Improve hygiene of alloc::format!

Author: petrochenkov

src/liballoc/lib.rs

@@ -171,3 +171,9 @@ pub mod vec;
 mod std {
     pub use core::ops; // RangeFull
 }
+
+#[doc(hidden)]
+#[unstable(feature = "liballoc_internals", issue = "0", reason = "implementation detail")]
+pub mod __export {
+    pub use core::format_args;
+}

src/liballoc/macros.rs

@@ -98,5 +98,5 @@ macro_rules! vec {
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
 macro_rules! format {
-    ($($arg:tt)*) => ($crate::fmt::format(::core::format_args!($($arg)*)))
+    ($($arg:tt)*) => ($crate::fmt::format($crate::__export::format_args!($($arg)*)))
 }