---

yaml
---
r: 214871
b: refs/heads/beta
c: a0f028d
h: refs/heads/master
i:
  214869: 09d3f9f
  214867: 9361b34
  214863: 264191b
v: v3

Author: bors

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: 103e79d26a60ef87df304799e8032c6b54698973
+refs/heads/beta: a0f028da07d313ad554623d5700dcbd16f3a4bde
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: 8c0aa6d64ebab528f7eb182812007155d6044972
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/src/doc/style/features/functions-and-methods/README.md

@@ -20,6 +20,7 @@ for any operation that is clearly associated with a particular
 type.
 
 Methods have numerous advantages over functions:
+
 * They do not need to be imported or qualified to be used: all you
   need is a value of the appropriate type.
 * Their invocation performs autoborrowing (including mutable borrows).

branches/beta/src/doc/style/features/functions-and-methods/input.md

@@ -159,7 +159,7 @@ fn foo(a: u8) { ... }
 Note that
 [`ascii::Ascii`](http://static.rust-lang.org/doc/master/std/ascii/struct.Ascii.html)
 is a _wrapper_ around `u8` that guarantees the highest bit is zero; see
-[newtype patterns]() for more details on creating typesafe wrappers.
+[newtype patterns](../types/newtype.md) for more details on creating typesafe wrappers.
 
 Static enforcement usually comes at little run-time cost: it pushes the
 costs to the boundaries (e.g. when a `u8` is first converted into an

branches/beta/src/doc/style/features/let.md

@@ -34,7 +34,7 @@ Prefer
 
 ```rust
 let foo = match bar {
-    Baz  => 0,
+    Baz => 0,
     Quux => 1
 };
 ```
@@ -44,7 +44,7 @@ over
 ```rust
 let foo;
 match bar {
-    Baz  => {
+    Baz => {
         foo = 0;
     }
     Quux => {
@@ -61,8 +61,8 @@ conditional expression.
 Prefer
 
 ```rust
-s.iter().map(|x| x * 2)
-        .collect::<Vec<_>>()
+let v = s.iter().map(|x| x * 2)
+                .collect::<Vec<_>>();
 ```
 
 over

branches/beta/src/doc/style/ownership/builders.md

@@ -16,7 +16,7 @@ If `T` is such a data structure, consider introducing a `T` _builder_:
    value. When possible, choose a better name: e.g. `Command` is the builder for
    `Process`.
 2. The builder constructor should take as parameters only the data _required_ to
-   to make a `T`.
+   make a `T`.
 3. The builder should offer a suite of convenient methods for configuration,
    including setting up compound inputs (like slices) incrementally.
    These methods should return `self` to allow chaining.

branches/beta/src/doc/trpl/README.md

@@ -15,7 +15,7 @@ language would.
 
 [rust]: http://rust-lang.org
 
-“The Rust Programming Language” is split into seven sections. This introduction
+“The Rust Programming Language” is split into eight sections. This introduction
 is the first. After this:
 
 * [Getting started][gs] - Set up your computer for Rust development.

branches/beta/src/doc/trpl/glossary.md

@@ -19,7 +19,7 @@ In the example above `x` and `y` have arity 2. `z` has arity 3.
 
 When a compiler is compiling your program, it does a number of different
 things. One of the things that it does is turn the text of your program into an
-‘abstract syntax tree’, or‘AST’. This tree is a representation of the
+‘abstract syntax tree’, or ‘AST’. This tree is a representation of the
 structure of your program. For example, `2 + 3` can be turned into a tree:
 
 ```text

branches/beta/src/doc/trpl/lifetimes.md

@@ -134,8 +134,29 @@ x: &'a i32,
 # }
 ```
 
-uses it. So why do we need a lifetime here? We need to ensure that any
-reference to the contained `i32` does not outlive the containing `Foo`.
+uses it. So why do we need a lifetime here? We need to ensure that any reference
+to a `Foo` cannot outlive the reference to an `i32` it contains.
+
+If you have multiple references, you can use the same lifetime multiple times:
+
+```rust
+fn x_or_y<'a>(x: &'a str, y: &'a str) -> &'a str {
+#    x
+# }
+```
+
+This says that `x` and `y` both are alive for the same scope, and that the
+return value is also alive for that scope. If you wanted `x` and `y` to have
+different lifetimes, you can use multiple lifetime parameters:
+
+```rust
+fn x_or_y<'a, 'b>(x: &'a str, y: &'b str) -> &'a str {
+#    x
+# }
+```
+
+In this example, `x` and `y` have different valid scopes, but the return value
+has the same lifetime as `x`.
 
 ## Thinking in scopes
 

branches/beta/src/doc/trpl/method-syntax.md

@@ -4,7 +4,7 @@ Functions are great, but if you want to call a bunch of them on some data, it
 can be awkward. Consider this code:
 
