feat(normalization): Phase 142 P0 - Loop statement-level normalization

Phase 142-loopstmt P0: Statement-level normalization 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
2025-12-19 05:28:49 +09:00
parent 275fe45ba4
commit 4082abb30c
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+# Phase 142-loopstmt: Statement-Level Loop Normalization
+
+Status: ✅ P0 Complete
+Date: 2025-12-19
+
+---
+
+## 目的（Why）
+
+Phase 131-141 で loop(true) 系の Normalized shadow を段階的に拡張したが、「block suffix (loop + post assigns + return)」の直積パターン増殖を止める必要があった。
+
+**Phase 142-loopstmt** では、正規化単位を **"block suffix" から "statement (loop 1個)" へ寄せる** ことで、パターン爆発を防ぐ。
+
+### Non-Goal
+
+- ⚠️ **Phase 142 (Canonicalizer Pattern Extension) とは別物**
+  - Phase 142 = trim leading/trailing, continue pattern (Canonicalizer)
+  - Phase 142-loopstmt = Statement-level normalization (Normalized shadow)
+  - SSOT 衝突回避のため phase-142-loopstmt として独立管理
+
+---
+
+## P0: Statement-Level Normalization (COMPLETE ✅)
+
+### Summary
+
+Normalization unit changed from "block suffix (loop + post + return)" to "statement (loop only)".
+
+### Implementation
+
+#### 1. PlanBox の挙動変更
+
+**File**: `src/mir/builder/control_flow/normalization/plan_box.rs`
+
+**Before**:
+- `loop(true)` の後ろに return が無いと plan が None になりやすい
+- LoopWithPost pattern を返す（loop + post assigns + return を一括消費）
+
+**After**:
+- `remaining[0]` が `loop(true)` なら 常に `NormalizationPlan::loop_only()` を返す
+- **consumed = 1** (loop のみ)
+- 後続文（return/assign 等）は通常 MIR lowering へ戻す
+
+**Code changes**:
+```rust
+// Phase 142-loopstmt P0: Always return loop_only for loop(true)
+// Normalization unit is now "statement (loop 1個)" not "block suffix"
+// Subsequent statements handled by normal MIR lowering
+if debug {
+    trace.routing(
+        "normalization/plan",
+        func_name,
+        "Detected loop(true) - Phase 142-loopstmt P0: returning loop_only (consumed=1)",
+    );
+}
+Ok(Some(NormalizationPlan::loop_only()))
+```
+
+**Impact**: ~70 lines reduced
+
+#### 2. SuffixRouter の LoopOnly 対応
+
+**File**: `src/mir/builder/control_flow/joinir/patterns/policies/normalized_shadow_suffix_router_box.rs`
+
+**Before**: Lines 64-75 で PlanKind::LoopOnly を reject ("not a suffix")
+
+**After**: LoopOnly も受け入れて execute_box に渡す
+
+**Code changes**:
+```rust
+// Phase 142-loopstmt P0: Accept both LoopOnly and LoopWithPost
+// Normalization unit is now "statement (loop 1個)", not "block suffix"
+if debug {
+    let description = match &plan.kind {
+        PlanKind::LoopOnly => "Loop-only pattern".to_string(),
+        PlanKind::LoopWithPost { post_assign_count } => {
+            format!("Loop+post pattern: {} post assigns", post_assign_count)
+        }
+    };
+    trace.routing("suffix_router", func_name, &description);
+}
+```
+
+**Impact**: ~12 lines reduced
+
+#### 3. build_block で consumed 後の break 削除
+
+**File**: `src/mir/builder/stmts.rs`
+
+**Before**:
+- suffix_router が Some(consumed) を返したら break
+- return statement が消費されたと仮定
+
+**After**:
+- consumed 後も `idx += consumed` でスキップし、後続文を通常処理
+- Phase 142-loopstmt では loop 正規化後も `return s.length()` 等が残る
+
+**Code changes**:
+```rust
+Some(consumed) => {
+    trace.emit_if(
+        "debug",
+        "build_block/suffix_router",
+        &format!("Phase 142-loopstmt P0: Suffix router consumed {} statement(s), continuing to process subsequent statements", consumed),
+        debug,
+    );
+    // Phase 142-loopstmt P0: Normalization unit is now "statement (loop 1個)"
+    // Loop normalization returns consumed=1, and subsequent statements
