Determining the bit width of operands in constraint

Hi Moderators,

I was trying a few variations of a simple addition operation in a SV constraint.
In edalink all constraints give desired results except SUM4

As per my understanding

Bit widths of operands and any intermediate expressions are determined before applying any operators

(Q1) In SUM4 wouldn’t both 2-bit operands be extended to 32-bits ?
I am not clear on reason behind it’s failure ?

(Q2) How does SUM4 differ fromSUM2 , SUM3 and SUM5 ?