256,
+                        found
+                    ));
+                    continue;
+                }
+
+                // Everything is fine, so exit the retry loop.
+                last_error = None;
+                break;
             }
-            if !ok {
-                panic!("failed to download openssl source")
-            }
-            let mut shasum = if target.contains("apple") || build.build.contains("netbsd") {
-                let mut cmd = Command::new("shasum");
-                cmd.arg("-a").arg("256");
-                cmd
-            } else {
-                Command::new("sha256sum")
-            };
-            let output = output(&mut shasum.arg(&tmp));
-            let found = output.split_whitespace().next().unwrap();
-            if found != OPENSSL_SHA256 {
-                panic!("downloaded openssl sha256 different\n\
-                        expected: {}\n\
-                        found:    {}\n", OPENSSL_SHA256, found);
+            if let Some(error) = last_error {
+                panic!("failed to download openssl source: {}", error);
             }
             t!(fs::rename(&tmp, &tarball));
         }

src/liballoc/lib.rs

@@ -121,6 +121,7 @@
 #![feature(unique)]
 #![feature(unsize)]
 #![feature(allocator_internals)]
+#![feature(on_unimplemented)]
 
 #![cfg_attr(not(test), feature(fused, fn_traits, placement_new_protocol, swap_with_slice, i128))]
 #![cfg_attr(test, feature(test, box_heap))]

src/liballoc/vec.rs

@@ -1543,6 +1543,7 @@ impl<T: Hash> Hash for Vec<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> Index<usize> for Vec<T> {
     type Output = T;
 
@@ -1554,6 +1555,7 @@ impl<T> Index<usize> for Vec<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> IndexMut<usize> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, index: usize) -> &mut T {
@@ -1562,8 +1564,8 @@ impl<T> IndexMut<usize> for Vec<T> {
     }
 }
 
-
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
     type Output = [T];
 
@@ -1572,7 +1574,9 @@ impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
         Index::index(&**self, index)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
     type Output = [T];
 
@@ -1581,7 +1585,9 @@ impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
         Index::index(&**self, index)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
     type Output = [T];
 
@@ -1590,7 +1596,9 @@ impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
         Index::index(&**self, index)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::Index<ops::RangeFull> for Vec<T> {
     type Output = [T];
 
@@ -1599,7 +1607,9 @@ impl<T> ops::Index<ops::RangeFull> for Vec<T> {
         self
     }
 }
+
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::Index<ops::RangeInclusive<usize>> for Vec<T> {
     type Output = [T];
 
@@ -1608,7 +1618,9 @@ impl<T> ops::Index<ops::RangeInclusive<usize>> for Vec<T> {
         Index::index(&**self, index)
     }
 }
+
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::Index<ops::RangeToInclusive<usize>> for Vec<T> {
     type Output = [T];
 
@@ -1619,41 +1631,52 @@ impl<T> ops::Index<ops::RangeToInclusive<usize>> for Vec<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::IndexMut<ops::Range<usize>> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
         IndexMut::index_mut(&mut **self, index)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::IndexMut<ops::RangeTo<usize>> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
         IndexMut::index_mut(&mut **self, index)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
         IndexMut::index_mut(&mut **self, index)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::IndexMut<ops::RangeFull> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, _index: ops::RangeFull) -> &mut [T] {
         self
     }
 }
+
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::IndexMut<ops::RangeInclusive<usize>> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut [T] {
         IndexMut::index_mut(&mut **self, index)
     }
 }
+
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+#[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
 impl<T> ops::IndexMut<ops::RangeToInclusive<usize>> for Vec<T> {
     #[inline]
     fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut [T] {

src/libcore/mem.rs

@@ -429,9 +429,11 @@ pub fn align_of_val<T: ?Sized>(val: &T) -> usize {
 
 /// Returns whether dropping values of type `T` matters.
 ///
-/// This is purely an optimization hint, and may be implemented conservatively.
-/// For instance, always returning `true` would be a valid implementation of
-/// this function.
+/// This is purely an optimization hint, and may be implemented conservatively:
+/// it may return `true` for types that don't actually need to be dropped.
+/// As such always returning `true` would be a valid implementation of
+/// this function. However if this function actually returns `false`, then you
+/// can be certain dropping `T` has no side effect.
 ///
 /// Low level implementations of things like collections, which need to manually
 /// drop their data, should use this function to avoid unnecessarily

src/librustc/middle/reachable.rs

@@ -336,6 +336,12 @@ struct CollectPrivateImplItemsVisitor<'a, 'tcx: 'a> {
 
 impl<'a, 'tcx: 'a> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx> {
     fn visit_item(&mut self, item: &hir::Item) {
+        // Anything which has custom linkage gets thrown on the worklist no
+        // matter where it is in the crate.
+        if attr::contains_name(&item.attrs, "linkage") {
+            self.worklist.push(item.id);
+        }
+
         // We need only trait impls here, not inherent impls, and only non-exported ones
         if let hir::ItemImpl(.., Some(ref trait_ref), _, ref impl_item_refs) = item.node {
             if !self.access_levels.is_reachable(item.id) {

src/librustc/mir/mod.rs

@@ -415,9 +415,11 @@ pub enum BorrowKind {
 ///////////////////////////////////////////////////////////////////////////
 // Variables and temps
 
