How to make a custom referenceable "Lecture" element and include its date in the outline?

[PgBiel]

@eike

I would like it if it were possible to write

metadata(dt)
label("lecture-date")

instead of

[#metadata(dt) <lecture-date>]

in the date function. But alas, label does not produce content and therefore cannot be joined with metadata. (And

metadata(dt)
[<lecture-date>]

does not work because of label scoping rules.)

Of note, this doesn’t have much to do with the label syntax you’re using, it’s just that you need to be in markup mode to attach a label; they’re special-cased. That is, #{ figure(...) <lbl> } won’t work but #[#figure(...) <lbl>] will.

Typst 0.12 will have a more useful hint when this generates an error (see Improve error message for labels in code mode · Issue #4317 · typst/typst · GitHub).