Bloomberg TS 5.6 Beta Feedback

Acknowledgement

• I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

We are in the process of evaluating the impact of TS 5.6 beta on Bloomberg code. Below are preliminary findings.

Overall, the only new diagnostics produced by this release are the excellent improvements to nullish/truthy checks.

Stricter type-checking of partial objects

We observed new errors related to nullish/truthy checks, all of which look like correct diagnostics. A few simplified examples are below:

const err = "bar";

// Right operand of ?? is unreachable because the left operand is never nullish.(2869)
const errorMessage = "foo " + err ?? "Unknown error";

// Right operand of ?? is unreachable because the left operand is never nullish.(2869)
const isActive = !someCondition ?? true;

// This kind of expression is always truthy.(2872)
if (myCheck === "foo" || "bar") {

}

The report contains TypeScript 5.6 beta feedback and simplified diagnostics, but names no file, test, or entry point to investigate. Confirm the reported diagnostics against the linked release notes and identify a reproducible repository case before defining any code change.