Unit.java

package scotch.data.unit;

import static java.util.Collections.emptyList;
import static scotch.runtime.RuntimeSupport.callable;
import static scotch.symbol.type.TypeDescriptors.sum;

import java.util.List;
import lombok.EqualsAndHashCode;
import scotch.runtime.Callable;
import scotch.symbol.DataConstructor;
import scotch.symbol.DataType;
import scotch.symbol.TypeParameters;
import scotch.symbol.Value;
import scotch.symbol.ValueType;
import scotch.symbol.type.TypeDescriptor;

@DataType(memberName = "()")
public abstract class Unit {

    public static final TypeDescriptor TYPE = sum("scotch.data.unit.()");
    private static final Callable<Unit> UNIT = callable(UnitData::new);

    @TypeParameters
    public static List<TypeDescriptor> parameters() {
        return emptyList();
    }

    @ValueType(forMember = "()")
    public static TypeDescriptor type() {
        return TYPE;
    }

    @Value(memberName = "()")
    public static Callable<Unit> unit() {
        return UNIT;
    }

    private Unit() {
        // intentionally empty
    }

    @Override
    public abstract boolean equals(Object o);

    @Override
    public abstract int hashCode();

    @Override
    public abstract String toString();

    @DataConstructor(memberName = "()", dataType = "()", ordinal = 0)
    @EqualsAndHashCode(callSuper = false)
    public static class UnitData extends Unit {

        private UnitData() {
            // intentionally empty
        }

        @Override
        public String toString() {
            return "()";
        }
    }
}