hakorune/docs/development/current/main/phase182-completion-report.md

Phase 182 Completion Report: JsonParser Simple Loop Implementation (P2/P1 Verification)

Date: 2025-12-08 Status: ✅ PARTIAL SUCCESS - Pattern routing verified, blockers identified Goal: Implement JsonParser simple loops (_parse_number, _atoi, _match_literal) using existing P2/P1 patterns

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Executive Summary

Phase 182 successfully verified that Pattern1 (Simple) and Pattern2 (Break) routing and execution work correctly for basic loop patterns. However, we discovered two fundamental blockers that prevent the actual JsonParser loops from working:

1. LoopBodyLocal variable handling - Current system assumes Trim-specific carrier promotion
2. String concatenation filter - Phase 178's conservative rejection of string operations

Achievement Status

Task	Status	Notes
182-1: Design Document	✅ COMPLETE	phase182-simple-loops-design.md created
182-2: Routing Whitelist	✅ COMPLETE	Added 3 methods, fixed _match_literal arity
182-3: Pattern Routing	✅ VERIFIED	P1/P2 route correctly with structure-only mode
182-5: Representative Tests	✅ PASSING	2 tests created, both PASS
182-6: Documentation	✅ COMPLETE	Updated architecture docs + CURRENT_TASK

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Detailed Results

Task 182-1: Design Document ✅

File: docs/development/current/main/phase182-simple-loops-design.md

Created comprehensive design memo covering:

• Target loop analysis (3 loops: _parse_number, _atoi, _match_literal)
• Pattern mapping (P2 Break × 2, P1 Simple × 1)
• Pipeline integration strategy (reuse PatternPipelineContext)
• Verification plan (structure-only tracing + representative tests)

Commit: 5d99c31c - "docs(joinir): Add Phase 182 simple loops design memo"

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Task 182-2: Routing Whitelist Update ✅

File: src/mir/builder/control_flow/joinir/routing.rs

Changes Made:

1. Added JsonParserBox._parse_number/2 → P2 Break
2. Added JsonParserBox._atoi/1 → P2 Break
3. Fixed JsonParserBox._match_literal arity: /2 → /3 (s, pos, literal)

Rationale:

• Phase 181 analysis identified these 3 loops as high-priority, low-difficulty targets
• Verified actual signatures from tools/hako_shared/json_parser.hako
• Arity counting follows Nyash convention (excludes implicit me parameter)

Commit: be063658 - "feat(joinir): Phase 182-2 Add _parse_number/_atoi to routing whitelist"

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Task 182-3: Pattern Routing Verification ✅

Method: Used NYASH_JOINIR_STRUCTURE_ONLY=1 + NYASH_JOINIR_DEBUG=1 tracing

Results:

Pattern1 (_match_literal) - ✅ SUCCESS

[trace:pattern] route: Pattern1_Minimal MATCHED
[joinir/pattern1] Generated JoinIR for Simple While Pattern
[joinir/pattern1] Functions: main, loop_step, k_exit

Pattern2 (Simple integer loop) - ✅ SUCCESS

[trace:pattern] route: Pattern2_WithBreak MATCHED
[pattern2/init] PatternPipelineContext: loop_var='i', loop_var_id=ValueId(5), carriers=3
[joinir/pattern2] Phase 170-D: Condition variables verified: {"i", "limit"}
[joinir/pattern2] Generated JoinIR for Loop with Break Pattern

Full JsonParser Loops - ❌ BLOCKED (Expected)

Blocker 1: LoopBodyLocal promotion error

[ERROR] ❌ [TrimLoopLowerer] Cannot promote LoopBodyLocal variables ["digit_pos"]:
No promotable Trim pattern detected

Blocker 2: String operation filter (Phase 178)

[pattern2/can_lower] Phase 178: String/complex update detected, rejecting Pattern 2 (unsupported)
[ERROR] ❌ [joinir/freeze] Loop lowering failed: JoinIR does not support this pattern

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Task 182-5: Representative Tests ✅

Created 2 representative tests in apps/tests/ (tracked directory):

Test 1: Pattern1 (Simple) - phase182_p1_match_literal.hako

Purpose: Verify Pattern1 routing and execution with early return Loop Structure: Simple while loop with conditional return (matches _match_literal logic)

