typesafe compile time manual dotty builder pattern example

builder$.java

import java.io.Serializable;
import java.time.LocalDate;
import java.util.UUID;
import scala..eq.colon.eq;
import scala..less.colon.less.;
import scala.runtime.BoxedUnit;
import scala.runtime.BoxesRunTime;
import scala.runtime.ModuleSerializationProxy;

public final class builder$ implements Serializable {
   public static final builder$ MODULE$;

   static {
      new builder$();
   }

   private builder$() {
      MODULE$ = this;
   }

   private Object writeReplace() {
      return new ModuleSerializationProxy(builder$.class);
   }

   public void main(String[] args) {
      UUID id = UUID.randomUUID();
      eq evidence$1 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = new PersonDetailBuilder(PersonDetailBuilder$.MODULE$.$lessinit$greater$default$1(), PersonDetailBuilder$.MODULE$.$lessinit$greater$default$2(), PersonDetailBuilder$.MODULE$.$lessinit$greater$default$3(), PersonDetailBuilder$.MODULE$.$lessinit$greater$default$4(), PersonDetailBuilder$.MODULE$.$lessinit$greater$default$5(), PersonDetailBuilder$.MODULE$.$lessinit$greater$default$6(), PersonDetailBuilder$.MODULE$.$lessinit$greater$default$7());
      eq evidence$2 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = PersonDetailBuilder_this.copy(scala.Some..MODULE$.apply(id), PersonDetailBuilder_this.copy$default$2(), PersonDetailBuilder_this.copy$default$3(), PersonDetailBuilder_this.copy$default$4(), PersonDetailBuilder_this.copy$default$5(), PersonDetailBuilder_this.copy$default$6(), PersonDetailBuilder_this.copy$default$7());
      LocalDate birthDay = LocalDate.of(1991, 12, 10);
      eq evidence$3 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = PersonDetailBuilder_this.copy(PersonDetailBuilder_this.copy$default$1(), scala.Some..MODULE$.apply("Sample"), PersonDetailBuilder_this.copy$default$3(), PersonDetailBuilder_this.copy$default$4(), PersonDetailBuilder_this.copy$default$5(), PersonDetailBuilder_this.copy$default$6(), PersonDetailBuilder_this.copy$default$7());
      eq evidence$4 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = PersonDetailBuilder_this.copy(PersonDetailBuilder_this.copy$default$1(), PersonDetailBuilder_this.copy$default$2(), scala.Some..MODULE$.apply(birthDay), PersonDetailBuilder_this.copy$default$4(), PersonDetailBuilder_this.copy$default$5(), PersonDetailBuilder_this.copy$default$6(), PersonDetailBuilder_this.copy$default$7());
      eq evidence$5 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = PersonDetailBuilder_this.copy(PersonDetailBuilder_this.copy$default$1(), PersonDetailBuilder_this.copy$default$2(), PersonDetailBuilder_this.copy$default$3(), scala.Some..MODULE$.apply(Marital$.Married), PersonDetailBuilder_this.copy$default$5(), PersonDetailBuilder_this.copy$default$6(), PersonDetailBuilder_this.copy$default$7());
      eq evidence$6 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = PersonDetailBuilder_this.copy(PersonDetailBuilder_this.copy$default$1(), PersonDetailBuilder_this.copy$default$2(), PersonDetailBuilder_this.copy$default$3(), PersonDetailBuilder_this.copy$default$4(), scala.Some..MODULE$.apply(BoxesRunTime.boxToInteger(1)), PersonDetailBuilder_this.copy$default$6(), PersonDetailBuilder_this.copy$default$7());
      eq evidence$8 = .MODULE$.refl();
      eq evidence$9 = .MODULE$.refl();
      eq evidence$10 = .MODULE$.refl();
      eq evidence$11 = .MODULE$.refl();
      eq evidence$12 = .MODULE$.refl();
      eq evidence$13 = .MODULE$.refl();
      PersonDetailBuilder PersonDetailBuilder_this = PersonDetailBuilder_this.copy(PersonDetailBuilder_this.copy$default$1(), PersonDetailBuilder_this.copy$default$2(), PersonDetailBuilder_this.copy$default$3(), PersonDetailBuilder_this.copy$default$4(), PersonDetailBuilder_this.copy$default$5(), scala.Some..MODULE$.apply(""), PersonDetailBuilder_this.copy$default$7());
      new PersonDetail((UUID)PersonDetailBuilder_this.id().get(), (String)PersonDetailBuilder_this.name().get(), (LocalDate)PersonDetailBuilder_this.birthDay().get(), (Marital)PersonDetailBuilder_this.marital().get(), BoxesRunTime.unboxToInt(PersonDetailBuilder_this.dependents().get()), (String)PersonDetailBuilder_this.address().get(), PersonDetailBuilder_this.desc());
      BoxedUnit var10000 = BoxedUnit.UNIT;
   }
}

builder.java

public final class builder {
   public static void main(String[] var0) {
      builder$.MODULE$.main(var0);
   }
}

builder.scala

import java.time.{ Period, LocalDate }
import java.util.UUID

sealed trait Count
sealed trait Zero extends Count
sealed trait Once extends Count

enum Marital {
  case Single, Married, Divorced
}

case class PersonDetail(
  id: UUID,
  name: String,
  birthDay: LocalDate,
  marital: Marital,
  dependents: Int,
  address: String,
  desc: Option[String],
) {
  inline def age() : Period = birthDay.until(LocalDate.now())

}

object PersonDetailBuilder {
  inline def apply() =
    new PersonDetailBuilder[Zero, Zero, Zero, Zero, Zero, Zero, Zero]()
}

case class PersonDetailBuilder[
  WithId <: Count, WithName <: Count, WithBirthDay <: Count,
  WithMarital <: Count, WithDependents <: Count, WithAddress <: Count,
  WithDesc <: Count
](
  id: Option[UUID] = None,
  name: Option[String] = None,
  birthDay: Option[LocalDate] = None,
  marital: Option[Marital] = None,
  dependents: Option[Int] = None,
  address: Option[String] = None,
  desc: Option[String] = None
) {
  type IsOnce[T] = =:=[T, Once]
  type IsZero[T] = =:=[T, Zero]

  inline def withId[I <: WithId : IsZero](id: UUID) =
    copy[Once, WithName, WithBirthDay, WithMarital, WithDependents, WithAddress, WithDesc](id = Some(id))
  inline def withName[N <: WithName : IsZero](name: String) =
    copy[WithId, Once, WithBirthDay, WithMarital, WithDependents, WithAddress, WithDesc](name = Some(name))
  inline def withBirthDay[BD <: WithBirthDay : IsZero](birthDay: LocalDate) =
    copy[WithId, WithName, Once, WithMarital, WithDependents, WithAddress, WithDesc](birthDay = Some(birthDay))
  inline def withMarital[M <: WithMarital : IsZero](marital: Marital) =
    copy[WithId, WithName, WithBirthDay, Once, WithDependents, WithAddress, WithDesc](marital = Some(marital))
  inline def withDependents[D <: WithDependents : IsZero](dependents: Int) =
    copy[WithId, WithName, WithBirthDay, WithMarital, Once, WithAddress, WithDesc](dependents = Some(dependents))
  inline def withAddress[A <: WithAddress: IsZero](address: String) =
    copy[WithId, WithName, WithBirthDay, WithMarital, WithDependents, Once, WithDesc](address = Some(address))
  inline def withDesc[DE <: WithDesc : IsZero](desc: String) =
    copy[WithId, WithName, WithBirthDay, WithMarital, WithDependents, WithAddress, Once](desc = Some(desc))

  inline def build[
    B <: WithId : IsOnce, N <: WithName : IsOnce, BD <: WithBirthDay : IsOnce,
    M <: WithMarital : IsOnce, D <: WithDependents : IsOnce, A <: WithAddress : IsOnce
  ]() =
    new PersonDetail(
      id.get, name.get, birthDay.get,
      marital.get, dependents.get,
      address.get, desc
    )
}

object builder {

  // this compile
  inline def testCompile() : Unit = {
     val detail = PersonDetailBuilder.apply()
       .withId(UUID.randomUUID())
       .withName("Sample")
       .withBirthDay(LocalDate.of(1991, 12, 10))
       .withMarital(Marital.Married)
       .withDependents(1)
       .withAddress("")
       .build()
  }

