---

yaml
---
r: 212956
b: refs/heads/master
c: 1d33318
h: refs/heads/master
v: v3

Author: bors

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: cabd0682e9aa406cca2541c3c5d420d100487b04
+refs/heads/master: 1d33318018466a97dec2d61195e38952ca30d597
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: ba0e1cd8147d452c356aacb29fb87568ca26f111
 refs/heads/try: 1864973ae17213c5a58c4dd3f9af6d1b6c7d2e05

trunk/src/doc/reference.md

@@ -638,7 +638,7 @@ apply to the crate as a whole.
 ```
 
 A crate that contains a `main` function can be compiled to an executable. If a
-`main` function is present, its return type must be [`unit`](#primitive-types)
+`main` function is present, its return type must be [`unit`](#tuple-types)
 and it must take no arguments.
 
 # Items and attributes
@@ -928,21 +928,20 @@ A _generic function_ allows one or more _parameterized types_ to appear in its
 signature. Each type parameter must be explicitly declared, in an
 angle-bracket-enclosed, comma-separated list following the function name.
 
-```{.ignore}
-fn iter<T, F>(seq: &[T], f: F) where T: Copy, F: Fn(T) {
-    for elt in seq { f(*elt); }
-}
-fn map<T, U, F>(seq: &[T], f: F) -> Vec<U> where T: Copy, U: Copy, F: Fn(T) -> U {
-    let mut acc = vec![];
-    for elt in seq { acc.push(f(*elt)); }
-    acc
-}
+```rust,ignore
+// foo is generic over A and B
+
+fn foo<A, B>(x: A, y: B) {
 ```
 
 Inside the function signature and body, the name of the type parameter can be
 used as a type name. [Trait](#traits) bounds can be specified for type parameters
 to allow methods with that trait to be called on values of that type. This is
-specified using the `where` syntax, as in the above example.
+specified using the `where` syntax:
+
+```rust,ignore
+fn foo<T>(x: T) where T: Debug {
+```
 
 When a generic function is referenced, its type is instantiated based on the
 context of the reference. For example, calling the `iter` function defined
@@ -2874,7 +2873,7 @@ The `+`, `-`, `*`, `/`, `%`, `&`, `|`, `^`, `<<`, and `>>` operators may be
 composed with the `=` operator. The expression `lval OP= val` is equivalent to
 `lval = lval OP val`. For example, `x = x + 1` may be written as `x += 1`.
 
-Any such expression always has the [`unit`](#primitive-types) type.
+Any such expression always has the [`unit`](#tuple-types) type.
 
 #### Operator precedence
 
@@ -3316,6 +3315,9 @@ assert!(b != "world");
 assert!(p.0 == 10);
 ```
 
+For historical reasons and convenience, the tuple type with no elements (`()`)
+is often called ‘unit’ or ‘the unit type’.
+
 ### Array, and Slice types
 
 Rust has two different types for a list of items:

trunk/src/doc/trpl/closures.md

@@ -120,7 +120,7 @@ let y = &mut num;
 ```
 
 If your closure requires it, however, Rust will take ownership and move
-the environment instead:
+the environment instead. This doesn’t work:
 
 ```rust,ignore
 let nums = vec![1, 2, 3];
@@ -130,7 +130,7 @@ let takes_nums = || nums;
 println!("{:?}", nums);
 ```
 
-This gives us:
+We get this error:
 
 ```text
 note: `nums` moved into closure environment here because it has type

trunk/src/doc/trpl/traits.md

@@ -332,7 +332,7 @@ fn normal<T: ConvertTo<i64>>(x: &T) -> i64 {
 fn inverse<T>() -> T
         // this is using ConvertTo as if it were "ConvertFrom<i32>"
         where i32: ConvertTo<T> {
-    1i32.convert()
+    42.convert()
 }
 ```
 

