selfhost: stub stage3 parser nodes under gate

CURRENT_TASK.md

@@ -37,8 +37,12 @@ Quick Next (today)
   3) Resolver/BoxIndex の prefix メタ反映 ✅ Done 2025‑09‑16
      - `plugin_meta_by_box` を構築し、`require_prefix` / `expose_short_names` を `resolve_using_target` へ適用。
      - `NYASH_PLUGIN_REQUIRE_PREFIX` が無効でも per-plugin meta で短名禁止を検知。
-  4) 自己ホスト経路で Ny 実装切替のゲート準備（現状は Python MVP 優先を維持）。
-  5) テスト:
+  4) Parser Stage‑3 下地 ✅ Done 2025‑09‑16
+     - `ParserBox.stage3_enable()` を追加し、Break/Continue/Throw/Try を JSON v0 に出力できるゲートを実装。
+     - `--stage3` CLI フラグから ParserBox へ渡す導線を追加。
+     - `docs/reference/architecture/parser_mvp_stage3.md` に Stage‑3 設計を記録。
+  5) 自己ホスト経路で Ny 実装切替のゲート準備（現状は Python MVP 優先を維持）。
+  6) テスト:
      - `source tools/dev_env.sh pyvm`
      - `NYASH_VM_USE_PY=1 ./tools/selfhost_stage2_smoke.sh`
      - `NYASH_VM_USE_PY=1 ./tools/selfhost_stage2_bridge_smoke.sh`
@@ -63,8 +67,8 @@ Current Status
 
 Open
 - Bridge/PHI の正規化: 短絡（入れ子）における merge/PHI incoming を固定化（rhs_end/fall_bb の順序）。
-- JSON v0 の拡張方針: break/continue/try/catch/finally の表現（受け皿設計 or 受理時の事前降下）。
-- per‑plugin meta の反映: `require_prefix/expose_short_names/prefix` を Resolver 挙動へ段階適用（導線は実装済み）。
+- JSON v0 の拡張方針: break/continue/try/catch/finally の表現（受け皿設計 or 受理時の事前降下）。➡ `docs/reference/architecture/parser_mvp_stage3.md`
+- per‑plugin meta の反映: `require_prefix/expose_short_names/prefix` を Resolver 挙動へ段階適用（導線は実装済み）。✅ 2025‑09‑16 prefix enforcement とテスト追加済み。
 - `me` の扱い: MVP は `NYASH_BRIDGE_ME_DUMMY=1` の仮注入を継続（将来撤去）。
 - LLVM 直結（任意）: JSON v0 → LLVM の導線追加は後回し。
 

apps/selfhost-compiler/boxes/parser_box.nyash

@@ -2,8 +2,20 @@
 box ParserBox {
   gpos
   usings_json
+  stage3
 
-  birth() { me.gpos = 0 me.usings_json = "[]" return 0 }
+  birth() { me.gpos = 0 me.usings_json = "[]" me.stage3 = 0 return 0 }
+
+  stage3_enable(flag) {
+    if flag == null { flag = 0 }
+    if flag == 0 { me.stage3 = 0 } else { me.stage3 = 1 }
+    return 0
+  }
+
+  stage3_enabled() {
+    if me.stage3 == 1 { return 1 }
+    return 0
+  }
 
