Function shape_is_subshape_of 

pub fn shape_is_subshape_of(
    cx: &mut Cx,
    child: &dyn Shape,
    parent: &dyn Shape,
) -> Result<bool>

Decide whether child is a subshape of parent.

The generic walk compares ids and symbols, consults the shape’s own is_subshape_of override, treats the core Any and AnyShape symbols as a top for non-effectful shapes, and otherwise recurses through the declared parents.