Hojun-Cho
9f8df525c2
check-(c): a package importing itself (any spelling) is a hard error, mirroring Go. Predicate is leaf==owner at the N_USE/installdecl seam — sound only after the PREP commits (dotted-test renames, package-less boundary directive). Identical wording both stages; diagnostics-only, byte-id-neutral. 948 pins the reject in both compilers; 708's pos_selfimp (which pinned the abolished self-import skip) converts to neg_selfimp + new pos_crossmod preserving the param-shadow tolerance the case existed for. Checks (a) unused and (b)/(d) name-membership stay deferred to the multi-package arc: imports are filename-keyed pulls, so those need import->file provenance this compiler lacks.