// regex_test — BLACK-BOX @test probes for lib/regex: the exported API
// only (compile / test / find / findall / strerror / result_free /
// result_freeall / finish) plus exported-type variant discrimination,
// payload extraction, and the regex/capture/charset struct shapes.
// This is the external `package regex_test` half of the Go foo / foo_test
// split (CLAUDE.md rule-9). The WHITE-BOX half — probes that bare-call
// unexported internals (thread/newmatch, run_thread / add_thread /
// delete_thread / search, find_last_groupstart / shift /
// parse_repetition, is_consuming_inst) — lives in
// lib/regex/whitebox_test.ww (`package regex`, unified with regex.ww) and
// runs as a separate root-package binary.
//
// Fold 2a ports compile()'s lit/any/match arms only; exec lives in
// later folds, so the compile_* cases pin the emitted inst PROGRAM
// (shape + payloads via indexed match-extraction), not matching.
// fold-6 tests exercise POSIX character classes (charclass_map +
// compile/exec arms). Earlier folds pin variant discrimination
// (including the nominally-distinct same-underlying
// inst_split/inst_jump/inst_groupstart `size` aliases and the
// inst_any/inst_skip/inst_groupend `void` aliases), payload extraction,
// the regex/capture struct shapes, and finish(). A failing row aborts
// via the assert/abort builtin (task #5 @test conversion).
//
// The parser rejects a qualified name in struct-literal position (#29), so
// the few struct payload rows below initialize a qualified typed local before
// injecting it into the exported union. This stays distinct from the
// white-box privacy boundary handled by the whitebox_test.ww split above.
package regex_test;

import regex;
import strings;


// inst_lit / inst_match carry distinguishable payloads (rune / bool).
@test fn lit_and_match() void = {
	let a: regex.inst = ('a': regex.inst_lit);
	match (a) {
	case let l: regex.inst_lit => { assert(!((l: rune) != 'a')); };
	case => abort();
	};

	let m: regex.inst = (true: regex.inst_match);
	match (m) {
	case let b: regex.inst_match => { assert(!(!(b: bool))); };
	case => abort();
	};
};

// The three `size`-aliased variants are nominally distinct: a value
// built as inst_split must match inst_split, never inst_jump /
// inst_groupstart, despite identical underlying storage.
@test fn size_aliases_distinct() void = {
	let sp: regex.inst = ((5: size): regex.inst_split);
	match (sp) {
	case let s: regex.inst_split => { assert(!((s: size) != (5: size))); };
	case let j: regex.inst_jump => abort();
	case let g: regex.inst_groupstart => abort();
	case => abort();
	};

	let jp: regex.inst = ((9: size): regex.inst_jump);
	match (jp) {
	case let j: regex.inst_jump => { assert(!((j: size) != (9: size))); };
	case let s: regex.inst_split => abort();
	case => abort();
	};

	let gs: regex.inst = ((2: size): regex.inst_groupstart);
	match (gs) {
	case let g: regex.inst_groupstart => { assert(!((g: size) != (2: size))); };
	case let s: regex.inst_split => abort();
	case => abort();
	};
};

// The `void`-aliased variants are likewise nominally distinct.
@test fn void_aliases_distinct() void = {
	let av: regex.inst_any;
	let an: regex.inst = av;
	match (an) {
	case let a: regex.inst_any => void;
	case let k: regex.inst_skip => abort();
	case let e: regex.inst_groupend => abort();
	case => abort();
	};

	let sv: regex.inst_skip;
	let sk: regex.inst = sv;
	match (sk) {
	case let k: regex.inst_skip => void;
	case let a: regex.inst_any => abort();
	case => abort();
	};

	let gv: regex.inst_groupend;
	let ge: regex.inst = gv;
	match (ge) {
	case let e: regex.inst_groupend => void;
	case let a: regex.inst_any => abort();
	case let k: regex.inst_skip => abort();
	case => abort();
	};
};

// inst_charset carries a struct payload; its fields survive the union
// round-trip.
@test fn charset_payload() void = {
	let value: regex.inst_charset;
	value.idx = 3;
	value.is_positive = true;
	let c: regex.inst = value;
	match (c) {
	case let cs: regex.inst_charset => {
		assert(!(cs.idx != (3: size)));
		assert(!(!cs.is_positive));
	};
	case => abort();
	};
};

// inst_repeat round-trips through the inst union with its plain `size`
// fields intact. Matching the nested (void | size) min/max bounds back
// out is DEFERRED: `match` on a tagged-union-typed struct field
// diverges cs≠ww (#26 — the wwstage frames it wider), so
// asserting the bounds here would seed a rule-10-divergent fixture.
@test fn repeat_payload() void = {
	let value: regex.inst_repeat;
	value.id = 1;
	value.origin = 4;
	value.min = (2: size);
	value.max = void;
	let r: regex.inst = value;
	match (r) {
	case let rp: regex.inst_repeat => {
		assert(!(rp.id != (1: size)));
		assert(!(rp.origin != (4: size)));
	};
	case => abort();
	};
};

// The regex/capture structs hold their fields; finish() is a no-op
// (no-free runtime) and must accept a built regex.
@test fn struct_shapes_and_finish() void = {
	let cap: regex.capture;
	cap.content = "abc";
	cap.start = 0;
	cap.start_bytesize = 0;
	cap.end = 3;
	cap.end_bytesize = 3;
	assert(!(cap.content.len != 3));
	assert(!(cap.end != (3: size)));

	// regex's insts/charsets ([]inst / []charset) are left empty here:
	// fold 1 ports no compile() to populate them, an empty `[]` literal
	// is unspellable as a typed slice (#25 — array→slice
	// element-coercion gap), and a struct-literal slice-field store
	// drops len/cap (#24). Declaring the regex zeroes both
	// slice headers to {0,0,0}; only n_reps is set explicitly.
	let re: regex.regex;
	re.n_reps = 0;
	assert(!(re.n_reps != (0: size)));
	assert(!(re.insts.len != 0));
	regex.finish(&re);
};

// rule-7 divergence: white-box probes of regex internals; mislabeled _test pending task #9 (in-pkg test harness via #5/-T dir-enum, #8 boundary).

// compile("abc") emits the 5-inst literal program: the leading
// unanchored inst_skip (regex.ha:261-263), one inst_lit per rune, the
// epilogue inst_match(false) (ha:475-477). compile()'s
// (regex | error | nomem) return is the first >24B tagged payload in
// the tree — the receive shapes here double as #38 sret consumers
// (typed-let + match here; scrutinee-direct in compile_empty_program).
@test fn compile_literal_program() void = {
	let c: (regex.regex | regex.error | nomem) = regex.compile("abc");
	match (c) {
	case let re: regex.regex => {
		assert(!(re.insts.len != 5));
		match (re.insts[0]) {
		case let k: regex.inst_skip => void;
		case => abort();
		};
		match (re.insts[1]) {
		case let l: regex.inst_lit => { assert(!((l: rune) != 'a')); };
		case => abort();
		};
		match (re.insts[2]) {
		case let l: regex.inst_lit => { assert(!((l: rune) != 'b')); };
		case => abort();
		};
		match (re.insts[3]) {
		case let l: regex.inst_lit => { assert(!((l: rune) != 'c')); };
		case => abort();
		};
		match (re.insts[4]) {
		case let m: regex.inst_match => { assert(!((m: bool))); };
		case => abort();
		};
		assert(!(re.charsets.len != 0));
		assert(!(re.n_reps != (0: size)));
		regex.finish(&re);
	};
	case => abort();
	};
};

// '.' compiles to inst_any between the literals (regex.ha:460-461):
// [skip, lit 'a', any, lit 'c', match(false)].
@test fn compile_any_program() void = {
	let c: (regex.regex | regex.error | nomem) = regex.compile("a.c");
	match (c) {
	case let re: regex.regex => {
		assert(!(re.insts.len != 5));
		match (re.insts[0]) {
		case let k: regex.inst_skip => void;
		case => abort();
		};
		match (re.insts[1]) {
		case let l: regex.inst_lit => { assert(!((l: rune) != 'a')); };
		case => abort();
		};
		match (re.insts[2]) {
		case let a: regex.inst_any => void;
		case => abort();
		};
		match (re.insts[3]) {
		case let l: regex.inst_lit => { assert(!((l: rune) != 'c')); };
		case => abort();
		};
		match (re.insts[4]) {
		case let m: regex.inst_match => { assert(!((m: bool))); };
		case => abort();
		};
		regex.finish(&re);
	};
	case => abort();
	};
};

