hakorune/docs/development/current/main/phases/phase-258/README.md

Status: Completed (2025-12-20) Scope: StringUtils.index_of_string/2（dynamic window scan）を JoinIR で受理して --profile quick を進める。 Related:

• Now: docs/development/current/main/10-Now.md
• Phase 257: docs/development/current/main/phases/phase-257/README.md
• Phase 259 (Next): docs/development/current/main/phases/phase-259/README.md
• Design goal: docs/development/current/main/design/join-explicit-cfg-construction.md

Phase 258: StringUtils.index_of_string/2 (dynamic window scan)

Current Status (SSOT)

• ✅ P0 完了（2025-12-21）
• Former first FAIL: json_lint_vm / StringUtils.index_of_string/2
• New first FAIL: json_lint_vm / StringUtils.is_integer/1（Phase 259へ移行）
• Shape summary (from quick log):
  • prelude: if substr.length()==0 return 0, if substr.length()>s.length() return -1
  • loop: loop(i <= s.length() - substr.length()) { if s.substring(i, i+substr.length()) == substr return i; i=i+1 }
  • post: return -1
  • caps: If,Loop,Return

Goal

• ✅ ./tools/smokes/v2/run.sh --profile quick が StringUtils.index_of_string/2 を突破し、次の FAIL へ進む

Proposed Approach (P0)

方針: Pattern6（ScanWithInit）を “needle length 付き scan” に最小拡張する（構造で解決）

Pattern6 との差分だけを足す:

• loop cond: i <= s.length() - substr.length()（bound 付き）
• window: substring(i, i + substr.length())
• needle: substr（String）

JoinIR 側は P0 では “毎回 length() を呼んでよい”。まず correctness を固定:

• needle_len = substr.length()
• bound = s.length() - needle_len
• stop: i > bound で k_exit（not-found return）
• match: s.substring(i, i + needle_len) == substr で return i
• step: i = i + 1

Tasks (Draft)

1. Fixture + integration smokes
2. Pattern6 extractor を拡張して index_of_string/2 の loop 形を accept（Fail-Fast）
3. Pattern6 lowerer を拡張（dynamic window length / bound）して JoinIR を生成
4. --verify / integration / quick を回して SSOT 更新