Function documentation_model_merged 

pub fn documentation_model_merged<'a>(
    primary: (&'a Path, &'a str),
    files: impl IntoIterator<Item = (&'a Path, &'a str)>,
) -> Option<DocModel>

#1885: the documentation model for the unit that primary declares, merged across every file in files that declares the same unit.

files is (path, text) for the candidate files — typically the unit’s files from the project’s unit→sources map; any that declare another unit, a different kind, or a suite are skipped, and primary need not be among them (it is always included). The page title and unit_span come from primary, the file the page was asked for. The lede is the unit’s module doc from whichever file carries it (at most one does; should a broken project have more, the first in path order wins). Entries are every file’s declarations, files in path order and each file’s in source order, each tagged with its DocEntry::file. The result is the same page whichever of the unit’s files is primary, apart from the title’s span.