feat(joinir): Phase 240-EX - Pattern2 header condition ExprLowerer integration

Implementation: - Add make_pattern2_scope_manager() helper for DRY - Header conditions use ExprLowerer for supported patterns - Legacy fallback for unsupported patterns - Fail-Fast on supported patterns that fail Tests: - 4 new tests (all pass) - test_expr_lowerer_supports_simple_header_condition_i_less_literal - test_expr_lowerer_supports_header_condition_var_less_var - test_expr_lowerer_header_condition_generates_expected_instructions - test_pattern2_header_condition_via_exprlowerer Also: Archive old phase documentation (34k lines removed) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2025-12-11 00:33:04 +09:00
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+# Phase 171-A: Blocked Loop Inventory
+
+**Date**: 2025-12-07
+**Status**: Initial inventory complete
+**Purpose**: Identify loops blocked by LoopBodyLocal variables in break conditions
+
+---
+
+## Overview
+
+This document catalogs loops that cannot be lowered by Pattern 2/4 because they use **LoopBodyLocal** variables in their break conditions. These are candidates for Pattern 5 carrier promotion.
+
+---
+
+## Blocked Loops Found
+
+### 1. TrimTest.trim/1 - Leading Whitespace Trim
+
+**File**: `local_tests/test_trim_main_pattern.hako`
+**Lines**: 20-27
+
+```hako
+loop(start < end) {
+    local ch = s.substring(start, start+1)
+    if ch == " " || ch == "\t" || ch == "\n" || ch == "\r" {
+        start = start + 1
+    } else {
+        break
+    }
+}
+```
+
+**Blocking Variable**: `ch` (LoopBodyLocal)
+
+**Analysis**:
+- Loop parameter: `start` (LoopParam)
+- Outer variable: `end` (OuterLocal)
+- Break condition uses: `ch` (LoopBodyLocal)
+- `ch` is defined inside loop body as `s.substring(start, start+1)`
+
+**Error Message**:
+```
+[trace:debug] pattern2: Pattern 2 lowerer failed: Variable 'ch' not bound in ConditionEnv
+```
+
+**Why Blocked**:
+Pattern 2 expects break conditions to only use:
+- LoopParam (`start`)
+- OuterLocal (`end`, `s`)
+
+But the break condition `ch == " " || ...` uses `ch`, which is defined inside the loop body.
+
+---
+
+### 2. TrimTest.trim/1 - Trailing Whitespace Trim
+
+**File**: `local_tests/test_trim_main_pattern.hako`
+**Lines**: 30-37
+
+```hako
+loop(end > start) {
+    local ch = s.substring(end-1, end)
+    if ch == " " || ch == "\t" || ch == "\n" || ch == "\r" {
+        end = end - 1
+    } else {
+        break
+    }
+}
+```
+
+**Blocking Variable**: `ch` (LoopBodyLocal)
+
+**Analysis**:
+- Loop parameter: `end` (LoopParam)
+- Outer variable: `start` (OuterLocal)
+- Break condition uses: `ch` (LoopBodyLocal)
+- `ch` is defined inside loop body as `s.substring(end-1, end)`
+
+**Same blocking reason as Loop 1.**
+
+---
+
+### 3. JsonParserBox - MethodCall in Condition
+
+**File**: `tools/hako_shared/json_parser.hako`
+
+```hako
+loop(i < s.length()) {
+    // ...
+}
+```
+
+**Blocking Issue**: `s.length()` is a MethodCall in the condition expression.
+
+**Error Message**:
+```
+[ERROR] ❌ MIR compilation error: [cf_loop/pattern4] Lowering failed:
+Unsupported expression in value context: MethodCall {
+    object: Variable { name: "s", ... },
+    method: "length",
+    arguments: [],
+    ...
+}
+```
+
+**Why Blocked**:
+Pattern 4's value context lowering doesn't support MethodCall expressions yet.
+
+**Note**: This is not a LoopBodyLocal issue, but a MethodCall limitation. May be addressed in Phase 171-D (Optional).
