split(fillet) broken

[MatthiasJ1]

b = extrude(Rectangle(10,10), 10)
b = split(b, Plane.XY.offset(2))

b = extrude(Rectangle(10,10), 10)
b = fillet(b.edges()<<Axis.Z, 4)
b = split(b, Plane.XY.offset(2))

[bernhard-42]

This works:

b = extrude(Rectangle(10,10), 10)
b = fillet(b.edges()<<Axis.Z, 4).solid()  # <===
b = split(b, Plane.XY.offset(2))

It seems to be a similar same problem as with extrude( ..., both=True)

obj = SlotCenterPoint((0, 0), (-6, 0), 5) - Pos(-6, 0) * Circle(1)
p2 = extrude(obj, 0.5, both=True)
s2 = split(p2, Plane.YZ.offset(-3), keep=Keep.BOTTOM)

fails, while

obj = SlotCenterPoint((0, 0), (-6, 0), 5) - Pos(-6, 0) * Circle(1)
p2 = extrude(obj, 0.5, both=True).solid()  # <===
s2 = split(p2, Plane.YZ.offset(-3), keep=Keep.BOTTOM)

succeeds.

Somehow in algebra mode a step is missing, because this works:

with BuildPart() as p:
    with BuildSketch() as s:
        Rectangle(10,10)
    extrude(amount=10)
    fillet(p.edges()<<Axis.Z, 4)
    split(bisect_by=Plane.XY.offset(2))

and this works:

with BuildPart() as p:
    with BuildSketch() as s:
        SlotCenterPoint((0, 0), (-6, 0), 5)
        with Locations((-6, 0)):
            Circle(1, mode=Mode.SUBTRACT)
    extrude(amount=0.5, both=True)
    split(bisect_by=Plane.YZ.offset(-3), keep=Keep.BOTTOM)

I guess this is something that happens in the builder at the end, but I can't find it.
Maybe @gumyr knows from experience what happens in the Builder that might need to be added to the direct API for algebra mode working without adding .solid()

[gumyr]

The problem here was multiple layers of Compound were getting added in some circumstances. I've changed the extrude operation to return Part(ShapeList(new_solids).solids()) which removes the extra Compound layer (which is what happens in the Builder when it's combined). I didn't change anything else because sometimes alternative shapes may be okay.

If you see any more of these, please let me know.