message: Raise exception for mismatched argument type
diff: @@ -618,7 +618,12 @@ class OpDefLibrary(object):
  attr_value = base_types[0]
  if input_arg.type_attr in attrs:
  if attrs[input_arg.type_attr] != attr_value:
  - assert False, "Unreachable"
  + raise TypeError(
  + "Input '%s' of '%s' Op has type %s that does not "
  + "match type %s of argument '%s'." %
  + (input_name, op_type_name, dtypes.as_dtype(attr_value).name,
  + dtypes.as_dtype(attrs[input_arg.type_attr]).name,
  + inferred_from[input_arg.type_attr]))
  else:
  for base_type in base_types:
  _SatisfiesTypeConstraint(base_type,
  