  // this should not compile
  // def testDidntCompile() : Unit = {
  //   val detail = PersonDetailBuilder.apply()
  //     .withId(UUID.randomUUID())
  //     .withName("Sample")
  //     .withBirthDay(LocalDate.of(1991, 12, 10))
  //     .build()
  // }

  def main(args: Array[String]) : Unit = {
    testCompile()
    // testDidntCompile()
  }
}

Count.java

public interface Count {
}

error.log

-- Error: builder.scala:92:14 --------------------------------------------------
92 |      .build()
   |              ^
   |           Cannot prove that M
   |
   |           where:    M is a type variable with constraint <: Zero
   |            =:= Once..
   |           I found:
   |
   |               <:<.refl[Nothing]
   |
   |           But method refl in object <:< does not match type M =:= Once.
1 error found

Marital$.java

import java.io.Serializable;
import java.util.NoSuchElementException;
import scala.deriving.Mirror.Singleton;
import scala.deriving.Mirror.Sum;
import scala.reflect.ClassTag.;
import scala.runtime.EnumValues;
import scala.runtime.ModuleSerializationProxy;

public final class Marital$ implements Serializable, Sum {
   public static final Marital$ MODULE$;
   public final EnumValues Marital$$$$values;
   Single,
   Married,
   Divorced;

   static {
      new Marital$();
   }

   private Marital$() {
      MODULE$ = this;
      this.Marital$$$$values = new EnumValues();
      Single = this.$new(0, "Single");
      Married = this.$new(1, "Married");
      Divorced = this.$new(2, "Divorced");
   }

   private Object writeReplace() {
      return new ModuleSerializationProxy(Marital$.class);
   }

   public Marital[] values() {
      return (Marital[])this.Marital$$$$values.values().toArray(.MODULE$.apply(Marital.class));
   }

   public Marital valueOf(String $name) {
      try {
         return (Marital)this.Marital$$$$values.fromName().apply($name);
      } catch (NoSuchElementException var3) {
         throw new IllegalArgumentException("key not found: ".concat($name));
      }
   }

   private Marital $new(int _$ordinal, String $name) {
      return new Singleton(_$ordinal, $name) {
         private final int _$ordinal$1;
         private final String $name$1;

         public {
            this._$ordinal$1 = _$ordinal$2;
            this.$name$1 = $name$2;
            Marital$.MODULE$.Marital$$$$values.register(this);
         }

         public int $ordinal() {
            return this._$ordinal$1;
         }

         public String toString() {
            return this.$name$1;
         }
      };
   }

   public int ordinal(Marital x$0) {
      return x$0.ordinal();
   }
}

Marital.java

import scala.Enum;

public enum Marital implements Enum {
   public int ordinal() {
      return this.$ordinal();
   }
}

Once.java

public interface Once extends Count {
}

PersonDetail$.java

import java.io.Serializable;
import java.time.LocalDate;
import java.util.UUID;
import scala.Function7;
import scala.Option;
import scala.deriving.Mirror.Product;
import scala.runtime.BoxesRunTime;
import scala.runtime.ModuleSerializationProxy;

public final class PersonDetail$ implements Function7, Serializable, Product {
   public static final PersonDetail$ MODULE$;

   static {
      new PersonDetail$();
   }

   private PersonDetail$() {
      MODULE$ = this;
   }

   private Object writeReplace() {
      return new ModuleSerializationProxy(PersonDetail$.class);
   }

   public PersonDetail apply(UUID id, String name, LocalDate birthDay, Marital marital, int dependents, String address, Option desc) {
      return new PersonDetail(id, name, birthDay, marital, dependents, address, desc);
   }

   public PersonDetail unapply(PersonDetail x$1) {
      return x$1;
   }

   public PersonDetail fromProduct(scala.Product x$0) {
      return new PersonDetail((UUID)x$0.productElement(0), (String)x$0.productElement(1), (LocalDate)x$0.productElement(2), (Marital)x$0.productElement(3), BoxesRunTime.unboxToInt((Object)x$0.productElement(4)), (String)x$0.productElement(5), (Option)x$0.productElement(6));
   }
}

