pub const fn concat_props<const N: usize>(
groups: &[&[PropMeta]],
) -> [PropMeta; N]Expand description
Join groups of prop metadata into one slice, at compile time.
The settings counterpart of usage_argv::spec::concat_flag_metas, for the same reason: a
flattened struct’s props belong in the parent’s registry, and the parent’s macro expansion
has only a type to reach them through.
N must be the summed length of groups. Two groups claiming the same name are refused
here, at compile time — the parent and the struct it flattens each declared it, a collision
neither expansion can see. A name is a key or an alias, because Registry::lookup checks
both and takes the first match: an alias colliding with another group’s key makes one of
the two unreachable by that name, which is the same bug as a duplicate key and quieter.