   esc_json(s) {
     local out = ""
@@ -613,12 +625,24 @@ box ParserBox {
     // Stage-3 acceptance (syntax only): break / continue → no-op expression
     if me.starts_with_kw(src, j, "break") == 1 {
       j = j + 5
+      if me.stage3_enabled() == 1 {
+        j = me.skip_ws(src, j)
+        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
+        me.gpos_set(j)
+        return "{\"type\":\"Break\"}"
+      }
       if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
       me.gpos_set(j)
       return "{\"type\":\"Expr\",\"expr\":{\"type\":\"Int\",\"value\":0}}"
     }
     if me.starts_with_kw(src, j, "continue") == 1 {
       j = j + 8
+      if me.stage3_enabled() == 1 {
+        j = me.skip_ws(src, j)
+        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
+        me.gpos_set(j)
+        return "{\"type\":\"Continue\"}"
+      }
       if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
       me.gpos_set(j)
       return "{\"type\":\"Expr\",\"expr\":{\"type\":\"Int\",\"value\":0}}"
@@ -629,6 +653,11 @@ box ParserBox {
       j = me.skip_ws(src, j)
       local e_throw = me.parse_expr2(src, j)
       j = me.gpos_get()
+      if me.stage3_enabled() == 1 {
+        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
+        me.gpos_set(j)
+        return "{\"type\":\"Throw\",\"expr\":" + e_throw + "}"
+      }
       if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
       me.gpos_set(j)
       return "{\"type\":\"Expr\",\"expr\":" + e_throw + "}"
@@ -640,7 +669,10 @@ box ParserBox {
       // parse try block
       local try_res = me.parse_block2(src, j)
       local at_t = try_res.lastIndexOf("@")
+      local try_json = try_res.substring(0, at_t)
       j = me.to_int(try_res.substring(at_t+1, try_res.length()))
+      local catches_json = "["
+      local catch_first = 1
       // zero or more catch
       local guard_ct = 0
       local max_ct = 100
@@ -651,10 +683,24 @@ box ParserBox {
         if me.starts_with_kw(src, j, "catch") == 1 {
           j = j + 5
           j = me.skip_ws(src, j)
+          local catch_type = null
+          local catch_param = null
           if src.substring(j, j+1) == "(" { j = j + 1 j = me.skip_ws(src, j)
             // optional type + name
-            if me.is_alpha(src.substring(j, j+1)) { local id1 = me.read_ident2(src, j) local at1 = id1.lastIndexOf("@") j = me.to_int(id1.substring(at1+1, id1.length())) j = me.skip_ws(src, j) }
-            if me.is_alpha(src.substring(j, j+1)) { local id2 = me.read_ident2(src, j) local at2 = id2.lastIndexOf("@") j = me.to_int(id2.substring(at2+1, id2.length())) j = me.skip_ws(src, j) }
+            if me.is_alpha(src.substring(j, j+1)) {
+              local id1 = me.read_ident2(src, j)
+              local at1 = id1.lastIndexOf("@")
+              catch_type = id1.substring(0, at1)
+              j = me.to_int(id1.substring(at1+1, id1.length()))
+              j = me.skip_ws(src, j)
+            }
+            if me.is_alpha(src.substring(j, j+1)) {
+              local id2 = me.read_ident2(src, j)
+              local at2 = id2.lastIndexOf("@")
+              catch_param = id2.substring(0, at2)
+              j = me.to_int(id2.substring(at2+1, id2.length()))
+              j = me.skip_ws(src, j)
+            }
             if src.substring(j, j+1) == ")" { j = j + 1 }
           }
           j = me.skip_ws(src, j)
@@ -662,16 +708,37 @@ box ParserBox {
           local c_res = me.parse_block2(src, j)
           local atc = c_res.lastIndexOf("@")
           j = me.to_int(c_res.substring(atc+1, c_res.length()))
+          if me.stage3_enabled() == 1 {
+            local entry = "{"
+            local wrote = 0
+            if catch_param != null && catch_param.length() > 0 { entry = entry + "\"param\":\"" + me.esc_json(catch_param) + "\"" wrote = 1 }
+            if catch_type != null && catch_type.length() > 0 { if wrote == 1 { entry = entry + "," } entry = entry + "\"typeHint\":\"" + me.esc_json(catch_type) + "\"" wrote = 1 }
+            local body_json = c_res.substring(0, atc)
+            if wrote == 1 { entry = entry + "," }
+            entry = entry + "\"body\":" + body_json + "}"
+            if catch_first == 0 { catches_json = catches_json + "," + entry } else { catches_json = catches_json + entry catch_first = 0 }
+          }
         } else { cont_ct = 0 }
       }
+      catches_json = catches_json + "]"
       // optional finally
       j = me.skip_ws(src, j)
+      local finally_json = null
       if me.starts_with_kw(src, j, "finally") == 1 {
         j = j + 7
         j = me.skip_ws(src, j)
         local f_res = me.parse_block2(src, j)
         local atf = f_res.lastIndexOf("@")
         j = me.to_int(f_res.substring(atf+1, f_res.length()))
+        finally_json = f_res.substring(0, atf)
+      }
+      if me.stage3_enabled() == 1 {
+        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
+        me.gpos_set(j)
+        local node = "{\"type\":\"Try\",\"try\":" + try_json + ",\"catches\":" + catches_json
+        if finally_json != null { node = node + ",\"finally\":" + finally_json }
+        node = node + "}"
+        return node
       }
       if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
       me.gpos_set(j)

apps/selfhost-compiler/compiler.nyash

@@ -33,8 +33,9 @@ static box Main {
   }
 
   // Parser delegation
-  parse_program(src) {
+  parse_program(src, stage3_flag) {
     local parser = new ParserBox()
+    if stage3_flag == 1 { parser.stage3_enable(1) }
     // Collect using metadata (no-op acceptance in Stage‑15)
     parser.extract_usings(src)
     me._usings = parser.get_usings_json()
@@ -53,17 +54,25 @@ static box Main {
     local src = "return 1+2*3"
     local read_tmp = 0
     local input_path = null
+    local stage3_mode = 0
     if args != null {
       local alen = args.length()
       local i = 0
       loop(i < alen) {
         local a = args.get(i)
-        if a == "--read-tmp" { read_tmp = 1 } else {
-          if a == "--min-json" { /* handled later */ } else {
-            // First non-flag arg as input path
+        if a == "--read-tmp" {
+          read_tmp = 1
+        } else {
+          if a == "--min-json" {
+            /* handled later */
+          } else {
+            if a == "--stage3" {
+              stage3_mode = 1
+            } else {
               if input_path == null { input_path = a }
             }
           }
+        }
         i = i + 1
       }
     }
@@ -85,7 +94,8 @@ static box Main {
       local alen = args.length()
       local i = 0
       loop(i < alen) {
-        if args.get(i) == "--min-json" { min_mode = 1 }
+        local arg = args.get(i)
+        if arg == "--min-json" { min_mode = 1 }
         i = i + 1
       }
     }
@@ -93,7 +103,7 @@ static box Main {
     if min_mode == 1 {
       json = "{\"version\":0,\"kind\":\"Program\",\"body\":[{\"type\":\"Return\",\"expr\":{\"type\":\"Int\",\"value\":0}}]}"
     } else {
-      json = me.parse_program(src)
+      json = me.parse_program(src, stage3_mode)
     }
 
     // Emit via EmitterBox (attach meta.usings when available)