Result: ✅ PASS

Result: MATCH
RC: 0

Verification:

• Correctly routes to Pattern1_Minimal
• 3 JoinIR functions generated (main, loop_step, k_exit)
• Early return mechanism works correctly
• String matching logic verified

Test 2: Pattern2 (Break) - phase182_p2_break_integer.hako

Purpose: Verify Pattern2 routing and execution with break statement Loop Structure: Integer accumulation with conditional break (simplified _atoi/_parse_number)

Result: ✅ PASS

PASS: P2 Break works correctly
RC: 0

Verification:

• Correctly routes to Pattern2_WithBreak
• Multi-carrier handling works (result + i)
• Break condition properly evaluated
• Integer arithmetic in carriers verified

Commit: d5b63e09 - "test(joinir): Phase 182-5 Add P1/P2 pattern verification tests"

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Task 182-6: Documentation Updates ✅

Files Updated:

1. docs/development/current/main/joinir-architecture-overview.md

   • Added Phase 182 verification status to Section 4.1 (JsonParser ループ空間と P1–P5)
   • Documented blockers and workaround strategies
   • Updated implementation status for _match_literal (✅ verified)

2. CURRENT_TASK.md

   • Added Phase 182 completion entry with detailed task breakdown
   • Documented both blockers with technical details
   • Created Phase 183 next steps (LoopBodyLocal handling + string ops)

Commit: 0772dc3e - "docs(joinir): Phase 182-6 Update documentation with P1/P2 verification results"

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Blockers Identified

Blocker 1: LoopBodyLocal Variable Handling

Problem: Current system attempts Trim-specific carrier promotion for all LoopBodyLocal variables.

Example:

loop(p < s.length()) {
    local ch = s.substring(p, p+1)      // LoopBodyLocal
    local digit_pos = digits.indexOf(ch) // LoopBodyLocal
    if digit_pos < 0 { break }
    // ...
}

Current Behavior:

1. LoopConditionScopeBox detects ch and digit_pos as LoopBodyLocal
2. TrimLoopLowerer tries to promote them to carriers
3. Promotion fails (not a Trim pattern) → Error

Required Fix:

• P1/P2 patterns should allow purely local variables (no carrier promotion needed)
• Only Trim pattern requires carrier promotion for ch
• Distinction: "LoopBodyLocal used in condition" (Trim) vs "LoopBodyLocal used in body only" (normal)

Impact: Blocks _parse_number, _atoi, and most other JsonParser loops

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Blocker 2: String Concatenation Filter (Phase 178)

Problem: Phase 178 conservatively rejects string concatenation in Pattern2/4 carrier updates.

Example:

loop(p < s.length()) {
    num_str = num_str + ch  // Rejected by filter
    p = p + 1
}

Current Behavior:

UpdateRhs::StringLiteral(_) | UpdateRhs::Other => {
    eprintln!("[pattern2/can_lower] Phase 178: String/complex update detected, rejecting Pattern 2 (unsupported)");
    return false;
}

Required Fix:

• Gradual enablement of string operations in P2/P4
• Distinguish between:
  • Simple concat: s = s + literal (should work)
  • Complex string ops: s = method_call() (may need special handling)
• Consider allowing string concat for JsonParser-specific functions

Impact: Blocks _parse_number, _parse_string, and all loops with string building

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Implementation Strategy (Phase 183+)

Option A: Minimal Fix (Recommended)

For Blocker 1 (LoopBodyLocal):

1. Add check in lower_loop_pattern2_with_break():

   if !ctx.loop_body_locals.is_empty() && !is_trim_pattern {
       // Allow LoopBodyLocal if not used in loop condition
       // (Trim pattern promotes to carrier, others remain local)
   }
   

2. Distinguish between:

   • Trim-style LoopBodyLocal (used in condition) → promote
   • Normal LoopBodyLocal (used in body only) → keep local

For Blocker 2 (String ops):

1. Relax filter in can_lower():

   UpdateRhs::StringLiteral(_) => {
       // Allow simple string literals for now
       // (JsonParser needs this for _parse_number, etc.)
   }
   UpdateRhs::Other => {
       // Still reject complex expressions
       return false;
   }
   

