>>> Signal(signed(10)).shift_right(11).shape()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mwk/amaranth/amaranth/hdl/_ast.py", line 970, in shape
    return Shape(a_shape.width, True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mwk/amaranth/amaranth/hdl/_ast.py", line 63, in __init__
    raise TypeError(f"Width of a signed value must be a positive integer, not {width}")
TypeError: Width of a signed value must be a positive integer, not 0