bug#69448: 30.0.50; Calc: Wrong unit conversion of sums

[Michael Heerdegen]

Hello,

this bug had been originally reported by "Kepa
<gnu.cognition199@slmails.com>" in emacs-help:

In Calc with this expression on top of stack:

3 m^3 / s + 70 m^3 / hr  [note: compatible units!]

u c
    - Old units: m^3/s
    - New utis: m^3/hr

==> 10870. m^3 / s

That's wrong - but would be correct with the same number and the
actually requested unit: The correct result is 10870 m^3 / hr.

Unit simplification (u s) before conversion leads to the correct result.

This bug is also present in 28.2.


Michael.