-newtype_index!(Local, "_");
-
-pub const RETURN_POINTER: Local = Local(0);
+newtype_index!(Local
+    {
+        DEBUG_NAME = "_",
+        const RETURN_POINTER = 0,
+    });
 
 /// Classifies locals into categories. See `Mir::local_kind`.
 #[derive(PartialEq, Eq, Debug)]
@@ -551,7 +553,7 @@ pub struct UpvarDecl {
 ///////////////////////////////////////////////////////////////////////////
 // BasicBlock
 
-newtype_index!(BasicBlock, "bb");
+newtype_index!(BasicBlock { DEBUG_NAME = "bb" });
 
 ///////////////////////////////////////////////////////////////////////////
 // BasicBlockData and Terminator
@@ -1131,7 +1133,7 @@ pub type LvalueProjection<'tcx> = Projection<'tcx, Lvalue<'tcx>, Local, Ty<'tcx>
 /// and the index is a local.
 pub type LvalueElem<'tcx> = ProjectionElem<'tcx, Local, Ty<'tcx>>;
 
-newtype_index!(Field, "field");
+newtype_index!(Field { DEBUG_NAME = "field" });
 
 impl<'tcx> Lvalue<'tcx> {
     pub fn field(self, f: Field, ty: Ty<'tcx>) -> Lvalue<'tcx> {
@@ -1196,8 +1198,11 @@ impl<'tcx> Debug for Lvalue<'tcx> {
 ///////////////////////////////////////////////////////////////////////////
 // Scopes
 
-newtype_index!(VisibilityScope, "scope");
-pub const ARGUMENT_VISIBILITY_SCOPE : VisibilityScope = VisibilityScope(0);
+newtype_index!(VisibilityScope
+    {
+        DEBUG_NAME = "scope",
+        const ARGUMENT_VISIBILITY_SCOPE = 0,
+    });
 
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 pub struct VisibilityScopeData {
@@ -1522,7 +1527,7 @@ pub struct Constant<'tcx> {
     pub literal: Literal<'tcx>,
 }
 
-newtype_index!(Promoted, "promoted");
+newtype_index!(Promoted { DEBUG_NAME = "promoted" });
 
 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum Literal<'tcx> {

src/librustc_borrowck/borrowck/mod.rs

@@ -759,7 +759,21 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 
                 let mut db = match err.cause {
                     MutabilityViolation => {
-                        self.cannot_assign(error_span, &descr, Origin::Ast)
+                        let mut db = self.cannot_assign(error_span, &descr, Origin::Ast);
+                        if let mc::NoteClosureEnv(upvar_id) = err.cmt.note {
+                            let node_id = self.tcx.hir.hir_to_node_id(upvar_id.var_id);
+                            let sp = self.tcx.hir.span(node_id);
+                            match self.tcx.sess.codemap().span_to_snippet(sp) {
+                                Ok(snippet) => {
+                                    let msg = &format!("consider making `{}` mutable", snippet);
+                                    db.span_suggestion(sp, msg, format!("mut {}", snippet));
+                                }
+                                _ => {
+                                    db.span_help(sp, "consider making this binding mutable");
+                                }
+                            }
+                        }
+                        db
                     }
                     BorrowViolation(euv::ClosureCapture(_)) => {
                         struct_span_err!(self.tcx.sess, error_span, E0595,

src/librustc_data_structures/indexed_vec.rs

@@ -40,39 +40,80 @@ impl Idx for u32 {
 
 #[macro_export]
 macro_rules! newtype_index {
+    // ---- public rules ----
+
+    // Use default constants
     ($name:ident) => (
-        newtype_index!($name, unsafe { ::std::intrinsics::type_name::<$name>() });
+        newtype_index!(
+            @type[$name]
+            @max[::std::u32::MAX]
+            @debug_name[unsafe {::std::intrinsics::type_name::<$name>() }]);
+    );
+
+    // Define any constants
+    ($name:ident { $($tokens:tt)+ }) => (
+        newtype_index!(
+            @type[$name]
+            @max[::std::u32::MAX]
+            @debug_name[unsafe {::std::intrinsics::type_name::<$name>() }]
+            $($tokens)+);
     );
 
