P&C on distance contraints silently discards changes that introduce new variables or have typos in the expression

[yeroca]

Describe the bug

If I point and click on a distance constraint in a sketch2 sketch, then type in a constraint that either contains a typo or introduces a new variable, ZDS will discard the change compleletely without any indication of an error, and leave the constraint unmodified.

Steps to Reproduce

1. Start a sketch
2. draw a line
3. add a distance constraint
4. modifiy the constraint, starting by double clicking on it.
5. use a new variable to constrain the length
6. observe that ZDS discards the change.

Expected Behavior

I expected that either ZDS wouldn't allow me to complete the change with an error, or that it would allow the change (perhaps showing it in red), and then allow me to modify it later, or add a definition for the new variable.

Screenshots and Recordings

Screencast.From.2026-06-20.11-22-26.mp4

Desktop OS

Fedora 44

Browser

No response

Version

v.1.3.2

Additional Context

No response