// compile("") is exactly [inst_match(false)]: the leading skip must
// not fire on immediate done (regex.ha:261 gates on `next is rune`),
// and the epilogue guard must fire on the empty program.
@test fn compile_empty_program() void = {
	match (regex.compile("")) {
	case let re: regex.regex => {
		assert(!(re.insts.len != 1));
		match (re.insts[0]) {
		case let m: regex.inst_match => { assert(!((m: bool))); };
		case => abort();
		};
		regex.finish(&re);
	};
	case => abort();
	};
};

// result_free (regex.ha:1114-1116) accepts a built result; free() is
// the documented no-op (no-free runtime), so the header must stay
// readable after — a future real free changes this row consciously.
// The local is spelled []regex.capture, not the regex.result alias:
// wwstage falsely loud-bails appending a capture value onto an alias-typed
// dst (#20); the alias + signature stay exercised by result_free itself.
// Reverts to `regex.result` when #20 lands.
@test fn result_free_noop() void = {
	let res: []regex.capture;
	let value: regex.capture;
	value.content = "x";
	value.start = 0;
	value.start_bytesize = 0;
	value.end = 1;
	value.end_bytesize = 1;
	append(res, value);
	regex.result_free(res);
	assert(!(len(res) != 1));
	assert(!(res[0].end != (1: size)));
	// The zero-header edge: find()'s no-match path returns an empty
	// result (regex.ha:915-916) the caller still result_free()s. The
	// bare decl is alias-typed — the #20 dodge above is append-only,
	// so the alias stays exercised in value position here.
	let empty: regex.result;
	regex.result_free(empty);
	assert(!(len(empty) != 0));
};

// strerror (regex.ha:1127) is identity on the boundary text — routed
// through a REAL compile() error, completing the exported error
// surface end to end.
@test fn strerror_identity() void = {
	match (regex.compile("a(")) {
	case let e: regex.error => {
		if (strings.compare(regex.strerror(e),
			"Unmatched '('") != 0) {
			abort();
		};
	};
	case => abort();
	};
};

// test() (regex.ha:901-904) — the exported boolean surface over the
// same inputs the search table pins, plus the two void rows.
type tcase = struct {
	expr: str,
	input: str,
	want: bool,
};

@test fn test_matches() void = {
	let rows: [8]tcase = [
		tcase { expr = "ab", input = "xab", want = true },
		tcase { expr = "bcd", input = "abcd", want = true },
		tcase { expr = "aa", input = "aaa", want = true },
		tcase { expr = "", input = "", want = true },
		tcase { expr = "b.d", input = "aßbxd", want = true },
		tcase { expr = "aa", input = "aaaa", want = true },
		tcase { expr = "ab", input = "xyz", want = false },
		tcase { expr = "ab", input = "a", want = false },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != rows[i].want));
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// find() (regex.ha:910-918) — the exported result surface: match rows
// reuse the search table's expectations; no-match rows return the
// empty result (ha:916) the caller still result_frees. Every row also
// cross-pins test() == (find() matched).
type fcase = struct {
	expr: str,
	input: str,
	matches: bool,
	start: size,
	sb: size,
	end: size,
	eb: size,
	content: str,
};

@test fn find_cases() void = {
	let rows: [8]fcase = [
		fcase { expr = "ab", input = "xab", matches = true,
			start = 1, sb = 1, end = 3, eb = 3, content = "ab" },
		fcase { expr = "bcd", input = "abcd", matches = true,
			start = 1, sb = 1, end = 4, eb = 4, content = "bcd" },
		fcase { expr = "aa", input = "aaa", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "aa" },
		fcase { expr = "", input = "", matches = true,
			start = 0, sb = 0, end = 0, eb = 0, content = "" },
		fcase { expr = "b.d", input = "aßbxd", matches = true,
			start = 2, sb = 3, end = 5, eb = 6, content = "bxd" },
		fcase { expr = "aa", input = "aaaa", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "aa" },
		fcase { expr = "ab", input = "xyz", matches = false, ... },
		fcase { expr = "ab", input = "a", matches = false, ... },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			if (rows[i].matches) {
				assert(!(len(res) != 1));
				assert(!(res[0].start != rows[i].start));
				if (res[0].start_bytesize != rows[i].sb) {
					abort();
				};
				assert(!(res[0].end != rows[i].end));
				if (res[0].end_bytesize != rows[i].eb) {
					abort();
				};
				let wc: str = rows[i].content;
				if (strings.compare(res[0].content, wc) != 0) {
					abort();
				};
			} else {
				assert(!(len(res) != 0));
			};
			// the two surfaces share search; pin their
			// agreement so an arm-swap in either D13 match
			// can't hide behind a one-sided table
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != (len(res) != 0)));
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// findall() (regex.ha:923-960) content/count rows ported from Hare's
// OWN findall table (+test.ha:719-731) via run_findall_case's checks
// (+test.ha:102-130: result count + results[i][0].content), restricted
// to the rows fold-2a can compile (the fo{2,} / a* rows ride the
// repeat/star folds). Variable-length expectations live in a flat
// targets pool indexed by per-row (toff, tcnt).
type facase = struct {
	expr: str,
	input: str,
	toff: i32,
	tcnt: i32,
};

@test fn findall_content() void = {
	let targets: [9]str = [
		"abc", "abあ", "abq",
		"a", "a",
		"", "", "", "",
	];
	let rows: [3]facase = [
		// multi-match + inst_any over the 3-byte あ
		facase { expr = "ab.",
			input = "hello abc and abあ test abq thanks",
			toff = 0, tcnt = 3 },
		// adjacent single-rune matches
		facase { expr = "a", input = "aa", toff = 3, tcnt = 2 },
		// zero-length: one empty match per position INCLUDING
		// end-of-string (the ha:942-945 break appends first)
		facase { expr = "", input = "abc", toff = 5, tcnt = 4 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: ([]regex.result | nomem) =
				regex.findall(&re, inp);
			assert(!(!(fr is []regex.result)));
			let results: []regex.result = fr as []regex.result;
			assert(!(len(results) != rows[i].tcnt));
			let k: i32 = 0;
			for (k < rows[i].tcnt) {
				let want: str = targets[rows[i].toff + k];
				if (strings.compare(results[k][0].content,
					want) != 0) {
					abort();
				};
				k += 1;
			};
			regex.result_freeall(results);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// findall() field rows: every capture index plus content per result,
// against a flat expectation pool. Pins adjacency (non-overlap), the
// one-result overlap pick, the multibyte zero-length advancement
// (utf8sz step != 1 splits idx from bytesize), the tail-match break,
// and the empty no-match slice. result_freeall on every row.
type fdcase = struct {
	expr: str,
	input: str,
	eoff: i32,
	ecnt: i32,
};

type fdexp = struct {
	start: size,
	sb: size,
	end: size,
	eb: size,
	content: str,
};