+
+---
+
+## Pattern5-A Target Decision
+
+### Selected Target: TrimTest Loop 1 (Leading Whitespace)
+
+We select the **first loop** from TrimTest as Pattern5-A target for the following reasons:
+
+1. **Clear structure**: Simple substring + equality checks
+2. **Representative**: Same pattern as many real-world parsers
+3. **Self-contained**: Doesn't depend on complex outer state
+4. **Testable**: Easy to write unit tests
+
+### Pattern5-A Specification
+
+**Loop Structure**:
+```hako
+loop(start < end) {
+    local ch = s.substring(start, start+1)
+    if ch == " " || ch == "\t" || ch == "\n" || ch == "\r" {
+        start = start + 1
+    } else {
+        break
+    }
+}
+```
+
+**Variables**:
+- `start`: LoopParam (carrier, mutated)
+- `end`: OuterLocal (condition-only)
+- `s`: OuterLocal (used in body)
+- `ch`: LoopBodyLocal (blocking variable)
+
+**Break Condition**:
+```
+!(ch == " " || ch == "\t" || ch == "\n" || ch == "\r")
+```
+
+---
+
+## Promotion Strategy: Design D (Evaluated Bool Carrier)
+
+### Rationale
+
+We choose **Design D** (Evaluated Bool Carrier) over other options:
+
+**Why not carry `ch` directly?**
+- `ch` is a StringBox, not a primitive value
+- Would require complex carrier type system
+- Would break existing Pattern 2/4 assumptions
+
+**Design D approach**:
+- Introduce a new carrier: `is_whitespace` (bool)
+- Evaluate `ch == " " || ...` in loop body
+- Store result in `is_whitespace` carrier
+- Use `is_whitespace` in break condition
+
+### Transformed Structure
+
+**Before (Pattern5-A)**:
+```hako
+loop(start < end) {
+    local ch = s.substring(start, start+1)
+    if ch == " " || ch == "\t" || ch == "\n" || ch == "\r" {
+        start = start + 1
+    } else {
+        break
+    }
+}
+```
+
+**After (Pattern2 compatible)**:
+```hako
+// Initialization (before loop)
+local is_whitespace = true  // Initial assumption
+
+loop(start < end && is_whitespace) {
+    local ch = s.substring(start, start+1)
+    is_whitespace = (ch == " " || ch == "\t" || ch == "\n" || ch == "\r")
+
+    if is_whitespace {
+        start = start + 1
+    } else {
+        break  // Now redundant, but kept for clarity
+    }
+}
+```
+
+**Key transformations**:
+1. Add `is_whitespace` carrier initialization
+2. Update loop condition to include `is_whitespace`
+3. Compute `is_whitespace` in loop body
+4. Original if-else becomes simpler (could be optimized away)
+
+---
+
+## Next Steps (Phase 171-C)
+
+### Phase 171-C-1: Skeleton Implementation ✅
+- Create `LoopBodyCarrierPromoter` box
+- Define `PromotionRequest` / `PromotionResult` types
+- Implement skeleton `try_promote()` method
+- Add `find_definition_in_body()` helper
+
+### Phase 171-C-2: Trim Pattern Promotion Logic
+- Detect substring + equality pattern
+- Generate `is_whitespace` carrier
+- Generate initialization statement
+- Generate update statement
+
+### Phase 171-C-3: Integration with Pattern 2/4
+- Call `LoopBodyCarrierPromoter::try_promote()` in routing
+- If promotion succeeds, route to Pattern 2
+- If promotion fails, return UnsupportedPattern
+
+### Phase 171-D: MethodCall Support (Optional)
+- Handle `s.length()` in loop conditions
+- May require carrier promotion for method results
+- Lower priority than Trim pattern
+
+---
+
+## Summary
+
+**Blocked Loops**:
+- 2 loops in TrimTest (LoopBodyLocal `ch`)
+- 1+ loops in JsonParser (MethodCall in condition)
+
+**Pattern5-A Target**:
+- TrimTest leading whitespace trim loop
+- Clear, representative, testable
