Add edge labels to our graphviz output

This adds the `EdgeKind` as a label to edges in the graphviz IR dump
output. This is useful for understanding why something is referenced by another
thing.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/ir/dot.rs b/src/ir/dot.rs
index e7e1f47b..7472dd8e 100644
--- a/src/ir/dot.rs
+++ b/src/ir/dot.rs
@@ -36,15 +36,16 @@ pub fn write_dot_file<P>(ctx: &BindgenContext, path: P) -> io::Result<()>
         try!(writeln!(&mut dot_file, r#"</table> >];"#));
 
         item.trace(ctx,
-                   &mut |sub_id: ItemId, _edge_kind| {
+                   &mut |sub_id: ItemId, edge_kind| {
             if err.is_some() {
                 return;
             }
 
             match writeln!(&mut dot_file,
-                           "{} -> {};",
+                           "{} -> {} [label={:?}];",
                            id.as_usize(),
-                           sub_id.as_usize()) {
+                           sub_id.as_usize(),
+                           edge_kind) {
                 Ok(_) => {}
                 Err(e) => err = Some(Err(e)),
             }