-    ($name:ident, $debug_name:expr) => (
+    // ---- private rules ----
+
+    // Base case, user-defined constants (if any) have already been defined
+    (@type[$type:ident] @max[$max:expr] @debug_name[$debug_name:expr]) => (
         #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord,
-         RustcEncodable, RustcDecodable)]
-        pub struct $name(u32);
-
-        impl $name {
-            // HACK use for constants
-            #[allow(unused)]
-            const fn const_new(x: u32) -> Self {
-                $name(x)
-            }
-        }
+            RustcEncodable, RustcDecodable)]
+        pub struct $type(u32);
 
-        impl Idx for $name {
+        impl Idx for $type {
             fn new(value: usize) -> Self {
-                assert!(value < (::std::u32::MAX) as usize);
-                $name(value as u32)
+                assert!(value < ($max) as usize);
+                $type(value as u32)
             }
             fn index(self) -> usize {
                 self.0 as usize
             }
         }
 
-        impl ::std::fmt::Debug for $name {
+        impl ::std::fmt::Debug for $type {
             fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                 write!(fmt, "{}{}", $debug_name, self.0)
             }
         }
-    )
+    );
+
+    // Rewrite final without comma to one that includes comma
+    (@type[$type:ident] @max[$max:expr] @debug_name[$debug_name:expr]
+            $name:ident = $constant:expr) => (
+        newtype_index!(@type[$type] @max[$max] @debug_name[$debug_name] $name = $constant,);
+    );
+
+    // Rewrite final const without comma to one that includes comma
+    (@type[$type:ident] @max[$_max:expr] @debug_name[$debug_name:expr]
+            const $name:ident = $constant:expr) => (
+        newtype_index!(@type[$type] @max[$max] @debug_name[$debug_name] const $name = $constant,);
+    );
+
+    // Replace existing default for max
+    (@type[$type:ident] @max[$_max:expr] @debug_name[$debug_name:expr]
+            MAX = $max:expr, $($tokens:tt)*) => (
+        newtype_index!(@type[$type] @max[$max] @debug_name[$debug_name] $(tokens)*);
+    );
+
+    // Replace existing default for debug_name
+    (@type[$type:ident] @max[$max:expr] @debug_name[$_debug_name:expr]
+            DEBUG_NAME = $debug_name:expr, $($tokens:tt)*) => (
+        newtype_index!(@type[$type] @max[$max] @debug_name[$debug_name] $($tokens)*);
+    );
+
+    // Assign a user-defined constant (as final param)
+    (@type[$type:ident] @max[$max:expr] @debug_name[$debug_name:expr]
+            const $name:ident = $constant:expr, $($tokens:tt)*) => (
+        pub const $name: $type = $type($constant);
+        newtype_index!(@type[$type] @max[$max] @debug_name[$debug_name] $($tokens)*);
+    );
 }
 
 #[derive(Clone, PartialEq, Eq)]

src/librustc_resolve/lib.rs

@@ -137,7 +137,7 @@ enum ResolutionError<'a> {
     /// error E0416: identifier is bound more than once in the same pattern
     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
     /// error E0426: use of undeclared label
-    UndeclaredLabel(&'a str),
+    UndeclaredLabel(&'a str, Option<Name>),
     /// error E0429: `self` imports are only allowed within a { } list
     SelfImportsOnlyAllowedWithin,
     /// error E0430: `self` import can only appear once in the list
@@ -263,13 +263,17 @@ fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
             err.span_label(span, "used in a pattern more than once");
             err
         }
-        ResolutionError::UndeclaredLabel(name) => {
+        ResolutionError::UndeclaredLabel(name, lev_candidate) => {
             let mut err = struct_span_err!(resolver.session,
                                            span,
                                            E0426,
                                            "use of undeclared label `{}`",
                                            name);
-            err.span_label(span, format!("undeclared label `{}`", name));
+            if let Some(lev_candidate) = lev_candidate {
+                err.span_label(span, format!("did you mean `{}`?", lev_candidate));
+            } else {
+                err.span_label(span, format!("undeclared label `{}`", name));
+            }
             err
         }
         ResolutionError::SelfImportsOnlyAllowedWithin => {
@@ -1790,9 +1794,13 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    /// Searches the current set of local scopes for labels.
+    /// Searches the current set of local scopes for labels. Returns the first non-None label that
+    /// is returned by the given predicate function
+    ///
     /// Stops after meeting a closure.
-    fn search_label(&self, mut ident: Ident) -> Option<Def> {
+    fn search_label<P, R>(&self, mut ident: Ident, pred: P) -> Option<R>
+        where P: Fn(&Rib, Ident) -> Option<R>
+    {
         for rib in self.label_ribs.iter().rev() {
             match rib.kind {
                 NormalRibKind => {}
@@ -1808,9 +1816,9 @@ impl<'a> Resolver<'a> {
                     return None;
                 }
             }
-            let result = rib.bindings.get(&ident).cloned();
-            if result.is_some() {
-                return result;
+            let r = pred(rib, ident);
+            if r.is_some() {
+                return r;
             }
         }
         None
@@ -3202,12 +3210,20 @@ impl<'a> Resolver<'a> {
             }
 
