Hey all! Newcomer here. I'm absolutely loving the language. I have a question though. The following code synthesizes without problems:
```py
from amaranth import *
from amaranth_boards.arty_s7 import ArtyS7_50Platform

class Top(Elaboratable):
    def elaborate(self, platform):
        m = Module()

        button_a = platform.request("button", 0).i
        button_b = platform.request("button", 1).i

        m.domains.cd = cd = ClockDomain()

        counter = Signal(4)
        m.d.cd += counter.eq(counter + 1)

        m.d.comb += cd.clk.eq(button_a & button_b) # Here

        for n in range(4):
            led = platform.request("led", n)
            m.d.comb += led.o.eq(counter[n])

        return m

ArtyS7_50Platform().build(Top(), do_program = True)
```
Yet if I replace line 16 with either `m.d.comb += cd.clk.eq(button_a)` or `m.d.comb += cd.clk.eq(button_b)` then Vivado refuses to go past placement. It seems so bizarre... does someone have a clue on why this might be happening? Board is an Arty S7, based on the Spartan 7.