29 lines
1.2 KiB
Markdown
29 lines
1.2 KiB
Markdown
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# Structured Exceptions via Result‑Mode (Draft)
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Problem
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- Language exceptions are hard to implement portably (unwinding, landing pads) and complicate SSA/CFG.
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Contribution (Nyash)
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- Express try/catch/finally with Result‑mode lowering (no MIR Throw/Catch): structured blocks and jumps.
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- Thread‑local ThrowCtx to aggregate nested `throw` to a single catch.
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- PHI‑Off: merge variables via edge‑copy; harness synthesizes PHIs.
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- Block‑Postfix Catch syntax: `{ body } catch (e) { … } [finally { … }]` with single‑catch policy.
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Method
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- Parser (gated): accept try/throw + postfix catch, normalize to `ASTNode::TryCatch`.
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- Bridge: set ThrowCtx on try entry; route `throw` to catch BB; bind catch param via incoming.
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- Finally: always runs; merge at exit with PHI‑off rules.
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Code References
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- Parser: `src/parser/statements.rs`
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- Bridge lowering: `src/runner/json_v0_bridge/lowering/{try_catch.rs, throw_ctx.rs}`
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- Smokes: `tools/test/smoke/bridge/try_result_mode.sh`
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Evaluation Plan
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- Semantic parity: PyVM vs. harness binaries on representative cases.
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- Control‑flow complexity: nested if/loop + finally; ensure merges are stable.
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Reproduce
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- `bash tools/test/smoke/bridge/try_result_mode.sh`
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