ww/lib/regex/whitebox_test.ww

// whitebox_test — in-package white-box @test probes for lib/regex
// internals NOT reachable from the black-box package regex_test: the
// thread/NFA-stepping engine (thread/newmatch, run_thread / add_thread /
// delete_thread / search), the program-shape leaves (find_last_groupstart
// / shift / parse_repetition), and is_consuming_inst. These bare-call
// unexported regex symbols, so they must live in `package regex` (unified
// with regex.ww) — Hare's same-package white-box model
// (ref/hare/regex/+test.ha colocates its internal tests inside the regex
// module; Hare excludes them from normal builds via build tags, ww via
// the non-T @test drop, #6). Load-bearing ww-compiler coverage (drove
// #34/#38/#44/#45/#48), not black-box-reachable.
//
// Canonical in-package white-box shape: `package regex;` in a *_test.ww
// file, assembled with the production `regex` sources by the package
// planner. Importing regex as a dependency still strips these tests.
// Public-API tests remain a separate `package regex_test` binary in
// lib/regex/regex_test.ww
// (CLAUDE.md rule 9).
package regex;

import io;
import memio;
import strings;
import types;

// The thread struct (regex.ha:55-64) is in tree ahead of its engine
// consumers so the pending #15/#17 fix probes exercise the real type.
// Pin the field layout via the P6-proven wide-literal append + a
// depth-1 read-back row per appended thread; the Hare `...` partial
// fill (P5) must zero everything the second row's literal omits.
// root_capture has NO row: every read route into it is
// compiler-blocked today — the depth-2 chain behind the index links
// the field as a global (#6 F4), the element let-copy is #7 F5, and
// a probed `&threads[i].root_capture` deref segfaults byte-id on
// both stages — so its row lands with those fixes.
type texp = struct {
	pc: size,
	start_idx: size,
	start_bytesize: size,
	matched: bool,
	failed: bool,
	// .len reads as i32 (check.c:1239), so the count columns match it
	ncaps: i32,
	nreps: i32,
};

@test fn thread_shape() void = {
	let rc: capture = capture {
		content = "ab", start = 1, start_bytesize = 1,
		end = 2, end_bytesize = 2,
	};
	let pcaps: []capture = [];
	append(pcaps, rc);
	let prep: []size = [];
	append(prep, (7: size));
	let threads: []thread = [];
	append(threads, thread {
		pc = 5,
		start_idx = 6,
		start_bytesize = 7,
		root_capture = rc,
		captures = pcaps,
		rep_counters = prep,
		matched = false,
		failed = true,
	});
	append(threads, thread { pc = 9, ... });
	let want: [2]texp = [
		texp { pc = 5, start_idx = 6, start_bytesize = 7,
			matched = false, failed = true,
			ncaps = 1, nreps = 1 },
		texp { pc = 9, start_idx = 0, start_bytesize = 0,
			matched = false, failed = false,
			ncaps = 0, nreps = 0 },
	];
	assert(!(len(threads) != len(want)));
	let i: i32 = 0;
	for (i < len(want)) {
		assert(!(threads[i].pc != want[i].pc));
		assert(!(threads[i].start_idx != want[i].start_idx));
		if (threads[i].start_bytesize != want[i].start_bytesize) {
			abort();
		};
		assert(!(threads[i].matched != want[i].matched));
		assert(!(threads[i].failed != want[i].failed));
		assert(!(threads[i].captures.len != want[i].ncaps));
		assert(!(threads[i].rep_counters.len != want[i].nreps));
		i += 1;
	};
};

// newmatch (regex.ha:66) must discriminate nominally against plain
// void — and against nomem, the third payload-free member — across
// run_thread's (void | newmatch | nomem) return boundary: the P8
// shape on the real lib type, one row per returned member.
fn nm_probe(x: i32) (void | newmatch | nomem) = {
	if (x == 1) {
		let nm: newmatch;
		return nm;
	};
	if (x == 2) {
		let n: nomem;
		return n;
	};
	return;
};

type nmexp = struct {
	arg: i32,
	want_nm: bool,
	want_void: bool,
	want_nomem: bool,
};

