An obvious inconvenient side-effect of this approach would be that if expressions are still typed left-to-right it would be very difficult to provide the kind o

An obvious inconvenient side-effect of this approach would be that if expressions are still typed left-to-right it would be very difficult to provide the kind of tab-completion that is common in IDEs and text editors, since the information necessary to narrow the range of a search only becomes available as you finish the expression.