 ```rust,ignore
-baz(bar(foo)));
+baz(bar(foo));
 ```
 
 We would read this left-to right, and so we see ‘baz bar foo’. But this isn’t the

branches/beta/src/doc/trpl/traits.md

@@ -285,7 +285,7 @@ fn bar<T, K>(x: T, y: K) where T: Clone, K: Clone + Debug {
 
 fn main() {
     foo("Hello", "world");
-    bar("Hello", "workd");
+    bar("Hello", "world");
 }
 ```
 

branches/beta/src/libcollectionstest/lib.rs

@@ -14,6 +14,7 @@
 #![feature(collections)]
 #![feature(collections_drain)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(hash)]
 #![feature(rand)]
 #![feature(rustc_private)]

branches/beta/src/libcore/mem.rs

@@ -52,20 +52,61 @@ pub use intrinsics::transmute;
 /// * `mpsc::{Sender, Receiver}` cycles (they use `Arc` internally)
 /// * Panicking destructors are likely to leak local resources
 ///
+/// # When To Use
+///
+/// There's only a few reasons to use this function. They mainly come
+/// up in unsafe code or FFI code.
+///
+/// * You have an uninitialized value, perhaps for performance reasons, and
+///   need to prevent the destructor from running on it.
+/// * You have two copies of a value (like `std::mem::swap`), but need the
+///   destructor to only run once to prevent a double free.
+/// * Transferring resources across FFI boundries.
+///
 /// # Example
 ///
-/// ```rust,no_run
+/// Leak some heap memory by never deallocating it.
+///
+/// ```rust
 /// use std::mem;
-/// use std::fs::File;
 ///
-/// // Leak some heap memory by never deallocating it
 /// let heap_memory = Box::new(3);
 /// mem::forget(heap_memory);
+/// ```
+///
+/// Leak an I/O object, never closing the file.
+///
+/// ```rust,no_run
+/// use std::mem;
+/// use std::fs::File;
 ///
-/// // Leak an I/O object, never closing the file
 /// let file = File::open("foo.txt").unwrap();
 /// mem::forget(file);
 /// ```
+///
+/// The swap function uses forget to good effect.
+///
+/// ```rust
+/// use std::mem;
+/// use std::ptr;
+///
+/// fn swap<T>(x: &mut T, y: &mut T) {
+///     unsafe {
+///         // Give ourselves some scratch space to work with
+///         let mut t: T = mem::uninitialized();
+///
+///         // Perform the swap, `&mut` pointers never alias
+///         ptr::copy_nonoverlapping(&*x, &mut t, 1);
+///         ptr::copy_nonoverlapping(&*y, x, 1);
+///         ptr::copy_nonoverlapping(&t, y, 1);
+///
+///         // y and t now point to the same thing, but we need to completely
+///         // forget `t` because we do not want to run the destructor for `T`
+///         // on its value, which is still owned somewhere outside this function.
+///         mem::forget(t);
+///     }
+/// }
+/// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn forget<T>(t: T) {
     unsafe { intrinsics::forget(t) }
@@ -267,8 +308,9 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
         ptr::copy_nonoverlapping(&*y, x, 1);
         ptr::copy_nonoverlapping(&t, y, 1);
 
-        // y and t now point to the same thing, but we need to completely forget `t`
-        // because it's no longer relevant.
+        // y and t now point to the same thing, but we need to completely
+        // forget `t` because we do not want to run the destructor for `T`
+        // on its value, which is still owned somewhere outside this function.
         forget(t);
     }
 }

branches/beta/src/libcoretest/lib.rs

@@ -14,6 +14,7 @@
 #![feature(box_syntax)]
 #![feature(unboxed_closures)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(test)]
 #![feature(rand)]
 #![feature(unicode)]

branches/beta/src/liblog/lib.rs

@@ -173,6 +173,7 @@
 #![feature(staged_api)]
 #![feature(box_syntax)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(std_misc)]
 
 use std::boxed;

branches/beta/src/librustc/diagnostics.rs

@@ -196,9 +196,13 @@ const Y: i32 = A;
 "##,
 
 E0015: r##"
-The only function calls allowed in static or constant expressions are enum
-variant constructors or struct constructors (for unit or tuple structs). This
-is because Rust currently does not support compile-time function execution.
+The only functions that can be called in static or constant expressions are
+`const` functions. Rust currently does not support more general compile-time
+function execution.
+
+See [RFC 911] for more details on the design of `const fn`s.
+
+[RFC 911]: https://github.com/rust-lang/rfcs/blob/master/text/0911-const-fn.md
 "##,
 