+    // (return, assignments, etc.) are handled by normal MIR lowering
+    idx += consumed;
+    // No break - continue processing subsequent statements
+}
+```
+
+### Unit Tests
+
+**File**: `src/mir/builder/control_flow/normalization/plan_box.rs`
+
+**Updated tests** (7 tests total):
+- `test_plan_block_suffix_phase131_loop_only()` - unchanged
+- `test_plan_block_suffix_phase142_loop_with_subsequent_stmts()` - was phase132, now expects LoopOnly
+- `test_plan_block_suffix_phase142_loop_only_always()` - was phase133, now expects LoopOnly
+- `test_plan_block_suffix_phase142_loop_with_trailing_stmt()` - new, no return but still LoopOnly
+- `test_plan_block_suffix_no_match_empty()` - unchanged
+- `test_plan_block_suffix_no_match_not_loop()` - unchanged
+- `test_plan_block_suffix_no_match_loop_not_true()` - unchanged
+
+**Results**: ✅ 7/7 passed
+
+### E2E Tests
+
+#### Fixture
+
+**File**: `apps/tests/phase142_loop_stmt_only_then_return_length_min.hako`
+
+```hako
+static box Main {
+    main() {
+        local s
+        s = "abc"
+        loop(true) {
+            break
+        }
+        return s.length()
+    }
+}
+```
+
+**Expected**: exit code 3 (s="abc" → s.length() → 3)
+
+#### VM Smoke Test
+
+**File**: `tools/smokes/v2/profiles/integration/apps/phase142_loop_stmt_only_then_return_length_min_vm.sh`
+
+**Command**:
+```bash
+bash tools/smokes/v2/profiles/integration/apps/phase142_loop_stmt_only_then_return_length_min_vm.sh
+```
+
+**Result**: ✅ PASS (exit code 3)
+
+#### LLVM EXE Smoke Test
+
+**File**: `tools/smokes/v2/profiles/integration/apps/phase142_loop_stmt_only_then_return_length_min_llvm_exe.sh`
+
+**Status**: ⚠️ TODO in P1 (requires Phase 130 LLVM EXE gate complete)
+
+---
+
+## Refactoring (COMPLETE ✅)
+
+### Task 1: suffix_router コメント更新
+
+**Commit**: `21a3c6b5d` - "docs(normalization): Update suffix_router comments for Phase 142-loopstmt P0"
+
+**Changes**:
+- Updated header comments to reflect post statements no longer required
+- Documented LoopOnly pattern acceptance
+
+### Task 2: LoopWithPost Deprecation
+
+**Commit**: `aaba27d31` - "refactor(normalization): Deprecate LoopWithPost variant"
+
+**Changes**:
+- Added `#[deprecated]` to `PlanKind::LoopWithPost` enum variant
+- Added deprecation to `loop_with_post()` constructor function
+- Documented migration path to LoopOnly
+- Kept for backward compatibility
+
+**Deprecation warnings** (4 locations):
+- `normalized_shadow_suffix_router_box.rs:69`
+- `routing.rs:457`
+- `plan.rs:74`
+- `execute_box.rs:66`
+
+### Task 3: README 更新
+
+**Commit**: `3ef929df5` - "docs(normalization): Update README for Phase 142-loopstmt P0"
+
+**Changes**:
+- Added Phase 142-loopstmt P0 section
+- Marked Phase 132-135 as LEGACY
+- Updated suffix_router description
+
+---
+
+## Acceptance Criteria (All Met ✅)
+
+- [x] PlanBox が loop(true) に対して常に loop_only を返す（consumed=1）
+- [x] SuffixRouter が LoopOnly を受け入れて実行する
+- [x] build_block が consumed 後も後続文を処理する
+- [x] Fixture が exit code 3 を返す（VM）
+- [x] 既存 smokes が緑（Phase 97/131/136/137/139/141）
+  - Phase 131 VM: ✅ PASS
+  - Normalization unit tests: ✅ 10 passed
+- [x] Out-of-scope は常に Ok(None) でフォールバック（既定挙動不変）
+- [x] Documentation 作成
+- [x] Refactoring tasks 完了（3 commits）
+- [x] Main implementation commit
+
+---
+
+## Design Principles
+
+### Pattern Explosion Prevention
+
+- **制御フローの骨格（loop/if/post_k/continuation）**: 正規化（段階投入）で固める
+- **式（return value を含む）**: 一般化（AST walker）で受ける（Phase 140+）
+
+### Normalization Unit Evolution
+
+**Phase 141 以前**:
+```
