Hojun-Cho
d09197af8e
Forward UTF-8 rune cursor per ref/hare/strings/iter.ha; iterator flattens Hare's anon-embedded utf8::decoder to explicit offs/src/reverse fields, next() copy-in/copy-out a local decoder and aborts on more/invalid per move()'s discipline. The iterator flattens Hare's anonymous-embedded utf8::decoder (ref/hare/strings/iter.ha:6-9) to explicit offs/src/reverse fields because ww has no anon-embed syntax. reverse is retained on the struct so riter populates it once utf8.prev (reverse DFA) and strings.prev land. next() copies the iterator's offs/src into a local utf8.decoder, delegates to utf8.next, then writes offs back; copy-in/copy-out is the cost of the flattened layout. more/invalid arms abort with "strings.next: invalid UTF-8", mirroring Hare's move() (ref/hare/strings/iter.ha:51-58) which aborts unconditionally on those arms. Deferred surface (no in-tree caller; follow-up tasks): prev, riter, iterstr, slice, position, move. prev specifically needs utf8.prev (reverse DFA), which isn't on the lib/encoding/utf8 surface yet. lib/strings/strings.ww moves off test/wcc/900_stdlib.c's standalone-compile list per the existing bufio/fmt/os precedent: the iterator's (rune | utf8.done) return type and the local utf8.decoder reference need cross-module type resolution, which the standalone w6c path doesn't do. Runtime coverage stays at 966_strings_run, which now exercises 21 signalled cases (was 15). The iterator's Hare-faithful `reverse: bool` field surfaced #33 (cstage cgen narrow-sret-field copy mis-width) during this port's pre-flight; that fix landed at0d96196ahead of this commit. Future bisecters tracking a narrow-field-related regression in lib/strings or sret-aware stdlib growth should consult #33 + this commit's bracket. The 4-arm match on utf8.next return surfaced #31 (wwstage fnretlookupmod) earlier in the same chain (b787641). Tests: - 6 new @test fns in stringstest.ww (signalled 16-21): empty, ASCII, 2-byte (café), 3-byte (こんにちは), 4-byte (🦀rust), mixed-width ("Hello, 世界! 🌍"). Each verifies forward iteration, done@EOI, and repeated next-after-done stays done (iter_empty). Multibyte literal limitation handled via `0xE9u32: rune` cast per existing pattern at stringstest.ww:82. 104/104 ok. 995_self_rebuild stays green (ww2==ww3==ww4 byte-id).