asynchronous input to flip flop clock

Ask him why he's using a latch? Note that latches are not built into the silicon, and hence are built out of fedback LUTs or with asynchronous control signals on the registers, i.e. complex structures that take more area, have worse performance, and are harder to timing analyze. Now, there are occasionally cases where a latch is necessary, but 99% of the time I see them they really want a register, or a latch is inferred by mistake because the user didn't define what a combinatorial node gets under a certain condition, and HDL dictates it "keeps its old value", i.e. a latch. And when I say 99% of the time, I'm lowballing my estimate.