             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
-                match self.search_label(label.node) {
+                match self.search_label(label.node, |rib, id| rib.bindings.get(&id).cloned()) {
                     None => {
+                        // Search again for close matches...
+                        // Picks the first label that is "close enough", which is not necessarily
+                        // the closest match
+                        let close_match = self.search_label(label.node, |rib, ident| {
+                            let names = rib.bindings.iter().map(|(id, _)| &id.name);
+                            find_best_match_for_name(names, &*ident.name.as_str(), None)
+                        });
                         self.record_def(expr.id, err_path_resolution());
                         resolve_error(self,
                                       label.span,
-                                      ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
+                                      ResolutionError::UndeclaredLabel(&label.node.name.as_str(),
+                                                                       close_match));
                     }
                     Some(def @ Def::Label(_)) => {
                         // Since this def is a label, it is never read.

src/librustdoc/html/static/rustdoc.css

@@ -394,7 +394,7 @@ h4 > code, h3 > code, .invisible > code {
 	padding: 0;
 }
 
-.content .item-list li { margin-bottom: 3px; }
+.content .item-list li { margin-bottom: 1em; }
 
 .content .multi-column {
 	-moz-column-count: 5;
@@ -773,17 +773,19 @@ span.since {
 	}
 
 	.sidebar {
-		height: 40px;
+		height: 45px;
 		min-height: 40px;
-		width: 100%;
-		margin: 0px;
-		padding: 0px;
+		width: calc(100% + 30px);
+		margin: 0;
+		margin-left: -15px;
+		padding: 0 15px;
 		position: static;
 	}
 
 	.sidebar .location {
 		float: right;
 		margin: 0px;
+		margin-top: 2px;
 		padding: 3px 10px 1px 10px;
 		min-height: 39px;
 		background: inherit;
@@ -798,7 +800,7 @@ span.since {
 	.sidebar img {
 		width: 35px;
 		margin-top: 5px;
-		margin-bottom: 0px;
+		margin-bottom: 5px;
 		float: left;
 	}
 

src/libstd/ffi/mod.rs

@@ -9,6 +9,157 @@
 // except according to those terms.
 
