libsyntax: deny warnings in doctests

src/libsyntax/ast.rs

@@ -908,13 +908,15 @@ pub enum Expr_ {
 /// separately. `position` represents the index of the associated
 /// item qualified with this Self type.
 ///
-///     <Vec<T> as a::b::Trait>::AssociatedItem
-///      ^~~~~     ~~~~~~~~~~~~~~^
-///      ty        position = 3
+/// ```ignore
+/// <Vec<T> as a::b::Trait>::AssociatedItem
+///  ^~~~~     ~~~~~~~~~~~~~~^
+///  ty        position = 3
 ///
-///     <Vec<T>>::AssociatedItem
-///      ^~~~~    ^
-///      ty       position = 0
+/// <Vec<T>>::AssociatedItem
+///  ^~~~~    ^
+///  ty       position = 0
+/// ```
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct QSelf {
     pub ty: P<Ty>,