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tracking: general effect-handler dispatch (post-CORE-02 residual) — silent arm-drop on 3 backends; DECISION: back-port loud failure now? #555
Description
Why this issue exists
CORE-02 was marked CLOSED 2026-05-19 (TECH-DEBT.adoc:237-250) under a title broader than what was delivered: the closure covered the Async slice only (#225 CPS line + #234/ADR-016 boundary detection). General algebraic-effect handler dispatch has no open tracking issue on any backend. This is it.
Per-backend truth (all file:line on main @ 20e27c8)
| Backend | handle/resume behaviour |
Class |
|---|---|---|
| core-WASM (default) | ExprHandle compiles body only — all arms silently dropped; ExprResume = arg passthrough (codegen.ml:1385-1397) |
silent miscompile |
| JS-text | erased ("Effect handlers are erased at MVP", js_codegen.ml:288-292) |
silent miscompile |
| Deno-ESM | ExprHandle → gen_expr body (arms dropped); TopEffect → "// effect declaration (erased)" (codegen_deno.ml:~1203, :1823) |
silent miscompile |
| WasmGC | loud UnsupportedFeature for handle/resume/try-catch (codegen_gc.ml:896-948) |
correct fencing — never back-ported |
| Interpreter | shallow single-shot tail-resume only: PerformEffect aborts the whole body; resume(v) returns v as the entire handle result, discarding post-perform code (in-code admission, interp.ml:248-263) |
semantically incomplete; matrix "interpreter-complete" overstates |
Execution-proven divergence — no effects required
fn main() -> Int {
return handle 41 { return(v) => v + 1 };
}
Interpreter: 42. Compiled wasm (default backend): 41. Compilation silent. The TopEffect-emits-nothing fence (effect-op calls → UnboundFunction) does not cover return arms, so this miscompile is reachable from fully effect-free programs. (Verified by Node instantiation, 2026-06-11.)
Test coverage
Zero runtime handler-dispatch tests on any path. tests/effects/basic_effect.affine is wired into no harness (and fails wasm codegen loudly when compiled by hand). Caution: tools/estate-rs-audit/data/results.post228.tsv records check-only PASS rows for it that grep like coverage.
Decision requested
Back-port the WasmGC loud-failure to core-WASM, JS-text, and Deno-ESM now (the exact fix codegen_gc.ml:903-906 already brands the silent behaviour "wrong"); implement real dispatch later. Also fix the CAPABILITY-MATRIX "interpreter-complete" cell to "shallow single-shot tail-resume" in the same PR.
Filed from the 2026-06-11 whole-picture survey.
Activity
hyperpolymath commentedon Jun 11, 2026
Decision executed (owner: yes, 2026-06-11): the loud-failure fence is back-ported to all three silently-wrong backends in PR #566 (core-WASM
UnsupportedFeature, JS-text/Deno-ESMfailwith→Errorat entry), with the 41-vs-42 probe landed as fixturehandle_return_arm.affineand a 4-test E2E Handler Fence suite (interpreter keeps working; all three compile backends must fail loudly). 385 tests green.This issue STAYS OPEN for the remaining scope: general handler dispatch on a wasm backend (EH proposal or general-handler CPS), deep/multi-shot resume semantics on the interpreter, and runtime dispatch tests once dispatch exists. The silent-wrong-value class is eliminated once #566 merges; the matrix effects-row touch-up follows after #565 lands.
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