rustc: Fix a missing application of the operator in fold_ty

Author: brson

src/rustc/middle/ty.rs

@@ -863,7 +863,7 @@ fn fold_sty(sty: sty, fldop: fn(t) -> t) -> sty {
 
 // Folds types from the bottom up.
 fn fold_ty(cx: ctxt, t0: t, fldop: fn(t) -> t) -> t {
-    let sty = fold_sty(get(t0).struct) {|t| fold_ty(cx, t, fldop) };
+    let sty = fold_sty(get(t0).struct) {|t| fold_ty(cx, fldop(t), fldop) };
     fldop(mk_t(cx, sty))
 }
 

src/test/run-pass/boxed-class-type-substitution.rs

@@ -0,0 +1,22 @@
+// Regression test that rustc doesn't recurse infinitely substituting
+// the boxed type parameter
+
+type Tree<T> = {
+    mut parent: option<T>,
+};
+
+fn empty<T>() -> Tree<T> { fail }
+
+class Box {
+    let tree: Tree<@Box>;
+
+    new() {
+        self.tree = empty();
+    }
+}
+
+enum layout_data = {
+    mut box: option<@Box>
+};
+
+fn main() { }