hdl._ast: make Signal.like work properly with ShapeCastables.

Fixes #1285.

Author: wanda-phi

amaranth/hdl/_ast.py

@@ -2177,13 +2177,14 @@ def like(cls, other, *, name=None, name_suffix=None, init=None, reset=None, src_
 
         Parameters
         ----------
-        other : Value
+        other : ValueLike
             Object to base this Signal on.
         """
+        cast_other = Value.cast(other)
         if name is not None:
             new_name = str(name)
         elif name_suffix is not None:
-            new_name = other.name + str(name_suffix)
+            new_name = cast_other.name + str(name_suffix)
         else:
             new_name = tracer.get_var_name(depth=2 + src_loc_at, default="$like")
         # TODO(amaranth-0.7): remove
@@ -2196,11 +2197,15 @@ def like(cls, other, *, name=None, name_suffix=None, init=None, reset=None, src_
         if isinstance(other, ValueCastable):
             shape = other.shape()
         else:
-            shape = Value.cast(other).shape()
+            shape = cast_other.shape()
         kw = dict(shape=shape, name=new_name)
-        if isinstance(other, Signal):
-            kw.update(init=other.init, reset_less=other.reset_less,
-                      attrs=other.attrs, decoder=other.decoder)
+        if isinstance(cast_other, Signal):
+            if isinstance(shape, ShapeCastable):
+                other_init = shape.from_bits(cast_other.init)
+            else:
+                other_init = cast_other.init
+            kw.update(init=other_init, reset_less=cast_other.reset_less,
+                      attrs=cast_other.attrs, decoder=cast_other.decoder)
         kw.update(kwargs)
         if init is not None:
             kw["init"] = init

tests/test_lib_data.py

@@ -641,6 +641,15 @@ def test_signal_like(self):
         s1 = Signal(data.StructLayout({"a": unsigned(1)}))
         s2 = Signal.like(s1)
         self.assertEqual(s2.shape(), data.StructLayout({"a": unsigned(1)}))
+        s3 = Signal.like(s1, name_suffix="a")
+        self.assertEqual(s3.as_value().name, "s1a")
+
+        s4 = Signal(data.StructLayout({"a": unsigned(2), "b": unsigned(3)}), init={"a": 1}, reset_less=True, attrs={"x": "y"})
+        s5 = Signal.like(s4)
+        self.assertEqual(s5.as_value().init, 0b00001)
+        self.assertEqual(s5.as_value().reset_less, True)
+        self.assertEqual(s5.as_value().attrs, {"x": "y"})
+
 
     def test_bug_837_array_layout_getitem_str(self):
         with self.assertRaisesRegex(TypeError,