package mb.nabl2.solver.solvers;

import org.metaborg.util.functions.PartialFunction2;

import mb.nabl2.terms.ITerm;

@FunctionalInterface
public interface CallExternal extends PartialFunction2<String, Iterable<? extends ITerm>, ITerm> {

}
package mb.nabl2.solver.solvers;

import org.metaborg.util.functions.PartialFunction2;

import mb.nabl2.terms.ITerm;

import java.util.Optional;

@FunctionalInterface
public interface CallExternal extends PartialFunction2<String, Iterable<? extends ITerm>, ITerm> {
    static CallExternal never() {
        return (t1, t2) -> Optional.empty();
    }
}
Add never() static method to CallExternal