Port of ref/hare/regex/regex.ha fold 1 (the data model). Lands the
full type model — error, the inst_* variants + 10-variant inst union
(the nominally-distinct same-underlying size/void aliases included),
result/capture, charset + items, the regex struct — plus finish().
Test 989_regex_run pins variant discrimination, payload extraction,
struct shapes, and finish() on cstage; w6c == w6c_ww byte-identical.
Two fold-1 constructs are held back behind filed compiler/fidelity
gaps, documented at their sites (regex tasks A–D):
- charclass_map (regex.ha:74-87): const [](str, *fn(rune) bool)
table — blocked on the array-literal->slice element-coercion
checker gap (type.c:402-404 #258 borrow uses exact type_eq,
no element decay). It needs `import ascii;`, so both land with
the consuming fold (compile) once the gap is fixed.
- finish() free()s; ww is a no-free runtime (rt/alloc.s:30), so the
faithful body drops the frees, as the port drops every Hare
free(). Kept as a no-op for API parity.
DEFERRED to later folds: compile()/exec/find/replace.
Hojun-Cho
b6a41ae063