Resolve failure of generic interface struct member

[dalance]

At

veryl/testcases/veryl/25_dependency_2.veryl

Line 64 in 917d06f

assign qux_if.qux = 0;

,
Changing from assign qux_if.qux = 0; to assign qux_if.qux.s = 0; causes the following error.

Error: undefined_identifier (https://doc.veryl-lang.org/book/07_appendix/02_semantic_error.html#undefined_identifier)

  × Package25 is undefined
    ╭─[/home/hatta/work/repos/veryl/testcases/veryl/25_dependency_2.veryl:64:12]
 63 │     inst qux_if      : veryl_sample4::qux_if::<Package25::<1>::S>;
 64 │     assign qux_if.qux.s = 0;
    ·            ──────┬─────
    ·                  ╰── Error location
 65 │     inst u6: Module25B::<Package25::<1>> (
    ╰────
  help: