System information

• Have I written custom code (as opposed to using a stock example script provided in TensorFlow): Yes
• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Linux
• TensorFlow installed from (source or binary): pip install tf-nightly-gpu-2.0-preview
• TensorFlow version (use command below): v1.12.1-1847-gc095504 2.0.0-dev20190514
• Python version: 3.7.3

Describe the current behavior
Autograph complains when compiling functions with keyword-only arguments.

Example output:
W0515 01:46:22.158518 139635868194560 ag_logging.py:145] Entity <function f at 0x7eff8120c1e0> could not be transformed and will be executed as-is. Some features (e.g. tensor-dependent conditionals and loops) may not work as expected. Error details can be found in the logs when running with the env variable AUTOGRAPH_VERBOSITY >= 1. Please report this to the AutoGraph team. Cause: Unexpected error transforming <function f at 0x7eff8120c1e0>. If you believe this is due to a bug, please set the verbosity to 10 (on Linux, export AUTOGRAPH_VERBOSITY=10) and attach the full output when filing the bug report. Caused by: inconsistent nodes: None (NoneType) and None (NoneType)

Describe the expected behavior
Autograph works for keyword-only arguments

Code to reproduce the issue

import tensorflow as tf
@tf.function
def f(*, a):
     return a*2

f(a=0)