Auto merge of #28529 - Manishearth:rollup, r=Manishearth

- Successful merges: #28463, #28507, #28522, #28525, #28526
- Failed merges:

Author: bors

src/doc/trpl/choosing-your-guarantees.md

@@ -321,7 +321,7 @@ there's a lot of concurrent access happening.
 
 # Composition
 
-A common gripe when reading Rust code is with types like `Rc<RefCell<Vec<T>>>` (or even more more
+A common gripe when reading Rust code is with types like `Rc<RefCell<Vec<T>>>` (or even more
 complicated compositions of such types). It's not always clear what the composition does, or why the
 author chose one like this (and when one should be using such a composition in one's own code)
 

src/doc/trpl/concurrency.md

@@ -26,8 +26,8 @@ to help us make sense of code that can possibly be concurrent.
 ### `Send`
 
 The first trait we're going to talk about is
-[`Send`](../std/marker/trait.Send.html). When a type `T` implements `Send`, it indicates
-to the compiler that something of this type is able to have ownership transferred
+[`Send`](../std/marker/trait.Send.html). When a type `T` implements `Send`, it
+indicates that something of this type is able to have ownership transferred
 safely between threads.
 
 This is important to enforce certain restrictions. For example, if we have a
@@ -42,13 +42,19 @@ us enforce that it can't leave the current thread.
 ### `Sync`
 
 The second of these traits is called [`Sync`](../std/marker/trait.Sync.html).
-When a type `T` implements `Sync`, it indicates to the compiler that something
+When a type `T` implements `Sync`, it indicates that something
 of this type has no possibility of introducing memory unsafety when used from
-multiple threads concurrently.
-
-For example, sharing immutable data with an atomic reference count is
-threadsafe. Rust provides a type like this, `Arc<T>`, and it implements `Sync`,
-so it is safe to share between threads.
+multiple threads concurrently through shared references. This implies that
+types which don't have [interior mutability](mutability.html) are inherently
+`Sync`, which includes simple primitive types (like `u8`) and aggregate types
+containing them.
+
+For sharing references across threads, Rust provides a wrapper type called
+`Arc<T>`. `Arc<T>` implements `Send` and `Sync` if and only if `T` implements
+both `Send` and `Sync`. For example, an object of type `Arc<RefCell<U>>` cannot
+be transferred across threads because
+[`RefCell`](choosing-your-guarantees.html#refcell%3Ct%3E) does not implement
+`Sync`, consequently `Arc<RefCell<U>>` would not implement `Send`.
 
 These two traits allow you to use the type system to make strong guarantees
 about the properties of your code under concurrency. Before we demonstrate
@@ -70,7 +76,7 @@ fn main() {
 }
 ```
 
-The `thread::spawn()` method accepts a closure, which is executed in a
+The `thread::spawn()` method accepts a [closure](closures.html), which is executed in a
 new thread. It returns a handle to the thread, that can be used to
 wait for the child thread to finish and extract its result:
 
@@ -215,29 +221,18 @@ fn main() {
 }
 ```
 
+Note that the value of `i` is bound (copied) to the closure and not shared
+among the threads.
 
-If we'd tried to use `Mutex<T>` without wrapping it in an `Arc<T>` we would have
-seen another error like:
-
-```text
-error: the trait `core::marker::Send` is not implemented for the type `std::sync::mutex::MutexGuard<'_, collections::vec::Vec<u32>>` [E0277]
- thread::spawn(move || {
-                  ^~~~~~~~~~~~~
-note: `std::sync::mutex::MutexGuard<'_, collections::vec::Vec<u32>>` cannot be sent between threads safely
- thread::spawn(move || {
-                  ^~~~~~~~~~~~~
-```
-
-You see, [`Mutex`](../std/sync/struct.Mutex.html) has a
-[`lock`](../std/sync/struct.Mutex.html#method.lock)
-method which has this signature:
+Also note that [`lock`](../std/sync/struct.Mutex.html#method.lock) method of
+[`Mutex`](../std/sync/struct.Mutex.html) has this signature:
 
 ```ignore
 fn lock(&self) -> LockResult<MutexGuard<T>>
 ```
 
-and because `Send` is not implemented for `MutexGuard<T>`, we couldn't have
-transferred the guard across thread boundaries on it's own.
+and because `Send` is not implemented for `MutexGuard<T>`, the guard cannot
+cross thread boundaries, ensuring thread-locality of lock acquire and release.
 
