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lib.data: improve reset value handling for Union.

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* Reject union initialization with more than one reset value.
* Replace the reset value specified in the class definition with
  the one provided during initalization instead of merging.
This commit is contained in:
Catherine 2023-02-28 15:38:10 +00:00
parent c7ef05c894
commit 35561ea11a
2 changed files with 24 additions and 1 deletions
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7
amaranth/lib/data.py
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@ -431,10 +431,15 @@ class _AggregateMeta(ShapeCastable, type):
class _Aggregate(View, metaclass=_AggregateMeta):
def __init__(self, target=None, *, name=None, reset=None, reset_less=None,
attrs=None, decoder=None, src_loc_at=0):
if self.__class__._AggregateMeta__layout_cls is UnionLayout:
if reset is not None and len(reset) > 1:
raise ValueError("Reset value for at most one field can be provided for "
"a union class (specified: {})"
.format(", ".join(reset.keys())))
if target is None and hasattr(self.__class__, "_AggregateMeta__reset"):
if reset is None:
reset = self.__class__._AggregateMeta__reset
else:
elif self.__class__._AggregateMeta__layout_cls is not UnionLayout:
reset = {**self.__class__._AggregateMeta__reset, **reset}
super().__init__(self.__class__, target, name=name, reset=reset, reset_less=reset_less,
attrs=attrs, decoder=decoder, src_loc_at=src_loc_at + 1)