This is very nice!

Also ensures correct parsing of A in the example below, making A.UnderlyingType equal B instead of string. This will be required to correctly parse and propagate markers (#49).

Could you update test/api/v1/guestbook_types.go with an example that covers this?

Suggestion but feel free to rename:

// UnderlyingType tests that A.UnderlyingType equals B instead of string.
// +kubebuilder:object:root=true
type UnderlyingType struct {
	A A `json:"a,omitempty"`
}

type A B
type B string

I think we need to adapt RenderTypeLink a bit in both renderers because we can now have a link in a title which isn't rendered as expected.

Added the test in two commits, where the 2nd (319af4e) shows the changes introduced by this PR.

Wondering if we should update the rendering so that the test types we added renders as they used to 🤔

Having different descriptions, I guess it is nice to show both Underlying1 and Underlying2 :)

Last changes are 👍 👍 .

I think that the last bits to fix are for the rendering.

In asciidoc, it looks like xref doesn't work well when used in a title. See the example below where the cross reference for Underlying2 doesn't work:

The only idea I have for now is to use link:#, which seems a bit hacky?

For markdown, we need to add the backquotes conditionally otherwise the link is not rendered:

What if we display Underlying type: in both adoc and markdown. And show the type as in a struct field?