* right now the errors are like this:

```
>>> m.domains["sync2"] = Signal().eq(Signal())
Traceback (most recent call last):
  File "/home/whitequark/Projects/glasgow/software/glasgow/support/arepl.py", line 47, in _run_code
    future = eval(code, self.locals)
             ^^^^^^^^^^^^^^^^^^^^^^^
  File "<console>", line 1, in <module>
TypeError: '_ModuleBuilderDomainSet' object does not support item assignment
>>> m.domain.sync2 = cd_sync2 = ClockDomain()
Traceback (most recent call last):
  File "/home/whitequark/Projects/glasgow/software/glasgow/support/arepl.py", line 47, in _run_code
    future = eval(code, self.locals)
             ^^^^^^^^^^^^^^^^^^^^^^^
  File "<console>", line 1, in <module>
  File "/home/whitequark/.local/pipx/venvs/glasgow/lib/python3.11/site-packages/amaranth/hdl/_dsl.py", line 132, in __setattr__
    raise AttributeError("Cannot assign 'd.{}' attribute; did you mean 'd.{} +='?"
AttributeError: Cannot assign 'd.sync2' attribute; did you mean 'd.sync2 +='?
```