---

yaml
---
r: 218189
b: refs/heads/tmp
c: b6c7dff
h: refs/heads/master
i:
  218187: 0897cac
v: v3

Author: steveklabnik

[refs]

@@ -25,7 +25,7 @@ refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
 refs/heads/beta: 18adf6230e2e229d4d73391cebff060afc5e5aaa
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
-refs/heads/tmp: 4b19be36319d6a0398b36a1d529d3defe30e31a2
+refs/heads/tmp: b6c7dff72864f91e5256f7d50b6d0a3f03ee3733
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f
 refs/tags/homu-tmp: e6596d0052e79e6393bbee3538bb122930d89887
 refs/tags/1.0.0-beta: 8cbb92b53468ee2b0c2d3eeb8567005953d40828

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

@@ -101,6 +101,8 @@ the lifetime `'a` has snuck in between the `&` and the `mut i32`. We read `&mut
 i32` as ‘a mutable reference to an i32’ and `&'a mut i32` as ‘a mutable
 reference to an `i32` with the lifetime `'a`’.
 
+# In `struct`s
+
 You’ll also need explicit lifetimes when working with [`struct`][structs]s:
 
 ```rust
@@ -137,6 +139,33 @@ x: &'a i32,
 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.
 
+## `impl` blocks
+
+Let’s implement a method on `Foo`:
+
+```rust
+struct Foo<'a> {
+    x: &'a i32,
+}
+
+impl<'a> Foo<'a> {
+    fn x(&self) -> &'a i32 { self.x }
+}
+
+fn main() {
+    let y = &5; // this is the same as `let _y = 5; let y = &_y;`
+    let f = Foo { x: y };
+
+    println!("x is: {}", f.x());
+}
+```
+
+As you can see, we need to declare a lifetime for `Foo` in the `impl` line. We repeat
+`'a` twice, just like on functions: `impl<'a>` defines a lifetime `'a`, and `Foo<'a>`
+uses it.
+
+## Multiple lifetimes
+
 If you have multiple references, you can use the same lifetime multiple times:
 
 ```rust

branches/tmp/src/doc/trpl/unsafe.md

@@ -8,7 +8,7 @@ this, Rust has a keyword, `unsafe`. Code using `unsafe` has less restrictions
 than normal code does.
 
 Let’s go over the syntax, and then we’ll talk semantics. `unsafe` is used in
-two contexts. The first one is to mark a function as unsafe:
+four contexts. The first one is to mark a function as unsafe:
 
 ```rust
 unsafe fn danger_will_robinson() {
@@ -27,15 +27,40 @@ unsafe {
 }
 ```
 
+The third is for unsafe traits:
+
+```rust
+unsafe trait Scary { }
+```
+
+And the fourth is for `impl`ementing one of those traits:
+
+```rust
+# unsafe trait Scary { }
+unsafe impl Scary for i32 {}
+```
+
 It’s important to be able to explicitly delineate code that may have bugs that
 cause big problems. If a Rust program segfaults, you can be sure it’s somewhere
 in the sections marked `unsafe`.
 
 # What does ‘safe’ mean?
 
-Safe, in the context of Rust, means “doesn’t do anything unsafe.” Easy!
+Safe, in the context of Rust, means ‘doesn’t do anything unsafe’. It’s also
+important to know that there are certain behaviors that are probably not
+desirable in your code, but are expressly _not_ unsafe:
 
-Okay, let’s try again: what is not safe to do? Here’s a list:
+* Deadlocks
+* Leaks of memory or other resources
+* Exiting without calling destructors
+* Integer overflow
+
+Rust cannot prevent all kinds of software problems. Buggy code can and will be
+written in Rust. These things aren’t great, but they don’t qualify as `unsafe`
+specifically.
+
+In addition, the following are all undefined behaviors in Rust, and must be
+avoided, even when writing `unsafe` code:
 
 * Data races
 * Dereferencing a null/dangling raw pointer
@@ -64,18 +89,6 @@ Okay, let’s try again: what is not safe to do? Here’s a list:
 [undef]: http://llvm.org/docs/LangRef.html#undefined-values
 [aliasing]: http://llvm.org/docs/LangRef.html#pointer-aliasing-rules
 
-Whew! That’s a bunch of stuff. It’s also important to notice all kinds of
-behaviors that are certainly bad, but are expressly _not_ unsafe:
-
-* Deadlocks
-* Leaks of memory or other resources
-* Exiting without calling destructors
-* Integer overflow
-
-Rust cannot prevent all kinds of software problems. Buggy code can and will be
-written in Rust. These things aren’t great, but they don’t qualify as `unsafe`
-specifically.
-
 # Unsafe Superpowers
 
