Phase 70-B relaxes runtime guard from "always error" to "unsupported only". Adds structural detection (is_supported_multihop_pattern) to distinguish: - Simple passthrough (no self-updates): ACCEPT - Complex patterns (self-conflict, etc): REJECT with [ownership/relay:runtime_unsupported] Changes: - plan_validator.rs: +is_supported_multihop_pattern() method + unit tests - normalized_joinir_min.rs: +2 integration tests for passthrough/rejection - phase70-relay-runtime-guard.md: Phase 70 series status table added Tests: normalized_dev 52/52 PASS, lib 950/950 PASS Design: Structural detection only (no by-name branching) 🤖 Generated with Claude Code Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
101 lines
3.0 KiB
Markdown
101 lines
3.0 KiB
Markdown
# Phase 70-A: Relay Runtime Guard
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**Status**: Implementation Phase
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**Date**: 2025-12-13
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---
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## Overview
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Phase 66 enabled multihop relay acceptance at the analysis/plan layer (`plan_to_p2_inputs_with_relay` / `plan_to_p3_inputs_with_relay`). However, the **runtime lowering path** (actual MIR generation) does not yet support multihop execution.
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This phase establishes a **Fail-Fast boundary** with a standardized error tag to clearly indicate "analysis OK, runtime not yet supported."
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---
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## Current State
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| Layer | Multihop Support | Status |
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|-------|-----------------|--------|
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| `plan_to_p2_inputs_with_relay` | ✅ Accepts | Phase 66 complete |
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| `plan_to_p3_inputs_with_relay` | ✅ Accepts | Phase 66 complete |
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| **P3 runtime lowering** | ❌ Rejects | Phase 70-A guard |
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| P2 runtime lowering | ❌ Not integrated | Future |
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---
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## Fail-Fast Tag
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**Standard Tag**: `[ownership/relay:runtime_unsupported]`
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When multihop relay (`relay_path.len() > 1`) is detected at runtime:
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```
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[ownership/relay:runtime_unsupported] Multihop relay not executable yet: var='sum', owner=ScopeId(0), relay_path=[ScopeId(2), ScopeId(1)]
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```
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**Diagnostic fields**:
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- Variable name being relayed
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- Owner scope ID
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- Relay path (inner → outer)
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- Relay path length
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---
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## Implementation Location
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**File**: `src/mir/builder/control_flow/joinir/patterns/pattern3_with_if_phi.rs`
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**Function**: `check_ownership_plan_consistency()`
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**Behavior**: On `relay_path.len() > 1`, return `Err` with standardized tag.
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---
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## Release Conditions (Phase 70-B+)
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The `[ownership/relay:runtime_unsupported]` guard can be removed when:
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1. **Exit PHI merge** implemented at owner scope
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2. **Boundary carrier propagation** for intermediate scopes
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3. **Integration tests** passing for 3+ layer nested loops
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4. **No regression** in existing Pattern3 tests
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---
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## Test Coverage
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**Test**: `test_phase70a_multihop_relay_runtime_unsupported_tag`
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Verifies:
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- 3-layer nested loop AST (L1 owns `sum`, L3 writes `sum`)
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- Runtime path returns `Err`
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- Error message contains `[ownership/relay:runtime_unsupported]`
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---
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## Phase 70 Series
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| Phase | Status | Description |
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|-------|--------|-------------|
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| Phase 70-A | ✅ Complete | Runtime guard with standard tag `[ownership/relay:runtime_unsupported]` |
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| Phase 70-B | ✅ Complete | Simple passthrough multihop support (contiguous path, no self-updates) |
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| Phase 70-C | ✅ Complete | Merge relay detection (multiple inner loops → same owner) |
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| Phase 70-D+ | 🚧 Future | Full runtime execution support (exit PHI merge, carrier propagation) |
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---
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## Related Documents
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- [Phase 65: Multihop Design](phase65-ownership-relay-multihop-design.md)
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- [Phase 66: Multihop Implementation](phase65-ownership-relay-multihop-design.md#phase-66-implementation-status)
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- [Phase 70-C: Merge Relay](phase70c-merge-relay.md)
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- [Phase 56: Ownership-Relay Architecture](phase56-ownership-relay-design.md)
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---
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## Changelog
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- **2025-12-13**: Phase 70-C completed - Merge relay detection and validation
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- **2025-12-13**: Phase 70-A created - Fail-Fast tag standardization
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