hakorune/docs/reference/ir/json_v0.md

Ny JSON IR v0 — Minimal Spec (Stage‑2)

Status: experimental but stable for Phase‑15 Stage‑2. Input to --ny-parser-pipe.

Version and root

• version: 0
• kind: "Program"
• body: array of statements

Statements (StmtV0)

• Return { expr }
• Extern { iface, method, args[] } (optional; passes through to ExternCall)
• Expr { expr } (expression statement; side effects only)
• Local { name, expr } (Stage‑2)
• If { cond, then: Stmt[], else?: Stmt[] } (Stage‑2)
• Loop { cond, body: Stmt[] } (Stage‑2; while(cond) body)
• Break (Stage‑3; exits current loop)
• Continue (Stage‑3; jumps to loop head)
• Try { try: Stmt[], catches?: Catch[], finally?: Stmt[] } (Stage‑3 skeleton; surface syntax uses cleanup, but the v0 field name remains finally for compatibility; currently lowered as sequential try body only when runtime support is absent)

Expressions (ExprV0)

• Int { value } where value is JSON number or digit string
• Str { value: string }
• Bool { value: bool }
• Binary { op: "+"|"-"|"*"|"/", lhs, rhs }
• Compare { op: "=="|"!="|"<"|"<="|">"|">=", lhs, rhs }
• Logical { op: "&&"|"||", lhs, rhs } (short‑circuit)
• Call { name: string, args[] } (function by name)
• Method { recv: Expr, method: string, args[] } (box method)
• New { class: string, args[] } (construct Box)
• Var { name: string }
• Throw { expr } (Stage‑3; currently degrades to expression statement when runtime semantics are disabled)

CFG conventions (lowered by the bridge)

• If: create then_bb, else_bb, merge_bb. Both branches jump to merge if unterminated.
• Loop: preheader -> cond_bb -> (body_bb or exit_bb), body jumps back to cond.
• Short‑circuit Logical: create rhs_bb, fall_bb, merge_bb with constants on fall path.
• All blocks end with a terminator (branch/jump/return).

PHI merging（Phase‑15 終盤の方針）

• MIR 生成層は PHI を生成しない（MIR13 運用）。If/Loop の合流は LLVM 層（llvmlite/Resolver）が PHI を合成。
• ループは既存 CFG（preheader→cond→{body|exit}; body→cond）の検出により、ヘッダ BB で搬送値の PHI を構築。
• 将来（LoopForm= MIR18）では LoopForm 占位命令から逆 Lowering で PHI を自動化予定。
• PHI‑off 運用（Builder 側の規約）: merge 内に copy を置かず、then/else の pred へ edge_copy のみを挿入（self‑copy は No‑Op）。use‑before‑def と重複 copy を原理的に回避する。

Type meta (emitter/LLVM harness cooperation)

• + with any string operand → string concat path（handle固定）。
• ==/!= with both strings → string compare path。

Special notes

• Var("me"): Bridge 既定では未定義エラー。デバッグ用に NYASH_BRIDGE_ME_DUMMY=1 でダミー NewBox{class} を注入可（NYASH_BRIDGE_ME_CLASS 省略時は Main）。
• --ny-parser-pipe は stdin の JSON v0 を受け取り、MIR→MIR‑Interp 経由で実行する。

Unified Members (Phase‑15)

• Source‑level unified members (stored/computed/once/birth_once) are lowered before JSON emission into regular slots/methods; JSON v0 remains unchanged.
• Lowering conventions:
  • stored → slot (initializer becomes a one‑time evaluation in construction path)
  • computed → synthetic getter method; field read becomes method call
  • once → synthetic getter + hidden Option<T> slot with first‑read initialization; uncaught exception on first read poisons the property and rethrows on subsequent reads
  • birth_once → hidden slot initialized before user birth body in declaration order; uncaught exception aborts construction
  • method postfix catch/cleanup lower to try/catch/finally when Stage‑3 is enabled; when disabled, bodies execute without handlers

CLI/Env cheatsheet

• Pipe: echo '{...}' | target/release/nyash --ny-parser-pipe
• File: target/release/nyash --json-file sample.json
• Verbose MIR dump: NYASH_CLI_VERBOSE=1
• me dummy: NYASH_BRIDGE_ME_DUMMY=1 NYASH_BRIDGE_ME_CLASS=ConsoleBox

Examples

Arithmetic

{"version":0,"kind":"Program","body":[
  {"type":"Return","expr":{
    "type":"Binary","op":"+",
    "lhs":{"type":"Int","value":1},
    "rhs":{"type":"Binary","op":"*","lhs":{"type":"Int","value":2},"rhs":{"type":"Int","value":3}}
  }}
]}

If with local + PHI merge

{"version":0,"kind":"Program","body":[
  {"type":"Local","name":"x","expr":{"type":"Int","value":1}},
  {"type":"If","cond":{"type":"Compare","op":"<","lhs":{"type":"Int","value":1},"rhs":{"type":"Int","value":2}},
    "then":[{"type":"Local","name":"x","expr":{"type":"Int","value":10}}],
    "else":[{"type":"Local","name":"x","expr":{"type":"Int","value":20}}]
  },
  {"type":"Return","expr":{"type":"Var","name":"x"}}
]}

• Break / Continue are emitted when Stage‑3 gate is enabled. When the bridge is compiled without Stage‑3 lowering, frontends may degrade them into Expr(Int(0)) as a safety fallback.
• Try nodes include optional catches entries of the form { param?: string, typeHint?: string, body: Stmt[] }. Until runtime exception semantics land, downstream lowers only the try body and ignores handlers/finally.