PersonDetail.java

import java.io.Serializable;
import java.time.LocalDate;
import java.util.UUID;
import scala.Function1;
import scala.Option;
import scala.Product;
import scala.runtime.BoxesRunTime;
import scala.runtime.Statics;
import scala.runtime.ScalaRunTime.;

public class PersonDetail implements Product, Serializable {
   private final UUID id;
   private final String name;
   private final LocalDate birthDay;
   private final Marital marital;
   private final int dependents;
   private final String address;
   private final Option desc;

   public static PersonDetail apply(UUID var0, String var1, LocalDate var2, Marital var3, int var4, String var5, Option var6) {
      return PersonDetail$.MODULE$.apply(var0, var1, var2, var3, var4, var5, var6);
   }

   public static Function1 curried() {
      return PersonDetail$.MODULE$.curried();
   }

   public static PersonDetail fromProduct(Product var0) {
      return PersonDetail$.MODULE$.fromProduct(var0);
   }

   public static Function1 tupled() {
      return PersonDetail$.MODULE$.tupled();
   }

   public static PersonDetail unapply(PersonDetail var0) {
      return PersonDetail$.MODULE$.unapply(var0);
   }

   public PersonDetail(UUID id, String name, LocalDate birthDay, Marital marital, int dependents, String address, Option desc) {
      this.id = id;
      this.name = name;
      this.birthDay = birthDay;
      this.marital = marital;
      this.dependents = dependents;
      this.address = address;
      this.desc = desc;
   }

   public int hashCode() {
      int var1 = -889275714;
      var1 = Statics.mix(var1, this.productPrefix().hashCode());
      var1 = Statics.mix(var1, Statics.anyHash(this.id()));
      var1 = Statics.mix(var1, Statics.anyHash(this.name()));
      var1 = Statics.mix(var1, Statics.anyHash(this.birthDay()));
      var1 = Statics.mix(var1, Statics.anyHash(this.marital()));
      var1 = Statics.mix(var1, this.dependents());
      var1 = Statics.mix(var1, Statics.anyHash(this.address()));
      var1 = Statics.mix(var1, Statics.anyHash(this.desc()));
      return Statics.finalizeHash(var1, 7);
   }

   public boolean equals(Object x$0) {
      boolean var14;
      if (this != (Object)x$0) {
         if (!(x$0 instanceof PersonDetail)) {
            var14 = false;
         } else {
            label80: {
               label83: {
                  PersonDetail var3 = (PersonDetail)x$0;
                  if (this.dependents() == var3.dependents()) {
                     label81: {
                        UUID var10000 = this.id();
                        UUID var4 = var3.id();
                        if (var10000 == null) {
                           if (var4 != null) {
                              break label81;
                           }
                        } else if (!var10000.equals(var4)) {
                           break label81;
                        }

                        String var10 = this.name();
                        String var5 = var3.name();
                        if (var10 == null) {
                           if (var5 != null) {
                              break label81;
                           }
                        } else if (!var10.equals(var5)) {
                           break label81;
                        }

                        LocalDate var11 = this.birthDay();
                        LocalDate var6 = var3.birthDay();
                        if (var11 == null) {
                           if (var6 != null) {
                              break label81;
                           }
                        } else if (!var11.equals(var6)) {
                           break label81;
                        }

                        Marital var12 = this.marital();
                        Marital var7 = var3.marital();
                        if (var12 == null) {
                           if (var7 != null) {
                              break label81;
                           }
                        } else if (!var12.equals(var7)) {
                           break label81;
                        }

                        var10 = this.address();
                        String var8 = var3.address();
                        if (var10 == null) {
                           if (var8 != null) {
                              break label81;
                           }
                        } else if (!var10.equals(var8)) {
                           break label81;
                        }

                        Option var13 = this.desc();
                        Option var9 = var3.desc();
                        if (var13 == null) {
                           if (var9 == null) {
                              break label83;
                           }
                        } else if (var13.equals(var9)) {
                           break label83;
                        }
                     }
                  }

                  var14 = false;
                  break label80;
               }

               var14 = true;
            }
         }

         if (!var14) {
            var14 = false;
            return var14;
         }
      }

      var14 = true;
      return var14;
   }

   public String toString() {
      return .MODULE$._toString(this);
   }

   public boolean canEqual(Object that) {
      return that instanceof PersonDetail;
   }

   public int productArity() {
      return 7;
   }

   public String productPrefix() {
      return "PersonDetail";
   }

   public Object productElement(int n) {
      Object var10000;
      switch(n) {
      case 0:
         var10000 = this._1();
         break;
      case 1:
         var10000 = this._2();
         break;
      case 2:
         var10000 = this._3();
         break;
      case 3:
         var10000 = this._4();
         break;
      case 4:
         var10000 = BoxesRunTime.boxToInteger(this._5());
         break;
      case 5:
         var10000 = this._6();
         break;
      case 6:
         var10000 = this._7();
         break;
      default:
         throw new IndexOutOfBoundsException(BoxesRunTime.boxToInteger(n).toString());
      }

      return var10000;
   }

   public String productElementName(int n) {
      String var10000;
      switch(n) {
      case 0:
         var10000 = "id";
         break;
      case 1:
         var10000 = "name";
         break;
      case 2:
         var10000 = "birthDay";
         break;
      case 3:
         var10000 = "marital";
         break;
      case 4:
         var10000 = "dependents";
         break;
      case 5:
         var10000 = "address";
         break;
      case 6:
         var10000 = "desc";
         break;
      default:
         throw new IndexOutOfBoundsException(BoxesRunTime.boxToInteger(n).toString());
      }

      return var10000;
   }

   public UUID id() {
      return this.id;
   }

   public String name() {
      return this.name;
   }

   public LocalDate birthDay() {
      return this.birthDay;
   }

   public Marital marital() {
      return this.marital;
   }

   public int dependents() {
      return this.dependents;
   }

   public String address() {
      return this.address;
   }

   public Option desc() {
      return this.desc;
   }

   public PersonDetail copy(UUID id, String name, LocalDate birthDay, Marital marital, int dependents, String address, Option desc) {
      return new PersonDetail(id, name, birthDay, marital, dependents, address, desc);
   }

   public UUID copy$default$1() {
      return this.id();
   }

   public String copy$default$2() {
      return this.name();
   }

   public LocalDate copy$default$3() {
      return this.birthDay();
   }

   public Marital copy$default$4() {
      return this.marital();
   }

   public int copy$default$5() {
      return this.dependents();
   }

   public String copy$default$6() {
      return this.address();
   }

   public Option copy$default$7() {
      return this.desc();
   }

   public UUID _1() {
      return this.id();
   }

   public String _2() {
      return this.name();
   }

   public LocalDate _3() {
      return this.birthDay();
   }

   public Marital _4() {
      return this.marital();
   }

   public int _5() {
      return this.dependents();
   }

   public String _6() {
      return this.address();
   }

   public Option _7() {
      return this.desc();
   }
}

PersonDetailBuilder$.java

import java.io.Serializable;
import scala.Option;
import scala.None.;
import scala.deriving.Mirror.Product;
import scala.runtime.ModuleSerializationProxy;

public final class PersonDetailBuilder$ implements Serializable, Product {
   public static final PersonDetailBuilder$ MODULE$;

   static {
      new PersonDetailBuilder$();
   }

   private PersonDetailBuilder$() {
      MODULE$ = this;
   }

   private Object writeReplace() {
      return new ModuleSerializationProxy(PersonDetailBuilder$.class);
   }

