hakorune/src/mir/join_ir/ownership

Ownership Analysis Module

Responsibility Boundary

This module is responsible for analysis only:

• ✅ Collecting reads/writes from AST/ProgramJSON
• ✅ Determining variable ownership (owned/relay/capture)
• ✅ Producing OwnershipPlan for downstream lowering

This module does NOT:

• ❌ Generate MIR instructions
• ❌ Modify JoinIR structures
• ❌ Perform lowering transformations

Core Types

Type	Purpose
ScopeId	Unique scope identifier
ScopeOwnedVar	Variable defined in this scope
RelayVar	Write to ancestor-owned variable
CapturedVar	Read-only reference to ancestor
OwnershipPlan	Complete analysis result

Invariants

1. carriers = owned_vars.filter(is_written)
2. No variable in both owned and relay
3. No variable in both owned and captures
4. Relay implies ancestor ownership exists

Design Philosophy

「読むのは自由、管理は直下 owned だけ」

• Owned: Variable defined in this scope (unique owner)
• Carrier: Owned AND written (managed as loop_step argument)
• Capture: Read-only reference to ancestor (via CapturedEnv)
• Relay: Write to ancestor → relay up to owner (exit PHI at owner)

Phase Status

• Phase 56: ✅ Interface skeleton
• Phase 57: ⏳ OwnershipAnalyzer implementation
• Phase 58: ⏳ P2 plumbing
• Phase 59: ⏳ P3 plumbing
• Phase 60: ⏳ Cleanup dev heuristics
• Phase 61: ⏳ Canonical promotion decision

Usage (Future)

let plan = OwnershipAnalyzer::analyze(&ast_node, parent_scope);
plan.verify_invariants()?;
let carriers: Vec<_> = plan.carriers().collect();

Example

local limit = 100      // owned by outer
loop {
    local sum = 0      // owned by loop
    if sum < limit {   // limit = capture (read-only)
        sum++          // sum = carrier (owned + written)
    }
}

OwnershipPlan (loop scope):

• owned_vars: [sum (written), limit (read-only)]
• relay_writes: []
• captures: [limit]
• condition_captures: [limit]

References

• Design Doc: phase56-ownership-relay-design.md
• JoinIR Architecture: joinir-architecture-overview.md