Spreadsheet: Stable circular definitions aren't errors

[water-ghosts]

• In cell A0, type a literal number (e.g. 5).
• In cell A1, type the formula =A0.
• Edit cell A0 to use the formula =A1.

Despite the circular reference, both cells still have the value 5:

If the circular definition isn't stable (e.g. A1 = A0 + 1 instead of A1 = A0), both cells instead get the value NaN:

In contrast, Google Sheets treats all circular definitions as errors:

This is arguably a feature, not a bug. If this is intended behavior, feel free to close this issue!

[Diogenes31]

I agree that it's a bug, I think that could create some very easy to miss errors in a spreadsheet that could cause much headache.

[kleinesfilmroellchen]

This does indeed look like a bug, though we want @alimpfard 's opinion here. We should display a custom error instead imho.