   public PersonDetailBuilder apply(Option id, Option name, Option birthDay, Option marital, Option dependents, Option address, Option desc) {
      return new PersonDetailBuilder(id, name, birthDay, marital, dependents, address, desc);
   }

   public PersonDetailBuilder unapply(PersonDetailBuilder x$1) {
      return x$1;
   }

   public  $lessinit$greater$default$1() {
      return .MODULE$;
   }

   public  $lessinit$greater$default$2() {
      return .MODULE$;
   }

   public  $lessinit$greater$default$3() {
      return .MODULE$;
   }

   public  $lessinit$greater$default$4() {
      return .MODULE$;
   }

   public  $lessinit$greater$default$5() {
      return .MODULE$;
   }

   public  $lessinit$greater$default$6() {
      return .MODULE$;
   }

   public  $lessinit$greater$default$7() {
      return .MODULE$;
   }

   public PersonDetailBuilder fromProduct(scala.Product x$0) {
      return new PersonDetailBuilder((Option)x$0.productElement(0), (Option)x$0.productElement(1), (Option)x$0.productElement(2), (Option)x$0.productElement(3), (Option)x$0.productElement(4), (Option)x$0.productElement(5), (Option)x$0.productElement(6));
   }
}

PersonDetailBuilder.java

import java.io.Serializable;
import scala.Option;
import scala.Product;
import scala.None.;
import scala.runtime.BoxesRunTime;

public class PersonDetailBuilder implements Product, Serializable {
   private final Option id;
   private final Option name;
   private final Option birthDay;
   private final Option marital;
   private final Option dependents;
   private final Option address;
   private final Option desc;

   public static PersonDetailBuilder apply(Option var0, Option var1, Option var2, Option var3, Option var4, Option var5, Option var6) {
      return PersonDetailBuilder$.MODULE$.apply(var0, var1, var2, var3, var4, var5, var6);
   }

   public static PersonDetailBuilder fromProduct(Product var0) {
      return PersonDetailBuilder$.MODULE$.fromProduct(var0);
   }

   public static PersonDetailBuilder unapply(PersonDetailBuilder var0) {
      return PersonDetailBuilder$.MODULE$.unapply(var0);
   }

   public static  $lessinit$greater$default$1() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$1();
   }

   public static  $lessinit$greater$default$2() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$2();
   }

   public static  $lessinit$greater$default$3() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$3();
   }

   public static  $lessinit$greater$default$4() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$4();
   }

   public static  $lessinit$greater$default$5() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$5();
   }

   public static  $lessinit$greater$default$6() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$6();
   }

   public static  $lessinit$greater$default$7() {
      return PersonDetailBuilder$.MODULE$.$lessinit$greater$default$7();
   }

   public PersonDetailBuilder(Option id, Option name, Option birthDay, Option marital, Option dependents, Option address, Option desc) {
      this.id = id;
      this.name = name;
      this.birthDay = birthDay;
      this.marital = marital;
      this.dependents = dependents;
      this.address = address;
      this.desc = desc;
   }

   public int hashCode() {
      return scala.runtime.ScalaRunTime..MODULE$._hashCode(this);
   }

   public boolean equals(Object x$0) {
      boolean var11;
      if (this != (Object)x$0) {
         if (!(x$0 instanceof PersonDetailBuilder)) {
            var11 = false;
         } else {
            label84: {
               label83: {
                  PersonDetailBuilder var3 = (PersonDetailBuilder)x$0;
                  Option var10000 = this.id();
                  Option var4 = var3.id();
                  if (var10000 == null) {
                     if (var4 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var4)) {
                     break label83;
                  }

                  var10000 = this.name();
                  Option var5 = var3.name();
                  if (var10000 == null) {
                     if (var5 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var5)) {
                     break label83;
                  }

                  var10000 = this.birthDay();
                  Option var6 = var3.birthDay();
                  if (var10000 == null) {
                     if (var6 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var6)) {
                     break label83;
                  }

                  var10000 = this.marital();
                  Option var7 = var3.marital();
                  if (var10000 == null) {
                     if (var7 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var7)) {
                     break label83;
                  }

