quantity-operator-expression
Available in: SysML
This checks that the second argument to quantity expressions is a measurement unit.
Example
attribute x = 5 [4]; // error: Invalid quantity expression, expected a measurement unit as the second argument
Use a measurement unit:
attribute x = 5 [SI::m]; // ok
Or a measurement unit with prefix:
attribute x = 5 [SI::milli * SI::m]; // ok