feat(mir): Loop Canonicalizer Phase 4 - router parity verification
## Summary
既存 Router と Canonicalizer の選択が一致することを dev-only で検証。
不一致は理由付き Fail-Fast（strict mode）。
## Changes
- src/mir/builder/control_flow/joinir/routing.rs:
- verify_router_parity() 実装
- cf_loop_joinir_impl でパリティチェック呼び出し
- 2つのユニットテスト追加
- test_parity_check_mismatch_detected
- test_parity_check_match_simple_while
- docs/development/current/main/phases/phase-137/phase-137-4-parity-verification.md:
- Phase 4 完全ドキュメント
## Verification Modes
- Debug mode (HAKO_JOINIR_DEBUG=1): ログのみ
- Strict mode (HAKO_JOINIR_STRICT=1): 不一致でエラー
## Known Mismatch
- skip_whitespace pattern:
- Canonicalizer: Pattern3IfPhi (構造認識)
- Router: Pattern2Break (has_break優先)
- Phase 5+ で分類ルール改善予定
## Tests
- Unit tests: 2 tests PASS
- Integration: skip_whitespace parity mismatch 検出確認
- cargo test --release --lib: 1046/1046 PASS
Phase 137-4 complete
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
This commit is contained in:
nyash-codex
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# Phase 137-4: Loop Canonicalizer Router Parity Verification
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**Status**: ✅ Complete
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**Date**: 2025-12-16
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## Summary
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Dev-only verification that Loop Canonicalizer and Router pattern detection agree on pattern classification. On mismatch, provides detailed diagnostic with Fail-Fast option.
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## Implementation
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### Location
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`src/mir/builder/control_flow/joinir/routing.rs`
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### Components
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1. **Parity Verification Function** (`verify_router_parity`)
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- Runs canonicalizer on the loop AST
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- Compares canonicalizer's chosen pattern with router's `ctx.pattern_kind`
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- Logs match/mismatch results
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- In strict mode, returns error on mismatch
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2. **Integration Point**
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- Called in `cf_loop_joinir_impl` after `LoopPatternContext` is created
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- Only runs when `joinir_dev_enabled()` returns true
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- Deferred until after ctx creation to access `ctx.pattern_kind`
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### Behavior Modes
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#### Debug Mode (Default)
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```bash
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HAKO_JOINIR_DEBUG=1 ./target/release/hakorune program.hako
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```
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- Logs parity check results to stderr
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- On mismatch: Logs warning but continues execution
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- On match: Logs success message
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#### Strict Mode
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```bash
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HAKO_JOINIR_STRICT=1 ./target/release/hakorune program.hako
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```
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- Same as debug mode, but on mismatch:
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- Returns error and stops compilation
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- Provides detailed mismatch diagnostic
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### Output Examples
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#### Match (Success)
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```
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[loop_canonicalizer/PARITY] OK in function 'foo':
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canonical and actual agree on Pattern1SimpleWhile
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```
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#### Mismatch (Warning in Debug)
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```
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[loop_canonicalizer/PARITY] MISMATCH in function 'main':
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canonical=Pattern3IfPhi, actual=Pattern2Break
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```
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#### Mismatch (Error in Strict)
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```
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[ERROR] ❌ MIR compilation error:
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[loop_canonicalizer/PARITY] MISMATCH in function 'main':
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canonical=Pattern3IfPhi, actual=Pattern2Break
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```
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#### Canonicalizer Failure
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```
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[loop_canonicalizer/PARITY] Canonicalizer failed for 'bar':
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Phase 3: Loop does not match skip_whitespace pattern
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```
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## Test Coverage
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### Unit Tests
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1. **`test_parity_check_mismatch_detected`**
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- Verifies mismatch detection on skip_whitespace pattern
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- Canonicalizer: Pattern3IfPhi (recognizes if-else structure)
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- Router: Pattern2Break (sees has_break flag)
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- Asserts inequality to document expected mismatch
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2. **`test_parity_check_match_simple_while`**
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- Verifies canonicalizer fails on Pattern1 (not yet implemented)
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- Router: Pattern1SimpleWhile
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- Canonicalizer: Fail-Fast (only supports skip_whitespace in Phase 3)
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### Integration Tests
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```bash
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# Verify mismatch detection (debug mode)
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HAKO_JOINIR_DEBUG=1 ./target/release/hakorune \
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tools/selfhost/test_pattern3_skip_whitespace.hako