docs/reference/architecture/parser_mvp_stage3.md

@@ -0,0 +1,52 @@
+# Parser MVP Stage-3 Design (Phase 15)
+
+Scope
+- Extend Stage-2 parser emission to cover control flow constructs usually seen in routine code bases:
+  - `break` / `continue`
+  - `throw expr`
+  - `try { ... } catch (Type err) { ... } finally { ... }`
+  - Alert: other Stage-3 ideas (switch/async) remain out of scope until after self-host parity.
+- Preserve existing Stage-2 behaviour (locals/loop/if/call/method/new/ternary) with no regressions.
+
+Guiding Principles
+- JSON v0 must remain stable for the Stage-2 path; Stage-3 additions should be feature-flagged or degrade safely when disabled.
+- Short-circuit semantics are already mirrored via logical nodes; Stage-3 should reuse the same block-building infrastructure (Bridge/VM/JIT) to avoid special cases.
+- Continue the "degrade to expression" approach when code generation is not ready (e.g. throw/try) so that Stage-2 tests stay green while the full implementation is developed.
+
+JSON v0 Additions
+| Construct  | JSON v0 Node                                    | Notes |
+|------------|-------------------------------------------------|-------|
+| break      | `{ "type": "Break" }`                          | Lowered into loop exit block with implicit jump. |
+| continue   | `{ "type": "Continue" }`                       | Lowered into loop head block jump. |
+| throw expr | `{ "type": "Throw", "expr": Expr }`           | Initial implementation can degrade to `{ "type": "Expr", "expr": expr }` until VM/JIT semantics are ready. |
+| try/catch/finally | `{ "type": "Try", "try": Stmt[], "catches": Catch[], "finally": Stmt[]? }` | Each `Catch` includes `{ "param": String?, "body": Stmt[] }`. Stage-1 implementation may treat as pass-through expression block. |
+
+Lowering Strategy (Bridge)
+1. **Break/Continue**
+   - Bridge stores loop header/exit blocks on a loop stack.
+   - `Break` maps to `Jump { target: loop_exit }`, `Continue` to `Jump { target: loop_head }`.
+   - MirBuilder already has `LoopBuilder`; expose helpers to fetch head/exit blocks.
+
+2. **Throw/Try**
+   - Phase 15 MVP keeps them syntax-only to avoid VM/JIT churn. Parser/Emitter produce nodes; Bridge either degrades (Expr) or logs a structured event for future handling.
+   - Document expectation: once runtime exception model is defined, nodes become non-degrading.
+
+3. **Metadata Events**
+   - Augment `crate::jit::observe` with `lower_shortcircuit`/`lower_try` stubs so instrumentation remains coherent when full support is wired.
+
+Testing Plan
+- Extend selfhost Stage-2 smoke file with guard cases (`return break` etc.) once lowering is live.
+- Create dedicated JSON fixtures under `tests/json_v0_stage3/` for break/continue/try once behaviour stabilises.
+- Update `tools/ny_stage2_shortcircuit_smoke.sh` to ensure Stage-3 constructs do not regress Stage-2 semantics (break/continue degrade). Timing: after lowering is implemented.
+
+Migration Checklist
+1. ParserBox emits Stage-3 nodes under `NYASH_PARSER_STAGE3=1` gate to allow gradual rollout.
+2. Emitter attaches Stage-3 JSON when gate is enabled (otherwise degrade to existing Stage-2 forms).
+3. Bridge honours Stage-3 nodes when gate is on; degrade with warning when off.
+4. PyVM/VM/JIT semantics gradually enabled (throw/try remain degrade until corresponding runtime support is merged).
+5. Documentation kept in sync (`CURRENT_TASK.md`, release notes).
+
+References
+- Stage-2 design (`parser_mvp_stage2.md`)
+- CURRENT_TASK stage checklist (Phase 15)
+- `docs/guides/language-guide.md` section “Exceptions & Flow Control” (update when Stage-3 fully lands).

src/runner/json_v0_bridge.rs

@@ -1,7 +1,7 @@
 use serde::{Deserialize, Serialize};
 use crate::mir::{
     MirModule, MirFunction, FunctionSignature, BasicBlockId, MirInstruction,
-    ConstValue, BinaryOp, MirType, EffectMask, MirPrinter,
+    ConstValue, BinaryOp, MirType, EffectMask, MirPrinter, ValueId,
 };
 
 #[derive(Debug, Deserialize, Serialize)]
@@ -24,6 +24,19 @@ enum StmtV0 {
     If { cond: ExprV0, then: Vec<StmtV0>, #[serde(rename="else", default)] r#else: Option<Vec<StmtV0>> },
     // Optional: loop (Stage-2)
     Loop { cond: ExprV0, body: Vec<StmtV0> },
+    Break,
+    Continue,
+    Try { #[serde(rename="try")] try_body: Vec<StmtV0>, #[serde(default)] catches: Vec<CatchV0>, #[serde(default)] finally: Vec<StmtV0> },
+}
+
+#[derive(Debug, Deserialize, Serialize, Clone, Default)]
+struct CatchV0 {
+    #[serde(rename="param", default)]
+    param: Option<String>,
+    #[serde(rename="typeHint", default)]
+    type_hint: Option<String>,
+    #[serde(default)]
+    body: Vec<StmtV0>,
 }
 