 In both unsafe functions and unsafe blocks, Rust will let you do three things

branches/tmp/src/librustc_driver/driver.rs

@@ -547,7 +547,7 @@ pub fn phase_2_configure_and_expand(sess: &Session,
                                                   sess.diagnostic()));
 
     krate = time(time_passes, "prelude injection", krate, |krate|
-                 syntax::std_inject::maybe_inject_prelude(krate));
+                 syntax::std_inject::maybe_inject_prelude(&sess.parse_sess, krate));
 
     time(time_passes, "checking that all macro invocations are gone", &krate, |krate|
          syntax::ext::expand::check_for_macros(&sess.parse_sess, krate));

branches/tmp/src/librustc_typeck/diagnostics.rs

@@ -1368,6 +1368,62 @@ struct Foo {
 ```
 "##,
 
+E0128: r##"
+Type parameter defaults can only use parameters that occur before them.
+Erroneous code example:
+
+```
+pub struct Foo<T=U, U=()> {
+    field1: T,
+    filed2: U,
+}
+// error: type parameters with a default cannot use forward declared
+// identifiers
+```
+
+Since type parameters are evaluated in-order, you may be able to fix this issue
+by doing:
+
+```
+pub struct Foo<U=(), T=U> {
+    field1: T,
+    filed2: U,
+}
+```
+
+Please also verify that this wasn't because of a name-clash and rename the type
+parameter if so.
+"##,
+
+E0130: r##"
+You declared a pattern as an argument in a foreign function declaration.
+Erroneous code example:
+
+```
+extern {
+    fn foo((a, b): (u32, u32)); // error: patterns aren't allowed in foreign
+                                //        function declarations
+}
+```
+
+Please replace the pattern argument with a regular one. Example:
+
+```
+struct SomeStruct {
+    a: u32,
+    b: u32,
+}
+
+extern {
+    fn foo(s: SomeStruct); // ok!
+}
+// or
+extern {
+    fn foo(a: (u32, u32)); // ok!
+}
+```
+"##,
+
 E0131: r##"
 It is not possible to define `main` with type parameters, or even with function
 parameters. When `main` is present, it must take no arguments and return `()`.
@@ -1382,6 +1438,30 @@ fn(isize, *const *const u8) -> isize
 ```
 "##,
 
+E0159: r##"
+You tried to use a trait as a struct constructor. Erroneous code example:
+
+```
+trait TraitNotAStruct {}
+
+TraitNotAStruct{ value: 0 }; // error: use of trait `TraitNotAStruct` as a
+                             //        struct constructor
+```
+
+Please verify you used the correct type name or please implement the trait
+on a struct and use this struct constructor. Example:
+
+```
+trait TraitNotAStruct {}
+
+struct Foo {
+    value: i32
+}
+
+Foo{ value: 0 }; // ok!
+```
+"##,
+
 E0166: r##"
 This error means that the compiler found a return expression in a function
 marked as diverging. A function diverges if it has `!` in the place of the
@@ -1978,11 +2058,8 @@ register_diagnostics! {
     E0122,
     E0123,
     E0127,
-    E0128,
     E0129,
-    E0130,
     E0141,
-    E0159,
     E0163,
     E0164,
     E0167,

branches/tmp/src/libsyntax/feature_gate.rs

@@ -155,6 +155,9 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Status)] = &[
 
     // Allows the definition of `const fn` functions.
     ("const_fn", "1.2.0", Active),
+
+    // Allows using #[prelude_import] on glob `use` items.
+    ("prelude_import", "1.2.0", Active),
 ];
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 
@@ -265,7 +268,8 @@ pub const KNOWN_ATTRIBUTES: &'static [(&'static str, AttributeType)] = &[
                                    and may be removed in the future")),
 
     // used in resolve
-    ("prelude_import", Whitelisted),
+    ("prelude_import", Gated("prelude_import",
+                             "`#[prelude_import]` is for use by rustc only")),
 
     // FIXME: #14407 these are only looked at on-demand so we can't
     // guarantee they'll have already been checked

branches/tmp/src/libsyntax/print/pprust.rs

@@ -120,11 +120,13 @@ pub fn print_crate<'a>(cm: &'a CodeMap,
         // of the feature gate, so we fake them up here.
 
         let no_std_meta = attr::mk_word_item(InternedString::new("no_std"));
+        let prelude_import_meta = attr::mk_word_item(InternedString::new("prelude_import"));
 
