feat(phase182): Upgrade 3 JOINIR_TARGETS functions from LowerOnly to Exec

Phase 182 implementation: JOINIR_TARGETS expansion for representative paths

## Changes
- Stage1UsingResolverBox.resolve_for_source/5: LowerOnly → Exec (default_enabled: true)
- StageBBodyExtractorBox.build_body_src/2: LowerOnly → Exec (default_enabled: true)
- StageBFuncScannerBox.scan_all_boxes/1: LowerOnly → Exec (default_enabled: true)

## Critical Finding: JOINIR_TARGETS is Loop-Only
Discovered that JOINIR_TARGETS is specifically for LOOP lowering only.
Adding if-lowering functions (like IfSelectTest.test/1) would be counterproductive
because is_loop_lowered_function() exclusion would disable if-lowering entirely.

## Test Results
- 4/5 selfhost loop tests: PASS with NYASH_JOINIR_CORE=1 NYASH_JOINIR_STRICT=1
- 1/5 if-select test: FAIL (requires Phase 183 architectural fix - Option A)
- No regressions in existing functionality

## Phase 183 Recommendation
Implement Option A: Create JOINIR_IF_TARGETS as separate table for if-lowering
functions, avoiding the mutual exclusion problem between loop and if lowering.

See: docs/private/roadmap2/phases/phase-182/FINDINGS.md for full analysis

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

CURRENT_TASK.md

@@ -1,8 +1,60 @@
 # Current Task
 
+## ⚠️ Phase 182: JOINIR_TARGETS Expansion (Partially Completed - 2025-12-04)
+
+**Status**: ⚠️ **3/4 Actions Completed** → Critical Architectural Finding Documented
+
+**Achievement**: Successfully upgraded 3 LowerOnly functions to Exec, but discovered **JOINIR_TARGETS is Loop-Only** - cannot add if-lowering functions without breaking architecture.
+
+### What Was Completed
+
+✅ **3/3 LowerOnly → Exec upgrades successful**:
+- `Stage1UsingResolverBox.resolve_for_source/5` → Exec (default_enabled: true)
+- `StageBBodyExtractorBox.build_body_src/2` → Exec (default_enabled: true)
+- `StageBFuncScannerBox.scan_all_boxes/1` → Exec (default_enabled: true)
+
+✅ **4/4 loop-based tests passing** with `NYASH_JOINIR_CORE=1 NYASH_JOINIR_STRICT=1`:
+- `apps/tests/loop_min_while.hako`
+- `apps/tests/peek_expr_block.hako`
+- `apps/tests/joinir_min_loop.hako`
+- `apps/tests/string_method_chain.hako`
+
+✅ **Architectural issue documented** in `docs/private/roadmap2/phases/phase-182/FINDINGS.md`
+
+### What Was NOT Completed
+
+❌ **IfSelectTest.test/1 NOT added** to JOINIR_TARGETS (would break if-lowering)
+
+**Root Cause**: `is_loop_lowered_function()` in `src/mir/join_ir/lowering/mod.rs` excludes ALL functions in JOINIR_TARGETS from if-lowering, regardless of Exec/LowerOnly status. Adding if-functions to JOINIR_TARGETS would disable their if-lowering capability.
+
+### Critical Finding
+
+**JOINIR_TARGETS Dual Purpose**:
+1. ✅ Function whitelist (for JoinIR loop lowering)
+2. ❌ Function blacklist (for if-lowering exclusion)
+
+This creates architectural conflicts for functions that need if-lowering.
+
+### Phase 183 Entry Criteria Status
+
+**Hard Requirements**:
+1. ✅ 3/3 LowerOnly → Exec upgrades complete
+2. ⚠️ 4/5 selfhost tests pass (loop-based only, if-select requires architectural fix)
+3. ✅ No regression in non-strict mode
+4. ❌ If-select test NOT unblocked (requires Option A: separate If targets table)
+
+**Recommendation**: Phase 183 should implement **separate JOINIR_IF_TARGETS table** (Option A in FINDINGS.md) before proceeding with LoopBuilder removal.
+
+### Files Changed
+
+- `src/mir/join_ir_vm_bridge_dispatch/targets.rs`: 3 Exec upgrades + loop-only warning added
+- `docs/private/roadmap2/phases/phase-182/FINDINGS.md`: Comprehensive findings document (300+ lines)
+
+---
+
 ## 🎉 Phase 181: JoinIR Unification Planning Completed (2025-12-04)
 
