Reflect whitelisted status via color in graphviz dot files

This makes it so that whitelisted items and edges outgoing from them are black,
while non-whitelisted items and their edges are gray.

Author: fitzgen

src/ir/dot.rs

@@ -32,10 +32,17 @@ where
     let mut err: Option<io::Result<_>> = None;
 
     for (id, item) in ctx.items() {
+        let is_whitelisted = ctx.whitelisted_items().contains(id);
+
         try!(writeln!(
             &mut dot_file,
-            r#"{} [fontname="courier", label=< <table border="0" align="left">"#,
-            id.as_usize()
+            r#"{} [fontname="courier", color={}, label=< <table border="0" align="left">"#,
+            id.as_usize(),
+            if is_whitelisted {
+                "black"
+            } else {
+                "gray"
+            }
         ));
         try!(item.dot_attributes(ctx, &mut dot_file));
         try!(writeln!(&mut dot_file, r#"</table> >];"#));
@@ -49,10 +56,15 @@ where
 
                 match writeln!(
                     &mut dot_file,
-                    "{} -> {} [label={:?}];",
+                    "{} -> {} [label={:?}, color={}];",
                     id.as_usize(),
                     sub_id.as_usize(),
-                    edge_kind
+                    edge_kind,
+                    if is_whitelisted {
+                        "black"
+                    } else {
+                        "gray"
+                    }
                 ) {
                     Ok(_) => {}
                     Err(e) => err = Some(Err(e)),
@@ -69,7 +81,7 @@ where
             for child in module.children() {
                 try!(writeln!(
                     &mut dot_file,
-                    "{} -> {} [style=dotted]",
+                    "{} -> {} [style=dotted, color=gray]",
                     item.id().as_usize(),
                     child.as_usize()
                 ));