As you can see here using an expression as a dimensional constraint value which uses unitless numbers is accepted as mm:
This could lead to problems when using spreadsheets. I found the folowing sequence that could create a problem:
1. Create sketch, draw rectangle, constraint it, pad.
2. Create spreadsheet, add cell value "2", alias cell
3. Create sketch001, carbon copy sketch, make all lines construction, draw rectangle, constraint relative to CC geometry by alias+0.5 (2+0.5=2.5) - constraints are accepted as 2.5mm
4. Pocket sketch001 with fixed length - Ok.
5. Try to change Pocket.Length=Pad.Length - spreadsheet.alias - non compatible units error.
6. Change spreadsheet.cell value to "2mm" to remedy - sketch001 constraints break - 2mm + 0.5 is wrong
7. Fix constraints to alias+0.5mm - all ok
8. Change cell to 2.5 (forget the mm) -> all is broken again
The assumption that when expression returns unitless number it should be treated as mm makes the user believe that all is ok when using unitless values in spreadsheets.
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