@test fn findall_fields() void = {
	let exp: [12]fdexp = [
		// ("ab", "abxab")
		fdexp { start = 0, sb = 0, end = 2, eb = 2, content = "ab" },
		fdexp { start = 3, sb = 3, end = 5, eb = 5, content = "ab" },
		// ("ab", "abab") — adjacent, non-overlapping
		fdexp { start = 0, sb = 0, end = 2, eb = 2, content = "ab" },
		fdexp { start = 2, sb = 2, end = 4, eb = 4, content = "ab" },
		// ("aa", "aaa") — ONE result: leftmost-longest then
		// advance-past; findall must not re-enter mid-match
		fdexp { start = 0, sb = 0, end = 2, eb = 2, content = "aa" },
		// ("", "ßx") — zero-length advancement over a 2-byte rune:
		// bytesize steps 0→2→3 while idx steps 0→1→2
		fdexp { start = 0, sb = 0, end = 0, eb = 0, content = "" },
		fdexp { start = 1, sb = 2, end = 1, eb = 2, content = "" },
		fdexp { start = 2, sb = 3, end = 2, eb = 3, content = "" },
		// ("b.d", "aßbxd") — multibyte before the match start
		// splits every idx from its bytesize
		fdexp { start = 2, sb = 3, end = 5, eb = 6, content = "bxd" },
		// ("ab", "xab") — tail match: the post-match seek lands at
		// end-of-string and the next search returns void
		fdexp { start = 1, sb = 1, end = 3, eb = 3, content = "ab" },
		// ("a*", "baa") — fold-3 rider: search's longest-pick beats
		// the zero-length candidate at 0 (the b*-over-"aaaabbbb"
		// semantics), so the greedy (1,3) "aa" leads; the trailing
		// end-of-string zero-length match takes the ha:942-945
		// break, pinning a real splitting pattern through the 2c
		// zero-length machinery
		fdexp { start = 1, sb = 1, end = 3, eb = 3, content = "aa" },
		fdexp { start = 3, sb = 3, end = 3, eb = 3, content = "" },
	];
	let rows: [8]fdcase = [
		fdcase { expr = "ab", input = "abxab", eoff = 0, ecnt = 2 },
		fdcase { expr = "ab", input = "abab", eoff = 2, ecnt = 2 },
		fdcase { expr = "aa", input = "aaa", eoff = 4, ecnt = 1 },
		fdcase { expr = "", input = "ßx", eoff = 5, ecnt = 3 },
		fdcase { expr = "b.d", input = "aßbxd", eoff = 8, ecnt = 1 },
		fdcase { expr = "ab", input = "xab", eoff = 9, ecnt = 1 },
		// no match → empty slice the caller still result_freealls
		fdcase { expr = "ab", input = "xyz", eoff = 10, ecnt = 0 },
		fdcase { expr = "a*", input = "baa", eoff = 10, ecnt = 2 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: ([]regex.result | nomem) =
				regex.findall(&re, inp);
			assert(!(!(fr is []regex.result)));
			let results: []regex.result = fr as []regex.result;
			assert(!(len(results) != rows[i].ecnt));
			let k: i32 = 0;
			for (k < rows[i].ecnt) {
				let w: fdexp = exp[rows[i].eoff + k];
				assert(!(results[k][0].start != w.start));
				if (results[k][0].start_bytesize != w.sb) {
					abort();
				};
				assert(!(results[k][0].end != w.end));
				if (results[k][0].end_bytesize != w.eb) {
					abort();
				};
				if (strings.compare(results[k][0].content,
					w.content) != 0) {
					abort();
				};
				k += 1;
			};
			regex.result_freeall(results);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};


// 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: regex.inst) i64 = {
	match (v) {
	case let l: regex.inst_lit => return 1000 + ((l: rune): i64);
	case regex.inst_skip => return 2000;
	case regex.inst_any => return 3000;
	case let s: regex.inst_split => return 4000 + ((s: size): i64);
	case let j: regex.inst_jump => return 5000 + ((j: size): i64);
	case let m: regex.inst_match => {
		if ((m: bool)) { return 6001; };
		return 6000;
	};
	case let g: regex.inst_groupstart => return 7000 + ((g: size): i64);
	case regex.inst_groupend => return 8000;
	case let c: regex.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;
	};
};

// Emitted-program pins for the fold-3 arms — deterministic, engine-
// independent: the exact inst sequence (kinds + jump/split targets)
// each metachar must compile to. Derived by hand-executing
// regex.ha:286-473 (insert-before + shift + the SIZE_MAX-sentinel
// jump fixup); the a|b row pins the whole jump_idxs pipeline
// including the sentinel overwrite at ha:470-473.
type pgmcase = struct {
	expr: str,
	soff: i32,
	scnt: i32,
};

@test fn fold3_programs() void = {
	let sigs: [25]i64 = [
		// "^a": anchored — no leading skip
		1097, 6000,
		// "a$": skip, lit a, match(TRUE)
		2000, 1097, 6001,
		// "a?": split jumps OVER the lit to the match
		2000, 4003, 1097, 6000,
		// "a*": split to match; jump back to the split
		2000, 4004, 1097, 5001, 6000,
		// "a+": split back to the lit
		2000, 1097, 4001, 6000,
		// "a|b": leading split to the second branch's skip; the
		// first branch's jump lands on the epilogue match (the
		// fixed-up SIZE_MAX sentinel)
		4004, 2000, 1097, 5006, 2000, 1098, 6000,
	];
	let rows: [6]pgmcase = [
		pgmcase { expr = "^a", soff = 0, scnt = 2 },
		pgmcase { expr = "a$", soff = 2, scnt = 3 },
		pgmcase { expr = "a?", soff = 5, scnt = 4 },
		pgmcase { expr = "a*", soff = 9, scnt = 5 },
		pgmcase { expr = "a+", soff = 14, scnt = 4 },
		pgmcase { expr = "a|b", soff = 18, scnt = 7 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			assert(!(re.insts.len != rows[i].scnt));
			let k: i32 = 0;
			for (k < rows[i].scnt) {
				if (instsig(re.insts[k])
						!= sigs[rows[i].soff + k]) {
					abort();
				};
				k += 1;
			};
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// The fold-3 compile-error surface, exact texts (regex.ha:289 / 296-299
// / 303-308 / 405-417 / 423-435 / 446-455). The "ab\|^cd" row is
// Hare's own ERROR fixture (+test.ha:634) — the escaped '|' must NOT
// set was_prev_rune_pipe, so the following '^' misplaces.
type cerow = struct {
	pat: str,
	want: str,
};

@test fn fold3_compile_errors() void = {
	let rows: [12]cerow = [
		cerow { pat = "\\", want = "Trailing backslash '\\'" },
		cerow { pat = "a\\", want = "Trailing backslash '\\'" },
		cerow { pat = "a^",
			want = "Anchor '^' not at start of whole pattern or alternation" },
		cerow { pat = "$a",
			want = "Anchor '$' not at end of whole pattern or alternation" },
		cerow { pat = "ab\\|^cd",
			want = "Anchor '^' not at start of whole pattern or alternation" },
		cerow { pat = "?", want = "Unused '?'" },
		cerow { pat = "*", want = "Unused '*'" },
		cerow { pat = "+", want = "Unused '+'" },
		// '^' appends nothing, so insts is still empty (ha:404's
		// len check, not the r_idx one)
		cerow { pat = "^*", want = "Unused '*'" },
		cerow { pat = "a*?", want = "Misused '?'" },
		cerow { pat = "a**", want = "Misused '*'" },
		cerow { pat = "a*+", want = "Misused '+'" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let p: str = rows[i].pat;
		match (regex.compile(p)) {
		case let e: regex.error => {
			let w: str = rows[i].want;
			assert(!(strings.compare((e: str), w) != 0));
		};
		case => abort();
		};
		i += 1;
	};
};