 E0018: r##"
@@ -842,6 +846,53 @@ struct Foo<T: 'static> {
     foo: &'static T
 }
 ```
+"##,
+
+E0378: r##"
+Method calls that aren't calls to inherent `const` methods are disallowed
+in statics, constants, and constant functions.
+
+For example:
+
+```
+const BAZ: i32 = Foo(25).bar(); // error, `bar` isn't `const`
+
+struct Foo(i32);
+
+impl Foo {
+    const fn foo(&self) -> i32 {
+        self.bar() // error, `bar` isn't `const`
+    }
+
+    fn bar(&self) -> i32 { self.0 }
+}
+```
+
+For more information about `const fn`'s, see [RFC 911].
+
+[RFC 911]: https://github.com/rust-lang/rfcs/blob/master/text/0911-const-fn.md
+"##,
+
+E0394: r##"
+From [RFC 246]:
+
+ > It is illegal for a static to reference another static by value. It is
+ > required that all references be borrowed.
+
+[RFC 246]: https://github.com/rust-lang/rfcs/pull/246
+"##,
+
+E0397: r##"
+It is not allowed for a mutable static to allocate or have destructors. For
+example:
+
+```
+// error: mutable statics are not allowed to have boxes
+static mut FOO: Option<Box<usize>> = None;
+
+// error: mutable statics are not allowed to have destructors
+static mut BAR: Option<Vec<i32>> = None;
+```
 "##
 
 }
@@ -891,9 +942,6 @@ register_diagnostics! {
     E0315, // cannot invoke closure outside of its lifetime
     E0316, // nested quantification of lifetimes
     E0370, // discriminant overflow
-    E0378, // method calls limited to constant inherent methods
-    E0394, // cannot refer to other statics by value, use the address-of
-           // operator or a constant instead
     E0395, // pointer comparison in const-expr
     E0396  // pointer dereference in const-expr
 }

branches/beta/src/librustc/lib.rs

@@ -29,6 +29,7 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
+#![feature(const_fn)]
 #![feature(core)]
 #![feature(duration)]
 #![feature(duration_span)]

branches/beta/src/librustc/middle/check_const.rs

@@ -199,8 +199,32 @@ impl<'a, 'tcx> CheckCrateVisitor<'a, 'tcx> {
     }
 
     /// Returns true if the call is to a const fn or method.
-    fn handle_const_fn_call(&mut self, def_id: ast::DefId, ret_ty: Ty<'tcx>) -> bool {
+    fn handle_const_fn_call(&mut self,
+                            expr: &ast::Expr,
+                            def_id: ast::DefId,
+                            ret_ty: Ty<'tcx>)
+                            -> bool {
         if let Some(fn_like) = const_eval::lookup_const_fn_by_id(self.tcx, def_id) {
+            if
+                // we are in a static/const initializer
+                self.mode != Mode::Var &&
+
+                // feature-gate is not enabled
+                !self.tcx.sess.features.borrow().const_fn &&
+
+                // this doesn't come from a macro that has #[allow_internal_unstable]
+                !self.tcx.sess.codemap().span_allows_unstable(expr.span)
+            {
+                self.tcx.sess.span_err(
+                    expr.span,
+                    &format!("const fns are an unstable feature"));
+                fileline_help!(
+                    self.tcx.sess,
+                    expr.span,
+                    "in Nightly builds, add `#![feature(const_fn)]` to the crate \
+                     attributes to enable");
+            }
+
             let qualif = self.fn_like(fn_like.kind(),
                                       fn_like.decl(),
                                       fn_like.body(),
@@ -249,13 +273,13 @@ impl<'a, 'tcx> CheckCrateVisitor<'a, 'tcx> {
         let suffix = if tcontents.has_dtor() {
             "destructors"
         } else if tcontents.owns_owned() {
-            "owned pointers"
+            "boxes"
         } else {
             return
         };
 
-        self.tcx.sess.span_err(e.span, &format!("mutable statics are not allowed \
-                                                 to have {}", suffix));
+        span_err!(self.tcx.sess, e.span, E0397,
+                 "mutable statics are not allowed to have {}", suffix);
     }
 
     fn check_static_type(&self, e: &ast::Expr) {
@@ -657,7 +681,7 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>,
                 }
                 Some(def::DefMethod(did, def::FromImpl(_))) |
                 Some(def::DefFn(did, _)) => {
-                    v.handle_const_fn_call(did, node_ty)
+                    v.handle_const_fn_call(e, did, node_ty)
                 }
                 _ => false
             };
@@ -677,7 +701,7 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>,
                 _ => None
             };
             let is_const = match method_did {
-                Some(did) => v.handle_const_fn_call(did, node_ty),
+                Some(did) => v.handle_const_fn_call(e, did, node_ty),
                 None => false
             };
             if !is_const {

branches/beta/src/librustc_trans/lib.rs

@@ -30,6 +30,7 @@
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(libc)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]