self.emit('\n{} = "tfr.build_list"({})'.format(list_val, ', '.join(vals)))
    self._emit_with_loc(' : ({}) -> {}'.format(', '.join(tys), out_type), node)
    return (list_val, out_type)

  def visit_Tuple(self, node):
    return [self.visit(elt) for elt in node.elts]

  def visit_UnaryOp(self, node):
    value, ty = self.visit(node.operand)
    if isinstance(node.op, ast.USub):