// fold-3 find/test rows — the group-free subset of Hare's own table
// (+test.ha:221-256 anchors/postfix, :622-650 whole-expression and
// multiple alternation; end == -1 resolved to rune-length per
// +test.ha:693-697) plus rob's dedup/leftmost/longest riders:
// `a*` over "aaaa" must yield ONE (0,4) (split spawns same-pc threads
// every step — the ha:872-889 dedup pin gone observable), `b+` over
// "abab" pins the leftmost trim (1,2 not 3,4), `b*`/`^b*` over
// "aaaabbbb" pin longest-pick vs anchored zero-length. The multibyte
// `b+` row keeps every idx != bytesize (B4). Reuses the fcase shape;
// every row also cross-pins test() == (find() matched).
@test fn fold3_find_cases() void = {
	let rows: [42]fcase = [
		fcase { expr = "^abc$", input = "abc", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "abc" },
		fcase { expr = "^abc$", input = "axc", matches = false, ... },
		fcase { expr = "^.$", input = "x", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "x" },
		fcase { expr = "^.$", input = "", matches = false, ... },
		fcase { expr = "^a+$", input = "a", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "a" },
		fcase { expr = "^a+$", input = "aaa", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "aaa" },
		fcase { expr = "^a+$", input = "", matches = false, ... },
		fcase { expr = "^a*$", input = "", matches = true,
			start = 0, sb = 0, end = 0, eb = 0, content = "" },
		fcase { expr = "^a*$", input = "aaaa", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "aaaa" },
		fcase { expr = "^a*$", input = "b", matches = false, ... },
		fcase { expr = "^a?$", input = "", matches = true,
			start = 0, sb = 0, end = 0, eb = 0, content = "" },
		fcase { expr = "^a?$", input = "a", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "a" },
		fcase { expr = "^a?$", input = "b", matches = false, ... },
		fcase { expr = "^a*", input = "aaaa", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "aaaa" },
		fcase { expr = "a*$", input = "aaaa", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "aaaa" },
		fcase { expr = "a*", input = "aaaa", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "aaaa" },
		fcase { expr = "b*", input = "aaaabbbb", matches = true,
			start = 4, sb = 4, end = 8, eb = 8, content = "bbbb" },
		fcase { expr = "^b*", input = "aaaabbbb", matches = true,
			start = 0, sb = 0, end = 0, eb = 0, content = "" },
		fcase { expr = "b*$", input = "aaaabbbb", matches = true,
			start = 4, sb = 4, end = 8, eb = 8, content = "bbbb" },
		fcase { expr = "b+", input = "abab", matches = true,
			start = 1, sb = 1, end = 2, eb = 2, content = "b" },
		// multibyte rider: 2-byte ß before the b's splits every
		// idx from its bytesize
		fcase { expr = "b+", input = "aßbb", matches = true,
			start = 2, sb = 3, end = 4, eb = 5, content = "bb" },
		fcase { expr = "ab|cd", input = "cd", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "cd" },
		fcase { expr = "ab|cd", input = "abc", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "ab" },
		fcase { expr = "ab|cd", input = "abcd", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "ab" },
		fcase { expr = "ab|cd", input = "bcd", matches = true,
			start = 1, sb = 1, end = 3, eb = 3, content = "cd" },
		fcase { expr = "^ab|cd", input = "bcd", matches = true,
			start = 1, sb = 1, end = 3, eb = 3, content = "cd" },
		fcase { expr = "^ab|cd", input = "zab", matches = false, ... },
		fcase { expr = "ab$|cd", input = "ab", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "ab" },
		fcase { expr = "ab$|cd", input = "abc", matches = false, ... },
		fcase { expr = "ab|cd$", input = "cde", matches = false, ... },
		fcase { expr = "ab|^cd", input = "bcd", matches = false, ... },
		fcase { expr = "ab|^cd", input = "cde", matches = true,
			start = 0, sb = 0, end = 2, eb = 2, content = "cd" },
		fcase { expr = "a|b|c|d|e", input = "e", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "e" },
		fcase { expr = "a|b|c|d|e", input = "xe", matches = true,
			start = 1, sb = 1, end = 2, eb = 2, content = "e" },
		fcase { expr = "a|b$|c$|d$|e", input = "cd", matches = true,
			start = 1, sb = 1, end = 2, eb = 2, content = "d" },
		fcase { expr = "a|b$|c$|d$|e", input = "ax", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "a" },
		fcase { expr = "a|b$|c$|d$|e", input = "cx", matches = false, ... },
		fcase { expr = "a|b$|c$|d$|e", input = "ex", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "e" },
		fcase { expr = "a|^b|^c|^d|e", input = "cd", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "c" },
		fcase { expr = "a|^b|^c|^d|e", input = "xa", matches = true,
			start = 1, sb = 1, end = 2, eb = 2, content = "a" },
		fcase { expr = "a|^b|^c|^d|e", input = "xc", matches = false, ... },
		fcase { expr = "a|^b|^c|^d|e", input = "xe", matches = true,
			start = 1, sb = 1, end = 2, eb = 2, content = "e" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			if (rows[i].matches) {
				assert(!(len(res) != 1));
				assert(!(res[0].start != rows[i].start));
				if (res[0].start_bytesize != rows[i].sb) {
					abort();
				};
				assert(!(res[0].end != rows[i].end));
				if (res[0].end_bytesize != rows[i].eb) {
					abort();
				};
				let wc: str = rows[i].content;
				if (strings.compare(res[0].content, wc) != 0) {
					abort();
				};
			} else {
				assert(!(len(res) != 0));
			};
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != (len(res) != 0)));
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// Emitted-program pins for the `[..]` arm: the charset inst lands where
// a literal would (and composes with fold-3's postfix/anchors), the
// charsets table grows one entry per bracket, negation rides
// is_positive. Derived by hand-executing regex.ha:265-275 + 313-314 +
// handle_bracket.
@test fn fold4_programs() void = {
	let sigs: [17]i64 = [
		// "[abc]": skip, charset 0 positive, match(false)
		2000, 10000, 6000,
		// "^[abc]$": anchored both ends — charset, match(TRUE)
		10000, 6001,
		// "[^ab]": skip, charset 0 NEGATED, match(false)
		2000, 11000, 6000,
		// "[ab][cd]": two brackets — charset 0, charset 1
		2000, 10000, 10001, 6000,
		// "[abc]*": the fold-3 a* shape with charset as the term
		2000, 4004, 10000, 5001, 6000,
	];
	let rows: [5]pgmcase = [
		pgmcase { expr = "[abc]", soff = 0, scnt = 3 },
		pgmcase { expr = "^[abc]$", soff = 3, scnt = 2 },
		pgmcase { expr = "[^ab]", soff = 5, scnt = 3 },
		pgmcase { expr = "[ab][cd]", soff = 8, scnt = 4 },
		pgmcase { expr = "[abc]*", soff = 12, scnt = 5 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			assert(!(re.insts.len != rows[i].scnt));
			let k: i32 = 0;
			for (k < rows[i].scnt) {
				if (instsig(re.insts[k])
						!= sigs[rows[i].soff + k]) {
					abort();
				};
			k += 1;
			};
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// cssig — flatten a charset element: lits as 1_000_000 + codepoint,
// ranges as start*10000 + end (codepoints stay < 10000 in these rows),
// class items as -2 (presence sentinel — fn-ptr address not stable).
// The element binds structurally, not via the `charset` alias — an
// alias-typed slice local's index read mis-scales in wwstage (#68).
fn cssig(cs: [](regex.charset_lit_item | regex.charset_range_item |
	regex.charset_class_item), k: size) i64 = {
	let cur: (regex.charset_lit_item | regex.charset_range_item |
		regex.charset_class_item) = cs[k];
	match (cur) {
	case let l: regex.charset_lit_item =>
		return 1000000 + ((l: rune): i64);
	case let range: regex.charset_range_item =>
		return (range.0: i64) * 10000 + (range.1: i64);
	case regex.charset_class_item => return -2;	// fn-ptr address not stable
	case => return -1;
	};
};

type cscase = struct {
	expr: str,
	eoff: i32,
	ecnt: i32,
};

// charsets-table content pins: literal vs range element discrimination,
// the first-char `]`/`[` literal rules, literal dashes, and multibyte
// codepoints in both element kinds (regex.ha:172-221 state machine).
@test fn fold4_charsets() void = {
	let exp: [15]i64 = [
		// "[abc]"
		1000097, 1000098, 1000099,
		// "[]ab]" — first-char ] is a literal
		1000093, 1000097, 1000098,
		// "[[ab]" — [ inside a bracket is a literal
		1000091, 1000097, 1000098,
		// "[a-c]"
		970099,
		// "[-a-c]" — leading literal dash
		1000045, 970099,
		// "[a-c-]" — trailing literal dash
		970099, 1000045,
		// "[ä-ö]" — multibyte range, codepoints 228..246
		2280246,
	];
	let rows: [7]cscase = [
		cscase { expr = "[abc]", eoff = 0, ecnt = 3 },
		cscase { expr = "[]ab]", eoff = 3, ecnt = 3 },
		cscase { expr = "[[ab]", eoff = 6, ecnt = 3 },
		cscase { expr = "[a-c]", eoff = 9, ecnt = 1 },
		cscase { expr = "[-a-c]", eoff = 10, ecnt = 2 },
		cscase { expr = "[a-c-]", eoff = 12, ecnt = 2 },
		cscase { expr = "[ä-ö]", eoff = 14, ecnt = 1 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			assert(!(re.charsets.len != 1));
			let cs0: [](regex.charset_lit_item | regex.charset_range_item |
				regex.charset_class_item) = re.charsets[0];
			assert(!((len(cs0): i32) != rows[i].ecnt));
			let k: i32 = 0;
			for (k < rows[i].ecnt) {
				if (cssig(cs0, (k: size))
						!= exp[rows[i].eoff + k]) {
					abort();
				};
				k += 1;
			};
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// The fold-4 compile-error surface, exact texts (regex.ha:267 / 211).
// The `[[:alpha:]]` POSIX-class arm is a loud ABORT, not an error —
// unpinnable in-process (it kills the runner); its boundary is
// source-audited (handle_bracket's class arm) until the POSIX fold.
@test fn fold4_compile_errors() void = {
	let rows: [4]cerow = [
		cerow { pat = "a[", want = "Unmatched '['" },
		cerow { pat = "[abc", want = "Unmatched '['" },
		cerow { pat = "[z-a]",
			want = "Descending bracket expression range '[z-a]'" },
		// the escape arm must not eat `[`: "\[" is a literal, the
		// SECOND `[` opens an unterminated bracket
		cerow { pat = "\\[[", want = "Unmatched '['" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let p: str = rows[i].pat;
		match (regex.compile(p)) {
		case let e: regex.error => {
			let w: str = rows[i].want;
			assert(!(strings.compare((e: str), w) != 0));
		};
		case => abort();
		};
		i += 1;
	};
};