+
+**Promotion Strategy**:
+- Design D: Evaluated Bool Carrier
+- Transform `ch` checks → `is_whitespace` carrier
+- Make compatible with Pattern 2
+
+**Implementation Status**:
+- Phase 171-A: ✅ Inventory complete
+- Phase 171-B: ✅ Target selected
+- Phase 171-C-1: ✅ Skeleton implementation complete
+- Phase 171-C-2: ✅ Trim pattern detection implemented
+  - `find_definition_in_body()`: AST traversal for variable definitions
+  - `is_substring_method_call()`: Detects `substring()` method calls
+  - `extract_equality_literals()`: Extracts string literals from OR chains
+  - `TrimPatternInfo`: Captures pattern details for carrier promotion
+- Phase 171-C-3: ✅ Integration with Pattern 2/4 routing complete
+- Phase 171-C-4: ✅ CarrierInfo integration complete (2025-12-07)
+  - `CarrierInfo::merge_from()`: Deduplicated carrier merging with deterministic sorting
+  - `TrimPatternInfo::to_carrier_info()`: Conversion to CarrierInfo with TrimLoopHelper
+  - Pattern 2/4 lowerers: Promoted carrier merging in `Promoted` branch
+  - 7 unit tests: Merge success/failure/duplication/determinism validation
+- Phase 171-C-5: ✅ TrimLoopHelper design complete (2025-12-07)
+  - `TrimLoopHelper` struct: Encapsulates Trim pattern lowering logic
+  - `CarrierInfo::trim_helper()`: Accessor for pattern-specific helper
+  - Module export: `mod.rs` updated with `pub use TrimLoopHelper`
+  - 4 unit tests: Helper creation and accessor validation
+
+---
+
+## Phase 171-C-3/4/5: Responsibility Positions and Data Flow
+
+### Responsibility Separation Principle
+
+The promotion system follows Box Theory's single responsibility principle:
+
+1. **router.rs**: Pattern table + `can_lower()`/`lower()` call abstraction (no Scope/condition logic)
+2. **Pattern 2/4 lowerer**: Holds LoopScope / ConditionScope / CarrierInfo / Promoter
+3. **LoopBodyCarrierPromoter**: LoopBodyLocal handling specialist box
+4. **TrimLoopHelper**: Trim pattern-specific helper (future extensibility)
+
+### Data Flow Diagram
+
+```
+LoopConditionScopeBox::analyze()
+        ↓
+    has_loop_body_local()?
+        ↓ true
+LoopBodyCarrierPromoter::try_promote()
+        ↓ Promoted { trim_info }
+    TrimPatternInfo::to_carrier_info()
+        ↓
+    CarrierInfo::merge_from()
+        ↓
+    TrimLoopHelper (attached to CarrierInfo)
+        ↓
+    Pattern 2/4 lowerer (JoinIR generation)
+```
+
+### Implementation Locations
+
+**Phase 171-C-4 Changes**:
+- `src/mir/join_ir/lowering/carrier_info.rs`: Added `merge_from()`, `trim_helper()`, `trim_helper` field
+- `src/mir/loop_pattern_detection/loop_body_carrier_promoter.rs`: Updated `to_carrier_info()` to attach TrimLoopHelper
+- `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`: Promoted branch now merges carriers
+- `src/mir/builder/control_flow/joinir/patterns/pattern4_with_continue.rs`: Promoted branch now merges carriers
+
+**Phase 171-C-5 Changes**:
+- `src/mir/loop_pattern_detection/trim_loop_helper.rs`: NEW - TrimLoopHelper struct with 4 unit tests
+- `src/mir/loop_pattern_detection/mod.rs`: Export TrimLoopHelper module
+
+---
+
+## Phase 171-impl-Trim: Trim 特例の実戦投入
+
+**Date**: 2025-12-08
+**Status**: ✅ Validation complete
+**Purpose**: Safely integrate Trim pattern detection into JoinIR pipeline with validation-only implementation
+
+### 設計原則
+
+> **「LoopBodyLocal を全面解禁」ではなく、Trim パターンだけを箱経由でホワイトリストに載せる**
+
+### 安全機構
+
+1. `TrimLoopHelper::is_safe_trim()` - 構造的に安全か判定
+2. `TrimLoopHelper::is_trim_like()` - Trim パターンに合致するか判定
+3. `TrimLoopHelper::has_valid_structure()` - 構造チェック
+
+### データフロー（Trim 特例）
+
+```
+LoopConditionScopeBox::analyze()
+        ↓
+    has_loop_body_local() == true
+        ↓
+LoopBodyCarrierPromoter::try_promote()
+        ↓ Promoted { trim_info }
+    TrimPatternInfo::to_carrier_info()
+        ↓
+    CarrierInfo::merge_from()
+        ↓
+    carrier_info.trim_helper()?.is_safe_trim()
+        ↓ true
+    ✅ Validation Success (TODO: JoinIR lowering in Phase 172)
+```
+
+### 実装状況
+
+- [x] Phase 171-impl-Trim-1: 受け入れ条件を 1 箇所に ✅
+  - `TrimLoopHelper::is_safe_trim()` implemented
+  - `Pattern2/4` で Trim 特例ルート実装
+  - Fail-Fast on unsafe patterns
+- [x] Phase 171-impl-Trim-2: TrimLoopHelper 判定メソッド ✅
+  - `is_trim_like()`, `has_valid_structure()` implemented
+  - 4+ ユニットテスト追加 (9 tests total, all passing)
+- [x] Phase 171-impl-Trim-3: E2E テスト ✅
+  - `local_tests/test_trim_main_pattern.hako` validated
+  - 出力: `[pattern2/trim] Safe Trim pattern detected`
+  - 出力: `✅ Trim pattern validation successful!`
+  - Status: Validation-only (JoinIR lowering deferred to Phase 172)
+- [x] Phase 171-impl-Trim-4: ドキュメント更新 ✅
+  - `phase171-pattern5-loop-inventory.md` updated
+  - `CURRENT_TASK.md` status tracking
+
+### 実装詳細
+
+**ファイル変更**:
+1. `src/mir/loop_pattern_detection/trim_loop_helper.rs`
+   - `is_safe_trim()`, `is_trim_like()`, `has_valid_structure()` methods
+   - 4 new unit tests for safety validation
+
+2. `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`
+   - Trim exception route with safety check
+   - `body_locals` extraction from loop body AST
+   - Validation message for successful detection
+
+3. `src/mir/builder/control_flow/joinir/patterns/pattern4_with_continue.rs`
+   - Same Trim exception logic as Pattern2
+   - `body_locals` extraction from normalized loop body
+
+4. `src/mir/loop_pattern_detection/loop_body_carrier_promoter.rs`
+   - `ASTNode::Local { variables, initial_values, .. }` handler
+   - Support for `local ch = expr` pattern recognition
+
+### テスト結果
+
+**ユニットテスト**: ✅ 9/9 passing
+- `test_is_safe_trim`
+- `test_is_safe_trim_empty_carrier`
+- `test_is_safe_trim_no_whitespace`
+- `test_has_valid_structure`
+- (+ 5 existing tests)
+
+**E2E テスト**: ✅ Validation successful
+```
+[pattern2/check] Analyzing condition scope: 3 variables
+[pattern2/check]   'ch': LoopBodyLocal
+[pattern2/promoter] LoopBodyLocal 'ch' promoted to carrier 'is_ch_match'
+[pattern2/trim] Safe Trim pattern detected, bypassing LoopBodyLocal restriction
+[pattern2/trim] Carrier: 'is_ch_match', original var: 'ch', whitespace chars: ["\r", "\n", "\t", " "]
+✅ Trim pattern validation successful! Carrier 'is_ch_match' ready for Phase 172 implementation.
+(Pattern detection: PASS, Safety check: PASS, JoinIR lowering: TODO)
+```
+
+**ビルド結果**: ✅ Success
+- `cargo build --release`: Success
+- `cargo test --lib trim_loop_helper`: 9/9 passing
+
+### 重要な発見
+
+1. **AST構造の理解**: `local ch = expr` は `ASTNode::Local { variables, initial_values, .. }` として表現される
+2. **body_locals 抽出**: Pattern2/4 で `LoopScopeShape.body_locals` を AST から抽出する必要があった
+3. **段階的実装**: Validation-only approach で安全性を先に確立し、JoinIR lowering は Phase 172 に分離
+
+### 次のステップ (Phase 172)
+
+- [ ] Phase 172-1: Trim pattern JoinIR generation
+  - Carrier initialization code
+  - Carrier update logic (substring + OR chain → bool)
+  - Exit PHI mapping
+- [ ] Phase 172-2: JsonParser loops への展開
+  - Similar pattern recognition
+  - Generalized carrier promotion
+Status: Historical