Rollup merge of #42016 - pietroalbini:stabilize/loop_break_value, r=nikomatsakis

Stabilize the loop_break_value feature

Tracking issue: #37339.

Documentation PRs already sent to the various repositories.

src/doc/unstable-book/src/SUMMARY.md

@@ -49,7 +49,6 @@
     - [link_llvm_intrinsics](language-features/link-llvm-intrinsics.md)
     - [linkage](language-features/linkage.md)
     - [log_syntax](language-features/log-syntax.md)
-    - [loop_break_value](language-features/loop-break-value.md)
     - [macro_reexport](language-features/macro-reexport.md)
     - [macro_vis_matcher](language-features/macro-vis-matcher.md)
     - [main](language-features/main.md)

src/doc/unstable-book/src/language-features/loop-break-value.md

@@ -1,83 +0,0 @@
-# `loop_break_value`
-
-The tracking issue for this feature is: [#37339]
-
-[#37339]: https://github.com/rust-lang/rust/issues/37339
-
-Documentation to be appended to section G of the book.
-
-------------------------
-
-### Loops as expressions
-
-Like most things in Rust, loops are expressions, and have a value; normally `()` unless the loop
-never exits.
-A `loop` can instead evaluate to a useful value via *break with value*:
-
-```rust
-#![feature(loop_break_value)]
-
-// Find the first square number over 1000:
-let mut n = 1;
-let square = loop {
-    if n * n > 1000 {
-        break n * n;
-    }
-    n += 1;
-};
-```
-
-The evaluation type may be specified externally:
-
-```rust
-#![feature(loop_break_value)]
-
-// Declare that value returned is unsigned 64-bit:
-let n: u64 = loop {
-    break 1;
-};
-```
-
-It is an error if types do not agree, either between a "break" value and an external requirement,
-or between multiple "break" values:
-
-```no_compile
-#![feature(loop_break_value)]
-
-loop {
-    if true {
-        break 1u32;
-    } else {
-        break 0u8;  // error: types do not agree
-    }
-};
-
-let n: i32 = loop {
-    break 0u32; // error: type does not agree with external requirement
-};
-```
-
-#### Break: label, value
-
-Four forms of `break` are available, where EXPR is some expression which evaluates to a value:
-
-1.  `break;`
-2.  `break 'label;`
-3.  `break EXPR;`
-4.  `break 'label EXPR;`
-
-When no value is given, the value `()` is assumed, thus `break;` is equivalent to `break ();`.
-
-Using a label allows returning a value from an inner loop:
-
-```rust
-#![feature(loop_break_value)]
-
-let result = 'outer: loop {
-    for n in 1..10 {
-        if n > 4 {
-            break 'outer n;
-        }
-    }
-};
-```

src/librustc/lib.rs

@@ -30,7 +30,6 @@
 #![feature(core_intrinsics)]
 #![feature(i128_type)]
 #![feature(libc)]
-#![feature(loop_break_value)]
 #![feature(never_type)]
 #![feature(nonzero)]
 #![feature(quote)]
@@ -45,6 +44,7 @@
 #![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![cfg_attr(stage0, feature(rustc_private))]
 #![cfg_attr(stage0, feature(staged_api))]
+#![cfg_attr(stage0, feature(loop_break_value))]
 
 #![recursion_limit="128"]
 

src/librustc_driver/lib.rs

@@ -23,7 +23,6 @@
 #![deny(warnings)]
 
 #![feature(box_syntax)]
-#![feature(loop_break_value)]
 #![feature(libc)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
@@ -32,6 +31,7 @@
 #![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![cfg_attr(stage0, feature(rustc_private))]
 #![cfg_attr(stage0, feature(staged_api))]
+#![cfg_attr(stage0, feature(loop_break_value))]
 
 extern crate arena;
 extern crate getopts;

src/librustc_typeck/lib.rs

@@ -76,7 +76,6 @@ This API is completely unstable and subject to change.
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(conservative_impl_trait)]
-#![feature(loop_break_value)]
 #![feature(never_type)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
@@ -84,6 +83,7 @@ This API is completely unstable and subject to change.
 #![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![cfg_attr(stage0, feature(rustc_private))]
 #![cfg_attr(stage0, feature(staged_api))]
+#![cfg_attr(stage0, feature(loop_break_value))]
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;

src/libsyntax/feature_gate.rs

@@ -297,9 +297,6 @@ declare_features! (
 
     (active, use_extern_macros, "1.15.0", Some(35896)),
 
-    // Allows `break {expr}` with a value inside `loop`s.
-    (active, loop_break_value, "1.14.0", Some(37339)),
-
     // Allows #[target_feature(...)]
     (active, target_feature, "1.15.0", None),
 
@@ -423,6 +420,8 @@ declare_features! (
     (accepted, pub_restricted, "1.18.0", Some(32409)),
     // The #![windows_subsystem] attribute
     (accepted, windows_subsystem, "1.18.0", Some(37499)),
+    // Allows `break {expr}` with a value inside `loop`s.
+    (accepted, loop_break_value, "1.19.0", Some(37339)),
 );
 // If you change this, please modify src/doc/unstable-book as well. You must
 // move that documentation into the relevant place in the other docs, and
@@ -1301,10 +1300,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     }
                 }
             }
-            ast::ExprKind::Break(_, Some(_)) => {
-                gate_feature_post!(&self, loop_break_value, e.span,
-                                   "`break` with a value is experimental");
-            }
             ast::ExprKind::Lit(ref lit) => {
                 if let ast::LitKind::Int(_, ref ty) = lit.node {
                     match *ty {

src/test/compile-fail/feature-gate-loop-break-value.rs

@@ -1,15 +0,0 @@
-// Copyright 2016 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() {
-    loop {
-        break 123; //~ ERROR `break` with a value is experimental
-    }
-}

src/test/compile-fail/loop-break-value.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(loop_break_value)]
 #![feature(never_type)]
 
 fn main() {

src/test/run-pass/diverging-fallback-control-flow.rs

@@ -15,7 +15,6 @@
 // like to revisit these and potentially change them. --nmatsakis
 
 #![feature(never_type)]
-#![feature(loop_break_value)]
 
 trait BadDefault {
     fn default() -> Self;

src/test/run-pass/loop-break-value.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(loop_break_value)]
 #![feature(never_type)]
 
 #[allow(unused)]

src/test/ui/loop-break-value-no-repeat.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(loop_break_value)]
 #![allow(unused_variables)]
 
 use std::ptr;

src/test/ui/loop-break-value-no-repeat.stderr

@@ -1,7 +1,7 @@
 error[E0571]: `break` with value from a `for` loop
-  --> $DIR/loop-break-value-no-repeat.rs:23:9
+  --> $DIR/loop-break-value-no-repeat.rs:22:9
    |
-23 |         break 22
+22 |         break 22
    |         ^^^^^^^^ can only break with a value inside `loop`
 
 error: aborting due to previous error