 Let's examine the body of the thread more closely:
 
@@ -317,22 +312,24 @@ use std::sync::mpsc;
 fn main() {
     let (tx, rx) = mpsc::channel();
 
-    for _ in 0..10 {
+    for i in 0..10 {
         let tx = tx.clone();
 
         thread::spawn(move || {
-            let answer = 42;
+            let answer = i * i;
 
             tx.send(answer);
         });
     }
 
-   rx.recv().ok().expect("Could not receive answer");
+    for _ in 0..10 {
+        println!("{}", rx.recv().unwrap());
+    }
 }
 ```
 
-A `u32` is `Send` because we can make a copy. So we create a thread, ask it to calculate
-the answer, and then it `send()`s us the answer over the channel.
+Here we create 10 threads, asking each to calculate the square of a number (`i`
+at the time of `spawn()`), and then `send()` back the answer over the channel.
 
 
 ## Panics

src/librustc/diagnostics.rs

@@ -298,10 +298,18 @@ const FOO: i32 = { 0 }; // but brackets are useless here
 ```
 "##,
 
+// FIXME(#24111) Change the language here when const fn stabilizes
 E0015: r##"
 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.
+`const` functions, and struct/enum constructors. `const` functions are only
+available on a nightly compiler. Rust currently does not support more general
+compile-time function execution.
+
+```
+const FOO: Option<u8> = Some(1); // enum constructor
+struct Bar {x: u8}
+const BAR: Bar = Bar {x: 1}; // struct constructor
+```
 
 See [RFC 911] for more details on the design of `const fn`s.
 

src/librustc/middle/check_const.rs

@@ -39,6 +39,7 @@ use util::nodemap::NodeMap;
 use rustc_front::hir;
 use syntax::ast;
 use syntax::codemap::Span;
+use syntax::feature_gate::UnstableFeatures;
 use rustc_front::visit::{self, FnKind, Visitor};
 
 use std::collections::hash_map::Entry;
@@ -709,10 +710,21 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>,
             if !is_const {
                 v.add_qualif(ConstQualif::NOT_CONST);
                 if v.mode != Mode::Var {
-                    span_err!(v.tcx.sess, e.span, E0015,
-                              "function calls in {}s are limited to \
-                               constant functions, \
-                               struct and enum constructors", v.msg());
+                    // FIXME(#24111) Remove this check when const fn stabilizes
+                    if let UnstableFeatures::Disallow = v.tcx.sess.opts.unstable_features {
+                        span_err!(v.tcx.sess, e.span, E0015,
+                                  "function calls in {}s are limited to \
+                                   struct and enum constructors", v.msg());
+                        v.tcx.sess.span_note(e.span,
+                                             "a limited form of compile-time function \
+                                              evaluation is available on a nightly \
+                                              compiler via `const fn`");
+                    } else {
+                        span_err!(v.tcx.sess, e.span, E0015,
+                                  "function calls in {}s are limited to \
+                                   constant functions, \
+                                   struct and enum constructors", v.msg());
+                    }
                 }
             }
         }

