Mirrors Hare's `fs::flag` and `io::whence`:
export type flag = enum i32 {
RDONLY = 0,
WRONLY = 1,
RDWR = 2,
CREATE = 64, // 0o100
TRUNC = 512, // 0o1000
};
export type whence = enum i32 { SET = 0, CUR = 1, END = 2 };
open/tryopen/lseek signatures take the enum types (`flags: flag`,
`w: whence`) so callers get type-checked: `os.open(p, os.flag.RDONLY,
0)` is the correct shape, and `os.flag.WRONLY | os.flag.CREATE |
os.flag.TRUNC` typechecks as a `flag` via the same-named-type rule.
Callers in selfhost/cmd/{ww,w6c,w6a,w6l,wwdump} updated from
`os.O_RDONLY` etc. to `os.flag.RDONLY`. SYS_* syscall numbers kept
as `def` for now (internal-only, ABI surface, no Hare analogue in
this scope).
selfhost/test/smoke.ww keeps its standalone-compile property by
using a numeric literal (`0`, RDONLY's value) for the open flags
arg — probe 6 in 990_selfhost compiles smoke.ww with no `use`
expansion, so cross-module type refs like `os.flag.RDONLY` can't
resolve there. Untyped 0 → flag via type_isnum.
Hojun-Cho
b9443b1f33