 //! Utilities related to FFI bindings.
+//!
+//! This module provides utilities to handle data across non-Rust
+//! interfaces, like other programming languages and the underlying
+//! operating system. It is mainly of use for FFI (Foreign Function
+//! Interface) bindings and code that needs to exchange C-like strings
+//! with other languages.
+//!
+//! # Overview
+//!
+//! Rust represents owned strings with the [`String`] type, and
+//! borrowed slices of strings with the [`str`] primitive. Both are
+//! always in UTF-8 encoding, and may contain nul bytes in the middle,
+//! i.e. if you look at the bytes that make up the string, there may
+//! be a `\0` among them. Both `String` and `str` store their length
+//! explicitly; there are no nul terminators at the end of strings
+//! like in C.
+//!
+//! C strings are different from Rust strings:
+//!
+//! * **Encodings** - Rust strings are UTF-8, but C strings may use
+//! other encodings. If you are using a string from C, you should
+//! check its encoding explicitly, rather than just assuming that it
+//! is UTF-8 like you can do in Rust.
+//!
+//! * **Character size** - C strings may use `char` or `wchar_t`-sized
+//! characters; please **note** that C's `char` is different from Rust's.
+//! The C standard leaves the actual sizes of those types open to
+//! interpretation, but defines different APIs for strings made up of
+//! each character type. Rust strings are always UTF-8, so different
+//! Unicode characters will be encoded in a variable number of bytes
+//! each. The Rust type [`char`] represents a '[Unicode scalar
+//! value]', which is similar to, but not the same as, a '[Unicode
+//! code point]'.
+//!
+//! * **Nul terminators and implicit string lengths** - Often, C
+//! strings are nul-terminated, i.e. they have a `\0` character at the
+//! end. The length of a string buffer is not stored, but has to be
+//! calculated; to compute the length of a string, C code must
+//! manually call a function like `strlen()` for `char`-based strings,
+//! or `wcslen()` for `wchar_t`-based ones. Those functions return
+//! the number of characters in the string excluding the nul
+//! terminator, so the buffer length is really `len+1` characters.
+//! Rust strings don't have a nul terminator; their length is always
+//! stored and does not need to be calculated. While in Rust
+//! accessing a string's length is a O(1) operation (becasue the
+//! length is stored); in C it is an O(length) operation because the
+//! length needs to be computed by scanning the string for the nul
+//! terminator.
+//!
+//! * **Internal nul characters** - When C strings have a nul
+//! terminator character, this usually means that they cannot have nul
+//! characters in the middle — a nul character would essentially
+//! truncate the string. Rust strings *can* have nul characters in
+//! the middle, because nul does not have to mark the end of the
+//! string in Rust.
+//!
+//! # Representations of non-Rust strings
+//!
+//! [`CString`] and [`CStr`] are useful when you need to transfer
+//! UTF-8 strings to and from languages with a C ABI, like Python.
+//!
+//! * **From Rust to C:** [`CString`] represents an owned, C-friendly
+//! string: it is nul-terminated, and has no internal nul characters.
+//! Rust code can create a `CString` out of a normal string (provided
+//! that the string doesn't have nul characters in the middle), and
+//! then use a variety of methods to obtain a raw `*mut u8` that can
+//! then be passed as an argument to functions which use the C
+//! conventions for strings.
+//!
+//! * **From C to Rust:** [`CStr`] represents a borrowed C string; it
+//! is what you would use to wrap a raw `*const u8` that you got from
+//! a C function. A `CStr` is guaranteed to be a nul-terminated array
+//! of bytes. Once you have a `CStr`, you can convert it to a Rust
+//! `&str` if it's valid UTF-8, or lossily convert it by adding
+//! replacement characters.
+//!
+//! [`OsString`] and [`OsStr`] are useful when you need to transfer
+//! strings to and from the operating system itself, or when capturing
+//! the output of external commands. Conversions between `OsString`,
+//! `OsStr` and Rust strings work similarly to those for [`CString`]
+//! and [`CStr`].
+//!
+//! * [`OsString`] represents an owned string in whatever
+//! representation the operating system prefers. In the Rust standard
+//! library, various APIs that transfer strings to/from the operating
+//! system use `OsString` instead of plain strings. For example,
+//! [`env::var_os()`] is used to query environment variables; it
+//! returns an `Option<OsString>`. If the environment variable exists
+//! you will get a `Some(os_string)`, which you can *then* try to
+//! convert to a Rust string. This yields a [`Result<>`], so that
+//! your code can detect errors in case the environment variable did
+//! not in fact contain valid Unicode data.
+//!
+//! * [`OsStr`] represents a borrowed reference to a string in a
+//! format that can be passed to the operating system. It can be
+//! converted into an UTF-8 Rust string slice in a similar way to
+//! `OsString`.
+//!
+//! # Conversions
+//!
+//! ## On Unix
+//!
+//! On Unix, [`OsStr`] implements the
+//! `std::os::unix:ffi::`[`OsStrExt`][unix.OsStrExt] trait, which
+//! augments it with two methods, [`from_bytes`] and [`as_bytes`].
+//! These do inexpensive conversions from and to UTF-8 byte slices.
+//!
+//! Additionally, on Unix [`OsString`] implements the
+//! `std::os::unix:ffi::`[`OsStringExt`][unix.OsStringExt] trait,
+//! which provides [`from_vec`] and [`into_vec`] methods that consume
+//! their arguments, and take or produce vectors of [`u8`].
+//!
+//! ## On Windows
+//!
+//! On Windows, [`OsStr`] implements the
+//! `std::os::windows::ffi::`[`OsStrExt`][windows.OsStrExt] trait,
+//! which provides an [`encode_wide`] method. This provides an
+//! iterator that can be [`collect`]ed into a vector of [`u16`].
+//!
+//! Additionally, on Windows [`OsString`] implements the
+//! `std::os::windows:ffi::`[`OsStringExt`][windows.OsStringExt]
+//! trait, which provides a [`from_wide`] method. The result of this
+//! method is an `OsString` which can be round-tripped to a Windows
+//! string losslessly.
+//!
+//! [`String`]: ../string/struct.String.html
+//! [`str`]: ../primitive.str.html
+//! [`char`]: ../primitive.char.html
+//! [`u8`]: ../primitive.u8.html
+//! [`u16`]: ../primitive.u16.html
+//! [Unicode scalar value]: http://www.unicode.org/glossary/#unicode_scalar_value
+//! [Unicode code point]: http://www.unicode.org/glossary/#code_point
+//! [`CString`]: struct.CString.html
+//! [`CStr`]: struct.CStr.html
+//! [`OsString`]: struct.OsString.html
+//! [`OsStr`]: struct.OsStr.html
+//! [`env::set_var()`]: ../env/fn.set_var.html
+//! [`env::var_os()`]: ../env/fn.var_os.html
+//! [`Result<>`]: ../result/enum.Result.html
+//! [unix.OsStringExt]: ../os/unix/ffi/trait.OsStringExt.html
+//! [`from_vec`]: ../os/unix/ffi/trait.OsStringExt.html#tymethod.from_vec
+//! [`into_vec`]: ../os/unix/ffi/trait.OsStringExt.html#tymethod.into_vec
+//! [unix.OsStrExt]: ../os/unix/ffi/trait.OsStrExt.html
+//! [`from_bytes`]: ../os/unix/ffi/trait.OsStrExt.html#tymethod.from_bytes
+//! [`as_bytes`]: ../os/unix/ffi/trait.OsStrExt.html#tymethod.as_bytes
+//! [`OsStrExt`]: ../os/unix/ffi/trait.OsStrExt.html
+//! [windows.OsStrExt]: ../os/windows/ffi/trait.OsStrExt.html
+//! [`encode_wide`]: ../os/windows/ffi/trait.OsStrExt.html#tymethod.encode_wide
+//! [`collect`]: ../iter/trait.Iterator.html#method.collect
+//! [windows.OsStringExt]: ../os/windows/ffi/trait.OsStringExt.html
+//! [`from_wide`]: ../os/windows/ffi/trait.OsStringExt.html#tymethod.from_wide
 
