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[P2] Interpreter: async numeric bitwise operations use saturating casts instead of ToInt32

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
csharp, typescript
Domain
compilers

Research direction

Start with Interpreter.Async.cs::EvaluateBinaryAsync and compare its numeric bitwise conversions with Interpreter.Calls.cs::EvaluateBinary, which already uses JsToInt32 and JsToUint32. Run the supplied async reproduction against the interpreter and Node. Done when the async results match Node while preserving the stated evaluation order, shift masking, and unsigned-result behavior.

Written by the indexing model from the issue text.

Description

bug priority: P2

The async interpreter's primitive-Number binary fast path casts operands directly to int, producing saturating conversions instead of ECMAScript ToInt32 wrapping. The same synchronous operations already match Node.

const large = 4294967297, zero = 0, infinite = Infinity, negative = -4294967297.75;
console.log("sync", large | zero, infinite | zero, negative | zero);
async function main() {
    await Promise.resolve(0);
    console.log("async", large | zero, infinite | zero, negative | zero);
}
main();

Node v22.23.2, exit0:

sync 1 0 -1
async 1 0 -1

Immutable interpreter baseline, exit0:

sync 1 0 -1
async 2147483647 2147483647 -2147483648

The await ensures the async evaluator is exercised. All operands are primitive Numbers; there are no objects, conversion hooks, BigInts, Symbols, computed keys, assignment, typed arrays or CLR interop involved. ToInt32 wraps 4294967297 to1, maps Infinity to0, and truncates then wraps -4294967297.75 to-1. The synchronous line is a positive control on the same values and same runtime.

Source lead: Interpreter.Async.cs::EvaluateBinaryAsync handles Bitwise/BitwiseShift with EvaluateBitwise(..., (int)l, (int)r) and unsigned right shift with (uint)(int)l. Interpreter.Calls.cs::EvaluateBinary already uses JsToInt32/JsToUint32. Reuse the JavaScript conversion rules in the async numeric fast path while retaining left-to-right evaluation, five-bit shift masking and unsigned Number results.

Found during #2514's binary ToNumeric review. That issue concerns object conversion yielding BigInt on the shared slow path; this reduction has primitive Number operands and returns entirely within the async fast path. Fresh all-state async/bitwise, exact4294967297, interpreter/ToInt32, bitwise/Infinity, async/ToInt32, interpreter/bitwise/overflow and async/bitwise/operands searches found no focused owner. Closed #1421 was read in full and concerns compiled unboxed numeric bitwise optimization, not the interpreter's async evaluator.

Evidence: ignored artifacts/p2-interpreter/2514-async-number-bitwise-truncation.ts, .node.log, .baseline.log, 2514-async-number-bitwise-truncation-results.json, 2514-async-number-bitwise-{focused-,}dedup.json, and saved #1421 body. Immutable baseline artifacts/p2-interpreter/baseline/SharpTS.dll SHA256 checked before invocation: B5FA2CADDEA116B83166442205B825130A663B682EDAABAA1312A26FB7909E85 (source fec823522). Commands use Node type stripping or dotnet BASELINE --no-tsconfig --noLib SOURCE.ts. No compiled failure, project build, tracked edit or introducing-commit claim is made.

Dominant language
C#
Stars
156
Forks
4
Avg merge
5h 24m
Merged PRs (30d)
68

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