 #[derive(Debug, Deserialize, Serialize, Clone)]
@@ -41,6 +54,7 @@ enum ExprV0 {
     Method { recv: Box<ExprV0>, method: String, args: Vec<ExprV0> },
     New { class: String, args: Vec<ExprV0> },
     Var { name: String },
+    Throw { expr: Box<ExprV0> },
 }
 
 pub fn parse_json_v0_to_module(json: &str) -> Result<MirModule, String> {
@@ -197,7 +211,16 @@ fn lower_expr(f: &mut MirFunction, cur_bb: BasicBlockId, e: &ExprV0) -> Result<(
             // merge with phi (use actual predecessors rhs_end and fall_bb)
             let out = f.next_value_id();
             if let Some(bb) = f.get_block_mut(merge_bb) {
-                bb.insert_instruction_after_phis(MirInstruction::Phi { dst: out, inputs: vec![(rhs_end, rval), (fall_bb, cdst)] });
+                let mut inputs: Vec<(BasicBlockId, ValueId)> = vec![(fall_bb, cdst)];
+                if rhs_end != fall_bb {
+                    inputs.push((rhs_end, rval));
+                } else {
+                    // Degenerate case: RHS ended in fall_bb (e.g., constant expression).
+                    // Reuse the constant to keep PHI well-formed.
+                    inputs.push((fall_bb, rval));
+                }
+                inputs.sort_by_key(|(bbid, _)| bbid.0);
+                bb.insert_instruction_after_phis(MirInstruction::Phi { dst: out, inputs });
             }
             Ok((out, merge_bb))
         }
@@ -280,6 +303,14 @@ fn lower_expr(f: &mut MirFunction, cur_bb: BasicBlockId, e: &ExprV0) -> Result<(
             Ok((dst, cur))
         }
         ExprV0::Var { name } => Err(format!("undefined variable in this context: {}", name)),
+        ExprV0::Throw { expr } => {
+            let (_ignored, cur) = lower_expr(f, cur_bb, expr)?;
+            let dst = f.next_value_id();
+            if let Some(bb) = f.get_block_mut(cur) {
+                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::Integer(0) });
+            }
+            Ok((dst, cur))
+        }
     }
 }
 
@@ -310,6 +341,14 @@ fn lower_expr_with_vars(
             }
             Err(format!("undefined variable: {}", name))
         }
+        ExprV0::Throw { expr } => {
+            let (_ignored, cur) = lower_expr_with_vars(f, cur_bb, expr, vars)?;
+            let dst = f.next_value_id();
+            if let Some(bb) = f.get_block_mut(cur) {
+                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::Integer(0) });
+            }
+            Ok((dst, cur))
+        }
         ExprV0::Call { name, args } => {
             // Special: array literal lowering in vars context
             if name == "array.of" {
@@ -469,6 +508,21 @@ fn lower_stmt_with_vars(
         StmtV0::Local { name, expr } => {
             let (v, cur) = lower_expr_with_vars(f, cur_bb, expr, vars)?; vars.insert(name.clone(), v); Ok(cur)
         }
+        StmtV0::Break => {
+            // Stage-3 placeholder: no-op until loop lowering supports break
+            Ok(cur_bb)
+        }
+        StmtV0::Continue => {
+            // Stage-3 placeholder: no-op until loop lowering supports continue
+            Ok(cur_bb)
+        }
+        StmtV0::Try { try_body, .. } => {
+            // Stage-3 placeholder: lower try body sequentially, ignore catches/finally for now
+            let mut tmp_vars = vars.clone();
+            let next_bb = lower_stmt_list_with_vars(f, cur_bb, try_body, &mut tmp_vars)?;
+            *vars = tmp_vars;
+            Ok(next_bb)
+        }
         StmtV0::If { cond, then, r#else } => {
             // Lower condition first
             let (cval, cur) = lower_expr_with_vars(f, cur_bb, cond, vars)?;