Member predicate EnumerableCollectionExpr::getAnEmptinessCheck
Gets an expression that tests whether this expression is empty.
If the returned expression has abstract value v, then this expression is
guaranteed to be empty if isEmpty is true, and non-empty if isEmpty is
false.
For example, if the expression x.Length != 0 evaluates to true then the
expression x is guaranteed to be non-empty.
Expr getAnEmptinessCheck(GuardValue v, boolean isEmpty)