@test fn newmatch_discriminates() void = {
	let rows: [3]nmexp = [
		nmexp { arg = 1, want_nm = true, want_void = false,
			want_nomem = false },
		nmexp { arg = 0, want_nm = false, want_void = true,
			want_nomem = false },
		nmexp { arg = 2, want_nm = false, want_void = false,
			want_nomem = true },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let r: (void | newmatch | nomem) = nm_probe(rows[i].arg);
		assert(!((r is newmatch) != rows[i].want_nm));
		assert(!((r is void) != rows[i].want_void));
		assert(!((r is nomem) != rows[i].want_nomem));
		i += 1;
	};
};

// is_consuming_inst must discriminate the three consuming kinds from
// the seven non-consuming ones across all 10 inst variants
// (regex.ha:553-555) — the tranche-A-deferred row, graduated by the
// #19 >48B by-value arg wiring. Sequential typed-let + helper calls,
// not a [10](inst, bool) table: tagged-element array literals
// under-copy (#12), and a cast/literal rvalue arg source is
// #38b-unwired, so each value goes through a typed let (the
// #19-landed ident source).
fn ic_one(v: inst, want: bool) void = {
	assert(!(is_consuming_inst(v) != want));
};

@test fn is_consuming_kinds() void = {
	let lit: inst = ('a': inst_lit);
	ic_one(lit, true);
	let av: inst_any;
	let any: inst = av;
	ic_one(any, true);
	let cs: inst = (inst_charset { idx = 0, is_positive = true });
	ic_one(cs, true);
	let kv: inst_skip;
	let sk: inst = kv;
	ic_one(sk, false);
	let sp: inst = ((5: size): inst_split);
	ic_one(sp, false);
	let jm: inst = ((6: size): inst_jump);
	ic_one(jm, false);
	let mt: inst = (false: inst_match);
	ic_one(mt, false);
	let gs: inst = ((2: size): inst_groupstart);
	ic_one(gs, false);
	let gv: inst_groupend;
	let ge: inst = gv;
	ic_one(ge, false);
	let rp: inst = (inst_repeat {
		id = 1, origin = 4, min = (2: size), max = void,
	});
	ic_one(rp, false);
};

// delete_thread (regex.ha:547-551) removes exactly the indexed
// element and preserves order; its frees are no-ops (no-free
// runtime), so the survivors' capture headers stay readable.
@test fn delete_thread_middle() void = {
	let caps: []capture = [];
	append(caps, capture {
		content = "x", start = 0, start_bytesize = 0,
		end = 1, end_bytesize = 1,
	});
	let ts: []thread = [];
	append(ts, thread { pc = 1, start_idx = 11, captures = caps, ... });
	append(ts, thread { pc = 2, start_idx = 22, ... });
	append(ts, thread { pc = 3, start_idx = 33, ... });
	delete_thread(1, &ts);
	assert(!(len(ts) != 2));
	assert(!(ts[0].pc != (1: size)));
	assert(!(ts[0].start_idx != (11: size)));
	assert(!(ts[0].captures.len != 1));
	assert(!(ts[1].pc != (3: size)));
	assert(!(ts[1].start_idx != (33: size)));
	assert(!(ts[1].captures.len != 0));
	// boundary rows: delete at the last index, then at index 0 down
	// to empty — the failed-sweep loop (regex.ha:891-896) deletes at
	// every position including both ends.
	delete_thread(1, &ts);
	assert(!(len(ts) != 1));
	assert(!(ts[0].pc != (1: size)));
	delete_thread(0, &ts);
	assert(!(len(ts) != 0));
};

