hakorune/docs/development/current/main/phase185-completion-report.md

Phase 185 Completion Report: Body-local Pattern2 Integration (Partial)

Date: 2025-12-09 Status: ⚠️ Partially Complete - Infrastructure integrated, init lowering blocked Duration: ~2 hours

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Executive Summary

Phase 185 successfully integrated Phase 184's body-local infrastructure into Pattern2's API and code structure, but discovered that body-local initialization lowering was never implemented in Phase 184. The integration skeleton is complete and builds successfully, but tests fail due to undefined ValueIds from uninitialized body-local variables.

Key outcome: Identified Phase 186 scope (body-local init lowering) as prerequisite for functional body-local variable support.

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Completed Work

✅ Task 185-1: Design Document

File: docs/development/current/main/phase185-body-local-integration.md

• Comprehensive architecture design
• Integration approach documented
• Test strategy defined
• Scope and constraints clarified

✅ Task 185-2: Pattern2 Integration Skeleton

Modified files:

1. src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs:

   • Added collect_body_local_variables() helper function
   • Created LoopBodyLocalEnv from collected locals
   • Pass body_local_env to lower_loop_with_break_minimal

2. src/mir/join_ir/lowering/loop_with_break_minimal.rs:

   • Added body_local_env: Option<&LoopBodyLocalEnv> parameter
   • Added imports for LoopBodyLocalEnv, UpdateEnv, emit_carrier_update_with_env
   • Modified carrier update emission to use UpdateEnv when body_local_env present
   • Backward compatibility: existing callers pass None

Build status: ✅ cargo build --release SUCCESS (0 errors)

Code quality:

• Clean separation of concerns
• Backward compatible API
• Box-first design principles followed

✅ Task 185-3: Pattern4 Deferred

Decision: Pattern4 uses different architecture (inline lowering, no emit_carrier_update).

Rationale:

• Pattern4 has custom inline update logic
• Variable resolution is hardcoded
• "Minimal" scope constraint
• Would require significant refactoring

Documentation: Clearly marked as future work in design doc.

✅ Task 185-4: Test Created, Blocker Identified

Test file: apps/tests/phase185_p2_body_local_int_min.hako

Test content: JsonParser-style loop with body-local integer calculation (local digit_pos = pos - start).

Test result: ❌ BLOCKED

Error:

[ERROR] use of undefined value ValueId(11)

Root cause identified: Body-local variables are collected but not initialized.

What works:

• ✅ Variable name collection: [pattern2/body-local] Collected local 'digit_pos' → ValueId(2)
• ✅ LoopBodyLocalEnv creation: Phase 185-2: Collected 1 body-local variables
• ✅ Pattern2 routing: Correctly detected and lowered to JoinIR

What doesn't work:

• ❌ Init expression lowering: local digit_pos = pos - start never lowered to JoinIR
• ❌ ValueId definition: ValueId(11) allocated but never assigned a value
• ❌ Runtime execution: VM error on use of undefined value

✅ Task 185-5: Documentation Updated

Updated files:

1. phase185-body-local-integration.md: Status section with detailed analysis
2. phase185-completion-report.md: This file
3. CURRENT_TASK.md: (will be updated after this report)

Documentation quality:

• Root cause clearly explained
• Phase 186 scope defined
• Alternative approaches provided
• Lessons learned documented

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Technical Analysis

What Was Assumed (Incorrectly)

Phase 184 was assumed to include:

• ✅ LoopBodyLocalEnv (storage) - Actually implemented
• ✅ UpdateEnv (resolution) - Actually implemented
• ✅ emit_carrier_update_with_env() - Actually implemented
• ❌ Body-local init lowering - NOT implemented

What Phase 184 Actually Delivered

Infrastructure only:

• Data structures (LoopBodyLocalEnv, UpdateEnv)
• API extensions (emit_carrier_update_with_env)
• Variable resolution priority logic
• Unit tests for storage and resolution

Missing piece:

• AST expression → JoinIR instruction lowering for body-local init
• Integration of init instructions into loop body
• Full E2E test (would have caught this)

What Phase 185 Accomplished

API integration:

• Pattern2 now accepts body_local_env parameter
• lower_loop_with_break_minimal ready to use UpdateEnv
• Backward compatibility maintained

Discovered gap:

• Identified init lowering as blocking issue
• Defined Phase 186 scope clearly
• Provided implementation roadmap

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Phase 186 Requirements

Goal

Implement body-local variable initialization lowering to make Phase 185 integration functional.

Scope

1. Expression lowering (local digit_pos = pos - start):

   • Lower AST BinOp nodes to JoinIR BinOp instructions
   • Lower AST Variable nodes to ValueId lookups in ConditionEnv
   • Handle nested expressions recursively

2. Init instruction insertion:

   • Emit init instructions at start of loop_step function
   • Before break condition, after parameter allocation
   • Update LoopBodyLocalEnv with resulting ValueIds

3. Helper refactoring:

   • Replace collect_body_local_variables() with collect_and_lower_body_locals()
   • Add lower_expr_to_joinir() helper function
   • Pass instruction vector to enable emission

Estimate

Full implementation: 6-7 hours

• Expression lowerer: 2-3 hours
• Integration: 2 hours
• Testing: 2 hours

Simplified (variables only): 2-3 hours

• Only support local temp = var (no binops)
• Defer complex expressions to Phase 187

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Files Modified

Source Code (3 files)

1. src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs

   • Lines added: ~35 (helper function + integration)
   • Changes: collect_body_local_variables(), LoopBodyLocalEnv creation, lower call update

2. src/mir/join_ir/lowering/loop_with_break_minimal.rs

   • Lines added: ~20 (imports + parameter + conditional emission)
   • Changes: body_local_env parameter, UpdateEnv usage, emit_carrier_update_with_env call

Documentation (3 files)

3. docs/development/current/main/phase185-body-local-integration.md

   • Lines: ~680 (comprehensive design + status update)

4. docs/development/current/main/phase185-completion-report.md

   • Lines: ~350 (this file)

Tests (1 file, non-functional)

5. apps/tests/phase185_p2_body_local_int_min.hako
   • Lines: ~25 (test blocked by init lowering)

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Build & Test Results

Build Status

$ cargo build --release
Compiling nyash-rust v0.1.0
Finished `release` profile [optimized] target(s) in 1m 07s

✅ SUCCESS - No compilation errors, no warnings in modified files

Test Execution

$ NYASH_JOINIR_CORE=1 ./target/release/hakorune apps/tests/phase185_p2_body_local_int_min.hako
[pattern2/body-local] Collected local 'digit_pos' → ValueId(2)
[pattern2/body-local] Phase 185-2: Collected 1 body-local variables
[pattern2/before_lowerer] About to call lower_loop_with_break_minimal with carrier_info.loop_var_name='pos'
[ERROR] use of undefined value ValueId(11)

❌ BLOCKED - Runtime error due to uninitialized body-local variable

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Validation Checklist

• Design document created
• Pattern2 integration skeleton implemented
• Build succeeds with no errors
• Backward compatibility maintained (existing tests pass)
• Pattern4 scope decision documented
• Test file created
• Test execution successful ❌ (blocked by init lowering)
• Representative test outputs correct value ❌ (blocked)
• Documentation updated with status and next steps
• Root cause analysis completed
• Phase 186 requirements defined

7/10 completed (3 blocked by missing init lowering)

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Lessons Learned

1. Infrastructure ≠ Implementation

Issue: Phase 184 delivered "infrastructure" but left core functionality (init lowering) unimplemented.

Impact: Phase 185 integration appeared complete (builds successfully) but fails at runtime.

Lesson: "Infrastructure" phases must include E2E test to validate full functionality, not just API structure.

2. Test Early, Test Often

Issue: Phase 184 had unit tests but no E2E test showing body-local variables actually working.

Impact: Missing init lowering wasn't discovered until Phase 185 integration testing.

Lesson: Even "infrastructure-only" phases need at least one E2E test demonstrating the feature works end-to-end.

3. Scope Boundaries Must Be Clear

Issue: Phase 184/185 scope boundary was unclear - where does "infrastructure" end and "implementation" begin?

Impact: Phase 185 assumed init lowering was done, wasted time on integration before discovering blocker.

Lesson: Explicitly document what IS and IS NOT in scope for each phase. Use "In Scope" / "Out of Scope" sections.

4. Pattern4 Architecture Differences

Issue: Pattern4 uses inline lowering (no emit_carrier_update), different from Pattern2.

Decision: Deferred Pattern4 integration to avoid scope creep.

Lesson: "Minimal" integration for Phase 185 was correct - Pattern4 needs its own refactoring phase.

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Next Steps

Immediate (Phase 186)

1. Implement body-local init lowering:

   • Add lower_expr_to_joinir() helper
   • Refactor collect_body_local_variables() to collect_and_lower_body_locals()
   • Emit init instructions in loop_step function

2. Test Phase 185 integration:

   • Run phase185_p2_body_local_int_min.hako
   • Verify output: 123
   • Confirm no [joinir/freeze] or SSA-undef errors

3. Document Phase 186 completion:

   • Update CURRENT_TASK.md
   • Mark Phase 185 as fully complete
   • Provide Phase 187 preview

Future (Phase 187+)

1. Phase 187: String UpdateKind support (careful, gradual)
2. Phase 188: Pattern4 body-local integration (refactor inline lowering)
3. Phase 189: JsonParser full loop coverage (_parse_number, _atoi, etc.)

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Conclusion

Phase 185 successfully prepared the API and code structure for body-local variable support in Pattern2, but revealed that the core initialization lowering was never implemented in Phase 184. This is a valuable discovery that clarifies the scope for Phase 186 and provides a clear implementation roadmap.

Value delivered:

• ✅ API integration skeleton (builds successfully)
• ✅ Root cause analysis (init lowering missing)
• ✅ Phase 186 requirements defined
• ✅ Test infrastructure in place

Phase 185 status: Partially complete - integration skeleton done, awaiting Phase 186 for functional completion.

Next phase: Phase 186 - Body-local Init Lowering (2-3 hours simplified, 6-7 hours full)