Add `nightly` feature, use for `unlikely` intrinsic

Cargo.toml

@@ -35,6 +35,7 @@ default = ["err-println"]
 # Enabling this feature makes shaders automatically reload when changed
 live-shader-reload = []
 err-println = []
+nightly = []
 
 [build-dependencies]
 gl_generator = "0.5"

src/grid.rs

@@ -150,7 +150,7 @@ impl<T> Grid<T> {
     /// better error messages by doing the bounds checking ourselves.
     #[inline]
     pub fn swap_lines(&mut self, src: index::Line, dst: index::Line) {
-        use std::intrinsics::unlikely;
+        use util::unlikely;
 
         unsafe {
             // check that src/dst are in bounds. Since index::Line newtypes usize,

src/lib.rs

@@ -20,7 +20,7 @@
 #![cfg_attr(feature = "clippy", deny(if_not_else))]
 #![cfg_attr(feature = "clippy", deny(wrong_pub_self_convention))]
 #![cfg_attr(test, feature(test))]
-#![feature(core_intrinsics)]
+#![cfg_attr(feature = "nightly", feature(core_intrinsics))]
 
 #![feature(proc_macro)]
 

src/term/mod.rs

@@ -630,7 +630,7 @@ impl ansi::Handler for Term {
         }
 
         unsafe {
-            if ::std::intrinsics::unlikely(self.cursor.line == self.grid.num_lines()) {
+            if ::util::unlikely(self.cursor.line == self.grid.num_lines()) {
                 panic!("cursor fell off grid");
             }
         }

src/util.rs

@@ -13,6 +13,15 @@
 // limitations under the License.
 use std::cmp;
 
+#[cfg(not(feature = "nightly"))]
+#[inline(always)]
+pub unsafe fn unlikely(x: bool) -> bool {
+    x
+}
+
+#[cfg(feature = "nightly")]
+pub use ::std::intrinsics::unlikely;
+
 /// Threading utilities
 pub mod thread {
     /// Like `thread::spawn`, but with a `name` argument