Improve description

Author: GuillaumeGomez

src/librustc/diagnostics.rs

@@ -113,37 +113,50 @@ putting the condition inside the body of the arm.
 "##,
 
 E0009: r##"
-In a pattern, all values that don't implement the Copy trait have to be binded the same way
-than the others. The goal here is to avoid to bind by-move and by-ref at the same time.
+In a pattern, all values that don't implement the `Copy` trait have to be bound
+the same way. The goal here is to avoid binding simultaneous by-move and by-ref.
+
+This limitation may be removed in a future version of Rust.
+
 Wrong example:
+
+```
 struct X { x: (), }
 
 let x = Some((X { x: () }, X { x: () }));
 match x {
-    Some((_y, ref _z)) => {},
+    Some((y, ref z)) => {},
     None => panic!()
 }
+```
 
 You have two solutions:
-* implement the Copy trait on the X structure:
-#[derive(Clone, Copy)]
+1. Bind the pattern's values the same way:
+
+```
 struct X { x: (), }
 
 let x = Some((X { x: () }, X { x: () }));
 match x {
-    Some((_y, ref _z)) => {},
+    Some((ref y, ref z)) => {},
+    // or Some((y, z)) => {}
     None => panic!()
 }
+```
+
+2. Implement the `Copy` trait for the X structure (however, please
+keep in mind that the first solution should be preferred!):
 
-* bind the the pattern's values the same way:
+```
+#[derive(Clone, Copy)]
 struct X { x: (), }
 
 let x = Some((X { x: () }, X { x: () }));
 match x {
-    Some((ref _y, ref _z)) => {},
-    // or Some((_y, _z)) => {}
+    Some((y, ref z)) => {},
     None => panic!()
 }
+```
 "##,
 
 E0162: r##"