62 lines
3.0 KiB
Markdown
62 lines
3.0 KiB
Markdown
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## Phase 78: BindingId for Promoted Carriers (dev-only)
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### Goal
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Make LoopBodyLocal promotion (DigitPos/Trim) **BindingId-aware** without relying on fragile name-based hacks like `format!("is_{}", name)`.
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This phase introduces a dev-only identity link:
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- `BindingId(original LoopBodyLocal)` → `BindingId(promoted carrier)` → `ValueId(join carrier param)`
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### Problem
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Promotion creates synthetic carrier names (例: `is_digit_pos`, `is_ch_match`) that do not exist as source-level bindings.
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- `PromotedBindingRecorder` expects both original/promoted names in `MirBuilder.binding_map`.
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- For promoted carriers this is not true by construction.
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- For LoopBodyLocal variables, promotion can happen before their `local` is lowered, so the original name may also be absent.
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### Solution (current state)
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#### 1) CarrierVar gets optional BindingId (dev-only)
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- `src/mir/join_ir/lowering/carrier_info.rs`
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- `CarrierVar.binding_id: Option<BindingId>` (feature `normalized_dev`)
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#### 2) CarrierBindingAssigner box
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- `src/mir/join_ir/lowering/carrier_binding_assigner.rs`
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- Ensures both sides have BindingIds:
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- If `original_name` is missing in `builder.binding_map`, allocate a temporary BindingId.
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- If `promoted_carrier_name` is missing, allocate a temporary BindingId.
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- Records:
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- `carrier_info.promoted_bindings[original_bid] = promoted_bid`
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- `CarrierVar.binding_id = Some(promoted_bid)` for the promoted carrier
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- Restores `builder.binding_map` after recording (synthetic names do not leak into the source map).
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#### 3) Pattern2/Pattern4 wiring
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- Pattern2 (break): `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`
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- Calls `CarrierBindingAssigner::assign_promoted_binding()` immediately after promotion.
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- Registers `BindingId → ValueId` via `ConditionEnv.register_carrier_binding()` after carrier join_id allocation.
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- Keeps legacy name-based aliasing (`digit_pos` → `is_digit_pos`) for now, but removes local “guess naming” by using the promoted carrier name returned by the promoter.
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- Pattern4 (continue): `src/mir/builder/control_flow/joinir/patterns/pattern4_with_continue.rs`
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- Calls `CarrierBindingAssigner::assign_promoted_binding()` after promotion (analysis metadata only, since Pattern4’s current lowering path does not use JoinValueSpace params).
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### Tests
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- Unit test (dev-only): `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`
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- `phase78_promoted_binding_is_recorded_for_digitpos`
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- Asserts:
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- `promoted_bindings` has one mapping
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- promoted carrier has `binding_id`
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- `ConditionEnv.binding_id_map[promoted_bid] == promoted_carrier.join_id`
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### Open Follow-ups (Phase 79+)
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1. Wire `ScopeManager::lookup_with_binding()` into ExprLowerer/ConditionLoweringBox call-sites (so BindingId actually drives resolution).
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2. Extend coverage to Trim and other promotion shapes (additional unit/E2E tests).
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3. Shrink/remove legacy name-based promoted lookup (`resolve_promoted_join_id`) after call-sites consistently provide BindingId.
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