Recursive binding added for local refs

[tsandall]

Topdown is creating a recursive binding when evaluating local references.

E.g., given the following data:

{
 "strings": ["foo", "bar"]
}

And the following query (expr1; expr2; expr3):

data.s = x; x[0]; x[0]

Topdown creates the following bindings:

After expr1: locals={x: data.s} refs={}
After expr2: locals={x: data.s} refs={x[0]: data.s[0]}
After expr3: locals={x: data.s} refs={x[0]: data.s[0], data.s[0]: data.s[0]}

The recursive binding after expr3 is added because of

opa/topdown/topdown.go

Line 1695 in 063aa97

return Continue(t, PlugValue(ref, t.Binding), v, iter)