# Phase 64 Implementation Report: Ownership P3 Production Integration

## Executive Summary

**Status**: ✅ Complete
**Date**: 2025-12-12
**Feature Gate**: `normalized_dev`
**Test Results**: 49/49 tests passing, no regressions

Successfully integrated OwnershipPlan analysis into production P3 (if-sum) route with dev-only validation and Fail-Fast consistency checks.

## Implementation Overview

### Changes Made

#### 1. Core API: `analyze_loop()` helper (`ast_analyzer.rs`)

**Purpose**: Analyze a single loop with parent context for P3 production integration.

```rust
pub fn analyze_loop(
    condition: &ASTNode,
    body: &[ASTNode],
    parent_defined: &[String],
) -> Result<OwnershipPlan, String>
```

**Features**:
- Creates temporary function scope for parent-defined variables
- Analyzes loop scope with condition (is_condition=true) and body
- Returns OwnershipPlan for loop scope only (not parent scope)
- Private helper `build_plan_for_scope()` for single-scope extraction

**Key Design**: Avoids analyzing entire function - only analyzes the specific loop being lowered.

#### 2. P3 Production Integration (`pattern3_with_if_phi.rs`)

**Location**: Inside `lower_pattern3_if_sum()` method, after ConditionEnv building

**Integration Point**:
```rust
#[cfg(feature = "normalized_dev")]
{
    use crate::mir::join_ir::ownership::analyze_loop;

    // Collect parent-defined variables
    let parent_defined: Vec<String> = self.variable_map.keys()
        .filter(|name| *name != &loop_var_name)
        .cloned()
        .collect();

    // Analyze loop
    match analyze_loop(condition, body, &parent_defined) {
        Ok(plan) => {
            // Run consistency checks
            check_ownership_plan_consistency(&plan, &ctx.carrier_info, &condition_binding_names)?;
            // Continue with existing lowering (analysis-only)
        }
        Err(e) => {
            // Warn and continue (analysis is optional)
        }
    }
}
```

**Key Design**: Analysis happens **after** ConditionEnv but **before** JoinIR lowering, ensuring:
- All existing infrastructure is available for comparison
- No behavior change to lowering (analysis-only)
- Fail-Fast on critical errors only (multi-hop relay)

#### 3. Consistency Checks (`check_ownership_plan_consistency()`)

**Check 1: Multi-hop relay rejection (Fail-Fast)**
```rust
for relay in &plan.relay_writes {
    if relay.relay_path.len() > 1 {
        return Err(format!(
            "Phase 64 limitation: multi-hop relay not supported. Variable '{}' has relay path length {}",
            relay.name, relay.relay_path.len()
        ));
    }
}
```

**Why Fail-Fast**: Multi-hop relay requires semantic design beyond Phase 64 scope.

**Check 2: Carrier set consistency (warn-only)**
```rust
let plan_carriers: BTreeSet<String> = plan.owned_vars
    .iter()
    .filter(|v| v.is_written)
    .map(|v| v.name.clone())
    .collect();

let existing_carriers: BTreeSet<String> = carrier_info.carriers
    .iter()
    .map(|c| c.name.clone())
    .collect();

if plan_carriers != existing_carriers {
    eprintln!("[phase64/ownership] Carrier set mismatch (warn-only, order SSOT deferred):");
    eprintln!("  OwnershipPlan carriers: {:?}", plan_carriers);
    eprintln!("  Existing carriers: {:?}", existing_carriers);
}
```

**Why warn-only**: Carrier order SSOT is deferred to Phase 65+. This is a monitoring check only.

**Check 3: Condition captures consistency (warn-only)**
```rust
let plan_cond_captures: BTreeSet<String> = plan.condition_captures
    .iter()
    .map(|c| c.name.clone())
    .collect();

if !plan_cond_captures.is_subset(condition_bindings) {
    let extra: Vec<_> = plan_cond_captures
        .difference(condition_bindings)
        .collect();
    eprintln!("[phase64/ownership] Extra condition captures in plan (warn-only): {:?}", extra);
}
```

**Why warn-only**: Some patterns may legitimately have extra captures during development.

#### 4. Regression Tests (`normalized_joinir_min.rs`)

**Test 1: `test_phase64_p3_ownership_prod_integration()`**
- **Pattern**: `loop(i < 10) { local sum=0; local i=0; sum=sum+i; i=i+1; }`
- **Verifies**:
  - Owned vars: sum (is_written=true), i (is_written=true, is_condition_only=true)
  - No relay writes (all loop-local)
  - Single-hop relay constraint