// fold-4 find/test rows — Hare's own bracket block (+test.ha:278-345)
// minus the group row (`(` is loud) and the POSIX-class rows (loud
// abort), plus multibyte riders (literal and range brackets over
// 2-byte runes, idx != bytesize) and an unanchored composition row.
// MATCH 0 -1 resolves to (0, runelen, input) per +test.ha:693-697;
// every input is ASCII unless noted. Cross-pins test() == find().
@test fn fold4_find_cases() void = {
	let rows: [72]fcase = [
		fcase { expr = "^test[abc]$", input = "testa", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testa" },
		fcase { expr = "^test[abc]$", input = "testb", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testb" },
		fcase { expr = "^test[abc]$", input = "testc", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testc" },
		fcase { expr = "^test[abc]$", input = "testd", matches = false, ... },
		fcase { expr = "^test[abc]*$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[abc]*$", input = "testa", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testa" },
		fcase { expr = "^test[abc]*$", input = "testaaa", matches = true,
			start = 0, sb = 0, end = 7, eb = 7, content = "testaaa" },
		fcase { expr = "^test[abc]*$", input = "testabc", matches = true,
			start = 0, sb = 0, end = 7, eb = 7, content = "testabc" },
		fcase { expr = "^test[abc]?$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[abc]?$", input = "testa", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testa" },
		fcase { expr = "^test[abc]+$", input = "testa", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testa" },
		fcase { expr = "^test[abc]+$", input = "test", matches = false, ... },
		fcase { expr = "^test[]abc]$", input = "test]", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test]" },
		fcase { expr = "^test[[abc]$", input = "test[", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test[" },
		fcase { expr = "^test[^abc]$", input = "testd", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testd" },
		fcase { expr = "^test[^abc]$", input = "test!", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test!" },
		fcase { expr = "^test[^abc]$", input = "testa", matches = false, ... },
		fcase { expr = "^test[^abc]$", input = "testb", matches = false, ... },
		fcase { expr = "^test[^abc]$", input = "testc", matches = false, ... },
		fcase { expr = "^test[^]abc]$", input = "test]", matches = false, ... },
		fcase { expr = "^test[^abc[]$", input = "test[", matches = false, ... },
		fcase { expr = "^test[^abc]*$", input = "testd", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testd" },
		fcase { expr = "^test[^abc]*$", input = "testqqqqq", matches = true,
			start = 0, sb = 0, end = 9, eb = 9, content = "testqqqqq" },
		fcase { expr = "^test[^abc]*$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[^abc]*$", input = "testc", matches = false, ... },
		fcase { expr = "^test[^abc]?$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[^abc]?$", input = "testd", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testd" },
		fcase { expr = "^test[^abc]?$", input = "testc", matches = false, ... },
		fcase { expr = "^test[^abc]+$", input = "testd", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testd" },
		fcase { expr = "^test[^abc]+$", input = "testddd", matches = true,
			start = 0, sb = 0, end = 7, eb = 7, content = "testddd" },
		fcase { expr = "^test[^abc]+$", input = "testc", matches = false, ... },
		fcase { expr = "^test[^abc]+$", input = "testcccc", matches = false, ... },
		fcase { expr = "^test[a-c]$", input = "testa", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testa" },
		fcase { expr = "^test[a-c]$", input = "testb", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testb" },
		fcase { expr = "^test[a-c]$", input = "testc", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testc" },
		fcase { expr = "^test[a-c]$", input = "testd", matches = false, ... },
		fcase { expr = "^test[a-c]$", input = "test!", matches = false, ... },
		fcase { expr = "^test[a-c]$", input = "test-", matches = false, ... },
		fcase { expr = "^test[-a-c]$", input = "test-", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test-" },
		fcase { expr = "^test[a-c-]$", input = "test-", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test-" },
		fcase { expr = "^test[a-c]*$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[a-c]*$", input = "testa", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testa" },
		fcase { expr = "^test[a-c]*$", input = "testabb", matches = true,
			start = 0, sb = 0, end = 7, eb = 7, content = "testabb" },
		fcase { expr = "^test[a-c]*$", input = "testddd", matches = false, ... },
		fcase { expr = "^test[a-c]?$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[a-c]?$", input = "testb", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testb" },
		fcase { expr = "^test[a-c]?$", input = "testd", matches = false, ... },
		fcase { expr = "^test[a-c]+$", input = "test", matches = false, ... },
		fcase { expr = "^test[a-c]+$", input = "testbcbc", matches = true,
			start = 0, sb = 0, end = 8, eb = 8, content = "testbcbc" },
		fcase { expr = "^test[a-c]+$", input = "testd", matches = false, ... },
		fcase { expr = "^test[^a-c]$", input = "testa", matches = false, ... },
		fcase { expr = "^test[^a-c]$", input = "testb", matches = false, ... },
		fcase { expr = "^test[^a-c]$", input = "testc", matches = false, ... },
		fcase { expr = "^test[^a-c]$", input = "testd", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testd" },
		fcase { expr = "^test[^a-c]$", input = "test!", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test!" },
		fcase { expr = "^test[^a-c]$", input = "test-", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "test-" },
		fcase { expr = "^test[^-a-c]$", input = "test-", matches = false, ... },
		fcase { expr = "^test[^a-c-]$", input = "test-", matches = false, ... },
		fcase { expr = "^test[^a-c-]*$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[^a-c-]*$", input = "test--", matches = false, ... },
		fcase { expr = "^test[^a-c-]*$", input = "testq", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testq" },
		fcase { expr = "^test[^a-c-]?$", input = "test", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "test" },
		fcase { expr = "^test[^a-c-]?$", input = "testq", matches = true,
			start = 0, sb = 0, end = 5, eb = 5, content = "testq" },
		fcase { expr = "^test[^a-c-]?$", input = "test-", matches = false, ... },
		fcase { expr = "^test[^a-c-]+$", input = "test", matches = false, ... },
		fcase { expr = "^test[^a-c-]+$", input = "testb", matches = false, ... },
		fcase { expr = "^test[^a-c-]+$", input = "testddd", matches = true,
			start = 0, sb = 0, end = 7, eb = 7, content = "testddd" },
		// multibyte riders: 2-byte runes in a literal bracket and a
		// codepoint range — idx != bytesize in every field (B4)
		fcase { expr = "^x[äö]$", input = "xä", matches = true,
			start = 0, sb = 0, end = 2, eb = 3, content = "xä" },
		fcase { expr = "^x[äö]$", input = "xq", matches = false, ... },
		fcase { expr = "^[à-ö]$", input = "á", matches = true,
			start = 0, sb = 0, end = 1, eb = 2, content = "á" },
		fcase { expr = "^[à-ö]$", input = "x", matches = false, ... },
		// unanchored leftmost-longest composition with fold-3's `+`
		fcase { expr = "[ab]+", input = "xxabyyba", matches = true,
			start = 2, sb = 2, end = 4, eb = 4, content = "ab" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			if (rows[i].matches) {
				assert(!(len(res) != 1));
				assert(!(res[0].start != rows[i].start));
				if (res[0].start_bytesize != rows[i].sb) {
					abort();
				};
				assert(!(res[0].end != rows[i].end));
				if (res[0].end_bytesize != rows[i].eb) {
					abort();
				};
				let wc: str = rows[i].content;
				if (strings.compare(res[0].content, wc) != 0) {
					abort();
				};
			} else {
				assert(!(len(res) != 0));
			};
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != (len(res) != 0)));
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// findall composition: charset × split (`+`) × the 2c machinery —
// non-overlapping greedy matches over mixed input.
@test fn fold4_findall() void = {
	let c: (regex.regex | regex.error | nomem) = regex.compile("[ab]+");
	match (c) {
	case let re: regex.regex => {
		let fr: ([]regex.result | nomem) =
			regex.findall(&re, "xxabyyba");
		assert(!(!(fr is []regex.result)));
		let results: []regex.result = fr as []regex.result;
		assert(!(len(results) != 2));
		assert(!(results[0][0].start != (2: size)));
		assert(!(results[0][0].end != (4: size)));
		if (strings.compare(results[0][0].content, "ab") != 0) {
			abort();
		};
		assert(!(results[1][0].start != (6: size)));
		assert(!(results[1][0].end != (8: size)));
		if (strings.compare(results[1][0].content, "ba") != 0) {
			abort();
		};
		regex.result_freeall(results);
		regex.finish(&re);
	};
	case => abort();
	};
};