 #![stable(feature = "rust1", since = "1.0.0")]
 

src/libstd/ffi/os_str.rs

@@ -32,18 +32,65 @@ use sys_common::{AsInner, IntoInner, FromInner};
 ///
 /// `OsString` and [`OsStr`] bridge this gap by simultaneously representing Rust
 /// and platform-native string values, and in particular allowing a Rust string
-/// to be converted into an "OS" string with no cost.
+/// to be converted into an "OS" string with no cost if possible.
+///
+/// `OsString` is to [`OsStr`] as [`String`] is to [`&str`]: the former
+/// in each pair are owned strings; the latter are borrowed
+/// references.
+///
+/// # Creating an `OsString`
+///
+/// **From a Rust string**: `OsString` implements
+/// [`From`]`<`[`String`]`>`, so you can use `my_string.`[`from`] to
+/// create an `OsString` from a normal Rust string.
+///
+/// **From slices:** Just like you can start with an empty Rust
+/// [`String`] and then [`push_str`][String.push_str] `&str`
+/// sub-string slices into it, you can create an empty `OsString` with
+/// the [`new`] method and then push string slices into it with the
+/// [`push`] method.
+///
+/// # Extracting a borrowed reference to the whole OS string
+///
+/// You can use the [`as_os_str`] method to get an `&`[`OsStr`] from
+/// an `OsString`; this is effectively a borrowed reference to the
+/// whole string.
+///
+/// # Conversions
+///
+/// See the [module's toplevel documentation about conversions][conversions] for a discussion on
+/// the traits which `OsString` implements for conversions from/to native representations.
 ///
 /// [`OsStr`]: struct.OsStr.html
+/// [`From`]: ../convert/trait.From.html
+/// [`from`]: ../convert/trait.From.html#tymethod.from
+/// [`String`]: ../string/struct.String.html
+/// [`&str`]: ../primitive.str.html
+/// [`u8`]: ../primitive.u8.html
+/// [`u16`]: ../primitive.u16.html
+/// [String.push_str]: ../string/struct.String.html#method.push_str
+/// [`new`]: #method.new
+/// [`push`]: #method.push
+/// [`as_os_str`]: #method.as_os_str
 #[derive(Clone)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct OsString {
     inner: Buf
 }
 
-/// Slices into OS strings (see [`OsString`]).
+/// Borrowed reference to an OS string (see [`OsString`]).
+///
+/// This type represents a borrowed reference to a string in the operating system's preferred
+/// representation.
+///
+/// `OsStr` is to [`OsString`] as [`String`] is to [`&str`]: the former in each pair are borrowed
+/// references; the latter are owned strings.
+///
+/// See the [module's toplevel documentation about conversions][conversions] for a discussion on
+/// the traits which `OsStr` implements for conversions from/to native representations.
 ///
 /// [`OsString`]: struct.OsString.html
+/// [conversions]: index.html#conversions
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct OsStr {
     inner: Slice

src/libstd/sys/windows/ext/ffi.rs

@@ -9,6 +9,62 @@
 // except according to those terms.
 