                  var10000 = this.dependents();
                  Option var8 = var3.dependents();
                  if (var10000 == null) {
                     if (var8 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var8)) {
                     break label83;
                  }

                  var10000 = this.address();
                  Option var9 = var3.address();
                  if (var10000 == null) {
                     if (var9 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var9)) {
                     break label83;
                  }

                  var10000 = this.desc();
                  Option var10 = var3.desc();
                  if (var10000 == null) {
                     if (var10 != null) {
                        break label83;
                     }
                  } else if (!var10000.equals(var10)) {
                     break label83;
                  }

                  var11 = true;
                  break label84;
               }

               var11 = false;
            }
         }

         if (!var11) {
            var11 = false;
            return var11;
         }
      }

      var11 = true;
      return var11;
   }

   public String toString() {
      return scala.runtime.ScalaRunTime..MODULE$._toString(this);
   }

   public boolean canEqual(Object that) {
      return that instanceof PersonDetailBuilder;
   }

   public int productArity() {
      return 7;
   }

   public String productPrefix() {
      return "PersonDetailBuilder";
   }

   public Object productElement(int n) {
      Option var10000;
      switch(n) {
      case 0:
         var10000 = this._1();
         break;
      case 1:
         var10000 = this._2();
         break;
      case 2:
         var10000 = this._3();
         break;
      case 3:
         var10000 = this._4();
         break;
      case 4:
         var10000 = this._5();
         break;
      case 5:
         var10000 = this._6();
         break;
      case 6:
         var10000 = this._7();
         break;
      default:
         throw new IndexOutOfBoundsException(BoxesRunTime.boxToInteger(n).toString());
      }

      return var10000;
   }

   public String productElementName(int n) {
      String var10000;
      switch(n) {
      case 0:
         var10000 = "id";
         break;
      case 1:
         var10000 = "name";
         break;
      case 2:
         var10000 = "birthDay";
         break;
      case 3:
         var10000 = "marital";
         break;
      case 4:
         var10000 = "dependents";
         break;
      case 5:
         var10000 = "address";
         break;
      case 6:
         var10000 = "desc";
         break;
      default:
         throw new IndexOutOfBoundsException(BoxesRunTime.boxToInteger(n).toString());
      }

      return var10000;
   }

   public Option id() {
      return this.id;
   }

   public Option name() {
      return this.name;
   }

   public Option birthDay() {
      return this.birthDay;
   }

   public Option marital() {
      return this.marital;
   }

   public Option dependents() {
      return this.dependents;
   }

   public Option address() {
      return this.address;
   }

   public Option desc() {
      return this.desc;
   }

   public PersonDetailBuilder copy(Option id, Option name, Option birthDay, Option marital, Option dependents, Option address, Option desc) {
      return new PersonDetailBuilder(id, name, birthDay, marital, dependents, address, desc);
   }

   public Option copy$default$1() {
      return this.id();
   }

   public Option copy$default$2() {
      return this.name();
   }

   public Option copy$default$3() {
      return this.birthDay();
   }

   public Option copy$default$4() {
      return this.marital();
   }

   public Option copy$default$5() {
      return this.dependents();
   }

   public Option copy$default$6() {
      return this.address();
   }

   public Option copy$default$7() {
      return this.desc();
   }

   public Option _1() {
      return this.id();
   }

   public Option _2() {
      return this.name();
   }

   public Option _3() {
      return this.birthDay();
   }

   public Option _4() {
      return this.marital();
   }

   public Option _5() {
      return this.dependents();
   }

   public Option _6() {
      return this.address();
   }

   public Option _7() {
      return this.desc();
   }
}

Zero.java

public interface Zero extends Count {
}

using constrained types for manually building typesafe builder in scala

• the user API will never set a field more than once (or you could set whether it could be more than once or just once)
• compile error if user forgot setting non optional field (controlled from PersonDetailBuilder#build type constraints)

Note: all *.java are decompiled using fernflower, while actual scala files in builder.scala