Fix for #1989, #1469: when marking in CC, walk fn@ box like other boxes

Author: nikomatsakis

src/rt/rust_cc.cpp

@@ -340,7 +340,8 @@ class mark : public shape::data<mark,shape::ptr> {
     void walk_fn2(char code) {
         switch (code) {
           case shape::SHAPE_BOX_FN: {
-              shape::data<mark,shape::ptr>::walk_fn_contents1();
+              shape::bump_dp<void*>(dp); // skip over the code ptr
+              walk_box2();               // walk over the environment ptr
               break;
           }
           case shape::SHAPE_BARE_FN:        // Does not close over data.

src/test/run-pass/issue-1989.rs

@@ -0,0 +1,24 @@
+// exec-env:RUST_CC_ZEAL=1
+
+enum maybe_pointy {
+    none,
+    p(@pointy)
+}
+
+type pointy = {
+    mut a : maybe_pointy,
+    mut f : fn@()->(),
+};
+
+fn empty_pointy() -> @pointy {
+    ret @{
+        mut a : none,
+        mut f : fn@()->(){},
+    }
+}
+
+fn main()
+{
+    let v = [empty_pointy(), empty_pointy()];
+    v[0].a = p(v[0]);
+}