 //! Windows-specific extensions to the primitives in the `std::ffi` module.
+//!
+//! # Overview
+//!
+//! For historical reasons, the Windows API uses a form of potentially
+//! ill-formed UTF-16 encoding for strings.  Specifically, the 16-bit
+//! code units in Windows strings may contain [isolated surrogate code
+//! points which are not paired together][ill-formed-utf-16].  The
+//! Unicode standard requires that surrogate code points (those in the
+//! range U+D800 to U+DFFF) always be *paired*, because in the UTF-16
+//! encoding a *surrogate code unit pair* is used to encode a single
+//! character.  For compatibility with code that does not enforce
+//! these pairings, Windows does not enforce them, either.
+//!
+//! While it is not always possible to convert such a string losslessly into
+//! a valid UTF-16 string (or even UTF-8), it is often desirable to be
+//! able to round-trip such a string from and to Windows APIs
+//! losslessly.  For example, some Rust code may be "bridging" some
+//! Windows APIs together, just passing `WCHAR` strings among those
+//! APIs without ever really looking into the strings.
+//!
+//! If Rust code *does* need to look into those strings, it can
+//! convert them to valid UTF-8, possibly lossily, by substituting
+//! invalid sequences with U+FFFD REPLACEMENT CHARACTER, as is
+//! conventionally done in other Rust APIs that deal with string
+//! encodings.
+//!
+//! # `OsStringExt` and `OsStrExt`
+//!
+//! [`OsString`] is the Rust wrapper for owned strings in the
+//! preferred representation of the operating system.  On Windows,
+//! this struct gets augmented with an implementation of the
+//! [`OsStringExt`] trait, which has a [`from_wide`] method.  This
+//! lets you create an [`OsString`] from a `&[u16]` slice; presumably
+//! you get such a slice out of a `WCHAR` Windows API.
+//!
+//! Similarly, [`OsStr`] is the Rust wrapper for borrowed strings from
+//! preferred representation of the operating system.  On Windows, the
+//! [`OsStrExt`] trait provides the [`encode_wide`] method, which
+//! outputs an [`EncodeWide`] iterator.  You can [`collect`] this
+//! iterator, for example, to obtain a `Vec<u16>`; you can later get a
+//! pointer to this vector's contents and feed it to Windows APIs.
+//!
+//! These traits, along with [`OsString`] and [`OsStr`], work in
+//! conjunction so that it is possible to **round-trip** strings from
+//! Windows and back, with no loss of data, even if the strings are
+//! ill-formed UTF-16.
+//!
+//! [ill-formed-utf-16]: https://simonsapin.github.io/wtf-8/#ill-formed-utf-16
+//! [`OsString`]: ../../../ffi/struct.OsString.html
+//! [`OsStr`]: ../../../ffi/struct.OsStr.html
+//! [`OsStringExt`]: trait.OsStringExt.html
+//! [`OsStrExt`]: trait.OsStrExt.html
+//! [`EncodeWide`]: struct.EncodeWide.html
+//! [`from_wide`]: trait.OsStringExt.html#tymethod.from_wide
+//! [`encode_wide`]: trait.OsStrExt.html#tymethod.encode_wide
+//! [`collect`]: ../../../iter/trait.Iterator.html#method.collect
 
 #![stable(feature = "rust1", since = "1.0.0")]
 

src/libsyntax/parse/parser.rs

@@ -2314,6 +2314,7 @@ impl<'a> Parser<'a> {
 
         while self.token != token::CloseDelim(token::Brace) {
             if self.eat(&token::DotDot) {
+                let exp_span = self.prev_span;
                 match self.parse_expr() {
                     Ok(e) => {
                         base = Some(e);
@@ -2323,6 +2324,16 @@ impl<'a> Parser<'a> {
                         self.recover_stmt();
                     }
                 }
+                if self.token == token::Comma {
+                    let mut err = self.sess.span_diagnostic.mut_span_err(
+                        exp_span.to(self.prev_span),
+                        "cannot use a comma after the base struct",
+                    );
+                    err.span_suggestion_short(self.span, "remove this comma", "".to_owned());
+                    err.note("the base struct must always be the last field");
+                    err.emit();
+                    self.recover_stmt();
+                }
                 break;
             }
 
@@ -2960,6 +2971,7 @@ impl<'a> Parser<'a> {
                 {                                  //     Foo<Bar<Baz<Qux, ()>>>
                     err.help(
                         "use `::<...>` instead of `<...>` if you meant to specify type arguments");
+                    err.help("or use `(...)` if you meant to specify fn arguments");
                 }
                 err.emit();
             }

src/test/compile-fail/index-help.rs

@@ -0,0 +1,15 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    let x = vec![1];
+    x[0i32]; //~ ERROR E0277
+             //~| NOTE vector indices are of type `usize` or ranges of `usize`
+}

src/test/parse-fail/require-parens-for-chained-comparison.rs

@@ -21,5 +21,6 @@ fn main() {
 
     f<X>();
     //~^ ERROR: chained comparison operators require parentheses
-    //~^^ HELP: use `::<...>` instead of `<...>`
+    //~| HELP: use `::<...>` instead of `<...>`
+    //~| HELP: or use `(...)`
 }

