Add backquotes to have better looking rust code

src/librustc/diagnostics.rs

@@ -75,11 +75,13 @@
 into a variable called `op_string` while simultaneously requiring the inner
 String to be moved into a variable called `s`.
 
+```
 let x = Some("s".to_string());
 match x {
     op_string @ Some(s) => ...
     None => ...
 }
+```
 
 See also Error 303.
 "##,
@@ -90,10 +92,12 @@
 referenced in the pattern guard code. Doing so however would prevent the name
 from being available in the body of the match arm. Consider the following:
 
+```
 match Some("hi".to_string()) {
     Some(s) if s.len() == 0 => // use s.
     ...
 }
+```
 
 The variable `s` has type String, and its use in the guard is as a variable of
 type String. The guard code effectively executes in a separate scope to the body
@@ -102,11 +106,13 @@
 innocuous, the problem is most clear when considering functions that take their
 argument by value.
 
+```
 match Some("hi".to_string()) {
     Some(s) if { drop(s); false } => (),
     Some(s) => // use s.
     ...
 }
+```
 
 The value would be dropped in the guard then become unavailable not only in the
 body of that arm but also in all subsequent arms! The solution is to bind by
@@ -218,6 +224,7 @@ struct X { x: (), }
 match was succesful. If the match is irrefutable (when it cannot fail to match),
 use a regular `let`-binding instead. For instance:
 
+```
 struct Irrefutable(i32);
 let irr = Irrefutable(0);
 
@@ -230,6 +237,7 @@ struct X { x: (), }
 // Try this instead:
 let Irrefutable(x) = irr;
 foo(x);
+```
 "##,
 
 E0165: r##"
@@ -237,6 +245,7 @@ struct X { x: (), }
 match was succesful. If the match is irrefutable (when it cannot fail to match),
 use a regular `let`-binding inside a `loop` instead. For instance:
 
+```
 struct Irrefutable(i32);
 let irr = Irrefutable(0);
 
@@ -250,6 +259,7 @@ struct X { x: (), }
     let Irrefutable(x) = irr;
     ...
 }
+```
 "##,
 
 E0170: r##"
@@ -304,6 +314,7 @@ enum Method { GET, POST }
 loop variable, consider using a `match` or `if let` inside the loop body. For
 instance:
 
+```
 // This fails because `None` is not covered.
 for Some(x) in xs {
     ...
@@ -323,6 +334,7 @@ enum Method { GET, POST }
         ...
     }
 }
+```
 "##,
 
 E0301: r##"
@@ -332,11 +344,13 @@ enum Method { GET, POST }
 exhaustive. For instance, the following would not match any arm if mutable
 borrows were allowed:
 
+```
 match Some(()) {
     None => { },
     option if option.take().is_none() => { /* impossible, option is `Some` */ },
     Some(_) => { } // When the previous match failed, the option became `None`.
 }
+```
 "##,
 
 E0302: r##"
@@ -346,11 +360,13 @@ enum Method { GET, POST }
 exhaustive. For instance, the following would not match any arm if assignments
 were allowed:
 
+```
 match Some(()) {
     None => { },
     option if { option = None; false } { },
     Some(_) => { } // When the previous match failed, the option became `None`.
 }
+```
 "##,
 
 E0303: r##"
@@ -358,9 +374,10 @@ enum Method { GET, POST }
 Updates to the borrow checker in a future version of Rust may remove this
 restriction, but for now patterns must be rewritten without sub-bindings.
 
-// Before.
-match Some("hi".to_string()) {
-    ref op_string_ref @ Some(ref s) => ...
+```
+// Code like this...
+match Some(5) {
+    ref op_num @ Some(num) => ...
     None => ...
 }
 
@@ -372,6 +389,7 @@ enum Method { GET, POST }
     }
     None => ...
 }
+```
 
 The `op_string_ref` binding has type &Option<&String> in both cases.