Stream: jco

Topic: Generated code triggers ILLEGAL_REASSIGNMENT due to const re

ktz_alias (Mar 17 2026 at 03:20):

Hi all,

After upgrading to Vite 8, we're seeing the following build-time error:

[ILLEGAL_REASSIGNMENT] Error: Unexpected re-assignment of const variable storagePtr

It appears in JS code generated by jco, for example:

function _liftFlatRecord(keysAndLiftFns) {
  return function _liftFlatRecordInner(ctx) {
    _debugLog('[_liftFlatRecord()] args', { ctx });
    const { memory, useDirectParams, storagePtr, storageLen, params } = ctx;

    if (useDirectParams) {
      storagePtr = params[0]; // <-- re-assignment causes ILLEGAL_REASSIGNMENT
    }

Dev mode works fine, but production build fails. Has anyone encountered this before, or have suggestions for handling const reassignment in generated code?

ktz_alias (Mar 17 2026 at 03:20):

As a workaround, changing the destructured binding from const to let avoids the error.

ktz_alias (Mar 17 2026 at 03:21):

jco 1.16.1 also generates the same code, but vite 7.3.1 does not report an error.
The issue becomes visible when using jco 1.17.0.

Victor Adossi (Mar 17 2026 at 11:41):

Thanks for the report @ktz_alias ! Will have a bug fix release out soon

Victor Adossi (Mar 17 2026 at 15:36):

OK new version of Jco is out -- 1.17.1, please let me know if you still run into this -- should be fixed

Victor Adossi (Mar 18 2026 at 10:01):

@ktz_alias would you mind re-checking this one too? I think you should be good now

Last updated: Mar 23 2026 at 16:19 UTC