Implement indexed_vec::Idx for ast::NodeId

src/libsyntax/ast.rs

@@ -23,6 +23,7 @@
 use ext::hygiene::SyntaxContext;
 use print::pprust;
 use ptr::P;
+use rustc_data_structures::indexed_vec;
 use symbol::{Symbol, keywords};
 use tokenstream::{ThinTokenStream, TokenStream};
 
@@ -275,6 +276,16 @@ fn default_decode<D: Decoder>(d: &mut D) -> Result<NodeId, D::Error> {
     }
 }
 
+impl indexed_vec::Idx for NodeId {
+    fn new(idx: usize) -> Self {
+        NodeId::new(idx)
+    }
+
+    fn index(self) -> usize {
+        self.as_usize()
+    }
+}
+
 /// Node id used to represent the root of the crate.
 pub const CRATE_NODE_ID: NodeId = NodeId(0);