In an assignment-condition, this is the part after the equals sign. Otherwise this is any other expression that is evaluated to be a boolean. (e.g. UnaryExpression, AndAndExpression, CmpExpression, etc.)
In an assignment-condition, in if (auto x = ...) this is the x
In an assignment-condition, this is true if scope is used to construct the variable.
In an assignment-condition, this is the optional explicit type
In an assignment-condition, these are the optional type constructors
In an if (or while) condition this represents: