C5 (tasks #10 + #41): the len() builtin's operand handling was an arm
enumeration that leaked FOUR siblings over time (#235 tuple-elem →
#19 indexed-elem → F2 len(xs[i].field) → FA2/FB1 len(*p)) — every
unhandled slice/str operand shape fell to a bare cgexpr fallback that
returned the slice DATA POINTER as the length. Silent ptr-garbage,
byte-id both stages, gate-blind. Probing at d642017 surfaced the full
family: len(*p) (param 48 / local 64), len(xs[i].field) (147),
len((*p)[i].field) (10), len(s.field) (75), len(p.field) (87) — plus
the same garbage for non-place operands len("abc") (40),
len(xs[1:3]) (48), len(mk()) (0). Review widened it twice more:
len(**pp) (chained deref, garbage 208 at e481cb8) and the EMPTY-slice
deref (len 0 reported as .ptr — masked by exit-code truncation, hence
the branchy test row).
The enumeration is closed by construction (ken's verdict): enumerated
fast-paths keep their pre-fix asm byte-identically (ident local/global,
#235 tuple element — not resolver-addressable, cgplaceaddr has no
TY_TUPLE hop — #19 indexed element, TY_ARRAY const fold), then ONE
uniform header-place route via cgplaceaddr resolves every other
slice/str place and reads the .len word at place+8 (the same offset
math as the ident arm). Non-place operands (string literal, slicing
expr, call result) die LOUD per rule 7 — previously the same silent
ptr-garbage; Hare instead const-folds len of literals, that parity is
filed as #46. The ident arm's off==0 non-let residue (MOVQ 8(BP)
garbage) now also routes resolver-or-loud. cstage's dispatch peel is
aligned to wwstage's existing TY_NAMED loop-chase (single-peel +
loud tail would have surfaced as cs-rejects/ww-accepts on 2-level
aliases).
Asm-neutrality: all five embedded main.combined.ww corpora compile
byte-identically under pristine-parent w6c vs fixed w6c; per-shape
pins (ident local/global, tuple, index, array) NEUTRAL + cs==ww.
802_lenidx_run grows 14 rows: the nine garbage shapes (incl. computed
index through a deref spine, param-vs-local *p, chained **pp, empty
slice), two neutrality controls (global and tuple fast-paths have
dedicated runs: 797, 903), three reject rows pinning the exact rule-7
text in BOTH stages; all fix rows verified FAILING against a pristine
build of the parent e481cb8 (12/19 fail there, 19/19 green here).
Consumers unblocked: regex fold-2b tranche C ha:795/798
len(threads[i].captures); lib/regex add_thread's (*threads).len
dodge (regex.ww:238, WHY comment cites #41) reverts to len(*threads)
with the tranche-C port, not here.
`len(xs[i])` over a [N]str/[]str (and []T slice) element returned the
element's .ptr, not its length, on BOTH stages (shared gap, not rule-10):
the len() builtin had no N_INDEX arm, so it fell to the bare-cgexpr
fallback, where the N_INDEX str/slice load (cgslicehdr) leaves AX=.ptr,
BX=.len, CX=.cap — and len() returned AX (the ptr) as the length.
Add an N_INDEX arm gated on a (TY_SLICE||TY_STR) element in both stages:
cgexpr the element, then MOVQ BX,AX to shuffle the len word into the
result reg — the same shape as the #14 .len pseudo-field fix. Byte-id
neutral (no bootstrap source uses len(indexed-element)); regenerated
w6c + wwdump combined.ww. New 802_lenidx_run pins runtime + cs==ww.
