def S:str = "hi"; S[0] silently segfaulted: a def is a compile-time
constant, never materialized as DATA (unlike let), so indexing it emitted
an unbacked main.S(SB) reference -> cstage ran into frame garbage,
wwstage link-failed. str[i] itself is valid ww (a deliberate Go-like
str[i]->u8 byte-index that lib/strings compare/dup depend on), so the fix
is narrow: the N_INDEX TY_STR arm now rejects an index whose operand is a
bare SK_DEF scalar-str symbol, both stages -- 'cannot index a def-constant
str; bind it to a let'. INDEX-ONLY: len(S) and &S are already loud, and a
def's .len/.ptr field reads (the load-bearing w6l INTERP) are N_DOT, a
different arm, and stay valid.
A rule-9 WHY-comment records str[i]->u8 as a sanctioned divergence from
Hare's strings.toutf8. The full make-it-work fold (len(S)->2, S[0]->byte)
is deferred (#16). byte-id 990-997 8/8. test/wcc/821 table-driven.
Hojun-Cho
03fc7c7abe