// add_thread (regex.ha:557-587): same-pc dedup suppression fires only
// when the existing thread is unmatched AND started strictly earlier
// than the parent (ha:561-565); otherwise the child appends,
// inheriting the parent's start/matched/failed with DUPLICATED
// capture/rep_counter slices (empty parent → empty dup, ha:569/572)
// and a zeroed root_capture.
@test fn add_thread_dedup_inherit() void = {
	let ts: []thread = [];
	append(ts, thread { pc = 0, start_idx = 5, start_bytesize = 4,
		matched = false, failed = true, ... });
	// inherit: fresh pc, parent fields copied, rest zeroed
	let r: (void | nomem) = add_thread(&ts, 0, 7);
	assert(!(!(r is void)));
	assert(!(len(ts) != 2));
	assert(!(ts[1].pc != (7: size)));
	assert(!(ts[1].start_idx != (5: size)));
	assert(!(ts[1].start_bytesize != (4: size)));
	assert(!(ts[1].matched));
	assert(!(!ts[1].failed));
	assert(!(ts[1].captures.len != 0));
	assert(!(ts[1].rep_counters.len != 0));
	assert(!(ts[1].root_capture.content.len != 0));
	assert(!(ts[1].root_capture.end != (0: size)));
	// same-pc same-start does NOT suppress (strict <, ha:563-565)
	let r2: (void | nomem) = add_thread(&ts, 0, 7);
	assert(!(!(r2 is void)));
	assert(!(len(ts) != 3));
	// an earlier-started unmatched existing thread DOES suppress
	let ts2: []thread = [];
	append(ts2, thread { pc = 0, start_idx = 5, ... });
	append(ts2, thread { pc = 7, start_idx = 2, ... });
	let r3: (void | nomem) = add_thread(&ts2, 0, 7);
	assert(!(!(r3 is void)));
	assert(!(len(ts2) != 2));
	// a MATCHED existing thread never suppresses
	let ts3: []thread = [];
	append(ts3, thread { pc = 0, start_idx = 5, ... });
	append(ts3, thread { pc = 7, start_idx = 2, matched = true, ... });
	let r4: (void | nomem) = add_thread(&ts3, 0, 7);
	assert(!(!(r4 is void)));
	assert(!(len(ts3) != 3));
	assert(!(ts3[2].pc != (7: size)));
	assert(!(ts3[2].start_idx != (5: size)));
};

// add_thread dup (regex.ha:568-573): the child carries a COPY of the
// parent's captures/rep_counters — values equal, backing independent
// in both directions (mutate parent → child unchanged, mutate child →
// parent unchanged). Empty parent → empty dup (the pre-flip rows above
// stay byte-for-byte). Driven directly, the dedup-test precedent.
@test fn add_thread_dup_independence() void = {
	let caps: []capture = [];
	append(caps, capture {
		content = "ab", start = 1, start_bytesize = 1,
		end = 2, end_bytesize = 2,
	});
	append(caps, capture {
		content = "c", start = 3, start_bytesize = 3,
		end = 4, end_bytesize = 4,
	});
	let reps: []size = [];
	append(reps, (5: size));
	append(reps, (6: size));
	let ts: []thread = [];
	append(ts, thread { pc = 0, start_idx = 1, captures = caps,
		rep_counters = reps, ... });
	let r: (void | nomem) = add_thread(&ts, 0, 9);
	assert(!(!(r is void)));
	assert(!(len(ts) != 2));
	// dup carried the parent's values
	assert(!(ts[1].captures.len != 2));
	assert(!(strings.compare(ts[1].captures[0].content, "ab") != 0));
	assert(!(ts[1].captures[0].start != (1: size)));
	assert(!(ts[1].captures[1].end != (4: size)));
	assert(!(ts[1].rep_counters.len != 2));
	assert(!(ts[1].rep_counters[0] != (5: size)));
	assert(!(ts[1].rep_counters[1] != (6: size)));
	// independence, parent → child: mutate the parent post-add
	ts[0].captures[0].start = 100;
	ts[0].captures[0].content = "zz";
	ts[0].rep_counters[0] = 77;
	assert(!(ts[1].captures[0].start != (1: size)));
	assert(!(strings.compare(ts[1].captures[0].content, "ab") != 0));
	assert(!(ts[1].rep_counters[0] != (5: size)));
	// independence, child → parent
	ts[1].captures[1].end = 200;
	ts[1].rep_counters[1] = 88;
	assert(!(ts[0].captures[1].end != (4: size)));
	assert(!(ts[0].rep_counters[1] != (6: size)));
	// empty parent → empty dup
	let ts2: []thread = [];
	append(ts2, thread { pc = 0, ... });
	let r2: (void | nomem) = add_thread(&ts2, 0, 3);
	assert(!(!(r2 is void)));
	assert(!(ts2[1].captures.len != 0));
	assert(!(ts2[1].rep_counters.len != 0));
};

