hakorune/docs/development/current/main/phase173-2_completion_summary.md

Phase 173-2 Completion Summary

Date: 2025-12-04 Status: Investigation Complete, Strategy Revision Required

Summary

Phase 173-2 investigation has been completed successfully. Through detailed VM tracing and code analysis, I identified the root cause of the static box method resolution issue and proposed two alternative implementation strategies.

What Was Accomplished ✅

1. Deep Investigation

• VM Execution Tracing: Used NYASH_CALLEE_RESOLVE_TRACE=1 and NYASH_DEBUG_FUNCTION_LOOKUP=1 to trace the complete execution flow
• MIR Lowering Analysis: Verified that static box internal calls (me.method()) correctly lower to Callee::Global
• VM Function Lookup: Confirmed all JsonParserBox methods are properly registered in the function table
• Error Point Identification: Pinpointed that the error occurs at the call site in Main, not in the VM execution

2. Root Cause Identified

Problem: Parser treats JsonParserBox as a variable (VarRef) instead of a type (TypeRef)

Evidence:

Main.main():
  JsonParserBox.parse("{\"x\":1}")
    ↓ Parser treats "JsonParserBox" as variable (VarRef)
    ↓ MIR generates Callee::Method with undefined receiver
    ↓ Receiver defaults to "InstanceBox"
    ↓ ERROR: "Unknown method 'parse' on InstanceBox"

Confirmed Working:

• Internal static box calls: me.method() within JsonParserBox ✅
• Function registration: All methods in VM function table ✅
• Function lookup: VM successfully finds functions ✅

Not Working:

• External static box calls: JsonParserBox.parse() from Main ❌

3. Strategy Revision

Original Plan Issues:

• Violated "Rust VM不変" (Rust VM unchanged) principle
• Required complex .hako compiler modifications
• Introduced scope creep (essentially building a type system)

Revised Recommendations:

Option 1: Minimal Parser Fix (Recommended)

Approach: Detect UsingAlias.method() pattern in parser, emit StaticBoxCall AST node

Changes required:

1. Parser (.hako): Add using alias table lookup in call expression parsing (~30 lines)
2. AST: Add StaticBoxCall node type or flag to existing MethodCall
3. MIR lowering (Rust): Handle StaticBoxCall → Callee::Global (~20 lines)

Effort: 2-3 hours Risk: Low (isolated, additive changes) Benefit: Clean solution, proper syntax support

Option 2: Workaround Documentation (Quick Exit)

Approach: Document workaround pattern, defer to Phase 174+ type system work

Pattern:

// Workaround: Create dummy instance
local parser = new JsonParserBox()
parser.parse("{}")  // Works via Global call lowering

Effort: 30 minutes Risk: None Benefit: Unblocks other work, defers complexity

Documentation Created

1. phase173-2_investigation_findings.md (330+ lines)

   • Complete technical analysis
   • Root cause explanation with call flow diagrams
   • Two implementation options with trade-offs
   • Test case status and diagnosis

2. CURRENT_TASK.md (updated)

   • Task 1-3 marked complete (investigation + JsonParserBox bugfix)
   • Task 4-6 revised with new strategy recommendations
   • Root cause summary added
   • Files created/modified list updated

3. phase173-2_completion_summary.md (this document)

   • High-level overview for stakeholders
   • Clear recommendations
   • Next steps

Technical Insights

Architecture Principle Adherence

✅ 箱化モジュール化 (Modular Boxing): Investigation maintained the principle of isolated, incremental changes ✅ Rust VM不変 (Rust VM Unchanged): Proposed solutions minimize Rust VM changes ✅ 段階的確認 (Staged Verification): Traced AST → MIR → VM flow systematically

Code Quality

• All investigation code is read-only (no modifications during investigation)
• Comprehensive tracing and logging used for debugging
• Clear separation of concerns maintained

Knowledge Gained

1. Static box internal calls work correctly: The MIR lowering already handles me.method() properly in static box context
2. VM infrastructure is sound: Function registration, lookup, and execution all work as expected
3. Parser is the bottleneck: The issue is purely at the parser level, not in VM or MIR lowering

Recommendation

Proceed with Option 1 (Minimal Parser Fix) because:

1. Well-scoped: Clear boundaries, minimal changes
2. Architecturally sound: Aligns with existing design principles
3. User-friendly: Provides the expected syntax (JsonParserBox.parse())
4. Low risk: Changes are additive and testable
5. Immediate value: Unblocks Phase 171-2 (hako_check integration)

Alternative: If time-constrained or if there are other higher-priority tasks, use Option 2 as an interim solution.

Next Steps

Immediate (Decision Required)

User/stakeholder should decide:

• Option 1: Implement minimal parser fix (2-3 hours)
• Option 2: Document workaround, defer to Phase 174+ (30 minutes)

After Decision

If Option 1:

1. Implement parser enhancement for UsingAlias.method() detection
2. Add StaticBoxCall AST node or flag
3. Modify MIR lowering to handle StaticBoxCall
4. Test with json_parser_min.hako (expect RC 0)
5. Run hako_check smoke tests (HC019/HC020)
6. Update documentation and commit

If Option 2:

1. Update using.md with workaround pattern and examples
2. Add note to LANGUAGE_REFERENCE_2025.md
3. Mark Phase 173 as "interim complete" with workaround
4. Schedule Phase 174 for comprehensive type system work
5. Update documentation and commit

Impact Assessment

Blocked/Unblocked

Currently Blocked:

• Phase 171-2: hako_check JsonParserBox integration
• Any code using using for static box libraries

Will Unblock (with Option 1):

• Phase 171-2: Can complete hako_check integration
• JsonParserBox as official standard library
• Future static box libraries (e.g., ProgramJSONBox usage)

Technical Debt

Option 1: Minimal debt (proper solution) Option 2: Moderate debt (workaround until Phase 174+)

Files for Review

Investigation Documents

• phase173-2_investigation_findings.md (detailed analysis, read first)
• phase173-2_completion_summary.md (this document, executive summary)
• phase173_task1-2_completion_report.md (Task 1-2 details)
• mir-nested-if-loop-bug.md (related bug found during investigation)

Test Cases

• apps/tests/json_parser_min.hako (currently fails, will pass after fix)

Reference

• docs/reference/language/using.md (Phase 173 static box section)
• docs/reference/language/LANGUAGE_REFERENCE_2025.md (static box usage)

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Created: 2025-12-04 Phase: 173-2 (using resolver + MIR lowering) Outcome: Investigation complete, two implementation options proposed Recommendation: Option 1 (minimal parser fix) Estimated Completion: 2-3 hours (Option 1) or 30 minutes (Option 2)