Rollup merge of #22960 - huonw:static-assert, r=huonw

The API this exposes is a little strange (being attached to `static`s),
so it makes sense to conservatively feature gate it. If it is highly
popular, it is possible to reverse this gating.

src/test/compile-fail/asm-misplaced-option.rs

@@ -10,13 +10,14 @@
 
 // ignore-android
 
-#![feature(asm)]
+#![feature(asm, rustc_attrs)]
 
 #![allow(dead_code, non_upper_case_globals)]
 
 #[cfg(any(target_arch = "x86",
           target_arch = "x86_64"))]
-pub fn main() {
+#[rustc_error]
+pub fn main() { //~ ERROR compilation successful
     // assignment not dead
     let mut x: isize = 0;
     unsafe {
@@ -33,7 +34,3 @@ pub fn main() {
     }
     assert_eq!(x, 13);
 }
-
-// At least one error is needed so that compilation fails
-#[static_assert]
-static b: bool = false; //~ ERROR static assertion failed

src/test/compile-fail/feature-gate-static-assert.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.
+
+#[static_assert] //~ ERROR `#[static_assert]` is an experimental feature
+static X: bool = true;
+
+fn main() {}

src/test/compile-fail/issue-6804.rs

@@ -8,13 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(rustc_attrs)]
 #![allow(dead_code)]
 
 // Matching against NaN should result in a warning
 
 use std::f64::NAN;
 
-fn main() {
+#[rustc_error]
+fn main() { //~ ERROR compilation successful
     let x = NAN;
     match x {
         NAN => {},
@@ -27,7 +29,3 @@ fn main() {
     };
     //~^^^ WARNING unmatchable NaN in pattern, use the is_nan method in a guard instead
 }
-
-// At least one error is needed so that compilation fails
-#[static_assert]
-static B: bool = false; //~ ERROR static assertion failed

src/test/compile-fail/nonbool_static_assert.rs

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

src/test/compile-fail/static-assert.rs

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

src/test/compile-fail/static-assert2.rs

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

src/test/run-pass/static-assert.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(static_assert)]
+
 #[static_assert]
 static b: bool = true;