src/test/run-pass/thin-lto-global-allocator.rs

@@ -0,0 +1,19 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -Z thinlto -C codegen-units=2
+// min-llvm-version 4.0
+
+#![feature(allocator_api, global_allocator)]
+
+#[global_allocator]
+static A: std::heap::System = std::heap::System;
+
+fn main() {}

src/test/ui/did_you_mean/issue-40396.stderr

@@ -5,6 +5,7 @@ error: chained comparison operators require parentheses
    |                                     ^^^^^^^^
    |
    = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
+   = help: or use `(...)` if you meant to specify fn arguments
 
 error: chained comparison operators require parentheses
   --> $DIR/issue-40396.rs:16:25
@@ -13,6 +14,7 @@ error: chained comparison operators require parentheses
    |                         ^^^^^^^
    |
    = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
+   = help: or use `(...)` if you meant to specify fn arguments
 
 error: chained comparison operators require parentheses
   --> $DIR/issue-40396.rs:20:37
@@ -21,6 +23,7 @@ error: chained comparison operators require parentheses
    |                                     ^^^^^^^^
    |
    = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
+   = help: or use `(...)` if you meant to specify fn arguments
 
 error: chained comparison operators require parentheses
   --> $DIR/issue-40396.rs:20:41
@@ -29,6 +32,7 @@ error: chained comparison operators require parentheses
    |                                         ^^^^^^
    |
    = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
+   = help: or use `(...)` if you meant to specify fn arguments
 
 error: aborting due to 4 previous errors
 

src/test/ui/struct-field-init-syntax.rs

@@ -0,0 +1,27 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -Z parse-only
+
+// issue #41834
+
+fn main() {
+    let foo = Foo {
+        one: 111,
+        ..Foo::default(),
+        //~^ ERROR cannot use a comma after struct expansion
+    };
+
+    let foo = Foo {
+        ..Foo::default(),
+        //~^ ERROR cannot use a comma after struct expansion
+        one: 111,
+    };
+}

src/test/ui/struct-field-init-syntax.stderr

@@ -0,0 +1,18 @@
+error: cannot use a comma after the base struct
+  --> $DIR/struct-field-init-syntax.rs:18:9
+   |
+18 |         ..Foo::default(),
+   |         ^^^^^^^^^^^^^^^^- help: remove this comma
+   |
+   = note: the base struct must always be the last field
+
+error: cannot use a comma after the base struct
+  --> $DIR/struct-field-init-syntax.rs:23:9
+   |
+23 |         ..Foo::default(),
+   |         ^^^^^^^^^^^^^^^^- help: remove this comma
+   |
+   = note: the base struct must always be the last field
+
+error: aborting due to 2 previous errors
+

src/test/ui/suggestions/closure-immutable-outer-variable.rs

@@ -0,0 +1,20 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Point at the captured immutable outer variable
+
+fn foo(mut f: Box<FnMut()>) {
+    f();
+}
+
+fn main() {
+    let y = true;
+    foo(Box::new(move || y = false) as Box<_>);
+}

src/test/ui/suggestions/closure-immutable-outer-variable.stderr

@@ -0,0 +1,10 @@
+error[E0594]: cannot assign to captured outer variable in an `FnMut` closure
+  --> $DIR/closure-immutable-outer-variable.rs:19:26
+   |
+18 |     let y = true;
+   |         - help: consider making `y` mutable: `mut y`
+19 |     foo(Box::new(move || y = false) as Box<_>);
+   |                          ^^^^^^^^^
+
+error: aborting due to previous error
+

src/test/ui/suggestions/suggest-labels.rs

@@ -0,0 +1,26 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+fn main() {
+    'foo: loop {
+        break 'fo;
+    }
+
+    'bar: loop {
+        continue 'bor;
+    }
+
+    'longlabel: loop {
+        'longlabel1: loop {
+            break 'longlable;
+        }
+    }
+}

src/test/ui/suggestions/suggest-labels.stderr

@@ -0,0 +1,20 @@
+error[E0426]: use of undeclared label `'fo`
+  --> $DIR/suggest-labels.rs:14:15
+   |
+14 |         break 'fo;
+   |               ^^^ did you mean `'foo`?
+
+error[E0426]: use of undeclared label `'bor`
+  --> $DIR/suggest-labels.rs:18:18
+   |
+18 |         continue 'bor;
+   |                  ^^^^ did you mean `'bar`?
+
+error[E0426]: use of undeclared label `'longlable`
+  --> $DIR/suggest-labels.rs:23:19
+   |
+23 |             break 'longlable;
+   |                   ^^^^^^^^^^ did you mean `'longlabel1`?
+
+error: aborting due to 3 previous errors
+