-**Status**: ✅ **All 4 Tasks Completed** → Phase 182 Implementation Ready
+**Status**: ✅ **All 4 Tasks Completed** → Phase 182 Implementation Partially Completed
 
 **Summary**: Phase 181 successfully completed comprehensive planning for JoinIR mainline unification before selfhost depth-2. All 4 tasks delivered detailed analysis totaling **1,698+ lines of documentation**, revealing critical insights that make Phase 182-183 implementation straightforward.
 

src/mir/join_ir_vm_bridge_dispatch/targets.rs

@@ -29,15 +29,25 @@ pub struct JoinIrTargetDesc {
 ///
 /// Phase 32 L-4: 全対象関数を一覧化し、Exec/LowerOnly の区分を明示する。
 /// Phase 82: このテーブルが唯一の SSOT。is_loop_lowered_function() はここから参照。
+/// Phase 182: representative paths 対応（3 upgrades - LOOP ONLY）
+///
+/// **重要**: このテーブルは LOOP lowering 専用です。
+/// If lowering の関数を追加すると、is_loop_lowered_function() で除外され、
+/// if-lowering が機能しなくなります。If 関数は is_joinir_if_toplevel_target() で管理。
 ///
 /// | 関数 | Kind | デフォルト有効 | 備考 |
 /// |-----|------|---------------|------|
 /// | Main.skip/1 | Exec | No | PHI canary のため env 必須 |
 /// | FuncScannerBox.trim/1 | Exec | Yes | A/B 実証済み、事実上本線 |
 /// | FuncScannerBox.append_defs/2 | Exec | No | Phase 82 SSOT統一で追加 |
-/// | Stage1UsingResolverBox.resolve_for_source/5 | LowerOnly | No | 構造検証のみ |
+/// | Stage1UsingResolverBox.resolve_for_source/5 | Exec | Yes | Phase 182: LowerOnly→Exec 昇格 |
-/// | StageBBodyExtractorBox.build_body_src/2 | LowerOnly | No | 構造検証のみ |
+/// | StageBBodyExtractorBox.build_body_src/2 | Exec | Yes | Phase 182: LowerOnly→Exec 昇格 |
-/// | StageBFuncScannerBox.scan_all_boxes/1 | LowerOnly | No | 構造検証のみ |
+/// | StageBFuncScannerBox.scan_all_boxes/1 | Exec | Yes | Phase 182: LowerOnly→Exec 昇格 |
+///
+/// Phase 181/182 設計ドキュメント:
+/// - docs/private/roadmap2/phases/phase-181/joinir-targets-mapping.md
+/// - docs/private/roadmap2/phases/phase-181/representative-paths-finalized.md
+/// - docs/private/roadmap2/phases/phase-182/FINDINGS.md (Phase 182 実装時発見事項)
 pub const JOINIR_TARGETS: &[JoinIrTargetDesc] = &[
     // Loop Exec（実行対応）
     JoinIrTargetDesc {
@@ -55,21 +65,21 @@ pub const JOINIR_TARGETS: &[JoinIrTargetDesc] = &[
         kind: JoinIrBridgeKind::Exec,
         default_enabled: false,
     },
-    // Loop LowerOnly（構造検証のみ）
+    // Phase 182 昇格: Stage-1/Stage-B infrastructure (LowerOnly → Exec)
     JoinIrTargetDesc {
         func_name: "Stage1UsingResolverBox.resolve_for_source/5",
-        kind: JoinIrBridgeKind::LowerOnly,
+        kind: JoinIrBridgeKind::Exec, // Phase 182: LowerOnly から昇格
-        default_enabled: false,
+        default_enabled: true,
     },
     JoinIrTargetDesc {
         func_name: "StageBBodyExtractorBox.build_body_src/2",
-        kind: JoinIrBridgeKind::LowerOnly,
+        kind: JoinIrBridgeKind::Exec, // Phase 182: LowerOnly から昇格
-        default_enabled: false,
+        default_enabled: true,
     },
     JoinIrTargetDesc {
         func_name: "StageBFuncScannerBox.scan_all_boxes/1",
-        kind: JoinIrBridgeKind::LowerOnly,
+        kind: JoinIrBridgeKind::Exec, // Phase 182: LowerOnly から昇格
-        default_enabled: false,
+        default_enabled: true,
     },
 ];