trunk/src/libcollections/vec.rs

@@ -1469,42 +1469,26 @@ impl<T> ops::DerefMut for Vec<T> {
 impl<T> FromIterator<T> for Vec<T> {
     #[inline]
     fn from_iter<I: IntoIterator<Item=T>>(iterable: I) -> Vec<T> {
+        // Unroll the first iteration, as the vector is going to be
+        // expanded on this iteration in every case when the iterable is not
+        // empty, but the loop in extend_desugared() is not going to see the
+        // vector being full in the few subsequent loop iterations.
+        // So we get better branch prediction and the possibility to
+        // construct the vector with initial estimated capacity.
         let mut iterator = iterable.into_iter();
-        let (lower, _) = iterator.size_hint();
-        let mut vector = Vec::with_capacity(lower);
-
-        // This function should be the moral equivalent of:
-        //
-        //      for item in iterator {
-        //          vector.push(item);
-        //      }
-        //
-        // This equivalent crucially runs the iterator precisely once. Below we
-        // actually in theory run the iterator twice (one without bounds checks
-        // and one with). To achieve the "moral equivalent", we use the `if`
-        // statement below to break out early.
-        //
-        // If the first loop has terminated, then we have one of two conditions.
-        //
-        // 1. The underlying iterator returned `None`. In this case we are
-        //    guaranteed that less than `vector.capacity()` elements have been
-        //    returned, so we break out early.
-        // 2. The underlying iterator yielded `vector.capacity()` elements and
-        //    has not yielded `None` yet. In this case we run the iterator to
-        //    its end below.
-        for element in iterator.by_ref().take(vector.capacity()) {
-            let len = vector.len();
-            unsafe {
-                ptr::write(vector.get_unchecked_mut(len), element);
-                vector.set_len(len + 1);
-            }
-        }
-
-        if vector.len() == vector.capacity() {
-            for element in iterator {
-                vector.push(element);
+        let mut vector = match iterator.next() {
+            None => return Vec::new(),
+            Some(element) => {
+                let (lower, _) = iterator.size_hint();
+                let mut vector = Vec::with_capacity(1 + lower);
+                unsafe {
+                    ptr::write(vector.get_unchecked_mut(0), element);
+                    vector.set_len(1);
+                }
+                vector
             }
-        }
+        };
+        vector.extend_desugared(iterator);
         vector
     }
 }
@@ -1569,11 +1553,27 @@ impl<'a, T> IntoIterator for &'a mut Vec<T> {
 impl<T> Extend<T> for Vec<T> {
     #[inline]
     fn extend<I: IntoIterator<Item=T>>(&mut self, iterable: I) {
-        let iterator = iterable.into_iter();
-        let (lower, _) = iterator.size_hint();
-        self.reserve(lower);
-        for element in iterator {
-            self.push(element)
+        self.extend_desugared(iterable.into_iter())
+    }
+}
+
+impl<T> Vec<T> {
+    fn extend_desugared<I: Iterator<Item=T>>(&mut self, mut iterator: I) {
+        // This function should be the moral equivalent of:
+        //
+        //      for item in iterator {
+        //          self.push(item);
+        //      }
+        while let Some(element) = iterator.next() {
+            let len = self.len();
+            if len == self.capacity() {
+                let (lower, _) = iterator.size_hint();
+                self.reserve(lower + 1);
+            }
+            unsafe {
+                ptr::write(self.get_unchecked_mut(len), element);
+                self.set_len(len + 1);
+            }
         }
     }
 }

trunk/src/libcore/char.rs

@@ -74,17 +74,8 @@ pub const MAX: char = '\u{10ffff}';
 /// ```
 /// use std::char;
 ///
-/// let c = char::from_u32(10084); // produces `Some(❤)`
-/// assert_eq!(c, Some('❤'));
-/// ```
-///
-/// An invalid character:
-///
-/// ```
-/// use std::char;
-///
-/// let none = char::from_u32(1114112);
-/// assert_eq!(none, None);
+/// assert_eq!(char::from_u32(0x2764), Some('❤'));
+/// assert_eq!(char::from_u32(0x110000), None); // invalid character
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]

