This appears to be distinct from
GROOVY-9798 though appearing in similar circumstances.
When using static compilation (only; @TypeChecked works fine), using a method reference as a parameter expecting a Function results in a compiler error:
This error occurs both when using static GnomeDto from(Gnome g) as GnomeDto::from (correctly marked as a static reference in Eclipse, in case relevant) and when using GnomeDto toDto() as Gnome::toDto. In both cases explicitly adding as Function to the method reference resolves the problem.