51 lines
1.8 KiB
Markdown
51 lines
1.8 KiB
Markdown
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# Phase 275: Coercion Implementation (truthiness / `==` / `+`)
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Status: ✅ completed (Phase 275 P0)
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Goal: implement the accepted coercion SSOT across backends (Rust VM + LLVM harness) and update language docs and fixtures so behavior cannot drift.
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Accepted SSOT decisions:
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- `docs/development/current/main/phases/phase-274/P3-DECISIONS.md`
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Language SSOT (updated after Phase 275):
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- `docs/reference/language/types.md`
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---
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## What changes in this phase
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Implement these semantics (A1/B2/C2):
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1) truthiness (boolean context)
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- `Void` in condition → **TypeError**
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- `BoxRef` in condition → **TypeError**, except explicit bridge boxes (BoolBox/IntegerBox/StringBox)
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- “object is always truthy” remains prohibited
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2) equality (`==`)
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- allow Int↔Float numeric comparison only (precise rule; no accidental true via float rounding)
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- Bool is not a number: no Bool↔Int coercion
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- other mixed kinds: deterministic `false` (not error)
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- BoxRef equality: identity only
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3) `+`
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- numeric add: Int+Int, Float+Float, Int↔Float promotion to Float
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- string concat: **String+String only**
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- String mixed (`"a"+1`, `1+"a"`) → TypeError (no implicit stringify)
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---
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## Acceptance criteria (minimum)
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- Rust VM behavior matches `P3-DECISIONS.md` for truthiness / `==` / `+`.
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- LLVM harness behavior matches Rust VM (no backend divergence).
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- `docs/reference/language/types.md` is updated to reflect the new executable SSOT.
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- New fixtures + smokes lock behavior (VM + LLVM) without introducing environment-variable sprawl.
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- No by-name hardcoding for “special cases”; if something must be special, it must be a documented bridge rule.
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---
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## Implementation guide
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- `docs/development/current/main/phases/phase-275/P0-INSTRUCTIONS.md`
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- `docs/development/current/main/phases/phase-275/P1-INSTRUCTIONS.md`
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