Spacing changes made to the example

src/libcore/macros.rs

@@ -358,10 +358,9 @@ macro_rules! try {
 /// # extern crate core;
 /// use core::fmt::Write;
 ///
-///  struct Example{
-///  }
+/// struct Example;
 ///
-///  impl Write for Example{
+/// impl Write for Example {
 ///     fn write_str(&mut self, _s: &str) -> core::fmt::Result {
 ///          unimplemented!();
 ///     }