gistfile1.diff

@@ -161,9 +165,18 @@ describe "A block" do
 
       lambda { @y.s(obj) { |a, b| } }.should raise_error(TypeError)
     end
+
+    it "raises an exception if #to_ary raises an exception" do
+      obj = mock("block yield to_ary raising an exception")
+      obj.should_receive(:to_ary).and_raise(ZeroDivisionError)
+
+      lambda { @y.s(obj) { |a, b| } }.should raise_error(ZeroDivisionError)
+    end
+
   end
 
   describe "taking |a, *b| arguments" do
+
     it "assigns 'nil' and '[]' to the arguments when no values are yielded" do
       @y.z { |a, *b| [a, b] }.should == [nil, []]
     end
diff --git a/vm/instructions.def b/vm/instructions.def
index e199f40..221e5aa 100644
--- a/vm/instructions.def
+++ b/vm/instructions.def
@@ -1320,6 +1320,9 @@ instruction cast_for_splat_block_arg() [ -- arguments ]
       if(CBOOL(obj->respond_to(state, G(sym_to_ary), cFalse))) {
         OnStack<1> os(state, obj);
         Object* ignored = obj->send(state, call_frame, G(sym_to_ary));
+        if(!ignored) {
+          RUN_EXCEPTION();
+        }
         if(!ignored->nil_p() && !kind_of<Array>(ignored)) {
           Exception::type_error(state, "to_ary must return an Array", call_frame);
           RUN_EXCEPTION();