Postpone deprecating try! until 1.39.0

src/libcore/macros.rs

@@ -300,9 +300,9 @@
 ///     Ok(())
 /// }
 /// ```
-#[rustc_deprecated(since = "1.38.0", reason = "use the `?` operator instead")]
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_deprecated(since = "1.39.0", reason = "use the `?` operator instead")]
 #[doc(alias = "?")]
 macro_rules! r#try {
     ($expr:expr) => (match $expr {

src/libstd/lib.rs

@@ -331,7 +331,8 @@
 pub use core::{assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::{unreachable, unimplemented, write, writeln, todo};
-#[allow(deprecated)]
+// FIXME: change this to `#[allow(deprecated)]` when we update nightly compiler.
+#[allow(deprecated_in_future)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::r#try;