(Pulling this specifically out of #377, the general := bug)

This proposal is about permitting a struct field (and other such l-values) on the left side of :=, as long as there's a new variable being created (the usual := rule).

That is, permit the t.i here:

func foo() {
    var t struct { i int }
    t.i, x := 1, 2
    ...
}

This should be backwards compatible with Go 1.

Edit: clarification: any l-value that = supports, not just struct fields.

/cc @griesemer @ianlancetaylor