         // #![feature(no_std)]
         let fake_attr = attr::mk_attr_inner(attr::mk_attr_id(),
                                             attr::mk_list_item(InternedString::new("feature"),
-                                                               vec![no_std_meta.clone()]));
+                                                               vec![no_std_meta.clone(),
+                                                                    prelude_import_meta]));
         try!(s.print_attribute(&fake_attr));
 
         // #![no_std]

branches/tmp/src/libsyntax/std_inject.rs

@@ -10,16 +10,35 @@
 
 use ast;
 use attr;
-use codemap::DUMMY_SP;
+use codemap::{DUMMY_SP, Span, ExpnInfo, NameAndSpan, MacroAttribute};
 use codemap;
 use fold::Folder;
 use fold;
 use parse::token::InternedString;
 use parse::token::special_idents;
-use parse::token;
+use parse::{token, ParseSess};
 use ptr::P;
 use util::small_vector::SmallVector;
 
+/// Craft a span that will be ignored by the stability lint's
+/// call to codemap's is_internal check.
+/// The expanded code uses the unstable `#[prelude_import]` attribute.
+fn ignored_span(sess: &ParseSess, sp: Span) -> Span {
+    let info = ExpnInfo {
+        call_site: DUMMY_SP,
+        callee: NameAndSpan {
+            name: "std_inject".to_string(),
+            format: MacroAttribute,
+            span: None,
+            allow_internal_unstable: true,
+        }
+    };
+    let expn_id = sess.codemap().record_expansion(info);
+    let mut sp = sp;
+    sp.expn_id = expn_id;
+    return sp;
+}
+
 pub fn maybe_inject_crates_ref(krate: ast::Crate, alt_std_name: Option<String>)
                                -> ast::Crate {
     if use_std(&krate) {
@@ -29,9 +48,12 @@ pub fn maybe_inject_crates_ref(krate: ast::Crate, alt_std_name: Option<String>)
     }
 }
 
-pub fn maybe_inject_prelude(krate: ast::Crate) -> ast::Crate {
+pub fn maybe_inject_prelude(sess: &ParseSess, krate: ast::Crate) -> ast::Crate {
     if use_std(&krate) {
-        inject_prelude(krate)
+        let mut fold = PreludeInjector {
+            span: ignored_span(sess, DUMMY_SP)
+        };
+        fold.fold_crate(krate)
     } else {
         krate
     }
@@ -80,8 +102,9 @@ fn inject_crates_ref(krate: ast::Crate, alt_std_name: Option<String>) -> ast::Cr
     fold.fold_crate(krate)
 }
 
-struct PreludeInjector;
-
+struct PreludeInjector {
+    span: Span
+}
 
 impl fold::Folder for PreludeInjector {
     fn fold_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
@@ -107,7 +130,7 @@ impl fold::Folder for PreludeInjector {
 
     fn fold_mod(&mut self, mut mod_: ast::Mod) -> ast::Mod {
         let prelude_path = ast::Path {
-            span: DUMMY_SP,
+            span: self.span,
             global: false,
             segments: vec![
                 ast::PathSegment {
@@ -131,27 +154,22 @@ impl fold::Folder for PreludeInjector {
             ident: special_idents::invalid,
             node: ast::ItemUse(vp),
             attrs: vec![ast::Attribute {
-                span: DUMMY_SP,
+                span: self.span,
                 node: ast::Attribute_ {
                     id: attr::mk_attr_id(),
                     style: ast::AttrOuter,
                     value: P(ast::MetaItem {
-                        span: DUMMY_SP,
+                        span: self.span,
                         node: ast::MetaWord(token::get_name(
                                 special_idents::prelude_import.name)),
                     }),
                     is_sugared_doc: false,
                 },
             }],
             vis: ast::Inherited,
-            span: DUMMY_SP,
+            span: self.span,
         }));
 
         fold::noop_fold_mod(mod_, self)
     }
 }
-
-fn inject_prelude(krate: ast::Crate) -> ast::Crate {
-    let mut fold = PreludeInjector;
-    fold.fold_crate(krate)
-}

branches/tmp/src/test/compile-fail/feature-gate-prelude_import.rs

@@ -0,0 +1,14 @@
+// Copyright 2015 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.
+
+#[prelude_import] //~ ERROR `#[prelude_import]` is for use by rustc only
+use std::prelude::v1::*;
+
+fn main() {}

branches/tmp/src/test/pretty/issue-4264.pp

@@ -1,4 +1,4 @@
-#![feature(no_std)]
+#![feature(no_std, prelude_import)]
 #![no_std]
 #[prelude_import]
 use std::prelude::v1::*;