Value sharing (type intersection) has received scant attention from researchers working on type systems. For example, Cardelli[2] mentions it in passing as a special case of parametric polymorphism but gives no explicit consideration to it. Language designers either dispense altogether with the notion of typed variables (for example Icon[5] and SETL[9]) or make every effort to restrict value sharing.
As far as the author knows, the work of Bailes on G[1] has been the sole exception to this trend. Bailes, however, arrives at value sharing as a necessary consequence of his well-motivated overall approach and gives little specific attention to it.
Prof Herman Venter