Can't refer `struct member` from `always_comb` block

[taichi-ishitani]

Veryl reports unknown_member error for the code below.

proto package foo_proto_pkg {
    const WIDTH: u32;
    struct foo_struct {
      foo: logic<WIDTH>,
    }
}
package foo_pkg::<W: u32> for foo_proto_pkg {
    const WIDTH: u32 = W;
    struct foo_struct {
      foo: logic<WIDTH>,
    }
}
interface foo_if::<PKG: foo_proto_pkg> {
    var foo: PKG::foo_struct;
    modport mp {
        foo: input,
    }
}
module foo_module::<PKG: foo_proto_pkg> {
    inst foo: foo_if::<PKG>;

    var _foo: logic;
    always_comb {
        _foo = foo.foo.foo;
    }
}

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  💥 "PKG" doesn't have member "foo_struct"
    ╭─[:24:16]
 23 │     always_comb {
 24 │         _foo = foo.foo.foo;
    ·                ─────┬─────
    ·                     ╰── Error location
 25 │     }
    ╰────
  help: