Function lowerable 

pub fn lowerable<'a>(
    def: &ComponentDef<'a>,
    all: &[ComponentDef<'a>],
    types: Option<&TypeRegistry>,
    interner: &Interner,
) -> Result<(), NotLowerable>

Whether this component’s view is expressible as plain DOM calls.

types is the file’s type registry: whether a persisted store’s record field, or a typed request’s as <T>, goes through the derived JSON codec is the codec’s own question (JsonShapes), asked here of the registry the lowering emits the codec from.