// The fold-5a compile-error surface, exact texts. ")" and "(" are
// Hare's own ERROR fixtures (+test.ha:276/606); "a("/"a)" graduate
// here from the metachar-loud table with their real texts. The
// anchor-in-group and groupstart-postfix rows are ww-added (no Hare
// table row carries these texts): they pin that the fold-3
// verbatim-dead arms (regex.ha:295-297/302-304 anchors,
// 413-414/434-435/453-454 Unused-on-groupstart) FIRE now that `(`
// emits inst_groupstart — the §9a A0 re-verify, as live rows.
@test fn fold5_compile_errors() void = {
	let rows: [9]cerow = [
		cerow { pat = ")", want = "Unmatched ')'" },
		cerow { pat = "(", want = "Unmatched '('" },
		cerow { pat = "a)", want = "Unmatched ')'" },
		cerow { pat = "a(", want = "Unmatched '('" },
		// ww-added: anchor-in-group arms (regex.ha:295-297/302-304)
		cerow { pat = "(^a)",
			want = "Anchor '^' in capture groups is unsupported" },
		cerow { pat = "(a$)",
			want = "Anchor '$' in capture groups is unsupported" },
		// ww-added: postfix on a bare groupstart
		// (regex.ha:413-414/434-435/453-454)
		cerow { pat = "(?", want = "Unused '?'" },
		cerow { pat = "(*", want = "Unused '*'" },
		cerow { pat = "(+", want = "Unused '+'" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let p: str = rows[i].pat;
		match (regex.compile(p)) {
		case let e: regex.error => {
			let w: str = rows[i].want;
			assert(!(strings.compare((e: str), w) != 0));
		};
		case => abort();
		};
		i += 1;
	};
};

// fold-5a find/test rows — the group rows of Hare's own table:
// group/alternation +test.ha:257-275, the jump-bug group rows
// :499-503 minus the `{,1}` form (5b) plus `(x?)?` :607, the
// POSIX-comment submatch-handling family :610-621 (MATCH-only root
// assertions, as Hare; the literally-duplicated (a*) pairs :614-617
// appear once), `a|(b)` :635, `(a|b|c|d|e)f` :640, and the
// nested-group block :649-665 minus the `{0,}`/`{1,}`/`{0,1}` twins
// (5b) and Hare's own TODO-disabled anchor-in-group rows. end == -1
// resolves to rune length (+test.ha:693-697). ncaps additionally pins
// len(res) = last-groupstart payload + 2 (the search length scan +
// pad fill — unset groups pad to zeroed captures, so `a|(b)` over "a"
// still yields 2). The multibyte row is ww-added (B4: every idx
// splits from its bytesize). `(a+|b)*` over "ab" is rob's
// thread-explosion stress row (group split × star respawn ×
// dedup/trim/leftmost pins). Cross-pins test() == (find() matched).
type f5case = struct {
	expr: str,
	input: str,
	matches: bool,
	ncaps: i32,
	start: size,
	sb: size,
	end: size,
	eb: size,
	content: str,
};

@test fn fold5_find_cases() void = {
	let rows: [32]f5case = [
		// group/alternation (+test.ha:257-275)
		f5case { expr = "^(cafe|b)x$", input = "cafex", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 5, eb = 5,
			content = "cafex" },
		f5case { expr = "^(cafe|b)x$", input = "bx", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "bx" },
		f5case { expr = "^(cafe|b)x$", input = "XXXx",
			matches = false, ... },
		f5case { expr = "^(Privat|Jagd)(haftpflicht|schaden)versicherungs(police|betrag)$",
			input = "Jagdhaftpflichtversicherungsbetrag",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 34, eb = 34,
			content = "Jagdhaftpflichtversicherungsbetrag" },
		f5case { expr = "^(Privat|Jagd)(haftpflicht|schaden)versicherungs(police|betrag)$",
			input = "Jagdhaftpflichtversicherungsbetrug",
			matches = false, ... },
		f5case { expr = "^(Privat|Jagd)(haftpflicht|schaden)versicherungs(police|betrag)$",
			input = "Jagdversicherungspolice",
			matches = false, ... },
		// jump bugs (+test.ha:499-503 minus `{,1}`; :607)
		f5case { expr = "ab?c", input = "ac", matches = true,
			ncaps = 1, start = 0, sb = 0, end = 2, eb = 2,
			content = "ac" },
		f5case { expr = "ab?c|z", input = "ac", matches = true,
			ncaps = 1, start = 0, sb = 0, end = 2, eb = 2,
			content = "ac" },
		f5case { expr = "(ab?c)?", input = "ac", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ac" },
		f5case { expr = "(ab?c)*", input = "ac", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ac" },
		f5case { expr = "(x?)?", input = "x", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 1, eb = 1,
			content = "x" },
		// submatch handling (+test.ha:610-621) — MATCH-only root
		// assertions, as Hare (POSIX submatch semantics diverge)
		f5case { expr = "(a|ab)(c|bcd)(d*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(a|ab)(bcd|c)(d*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(ab|a)(c|bcd)(d*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(ab|a)(bcd|c)(d*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(a*)(b|abc)(c*)", input = "abc",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 3, eb = 3, content = "abc" },
		f5case { expr = "(a*)(abc|b)(c*)", input = "abc",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 3, eb = 3, content = "abc" },
		f5case { expr = "(a|ab)(c|bcd)(d|.*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(a|ab)(bcd|c)(d|.*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(ab|a)(c|bcd)(d|.*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		f5case { expr = "(ab|a)(bcd|c)(d|.*)", input = "abcd",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "abcd" },
		// alternation with a group (+test.ha:635) — the (b) branch
		// never runs on "a"; the pad fill still yields 2 captures
		f5case { expr = "a|(b)", input = "a", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 1, eb = 1,
			content = "a" },
		// multiple alternation inside a group (+test.ha:640)
		f5case { expr = "(a|b|c|d|e)f", input = "ef", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ef" },
		// nested groups (+test.ha:649-665 minus the `{…}` twins)
		f5case { expr = "((a))", input = "abc", matches = true,
			ncaps = 3, start = 0, sb = 0, end = 1, eb = 1,
			content = "a" },
		f5case { expr = "((a)(b)c)(d)", input = "abcd", matches = true,
			ncaps = 5, start = 0, sb = 0, end = 4, eb = 4,
			content = "abcd" },
		f5case { expr = "((((((((((a))))))))))", input = "a",
			matches = true, ncaps = 11, start = 0, sb = 0,
			end = 1, eb = 1, content = "a" },
		f5case { expr = "(((((((((a)))))))))", input = "a",
			matches = true, ncaps = 10, start = 0, sb = 0,
			end = 1, eb = 1, content = "a" },
		f5case { expr = "(([a-z]+):)?([a-z]+)$", input = "smil",
			matches = true, ncaps = 4, start = 0, sb = 0,
			end = 4, eb = 4, content = "smil" },
		f5case { expr = "^((a)c)?(ab)$", input = "ab", matches = true,
			ncaps = 4, start = 0, sb = 0, end = 2, eb = 2,
			content = "ab" },
		f5case { expr = "(a+|b)*", input = "ab", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ab" },
		f5case { expr = "(a+|b)+", input = "ab", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ab" },
		// ww-added multibyte group row (B4)
		f5case { expr = "(ä|b)x", input = "äx", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 3,
			content = "äx" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			if (rows[i].matches) {
				assert(!((len(res): i32) != rows[i].ncaps));
				assert(!(res[0].start != rows[i].start));
				if (res[0].start_bytesize != rows[i].sb) {
					abort();
				};
				assert(!(res[0].end != rows[i].end));
				if (res[0].end_bytesize != rows[i].eb) {
					abort();
				};
				let wc: str = rows[i].content;
				if (strings.compare(res[0].content, wc) != 0) {
					abort();
				};
			} else {
				assert(!(len(res) != 0));
			};
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != (len(res) != 0)));
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// `(a+|b)?` over "ab" (+test.ha:665) matches (0,1) "a" — the
// non-greedy END pins that the optional group stops at the leftmost-
// longest SINGLE term, not the star/plus whole-string sweep above.
@test fn fold5_optional_group() void = {
	let c: (regex.regex | regex.error | nomem) = regex.compile("(a+|b)?");
	match (c) {
	case let re: regex.regex => {
		let fr: (regex.result | nomem) = regex.find(&re, "ab");
		assert(!(!(fr is regex.result)));
		let res: regex.result = fr as regex.result;
		assert(!(len(res) != 2));
		assert(!(res[0].start != (0: size)));
		assert(!(res[0].end != (1: size)));
		assert(!(strings.compare(res[0].content, "a") != 0));
		regex.result_free(res);
		regex.finish(&re);
	};
	case => abort();
	};
};

