When the left-hand-side expression is wider than the right-hand-side expression, pad the left-hand side on the left. Apply the following rules:
- If the right-hand expression is signed, it pads the left-hand with the sign bit.
- The left-hand expression is padded with 0 if the right-hand expression is unsigned.
- For unsized x or z constants only, the following rule applies:
If the right-hand expression's leftmost bit equals z (high impedance) or x (unknown), pad the left-hand expression with that same value. Do this regardless of whether the right-hand expression is signed or unsigned.