src/libsyntax/ext/expand.rs

@@ -684,15 +684,15 @@ fn contains_macro_use(fld: &mut MacroExpander, attrs: &[ast::Attribute]) -> bool
 // logic as for expression-position macro invocations.
 pub fn expand_item_mac(it: P<ast::Item>,
                        fld: &mut MacroExpander) -> SmallVector<P<ast::Item>> {
-    let (extname, path_span, tts) = match it.node {
+    let (extname, path_span, tts, span, attrs, ident) = it.and_then(|it| { match it.node {
         ItemMac(codemap::Spanned {
-            node: MacInvocTT(ref pth, ref tts, _),
+            node: MacInvocTT(pth, tts, _),
             ..
         }) => {
-            (pth.segments[0].identifier.name, pth.span, (*tts).clone())
+            (pth.segments[0].identifier.name, pth.span, tts, it.span, it.attrs, it.ident)
         }
         _ => fld.cx.span_bug(it.span, "invalid item macro invocation")
-    };
+    }});
 
     let fm = fresh_mark();
     let items = {
@@ -706,56 +706,56 @@ pub fn expand_item_mac(it: P<ast::Item>,
             }
 
             Some(rc) => match *rc {
-                NormalTT(ref expander, span, allow_internal_unstable) => {
-                    if it.ident.name != parse::token::special_idents::invalid.name {
+                NormalTT(ref expander, tt_span, allow_internal_unstable) => {
+                    if ident.name != parse::token::special_idents::invalid.name {
                         fld.cx
                             .span_err(path_span,
                                       &format!("macro {}! expects no ident argument, given '{}'",
                                                extname,
-                                               it.ident));
+                                               ident));
                         return SmallVector::zero();
                     }
                     fld.cx.bt_push(ExpnInfo {
-                        call_site: it.span,
+                        call_site: span,
                         callee: NameAndSpan {
                             format: MacroBang(extname),
-                            span: span,
+                            span: tt_span,
                             allow_internal_unstable: allow_internal_unstable,
                         }
                     });
                     // mark before expansion:
                     let marked_before = mark_tts(&tts[..], fm);
-                    expander.expand(fld.cx, it.span, &marked_before[..])
+                    expander.expand(fld.cx, span, &marked_before[..])
                 }
-                IdentTT(ref expander, span, allow_internal_unstable) => {
-                    if it.ident.name == parse::token::special_idents::invalid.name {
+                IdentTT(ref expander, tt_span, allow_internal_unstable) => {
+                    if ident.name == parse::token::special_idents::invalid.name {
                         fld.cx.span_err(path_span,
                                         &format!("macro {}! expects an ident argument",
                                                 extname));
                         return SmallVector::zero();
                     }
                     fld.cx.bt_push(ExpnInfo {
-                        call_site: it.span,
+                        call_site: span,
                         callee: NameAndSpan {
                             format: MacroBang(extname),
-                            span: span,
+                            span: tt_span,
                             allow_internal_unstable: allow_internal_unstable,
                         }
                     });
                     // mark before expansion:
                     let marked_tts = mark_tts(&tts[..], fm);
-                    expander.expand(fld.cx, it.span, it.ident, marked_tts)
+                    expander.expand(fld.cx, span, ident, marked_tts)
                 }
                 MacroRulesTT => {
-                    if it.ident.name == parse::token::special_idents::invalid.name {
+                    if ident.name == parse::token::special_idents::invalid.name {
                         fld.cx.span_err(path_span,
                                         &format!("macro_rules! expects an ident argument")
                                         );
                         return SmallVector::zero();
                     }
 
                     fld.cx.bt_push(ExpnInfo {
-                        call_site: it.span,
+                        call_site: span,
                         callee: NameAndSpan {
                             format: MacroBang(extname),
                             span: None,
@@ -767,7 +767,7 @@ pub fn expand_item_mac(it: P<ast::Item>,
                     });
                     // DON'T mark before expansion.
 