// submatch rows (+test.ha:704-708 via run_submatch_case :72-100) —
// THE 5a acceptance gate: per-group .content equality through find(),
// root first. The second row is ww-added (B4): a 2-byte ß inside both
// captured groups splits every byte offset the contents are sliced
// from. Targets live in a flat pool indexed by (toff, tcnt), the
// findall_content shape.
type smcase = struct {
	expr: str,
	input: str,
	toff: i32,
	tcnt: i32,
};

@test fn fold5_submatches() void = {
	let targets: [6]str = [
		"aaa bbb ccc", "bbb", "ccc",
		"aaa bßb cßc", "bßb", "cßc",
	];
	let rows: [2]smcase = [
		smcase { expr = "aaa ([^ ]*) (...)", input = "aaa bbb ccc",
			toff = 0, tcnt = 3 },
		// ww-added multibyte variant
		smcase { expr = "aaa ([^ ]*) (...)", input = "aaa bßb cßc",
			toff = 3, tcnt = 3 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			assert(!((len(res): i32) != rows[i].tcnt));
			let k: i32 = 0;
			for (k < rows[i].tcnt) {
				let want: str = targets[rows[i].toff + k];
				if (strings.compare(res[k].content,
					want) != 0) {
					abort();
				};
				k += 1;
			};
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// 5b compile-error rows end-to-end through compile() — the two
// parse_repetition texts surface verbatim (+test.ha:461-463 ERROR
// rows). "a{" is the GRADUATED metachar-loud row: with `{` ported the
// deferred-metachar table empties — every metacharacter compiles, and
// the only loud surface left in lib/regex is the POSIX-class runtime
// abort (a fold-4 pin, not an error row). "a{" has no `}` in the
// rest, so it lands on the ha:491-493 syntax text.
@test fn fold5b_compile_errors() void = {
	let rows: [4]cerow = [
		cerow { pat = "^x(abc){-1,2}$",
			want = "Negative repetition count '{-n}'" },
		cerow { pat = "^x(abc){x,2}$",
			want = "Repetition expression syntax error '{n}'" },
		cerow { pat = "^x(abc){0,-2}$",
			want = "Negative repetition count '{-n}'" },
		cerow { pat = "a{",
			want = "Repetition expression syntax error '{n}'" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let p: str = rows[i].pat;
		match (regex.compile(p)) {
		case let e: regex.error => {
			let w: str = rows[i].want;
			assert(!(strings.compare((e: str), w) != 0));
		};
		case => abort();
		};
		i += 1;
	};
};

// fold-5b find/test rows — Hare's own {m,n} matrix (+test.ha:443-460
// incl. the open-ended (0,7) row and the `{,0}de` pair), the `\{`/`\}`
// escape pair :437-438 (pins that ESCAPED braces never enter the `{`
// arm), the 5a carve-out :635 `(a|(b?|c*){,1}|d+|e)` come home, the
// `{0,}`/`{1,}`/`{0,1}` nested twins :649-665 (each must agree with
// its 5a `*`/`+`/`?` sibling's result on the same input — the
// cross-spelling invariant), and the "Various" composed rows :462-485
// minus the [[:class:]] row (POSIX class is a runtime loud abort, the
// fold-4 ruling — excluded until the POSIX fold). end == -1 resolves
// to rune length (+test.ha:693-697). The multibyte `{2}` row and the
// long-input `{1,}` thread/counter-explosion stress row are ww-added
// (B4 lesson; rob's rider). Cross-pins test() == (find() matched);
// the 5a/4/3 tables above re-run untouched in the same binary — the
// dedup/trim/leftmost regression net under the new repeat spawns.
@test fn fold5b_find_cases() void = {
	let rows: [30]f5case = [
		// {m,n} matrix (+test.ha:443-460)
		f5case { expr = "^x(abc){2}$", input = "xabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 7, eb = 7, content = "xabcabc" },
		f5case { expr = "^x(abc){3}$", input = "xabcabc",
			matches = false, ... },
		f5case { expr = "^x(abc){1,2}$", input = "xabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 4, eb = 4, content = "xabc" },
		f5case { expr = "^x(abc){1,2}$", input = "xabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 7, eb = 7, content = "xabcabc" },
		f5case { expr = "^x(abc){1,2}$", input = "xabcabcabc",
			matches = false, ... },
		f5case { expr = "^x(abc){,2}$", input = "xabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 4, eb = 4, content = "xabc" },
		f5case { expr = "^x(abc){,2}$", input = "xabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 7, eb = 7, content = "xabcabc" },
		// the open-ended (0,7) row :450
		f5case { expr = "^x(abc){,2}", input = "xabcabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 7, eb = 7, content = "xabcabc" },
		f5case { expr = "^x(abc){,0}de", input = "xde",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 3, eb = 3, content = "xde" },
		f5case { expr = "^x(abc){,0}de", input = "xe",
			matches = false, ... },
		f5case { expr = "^x(abc){,2}$", input = "xabcabcabc",
			matches = false, ... },
		f5case { expr = "^x(abc){1,}$", input = "xabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 4, eb = 4, content = "xabc" },
		f5case { expr = "^x(abc){1,}$", input = "xabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 7, eb = 7, content = "xabcabc" },
		f5case { expr = "^x(abc){3,}$", input = "xabcabc",
			matches = false, ... },
		f5case { expr = "^x(abc){3,}$", input = "xabcabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 10, eb = 10, content = "xabcabcabc" },
		f5case { expr = "^x(abc){2,2}$", input = "xabcabc",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 7, eb = 7, content = "xabcabc" },
		f5case { expr = "^x(abc){2,2}$", input = "xabc",
			matches = false, ... },
		f5case { expr = "^x(abc){2,2}$", input = "xabcabcabc",
			matches = false, ... },
		// escaped braces stay literal (+test.ha:437-438)
		f5case { expr = "^x(abc)\\{,2\\}$", input = "xabc{,2}",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 8, eb = 8, content = "xabc{,2}" },
		f5case { expr = "^x(abc)\\{,2\\}$", input = "xabcabc{,2}",
			matches = false, ... },
		// the 5a carve-out comes home (+test.ha:635)
		f5case { expr = "(a|(b?|c*){,1}|d+|e)", input = "e",
			matches = true, ncaps = 3, start = 0, sb = 0,
			end = 1, eb = 1, content = "e" },
		// nested twins: each agrees with its 5a sibling
		// (+test.ha:662-666: {0,} vs *, {1,} vs +, {0,1} vs ?)
		f5case { expr = "(a+|b){0,}", input = "ab", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ab" },
		f5case { expr = "(a+|b){1,}", input = "ab", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 2, eb = 2,
			content = "ab" },
		f5case { expr = "(a+|b){0,1}", input = "ab", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 1, eb = 1,
			content = "a" },
		// "Various" composed rows (+test.ha:462-485; the M15 4QN
		// [[:class:]] row is excluded — POSIX class is a runtime
		// loud abort until the POSIX fold)
		f5case { expr = "^.(1024)?(face)*(1024)*ca*(f+e?cafe)(babe)+$",
			input = "X1024facefacecaaaaafffcafebabebabe",
			matches = true, ncaps = 6, start = 0, sb = 0,
			end = 34, eb = 34,
			content = "X1024facefacecaaaaafffcafebabebabe" },
		f5case { expr = ".(1024)?(face)*(1024)*ca*(f+e?cafe)(babe)+",
			input = "X1024facefacecaaaaafffcafebabebabe",
			matches = true, ncaps = 6, start = 0, sb = 0,
			end = 34, eb = 34,
			content = "X1024facefacecaaaaafffcafebabebabe" },
		f5case { expr = "^.(1024)?(face)*(1024)*ca*(f+e?cafe)(babe)+$",
			input = "1024facefacecaaaaafffcafebabebabe",
			matches = false, ... },
		f5case { expr = ".(1024)?(face)*(1024)*ca*(f+e?cafe)(babe)+",
			input = "1024facefacecaaaaafffcafebabebabe",
			matches = true, ncaps = 6, start = 3, sb = 3,
			end = 33, eb = 33,
			content = "4facefacecaaaaafffcafebabebabe" },
		// ww-added multibyte repeat row (B4)
		f5case { expr = "^(ä|b){2}x$", input = "äbx", matches = true,
			ncaps = 2, start = 0, sb = 0, end = 3, eb = 4,
			content = "äbx" },
		// ww-added (rob's rider): long-input {1,} — thread/counter
		// explosion stress under repeat spawns
		f5case { expr = "(a+|b){1,}", input = "aaaabbbbaaaabbbb",
			matches = true, ncaps = 2, start = 0, sb = 0,
			end = 16, eb = 16, content = "aaaabbbbaaaabbbb" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			if (rows[i].matches) {
				assert(!((len(res): i32) != rows[i].ncaps));
				assert(!(res[0].start != rows[i].start));
				if (res[0].start_bytesize != rows[i].sb) {
					abort();
				};
				assert(!(res[0].end != rows[i].end));
				if (res[0].end_bytesize != rows[i].eb) {
					abort();
				};
				let wc: str = rows[i].content;
				if (strings.compare(res[0].content, wc) != 0) {
					abort();
				};
			} else {
				assert(!(len(res) != 0));
			};
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != (len(res) != 0)));
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// findall × repeat composition (+test.ha:724 `fo{2,}`) — the greedy
// per-position longest pick plus the non-overlap advance over a
// repeat-counted program.
@test fn fold5b_findall() void = {
	let targets: [4]str = ["foo", "fooo", "foo", "foo"];
	let rows: [1]facase = [
		facase { expr = "fo{2,}", input = "fo foo fooofoof oofoo",
			toff = 0, tcnt = 4 },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: ([]regex.result | nomem) =
				regex.findall(&re, inp);
			assert(!(!(fr is []regex.result)));
			let results: []regex.result = fr as []regex.result;
			assert(!(len(results) != rows[i].tcnt));
			let k: i32 = 0;
			for (k < rows[i].tcnt) {
				let want: str = targets[rows[i].toff + k];
				if (strings.compare(results[k][0].content,
					want) != 0) {
					abort();
				};
				k += 1;
			};
			regex.result_freeall(results);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};

// compile error: `[[:` with no valid class name
// ref/hare/regex/+test.ha — no direct cite; error string from
// regex.ha:203 "No character class after '[:'".
@test fn fold6_compile_errors() void = {
	let rows: [1]cerow = [
		cerow { pat = "[[:xyz", want = "No character class after '[:'" },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let p: str = rows[i].pat;
		match (regex.compile(p)) {
		case let e: regex.error => {
			let w: str = rows[i].want;
			assert(!(strings.compare((e: str), w) != 0));
		};
		case => abort();
		};
		i += 1;
	};
};

// charsets-table content pin: a POSIX class bracket emits ONE
// charset_class_item element (cssig → -2), not a literal expansion.
// ref/hare/regex/+test.ha:305-308 POSIX class rows.
@test fn fold6_charsets() void = {
	// "[[:digit:]]" → 1 charset, 1 class elem
	let c: (regex.regex | regex.error | nomem) = regex.compile("[[:digit:]]");
	match (c) {
	case let re: regex.regex => {
		assert(!(re.charsets.len != 1));
		let cs0: [](regex.charset_lit_item | regex.charset_range_item |
			regex.charset_class_item) = re.charsets[0];
		assert(!((len(cs0): i32) != 1));
		assert(!(cssig(cs0, 0) != -2));
		regex.finish(&re);
	};
	case => abort();
	};
};

// end-to-end find/test rows for all 12 POSIX classes + negation.
// ref/hare/regex/+test.ha:278-345 POSIX subset.
@test fn fold6_find_cases() void = {
	let rows: [28]fcase = [
		// digit
		fcase { expr = "[[:digit:]]", input = "5", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "5" },
		fcase { expr = "[[:digit:]]", input = "a", matches = false, ... },
		// alpha
		fcase { expr = "^[[:alpha:]]+$", input = "abc", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "abc" },
		fcase { expr = "^[[:alpha:]]+$", input = "abc1", matches = false, ... },
		// alnum
		fcase { expr = "^[[:alnum:]]+$", input = "abc9", matches = true,
			start = 0, sb = 0, end = 4, eb = 4, content = "abc9" },
		fcase { expr = "^[[:alnum:]]+$", input = "abc!", matches = false, ... },
		// space
		fcase { expr = "[[:space:]]", input = " ", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = " " },
		fcase { expr = "[[:space:]]", input = "a", matches = false, ... },
		// upper
		fcase { expr = "^[[:upper:]]+$", input = "ABC", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "ABC" },
		fcase { expr = "^[[:upper:]]+$", input = "ABc", matches = false, ... },
		// lower
		fcase { expr = "^[[:lower:]]+$", input = "abc", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "abc" },
		fcase { expr = "^[[:lower:]]+$", input = "abC", matches = false, ... },
		// xdigit
		fcase { expr = "^[[:xdigit:]]+$", input = "0aF", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "0aF" },
		fcase { expr = "^[[:xdigit:]]+$", input = "0g", matches = false, ... },
		// blank (space or tab)
		fcase { expr = "[[:blank:]]", input = "\t", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "\t" },
		fcase { expr = "[[:blank:]]", input = "a", matches = false, ... },
		// punct
		fcase { expr = "[[:punct:]]", input = ".", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "." },
		fcase { expr = "[[:punct:]]", input = "a", matches = false, ... },
		// graph
		fcase { expr = "[[:graph:]]", input = "!", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "!" },
		fcase { expr = "[[:graph:]]", input = " ", matches = false, ... },
		// print
		fcase { expr = "[[:print:]]", input = " ", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = " " },
		fcase { expr = "[[:print:]]", input = "\x01", matches = false, ... },
		// cntrl
		fcase { expr = "[[:cntrl:]]", input = "\x01", matches = true,
			start = 0, sb = 0, end = 1, eb = 1, content = "\x01" },
		fcase { expr = "[[:cntrl:]]", input = "a", matches = false, ... },
		// negated class
		fcase { expr = "^[^[:digit:]]+$", input = "abc", matches = true,
			start = 0, sb = 0, end = 3, eb = 3, content = "abc" },
		fcase { expr = "^[^[:digit:]]+$", input = "ab5", matches = false, ... },
		// composition: digit+ in surrounding text
		fcase { expr = "[[:digit:]]+", input = "abc123def",
			matches = true, start = 3, sb = 3, end = 6, eb = 6,
			content = "123" },
		fcase { expr = "[[:digit:]]+", input = "nodigits",
			matches = false, ... },
	];
	let i: i32 = 0;
	for (i < len(rows)) {
		let ex: str = rows[i].expr;
		let inp: str = rows[i].input;
		let c: (regex.regex | regex.error | nomem) = regex.compile(ex);
		match (c) {
		case let re: regex.regex => {
			let fr: (regex.result | nomem) = regex.find(&re, inp);
			assert(!(!(fr is regex.result)));
			let res: regex.result = fr as regex.result;
			if (rows[i].matches) {
				assert(!(len(res) != 1));
				assert(!(res[0].start != rows[i].start));
				if (res[0].start_bytesize != rows[i].sb) {
					abort();
				};
				assert(!(res[0].end != rows[i].end));
				if (res[0].end_bytesize != rows[i].eb) {
					abort();
				};
				let wc: str = rows[i].content;
				if (strings.compare(res[0].content, wc) != 0) {
					abort();
				};
			} else {
				assert(!(len(res) != 0));
			};
			let tr: (bool | nomem) = regex.test(&re, inp);
			assert(!(!(tr is bool)));
			assert(!((tr as bool) != (len(res) != 0)));
			regex.result_free(res);
			regex.finish(&re);
		};
		case => abort();
		};
		i += 1;
	};
};