`[_]T = [...]` (canonical Hare array-length inference) silently
miscompiled to a zero-length array: the parser already left the array
type's length child nil as the infer sentinel — distinct from an
explicit [N] — but neither checker stamped the real count, so `len(x)`
returned 0 with no diagnostic (rule-7 silent miscompile). Module-level
was worse on wwstage, where `x.len` on ANY global array (even an
explicit [N]) fell to the SB fallback and mis-emitted `MOVQ len(SB), AX`
(linker: undefined reference to len).
The length lives in the stamped TYPE and cgen already keys stride /
length / data-emission off it, so stamping the inferred count at the one
checker inference point closes it permanently (rob's #7 ruling):
- check.c clet + module-level N_LET pass-2: count the initializer's
elements and patch the array type's length (the Sym too, so a later
x.len reads the inferred alen). No-init / non-array init can't infer
-> loud error, never a silent zero-length array.
- check.ww inferarraylen: the wwstage twin — stamp a synthesized
N_INTLIT length child before resolvewalk caches the array tinfo;
same loud-error rule. Idempotent for the module-level double-call.
- cgenexpr.ww cgdot: the missing wwstage arm for a top-level [N]T
global's .len / .ptr (cstage cgen.c:8011 already had it).
- cgenutil.ww letslotsize: drop the now-redundant [_] slot-size
intercept — a workaround for this very bug; the stamped length flows
through the general slotsize path (rule 7).
Both stages converge byte-identical; new table-driven test 684 covers
[_]int/[_]str/[_]u8 local + module-level, len + element read-back,
dual-stage runtime + asm byte-id, plus three negative no-infer rows.
Hojun-Cho
7ca32432b1