x_rotation and y_rotation selector arguments are swapped
In the newest snapshots, the renamed entity selector arguments for detecting rotation appear to be outputting each other's values. x_rotation will output the entity's pitch while y_rotation will output the entity's yaw. Here are a couple screenshots from my testing that demonstrate it.
2018-01-18, 03:19 PM
2018-01-20, 04:56 AM
2018-01-18, 10:57 PM
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