2. Add function-specific whitelist if needed

Option B: Comprehensive Refactor (Future)

1. Create LoopBodyLocalRole enum:

   enum LoopBodyLocalRole {
       ConditionCarrier,  // Trim pattern (promote)
       BodyOnly,          // Normal pattern (local)
   }
   

2. Extend UpdateRhs to track string operation complexity

3. Add gradual string operation support (Phase 184+)

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Metrics

Code Changes

Metric	Count
Files Modified	3
Files Created (docs)	2
Files Created (tests)	2
Lines Added (code)	~10
Lines Added (docs)	~350
Lines Added (tests)	~60

Commits

Commit SHA	Description
5d99c31c	docs(joinir): Add Phase 182 simple loops design memo
be063658	feat(joinir): Phase 182-2 Add _parse_number/_atoi to routing whitelist
d5b63e09	test(joinir): Phase 182-5 Add P1/P2 pattern verification tests
0772dc3e	docs(joinir): Phase 182-6 Update documentation with P1/P2 verification results

Total Commits: 4 Build Status: ✅ All builds successful Test Status: ✅ 2/2 representative tests PASS Global Tests: Not run (blockers prevent JsonParser loops from compiling)

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Lessons Learned

What Worked Well

1. Structure-based routing (NYASH_JOINIR_STRUCTURE_ONLY=1) is excellent for development
2. PatternPipelineContext reuse - No new infrastructure needed
3. Existing P1/P2 lowerers - Worked perfectly for basic cases
4. Phase 181 analysis - Accurate predictions saved time

What Needs Improvement

1. LoopBodyLocal handling - Too Trim-specific, needs generalization
2. String operation filter - Too conservative, needs gradual relaxation
3. Test coverage - Need tests for LoopBodyLocal edge cases

Design Insights

1. Trim pattern is special - Requires carrier promotion, but not all patterns do
2. String ops are common - JsonParser heavily uses string building
3. Filter granularity - Need finer-grained control than "accept all" or "reject all"
4. Pattern verification approach - Starting with simplified tests was correct strategy

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Recommendations for Phase 183

High Priority

1. LoopBodyLocal handling

   • Add role-based distinction (condition vs body-only)
   • Allow body-only locals in P1/P2 without promotion
   • Keep Trim-specific promotion for condition locals

2. String concat enablement

   • Allow simple string concatenation in P2/P4
   • Add safety checks (e.g., carrier type verification)
   • Document supported vs unsupported string operations

Medium Priority

3. Test coverage expansion

   • Add tests for LoopBodyLocal edge cases
   • Add tests for string concat patterns
   • Add negative tests (verify correct rejection)

4. Documentation refinement

   • Create decision tree for LoopBodyLocal handling
   • Document string operation support matrix

Low Priority

5. Refactoring opportunities
   • Consider LoopBodyLocalRole enum (future)
   • Consider UpdateRhs extension for operation types
   • Consider function-specific routing configuration

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Conclusion

Phase 182 successfully verified the foundation for JsonParser simple loop support:

✅ Pattern1 and Pattern2 routing works correctly ✅ Basic execution verified with representative tests ✅ Blockers identified with clear remediation paths

The blockers are architectural constraints rather than bugs:

• LoopBodyLocal promotion is Trim-specific by design
• String operation filter is conservative by design (Phase 178)

Next Steps: Phase 183 will address both blockers with minimal, targeted fixes to enable JsonParser loops while maintaining the existing architecture's safety guarantees.

Success Criteria Met:

• Pattern routing verified ✅
• Representative tests created ✅
• Blockers documented ✅
• Remediation paths identified ✅
• Documentation updated ✅

Overall Assessment: Successful verification phase with clear path forward for full implementation in Phase 183.

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References

• Design Document: docs/development/current/main/phase182-simple-loops-design.md
• Phase 181 Analysis: docs/development/current/main/phase181-jsonparser-loop-roadmap.md
• Architecture Overview: docs/development/current/main/joinir-architecture-overview.md
• Test Files:
  • apps/tests/phase182_p1_match_literal.hako
  • apps/tests/phase182_p2_break_integer.hako
• Routing Code: src/mir/builder/control_flow/joinir/routing.rs
• Pattern2 Filter: src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs