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Implement RFC 46: Change Shape.cast(range(1)) to unsigned(0).

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Wanda 2024-02-03 03:13:51 +01:00 • committed by Catherine
parent 1fe7bd010f
commit 089213e19f
3 changed files with 12 additions and 4 deletions
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6
amaranth/hdl/_ast.py
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@ -93,8 +93,8 @@ class Shape:
* a :class:`Shape`, where the result is itself;
* an :class:`int`, where the result is :func:`unsigned(obj) <unsigned>`;
* a :class:`range`, where the result is wide enough to represent any element of the range,
and is signed if any element of the range is signed;
* a :class:`range`, where the result has minimal width required to represent all elements
of the range, and is signed if any element of the range is signed;
* an :class:`enum.Enum` whose members are all :ref:`constant-castable <lang-constcasting>`
or :class:`enum.IntEnum`, where the result is wide enough to represent any member of
the enumeration, and is signed if any member of the enumeration is signed;
@ -121,6 +121,8 @@ class Shape:
signed = obj[0] < 0 or obj[-1] < 0
width = max(bits_for(obj[0], signed),
bits_for(obj[-1], signed))
if obj[0] == obj[-1] == 0:
width = 0
return Shape(width, signed)
elif isinstance(obj, type) and issubclass(obj, Enum):
# For compatibility with third party enumerations, handle them as if they were