Make py.Iter and make FOR_ITER use it

Author: ncw

py/internal.go

@@ -220,3 +220,15 @@ func SetAttr(self Object, keyObj Object, value Object) Object {
 	// FIXME should be TypeError
 	panic(fmt.Sprintf("TypeError: attribute name must be string, not '%s'", self.Type().Name))
 }
+
+// Call __next__ for the python object
+func Next(self Object) Object {
+	if I, ok := self.(I__next__); ok {
+		return I.M__next__()
+	} else if res, ok := TypeCall0(self, "__next__"); ok {
+		return res
+	}
+
+	// FIXME should be TypeError
+	panic(fmt.Sprintf("TypeError: '%s' object is not iterable", self.Type().Name))
+}

vm/eval.go

@@ -667,8 +667,7 @@ func do_FOR_ITER(vm *Vm, delta int32) {
 		}
 	}()
 	// FIXME should look in instance dictionary
-	it := vm.TOP().(py.I__next__)
-	r := it.M__next__()
+	r := py.Next(vm.TOP())
 	vm.PUSH(r)
 }