**Test 2: `test_phase64_p3_multihop_relay_detection()`**
- **Pattern**: Nested loops with function-scoped variable written in inner loop
- **Verifies**:
  - Multi-hop relay detection (relay_path.len() = 2)
  - Documents that rejection happens in consistency check (not analyze_loop)

### Test Results

```bash
# Phase 64 specific tests
cargo test --features normalized_dev --test normalized_joinir_min test_phase64
# Result: 2/2 passed

# Ownership module tests
cargo test --features normalized_dev --lib ownership
# Result: 23/23 passed

# Full normalized_joinir_min suite
cargo test --features normalized_dev --test normalized_joinir_min
# Result: 49/49 passed (no regressions)
```

## Design Decisions

### Why `analyze_loop()` instead of full function analysis?

**Decision**: Create a loop-specific helper that analyzes only the loop scope.

**Rationale**:
- P3 production route only needs loop-level information
- Full function analysis would require threading through call stack
- Loop-specific API matches the existing P3 lowering architecture
- Simpler to test and verify correctness

### Why dev-only (normalized_dev feature)?

**Decision**: Gate all new code with `#[cfg(feature = "normalized_dev")]`.

**Rationale**:
- Analysis-only implementation (no behavior change)
- Early detection of inconsistencies without risk
- Allows iterative refinement before canonical promotion
- Easy to disable if issues are discovered

### Why Fail-Fast only for multi-hop relay?

**Decision**: Only reject multi-hop relay (`relay_path.len() > 1`), warn for other mismatches.

**Rationale**:
- Multi-hop relay requires semantic design (Phase 65+)
- Carrier set mismatches might indicate existing edge cases (monitor first)
- Condition capture extras might be expected during development
- Fail-Fast only for truly blocking issues

### Why integrate after ConditionEnv building?

**Decision**: Call `analyze_loop()` after ConditionEnv is built but before JoinIR lowering.

**Rationale**:
- ConditionEnv provides condition_bindings for comparison
- CarrierInfo is available from PatternPipelineContext
- ExitMeta will be available after lowering for future comparison
- No behavior change - analysis is non-invasive

## Constraints and Limitations

### Phase 64 Constraints

1. **Single-hop relay only**: `relay_path.len() > 1` → Err
2. **Analysis-only**: No changes to lowering behavior
3. **Dev-only**: `#[cfg(feature = "normalized_dev")]` throughout
4. **Warn-only mismatches**: Carrier set and condition captures

### Known Limitations

1. **No carrier order SSOT**: Existing CarrierInfo order is preserved
2. **No owner-based init**: Legacy `FromHost` initialization unchanged
3. **No multi-hop relay support**: Out of scope for Phase 64
4. **Parent context simplification**: Uses all `variable_map` keys except loop_var

## Future Work (Phase 65+)

### Phase 65: Carrier Order SSOT

**Goal**: Use OwnershipPlan to determine carrier order (upgrade warn to error).

**Changes**:
- Make OwnershipPlan the source of truth for carrier set
- Remove existing carrier inference logic
- Enforce carrier order consistency (fail on mismatch)

### Phase 66: Owner-Based Initialization

**Goal**: Replace legacy `FromHost` with owner-based initialization.

**Changes**:
- Use OwnershipPlan to determine initialization strategy
- Implement proper initialization for relay writes
- Handle condition-only carriers correctly

### Phase 67+: Multi-Hop Relay Support

**Goal**: Remove `relay_path.len() > 1` limitation.

**Semantic Design Needed**:
- How to represent multi-hop relay in JoinIR
- PHI insertion strategy for intermediate loops
- Boundary input/output handling
- Exit line connection across multiple loops

## References

- **Phase 62**: [Ownership P3 Route Design](phase62-ownership-p3-route-design.md)
- **Phase 63**: [AST Ownership Analyzer](../../../private/roadmap2/phases/normalized_dev/phase-63-ast-ownership-analyzer.md)
- **Phase 64 Summary**: [PHASE_64_SUMMARY.md](PHASE_64_SUMMARY.md)
- **JoinIR Architecture**: [joinir-architecture-overview.md](joinir-architecture-overview.md)

## Conclusion

Phase 64 successfully connects OwnershipPlan analysis to production P3 route with:
- ✅ Dev-only validation (no behavior change)
- ✅ Fail-Fast for critical errors (multi-hop relay)
- ✅ Comprehensive consistency checks (carrier set, condition captures)
- ✅ Full test coverage (49/49 tests passing)
- ✅ Zero regressions

The implementation provides a solid foundation for Phase 65+ enhancements while maintaining existing functionality.
