Add XFAIL'ed test for return-in-iter, call unimpl when we find it. Closes #100.

src/Makefile

@@ -370,6 +370,7 @@ TEST_XFAILS_X86 :=  $(MUT_BOX_XFAILS) \
                     test/run-pass/fn-lval.rs \
                     test/run-pass/generic-fn-infer.rs \
                     test/run-pass/generic-recursive-tag.rs \
+                    test/run-pass/iter-ret.rs \
                     test/run-pass/mlist-cycle.rs \
                     test/run-pass/mutable-vec-drop.rs \
                     test/run-pass/obj-as.rs \
@@ -430,6 +431,7 @@ TEST_XFAILS_LLVM := $(addprefix test/run-pass/, \
                       import.rs \
                       inner-module.rs \
                       iter-range.rs \
+                      iter-ret.rs \
                       large-records.rs \
                       lazy-and-or.rs \
                       lazy-init.rs \

src/boot/me/trans.ml

@@ -4532,6 +4532,8 @@ let trans_visitor
             calls
 
       | Ast.STMT_ret atom_opt ->
+          if get_stmt_depth cx stmt.id > 0
+          then unimpl (Some stmt.id) "ret within iterator-block";
           begin
             match atom_opt with
                 None -> ()

src/test/run-pass/iter-ret.rs

@@ -0,0 +1,13 @@
+iter x() -> int {
+}
+
+fn f() -> bool {
+    for each (int i in x()) {
+        ret true;
+    }
+    ret false;
+}
+
+fn main(vec[str] args) -> () {
+  f();
+}