Repository navigation
[TS] Compute Array.join from elements and separator #433
Description
Resolution (2026-10-14)
Audited against usvm main at 19866c959d.
Array.join computes from elements and separator through the source model, with nullish/runtime-kind handling and explicit residual conversions. Concrete Number formatting and symbolic safe integers are supported; symbolic fractions/unsafe integers remain residual. Implementation: usvm #410.
Validation: All 11 TsGapModelsSourceTest regressions passed, including join composition, numeric boundaries and native replay.
Original report and acceptance context, retained for traceability
Problem
The Array.join approximation returns the same fixed string regardless of array contents or separator.
Minimal TypeScript example
export function joined(): string {
return [1, 2].join("-");
}Expected behavior
joined() returns "1-2". Convert elements in order, honor the separator and preserve the supported sparse/undefined behavior. Keep unsupported element conversions explicit.
Current source evidence
Checked against USVM main 53dce8f3bca2713642c783ba8308a6a360a9e516. This exact snippet is a proposed regression from source audit; it has not yet been run as a new end-to-end test. #368 audits the existing call approximations but does not implement these individual fixes.
Acceptance criteria
- A focused test checks the symbolic outcome without reporting an approximation as exact semantics.
- The supported case agrees with concrete TypeScript/Node.js replay.
- Unsupported operand or environment cases remain explicit.
Activity