// run_thread (regex.ha:589-742) driven directly over compile("ab")'s
// real program [skip, lit 'a', lit 'b', match(false)] — the arms
// fold-2a can emit. Phases: parked-skip spawn (len 1→2, parent pc
// unmoved — the unanchored-restart engine), lit advance, lit
// mismatch (failed=true AND pc still steps — ha:741 runs regardless
// of the arm's verdict), EOF on a consuming pc (failed, pc frozen),
// match arm (root_capture spans start_bytesize..str_bytesize +
// matched + `is newmatch`), and the matched-thread early return
// (ha:599-601).
@test fn run_thread_literal_program() void = {
	// typed-let + match receive, the compile_literal_program shape
	let c: (regex | error | nomem) = compile("ab");
	match (c) {
	case let re: regex => {
		// skip spawn: thread 0 parks on the skip, child enters at pc 1
		let ra: (rune | io.eof) = 'a';
		let ts: []thread = [];
		append(ts, thread { pc = 0, ... });
		let r1: (void | newmatch | nomem) = run_thread(0, &re, "ab", &ts, ra, 0, 0);
		assert(!(!(r1 is void)));
		assert(!(len(ts) != 2));
		assert(!(ts[0].pc != (0: size)));
		assert(!(ts[1].pc != (1: size)));
		assert(!(ts[1].failed));

		// lit match advances pc past 'a'
		let r2: (void | newmatch | nomem) = run_thread(1, &re, "ab", &ts, ra, 0, 0);
		assert(!(!(r2 is void)));
		assert(!(ts[1].pc != (2: size)));
		assert(!(ts[1].failed));

		// lit mismatch fails the thread; pc steps anyway (ha:741)
		let rx: (rune | io.eof) = 'x';
		let r3: (void | newmatch | nomem) = run_thread(1, &re, "ab", &ts, rx, 1, 1);
		assert(!(!(r3 is void)));
		assert(!(!ts[1].failed));
		assert(!(ts[1].pc != (3: size)));

		// EOF on a consuming pc fails the thread before pc steps
		let ev: io.eof;
		let reof: (rune | io.eof) = ev;
		let ts2: []thread = [];
		append(ts2, thread { pc = 1, ... });
		let r4: (void | newmatch | nomem) = run_thread(0, &re, "ab", &ts2, reof, 2, 2);
		assert(!(!(r4 is void)));
		assert(!(!ts2[0].failed));
		assert(!(ts2[0].pc != (1: size)));

		// match arm: root_capture spans start_bytesize..str_bytesize,
		// matched set, newmatch returned
		let ts3: []thread = [];
		append(ts3, thread { pc = 3, ... });
		let r5: (void | newmatch | nomem) = run_thread(0, &re, "ab", &ts3, reof, 2, 2);
		assert(!(!(r5 is newmatch)));
		assert(!(!ts3[0].matched));
		assert(!(ts3[0].failed));
		assert(!(ts3[0].root_capture.start != (0: size)));
		assert(!(ts3[0].root_capture.start_bytesize != (0: size)));
		assert(!(ts3[0].root_capture.end != (2: size)));
		assert(!(ts3[0].root_capture.end_bytesize != (2: size)));
		assert(!(strings.compare(ts3[0].root_capture.content, "ab") != 0));

		// an already-matched thread is inert (ha:599-601): void
		// return, state untouched
		let r6: (void | newmatch | nomem) = run_thread(0, &re, "ab", &ts3, ra, 3, 3);
		assert(!(!(r6 is void)));
		assert(!(ts3[0].root_capture.end != (2: size)));

		// idx/bytesize split: every all-ASCII row has idx ==
		// bytesize, so a port swapping start/start_bytesize (or
		// end/end_bytesize) in root_capture passes them. One 2-byte
		// rune ('ß') consumed before the match start makes all four
		// values distinct: start=1 start_bytesize=2 end=3
		// end_bytesize=4; content = bytes[2:4] = "ab".
		let ts4: []thread = [];
		append(ts4, thread { pc = 3, start_idx = 1, start_bytesize = 2, ... });
		let r7: (void | newmatch | nomem) = run_thread(0, &re, "ßab", &ts4, reof, 3, 4);
		assert(!(!(r7 is newmatch)));
		assert(!(ts4[0].root_capture.start != (1: size)));
		assert(!(ts4[0].root_capture.start_bytesize != (2: size)));
		assert(!(ts4[0].root_capture.end != (3: size)));
		assert(!(ts4[0].root_capture.end_bytesize != (4: size)));
		assert(!(strings.compare(ts4[0].root_capture.content, "ab") != 0));
		finish(&re);
	};
	case => abort();
	};
};

// The anchored route (ha:621-624) needs a (true: inst_match) program
// — compile() can't emit `$` yet, so it is HAND-BUILT — pinned from
// both sides: anchored + string-not-exhausted fails the thread;
// anchored + EOF falls through to the match (empty content).
@test fn run_thread_anchored_route() void = {
	let insts: []inst = [];
	append(insts, (true: inst_match));
	let re: regex;
	re.insts = insts;
	re.n_reps = 0;

	let ra: (rune | io.eof) = 'a';
	let ts: []thread = [];
	append(ts, thread { pc = 0, ... });
	let r1: (void | newmatch | nomem) = run_thread(0, &re, "ab", &ts, ra, 0, 0);
	assert(!(!(r1 is void)));
	assert(!(!ts[0].failed));
	assert(!(ts[0].matched));

	let ev: io.eof;
	let reof: (rune | io.eof) = ev;
	let ts2: []thread = [];
	append(ts2, thread { pc = 0, ... });
	let r2: (void | newmatch | nomem) = run_thread(0, &re, "", &ts2, reof, 0, 0);
	assert(!(!(r2 is newmatch)));
	assert(!(!ts2[0].matched));
	assert(!(ts2[0].root_capture.content.len != 0));
	assert(!(ts2[0].root_capture.end != (0: size)));
};

// search (regex.ha:746-898) driven DIRECTLY (private fn, package-regex
// test) over memio-backed streams — the exec surface (test/find) is
// tranche D. Each match row pins the root capture's four indices plus
// content; the multibyte row keeps idx != bytesize honest. Rows share
// (expr, input, need_captures, want) shape — the P12 struct-row table.
type scase = struct {
	expr: str,
	input: str,
	nc: bool,
	start: size,
	sb: size,
	end: size,
	eb: size,
	content: str,
};

@test fn search_matches() void = {
	let rows: [6]scase = [
		// full match mid-string: skip-respawn + dispatch +
		// all_matched exit
		scase { expr = "ab", input = "xab", nc = true,
			start = 1, sb = 1, end = 3, eb = 3, content = "ab" },
		// mismatch-restart: the idx-0 child fails and is swept; the
		// restarted thread wins (failed-sweep interplay)
		scase { expr = "bcd", input = "abcd", nc = true,
			start = 1, sb = 1, end = 4, eb = 4, content = "bcd" },
		// leftmost-longest best-pick + first_match_idx trim
		scase { expr = "aa", input = "aaa", nc = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "aa" },
		// zero-length: the all_matched path with matchlen 0 must
		// NOT take the need_captures=false early-exit (ha:845
		// requires matchlen > 0) — hence nc=false expecting the
		// FULL one-capture result, not the empty early-exit slice
		scase { expr = "", input = "", nc = false,
			start = 0, sb = 0, end = 0, eb = 0, content = "" },
		// multibyte: the 2-byte ß before the match start splits
		// every idx from its bytesize; inst_any consumes 'x'
		scase { expr = "b.d", input = "aßbxd", nc = true,
			start = 2, sb = 3, end = 5, eb = 6, content = "bxd" },
		// dedup-heavy: same-pc threads spawn on every step across
		// >=3 passes (ha:872-889); the pick must stay stable.
		// Result stability is the only external pin available this
		// fold: 2a programs are all fixed-length, every match ties
		// on match_len, and best-pick's insertion-order tiebreak
		// alone yields leftmost — so the dedup sweep and the
		// leftmost trim are result-invisible (mutation-verified:
		// disabling either still passes this table; disabling the
		// failed sweep hangs). Both turn result- and
		// termination-visible with the split/star fold.
		scase { expr = "aa", input = "aaaa", nc = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "aa" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex | error | nomem) = compile(ex);
		match (c) {
		case let re: regex => {
			let strm: memio.stream =
				memio.fixed(strings.toutf8(inp));
			let r: (void | []capture | nomem) =
				search(&re, inp, &strm.vt, rows[i].nc);
			assert(!(!(r is []capture)));
			let caps: []capture = r as []capture;
			assert(!(len(caps) != 1));
			assert(!(caps[0].start != rows[i].start));
			assert(!(caps[0].start_bytesize != rows[i].sb));
			assert(!(caps[0].end != rows[i].end));
			assert(!(caps[0].end_bytesize != rows[i].eb));
			let wc: str = rows[i].content;
			if (strings.compare(caps[0].content, wc) != 0) {
				abort();
			};
			result_free(caps);
			finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// ha:845-847: a non-zero-length newmatch with need_captures=false
// returns the empty result immediately, skipping the best-pick pass.
@test fn search_early_exit() void = {
	let c: (regex | error | nomem) = compile("ab");
	match (c) {
	case let re: regex => {
		let strm: memio.stream = memio.fixed(strings.toutf8("xab"));
		let r: (void | []capture | nomem) =
			search(&re, "xab", &strm.vt, false);
		assert(!(!(r is []capture)));
		let caps: []capture = r as []capture;
		assert(!(len(caps) != 0));
		result_free(caps);
		finish(&re);
	};
	case => abort();
	};
};

// void rows: no match anywhere ("ab" over "xyz" — every thread fails,
// the list drains, ha:777-779) and EOF mid-pattern ("ab" over "a" —
// the consuming-inst EOF fail).
@test fn search_no_match() void = {
	let c: (regex | error | nomem) = compile("ab");
	match (c) {
	case let re: regex => {
		let strm: memio.stream = memio.fixed(strings.toutf8("xyz"));
		let r: (void | []capture | nomem) =
			search(&re, "xyz", &strm.vt, true);
		assert(!(!(r is void)));
		let strm2: memio.stream = memio.fixed(strings.toutf8("a"));
		let r2: (void | []capture | nomem) =
			search(&re, "a", &strm2.vt, true);
		assert(!(!(r2 is void)));
		finish(&re);
	};
	case => abort();
	};
};

// find_last_groupstart (regex.ha:104-119) — driven directly (private
// fn): no inst_groupstart exists in any fold-3 program, so the error
// arm is the live one; pin its exact text. A hand-built groupstart
// row pins the success arm the group fold will rely on.
@test fn find_last_groupstart_cases() void = {
	let insts: []inst = [];
	append(insts, ('a': inst_lit));
	match (find_last_groupstart(insts)) {
	case let e: error => {
		if (strings.compare((e: str), "Unmatched ')'") != 0) {
			abort();
		};
	};
	case => abort();
	};
	append(insts, ((1: size): inst_groupstart));
	append(insts, ('b': inst_lit));
	match (find_last_groupstart(insts)) {
	case let sz: size => { assert(!(sz != 1)); };
	case => abort();
	};
};

// instsig (copy; the external black-box file keeps the
// original for its fold3/fold4 program-shape pins).
// instsig — flatten an inst for the table-driven program pins below:
// kind base + payload. Takes the 56B inst by value (the #19-landed
// is_consuming_inst shape).
fn instsig(v: inst) i64 = {
	match (v) {
	case let l: inst_lit => return 1000 + ((l: rune): i64);
	case inst_skip => return 2000;
	case inst_any => return 3000;
	case let s: inst_split => return 4000 + ((s: size): i64);
	case let j: inst_jump => return 5000 + ((j: size): i64);
	case let m: inst_match => {
		if ((m: bool)) { return 6001; };
		return 6000;
	};
	case let g: inst_groupstart => return 7000 + ((g: size): i64);
	case inst_groupend => return 8000;
	case let c: inst_charset => {
		// fold 4: 10xxx positive / 11xxx negated, + charset index
		if (c.is_positive) { return 10000 + (c.idx: i64); };
		return 11000 + (c.idx: i64);
	};
	case => return 9999;
	};
};

// shift (regex.ha:123-133) — driven directly over a sub-slice view:
// jump/split payloads in the view bump by one, the element before the
// view and non-jump kinds are untouched (the PE3/PE4 shapes).
@test fn shift_direct() void = {
	let insts: []inst = [];
	append(insts, ((3: size): inst_jump));
	append(insts, ('a': inst_lit));
	append(insts, ((5: size): inst_split));
	append(insts, ((7: size): inst_jump));
	shift(insts[1:]);
	assert(!(instsig(insts[0]) != 5003));
	assert(!(instsig(insts[1]) != 1097));
	assert(!(instsig(insts[2]) != 4006));
	assert(!(instsig(insts[3]) != 5008));
};

// run_thread inst_groupstart / inst_groupend driven over HAND-BUILT
// programs (the anchored-route precedent): compile() composition is
// pinned by the find/submatch tables below; these pin the arm
// mechanics — fill-grow to idx+1, the SIZE_MAX open sentinel,
// innermost-unclosed close order, content from the bytesize span,
// and the closed-group re-entry overwrite (the ha:642 assert's
// PASSING direction).
@test fn run_thread_group_arms() void = {
	// groupstart (ha:636-652): grows captures to idx+1 (zero-filled
	// below idx), stamps start/start_bytesize, opens with
	// end = end_bytesize = SIZE_MAX
	let insts: []inst = [];
	append(insts, ((1: size): inst_groupstart));
	append(insts, ('a': inst_lit));
	append(insts, (false: inst_match));
	let re: regex;
	re.insts = insts;
	re.n_reps = 0;
	let ra: (rune | io.eof) = 'a';
	let ts: []thread = [];
	append(ts, thread { pc = 0, ... });
	let r1: (void | newmatch | nomem) = run_thread(0, &re, "ab", &ts, ra, 2, 3);
	assert(!(!(r1 is void)));
	assert(!(ts[0].captures.len != 2));
	// the fill element below idx is zeroed
	assert(!(ts[0].captures[0].end != (0: size)));
	assert(!(ts[0].captures[0].content.len != 0));
	// the opened group: start stamped, end still the open sentinel
	assert(!(ts[0].captures[1].start != (2: size)));
	assert(!(ts[0].captures[1].start_bytesize != (3: size)));
	assert(!(ts[0].captures[1].end != types.SIZE_MAX));
	assert(!(ts[0].captures[1].end_bytesize != types.SIZE_MAX));
	// groupstart is non-consuming: pc stepped through it, then the
	// lit consumed
	assert(!(ts[0].pc != (2: size)));

	// groupend (ha:653-668): two open groups — the INNERMOST
	// (highest index) closes first; back-to-back groupends close
	// inner then outer in ONE call; content = str_bytes[
	// start_bytesize:end_bytesize]
	let insts2: []inst = [];
	let gv: inst_groupend;
	let ge: inst = gv;
	append(insts2, ge);
	append(insts2, ge);
	append(insts2, ('x': inst_lit));
	append(insts2, (false: inst_match));
	let re2: regex;
	re2.insts = insts2;
	re2.n_reps = 0;
	let caps: []capture = [];
	append(caps, capture { content = "", start = 1, start_bytesize = 1,
		end = types.SIZE_MAX, end_bytesize = types.SIZE_MAX });
	append(caps, capture { content = "", start = 2, start_bytesize = 2,
		end = types.SIZE_MAX, end_bytesize = types.SIZE_MAX });
	let ts2: []thread = [];
	append(ts2, thread { pc = 0, captures = caps, ... });
	let rx: (rune | io.eof) = 'x';
	let r2: (void | newmatch | nomem) = run_thread(0, &re2, "abcd", &ts2, rx, 3, 4);
	assert(!(!(r2 is void)));
	assert(!(ts2[0].captures[1].end != (3: size)));
	assert(!(ts2[0].captures[1].end_bytesize != (4: size)));
	assert(!(strings.compare(ts2[0].captures[1].content, "cd") != 0));
	assert(!(ts2[0].captures[0].end != (3: size)));
	assert(!(ts2[0].captures[0].end_bytesize != (4: size)));
	assert(!(strings.compare(ts2[0].captures[0].content, "bcd") != 0));
	assert(!(ts2[0].pc != (3: size)));

	// closed-group re-entry: groupstart over an already-CLOSED idx
	// passes the ha:642 assert (end != SIZE_MAX) and re-opens fresh
	let insts3: []inst = [];
	append(insts3, ((0: size): inst_groupstart));
	append(insts3, ('a': inst_lit));
	append(insts3, (false: inst_match));
	let re3: regex;
	re3.insts = insts3;
	re3.n_reps = 0;
	let caps3: []capture = [];
	append(caps3, capture { content = "ab", start = 0, start_bytesize = 0,
		end = 2, end_bytesize = 2 });
	let ts3: []thread = [];
	append(ts3, thread { pc = 0, captures = caps3, ... });
	let r3: (void | newmatch | nomem) = run_thread(0, &re3, "aba", &ts3, ra, 2, 2);
	assert(!(!(r3 is void)));
	assert(!(ts3[0].captures.len != 1));
	assert(!(ts3[0].captures[0].start != (2: size)));
	assert(!(ts3[0].captures[0].end != types.SIZE_MAX));
	assert(!(ts3[0].captures[0].content.len != 0));
};

// parse_repetition rows (regex.ha:486-545) — DIRECT private-fn table
// (the leaf fn lands ahead of its `{`-arm consumer; tranche-A
// precedent). Expectations hand-executed from Hare's own code paths:
// the input is everything AFTER `{` (compile passes iterstr's rest),
// single-arg `{n}` sets max = min and replen = len(n) (ha:500-503,
// 539-541); two-arg replen = len(min) + 1 + len(max) (ha:543); an
// empty min is 0 (ha:524) while an empty max stays void (ha:527 —
// the `{n,}` open bound); a `,` BEYOND the first `}` is not a
// two-arg form (ha:499). The two error texts are byte-exact
// (ha:492/521/531-536). max_void distinguishes "expect void" from
// "expect maxv"; err != "" rows expect that exact error.
type prrow = struct {
	input: str,
	minv: size,
	maxv: size,
	max_void: bool,
	replen: size,
	err: str,
};

@test fn parse_repetition_cases() void = {
	let rows: [13]prrow = [
		prrow { input = "2}", minv = 2, maxv = 2, max_void = false,
			replen = 1, err = "" },
		prrow { input = "2}$", minv = 2, maxv = 2, max_void = false,
			replen = 1, err = "" },
		// comma AFTER the endbrace — still single-arg (ha:499)
		prrow { input = "2},5", minv = 2, maxv = 2, max_void = false,
			replen = 1, err = "" },
		prrow { input = "1,2}", minv = 1, maxv = 2, max_void = false,
			replen = 3, err = "" },
		prrow { input = ",2}", minv = 0, maxv = 2, max_void = false,
			replen = 2, err = "" },
		prrow { input = ",0}", minv = 0, maxv = 0, max_void = false,
			replen = 2, err = "" },
		prrow { input = "2,}", minv = 2, maxv = 0, max_void = true,
			replen = 2, err = "" },
		prrow { input = ",}", minv = 0, maxv = 0, max_void = true,
			replen = 1, err = "" },
		prrow { input = "12,34}xyz", minv = 12, maxv = 34,
			max_void = false, replen = 5, err = "" },
		prrow { input = "-1,2}", minv = 0, maxv = 0, max_void = false,
			replen = 0, err = "Negative repetition count '{-n}'" },
		prrow { input = "x,2}", minv = 0, maxv = 0, max_void = false,
			replen = 0,
			err = "Repetition expression syntax error '{n}'" },
		prrow { input = "0,-2}", minv = 0, maxv = 0, max_void = false,
			replen = 0, err = "Negative repetition count '{-n}'" },
		// no endbrace at all (ha:491-493)
		prrow { input = "2", minv = 0, maxv = 0, max_void = false,
			replen = 0,
			err = "Repetition expression syntax error '{n}'" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let r: (repparts | error) = parse_repetition(rows[i].input);
		match (r) {
		case let t: repparts => {
			assert(!(rows[i].err.len > 0));
			// .min is always size after a successful parse
			// (ha:523-525 — empty min defaults to 0)
			assert(!(!(t.min is size)));
			assert(!(t.min as size != rows[i].minv));
			if (rows[i].max_void) {
				assert(!(!(t.max is void)));
			} else {
				assert(!(!(t.max is size)));
				assert(!(t.max as size != rows[i].maxv));
			};
			assert(!(t.replen != rows[i].replen));
		};
		case let e: error => {
			assert(!(rows[i].err.len == 0));
			if (strings.compare((e: str), rows[i].err) != 0) {
				abort();
			};
		};
		};
		i += 1;
	};
};