Fix a leak when box types are used via type descriptors.

src/Makefile

@@ -488,6 +488,7 @@ TEST_XFAILS_LLVM := $(TASK_XFAILS) \
                       lazy-and-or.rs \
                       lazy-init.rs \
                       lazychan.rs \
+                      leak-box-as-tydesc.rs \
                       lib-deque.rs \
                       lib-int.rs \
                       lib-io.rs \

src/boot/me/trans.ml

@@ -2562,8 +2562,8 @@ let trans_visitor
 
   and get_tydesc (idopt:node_id option) (ty:Ast.ty) : Il.cell =
     log cx "getting tydesc for %a" Ast.sprintf_ty ty;
-    let (ty, mut) = simplified_ty_innermost_was_mutable ty in
-    match ty with
+    let (ty', mut) = simplified_ty_innermost_was_mutable ty in
+    match ty' with
         Ast.TY_param (idx, _) ->
           (get_ty_param_in_current_frame idx)
       | t when has_parametric_types t ->

src/test/run-pass/leak-box-as-tydesc.rs

@@ -0,0 +1,7 @@
+fn leaky[T](T t) {
+}
+
+fn main() {
+  auto x = @10;
+  leaky[@int](x);
+}