95 lines
5.1 KiB
Markdown
95 lines
5.1 KiB
Markdown
# Ny JSON IR v0 — Minimal Spec (Stage‑2)
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Status: experimental but stable for Phase‑15 Stage‑2. Input to `--ny-parser-pipe`.
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Version and root
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- `version`: 0
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- `kind`: "Program"
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- `body`: array of statements
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Statements (`StmtV0`)
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- `Return { expr }`
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- `Extern { iface, method, args[] }` (optional; passes through to `ExternCall`)
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- `Expr { expr }` (expression statement; side effects only)
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- `Local { name, expr }` (Stage‑2)
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- `If { cond, then: Stmt[], else?: Stmt[] }` (Stage‑2)
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- `Loop { cond, body: Stmt[] }` (Stage‑2; while(cond) body)
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- `Break` (Stage‑3; exits current loop)
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- `Continue` (Stage‑3; jumps to loop head)
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- `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)
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Expressions (`ExprV0`)
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- `Int { value }` where `value` is JSON number or digit string
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- `Str { value: string }`
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- `Bool { value: bool }`
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- `Binary { op: "+"|"-"|"*"|"/", lhs, rhs }`
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- `Compare { op: "=="|"!="|"<"|"<="|">"|">=", lhs, rhs }`
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- `Logical { op: "&&"|"||", lhs, rhs }` (short‑circuit)
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- `Call { name: string, args[] }` (function by name)
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- `Method { recv: Expr, method: string, args[] }` (box method)
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- `New { class: string, args[] }` (construct Box)
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- `Var { name: string }`
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- `Throw { expr }` (Stage‑3; currently degrades to expression statement when runtime semantics are disabled)
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CFG conventions (lowered by the bridge)
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- If: create `then_bb`, `else_bb`, `merge_bb`. Both branches jump to merge if unterminated.
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- Loop: `preheader -> cond_bb -> (body_bb or exit_bb)`, body jumps back to cond.
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- Short‑circuit Logical: create `rhs_bb`, `fall_bb`, `merge_bb` with constants on fall path.
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- All blocks end with a terminator (branch/jump/return).
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PHI merging（Phase‑15 終盤の方針）
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- 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。
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- 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。
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- 将来（LoopForm= MIR18）では LoopForm 占位命令から逆 Lowering で PHI を自動化予定。
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- 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。
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Type meta (emitter/LLVM harness cooperation)
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- `+` with any string operand → string concat path（handle固定）。
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- `==/!=` with both strings → string compare path。
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Special notes
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- `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`）。
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- `--ny-parser-pipe` は stdin の JSON v0 を受け取り、MIR→MIR‑Interp 経由で実行する。
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Unified Members (Phase‑15)
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- Source‑level unified members (stored/computed/once/birth_once) are lowered before JSON emission into regular slots/methods; JSON v0 remains unchanged.
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- Lowering conventions:
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- stored → slot (initializer becomes a one‑time evaluation in construction path)
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- computed → synthetic getter method; field read becomes method call
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- once → synthetic getter + hidden `Option<T>` slot with first‑read initialization; uncaught exception on first read poisons the property and rethrows on subsequent reads
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- birth_once → hidden slot initialized before user `birth` body in declaration order; uncaught exception aborts construction
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- method postfix `catch/cleanup` lower to try/catch/finally when Stage‑3 is enabled; when disabled, bodies execute without handlers
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CLI/Env cheatsheet
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- Pipe: `echo '{...}' | target/release/nyash --ny-parser-pipe`
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- File: `target/release/nyash --json-file sample.json`
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- Verbose MIR dump: `NYASH_CLI_VERBOSE=1`
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- me dummy: `NYASH_BRIDGE_ME_DUMMY=1 NYASH_BRIDGE_ME_CLASS=ConsoleBox`
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Examples
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Arithmetic
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```json
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{"version":0,"kind":"Program","body":[
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{"type":"Return","expr":{
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"type":"Binary","op":"+",
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"lhs":{"type":"Int","value":1},
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"rhs":{"type":"Binary","op":"*","lhs":{"type":"Int","value":2},"rhs":{"type":"Int","value":3}}
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}}
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]}
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```
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If with local + PHI merge
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```json
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{"version":0,"kind":"Program","body":[
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{"type":"Local","name":"x","expr":{"type":"Int","value":1}},
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{"type":"If","cond":{"type":"Compare","op":"<","lhs":{"type":"Int","value":1},"rhs":{"type":"Int","value":2}},
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"then":[{"type":"Local","name":"x","expr":{"type":"Int","value":10}}],
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"else":[{"type":"Local","name":"x","expr":{"type":"Int","value":20}}]
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},
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{"type":"Return","expr":{"type":"Var","name":"x"}}
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]}
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```
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- `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.
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- `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`.
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