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hdl.ast: make it impossible to construct *Castable instances.

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Fixes #1072.
This commit is contained in:
Wanda 2024-02-09 03:09:42 +01:00 committed by Catherine
parent ace7aea375
commit 09854fa775
2 changed files with 22 additions and 0 deletions
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12
amaranth/hdl/_ast.py
View file

@ -191,6 +191,12 @@ class ShapeCastable:
The source code of the :mod:`amaranth.lib.data` module can be used as a reference for The source code of the :mod:`amaranth.lib.data` module can be used as a reference for
implementing a fully featured shape-castable object. implementing a fully featured shape-castable object.
""" """
def __init__(self, *args, **kwargs):
if type(self) is ShapeCastable:
raise TypeError("Can't instantiate abstract class ShapeCastable")
super().__init__(*args, **kwargs)
def __init_subclass__(cls, **kwargs): def __init_subclass__(cls, **kwargs):
if cls.as_shape is ShapeCastable.as_shape: if cls.as_shape is ShapeCastable.as_shape:
raise TypeError(f"Class '{cls.__name__}' deriving from 'ShapeCastable' must override " raise TypeError(f"Class '{cls.__name__}' deriving from 'ShapeCastable' must override "
@ -1616,6 +1622,12 @@ class ValueCastable:
from :class:`ValueCastable` is mutable, it is up to the user to ensure that it is not mutated from :class:`ValueCastable` is mutable, it is up to the user to ensure that it is not mutated
in a way that changes its representation after the first call to :meth:`as_value`. in a way that changes its representation after the first call to :meth:`as_value`.
""" """
def __init__(self, *args, **kwargs):
if type(self) is ValueCastable:
raise TypeError("Can't instantiate abstract class ValueCastable")
super().__init__(*args, **kwargs)
def __init_subclass__(cls, **kwargs): def __init_subclass__(cls, **kwargs):
if not hasattr(cls, "as_value"): if not hasattr(cls, "as_value"):
raise TypeError(f"Class '{cls.__name__}' deriving from `ValueCastable` must override " raise TypeError(f"Class '{cls.__name__}' deriving from `ValueCastable` must override "

10
tests/test_hdl_ast.py
View file

@ -191,6 +191,11 @@ class ShapeCastableTestCase(FHDLTestCase):
sc = MockShapeCastable(MockShapeCastable(unsigned(1))) sc = MockShapeCastable(MockShapeCastable(unsigned(1)))
self.assertEqual(Shape.cast(sc), unsigned(1)) self.assertEqual(Shape.cast(sc), unsigned(1))
def test_abstract(self):
with self.assertRaisesRegex(TypeError,
r"^Can't instantiate abstract class ShapeCastable$"):
ShapeCastable()
class ShapeLikeTestCase(FHDLTestCase): class ShapeLikeTestCase(FHDLTestCase):
def test_construct(self): def test_construct(self):
@ -1400,6 +1405,11 @@ class ValueCastableTestCase(FHDLTestCase):
vc = MockValueCastable(MockValueCastable(Signal())) vc = MockValueCastable(MockValueCastable(Signal()))
self.assertIsInstance(Value.cast(vc), Signal) self.assertIsInstance(Value.cast(vc), Signal)
def test_abstract(self):
with self.assertRaisesRegex(TypeError,
r"^Can't instantiate abstract class ValueCastable$"):
ValueCastable()
class ValueLikeTestCase(FHDLTestCase): class ValueLikeTestCase(FHDLTestCase):
def test_construct(self): def test_construct(self):