-                    let allow_internal_unstable = attr::contains_name(&it.attrs,
+                    let allow_internal_unstable = attr::contains_name(&attrs,
                                                                       "allow_internal_unstable");
 
                     // ensure any #[allow_internal_unstable]s are
@@ -777,18 +777,19 @@ pub fn expand_item_mac(it: P<ast::Item>,
                         feature_gate::emit_feature_err(
                             &fld.cx.parse_sess.span_diagnostic,
                             "allow_internal_unstable",
-                            it.span,
+                            span,
                             feature_gate::GateIssue::Language,
                             feature_gate::EXPLAIN_ALLOW_INTERNAL_UNSTABLE)
                     }
 
+                    let export = attr::contains_name(&attrs, "macro_export");
                     let def = ast::MacroDef {
-                        ident: it.ident,
-                        attrs: it.attrs.clone(),
+                        ident: ident,
+                        attrs: attrs,
                         id: ast::DUMMY_NODE_ID,
-                        span: it.span,
+                        span: span,
                         imported_from: None,
-                        export: attr::contains_name(&it.attrs, "macro_export"),
+                        export: export,
                         use_locally: true,
                         allow_internal_unstable: allow_internal_unstable,
                         body: tts,
@@ -800,7 +801,7 @@ pub fn expand_item_mac(it: P<ast::Item>,
                     return SmallVector::zero();
                 }
                 _ => {
-                    fld.cx.span_err(it.span,
+                    fld.cx.span_err(span,
                                     &format!("{}! is not legal in item position",
                                             extname));
                     return SmallVector::zero();

src/libsyntax/feature_gate.rs

@@ -197,6 +197,12 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Option<u32>, Status
 
     // allow overloading augmented assignment operations like `a += b`
     ("augmented_assignments", "1.5.0", None, Active),
+
+    // allow `#[no_debug]`
+    ("no_debug", "1.5.0", None, Active),
+
+    // allow `#[omit_gdb_pretty_printer_section]`
+    ("omit_gdb_pretty_printer_section", "1.5.0", None, Active),
 ];
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 
@@ -320,8 +326,13 @@ pub const KNOWN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGat
     ("link_section", Whitelisted, Ungated),
     ("no_builtins", Whitelisted, Ungated),
     ("no_mangle", Whitelisted, Ungated),
-    ("no_debug", Whitelisted, Ungated),
-    ("omit_gdb_pretty_printer_section", Whitelisted, Ungated),
+    ("no_debug", Whitelisted, Gated("no_debug",
+                                    "the `#[no_debug]` attribute \
+                                     is an experimental feature")),
+    ("omit_gdb_pretty_printer_section", Whitelisted, Gated("omit_gdb_pretty_printer_section",
+                                                       "the `#[omit_gdb_pretty_printer_section]` \
+                                                        attribute is just used for the Rust test \
+                                                        suite")),
     ("unsafe_no_drop_flag", Whitelisted, Gated("unsafe_no_drop_flag",
                                                "unsafe_no_drop_flag has unstable semantics \
                                                 and may be removed in the future")),

src/test/auxiliary/cross_crate_spans.rs

@@ -11,6 +11,7 @@
 #![crate_type = "rlib"]
 
 #![allow(unused_variables)]
+#![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
 
 // no-prefer-dynamic

src/test/compile-fail/feature-gate-no-debug.rs

@@ -0,0 +1,12 @@
+// 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.
+
+#[no_debug] //~ ERROR the `#[no_debug]` attribute is
+fn main() {}

src/test/compile-fail/feature-gate-omit-gdb-pretty-printer-section.rs

@@ -0,0 +1,12 @@
+// 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.
+
+#[omit_gdb_pretty_printer_section] //~ ERROR the `#[omit_gdb_pretty_printer_section]` attribute is
+fn main() {}

src/test/debuginfo/associated-types.rs

@@ -80,6 +80,7 @@
 
 #![allow(unused_variables)]
 #![allow(dead_code)]
+#![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
 
 trait TraitWithAssocType {

src/test/debuginfo/basic-types-globals-metadata.rs

@@ -44,6 +44,7 @@
 
 #![allow(unused_variables)]
 #![allow(dead_code)]
+#![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
 
 // N.B. These are `mut` only so they don't constant fold away.

src/test/debuginfo/basic-types-globals.rs

@@ -49,6 +49,7 @@
 // gdb-command:continue
 
 #![allow(unused_variables)]
+#![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
 
 // N.B. These are `mut` only so they don't constant fold away.