hakorune/docs/development/current/main/phases/phase-279/P0-COMPLETION.md

Phase 279 P0: Type propagation pipeline SSOT unification — completion

Status: ✅ completed (2025-12-22)

Goal:

• Eliminate "2本のコンパイラ" (two compilers) problem
• Root fix for order drift where identical fixtures pass in one route but fail in another
• Unify type propagation into single SSOT entry with fixed order

SSOT implementation:

• src/mir/type_propagation/pipeline.rs - SSOT type propagation pipeline
• TypePropagationPipeline::run() - Single entry point for all routes

Pipeline steps (fixed order):

1. Copy propagation (initial)
2. BinOp re-propagation (numeric promotion: Int+Float→Float)
3. Copy propagation (propagate promoted types)
4. PHI type inference (private step - cannot bypass)

Callers (both routes now use SSOT):

• src/mir/builder/lifecycle.rs::finalize_module() - Builder lifecycle route
• src/mir/join_ir_vm_bridge/joinir_function_converter.rs::propagate_types() - JoinIR bridge route

Fail-fast guard (structural guarantee):

• PHI type inference is private step inside TypePropagationPipeline
• lifecycle.rs and joinir_function_converter.rs cannot call PhiTypeResolver directly
• Only public API: TypePropagationPipeline::run()
• Order drift is structurally impossible (private encapsulation)

Environment variables (reused existing flags):

• NYASH_PHI_GLOBAL_DEBUG=1 - PHI type inference debug output
• NYASH_BINOP_REPROP_DEBUG=1 - BinOp re-propagation debug output
• No new environment variables (Phase 279 P0 policy)

Files changed (6 total):

• New: src/mir/type_propagation/mod.rs - Module definition
• New: src/mir/type_propagation/pipeline.rs - SSOT pipeline (~300 lines)
• Modified: src/mir/mod.rs - Add type_propagation module export
• Modified: src/mir/builder/lifecycle.rs - Replace with SSOT call (~400 lines removed)
• Modified: src/mir/join_ir_vm_bridge/joinir_function_converter.rs - Replace with SSOT call (~100 lines removed)
• Modified: docs/development/current/main/phases/phase-279/README.md - Document SSOT entry

Code reduction:

• ~500 lines of duplicate BinOp re-propagation logic removed
• 2 implementations consolidated into 1 SSOT

Regression testing:

• ✅ Lifecycle route (VM backend): Phase 275 fixture - exit=3
• ✅ JoinIR route (VM backend): loop_min_while.hako - exit=0
• ✅ LLVM harness: Phase 275 fixture - compiled and executed successfully

Acceptance criteria met:

• ✅ Single SSOT entry for type propagation (TypePropagationPipeline::run())
• ✅ Both routes call SSOT entry (lifecycle.rs + joinir_function_converter.rs)
• ✅ No duplicate BinOp re-propagation logic
• ✅ Fixed order: Copy → BinOp → Copy → PHI
• ✅ Fail-fast guard prevents PHI-before-BinOp (structural guarantee)
• ✅ All regression tests pass
• ✅ Documentation reflects SSOT entry point

Next phase:

• Phase 280 (planned): Further compiler unification work