Support syntax [scriptCall(?param:Type)]

[AndreVanDelft]

It should be possible to shorten

var param:AType = null; scriptCall(?param); {use param}

to

scriptCall(?param:AType); {use param}

So the second form is short hand for the first one.
Note that a var or val script expression should be the direct non-leftmost operand of a sequential operator; the identifier is then defined more to the right of the declaration.