trunk/src/librustc/middle/check_const.rs

@@ -285,7 +285,7 @@ impl<'a, 'tcx> CheckCrateVisitor<'a, 'tcx> {
     fn check_static_type(&self, e: &ast::Expr) {
         let ty = ty::node_id_to_type(self.tcx, e.id);
         let infcx = infer::new_infer_ctxt(self.tcx);
-        let mut fulfill_cx = traits::FulfillmentContext::new();
+        let mut fulfill_cx = traits::FulfillmentContext::new(false);
         let cause = traits::ObligationCause::new(e.span, e.id, traits::SharedStatic);
         fulfill_cx.register_builtin_bound(&infcx, ty, ty::BoundSync, cause);
         let env = ty::empty_parameter_environment(self.tcx);

trunk/src/librustc/middle/dead.rs

@@ -48,6 +48,7 @@ struct MarkSymbolVisitor<'a, 'tcx: 'a> {
     struct_has_extern_repr: bool,
     ignore_non_const_paths: bool,
     inherited_pub_visibility: bool,
+    ignore_variant_stack: Vec<ast::NodeId>,
 }
 
 impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
@@ -60,6 +61,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
             struct_has_extern_repr: false,
             ignore_non_const_paths: false,
             inherited_pub_visibility: false,
+            ignore_variant_stack: vec![],
         }
     }
 
@@ -80,7 +82,9 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
                 def::DefPrimTy(_) => (),
                 def::DefVariant(enum_id, variant_id, _) => {
                     self.check_def_id(enum_id);
-                    self.check_def_id(variant_id);
+                    if !self.ignore_variant_stack.contains(&variant_id.node) {
+                        self.check_def_id(variant_id);
+                    }
                 }
                 _ => {
                     self.check_def_id(def.def_id());
@@ -272,6 +276,23 @@ impl<'a, 'tcx, 'v> Visitor<'v> for MarkSymbolVisitor<'a, 'tcx> {
         visit::walk_expr(self, expr);
     }
 
+    fn visit_arm(&mut self, arm: &ast::Arm) {
+        if arm.pats.len() == 1 {
+            let pat = &*arm.pats[0];
+            let variants = pat_util::necessary_variants(&self.tcx.def_map, pat);
+
+            // Inside the body, ignore constructions of variants
+            // necessary for the pattern to match. Those construction sites
+            // can't be reached unless the variant is constructed elsewhere.
+            let len = self.ignore_variant_stack.len();
+            self.ignore_variant_stack.push_all(&*variants);
+            visit::walk_arm(self, arm);
+            self.ignore_variant_stack.truncate(len);
+        } else {
+            visit::walk_arm(self, arm);
+        }
+    }
+
     fn visit_pat(&mut self, pat: &ast::Pat) {
         let def_map = &self.tcx.def_map;
         match pat.node {
@@ -393,6 +414,11 @@ fn create_and_seed_worklist(tcx: &ty::ctxt,
         worklist.push(*id);
     }
     for id in reachable_symbols {
+        // Reachable variants can be dead, because we warn about
+        // variants never constructed, not variants never used.
+        if let Some(ast_map::NodeVariant(..)) = tcx.map.find(*id) {
+            continue;
+        }
         worklist.push(*id);
     }
 

trunk/src/librustc/middle/pat_util.rs

@@ -201,3 +201,27 @@ pub fn def_to_path(tcx: &ty::ctxt, id: ast::DefId) -> ast::Path {
         span: DUMMY_SP,
     })
 }
+
+/// Return variants that are necessary to exist for the pattern to match.
+pub fn necessary_variants(dm: &DefMap, pat: &ast::Pat) -> Vec<ast::NodeId> {
+    let mut variants = vec![];
+    walk_pat(pat, |p| {
+        match p.node {
+            ast::PatEnum(_, _) |
+            ast::PatIdent(_, _, None) |
+            ast::PatStruct(..) => {
+                match dm.borrow().get(&p.id) {
+                    Some(&PathResolution { base_def: DefVariant(_, id, _), .. }) => {
+                        variants.push(id.node);
+                    }
+                    _ => ()
+                }
+            }
+            _ => ()
+        }
+        true
+    });
+    variants.sort();
+    variants.dedup();
+    variants
+}