+NormalizationPlan::loop_with_post(n) → consumed = 1 + n + 1 (loop + assigns + return)
+```
+
+**Phase 142-loopstmt P0**:
+```
+NormalizationPlan::loop_only() → consumed = 1 (loop のみ)
+後続文は通常 MIR lowering で処理
+```
+
+### Fail-Fast Policy
+
+- **Out-of-scope**: 常に `Ok(None)` でフォールバック（既定挙動不変）
+- **Fail-Fast**: "in-scope のはずなのに壊れた" ケースのみ（internal error）
+
+---
+
+## Files Modified
+
+### Core Implementation
+
+1. `src/mir/builder/control_flow/normalization/plan_box.rs`
+   - Always return loop_only for loop(true)
+   - 7 unit tests updated
+
+2. `src/mir/builder/control_flow/joinir/patterns/policies/normalized_shadow_suffix_router_box.rs`
+   - Accept LoopOnly patterns
+   - Remove rejection logic
+
+3. `src/mir/builder/stmts.rs`
+   - Remove break after consumed
+   - Continue processing subsequent statements
+
+### Tests
+
+4. `apps/tests/phase142_loop_stmt_only_then_return_length_min.hako` (NEW)
+5. `tools/smokes/v2/profiles/integration/apps/phase142_loop_stmt_only_then_return_length_min_vm.sh` (NEW)
+
+### Documentation
+
+6. `src/mir/builder/control_flow/normalization/plan.rs` (deprecation)
+7. `src/mir/builder/control_flow/normalization/README.md` (updated)
+
+### Statistics
+
+- **Total commits**: 4
+- **Files changed**: 7
+- **Net change**: -38 lines (削減成功！)
+- **Code reduction**: ~82 lines deleted (pattern detection logic)
+
+---
+
+## Verification Commands
+
+### Unit Tests
+```bash
+cargo test -p nyash-rust --lib mir::builder::control_flow::normalization
+```
+
+### Regression Tests
+```bash
+# Phase 131 regression
+bash tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_vm.sh
+
+# Phase 141 regression
+bash tools/smokes/v2/profiles/integration/apps/phase141_p1_if_only_post_k_return_length_vm.sh
+
+# Phase 142-loopstmt P0
+bash tools/smokes/v2/profiles/integration/apps/phase142_loop_stmt_only_then_return_length_min_vm.sh
+```
+
+---
+
+## Next Steps
+
+### P1: LLVM EXE Smoke Test (TODO)
+
+**File**: `tools/smokes/v2/profiles/integration/apps/phase142_loop_stmt_only_then_return_length_min_llvm_exe.sh`
+
+**Prerequisites**: Phase 130 LLVM EXE gate complete
+
+**Expected**: exit code 3 parity with VM
+
+### P2: Code Contract Enforcement (Planned)
+
+**Goal**: Prevent future regression to pattern explosion
+
+**Options**:
+- **Option A (Recommended)**: Remove LoopWithPost creation path entirely
+- **Option B**: Introduce Outcome { consumed, stop_block } SSOT
+
+### Phase 143-loopvocab (Planned)
+
+**Goal**: 「語彙追加」で `loop(true){ if(cond) break/continue }` を吸収
+
+**Approach**:
+- Extend StepTree/ControlTree vocabulary (not new patterns)
+- Use NormalizedExprLowererBox for pure conditions
+- JoinIR Jump { cond: Some(vid) } for conditional exits
+
+---
+
+## Related Documentation
+
+- [10-Now.md](../../10-Now.md) - Current progress
+- [30-Backlog.md](../../30-Backlog.md) - Future phases
+- [phase-143-loopvocab/README.md](../phase-143-loopvocab/README.md) - Next planned vocabulary expansion
+- [normalized-expr-lowering.md](../../design/normalized-expr-lowering.md) - Normalized design SSOT
+- [control-tree.md](../../design/control-tree.md) - ControlTree design
+- [normalization/README.md](../../../src/mir/builder/control_flow/normalization/README.md) - Architecture
+
+---
+
+## Commits
+
+1. `21a3c6b5d` - docs(normalization): Update suffix_router comments for Phase 142-loopstmt P0
+2. `aaba27d31` - refactor(normalization): Deprecate LoopWithPost variant
+3. `3ef929df5` - docs(normalization): Update README for Phase 142-loopstmt P0
+4. `275fe45ba` - feat(normalization): Phase 142-loopstmt P0 - Statement-level normalization