Auto merge of #21257 - alexcrichton:issue-20064, r=pnkfelix

These two attributes are used to change the entry point into a Rust program, but
for now they're being put behind feature gates until we have a chance to think
about them a little more. The #[start] attribute specifically may have its
signature changed.

This is a breaking change to due the usage of these attributes generating errors
by default now. If your crate is using these attributes, add this to your crate
root:

    #![feature(start)] // if you're using the #[start] attribute
    #![feature(main)]  // if you're using the #[main] attribute

cc #20064

src/test/compile-fail/feature-gate-main.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.
+
+#[main]
+fn foo() {} //~ ERROR: declaration of a nonstandard #[main] function may change over time

src/test/compile-fail/feature-gate-start.rs

@@ -0,0 +1,13 @@
+// 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.
+
+#[start]
+fn foo() {} //~ ERROR: a #[start] function is an experimental feature
+

src/test/compile-fail/issue-9575.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(start)]
+
 #[start]
 fn start(argc: isize, argv: *const *const u8, crate_map: *const u8) -> isize {
     //~^ ERROR incorrect number of function parameters

src/test/compile-fail/lang-item-missing.rs

@@ -14,6 +14,7 @@
 // error-pattern: requires `sized` lang_item
 
 #![no_std]
+#![feature(start)]
 
 #[start]
 fn start(argc: isize, argv: *const *const u8) -> isize {

src/test/compile-fail/lint-dead-code-2.rs

@@ -10,6 +10,7 @@
 
 #![allow(unused_variables)]
 #![deny(dead_code)]
+#![feature(main, start)]
 
 struct Foo;
 

src/test/compile-fail/multiple-main-2.rs

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

src/test/compile-fail/multiple-main-3.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(main)]
+
 #[main]
 fn main1() {
 }

src/test/compile-fail/privacy1.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(lang_items)]
+#![feature(lang_items, start)]
 #![no_std] // makes debugging this test *a lot* easier (during resolve)
 
 #[lang="sized"]

src/test/compile-fail/privacy2.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(start)]
 #![no_std] // makes debugging this test *a lot* easier (during resolve)
 
 // Test to make sure that globs don't leak in regular `use` statements.

src/test/compile-fail/privacy3.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(start)]
 #![no_std] // makes debugging this test *a lot* easier (during resolve)
 
 // Test to make sure that private items imported through globs remain private

src/test/compile-fail/privacy4.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(lang_items)]
+#![feature(lang_items, start)]
 #![no_std] // makes debugging this test *a lot* easier (during resolve)
 
 #[lang = "sized"] pub trait Sized {}