Issues with negative Numbers and Sizes

[laeubi]

I'm facing several issues with negative numbers, eg
top: -@variable
outputes
top: - 2.5mm;
(there is a space betwenn the minus sign an the value)

Using
top: @eval(-1*@variable)
outputs
top: 2.5mm

Using
top: @eval(-@variable)
outputs
org.zkoss.zuss.ZussException: Unable to negate a size, 2.5mm

From the source I can't see why it should not be possible to negate a size (since it's an ordinary number with a unit), so thin can be added. Another strange thing is that the negate operator only negates sizes and colors but not Numbers.

[laeubi]

Testcase

@VARIABLE: 2.5mm;

div1 {
    top: -@VARIABLE;
}
div2 {
    top: @eval(-1*@VARIABLE);
}
div 3 {
    top: @eval(-@VARIABLE);
}

[laeubi]

I created a pull request that fixes case 2 and 3, @tomyeh do you have any cahnce in looking at case 1? I currently can't see where to start to debugg that problem.