hakorune/docs/private/papers/public/block_postfix_catch.md

Block‑Postfix Catch Language Design (Draft)

Goal

• Make exception boundaries explicit by attaching catch/cleanup to standalone blocks.

Design

• Syntax: { body } catch (e) { handler } [cleanup { … }] and { body } cleanup { … }.
• Policy: single catch (branch inside the catch); scope limited to the same block; no implicit propagation.
• Static check (MVP): direct throw in a standalone block requires an immediate postfix catch.

Implementation Notes

• Parser (gated): normalize postfix to ASTNode::TryCatch.
• Bridge(Result‑mode): ThrowCtx routes nested throw to the single catch; merge with PHI‑off.
• Friendly errors: disallow top‑level leading catch/cleanup, and attaching to structural if/loop blocks.

References

• Parser: src/parser/statements.rs
• Smokes: src/tests/parser_block_postfix_{catch,errors}.rs

Open Questions

• Multiple catch with type hierarchy; effects typing for static checks; formatter support.