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# Verify strict mode error
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HAKO_JOINIR_STRICT=1 ./target/release/hakorune \
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tools/selfhost/test_pattern3_skip_whitespace.hako
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# Expected: Exit with error due to mismatch
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```
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## Known Mismatches
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### skip_whitespace Pattern
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**Structure**:
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```nyash
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loop(p < len) {
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if is_ws == 1 {
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p = p + 1
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} else {
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break
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}
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}
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```
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**Mismatch**:
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- **Canonicalizer**: Pattern3IfPhi
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- Recognizes specific if-else structure with conditional carrier update
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- Sees: `if cond { carrier += 1 } else { break }` as Pattern3 variant
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- **Router**: Pattern2Break
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- Classification based on `has_break` flag
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- Priority: break detection takes precedence over if-else structure
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**Resolution Strategy**:
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- Phase 4: Document and observe (current)
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- Phase 5+: Refine classification rules to handle hybrid patterns
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- Option A: Extend Pattern3 to include "break-in-else" variant
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- Option B: Create new Pattern6 for this specific structure
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- Option C: Make router defer to canonicalizer's decision
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## Design Rationale
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### Why Two Systems?
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1. **Router (Existing)**
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- Feature-based classification (`has_break`, `has_continue`, etc.)
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- Fast, simple flags
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- Priority-based (e.g., break > if-else)
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2. **Canonicalizer (New)**
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- Structure-based pattern matching
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- Deep AST analysis
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- Recognizes specific code idioms
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### Why Parity Check?
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- **Incremental Migration**: Allows canonicalizer development without breaking router
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- **Safety Net**: Catches classification divergence early
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- **Documentation**: Explicitly records where systems disagree
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- **Flexibility**: Dev-only, no production overhead
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### Why Dev-Only?
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- **No Performance Impact**: Zero cost in release builds (flag-gated)
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- **Development Insight**: Helps refine both systems
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- **Fail-Fast Option**: Strict mode for CI/validation
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- **Graceful Degradation**: Debug mode allows execution to continue
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## Acceptance Criteria
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- ✅ Flag OFF: No behavioral change
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- ✅ Dev-only: Match/mismatch observable
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- ✅ Strict mode: Mismatch stops compilation
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- ✅ Debug mode: Mismatch logs warning
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- ✅ Unit tests: 2 tests passing
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- ✅ Integration test: skip_whitespace mismatch detected
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- ✅ All tests: `cargo test --release --lib` passes (1046/1046)
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## Future Work
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### Phase 5: Pattern Classification Refinement
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- Resolve skip_whitespace classification (Pattern2 vs Pattern3)
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- Extend Pattern3 to handle break-in-else variant
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- OR: Create Pattern6 for "conditional update with early exit"
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### Phase 6: Canonicalizer Expansion
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- Add Pattern1 (Simple While) to canonicalizer
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- Add Pattern2 (Conditional Break) variants
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- Add Pattern4 (Continue) support
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- Add Pattern5 (Infinite Early Exit) support
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### Phase 7: Router Migration
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- Consider migrating router to use canonicalizer decisions
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- Option: Make `ctx.pattern_kind = decision.chosen` if canonicalizer succeeds
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- Gradual transition from feature-based to structure-based routing
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## References
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- **Phase 137-2**: Loop Canonicalizer observation (dev-only logging)
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- **Phase 137-3**: skip_whitespace pattern recognition
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- **Design SSOT**: `docs/development/current/main/design/loop-canonicalizer.md`
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- **JoinIR Architecture**: `docs/development/current/main/joinir-architecture-overview.md`
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