148 lines
4.1 KiB
Markdown
148 lines
4.1 KiB
Markdown
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# Phase 275 P0 (impl): Coercion SSOT rollout
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Status: planned / implementation guide
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This is the “next instruction sheet” for implementing the accepted coercion SSOT (A1/B2/C2) across backends.
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SSOT decisions:
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- `docs/development/current/main/phases/phase-274/P3-DECISIONS.md`
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---
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## Scope (P0)
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Implement and lock these three rule sets:
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- truthiness: `Void`/`BoxRef` fail-fast (with bridge-box exceptions)
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- equality: B2 (Number-only, precise Int↔Float)
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- `+`: C2 (Number-only promotion; String+String only; String mixed → TypeError)
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Backends in scope:
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- Rust VM (primary SSOT)
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- LLVM harness (llvmlite path) parity with Rust VM
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Out of scope:
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- adding new language features (keywords)
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- expanding env var toggles
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- rewriting the optimizer broadly (only touch what is required to enforce semantics)
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---
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## Step 0: Lock reference + plan
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- Keep `docs/reference/language/types.md` as “current executable SSOT” until the implementation is complete.
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- After implementation + tests land, update `types.md` to the new semantics (it becomes SSOT again).
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---
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## Step 1: Rust VM — truthiness (A1)
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Target:
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- `src/backend/abi_util.rs::to_bool_vm` (or equivalent truthiness entry)
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Changes:
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- `Void` in boolean context → return `TypeError`
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- `BoxRef`:
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- allow only explicit bridge boxes: BoolBox/IntegerBox/StringBox
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- treat VoidBox as Void (→ TypeError)
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- other BoxRef types → TypeError
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Acceptance:
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- A dedicated fixture demonstrates `if Void { ... }` is a runtime error (fail-fast).
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---
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## Step 2: Rust VM — equality (B2)
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Target:
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- `src/backend/abi_util.rs::eq_vm` (and any helpers it relies on)
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Changes:
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- Remove Bool↔Int coercion.
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- Keep Int↔Float comparison, but make it precise:
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- if Float is NaN → false
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- if Float is integral and within i64 exact range → compare as Int exactly
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- otherwise → false
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- Mixed kinds (except Int↔Float) → false (not error).
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- BoxRef equality stays identity.
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Acceptance:
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- Tests cover:
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- `1 == 1.0` true
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- `1 == 1.1` false
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- `true == 1` false (or TypeError if you choose a transition rule; document explicitly)
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---
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## Step 3: Rust VM — `+` (C2)
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Target:
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- `src/backend/mir_interpreter/helpers.rs::eval_binop` for `BinaryOp::Add`
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Changes:
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- Numeric:
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- Int+Int → Int
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- Float+Float → Float
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- Int+Float / Float+Int → Float (Int promoted to Float)
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- String:
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- String+String → concat
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- String mixed → TypeError (no implicit stringify)
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- Everything else → TypeError
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Acceptance:
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- Tests cover:
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- `1 + 2.0` → `3.0`
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- `"a" + "b"` → `"ab"`
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- `"a" + 1` → TypeError
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---
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## Step 4: LLVM harness parity
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Targets (likely):
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- `src/llvm_py/instructions/binop.py` for `+`
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- `src/llvm_py/instructions/compare.py` for `==`
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- truthiness for branch conditions (inspect branch lowering):
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- `src/llvm_py/instructions/controlflow/branch.py`
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- and any “truthy” conversions used in control-flow lowering
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Notes:
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- LLVM harness uses MIR JSON metadata (`value_types`) for discriminating raw vs handle.
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- Keep behavior identical to Rust VM; do not re-introduce “string mixed concat”.
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Acceptance:
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- VM and LLVM smokes use the same fixtures and produce identical exit codes.
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---
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## Step 5: Fixtures + smoke tests (SSOT lock)
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Create minimal, self-contained fixtures under `apps/tests/` and add smokes under `tools/smokes/v2/profiles/integration/apps/`.
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Suggested fixtures (names; adjust as needed):
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- `apps/tests/phase275_p0_truthiness_void_error_min.hako`
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- `apps/tests/phase275_p0_eq_number_only_min.hako`
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- `apps/tests/phase275_p0_plus_number_only_min.hako`
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Smoke targets:
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- VM: `..._vm.sh`
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- LLVM: `..._llvm.sh` (harness/EXE path consistent with current infra)
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Rules:
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- No reliance on hidden env toggles.
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- If a test needs runtime-unknown values, avoid externs that aren’t supported on VM/LLVM.
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---
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## Step 6: Update SSOT docs
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After the implementation is complete and tests pass:
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- Update `docs/reference/language/types.md` to the new semantics:
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- truthiness: Void/BoxRef fail-fast
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- equality: B2
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- `+`: C2
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- Update Phase 274/275 status:
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- `docs/development/current/main/phases/phase-274/README.md`
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- `docs/development/current/main/10-Now.md`
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- `docs/development/current/main/30-Backlog.md`
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